@article {3228, title = {Indirect Detection of Short-lived Hydride Intermediates of Iridium N-Heterocyclic Carbene Complexes via Chemical Exchange Saturation Transfer (CEST) Spectroscopy}, journal = {The Journal of Physical Chemistry C}, year = {2019}, month = {06/2019}, abstract = {

For the first time, chemical exchange saturation transfer (CEST) nuclear magnetic resonance (NMR) is utilized to study short-lived hydride intermediates in the catalytic cycle of an organometallic complex [Ir(IMes)(Py)3(H)2]Cl. These complexes are typically not observable by other NMR techniques because they are low concentrated and undergo reversible ligand exchange with the main complex. The intermediatecomplexes [Ir(Cl)(IMes)(Py)2(H)2] and [Ir(CD3OD)(IMes)(Py)2(H)2]are detected, assigned, and characterized in solution, in situ and at room temperature. Understanding the spin dynamics in these complexes is necessary for enhancing the performance of the nuclear spin hyperpolarization technique signal amplification by reversible exchange. By eliminating [Ir(Cl (IMes)(Py)2(H)2] and manipulating the spin system by radiofrequency irradiation, the nuclear spin singlet lifetime of the hydride protons was increased by more than an order of magnitude, from 2.2 \± 0.1 to 27.2 \± 1.2 s. Because of its simplicity and ability to unravel unobservable chemical species, the utilized CEST NMR approach has a large application potential for studying short-lived hydride intermediates incatalytic reactions.

}, doi = {https://doi.org/10.1021/acs.jpcc.9b04179}, url = {https://pubs.acs.org/doi/10.1021/acs.jpcc.9b04179$\#$}, author = {Stephan Knecht and Sara Hadjiali and Danila A Barskiy and Alexander Pines and Grit Sauer and Alexey Kiryutin and Konstantin Ivanov and Alexandra Yurkovskaya and Gerd Buntkowsky} } @article {3531, title = {Rotaxane probes for the detection of hydrogen peroxide by 129Xe hyperCEST NMR}, journal = {Angewandte Chemie International Edition}, year = {2019}, doi = {10.1002/anie.201903045}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201903045}, author = {Klass, Sarah H and Truxal, Ashley E and Fiala, T A and Kelly, Joseph and Nguyen, Dang and Finbloom, Joel A and Wemmer, David E and Pines, Alexander and Francis, Matthew B} } @article {3194, title = {SABRE: Chemical kinetics and spin dynamics of the formation of hyperpolarization}, journal = {Progress in Nuclear Magnetic Resonance Spectroscopy}, year = {2019}, month = {05/2019}, doi = {10.1016/j.pnmrs.2019.05.005}, url = {https://www.sciencedirect.com/science/article/pii/S007965651930024X}, author = {Danila Barskiy and Stephan Knecht and Alexandra Yurkovskaya and Konstantin Ivanov} } @article {3193, title = {Zero-Field Nuclear Magnetic Resonance of Chemically Exchanging Systems}, journal = {Nature Communications}, volume = {10}, year = {2019}, month = {07/2019}, abstract = {

Zero- to ultralow-field (ZULF) nuclear magnetic resonance (NMR) is an emerging tool for precision chemical analysis. In this work, we study dynamic processes and investigate the influence of chemical exchange on ZULF NMR J-spectra. We develop a computational approach that allows quantitative calculation of J-spectra in the presence of chemical exchange and apply it to study aqueous solutions of [15N]ammonium (15N) as a model system. We show that pH-dependent chemical exchange substantially affects the J-spectra and, in some cases, can lead to degradation and complete disappearance of the spectral features. To demonstrate potential applications of ZULF NMR for chemistry and biomedicine, we show a ZULF NMR spectrum of [2-13C]pyruvic acid hyperpolarized via dissolution dynamic nuclear polarization (dDNP). We foresee applications of affordable and scalable ZULF NMR coupled with hyperpolarization to study chemical exchange phenomena in vivo and in situations where high-field NMR detection is not possible to implement.

}, doi = {https://doi.org/10.1038/s41467-019-10787-9}, url = {https://www.nature.com/articles/s41467-019-10787-9?fbclid=IwAR1MB5nAamCMGynKRk0sjD6V8rTlZ329IvrVKrCwIO8QjrEH4wD23BV5gak}, author = {Danila Barskiy and Michael Tayler and Irene Marco-Rius and John Kurhanewicz and Daniel Vigneron and Sevil Cikrikci and Ayca Aydogdu and Moritz Reh and Andrey Pravdivtsev and Jan-Bernd H{\"o}vener and John Blanchard and Teng Wu and Dmitry Budker and Alexander Pines} } @article {3196, title = {Hyperpolarized NMR Spectroscopy: d-DNP, PHIP, and SABRE Techniques}, journal = {Chemistry - An Aisan Journal}, volume = {13}, year = {2018}, month = {08/2018}, abstract = {

The intensity of NMR signals can be enhanced by several orders of magnitude by using various techniques for the hyperpolarization of different molecules. Such approaches can overcome the main sensitivity challenges facing modern NMR/magnetic resonance imaging (MRI) techniques, whilst hyperpolarized fluids can also be used in a variety of applications in material science and biomedicine. This Focus Review considers the fundamentals of the preparation of hyperpolarized liquids and gases by using dissolution dynamic nuclear polarization (d-DNP) and parahydrogen-based techniques, such as signal amplification by reversible exchange (SABRE) and parahydrogen-induced polarization (PHIP), in both heterogeneous and homogeneous processes. The various new aspects in the formation and utilization of hyperpolarized fluids, along with the possibility of observing NMR signal enhancement, are described.

