| Summary: | I n this study novel triplex forming DNA probes have been designed in order to detect Ag+ ion in low concentrations. The use of triplex forming oligonucleotides is a convenient in applications of sensing biomolecules due to their sequence specificity and programmability. However, the use of triplexes has its own obstacles. While antiparallel triplex forming sequences tend to prefer G-quadruplex formation over triplexes, parallel triplexes are also challenging because their formation is triggered by lowering the pH, or using of high concentrations of cations for the stabilization of C-G·C triplets, ie. Ag+. While due to electrostatic forces C-G·C triplets stabilize in the presence of cations, this limits possible choices for a triplex forming sequence. A better understanding of the impact of the sequence and designing accordingly may improve the stability of a triplex and lower the need for high cation concentration. Here we have present Triplex-forming DNA-based probes with different distributions of C-G·C triplets for detection of Ag+ and show the impact of the C-G·C triplet distribution on the stability of parallel triplexes. Our results indicate Ag+ detection as low as 20 nM and show dramatic increase in stability when C-G·C triplets are positioned at the flanks of the triplex
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