Soliton Dynamics in the Eilbeck-Lomdahl-Scott Model for Hydrogen-Bonded Polypeptides

Abstract

The transfer of vibrational energy along quasi-one-dimensional molecular systems such as chains of hydrogen-bonded peptide groups (PG’s) by means of self-trapped states (solitary waves or solitons) was first suggested by Davydov and Kislukha¹ in order to explain how the energy released by hydrolysis of adenosine triphosphate can be localized and moved along proteins providing important biological processes^{2, 3}. The soliton formation in this model¹,³ is due to the coupling of the high-frequency intramolecular C = 0 stretch mode (the amide-I excitation, with frequency about 1665 cm⁻¹) in PG’s and the acoustic mode (the intermolecular relative displacement field) of PG’s with associated side groups through the dependence of the amide-I energy on the distances to neighbouring left and right molecules (PG’s). After the numerous theoretical studies³ on this acoustic-mode-coupled soliton theory, the experimental results performed by Careri and cowor-kers⁴ for crystalline acetanilide (ACN) became very important for the question of the existence of self-trapped localized states in quasi-one-dimensional molecular systems since the material ACN contains chains of hydrogen-bonded PG’s similar to protein molecules.