Decrease In Specific Activity Research Articles

Sevoflurane acts as an antidepressant by suppression of GluN2D-containing NMDA receptors on interneurons.

Sevoflurane, a commonly used inhaled anaesthetic known for its favourable safety profile and rapid onset and offset, has not been thoroughly investigated as a potential treatment for depression. In this study, we reveal the mechanism through which sevoflurane delivers enduring antidepressant effects. To assess the antidepressant effects of sevoflurane, behavioural tests were conducted, along with in vitro and ex vivo whole-cell patch-clamp recordings, to examine the effects on GluN1-GluN2 incorporated N-methyl-d-aspartate (NMDA) receptors (NMDARs) and neuronal circuitry in the medial prefrontal cortex (mPFC). Multiple-channel electrophysiology in freely moving mice was performed to evaluate sevoflurane's effects on neuronal activity, and GluN2D knockout (grin2d-/-) mice were used to confirm the requirement of GluN2D for the antidepressant effects. Repeated exposure to subanaesthetic doses of sevoflurane produced sustained antidepressant effects lasting up to 2 weeks. Sevoflurane preferentially inhibited GluN2C- and GluN2D-containing NMDARs, causing a reduction in interneuron activity. In contrast, sevoflurane increased action potentials (AP) firing and decreased spontaneous inhibitory postsynaptic current (sIPSC) in mPFC pyramidal neurons, demonstrating a disinhibitory effect. These effects were absent in grin2d-/- mice, and both pharmacological blockade and genetic knockout of GluN2D abolished sevoflurane's antidepressant actions, suggesting that GluN2D is essential for its antidepressant effect. Sevoflurane directly targets GluN2D, leading to a specific decrease in interneuron activity and subsequent disinhibition of pyramidal neurons, which may underpin its antidepressant effects. Targeting the GluN2D subunit could hold promise as a potential therapeutic strategy for treating depression.

Engineering of cofactor preference and catalytic activity of methanol dehydrogenase by growth-coupled directed evolution

Methanol, produced from carbon dioxide, natural gas, and biomass, has drawn increasing attention as a promising green carbon feedstock for biomanufacturing due to its sustainable and energy-rich properties. Nicotinamide adenine dinucleotide (NAD+)-dependent methanol dehydrogenase (MDH) catalyzes the oxidation of methanol to formaldehyde via NADH generation, providing a highly active C1 intermediate and reducing power for subsequent biosynthesis. However, the unsatisfactory catalytic efficiency and cofactor bias of MDH significantly impede methanol valorization, especially in nicotinamide adenine dinucleotide phosphate (NADP+)-dependent biosynthesis. Herein, we employed synthetic NADH and NADPH auxotrophic Escherichia coli strains as growth-coupled selection platforms for the directed evolution of MDH from Bacillus stearothermophilus DSM 2334. NADH or NADPH generated by MDH-catalyzed methanol oxidation enabled the growth of synthetic cofactor auxotrophs, establishing a positive correlation between the cell growth rate and MDH activity. Using this principle, MDH mutants exhibiting a 20-fold improvement in catalytic efficiency (kcat/Km) and a 90-fold cofactor specificity switch from NAD+ to NADP+ without a decrease in specific enzyme activity, were efficiently screened from random and semi-rationally designed libraries. We envision that these mutants will advance methanol valorization and that the synthetic cofactor auxotrophs will serve as versatile selection platforms for the evolution of NAD(P)+-dependent enzymes.

Changes in radioactive contamination of living ground cover plants in black alder stands since the Chornobyl accident in the forests of Zhytomyr Polissia

