title: Dewar Lesion Formation in Single- and Double-Stranded DNA is Quenched by Neighboring Bases.
abstract: UV-induced Dewar lesion formation is investigated in single- and double-stranded oligonucleotides with ultrafast vibrational spectroscopy. The quantum yield for the conversion of the (6-4) lesion to the Dewar isomer in DNA strands is reduced by a factor of 4 in comparison to model dinucleotides. Time resolved spectroscopy reveals a fast process in the excited state with spectral characteristics of bases which are adjacent to the excited (6-4) lesion. These kinetic components have large amplitudes and indicate that an additional quenching channel acts in the stranded DNA systems and reduces the Dewar formation yield. Presumably relaxation evolves via a charge transfer to the neighboring guanine and the paired cytosine participates in a double-stranded oligomer. Changes in the decay of the relaxed excited electronic state of the (6-4) chromophore point to modifications in the excited state energy landscape which may lead to an additional reduction of the Dewar formation yield.
authors.affiliation: †BioMolecular Optics and Center for Integrated Protein Science, Ludwig-Maximilians- Universität München Oettingenstrasse 67, 80538 München, Germany.|‡Center for Integrated Protein Science at the Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München, Germany.
authors.forename: Dominik B
authors.initials: DB
authors.lastname: Bucher
authors.affiliation: †BioMolecular Optics and Center for Integrated Protein Science, Ludwig-Maximilians- Universität München Oettingenstrasse 67, 80538 München, Germany.
authors.forename: Bert M
authors.initials: BM
authors.lastname: Pilles
authors.affiliation: ‡Center for Integrated Protein Science at the Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Carell
authors.affiliation: †BioMolecular Optics and Center for Integrated Protein Science, Ludwig-Maximilians- Universität München Oettingenstrasse 67, 80538 München, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Zinth
mesh_terms: D020029:Base Pairing; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
chemical_list: D004247:DNA