Selection Of Optimal Conditions Research Articles

Optimization of Extraction of Phlorotannins from the Arctic Fucus vesiculosus Using Natural Deep Eutectic Solvents and Their HPLC Profiling with Tandem High-Resolution Mass Spectrometry.

Phlorotannins are secondary metabolites produced mainly by brown seaweeds (Phaeophyceae) and belong to the class of polyphenolic compounds with diverse bioactivities. The key factors in the extraction of polyphenols are the selection of a suitable solvent, method of extraction and selection of optimal conditions. Ultrasonic-assisted extraction (UAE) is one of the advanced energy-saving methods suitable for the extraction of labile compounds. Methanol, acetone, ethanol and ethyl acetate are the most commonly used solvents for polyphenol extraction. As alternatives to toxic organic solvents, a new class of green solvents, natural deep eutectic solvents (NADES), has been proposed for the efficient extraction of a wide range of natural compounds including polyphenols. Several NADES were screened previously for the extraction of phlorotannins; however, the extraction conditions were not optimized and chemical profiling of NADES extract was not performed. The purpose of this work was to study the effect of selected extraction parameters on the phlorotannin content in NADES extract from Fucus vesiculosus, optimization of extraction conditions and chemical profiling of phlorotannins in the NADES extract. A fast and green NADES-UAE procedure was developed for the extraction of phlorotannins. Optimization was performed through an experimental design and showed that NADES (lactic acid:choline chloride; 3:1) provides a high yield (137.3 mg phloroglucinol equivalents per g dry weight of algae) of phlorotannins under the following extraction conditions: extraction time 23 min, 30.0% water concentration and 1:12 sample to solvent ratio. The antioxidant activity of the optimized NADES extract was equal to that of EtOH extract. In total, 32 phlorotannins have been identified (one trimer, two tetramers, six pentamers, four hexamers, six heptamers, six octamers and seven nonamers) in NADES extracts from arctic F. vesiculosus using the HPLC-HRMS and MS/MS technique. It was noted that all the above-mentioned phlorotannins were identified in both EtOH and NADES extracts. Our results suggest that NADES could be considered as an alternative to the conventional techniques for the effective extraction of phlorotannins from F. vesiculosus with high antioxidant potential.

Integrated Methodology of Soft Computing for Process Modeling and Optimization of Duplex Turn Cutting of Titanium Alloy

Duplex turning (DT) is a novel concept of metal cutting where two tools are employed to cut the objects in lieu of single tool. It shows many benefits over conventional turning in terms of superior dynamic balancing, lower cutting forces and tool wears, better surface finish, reduction in vibration with additional support for workpiece. It is a complex method and the resulting experimental analysis becomes difficult and expensive. In such conditions, modeling techniques show their potential for parametric study, prediction of data for optimization and selection of optimal condition. Generally, soft computing-based Artificial Neural Network (ANN) is applied for modeling and prediction for complicated processes while Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) shows their potential for optimization of complex problems over Genetic Algorithm. Therefore, ANN and NSGA-II techniques are employed for modeling and optimization of DT process to minimize the surface roughness and cutting forces (primary and secondary). Finally, results reflect that ANN efficiently predicts the responses at different input combinations within training data set with absolute percentage errors as 2.55% for roughness, while 3.05% and 3.14% for cutting forces (primary and secondary), respectively. In the same way, optimized results also found within the range of acceptability with percentage errors as 2.57% for roughness, while 3.25% and 3.15% for primary and secondary forces, respectively.