The results of research conducted over the past 30 years in the forest ecosystems of Zhytomyr Polissia, in the areas affected by radioactive contamination as a result of the Chornobyl accident. In the course of the research carried out at the Poliskyi Branch of the Ukrainian Research Institute of Forestry and Forest Melioration named after G. M. Vysotsky, methods of forest radioecology, botany, and forestry were used, and the results were processed using statistical analysis. The peculiarities of radioactive contamination of the most common herbaceous and dwarf-shrub plants in the stands of black alder in damp fairly fertile site types were studied. As indicators characterizing these features, we used 137Cs specific activity in the aboveground part of plants and the transfer factor of radionuclide to plant phytomass from the soil. It was found that the highest values of the transfer factor of 137Cs from the soil to the aerial part of the plant phytomass in 1999 are characteristic of ferns: for Dryopteris cristata (L.) A. Gray (276.9 m2∙kg-1∙10-3), Dryopteris carthusiana (Vill.) H. P. Fuchs (236.5 m2∙kg-1∙10-3), Thelypteris palustris Schott (171.2 m2∙kg-1∙10-3), and Athyrium filix-femina (L.) Roth (164.0 m2∙kg-1∙10-3). It was found that among the higher plants, the highest values of this indicator are for the Agrostis stolonifera L. (263.5 m2∙kg-1∙10-3), Galium uliginosum L. (155.8 m2∙kg-1∙10-3) and Maianthemum bifolium (L.) F. W. Schmidt (155.4 m2∙kg-1∙10-3). It was found out that the previously noted trends and interspecific differences in radionuclide accumulation persist after 22 years. It is shown, using the example of three plant species (Lysimachia vulgaris L., Galium uliginosum, and Maianthemum bifolium), that during the observation period (1991-2021) there is a gradual decrease in radioactive contamination of living ground cover plants and the intensity of 137Cs intake into them. This is explained by the decay of the radioactive element, its entry into various perennial components of forest ecosystems, some fixation in the soil, and, possibly, its removal beyond their borders. The established decrease in 137Cs specific activity in the aboveground part of plants is described by linear equations: for Lysimachia vulgaris – Am = –605.34a + 3745.6; R² = 0.98; Galium uliginosum – Am = –5107.5a + 30698; R² = 0.99; Maianthemum bifolium – Am = –4661.6 a + 28280; R² = 0.98. The identified peculiarities of radioactive contamination of various plant species, changes in 137Cs specific activity in them, and transfer factors of the radionuclide from the soil in stands of black alder in damp fairly fertile site types can be used in scientific works to predict possible changes in its redistribution within the ecosystem, as well as in the practice of harvesting medicinal plants in areas contaminated with radionuclides.

Produksi Enzim Spesifik Xilanase pada Variasi Suhu Konsorsium Trikultur Bakteri Termofilik

Xylanase is an extracellular enzyme that is capable of hydrolyzing xylan (hemicellulose) into xylose and xylo-oligosaccharides. Xylanase can be produced by microbes through a fermentation process, the microbes used are thermophilic bacteria. Thermophilic bacteria are microorganisms that are capable of producing thermostable enzymes through fermentation. The bacteria used are MSS11, MS 16 and MS 18. These thermophilic bacteria can live at temperatures above 45°C-80°C. To determine specific enzyme activity, enzyme and protein activity values were tested using a 540 nm (enzyme) and 750 nm (protein) septovotometer. The method used in this research is descriptive in triplicate. The research was carried out at the Microbiology Laboratory, Faculty of Mathematics and Natural Sciences, Padang State University on December 23 2023. Beechwood medium which had been mixed with MSS 11, MS 16, and MS 18 bacteria was then incubated at temperatures of 55℃, 65℃ and 75℃ so that specific enzyme activity was obtained. Of these three temperatures, the optimum specific enzyme activity of xylanase is 65℃, where the specific enzyme value obtained at 65℃ is 3.31 U/mg. Meanwhile, at low temperatures, namely at 55℃, the enzymatic reaction is slow, namely it has an enzyme activity value of 1.02 U/mg. Finally, at a temperature of 75, there was a decrease in specific enzyme activity, where the specific enzyme activity value was 3.12 U/mg.

Sulfur-tolerant mechanism in catalytic combustion of toluene over Co/5Mg-γ-Al2O3 catalyst: Dual functions of MgO

Using toluene catalytic combustion as a probe reaction, simulating quantitative sulfur poisoning by in situ thermal decomposition of ammonium sulfate solution, the study used MgO modified γ-Al2O3 to support cobalt-based catalyst, and the result displayed that the catalyst exhibited excellent sulfur poisoning resistance. The successful construction of MgO-Al2O3 heterogeneous interface weakened the interaction between Co and Al and reduced the production of inactive CoAl2O4. Besides that, it fixed sulfur species and formed MgSO4 to protect active components. The dual function of MgO have been proved by various characterization experiments. The modification of γ-Al2O3 by the appropriate amount of MgO could improve the catalytic activity of Co/γ-Al2O3. Meanwhile, T100 increased from 300 °C to 330 °C after 1.6 wt% sulfur poisoning and we concluded that the decrease in catalytic performance was not caused by the loss of active Co, but by the decrease of specific surface area and lattice oxygen activity.

