Biophysical studies of the mechanisms of charge separation and recombination in bacterial photosynthetic reaction centers

细菌光合反应中心电荷分离与重组机制的生物物理研究

• 批准号: 182537781
• 负责人: Dr. Miguel Saggu
• 金额: --
• 依托单位: Department of Chemistry
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2011-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/182537781?language=en
• 关键词: Biophysical; studies; mechanisms; charge; separation

Photosynthesis is the most important process for solar energy conversion on earth. The energy is used to drive important cellular processes such as synthesis of ATP or NADPH, which are subsequently used to reduce CO2 to carbohydrates. The primary reactions of photosynthesis occur in the reaction center (RC), which is a membrane-integral pigment-protein. A striking feature of the RC structure is the presence of an approximate local C2 axis of symmetry defined by the photosynthetic pigmets in the so-called L- and M-branches. An important question in this context is how the organized environment in proteins modulates the spectral and redox properties of bound prosthetic groups with important functional consequences such as electron transfer (ET) almost exclusively along the L-branch. The aim of this project is to investigate the molecular mechanisms of electron transfer processes in wild-type bacterial photosynthetic reaction centers and several mutants that lack the Bacteriopheophytin cofactor HL resulting in a high yield M-side ET. For this goal RCs from purple bacteria like Rhodobacter sphaeroides or Rhodobacter capsulatus are ideally suited. They allow a direct observation of the light-induced electron transfer processes since the fully functional RC can be isolated biochemically and protocols were developed to manipulate the RC structure by site-directed mutagenesis. From the proposed studies a deeper insight into the mechanism of the unidirectionality of charge-transfer is expected. In detail, solid-state NMR experiments like photo-CIDNP and REDOR are envisaged to obtain local structural information on a particular tyrosyl that is believed to modulate reaction energetics and triggers the key step of charge separation.

光合作用是地球上太阳能转化最重要的过程。该能量用于驱动重要的细胞过程，例如 ATP 或 NADPH 的合成，随后用于将二氧化碳还原为碳水化合物。光合作用的主要反应发生在反应中心（RC），它是一种膜整合色素蛋白。 RC 结构的一个显着特征是存在由所谓的 L 和 M 分支中的光合色素定义的近似局部 C2 对称轴。在这种情况下，一个重要的问题是蛋白质中的组织环境如何调节结合辅基的光谱和氧化还原特性，并产生重要的功能后果，例如几乎完全沿着 L 分支的电子转移 (ET)。该项目的目的是研究野生型细菌光合反应中心和几种缺乏细菌脱镁叶绿素辅因子 HL 的突变体中电子转移过程的分子机制，从而产生高产的 M 侧 ET。对于这一目标，来自球形红杆菌或荚膜红杆菌等紫色细菌的 RC 非常适合。它们允许直接观察光诱导的电子转移过程，因为功能齐全的 RC 可以通过生化方法分离，并且开发了通过定点诱变操纵 RC 结构的方案。从所提出的研究中，预计可以更深入地了解电荷转移单向性的机制。具体而言，固态核磁共振实验（如 photo-CIDNP 和 REDOR）旨在获取特定酪氨酰的局部结构信息，该酪氨酰被认为可以调节反应能量并触发电荷分离的关键步骤。