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1.
Nat Commun ; 11(1): 5068, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033251

RESUMO

The mineralized collagen fibril is the basic building block of bone, and is commonly pictured as a parallel array of ultrathin carbonated hydroxyapatite (HAp) platelets distributed throughout the collagen. This orientation is often attributed to an epitaxial relationship between the HAp and collagen molecules inside 2D voids within the fibril. Although recent studies have questioned this model, the structural relationship between the collagen matrix and HAp, and the mechanisms by which collagen directs mineralization remain unclear. Here, we use XRD to reveal that the voids in the collagen are in fact cylindrical pores with diameters of ~2 nm, while electron microscopy shows that the HAp crystals in bone are only uniaxially oriented with respect to the collagen. From in vitro mineralization studies with HAp, CaCO3 and γ-FeOOH we conclude that confinement within these pores, together with the anisotropic growth of HAp, dictates the orientation of HAp crystals within the collagen fibril.


Assuntos
Colágeno/química , Minerais/química , Orientação Espacial , Osso e Ossos/química , Criança , Colágeno/ultraestrutura , Cristalização , Durapatita/química , Elétrons , Feminino , Humanos , Modelos Moleculares , Tomografia , Difração de Raios X
2.
Yakugaku Zasshi ; 140(10): 1225-1233, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32999201

RESUMO

This article describes our stereoselective and site-selective chemical methods for exploiting cationic heterocycles as electron-withdrawing groups (EWGs). We envisioned that the phosphoramide N-H proton of a pyridyl phosphoramide 3 would be activated by the cationic pyridinium moiety that is formed upon protonation. The resulting imide-like N-H proton and the acidic pyridinium proton of the pyridinium phosphoramide 3⋅HX cooperate together, making 3⋅HX a highly acidic dual Brønsted acid. The catalytic ability of 3⋅HX was demonstrated in the development of the first asymmetric Diels-Alder reaction between 1-amide dienes and maleimides. Focusing on the activation of N-bromosuccinimide (NBS) because of its structural similarity to maleimides, the enantioselective bromolactonization of trisubstituted olefinic acids was accomplished utilizing pyridyl phosphoramide 3f as a Brønsted base catalyst bearing an acidic N-H proton. Lastly, our strategy for the site-selective acylation of polyol compounds is described. In our system, a pyridine aldoxime ester 10, used as a mild acylating reagent, was activated by a catalytic amount of Lewis acid via the inductive effect of the cationic pyridinium moiety. The resulting metal complex preferentially attracted the alcohol with a Lewis basic site, thereby facilitating selective acylation via a template effect. This metal-template-driven strategy allowed for the site-selective acylation of diverse α-hydroxyamides, including unprotected N-glycolyl aminosugars.


Assuntos
Cátions/química , Cátions/síntese química , Química Orgânica/métodos , Desenvolvimento de Medicamentos/métodos , Elétrons , Compostos Heterocíclicos/química , Compostos Heterocíclicos/síntese química , Acilação , Amidas/química , Catálise , Complexos de Coordenação/química , Reação de Cicloadição , Ésteres/química , Compostos de Pralidoxima/química , Estereoisomerismo
3.
Science ; 369(6508): 1160-1161, 2020 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-32883846
4.
Waste Manag ; 118: 481-490, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32979779

RESUMO

Although commonly viewed as a promising method, dry anaerobic digestion is not been widely applied to dispose of food wastes, especially in developing countries because of its insufficiency in handling with lower mass transfer and high acidic accumulation of the system. Zero valent iron (ZVI) has been found to demonstrate superior performance such as enhancing methane production. However, up to date, the mechanism of ZVI remains unclear. In this study, adding 5 g/L ZVI could improve interspecies hydrogen transfer (IHT) to enhance the dry anaerobic digestion of food wastes, but was unable to resist the shocks of high organic loading. With increasing ZVI dosage to 10 g/L, the performances of digestion systems were improved to maintain the systems stable. With 10 g/L of ZVI addition, electron transfer capacity of the sludge increased by 5.4 folds, and electroactive proteins of sludge increased by 2.3 folds. Microbial community analysis also indicated that the relative abundances of Methanothrix and Methanosarcina performing direct interspecies electron transfer were enriched to 67.5% and 27.2% with 10 g/L ZVI addition, respectively. These results suggested that direct interspecies electron transfer could be established with a proper dosage of ZVI that served as a conductive material to connect electron exchange among microorganisms. Thus, ZVI played a dual role including improving interspecies hydrogen transfer and promoting direct interspecies electron transfer to keep the systems efficient to treat high-solid food wastes.


