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 – T₃₃, T₅C₂₈, T₅C₅T₂₃, and T₁₅C₅T₁₃ – could not be separated through CE‐LIF in the absence of Hg²⁺. At 0.3 mM 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, T₁₅, 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.