Determination of the molecular conformation of uridine in aqueous solution by proton magnetic resonance spectroscopy. Comparison with β-pseudouridine

1970 ◽  
Vol 48 (18) ◽  
pp. 2866-2870 ◽  
Author(s):  
Barry J. Blackburn ◽  
Arthur A. Grey ◽  
Ian C. P. Smith ◽  
Frank E. Hruska
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Molecular Conformation ◽  
Chemical Shifts ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Resonance Spectroscopy ◽  
Proton Coupling ◽  
Anti Conformation

A complete analysis of the 220 MHz proton magnetic resonance spectrum of aqueous uridine is reported. From the data a model for the molecular conformation is presented and compared with that of β-pseudouridine. It is concluded that in both compounds the ribose rings are in rapid equilibrium between classical puckered structures. The temperature-independence of the ribose proton coupling constants and chemical shifts suggests that all the conformers involved in this equilibrium have very similar energies. Both compounds exhibit a preference for the gauche–gauche rotamer about the exocyclic 4′—5′ bond; this conclusion is shown to be independent of the parameters in the Karplus equation or the energy minima chosen for the rotamers. The anti conformation of the uracil base is shown to exist in both compounds. It is proposed that the special structural significance of β-pseudouridine in transfer RNA must be due to the potential hydrogen bond that may be formed by the nitrogen atom at position one in uracil.

Nuclear magnetic resonance spectra of the epihalohydrins. I. Signs of long-range spin–spin coupling constants in epichlorohydrin

1970 ◽  
Vol 48 (7) ◽  
pp. 1033-1045 ◽  
Author(s):  
C. J. Macdonald. ◽  
T. Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Program Analysis ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Complete Analysis ◽  
Acetonitrile Solution ◽  
Ambiguous Result

The complete analysis of the proton magnetic resonance spectrum of epichlorohydrin as 10 mole% solutions in benzene and in acetonitrile is reported. Extensive tickling experiments demonstrate that the cisoid coupling constants over four bonds are negative, while the corresponding transoid coupling constants are positive. Detailed results for the benzene solution, in which the non-equivalent protons of the —CH2Cl moiety have almost identical chemical shifts, show that although all the resonances may be unequivocally identified and measured to a high order of precision (± 0.03 Hz), an iterative computer fit (LAOCOON-3) has a larger uncertainty for the derived parameters than indicated by the "probable errors" furnished by the computer program. Analysis of the acetonitrile solution, however, furnishes a less ambiguous result. In addition, it is noted that use of relative apparent intensities of resonance peaks can lead to the wrong sign of those coupling constants whose magnitudes are near zero.

The Proton Magnetic Resonance Spectrum of p-Methylbenzylbromide, Conformational Preference of the Bromomethyl Rotor

1974 ◽  
Vol 52 (20) ◽  
pp. 3489-3494 ◽  
Author(s):  
Kalvin Chum ◽  
J. Brian Rowbotham ◽  
Ted Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Alternative Model ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
The Other ◽  
Complete Analysis ◽  
Conformational Preference

A complete analysis is given of the nine-spinproton magnetic resonance spectrum of p-methylbenzyl bromide as a 20 mol% solution in acetone-d6 The long-range coupling constants between methyl and ring protons are the same as those in toluene. The coupling constants between the methylene protons and the other protons in the molecule are consistent with a two-fold barrier of 500 ± 200 cal/mol for the bromomethyl group, the preferred conformation having the C—Br bond in a plane perpendicular to the aromatic plane. An alternative model, in which a C—H bond of the bromomethyl rotor prefers the aromatic plane to the extent of 3 kcal/mol, is considered unlikely.

Studies of specifically fluorinated carbohydrates. Part II. Nuclear magnetic resonance studies of pentopyranosyl fluoride derivatives

1969 ◽  
Vol 47 (1) ◽  
pp. 19-30 ◽  
Author(s):  
L. D. Hall ◽  
J. F. Manville
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Magnetic Resonance Studies ◽  
Conformational Model ◽  
Nuclear Magnetic

Detailed studies, by 1H and 19F nuclear magnetic resonance spectroscopy, of a series of fully esterified pentopyranosyl fluorides, show that all such derivatives favor that conformer in which the fluorine substituent is axially oriented. This conclusion is supported by separate considerations of the vicinal and geminal19F–1H and 1H–1H coupling constants, of the long-range (4J) 1H–1H and 19F–1H coupling constants and of the 19F chemical shifts. The limitations of the above conformational model are discussed.

