Analysis of DNA complexes with small solutes by CE with LIF detection

In this article, we describe the analysis of aptamers for Hg(2+) ions through CE with LIF (CE-LIF) detection using 2% poly(ethylene oxide) solutions containing OliGreen (fluorophore). In the presence of an EOF, DNA strands migrating against the EOF were detected at the cathode end. Four DNA strands - T(33), T(5)C(28), T(5)C(5)T(23), and T(15)C(5)T(13) - could not be separated through CE-LIF in the absence of Hg(2+). At 0.3 mM Hg(2+), however, all four were partially separated within 20 min, with SDs of the migration times all being less than 2.5%. From the CE, fluorescence, and ellipticity data, we concluded that the conformations of these four DNA strands all changed from random-coil to folded structures as a result of T-Hg(2+)-T bonding. In addition, we found that this CE approach provided different electropherograms patterns for T(7), T(15), and T(33) in the absence and presence of Hg(2+), indicating various interactions of the DNA strands with Hg(2+). Using this simple, high-resolution CE approach, we also demonstrated that adenosine triphosphate has a stronger interaction with the adenosine triphosphate aptamer than with either the platelet-derived growth factor aptamer or T(33). This CE approach holds great potential for screening aptamers for small solutes, studying the catalytic activity of DNAzymes, and evaluating the biological functions of microRNA.