Establishing brown trout primary hepatocyte spheroids as a new alternative experimental model—Testing the effects of 5α-dihydrotestosterone on lipid pathways

Three-dimensional (3D) fish liver cultures mimic the in vivo cellular microenvironment, which is ideal for ecotoxicological research. Despite that, the application of these cultures to evaluate toxic effects in fish is scarce. A 3D model of brown trout (Salmo trutta f. fario) primary hepatocyte spheroids was optimized in this study by using DMEM/F-12 with 15 mM of HEPES, 10 mL/L of an antibiotic and antimycotic solution and FBS 10% (v/v), at 18 °C with ∼100 rpm. The selection of optimal conditions was based on a multiparametric characterization of the spheroids, including biometry, viability, microanatomy and immunohistochemistry. Biometric and morphologic stabilization of spheroids was reached within 12-16 days of culture. To our knowledge, this study is the first to culture and characterize viable spheroids from brown trout primary hepatocytes for over 30 days. Further, the 3D model was tested to explore the androgenic influences on lipidic target genes after 96 h exposures to control, solvent control, 10 and 100 µM of 5α-dihydrotestosterone (DHT), a non-aromatizable androgen. Spheroids exposed to 100 µM of DHT had decreased sphericity. DHT at 100 µM also significantly down-regulated Acox1-3I, PPARγ and fatty acid synthesis targets (i.e., ACC), and significantly up-regulated Fabp1. Acsl1 was significantly up-regulated after exposure to both 10 and 100 µM of DHT. The results support that DHT modulates distinct lipidic pathways in brown trout and show that this 3D model is a new valuable tool for physiological and toxicological mechanistic studies.

How cereal flours, starters, enzymes, and process parameters affect the in vitro digestibility of sourdough bread

Digestibility of leavened baked goods relies on multiple factors: starch bioavailability and protein hydrolysis during food processing and digestion, presence of antinutritional factors, and satiety and gastrointestinal symptoms after intake. Several studies highlighted that bread digestibility might be positively affected by long-time sourdough fermentation. Nevertheless, most research is focused on single factors and their effect on digestibility, excluding the potential complementary effects of more than one factor. In this work, a multitude of factors influencing the the in vitro starch and protein digestibility and predicted glycemic index were assessed simultaneously. Forty-six different breads made with various raw material/ingredients (flour, enzymes, lactic acid bacteria cytoplasmic extracts and gluten), type of sourdoughs (fresh or commercial liquid or dried), strains of lactic acid bacteria and yeasts, and time and temperature of fermentation, were preliminarily investigated. Further selection of optimal conditions was based on statistical analysis and final breads were further characterized for their peptide profiles, total free amino acids and quality indexes of the digestible protein fraction.Among the factors considered, results identified a claimed in vitro digestibility for breads made with whole wheat, spelt, and rye flours, obtained with lactic acid bacteria strains selected for the peptidase activity, added of fungal proteases, and fermented at the optimal temperature of 37 °C.

Influence of Impurities on the Process of Obtaining Calcium Carbonate during the Processing of Phosphogypsum.

The article is devoted to the study of the influence of residual sulfuric and phosphoric acids on the process of processing large-tonnage phosphogypsum (PG) waste into calcium carbonate. In the Russian Federation, about 10 percent of existing phosphogypsum waste is processed into construction materials. Acidic impurities (phosphoric and sulfuric acids) in their composition are an obstacle to the use of phosphogypsum for the production of binders. This study finds that impurities also reduce the chemical activity of phosphogypsum. At the same time, the paper focuses on the potential of phosphogypsum for the production of calcium carbonate. This article investigated the amount of impurities in phosphogypsum. The results show that during automatic washing of phosphogypsum, losses are approximately 30–35 wt. %. It was also found that phosphogypsum by 22% consists of impurities of phosphoric and sulfuric acid. These acids are characteristic waste products of extraction phosphoric acid (EPA) production. By ASTM C471M-20ae1, the content of calcium sulfate dehydrate and hemihydrate before and after washing was determined. A thermodynamic calculation of the proposed interaction of phosphogypsum with carbonates showed that the characteristic reaction is possible. The conversion process of phosphogypsum to get the corresponding calcium carbonate was carried out at 70 °C. Data on the chemical composition of the reaction products, obtained by X-ray fluorescence analysis on a Shimadzu EDX-7000 spectrometer, showed that some reactions proceed incompletely and need the selection of optimal conditions. The potential commercial benefits of processing phosphogypsum by carbonization were defined for products such as calcium carbonate or its derivatives.

