PUMP-PROBE SPECTROSCOPY OF PROTON-COUPLED ELECTRON TRANSFER IN PROTEINS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 这个研究项目的主要目标是利用超快振动光谱学提供的独特信息来发展对与生物学相关的超快过程的基本见解。因此，我们打算(1)确定参与电子转移的中间态的关键振动特征，(2)确定电荷在强耦合施主-受主系统中的迁移程度，(3)研究超快质子耦合电子转移等反应的动力学，其中快速键断裂和成键事件发生在类似于电荷迁移的时间尺度上，(4)了解激发态生色团核动力学的性质，以及(5)探索离域、多颜料系统中电子激发态的性质。 我们打算进行的与动力学相关的ET实验类型将利用最先进的实验方法和仪器来研究快速、亚纳秒时间尺度上的分子振动。光抽运探测实验、光抽运/红外探测实验和动力学斯托克斯漂移实验将与瞬变光学抽运探测实验相关联。 这项工作将描绘对蛋白质介导的质子耦合电子转移(PCET)反应重要的结构-功能关系。这些研究将依赖于新的四α-螺旋蛋白质的设计，这些蛋白质被设计成结合供体-间隔物-受体(D-Sp-A)超分子和共价连接的多辅助因子组件。虽然这些系统相对于生物蛋白质具有更低的结构复杂性，因为它们主要利用螺旋束基序，但它们能够独立调节围绕D、A和生色团的局部静电力；此外，这些四α-螺旋蛋白质的设计特征允许控制辅因子第一和第二球氢键相互作用的性质。我们将使用光泵/光探针和可见光泵浦/红外探针光谱方法来研究这类体系中的光诱导PCET反应，并将观察到的动力学与多肽基质的特定响应关联起来。这些数据提供了关键信息，使我们能够充分利用强大的计算方法来详细说明蛋白质设计，以实现预期的功能。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The primary goal of this research project is to exploit the unique information that ultrafast vibrational spectroscopy provides to develop fundamental insights into ultrafast processes relevant to biology. We thereby intend to (1) identify key vibrational signatures of intermediate states involved in electron transfer, (2) ascertain the extent to which charge migrates in strongly coupled donor-acceptor systems, (3) examine the dynamics of reactions such as ultrafast proton-coupled electron transfer in which fast bond-breaking and bond-forming events occur on time scales similar to charge migration, (4) understand the nature of excited-state chromophore nuclear dynamics, and (5) probe the nature of electronically excited states in delocalized, multi-pigment systems. The types of dynamics-correlated ET experiments that we intend to pursue will utilize state-of-the-art experimental methodologies and instrumentation to study molecular vibrations on fast, sub-nanosecond time scales. Optical pump-probe, optical-pump/infrared-probe and dynamics Stokes shift experiments will be correlated with experiments such as transient optical pump-probe experiments. This work will delineate structure-function relationships important to protein-mediated, proton-coupled electron-transfer (PCET) reactions. These investigations will rely on the design of de novo tetra-alpha-helical proteins engineered to bind donor - spacer - acceptor (D-Sp-A) supermolecules and covalently linked multi-cofactor assemblies. While these systems possess reduced structural complexity with respect to biological proteins, in the sense that they exploit mainly helical bundle motifs, they enable independent modulation of the local electrostatic forces that surround D, A, and chromophore; furthermore, design features of these tetra-alpha-helical proteins allow control over the nature of cofactor first- and second-sphere H-bonding interactions. We will examine photoinduced PCET reactions in such systems using optical pump / optical probe and visible pump / IR probe spectroscopic methods, and correlate the observed dynamics with specific responses of the peptide matrix. Such data provide key information that will enable us to fully exploit powerful computational approaches to elaborate protein design to effect desired function.