Vibrational Dynamics and Heat Capacity of Poly(L-lysine)

Poly(L-lysine) is a polypeptide having a bulky hydrophobic side chain. A systematic study of the full vibrational dynamics, including phonon dispersion, for the α-helical form of this biopolymer has been reported using Wilson’s GF matrix method as modified by Higgs for an infinite polymeric chain. The calculated frequencies explain well the IR and Raman spectra. A comparison of the amide modes with other α-helical polypeptides is reported here. Spectral frequencies have been obtained for the N-deuterated species to check the validity of force field and correctness of assignments. Heat capacity has also been calculated from dispersion curves via density-of-states using Debye relation in the temperature range 50–500 K. The calculated values are found to be in close agreement with the recent experimental data of Roles et al. [Biopolymers, 33, 753 (1993)].