Ratio Of Specific Activity Research Articles

Bioenergetics and mitochondrial deregulation underlie self-sustained persistency of atrial fibrillation in an ovine model

Abstract Background Atrial fibrillation (AF) often transitions from paroxysmal to more sustained forms in a 4-15/100 person-year range(1). It is well-recognized from both clinical and animal studies that some individuals undergo this transition much more readily than others, but the underlying mechanisms remain unclear. Purpose To identify potential differences in atrial bioenergetics between animals developing stable AF (AF-S) versus those resistant to this transition (AF-R) in a sheep AF-model. Methods AF was induced through repeated bursts of atrial tachystimulation (2). Stability of AF was monitored with telemetry. In-vivo electrophysiological remodeling was assessed via contact mapping. Metabolic and bioenergetic remodeling were evaluated using frozen left atrial appendage (LAA) tissues and isolated LAA mitochondria. Results AF-S sheep developed stable (>24-hour self-sustained) AF after 13 (range 5-22) days on average, whereas AF-R sheep failed to develop stable AF despite 120-day tachystimulation. Contact mapping and histological analysis revealed similar electro-anatomical remodeling in AF-S and AF-R groups, with the only significant difference observed in the decrease of activation time and conduction velocity in the AF-S atria. Both AF-S and AF-R animals displayed a notable increase in mitochondrial mass. Proteomic analysis showed significant differences in metabolism-related proteins and pathways between AF-S and AF-R, in particular concerning the anaplerotic supplementation of the tricarboxylic acid cycle at the level of α-ketoglutarate. Furthermore, compared to AF-R, AF-S LAA exhibited a 45% increase in succinate content, and a 23% decrease in ATP and Creatine Phosphate (PCr) content, suggesting a pathological metabolic alteration linked to a bioenergetic default. AF-S mitochondria presented abnormal succinate-oxidation, associated with a significant 20% decrease in ATP-synthesis rate, 22% increase in ROS-production, mitochondrial-membrane hyperpolarization, and decreased Complex I/II specific activity ratio. AF-S mitochondria alterations were prevented by complex I inhibitor S1QEL1.1, hinting to a participation of mitochondrial ROS into the mechanism of AF stabilization. In vivo acute intravenous perfusion of succinate in rats made them more susceptible to more frequent (OR 35 CI=[1.63-449.80]) and longer AF episodes upon treansesophageal stimulation; this vulnerability to AF was prevented by intraperitoneal pretreatment with SQEL1.1. Conclusions Resistance to AF-stabilization is associated with specific bioenergetic remodeling. These findings provide new mechanistic insights into AF-resistance and might open avenues for novel therapeutic strategies for AF-management.

Transfer of 137Cs and 90Sr from soil-to-potato: Interpretation of the association from global fallout in Aomori to accidental release in Fukushima and Chornobyl

Ceasium-137 and 90Sr are major artificial radionuclides that have been released into the environment. Soil-to-plant transfer of radionuclides is an important route to food contamination. The radionuclide activity concentrations in crops must be quantitatively predicted for estimating the internal radiation doses from food ingestion. In this study, soil and potato samples were collected from three study sites contaminated with different sources of 137Cs and 90Sr: Aomori Prefecture (global fallout) and two accidental release areas (Fukushima Prefecture and the Chornobyl exclusion zone). The 137Cs activity concentrations in the soil and potato samples widely ranged from 1.0 to 250,000 and from 0.048 to 200,000 Bq kg−1 dry weight, respectively. The soil-to-potato transfer factor of 137Cs also ranged widely (0.0015–1.1) and decreased with increasing concentration of exchangeable K. Meanwhile, the activity concentrations of 90Sr in the soil and potato samples were 0.50–64,000 and 0.027–18,000 Bq kg−1 dry weight respectively, and the soil-to-potato transfer factor of 90Sr was 0.023–0.74, decreasing with increasing concentration of exchangeable Ca. The specific activity ratios of 137Cs/Cs and 90Sr/Sr in the exchangeable fraction were similar to those in potatoes, with a factor of 3 in the ±95 % confidence intervals over six orders of magnitude and a factor of 2 in the ±95 % confidence intervals over five orders of magnitude, respectively. According to the data, the accuracy of predicting the activity concentrations of 137Cs and 90Sr in potatoes can be improved by applying the specific activity ratios of 137Cs/Cs and 90Sr/Sr in the exchangeable fraction. This approach accounts for variable factors such as the effects of K and Ca fertilization and soil characteristics. It also emphasizes the benefit of determining the stable Cs and Sr concentrations in potatoes and other crops prior to possible future contamination.

