Thymine dimerization in DNA is an ultrafast photoreaction.
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 approximately 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.
Schreier
Wolfgang J
WJ
Department für Physik, Ludwig-Maximilians-Universität, Oettingenstrasse 67, D-80538 München, Germany.
Schrader
Tobias E
TE
Koller
Florian O
FO
Gilch
Peter
P
Crespo-Hernández
Carlos E
CE
Swaminathan
Vijay N
VN
Carell
Thomas
T
Zinth
Wolfgang
W
Kohler
Bern
B
D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D019281:Dimerization; D007700:Kinetics; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D017785:Photons; D011740:Pyrimidine Dimers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014466:Ultraviolet Rays
D009838:Oligodeoxyribonucleotides; D011740:Pyrimidine Dimers; D004247:DNA