Synthesis and electrochemistry of anthraquinone-oligodeoxynucleotide conjugates

Electroactive oligodeoxynucleotides (ODNs) with specific base sequences hav e a potential application as electrical sensors for DNA molecules. To this end, a phosphoramidite that bears a 9,10-anthraquinone (AQ) group tethered to the 2'-O of the uridine via a hexylamino linker, 2'-0-[6-[2-oxo(9,10-ant hraquinon-2-yl)amino]hexyl]-5'-O-(4,4'-dimethoxytrityl)uridine 3'-[2-(cyano ethyl)bis(1-methylethyl)phosphoramidite] (3), has been synthesized and used to prepare three ODNs with tethered AQs using standard phosphoramidite che mistry. The synthetic methodology thus allows the synthesis of ODNs with el ectroactive tags attached to given locations in the base sequence. Cyclic v oltammetric behavior of these AQ-ODN conjugates was examined in aqueous buf fer solutions at a hanging mercury drop electrode. At slow sweep rates, nea rly reversible two-electron waves characteristic of an adsorbed anthraquino ne/hydroquinone redox couple was observed for all of the AQ-ODN conjugates. Approximate Langmuirian isotherms were found for the AQ-ODNs with molecula r footprints, calculated from the saturation coverages, that scaled with mo lecular size. The cyclic voltammetric response of the duplexes formed from the AQ-ODNs and their complementary ODN was complicated by the competitive adsorption of the individual ODNs and possibly the duplex species as well.