Ten-atom silver cluster signaling and tempering DNA hybridization.
Silver clusters with ∼10 atoms are molecules, and specific species develop within DNA strands. These molecular metals have sparsely organized electronic states with distinctive visible and near-infrared spectra that vary with cluster size, oxidation, and shape. These small molecules also act as DNA adducts and coordinate with their DNA hosts. We investigated these characteristics using a specific cluster-DNA conjugate with the goal of developing a sensitive and selective biosensor. The silver cluster has a single violet absorption band (λ(max) = 400 nm), and its single-stranded DNA host has two domains that stabilize this cluster and hybridize with target oligonucleotides. These target analytes transform the weakly emissive violet cluster to a new chromophore with blue-green absorption (λ(max) = 490 nm) and strong green emission (λ(max) = 550 nm). Our studies consider the synthesis, cluster size, and DNA structure of the precursor violet cluster-DNA complex. This species preferentially forms with relatively low amounts of Ag(+), high concentrations of the oxidizing agent O2, and DNA strands with ≳20 nucleotides. The resulting aqueous and gaseous forms of this chromophore have 10 silvers that coalesce into a single cluster. This molecule is not only a chromophore but also an adduct that coordinates multiple nucleobases. Large-scale DNA conformational changes are manifested in a 20% smaller hydrodynamic radius and disrupted nucleobase stacking. Multidentate coordination also stabilizes the single-stranded DNA and thereby inhibits hybridization with target complements. These observations suggest that the silver cluster-DNA conjugate acts like a molecular beacon but is distinguished because the cluster chromophore not only sensitively signals target analytes but also stringently discriminates against analogous competing analytes.
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
Jeffrey T
JT
Petty
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
Orlin O
OO
Sergev
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
Andrew G
AG
Kantor
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
Ian J
IJ
Rankine
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
Mainak
M
Ganguly
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
Frederic D
FD
David
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
Sandra K
SK
Wheeler
Department of Chemistry, Furman University, Greenville, South Carolina 29613, United States.
John F
JF
Wheeler
D001483:Base Sequence; D004396:Coloring Agents / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000737:chemistry; D009690:Nucleic Acid Conformation; D009693:Nucleic Acid Hybridization / Q000379:methods*; D009841:Oligonucleotides / Q000737:chemistry; D012834:Silver / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods
D004396:Coloring Agents; D004277:DNA, Single-Stranded; D009841:Oligonucleotides; D012834:Silver; D004247:DNA