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Sample records for coli ammonium channel

  1. Ammonium recruitment and ammonia transport by E. coli ammonia channel AmtB.

    PubMed

    Nygaard, Thomas P; Rovira, Carme; Peters, Günther H; Jensen, Morten Ø

    2006-12-15

    To investigate substrate recruitment and transport across the Escherichia coli Ammonia transporter B (AmtB) protein, we performed molecular dynamics simulations of the AmtB trimer. We have identified residues important in recruitment of ammonium and intraluminal binding sites selective of ammonium, which provide a means of cation selectivity. Our results indicate that A162 guides translocation of an extraluminal ammonium into the pore lumen. We propose a mechanism for transporting the intraluminally recruited proton back to periplasm. Our mechanism conforms to net transport of ammonia and can explain why ammonia conduction is lost upon mutation of the conserved residue D160. We unify previous suggestions of D160 having either a structural or an ammonium binding function. Finally, our simulations show that the channel lumen is hydrated from the cytoplasmic side via the formation of single file water, while the F107/F215 stack at the inner-most part of the periplasmic vestibule constitutes a hydrophobic filter preventing AmtB from conducting water.

  2. Ammonium Recruitment and Ammonia Transport by E. coli Ammonia Channel AmtB

    PubMed Central

    Nygaard, Thomas P.; Rovira, Carme; Peters, Günther H.; Jensen, Morten Ø.

    2006-01-01

    To investigate substrate recruitment and transport across the Escherichia coli Ammonia transporter B (AmtB) protein, we performed molecular dynamics simulations of the AmtB trimer. We have identified residues important in recruitment of ammonium and intraluminal binding sites selective of ammonium, which provide a means of cation selectivity. Our results indicate that A162 guides translocation of an extraluminal ammonium into the pore lumen. We propose a mechanism for transporting the intraluminally recruited proton back to periplasm. Our mechanism conforms to net transport of ammonia and can explain why ammonia conduction is lost upon mutation of the conserved residue D160. We unify previous suggestions of D160 having either a structural or an ammonium binding function. Finally, our simulations show that the channel lumen is hydrated from the cytoplasmic side via the formation of single file water, while the F107/F215 stack at the inner-most part of the periplasmic vestibule constitutes a hydrophobic filter preventing AmtB from conducting water. PMID:17012311

  3. The pivotal twin histidines and aromatic triad of the Escherichia coli ammonium channel AmtB can be replaced

    PubMed Central

    Hall, Jason A.; Kustu, Sydney

    2011-01-01

    In Escherichia coli, each subunit of the trimeric channel protein AmtB carries a hydrophobic pore for transport of NH4+ across the cytoplasmic membrane. Positioned along this substrate conduction pathway are two conserved elements—a pair of hydrogen-bonded histidines (H168/H318) located within the pore itself and a set of aromatic residues (F107/W148/F215) at its periplasmic entrance—thought to be critical to AmtB function. Using site-directed mutagenesis and suppressor genetics, we examined the requirement for these elements in NH4+ transport. This analysis shows that AmtB can accommodate, by either direct substitution or suppressor generation, acidic residues at one or both positions of the H168/H318 twin-histidine site while retaining near wild-type activity. Similarly, study of the F107/W148/F215 triad indicates that good-to-excellent AmtB function is preserved upon individual and simultaneous replacement of these aromatic amino acids with aliphatic residues. Our findings lead us to conclude that these elements and their component parts are not required for AmtB function, but instead serve to optimize its performance. PMID:21775672

  4. The pivotal twin histidines and aromatic triad of the Escherichia coli ammonium channel AmtB can be replaced.

    PubMed

    Hall, Jason A; Kustu, Sydney

    2011-08-09

    In Escherichia coli, each subunit of the trimeric channel protein AmtB carries a hydrophobic pore for transport of NH(4)(+) across the cytoplasmic membrane. Positioned along this substrate conduction pathway are two conserved elements--a pair of hydrogen-bonded histidines (H168/H318) located within the pore itself and a set of aromatic residues (F107/W148/F215) at its periplasmic entrance--thought to be critical to AmtB function. Using site-directed mutagenesis and suppressor genetics, we examined the requirement for these elements in NH(4)(+) transport. This analysis shows that AmtB can accommodate, by either direct substitution or suppressor generation, acidic residues at one or both positions of the H168/H318 twin-histidine site while retaining near wild-type activity. Similarly, study of the F107/W148/F215 triad indicates that good-to-excellent AmtB function is preserved upon individual and simultaneous replacement of these aromatic amino acids with aliphatic residues. Our findings lead us to conclude that these elements and their component parts are not required for AmtB function, but instead serve to optimize its performance.

  5. The W148L substitution in the Escherichia coli ammonium channel AmtB increases flux and indicates that the substrate is an ion

    PubMed Central

    Fong, Rebecca N.; Kim, Kwang-Seo; Yoshihara, Corinne; Inwood, William B.; Kustu, Sydney

    2007-01-01

    The Amt/Mep ammonium channels are trimers in which each monomer contains a long, narrow, hydrophobic pore. Whether the substrate conducted by these pores is NH3 or NH4+ remains controversial. Substitution of leucine for the highly conserved tryptophan 148 residue at the external opening to Escherichia coli AmtB pores allowed us to address this issue. A strain carrying AmtBW148L accumulates much larger amounts of both [14C]methylammonium and [14C]methylglutamine in a washed cell assay than a strain carrying wild-type AmtB. Accumulation of methylammonium occurs within seconds and appears to reflect channel conductance, whereas accumulation of methylglutamine, which depends on the ATP-dependent activity of glutamine synthetase, increases for many minutes. Concentration of methylammonium was most easily studied in strains that lack glutamine synthetase. It is eliminated by the protonophore carbonyl cyanide m-chlorophenyl hydrazone and is ≈10-fold higher in the strain carrying AmtBW148L than wild-type AmtB. The results indicate that AmtB allows accumulation of CH3NH3+ ion in response to the electrical potential across the membrane and that the rate of flux through AmtBW148L is ≈10 times faster than through wild-type AmtB. We infer that both mutant and wild-type proteins also carry NH4+. Contrary to our previous views, we assess that E. coli AmtB does not differ from plant Amt proteins in this regard; both carry ions. We address the role of W148 in decreasing the activity and increasing the selectivity of AmtB and the implications of our findings with respect to the function of Rh proteins, the only known homologues of Amt/Mep proteins. PMID:17998534

  6. Steady state growth of E. Coli in low ammonium environment

    NASA Astrophysics Data System (ADS)

    Kim, Minsu; Deris, Barret; Zhang, Zhongge; Hwa, Terry

    2011-03-01

    Ammonium is the preferred nitrogen source for many microorganisms. In medium with low ammonium concentrations, enteric bacteria turn on the nitrogen responsive (ntr) genes to assimilate ammonium. Two proteins in E. coli, Glutamine synthetase (GS) and the Ammonium/methylammonium transporter AmtB play crucial roles in this regard. GS is the major ammonium assimilation enzyme below 1mM of NH4 + . AmtB is an inner membrane protein that transports NH4 + across the cell membrane against a concentration gradient. In order to study ammonium uptake at low NH4 + concentration at neutral pH, we developed a microfluidic flow chamber that maintains a homogenous nutrient environment during the course of exponential cell growth, even at very low concentration of nutrients. Cell growth can be accurately monitored using time-lapse microscopy. We followed steady state growth down to micro-molar range of NH4 + for the wild type and Δ amtB strains. The wild type strain is able to maintain the growth rate from 10mM down to a few uM of NH4 + , while the mutant exhibited reduced growth below ~ 20 ~uM of NH4 + . Simultaneous characterization of the expression levels of GS and AmtB using fluorescence reporters reveals that AmtB is turned on already at 1mM, but contributes to function only below ~ 30 ~uM in the wild-type. Down to ~ 20 ~uM of NH4 + , E.~coli can compensate the loss of AmtB by GS alone.

  7. Resistance to phenicol compounds following adaptation to quaternary ammonium compounds in Escherichia coli.

    PubMed

    Soumet, C; Fourreau, E; Legrandois, P; Maris, P

    2012-07-06

    Bacterial adaptation to quaternary ammonium compounds (QACs) is mainly documented for benzalkonium chloride (BC) and few data are available for other QACs. The aim of this study was to assess the effects of repeated exposure to different quaternary ammonium compounds (QACs) on the susceptibility and/or resistance of bacteria to other QACs and antibiotics. Escherichia coli strains (n=10) were adapted by daily exposure to increasingly sub-inhibitory concentrations of a QAC for 7 days. Three QACs were studied. Following adaptation, we found similar levels of reduction in susceptibility to QACs with a mean 3-fold increase in the minimum inhibitory concentration (MIC) compared to initial MIC values, whatever the QAC used during adaptation. No significant differences in antibiotic susceptibility were observed between the tested QACs. Antibiotic susceptibility was reduced from 3.5- to 7.5-fold for phenicol compounds, β lactams, and quinolones. Increased MIC was associated with a shift in phenotype from susceptible to resistant for phenicol compounds (florfenicol and chloramphenicol) in 90% of E. coli strains. Regardless of the QAC used for adaptation, exposure to gradually increasing concentrations of this type of disinfectant results in reduced susceptibility to QACs and antibiotics as well as cross-resistance to phenicol compounds in E. coli strains. Extensive use of QACs at sub-inhibitory concentrations may lead to the emergence of antibiotic-resistant bacteria and may represent a public health risk.

  8. Ammonium sorption to channel and riparian sediments: A transient storage pool for dissolved inorganic nitrogen

    USGS Publications Warehouse

    Triska, Frank J.; Jackman, Alan P.; Duff, John H.; Avanzino, Ronald J.

    1994-01-01

    Sediment (0.5 mm–2.0 mm grain size) was incubated in nylon bags (200 μm mesh) below the water table in the channel and in two transects of shallow wells perpendicular to the banks (to 18 m) of a third-order stream during August, 1987. One transect of wells drained steep old-growth forest, and the other a steep 23 year-old clear-cut partially regenerated in alder. At approximately 6-week intervals between October, 1987, and June, 1988, bags were retrieved. Total exchangeable ammonium was determined on sediment, and dissolved oxygen, nitrate and ammonium were determined in stream and well water. Exchangeable ammonium ranged from 10 μeq/100 g of sediment in the stream where nitrification potential and subsurface exchange with stream water were high, to 115 μeq/100 g sediment 18 m inland where channel water-groundwater mixing and nitrification potential were both low. Sorbed ammonium was highest during summer/autumn base flow and lowest during winter storm flow. Both channel and well water contained measurable dissolved oxygen at all times. Ammonium concentration was typically < 10 μg-N/L in channel water, increased with distance inland, but did not exceed 365 μg-N/L at any site. Nitrate concentration was typically higher in well water than channel water. Nitrate levels increased dramatically in wells at the base of the clear-cut following the onset of autumn rains. The results indicate a potential for temporary storage of ammonium on riparian sediments which may influence biotic nitrogen cycling, and alter the timing and form of dissolved inorganic nitrogen transport from the watershed.

  9. Properties of the Inner Pore Region of TRPV1 Channels Revealed by Block with Quaternary Ammoniums

    PubMed Central

    Jara-Oseguera, Andrés; Llorente, Itzel; Rosenbaum, Tamara; Islas, León D.

    2008-01-01

    The transient receptor potential vanilloid 1 (TRPV1) nonselective cationic channel is a polymodal receptor that activates in response to a wide variety of stimuli. To date, little structural information about this channel is available. Here, we used quaternary ammonium ions (QAs) of different sizes in an effort to gain some insight into the nature and dimensions of the pore of TRPV1. We found that all four QAs used, tetraethylammonium (TEA), tetrapropylammonium (TPrA), tetrabutylammonium, and tetrapentylammonium, block the TRPV1 channel from the intracellular face of the channel in a voltage-dependent manner, and that block by these molecules occurs with different kinetics, with the bigger molecules becoming slower blockers. We also found that TPrA and the larger QAs can only block the channel in the open state, and that they interfere with the channel's activation gate upon closing, which is observed as a slowing of tail current kinetics. TEA does not interfere with the activation gate, indicating that this molecule can reside in its blocking site even when the channel is closed. The dependence of the rate constants on the size of the blocker suggests a size of around 10 Å for the inner pore of TRPV1 channels. PMID:18955595

  10. Identification of quaternary ammonium compounds as potent inhibitors of hERG potassium channels.

    PubMed

    Xia, Menghang; Shahane, Sampada A; Huang, Ruili; Titus, Steven A; Shum, Enoch; Zhao, Yong; Southall, Noel; Zheng, Wei; Witt, Kristine L; Tice, Raymond R; Austin, Christopher P

    2011-05-01

    The human ether-a-go-go-related gene (hERG) channel, a member of a family of voltage-gated potassium (K(+)) channels, plays a critical role in the repolarization of the cardiac action potential. The reduction of hERG channel activity as a result of adverse drug effects or genetic mutations may cause QT interval prolongation and potentially leads to acquired long QT syndrome. Thus, screening for hERG channel activity is important in drug development. Cardiotoxicity associated with the inhibition of hERG channels by environmental chemicals is also a public health concern. To assess the inhibitory effects of environmental chemicals on hERG channel function, we screened the National Toxicology Program (NTP) collection of 1408 compounds by measuring thallium influx into cells through hERG channels. Seventeen compounds with hERG channel inhibition were identified with IC(50) potencies ranging from 0.26 to 22μM. Twelve of these compounds were confirmed as hERG channel blockers in an automated whole cell patch clamp experiment. In addition, we investigated the structure-activity relationship of seven compounds belonging to the quaternary ammonium compound (QAC) series on hERG channel inhibition. Among four active QAC compounds, tetra-n-octylammonium bromide was the most potent with an IC(50) value of 260nM in the thallium influx assay and 80nM in the patch clamp assay. The potency of this class of hERG channel inhibitors appears to depend on the number and length of their aliphatic side-chains surrounding the charged nitrogen. Profiling environmental compound libraries for hERG channel inhibition provides information useful in prioritizing these compounds for cardiotoxicity assessment in vivo. Published by Elsevier Inc.

  11. Identification of quaternary ammonium compounds as potent inhibitors of hERG potassium channels

    PubMed Central

    Xia, Menghang; Shahane, Sampada; Huang, Ruili; Titus, Steven A.; Shum, Enoch; Zhao, Yong; Southall, Noel; Zheng, Wei; Witt, Kristine L.; Tice, Raymond R.; Austin, Christopher P.

    2011-01-01

    The human ether-a-go-go-related gene (hERG) channel, a member of a family of voltage-gated potassium (K+) channels, plays a critical role in the repolarization of the cardiac action potential. The reduction of hERG channel activity as a result of adverse drug effects or genetic mutations may cause QT interval prolongation and potentially lead to acquired long QT syndrome. Thus, screening for hERG channel activity is important in drug development. Cardiotoxicity associated with the inhibition of hERG channels by environmental chemicals is also a public health concern. To assess the inhibitory effects of environmental chemicals on hERG channel function, we screened the National Toxicology Program (NTP) collection of 1408 compounds by measuring thallium influx into cells through hERG channels. Seventeen compounds with hERG channel inhibition were identified with IC50 potencies ranging from 0.26 to 22 μM. Twelve of these compounds were confirmed as hERG channel blockers in an automated whole cell patch clamp experiment. In addition, we investigated the structure-activity relationship of seven compounds belonging to the quaternary ammonium compound (QAC) series on hERG channel inhibition. Among four active QAC compounds, tetra-n-octylammonium bromide was the most potent with an IC50 value of 260 nM in the thallium influx assay and 80 nM in the patch clamp assay. The potency of this class of hERG channel inhibitors appears to depend on the number and length of their aliphatic side-chains surrounding the charged nitrogen. Profiling environmental compound libraries for hERG channel inhibition provides information useful in prioritizing these compounds for cardiotoxicity assessment in vivo. PMID:21362439

  12. Identification of quaternary ammonium compounds as potent inhibitors of hERG potassium channels

    SciTech Connect

    Xia Menghang; Shahane, Sampada A.; Huang, Ruili; Titus, Steven A.; Shum, Enoch; Zhao Yong; Southall, Noel; Zheng, Wei; Witt, Kristine L.; Tice, Raymond R.; Austin, Christopher P.

    2011-05-01

    The human ether-a-go-go-related gene (hERG) channel, a member of a family of voltage-gated potassium (K{sup +}) channels, plays a critical role in the repolarization of the cardiac action potential. The reduction of hERG channel activity as a result of adverse drug effects or genetic mutations may cause QT interval prolongation and potentially leads to acquired long QT syndrome. Thus, screening for hERG channel activity is important in drug development. Cardiotoxicity associated with the inhibition of hERG channels by environmental chemicals is also a public health concern. To assess the inhibitory effects of environmental chemicals on hERG channel function, we screened the National Toxicology Program (NTP) collection of 1408 compounds by measuring thallium influx into cells through hERG channels. Seventeen compounds with hERG channel inhibition were identified with IC{sub 50} potencies ranging from 0.26 to 22 {mu}M. Twelve of these compounds were confirmed as hERG channel blockers in an automated whole cell patch clamp experiment. In addition, we investigated the structure-activity relationship of seven compounds belonging to the quaternary ammonium compound (QAC) series on hERG channel inhibition. Among four active QAC compounds, tetra-n-octylammonium bromide was the most potent with an IC{sub 50} value of 260 nM in the thallium influx assay and 80 nM in the patch clamp assay. The potency of this class of hERG channel inhibitors appears to depend on the number and length of their aliphatic side-chains surrounding the charged nitrogen. Profiling environmental compound libraries for hERG channel inhibition provides information useful in prioritizing these compounds for cardiotoxicity assessment in vivo.

  13. Characterization of three novel mechanosensitive channel activities in Escherichia coli.

    PubMed

    Edwards, Michelle D; Black, Susan; Rasmussen, Tim; Rasmussen, Akiko; Stokes, Neil R; Stephen, Terri-Leigh; Miller, Samantha; Booth, Ian R

    2012-01-01

    Mechanosensitive channels sense elevated membrane tension that arises from rapid water influx occurring when cells move from high to low osmolarity environments (hypoosmotic shock). These non-specific channels in the cytoplasmic membrane release osmotically-active solutes and ions. The two major mechanosensitive channels in Escherichia coli are MscL and MscS. Deletion of both proteins severely compromises survival of hypoosmotic shock. However, like many bacteria, E. coli cells possess other MscS-type genes (kefA, ybdG, ybiO, yjeP and ynaI). Two homologs, MscK (kefA) and YbdG, have been characterized as mechanosensitive channels that play minor roles in maintaining cell integrity. Additional channel openings are occasionally observed in patches derived from mutants lacking MscS, MscK and MscL. Due to their rare occurrence, little is known about these extra pressure-induced currents or their genetic origins. Here we complete the identification of the remaining E. coli mechanosensitive channels YnaI, YbiO and YjeP. The latter is the major component of the previously described MscM activity (~300 pS), while YnaI (~100 pS) and YbiO (~1000 pS) were previously unknown. Expression of native YbiO is NaCl-specific and RpoS-dependent. A Δ7 strain was created with all seven E. coli mechanosensitive channel genes deleted. High level expression of YnaI, YbiO or YjeP proteins from a multicopy plasmid in the Δ7 strain (MJFGH) leads to substantial protection against hypoosmotic shock. Purified homologs exhibit high molecular masses that are consistent with heptameric assemblies. This work reveals novel mechanosensitive channels and discusses the regulation of their expression in the context of possible additional functions.

  14. Role of the Escherichia coli glnALG operon in regulation of ammonium transport

    SciTech Connect

    Jayakuman, A.; Schulman, I.; MacNeil, D.; Barnes, E.M. Jr.

    1986-04-01

    Escherichia coli expresses a specific ammonium (methylammonium) transport system (Amt) when cultured with glutamate or glutamine as the nitrogen source. Over 95% of this Amt activity is repressed by growth of wild-type cells on media containing ammonia. The control of Amt expression was studied with strains containing specific mutations in the glnALG operon. GlnA/sup -/ (glutamine synthetase deficient) mutants, which contain polar mutations on glnL and glnG genes and therefore have the Reg/sup -/ phenotype (fail to turn on nitrogen-regulated operons such as histidase), expressed less than 10% of the Amt activity observed for the parental strain. Similarly, low levels of Amt were found in GlnG mutants having the GlnA/sup +/ Reg/sup -/ phenotype. However, GlnA/sup -/ RegC mutants (a phenotype constitutive for histidase) contained over 70% of the parental Amt activity. At steady-state levels, GlnA/sup -/ RegC mutants accumulated chemically unaltered (/sup 14/C)methylammonium against a 60- to 80-fold concentration gradient, whereas the labeled substrate was trapped within parental cells as ..gamma..-glutamylmethylamide. GlnL Reg/sup -/ mutants (normal glutamine synthetase regulation) had less than 4% of the Amt activity observed for the parental strain. However, the Amt activity of GlnL RegC mutants was slightly higher than that of the parental strain and was not repressed during growth of cells in media containing ammonia. These findings demonstrate that glutamine synthetase is not required for Amt in E. coli. The loss of Amt in certain GlnA/sup -/ strains is due to polar effects on glnL nd glnG genes, whose products are involved in expression of nitrogen-regulated genes, including that for Amt.

  15. Quaternary ammonium compounds as structural probes of single batrachotoxin-activated Na+ channels

    PubMed Central

    1991-01-01

    Quaternary ammonium (QA) blockers are well-known structural probes for studying the permeation pathway of voltage-gated K+ channels. In this study we have examined the effects of a series of n-alkyl- trimethylammonium compounds (Cn-QA) on batrachotoxin (BTX)-activated Na+ channels from skeletal muscle incorporated into planar lipid bilayers. We found that these amphipathic QA compounds (Cn-QA where n = 10-18) block single Na+ channels preferentially from the internal side with equilibrium dissociation constants (KD) in the submicromolar to micromolar range. External application of amphipathic QA compounds is far less effective, by a factor of greater than 200. The block can be described by a QA molecule binding to a single site in the Na+ channel permeation pathway. QA binding affinity is dependent on transmembrane voltage with an effective valence (delta) of approximately 0.5. QA dwell times (given as mean closed times, tau c) increase as a function of n-alkyl chain length, ranging from approximately 13 ms for C10-QA to 500 ms for C18-QA at +50 mV. The results imply that there is a large hydrophobic region within the Na+ channel pore which accepts up to 18 methylene groups of the Cn-QA cation. This hydrophobic domain may be of clinical significance since it also interacts with local anesthetics such as cocaine and mepivacaine. Finally, like BTX-activated Na+ channels in bilayers, unmodified Na+ channels in GH3 cells are also susceptible to QA block. Amphipathic QA cations elicit both tonic and use-dependent inhibitions of normal Na+ currents in a manner similar to that of local anesthetic cocaine. We conclude that amphipathic QA compounds are valuable structural probes to study the permeation pathway of both normal and BTX-activated Na+ channels. PMID:1662681

  16. On the Equivalence Point for Ammonium (De)protonation during Its Transport through the AmtB Channel

    PubMed Central

    Bostick, David L.; Brooks, Charles L.

    2007-01-01

    Structural characterization of the bacterial channel, AmtB, provides a glimpse of how members of its family might control the protonated state of permeant ammonium to allow for its selective passage across the membrane. In a recent study, we employed a combination of simulation techniques that suggested ammonium is deprotonated and reprotonated near dehydrative phenylalanine landmarks (F107 and F31, respectively) during its passage from the periplasm to the cytoplasm. At these landmarks, ammonium is forced to maintain a critical number (∼3) of hydrogen bonds, suggesting that the channel controls ammonium (de)protonation by controlling its coordination/hydration. In the work presented here, a free energy-based analysis of ammonium hydration in dilute aqueous solution indicates, explicitly, that at biological pH, the transition from ammonium (\\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{NH}}_{4}^{+}\\end{equation*}\\end{document}) to ammonia (NH3) occurs when these species are constrained to donate three hydrogen bonds or less. This result demonstrates the viability of the proposal that AmtB indirectly controls ammonium (de)protonation by directly controlling its hydration. PMID:17434945

  17. On the equivalence point for ammonium (de)protonation during its transport through the AmtB channel.

    PubMed

    Bostick, David L; Brooks, Charles L

    2007-06-15

    Structural characterization of the bacterial channel, AmtB, provides a glimpse of how members of its family might control the protonated state of permeant ammonium to allow for its selective passage across the membrane. In a recent study, we employed a combination of simulation techniques that suggested ammonium is deprotonated and reprotonated near dehydrative phenylalanine landmarks (F107 and F31, respectively) during its passage from the periplasm to the cytoplasm. At these landmarks, ammonium is forced to maintain a critical number ( approximately 3) of hydrogen bonds, suggesting that the channel controls ammonium (de)protonation by controlling its coordination/hydration. In the work presented here, a free energy-based analysis of ammonium hydration in dilute aqueous solution indicates, explicitly, that at biological pH, the transition from ammonium (NH(4)(+)) to ammonia (NH(3)) occurs when these species are constrained to donate three hydrogen bonds or less. This result demonstrates the viability of the proposal that AmtB indirectly controls ammonium (de)protonation by directly controlling its hydration.

  18. Quaternary ammonium block of mutant Na+ channels lacking inactivation: features of a transition-intermediate mechanism

    PubMed Central

    Kimbrough, J T; Gingrich, K J

    2000-01-01

    The quaternary ammonium (QA) lidocaine derivative QX-314 (2-(triethylamino)-N--(2,6-dimethylphenyl)-acetamide) induces internal pore blockade of single cardiac Na+ channels enzymatically modified (papain) to eliminate fast inactivation. The mechanism involves dual, interacting blocking modes (rapid and discrete) with binding domains deep in the pore from the cytoplasmic mouth, and where the rapid blocked configuration serves as a transition-intermediate for the development of discrete block. The primary goals of this study were to test for this mechanism in a recombinant Na+ channel genetically engineered to selectively lack fast inactivation, and if present, to explore the underlying structural features. Fast inactivation was removed in rat skeletal muscle μ1 Na+ channels (RSkM1) with an IFM-QQQ mutation in the cytoplasmic III-IV interdomain (QQQ). QQQ was expressed in Xenopus oocytes and single-channel activity was studied in cell-free, inside-out membrane patches. Application of QX-314 (QX, 0-4 mM) to the cytoplasmic membrane surface caused two distinct modalities of single-channel blockade: reduction of unitary current and interruptions of current lasting tens of milliseconds. These are consistent with rapid and discrete pore block, respectively. The voltage and concentration dependence of block indicates that the modes interact and have binding sites that share a deep location in the pore, at ≈65 % of the membrane electric field in from the cytoplasmic mouth. Mutation of phenylalanine (F1579) in domain IV-S6, critical in local anaesthetic block, to alanine in QQQ (QQQ-F1579A) disabled discrete block but notably failed to alter rapid block, single-channel gating and slope conductance. Amplitude distribution analysis was applied to long bursts (> 50 ms) of QQQ-F1579A activity to investigate the kinetics of rapid block. Computed rapid blocking and unblocking rate constants are 42 000 ± 18 000 M−1 ms−1 and 82 ± 22 ms−1, respectively (n = 3, -20 mV). The

  19. The Escherichia coli AmtB protein as a model system for understanding ammonium transport by Amt and Rh proteins.

    PubMed

    Merrick, M; Javelle, A; Durand, A; Severi, E; Thornton, J; Avent, N D; Conroy, M J; Bullough, P A

    2006-01-01

    The Escherichia coli ammonium transport protein (AmtB) has become the model system of choice for analysis of the process of ammonium uptake by the ubiquitous Amt family of inner membrane proteins. Over the past 6 years we have developed a range of genetic and biochemical tools in this system. These have allowed structure/function analysis to develop rapidly, offering insight initially into the membrane topology of the protein and most recently leading to the solution of high-resolution 3D structures. Genetic analysis has revealed a novel regulatory mechanism that is apparently conserved in prokaryotic Amt proteins and genetic approaches are also now being used to dissect structure/function relationships in Amt proteins. The now well-recognised homology between the Amt proteins, found in archaea, eubacteria, fungi and plants, and the Rhesus proteins, found characteristically in animals, also means that studies on E. coli AmtB can potentially shed light on structure/function relationships in the clinically important Rh proteins.

  20. The selectivity of different external binding sites for quaternary ammonium ions in cloned potassium channels.

    PubMed

    Jarolimek, W; Soman, K V; Brown, A M; Alam, M

    1995-09-01

    Tetraethylammonium (TEA) is thought to be the most effective quaternary ammonium (QA) ion blocker at the external site of K+ channels, and small changes to the TEA ion reduce its potency. To examine the properties of the external QA receptor, we applied a variety of QA ions to excised patches from human embryonic kidney cells or Xenopus oocytes transfected with the delayed rectifying K+ channels Kv 2.1 and Kv 3.1. In outside-out patches of Kv 3.1, the relative potencies were TEA > tetrapropylammonium (TPA) > tetrabutylammonium (TBA). In contrast to Kv 3.1, the relative potencies in Kv 2.1 were TBA > TEA > TPA. In Kv 3.1 and Kv 2.1, external tetrapentylammonium (TPeA) blocked K+ currents in a fast, reversible and, in contrast to TEA, time-dependent manner. The external binding of TPeA appeared to be voltage independent, unlike the effects of TPeA applied to inside-out patches. External n-alkyl-triethylammonium compounds (C8, C10 chain length) had a lower affinity than TEA in Kv 3.1, but a higher affinity than TEA in Kv 2.1. In Kv 3.1, the decrease in QA affinity was large when one or two methyl groups were substituted for ethyl groups in TEA, but minor when propyl groups replaced ethyl groups. Changes in the free energy of binding could be correlated to changes in the free energy of hydration of TEA derivatives calculated by continuum methodology. These results reveal a substantial hydrophobic component of external QA ion binding to Kv 2.1, and to a lesser degree to Kv 3.1, in addition to the generally accepted electrostatic interactions. The chain length of hydrophobic TEA derivatives affects the affinity for the hydrophobic binding site, whereas the hydropathy of QA ions determines the electrostatic interaction energy.

  1. Changes in Escherichia coli Associated with Acquired Tolerance for Quaternary Ammonium Compounds 1

    PubMed Central

    Maxcy, R. B.; Tiwari, N. P.; Soprey, P. R.

    1971-01-01

    Acquired tolerance for a quaternary ammonium compound produced a tolerance for a similar compound. Tolerance was associated with the structure and the extent of adsorption of the compound. Morphological changes and resistance to disruption by pressure and by sonic treatment accompanied the development of tolerance. An otherwise weakened culture evolved with the acquisition of tolerance. The maximum obtainable viable population density of tolerant cells in growth medium was approximately 5% of that obtained in the parent culture. Tolerant cultures died off more rapidly in the original growth medium as well as when washed cell suspensions were stored at 5 C. Since acquired tolerance was associated with an otherwise weakened culture, the occurrence of the tolerant cells to limit the efficacy of quaternary ammonium compounds in sanitation operations is highly unlikely. PMID:4938103

  2. Substrate binding, deprotonation, and selectivity at the periplasmic entrance of the Escherichia coli ammonia channel AmtB.

    PubMed

    Javelle, Arnaud; Lupo, Domenico; Ripoche, Pierre; Fulford, Tim; Merrick, Mike; Winkler, Fritz K

    2008-04-01

    The conduction mechanism of Escherichia coli AmtB, the structurally and functionally best characterized representative of the ubiquitous Amt/Rh family, has remained controversial in several aspects. The predominant view has been that it facilitates the movement of ammonium in its uncharged form as indicated by the hydrophobic nature of a pore located in the center of each subunit of the homotrimer. Using site-directed mutagenesis and a combination of biochemical and crystallographic methods, we have investigated mechanistic questions concerning the putative periplasmic ammonium ion binding site S1 and the adjacent periplasmic "gate" formed by two highly conserved phenylalanine residues, F107 and F215. Our results challenge models that propose that NH(4)(+) deprotonation takes place at S1 before NH(3) conduction through the pore. The presence of S1 confers two critical features on AmtB, both essential for its function: ammonium scavenging efficiency at very low ammonium concentration and selectivity against water and physiologically important cations. We show that AmtB activity absolutely requires F215 but not F107 and that removal or obstruction of the phenylalanine gate produces an open but inactive channel. The phenyl ring of F215 must thus play a very specific role in promoting transfer and deprotonation of substrate from S1 to the central pore. We discuss these results with respect to three distinct mechanisms of conduction that have been considered so far. We conclude that substrate deprotonation is an essential part of the conduction mechanism, but we do not rule out net electrogenic transport.

  3. Substrate binding, deprotonation, and selectivity at the periplasmic entrance of the Escherichia coli ammonia channel AmtB

    PubMed Central

    Javelle, Arnaud; Lupo, Domenico; Ripoche, Pierre; Fulford, Tim; Merrick, Mike; Winkler, Fritz K.

    2008-01-01

    The conduction mechanism of Escherichia coli AmtB, the structurally and functionally best characterized representative of the ubiquitous Amt/Rh family, has remained controversial in several aspects. The predominant view has been that it facilitates the movement of ammonium in its uncharged form as indicated by the hydrophobic nature of a pore located in the center of each subunit of the homotrimer. Using site-directed mutagenesis and a combination of biochemical and crystallographic methods, we have investigated mechanistic questions concerning the putative periplasmic ammonium ion binding site S1 and the adjacent periplasmic “gate” formed by two highly conserved phenylalanine residues, F107 and F215. Our results challenge models that propose that NH4+ deprotonation takes place at S1 before NH3 conduction through the pore. The presence of S1 confers two critical features on AmtB, both essential for its function: ammonium scavenging efficiency at very low ammonium concentration and selectivity against water and physiologically important cations. We show that AmtB activity absolutely requires F215 but not F107 and that removal or obstruction of the phenylalanine gate produces an open but inactive channel. The phenyl ring of F215 must thus play a very specific role in promoting transfer and deprotonation of substrate from S1 to the central pore. We discuss these results with respect to three distinct mechanisms of conduction that have been considered so far. We conclude that substrate deprotonation is an essential part of the conduction mechanism, but we do not rule out net electrogenic transport. PMID:18362341

  4. A solid phase honey-like channel method for synthesizing urea-ammonium chloride cocrystals on industrial scale

    NASA Astrophysics Data System (ADS)

    Xue, Bingchun; Mao, Meiling; Liu, Yanhong; Guo, Jinyu; Li, Jing; Liu, Erbao

    2016-05-01

    Unanticipated a new and simple urea-ammonium chloride cocrystal synthesis method on industrial scale was found during attempts to produce a kind of granulated compound fertilizer. The aggregation of fertilizer powder can make the interaction among particles from loose to close, which generate mechanical pressure and in turn act as the driving force to benefit cocrystal growth. Additionally, the honeycomb-like channels constructed by other coexisting compound make the water evaporates more moderate, which can help the formation of supersaturated solution at suitable rate, further promote the growth of cocrystal. This approach possibly opens a new route toward the developing methodologies for cocrystal synthesis.

  5. Ammonium channel expression is essential for brain development and function in the larva of Ciona intestinalis.

    PubMed

    Marino, Rita; Melillo, Daniela; Di Filippo, Miriam; Yamada, Atsuko; Pinto, Maria Rosaria; De Santis, Rosaria; Brown, Euan R; Matassi, Giorgio

    2007-07-01

    Ammonium uptake into the cell is known to be mediated by ammonium transport (Amt) proteins, which are present in all domains of life. The physiological role of Amt proteins remains elusive; indeed, loss-of-function experiments suggested that Amt proteins do not play an essential role in bacteria, yeast, and plants. Here we show that the reverse holds true in the tunicate Ciona intestinalis. The genome of C. intestinalis contains two AMT genes, Ci-AMT1a and Ci-AMT1b, which we show derive from an ascidian-specific gene duplication. We analyzed Ci-AMT expression during embryo development. Notably, Ci-AMT1a is expressed in the larval brain in a small number of cells defining a previously unseen V-shaped territory; these cells connect the brain cavity to the external environment. We show that the knockdown of Ci-AMT1a impairs the formation of the brain cavity and consequently the function of the otolith, the gravity-sensing organ contained in it. We speculate that the normal mechanical functioning (flotation and free movement) of the otolith may require a close regulation of ammonium salt(s) concentration in the brain cavity, because ammonium is known to affect both fluid density and viscosity; the cells forming the V territory may act as a conduit in achieving such a regulation.

  6. Ultra-deep blockade of Na+ channels by a quaternary ammonium ion: catalysis by a transition-intermediate state?

    PubMed Central

    Gingrich, K J; Beardsley, D; Yue, D T

    1993-01-01

    1. Individual Na+ channels from isolated guinea-pig ventricular heart cells were studied using the patch-clamp technique. To localize the selectivity region of the channels we investigated their blockade by a permanently charged quaternary ammonium ion (QX-314, 2-(triethylamino)-N-(2,6-dimethylphenyl)acetamide, 0-5 mM) that was applied to the cytoplasmic side of the channel. 2. Resolution of individual blocking events was enhanced by covalent removal of fast inactivation following brief internal exposure to the enzyme papain. The improved resolution reveals the existence of two distinct modalities of blockade: reduction of unitary current, and millisecond interruptions of current. 3. Both modes of internal block could be potentiated by lowering external Na+ concentration. This finding argues that the two corresponding sites of interaction are both located within the channel pore. 4. Analysis of the voltage dependence of block placed both binding sites deep within the pore, at 70% of the electric field from the cytoplasmic entrance. Combined with recent studies localizing block by external Cd2+, the present results argue that the selectivity region of Na+ channels is quite narrow (spanning about 10% of the electric field), and located near the external side of the channel. 5. The manner in which the two blocking processes interact, along with the physical proximity of their binding sites, leads us to propose that the block configuration responsible for the reduction in unitary current serves as a transition intermediate that catalyses formation of the discrete-block complex. PMID:8120809

  7. Inhibition of slow-wave repolarization and Ca(2+)-activated K+ channels by quaternary ammonium ions.

    PubMed

    Carl, A; Frey, B W; Ward, S M; Sanders, K M; Kenyon, J L

    1993-03-01

    We studied the effects of the K+ channel blocker tetrapentylammonium (TPeA) on the electrical activity of intact circular smooth muscle from canine colon. TPeA (10 and 20 microM) increased slow-wave duration and "locked" the membrane potential around -30 mV plateau potential after several minutes of application, suggesting that K+ channels are essential for termination of colonic slow waves. Repolarization and normal slow-wave activity resumed after 20-30 min of washout. The patch-clamp technique was used to study the block of large-conductance Ca(2+)-activated K+ channels (BK channels) by TPeA and tetraethylammonium (TEA) in excised and cell-attached patches from isolated colonic smooth muscle cells. Channel block was characterized by a voltage-dependent dissociation constant [Kd(V)] for the binding of TEA and TPeA to a blocking site located a fraction of the distance across the membrane field (delta). The extracellular TEA binding site had a Kd(0) of 0.33 mM and a delta of 0.23. The extracellular TPeA binding site had a Kd(0) of 2.2 mM but showed significantly less voltage dependence (delta = 0.02). The intracellular binding site for TEA was of low affinity [Kd(0) = 76 mM]. Intracellular TPeA was the most potent blocker of BK channel current [Kd(0) = 11.7 microM]. The voltage dependence of block by intracellular TPeA (delta = -0.21) was not significantly different from that of intracellular TEA (delta = -0.3). Internal TPeA (10 microM) also blocked a 70-pS K+ channel and a 23-pS K+ channel.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. Formation mechanisms of channels on Titan through dissolution by ammonium sulfate and erosion by liquid ammonia and ethane

    NASA Astrophysics Data System (ADS)

    Gilliam, Ashley E.; Lerman, Abraham

    2016-11-01

    Data obtained from the Cassini Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS), and Synthetic Aperture Radar (SAR) instruments have revealed an array of fluvial channels on Titan's surface, often several hundreds of kilometers in length. The paucity of impact craters on Titan's surface suggests a formation by fluvial erosion into the water-ice bedrock. Additionally, at the landing site, the Huygens Probe Descent Imager and Spectral Radiometer (DISR) imaged Earth-like rounded cobbles 0.3-15 cm in diameter composed of water ice, reminiscent of rounded stream clasts on Earth. In this paper we examine different fluvial features on Titan, identified by the Cassini spacecraft, and evaluate the possibilities of channel formation by dissolution of ice by a concentrated solution of ammonium sulfate, and by mechanical erosion by flow of liquid ammonia and liquid ethane. We find that chemical erosion of Titan's channels could be completed in 280 to 1100 years (all units of time in this paper are Terrestrial, not Titanian), much shorter than the period of about 84,000 years that a concentrated (NH4)2SO4-H2O solution could exist as a liquid on the Titan surface. Mechanical erosion of Titan's channels is generally a much slower process, on the order of 102 to 105 years to completion, and is also slower than mechanical erosion of a model river on Earth, averaging 103 to 104 years. The erosional sequence of the channels on Titan may have started after the formation of water-ice on the surface by the process of chemical dissolution by (NH4)2SO4-H2O, overlapping, or followed by, a period of mechanical erosion by liquid NH3. A final stage on the cooling surface of Titan might have been characterized by liquid C2H6 as an agent of mechanical erosion.

  9. Deprotonation by Dehydration: The Origin of Ammonium Sensing in the AmtB Channel

    PubMed Central

    Bostick, David L; III, Charles L. Brooks

    2007-01-01

    The AmtB channel passively allows the transport of NH4 + across the membranes of bacteria via a “gas” NH3 intermediate and is related by homology (sequentially, structurally, and functionally) to many forms of Rh protein (both erythroid and nonerythroid) found in animals and humans. New structural information on this channel has inspired computational studies aimed at clarifying various aspects of NH4 + recruitment and binding in the periplasm, as well as its deprotonation. However, precise mechanisms for these events are still unknown, and, so far, explanations for subsequent NH3 translocation and reprotonation at the cytoplasmic end of the channel have not been rigorously addressed. We employ molecular dynamics simulations and free energy methods on a full AmtB trimer system in membrane and bathed in electrolyte. Combining the potential of mean force for NH4 +/NH3 translocation with data from thermodynamic integration calculations allows us to find the apparent pKa of NH4 + as a function of the transport axis. Our calculations reveal the specific sites at which its deprotonation (at the periplasmic end) and reprotonation (at the cytoplasmic end) occurs. Contrary to most hypotheses, which ascribe a proton-accepting role to various periplasmic or luminal residues of the channel, our results suggest that the most plausible proton donor/acceptor at either of these sites is water. Free-energetic analysis not only verifies crystallographically determined binding sites for NH4 + and NH3 along the transport axis, but also reveals a previously undetermined binding site for NH4 + at the cytoplasmic end of the channel. Analysis of dynamics and the free energies of all possible loading states for NH3 inside the channel also reveal that hydrophobic pressure and the free-energetic profile provided by the pore lumen drives this species toward the cytoplasm for protonation just before reaching the newly discovered site. PMID:17291160

  10. Evaluation of aqueous and alcohol-based quaternary ammonium sanitizers for inactivating Salmonella spp., Escherichia coli O157:H7, and Listeria monocytogenes on peanut and pistachio shells.