Preparation of Ficin Complexes with Carboxymethylchitosan and <i>N</i>-(2-Hydroxy)propyl-3-Trimethyl Ammonium Chitosan and the Study of Their Structural Features

Chitosan derivatives – сarboxymethyl chitosan and N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan with molecular weights of 200, 350, and 600 kDa have been synthesized. Complexes of ficin with chitosan and its named derivatives have been obtained. IR spectra of chitosan, carboxymethylchitosan, and N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan and their complexes with ficin were recorded. The analysis of the spectra confirmed the formation of conjugates between the macromolecules of polysaccharides and ficin. The optimal ratio of protein content (0.7 mg/g of carrier) and specific activity (1590 units/mg of protein) was found during the complexation of ficin with the N-(2-hydroxy)propyl-3-trimethylammonium chitosan matrix with the molecular weight 350 kDa. The efficiency of ficin complexation (in terms of specific catalytic activity) with N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan (350 kDa) exceeds that of chitosan (350 kDa) and carboxymethylchitosan (350 kDa) 2.4 and 9.8 times respectively. The types of interactions, first binding energies, amino acid composition of ficin surfaces, which interact with the carrier in the process of complexation, were studied by molecular docking. It has been established that bonds and interactions with chitosan and its derivatives are formed, among other things, with the participation of amino acid residues located near the ficin active site (Cys25 and His162), which explains the change in the proteolytic activity of the obtained complexes. Ficin complexes with N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan are soluble in a wide pH range and, therefore, may be more promising than protease-chitosan complexes in the development of medical preparations and biocatalysts for the food, brewing, and leather industries.

Novel Immobilized Biocatalysts Based on Cysteine Proteases Bound to 2-(4-Acetamido-2-sulfanilamide) Chitosan and Research on Their Structural Features.

Briefly, 2-(4-Acetamido-2-sulfanilamide) chitosan, which is a chitosan water-soluble derivative, with molecular weights of 200, 350, and 600 kDa, was successfully synthesized. The immobilization of ficin, papain, and bromelain was carried out by complexation with these polymers. The interaction mechanism of 2-(4-acetamido-2-sulfanilamide) chitosan with bromelain, ficin, and papain was studied using FTIR spectroscopy. It was found that the hydroxy, thionyl, and amino groups of 2-(4-acetamido-2-sulfanilamide) chitosan were involved in the complexation process. Molecular docking research showed that all amino acid residues of the active site of papain formed hydrogen bonds with the immobilization matrix, while only two catalytically valuable amino acid residues took part in the H-bond formation for bromelain and ficin. The spectral and in silico data were in good agreement with the catalytic activity evaluation data. Immobilized papain was more active compared to the other immobilized proteases. Moreover, the total and specific proteolytic activity of papain immobilized on the carrier with a molecular weight of 350 kDa were higher compared to the native one due to the hyperactivation. The optimal ratio of protein content (mg × g −1 of carrier), total activity (U × mL−1 of solution), and specific activity (U × mg−1 of protein) was determined for the enzymes immobilized on 2-(4-acetamido-2-sulfanilamide) chitosan with a molecular weight of 350 kDa.

