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Objective: Fluorogens are synthetic molecules that become fluorescent in specific environments, i.e. in pockets of fluorogen-activating protein (FAP). In pursuit of increased diversity of fluorescent labeling methods, our group is interested in developing new FAP-fluorogen pairs with unique features. Methods: In this study, we focused on synthesis of prospective fluorogens for NanoLuc luciferase used as FAP. A row of orto-substituted aryliden-imidazolones and their derivatives containing styrene moiety was synthesized and tested in vitro with purified NanoLuc protein. The selected dye was used as fluorogen in widefield microscopy of live HEK 293 cells transiently transfected with NanoLuc-H2B coding plasmid. Results and Discussion: The structure of the GFP and Kaede proteins chromophores is very similar to the structure of the luciferins of the NanoLuc luciferase. In this regards, we synthesized a series of such arylidene-imidazolones and tested them with NanoLuc protein. It was found that some the created compounds are able to bind to the NanoLuc protein and form fluorescent complexes. One of them had a high affinity for NanoLuc protein and was used as a successful fluorogen in pair with NanoLuc in live cell microscopy. Conclusions: We report a series of orto-substituted aryliden-imidazolones and their derivatives containing styrene moiety. These compounds can be used as ligands of NanoLuc protein. Together with NanoLuc these fluorogens can be used for genetically encoded labeling in fluorescence microscopy, as demonstrated by staining HEK293 cells. [ABSTRACT FROM AUTHOR]

Objective: Lipid droplets (adiposomes) are cellular organelles with distinguish structure and functions that play significant role in energy homeostasis and lipotoxicity and oxidative stress prevention, therefore represent a desirable target for fluorescent labeling. In this work, we proposed a number of new fluorogenic compounds—arylidene-rhodanines and their acyclic analogues – substances that label lipid droplets due to structural fragments responsible for the appearance of fluorescence in a lipophilic environment. Methods: The target arylidene-rhodanines and their acyclic analogues were obtained using modified literature methods of Knoevenagel condensation, the optical properties of the resulting compounds in a standard set of solvents were studied and then the most promising substances were tested as fluorescent dyes on Hela Kyoto cells using widefield microscopy. Discussion: We discovered that the derivatives containing a 2,5-dimethoxybenzylidene fragment or similar groups are characterized by a noticeable variation in fluorescence quantum yield depending on the environment properties. Cellular labeling of such compounds was studied. We showed that incubation of Hela Kyoto cells with substances (In) and (III) led to fluorescence appearance in the BFP channel, associated with the location of lipid droplets detected in the cells when visualized in transmitted light. Conclusions: As a result, we found that two obtained compounds—dimethoxybenzylidene-rhodanine and dimethoxybenzylidene-malononitrile – can be used as selective fluorogenic dyes for lipid droplets labeling in live Hela Kyoto cells under widefield fluorescent microscopy conditions. [ABSTRACT FROM AUTHOR]

We report a novel mutant of FAST–FAST T70V. The fluorescent properties of the complex were studied to show that the T70V mutation only slightly affects the fluorescent properties but has no effect on the photostability of the protein–fluorogen complex. Thus, evidence was obtained showing that the threonine alcohol group is not involved in the irreversible photodegradation of the complex, despite the possible contact of the amino acid with the fluorogen. [ABSTRACT FROM AUTHOR]

Surface modification of polystyrene and Nafion™ films with a cationic polyelectrolyte poly(diallyldimethylammonium chloride), or PDADMAC, through adsorption of the polyelectrolyte from its aqueous solutions was studied. It was established that the PDADMAC adsorption layers strongly adhere to the polystyrene films, thus hydrophilizing their surface. Attempts to modify the surface of Nafion™ films revealed that PDADMAC is localized in channels of the swollen polymer film without any noticeable effect on the characteristics of the film surface. [ABSTRACT FROM AUTHOR]

The unification of the early and late-time universe on the basis of the holographic principle taking into account the properties of the viscosity of the fluid in the spatial Friedman–Lemeter–Robertson–Walker metric is considered. In the description, the idea of generalized holographic dark energy cut-off proposed by Nojiri and Odintsov is used. To study the evolution of the unified Universe, a generalized equation of state of the dark fluid is used, including two asymptotic cases. As an example, a cosmological model with a constant thermodynamic parameter and a constant bulk viscosity is studied. Analytical expression for infrared radius in terms of the particle horizon and the energy conservation law are obtained from the holographic point of view. The viscous fluid describing the unification of the early and late-time Universe is represented as a generalized holographic energy. [ABSTRACT FROM AUTHOR]

