Fucoxanthin chlorophyll-binding proteins (FCPs) are the major light-harvesting complexes of diatoms. In this work, FCPs isolated from Cyclotella meneghiniana have been studied by means of optically detected magnetic resonance (ODMR) and time-resolved electron paramagnetic resonance (TR-EPR), with the aim to characterize the photoprotective mechanism based on triplet–triplet energy transfer (TTET). The spectroscopic properties of the chromophores carrying the triplet state have been interpreted on the basis of a delved analysis of the recently solved crystallographic structures of FCP. The results point toward a photoprotective role for two fucoxanthin molecules exposed to the exterior of the FCP monomers. This shows that FCP has adopted a structural strategy different from that of related light-harvesting complexes from plants and other microalgae, in which the photoprotective role is carried out by two highly conserved carotenoids in the interior of the complex.

岩藻黄质叶黄素结合蛋白（FCPs）是硅藻的主要光捕获复合体。在这项工作中，从米氏小环藻分离的FCP已经通过光学检测磁共振（ODMR）和时间分辨电子顺磁共振（TR-EPR）进行了研究，目的是表征基于三重态-三重态能量转移（TTET）的光保护机理。带有三重态的发色团的光谱性质已经根据对FCP最近解决的晶体结构的深入分析得到了解释。结果表明暴露于FCP单体外部的两个岩藻黄质分子具有光保护作用。这表明FCP采用了与植物和其他微藻的相关光采复合物不同的结构策略，其中光保护作用是由复合物内部的两个高度保守的类胡萝卜素发挥的。