@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 {271, title = {{\textquoteright}Ex situ{\textquoteright} magnetic resonance volume imaging}, journal = {Chemical Physics Letters}, volume = {467}, year = {2009}, note = {Chem Phys Lett386VCTimes Cited:2Cited References Count:25}, month = {Jan 5}, pages = {398-401}, abstract = {

The portable NMR community has introduced advances that have allowed for a variety of studies. Imaging of static and moving objects has almost become standardized. The inherent static field gradients of portable systems have, however, limited such studies to imaging of slices perpendicular to the main gradient; full volume imaging in transportable, open systems has not been actively pursued. We present a true three-dimensional image of a phantom in an ex situ, electromagnet-based system. The basic concepts and designs put forth here extend in a straightforward fashion to higher fields and imaging of larger samples by ex situ methodologies. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {array}, isbn = {0009-2614}, doi = {Doi 10.1016/J.Cplett.2008.11.069}, url = {://WOS:000261909700037}, author = {Demas, V. and Franck, J. M. and Bouchard, L. S. and Sakellariou, D. and Meriles, C. A. and Martin, R. and Prado, P. J. and Bussandri, A. and Reimer, J. A. and Pines, A.} } @article {296, title = {Erwin L Hahn - Scientist, Mentor, Friend}, journal = {Journal of Magnetic Resonance}, volume = {179}, year = {2006}, note = {J Magn Reson035CMTimes Cited:1Cited References Count:1}, month = {Mar}, pages = {5-7}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2006.01.012}, url = {://WOS:000236977600002}, author = {Pines, A.} } @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 {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 {375, title = {Evidence of nonspecific surface interactions between laser-polarized xenon and myoglobin in solution}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {97}, year = {2000}, note = {P Natl Acad Sci USA345XMTimes Cited:40Cited References Count:35}, month = {Aug 15}, pages = {9472-9475}, abstract = {

The high sensitivity of the magnetic resonance properties of xenon to its local chemical environment and the large Xe-129 NMR signals attainable through optical pumping have motivated the use of xenon as a probe of macromolecular structure and dynamics. In the present work, we report evidence for nonspecific interactions between xenon and the exterior of myoglobin in aqueous solution, in addition to a previously reported internal binding interaction. Xe-129 chemical shift measurements in denatured myoglobin solutions and under native conditions with varying xenon concentrations confirm the presence of nonspecific interactions. Titration data are modeled quantitatively with treatment of the nonspecific interactions as weak binding sites. Using laser-polarized xenon to measure Xe-129 spin-lattice relaxation times (T-1), we observed a shorter T-1 in the presence of 1 mM denatured apomyoglobin in 6 M deuterated urea (T-1 = 59 +/- 1 s) compared with that in 6 M deuterated urea alone (T-1 = 291 +/- 2 s), suggesting that nonspecific xenon-protein interactions can enhance Xe-129 relaxation. An even shorter T1 was measured in ? mM apomyoglobin in D2O (T-1 = 15 +/- 0.3 s), compared with that in D2O alone (T-1 = 506 +/- 5 s). This difference in relaxation efficiency likely results from couplings between laser-polarized xenon and protons in the binding cavity of apomyoglobin that may permit the transfer of polarization between these nuclei via the nuclear Overhauser effect.

}, keywords = {binding}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.170278897}, url = {://WOS:000088840500026}, author = {Rubin, S. M. and Spence, M. M. and Goodson, B. M. and Wemmer, D. E. 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.} } @proceedings {389, title = {Enhanced Surface NMR of Zeolites and Related Material Using Laser-Polarized Xenon}, journal = {Proc. 12th Int. Zeolite Conf.}, year = {1999}, pages = {2943-2950}, author = {Brunner, E. and Haake, M. and Pines, A. and Reimer, J. and Seydoux, R.} } @article {393, title = {Effects of diffusion on magnetic resonance imaging of laser-polarized xenon gas}, journal = {Journal of Chemical Physics}, volume = {108}, year = {1998}, note = {J Chem PhysZh114Times Cited:30Cited References Count:24}, month = {Apr 15}, pages = {6233-6239}, abstract = {

