Vol 43, No 11 (2024)

Bilirubin, a bile pigment having photochemical activity, plays an important role in the body. Photonics (photophysics and photochemistry) of bilirubin has attracted scientific and practical interest of researchers up to the present day. This is because its molecule is capable of ultrafast photoisomerization processes, and also contains two interacting dipyrromethenone chromophores. Furthermore, the photochemical reactions of bilirubin are used in the widespread phototherapy of neonatal jaundice (neonatal hyperbilirubinemia), carried out to reduce the level of bilirubin in the body. This review briefly considers photonics of bilirubin, as well as its main photochemical reactions in phototherapy of neonatal hyperbilirubinemia.

Soy lecithin (RH) oxidation, initiated with different AIBN concentration, has been studied in a wide range of lecithin concentrations (0.027−0.4 mol/l). It was found that the oxidizability parameter a = k_p /(2k_t)^0.5, where k_p and k_t are the rate constants of chain propagation and termination reduced significantly at higher lecithin concentration, while a linear dependence of oxidation rate on (AIBN)^0.5 remained. The antiradical activity ( fk_inh) of different antioxidants (AO) was evaluated at [RH] = 0.4 mol/l, which showed that the antiradical activity of phenols (PhOH) in lecithin is significantly lower than in hydrocarbons. The antiradical activity and inhibitory effects of lecithin oxidation decrease in the following raw: α-tocopherol > 3,6-di-tert-butyl-1,2-benzoquinone > > quercetin > 2,4,6-tri-tret-butylphenol.

A model is proposed to study the effect of regiodefects on the behavior of ferroelectric polymers in an electric field at low temperatures. Within the framework of the model, it is shown that there is a smooth reorientation of the dipole moments of monomers near the refiodefects, which is in agreement with the data obtained in molecular dynamics (MD) calculations. An analytical expression is obtained for the dependence of the average polarization on temperature, electric field, and concentration of regiodefects. Comparison with MD calculations allows us to estimate the bond stiffness of neighboring monomers and the induced electric field. The quantum version of the proposed model is investigated. It is shown that the ground state is singlet, and excitations can be either gapful or gapless, depending on the parity of the number of monomers between defects. There is a plateau on the zero-temperature magnetization curve.

The article is devoted to the study of thermal denaturation of the plasminogen molecule during induced oxidation by hypochlorite in a concentration range (30, 62.5, 125 and 250 µM). By differential scanning calorimetry, it was determined that in the presence of an oxidizing agent, the enthalpy of denaturation of the plasminogen molecule decreases. This is most noticeable for the peak showing the melting of the K4-K5 domains. These results are consistent with previously obtained data on the oxidative modification of amino acid residues of plasminogen treated with different concentrations of hypochlorite using the HPLC-MS/MS method. Taken together, these data and the results of previous studies indicate that the structure of Glu-plasminogen is adapted to moderate HOCl-induced oxidation.

The chemically inert luminophore, chemiluminescence enhancer 1,10-phenanthroline-tris(thenoyl-trifluoroacetonate) of trivalent europium, increases the intensity of the light emission by an order of magnitude during the initiated oxidation of lipid samples of vegetable origin (sunflower oil). The introduction of the light enhance r into the chemiluminescence system leads to altering the kinetic profile, removing characteristic peaks on the kinetic curves at the end of the induction period of the oxidation process, but without changing the induction period itself. With the mathematical computer modeling based on a kinetic scheme of 23 elementary reactions, it was shown that the observed kinetic behavior can be rationalized by a disproportionate increase in quantum yields of chemiluminescence derived from different electronically excited products (light emitters) formed during the oxidation process.

A high sensitive method for the quantitative rapid determination of cardiac Troponin I in human serum has been developed. The method is based on an enzyme-linked immunosorbent assay on magnetic particles in the volume of a blood serum sample, which can significantly reduce the diffusion limits typical for common ELISA. Alkaline phosphatase which is a high-performance enzyme was used as an enzyme label. The enzyme demonstrated a catalytic efficiency (k_cat/K_m) = 26500 1/(s∙mM) in combination with the substrate 1-naphtyl phosphate monosodium salt. The planar electrochemical sensors manufactured by industrial screen-printing technology were used for signal detection. The detection was carried out in differential pulse voltammetry mode. The calculated limit of detection by the enzymatic reaction product was 0.075 μM which significantly exceeded the sensitivity of colorimetric methods. The combination of the proposed methods and approaches makes it possible to obtain a quantitative analysis for cardiac TnI in human serum within 20 minutes with an estimated detection limit of 7 pg/mL and an upper reference limit of normal analyte concentration (99-th percentile) of 22 pg/mL.

In this work, the mechanisms of formation of the bisretinoid oxidation products in lipofuscin granules isolated from the retinal pigment epithelium cells of the human eye have been studied. The physico-chemical characteristics of the bisretinoid photooxidation products are described. The methods of IR spectroscopy, Raman spectroscopy, fluorescence spectroscopy, scanning confocal microscopy, time-of-flight mass spectrometry of secondary ions (TOF.SIMS) and HPLC were used for the study. The properties of the products of photooxidation and degradation of the fluorophore of lipofuscin granules, including synthetic N-retinylidene-N-retinylethanolamine (A2E), are described in detail. It has been shown that the products of oxidative degradation of lipofuscin granules are similar to the products of photooxidation of the main bisretinoid of lipofuscin granules – A2E. These data are important both for understanding the mechanisms of formation of cytotoxic products in lipofuscin granules and for establishing their chemical nature.

The phase behavior of mixtures of linear flexible polymers and V-shaped liquid crystals is inspected using a combination of Flory – Huggins theory of polymer solutions and Landau – de Gennes theory of nematic ordering. The influence of the architecture of V-shaped molecules on the system’s phase diagrams is examined.

Hybrid nanosystems based on iron oxide nanoparticles (IONPs) and human serum albumin (HSA) have been synthesized. Size and composition of HSA@IONPs nanosystems were characterized using UV/visible spectrophotometry (particularly, using the Bradford protein assay), dynamic light scattering and electron magnetic resonance. Methylene blue, as a model photosensitizer, was non-covalently bound to the nanosystems (5.8 μg per 1 mg of IONPs). The nanosystems were subjected to phototoxicity studies to confirm their suitability for photodynamic therapy, and the survival of cultured human breast adenocarcinoma MCF-7 tumor cells was analyzed. An increase in photoinduced cytotoxicity was observed when the photosensitizer was accumulated by cells upon delivery by the nanosystems, compared with a free photosensitizer at equivalent concentrations. HSA@IONPs are discussed as a promising platform for targeted delivery of a photosensitizer to tumor cells.