Photosynthetic water oxidation to molecular oxygen: apparatus and mechanism

Abstract

The invention of a molecular device that permits the cleavage of water into molecular oxygen and metabolically bound hydrogen by solar radiation is of paramount importance for the energetics of the whole biosphere. This event which occurred about 2^3 billion years ago had two consequences of crucial relevance: (i) the huge water pool on the Earth's surface became available as hydrogen source and (ii) the formation of O2 as `waste' product of photosynthesis led to the present day aerobic atmosphere and consequently led to formation of the essential protective ozone layer to solar UV-B irradiation. The advent of O2 in the atmosphere made way for much more (factor of v 10) e¤cient exploitation of the Gibbs energy of food through aerobic respiration in heterotrophic organisms (for a review, see [1]). In the light of its pivotal role for the bioenergetics of all higher forms of living matter, the unravelling of the `secrets' of photosynthetic water cleavage is a most important and exciting challenge of basic research. However, in addition it o¡ers the hopeful idea that the underlying principles of the natural system as a masterpiece can inspire the construction of biomimetic devices that eventually permit e¤cient solar energy exploitation to satisfy the increasing Gibbs energy demand of mankind's civilization without the burden of technologies that give rise to serious pollution of the atmosphere and/or the production of dangerous waste material like radioactive substances.