Vectorial proton transfer among carbonyl oxygen atoms was studied in two models of tripeptide via quantum chemical calculations using the hybrid B3LYP functional and the 6-31++G basis set. Two principal proton transfer pathways were found: a first path involving isomerization of the proton around the double bond of the carbonyl group, and a second based on the large conformational flexibility of the tripeptide model where all carbonyl oxygen atoms cooperate. The latter pathway has a rate-determining step energy barrier that is only around half of that for the first pathway. As conformational flexibility plays a crucial role in second pathway, the effect of attaching methyl groups to the alpha carbon atoms was studied. The results obtained are presented for all four possible stereochemical configurations.

• MeSH
• Protein Conformation MeSH
• Models, Molecular * MeSH
• Pliability MeSH
• Oligopeptides chemistry   MeSH
• Protons * MeSH
• Stereoisomerism MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Oligopeptides MeSH
• Protons * MeSH