The problem of stretching a flexible polymer with given conditions at the ends, under the action of a fixed force, is considered. A mathematical model is constructed for different energy functions describing the elasticity of the polymer and different immobilization methods. It is shown that the dependence of stretching on the polymer length is linear. Numerical results are given. The results obtained allow to improve the analysis of experimental data on polymer stretching. The theory offers several verifiable predictions, and experimental methods are proposed to improve the accuracy of measurements.
A study was conducted to investigate the antiulcer activity of the polysaccharide from Solanum tuberosum L. in chronic and acute ulcer models proposed by Selye and Okabe. The antiulcer effect was assessed by determining and comparing the ulcer index in the treated animals and a control. The groups of treated animals that received a daily administration of polysaccharide for 7 and 3 days showed a significant decrease in the ulcer index when compared with that of the control group of animals given physiological saline. In the presence of polysaccharide, the incidence of pathological conditions (hyperemia, edema, and internal bleeding) decreased substantially regardless of the dose. This indicates that the polysaccharide may effectively prevent changes associated with the development of ulcerative colitis in the “August” line rats in the ulcer model adduced by Selye. According to Okabe, the polysaccharide dose (0.5 mg/animal) even in a single administration led to significant and in some cases almost complete healing of ulcers.
Сryoprotective properties of cholesterol/randomly methylated beta-cyclodextrin (RAMEB) inclusion complexes with respect to human spermatozoa have been investigated. The influence of different concentrations of RAMEB and cholesterol/RAMEB inclusion complexes on sperm membranes has been explored. It was shown that obvious cytotoxicity of RAMEB against spermatozoa is due to the interaction between cyclodextrins and lipid components of the membrane, in particular cholesterol extraction. Cholesterol/RAMEB inclusion complexes are significantly less cytotoxic. The dependence of cholesterol concentration in sperm membranes on the concentration of cholesterol/RAMEB inclusion complexes in the sample was established. It was demonstrated that incubation of spermatozoa with 2 mg/ml of cholesterol inclusion complexes before cryopreservation caused a statistically significant increase in survival rate (by 13.8%) and in the proportion of progressively motile spermatozoa (by 14.8%) post-thaw. X-ray diffraction revealed that the concentrations of RAMEB or cholesterol/RAMEB inclusion complexes (2, 4 and 8 mg/mL) do not affect the average size of ice crystals formed in the sample during cryopreservation in the samples. The mechanism of the cryoprotective effect of cholesterol/RAMEB inclusion complexes is proposed.
This study analyzed genetic data using DNA isolated from museum specimens of polar bears in the collection of the Zoological Institute of the Russian Academy of Sciences. The unique data obtained in this study made it possible to characterize the population structure of polar bears in the past and to lay the foundation for further research. Methods of DNA isolation used in archaeogenetics and paleogenetics were applied to historical materials. These methods provided a sufficient quantity and quality of DNA suitable for high-throughput sequencing. The analysis of genetic variants made it possible to reveal the population structure of spatial and temporal polar bear populations in the Russian Arctic regions and its changes associated with the economic activities that unfolded in the first third of the 20th century.
Products with a complex spatial organization were formed during ab initio synthesis using the large fragment of the Bst DNA polymerase. Using the analysis of AFM images of products obtained with the addition of a minimal amount of the nicking endonuclease Nt. BspD6I during this synthesis it was possible to describe the structures that formed as a result of this synthesis and suggest that their formation occurs by the mechanism of recombination-dependent replication.
