@article {3083, title = {Realization of portable room temperature nanodiamond 13C hyperpolarizer}, year = {Submitted}, author = {A. Ajoy and R. Nazaryan and E. Druga and K. Liu and B. Han and J.T. Oon and M. Gierth and R. Tsang and J.H. Walton and C.A. Meriles and J.A. Reimer and D. Suter and A. Pines} } @article {3170, title = {Dynamics of frequency-swept nuclear spin optical pumping in powdered diamond at low magnetic fields}, journal = {Proceedings of the National Academy of Science}, year = {2019}, month = {01/2019}, abstract = {

A broad effort is underway to improve the sensitivity of NMR through the use of dynamic nuclear polarization. Nitrogen vacancy (NV) centers in diamond offer an appealing platform because these paramagnetic defects can be optically polarized efficiently at room temperature. However, work thus far has been mainly limited to single crystals, because most polarization transfer protocols are sensitive to misalignment between the NV and magnetic field axes. Here we study the spin dynamics of NV\−13C pairs in the simultaneous presence of optical excitation and microwave frequency sweeps at low magnetic fields. We show that a subtle interplay between illumination intensity, frequency sweep rate, and hyperfine coupling strength leads to efficient, sweep-direction-dependent 13C spin polarization over a broad range of orientations of the magnetic field. In particular, our results strongly suggest that finely tuned, moderately coupled nuclear spins are key to the hyperpolarization process, which makes this mechanism distinct from other known dynamic polarization channels. These findings pave the route to applications where powders are intrinsically advantageous, including the hyperpolarization of target fluids in contact with the diamond surface or the use of hyperpolarized particles as contrast agents for in vivo imaging.

}, issn = {0027-8424}, doi = { https://doi.org/10.1073/pnas.1811994116 }, url = {https://www.pnas.org/content/early/2019/01/23/1811994116}, author = {P.R. Zangara and S. Dhomkar and A. Ajoy and K. Liu and R. Nazaryan and D. Pagliero and D. Suter and J. Reimer and A. Pines and C. Meriles} } @article {2981, title = {Wide dynamic range magnetic field cycler: Harnessing quantum control at low and high fields}, journal = {Review of Scientific Instruments }, volume = {90}, year = {2019}, month = {01/2019}, abstract = {

We describe the construction of a fast field cycling device capable of sweeping a 4-order-of-magnitude range of magnetic fields, from \∼1 mT to 7 T, in under 700 ms, and which is further extendable to a 1 nT-7 T range. Central to this system is a high-speed sample shuttling mechanism between a superconducting magnet and a magnetic shield, with the capability to access arbitrary fields in between with high resolution. Our instrument serves as a versatile platform to harness the inherent dichotomy of spin dynamics on offer at low and high fields\—in particular, the low anisotropy, fast spin manipulation, and rapid entanglement growth at low field as well as the long spin lifetimes, spin specific control, and efficient inductive measurement possible at high fields. Exploiting these complementary capabilities in a single device opens up applications in a host of problems in quantum control, sensing, and information storage, besides in nuclear hyperpolarization, relaxometry, and imaging. In particular, in this paper, we focus on the ability of the device to enable low-field hyperpolarization of 13C nuclei in diamond via optically pumped electronic spins associated with nitrogen vacancy defect centers.

}, doi = {https://doi.org/10.1063/1.5064685}, url = {https://aip.scitation.org/doi/10.1063/1.5064685}, author = {A. Ajoy and X. Lv and E. Druga and K. Liu and B. Safvati and A. Morabe and M. Fenton and R. Nazaryan and S. Patel and T. Sjolander and J. Reimer and D Sakellariou and C. Meriles and A. Pines} } @article {2980, title = {Enhanced dynamic nuclear polarization via swept microwave frequency combs}, journal = {Proc. Natl. Acad. Sci}, year = {2018}, month = {10/2018}, abstract = {

Dynamic nuclear polarization (DNP) has enabled enormous gains in magnetic resonance signals and led to vastly accelerated NMR/MRI imaging and spectroscopy. Unlike conventional cw-techniques, DNP methods that exploit the full electron spectrum are appealing since they allow direct participation of all electrons in the hyperpolarization process. Such methods typically entail sweeps of microwave radiation over the broad electron linewidth to excite DNP but are often inefficient because the sweeps, constrained by adiabaticity requirements, are slow. In this paper, we develop a technique to overcome the DNP bottlenecks set by the slow sweeps, using a swept microwave frequency comb that increases the effective number of polarization transfer events while respecting adiabaticity constraints. This allows a multiplicative gain in DNP enhancement, scaling with the number of comb frequencies and limited only by the hyperfine-mediated electron linewidth. We demonstrate the technique for the optical hyperpolarization of 13C nuclei in powdered microdiamonds at low fields, increasing the DNP enhancement from 30 to 100 measured with respect to the thermal signal at 7T. For low concentrations of broad linewidth electron radicals [e.g., TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl)], these multiplicative gains could exceed an order of magnitude.

}, doi = {1807125115}, url = {https://doi.org/10.1073/pnas.1807125115}, author = {Ashok Ajoy and Kristina Liu and Xudong Lv and Raffi Nazaryan and G.Wang and E . Druga and Jeff Reimer and Ditter Suter and C. Ramanathan and C.A Meriles and Alexander Pines} } @article {2979, title = {Orientation independent room-temperature optical 13C hyperpolarization in powdered diamond}, journal = {Science Advances}, volume = {4}, year = {2018}, month = {05/2018}, abstract = {

Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of nuclear magnetic resonance beyond the traditional limits imposed by magnetic field strength and temperature. Among the various alternative implementations, the use of nitrogen vacancy (NV) centers in diamond\—a paramagnetic point defect whose spin can be optically polarized at room temperature\—has attracted widespread attention, but applications have been hampered by the need to align the NV axis with the external magnetic field. We overcome this hurdle through the combined use of continuous optical illumination and a microwave sweep over a broad frequency range. As a proof of principle, we demonstrate our approach using powdered diamond with which we attain bulk 13C spin polarization in excess of 0.25\% under ambient conditions. Remarkably, our technique acts efficiently on diamond crystals of all orientations and polarizes nuclear spins with a sign that depends exclusively on the direction of the microwave sweep. Our work paves the way toward the use of hyperpolarized diamond particles as imaging contrast agents for biosensing and, ultimately, for the hyperpolarization
of nuclear spins in arbitrary liquids brought in contact with their surface.

}, doi = {10.1126/sciadv.aar5492 }, url = {http://advances.sciencemag.org/content/4/5/eaar5492}, author = {Ashok Ajoy and Kristina Liu and Raff Nazaryan and Xudong Lv and Pablo R. Zangara and Benjamin Safvati and Guoqing Wang and Daniel Arnold and Grace Li and Arthur Lin and Priyanka Raghavan and Emanuel Druga and Siddharth Dhomkar and Daniela Pagliero and Jeffrey A. Reimer and Dieter Suter and Carlos A. Meriles and Alexander Pines} } @article {2963, title = {Rapid Catalyst Capture Enables Metal-Free para-Hydrogen-Based Hyperpolarized Contrast Agents}, journal = {The Journal of Physical Chemistry Letters}, volume = {9}, year = {2018}, month = {05/2018}, pages = {2721{\textendash}2724}, abstract = {

Hyperpolarization techniques based on the use of\ para-hydrogen provide orders of magnitude signal enhancement for magnetic resonance spectroscopy and imaging. The main drawback limiting widespread applicability of\ para-hydrogen-based techniques in biomedicine is the presence of organometallic compounds (the polarization transfer catalysts) in solution with hyperpolarized contrast agents. These catalysts are typically complexes of platinum-group metals, and their administration in vivo should be avoided. Herein, we show how extraction of a hyperpolarized compound from an organic phase to an aqueous phase combined with a rapid (less than 10 s) Ir-based catalyst capture by metal scavenging agents can produce pure\ para-hydrogen-based hyperpolarized contrast agents, as demonstrated by high-resolution nuclear magnetic resonance (NMR) spectroscopy and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The presented methodology enables fast and efficient means of producing pure hyperpolarized aqueous solutions for biomedical and other uses.

}, doi = {10.1021/acs.jpclett.8b01007}, url = {https://pubs.acs.org/doi/abs/10.1021/acs.jpclett.8b01007}, author = {Danila A Barskiy and Lucia A Ke and Xingyang Li and Vincent Stevenson and Nevin Widarman and Hao Zhang and Ashley Truxal and Alexander Pines} } @article {1863, title = {Decoherence-protected transitions of nitrogen-vacancy centers in 99\% 13C-enriched diamond}, journal = {arXiv:1506.05484}, year = {2015}, month = {06/2015}, author = {Anna J. Parker and Hai-Jing Wang and Yiran Li and Alexander Pines and Jonathan P. King} } @article {1924, title = {~Measurement of untruncated nuclear spin interactions via zero-to ultralow-field nuclear magnetic resonance}, journal = {Physical Review B}, year = {2015}, author = {John W. Blanchard and Tobias F. Sjolander and Jonathan P. King and Micah Ledbetter and Emma H. Levine and Vikram S. Bajaj and Dmitri Budker and Alexander Pines} } @article {1627, title = {Zero-field nuclear magnetic resonance spectroscopy of viscous liquids}, journal = {Journal of Magnetic Resonance}, volume = {250}, year = {2015}, month = {01/2015}, pages = {1-6}, doi = {Doi:10.1016/j.jmr.2014.10.012}, author = {Shimizu, Y. and Blanchard, J.W. and Pustelny, S. and Saielli, G. and Bagno, A. and Ledbetter, M.P. and Budker, D. and Pines, A.} } @article {1450, title = {Long-lived Heteronuclear Spin-Singlet States in Liquids at a Zero Magnetic Field}, journal = {Physical Review Letters}, volume = {112}, year = {2014}, pages = {077601}, chapter = {077601}, author = {Emondts, M. and Ledbetter, M. P. and Pustelny, S. and Theis, T. and Patton, B. and Blanchard, J. W. and Butler, M. C. and Budker, D. and Pines, A.} } @article {1477, title = {Optically-detected nuclear quadrupolar interaction of 14N in nitrogen-vacancy centers in diamond}, journal = {Physical Review B}, volume = {89}, year = {2014}, pages = {205202}, doi = {10.1103/PhysRevB.89.205202}, author = {Shin, C. S. and Butler, M. C. and Wang, H. J. and Avalos, C. E. and Seltzer, S. J. and Liu, R. and Pines, A. and Bajaj, V.S.} } @article {1475, title = {Ultra-Low-Field NMR Relaxation and Diffusion Measurements Using an Optical Magnetometer (Cover Article)}, journal = {Angewandte Chemie}, volume = {53}, year = {2014}, month = {09/2014}, pages = {1-6}, doi = {DOI: 10.1002/anie.201403416}, author = {Ganssle, P. J. and Shin, H. D. and Seltzer, S. J. and Bajaj, V.S. and Ledbetter, M. P. and Budker, D. and Knappe, S. and Kitching, J. and Pines, A} } @article {1117, title = {Chemical analysis using J-coupling multiplets in zero-field NMR}, journal = {Chemical Physics Letters}, volume = {580}, year = {2013}, month = {08/2013}, pages = {160-165}, abstract = {

Zero-field nuclear magnetic resonance (NMR) spectroscopy is emerging as a new, potentially portable, and cost-effective NMR modality with the ability to provide information-rich, high-resolution spectra. We present simple rules for analysis of zero-field NMR spectra based on first-order perturbation theory and the addition of angular momenta. These rules allow for the prediction of observed spectral lines without numerical simulation. Results are presented for a few small organic molecules with characteristic spin topologies, demonstrating unambiguous assignment of peaks, highlighting the potential of zero-field NMR as a tool for chemical identification.

}, isbn = {0009-2614}, doi = {http://dx.doi.org/10.1016/j.cplett.2013.06.042}, url = {http://www.sciencedirect.com/science/article/pii/S0009261413008191}, author = {Theis, Thomas and Blanchard, John W. and Butler, Mark C. and Ledbetter, Micah P. and Budker, Dmitry and Pines, Alexander} } @article {245, title = {Fundamental Aspects of Parahydrogen Enhanced Low-Field Nuclear Magnetic Resonance}, journal = {Physical Review Letters}, volume = {110}, year = {2013}, note = {Phys Rev Lett113RITimes Cited:0Cited References Count:28}, month = {Mar 26}, pages = {137602}, abstract = {

We report new phenomena in low-field H-1 nuclear magnetic resonance (NMR) spectroscopy using parahydrogen induced polarization (PHIP), enabling determination of chemical shift differences, delta nu, and the scalar coupling constant J. NMR experiments performed with thermal polarization in millitesla magnetic fields do not allow the determination of scalar coupling constants for homonuclear coupled spins in the inverse weak coupling regime (delta nu \< J). We show here that low-field PHIP experiments in the inverse weak coupling regime enable the precise determination of delta nu and J. Furthermore we experimentally prove that observed splittings are related to delta nu in a nonlinear way. Naturally abundant C-13 and Si-29 isotopes lead to heteronuclear J-coupled H-1-multiplet lines with amplitudes significantly enhanced compared to the amplitudes for thermally prepolarized spins. PHIP-enhanced NMR in the millitesla regime allows us to measure characteristic NMR parameters in a single scan using samples containing rare spins in natural abundance. DOI: 10.1103/PhysRevLett.110.137602

}, keywords = {exchange}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.110.137602}, url = {://WOS:000316685100032}, author = {Colell, J. and Turschmann, P. and Gloggler, S. and Schleker, P. and Theis, T. and Ledbetter, M. and Budker, D. and Pines, A. and Blumich, B. and Appelt, S.} } @article {247, title = {High-Resolution Zero-Field NMR J-Spectroscopy of Aromatic Compounds}, journal = {Journal of the American Chemical Society}, volume = {135}, year = {2013}, note = {J Am Chem Soc103RNTimes Cited:0Cited References Count:59}, month = {02/2013}, pages = {3607-3612}, abstract = {

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) J-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range J-couplings. The measurement of J-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation.

}, keywords = {density}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja312239v}, url = {://WOS:000315936700050}, author = {Blanchard, J. W. and Ledbetter, M. P. and Theis, T. and Butler, M. C. and Budker, D. and Pines, A.} } @article {246, title = {Multiplets at zero magnetic field: The geometry of zero-field NMR}, journal = {The Journal of Chemical Physics}, volume = {138}, year = {2013}, month = {05/14/}, pages = {184202-15}, keywords = {Zeeman effect}, url = {http://dx.doi.org/10.1063/1.4803144}, author = {Butler, Mark C. and Ledbetter, Micah P. and Theis, Thomas and Blanchard, John W. and Budker, Dmitry and Pines, Alexander} } @article {1094, title = {Parahydrogen-induced polarization at zero magnetic field}, journal = {The Journal of Chemical Physics}, volume = {138}, year = {2013}, month = {06/2013}, pages = {234201}, abstract = {

We use symmetry arguments and simple model systems to describe the conversion of the singlet state of parahydrogen into an oscillating sample magnetization at zero magnetic field. During an initial period of free evolution governed by the scalar-coupling Hamiltonian HJ, the singlet state is converted into scalar spin order involving spins throughout the molecule. A short dc pulse along the z axis rotates the transverse spin components of nuclear species I and S through different angles, converting a portion of the scalar order into vector order. The development of vector order can be described analytically by means of single-transition operators, and it is found to be maximal when the transverse components of I are rotated by an angle of \±π/2 relative to those of S. A period of free evolution follows the pulse, during which the vector order evolves as a set of oscillating coherences. The imaginary parts of the coherences represent spin order that is not directly detectable, while the real parts can be identified with oscillations in the z component of the molecular spin dipole. The dipole oscillations are due to a periodic exchange between Iz and Sz, which have different gyromagnetic ratios. The frequency components of the resulting spectrum are imaginary, since the pulse cannot directly induce magnetization in the sample; it is only during the evolution under HJ that the vector order present at the end of the pulse evolves into detectable magnetization. \© 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4805062]

}, doi = {doi: http://dx.doi.org/10.1063/1.4805062}, url = {http://link.aip.org/link/?JCP/138/234201\&aemail=author}, author = {Butler, Mark C. and Kervern, Gwendal and Theis, Thomas and Ledbetter, Micah P. and Ganssle, Paul J. and Blanchard, John W. and Budker, Dmitry and Pines, Alexander} } @article {1318, title = {Suppression of electron spin decoherence of the diamond NV center by a transverse magnetic field}, journal = {Physical Review B}, volume = {88}, year = {2013}, month = {10/2013}, abstract = {

We demonstrate that the spin decoherence of nitrogen vacancy (NV) centers in diamond can be suppressed by a transverse magnetic field if the electron spin bath is the primary decoherence source. The NV spin coherence, created in \“a decoherence-free subspace,\” is protected by the transverse component of the zero-field splitting, increasing the spin-coherence time about twofold. The decoherence due to the electron spin bath is also suppressed at magnetic fields stronger than \∼25 G when applied parallel to the NV symmetry axis. Our method can be used to extend the spin-coherence time of similar spin systems for applications in quantum computing, field sensing, and other metrologies.

