The interaction of human hemoglobin with erythrosin. Comparison of hemoglobins with variously liganded heme groups.

The interactions of erythrosin with deoxyhemoglobin, oxyhemoglobin, carbonmonoxyhemoglobin, methemoglobin, cyanomethemoglobin and hemoglobin alpha and beta chains have been studied by using the equilibrium dialysis, the difference and circular dichroic (CD) spectra and stopped-flow method. The values of equilibrium and kinetic parameters, as well as CD characteristics, show that in addition to a number of weak binding sites hemoglobin contain four, relatively strong binding sites, one per chain. The properties of the strong binding sites depend on the ligand of the heme group and the charge of the heme group is not directly responsible for this fact. Consequently the properties of deoxyhemoglobin and methemoglobin, differing from the mutually close properties of the other derivatives, confirm that the state of the heme group affects the conformation of hemoglobin molecules in solution. These results are in a good agreement with the classification established on the heme iron spin state.