The conformational analysis of leukotriene D4 in aqueous solution based on high-field nuclear magnetic resonance measurements

1984 ◽  
Vol 62 (8) ◽  
pp. 1640-1645 ◽  
Author(s):  
Makiko Sugiura ◽  
Helmut Beierbeck ◽  
George Kotovych ◽  
Patrice C. Bélanger
Keyword(s):  
Conformational Analysis ◽  
Nuclear Overhauser Effect ◽  
Relaxation Times ◽  
Coupling Constants ◽  
Leukotriene D4 ◽  
Proton Proton ◽  
Proton Coupling ◽  
Overhauser Effect ◽  
Vicinal Proton ◽  
Nuclear Overhauser

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.

The synthesis and the nuclear magnetic resonance study of β-lactam derivatives of 1,5-benzothiazepines

1988 ◽  
Vol 66 (2) ◽  
pp. 279-282 ◽  
Author(s):  
Aron Szöllösy ◽  
George Kotovych ◽  
Gábor Tóth ◽  
Albert Lévai
Keyword(s):  
Nuclear Overhauser Effect ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Magnetic Resonance Study ◽  
Proton Proton ◽  
Proton Coupling ◽  
Overhauser Effect ◽  
Vicinal Proton ◽  
Nuclear Overhauser ◽  
Derivatives Of

The synthesis and stereochemistry of seven β-lactam derivatives of 1,5-benzothiazepines are presented. The configurational and conformational analysis is based on nuclear Overhauser effect experiments, together with analysis of the vicinal proton–proton coupling constants. In the preferred conformation, the seven-membered ring is in a half-chair. Only for one compound, 2-aza-4-bromo-4-methyl-5,7-diphenyl-8-thiatricyclo[7.4.0.02,5]trideca-Δ1,9,10,12-trien-3-one, were two diastereomers isolated (compounds 6a and 6b). Six of the compounds have the 4S*, 5R*, 7R* configuration while compound 6b has the 4R*, 5R*,7R* configuration.

Conformation of purine mononucleotides by H{H} and P{H} nuclear Overhauser effects

1983 ◽  
Vol 61 (7) ◽  
pp. 1456-1464 ◽  
Author(s):  
H. Santos ◽  
A. V. Xavier ◽  
C.F.G.C. Geraldes
Keyword(s):  
Aqueous Solution ◽  
Nuclear Overhauser Effect ◽  
Coupling Constants ◽  
Glycosidic Bond ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
Group A ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects

The proton–proton and phosphorus–proton nuclear Overhauser effect (nOe) of guanosine 5′-monophosphate (5′-GMP) was measured in aqueous solution at different pH values and in the presence of excess LaIII at acid pH. These data and nOe data from the literature for other mononucleotides were used together with vicinal proton–proton coupling constants to investigate the conformations of mononucleotides in aqueous solution, especially their rotational state about the glycosidic bond. Comparison of observed and calculated enhancements using various conformational models for the glycosidic bond gave predominantly anti conformations for 5′-AMP and 5′-GMP and a mixture of syn and anti conformations for 2′-AMP, 2′-GMP, 3′-AMP, and 3′-GMP. Protonation of 5′-GMP at N-7 of the guanine base alters the amplitude of its torsion angle within the anti range. The agreement between the glycosidic nucleotide conformations defined by nOe and by the lanthanide probe method is good but not perfect. As complexation of 5′-GMP with LaIII through the phosphate group has only a small effect on the conformation of its exocyclic group, a comparison of the two methods is justified.

Conformational analysis of key disaccharide components of Brucella A and M antigens

1990 ◽  
Vol 68 (7) ◽  
pp. 979-988 ◽  
Author(s):  
Thomas Peters ◽  
Jean-Robert Brisson ◽  
David R. Bundle
Keyword(s):  
Conformational Analysis ◽  
Boltzmann Distribution ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Structural Elements ◽  
Torsion Angles ◽  
Proton Proton ◽  
Vicinal Proton ◽  
Polysaccharide Antigens ◽  
Nuclear Overhauser

The synthetic α 1,2 and α 1,3 disaccharide methyl glycosides of 4-amino-4,6-dideoxy-D-mannose 1–6 that constitute key structural elements of Brucella A and M antigens were analyzed by 1H and 13C nuclear magnetic resonance spectroscopy. A detailed conformational analysis was performed for the N-acetylated derivatives 1 and 4 as well as for the amino derivatives 2 and 5. Potential energy calculations using the GESA program established the global minima for the disaccharides 1, 2, 4, and 5, and mapped the energy surface as a function of the glycosidic torsion angles [Formula: see text] and ψ. Ensemble averaged nuclear Overhauser enhancements, weighted according to the Boltzmann distribution function, were derived for each of the four disaccharides. This procedure improved the fit between experimentally and theoretically derived nOe values, when compared to interpretations based on a single conformer model. The Brucella A and M antigens are homopolymers of 4-formamido-4,6-dideoxy-D-mannose and, as.N-formyl groups (saccharides 3, 6, and 8) are essential for the binding of these antigens to their respective antibodies, amide conformation was analyzed by examination of the vicinal proton–proton and proton–carbon coupling constants of the model monosaccharide 8. The conformational properties of the model compounds 1–8 were used to model the Brucella A and M polysaccharide antigens. Keywords: conformational analysis, disaccharide conformation, nuclear Overhauser measurements, molecular modeling, Brucella antigen.

