Gas phase photophysics and photochemistry of biologically relevant species

俄勒冈州州立大学的Wei Kong得到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物理和光化学信息，包括核酸碱基，吲哚及其与水分子的复合物。 该方法涉及共振增强多光子电离（REMPI）和激光诱导荧光（LIF）光谱的超音速冷却的气相物种，和偏振光谱的定向样品嵌入超流氦液滴。 具体而言，PI将研究（1）嘧啶核酸碱基中的能量处置和溶剂对衰变动力学的影响，（2）所有五种关键核酸碱基的跃迁偶极子方向，以及（3）吲哚激发电子态的性质和起源。 预计成果将产生跨学科的影响，鼓励加强对生物化学反应的理解。生物学相关物种的高分辨率光谱研究通常受到其宽光吸收光谱的阻碍，但这里使用的偏振光谱可以有效地确定电子跃迁偶极方向。 使用超流氦液滴作为分子载体进一步增强了可以获得的分子信息。 Kong对核酸碱基光稳定性起源的研究有望影响关于水对生命起源的重要性的讨论。 此外，跃迁偶极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的定量测量的能力。

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.