Abstract 73: Specific Activity of GSTs and Protein Expression of GSTT1, GSTP1 and CYP1A1 in Head and Neck Cancer

Abstract Purpose: Rising incidence of head and neck cancer have been observed in developing countries over last decade. It has been postulated that carcinogen detoxifying genes may be involved directly or indirectly in pathogenesis of head and neck cancer. Three genes (CYP1A1, GSTM1 and GSTP1) were studied for their association with head and neck cancer. Cytochrome P450 1A1 (CYP1A1) is phase I enzyme while glutathione S transferases (GSTs) constitute the phase II detoxification enzymes. Abnormal protein expression of CYP1A1 and GSTs lead to cancer initiation. Methods: The current case control study was designed to evaluate the possible associations of these enzymes with head and neck cancer. Serum GSTs activity was determined by using ELISA and CYP1A1, GSTT1, GSTP1 expression in tissue by immunohistochemistry with specific antibodies. Results: Mean serum GSTs specific activity was 7.7 (+11.5)U/L and control was 11.4 (+7.5)U/L. Significant decrease (P<0.05) in GSTs specific activity was observed in head and neck cancer patients compared to controls (P<0.001). Moreover, CYP1A1 and GSTT1 was down expressed whereas GSTP1 was over expressed in head and neck cancer tissues compared with adjacent normal control tissue. Conclusion: Conclusion: Decreased activity of GSTs, reduced expression of GSTs, CYP1A1, GSTT1 and increased expression of GSTP1 may contribute to head and neck cancer development in Pakistani population. Citation Format: Nosheen Masood, Azra Yasmin. Specific Activity of GSTs and Protein Expression of GSTT1, GSTP1 and CYP1A1 in Head and Neck Cancer [abstract]. In: Proceedings of the 11th Annual Symposium on Global Cancer Research; Closing the Research-to-Implementation Gap; 2023 Apr 4-6. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(6_Suppl):Abstract nr 73.

Improving Durability of Fuel Cells with Platinum-rich Alloy Cathode Catalysts

Pt3Co-alloy based nanoparticle catalysts are very active for oxygen reduction reaction (ORR) thereby enabling high performance of proton exchange membrane fuel cells (PEMFC) for automotive propulsion. However, these catalyst materials degrade due to a combination of electrochemical surface area (ECSA) loss and dissolution of cobalt-alloying element from the nanoparticles. Dissolution of cobalt has a two-fold impact on the durability of fuel cells—i) a loss in the low-current density kinetic region due to a decrease in specific activity and ii) a loss in the high-current density transport region due to Co2+ contamination of the ionomer phase. Cobalt dissolution-contamination needs to be mitigated as it limits fuel cell performance and lifetime for heavy-duty automotive applications. In this article, we study the use of PtCo-alloy catalysts with Pt-rich compositions using catalyst-specific accelerated stress test measurement in membrane electrode assemblies to decrease the amount of dissolved Co and mitigate its subsequent contamination effects. We demonstrate Pt5Co and Pt7Co compositions to enable significant improvements in durability (∼50 mV and ∼100 mV with respect to Pt3Co after 30,000 voltage cycles) with a minor but acceptable compromise in the initial specific activity of the catalyst.