}, doi = {10.1103/PhysRevB.88.161412}, url = {http://prb.aps.org/abstract/PRB/v88/i16/e161412}, author = {Shin, Chang S. and Avalos, Claudia E. and Butler, Mark C. and Wang, Hai-Jing and Seltzer, Scott J. and Liu, Ren-Bao and Pines, Alexander and Bajaj, Vikram S.} } @article {251, title = {Liquid-State Nuclear Spin Comagnetometers}, journal = {Physical Review Letters}, volume = {108}, year = {2012}, note = {Phys Rev Lett973FATimes Cited:0Cited References Count:36}, month = {Jun 15}, abstract = {

We discuss nuclear spin comagnetometers based on ultralow-field nuclear magnetic resonance in mixtures of miscible solvents, each rich in a different nuclear spin. In one version thereof, Larmor precession of protons and F-19 nuclei in a mixture of thermally polarized pentane and hexafluorobenzene is monitored via a sensitive alkali-vapor magnetometer. We realize transverse relaxation times in excess of 20 s and suppression of magnetic field fluctuations by a factor of 3400. We estimate it should be possible to achieve single-shot sensitivity of about 5 x 10(-9) Hz, or about 5 x 10(-11) Hz in approximate to 1 day of integration. In a second version, spin precession of protons and Xe-129 nuclei in a mixture of pentane and hyperpolarized liquid xenon is monitored using superconducting quantum interference devices. Application to spin-gravity experiments, electric dipole moment experiments, and sensitive gyroscopes is discussed.

}, keywords = {nmr}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.108.243001}, url = {://WOS:000306342000010}, author = {Ledbetter, M. P. and Pustelny, S. and Budker, D. and Romalis, M. V. and Blanchard, J. W. and Pines, A.} } @article {248, title = {Zero-Field NMR Enhanced by Parahydrogen in Reversible Exchange}, journal = {Journal of the American Chemical Society}, volume = {134}, year = {2012}, note = {J Am Chem Soc909GLTimes Cited:2Cited References Count:40}, month = {02/2012}, pages = {3987-3990}, abstract = {

We have recently demonstrated that sensitive and chemically specific NMR spectra can be recorded in the absence of a magnetic field using hydrogenative parahydrogen induced polarization (PHIP)(1-3) and detection with an optical atomic magnetometer. Here, we show that non-hydrogenative para-hydrogen-induced polarization(4-6) (NH-PHIP) can also dramatically enhance the sensitivity of zero-field NMR. We demonstrate the detection of pyridine, at concentrations as low as 6 mM in a sample volume of 250 mu L, with sufficient sensitivity to resolve all identifying spectral features, as supported by numerical simulations. Because the NH-PHIP mechanism is nonreactive, operates in situ, and eliminates the need for a prepolarizing magnet, its combination with optical atomic magnetometry will greatly broaden the analytical capabilities of zero-field and low-field NMR.

}, keywords = {gas}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja2112405}, url = {://WOS:000301550800015}, author = {Theis, T. and Ledbetter, M. P. and Kervern, G. and Blanchard, J. W. and Ganssle, P. J. and Butler, M. C. and Shin, H. D. and Budker, D. and Pines, A.} } @article {258, title = {Near-Zero-Field Nuclear Magnetic Resonance}, journal = {Physical Review Letters}, volume = {107}, year = {2011}, note = {Phys Rev Lett813YOTimes Cited:5Cited References Count:26}, month = {Sep 1}, abstract = {

We investigate nuclear magnetic resonance (NMR) in near zero field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J coupling). This is in stark contrast to the high-field case, where heteronuclear J couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with nontrivial spectra.

}, keywords = {mri}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.107.107601}, url = {://WOS:000294406600017}, author = {Ledbetter, M. P. and Theis, T. and Blanchard, J. W. and Ring, H. and Ganssle, P. and Appelt, S. and Blumich, B. and Pines, A. and Budker, D.} } @article {253, title = {Parahydrogen-enhanced zero-field nuclear magnetic resonance}, journal = {Nature Physics}, volume = {7}, year = {2011}, note = {Nat Phys786FYTimes Cited:9Cited References Count:31}, month = {Jul}, pages = {571-575}, abstract = {

Nuclear magnetic resonance, conventionally detected in magnetic fields of several tesla, is a powerful analytical tool for the determination of molecular identity, structure and function. With the advent of prepolarization methods and detection schemes using atomic magnetometers or superconducting quantum interference devices, interest in NMR in fields comparable to the Earth\&$\#$39;s magnetic field and below (down to zero field) has been revived. Despite the use of superconducting quantum interference devices or atomic magnetometers, low-field NMR typically suffers from low sensitivity compared with conventional high-field NMR. Here we demonstrate direct detection of zero-field NMR signals generated through parahydrogen-induced polarization, enabling high-resolution NMR without the use of any magnets. The sensitivity is sufficient to observe spectra exhibiting (13)C-(1)H scalar nuclear spin-spin couplings (known as J couplings) in compounds with (13)C in natural abundance, without the need for signal averaging. The resulting spectra show distinct features that aid chemical fingerprinting.

}, keywords = {order}, isbn = {1745-2473}, doi = {Doi 10.1038/Nphys1986}, url = {://WOS:000292290000017}, author = {Theis, T. and Ganssle, P. and Kervern, G. and Knappe, S. and Kitching, J. and Ledbetter, M. P. and Budker, D. and Pines, A.} } @article {256, title = {Relaxivity of Gadolinium Complexes Detected by Atomic Magnetometry}, journal = {Magnetic Resonance in Medicine}, volume = {66}, year = {2011}, note = {Magn Reson Med799AVTimes Cited:1Cited References Count:23}, month = {Aug}, pages = {605-608}, abstract = {

Laser atomic magnetomeby is a portable and low-cost yet highly sensitive method for low magnetic field detection. In this work, the atomic magnetometer was used in a remote-detection geometry to measure the relaxivity of aqueous gadolinium-diethylenetriamine pentaacetic acid Gd(DTPA) at the Earth\&$\#$39;s magnetic field (40 mu T). The measured relaxivity of 9.7 +/- 2.0 s(-1) mM(-1) is consistent with field-cycling experiments measured at slightly higher magnetic fields, but no cryogens or strong and homogeneous magnetic field were required for this experiment. The field-independent sensitivity of 80 fT Hz(-1/2) allowed an in vitro detection limit of similar to 10 mu M Gd(DTPA) to be measured in aqueous buffer solution. The low detection limit and enhanced relaxivity of Gd-containing complexes at Earth\&$\#$39;s field motivate continued development of atomic magnetometry toward medical applications. Magn Reson Med 66:605-608, 2011. (C) 2011 Wiley-Liss, Inc.

}, keywords = {nmr}, isbn = {0740-3194}, doi = {Doi 10.1002/Mrm.22811}, url = {://WOS:000293256800033}, author = {Michalak, D. J. and Xu, S. J. and Lowery, T. J. and Crawford, C. W. and Ledbetter, M. and Bouchard, L. S. and Wemmer, D. E. and Budker, D. and Pines, A.} } @article {269, title = {Distortion-free magnetic resonance imaging in the zero-field limit}, journal = {Journal of Magnetic Resonance}, volume = {200}, year = {2009}, note = {J Magn Reson526AWTimes Cited:6Cited References Count:29}, month = {Oct}, pages = {285-290}, abstract = {

MRI is a powerful technique for clinical diagnosis and materials characterization. Images are acquired in a homogeneous static magnetic field much higher than the fields generated across the field of view by the spatially encoding field gradients. Without such a high field, the concomitant components of the field gradient dictated by Maxwell\&$\#$39;s equations lead to severe distortions that make imaging impossible with conventional MRI encoding. In this paper, we present a distortion-free image of a phantom acquired with a fundamentally different methodology in which the applied static field approaches zero. Our technique involves encoding with pulses of uniform and gradient field, and acquiring the magnetic field signals with a SQUID. The method can be extended to weak ambient fields, potentially enabling imaging in the Earth\&$\#$39;s field without cancellation coils or shielding. Other potential applications include quantum information processing and fundamental studies of long-range ferromagnetic interactions. (C) 2009 Elsevier Inc. All rights reserved.

}, keywords = {gradients}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2009.07.016}, url = {://WOS:000272260900015}, author = {Kelso, N. and Lee, S. K. and Bouchard, L. S. and Demas, V. and M{\"u}ck, M. and Pines, A. and Clarke, J.} } @article {268, title = {Optical detection of NMR J-spectra at zero magnetic field}, journal = {Journal of Magnetic Resonance}, volume = {199}, year = {2009}, note = {J Magn Reson456YJTimes Cited:19Cited References Count:26}, month = {Jul}, pages = {25-29}, abstract = {

Scalar couplings of the form JI(1) . I(2) between nuclei impart valuable information about molecular structure to nuclear magnetic-resonance spectra. Here we demonstrate direct detection of J-spectra due to both heteronuclear and homonuclear J-coupling in a zero-field environment where the Zeeman interaction is completely absent. We show that characteristic functional groups exhibit distinct spectra with straightforward interpretation for chemical identification. Detection is performed with a microfabricated optical atomic magnetometer, providing high sensitivity to samples of microliter volumes. We obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz statistical uncertainty. We anticipate that the technique described here will provide a new modality for high-precision\" J spectroscopy\" using small samples oil microchip devices for multiplexed Screening, assaying, and sample identification in chemistry and biomedicine. (C) 2009 Elsevier Inc. All rights reserved.

}, keywords = {cells}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2009.03.008}, url = {://WOS:000266890300004}, author = {Ledbetter, M. P. and Crawford, C. W. and Pines, A. and Wemmer, D. E. and Knappe, S. and Kitching, J. and Budker, D.} } @article {272, title = {Picomolar sensitivity MRI and photoacoustic imaging of cobalt nanoparticles}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {106}, year = {2009}, note = {P Natl Acad Sci USA420HDTimes Cited:43Cited References Count:41}, month = {Mar 17}, pages = {4085-4089}, abstract = {

Multimodality imaging based on complementary detection principles has broad clinical applications and promises to improve the accuracy of medical diagnosis. This means that a tracer particle advantageously incorporates multiple functionalities into a single delivery vehicle. In the present work, we explore a unique combination of MRI and photoacoustic tomography (PAT) to detect picomolar concentrations of nanoparticles. The nanoconstruct consists of ferromagnetic (Co) particles coated with gold (Au) for biocompatibility and a unique shape that enables optical absorption over a broad range of frequencies. The end result is a dual-modality probe useful for the detection of trace amounts of nanoparticles in biological tissues, in which MRI provides volume detection, whereas PAT performs edge detection.

}, keywords = {cancer}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0813019106}, url = {://WOS:000264278800008}, author = {Bouchard, L. S. and Anwar, M. S. and Liu, G. L. and Hann, B. and Xie, Z. H. and Gray, J. W. and Wang, X. D. and Pines, A. and Chen, F. F.} } @article {275, title = {Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {105}, year = {2008}, note = {P Natl Acad Sci USA266XBTimes Cited:8Cited References Count:17}, month = {Feb 19}, pages = {2271-2273}, abstract = {

We report the detection of nuclear magnetic resonance (NMR) using an anisotropic magnetoresistive (AMR) sensor. A \"remote-detection\" arrangement was used in which protons in flowing water were prepolarized in the field of a superconducting NMR magnet, adiabatically inverted, and subsequently detected with an AMR sensor situated downstream from the magnet and the adiabatic inverter. AMR sensing is well suited for NMR detection in microfluidic \"lab-on-a-chip\" applications because the sensors are small, typically on the order of 10 mu m. An estimate of the sensitivity for an optimized system indicates that approximate to 6 x 10(13) protons in a volume of 1,000 mu m(3), prepolarized in a 10-kG magnetic field, can be detected with a signal-to-noise ratio of 3 in a 1-Hz bandwidth. This level of sensitivity is competitive with that demonstrated by microcoils in superconducting magnets and with the projected sensitivity of microfabricated atomic magnetometers.

}, keywords = {mri}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0712129105}, url = {://WOS:000253469900006}, author = {Verpillat, F. and Ledbetter, M. P. and Xu, S. and Michalak, D. J. and Hilty, C. and Bouchard, L. S. and Antonijevic, S. and Budker, D. and Pines, A.} } @article {276, title = {Temperature response of (129)Xe depolarization transfer and its application for ultrasensitive NMR detection}, journal = {Physical Review Letters}, volume = {100}, year = {2008}, note = {Phys Rev Lett320JWTimes Cited:12Cited References Count:8}, month = {Jun 27}, abstract = {

Trapping xenon in functionalized cryptophane cages makes the sensitivity of hyperpolarized (HP) (129)Xe available for specific NMR detection of biomolecules. Here, we study the signal transfer onto a reservoir of unbound HP xenon by gating the residence time of the nuclei in the cage through the temperature-dependant exchange rate. Temperature changes larger than similar to 0.6 K are detectable as an altered reservoir signal. The temperature response is adjustable with lower concentrations of caged xenon providing more sensitivity at higher temperatures. Ultrasensitive detection of functionalized cryptophane at 310 K is demonstrated with a concentration of 10 nM, corresponding to a similar to 4000-fold sensitivity enhancement compared to conventional detection. This makes HPNMR capable of detecting such constructs in concentrations far below the detection limit of benchtop uv-visible light absorbance.

}, keywords = {biosensors}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.100.257603}, url = {://WOS:000257230500066}, author = {Schroeder, L. and Meldrum, T. and Smith, M. and Lowery, T. J. and Wemmer, D. E. and Pines, A.} } @article {277, title = {Temperature-controlled molecular depolarization gates in nuclear magnetic resonance}, journal = {Angewandte Chemie-International Edition}, volume = {47}, year = {2008}, note = {Angew Chem Int Edit308BXTimes Cited:13Cited References Count:19}, pages = {4316-4320}, keywords = {mri}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200800382}, url = {://WOS:000256364400007}, author = {Schroder, L. and Chavez, L. and Meldrum, T. and Smith, M. and Lowery, T. J. and Wemmer, D. E. and Pines, A.} } @article {279, title = {Zero-field remote detection of NMR with a microfabricated atomic magnetometer}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {105}, year = {2008}, note = {P Natl Acad Sci USA266XBTimes Cited:37Cited References Count:26}, month = {Feb 19}, pages = {2286-2290}, abstract = {

We demonstrate remote detection of nuclear magnetic resonance (NMR) with a microchip sensor consisting of a microfluidic channel and a microfabricated vapor cell (the heart of an atomic magnetometer). Detection occurs at zero magnetic field, which allows operation of the magnetometer in the spin-exchange relaxation-free (SERF) regime and increases the proximity of sensor and sample by eliminating the need for a solenoid to create a leading field. We achieve pulsed NMR linewidths of 26 Hz, limited, we believe, by the residence time and flow dispersion in the encoding region. In a fully optimized system, we estimate that for 1 s of integration, 7 x 10(13) protons in a volume of 1 mm(3), prepolarized in a 10-kG field, can be detected with a signal-to-noise ratio of approximate to 3. This level of sensitivity is competitive with that demonstrated by microcoils in 100-kG magnetic fields, without requiring superconducting magnets.

