We report on the biosynthesis of 65 kDa A−B−A triblock copolymers consisting of pH-responsive (acidic) silklike blocks and nonresponsive collagenlike blocks, and we show that at pH values where the ...silklike blocks become uncharged, these polymers form transparent high-modulus gels, that is, 7−15 kPa at 8 g·L−1, that consist of supramolecular nanotapes with a height of 2.8 nm, a width of ∼14 nm, and an average length of >10 μm. At the concentrations employed, both of these protein triblocks essentially form the same structure, irrespective of block order. The amount of product isolated from the extracellular medium is in the gram per liter range. This high yield makes various applications of this promising class of biocompatible materials possible.
While vanadium dioxide (VO sub(2)) is one of the most extensively studied highly correlated materials, there are intriguing similarities and differences worth exploring in another highly correlated ...oxide, niobium dioxide (NbO sub(2)). Both materials exhibit a thermally-induced first-order insulator-metal transition at a material-dependent critical temperature, which is considerably higher in NbO sub(2) than in VO sub(2)- approximately 1080 K and 340 K in bulk, respectively. This transition, evidenced by up to 6 orders of magnitude change in DC and optical conductivities, can also be induced in VO sub(2) via photo-doping on a sub-picosecond timescale. Here, we present the first ultrafast pump-probe studies on the optically-induced transition of NbO sub(2) thin films and the comparison with similar VO sub(2) films. It is observed that NbO sub(2) films transition faster and exhibit significantly faster recovery time than VO sub(2) films of similar thickness and microstructure, showcasing that NbO sub(2) is a promising material for next generation high-speed optoelectronic devices.
Trigger the block: Stable biocompatible protein polymersomes can be generated by a triggered templated self‐assembly route (see picture). Pluronic L121 vesicles (red core with blue corona) take up a ...biosynthetic triblock copolymer CSXSXC into their unilamellar shell. In response to changes in pH (trigger), the S block becomes hydrophobic and adapts to the template vesicle, thus directing the formation of protein polymersomes.
We have observed threshold switching (TS) with minimal hysteresis and a small threshold electric field (60-90 kV/cm) in Nb/NbO 2 /TiN structures. The TS was unipolar with certain repeatability. A ...less sharp but still sizable change in the device resistance can be observed up to 150°C. The TS without Nb capping layer exhibited hysteretic characteristics. It was proposed that the surface Nb 2 O 5 layer on NbO 2 could significantly modify the TS in this vertical device. This understanding of the surface effect will allow further control of the non-linear IV characteristics for NbO 2 -based switches or selector devices.
We report on self-healing, pH-responsive hydrogels that are entirely protein-based. The protein is a denovo designed recombinant triblock polypeptide of 66 kg/mol consisting of a silk-like middle ...block (GAGAGAGH)48, flanked by two long collagen-inspired hydrophilic random coil side blocks. The pH-dependent charge on the histidines in the silk block controls folding and stacking of the silk block. At low pH the protein exists as monomers, but above pH 6 it readily self-assembles into long fibers. At higher concentrations the fibers form self-healing physical gels. Optimal gel strength and self-healing are found at a pH of around 7. The modulus of a 2 wt % gel at pH 7 is G′ = 1700 Pa. Being protein-based, and amenable to further sequence engineering, we expect that these proteins are promising scaffold materials to be developed for a broad range of biomedical applications.
There has been extensive debate about both the necessity of orthogonal confirmation of next-generation sequencing (NGS) results in Clinical Laboratory Improvement Amendments–approved laboratories and ...return of research NGS results to participants enrolled in research studies. In eMERGE-PGx, subjects underwent research NGS using PGRNseq and orthogonal targeted genotyping in clinical laboratories, which prompted a comparison of genotyping results between platforms. Concordance (percentage agreement) was reported for 4077 samples tested across nine combinations of research and clinical laboratories. Retesting was possible on a subset of 1792 samples, and local laboratory directors determined sources of genotype discrepancy. Research NGS and orthogonal clinical genotyping had an overall per sample concordance rate of 0.972 and per variant concordance rate of 0.997. Genotype discrepancies attributed to research NGS were because of sample switching (preanalytical errors), whereas the majority of genotype discrepancies (92.3%) attributed to clinical genotyping were because of allele dropout as a result of rare variants interfering with primer hybridization (analytical errors). These results highlight the analytical quality of clinically significant pharmacogenetic variants derived from NGS and reveal important areas for research and clinical laboratories to address with quality management programs.
Upon a heating‐induced metal–instulator transition (MIT) in VO2, microscopic metallic VO2 puddles nucleate and coarsen within the insulating matrix. This coexistence of the two phases across the ...transition spans distinct length scales as their relative domain sizes change. Far‐field optical probing is applied to follow the dynamic evolution of the highly correlated metallic domains as the MIT progresses.
Emerging DNA-based nanotechnologies would benefit from the ability to modulate the properties (e.g., solubility, melting temperature, chemical stability) of diverse DNA templates (single molecules or ...origami nanostructures) through controlled, self-assembling coatings. We here introduce a DNA coating agent, called C8–BSso7d, which binds to and coats with high specificity and affinity, individual DNA molecules as well as folded origami nanostructures. C8–BSso7d coats and protects without condensing, collapsing or destroying the spatial structure of the underlying DNA template. C8–BSso7d combines the specific nonelectrostatic DNA binding affinity of an archeal-derived DNA binding domain (Sso7d, 7 kDa) with a long hydrophilic random coil polypeptide (C8, 73 kDa), which provides colloidal stability (solubility) through formation of polymer brushes around the DNA templates. C8–BSso7d is produced recombinantly in yeast and has a precise (but engineerable) amino acid sequence of precise length. Using electrophoresis, AFM, and fluorescence microscopy we demonstrate protein coat formation with stiffening of one-dimensional templates (linear dsDNA, supercoiled dsDNA and circular ssDNA), as well as coat formation without any structural distortion or disruption of two-dimensional DNA origami template. Combining the programmability of DNA with the nonperturbing precise coating capability of the engineered protein C8–BSso7d holds promise for future applications such as the creation of DNA–protein hybrid networks, or the efficient transfection of individual DNA nanostructures into cells.
Ultrafast optical pump–optical probe and optical pump–terahertz probe spectroscopy were performed on vanadium dioxide (VO2) and vanadium sesquioxide (V2O3) thin films over a wide temperature range. A ...comparison of the experimental data from these two different techniques and two different vanadium oxides, in particular a comparison of the spectral weight oscillations generated by the photoinduced longitudinal acoustic modulation, reveals the strong electron-phonon coupling that exists in both materials. The low-energy Drude response of V2O3 appears more amenable than VO2 to ultrafast strain control. Additionally, our results provide a measurement of the temperature dependence of the sound velocity in both systems, revealing a four- to fivefold increase in VO2 and a three- to fivefold increase in V2O3 across the insulator-to-metal phase transition. Our data also confirm observations of strong damping and phonon anharmonicity in the metallic phase of VO2, and suggest that a similar phenomenon might be at play in the metallic phase of V2O3. More generally, our simple table-top approach provides relevant and detailed information about dynamical lattice properties of vanadium oxides, paving the way to similar studies in other complex materials.
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