Gas phase photophysics and photochemistry of biologically relevant species

俄勒冈州立大学的孔伟（Wei Kong）获得了实验物理化学计划的支持，其研究旨在获得生物相关物种的光物理和光化学信息，包括核酸碱基、吲哚及其与水分子的配合物。该方法涉及超声冷却气相物质的共振增强多光子电离（REMPI）和激光诱导荧光（LIF）光谱，以及嵌入超流氦滴的定向样品的极化光谱。具体而言，PI将研究(1)嘧啶核酸碱基的能量处置和溶剂对衰变动力学的影响，(2)所有五个关键核酸碱基的过渡偶极子方向，以及(3)吲哚激发态的性质和来源。结果有望产生跨学科的影响，鼓励加强对生化反应的理解。生物相关物种的高分辨率光谱研究常常受到其广泛的光吸收光谱的阻碍，但极化光谱可以有效地确定电子跃迁偶极子方向。利用超流氦液滴作为分子载体，进一步提高了可获得的分子信息。孔对核酸碱基光稳定性起源的研究预计将影响有关水对生命起源的重要性的讨论。此外，跃迁偶极子方向的测量将提高圆二色光谱的可预测性，提高其作为生物聚合物构象定量测量的能力。

Wei Kong of Oregon State University is supported by the Experimental Physical Chemistry Program for research that aims to obtain photophysical and photochemical information on biologically relevant species including nucleic acid bases, indole, and their complexes with water molecules. The approach involves resonance enhanced multiphoton ionization (REMPI) and laser induced fluorescence (LIF) spectroscopy of supersonically cooled gas phase species, and polarization spectroscopy of oriented samples embedded in superfluid helium droplets. Specifically, the PI will investigate (1) the energy disposal in pyrimidine nucleic acid bases and the effect of solvent on the decay dynamics, (2) the directions of transition dipoles of all five key nucleic acid bases, and (3) the nature and origin of the the excited electronic states of indole. Outcomes are expected to have interdisciplinary impact, encouraging enhanced understanding of biochemical reactions. High-resolution spectroscopic studies of biologically relevant species are often hindered by their broad light absorption spectra, but polarization spectroscopy as used here can enable electronic transition dipole directions to be determined effectively. The use of superfluid helium droplets as molecular carriers further enhances the molecular information that can be acquired. Kong's research on the origin of the photostability of nucleic acid bases is expected to impact discussion concerning how water is important to the origin of life. As well, the measurements of transition dipole directions will improve the predictability of circular dichroism spectroscopy, improving its capability as a quantitative measure of biopolymer conformation.