Deciphering performance and potential mechanism of anammox-based nitrogen removal process responding to nanoparticulate and ionic forms of different heavy metals through big data analysis

As a promising process to remove nitrogen, anaerobic ammonium oxidation (anammox) is sensitive to environmental factors and toxic substances (antibiotics, heavy metals, sulfides, etc.). Especially, the nitrogen removal efficiency and biological activity of the anammox system were greatly inhibited by heavy metals. Few studies have been devoted to systematically investigating the effects and quantitatively deciphering the mechanism of different heavy metals on anammox-based systems. Based on the big data analysis of previous publications, the ionic heavy metals contributed to the greater decrease of specific anammox activity (SAA) than their nanoparticulate forms. Especially the inhibition ratio of SAA severely deteriorated under Cu2+ and CuO NPs, reaching 85 % and 81 %, respectively. This inhibition effect of heavy metals on nitrogen removal was also verified by the correlation analysis. Moreover, Logistic kinetic model was suitable to fit the inhibition periods of heavy metals, and Gaussian model could accurately predict nitrogen removal rate (R2 over 0.95) better than artificial neural network model. Based on quantitatively calculation of three independent nitrogen removal processes, nano heavy metals had a slight promotion effect on the ammonia oxidation process that proliferated amoA, while Ni2+ and CuO nanoparticulate inhibited nitrite oxidation process severely accompanying by the augmentation of resistance genes. Importantly, the anammox process was restrained by all heavy metals, verifying that anammox played a key role in the whole nitrogen removal process. This big data analysis provides a useful direction that it should give priority to ionic heavy metal and the copper element for anammox-based process under stress of heavy metals.

Formation and Characterization of a Stable Monolayer of Active Acetylcholinesterase on Planar Gold.

Enzyme activity is the basis for many biosensors where a catalytic event is used to detect the presence and amount of a biomolecule of interest. To create a practical point-of-care biosensor, these enzymes need to be removed from their native cellular environments and immobilized on an abiological surface to rapidly transduce a biochemical signal into an interpretable readout. This immobilization often leads to loss of activity due to unfolded, aggregated, or improperly oriented enzymes when compared to the native state. In this work, we characterize the formation and surface packing density of a stable monolayer of acetylcholinesterase (AChE) immobilized on a planar gold surface and quantify the extent of activity loss following immobilization. Using spectroscopic ellipsometry, we determined that the surface concentration of AChE on a saturated Au surface in a buffered solution was 2.77 ± 0.21 pmol cm-2. By calculating the molecular volume of hydrated AChE, corresponding to a sphere of 6.19 nm diameter, divided by the total volume at the AChE-Au interface, we obtain a surface packing density of 33.4 ± 2.5% by volume. This corresponds to 45.1 ± 3.4% of the theoretical maximum monolayer coverage, assuming hexagonal packing. The true value, however, may be larger due to unfolding of enzymes to occupy a larger volume. The enzyme activity and kinetic measurements showed a 90.6 ± 1.4% decrease in specific activity following immobilization. Finally, following storage in a buffered solution for over 100 days at both room temperature and 4 °C, approximately 80% of this enzyme activity was retained. This contrasts with the native aqueous enzyme, which loses approximately 75% of its activity within 1 day and becomes entirely inactive within 6 days.

Sulphoraphane Affinity-Based Chromatography for the Purification of Myrosinase from Lepidium sativum Seeds.

Sulforaphane and other natural isothiocyanates released from the respective plant glucosinolates by the plant enzyme myrosinase (β-thioglucoside glucohydrolase) show extensive anticancer and antimicrobial effects. In this study, myrosinase from garden cress (Lepidium sativum) seeds was purified to electrophoretic homogeneity by a fast and easy strategy consisting of fractionation by isoelectric precipitation with ammonium sulphate (AS) and affinity chromatography using sulforaphane (SFN) attached to cellulose resin. The overall purification of enzyme with respect to crude extract was 169-fold and recovery of 37%. Under non-reducing conditions, two protein bands exhibiting myrosinase activity with masses of about 114 and 122 kDa, respectively, and a 58 kDa protein band with no activity were detected by SDS-PAGE and zymography on polyacrylamide gel. MALDI-Tof/Tof of tryptic fragments obtained from the respective protein bands detected sequence motifs homologous to the regions responsible for glycoside-substrate binding and similarities to members of the enzyme subfamilies β-glucosidases and myrosinases GH. The enzyme hydrolyzed both the natural (sinigrin, sinalbin, glucoraphanin) and the synthetic (p-nitrophenol-β-D-glucopyranoside (pNPG)) substrates. The highest catalytic activity of purified enzyme was achieved against sinigrin. The KM and Vmax values of the enzyme for sinigrin were found to be 0.57 mM, and 1.3 mM/s, respectively. The enzyme was strongly activated by 30 μM ascorbic acid. The optimum temperature and pH for enzyme was 50 °C and pH 6.0, respectively. The purified enzyme could be stored at 4 °C and slightly acidic pH for at least 45 days without a significant decrease in specific activity.