}, keywords = {mri}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0711505105}, url = {://WOS:000253469900009}, author = {Ledbetter, M. P. and Savukov, I. M. and Budker, D. and Shah, V. and Knappe, S. and Kitching, J. and Michalak, D. J. and Xu, S. and Pines, A.} } @article {289, title = {Sensitivity enhancement by exchange mediated magnetization transfer of the xenon biosensor signal}, journal = {Journal of Magnetic Resonance}, volume = {184}, year = {2007}, note = {J Magn Reson127EUTimes Cited:7Cited References Count:18}, month = {Jan}, pages = {72-77}, abstract = {

Hyperpolarized xenon associated with ligand derivatized cryptophane-A cages has been developed as a NMR based biosensor. To optimize the detection sensitivity we describe use of xenon exchange between the caged and bulk dissolved xenon as an effective signal amplifier. This approach, somewhat analogous to \&$\#$39;remote detection\&$\#$39; described recently, uses the chemical exchange to repeatedly transfer spectroscopic information from caged to bulk xenon, effectively integrating the caged signal. After an optimized integration period, the signal is read out by observation of the bulk magnetization. The spectrum of the caged xenon is reconstructed through use of a variable evolution period before transfer and Fourier analysis of the bulk signal as a function of the evolution time. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {resonance}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2006.09.010}, url = {://WOS:000243568900009}, author = {Garcia, S. and Chavez, L. and Lowery, T. J. and Han, S. I. and Wemmer, D. E. and Pines, A.} } @article {294, title = {Molecular imaging using a targeted magnetic resonance hyperpolarized biosensor}, journal = {Science}, volume = {314}, year = {2006}, note = {Science096MWTimes Cited:109Cited References Count:20}, month = {Oct 20}, pages = {446-449}, abstract = {

A magnetic resonance approach is presented that enables high-sensitivity, high-contrast molecular imaging by exploiting xenon biosensors. These sensors link xenon atoms to specific biomolecular targets, coupling the high sensitivity of hyperpolarized nuclei with the specificity of biochemical interactions. We demonstrated spatial resolution of a specific target protein in vitro at micromolar concentration, with a readout scheme that reduces the required acquisition time by \>3300-fold relative to direct detection. This technique uses the signal of free hyperpolarized xenon to dramatically amplify the sensor signal via chemical exchange saturation transfer (CEST). Because it is similar to 10,000 times more sensitive than previous CEST methods and other molecular magnetic resonance imaging techniques, it marks a critical step toward the application of xenon biosensors as selective contrast agents in biomedical applications.

}, keywords = {agents}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.1131847}, url = {://WOS:000241382500036}, author = {Schroder, L. and Lowery, T. J. and Hilty, C. and Wemmer, D. E. and Pines, A.} } @article {299, title = {Optimization of xenon biosensors for detection of protein interactions}, journal = {Chembiochem}, volume = {7}, year = {2006}, note = {Chembiochem003SDTimes Cited:39Cited References Count:25}, month = {Jan}, pages = {65-73}, abstract = {

Hyperpolarized Xe-129 NMR spectroscopy can detect the presence of specific low-concentration biomolecular analytes by means of a xenon biosensor that consists of a water-soluble, targeted cryptophane-A cage that encapsulates the xenon. In this work, we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein-bound resonances. The effects of diastereomer overlap, dipole-dipole coupling, chemical-shift anisotropy, xenon exchange, and biosensor conformotional exchange on the protein-bound biosensor signal were assessed. It was found that an optimal protein-bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length. Both the line width and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.

}, keywords = {complexes}, isbn = {1439-4227}, doi = {Doi 10.1002/Cbic.200500327}, url = {://WOS:000234701000012}, author = {Lowery, T. J. and Garcia, S. and Chavez, L. and Ruiz, E. J. and Wu, T. and Brotin, T. and Dutasta, J. P. and King, D. S. and Schultz, P. G. and Pines, A. and Wemmer, D. E.} } @article {300, title = {Solid-state NMR structural studies of the fibril form of a mutant mouse prion peptide PrP89-143(P101L)}, journal = {Solid State Nuclear Magnetic Resonance}, volume = {29}, year = {2006}, note = {Solid State Nucl Mag999VATimes Cited:22Cited References Count:34}, month = {Feb}, pages = {183-190}, abstract = {

The peptide fragment 89-143 of the prion protein (carrying a P101L mutation) is biologically active in transgenic mice when in a fibrillar form. Injection of these fibrils into transgenic mice (expressing full length PrP with the P101L mutation) induces a neurodegenerative prion disease (Kaneko et al., J. Mol. Biol. 295 (2000) 997). Here we present solid-state NMR studies of PrP89-143(P101L) fibrils, probing the conformation of residues in the hydrophobic segment 112-124 with chemical shifts. The conformations of glycine residues were analyzed using doubly C-13 = 0 labeled peptides by two-dimensional (2D) double-quantum correlation, and double-quantum filtered dephasing distance measurements. MQ-NMR experiments were carried out to probe the relative alignment of the individual peptides fibrils. These NMR studies indicate that the 112-124 segment adopts an extended beta-sheet conformation, though not in a parallel, in register alignment. There is evidence for conformational variability at Gly 113. DQ correlation experiments provide useful information in regions with conformational heterogeneity. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {identification}, isbn = {0926-2040}, doi = {Doi 10.1016/J.Ssnmr.2005.09.017}, url = {://WOS:000234417500020}, author = {Lim, K. H. and Nguyen, T. N. and Damo, S. M. and Mazur, T. and Ball, H. L. and Prusiner, S. B. and Pines, A. and Wemmer, D. E.} } @article {301, title = {Spectrally resolved magnetic resonance imaging of a xenon biosensor}, journal = {Angewandte Chemie-International Edition}, volume = {45}, year = {2006}, note = {Angew Chem Int Edit997CZTimes Cited:48Cited References Count:14}, pages = {70-73}, keywords = {delivery}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200502693}, url = {://WOS:000234223900007}, author = {Hilty, C. and Lowery, T. J. and Wemmer, D. E. and Pines, A.} } @article {298, title = {SQUID-detected microtesla MRI in the presence of metal}, journal = {Journal of Magnetic Resonance}, volume = {179}, year = {2006}, note = {J Magn Reson035CMTimes Cited:36Cited References Count:23}, month = {Mar}, pages = {146-151}, abstract = {

In magnetic resonance imaging performed at fields of I T and above, the presence of a metal insert can distort the image because of susceptibility differences within the sample and modification of the radiofrequency fields by screening currents. Furthermore, it is not feasible to perform nuclear magnetic resonance (NMR) spectroscopy or acquire a magnetic resonance image if the sample is enclosed in a metal container. Both problems can be overcome by substantially lowering the NMR frequency. Using a microtesla imaging system operating at 2.8 kHz, with a superconducting quantum interference device as the signal detector, we have obtained distortion-free images of a phantom containing a titanium bar and three-dimensional images of an object enclosed in an aluminum can; in both cases high-field images are inaccessible. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {nmr}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2005.11.005}, url = {://WOS:000236977600019}, author = {Mossle, M. and Han, S. I. and Myers, W. R. and Lee, S. K. and Kelso, N. and Hatridge, M. and Pines, A. and Clarke, J.} } @article {297, title = {Xenon biosensor amplification via dendrimer-cage supramolecular constructs}, journal = {Journal of the American Chemical Society}, volume = {128}, year = {2006}, note = {J Am Chem Soc043HFTimes Cited:37Cited References Count:21}, month = {May 17}, pages = {6334-6335}, keywords = {chemistry}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja061735s}, url = {://WOS:000237590400033}, author = {Mynar, J. L. and Lowery, T. J. and Wemmer, D. E. and Pines, A. and Frechet, J. M. J.} } @article {313, title = {Distinguishing multiple chemotaxis Y protein conformations with laser-polarized Xe-129 NMR}, journal = {Protein Science}, volume = {14}, year = {2005}, note = {Protein Sci907SSTimes Cited:23Cited References Count:27}, month = {Apr}, pages = {848-855}, abstract = {

The chemical shift of the Xe-129 NMR signal has been shown to be extremely sensitive to the local environment around the atom and has been used to follow processes such as ligand binding by bacterial periplasmic binding proteins. Here we show that the Xe-129 shift can sense more subtle changes: magnesium binding, BeF3- activation, and peptide binding by the Escherichia coli chemotaxis Y protein. H-1-N-15 correlation spectroscopy and X-ray crystallography were used to identify two xenon-binding cavities in CheY that are primarily responsible for the shift changes. One site is near the active site, and the other is near the peptide binding site.

}, keywords = {cavity}, isbn = {0961-8368}, doi = {Doi 10.1110/Ps.041231005}, url = {://WOS:000227738900002}, author = {Lowery, T. J. and Doucleff, M. and Ruiz, E. J. and Rubin, S. M. and Pines, A. and Wemmer, D. E.} } @article {317, title = {NMR-based biosensing with optimized delivery of polarized Xe-129 to solutions}, journal = {Analytical Chemistry}, volume = {77}, year = {2005}, note = {Anal Chem942GLTimes Cited:30Cited References Count:37}, month = {Jul 1}, pages = {4008-4012}, abstract = {

Laser-enhanced (LE) Xe-129 nuclear magnetic resonance (NMR) is an exceptional tool for sensing extremely small physical and chemical changes; however, the difficult mechanics of bringing polarized xenon and samples of interest together have limited applications, particularly to biological molecules. Here we present a method for accomplishing solution Xe-129 biosensing based on flow (bubbling) of LE Xe-129 gas through a solution in situ in the NMR probe, with pauses for data acquisition. This overcomes fundamental limitations of conventional solution-state LE Xe-129 NMR, e.g., the difficulty in transferring hydrophobic xenon into aqueous environments, and the need to handle the sample to refresh LE Xe-129 after an observation pulse depletes polarization. With this new method, we gained a factor of \> 100 in sensitivity due to improved xenon transfer to the solution and the ability to signal average by renewing the polarized xenon. Polarized xenon in biosensors was detected at very low concentrations, \<= 250 nanomolar, while retaining all the usual information from NMR. This approach can be used to simultaneously detect multiple sensors with different chemical shifts and is also capable of detecting signals from opaque, heterogeneous samples, which is a unique advantage over optical methods. This general approach is adaptable for sensing minute quantities of xenon in heterogeneous in vitro samples, in miniaturized devices and should be applicable to certain in-vivo environments.

}, keywords = {blood}, isbn = {0003-2700}, doi = {Doi 10.1021/Ac0500479}, url = {://WOS:000230270800035}, author = {Han, S. I. and Garcia, S. and Lowery, T. J. and Ruiz, E. J. and Seeley, J. A. and Chavez, L. and King, D. S. and Wemmer, D. E. and Pines, A.} } @article {309, title = {SQUID-detected in vivo MRI at microtesla magnetic fields}, journal = {Ieee Transactions on Applied Superconductivity}, volume = {15}, year = {2005}, note = {Ieee T Appl SuperconPart 1935FOTimes Cited:24Cited References Count:15}, month = {Jun}, pages = {757-760}, abstract = {

We use a low transition temperature (T(c)) Super-conducting Quantum Interference Device (SQUID) to perform in vivo magnetic resonance imaging (MRI) at magnetic fields around 100 microtesla, corresponding to proton Larmor frequencies of about 5 kHz. In such low fields, broadening of the nuclear magnetic resonance lines due to inhomogeneous magnetic fields and susceptibility variations of the sample are minimized, enabling us to obtain high quality images. To reduce environmental noise the signal is detected by a second-order gradiometer, coupled to the SQUID, and the experiment is surrounded by a 3-mm thick Al shield. To increase the signal-to-noise ratio (SNR), we prepolarize the samples in a field up to 100 mT. Three-dimensional images are acquired in less than 6 minutes with a standard spin-echo phase-encoding sequence. Using encoding gradients of similar to 100 mu T/m we obtain three-dimensional images of bell peppers with a resolution of 2 x 2 x 8 mm(3). Our system is ideally suited to acquiring images of small, peripheral parts of the human body such as hands and arms. In vivo images of an arm, acquired at 132 mu T, show 24-mm sections of the forearm with a resolution of 3 x 3 mm(2). and a SNR of 10. We discuss possible applications of MRI at these low magnetic fields.

}, keywords = {nmr}, isbn = {1051-8223}, doi = {Doi 10.1109/Tasc.2005.850043}, url = {://WOS:000229765300170}, author = {Mossle, M. and Myers, W. R. and Lee, S. K. and Kelso, N. and Hatridge, M. and Pines, A. and Clarke, J.} } @article {314, title = {SQUID-detected MRI at 132 mu T with T(1)-weighted contrast established at 10 mu T-300 mT}, journal = {Magnetic Resonance in Medicine}, volume = {53}, year = {2005}, note = {Magn Reson Med888NETimes Cited:73Cited References Count:20}, month = {Jan}, pages = {9-14}, abstract = {

T(1)-weighted contrast MRI with prepolarization was detected with a superconducting quantum interference device (SQUID). A spin evolution period in a variable field between prepolarization and detection enabled the measurement of T(1) in fields between 1.7 muT and 300 mT; T, dispersion curves of agarose gel samples over five decades in frequency were obtained. SQUID detection at 5.6 kHz drastically reduces the field homogeneity requirements compared to conventional field-cycling methods using Faraday coil detection. This allows T(1) dispersion measurements to be easily combined with MRI, so that T(1) in a wide range of fields can be used for tissue contrast. Images of gel phantoms with T(1)-weighted contrast at four different fields between 10 muT and 300 mT demonstrated dramatic contrast enhancement in low fields. A modified inversion recovery technique further enhanced the contrast by selectively suppressing the signal contribution for a specific value of the low-field T(1). Published 2004 Wiley-Liss, Inc.

}, keywords = {dispersion}, isbn = {0740-3194}, doi = {Doi 10.1002/Mrm.20316}, url = {://WOS:000226380700003}, author = {Lee, S. K. and Mossle, M. and Myers, W. and Kelso, N. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {320, title = {Xenon NMR as a probe for microporous and mesoporous solids, polymers, liquid crystals, solutions, flames, proteins, imaging}, journal = {Actualite Chimique}, year = {2005}, note = {Actual ChimiqueSuppl. 287952GHTimes Cited:3Cited References Count:89}, month = {Jun}, pages = {16-34}, abstract = {

We present in this paper some examples of the applications of the Nuclear Magnetic Resonance (NMR) of xenon used as a probe in the study of different chemical environments: determination of the porosity of micro-and mesoporous solids, evaluation of the concentrations and sizes of amorphous domains in solid polymers, characterization of liquid crystals, study of combustion processes at high temperature, determination of the structure and dynamics of organic systems and proteins in solution, assessment of cerebral blood flow.

}, keywords = {silica-gels}, isbn = {0151-9093}, url = {://WOS:000230991500005}, author = {Bartik, K. and Choquet, P. and Constantinesco, A. and Duhamel, G. and Fraissard, J. and Hyacinthe, J. N. and Jokisaari, J. and Locci, E. and Lowery, T. J. and Luhmer, M. and Meersmann, T. and Moudrakovski, I. L. and Pavlovskaya, G. E. and Pierce, K. L. and Pines, A. and Ripmeester, J. A. and Telkki, V. V. and Veeman, W. S.} } @article {333, title = {Design of a conformation-sensitive xenon-binding cavity in the ribose-binding protein}, journal = {Angewandte Chemie-International Edition}, volume = {43}, year = {2004}, note = {Angew Chem Int Edit877MVTimes Cited:10Cited References Count:20}, pages = {6320-6322}, keywords = {probe}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200460629}, url = {://WOS:000225575600015}, author = {Lowery, T. J. and Rubin, S. M. and Ruiz, E. J. and Pines, A. and Wemmer, D. E.} } @article {325, title = {Development of a functionalized xenon biosensor}, journal = {Journal of the American Chemical Society}, volume = {126}, year = {2004}, note = {J Am Chem Soc872UHTimes Cited:60Cited References Count:76}, month = {Nov 24}, pages = {15287-15294}, abstract = {

NMR-based biosensors that utilize laser-polarized xenon offer potential advantages beyond current sensing technologies. These advantages include the capacity to simultaneously detect multiple analytes, the applicability to in vivo spectroscopy and imaging, and the possibility of \"remote\" amplified detection. Here, we present a detailed NMR characterization of the binding of a biotin-derivatized caged-xenon sensor to avidin. Binding of \"functionalized\" xenon to avidin leads to a change in the chemical shift of the encapsulated xenon in addition to a broadening of the resonance, both of which serve as NMR markers of ligand-target interaction. A control experiment in which the biotin-binding site of avidin was blocked with native biotin showed no such spectral changes, confirming that only specific binding, rather than nonspecific contact, between avidin and functionalized xenon leads to the effects on the xenon NMR spectrum. The exchange rate of xenon (between solution and cage) and the xenon spin-lattice relaxation rate were not changed significantly upon binding. We describe two methods for enhancing the signal from functionalized xenon by exploiting the laser-polarized xenon magnetization reservoir. We also show that the xenon chemical shifts are distinct for xenon encapsulated in different diastereomeric cage molecules. This demonstrates the potential for tuning the encapsulated xenon chemical shift, which is a key requirement for being able to multiplex the biosensor.

