DNA-Based Ultrasensitive Cu(II) Sensor: Troponyl-Thymidine Oligo (T*₄T) Forms Copper-Mediated Duplex Structure

DNA-metal complexes provide new dimensions in synthesizing DNA-based conducting biomaterials such as aptamers, DNAzymes, and their metal base pairing duplex structure. Structural modifications in the native DNA generate metal-specific binding sites in addition to phosphate backbone and nucleobase sites. One of the natural nonbenzenoid aromatic molecules, Tropolone, exhibits ion-specific binding with Cu(II) ion. In the repertoire of DNA metal sensors, troponyl-DNA can be explored for developing DNA-based Cu-sensors owing to the excellent Cu²⁺ binding affinity of Tropolone ligand. This report describes the synthesis of DNA penta-oligomer containing the repeated sequence of tr-dTnucleoside (T^*) as (5'-T^*T^*T^*T^*T-3') and its binding affinity with Cu(II) ions. Its Cu(II) mediated duplex-like dimer structure shows promising electrical conductivity at pico-molar [Cu²⁺] in acetonitrile. Hence, troponyl-DNA can be applied for making Cu(II) ion sensing devices.