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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Reveal of Uranium Bioremediation Mechanisms by Bacillus Species through Proteomics Studies

Radionuclides, such as Uranium (U) and heavy metals continue to pose threats to the ecosystem health and processes at the Department of Energy (DOE) managed, Savannah River Site (SRS), located along the Savannah River near Aiken, SC. Such co-contaminated environments are difficult to remediate using conventional excavation and disposal or pump-and-treat approaches. Globally, more than 109 tons of uranium contaminated areas pose a long term threat to human and ecological health. Even with presented low concentrations in the brain, central nervous effects are still observed. Uranium and depleted uranium (DU) have long term effects on the kidneys. Some small general health effects include severe headaches and breathing problems. Uranus ions are toxic to living cells because they inhibit metabolism of carbohydrates by blocking ATP binding sites. Bioremediation by microorganisms represents an alternative solution, which is advantageous because of the possibility of biosorbent regeneration, cost-effectiveness, increased metal removal and easy recovery of some valuable metals. Bacillus sp. bacterium was previously used in the bioremediation of heavy metals in coal mine run off waters of SRS. However, its ability to bioremediate uranium was unknown so far. Hence, in the present study, uranium bioremediation by Bacillus sp. bacterium was investigated. The mechanism of bioremediation was also revealed through proteomics studies. Heavy metals contamination poses a serious threat to water, soil and human health. Soil and water are contaminated due to excessive exploitation of uranium mines for generation of nuclear energy and weaponry. It is not degradable easily and persist in soil and water for a long period of time due to its long half- life. Savannah river site (SRS) is one of the uranium contaminated sites. The physical or chemical remediation techniques are costly and complex. Microbial system approaches with competent bacteria has received increased attention due to its adaptability in various environmental matrices and cost effectiveness. However, even though there are multiple suggested pathways (F1), the specific mechanisms that drive this behavior are still unclear, especially with popular microorganisms such as Bacillus species. In a previous research (Ibeanusi et al, 2003) Bacillus sp. was shown to detoxify and precipitate a variety of heavy metals in coal pile runoff waters of SRS site. Additionally, genomic analysis demonstrated that this microorganism posses multiple attributes for chemical transport regulation and metabolic pathways. U remediation occurs during the first 20 hours of exposure. During this time period, Bacillus sp. may work primarily under two mechanisms - sorption and accumulation. These two mechanisms simultaneously work to protect the microorganism from high concentrations. Figure 10 demonstrates that certain proteins are up regulated and down regulated under extreme stressful conditions. Membrane fraction proteins were up regulated. Cytosolic fraction proteins were down regulated. This protein information coincides with the adsorption behavior. Bacillus sp. is a good candidate for U remediation at various concentrations.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Perspective on Technical Lignin Fractionation

Technical lignin extracted from pulping and biorefining processes provides a class of complex and polydisperse phenolic polymers. Preparation of lignin with lower structural complexity and polydispersity through lignin fractionation is one of the primary solutions to engineer lignin into a value-added material. Sequential lignin fraction by pH controlled precipitation from 12 to 1 is one of the primary developed methods. Partial solubility of lignin in organic solvents is another promising method for lignin fractionation. Organic solvents with different polarity and solubility factors are able to fractionate lignin, yielding a more homogeneous chemical structure. As a modification of the lignin fractionation process using solvents, water/organic solvents mixture, such as propan-2-one, alcohols, and acetic acid, from room to high temperature has been proposed as a greener method for lignin fractionation. Using membrane technology is another promising method and current results indicate a good potential for lignin recovery and fractionation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Membrane Profiling by Free Flow Electrophoresis and SWATH-MS to Characterize Subcellular Compartment Proteomes in Mesembryanthemum crystallinum

The study of subcellular membrane structure and function facilitates investigations into how biological processes are divided within the cell. However, work in this area has been hampered by the limited techniques available to fractionate the different membranes. Free Flow Electrophoresis (FFE) allows for the fractionation of membranes based on their different surface charges, a property made up primarily of their varied lipid and protein compositions. In this study, high-resolution plant membrane fractionation by FFE, combined with mass spectrometry-based proteomics, allowed the simultaneous profiling of multiple cellular membranes from the leaf tissue of the plant Mesembryanthemum crystallinum. Comparisons of the fractionated membranes’ protein profile to that of known markers for specific cellular compartments sheds light on the functions of proteins, as well as provides new evidence for multiple subcellular localization of several proteins, including those involved in lipid metabolism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Effects of motor patterns on water-soluble and membrane proteins and cholinesterase activity in subcellular fractions of rat brain tissue

