Barrierless Photoisomerization of 11-<i>cis</i> Retinal Protonated Schiff Base in Solution

Bassolino, Giovanni; Sovdat, Tina; Duarte, Alex Soares; Lim, Jong Min; Schnedermann, Christoph; Liebel, Matz; Odell, Barbara; Claridge, Timothy D. W.; Fletcher, Stephen P.; Kukura, Philipp

doi:10.1021/jacs.5b06492

Cited by 29 publications

(31 citation statements)

References 37 publications

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“…The protonated 11-cis chromophore in solution exhibited an even lower quantum yield of 0.19 (±0.04) outside the protein pocket. 37 These results evidence an anomalous isotope effect where symmetric deuteration of the isomerizing bond produces a higher isomerization quantum yield while asymmetric isotopic substitution significantly lowers the yield.…”

Section: Isomerization Quantum Yieldmentioning

confidence: 87%

“…Each sample was stirred constantly during the measurement and illuminated for 20 min corresponding to a bleaching of <15 % of the initial molecules. The quantum yield of the 11-cis chromophore in methanol was measured according to the procedure described by Sovdat et al 37,47 Statistical significance (n=4) was determined based on a t-test at 99% confidence interval to yield p (11,12-H2 regenerated)=0.111, t (11,12-…”

Section: Quantum Yield Measurementsmentioning

confidence: 99%

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Evidence for a vibrational phase-dependent isotope effect on the photochemistry of vision

et al. 2018

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Vibronic coupling is key to efficient energy flow in molecular systems and a critical component of most mechanisms invoking quantum effects in biological processes. Despite increasing evidence for coherent coupling of electronic states being mediated by vibrational motion, it is not clear how and to what degree properties associated with vibrational coherence such as phase and coupling of atomic motion can impact the efficiency of light-induced processes under natural, incoherent illumination. Here, we show that deuteration of the H-C=C-H double-bond of the 11-cis retinal chromophore in the visual pigment rhodopsin significantly and unexpectedly alters the photoisomerization yield while inducing smaller changes in the ultrafast isomerization dynamics assignable to known isotope effects. Combination of these results with non-adiabatic molecular dynamics simulations reveals a vibrational phase-dependent isotope effect that we suggest is an intrinsic attribute of vibronically coherent photochemical processes.

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Section: Isomerization Quantum Yieldmentioning

confidence: 87%

Section: Quantum Yield Measurementsmentioning

confidence: 99%

Evidence for a vibrational phase-dependent isotope effect on the photochemistry of vision

et al. 2018

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“…Rhodopsins also show high 65% quantum yields for isomerization to all- trans . The cis isomer is found to behave much faster than all- trans in MeOH at early times, but showed the same slow (4 ps) behavior on the longer timescale 24–26 . To account for both fast and slow dynamics, as well as the low quantum yield of only 0.22 in solution, it was proposed that a primary role of the protein is to adjust the ratio between ground-state chromophore conformations that lead to reactive and nonreactive decay channels 27 .…”

Section: Introductionmentioning

confidence: 91%

Intrinsic photoisomerization dynamics of protonated Schiff-base retinal

et al. 2019

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The retinal protonated Schiff-base (RPSB) in its all-trans form is found in bacterial rhodopsins, whereas visual rhodopsin proteins host 11-cis RPSB. In both cases, photoexcitation initiates fast isomerization of the retinal chromophore, leading to proton transport, storage of chemical energy or signaling. It is an unsolved problem, to which degree this is due to protein interactions or intrinsic RPSB quantum properties. Here, we report on time-resolved action-spectroscopy studies, which show, that upon photoexcitation, cis isomers of RPSB have an almost barrierless fast 400 fs decay, whereas all-trans isomers exhibit a barrier-controlled slow 3 ps decay. Moreover, formation of the 11-cis isomer is greatly favored for all-trans RPSB when isolated. The very fast photoresponse of visual photoreceptors is thus directly related to intrinsic retinal properties, whereas bacterial rhodopsins tune the excited state potential-energy surface to lower the barrier for particular double-bond isomerization, thus changing both the timescale and specificity of the photoisomerization.

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“…Retinal, and its protonated Schiff base, are both known to undergo ultrafast IC via low energy CIs located along Z/E photoisomerism coordinates. 87,[165][166][167][168][169][170][171] The lens, which focuses light onto the retina, contains many molecular constituents that help protect it (and the surrounding environment) from hard UV radiation. Kynurenines (see inset of Fig.…”

Section: Molecular Constituents In Natural Sunscreensmentioning

confidence: 99%

Photoprotection: extending lessons learned from studying natural sunscreens to the design of artificial sunscreen constituents

et al. 2017

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Evolution has ensured that plants and animals have developed effective protection mechanisms against the potentially harmful effects of incident ultraviolet radiation (UVR). Tanning is one such mechanism in humans, but tanning only occurs post-exposure to UVR. Hence, there is ever growing use of commercial sunscreens to pre-empt overexposure to UVR. Key requirements for any chemical filter molecule used in such a photoprotective capacity include a large absorption cross-section in the UV-A and UV-B spectral regions and the availability of one or more mechanisms whereby the absorbed photon energy can be dissipated without loss of the molecular integrity of the chemical filter. Here we summarise recent experimental (mostly ultrafast pump-probe spectroscopy studies) and computational progress towards unravelling various excited state decay mechanisms that afford the necessary photostability in chemical filters found in nature and those used in commercial sunscreens. We also outline ways in which a better understanding of the photophysics and photochemistry of sunscreen molecules selected by nature could aid the design of new and improved commercial sunscreen formulations.

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Barrierless Photoisomerization of 11-cis Retinal Protonated Schiff Base in Solution

Cited by 29 publications

References 37 publications

Evidence for a vibrational phase-dependent isotope effect on the photochemistry of vision

Evidence for a vibrational phase-dependent isotope effect on the photochemistry of vision

Intrinsic photoisomerization dynamics of protonated Schiff-base retinal

Photoprotection: extending lessons learned from studying natural sunscreens to the design of artificial sunscreen constituents

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