IN-VIVO SPECTROSCOPIC STUDY OF PHOTORECEPTOR PIGMENTS OF BLEPHARISMA-JAPONICUM RED AND BLUE CELLS

In the coloured ciliate Blepharisma japonicum, step-up photophobic res ponses are triggered by the endogenous pigment blepharismin. Blepharis min, red in dark-grown cells, is intracellularly photooxidized into a blue form (oxyblepharismin), still acting as photosensing pigment. Wit h the aim of correlating the spectroscopic properties of blepharismin and oxyblepharismin in vivo with their photophysiological features, op tical absorption, steady-state and time-resolved fluorescence spectra have been measured on cell suspensions. Both in blepharismin and oxybl epharismin in their physiological molecular environment, three fluores cent species have been observed, with virtually the same lifetimes (si milar to 0.2 ns, similar to 1.0 ns, similar to 3.5 ns), but significan tly different relative amplitudes. In red cells the long-living compon ent has a very low relative amplitude(similar to 4%) and the short-liv ing one is largely predominant(> 78%), whereas in blue cells the slowl y decaying species has a slightly higher relative amplitude (similar t o 40%) than the intermediately (similar to 31%) and the fast decaying species (similar to 29%). Together with the spectral width of time-gat ed spectra, these data are discussed in connection with current hypoth eses on the structures of the chromophores. No meaningful difference i n the above-mentioned spectroscopic parameters was observed after 30 m in of UV-B irradiation, showing that no significant difference exists between red and blue blepharismin as far as UV-B lability is concerned .