Selection of optimal conditions for the lactic acid biosynthesis

Lactic acid is used in various industries: chemical, food, cosmetic, pharmaceutical, agriculture and polymer production. 40% of the domestic market demand for lactic acid is met through imports, while the main methods for producing lactic acid are microbiological or synthetic. The most rational is microbiological synthesis, however, when it is implemented, valuable sugar-containing substrates (crystalline sucrose, molasses, sugar syrup) are used, which significantly affects the cost of the final product. There was an obvious need to search for new technologies for the production of lactic acid. Prospective and cost-effective is the processing of whey into lactic acid using bacterial fermentation of the lactose contained in the whey. The aim of the study is to screen cultures of microorganisms capable of fermenting lactose contained in milk whey and to select the composition of the medium that provides the maximum yield of lactic acid. Strains of lactic acid bacteria were used in the experiment: Leuconostocmesenteroides subsp. mesenteroides 122 (B1699), Lactobacillus brevis B78 (B5728), Lactobacillus plantarum K9 (B5466), Lactobacillus casei C1 (B5726), Lactobacillus acidophilus (B9012), Lactobacillus paracasei BT 24/88 (B6253), Lactobacillus paracasei 139 (B2430), obtained from the Russian National Collection of Industrial Microorganisms (Scientific Center "Kurchatov Institute" -Research Institute for Genetics and Selection of Industrial Microorganisms). The authors determined the optimal composition of the medium for the biosynthesis of lactic acid by selecting the concentrations of yeast autolysate and salt solution that provide the maximum yield of lactic acid. The authors also selected the optimal duration of lactic acid biosynthesis. The study of the acid-forming ability of strains of lactic acid bacteria showed that of the strains studied, Lactobacillus casei C1 (B5726) showed the greatest ability to ferment lactose by synthesizing lactic acid, which correlates with the data on assimilation of lactose by the culture. The optimal cultivation time (132 h) and the concentration of yeast lysate (5%) in a nutrient medium based on curd whey were selected. With optimal parameters, the maximum concentration of lactic acid in the culture liquid of Lactobacillus casei C1 (B5726) was 54.77 g / L, which is comparable with the currently used producers in the industrial production of lactic acid.

Development of the "Dissolution" Test Method for Tablets of Sodium 4,4'-(propanediamido)dibenzoate with Sustained Release

Introduction. Non-alcoholic fatty liver disease is one of the most common chronic diseases of this parenchymal organ among the adult population. The search and creation of supporting drugs is an urgent task of modern pharmacy. The malonic acid derivative, sodium 4,4'-(propanediamido) dibenzoate, synthesized by the employees of the Department of Organic Chemistry of the SPСPU, has antisteatous activity, is a potential agent for the treatment of liver diseases. Sustained release tablets were prepared based on sodium 4,4'-(propanediamido)dibenzoate. An integral part of the pharmaceutical development of a medicinal product is the development of a method for conducting the Dissolution test and the selection of optimal conditions, which became the purpose of this study.Aim. To develop the "Dissolution" test method for the sustained-release tablets based on sodium 4,4'-(propanediamido)dibenzoate.Materials and methods. The objects of research are the active pharmaceutical ingredient sodium 4,4'-(propanediamido)dibenzoate, as well as sustained-release tablets based on this substance. Equilibrium biopharmaceutical solubility was determined by UV-spectrophotometry. To establish the conditions for the "Dissolution" test, an ERWEKA DT-620 dissolution tester (ERWEKA GmbH, Germany) was used.Results and discussion. The suitability of the UV-spectrophotometry method for the quantitative determination of sodium 4,4'-(propanediamido) dibenzoate in solutions was determined. The established high biopharmaceutical solubility of sodium 4,4'-(propanediamido)dibenzoate in a buffer solution with a pH of 6,8, as well as in a 0,01 M solution of hydrochloric acid with a pH of 2,6, determined the choice of these media for the "Dissolution" test of the dosage form. The apparatus "Rotating basket" (rotation speed of 100 rpm in a dissolution medium with a volume of 1000 ml) was reasonably chosen for the test on the basis of the obtained linear dependence of the rate of release of the substance on time, as well as the best test results by the end of the experiment.Conclusion. A study of the biopharmaceutical properties of the original substance with antisteatous activity has been carried out. High biopharmaceutical solubility was established in media with pH 2,6 and pH 6,8. The conditions of the "Dissolution" test for sustained-release tablets based on the original sodium 4,4'-(propanediamido)dibenzoate were experimentally substantiated.