Proton magnetic resonance study of the conformation of the pyrrolidine ring in some proline-thiohydantoins

1988 ◽  
Vol 53 (11) ◽  
pp. 2503-2510 ◽  
Author(s):  
Jef J. M. Sleeckx ◽  
Marc J. O. Anteunis ◽  
Frans A. M. Borremans
Keyword(s):  
Present Model ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Proton Magnetic Resonance Study ◽  
Vicinal Proton ◽  
Different Temperatures ◽  
Experimental Justification ◽  
State Assumption ◽  
Methyl Phenyl

The conformational behaviour of a series of N-substituted thiohydantoins of proline was studied by proton NMR. The pseudorotational parameters of the proline moiety were calculated from the ten vicinal proton-proton coupling constants assuming a two state equilibrium (N ⇋ S). The effect of the different substituents (methyl, phenyl, para-nitrophenyl) at the thiohydantoin nitrogen on the conformation of the pyrrolidine rings is discussed. The spectra of proline-N-methylthiohydantoin were recorded at different temperatures in octadeuterotoluene solution. The conformational analysis of these spectra showed that the ratio of the populations of the N and S forms changes considerably with temperature, while the conformational identity of both the N and S forms remains strictly preserved. These facts provide an additional experimental justification of the two-state assumption, at least so for the present model compounds.

Vicinal proton—proton coupling constants. Basis set dependence in SCF ab initio calculations

1993 ◽  
Vol 206 (1-4) ◽  
pp. 253-259 ◽  
Author(s):  
Jesús San-Fabián ◽  
Joaquín Guilleme ◽  
Ernesto Díez ◽  
Paolo Lazzeretti ◽  
Massimo Malagoli ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Coupling Constants ◽  
Basis Set ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Vicinal proton–proton coupling constants: MCSCF ab initio calculations of ethane

1999 ◽  
Vol 314 (1-2) ◽  
pp. 168-175 ◽  
Author(s):  
J. Guilleme ◽  
J. San Fabián ◽  
J. Casanueva ◽  
E. Dı́ez
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Beiträge zur Chemie des Silieiums und Germaniums, XXIX [1] 29Si-NMR-spektroskopische Untersuchungen von geradkettigen und verzweigten Silanen / Contributions to the Chemistry of Silicon and Germanium, XXIX [1] 29Si NMR Spectroscopic Investigations on Straight and Branched Silanes

1980 ◽  
Vol 35 (3) ◽  
pp. 282-296 ◽  
Author(s):  
Josef Hahn
Keyword(s):  
Nuclear Overhauser Effect ◽  
Empirical Relationship ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
29Si Nmr ◽  
Overhauser Effect ◽  
Coupling Parameters ◽  
Nuclear Overhauser ◽  
Silicon And Germanium

,The structure of the straight silanes SinH2n+2 (1 ≤ n ≤ 7) and of the branched isomers isotetrasilane, iso- and neopentasilane, 2-silyl- and 3-silylpentasilane, 2,3-disilyltetrasilane as well as 2-silyl- and 3-silylhexasilane could be unambiguously elucidated by 29Si NMR spectroscopy. Systematic trends in the chemical shift and coupling parameters were observed and an empirical relationship between δ(29Si) of a 29Si nucleus and the number of the neighbouring silicon atoms in αβor γposition is given. In 1H decoupled spectra the nuclear Overhauser effect on the 29Si resonance was found to increase with increasing distance of the 29Si nucleus from the end of the chain. A complete analysis of the multi spin systems of disilane, trisilane and isotetrasilane was performed and the signs of the 29Si,H- and H,H-long range coupling constants were determined with regard to the negative sign of 1J(29SiH).

Cross-linked polydimethylsiloxane colloid as novel contrast agent for gastrointestinal magnetic resonance imaging: Transient nuclear Overhauser effect within the interface

2020 ◽  
Vol 35 (2) ◽  
pp. 264-273
Author(s):  
Fu-Hu Su ◽  
Wang-Chuan Xiao ◽  
Sheann-Huei Lin ◽  
Qiyong Li
Keyword(s):  
Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Relaxation Times ◽  
Resonance Imaging ◽  
Transverse Relaxation ◽  
Overhauser Effect ◽  
Nuclear Magnetic Resonance Spectra ◽  
Relaxation Experiments ◽  
Longitudinal Relaxation ◽  
Nuclear Overhauser

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.

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