}, doi = {10.1002/asia.201800551}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/asia.201800551}, author = {Kirill Kovtunov and Ekaterina Pokochueva and Oleg Salnikov and Samuel Cousin and Dennis Kurzbach and Basile Vuichoud and Sami Jannin and Eduard Chekmenev and Boyd Goodson and Danila Barskiy and Igor Koptyug} } @article {2581, title = {Optically-pumped dynamic nuclear hyperpolarization in 13C enriched diamond}, journal = {Phys. Rev. B Rapid Communications}, year = {2018}, abstract = {

We investigate nuclear spin hyperpolarization from optically polarized nitrogen vacancy centers in isotopically enriched diamonds with 13C concentrations up to 100\%.\ 13C enrichment leads to hyperfine structure of the nitrogen vacancy electron spin resonance spectrum and dynamic nuclear polarization enhancement profile. We show that strongly-coupled \cthirt spins in the first shell surrounding a nitrogen vacancy center generate resolved hyperfine splittings, but do not act as an intermediary in the transfer of hyperpolarization of bulk nuclear spins. High levels of \cthirt enrichment are desirable to increase the efficiency of hyperpolarization for magnetic resonance signal enhancement, imaging contrast agents, and as a platform for quantum sensing and many-body physics.

}, url = {https://journals.aps.org/prb/accepted/0707cOeaT9fE2916845f0be02a174d447e77534ff}, author = {Parker, AJ and Jeong, K and Avalos, CE and Hausmann, BJM and Vassiliou, CC and Pines, A and King, JP} } @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 {3195, title = {Selective Single-Site Pd-In Hydrogenation Catalyst for Production of Enhanced Magnetic Resonance Signals using Parahydrogen}, journal = {Chemistry - A European Journal}, volume = {24}, year = {2018}, month = {01/2018}, chapter = {2547}, abstract = {

Pd\−In/Al2O3\ single-site catalyst was able to show high selectivity (up to 98\ \%) in the gas phase semihydrogenation of propyne. Formation of intermetallic Pd\−In compound was studied by XPS during reduction of the catalyst. FTIR\−CO spectroscopy confirmed single-site nature of the intermetallic Pd\−In phase reduced at high temperature. Utilization of Pd\−In/Al2O3\ in semihydrogenation of propyne with parahydrogen allowed to produce \≈3400-fold NMR signal enhancement for reaction product propene (polarization=9.3\ \%), demonstrating the large contribution of pairwise hydrogen addition route. Significant signal enhancement as well as the high catalytic activity of the Pd\−In catalyst allowed to acquire\ 1H MR images of flowing hyperpolarized propene gas selectively for protons in CH, CH2\ and CH3\ groups. This observation is unique and can be easily transferred to the development of a useful MRI technique for an in situ investigation of selective semihydrogenation in catalytic reactors.

}, doi = {10.1002/chem.201705644}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/chem.201705644}, author = {Dudari Burueva and Kirill Kovtunov and Andrey Bukhtiyarov and Danila Barskiy and Igor Prosvirin and Igor Mashkovsky and Galina Baeva and Valerii Bukhtiyarov and Aleksandr Stakheev and Igor Koptyug} } @article {2421, title = {13C-Decoupled J-Coupling Spectroscopy Using Two-Dimensional Nuclear Magnetic Resonance at Zero-Field}, journal = {The Journal of Physical Chemistry Letters}, volume = {8}, year = {2017}, pages = {1512-1516}, author = {Sjolander, TF and Tayer, MCD and Kentner, A and Budker, D and Pines, A} } @article {2422, title = {Antisymmetric Couplings Enable Direct Observation of Chirality in Nuclear Magnetic Resonance Spectroscopy}, journal = {The Journal of Physical Chemistry Letters}, volume = {8}, year = {2017}, pages = {710-714}, author = {King, JP and Sjolander, TF and Blanchard, JW} } @article {2812, title = {Distance-dependent magnetic resonance tuning as a versatile MRI sensing platform for biological targets}, journal = {Nature Materials}, volume = {16}, year = {2017}, pages = {537 - 542}, chapter = {537}, author = {Choi, J.-S. and Kim, S. and Yoo, D. and Shin, T.-H. and Kim, H. and Gomes, M.D. and Kim, S. H. and Pines, A. and Cheon, J.} } @article {2699, title = {Invited Review Article: Instrumentation for nuclear magnetic resonance in zero and ultralow magnetic field}, journal = {Review of Scientific Instruments}, volume = {88}, year = {2017}, month = {09/2017}, abstract = {

We review experimental techniques in our laboratory for nuclear magnetic resonance (NMR) in zero and ultralow magnetic field (below 0.1 μT) where detection is based on a low-cost, non-cryogenic, spin-exchange relaxation free 87Rb atomic magnetometer. The typical sensitivity is 20-30 fT/Hz1/2 for signal frequencies below 1 kHz and NMR linewidths range from Hz all the way down to tens of mHz. These features enable precision measurements of chemically informative nuclear spin-spin couplings as well as nuclear spin precession in ultralow magnetic fields.