    PubMed

    McEgan, Rachel; Danyluk, Michelle D

    2015-05-01

    This study evaluated the efficacy of aqueous (aQUAT) and isopropyl alcohol-based quaternary ammonium (ipQUAT) sanitizers for reducing Salmonella spp., Escherichia coli O157:H7, or Listeria monocytogenes populations on peanut and pistachio shell pieces. Inoculated nutshells were mixed with QUAT sanitizers, water, or 70% ethanol and enumerated immediately or after incubation at 30 °C for 48 h. None of the treatments had any immediate effect on Salmonella or E. coli O157:H7 populations on the peanut or pistachio shells. L. monocytogenes populations declined immediately on the peanut and pistachio shells treated with aQUAT or ipQUAT. After incubation, Salmonella and E. coli O157:H7 populations increased significantly on the water- or aQUAT-treated peanut and pistachio shells. L. monocytogenes populations also increased significantly on the water- or aQUAT-treated peanut shells, but levels did not change on the water-treated pistachio shells and levels were just above the limit of detection on the aQUAT-treated pistachio shells. After treatment with ipQUAT and 48-h incubation, Salmonella and E. coli O157:H7 populations decreased to or below the limit of detection on both shell types; L. monocytogenes populations remained at or below the limit of detection on both shell types. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Delimiting the Binding Site for Quaternary Ammonium Lidocaine Derivatives in the Acetylcholine Receptor Channel

    PubMed Central

    Pascual, Juan M.; Karlin, Arthur

    1998-01-01

    The triethylammonium QX-314 and the trimethylammonium QX-222 are lidocaine derivatives that act as open-channel blockers of the acetylcholine (ACh) receptor. When bound, these blockers should occlude some of the residues lining the channel. Eight residues in the second membrane-spanning segment (M2) of the mouse-muscle α subunit were mutated one at a time to cysteine and expressed together with wild-type β, γ, and δ subunits in Xenopus oocytes. The rate constant for the reaction of each substituted cysteine with 2-aminoethyl methanethiosulfonate (MTSEA) was determined from the time course of the irreversible effect of MTSEA on the ACh-induced current. The reactions were carried out in the presence and absence of ACh and in the presence and absence of QX-314 and QX-222. These blockers had no effect on the reactions in the absence of ACh. In the presence of ACh, both blockers retarded the reaction of extracellularly applied MTSEA with cysteine substituted for residues from αVal255, one third of the distance in from the extracellular end of M2, to αGlu241, flanking the intracellular end of M2, but not with cysteine substituted for αLeu258 or αGlu262, at the extracellular end of M2. The reactions of MTSEA with cysteines substituted for αLeu258 and αGlu262 were considerably faster in the presence of ACh than in its absence. That QX-314 and QX-222 did not protect αL258C and αE262C against reaction with MTSEA in the presence of ACh implies that protection of the other residues was due to occlusion of the channel and not to the promotion of a less reactive state from a remote site. Given the 12-Å overall length of the blockers and the α-helical conformation of M2 in the open state, the binding site for both blockers extends from αVal255 down to αSer248. PMID:9806969

  12. Physiological, biomass elemental composition and proteomic analyses of Escherichia coli ammonium-limited chemostat growth, and comparison with iron- and glucose-limited chemostat growth

    PubMed Central

    Folsom, James Patrick

    2015-01-01

    Escherichia coli physiological, biomass elemental composition and proteome acclimations to ammonium-limited chemostat growth were measured at four levels of nutrient scarcity controlled via chemostat dilution rate. These data were compared with published iron- and glucose-limited growth data collected from the same strain and at the same dilution rates to quantify general and nutrient-specific responses. Severe nutrient scarcity resulted in an overflow metabolism with differing organic byproduct profiles based on limiting nutrient and dilution rate. Ammonium-limited cultures secreted up to 35  % of the metabolized glucose carbon as organic byproducts with acetate representing the largest fraction; in comparison, iron-limited cultures secreted up to 70  % of the metabolized glucose carbon as lactate, and glucose-limited cultures secreted up to 4  % of the metabolized glucose carbon as formate. Biomass elemental composition differed with nutrient limitation; biomass from ammonium-limited cultures had a lower nitrogen content than biomass from either iron- or glucose-limited cultures. Proteomic analysis of central metabolism enzymes revealed that ammonium- and iron-limited cultures had a lower abundance of key tricarboxylic acid (TCA) cycle enzymes and higher abundance of key glycolysis enzymes compared with glucose-limited cultures. The overall results are largely consistent with cellular economics concepts, including metabolic tradeoff theory where the limiting nutrient is invested into essential pathways such as glycolysis instead of higher ATP-yielding, but non-essential, pathways such as the TCA cycle. The data provide a detailed insight into ecologically competitive metabolic strategies selected by evolution, templates for controlling metabolism for bioprocesses and a comprehensive dataset for validating in silico representations of metabolism. PMID:26018546

  13. Free RCK arrangement in Kch, a putative escherichia coli potassium channel, as suggested by electron crystallography.

    PubMed

    Kuang, Qie; Purhonen, Pasi; Jegerschöld, Caroline; Koeck, Philip J B; Hebert, Hans

    2015-01-06

    The ligand-gated potassium channels are stimulated by various kinds of messengers. Previous studies showed that ligand-gated potassium channels containing RCK domains (the regulator of the conductance of potassium ion) form a dimer of tetramer structure through the RCK octameric gating ring in the presence of detergent. Here, we have analyzed the structure of Kch, a channel of this type from Escherichia coli, in a lipid environment using electron crystallography. By combining information from the 3D map of the transmembrane part of the protein and docking of an atomic model of a potassium channel, we conclude that the RCK domains face the solution and that an RCK octameric gating ring arrangement does not form under our crystallization condition. Our findings may be applied to other potassium channels that have an RCK gating ring arrangement.

  14. The Dionaea muscipula ammonium channel DmAMT1 provides NH₄⁺ uptake associated with Venus flytrap's prey digestion.

    PubMed

    Scherzer, Sönke; Krol, Elzbieta; Kreuzer, Ines; Kruse, Jörg; Karl, Franziska; von Rüden, Martin; Escalante-Perez, Maria; Müller, Thomas; Rennenberg, Heinz; Al-Rasheid, Khaled A S; Neher, Erwin; Hedrich, Rainer

    2013-09-09

    Ammonium transporter (AMT/MEP/Rh) superfamily members mediate ammonium uptake and retrieval. This pivotal transport system is conserved among all living organisms. For plants, nitrogen represents a macronutrient available in the soil as ammonium, nitrate, and organic nitrogen compounds. Plants living on extremely nutrient-poor soils have developed a number of adaptation mechanisms, including a carnivorous lifestyle. This study addresses the molecular nature, function, and regulation of prey-derived ammonium uptake in the Venus flytrap, Dionaea muscipula, one of the fastest active carnivores. The Dionaea muscipula ammonium transporter DmAMT1 was localized in gland complexes where its expression was upregulated upon secretion. These clusters of cells decorating the inner trap surface are engaged in (1) secretion of an acidic digestive enzyme cocktail and (2) uptake of prey-derived nutrients. Voltage clamp of Xenopus oocytes expressing DmAMT1 and membrane potential recordings with DmAMT1-expressing Dionaea glands were used to monitor and compare electrophysiological properties of DmAMT1 in vitro and in planta. DmAMT1 exhibited the hallmark biophysical properties of a NH4(+)-selective channel. At depolarized membrane potentials (Vm = 0), the Km (3.2 ± 0.3 mM) indicated a low affinity of DmAMT1 for ammonium that increased systematically with negative going voltages. Upon hyperpolarization to, e.g., -200 mV, a Km of 0.14 ± 0.015 mM documents the voltage-dependent shift of DmAMT1 into a NH4(+) transport system of high affinity. We suggest that regulation of glandular DmAMT1 and membrane potential readjustments of the endocrine cells provide for effective adaptation to varying, prey-derived ammonium sources. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Quantitative estimation of channeling from early glycolytic intermediates to CO in intact Escherichia coli.

    PubMed

    Shearer, Georgia; Lee, Jennifer C; Koo, Jia-An; Kohl, Daniel H

    2005-07-01

    A pathway intermediate is said to be 'channeled' when an intermediate just made in a pathway has a higher probability of being a substrate for the next pathway enzyme compared with a molecule of the same species from the aqueous cytoplasm. Channeling is an important phenomenon because it might play a significant role in the regulation of metabolism. Whereas the usual mechanism proposed for channeling is the (often) transient interaction of sequential pathway enzymes, many of the supporting data come from results with pure enzymes and dilute cell extracts. Even when isotope dilution techniques have utilized whole-cell systems, most often only a qualitative assessment of channeling has been reported. Here we develop a method for making a quantitative calculation of the fraction channeled in glycolysis from in vivo isotope dilution experiments. We show that fructose-1,6-bisphosphate, in whole cells of Escherichia coli, was strongly channeled all the way to CO2, whereas fructose-6-phosphate was not. Because the signature of channeling is lost if any downstream intermediate prior to CO2 equilibrates with molecules in the aqueous cytosol, it was not possible to evaluate whether glucose-6-phosphate was channeled in its transformation to fructose-6-phosphate. The data also suggest that, in addition to pathway enzymes being associated with one another, some are free in the aqueous cytosol. How sensitive the degree of channeling is to growth or experimental conditions remains to be determined.

  16. Estimation of the pore size of the large-conductance mechanosensitive ion channel of Escherichia coli.

    PubMed Central

    Cruickshank, C C; Minchin, R F; Le Dain, A C; Martinac, B

    1997-01-01

    The open channel diameter of Escherichia coli recombinant large-conductance mechanosensitive ion channels (MscL) was estimated using the model of Hille (Hille, B. 1968. Pharmacological modifications of the sodium channels of frog nerve. J. Gen. Physiol. 51:199-219) that relates the pore size to conductance. Based on the MscL conductance of 3.8 nS, and assumed pore lengths, a channel diameter of 34 to 46 A was calculated. To estimate the pore size experimentally, the effect of large organic ions on the conductance of MscL was examined. Poly-L-lysines (PLLs) with a diameter of 37 A or larger significantly reduced channel conductance, whereas spermine (approximately 15 A), PLL19 (approximately 25 A) and 1,1'-bis-(3-(1'-methyl-(4,4'-bipyridinium)-1-yl)-propyl)-4,4'-b ipyridinium (approximately 30 A) had no effect. The smaller organic ions putrescine, cadaverine, spermine, and succinate all permeated the channel. We conclude that the open pore diameter of the MscL is approximately 40 A, indicating that the MscL has one of the largest channel pores yet described. This channel diameter is consistent with the proposed homohexameric model of the MscL. PMID:9336188

  17. On the mobility, membrane location and functionality of mechanosensitive channels in Escherichia coli.

    PubMed

    van den Berg, Jonas; Galbiati, Heloisa; Rasmussen, Akiko; Miller, Samantha; Poolman, Bert

    2016-09-06

    Bacterial mechanosensitive channels protect cells from structural damage during hypoosmotic shock. MscS, MscL and MscK are the most abundant channels in E. coli and arguably the most important ones in osmoprotection. By combining physiological assays with quantitative photo-activated localization microscopy (qPALM), we find an almost linear relationship between channel abundance and cell survival. A minimum of 100 MscL (or MscS) channels is needed for protection when a single type of channel is expressed. Under native-like conditions MscL, MscS as well as MscK distribute homogeneously over the cytoplasmic membrane and the lateral diffusion of the channels is in accordance with their relative protein mass. However, we observe cluster formation and a reduced mobility of MscL when the majority of the subunits of the pentameric channel contain the fluorescent mEos3.2 protein. These data provide new insights into the quantitative biology of mechanosensitive channels and emphasizes the need for care in analysing protein complexes even when the fluorescent tag has been optimized for monomeric behaviour.

  18. Amount and avidity of antibody to Escherichia coli O antigen measured with the ammonium sulphate precipitation technique in children with urinary tract infections.

    PubMed

    Ahlstedt, S; Jodal, U; Hanson, L A

    1975-01-01

    The antibody amounts and avidities were analyzed in 13 patients with acute primary pyelonephritis, 11 patients with acute primary cystitis, and one with ureterocele and recurrent infections, using the ammonium sulphate precipitation (ASP) technique. The ASP titrations did not discriminate as well between pyelonephritis and cystitis as do the determinations with the indirect hemagglutination technique. The increase of antibody titer and avidity detected by the ASP method in some of the cystitis patients suggested a deeper tissue involvement in some cases resulting in antibodies demonstrable with this technique. Since control patients also showed a somewhat heterogenous antibody response regarding titer and avidity it cannot be excluded that stimulation by Escherichia coli antigens in the gut is detected by the ASP method.

  19. Porin channels in Escherichia coli: studies with beta-lactams in intact cells.

    PubMed Central

    Nikaido, H; Rosenberg, E Y; Foulds, J

    1983-01-01

    Wild-type Escherichia coli K-12 produces two porins, OmpF (protein 1a) and OmpC (protein 1b). In mutants deficient in both of these "normal" porins, secondary mutants that produce a "new" porin, protein PhoE (protein E), are selected for. We determined the properties of the channels produced by each of these porins by measuring the rates of diffusion of various cephalosporins through the outer membrane in strains producing only one porin species. We found that all porin channels retarded the diffusion of more hydrophobic cephalosporins and that with monoanionic cephalosporins a 10-fold increase in the octanol-water partition coefficient of the solute produced a 5- to 6-fold decrease in the rate of penetration. Electrical charges of the solutes had different effects on different channels. Thus, with the normal porins (i.e., OmpF and OmpC proteins) additional negative charge drastically reduced the penetration rate through the channels, whereas additional positive charge significantly accelerated the penetration. In contrast, diffusion through the PhoE channel was unaffected by the presence of an additional negative charge. We hypothesize that the relative exclusion of hydrophobic and negatively charged solutes by normal porin channels is of ecological advantage to E. coli, which must exclude hydrophobic and anionic bile salts in its natural habitat. The properties of the PhoE porin are also consistent with the recent finding (M. Argast and W. Boos, J. Bacteriol. 143:142-150, 1980; J. Tommassen and B. Lugtenberg, J. Bacteriol. 143:151-157, 1980) that its biosynthesis is derepressed by phosphate starvation; the channel may thus act as an emergency pore primarily for the uptake of phosphate and phosphorylated compounds. Images PMID:6294048

  20. Effect of higher minimum inhibitory concentrations of quaternary ammonium compounds in clinical E. coli isolates on antibiotic susceptibilities and clinical outcomes.

    PubMed

    Buffet-Bataillon, S; Branger, B; Cormier, M; Bonnaure-Mallet, M; Jolivet-Gougeon, A

    2011-10-01

    Quaternary ammonium compounds (QACs) are cationic surfactants used as preservatives and environmental disinfectants. Limited data are available regarding the effect of QACs in the clinical setting. We performed a prospective cohort study in 153 patients with Escherichia coli bacteraemia from February to September 2008 at University Hospital in Rennes. The minimum inhibitory concentrations (MICs) of antibiotics and QACs alkyldimethylbenzylammonium chloride (ADBAC) and didecyldimethylammonium chloride (DDAC) were determined by the agar dilution method. The capacity of biofilm production was assayed using the Crystal Violet method, and mutation frequencies by measuring the capacity of strains to generate resistance to rifampicin. Logistic regression analysis showed that one of the significant factors related to low MICs for ADBAC (≤16 mg/L) and DDAC (≤8 mg/L), was cotrimoxazole susceptibility (odds ratio: 3.72; 95% confidence interval: 1.22-11.24; P=0.02 and OR: 3.61; 95% CI: 1.56-7.56; P<0.01, respectively). Antibiotic susceptibility to cotrimoxazole was strongly associated with susceptibility to amoxicillin and nalidixic acid (P<0.01). Community-acquired or healthcare-associated bacteraemia, severity of bacteraemia, and patient outcome were independent of the MICs of ADBAC and DDAC. Our findings demonstrate an epidemiological relationship between higher MIC values of QACs in clinical E. coli isolates and antibiotic resistance.

  1. Closed-state inactivation involving an internal gate in Kv4.1 channels modulates pore blockade by intracellular quaternary ammonium ions.

    PubMed

    Fineberg, Jeffrey D; Szanto, Tibor G; Panyi, Gyorgy; Covarrubias, Manuel

    2016-08-09

    Voltage-gated K(+) (Kv) channel activation depends on interactions between voltage sensors and an intracellular activation gate that controls access to a central pore cavity. Here, we hypothesize that this gate is additionally responsible for closed-state inactivation (CSI) in Kv4.x channels. These Kv channels undergo CSI by a mechanism that is still poorly understood. To test the hypothesis, we deduced the state of the Kv4.1 channel intracellular gate by exploiting the trap-door paradigm of pore blockade by internally applied quaternary ammonium (QA) ions exhibiting slow blocking kinetics and high-affinity for a blocking site. We found that inactivation gating seemingly traps benzyl-tributylammonium (bTBuA) when it enters the central pore cavity in the open state. However, bTBuA fails to block inactivated Kv4.1 channels, suggesting gated access involving an internal gate. In contrast, bTBuA blockade of a Shaker Kv channel that undergoes open-state P/C-type inactivation exhibits fast onset and recovery inconsistent with bTBuA trapping. Furthermore, the inactivated Shaker Kv channel is readily blocked by bTBuA. We conclude that Kv4.1 closed-state inactivation modulates pore blockade by QA ions in a manner that depends on the state of the internal activation gate.

  2. Closed-state inactivation involving an internal gate in Kv4.1 channels modulates pore blockade by intracellular quaternary ammonium ions

    PubMed Central

    Fineberg, Jeffrey D.; Szanto, Tibor G.; Panyi, Gyorgy; Covarrubias, Manuel

    2016-01-01

    Voltage-gated K+ (Kv) channel activation depends on interactions between voltage sensors and an intracellular activation gate that controls access to a central pore cavity. Here, we hypothesize that this gate is additionally responsible for closed-state inactivation (CSI) in Kv4.x channels. These Kv channels undergo CSI by a mechanism that is still poorly understood. To test the hypothesis, we deduced the state of the Kv4.1 channel intracellular gate by exploiting the trap-door paradigm of pore blockade by internally applied quaternary ammonium (QA) ions exhibiting slow blocking kinetics and high-affinity for a blocking site. We found that inactivation gating seemingly traps benzyl-tributylammonium (bTBuA) when it enters the central pore cavity in the open state. However, bTBuA fails to block inactivated Kv4.1 channels, suggesting gated access involving an internal gate. In contrast, bTBuA blockade of a Shaker Kv channel that undergoes open-state P/C-type inactivation exhibits fast onset and recovery inconsistent with bTBuA trapping. Furthermore, the inactivated Shaker Kv channel is readily blocked by bTBuA. We conclude that Kv4.1 closed-state inactivation modulates pore blockade by QA ions in a manner that depends on the state of the internal activation gate. PMID:27502553

  3. Mechanosensitive channels of Escherichia coli: the MscL gene, protein, and activities

    NASA Technical Reports Server (NTRS)

    Sukharev, S. I.; Blount, P.; Martinac, B.; Kung, C.

    1997-01-01

    Although mechanosensory responses are ubiquitous and diverse, the molecular bases of mechanosensation in most cases remain mysterious MscL, a mechanosensitive channel of large conductance of Escherichia coli and its bacterial homologues are the first and currently only channel molecules shown to directly sense mechanical stretch of the membrane. In response to the tension conveyed via the lipid bilayer, MscL increases its open probability by several orders of magnitude. In the present review we describe the identification, cloning, and first sets of biophysical and structural data on this simplest mechanosensory molecule. We discovered a 2.5-ns mechanosensitive conductance in giant E. coli spheroplasts. Using chromatographies to enrich the target and patch clamp to assay the channel activity in liposome-reconstituted fractions, we identified the MscL protein and cloned the mscL gene. MscL comprises 136 amino acid residues (15 kDa), with two highly hydrophobic regions, and resides in the inner membrane of the bacterium. PhoA-fusion experiments indicate that the protein spans the membrane twice with both termini in the cytoplasm. Spectroscopic techniques show that it is highly helical. Expression of MscL tandems and covalent cross-linking suggest that the active channel complex is a homo-hexamer. We have identified several residues, which when deleted or substituted, affect channel kinetics or mechanosensitivity. Although unique when discovered, highly conserved MscL homologues in both gram-negative and gram-positive bacteria have been found, suggesting their ubiquitous importance among bacteria.

  4. Mechanosensitive channels of Escherichia coli: the MscL gene, protein, and activities

    NASA Technical Reports Server (NTRS)

    Sukharev, S. I.; Blount, P.; Martinac, B.; Kung, C.

    1997-01-01

    Although mechanosensory responses are ubiquitous and diverse, the molecular bases of mechanosensation in most cases remain mysterious MscL, a mechanosensitive channel of large conductance of Escherichia coli and its bacterial homologues are the first and currently only channel molecules shown to directly sense mechanical stretch of the membrane. In response to the tension conveyed via the lipid bilayer, MscL increases its open probability by several orders of magnitude. In the present review we describe the identification, cloning, and first sets of biophysical and structural data on this simplest mechanosensory molecule. We discovered a 2.5-ns mechanosensitive conductance in giant E. coli spheroplasts. Using chromatographies to enrich the target and patch clamp to assay the channel activity in liposome-reconstituted fractions, we identified the MscL protein and cloned the mscL gene. MscL comprises 136 amino acid residues (15 kDa), with two highly hydrophobic regions, and resides in the inner membrane of the bacterium. PhoA-fusion experiments indicate that the protein spans the membrane twice with both termini in the cytoplasm. Spectroscopic techniques show that it is highly helical. Expression of MscL tandems and covalent cross-linking suggest that the active channel complex is a homo-hexamer. We have identified several residues, which when deleted or substituted, affect channel kinetics or mechanosensitivity. Although unique when discovered, highly conserved MscL homologues in both gram-negative and gram-positive bacteria have been found, suggesting their ubiquitous importance among bacteria.

  5. Characterisation of channels induced in planar bilayer membranes by detergent solubilised Escherichia coli porins.

    PubMed

    Lakey, J H; Watts, J P; Lea, E J

    1985-07-25

    Purified OmpF, OmpC, NmpC, PhoE and Lc (Protein 2) porins from the Escherichia coli outer membrane were incorporated into planar phospholipid bilayer membranes and the permeability properties of the pores studied. Triton X-100 solubilised porin samples showed large and reproducible increases in membrane conductivity composed of discreet single-channel events. The magnitude of the cation selectivity found for the porins was in the order OmpC greater than OmpF greater than NmpC = Lc; PhoE was anion selective. For the cation selective porins the cation/anion permeability ratios in a variety of solutes ranged from 6 to 35. Further information on the internal structure of the porins was obtained by examination of the single-channel conductance and this was used to interpret macroscopic observations and to estimate single-channel diameters. The same porins solubilised in SDS exhibited slight conductance increase with no observable single-channel activity. Use of on-line microcomputer techniques confirmed the ohmic current vs. voltage behaviour for all the single porin channels examined.

  6. The effects of parabens on the mechanosensitive channels of E. coli.

    PubMed

    Nguyen, Thom; Clare, Brian; Guo, Wei; Martinac, Boris

    2005-07-01

    Parabens are alkyl esters of p-hydroxybenzoic acid used as preservatives in a wide range of food, pharmaceutical, and cosmetic products. Despite their common use for over 50 years, their mechanism of action is still unclear. In this study we examined the effects of ethyl and propyl paraben, on gating of the E. coli mechanosensitive channel of large conductance (MscL) reconstituted into azolectin liposomes. We found that propyl and ethyl paraben spontaneously activate MscL. Moreover, the addition of propyl paraben caused an increase in MscL activity and the lowering of p(1/2), the pressure at which the MscL was opened 50% of the time, the DeltaG(o), the free energy required to open the MscL, and the parameter alpha, which describes the channel sensitivity to pressure. In addition, in silico studies showed that propyl paraben binds to the channel gate of the MscL. The mechanosensitive channel of small conductance was also found to be spontaneously activated by parabens. In summary, our study indicates that one of the previously unidentified mechanisms of action of parabens as antimicrobial agents is via an interaction with the mechanosensitive channels to upset the osmotic gradients in bacteria.

  7. Examining Escherichia coli glycolytic pathways, catabolite repression, and metabolite channeling using Δpfk mutants

    SciTech Connect

    Hollinshead, Whitney D.; Rodriguez, Sarah; Martin, Hector Garcia; Wang, George; Baidoo, Edward E. K.; Sale, Kenneth L.; Keasling, Jay D.; Mukhopadhyay, Aindrila; Tang, Yinjie J.

    2016-10-10

    Background: Glycolysis breakdowns glucose into essential building blocks and ATP/NAD(P)H for the cell, occupying a central role in its growth and bio-production. Among glycolytic pathways, the Entner Doudoroff pathway (EDP) is a more thermodynamically favorable pathway with fewer enzymatic steps than either the Embden-Meyerhof-Parnas pathway (EMPP) or the oxidative pentose phosphate pathway (OPPP). However, Escherichia coli do not use their native EDP for glucose metabolism. Results: Overexpression of edd and eda in E. coli to enhance EDP activity resulted in only a small shift in the flux directed through the EDP (~20 % of glycolysis flux). Disrupting the EMPP by phosphofructokinase I (pfkA) knockout increased flux through OPPP (~60 % of glycolysis flux) and the native EDP (~14 % of glycolysis flux), while overexpressing edd and eda in this ΔpfkA mutant directed ~70 % of glycolytic flux through the EDP. The downregulation of EMPP via the pfkA deletion significantly decreased the growth rate, while EDP overexpression in the ΔpfkA mutant failed to improve its growth rates due to metabolic burden. However, the reorganization of E. coli glycolytic strategies did reduce glucose catabolite repression. The ΔpfkA mutant in glucose medium was able to cometabolize acetate via the citric acid cycle and gluconeogenesis, while EDP overexpression in the ΔpfkA mutant repressed acetate flux toward gluconeogenesis. Moreover, 13C-pulse experiments in the ΔpfkA mutants showed unsequential labeling dynamics in glycolysis intermediates, possibly suggesting metabolite channeling (metabolites in glycolysis are pass from enzyme to enzyme without fully equilibrating within the cytosol medium). Conclusions: We engineered E. coli to redistribute its native glycolytic flux. The replacement of EMPP by EDP did not improve E. coli glucose utilization or biomass growth, but alleviated catabolite repression. More importantly, our results supported the hypothesis of channeling in

  8. Examining Escherichia coli glycolytic pathways, catabolite repression, and metabolite channeling using Δpfk mutants

    DOE PAGES

    Hollinshead, Whitney D.; Rodriguez, Sarah; Martin, Hector Garcia; ...

    2016-10-10

    Background: Glycolysis breakdowns glucose into essential building blocks and ATP/NAD(P)H for the cell, occupying a central role in its growth and bio-production. Among glycolytic pathways, the Entner Doudoroff pathway (EDP) is a more thermodynamically favorable pathway with fewer enzymatic steps than either the Embden-Meyerhof-Parnas pathway (EMPP) or the oxidative pentose phosphate pathway (OPPP). However, Escherichia coli do not use their native EDP for glucose metabolism. Results: Overexpression of edd and eda in E. coli to enhance EDP activity resulted in only a small shift in the flux directed through the EDP (~20 % of glycolysis flux). Disrupting the EMPP bymore » phosphofructokinase I (pfkA) knockout increased flux through OPPP (~60 % of glycolysis flux) and the native EDP (~14 % of glycolysis flux), while overexpressing edd and eda in this ΔpfkA mutant directed ~70 % of glycolytic flux through the EDP. The downregulation of EMPP via the pfkA deletion significantly decreased the growth rate, while EDP overexpression in the ΔpfkA mutant failed to improve its growth rates due to metabolic burden. However, the reorganization of E. coli glycolytic strategies did reduce glucose catabolite repression. The ΔpfkA mutant in glucose medium was able to cometabolize acetate via the citric acid cycle and gluconeogenesis, while EDP overexpression in the ΔpfkA mutant repressed acetate flux toward gluconeogenesis. Moreover, 13C-pulse experiments in the ΔpfkA mutants showed unsequential labeling dynamics in glycolysis intermediates, possibly suggesting metabolite channeling (metabolites in glycolysis are pass from enzyme to enzyme without fully equilibrating within the cytosol medium). Conclusions: We engineered E. coli to redistribute its native glycolytic flux. The replacement of EMPP by EDP did not improve E. coli glucose utilization or biomass growth, but alleviated catabolite repression. More importantly, our results supported the hypothesis of channeling in the

  9. A multi-commuted flow injection system with a multi-channel propulsion unit placed before detection: Spectrophotometric determination of ammonium.

    PubMed

    Oliveira, Sara M; Lopes, Teresa I M S; Tóth, Ildikó V; Rangel, António O S S

    2007-09-26

    A flow system with a multi-channel peristaltic pump placed before the solenoid valves is proposed to overcome some limitations attributed to multi-commuted flow injection systems: the negative pressure can lead to the formation of unwanted air bubbles and limits the use of devices for separation processes (gas diffusion, dialysis or ion-exchange). The proposed approach was applied to the colorimetric determination of ammonium nitrogen. In alkaline medium, ammonium is converted into ammonia, which diffuses over the membrane, causing a pH change and subsequently a colour change in the acceptor stream (bromothymol blue solution). The system allowed the re-circulation of the acceptor solution and was applied to ammonium determination in surface and tap water, providing relative standard deviations lower than 1.5%. A stopped flow approach in the acceptor stream was adopted to attain a low quantification limit (42 microgL(-1)) and a linear dynamic range of 50-1000 microgL(-1) with a determination rate of 20 h(-1).

  10. Role of the lateral channel in catalase HPII of Escherichia coli.

    PubMed

    Sevinc, M S; Maté, M J; Switala, J; Fita, I; Loewen, P C

    1999-03-01

    The heme-containing catalase HPII of Escherichia coli consists of a homotetramer in which each subunit contains a core region with the highly conserved catalase tertiary structure, to which are appended N- and C-terminal extensions making it the largest known catalase. HPII does not bind NADPH, a cofactor often found in catalases. In HPII, residues 585-590 of the C-terminal extension protrude into the pocket corresponding to the NADPH binding site in the bovine liver catalase. Despite this difference, residues that define the NADPH pocket in the bovine enzyme appear to be well preserved in HPII. Only two residues that interact ionically with NADPH in the bovine enzyme (Asp212 and His304) differ in HPII (Glu270 and Glu362), but their mutation to the bovine sequence did not promote nucleotide binding. The active-site heme groups are deeply buried inside the molecular structure requiring the movement of substrate and products through long channels. One potential channel is about 30 A in length, approaches the heme active site laterally, and is structurally related to the branched channel associated with the NADPH binding pocket in catalases that bind the dinucleotide. In HPII, the upper branch of this channel is interrupted by the presence of Arg260 ionically bound to Glu270. When Arg260 is replaced by alanine, there is a threefold increase in the catalytic activity of the enzyme. Inhibitors of HPII, including azide, cyanide, various sulfhydryl reagents, and alkylhydroxylamine derivatives, are effective at lower concentration on the Ala260 mutant enzyme compared to the wild-type enzyme. The crystal structure of the Ala260 mutant variant of HPII, determined at 2.3 A resolution, revealed a number of local structural changes resulting in the opening of a second branch in the lateral channel, which appears to be used by inhibitors for access to the active site, either as an inlet channel for substrate or an exhaust channel for reaction products.

  11. Stoichiometry of the large conductance bacterial mechanosensitive channel of E. coli. A biochemical study

    NASA Technical Reports Server (NTRS)

    Sukharev, S. I.; Schroeder, M. J.; McCaslin, D. R.

    1999-01-01

    MscL, a 15 kDa transmembrane protein, is the only component involved in the formation of a 3 nS channel in the inner membrane of Escherichia coli that opens in response to mechanical or osmotic stress. While previous data had suggested that the functional MscL complex might be a hexamer, a recent crystallographic study of the MscL homologue from M. tuberculosis reveals a pentameric structure. The present work further examines the stoichiometry of the E. coli MscL using a variety of biochemical approaches. Detergent-purified 6His-MscL in solution and MscL in the membrane could be chemically crosslinked with the products displaying ladderlike patterns on SDS gels. Three crosslinking agents (EDC, DMS, and DMA) used at saturating concentrations invariably generated pentamers as the largest product. DSS produced additional bands corresponding to larger complexes although the pentamer band appeared to be the predominant product at high levels of crosslinker. It is not clear whether these extra bands reflect a difference in the crosslinking chemistry of DSS or whether its spacer arm is the longest of those used, or a combination of both facts. For the detergent-solubilized 6His-MscL both sedimentation equilibrium and gel chromatography showed the presence of multiple species. Thus the longer spacer arm could permit both intra- and intercomplex linkages. Nonetheless, the patterns obtained with all agents are consistent with and strongly suggest a pentameric organization for the MscL channel. Expression of MscL as genetically engineered double or triple subunit tandems yields low numbers of functional channels as compared to expressed monomers. The double-tandem assemblies must have an even number of subunits and crosslinking in the membrane confirmed hexamerization. Gel chromatography clearly demonstrated that the channels formed from the double tandems were larger than those formed from WT MscL, consistent with the native channel being pentameric. The observation that

  12. Stoichiometry of the large conductance bacterial mechanosensitive channel of E. coli. A biochemical study

    NASA Technical Reports Server (NTRS)

    Sukharev, S. I.; Schroeder, M. J.; McCaslin, D. R.

    1999-01-01

    MscL, a 15 kDa transmembrane protein, is the only component involved in the formation of a 3 nS channel in the inner membrane of Escherichia coli that opens in response to mechanical or osmotic stress. While previous data had suggested that the functional MscL complex might be a hexamer, a recent crystallographic study of the MscL homologue from M. tuberculosis reveals a pentameric structure. The present work further examines the stoichiometry of the E. coli MscL using a variety of biochemical approaches. Detergent-purified 6His-MscL in solution and MscL in the membrane could be chemically crosslinked with the products displaying ladderlike patterns on SDS gels. Three crosslinking agents (EDC, DMS, and DMA) used at saturating concentrations invariably generated pentamers as the largest product. DSS produced additional bands corresponding to larger complexes although the pentamer band appeared to be the predominant product at high levels of crosslinker. It is not clear whether these extra bands reflect a difference in the crosslinking chemistry of DSS or whether its spacer arm is the longest of those used, or a combination of both facts. For the detergent-solubilized 6His-MscL both sedimentation equilibrium and gel chromatography showed the presence of multiple species. Thus the longer spacer arm could permit both intra- and intercomplex linkages. Nonetheless, the patterns obtained with all agents are consistent with and strongly suggest a pentameric organization for the MscL channel. Expression of MscL as genetically engineered double or triple subunit tandems yields low numbers of functional channels as compared to expressed monomers. The double-tandem assemblies must have an even number of subunits and crosslinking in the membrane confirmed hexamerization. Gel chromatography clearly demonstrated that the channels formed from the double tandems were larger than those formed from WT MscL, consistent with the native channel being pentameric. The observation that

  13. Single residue substitutions that change the gating properties of a mechanosensitive channel in Escherichia coli

    NASA Technical Reports Server (NTRS)

    Blount, P.; Sukharev, S. I.; Schroeder, M. J.; Nagle, S. K.; Kung, C.

    1996-01-01

    MscL is a channel that opens a large pore in the Escherichia coli cytoplasmic membrane in response to mechanical stress. Previously, we highly enriched the MscL protein by using patch clamp as a functional assay and cloned the corresponding gene. The predicted protein contains a largely hydrophobic core spanning two-thirds of the molecule and a more hydrophilic carboxyl terminal tail. Because MscL had no homology to characterized proteins, it was impossible to predict functional regions of the protein by simple inspection. Here, by mutagenesis, we have searched for functionally important regions of this molecule. We show that a short deletion from the amino terminus (3 amino acids), and a larger deletion of 27 amino acids from the carboxyl terminus of this protein, had little if any effect in channel properties. We have thus narrowed the search of the core mechanosensitive mechanism to 106 residues of this 136-amino acid protein. In contrast, single residue substitutions of a lysine in the putative first transmembrane domain or a glutamine in the periplasmic loop caused pronounced shifts in the mechano-sensitivity curves and/or large changes in the kinetics of channel gating, suggesting that the conformational structure in these regions is critical for normal mechanosensitive channel gating.

  14. A large-conductance mechanosensitive channel in E. coli encoded by mscL alone

    NASA Astrophysics Data System (ADS)

    Sukharev, Sergei I.; Blount, Paul; Martinac, Boris; Blattner, Frederick R.; Kung, Ching

    1994-03-01

    ALL cellular organisms respond to vibration, touch, gravity or changes in osmolarity, although the molecules on which such mechanosensations depend are unknown. Candidates include certain channels that gate in response to membrane stretch1,2. Patch-clamp experiments with Escherichia coli envelope have revealed a mechanosensitive channel with very large conductance (MscL) and one with a smaller conductance (MscS)3-6 which may be important in osmoregulation. Here we have solubilized and fractionated the envelope, reconstituted the MscL activity in vitro, and traced it to a small protein, whose gene, mscL, we then cloned. Insertional disruption of mscL removes the channel activity, whereas re-expression of mscL borne on an expression plasmid restores it. MscL-channel activities were observed in material from a cell-free expression system with mscL as the only template. The mscL nucleotide sequence predicts a unique protein of only 136 amino acids, with a highly hydrophobic core and very different from porins or other known proteins.

  15. Single residue substitutions that change the gating properties of a mechanosensitive channel in Escherichia coli

    NASA Technical Reports Server (NTRS)

    Blount, P.; Sukharev, S. I.; Schroeder, M. J.; Nagle, S. K.; Kung, C.

    1996-01-01

    MscL is a channel that opens a large pore in the Escherichia coli cytoplasmic membrane in response to mechanical stress. Previously, we highly enriched the MscL protein by using patch clamp as a functional assay and cloned the corresponding gene. The predicted protein contains a largely hydrophobic core spanning two-thirds of the molecule and a more hydrophilic carboxyl terminal tail. Because MscL had no homology to characterized proteins, it was impossible to predict functional regions of the protein by simple inspection. Here, by mutagenesis, we have searched for functionally important regions of this molecule. We show that a short deletion from the amino terminus (3 amino acids), and a larger deletion of 27 amino acids from the carboxyl terminus of this protein, had little if any effect in channel properties. We have thus narrowed the search of the core mechanosensitive mechanism to 106 residues of this 136-amino acid protein. In contrast, single residue substitutions of a lysine in the putative first transmembrane domain or a glutamine in the periplasmic loop caused pronounced shifts in the mechano-sensitivity curves and/or large changes in the kinetics of channel gating, suggesting that the conformational structure in these regions is critical for normal mechanosensitive channel gating.

  16. Single-channel measurements of an N-acetylneuraminic acid-inducible outer membrane channel in Escherichia coli

    PubMed Central

    Giri, Janhavi; Tang, John M.; Wirth, Christophe; Peneff, Caroline M.

    2012-01-01

    NanC is an Escherichia coli outer membrane protein involved in sialic acid (Neu5Ac, i.e., N-acetylneuraminic acid) uptake. Expression of the NanC gene is induced and controlled by Neu5Ac. The transport mechanism of Neu5Ac is not known. The structure of NanC was recently solved (PDB code: 2WJQ) and includes a unique arrangement of positively charged (basic) side chains consistent with a role in acidic sugar transport. However, initial functional measurements of NanC failed to find its role in the transport of sialic acids, perhaps because of the ionic conditions used in the experiments. We show here that the ionic conditions generally preferred for measuring the function of outer-membrane porins are not appropriate for NanC. Single channels of NanC at pH 7.0 have: (1) conductance 100 pS to 800 pS in 100 mM KCl to 3 M KCl), (2) anion over cation selectivity (Vreversal = +16 mV in 250 mM KCl || 1 M KCl), and (3) two forms of voltage-dependent gating (channel closures above ±200 mV). Single-channel conductance decreases by 50% when HEPES concentration is increased from 100 μM to 100 mM in 250 mM KCl at pH 7.4, consistent with the two HEPES binding sites observed in the crystal structure. Studying alternative buffers, we find that phosphate interferes with the channel conductance. Single-channel conductance decreases by 19% when phosphate concentration is increased from 0 mM to 5 mM in 250 mM KCl at pH 8.0. Surprisingly, TRIS in the baths reacts with Ag|AgCl electrodes, producing artifacts even when the electrodes are on the far side of agar–KCl bridges. A suitable baseline solution for NanC is 250 mM KCl adjusted to pH 7.0 without buffer. PMID:22246445

  17. Domain organization of the MscS mechanosensitive channel of Escherichia coli

    PubMed Central

    Miller, Samantha; Bartlett, Wendy; Chandrasekaran, Subramanian; Simpson, Sally; Edwards, Michelle; Booth, Ian R.

