The protein dynamical transition is independent of hydration

Johanna Kölbel, Moritz L. Anuschek, Ivonne Stelzl, Supawan Santitewagun, Wolfgang Frieß, J. Axel Zeitler
Condensed Matter, Disordered Systems and Neural Networks, Disordered Systems and Neural Networks (cond-mat.dis-nn), Biological Physics (, Chemical Physics (physics.chem-ph)
2023-05-09 16:00:00
Terahertz time-domain spectroscopy and differential scanning calorimetry were used to study the role of the dynamics of biomolecules decoupled from solvent effects. Lyophilised sucrose exhibited steadily increasing absorption with temperature as anharmonic excitations commence as the system emerges from a deep minimum of the potential energy landscape where harmonic vibrations dominate. The polypeptide bacitracin and two globular proteins, lysozyme and human serum albumin, showed a more complex temperature dependence. Further analysis focused on the spectral signature below and above the boson peak. We found evidence for the onset of anharmonic motions that are characteristic for partial unfolding and molecular jamming in the dry biomolecules. The activation of modes of the protein molecules at temperatures comparable to the protein dynamical transition temperature was observed in the absence of hydration. No evidence for Fr\"ohlich coherence, postulated to facilitate biological function, was found in our experiments.
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