Spectroelectrochemical determination of the redox potentials of pheophytin a and primary quinone QA in photosystem II from thermosynechococcus elongatus

Abstract

Thin-layer cell spectroelectrochemistry was applied for the first time to measure the redox potentials of pheophytin (Phe) a and the primary quinone QA in photosystem (PS) II core complexes from a thermophilic cyanobacterium Thermosynechococcus elongatus. The determined potentials for oxygen-evolving PS II from a T. elongatus wild type strain were −522 ± 3 mV and −140 ± 2 mV for Phe a and QA, respectively. Based on the determined values together with kinetic analytical data in literature, a renewed diagram is proposed for the energetics in PS II, and further, modification of the redox properties for acclimation to cultivate conditions is also discussed.