    2003-01-01

    The major structural features of the Escherichia coli MscS mechanosensitive channel protein have been explored using alkaline phosphatase (PhoA) fusions, precise deletions and site-directed mutations. PhoA protein fusion data, combined with the positive-inside rule, strongly support a model in which MscS crosses the membrane three times, adopting an Nout–Cin configuration. Deletion data suggest that the C-terminal domain of the protein is essential for the stability of the MscS channel, whereas the protein will tolerate small deletions at the N-terminus. Four mutants that exhibit either gain-of-function (GOF) or loss-of-function have been identified: a double mutation I48D/S49P inactivates MscS, whereas the MscS mutants T93R, A102P and L109S cause a strong GOF phenotype. The similarity of MscS to the last two domains of MscK (formerly KefA) is reinforced by the demonstration that expression of a truncated MscK protein can substitute for MscL and MscS in downshock survival assays. The data derived from studies of the organization, conservation and the influence of mutations provide significant insights into the structure of the MscS channel. PMID:12505982

  18. Pore mutations of the Escherichia coli MscS channel affect desensitization but not ionic preference.

    PubMed

    Edwards, Michelle D; Bartlett, Wendy; Booth, Ian R

    2008-04-15

    Mechanosensitive channels rescue bacterial cells from a fate of lysis when they transfer from a high- to low-osmolarity environment. Of three Escherichia coli mechanosensitive proteins studied to date, only MscS-Ec demonstrates a small anionic preference and a desensitized, nonconducting state under sustained pressure. Little is known about the mechanisms generating these distinctive properties. Eliminating the sole positive charge in the MscS-Ec pore region (Arg(88)) did not alter anionic preference. Adding positive charges at either end of the pore did not augment anionic preference, and placing negative charges within the pore did not diminish it. Thus, pore charges do not control this characteristic. However, from this analysis we identified mutations in the hinge region of the MscS-Ec pore helix (at Gly(113)) that profoundly affected ability of the channel to desensitize. Substitution with nonpolar (Ala, Pro) or polar (Asp, Arg, Ser) residues inhibited transition to the desensitized state. Interestingly, Gly(113) replaced with Met did not impede desensitization. Thus, although Gly is not specifically required at position 113, MscS desensitization is strongly influenced by the residue situated here. Mutations at residues further into the pore also regulated desensitization. Transition to this unique mechanosensitive channel state is discussed in terms of existing data.

  19. Quantification of Fluoroquinolone Uptake through the Outer Membrane Channel OmpF of Escherichia coli.

    PubMed

    Cama, Jehangir; Bajaj, Harsha; Pagliara, Stefano; Maier, Theresa; Braun, Yvonne; Winterhalter, Mathias; Keyser, Ulrich F

    2015-11-04

    Decreased drug accumulation is a common cause of antibiotic resistance in microorganisms. However, there are few reliable general techniques capable of quantifying drug uptake through bacterial membranes. We present a semiquantitative optofluidic assay for studying the uptake of autofluorescent drug molecules in single liposomes. We studied the effect of the Escherichia coli outer membrane channel OmpF on the accumulation of the fluoroquinolone antibiotic, norfloxacin, in proteoliposomes. Measurements were performed at pH 5 and pH 7, corresponding to two different charge states of norfloxacin that bacteria are likely to encounter in the human gastrointestinal tract. At both pH values, the porins significantly enhance drug permeation across the proteoliposome membranes. At pH 5, where norfloxacin permeability across pure phospholipid membranes is low, the porins increase drug permeability by 50-fold on average. We estimate a flux of about 10 norfloxacin molecules per second per OmpF trimer in the presence of a 1 mM concentration gradient of norfloxacin. We also performed single channel electrophysiology measurements and found that the application of transmembrane voltages causes an electric field driven uptake in addition to concentration driven diffusion. We use our results to propose a physical mechanism for the pH mediated change in bacterial susceptibility to fluoroquinolone antibiotics.

  20. The projection structure of Kch, a putative potassium channel in Escherichia coli, by electron crystallography.

    PubMed

    Kuang, Qie; Purhonen, Pasi; Jegerschöld, Caroline; Hebert, Hans

    2014-01-01

    The kch gene, the only potassium channel gene in Escherichia coli, has the property to express both full-length Kch and its cytosolic domain (RCK) due to a methionine at position 240. The RCK domains are believed to form an octameric ring structure and regulate the gating of the potassium channels after having bound certain ligands. Several different gating ring structures have been reported for the soluble RCK domains, however, these were studied isolated from their transmembrane parts. We previously reported an octameric structure of Kch in solution by electron microscopy and single particle reconstruction, composed of two tetrameric full-length proteins through RCK interaction. To exclude the effect of the detergent, we have now performed an electron crystallographic study of the full-length Kch in membrane bound form. Well-ordered two-dimensional crystals were grown in a natural phospholipid environment. A projection map merged from the fifteen best images extended to 6Å resolution. The c12 two-sided plane group of the two-dimensional crystals showed that Kch crystallized as two symmetrically related overlapping layers. The arrangement suggests that the two layers of RCK domains are shifted with respect to each other and the RCK octameric gating ring of Kch does not form under the crystallization condition.

  1. The channel-tunnel HI1462 of Haemophilus influenzae reveals differences to Escherichia coli TolC.

    PubMed

    Polleichtner, Georg; Andersen, Christian

    2006-06-01

    Efflux pumps play a major role in multidrug resistance of pathogenic bacteria. The TolC homologue HI1462 was identified as the single channel-tunnel in Haemophilus influenzae required to form a functional multidrug efflux pump. The outer-membrane protein was expressed in Escherichia coli, purified and reconstituted in black lipid membranes. It exhibited a comparatively small single-channel conductance of 43 pS in 1 M KCl and is the first known TolC homologue which is anion-selective. The HI1462 structure was modelled and an arginine residue lining the tunnel entrance was identified. The channel-tunnel of a mutant with the arginine substituted by an alanine residue was cation-selective and had a sevenfold higher single-channel conductance compared to wild-type. These results confirm that the arginine is responsible for anion selectivity and forms a salt bridge with a glutamate residue of the adjacent monomer, establishing a circular network, which keeps the tunnel entrance in a tightly closed conformation. In in vivo experiments, both the wild-type HI1462 and the mutant were able to substitute for E. coli TolC in the haemolysin secretion system, but not in the AcrAB/TolC multidrug efflux pump. The structure-function relationship of HI1462 is discussed in the context of the well-studied TolC channel-tunnel of E. coli.

  2. Potassium uptake supporting plant growth in the absence of AKT1 channel activity: Inhibition by ammonium and stimulation by sodium

    NASA Technical Reports Server (NTRS)

    Spalding, E. P.; Hirsch, R. E.; Lewis, D. R.; Qi, Z.; Sussman, M. R.; Lewis, B. D.

    1999-01-01

    A transferred-DNA insertion mutant of Arabidopsis that lacks AKT1 inward-rectifying K+ channel activity in root cells was obtained previously by a reverse-genetic strategy, enabling a dissection of the K+-uptake apparatus of the root into AKT1 and non-AKT1 components. Membrane potential measurements in root cells demonstrated that the AKT1 component of the wild-type K+ permeability was between 55 and 63% when external [K+] was between 10 and 1,000 microM, and NH4+ was absent. NH4+ specifically inhibited the non-AKT1 component, apparently by competing for K+ binding sites on the transporter(s). This inhibition by NH4+ had significant consequences for akt1 plants: K+ permeability, 86Rb+ fluxes into roots, seed germination, and seedling growth rate of the mutant were each similarly inhibited by NH4+. Wild-type plants were much more resistant to NH4+. Thus, AKT1 channels conduct the K+ influx necessary for the growth of Arabidopsis embryos and seedlings in conditions that block the non-AKT1 mechanism. In contrast to the effects of NH4+, Na+ and H+ significantly stimulated the non-AKT1 portion of the K+ permeability. Stimulation of akt1 growth rate by Na+, a predicted consequence of the previous result, was observed when external [K+] was 10 microM. Collectively, these results indicate that the AKT1 channel is an important component of the K+ uptake apparatus supporting growth, even in the "high-affinity" range of K+ concentrations. In the absence of AKT1 channel activity, an NH4+-sensitive, Na+/H+-stimulated mechanism can suffice.

  3. Potassium uptake supporting plant growth in the absence of AKT1 channel activity: Inhibition by ammonium and stimulation by sodium

    NASA Technical Reports Server (NTRS)

    Spalding, E. P.; Hirsch, R. E.; Lewis, D. R.; Qi, Z.; Sussman, M. R.; Lewis, B. D.

    1999-01-01

    A transferred-DNA insertion mutant of Arabidopsis that lacks AKT1 inward-rectifying K+ channel activity in root cells was obtained previously by a reverse-genetic strategy, enabling a dissection of the K+-uptake apparatus of the root into AKT1 and non-AKT1 components. Membrane potential measurements in root cells demonstrated that the AKT1 component of the wild-type K+ permeability was between 55 and 63% when external [K+] was between 10 and 1,000 microM, and NH4+ was absent. NH4+ specifically inhibited the non-AKT1 component, apparently by competing for K+ binding sites on the transporter(s). This inhibition by NH4+ had significant consequences for akt1 plants: K+ permeability, 86Rb+ fluxes into roots, seed germination, and seedling growth rate of the mutant were each similarly inhibited by NH4+. Wild-type plants were much more resistant to NH4+. Thus, AKT1 channels conduct the K+ influx necessary for the growth of Arabidopsis embryos and seedlings in conditions that block the non-AKT1 mechanism. In contrast to the effects of NH4+, Na+ and H+ significantly stimulated the non-AKT1 portion of the K+ permeability. Stimulation of akt1 growth rate by Na+, a predicted consequence of the previous result, was observed when external [K+] was 10 microM. Collectively, these results indicate that the AKT1 channel is an important component of the K+ uptake apparatus supporting growth, even in the "high-affinity" range of K+ concentrations. In the absence of AKT1 channel activity, an NH4+-sensitive, Na+/H+-stimulated mechanism can suffice.

  4. Function and Expression of an N-Acetylneuraminic Acid-Inducible Outer Membrane Channel in Escherichia coli

    PubMed Central

    Condemine, Guy; Berrier, Catherine; Plumbridge, Jacqueline; Ghazi, Alexandre

    2005-01-01

    The Escherichia coli yjhA (renamed nanC) gene encodes a protein of the KdgM family of outer membrane-specific channels. It is transcribed divergently from fimB, a gene involved in the site-specific inversion of the region controlling transcription of the fimbrial structural genes but is separated from it by one of the largest intergenic regions in E. coli. We show that nanC expression is induced by N-acetylneuraminic acid and modulated by N-acetylglucosamine. This regulation occurs via the NanR and NagC regulators, which also control fimB expression. nanC expression is also activated by the regulators cyclic AMP-catabolite activator protein, OmpR, and CpxR. When the NanC protein was reconstituted into liposomes, it formed channels with a conductance of 450 pS at positive potential and 300 to 400 pS at negative potential in 800 mM KCl. The channels had a weak anionic selectivity. In an ompR background, where the general porins OmpF and OmpC are absent, NanC is required for growth of E. coli on N-acetylneuraminic acid as the sole carbon source. All these results suggest that NanC is an N-acetylneuraminic acid outer membrane channel protein. PMID:15743943

  5. Single channel atmospheric pressure transporting plasma and plasma stream demultiplexing: physical characterization and application to E. coli bacteria inactivation

    NASA Astrophysics Data System (ADS)

    Valinataj Omran, A.; Sohbatzadeh, F.; Siadati, S. N.; Hosseinzadeh Colagar, A.; Akishev, Y.; Arefi-Khonsari, F.

    2017-08-01

    In this article, we developed transporting plasma sources that operate at atmospheric pressure. The effect of electrode configuration on plasma transporting was investigated. In order to increase the transporting plasma cross-section, we converted a plasma stream into four plasma channels by a cylindrical housing. Electron excitation and rotational temperatures were estimated using optical emission spectroscopy. Furthermore, the electrical and temporal characteristics of the plasma, discharge power and charge deposition on the target were investigated. The propagation characteristics of single and multi-channel transporting plasma were compared with the same cross-sectional area. Two configurations for multi-channels were designed for this purpose. Escherichia coli bacteria were exposed to the single and multi-channel transporting discharge for different time durations. After exposure, the results indicated that the inactivation zones were significantly increased by a multi-channel transporting plasma. Finally, E. coli inactivation by those plasma apparatuses was compared with that of several standard antimicrobial test discs such as Gentamicin, Tetracycline, Amoxicillin and Cefixime.

  6. Substrate recognition in the Escherichia coli ammonia channel AmtB: a QM/MM investigation.

    PubMed

    Nygaard, Thomas P; Alfonso-Prieto, Mercedes; Peters, Günther H; Jensen, Morten Ø; Rovira, Carme

    2010-09-16

    Although the Escherichia coli ammonia transporter B (AmtB) protein has been the focus of several recent studies, there are still many questions and controversies regarding substrate binding and recognition. Specifically, how and where AmtB differentiates between substrates is not yet fully understood. The present computational study addresses the importance of intermolecular interactions with respect to substrate recruitment and recognition by means of ab initio QM/MM simulations. On the basis of calculations with substrates NH(3), NH(4)(+), Na(+), and K(+) positioned at the periplasmic binding site (Am1) and NH(3) and NH(4)(+) at intraluminal binding sites (Am1a/b), we conclude that D160 is the single most important residue for substrate recruitment, whereas cation-π interactions to W148 and F107 are found to be less important. Regarding substrate recruitment and recognition, we find that only NH(4)(+) and K(+) reach the Am1 site. However, NH(4)(+) has the largest affinity for this site due to its better dehydration compensation, while charge stabilization effects favor the binding of NH(4)(+) over NH(3) (i.e., if NH(3) would enter the Am1 site, it is likely to be protonated). Therefore, we conclude that the Am1 site selects NH(4)(+) over Na(+), K(+) and NH(3). Our calculations also suggest that translocation of NH(4)(+) from Am1 into the channel lumen is driven by rotation of the A162-G163 peptide bond, which coordinates NH(4)(+) but not NH(3) at both Am1 and Am1a/b sites.

  7. Diffusion of beta-lactam antibiotics through the porin channels of Escherichia coli K-12.

    PubMed Central

    Yoshimura, F; Nikaido, H

    1985-01-01

    Diffusion rates of various beta-lactam antibiotics through the OmpF and OmpC porin channels of Escherichia coli K-12 were measured by the use of reconstituted proteoliposomes. The results can be interpreted on the basis of the gross physicochemical properties of the antibiotics along the following lines. (i) As noted previously (Nikaido et al., J. Bacteriol., 153:232-240, 1983), there was a monotonous dependence of the penetration rate on the hydrophobicity of the molecule among the classical monoanionic beta-lactams, and a 10-fold increase in the octanol-water partition coefficient of the uncharged molecule decreased the penetration rate by a factor of 5 to 6. (ii) Compounds with exceptionally bulky side chains, such as mezlocillin, piperacillin, and cefoperazone, showed much slower penetration rates than expected from their hydrophobicity. (iii) The substituted oxime side chain on the alpha-carbon of the substituent group at position 7 of the cephem nucleus decreased the penetration rate almost by an order of magnitude; this appears to be largely due to the steric effect. (iv) The presence of a methoxy group at position 7 of the cephalosporins also reduced the penetration rate by 20%, probably also due to the steric hindrance. (v) Zwitterionic compounds penetrated very rapidly, and the correlation between the rate and hydrophobicity appeared to be much weaker than with the monoanionic compounds. Imipenem showed the highest permeability among the compounds tested, presumably due, at least in part, to its compact molecular structure. (vi) Compounds with two negative charges penetrated more slowly than did analogs with only one negatively charged group. Among them, only moxalactam, ceftriaxone, and azthreonam showed penetration rates corresponding to, or higher than, 10% of that of imipenem. PMID:2580479

  8. Ammonium sulfamate

    Integrated Risk Information System (IRIS)

    Ammonium sulfamate ; CASRN 7773 - 06 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogen

  9. Ammonium methacrylate

    Integrated Risk Information System (IRIS)

    Ammonium methacrylate ; CASRN 16325 - 47 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  10. Ammonium acetate

    Integrated Risk Information System (IRIS)

    Ammonium acetate ; CASRN 631 - 61 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  11. Helicity, membrane incorporation, orientation and thermal stability of the large conductance mechanosensitive ion channel from E. coli

    NASA Technical Reports Server (NTRS)

    Arkin, I. T.; Sukharev, S. I.; Blount, P.; Kung, C.; Brunger, A. T.

    1998-01-01

    In this report, we present structural studies on the large conductance mechanosensitive ion channel (MscL) from E. coli in detergent micelles and lipid vesicles. Both transmission Fourier transform infrared spectroscopy and circular dichroism (CD) spectra indicate that the protein is highly helical in detergents as well as liposomes. The secondary structure of the proteins was shown to be highly resistant towards denaturation (25-95 degrees C) based on an ellipticity thermal profile. Amide H+/D+ exchange was shown to be extensive (ca. 66%), implying that two thirds of the protein are water accessible. MscL, reconstituted in oriented lipid bilayers, was shown to possess a net bilayer orientation using dichroic ratios measured by attenuated total-reflection Fourier transform infrared spectroscopy. Here, we present and discuss this initial set of structural data on this new family of ion-channel proteins.

  12. Helicity, membrane incorporation, orientation and thermal stability of the large conductance mechanosensitive ion channel from E. coli

    NASA Technical Reports Server (NTRS)

    Arkin, I. T.; Sukharev, S. I.; Blount, P.; Kung, C.; Brunger, A. T.

    1998-01-01

    In this report, we present structural studies on the large conductance mechanosensitive ion channel (MscL) from E. coli in detergent micelles and lipid vesicles. Both transmission Fourier transform infrared spectroscopy and circular dichroism (CD) spectra indicate that the protein is highly helical in detergents as well as liposomes. The secondary structure of the proteins was shown to be highly resistant towards denaturation (25-95 degrees C) based on an ellipticity thermal profile. Amide H+/D+ exchange was shown to be extensive (ca. 66%), implying that two thirds of the protein are water accessible. MscL, reconstituted in oriented lipid bilayers, was shown to possess a net bilayer orientation using dichroic ratios measured by attenuated total-reflection Fourier transform infrared spectroscopy. Here, we present and discuss this initial set of structural data on this new family of ion-channel proteins.

  13. Electron crystallography of PhoE porin, an outer membrane, channel- forming protein from E. coli

    SciTech Connect

    Walian, P.J.

    1989-11-01

    One approach to studying the structure of membrane proteins is the use of electron crystallography. Dr. Bing Jap has crystallized PhoE pore-forming protein (porin) from the outer membrane of escherichia coli (E. coli) into monolayer crystals. The findings of this research and those of Jap (1988, 1989) have determined these crystals to be highly ordered, yielding structural information to a resolution of better than 2.8 angstroms. The task of this thesis has been to collect and process the electron diffraction patterns necessary to generate a complete three-dimensional set of high resolution structure factor amplitudes of PhoE porin. Fourier processing of these amplitudes when combined with the corresponding phase data is expected to yield the three-dimensional structure of PhoE porin at better than 3.5 angstroms resolution. 92 refs., 33 figs., 3 tabs. (CBS)

  14. Magnolol and honokiol regulate the calcium-activated potassium channels signaling pathway in Enterotoxigenic Escherichia coli-induced diarrhea mice.

    PubMed

    Deng, Yanli; Han, Xuefeng; Tang, Shaoxun; Xiao, Wenjun; Tan, Zhiliang; Zhou, Chuanshe; Wang, Min; Kang, Jinghe

    2015-05-15

    To explore the regulatory mechanisms of magnolol and honokiol on calcium-activated potassium channels signaling pathway in Enterotoxigenic Escherichia coli (ETEC)-induced diarrhea mice, the concentrations of serum chloride ion (Cl(-)), sodium ion (Na(+)), potassium ion (K(+)) and calcium ion (Ca(2+)) were measured. Additionally, the mRNA expressions of calmodulin 1 (CaM), calcium/calmodulin-dependent protein kinase II alpha subunit (CaMKIIα) and beta subunit (CaMKIIβ), ryanodine receptor 1, inositol 1,4,5-trisphosphate receptors (IP3 receptors), protein kinases C (PKC), potassium intermediate/small conductance calcium-activated channels (SK) and potassium large conductance calcium-activated channels(BK)were determined. A diarrhea mouse model was established using ETEC suspensions (3.29×10(9)CFU/ml) at a dosage of 0.02ml/g live body weight (BW). Magnolol or honokiol was intragastrically administered at dosages of 100 (M100 or H100), 300 (M300 or H300) and 500 (M500 or H500) mg/kg BW according to a 3×3 factorial arrangement. Magnolol and honokiol increased the Cl(-) and K(+) concentrations, further, upregulated the CaM, BKα1 and BKβ3 mRNA levels but downregulated the IP3 receptors 1, PKC, SK1, SK2, SK3, SK4 and BKβ4 mRNA expressions. Magnolol and honokiol did not alter the CaMKIIα, CaMKIIβ, ryanodine receptor 1, IP3 receptor 2, IP3 receptor 3, BKβ1 and BKβ2 mRNA expressions. These results clarify that magnolol and honokiol, acting through Ca(2+) channel blockade, inhibit the activation of IP3 receptor 1 to regulate the IP3-Ca(2+) store release, activate CaM to inhibit SK channels, and effectively suppress PKC kinases to promote BKα1 and BKβ3 channels opening and BKβ4 channel closing, which modulates the intestinal ion secretion. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Fluctuation of densities of bacteriophages and Escherichia coli present in natural biofilms and water of a main channel and a small tributary.

    PubMed

    Hirotani, Hiroshi; Yu, Ma; Yamada, Takeshi

    2013-01-01

    Fluctuation of bacteriophage and Escherichia coli densities in naturally developed riverbed biofilms were investigated for a 1-year period. E. coli ranged from 1,500 to 15,500 most probable number (MPN)/100 mL and from 580 to 18,500 MPN/cm(2) in the main channel in the river water and biofilms, respectively. However, the fluctuations were much greater in the tributary, ranging from 0.8 to 100 MPN/100 mL and from 0.3 to 185 MPN/cm(2) in water and biofilms, respectively. The fluctuations of coliphages were also greater in the tributary than in the main channel. FRNA phage serotyping results indicated no significant differences in the source type of the fecal contamination in the main channel and tributary sampling stations. Significant correlations between phage groups in biofilms and water were found at both main channel and tributary. It was assumed that natural biofilms developed in the streambed captured and retained somatic phages in the biofilms for a certain period of time in the main channel site. At the location receiving constant and heavy contamination, the usage of phage indicators may provide additional information on the presence of viruses. In the small tributary it may be possible to estimate the virus concentration by monitoring the E. coli indicator.

  16. Susceptibility to disinfectants in antimicrobial-resistant and -susceptible isolates of Escherichia coli, Enterococcus faecalis and Enterococcus faecium from poultry-ESBL/AmpC-phenotype of E. coli is not associated with resistance to a quaternary ammonium compound, DDAC.

    PubMed

    Wieland, N; Boss, J; Lettmann, S; Fritz, B; Schwaiger, K; Bauer, J; Hölzel, C S

    2017-06-01

    The spread of bacteria that are simultaneously resistant to disinfectants and antimicrobials would constitute an unsettling scenario. In order to explore an association between antimicrobial resistance and reduced susceptibility to biocides/microbicides (disinfectants) in agriculture, we investigated Escherichia coli (n = 438) and enterococci (n = 120) isolated from six different flocks of the same poultry farm with known history of antimicrobial treatment. Susceptibility to disinfectants (formic acid and a quaternary ammonium compound (QAC), didecyldimethylammoniumchloride-DDAC) was assessed by macrodilution according to guidelines of the German Veterinary Society. Escherichia coli, Enterococcus faecalis and Enterococcus faecium were screened (i) for reduced biocide susceptibility and (ii) for an association of biocide susceptibility and antimicrobial resistance including the production of extended-spectrum beta-lactamases (ESBL) and the hyperproduction of AmpC-type beta-lactamases. DDAC inhibited ESBL/AmpC(hyper)-producing E. coli (n = 53) from poultry at similar or slightly lower inhibitory concentrations, compared with non-ESBL/AmpC strains (median MIC = 0·36 vs 1·44 mg l(-1) ). In contrast, DDAC-MICs were positively correlated with several other antibiotic MICs (e.g. piperacillin and sulphamethoxazole + trimethoprim in E. coli, chloramphenicol in E. faecalis) and increased DDAC-MICs were statistically linked to high-level aminoglycoside resistance in enterococci (streptomycin high level). DDAC-MICs did not correlate with the presence of the integron marker qacEDelta1. This study provides indication that residual disinfectant might be able to select antimicrobial-resistant enterococci, but not ESBL-/AmpC (hyper)producing E. coli from poultry. While ESBL-/AmpC-E. coli were inhibited at disinfectant concentrations comparable to or lower than wildtype values, low concentrations of QACs might be able to select other antimicrobial-resistant E. coli

  17. Channels

    NASA Image and Video Library

    2014-04-29

    Two channels are visible in this image from NASA 2001 Mars Odyssey spacecraft . The smaller one near the bottom did not carve as deeply as the larger channel at the top. The channel near the top of the image is near the origin of Mamers Valles.

  18. Probing the proton channels in subunit N of Complex I from Escherichia coli through intra-subunit cross-linking.

    PubMed

    Tursun, Ablat; Zhu, Shaotong; Vik, Steven B

    2016-12-01

    Respiratory Complex I appears to have 4 sites for proton translocation, which are coupled to the oxidation of NADH and reduction of coenzyme Q. The proton pathways are thought to be made of offset half-channels that connect to the membrane surfaces, and are connected by a horizontal path through the center of the membrane. In this study of the enzyme from Escherichia coli, subunit N, containing one of the sites, was targeted. Pairs of cysteine residues were introduced into neighboring α-helices along the proposed proton pathways. In an effort to constrain conformational changes that might occur during proton translocation, we attempted to form disulfide bonds or methanethiosulfonate bridges between two engineered cysteine residues. Cysteine modification was inferred by the inability of PEG-maleimide to shift the electrophoretic mobility of subunit N, which will occur upon reaction with free sulfhydryl groups. After the cross-linking treatment, NADH oxidase and NADH-driven proton translocation were measured. Ten different pairs of cysteine residues showed evidence of cross-linking. The most significant loss of enzyme activity was seen for residues near the essential Lys 395. This residue is positioned between the proposed proton half-channel to the periplasm and the horizontal connection through subunit N, and is also near the essential Glu 144 of subunit M. The results suggest important conformational changes in this region for the delivery of protons to the periplasm, or for coupling the actions of subunit N to subunit M. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Insensitive Ammonium Nitrate.

    DTIC Science & Technology

    is reduced by replacing the ammonium nitrate with a solid solution of potassium nitrate in form III ammonium nitrate wherein the potassium nitrate...constitutes from more than zero to less than 50 weight percent of the solid solution . (Author)

  20. Protection of the DNA during the exposure of Escherichia coli cells to a toxic metabolite: the role of the KefB and KefC potassium channels.

    PubMed

    Ferguson, G P; Battista, J R; Lee, A T; Booth, I R

    2000-01-01

    The effect of the toxic metabolite methylglyoxal on the DNA of Escherichia coli cells has been investigated. Exposure of E. coli cells to methylglyoxal reduces the transformability of plasmid DNA and results in the degradation of genomic DNA. The activity of the KefB and KefC potassium channels protects E. coli cells against methylglyoxal and limits the amount of DNA damage. In mutants lacking KefB and KefC, methylglyoxal-induced DNA damage was reduced by incubation with a weak acid that lowers the pHi to the same extent as through KefB and KefC activation. This provides evidence that acidification of the cytoplasm protects E. coli DNA against methylglyoxal. By the analysis of cells lacking UvrA, we demonstrate that this repair protein is required for the degradation of the DNA upon methylglyoxal exposure. However, protection by KefB and KefC occurred independently of UvrA. Although we present evidence that exposure of E. coli cells to methylglyoxal results in DNA degradation, our results suggest this event is not essential for methylglyoxal-induced death. The implications of these findings will be discussed.

  1. Tetramethyl ammonium as masking agent for molecular stencil patterning in the confined space of the nano-channels of 2D hexagonal-templated porous silicas.

    PubMed

    Zhang, Kun; Albela, Belén; He, Ming-Yuan; Wang, Yimeng; Bonneviot, Laurent

    2009-04-28

    The molecular stencil patterning (MSP) technique is a new surface molecular engineering technique developed for cation-templated porous silicas to graft several functions with vicinity control. First, tetramethylammonium ions (TMA(+)) are introduced by ion exchange of the cetyltrimethyl-ammonium template (CTA(+)). Then, the coverage is controlled to create a masking array of cations, the pattern of which is produced by mutual electrostatic repulsion. A first function is grafted, here monopodal trimethylsilyl groups (TMS) or dipodal ethyl-1,2-bis(dimethylsilyl) (EBDMS) groups. After the removal of the masking cations, a second function is grafted using here N-(2-aminoethyl)-3-amino-propyltrimethoxysilane precursor. The distribution of N-(2-aminoethyl)-3-amino-propylsilyl functions (AAPS) is probed by complexation to Cu(ii) ions. X-Ray diffraction, N(2) adsorption-desorption isotherms, (13)C solid-state NMR, IR, UV-visible and electron paramagnetic resonance (EPR) techniques show that MSP can produce isolation of AAPS by TMS, or even better by EBDMS groups, with preservation of the silica pore structure.

  2. The Deletion of Several Amino Acid Stretches of Escherichia coli Alpha-Hemolysin (HlyA) Suggests That the Channel-Forming Domain Contains Beta-Strands

    PubMed Central

    Benz, Roland; Maier, Elke; Bauer, Susanne; Ludwig, Albrecht

    2014-01-01

    Escherichia coli α-hemolysin (HlyA) is a pore-forming protein of 110 kDa belonging to the family of RTX toxins. A hydrophobic region between the amino acid residues 238 and 410 in the N-terminal half of HlyA has previously been suggested to form hydrophobic and/or amphipathic α-helices and has been shown to be important for hemolytic activity and pore formation in biological and artificial membranes. The structure of the HlyA transmembrane channel is, however, largely unknown. For further investigation of the channel structure, we deleted in HlyA different stretches of amino acids that could form amphipathic β-strands according to secondary structure predictions (residues 71–110, 158–167, 180–203, and 264–286). These deletions resulted in HlyA mutants with strongly reduced hemolytic activity. Lipid bilayer measurements demonstrated that HlyAΔ71–110 and HlyAΔ264–286 formed channels with much smaller single-channel conductance than wildtype HlyA, whereas their channel-forming activity was virtually as high as that of the wildtype toxin. HlyAΔ158–167 and HlyAΔ180–203 were unable to form defined channels in lipid bilayers. Calculations based on the single-channel data indicated that the channels generated by HlyAΔ71–110 and HlyAΔ264–286 had a smaller size (diameter about 1.4 to 1.8 nm) than wildtype HlyA channels (diameter about 2.0 to 2.6 nm), suggesting that in these mutants part of the channel-forming domain was removed. Osmotic protection experiments with erythrocytes confirmed that HlyA, HlyAΔ71–110, and HlyAΔ264–286 form defined transmembrane pores and suggested channel diameters that largely agreed with those estimated from the single-channel data. Taken together, these results suggest that the channel-forming domain of HlyA might contain β-strands, possibly in addition to α-helical structures. PMID:25463653

  3. The deletion of several amino acid stretches of Escherichia coli alpha-hemolysin (HlyA) suggests that the channel-forming domain contains beta-strands.

    PubMed

    Benz, Roland; Maier, Elke; Bauer, Susanne; Ludwig, Albrecht

    2014-01-01

    Escherichia coli α-hemolysin (HlyA) is a pore-forming protein of 110 kDa belonging to the family of RTX toxins. A hydrophobic region between the amino acid residues 238 and 410 in the N-terminal half of HlyA has previously been suggested to form hydrophobic and/or amphipathic α-helices and has been shown to be important for hemolytic activity and pore formation in biological and artificial membranes. The structure of the HlyA transmembrane channel is, however, largely unknown. For further investigation of the channel structure, we deleted in HlyA different stretches of amino acids that could form amphipathic β-strands according to secondary structure predictions (residues 71-110, 158-167, 180-203, and 264-286). These deletions resulted in HlyA mutants with strongly reduced hemolytic activity. Lipid bilayer measurements demonstrated that HlyAΔ71-110 and HlyAΔ264-286 formed channels with much smaller single-channel conductance than wildtype HlyA, whereas their channel-forming activity was virtually as high as that of the wildtype toxin. HlyAΔ158-167 and HlyAΔ180-203 were unable to form defined channels in lipid bilayers. Calculations based on the single-channel data indicated that the channels generated by HlyAΔ71-110 and HlyAΔ264-286 had a smaller size (diameter about 1.4 to 1.8 nm) than wildtype HlyA channels (diameter about 2.0 to 2.6 nm), suggesting that in these mutants part of the channel-forming domain was removed. Osmotic protection experiments with erythrocytes confirmed that HlyA, HlyAΔ71-110, and HlyAΔ264-286 form defined transmembrane pores and suggested channel diameters that largely agreed with those estimated from the single-channel data. Taken together, these results suggest that the channel-forming domain of HlyA might contain β-strands, possibly in addition to α-helical structures.

  4. Channels

    NASA Image and Video Library

    2015-11-20

    Today's VIS image shows a number of unnamed channels located on the northeastern margin of Terra Sabaea. Orbit Number: 61049 Latitude: 33.5036 Longitude: 58.6967 Instrument: VIS Captured: 2015-09-18 12:54 http://photojournal.jpl.nasa.gov/catalog/PIA20097

  5. Site-directed mutagenesis of tyrosine 118 within the central constriction site of the LamB (Maltoporin) channel of Escherichia coli. I. Effect on ion transport.

    PubMed Central

    Orlik, Frank; Andersen, Christian; Benz, Roland

    2002-01-01

    The three-dimensional structure of the malto-oligosaccharide-specific LamB-channel of Escherichia coli (also called maltoporin) is known from x-ray crystallography. The central constriction of the channel formed by the external loop 3 is controlled by a tyrosine residue (Y118). Y118 was replaced by site-directed mutagenesis by ten other amino acids (alanine, isoleucine, asparagine, serine, cysteine, aspartic acid, arginine, histidine, phenylalanine, and tryptophane) including neutral ones, negatively and positively charged amino acids to study the effect of their size, hydrophobicity, and charge on ion transport through LamB. The mutant proteins were purified to homogeneity. They were reconstituted into lipid bilayer membranes and single-channel conductance and ion selectivity were measured to get insight into the mechanism of ion transport through LamB. The mutation of Y118 to any other nonaromatic amino acid led to a substantial increase of the single-channel conductance by more than a factor of six at maximum. The highest effect was observed for Y118D. Additionally, a nonlinear relationship between the salt concentration in the aqueous phase and the channel conductance was observed for this mutant, indicating strong discrete charge effects on ion conductance. For all other mutants, with the exception of Y118R, linear relationships were found between single-channel conductance and bulk aqueous concentration. The individual hydrophobicity indices of the amino acids introduced inside the central constriction of the LamB channel had a somewhat smaller effect on the single-channel conductance as compared with the effect of their size and charge. PMID:11964234

  6. Escherichia coli membranes depleted of SecYEG elicit SecA-dependent ion-channel activity but lose signal peptide specificity.

    PubMed

    Lin, Bor-Ruei; Hsieh, Ying-Hsin; Jiang, Chun; Tai, Phang C

    2012-11-01

    We have developed a sensitive method to detect the opening of SecA-dependent, protein-conducting channels in Xenopus oocytes. In this study, we determined the ionic current activities of the SecA-dependent channel from membrane vesicles depleted of SecYEG. We found that these SecYEG-depleted membranes produced SecA-dependent ionic currents in the oocytes, as did membranes containing SecYEG. However, reconstituted membranes depleted of SecYEG required higher concentrations of SecA to elicit ionic currents like those in membranes containing SecYEG. In contrast to membranes containing SecYEG, the proofreading capacity of signal peptides was lost for those membranes lacking SecYEG. These findings are consistent with loss of signal peptide specificity in channel activity from membranes of SecY suppressor or SecY plug domain mutants. The signal peptide specificity of the reconstituted membranes, like SecA-liposomes, can be restored by the addition of SecYEG proteoliposomes. On the other hand, the channel activity efficiency of reconstituted membranes was fully restored, while SecA-liposomes could only be partially enhanced by the addition of SecYEG, indicating that, in addition to SecYEG, other membrane proteins contribute to the efficiency of channel activity. The SecA-dependent channels in membranes that lacked SecYEG also lost ion selectivity to monovalent cations but retained selective permeability to large anions. Thus, the electrophysiological evidence presented here indicates that SecYEG is not obligatory for the channel activity of Escherichia coli membranes, as previously shown for protein translocation, and that SecYEG is important for maintenance of the efficiency and specificity of SecA-dependent channels.

  7. Purification of the small mechanosensitive channel of Escherichia coli (MscS): the subunit structure, conduction, and gating characteristics in liposomes

    NASA Technical Reports Server (NTRS)

    Sukharev, Sergei

    2002-01-01

    The small mechanosensitive channel, MscS, is a part of the turgor-driven solute efflux system that protects bacteria from lysis in the event of osmotic downshift. It has been identified in Escherichia coli as a product of the orphan yggB gene, now called mscS (Levina et al., 1999, EMBO J. 18:1730). Here I show that that the isolated 31-kDa MscS protein is sufficient to form a functional mechanosensitive channel gated directly by tension in the lipid bilayer. MscS-6His complexes purified in the presence of octylglucoside and lipids migrate in a high-resolution gel-filtration column as particles of approximately 200 kDa. Consistent with that, the protein cross-linking patterns predict a hexamer. The channel reconstituted in soybean asolectin liposomes was activated by pressures of 20-60 mm Hg and displayed the same asymmetric I-V curve and slight anionic preference as in situ. At the same time, the single-channel conductance is proportional to the buffer conductivity in a wide range of salt concentrations. The rate of channel activation in response to increasing pressure gradient across the patch was slower than the rate of closure in response to decreasing steps of pressure gradient. Therefore, the open probability curves were recorded with descending series of pressures. Determination of the curvature of patches by video imaging permitted measurements of the channel activity as a function of membrane tension (gamma). Po(gamma) curves had the midpoint at 5.5 +/- 0.1 dyne/cm and gave estimates for the energy of opening DeltaG = 11.4 +/- 0.5 kT, and the transition-related area change DeltaA = 8.4 +/- 0.4 nm(2) when fitted with a two-state Boltzmann model. The correspondence between channel properties in the native and reconstituted systems is discussed.

  8. Purification of the small mechanosensitive channel of Escherichia coli (MscS): the subunit structure, conduction, and gating characteristics in liposomes

    NASA Technical Reports Server (NTRS)

    Sukharev, Sergei

    2002-01-01

    The small mechanosensitive channel, MscS, is a part of the turgor-driven solute efflux system that protects bacteria from lysis in the event of osmotic downshift. It has been identified in Escherichia coli as a product of the orphan yggB gene, now called mscS (Levina et al., 1999, EMBO J. 18:1730). Here I show that that the isolated 31-kDa MscS protein is sufficient to form a functional mechanosensitive channel gated directly by tension in the lipid bilayer. MscS-6His complexes purified in the presence of octylglucoside and lipids migrate in a high-resolution gel-filtration column as particles of approximately 200 kDa. Consistent with that, the protein cross-linking patterns predict a hexamer. The channel reconstituted in soybean asolectin liposomes was activated by pressures of 20-60 mm Hg and displayed the same asymmetric I-V curve and slight anionic preference as in situ. At the same time, the single-channel conductance is proportional to the buffer conductivity in a wide range of salt concentrations. The rate of channel activation in response to increasing pressure gradient across the patch was slower than the rate of closure in response to decreasing steps of pressure gradient. Therefore, the open probability curves were recorded with descending series of pressures. Determination of the curvature of patches by video imaging permitted measurements of the channel activity as a function of membrane tension (gamma). Po(gamma) curves had the midpoint at 5.5 +/- 0.1 dyne/cm and gave estimates for the energy of opening DeltaG = 11.4 +/- 0.5 kT, and the transition-related area change DeltaA = 8.4 +/- 0.4 nm(2) when fitted with a two-state Boltzmann model. The correspondence between channel properties in the native and reconstituted systems is discussed.

  9. Crystal structure of the archaeal ammonium transporter Amt-1 from Archaeoglobus fulgidus.

    PubMed

    Andrade, Susana L A; Dickmanns, Antje; Ficner, Ralf; Einsle, Oliver

    2005-10-18

    Ammonium transporters (Amts) are integral membrane proteins found in all kingdoms of life that fulfill an essential function in the uptake of reduced nitrogen for biosynthetic purposes. Amt-1 is one of three Amts encoded in the genome of the hyperthermophilic archaeon Archaeoglobus fulgidus. The crystal structure of Amt-1 shows a compact trimer with 11 transmembrane helices per monomer and a central channel for substrate conduction in each monomer, similar to the known crystal structure of AmtB from Escherichia coli. Xenon derivatization has been used to identify apolar regions of Amt-1, emphasizing not only the hydrophobicity of the substrate channel but also the unexpected presence of extensive internal cavities that should be detrimental for protein stability. The substrates ammonium and methylammonium have been used for cocrystallization experiments with Amt-1, but the identification of binding sites that are distinct from water positions is not unambiguous. The well ordered cytoplasmic C terminus of the protein in the Amt-1 structure has allowed for the construction of a docking model between Amt-1 and a homology model for its physiological interaction partner, the P(II) protein GlnB-1. In this model, GlnB-1 binds tightly to the cytoplasmic face of the transporter, effectively blocking conduction through the three individual substrate channels.

  10. Genetic screen for potassium leaky small mechanosensitive channels (MscS) in Escherichia coli: recognition of cytoplasmic β domain as a new gating element.

