Sharp Switching of DNAzyme Activity through the Formation of a CuII -Mediated Carboxyimidazole Base Pair.

DNAzymes are widely used as functional units for creating DNA-based sensors and devices. Switching of DNAzyme activity by external stimuli is of increasing interest. Herein we report a CuII -responsive DNAzyme rationally designed by incorporating one of the most stabilizing artificial metallo-base pairs, a CuII -mediated carboxyimidazole base pair (ImC -CuII -ImC ), into a known RNA-cleaving DNAzyme. Cleavage of the substrate was suppressed without CuII , but the reaction proceeded efficiently in the presence of CuII ions. This is due to the induction of a catalytically active structure by ImC -CuII -ImC pairing. The on/off ratio was as high as 12-fold, which far exceeds that of the previously reported DNAzyme with a CuII -mediated hydroxypyridone base pair. The DNAzyme activity can be regulated specifically in response to CuII ions during the reaction through the addition, removal, or reduction of CuII . This approach should advance the development of stimuli-responsive DNA systems with a well-defined sharp switching function.