Kinetics of carbon monoxide and oxygen binding to hemoglobin in human red blood cell suspensions studied by laser flash photolysis.

The reaction kinetics of the binding of CO and O2 to hemoglobin (Hb) in human red blood cell (RBC) suspensions have been examined using a 300 ns dye laser to photodissociate HbCO or HbO2. Fast (halftime approximately or equal to 10 microsecond) and slow (approximately or equal to 5 ms) processes were seen after photolysis. The results indicate that neither the rate constants nor the activation energies for the binding of CO to the fast reacting form of Hb in the RBC are significantly different from that measured in solution in spite of the different environments. Rate constants determined for O2 binding in RBC were intermediate between rates observed for reaction with fast ans slow reacting forms of Hb and probably consist of contributions from each. The slow recombination of CO and O2 probably has contributions both from reaction with slow reacting forms of Hb and from ligand that had diffused away from the RBC after photolysis.