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

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 该研究项目的主要目标是利用超快振动光谱提供的独特信息，以发展与生物学相关的超快过程的基本见解。因此，我们打算（1）确定电子转移中涉及的中间态的关键振动特征，（2）确定强耦合供体-受体系统中电荷迁移的程度，（3）检查反应的动力学，如超快质子耦合电子转移，其中快速键断裂和键形成事件发生在类似于电荷迁移的时间尺度上，（4）理解激发态发色团核动力学的性质，以及（5）探测离域多色素系统中电子激发态的性质。 我们打算追求的动力学相关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。光学泵浦-探测、光学泵浦/红外探测和动力学斯托克斯位移实验将与瞬态光学泵浦-探测实验等实验相关联。 这项工作将描绘蛋白质介导的质子耦合电子转移（PCET）反应的重要结构-功能关系。 这些研究将依赖于设计从头四-α-螺旋蛋白，其被工程化以结合供体-间隔区-受体（D-Sp-A）超分子和共价连接的多辅因子组装体。 虽然这些系统具有相对于生物蛋白质降低的结构复杂性，在这个意义上，它们主要利用螺旋束基序，它们能够独立调制的局部静电力，围绕D，A和发色团;此外，这些四-α-螺旋蛋白质的设计特征允许控制辅因子的第一和第二球氢键相互作用的性质。 我们将研究光诱导PCET反应在这样的系统中使用光泵/光探针和可见光泵/ IR探针光谱方法，并与所观察到的动态与肽基质的特定响应。 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精心设计蛋白质以实现所需的功能。

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.