The role of the light antenna protein LHC-II in the structure and dynamic reorganization of photosynthetic membranes

研究背景脂多糖（Lipopolysaccharide，LPS）是一种复杂的脂多糖，是革兰氏阴性菌外膜的主要结构成分，也是革兰氏阴性菌从细胞中释放出的一种强有力的毒素（内毒素）。重要的是，我们了解LPS-脂质分子相互作用可能会影响毒性。我们先前发现LPS插入模型膜并引起主要扰动：（i）脂质小管形成，（ii）膜穿孔和（iii）多层形成。这些变化被认为是局部静电相互作用的结果，但其具体机制还有待进一步研究。(2)确认LPS源的致病性和膜破坏性之间的任何相关性。(3)测定LPS在膜上引起的物理性质变化。(4)测试LPS作用的生物相关抑制剂。新奇/及时性我们是第一个观察到LPS对支持的脂质双层的扰动的小组，凭借我们在该系统中的专业知识和所需的实验技术，我们处于有利地位，可以揭示潜在的分子机制。虽然许多人已经研究了致病性（内毒素休克）或分离的LPS（物理表征），但LPS在组合的脂质/LPS模型系统上引起的动态变化尚未得到充分研究。实验方法国家的最先进的显微镜将被用来可视化动态膜组织的变化在纳米级（原子力显微镜（AFM），1纳米分辨率在8 fps）和跟踪膜流动性（荧光显微镜）。这将允许定性评估来自不同细菌（致病性/非致病性）的LPS对不同脂质系统（带电的，“脂筏”样）的影响。将使用差示扫描量热法（熔融转变温度）、石英晶体微量天平（质量/粘度）和朗缪尔槽测量（膜侧压）对膜上LPS诱导的物理变化进行定量分析。多层膜的特征在于中子反射率（层厚度）。最后，将筛选免疫系统的各种组分（例如LPS结合蛋白）抑制LPS诱导的损伤的能力。

BackgroundLipopolysaccharide (LPS) is a complex lipoglycan, which acts as a major structural component of the outer membrane of Gram-negative bacteria and potent toxin when released from cells ("endotoxin"). It is important that we understand LPS-lipid molecular interactions which may affect toxicity. We previously found that LPS inserts into model membranes and causes major perturbations: (i) lipid tubule formation, (ii) membrane perforation and (iii) multilayer formation. These changes were proposed to be governed by local electrostatic interactions, however, a detailed mechanism is required.Objectives(1) Elucidate the molecular basis of LPS-lipid interaction.(2) Qualify any correlation between pathogenicity of LPS source and membrane disruptiveness.(3) Determine physical property changes induced by LPS on membranes.(4) Test biologically-relevant inhibitors of LPS action.Novelty/TimelinessWe were the first group to observe perturbation of supported lipid bilayers by LPS and with our expertise in this system and required experimental techniques, we are uniquely-placed to reveal the underlying molecular mechanism. Whilst many have investigated either the pathogenicity (endotoxic shock) or isolated LPS (physical characterization), the dynamic changes caused by LPS on a combined lipid/LPS model system have not been fully investigated. Experimental approachState-of-the-art microscopy will be used to visualize dynamic membrane organizational changes at the nanoscale (atomic force microscopy (AFM), 1-nm-resolution at 8 fps) and track membrane fluidity (fluorescence microscopy). This will allow qualitative assessment of the effect of LPS from different bacteria (pathogenic/ non-pathogenic) on different lipid systems (charged, "lipid raft"-like). A quantitative analysis of physical changes induced by LPS on membranes will be undertaken using differential scanning calorimetry (melting transition temperatures), quartz crystal microbalance (mass/viscosity) and Langmuir trough measurements (membrane lateral pressure). Multilayers will be characterized with neutron reflectivity (layer thickness). Finally, various components of the immune system (e.g. LPS Binding Protein) will be screened for ability to inhibit LPS-induced damage.