Anharmonic transitions in nearly dry L-cysteine I

TL;DR

This study investigates the dynamical transitions in nearly dry L-cysteine I, revealing temperature-dependent structural and vibrational changes that influence biochemical interactions and macromolecular activity.

Contribution

It provides a detailed analysis of the temperature-dependent dynamical transitions in L-cysteine, linking them to specific molecular events affecting bioactivity.

Findings

Activation of rigid rotors below 100 K

Phonon interactions with water dimers between 100 K and 180-220 K

Water rotational barriers overcome above 180-220 K

Abstract

Two special dynamical transitions of universal character have been recently observed in macromolecules at $T_{D}\sim 180 - 220$ K and $T^{*}\sim 100$ K. Despite their relevance, a complete understanding of the nature of these transitions and their consequences for the bio-activity of the macromolecule is still lacking. Our results and analysis concerning the temperature dependence of structural, vibrational and thermodynamical properties of the orthorhombic polymorph of the amino acid L-cysteine (at a hydration level of 3.5%) indicated that the two referred temperatures define the triggering of very simple and specific events that govern all the biochemical interactions of the biomolecule: activation of rigid rotors ($T<T^{*}$), phonon-phonon interactions with phonons of water dimer ($T^{*}<T<T_{D}$), and water rotational barriers surpassing ($T>T_{D}$).