Double elimination voltammetry of short oligonucleotides
In connection with adsorptive stripping (AdS) technique, elimination voltammetry with linear scan (EVLS) in double mode was successfully employed in the analysis of homo-ODNs: 5'-AAA AAA AAA-3' (dA(9)) and 5'-CCC CCC CCC-3' (dC(9)), and hetero-ODNs: 5'-CCC AAA CCC-3' (H3), 5'-CAC CAC CAC-3' (H4), and 5'-ACC CAC CCA-3' (H9) on hanging mercury drop electrode (HMDE). Analogously to single EVLS function E4 (conserving the diffusion current I-d and eliminating kinetic and charging currents I-k, I-c) for the electroactive substance adsorbed, the double EVLS function E4 yields well readable peak-counterpeaks of reducible nucleic acid bases (adenine A and cytosine C). In comparison with single EVLS these peak-counterpeaks are higher by more than one order of magnitude (twenty times for dA(9), fourteen times for dC(9), from eight to sixteen times for hetero-ODNs). The increase of reduction signals with higher resolution was also observed using other two EVLS functions in double mode, the functions E5 eliminating I-c and I-d, but conserving I-k and E6 eliminating I-d and I-k, but conserving I-c. The amplifications of double / single EVLS signals of A and C range from 3.4 to 8.4, and from 3.1 to 8.3 for E5 and E6, respectively. It was proved that AdS double EVLS offers a new, fast, simple and inexpensive electroanalytical tool, which can be considered as a device not only for very good resolution of A and C in ODNs, but also for sensitive detection of changes in the primary structure of nucleic acid bases in ODN chains, depending on experimental conditions, such as pH, temperature, and time and potential of accumulation.