Effect of irradiation spectral range on porphyrin—Protein complexes

The influence of irradiation on protein- porphyrin complexes at various spectral ranges was studied. Limited applicability of evaluating protein damage degree in terms of fluorescence quenching of the tryptophan protein residues was shown. Depending on the conditions of photoirradiation and the way of porphyrins interaction with bovine serum albumin (BSA), photoirradiation of the porphyrin-protein complexes may result in proteolysis or photolinking inside the protein globule, and in some cases, in destruction of the complex itself. P1 5-(4′-N-tertbutyloxycarbonylglicinaminophenyl)-10,15,20-triphenylporphine, unlike 5,10,15,20-tetraphenylporphin (TPP), has fixed localization in the protein due to “anchor” group providing the stability of the photoinduced transformations of a protein globule. For all porphyrin-protein systems studied, irradiation by light at the Soret band range for P1-protein systems leads to proteolysis of BSA globule, while the irradiation by light with the wavelength more than 500 nm, does not result in total protein damage, but causes oxidation of susceptible amino acid residues. The measurement of the hydrodynamic radii of a protein globule before and after irradiation provided objective information on the proceeding photoinduced processes (proteolysis and crosslinking) which can be used for predicting the mechanism of the cell damage (necrosis, autophagy, apoptosis).