基于同步辐射光电离-分子束质谱技术的天然糖类及其水合团簇的动力学研究

Natural sugars, as an important biomolecule, realize its biological functions in aqueous or physiological environments. It is hard to understand its intrinsic properties and the interaction between biomolecules and solvent molecules for it was masked and equalized by the aqueous environments. Gas phase biomolecules and its hydrated clusters, which were generated by heating up or laser desorption in a supersonic jet, would be the typical model system to research its intrinsic properties and its microsolvation effects at the levle of atom and molecule. For the absence of aromatic group, REMPI (Resonance Enhanced Multiphoton Ionization) is inapplicable to the natural sugar molecules. And the artificial attaching an aromatic ring would distribute its intrinsic property (including its solvation properties). In present research project, we plan to detect directly and study the natural sugars molecules and its hydrated clusters in the gas phase by employing synchrotron VUV single photon ionization. Combining measurement of the cation and fragments' PIE with ab initio/DFT calculations, we expect to obtain some important physical chemistry parameters such as ionization energies (IE), appearance energies (AE), enthalpy etc， which would help us to find a proper approach to detect sugars in the gas phase by the use of photoionization mass spectrometry. Thereafter, we will study and compare photoionization and photo fragmentation dynamics of the molecules and clusters and expect to obtain informations on the favorite configurations of sugar molecules in hydrated complexes which is affected by water solvents (i.e microsolvation). The objects in present project would be the typical sugars including glycolaldehyde, deoxyribose, glucose and their hydrated clusters in the gas phase.

天然糖类是一类重要的生物分子。但实现其生物功能所需的液相环境，掩盖或者平均化了分子本身的特性及其与溶剂水分子作用的物理化学本质。分子束中通过加热或激光解析气化后的天然糖类及其水合团簇，是在原子分子水平上研究分子及其微溶剂化效应的模型体系。由于共振增强多光子电离无法直接对不含芳香环的天然糖类分子进行探测研究，而人为引入芳香环将影响分子的固有性质。本项目中拟应用同步辐射真空紫外单光子电离方法和光电离效率谱(PIE)测量技术，对分子束中天然糖类及其水合团簇进行探测研究。首先获得其电离能、碎片离子出现势、电离截面等物化参数，为探索应用光电离质谱技术探测天然糖类及其水合团簇提出方案建议；进一步：结合理论计算，拟通过研究和比较分子和团簇的光电离解离动力学机理，获得水分子影响团簇中糖类分子最优构型的相关信息(即微溶剂化效应)。本项目拟将羟基乙醛、脱氧核糖和吡喃葡萄糖及其水合团簇作为研究的模型分子体系。

在该基金项目的支持下，我们重点开展了乙醇二聚体和正丙醇分子、类糖有机分子及其团簇体系的光电离和光解离的动力学研究。研究中主要应用超声膨胀分子束源，同步辐射真空紫外光源和反射式飞行时间质谱分析器获得相关的实验数据。结合DFT理论计算，对分子在真空紫外条件下发生的光电离解离的动力学过程进行了研究，着重对其在光电离解离过程中发生的离子分子反应的解离机理在理论和实验上进行了深入的探讨。最新研究表明：正丙醇二聚体发生的解离过程中存在一个多次氢/质子转移解离通道。该结果对于我们在解释质谱分析生物大分子过程中出现的解离碎片，有很重要学术价值和借鉴意义。除此之外，该项目还支持课题组应用激光后电离质谱法开展了生物组织中药物分子的分子成像的研究。我们还开展了拉曼光谱和表面增强拉曼的基础和应用研究。本项目的资助下，共发表SCI收录论文9篇。