Fission product isotope ratios as event characterization tools Part I: Particulate debris, isotopic activity ratios

Abstract The main goal of this work is to develop quantitatively reliable tools that can be used to identify the origin of a nuclear event, e. g. discriminate between a nuclear explosion and an accidental reactor release. A model has been developed, which takes into account the wide range of conditions and parameters, which may exist in connection with nuclear events. Using the model, specific isotope activity ratios are defined, promising to be effective in event characterization, while reducing the influence of various nuclear scenarios to a minimum. Besides, an attempt was made to quantify the concept of “short irradiation reactor” and to set its limits, as related to an event characterization method.

Radiation monitoring of drinking water in the vicinity of the Beloyarsk NPP

The article provides a radiation-hygienic assessment of the current state of drinking water supply sources for the population in the observation area of the the Beloyarsk NPP and the Institute of Nuclear Materials. We determined the content of natural (234U,238U,226Ra,228Ra,210Po,222Rn,210Pb,228Th,230Th,232Th) and technogenic (3H,14C,60Co,90Sr,134Cs,137Cs,238Pu,239,240Pu,241Am) radionuclides in drinking water of tap water, water boreholes and water wells in test settlements located at different distances and directions from radiation hazardous facilities. Results of monitoring of water sources in 2012–2013 and 2019 showed the radiation safety of drinking water in the vicinity of the Beloyarsk NPP according to several criteria. Thus, the maximum levels of the gross specific alpha-activity of radionuclides in water samples were 3.9 times lower than the control level (0.2 Bq/kg), the gross specific beta-activity was 5.7 times lower than the control level (1 Bq/ kg). Over the entire observation period, none of the drinking water samples exceeded the control levels both for individual radionuclides and for the sum of the ratios of specific activities to control levels. The content of natural and artificial radionuclides in drinking water near the Beloyarsk NPP decreases in the following order: water wells > water boreholes > tap water. For the past 20 years, there was a decrease in tritium specific activity in drinking water of the Beloyarsk NPP region by 20–35%, depending on the source of water supply. It was noted that the launch of the BN-800 reactor also did not lead to an increase in the content of other artificial radionuclides (90Sr,137Cs) in groundwater. The average annual effective dose of internal exposure of the population due to drinking water consumption in the vicinity of the Beloyarsk NPP is 0.05 mSv, according to conservative estimates – 0.07 mSv, which is below the radiation safety threshold (0.1 mSv/a) recommended by the WHO. Natural radionuclides play the primary role in the formation of the annual average effective dose for internal irradiation (98.9%) due to drinking water consumption on the considered territories.210Po makes the largest contribution to the dose from natural radioisotopes – 43%, somewhat less is made by210Pb – 25%. The third place in the dose formation from natural radionuclides belongs to234U (8%),228Ra (7%),226Ra (6%) and230Th (6%). The contribution of other natural radioisotopes in the formation of the internal radiation dose from drinking water consumption does not exceed 2-3%. The contribution of technogenic radionuclides to the annual average effective dose from the consumption of drinking water is negligible (about 1%). Of the technogenic components,90Sr (60%),3H (20%), and241Am (12%) play the most significant role in the formation of the internal exposure dose.

Switching the substrate specificity of lysoplasmalogen-specific phospholipase D.

