Animal models of diseases are invaluable tools of modern medicine. More than forty years have passed since the first successful experiments and the spectrum of available models, as well as the list ...of methods for creating them, have expanded dramatically. The major step forward in creating specific disease models was the development of gene editing techniques, which allowed for targeted modification of the animal's genome. In this review, we discuss the available tools for creating transgenic animal models, such as transgenesis methods, recombinases, and nucleases, including zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), and CRISPR/Cas9 systems. We then focus specifically on the models of atherosclerosis, especially mouse models that greatly contributed to improving our understanding of the disease pathogenesis and we outline their characteristics and limitations.
Amphiphilic sulfo- or amino-containing molecular brushes are synthesized by the radical copolymerization of methacrylic esters containing oligo(ethylene glycol) and/or oligo(propylene glycol) blocks ...of varying length and arrangement with 2-acrylamido-2-methylpropanesulfonic acid or
N
-(3-dimethylaminopropyl)methacrylamide in solutions (water, ethyl acetate, toluene). In copolymerization with 2-acrylamido-2-methylpropanesulfonic acid in water, the compositional homogeneity of the copolymers grows appreciably with increasing concentration of initial solutions. It is shown that the structure of macromonomers has almost no effect on their reactivity ratios in copolymerization with
N
-(3-dimethylaminopropyl)methacrylamide in organic solvents. The synthesized amino-containing molecular brushes exhibit stimuli-responsive properties in aqueous solutions, and the arrangement of hydrophilic and hydrophobic blocks in the side chains of macromolecules affects dependences of the phase transition temperature on polymer concentration and рН.
Formation of amyloid-beta (Aβ) oligomer pores in the membrane of neurons has been proposed to explain neurotoxicity in Alzheimer's disease (AD). Here, we present the three-dimensional structure of an ...Aβ oligomer formed in a membrane mimicking environment, namely an Aβ(1-42) tetramer, which comprises a six stranded β-sheet core. The two faces of the β-sheet core are hydrophobic and surrounded by the membrane-mimicking environment while the edges are hydrophilic and solvent-exposed. By increasing the concentration of Aβ(1-42) in the sample, Aβ(1-42) octamers are also formed, made by two Aβ(1-42) tetramers facing each other forming a β-sandwich structure. Notably, Aβ(1-42) tetramers and octamers inserted into lipid bilayers as well-defined pores. To establish oligomer structure-membrane activity relationships, molecular dynamics simulations were carried out. These studies revealed a mechanism of membrane disruption in which water permeation occurred through lipid-stabilized pores mediated by the hydrophilic residues located on the core β-sheets edges of the oligomers.
The synthesis and solution properties of thermoresponsive polymer molecular brushes based on five novel diblock macromonomers (methoxy oligo(ethylene glycol)
e
-
block
-oligo(propylene glycol)
p
...methacrylates, OEG
e
OPG
p
MA, where
e
= 7.0–10.3 and
p
= 2.8–10.3) have been studied. The effect of synthesis conditions on the rate of radical solution polymerization in ethyl acetate, maximum conversions of macromonomers, and molecular weight characteristics of polymers has been shown. Homopolymers of OEG
e
OPG
p
MA exhibited pronounced surface-active properties. The influence of the length of oligo(propylene glycol) block on the degree of reduction of surface (air–water) and interfacial (hexane-water) tension was shown. The aggregation behavior of polymers was investigated by dynamic light scattering and fluorimetry using pyrene as a fluorescent probe. The dependence of critical micelle concentration on the length of the oligo(propylene glycol) block was shown. The polymers have a critical solution temperature within the range of 34–71 °C depending on the length of oligo(oxyalkylene) blocks and polymer concentration. The relationship between the distribution coefficient of macromonomers in water–oil systems and the LCST of polymers based on them has been established.
Search for a cheap and efficient route of graphene fabrication is still far from its conclusion, and reduction of graphene oxide (GO) is considered one of the most promising ways to achieve this ...goal. Here we perform combined experimental and computational analysis of a simple yet efficient and environment-friendly method for reducing GO using nanosecond infrared laser irradiation, which can be performed under ambient conditions and does not require an inert atmosphere or vacuum. We demonstrate that ultrafast heating up to 3800 K leads to a fascinating regime of high quality GO reduction even in the presence of atmospheric air. This surprising effect is achieved as an interplay between two seemingly opposite processes: combustion on the highly-defective areas of GO, such as grain boundaries, and defect annealing in its bulk part. As a result, under particular pulse regimes, after a small loss of mass (primarily from its edges), GO transforms into rGO with a high local order and low Raman I(D)/I(G) ratio.
