Stuttgart 2012 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 17: Femtosecond Spectroscopy IV

MO 17.7: Vortrag

Donnerstag, 15. März 2012, 12:15–12:30, V38.03

Time-resolved spectroscopy of triplet states of thymidylic acids — •Bert Manuel Pilles — LMU Munich

Solar UV radiation is known to induce harmful mutagenic products in DNA. The major photoproduct is the cyclobutane pyrimidine dimer (CPD) between neighboring thymine residues. In recent studies it was shown that the photodimerization reaction induced via 266 nm excitation occurs predominantly on a 1 ps time scale . This finding suggests that the reaction occurs via a singlet pathway [1,2]. Nevertheless triplet states are discussed to be possible precursors of thymine dimer formation.

We used time resolved UV pump, IR probe spectroscopy - covering picoseconds to microseconds - to investigate different single stranded thymidylic acids (TpT, (dT)18) and the corresponding mononucleotide (thymidine monophosphate, TMP). We show that femtosecond infrared spectroscopy can address triplet specific bands and that the excitation of the samples leads to the formation of triplet states that decay on the ns time scale. Different quenching mechanisms (CPD formation, self quenching, oxygen quenching) will be discussed.

[1]: Schreier, W. J., J. Kubon, et al. (2009). "Thymine Dimerization in DNA Model Systems: Cyclobutane Photolesion Is Predominantly Formed via the Singlet Channel." Journal of the American Chemical Society 131(14): 5038-5039.

[2]: Schreier, W. J., T. E. Schrader, et al. (2007). "Thymine dimerization in DNA is an ultrafast photoreaction." Science 315(5812): 625-629.