Ultrafast excited state dynamics of silver ion-mediated cytosine-cytosine base pairs in metallo-DNA.
Forrest R KohlYuyuan ZhangAaron P CharnayLara Martínez FernándezBern KohlerPublished in: The Journal of chemical physics (2021)
To better understand the nexus between structure and photophysics in metallo-DNA assemblies, the parallel-stranded duplex formed by the all-cytosine oligonucleotide, dC20, and silver nitrate was studied by circular dichroism (CD), femtosecond transient absorption spectroscopy, and time-dependent-density functional theory calculations. Silver(I) ions mediate Cytosine-Cytosine (CC) base pairs by coordinating to the N3 atoms of two cytosines. Although these silver(I) mediated CC base pairs resemble the proton-mediated CC base pairs found in i-motif DNA at first glance, a comparison of experimental and calculated CD spectra reveals that silver ion-mediated i-motif structures do not form. Instead, the parallel-stranded duplex formed between dC20 and silver ions is proposed to contain consecutive silver-mediated base pairs with high propeller twist-like ones seen in a recent crystal structure of an emissive, DNA-templated silver cluster. Femtosecond transient absorption measurements with broadband probing from the near UV to the near IR reveal an unusually long-lived (>10 ns) excited state in the dC20 silver ion complex that is not seen in dC20 in single-stranded or i-motif forms. This state is also absent in a concentrated solution of cytosine-silver ion complexes that are thought to assemble into planar ribbons or sheets that lack stacked silver(I) mediated CC base pairs. The large propeller twist angle present in metal-mediated base pairs may promote the formation of long-lived charged separated or triplet states in this metallo-DNA.
Keyphrases
- gold nanoparticles
- silver nanoparticles
- density functional theory
- single molecule
- circulating tumor
- cell free
- dendritic cells
- nucleic acid
- immune response
- nitric oxide
- gene expression
- epithelial mesenchymal transition
- molecular dynamics simulations
- drinking water
- cerebral ischemia
- dna methylation
- binding protein
- genome wide
- multidrug resistant
- single cell
- high speed
- aqueous solution