Protonenresonanz-Spektroskopie ungesättigter Ringsysteme I

1965 ◽  
Vol 20 (10) ◽  
pp. 948-956 ◽  
Author(s):  
Harald Günther
Keyword(s):  
Magnetic Resonance ◽  
Concentration Dependence ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Electron System ◽  
Coupling Constants ◽  
Resonance Signal ◽  
Aromatic Character ◽  
Additional Support ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of 1.6-methano- and 1.6-oxido-cyclodecapentaene are described and analyzed in terms of chemical shifts and coupling constants. The results are discussed in connection with the structure and possible aromatic character of these compounds. Measurements of the concentration dependence of the chloroform resonance signal in solutions of both compounds give additional support for the presence of a delocalized 10 π-electron system.

Nuclear magnetic resonance studies of the solution chemistry of metal complexes. XIV. The aqueous chemistry of trimethyllead(IV) and its carboxylic acid complexes

1977 ◽  
Vol 55 (18) ◽  
pp. 3255-3260 ◽  
Author(s):  
T. L. Sayer ◽  
S. Backs ◽  
C. A. Evans ◽  
E. K. Millar ◽  
D. L. Rabenstein
Keyword(s):  
Carboxylic Acid ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
Formation Constants ◽  
Solution Chemistry ◽  
Resonance Spectroscopy ◽  
Coupling Constant ◽  
Proton Coupling

The aqueous solution chemistry of the trimethyllead(IV) species and the trimethyllead(IV) complexes of six carboxylic acids of pKa values ranging from 2.75 to 4.95 has been investigated by proton magnetic resonance spectroscopy. Equilibrium constants for the reaction of (CH3)3Pb+ with hydroxide ion to form (CH3)3PbOH and ((CH3)3Pb)2OH+, and the formation constants of the carboxylic acid complexes were determined from the pH dependence of the chemical shift of the methyl protons of trimethyllead. The formation constants of the complexes increase as the pKa of the ligand increases. The lead-207-proton coupling constant was found to be insensitive to complexation.

Effect of solvent and anion upon the proton magnetic resonance spectrum of the 1-methylpyridinium ion

1968 ◽  
Vol 46 (17) ◽  
pp. 2787-2791 ◽  
Author(s):  
W. F. Reynolds ◽  
U. R. Priller
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Proton Magnetic Resonance Spectrum ◽  
Concentrated Solutions ◽  
Nonpolar Medium ◽  
Ion Proton ◽  
Acetonitrile Solutions ◽  
Proton Chemical Shifts ◽  
Pyridinium Ion

The proton magnetic resonance spectra of 1-methylpyridinium bromide and iodide have been measured over a range of concentrations in different solvents. It is found that, with the exception of acetonitrile solutions, the infinite dilution chemical shifts are related to solvent dielectric constant. Extrapolated shifts for a nonpolar medium agree with previously calculated chemical shifts for the pyridinium ion. Proton chemical shifts in concentrated solutions are affected by cation–anion interactions. These interactions are interpreted in terms of ion pair formation.

scholarly journals Carbon-13 nuclear magnetic resonance spectra of oxazoles

1979 ◽  
Vol 57 (23) ◽  
pp. 3168-3170 ◽  
Author(s):  
Henk Hiemstra ◽  
Hendrik A. Houwing ◽  
Okko Possel ◽  
Albert M. van Leusen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Proton Coupling ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nmr spectra of oxazole and eight mono- and disubstituted derivatives have been analyzed with regard to the chemical shifts and the various carbon–proton coupling constants of the ring carbons. The data of the parent oxazole are compared with thiazole and 1-methylimidazole.

The analysis of the proton magnetic resonance spectra of heteroaromatic systems. V. Diazanaphthalenes

1965 ◽  
Vol 18 (5) ◽  
pp. 707 ◽  
Author(s):  
PJ Black ◽  
ML Heffernan
Keyword(s):  
Carbon Tetrachloride ◽  
Magnetic Resonance ◽  
Long Range ◽  
Iterative Procedure ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Direct Calculation ◽  
Coupling Constants ◽  
Dilute Solutions ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of the four isomeric diazanaphthalenes, quinoxaline, phthalazine, quinazoline, and cinnoline, all as dilute solutions in carbon tetrachloride and acetone, have been investigated at 100 Mc/s. The chemical shifts and coupling constants have been obtained by direct calculation or, where appropriate, by an iterative procedure. Long-range coupling constants between protons separated by five and six bonds have been observed.

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