ABSTRACT
Electroactive oligodeoxynucleotides (ODNs) with specific base sequences have 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'-O-[6-[2-oxo(9, 10-anthraquinon-2-yl)amino]hexyl]-5'-O-(4,4'-dimethoxytrityl)uridi ne 3'-[2-(cyanoethyl)bis(1-methylethyl)phosphoramidite] (3), has been synthesized and used to prepare three ODNs with tethered AQs using standard phosphoramidite chemistry. The synthetic methodology thus allows the synthesis of ODNs with electroactive tags attached to given locations in the base sequence. Cyclic voltammetric behavior of these AQ-ODN conjugates was examined in aqueous buffer solutions at a hanging mercury drop electrode. At slow sweep rates, nearly reversible two-electron waves characteristic of an adsorbed anthraquinone/hydroquinone redox couple was observed for all of the AQ-ODN conjugates. Approximate Langmuirian isotherms were found for the AQ-ODNs with molecular footprints, calculated from the saturation coverages, that scaled with molecular 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.
Subject(s)
Anthraquinones/chemical synthesis , Oligodeoxyribonucleotides/chemical synthesis , Adsorption , Anthraquinones/chemistry , Electrochemistry/methods , Indicators and Reagents , Kinetics , Magnetic Resonance Spectroscopy , Molecular Sequence Data , Oligodeoxyribonucleotides/analysis , Oligodeoxyribonucleotides/chemistryABSTRACT
Chronoamperometry has been widely employed to determine kinetic rate constants for electron-transfer reactions of surface-confined redox couples. When the mechanism for the transformation is more complicated than a one-electron transfer, deviations can be expected from an exponential decay of the current transient. Theory is presented in this paper for irreversible, two-step and three-step consecutive reaction mechanisms in the form of analytical solutions of the corresponding differential equations. The theory should find application to surface electrode reactions with two-electron "n-values".
