Dynamics of Electron Transfer-PSI/Ferredoxin

智力价值这个项目的目标是制作一部关于分子工作的电影。这种感兴趣的分子称为光系统I(PSI)，存在于所有绿色植物中。它们与另一种分子(光系统II)一起负责光合作用，光合作用通过降解二氧化碳(全球变暖的一个重要因素)和分解水来提供大气中的氧气来维持我们的生物圈。制作这部电影需要使用斯坦福大学世界上第一台X射线激光器(美国能源部的直线加速器相干光源(LCLS))，这种激光器可以产生非常简短的分子群X射线衍射图像。这个项目是对分子的“纳米晶体”的研究，这些分子是周期性排列的团簇，每一面可能包含20个分子。这些分子必须是湿的，在真空中通过微米尺寸的特殊液体喷射在X射线束上。这种气体聚焦喷射器(有点类似于喷墨打印机)是在前一次拨款中由美国国家科学基金会资助开发的。在首次尝试通过膜蛋白纳米系统的快照衍射记录原子运动时，将使用红色激光束启动第二个分子(铁氧还蛋白)与PSI的分离(或“脱离”)，然后，在短暂的延迟后，将记录X射线快照。电影的帧将通过改变延迟时间来累积。对于每个帧，每秒从LCLS探测器读出60次的几个快照将被加在一起。更广泛的影响该项目的更广泛的影响包括培训博士后研究人员和一名研究生，并在期刊和网络上传播结果。此外，该项目和成果还将在多个推广计划中得到积极推广，包括劳伦斯·伯克利实验室推广计划、亚利桑那州立大学物理开放日、亚利桑那科学博览会、亚利桑那州立大学艾林中心推广计划和亚利桑那高中教师培训计划。我们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教学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一个原子机制。

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.