    PubMed

    Koprowski, Piotr; Grajkowski, Wojciech; Isacoff, Ehud Y; Kubalski, Andrzej

    2011-01-07

    Mechanosensitive membrane channels in bacteria respond to the mechanical stretching of the membrane. They will open when bacteria are subjected to rapid osmotic down shock. MscS is a bacterial mechanosensitive channel of small conductance. It is a heptameric membrane protein whose transmembrane part, including the gate and its kinetics, has been well characterized. MscS has a large cytoplasmic domain of a cage-like shape that changes its conformation upon gating, but its involvement in gating is not understood. We screened MscS for mutations that cause potassium leak in Escherichia coli strains deficient in potassium transport systems. We did a phenotypic analysis of single and multiple mutants and recorded the single channel activities of some of them. After these analyses, we attributed the effects of a number of mutations to particular functional states of the channel. Our screen revealed that MscS leaks potassium in a desensitized and in an inactivated state. It also appeared that the lower part of TM3 (transmembrane, pore-forming helix) and the cytoplasmic β domain are tightly packed in the inactivated state but are dissociated in the open state. We attribute the TM3-β interaction to stabilization of the inactivated state in MscS and to the control of tight closure of its membrane pore.

  11. NMR and ion selective electrode studies of hydraphile channels correlate with biological activity in E. coli and B. subtilis

    PubMed Central

    Leevy, W. Matthew; Weber, Michelle E.; Schlesinger, Paul H.; Gokel, George W.

    2008-01-01

    Previous sodium ion transport results obtained by NMR methods are compared with those obtained by a new ISE technique and are found to correlate well with each other and with the biological activity against E. coli and B. subtilis. PMID:15614382

  12. Ammonium nitrate explosive systems

    DOEpatents

    Stinecipher, Mary M.; Coburn, Michael D.

    1981-01-01

    Novel explosives which comprise mixtures of ammonium nitrate and an ammonium salt of a nitroazole in desired ratios are disclosed. A preferred nitroazole is 3,5-dinitro-1,2,4-triazole. The explosive and physical properties of these explosives may readily be varied by the addition of other explosives and oxidizers. Certain of these mixtures have been found to act as ideal explosives.

  13. Escherichia coli α-Hemolysin Triggers Shrinkage of Erythrocytes via KCa3.1 and TMEM16A Channels with Subsequent Phosphatidylserine Exposure*

    PubMed Central

    Skals, Marianne; Jensen, Uffe B.; Ousingsawat, Jiraporn; Kunzelmann, Karl; Leipziger, Jens; Praetorius, Helle A.

    2010-01-01

    α-Hemolysin from Escherichia coli (HlyA) readily lyse erythrocytes from various species. We have recently demonstrated that this pore-forming toxin provokes distinct shrinkage and crenation before it finally leads to swelling and lysis of erythrocytes. The present study documents the underlying mechanism for this severe volume reduction. We show that HlyA-induced shrinkage and crenation of human erythrocytes occur subsequent to a significant rise in [Ca2+]i. The Ca2+-activated K+ channel KCa3.1 (or Gardos channel) is essential for the initial shrinkage, because both clotrimazole and TRAM-34 prevent the shrinkage and potentiate hemolysis produced by HlyA. Notably, the recently described Ca2+-activated Cl− channel TMEM16A contributes substantially to HlyA-induced cell volume reduction. Erythrocytes isolated from TMEM16A−/− mice showed significantly attenuated crenation and increased lysis compared with controls. Additionally, we found that HlyA leads to acute exposure of phosphatidylserine in the outer leaflet of the plasma membrane. This exposure was considerably reduced by KCa3.1 antagonists. In conclusion, this study shows that HlyA triggers acute erythrocyte shrinkage, which depends on Ca2+-activated efflux of K+ via KCa3.1 and Cl− via TMEM16A, with subsequent phosphatidylserine exposure. This mechanism might potentially allow HlyA-damaged erythrocytes to be removed from the bloodstream by macrophages and thereby reduce the risk of intravascular hemolysis. PMID:20231275

  14. 70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM NITRATE IN STORAGE. APRIL 18, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  15. Acute ammonium dichromate poisoning.

    PubMed

    Meert, K L; Ellis, J; Aronow, R; Perrin, E

    1994-10-01

    We report the ingestion of ammonium dichromate by a child that resulted in multiple-organ-system failure and death. Exchange transfusion and hemodialysis were ineffective in removing significant amounts of chromium or causing sustained clinical improvement. We suggest that immediate, large doses of the reducing agent ascorbic acid would allow effective reduction of hexavalent chromium with less cellular toxicity.

  16. Distribution of Escherichia coli and Enterococci in water, sediments, and bank soils along North Shore Channel between Bridge Street and Wilson Avenue, Metropolitan Water Reclamation District of Greater Chicago

    USGS Publications Warehouse

    Byappanahalli, Muruleedhara; Whitman, Richard L.; Shively, Dawn; Przybyla-Kelly, Katarzyna; Lukasik, Ashley M.

    2010-01-01

    The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) wished to know the distribution and potential sources of fecal indicator bacteria, E. coli and enterococci, in water, sediments, and upland soils along an upstream and downstream portion of the North Shore Channel (NSC) that is the receiving stream for the District’s North Side Water Reclamation Plant (NSWRP) outfall. Biweekly water and sediment samples were collected between August and October 2008 and included the following locations upstream of the outfall: Bridge Street (UPS-1), Oakton Street (UPS-2), the NSWRP outfall (OF), and downstream: Foster Avenue (DNS-1), and Wilson Avenue (DNS-2). E. coli and enterococci were consistently found in water and sediments at all sampling locations, with bacterial densities in water increasing below the NSWRP outfall; bacterial densities in sediment were more variable. On a relative measurement basis (i.e., 100 ml=100 g), both E. coli and enterococci densities were significantly higher in sediments than water. E. coli and enterococci were consistently recovered from bank soil along wooded, grassy, erosional, and depositional areas at two recreational parks, as well as other riparian areas along the river. Thus, soils along the river basin are likely sources of these bacteria to the NSC channel, introduced through runoff or other physical processes. Tributaries, such as the North Branch of the Chicago River (NBCR) that flow into NSC near Albany Ave, may provide a constant source of E. coli and enterococci to the NSC. Additionally, storm sewer outfalls may increase E. coli loadings to NSC during wet weather conditions. Our findings suggest that the abundance of nonpoint sources contributing to the overall fecal indicator bacteria (FIB) load in the NSC channel may complicate bacteria source determination and remediation efforts to protect the stream water quality.

  17. Protection of Escherichia coli cells against extreme turgor by activation of MscS and MscL mechanosensitive channels: identification of genes required for MscS activity.

    PubMed Central

    Levina, N; Tötemeyer, S; Stokes, N R; Louis, P; Jones, M A; Booth, I R

    1999-01-01

    Mechanosensitive channels are ubiquitous amongst bacterial cells and have been proposed to have major roles in the adaptation to osmotic stress, in particular in the management of transitions from high to low osmolarity environments. Electrophysiological measurements have identified multiple channels in Escherichia coli cells. One gene, mscL, encoding a large conductance channel has previously been described, but null mutants were without well-defined phenotypes. Here, we report the characterization of a new gene family required for MscS function, YggB and KefA, which has enabled a rigorous test of the role of the channels. The channel determined by KefA does not appear to have a major role in managing the transition from high to low osmolarity. In contrast, analysis of mutants of E.coli lacking YggB and MscL shows that mechanosensitive channels are designed to open at a pressure change just below that which would cause cell disruption leading to death. PMID:10202137

  18. Ammonium imidazolium dichromate.

    PubMed

    Zhu, Run-Qiang

    2012-04-01

    In the crystal structure of the title compound, (C(3)H(5)N(2))(NH(4))[Cr(2)O(7)], the anions and cations are linked through N-H⋯O hydrogen bonds, resulting in a three-dimensional structure which contains three kinds of layers parallel to (001). One layer contains imidazole cations, the other two layers the ammonium cations and dichromate anions. The dichromate anion has an eclipsed conformation with a dihedral angle of 14.65 (18)° between the mean planes of the O-P-O-P-O backbone.

  19. Adjusting ammonium uptake via phosphorylation.

    PubMed

    Lanquar, Viviane; Frommer, Wolf B

    2010-06-01

    In plants, AMT/MEP/Rh superfamily mediates high affinity ammonium uptake. AMT/MEP transporters form a trimeric complex, which requires a productive interaction between subunits in order to be functional. The AMT/MEP C-terminal domain is highly conserved in more than 700 AMT homologs from cyanobacteria to higher plants with no cases found to be lacking this domain. AMT1;1 exists in active and inactive states, probably controlled by the spatial positioning of the C-terminus. Ammonium triggers the phosphorylation of a conserved threonine residue (T460) in the C-terminus of AMT1;1 in a time- and concentration-dependent manner. The T460 phosphorylation level correlates with a decrease of root ammonium uptake. We propose that ammonium-induced phosphorylation modulates ammonium uptake as a general mechanism to protect against ammonium toxicity.

  20. Adjusting ammonium uptake via phosphorylation

    PubMed Central

    Lanquar, Viviane

    2010-01-01

    In plants, AMT/MEP/Rh superfamily mediates high affinity ammonium uptake. AMT/MEP transporters form a trimeric complex, which requires a productive interaction between subunits in order to be functional. The AMT/MEP C-terminal domain is highly conserved in more than 700 AMT homologs from cyanobacteria to higher plants with no cases found to be lacking this domain. AMT1;1 exists in active and inactive states, probably controlled by the spatial positioning of the C-terminus. Ammonium triggers the phosphorylation of a conserved threonine residue (T460) in the C-terminus of AMT1;1 in a time- and concentration-dependent manner. The T460 phosphorylation level correlates with a decrease of root ammonium uptake. We propose that ammonium-induced phosphorylation modulates ammonium uptake as a general mechanism to protect against ammonium toxicity. PMID:20418663

  1. Hydrothermal synthesis of ammonium illite

    USGS Publications Warehouse

    Sucha, V.; Elsass, F.; Eberl, D.D.; Kuchta, L'.; Madejova, J.; Gates, W.P.; Komadel, P.

    1998-01-01

    Synthetic gel and glass of illitic composition, natural kaolinite, and mixed-layer illite-smectite were used as starting materials for hydrothermal synthesis of ammonium illite. Ammonium illite was prepared from synthetic gel by hydrothermal treatment at 300??C. The onset of crystallization began within 3 h, and well-crystallized ammonium illite appeared at 24 h. Increasing reaction time (up to four weeks) led to many illite layers per crystal. In the presence of equivalent proportions of potassium and ammonium, the gel was transformed to illite with equimolar contents of K and NH4. In contrast, synthesis using glass under the same conditions resulted in a mixture of mixed-layer ammonium illite-smectite with large expandability and discrete illite. Hydrothermal treatments of the fine fractions of natural kaolinite and illite-smectite produced ammonium illite from kaolinite but the illite-smectite remained unchanged.

  2. Ammonium assimilation in cyanobacteria.

    PubMed

    Muro-Pastor, M Isabel; Reyes, Jose C; Florencio, Francisco J

    2005-01-01

    In cyanobacteria, after transport by specific permeases, ammonium is incorporated into carbon skeletons by the sequential action of glutamine synthetase (GS) and glutamate synthase (GOGAT). Two types of GS (GSI and GSIII) and two types of GOGAT (ferredoxin-GOGAT and NADH-GOGAT) have been characterized in cyanobacteria. The carbon skeleton substrate of the GS-GOGAT pathway is 2-oxoglutarate that is synthesized by the isocitrate dehydrogenase (IDH). In order to maintain the C-N balance and the amino acid pools homeostasis, ammonium assimilation is tightly regulated. The key regulatory point is the GS, which is controlled at transcriptional and posttranscriptional levels. The transcription factor NtcA plays a critical role regulating the expression of the GS and the IDH encoding genes. In the unicellular cyanobacterium Synechocystis sp. PCC 6803, NtcA controls also the expression of two small proteins (IF7 and IF17) that inhibit the activity of GS by direct protein-protein interaction. Cyanobacteria perceive nitrogen status by sensing the intracellular concentration of 2-oxoglutarate, a signaling metabolite that is able to modulate allosterically the function of NtcA, in vitro. In vivo, a functional dependence between NtcA and the signal transduction protein PII in controlling NtcA-dependent genes has been also shown.

  3. Properties of the FhuA channel in the Escherichia coli outer membrane after deletion of FhuA portions within and outside the predicted gating loop.

    PubMed

    Killmann, H; Benz, R; Braun, V

    1996-12-01

    Escherichia coli transports Fe3+ as a ferrichrome complex through the outer membrane in an energy-dependent process mediated by the FhuA protein. A FhuA deletion derivative lacking residues 322 to 355 (FhuA delta322-355) forms a permanently open channel through which ferrichrome diffused. This finding led to the concept that the FhuA protein forms a closed channel that is opened by input of energy derived from the electrochemical potential across the cytoplasmic membrane, mediated by the Ton system. In this study, we constructed various FhuA derivatives containing deletions inside and outside the gating loop. FhuA delta322-336 bound ferrichrome and displayed a residual Ton-dependent ferrichrome transport activity. FhuA delta335-355 no longer bound ferrichrome but supported ferrichrome diffusion through the outer membrane in the absence of the Ton system. FhuA delta335-355 rendered cells sensitive to sodium dodecyl sulfate and supported diffusion of maltotetraose and maltopentaose in a lamB mutant lacking the maltodextrin-specific channel in the outer membrane. Cells expressing FhuA delta70-223, which has a large deletion outside the gating loop, were highly sensitive to sodium dodecyl sulfate and grew on maltodextrins but showed only weak ferrichrome uptake, suggesting formation of a nonspecific pore through the outer membrane. FhuA delta457-479 supported Ton-dependent uptake of ferrichrome. None of these FhuA deletion derivatives formed pores in black lipid membranes with a stable single-channel conductance. Rather, the conductance displayed a high degree of current noise, indicating a substantial influence of the deletions on the conformation of the FhuA protein. FhuA also supports infection by the phages T1, T5, and phi80 and renders cells sensitive to albomycin and colicin M. Cells expressing FhuA delta322-336 were sensitive to albomycin and colicin M but were only weakly sensitive to T5 and phi480 and insensitive to T1. Cells expressing FhuA delta335-355 were

  4. Molar concentrations of sorbitol and polyethylene glycol inhibit the Plasmodium aquaglyceroporin but not that of E. coli: involvement of the channel vestibules.

    PubMed

    Song, Jie; Almasalmeh, Abdulnasser; Krenc, Dawid; Beitz, Eric

    2012-05-01

    The aquaglyceroporins of Escherichia coli, EcGlpF, and of Plasmodium falciparum, PfAQP, are probably the best characterized members of the solute-conducting aquaporin (AQP) subfamily. Their crystal structures have been elucidated and numerous experimental and theoretical analyses have been conducted. However, opposing reports on their rates of water permeability require clarification. Hence, we expressed EcGlpF and PfAQP in yeast, prepared protoplasts, and compared water and glycerol permeability of both aquaglyceroporins in the presence of different osmolytes, i.e. sucrose, sorbitol, PEG300, and glycerol. We found that water permeability of PfAQP strongly depends on the external osmolyte, with full inhibition by sorbitol, and increasing water permeability when glycerol, PEG300, and sucrose were used. EcGlpF expression did not enhance water permeability over that of non-expressing control protoplasts regardless of the osmolyte. Glycerol permeability of PfAQP was also inhibited by sorbitol, but to a smaller extent, whereas EcGlpF conducted glycerol independently of the osmolyte. Mixtures of glycerol and urea passed PfAQP equally well under isosmotic conditions, whereas under hypertonic conditions in a countercurrent with water, glycerol was clearly preferred over urea. We conclude that PfAQP has high and EcGlpF low water permeability, and explain the inhibiting effect of sorbitol on PfAQP by its binding to the extracellular vestibule. The preference for glycerol under hypertonic conditions implies that in a physiological setting, PfAQP mainly acts as a water/glycerol channel rather than a urea facilitator.

  5. Ammonium Regulation in Aspergillus nidulans

    PubMed Central

    Pateman, J. A.; Kinghorn, J. R.; Dunn, Etta; Forbes, E.

    1973-01-01

    l-Glutamate uptake, thiourea uptake, and methylammonium uptake and the intracellular ammonium concentration were measured in wild-type and mutant cells of Aspergillus nidulans held in various concentrations of ammonium and urea. The levels of l-glutamate uptake, thiourea uptake, nitrate reductase, and hypoxanthine dehydrogenase activity are determined by the extracellular ammonium concentration. The level of methylammonium uptake is determined by the intracellular ammonium concentration. The uptake and enzyme characteristics of the ammonium-derepressed mutants, meaA8, meaB6, DER3, amrA1, xprD1, and gdhA1, are described. The gdhA mutants lack normal nicotinamide adenine dinucleotide phosphate-glutamate dehydrogenase (NADP-GDH) activity and are derepressed with respect to both external and internal ammonium. The other mutant classes are derepressed only with respect to external ammonium. The mutants meaA8, DER3, amrA1, and xprD1 have low levels of one or more of the l-glutamate, thiourea, and methylammonium uptake systems. A model for ammonium regulation in A. nidulans is put forward which suggests: (i) NADP-GDH located in the cell membrane complexes with extracellular ammonium. This first regulatory complex determines the level of l-glutamate uptake, thiourea uptake, nitrate reductase, and xanthine dehydrogenase by repression or inhibition, or both. (ii) NADP-GDH also complexes with intracellular ammonium. This second and different form of regulatory complex determines the level of methylammonium uptake by repression or inhibition, or both. PMID:4145865

  6. A maritime pine antimicrobial peptide involved in ammonium nutrition.

    PubMed

    Canales, Javier; Avila, Concepción; Cánovas, Francisco M

    2011-09-01

    A large family of small cysteine-rich antimicrobial peptides (AMPs) is involved in the innate defence of plants against pathogens. Recently, it has been shown that AMPs may also play important roles in plant growth and development. In previous work, we have identified a gene of the AMP β-barrelin family that was differentially regulated in the roots of maritime pine (Pinus pinaster Ait.) in response to changes in ammonium nutrition. Here, we present the molecular characterization of two AMP genes, PpAMP1 and PpAMP2, showing different molecular structure and physicochemical properties. PpAMP1 and PpAMP2 displayed different expression patterns in maritime pine seedlings and adult trees. Furthermore, our expression analyses indicate that PpAMP1 is the major form of AMP in the tree, and its relative abundance is regulated by ammonium availability. In contrast, PpAMP2 is expressed at much lower levels and it is not regulated by ammonium. To gain new insights into the function of PpAMP1, we over-expressed the recombinant protein in Escherichia coli and demonstrated that PpAMP1 strongly inhibited yeast growth, indicating that it exhibits antimicrobial activity. We have also found that PpAMP1 alters ammonium uptake, suggesting that it is involved in the regulation of ammonium ion flux into pine roots. © 2011 Blackwell Publishing Ltd.

  7. Toxicokinetics of ammonium perfluorohexanoate.

    PubMed

    Iwai, Hiroyuki

    2011-10-01

    Excretion patterns and rates of ammonium perfluorohexanoate (APFHx) after administration of a single and multiple (14 days) oral dose(s) at 50 mg/kg to male and female mice and rats were examined. The test substance was [(14)C]-labeled APFHx. After a single oral administration, total excretion was rapid, with mean recoveries of over 90% of the dose at 24 hours after administration, irrespective of gender or species. The major route of elimination was via the urine (means of percentage recovery between 73.0 and 90.2% of the dose), followed by the feces (means of percentage recovery between 7.0 and 15.5% of the dose). Elimination via expired air was negligible. For the multiple dose tests, multiple (13 daily doses) oral administration of APFHx was followed by a single oral administration of [(14)C]-APFHx. Excretion was rapid, with mean recoveries of over 90% of the administered dose (mean values >95% of the ultimately recovered material) at 24 hours after dosing, irrespective of gender or species. The major route of elimination was via the urine (means of percentage recovery between 77.8 and 83.4% of the dose), followed by the feces (means of percentage recovery between 9.6 and 12.9% of the dose).

  8. Substrate-triggered recruitment of the TolC channel-tunnel during type I export of hemolysin by Escherichia coli.

    PubMed

    Balakrishnan, L; Hughes, C; Koronakis, V

    2001-10-26

    A defining event in type I export of hemolysin by Escherichia coli is the substrate-triggered recruitment of the TolC channel-tunnel by an inner membrane complex. This complex comprises a traffic ATPase (HlyB) and the 478 residue adaptor protein (HlyD), which contacts TolC during recruitment. HlyD has a large periplasmic domain (amino acid residues 81-478) linked by a single transmembrane helix to a small N-terminal cytosolic domain (1-59). Export was disabled by deletion of the ca 60 amino acid residue cytosolic domain of HlyD, even though the truncated HlyD (HlyDDelta45) was, like the wild-type, able to trimerise in the cytosolic membrane, and interact with the traffic ATPase. The mutant HlyB/HlyDDelta45 inner membrane complex engaged the hemolysin substrate, but this substrate-engaged complex failed to trigger recruitment of TolC. Further analyses showed that HlyDDelta45 was specifically unable to bind the substrate. The result suggests that substrate engagement by the traffic ATPase alone is insufficient to trigger TolC recruitment, and that substrate binding to the HlyD cytosolic domain is essential. Analysis of three further N-terminal deletion variants, HlyDDelta26, HlyDDelta26-45 and HlyDDelta34-38, indicated that an extreme N-terminal amphipathic helix and a cytosolic cluster of charged residues are central to the cytosolic domain function. The cytosolic amphipathic helix was not essential for substrate engagement or TolC recruitment, but export was impaired without it. In contrast, when the charged amino acid residues were deleted, the substrate was still engaged by HlyD but engagement was unproductive, i.e. TolC recruitment was not triggered. Our results are compatible with the HlyD cytosolic domain mediating transduction of the substrate binding signal directly, presumably to the HlyD periplasmic domain, to trigger recruitment of TolC and assemble the type I export complex.

  9. Ammonium nitrate cold pack ingestion.

    PubMed

    Challoner, K R; McCarron, M M

    1988-01-01

    Disposable ammonium nitrate cold packs are widely used in emergency departments instead of ice bags. Five confused or suicidal patients who tore open a pack and ingested from 64 to 234 grams of ammonium nitrate in a single dose, and another patient who attempted to do so, are reported. It is known that chronic ingestion of 6 to 12 grams/day of ammonium nitrate may cause gastritis, acidosis, isosmotic diuresis, and nitrite toxicity manifesting as methemoglobinemia or vasodilatation. None of these patients developed severe toxicity, although three had symptoms of gastritis, three had slight methemoglobinemia, and two had mild hypotension. The product was removed from the stomach promptly in three of the five patients. None had pre-existing renal or intestinal dysfunction, which are known to enhance ammonium nitrate toxicity.

  10. High performance ammonium nitrate propellant

    NASA Technical Reports Server (NTRS)

    Anderson, F. A. (Inventor)

    1979-01-01

    A high performance propellant having greatly reduced hydrogen chloride emission is presented. It is comprised of: (1) a minor amount of hydrocarbon binder (10-15%), (2) at least 85% solids including ammonium nitrate as the primary oxidizer (about 40% to 70%), (3) a significant amount (5-25%) powdered metal fuel, such as aluminum, (4) a small amount (5-25%) of ammonium perchlorate as a supplementary oxidizer, and (5) optionally a small amount (0-20%) of a nitramine.

  11. 21 CFR 184.1138 - Ammonium chloride.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... GRAS § 184.1138 Ammonium chloride. (a) Ammonium chloride (NH4Cl, CAS Reg. No. 12125-02-9) is produced by the reaction of sodium chloride and an ammonium salt in solution. The less soluble sodium salt... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium chloride. 184.1138 Section 184.1138...

  12. 21 CFR 184.1137 - Ammonium carbonate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...). It is prepared by the sublimation of a mixture of ammonium sulfate and calcium carbonate and occurs... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ammonium carbonate. 184.1137 Section 184.1137 Food... Specific Substances Affirmed as GRAS § 184.1137 Ammonium carbonate. (a) Ammonium carbonate ((NH4)2CO3, CAS...

  13. 21 CFR 184.1137 - Ammonium carbonate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...). It is prepared by the sublimation of a mixture of ammonium sulfate and calcium carbonate and occurs... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ammonium carbonate. 184.1137 Section 184.1137 Food... Specific Substances Affirmed as GRAS § 184.1137 Ammonium carbonate. (a) Ammonium carbonate ((NH4)2CO3, CAS...

  14. 21 CFR 184.1137 - Ammonium carbonate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...). It is prepared by the sublimation of a mixture of ammonium sulfate and calcium carbonate and occurs... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ammonium carbonate. 184.1137 Section 184.1137 Food... Specific Substances Affirmed as GRAS § 184.1137 Ammonium carbonate. (a) Ammonium carbonate ((NH4)2CO3, CAS...

  15. 21 CFR 184.1137 - Ammonium carbonate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...). It is prepared by the sublimation of a mixture of ammonium sulfate and calcium carbonate and occurs... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium carbonate. 184.1137 Section 184.1137 Food... Specific Substances Affirmed as GRAS § 184.1137 Ammonium carbonate. (a) Ammonium carbonate ((NH4)2CO3, CAS...

  16. 21 CFR 184.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ammonium bicarbonate. 184.1135 Section 184.1135... Listing of Specific Substances Affirmed as GRAS § 184.1135 Ammonium bicarbonate. (a) Ammonium bicarbonate.... Crystals of ammonium bicarbonate are precipitated from solution and subsequently washed and dried. (b) The...

  17. 21 CFR 184.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ammonium bicarbonate. 184.1135 Section 184.1135... Listing of Specific Substances Affirmed as GRAS § 184.1135 Ammonium bicarbonate. (a) Ammonium bicarbonate.... Crystals of ammonium bicarbonate are precipitated from solution and subsequently washed and dried. (b) The...

  18. 21 CFR 184.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium bicarbonate. 184.1135 Section 184.1135... Listing of Specific Substances Affirmed as GRAS § 184.1135 Ammonium bicarbonate. (a) Ammonium bicarbonate.... Crystals of ammonium bicarbonate are precipitated from solution and subsequently washed and dried. (b) The...

  19. 21 CFR 184.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ammonium bicarbonate. 184.1135 Section 184.1135... Listing of Specific Substances Affirmed as GRAS § 184.1135 Ammonium bicarbonate. (a) Ammonium bicarbonate.... Crystals of ammonium bicarbonate are precipitated from solution and subsequently washed and dried. (b) The...

  20. Solubility of the Sodium and Ammonium Salts of Oxalic Acid in Water with Ammonium Sulfate.

    PubMed

    Buttke, Lukas G; Schueller, Justin R; Pearson, Christian S; Beyer, Keith D

    2016-08-18

    The solubility of the sodium and ammonium salts of oxalic acid in water with ammonium sulfate present has been studied using differential scanning calorimetry, X-ray crystallography, and infrared spectroscopy. The crystals that form from aqueous mixtures of ammonium sulfate/sodium hydrogen oxalate were determined to be sodium hydrogen oxalate monohydrate under low ammonium sulfate conditions and ammonium hydrogen oxalate hemihydrate under high ammonium sulfate conditions. Crystals from aqueous mixtures of ammonium sulfate/sodium oxalate were determined to be ammonium oxalate monohydrate under moderate to high ammonium sulfate concentrations and sodium oxalate under low ammonium sulfate concentrations. It was also found that ammonium sulfate enhances the solubility of the sodium oxalate salts (salting in effect) and decreases the solubility of the ammonium oxalate salts (salting out effect). In addition, a partial phase diagram for the ammonium hydrogen oxalate/water system was determined.

  1. E. Coli

    MedlinePlus

    ... Emergency Room? What Happens in the Operating Room? E. Coli KidsHealth > For Kids > E. Coli A A A What's in this article? What ... Doctor Do? What Can Kids Do? en español E. coli What Is It? E. coli is a common ...

  2. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  3. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  4. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  5. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  6. Molecular determinants for binding of ammonium ion in the ammonia transporter AmtB-A quantum chemical analysis.

    PubMed

    Liu, Yuemin; Hu, Xiche

    2006-02-02

    The transport of ammonium across the cell membrane represents an important biological process in all living organisms. The mechanisms for ammonium translocation were analyzed by computer simulations based on first principles. Intermolecular interaction energies between the differentially methylated ammonium and the ammonium channel protein AmtB were calculated by means of the supermolecular approach at the MP2/6-311+G* level based on the high-resolution crystal structures of ligand-bound protein complexes. Our analysis attributes the molecular determinants for protein-ligand recognition in ammonium transporter AmtB to the aromatic cage formed by three aromatic residues Phe103, Phe107, and Trp148, as well as Ser219. The former residues are involved in cation-pi interactions with the positively charged methylated ammoniums. The latter residue acts as a hydrogen bond acceptor to ammonium. Thus, this work provides directly the missing evidence for the hypothesized role played by the wider vestibule site of AmtB at the periplasmic side of the membrane in "recruiting" NH(4)(+) or methylammonium ions as proposed by Khademi et al. (Science 2004, 305, 1587). In addition, a hybrid quantum mechanics/molecular mechanics scheme was applied to optimize the structures of differentially methylated ammoniums in the AmtB protein, which generated structural and energetic data that provide a satisfactory explanation to the experimental observation that tetramethylammonium is not inhibitory to conducting ammonium and methylammonium in the ammonium transport channel.

  7. TREATMENT OF AMMONIUM NITRATE SOLUTIONS

    DOEpatents

    Boyer, T.W.; MacHutchin, J.G.; Yaffe, L.

    1958-06-10

    The treatment of waste solutions obtained in the processing of neutron- irradiated uranium containing fission products and ammonium nitrate is described. The object of this process is to provide a method whereby the ammonium nitrate is destroyed and removed from the solution so as to permit subsequent concentration of the solution.. In accordance with the process the residual nitrate solutions are treated with an excess of alkyl acid anhydride, such as acetic anhydride. Preferably, the residual nitrate solution is added to an excess of the acetic anhydride at such a rate that external heat is not required. The result of this operation is that the ammonium nitrate and acetic anhydride react to form N/sub 2/ O and acetic acid.

  8. Benzylic Ammonium Ylide Mediated Epoxidations

    PubMed Central

    Roiser, Lukas; Robiette, Raphaël; Waser, Mario

    2016-01-01

    A high yielding synthesis of stilbene oxides using ammonium ylides has been developed. It turned out that the amine leaving group plays a crucial role as trimethylamine gives higher yields than DABCO or quinuclidine. The amine group also influences the diastereoselectivity, and detailed DFT calculations to understand the key parameters of these reactions have been carried out. PMID:27766017

  9. E. Coli

    MedlinePlus

    ... We Are Organization Director, Anthony Fauci, M.D. History What We ... Escherichia coli ( E. coli ) bacteria live in the intestines of people and animals, and are key to a healthy intestinal tract. ...

  10. 21 CFR 582.1139 - Ammonium hydroxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1139 Ammonium hydroxide. (a) Product. Ammonium hydroxide. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding...

  11. 21 CFR 582.1137 - Ammonium carbonate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1137 Ammonium carbonate. (a) Product. Ammonium carbonate. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding...

  12. 21 CFR 582.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1135 Ammonium bicarbonate. (a) Product. Ammonium bicarbonate. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding...

  13. 21 CFR 582.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1143 Ammonium sulfate. (a) Product. Ammonium sulfate. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding practice. ...

  14. 76 FR 62311 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-07

    ... to best notify agents (AN Agents) when ammonium nitrate purchasers (AN Purchasers) submit those AN... directly to ammonium nitrate sellers (AN Sellers) when it is not possible for an AN Seller to verify the...

  15. 21 CFR 582.7133 - Ammonium alginate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Ammonium alginate. 582.7133 Section 582.7133 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Ammonium alginate. (a) Product. Ammonium alginate. (b) Conditions of use. This substance is...

  16. 21 CFR 556.375 - Maduramicin ammonium.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... residues of maduramicin ammonium in chickens as follows: (a) A tolerance for maduramicin ammonium (marker residue) in chickens is 0.38 parts per million in fat (target tissue). A tolerance refers to the... animals. (b) The safe concentrations for total maduramicin ammonium residues in uncooked edible...

  17. 21 CFR 184.1138 - Ammonium chloride.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    .... No. 12125-02-9) is produced by the reaction of sodium chloride and an ammonium salt in solution. The less soluble sodium salt separates out at elevated temperatures, and ammonium chloride is recovered... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ammonium chloride. 184.1138 Section 184.1138...

  18. 21 CFR 184.1138 - Ammonium chloride.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    .... No. 12125-02-9) is produced by the reaction of sodium chloride and an ammonium salt in solution. The less soluble sodium salt separates out at elevated temperatures, and ammonium chloride is recovered... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ammonium chloride. 184.1138 Section 184.1138...

  19. 21 CFR 184.1138 - Ammonium chloride.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    .... No. 12125-02-9) is produced by the reaction of sodium chloride and an ammonium salt in solution. The less soluble sodium salt separates out at elevated temperatures, and ammonium chloride is recovered... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium chloride. 184.1138 Section 184.1138...

  20. 21 CFR 184.1138 - Ammonium chloride.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... No. 12125-02-9) is produced by the reaction of sodium chloride and an ammonium salt in solution. The less soluble sodium salt separates out at elevated temperatures, and ammonium chloride is recovered... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ammonium chloride. 184.1138 Section 184.1138...

  1. 76 FR 47238 - Ammonium Nitrate From Russia

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-04

    ... COMMISSION Ammonium Nitrate From Russia Determination On the basis of the record \\1\\ developed in the subject... order on ammonium nitrate from Russia would be likely to lead to continuation or recurrence of material... Commission are contained in USITC Publication 4249 (August 2011), entitled Ammonium Nitrate from...

  2. 76 FR 11273 - Ammonium Nitrate From Russia

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-01

    ... COMMISSION Ammonium Nitrate From Russia AGENCY: United States International Trade Commission. ACTION: Institution of a five-year review concerning the suspended investigation on ammonium nitrate from Russia... investigation on ammonium nitrate from Russia would be likely to lead to continuation or recurrence of...

  3. 21 CFR 582.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Ammonium bicarbonate. 582.1135 Section 582.1135 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1135 Ammonium bicarbonate. (a) Product. Ammonium bicarbonate. (b) Conditions of use. This...

  4. 21 CFR 582.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Ammonium bicarbonate. 582.1135 Section 582.1135 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1135 Ammonium bicarbonate. (a) Product. Ammonium bicarbonate. (b) Conditions of use. This...

  5. 21 CFR 582.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Ammonium bicarbonate. 582.1135 Section 582.1135 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1135 Ammonium bicarbonate. (a) Product. Ammonium bicarbonate. (b) Conditions of use. This...

  6. 21 CFR 582.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Ammonium bicarbonate. 582.1135 Section 582.1135 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1135 Ammonium bicarbonate. (a) Product. Ammonium bicarbonate. (b) Conditions of use. This...

  7. Extraction of urea and ammonium ion

    NASA Technical Reports Server (NTRS)

    Anselmi, R. T.; Husted, R. R.; Schulz, J. R.

    1977-01-01

    Water purification system keeps urea and ammonium ion concentration below toxic limits in recirculated water of closed loop aquatic habitat. Urea is first converted to ammonium ions and carbon dioxide by enzygmatic action. Ammonium ions are removed by ion exchange. Bioburden is controlled by filtration through 0.45 micron millipore filters.

  8. 21 CFR 184.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ammonium sulfate. 184.1143 Section 184.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Specific Substances Affirmed as GRAS § 184.1143 Ammonium sulfate. (a) Ammonium sulfate ((NH4)2SO4, CAS...

  9. 21 CFR 582.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Ammonium sulfate. 582.1143 Section 582.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1143 Ammonium sulfate. (a) Product. Ammonium sulfate. (b) Conditions of use. This...

  10. 21 CFR 582.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Ammonium sulfate. 582.1143 Section 582.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1143 Ammonium sulfate. (a) Product. Ammonium sulfate. (b) Conditions of use. This...

  11. 21 CFR 184.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium sulfate. 184.1143 Section 184.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT... GRAS § 184.1143 Ammonium sulfate. (a) Ammonium sulfate ((NH4)2SO4, CAS Reg. No. 7783-20-2)...

  12. 21 CFR 184.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ammonium sulfate. 184.1143 Section 184.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Specific Substances Affirmed as GRAS § 184.1143 Ammonium sulfate. (a) Ammonium sulfate ((NH4)2SO4, CAS...

  13. 21 CFR 184.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ammonium sulfate. 184.1143 Section 184.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Specific Substances Affirmed as GRAS § 184.1143 Ammonium sulfate. (a) Ammonium sulfate ((NH4)2SO4, CAS...

  14. 21 CFR 582.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Ammonium sulfate. 582.1143 Section 582.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1143 Ammonium sulfate. (a) Product. Ammonium sulfate. (b) Conditions of use. This...

  15. 21 CFR 582.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Ammonium sulfate. 582.1143 Section 582.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1143 Ammonium sulfate. (a) Product. Ammonium sulfate. (b) Conditions of use. This...

  16. Extraction of urea and ammonium ion

    NASA Technical Reports Server (NTRS)

    Anselmi, R. T.; Husted, R. R.; Schulz, J. R.

    1977-01-01

    Water purification system keeps urea and ammonium ion concentration below toxic limits in recirculated water of closed loop aquatic habitat. Urea is first converted to ammonium ions and carbon dioxide by enzygmatic action. Ammonium ions are removed by ion exchange. Bioburden is controlled by filtration through 0.45 micron millipore filters.

  17. 21 CFR 582.1141 - Ammonium phosphate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Ammonium phosphate. 582.1141 Section 582.1141 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1141 Ammonium phosphate. (a) Product. Ammonium phosphate (mono- and dibasic). (b) Conditions...

  18. 21 CFR 582.1141 - Ammonium phosphate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Ammonium phosphate. 582.1141 Section 582.1141 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1141 Ammonium phosphate. (a) Product. Ammonium phosphate (mono- and dibasic). (b) Conditions...

  19. 21 CFR 582.1141 - Ammonium phosphate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Ammonium phosphate. 582.1141 Section 582.1141 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1141 Ammonium phosphate. (a) Product. Ammonium phosphate (mono- and dibasic). (b) Conditions...

  20. 21 CFR 582.1141 - Ammonium phosphate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Ammonium phosphate. 582.1141 Section 582.1141 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1141 Ammonium phosphate. (a) Product. Ammonium phosphate (mono- and dibasic). (b) Conditions...

  1. 21 CFR 582.1141 - Ammonium phosphate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Ammonium phosphate. 582.1141 Section 582.1141 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1141 Ammonium phosphate. (a) Product. Ammonium phosphate (mono- and dibasic). (b) Conditions...

  2. Structural basis for Mep2 ammonium transceptor activation by phosphorylation

    PubMed Central

    van den Berg, Bert; Chembath, Anupama; Jefferies, Damien; Basle, Arnaud; Khalid, Syma; Rutherford, Julian C.

    2016-01-01

    Mep2 proteins are fungal transceptors that play an important role as ammonium sensors in fungal development. Mep2 activity is tightly regulated by phosphorylation, but how this is achieved at the molecular level is not clear. Here we report X-ray crystal structures of the Mep2 orthologues from Saccharomyces cerevisiae and Candida albicans and show that under nitrogen-sufficient conditions the transporters are not phosphorylated and present in closed, inactive conformations. Relative to the open bacterial ammonium transporters, non-phosphorylated Mep2 exhibits shifts in cytoplasmic loops and the C-terminal region (CTR) to occlude the cytoplasmic exit of the channel and to interact with His2 of the twin-His motif. The phosphorylation site in the CTR is solvent accessible and located in a negatively charged pocket ∼30 Å away from the channel exit. The crystal structure of phosphorylation-mimicking Mep2 variants from C. albicans show large conformational changes in a conserved and functionally important region of the CTR. The results allow us to propose a model for regulation of eukaryotic ammonium transport by phosphorylation. PMID:27088325

  3. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, M.; Yoo, C. S.

    2014-05-01

    Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

  4. The mechanism of ammonia transport based on the crystal structure of AmtB of Escherichia coli.

    PubMed

    Zheng, Lei; Kostrewa, Dirk; Bernèche, Simon; Winkler, Fritz K; Li, Xiao-Dan

    2004-12-07

    Ammonium is one of the most important nitrogen sources for bacteria, fungi, and plants, but it is toxic to animals. The ammonium transport proteins (methylamine permeases/ammonium transporters/rhesus) are present in all domains of life; however, functional studies with members of this family have yielded controversial results with respect to the chemical identity (NH(4)(+) or NH(3)) of the transported species. We have solved the structure of wild-type AmtB from Escherichia coli in two crystal forms at 1.8- and 2.1-A resolution, respectively. Substrate transport occurs through a narrow mainly hydrophobic pore located at the center of each monomer of the trimeric AmtB. At the periplasmic entry, a binding site for NH(4)(+) is observed. Two phenylalanine side chains (F107 and F215) block access into the pore from the periplasmic side. Further into the pore, the side chains of two highly conserved histidine residues (H168 and H318) bridged by a H-bond lie adjacent, with their edges pointing into the cavity. These histidine residues may facilitate the deprotonation of an ammonium ion entering the pore. Adiabatic free energy calculations support the hypothesis that an electrostatic barrier between H168 and H318 hinders the permeation of cations but not that of the uncharged NH(3.) The structural data and energetic considerations strongly indicate that the methylamine permeases/ammonium transporters/rhesus proteins are ammonia gas channels. Interestingly, at the cytoplasmic exit of the pore, two different conformational states are observed that might be related to the inactivation mechanism by its regulatory partner.

  5. E. Coli

    MedlinePlus

    ... of Your Teeth El cuidado de los dientes Video: Getting an X-ray E. Coli KidsHealth > For Kids > E. Coli Print A A A What's in ... recalls affecting contaminated vegetables or other products. But kids can ... inside. Don't swallow lake, ocean, or pool water. If the water contains ...

  6. Isolation and stable nitrogen isotope analysis of ammonium ions in ammonium nitrate prills using sodium tetraphenylborate.