Albino rats were kept for a year under conditions of daily motor load or constant hypokinesia. An increase in motor activity results in a rise in the acetylcholinesterase activity determined in the synaptosomal and purified mitochondrial fractions while hypokinesia induces a pronounced decrease in this enzyme activity. The butyrylcholinesterase activity somewhat decreases in the synaptosomal fraction after hypokinesia but does not change under the motor load pattern. Motor load causes an increase in the amount of synaptosomal water-soluble proteins possessing an intermediate electrophoretic mobility and seem to correspond to the brain-specific protein 14-3-2. In the synaptosomal fraction the amount of membrane proteins with a low electrophoretic mobility and with the cholinesterase activity rises. Hypokinesia, on the contrary, decreases the amount of these membrane proteins.

Pevzner, L. Z.↗
NASA NTRS1998

Identification of sucrose synthase as an actin-binding protein

Several lines of evidence indicate that sucrose synthase (SuSy) binds both G- and F-actin: (i) presence of SuSy in the Triton X-100-insoluble fraction of microsomal membranes (i.e. crude cytoskeleton fraction); (ii) co-immunoprecipitation of actin with anti-SuSy monoclonal antibodies; (iii) association of SuSy with in situ phalloidin-stabilized F-actin filaments; and (iv) direct binding to F-actin, polymerized in vitro. Aldolase, well known to interact with F-actin, interfered with binding of SuSy, suggesting that a common or overlapping binding site may be involved. We postulate that some of the soluble SuSy in the cytosol may be associated with the actin cytoskeleton in vivo.

Non-NASA Center↗
DOE OSTI2023

Technical Lignin Fractionation: A Powerful Tool for Lignin Structure Homogenization and Its Application

Extracted lignin as a by-product of pulping and bio-refining processes is the main available bio-phenolic polymer. The structural complexity, polydispersity, and black color of lignin are the main limiting factors for its application. Preparation of lignin with lower structural complexity and polydispersity through lignin fractionation is one of the primary solutions to engineer lignin into a value-added material. Sequential lignin fractionation was developed based on pH reduction from alkaline to acidic using mineral acids and was recently optimized using carbon dioxide as a pH controller. The partial solubility of lignin in organic solvents is another promising method for lignin fractionation. Organic solvents with different polarity and solubility factors are able to fractionate lignin, yielding a more homogeneous chemical structure. As a modification of the lignin fractionation process, the use of solvents, water/organic solvent mixtures, such as alcohols, and acetic acid from room to high temperature has been proposed as a greener method for lignin fractionation. Using membrane technology is another promising method and current results indicate its good potential for lignin recovery and fractionation.

Sadeghifar, Hasan↗
NASA NTRS1988

Inhibition of nitrate transport by anti-nitrate reductase IgG fragments and the identification of plasma membrane associated nitrate reductase in roots of barley seedlings

Membrane associated nitrate reductase (NR) was detected in plasma membrane (PM) fractions isolated by aqueous two-phase partitioning from barley (Hordeum vulgare L. var CM 72) roots. The PM associated NR was not removed by washing vesicles with 500 millimolar NaCl and 1 millimolar EDTA and represented up to 4% of the total root NR activity. PM associated NR was stimulated up to 20-fold by Triton X-100 whereas soluble NR was only increased 1.7-fold. The latency was a function of the solubilization of NR from the membrane. NR, solubilized from the PM fraction by Triton X-100 was inactivated by antiserum to Chlorella sorokiniana NR. Anti-NR immunoglobulin G fragments purified from the anti-NR serum inhibited NO3- uptake by more than 90% but had no effect on NO2- uptake. The inhibitory effect was only partially reversible; uptake recovered to 50% of the control after thorough rinsing of roots. Preimmune serum immunoglobulin G fragments inhibited NO3- uptake 36% but the effect was completely reversible by rinsing. Intact NR antiserum had no effect on NO3- uptake. The results present the possibility that NO3- uptake and NO3- reduction in the PM of barley roots may be related.

