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Excited-state structural dynamics of 5-fluorouracil
Brant E Billinghurst1, Ralph Yeung, Glen R Loppnow
1Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
The Journal of Physical Chemistry. A
|May 12, 2006
Summary
The methyl group in thymine influences its photochemistry, similar to 5-fluorouracil. This supports the "mass barrier" hypothesis explaining differences in excited-state dynamics between thymine and uracil.
Area of Science:
- Photochemistry
- Molecular Spectroscopy
- Biophysical Chemistry
Background:
- Thymine and uracil are DNA/RNA nucleobases.
- UV-induced thymine photoproducts are linked to skin cancer.
- Previous work suggested thymine's methyl group affects excited-state dynamics.
Purpose of the Study:
- To test the "mass barrier" hypothesis for thymine's photochemistry.
- To investigate the excited-state structural dynamics of 5-fluorouracil.
- To compare the photochemical behavior of 5-fluorouracil with thymine.
Main Methods:
- Measured resonance Raman spectra of 5-fluorouracil.
- Analyzed spectra using time-dependent wave packet formalism.
- Compared 5-fluorouracil spectra with thymine spectra.
Main Results:
- 5-Fluorouracil and thymine exhibit similar resonance Raman spectra.
- Analysis indicates up to 81% of reorganization energy is directed along relevant modes.
- Results align with findings for thymine.
Conclusions:
- The "mass barrier" hypothesis is supported by the 5-fluorouracil data.
- The methyl group's role in localizing vibrations is consistent across thymine and 5-fluorouracil.
- Excited-state dynamics are influenced by structural features of nucleobases.