Biophysics最新文献

Previously, it has been shown that a series of physiological and biochemical changes occur in Yakutian long-tailed ground squirrels during autumn (the pre-hibernation period), involving the brain, heart, skeletal muscles, and other organs. This study was conducted to analyze the composition of peripheral blood cells obtained from Yakutian ground squirrels in autumn. For the first time, an increase in the total number of leukocytes, particularly granulocytes, and a decrease in the number of lymphocytes were observed when compared with samples obtained in summer; a leukogram shift from the lymphocytic to the granulocytic fraction was revealed. Significant increase in platelet counts and thrombocrit with preservation of the percentage ratio of mature and young cell fractions was shown. To date, information on the cellular components of blood during the autumn season when hibernators prepare for winter months of hibernation remains scarce. Nonetheless, the results of our study indicate that very significant adaptive changes occur in leukocytes and platelets of ground squirrels in this period. Possible causes of these changes are discussed.

Biomolecular solvation plays a key role in nature. Biological activity and target functions of molecules depend on the features of the process. However, hydration of biomolecules is an intricate problem in both experimental research and computer simulations. The possibilities of the non-empirical 3D-SDFT/3D-RISM approach based on the 3D-distribution of the solvent atomic density to study the features of biomolecule hydration were demonstrated with examples of a number of amino acids (Gly-ZW, L-Ala-ZW, L-Val-ZW, and L-Pro-ZW), two model proteins (bovine pancreatic trypsin inhibitor (BPTI)) and protein tyrosine phosphatase 1B (PTP1B)), and PTP1B complexes with inhibitors. The results showed that using this approach it is possible to simultaneously obtain a detailed and holistic description of the hydration shell structure of biomolecules.

This paper presents the transformation mechanism of a signal from the magnetic component of a low-frequency electromagnetic field with extremely low energy into a chemical and biochemical response in aqueous solutions of nucleic acids and proteins. The developed theoretical model shows that oxidative DNA damage and conformational transitions in proteins are based on a universal mechanism for changing the amount of the most long-lived form, hydrogen peroxide, in a chemical oscillator of mutual transformations of reactive oxygen species under a low-intensity electromagnetic field. It has been experimentally found that the content of hydrogen peroxide in solutions of biopolymers resonantly depends on the frequency of the applied field. Conformational changes in proteins are accompanied by increasing accessibility and activity of the nucleophilic centers, which are potential targets for reactive oxygen species. Complete unfolding and denaturation of the protein amino-acid chain in a low-frequency electromagnetic field did not occur. It has been shown that the enhanced formation of hydrogen peroxide at 3 and 50 Hz leads to oxidative modification of nitrogenous bases in DNA.

The important photophysical process that determines the efficiency of photosensitizers is saturation of the triplet state through the intersystem crossing during light absorption. We studied the C₆₀ fullerene complexes with the amino acids (glycine, lysine, methionine, and threonine) as promising photosensitizers. The calculations for all these complexes demonstrate high values of the transition rate constants to the triplet states and a high probability of generating reactive oxygen species upon excitation in visible light. The carboxyl groups of amino acids, which are not involved in electronic excitation, can be used to conjugate photoactive complexes with a tumor-targeting drug delivery system, such as specific DNA aptamers.

Changes in the properties of polysaccharides in an electrochemically activated aqueous solution have been studied using UV-Vis spectrometry, time-of-flight secondary ion mass spectrometry and scanning electron microscopy. It is shown that the studied solutions of polysaccharides of plant origin (agar, soluble starch, and food starch) are subject to modification, the direction of which is determined by the fraction of electrochemically activated solution used (catholyte or anolyte). The identified features may be in demand when developing new ways to control the properties of biological raw materials in food production technology. It was noted that the technology of an electrochemically activated aqueous solution, which has been classified as “green,” can be reproduced on an industrial scale.

