Theoretical study on the nature of the hydrogen bonds in an α-helical polymer and its model systems

Abstract

The semi-empirical CNDO/2 SCF (self-consistent field) MO (molecular orbital) method using the tight-binding approximation for polymers was applied to polyglycine. The CNDO/2 calculations were also performed on model systems of this polymer. From the calculated results, the characteristics of the hydrogen bond in the α-helix were derived by comparison with those in the model systems. It was found that the hydrogen bond in the α-helix is very stable against proton transfer whereas the hydrogen bond in the model system is not so stable; this characteristic difference between the two systems is due to the coupling of two π-electron systems through hydrogen bonding in the α-helix.