Relaxation dynamics of myoglobin in solution

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Abstract
The geminate rebinding kinetics of MbCO in solution at high temperature (260–300 K) shows nonexponential behavior (stretched, β∼1/2) that may be related to nonequilibrium relaxation of the distal pocket. A two-pulse photolysis experiment, which probes a kinetically selected subpopulation, demonstrates that the nonexponential behavior arises from a fluctuationally averaged system and also reveals slow interconversion times for large-scale protein motions. Measurements as a function of temperature lead to a direct determination of the Arrhenius barrier at the heme (18±2 kJ/mole).