Investigation on the structure of dipeptides: A DFT study

We present here the hybrid DFT level study of a series of dipeptide at 6-31g∗ basis. A rigorous computation has been performed on a series of dipeptide (keeping valine as a fixed component in the N-terminus and the component in the C-terminus are varied with eight different combinations) to investigate various geometrical parameters to understand the effect of amino acid sequence in the dipeptides. Bond lengths, bond angles have been reported. Geometry around α-carbon atom is discussed. The analysis of dihedral angles shows deviations from planarity. This has been explained in terms of the cumulative effect of steric hindrance of -R group and H-bonding. To get an idea about its conformational stability, a rigid potential energy scan has also been performed on valine by rotating -COOH and -CH(CH3)2 groups separately.