The origin of vibrational mode couplings in various secondary structural motifs of polypeptides

AUTOR(ES)

Moran, Andrew

FONTE

National Academy of Sciences

RESUMO

Electrostatic (through-space) and covalent (through-bond) contributions to couplings involving the CO and C—N vibrational stretching modes of the amide group in the α-helix and the parallel and antiparallel β-sheet structures of alanine polypeptides are analyzed. Coupling constants computed at the density functional theory level are compared with the transition dipole coupling model and the complete electrostatic interaction between transition densities. We find that the transition densities of CO modes are localized, and the electrostatic mechanism then holds. In contrast, the C—N mode transition densities are delocalized, and covalent contributions to the coupling are significant.

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