Conformational Study of a Series of Dipeptides with Glycine

Abstract

DFT calculations has been done by applying 6-31G* basis set on a series of dipeptides with glycine fixed at N-terminus position and the C-terminus position varied with eight different amino acids to get the optimized structures. Different geometrical parameters (bond angle, bond length, geometry around the α-carbon atom) are thoroughly investigated to study the effect of amino acid sequence on dipeptide. From dihedral angle data analysis it can be said that the combined effect of the sterric hindrance of – R group and hydrogen bonding is responsible for the deviation of amide plane from planarity. A potential energy scan is performed on glycine by rotating - COOH and – NH2 groups separately, keeping the rest of the molecule fixed to get some idea about the conformational stability. The energy barrier to rotation is also calculated.