Most RNA-cleaving DNAzymes require a metal ion to interact with the scissile phosphate for activity. Therefore, few unmodified DNAzymes work with thiophilic metals because of their low affinity for phosphate. Recently, an Ag-specific Ag10c DNAzyme was reported via in vitro selection. Herein, Ag10c is characterized to rationalize the role of the strongly thiophilic Ag. Systematic mutation studies indicate that Ag10c is a highly conserved DNAzyme and its Ag binding is unrelated to C-Ag-C interaction. Its activity is enhanced by increasing Na concentrations in buffer. At the same metal concentration, activity decreases in the following order: Li > Na > K. Ag10c binds one Na ion and two Ag ions for catalysis. The pH-rate profile has a slope of ∼1, indicating a single deprotonation step. Phosphorothioate substitution at the scissile phosphate suggests that Na interacts with the pro-R oxygen of the phosphate, and dimethyl sulfate footprinting indicates that the DNAzyme loop is a silver aptamer binding two Ag ions. Therefore, Ag exerts its function allosterically, while the scissile phosphate interacts with Na, Li, Na, or Mg. This work suggests the possibility of isolating thiophilic metal aptamers based on DNAzyme selection, and it also demonstrates a new Ag aptamer.

In this work, the effect of Ag+ on DNA sensitized Tb3+ luminescence was studied initially using the Ag+-specific RNA-cleaving DNAzyme, Ag10c. While we expected to observe luminescence quenching by Ag+, a significant enhancement was produced. Based on this observation, simple DNA oligonucleotide homopolymers were used with systematically varied sequence and length. We discovered that both poly-G and poly-T DNA have a significant emission enhancement by Ag+, while the absolute intensity is stronger with the poly-G DNA, indicating that a G-quadruplex DNA is not required for this enhancement. Using the optimized length of the G7 DNA (an oligo constituted with seven guanines), Ag+ was measured with a detection limit of 57.6 nM. The signaling kinetics, G7 DNA conformation, and the binding affinity of Tb3+ to the DNA in the presence or absence of Ag+ are also studied to reveal the mechanism of emission enhancement. This observation is useful not only for label-free detection of Ag+, but also interesting for the rational design of new biosensors using Tb3+ luminescence.

Seismic lines are prominent linear disturbances across boreal Canada with large-scale consequences to wildlife and ecosystem function. Although seismic line restoration has been observed to improve tree growth and survival, application in peatlands has been shown to alter ecosystem functions such as hydrology and carbon storage. The most common active restoration method is called mechanical mounding where the classic technique inverts the peat profile. New mounding methods that maintain the peat profile may provide benefits by preserving existing vegetation and reducing disturbance. To determine the effects of different mounding methods on soil quality, peat cores were collected and analyzed from two different sites for various soil properties (C/N ratios, δ13C, δ15N, Fourier transform infrared (FTIR) spectroscopy humification indices). Vegetation surveys were also conducted. The two sites are both a collection of seismic lines crossing poor fens in Alberta. One site was treated with the classic method while the other was treated with two new mounding methods. Classic mechanical mounding significantly increased the degree of decomposition, indicative of lower substrate quality. Mechanical mounding also greatly reduced moss cover and introduced large amounts of bare ground cover. The two newer mounding methods did not result in these changes and were largely comparable to natural peat properties and vegetation communities. Preserving the peat profile in new mounding methods may support faster return of ecosystem function.