Analytical Applications of Nonlinear Infrared Spectroscopy

威斯康星州大学的John Wright教授的这个项目是基于最近的关键实验，这些实验已经证明，具有振动跃迁的共振可以充分增强核极化率，使其超过非共振的电子极化率，并且模式耦合足够大，多重共振可以成倍地增强非线性光学过程。 这些实验证明了一个新的家庭的多共振振动增强非线性光学光谱的可行性。 这些光谱类似于二维NMR方法，并且它们对分子内和分子间相互作用独特地敏感。 从生物学的角度来看，它们可以被认为是一种双色染色剂，可以使分子相互作用可视化并识别相互作用中涉及的功能。 随着新技术的空间成像能力的发展，这种类比在未来可能变得重要。 该项目旨在将这些新方法应用于生物化学中的核心问题，其中相互作用起着核心作用。 有许多不同的分子相互作用，但这个建议将集中在应用新的方法来研究由生物分子结构中的氢键引起的光谱相关性。 这种相关性将在二维光谱中交叉峰的相对强度中得到证明，从而反映了两个共振之间的相互作用，并且在线变窄的交叉峰中的线位置偏移中得到证明。在分子水平上，生物分子的结构在很大程度上取决于称为氢键的相互作用。 虽然氢键可以在相对简单的系统中被理解，但在复杂的三维生物分子结构中氢键的性质和程度要难得多。 将在本项目主持下完成的光谱实验为完成这一特性鉴定提供了一种灵敏和直接的手段。 随着对氢键作用的更好理解，复杂的生物分子结构可能被建模，甚至可能被预测为天然分子的合成类似物。

This project by Professor John Wright of the University of Wisconsin is predicated on recent key experiments that have demonstrated that resonance with vibrational transitions can enhance the nuclear polarizability sufficiently to exceed the nonresonant electronic polarizability, and that mode coupling is sufficiently large that multiple resonances can multiplicatively enhance nonlinear optical processes. These experiments demonstrate the feasibility for a new family of multiresonant vibrationally enhanced nonlinear optical spectroscopies. These spectroscopies are analogous to 2-dimensional NMR methods and they are uniquely sensitive to intra- and intermolecular interactions. From a biological perspective, they can be considered as a two- color stain that allows visualization of molecular interactions and identification of the functionalities involved in the interaction. This analogy might become important in the future as the spatial imaging capabilities of the new technology are developed. The project seeks to apply these new approaches to central problems in biochemistry where interactions play a central role. There are many different molecular interactions but this proposal will focus on applying the new method to study of the spectral correlations that are induced by the hydrogen bonding in a biomolecule structure. The correlations will be evidenced both in the relative intensities of cross-peaks in the 2-D spectra, thus reflecting the interactions between the two resonances, and in the line position shifts in line-narrowed cross-peaks.At the molecular level, the structures of biomolecules depend to a large degree on the interactions known as hydrogen bonding. Although hydrogen bonding may be understood in relatively simple systems, the nature and extent of hydrogen bonding in a complex three-dimensional biomolecular structure is far more difficult to characterize. The spectroscopic experiments to be completed under the auspices of this project provide a sensitive and direct means to complete that characterization. With the role of hydrogen bonding better understood, complex biomolecular structures may be modeled and perhaps even predicted for synthetic analogs of natural molecules.