Bacterial Photosynthetic Design Probed by Multidimensional Spectroscopies

光合生物使用精心设计的天线阵列来收集太阳能，并将其转移到反应中心，效率约为95%。这种惊人效率的核心是能量景观，它提供了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，二维电子光谱（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以提高光合效率。拟议的工作将加强研究自然和人工系统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电子结构和多发色团组装动力学理论模型的发展。从紫色细菌作为模型系统获得的理解将为我们了解更复杂的植物光系统提供信息，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。其中包括组织和参与APS物理学本科女性会议（CUWiPs）。这些会议汇集了来自全国各地的女大学生，教育她们有关职业机会和最先进的物理学研究，从而加强了美国物理学领域的女性网络。该项目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，培养不同年龄段和背景的儿童对物理的热爱。该项目旨在推动多维光谱学的前沿，以解决以下有关细菌光合作用的开放性问题：i）关键蛋白质或辅因子动力学是否增强紫色细菌的能量转移和电荷分离？ii）紫色细菌如何重塑它们的能量景观，以调节高光照和低光照条件下的能量转移？为了解决问题i），将使用电子和振动多维光谱的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。超越对分离组分的研究，以解决问题ii）整个细胞的2DES将用于绘制紫色细菌的完整能量转移和电荷分离途径：从可见光到近红外波长，具有超快时间分辨率。丰富的光谱数据将在拟议的实验中获得将提供关键的反馈紫色bacteries.This项目的能量转移和电荷分离的理论建模是由物理学系的生命系统的物理程序和分子生物物理集群在分子和细胞生物科学的司联合支持。

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.