Moscow University Chemistry Bulletin最新文献

In this paper, we analyze the behavior of low-molecular-weight non-Newtonian fluids (liquid paraffin, silicone oil, and FC70 oil) in which the shear thinning phenomenon is observed at low shear rates. Over a wide range of a high shear rate, the behavior is described, which is similar to the Newtonian behavior in the case when the shear viscosity is practically constant. In terms of the structural rheological model, an explanation is proposed for this type of the Newtonian flow.

The adsorption of cationic and anionic polyelectrolytes (PEs) from aqueous solutions on the polystyrene surface is studied by quartz crystal microbalance (QCM) and contact angle measurements. It is shown that, despite the multilayer nature of adsorption, only a monolayer of PE macromolecules is firmly retained on the polymer surface, and the polystyrene surface is hydrophilized. It is shown that with the complete monolayer filling of the surface, the degree of modification of the polystyrene surface does not depend on the nature of the studied PEs, and the modifying monolayers provide the value of the polystyrene/water interfacial energy, which indicates the potential biocompatibility of the material based on the modified polystyrene.

The expression of PD-L1 protein is quantified in 56 samples of urothelial bladder cancer (BC). PD-L1 expression is detected in all BC samples, while in non-muscle-invasive bladder cancer (NMIBC) this score is 1.5 times higher than in muscle-invasive bladder cancer (MIBC) (p = 0.001). High PD-L1 expression level (≥30%) is observed in 20% of MIBC samples and among NMIBC tumors in 68% of cases, i.e., 3.4 times more often (p = 0.0004). The last fact justifies the prospect of starting therapy with immune checkpoint inhibitors at the onset of the disease for NMIBC.

It is shown that the removal of CO₂ from a gas can be implemented in a disk film absorber using water as an absorbent. The proposed technical solution is focused on solving various decarbonization problems.

In this review, the methods used to study internal rotation in the ground (S₀) and excited (S₁) electronic states in the following series of α,β-unsaturated carbonyl compounds: R₄R₃C = CR₂–COR₁, where R₁ = H, R₁ = F, R₁ = C_I; R₂ = H, R₂ = CH₃, R₂ = F; and R₃ = R₄ = H = CH₃, are compared. Differences in the values of (0-v)-transitions of torsional vibration for s-trans- and s-cis-isomers for some studied compounds are revealed in the methods of analysis of the vibrational structure of the n-π*-transition of high-resolution UV absorption spectra and Fourier-transform IR spectra used in the study of the internal rotation in the (S₀) electronic state. The reasons for such differences are established. It is shown that in the (S₀) state, a more reliable determination of the values of (0-v)-transitions of the torsional vibration of both isomeric forms of molecules is obtained in the method of analysis of the vibrational structure of n-π*-transition of UV absorption spectra. A new assignment for transitions of the torsional vibration of the s-trans isomer of acrolein in the spectrum of the cavity ringdown spectroscopy (CRDS) method in the excited (S₁) state is proposed. It is concluded that the method of analyzing the vibrational structure of the n-π*-transition of high-resolution UV absorption spectra of vapors of the studied compounds is more reliable and accurate when studying the internal rotation in both electronic states.

Recently, increased attention has been paid to the study of the amino acid (AA) composition of gelatins, which is associated with the quality of the corresponding gels as intermediates for human and animal nutrition. In a brief review, a modification of the general method of acid extraction of collagens for the preparation of gelatins using enzymes (such as papain, actinidin, and others) is considered and the corresponding changes in the amino acid composition of gelatins are discussed. It is clear that there are changes in the content of glycine in gelatins from any collagens, but in all cases the content of glycine is about a third of the content of all amino acids (as in the original collagens). It is important that the content of imino acids (the sum of proline and hydroxyproline, which largely determines the properties of gels) in gelatins from any collagens with the use of all the studied enzymes is much higher than without them. In addition, the content of imino acids in gelatin from the bovine skin of cows with the use of any enzymes is significantly higher than in gelatins from the skin of pigs and fish. This also holds true for other key proteinogenic AAs. The reverse trend is observed only for a few AAs: serine, threonine, tyrosine, and phenylalanine, whose content is low in gelatins from any collagens.

This paper studies the preparation of a carbohydrate derivative of lipotripeptide (N-lactitol-Gly)₂-LysC₁₆ of an irregular structure with two terminal residues of D-galactose, a branching link based on aliphatic L-lysine and its carbohydrate-free analog with 1-pyrenbutanol as a fluorescent label in a hydrophobic fragment. The developed synthesis scheme includes universal approaches of peptide chemistry and the stages of the formation of an acyclic carbohydrate based on lactose in the hydrophilic domain of amphiphile. The compounds are designed to create compositions of the vector BAS delivery systems with the ability to visualize the process of interaction with the target cells.

The 2019 coronavirus disease (COVID-19) outbreak has become global. The unprecedented socioeconomic impact of the pandemic has highlighted the need to improve the existing diagnostic methods and develop new methods to control the spread of the disease. Traditional technologies such as quantitative real-time polymerase chain reaction (qRT-PCR) have been considered the gold standard for testing for COVID-19 since the SARS-CoV-2 genome sequence was published. However, they are time-consuming, labor-intensive, and do not guarantee the absence of false results. Electrochemical biosensors present alternative approaches to detect viral nucleic acids or viral antigens. The sensitivity and relatively low cost of the sensors and equipment, convenient management, rapid analysis, and suitability for miniaturization may contribute to the development of point-of-care (POC) testing for COVID-19. This review examines and critically discusses modern electrochemical biosensors for detecting SARS-CoV-2 and related technologies.

Polymers are widely applied as drug delivery systems and implant coatings. This review studies the mechanisms of the interactions of biomedical polymers with model cell membranes (liposomes) and real biological objects—bacterial cell surfaces. A comparative analysis of the composition, structure, and surface charge of different types of biological membranes is outlined. We consider the main methods and approaches for studying the effect of polymers on the structure and physical and chemical properties of membranes to uncover adsorption, defects in the bilayer, violations of the integrity of the bilayer, changes in cell morphology, etc. The correlation between the observed effects on the model and real objects is analyzed. One of the important tasks of the review is to discover the key polymer’s characteristic (structure, size, charge, etc.) for designing new high-molecular compounds with the specified biological properties.

An electrochemical immunosensor based on screen-printed graphite electrodes is developed for the determination of the antibiotic chloramphenicol in water and milk samples. It is shown that the immobilization of chloramphenicol-specific antibodies in the liquid-crystal layer of the membrane-like didodecyldimethylammonium bromide preserves the mobility and accessibility of active centers of antibodies, and the addition of gold nanoparticles improves the electron transfer from the electrode surface to the redox centers of horseradish peroxidase, which is used as a label. The limit of detection of chloramphenicol is 0.02 μg/L in water and 0.04 μg/L in milk. This method can be used to determine the residual amounts of chloramphenicol in animal products.