NASA Discipline Number 61-10↗
NASA NTRS1989

Evidence for a plasma-membrane-bound nitrate reductase involved in nitrate uptake of Chlorella sorokiniana

Anti-nitrate-reductase (NR) immunoglobulin-G (IgG) fragments inhibited nitrate uptake into Chlorella cells but had no affect on nitrate uptake. Intact anti-NR serum and preimmune IgG fragments had no affect on nitrate uptake. Membrane-associated NR was detected in plasma-membrane (PM) fractions isolated by aqueous two-phase partitioning. The PM-associated NR was not removed by sonicating PM vesicles in 500 mM NaCl and 1 mM ethylenediaminetetraacetic acid and represented up to 0.8% of the total Chlorella NR activity. The PM NR was solubilized by Triton X-100 and inactivated by Chlorella NR antiserum. Plasma-membrane NR was present in ammonium-grown Chlorella cells that completely lacked soluble NR activity. The subunit sizes of the PM and soluble NRs were 60 and 95 kDa, respectively, as determined by sodium-dodecyl-sulfate electrophoresis and western blotting.

Non-NASA Center↗
NASA NTRS1992

Comparison of developmental gradients for growth, ATPase, and fusicoccin-binding activity in mung bean hypocotyls

A comparison has been made of the developmental gradients along a mung bean (Vigna radiata L.) hypocotyl of the growth rate, plasma membrane ATPase, and fusicoccin-binding protein (FCBP) activity to determine whether they are interrelated. The hook and four sequential 7.5 millimeter segments of the hypocotyl below the hook were cut. A plasma membrane-enriched fraction was isolated from each section by aqueous two-phase partitioning and assayed for vanadate-sensitive ATPase and FCBP activity. Each gradient had a distinctive and different pattern. Endogenous growth rate was maximal in the second section and much lower in the others. Vanadate-sensitive ATPase activity was maximal in the third section, but remained high in the older sections. Amounts of ATPase protein, shown by specific antibody binding, did not correlate with the amount of vanadate-sensitive ATPase activity in the three youngest sections. FCBP activity was almost absent in the first section, then increased to a maximum in the oldest sections. These data show that the growth rate is not determined by the ATPase activity, and that there are no fixed ratios between the ATPase and FCBP.

Non-NASA Center↗
DOE OSTI2023

Post-Hydration Crosslinking of Ion Exchange Membranes to Control Water Content

The utilization of crosslinking as a technique to limit excess water uptake in ion exchange membranes is a well-established approach. However, traditional methods involve performing the crosslinking reaction before the membrane self-segregates into hydrophilic and hydrophobic domains upon exposure to water. In this study, we employ numerical and molecular simulations to explore the potential of post-hydration crosslinking of the polymer at subsaturated conditions. This process allows for the development of a nanosegregated morphology, which establishes well-connected but narrow water channels, while limiting additional sorption of water. The significant reduction in membrane swelling observed in our study indicates that post-hydration crosslinking could be a promising approach to regulate water uptake in ion exchange membranes. Here based on our analyses, we propose chemical crosslinking strategies that may yield high membrane gel fractions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Framework for predicting the fractionation of complex liquid feeds via polymer membranes

The separation of complex liquid hydrocarbon mixtures was recently demonstrated using the glassy polymer SBAD-1, showing that small molecule fractionation is possible by such organic membrane materials. Here, in this work, we develop a framework that will enable workable predictions of permeate flux and composition in complex hydrocarbon liquids through intrinsically porous glassy polymers. The predictions are made by incorporating experimentally-derived unary sorption and diffusion parameters in a Maxwell-Stefan framework coupled with multicomponent sorption models and various distinct diffusion phenomena. Across the range of sorption and diffusion phenomena considered, both the conventional Flory-Huggins model and the proposed Langmuir + Flory-Huggins sorption model combined with a simple average guest diffusivity or a more complex free-volume theory-based transport resulted in the lowest prediction error for three chosen multicomponent separations. The proposed Maxwell-Stefan framework simply requires pure component transport parameters to allow a fast approximation of the separation of multicomponent liquid hydrocarbon feeds that can potentially be extended to more complex feeds such as crude oil fractions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2000