    PubMed

    Howa, John D; Lott, Michael J; Ehleringer, James R

    2014-07-15

    Because of the threat of bombings using improvised explosives containing ammonium nitrate (AN), law enforcement and intelligence communities have been interested in stable isotope techniques for tracking and discriminating AN sources. Separate analysis of the AN component ions ammonium and nitrate would add discriminatory power to these techniques. Ammonium ions in dissolved AN solution were isolated from samples by precipitation using sodium tetraphenylborate solution. We tested the isolation of ammonium from nitrates using solutions of ammonium and nitrate salts with different (15)N/(14)N isotope ratios. Ammonium tetraphenylborate and AN were separately analyzed for their (15)N/(14)N isotope ratios using EA-ConFlo-IRMS, and the (15)N/(14)N isotope ratios of the nitrate ions were calculated using mass balance. Ammonium and nitrate nitrogen isotope ratios were plotted as two separate variables. Isolation of ammonium precipitate from solutions containing dissolved nitrates did not influence the nitrogen isotope ratios of test ammonium salts. A survey set of 42 AN samples showed that the ammonium and nitrate (15)N/(14)N isotope ratios were not significantly correlated, and the paired mean differences were not statistically significant. Both ammonium and nitrate were depleted in (15)N relative to their theoretical atmospheric sources. Isolation of the ammonium ion from AN adds another dimension for the discrimination of forensic AN samples. This technique using sodium tetraphenylborate is robust and does not require specialized equipment. Our observations indicated that ammonium nitrogen and nitrate nitrogen have independent sources of isotopic variation. Copyright © 2014 John Wiley & Sons, Ltd.

  7. Structural study of ammonium metatungstate

    SciTech Connect

    Christian, Joel B. Whittingham, M. Stanley

    2008-08-15

    Several techniques have been used to study the structure of the Keggin-type polyoxometalate salt ammonium metatungstate (AMT)-(NH{sub 4}){sub 6}[H{sub 2}W{sub 12}O{sub 40}]*nH{sub 2}O, a potential fuel cell catalyst. The dehydrated salt is comprised of a mixture of crystallites of different unit cells in a centered eutactic cubic configuration, with an average unit cell of a{approx_equal}12.295. Varied orientations of the Keggin ions in the cubic arrangement create the differences, and orientational variation within each unit cell size represents an energy well. Progressive hydration of each crystallite leads to expansion of the lattice, with the degree of expansion depending on the locations of the water added in relation to the Keggin ion, which is influenced by cation location and hydrogen bonding. The structural hypothesis is supported by electron diffraction of single and multicrystal samples, by powder density measurements, X-ray powder diffraction studies, synchrotron powder X-ray diffraction, and a priori structural modeling studies. Based on the structure, projected active site densities are compared with nanostructured platinum catalysts for fuel cell application. - Graphical abstract: The structure of ammonium metatungstate powders are highly dependent on hydration and POM molecule rotation, with cation and hydrogen bonding forces directing a mixture of structures that have been studied with bulk and single-crystal methods. The illustration shows Monte Carlo simulated anion structural disorder for the fully dehydrated form of the title compound.

  8. Phase Diagram of Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-06-01

    Ammonium Nitrate (AN) has often been subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood - resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety, in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN, in different chemical environments, at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 15 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 673 K. The present study has been supported by the U.S. DHS under Award Number 2008-ST-061-ED0001.

  9. Synthesis and characterization of chitosan based dye containing quaternary ammonium group.

    PubMed

    Tang, Ruilin; Zhang, Ying; Zhang, Yang; Yu, Zhiming

    2016-03-30

    A new antimicrobial biopolymer dye was synthesized by reaction of quaternary ammonium salt of chitosan and reactive red x-3b. And quaternary ammonium salt of chitosan was produced by grafting glycidyltrimethylammonium chloride on chitosan. The synthesized materials were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), solubility test and antimicrobial test. Results show that the antimicrobial biopolymer dye was combined by N(+)(CH3)3 of quaternary ammonium salt of chitosan and sulfonic group of reactive red x-3b. Water solubility of chitosan biopolymer dye was increased as well as pH value. In addition, antibacterial property of new synthesized dye was excellent, whose antibacterial rates of Staphylococcus and Escherichia coli were both bigger than 99%. These results may provide new perspectives on improving the decorative properties and antimicrobial properties in wood industry.

  10. Expression, purification and crystallization of the ammonium transporter Amt-1 from Archaeoglobus fulgidus

    SciTech Connect

    Andrade, Susana L. A. Dickmanns, Antje; Ficner, Ralf; Einsle, Oliver

    2005-09-01

    The ammonium transporter Amt-1 from the cytoplasmic membrane of the hyperthermophilic archaeon A. fulgidus has been purified and crystallized. Ammonium transporters (Amts) are a class of membrane-integral transport proteins found in organisms from all kingdoms of life. Their key function is the transport of nitrogen in its reduced bioavailable form, ammonia, across cellular membranes, a crucial step in nitrogen assimilation for biosynthetic purposes. The genome of the hyperthermophilic archaeon Archaeoglobus fulgidus has been annotated with three individual genes for ammonium transporters, amt1–3, the roles of which are as yet unknown. The amt1 gene product has been produced by heterologous overexpression in Escherichia coli and the resulting protein has been purified to electrophoretic homogeneity. Crystals of Amt-1 have been obtained by sitting-drop vapour diffusion and diffraction data have been collected.

  11. Antimicrobial cotton containing N-halamine and quaternary ammonium groups by grafting copolymerization

    NASA Astrophysics Data System (ADS)

    Liu, Ying; Liu, Yin; Ren, Xuehong; Huang, T. S.

    2014-03-01

    The monomer (3-acrylamidopropyl)trimethylammonium chloride (APTMAC) was used to treat cotton fibers by grafting copolymerization. The grafted cotton fabrics were characterized by SEM image and FTIR spectra. The treated samples with quaternary ammonium groups could decrease 96.08% of Staphylococcus aureus and 48.74% of Escherichia coli O157:H7 within 30 min. After chlorination with dilute sodium hypochlorite, the treated cotton fabrics containing both N-halamine and quaternary ammonium groups effectively inactivated 100% (log reduction 5.82) of S. aureus and 100% (log reduction 6.26) of E. coli O157:H7 within 5 min of contact time. The grafting process of cotton fabric has small effect on the thermal stability and tensile strength, which favors the practical application. Compared to the traditional pad-dry-cure method to produce antibacterial materials, the radical grafting copolymerization method occurred in water without any organic solvents involved in the whole treatment.

  12. Quaternary ammonium salt of chitosan: preparation and antimicrobial property for paper

    PubMed Central

    Liu, Pengtao; Meng, Weisheng; Wang, Shuai; Sun, Yonghui; Ashraf, Muhammad Aqeel

    2015-01-01

    A series of 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) was prepared by the reaction of chitosan with glycidyl trimethyl ammonium chloride. Structure of HACC was characterized by FT IR and 1H NMR spectroscopies, and it was proved that substitution reaction mainly occurs on the N element. Antimicrobial activities of HACC was examined against S. aureus, E. coli, and A. niger. Results indicatd that the inhibitory effects of HACC solutions were varied with HACC concentration, quaternization degrees, pH values, metal ions, and heat treatment. The antimicrobial properties of handsheets prepared from HACC were studied by the inhibition zone method, and the sheets had good antimicrobial properties against S. aureus and E. coli, and low inhibition rate against A. niger. PMID:28352739

  13. New biocide with both N-chloramine and quaternary ammonium moieties exerts enhanced bactericidal activity.

    PubMed

    Li, Lingdong; Pu, Tianyun; Zhanel, George; Zhao, Nan; Ens, Werner; Liu, Song

    2012-09-01

    Considering the rise of antibiotic resistance, the development of new antibacterial agents with improved biocidal functions is urgently required. In this study, ionic 5,5-dimethylhydantoin (DMH) analogues containing either a quaternary ammonium moiety (2)-4) or a phosphonate functional group (5),-6), were designed and synthesized to investigate the possible enhancing effect of quaternary ammonium moieties on the antibacterial performance of N-chloramines. These ionic DMH analogues were converted to their N-chloramine counterparts either in free form or after being covalently immobilized on a polymer surface via the "click" chemistry method. In the subsequent antimicrobial assessment against multi-drug-resistant Escherichia coli (MDR-E. coli) and methicillin-resistant Staphylococcus aureus (MRSA), chlorinated 2 and 3, the cyclic N-chloramines with a structural cation, exhibited distinctly enhanced biocidal functions in solution and after immobilization on surfaces. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  15. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  16. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  17. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  18. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  19. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  20. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  1. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-01

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  2. 76 FR 46907 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-03

    ... comments. SUMMARY: This proposed rule would implement anti-terrorism measures to better secure the homeland... purpose of preventing the use of ammonium nitrate in an act of terrorism. This proposed rule seeks comment... Regulations Addressing Ammonium Nitrate a. Chemical Facility Anti-Terrorism Standards b. U.S. Coast...

  3. Biodegradation of rocket propellant waste, ammonium perchlorate

    NASA Technical Reports Server (NTRS)

    Naqvi, S. M. Z.; Latif, A.

    1975-01-01

    The short term effects of ammonium perchlorate on selected organisms were studied. A long term experiment was also designed to assess the changes incurred by ammonium perchlorate on the nitrogen and chloride contents of soil within a period of 3 years. In addition, an attempt was made to produce methane gas from anaerobic fermentation of the aquatic weed, Alternanthera philoxeroides.

  4. Dielectric relaxations in partly deuterated ammonium dichromate

    NASA Astrophysics Data System (ADS)

    Gilchrist, John le G.

    1987-12-01

    Two dielectric relaxations in partly deuterated ammonium dichromate are attributed to reorientations of mixed-isotope ammonium ions. Loss peaks were observed between 20 and 40 K and obey the Arrhenius law with activation energy 1.5 kcal/mol for the stronger relaxation. The dipole moment is of the order of 0.015 D.

  5. Ammonium nonanoate broadcast application over onions

    USDA-ARS?s Scientific Manuscript database

    Ammonium nonanoate occurs in nature and is primarily formed from biodegradation of higher fatty acids. Racer (40% ammonium nonaoate) is a potential contact herbicide for weed control in organic crop production. Field research was conducted in southeast Oklahoma (Atoka County, Lane, OK) to determin...

  6. Evolution of Electrogenic Ammonium Transporters (AMTs)

    DOE PAGES

    McDonald, Tami R.; Ward, John M.

    2016-03-31

    The ammonium transporter gene family consists of three main clades, AMT, MEP, and Rh. The evolutionary history of the AMT/MEP/Rh gene family is characterized by multiple horizontal gene transfer events, gene family expansion and contraction, and gene loss; thus the gene tree for this family of transporters is unlike the organismal tree. The genomes of angiosperms contain genes for both electrogenic and electroneutral ammonium transporters, but it is not clear how far back in the land plant lineage electrogenic ammonium transporters occur. Here, we place Marchantia polymorpha ammonium transporters in the AMT/MEP/Rh phylogeny and we show that AMTs from themore » liverwort M. polymorpha are electrogenic. This information suggests that electrogenic ammonium transport evolved at least as early as the divergence of bryophytes in the land plant lineage.« less

  7. Evolution of Electrogenic Ammonium Transporters (AMTs)

    SciTech Connect

    McDonald, Tami R.; Ward, John M.

    2016-03-31

    The ammonium transporter gene family consists of three main clades, AMT, MEP, and Rh. The evolutionary history of the AMT/MEP/Rh gene family is characterized by multiple horizontal gene transfer events, gene family expansion and contraction, and gene loss; thus the gene tree for this family of transporters is unlike the organismal tree. The genomes of angiosperms contain genes for both electrogenic and electroneutral ammonium transporters, but it is not clear how far back in the land plant lineage electrogenic ammonium transporters occur. Here, we place Marchantia polymorpha ammonium transporters in the AMT/MEP/Rh phylogeny and we show that AMTs from the liverwort M. polymorpha are electrogenic. This information suggests that electrogenic ammonium transport evolved at least as early as the divergence of bryophytes in the land plant lineage.

  8. Evolution of Electrogenic Ammonium Transporters (AMTs)

    PubMed Central

    McDonald, Tami R.; Ward, John M.

    2016-01-01

    The ammonium transporter gene family consists of three main clades, AMT, MEP, and Rh. The evolutionary history of the AMT/MEP/Rh gene family is characterized by multiple horizontal gene transfer events, gene family expansion and contraction, and gene loss; thus the gene tree for this family of transporters is unlike the organismal tree. The genomes of angiosperms contain genes for both electrogenic and electroneutral ammonium transporters, but it is not clear how far back in the land plant lineage electrogenic ammonium transporters occur. Here, we place Marchantia polymorpha ammonium transporters in the AMT/MEP/Rh phylogeny and we show that AMTs from the liverwort M. polymorpha are electrogenic. This information suggests that electrogenic ammonium transport evolved at least as early as the divergence of bryophytes in the land plant lineage. PMID:27066024

  9. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  10. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  11. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  12. Guiding E.coli to nanosensors

    NASA Astrophysics Data System (ADS)

    Park, Dong-Won; So, Hye-Mi; Kim, Beom Soo; Kong, Ki-Jeong; Chang, Hyunju; Lee, Jeong-O.

    2009-03-01

    Electronic nanosensors based on nanomaterials such as carbon nanotubes and nanowires are expected to have ultimate sensitivity. However, as an inherent problem of nanosensors, they have extremely small sensor surface for reaction. Therefore, simple diffusion of target biomolecules is not enough for such nanosensors, and the problem is even more serious in the case of motile bacteria. Previously, we have shown that we could estimate the titer of E.coli with arrays of single-walled carbon nanotube field effect transistors (SWNT-FET) combined with statistical method. Still, sensitivity of our method is inferior compared with incubation method, due to the limited sensor surface area. In this work, we actively guide E.coli to the sensor surface using micro-fabricated channels. Arrow-shaped and funnel shaped microstructures were fabricated in the channel to guide E. coli to the sensor surface, and we used green fluorescent protein expressed E.coli to monitor the guiding of E.coli.

  13. Different transport mechanisms in plant and human AMT/Rh-type ammonium transporters.

    PubMed

    Mayer, Maria; Schaaf, Gabriel; Mouro, Isabelle; Lopez, Claude; Colin, Yves; Neumann, Petra; Cartron, Jean-Pierre; Ludewig, Uwe

    2006-02-01

    The conserved family of AMT/Rh proteins facilitates ammonium transport across animal, plant, and microbial membranes. A bacterial homologue, AmtB, forms a channel-like structure and appears to function as an NH3 gas channel. To evaluate the function of eukaryotic homologues, the human RhCG glycoprotein and the tomato plant ammonium transporter LeAMT1;2 were expressed and compared in Xenopus oocytes and yeast. RhCG mediated the electroneutral transport of methylammonium (MeA), which saturated with Km = 3.8 mM at pHo 7.5. Uptake was strongly favored by increasing the pHo and was inhibited by ammonium. Ammonium induced rapid cytosolic alkalinization in RhCG-expressing oocytes. Additionally, RhCG expression was associated with an alkali-cation conductance, which was not significantly permeable to NH4+ and was apparently uncoupled from the ammonium transport. In contrast, expression of the homologous LeAMT1;2 induced pHo-independent MeA+ uptake and specific NH4+ and MeA+ currents that were distinct from endogenous currents. The different mechanisms of transport, including the RhCG-associated alkali-cation conductance, were verified by heterologous expression in appropriate yeast strains. Thus, homologous AMT/Rh-type proteins function in a distinct manner; while LeAMT1;2 carries specifically NH4+, or cotransports NH3/H+, RhCG mediates electroneutral NH3 transport.

  14. Synthesis and Antibacterial Activity of Quaternary Ammonium 4-Deoxypyridoxine Derivatives

    PubMed Central

    Shtyrlin, Nikita V.; Sapozhnikov, Sergey V.; Galiullina, Albina S.; Kayumov, Airat R.; Bondar, Oksana V.; Mirchink, Elena P.; Isakova, Elena B.; Firsov, Alexander A.; Balakin, Konstantin V.

    2016-01-01

    A series of novel quaternary ammonium 4-deoxypyridoxine derivatives was synthesized. Two compounds demonstrated excellent activity against a panel of Gram-positive methicillin-resistant S. aureus strains with MICs in the range of 0.5–2 μg/mL, exceeding the activity of miramistin. At the same time, both compounds were inactive against the Gram-negative E. coli and P. aeruginosa strains. Cytotoxicity studies on human skin fibroblasts and embryonic kidney cells demonstrated that the active compounds possessed similar toxicity with benzalkonium chloride but were slightly more toxic than miramistin. SOS-chromotest in S. typhimurium showed the lack of DNA-damage activity of both compounds; meanwhile, one compound showed some mutagenic potential in the Ames test. The obtained results make the described chemotype a promising starting point for the development of new antibacterial therapies. PMID:27800491

  15. Synthesis and Antibacterial Activity of Quaternary Ammonium 4-Deoxypyridoxine Derivatives.

    PubMed

    Shtyrlin, Nikita V; Sapozhnikov, Sergey V; Galiullina, Albina S; Kayumov, Airat R; Bondar, Oksana V; Mirchink, Elena P; Isakova, Elena B; Firsov, Alexander A; Balakin, Konstantin V; Shtyrlin, Yurii G

    2016-01-01

    A series of novel quaternary ammonium 4-deoxypyridoxine derivatives was synthesized. Two compounds demonstrated excellent activity against a panel of Gram-positive methicillin-resistant S. aureus strains with MICs in the range of 0.5-2 μg/mL, exceeding the activity of miramistin. At the same time, both compounds were inactive against the Gram-negative E. coli and P. aeruginosa strains. Cytotoxicity studies on human skin fibroblasts and embryonic kidney cells demonstrated that the active compounds possessed similar toxicity with benzalkonium chloride but were slightly more toxic than miramistin. SOS-chromotest in S. typhimurium showed the lack of DNA-damage activity of both compounds; meanwhile, one compound showed some mutagenic potential in the Ames test. The obtained results make the described chemotype a promising starting point for the development of new antibacterial therapies.

  16. Salting out of proteins using ammonium sulfate precipitation.

    PubMed

    Duong-Ly, Krisna C; Gabelli, Sandra B

    2014-01-01

    Protein solubility is affected by ions. At low ion concentrations (<0.5 M), protein solubility increases along with ionic strength. Ions in the solution shield protein molecules from the charge of other protein molecules in what is known as 'salting-in'. At a very high ionic strength, protein solubility decreases as ionic strength increases in the process known as 'salting-out'. Thus, salting out can be used to separate proteins based on their solubility in the presence of a high concentration of salt. In this protocol, ammonium sulfate will be added incrementally to an E. coli cell lysate to isolate a recombinantly over-expressed protein of 20 kDa containing no cysteine residues or tags.

  17. The nucleation kinetics of ammonium metavanadate precipitated by ammonium chloride

    NASA Astrophysics Data System (ADS)

    Du, Guangchao; Sun, Zhaohui; Xian, Yong; Jing, Han; Chen, Haijun; Yin, Danfeng

    2016-05-01

    The nucleation kinetics of ammonium metavanadate (NH4VO3) was investigated under conditions of the simulated process for precipitation of NH4VO3 from the vanadium-containing solution. Induction periods for the nucleation of NH4VO3 were experimentally determined as a function of supersaturation at temperatures from 30 to 45 °C. Using the classical nucleation theory, the interfacial tension between NH4VO3 and supersaturated solution, the nucleation rate and critical radius of nucleus for the homogeneous nucleation of NH4VO3 were estimated. With temperature increasing, the calculated interfacial tension gradually decreased from 29.78 mJ/m2 at 30 °C to 23.66 mJ/m2 at 45 °C. The nucleation rate was found to proportionally increase but the critical radius of nucleus exponentially decreased, with increase in supersaturation ratio at a constant temperature. The activation energy for NH4VO3 nucleation was obtained from the relationship between temperature and induction period, ranging from 79.17 kJ/mol at S=25 to 115.50 kJ/mol at S=15. FT-IR and Raman spectrum indicated that the crystals obtained in the precipitation process were NH4VO3.

  18. Riparian nitrogen dynamics in a humid tropical watershed: ammonium removal from groundwater at the stream/aquifer interface

    NASA Astrophysics Data System (ADS)

    Brereton, R. L.; McDowell, W. H.

    2013-12-01

    Many studies have documented the ability of riparian zones to remove dissolved nitrogen from groundwater before subsurface flow paths deliver it to surface water. Few studies have moved beyond describing biogeochemical patterns and demonstrated in-situ pathways of nitrogen removal. In this study we adapt push-pull methods commonly used to measure in-situ denitrification, in order to explore possible pathways of ammonium removal in the Rio Icacos watershed, Luquillo Mountains, Puerto Rico. Earlier studies have shown that this watershed has a distinctive pattern of nitrogen biogeochemistry along groundwater flow paths through the soil catena; hillslope groundwater carries nitrate concentrations of up to 1 mg N/l and little ammonium, while riparian groundwater carries ammonium concentrations of up to 1.5 mg N/l and little nitrate. Ammonium concentrations in streams are uniformly low. The pathway of ammonium removal was investigated by modified push-pull tests with ammonium additions. A dosing solution of 10 l ambient groundwater was extracted, amended with 32 mg/l NH4-N and a bromide tracer and bubbled with SF6 to maintain anoxic conditions, and then re-injected into a minipiezometer. Minipiezometers were placed 75 cm depth and 30-100 cm distance from the edge of the stream channel. The dosing solution was allowed to incubate between 2 and 6 hr, then withdrawn and sampled at regular intervals. Ammonium removal for each time point was calculated as the difference between the tracer recovery (sample concentration/initial concentration) and the ammonium recovery. Ammonium removal at all time points ranged from 7% to 14%. No nitrate was detected either before or during push-pulls, indicating that nitrification (without tightly coupled denitrification) could not account for the observed ammonium removal. Consistent anoxic conditions and a sulfidic smell also indicate that oxygen needed for nitrification is not prevalent in the aquifer. Future studies with isotopic tracers

  19. 21 CFR 73.1298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) Identity. (1) The color additive ferric ammonium ferrocyanide is the blue pigment obtained by oxidizing... product is filtered, washed, and dried. The pigment consists principally of ferric ammonium...

  20. 21 CFR 73.1298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Identity. (1) The color additive ferric ammonium ferrocyanide is the blue pigment obtained by oxidizing... product is filtered, washed, and dried. The pigment consists principally of ferric ammonium...

  1. 21 CFR 73.1298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...) Identity. (1) The color additive ferric ammonium ferrocyanide is the blue pigment obtained by oxidizing... product is filtered, washed, and dried. The pigment consists principally of ferric ammonium...

  2. 21 CFR 73.1298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) Identity. (1) The color additive ferric ammonium ferrocyanide is the blue pigment obtained by oxidizing... product is filtered, washed, and dried. The pigment consists principally of ferric ammonium...

  3. Phase diagram of ammonium nitrate

    SciTech Connect

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-07

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ′} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  4. Substrate specificity of Rhbg: ammonium and methyl ammonium transport

    PubMed Central

    Abdulnour-Nakhoul, Solange M.; Boulpaep, Emile L.; Rabon, Edd; Schmidt, Eric; Hamm, L. Lee

    2010-01-01

    Rhbg is a nonerythroid membrane glycoprotein belonging to the Rh antigen family. In the kidney, Rhbg is expressed at the basolateral membrane of intercalated cells of the distal nephron and is involved in NH4+ transport. We investigated the substrate specificity of Rhbg by comparing transport of NH3/NH4+ with that of methyl amine (hydrochloride) (MA/MA+), often used to replace NH3/NH4+, in oocytes expressing Rhbg. Methyl amine (HCl) in solution exists as neutral methyl amine (MA) in equilibrium with the protonated methyl ammonium (MA+). To assess transport, we used ion-selective microelectrodes and voltage-clamp experiments to measure NH3/NH4+- and MA/MA+-induced intracellular pH (pHi) changes and whole cell currents. Our data showed that in Rhbg oocytes, NH3/NH4+ caused an inward current and decrease in pHi consistent with electrogenic NH4+ transport. These changes were significantly larger than in H2O-injected oocytes. The NH3/NH4+-induced current was not inhibited in the presence of barium or in the absence of Na+. In Rhbg oocytes, MA/MA+ caused an inward current but an increase (rather than a decrease) in pHi. MA/MA+ did not cause any changes in H2O-injected oocytes. The MA/MA+-induced current and pHi increase were saturated at higher concentrations of MA/MA+. Amiloride inhibited MA/MA+-induced current and the increase in pHi in oocytes expressing Rhbg but had no effect on control oocytes. These results indicate that MA/MA+ is transported by Rhbg but differently than NH3/NH4+. The protonated MA+ is likely a direct substrate whose transport resembles that of NH4+. Transport of electroneutral MA is also enhanced by expression of Rhbg. PMID:20592240

  5. Substrate specificity of Rhbg: ammonium and methyl ammonium transport.

    PubMed

    Nakhoul, Nazih L; Abdulnour-Nakhoul, Solange M; Boulpaep, Emile L; Rabon, Edd; Schmidt, Eric; Hamm, L Lee

    2010-09-01

    Rhbg is a nonerythroid membrane glycoprotein belonging to the Rh antigen family. In the kidney, Rhbg is expressed at the basolateral membrane of intercalated cells of the distal nephron and is involved in NH4+ transport. We investigated the substrate specificity of Rhbg by comparing transport of NH3/NH4+ with that of methyl amine (hydrochloride) (MA/MA+), often used to replace NH3/NH4+, in oocytes expressing Rhbg. Methyl amine (HCl) in solution exists as neutral methyl amine (MA) in equilibrium with the protonated methyl ammonium (MA+). To assess transport, we used ion-selective microelectrodes and voltage-clamp experiments to measure NH3/NH4+- and MA/MA+-induced intracellular pH (pH(i)) changes and whole cell currents. Our data showed that in Rhbg oocytes, NH3/NH4+ caused an inward current and decrease in pH(i) consistent with electrogenic NH4+ transport. These changes were significantly larger than in H2O-injected oocytes. The NH3/NH4+-induced current was not inhibited in the presence of barium or in the absence of Na+. In Rhbg oocytes, MA/MA+ caused an inward current but an increase (rather than a decrease) in pH(i). MA/MA+ did not cause any changes in H2O-injected oocytes. The MA/MA+-induced current and pH(i) increase were saturated at higher concentrations of MA/MA+. Amiloride inhibited MA/MA+-induced current and the increase in pH(i) in oocytes expressing Rhbg but had no effect on control oocytes. These results indicate that MA/MA+ is transported by Rhbg but differently than NH3/NH4+. The protonated MA+ is likely a direct substrate whose transport resembles that of NH4+. Transport of electroneutral MA is also enhanced by expression of Rhbg.

  6. 76 FR 70366 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-14

    ...- accessible Internet access could obtain the access necessary to register online. 3. How to best notify... ammonium nitrate sellers (AN Sellers) when it is not possible for an AN Seller to verify the identity of...

  7. Biodegradation of rocket propellent waste, ammonium perchlorate

    NASA Technical Reports Server (NTRS)

    Naqui, S. M. Z.

    1975-01-01

    The impact of the biodegradation rate of ammonium perchlorate on the environment was studied in terms of growth, metabolic rate, and total biomass of selected animal and plant species. Brief methodology and detailed results are presented.

  8. Toxicology of ammonium sulfate in the lung

    SciTech Connect

    Pepelko, W.E.; Mattox, J.K.; Cohen, A.L.

    1980-01-01

    Despite the relatively low toxicity of ammonium sulfate in experimental animals, it cannot be concluded that increased sulfuric acid production is harmless to human health. Many other pollutants are present in ambient air with possible synergistic effects. Sulfuric acid undoubtedly reacts to produce other sulfates in ambient air which are often much more toxic. For example zinc sulfate and zinc ammonium sulfate are much more irritating to the lung than ammonium sulfate. In order to assess with more certainty the health effects of increased sulfuric acid production, it will be necessary to determine accurately that proportion inhaled as free sulfuric acid compared with ammonium sulfate as well as the proportion and kinds of other sulfates present in the atmosphere.

  9. Resistance to quaternary ammonium compounds in food-related bacteria.

    PubMed

    Sidhu, Maan Singh; Sørum, Henning; Holck, Askild

    2002-01-01

    Microbial resistance to antimicrobial agents continues to be a major problem. The frequent use and misuse of disinfectants based on quaternary ammonium compounds (QACs) in food-processing industries have imposed a selective pressure and may contribute to the emergence of disinfectant-resistant microorganisms. A total number of 1,325 Gram-negative isolates (Escherichia coli, other coliforms Vibrio spp., and Aeromonas spp.) and 500 Enterococcus spp. from food and food-processing industries and fish farming were screened for natural resistance to the QAC-based disinfectant benzalkonium chloride (BC). Of the 1,825 isolates, 16 strains, mainly from meat retail shops, showed low-level resistance to BC. None of the Enterococcus spp. from broiler, cattle, and pigs, the antibiotic-resistant E. coli from pig intestine and fish pathogens Vibrio spp. and Aeromonas spp. from the Norwegian fish farming industry were resistant to BC. The BC-resistant strains were examined for susceptibility to 15 different antibiotics, disinfectants, and dyes. No systematic cross-resistance between BC and any of the other antimicrobial agents tested was detected. Stable enhanced resistance in Enterobacter cloacae isolates was demonstrated by step-wise adaptation in increasing concentrations of BC. In conclusion, BC resistance among food-associated Gram-negative bacteria and Enterococcus spp. is not frequent, but resistance may develop to user concentrations after exposure to sublethal concentrations of BC.

  10. Electrochemically and Bioelectrochemically Induced Ammonium Recovery

    PubMed Central

    Gildemyn, Sylvia; Luther, Amanda K.; Andersen, Stephen J.; Desloover, Joachim; Rabaey, Korneel

    2015-01-01

    Streams such as urine and manure can contain high levels of ammonium, which could be recovered for reuse in agriculture or chemistry. The extraction of ammonium from an ammonium-rich stream is demonstrated using an electrochemical and a bioelectrochemical system. Both systems are controlled by a potentiostat to either fix the current (for the electrochemical cell) or fix the potential of the working electrode (for the bioelectrochemical cell). In the bioelectrochemical cell, electroactive bacteria catalyze the anodic reaction, whereas in the electrochemical cell the potentiostat applies a higher voltage to produce a current. The current and consequent restoration of the charge balance across the cell allow the transport of cations, such as ammonium, across a cation exchange membrane from the anolyte to the catholyte. The high pH of the catholyte leads to formation of ammonia, which can be stripped from the medium and captured in an acid solution, thus enabling the recovery of a valuable nutrient. The flux of ammonium across the membrane is characterized at different anolyte ammonium concentrations and currents for both the abiotic and biotic reactor systems. Both systems are compared based on current and removal efficiencies for ammonium, as well as the energy input required to drive ammonium transfer across the cation exchange membrane. Finally, a comparative analysis considering key aspects such as reliability, electrode cost, and rate is made. This video article and protocol provide the necessary information to conduct electrochemical and bioelectrochemical ammonia recovery experiments. The reactor setup for the two cases is explained, as well as the reactor operation. We elaborate on data analysis for both reactor types and on the advantages and disadvantages of bioelectrochemical and electrochemical systems. PMID:25651406

  11. Electrochemically and bioelectrochemically induced ammonium recovery.

    PubMed

    Gildemyn, Sylvia; Luther, Amanda K; Andersen, Stephen J; Desloover, Joachim; Rabaey, Korneel

    2015-01-22

    Streams such as urine and manure can contain high levels of ammonium, which could be recovered for reuse in agriculture or chemistry. The extraction of ammonium from an ammonium-rich stream is demonstrated using an electrochemical and a bioelectrochemical system. Both systems are controlled by a potentiostat to either fix the current (for the electrochemical cell) or fix the potential of the working electrode (for the bioelectrochemical cell). In the bioelectrochemical cell, electroactive bacteria catalyze the anodic reaction, whereas in the electrochemical cell the potentiostat applies a higher voltage to produce a current. The current and consequent restoration of the charge balance across the cell allow the transport of cations, such as ammonium, across a cation exchange membrane from the anolyte to the catholyte. The high pH of the catholyte leads to formation of ammonia, which can be stripped from the medium and captured in an acid solution, thus enabling the recovery of a valuable nutrient. The flux of ammonium across the membrane is characterized at different anolyte ammonium concentrations and currents for both the abiotic and biotic reactor systems. Both systems are compared based on current and removal efficiencies for ammonium, as well as the energy input required to drive ammonium transfer across the cation exchange membrane. Finally, a comparative analysis considering key aspects such as reliability, electrode cost, and rate is made. This video article and protocol provide the necessary information to conduct electrochemical and bioelectrochemical ammonia recovery experiments. The reactor setup for the two cases is explained, as well as the reactor operation. We elaborate on data analysis for both reactor types and on the advantages and disadvantages of bioelectrochemical and electrochemical systems.

  12. Escherichia Coli

    ERIC Educational Resources Information Center

    Goodsell, David S.

    2009-01-01

    Diverse biological data may be used to create illustrations of molecules in their cellular context. I describe the scientific results that support a recent textbook illustration of an "Escherichia coli cell". The image magnifies a portion of the bacterium at one million times, showing the location and form of individual macromolecules. Results…

  13. Escherichia Coli

    ERIC Educational Resources Information Center

    Goodsell, David S.

    2009-01-01

    Diverse biological data may be used to create illustrations of molecules in their cellular context. I describe the scientific results that support a recent textbook illustration of an "Escherichia coli cell". The image magnifies a portion of the bacterium at one million times, showing the location and form of individual macromolecules. Results…

  14. 21 CFR 172.430 - Iron ammonium citrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Iron ammonium citrate. 172.430 Section 172.430... CONSUMPTION Anticaking Agents § 172.430 Iron ammonium citrate. Iron ammonium citrate may be safely used in... human consumption so that the level of iron ammonium citrate does not exceed 25 parts per million (0...

  15. 21 CFR 172.430 - Iron ammonium citrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Iron ammonium citrate. 172.430 Section 172.430 Food... Anticaking Agents § 172.430 Iron ammonium citrate. Iron ammonium citrate may be safely used in food in... consumption so that the level of iron ammonium citrate does not exceed 25 parts per million (0.0025 percent...

  16. 21 CFR 172.430 - Iron ammonium citrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Iron ammonium citrate. 172.430 Section 172.430... CONSUMPTION Anticaking Agents § 172.430 Iron ammonium citrate. Iron ammonium citrate may be safely used in... human consumption so that the level of iron ammonium citrate does not exceed 25 parts per million (0...

  17. 21 CFR 172.430 - Iron ammonium citrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Iron ammonium citrate. 172.430 Section 172.430... CONSUMPTION Anticaking Agents § 172.430 Iron ammonium citrate. Iron ammonium citrate may be safely used in... human consumption so that the level of iron ammonium citrate does not exceed 25 parts per million (0...

  18. 77 FR 65532 - Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation: Notice of Rescission of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-29

    ... International Trade Administration Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation: Notice... the antidumping duty order on solid fertilizer grade ammonium nitrate (ammonium nitrate) from the... Administrative Review: Solid Fertilizer Grade Ammonium Nitrate (Ammonium Nitrate) from the Russian...

  19. Ammonium ion transport by the AMT/Rh homologue LeAMT1;1.

    PubMed

    Mayer, Maria; Dynowski, Marek; Ludewig, Uwe

    2006-06-15

    AMT (ammonium transporter)/Rh (Rhesus) ammonium transporters/channels are identified in all domains of life and fulfil contrasting functions related either to ammonium acquisition or excretion. Based on functional and crystallographic high-resolution structural data, it was recently proposed that the bacterial AmtB (ammonium transporter B) is a gas channel for NH3 [Khademi, O'Connell, III, Remis, Robles-Colmenares, Miercke and Stroud (2004) Science 305, 1587-1594; Zheng, Kostrewa, Berneche, Winkler and Li (2004) Proc. Natl. Acad. Sci. U.S.A. 101, 17090-17095]. Key residues, proposed to be crucial for NH3 conduction, and the hydrophobic, but obstructed, pore were conserved in a homology model of LeAMT1;1 from tomato. Transport by LeAMT1;1 was affected by mutations of residues that were predicted to constitute the aromatic recruitment site for NH4+ at the external pore entrance. Despite the structural similarities, LeAMT1;1 was shown to transport only the ion; each transported 14C-methylammonium molecule carried a single positive elementary charge. Similarly, NH4+ (or H+/NH3) was transported, but NH3 conduction was excluded. It is concluded that related proteins and a similar molecular architecture can apparently support contrasting transport mechanisms.

  20. Transcription Factor OsDOF18 Controls Ammonium Uptake by Inducing Ammonium Transporters in Rice Roots

    PubMed Central

    Wu, Yunfei; Yang, Wenzhu; Wei, Jinhuan; Yoon, Hyeryung; An, Gynheung

    2017-01-01

    Nitrogen is one of the most important mineral elements for plant growth. We studied the functional roles of Oryza sativa DNA BINDING WITH ONE FINGER 18 (OsDOF18) in controlling ammonium uptake. The growth of null mutants of OsDOF18 was retarded in a medium containing ammonium as the sole nitrogen source. In contrast, those mutants grew normally in a medium with nitrate as the sole nitrogen source. The gene expression was induced by ammonium but not by nitrate. Uptake of ammonium was lower in osdof18 mutants than in the wild type, while that of nitrate was not affected by the mutation. This indicated that OsDOF18 is involved in regulating ammonium transport. Among the 10 ammonium transporter genes examined here, expression of OsAMT1;1, OsAMT1;3, OsAMT2;1, and OsAMT4;1 was reduced in osdof18 mutants, demonstrating that the ammonium transporter genes function downstream of OsDOF18. Genes for nitrogen assimilation were also affected in the mutants. These results provide evidence that OsDOF18 mediates ammonium transport and nitrogen distribution, which then affects nitrogen use efficiency. PMID:28292004

  1. Original method for synthesis of chitosan-based antimicrobial agent by quaternary ammonium grafting.

    PubMed

    Oyervides-Muñoz, Ernesto; Pollet, Eric; Ulrich, Gilles; de Jesús Sosa-Santillán, Gerardo; Avérous, Luc

    2017-02-10

    Functionalized high molar mass chitosan derivatives with increased antibacterial properties were prepared by the reaction of chitosan with different quaternary ammonium salts. Benzalkonium bromide, pyridinium bromide and triethyl ammonium bromide were synthesized by a quaternization reaction between 1,4-dibromobutane and the respective tertiary amines (N, N-dimethylbenzylamine, triethylamine and pyridine) to obtain three ammonium salts with a bromide end-group capable of reacting with a functional group from the chitosan backbone. The ammonium salts were chemically grafted along the chitosan macromolecular chains. Four different chitosan derivatives were obtained and their chemical structures analyzed and confirmed by (1)H NMR and FT-IR. The corresponding thermal stability was analyzed by TGA. Antibacterial activity has been assessed by determining their minimal inhibitory concentration upon Escherichia coli and Staphylococcus aureus. Furthermore, the antibiogram method was used to complement the antibacterial analysis. The bacteria inhibitory property of the chitosan derivatives exhibited a remarkable improvement compared to unmodified chitosan. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Nitrogen cycling between sediment and the shallow-water column in the transition zone of the Potomac River and Estuary. II. The role of wind-driven resuspension and adsorbed ammonium

    USGS Publications Warehouse

    Simon, N.S.

    1989-01-01

    During periods of sediment resuspension, desorption of ammonium from sediment solids can be the major pathway for enriching the water column with the ammonium that is produced by bacterial degradation of organic matter in the bottom material. This hyopthesis is based on a three-year study of diffusive flux in the transition zone of the Potomac River at a site 35 m from the Virginia shore where the average water-column depth is approximately 1 m over sandy sediment. A diffusion-controlled sampler was used to collect water samples at the interface between the water column and sediment and at several tens of centimeters into the sediment. Interstitial water concentration gradients showed that diffusive flux of ammonium from the sandy shallow-water sediments was approximately 1% of the diffusive flux of ammonium from the silty channel sediments in the same zone of the Potomac River. Organic nitrogen and bound or adsorbed ammonium were the predominant nitrogen forms in the sediment. Adsorbed ammonium concentrations ranged from nondetectable to 3??7 ??mol g-1 of sediment. Concentrations of adsorbed ammonium per gram of sediment were one to three orders of magnitude more than interstitial water ammonium concentrations. Desorption of ammonium from sediment solids appeared to be the controlling factor in the degree of water-column ammonium enrichment. In laboratory experiments that simulated sediment resuspension, 40-80% of the adsorbed ammonium predicted to desorb did so after approximately 30 min of mixing. Based on calculations for 1 m2 to a depth of 4 cm, one resuspenion event lasting minutes could mix more ammonium into the water column from desorption of ammonium from sediment solids than could be delivered to the water column by diffusive flux from shallow-water sediments in 10-1000 days and would be comparable to enrichment by ammonium diffusive flux for 5-50 days from channel sediments in the same river zone. ?? 1989.

  3. Crystallization characteristics of ammonium uranyl carbonate (AUC) in ammonium carbonate solutions

    NASA Astrophysics Data System (ADS)

    Tae-Joon, Kim; Kyung-Chai, Jeong; Jin-Ho, Park; In-Soon, Chang; Cheong-Song, Choi

    1994-05-01

    Ammonium carbonate solutions with an excessive amount of NH 3 were produced in a commercial AUC (ammonium uranyl carbonate) conversion plant. In this study the AUC crystals, precipitated with uranyl nitrate and ammonium carbonate solutions prepared in the laboratory, were characterized to determine the feasibility of recycling ammonium carbonate solution. The AUC crystals were easily agglomerated with the increasing concentration of CO 32- and mole ratio of {NH 4+}/{CO 32-} in ammonium carbonate solution. Effects of a mixing system for the solution in the AUC crystallizer and the feed location of the solution on the agglomeration of AUC crystals were also studied along with the effects of agglomerated AUC powders on UO 2 powders. Finally, the feasibility of manufacturing UO 2 fuel with a sintered pellet density of 10.52 g/cm 3, using the AUC powders generated in this experiment, was demonstrated.

  4. Calcium sulphate in ammonium sulphate solution

    USGS Publications Warehouse

    Sullivan, E.C.

