Nuclear magnetic resonance studies of the microscopic protonation of L-cysteine |
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Authors: | D B Walters D E Leyden |
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Affiliation: | Chemistry Department, University of Georgia, Athens, Georgia-30602 U.S.A. |
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Abstract: | The protonation scheme of L-cysteine has been investigated by nuclear magnetic resonance. Chemical shift data as a function of pH are given for L-cysteine, L-cysteine methyl ester and S-methyl-L-cysteine. Use of derivatives of L-cysteine permits determination of the effect of protonation of the amino, sulfhydryl and carboxylic sites on the chemical shift of the -CH and -CH2 protons. On the basis of these results, a set of simultaneous equations was written whose solution yielded the fraction of protonation of each site upon the addition of n equivalents of acid to the initially completely deprotonated molecule. |
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