DNA damage









                                  DNA is electrochemically active







              DNA-modified electrode = a simple electrochemical sensor for DNA damage





              DNA-modified electrode = a simple electrochemical sensor for DNA damage

                                 chemical modification of DNA can:

•            cause strand breakage detectable primarily with mercury (amalgam) electrodes

•            cause distotions of the double helix detectable primarily with mercury (amalgam)
electrodes

•            hit electroactive sites of nucleobases thus affecting their electrochemical activity
(mercury or carbon electrodes)

•            result in introducing new electroactive moieties (principially any electrode -
depending on the electroactive group introduced)

                       Detecting strand breaks with mercury-based electrodes

    difference in behavior of covalently closed circular and nicked or linear DNAs at a mercury
                                             electrode





                     High sensitivity of ssb detection with mercury electrodes

•           one break in ~1% of a ~3 kbp plasmid molecules can be detected

•           that is one lesion among ~2x10^5 intact nucleotides

•           200 ng of DNA per analysis (better sensitivity than agarose electrophoresis)

•           detection of multiple strand breaks in one molecule possible (not possible by means of
native electrophoresis)





example of the sensor application: detection DNA damaging agents in waste (industrial) waters
(uranium mines, Dolní Rožínka)





     similar responses to DNA damage like with the HMDE can be obtained



•             with mercury film electrodes (Kubičárová 2000)









•             with amalgam electrodes (Cahová-Kuchaříková, Fadrná, Yosypchuk, Novotný 2004)



studies of cleavage of DNA at the electrode surface by electrochemically generated reactive species



Peak 3 intensity (=the amount of SB, degree of DNA damage) depends on the potetial applied:



                                           přidat chrom

                        Detection of DNA degradation with carbon electrodes





                                        Damage to DNA bases





                                             cisplatin

                                             cisplatin











                            apurinic sites detected by exonuclease III





                 Utilization of an electroactive marker in detection of DNA damage

                                           (OsO[4],bipy)