EFFECT OF INTRACHAIN HYDROGEN-BOND ON THE FORMATION OF L-AMINO-ACIDS ALONG ALPHA-HELIX OF PEPTIDE

The model of right-handed alpha helix of peptide, in which the intrachain hydrogen bonds between amino acid residues are in the direction of the axis of the helix, is used to compute the energy differences between D- and L-form residues. The dominant intramolecular interactions involved are the Coulomb interaction for the residues with charged and polarized R group and van der Waals interaction for the hydrophobic residues respectively. The results obtained show that the energy states of L-forms are lower than those of the corresponding D-forms. Therefore, L-form states are more stable. The racemization of the amino add after the residue has been dislocated from the peptide chain is interpreted as the consequence of the parity conservation of the electromagnetic interaction.