    1905-01-01

    Calcium sulphate, at 25?? C., is two-thirds as soluble in dilute (o.i mol per liter) and twice as soluble in concentrated (3 mois per liter) ammonium sulphate solution as in water. The specific electric conductivity of concentrated ammonium sulphate solutions is lessened by saturating with calcium sulphate. Assuming that dissociation of ammonium sulphate takes place into 2NH4?? and SO4" and of calcium sulphate into Ca and SO4" only, and that the conductivity is a measure of such dissociation, the solubility of calcium sulphate in dilute ammonium sulphate solutions is greater than required by the mass-law. The conductivity of the dilute mixtures may be accurately calculated by means of Arrhenius' principle of isohydric solutions. In the data obtained in these calculations, the concentration of non-dissociated calcium sulphate decreases with increasing ammonium sulphate. The work as a whole is additional evidence of the fact that we are not yet in possession of all the factors necessary for reconciling the mass-law to the behavior of electrolytes. The measurements above described were made in the chemical laboratory of the University of Michigan.

  5. Expression, purification and crystallization of the ammonium transporter Amt-1 from Archaeoglobus fulgidus.

    PubMed

    Andrade, Susana L A; Dickmanns, Antje; Ficner, Ralf; Einsle, Oliver

    2005-09-01

    Ammonium transporters (Amts) are a class of membrane-integral transport proteins found in organisms from all kingdoms of life. Their key function is the transport of nitrogen in its reduced bioavailable form, ammonia, across cellular membranes, a crucial step in nitrogen assimilation for biosynthetic purposes. The genome of the hyperthermophilic archaeon Archaeoglobus fulgidus has been annotated with three individual genes for ammonium transporters, amt1-3, the roles of which are as yet unknown. The amt1 gene product has been produced by heterologous overexpression in Escherichia coli and the resulting protein has been purified to electrophoretic homogeneity. Crystals of Amt-1 have been obtained by sitting-drop vapour diffusion and diffraction data have been collected.

  6. Ammonium Increases TRPC1 Expression Via Cav-1/PTEN/AKT/GSK3β Pathway.

    PubMed

    Wang, Wei; Gu, Li; Verkhratsky, Alexei; Peng, Liang

    2017-03-01

    Hyperammonemia occurring following acute liver failure is the primary cause of hepatic encephalopathy. In the brain, ammonium is catabolised by glutamine synthetase expressed exclusively in astroglia; ammonium overload impairs astroglial homeostatic systems. Previously, we had reported that chronic treatment with 3 mM ammonia increased expression of transient receptor potential canonic 1 (TRPC1) channels and Ca(2+) release from intracellular Ca(2+) stores (Liang et al. in Neurochem Res 39:2127-2135, 2014). Glycogen synthase kinase 3β (GSK-3β) has a key role in several astroglial signalling pathways and is known to be affected in various CNS diseases. We have studied the involvement of Cav-1/PTEN/AKT/GSK-3β signalling system in regulation of TRPC1 gene expression by ammonium. Effects of chronic (1-5 days) treatment with ammonium chloride (ammonium), at pathologically relevant concentrations of 1-5 mM were investigated on primary cultures of mouse cerebral astrocytes. We quantified expression of caveolin-1 (Cav-1), membrane content of phosphatase and tensin homologue (PTEN), phosphorylation of AKT and GSK-3β, and expression of TRPC1 channels. Ammonium significantly increased expression of Cav-1 mRNA and protein, mRNA of TRPC1 as well as membrane content of PTEN; conversely phosphorylation of AKT and GSK-3β were significantly decreased. These changes were abolished following astrocytes treatment with siRNA specific to Cav-1, indicating the involvement of Cav-1/PTEN/PI3K/AKT pathway. Similar results were found in the brains of adult mice subjected to intraperitoneal injection of urease (a model for hyperammoniemia) for 1-5 days. In transgenic mice tagged with an astrocyte-specific or neurone-specific markers (used for fluorescence-activated cell sorting of astrocytes vs. neurones) and treated with intraperitoneal injections of urease for 3 days, the Cav-1 gene mRNA expression was up-regulated in astrocytes, but not in neurones. The up-regulation of TRPC1 gene

  7. On the evaporation of ammonium sulfate solution

    SciTech Connect

    Drisdell, Walter S.; Saykally, Richard J.; Cohen, Ronald C.

    2009-07-16

    Aqueous evaporation and condensation kinetics are poorly understood, and uncertainties in their rates affect predictions of cloud behavior and therefore climate. We measured the cooling rate of 3 M ammonium sulfate droplets undergoing free evaporation via Raman thermometry. Analysis of the measurements yields a value of 0.58 {+-} 0.05 for the evaporation coefficient, identical to that previously determined for pure water. These results imply that subsaturated aqueous ammonium sulfate, which is the most abundant inorganic component of atmospheric aerosol, does not affect the vapor-liquid exchange mechanism for cloud droplets, despite reducing the saturation vapor pressure of water significantly.

  8. Antimicrobial and Hemolytic Studies of a Series of Polycations Bearing Quaternary Ammonium Moieties: Structural and Topological Effects

    PubMed Central

    Mayr, Judith; Bachl, Jürgen; Schlossmann, Jens; Díaz Díaz, David

    2017-01-01

    A series of polycations bearing quaternary ammonium moieties have shown antimicrobial activity against the Gram-negative bacterium Escherichia coli. Different polymer topologies governed by a disubstituted aromatic core as well as different diamine-based linkers were found to influence the antimicrobial properties. Moreover, the hemolytic activity against human red blood cells was measured and demonstrated good biocompatibility and selectivity of these polycations for bacteria over mammalian cells. PMID:28146105

  9. Evidence of ammonium ion-exchange properties of natural bentonite and application to ammonium detection.

    PubMed

    Zazoua, A; Kazane, I; Khedimallah, N; Dernane, C; Errachid, A; Jaffrezic-Renault, N

    2013-12-01

    Ammonium exchange with hybrid PVC-bentonite (mineral montmorillonite clay) thin film was revealed using FTIR spectroscopy, EDX, cyclic voltammetry and electrochemical impedance spectroscopy. The effect of ammonium exchange on the charge transfer resistance of PVC-bentonite hybrid thin film was attributed to a modification of the intersheet distance and hydration of bentonite crystals. The obtained impedimetric ammonium sensor shows a linear range of detection from 10(-4)M to 1M and a detection limit around 10(-6)M. © 2013.

  10. Impact of flow conditions on ammonium uptake and microbial community structure in benthic biofilms

    NASA Astrophysics Data System (ADS)

    Arnon, Shai; Yanuka, Keren; Nejidat, Ali

    2010-05-01

    Excess nitrogen in surface waters is widely recognized to be a major global problem that adversely affects ecosystems, human health, and the economy. Today, most efforts to understand and model nutrient dynamics at large scales relies on macro-scale parameterization, such as mean channel geometry and velocity with uniform flow assumptions, as well as gross averages of in-situ nutrient transformation rates. However, there is increasing evidence that nutrient transformations in hyporheic zone are regulated by coupling between physical, chemical, and microbiological processes. Ignoring this greatly hinders the estimation of average biochemical transformation rates under the variable flow conditions found in aquatic systems. We used a combination of macro- and micro-scale observations in laboratory flumes to show that interplay between hydrodynamic transport, redox gradients, and microbial metabolism controls ammonium utilization by hyporheic microbial communities. Biofilm structural characteristics were quantified using denaturing gradient gel electrophoresis (DGGE) and real time PCR, while redox and pH gradients were measured using microelectrodes. We found that overlying velocities had profound effect on ammonium uptake due to mass transfer of ammonium from the bulk water to the benthic biofilms, but also due to the delivery of oxygen into the sediment bed. Under laminar flow conditions we didn't observe any change of ammonium uptake as a response to increase in overlying velocity. However, under non-laminar conditions we observe monotonic increase in ammonium uptake, with the greatest uptake under the fastest flow condition. We will discuss ammonium uptake rates results in the context of the different microbial communities and the micro-scale observations that were obtained using the microelectrodes. We anticipate that combined knowledge of the response of the microbial community and bulk nitrogen utilization rates to flow conditions will support the development of

  11. 21 CFR 573.170 - Ammonium formate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive... is manufactured by the reaction of 99.5 percent ammonia gas and 99 percent formic acid in a continuous loop reactor to produce a solution made up of 37 percent ammonium salt of formic acid and 62...

  12. 21 CFR 573.170 - Ammonium formate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ..., FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...) The additive is manufactured by the reaction of 99.5 percent ammonia gas and 99 percent formic acid in a continuous loop reactor to produce a solution made up of 37 percent ammonium salt of formic acid...

  13. 21 CFR 573.170 - Ammonium formate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ..., FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...) The additive is manufactured by the reaction of 99.5 percent ammonia gas and 99 percent formic acid in a continuous loop reactor to produce a solution made up of 37 percent ammonium salt of formic acid...

  14. 21 CFR 573.170 - Ammonium formate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...) The additive is manufactured by the reaction of 99.5 percent ammonia gas and 99 percent formic acid in a continuous loop reactor to produce a solution made up of 37 percent ammonium salt of formic acid...

  15. 21 CFR 556.375 - Maduramicin ammonium.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS TOLERANCES FOR RESIDUES OF NEW ANIMAL DRUGS IN FOOD Specific Tolerances for Residues of New Animal Drugs § 556.375 Maduramicin ammonium. A tolerance is established for...

  16. 21 CFR 556.375 - Maduramicin ammonium.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS TOLERANCES FOR RESIDUES OF NEW ANIMAL DRUGS IN FOOD Specific Tolerances for Residues of New Animal Drugs § 556.375 Maduramicin ammonium. A tolerance is established for...

  17. Ambient Ammonium Contribution to total Nitrogen Deposition

    EPA Science Inventory

    There has been a wealth of evidence over the last decade illustrating the rising importance of reduced inorganic nitrogen (NHx = ammonia gas, NH3, plus particulate ammonium, p-NH4) in the overall atmospheric mass balance and deposition of nitrogen as emissions of oxidized nitrog...

  18. 21 CFR 184.1133 - Ammonium alginate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...-34-9) is the ammonium salt of alginic acid, a natural polyuronide constituent of certain brown algae..., § 170.3(n)(9) of this chapter 0.4 Stabilizer, thickener, § 170.3(o)(28) of this chapter. Fats and...

  19. 21 CFR 184.1133 - Ammonium alginate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...-34-9) is the ammonium salt of alginic acid, a natural polyuronide constituent of certain brown algae..., § 170.3(n)(9) of this chapter 0.4 Stabilizer, thickener, § 170.3(o)(28) of this chapter. Fats and...

  20. 21 CFR 184.1133 - Ammonium alginate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...: Category of food Maximum level of use in food (as served) (percent) Functional use Confections, frostings... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium alginate. 184.1133 Section 184.1133 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD...

  1. Diamond Head Revisited with Ammonium Dichromate.

    ERIC Educational Resources Information Center

    Arrigoni, Edward

    1981-01-01

    The classroom demonstration using ammonium dichromate to simulate a volcanic eruption can be modified into a more dramatic and accurate representation of the geologic processes involved in the formation of a volcanic crater. The materials, demonstration setup, safety procedures, and applications to instruction are presented. (Author/WB)

  2. Cyclo­hexyl­ammonium nitrate

    PubMed Central

    Bagabas, Abdulaziz A.; Aboud, Mohamed F. A.; Shemsi, Ahsan M.; Addurihem, Emad S.; Al-Othman, Zeid A.; Chidan Kumar, C. S.; Fun, Hoong-Kun

    2014-01-01

    In the title salt, C6H14N+·NO3 −, the cyclo­hexyl ring adopts a chair conformation. The ammonium group occupies an equatorial position and the crystal struture is stabilized by inter­molecular N—H⋯O hydrogen-bonding inter­actions, resulting in a three-dimensional network. PMID:24764971

  3. 21 CFR 184.1133 - Ammonium alginate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...: Category of food Maximum level of use in food (as served) (percent) Functional use Confections, frostings... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ammonium alginate. 184.1133 Section 184.1133 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD...

  4. 21 CFR 184.1139 - Ammonium hydroxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... HUMAN CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of... ingredient as generally recognized as safe (GRAS) as a direct human food ingredient is based upon the... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium hydroxide. 184.1139 Section 184.1139...

  5. 21 CFR 184.1143 - Ammonium sulfate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium sulfate. 184.1143 Section 184.1143 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing...

  6. 21 CFR 184.1133 - Ammonium alginate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium alginate. 184.1133 Section 184.1133 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific Substances Affirmed as...

  7. 21 CFR 184.1139 - Ammonium hydroxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium hydroxide. 184.1139 Section 184.1139 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific Substances Affirmed as...

  8. 21 CFR 184.1135 - Ammonium bicarbonate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium bicarbonate. 184.1135 Section 184.1135 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific Substances Affirmed as...

  9. 21 CFR 184.1137 - Ammonium carbonate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium carbonate. 184.1137 Section 184.1137 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific Substances Affirmed as...

  10. The mechanism of ammonia transport based on the crystal structure of AmtB of Escherichia coli

    PubMed Central

    Zheng, Lei; Kostrewa, Dirk; Bernèche, Simon; Winkler, Fritz K.; Li, Xiao-Dan

    2004-01-01

    Ammonium is one of the most important nitrogen sources for bacteria, fungi, and plants, but it is toxic to animals. The ammonium transport proteins (methylamine permeases/ammonium transporters/rhesus) are present in all domains of life; however, functional studies with members of this family have yielded controversial results with respect to the chemical identity (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{NH}}_{4}^{+}\\end{equation*}\\end{document} or NH3) of the transported species. We have solved the structure of wild-type AmtB from Escherichia coli in two crystal forms at 1.8- and 2.1-Å resolution, respectively. Substrate transport occurs through a narrow mainly hydrophobic pore located at the center of each monomer of the trimeric AmtB. At the periplasmic entry, a binding site for \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{NH}}_{4}^{+}\\end{equation*}\\end{document} is observed. Two phenylalanine side chains (F107 and F215) block access into the pore from the periplasmic side. Further into the pore, the side chains of two highly conserved histidine residues (H168 and H318) bridged by a H-bond lie adjacent, with their edges pointing into the cavity. These histidine residues may facilitate the deprotonation of an ammonium ion entering the pore. Adiabatic free energy calculations support the hypothesis that an electrostatic barrier between H168 and H318 hinders the permeation of cations but not that of the uncharged NH3. The structural data and energetic considerations strongly indicate that the methylamine permeases/ammonium transporters/rhesus proteins are

  11. PRN 88-2: Clustering of Quaternary Ammonium Compounds

    EPA Pesticide Factsheets

    This Notice announces that EPA has clustered the Quaternary Ammonium Compounds into four groups for the purpose of testing chemicals to build a database that will support continued registration of the entire family of quaternary ammonium compounds

  12. 21 CFR 184.1296 - Ferric ammonium citrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... granules or as a brownish-yellowish powder. (2) Ferric ammonium citrate (iron (III) ammonium citrate, CAS... granules, as a powder, or as transparent green crystals. (b) The ingredients meet the specifications of the...

  13. Pore mutations in ammonium transporter AMT1 with increased electrogenic ammonium transport activity.

    PubMed

    Loqué, Dominique; Mora, Silvia I; Andrade, Susana L A; Pantoja, Omar; Frommer, Wolf B

    2009-09-11

    AMT/Mep ammonium transporters mediate high affinity ammonium/ammonia uptake in bacteria, fungi, and plants. The Arabidopsis AMT1 proteins mediate uptake of the ionic form of ammonium. AMT transport activity is controlled allosterically via a highly conserved cytosolic C terminus that interacts with neighboring subunits in a trimer. The C terminus is thus capable of modulating the conductivity of the pore. To gain insight into the underlying mechanism, pore mutants suppressing the inhibitory effect of mutations in the C-terminal trans-activation domain were characterized. AMT1;1 carrying the mutation Q57H in transmembrane helix I (TMH I) showed increased ammonium uptake but reduced capacity to take up methylammonium. To explore whether the transport mechanism was altered, the AMT1;1-Q57H mutant was expressed in Xenopus oocytes and analyzed electrophysiologically. AMT1;1-Q57H was characterized by increased ammonium-induced and reduced methylammonium-induced currents. AMT1;1-Q57H possesses a 100x lower affinity for ammonium (K(m)) and a 10-fold higher V(max) as compared with the wild type form. To test whether the trans-regulatory mechanism is conserved in archaeal homologs, AfAmt-2 from Archaeoglobus fulgidus was expressed in yeast. The transport function of AfAmt-2 also depends on trans-activation by the C terminus, and mutations in pore-residues corresponding to Q57H of AMT1;1 suppress nonfunctional AfAmt-2 mutants lacking the activating C terminus. Altogether, our data suggest that bacterial and plant AMTs use a conserved allosteric mechanism to control ammonium flux, potentially using a gating mechanism that limits flux to protect against ammonium toxicity.

  14. Quaternary ammonium derivatives as spasmolytics for irritable bowel syndrome.

    PubMed

    Evangelista, S

    2004-01-01

    Quaternary ammonium derivatives such as cimetropium, n-butyl scopolammonium, otilonium and pinaverium bromide have been discovered and developed as potent spasmolytics of the gastrointestinal tract. Their pharmacological activity has been proven in both "in vivo" and "in vitro" studies of hypermotility. "In vitro" experiments showed that they possess antimuscarinic activity at nM level but only pinaverium and otilonium are endowed with calcium channel blocker properties. These latter compounds relaxed the gastrointestinal smooth muscle mainly through a specific inhibition of calcium ion influx through L-type voltage operated calcium channels. Molecular pharmacology trials have indicated that pinaverium and otilonium can bind specific subunits of the calcium channel in the external surface of the plasma membrane and in this way they block the machinery of the contraction. Recent evidence showed that otilonium is able to bind tachykinin NK(2) receptors and not only inhibits one of the major contractile agents but can reduce the activation of afferent nerves devoted to the passage of sensory signals from the periphery to the central nervous system. Thanks to their typical physico-chemical characteristics, they are poorly absorbed by the systemic circulation and generally remain in the gastrointestinal tract where they exert the muscle relaxant activity by a local activity. Some differences exists in the absorption among these compounds: both n-butyl scopolammonium and cimetropium are partially taken up in the bloodstream, pinaverium has a low absorption (8-10 %) but is endowed with an excellent hepato-biliary excretion and otilonium, which has the lowest absorption (3 %), is almost totally excreted by faeces. Quaternary ammonium derivatives are widely used for the treatment of irritable bowel syndrome and recent meta-analyses have supported their efficacy in this disease. Due to its therapeutic index, the use of n-butyl scopolammonium is more indicated to treat acute

  15. Contribution of ammonium ions to the lethality and antimetamorphic effects of ammonium perchlorate.

    PubMed

    Goleman, Wanda L; Carr, James A

    2006-04-01

    Ammonium perchlorate (AP) is a widespread military waste product in the United States and is a potent thyroid function disruptor in all vertebrates tested thus far. To determine the relative contribution of ammonium ions to the toxicity of AP, we exposed embryonic and larval Xenopus laevis to various concentrations of sodium perchlorate (SP) or ammonium chloride (AC). Ammonium perchlorate was significantly more lethal than SP; 5-d LC50s were 83 and 2,780 mg/L, respectively. To determine whether ammonium ions contribute to the antithyroid effects of AP, we exposed embryonic and larval X. laevis to two sublethal, environmentally relevant concentrations of AP or identical concentrations of AC or SP. At the smaller concentration, only AP delayed metamorphosis and reduced hindlimb growth. Sodium perchlorate and AP, but not AC, prevented metamorphosis and reduced hindlimb growth at the greater concentration. Although AP was slightly more effective in reducing outward manifestations of thyroid disruption, both perchlorate salts, unlike AC, caused profound histopathologic changes in the thyroid. Exposure to the higher concentration of either perchlorate salt produced a feminizing effect, resulting in a skewed sex ratio. We conclude that ammonium ions contribute significantly to the toxicity of AP but not to the direct antithyroid effects of perchlorate.

  16. Effect of ammonium metavanadate on the murine immune response

    SciTech Connect

    Cohen, M.D.; Wei, C.I.; Tan, H.; Kao, K.J.

    1986-01-01

    Female B/sub 6/C/sub 3/F/sub 1/ mice were exposed to ammonium metavanadate (NH/sub 4/VO/sub 3/) by intraperitoneal injection every 3 d at 2.5, 5.0, or 10 mg V/kg for 3, 6, or 9 w and were then assayed for alterations in immunoresponsiveness. Resistance to Escherichia coli endotoxin lethality increased in a dose-dependent manner up to 6 w of exposure, while resistance to viable gram-positive Listeria lethality was depressed in a dose-dependent manner. Comparison of LD20 values indicated a 250-fold decrease in resistance to Listeria at the lowest vanadium exposure and a 40% increase in resistance to endotoxin after the highest vanadium exposure. Peritoneal macrophage phagocytic capacities were decreased in a dose-dependent manner, but viabilities remained unaffected. Rosetting capacity of splenic lymphocytes was increased following vanadium exposure. Liver and splenic enlargement was observed, and examination of splenic tissue indicated enhanced formation of megakaryocytes and red blood cell precursors. Subchronic exposure to vanadium may thus disrupt the normal function of the immune system.

  17. 21 CFR 172.430 - Iron ammonium citrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Iron ammonium citrate. 172.430 Section 172.430... ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking Agents § 172.430 Iron ammonium citrate. Iron ammonium citrate may be safely used in food in accordance with the following...

  18. 40 CFR 721.10582 - Quaternary ammonium compound (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Quaternary ammonium compound (generic... Specific Chemical Substances § 721.10582 Quaternary ammonium compound (generic). (a) Chemical substance and... ammonium compound (PMN P-10-571) is subject to reporting under this section for the significant new...

  19. 40 CFR 721.10591 - Tertiary ammonium compound (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tertiary ammonium compound (generic... Specific Chemical Substances § 721.10591 Tertiary ammonium compound (generic). (a) Chemical substance and... ammonium compound (PMN P-11-110) is subject to reporting under this section for the significant new...

  20. 40 CFR 721.10582 - Quaternary ammonium compound (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Quaternary ammonium compound (generic... Specific Chemical Substances § 721.10582 Quaternary ammonium compound (generic). (a) Chemical substance and... ammonium compound (PMN P-10-571) is subject to reporting under this section for the significant new...

  1. 40 CFR 721.10591 - Tertiary ammonium compound (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tertiary ammonium compound (generic... Specific Chemical Substances § 721.10591 Tertiary ammonium compound (generic). (a) Chemical substance and... ammonium compound (PMN P-11-110) is subject to reporting under this section for the significant new...

  2. A new potentiometric ammonium electrode for biosensor construction.

    PubMed

    Karakuş, Emine; Pekyardimci, Sule; Kiliç, Esma

    2006-01-01

    New ammonium-selective membrane electrode based on poly(vinyl chloride) (PVC) membrane containing palmitic acid (a long-chain fatty acid) and nonactin as an ammonium ionophore for the determination of ammonium ions in the 10(-7) - 10(-1) mol/L concentration range was prepared and compared to those of the electrode prepared by using carboxylated PVC. Sebacate was used as a plasticiser for both of the ammonium sensor membranes. The analytical characteristics of the ammonium electrodes was investigated. The effect of pH, buffer concentration, temperature and stirring rate on the response to ammonium electrode was investigated. The linear working range and sensitivity of the electrodes were also determined. Ammonium electrodes give Nernstian response (52-58 mV/p[NH4+]) throughout the ammonium ion concentration range of 10(-1) to 10(-6)M with detection limits of 10(-6)M ammonium ions. The ammonium-selective electrodes prepared by using the PVC membranes containing palmitic acid showed more effective performance than those of the carboxylated PVC. The ammonium ion sensor has potential application in the analysis of ammonium ions for biosensor construction.

  3. 21 CFR 182.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum ammonium sulfate. 182.1127 Section 182.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b...

  4. 21 CFR 182.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Aluminum ammonium sulfate. 182.1127 Section 182.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b...

  5. 21 CFR 182.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Aluminum ammonium sulfate. 182.1127 Section 182...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b) Conditions of use. This substance is generally...

  6. 21 CFR 582.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Aluminum ammonium sulfate. 582.1127 Section 582.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b) Conditions of...

  7. 21 CFR 582.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Aluminum ammonium sulfate. 582.1127 Section 582.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b) Conditions of...

  8. 21 CFR 582.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Aluminum ammonium sulfate. 582.1127 Section 582.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b) Conditions of...

  9. 21 CFR 582.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Aluminum ammonium sulfate. 582.1127 Section 582.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b) Conditions of...

  10. 21 CFR 582.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum ammonium sulfate. 582.1127 Section 582.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b) Conditions of...

  11. 21 CFR 182.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Aluminum ammonium sulfate. 182.1127 Section 182.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b...

  12. 21 CFR 182.1127 - Aluminum ammonium sulfate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Aluminum ammonium sulfate. 182.1127 Section 182.1127 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1127 Aluminum ammonium sulfate. (a) Product. Aluminum ammonium sulfate. (b...

  13. 78 FR 32690 - Certain Ammonium Nitrate From Ukraine

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-31

    ... COMMISSION Certain Ammonium Nitrate From Ukraine Determination On the basis of the record \\1\\ developed in... antidumping duty order on certain ammonium nitrate from Ukraine would be likely to lead to continuation or... Publication 4396 (May 2013), entitled Certain Ammonium Nitrate from Ukraine: Investigation No....

  14. 40 CFR 721.10511 - Quaternary ammonium salts (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Quaternary ammonium salts (generic... Specific Chemical Substances § 721.10511 Quaternary ammonium salts (generic). (a) Chemical substance and... ammonium salts (PMNs P-07-320, P-07-321, P-07-322, P-07-323, and P-07-324) are subject to reporting...

  15. 40 CFR 721.10430 - Tetra alkyl ammonium salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tetra alkyl ammonium salt (generic... Specific Chemical Substances § 721.10430 Tetra alkyl ammonium salt (generic). (a) Chemical substance and... ammonium salt (PMN P-97-823) is subject to reporting under this section for the significant new...

  16. 40 CFR 721.10511 - Quaternary ammonium salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Quaternary ammonium salts (generic... Specific Chemical Substances § 721.10511 Quaternary ammonium salts (generic). (a) Chemical substance and... ammonium salts (PMNs P-07-320, P-07-321, P-07-322, P-07-323, and P-07-324) are subject to reporting...

  17. 40 CFR 721.10430 - Tetra alkyl ammonium salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tetra alkyl ammonium salt (generic... Specific Chemical Substances § 721.10430 Tetra alkyl ammonium salt (generic). (a) Chemical substance and... ammonium salt (PMN P-97-823) is subject to reporting under this section for the significant new...

  18. Electricity production coupled to ammonium in a microbial fuel cell.

    PubMed

    He, Zhen; Kan, Jinjun; Wang, Yanbing; Huang, Yuelong; Mansfeld, Florian; Nealson, Kenneth H

    2009-05-01

    The production of electricity from ammonium was examined using a rotating-cathode microbial fuel cell (MFC). The addition of ammonium chloride, ammonium sulfate, or ammonium phosphate (monobasic) resulted in electricity generation, while adding sodium chloride, nitrate, or nitrite did not cause any increase in current production. The peak current increased with increasing amount of ammonium addition up to 62.3 mM of ammonium chloride, suggesting that ammonium was involved in electricity generation either directly as the anodic fuel or indirectly as substrates for nitrifiers to produce organic compounds for heterotrophs. Adding nitrate or nitrite with ammonium increased current production compared to solely ammonium addition. Using 16S rRNA-linked molecular analyses, we found ammonium-oxidizing bacteria and denitrifying bacteria on both the anode and cathode electrodes, whereas no anammox bacteria were detected. The dominant ammonium-oxidizing bacteria were closely related to Nitrosomonas europaea. The present MFC achieved an ammonium removal efficiency of 49.2 +/- 5.9 or 69.7 +/- 3.6%, depending on hydraulic retention time, but exhibited a very low Coulombic efficiency.

  19. 21 CFR 184.1141a - Ammonium phosphate, monobasic.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ammonium phosphate, monobasic. 184.1141a Section... SAFE Listing of Specific Substances Affirmed as GRAS § 184.1141a Ammonium phosphate, monobasic. (a) Ammonium phosphate, monobasic (NH4H2PO4, CAS Reg. No. 7722-76-1) is manufactured by reacting ammonia with...

  20. 21 CFR 184.1141a - Ammonium phosphate, monobasic.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ammonium phosphate, monobasic. 184.1141a Section... SAFE Listing of Specific Substances Affirmed as GRAS § 184.1141a Ammonium phosphate, monobasic. (a) Ammonium phosphate, monobasic (NH4H2PO4, CAS Reg. No. 7722-76-1) is manufactured by reacting ammonia with...

  1. 21 CFR 184.1141a - Ammonium phosphate, monobasic.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium phosphate, monobasic. 184.1141a Section... SAFE Listing of Specific Substances Affirmed as GRAS § 184.1141a Ammonium phosphate, monobasic. (a) Ammonium phosphate, monobasic (NH4H2PO4, CAS Reg. No. 7722-76-1) is manufactured by reacting ammonia with...

  2. 40 CFR 721.10302 - Zinc ammonium phosphate (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Zinc ammonium phosphate (generic). 721... Substances § 721.10302 Zinc ammonium phosphate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as zinc ammonium phosphate (PMN P...

  3. 21 CFR 184.1141b - Ammonium phosphate, dibasic.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ammonium phosphate, dibasic. 184.1141b Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1141b Ammonium phosphate, dibasic. (a) Ammonium phosphate, dibasic ((NH4)2HPO4, CAS Reg. No. 7783-28-0) is manufactured by reacting ammonia with phosphoric...

  4. 40 CFR 721.10302 - Zinc ammonium phosphate (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Zinc ammonium phosphate (generic). 721... Substances § 721.10302 Zinc ammonium phosphate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as zinc ammonium phosphate (PMN P...

  5. 21 CFR 184.1141b - Ammonium phosphate, dibasic.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ammonium phosphate, dibasic. 184.1141b Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1141b Ammonium phosphate, dibasic. (a) Ammonium phosphate, dibasic ((NH4)2HPO4, CAS Reg. No. 7783-28-0) is manufactured by reacting ammonia with phosphoric...

  6. 21 CFR 184.1141a - Ammonium phosphate, monobasic.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ammonium phosphate, monobasic. 184.1141a Section... SAFE Listing of Specific Substances Affirmed as GRAS § 184.1141a Ammonium phosphate, monobasic. (a) Ammonium phosphate, monobasic (NH4H2PO4, CAS Reg. No. 7722-76-1) is manufactured by reacting ammonia with...

  7. 40 CFR 721.10302 - Zinc ammonium phosphate (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Zinc ammonium phosphate (generic). 721... Substances § 721.10302 Zinc ammonium phosphate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as zinc ammonium phosphate (PMN P...

  8. 21 CFR 184.1141b - Ammonium phosphate, dibasic.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ammonium phosphate, dibasic. 184.1141b Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1141b Ammonium phosphate, dibasic. (a) Ammonium phosphate, dibasic ((NH4)2HPO4, CAS Reg. No. 7783-28-0) is manufactured by reacting ammonia with phosphoric...

  9. 21 CFR 184.1141b - Ammonium phosphate, dibasic.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ammonium phosphate, dibasic. 184.1141b Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1141b Ammonium phosphate, dibasic. (a) Ammonium phosphate, dibasic ((NH4)2HPO4, CAS Reg. No. 7783-28-0) is manufactured by reacting ammonia with phosphoric...

  10. 76 FR 23569 - Termination of the Suspension Agreement on Solid Fertilizer Grade Ammonium Nitrate From the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-27

    ... International Trade Administration Termination of the Suspension Agreement on Solid Fertilizer Grade Ammonium... (``AD'') Investigation on Solid Fertilizer Grade Ammonium Nitrate from the Russian Federation (``the... determine whether imports of solid fertilizer grade ammonium nitrate (``ammonium nitrate'') from Russia...

  11. 76 FR 49449 - Continuation of Antidumping Duty Order on Solid Fertilizer Grade Ammonium Nitrate From the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-10

    ... International Trade Administration Continuation of Antidumping Duty Order on Solid Fertilizer Grade Ammonium... duty investigation on solid fertilizer grade ammonium nitrate (``ammonium nitrate'') from the Russian... Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation and Notice of Antidumping Duty...

  12. Detonation Properties of Ammonium Dinitramide (ADN)

    NASA Astrophysics Data System (ADS)

    Wätterstam, A.; Östmark, H.; Helte, A.; Karlsson, S.

    1999-06-01

    Ammonium Dinitramide, ADN, has a potential as an oxidizer for underwater high explosives. Pure ADN has a large reaction-zone length and shows a strong non-ideal behaviour. The work presented here is an extension of previous work.(Sensitivity and Performance Characterization of Ammonium Dinitramide (ADN). Presented at 11th International Detonation Symposium, Snowmass, CO, 1998.) Experiments for determining the detonation velocity as a function of inverse charge radius and density, reaction-zone length and curvature, and the detonation pressure are presented. Measurements of pressure indicates that no, or weak von-Neumann spike exists, suggesting an immediate chemical decomposition. Experimental data are compared with predicted using thermochemical codes and ZND-theory.

  13. Decomposition of free chlorine with tertiary ammonium.

    PubMed

    Katano, Hajime; Uematsu, Kohei; Tatsumi, Hirosuke; Tsukatani, Toshihide

    2010-01-01

    The reaction of free chlorine with tertiary ammonium or amine compounds in aqueous solution was studied by the amperometry at a rotating Pt-disk electrode. The amperometric method can be applied to follow the concentration of free chlorine (c(Cl)) even in the presence of chloramine species. By addition of mono- and dibutylammonium to the solution containing free chlorine, the step-like decrease in c(Cl) was observed, indicating the rapid formation of the stable chloramine species. By addition of tributylammonium, the c(Cl) was decreased exponentially to nearly zero even if the free chlorine was present initially in excess. The c(Cl)-t curves can be explained by tributylammonium-species-catalyzed decomposition of free chlorine to chloride ion. The catalytic decomposition was observed also with the tertiary-ammonium-based anion-exchange resins. Furthermore, the anion-exchange resins exhibited the decomposition of not only free chlorine but also chloramines in water.

  14. Ammonium chloride poisoning in chronic renal disease

    PubMed Central

    Levene, Donald L.; Knight, Allan

    1974-01-01

    A 58-year-old woman with a long history of renal stone disease and urinary tract infection presented to the emergency room with exhaustion and air hunger. Laboratory data confirmed profound metabolic acidosis. Unduly large quantities of bicarbonate and potassium were required for correction of the deficits. She had been taking 6 g daily of ammonium chloride as a urine-acidifying agent for a period of six months in addition to agents directed against urinary tract infection. The combination of impaired renal function and effective hydrogen ion loading resulted in profound systemic acidosis. The metabolic derangements associated with the administration of ammonium chloride and its use as a therapeutic agent are discussed. PMID:4850503

  15. Corrosion and repairs of ammonium carbamate decomposers

    SciTech Connect

    De Romero, M.F.; Galban, J.P.

    1996-05-01

    Corrosion-erosion problems occurred in the carbon steel base metal of the ammonium carbamate decomposers in an urea extraction process lined with type 316L (UNS S31603) urea grade stainless steel. The cladding was replaced by weld overlay using a semiautomatic gas metal arc welding process. The first layer was alloy 25%Cr-15%Ni-2%Mo (UNS W30923); the second layer was alloy 25%Cr-22%Ni-2%Mo (UNS W31020).

  16. Nitrate, ammonium, and potassium sensing and signaling.

    PubMed

    Ho, Cheng-Hsun; Tsay, Yi-Fang

    2010-10-01

    Plants acquire numerous nutrients from the soil. In addition, nutrients elicit many physiological and morphological responses especially in roots. Recently, there has been significant progress in identifying the sensing and regulatory mechanisms of several essential nutrients. In this review, we describe the newly identified signaling components of nitrate, ammonium, and potassium, focusing specifically on the initial sensing steps. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Anticaking and antidusting composition for ammonium nitrate

    SciTech Connect

    Newman, A.W.; Bishop, M.L.

    1988-01-05

    An aqueous liquid anticaking and antidusting composition is described comprising, from 20 to 30 parts of a sodium naphthalene sulfonate, from 17 to 28 parts of an ammonium naphthalene sulfonate, the naphthalene of the aforesaid sulfonates being selected from naphthalene and methyl-substituted derivatives thereof, and from 30 to 80 parts of water, the composition being neutralized with acid to a pH of from about 5 to about 7.

  18. Review of Ammonium Dinitramide Toxicity Studies

    DTIC Science & Technology

    2011-01-01

    Dean, K. W., Pace, D. M ., and Carmichael, A. J . Effects of ammonium dinitramide in human liver slices: An EPR/spin trapping study. Armstrong...Steel-Goodwin, L., Kuhlmann, K. J ., Miller, C., Pace, M . D., and Carmichael, A. J . Effects of reactive oxygen and nitrogen species induced by...Biotechnology Branch Teresa R. Sterner Henry M . Jackson Foundation for the Advancement of Military Medicine Wright-Patterson AFB, OH

  19. Oxidation of ammonium sulfite in aqueous solutions using ozone technology

    NASA Astrophysics Data System (ADS)

    Li, Yue; Shang, Kefeng; Lu, Na; Li, Jie; Wu, Yan

    2013-03-01

    How to deal with unstable ammonium sulfite, the byproduct of flue gas desulfuration by ammonia absorption methods, has been a difficult problem in recent years. Oxidation of ammonium sulfite in aqueous solutions using ozone produced by a surface discharge system was investigated in the paper. The oxidation efficiency of ammonium sulfite by ozone and traditional air aeration were compared, and the factors including ozone concentration, gas flow rate, initial concentration of ammonium sulfite solution and reaction temperature were discussed. The results show that the oxidation efficiency of ammonium sulfite by ozone technology reached nearly 100% under the optimum conditions, which had a significant increase compared with that by air aeration.

  20. PROCESS FOR THE PRODUCTION OF AMMONIUM URANIUM FLUORIDE

    DOEpatents

    Ellis, A.S.; Mooney, R.B.

    1953-08-25

    This patent relates to the preparation of ammonium uranium fluoride. The process comprises adding a water soluble fluoride to an aqueous solution of a uranous compound containing an ammonium salt, and isolating the resulting precipitate. This patent relates to the manufacture of uranium tetnafluoride from ammonium uranium fluoride, NH/sub 4/UF/sub 5/. Uranium tetrafluoride is prepared by heating the ammonium uranium fluoride to a temperature at which dissociation occurs with liberation of ammonium fluoride. Preferably the process is carried out under reduced pressure, or in a current of an inert gas.

  1. Equation of State of Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Robbins, David L.; Sheffield, Stephen A.; Dattelbaum, Dana M.; Velisavljevic, Nenad; Stahl, David B.

    2009-12-01

    Ammonium nitrate (AN) is a widely used fertilizer and mining explosive. AN is commonly used in ammonium nitrate-fuel oil (ANFO), which is a mixture of explosive-grade AN prills and fuel oil in a 94:6 ratio by weight. ANFO is a non-ideal explosive with measured detonation velocities around 4 km/s. The equation of state properties and known initiation behavior of neat AN are limited. We present the results of a series of gas gun-driven plate impact experiments on pressed neat ammonium nitrate at 1.72 g/cm3. No evidence of initiation was observed under shock loading to 22 GPa. High pressure x-ray diffraction experiments in diamond anvil cells provided insight into the high pressure phase behavior over the same pressure range (to 25 GPa), as well as a static isotherm at ambient temperature. From the isotherm and thermodynamic properties at ambient conditions, a preliminary unreacted equation of state (EOS) has been developed based on the Murnaghan isotherm and Helmholtz formalism [1], which compares favorably with the available experimental Hugoniot data on several densities of AN.

  2. Herbicide: fatal ammonium thiocyanate and aminotriazole poisoning.

    PubMed

    Legras, A; Skrobala, D; Furet, Y; Kintz, P; Forveille, E; Dequin, P F; Perrotin, D

    1996-01-01

    To describe fatal herbicide poisoning with Radoxone TL composed of aminotriazole and ammonium thiocyanate. A 54-year-old man was hospitalized because of unexplained coma with myoclonic jerks and vascular collapse. Despite symptomatic treatment with mechanical ventilation and vascular filling, life-threatening shock occurred with oliguria, profound metabolic acidosis and cardiac arrest. Hyperchloremia (141 mmol/L) with reversed anion gap (-19) suggested interference with chloride measurement caused by halogens (Br,F,I) or other anions such as thiocyanate. Eventually a weed killer, Radoxone TL containing ammonium thiocyanate, was found at the patient's house. Thiocyanate and aminotriazole blood levels were 750 mg/L and 138 mg/L respectively more than 12 hours after ingestion. After prolonged cardiopulmonary resuscitation, continuous venovenous hemodiafiltration was performed. Despite hemodynamic recovery the patient died 48 hours later of postanoxic coma. Aminotriazole, a systemic nonselective herbicide, is often associated with ammonium thiocyanate which enhances its activity. Experimental studies and previous fatal cases suggest a predominant toxicity of thiocyanate. Early diagnosis is important.

  3. Preparation, characterization and antibacterial activity of O-acetyl-chitosan-N-2-hydroxypropyl trimethyl ammonium chloride.

