Paramagnetic effects in flavin spectroscopy. A 13C nuclear magnetic resonance study

1978 ◽  
Vol 56 (8) ◽  
pp. 1045-1051 ◽  
Author(s):  
Donald David Macmurchie ◽  
Robert John Cushley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Paramagnetic Species ◽  
Basic Solution ◽  
Line Broadening ◽  
Magnetic Resonance Study ◽  
Nmr Spectrum ◽  
13C Nuclear Magnetic Resonance ◽  
Specific Line ◽  
C Nmr

Experiments are described whose results indicate that semiquinones produced by intramolecular photoreduction of FMN in basic solution are responsible for specific line broadening observed in the 13C nmr spectrum. Tests with oxidizing agents as well as singlet and triplet quenchers are shown to support this theory rather than the proposition that the paramagnetic species effective in relaxation enhancement is a flavin triplet state. A mechanism for the production of semiquinones and their interaction with the FMN population is discussed.

A 1H and 13C nuclear magnetic resonance study of carnosine

1986 ◽  
Vol 64 (11) ◽  
pp. 2132-2138 ◽  
Author(s):  
Jan O. Friedrich ◽  
Roderick E. Wasylishen
Keyword(s):  
Chemical Shifts ◽  
Imidazole Ring ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Basic Solution ◽  
Magnetic Resonance Study ◽  
Nmr Spectrum ◽  
13C Nuclear Magnetic Resonance ◽  
Nmr Techniques ◽  
C Nmr

The proton and carbon-13 resonance signals of carnosine (β-alanyl-L-histidine) were unambiguously assigned using a variety of nmr techniques including proton–carbon chemical shift correlations, titrations of nmr chemical shifts, coupling constants, and isotope shifts. From the 13C nmr titration, carnosine's three pKa values were estimated to be 2.7, 7.1, and 10.6, and it was found that the imidazole ring existed predominantly as the 3-H tautomer in basic solution. Conformational information about the Cα—Cβ bond and about the N—Cα bond was deduced from observed 3J(C,H) and 3J(H,H) values. The 13C nmr spectrum of carnosine in solution is also compared with that obtained for a solid sample.

1H and 13C nuclear magnetic resonance study of the complexation of uranyl ion with malic acid

1982 ◽  
Vol 60 (8) ◽  
pp. 1007-1018 ◽  
Author(s):  
M. Teresa Nunes ◽  
Victor M. S. Gil ◽  
António V. Xavier
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Malic Acid ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Molar Ratios ◽  
Nmr Study ◽  
13C Nuclear Magnetic Resonance ◽  
Ph Range ◽  
C Nmr

A full pH range 1H and 13C nmr study was performed of the complexation of UO22+ with malic acid, for variable concentrations and molar ratios. Spectral evidence for the existence of at least five complexes was found, and their stoichiometry and dependence on pH were investigated. Information on the conformation of the bound ligand molecules was also obtained.

Hindered Rotation in Poly(N-acyl)iminoalkylenes - A 13C Nuclear Magnetic Resonance Study

1995 ◽  
Vol 50 (9) ◽  
pp. 1404-1411 ◽  
Author(s):  
Bernabé L. Rivas ◽  
Klaus Albert ◽  
Kurt E. Geckeler ◽  
Ernst Bayer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Cationic Polymerization ◽  
Nmr Spectra ◽  
Nuclear Magnetic Resonance Study ◽  
Side Chain ◽  
Magnetic Resonance Study ◽  
Hindered Rotation ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

AbstractPoly(N-acetyl)iminoethylene. poly(N-propionyl)iminoethylene and poly(N-acetyl)-2,2-dimethyliminoethylene were prepared by cationic polymerization in solution of 2-methyl- 2-oxazoline, 2-ethyl-2-oxazoline, and 2,4,4-trimethyl-2-oxazoline respectively. The 13C NMR spectra of the polymers obtained showed different sets of shifts for the carbon atoms of the backbone as well as for the N-acylimino side chain due to the restricted rotation of the Nacylimino group. The temperature dependence of the N-acylimino side chain signals showed a different coalescence behaviour depending on the substituents at both the main and the side chain.

A 1H and 13C nuclear magnetic resonance study of silicon and germanium chalcogenide derivatives

1979 ◽  
Vol 57 (24) ◽  
pp. 3253-3256 ◽  
Author(s):  
John E. Drake ◽  
Boris M. Glavinćevski ◽  
Robyn Humphries ◽  
Abdul Majid
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
General Pattern ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Methyl Substitution ◽  
Nmr Parameters ◽  
13C Nuclear Magnetic Resonance ◽  
Silicon And Germanium ◽  
C Nmr

This paper reports the 1H and 13C nmr parameters of the disilyl- and digermyl-chalcogenide species (MenH3−nM)2E, where M = Si, Ge; E = O, S, Se, Te and n = 0 to 3. The general pattern of changing shifts is markedly influenced by methyl substitution.

13C nuclear magnetic resonance study of cyclodipeptides containing 13C enriched hydrophobic amino acids

1980 ◽  
Vol 45 (2) ◽  
pp. 482-490 ◽  
Author(s):  
Jaroslav Vičar ◽  
François Piriou ◽  
Pierre Fromageot ◽  
Karel Bláha ◽  
Serge Fermandjian
Keyword(s):  
Amino Acids ◽  
Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Magnetic Resonance Study ◽  
Side Chain Conformation ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrophobic Amino Acids

The diastereoisomeric pairs of cyclodipeptides cis- and trans-cyclo(Ala-Ala), cyclo(Ala-Phe), cyclo(Val-Val) and cyclo(Leu-Leu) containing 85% 13C enriched amino-acid residues were synthesized and their 13C-13C coupling constants were measured. The combination of 13C-13C and 1H-1H coupling constants enabled to estimate unequivocally the side chain conformation of the valine and leucine residues.

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