EFFECTS OF HYDROXYLAMINE, DIGITONIN AND TRITON X-100 ON PHOTORECEPTOR(PARAFLAGELLAR SWELLING) AND PHOTORECEPTION OF EUGLENA-GRACILIS

We present experiments that test the effects of agents commonly used i n visual pigment investigations, namely hydroxylamine (NH2OH), digiton in and triton X-100, on the photoreceptor and photoreception of Euglen a. Hydroxylamine reacts with free and opsin-bound retinal, in aqueous solution, to form stable oximes, whereas digitonin and triton X-100 ar e the most common extractants of rhodopsin. Since previous data indica te that the chromophore present in Euglena photoreceptor is retinal, w e investigated the influence of these chemicals on this organelle. The effects of these agents were studied by means of phase contrast, fluo rescence and transmission electron microscopy and photobehaviour exper iments. Hydroxylamine inhibited the formation of the Euglena photorece ptor. Photoaccumulation experiments on hydroxylamine-treated cells sho wed that they are unable to perceive light. Digitonin solubilized the crystalline structure of the photoreceptor, whereas the triton effect was limited to the membranous structures of the cell, leaving the phot oreceptor unimpaired.