Assuntos
Hidrogênio , Ferro , Anaerobiose , Reatores Biológicos , Elétrons , Metano , Esgotos
5.
Nat Commun ; 11(1): 4511, 2020 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-32908128

RESUMO

Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) allows structure determination of membrane proteins and time-resolved crystallography. Common liquid sample delivery continuously jets the protein crystal suspension into the path of the XFEL, wasting a vast amount of sample due to the pulsed nature of all current XFEL sources. The European XFEL (EuXFEL) delivers femtosecond (fs) X-ray pulses in trains spaced 100 ms apart whereas pulses within trains are currently separated by 889 ns. Therefore, continuous sample delivery via fast jets wastes >99% of sample. Here, we introduce a microfluidic device delivering crystal laden droplets segmented with an immiscible oil reducing sample waste and demonstrate droplet injection at the EuXFEL compatible with high pressure liquid delivery of an SFX experiment. While achieving ~60% reduction in sample waste, we determine the structure of the enzyme 3-deoxy-D-manno-octulosonate-8-phosphate synthase from microcrystals delivered in droplets revealing distinct structural features not previously reported.


Assuntos
Cristalografia/instrumentação , Elétrons , Dispositivos Lab-On-A-Chip , Lasers , Aldeído Liases/ultraestrutura , Proteínas de Escherichia coli/ultraestrutura , Hidrodinâmica
6.
Urologiia ; (4): 14-17, 2020 Sep.
Artigo em Russo | MEDLINE | ID: mdl-32897008

RESUMO

OBJECTIVES: the study of the nature and severity of the reorganization of the structural elements of the bladder wall on experimental models of IC / BPS at the optical and ultrastructural levels. MATERIALS AND METHODS: The experimental model of IC / SBMP was created on 22 white New Zealand female rabbits weighing 1500-2000 g. The animals were divided into 2 groups: group 1 - 15 rabbits, which were introduced into the bladder wall urine taken from the animals bladder; Group 2 (control) - 7 animals that were injected into the bladder wall with a 0.9% NaCl solution. The biomaterial was examined by electron microscopy. The structural elements of the lamina propria of the bladder mucosa were evaluated. RESULTS: In the bladder mucosa of the experimental model, perivascular infiltration by inflammatory cells, pronounced edema of the lamina propria of the bladder mucosa, and the presence of numerous plasma cells having close contacts with macrophages, fibroblasts, and lymphocytes were revealed. In the nucleus of lymphocytes of a peripherally located supercondensed heterochromatin showed their apoptotic state. Edematous fluid was determined, penetrating mainly through the fenestra, located in the peripheral parts of the endothelial cells of capillaries and postcapillary venules. CONCLUSION: The study of the structural elements of the lamina propria of the bladder mucosa in the experiment by the method of electron microscopy made it possible to identify changes caused by the inflammatory process, both of an acute and productive nature. The results obtained showed that toxic damage to the lamina propria of the bladder mucosa causes apoptosis of fibroblasts of the lamina propria, leads to loosening of collagen fibers and, ultimately, to a decrease in the protective factors of the mucous membrane.