Selection of optimal conditions for obtaining malt from buckwheat

Buckwheat can be used in the production of specialized products (including therapeutic and preventive ones) for consumers suffering from gluten intolerance. Buckwheat malt in Russia is not produced on an industrial scale, it is purchased in European countries. It is necessary to know the parameters of processing domestic varieties of buckwheat for the production of buckwheat malt. Mathematical planning methods were used to predict the influence of the main factors of buckwheat germination on the activity of its hydrolytic enzymes for the production of malt with high enzymatic capacity. Dikul buckwheat was studied. Soaking of buckwheat was carried out by air-water method at a temperature of 15-16 °C in tap water to a relative humidity of 46-50 %, air and water pauses were alternated every 4 hours. Germination was carried out for 6 to 7 days at a temperature of 15 to 16 °C until the maximum activity of hydrolytic enzymes of amylolytic and proteolytic action was achieved. The sprouted grain was subjected to fermentation, for which it was left alone for 12-24 hours until the temperature in the middle layer rose to 50-55 °C, stirred and blown with conditioned air with such intensity that the humidity of the malt was 50-52 %, and the temperature in all layers was 67-68 °C for 5 days. Drying was carried out with a gradual increase in temperature from 67-68 °C to 74-75 °C for 16 hours to a humidity of 5-6 %. We predicted how the main factors of buckwheat germination affect the activity of its hydrolytic enzymes. The main factors affecting the activity of enzymes during germination: malting temperature, °C; malting humidity, %; malting duration, day. The criteria for evaluating the influence of the selected parameters were the abilities, units/g of dry substances: amylolytic, saccharifying, and proteolytic. For statistical processing of the study data, central rotatable uniform planning was used, which made it possible to obtain a regression equation that adequately describes the process of buckwheat germination in the course of 20 experiments in 3-fold repetition. To assess the adequacy of the mathematical model, an analysis of variance (ANOVA) of the experiment was performed in the Design Expert program (Stat-EaseInc.). The following values of the output parameters were obtained, units / g of dry substances – amylolytic capacity of 326.7, saccharifying capacity of 40.9 and proteolytic capacity of 381.9 units/g. at the appropriate input: temperature 15 °C; humidity 48 %; duration of malting 6 days.

Acidophilic chemolithotrophic microorganisms: prospects for use in biohydrometallurgy and microbial fuel cells

Acidophilic chemolithotrophic microorganisms are used in biohydrometallurgy for the extraction of metals from sulphide ores. Some types of microorganisms belonging to this group are capable of generating electricity under certain conditions. This circumstance determined a recent upsurge of research interest in their use in biofuel cells. Under a constant supply of the substrate to the bioelectrochemical system, acidophilic chemolithotrophic microorganisms are capable of producing electricity for a prolonged period of time. The use of extremophiles in microbial fuel cells is of particular interest, since these microorganisms can serve as bioelectrocatalysts at extreme pH, salinity and temperature, while the vast majority of microorganisms are unable to survive under these conditions. Therefore, selection of optimal conditions and approaches to controlling the work of acidophilic chemolithotrophic microorganisms in such fuel cells is of particular importance. On this basis, a technology for the simulteneous bioleaching of metals from poor ores and the generation of electricity can be developed. Biofuel cells operating at low pH values using acidophilic chemolithotrophic microorganisms are yet to be investigated. The number of studies on acidophilic electroactive microorganisms is very limited. In this regard, the purpose of this review was to consider the prospects for the use of acidophilic chemolithotrophic microorganisms as bioagents in microbial fuel cells. The reviewed publications demonstrate that chemolithotrophic microorganisms can act as both anodic (metal-reducing, sulphur-oxidizing microorganisms) and cathodic (metal-oxidizing prokaryotes, sulfate reducers) highly efficient bioagents capable of using mining wastes as substrates.

