DNA mismatch detection by resonance energy transfer between ruthenium(II) and osmium(II) tris(2,2′-bipyridyl) chromophores

Octahedral tris-chelate complexes [M-II(bPY)(3)](2+) (M = Ru or Os, bpy = 2,2'-bipyridyl), covalently attached to the 3'- and 5'phosphates of two oligonucleotides, are juxtaposed when hybridized contiguously to a fully complementary DNA target. Visible metal-to-ligand charge-transfer (MLCT) excitation of the [Ru-II(bPY)(3)](2+) unit leads to resonance energy transfer to the MLCT state of the [Os-II- (bpy)(3)](2+) moiety, with the energy transfer efficiency depending on the degree of hybridization. The extent of attenuation of the intense red luminescence from the Ru-II chromophore hence allows highly sensitive structural probing of the assembly and constitutes a novel approach to DNA sensing which is capable of detecting mutations.