Assuntos
Cistite Intersticial , Animais , Elétrons , Células Endoteliais , Feminino , Microscopia Eletrônica , Membrana Mucosa , Coelhos
7.
J Environ Sci (China) ; 97: 132-140, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32933728

RESUMO

As a novel alternative to traditional perfluoroalkyl substances (PFASs), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), hexafluoroproplyene oxide trimer acid (HFPO-TA) has been detected worldwide in surface water. Moreover, recent researches have demonstrated that HFPO-TA has stronger bioaccumulation potential and higher hepatotoxicity than PFOA. To treat these contaminants e.g. PFOA and PFOS, some photochemical techniques by adding exogenous substances had been reported. However, there is still no report for the behavior of HFPO-TA itself under direct UV irradiation. The current study investigated the photo-transformation of HFPO-TA under UV irradiation in aqueous solution. After 72 hr photoreaction, 75% degradation ratio and 25% defluorination ratio were achieved under ambient condition. Reducing active species, i.e., hydrated electrons and active hydrogen atoms, generated from water splitting played dominant roles in degradation of HFPO-TA, which was confirmed by different effects of reaction atmospheres and quenching experiments. A possible degradation pathway was proposed based on the products identification and theoretical calculations. In general, HFPO-TA would be transformed into shorter-chain PFASs, including hexafluoropropylene oxide dimer acid (HFPO-DA), perfluoropropionic acid (PFA) and trifluoroacetate (TFA). This research provides basic information for HFPO-TA photodegradation process and is essential to develop novel remediation techniques for HFPO-TA and other alternatives with similar structures.


Assuntos
Fluorcarbonetos , Caprilatos , Elétrons , Óxidos , Fotólise , Raios Ultravioleta
8.
Ecotoxicol Environ Saf ; 204: 111136, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32798755

RESUMO

High temperature can lead to increased production of excess light energy, thus reducing photosynthetic capacity in plants. Photosynthetic cyclic electron flow (CEF) in photosystem I (PSI) can effectively protect photosystems, but its physiological mechanism under high temperature is poorly understood. In this study, antimycin A (AA) and thenoyltrifluoroacetone (TTFA) were used to inhibit PGR5-and NDH-dependent CEF pathways, respectively, to reveal the photoprotective functions of CEF for PSII in tobacco leaves under high temperature stress (37 °C, HT). High temperatures caused decreases in maximal photochemistry efficiency (Fv/Fm) and damaged photosystem II (PSII) in tobacco leaves. Under AA inhibition of PGR5-dependent CEF, high temperature increased the fluorescence intensity of point O (Fo) in OJIP curves, i.e., the energy absorption per active reaction center (ABS/RC), the trapping rate of the reaction center (TRo/RC), and the electron transport efficiency per reaction center (ETo/RC) in tobacco leaves. High temperature induced an increase in the hydrogen peroxide content and a decrease in pigment content in tobacco leaves. Under the high temperature treatment, inhibition of PGR5-dependent CEF reduced the activities of the PSII reaction center significantly, destroyed the oxygen-evolving complex (OEC), and impeded photosynthetic electron transfer from PSII to the plastoquinone (PQ) pool in tobacco leaves. The TTFA treatment inhibited the NDH-dependent pathway under high temperature conditions, with the relative fluorescence intensity of point I (VI) decreased significantly, and the content of hydrogen peroxide and superoxide anion increased significantly. Additionally, Fo and the redox degree of the PSII donor side (Wk) increased, and pigment content decreased compared to the control, but with little change compared to high temperature treatment, indicating that the inhibition of the NDH-dependent pathway directly weakened the capacity of the PQ pool to lead to the accumulation of reactive oxygen species (ROS) in tobacco leaves. In conclusion, CEF alleviated damage to the photosynthetic apparatus in tobacco leaves by increasing PSII heat dissipation, reducing ROS production, and maintaining the stability of the PQ pool to accommodate photosynthetic electron flow.


Assuntos
Temperatura Alta , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema I/metabolismo , Tabaco/metabolismo , Clorofila/metabolismo , Transporte de Elétrons , Elétrons , Fluorescência , Oxirredução , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/metabolismo , Temperatura , Tabaco/fisiologia
9.
J Environ Sci (China) ; 96: 171-177, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32819691

