Drug-protein interactions: Two-site binding of heterocyclic ligands to a monomeric hemoglobin

The reactivity response of the heme proteins to the heterotropic effecters, purine, caffeine, theophylline, and (C2H5N+, have been examined. The heterotropic effecters influence the heme ligation affinities. The heme axial ligation of pyridine and pyrazole;have not influenced the hemoglobin's affinity for caffeine and theophylline. The imidazole ligation indicates a mutual interaction between the heme active site and the noncoordinate binding site.