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Conical intersection dynamics of the primary photoisomerization event in vision

机译：视觉中主要光异构化事件的圆锥形相交动力学

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摘要

Ever since the conversion of the 11-cis retinal chromophore to its all-trans form in rhodopsin was identified as the primary photochemical event in vision, experimentalists and theoreticians have tried to unravel the molecular details of this process. The high quantum yield of 0.65 (ref. 2), the production of the primary ground-state rhodopsin photoproduct within a mere 200 fs (refs 3-7), and the storage of considerable energy in the first stable bathorhodopsin intermediate all suggest an unusually fast and efficient photoactivated one-way reaction. Rhodopsin's unique reactivity is generally attributed to a conical intersection between the potential energy surfaces of the ground and excited electronic states enabling the efficient and ultrafast conversion of photon energy into chemical energy. But obtaining direct experimental evidence for the involvement of a conical intersection is challenging: the energy gap between the electronic states of the reacting molecule changes significantly over an ultrashort time-scale, which calls for observational methods that combine high temporal resolution with a broad spectral observation window. Here we show that ultrafast optical spectroscopy with sub-20-fs time resolution and spectral coverage from the visible to the near-infrared allows us to follow the dynamics leading to the conical intersection in rhodopsin isomerization. We track coherent wave-packet motion from the photoexcited Franck-Condon region to the photoproduct by monitoring the loss of reactant emission and the subsequent appearance of photoproduct absorption, and find excellent agreement between the experimental observations and molecular dynamics calculations that involve a true electronic state crossing. Taken together, these findings constitute the most compelling evidence to date for the existence and importance of conical intersections in visual photochemistry.
机译：自从视紫红质中11-顺式视网膜生色团转变为全反式形式被认为是视觉中的主要光化学事件以来，实验家和理论家就试图揭示这一过程的分子细节。 0.65的高量子产率（参考2），仅200 fs内的初级基态视紫红质光产物的产生（参考3-7）以及在第一个稳定的视紫红质中间体中的大量能量存储均表明存在异常情况快速有效的光活化单向反应。视紫红质的独特反应性通常归因于地面势能表面与激发电子态之间的圆锥形交点，从而使光子能高效，超快地转化为化学能。但是，要获得有关锥形相交的直接实验证据是具有挑战性的：反应分子电子态之间的能隙在超短时间范围内会发生显着变化，这要求将高时间分辨率与宽光谱观察相结合的观察方法窗口。在这里，我们显示具有20fs以下时间分辨率和从可见光到近红外范围的光谱覆盖范围的超快速光谱使我们能够追踪视紫红质异构化中圆锥形相交的动力学。我们通过监测反应物的发射损失和随后光产物吸收的出现，跟踪从光激发的弗兰克-康登区到光产物的相干波包运动，并发现实验观察和涉及真实电子状态的分子动力学计算之间的极好的一致性穿越。综上所述，这些发现构成了迄今为止在视觉光化学中圆锥形交叉点的存在和重要性的最有说服力的证据。

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  • 来源
    《Nature》 |2010年第7314期|P.440-443|共4页
  • 作者

    Dario Polli; Piero Altoe; Oliver Weingart; Katelyn M. Spillane; Cristian Manzoni; Daniele Brida; Gaia Tomasello; Giorgio Orlandi; Philipp Kukura; Richard A. Mathies; Marco Garavelli; Giulio Cerullo;

  • 作者单位

    IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32,20133 Milano, Italy;

    rnDipartimentodi Chimica 'G.Ciamician', Universita di Bologna, V. F. Selmi 2,40126 Bologna, Italy;

    rnLehrstuhl fuer theoretische Chemie, Universitaet Duisburg-Essen, Universitaetsstrasse 5,45117 Essen, Germany Max-Planck-lnstitut fuer Kohlenforschung, Kaiser-Wilhelm-Platz 1,45470 Muelheim an der Ruhr, Germany;

    Chemistry Department, University of California at Berkeley, Berkeley, California 94720, USA;

    rnIFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32,20133 Milano, Italy;

    rnIFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32,20133 Milano, Italy;

    rnDipartimentodi Chimica 'G.Ciamician', Universita di Bologna, V. F. Selmi 2,40126 Bologna, Italy;

    rnDipartimentodi Chimica 'G.Ciamician', Universita di Bologna, V. F. Selmi 2,40126 Bologna, Italy;

    rnDepartment of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, Oxford OX1 3QZ, UK;

    rnChemistry Department, University of California at Berkeley, Berkeley, California 94720, USA;

    rnDipartimentodi Chimica 'G.Ciamician', Universita di Bologna, V. F. Selmi 2,40126 Bologna, Italy;

    rnIFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32,20133 Milano, Italy;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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