Bacterial Photosynthetic Design Probed by Multidimensional Spectroscopies

光合作用生物利用精密的天线阵列收集太阳能并将其传输到反应中心，效率约为95%。这种惊人效率的核心是能量格局，它提供天线和反应中心之间的定向超快能量转移，以及反应中心内的定向电荷分离。近年来，二维电子能谱(2DES)已成为研究光合作用中能量传递和电荷分离的有力手段。2DES和其他光谱测量表明，关键的电子-振动动力学可能会提高光合作用效率。建议的工作将加强研究天然和人工体系中的能量转移和电荷分离的实验工具。细菌光系统的广泛实验表征将推动多发色组装的电子结构和动力学理论模型的发展。从紫色细菌中获得的作为模型系统的理解将有助于我们理解更复杂的植物光系统，并可能指导人工捕光材料的设计。拟议的工作将为研究生和本科生提供广泛的科学培训，并将支持广泛的外联活动。其中包括组织和参加APS物理专业女本科生会议。这些会议将来自全国各地的本科生女性聚集在一起，向她们提供有关物理学领域的职业机会和最新研究的教育，从而加强美国物理学领域的女性网络。该提议旨在通过参加一年一度的物理奥林匹克竞赛和女童子军科学探索日，在不同年龄段和背景的儿童中培养对物理的热爱。该项目旨在推动多维光谱学的前沿，以解决以下关于细菌光合作用的公开问题：i)关键蛋白质或辅因子动力学是否促进紫色细菌中的能量转移和电荷分离？Ii)紫色细菌如何在强光和弱光条件下重塑其能量格局，以调节能量转移？为了解决问题I)将使用电子和振动多维光谱调色板对细菌反应中心进行前所未有的详细研究，提供电荷分离过程中色素和周围蛋白质的动态图像。超越对分离成分的研究来解决问题II)将使用整个细胞的2DES来绘制紫色细菌的完整能量转移和电荷分离路径：从可见光到近红外波长，具有超快的时间分辨率。将在拟议的实验中获得的丰富的光谱数据将为紫色细菌中的能量转移和电荷分离的理论建模提供关键的反馈。该项目由物理学部的生命系统物理计划和分子和细胞生物科学部的分子生物物理组共同支持。

Photosynthetic organisms employ elaborate antenna arrays to harvest solar energy and transfer it to reaction centers with ~95% efficiency. At the heart of this stunning efficiency is the energy landscape that provides directional ultrafast transfer of energy between the antennae and reaction centers, and directional charge separation within reaction centers. Recently two-dimensional electronic spectroscopy (2DES) has emerged as a powerful method for studying energy transfer and charge separation in photosynthesis. 2DES and other spectroscopic measurements have suggested that key electronic-vibrational dynamics may enhance photosynthetic efficiency. The proposed work will enhance the experimental tools for studying energy transfer and charge separation in natural and artificial systems. The extensive experimental characterization of bacterial photosystems will drive the development of theoretical models of the electronic structure and dynamics of multichromophoric assemblies. The understanding gained from purple bacteria as a model system will inform our understanding of the more complex plant photosystems and may guide the design of artificial light-harvesting materials. The proposed work will provide extensive scientific training for graduate and undergraduate students and will also support a wide range of outreach activities. These include the organization and participation in the APS Conferences for Undergraduate Women in Physics (CUWiPs). These meetings bring together undergraduate women from the across the country, educating them about career opportunities and state-of-the-art research in Physics, thereby strengthening the network of women in Physics in the US. The proposal aims to foster a love of physics among children from diverse age groups and backgrounds through participation in the yearly Physics Olympiad and science exploration days for Girl Scouts troops.This project aims to push the frontiers of multidimensional spectroscopy to address the following open questions about bacterial photosynthesis: i) Do key protein or cofactor dynamics enhance energy transfer and charge separation in purple bacteria? ii) How do purple bacteria remodel their energy-landscape to regulate energy transfer under high and low light conditions? To address question i) bacterial reaction centers will be studied in unprecedented detail with a palette of electronic and vibrational multidimensional spectroscopies, providing a dynamical picture of the pigments and surrounding protein during charge separation. Moving beyond studies of the isolated components to address question ii) 2DES of whole cells will be used to map the complete energy transfer and charge separation pathways of purple bacteria: from the visible to near-infrared wavelengths with ultrafast time resolution. The rich spectroscopic data to be obtained in the proposed experiments will provide critical feedback to theoretical modeling of energy transfer and charge separation in purple bacteria.This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Molecular Biophysics Cluster in the Division of Molecular and Cellular Biosciences.