The article considers the main provisions of three versions of perturbation theory: BH (D. Henderson and J.A. Barker), WCA (J.D. Weeks, D. Chandler, and H.C. Andersen), and KLRR (H.S. Kang, C.S. Lee, T. Ree, and F.H. Ree) used to calculate the thermodynamic properties of binary mixtures of dense gases in a wide range of pressures and temperatures. The interaction of molecules is described using the spherically symmetric pair potential exp-6. Verification was carried out by comparing experimental data on the compression of binary helium–hydrogen and ammonia–hydrogen mixtures, as well as on shock-wave compression of liquid N2, O2 with the results of equilibrium thermodynamic calculations and Monte Carlo simulations. It is shown that for thermodynamic simulation of the properties of binary mixtures, the most accurate version of perturbation theory is the modernized KLRR-T theory. [ABSTRACT FROM AUTHOR]

Using the equation of state, on the basis of perturbation theory, the thermophysical properties of the main combustion products N2, O2, CO2, and H2 of organic substances are calculated under normal conditions and in the region of high pressures. The method of calculating the viscosity of individual substances based on the Chapman–Enskog equation using the values of the radial distribution function is analyzed. [ABSTRACT FROM AUTHOR]

A methodological approach has been proposed for studying the effect of solvent nature on the adhesive properties of films of binary copolymers with different chain microstructures. The approach is based on a complex analysis of the thermodynamic work of adhesion in polymer–liquid model systems and the results of mechanical tests in combination with quantum-chemical calculations. The approach has been used for the first time for copolymers of styrene and n-butyl acrylate having gradient and random distributions of comonomer units over the chains, with the copolymers being synthesized by radical polymerization with reversible chain transfer. The results obtained have shown that the adhesive properties of the binary copolymer films may be regulated by varying the chemical nature of solvents from which they are formed. [ABSTRACT FROM AUTHOR]

The molecular dynamics method was used for simulation of thermal decomposition of hydrogen molecules. As a test substances, we used liquid hydrogen. Interaction between hydrogen molecules in the system was described by the ReaxFF potential force field (2008). We show the time dependences of change in the amount of decomposition products. The activation energy of the reaction of hydrogen dissociation is calculated, which is in good agreement with the results by other authors and the reference literature. [ABSTRACT FROM AUTHOR]

Analytical expressions and a numerical method for calculation of distribution functions of hard spheres gij(r) based on inverting the Laplace transform for functions rgij(r) obtained from the Percus—Yevick equation are obtained. The method for calculation of radial distribution functions is applicable for any distances between hard spheres; it is verified by comparison of numerical results and Monte Carlo simulations. The application of the developed method for calculation of the radial distribution functions of metal atoms is demonstrated. Distribution functions are required to construct a universal theoretical model of equation of state capable of describing both dense multicomponent gas and condensed substances (liquid or solid phases) with high accuracy which is substantially faster than computer experiments (Monte Carlo and molecular dynamics methods). [ABSTRACT FROM AUTHOR]

Molecular theory of wetting was used to calculate the specific free surface energy of membranes based on amorphous polymers of varied chemical structure from experimental wetting angles obtained for test fluids. A relationship was found between the dispersion component of the surface energy of a membrane, its gas permeability, and free volume of the polymer. This makes it possible to employ the wetting method to prognosticate the transport properties of polymeric membranes. In wetting of membranes with aqueous solutions of alcohols, the concentration of an alcohol corresponding to the onset of its sorption into the membrane was determined. The correlation of the value obtained with the alcohol concentration that corresponds to the onset of sorption and is determined independently by the gravimetric method enables use of wetting angles for optimizing the conditions of experiments on nanofiltration and pervaporation. [ABSTRACT FROM AUTHOR]

The effect of polyketone (PK) γ-irradiation dose on the energy characteristics of the PK surface, the specific free surface energy, and the interfacial energy at the boundary between polar (water) and nonpolar (octane) liquids has been studied for the first time. The most significant changes in the energy characteristics of the surface occur at doses up to 100 kGy, and improvement in PK adhesion to the polar and nonpolar phases is observed at doses above 75 and 200 kGy, respectively. [ABSTRACT FROM AUTHOR]

Langmuir's method was used to investigate the structures of water/air-boundary monolayers of statistical and gradient copolymers of styrene and acrylic acid. The differences found in the laws governing the formation of monolayers of copolymers of different microstructure enable us to anticipate the technique of transferring these monolayers onto a solid support from an energetically homogeneous moving boundary, combined with variation in the microstructure of the copolymers, to be very promising for the fine control of their adhesion characteristics. [ABSTRACT FROM AUTHOR]

