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Spectroscopy
Volume 24 (2010), Issue 3-4, Pages 309-316
http://dx.doi.org/10.3233/SPE-2010-0437

DNA photodamage: Study of cyclobutane pyrimidine dimer formation in a locked thymine dinucleotide

W. J. Schreier,1 J. Kubon,1 P. Clivio,2 W. Zinth,1,3 and P. Gilch1,4

1Fakultät für Physik, LMU München, Lehrstuhl für BioMolekulare Optik, München, Germany and Munich Center for Integrated Protein Science CIPSM, München, Germany
2Institut de Chimie Moléculaire de Reims, Université de Reims Champagne Ardenne, Reims, France
3Fakultät für Physik, LMU München, Lehrstuhl für BioMolekulare Optik, Oettingen str. 67, 80538 München, Germany and Munich Center for Integrated Protein Science CIPSM, München, Germany
4Institut für Physikalische Chemie, Heinrich-Heine-Universität, Düsseldorf Universitäts str. 1, 40225 Düsseldorf, Germany

Copyright © 2010 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The cyclobutane pyrimidine dimer (CPD) formed between two adjacent thymine bases is the most abundant DNA photolesion induced by UV radiation. The quantum yield of this reaction is on the order of ~1% in DNA. This small quantum yield hampers the study of damage formation in naturally occurring DNA. Investigations with increased accuracy become possible for a locked nucleotide model compound TLpTL which exhibits a quantum yield of about 10% for CPD formation. Time resolved IR spectroscopy on TLpTL and two other DNA model compounds (TpT and (dT)18) reveals that: (i) The absorption changes after ~1 ps are due to CPD photodamage. (ii) The quantum efficiency of CPD formation on the few picosecond time scale equals the quantum efficiency reported in stationary experiments. CPD photodamage formation in the investigated DNA constructs is thus predominantly formed from the primarily photoexcited singlet ππ* state, whereas the triplet channel does not play an essential role.