Electroanalytical determination of d(GCGAAGC) hairpin

Hairpins (or hairpin-like structures) may play a major role in expansion events of triplet repeat expansion diseases (X syndrome, Huntington's disease, Friedreich's ataxia). The d(GCGAAGC) fragment has been found in the replication origins of phage phiX 174 and herpes simplex virus, in a promoter region of an Escherichia coli heat-shock gene, and in rRNA genes. The paper deals with the application of electrochemical methods to the determination of the DNA heptamer-d(GCGAAGC) which forms very stable hairpin structure in aqueous solutions. On mercury electrodes, this hairpin provides voltammetric reduction signals of adenine and cytosine, and oxidation signals of guanine. Both signals have been studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and elimination voltammetry with linear scan (EVLS) in dependence on pH, accumulation time, scan rate, and loop sequences. The EVLS in combination with the adsorptive stripping was employed to the determination of the detection limit (LD) of this mini-hairpin (2 nM). Multidimensional voltammetric data were worked up by Fourier Transform (FT) and for the first coefficient a confidence ellipse was calculated in order to drop out some outlier data. The same method was used also for detection limit determinations. The values of LD obtained by two approaches were compared.