title: DNA sequence and ancillary ligand modulate the biexponential emission decay of intercalated [Ru(L)2dppz]2+ enantiomers.
abstract: The bi-exponential emission decay of [Ru(L)(2)dppz](2+) (L = N,N'-diimine ligand) bound to DNA has been studied as a function of polynucleotide sequence, enantiomer, and nature of L (phenanthroline vs. bipyridine). The lifetimes (τ(i)) and pre-exponential factors (α(i)) depend on all three parameters. With [poly(dA-dT)](2), the variation of α(i) with [Nu]/[Ru] has little dependence on L for Λ-[Ru(L)(2)dppz](2+) but a substantial dependence for Δ-[Ru(L)(2)dppz](2+). With [poly(dG-dC)](2), by contrast, the Λ-enantiomer α(i) values depend strongly on the nature of L, whereas those of the Δ-enantiomer are relatively unaffected. DNA-bound linked dimers show similar photophysical behaviour. The lifetimes are identified with two geometries of minor-groove intercalated [Ru(L)(2) dppz](2+), resulting in differential water access to the phenazine nitrogen atoms. Interplay of cooperative and anti-cooperative binding resulting from complex-complex and complex-DNA interactions is responsible for the observed variations of α(i) with binding ratio. [Ru(phen)(2)dppz](2+) emission is quenched by guanosine in DMF, which may further rationalise the shorter lifetimes observed with guanine-rich DNA.
authors.affiliation: Department of Chemistry, Imperial College London, London SW7 2AZ, UK.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: McKinley
authors.forename: Johanna
authors.initials: J
authors.lastname: Andersson
authors.forename: Per
authors.initials: P
authors.lastname: Lincoln
authors.forename: Eimer M
authors.initials: EM
authors.lastname: Tuite
mesh_terms: D000595:Amino Acid Sequence; D004247:DNA / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D012428:Ruthenium; D004247:DNA