Cation Binding to DNA Studied by Ion-Transfer Voltammetry at Micropipets

Abstract

Two new approaches to the study of ion binding to DNA have been developed. Both are based on measurement of ion transfer across the interface between two immiscible electrolyte solutions. In the first method, the cation of interest is initially present in the aqueous phase and transferred to the organic phase contained in a micropipet when its potential is made sufficiently negative. Upon addition of high-molecular-weight DNA to the aqueous phase, the concentration of free cation decreases, which results in a decrease in the ion-transfer current. The corresponding binding constant can be extracted from the dependence of normalized steady-state current vs DNA concentration without the knowledge of micropipet size, binding kinetics, or diffusion coefficient values. In the second method, the cation of interest is present in the organic phase inside the pipet and oligonucleotides (fragments of DNA) are added to the external aqueous phase. The transfer of the cation to the aqueous phase may be facilitated by t...