Photosynthetic organisms have diversified light-harvesting complexes (LHCs) to collect solar energy efficiently, leading to an acquisition of their ecological niches. Herein we report on biochemical and spectroscopic characterizations of fucoxanthin chlorophyll a/c-binding protein (FCP) complexes isolated from a marine pinguiophyte Glossomastix chrysoplasta. The pinguiophyte FCP showed one subunit band in SDS-PAGE and one protein-complex band with a molecular weight at around 66 kDa in clear-native PAGE. By HPLC analysis, the FCP possesses chlorophylls a and c, fucoxanthin, and violaxanthin. To clarify excitation-energy-relaxation processes in the FCP, we measured time-resolved fluorescence spectra at 77 K of the FCP adapted to pH 5.0, 6.5, and 8.0. Fluorescence curves measured at pH 5.0 and 8.0 showed shorter lifetime components compared with those at pH 6.5. The rapid decay components at pH 5.0 and 8.0 are unveiled by fluorescence decay-associated (FDA) spectra; fluorescence decays occur in the 270 and 160-ps FDA spectra only at pH 5.0 and 8.0, respectively. In addition, energy-transfer pathways with time constants of tens of picoseconds are altered under the basic pH condition but not the acidic pH condition. These findings provide novel insights into pH-dependent energy-transfer and energy-quenching machinery in not only FCP family but also photosynthetic LHCs.

光合生物已经利用多种光采复合物（LHC）高效收集太阳能，从而获得了其生态位。在这里，我们报道了从海洋松藻植物Glossomastix chrysoplasta分离出的岩藻黄质叶绿素a / c-结合蛋白（FCP）复合物的生化和光谱学表征。松果体FCP在SDS-PAGE中显示一个亚基带，在纯天然PAGE中显示一个分子量约66 kDa的蛋白质复合带。通过HPLC分析，FCP具有叶绿素a和c，岩藻黄质和紫黄质。为了阐明FCP中的激发能量松弛过程，我们测量了FCP在77 K时的pH值，6.5和8.0的时间分辨荧光光谱。与pH 6.5相比，在pH 5.0和8.0下测得的荧光曲线显示出较短的寿命成分。通过荧光衰变相关（FDA）光谱揭示了pH 5.0和8.0时的快速衰变成分。荧光衰减仅在pH 5.0和8.0时分别在270和160 ps FDA光谱中发生。另外，在碱性pH条件下，时间常数为数十皮秒的能量转移途径被改变，而在酸性pH条件下，能量转移途径没有改变。这些发现不仅为FCP系列而且为光合LHCs提供了pH依赖的能量转移和能量猝灭机制的新颖见解。