Aqueous Suspensions of Fumed Silica and Adsorption of Proteins

Thermally stimulated depolarization spectra of frozen aqueous suspensions of fumed silica show a dependence of relaxation processes on the concentration of silica (CSiO2) due to a change in the particle-particle interaction (their electrical double layers) and the concentration of bulk water (ice) with increasing CSiO2. A significant fraction of agglomerates of primary particle aggregates are not decomposed in aqueous suspensions of fumed silica. The thickness of an interfacial water layer perturbed by the silica surface or protein molecules was estimated from the dependence of 1H NMR signal intensity of unfrozen water on temperature below 273 K, separating the signals of water molecules weakly and strongly bound to the surface. Protein molecules adsorbed on fumed silica aggregates form hydrogen bonds with identical withSiOH or identical withSiO- groups by amino groups, e.g., H+NR from the zwitterion fragments. Aqueous suspensions of mechanochemically activated fumed silica do not lose protein adsorption ability during a long period in which the particles remain as microscaled agglomerates. According to AM1-SM1 calculations, complexes such as identical withSiO(H)···H+NRCOO- are stabilized in aqueous suspensions of silica and the protein desorption rate decreases with increasing molecular weight of proteins.

Influence of morphology and composition of fumed oxides on changes in their structural and adsorptive characteristics on hydrothermal treatment in steam phase at different temperatures

A series of fumed oxides such as silica, titania, alumina, silica/alumina (SA), silica/titania (ST), and alumina/silica/titania (AST), initial and hydrothermally treated (HTT) in the steam phase at T(HTT)=150, 250, and 350 degrees C was studied by adsorption, AFM, XRD, FTIR, and theoretical methods. Diminution of the size of primary particles (corresponding to increasing S(BET)) of initial silica and mixed oxides results in enhancement of their structural changes on HTT with elevating T(HTT) and increasing density of packing of primary particles in the secondary structures. Relative changes in the texture of treated fumed silicas are smaller than those of mesoporous silica gels occurring under similar HTT conditions. On HTT, aggregates of primary particles and their agglomerates become denser but their surface layers become looser because of transfer of silica fragments from one particle to another, and the smaller the initial primary particles, the greater the relative diminution of the specific surface area S(BET) for the same type of primary particle packing in aggregates. Relative changes in the pore volume V(p) (or V(BJHd)) on HTT are more complex than that of S(BET), as for many samples the V(p) value increases especially at T(HTT)=150 degrees C. Alumina and titania partially inhibit structural changes on HTT, which decrease in the series silica > SA > AST approximately ST.

Septoria blotch epidemic process on spring wheat varieties

The Septoria blotch of spring wheat leaves and ears is one of the most economically significant infections in the Siberian region. In the control systems of Septoria blotch the main ecologically safe element is resistant varieties, which are designed to slow down the pathogens reproduction rate and slow down or stop the development of the epiphytotic process. The purpose of the work was to clarify the species composition of Septoria blotch pathogens for West Siberian regions and spring wheat varieties, to study the epiphytotic process of Septoria differentially on the leaves and ears of varieties, and to evaluate the activity of seed transmission of Parastagonospora nodorum. Studies were carried out in 2016-2018 according to generally accepted methods. Septoria leaf and ear blotch of spring wheat is widespread in West Siberia and the Trans-Urals, causing a decrease in yield by up to 50 % or more with the deterioration in grain quality. The causative agents of the disease are P. nodorum, Septoria tritici, and P. avenae f. sp. triticae, and the species ratio varied across the regions and varieties, and within plant organs. In Novosibirsk Region, P. nodorum completely dominated; S. tritici was 13.8 times less common; and P. avenae f. sp. triticae was a singleton. In Tyumen Region, the dominance of P. nodorum was disrupted in some geographic locations by S. tritici and P. avenae f. sp. triticae. In Altai Krai, P. nodorum predominated at all points studied; S. tritici and P. avenae f. sp. triticae were found everywhere, but 5.6 and 8.6 times less often, respectively. The study of spring wheat varieties of different origins has not revealed any samples immune to Septoria blotch. A differentiated manifestation of resistance to Septoria leaf and ear disease has been established. Some varieties show complex resistance, combining reduced susceptibility to Septoria leaf and ear disease. Seed infection with P. nodorum in the regions of Siberia reached 7 thresholds and was largely (52.5 %) determined by the August weather conditions. The study of the collection of spring wheat varieties from three Siberian regions has revealed the following trend. Transmission of P. nodorum with the seeds of varieties was the most active (7.6 %) in Novosibirsk Region and somewhat weaker in Omsk Region (5.7 %). The most favorable phytosanitary situation was in Kurgan Region, where varieties transmitted P. nodorum to a low degree (2.1 %), below the threshold.

