title: Photosensitized formation of singlet oxygen by phycobiliproteins in neutral aqueous solutions.
abstract: Phycobiliproteins (PBPs) are a type of promising sensitizers for photodynamic therapy (PDT). Upon irradiation (lambda>500nm) of an oxygen-saturated aqueous solution of phycobiliproteins, particularly, C-phycocyanin (C-PC), allophycocyanin (APC) or R-phycoerythrin (R-PE), the formation of singlet oxygen (1O2) was detected by using imidazole in the presence of p-nitrosodimethylaniline (RNO). The bleaching of RNO caused by the presence of imidazole in our system showed typical concentration dependence with a maximum at about 8mM imidazole, which is in agreement with the formation of 1O2. In addition, the generation of 1O2 was verified further in the presence of D2O and specific singlet oxygen quencher 1,4-diazabicyclo [2,2,2] octane (DABCO) and sodium azide (NaN3). Our experimental results indicated that APC possesses high ability to generate reactive oxygen species and the relative quantum yields of photogeneration of 1O2 by PBPs are as follows: APC > C-PC > R-PE.
authors.affiliation: Center for Molecular Science, Intstitute of Chemistry, The Chinese Academy of Sciences, Beijing.
authors.forename: S P
authors.initials: SP
authors.lastname: Zhang
authors.forename: J Q
authors.initials: JQ
authors.lastname: Zhao
authors.forename: L J
authors.initials: LJ
authors.lastname: Jiang
mesh_terms: D000814:Aniline Compounds; D001426:Bacterial Proteins / Q000737:chemistry / Q000528:radiation effects*; D003903:Deuterium; D016166:Free Radical Scavengers; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles; D007202:Indicators and Reagents; D008027:Light; D045342:Light-Harvesting Protein Complexes; D010100:Oxygen / Q000737:chemistry*; D010798:Phycocyanin / Q000737:chemistry / Q000528:radiation effects; D010799:Phycoerythrin / Q000737:chemistry / Q000528:radiation effects; D010940:Plant Proteins / Q000737:chemistry / Q000528:radiation effects*; D026082:Singlet Oxygen; D012996:Solutions; D013053:Spectrophotometry; D014867:Water
chemical_list: D000814:Aniline Compounds; D001426:Bacterial Proteins; D016166:Free Radical Scavengers; D007093:Imidazoles; D007202:Indicators and Reagents; D045342:Light-Harvesting Protein Complexes; D010940:Plant Proteins; D012996:Solutions; C002497:allophycocyanin; D014867:Water; C016619:4-nitroso-N-methylaniline; D010798:Phycocyanin; D010799:Phycoerythrin; D026082:Singlet Oxygen; D003903:Deuterium; D010100:Oxygen