THE DEPENDENCE OF THE QUANTUM YIELD OF LIGAND PHOTODISSOCIATION FROM HAEM PROTEINS ON ULTRAFAST RECOMBINATION

Abstract— Measurements of relative photolysis yields in nanosecond flash photolysis studies of carbon monoxide and dioxygen complexes of haemoglobin and myoglobin are compared with published values of the quantum efficiency for photodissociation obtained from microsecond flash or continuous photolysis studies. It is shown that the differences in quantum yield between HbCO and MbCO and between Hb02 and Mb02 can be correlated with the different extent of ultrafast recombination observed in the nanosecond experiments. Furthermore, the temperature dependence of the quantum yield in the case of HbCO can be entirely attributed to the effect of temperature on the ultrafast recombination.

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