Beta-amyloid peptide (Aβ) plays an important role in the mechanism of neurodegeneration in Alzheimer’s disease. A fragment of beta-Aβ(25–35) amyloid peptide with the sequence GSNKGAIIGLM is considered to be the functional domain of the amyloid Aβ peptide responsible for its neurotoxic properties and the biologically active Aβ region. Conformational analysis by the method of molecular mechanics of each peptide segment of the C-terminal part of the peptide revealed a limited number of the most probable conformations and clearly defined the forces stabilizing the structures. The results we obtained showed that the Aβ(25–35) peptide energetically preferentially adopts the a-helical conformation at the C-terminal octapeptide segment. The molecular dynamics method was used to model the intramolecular mobility pattern of the Aβ(25–35) peptide molecule. It is shown that in the low-energy conformations of the Aβ(25–35) peptide, the flexible structures in its N-terminal region were oriented differently with respect to the structures in the C-terminal part.

The spectra of surface-enhanced Raman scattering of D-amino acid oxidase from pig kidney were recorded and analyzed using silver nanoparticles; characteristic spectral parameters of changes in the conformation of the flavinadenine dinucleotide cofactor during activation of the enzyme by D-amino acids were revealed. It was found that the time during which changes in the conformation of the flavinadenine dinucleotide were recorded depended on the substrate specificity of the enzyme: in the presence of D-alanine, this took several seconds, and in the presence of D-serine, minutes.

The therapeutic effect of high-dose inhalation of nitrogen oxide gas (at a NO concentration of at least 1000 ppm) in two HIV-infected patients was demonstrated. Inhaled NO therapy led to a rapid decrease in viral load to an undetectable level, which persisted even after the period of analytical interruption of treatment. It was assumed that the relief of HIV infection was due to nitrosonium cations NO⁺ formed in the blood from neutral NO molecules. The subsequent conversion of NO⁺ cations in their reaction with hydroxyl anions into nitrite anions was prevented by the binding of NO⁺ cations with chlorine anions and the formation of nitrosochloride in the blood. The entry of this agent from the blood into cells and tissues provided the transfer of NO⁺ cations into them. The interaction of nitrosochloride with thiols could lead to the appearance of corresponding S-nitrosothiols in cells and tissues as NO donors.

The STP polysaccharide was isolated from an aqueous extract of Solanum tuberosum L. and purified by ion exchange chromatography and gel filtration. Its molecular mass was determined by gel-penetrating chromatography and high-performance liquid chromatography, and its monosaccharide composition was analyzed by high-performance liquid chromatography and gas chromatography using a flame ionization detector and a capillary column. It was shown that STP polysaccharide consists of galactose and arabinose at 37.5% and 23.5%, respectively, as well as uronic acids (9.7%), glucose monosaccharide residues (15%), and proteins (at least 9%). The molecular mass of STP is 70 kDa. The method of IR-Fourier spectroscopy was used for the structural analysis of STP. The mitogenic activity of the extracted polysaccharide was comparable to the activity of lipopolysaccharide.

The aim of the work was to develop and test a combined method to assess the structural and functional features of a burn wound and periwound area with the use of microwave dielectrometry and Doppler flowmetry. The study included 20 Wistar rats used to model a contact thermal injury and 10 intact rats. The wound condition was assessed 24 and 72 hours after burn injury. The dielectric properties of tissues were studied using a hardware and software complex for microwave (MW) resonant near-field probing. A sharp coordinated decrease in microcirculation intensity and dielectric permittivity was observed in wound tissues in the early post-injury period (day 1 after injury). The parameters gradually and partially restored by the end of day 3 after burning. A compensatory increase in microcirculatory blood flow was detected in the periwound area, leading to a higher degree of tissue hydration and, consequently, higher values of the two parameters. A regulatory imbalance of factors that ensure the capillary blood flow in the wound area and surrounding tissues was found to develop after a thermal injury. The imbalance was compensatory in nature and contributed to the inhibition of regeneration processes in the absence of adequate correction. Thus, a combination of the two methods used in the study may potentially provide more specific information in order to describe the structural and functional features of a tissue of interest and their dynamics, as was demonstrated with the example of an experimental burn wound.