@article {3083, title = {Realization of portable room temperature nanodiamond 13C hyperpolarizer}, year = {Submitted}, author = {A. Ajoy and R. Nazaryan and E. Druga and K. Liu and B. Han and J.T. Oon and M. Gierth and R. Tsang and J.H. Walton and C.A. Meriles and J.A. Reimer and D. Suter and A. Pines} } @article {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 {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 {446, title = {Coherent Isotropic Averaging in Zero-Field Nuclear-Magnetic-Resonance .2. Cubic Sequences and Time-Reversal of Spin Couplings}, journal = {Journal of Chemical Physics}, volume = {103}, year = {1995}, note = {J Chem PhysRu109Times Cited:8Cited References Count:35}, month = {Sep 8}, pages = {3982-3997}, abstract = {

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

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

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

}, keywords = {couplings}, isbn = {0021-9606}, doi = {Doi 10.1063/1.469584}, url = {://WOS:A1995RU10900011}, author = {Llor, A. and Olejniczak, Z. and Pines, A.} } @article {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 {493, title = {A study of nanostructure assemblies and guest-host interactions in sodium zeolite-Y using Na-23 double rotation NMR}, journal = {Nanotechnology}, year = {1992}, pages = {182-186}, author = {Jelinek, R. and Pines, A. and Ozkar, S. and Ozin, G.A.} } @article {507, title = {Scaling and Time-Reversal of Spin Couplings in Zero-Field Nmr}, journal = {Physical Review Letters}, volume = {67}, year = {1991}, note = {Phys Rev LettGj319Times Cited:13Cited References Count:25}, month = {Oct 7}, pages = {1989-1992}, abstract = {

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

}, keywords = {nqr}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.67.1989}, url = {://WOS:A1991GJ31900014}, author = {Llor, A. and Olejniczak, Z. and Sachleben, J. and Pines, A.} }