title: Crystal structures of Λ-[Ru(phen)₂dppz]²⁺ with oligonucleotides containing TA/TA and AT/AT steps show two intercalation modes.
abstract: The ruthenium complex [Ru(phen)(2)(dppz)](2+) (where phen is phenanthroline and dppz                 dipyridophenazine is known as a 'light switch' complex because its luminescence in solution is significantly enhanced in the presence of DNA. This property is poised to serve in diagnostic and therapeutic applications, but its binding mode with DNA needs to be elucidated further. Here, we describe the crystal structures of the Λ enantiomer bound to two oligonucleotide duplexes. The dppz ligand intercalates symmetrically and perpendicularly from the minor groove of the d(CCGGTACCGG)(2) duplex at the central TA/TA step, but not at the central AT/AT step of d(CCGGATCCGG)(2). In both structures, however, a second ruthenium complex links the duplexes through the combination of a shallower angled intercalation into the C(1)C(2)/G(9)G(10) step at the end of the duplex, and semi-intercalation into the G(3)G(4) step of an adjacent duplex. The TA/TA specificity of the perpendicular intercalation arises from the packing of phenanthroline ligands against the adenosine residue.
authors: Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK.
authors: Hakan
authors: H
authors: Niyazi
authors: James P
authors: JP
authors: Hall
authors: Kyra
authors: K
authors: O'Sullivan
authors: Graeme
authors: G
authors: Winter
authors: Thomas
authors: T
authors: Sorensen
authors: John M
authors: JM
authors: Kelly
authors: Christine J
authors: CJ
authors: Cardin
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007364:Intercalating Agents / Q000737:chemistry*; D008958:Models, Molecular; D009841:Oligonucleotides / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D007364:Intercalating Agents; D009841:Oligonucleotides; D009942:Organometallic Compounds; C466600:Ru(phen)(2)dipyrido(3,2-a-2',3'-c)phenazine; D012428:Ruthenium