feasibility study for the application of our newly developed highlyefficient and robustfluorescence-resonance-energy-transfer (FRET) system to DNA. A 2′-oligodeoxynucleotide, 12, equipped with a quinolinone derivative as donor and a (bathophenanthroline)ruthenium(II) complex as acceptor and having a single uridine as potential cleavage site under basic conditions revealed an intensive FRET, which almost vanished