Lysoplasmalogen‐specific phospholipase D (LyPls‐PLD) catalyzes reactions in a manner similar to those catalyzed by glycerophosphodiester phosphodiesterase (GDPD) and other well‐known PLDs. Although these enzymes hydrolyze the glycerophosphodiester bond, their substrate specificities are completely different. Previously, we reported that LyPls‐PLD from Thermocrispum sp. RD004668 shows only 53% activity with 1‐hexadecyl‐2‐hydroxy‐sn‐glycero‐3‐phosphocholine (LysoPAF) relative to the 100% activity it shows with choline lysoplasmalogen (LyPlsCho). Lipoprotein‐associated phospholipase A2 (Lp‐PLA2) activity can be used to evaluate for cardiovascular disease. Hence, development of a point‐of‐care testing kit requires a LysoPAF‐specific PLD (LysoPAF‐PLD) to measure Lp‐PLA2 activity. Rational site‐directed mutagenesis and kinetic analysis were applied to generate LysoPAF‐PLD from LyPls‐PLD and to clarify the mechanisms underlying the substrate‐recognition ability of LyPls‐PLD. Our results suggest that LyPls‐PLD variants A47, M71, N173, F211, and W282 are possibly involved in substrate recognition and that F211L may substantially alter substrate preference. Moreover, the specific activity ratio LysoPAF/LyPlsCho corresponding to F211L was up to 25‐fold higher than that corresponding to the wild‐type enzyme. Thus, we succeeded in switching from LyPlsCho‐ to LysoPAF‐PLD. These results suggest that the F211L variant may be utilized to measure Lp‐PLA2 activity. Kinetic analyses demonstrated that product release was the rate‐limiting step of the reaction, with flexibility of the sn‐1 ether‐linked vinyl/alkyl chain of the substrate being essential for substrate binding and product release. Our findings may lead to a better understanding of the differences between homologous enzymes (such as PLD, sphingomyelinase D, and GDPD of the phosphatidylinositol‐phosphodiesterase superfamily) in relation to substrate recognition.Enzyme EC 3.1.4.2 (currently assigned).

Method Development for Ficin Entrapment into Gels Based on Food-Grade Chitosan and Chitosan Succinate

Ficin was immobilized by entrapment into gels based on food-grade chitosan and chitosan succinate. The optimum ratio of protein content (mg/g of carrier), total activity (in U/mL of solution), and specific activity (in U/mg of protein) was achieved when ficin was immobilized by entrapment into the gels (based on food-grade chitosan and chitosan succinate) using glycine buffer at pH 9.0 and 9.5, respectively. The proposed technology is accessible for Russian laboratories and is promising for further investigation of the immobilized ficin preparations in medicine and the pharmaceutical industry because of the combination of relatively inexpensive components.

Estimation of cooling water activation in high-energy heavy ion medical accelerator

The estimation of air, material, and cooling water activation is essential for designing a robust nuclear safety protocol for high-energy heavy ion medical accelerators. Demineralized cooling water activation is simulated for the C-12 ion beam medical accelerator (synchrotron) with a maximum energy of 430 MeV/u. Three conservative scenarios are proposed for the estimation of demineralized cooling water activation. Simulations were performed by using a combination of MCNPX2.7.0 and VCINDER codes. Simulation parameters were optimized to match the volume of the cooling water in the accelerator system. The sums of the ratios of specific activities to unrestricted release limits were calculated for the three scenarios as a function of decay time. All activity concentrations are far less than the corresponding unrestricted release limits after a 1-day decay time because the sums of the ratios are all less than 1.0. Noticeable hazardous radioactive elements were found to be H-3, Be-7, and C-11 which have relatively long half-life times. Although hazardous radioactive elements with relatively short half-life times (within 10 min), such as N-13, O-14, and O-15, are also produced in large concentrations, there are no unrestricted release limits specified in the table issued by the National and International Radiation Protection Ordinances. The estimation of cooling water activation is useful for designing a nuclear safety protocol for high-energy heavy ion medical accelerator facilities. Specifically, the results suggest that the direct discharge of the cooling water waste into the environment (in case of an accident or the end of the life cycle of cooling water) must not be permitted. A separate reservoir for cooling water waste collection is recommended with a dedicated real-time measuring equipment to measure the concentrations of H-3, Be-7, C-11, N-13, O-14, and O-15 separately.

Разработка методики включения фицина в гель на основе пищевого хитозана и сукцината хитозана

Осуществлена иммобилизация фицина за счет включения в гель на основе пищевого хитозана и сукцината хитозана. Оптимальное соотношение содержания белка (мг/г носителя), общей активности (в ед/мл раствора) и удельной активности (в ед/мг белка) выявлено при иммобилизации фицина за счет включения в гель на основе пищевого хитозана и сукцината хитозана при использовании глицинового буфера с рН 9,0 и 9,5 соответственно. Благодаря сочетанию относительно недорогих компонентов предлагаемый нами технологичный метод доступен для отечественных лабораторий и дает перспективы дальнейшего исследования иммобилизованного фицина с целью использования в медицине и фармацевтической промышленности.

