Properties of Nanoscale Carbon Coatings Obtained by the Pulsed Vacuum-Arc Method on Silicon

The complex of properties including the structure, adhesive strength, internal stresses, tribological properties, microhardness and crack-resistance of nanoscale carbon coatings obtained by the pulsed vacuum-arc method on single-crystal silicon substrates was investigated. Two types of samples of the carbon coating: type (i) formed at the normal location of the substrate relative to the geometric axis of the plasma flow (θ = 0°); type (ii) obtained at an angle θ = 70° were studied. The analysis of the experimental results showed, that the angle of plasma flow incidence relative to the substrate drastically affects the properties of carbon coatings. The structure, adhesion, internal stresses, wear resistance, crack resistance are interrelated and determined by the radiation-diffusion sealing during the process of carbon coating deposition from the carbon plasma flow. Nanoscale carbon coatings can significantly improve the strength and tribological properties of different tools, parts and products. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3530

Analysis of the intestinal microbiome in colorectal cancer

Aim. To conduct a comparative analysis of the microbiome of biopsies of a tumor and normal intestinal epithelium of patients diagnosed with colorectal cancer and to identify of functional activities of the obtained bacterial isolates that affect the development of the tumor. Methods. The study included 50 patients with malignant neoplasms of the colon: 36 men and 24 women. The mean age of the patients was 64.1±10.2 years. To analyze the microbiota of the biopsies, DNA samples were obtained from the tissue of the unaffected colon mucosa and tumor of the patients. Bacterial 16S rRNA genes fragments were amplified using bar-coded primer bakt_341f. Metagenomic next-generation sequencing was performed using the MiSeq platform (Illumina, USA). The obtained data were processed by bioinformatic methods using the QIIME package. Recognition of microorganisms depending on the morphotype and gram staining of the microflora was carried out using combination differential media and biochemical tests. Statistical analysis was carried out using Microsoft Excel, Service Pack 2 for Office XP, Statistica 6.0 (StatSoft). A comparative analysis was performed with the Student's t-test and the Mann-Whitney test in case of unmet conditions of validity. Alpha diversity of bacterial communities was quantified by the Shannon diversity index and the UniFrac distance for beta diversity analysis. Results. In patients with colorectal cancer, 5 bacterial phyla were isolated, the predominant of which were Firmicutes and Bacteroidetes, while the content of Actinobacteria was low. In addition, a higher number of representatives of Fusobacteria was observed in the tumor tissue compared to the tissue of a healthy mucosa, at a distance of 5 centimeters proximal to the tumor. The results of this study indicate that the microbiome of a tumor and a healthy mucosa fundamentally differ from each other not only in morphotype and gram staining but also in antagonistic, hemolytic and ribonucleolytic activities. Conclusion. Colonization of the tumor by dominant aggressive Gram-negative bacteria leads to significant changes in the tumor microbiome composition compared with normal mucosa, whose representatives are displaced from the damaged epithelium by more aggressive strains

Phylotyping and genotyping of Escherichia coli isolates obtained from patients with colorectal cancer

© 2020, Advanced Scientific Research. All rights reserved. Objective of the research was to phylotype the E. coli isolates from the malignant and adjacent normal epithelium of the rectal mucosa of patients diagnosed with colorectal cancer, identifying and discriminating phylogroups by a set of genes, and also genotyping them by the fimH-gene locus by identifying fimH types. Samples of bacterial cultures isolated from paired biopsy specimens of patients diagnosed with colorectal cancer were subjected to molecular genetic research for species identification, as well as E. coli phylo- and genotyping. By sequencing the 16S rRNA locus, bacterial cultures are identified both as isolates of monocultures of E. coli and as mixed cultures of E. coli and K. pneumonia. The procedure for the phylotyping of E. coli isolates by identifying and discriminating phylogroups by a set of genes established the affiliation of samples of bacterial cultures with phylogroups A and B2. The genotyping procedure for E. coli isolates at the fimH gene locus by identifying the fimH types characterized the studied samples by signs of the third (f-3), fourth (f-4), and seventh (f-7) types, respectively. The strategy for identifying fimH-types during genotyping of E. coli at the fimH-gene locus has been improved, based on the analysis of SNP sequenced DNA sequences, and includes 52 fimH-types, three of which are justified in this paper

Crystal structure of binase does not reflect its native conformation

Cytotoxic ribonucleases (RNases) of the T1 family, including binase, the secreted guanyl-preferring RNase of Bacillus pumilus, are considered as promising agents of alternative anticancer chemotherapy. Binase has a selective apoptosis-inducing action against cells expressing oncogenes ras, kit, AML-ETO. The crystal structure of the binase mutant with two-point amino acid substitutions at positions 43 and 81 (Glu43Ala/Phe81Ala) indicates the absence of dimeric forms, which are characteristic for the wild-type binase. We studied the native structural organization of the Glu43Ala/Phe81Ala mutant. It was found that the mutant enzyme, similarly to the wild-type binase, possesses catalytically active dimers of different stability levels identified not only under denaturing gel electrophoresis, but also under native conditions. The results of the study show that binase exists predominantly in the dimeric form, whereas the Glu43Ala/Phe81Ala mutant approximately equally represented by both dimers and monomers formed as a result of the decomposition of unstable dimers. Although the catalytic activity of the mutant with respect to the natural substrate, RNA, was lower, as compared to the wild-type enzyme, it exhibited a 32–35% higher cytotoxicity against human adenocarcinoma cells. The data obtained indicate the contribution of the structural organization of RNases to their cytotoxicity and confirm the significance of the analysis of the native conformation of cytotoxic proteins

Наноструктурні покриття на основі аморфного вуглецю і наночастинок золота, отримані імпульсним вакуумно-дуговим методом

Імпульсним вакуумно-дуговим методом отримані наноструктурні покриття на основі алмазоподібного вуглецю та вуглецю, легованого золотом, товщиною 100-300 нм на підкладках з кремнію. Досліджено структуру методом просвічуючої електронної мікроскопії високої роздільної здатності, елементний склад методом рентгенівського мікроаналізу, визначено твердість, адгезійні та трибологічні характеристики, величину внутрішніх напружень, а також електропровідність і оптичні характеристики. Встановлено, що наночастинки золота у вуглецевій матриці мають кристалічну структуру і розмір близько 5 нм. При змінюванні вмісту золота від 1 до 25 % трибологічні властивості погіршуються, а питомий опір зменшується з 920 до 0.06 мОм×м. Запропонована методика легування вуглецевого алмазоподібного покриття золотом дозволяє в широких межах змінювати питомий опір і коефіцієнт пропускання при збереженні високої зносостійкості і низького коефіцієнту тертя.Nanostructured coatings based on diamond-like carbon and gold-doped carbon with a thickness of 100- 300 nm were obtained by a pulsed vacuum-arc method on silicon substrates. The structure of the coatings was studied by high-resolution transmission electron microscopy, the elemental composition was studied by X-ray microanalysis. In addition, hardness, adhesive and tribological characteristics, the magnitude of internal stresses, as well as electrical conductivity and optical characteristics were also investigated. It was found that gold nanoparticles in the carbon matrix have a crystal structure and their size is about 5 nm. A change in the gold content from 1 to 25 % leads to a deterioration in the tribological properties of the coating, while the resistivity decreases from 920 to 0.06 mΩ∙m. The technique proposed in this study for the doping of a diamond-like carbon coating with gold allows varying the resistivity and transmittance over a wide range while maintaining high wear resistance and low friction coefficient