Large Scale Isolation and Purification of Eyespot Granules from Euglena gracilis var. bacillaris

Large volumes of eyespot granules were isolated from homogenates of Euglena gracilis Klebs var. bacillaris Pringsheim by flotation centrifugation in a Beckman Ti-15 zonal rotor, and were further purified by centrifugation in a swinging bucket rotor. Examination with the electron microscope showed the eyespot granules to be free from other cellular material. Freezing had no apparent effect on the structure or on the absorption properties of the eyespots. Absorption spectra of pure fractions of eyespot granules free of chloroplast contamination showed the previously reported curves in the range of 360 to 520 nanometers, as well as a peak at 660 to 675 nanometers. The procedure for the large scale isolation of eyespot granules from Euglena gracilis is compared with other methods which have employed conventional centrifugation, and the significance of the use of zonal rotors for isolating large quantities of pure eyespot granules is discussed.