RESUMO

Microbial fuel cells (MFC) utilize microbes as catalysts to convert chemical energy to electricity. Inocula used for MFC operation must therefore contain active microbial population. The dye reduction-based electron-transfer activity monitoring (DREAM) assay was employed to evaluate different inocula used in MFCs for their microbial bioelectrical activity. The assay utilizes the redox property of Methylene Blue to undergo color change from blue to colorless state upon microbial reduction. The extent of Methylene Blue reduction was denoted as the DREAM assay coefficient. DREAM assay was initially performed on a microbial culture along with the growth curve and estimation of colony forming units (CFUs). DREAM coefficient correlated to the CFU/mL obtained over time as growth progressed. The assay was then extended to water samples (domestic sewage, lake and a man-made pond) serving as inocula in MFCs. Domestic wastewater gave the highest DREAM coefficient (0.300 ± 0.05), followed by pond (0.224 ± 0.07) and lake (0.157 ± 0.04) water samples. Power density obtained conformed to the DREAM coefficient values, with the three samples generating power densities of 46.45 ± 5.1, 36.12 ± 3.2 and 25.08 ± 4.3 mW/m2 respectively. We have also studied the role of addition of various carbon sources and their concentrations towards improving the sensitivity of the assay. The DREAM assay is a rapid, easy-to-perform and cost-effective method to assess inocula for their suitability as anolytes in terms of electron transfer potential in MFCs.


Assuntos
Fontes de Energia Bioelétrica , Corantes , Eletricidade , Eletrodos , Elétrons , Oxirredução , Águas Residuárias
10.
J Environ Manage ; 275: 111216, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32858270

RESUMO

Lignocellulosic materials can be used as slow release electron donor (SRED) for biological sulfate reduction, potentially enhancing the subsequent metal sulfide precipitation. Lignocellulosic materials require a pre-treatment step in other biotechnological applications, but pre-treatment strategies for its use as a SRED for biological sulfate reduction have not yet been tested. Three pre-treatments strategies (mechanical, acid, and mechanical followed by acid pre-treatment) were tested to enhance electron donor release from brewery spent grain (BSG), and compared to a non-pre-treated control. Mechanical pre-treatment provided the highest sulfate removal rate (82.8 ± 8.8 mg SO42-.(g TVS.day)-1), as well as the highest final sulfide concentration (441.0 ± 34.4 mg.L-1) at mesophilic conditions. BSG submitted to mechanical pre-treatment was also assessed under psychrophilic and thermophilic conditions. Under mesophilic and psychrophilic conditions, both sulfate reduction and methane production occurred. Under psychrophilic conditions, the sulfate reduction rate was lower (25 ± 2.0 mg SO42-.(g TVS.day)-1), and the sulfide formation depended on lactate addition. A metal precipitation assay was conducted to assess whether the use of SRED enhances metal recovery. Zinc precipitation and recovery with chemical or biogenic sulfide from the BSG batches were tested. Sulfide was provided in a single spike or slowly added, mimicking the effect of SRED. ZnS was formed in all conditions, but better settling particles were obtained when sulfide was slowly added, regardless of the sulfide source.


Assuntos
Reatores Biológicos , Elétrons , Oxirredução , Sulfatos , Sulfetos , Temperatura
12.
Water Res ; 183: 116060, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32750534

RESUMO

Chlorinated aliphatic hydrocarbons (CAHs) have been frequently detected in aquifers in recent years. Owing to the bioaccumulation and toxicity of CAHs, it is essential to explore high-efficiency technologies for their complete dechlorination in groundwater. At present, the most widely used abiotic and biotic remediation technologies are based on zero-valent iron (ZVI) and functional anaerobic bacteria (FAB), respectively. However, the main obstacles to the full potential of both technologies in the field include their lowered efficiencies and increased economic costs due to the co-existence of a variety of natural electron acceptors in the environment, such as dissolved oxygen (DO), nitrate (NO3-), sulfate (SO42-), ferric iron (Fe (III)), bicarbonate (HCO3-), and even water, which compete for electrons with the target contaminants. Therefore, a clear understanding of the mechanisms governing electron competition and electron selectivity is significant for the accurate evaluation of the effectiveness of both technologies under natural hydrochemical conditions. We collected data from both abiotic and biotic CAH-remediation systems, summarized the dechlorination and undesired reactions in groundwater, discussed the characterization methods and general principles of electron competition, and described strategies to improve electron selectivity in both systems. Furthermore, we reviewed the emerging ZVI-FAB coupled system, which integrates abiotic and biotic processes to enhance dechlorination performance and electron utilization efficiency. Lastly, we propose future research needs to quantitatively understand the electron competition in abiotic, biotic, and coupled systems in more detail and to promote improved electron selectivity in groundwater remediation.


