Molecular Structures of Interfacial Proteins Studied by Isotope Labeling and Sum Frequency Generation Vibrational Spectroscopy

在化学系化学测量和成像项目的支持下，密歇根大学的陈展教授和他的团队正在开发一种创新的方法来阐明表面结合蛋白的详细分子结构。他们的方法使用选择性重原子（同位素）标记和先进的光谱方法来获得关于蛋白质在界面上的吸附如何影响其结构和功能的关键知识。这些相互作用影响了一系列的应用，如生物医学材料的生物相容性，防污涂层的性能，生物传感器的选择性和灵敏度，以及生物燃料电池的效率。这项高度跨学科的研究为研究生和本科生提供了教育机会。陈教授和他的学生也在努力吸引高中生（包括那些来自弱势群体的学生，包括女性），并通过每年夏天的课程提高他们对科学的兴趣。本项目的重点是开发一种普遍适用的方法，利用同位素标记和和频产生（SFG）振动光谱来表征界面上蛋白质的构象和取向。利用模型细胞膜相关抗菌肽tachyplesin I，一种可以在石墨烯界面上保留其天然结构的蛋白质GB1突变体，以及一种在石墨烯上变性的野生型蛋白质GB1，陈教授和他的团队正在开发SFG同位素标记方法来表征固体/液体界面上的各种蛋白质二级结构；从界面蛋白的晶体结构推断出由于界面相互作用而引起的取向和轻微构象变化；并确定变性界面蛋白的构象。通过分子动力学模拟和哈密顿方法获得的结果与同位素标记蛋白质的SFG实验测量数据进行了比较，以确定最可能的蛋白质构象和界面取向。该方法还可用于确定晶体结构未知的蛋白质的界面结构，为研究界面生物分子增加了强大的光谱工具。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Zhan Chen and his group at the University of Michigan are developing an innovative approach to elucidate detailed molecular structures of surface-bound proteins. Their approach uses selective heavy-atom (isotope) labeling and advanced spectroscopic methods to derive crucial knowledge about how adsorption of proteins at interfaces affects their structure and function. These interactions impact a range of applications, such as biocompatibility of biomedical materials, performance of antifouling coatings, selectivity and sensitivity of biosensors, and efficiency of biofuel cells. This highly interdisciplinary research provides educational opportunities for graduate and undergraduate students. Professor Chen and his students are also working to engage high school students (including those from underrepresented groups, including women) and to enhance their interest in science through a class taught each summer. This project focuses on the development of a generally applicable methodology to characterize the conformation and orientation of proteins at interfaces using isotope labeling and sum frequency generation (SFG) vibrational spectroscopy. Using a model cell membrane-associated antimicrobial peptide tachyplesin I, a protein GB1 mutant which can retain its native structure at the graphene interface, and a wild-type protein GB1 which denatures on graphene, Professor Chen and his group are developing SFG isotope labeling methods to characterize various protein secondary structures at the solid/liquid interface; to deduce orientations and slight conformation changes of interfacial proteins from crystal structures due to interfacial interactions; and to determine conformations of denatured interfacial proteins. Results obtained from molecular dynamics simulations and the Hamiltonian approach are compared to the experimentally measured SFG data from isotopically labeled proteins to determine the most likely protein conformations and orientations at the interface. This method can also be used to determine interfacial structures of proteins with unknown crystal structures, adding a powerful spectroscopic tool for studying interfacial biological molecules.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.