Charge-transfer transitions in protein circular dichroism spectra

摘要

Two peptide dimers (N-acetyl-glycine-N'methylamide and a hydrogen-bonded dimer of N-methylacetamide) were considered as models for charge-transfer transitions in proteins. Electronic structure calculations at the CASSCF and CASPT2 levels of theory were performed to determine the transition densities and excitation energies for these systems in two separate configurations. These transition properties were incorporated within the matrix method which couples the individual monomer transitions in a protein. The effects of including the charge-transfer transitions on circular dichroism spectra were considered for ideal α-helix and β-sheet structures.