Resonance light scattering study of aggregation of two water soluble porphyrins due to their interaction with bovine serum albumin

The interaction of the water soluble meso-tetrakis(p-sulfonato-phenyl)porphyrin (TPPS4) and meso-tetrakis(4-N-methyl-pyridiniumyl)porphyrin (TMPyP) with bovine serum albumin (BSA) in aqueous solutions has been studied by optical absorption, fluorescence and resonance light scattering spectroscopies. The formation of two types of aggregates due to this interaction has been demonstrated: aggregates of the TPPS4 on the BSA molecule surface and aggregates of BSA molecules around the TPPS4 molecule. The reduction of integral fluorescence intensity of TPPS4 due to the porphyrin aggregation and its increase due to the BSA aggregation have been demonstrated. The influence of the porphyrin charge on the aggregation process has been also clearly observed and explained on the basis of known BSA binding properties.