Epitaxial graphene on SiC(0001): functional electrical microscopy studies and effect of atmosphere

Surface potential distribution, V(CPD), and evolution of atmospheric adsorbates on few and multiple layers (FLG and MLG) of graphene grown on SiC(0001) substrate have been investigated by electrostatic and Kelvin force microscopy techniques at T = 20-120 °C. The change of the surface potential distribution, ΔV(CPD), between FLG and MLG is shown to be temperature dependent. The enhanced ΔV(CPD) value at 120 °C is associated with desorption of adsorbates at high temperatures and the corresponding change of the carrier balance. The nature of the adsorbates and their evolution with temperature are considered to be related to the process of adsorption and desorption of the atmospheric water on MLG domains. We demonstrate that both the nano- and microscale wettability of the material are strongly dependent on the number of graphene layers.

Tuning epitaxial graphene sensitivity to water by hydrogen intercalation

The effects of humidity on the electronic properties of quasi-free standing one layer graphene (QFS 1LG) are investigated via simultaneous magneto-transport in the van der Pauw geometry and local work function measurements in a controlled environment. QFS 1LG on 4H-SiC(0001) is obtained by hydrogen intercalation of the interfacial layer. In this system, the carrier concentration experiences a two-fold increase in sensitivity to changes in relative humidity as compared to the as-grown epitaxial graphene. This enhanced sensitivity to water is attributed to the lowering of the hydrophobicity of QFS 1LG, which results from spontaneous polarization of 4H-SiC(0001) strongly influencing the graphene. Moreover, the superior carrier mobility of the QFS 1LG system is retained even at the highest humidity. The work function maps constructed from Kelvin probe force microscopy also revealed higher sensitivity to water for 1LG compared to 2LG in both QFS 1LG and as-grown systems. These results point to a new field of applications for QFS 1LG, i.e., as humidity sensors, and the corresponding need for metrology in calibration of graphene-based sensors and devices.

Features of Cytokine and VEGFA Gene Expression Modified with SARS-CoV-2 Virus in an In Vitro Experiment (Using the Example of the SARS-CoV-2 Vaccine Antigen)

The influence of SARS-CoV-2 antigen on the cytokine-producing function of immune cells was studied. We observed suppression of the production of proinflammatory cytokines by 11-46% relative to the spontaneous level under the influence of SARS-CoV-2 antigen vaccine simulator, as well as when it was co-administered with cortisol (IL-6 by 1.8 times and IFNγ by 1.57 times) compared with control samples. IL-8 production was reduced by 1.72 times relative to its spontaneous level. IL-8 production was reduced by 1.72 times relative to its spontaneous level. Under conditions of SARS-CoV-2 stimulation with the vaccine antigen in vitro, an increase in the relative scaled expression of the VEGFA gene by 2.16 times relative to the spontaneous level was observed, which can be regarded as a model "cytokine storm" scenario. The obtained experimental data verify the ideas about the pathogenetic mechanisms of the COVID-19 and can contribute to the development of new approaches to the correction of its complications.

[Suppression of vascular endothelium hyperpermeability by cell-permeating peptide inhibitors of myosin light chain kinase]

Novel peptides originating from the peptide inhibitor of myosin light chain kinase, L-PIK (Arg-Lys-Lys-Tyr-Lys-Tyr-Arg-Arg-Lys), have been studied for ability to attenuate the thrombin-induced hyperpermeability of endothelial cell monolayer in culture. Peptides [NalphaMeArg1]-Lys-Lys-Tyr-Lys-Tyr-Arg-(D)Arg8-Lys and H-Arg(NO2)Lys-Lys-Tyr-Lys-Tyr-Arg-Arg-Lys-NH2 (designated PIK2 and PIK4, respectively) appeared to be the most effective inhibitors of endothelial cell monolayer hyperpermebility, and surpassed other known peptide inhibitors of myosin light chain kinase derived from original L-PIK. Our results validate PIK2 and PIK4 as the leading molecules for the development of novel drugs intended to counteract pathological hyperpermeability of vascular endothelium.