| Project/Area Number |
08044223
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Field |
植物生理
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| Research Institution | Waseda University |
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Principal Investigator |
SAKURAI Hidehiro Waseda Univ., Sch.of Education, Professor, 教育学部, 教授 (10063645)
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| Co-Investigator(Kenkyū-buntansha) |
BRETTEL Klaus CEA (France), DBCM,Researcher, DBCM, researcher
SETIF Pierre CEA (France), DBCM,Research director, DBCM, research d
INOUE Kazuhito KANAGAWA Univ., Fac.of Science, Lecturer, 理学部, 講師 (20221088)
KUSUMOTO Noriaki Waseda Univ., Sch.of Education, Senior Res.Assoc., 教育学部, 助手 (60277861)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥8,700,000 (Direct Cost: ¥8,700,000)
Fiscal Year 1997: ¥4,500,000 (Direct Cost: ¥4,500,000)
Fiscal Year 1996: ¥4,200,000 (Direct Cost: ¥4,200,000)
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| Keywords | photosynthesis / reaction center / green sulfur bacteria / cytochrome / iron-sulfur cluster / flash-absorption spectroscopy / menaquinone-7 / Fe-Sセンター / 閃光分光 |
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| Research Abstract |
Electron transfer kinetics in the reaction center (Re) complex from the green sulfur bacterium Chlorobium tepidum which binds two cytochrome c (cyt c) were studied by flash-absorption spectroscopy. Photooxidized P84O^+ was reduced 95% and 80% after 1 ms by cyt c with t^<1/2> of about 65 mus and 100 muz s after the 1st and the 2nd flashes, respectively . The observed rates, the establishment of redox equilibrium after each flash and the total amount of photooxidizable cyt c are consistent with the presence of 2 equivalent cyt c per photooxidizable P840. The data were well fitted assuming a midpoint potential difference of -53 mV for electron transfer from one cyt c to P8404^+, * Em being independent of the oxidation state of the other cyt c. These observations support a model with 2 monoheme cyt c which are symmetrically arranged around the RC core. The purified RC complex binds 0.6-1.2 menaquinone-7 (MQ) . However, no transient signal due to MQ could be observed between 360 and 450 nm in the time window from 10 ns to 4 mu s. On the acceptor side, purified RC can stably hold up to 3 electrons in the mu s time range.
However, after the 4th flash, a charge recombination reaction with t^<1/2> of 20 ns was first observed. From our data, there is no evidence for involvement of MQ in charge separation in the RC of green sulfur bacteria.
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