Study of Ruthenium Contamination Effect on Oxygen Reduction Activity of Platinum-Based PEMFC and DMFC Cathode Catalyst

Proton exchange membrane fuel cells (PEMFC) and PEM-based direct methanol fuel cells (DMFC) are promising energy sources for vehicular, stationary and portable applications. While PEMFC-based power systems have already reached a limited commercialization level, durability remains to be one of the main obstacles on the path towards their broad commercialization. One of the degradation mechanisms reducing durability of reformate-based PEMFC and DMFC is ruthenium contamination of the cathode catalyst [i] following ruthenium dissolution from the anode PtRu catalyst and its cross-over to the cathode [ii].The aim of our research is to quantitatively measure the effect of ruthenium contamination on the oxygen reduction reaction (ORR) activity of a typical cathode catalyst. For this purpose, various and precisely known amounts of ruthenium (equivalent to 0.15-4 ruthenium monolayers) were deposited on a commercial 50%Pt/C catalyst (Johnson Matthey HiSPEC8000) using electroless reduction method. The obtained Ru-contaminated Pt/C catalysts were examined using TGA, SEM-EDS, XPS, HR-TEM and STEM-EDS to determine their composition, particles size distribution and structure. Cyclic-voltammetry with rotating–disk–electrode was used to quantitatively determine the effect of ruthenium contamination on the ORR specific activity.It was found that ORR activity exhibits a pseudo-exponential decay with increased ruthenium coverage. At a contamination level of 0.15 equivalent ruthenium monolayer (EDS %at Ru3Pt97, XPS %at Ru7Pt93) a massive, ~45%, decrease in ORR specific activity was measured. At a contamination level of 1 equivalent ruthenium monolayer (EDS %at Ru27Pt73, XPS %at Pt50Ru50) almost a complete inhibition of ORR activity was observed. Ruthenium deposition on platinum in the form of bi-layer islands and 3d-clusters and deactivation of platinum atoms surrounding ruthenium deposition sites were proposed as a possible explanation for the pseudo-exponential decay of the ORR activity. The obtained results allowed us to estimate the decrease in power density of reformate-based PEMFC and DMFC due to ruthenium contamination by 0.15 equivalent monolayer at roughly 10%.Assuming that the decrease in ORR activity is originating from the strong O and OH binding to ruthenium, DFT-calculated O and OH binding energies to ruthenium and platinum were used to estimate ORR activity on model Run/Pt(111) surfaces that represent Ru-contaminated Pt/C catalyst. The estimated ORR activities have shown a dependence on ruthenium contamination that was qualitatively similar to experimental results, indicating that the strong O and OH binding to ruthenium have indeed a negative effect on the ORR activity.[i] L. Gancs, B. N. Hult, N. Hakim, S. Mukerjee, Electrochem. Solid-State Lett., 2007, 10, 9, B150[ii] P. Piela, C. Eickes, E. Brosha, F. Garzon, P. Zelenay, Journal of The Electrochemical Society, 2004, 151 (12), A2053–A2059

The Influence of Specific Activity on the Biodistribution of 18F-rhPSMA-7.3: A Retrospective Analysis of Clinical PET Data.

We investigated whether the time between synthesis and injection and the resulting decrease in specific activity affects the normal-organ and tumor uptake of the PSMA ligand 18F-rhPSMA-7.3 in patients with prostate cancer. Methods: The biodistribution of 18F-rhPSMA-7.3 on PET/CT scans obtained with a high specific activity (median, 178.9 MBq/µg; n = 42) and a low specific activity (median, 19.3 MBq/µg; n = 42) was compared. Results: Tracer uptake by the parotid gland, submandibular gland, and spleen was moderately but significantly lower in the low-specific-activity group than in the high-specific-activity group (median SUVmean, 16.7 vs. 19.2; 18.1 vs. 22.3; and 7.8 vs. 9.6, respectively). No other statistically significant differences were found for normal organs or tumor lesions. Conclusion: A 10-fold decrease in specific activity has only minor effects on the biodistribution of 18F-rhPSMA-7.3. These findings suggest that 18F-labeled PSMA ligands can be centrally produced and shipped to PET clinics in a similar way to 18F-FDG.

