Vol 43, No 2 (2024)

In our previous works, using an exactly solvable model as an example, we demonstrated the validity of the reaction operator in the basic equation of spin chemistry. However, in these works, only recombination from the singlet state was considered. Although the general relations allowed us to consider the general case. In the present paper, such a general case is analyzed. The radical pair comes into contact in a mixed singlet-triplet state, and recombination proceeds from both the singlet and triplet states. The result obtained fully corresponds to the basic equation of spin chemistry.

The effect of terahertz radiation on clusterization of bovine serum albumin (BSA) molecules and on BSA binding with nickel, cobalt and cadmium ions is investigated by means of high performance liquid chromatography and EPR spectroscopy under variation of the concentration of molecular oxygen in solution. Irradiation is detected to remove steric hindrance for oxygen adsorption. The degree of nickel and cobalt ion binding with irradiated BSA samples is substantially higher than with non-irradiated ones, while for cadmium the binding degree is the same and rather low in both cases. The functional groups in BSA molecule participating in metal ion binding are revealed by means of modeling.

Linkage isomerization NO₂-ONO (nitro-nitrito) in the complex cation [Co(NH₃)₅NO₂]²⁺ is a well-studied classical reaction. It is believed that the photoisomerization of the nitro form to nitrito in the crystalline phase achieves complete transformation at low temperature, while the reverse transformation proceeds as a first-order thermal intramolecular reaction upon heating of the crystals. To date, there is no information about the possibility of reverse photoisomerization. In this work, photoisomerization in [Co(NH₃)₅NO₂]Cl(NO₃) crystals is investigated by the analysis of crystal deformation caused by the transformation at different wavelengths. A change in the lattice parameters during the transformation leads to reliably measurable elongation and bending of acicular crystals. It is shown that the limiting elongation of the crystal under prolonged irradiation depends on the wavelength, which proves the reversibility of photoisomerization. The quantum yield of the reverse reaction is estimated to be 0.04 of the quantum yield of the direct reaction.

The problem of reversible transformation and trapping of small-radius polarons in a lithium niobate crystal is considered within the framework of the integral encounter theory which is binary in the concentration of reatants. Analytical solutions are obtained for the relaxation kinetics of polarons, their lifetimes, and the rate constants of the corresponding channels of a multistage reaction controlled by polaron mobility. The temperature and concentration dependences of the observed quantities are analyzed. It is shown that at low temperatures polarons accumulate in a bound state characterized by an anomalously low relaxation rate.

The photochemistry of the [Ir^IIICl₆]^3- complex in aqueous solutions was studied by the methods of stationary and laser flash photolysis. As the result of a light quantum absorption, parallel processes of photoaquatation and photoionization occur. The aquated electron e_a^–_q, which is formed with a quantum yield of 0.12 (excitation at 266 nm), is predominantly decayed in reactions with the initial complex and dissolved oxygen. The rate constant of e_a^–_q capture by the [Ir^IIICl₆]^3- complex was measured. The main final photolysis products are Ir(III) complexes with different compositions of ligands, as well as several percents of Ir(IV) complexes. The formation of final products occurs in the time range from milliseconds to seconds.

The interaction of glycyrrhizin with the transmembrane domain of the E-protein of the SARS-CoV-2 virus (E-protein Trans-Membrane domain, ETM) in a homogeneous aqueous solution and in a model lipid membrane was studied using the selective nuclear Overhauser effect (selective NOESY) and NMR relaxation methods. The selective NOESY showed the presence of the interaction of glycyrrhizin with ETM in an aqueous solution, which is consistent with the literature modeling data, which indicate the possibility of penetration of the glycyrrhizin molecule into the channel formed by the ETM molecules. However, this conclusion is not confirmed by NOESY experiments in model lipid membranes, DMPC/DHPC bicelles. At the same time, the NMR relaxation method revealed the effect of glycyrrhizin on the mobility of both lipids and ETM molecules in bicelles. This suggests that GA affects the activity of the coronavirus E-protein indirectly through lipids.

The behaviour of dioxadet molecules in water is studied by the molecular dynamics simulation. This substance has anti-cancer properties and is used in clinical practice. However, its properties have not yet studied at the molecular level. This paper presents the first attempt of such investigation. Parametrization of dioxadet molecule was carried out using different available services: ATB, SwissParam as well as AmberTools in a standard form and with the use of additional quantum-chemical calculations. The obtained models are compared with each other. The number of hydrogen bonds of the molecule with water was calculated, the analysis of hydrated water was carried out. It was shown that the dioxadet molecules in water tend to associate. All the models obtained show similar properties, but the quantitative characteristics differ noticeably. Further research is needed to select the best model. Molecule topology files are available for use.

The Cytotoxicity indices (IC50) of Keggin’s phosphorus-molybdenum heteropoly acids (HPCAs) and their sodium and potassium salts on dog kidney cells (MDSC) were determined. The antiviral activity of these compounds against topical strains of influenza A (H3N2 and H1N1) was revealed. The dependence of the biological properties of polyoxometalates (POMs) on the elemental composition of their molecules has been confirmed. It has been shown that when some of the molybdenum atoms are replaced by vanadium atoms, HPCA and their salts acquire higher cytotoxicities, which increase monotonically as the number of substitutions increases. For the first time, the dependence of the biological activity of HPCA and their salts on the mass of cations has been established and interpreted. In vivo (on white outbred mice) the values of semi-lethal doses (DL50) of these compounds were established. For aqueous solutions of sodium and potassium salts of GPCA in a wide range of concentrations (from 0.05 μM to 15 μM), the values of the toxicity index (It) were determined on the model of motile cells. It has been established that GPCA and their salts are classified as moderately dangerous toxic substances and have selective antiviral activity, which at low concentrations (less than 15 μM) for influenza A strains is manifested mainly by a decrease in hemagglutination activity (HA).

The NIR-luminescence of suspension of silver nanoparticles stabilized in distilled water has been investigated by photoexcitation of surface plasmon resonance (SPR). The observed short-living luminescence with the spectral maximum at 1300 nm is attributed to the singlet oxugen molecules luminescence. The singlet oxygen generation is assumed to pass in two stages as a result of three-photon process. First the one-photon SPR excitation of silver nanoparticle is occurred and leads to superoxide oxygen generation on the nanoparticle surface. Next the superoxide anion absorbs two more photons of the same laser pulse resulting in electron photodetachment with singlet oxygen formation. During a long period of UV-irradiation the studying suspension ceases to be photostable and sedimentation occurs. The sedimentation may be related to disturbance of nanoparticles steric stability resulting in more efficient superoxide anion adsorption on nanoparticles surface with silver oxide formation.