    PubMed

    Cai, Jinping; Dang, Qifeng; Liu, Chengsheng; Wang, Teng; Fan, Bing; Yan, Jingquan; Xu, Yanyan

    2015-09-01

    Chitosan-N-2-hydroxypropyl trimethyl ammonium chloride (QTS) was prepared by reaction of chitosan (CS) and glycidyl trimethylammonium chloride. Later, O-acetyl-chitosan-N-2-hydroxypropyl trimethyl ammonium chloride (AQTS) was synthesized by reaction of QTS with acetic acid in the presence of SOCl2. Both derivatives were characterized by FTIR, (1)H NMR, TGA, and XRD techniques. The degree of quaternization of QTS was 85.5%, and the degree of acetyl (DA) of AQTS was from 1.63 to 2.31. Compared with CS, the solubility of QTS and AQTS was improved at different levels, especially AQTS, it could be dissolved in many organic solvents, water, and aqueous solution. Notably, the solubility of AQTS in organic solvents increased as DA increased, while the solubility in water was reversed. The results of CS, QTS, and AQTS against Escherichia coli and Staphylococcus aureus showed that QTS and AQTS exhibited higher antibacterial activity than CS, and the antibacterial activity of AQTS decreased with increased DA. Moreover, the inhibition effect was AQTS1 (DA 1.63)>AQTS2 (DA 2.02)>QTS>AQTS3 (DA 2.31). On the basis of the results of the present study, it could be emphasized that hydrophobicity and positive charge density might strongly affect the antibacterial activity of quaternary ammonium chitosan derivatives. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Ammonium Ion Currents in the Squid Giant Axon

    PubMed Central

    Binstock, Leonard; Lecar, Harold

    1969-01-01

    Voltage-clamp studies on intact and internally perfused squid giant axons demonstrate that ammonium can substitute partially for either sodium or potassium. Ammonium carries the early transient current with 0.3 times the permeability of sodium and it carries the delayed current with 0.3 times the potassium permeability. The conductance changes observed in voltage clamp show approximately the same time course in ammonium solutions as in the normal physiological solutions. These ammonium ion permeabilities account for the known effects of ammonium on nerve excitability. Experiments with the drugs tetrodotoxin (TTX) and tetraethyl ammonium chloride (TEA) demonstrate that these molecules block the early and late components of the current selectively, even when both components are carried by the same ion, ammonium. PMID:5767336

  5. Ammonium secretion by Malpighian tubules of Drosophila melanogaster: application of a novel ammonium-selective microelectrode.

    PubMed

    Browne, Austin; O'Donnell, Michael J

    2013-10-15

    Ammonia is a toxic nitrogenous waste product of amino acid metabolism that may accumulate to high levels in the medium ingested by larvae of the fruit fly Drosophila melanogaster. Here we report measurements of haemolymph NH4(+) concentration and the secretion of NH4(+) by the Malpighian (renal) tubules. Measurement of NH4(+) concentrations in secreted droplets is complicated either by the requirement for large sample volumes for enzymatic assays or by the inadequate selectivity of NH4(+)-selective microelectrodes based on nonactin. We have developed a novel liquid membrane NH4(+)-selective microelectrode based on a 19-membered crown compound (TD19C6), which has been used previously in ammonium-selective macroelectrodes. In conjunction with an improved technique for correcting for interference of potassium, NH4(+)-selective microelectrodes based on TD19C6 permit accurate measurement of ammonium concentration in haemolymph samples and nanolitre droplets of fluid secreted by the Malpighian tubules of D. melanogaster. The results indicate that active secretion of ammonium into the Malpighian tubule lumen is sufficient to maintain concentrations of ~1 mmol l(-1) ammonium in the haemolymph of larvae reared on diets containing 100 mmol l(-1) ammonium chloride.

  6. Vacuolar ion channels in the liverwort Marchantia polymorpha: influence of ion channel inhibitors.

    PubMed

    Koselski, Mateusz; Trebacz, Kazimierz; Dziubinska, Halina

    2017-05-01

    Potassium-permeable slow activating vacuolar channels (SV) and chloride-permeable channels in the vacuole of the liverwort Marchantia polymorpha were characterized in respect to calcium dependence, selectivity, and pharmacology. The patch-clamp method was used in the study of ion channel activity in the vacuoles from the liverwort Marchantia polymorpha. The whole-vacuole recordings allowed simultaneous observation of two types of currents-predominant slow activated currents recorded at positive voltages and fast activated currents recorded at negative voltages. Single-channel recordings carried out in the gradient of KCl indicated that slow activated currents were carried by potassium-permeable slowly activating vacuolar channels (SV) and fast activated currents-by chloride-permeable channels. Both types of the channels were dependent in an opposite way on calcium, since elimination of this ion from the cytoplasmic side caused inhibition of SV channels, but the open probability of chloride-permeable channels even increased. The dependence of the activity of both channels on different types of ion channel inhibitors was studied. SV channels exhibited different sensitivity to potassium channel inhibitors. These channels were insensitive to 3 mM Ba(2+), but were blocked by 3 mM tetraethyl ammonium (TEA). Moreover, the activity of the channels was modified in a different way by calcium channel inhibitors. 200 µM Gd(3+) was an effective blocker, but 50 µM ruthenium red evoked bursts of the channel activity resulting in an increase in the open probability. Different effectiveness of anion channel inhibitors was observed in chloride-permeable channels. After the application of 100 µM Zn(2+), a decrease in the open probability was recorded but the channels were still active. 50 µM DIDS was more effective, as it completely blocked the channels.

  7. Diarrheagenic Escherichia coli

    PubMed Central

    Nataro, James P.; Kaper, James B.

    1998-01-01

    Escherichia coli is the predominant nonpathogenic facultative flora of the human intestine. Some E. coli strains, however, have developed the ability to cause disease of the gastrointestinal, urinary, or central nervous system in even the most robust human hosts. Diarrheagenic strains of E. coli can be divided into at least six different categories with corresponding distinct pathogenic schemes. Taken together, these organisms probably represent the most common cause of pediatric diarrhea worldwide. Several distinct clinical syndromes accompany infection with diarrheagenic E. coli categories, including traveler’s diarrhea (enterotoxigenic E. coli), hemorrhagic colitis and hemolytic-uremic syndrome (enterohemorrhagic E. coli), persistent diarrhea (enteroaggregative E. coli), and watery diarrhea of infants (enteropathogenic E. coli). This review discusses the current level of understanding of the pathogenesis of the diarrheagenic E. coli strains and describes how their pathogenic schemes underlie the clinical manifestations, diagnostic approach, and epidemiologic investigation of these important pathogens. PMID:9457432

  8. Lava Channels

    NASA Image and Video Library

    2013-12-03

    The channels and linear depression in this image captured by NASA 2001 Mars Odyssey spacecraft are located on the western margin of the Elysium Volcanic complex. The channels were created by lava flow.

  9. Dynamics of the Escherichia coli proteome in response to nitrogen starvation and entry into the stationary phase.

    PubMed

    Sanchuki, Heloisa B S; Gravina, Fernanda; Rodrigues, Thiago E; Gerhardt, Edileusa C M; Pedrosa, Fábio O; Souza, Emanuel M; Raittz, Roberto T; Valdameri, Glaucio; de Souza, Gustavo A; Huergo, Luciano F

    2017-03-01

    Nitrogen is needed for the biosynthesis of biomolecules including proteins and nucleic acids. In the absence of fixed nitrogen prokaryotes such as E. coli immediately ceases growth. Ammonium is the preferred nitrogen source for E. coli supporting the fastest growth rates. Under conditions of ammonium limitation, E. coli can use alternative nitrogen sources to supply ammonium ions and this reprogramming is led by the induction of the NtrC regulon. Here we used label free proteomics to determine the dynamics of E. coli proteins expression in response to ammonium starvation in both the short (30min) and the longer (60min) starvation. Protein abundances and post-translational modifications confirmed that activation of the NtrC regulon acts as the first line of defense against nitrogen starvation. The ribosome inactivating protein Rmf was induced shortly after ammonium exhaustion and this was preceded by induction of other ribosome inactivating proteins such as Hpf and RaiA supporting the hypothesis that ribosome shut-down is a key process during nitrogen limitation stress. The proteomic data revealed that growth arrest due to nitrogen starvation correlates with the accumulation of proteins involved in DNA condensation, RNA and protein catabolism and ribosome hibernation. Collectively, these proteome adaptations will result in metabolic inactive cells which are likely to exhibit multidrug tolerance. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Polymeric Quaternary Ammonium Compounds: Versatile Antimicrobial Materials.

    PubMed

    Zubris, Deanna L; Minbiole, Kevin P C; Wuest, William M

    2017-01-01

    Polymeric Quaternary Ammonium Compounds (polyQACs) comprise a broad class of materials with applications in medical implants, food processing, and surface sanitizing, amongst many others. These polymeric substances are especially promising due to their potent antibacterial activity and limited hemolytic toxicity. In particular, many polyQACs have superior therapeutic indices and a lower likelihood of developing antibacterial resistance in comparison to their monomers, making them ideal materials for wound dressings, catheters, and other biomedical applications. This review outlines the history and development, previous successes, current state of the research, and future directions of polyQACs in society.

  11. Mild ammonium stress increases chlorophyll content in Arabidopsis thaliana.

    PubMed

    Sanchez-Zabala, Joseba; González-Murua, Carmen; Marino, Daniel

    2015-01-01

    Nitrate (NO3(-)) and ammonium (NH4(+)) are the main forms of nitrogen available in the soil for plants. Excessive NH4(+) accumulation in tissues is toxic for plants and exclusive NH4(+)-based nutrition enhances this effect. Ammonium toxicity syndrome commonly includes growth impairment, ion imbalance and chlorosis among others. In this work, we observed high intraspecific variability in chlorophyll content in 47 Arabidopsis thaliana natural accessions grown under 1 mM NH4(+) or 1 mM NO3(-) as N-source. Interestingly, chlorophyll content increased in every accession upon ammonium nutrition. Moreover, this increase was independent of ammonium tolerance capacity. Thus, chlorosis seems to be an exclusive effect of severe ammonium toxicity while mild ammonium stress induces chlorophyll accumulation.

  12. Optimization of culture conditions for enhanced lysine production using engineered Escherichia coli.

    PubMed

    Ying, Hanxiao; He, Xun; Li, Yan; Chen, Kequan; Ouyang, Pingkai

    2014-04-01

    In this study, culture conditions, including dissolved oxygen (DO) content, presence of osmoprotectants, residual glucose concentration, and ammonium sulfate-feeding strategies, were investigated for decreasing the inhibition effects of acetic acid, ammonium, and osmotic stress on L-lysine fermentation by Escherichia coli. The results revealed that higher DO content and lower residual glucose concentration could decrease acetic acid accumulation, betaine supplementation could enhance osmotic stress tolerance, and variable speed ammonium sulfate-feeding strategy could decrease ammonium inhibition. Thus, with 25 % DO content, 0-5.0 g/L of residual glucose concentration, and 1.5 g/L of betaine supplementation, 134.9 g/L of L-lysine was obtained after 72 h of culture, with L-lysine yield and productivity of 45.4 % and 1.9 g/(L · h), respectively.

  13. Ammonium dichromate poisoning: A rare cause of acute kidney injury.

    PubMed

    Radhakrishnan, H; Gopi, M; Arumugam, A

    2014-11-01

    Ammonium dichromate is an inorganic compound frequently used in screen and color printing. Being a strong oxidizing agent, it causes oxygen free radical injury resulting in organ failure. We report a 25-year-old female who presented with acute kidney injury after consumption of ammonium dichromate. She was managed successfully with hemodialysis and supportive measures. This case is reported to highlight the toxicity of ammonium dichromate.

  14. Ammonium nitrate: a promising rocket propellant oxidizer

    PubMed

    Oommen; Jain

    1999-06-30

    Ammonium nitrate (AN) is extensively used in the area of fertilizers and explosives. It is present as the major component in most industrial explosives. Its use as an oxidizer in the area of propellants, however, is not as extensive as in explosive compositions or gas generators. With the growing demand for environmental friendly chlorine free propellants, many attempts have been made of late to investigate oxidizers producing innocuous combustion products. AN, unlike the widely used ammonium perchlorate, produces completely ecofriendly smokeless products. Besides, it is one of the cheapest and easily available compounds. However, its use in large rocket motors is restricted due to some of its adverse characteristics like hygroscopicity, near room temperature phase transformation involving a volume change, and low burning rate (BR) and energetics. The review is an attempt to consolidate the information available on the various issues pertaining to its use as a solid propellant oxidizer. Detailed discussions on the aspects relating to phase modifications, decomposition chemistry, and BR and energetics of AN-based propellants, are presented. To make the review more comprehensive brief descriptions of the history, manufacture, safety, physical and chemical properties and various other applications of the salt are also included. Copyright 1999 Elsevier Science B.V.

  15. Reassimilation of ammonium in Lotus japonicus.

    PubMed

    Betti, Marco; García-Calderón, Margarita; Pérez-Delgado, Carmen M; Credali, Alfredo; Pal'ove-Balang, Peter; Estivill, Guillermo; Repčák, Miroslav; Vega, José M; Galván, Francisco; Márquez, Antonio J

    2014-10-01

    This review summarizes the most recent results obtained in the analysis of two important metabolic pathways involved in the release of internal sources of ammonium in the model legume Lotus japonicus: photorespiratory metabolism and asparagine breakdown mediated by aparaginase (NSE). The use of photorespiratory mutants deficient in plastidic glutamine synthetase (GS2) enabled us to investigate the transcriptomics and metabolomic changes associated with photorespiratory ammonium accumulation in this plant. The results obtained indicate the existence of a coordinate regulation of genes involved in photorespiratory metabolism. Other types of evidence illustrate the multiple interconnections existing among the photorespiratory pathway and other processes such as intermediate metabolism, nodule function, and secondary metabolism in this plant, all of which are substantially affected in GS2-deficient mutants because of the impairment of the photorespiratory cycle. Finally, the importance of asparagine metabolism in L. japonicus is highlighted because of the fact that asparagine constitutes the vast majority of the reduced nitrogen translocated between different organs of this plant. The different types of NSE enzymes and genes which are present in L. japonicus are described. There is a particular focus on the most abundant K(+)-dependent LjNSE1 isoform and how TILLING mutants were used to demonstrate by reverse genetics the importance of this particular isoform in plant growth and seed production. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  16. Safety Testing of Ammonium Nitrate Based Mixtures

    NASA Astrophysics Data System (ADS)

    Phillips, Jason; Lappo, Karmen; Phelan, James; Peterson, Nathan; Gilbert, Don

    2013-06-01

    Ammonium nitrate (AN)/ammonium nitrate based explosives have a lengthy documented history of use by adversaries in acts of terror. While historical research has been conducted on AN-based explosive mixtures, it has primarily focused on detonation performance while varying the oxygen balance between the oxidizer and fuel components. Similarly, historical safety data on these materials is often lacking in pertinent details such as specific fuel type, particle size parameters, oxidizer form, etc. A variety of AN-based fuel-oxidizer mixtures were tested for small-scale sensitivity in preparation for large-scale testing. Current efforts focus on maintaining a zero oxygen-balance (a stoichiometric ratio for active chemical participants) while varying factors such as charge geometry, oxidizer form, particle size, and inert diluent ratios. Small-scale safety testing was conducted on various mixtures and fuels. It was found that ESD sensitivity is significantly affected by particle size, while this is less so for impact and friction. Thermal testing is in progress to evaluate hazards that may be experienced during large-scale testing.

  17. TRP Channels

    PubMed Central

    Venkatachalam, Kartik; Montell, Craig

    2011-01-01

    The TRP (Transient Receptor Potential) superfamily of cation channels is remarkable in that it displays greater diversity in activation mechanisms and selectivities than any other group of ion channels. The domain organizations of some TRP proteins are also unusual, as they consist of linked channel and enzyme domains. A unifying theme in this group is that TRP proteins play critical roles in sensory physiology, which include contributions to vision, taste, olfaction, hearing, touch, and thermo- and osmosensation. In addition, TRP channels enable individual cells to sense changes in their local environment. Many TRP channels are activated by a variety of different stimuli and function as signal integrators. The TRP superfamily is divided into seven subfamilies: the five group 1 TRPs (TRPC, TRPV, TRPM, TRPN, and TRPA) and two group 2 subfamilies (TRPP and TRPML). TRP channels are important for human health as mutations in at least four TRP channels underlie disease. PMID:17579562

  18. Tetra­ammonium diaqua­diperoxidoocta­molybdate(VI) tetra­hydrate

    PubMed Central

    Ward, Antony J.; Arrow, Gregory J.; Maschmeyer, Thomas; Masters, Anthony F.; Turner, Peter; Clegg, Jack K.

    2009-01-01

    The title compound (NH4)4[Mo8O24(O2)2(H2O)2]·4H2O, consists of an octa­molybdate cluster with a crystallographic centre of symmetry. The clusters pack in a cubic close packing arrangement defining channels containing water mol­ecules and ammonium cations, which exhibit hydrogen bonding with neighbouring clusters. Hydrogen bonding also exists between the coordinated water mol­ecules of one cluster with one of the O atoms of the peroxido fragment in a neighbouring cluster. PMID:21582647

  19. Evidence for ammonium-bearing minerals in Ceres

    NASA Technical Reports Server (NTRS)

    King, T. V. V.; Clark, R. N.; Calvin, W. M.; Sherman, D. M.; Swayze, G. A.; Brown, R. H.

    1991-01-01

    Evidence for ammonium-bearing minerals was found on the surface of the largest asteroid Ceres. The presence of ammonium-bearing clays suggests that Ceres has experienced a period of alteration by substantial amounts of an ammonium-bearing fluid. The presence of the ammonium-bearing clays does not preclude Ceres maintaining a volatile inventory in the core or in a volatile-rich zone at some distance below the surface. Telescopic observations of Ceres, using the 3.0 meter NASA Infrared telescope facility prompted this reevaluation of its surface mineralogy.

  20. Inhibition of Injured Escherichia coli by Several Selective Agents 1

    PubMed Central

    Scheusner, D. L.; Busta, F. F.; Speck, M. L.

    1971-01-01

    A population of Escherichia coli ML30 cells was exposed to a quaternary ammonium compound, and injury to the cells was measured by a comparison of counts on Trypticase Soy Agar and Violet Red Bile Agar. Substantial injury could not be detected with a minimal medium. The ingredients of Violet Red Bile Agar were tested against damaged cells. The bile salts mixture alone in the medium prevented as many injured cells from growing as did any combination of the selective agents and inhibited as many injured bacteria as were inhibited by Violet Red Bile Agar itself. These dyes and salts were similarly assayed in minimal agar, and comparable results were obtained. Individual bile salts and other potential selective agents were added to the minimal medium, and the media were tested for inhibition of injured E. coli. Sodium deoxycholate was the bile salt most inhibitory to damaged E. coli cells. PMID:4924998

  1. Investigation of quaternary ammonium silane-coated sand filter for the removal of bacteria and viruses from drinking water.

    PubMed

    Torkelson, A A; da Silva, A K; Love, D C; Kim, J Y; Alper, J P; Coox, B; Dahm, J; Kozodoy, P; Maboudian, R; Nelson, K L

    2012-11-01

    To develop an anti-microbial filter media using an attached quaternary ammonium compound (QAC) and evaluate its performance under conditions relevant to household drinking water treatment in developing countries. Silica sand was coated with dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride via covalent silane chemistry. Filter columns packed with coated media were challenged with micro-organisms under different water quality conditions. The anti-bacterial properties were investigated by visualizing Escherichia coli (E. coli) attachment to coated media under fluorescence microscopy combined with a live/dead stain. A 9-cm columns with a filtration velocity of 18 m h(-1) achieved log(10) removals of 1·7 for E. coli, 1·8 for MS2 coliphage, 1·9 for Poliovirus type 3 and 0·36 for Adenovirus type 2, compared to 0·1-0·3 log(10) removals of E. coli and MS2 by uncoated sand. Removal scaled linearly with column length and decreased with increasing ionic strength, flow velocity, filtration time and humic acid presence. Escherichia coli attached to QAC-coated sand were observed to be membrane-permeable, providing evidence of inactivation. Filtration with QAC-coated sand provided higher removal of bacteria and viruses than filtration with uncoated sand. However, major limitations included rapid fouling by micro-organisms and natural organic matter and low removal of viruses PRD1 and Adenovirus 2. QAC-coated media may be promising for household water treatment. However, more research is needed on long-term performance, options to reduce fouling and inactivation mechanisms. © 2012 The Authors Journal of Applied Microbiology © 2012 The Society for Applied Microbiology.

  2. How does glutamine synthetase activity determine plant tolerance to ammonium?

    PubMed

    Cruz, C; Bio, A F M; Domínguez-Valdivia, M D; Aparicio-Tejo, P M; Lamsfus, C; Martins-Loução, M A

    2006-04-01

    The wide range of plant responses to ammonium nutrition can be used to study the way ammonium interferes with plant metabolism and to assess some characteristics related with ammonium tolerance by plants. In this work we investigated the hypothesis of plant tolerance to ammonium being related with the plants' capacity to maintain high levels of inorganic nitrogen assimilation in the roots. Plants of several species (Spinacia oleracea L., Lycopersicon esculentum L., Lactuca sativa L., Pisum sativum L. and Lupinus albus L.) were grown in the presence of distinct concentrations (0.5, 1.5, 3 and 6 mM) of nitrate and ammonium. The relative contributions of the activity of the key enzymes glutamine synthetase (GS; under light and dark conditions) and glutamate dehydrogenase (GDH) were determined. The main plant organs of nitrogen assimilation (root or shoot) to plant tolerance to ammonium were assessed. The results show that only plants that are able to maintain high levels of GS activity in the dark (either in leaves or in roots) and high root GDH activities accumulate equal amounts of biomass independently of the nitrogen source available to the root medium and thus are ammonium tolerant. Plant species with high GS activities in the dark coincide with those displaying a high capacity for nitrogen metabolism in the roots. Therefore, the main location of nitrogen metabolism (shoots or roots) and the levels of GS activity in the dark are an important strategy for plant ammonium tolerance. The relative contribution of each of these parameters to species tolerance to ammonium is assessed. The efficient sequestration of ammonium in roots, presumably in the vacuoles, is considered as an additional mechanism contributing to plant tolerance to ammonium nutrition.

  3. Antifungal activity of gemini quaternary ammonium salts.

    PubMed

    Obłąk, Ewa; Piecuch, Agata; Krasowska, Anna; Luczyński, Jacek

    2013-12-14

    A series of gemini quaternary ammonium chlorides and bromides with various alkyl chain and spacer lengths was synthesized. The most active compounds against fungi were chlorides with 10 carbon atoms within the hydrophobic chain. Among these compounds were few with no hemolytic activity at minimal inhibitory concentrations. None of the tested compounds were cytotoxic and mutagenic. Cationic gemini surfactants poorly reduced the adhesion of microorganisms to the polystyrene plate, but inhibited the filamentation of Candida albicans. One of the tested compounds eradicated C. albicans and Rodotorula mucilaginosa biofilm, what could be important in overcoming catheter-associated infections. It was also shown that gemini surfactants enhanced the sensitivity of C. albicans to azoles and polyenes, thus they might be potentially used in combined therapy against fungi. Copyright © 2013. Published by Elsevier GmbH.

  4. Metabolic engineering of a diazotrophic bacterium improves ammonium release and biofertilization of plants and microalgae.

    PubMed

    Ambrosio, Rafael; Ortiz-Marquez, Juan Cesar Federico; Curatti, Leonardo

    2017-03-01

    The biological nitrogen fixation carried out by some Bacteria and Archaea is one of the most attractive alternatives to synthetic nitrogen fertilizers. However, with the exception of the symbiotic rhizobia-legumes system, progress towards a more extensive realization of this goal has been slow. In this study we manipulated the endogenous regulation of both nitrogen fixation and assimilation in the aerobic bacterium Azotobacter vinelandii. Substituting an exogenously inducible promoter for the native promoter of glutamine synthetase produced conditional lethal mutant strains unable to grow diazotrophically in the absence of the inducer. This mutant phenotype could be reverted in a double mutant strain bearing a deletion in the nifL gene that resulted in constitutive expression of nif genes and increased production of ammonium. Under GS non-inducing conditions both the single and the double mutant strains consistently released very high levels of ammonium (>20mM) into the growth medium. The double mutant strain grew and excreted high levels of ammonium under a wider range of concentrations of the inducer than the single mutant strain. Induced mutant cells could be loaded with glutamine synthetase at different levels, which resulted in different patterns of extracellular ammonium accumulation afterwards. Inoculation of the engineered bacteria into a microalgal culture in the absence of sources of C and N other than N2 and CO2 from the air, resulted in a strong proliferation of microalgae that was suppressed upon addition of the inducer. Both single and double mutant strains also promoted growth of cucumber plants in the absence of added N-fertilizer, while this property was only marginal in the parental strain. This study provides a simple synthetic genetic circuit that might inspire engineering of optimized inoculants that efficiently channel N2 from the air into crops.

  5. 21 CFR 73.2298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... of the eye, in amounts consistent with good manufacturing practice. (c) Labeling. The color additive... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2298 Ferric ammonium ferrocyanide. (a) Identity and specifications.The color additive ferric ammonium ferrocyanide shall conform in identify and...

  6. 21 CFR 73.1298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1298 Ferric ammonium ferrocyanide. (a) Identity. (1) The color additive ferric ammonium ferrocyanide is the blue pigment obtained by oxidizing... with smaller amounts of ferric ferrocyanide and ferric sodium ferrocyanide. (2) Color additive mixtures...

  7. 21 CFR 73.2298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... of the eye, in amounts consistent with good manufacturing practice. (c) Labeling. The color additive... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2298 Ferric ammonium ferrocyanide. (a) Identity and specifications.The color additive ferric ammonium ferrocyanide shall conform in identify and...

  8. 75 FR 14082 - Ammonium Salts of Fatty Acids (C8

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-24

    ... AGENCY 40 CFR Part 180 Ammonium Salts of Fatty Acids (C 8 -C 18 Saturated); Exemption from the... fatty acids (C 8 -C 18 saturated) applied pre- and post-harvest on all raw agricultural commodities when... eliminates the need to establish a maximum permissible level for residues of ammonium salts of fatty acids (C...

  9. 40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... compound. 721.655 Section 721.655 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.655 Ethoxylated alkyl quaternary ammonium compound. (a) Chemical... as an ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject to reporting...

  10. 40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... compound. 721.655 Section 721.655 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.655 Ethoxylated alkyl quaternary ammonium compound. (a) Chemical... as an ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject to reporting...

  11. 40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... compound. 721.655 Section 721.655 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.655 Ethoxylated alkyl quaternary ammonium compound. (a) Chemical... as an ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject to reporting...

  12. 40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... compound. 721.655 Section 721.655 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.655 Ethoxylated alkyl quaternary ammonium compound. (a) Chemical... as an ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject to reporting...

  13. 40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... compound. 721.655 Section 721.655 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.655 Ethoxylated alkyl quaternary ammonium compound. (a) Chemical... as an ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject to reporting...

  14. 21 CFR 73.2298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... of the eye, in amounts consistent with good manufacturing practice. (c) Labeling. The color additive... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2298 Ferric ammonium ferrocyanide. (a) Identity and specifications.The color additive ferric ammonium ferrocyanide shall conform in identify and...

  15. 21 CFR 73.2298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... of the eye, in amounts consistent with good manufacturing practice. (c) Labeling. The color additive... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2298 Ferric ammonium ferrocyanide. (a) Identity and specifications.The color additive ferric ammonium ferrocyanide shall conform in identify and...

  16. 21 CFR 73.1025 - Ferric ammonium citrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1025 Ferric ammonium citrate. (a) Identity. The color additive ferric ammonium citrate consists of complex chelates prepared by the interaction of... general and ophthalmic surgery subject to the following conditions: (1) The dyed suture shall conform in...

  17. Racer (Ammonium Nonanoate) weed control evaluation for onions

    USDA-ARS?s Scientific Manuscript database

    Racer has been labeled as a herbicide for food use and is currently under consideration as an organic herbicide for organically grown food crops. The main component (40%) of Racer is ammonium nonanoate (ammonium pelargonate), which occurs in nature and primarily formed from biodegradation of higher...

  18. 40 CFR 721.6070 - Alkyl phosphonate ammonium salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl phosphonate ammonium salts. 721... Substances § 721.6070 Alkyl phosphonate ammonium salts. (a) Chemical substances and significant new uses... salts (PMNs P-93-725 and P-93-726) are subject to reporting under this section for the significant...

  19. 40 CFR 721.6070 - Alkyl phosphonate ammonium salts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkyl phosphonate ammonium salts. 721... Substances § 721.6070 Alkyl phosphonate ammonium salts. (a) Chemical substances and significant new uses... salts (PMNs P-93-725 and P-93-726) are subject to reporting under this section for the significant...

  20. 40 CFR 721.6070 - Alkyl phosphonate ammonium salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkyl phosphonate ammonium salts. 721... Substances § 721.6070 Alkyl phosphonate ammonium salts. (a) Chemical substances and significant new uses... salts (PMNs P-93-725 and P-93-726) are subject to reporting under this section for the significant...

  1. 40 CFR 721.6070 - Alkyl phosphonate ammonium salts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkyl phosphonate ammonium salts. 721... Substances § 721.6070 Alkyl phosphonate ammonium salts. (a) Chemical substances and significant new uses... salts (PMNs P-93-725 and P-93-726) are subject to reporting under this section for the significant...

  2. 40 CFR 721.6070 - Alkyl phosphonate ammonium salts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkyl phosphonate ammonium salts. 721... Substances § 721.6070 Alkyl phosphonate ammonium salts. (a) Chemical substances and significant new uses... salts (PMNs P-93-725 and P-93-726) are subject to reporting under this section for the significant...

  3. 40 CFR 180.473 - Glufosinate ammonium; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... residues of the herbicide glufosinate-ammonium (butanoic acid, 2-amino-4-(hydroxymethylphosphinyl...-propionic acid, expressed as 2-amino-4-(hydroxymethylphosphinyl)butanoic acid equivalents, in or on the... ammonium, butanoic acid, 2-amino-4-(hydroxymethylphosphinyl)-, monoammonium salt and its metabolite, 3...

  4. THE MASS ACCOMMODATION COEFFICIENT OF AMMONIUM NITRATE AEROSOL. (R823514)

    EPA Science Inventory

    The mass transfer rate of pure ammonium nitrate between the aerosol and gas phases was
    quantified experimentally by the use of the tandem differential mobility analyzer/scanning mobility
    particle sizer (TDMA/SMPS) technique. Ammonium nitrate particles 80-220 nm in diameter<...

  5. THE MASS ACCOMMODATION COEFFICIENT OF AMMONIUM NITRATE AEROSOL. (R823514)

    EPA Science Inventory

    The mass transfer rate of pure ammonium nitrate between the aerosol and gas phases was
    quantified experimentally by the use of the tandem differential mobility analyzer/scanning mobility
    particle sizer (TDMA/SMPS) technique. Ammonium nitrate particles 80-220 nm in diameter<...

  6. 46 CFR 148.220 - Ammonium nitrate-phosphate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Ammonium nitrate-phosphate fertilizers. 148.220 Section... § 148.220 Ammonium nitrate-phosphate fertilizers. (a) This section applies to the stowage and transportation of uniform, nonsegregating mixtures of nitrogen/phosphate or nitrogen/potash type fertilizers,...

  7. 46 CFR 148.220 - Ammonium nitrate-phosphate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Ammonium nitrate-phosphate fertilizers. 148.220 Section... § 148.220 Ammonium nitrate-phosphate fertilizers. (a) This section applies to the stowage and transportation of uniform, nonsegregating mixtures of nitrogen/phosphate or nitrogen/potash type fertilizers,...

  8. 46 CFR 148.220 - Ammonium nitrate-phosphate fertilizers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Ammonium nitrate-phosphate fertilizers. 148.220 Section... § 148.220 Ammonium nitrate-phosphate fertilizers. (a) This section applies to the stowage and transportation of uniform, nonsegregating mixtures of nitrogen/phosphate or nitrogen/potash type fertilizers,...

  9. 46 CFR 148.220 - Ammonium nitrate-phosphate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Ammonium nitrate-phosphate fertilizers. 148.220 Section... § 148.220 Ammonium nitrate-phosphate fertilizers. (a) This section applies to the stowage and transportation of uniform, nonsegregating mixtures of nitrogen/phosphate or nitrogen/potash type fertilizers,...

  10. Shock wave synthesis of amino acids from solutions of ammonium formate and ammonium bicarbonate

    NASA Astrophysics Data System (ADS)

    Suzuki, Chizuka; Furukawa, Yoshihiro; Kobayashi, Takamichi; Sekine, Toshimori; Nakazawa, Hiromoto; Kakegawa, Takeshi

    2015-07-01

    The emergence of life's building blocks, such as amino acids and nucleobases, on the prebiotic Earth was a critical step for the beginning of life. Reduced species with low mass, such as ammonia, amines, or carboxylic acids, are potential precursors for these building blocks of life. These precursors may have been provided to the prebiotic ocean by carbonaceous chondrites and chemical reactions related to meteorite impacts on the early Earth. The impact of extraterrestrial objects on Earth occurred more frequently during this period than at present. Such impacts generated shock waves in the ocean, which have the potential to progress chemical reactions to form the building blocks of life from reduced species. To simulate shock-induced reactions in the prebiotic ocean, we conducted shock-recovery experiments on ammonium bicarbonate solution and ammonium formate solution at impact velocities ranging from 0.51 to 0.92 km/s. In the products from the ammonium formate solution, several amino acids (glycine, alanine, ß-alanine, and sarcosine) and aliphatic amines (methylamine, ethylamine, propylamine, and butylamine) were detected, although yields were less than 0.1 mol % of the formic acid reactant. From the ammonium bicarbonate solution, smaller amounts of glycine, methylamine, ethylamine, and propylamine were formed. The impact velocities used in this study represent minimum cases because natural meteorite impacts typically have higher velocities and longer durations. Our results therefore suggest that shock waves could have been involved in forming life's building blocks in the ocean of prebiotic Earth, and potentially in aquifers of other planets, satellites, and asteroids.

  11. Assimilation of ammonium and nitrate nitrogen by bean plants

    SciTech Connect

    Volk, R.J. ); Chaillou, S.; Morot-Gaudry, J.F. ); Mariotti, A. )

    1989-04-01

    Enhanced growth is often observed in plants growing on combined ammonium and nitrate nutrition. The physiological basis for such enhancement was examined by exposing non-nodulated bean (Phaseolus vulgaris L.) plants to {sup 15}N-labeled, 1.0 mM N solutions containing 0, 33, 67 or 100% of the N as ammonium, the balance being nitrate. Maximal total N uptake and biomass production were attained by plants receiving 33% ammonium. A higher proportion of incoming ammonium than nitrate was incorporated into root protein. This was accompanied by increased partitioning of plant biomass to roots. It was concluded that as a consequence of greater N metabolism in the root under mixed ammonium and nitrate nutrition, the root became a more active sink for photosynthate. Concurrently, the augmented supply of N to the shoot enhanced net photosynthesis as reflected in increased plant biomass.

  12. Control of ammonium assimilation in Rhizobium 32H1.

    PubMed Central

    Ludwig, R A

    1978-01-01

    The symbiotic, nitrogen-fixing bacterium Rhizobium sp. 32H1 is a specialized ammonium producer during symbiosis. However, during free-living growth, Rhizobium 32H1 assimilates ammonium very poorly. Two pathways of ammonium assimilation exist in enteric bacteria. One is mediated by glutamate dehydrogenase, and the other is mediated by glutamine synthetase-glutamate synthase. The former pathway is altogether inoperative in Rhizobium 32H1; the latter pathway operates at a slow rate and is under strict negative control by ammonium itself. Rhizobium 32H1 glutamine synthetase activity is modulated by both repression-derepression and reversible adenylylation. For a biochemical process lacking an alternative pathway, such a regulatory pattern exacerbates the very process. This suggests that Rhizobium 32H1 restricts its own ammonium assimilation to maximize the contribution of fixed nitrogen to the host plant during symbiosis. PMID:27498

  13. Reactive Uptake of Dimethylamine by Ammonium Sulfate and Ammonium Sulfate-Sucrose Mixed Particles.

    PubMed

    Chu, Yangxi; Chan, Chak K

    2017-01-12

    Short-chain alkyl amines can undergo gas-to-particle partitioning via reactive uptake by ammonium salts, whose phases have been thought to largely influence the extent of amine uptake. Previous studies mainly focused on particles of single ammonium salt at either dry or wet conditions without any addition of organic compounds. Here we report the uptake of dimethylamine (DMA) by ammonium sulfate (AS) and AS-sucrose mixed particles at different relative humidities (RHs) using an electrodynamic balance coupled with in situ Raman spectroscopy. DMA is selected as a representative of short-chain alkyl amines, and sucrose is used as a surrogate of viscous and hydrophilic organics. Effective DMA uptake was observed for most cases, except for the water-limiting scenario at <5% RH and the formation of an ultraviscous sucrose coating at 10% RH and below. DMA uptake coefficients (γ) were estimated using the particle mass measurements during DMA uptake. Addition of sucrose can increase γ by absorbing water or inhibiting AS crystallization and decrease γ by elevating the particle viscosity and forming a coating layer. DMA uptake can be facilitated for crystalline AS or retarded for aqueous AS with hydrophilic viscous organics (e.g., secondary organic material formed via the oxidation of biogenic volatile organic compounds) present in aerosol particles.

  14. Hybrid organic-inorganic crystals based on ammonium dihydrogen phosphate and ammonium salicylate

    NASA Astrophysics Data System (ADS)

    Voronov, A. P.; Salo, V. I.; Puzikov, V. M.; Babenko, G. N.; Roshal, A. D.; Tkachenko, V. F.

    2011-11-01

    ADP-NH 4Sal hybrid crystals are grown from aqueous solutions. The influence of the acidity of the mixed solution on the conditions of co-crystallization of the components is studied. The spectral and scintillation characteristics are determined. Co-crystallization of ammonium salicylate (NH 4Sal) and ammonium dihydrogen phosphate (ADP, NH 4H 2PO 4) is shown to be feasible, the structure of the doping addition being defined by the solution рН. In basic and weak acidic media the hybrid crystals ADP:NH 4Sal are formed in which salicylate anions are located in the interplanar space between the {110}-type planes in the lattice of ADP. The luminescence spectra contain an emission band maximum with λ max=360 nm. In acidic solutions there are ADP:HSal crystals in which salicylic acid molecules captured by the growth macrosteps are located in the interplanar space of the prismatic {100} and pyramidal {101} growth sectors. The luminescence band undergoes bathochromic shift to λmax=400 nm. The sensitivity of ADP:NH 4Sal scintillation crystals to fast neutrons depends on the concentration of ammonium salicylate in ADP matrix. The highest neutron sensitivity is characteristic of the co-doped ADP:NH 4Sal/Tl scintillation crystals.

  15. Microbial Senses and Ion Channels

    NASA Astrophysics Data System (ADS)

    Kung, Ching; Zhou, Xin-Liang; Su, Zhen-Wei; Haynes, W. John; Loukin, Sephan H.; Saimi, Yoshiro

    The complexity of animals and plants is due largely to cellular arrangement. The structures and activities of macromolecules had, however, evolved in early microbes long before the appearance of this complexity. Among such molecules are those that sense light, heat, force, water, and ligands. Though historically and didactically associated with the nervous system, ion channels also have deep evolutionary roots. For example, force sensing with channels, which likely began as water sensing through membrane stretch generated by osmotic pressure, must be ancient and is universal in extant species. Extant microbial species, such as the model bacterium Escherichia coli and yeast Saccharomyces cerevisiae, are equipped with stretch-activated channels. The ion channel proteins MscL and MscS show clearly that these bacterial channels receive stretch forces from the lipid bilayer. TRPY1, the mechanosensitive channel in yeast, is being developed towards a similar basic understanding of channels of the TRP (transientreceptor- potential) superfamily. TRPY1 resides in the vacuolar membrane and releases Ca2+ from the vacuole to the cytoplasm upon hyperosmotic shock. Unlike in most TRP preparations from animals, the mechanosensitivity of TRPY1 can be examined directly under patch clamp in either whole-vacuole mode or excised patch mode. The combination of direct biophysical examination in vitro with powerful microbial genetics in vivo should complement the study of mechanosensations of complex animals and plants.

  16. TRP Channels

    NASA Astrophysics Data System (ADS)

    Voets, Thomas; Owsianik, Grzegorz; Nilius, Bernd

    The TRP superfamily represents a highly diverse group of cation-permeable ion channels related to the product of the Drosophila trp (transient receptor potential) gene. The cloning and characterization of members of this cation channel family has experienced a remarkable growth during the last decade, uncovering a wealth of information concerning the role of TRP channels in a variety of cell types, tissues, and species. Initially, TRP channels were mainly considered as phospholipase C (PLC)-dependent and/or store-operated Ca2+-permeable cation channels. More recent research has highlighted the sensitivity of TRP channels to a broad array of chemical and physical stimuli, allowing them to function as dedicated biological sensors involved in processes ranging from vision to taste, tactile sensation, and hearing. Moreover, the tailored selectivity of certain TRP channels enables them to play key roles in the cellular uptake and/or transepithelial transport of Ca2+, Mg2+, and trace metal ions. In this chapter we give a brief overview of the TRP channel superfamily followed by a survey of current knowledge concerning their structure and activation mechanisms.

  17. Rippley Channel

    NASA Technical Reports Server (NTRS)

    2006-01-01

    18 September 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a narrow channel on the upper east flank of the martian volcano, Hadriaca Patera. Because it is located on a volcano, most likely this channel was formed by lava, perhaps as a lava tube at which the thin roof later collapsed. Large ripples of windblown sediment now occur on the channel floor; their crests are generally perpendicular to the channel walls, suggesting that winds blow up and down through this channel.

    Location near: 30.5oS, 266.2oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Autumn

  18. Rippley Channel

    NASA Technical Reports Server (NTRS)

    2006-01-01

    18 September 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a narrow channel on the upper east flank of the martian volcano, Hadriaca Patera. Because it is located on a volcano, most likely this channel was formed by lava, perhaps as a lava tube at which the thin roof later collapsed. Large ripples of windblown sediment now occur on the channel floor; their crests are generally perpendicular to the channel walls, suggesting that winds blow up and down through this channel.

    Location near: 30.5oS, 266.2oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Autumn

  19. Inhibition of biofouling by modification of forward osmosis membrane using quaternary ammonium cation.

    PubMed

    Park, Kang-Hee; Yu, Sang-Hyun; Kim, Han-Shin; Park, Hee-Deung

    2015-01-01

    In the operation of the forward osmosis (FO) process, biofouling of the membrane is a potentially serious problem. Development of an FO membrane with antibacterial properties could contribute to a reduction in biofouling. In this study, quaternary ammonium cation (QAC), a widely used biocidal material, was conjugated with a silane coupling agent (3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride) and used to modify an FO membrane to confer antibacterial properties. Fourier transform infrared spectroscopy (FT-IR) demonstrated that the conjugated QAC was successfully immobilized on the FO membrane via covalent bonding. Bacterial viability on the QAC-modified membrane was confirmed via colony count method and visualized via bacterial viability assay. The QAC membrane decreased the viability of Escherichia coli to 62% and Staphylococcus aureus to 77% versus the control membrane. Inhibition of biofilm formation on the QAC modified membrane was confirmed via anti-biofilm tests using the drip-flow reactor and FO unit, resulting in 64% and 68% inhibition in the QAC-modified membrane against the control membrane, respectively. The results demonstrate the effectiveness of the modified membrane in reducing bacterial viability and inhibiting biofilm formation, indicating the potential of QAC-modified membranes to decrease operation costs incurred by biofouling.

