Researchers from Ume University, Sweden, have explored two different ways that allow unprecedented experimental insights into the reaction sequence leading to the formation of oxygen molecules in photosynthesis. The two studies have been published in the scientific journal Nature Communications.
"The new knowledge will help improving present day synthetic catalysts for water oxidation, which are key components for building artificial leaf devices for the direct storage of solar energy in fuels like hydrogen, ethanol or methanol," says Johannes Messinger, Professor in Biological Chemistry and leader of the Artificial photosynthesis research group at Ume University.
Every child learns at school that the oxygen we breathe is produced by photosynthesis in plants and by cyanobacteria that live in lakes and the oceans. However, exactly how that happens is still under intense research.
Oxygen formation in photosynthesis occurs in a reaction sequence that is completed within one thousandth of a second. Thus, it is not surprising that it has been so difficult to prove experimentally how precisely a catalyst consisting of four manganese ions and one calcium ion (Mn4Ca cluster) performs this reaction sequence in photosystem II. Almost all molecular details we presently 'know' about the last critical steps are based on calculations. Johannes Messinger and his research group at Ume University have now explored two different ways for obtaining experimental insight into the mechanism of oxygen formation.
In the first study, the researchers slowed down the reaction sequence more than 40-times by exchanging the calcium of the cluster against strontium, and a nearby chloride ion against an iodide ion.
"We could show that in the last short-lived intermediate state before oxygen formation, the two water molecules are 'arrested', meaning that they are more than 1000-times more tightly bound to the Mn4Ca cluster than in all earlier
|Contact: Johannes Messinger|