DETECTION OF HYDROXYL RADICAL IN INTACT-CELLS OF CHLORELLA-VULGARIS

Using ESR with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin-trapp ing reagent, we measured the levels of free radical species generated from living cells of Chlorella vulgaris var. vulgails (IAM C-534). To investigate the production of free radicals in the living Chlorella vu lgaris cells, the influence of DMPO toward the intact cells of the Chl orella vulgaris using the O-2 evolution rate was first studied as a gu ide. Since the O-2 evolution rate was not changed by DMPO, it was judg ed that DMPO has no toxicity toward the intact cells of Chlorella vulg aris. Only hydroxyl radicals (. OH) were detected as the DMPO-OH adduc t in the suspension of intact cells of Chlorella vulgaris irradiated w ith visible light. Moreover, since production of . OH was inhibited by some hydroxyl radical scavengers such as KI and ethanol, production o f . OH was proved to be due to hydroxyl radicals. It was also clear th at the intensity of . OH increased with increasing irradiation intensi ty of visible light. Therefore, it was suggested that . OH might be on e of the photoinhibition factors of the intact Chlorella vulgaris cell s in severe light conditions.