Quantum Yield of Cyclobutane Pyrimidine Dimer Formation Via the Triplet Channel Determined by Photosensitization

Abstract

UV-induced formation of the cyclobutane pyrimidine dimer (CPD) lesion is investigated by stationary and time-resolved photosensitization experiments. The photosensitizer 2'-methoxyacetophenone with high intersystem crossing efficiency and large absorption cross-section in the UV-A range was used. A diffusion controlled reaction model is presented. Time-resolved experiments confirmed the validity of the reaction model and provided information on the dynamics of the triplet sensitization process. With a series of concentration dependent stationary illumination experiments, we determined the quantum efficiency for CPD formation from the triplet state of the thymine dinucleotide TpT to be 4 ± 0.2%.

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

“…1d, e). Since the C 6 -C 6 0 bond is already preformed in the 3 BR species, it is likely that the ThiT dimerization is triggered by the formation of the biradical intermediate, as suggested in the literature [5,14].…”

“…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.…”

“…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. As a consequence, this pathway yields very weak spectroscopic signals that preclude unambiguous statements regarding the mechanism [5][6][7]. In order to enhance the triplet signals, photosensitization is commonly used, increasing the ThiT dimerization yield [5,[17][18][19].…”

“…As a consequence, this pathway yields very weak spectroscopic signals that preclude unambiguous statements regarding the mechanism [5][6][7]. In order to enhance the triplet signals, photosensitization is commonly used, increasing the ThiT dimerization yield [5,[17][18][19]. This enhancement can also play a role with photosensitizers acting as phototoxic drugs [20].…”

“…Using the photosensitizer 2 0 -methoxyacetophenone and the dinucleotide TpT, stationary and time-resolved experiments provided two time constants, 22.5 and 62 ns, for the decay of the TpT in the triplet manifold [5]. These constants have been related to a local triplet state ( 3 L, see Fig.…”