FLUOROMETRIC EVIDENCE FOR FLAVINS IN ISOLATED EYESPOTS OF EUGLENA GRACILIS VAR. BACILLARIS

Abstract— Fluorometric evidence suggesting the presence of flavins in isolated eyespots of Euglena gracilis var. bacillaris is reported for the first time. Fluorescence spectra of eyespots and flavin standards show maxima at 540nm and 530nm, respectively. Excitation spectra show matching major peaks at 360–370 nm and at 450nm. The addition of riboflavin standard to eyespot samples increases fluorescence intensity without major corresponding shifts in wavelength maxima. Photolysis of eyespot samples in the presence of EDTA effects a decrease in the fluorescence intensity; the fluorescence is quantitatively restored to its initial value by bubbling the photolyzed solution with air. Preliminary quantitative data, obtained by fluorescence measurements, indicate the presence of ca. 5 × 10^-4μg flavin/ml eyespot sample. While flavins have been hypothesized to be components of the photoreceptor system, they have been reported previously only in the paraflagellar bodies of intact cells. Emission and excitation data obtained by us for eyespots are similar to those previously reported by other investigators for paraflagellar bodies, but our studies now suggest the presence of flavins also in Euglena eyespots.