title: Distinct conformations of DNA-stabilized fluorescent silver nanoclusters revealed by electrophoretic mobility and diffusivity measurements.
abstract: Silver-DNA nanoclusters (Ag:DNAs) are novel fluorophores under active research and development as alternative biomolecular markers. Comprised of a few-atom Ag cluster that is stabilized in water by binding to a strand of DNA, they are also interesting for fundamental explorations into the properties of metal molecules. Here, we use in situ calibrated electrokinetic microfluidics and fluorescence correlation spectroscopy to determine the size, charge, and conformation of a select set of Ag:DNAs. Among them is a pair of spectrally distinct Ag:DNAs stabilized by the same DNA sequence, for which it is known that the silver cluster differs by two atoms. We find these two Ag:DNAs differ in size by ∼30%, even though their molecular weights differ by less than 3%. Thus a single DNA sequence can adopt very different conformations when binding slightly different Ag clusters. By comparing spectrally identical Ag:DNAs that differ in sequence, we show that the more compact conformation is insensitive to the native DNA secondary structure. These results demonstrate electrokinetic microfluidics as a practical tool for characterizing Ag:DNA.
authors.affiliation: Mechanical Engineering Department, University of California, Santa Barbara, California, United States.
authors.forename: Til
authors.initials: T
authors.lastname: Driehorst
authors.forename: Patrick
authors.initials: P
authors.lastname: O'Neill
authors.forename: Peter M
authors.initials: PM
authors.lastname: Goodwin
authors.forename: Sumita
authors.initials: S
authors.lastname: Pennathur
authors.forename: D Kuchnir
authors.initials: DK
authors.lastname: Fygenson
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D004058:Diffusion; D024202:Electrophoretic Mobility Shift Assay / Q000295:instrumentation / Q000379:methods*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D055029:Inverted Repeat Sequences; D053768:Metal Nanoparticles / Q000737:chemistry*; D046210:Microfluidic Analytical Techniques; D009690:Nucleic Acid Conformation; D012834:Silver / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D012834:Silver; D004247:DNA