Vibrational dynamics of poly(L‐histidine)

Abstract

Normal mode analysis and their dispersion for poly(L-histidine) (PLH) are reported by using Urey Bradley force field and Fourier Transform IR PLH exists in the a helical form. There are 17 atoms in one residue, which gives rise to 51 dispersion curves. To simplify, it is convenient to discuss the normal frequencies under three separate heads namely amide modes, side chain modes, and mixed mode. The calculated frequencies are found to be in reasonably good agreement with the Fourier Transform IR spectra. There exists exchange of character, attraction, and repulsion for selective dispersion curves with change in the phase value. Contributions to the heat capacity were calculated separately for the side chain, backbone, and mixed modes. The major contribution comes from the side chain and mixed modes. The sum of these three contributions gives the total heat capacity, which is in agreement with the reported experimental value.