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

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• DNAzymes are increasingly recognized for their potential as transition metal ion sensors.
• Self-cleaving DNAzymes offer a platform for developing sensitive detection systems.
• Modifying DNAzymes with specific chemical groups can enhance their ligand-binding properties.

Purpose of the Study:

• To investigate the impact of various transition metals on the activity of an imidazole-modified DNAzyme.
• To evaluate the selectivity and affinity of the modified DNAzyme for specific metal ions.
• To demonstrate the utility of modified nucleotides in creating novel metal ion biosensors.

Main Methods:

• Synthesis of an imidazole-modified, self-cleaving DNAzyme (9(25)-11).
• Assay of intramolecular cleavage rates in the presence of different transition metal ions.
• Determination of binding affinity (Kd) for inhibitory metal ions.

Main Results:

• The DNAzyme 9(25)-11 exhibited M(2+)-independent activity.
• Mercury ions (Hg2+) strongly inhibited the DNAzyme's cleavage activity.
• A high affinity and selectivity for Hg2+ was observed, with a Kd of 110 +/- 9 nM.
• The presence of imidazole moieties in the DNAzyme is postulated to be responsible for the Hg2+ affinity.

Conclusions:

• Modified nucleotides, specifically imidazole groups, can be utilized to develop selective DNAzyme sensors for metal ions.
• This approach is particularly useful for detecting metal ions like Hg2+ that may not bind strongly to unmodified nucleic acids.
• The developed DNAzyme shows promise as a sensitive and selective biosensor for mercury detection.