Excited-State Proton Transfer in Chemistry and Biology

要阐明超快反应的机制，需要分子在光激发下被激活。对于光致电子转移，这种分子很容易获得。对于光致质子转移，分子需要在激发态变成强酸(光酸)。尽管重排生成永久性酸的分子，即光酸产生器，在平版印刷工业中很重要，但作为暂时性酸的分子更难以捉摸。该计划试图开发这种分子--该领域的各种研究人员普遍感兴趣--并且在使用理论有机化学和有机合成的原理来提供这种试剂方面是独一无二的。在这个过程中，该集团正在生产酸度接近强矿物酸的光酸。最近，利用绿色荧光蛋白(GFP)的独特机制，这些方法已经扩展到生物学中的光酸，绿色荧光蛋白通过继电机制表现出质子转移级联。通过拆解GFP并将其重新组合在一起，该小组正在阐明这种革命性蛋白质的光物理细节，并将其应用于许多相关系统。除了继续这些研究，他们还建议将这些原理应用于GFP发色团的开发，剥离其保护蛋白质桶，并应用于一种新类型的传感器，这种传感器同时使用荧光关闭开关和质子转移来提供传感过程中的两个变量。他们进一步建议继续研究新的光酸，揭示离子对动力学的细节和非对映选择性对酸解离的影响。我们将研究包括超临界介质和分子喷注在内的一系列物体。所提出的活动的智力价值在于设计和合成新的“超级”光酸，验证超快质子转移的分子细节模型，以及将这些模型用于生物学中的质子转移。拟议活动的更广泛影响包括为更大的光谱学家和光生物学家社区开发新的光谱和机械工具，通过在会议和文献中传播这些成果来转让这项技术和知识库，与一些实验室的科学家合作，以及培养一批精通有机合成、光谱学、机械化学和合作研究的未来科学家。作为这项工作的一部分，托尔伯特教授将在拨款的第一年访问10所历史悠久的黑人大学，比较它们在培养化学研究生院本科生方面所做的努力，并将这些努力与他在克拉克亚特兰大大学的经历进行比较，以提高他在克拉克亚特兰大大学招收非裔美国人的效率。

Elucidating the mechanism of ultrafast reactions requires molecules which are activated upon photoexcitation. For photoinduced electron transfer, such molecules are readily available. For photoinduced proton transfer, molecules are required which become strong acids (photoacids) in the excited state. Although molecules which rearrange to generate permanent acids, i.e., photoacid generators, are important in the lithographic industry, molecules which are transient acids are more elusive. This program has sought to develop such molecules--of general interest to a variety of investigators in the field--and is unique in using the principles of theoretical organic chemistry and organic synthesis to provide such reagents. The group, in the process, is producing photoacids with acidities approaching that of strong mineral acids. More recently, these methods have been extended to photoacids in biology, taking advantage of the unique mechanism of the green fluorescent protein (GFP), which exhibits a proton transfer cascade through a relay mechanism. By taking GFP apart and putting it back together, the group is elucidating the details of the photophysics of this revolutionary protein and applying them to a number of related systems. In addition to continuing these studies, they propose to apply these principles to the development of GFP chromophores, stripped of their protective protein barrel,and to a new category of sensors which use both fluorescence off-on switching and proton transfer to give two variables in the sensing process. They further propose to continue studies on new photoacids which reveal details of ion-pair dynamics and effects of diastereoselectivity on acid dissociation. A wide array of objects including supercritical media and molecular jets will be studied.The intellectual merit of the proposed activity lies in the design and synthesis of new "super" photoacids, the validation of models for the molecular details of ultrafast proton transfer, and the use of those models in proton transfer in biology. The broader impacts of the proposed activity encompass the development of new spectroscopic and mechanistic tools for the larger community of spectroscopists and photobiologists, the transfer of this technology and knowledge base through dissemination of these results at conferences and the literature, the collaboration with scientists in a number of laboratories, and the development of a set of future scientists skilled in organic synthesis, spectroscopy, mechanistic chemistry, and collaborative research. As part of this effort, Prof. Tolbert will visit 10 historically black universities the first year of the grant to compare their efforts in building undergraduates for graduate school in chemistry and compare those with his experience at Clark Atlanta University in order to improve his effectiveness in recruitment of African-Americans to Clark Atlanta.