Comparison of GLUT1, GLUT3, and GLUT4 mRNA and the subcellular distribution of their proteins in normal human muscle

Basal, "insulin-independent" glucose uptake into skeletal muscle is provided by glucose transporters positioned at the plasma membrane. The relative amount of the three glucose transporters expressed in muscle has not been previously quantified. Using a combination of qualitative and quantitative ribonuclease protection assay (RPA) methods, we found in normal human muscle that GLUT1, GLUT3, and GLUT4 mRNA were expressed at 90 +/- 10, 46 +/- 4, and 156 +/- 12 copies/ng RNA, respectively. Muscle was fractionated by DNase digestion and differential sedimentation into membrane fractions enriched in plasma membranes (PM) or low-density microsomes (LDM). GLUT1 and GLUT4 proteins were distributed 57% to 67% in LDM, whereas GLUT3 protein was at least 88% in the PM-enriched fractions. These data suggest that basal glucose uptake into resting human muscle could be provided in part by each of these three isoforms.

NASA Discipline Regulatory Physiology↗
NASA NTRS1998

A novel calmodulin-regulated Ca2+-ATPase (ACA2) from Arabidopsis with an N-terminal autoinhibitory domain

To study transporters involved in regulating intracellular Ca2+, we isolated a full-length cDNA encoding a Ca2+-ATPase from a model plant, Arabidopsis, and named it ACA2 (Arabidopsis Ca2+-ATPase, isoform 2). ACA2p is most similar to a "plasma membrane-type" Ca2+-ATPase, but is smaller (110 kDa), contains a unique N-terminal domain, and is missing a long C-terminal calmodulin-binding regulatory domain. In addition, ACA2p is localized to an endomembrane system and not the plasma membrane, as shown by aqueous-two phase fractionation of microsomal membranes. ACA2p was expressed in yeast as both a full-length protein (ACA2-1p) and an N-terminal truncation mutant (ACA2-2p; Delta residues 2-80). Only the truncation mutant restored the growth on Ca2+-depleted medium of a yeast mutant defective in both endogenous Ca2+ pumps, PMR1 and PMC1. Although basal Ca2+-ATPase activity of the full-length protein was low, it was stimulated 5-fold by calmodulin (50% activation around 30 nM). In contrast, the truncated pump was fully active and insensitive to calmodulin. A calmodulin-binding sequence was identified within the first 36 residues of the N-terminal domain, as shown by calmodulin gel overlays on fusion proteins. Thus, ACA2 encodes a novel calmodulin-regulated Ca2+-ATPase distinguished by a unique N-terminal regulatory domain and a non-plasma membrane localization.

Non-NASA Center↗
NASA NTRS1973

Ultrafiltration by a compacted clay membrane. I - Oxygen and hydrogen isotopic fractionation. II - Sodium ion exclusion at various ionic strengths.

Laboratory experiments were carried out to determine the magnitude of the isotopic fractionation of distilled water and of 0.01N NaCl forced to flow at ambient temperature under a hydraulic pressure drop of 100 bars across a montmorillonite disk compacted to a porosity of 35% by a pressure of 330 bars. The ultrafiltrates in both experiments were depleted in D by 2.5% and in O-18 by 0.8% relative to the residual solution. No additional isotopic fractionation due to a salt-filtering mechanism was observed at NaCl concentrations up to 0.01N. Adsorption is most likely the principal mechanism which produces isotopic fractionation, but molecular diffusion may play a minor role. The results suggest that oxygen and hydrogen isotopic fractionation of ground water during passage through compacted clayey sediments should be a common occurrence, in accord with published interpretations of isotopic data from the Illinois and Alberta basins. It is shown how it is possible to proceed from the ion exchange capacity of clay minerals and, by means of the Donnan membrane equilibrium concept and the Teorell-Meyer-Siever theory, develop a theory to explain why and to what extent ultrafiltration occurs when solutions of known concentration are forced to flow through a clay membrane.