Molecular diffusion during the application of magnetic field gradients can distort magnetic resonance images. A systematic characterization of these distortions in one dimension was performed using highly spin-polarized xenon gas. By varying the strength of the applied gradient and the geometric dimension of the sample, the evolution of these image distortions between the regimes of strong and weak diffusion was observed. These results are compared with numerical simulations. By directly measuring the displacement distribution of the polarized xenon atoms, it is shown that in the weak-diffusion regime the image distortions originate from the restricted diffusive motion near the sample boundaries, in agreement with previous theoretical work. Additionally, it is shown that the effects of diffusion can be utilized to enhance the contrast between the boundaries and bulk in the images of polarized gas samples, and thus may be exploited as a means of boundary detection in such systems. (C) 1998 American Institute of Physics. [S0021-9606(98)02915-8].

}, keywords = {xe-129}, isbn = {0021-9606}, doi = {Doi 10.1063/1.476030}, url = {://WOS:000073073700018}, author = {Song, Y. Q. and Goodson, B. M. and Sheridan, B. and de Swiet, T. M. and Pines, A.} } @article {404, title = {Enhancement of C-13 NMR signals in solid C-60 and C-70 using laser-polarized xenon}, journal = {Chemical Physics Letters}, volume = {290}, year = {1998}, note = {Chem Phys LettZw963Times Cited:30Cited References Count:31}, month = {Jun 26}, pages = {112-116}, abstract = {

NMR signals emanating from surface nuclei of solids may be enhanced by the transfer of spin polarization from laser-polarized noble gases via SPINOE (spin polarization induced nuclear Overhauser effect). The present contribution describes experiments in which the spin polarization is transferred under magic angle spinning (MAS) from laser-polarized Xe-129 to C-13, a nuclear spin with a low gyromagnetic ratio in the fullerenes C-60 and C-70, polycrystalline materials with a low surface area. In C-70, differential enhancement of the NMR is observed for the different atomic sites in the molecule. (C) 1998 Elsevier Science B.V. All rights reserved.

}, keywords = {c60}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(98)00473-4}, url = {://WOS:000074466600018}, author = {Brunner, E. and Haake, M. and Pines, A. and Reimer, J. A. and Seydoux, R.} } @article {411, title = {Enhancement of surface NMR by laser-polarized noble gases}, journal = {Physical Review B}, volume = {55}, year = {1997}, note = {Phys Rev BWy504Times Cited:65Cited References Count:34}, month = {May 1}, pages = {11604-11610}, abstract = {

The transfer of spin polarization from laser-polarized helium and xenon to spins such as H-1 and C-13 On the surface of high-surface-area solids (Aerosil) is demonstrated over a temperature range from 4 to 200 K. The transfer mechanism is dipole-dipole cross relaxation between the spins of the adsorbed mobile noble gas and the surface spins (spin-polarization-induced nuclear Overhauser effect). The enhancement of surface proton magnetization by laser-polarized helium at 4 K and 10 K is between one and twofold. Using laser-polarized xenon, enhancement factors of up to 20 were obtained when compared to the Boltzmann polarization in a field of 4.2 T and at a temperature of 130 K.