}, keywords = {drug discovery}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja0483037}, url = {://WOS:000225233600051}, author = {Spence, M. M. and Ruiz, E. J. and Rubin, S. M. and Lowery, T. J. and Winssinger, N. and Schultz, P. G. and Wemmer, D. E. and Pines, A.} } @article {335, title = {Diamagnetic clusters of paramagnetic endometallofullerenes: A solid-state MAS NMR study}, journal = {Journal of Physical Chemistry B}, volume = {108}, year = {2004}, note = {J Phys Chem B846BKTimes Cited:10Cited References Count:39}, month = {Aug 19}, pages = {12450-12455}, abstract = {

Solid powder samples of complexes of the endometallofullerenes (EMF) La@C-82 and Y@C-82 with hexamethylphosphoramide (HMPA) were studied by magic-angle spinning (MAS) NMR. We have obtained well-resolved P-31 NMR spectra and C-13 NMR spectra for both La-EMF/HMPA and Y-EMF/HMPA and La-139 spectra for the La-EMF/HMPA. The (31)p measurements on La-EMF/HMPA and Y-EMF/HMPA have revealed considerable chemical shifts of (31)p signals relative to pure HMPA. Two-dimensional exchange P-31 experiments revealed that HMPA molecules at different sites in the EMF/HMPA complex do not change positions at a time scale of up to 1 s. Both EMF samples demonstrate a vast chemical shift range for 31p of the bound HMPA molecules. In addition, the La-EMF/HMPA exhibits the enormous spreading of the chemical shifts for La-139. The experimental results suggest that paramagnetic La@C-82 and Y@C-92 in the solid state form clusters (nanoparticles) in which the exchange coupling of the EMF takes place with quenching of the most electron spins.

}, keywords = {complexes}, isbn = {1520-6106}, doi = {Doi 10.1021/Jp048610z}, url = {://WOS:000223289500027}, author = {Koltover, V. K. and Logan, J. W. and Heise, H. and Bubnov, V. P. and Estrin, Y. I. and Kareev, I. E. and Lodygina, V. P. and Pines, A.} } @article {334, title = {Isotropic-liquid crystalline phase diagram of a CdSe nanorod solution}, journal = {Journal of Chemical Physics}, volume = {120}, year = {2004}, note = {J Chem Phys763JETimes Cited:27Cited References Count:29}, month = {Jan 15}, pages = {1149-1152}, abstract = {

We report the isotropic-liquid crystalline phase diagram of 3.0 nm x 60 nm CdSe nanorods dispersed in anhydrous cyclohexane. The coexistence concentrations of both phases are found to be lower and the biphasic region wider than the results predicted by the hard rod model, indicating that the attractive interaction between the nanorods may be important in the formation of the liquid crystalline phase in this system. (C) 2004 American Institute of Physics.

}, keywords = {model}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1640331}, url = {://WOS:000188081000002}, author = {Li, L. S. and Marjanska, M. and Park, G. H. J. and Pines, A. and Alivisatos, A. P.} } @article {331, title = {Microtesla MRI with a superconducting quantum interference device}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {101}, year = {2004}, note = {P Natl Acad Sci USA823ZCTimes Cited:76Cited References Count:29}, month = {May 25}, pages = {7857-7861}, abstract = {

MRI scanners enable fast, noninvasive, and high-resolution imaging of organs and soft tissue. The images are reconstructed from NMR signals generated by nuclear spins that precess in a static magnetic field B(0) in the presence of magnetic field gradients. Most clinical MRI scanners operate at a magnetic field B(0) = 1.5 T, corresponding to a proton resonance frequency of 64 MHz. Because these systems rely on large superconducting magnets, they are costly and demanding of infrastructure. On the other hand, low-field imagers have the potential to be less expensive, less confining, and more mobile. The major obstacle is the intrinsically low sensitivity of the low-field NMR experiment. Here, we show that prepolarization of the nuclear spins and detection with a superconducting quantum interference device (SQUID) yield a signal that is independent of B(0), allowing acquisition of high-resolution MRIs in microtesla fields. Reduction of the strength of the measurement field eliminates inhomogeneous broadening of the NMR lines, resulting in enhanced signal-to-noise ratio and spatial resolution for a fixed strength of the magnetic field gradients used to encode the image. We present high-resolution images of phantoms and other samples and T(1)-weighted contrast images acquired in highly inhomogeneous magnetic fields of 132 muT; here, T, is the spin-lattice relaxation time. These techniques could readily be adapted to existing multichannel SQUID systems used for magnetic source imaging of brain signals. Further potential applications include low-cost systems for tumor screening and imaging peripheral regions of the body.

}, keywords = {system}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0402382101}, url = {://WOS:000221652000005}, author = {McDermott, R. and Lee, S. K. and ten Haken, B. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {337, title = {Rational reduction of periodic propagators for off-period observations}, journal = {Journal of Magnetic Resonance}, volume = {166}, year = {2004}, note = {J Magn Reson767TUTimes Cited:2Cited References Count:19}, month = {Feb}, pages = {174-181}, abstract = {

Many common solid-state nuclear magnetic resonance problems take advantage of the periodicity of the underlying Hamiltonian to simplify the computation of an observation. Most of the time-domain methods used, however, require the time step between observations to be some integer or reciprocal-integer multiple of the period, thereby restricting the observation bandwidth. Calculations of off-period observations are usually reduced to brute force direct methods resulting in many demanding matrix multiplications. For large spin systems, the matrix multiplication becomes the limiting step. A simple method that can dramatically reduce the number of matrix multiplications required to calculate the time evolution when the observation time step is some rational fraction of the period of the Hamiltonian is presented. The algorithm implements two different optimization routines. One uses pattern matching and additional memory storage, while the other recursively generates the propagators via time shifting. The net result is a significant speed improvement for some types of time-domain calculations. (C) 2003 Published by Elsevier Inc.

}, keywords = {simulation}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2003.10.002}, url = {://WOS:000188469400005}, author = {Blanton, W. B. and Logan, J. W. and Pines, A.} } @article {322, title = {SQUID-detected liquid state NMR in microtesla fields}, journal = {Journal of Physical Chemistry A}, volume = {108}, year = {2004}, note = {J Phys Chem A772FTTimes Cited:32Cited References Count:36}, month = {Feb 12}, pages = {957-963}, abstract = {

Nuclear magnetic resonance (NMR) experiments performed in magnetic fields on the order of microtesla yield line widths comparable to the lifetime limit even in grossly inhomogeneous magnets. The potential loss in sensitivity is overcome by combining prepolarization in fields on the order of millitesla and signal detection with a Superconducting Quantum Interference Device (SQUID). The enhanced spectral resolution attainable in microtesla fields enables NMR studies of pure liquids and solutions without the need for strong magnets. We have investigated a variety of heteronuclear systems in both the weak and strong J-coupling regimes. Six different nuclear species have been detected with the same experimental apparatus. NMR signals of thermally polarized protons were obtained in fields as low as 554 nT.

}, keywords = {water}, isbn = {1089-5639}, doi = {Doi 10.1021/Jp035181g}, url = {://WOS:000188831500005}, author = {Trabesinger, A. H. and McDermott, R. and Lee, S. K. and M{\"u}ck, M. and Clarke, J. and Pines, A.} } @article {332, title = {SQUID-detected magnetic resonance imaging in microtesla magnetic fields}, journal = {Journal of Low Temperature Physics}, volume = {135}, year = {2004}, note = {J Low Temp Phys824TWTimes Cited:37Cited References Count:34}, month = {Jun}, pages = {793-821}, abstract = {

We describe studies of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) of liquid samples at room temperature in microtesla magnetic fields. The nuclear spins are prepolarized in a strong transient field. The magnetic signals generated by the precessing spins, which range in frequency from tens of Hz to several kHz, are detected by a low-transition temperature dc SQUID (Superconducting QUantum Interference Device) coupled to an untuned, superconducting flux transformer configured as an axial gradiometer. The combination of prepolarization and frequency-independent detector sensitivity results in a high signal-to-noise ratio and high spectral resolution (similar to 1 Hz) even in grossly inhomogeneous magnetic fields. In the NMR experiments, the high spectral resolution enables us to detect the 10-Hz splitting of the spectrum of protons due to their scalar coupling to a P-31 nucleus. Furthermore, the broadband detection scheme combined with a non-resonant field-reversal spin echo allows the simultaneous observation of signals from protons and P-31 nuclei, even though their NMR resonance frequencies differ by a factor of 2.5. We extend our methodology to MRI in microtesla fields, where the high spectral resolution translates into high spatial resolution. We demonstrate two-dimensional images of a mineral oil phantom and slices of peppers, with a spatial resolution of about 1 mm. We also image an intact pepper using slice selection, again with 1-mm, resolution. A further experiments we demonstrate T-1-contrast imaging of a water phantom, some parts of which were doped with a paramagnetic salt to reduce the longitudinal relaxation time T-1. Possible applications of this MRI technique include screening for tumors and integration with existing multichannel SQUID systems for brain imaging.

}, keywords = {mri}, isbn = {0022-2291}, doi = {Doi 10.1023/B:Jolt.0000029519.09286.C5}, url = {://WOS:000221710600023}, author = {McDermott, R. and Kelso, N. and Lee, S. K. and Mossle, M. and M{\"u}ck, M. and Myers, W. and ten Haken, B. and Seton, H. C. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {343, title = {Applications of Laser-Polarized 129 XE NMR to Biomolecular Assays}, journal = {Magnetic Resonance Imaging}, year = {2003}, pages = {1235-1239}, doi = {10.1016/J.Mri.2003.08.025}, author = {Lowery, T.J. and Rubin, S.M. and Ruiz, E.J. and Spence, M.M. and Winssinger, N. and Schultz, P.G. and Pines, A. and Wemmer, D.E.} } @article {339, title = {High-resolution NMR correlation spectra of disordered solids}, journal = {Journal of the American Chemical Society}, volume = {125}, year = {2003}, note = {J Am Chem Soc663JYTimes Cited:70Cited References Count:46}, month = {Apr 9}, pages = {4376-4380}, abstract = {

We show how high-resolution NMR spectra can be obtained for solids for which the spectra are normally broadened due to structural disorder. The method relies on correlations in the chemical shifts between pairs of coupled spins. It is found experimentally that there are strong correlations in the chemical shifts between neighboring spins in both phosphorus-31 and carbon-13 spectra. These correlations can be exploited not only to provide resolution in two-dimensional spectra, but also to yield \"chains\" of correlated chemical shifts, constituting a valuable new source of structural information for disordered materials.

}, keywords = {SPECTROSCOPY}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja0292389}, url = {://WOS:000182003500067}, author = {Sakellariou, D. and Brown, S. P. and Lesage, A. and Hediger, S. and Bardet, M. and Meriles, C. A. and Pines, A. and Emsley, L.} } @article {354, title = {Detection and characterization of xenon-binding sites in proteins by Xe-129 NMR spectroscopy}, journal = {Journal of Molecular Biology}, volume = {322}, year = {2002}, note = {J Mol Biol597PTTimes Cited:53Cited References Count:54}, month = {Sep 13}, pages = {425-440}, abstract = {

Xenon-binding sites in proteins have led to a number of applications of xenon in biochemical and structural studies. Here we further develop the utility of Xe-129 NMR in characterizing specific xenon-protein interactions. The sensitivity of the Xe-129 chemical shift to its local environment and the intense signals attainable by optical pumping make xenon a useful NMR reporter of its own interactions with proteins. A method for detecting specific xenon-binding interactions by analysis of Xe-129 chemical shift data is illustrated using the maltose binding protein (MBP) from Escherichia coli as an example. The crystal structure of MBP in the presence of 8 atm of xenon confirms the binding site determined from NMR data. Changes in the structure of the xenon-binding cavity upon the binding of maltose by the protein can account for the sensitivity of the Xe-129 chemical shift to MBP conformation. Xe-129 NMR data for xenon in solution with a number of cavity containing phage T4 lysozyme mutants show that xenon can report on cavity structure. In particular, a correlation exists between cavity size and the binding-induced Xe-129 chemical shift. Further applications of Xe-129 NMR to biochemical assays, including the screening of proteins for xenon binding for crystallography are considered. (C) 2002 Elsevier Science Ltd. All rights reserved

}, keywords = {nonpolar cavity}, isbn = {0022-2836}, doi = {Doi 10.1016/S0022-2836(02)00739-8}, url = {://WOS:000178230500014}, author = {Rubin, S. M. and Lee, S. Y. and Ruiz, E. J. and Pines, A. and Wemmer, D. E.} } @article {361, title = {Efficient triple-quantum excitation in modified RIACT MQMAS NMR for I=3/2 nuclei}, journal = {Journal of Magnetic Resonance}, volume = {154}, year = {2002}, note = {J Magn Reson527MFTimes Cited:15Cited References Count:31}, month = {Feb}, pages = {196-204}, abstract = {

A new approach involving the creation of triple-quantum (TQ) coherences from both TQ and central transitions (CT) is investigated, in order to enhance the efficiency of triple-quantum excitation for I = 3/2 nuclei. The RIACT excitation scheme, a soft pi/2 and hard spin-locking pulse, is shown to induce both adiabatic coherence transfer between CT and TQ coherences and TQ nutation. By combining the RIACT scheme with the presaturation of the satellite transitions, a significant improvement in the TQ excitation can be achieved mainly through enhanced CT polarization via the RIACT mechanism, in particular for nuclei with moderate to large quadrupole coupling constants (greater than or equal to2.0 MHz). There also exists a nontrivial contribution from the TQ transition, which depends on the size of the quadrupole interaction. (C) 2002 Elsevier Science (USA).

}, keywords = {coherence}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2001.2471}, url = {://WOS:000174189300005}, author = {Lim, K. H. and Charpentier, T. and Pines, A.} } @article {359, title = {Investigations of low-amplitude radio frequency pulses at and away from rotary resonance conditions for I=5/2 Nuclei}, journal = {Solid State Nuclear Magnetic Resonance}, volume = {22}, year = {2002}, note = {Solid State Nucl Mag613WLTimes Cited:8Cited References Count:40}, month = {Sep-Nov}, pages = {97-109}, abstract = {

Additional experimental evidence of rotary resonance effects for multiple-quantum coherence conversion in a spin-5/2 system is presented. Two-dimensional plots of the relative efficiency of MQ excitation and conversion are given as a function of radio frequency (rf) amplitude and pulse width. Data are presented for the excitation of five-quantum coherence (5QC), as well as for 5QC to three-quantum coherence (3QC) conversion, 5QC to 1QC (the central transition coherence) conversion, and 3QC to 1 QC conversion. A two-fold increase in the signal-to-noise ratio is achieved by substituting low amplitude rf pulses in place of hard rf pulses for 5QC excitation and 5QC to 3QC conversion in a mixed multiple-quantum magic angle spinning (MAS) (MMQMAS) experiment. The anisotropic line shape for the low-amplitude rf pulse version of the MMQMAS experiment was observed to be distorted from the MAS line shape. The cause and implications of the distortion are discussed. (C) 2002 Elsevier Science (USA).

}, keywords = {solid-state}, isbn = {0926-2040}, doi = {Doi 10.1006/Snmr.2002.0084}, url = {://WOS:000179154400003}, author = {Logan, J. W. and Urban, J. T. and Walls, J. D. and Lim, K. H. and Jerschow, A. and Pines, A.} } @conference {355, title = {"Lighting Up" NMR and MRI in Colloidal and Interfacial Systems}, booktitle = {Magnetic Resonance in Colloid and Interface Sciences}, year = {2002}, month = {2002}, pages = {97-106}, publisher = {Kluwer Academic Publishers, Netherlands}, organization = {Kluwer Academic Publishers, Netherlands}, address = {St. Petersburg, Russia}, author = {Pines, A. and Logan, J.W. and Spence, M. M.}, editor = {J. Fraissard and O. Lapina, eds} } @article {347, title = {Rotary resonance recoupling for half-integer quadrupolar nuclei in solid-state nuclear magnetic resonance spectroscopy}, journal = {Journal of Chemical Physics}, volume = {117}, year = {2002}, note = {J Chem Phys599CVTimes Cited:22Cited References Count:53}, month = {Oct 15}, pages = {7024-7033}, abstract = {

Investigations were made of rotary resonance recouplings (R-3) of chemical shift anisotropy (CSA), heteronuclear dipolar (HTD), and homonuclear dipolar (HMD) couplings involving half-integer quadrupolar nuclei under magic-angle sample spinning condition. Under rotary resonance conditions provided by a low amplitude rf field and a high spinning speed, the spectrum of the central transition coherence of half-integer quadrupolar nuclei shows recouplings of CSA, HTD, and HMD interactions that depend on the ratio of the rf field to the spinning speed. These new properties can be used to extract electronic and structural information about the sample that are otherwise difficult to extract in the presence of a dominant quadrupolar interaction. An average Hamiltonian theory is used to explain the recoupling properties of various interactions. Experimental implementations of the R-3 are demonstrated on model compounds with spin-3/2 systems. (C) 2002 American Institute of Physics.

