The rapid component of electron paramagnetic resonance signal II: a candidate for the physiological donor to photosystem II in spinach chloroplasts.

TLDR: Electrochemical and kinetic evidence is consistent with the hypothesis that the Signal IIf species, F, is identical with Z, the physiological donor to P680, and a model is proposed in which Q minus, the reduced Photosystem II primary acceptor, and D, a one-electron 480 mV donor endogenous to the chloroplast suspension, compete in the reduction of Signal I if.

About: This article is published in Biochimica et Biophysica Acta.The article was published on 1975-02-17 and is currently open access. It has received 101 citations till now. The article focuses on the topics: DCMU & P680.

Figures

Fig. 1. EPR spectra of Signal II in dark-adapted, untreated (a,b) and tris-\'/ashed (c,d) chloroplasts under various illumination conditions:

Fig. 8 sho\'/s the complete redox titration (a) and Nernst plot (b)

Fig. 5. Polarographic detection of PO oxidation in tris-washed chloroplasts in the absence (a) and presence (b) of 2 x In-5 M OCMU. PO concentration, 1 x 10-4 M; saturating flashes spaced 1 s apart; polarizing potential applied to the electrode, -0.325 V (vs. S.C.E.). Reduction of oxidized PO at the electrode surface results in an electrode current (i) increase which is subsequently amplified and recorded as a positive-going signal.

Fig. 7. Flash-induced Signal IIf EPR response at various reduction potentials in tris-washed chloroplasts in the absence (left side of figure) and presence (right) of 10-4 11 DCMU. The ferri/ferrocyanide couple (FeCN) \Alas used to obtain potentials of +437 ~V (a) and +519mV (c); the cyano-