Intramolecular Vibrational Excitation of Protein Unfolding and Refolding Dynamics

这个项目使用时间分辨荧光光谱学来研究当小蛋白质从平衡结构或天然结构移位时，它们在结构上是如何变化的。这项计划中的研究利用了该实验室开发的一种新方法，该方法使用从激发态电子生色团转移的振动能量来驱动宿主蛋白质从其固有结构连接到一系列部分未折叠的状态，这些状态可能对应于折叠/展开路径上的晚期中间体。由于中间结构是在有利于天然结构的溶液条件下光学产生的，所以通过使用即时和延迟荧光方法，在非常宽的时间范围内，在皮秒到毫秒的范围内，通过使用即时和延迟荧光方法，可以通过独立控制溶剂组成或温度来表征产生未折叠中间体之后的复性反应。锌(II)取代的细胞色素c和无金属的细胞色素c是主要研究体系。在计划的实验中，细胞色素c中的卟啉发色团既是去折叠反应的触发剂，也是传感器。色氨酸残基也将被用作由卟啉引发的反应的远程传感器。这项研究直接检验了中心假设，即蛋白质在生理条件下快速折叠是因为它们在漏斗状势能表面上随机运动，而漏斗状势能表面具有漏斗最小的天然结构。这项研究还将对更广泛的蛋白质结构和功能领域产生影响，这些领域与光生物和酶催化反应中导致构象变化的跨越障碍过程有关。该项目在PI和co-PI的本科生和研究生课程教学中发挥着不可或缺的作用。它提供关键的讲座主题和应用，甚至在入门课程中也是如此。研究参与者接触到从结构生物学到化学物理的广泛学科。鼓励本科生从大一开始在实验室工作，他们通常在大四之前为出版物投稿。此外，该项目还与一项新的外展计划相关联，该计划将由主计委和合作主计团访问密歇根州兰辛地区的高中，在化学和物理课堂上就激光光谱学在生物物理化学、结构生物学和相关学科中的使用进行演讲。然后，有兴趣的学生和他们的老师将被邀请访问PI、联合PI和他们的研究生，参观研究实验室，谈论科学和工程方面的职业，也许还会参与研究项目。这一外展计划将导致与来自代表性不足群体的学生进行互动，这些学生将被招募到密歇根州立大学攻读科学本科课程。这一努力旨在加强密歇根州立大学化学系现有的努力，从代表性不足的群体中招收和留住学生。

This project employs time-resolved fluorescence spectroscopy to study how small proteins change in structure when they are displaced from the equilibrium or native structure. The planned research exploits a new method developed in this laboratory that uses the vibrational energy transferred from an excited-state electronic chromophore to drive the host protein to which it is attached from its native structure to a range of partially unfolded states that probably correspond to late intermediates along the folding/unfolding pathway. Because the intermediate structures are generated optically under the solution conditions that favor the native structure, the refolding reactions that follow the production of unfolded intermediates can be characterized with independent control of the solvent composition or temperature over a very wide range of timescales, over the picosecond to millisecond regime, through the use of prompt and delayed fluorescence methods. Zinc(II)-substituted and metal-free cytochromes c are the main systems to be studied. The porphyrin chromophore in cytochrome c serves in the planned experiments as both the trigger and the sensor for the unfolding and refolding reactions. A tryptophan residue will also be used as a remote sensor for the reactions that are triggered by the porphyrin. This research provides a direct test of the central hypothesis that proteins fold rapidly under physiological conditions because they move randomly on a funnel-shaped potential-energy surface that has the native structure at the funnel's minimum. The research will also have an impact on the broader fields of protein structure and function that relate to the barrier-crossing processes that lead to conformational changes during photobiological and enzyme-catalyzed reactions.This project plays an integral part in the teaching of undergraduate and graduate courses by the PI and co-PI. It provides key lecture topics and applications even in introductory courses. Research participants are exposed to a wide range of disciplines ranging from structural biology to chemical physics. Undergraduate students are encouraged to start working in the laboratory in the freshman year, and they usually contribute to publications by the senior year. Additionally, this project is associated with a new outreach program that will feature visits by the PI and co-PI to high schools in the Lansing, Michigan area to give presentations to Chemistry and Physics classes on the use of laser spectroscopy in biophysical chemistry, structural biology, and related disciplines. Interested students and their teachers will then be invited to visit the PI, co-PI, and their graduate students, to see the research laboratories, to talk about careers in science and engineering, and perhaps to get involved in research projects. This outreach plan will lead to interactions with students from underrepresented groups who will be recruited to undertake undergraduate studies in the sciences at Michigan State University. This effort is intended to augment an existing effort by the Department of Chemistry at MSU to recruit and retain students from underrepresented groups.