Single-stranded DNA encapsulates silver clusters, and we consider blue-green and near-infrared chromophores whose spectra are directed by DNA structural changes.  We show how these changes are used to detect oligonucleotides.  A common type of DNA template has two components: the 3' sequence hybridizes with target oligonucleotides and the 5' sequence forms specific silver clusters. These composite strands exclusively harbor an ~11 silver atom cluster that absorbs at 400 nm with limited emission. When a target hybridizes with these single-stranded conjugates, cluster absorption shifts and strong emission develops. Fluorescence anisotropy, fluorescence correlation spectroscopy, size exclusion chromatography, elemental analysis, and temperature-dependent spectral measurements identify two structural and thermodynamic changes accompanying hybridization. First, the violet cluster folds its single-stranded host and inhibits DNA hybridization.  Second, the violet cluster dimerizes its DNA host and forms a near-infrared cluster.  Our key conclusion is that silver clusters are both chromophoric reporters and ligands that modulate analyte-sensor interactions.

DNA-templated silver clusters

247th National Meeting (2014)

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