The reduction potential of the β-carotene•+/β-carotene couple in an aqueous micro-heterogeneous environment

There is a resurgence of interest in the role of electron transfer reactions involving beta-carotene photosynthesis. There is also current debate on the health benefits of dietary carotenoids and the possible deleterious effects on certain subpopulations snell as smokers. The impact of dietary carotenoids on health may well he also related to radical reactions. A key parameter in biological systems is therefore the one-electron reduction potential of the carotenoid radical cation, non reported for the first time in a model biological aqueous environment, The value obtained is 1.06 +/- 0.01 V and is sufficiently high to oxidise cell membrane proteins, but is low enough to repair P-680(.+) in the photosynthetic reaction centre. (C) 2000 Federation of European Biochemical Societies.