CYCLIC VOLTAMMETRY WITH RNA-MODIFIED MERCURY-ELECTRODE

RNA was analyzed by means of cyclic voltammetry (CV) in combination with a hanging mercury drop electrode (HMDE) using conventional adsorptive stripping voltammetry (AdSV) and adsorptive transfer stripping voltammetry (AdTSV) involving the RNA-modified electrode. The immobilization of RNA at HMDE is sufficiently stable and the RNA-modified electrode can be used for analytical purposes. The immobilized tRNA produces a small faradaic cathodic peak CA (due to reduction of adenine and cytosine residues) and an anodic peak G (due to guanine) if a neutral medium containing ammonium ions is used as a background electrolyte. The potentials of peaks CA and G correspond to those of DNA. Peak G can be used for the determination of RNA and DNA in the mixture if RNA is specifically hydrolyzed by ribonuclease A and AdTS CV is performed before and after the enzymatic hydrolysis. The presence of RNase and of the RNA hydrolysate in the analyzed preparation does not interfere with the analysis, which enables AdTS CV to be performed directly with the hydrolyzed sample without any purification or separation steps. In a weakly alkaline background electrolyte tRNA produces a cathodic peak at -1.36 V/SCE which differs by almost 100 mV from the more negative peak of DNA, thus providing the possibility of monitoring RNA and DNA signals in the mixture. Submicrogram amounts of RNA and DNA in a mixture can easily be analyzed in both neutral and alkaline media.