Vegetative Propagation of Deciduous Rhododendrons using Root Stimulating Agents

The genus Rhododendron L. is the largest in the heather family Ericaceae DC. Rhododendrons are decorative evergreen, semi-evergreen and deciduous shrubs that have gained great popularity in green building, ornamental gardening and breeding. Among all groups of rhododendrons, deciduous are the most promising for cultivation in Central Russia due to their high winter hardiness, unpretentiousness and exceptional decorative effect. The article presents the results of experiments carried out at the GBS RAS in 2017-2020 on vegetative propagation of 50 species and varieties of deciduous rhododendrons. Vegetative propagation of deciduous rhododendrons is a rather laborious long process. Cutting deciduous rhododendrons has its own nuances and is considered problematic. In this regard, the selection of optimal conditions for the propagation of rhododendrons, which can enrich the cultural flora of the North-West, central Russia, the Urals and Siberia, was the main goal of this work.

Thermal preferences of two spider species: an orb-web weaver and a synanthropic funnel-web weaver

Temperature, an important factor in the ecological niche, determines the individual fitness, distribution and abundance of many spider species. Typically, spiders from different habitats have different thermal preferences, which vary depending on the season, time of day, and reproductive status. Selected temperatures may also depend on thermal acclimation of animals. The study aimed at determining preferred temperatures of females of two spider species, synanthropic Eratigena atrica and garden Araneus diadematus, exposed to low (14°C) and high (23°C) acclimation temperatures. The mean preferred temperature observed in a thermal gradient varied between the species: E. atrica selected 13.7 ± 1.0°C, while A. diadematus selected 22.5 ± 1.5°C, irrespective of the acclimation temperature. Accordingly, thermal niche overlaps between the species were significantly lower than predicted by the random distribution. E. atrica changed their thermal environment on average 12.8 ± 1.9 times during the test, which made them more mobile than A. diadematus, changing their thermal environment 2.7 ± 0.5 times. On the other hand, the thermal niche breadth of A. diadematus acclimated to warm temperature was wider than that of E. atrica. The female behaviour may be related to the selection of optimal conditions with regard to food availability (location for web construction), shelter and/or, in the case of E. atrica, embryonic development.

Study of electrochemical deposition of Ni-Mo thin films from alkaline electrolytes

The process of co-deposition of Ni with Mo from alkaline electrolytes was studied by taking linear and cyclic polarization curves of Pt electrode at various concentrations of initial components and potential scan rates. Solutions of Na2MoO4∙2H2O and NiSO4∙7H2O were used as sources of ions of the main components in NH4OH electrolyte. It was found that co-deposition of nickel with molybdenum goes through the oxide formation stage, and a solid solution of these two metals is deposited on the cathode surface. The film obtained at constant current on Ni electrode under optimal conditions was found amorphous, but additional thermal treatment at 500 °C for one hour made it polycrystalline. This was confirmed by peaks in X-ray diffraction patterns, corresponding to NiMoO4, Ni, and MoO3. The proposed electrolyte and electrolysis conditions allow to obtain thin films with molybdenum content ranging from 17.1 to 50.9 at.%. The co-deposition of Ni with Mo is limited by diffusion of these ions to the cathode surface. The knowledge of the mechanism of co-deposition of Ni and Mo will make possible a selection of optimal conditions for deposition of alloys of the required composition with satisfactory electrocatalytic properties.

