Kinetics of oxygen and carbon monoxide binding to synthetic analogs of the myoglobin and hemoglobin active sites.

Kinetics of reversible oxygenation and carbon monoxide complex formation of the simple heme compounds pyrroheme-N-[3-(1-imidazolyl)propyl]amide and pyrroheme-3-(3-pyridyl)propyl ester have been measured in different solvent environments. The oxygen on and off rates and equilibria of these compounds can be made to closely match those of myoglobin, of hemoglobin alpha chains, or of the various steps for hemoglobin by varying solvent environment or the basicity of the proximal base. These results suggest that the protein could alter oxygen on rates by varying the basicity of the proximal base and the off rates by changing the polarity of the distal environment.