Istituto di Biofisica     
Angelini N., Cubeddu R., Ghetti F., Lenci F., Taroni P., Valentini G. In vivo spectroscopic study of photoreceptor pigments of Blepharisma japonicum red and blue cells. In: Biochimica et Biophysica Acta-Bioenergetics, vol. 1231 (3) pp. 247 - 254. Elsevier, 1995.
In the coloured ciliate Blepharisma japonicum, step-up photophobic responses are triggered by the endogenous pigment blepharismin. Blepharismin, red in dark-grown cells, is intracellularly photooxidized into a blue form (oxyblepharismin), still acting as photosensing pigment. With the aim of correlating the spectroscopic properties of blepharismin and oxyblepharismin in vivo with their photophysiological features, optical absorption, steady-state and time-resolved fluorescence spectra have been measured on cell suspensions. Both in blepharismin and oxyblepharismin in their physiological molecular environment, three fluorescent species have been observed, with virtually the same lifetimes ( not, vert, similar 0.2 ns, not, vert, similar 1.0 ns, not, vert, similar 3.5 ns), but significantly different relative amplitudes. In red cells the long-living component has a very low relative amplitude (not, vert, similar 4%) and the short-living one is largely predominant (> 78%), whereas in blue cells the slowly decaying species has a slightly higher relative amplitude (not, vert, similar 40%) than the intermediately (not, vert, similar 31%) and the fast decaying species (not, vert, similar 29%). Together with the spectral width of time-gated spectra, these data are discussed in connection with current hypotheses on the structures of the chromophores. No meaningful difference in the above-mentioned spectroscopic parameters was observed after 30 min of UV-B irradiation, showing that no significant difference exists between red and blue blepharismin as far as UV-B lability is concerned.
DOI: 10.1016/0005-2728(95)00080-3
Subject Blepharismin-binding protein
Time-gated fluorescence
Ultraviolet B
B. japonicum

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