}, keywords = {polarization}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1506907}, url = {://WOS:000178317300016}, author = {Wi, S. and Logan, J. W. and Sakellariou, D. and Walls, J. D. and Pines, A.} } @article {360, title = {Sensitivity enhancement in multiple-quantum NMR experiments with CPMG detection}, journal = {Journal of Magnetic Resonance}, volume = {157}, year = {2002}, note = {J Magn Reson589DHTimes Cited:12Cited References Count:12}, month = {Jul}, pages = {160-162}, abstract = {

We present a modified multiple-quantum (MQ) experiment, which implements the Carr-Purcell-Meiboom-Gill (CPMG) detection scheme in the static MQ NMR experiment proposed by W. S. Warren et al. (1980, J. Chem. Phys. 73, 2084-2099) and exploited further by O. N. Antzutkin and R. Tycko (1999, J. Chem. Phys. 110, 2749-2752). It is demonstrated that a significant enhancement in the sensitivity can be achieved by acquiring echo trains in the MQ experiments for static powder samples. The modified scheme employing the CPMG detection was superior to the original MQ experiment, in particular for the carbonyl carbon with a very large chemical shift anisotropy. (C) 2002 Elsevier Science (USA).

}, keywords = {dynamics}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2002.2578}, url = {://WOS:000177742400019}, author = {Lim, K. H. and Nguyen, T. and Mazur, T. and Wemmer, D. E. and Pines, A.} } @article {351, title = {Theoretical investigations of I=5/2 quadrupolar spin dynamics in the sudden-passage regime}, journal = {Journal of Chemical Physics}, volume = {117}, year = {2002}, note = {J Chem Phys566JRTimes Cited:3Cited References Count:44}, month = {Jul 8}, pages = {518-532}, abstract = {

The theoretical approach utilizing bimodal Floquet theory in the quadrupolar/central-transition interaction frame, presented in an earlier article [J. D. Walls, K. H. Lim, and A. Pines, J. Chem. Phys. 116, 79 (2002)], is extended to describe the more complicated spin dynamics of I=5/2 spin systems. Rotary resonance effects occur when the strength of the radio-frequency irradiation, omega(1), matches the sample spinning speed, omega(r), at the conditions omega(1) = 2/3nomega(r) (n integral). At these conditions, conversions of both triple-quantum and five-quantum coherences to central-quantum coherence are observed. Between rotary resonance conditions [ 2n/3omega(r)\<ω(1)\<[2(n+1)]/3ω(r)], five-quantum as well as triple-quantum coherences can be created from equilibrium z-magnetization via a nutation mechanism. In addition, effective transfer between five-quantum and triple-quantum coherences also is observed in between rotary resonance conditions. These effects have been investigated theoretically and verified by both numerical calculations and experimental results. (C) 2002 American Institute of Physics.

}, keywords = {SPECTROSCOPY}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1483256}, url = {://WOS:000176424800003}, author = {Walls, J. D. and Lim, K. H. and Logan, J. W. and Urban, J. T. and Jerschow, A. and Pines, A.} } @article {350, title = {Theoretical studies of the spin dynamics of quadrupolar nuclei at rotational resonance conditions}, journal = {Journal of Chemical Physics}, volume = {116}, year = {2002}, note = {J Chem Phys503ECTimes Cited:12Cited References Count:20}, month = {Jan 1}, pages = {79-90}, abstract = {

A theory of the spin dynamics of I=3/2 quadrupolar nuclei in the sudden-passage limit is discussed in relation to the recently observed rotational resonance (RR) effects on the excitation and conversion of triple-quantum coherence in the FASTER multiple-quantum magic-angle spinning (MQMAS) experiments [T. Vosegaard, P. Florian, D. Massiot, and P. J. Grandinetti, J. Chem. Phys. 114, 4618 (2001)]. A novel interaction frame, which combines the quadrupolar interaction with the central transition radio frequency irradiation, is shown to be useful in understanding the complex spin dynamics at and away from RR conditions. Analytical expressions for the Hamiltonian obtained from bimodal Floquet theory are included in order to provide insight into the spin dynamics observed in the FASTER MQMAS experiments. Numerical simulations have been performed and were found to support the theoretical formalism. (C) 2002 American Institute of Physics.

}, keywords = {solids}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1421613}, url = {://WOS:000172784700010}, author = {Walls, J. D. and Lim, K. H. and Pines, A.} } @article {371, title = {Dynamic NMR microscopy of gas phase Poiseuille flow}, journal = {Journal of Magnetic Resonance}, volume = {149}, year = {2001}, note = {J Magn Reson421TCTimes Cited:17Cited References Count:16}, month = {Mar}, pages = {144-148}, abstract = {

Dynamic NMR microscopy has been used to study xenon gas undergoing Poiseuille flow in the regime where deterministic and stochastic motions are the same order of magnitude. For short observation time, the flow profile images are largely influenced by the longitudinal diffusion, manifested by large displacements in both positive and negative directions. For longer observation time, the effect of the mixing between the fast and slow flow components due to transverse diffusion becomes apparent. A spin-echo version of the dynamic NMR experiment yields images exhibiting strong distortions for longer observation time due to fast diffusion under the \"natural\" gradient from magnetic field inhomogeneity (compared to results obtained with a stimulated echo version). This effect is used as an edge-enhancement filter by employing a longer time duration of the imaging gradient in a stimulated echo experiment. (C) 2001 Academic Press.

}, keywords = {transport}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2000.2283}, url = {://WOS:000168078800021}, author = {Kaiser, L. G. and Logan, J. W. and Meersmann, T. and Pines, A.} } @article {373, title = {An experimental and theoretical investigation of the chemical shielding tensors of C-13(alpha) of alanine, valine, and leucine residues in solid peptides and in proteins in solution}, journal = {Journal of the American Chemical Society}, volume = {123}, year = {2001}, note = {J Am Chem Soc486FTTimes Cited:47Cited References Count:31}, month = {Oct 24}, pages = {10362-10369}, abstract = {

We have carried out a solid-state magic-angle sample-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic investigation of the C-13(alpha), chemical shielding tensors of alanine, valine, and leucine residues in a series of crystalline peptides of known structure. For alanine and leucine, which are not branched at the beta -carbon, the experimental chemical shift anisotropy (CSA) spans (Omega) are large, about 30 ppm, independent of whether the residues adopt helical or sheet geometries, and are in generally good accord with Omega values calculated by using ab initio Hartree-Fock quantum chemical methods. The experimental Omegas for valine C-alpha in two peptides (in sheet geometries) are also large and in good agreement with theoretical predictions. In contrast, the \"CSAs\" (Delta sigma*) obtained from solution NMR data for alanine, valine, and leucine residues in proteins show major differences, with helical residues having Delta sigma* values of similar to6 ppm while sheet residues have Delta sigma* approximate to 27 ppm. The origins of these differences are shown to be due to the different definitions of the CSA, When defined in terms of the solution NMR CSA, the solid-state results also show small helical but large sheet CSA values. These results are of interest since they lead to the idea that only the beta -branched amino acids threonine, valine, and isoleucine can have small (static) tensor spans, Omega (in helical creometries), and that the small helical \"CSAs\" seen in solution NMR are overwhelmingly dominated by changes in tensor orientation, from sheet to helix. These results have important implications for solid-state NMR structural studies which utilize the CSA span, Omega, to differentiate between helical and sheet residues. Specifically, there will be only a small degree of spectral editing possible in solid proteins since the spans, Omega, for the dominant nonbranched amino acids are quite similar. Editing on the basis of Omega will, however, be very effective for many Thr, Val, and Hen residues, which frequently have small (similar to 15-20 ppm) helical CSA (Omega) spans.

}, keywords = {threonine}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja0115060}, url = {://WOS:000171808300025}, author = {Havlin, R. H. and Laws, D. D. and Bitter, H. M. L. and Sanders, L. K. and Sun, H. H. and Grimley, J. S. and Wemmer, D. E. and Pines, A. and Oldfield, E.} } @article {372, title = {High-resolution NMR of quadrupolar nuclei using mixed multiple-quantum coherences}, journal = {Journal of Magnetic Resonance}, volume = {149}, year = {2001}, note = {J Magn Reson431JNTimes Cited:17Cited References Count:16}, month = {Apr}, pages = {268-270}, abstract = {

A multiple-quantum magic angle spinning (MQMAS) NMR experiment of quadrupolar nuclei is demonstrated, which uses two different multiple quantum coherences in tl to refocus the quadrupolar broadening. This experiment has the potential of achieving improved resolution over current techniques. (C) 2001 Academic Press.

}, keywords = {pulses}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2001.2303}, url = {://WOS:000168628200013}, author = {Jerschow, A. and Logan, J. W. and Pines, A.} } @article {370, title = {Solid-state NMR studies of the secondary structure of a mutant prion protein fragment of 55 residues that induces neurodegeneration}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {98}, year = {2001}, note = {P Natl Acad Sci USA476PCTimes Cited:51Cited References Count:26}, month = {Sep 25}, pages = {11686-11690}, abstract = {

The secondary structure of a 55-residue fragment of the mouse prion protein, MoPrP(89-143), was studied in randomly aggregated (dried from water) and fibrillar (precipitated from water/ acetonitrile) forms by C-13 solid-state NMR. Recent studies have shown that the fibrillar form of the P101L mutant of MoPrP(89-143) is capable of inducing prion disease in transgenic mice, whereas unaggregated or randomly aggregated samples do not provoke disease. Through analysis of C-13 chemical shifts, we have determined that both wild-type and mutant sequence MoPrP(89-143) form a mixture of beta -sheet and alpha -helical conformations in the randomly aggregated state although the beta -sheet content in MoPrP(89-143, P101L) is significantly higher than in the wild-type peptide. In a fibrillar state, MoPrP(89-143, P101L) is completely converted into beta -sheet, suggesting that the formation of a specific beta -sheet structure may be required for the peptide to induce disease. Studies of an analogous peptide from Syrian hamster PrP verify that sequence alterations in residues 101-117 affect the conformation of aggregated forms of the peptides.

}, keywords = {diseases}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.201404298}, url = {://WOS:000171237100125}, author = {Laws, D. D. and Bitter, H. M. L. and Liu, K. and Ball, H. L. and Kaneko, K. and Wille, H. and Cohen, F. E. and Prusiner, S. B. and Pines, A. and Wemmer, D. E.} } @article {377, title = {ChemQuizzes for Introductory Chemistry Instruction}, year = {2000}, publisher = {Norton Publishing}, type = {CD}, address = {New York}, author = {Laws, D. and Pines, A.} } @article {376, title = {Exploring single-file diffusion in one-dimensional nanochannels by laser-polarized Xe-129 NMR spectroscopy (Cover Article)}, journal = {Journal of Physical Chemistry A}, volume = {104}, year = {2000}, note = {J Phys Chem A383EFTimes Cited:75Cited References Count:22}, month = {Dec 21}, pages = {11665-11670}, abstract = {

Single-file diffusion behavior is expected for atoms and molecules in one-dimensional gas phases of nanochannels with transverse dimensions that do not allow for the particles to bypass each other. Although single-file diffusion may play an important role in a wide range of industrial catalytic, geologic, and biological processes, experimental evidence is scarce despite the fact that the dynamics differ substantially from ordinary diffusion. We demonstrate the application of continuous-flow laser-polarized Xe-129 NMR spectroscopy for the study of gas transport into the effectively one-dimensional channels of a microporous material. The novel methodology makes it possible to monitor diffusion over a time scale of tens of seconds, often inaccessible by conventional NMR experiments. The technique can also be applied to systems with very small mobility factors or diffusion constants that are difficult to determine by currently available methods for diffusion measurement. Experiments using xenon in nanochannel systems can distinguish between unidirectional diffusion and single-file diffusion. The experimental observations indicate that single-file behavior for xenon in an organic nanochannel is persistent even at long diffusion times of over tens of seconds. Finally;using continuous flow laser-polarized Xe-129 NMR spectroscopy, we describe an intriguing correlation between the observed NMR line shape of xenon within the nanochannels and the gas transport into these channels.

}, keywords = {model}, isbn = {1089-5639}, doi = {Doi 10.1021/Jp002322v}, url = {://WOS:000165869600001}, author = {Meersmann, T. and Logan, J. W. and Simonutti, R. and Caldarelli, S. and Comotti, A. and Sozzani, P. and Kaiser, L. G. and Pines, A.} } @article {374, title = {A porous crystalline molecular solid explored by hyperpolarized xenon}, journal = {Angewandte Chemie-International Edition}, volume = {39}, year = {2000}, note = {Angew Chem Int Edit343KUTimes Cited:116Cited References Count:38}, pages = {2695-2698}, keywords = {c-13}, isbn = {1433-7851}, doi = {Doi 10.1002/1521-3773(20000804)39:15<2695::Aid-Anie2695>3.0.Co;2-M}, url = {://WOS:000088702200008}, author = {Sozzani, P. and Comotti, A. and Simonutti, R. and Meersmann, T. and Logan, J. W. and Pines, A.} } @article {378, title = {Visualization of gas flow and diffusion in porous media}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {97}, year = {2000}, note = {P Natl Acad Sci USA294ZRTimes Cited:29Cited References Count:18}, month = {Mar 14}, pages = {2414-2418}, abstract = {

The transport of gases in porous materials is a crucial component of many important processes in science and technology. In the present work, we demonstrate how magnetic resonance microscopy with continuous flow laser-polarized noble gases makes it possible to \"light up\" and thereby visualize, with unprecedented sensitivity and resolution, the dynamics of gases in samples of silica aerogels and zeolite molecular sieve particles. The \"polarization-weighted\" images of gas transport in aerogel fragments are correlated to the diffusion coefficient of xenon obtained from NMR pulsed-field gradient experiments. The technique provides a unique means of studying the combined effects of flow and diffusion in systems with macroscopic dimensions and microscopic internal pore structure.

}, keywords = {xenon}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.050012497}, url = {://WOS:000085941400005}, author = {Kaiser, L. G. and Meersmann, T. and Logan, J. W. and Pines, A.} } @article {384, title = {Study of xenon binding in cryptophane-A using laser-induced NMR polarization enhancement}, journal = {Journal of the American Chemical Society}, volume = {121}, year = {1999}, note = {J Am Chem Soc189BTTimes Cited:73Cited References Count:64}, month = {Apr 14}, pages = {3502-3512}, abstract = {

In solution, spin-polarization transfer between laser-polarized xenon and the hydrogen nuclei of nearby molecules leads to signal enhancements in the resolved H-1 NMR spectrum, offering new opportunities for probing the chemical environment of xenon atoms. Following binding of laser-polarized xenon to molecules of cryptophane-A, selective enhancements of the H-1 NMR signals were observed. A theoretical framework for the interpretation of such experimental results is provided, and the spin polarization-induced nuclear Overhauser effects are shown to yield information about the molecular environment of xenon. The observed selective H-1 enhancements allowed xenon-proton internuclear distances to be estimated. These distances reveal structural characteristics of the complex, including the preferred molecular conformations adopted by cryptophane-A upon binding of xenon.

