Investigation of the photodissociation quantum efficiency of hemoglobin derivatives

Abstract

The limit quantum efficiency of light interaction with oxyhemoglobin and carboxyhemoglobin at wavelengths of 525, 605 and 850 nm corresponding to the maxima of the action spectrum is studied. Obtained in vivo evaluations of the quantum yield of photodissociation of oxyhemoglobin HbO 2 and carboxyhemoglobin HbCO range from 0.1 to 0.14 for HbO 2 and from 0.76 to 0.90 for HbCO. The yield of photodissociation of carboxyhemoglobin is 6-8 times higher than that of oxyhemoglobin. Saturation of the processes of photodissociation is achieved with the same photon flux of approximately 11×1016 photons per second.The relatively low photodissociation quantum yield of oxyhemoglobin compaired to HbCO under conditions of in vivo experiment is hardly explain by geminate recombination or rebinding of ligands with heme, since irradiation was carried out continuously in contrast to experiments with time-resolved flash-photolysis which were used practically in all works devoted to the study of the kinetics of photodissociation of the ligand-heme complex and the determination of the quantum yield of the reaction. Most likely, the explanation of the relatively low quantum yield for HbO 2 should be explained by the protective properties of the structure of the oxyhemoglobin molecules and their environment in blood of a living organism.A significant difference in the quantum yields of photodissociation of oxy- and carboxyhemoglobin makes possible a selective forced decomposition of HbCO in blood with a minimal effect on HbO 2 component.