Coplen, T. B.↗
DOE OSTI2025

The Role of Water Volume Fraction on Water Adsorption in Anion Exchange Membranes

Water absorption plays a key role in the performance of polymeric anion exchange membranes. It influences important properties such as ionic conductivity and mechanical strength and alters their performance as solid electrolytes in hydrogen electrochemical devices for energy conversion. However, computational approaches that address the relationship between the polymer design and the absorption process are scarce. In this work, we introduce a simple thermodynamic model to predict the water absorption isotherms of polyelectrolyte membranes in contact with a water vapor reservoir that incorporates the specific chemical design of the polymers. The model accurately predicts the water content and macrostructural properties of polynorbornene membranes as a function of the water activity and successfully captures the effect of various polymer design parameters. The energy of pairwise attractive interactions predicted by our model provides a means to interpret the absorption process at the molecular level. The model also reveals the most significant favorable and unfavorable contributions to the free energy and indicates that their balance is solely governed by the water volume fraction, regardless of the polymer design. This universal behavior leads to important implications in the search for better ion exchange membranes.

Zaldivar, Gervasio [New York University, Brooklyn,↗
DOE OSTI2023

Cation–polymer interactions and local heterogeneity determine the relative order of alkali cation diffusion coefficients in PEGDA hydrogels

Current research efforts are focused on endowing polymer membranes with ion–ion selectivity by incorporating ion–polymer interactions into materials to bias the selective partitioning and or diffusivity of one species over another. However, little is known about the impact of such interactions on the mechanisms of ion transport. In this study, we probe the influence of cation–polymer interactions on cation, anion, and salt diffusivity in a model membrane material, poly(ethylene glycol) diacrylate (PEGDA) by modeling concentrated polyethylene oxide solutions via molecular dynamics simulations. These results are compared to published experimental data for LiCl, NaCl, and KCl diffusion in PEGDA. Experimentally, the order of salt and cation diffusion coefficients for LiCl, NaCl, and KCl deviate from the order in aqueous solutions. Here, simulations identify these deviations to arise from cation–polymer coordination in the membrane. Both the fraction of bound cations and the average binding lifetime increases with decreasing cation hydration free energy (moving down the alkali series), leading to different diffusivity trends in the membrane compared to solution. However, to recover the experimentally observed order of diffusivities cations and salt in our simulations, we needed to incorporate membrane heterogeneity explicitly via a polymer charge scaling procedure. Together, our results indicate that cation–polymer interactions, as well as spatial heterogeneity within the membrane, play a critical role in dictating the observed order of alkali cation and salt diffusion coefficients in membranes.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Membrane–Electrolyte System Approach to Understanding Ionic Conductivity and Crossover in Alkaline Flow Cells

Membrane transport properties are crucial for electrochemical devices, and these properties are influenced by the composition and concentration of the electrolyte in contact with the membrane. We apply this general membrane-electrolyte system approach to alkaline flow batteries, studying conductivity and ferricyanide crossover of Nafion and E-620. We report undetectable crossover for as-received Nafion and E-620 after both sodium and potassium exchange, but high ferricyanide permeability of 10 –7 to 10 –8 cm2 s –1 for Nafion subjected to pre-treatment prevalent in the flow battery literature. We show how the electrolyte mass fraction in hydrated membranes regulates the influence of ion concentration on membrane conductivity, identifying that increasing electrolyte concentration may not increase 1 membrane conductivity even when it increases electrolyte conductivity. To illustrate this behavior we introduce a new metric, the membrane penalty, as the ratio of the conductivity of the electrolyte to that of the membrane equilibrated with the electrolyte. We discuss the tradeoff between flow battery volumetric capacity and areal power density that arises from these findings. Finally, we apply insights from this approach to provide recommendations for use of membranes in alkaline flow cells, and electrochemical reactors in general.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

Electron Transport in Paracoccus Halodenitrificans and the Role of Ubiquinone

The membrane-bound NADH oxidase of Paracoccus halodenitrificans was inhibited by dicoumarol, 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), and exposure to ultraviolet light (at 366 nm). When the membranes were extracted with n-pentane, NADH oxidase activity was lost. Partial restoration was achieved by adding the ubiquinone fraction extracted from the membranes. Succinate oxidation was not inhibited by dicoumarol or HQNO but was affected by ultraviolet irradiation or n-pentane extraction. However, the addition of the ubiquinone fraction to the n-pentane-extracted membranes did not restore enzyme activity. These observations suggested the reducing equivalents from succinate entered the respiratory chain on the oxygen side of the HQNO-sensitive site and probably did not proceed through a quinone.

Hochstein, L. I.↗