[Accessibility of porphyrin macrocycle in myoglobin at various pH levels. Fluorescence study of the porphyrin-globin complex].

The fluorescent properties of the complexes of apoMb-PPIX and dimethyl-PPIX were studied in a wide range of pH and ionic strength. The quenching of fluorescence of PPIX in the complex by I- is shown to be of dynamic type Increasing of the Stern--Volmer constant was observed in the acidic region of pH. From the sections of space-filled model of Mb the static accessibility of porphine macrocyte was calculated. It is proposed that the revealed peculiarities of the myoglobin structure allow to interprete the data on the quenching of fluorescence of PPIX by iodid ion.