The effect of macromolecular polyanions on the functional properties of human hemoglobin

The binding of dextran sulphate and heparin to human hemoglobin and their effect on the properties of gas transport have been investigated. Both dextran sulphate and heparin are strongly bound by oxy-hemoglobin as well as deoxyhemoglobin and the stoichiometry of the binding (polyanion/tetrameric hemoglobin) is less than unity; sedimentation analysis gives indication for the existence of octomers. The oxygen affinity of hemoglobin is decreased, to the same extent, by both dextran sulphate and heparin. This effect is pH-dependent. In addition the polyanions affect the position and the magnitude of the Bohr effect. In the presence of dextran sulphate the recombination of hemoglobin with carbon monoxide after flash photolysis is biphasic and the fraction of quickly reacting material increases with dilution of the protein.