DETERMINATION OF THE PRIMARY CHARGE SEPARATION RATE IN ISOLATED PHOTOSYSTEM-II REACTION CENTERS WITH 500-FS TIME RESOLUTION
DETERMINATION OF THE PRIMARY CHARGE SEPARATION RATE IN ISOLATED PHOTOSYSTEM-II REACTION CENTERS WITH 500-FS TIME RESOLUTION
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DOI：
10.1073/pnas.86.2.524
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发表时间：
1989-01-01
影响因子：
11.1
通讯作者：
GOVINDJEE
中科院分区：
文献类型：
--
作者：
WASIELEWSKI, MR;JOHNSON, DG;GOVINDJEE
我们直接测量了在4 ℃激发分离的菠菜光系统II反应中心后氧化叶绿素a电子供体（P680+）和还原电子受体脱镁叶绿素a-（Pheoa-）的形成速率。C.反应中心复合物由D1、D2和细胞色素B-559蛋白以及细胞色素B-559蛋白组成，并通过稳定蛋白复合物的程序制备。瞬态吸收差光谱测量从440至850 nm作为时间的函数与500 fs的分辨率以下610 nm的激光激发。P680+-Pheoa-的形成由P680+在820 nm处的条带的出现和由于Pheoa-的形成而在505和540 nm处的相应吸光度变化指示。820-nm带的出现是单指数的，其中τ = 3.0 .+-. 0.6 PS.在650 nm处监测的P680的最低激发单重态I8 P680的衰变时间常数为τ = 2.6 .+-. 0.6在实验误差范围内，与P680+的出现一致。用连二亚硫酸钠和甲基紫精处理光系统II反应中心，然后暴露于激光激发，已知导致Pheoa-积累的条件，导致由于1*P680而形成瞬态吸收光谱。我们没有发现在Pheoa-形成之前存在电子受体的证据。
We have measured directly the rate of formation of the oxidized chlorophyll a electron donor (P680+) and the reduced electron acceptor pheophytin a- (Pheoa-) following excitation of isolated spinach photosystem II reaction centers at 4.degree. C. The reaction-center complex consists of D1, D2, and cytochrome b-559 proteins and cytochrome b-559 proteins and was prepared by a procedure that stabilizes the protein complex. Transient absorption difference spectra were measured from 440 to 850 nm as a function of time with 500-fs resolution following 610-nm laser excitation. The formation of P680+-Pheoa- is indicated by the appearance of a band due to P680+ at 820 nm and corresponding absorbance changes at 505 and 540 nm due to formation of Pheoa-. The appearance of the 820-nm band is monoexponential with .tau.=3.0 .+-. 0.6 ps. The time constant for decay of I8P680, the lowest excited singlet state of P680, monitored at 650 nm, is .tau.=2.6 .+-. 0.6 ps and agrees with that of the appearance of P680+ within experimental error. Treatment of the photosystem II reaction centers with sodium dithionite and methyl viologen followed by exposure to laser excitation, conditions known to result in accumulation of Pheoa-, results in formation of a transient absorption spectrum due to 1*P680. We find no evidence for an electron acceptor that precedes the formation of Pheoa-.