Steering electrons on moving pathways.
Steering electrons on moving pathways.
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DOI：
10.1021/ar900123t
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发表时间：
2009-10-20
影响因子：
18.3
通讯作者：
Xiao, Dequan
中科院分区：
文献类型：
--
作者：
Beratan, David N.;Skourtis, Spiros S.;Balabin, Ilya A.;Balaeff, Alexander;Keinan, Shahar;Venkatramani, Ravindra;Xiao, Dequan
电子转移（ET）反应提供了化学，生物化学和物理学之间的联系。这些反应支撑着生物能量学的“发电厂”和“电网”，它们挑战我们理解进化如何操纵结构来控制ET动力学。然而，电子转移机制的球杆模型未能捕捉到ET分子丰富的电子和核动力学：这些静态表示掩盖了例如热可及分子构象的范围。电子隧穿概率随距离的指数衰减以及耦合路径之间的微妙干扰放大了结构波动对电子转移动力学的影响。在周围介质的波动也可以切换运输之间的连贯性和不连贯的ET机制，并可能门ET，使其动力学是有限的构象相互转换时间，而不是由固有的ET时间尺度。此外，制备一个电荷极化的施主态，或具有线性或角动量的施主态，可以具有深刻的动力学和动力学后果。在这个帐户中，我们建立了一个词汇来描述如何构象合奏和准备供体状态影响ET动力学的大分子。这一框架有助于揭示功能性生物ET途径的丰富性，这些途径在波动的大分子结构中进化。描述非绝热ET的概念框架似乎非常简单：计算系综平均（均方）供体-受体（DA）隧道相互作用<HDA2>，和弗兰克-康登加权态密度ρFC，以描述速率：（2π/）<HDA2>ρFC。热平均电子耦合和弗兰克-康登因子的现代描述在生物学、化学和纳米科学中建立了一个有用的预测框架。描述几何和能量波动对ET的影响使我们能够解决一系列丰富的机械和动力学难题。蛋白质的折叠对ET动力学的影响有多强，热波动是否会“洗掉”结构的特征？除了平均隧道势垒结构外，热涨落对ET动力学的影响是什么？当供体和受体在蛋白质中重新定位时，电子偶联机制是否会发生变化？对ET动力学有何影响？涨落会影响主导隧穿的少数物种吗？电子和桥振动之间的能量交换能否产生振动特征，标记电子穿过的一些D到A路径，从而消除未标记的路径，否则这些路径将有助于DA耦合（如在其他“哪种方式”或双缝实验中）？介质涨落能驱动隧穿-跳跃机制转变吗？施主-态双折射--特别是它对受主的极化和它的动量特性（这可能会在施主轨道振幅之间引入复杂的而不是纯粹的真实的关系）--如何影响电子动力学？在这个帐户中，我们描述了我们最近的研究，解决了令人困惑的问题，构象分布，激发态极化和电子动力学效应如何影响ET的大分子。事实上，构象和动力学效应出现在所有的运输制度，包括隧道，共振运输，跳跃制度。重要的是，这些作用可以诱导ET机制之间的转换。
Electron transfer (ET) reactions provide a nexus among chemistry, biochemistry, and physics. These reactions underpin the “power plants” and “power grids” of bioenergetics, and they challenge us to understand how evolution manipulates structure to control ET kinetics. Ball-and-stick models for the machinery of electron transfer, however, fail to capture the rich electronic and nuclear dynamics of ET molecules: these static representations disguise, for example, the range of thermally accessible molecular conformations. The influence of structural fluctuations on electron-transfer kinetics is amplified by the exponential decay of electron tunneling probabilities with distance, as well as the delicate interference among coupling pathways. Fluctuations in the surrounding medium can also switch transport between coherent and incoherent ET mechanisms—and may gate ET so that its kinetics is limited by conformational interconversion times, rather than by the intrinsic ET time scale. Moreover, preparation of a charge-polarized donor state, or of a donor state with linear or angular momentum, can have profound dynamical and kinetic consequences. In this Account, we establish a vocabulary to describe how the conformational ensemble and the prepared donor state influence ET kinetics in macromolecules. This framework is helping to unravel the richness of functional biological ET pathways, which have evolved in within fluctuating macromolecular structures. The conceptual framework for describing nonadiabatic ET seems disarmingly simple: compute the ensemble averaged (mean-squared) donor–acceptor (DA) tunneling interaction, <HDA2>, and the Franck–Condon weighted density of states, ρFC, to describe the rate: (2π/ħ) <HDA2> ρFC. Modern descriptions of the thermally averaged electronic coupling and of the Franck–Condon factor establish a useful predictive framework in biology, chemistry, and nanoscience. Describing the influence of geometric and energetic fluctuations on ET allows us to address a rich array of mechanistic and kinetic puzzles. How strongly is a protein’s fold imprinted on the ET kinetics, and might thermal fluctuations “wash out” signatures of structure? What is the influence of thermal fluctuations on ET kinetics beyond averaging of the tunneling barrier structure? Do electronic coupling mechanisms change as donor and acceptor reposition in a protein, and what are the consequences for the ET kinetics? Do fluctuations access minority species that dominate tunneling? Can energy exchanges between the electron and bridge vibrations generate vibronic signatures that label some of the D-to-A pathway traversed by the electron, thus eliminating unmarked pathways that would otherwise contribute to the DA coupling (as in other “which way” or double-slit experiments)? Might medium fluctuations drive tunneling–hopping mechanistic transitions? How does the donor-state preparation—in particular its polarization toward the acceptor and its momentum characteristics (which may introduce complex rather than pure real relationships among donor orbital amplitudes)—influence the electronic dynamics? In this Account, we describe our recent studies that address puzzling questions of how conformational distributions, excited-state polarization, and electronic dynamical effects influence ET in macromolecules. Indeed, conformational and dynamical effects arise in all transport regimes, including the tunneling, resonant transport, and hopping regimes. Importantly, these effects can induce switching among ET mechanisms.
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影响因子：
15
作者：
Chakrabarti, Subhasis;Parker, Matthew F. L.;Waldeck, David H.
通讯作者：
Waldeck, David H.
影响因子：
15
作者：
HOFFMAN, BM;RATNER, MA
通讯作者：
RATNER, MA
影响因子：
64.8
作者：
Davis, WB;Svec, WA;Wasielewski, MR
通讯作者：
Wasielewski, MR
影响因子：
2.8
作者：
Cave, RJ;Newton, MD
通讯作者：
Newton, MD
DOI：
10.1073/pnas.94.8.3703
发表时间：
1997-04-15
影响因子：
11.1
作者：
Daizadeh, I;Medvedev, ES;Stuchebrukhov, AA
通讯作者：
Stuchebrukhov, AA