Intrinsic photoisomerization dynamics of protonated Schiff-base retinalстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 26 апреля 2019 г.
Аннотация: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 actionspectroscopy
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 potentialenergy
surface to lower the barrier for particular double-bond isomerization, thus changing
both the timescale and specificity of the photoisomerization.