n nnnThe far-red limit of photosystem II (PSII) photochemistry wasstudied in PSII-enriched membranes and PSII core preparationsfrom spinach (Spinacia oleracea) after application of laserflashes between 730 and 820 nm. Light up to 800 nm was foundto drive PSII activity in both acceptor side reduction and oxidationof the water-oxidizing CaMn4 cluster. Far-red illumination inducedenhancement of, and slowed down decay kinetics of, variablefluorescence. Both effects reflect reduction of the acceptorside of PSII. The effects on the donor side of PSII were monitoredusing electron paramagnetic resonance spectroscopy. Signalsfrom the S2-, S3-, and S0-states could be detected after one,two, and three far-red flashes, respectively, indicating thatPSII underwent conventional S-state transitions. Full PSII turnoverwas demonstrated by far-red flash-induced oxygen release, withoxygen appearing on the third flash. In addition, both the pheophytinanion and the Tyr Z radical were formed by far-red flashes.The efficiency of this far-red photochemistry in PSII decreaseswith increasing wavelength. The upper limit for detectable photochemistryin PSII on a single flash was determined to be 780 nm. In photoaccumulationexperiments, photochemistry was detectable up to 800 nm. Implicationsfor the energetics and energy levels of the charge separatedstates in PSII are discussed in light of the presented results.展开▼
机译：ABSTRACTn n
n TOP n <字体颜色= 464c53>抽象 n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n n nnn光系统II（PSII）光化学的远红外极限是 研究d在730至820 nm之间的激光 闪光后，用菠菜（ Spinacia oleracea ）富含PSII的膜和PSII核心制剂 。发现高达800 nm的光 在水氧化CaMn 4 团簇的受主侧还原和氧化 中均能驱动PSII活性。远红外照明诱导可变 荧光增强 并减慢其衰减动力学。两种效果都反映了PSII受体 的减少。使用电子顺磁共振波谱法监测对PSII供体侧的影响 。在一个状态后，可以检测到来自S 2 -，S 3 -和S 0 状态的信号 ， 分别闪烁两次和三个远红色，表明 PSII经历了常规的S状态转换。 PSII完全转换 表现为远红闪光诱导的氧气释放，第三次闪光出现 氧气。此外，脱镁叶绿素 阴离子和Tyr Z自由基都是由远红闪光形成的。 PSII中这种远红光化学的效率降低了 随波长增加。一次闪光中PSII中可检测到的光化学 的上限确定为780 nm。在光积累 实验中，可检测到高达800 nm的光化学。根据给出的结果，讨论了PSII中电荷分离的 态的能量和能级的含义 。
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