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Complex Reorientation Dynamics of Sizable Glass-Formers with Polar Rotors Revealed by Dielectric Spectroscopy.

ABSTRACT: We present the results of dielectric measurements for three sizable glass-formers with identical nonpolar cores linked to various dipole-labeled rotors that shed new light on the picture of reorientation of anisotropic systems with significant moment of inertia revealed by broadband dielectric spectroscopy. The dynamics of sizable glass-formers formed by partially rigid molecular cores linked to small polar rotors in many respects differs from that of typical glass-formers. For instance, the extraordinarily large prefactors (τ₀ > 10^-12 s) in the Vogel-Fulcher-Tammann equation were found. The rich and highly diverse relaxation pattern was governed by the location of a dipole, its ability to rotate freely, and the degree of coupling to the motion of the entire sizable system.

SUBMITTER: Rams-Baron M

PROVIDER: S-EPMC8630796 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature

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Complex Reorientation Dynamics of Sizable Glass-Formers with Polar Rotors Revealed by Dielectric Spectroscopy.

Rams-Baron Marzena M Yao Beibei B Cheng Shinian S Dulski Mateusz M Paluch Marian M

The journal of physical chemistry letters 20211115 46

We present the results of dielectric measurements for three sizable glass-formers with identical nonpolar cores linked to various dipole-labeled rotors that shed new light on the picture of reorientation of anisotropic systems with significant moment of inertia revealed by broadband dielectric spectroscopy. The dynamics of sizable glass-formers formed by partially rigid molecular cores linked to small polar rotors in many respects differs from that of typical glass-formers. For instance, the ext ...[more]

PMID: 34780195

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Project description:Customarily, the studies of dynamics of hydrated proteins are focused on the fast hydration water ν-relaxation, the slow structural α-relaxation responsible for a single glass transition, and the protein dynamic transition (PDT). Guided by the analogy with the dynamics of highly asymmetric mixtures of molecular glass-formers, we explore the possibility that the dynamics of hydrated proteins are richer than presently known. By providing neutron scattering, dielectric relaxation, calorimetry, and deuteron NMR data in two hydrated globular proteins, myoglobin and BSA, and the fibrous elastin, we show the presence of two structural α-relaxations, α1 and α2, and the hydration water ν-relaxation, all coupled together with interconnecting properties. There are two glass transition temperatures T g α1and T g α2 corresponding to vitrification of the α1 and α2 processes. Relaxation time τα2(T) of the α2-relaxation changes its Arrhenius temperature dependence to super-Arrhenius on crossing T g α1 from below. The ν-relaxation responds to the two vitrifications by changing the T-dependence of its relaxation time τν(T) on crossing consecutively T g α2 and T g α1. It generates the PDT at T d where τν(T d) matches about five times the experimental instrument timescale τexp, provided that T d > T g α1. This condition is satisfied by the hydrated globular proteins considered in this paper, and the ν-relaxation is in the liquid state with τν(T) having the super-Arrhenius temperature dependence. However, if T d < T g α1, the ν-relaxation fails to generate the PDT because it is in the glassy state and τν(T) has Arrhenius T-dependence, as in the case of hydrated elastin. Overall, the dynamics of hydrated proteins are the same as the dynamics of highly asymmetric mixtures of glass-formers. The results from this study have expanded the knowledge of the dynamic processes and their properties in hydrated proteins, and impact on research in this area is expected.

Dataset Information

Complex Reorientation Dynamics of Sizable Glass-Formers with Polar Rotors Revealed by Dielectric Spectroscopy.

Publications

Complex Reorientation Dynamics of Sizable Glass-Formers with Polar Rotors Revealed by Dielectric Spectroscopy.

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