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

In this article, we describe the analysis of aptamers for Hg²⁺ 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, T₅C_28, T₅C ₅T_23, and T₁₅C₅T₁₃ - could not be separated through CE-LIF in the absence of Hg²⁺. At 0.3mM Hg²⁺, 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-Hg²⁺-T bonding. In addition, we found that this CE approach provided different electropherograms patterns for T₇, T_15, and T₃₃ in the absence and presence of Hg²⁺, indicating various interactions of the DNA strands with Hg²⁺. 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 T₃₃. 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.