Assuntos
Água Subterrânea , Hidrocarbonetos Clorados , Poluentes Químicos da Água/análise , Elétrons , Ferro
13.
J Chromatogr A ; 1627: 461421, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823116

RESUMO

Herein we present an efficient, column-switching method that relies on a custom-made T-union passive diffusion micromixer to assist water dilution and promote trap solute focusing of a high sample volume dissolved in pure organic solvent using a 0.075 mm i.d. nano-LC column. This method allows injecting 20 µL (or higher) of sample volume, speeding up the analysis time, with a 400-fold increase of the limits of quantitation for selected compounds. Five pesticides in different media were used as model compounds, and the analyses were carried out with a triple quadrupole mass spectrometer equipped with a Liquid Electron Ionization (LEI) LC-MS interface working in multiple reaction monitoring (MRM) mode. The system microfluidics were investigated using COMSOL modeling software. Robustness of the entire system was evaluated using a post-extraction addition soil extracts with limits of detection values spanning from 0.10 to 0.45 µg/L. Reproducible results in terms of peak area, peak shape, and retention times were achieved in soil matrix. Repeatability test on peak area variations were lower than 10%.


Assuntos
Cromatografia de Fase Reversa/métodos , Elétrons , Microfluídica/métodos , Nanopartículas/química , Espectrometria de Massas em Tandem/métodos , Água/química , Acetonitrilos/química , Difusão , Limite de Detecção , Praguicidas/análise , Reprodutibilidade dos Testes , Solventes/química
14.
Bioresour Technol ; 316: 123901, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32739579

RESUMO

The enhancement of zerovalent iron (ZVI) on anaerobic digestion (AD) has been proved, but there are still some problems that constrain the large-scale application of ZVI, such as the destruction of cell membrane and the inhibition of methanogenesis led by rapid H2 accumulation. Aiming at these problems, sulfidated microscale zerovalent iron (S-mZVI) was employed to evaluate its effect on anaerobic co-digestion (AcoD) of waste activated sludge (WAS) and food waste (FW). Experimental results showed that S-mZVI promoted the direct interspecies electron transfer (DIET) between specific bacteria and methanogens, resulting in higher methane yield. At S-mZVI 10 g/L, the cumulative methane yield and ETS activity reached 264.78 mL/g-VS and 24.62 mg INTF/(g-TS h), which was 1.33 and 1.83 times that of blank. Microbiological analysis demonstrated that the abundance of DIET-related microorganisms such as Syntrophomonas, Methanosarcina and Methanobacterium increased with the increasing dosage of S-mZVI.


Assuntos
Eliminação de Resíduos , Esgotos , Anaerobiose , Reatores Biológicos , Elétrons , Alimentos , Ferro , Metano
15.
Bioresour Technol ; 316: 123919, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32771939

RESUMO

Ferricyanide is often used in microbial fuel cells (MFCs) to avoid oxygen intrusion that occurs with air cathodes. However, MFC internal resistances using ferricyanide can be larger than those with air cathodes even though ferricyanide results in higher power densities. Using a graphite fiber brush cathode and a ferricyanide catholyte (FC-B) the internal resistance was 62 ± 4 mΩ m2, with 84 ± 8 mΩ m2 obtained using ferricyanide and a flat carbon paper cathode (FC-F) and only 51 ± 1 mΩ m2 using a 70% porosity air cathode (A-70). The FC-B MFCs produced the highest maximum power density of all configurations examined: 2.46 ± 0.26 W/m2, compared to 1.33 ± 0.14 W/m2 for the A-70 MFCs. The electrode potential slope (EPS) analysis method showed that electrode resistances were similar for ferricyanide and air-cathode MFCs, and that higher power was due to the larger experimental working potential (500 ± 12 mV) of ferricyanide compared to the air cathode (233 ± 5 mV).


