Tug-of-War between DNA Chelation and Silver Agglomeration in DNA–Silver Cluster Chromophores

Abstract

Supramolecular chromophores form when a DNA traps silvers that then coalesce into clusters with discrete, molecular electronic states. However, DNA strands are polymeric ligands that disperse silvers and thus curb agglomeration. We study this competition using two chromophores that share three common components: a dimeric DNA scaffold, Ag + -nucleobase base pairs, and Ag 0 chromophores. The DNA host C 4 -A 2 -iC 4 T mimics structural elements in a DNA-cluster crystal structure using a phosphodiester backbone with combined 5′ → 3′ and 3′ → 5′ (indicated by "i") directions. The backbone directions must alternate to form the two silver clusters, and this interdependence supports a silver-linked structure. This template creates two chromophores with distinct sizes, charges, and hence spectra: (C 4 -A 2 -iC 4 T) 2 /Ag 11 7+ with λ abs /λ em = 430/520 nm and (C 4 -A 2 -iC 4 T) 2 /Ag 14 8+ with λ abs /λ em = 510/630 nm. The Ag + and Ag 0 constituents in these partially oxidized clusters are linked with structural elements in C 4 -A 2 -iC 4 T. Ag + alone binds sparsely but strongly to form C 4 -A 2 -iC 4 T/3−4 Ag + and (C 4 -A 2 -iC 4 T) 2 /7−8 Ag + complexes, and these stoichiometries suggest that Ag + cross-links pairs of cytosines to form a hairpin with a metallo-C 4 /iC 4 duplex and an adenine loop. The Ag 0 are chemically orthogonal because they can be oxidatively etched without disrupting the underlying Ag + −DNA matrix, and their reactivity is attributed to their valence electrons and weaker chelation by the adenines. These studies suggest that Ag + disperses with the cytosines to create an adenine binding pocket for the Ag 0 cluster chromophores.

Interrupted DNA and Slow Silver Cluster Luminescence

“…These five strands preserve key elements of their parent (C 2 A) 6 by developing chromophores with λ abs = 435–444 nm and λ em = 527–536 nm, and each is distinctive partly because of the 5′→3′ DNA polarity (Figures A and S1 and Table S1). Only a specific silver cluster chromophore is synthesized, as suggested by the consistent absorption maximum from 2–10 Ag/DNA and by a consistent emission maximum using λ ex = 400–500 nm (Figure S2). − Furthermore, these chromophores are like other DNA-bound silver molecules with ∼7–26% fluorescence quantum yields and 1.4–2.2 ns fluorescence lifetimes. ,, These similarities suggest that thymine is a neutral substitution, but it indirectly alters the silver cluster adduct because pronounced red luminescence develops alongside the dominant green emission (Figure A, red arrow).…”

Coordination‐Driven One‐Step Rapid Self‐Assembly Synthesis of Dual‐Functional Ag@Pt Nanozyme

“…[14,15] Nanozyme containing nucleic acids as a template can exhibit unique catalytic properties due to the physicochemical properties of nucleic acids, which include programmability, easy modification, facile synthesis, low price, and biosafety. [16] There are three main modes of interaction between nucleic acid templates and metal ions: 1) chelate of nucleobases with metal ions occurs through coordinated electrons, [17,18] 2) electrostatic interactions with the phosphate backbone provide binding sites, [19] and 3) the unique spatial structure provides nanomaterials with a microenvironment and maintains their stability. [20] Thus, nucleic acids would have unexpected functions as nanozymes synthesis templates.…”

pH-Switchable phenylalanine-templated copper nanoclusters: CO2 probing and efficient peroxidase mimicking activity

“…1,12,13 The photophysical properties of the MNCs are influenced by both metal ions and ligands used as templates. 2,12,14 Several templates have been employed for the facile formation of stable MNCs which include DNA, 15,16 proteins, [17][18][19] polymers, 20 thiol-containing compounds, 21,22 and other small molecules. 2,3 However, unlike macromolecules, the formation of NCs using small molecules is more challenging.…”