Mechanism of Proton Transfer in Short Protonated Oligopeptides. 1. N-Methylacetamide and N2-Acetyl-N1-methylglycinamide
| Authors | |
|---|---|
| Year of publication | 2003 |
| Type | Article in Periodical |
| Magazine / Source | J. Phys. Chem. A |
| MU Faculty or unit | |
| Citation | |
| Web | http://dx.doi.org/10.1021/jp027689+ |
| Field | Nuclear and quantum chemistry, photochemistry |
| Keywords | proton transfer; proton exchange; proton interaction; DFT |
| Description | A study of proton transfer in models of a single peptide unit (N-methylacetamide) and diamide (N2-acetyl-N1-methylglycinamide) as well as the influence of a single water molecule on proton transfer is presented here. Three proton pathways in protonated N-methylacetamide are considered: isomerization, inversion, and 1,3-proton shift. The isomerization step exhibits the lowest energy barrier. When a single water molecule was added, no significant influence on proton isomerization was observed. In the diamide model, the isomerization-jump mechanism of proton transfer along diamide carbonyl oxygens was inspected, and the proton isomerization steps were found to be the most energy-demanding processes (~17 kcal mol-1). The presence of a single water molecule leads to a different, lower-energy-barrier proton-transfer mechanism with proton exchange. The highest energy barrier is only 7.6 kcal mol-1. Possible competing pathways are also discussed. |
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