DNA Mismatch Detection by Resonance Energy Transfer between Ruthenium(II) and Osmium(II) Tris(2,2-bipyridyl) Chromophores

Octahedral tris-chelate complexes [MII(bpy)3]^2+ (M = Ru or Os, bpy = 2,2ʹ-bipyridyl), covalently attached to the 3ʹ- and 5ʹ-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 [RuII(bpy)3]^2+ unit leads to resonance energy transfer to the MLCT state of the [OsII(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 RuII chromophore hence allows highly sensitive structural probing of the assembly and constitutes a novel approach to DNA sensing which is capable of detecting mutations.