Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) primarily enters the cell by binding the virus's spike (S) glycoprotein to the angiotensin-converting enzyme 2 receptor on the cell ...surface, followed by proteolytic cleavage by host proteases. Studies have identified furin and transmembrane protease serine 2 proteases in priming and triggering cleavages of the S glycoprotein, converting it into a fusion-competent form and initiating membrane fusion, respectively. Alternatively, SARS-CoV-2 can enter the cell through the endocytic pathway, where activation is triggered by lysosomal cathepsin L. However, other proteases are also suspected to be involved in both entry routes. In this study, we conducted a genome-wide bioinformatics analysis to explore the capacity of human proteases in hydrolyzing peptide bonds of the S glycoprotein. Predictive models of sequence specificity for 169 human proteases were constructed and applied to the S glycoprotein together with the method for predicting structural susceptibility to proteolysis of protein regions. After validating our approach on extensively studied S2' and S1/S2 cleavage sites, we applied our method to each peptide bond of the S glycoprotein across all 169 proteases. Our results indicate that various members of the proprotein convertase subtilisin/kexin type, type II transmembrane family serine protease, and kallikrein families, as well as specific coagulation factors, are capable of cleaving S2' or S1/S2 sites. We have also identified a potential cleavage site of cathepsin L at the K790 position within the S2' loop. Structural analysis suggests that cleavage of this site induces conformational changes similar to the cleavage at the R815 (S2') position, leading to the exposure of the fusion peptide and subsequent fusion with the membrane. Other potential cleavage sites and the influence of mutations in common SARS-CoV-2 variants on proteolytic efficiency are discussed.IMPORTANCEThe entry of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) into the cell, activated by host proteases, is considerably more complex in coronaviruses than in most other viruses and is not fully understood. There is evidence that other proteases beyond the known furin and transmembrane protease serine 2 can activate the spike protein. Another example of uncertainty is the cleavage site for the alternative endocytic route of SARS-CoV-2 entrance, which is still unknown. Bioinformatics methods, modeling protease specificity and estimating the structural susceptibility of protein regions to proteolysis, can aid in studying this topic by predicting the involved proteases and their cleavage sites, thereby substantially reducing the amount of experimental work. Elucidating the mechanisms of spike protein activation is crucial for preventing possible future coronavirus pandemics and developing antiviral drugs.
We consider nonlocal symmetries that all or all even (all odd) equations of the AKNS hierarchy have. We construct examples of solutions simultaneously satisfying several nonlocal equations of the ...AKNS hierarchy. We present a detailed study of single-phase solutions.
•BaFe12−xTixO19 (x ≤ 1) hexaferrites polycrystalline ceramics was investigated.•Substitution model by titanium cations was defined.•Mossbauer and Raman spectrometry was established.•The saturation ...magnetization decreasing with substitution level increasing was shown.•Dielectric constant and dielectric loss tangent values and temperature dependence were measured.
Titanium substituted BaFe12−xTixO19 (x ≤ 1) barium hexaferrites have been synthesized using the solid phase method. The phase purity and the crystal structure of the obtained solid solutions have been studied by X-ray diffraction. It was found that the unit cell parameters change a non-monotonically. The a parameter has a maximum of 5.896 Å at x = 0.25 and then it decreases almost linearly down to 5.886 Å at x = 1. The c parameter almost linearly increases from 23.216 Å up to 23.282 Å with x increasing. It has been discovered that titanium cations are located in the following positions: 4fIV tetrahedral and octahedral 4fVI and 12k ones. Results of the Mossbauer and Raman spectrometry confirm the established substitution mechanism. The homogeneous ferrimagnetic ordering is detected by magnetic measurements down to ~35 K. Below this temperature the noncollinear magnetic structure is formed as a result of Fe2+ cations change in the spin state from high to low configuration. Magnetization for all the samples is saturated at room temperature in fields of ~1 T. The saturation magnetization decreases from ~70.6 emu/g for x = 0.25 to ~56.7 emu/g for x = 1. The real part of the dielectric constant has value of ~0.2 for all the samples and gradually decreases at heating from room temperature up to ~500 K, after which it begins to increase sharply. The dielectric loss tangent has a maximum in the region of ~500 K and reaches a value of ~0.25 at a frequency of 104 Hz. With increasing the substitution level, the dielectric constant and the dielectric loss of all the samples increase.
