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Science 2 February 2007:
Vol. 315. no. 5812, pp. 625 - 629
DOI: 10.1126/science.1135428
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Reports

Thymine Dimerization in DNA Is an Ultrafast Photoreaction

Wolfgang J. Schreier,1 Tobias E. Schrader,1 Florian O. Koller,1 Peter Gilch,1 Carlos E. Crespo-Hernández,2 Vijay N. Swaminathan,3 Thomas Carell,3 Wolfgang Zinth,1* Bern Kohler2*

Femtosecond time-resolved infrared spectroscopy was used to study the formation of cyclobutane dimers in the all-thymine oligodeoxynucleotide (dT)18 by ultraviolet light at 272 nanometers. The appearance of marker bands in the time-resolved spectra indicates that the dimers are fully formed ~1 picosecond after ultraviolet excitation. The ultrafast appearance of this mutagenic photolesion points to an excited-state reaction that is approximately barrierless for bases that are properly oriented at the instant of light absorption. The low quantum yield of this photoreaction is proposed to result from infrequent conformational states in the unexcited polymer, revealing a strong link between conformation before light absorption and photodamage.

1 Department für Physik, Ludwig-Maximilians-Universität, Oettingenstrasse 67, D-80538 München, Germany.
2 Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA.
3 Fakultät für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, D-81377 München, Germany.

* To whom correspondence should be addressed. E-mail: kohler{at}chemistry.ohio-state.edu (B.K.); wolfgang.zinth{at}physik.uni-muenchen.de (W.Z.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
UV excitation of single DNA and RNA strands produces high yields of exciplex states between two stacked bases.
T. Takaya, C. Su, K. de La Harpe, C. E. Crespo-Hernandez, and B. Kohler (2008)
PNAS 105, 10285-10290
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Science. ISSN 0036-8075 (print), 1095-9203 (online)