Absolute and relative measurement of the 243Am half-life

The half-life of 243Am has been measured by an absolute and a relative method, i.e. by determining the specific activity of 243Am and the specific activity ratio with 241Am. A mixed 241,243Am reference material was produced and certified for its americium mass content and its isotope amount ratios. The characterisation of the mass content of 243Am was established by isotope dilution mass spectrometry using an 241Am spike, produced from highly enriched 241Pu material. The isotope amount ratios n(241Am)/n(243Am) and n(242mAm)/n(243Am) were measured by thermal ionisation mass spectrometry. Activity measurements were performed by alpha-particle counting at a defined solid angle, as well as high-resolution alpha-particle spectrometry. From the 243Am/241Am activity and isotopic amount ratios, a value of 16.988 (24) was derived for the 243Am/241Am half-life ratio. Using a value of 432.6 (6) a for the 241Am half-life, the corresponding 243Am half-life value, 7349 (15) a, is in good agreement with the result obtained from the absolute method, 7342 (14) a. The mean value, 7345 (14) a, agrees well with data from literature and lowers the relative standard uncertainty to 0.2%.

Mixed feeding schedules switching between dietary crude protein levels for mono-sex male Nile tilapia (Oreochromis niloticus)

The optimal mixed feeding schedule for mono-sex male Nile tilapia (Oreochromis niloticus) was investigated in the current study. The fish (4.01 ± 0.02 g initial weight and 5.84 ± 0.04 cm initial length) were fed up to satiation with high protein (HP, 32.80 % protein on dry basis) and low protein (LP, 28.64 % protein on dry basis) diets in different schedules: alternately every other day (1HP/1 L P), alternately every other week (7HP/7 L P) and alternately every two weeks (14HP/14 L P), in comparison to continuously feeding by HP (positive control) or by LP (negative control) alone. At the end of eight weeks of trial, superior growth performance and feed utilization were observed in fish receiving HP, 1HP/1 L P and 7HP/7 L P relative to the remaining treatments. The specific activity of digestive enzymes (pepsin, trypsin, amylase, lipase, and activity ratio of amylase to trypsin) was modulated, indicating physiological responses for improving nutrient utilization due to the different feeding regimens. All fish mainly utilized carbohydrates rather than lipid and protein, or probably the protein-sparing effect was predominant, as indicated by the positive correlation between amylase specific activity and protein efficiency ratio (r = 0.681, P < 0.01), across five feeding schedules. There were no negative effects of mixed feeding schedules on flesh quality and carcass composition in any experimental group. However, based on economic analysis, fish receiving 1HP/1LP schedule had reduced cost of tilapia production relative to the other treatments. Therefore, the optimal feeding schedule for mono-sex male tilapia is 1HP/1LP, which should be used as a practical feeding guideline for mono-sex male Nile tilapia production.

Q301P mutant of Vibrio PR protease affects activities under low-temperature and high-pressure conditions

We characterized a protease of the M4 family from the cold-adapted Vibrio sp. Pr21 that was isolated from seawater at 320-m deep in Sagami Bay, Japan, and named it as PR protease based on the strain name Pr21. The PR protease had activities at 10-60°C and 0.1-350MPa, with the optimal temperature and pressure at 40°C and 250MPa. The mutant 10C9 (Q301P) obtained by error-prone PCR had higher activities than the wild-type enzyme at 10-60°C, and the Q301P mutation contributed to the increase of the activity. The specific activity value of 10C9 was also higher than that of the wild-type enzyme at 0.1-200MPa, but the specific activity ratios (1.28-1.59) of 10C9/wild-type enzyme at 50-200MPaat 30°C were smaller than those at 10-60°C (1.73-4.39) at 0.1MPa. The catalytic efficiency value of 10C9 was lower than that of the wild-type enzyme at 200MPa. The homology models of PR protease suggested that the side chain of Q301 was hydrogen-bonded with the carbonyl oxygen atom of the main chain of N234 in the wild-type enzyme, and P301 had no contact with N234 in 10C9. The break of the hydrogen bond in 10C9 might strengthen the increase of the flexibility of the β-sheet near the substrate binding pocket under high-temperature conditions, whereas the flexibility of the β-sheet in 10C9 might be moderately increased compared to that in the wild-type enzyme under high-pressure conditions.

