Modification of Photosystem I reaction center by extraction-reconstitution of pigment cofactors

1.经乙醚处理后，PSAA/BPSI复合体中的大部分Chlα被去除而不损失P700，得到Chlα/P700比值为12的天线耗竭的PSI RC复合体。当Chl b与磷脂酰甘油一起加入时，P700中的9-14 Chl b结合到天线耗竭的复合体中的Chlα结合部位，结合的Chl b起到与原位Chlα一样的天线作用。PSI RC的飞秒瞬时吸收光谱，其中一个(或多个？)结果表明，在P700中性条件下，在630 nm激发下，还原的A0与激发的P700的量之比随温度的降低而降低。在生理温度下，即使大约100%的PSI RC表现出亚皮秒的一次电荷分离，在9K时，最多有40%的RC可以发生一次电荷分离。结果表明，一种…不完全PSI RC.3的电荷分离涉及更多的常规过程。为了尝试构建锌-叶绿素α而不是镁-叶绿素，将小球藻细胞培养在高浓度的锌离子和谷氨酸中。光照下自养生长的小球藻，锌浓度大于0.5 mmoL/l对小球藻有致死作用。然而，当小球藻在黑暗中异养生长时，即使在67 mmol/l的锌存在下，小球藻在较长的滞后期仍具有增殖能力。接种锌的细胞在生长初期的415和670 nm处有Chl的吸收光谱。在生长过程中，出现Chl形式，峰位于680 nm。目前正在对接种锌的细胞中的CHL进行鉴定。以叶绿素α/P700比值为10的菠菜P700为底物，在pH为11.5，10℃的条件下，建立了选择性降解P700和Ao的方法。PH和温度越高，P100和Ao的降解越快。当pH回到8时，P700的降解立即停止，但没有恢复。P700的吸收峰暂时移动到670 nm，然后消失。P700和/或A_o的重建目前正在进行中。较少

1. Most Chl α in the PsaA/B PSI complexes was removed without any loss of P700 by ether treatment, yielding the antenna-depleted PSI RC complexes that have a Chl α/P700 ratio of 12. On addition of Chl b with a phosphatidylglycerol, 9 - 14 Chl b per P700 bound to the Chl α - binding sites in the antenna-depleted complexes and the bound Chl b acted as antenna as efficiently as in situ Chl α.2. A femtosecond transient absorption spectroscopy of the PSI RC in which one (or more?) of the PSI electron-transport co factor (s) was extracted by the treatment of PSI complex with water-containing ether, showed that under the P700-neutral conditions and upon the 630 nm excitation, the ratio of the amount of the reduced Ao to that of the excited P700 decreased as the temperature goes down. At most 40 % of the RC can undergo the primary charge separation at 9 K, even though about 100 % PSI RC shows subpicosecond primary charge separation at a physiological temperature. The results suggest that a the … More rmal process is involved in the charge separation of the incomplete PSI RC.3. In order to try to construct Zn-Chl α instead of Mg-Chl, Chlorella cells were cultured at the high concentration of Zn^<2+>. Zn of more than 0.5 mmol/1 was lethal to Chlorella when grown autotrophically in the light. However, when grown heterotropphically in the dark, Chlorella had an ability to proliferate after long lag phase even in the presence of 67 mmol/1 of Zn. The Zn-inoculated cells showed the absorption spectrum of Chl with peaks at 415 and 670nm at the beginning of the growth. During the growth, there appeared a Chl form with a peak at 680 nm. Identification of the Chls in the Zn-inoculated cells is now in progress.4. The method for a selective degradation of P700 and A_o was established with spinach P700-enncned complexes that had a Chl α/P700 ratio of 10 by incubation in pH11.5 at 10 ℃. The degradation of P100 and A_o proceeded more rapid with making pH or temperature higher. The degradation stopped immediately, but did not recover, by backing pH to 8. The absorption peak of P700 temporarily shifted to 670 nm and then disappeared by this treatment. The reconstitution of P700 and/or A_o is now in progress with this preparation. Less