Thymine Dimerization in DNA Model Systems: Cyclobutane Photolesion Is Predominantly Formed via the Singlet Channel

Abstract

UV-induced formation of cylcobutane pyrimidine dimers (CPD) in all thymine DNA models have been studied by femtosecond IR spectroscopy. CPDs are shown to form within approximately 1 ps during the decay of the initially excited (1)pi pi * state. The quantum yields phi(D)(ps) determined after the (1)pi pi * decay equal the final yield phi(D)(cw). This gives evidence for a predominance of the singlet channel in CPD formation.

The Formation of DNA Photodamage: The Role of Exciton Localization

“…[16] Schreier et al [17,18] discuss an additional factor for DNA photostability. On the basis of femtosecond time-resolved infrared spectroscopy experiments on single-stranded all-thymine DNA oligonucleotides, they find that the relative orientation of the nucleobases is crucial for the quantum yield of the photoreaction.…”

Ultrafast spectroscopy of UV-induced DNA-lesions — on the search for strategies which keep DNA alive

“…We present results from different model systems (dinucleotides, dimers and single strands). The experiments reveal that the formation of the CPD lesion occurs within ~ 1ps, i. e. during the ultra-rapid decay of the excited singlet state [2][3][4][5][6]. For this reaction a favourable arrangement of the adjacent thymine molecules is a prerequisite and variations of the arrangement influence the quantum efficiency [4,6].…”

“…1, right), i. e. in the spectral range with very low solar irradiation, populates the excited ππ* state of thymine which decays on the time scale of a few hundred fs [2 -4]. We could show recently that the formation of the CPD lesion occurs on the same time scale [5,6]. The CPD and the T(6-4)T photolesions are primary products resulting from the absorption of one photon in the UV-C range and have very low formation yields in the range of ca.…”

Aerobic oxidation of alcohols on Au/TiO2 catalyst: new insights on the role of active sites in the oxidation of primary and secondary alcohols

“…This photolesion, which can take place in both the singlet and triplet manifolds, has been extensively investigated spectroscopically [2][3][4][5][6][7] and computationally [8][9][10][11][12][13][14][15]. The triplet pathway is a much slower process [7] and exhibits a smaller yield [6,16] than the singlet mechanism due to inefficient intersystem crossing.…”