Exploring the therapeutic potential of modern and ancestral phenylalanine/tyrosine ammonia-lyases as supplementary treatment of hereditary tyrosinemia

Phenylalanine/tyrosine ammonia-lyases (PAL/TALs) have been approved by the FDA for treatment of phenylketonuria and may harbour potential for complementary treatment of hereditary tyrosinemia Type I. Herein, we explore ancestral sequence reconstruction as an enzyme engineering tool to enhance the therapeutic potential of PAL/TALs. We reconstructed putative ancestors from fungi and compared their catalytic activity and stability to two modern fungal PAL/TALs. Surprisingly, most putative ancestors could be expressed as functional tetramers in Escherichia coli and thus retained their ability to oligomerize. All ancestral enzymes displayed increased thermostability compared to both modern enzymes, however, the increase in thermostability was accompanied by a loss in catalytic turnover. One reconstructed ancestral enzyme in particular could be interesting for further drug development, as its ratio of specific activities is more favourable towards tyrosine and it is more thermostable than both modern enzymes. Moreover, long-term stability assessment showed that this variant retained substantially more activity after prolonged incubation at 25 °C and 37 °C, as well as an increased resistance to incubation at 60 °C. Both of these factors are indicative of an extended shelf-life of biopharmaceuticals. We believe that ancestral sequence reconstruction has potential for enhancing the properties of enzyme therapeutics, especially with respect to stability. This work further illustrates that resurrection of putative ancestral oligomeric proteins is feasible and provides insight into the extent of conservation of a functional oligomerization surface area from ancestor to modern enzyme.

Оптимизация методики иммобилизации фицина с использованием глутарового альдегида

Ficin was covalently immobilized on an acid-soluble matrix of medium (200 kDa) and high molecular weight (350 kDa) chitosans. The enzyme molecules were immobilized in a protein film and copolymerized with glutaraldehyde. The optimal ratio of protein content, total activity and specific activity was observed as a result of ficin covalent immobilization on a matrix of medium-molecular chitosan with 15% glutaraldehyde and high-molecular chitosan with 10% glutaraldehyde. The obtained biocatalysts are promising for industrial applications. ficin, chitosan, glutaraldehyde, covalent immobilization. This work was financially supported by a grant from the President of the Russian Federation for state support to young Russian scientists-doctors of sciences MD-1982.2020.4. Agreement 075-15-2020-325).

Comparison of CSTR and AnMBR for anaerobic digestion of WAS and lipid-rich flotation sludge from the dairy industry

Process stability and limitations of loading capacity of anaerobic membrane bioreactors (AnMBRs) and continuously stirred tank reactors (CSTRs) for the treatment of WAS and a lipid-rich flotation sludge from the dairy industry were investigated in pilot scale. The digesters were operated with increasing shares of lipids up to 85% at low sludge retention times (SRT) down to 10 days. High shares of lipids are favorable for treating wastewater sludges from industrial WWTPs on-site instead of their disposal, but often lead to long chain fatty acid (LCFA) accumulations and digester failures. In this study, high COD removals were obtained in all digesters resulting in methane yields over 250 L/kg CODin. Methane production and COD removal followed substrate first-order kinetics. High lipid shares of CODlipid > 80% did not inhibit COD degradation. Process stability was determined based on the ratio of specific methanogenic activity and mean acetate conversion in the digesters. Process stability depended mainly on SRT and lipid shares in the substrate as both parameters affected the degradable lipid content in the anaerobic sludge. Shorter SRTs and higher shares of lipids in particular reduced process stability as observed by inhibitions of acetoclastic methanogenesis. The OLR was not a decisive factor. When treating COD shares of lipids higher than 80%, SRT should exceed 15 d. COD shares of lipids below 80% were also successfully treated at SRT of 10 d. Residual degradable lipid content of anaerobic sludge negatively influenced process stability starting from 50 mg lipid/g TS. The performance of an AnMBR in terms of COD degradation and process stability corresponds to a CSTR with equal SRT, but can be operated with higher OLRs. At equal HRT compared to a CSTR, the AnMBR offers a higher process stability by extending the SRT.

