Effects of solvent composition and viscosity on the rates of CO binding to heme proteins.

摘要: The rate of CO binding to myoglobin increases 4-fold, from 5 X 10(5) M-1 s-1 2 10(6) s-1, in going 0 80% glycerol phosphate buffer at pH 7, 20 degrees C. Under the same conditions, protoheme decreases monotonically about 1 10(8) 10(7) s-1. kinetic behavior neutral is that expected for a diffusion-controlled reaction. Increasing solvent viscosity causes decrease observed second order constant. In contrast, indicates quite clearly internal, nondiffusive processes are limiting speed enhancement due an increase standard chemical potential ligand molecule as polyalcohol concentration increased. Both types 0.1 N NaOH; first and then At low concentrations, reaction limited by process. high becomes exhibits dependence on reciprocal viscosity. data all these conditions have been analyzed empirically terms single free energy barrier more specifically consecutive scheme.