An improved version of the equation of state model for two-component fluid mixtures whose molecules interact with the Exp-6 type potential has been proposed in previous works. The thermodynamic parameters of N, O, and CO shock-wave compression are calculated using the equation of state model for two-component fluid mixtures based on perturbation theory. Products of compression of these substances are two-component mixtures. Analogous calculations are also performed using an effective one-fluid model. A comparison of the results obtained with the available experimental data and results of Monte Carlo simulation allows us to conclude that the proposed theoretical equation of state model is superior to effective one-fluid model in accuracy and reliably describes the thermodynamic properties of two-component fluid mixtures in a wide pressure and temperature ranges. [ABSTRACT FROM AUTHOR]

The thermal decomposition of methane at constant temperatures and densities ranging from 0.05 to 0.524 g/cm3 has been simulated using methods of molecular dynamics and equilibrium thermodynamics. The molecular-dynamics simulation of the initial stage of methane decomposition has been performed using the reaction force field ReaxFF-lg at temperatures of 2500–4000 K. The simulation results showed that the methane decomposition consists of the successive formation and decay of radicals and light hydrocarbons and their replacement with polyatomic hydrocarbons of increasing complexity, similar to polycyclic aromatic hydrocarbons, whose decomposition and aggregation leads to generation of condensed-carbon nucleation centers. In turn, the results of the thermodynamic calculations indicate that the methane decomposition begins and occurs at lower temperatures as compared with the results of ultrashort nonequilibrium calculations by the molecular dynamics method. Thus, the application of molecular dynamics and thermodynamics methods for the same process presents extreme versions of possible sequences of states in the cases of ultrashort nonequilibrium and long-term, similar to equilibrium, processes of methane thermal decomposition. [ABSTRACT FROM AUTHOR]

A theoretical model of the equation of state of a two-component fluid with the exp-6 interaction potential has been developed. The model was created based on an improved version of perturbation theory. A technique for calculating the excessive Helmholtz energy of the two-component fluid is proposed. The technique is based on applying the Laplace transform for hard sphere distribution functions g( r); it considerably reduces time expenditures and increases the accuracy of calculations as compared to the technique that uses the functions g( r) directly. Based on the model proposed, the thermodynamic parameters of the two-component mixture of helium and hydrogen are calculated. To eliminate the problem of nonadditivity of hard sphere diameters and to obtain the best agreement of the calculated thermodynamic parameters with data of a computer experiment according to the Monte Carlo method, different schemes for separating the potential of interaction between helium atoms and hydrogen molecules into the reference and perturbing components were investigated. [ABSTRACT FROM AUTHOR]

The surface properties of polynorbornenes obtained via metathesis polymerization are investigated via the wetting method. The incorporation of trimethylsilyl groups into the monomer unit causes decreases in the specific free surface energies of the investigated polymers. It is found that the dispersion terms of the specific free surface energies correlate with the free-volume and gas-permeability values of the polymers. As shown through the methods of differential scanning calorimetry and FTIR spectroscopy, during heating in air, the considered polynorbornenes undergo oxidative crosslinking, which increases their specific free surface energies. The interphase energies of crosslinked polynorbornenes are determined at their interfaces with liquids modeling polar and nonpolar phases, and the values of the work of adhesion of the crosslinked polynorbornenes to the model liquids are calculated. It is shown that the work of adhesion of the polymer to the polar phase decreases after introduction of trimethylsilyl groups, while the combination of polar and nonpolar phases give rise to an increase in the work of adhesion. [ABSTRACT FROM AUTHOR]

The capacities of the wetting method for the characterization of the surface structure of polymers and surfactant adsorption layers on polymer surfaces and also the determination of the energy characteristics of polymer surfaces at different interfaces, which are used to optimize the choice of polymers in the solution of actual practical problems, are demonstrated. [ABSTRACT FROM AUTHOR]

The thermodynamic parameters of the two-component mixture of hydrogen atoms and molecules are calculated on the basis of perturbation theory with the use of the basic system of hard spheres. To eliminate the nonadditivity of hard sphere diameters and to obtain the best agreement of the calculated thermodynamic parameters with the Monte Carlo data, different schemes of subdivision of the interaction potential of hydrogen atoms and molecules into the basic and perturbing components are investigated. [ABSTRACT FROM AUTHOR]

