
%0 Journal Article
%A Hoff, AJ 
%A Kropacheva, TN 
%T Electrochemical oxidation of pigment cofactors in photosystem II reaction centers
%J Science Access
%D 2001/01/01
%V 3
%N 1
%P -
%K 
%R https://doi.org/10.1071/SA0403478
%U https://www.publish.csiro.au/paper/SA0403478 
%X The oxidation of Chla and Pheoa in spinach D1-D2Cytb559 pigment-protein complex involved in plant photosynthesis was investigated by optical spectroelectrochemistry. To impose the potential a mixture of high-potential mediators (tris(1,10-phenanthroline) iron(II) and its mixed ligand complexes) was used. From 0.72 to 0.90V (vs.NHE) irreversible bleaching of b -carotene and Chla absorbing at 674nm occurs. Between 0.95 and 1.0V bleaching of the Chla Qy and Soret bands is partially reversible (up to 25%). The difference spetrum of the rereduced minus oxidized sample shows a maximum at 672-673nm, while the irreversibly oxidized component absorbs at 676-677nm. The loss of Soret band absorbance looks similar to that at potentials 1.0V is then associated with 0-1 Chla and the two Pheoa molecules. If our interpretation is correct, then our measurements constitute the first direct determination of the oxidative midpoint potential of P680, viz. 0.95-1.0V. 