Microextraction-colorimetric determination of anionic surfactants in natural and waste waters

An eco-friendly, simple, rapid and cheap method for determining anionic surfactants in natural and waste waters by microextraction-colorimetric method has been developed. The essence of the proposed approach consisted in extraction and concentration of analytes in an acidic medium in the form of associates with organic reagents (methylene blue and acridine yellow) by dispersion liquid-liquid microextraction using a mixture of chloroform-acetonitrile as an extracting and dispersing solvent, followed by aggregation of extractant microparticles by centrifugation and subsequent measurements of color characteristics using a smartphone. The values of the basic components of the RGB colorimetric system were used as an analytical signal to calculate the final color: The selection of optimal conditions for microextraction concentration of anionic surfactants from natural waters (the nature of the extracting and dispergating solvents, the volume of the dispergating solvent) was performed for the sodium dodecyl sulfate — methylene blue system. To study the colorimetric characteristics of the prepared extracts, a smartphone «iPhone X» was used as a color-registering device equipped with a specialized software product «RGBer». To minimize the measurement error by fixing the distance to the object under study and lighting conditions, we propose an installation that increases the accuracy and sensitivity of the determination and makes the method more mobile. The total content of the most common components of detergents was determined: sodium dodecyl sulfate, sulfonol, laureth sulfate and disodium laureth-3-sulfosuccinate. The detection limits ranged within 0.01 – 0.02 and 0.05 mg/liter. The range of detectable contents for all analytes was 0.05 – 1.0 mg/liter. For the determined surfactants, the equations of the relationship between the analytical signal and the concentration were obtained. The calibration graphs are linear with coefficients of the approximation reliability ≤0.98. The correctness of the method was tested on samples of natural water using the spike test procedure. The relative standard deviation of the analysis results does not exceed 0.13. The analysis duration is 20 – 30 min.

Optimization of glycine and thiotriazoline compound analysis by high-performance liquid chromatography

Украина занимает одно из первых мест в Европе по показателям цереброваскулярной заболеваемости и смертности от инсульта. Поэтому создание новых лекарственных средств для лечения этих патологий – актуальная задача современной фармации, а создание нового комбинированного препарата на основе глицина (нейротрасмиттерной аминокислоты) и тиотриазолина (антиоксиданта) целесообразно и актуально. Для нового комбинированного лекарственного средства предложена рациональная лекарственная форма – таблетки. Для созданных комбинированных таблеток необходимо разработать методы стандартизации. Чаще всего для стандартизации готовых лекарственных форм и аптечного, и заводского изготовления используют физико-химические методы исследования. Наше внимание привлек метод высокоэффективной жидкостной хроматографии, который позволяет одновременно провести стандартизацию действующих веществ в одной навеске. Для разработки методики ВЭЖХ прежде всего необходимо подобрать оптимальные условия проведения анализа действующих веществ. Цель работы – подбор оптимальных условий одновременного определения глицина с тиотриазолином в модельной смеси методом ВЭЖХ. Материалы и методы . В ходе исследований использовали глицин, тиотриазолин. Исследования проводили с использованием модульной системы ВЭЖХ BISCHOFF со спектрофотометрическим детектором Lambda 1010. Использовали колонки Prontosil 120-5-CN, Hypersil ODS-C18-5u. В качестве элюента использовали воду, 0,05 % водный раствор трифторуксусной кислоты Bu 4 NHSO 4 3,4 г/л в воде, Bu 4 NHSO 4 3,4 г/л, 0,02 М Na 2 HPO 4 в воде, Bu 4 NHSO 4 3,4 г/л, 0,05 % раствор трифторуксусной кислоты в воде. Результаты. Согласно полученным результатам, среди различных использованных элюентов и фаз в дальнейшем для совместного определения глицина с тиотриазолином и в модельной смеси, и в комбинированных лекарственных формах целесообразно использовать в качестве элюента тетрабутиламмоний в условиях ион парного хроматографирования на обратной фазе с одновременным использованием кислого буфера – 0,05 % раствора трифторуксусной кислоты. Выводы. В ходе исследований подобраны оптимальные условия одновременного определения глицина с тиотриазолином в одной навеске. Установили, что определение действующих веществ необходимо проводить в условиях ион парного хроматографирования на обратной фазе при использовании элюента тетрабутиламмония с одновременным использованием кислого буфера – 0,05 % раствора трифторуксусной кислоты.

