title: Excited-state structural dynamics of 5-fluorouracil.
abstract: 5-Fluorouracil is an analogue of thymine and uracil, nucleobases found in DNA and RNA, respectively. The photochemistry of thymine is significant; UV-induced photoproducts of thymine in DNA lead to skin cancer and other diseases. In previous work, we have suggested that the differences in the excited-state structural dynamics of thymine and uracil arise from the methyl group in thymine acting as a mass barrier, localizing the vibrations at the photochemical active site. To further test this hypothesis, we have measured the resonance Raman spectra of 5-fluorouracil at wavelengths throughout its 267 nm absorption band. The spectra of 5-fluorouracil and thymine are very similar. Self-consistent analysis of the resulting resonance Raman excitation profiles and absorption spectrum using a time-dependent wave packet formalism suggests that, at most, 81% of the reorganization energy upon excitation is directed along photochemically relevant modes. This compares well with what was found for thymine, supporting the mass barrier hypothesis.
authors: Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
authors: Brant E
authors: BE
authors: Billinghurst
authors: Ralph
authors: R
authors: Yeung
authors: Glen R
authors: GR
authors: Loppnow