Violation of the fluctuation-dissipation theorem in a protein system

TL;DR

This study uses molecular dynamics simulations to show that the fluctuation-dissipation theorem is violated in a quenched protein system, indicating an effective temperature higher than the environment's, with implications for energy transduction.

Contribution

It demonstrates the violation of the fluctuation-dissipation theorem in a protein model and introduces the concept of an effective temperature related to energy transduction.

Findings

Fluctuation-dissipation relation is violated in quenched myosin.

Effective temperature of myosin exceeds environmental temperature.

Relation between effective temperature and ATP hydrolysis energy transduction.

Abstract

We report the results of molecular dynamics simulations of the protein myosin carried out with an elastic network model. Quenching the system, we observe glassy behavior of a density correlation function and a density response function that are often investigated in structure glasses and spin glasses. In the equilibrium, the fluctuation-response relation, a representative relation of the fluctuation-dissipation theorem, holds that the ratio of the density correlation function to the density response function is equal to the temperature of the environment. We show that in the quenched system that we study, this relation can be violated. In the case that this relation does not hold, this ratio can be regarded as an effective temperature. We find that this effective temperature of myosin is higher than the temperature of the environment. We discuss the relation between this effective temperature and energy transduction that occurs after ATP hydrolysis in the myosin molecule.