Photosynthetic organisms had to evolve diverse mechanisms of light-harvesting to supply photosynthetic apparatus with enough energy. Cryptophytes represent one of the groups of photosynthetic organisms combining external and internal antenna systems. They contain one type of immobile phycobiliprotein located at the lumenal side of the thylakoid membrane, together with membrane-bound chlorophyll a/c antenna (CAC). Here we employ femtosecond transient absorption spectroscopy to study energy transfer pathways in the CAC proteins of cryptophyte Rhodomonas salina. The major CAC carotenoid, alloxanthin, is a cryptophyte-specific carotenoid, and it is the only naturally-occurring carotenoid with two triple bonds in its structure. In order to explore the energy transfer pathways within the CAC complex, three excitation wavelengths (505, 590, and 640 nm) were chosen to excite pigments in the CAC antenna. The excitation of Chl c at either 590 or 640 nm proves efficient energy transfer between Chl c and Chl a. The excitation of alloxanthin at 505 nm shows an active pathway from the S₂ state with efficiency around 50%, feeding both Chl a and Chl c with approximately 1:1 branching ratio, yet, the S₁-route is rather inefficient. The 57 ps energy transfer time to Chl a gives ~25% efficiency of the S₁ channel. The low efficiency of the S₁ route renders the overall carotenoid-Chl energy transfer efficiency low, pointing to the regulatory role of alloxanthin in the CAC antenna.

光合生物必须发展各种光收集机制，以向光合装置提供足够的能量。隐生植物代表结合了外部和内部天线系统的光合生物之一。它们包含一种位于类囊体膜腔侧的不动性藻胆蛋白，以及与膜结合的叶绿素a / c触角（CAC）。在这里，我们使用飞秒瞬态吸收光谱研究隐藻类红景天盐藻CAC蛋白中的能量转移途径。主要的CAC类胡萝卜素，四氢黄嘌呤，是一种隐植物特有的类胡萝卜素，它是唯一的天然存在的类胡萝卜素，其结构中具有两个三键。为了探索CAC复合体内的能量转移途径，选择了三种激发波长（505、590和640 nm）来激发CAC天线中的颜料。叶绿素的激发Ç在任一或590 640纳米证明叶绿素之间的有效能量转移Ç和叶绿素一个。在505 nm激发的别黄嘌呤激发显示出从S ₂状态到50％左右的活性路径，同时以大约1：1的分支比向Chl a和Chl c供料，而S ₁-route效率很低。57个ps的能量转移时间叶绿素一个给出〜了S的25％的效率₁信道。S ₁路径的低效率使整个类胡萝卜素-Chl能量转移效率降低，这表明ACL中天青素的调节作用。