}, doi = {https://doi.org/10.1063/1.5003347}, url = {http://aip.scitation.org/doi/abs/10.1063/1.5003347}, author = {Tayler, MCD and Theis, Thomas and Tobias F. Sjolander and John W. Blanchard and Kentner, A and Pustelny, S and Pines, Alexander and Budker, Dmitry} } @article {2516, title = {Measuring molecular parity nonconservation using nuclear magnetic resonance spectroscopy}, journal = {ArXiv}, year = {2017}, author = {Eills, J and Blanchard, JW and Bougas, L and Kozlov, MG and Pines, A and Budker, D} } @article {2698, title = {Measuring molecular parity nonconservation using nuclear-magnetic-resonance spectroscopy}, journal = {Physical Review A}, volume = {96}, year = {2017}, month = {10/2017}, abstract = {

The weak interaction does not conserve parity and therefore induces energy shifts in chiral enantiomers that should in principle be detectable in molecular spectra. Unfortunately, the magnitude of the expected shifts are small and in spectra of a mixture of enantiomers, the energy shifts are not resolvable. We propose a nuclear-magnetic-resonance (NMR) experiment in which we titrate the chirality (enantiomeric excess) of a solvent and measure the diasteriomeric splitting in the spectra of a chiral solute in order to search for an anomalous offset due to parity nonconservation (PNC). We present a proof-of-principle experiment in which we search for PNC in the 13C resonances of small molecules, and use the 1H resonances, which are insensitive to PNC, as an internal reference. We set a constraint on molecular PNC in 13C chemical shifts at a level of 10\−5 ppm, and provide a discussion of important considerations in the search for molecular PNC using NMR spectroscopy.

}, doi = {https://doi.org/10.1103/PhysRevA.96.042119}, url = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.96.042119}, author = {John W. Blanchard and J. Ellis and Bougas, L and M. G. Kozlov and Alexander Pines and Dmitri Budker} } @article {2391, title = {An optimized microfabricated platform for the optical generation and detection of hyperpolarized 129Xe}, journal = {Scientific Reports }, year = {2017}, url = {http://www.nature.com/articles/srep43994}, author = {Daniel J. Kennedy and Scott J. Seltzer and Ricardo Jimenez-Martinez and Hattie L. Ring and Nicholas Malecek and Svenja Knappe and Elizabeth Donley and John Kitching and Vikram S. Bajaj and Alexander Pines} } @article {2580, title = {Understanding the magnetic resonance spectrum of nitrogen vacancy centers in an ensemble of randomly-oriented nanodiamonds}, journal = {J. Phys. Chem. C}, year = {2017}, author = {Jeong, K and Parker, AJ and Page, RH and Pines, A and Vassiliou, C and King, JP} } @article {2070, title = {Transition-Selective Pulses in Zero-Field Nuclear Magnetic Resonance}, journal = {The Journal of Physical Chemistry}, volume = {120}, year = {2016}, month = {05/2016}, chapter = {4343}, doi = {10.1021/acs.jpca.6b04017}, url = {http://pubs.acs.org/doi/abs/10.1021/acs.jpca.6b04017}, author = {Sjolander, TF and Tayler, M and King, JP and Budker, D and Pines, A} } @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 {1866, title = {Investigation of DOTA-Metal Chelation Effects on 129Xe Chemical Shift}, journal = {ChemPhysChem}, year = {2015}, author = {Keunhong Jeong and Clancy C. Slack and Christophoros C. Vassiliou and Phuong Dao and Muller D Gomes and Daniel J. Kennedy and Ashley E. Truxal and Lindsay J Sperling and Matthew B. Francis and David E. Wemmer and Alexander Pines} } @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 {1875, title = {Room temperature in situ nuclear spin hyperpolarization from optically pumped nitrogen vacancy centers in diamond}, journal = {Nature Communications}, year = {2015}, author = {Jonathan P. King and Keunhong Jeong and Christophoros C. Vassiliou and Chang S. Shin and Ralph H. Page and Claudia E. Avalos and Hai-Jing Wang and Alexander Pines} } @article {1598, title = {Gradient-free microfluidic flow labeling using thin magnetic films and remotely detected MRI (Cover Article)}, journal = {Journal of Magnetic Resonance}, volume = {249}, year = {2014}, month = {12/2014}, pages = {135-140}, author = {Halpern-Manners, N.W. and Kennedy, D.J. and Trease, D.R. and Teisseyre, T.Z. and Malecek, N.S. and Pines, A. and Bajaj, V.S.} } @article {1478, title = {Optical hyperpolarization and NMR detection of 129Xe on a microfluidic chip}, journal = {Nature Communication}, volume = {5}, year = {2014}, pages = {3908}, doi = {10.1038/ncomms4908}, author = {Jimenez-Martinez, R. and Kennedy, D. J. and Rosenbluh, M. and Donley, E. A. and Knappe, S. and Seltzer, S. J. and Ring, H. and Bajaj, V.S. and Kitching, J.} } @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 {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 {249, title = {Room-temperature operation of a radiofrequency diamond magnetometer near the shot-noise limit}, journal = {Journal of Applied Physics}, volume = {112}, year = {2012}, note = {J Appl Phys061ECTimes Cited:1Cited References Count:15}, month = {Dec 15, 2012}, pages = {124519}, chapter = {124519}, abstract = {

We operate a nitrogen-vacancy (NV-) diamond magnetometer at ambient temperatures and study the dependence of its bandwidth on experimental parameters including optical and microwave excitation powers. A model based on the Bloch equations is used to analyze the NV center\&$\#$39;s response time, tau, during continuous optical and microwave irradiation, and tau(-1) is shown to be a weighted average of T-1(-1) and T-2(-1), where T-1 and T-2 are the longitudinal and transverse relaxation times of the electron spin during optical irradiation. We measured a maximum detection bandwidth of similar to 1.6 MHz with optical excitation intensity of similar to 2.3MW/cm(2), limited by the available optical power. The sensitivity of the NV ensemble for continuous-wave magnetometry in the presence of photon shot noise is analyzed. Two detection schemes are compared, one involving modulation of the fluorescence by an oscillating magnetic field while the microwave frequency is held constant, and the other involving double modulation of the fluorescence when the microwave frequency is modulated during the detection. For the first of these methods, we measure a sensitivity of 4.6 +/- 0.3 nT/root Hz, unprecedented in a detector with this active volume of similar to 10 mu m(3) and close to the photon-shot-noise limit of our experiment. The measured bandwidth and sensitivity of our device should allow detection of micro-scale NMR signals with microfluidic devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4771924]

