Exploring chirality and chiral recognition on the molecular level using spectroscopic and ab initio methods

如果一个物体的镜像不能与自身重叠，那么这个物体就是手性的。我们的右手和左手是我们在日常生活中最熟悉的手性物体。手性对象与另一个手性实体的交互方式不同，就像右手可以与另一只右手握手，但不能与左手握手一样。几乎所有重要的生物分子都是手性的。手性和手性识别对生命系统至关重要，在生命科学中具有重要的基础意义。我小组的研究重点是利用实验红外光谱和从头算方法在分子水平上理解手性和手性识别现象。在前两年的资助期内，我们成功地设计和建造了两台高精密的光谱仪器，用于手性识别的高分辨率红外光谱表征。其中之一是结合脉冲狭缝射流膨胀的中红外腔环降光谱仪。另一种是中红外快速扫描光谱仪与自制的像散镜多通单元相结合。这提供了宽光谱范围的快速实时扫描，并补充了我们的腔环down光谱仪的能力。用这两种仪器测量的手性分子簇的高分辨率红外激光光谱提供了手性分子复合物的结构和动力学信息的详细和定量的信息。结合我们的从头计算，我们了解了氢键和色散相互作用在手性识别中的作用。我们的工作可能最终导致手性鉴别的新分子模型的形成。与我们的手性识别研究相辅相成，我们已经开始使用傅立叶变换振动圆二色光谱和从头计算建模来确定手性分子的绝对结构。目标是探索分子结构与光学活性之间的联系，并最终开发一种指纹识别方法，用于识别具有特定手性的手性分子。

An object is chiral if its mirror image can not be superimposed on itself. Our right and left hands are the most familiar chiral objects we encounter in daily life. A chiral object interacts differently with another chiral entity, just in the same sense as a right hand can execute a proper hand shake with another right hand but not with a left hand. Nearly all important biological molecules are chiral. Chirality and chiral recognition are essential for living systems and are of fundamental importance in the life sciences.     The research in my group focuses on understanding the phenomena of chirality and chiral recognition on the molecular level using experimental infrared spectroscopic and ab initio methods. In the first two year granting period, we have successfully designed and constructed two highly sophisticated spectroscopic instruments for the high resolution infrared spectroscopic characterization of chiral recognition. One of them is a mid-infrared cavity ring down spectrometer in combination with a pulse slit jet expansion. The other is a mid-infrared rapid scan spectrometer coupled with a home made astigmatic mirror multipass cell. This provides fast real time scanning of a wide spectral range and complements the capability of our cavity ring down spectrometer. The high resolution infrared laser spectra of chiral clusters measured with the two instruments provide detailed and quantitative information about the structural and dynamical information of the chiral molecular complexes. In combination with our ab initio calculations, we learn about the roles that the hydrogen bonds and dispersion interactions play in chiral recognition. Our work may eventually lead to the formulation of new molecular models for chiral discrimination.     Complementary to our chiral recognition research, we have started to work on the absolute structural determinations of chiral molecules using Fourier transform vibrational circular dichroism spectroscopy and ab initio modeling. The goal is to explore the link between molecular structure and optical activity, and ultimately to develop a fingerprinting method for the identification of chiral molecules with a particular handedness.