The energy characteristics of surfaces of new polymers belonging to the class of poly(olefin ketone)s at the interfaces with air and polar (water) and nonpolar (octane) liquids were determined by the ?ontact angle method. The objects of the study were binary copolymer (propyl-ene-carbon monoxide, PCO) and ternary copolymers (propylene-carbon monoxide-ethyl-ene-carbon monoxide, PECO; but-1-ene-carbon monoxide-ethylene-carbon monoxide, BECO). It was shown that the ternary copolymers can be recommended for further medicobio-logical tests as a base for the development of hemocompatible materials. The equilibrium values of the interfacial energy of poly(olefin ketone)s at the interfaces with water and octane make it possible to predict their adhesion properties for designing composite materials. [ABSTRACT FROM AUTHOR]

Analytical expressions are derived and a computational algorithm and program for calculating distribution functions of rigid spheres g ij( r) necessary for calculations of the thermodynamic parameters of a binary fluid mixture are developed in the context of perturbation theory using the procedure based on the inversion of the Laplace transform for functions rg ij( r) obtained from the Percus–Yevick equation. [ABSTRACT FROM AUTHOR]

Experimental and calculated detonation characteristics of powerful insensitive explosives are given. Features of explosives with a high hydrogen content are discussed. The relationship between the power and sensitivity characteristics of explosives and the structure of their molecules are considered. Prospects for the development of powerful explosives are discussed. [ABSTRACT FROM AUTHOR]

Surface tension of aqueous binary mixtures of Pluronic F68 and low-molecular-weight cationic surfactants is measured. The synergistic a decrease in surface tension is revealed. It is shown that this effect is controlled by the chemical structure of cationic surfactants and determined by an increased (compared to the bulk) content of Pluronic F68 in the surface layer, which is formed due to the adsorption of the individual molecules of mixture components. [ABSTRACT FROM AUTHOR]

Wetting and adsorption modification of polystyrene surface with aqueous solutions of F68-cationic surfactant mixtures are studied. The synergism of wetting is revealed. It is established that the degree of synergism upon wetting is determined by the synergism of surfactant adsorption on a solid surface and peculiarities of the formation of mixed adsorption layers of surfactants. It is shown that low-molecular-weight cationic surfactants can be used to increase the efficiency of the modification of polymer surfaces with Pluronics. [ABSTRACT FROM AUTHOR]

Wetting of low-energy surfaces (polymers, hydrophobized glass) by the aqueous solutions of binary mixtures of nonionic (Triton X-100) and cationic (cetyltrimethylammonium bromide) surfactants at the molar fraction of cationic surfactant α = 0.2, 0.5, and 0.8 was studied in the wide concentration range. It was shown that the contact angles of mixed solutions at low-energy surfaces could be predicted on the basis of surface tension isotherms. Concentration ranges of wetting synergism were determined. [ABSTRACT FROM AUTHOR]

Wetting of glass by aqueous solutions of binary mixtures of cationic and nonionic surfactants was studied in the range of overall concentrations c0 = 10–8–10–2 M at the molar fraction of cationic surfactant α = 0.2, 0.5, and 0.8. It was established that the character of glass wetting is determined by the presence of cationic surfactant in the mixture: contact angle isotherms θ(c0) exhibit maximum, as in the case of individual cationic component solutions. Maximal θ values are virtually independent of the nature of cationic surfactant and its molar fraction in the mixture. It was shown that the synergistic effect in glass wetting is controlled by the chemical structure of surfactant cation. [ABSTRACT FROM AUTHOR]

The influence of a strong field resonant to the Raman transition on the behavior of the Stokes harmonic in saturated two-wave stimulated Raman scattering is theoretically considered based on the description of a gas of three-level atoms by medium density matrix equations. The vibrational mode of energy redistribution between laser and scattered radiation, threshold with respect to the resonant field intensity, is predicted. The action of optical fields on the absorption and amplification of the resonant field in a Raman medium is described. [ABSTRACT FROM AUTHOR]

Objective: A number of previously synthesized fluorogenic arylidene-imidazolones, which predominantly stain the endoplasmic reticulum (ER) of living cells, were studied by time-resolved fluorescence microscopy. It was suggested that the use of fluorescence microscopy of this type can enhance the selectivity of ER staining. Methods: The lifetimes of arylidene-imidazolone compounds in set of solvents with different polarity were measured with time-correlated single photon counting spectroscopy. Live HeLa Kyoto cells were stained with studied dyes and analyzed with time-resolved fluorescence microscopy. Results and discussion: It was found that most of the studied compounds show bi- or triexponential fluorescence decay patterns in solutions. In live cell culture dye (I) showed a monoexponential decay pattern, while dyes (II–IV) were better fitted by a biexponential function. Dyes (I), (III), and (IV) stained both ER and adiposomes, while dye (II) stained only ER. Conclusions: It is shown that under FLIM conditions discriminative filtering of cellular organelles stained with studied fluorogenic dyes is possible and applicable if the difference of mean amplitude-weighted lifetime is more than 0.1 ns, thus increasing the selectivity of ER staining in live cells. [ABSTRACT FROM AUTHOR]

