Solvent-Assisted Rearrangements between Tautomers of Protonated Peptides

Autor:	Ivan K. Chu, Tamer Shoeib, K. W. Michael Siu, Alwin Cunje, Christopher F. Rodriquez, and Alan C. Hopkinson
Rok vydání:	2000
Předmět:	Solvent Formamide Bond length chemistry.chemical_compound Chemistry Stereochemistry Amide Molecule Peptide bond Protonation Physical and Theoretical Chemistry Medicinal chemistry Tautomer
Zdroj:	The Journal of Physical Chemistry A. 104:5023-5028
ISSN:	1520-5215 1089-5639
DOI:	10.1021/jp9940203
Popis:	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 A, whereas protonation at the carbonyl oxygen leads to a decrease in the C-N bond distance from 1.336 to 1.321 A. Solvent-catalyzed tautomerism may play an important role in the fragmentation of electrosprayed, protonated peptides in the gas phase.
Databáze:	OpenAIRE
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