Requirement of an acidic proton in substances which act as accelerators of the deactivation reactions in the water-splitting enzyme system of photosynthesis

Abstract

Recently it was found [1,2], that the positive charges generated by photosystem II, which are responsible for water oxidation (these charges are designated as trapped holes, cf. [3] ), can be destabilized by a class of substances, designated ADRYagents* [4]. The molecular mechanism of the ADRY effect remains to be elucidated, but in the last year results were obtained leading to the conclusion that the acidic NH-group, present in all ADRY-agents so far known, is an important functional element [4]. In this paper it will be shown that substances which contain an acidic OH-group instead of an acidic NH. group, can act as ADRY agents. Furthermore, it was found that the N-methylderivatives of the ADRY agents ANT 2a and ANT 2p do not act as ADRY substances. From these results it is concluded that the presence of an acidic group in the