2001 Fiscal Year Final Research Report Summary
Modification of Photosystem I reaction center by extraction-reconstitution of pigment cofactors
| Project/Area Number |
11640656
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
植物生理
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| Research Institution | Teikyo University |
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Principal Investigator |
IKEGAMI Isamu Faculty of Pharmaceutical Sciences., Teikyo University, Professor, 薬学部, 教授 (10082322)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Photosynthesis / Photosystem I / Chlorophyll / Photosvnthetic reaction center / P700 / Primay process / Photosynthetic pigments / Electron transfer |
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| Research Abstract |
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
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Research Products
(12 results)
