Moscow University Chemistry Bulletin最新文献

The carotenoid astaxanthin has a variety of biological activities and antioxidant properties. Due to its lipophilic nature, astaxanthin can be used to protect against lipid peroxidation, in which iron ions play an important role. The effect of Fe²⁺ ions on the oxidative degradation of astaxanthin in phospholipid liposomes was previously studied. In this paper, we study the interaction of astaxanthin with Fe³⁺ and Fe²⁺ in organic solvents of various polarities in the absence of lipids. It is shown that in the presence of Fe³⁺, astaxanthin oxidation and degradation occurs in methanol and dichloromethane. The formation of an intermediate product with an absorption maximum at 876 nm is recorded spectrophotometrically. Electron paramagnetic resonance (EPR) proves the radical nature of the intermediate product, whose signal intensity decreased over time, with the signal remaining for up to 3 days. Based on the obtained results, it can be assumed that the radical product formed in the reaction with Fe³⁺ is the radical cation of astaxanthin. At the same time, no changes are detected when astaxanthin is incubated with Fe²⁺: the absorption spectrum does not change and no radical product is formed.

A structural rheological model is presented, including kinetic equations of the processes of formation and destruction of aggregates of particles or associates of macromolecules. The shape of rheological curves is determined by the state of the matter’s structure and the change in the structure as a result of an oscillating shear flow. An integral characteristic of the structure is the number of meshes or contacting particles-macromolecules per unit volume. Rheological equations contain three (or two) coefficients (parameters) that have a clear physical meaning; their value is determined by the physicochemical and structural state of the system during the flow. The viscous and elastic properties of polymers are considered independently of each other. The rheological equations of the model are used to interpret the frequency dependences of the dynamic modules of some melts and polymer solutions. The existing relationship between the coefficients of rheological equations that describe viscosity, and elasticity is explained by their common structural nature.

A kinetic model of the functioning of the glutamate excitatory synapse with glutamate and N‑acetylaspartylglutamate as neurotransmitters in a three-component system, taking into account neuroglial astrocytic cells and the enzyme glutamate carboxypeptidase, is developed. The model is based on structural and chemical data and describes the dynamic behavior of the coupled metabolites of N-acetylaspartic and N‑acetylaspartyl glutamic acids, the most highly concentrated low-molecular agents in the human brain. Within the framework of the simulation, the biphasic nature of the process that provides amplification of the excitation signal is shown, the dynamics of the increase in the number of excited cells (the basis of the blood-oxygen-level-dependent (BOLD) signal) is presented, and the dynamics of a pulsed decrease in the concentration of N-acetylaspartate in the excitation zone is described.

The synthesis and rearrangement reactions of 2-methoxyphenyl chloroacetate in the presence of low amounts of catalysts to form o- and p-hydroxy-3-methoxyphenacyl chlorides are described in this study. A method for obtaining m-methoxyphenyl chloroacetate is developed, based on the chloroacetylation of m‑methoxyphenol in benzene solution.. The reactions of m-methoxyphenyl chloroacetate are rearranged for the first time in the presence of low amounts of FeCl₃, MoCl₅, WCl₆, ZnCl₂, SnCl₄, VCl₃, FeCl₃⋅6H₂O, Fe₂(SO₄)₃, iron acetylacetonate (IAA), and iron salicylate (ISA). The reaction leads to the formation of 2‑hydroxy-4-methoxyphenacyl chlorides and 4-hydroxy-2-methoxyphenacyl chlorides. The percentage ratio of isomers depends on the reaction conditions. The synthesis of 4-methoxyphenyl chloroacetate via reaction with diphenylthiocarbazone in the presence of dimethylformamide is studied. The structure of the substances is elucidated with UV, IR, and NMR spectroscopies.

