Protein Dynamical Transition in Terahertz Dielectric Response

TL;DR

This study detects the 200 K protein dynamical transition in terahertz dielectric response, revealing anharmonicity and subpicosecond motions, challenging previous harmonic assumptions and expanding understanding of protein dynamics.

Contribution

First observation of the protein dynamical transition in terahertz dielectric response, linking dielectric properties to protein motions at subpicosecond scales.

Findings

Dielectric loss $ ext{ε}''$ increases sharply above 200 K.

Anharmonicity in protein motions is indicated below 200 K.

Protein motions extend to subpicosecond time scales.

Abstract

The 200 K protein dynamical transition is observed for the first time in the teraherz dielectric response. The complex dielectric permittivity $\epsilon$ = $\epsilon$' + i$\epsilon$" is determined in the 0.2 - 2.0 THz and 80-294 K ranges. $\epsilon$" has a linear temperature dependence up to 200 K then sharply increases. The low temperature linear dependence in $\epsilon$" indicates anharmonicity for temperatures 80 K < T < 180 K, challenging the assumed harmonicity below 200K. The temperature dependence is consistent with beta relaxation response and shows the protein motions involved in the dynamical transition extend to subpicosecond time scales.