Conical intersection dynamics of the primary photoisomerization event in vision
| Autor: | Richard A. Mathies, Daniele Brida, Marco Garavelli, Philipp Kukura, Giulio Cerullo, Katelyn M. Spillane, G. Orlandi, Dario Polli, Gaia Tomasello, Piero Altoè, Oliver Weingart, Cristian Manzoni |
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| Přispěvatelé: | D. Polli, Piero Altoe`, O. Weingart, K. M. Spillane, C. Manzoni, D. Brida, G. Tomasello, G. Orlandi, P. Kukura, R. A. Mathie, M. Garavelli, G. Cerullo |
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Rhodopsin
Chemie Electrons Photochemistry Molecular physics Vibration Isomerism Animals Spectroscopy Vision Ocular Multidisciplinary biology Chemistry Avoided crossing Conical intersection Chromophore Photochemical Processes Potential energy Cis trans isomerization Kinetics Excited state biology.protein Retinaldehyde Quantum Theory Cattle |
| Zdroj: | Nature (Lond.) 467 (2010): 440–443. doi:10.1038/nature09346 info:cnr-pdr/source/autori:Polli, Dario; Altoe, Piero; Weingart, Oliver; Spillane, Katelyn M.; Manzoni, Cristian; Brida, Daniele; Tomasello, Gaia; Orlandi, Giorgio; Kukura, Philipp; Mathies, Richard A.;Garavelli, Marco; Cerullo, Giulio/titolo:Conical intersection dynamics of the primary photoisomerization event in vision/doi:10.1038%2Fnature09346/rivista:Nature (Lond.)/anno:2010/pagina_da:440/pagina_a:443/intervallo_pagine:440–443/volume:467 |
| DOI: | 10.1038/nature09346 |
| Popis: | The primary photochemical event in vision, isomerization of the 11-cis chromophore in rhodopsin to the all-trans form, is one of the fastest natural photochemical processes known, taking less than a millionth of a millionth of a second. The molecular details of reactions of such rapidity are a stiff challenge to experimenters, but Polli et al. now report the characterization of the reaction using ultrafast optical spectroscopy with sub-20-femtosecond time resolution and spectral coverage from the visible to the near infrared. The data confirm that rhodopsin's extreme reactivity results from a molecular funnel mechanism that involves a 'conical intersection' between the potential energy surfaces of the starting and product molecules. Chemical reactions are usually described in terms of the movement of nuclei between the potential energy surfaces of ground and excited electronic states. Crossings known as conical intersections permit efficient transitions between the surfaces. It is shown here that ultrafast optical spectroscopy, with sub-20-fs time resolution and spectral coverage from the visible to the near-infrared, can map the isomerization of rhodopsin with sufficient resolution to shown that a conical intersection is important in this crucial event in vision. 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 vision1, 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 intermediate8 all suggest an unusually fast and efficient photoactivated one-way reaction9. Rhodopsin's unique reactivity is generally attributed to a conical intersection between the potential energy surfaces of the ground and excited electronic states10,11 enabling the efficient and ultrafast conversion of photon energy into chemical energy12,13,14,15,16. 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 timescale, 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. |
| Databáze: | OpenAIRE |
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