}, keywords = {spin}, isbn = {0021-8979}, doi = {Doi 10.1063/1.4771924}, url = {http://link.aip.org/link/doi/10.1063/1.4771924}, author = {Shin, C. S. and Avalos, C. E. and Butler, M. C. and Trease, D. R. and Seltzer, S. J. and Mustonen, J. P. and Kennedy, D. J. and Acosta, V. M. and Budker, D. and Pines, A. and Bajaj, V. S.} } @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 {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 {260, title = {Investigation of antirelaxation coatings for alkali-metal vapor cells using surface science techniques}, journal = {Journal of Chemical Physics}, volume = {133}, year = {2010}, note = {J. Chem. Phys.ISI Document Delivery No.: 667NNTimes Cited: 6Cited Reference Count: 81Seltzer, S. J. Michalak, D. J. Donaldson, M. H. Balabas, M. V. Barber, S. K. Bernasek, S. L. Bouchiat, M. -A. Hexemer, A. Hibberd, A. M. Kimball, D. F. Jackson Jaye, C. Karaulanov, T. Narducci, F. A. Rangwala, S. A. Robinson, H. G. Shmakov, A. K. Voronov, D. L. Yashchuk, V. V. Pines, A. Budker, D.Office of Science, Office of Basic Energy Sciences, Materials Sciences Division and Nuclear Science Division, of the U. S. Department of Energy [DE-AC02-05CH11231]; NSF/DST [PHY-0425916]; Office of Naval Research (ONR) [N0001409WX21049]The authors thank Daniel Fischer, Kristin Schmidt, and Ed Kramer for assistance with the NEXAFS measurements, and Joel Ager, Joshua Wnuk, David Trease, and Gwendal Kervern for helpful discussions and other assistance. S.J.S., D.J.M., M. H. D., A. P., and D. B., the Advanced Light Source, and the DSC, FTIR, and AFM studies were supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences Division and Nuclear Science Division, of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231 at Lawrence Berkeley National Laboratory. Other parts of this work were funded by the NSF/DST under Grant No. PHY-0425916 for U.S.-India cooperative research, by an Office of Naval Research (ONR) MURI grant, and by ONR under Grant No. N0001409WX21049.AMER INST PHYSICSMELVILLE}, month = {October 11, 2010}, pages = {144703}, type = {Article}, chapter = {144703}, abstract = {

Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10 000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of CvC double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489922]

}, keywords = {SPECTROSCOPY}, isbn = {0021-9606}, doi = {10.1063/1.3489922}, url = {http://link.aip.org/link/doi/10.1063/1.3489922}, author = {Seltzer, S. J. and Michalak, D. J. and Donaldson, M. H. and Balabas, M. V. and Barber, S. K. and Bernasek, S. L. and Bouchiat, M. A. and Hexemer, A. and Hibberd, A. M. and Kimball, D. F. J. and Jaye, C. and Karaulanov, T. and Narducci, F. A. and Rangwala, S. A. and Robinson, H. G. and Shmakov, A. K. and Voronov, D. L. and Yashchuk, V. V. and Pines, A. and Budker, D.} } @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 {282, title = {NMR imaging of catalytic hydrogenation in microreactors with the use of para-hydrogen}, journal = {Science}, volume = {319}, year = {2008}, note = {Science254HBTimes Cited:55Cited References Count:33}, month = {Jan 25}, pages = {442-445}, abstract = {

Catalysis is vital to industrial chemistry, and the optimization of catalytic reactors attracts considerable resources. It has proven challenging to correlate the active regions in heterogeneous catalyst beds with morphology and to monitor multistep reactions within the bed. We demonstrate techniques, using magnetic resonance imaging and para- hydrogen ( p-H(2)) polarization, that allow direct visualization of gas- phase flow and the density of active catalyst in a packed- bed microreactor, as well as control over the dynamics of the polarized state in space and time to facilitate the study of subsequent reactions. These procedures are suitable for characterizing reactors and reactions in microfluidic devices where low sensitivity of conventional magnetic resonance would otherwise be the limiting factor.

}, keywords = {chip}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.1151787}, url = {://WOS:000252576600031}, author = {Bouchard, L. S. and Burt, S. R. and Anwar, M. S. and Kovtunov, K. V. and Koptyug, I. V. 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 {290, title = {Para-hydrogen-enhanced hyperpolarized gas-phase magnetic resonance imaging}, journal = {Angewandte Chemie-International Edition}, volume = {46}, year = {2007}, note = {Angew Chem Int Edit174ZPTimes Cited:28Cited References Count:37}, pages = {4064-4068}, keywords = {he-3}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200700830}, url = {://WOS:000246981900008}, author = {Bouchard, L. S. and Kovtunov, K. V. and Burt, S. R. and Anwar, M. S. and Koptyug, I. V. and Sagdeev, R. Z. and Pines, A.} } @article {285, title = {Para-hydrogen-induced polarization in heterogeneous hydrogenation reactions}, journal = {Journal of the American Chemical Society}, volume = {129}, year = {2007}, note = {J Am Chem Soc160MRTimes Cited:36Cited References Count:45}, month = {May 2}, pages = {5580-5586}, abstract = {

