W. Fudickar, M. Bauch, H. Ihmels, T. Linker
DNA-Triggered Enhancement of Singlet Oxygen Production by Pyridinium Alkynylanthracenes
Chem. Eur. J. 2021, 27, 13591–13604
DOI: 10.1002/chem.202101918
There is an ongoing interest in 1O2 sensitizers, whose activity is selectively controlled by their interaction with DNA. To this end, we synthesized three isomeric pyridinium alkynylanthracenes 2o-p and a water-soluble trapping reagent for 1O2. In water and in the absence of DNA, these dyes show a poor efficiency to sensitize the photooxygenation of the trapping reagent as they decompose due to electron transfer processes. In contrast, in the presence of DNA 1O2 is generated from the excited DNA-bound ligand. The interactions of 2o-p with DNA were investigated by thermal DNA melting studies, UV/vis and fluorescence spectroscopy, and linear and circular dichroism spectroscopy. Our studies revealed an intercalative binding with an orientation of the long pyridyl-alkynyl axis parallel to the main axis of the DNA base pairs. In the presence of poly(dA:dT), all three isomers show an enhanced formation of singlet oxygen, as indicated by the reaction of the latter with the trapping reagent. With green light irradiation of isomer 2o in poly(dA:dT), the conversion rate of the trapping reagent is enhanced by a factor >10. The formation of 1O2 was confirmed by control experiments under\r\nanaerobic conditions, in deuterated solvents, or by addition of 1O2 quenchers. When bound to poly(dG:dC), the opposite effect was observed only for isomers 2o and 2m, namely the trapping reagent reacted significantly slower. Overall, we showed that pyridinium alkynylanthracenes are very useful intercalators, that exhibit an enhanced photochemical 1O2 generation in the DNA-bound state.
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