Constructing Environmental Radon Gas Detector and Measuring Concentration in Residential Buildings

Background: From the health physics perspective, radon gas is one of the most dangerous gases in residential and business environments. According to the WHO (World Health Organization), radon gas is considered the second cause of lung cancer in societies after smoking. Methods: In this study, the environmental radon gas has been measured using a built radon gas detector on a specific preamplifier circuit and then the perceived results were compared with an Alpha-Guard detector. Specific activity and output ratio on radon concentration in air were measured on three different floors of a residential building covered by different materials. Results: The results showed a good correlation between the outputs and data gathered by the Alpha-Guard. In underground covered by plaster and cement, the detector responses showed approximately double amounts in comparison with the ground floor. The different covered places revealed dissimilar responses, so that the screened granite had greater amounts by 347 ± 37 Bq/m3. Besides, the minimum response was revealed on the first floor using Alpha-Guard by 47 ± 6 Bq/m3. Results confirmed that on each floor, which has a good ventilation system, the exposure due to the radon isotopes can be immensely reduced. Conclusions: This system can also be used to measure the radon concentration changes in the environment and groundwater.

About development of control levels of specific total alpha-activity in water samples for a number of sources of the centralized economic and drinking water supply in the Republic of Khakassia

The aim of the work is to develop control levels of specific total alpha-activity of water samples for a number of sources of centralized drinking water supply in the Republic of Khakassia on the basis of the results of long-term laboratory studies. Materials and methods. The analysis is carried out on the basis of the results of laboratory studies of water sources of centralized drinking water supply of the population of the Republic of Khakassia, performed by accredited testing laboratories of institutions of the state sanitary and epidemiological service of the Republic for the period from 2001 to 2018, using alpha-beta radiometric, alpha-spectrometric methods with radiochemical preparation of counting samples, gamma-spectrometric method. The control levels of specific total alpha-activity of water samples from the sources of centralized drinking water supply in the Republic of Khakassia were established by the statistical maximum – the sum of the average value with a doubled standard deviation, with the volume of research more than 30, and the maximum value with the volume of research less than 30. Results. About half of the studied water samples from the sources of the centralized drinking water supply of the Republic of Khakassia, annually, are noted with exceeding the control level of specific total alpha-activity (0,2 Bq/kg). The values obtained in the studied samples vary up to 5,57 Bq/kg. During the observation period, samples of water exceeding the reference level of specific total alpha-activity (0.2 Bq/kg) were identified in settlements of the Altai, Askizsky, Beysky, Bogradsky, Ordzhonikidzevsky, Tashtypsky, Ust–Abakansky, Shira districts and the city of Sorsk, smt. Prigorsk (Chernogorsk). In previous studies, it was found that high levels of specific total alpha-activity in the country are mainly due to natural radionuclides uranium-238 (238U), uranium-234 (234U). In a number of settlements of the Republic, the sum of the ratio of specific activities of natural radionuclides to the corresponding levels of intervention exceeds 1,0. Average annual individual effective doses of internal exposure to natural radionuclides of drinking water, at or above 0,1 mSv/year (values in the range of 0,1-0,2 mSv/year), which does not require urgent radiation protection measures. At the same time, monitoring of indicators of radiation safety of water sources of water supply should be carried out in accordance with the established requirements. In this connection, in order to improve control, for the rapid assessment of the radiation situation and making timely decisions to ensure radiation safety of the population, the calculation of control levels of specific total alpha-activity was carried out. As a result of calculations, specific values of control levels for each of water source were obtained. The calculated values range from 0,2 to 2,6 Bq/kg. Conclusion. The control levels are “site standards” and are calculated for each of the source of water supply. Their excess will be considered as a signal of “negative change” of the radiation situation”, which may be associated with an increase of the specific activities of 234U, 238U, or the appearance of highly radiotoxic radionuclides: 226Ra, 210Po, 228Ra.