We demonstrate the creation and observation of para-hydrogen-induced polarization in heterogeneous hydrogenation reactions. Wilkinson\&$\#$39;s catalyst, RhCl(PPh3)(3), supported on either modified silica gel or a polymer, is shown to hydrogenate styrene into ethylbenzene and to produce enhanced spin polarizations, observed through NMR, when the reaction was performed with H-2 gas enriched in the para spin isomer. Furthermore, gaseous phase para-hydrogenation of propylene to propane with two catalysts, the Wilkinson\&$\#$39;s catalyst supported on modified silica gel and Rh(cod)(sulfos) (cod = cycloocta-1,5-diene; sulfos = -O3S(C6H4)CH2C(CH2PPh2)(3)) supported on silica gel, demonstrates heterogeneous catalytic conversion resulting in large spin polarizations. These experiments serve as a direct verification of the mechanism of heterogeneous hydrogenation reactions involving immobilized metal complexes and can be potentially developed into a practical tool for producing catalyst-free fluids with highly polarized nuclear spins for a broad range of hyperpolarized NMR and MRI applications.

}, keywords = {alignment}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja068653o}, url = {://WOS:000245946400064}, author = {Koptyug, I. V. and Kovtunov, K. V. and Burt, S. R. and Anwar, M. S. and Hilty, C. and Han, S. I. and Pines, A. and Sagdeev, R. Z.} } @article {287, title = {Time-of-flight flow imaging of two-component flow inside a microfluidic chip}, journal = {Physical Review Letters}, volume = {98}, year = {2007}, note = {Phys Rev Lett124OYTimes Cited:21Cited References Count:16}, month = {Jan 5}, abstract = {

Here we report on using NMR imaging and spectroscopy in conjunction with time-of-flight tracking to noninvasively tag and monitor nuclear spins as they flow through the channels of a microfluidic chip. Any species with resolvable chemical-shift signatures can be separately monitored in a single experiment, irrespective of the optical properties of the fluids, thereby eliminating the need for foreign tracers. This is demonstrated on a chip with a mixing geometry in which two fluids converge from separate channels, and is generally applicable to any microfluidic device through which fluid flows within the nuclear spin-lattice relaxation time.

}, keywords = {microchannels}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.98.017601}, url = {://WOS:000243379700050}, author = {Harel, E. and Hilty, C. and Koen, K. and McDonnell, E. 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 {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 {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 {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 {321, title = {Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry}, journal = {Physical Review Letters}, volume = {93}, year = {2004}, note = {Phys Rev Lett863ATTimes Cited:32Cited References Count:22}, month = {Oct 15}, abstract = {

We report the use of an atomic magnetometer based on nonlinear magneto-optical rotation with frequency-modulated light to detect nuclear magnetization of xenon gas. The magnetization of a spin-exchange-polarized xenon sample (1.7 cm(3) at a pressure of 5 bars, natural isotopic abundance, polarization 1\%), prepared remotely to the detection apparatus, is measured with an atomic sensor. An average magnetic field of similar to10 nG induced by the xenon sample on the 10 cm diameter atomic sensor is detected with signal-to-noise ratio similar to10, limited by residual noise in the magnetic environment. The possibility of using modern atomic magnetometers as detectors of nuclear magnetic resonance and in magnetic resonance imaging is discussed. Atomic magnetometers appear to be ideally suited for emerging low-field and remote-detection magnetic resonance applications.

}, keywords = {mri}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.93.160801}, url = {://WOS:000224533300012}, author = {Yashchuk, V. V. and Granwehr, J. and Kimball, D. F. and Rochester, S. M. and Trabesinger, A. H. and Urban, J. T. and Budker, D. 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 {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 {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 {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 {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 {390, title = {Gas flow MRI using circulating laser-polarized Xe-129}, journal = {Journal of Magnetic Resonance}, volume = {138}, year = {1999}, note = {J Magn Reson196HXTimes Cited:35Cited References Count:15}, month = {May}, pages = {155-159}, abstract = {

We describe an experimental approach that combines multidimensional NMR experiments with a steadily renewed source of laser-polarized Xe-129. Using a continuous flow system to circulate the gas mixture, gas phase NMR signals of laser-polarized Xe-129 can be observed with an enhancement of three to four orders of magnitude compared to the equilibrium Xe-129 NMR signal. Due to the fact that the gas flow recovers the nonequilibrium Xe-129 nuclear spin polarization in 0.2 to 4 s, signal accumulation on the time scale of seconds is feasible, allowing previously inaccessible phase cycling and signal manipulation. Several possible applications of MRI of laser-polarized Xe-129 under continuous flow conditions are presented here. The spin density images of capillary tubes demonstrate the feasibility of imaging under continuous how. Dynamic displacement profiles, measured by a pulsed gradient spin echo experiment, show entry flow properties of the gas passing through a constriction under laminar flow conditions. Further, dynamic displacement profiles of Xe-129, flowing through polyurethane foams with different densities and pore sizes, are presented. (C) 1999 Academic Press.

