Novel High-Field EPR Studies of Photosynthetic Reaction Centers

[600940] Budil本项目旨在利用新型高场电子磁共振方法表征光合生物中控制主要光反应的结构特征。优异的高场光谱分辨率为探测主反应物自由基的结构提供了一种新的手段。高频的取向选择性将被用于进行“g-磁光选择”实验，该实验将把主要反应物的磁性与光学性质联系起来。在可能的情况下，将进行单晶研究，以便将反应物的磁张量与RC的基态结构直接联系起来。结构影响也将通过一种新的“静电作图”方法进行研究，在这种方法中，使用位点定向诱变将氮氧化物自旋标签引入蛋白质的特定氨基酸残基。高频氮氧化物光谱的电场灵敏度将能够直接探索反应中心选定位置的局部静电，为指导初级光化学的蛋白质微环境提供重要的新信息。这个项目更广泛的研究目标是开发新的磁共振技术来探测动态大分子结构，直接关注光合生物中光化学反应中心的结构和功能。高频电子磁共振将用于探测主反应物和周围蛋白质的微观结构，以及光化学反应动力学。该计划的教育目标将把先进的物理概念，重点是磁共振方法，融入到分子生物学的培训中。通过与当地创业公司合作，直接参与新的生物物理方法的开发，将为学生创造新的机会，以增加他们在东北大学的合作教育经验。＊＊＊

9600940 Budil This project is directed towards characterizing the structural features governing the primary light reaction in photosynthetic organisms using novel high-field electron magnetic resonance methods. The excellent spectral resolution at high field provides a new means of probing the structure of the primary reactant radicals. Orientation selectivity at high frequency will be exploited to carry out "g-magnetophotoselection" experiments that will relate magnetic properties to the optical properties of the primary reactants. Where possible, single crystal studies will be undertaken in order to correlate the magnetic tensors of the reactants directly with the ground state structure of the RC. Structural influences will also be investigated by a novel "electrostatic mapping" approach in which nitroxide spin labels are introduced at specific amino acid residues of the protein using site-directed mutagenesis. The electric field sensitivity of high-frequency nitroxide spectra will enable direct exploration of local electrostatics at selected sites in the reaction center, providing significant new information about the protein microenvironment that guides the primary photochemistry. %%% The broader research goal of this project is to develop new magnetic resonance techniques for probing dynamic macromolecular structures, with an immediate focus on the structure and function of the photochemical reaction centers in photosynthetic organisms. High-frequency electron magnetic resonance will be used to probe the microscopic structure of the primary reactants and the surrounding protein, as well as the photochemical reaction dynamics. The educational goals of this program will integrate advanced physical concepts, with an emphasis on magnetic resonance methods, into training in molecular biology. New opportunities will be created for students to augment their cooperative education experience at Northeastern University by engaging directly in the development of new biophysical methodologies in collaboration with local entrepreneurial companies. ***