Improving the activity and enantioselectivity of PvEH1, a Phaseolus vulgaris epoxide hydrolase, for o-methylphenyl glycidyl ether by multiple site-directed mutagenesis on the basis of rational design

Substrate spectrum assay exhibited that PvEH1, which is an epoxide hydrolase from P. vulgaris, had the highest specific activity and enantiomeric ratio (E) for racemic o-methylphenyl glycidyl ether (rac-1) among tested aryl glycidyl ethers (1–5). To produce (R)-1 via kinetic resolution of rac-1 efficiently, the catalytic properties of PvEH1 were further improved on the basis of rational design. Firstly, the seven single-site variants of PvEH1-encoding gene (pveh1) were PCR-amplified as designed, and expressed in E. coli BL21(DE3). Among all expressed single-site mutants, PvEH1L105I and PvEH1V106I had the highest specific activities of 17.6 and 16.4 U/mg protein, respectively, while PvEH1L196D had an enhanced E value of 9.2. Secondly, to combine their respective merits, one triple-site variant, pveh1L105I/V106I/L196D, was also amplified, and expressed. The specific activity, E value, and catalytic efficiency of PvEH1L105I/V106I/L196D were 23.1 U/mg, 10.9, and 6.65 mM−1 s−1, respectively, which were 2.0-, 1.8- and 2.4-fold higher than those of wild-type PvEH1. The source of PvEH1L105I/V106I/L196D with enhanced E value for rac-1 was preliminarily analyzed by molecular docking simulation. Finally, the scale-up kinetic resolution of 100 mM rac-1 was conducted using 5 mg wet cells/mL E. coli/pveh1L105I/V106I/L196D at 25 °C for 1.5 h, producing (R)-1 with 95.0% ees, 32.1% yield and 3.52 g/L/h space-time yield.

Cell Phone EMF Affects Rat Pulmonary Tc-MIBI Uptake and Oxidative Stress

99mTc-MIBI is a radiopharmaceutical which has trend to accumulate in the heart, but its absorption in pulmonary system may alter heart accumulation and so affect the heart imaging. We aimed to assess the effects of cell phone EMF on lung accumulation of 99mTc-MIBI and oxidative stress. Male albino Wistar rats were randomly divided into 12 groups: four for 99mTc and 99mTc-MIBI control, four for 99mTc 900 and 1800 MHz, four for 99mTc-MIBI 900 and 1800 MHz. After injection of radiopharmaceutical in rats’ tail vein, the animals were housed in standard cages for expose to 900 or 1800 MHz in time of 15 or 30 min. Activity of 99mTc and 99mTc-MIBI in the lungs was being assayed using a dose calibrator. Concentration of malondialdehyde (MDA) and catalase (CAT) was measured in serum. After 15 and 30 min EMF radiation, in both groups of 900 and 1800 MHz, lung specific activity was increased the same as control group; meanwhile, in 15 min 900 MHz group, there was a significant increase in lung-to-heart specific activity ratio compared to other groups. Data showed a permanent increase in 900 MHz group CAT activity. MDA level had not any significant changes. The use of cell phone EMF during the preparation and imaging process could increase absorption of radiopharmaceutical by the pulmonary system and may affect lung-to-heart specific activity ratio, so affect to correct diagnosis by the physician.