1,721,002 research outputs found
PROTON-DETECTED C,H CORRELATION VIA LONG-RANGE COUPLINGS WITH SOFT PULSES - DETERMINATION OF COUPLING-CONSTANTS
No full textAdiabatic TOCSY for C,C and H,H J-transfer
No full textAdiabatic pulses have been widely used for broadband decoupling and spin inversion at high magnetic fields. In this paper we propose adiabatic pulses and supercycles that can be used at high magnetic fields like 800 or 900 MHz to obtain broadband TOCSY sequences with C,C or H,H J-transfer. The new mixing sequences are equal or even superior to the well known DIPSI-2,3 experiments with respect to bandwidth. They prove robust against pulse miscalibration and B-1 inhomogeneity and are therefore attractive for fully automated spectrometer environments. These adiabatic mixing sequences have been incorporated in a novel z-filter HCCH-TOCSY experiment
DETERMINATION OF CARBON CARBON CONNECTIVITIES, ASSIGNMENT OF QUATERNARY CARBONS, AND EXTRACTION OF CARBON CARBON COUPLING-CONSTANTS BY CARBON-RELAYED HYDROGEN CARBON SPECTROSCOPY
No full textRECOGNITION OF NMR PROTON SPIN SYSTEMS OF CYCLOSPORIN A VIA HETERONUCLEAR PROTON CARBON LONG-RANGE COUPLINGS
No full textResolution enhancement in spectra of natural products dissolved in weakly orienting media with the help of 1H homonuclear dipolar decoupling during acquisition: Application to 1H-13C dipolar couplings measurements.
No full textIn weakly orienting media such as poly-gamma-benzyl-L-glutamate (PBLG) a polymer that forms a chiral liquid crystal in organic solvents, the spectral resolution for embedded molecules is usually poor because of numerous H-1, 1H dipolar couplings that generally broaden proton spectra. Therefore H-1, C-13 dipolar couplings are difficult or impossible to measure. Here, we incorporate Flip-Flop decoupling during detection into an HSQC experiment. Flip-Flop removes the H-1, H-1 dipolar couplings and scales the chemical shifts of the protons as well as the H-1, C-13 dipolar Couplings during detection. A resolution gain by a factor 1.5-4.2 and improved signal intensity by an average factor of 1.6-1.7 have been obtained. This technique is demonstrated on (+)-menthol dissolved in a PBLG/CDCl3 phase. (c) 2006 Elsevier Inc. All rights reserved
OPTIMIZED HETERONUCLEAR CROSS POLARIZATION IN LIQUIDS
No full textIt is demonstrated by theory, simulation, and experiment that it is possible to optimize heteronuclear cross-polarization experiments in liquids to such an extent that it becomes possible to transfer polarization uniformly through heteronuclear one-bond and long-range couplings. It is found that cross polarization is competitive with pulsed transfers, such as INEPT or DEPT, for the preparation of directly detected low-gamma nuclei. However for proton detection after two-way transfer, experiments employing heteronuclear multiple quantum coherence are usually more sensitive than cross-polarization experiments
ASSIGNMENT OF CARBONYL GROUPS AND SEQUENCE-ANALYSIS IN PEPTIDES BY INVERSE CORRELATION USING LONG-RANGE COUPLINGS
No full textDetermination of psi torsion angle restraints from (3)J(C-alpha,C-alpha) and 3J(C-alpha,H-N) coupling constants in proteins
No full textHomonuclear (3)J(C-alpha,C-alpha) and heteronuclear (3)J(C-alpha,H-N) coupling constants have been determined in the protein ubiquitin. Despite the fact that all amide bonds in ubiquitin have a trans conformation, considerable spread in the size of the coupling constants can be observed. The (3)J(C-alpha,H-N) coupling constants vary from 0.0 to 1.0 Hz, and the (3)J(C-alpha,C-alpha) coupling constants that could be determined vary from 1.1 to 2.2 Hz. Interpretation of the coupling constants reveals a non-Karplus-type dependence and suggests that vicinal homonuclear (3)J(C-alpha,C-alpha) and heteronuclear (3)J(C-alpha,H-N) depend on the phi(i-1) torsion angle. The proposed sensitive E.COSY-type HNCO[C-alpha] experiment for the measurement of vicinal (3)J(C-alpha,H-N) coupling constants can be used in protonated and deuterated proteins, and the quantitative J correlation experiment HN(COCA)CA can be carried out on perdeuterated proteins for the measurement of (3)J(C-alpha,C-alpha) that provide unique torsion angle information in these proton sparse proteins
THE ELUCIDATION OF THE CONSTITUTION OF GLYCOPEPTIDES BY THE NMR SPECTROSCOPIC COLOC TECHNIQUE
No full textMeasuring the chi(1) torsion angle in protein by CH-CH cross-correlated relaxation: A new resolution-optimised experiment
Full text linkHere we introduce an experiment with high sensitivity and resolution for the measurement of CH-CH dipolar-dipolar cross-correlated relaxation rates (CCRR) in protein side-chains. The new methodology aims to the determination of structural and dynamical parameters around the torsion angle chi(1) by measuring C(alpha)H(alpha)-C(beta)H(beta) cross-correlated relaxation rates. The method is validated on the protein ubiquitin: the chi(1) angles determined from the CCRR data are compared with the chi(1) angles of a previously determined NMR structure. The agreement between the two data sets is excellent for most residues. The few discrepancies that were found between the CCR-derived chi(1) angles and the angles of the previously determined NMR structure could be explained by taking internal motion into account. The new methodology represents a very powerful tool to determine both structure and dynamics of protein side-chains in only one experiment.</p
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