Quantum Mechanical Partitioning of the Energies of Polypeptides: Conformational Study of Polyglycine

The total energy of a polypeptide is partitioned into the interaction energies between pairs of residues. The interactions between adjacent residues are evaluated by quantum mechanical methods. An empirical hydrogen bond potential based on the quantum mechanical interaction between amide units is formulated and used to calculate the interaction energy between nonadjacent residues. This treatment is used to study regular helical conformations of an isolated single strand of polyglycine. The a: helix is found most stable while the 310 and 27 helices are also low-energy structures. The calculated results are compared to those obtained via classical partitioning procedures as well as experiment