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Abstract
The procedure for in situ TEM measurements of bonding strength (adhesion) between diamond and the metal matrix using a Hysitron PI 95 TEM Picoindenter holder for mechanical tests and ...Push-to-Pull devices was proposed. For tensile tests, dog-bone shaped lamellae 280–330 nm thick and ~ 2.5 µm long were used as objects of study. The lamellae were manufactured using the focused ion beam technology from the metal–diamond interface of diamond-containing composite material with a single-phase binder made of Fe–Co–Ni alloy. The experimentally determined bonding strength was 110 MPa.
Polymorphic Modifications of Chitosan Baklagina, Y. G.; Klechkovskaya, V. V.; Kononova, S. V. ...
Crystallography reports,
05/2018, Letnik:
63, Številka:
3
Journal Article
Recenzirano
This work describes the analysis of the crystal structures of chitosan, its main polymorphic modifications, and its characteristic mutual chain packing and hydrogen bond systems in the crystalline ...regions of conformers. The analysis takes into consideration the crystal structures of chitosan complexes (salts) with organic and inorganic acids and their structural transformations. Notably, the transformation of the hydrated form of chitosan into anhydrous is found to be irreversible and occurs either at high temperatures or through a less stable form of hydrated salts. The interaction with polyanions during the formation of multilayer films can be considered as a way to form the anhydrous crystalline form of chitosan.
Low-density structured targets are widely used to study some isolated problems of ICF. Here we compare selected laser experiments with our targets, mostly non-thermonuclear, non-standard, ...individually designed for plasma features quantitative investigations. The mutual cross-check and verification is done in past few years, because "noizy" nature is more pronounced at less density. Our targets were applied on European drivers of LULI 2000, PALS, LIL, PHELIX, also on GEKKO-XII, in Russian-Indian laser-foam interaction series.
This study is aimed at the development of novel chromium-doped Fe-Co-Ni binders for diamond cutting tools with enhanced mechanical properties, wear resistance and adhesion to diamond single crystals. ...Fe-Co-Ni-Cr powder mixtures were prepared by mechanical alloying to obtain uniform elemental distribution. The dependence of the mechanical properties of hot-pressed Fe-Co-Ni-Cr binders on Cr concentration has been studied. The Fe-Co-Ni-7%Cr binder fabricated by means of mechanical alloying and hot pressing is characterized by the maximal strength (3220 MPa) and hardness (114 HRB), which are due to the reduced stacking faults energy, caused by dissolution of chromium in α-Fe solid solution, and formation of Cr2O3 nanoparticles, which impede the dislocation gliding. The wear resistance of the Fe-Co-Ni-7%Cr binder with uniformly dissolved chromium is tenfold higher than that of the binder having the same composition but containing chromium as an individual phase. The presence of Cr in the binder leads to the improvement of its adhesion to diamond single crystals. Studies of the surface of diamond single crystals at fractures of diamond-containing segments showed that adhesion was improved due to the formation of chromium carbide (Cr3C2) sublayers.
•Fe-Co-Ni-Cr powder mixtures with uniform elemental distribution were prepared.•Cr addition into Fe-Co-Ni binders leads to bending strength improvement (3220 MPa).•The uniform dissolution of Cr in Fe-Co-Ni binder increases its wear resistance tenfold.•Binder to diamond adhesion is significantly enhanced in the presence of chromium.
In this study, wide-angle X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy were employed to address the crystalline structure and morphology of ...poly(p-xylylene)–PbS nanocomposite thin films prepared by vapor deposition polymerization as well as their evolution upon thermal annealing. It was found that as-synthesized samples with different PbS contents demonstrate similar diffraction patterns that cannot be fully ascribed to a decrease in crystallite size, indicating distorted crystal structure of PbS nanoparticles compared to the bulk PbS. X-ray absorption spectroscopy reveals wide distribution of Pb–S bond lengths with a minimum value of 2.67 Å, which can be attributed to the presence of molecular (PbS) n clusters in the studied films. It was shown that thermal annealing can be used to control the size of PbS nanoparticles and, as a consequence, optical properties of the composite films. The UV–vis absorption spectra demonstrate pronounced red shift of the absorption edge correlated with the growth of PbS nanoparticles upon annealing. Comprehensive analysis of several theoretical models describing the effect of nanoparticles size on optical band gap of the composite material has been performed and compared with the experimental data.
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