title: Viscosity scaling and protein dynamics.
abstract: The rates of molecular motions in the interior of some proteins were found to scale with an inverse power of the external solvent viscosity. The data were explained by a flexible protein structure whose dynamics is partially controlled by the solvent. Reaction dynamics in the presence of structural fluctuations with finite lifetimes lead to a dynamic friction coefficient defined by a generalized Langevin equation and a fluctuation-dissipation theorem. A model for the dynamic friction is derived assuming that the fluctuation spectrum at the reaction site involves two components: solvent-independent diffusion of local structural defects in the protein matrix and global fluctuations coupled to the solvent. The theory is applied to the viscosity dependence of molecular oxygen-binding rates in sperm whale myoglobin.
mesh_terms: D008433:Mathematics; D011487:Protein Conformation; D011506:Proteins; D013816:Thermodynamics; D014783:Viscosity
chemical_list: D011506:Proteins