Ultrafast excited state dynamics in the monomeric and trimeric photosystem I core complex of Spirulina platensis probed by two-dimensional electronic spectroscopy.
Ultrafast excited state dynamics in the monomeric and trimeric photosystem I core complex of Spirulina platensis probed by two-dimensional electronic spectroscopy.
复制标题
通过二维电子光谱探测钝顶螺旋藻单体和三聚光系统 I 核心复合物中的超快激发态动力学。
DOI：
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发表时间：
2022
影响因子：
4.4
通讯作者：
M. Maiuri
中科院分区：
文献类型：
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作者：
Mattia Russo;A. P. Casazza;G. Cerullo;S. Santabarbara;M. Maiuri
光系统I （PSI）是一种由核心部分和光收集天线组成的天然超复合体，在光合作用电子传递链中起着至关重要的作用。进化适应决定了叶绿素（Chls）的类型、数量、排列和吸收的巨大变化，这些叶绿素负责光收集和电荷分离的早期步骤。例如，长波长chl（称为红色形式）在蓝藻核心中的具体位置已被深入研究，但所涉及的发色团的分配仍然存在争议。在蓝藻螺旋藻PSI核心的三聚体中观察到最红移的Chl - a形式，其吸收中心位于~ 740 nm。本文利用二维电子能谱技术研究了platensis PSI核心分离的三聚体和单体的光激发动力学。通过全局分析，我们解析并比较了本体Chl和红色形式之间的直接下坡和上坡激发能转移（EET）过程，观察到单体（在740 nm处缺乏最远红色Chl形式）和三聚体之间的显著差异，后者的超快EET成分从500到100 fs加速了5倍。我们的研究结果强调了EET动力学的复杂性，发生在广泛的时间常数范围内，以及它们对所涉及的能量分布和辅因子排列的敏感性。单体和三聚体形式的比较，在天线尺寸和红色形式的程度上都有所不同，使我们能够提取有关PSI功能的重要信息。
Photosystem I (PSI), a naturally occurring supercomplex composed of a core part and a light-harvesting antenna, plays an essential role in the photosynthetic electron transfer chain. Evolutionary adaptation dictates a large variability in the type, number, arrangement, and absorption of the Chlorophylls (Chls) responsible for the early steps of light-harvesting and charge separation. For example, the specific location of long-wavelength Chls (referred to as red forms) in the cyanobacterial core has been intensively investigated, but the assignment of the chromophores involved is still controversial. The most red-shifted Chl a form has been observed in the trimer of the PSI core of the cyanobacterium Spirulina platensis, with an absorption centered at ∼740 nm. Here, we apply two-dimensional electronic spectroscopy to study photoexcitation dynamics in isolated trimers and monomers of the PSI core of S. platensis. By means of global analysis, we resolve and compare direct downhill and uphill excitation energy transfer (EET) processes between the bulk Chls and the red forms, observing significant differences between the monomer (lacking the most far red Chl form at 740 nm) and the trimer, with the ultrafast EET component accelerated by five times, from 500 to 100 fs, in the latter. Our findings highlight the complexity of EET dynamics occurring over a broad range of time constants and their sensitivity to energy distribution and arrangement of the cofactors involved. The comparison of monomeric and trimeric forms, differing both in the antenna dimension and in the extent of red forms, enables us to extract significant information regarding PSI functionality.