Logarithmic decay in single-particle relaxations of hydrated lysozyme powder

TL;DR

This study uses molecular dynamics simulations to reveal that hydrated lysozyme exhibits logarithmic decay in amino acid and hydrogen atom dynamics over picoseconds to nanoseconds, resembling glass-forming liquids.

Contribution

It demonstrates the presence of logarithmic decay in protein dynamics, linking biological molecules to glassy relaxation behaviors predicted by mode coupling theory.

Findings

Logarithmic decay observed over 3 decades of time.

Resembles beta-relaxation in glass-forming liquids.

Suggests analogy between protein and glass dynamics.

Abstract

We present the self-dynamics of protein amino acids of hydrated lysozyme powder around the physiological temperature by means of molecular dynamics (MD) simulations. The self-intermediate scattering functions (SISF) of the amino acid residue center-of-mass and of the protein hydrogen atoms display a logarithmic decay over 3 decades of time, from 2 picoseconds to 2 nanoseconds, followed by an exponential alpha-relaxation. This kind of slow dynamics resembles the relaxation scenario within the beta-relaxation time range predicted by the mode coupling theory (MCT) in the vicinity of higher-order singularities. These results suggest a strong analogy between the single-particle dynamics of the protein and the dynamics of colloidal, polymeric and molecular glass-forming liquids.