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Pyrimidine dimer splitting in covalently linked dimer-arylamine systems.
1Department of Chemistry and Biochemistry, Arizona State University, Tempe 85287-1604.
Journal of Photochemistry and Photobiology. B, Biology
|January 31, 1992
Summary
Pyrimidine dimers split when sensitized by electron donors. Linked arylamine sensitizers showed varying efficiencies, with solvent polarity significantly impacting photosplitting rates via electron transfer mechanisms.
Area of Science:
- Photochemistry
- Organic Chemistry
- Biophysical Chemistry
Background:
- Cyclobutadipyrimidines, or pyrimidine dimers, are DNA photoproducts.
- Photosplitting of pyrimidine dimers can be sensitized by electron donors.
Purpose of the Study:
- To synthesize and investigate dimer-arylamine compounds as intramolecular photosensitizers for pyrimidine dimer splitting.
- To explore the influence of structural modifications and solvent polarity on photosplitting efficiency.
Main Methods:
- Synthesis of dimer-arylamine conjugates.
- Spectroscopic analysis (absorption spectra).
- Photochemical experiments measuring quantum yields (phi spl) in various solvents.
Main Results:
- Two diastereomers of dimer-arylamine showed distinct splitting efficiencies.
- Photosplitting efficiency was highly solvent-dependent, increasing with decreased polarity.
- Absorption maxima for dimer-arylamines were observed around 300 nm.
Conclusions:
- A mechanism involving photoinduced electron transfer from arylamine to dimer, followed by dimer radical anion splitting, is proposed.
- Solvent effects on photosplitting are attributed to the retardation of back electron transfer, potentially via Marcus inverted behavior.
- The findings suggest a possible mechanism for efficient dimer splitting by photolyases involving hydrophobic active sites.