}, keywords = {he-3}, isbn = {0163-1829}, doi = {Doi 10.1103/Physrevb.55.11604}, url = {://WOS:A1997WY50400096}, author = {Room, T. and Appelt, S. and Seydoux, R. and Hahn, E. L. and Pines, A.} } @article {426, title = {Enhancement of solution NMR and MRI with laser-polarized xenon}, journal = {Science}, volume = {271}, year = {1996}, note = {ScienceUc778Times Cited:230Cited References Count:41}, month = {Mar 29}, pages = {1848-1851}, abstract = {

Optical pumping with laser light can be used to polarize the nuclear spins of gaseous xenon-129. When hyperpolarized xenon-129 is dissolved in liquids, a time-dependent departure of the proton spin polarization from its thermal equilibrium is observed, The variation of the magnetization is an unexpected manifestation of the nuclear Overhauser effect, a consequence of cross-relaxation between the spins of solution protons and dissolved xenon-129. Time-resolved magnetic resonance images of both nuclei in solution show that the proton magnetization is selectively perturbed in regions containing spin-polarized xenon-129. This effect could find use in nuclear magnetic resonance spectroscopy of surfaces and proteins and in magnetic resonance imaging.

}, keywords = {resonance}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.271.5257.1848}, url = {://WOS:A1996UC77800041}, author = {Navon, G. and Song, Y. Q. and Room, T. and Appelt, S. and Taylor, R. E. and Pines, A.} } @article {470, title = {Effects of Double Rotation on Homonuclear Spin Systems}, journal = {Journal of Magnetic Resonance Series A}, volume = {102}, year = {1993}, note = {J Magn Reson Ser AKz354Times Cited:3Cited References Count:13}, month = {Mar}, pages = {29-33}, keywords = {solids}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1993.1064}, url = {://WOS:A1993KZ35400005}, author = {Wu, Y. and Peng, Z. Y. and Olejniczak, Z. and Sun, B. Q. and Pines, A.} } @article {591, title = {Effect of Correlated Proton Jumps on the Zero-Field Nmr-Spectrum of Solid P-Toluic Acid}, journal = {Journal of Physical Chemistry}, volume = {91}, year = {1987}, note = {J Phys Chem-UsH0705Times Cited:15Cited References Count:14}, month = {Apr 23}, pages = {2240-2242}, isbn = {0022-3654}, doi = {Doi 10.1021/J100293a006}, url = {://WOS:A1987H070500006}, author = {Jarvie, T. P. and Thayer, A. M. and Millar, J. M. and Pines, A.} } @article {654, title = {Experiments on Selective Excitation of Multiple-Quantum Transitions in Nmr-Spectroscopy}, journal = {Journal of Chemical Physics}, volume = {74}, year = {1981}, note = {J Chem PhysLg574Times Cited:57Cited References Count:23}, pages = {2808-2818}, isbn = {0021-9606}, doi = {Doi 10.1063/1.441452}, url = {://WOS:A1981LG57400021}, author = {Warren, W. S. and Pines, A.} } @article {675, title = {Experimental Results on Deuterium Nmr in the Solid-State by Magic Angle Sample Spinning}, journal = {Chemical Physics}, volume = {42}, year = {1979}, note = {Chem PhysHl541Times Cited:50Cited References Count:15}, pages = {423-428}, isbn = {0301-0104}, doi = {Doi 10.1016/0301-0104(79)80092-0}, url = {://WOS:A1979HL54100022}, author = {Ackerman, J. L. and Eckman, R. and Pines, A.} } @article {698, title = {Effect of Phase-Transitions on C-13 Nuclear Magnetic-Resonance Spectra in Para-Azoxydianisole, a Nematic Liquid-Crystal}, journal = {Journal of the American Chemical Society}, volume = {96}, year = {1974}, note = {J Am Chem SocT8383Times Cited:28Cited References Count:14}, pages = {5590-5591}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00824a057}, url = {://WOS:A1974T838300057}, author = {Pines, A. and Chang, J. J.} } @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 {706, title = {Enhanced Inhomogeneous Nuclear Spin Echoes for Dilute Spins in Solids}, journal = {Chemical Physics Letters}, volume = {23}, year = {1973}, note = {Chem Phys LettS0678Times Cited:16Cited References Count:14}, pages = {614-616}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(73)89042-6}, url = {://WOS:A1973S067800042}, author = {Pines, A. and Shattuck, T. W.} }