Theoretical Research on Primary Chemical Reactions in Photosynthesis.

光合作用初级化学反应的理论研究。

• 批准号: 60580224
• 负责人: KUSUNOKI Masami
• 金额: $ 0.77万
• 依托单位: Meiji University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60580224/
• 关键词: Elementary process of intermolecular electron transfer; Elastic electron-tunneling mechanism; Doubleexchange mechanism; Promoting mode phonon-induced electron-tunneling mechamism; Anharmonicity of moleccular vibration; Charge separation process; Pho

1. A molecular orbital theory for many electron system was applied to formulate and classify possible mechanisms in elementary intermolecular electron-transfer(ET) process. The ET matrix element was found to contain four terms which represent an elastic electron-tunneling process( <T_1> ), a doubleexchange process via occupied molecular orbitals( <T_2> ), an inelastic electron-tunneling process( <T_3> ) and a nuclear nonadiabaticity process( <T_4> ). A significant finding is that the <T_3> , which arises from the Coulombic interaction between electron and promoting modes of molecular vibration, can be greatly enhanced far beyond <T_1> when the vibrating charges exist as close as the ET pathway because of its quasi-one dimensionarity.2. A theoretical formula for the Franck-Condon factor in the ET rate taking account of the anharmonicity (3rd and 4th) of molecular vibration was derived with use of the Green's function technique in many-body problems. The effect of anharmonicity was estim … More ated to change the rate constant at most by one order of magnitude. It is likely to be responsible for negative activation processes such as the (Bchl) <2^+> I <Q(_A^-)> <-!>> <(BChl)_2> I <Q_A> reaction in bacteria.3. The enhancement of the ET rate over the classical Marcus theory in the inverted region where the energy gap exceeds the reorganization energy was ascribed to the "phonon side-bands" of high frequency modes of molecular vibrations such as the C-C and C-H bond Stretchings.4. The observed <H_2> O/ <D_2> O isotope effect in cytochrome oxidation reactions seems to indicate the predominance of the <T_3> term, i.e. the promoting mode phonon-induced electron-tunneling mechanism, in biological systems.5. As regards the charge separation process in photosynthetic bacteria, we estimated the <T_3> for each predicted shortest ET pathway which includes hydrogen-bonds and obtained the calculated rate constants and quantum yield in good agreement with experimental results.6. In order to establish the molecular mechanism of photosynthetic water-splitting reaction based on our "microsurface model of catalytic binuclear manganese complex, we optimized the geometries of the <S_0> and <S_1> states with use of ab initio molecualr orbital method. The resultant Mn-Mn atomic distances agree well with those obtained from the EXAFS analysis. Further, the <S_1> state was found to be more stable than the <S_0> state in agreement with the experimental fact. Less

1.应用多电子体系的分子轨道理论，对分子间电子转移（ET）过程中可能的机理进行了描述和分类。发现ET矩阵元包含四项，分别代表弹性电子隧穿过程（<T_1>）、通过占据分子轨道的双交换过程（<T_2>）、非弹性电子隧穿过程（<T_3>）和核非绝热性过程（<T_4>）。一个重要的发现是，<T_3>由于电子与分子振动的促进模式之间的库仑相互作用，由于它的准一维性，它可以大大增强，远远超过<T_1>振动电荷存在时的ET途径.利用多体问题中的绿色函数方法，导出了考虑分子振动非谐性（3阶和4阶）时电子转移率中Franck-Condon因子的理论公式。对非谐性的影响进行了估计， ...更多信息 速率常数最多改变一个数量级。它可能是负激活过程的原因，如（Bchl）&lt;2^+&gt; I &lt;Q（_A^-）&gt; &lt;-！&gt;&gt;细菌内的&lt;（BChl）_2&gt; I<Q_A>反应.在能隙超过重组能的反转区域，电子转移速率比经典Marcus理论的增强归因于分子振动高频模式的“声子边带”，如C-C和C-H键的伸缩.在<H_2><D_2>细胞色素氧化反应中观察到的O/ O同位素效应似乎表明了该<T_3>术语在生物系统中的主导地位，即促进模式声子诱导的电子隧穿机制.对于光合细菌中的电荷分离过程，我们估算<T_3>了每一个预测的最短ET途径，其中包括氢键，并得到了计算的速率常数和量子产率与实验结果吻合良好.为了建立基于双核锰配合物催化微表面模型的光合水裂解反应的分子机理，我们<S_0><S_1>采用从头算分子轨道方法优化了双核锰配合物的构型.由此得到的Mn-Mn原子距离与EXAFS分析结果吻合得很好。此外，发现该<S_1>状态比<S_0>与实验事实一致的状态更稳定。少

项目成果

Masami Kusunoki: "Theory of "Non-chemical" Electron Transfer in Molecular Systems. I. On the Possible Mechanisms in the Non-adiabatic Limit." J. Chem. Phys.

Masami Kusunoki：“分子系统中的“非化学”电子转移理论。I.关于非绝热极限的可能机制。”

Masami Kusunoki: "The Promoting-Mode Phonon-Induced Electron-Tunneling through Bridging Chains. I. The <H_2> O/ <D_2> O Isotope Effect in Cytochrome Oxidation-Reduction Reactions." J. Chem. Phys.

Masami Kusunoki：“通过桥链促进模式声子诱导电子隧道。I. 细胞色素氧化还原反应中的 <H_2> O/ <D_2> O 同位素效应。”

Masami Kusunoki: "Molecular Orbital Study (IV) On the "Microsurface" Model of Catalytic Binuclear Manganese Complex in Photosynthetic Water-Splitting and Oxygen-Evolving Reaction." Progress in Photosynthetic Research(Biggens, J. ed.), Martinus Nijhoff Pub

Masami Kusunoki：“光合水分解和析氧反应中催化双核锰配合物“微表面”模型的分子轨道研究（IV）。”

Masami Kusunoki: J.Chem.Phys.

楠木正美：J.Chem.Phys。

Biggens,J.ed.Masami Kusunoki: Progress in Photosynthesis Research Martinus Nijhoff Publishers.1. 729-732 (1987)

Biggens，J.ed.Masami Kusunoki：光合作用研究进展 Martinus Nijhoff 出版社。1。