Long-term dynamics of radionuclide contamination formation in the industrial іchthyofauna of the Kaniv Reservoir

The aim the study is to determine the temporal parameters of the long-lived radionuclides specific activity decrease in the commercial fish species of the Kaniv Reservoir for the period 1987–2021. Rutilus rutilus, Scardinius erythrophthalmus, Blissa bjoerkna, Abramis brama, Pelecus cultratus (peaceful species) and Esox lucius, Stizostedion lucioperca (carnivorous species) were selected in the middle and lower parts of the reservoir in January 2021 to determine the current levels of radioactive contamination in the representatives of the commercial ichthyofauna of the Kaniv Reservoir. The specific activity of 90Sr and 137Cs was determined in the entire body of fish by conventional radiochemical and gamma-spectrometric methods. The analysis of the dynamic characteristics of the radionuclides content in the representatives of the reservoir ichthyofauna was carried out on the basis of the results of studies of 90Sr and 137Cs content in fish during 1987–2012 and their specific activity in the body in 2021. In 2021, the average specific activity of 90Sr in fish was 0.6–1.6 Bq/kg, 137Cs - 2.4–13.2 Bq/kg. According to the results of previous studies, the average specific content of 90Sr in the fish of the Kaniv Reservoir decreased by approximately 6.5 times - from 60 ± 30 to 9 ± 3 Bq / kg during 1987-1993, and by 2003 it decreased by another 5 times up to 1.8 ± 0.8 Bq / kg and did not exceed the values recorded in freshwater fish in Ukraine before the Chernobyl accident in 1979–1985. Consequently, during the period of 2003–2021 the levels of 90Sr content in fish from the Kaniv Reservoir remained virtually unchanged. Based on the data on 137Cs accumulation in various feeding types fish in the Kaniv Reservoir, time parameters describing a decrease in the element specific activity were determined. During 1987–2021 the rate of decrease in 137Cs content in peaceful and predatory fish did not differ significantly and amounted to 0.10 ± 0.01 year-1, the period of effective half-decrease was 6.7 ± 0.7 years. Analysis of long-term data made it possible to distinguish 2 periods during which the specific activity of 137Cs in the fish organism decreased at different rates. In 1987-2004, 137Cs content levels in peaceful fish decreased from 70 ± 22 to 6.1 ± 2.2 Bq/kg, in carnivorous species - from 202 ± 41 to 19.8 ± 7.6 B/ kg, i.e. approximately by 10–11 times, which corresponds to a half-decrease of about 6 years. In 2004–2021 the element content in peaceful fish decreased to 2.9 ± 0.7 Bq/kg, in predatory fish - to 7.3 ± 4.1 Bq/kg, that is, by another 2–3 times, which corresponds to a half-decrease of 12 ± 3 years. Thus, it was found that the rate of decrease in 137Cs specific activity in fish slows down over time. The obtained parameters will make it possible to predict with a high degree of accuracy the dynamics of the radionuclide contamination formation in ichthyofauna in the event of artificial radionuclides entering aquatic ecosystems as a result of emergency situations. Key words: Kaniv Reservoir, fish, radionuclides, longterm dynamics, rate of decrease.

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.

Fatigue of anammox consortia under long-term 1,4-dioxane exposure and recovery potential: N-kinetics and microbial dynamics

