123Te and 125Te Fourier Transform NMR Investigations

1977 ◽  
Vol 32 (11) ◽  
pp. 1263-1265 ◽  
Author(s):  
K. U. Buckler ◽  
J. Kronenbitter ◽  
. Lutz ◽  
A. Nollle

Abstract The NMR signals of 123Te and 125Te have been observed in solutions of K2TeO3 and Na2TeO3 in D2O. In these solutions the ratios of Larmor frequencies ν(125Te)/ν(123Te), ν(125Te)/v(2H) and ν(125Te)/ν(23Na) have been determined with high accuracy. With the measured chemical shifts of 2H, 23Na, 125Te relative to infinitely diluted solutions the ratios of the Larmor frequencies are extrapolated and values of the magnetic moments are given. The relaxation times T1 and T2 are very different for 125Te in TeO32-: a ratio T1/T2 of 8.2 ± 0.4 has been found. No nuclear Overhauser effect due to dipole-dipole interaction of 125Te with the water protons has been detected.

2019 ◽  
Author(s):  
Georg Kuenze ◽  
Richard Bonneau ◽  
Julia Koehler Leman ◽  
Jens Meiler

AbstractComputational methods to predict protein structure from nuclear magnetic resonance (NMR) restraints that only require assignment of backbone signals hold great potential to study larger proteins and complexes. Additionally, computational methods designed to work with sparse data add atomic detail that is missing in the experimental restraints, allowing application to systems that are difficult to investigate. While specific frameworks in the Rosetta macromolecular modeling suite support the use of certain NMR restraint types, use of all commonly measured restraint types together is precluded. Here, we introduce a comprehensive framework into Rosetta that reconciles CS-Rosetta, PCS-Rosetta and RosettaNMR into a single framework, that, in addition to backbone chemical shifts and nuclear Overhauser effect distance restraints, leverages NMR restraints derived from paramagnetic labeling. Specifically, RosettaNMR incorporates pseudocontact shifts, residual dipolar couplings, and paramagnetic relaxation enhancements, measured at multiple tagging sites. We further showcase the generality of RosettaNMR for various modeling challenges and benchmark it on 28 structure prediction cases, eight symmetric assemblies, two protein-protein and three protein-ligand docking examples. Paramagnetic restraints generated more accurate models for 85% of the benchmark proteins and, when combined with chemical shifts, sampled high-accuracy models (≤ 2Å) in 50% of the cases.Significance StatementComputational methods such as Rosetta can assist NMR structure determination by employing efficient conformational search algorithms alongside physically realistic energy functions to model protein structure from sparse experimental data. We have developed a framework in Rosetta that leverages paramagnetic NMR data in addition to chemical shift and nuclear Overhauser effect restraints and extends RosettaNMR calculations to the prediction of symmetric assemblies, protein-protein and protein-ligand complexes. RosettaNMR generated high-accuracy models (≤ 2Å) in 50% of cases for a benchmark set of 28 monomeric and eight symmetric proteins and predicted protein-protein and protein-ligand interfaces with up to 1Å accuracy. The method expands Rosetta’s rich toolbox for integrative data-driven modeling and promises to be broadly useful in structural biology.


2020 ◽  
Vol 35 (2) ◽  
pp. 264-273
Author(s):  
Fu-Hu Su ◽  
Wang-Chuan Xiao ◽  
Sheann-Huei Lin ◽  
Qiyong Li

With good contrast in T1 and T2 weighted imaging as well as low toxicity in 3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, this work proposes the cross-linked polydimethylsiloxane colloids as a novel non-ionic contrast agent for gastrointestinal magnetic resonance imaging. The experiments of nuclear magnetic resonance spectra and relaxation show that within the interface of the colloids, there are nuclear Overhauser effect and transient nuclear Overhauser effect (cross-relaxation). Regarding the longitudinal relaxation experiments of CH2CH2O segments of Tween 80, a two spins system is found and modeled well by the equation [Formula: see text] which is deduced based on the transient nuclear Overhauser effect proposed by Solomon. The arbitrary constant X is additionally added with the initial conditions ( Iz −  I0) t=0 = −2 XS0 and ( Sz −  S0) t=0 = −2 S0. For the two spins system, D1 and T1 are corresponding to longitudinal relaxation times of the bound water and the CH2CH2O respectively. Concerning the transverse relaxation experiments of the CH2CH2O, they agree with the equation with three exponential decays, defined by three relaxation times, likely corresponding to three mechanisms. These mechanisms possibly are intramolecular and intermolecular dipole–dipole (DD) interactions and scalar coupling. Within the interface, hydrogen bonding causes the positive nuclear Overhauser effect of the CH2CH2O’s nuclear magnetic resonance spectra, the transient nuclear Overhauser effect of the CH2CH2O’s longitudinal relaxation experiments and the intermolecular dipole–dipole interactions of the CH2CH2O’s transverse relaxation experiments.


