Unconventional magnetism of non-uniform distribution of Co in TiO2 nanoparticles

High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) analysis, electron paramagnetic resonance (EPR), X-ray absorption spectroscopy (XAS), magnetic methods, and density-functional theory (DFT) calculations were applied for the investigations of Co-doped anatase TiO2 nanoparticles (∼20 nm). It was found that high-spin Co2+ ions prefer to occupy the interstitial positions in the TiO2 lattice which are the most energetically favourable in compare to the substitutional those. A quantum mechanical model which operates mainly on two types of Co2+ – Co2+ dimers with different negative exchange interactions and the non-interacting paramagnetic Co2+ ions provides a satisfactorily description of magnetic properties for the TiO2:Co system. © 2020 Elsevier B.V.Russian Foundation for Basic Research. Ministry of Science and Higher Education of the Russian Federatio

High catalytic activity of palladium nanoparticle clusters supported on a spherical polymer network

© The Royal Society of Chemistry 2015. In this communication we report the synthesis of Pd nanoparticle clusters achieved via the assembly of Pd nanoparticles on the surface of a spherical polymer network. The network exhibits flexibility and adapts to the cluster formation. The nanoclusters display high catalytic activity toward p-nitrophenol reduction and the Suzuki-Miyaura coupling reaction

Lipoplexes of dicationic gemini surfactants with DNA: Structural features of DNA compaction and transfection efficiency

© 2015, Pleiades Publishing, Ltd. The internal structure of DNA lipoplexes with hydroxyethylated alkylammonium gemini surfactants (GS) with high transfection activity was studied by circular dichroism. It was shown that the efficiency of transfection of HEK293T cells with the pEGFP-N1 circular plasmid was different from zero only in the region of existence of chiral supramolecular DNA-GS complexes and reaches a maximum at concentrations at which the spontaneous aggregation of components is observed

The polyacrylic acid/modified chitosan capsules with tunable release of small hydrophobic probe and drug

© 2015 Elsevier B.V. Nanocapsules (≤200. nm) with a protection effect toward small hydrophobic guests (p-nitrophenyl laurate and acetylsalicylic acid, aspirin) and a tunable sustained release behavior have been fabricated through the layer-by-layer deposition of polyacrylic acid and modified chitosan. Cationic surfactant, cetyltrimethylammonium bromide, was used to increase the affinity of polyelectrolyte to the substrate. The release profile was monitored through original protocol involving a fast cleavage of the substrate released and a spectrophotometric control of the product. The shell permeability of the capsules and hence their protective effect may be tuned through the variation of the number of layers deposited, the sonication, and the adjustment of solution pH. Importantly, the dispersed loads serving as a template for the capsule fabrication may control their properties, including shell permeability

Anticorrosive effects and antimicrobial properties of alkyldimethyl(hydroxyalkyl)ammonium bromides

Quaternary ammonium compounds containing the hydroxyalkyl moiety in the head group have been synthesized. These compounds exhibit a micelle-forming ability, high anticorrosive activity, and antimicrobial action. The compounds of the formula R(CH3)2N+(CH2CH 2CH2OH)Br- with R = C14H 29-C18H37 are characterized by a protective effect higher than 90-99% at 10 mg/l with respect to hydrogen sulfide corrosion, inhibiting properties against carbon dioxide corrosion (84-98% at 10-25 mg/l), and bactericidal action on sulfate-reducing bacteria (10-50 mg/l). © 2011 Pleiades Publishing, Ltd

Stability of amplitude chimeras in oscillator networks

This work was supported by DFG in the framework of SFB 91

Helical Chirality: a Link between Local Interactions and Global Topology in DNA

DNA supercoiling plays a major role in many cellular functions. The global DNA conformation is however intimately linked to local DNA-DNA interactions influencing both the physical properties and the biological functions of the supercoiled molecule. Juxtaposition of DNA double helices in ubiquitous crossover arrangements participates in multiple functions such as recombination, gene regulation and DNA packaging. However, little is currently known about how the structure and stability of direct DNA-DNA interactions influence the topological state of DNA. Here, a crystallographic analysis shows that due to the intrinsic helical chirality of DNA, crossovers of opposite handedness exhibit markedly different geometries. While right-handed crossovers are self-fitted by sequence-specific groove-backbone interaction and bridging Mg2+ sites, left-handed crossovers are juxtaposed by groove-groove interaction. Our previous calculations have shown that the different geometries result in differential stabilisation in solution, in the presence of divalent cations. The present study reveals that the various topological states of the cell are associated with different inter-segmental interactions. While the unstable left-handed crossovers are exclusively formed in negatively supercoiled DNA, stable right-handed crossovers constitute the local signature of an unusual topological state in the cell, such as the positively supercoiled or relaxed DNA. These findings not only provide a simple mechanism for locally sensing the DNA topology but also lead to the prediction that, due to their different tertiary intra-molecular interactions, supercoiled molecules of opposite signs must display markedly different physical properties. Sticky inter-segmental interactions in positively supercoiled or relaxed DNA are expected to greatly slow down the slithering dynamics of DNA. We therefore suggest that the intrinsic helical chirality of DNA may have oriented the early evolutionary choices for DNA topology

Novel membrane mimetic systems based on amphiphilic oxyethylated calix[4]arene: Aggregative and liquid crystalline behavior

Self-organization of amphiphilic calixarenes oxyethylated at a lower rim has been investigated in water and water-organic solutions. In the range of isotropic solutions three types of structural transitions were indicated by a complex of methods. The first critical point indicated by surface tension, dynamic light scattering and atomic force microscopy methods is probably connected with the formation of " infinite" organized structures (of hundreds nanometers in size) through the open association model. This aggregative phenomenon covers the concentration range below 10-3M. In the case of aqueous calixarene solutions these large aggregates co-exist with small micelle-like particles and undergo a rearrangement with an increase in the concentration. The second structural transition occurs beyond 10-3M. It is revealed in aqueous calixarene solutions by surface tension, spine probe, viscosimetry and dynamic light scattering methods. Small aggregates (~10nm in diameter) are formed in this range through a closed model typical for conventional surfactants. The third transition indicated by viscosimetry and in single case by tensiometry can be connected with an elongation of aggregates. The polarization microscopy and X-ray diffraction studies reveal the anisotropic behavior with the concentration of solutions. Parameters of the existence of liquid crystalline mesophases are found to be influenced by the structure of substituents at both the upper and lower rims, as well as by the nature of solvent. © 2010 Elsevier B.V