The changes of the surface properties of Au, GaN, and SiO after UV light irradiation were used to actively influence the process of formation of Pseudomonas aeruginosa films. The interfacial properties of the substrates were characterized by X-ray photoelectron spectroscopy and atomic force microscopy. The changes in the P. aeruginosa film properties were accessed by analyzing adhesion force maps and quantifying the intracellular Ca concentration. The collected analysis indicates that the alteration of the inorganic materials' surface chemistry can lead to differences in biofilm formation and variable response from P. aeruginosa cells.
Bacterial behavior is often controlled by structural and composition elements of their cell wall. Using genetic mutant strains that change specific aspects of their surface structure, we modified bacterial behavior in response to semiconductor surfaces. We monitored the adhesion, membrane potential, and catalase activity of the Gramnegative bacterium Escherichia coli (E. coli) that were mutant for genes encoding components of their surface architecture, specifically flagella, fimbriae, curli, and components of the lipopolysaccharide membrane, while on gallium nitride (GaN) surfaces with different surface potentials. The bacteria and the semiconductor surface properties were recorded prior to the biofilm studies. The data from the materials and bioassays characterization supports the notion that alteration of the surface structure of the E. coli bacterium resulted in changes to bacterium behavior on the GaN medium. Loss of specific surface structure on the E. coli bacterium reduced its sensitivity to the semiconductor interfaces, while other mutations increase bacterial adhesion when compared to the wild-type control E. coli bacteria. These results demonstrate that bacterial behavior and responses to GaN semiconductor materials can be controlled genetically and can be utilized to tune the fate of living bacteria on GaN surfaces.
A simple treatment of UV light exposure can change the interfacial properties of variably doped GaN substrates. The changes in surface charge and chemistry after exposure to UV light were studied as way to alter the behavior of Pseudomonas aeruginosa films. The properties of GaN surfaces were characterized by atomic force microscopy, Kelvin probe force microscopy, and X-ray photoelectron spectroscopy. The Pseudomonas aeruginosa film responses were quantified by analyzing changes in the amount of catalase, reactive oxygen species, and intracellular Ca 2+ concentrations. The comprehensive analysis supports the notion that the response of P. aeruginosa biofilms can be controlled by the properties of the interface and the amount of time the film is in contact with it.
The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202004655. material types along with target microorganisms that will be critical for future research on programmable biointerfacial structures.
Brine desalination is important for minimizing the environmental impact of contaminated wastewater, yet current desalination techniques have high energy requirements. Solvent-based desalination (SBD) method, which is the process of extracting fresh water using an organic solvent, has existed for decades, yet has not reached competitive efficiencies. In this work, 10 organic solvents were tested for SBD efficacy via synergetic studies using bench-scale extraction experiments and molecular dynamics (MD) simulations. The SBD effectiveness was correlated to the computationally observed ability of the solvent to form one of the three morphologies in water: ordered, disordered, or partial nanoscale. We correlated that solvents that form ordered and disordered morphologies were not able to clean up the water. Solvents that were able to cause low salinity in water showed computationally observed partial nanoscale phase separation, where nanometer-scale aggregated solvent phases were able to effectively reject salt ions while capturing comparatively large amounts of water molecules. The formation of a partial nanoscale phase is likely driven by the solvent structure with bulky hydrocarbons adjacent to hydrophilic end groups. Our results make a step toward the rational design of solvents that may allow for efficient SBD and thus a low-cost source of fresh water.
Aquaporins can facilitate the passive movement of water and small polar molecules and some ions. The barley Nodulin 26-like Intrinsic Protein (HvNIP2;1) embedded in liposomes and examined through stopped-flow light scattering spectrophotometry and Xenopus oocyte swelling assays was found to permeate water, boric and germanic acids, sucrose and L-arabinose but not D-glucose or D-fructose. Other saccharides, such as neutral (D-mannose, D-galactose, D-xylose, D-mannoheptaose) and charged (N-acetyl D-glucosamine, D-glucosamine, D-glucuronic acid) aldoses, disaccharides (lactose, cellobiose, gentiobiose, trehalose), trisaccharide raffinose, and urea, glycerol, and acyclic polyols were permeated to a much lower extent. Apparent permeation of hydrated KCl and MgSO4 ion pairs was observed, while CH3COONa and NaNO3 permeated at significantly lower rates. Experiments with boric acid and sucrose revealed no apparent interaction between solutes when permeated together, and AgNO3 blocked the permeation of all solutes. Full-scale steered molecular dynamics simulations of HvNIP2;1 and spinach SoPIP2;1 revealed possible rectification for water, boric acid, and sucrose transport, and defined key residues interacting with permeants. In a biological context, the simulated sucrose rectification could mediate its apoplastic-to-intracellular transport but not the reverse, thus, constituting a novel element of plant saccharide-transporting machinery. Phylogenomic analyses of 164 Viridiplantae and 2,993 Archaean, bacterial, fungal, and Metazoan aquaporins rationalised solute poly-selectivity in NIP3 sub-clade entries and suggested that they diversified from other sub-clades to acquire a unique specificity of saccharide transporters. Solute specificity definition in NIP aquaporins could inspire developing plants for sustained food production.
RNA-based therapeutics hold a great promise in treating a variety of diseases. However, double-stranded RNAs (dsRNAs) are inherently unstable, highly charged, and stiff macromolecules that require a delivery vehicle. Cationic ligand functionalized gold nanoparticles (AuNPs) are able to compact nucleic acids and assist in RNA delivery. Here, we use large-scale all-atom molecular dynamics simulations to show that correlations between ligand length, metal core size, and ligand excess free volume control the ability of nanoparticles to bend dsRNA far below its persistence length. The analysis of ammonium binding sites showed that longer ligands that bind deep within the major groove did not cause bending. By limiting ligand length and, thus, excess free volume, we have designed nanoparticles with controlled internal binding to RNA's major groove. NPs that are able to induce RNA bending cause a periodic variation in RNA's major groove width. Density functional theory studies on smaller models support large-scale simulations. Our results are expected to have significant implications in packaging of nucleic acids for their applications in nanotechnology and gene delivery.
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