title: Time-resolved fluorescence spectroscopy and photolysis of the photoreceptor blepharismin.
abstract: Blepharismin is the photoreceptor for the photophobic response in the ciliate Blepharisma japonicum (Scevoli, P., Bisi, F., Colombetti, G., Ghetti, F., Lenci, F., and Passarelli, V. (1987) J. Photochem. Photobiol.: B. Biol. 1, 75-84; Lenci, F., Ghetti, F., Gioffre, D., Heelis, P.F., Thomas, B., Phillips, G.O., and Song, P.-S. (1989) J. Photochem. Photobiol.: B. Biol. 3, 449-453). Blepharismin was solubilized from the red cells with 2% n-octylglucopyranoside. A crude pigment-protein preparation was then successively subjected to Bio-Gel A1.5 filtration, FPLC/hydroxyapatite and FPLC/DEAE ion-exchange chromatography. At least two spectrally distinct forms of blepharismin, with the respective absorbance maxima at 597 +/- 1 and 601 +/- 1 nm, were resolved. The steady state fluorescence emission maxima were at 602.5 and 617.5 nm, respectively. The fluorescence decay curves for these pigments were non-exponential. The major component possesses relatively short fluorescence lifetime (200-500 ps) for the former, according to a global analysis. This analysis suggests that the excited state of the shorter wavelength-absorbing form of blepharismin undergoes primary photoprocess faster than that of the free parental chromophore hypericin. Photolysis of blepharismin in solution yielded a irreversible product, accompanied by a 10-12 nm bathochromic shift of the absorbance maximum. However, the mechanistic nature of the time-resolved fluorescence and the photochemistry of blepharismin remains to be elucidated.
authors.affiliation: Department of Chemical Process Engineering, Hokkaido University, Sapporo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamazaki
authors.forename: I
authors.initials: I
authors.lastname: Yamazaki
authors.forename: Y
authors.initials: Y
authors.lastname: Nishimura
authors.forename: R
authors.initials: R
authors.lastname: Dai
authors.forename: P S
authors.initials: PS
authors.lastname: Song
mesh_terms: D000818:Animals; D016798:Ciliophora / Q000737:chemistry*; D015200:Fluoroimmunoassay; D010786:Photoreceptor Cells / Q000737:chemistry*; D011083:Polycyclic Compounds / Q000737:chemistry; D015800:Protozoan Proteins / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D011083:Polycyclic Compounds; D015800:Protozoan Proteins; C021252:stentorin I