Kawato Shota, Uragami Chiasa, Inada Kazuki, Sato Shinichi, Kimura Yukihiro, Kitoh-Nishioka Hirotaka, Hashimoto Hideki, Saga Yoshitaka
Faculty of Science and Engineering, Kindai University, Higashio̅saka, Osaka 577-8502, Japan.
School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Hyogo 669-1330, Japan.
J Phys Chem Lett. 2025 Jun 26;16(25):6364-6371. doi: 10.1021/acs.jpclett.5c01325. Epub 2025 Jun 16.
Carotenoid plays important roles in both photon capture and photoprotection in photosynthetic light-harvesting (LH) proteins. Chemically modified LH proteins will expand our knowledge of the photofunctional roles of carotenoids. Here, we investigate spectral properties of carotenoid and energy transfer dynamics concerning photoprotection in LH2 that lacks B800 bacteriochlorophyll (BChl) (B800-depleted LH2). B800-depleted LH2 produced a blue shift of the absorption band of carotenoid in LH2. Resonance Raman spectroscopy indicated alteration of the geometric distortion of the conjugated polyene chain of the bound carotenoid by the B800 removal. The distortion of the carotenoid chain in B800-depleted LH2 would contribute to the blue shift of the carotenoid absorption. The B800 removal induced the rapid generation of the T state of carotenoid by excitation of B850 BChl . The new energy flow pathway may serve as an alternative photoprotection mechanism, preventing the formation of the B850 T state.
类胡萝卜素在光合捕光（LH）蛋白的光子捕获和光保护过程中均发挥着重要作用。对LH蛋白进行化学修饰将拓展我们对类胡萝卜素光功能作用的认识。在此，我们研究了缺乏B800细菌叶绿素（BChl）（B800缺失型LH2）的LH2中类胡萝卜素的光谱特性以及与光保护相关的能量传递动力学。B800缺失型LH2使LH2中类胡萝卜素的吸收带发生蓝移。共振拉曼光谱表明，去除B800会改变结合态类胡萝卜素共轭多烯链的几何扭曲。B800缺失型LH2中类胡萝卜素链的扭曲有助于类胡萝卜素吸收的蓝移。去除B800通过激发B850 BChl诱导类胡萝卜素快速产生T态。这种新的能量流动途径可能作为一种替代的光保护机制，防止B850 T态的形成。
