DiSC2(5) (3,3′-Diethylthiadicarbocyanine, iodide) binds to DNA-DNA or PNA-DNA duplexes with a large blue-shift of the absorption spectrum. Binding of the dye to PNA-DNA hybrid, in particular, blue-shifts the dye absorption spectrum by as much as 115 nm, offering a visual method to detect nucleic acid hybridization (1,2).