Tug-of-War between Internal and External Frictions and Viscosity Dependence of Rate in Biological Reactions

The role of water in biological processes is studied in three reactions, namely, the Fe-CO bond rupture in myoglobin, GB1 unfolding, and insulin dimer dissociation. We compute both internal and external components of friction on relevant reaction coordinates. In all of the three cases, the cross-correlation between forces from protein and water is found to be large and negative that serves to reduce the total friction significantly, increase the calculated reaction rate, and weaken solvent viscosity dependence. The computed force spectrum reveals bimodal 1/f noise, suggesting the use of a non-Markovian rate theory.

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This paper examines the role of water in biological processes through the study of three reactions: Fe-CO bond rupture in myoglobin, GB1 unfolding, and insulin dimer dissociation. The research shows that the cross-correlation between forces from protein and water is large and negative, significantly reducing total friction, increasing reaction rates, and weakening solvent viscosity dependence. The computed force spectrum also suggests the use of a non-Markovian rate theory.