Vol 69, No 5 (2024)

Optical tweezers and atomic force microscopy were used for comparative evaluation of the interaction force between the lipopolysaccharide of Yersinia pseudotuberculosis and monoclonal antibodies. This paper discusses the peculiarities of two methods which allow determining significant differences in the values of the measured force required to rupture the interaction of probe sensitized by lipopolysaccharide (polystyrene microsphere for optical tweezers and silicon nitride cantilever for atomic force microscopy) with substrate (glass and mica, respectively) covered with monoclonal antibodies. In atomic force microscopy, the cantilever slides along the substrate for some time after the piezo stage is brought to a stop, causing changes in the spatial structure of sensitins and, therefore, redistribution of multiple bonds between the lipopolysaccharide agglomerate and antibodies. No significant displacement of the microsphere along the substrate occurs when an optical tweezers setup is used, and, unlike atomic force microscopy, the breaking of a complex bond between lipopolysaccharide and complementary antibodies is recorded in the form of a single and short-term (1–2 ms) leap of the photodetector signal employing optical tweezers. The recorded values of the force required to rupture the interaction measured by both methods are relative and vary depending on the chosen experimental conditions. It is shown that the non-specific component of the force needed to break the interaction measured by atomic force microscopy is significantly higher than that determined with optical tweezers.

The experimentally obtained structures of 48 complexes of the ACE2 receptor with the S protein’s RBD of the coronaviruses SARS-CoV and SARS-CoV-2 (including mutant forms of the latter) were assessed and the dissociation constant was calculated for them. Prediction of binding affinity was carried out using ProBAN, a neural network algorithm, previously developed by the authors, and a number of other algorithms for estimating the Gibbs free energy such as Prodigy, FoldX, DFIRE and RosettaDock. A comparison of the evaluation results shows that ProBAN has the best prediction quality (Pearson correlation − 0.56, MAE − 0.7 kcal/mol) of all the analyzed algorithms. The results obtained suggest better quality of affinity prediction for other protein-protein complexes. Information about the complexes under study and prediction results are available in the repository at the link: https://github.com/EABogdanova/ProBAN_RBD-ACE2.

Using fluorescent confocal microscopy it has been shown that proteins belonging to the septin family such as Septin 2, 3, 5, 7, and 9 are present in the somatic muscle of the earthworm Lumbricus terrestris. Septins 2 and 9 are associated with the lack of their specific concentrations in a cholinergic synapse, while septins 3, 5, and especially 7 levels correlate with quantitatively expressed binding in their localization to the motor end plate. It is assumed that Septins 3, 5 and, mostly, 7 can be involved in the mechanisms of modulation of quantal release of neurotransmitters.

Effects of acoustic shock waves on membrane permeability of Gram-negative bacteria P. aeruginosa for an anionic photosensitizer, such as erythrosine, were studied. Shock waves were generated by rapid local medium heating due to nonradiative relaxation of high electronically excited states of photosensitizer molecules introduced with a high-power laser pulse. It has been shown that upon exposure to shock waves bacteria display an increase in membrane permeability; erythrosine enters the cells, followed by an increase in the photodynamic efficacy on microorganisms.

The aim of our experimental research was to explore the formation of behavioral skills such as active avoidance learning in different species of rats in the three-arm maze. To determine which species is the most trainable, our study used 100 white outbred, 30 Long Evans and 30 Dumbo rats. The conditioned stimulus was a combination of playing the sound and turning off the light in a randomly selected target arm of the maze. 5 sec after the buzzer started to sound the light was turned off, then an unconditioned stimulus, the electric power, was applied to non-target arm, and the light was turned on. The task of the rat was to change the arm and enter the target (safety) arm of the maze after the sound stimulus. When the task was done, the floor of non-target arm was not charged furhter and the light was turned off. The interval between conditioned/unconditioned stimulus combinations was 30 s, it took 1 month to train each rat species and 20 sessions with different combinations of stimuli were used every day. The rat was considered trained when the probability of achieving the goal within a time limit not exceeding 6 s is 70% or higher of cases. It has been found that Dumbo rats are the best animals to train quickly in large groups to respond to an irritating stimulus.

It has been proposed that only the introduction of endogenous nitric oxide (NO) into dinitrosyl iron complexes (DNIC) or S-nitrosothiols (RS-NO) can ensure stabilization of NO that is critical for operating in an auto/paracrine manner as a regulator of biological processes in living organisms. Without this introduction, the majority of endogenous NO disappears due to aggressive intra/intercellular environment thereby eliminating it from metabolic processes. Administration of exogenous NO in human and animal organisms (the only possible route of administration is via inhalation when it is in the gaseous state) does not lead to formation of DNIC or RS-NO in blood or other tissues. Hence, the majority of exogenous NO during its inhalation is converted into nitrosonium cations (NO+), the emergence of which is evidenced by their conversion into RS-NO when various thiol-containing compounds are administered to animal blood concomitantly. In turn, RS-NO formation in those animals was manifested by hypotensive effect on them. NO molecule transformation into nitrosonium cations may also occur during DNIC formation induced by a disproportionation reaction of endogenous NO molecules binding with Fe2+ ions in pairs. Subsequent binding of Fe(NO)2 groups to thiol-containing ligands that occur during this reaction promotes formation of rather stable DNICs that act as donors of both neutral molecules of NO and nitrosonium cations (NO+) in living organisms. The transfer of NO and NO+ to targets for nitrosation reactions occurs by the interaction of low molecular DNICs with heme groups of heme-containing proteins (for example, guanylate cyclase) or thiol groups in low molecular or protein thiol-containing compounds. This paper presents different results of NO and NO+ transfer in living organisms disussing both positive, regulatory and negative, toxic effects of it.

Building forecasting the flowering time helps researchers to create varieties with maximum efficiency and value under a changing climate. This paper proposes an algorithm for parameterization of the wild chickpea flowering time model by using machine learning through knowledge transfer to combine multiple input-target sets. The resulting model showed high accuracy based on genetic and climatic data on only the first 20 days after sowing – the average absolute error is slightly greater than 5 days, the Pearson correlation coefficient is 0.93. It was found that maximum and minimum temperatures have the strongest effect on the timing of flowering. At the same time, all weather factors by the 7–10 day from the date of sowing affect a solution of the model.