}, keywords = {SPECTROSCOPY}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja9841916}, url = {://WOS:000079884800033}, author = {Luhmer, M. and Goodson, B. M. and Song, Y. Q. and Laws, D. D. and Kaiser, L. and Cyrier, M. C. and Pines, A.} } @article {402, title = {A high-resolution(17)O NMR study of siliceous zeolite faujasite}, journal = {Journal of the American Chemical Society}, volume = {120}, year = {1998}, note = {J Am Chem SocZj097Times Cited:66Cited References Count:19}, month = {Apr 15}, pages = {3510-3511}, keywords = {workstation computers}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja9743001}, url = {://WOS:000073179200032}, author = {Bull, L. M. and Cheetham, A. K. and Anupold, T. and Reinhold, A. and Samoson, A. and Sauer, J. and Bussemer, B. and Lee, Y. and Gann, S. and Shore, J. and Pines, A. and Dupree, R.} } @article {396, title = {NMR of supercritical laser-polarized xenon}, journal = {Chemical Physics Letters}, volume = {292}, year = {1998}, note = {Chem Phys Lett112EZTimes Cited:25Cited References Count:35}, month = {Aug 14}, pages = {686-690}, abstract = {

The feasibility of producing supercritical laser-polarized xenon for nuclear magnetic resonance (NMR) investigations was studied. Using a high-pressure capillary tube, a supercritical xenon sample (52 degrees C, 65 atm) was produced with a Xe-129 polarization approximately 140 times the equilibrium value. The polarization was observed to last for hundreds of seconds, in agreement with previous studies. These preliminary results suggest that supercritical laser-polarized xenon may be used as a polarizing solvent for numerous NMR applications. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

}, keywords = {gas}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(98)00732-5}, url = {://WOS:000075482300049}, author = {Haake, M. and Goodson, B. M. and Laws, D. D. and Brunner, E. and Cyrier, M. C. and Havlin, R. H. and Pines, A.} } @book {386, title = {Proc. of the Int. School of Physics, Enrico Fermi Course CXXXIX - Magnetic Resonance and Brain Funtion: Approaches from Physics}, series = {Lectures on Pulsed NMR}, year = {1998}, pages = {210}, publisher = {IOS Press}, organization = {IOS Press}, edition = {3rd}, chapter = {45-210}, author = {Emsley, L. and Laws, D. and Pines, A.} } @article {418, title = {Determination of dihedral angles in peptides through experimental and theoretical studies of alpha-carbon chemical shielding tensors}, journal = {Journal of the American Chemical Society}, volume = {119}, year = {1997}, note = {J Am Chem SocXt037Times Cited:90Cited References Count:57}, month = {Aug 20}, pages = {7827-7831}, abstract = {

A simple method for the determination of backbone dihedral angles in peptides and proteins is presented. The chemical-shift anisotropies (CSA) of the central alanine alpha-carbon in powdered crystalline tripeptides, whose structures have been determined previously by X-ray crystallography, were measured by cross-polarization magic-angle-spinning nuclear magnetic resonance. The experimental CSA values were correlated with ab initio chemical-shielding calculations over Ramanchandran phi/psi space on an N-formyl-L-alanine amide fragment. Using this correlation, phi/psi probability surfaces for one of the tripeptides were calculated based only on the alpha-carbon CSA, allowing a prediction of backbone angles. Dihedral angles predicted by these calculations fall within +/-12 degrees of the values determined by crystallography. This approach should be useful in the determination of solid-slate protein structure.

}, keywords = {crystal-structure}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja970124k}, url = {://WOS:A1997XT03700025}, author = {Heller, J. and Laws, D. D. and Tomaselli, M. and King, D. S. and Wemmer, D. E. and Pines, A. and Havlin, R. H. and Oldfield, E.} } @article {415, title = {A novel detection-estimation scheme for noisy NMR signals: Applications to delayed acquisition data}, journal = {Journal of Magnetic Resonance}, volume = {128}, year = {1997}, note = {J Magn ResonYc696Times Cited:47Cited References Count:59}, month = {Sep}, pages = {30-41}, abstract = {

Many potentially interesting and useful classes of NMR experiments generate data for which conventional spectral estimation and quantification aa the Fourier transform are unsatisfactory. In particular, recently introduced solid-state NMR experiments which involve long delays before data acquisition fall into this category, as the free induction decays are heavily \&$\#$39;\&$\#$39;truncated\&$\#$39;\&$\#$39; and have low signal-to-noise ratios. A novel detection-estimation scheme is introduced in order to analyze data from such experiments and others where the sensitivity is low and/or the data record is strongly damped or truncated, Based on the assumption of exponential data modeling, the number of signals present is first detected using criteria derived from information theory and the spectral parameters are then estimated using the matrix pencil method, Monte Carlo simulations and experimental. applications are carried out to demonstrate its superior statistical and computational performances and its general applicability to delayed acquisition data. Over the range of note levels investigated, it is found that this approach is essentially near-optimal in the sense that the estimated spectral parameters have biases almost equal to zero and variances very close to their theoretical Cramer-Rao lower bounds. Compared to the popular method of linear prediction with singular value decomposition, this method not only improves the estimation accuracy (by a factor of 2-4) with a lower \&$\#$39;\&$\#$39;break-down\&$\#$39;\&$\#$39; signal-to-noise threshold (approximate to 1.5 dB), but also reduces the computational cost by about an order of magnitude, It also holds great promise in effectively reducing truncation artifacts. It is concluded that this approach not only facilitates the analysis of delayed acquisition data, but can also become a valuable tool in the routine quantification of general NMR spectra, ia listing of programs is also included in the Appendix. (C) 1997 Academic Press.

}, keywords = {resolution}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.1997.1215}, url = {://WOS:A1997YC69600004}, author = {Lin, Y. Y. and Hodgkinson, P. and Ernst, M. and Pines, A.} } @article {409, title = {Selective enhancement of NMR signals for alpha-cyclodextrin with laser-polarized xenon}, journal = {Angewandte Chemie-International Edition in English}, volume = {36}, year = {1997}, note = {Angew Chem Int EditYh944Times Cited:48Cited References Count:29}, month = {Nov 14}, pages = {2368-2370}, keywords = {solids}, isbn = {0570-0833}, doi = {Doi 10.1002/Anie.199723681}, url = {://WOS:A1997YH94400025}, author = {Song, Y. Q. and Goodson, B. M. and Taylor, R. E. and Laws, D. D. and Navon, G. and Pines, A.} } @article {414, title = {Spin dynamics in dipole-coupled molecular systems}, journal = {Abstracts of Papers of the American Chemical Society}, volume = {214}, year = {1997}, note = {Abstr Pap Am Chem SPart 2Xq859Times Cited:0Cited References Count:0}, month = {Sep 7}, pages = {22-PHYS}, isbn = {0065-7727}, url = {://WOS:A1997XQ85900540}, author = {Lin, Y. Y. and Pines, A.} } @article {428, title = {Application of rotational resonance to inhomogeneously broadened systems}, journal = {Chemical Physics Letters}, volume = {251}, year = {1996}, note = {Chem Phys LettUd924Times Cited:17Cited References Count:28}, month = {Mar 22}, pages = {223-229}, abstract = {

A protocol is presented for the determination of internuclear distances using rotational-resonance magnetization-exchange NMR in systems with inhomogeneously broadened lines. Non-linear least-square fitting procedures are used to obtain the distance, the inhomogeneous broadening, the zero-quantum relaxation time, and error estimates for these parameters. We apply this procedure to a biological system of unknown structure.

}, keywords = {nmr}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(96)00098-X}, url = {://WOS:A1996UD92400015}, author = {Heller, J. and Larsen, R. and Ernst, M. and Kolbert, A. C. and Baldwin, M. and Prusiner, S. B. and Wemmer, D. E. and Pines, A.} } @article {434, title = {Rotational diffusion measurements of suspended colloidal particles using two-dimensional exchange nuclear magnetic resonance}, journal = {Journal of Chemical Physics}, volume = {104}, year = {1996}, note = {J Chem PhysTn837Times Cited:13Cited References Count:24}, month = {Jan 8}, pages = {509-520}, abstract = {

We present here an experimental and theoretical study of the application of two-dimensional exchange nuclear magnetic resonance spectroscopy (NMR) to the investigation of the rotational diffusion of colloidal particles. The theoretical discussion includes the nature of the NMR frequency time-correlation function where the NMR interaction is represented by the chemical shift anisotropy (CSA). Time-correlation functions for the isotropic rotational diffusion of a suspension of colloidal particles containing single and multiple sites are derived in addition to time-correlation functions for the rotational diffusion of a suspension of symmetric top particles containing an isotropic distribution of a single CSA interaction. Simulations of two-dimensional exchange spectra for particles undergoing isotropic rotational diffusion are presented. We performed two-dimensional exchange NMR experiments on a colloidal suspension of spherical poly(methyl methacrylate) (PMMA) particles which were synthesized with a 20\% enrichment in C-13 at the carbonyl site. Rotational diffusion time-correlation functions determined from the experimental exchange spectra are consistent with the composition of the colloidal suspension. Detailed explanations of the syntheses of the enriched methyl C-13-(carbonyl)-methacrylate monomer and the small quantities of 20\% enriched C-13-(carbonyl)-poly(methyl methacrylate) microspheres used for this study are presented. (C) 1996 American Institute of Physics.

}, keywords = {scattering}, isbn = {0021-9606}, doi = {Doi 10.1063/1.470847}, url = {://WOS:A1996TN83700009}, author = {Barrall, G. A. and Schmidt-Rohr, K. and Lee, Y. K. and Landfester, K. and Zimmermann, H. and Chingas, G. C. and Pines, A.} } @article {429, title = {Solid-state NMR studies of the prion protein H1 fragment}, journal = {Protein Science}, volume = {5}, year = {1996}, note = {Protein SciVa138Times Cited:74Cited References Count:53}, month = {Aug}, pages = {1655-1661}, abstract = {

Conformational changes in the prion protein (PrP) seem to be responsible for prion diseases. We have used conformation-dependent chemical-shift measurements and rotational-resonance distance measurements to analyze the conformation of solid-state peptides lacking long-range order, corresponding to a region of PrP designated H1. This region is predicted to undergo a transformation of secondary structure in generating the infectious form of the protein. Solid-state NMR spectra of specifically C-13-enrrched samples of H1, residues 109-122 (MKHMAGAAAAGAVV) of Syrian hamster PrP, have been acquired under cross-polarization and magic-angle spinning conditions. Samples lyophilized from 50\% acetonitrile/50\% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117. Complete conversion to the helical conformation was not observed and conversion from alpha-helix back to beta-sheet, as inferred from the solid-state NMR spectra, occurred when samples were exposed to water. Rotational-resonance experiments were performed on seven doubly C-13-labeled H1 samples dried from water. Measured distances suggest that the peptide is in an extended, possibly beta-strand, conformation. These results are consistent with the experimental observation that PrP can exist in different conformational states and with structural predictions based on biological data and theoretical modeling that suggest that H1 may play a key role in the conformational transition involved in the development of prion diseases.

}, keywords = {alpha-helices}, isbn = {0961-8368}, url = {://WOS:A1996VA13800019}, author = {Heller, J. and Kolbert, A. C. and Larsen, R. and Ernst, M. and Bekker, T. and Baldwin, M. and Prusiner, S. B. and Pines, A. and Wemmer, D. E.} } @article {449, title = {C-13 Chemical-Shift Tensor Correlation Via Spin-Diffusion in Solid Tropolone Using Switched-Angle Spinning Spectroscopy}, journal = {Journal of Chemical Physics}, volume = {103}, year = {1995}, note = {J Chem PhysTh657Times Cited:7Cited References Count:42}, month = {Dec 8}, pages = {9844-9854}, abstract = {

In switched-angle spinning spectroscopy (SAS) a sample is spun about different angles, beta, relative to the magnetic field, during various periods of the experiment. In the present work, SAS is combined with two-dimensional exchange spectroscopy in order to correlate carbon-13 chemical shift tensors of the carbonyl (1) and hydroxyl (2) carbons of tropolone. Experiments were performed on a sample enriched to 25 at. \% in each of these sites (at different molecules). At this level of enrichment the dominant exchange mechanism between the two sites involves spin diffusion, The experiment consists of a preparation period during which the sample spins at the magic angle and the magnetization of one of the sites is quenched by means of a selective pulse sequence. During the rest of the experiment the sample spins with its axis away from the magic angle except for a short period just before the detection where the axis is switched to the magic angle in order to select the magnetization to be detected. Experiments were performed for all four possible combinations of the initial and final magnetizations, thus providing chemical shift correlations between carbons 1,1\&$\#$39;,2, and 2\&$\#$39; in the two magnetically inequivalent (but symmetry related) molecules in the unit cell. Combining these results with the known crystal structure of tropolone (neglecting a small tilt between the perpendicular to the molecular plane and the crystallographic c-axis) provides information on the orientation and magnitude of the chemical shift tensors of the two types of carbons, The principal values (in ppm) are sigma(xx)(1)=65, sigma(yy)(1)=33, sigma(zz)(1)=-98, sigma(xx)(2)=77, sigma(yy)(2)=17, and sigma(zz)(2)=-94. Assuming sigma(zz) to be perpendicular to the molecular plane, the orientations of the sigma(yy) s\&$\#$39; are 12 degrees off the C-1=0 bond (toward the hydroxyl carbon) for carbon 1 and 10 degrees off the C-3=C-2 bond (away from the carbonyl carbon) for carbon 2. (C) 1995 American Institute of Physics.

}, keywords = {spectra}, isbn = {0021-9606}, doi = {Doi 10.1063/1.469951}, url = {://WOS:A1995TH65700040}, author = {Larsen, R. G. and Lee, Y. K. and He, B. and Yang, J. O. and Luz, Z. and Zimmermann, H. and Pines, A.} } @article {446, title = {Coherent Isotropic Averaging in Zero-Field Nuclear-Magnetic-Resonance .2. Cubic Sequences and Time-Reversal of Spin Couplings}, journal = {Journal of Chemical Physics}, volume = {103}, year = {1995}, note = {J Chem PhysRu109Times Cited:8Cited References Count:35}, month = {Sep 8}, pages = {3982-3997}, abstract = {

We present a special case of the theory of coherent isotropic averaging in zero-field NMR, given in part I of this work. In a zero external field, combinations of the magnetic-field pulses restricted to pi/2 rotations along the three coordinate axes can selectively average internal spin Hamiltonians while preserving the intrinsic invariance of the spectrum with respect to the sample orientation. Compared with the general case, the limits of the allowed scaling factors of first- and second-rank interactions are slightly reduced. For instance, time reversal is possible for second-rank tensors with a -1/5 scaling factor, instead of -1/4 in general. Finite pulse compensations are analyzed and experimental illustrations are given for two optimum time-reversal sequences. The cubic sequences, though less efficient than the icosahedral sequences, are technically more feasible and may be used in zero-field experiments such as decoupling (by rank or nuclear species), time reversal or multipolar experiments (the zero-field equivalent of multiple-quantum NMR). (C) 1995 American Institute of Physics.

}, keywords = {nqr}, isbn = {0021-9606}, doi = {Doi 10.1063/1.469585}, url = {://WOS:A1995RU10900012}, author = {Llor, A. and Olejniczak, Z. and Pines, A.} } @article {447, title = {Coherent Isotropic Averaging in Zero-Field Nuclear-Magnetic-Resonance .1. General-Theory and Icosahedral Sequences}, journal = {Journal of Chemical Physics}, volume = {103}, year = {1995}, note = {J Chem PhysRu109Times Cited:9Cited References Count:59}, month = {Sep 8}, pages = {3966-3981}, abstract = {

We present a general theory of coherent isotropic averaging in nuclear magnetic resonance (NMR). In a zero external field, magnetic-field pulses can selectively average the internal spin Hamiltonians, while preserving the intrinsic invariance of the spectrum with respect to the sample orientation. The theory predicts the limits of the scaling factors for tenser interactions of different ranks. Time reversal is found to be possible for first- and second-rank tensors with scaling factors of -1/3 and -1/4, respectively. Explicit sequences, based on icosahedral symmetry, are given for a number of optimal scaling factors. To illustrate the theory, an experiment is also presented in the special case of rank-selective decoupling. As in high-field NMR, applications can be expected from the introduction of coherent averaging schemes for zero-held techniques: for example, decouplings (by rank or nuclear species), time reversal, and multipolar experiments (zero-field analog of multiple-quantum NMR). (C) 1995 American Institute of Physics.

}, keywords = {couplings}, isbn = {0021-9606}, doi = {Doi 10.1063/1.469584}, url = {://WOS:A1995RU10900011}, author = {Llor, A. and Olejniczak, Z. and Pines, A.} } @article {448, title = {Linear Prediction with Singular-Value Decomposition for Removing Phase Artifacts in 2d Vacsy Spectra}, journal = {Journal of Magnetic Resonance Series A}, volume = {112}, year = {1995}, note = {J Magn Reson Ser AQd079Times Cited:8Cited References Count:20}, month = {Jan}, pages = {112-117}, keywords = {signals}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1995.1018}, url = {://WOS:A1995QD07900018}, author = {Lee, Y. K. and Vold, R. L. and Hoatson, G. L. and Lin, Y. Y. and Pines, A.} } @article {438, title = {Xe-129 Nmr-Studies of Hyper-Cross-Linked Polyarylcarbinols - Rigid Versus Flexible Structures}, journal = {Chemistry of Materials}, volume = {7}, year = {1995}, note = {Chem MaterRk993Times Cited:27Cited References Count:30}, month = {Jul}, pages = {1325-1332}, abstract = {

Xenon NMR is used with adsorption measurements to infer information about the microstructure of some novel hyper-cross-linked polyarylcarbinols. It is shown that rigidrod connecting units are necessary for microporosity in these systems, as hyper-cross-linked polymers based on flexible structures are found to have conventional surface areas and xenon NMR spectra. A microporous polymer based on rigid triarylcarbinol monomers shows high xenon uptake and a linear chemical shift variation with pressure at room temperature. Spin-lattice relaxation and cross-polarization dynamics are studied at low temperatures. In this regime the xenon has extremely long equilibration times, and the adsorption dynamics are complicated but give important insight into the polymer topology. The data are compared with two possible models of the polymer microstructwre.

