Dynamics of Electron Transfer-PSI/Ferredoxin

这个项目的目的是拍一部分子工作的电影。我们感兴趣的分子被称为光系统I (PSI)，存在于所有的绿色植物中。与另一种分子（光系统II）一起，它们负责光合作用，通过降解二氧化碳（全球变暖的重要因素）和分解水为大气提供氧气来维持我们的生物圈。制作这部电影将需要使用世界上第一台x射线激光器，在斯坦福大学（美国能源部的直线相干光源（LCLS）），它产生极短的“快照”x射线衍射图像的分子群。这个项目是对分子的“纳米晶体”的研究，它是周期性排列的簇，每边大约含有20个分子。这些分子必须是湿的，在真空中以微米级的特殊液体射流的形式通过x射线束喷射。这种气体聚焦喷射器（有点类似于喷墨打印机）是在NSF以前的资助下开发的。在第一次尝试中，通过膜蛋白纳米晶体的快照衍射记录原子运动，将使用红色激光束启动从PSI分离（或“脱离”）第二个分子（铁氧还蛋白），然后，经过短暂的延迟，将记录x射线快照。通过改变延迟时间，电影的帧数就会累积起来。从LCLS探测器每秒读取60次的几个快照将被加在一起。该项目的广泛影响包括培养博士后研究人员和一名研究生，并在期刊和网络上传播研究结果。此外，该项目和结果将在一些外展计划中积极推广，包括劳伦斯伯克利实验室外展计划、亚利桑那州立大学物理开放日、亚利桑那科学博览会、亚利桑那州立大学埃林中心外展计划和亚利桑那高中教师培训计划。将继续参与这些项目，在这些项目中，研究的方法和结果将以一种教学上合理的方式向学生解释。这项工作与减少全球变暖的努力直接相关，因为它为光合作用过程中的关键步骤提供了原子机制。

Intellectual MeritThis project aims to make a movie of molecules at work. The molecule of interest is called Photosystem I (PSI), and is present in all green plants. Together with another molecule (Photosystem II), these are responsible for photosynthesis, which maintains our biosphere by degrading carbon dioxide (an important contributor to Global Warming) and by splitting water to provide the oxygen in our atmosphere. Making this movie will entail use of the world's first X-ray laser, at Stanford (the DOE's Linac Coherent Light Source(LCLS)), which produces extremely brief "snap-shot" X-ray diffraction images of groups of molecules. This project is a study of "nanocrystals" of the molecules, which are periodically arranged clusters containing perhaps 20 molecules on a side. The molecules, which must be wet, are sprayed in a vacuum across the X-ray beam in a special liquid jet of micron dimensions. This gas-focussing jet (somewhat similar to an ink-jet printer) was developed under NSF support in a previous grant. In this first attempt to record atomic motion by snap-shot diffraction from membrane protein nanocrsystals, a red laser beam will be used to initiate the separation (or "undocking") of a second molecule (ferredoxin) from PSI, then, after a brief delay, an X-ray snapshot will be recorded. Frames of a movie will be accumulated by varying the delay time. Several snapshots, read out from the LCLS detector 60 times per second, will be added together for each frame. Broader Impacts The broader impact of the project includes the training of postdoctoral researchers and a graduate student, and the dissemination of the results in journals and on the web. In addition the project and results will be actively promoted in a number of outreach programs, including the Lawrence Berkeley Laboratory Outreach program, the Open Days at ASU Physics, the Arizona Science Fair, the Outreach program of the Eyring Center at ASU and in the Arizona High School Teacher Training Program. There will be continued participation in these programs, where the methods and results of the research are explained to students in a pedagogically sound manner. This work is directly relevant to efforts to reduce global warming since it provides an atomic mechanism for a crucial step in the process of photosynthesis.