1995 Fiscal Year Final Research Report Summary
Pulsed ENDOR studies of the local structure and function of water oxidizing system in Photosynthesis.
| Project/Area Number |
06452073
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理学一般
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| Research Institution | Faculty of Science, Kwansei Gakuin University |
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Principal Investigator |
KAWAMORI Asako Kwansei Gakuin University, Department of Physics, Professor., 理学部, 教授 (40079661)
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| Co-Investigator(Kenkyū-buntansha) |
KODERA Yoshio Kitazato University, Department of Physics, Assistant, 理学部, 助手 (60265733)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Pulsed ENDOR / Pulsed ELDOR / Water oxidizing complex / Tyrosine Z / Tyrosine D / Plastoquinone / ESEEM / Photosystem II |
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| Research Abstract |
The EPR line shape of tyrosine Z (Yz) radical in Tris-treated PS II has been studied by pulsed ENDOR and was found to change at lower pH below 6.5. Based on the observed hyperfine interaction parameters, the electronic state was found to be that of cation radical. This radical mediates the electron transfer from water to the reaction center P680 and its hydrogen bonds with other amino acids play an important role. Pulsed ENDOR is a powerful mean to study the local effect of hydrogen bonding. Not only the surrounding structure of Yz radical is flexible as studied by matrix ENDOR,but also the electronic structure is responsible to the reactivity of the radical.
In the acceptor side of PS II the non-hem iron was depleted or Zn-substituted. ESEEM study of the acceptor quinone (Q_A^-) showed 2 nitrogen couplings with this molecule. The one is assigned to histidine and the other to a peptide nitrogen. Pulsed ENDOR has shown the existence of exchangeable protons including two hydrogen bonds. CN treatment of PS II resulted in the loss of nitrogen signal from ESEEM of Q_A^-, that was assigned to histidine, along with structural change in the hydrogen bondings.
New technique called ELDOR has been applied to detect the dipolar interaction between radicals. In the donor side of Ca-depleted PS II,the distances from tyrosine D (Yd) to the trapped Yz^+, S_3 signal species, and the Mn cluster were determined to be 29,30 and 27 A respectively.
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Research Products
(27 results)