Physicochemical properties of drug/drug candidates are still key inputs for drug discovery and development studies. The most important physicochemical properties of these substances are lipophilicity, solubility, acid/base character, permeability, and bio-accessibility. Among them, the knowledge about solubility is a crucial physicochemical property of drugs and is of high demand both in industry and academia. The aims of the current study are: to determine the solubility of mesalazine in the non-aqueous propylene glycol (PG) + 2-propanol and aqueous 1,4-dioxane binary mixtures at biorelevant temperature (310.2 K) by using co-solvency method, to perform density analysis in non-aqueous and aqueous binary mixtures for saturated systems, to characterize mesalazine equilibrated in the saturated solutions by XRD analyses. In this research, the solubility values of mesalazine were determined in the non-aqueous (propylene glycol (PG) + 2-propanol) and aqueous (1,4-dioxane + water) binary mixtures at biorelevant temperature (310.2 K) using the common shake-flask method. The experimental molar solubility (C_M) of mesalazine values in the diluted solutions was determined in the PG + 2-propanol and 1,4-dioxane + water binary mixtures using a plotted calibration curve (R² = 0.999) at 310.2 K. The maximum solubility in the molarity scale was obtained in neat PG (C_M = 1.03  ×  10^– 2 mol/L), and the minimum solubility in the neat 2-propanol (C_M = 5.14  ×  10^–4 mol/L) in non-aqueous binary mixtures. The maximum solubility value was obtained in 0.4 mass fraction (C_M = 1.68 ×  10^–2 mol/L) of 1,4-dioxane + water and the minimum solubility was obtained in neat 1,4-dioxane (C_M = 3.34 × 10^–3 mol/L) at 310.2 K. Density data were also determined and correlated with Jouyban–Acree model for saturated systems in non-aqueous and aqueous binary mixtures. The characterization tests of mesalazine equilibrated in saturated solutions were performed by X-ray diffraction (XRD) analyses from 10° to 70°. XRD analysis showed that the crystallinity of mesalazine remained unchanged and did not show any polymorphic transformation during the drug dissolution in the investigated binary mixture. Up to now, no data was reported for mesalazine solubility in these binary mixtures at biorelevant temperature.

Comparative immunofluorescence analysis of TUBB3 expression in primary and metastatic tissues from transplanted mouse tumors demonstrates a marked increase in both the level and intensity of TUBB3 expression in highly metastatic Lewis lung carcinoma, relative to the less metastatic LC-67 tumor. These in vivo findings give experimental evidence that the tumor-associated protein TUBB3 contributes to metastatic potential and underscore its relevance as a prognostic marker of tumor aggressiveness.

The prediction and optimization of properties of retinal-containing proteins under two-photon excitation conditions is an important issue for the practical application of channelrhodopsins in optogenetics. Nonlinear two-photon absorption can also lead to photoactivation of visual rhodopsins in the IR range within 950–1000 nm. The factors that influence the two-photon absorption cross section of type I and type II retinal-containing proteins during transition to the first singlet electronically excited state are analyzed in this study with high-level quantum chemistry methods. It is shown that two channels through permanent dipole moments of the initial and final states make the main contribution to the two-photon absorption cross section during the S₀ → S₁ transition in the case of rhodopsins. A fast numerical convergence of the sum-over-states formalism provides direct evidence for the applicability of the two-level model for calculating TPA cross-sections in rhodopsins. This is due to the high transition dipole moment and significant redistribution of electron density during the S₀ → S₁ transition. An unambiguous correlation between the calculated cross section values and the difference in average dipole moments of the initial and final states makes it possible to explain the strong dependence of the cross section on the protein environment of the chromophore group in various rhodopsins (340–610 GM). It also allows us to predict the influence of the protein electrostatic field on the nonlinear photophysical properties of retinal.

Electronic excitation energies and dipole moments have been computed using multiconfiguration CASSCF method further corrected to the second order perturbation theory XMCQDPT2 for a molecular-cluster modeling the active site of (6–4) photolyase containing а thymine–thymine (6–4) photoproduct. A set of models is considered in which the excitation energies change in a wide range since anionic phosphate groups of the photoproduct and cofactor flavin adenine dinucleotide (FADH^–) are included in the models. The results demonstrate that an account for solvent effects using a PCM model reproduces the screening of the negative charges of the phosphate groups by the environment of the active site. The limits of the two-state model for estimating the electronic coupling matrix elements of the electron transfer reactions are investigated. The electronic coupling matrix elements may become overestimated due to the presence of a bright excited state in the flavin excitation spectrum.

N,N,N',N'-Tetramethyl-N,N'-bis(sulfo)biphenyl-4,4'-diaminium mesylate ([TMBSPD][OMs]₂) was synthesized as a recyclable ionic liquid and characterized by various techniques. This ionic liquid was efficiently applied as a multifunctional promoter for the three-component synthesis of 2-amino-3-cyano-4H-pyrans. The 2-amino-3-cyano-4H-pyrans were prepared not only in high to excellent yields but also no toxic solvent or catalyst was used. [TMBSPD][OMs]₂ ionic liquid was also recovered and reused four times without the considerable decreasing in its activity. Also, some new derivatives of the 2-amino-3-cyano-4H-pyrans were synthesized by this method.

In the present study, the solubility values of amlodipine besylate (AMB) in the binary mixtures of polyethylene glycol 400 and ethanol were determined using the shake-flask method at 293.2 to 313.2 K under atmospheric pressure (≈85 kPa) and correlated to some cosolvency and activity coefficient models. Additionally, the density of saturated mixtures was also measured and represented by the Jouyban–Acree model at various temperatures. The accuracy of each model was marked by the mean relative deviations (MRD%) of the back-calculated solubility and density data. The generated data in this work could be useful in the different steps of discovery and development of various formulations of AMB.