Haehnel W
Biochim Biophys Acta. 1977 Mar 11;459(3):418-41. doi: 10.1016/0005-2728(77)90043-3.
The light-induced reaction kinetics of electron carriers between the two light reactions were studied in spinach chloroplasts. 1. The difference spectrum of the absorbance changes of plastocyanin in situ was separated from superimposing absorbance changes by flash titration described in the preceding paper (Haehnel, W. (1973) Biochim. Biophys. Acta 305, 618-631). Relative amounts of 2 : 1 electron equivalents were observed for plastocyanin and chlorophyll a1 (P-700). 2. A balance of the electron equivalents released from reduced plastoquinone and simultaneously accepted by oxidized plastocyanin, cytochrome f and chlorophyll a1 indicated a quantitative electron transfer. Additional electron carriers between plastoquinone and light reaction I can be excluded with an accuracy of about +/-0.3 electron equivalents per light reaction II. 3. The time course of the absorbance changes of plastocyanin was measured at 584 nm with negligible interference with other absorbance changes. The reduction kinetics show an initial lag followed by a rise with a half time of about 20 ms. The redox states of plastocyanin and chlorophyll a1 during this reduction via the rate-limiting step between the light reactions and during oxidation by weak far-red light suggest a true equilibrium constant of about 20. 4. The simultaneous oxidation and reduction kinetics of plastoquinone, cytochrome f, plastocyanin and chlorophyll a1 induced by two successive groups of saturating flashes after far-red illumination were measured. The oxidation kinetics of plastocyanin and the simultaneous reduction kinetics of chlorophyll a1 after the single flashes indicate a quantitative electron transfer with a half time of 200 mus. 5. The fast reduction of chlorophyll a1 by plastocyanin showed no effect of the inhibitors 3-(3',4'-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone or of reduced phenazine methosulfate. But it was completed inhibited after KCN incubation. 6. The oxidation kinetics of cytochrome f were reinvestigated with high time resolution from the difference of absorbance changes at 554 minus 540 nm to minimize the disturbing interference with other absorbance changes. Absorbance changes measured 554 nm alone do not reflect kinetics of cytochrome f. The half time of the oxidation was faster than 40 microns. 7. The observed reaction kinetics gave evidence for a function of cytochrome f between plastoquinone and chlorophyll a1 in parallel to plastocyanin. In addition, they indicate that the greater portion of linear electron transport passes plastocyanin. The complex interaction between cytochrome f and chlorophyll a1 is discussed.
对菠菜叶绿体中两个光反应之间电子载体的光诱导反应动力学进行了研究。1. 通过前文所述的闪光滴定法（Haehnel, W. (1973) Biochim. Biophys. Acta 305, 618 - 631），从叠加的吸光度变化中分离出质体蓝素原位吸光度变化的差异光谱。观察到质体蓝素与叶绿素a1（P - 700）的电子当量相对量为2 : 1。2. 还原型质体醌释放的电子当量与同时被氧化型质体蓝素、细胞色素f和叶绿素a1接受的电子当量之间的平衡表明存在定量的电子转移。每个光反应II中，质体醌与光反应I之间额外的电子载体可以以约±0.3电子当量的精度排除。3. 在584 nm处测量质体蓝素吸光度变化的时间进程，与其他吸光度变化的干扰可忽略不计。还原动力学显示出初始延迟，随后上升，半衰期约为20毫秒。在通过光反应之间的限速步骤进行还原过程中以及在弱远红光氧化过程中，质体蓝素和叶绿素a1的氧化还原状态表明真实平衡常数约为20。4. 测量了远红光照射后两组连续饱和闪光诱导的质体醌、细胞色素f、质体蓝素和叶绿素a1的同时氧化和还原动力学。单次闪光后质体蓝素的氧化动力学和叶绿素a1的同时还原动力学表明存在定量电子转移，半衰期为200微秒。5. 质体蓝素对叶绿素a1的快速还原不受抑制剂3 - (3',4'-二氯苯基)-1,1 - 二甲基脲、2,5 - 二溴 - 3 - 甲基 - 6 - 异丙基 - 对苯醌或还原型吩嗪硫酸甲酯的影响。但在KCN孵育后完全被抑制。6. 从554减去540 nm处吸光度变化的差异，以高时间分辨率重新研究细胞色素f的氧化动力学，以最小化对其他吸光度变化的干扰。仅在554 nm处测量的吸光度变化不能反映细胞色素f的动力学。氧化的半衰期快于40微秒。7. 观察到的反应动力学证明细胞色素f在质体醌和叶绿素a1之间起作用，与质体蓝素并行。此外，它们表明线性电子传递的较大部分通过质体蓝素。讨论了细胞色素f与叶绿素a1之间的复杂相互作用。