}, keywords = {xenon}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.1998.1675}, url = {://WOS:000080303900021}, author = {Brunner, E. and Haake, M. and Kaiser, L. and Pines, A. and Reimer, J. A.} } @book {385, title = {Proc. of the Int. School of Physics, Enrico Fermi Course CXXXIX - Magnetic Resonance and Brain Funtion: Approaches from Physics}, series = {NMR and MRI of Laser-Polarized Noble Gases in Molecules}, year = {1999}, publisher = {IOS Press}, organization = {IOS Press}, chapter = {211-226}, author = {Goodson, B.M. and Kaiser, L. and Pines, A.} } @article {388, title = {Relaxation-selective magnetic resonance imaging}, journal = {Chemical Physics Letters}, volume = {311}, year = {1999}, note = {Chem Phys Lett244VRTimes Cited:1Cited References Count:15}, month = {Oct 1}, pages = {379-384}, abstract = {

The Bloch equations with T-2 relaxation can be inverted in closed form with respect to T-2, using inverse scattering theory. Hence, radio frequency pulses can be calculated that cause a final magnetization response that is any desired function of T-2, provided that function is physically realizable (however, there are strong constraints on what is physically realizable). A useful subclass of such pulses are \&$\#$39;dressing\&$\#$39; pulses, which store the magnetization on the z-axis, with magnitude a given function of T-2. This enables spins to be selectively nulled according to their T-2- this is demonstrated by obtaining a relaxation-selective image of a phantom. (C) 1999 Elsevier Science B.V. All rights reserved.

}, keywords = {optimization}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(99)00890-8}, url = {://WOS:000083071900007}, author = {Bush, S. D. and Rourke, D. E. and Kaiser, L. G. 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 {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 {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 {430, title = {Isotropic second-order dipolar shifts in the rotating frame}, journal = {Journal of Chemical Physics}, volume = {104}, year = {1996}, note = {J Chem PhysUm909Times Cited:9Cited References Count:44}, month = {Jun 1}, pages = {8258-8268}, abstract = {

An experiment is described that utilizes the truncation of the Hamiltonian in the rotating frame by a radio-frequency field designed to yield an isotropic shift for the dipolar coupling. This approach allows the measurement of a normally orientation-dependent coupling constant by a single isotropic value. The dipolar isotropic shift is closely related to the field-dependent chemical shift in solids due to the second-order dipolar perturbation observed in magic-angle spinning experiments. In the rotating frame, larger shifts of up to 1000 Hz can be observed for the case of a one-bond C-H coupling compared to a shift of a few Hertz in the laboratory-frame experiment. In addition to the isotropic shift, a line broadening due to the P-4(cos beta) terms is observed when the experiment is carried out under magic-angle sample spinning (MAS) conditions, leading to the requirement of higher-order averaging such as double rotation (DOR) for obtaining narrow lines. As an application of this new experiment the separation of CH, CH2, and CH3 groups in a 2D spectrum under MAS is demonstrated. Implemented under DOR it could be used as a technique to select carbon atoms according to the number of directly attached protons. (C) 1996 American Institute of Physics.

}, keywords = {spins}, isbn = {0021-9606}, doi = {Doi 10.1063/1.471579}, url = {://WOS:A1996UM90900008}, author = {Ernst, M. and Kolbert, A. C. and Schmidt-Rohr, K. and Pines, A.} } @article {431, title = {Second-order recoupling of chemical-shielding and dipolar-coupling tensors under spin decoupling in solid-state NMR}, journal = {Journal of Chemical Physics}, volume = {105}, year = {1996}, note = {J Chem PhysVd768Times Cited:55Cited References Count:53}, month = {Sep 1}, pages = {3387-3397}, abstract = {

The source of the residual line broadening in continuous-wave (cw) decoupled spectra under magic-angle sample spinning conditions is reexamined. It is shown that an important contribution to the line broadening comes from a second-order recoupling of the heteronuclear dipolar-coupling tensor and the chemical-shielding tensor of the irradiated spin. Such an interference between the two tensors leads to a sum of a zeroth-rank, a second-rank, and a fourth-rank tensor component in the Hamiltonian. The zeroth-rank and the fourth-rank tensor components are not averaged out under magic-angle sample spinning (MAS) conditions, requiring the use of higher-order averaging such as double rotation (DOR) for obtaining narrow lines. This broadening is distinctly different from off-resonance decoupling effects which transform as a second-rank tensor and can be averaged out by MAS. The properties of this second-order recoupling as a source of structural information are explored, and the conditions for removing the broadening in systems with weak homonuclear dipolar-coupling networks are discussed. (C) 1996 American Institute of Physics.

}, keywords = {waltz-16}, isbn = {0021-9606}, doi = {Doi 10.1063/1.472224}, url = {://WOS:A1996VD76800005}, author = {Ernst, M. and Bush, S. and Kolbert, A. C. and Pines, A.} } @article {425, title = {Si-29 high resolution solid state nuclear magnetic resonance spectroscopy of porous silicon}, journal = {Journal of Non-Crystalline Solids}, volume = {202}, year = {1996}, note = {J Non-Cryst SolidsVe406Times Cited:13Cited References Count:33}, month = {Jul}, pages = {68-76}, abstract = {

Porous silicon has been characterized by Si-29 nuclear magnetic resonance spectroscopy under conditions of static samples, magic angle spinning, decoupling and cross polarization. In a free induction decay experiment, two Si-29 resonances at -80 and -111 ppm were obtained. Cross polarization resulted in a single resonance at -97 ppm. Magic angle spinning and decoupling slightly reduce the linewidth of the Si-29 cross polarized signal, The minor narrowing effect and thr relaxation behavior in the laboratory and rotating frame indicate a homogeneous contribution to the linewidth. The relaxation data suggest that the resonance observed under cross polarization conditions arises from SiH or SiH2 structural elements.

