Self Association of Folic Acid in Aqueous Solution by Proton Magnetic Resonance

1972 ◽  
Vol 50 (14) ◽  
pp. 2357-2363 ◽  
Author(s):  
Yui-Fai Lam ◽  
George Kotowycz
Keyword(s):  
Aqueous Solution ◽  
Folic Acid ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Disodium Salt ◽  
Intermolecular Association ◽  
Self Association ◽  
Hydrophobic Portion ◽  
Proton Chemical Shifts

Proton magnetic resonance experiments on the disodium salt of folic acid in aqueous solutions (pD 7.1) indicate that the folate ion exists in an unfolded, extended conformation in solution. However, based on a temperature and concentration dependence of the proton chemical shifts, folate ions are involved in intermolecular association consisting of a vertical stacking interaction. A stacking model is proposed for the association with the hydrophilic ends of the molecule alternating in orientation with respect to the hydrophobic portion of the neighboring molecules.

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.

A Proton Magnetic Resonance Study of the Ultraviolet Photoproduct of d(TpT) in Aqueous Solution

1975 ◽  
Vol 53 (8) ◽  
pp. 1193-1203 ◽  
Author(s):  
Frank E. Hruska ◽  
Donald J. Wood ◽  
Kelvin K. Ogilvie ◽  
James L. Charlton
Keyword(s):  
Aqueous Solution ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Magnetic Resonance Study ◽  
Parent Molecule ◽  
Terminal Fragment ◽  
Proton Magnetic Resonance Study ◽  
Cyclobutane Ring

The p.m.r. data of d(TpT) and its predominant u.v. photoproduct d(T[p]T) in aqueous solution are compared. The data are consistent with the presence of a cis-syn cyclobutane ring in d(T[p]T). Consideration of the H1′ chemical shifts leads to the conclusion that changes in the sugar–base torsion angle of both nucleotide fragments of the parent molecule are required to bring the thymine bases into alignment for photodimerization. The coupling constants indicate that the conformation of the 5′-terminal fragment is only slightly affected by the cyclobutane ring formation. Photodimerization brings about a distortion of the sugar pucker in the 3′-terminal fragment. In this fragment both the gauche-gauche and gauche-trans conformers are significantly populated whereas the trans-gauche form is excluded.

THE PROTON MAGNETIC RESONANCE SPECTRA AND TAUTOMERIC EQUILIBRIA OF ALDOSES IN DEUTERIUM OXIDE

1966 ◽  
Vol 44 (3) ◽  
pp. 249-262 ◽  
Author(s):  
R. U. Lemieux ◽  
J. D. Stevens
Keyword(s):  
Aqueous Solution ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Deuterium Oxide ◽  
Chair Conformation ◽  
Hydroxyl Group ◽  
Equatorial Orientation ◽  
Tautomeric Equilibria ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of D-xylose, D-lyxose, D-arabinose, D-ribose, D-glucose, D-mannose, and D-galactose were determined at 100 Mc.p.s. in deuterium oxide. The chemical shifts and structures of a number of ring protons in these compounds were determined either by spin-decoupling experiments or by synthesis of specifically deuterated compounds. The proton magnetic resonance parameters are shown to provide considerable information on the conformations and tautomeric equilibria for the sugars in aqueous solution. It is concluded that, for aldopyranoses in a chair conformation, the chemical shift of equatorial protons at a given position is virtually independent of configurational changes at other positions. However, an axial proton is shielded about 0.3 p.p.m. less by an axial hydroxyl group at a neighboring position than when the hydroxyl group is in an equatorial orientation. An axial hydroxyl group leads to deshielding of an opposing axial proton by about 0.35 p.p.m. By using the chemical shifts of the ring protons of β-D-xylopyranose and β-D-glucopyranose as reference point, the chemical shifts of protons in other pyranose structures could be anticipated to within a useful degree of accuracy.Evidence was obtained that D-ribose and 2-deoxy-D-ribose exist in aqueous solution both in the pyranose and in the furanose forms. None of the other pentoses showed readily detectable amounts of the furanose forms at equilibrium. Although D-allose does not give readily detectable amounts of the furanose forms when at equilibrium in aqueous solutions, D-altrose does. D-Talose showed only two forms, one of which was the β-pyranose structure.

The Association between Purine Nucleosides and Benzene in Aqueous Solution, Studied by Proton Magnetic Resonance and Nuclear Overhauser Enhancements

1973 ◽  
Vol 28 (7-8) ◽  
pp. 361-369 ◽  
Author(s):  
Hans-Dietrich Lüdemann ◽  
Eberhard v. Goldammer
Keyword(s):  
Aqueous Solution ◽  
Magnetic Resonance ◽  
Aqueous Solutions ◽  
Torsion Angle ◽  
Proton Magnetic Resonance ◽  
Solvent Dependence ◽  
Enhancement Factors ◽  
Pmr Spectra ◽  
Self Association ◽  
Nuclear Overhauser

Abstract The dependence of the PMR spectra of three purine nucleosides (inosine, adenosine and deoxyadenosine) on temperature, concentration and addition of benzene (0.12 molal) has been investigated in aqueous solution. The interaction of benzene with the nucleosides is deduced from the spectra. Enthalpies of self association have been determined as 2.2± 0.1 kcal·mole-1 for dA and I. The corresponding values obtained for hetero association with benzene are 2.7 ± 0.2 kcal·mole-1 for dA and 2.3± 0.2 kcal·mole-1 for I. The formation of edge to face complexes is concluded. Additional evidence for this type of hetero association has been obtained from the concentration and solvent dependence of the nuclear Overhauser enhancements (NOE) of solutions of the nucleosides. The enhancement factors of aqueous solutions of dA and I depend on the concentrations of the nucleosides. In solutions containing I the NOE found previously in DMSO and the NOE observed in D2O differ significantly 1. The results obtained can be explained by a change of the average glycosyl torsion angle of approximately 10° to 15° in the two solvents.

Proton Magnetic Resonance Studies of Dinucleotide Conformation in Aqueous Solution. 2′-Deoxythymidylyl-(3′,5′)-2′-deoxy-3′-thymidylate, d(TpTp)

1975 ◽  
Vol 53 (18) ◽  
pp. 2781-2790 ◽  
Author(s):  
Donald J. Wood ◽  
Kelvin K. Ogilvie ◽  
Frank E. Hruska
Keyword(s):  
Aqueous Solution ◽  
Spectral Analysis ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Gauche Conformation ◽  
Magnetic Resonance Studies ◽  
Important Observation ◽  
Conformational Properties

Proton magnetic resonance studies of 2′-deoxythymidine, its 3′-and 5′-monophosphate, its 3′,5′-diphosphate, and the dimer molecules d(TpT) and d(TpTp) in aqueous solution are de scribed. Spectral analysis yields 1H–1H and 1H–31P coupling constants and 1H chemical shifts which can be discussed in terms of the conformational properties of the nucleoside fragments. An important observation is the apparent phosphate–phosphate interaction in a 3′,5′-diphosphate fragment which stabilizes the gauche-gauche conformation about the C4′—C5′ bond.

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