High affinity DNAzyme-based ligands for transition metal cations - a prototype sensor for Hg2+

Inspired by recent interest in DNAzymes as transition metal ion sensors, a survey of the effects of various transition metals on the intramolecular cleavage rate of an imidazole modified, M2+-independent, self-cleaving "9(25)-11" DNA is reported. In particular, 9(25)-11 activity was strongly inhibited by Hg2+ (K-d(APP) = 110 +/- 9 nM). It is postulated that the affinity and selectivity of 9(25)-11 for Hg2+ stems from the fact that this synthetically modified DNAzyme contains imidazoles. This study demonstrates the utility of modified nucleotides in developing DNAzyme sensors for metals ions, especially those for which unmodified nucleic acids might not serve as inherently good ligands.