THE TRANSITION FROM INHOMOGENEOUS TO HOMOGENEOUS KINETICS IN CO BINDING TO MYOGLOBIN

Heme proteins react inhomogeneously with ligands at cryogenic temperat ures and homogeneously at room temperature. We have identified and cha racterized a transition from inhomogeneous to homogeneous behavior at intermediate temperatures in the time dependence of CO binding to hors e myoglobin. The turnover is attributed to a functionally important te rtiary protein relaxation process during which the barrier increases d ynamically. This is verified by a combination of theory and multipulse measurements. A likely biological significance of this effect is in t he autocatalysis of the ligand release process.