For seven representative tripeptide conformations, we carried out ab initio geometry
optimizations and vibrational analyses. By using the Hessian matrix reconstruction method
developed in the present paper, both the diagonal and off-diagonal coupling force constants
of a given tripeptide were calculated and the relationship between the three-dimensional
conformation and local amide I mode frequency was discussed. Isotope labeling effects on
both the amide I local and normal modes were elucidated. It was found that the C= O bond …