Binding of imidazoles to manganese (III) protoporphyrin in water.

摘要: Equilibrium constants for the addition of water to manganese(III) protoporphyrin in acetone were measured at 21 degrees C by visible absorption method. The binding first and second molecules determined be 209 +/- 3 M-1 22 1 M-1, respectively. This observation suggests that fifth sixth coordination positions are coordinated two is monomeric. Addition 1-methylimidazole 2-methylimidazole was also investigated spectrophotometrically, respective monoimidazole adducts found born appreciable amounts. imidazole 24.7 1.0 16.5 0.9 0.1 M tris(hydroxymethyl)aminomethane buffer pH 8.0 C. steric effect 2-methyl group te aquomanganese(III) (2-methylimidazole) species expected mimic proximal strain alpha subunits human adult hemoglobin. energy associated with Mn(III)-imidazole bond model complex estimated 240 cal/mol. small Mn-(III)-imidazole easily tensed a slight implies major part quaternary transition hemoglobin inositol hexaphosphate widely delocalized around globin moiety, as has been proposed