A Split DNA Scaffold for a Green Fluorescent Silver Cluster
2019
He, Chen | Goodwin, Peter M. | Yunus, Ahmed I. | Dickson, Robert M. | Petty, Jeffrey T.
Silver molecules are chromophores with diverse spectra and rich photophysics, and DNA strands act as ligands that develop specific molecular silver species. For example, C₄AC₄T*C₃GT₄ selectively yields a Ag₁₀⁶⁺ fluorophore with λₑₓ/λₑₘ = 490/550 nm. This single-stranded DNA coordinates and protects the cluster, and its integrity was challenged by breaking the phosphodiester backbone at the innocuous T*. The resulting C₄AC₄T and C₃GT₄ fragments also develop the same Ag₁₀⁶⁺ fluorophore but only when all three components (two fragments + Ag) are present. This C₄AC₄T/C₃GT₄/Ag₁₀⁶⁺ complex is favored by higher DNA concentrations and preferentially forms when hybridization forces C₄AC₄T and C₃GT₄ onto a shared DNA duplex. The C₄AC₄T/C₃GT₄ assembly reverses when the cluster photodegrades, which suggests that the cluster is labile. C₄AC₄T forms an alternate cluster at low temperatures, but C₃GT₄ recovers the λ = 490 nm fluorophore at higher temperatures. Thus, the reciprocal interactions between the host DNA strands and the cluster adduct combine to create a highly specific, split-DNA fluorescent Ag cluster capable of sensing target DNA sequences with high specificity and on–off contrast.
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