Localization of Annexin V and Agrin in the Intact Sciatic Nerve of Mice

Immunohistochemistry methods are widely used in modern microscopic studies. The advantage of immunoelectron microscopy is the possibility of localization of functional proteins in the ultrastructures of the cell. However, different tissues and antigens react differently to the traditionally used fixatives. Selection of optimal conditions for the preparation of immunologically labeled samples for electron microscopic studies is largely based on empirical experience and depends not only on the type of tissue, but also on the purpose of the study. Nervous tissue combines mechanically weak (myelin) and dense (collagen, cell wall) structures, which poses the controversial task of simultaneously ensuring the fixation of the structure of the tissue and the interaction of antibodies with antigen throughout the entire thickness of the sample. This paper presents the method of immunohistochemical labeling, adapted for the study of the localization of annexin V and agrin in the ultrastructure of different parts of the mouse sciatic nerve. Obtained results revealed the preferential localization of both proteins in the myelin sheaths of nerve fibers, which indicates the possible role of these proteins in the functioning of myelin. The density of anti-agrin precipitate in the skin branch is significantly higher than in the tibial, whereas annexin V is more evenly distributed.

A model-based approach for the rational design of the freeze-thawing of a protein-based formulation

Proteins are unstable molecules that may be severely injured by stresses encountered during freeze-thawing. Despite this, the selection of freeze-thaw conditions is currently empirical, and this results in reduced process control. Here we propose a mathematical model that takes into account the leading causes of protein instability during freeze-thawing, i.e. cold denaturation and surface-induced unfolding, and may guide the selection of optimal operating conditions. It is observed that a high cooling rate is beneficial for molecules that are extremely sensitive to cold denaturation, while the opposite is true when ice-induced unfolding is dominant. In all cases, a fast thawing rate is observed to be beneficial. The simulation outputs are confirmed by experimental data for myoglobin and lactate dehydrogenase, suggesting that the proposed modeling approach can reproduce the main features of protein behavior during freeze-thawing. This approach can therefore guide the selection of optimal conditions for protein-based formulations that are stored in a frozen or freeze-dried state.

Мембраны из сплавов палладия для получения особочистого водорода

In the present study, using the improved technology, high-quality vacuum-tight foils 10 – 20 µm in thickness were prepared from effective Pd – 6 wt. % In – 0.5 wt. % Ru, Pd – 6 wt. % Ru, Pd – 40 wt. % Cu palladium alloys. Using a combination of deformation and annealing modes, the Pd – 40 wt. % Cu alloy foil consisting of the ordered β-phase (97%) with the CsCl-type structure that exhibits the maximum hydrogen permeability in this system. The mechanical properties and hydrogen permeability of the prepared foils were studied and compared with those of alloy foils 50 µm thickness. The thermal concentration dilatation in hydrogen was studied at different temperatures. Data on the dilatation of palladium-based membranes are of primary importance for designing membrane filtering elements and selection of optimal conditions for their operation, since these data determine the operation life membranes. Based on the Pd – 6 wt. % In – 0.5 wt. % Ru alloy, the Pd – 6 wt. % In – 0.5 wt. % Ru – 1.25 wt. % Co alloy was developed; it is characterized by increased strength characteristics and lower α ↔ β hydride transition temperature.

Halotolerant strain of Chlorococcum oleofaciens from the Lake Elton Biosphere Reserve