Long-term exposure of anammox process to 1,4-dioxane was investigated using periodic anammox baffled reactor (PABR) under different 1,4-dioxane concentrations. The results generally indicated that PABR (composed of 4 compartments) has robust resistance to 10 mg-dioxane/L. The 1st compartment acted as a shield to protect subsequent compartments from 1,4-dioxane toxicity through secretion of high extracellular polymeric substance (EPS) of 152.9 mg/gVSS at 10 mg-dioxane/L. However, increasing 1,4-dioxane to 50 mg/L significantly inhibited anammox bacteria; e.g., ~ 93% of total nitrogen removal was lost within 14 days. The inhibition of anammox process at this dosage was most likely due to bacterial cell lysis, resulting in the decrease of EPS secretion and specific anammox activity (SAA) to 105.9 mg/gVSS and 0.04 mg N/gVSS/h, respectively, in the 1st compartment. However, anammox bacteria were successfully self-recovered within 41 days after the cease of 1,4-dioxane exposure. The identification of microbial compositions further emphasized the negative impacts of 1,4-dioxane on abundance of C. Brocadia among samples. Furthermore, the development of genus Planococcus in the 1st compartment, where removal of 1,4-dioxane was consistently observed, highlights its potential role as anoxic 1,4-dioxane degrader. Overall, long-term exposure to 1,4-dioxane should be controlled not exceeding 10 mg/L for a successful application.

Distribution and behaviour of 233Pa in 2LiF-BeF2 molten salt.

Distribution and behavior of 233Pa, essential in the thorium–uranium nuclear fuel cycle, were studied in 2LiF–BeF2 (66 : 34 mole%, FLiBe) molten salt by γ-ray spectrometry. The experiments showed that 233Pa deposited slightly on the surface of graphite crucible. The addition of Hastelloy and metallic lithium decreased the 233Pa specific activity in the salt by 1 to 2 orders of magnitude rapidly. Analysis indicated that reductive deposition of 233Pa was responsible for the rapid decrease of 233Pa specific activity in the salt. Additional experiments strongly supported the mechanism of reductive deposition of 233Pa induced by Hastelloy and metallic lithium. In view of the large deposition of 233Pa on Hastelloy, the possible influence of fissile nuclide 233U produced from 233Pa decay on the operation of thorium-based molten salt reactor was discussed.

Pegylated catalase as a potential alternative to treat vitiligo and UV induced skin damage

The metabolic function of catalase (CAT) is to prevent oxidative damage to tissues through the hydrolysis of hydrogen peroxide, which is a strong oxidizing agent. It has been suggested as an alternative to treat skin diseases related to oxidative stress, such as vitiligo. Owing to the instability associated to the protein nature, topical use of CAT is challenging and, in this sense, PEGylation can be an interesting alternative. Here, we conjugated CAT to methoxy-poly(ethylene oxide) (mPEG) of 10, 20 and 40 kDa, by means of a nucleophilic attack of ε-amino groups to an electron-deficient carbonyl group of the reactive PEG, resulting in site specifically PEGylated bioconjugates. PEGylation yields ranged from 31% ± 2% for CAT-PEG40 to 59% ± 4% for CAT-PEG20 and were strongly affected by the reaction pH owing to the protonation/deprotonation state of primary amines of lysine and N-terminal residues. PEGylated conjugates were purified by size-exclusion chromatography (purity > 95%) and characterized by circular dichroism. Irrespectively of MW, PEG did not affected CAT secondary and tertiary structure, but a decrease in specific activity was observed, more pronounced when PEGs of higher MWs were used. However, this loss of activity is compensated by the increased long-term stability, with a gain of >5 times in t1/2. In vitro antioxidant activity of CAT-PEG20 showed complete elimination of lipid peroxidation at the skin upper layer (stratum corneum) suitable for a topical use to treat vitiligo, as well as other skin conditions related to oxidative stress.

Dihydroquercetin increases the adaptive potential of wild soybean against copper sulfate and cadmium sulfate toxicity

In this study, the mechanism of the biochemical adaptation of wild soybean to the experimentally modeled effects of cadmium sulfate and copper sulfate in approximately double permissible concentration was investigated. The extracted concentrations of cadmium and copper in the experimental soil were determined by inversion voltammetry - 1.46 and 48.25 mg/kg, respectively. Growing soybeans in soil with the addition of copper and cadmium sulfates led to an increase in the concentration of malonic dialdehyde in soybean seeds relative to control by 62% and 38%, respectively, which confirmed the strengthening of oxidative processes. There was also an increase in the specific activity of peroxidase by 198% under the action of copper sulfate and 122% under the action of cadmium sulfate. Copper in the studied concentration was more toxic than cadmium. Acid phosphatase showed stable specific activity under the action of the studied metals. PAGE revealed multiple forms that were absent from the control: under the action of copper sulfate-AP7, AP12; cadmium sulfate-AP12. Dihydroquercetin treatment of soybean seeds before sowing in soil contaminated with copper and cadmium sulfates led to a decrease in the level of malonic dialdehyde by 20% and 11%, respectively, and a decrease in the specific activity of peroxidase by an average of 12%. There was a decrease in specific activity and the appearance of new multiple forms of acid phosphatase: under the action of copper sulfate by 18%, AP13; cadmium sulfate - 25%, AP2 and AP13. Thus, we suggest that flavonoids may take part in the adaptation of plants to the effects of copper and cadmium.

