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Observation of Fragile-to-Strong Dynamic Crossover in Protein Hydration Water

Sow-Hsin Chen·Li Liu·Emiliano Fratini·Piero Baglioni·Antonio Faraone·Eugene Mamontov
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Abstract

At low temperatures proteins exist in a glassy state, a state which has no conformational flexibility and shows no biological functions. In a hydrated protein, at and above 220 K, this flexibility is restored and the protein is able to sample more conformational sub-states, thus becomes biologically functional. This 'dynamical' transition of protein is believed to be triggered by its strong coupling with the hydration water, which also shows a similar dynamic transition. Here we demonstrate experimentally that this sudden switch in dynamic behavior of the hydration water on lysozyme occurs precisely at 220 K and can be described as a Fragile-to-Strong dynamic crossover (FSC). At FSC, the structure of hydration water makes a transition from predominantly high-density (more fluid state) to low-density (less fluid state) forms derived from existence of the second critical point at an elevated pressure.

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Sow-Hsin Chen, Li Liu, Emiliano Fratini, Piero Baglioni, Antonio Faraone, Eugene Mamontov. 2006-05-11. Observation of Fragile-to-Strong Dynamic Crossover in Protein Hydration Water. https://doi.org/10.1073/pnas.0602474103

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