Chlorococcum oleofaciens is one of the most studied representatives of the Chlorococcum genus, both on the ultrastructural and molecular levels. This alga is very interesting due to its ability to hypersynthetize saturated and unsaturated fatty acids and the possibility of using it as a promising object for biofuel production. This research is devoted to the study of the halotolerant strain of Ch. oleofaciens Ch-1 extracted from the water of the Khara River (Lake Elton Biosphere Reserve, Russia, a UNESCO World Heritage site), mineralization of 14‰. The strain Ch. oleofaciens Ch-1 was studied at the morphological level (light microscopy), as well as using molecular genetics methods (18S rDNA). The objectives of the study included establishing the range of halotolerance of the allocated strain of Ch. oleofaciens as a whole, revealing borders of level of mineralization that are optimum for algae growth, and also tracing features of its morphology and cycle of development in the conditions of various salinity. In the course of the studies performed it was established that the extracted strain of Ch. oleofaciens Ch-1 differed from the typical one by greater variability of some morphological features and had a wide ecological valence: the range of its halotolerance was 0–60‰. The maximum values of quantitative development of Ch. oleofaciens Ch-1 were registered at mineralization of 0–14‰. It is shown that with increasing salinity in the development cycle of the strain, the duration of the adaptation phase increases, the exponential phase decreases, small celled forms are replaced by large celled forms and reproduction features are noted. The obtained results can be used for selection of optimal conditions for cultivation of the halotolerant strain of Ch. oleofaciens for biotechnological purposes.

METHODICAL SUPPORT FOR CONTROL OVER THE CONCENTRATION OF PERSISTENT ORGANIC POLLUTANT HEXACHLOROBENZENE IN BLOOD

Introduction. Persistent organic pollutants (POP) are extremely dangerous compounds contaminating the environment and exerting the negative impact on human health. Organochlorine pesticides, including hexachlorobenzene, are a specific group among POP. Our research goal is methodological support for the hexachlorobenzene content control in human biological environments. Material and methods. We developed highly both sensitive and selective procedure for determining hexachlorobenzene in blood. Hexachlorobenzene determination in blood is based on the application of capillary gas chromatography with linear programming of a column temperature, electron capture detector (ECD), and extraction with an organic solvent at a sample preparation stage. When implementing the developed methodology, the following indices were evaluated: accuracy and error characteristics of the analysis results. The lower limit of hexachlorobenzene quantification (LOQ) in blood amounted to 0.000024 µg/cm3, with the range of detectable concentrations from 0.00015 to 0.005 (determination method error ≥ 20%), which allows to adequately diagnose chemical burden with a highly toxic persistent organic pollutant in blood. Results. The results of quantitative chemical analysis of hexachlorobenzene contents in blood had the following quality indices: precision and correctness amounted to 15.621%; repeatability - 3.45%; reproducibility - 4.65%. In the process of testing the method, concentrations of hexachlorobenzene in the range of 0.0003 ± 0.0001 ÷ 0.0007 ± 0.0001 μg/cm3 were detected in the blood of the examined group. Discussion. The high efficiency of gas chromatography determination of hexachlorobenzene in blood was achieved via selection of optimal conditions for chromatographic analysis: capillary column HP-1- 35m∙0.32mm∙0.25µm with linear programming of column temperature, carrier gas (nitrogen), electron capture detector (ECD). The developed method of the preparing a blood sample for analysis, including liquid extraction with toluene, protein denaturation by centrifuging the biological medium at 7000 rpm for 15 min at pH of 6-7 in combination with gas chromatographic analysis and an electron capture detector (ECD) made it possible to complete extraction of hexachlorobenzene from blood in an amount of 99.7%.

The selection of optimal conditions for the process of obtaining humic acid from brown coal

The type of plant substance from which brown coal is formed and the conditions in which it forms largely influence its characteristics and properties. On account of a lower degree of coalification and calorific value compared to hard coal and a high content of humic substances, brown coal is becoming a valuable fertiliser component. Humic acids contained in brown coal are also found in the soil’s humus substances, and their beneficial sorptive and complexing properties are a factor speaking in favour of their use both in agriculture and in other branches of the economy. The article presents the manner of preparing a sample of brown coal in order to determine the content of humic acid intended in particular for use in making chemical fertilisers and for other applications, particularly in agriculture. The optimum conditions in which the amount of humic acid in the sample is the highest were determined. The influence of the proportions of water, KOH, and brown coal, temperature, and mixing time on the solubility of the sample of brown coal was analysed. The solutions were mixed in mixers built especially for this purpose. The solubility of brown coal in the prepared solutions was controlled UV-ViS spectrophotometrically.