Binding studies of four free base porphyrins and six iron (+3) porphyrins with human serum albumin.

The binding stoichiometry and binding equilibria of human serum albumin with water-soluble four free base porphyrins and six chloroiron (+3) porphyrins have been determined in 0.1M phosphate buffer, pH 7.2, by fluorescence quenching and filtration methods. The binding stoichiometry is observed to be 1:1, porphyrin to protein. The dissociation constants, Kd, between the porphyrins and the protein are found to be 1-4 microM. A binding mechanism between the protein and the porphyrins has been presented.