Participation of the g = 1.9 and g = 1.82 EPR forms of the semiquinone‐iron complex, QA −·Fe2+ of photosystem II in the generation of the Q and C thermoluminescence bands, respectively

[摘要]

Following illumination at 200 K, the charge recombination reactions and the origin of the thermoluminescence (TL) bands appearing at about 0°C (Q band) and +50°C (C band) in the glow curve were investigated by comparative TL and EPR measurements in DCMU-treated photosystem II particles. Decay half-time measurements carried out at −25°C and +25°C, respectively, suggest that the S₂ state (multi-line signal) undergoes charge recombination with the g = 1.9 form of the semiquinone-iron complex, Q_A ⁻·Fe²⁺, resulting in the appearance of the Q band, and that the g = 1.82 form of Q_A ⁻·Fe²⁺ back-reacts with the oxidized tyrosine, Y_D ⁺ (Signal II_s), accounting for the generation of the C band.

[学科分类] 生物化学/生物物理

[关键词] Photosystem II;Semiquinone-iron complex;Thermoluminescence;Charge recombination;EPR;PS II;photosystem II;QA and QB;primary and secondary quinone acceptors of PS II;TL;thermoluminescence;EPR;electron paramagnetic resonance;DCMU;3-(3;4-dichlorophenyl)-1;1-dimethyl-urea;YD;tyrosine-160 on the D2 protein;accessory electron donor in PS II;Chl;chlorophyl