}, keywords = {adsorption}, isbn = {0897-4756}, doi = {Doi 10.1021/Cm00055a008}, url = {://WOS:A1995RK99300008}, author = {Urban, C. and Mccord, E. F. and Webster, O. W. and Abrams, L. and Long, H. W. and Gaede, H. and Tang, P. and Pines, A.} } @article {445, title = {Xenon Nmr-Study of a Nematic Liquid-Crystal Confined to Cylindrical Submicron Cavities}, journal = {Journal of Physical Chemistry}, volume = {99}, year = {1995}, note = {J Phys Chem-UsRm901Times Cited:17Cited References Count:37}, month = {Aug 3}, pages = {11989-11993}, abstract = {

NMR studies of xenon gas dissolved in the liquid crystal ZLI 1132 confined to submicron cylindrical cavities are reported. Spectra taken as a function of temperature yield a clear indication of the nematic to isotropic phase transition of the confined liquid crystals. In the nematic phase at 21 degrees C, the resonance line of dissolved Xe-129 exhibits a chemical shift anisotropy of 15 ppm due to a random distribution of director axes in the plane perpendicular to the long axis of the cylinder. The anisotropy and temperature dependence of the confined system are compared to control experiments that use the bulk liquid crystal. The quadrupolar splitting observed in the Xe-131 NMR spectrum of the confined liquid crystalline solution of xenon gas is slightly greater than that found in the bulk. Two-dimensional exchange NMR demonstrates that the xenon atoms probe different average liquid crystal directors within a single cavity on a 20 ms time scale and that interpore exchange occurs on a time scale of 400 ms. The exchange data indicate that changes in the orientation of the director within individual cavities occur on a length scale of about 2 mu m.

}, keywords = {mixtures}, isbn = {0022-3654}, doi = {Doi 10.1021/J100031a029}, url = {://WOS:A1995RM90100029}, author = {Long, H. W. and Luzar, M. and Gaede, H. C. and Larsen, R. G. and Kritzenberger, J. and Pines, A. and Crawford, G. P.} } @article {464, title = {2-Dimensional Xe-129 Exchange Nmr Measurements of Xenon Dynamics in Na-a Zeolite}, journal = {Zeolites and Related Microporous Materials: State of the Art 1994}, volume = {84}, year = {1994}, note = {Stud Surf Sci CatalPart a-CBd02eTimes Cited:3Cited References Count:21Studies in Surface Science and Catalysis}, pages = {519-526}, abstract = {Two-dimensional (2D) exchange NMR is a powerful tool for measuring the dynamics and energetics of adsorbed xenon atoms undergoing slow exchange between the alpha-cages of Na-A zeolite. In this proceedings, we present recently published results, as well as additional discussion and data obtained, using 2D Xe-129 NMR to determine rate coefficients for intercage xenon hopping and to correlate them with adsorption and activation energies. Variable-temperature experiments establish the activation energy for hopping between alpha-cages to be 60+/-10 kJ/mol. The dependence of these kinetic and thermodynamic quantities on xenon occupancy of the alpha-cages reflects the importance of intracage interactions on the behavior of the adsorbed guest molecules.}, keywords = {cavities}, isbn = {0167-2991}, url = {://WOS:A1994BD02E00063}, author = {Janicke, M. and Chmelka, B. F. and Larsen, R. G. and Shore, J. and Schmidt-Rohr, K. and Emsley, L. and Long, H. and Pines, A.} } @article {461, title = {3-Dimensional Variable-Angle Nuclear-Magnetic-Resonance Exchange Spectroscopy without Rotor Axis Hopping}, journal = {Journal of Chemical Physics}, volume = {101}, year = {1994}, note = {J Chem PhysNy002Times Cited:12Cited References Count:48}, month = {Aug 1}, pages = {1852-1864}, abstract = {

Slow, large-amplitude chain motions play an important role in determining the macroscopic mechanical properties of polymers. Although such motions have been studied quantitatively by two-dimensional (2D) nuclear: magnetic resonance (NMR) exchange experiments, overlapping anisotropic patterns hamper spectral analysis, and limit applications. Variable angle correlation spectroscopy (VACSY) has proven useful in resolving such problems for rapidly spinning samples by separating anisotropic spectral patterns according to isotropic chemical shifts. In a previous study [J. Am. Chem. Sec. 115, 4825 (1993)], we described a three-dimensional (3D) NMR experiment that incorporates; the VACSY method and a hop of the rotor axis to correlate the isotropic chemical shifts to 2D anisotropic exchange patterns. The hop of the rotor axis, however, presents experimental difficulties and limits the range of motional rates that may be studied. We present in this paper a new 3D VACSY exchange experiment that obtains the same correlations without the need for the rotor axis hop. A series of 2D exchange spectra are recorded with the sample spinning at different rotation axis angles.\&$\#$39; Then using the scaling of the anisotropic frequency at the different angles, we construct the data onto a 3D matrix so that a Fourier transformation directly yields the desired correlations. The technique is applied to C-13 exchange NMR to study the slow molecular motion of ordered isotactic polypropylene.

}, keywords = {distributions}, isbn = {0021-9606}, doi = {Doi 10.1063/1.467696}, url = {://WOS:A1994NY00200011}, author = {Lee, Y. K. and Emsley, L. and Larsen, R. G. and Schmidt-Rohr, K. and Hong, M. and Frydman, L. and Chingas, G. C. and Pines, A.} } @article {459, title = {Multiple-Pulse Nuclear-Magnetic-Resonance of Optically Pumped Xenon in a Low Magnetic-Field}, journal = {Physical Review A}, volume = {50}, year = {1994}, note = {Phys Rev ANx001Times Cited:23Cited References Count:38}, month = {Jul}, pages = {567-574}, abstract = {

Multiple-pulse coherent averaging methods are used to increase the resolution and frequency range of optically pumped xenon NMR in nutation and point-by-point precession experiments. We observe quadrupolar splittings in Xe-131 spectra due to the macroscopic asymmetry of pumping cells similar to those reported previously, but with reduced demands on magnetic-field homogeneity. Cell treatment with hydrogen gas increases the quadrupolar splittings by a factor of 3 over bare Pyrex cells.

}, keywords = {ne-21}, isbn = {1050-2947}, doi = {Doi 10.1103/Physreva.50.567}, url = {://WOS:A1994NX00100070}, author = {Raftery, D. and Long, H. W. and Shykind, D. and Grandinetti, P. J. and Pines, A.} } @article {482, title = {Cross Polarization from Laser-Polarized Solid Xenon to (Co2)-C-13 by Low-Field Thermal Mixing}, journal = {Chemical Physics Letters}, volume = {205}, year = {1993}, note = {Chem Phys LettKv519Times Cited:61Cited References Count:11}, month = {Apr 9}, pages = {168-170}, abstract = {

The first observation of nuclear spin polarization enhancement in a molecular species by coupling to laser-polarized xenon is reported. The spins of (CO2)-C-13 were cooled by inclusion into the xenon solid followed by thermal mixing in magnetic fields comparable to the heteronuclear dipolar interactions. High-field NMR detection yielded enhancement factors of up to 200. Moreover, a change in the sense of the helicity of the optical pumping light results in a sign reversal of the spin temperature and hence an inversion of the C-13 NMR signal.

}, keywords = {nmr}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(93)89223-5}, url = {://WOS:A1993KV51900008}, author = {Bowers, C. R. and Long, H. W. and Pietrass, T. and Gaede, H. C. and Pines, A.} } @article {475, title = {High-Field Cross-Polarization Nmr from Laser-Polarized Xenon to a Polymer Surface}, journal = {Journal of the American Chemical Society}, volume = {115}, year = {1993}, note = {J Am Chem SocLx752Times Cited:77Cited References Count:16}, month = {Sep 8}, pages = {8491-8492}, keywords = {gas}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00071a086}, url = {://WOS:A1993LX75200086}, author = {Long, H. W. and Gaede, H. C. and Shore, J. and Reven, L. and Bowers, C. R. and Kritzenberger, J. and Pietrass, T. and Pines, A. and Tang, P. and Reimer, J. A.} } @article {476, title = {Nmr-Study of Xenon Dynamics and Energetics in Na-a Zeolite}, journal = {Chemical Physics Letters}, volume = {214}, year = {1993}, note = {Chem Phys LettMd614Times Cited:56Cited References Count:22}, month = {Oct 29}, pages = {220-226}, abstract = {

For xenon atoms adsorbed in Na-A zeolite, electronic interactions cause shifts in NMR frequencies, resulting in a spectrum with discrete peaks from xenon atoms in cages with different xenon occupancies. Using two-dimensional exchange NMR, it is possible to determine the microscopic rates of intercage motion and to relate them to the adsorption and activation energies of the xenon atoms. The dependence of the adsorption energies on xenon cage occupancy reflects the importance of the intercage interactions and is directly related to the cage occupancy distribution. Variable temperature measurements yield an activation energy of about 60 kJ/mol for the transfer of a xenon from one cage to another.

}, keywords = {xe}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(93)90085-F}, url = {://WOS:A1993MD61400015}, author = {Larsen, R. G. and Shore, J. and Schmidt-Rohr, K. and Emsley, L. and Long, H. and Pines, A. and Janicke, M. and Chmelka, B. F.} } @article {478, title = {Pure-Absorption-Mode Lineshapes and Sensitivity in 2-Dimensional Dynamic-Angle Spinning Nmr}, journal = {Journal of Magnetic Resonance Series A}, volume = {103}, year = {1993}, note = {J Magn Reson Ser ALj625Times Cited:98Cited References Count:20}, month = {Jun 1}, pages = {72-81}, keywords = {nuclei}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1993.1132}, url = {://WOS:A1993LJ62500010}, author = {Grandinetti, P. J. and Baltisberger, J. H. and Llor, A. and Lee, Y. K. and Werner, U. and Eastman, M. A. and Pines, A.} } @article {477, title = {Side-Band Patterns in Dynamic-Angle-Spinning Nmr}, journal = {Journal of Magnetic Resonance Series A}, volume = {102}, year = {1993}, note = {J Magn Reson Ser AKz480Times Cited:19Cited References Count:26}, month = {Apr}, pages = {195-204}, keywords = {samples}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1993.1091}, url = {://WOS:A1993KZ48000011}, author = {Grandinetti, P. J. and Lee, Y. K. and Baltisberger, J. H. and Sun, B. Q. and Pines, A.} } @article {474, title = {Spin-Polarized Xe-129 Nmr-Study of a Polymer Surface}, journal = {Journal of Physical Chemistry}, volume = {97}, year = {1993}, note = {J Phys Chem-UsKp603Times Cited:51Cited References Count:48}, month = {Feb 25}, pages = {1649-1655}, abstract = {

A method for NMR studies of low surface area materials using optically pumped xenon gas is described. The method has been used to investigate spin-polarized xenon adsorbed onto poly(acrylic acid). The temperature dependence of the xenon-surface interaction, as measured by the xenon chemical shifts extrapolated to zero pressure, is shown to be consistent with a simple model of chemical exchange between the gas and adsorbed phases. The magnitude of the surface contribution to the Xe-129 chemical shift indicates a relatively strong interaction between xenon and poly(acrylic acid), possibly due to the polar carboxylic acid functional groups at the polymer surface. From the pressure dependence of the Xe-129 shift, the diffusion coefficient of xenon on poly(acrylic acid) is estimated to be 3.3 x 10(-5) cm2/s.

}, keywords = {temperature}, isbn = {0022-3654}, doi = {Doi 10.1021/J100110a029}, url = {://WOS:A1993KP60300029}, author = {Raftery, D. and Reven, L. and Long, H. and Pines, A. and Tang, P. and Reimer, J. A.} } @article {480, title = {Variable-Angle 3-Dimensional Exchange Nuclear-Magnetic-Resonance Spectroscopy for the Study of Molecular-Motion in Complex Solids}, journal = {Journal of the American Chemical Society}, volume = {115}, year = {1993}, note = {J Am Chem SocLf062Times Cited:14Cited References Count:23}, month = {Jun 2}, pages = {4825-4829}, abstract = {

Although molecular motions are responsible for many of the macroscopic properties observed in solids, especially in polymers, methods for studying these processes in all but the simplest systems are scarce. In the present study we introduce a three-dimensional nuclear magnetic resonance experiment for characterizing ultraslow molecular motions in complex solid systems. The technique extracts dynamic information by resolving the two-dimensional exchange distributions that can be observed in spectra of static samples, according to the isotropic chemical shifts of individual molecular sites. These three-dimensional correlations are achieved by processing signals arising from a fast-spinning solid sample using two independent macroscopic axes of rotation as extraction parameters, an approach which becomes practical due to the simple scaling behavior of anisotropic chemical shifts with respect to the axis of sample rotation. The principles involved in this new spectroscopic technique are discussed, and the method is illustrated with an application to the analysis of motions in isotactic polypropylene.

}, keywords = {jumps}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00064a050}, url = {://WOS:A1993LF06200050}, author = {Frydman, L. and Lee, Y. K. and Emsley, L. and Chingas, G. C. and Pines, A.} } @article {496, title = {Correlation of Isotropic and Anisotropic Chemical-Shifts in Solids by 2-Dimensional Variable-Angle-Spinning Nmr}, journal = {Israel Journal of Chemistry}, volume = {32}, year = {1992}, note = {Israel J ChemKt517Times Cited:29Cited References Count:19}, pages = {161-164}, abstract = {

We describe a new solid-state nuclear magnetic resonance (NMR) technique for correlating anisotropic and isotropic chemical shifts in powdered samples. Two-dimensional (2D) NMR spectra are obtained by processing signals acquired in independent experiments for different angles between the sample spinning axis and the Zeeman magnetic field. This 2D NMR approach can therefore resolve individual static anisotropic lineshapes according to their isotropic chemical shift frequencies, without use of sudden mechanical motions or multiple-pulse irradiation schemes. Applications of the technique are illustrated with an analysis of the chemical shift anisotropy for the eight distinct C-13 sites in tyrosine.

}, keywords = {magic-angle}, isbn = {0021-2148}, url = {://WOS:A1992KT51700005}, author = {Frydman, L. and Chingas, G. C. and Lee, Y. K. and Grandinetti, P. J. and Eastman, M. A. and Barrall, G. A. and Pines, A.} } @article {499, title = {Double-Tuned Hopping-Coil Probe for Dynamic-Angle-Spinning Nmr}, journal = {Journal of Magnetic Resonance}, volume = {98}, year = {1992}, note = {J Magn ResonHz623Times Cited:29Cited References Count:13}, month = {Jun 15}, pages = {333-341}, keywords = {axis}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(92)90136-U}, url = {://WOS:A1992HZ62300008}, author = {Eastman, M. A. and Grandinetti, P. J. and Lee, Y. K. and Pines, A.} } @article {489, title = {Nmr of Optically Pumped Xenon Thin-Films}, journal = {Chemical Physics Letters}, volume = {191}, year = {1992}, note = {Chem Phys LettHp501Times Cited:25Cited References Count:25}, month = {Apr 10}, pages = {385-390}, abstract = {

NMR of Xe-129 has been observed in thin films of xenon frozen onto the surfaces of glass sample cells with various geometries. The Xe-129 polarization was enhanced by optical pumping, and the xenon was then transferred to a high-field pulsed NMR spectrometer allowing the observation of strong signals from xenon films of approximately 1-mu-m thickness. The line shape depends on the film geometry because of the bulk diamagnetic susceptibility chi(D) of solid xenon. The spectral line shape and resonance frequency also depend on temperature.

}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(92)85396-R}, url = {://WOS:A1992HP50100002}, author = {Raftery, D. and Long, H. and Reven, L. and Tang, P. and Pines, A.} } @article {497, title = {Variable-Angle Correlation Spectroscopy in Solid-State Nuclear-Magnetic-Resonance}, journal = {Journal of Chemical Physics}, volume = {97}, year = {1992}, note = {J Chem PhysJr338Times Cited:90Cited References Count:28}, month = {Oct 1}, pages = {4800-4808}, abstract = {

We describe here a new solid-state nuclear-magnetic-resonance (NMR) experiment for correlating anisotropic and isotropic chemical shifts of inequivalent nuclei in powdered samples. Spectra are obtained by processing signals arising from a spinning sample, acquired in independent experiments as a function of the angle between the axis of macroscopic rotation and the external magnetic field. This is in contrast to previously proposed techniques, which were based on sudden mechanical flippings or multiple-pulse sequences. We show that the time evolution of variable-angle-spinning signals is determined by a distribution relating the isotropic frequencies of the spins with their corresponding chemical shift anisotropies. Fourier transformation of these data therefore affords a two-dimensional NMR spectrum, in which line shapes of isotropic and anisotropic interactions are correlated. Theoretical and experimental considerations involved in the extraction of this spectral information are discussed, and the technique is illustrated by an analysis of C-13 NMR anisotropy in glycine, cysteine, and p-anisic acid.

