| NUKLEONIKA 2009, 54(1):11-16
CHARGE TRANSFER IN DNA AND REPAIR OF OXIDATIVE DAMAGESylwia Męczyńska, Irena Szumiel Department of Radiobiology and Health Protection, Institute of Nuclear Chemistry and Technology, 16 Dorodna Str., 03-195 Warsaw, Poland The possibility of a biological role of an unusual function of DNA sequences is discussed, namely, signaling by charge transfer within chromatin. Although a general conclusion on its biological significance is premature, the idea of charge transfer accompanying repair of some types of oxidative DNA damage is based on sound experimental data. Both physical and chemical experiments reviewed here provided results indicating that DNA duplex under certain conditions (among them – hydration) – can behave as narrow band gap semiconductor. With the use of model molecules it was shown that charge transfer most probably occurs by hopping between guanine residues and tunneling through thymine-adenine (TA) base pairs. Charge transfer is nucleotide sequence and distance dependent. Furthermore, the pi-stacked base pairs must be perfectly matched to mediate charge transfer and in a damaged double helix this condition is not fulfilled. Hence, the possibility that charge transfer takes place in oxidatively damaged DNA after UV or X-irradiation and it becomes interrupted by mismatched base pairs, thus signaling the mismatch or strand break to the repair machinery. Function of base damage repair enzymes which contain [4Fe-4S] clusters is discussed in this context. Close X |