Laser kinetic spectroscopy studies of the reaction of human hemoglobin with molecular oxygen

摘要

Abstract: The process of the oxygen photodissociation and rebinding with human hemoglobin have been studied by the time-resolved absorption spectroscopy. The primary quantum yield $gamma$- o$/ does not depend on the pH and its estimated value is 0.3 $POM 0.1. The apparent quantum yield $gamma corresponding to the portion of O$-2$/ molecules which escape from the protein to the solvent depends on the pH. It has been shown that the entrance and exit of the oxygen molecules into/from the globin matrix is controlled by the same Bohr residues. The pK values were calculated and the attribution was made. The unusual behavior of the oxygenation parameters at pH $GRT 8.5 was observed and explained by the action of the $alpha@140-Tyr and $beta@145-Tyr. The picosecond ligand rebinding dynamics were measured and the phenomenon of the pK value change was studied. It was explained by the subunit tertiary structure relaxation in terms of the transition between deoxy-R- and oxy-R- structures of the tetramer protein. !27