Reactivity differences between haemoglobins, Part XI. The reaction of human methaemoglobin A and pigeon methaemoglobin with imidazole

Abstract

The affinity of human methaemoglobin A and pigeon methaemoglobin A for imidazole has been determined as a function of pH and temperature at constant ionic strength. The variation with pH of ΔG° and ΔH of complex formation is different from that observed for charged ligands. The differences between the behaviour of the two methaemoglobins are smaller than in the reaction with azide ions. These observations are interpreted in terms of the structure of methaemoglobin in the vicinity of the iron atom.