}, keywords = {dipolar}, isbn = {0022-3093}, doi = {Doi 10.1016/0022-3093(96)00144-5}, url = {://WOS:A1996VE40600008}, author = {Pietrass, T. and Bifone, A. and Roth, R. D. and Koch, V. P. and Alivisatos, A. P. 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.} } @inbook {436, title = {Synthetic Peptides Model α - Helix - β - Sheet Conformational Changes in the Prion Protien}, booktitle = {Peptides: Chemistry, Structure and Biology}, year = {1996}, pages = {468-470}, publisher = {Mayflower Scientific Ltd.}, organization = {Mayflower Scientific Ltd.}, author = {Baldwin, M.A. and Zhang, H. and Bekker, T. and Zhou, S. and Nguyen, J. and Kolbert, A.C. and Heller, J. and James, T.L. and Wemmer, D.E. and Pines, A. and Cohen, F.E. and Prusiner, S.B.}, editor = {Hidges, Pravin T.P Kaumaya and Robert S.} } @article {441, title = {Magnetic-Resonance Evidence for Metallic State in Highly Conducting Polyaniline}, journal = {Synthetic Metals}, volume = {69}, year = {1995}, note = {Synthetic MetQl601Times Cited:9Cited References Count:12}, month = {Mar 1}, pages = {243-244}, abstract = {

Polyaniline doped with camphor sulfonic acid (PANI-CSA) has been shown to yield a material which, after processing from solutions in meta-cresol, exhibit a temperature independent magnetic susceptibility down to 50K. Below 50K a Curie like contribution sets in. We also report C-13 NMR experiments which clearly show that the C-13 spin lattice relaxation rates obey the Korringa relation for relaxation via the hyperfine coupling to conduction electrons.

}, keywords = {polymers}, isbn = {0379-6779}, doi = {Doi 10.1016/0379-6779(94)02435-2}, url = {://WOS:A1995QL60100097}, author = {Sariciftci, N. S. and Kolbert, A. C. and Cao, Y. and Heeger, A. J. and Pines, A.} } @article {454, title = {Surface Study of Supported Metal Particles by Xe-129 Nmr}, journal = {Physical Review Letters}, volume = {74}, year = {1995}, note = {Phys Rev LettQt449Times Cited:21Cited References Count:26}, month = {Apr 17}, pages = {3277-3280}, keywords = {states}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.74.3277}, url = {://WOS:A1995QT44900047}, author = {Bifone, A. and Pietrass, T. and Kritzenberger, J. and Pines, A. and Chmelka, B. F.} } @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 {463, title = {Measurement of Internuclear Distances by Switched Angle Spinning Nmr}, journal = {Journal of Physical Chemistry}, volume = {98}, year = {1994}, note = {J Phys Chem-UsPc619Times Cited:11Cited References Count:20}, month = {Aug 18}, pages = {7936-7938}, abstract = {

Dipolar switched angle spinning, an NMR technique due to Terao et al. [Terao, T.; Miura H.; Saika, A, J. Chem. Phys. 1986, 85, 3816], has been used to measure C-13-C-13 distances in the solid state. The experiment involves rotation of the sample at two different angles during different periods of a two-dimensional experiment. An evolution period with off-magic-angle spinning and chemical shift refocusing, followed by detection of the signal under magic angle spinning, yields scaled Pake patterns in omega(1), correlated with their isotropic shifts in omega(2) allowing the high-resolution measurement of dipolar couplings. We demonstrate this experiment on samples of doubly C-13 labeled zinc acetate and a 14 amino acid peptide, in which we show that under optimal conditions distances of up to 5 Angstrom may be measured.

}, keywords = {protein}, isbn = {0022-3654}, doi = {Doi 10.1021/J100084a003}, url = {://WOS:A1994PC61900003}, author = {Kolbert, A. C. and Grandinetti, P. J. and Baldwin, M. and Prusiner, S. B. and Pines, A.} } @article {462, title = {Xe-129 Nmr-Study of Tio2 (Anatase)-Supported V2o5 Catalysts}, journal = {Journal of Physical Chemistry}, volume = {98}, year = {1994}, note = {J Phys Chem-UsPk740Times Cited:19Cited References Count:61}, month = {Oct 6}, pages = {10173-10179}, abstract = {

TiO2 (anatase), V2O5, and V2O5/TiO2 (anatase) catalysts with 1.3\%, 3.0\%, and 9.8\% weight loadings of V2O5 have been studied using temperature-dependent xenon-129 NMR spectroscopy. The intrinsic chemical shift values due to the interaction of xenon with the surface are 109 +/- 3 ppm for TiO2 (anatase) and 93 +/- 5 ppm for V2O5. The V2O5/TiO2 catalysts provide strong adsorption sites for xenon which cause an initial decrease of the chemical shift values at low xenon loadings. Additionally, the spectra of pure V2O5 reveal two distinct environments for the xenon atoms, consistent with the hysteresis of the isotherm and the existence of pores. Two-dimensional exchange spectroscopy was used to measure the rates and activation energy of xenon moving between these two environments.

