Proton transfer in histidine hydrochloride induced by a dipolar aprotic solvent

A 1H NMR study of histidine hydrochloride dissolved in water/dimethyl sulfoxide mixtures gives evidence that dimethyl sulfoxide is able to induce a proton transfer from the imidazolinium nitrogens (mainly N3) to the carboxylate group when its mole fraction becomes greater than 42%. The new tautomeri...

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Bibliographic Details
Published in:The Journal of biological chemistry 1981-08, Vol.256 (16), p.8569-8572
Main Authors: Halle, J C, Simonnin, M P
Format: Article
Language:English
Subjects:
Dimethyl Sulfoxide
Histidine
Hydrogen-Ion Concentration
Kinetics
Magnetic Resonance Spectroscopy
Mathematics
Solvents
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Summary:A 1H NMR study of histidine hydrochloride dissolved in water/dimethyl sulfoxide mixtures gives evidence that dimethyl sulfoxide is able to induce a proton transfer from the imidazolinium nitrogens (mainly N3) to the carboxylate group when its mole fraction becomes greater than 42%. The new tautomeric equilibrium AH2++- in equilibrium AH2+ is quantitatively studied as a function of the solvent composition. In pure dimethyl sulfoxide, this equilibrium is strongly biased toward the monocation AH2+, which represents 91% of the total histidine hydrochloride.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(19)68881-2