Gas phase photophysics and photochemistry of biologically relevant species

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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.