title: Photosensitized protein damage by dimethoxyphosphorus(V) tetraphenylporphyrin.
abstract: For the purpose of the basic study of photodynamic therapy, the activity of the water-soluble P(V)porphyrin, dimethoxyP(V)tetraphenylporphyrin chloride (DMP(V)TPP), on photosensitized protein damage was examined. The quantum yield of singlet oxygen generation by DMP(V)TPP (0.64) was comparable with that of typical porphyrin photosensitizers. Absorption spectrum measurement demonstrated the binding interaction between DMP(V)TPP and human serum albumin, a water-soluble protein. Photo-irradiated DMP(V)TPP 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 DMP(V)TPP by human serum albumin supported the electron transfer mechanism. The estimated contribution of the electron transfer mechanism is 0.64. These results suggest that the activity of DMP(V)TPP can be preserved under lower oxygen concentration condition such as tumor.
authors.affiliation: Faculty of Engineering, Shizuoka University, Johoku 3-5-1, Hamamatsu, Shizuoka 432 8561, Japan. tkhirak@ipc.shizuoka.ac.jp
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Hirakawa
authors.forename: Norihito
authors.initials: N
authors.lastname: Fukunaga
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Arai
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Okazaki
mesh_terms: D004579:Electron Transport; D006801:Humans; D008027:Light; D010084:Oxidation-Reduction; D017319:Photosensitizing Agents / Q000737:chemistry / Q000378:metabolism*; D011166:Porphyrins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D026082:Singlet Oxygen / Q000378:metabolism; D019810:Sodium Azide / Q000737:chemistry / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D012709:Serum Albumin; C409084:tetraphenylporphyrin; D026082:Singlet Oxygen; D019810:Sodium Azide