}, keywords = {nay zeolite}, isbn = {0022-3654}, doi = {Doi 10.1021/J100091a037}, url = {://WOS:A1994PK74000037}, author = {Kritzenberger, J. and Gaede, H. C. and Shore, J. S. and Pines, A. and Bell, A. T.} } @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 {488, title = {Solid-state Al-27 NMR studies of aluminophosphate molecular sieves}, journal = {Solid State Nuclear Magnetic Resonance}, volume = {1}, year = {1992}, note = {Solid State Nucl MagV26hsTimes Cited:12Cited References Count:33}, month = {Nov}, pages = {217-225}, abstract = {Solid-state Al-27 NMR spectra of several aluminophosphate molecular sieves have been recorded with conventional magic-angle spinning (MAS), double-rotation (DOR) and quadrupole nutation with fast MAS. Enhanced resolution was obtained in the quadrupole nutation experiment at certain radiofrequency pulse strengths. This extra resolution can be comparable to that attainable using DOR, and does not introduce spinning sidebands.}, keywords = {double-rotation}, isbn = {0926-2040}, url = {://WOS:000208537300007}, author = {Rocha, J. and Klinowski, J. and Barrie, P. J. and Jelinek, R. and Pines, A.} } @article {508, title = {Study of the Aluminophosphates Alpo4-21 and Alpo4-25 by Al-27 Double-Rotation Nmr}, journal = {Journal of the American Chemical Society}, volume = {113}, year = {1991}, note = {J Am Chem SocFn005Times Cited:53Cited References Count:16}, month = {May 22}, pages = {4097-4101}, abstract = {

Aluminum-27 double-rotation NMR in a magnetic field of 11.7 T distinguishes the extremely distorted five-coordinated aluminum sites in the molecular sieve precursor ALPO4(-21). Upon calcination, ALPO4(-21) transforms to ALPO4(-25), which has two tetrahedral aluminum sites with similar isotropic chemical shifts that cannot be resolved in an 11.7 T field. The two tetrahedral environments, however, have a different quadrupole coupling constants and are distinguished by double rotation at 4.2 T field. The quadrupole coupling constants obtained for these sites indicates that the tetrahedral aluminum environments are less distorted in the hydrated material.

}, keywords = {nuclei}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00011a007}, url = {://WOS:A1991FN00500007}, author = {Jelinek, R. and Chmelka, B. F. and Wu, Y. and Grandinetti, P. J. and Pines, A. and Barrie, P. J. and Klinowski, J.} } @article {513, title = {Berrys Phase}, journal = {Annual Review of Physical Chemistry}, volume = {41}, year = {1990}, note = {Annu Rev Phys ChemEf685Times Cited:96Cited References Count:286}, pages = {601-646}, isbn = {0066-426X}, doi = {Doi 10.1146/Annurev.Pc.41.100190.003125}, url = {://WOS:A1990EF68500020}, author = {Zwanziger, J. W. and Koenig, M. and Pines, A.} } @article {512, title = {Non-Abelian Effects in a Quadrupole System Rotating around 2 Axes}, journal = {Physical Review A}, volume = {42}, year = {1990}, note = {Phys Rev ADy007Times Cited:30Cited References Count:22}, month = {Sep 1}, pages = {3107-3110}, isbn = {1050-2947}, doi = {Doi 10.1103/Physreva.42.3107}, url = {://WOS:A1990DY00700066}, author = {Zwanziger, J. W. and Koenig, M. and Pines, A.} } @article {586, title = {Theory of Line-Shapes for Zero-Field Nmr in the Presence of Molecular-Motion}, journal = {Journal of Chemical Physics}, volume = {87}, year = {1987}, note = {J Chem PhysL1661Times Cited:10Cited References Count:41}, month = {Dec 15}, pages = {6867-6876}, isbn = {0021-9606}, doi = {Doi 10.1063/1.453381}, url = {://WOS:A1987L166100011}, author = {Meier, P. and Kothe, G. and Jonsen, P. and Trecoske, M. and Pines, A.} } @article {597, title = {Zero-Field Nmr of Solid Bis(Mu-Hydrido)Decacarbonyltriosmium}, journal = {Journal of Physical Chemistry}, volume = {90}, year = {1986}, note = {J Phys Chem-UsA5026Times Cited:5Cited References Count:26}, month = {Mar 13}, pages = {1065-1069}, isbn = {0022-3654}, doi = {Doi 10.1021/J100278a021}, url = {://WOS:A1986A502600021}, author = {Zax, D. B. and Bielecki, A. and Kulzick, M. A. and Muetterties, E. L. and Pines, A.} } @article {668, title = {On the short time behavior of the dipolar signal in relaxation measurements by the pulse method}, journal = {Physica}, year = {1980}, pages = {215-218}, author = {Emid, S. and Konijnendijk, J. and Schmidt, J. and Pines, A.} } @article {674, title = {Multiple Quantum Coherence in Dipolar Relaxation Measurements}, journal = {Physica B \& C}, volume = {96}, year = {1979}, note = {Physica B \& CHb239Times Cited:26Cited References Count:9}, pages = {333-336}, isbn = {0378-4371}, doi = {Doi 10.1016/0378-4363(79)90018-4}, url = {://WOS:A1979HB23900006}, author = {Emid, S. and Bax, A. and Konijnendijk, J. and Smidt, J. and Pines, A.} } @article {703, title = {C-13 and N-15 chemical shielding anisotropy in acetonitrile}, journal = {Chemical Physics Letters}, year = {1974}, pages = {78}, author = {Kaplan, S. and Pines, A. and Griffin, R.G. and Waugh, J.S.} } @article {704, title = {Chemical Shielding Anisotropy of C-13 and N-15 in Acetonitrile}, journal = {Chemical Physics Letters}, volume = {25}, year = {1974}, note = {Chem Phys LettS5222Times Cited:46Cited References Count:8}, pages = {78-79}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(74)80336-2}, url = {://WOS:A1974S522200017}, author = {Kaplan, S. and Pines, A. and Griffin, R. G. and Waugh, J. S.} } @proceedings {714, title = {Proton-enhance NMR of dilute spins in solids, proceedings of the congress ampere}, journal = {The Congress Ampere}, year = {1972}, pages = {11-17}, publisher = {North Holland Publishers}, address = {Turku, Finland}, author = {Waugh, J.S. and Gibby, M.G. and Kaplan, S. and Pines, A.} }