The Davydov Hamiltonian leads to stochastic energy transfer in proteins

Abstract

A new set of equations of motion for the semiclassical Davydov model at finite temperature, which satisfy both the classical statistics of the lattice motion and the quantum statistics of the quasiparticle, is used. The Davydov soliton, defined as the exact one-quantum ground state of the Davydov Hamiltonian, is shown to disappear in the subpicosecond timescale. However, in contrast with previous simulations, the quasiparticle states are essentially localised at 310 K, and the Davydov model remains a possible mechanism for energy transfer in proteins. The dynamics at biological temperatures consists of a stochastic hopping of the quantum quasiparticle from site to site. The biological implications are discussed and in order to stimulate experimental tests of the theory the predicted absorption spectrum of the Davydov model is presented.