用电子动量谱学研究若干生物单元分子的构像问题

This project applies electron momentum spectroscopy approach (EMS) and focus point analysis (FPA) to study conformationally versatile elementary biomolecules，such as amino and monosaccharose. In past, it is very difficult to investigate these biological molecules with the first and second generation electron momentum spectrometers. In addition, to evaluate systematically and accurately the abundance of each conformer in the gas phase cost the complicate and deliberate calculations. So the experimental and theoretical studies of EMS on large systems remain very insufficient. For the sake of the analysis above, the main contents of the present project are (1) A focal point analysis based on quantum chemistry computations is carried out to determine how the conformational proportion differences; (2) According to the computed results from the first step, obtaining the orbital ionization energy and momentum distributions of the biological molecules by means of highly accurate one-particle Green function theory and EMS; (3) Based on the combined theoretical and experimental results, analyzing the conformational differences and abundance for some biological molecule, and coming to the conclusions. The system we will focus on is some important biological molecules. The main purpose of this project is to study the electric structure and conformational abundance of some conformationally versatile molecules. We expect this project will extend the applications of such biomolecules in medical field and help us to understand the process of metabolism of all living matter.

本项目结合电子动量谱学和焦点分析法对以氨基酸类和单糖类为代表的若干生物单元分子的构像问题展开研究。第一、二代的电子动量谱仪难以实现对生物分子系统而全面的实验研究，理论分析这些分子的构像分布也需要大量的理论计算和模拟。因此，目前利用电子动量谱学方法对生物分子构像问题的研究还很少。本项目拟展开的研究内容：（1）采用以量子化学理论为基础的焦点分析法对若干生物单元分子的构像分布展开计算和讨论；（2）以研究内容（1）得到的不同构像成分所占的百分比为基础，结合单粒子格林函数和电子动量谱学理论计算得到轨道电离能谱和动量分布；（3）对比理论结果和实验数据，对分子的构像成分及其所占比例作出分析，给出结论。本项目的研究对象是一些重要的生物单元分子，研究这些分子的电子结构和构像分布，进而加强此类分子在生物学、药物科学等领域中的广泛应用，有助于人类了解生命体的代谢过程。

构像是生物类单元分子最基础的结构特性，当构像发生变化时，其电子分布、轨道能级、分子振动都会随之发生改变。本项目结合电子动量谱学和焦点分析法对氨基酸类的生物单元分子(甘氨酸和丙氨酸)以及具有高对称性分子的构像问题展开研究。具体研究内容如下：（1）研究了甘氨酸生物分子在298-500 K大温度范围内的构像分布，并在实验温度下将计算结果与电子动量谱学实验数据进行对比分析，为了能够对实验数据做出合理的解释，采用分子动力学方法讨论了甘氨酸不同构像之间的转换机理；（2）研究了实验温度下丙氨酸构像的成分比例，得到了含有8种构像成分的最外价轨道电子动量谱图；（3）通过研究偏式、顺式和反式二氯乙烯同分异构体的四个芯轨道的电子动量谱图，在动量空间发现了相互干涉作用，求出不同异构体相邻原子间的间距；（4）对苯分子展开了电子动量谱学的实验和理论研究，发现了苯分子最高占据轨道中的“翘起”可能是由于Jahn-Teller效应，3e1u、1b2u和2b1u三个轨道中出现了分子内衍射效应。