Potential functions for hydrogen bond interactions. I. A modified Lippincott-Schroeder potential function for NH...O interaction between peptide groups

Abstract

The usual Lippincott-Schroeder (L...S) potential function has been modified to take care of bent hydrogen bonds and a procedure has been developed to obtain the interaction energy as a function of R, the N...O distance, and θ, the angle between the N---H and N...O directions. The function is designed to fit the experimental observations on proton dynamics, like infrared spectra, and to have a specified minimum energy (V_min) at R_min for θ = o°. Depending on the way in which the hydrogen bond energy (V_hb) merges with the non-bonded interaction between N, H and O (V_nb), different values of the parameters, A, b, B in the L...S potential function can be obtained. The best values are determined by making a comparison between the observed distribution of data in the (R, θ) plane, and the theoretically predicted one, using the function V_hb(R,θ)). Both the X-ray data compiled by Ramachandran and Ramakrishnan², and the set of available neutron diffraction data analysed in this paper are used for this purpose.