Comparison of conformational behavior of the short alanine peptides and their boron analogues

摘要

Conformational behavior of short terminally blocked alanine peptides up to three residues has been analyzed by means of a new computer program V_(ADER). The program is based on Single-Coordinate-Driving method and it employs quantum chemistry energy calculation. The semiempirical AMl method has been used in this study. Conformational behavior of alanine peptides has been compared with their boron analogues. It has been found that: 1. Semiempirical AMl method creates an artifact in energy calculation of boron analogues for geometries where the dihedral angles are around zero value. In such a case, ab initio methods have to be employed. 2. Boron analogues appear conformationally more flexible. They exhibit much higher number of energy minima along the PES. It has also been concluded that the program V_(ADER) is able to give quite a good estimation of stationary points. All stationary points found by V_(ADER) for monomers and those stationary points with relative energy less that 2.0 kcal/mol found for the dimers were subjected to frequency analysis of the Hessian matrix. In all cases, they were confirmed as stationary points of the same category as predicted by V_(ADER).