The synthesis of triple-helix-forming oligonucleotides (TFOs) linked to a series of cyanine monomethines has been performed. Eight cyanines including one thiocyanine, four thiazole orange analogues, and three quinocyanines were attached to the 5′-end of 10-mer pyrimidine TFOs. The binding properties of these modified TFOs with their double-stranded DNA target were studied by absorption and steady-state fluorescence spectroscopy. The ...