}, keywords = {axis}, isbn = {0021-9606}, doi = {Doi 10.1063/1.463860}, url = {://WOS:A1992JR33800022}, author = {Frydman, L. and Chingas, G. C. and Lee, Y. K. and Grandinetti, P. J. and Eastman, M. A. and Barrall, G. A. and Pines, A.} } @article {501, title = {High-Field Nmr of Adsorbed Xenon Polarized by Laser Pumping}, journal = {Physical Review Letters}, volume = {66}, year = {1991}, note = {Phys Rev LettEv897Times Cited:202Cited References Count:35}, month = {Feb 4}, pages = {584-587}, abstract = {

Optical pumping has been used to enhance the pulsed NMR signal of Xe-129, allowing the detection of low-pressure xenon gas and of xenon adsorbed on powdered solids. We observe an increase in sensitivity of more than 2 orders of magnitude over conventional NMR, the current limitation being the laser power. Adsorbed xenon is observed at 298 K on graphitized carbon (10 m2/g) and on powdered benzanthracene (approximately 0.5 m2/g) below 170 K. The increased sensitivity of this technique allows the study of a large class of amorphous materials with surface areas below 10 m2/g including semiconductors, polymers, metal oxides, and catalysts.

}, keywords = {solids}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.66.584}, url = {://WOS:A1991EV89700017}, author = {Raftery, D. and Long, H. and Meersmann, T. and Grandinetti, P. J. and Reven, L. and Pines, A.} } @article {510, title = {Measurement of Xenon Distribution Statistics in Na-a Zeolite Cavities}, journal = {Physical Review Letters}, volume = {66}, year = {1991}, note = {Phys Rev LettEv897Times Cited:78Cited References Count:21}, month = {Feb 4}, pages = {580-583}, abstract = {

Xe-129 NMR spectroscopy has been used to probe directly the distribution of xenon atoms confined in atomic-size Na-A zeolite cavities. For mean xenon occupancies less than about three Xe atoms per a-cage, the guest populations are well described by binomial statistics. At higher guest loadings the finite volumes of the xenon atoms become significant, as reflected by a fit of the experimental populations with a hypergeometric distribution, with a maximum of seven Xe atoms per cage. At the highest xenon loadings the experimental distribution is narrower than hypergeometric, as predicted by Monte Carlo simulations.

}, keywords = {fluids}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.66.580}, url = {://WOS:A1991EV89700016}, author = {Chmelka, B. F. and Raftery, D. and Mccormick, A. V. and Demenorval, L. C. and Levine, R. D. and Pines, A.} } @article {511, title = {Nmr-Study of the Distribution of Aromatic-Molecules in Nay Zeolite}, journal = {Journal of Physical Chemistry}, volume = {95}, year = {1991}, note = {J Phys Chem-UsEr473Times Cited:70Cited References Count:64}, month = {Jan 10}, pages = {303-310}, abstract = {

Local and macroscopic distributions of adsorbed benzene, 1,3,5-trimethylbenzene, and hexamethylbenzene (HMB) molecules among the intracrystalline of NaY zeolite samples have been investigated by Xe-129 and multiple-quantum NMR. Xenon-129 NMR, a sensitive probe of macroscopic distributions of molecules in zeolites at room temperature, demonstrates the importance of sample heat treatment in distributing an adsorbate homogeneously throughout a collection of zeolite particles. NaY samples containing organic guests adsorbed a temperatures near the bulk species\&$\#$39; melting point produce multiple or broad xenon lines characteristic of macroscopic (i.e., interparticle) adsorbate concentration gradients. After thorough heat treatment of the samples at elevated temperatures, the xenon spectrum collapses to a single sharp line, consistent with a macroscopically uniform distribution. For HMB adsorbed in NaY, \"counting\" hydrogen clusters by multiple-quantum NMR reveals intraparticle HMB distributions consistent with one molecular per cavity at low loadings (average bulk loading less-than-or-equal-to 1 molecule per cavity) and two molecules per cavity at higher loadings.

}, keywords = {catalysts}, isbn = {0022-3654}, doi = {Doi 10.1021/J100154a056}, url = {://WOS:A1991ER47300056}, author = {Chmelka, B. F. and Pearson, J. G. and Liu, S. B. and Ryoo, R. and Demenorval, L. C. and Pines, A.} } @article {507, title = {Scaling and Time-Reversal of Spin Couplings in Zero-Field Nmr}, journal = {Physical Review Letters}, volume = {67}, year = {1991}, note = {Phys Rev LettGj319Times Cited:13Cited References Count:25}, month = {Oct 7}, pages = {1989-1992}, abstract = {

We report the observation of spin echoes resulting from the time reversal of isotropic many-body spin couplings in zero-field NMR. The coherent-averaging pulse sequences responsible for the scaling and the time reversal of isotropic interactions of first and second rank are based on cubic and icosahedral symmetry.

}, keywords = {nqr}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.67.1989}, url = {://WOS:A1991GJ31900014}, author = {Llor, A. and Olejniczak, Z. and Sachleben, J. and Pines, A.} } @article {523, title = {Investigations of Adsorbed Organic-Molecules in Na-Y Zeolite by Xe-129 Nmr}, journal = {Journal of Physical Chemistry}, volume = {94}, year = {1990}, note = {J Phys Chem-UsCh532Times Cited:61Cited References Count:26}, month = {Jan 11}, pages = {27-31}, isbn = {0022-3654}, doi = {Doi 10.1021/J100364a006}, url = {://WOS:A1990CH53200006}, author = {Demenorval, L. C. and Raftery, D. and Liu, S. B. and Takegoshi, K. and Ryoo, R. and Pines, A.} } @article {514, title = {Nmr Experiments with a New Double Rotor}, journal = {Journal of Magnetic Resonance}, volume = {89}, year = {1990}, note = {J Magn ResonDu813Times Cited:113Cited References Count:13}, month = {Sep}, pages = {297-309}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(90)90236-3}, url = {://WOS:A1990DU81300008}, author = {Wu, Y. and Sun, B. Q. and Pines, A. and Samoson, A. and Lippmaa, E.} } @inbook {555, title = {Calcination-dependence ofplatinum cluster formation in NaY zeolite: A xenon-129 NMR study}, booktitle = {Structure and Reactivity of Surfaces}, year = {1989}, pages = {269-278}, publisher = {Elsevier Science Publishers}, organization = {Elsevier Science Publishers}, address = {Amsterdam}, author = {Chmelka, B.F. and de Menorval, L.C. and Csencsits, R. and Ryoo, R. and Liu, S.B. and Radke, C.J. and Petersen, E.E. and Pines, A.}, editor = {C. Morterra, A. Zecchina, and G. Costa} } @article {559, title = {Broad-Band Heteronuclear Spin Decoupling in Solids}, journal = {Chemical Physics Letters}, volume = {144}, year = {1988}, note = {Chem Phys LettM4326Times Cited:19Cited References Count:11}, month = {Mar 4}, pages = {324-327}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(88)87122-7}, url = {://WOS:A1988M432600002}, author = {Suter, D. and Pines, A. and Lee, J. H. and Drobny, G.} } @article {568, title = {Diffusive Motion in Alkali Silicate Melts - an Nmr-Study at High-Temperature}, journal = {Geochimica Et Cosmochimica Acta}, volume = {52}, year = {1988}, note = {Geochim Cosmochim AcM3100Times Cited:79Cited References Count:67}, month = {Feb}, pages = {527-538}, isbn = {0016-7037}, doi = {Doi 10.1016/0016-7037(88)90108-1}, url = {://WOS:A1988M310000028}, author = {Liu, S. B. and Stebbins, J. F. and Schneider, E. and Pines, A.} } @article {565, title = {High-Resolution Solid-State Nmr Averaging of 2nd-Order Effects by Means of a Double-Rotor}, journal = {Molecular Physics}, volume = {65}, year = {1988}, note = {Mol PhysR5253Times Cited:405Cited References Count:34}, month = {Nov}, pages = {1013-1018}, isbn = {0026-8976}, doi = {Doi 10.1080/00268978800101571}, url = {://WOS:A1988R525300018}, author = {Samoson, A. and Lippmaa, E. and Pines, A.} } @article {564, title = {Iterative Schemes for Bilinear Operators - Application to Spin Decoupling}, journal = {Journal of Magnetic Resonance}, volume = {77}, year = {1988}, note = {J Magn ResonN1647Times Cited:752Cited References Count:31}, month = {Apr}, pages = {274-293}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(88)90178-3}, url = {://WOS:A1988N164700006}, author = {Shaka, A. J. and Lee, C. J. and Pines, A.} } @article {561, title = {Phase-Incremented Multiple-Quantum Nmr Experiments}, journal = {Journal of Magnetic Resonance}, volume = {76}, year = {1988}, note = {J Magn ResonL9552Times Cited:49Cited References Count:17}, month = {Jan}, pages = {149-154}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(88)90209-0}, url = {://WOS:A1988L955200015}, author = {Shykind, D. N. and Baum, J. and Liu, S. B. and Pines, A.} } @article {569, title = {Probing Metal Cluster Formation in Nay Zeolite by Xe-129 Nmr}, journal = {Journal of the American Chemical Society}, volume = {110}, year = {1988}, note = {J Am Chem SocP0739Times Cited:33Cited References Count:18}, month = {Jun 22}, pages = {4465-4467}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00221a086}, url = {://WOS:A1988P073900086}, author = {Chmelka, B. F. and Ryoo, R. and Liu, S. B. and Demenorval, L. C. and Radke, C. J. and Petersen, E. E. and Pines, A.} } @article {583, title = {Distribution of Hexamethylbenzene in a Zeolite Studied by Xe-129 and Multiple-Quantum Nmr}, journal = {Journal of Physical Chemistry}, volume = {91}, year = {1987}, note = {J Phys Chem-UsL6632Times Cited:63Cited References Count:16}, month = {Dec 31}, pages = {6575-6577}, isbn = {0022-3654}, doi = {Doi 10.1021/J100311a003}, url = {://WOS:A1987L663200003}, author = {Ryoo, R. and Liu, S. B. and Demenorval, L. C. and Takegoshi, K. and Chmelka, B. and Trecoske, M. and Pines, A.} } @article {573, title = {Heteronuclear Zero-Field Nmr of Liquid-Crystals}, journal = {Journal of Magnetic Resonance}, volume = {72}, year = {1987}, note = {J Magn ResonH2852Times Cited:1Cited References Count:13}, month = {May}, pages = {567-573}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(87)90164-8}, url = {://WOS:A1987H285200020}, author = {Thayer, A. M. and Luzar, M. and Pines, A.} } @article {577, title = {Multiple Quantum Nmr Excitation with a One-Quantum Hamiltonian}, journal = {Chemical Physics}, volume = {114}, year = {1987}, note = {Chem PhysH4338Times Cited:45Cited References Count:16}, month = {May 15}, pages = {103-109}, isbn = {0301-0104}, doi = {Doi 10.1016/0301-0104(87)80023-X}, url = {://WOS:A1987H433800010}, author = {Suter, D. and Liu, S. B. and Baum, J. and Pines, A.} } @article {587, title = {Quenching of Residual Fields by Nonaxially Symmetrical Dipolar Coupling in Zero-Field Nmr}, journal = {Journal of Magnetic Resonance}, volume = {73}, year = {1987}, note = {J Magn ResonJ1554Times Cited:1Cited References Count:22}, month = {Jul}, pages = {459-466}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(87)90008-4}, url = {://WOS:A1987J155400008}, author = {Luzar, M. and Thayer, A. M. and Pines, A.} } @article {589, title = {Relaxation Mechanisms and Effects of Motion in Albite (Naalsi3o8) Liquid and Glass - a High-Temperature Nmr-Study}, journal = {Physics and Chemistry of Minerals}, volume = {15}, year = {1987}, note = {Phys Chem MinerL0167Times Cited:40Cited References Count:57}, pages = {155-162}, isbn = {0342-1791}, doi = {Doi 10.1007/Bf00308778}, url = {://WOS:A1987L016700007}, author = {Liu, S. B. and Pines, A. and Brandriss, M. and Stebbins, J. F.} } @article {590, title = {Theory of Multiple-Pulse Nmr at Low and Zero Fields}, journal = {Journal of Magnetic Resonance}, volume = {75}, year = {1987}, note = {J Magn ResonK7509Times Cited:14Cited References Count:18}, month = {Oct 15}, pages = {110-124}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(87)90318-0}, url = {://WOS:A1987K750900010}, author = {Lee, C. J. and Suter, D. and Pines, A.} } @article {572, title = {Zero-Field Nmr of Nematic Liquid-Crystals with Positive and Negative Magnetic-Susceptibility Anisotropies}, journal = {Journal of Physical Chemistry}, volume = {91}, year = {1987}, note = {J Phys Chem-UsG8355Times Cited:4Cited References Count:22}, month = {Apr 9}, pages = {2194-2197}, isbn = {0022-3654}, doi = {Doi 10.1021/J100292a043}, url = {://WOS:A1987G835500043}, author = {Thayer, A. M. and Luzar, M. and Pines, A.} } @article {588, title = {Zero-Field Nmr of Uniaxial and Biaxial Smectic Liquid-Crystals}, journal = {Molecular Physics}, volume = {62}, year = {1987}, note = {Mol PhysL0770Times Cited:2Cited References Count:30}, month = {Oct 20}, pages = {573-583}, isbn = {0026-8976}, doi = {Doi 10.1080/00268978700102411}, url = {://WOS:A1987L077000003}, author = {Luzar, M. and Thayer, A. M. and Pines, A.} } @article {571, title = {Zero-Field Nmr-Study of the Biaxial Smectic-E Phase}, journal = {Liquid Crystals}, volume = {2}, year = {1987}, note = {Liq CrystH5818Times Cited:3Cited References Count:12}, month = {Mar-Apr}, pages = {241-244}, isbn = {0267-8292}, doi = {Doi 10.1080/02678298708086296}, url = {://WOS:A1987H581800012}, author = {Thayer, A. M. and Luzar, M. and Pines, A.} } @article {608, title = {Theory of Chemical-Exchange in Zero-Field Nmr - 2-Site Flips}, journal = {Journal of Chemical Physics}, volume = {85}, year = {1986}, note = {J Chem PhysE5176Times Cited:9Cited References Count:13}, month = {Nov 1}, pages = {4873-4880}, isbn = {0021-9606}, doi = {Doi 10.1063/1.451722}, url = {://WOS:A1986E517600014}, author = {Jonsen, P. and Luzar, M. and Pines, A. and Mehring, M.} } @article {600, title = {Zero-Field Nuclear-Magnetic-Resonance of a Nematic Liquid-Crystal}, journal = {Journal of Physical Chemistry}, volume = {90}, year = {1986}, note = {J Phys Chem-UsA8609Times Cited:10Cited References Count:32}, month = {Apr 10}, pages = {1577-1581}, isbn = {0022-3654}, doi = {Doi 10.1021/J100399a024}, url = {://WOS:A1986A860900024}, author = {Thayer, A. M. and Millar, J. M. and Luzar, M. and Jarvie, T. P. and Pines, A.} } @inbook {682, title = {Double quantum NMR in solids}, booktitle = {Magnetic Resonance in Condensed Matter: Recent developments}, year = {1977}, pages = {127-129}, publisher = {University of Ljubljana Press}, organization = {University of Ljubljana Press}, author = {Pines, A. and Vega, S. and Ruben, D.J. and Shattuck, T.W. and Wemmer, D.}, editor = {Lahajanr, R. Blinc and G.} } @article {711, title = {Electrochemical Synthesis of Cis-3,4-Dicarbomethoxycyclobutene}, journal = {Israel Journal of Chemistry}, volume = {11}, year = {1973}, note = {Israel J ChemP7708Times Cited:5Cited References Count:13}, pages = {75-77}, isbn = {0021-2148}, url = {://WOS:A1973P770800010}, author = {Leftin, J. H. and Redpath, D. and Pines, A. and Gilav, E.} } @article {733, title = {3 Geometrical Isomers of a 2,4-Disubstituted Bicyclobutane}, journal = {Chemical Communications}, year = {1968}, note = {Chem CommunA9390Times Cited:4Cited References Count:5}, pages = {396-\&}, isbn = {1359-7345}, doi = {Doi 10.1039/C19680000396}, url = {://WOS:A1968A939000036}, author = {Leftin, J. H. and Gilav, E. and Pines, A.} }