Chemical and Pharmaceutical Bulletin
Online ISSN : 1347-5223
Print ISSN : 0009-2363
ISSN-L : 0009-2363
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Synthesis of One Double Bond-Inserted Retinal Analogs and Their Binding Experiments with Opsins: Preparation of Novel Red-Shifted Channelrhodopsin Variants
Takashi OkitsuYumiko YamanoYi-Chung ShenToshikazu SasakiYuka KobayashiShoko MorisawaTakahiro YamashitaYasushi ImamotoYoshinori ShichidaAkimori Wada
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2020 Volume 68 Issue 3 Pages 265-272


In optogenetics, red-shifted channelrhodopsins (ChRs) are eagerly sought. We prepared six kinds of new chromophores with one double bond inserted into the polyene side chain of retinal (A1) or 3,4-didehydroretinal (A2), and examined their binding efficiency with opsins (ReaChR and ChrimsonR). All analogs bound with opsins to afford new ChRs. Among them, A2-10ex (an extra double bond is inserted at the C10–C11 position of A2) showed the greatest red-shift in the absorption spectrum of ChrimsonR, with a maximum absorbance at 654 nm (67 nm red-shifted from that of A1-ChrimsonR). Moreover, a long-wavelength spectral boundary of A2-10ex-ChrimsonR was extended to 756 nm, which reached into the far-red region (710–850 nm).

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