Investigation of the Pathways of Excess Electron Transfer in DNA with Flavin‐Donor and Oxetane‐Acceptor Modified DNA Hairpins

Abstract

Oxetane is a potential intermediate that is enzymatically formed during the repair of (6-4) DNA lesions by special repair enzymes (6-4 DNA photolyases). These enzymes use a reduced and deprotonated flavin to cleave the oxetane by single electron donation. Herein we report synthesis of DNA hairpin model compounds containing a flavin as the hairpin head and two different oxetanes in the stem structure of the hairpin. The data show that the electron moves through the duplex even over distances of 17 A. Attempts to trap the moving electron with N2O showed no reduction of the cleavage efficiency showing that the electron moves through the duplex and not through solution. The electron transfer is sequence dependent. The efficiency is reduced by a factor of 2 in GC rich DNA hairpins.

Investigation of Excess‐Electron Transfer in DNA Double‐Duplex Systems Allows Estimation of Absolute Excess‐Electron Transfer and CPD Cleavage Rates

“…[11] Even though the principle mechanism of excess-electron transfer, and in particular the distance dependence, [12][13][14][15][16][17][18] has been clarified, conflicting data still exist, for example, for the sequence dependence of the transfer reaction. [19][20][21][22][23][24][25][26][27] In addition, the question of whether excess-electron transfer depends on the transfer direction in the DNA duplex has not been satisfactorily investigated. Finally, we are just beginning to understand absolute hopping rates.…”

“…Finally, we are just beginning to understand absolute hopping rates. [19,21,28] We believe that some of the problems associated with research on electron transfer in DNA arise because different electron donors and acceptors are used in different experiments. For example, we recently showed that the rate by which a given acceptor reacts with an electron Abstract: To investigate the parameters and rates that determine excess-electron transfer processes in DNA duplexes, we developed a DNA doubleduplex system containing a reduced and deprotonated flavin donor at the junction of two duplexes with either the same or different electron acceptors in the individual duplex substructures.…”

Model Studies on a Carprofen Derivative as Dual Photosensitizer for Thymine Dimerization and (6–4) Photoproduct Repair

“…[23][24][25][26][27][28] Besides, it has been shown that, for diaryl-substituted oxetanes, splitting can also occur both from radical anions and cations. [29,30] The results obtained so far concern either the pyrimidine base alone or DNA hairpin model compounds; [31] no study has been realized on nucleoside-derived oxetanes.…”

Charge transfer dynamics in DNA revealed by time-resolved spectroscopy

“…From this finding, they excluded a contribution of the solvated electron, which can be generated by electron ejection from the photoexcited donor to the solvent mediating the negative charge to the acceptor. 42 Thus, the EET should be mediated by nucleobases in DNA. These are also important conclusions of their studies.…”