More than five hundred images of individual macromolecules of random styrene-butadiene copolymers and styrene-isoprene block copolymers dissolved in a polystyrene matrix were analyzed. The presence ...of density fluctuations inside the macromolecular coil has been established. Within the framework of the model of harmonic oscillations, the radial distribution of such density fluctuations is estimated.
The paper considers methods for continuous mass measurement of dielectric material samples during microwave heat treatment at a frequency of 2.45 GHz. It is shown that the direct measurement of the ...sample mass by electronic scales during microwave treatment is complicated, since it is not possible to use conductive materials inside the process chamber due to induction of currents, which distort the measurement results. The paper proposes a technique for continuously measuring the mass of dielectric material samples during microwave heat treatment. The technique is based on thermogravimetric analysis methods. A unique measurement system has been developed, which utilizes this technique and consists of the following individual modules: a sample hanger located inside the process chamber, and a strain gauge, spectrometer and signal processing and conversion systems located outside the chamber. The use of a modular configuration makes it possible to distance the measurement system as far as possible from the source of electromagnetic radiation, avoid signal distortion, and isolate the measuring equipment from microwave exposure. The developed technique for continuously measuring sample mass during microwave heat treatment was tested, and the resulting dependences of mass changes revealed two characteristic stages of material carbonization, which differ based on the sample mass variation rate. The total error of the technique is less than 1%, with the quantization error during analog-to-digital conversion being the main contributor. The proposed technique can be used in automated control systems associated with microwave treatment of materials.
A comparative study of anticorrosive inhibited polymer films on the tungsten surface formed from an aqueous solution of inhibited formulations (INFOR) containing organosilane and corrosion inhibitors ...was carried out by means of the prolonged exposure of a tungsten product in a modifying solution and by the method of cataphoretic deposition (CPD). Depending on the method of forming films on tungsten, the molecular organization of the near-surface layers was studied (ATR-FTIR), and the subprimary structure of the films was explored (TEM). The optimal modes of cataphoresis deposition (CPD duration and current density applied to the sample) for the formation of a protective inhibited polymer film on the tungsten surface were established by means of SEM. The energy and thermochemical characteristics (sessile drop and DSC methods), as well as operational (adhesive behavior) and protective filming ability (EIS and corrosion behavior), according to the method of formation of inhibited polymer film, were determined. Based on the combined characteristics of the films obtained by the two methods and the deposition modes, the CPD method showed better performance than the electroless dipping method.
We consider a simplest two-dimensional reduction of the remarkable three-dimensional Hirota–Ohta system. The Lax pair of the Hirota–Ohta system was extended to a Lax triad by adding extra third ...linear equation, whose compatibility conditions with the Lax pair of the Hirota–Ohta imply another remarkable systems: the Kulish–Sklyanin system (KSS) together with its first higher commuting flow, which we can call the vector complex mKdV. This means that any common particular solution of both these two-dimensional integrable systems yields a corresponding particular solution of the three-dimensional Hirota–Ohta system. Using the Zakharov–Shabat dressing method, we derive the
-soliton solutions of these systems and analyze their interactions, i.e., explicitly derive the shifts of the relative center-of-mass coordinates and the phases as functions of the discrete eigenvalues of the Lax operator. Next, we relate Hirota–Ohta-type system to these nonlinear evolution equations and obtain its
-soliton solutions.
Diffusion coefficients of ions and water have been measured in two- and three-component concentrated (“water-in-salt”) aqueous solutions of KOAc and LiOAc, which were proposed as new electrolytes for ...water-based Li-ion batteries. It was demonstrated that the diffusion coefficient for acetate anion is greater than for lithium cation one in the KOAc-containing solutions and the difference grows under increasing concentration of potassium acetate. Water diffusion is also faster comparing with lithium cation and acetate anion in all solutions studied. Temperature dependences of spin–lattice relaxation rates (1/
T
1
) of
1
H,
7
Li, and
39
K nuclei have been measured for both ions and water. The dependences do not reach their maxima for most samples, and only for acetate anion in sample IV (31.9 mol KOAc–8.0 mol LiOAc–H
2
O) it turned out to be possible the reliable calculation of the rotational correlation time
τ
c
. Comparison of the translational (via D) and rotational (via
τ
c
) mobility of the acetate anion near the eutectic point showed that the Stokes–Einstein relation is valid for this solution only in a small high-temperature part of the studied range, but not for the lower temperatures.
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