Polyamines induced nematode stress tolerance in Solanum lycopersicum through altered physico-chemical attributes

Root-knot nematodes are one of the important phytoparasites that adversely affect the growth and development in plants, thus affecting its productivity. Various chemical nematicides are available commercially, having adverse effect on the environment and non-target organisms. So, it becomes necessary to explore some eco-friendly strategies to manage these parasites. Polyamines recognised as potential phytohormone, enhance the plant survival during stressful conditions. Thus, present study was undertaken to evaluate the stress protective properties of two polyamines in tomato seedlings under nematode stress. Uniform sized tomato (cv. Pusa Ruby) seeds were sterilized and treated with different concentrations (0.5, 0.7 and 0.9 mM) of two polyamines i.e. putrescine and spermine. Seeds are allowed to germinate in in-vitro conditions and subjected to nematode inoculation with second stage juveniles of Meloidogyne incognita @5J2s per seedlings after germination. Various morphological and biochemical parameters were analysed after one day of nematode inoculation. Nematode invasion alters the morphological and biochemical parameters whereas polyamines treatment restores them to control level. Significant decrease in specific activities of antioxidative enzymes viz: superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, glutathione peroxidase, polyphenol peroxidase, and pyrogallol peroxidase was observed in polyamines treated seedlings except guaiacol peroxidase and phenylalanine lyase with maximum activity change by spermine application comparing with nematode inoculated seedlings. Chlorophyll content also increases significantly with spermine treatment. Non-enzymatic antioxidants analysis also revealed the anti-stress properties of polyamines as the total phenolic, ascorbic acid content significantly increases whereas decreased glutathione content was observed with polyamine application. Results obtained from confocal microscopy also revealed the inhibition of reduced glutathione and H2O2 content in polyamine treated seedlings indicated by weak intensity of fluorescence when compared with nematode inoculated seedlings with lower intensity in spermine applied seedlings.

Probing the dynamics between the substrate and the product towards glucose tolerance of Halothermothrix orenii β-glucosidase

Most β-Glucosidase (B8CYA8) are prone to inhibition by glucose. Experimentally observed specific activity of B8CYA8 on 20 mM, 50 mM, and 100 mM p-nitrophenyl-β-D-glucopyranoside (pNPGlc) substrate concentrations show surprise dependence on the presence of 0–3 M glucose at 335 K. We found that at high substrate concentration, the enzyme shows stimulation in specific activity with glucose and the glucose inhibition curve shifts toward the right with the increase in the substrate concentration. We employed atomistic molecular dynamics simulations of β-Glucosidase from Halothermothrix orenii at different glucose and pNPGlc concentrations to provide microscopic explanations to the experimentally observed non-monotonic glucose concentration dependence of the enzyme activity. Our results show that accumulation of substrate (pNPGlc) near the B8CYA8 catalytic site residues E166 and E354 and in the active site tunnel increases up to 0.5 M glucose when the specific activity is the highest. The number of pNPGlc in the tunnel decreases drastically when glucose concentration is more than 0.5 M, and hence the specific activity decreases. Potential of mean force (PMF) calculations showed that the most favorable interaction between pNPGlc and β-Glucosidase exists at 0.5 M glucose while at deficient and high glucose concentrations, the binding energy between the substrate and β-Glucosidase is very low. These studies provide the molecular basis towards understanding inhibition and stimulation of β-Glucosidase activity in the presence of glucose and may enable the optimum use of enzymes for the efficient conversion of high biomass loading saccharification reactions. Communicated by Ramaswamy H. Sarma