Assuntos
Fontes de Energia Bioelétrica , Eletricidade , Eletrodos , Elétrons , Oxidantes , Oxigênio
16.
Water Res ; 185: 116142, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32823193

RESUMO

Natural dissolved organic matter (DOM) is ubiquitous in environment and plays an important role in numerous environmental processes. Although the molecular basis of the reactivity of DOM remains poorly understood due to its extreme complexity, redox-active carbonyls (aromatic ketones/aldehydes and quinones) within DOM are believed vitally important. Except the rough determination of total carbonyls (including non-redox active -COOR) based on inflexible 13C chemical shift range by expensive and time-consuming solid-state nuclear magnetic resonance (NMR), there is no ready method to quantify redox-active carbonyls in DOM. Here we show that after treatment with sodium borohydride (NaBH4) by selectively eliminating redox-active carbonyls, quenched fluorescence of carbon quantum dots (CD) by DOM recovered dramatically, and displayed a good linear relationship between redox-active carbonyls detected and DOM concentration (R2 ≥ 0.977), thus allowing first quantitative determination of the redox-active carbonyls of DOM. Eight DOM isolates present 0.59%-0.90% redox-active carbonyls by the current method. And this method is robust from coexisting proteins and salts. This method could provide better or equal instructive results compared with solid-state NMR for total carbonyls or electrochemical method for electron-accepting capacities (EAC). Our results provide the underlying structural basis of many important geochemical processes that mediated by DOM. We posit that this method could apply to other complex molecular systems such as the atmospheric aerosols and extracellular polymeric substances (EPS), too.


Assuntos
Técnicas Eletroquímicas , Elétrons , Oxirredução
17.
Water Res ; 185: 116235, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32823195

RESUMO

Ozonation of secondary wastewater treatment plant effluent for the abatement of organic micropollutants requires an accurate process control, which can be based on monitoring ozone-induced changes in dissolved organic matter (DOM). This study presents a novel automated analytical system for monitoring changes in the electron donating capacity (EDC) and UV absorbance of DOM during ozonation. In a first step, a quantitative photometric EDC assay was developed based on electron-transfer reactions from phenolic moieties in DOM to an added chemical oxidant, the radical cation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS·+). The assay is highly sensitive (limit of quantification ∼0.5 mgDOC·L-1) and EDC values of model DOM isolates determined by this assay were in good agreement with values determined previously by mediated electrochemical oxidation (slope = 1.01 ± 0.07, R2 = 0.98). In a second step, the photometric EDC measurement method was transferred onto an automated fluidic system coupled to a photometer (EDC analyzer). The EDC analyzer was then used to monitor changes in EDC and UV absorbance of secondary wastewater effluent treated with ozone. While both parameters exhibited a dose-dependent decrease, a more pronounced decrease in EDC as compared to UV absorbance was observed at specific ozone doses up to 0.4 mgO3·gDOC-1. The concentration of 17α-ethinylestradiol, a phenolic micropollutant with a high ozone reactivity, decreased proportionally to the EDC decrease. In contrast, abatement of less ozone-reactive micropollutants and bromate formation started only after a pronounced initial decrease in EDC. The on-line EDC analyzer presented herein will enable a comprehensive assessment of the combination of EDC and UV absorbance as control parameters for full-scale ozonation.


Assuntos
Ozônio , Poluentes Químicos da Água , Purificação da Água , Bromatos , Elétrons , Águas Residuárias/análise
18.
Water Res ; 185: 116238, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32745745

