Vishakha Monga - McMaster University

Placement: University of Alberta
Supervisor: Dr. Glen Loppnow
Currently:  Graduate Student, University of British Columbia

Application of Raman Spectroscopy to Nucleic Acid Structure, Interactions and Photochemistry: Thymine and Thymidine

At the molecular level, absorption of UV light by DNA leads to the formation of thymidine dimers, which can be subsequently repaired by various repair enzymes in the cell. To develop a foundation for probing DNA damage and repair with Raman spectroscopy, Raman spectra of thymine and thymidine in a number of solvents were obtained. From the spectra, it was observed that the frequencies and relative intensities of the Raman peaks change with solvent. These changes in the vibrational bands were analyzed and explained at the molecular level by correlating them to various solvent parameters, such as hydrogen bonding ability, polarity, and polarizability. The Raman band frequency shifts correlated well with the hydrogen bonding properties of the solvent. Based on this correlation and the vibrational assignments of the peaks, a model was proposed in which thymine interacts with solvents mainly at the N-H sites in the molecule.

To determine the mechanism of light-induced DNA damage, a time-resolved resonance Raman apparatus was designed and built. Initial resonance Raman spectra of thymine and thymidine excited at 217 nm with this setup yielded data comparable to literature spectra. These results suggest time-resolved spectroscopy of DNA damage is feasible and is currently in progress.