| Autor: |
Rodriquez, C. F., Cunje, A., Shoeib, T., Chu, I. K., Hopkinson, A. C., Siu, K. W. M. |
| Zdroj: |
The Journal of Physical Chemistry - Part A; June 2000, Vol. 104 Issue: 21 p5023-5028, 6p |
| Abstrakt: |
The presence of an interacting water or methanol molecule has been shown to catalyze the 1,3-proton shift in a peptide linkage between the tautomers of protonated formamide and glycylglycylglycine. Density functional theory calculations at the B3LYP/6-31++G(d,p) level of theory show that, for glycylglycylglycine, the forward barrier of this shift decreases from a free energy at 298 K of 39.6 kcal/mol in the absence of solvent to 26.7 kcal/mol in the presence of water and to 22.0 kcal/mol in the presence of methanol. Protonation at the amide nitrogen of the second residue results in a large increase in the C−N bond distance from 1.336 to 1.519 Å, whereas protonation at the carbonyl oxygen leads to a decrease in the C−N bond distance from 1.336 to 1.321 Å. Solvent-catalyzed tautomerism may play an important role in the fragmentation of electrosprayed, protonated peptides in the gas phase. |
| Databáze: |
Supplemental Index |
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