[Study on the interaction of methyl pheophorbide-a and bovine serum albumins by fluorescence]

The binding reaction of methyl pheophorbide-a with bovine serum albumins (BSA) in aqueous solution was studied by fluorescence and UV-Vis absorption spectra. The results indicated that the combination reaction of them was a single static quenching process. In aqueous solution, methyl pheophorbide-a strongly bound BSA with the apparent molar ratio of 2 : 1 because of methyl pheophorbide-a polymerized by itself. The binding constant KB was 6.7 x 10(4) L x mol(-1). In mixture solvent of tetrahydrofuran and water, methyl pheophorbide-a existed as single molecule and bound BSA with a molar ratio of 1: 1. There is single position for combining methyl pheophorbide-a with BSA. The shortest binding distance (r = 3.50 nm) and energy transfer efficiencies (E = 0.39) between donor (BSA) and acceptor (methyl pheophorbide-a) were obtained by Förster's nonradiative energy transfer mechanism.