Objective: The phenomenon of chemiluminescence - the emission of light by a substance after oxidation - has been known for a very long time. Substances capable of chemiluminescence are actively used for the detection and quantitative determination of a wide variety of analytes. In this work, we studied the possibility of using 3-amino-coumaranones for the detection of hydrogen peroxide and urease activity study. Methods: In this work, we synthesized a series of 3-amino-coumaran-2-one derivatives, which can be divided into two groups: amide derivatives and urea derivatives. The optical and chemiluminescent properties of all the obtained compounds were studied under various conditions. Results and Discussion: In this work, a series of 3-amino-coumaranones was synthesized. It has been found that amide derivatives and derivatives of asymmetrically substituted ureas have significant chemiluminescence under various conditions. The introduction of the electron-donor groups in the coumaranone moiety and increasing of the conjugated π-system of coumaranones allow to shift 30–40 nm of the chemiluminescence maxima to the long-wavelength region. For N,N-disubstituted unsymmetrical urea derivatives it is shown that the luminescence intensity can be different under various conditions. It has been shown that derivatives of N,N-disubstituted unsymmetrical ureas can be used for the determination of hydrogen peroxide, and some compounds, due to their bright luminescence in the presence of urease, can be used as indicators of its enzymatic activity. Conclusions: We showed that some 3-amino-coumaranones can be used for detecting the urease and hydrogen peroxide. [ABSTRACT FROM AUTHOR]

The deformation of a water-saturated region during filtration in a porous medium with variable capillary pressure is considered. The numerical calculations show that the capillary-pressure gradient directed along the liquid-gas interface leads to deformation of the region, which is eventually divided into two disconnected regions. It is assumed that the process under consideration describes one of the possible mechanisms of fragmentation of filtration flows. [ABSTRACT FROM AUTHOR]

RAFT polymerization was applied for the synthesis of hydrophilic poly(N,N-dimethylaminoethyl methacrylate) and random copolymers of N,N-dimethylaminoethyl methacrylate, containing 5 or 10 mol % of hydrophobic monomers methyl acrylate, methyl methacrylate, or butyl acrylate. The influence of chemical nature of hydrophobic comonomer and the copolymer composition on physico-chemical properties of polymers and their ability to strengthen friable (bulk) materials like quartz sand, clay, or limestone was systematically studied. It is shown that synthesized copolymers have relatively low glass transition temperatures, form aggregatively stable molecular solutions in water in a wide range of pH values, and have a pronounced surface activity, while their dried films demonstrate water-repellent properties. It is found that amphiphilic copolymers with a small content of hydrophobic comonomer units are much more effective as stabilizers of soils (bulk materials) in terms of mechanical strength and durability than the original hydrophilic homopolymer. [ABSTRACT FROM AUTHOR]

Irradiation of polyamide-6 (PA) with γ-rays reduces its resistance to subsequent IR laser radiation. The average rate of laser ablation of PA, preliminarily irradiated with γ-rays at a dose above ~300 kGy, is almost dose-invariant and is 30% higher than that of the initial unirradiated polymer. The pattern of the dose dependence of the laser ablation rate for the samples pre-irradiated with a dose of 3.24 MGy at a dose rate of 4.2 Gy/s is mixed in character, varying from the shape characteristic of the initial polymer at the initial stage to the shape typical of the maximum radiation dose in the stationary laser ablation mode. One of the products of PA laser ablation is a dispersed polymer, consisting of nano- to micrometer-sized particles, the size range of these particles shifting toward smaller values with an increase in the γ radiation dose, a trend that is explained by a decrease in melt viscosity. [ABSTRACT FROM AUTHOR]

The effect of processing of polyacrylonitrile membranes by IR radiation at a temperature of 100– 150°С is studied. The influence of the processing temperature on the film structure is ascertained. In a film heated at 100°С, a small amount of the double C=N bonds is found. Its further heating to 120°С is accompanied by a change in the chain conformation and an increase in the content of C=N bonds. It is shown that, upon IR processing at 120°С, polyacrylonitrile ceases to dissolve in N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and dimethyl sulfoxide. Heating at 150°С gives rise to the appearance of conjugated С=N–C=N bonds. The analysis of AFM micrographs demonstrates that the processing of the membranes by IR radiation makes their surface rougher, while the size of pores changes slightly. The permeability of the membranes in various media is measured. [ABSTRACT FROM AUTHOR]