1980 ◽  
Vol 58 (23) ◽  
pp. 2649-2659 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts

Proton magnetic resonance studies at 400 MHz allowed the complete assignment of the spectra for (6R)-prostaglandin I1 in phosphate buffer and in CDCl3 solutions. The spectral analysis was based on the nuclear Overhauser effect difference measurements, which also provide accurate chemical shifts and coupling constants. Conformational differences in the two solvents for the ring portion of the molecule are indicated.


1976 ◽  
Vol 54 (12) ◽  
pp. 1918-1922 ◽  
Author(s):  
H. Beierbeck ◽  
R. Martino ◽  
John K. Saunders ◽  
Claude Benezra

The nuclear Overhauser effect (nOe) observed between phosphorus and hydrogen together with carbon and phosphorus spin lattice relaxation time (T1) data are presented for a number of phosphorus containing compounds. The dominant mechanism for phosphorus relaxation is shown to be the dipole-dipole interaction between phosphorus and hydrogen. From the nOe and T1 data the determination of phosphorus–hydrogen internuclear distances is demonstrated.


1984 ◽  
Vol 62 (8) ◽  
pp. 1640-1645 ◽  
Author(s):  
Makiko Sugiura ◽  
Helmut Beierbeck ◽  
George Kotovych ◽  
Patrice C. Bélanger

The conformational analysis of LTD4 in D2O was carried out based on the analysis of vicinal proton–proton coupling constants, nonselective proton longitudinal relaxation times, and nuclear Overhauser effect data. The H6—C6 to C12 region of the molecule is transoid, the predominant rotamer about C5—C6 is gauche, and two rotamers can be used to describe the rotation about C12—C13. There are three rotamers that can be used to describe the rotation about the C21—C22 bond of cysteine. Finally, chelation between an Yb3+, shift reagents and LTD4 was not observed.


1971 ◽  
Vol 49 (6) ◽  
pp. 904-913 ◽  
Author(s):  
S. Combrisson ◽  
B. Roques ◽  
P. Rigny ◽  
J. J. Basselier

The equations of the nuclear Overhauser effect (n.O.e.) in exchanging systems predict relative increases for proton signals where the life times for exchange are of the same order of magnitude as the relaxation times. This method allows one to obtain structural informations. Hence, for a temperature sufficiently below that of the coalescence, it allows one to infer a conformational preference by an examination of the relative increase in intensity with respect to spatial position of exchange sites. We have hereby determined the conformations of formyl-2 bromo-4 thiophene and acetyl-2 dibromo-4,5 thiophene. The compounds show at ambient temperature a single rotamer OS-cis. Formyl-2 bromo-4 furan exists at −90 °C in an equilibrium between the rotamers OO-cis and OO-trans. In this case, the results of different irradiations show OO-cis to be the preferred rotamer. Moreover, this method is able to give indications of the life time on different sites. We also give an evaluation of the limits of the method.


1986 ◽  
Vol 64 (10) ◽  
pp. 1998-2005 ◽  
Author(s):  
E. Kiehlmann ◽  
A. S. Tracey

The 1Hmr spectra of 20 catechin derivatives substituted at C-6/C-8 by bromine and/or hydrogen and at oxygen by methyl, acetyl, and/or hydrogen have been analyzed in deuterated acetone, acetonitrile, and chloroform. Because of its dependence on the nature of the solvent and of the oxygen substituent, the difference between H-6 and H-8 chemical shifts has been found to be an unreliable criterion for the distinction between 8-bromo and 6-bromo isomers. In methylated catechins, double irradiation of H-8 and H-6 enhances one (MeO-7) and two (MeO-5 and MeO-7) methoxy signals, respectively, via the nuclear Overhauser effect. This permits unambiguous assignment of chemical shifts to all ring A protons. The H-6 and H-8 resonance frequencies of catechin have been determined by decoupling of the OH-5 and OH-7 protons.


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