Photosensitized damage of protein by fluorinated diethoxyphosphorus(V)porphyrin

The effect of the axial ligand fluorination of the water-soluble P(V)porphyrin complex on photosensitized protein damage was examined. The activity of singlet oxygen generation by diethoxyP(V) porphyrin was slightly improved by the fluorination of the ethoxy chains. Absorption spectrum measurements demonstrated the binding interaction between the P(V)porphyrins and human serum albumin, a water-soluble protein. Photo-irradiated P(V)porphyrins damaged the amino acid residue of human serum albumin, resulting in the decrease of the fluorescence intensity from the tryptophan residue of human serum albumin. A singlet oxygen quencher, sodium azide, could not completely inhibit the damage of human serum albumin, suggesting that the electron transfer mechanism contributes to protein damage as does singlet oxygen generation. The decrease of the fluorescence lifetime of P(V)porphyrin by human serum albumin supported the electron transfer mechanism. The estimated contributions of the electron transfer mechanism are 0.57 and 0.44 for the fluorinated and non-fluorinated P(V)porphyrins, respectively. The total quantum yield of the protein photo-oxidation was slightly enhanced by this axial fluorination.