Proton Affinity and Structural Differences in Oligopeptides Determined by the Extended Cooks Kinetic Method and IRMPD Spectroscopy

摘要

Using the extended Cooks' kinetic method and CID single reference bracketing techniques, A_(2,3)X peptides were demonstrated to be more basic than XA_(2,3) peptides. Theoretical IR spectra of selected low energy conformers match IRMPD spectra very well. Molecular modeling suggest that A_(2,3)Dap peptides adopt a helix-like conformation while DapA_(2,3) peptides adopt random coils. Cooperative interactions between the helix macrodipole and charge site in A_(2,3)X peptides presumed to be the source of higher basicity.