RESUMO

Lately, extracellular electron transfer (EET) is widely disclosed on the surface of the bioelectrodes, and conductive (bio)carriers involved in anaerobic biodegradation/biosynthesis. By electrostimulation, microbial consortia colonize the electrodes and accelerate substrate (waste/wastewater) metabolization on the bioanode or biosynthesize value-added products (methane, acetate, etc.) on the biocathode. However, the connections and contributions of planktonic microbial communities have not been effectually understood. Herein, electromethanogenesis were comprehensively investigated in response to different driving-force modes: intermittent electric field applied by manual on-off or natural solar power and continuous electrical field. Intermittent modes implied preferable electron transfer efficiency, higher methane yield and energy recovery efficiencies from wastewater by the microbes in the bulk solutions. Microbial community analysis revealed that less electroactive microorganisms and acetotrophic methanogens in the bulk solutions were accommodated under the intermittent modes than the continuous electrical field, whereas more fermentative bacteria and hydrogenotrophic methanogens evolved in the intermittent driving modes, implying that the interspecies electron transfer both on and away from the electrodes were favorably regulated. Redundancy and network analysis proved that more complicated ecological interactions were shown in the bulk solutions with the periodic on/off of electrical field. These results hinted that the electrostimulation effectively regulated EET bacteria, even in the bulk solutions, while more efficient electron flow to methane through interspecies electron transfer was developed during the intermittent driving regulation.


Assuntos
Elétrons , Águas Residuárias , Eletrodos , Transporte de Elétrons , Metano
19.
Artigo em Japonês | MEDLINE | ID: mdl-32814736

RESUMO

PURPOSE: The purpose of this study was to improve the accuracy of dose-distribution calculations by understanding how the calculated dose varies with the change in the relative electron density replacing polymethyl methacrylate (PMMA) in patient-specific quality assurance. METHOD: We calculated the relative electron density at which dose attenuation in each dose calculation algorithm coincides with the measured value of the dose attenuation of single-field irradiation. Next, the dose change was calculated by changing the relative electron density or physical electron density for substituting PMMA for each X-ray energy and calculation algorithm. Furthermore, using clinical plans, changes in point-dose verification and dose-distribution verification that occurred when the relative electron density or physical electron density was varied were investigated. RESULTS: The dose attenuation varies depending on the dose-calculation algorithm, and the optimum value of the electron density is different for each. After the electron density optimization, the point dose verification using the 97.1% to 98.3% (3%/3 mm), 90.0% to 94.3% (2%/3 mm) and gained a dominant improvement tendency (P<0.001). CONCLUSIONS: We clarified dose change accompanying relative electron density or physical electron density change. We concluded that the accuracy of dose-distribution calculation for verification improves by replacing PMMA with optimal relative electron density or physical electron density.


Assuntos
Elétrons , Polimetil Metacrilato , Algoritmos , Humanos , Imagens de Fantasmas , Radiometria , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
20.
PLoS One ; 15(8): e0236894, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785279

RESUMO

High-quality three-dimensional structural data is of great value for the functional interpretation of biomacromolecules, especially proteins; however, structural quality varies greatly across the entries in the worldwide Protein Data Bank (wwPDB). Since 2008, the wwPDB has required the inclusion of structure factors with the deposition of x-ray crystallographic structures to support the independent evaluation of structures with respect to the underlying experimental data used to derive those structures. However, interpreting the discrepancies between the structural model and its underlying electron density data is difficult, since derived sigma-scaled electron density maps use arbitrary electron density units which are inconsistent between maps from different wwPDB entries. Therefore, we have developed a method that converts electron density values from sigma-scaled electron density maps into units of electrons. With this conversion, we have developed new methods that can evaluate specific regions of an x-ray crystallographic structure with respect to a physicochemical interpretation of its corresponding electron density map. We have systematically compared all deposited x-ray crystallographic protein models in the wwPDB with their underlying electron density maps, if available, and characterized the electron density in terms of expected numbers of electrons based on the structural model. The methods generated coherent evaluation metrics throughout all PDB entries with associated electron density data, which are consistent with visualization software that would normally be used for manual quality assessment. To our knowledge, this is the first attempt to derive units of electrons directly from electron density maps without the aid of the underlying structure factors. These new metrics are biochemically-informative and can be extremely useful for filtering out low-quality structural regions from inclusion into systematic analyses that span large numbers of PDB entries. Furthermore, these new metrics will improve the ability of non-crystallographers to evaluate regions of interest within PDB entries, since only the PDB structure and the associated electron density maps are needed. These new methods are available as a well-documented Python package on GitHub and the Python Package Index under a modified Clear BSD open source license.


Assuntos
Biologia Computacional , Bases de Dados de Proteínas , Elétrons , Proteínas/química
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