Theoretical studies on the conformation of peptides in solution I. Conformation of N-acetyl glycine N-methyl amide in solution

Abstract

A theoretical prediction of the most preferred conformation of N-acetyl glycine N-methyl amide in CCl4 is attempted. The calculation of the intrinsic or intramolecular interaction energies employs the method of partitioned energy potential. The intramolecular electrostatic energies include terms up to octopole segmental moments. It is pointed out that a truncation of the multipole interaction series at the monopole term is unjustified in this case. The calculation of intermolecular interactions with the environment is based on the method of continuum reaction field, including electrostatic, dispersion and cavity terms, which depend on the conformations through molecular dipole moments, molecular volume, and molecular exposed surface area. The most stable conformation predicted in this study (Φ = 255°, Φ = 105°) closely corresponds to the minimum in intramolecular electrostatic interactions. For other solvents intramolecular interactions and solvent effects may be of comparable importance in determining the most stable conformation of the solute molecule.