在Ru(bpy) 3(2+) - 氨酸复合体中,跨越了四个分子内质子合电子转移的机械区域
Tania Irebo1, Ming-Tian Zhang, Todd F Markle
1Photochemistry and Molecular Science, Department of Chemistry, Ångström Laboratory, Uppsala University, Box 532, SE-751 20 Uppsala, Sweden.
Journal of the American Chemical Society
|August 23, 2012
概括
这项研究揭示了模型系统中质子合电子转移 (PCET) 的新机制,逐步识别了电子第一和质子第一通路. 这些发现扩大了我们对酶和能量转化中的PCET反应的理解.
科学领域:
- 摄影化学的使用.
- 化学动力学 化学动力学
- 生物物理化学 生物物理化学
背景情况:
- 质子合电子转移 (PCET) 在生物系统和能量转化中至关重要.
- 之前的研究在Ru-TyrOH模型中确定了协同的电子-质子 (CEP) 转移和来自铁酸的电子转移.
- 了解PCET机制是设计高效的人工系统的关键.
研究的目的:
- 在Ru-TyrOH模型系统中系统地重新研究PCET机制.
- 为了识别和描述除CEP和酸盐转移之外的其他PCET途径.
- 阐明pH值和氧化剂强度对PCET机制竞争的影响.
主要方法:
- 激光闪光灭动力学被用来研究PCET速率.
- 动态同位素效应 (KIE) 用H/D替代来测量.
- 对于多种Ru-TyrOH变体,在广泛的pH范围 (1-12.5) 中分析了PCET率.
主要成果:
- 确定了两种新的机械机制:在低pH值时逐步电子第一PCET和在pH10左右的逐步质子第一PCET.
- 不同的PCET机制之间的竞争取决于溶液pH值和Ru (III/II) 氧化剂的电化学潜力.
- 动力数据和KIE提供了这些独特路径的证据.
结论:
- Ru-TyrOH系统表现出多样化的PCET机制,包括以前未被描述的阶段性途径.
- 在这些模型系统中,水和氧化物离子充当主要的质子受体.
- 这些发现提供了关于PCET在激素酶和光化学应用中的机制复杂性的见解.
更多相关视频
相关概念视频
Electron Transport Chain: Complex III and IV
During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
ATP Synthase: Mechanism
In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...
Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.


