title: DNA binding of an ethidium intercalator attached to a monolayer-protected gold cluster.
abstract: Ethidium intercalation has been investigated as a means of inducing binding of Au nanoparticles to DNA. The ethidium sites are attached to the nanoparticles as thiolate ligands, using 3,8-diamino-5-mercaptododecyl-6-phenylphenanthridinium (ethidium thiolate). Each nanoparticle bears only one or two ethidium thiolate ligands. The rest of the thiolate monolayer ligands on the monolayer-protected Au clusters (MPCs) were either N-(2-mercaptopropionyl)glycine (tiopronin/ethidium MPC) or trimethyl(mercaptoundecyl)ammonium (TMA/ethidium MPC). In solution mixtures of DNA and MPCs, the energy-transfer quenching of the ethidium ligands by the metal-like MPC core is partially released by ethidium binding to DNA, as observed by an increase in the intensity of ethidium fluorescence. Binding of the cationic TMA/ethidium MPC to DNA was efficient and rapid. The negatively charged tiopronin/ethidium MPC, in contrast, exhibits slow intercalation kinetics, relative to ethidium cation not attached to an MPC. The slow kinetics were analyzed as two competing binding interactions. The tiopronin/ethidium MPC binding to DNA was imaged by AFM.
authors.affiliation: Kenan Laboratories of Chemistry, University of North Carolina, Chapel Hill 27599, USA.
authors.forename: Gangli
authors.initials: G
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Royce W
authors.initials: RW
authors.lastname: Murray
mesh_terms: D004247:DNA / Q000737:chemistry*; D004996:Ethidium / Q000737:chemistry; D005453:Fluorescence; D017979:Gold Colloid / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D007700:Kinetics; D036103:Nanotechnology
chemical_list: D017979:Gold Colloid; D007364:Intercalating Agents; D004247:DNA; D004996:Ethidium