Resonance Raman Studies of Electron-Nuclear Coupling, Time Resolved Dynamics, and Magnetic Perturbations of Biomolecules

了解振动能量在激活生物分子以执行其各种功能中的作用是扩展现有生物分子反应动力学知识的主要目标。本项目使用温度相关的超快动力学、共振拉曼散射和飞秒相干光谱来探测血红素蛋白等生物分子的结构/功能/动力学关系。相干技术是一种独特的探测室温以下区域（kBT ~ 200cm-1）振动谱的方法，该区域包含最有可能用作反应坐标的热可达模式。低频血红素扭曲（例如，褶皱和圆顶）涉及与电子传递和配体结合等基本反应相关的能量重组。相干光谱研究使用血红素模型配合物；DFT计算、x射线结构和正坐标结构分解来量化蛋白质诱导的对称性降低血红素的畸变，这些畸变激活了这些（非谐波）低频模式。这些模式的相位和振幅激发谱增加了对触发反应坐标相干振荡的非辐射电子-核耦合机制的理解。其他技术，如核共振振动波谱和磁场摄动被应用于低频（非谐波）运动的分配和表征。新的温度依赖的超快动力学研究揭示了蛋白质特异性的熵和焓对配体结合过渡态屏障的贡献。新的实验表明，血红素蛋白系统中的动态配体识别机制取决于相对于其熵产生时间的解离态寿命。飞秒受激拉曼散射仪器也正在开发中，并应用于金属配体电荷转移带的研究。这将被用作对血红素发色团的结构、功能、动力学和非调和性的重要独立探测，也可以应用于其他生物系统。本项目研究蛋白质动力学的基本方面，并着重于血红素蛋白活性位点的电子-核偶联。这种相互作用的研究对生命系统的基本理解至关重要。学生（包括研究生和本科生）将接受尖端光学和生物技术的培训，通过加强学术，生物技术和光子学行业的人力资源基础设施来造福社会。所获得的知识将通过讲座、研讨会和发表的论文进行传播。由于这个项目，还将向代表性不足的群体和一般公众进行外联。该项目由生物科学理事会分子和细胞生物科学部的分子生物物理学项目和数学与物理科学理事会的物理部共同支持。

Understanding the role of vibrational energy in activating biomolecules to perform their various functions is a major goal that will extend existing knowledge of biomolecular reaction dynamics. Temperature dependent ultrafast kinetics, resonance Raman scattering, and femtosecond coherence spectroscopy, are used in this project to probe the structure/function/dynamics relationships of biomolecules such as heme proteins. Coherence techniques are a unique probe of the vibrational spectrum in the region below room temperature (kBT ~ 200cm-1), which contains the thermally accessible modes most likely to be utilized as reaction coordinates. Low-frequency heme distortions (e.g., ruffling and doming) are involved in the reorganization of energy associated with such fundamental reactions such as electron transport and ligand binding. The coherence spectroscopy studies use heme model complexes; DFT calculations, x-ray structures, and normal coordinate structural decomposition to quantify the protein-induced symmetry lowering distortions of the heme that activate these (anharmonic) low frequency modes. Phase and amplitude excitation profiles of these modes increase understanding of the non-radiative electron-nuclear coupling mechanisms that trigger the coherent oscillations of reaction coordinates. Other techniques, such as nuclear resonance vibrational spectroscopy and magnetic field perturbations are applied to aid in the assignment and characterization of the low frequency (anharmonic) motions. Novel temperature dependent ultrafast kinetic studies reveal the protein-specific entropic and enthalpic contributions to ligand binding transition state barriers. New experiments suggest a dynamic ligand discrimination mechanism in heme protein systems that depend upon the lifetime of the dissociated state relative to its entropy production time. Femtosecond stimulated Raman scattering instrumentation is also being developed and applied to the study of metal-ligand charge transfer bands. This will be used as an important independent probe of the structure, function, dynamics, and anharmonicity of the heme chromophore that can be applied to other biological systems as well.This project investigates fundamental aspects of protein dynamics and focuses on the electron-nuclear coupling at the active site of heme proteins. Studies of such interactions are crucial to the basic understanding of living systems. Students (both graduate and undergraduate) will be trained in cutting edge optical and biological techniques that benefit society through the enhancement of the human resource infrastructure of the academic, biotechnology, and photonics industries. The knowledge obtained will be disseminated through lectures, seminars, and published papers. Outreach to underrepresented groups and the general public will also take place as a result of this project. This project is jointly supported by the Molecular Biophysics Program in the Division of Molecular and Cellular Biosciences in the Directorate for Biological Sciences and the Division of Physics in the Mathematical and Physical Sciences Directorate.