  20. [Antimicrobial action of ammonium salts of fused heterocycles containing ortho-nitrogen].

    PubMed

    Stankeviciene, Laimute; Grigonis, Aidas; Matusevicius, Algimantas; Janusiene, Laima; Stankevicius, Antanas

    2003-01-01

    By alkylation of hexamethylenetetramine with halogenated derivatives of ketones, ethers, esters or amides of acids, alkyl- and aralkyl halides the corresponding N-monoalkylated compounds of hexamethylenetetramine were obtained. The quaternization of pyridine nitrogen in 5,6-benzoquinoline, 8-hydroxyquinoline, quinoline, 1,10-phenanthroline molecules with alkyl- or aralkylhalides was carried out. The susceptibility of Gram-positive (Streptococcus agalactiae and Staphylococcus aureus) and Gram-negative (E. coli, Salmonella cholerae suis, Salmonella enteridis Gartneri) microorganisms to synthesized quaternary ammonium salts by disc difussion method has been detected. The bacteriostatic action of 0.5-1% solutions of all compounds was assessed in comparison with benzalkonium chloride. It was shown, that the most effectiveness against all strains is possessed by quaternary hexamethylenetetramine ammonium salts, and especially salts, containing 1-propynyl- or hydroxycarbamoylmethyl radicals. The action of these two compounds against Salmonella and Streptococcus was stronger than the action of benzalkonium chloride. Susceptibility of Pseudomonas aeruginosa to these compounds were detected. It was shown, that 1% solutions of chlorides of N-(1-propynyl) hexamethylenetetramonium and N-(hydroxycarbamoylmethyl) hexamethylenetetrammonium demonstrate the same bacteriostatic action against P. aeruginosa as well as benzalkonium chloride.

  1. Escherichia coli biofilms

    PubMed Central

    Beloin, Christophe; Roux, Agnès; Ghigo, Jean-Marc

    2008-01-01

    Escherichia coli is a predominant species among facultative anaerobic bacteria of the gastrointestinal tract. Both its frequent community lifestyle and the availability of a wide array of genetic tools contributed to establish E. coli as a relevant model organism for the study of surface colonization. Several key factors, including different extracellular appendages, are implicated in E. coli surface colonization and their expression and activity are finely regulated, both in space and time, to ensure productive events leading to mature biofilm formation. This chapter will present known molecular mechanisms underlying biofilm development in both commensal and pathogenic E. coli. PMID:18453280

  2. Introduction of the Escherichia coli gdhA gene into Rhizobium phaseoli: effect on nitrogen fixation.

    PubMed Central

    Bravo, A; Becerril, B; Mora, J

    1988-01-01

    Rhizobium phaseoli lacks glutamate dehydrogenase (GDH) and assimilates ammonium by the glutamine synthetase-glutamate synthase pathway. A strain of R. phaseoli harboring the Escherichia coli GDH structural gene (gdhA) was constructed. GDH activity was expressed in R. phaseoli in the free-living state and in symbiosis. Nodules with bacteroids that expressed GDH activity had severe impairment of nitrogen fixation. Also, R. phaseoli cells that lost GDH activity and assimilated ammonium by the glutamine synthetase-glutamate synthase pathway preferentially nodulated Phaseolus vulgaris. PMID:2892830

  3. Electrogenic ammonium transport by renal Rhbg.

    PubMed

    Nakhoul, N L; Schmidt, E; Abdulnour-Nakhoul, S-M; Hamm, L L

    2006-01-01

    The recently cloned, non-erythrocyte Rh glycoproteins (Rhbg and Rhcg) are expressed in the intercalated cells of the renal collecting duct. The apical Rhcg and the basolateral Rhbg are likely involved in NH3 and/or NH4+ transport, yet the characteristics of this transport are not yet certain. In this study we investigated the mechanism of NH4+ transport by Rhbg and Rhcg expressed in Xenopus oocytes. We used a two-electrode voltage-clamp and ion-selective microelectrodes to measure NH4+-induced currents (I(NH4)) and changes in pHi, respectively. In oocytes expressing Rhcg, exposure to bath [NH4+] of 2.5-20 mM induced inward currents that were slightly more than those in H2O-injected (control) oocytes. I-V plots in the presence of NH4+ showed a small increase in slope conductance only at positive potentials. On the other hand, in oocytes expressing Rhbg, 5 mM NH4+ induced an inward I(NH4) of -79 nA, decreased pHi (DeltapHi) by 0.13 at a rate (dpHi/dt) of -2 7 x 10(-4) pH/s and depolarized the cell by 45 mV. These changes were significantly more than those in control oocytes. I-V plots in the presence of NH4+ showed substantial increase in conductance. Amiloride (1 mM) inhibited I(NH4), DeltapHi and dpHi/dt in oocytes expressing Rhbg but not in control oocytes. Raising bath [NH4+] in increments from 1 to 20 mM elicited a faster dpHi/dt, a larger decrease in pHi and a larger depolarization. Net NH4+ flux by Rhbg (estimated from dpHi/dt) was proportional to [NH4+] gradient and followed saturation kinetics with an apparent Km of 2.3 mM. Methyl ammonium (5 mM) induced a current of -63 nA in Rhbg oocytes but did not cause any change in control oocytes. These data indicate that: 1) Rhbg transport of NH4+ is electrogenic. 2) Methyl ammonium is transported by Rhbg. 3) NH4+ transport by Rhbg is saturated at high concentrations with Michaelis-Menten kinetics.

  4. Size-dependent reactions of ammonium bisulfate clusters with dimethylamine.

    PubMed

    Bzdek, Bryan R; Ridge, Douglas P; Johnston, Murray V

    2010-11-04

    The reaction kinetics of ammonium bisulfate clusters with dimethylamine (DMA) gas were investigated using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Clusters ranged in size from 1 to 10 bisulfate ions. Although displacement of the first several ammonium ions by DMA occurred with near unit efficiency, displacement of the final ammonium ion was cluster size dependent. For small clusters, all ammonium ions are exposed to incoming DMA molecules, allowing for facile exchange ("surface" exchange). However, with increasing cluster size, an ammonium ion can be trapped in an inaccessible region of the cluster ("core" exchange), thereby rendering exchange difficult. DMA was also observed to add onto existing dimethylaminium bisulfate clusters above a critical size, whereas ammonia did not add onto ammonium bisulfate clusters. The results suggest that as the cluster size increases, di-dimethylaminium sulfate formation becomes more favorable. The results of this study give further evidence to suggest that ambient sub-3 nm diameter particles are likely to contain aminium salts rather than ammonium salts.

  5. Population of Nitrifying Bacteria and Nitrification in Ammonium Saturated Clinoptilolite

    NASA Technical Reports Server (NTRS)

    McGilloway, R. L.; Weaver, R. W.; Ming, Douglas W.; Gruener, J.

    1999-01-01

    As humans begin to spend longer periods of time in space, plants will be incorporated into life support systems. Ammonium saturated clinoptilolite is one plant growth substrate but a balance between ammonium and nitrate is needed. A laboratory study was conducted to determine effects of nitrifying bacteria on ammonium concentrations and kinetics of nitrification. Columns containing clinoptilolite substrate amended with nitrifying bacteria obtained from soil enrichment were analyzed weekly for a 90 day period. The enrichment culture initially contained 1 x 10(exp 5) ammonium oxidizing bacteria and 1 x 10(exp 2) nitrite oxidizing bacteria per gram of substrate. Populations of ammonium oxidizing bacteria increased to 1 x 10(exp 6) and nitrite oxidizing bacteria increased to 1 x 10(exp 3) per gram of substrate. The nitrification rate was approximately 0.25mg NO3(-)-N/kg.hr. Experiments were also conducted to enumerate nitrifying bacteria in a clinoptilolite substrate used to grow wheat (Triticum aestivum L.). Seventy days following the initial inoculation with an unknown number of commercial nitrifying bacteria, 1 x 10(exp 5) ammonium oxidizing bacteria per gram of substrate were present. The number of nitrite oxidizing bacteria was between 1 x 10(exp 3) to 10(exp 4) per gram of substrate as measured by the most probable number method. Nitrification rates were approximately 0.20mg NO3(-)-N/kg.hr. Clinoptilolite readily exchanged sufficient concentrations of ammonium to support nitrifying bacteria and they survived well in this medium.

  6. Effective ammonium removal by anaerobic oxidation in microbial fuel cells.

    PubMed

    Jadhav, Dipak A; Ghangrekar, Makarand M

    2015-01-01

    Dual-chamber microbial fuel cells (MFCs), made of clayware cylinder, were operated at different chemical oxygen demands: ammonium-nitrogen (COD:NH4+) ratio (1:1, 10:1 and 5:1) under batch mode for simultaneous removal of ammonia and organic matter from wastewater. Ammonium-N removal efficiencies of 63-32.66% were obtained for COD:NH4+ ratio of 1:10, respectively. Average COD removal efficiencies demonstrated by these MFCs were about 88%; indicating effective use of MFCs for treatment of wastewater containing organic matter and high ammonia concentration. MFCs operated with COD:NH4+ ratio of 10:1 produced highest volumetric power density of 752.88 mW/m3. The ammonium-N removal slightly increased when microbes were exposed to only ammonium as a source of electron when organic source was not supplemented. When this MFC was operated with imposed potential on cathode and without aeration in the cathode chamber, oxidation of ammonium ions at a faster rate confirmed anaerobic oxidation. During the non-turnover condition of cyclic voltammetry, MFC operated with COD:NH4+ ratio of 10:1 gave higher oxidative and reductive currents than MFC operated with COD:NH4+ ratio of 1:1 due to higher redox species. Successful application of such an anammox process for ammonium oxidation in MFCs will be useful for treatment of wastewater containing higher ammonium concentration and harvesting energy in the form of electricity.

  7. Population of Nitrifying Bacteria and Nitrification in Ammonium Saturated Clinoptilolite

    NASA Technical Reports Server (NTRS)

    McGilloway, R. L.; Weaver, R. W.; Ming, Douglas W.; Gruener, J.

    1999-01-01

    As humans begin to spend longer periods of time in space, plants will be incorporated into life support systems. Ammonium saturated clinoptilolite is one plant growth substrate but a balance between ammonium and nitrate is needed. A laboratory study was conducted to determine effects of nitrifying bacteria on ammonium concentrations and kinetics of nitrification. Columns containing clinoptilolite substrate amended with nitrifying bacteria obtained from soil enrichment were analyzed weekly for a 90 day period. The enrichment culture initially contained 1 x 10(exp 5) ammonium oxidizing bacteria and 1 x 10(exp 2) nitrite oxidizing bacteria per gram of substrate. Populations of ammonium oxidizing bacteria increased to 1 x 10(exp 6) and nitrite oxidizing bacteria increased to 1 x 10(exp 3) per gram of substrate. The nitrification rate was approximately 0.25mg NO3(-)-N/kg.hr. Experiments were also conducted to enumerate nitrifying bacteria in a clinoptilolite substrate used to grow wheat (Triticum aestivum L.). Seventy days following the initial inoculation with an unknown number of commercial nitrifying bacteria, 1 x 10(exp 5) ammonium oxidizing bacteria per gram of substrate were present. The number of nitrite oxidizing bacteria was between 1 x 10(exp 3) to 10(exp 4) per gram of substrate as measured by the most probable number method. Nitrification rates were approximately 0.20mg NO3(-)-N/kg.hr. Clinoptilolite readily exchanged sufficient concentrations of ammonium to support nitrifying bacteria and they survived well in this medium.

  8. pH sensitivity of ammonium transport by Rhbg

    PubMed Central

    Abdulnour-Nakhoul, Solange M.; Schmidt, Eric; Doetjes, Rienk; Rabon, Edd; Hamm, L. Lee

    2010-01-01

    Rhbg is a membrane glycoprotein that is involved in NH3/NH4+ transport. Several models have been proposed to describe Rhbg, including an electroneutral NH4+/H+ exchanger, a uniporter, an NH4+ channel, or even a gas channel. In this study, we characterized the pH sensitivity of Rhbg expressed in Xenopus oocytes. We used two-electrode voltage clamp and ion-selective microelectrodes to measure NH4+-induced [and methyl ammonium (MA+)] currents and changes in intracellular pH (pHi), respectively. In oocytes expressing Rhbg, 5 mM NH4Cl (NH3/NH4+) at extracellular pH (pHo) of 7.5 induced an inward current, decreased pHi, and depolarized the cell. Raising pHo to 8.2 significantly enhanced the NH4+-induced current and pHi changes, whereas decreasing bath pH to 6.5 inhibited these changes. Lowering pHi (decreased by butyrate) also inhibited the NH4+-induced current and pHi decrease. In oocytes expressing Rhbg, 5 mM methyl amine hydrochloride (MA/MA+), often used as an NH4Cl substitute, induced an inward current, a pHi increase (not a decrease), and depolarization of the cell. Exposing the oocyte to MA/MA+ at alkaline bath pH (8.2) enhanced the MA+-induced current, whereas lowering bath pH to 6.5 inhibited the MA+ current completely. Exposing the oocyte to MA/MA+ at low pHi abolished the MA+-induced current and depolarization; however, pHi still increased. These data indicate that 1) transport of NH4+ and MA/MA+ by Rhbg is pH sensitive; 2) electrogenic NH4+ and MA+ transport are stimulated by alkaline pHo but inhibited by acidic pHi or pHo; and 3) electroneutral transport of MA by Rhbg is likely but is less sensitive to pH changes. PMID:20810915

  9. pH sensitivity of ammonium transport by Rhbg.

    PubMed

    Nakhoul, Nazih L; Abdulnour-Nakhoul, Solange M; Schmidt, Eric; Doetjes, Rienk; Rabon, Edd; Hamm, L Lee

    2010-12-01

    Rhbg is a membrane glycoprotein that is involved in NH(3)/NH(4)(+) transport. Several models have been proposed to describe Rhbg, including an electroneutral NH(4)(+)/H(+) exchanger, a uniporter, an NH(4)(+) channel, or even a gas channel. In this study, we characterized the pH sensitivity of Rhbg expressed in Xenopus oocytes. We used two-electrode voltage clamp and ion-selective microelectrodes to measure NH(4)(+)-induced [and methyl ammonium (MA(+))] currents and changes in intracellular pH (pH(i)), respectively. In oocytes expressing Rhbg, 5 mM NH(4)Cl (NH(3)/NH(4)(+)) at extracellular pH (pH(o)) of 7.5 induced an inward current, decreased pH(i), and depolarized the cell. Raising pH(o) to 8.2 significantly enhanced the NH(4)(+)-induced current and pH(i) changes, whereas decreasing bath pH to 6.5 inhibited these changes. Lowering pH(i) (decreased by butyrate) also inhibited the NH(4)(+)-induced current and pH(i) decrease. In oocytes expressing Rhbg, 5 mM methyl amine hydrochloride (MA/MA(+)), often used as an NH(4)Cl substitute, induced an inward current, a pH(i) increase (not a decrease), and depolarization of the cell. Exposing the oocyte to MA/MA(+) at alkaline bath pH (8.2) enhanced the MA(+)-induced current, whereas lowering bath pH to 6.5 inhibited the MA(+) current completely. Exposing the oocyte to MA/MA(+) at low pH(i) abolished the MA(+)-induced current and depolarization; however, pH(i) still increased. These data indicate that 1) transport of NH(4)(+) and MA/MA(+) by Rhbg is pH sensitive; 2) electrogenic NH(4)(+) and MA(+) transport are stimulated by alkaline pH(o) but inhibited by acidic pH(i) or pH(o); and 3) electroneutral transport of MA by Rhbg is likely but is less sensitive to pH changes.

  10. Ammonium Hydrosulfide and Jupiter's Great Red Spot

    NASA Astrophysics Data System (ADS)

    Loeffler, M. J.; Hudson, R.; Chanover, N.; Simon, A. A.

    2014-12-01

    The color and composition of Jupiter's Great Red Spot (GRS) has been debated for more than a century. While there are numerous hypotheses for the origin of Jupiter's GRS, recent work suggests that the GRS's color could originate from multiple components (Carlson et al., 2012; Simon et al., submitted). In light of this, we have recently begun conducting in situ laboratory experiments that test whether ammonium hydrosulfide, NH4SH, or its radiation decomposition products contribute to the GRS spectrum. In this presentation, we will discuss some of our most recent results, where we have studied the stability of NH4SH samples as a function of temperature using infrared and mass spectrometry. Funding for this work has been provided by NASA's Planetary Atmospheres and Outer Planets Research programs. ReferencesCarlson, R. W., K. H. Baines, M. S. Anderson, G. Filacchione. Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter's Great Red Spot, DPS, 44, 2012. Simon, A. A., J. Legarreta, F. Sanz-Requena, S. Perez-Hoyos, E. Garcia-Melendo, R. W. Carlson. Spectral Comparison and Stability of Red Regions on Jupiter. J. Geophys. Res. - Planets, submitted.

  11. Combustion of ammonium and hydrazine azides

    SciTech Connect

    Fogelzang, A.E.; Egorshev, V.Y.; Sinditsky, V.P.; Kolesov, B.I. )

    1992-09-01

    This paper reports that steady-state combustion of ammonium azide (AA) and hydrazne azide (HA) was studied in a window constant-pressure bomb over a pressure range of 0.1-36 MPa. HA burns three to four times faster than AA over the whole pressure range. The temperature distribution in the combustion wave of AA and HA was measured using 5-{mu}m-thick {pi}-shaped tungsten-rhenium tape thermocouples. The combustion temperature of both compounds is 240-430 K higher than the temperature calculated for the thermodynamically equilibrium composition of the combustion products due to the presence of large amounts of ammonia (0.97 and 0.87 mol per AA and HA mole, respectively). The burning surface is formed via dissociation of the salts into hydrazoic acid HN{sub 3} and the parent base. The growth of the surface temperature with pressure is determined by the dissociation enthalpy of the slats. The burning rate of these compounds is determined by heat release in the gas phase.

  12. Ambient Ammonium Contribution to total Nitrogen Deposition ...

    EPA Pesticide Factsheets

    There has been a wealth of evidence over the last decade illustrating the rising importance of reduced inorganic nitrogen (NHx = ammonia gas, NH3, plus particulate ammonium, p-NH4) in the overall atmospheric mass balance and deposition of nitrogen as emissions of oxidized nitrogen have decreased throughout a period of stable or increasing NH3 emissions. In addition, the fraction of ambient ammonia relative to p-NH4 generally has risen as a result of decreases in both oxides of nitrogen and sulfur emissions. EPA plans to consider ecological effects related to deposition of nitrogen, of which NHx is a contributing component, in the review of secondary National Ambient Air Quality Standards (NAAQS) for oxides of nitrogen and sulfur (NOx/SOx standard). Although these ecological effects are associated with total nitrogen deposition, it will be important to understand the emissions sources contributing to the total nitrogen deposition and to understand how much of the total nitrogen deposition is from deposition of NHx versus other nitrogen species. Because p-NH4 contributes to nitrogen deposition and can also be a significant component of particulate matter, there is a potential overlap in addressing nitrogen based deposition effects in the secondary PM and NOx/SOx NAAQS. Consequently, there is a policy interest in quantifying the contribution of p-NH4 to total nitrogen deposition. While dry deposition of p-NH4 is calculated through a variety of modeling app

  13. Quaternary Ammonium Biocides: Efficacy in Application

    PubMed Central

    2014-01-01

    Quaternary ammonium compounds (QACs) are among the most commonly used disinfectants. There has been concern that their widespread use will lead to the development of resistant organisms, and it has been suggested that limits should be place on their use. While increases in tolerance to QACs have been observed, there is no clear evidence to support the development of resistance to QACs. Since efflux pumps are believe to account for at least some of the increased tolerance found in bacteria, there has been concern that this will enhance the resistance of bacteria to certain antibiotics. QACs are membrane-active agents interacting with the cytoplasmic membrane of bacteria and lipids of viruses. The wide variety of chemical structures possible has seen an evolution in their effectiveness and expansion of applications over the last century, including non-lipid-containing viruses (i.e., noroviruses). Selection of formulations and methods of application have been shown to affect the efficacy of QACs. While numerous laboratory studies on the efficacy of QACs are available, relatively few studies have been conducted to assess their efficacy in practice. Better standardized tests for assessing and defining the differences between increases in tolerance versus resistance are needed. The ecological dynamics of microbial communities where QACs are a main line of defense against exposure to pathogens need to be better understood in terms of sublethal doses and antibiotic resistance. PMID:25362069

  14. Aerosol isotopic ammonium signatures over the remote Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Lin, C. T.; Jickells, T. D.; Baker, A. R.; Marca, A.; Johnson, M. T.

    2016-05-01

    We report aerosol ammonium 15N signatures for samples collected from research cruises on the South Atlantic and Caribbean using a new high sensitivity method. We confirm a pattern of isotopic signals from generally light (δ15N -5 to -10‰), for aerosols with very low (<2 nmol m-3) ammonium concentrations from the remote high latitude ocean, to generally heavier values (δ15N +5 to +10‰), for aerosols collected in temperate and tropical latitudes and with higher ammonium concentrations (>2 nmol m-3). We discuss whether this reflects a mixing of aerosols from two end-members (polluted continental and remote marine emissions), or isotopic fractionation during aerosol transport.

  15. Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

    PubMed Central

    Xue, Yan; Xiao, Huining; Zhang, Yi

    2015-01-01

    Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers. PMID:25667977

  16. Optogenetic techniques for the study of native potassium channels.

    PubMed

    Sandoz, Guillaume; Levitz, Joshua

    2013-01-01

    Optogenetic tools were originally designed to target specific neurons for remote control of their activity by light and have largely been built around opsin-based channels and pumps. These naturally photosensitive opsins are microbial in origin and are unable to mimic the properties of native neuronal receptors and channels. Over the last 8 years, photoswitchable tethered ligands (PTLs) have enabled fast and reversible control of mammalian ion channels, allowing optical control of neuronal activity. One such PTL, maleimide-azobenzene-quaternary ammonium (MAQ), contains a maleimide (M) to tether the molecule to a genetically engineered cysteine, a photoisomerizable azobenzene (A) linker and a pore-blocking quaternary ammonium group (Q). MAQ was originally used to photocontrol SPARK, an engineered light-gated potassium channel derived from Shaker. Potassium channel photoblock by MAQ has recently been extended to a diverse set of mammalian potassium channels including channels in the voltage-gated and K2P families. Photoswitchable potassium channels, which maintain native properties, pave the way for the optical control of specific aspects of neuronal function and for high precision probing of a specific channel's physiological functions. To extend optical control to natively expressed channels, without overexpression, one possibility is to develop a knock-in mouse in which the wild-type channel gene is replaced by its light-gated version. Alternatively, the recently developed photoswitchable conditional subunit technique provides photocontrol of the channel of interest by molecular replacement of wild-type complexes. Finally, photochromic ligands also allow photocontrol of potassium channels without genetic manipulation using soluble compounds. In this review we discuss different techniques for optical control of native potassium channels and their associated advantages and disadvantages.

  17. The ammonium nitrate and its mechanism of decomposition in the gas phase: a theoretical study and a DFT benchmark.

    PubMed

    Cagnina, Stefania; Rotureau, Patricia; Fayet, Guillaume; Adamo, Carlo

    2013-07-14

    The decomposition mechanism of ammonium nitrate in the gas phase was investigated and fully characterized by means of CBS-QB3 calculations. Five reaction channels were identified, leading to the formation of products (N2, H2O, O2, OH, HNO, NO3) found in the experimental works. The identified mechanism well underlines the origin of the chemical hazard of ammonium nitrate which is related to the exothermicity of the lowest decomposition channels. Furthermore, the high barrier to overcome in the rate determining step well explained the fact that the reaction is not usually spontaneous and requires a significant external stimulus for its onset. An accurate DFT benchmark study was then conducted to determine the most suitable exchange-correlation functional to accurately describe the reaction profile both in terms of structures and thermochemistry. This evaluation supports the use of the M06-2X functional as the best option for the study of ammonium nitrate decomposition and related reactions. Indeed, this level of theory provided the lowest deviations with respect to CBS-QB3 reference values, outperforming functionals especially developed for reaction kinetics.

  18. Mechanosensitive Channels

    NASA Astrophysics Data System (ADS)

    Martinac, Boris

    Living cells are exposed to a variety of mechanical stimuli acting throughout the biosphere. The range of the stimuli extends from thermal molecular agitation to potentially destructive cell swelling caused by osmotic pressure gradients. Cellular membranes present a major target for these stimuli. To detect mechanical forces acting upon them cell membranes are equipped with mechanosensitive (MS) ion channels. Functioning as molecular mechanoelectrical transducers of mechanical forces into electrical and/or chemical intracellular signals these channels play a critical role in the physiology of mechanotransduction. Studies of prokaryotic MS channels and recent work on MS channels of eukaryotes have significantly increased our understanding of their gating mechanism, physiological functions, and evolutionary origins as well as their role in the pathology of disease.

  19. Channel catfish

    USDA-ARS?s Scientific Manuscript database

    This book chapter provides a comprehensive overview of channel catfish aquaculture. Sections include fish biology; commercial culture; culture facilities; production practices; water quality management; nutrition, feeding and feed formulation; infectious diseases; harvesting and processing; and the...

  20. Pathogenic Escherichia coli

    USDA-ARS?s Scientific Manuscript database

    Escherichia coli, a member of the Enterobacteriaceae family, is a part of the normal flora of the intestinal tract of humans and a variety of animals. E. coli strains are classified on the basis of antigenic differences in two surface components (serotyping), the somatic antigen (O) of the lipopoly...

  1. PATHOGENIC ESCHERICHIA COLI

    EPA Science Inventory

    Escherichia coli is a bacterial species which inhabits the gastrointestinal tract of man and warm-blooded animals. Because of the ubiquity of this bacterium in the intestinal flora, it serves as an important indicator organism of fecal contamination. E. coli, aside from serving a...

  2. Diarrheagenic Escherichia coli.

    PubMed

    Gomes, Tânia A T; Elias, Waldir P; Scaletsky, Isabel C A; Guth, Beatriz E C; Rodrigues, Juliana F; Piazza, Roxane M F; Ferreira, Luís C S; Martinez, Marina B

    2016-12-01

    Most Escherichia coli strains live harmlessly in the intestines and rarely cause disease in healthy individuals. Nonetheless, a number of pathogenic strains can cause diarrhea or extraintestinal diseases both in healthy and immunocompromised individuals. Diarrheal illnesses are a severe public health problem and a major cause of morbidity and mortality in infants and young children, especially in developing countries. E. coli strains that cause diarrhea have evolved by acquiring, through horizontal gene transfer, a particular set of characteristics that have successfully persisted in the host. According to the group of virulence determinants acquired, specific combinations were formed determining the currently known E. coli pathotypes, which are collectively known as diarrheagenic E. coli. In this review, we have gathered information on current definitions, serotypes, lineages, virulence mechanisms, epidemiology, and diagnosis of the major diarrheagenic E. coli pathotypes. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

  3. A role for mechanosensitive channels in chloroplast and bacterial fission.

    PubMed

    Wilson, Margaret; Haswell, Elizabeth

    2012-02-01

    The division site in both chloroplasts and bacteria is established by the medial placement of the FtsZ ring, a process that is in part regulated by the evolutionarily conserved components of the Min system. We recently showed that mechanosensitive ion channels influence FtsZ ring assembly in both Arabidopsis thaliana chloroplasts and in Escherichia coli; in chloroplasts they do so through the same genetic pathway as the Min system. Here we describe the effect of heterologous expression of the Arabidopsis MS channel homolog MSL2 on FtsZ ring placement in E. coli. We also discuss possible molecular mechanisms by which MS channels might influence chloroplast or bacterial division.

  4. Studying mechanosensitive ion channels with an automated patch clamp.

    PubMed

    Barthmes, Maria; Jose, Mac Donald F; Birkner, Jan Peter; Brüggemann, Andrea; Wahl-Schott, Christian; Koçer, Armağan

    2014-03-01

    Patch clamp electrophysiology is the main technique to study mechanosensitive ion channels (MSCs), however, conventional patch clamping is laborious and success and output depends on the skills of the operator. Even though automated patch systems solve these problems for other ion channels, they could not be applied to MSCs. Here, we report on activation and single channel analysis of a bacterial mechanosensitive ion channel using an automated patch clamp system. With the automated system, we could patch not only giant unilamellar liposomes but also giant Escherichia coli (E. coli) spheroplasts. The tension sensitivity and channel kinetics data obtained in the automated system were in good agreement with that obtained from the conventional patch clamp. The findings will pave the way to high throughput fundamental and drug screening studies on mechanosensitive ion channels.

  5. 21 CFR 73.2298 - Ferric ammonium ferrocyanide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2298 Ferric ammonium ferrocyanide. (a... ferrocyanide is safe for use in coloring externally applied cosmetics, including cosmetics applied to the area...

  6. Chemical Advisory - Solid Ammonium Nitrate (AN) Storage, Handling and Management

    EPA Pesticide Factsheets

    Advisory contains information on recent and past accidents involving AMMONIUM NITRATE (commonly referred to as AN), on the hazards of AN, how to manage these hazards, and appropriate steps for community emergency planning and proper emergency response.

  7. Formation of urea and guanidine by irradiation of ammonium cyanide.

    NASA Technical Reports Server (NTRS)

    Lohrmann, R.

    1972-01-01

    Aqueous solutions of ammonium cyanide yield urea, cyanamide and guanidine when exposed to sunlight or an unfiltered 254 nm ultraviolet source. The prebiotic significance of these results is discussed.

  8. Direct esterification of ammonium salts of carboxylic acids

    DOEpatents

    Halpern, Yuval [Skokie, IL

    2003-06-24

    A non-catalytic process for producing esters, the process comprising reacting an ammonium salt of a carboxylic acid with an alcohol and removing ammonia from the reaction mixture. Selectivities for the desired ester product can exceed 95 percent.

  9. 21 CFR 184.1296 - Ferric ammonium citrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... brown or garnet red scales or granules or as a brownish-yellowish powder. (2) Ferric ammonium citrate... occurs as thin transparent green scales, as granules, as a powder, or as transparent green crystals. (b...

  10. 21 CFR 184.1296 - Ferric ammonium citrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... brown or garnet red scales or granules or as a brownish-yellowish powder. (2) Ferric ammonium citrate... occurs as thin transparent green scales, as granules, as a powder, or as transparent green crystals. (b...

  11. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food...

  12. Formation of urea and guanidine by irradiation of ammonium cyanide.

    NASA Technical Reports Server (NTRS)

    Lohrmann, R.

    1972-01-01

    Aqueous solutions of ammonium cyanide yield urea, cyanamide and guanidine when exposed to sunlight or an unfiltered 254 nm ultraviolet source. The prebiotic significance of these results is discussed.

  13. High-affinity ammonium transporters and nitrogen sensing in mycorrhizas.

    PubMed

    Javelle, Arnaud; André, Bruno; Marini, Anne Marie; Chalot, Michel

    2003-02-01

    Most terrestrial plants live in mutualistic symbiosis with root-infecting mycorrhizal fungi. This association requires a molecular dialogue between the two partners. However, the nature of the chemical signals that induce hyphal differentiation are not well characterized and the mechanisms for signal reception are still unknown. In addition to its role in ammonium scavenging, the Mep2 protein from Saccharomyces cerevisiae has been proposed to act as an ammonium sensor that is essential for pseudohyphal differentiation in response to ammonium limitation. We propose that the high-affinity ammonium transporters from mycorrhizal fungi act in a similar manner to sense the environment and induce, via as-yet-unidentified signal transduction cascades, the switch in the mode of fungal growth observed during the formation of mycorrhiza.

  14. Deliquescence behavior of organic/ammonium sulfate aerosol

    NASA Astrophysics Data System (ADS)

    Brooks, Sarah D.; Wise, Matthew E.; Cushing, Melinda; Tolbert, Margaret A.

    2002-10-01

    Recent studies have shown that tropospheric aerosols composed of internal mixtures of organics with sulfates are quite common with the organic composing up to 50% of the particle mass. The influences of the organics on the chemical and physical properties of the aerosol are not known. In this paper, we report the solubility of a series of dicarboxylic acids in saturated ammonium sulfate solution as a function of temperature. We also report the deliquescence relative humidity (DRH) of the pure dicarboxylic acids and of mixtures of dicarboxylic acids with ammonium sulfate. For the systems studied, we find that the presence of water-soluble dicarboxylic acids caused deliquescence to occur at a lower relative humidity (RH) than pure ammonium sulfate. In contrast, the less soluble dicarboxylic acids had no measurable effect on the deliquescence relative humidity of ammonium sulfate.

  15. The effect of ammonium sulfate injection on peripheral nerve.

    PubMed

    Kobayashi, J; Mackinnon, S E; Langer, J C; Hertl, M C; Hunter, D A; Tarasidis, G

    1997-08-01

    Local anesthetic drugs with prolonged nerve-block effect would have clinical application for postoperative or neuromatous pain relief. This study evaluated the possibility of peripheral nerve neurotoxicity by injection of 10 percent ammonium sulfate. Both intrafascicular and extrafascicular injection of 10 percent ammonium sulfate were tested in the rat sciatic nerve model. One percent lidocaine HCl, 5 percent phenol, and normal saline were similarly injected for comparison. Using histologic studies and motor function evaluation with walking-track analysis, 10 percent ammonium sulfate was found to be neurotoxic when it is injected intrafascicularly; however, extrafascicular injection of this drug did not cause significant nerve injury. The neurotoxicity of the 10 percent ammonium sulfate solution was intermediate between the neurotoxicity of 0.1 percent lidocaine hydrochloride and the marked neurotoxicity of 5 percent phenol solution.

  16. 14N NQR and relaxation in ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Stephenson, David

    2015-04-01

    The complete 14N nuclear quadrupole resonance (NQR) spectrum of ammonium nitrate is presented recorded using two double resonance techniques - double contact cross relaxation and zero field NQR. The spectra gave the quadrupole coupling constant (Qcc) and asymmetry parameter ( η) values for the nitro of 611 kHz, 0.229 and that for the ammonium nitrogen of 242 kHz, 0.835. The three relaxation transition probabilities have been determined for both the nitro and ammonium nitrogen atoms. The bi-exponential relaxation times (T 1) were measured at 295 K. The values for nitro are 16.9 s and 10.5 s and that of the ammonium are 23.0 s and 16.4 s.

  17. Nitrogen removal with the anaerobic ammonium oxidation process.

    PubMed

    Hu, Ziye; Lotti, Tommaso; van Loosdrecht, Mark; Kartal, Boran

    2013-08-01

    Anaerobic ammonium-oxidizing (anammox) bacteria convert ammonium to N2 with nitrite as the terminal electron acceptor in the absence of O2. Nitritation-anammox bioreactors provide a cost-effective and environment-friendly alternative to conventional nitrification/denitrification nitrogen removal systems. Currently, this process is only applied for ammonium removal from wastewater with high ammonium load and temperature. Nevertheless, recent results obtained with laboratory-scale bioreactors suggest new possible routes of application of the Nitritation-anammox technology including (1) municipal wastewater treatment, removal of (2) methane in combination with nitrite-reducing methane-oxidizing bacteria, (3) nitrate coupled to organic acid oxidation and (4) nitrogen oxides. The current review summarizes the state-of-the-art of the application of Nitritation-anammox systems and discusses the possibilities of utilizing these recent results for wastewater treatment.

  18. Studies on the Chick-lethal Toxin of Escherichia coli

    PubMed Central

    Truscott, R. B.

    1973-01-01

    A toxin which is lethal for two week old chicks has been recovered from strains of Escherichia coli O78:K80 of bovine and avian origin and from avian isolates of serogroups O2, O45 and O109. The toxin is heat-labile, antigenic, high in protein, inactivated by pronase, trypsin, amylase, and pancreatic lipase. The toxin may be precipitated by ammonium sulfate or TCA treatment from the supernatant obtained by repeated centrifugation of sonicated cells. Considerable purification has been obtained by column chromatography using Sepharose 6B. PMID:4270809

  19. Synthesis, characterization and antibacterial properties of dihydroxy quaternary ammonium salts with long chain alkyl bromides.

    PubMed

    Liu, Wen-Shuai; Wang, Chun-Hua; Sun, Ju-Feng; Hou, Gui-Ge; Wang, Yu-Peng; Qu, Rong-Jun

    2015-01-01

    Five N-methyl-N-R-N,N-bis(2-hydroxyethyl) ammonium bromides (R = -benzyl (chloride, BNQAS), -dodecyl (C12QAS), -tetradecyl (C14QAS), -hexadecyl (C16QAS), -octadecyl (C18QAS)) were prepared based on N-methyldiethanolamine (MDEA) and halohydrocarbon. Five QAS were characterized by FTIR, NMR, and MS. BNQAS, C12QAS, C14QAS, and C16QAS were confirmed by X-ray single-crystal diffraction. Their antibacterial properties indicated good antibacterial abilities against E. coli, S. aureus, B. subtilis, especially C12QAS with the best antibacterial ability (100% to E. coli, 95.65% to S. aureus, and 91.41% to B. subtilis). In addition, C12QAS also displayed the best antifungal activities than BNQAS and C18QAS against Cytospora mandshurica, Botryosphaeria ribis, Physalospora piricola, and Glomerella cingulata with the ratio of full marks. The strategy provides a facile way to design and develop new types of antibacterial drugs for application in preventing the fruit rot, especially apple. © 2014 John Wiley & Sons A/S.

  20. Antibacterial Activity, in Vitro Cytotoxicity, and Cell Cycle Arrest of Gemini Quaternary Ammonium Surfactants.

    PubMed

    Zhang, Shanshan; Ding, Shiping; Yu, Jing; Chen, Xuerui; Lei, Qunfang; Fang, Wenjun

    2015-11-10

    Twelve gemini quaternary ammonium surfactants have been employed to evaluate the antibacterial activity and in vitro cytotoxicity. The antibacterial effects of the gemini surfactants are performed on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with minimum inhibitory concentrations (MIC) ranging from 2.8 to 167.7 μM. Scanning electron microscopy (SEM) analysis results show that these surfactants interact with the bacterial cell membrane, disrupt the integrity of the membrane, and consequently kill the bacteria. The data recorded on C6 glioma and HEK293 human kidney cell lines using an MTT assay exhibit low half inhibitory concentrations (IC50). The influences of the gemini surfactants on the cell morphology, the cell migration ability, and the cell cycle are observed through hematoxylin-eosin (HE) staining, cell wound healing assay, and flow cytometric analyses, respectively. Both the values of MIC and IC50 decrease against the growth of the alkyl chain length of the gemini surfactants with the same spacer group. In the case of surfactants 12-s-12, the MICs and IC50s are found to decrease slightly with the spacer chain length changing from 2 to 8 and again to increase at higher spacer length (s = 10-12). All of the gemini surfactants show great antibacterial activity and cytotoxicity, and they might exhibit potential applications in medical fields.

  1. Analytical techniques for determining bound ammonium

    SciTech Connect

    Altaner, S.P.; Krohn, M.D

    1985-01-01

    Ammonium (NH/sub 4//sup +/) has been found to substitute for alkali cations in feldspars, micas, smectites, and alunites several Hg/Au-bearing hot springs deposits and volcanogenic stratabound Pb/Zn deposits. The authors compared four analytical techniques for determining the NH/sub 4//sup +/ content in rocks from these types of deposit and in synthetic NH/sub 4//sup +/-bearing feldspars, micas, and alunites: 1) X-ray diffraction (XRD), 2) mid- and 3) near-infrared spectroscopy (MIR and NIR) and 4) ion chromatography (IC). MIR analysis of synthetic minerals indicates that 7 ..mu..m band depth depends upon mineral type but that, for a given mineral, band depth is directly proportional to NH/sub 4//sup +/ concentration. NIR reflectance spectroscopy gives a rapid qualitative determination of NH/sub 4//sup +/ and allows positive field identification of NH/sub 4//sup +/. 4) IC gives a measure of the percent of NH/sub 4//sup +/ substitution by determining NH/sub 4//sup +/, K/sup +/, and Na/sup +/ concentrations. The procedure involves sample dissolution by HCl and HF in a microwave oven followed by separation and detection by an ion chromatograph. They estimate the detection limits of these analytical techniques for NH/sub 4//sup +/ concentration to be: XRD, 10-20% NH/sub 4//sup +/; MIR, 1-5% NG/sub 4//sup +/; and IC, <1% NH/sub 4//sup +/. Determination of NH/sub 4//sup +/ abundance in rocks will help to delineate the relationship of NH/sub 4//sup +/-bearing minerals to mineralization in ore deposits and promises to be an excellent method for prospecting.

  2. Redox potentials in ammonium nitrate solutions

    SciTech Connect

    Ngameni, E.; Ammaa, B.B.; Wandji, R.; Bessiere, J.

    1995-03-01

    The redox potentials of M{sup n+}/M (M{sup n+} = Cu{sup 2+}, Pb{sup 2+}, Sn{sup 2+}, Cd{sup 2+}, Ag{sup +}, Zn{sup 2+}, Hg{sup 2+}), M{sup n+}/M {sup (n{minus}m)+} (Fe{sup 3+}/Fe{sup 2+}, Fe(CN){sub 6}3{minus}/Fe(CN){sub 6}{sup 4{minus}}), and AgX/Ag, X{sup {minus}} (X = Cl, Br, and I) have been measured in aqueous solutions of ammonium nitrate (1--14 M). The variation of salvation of ions, characterized by the solvent transfer coefficient f{sup tr}, is calculated from the normal redox potentials of the systems. For all the cases, the potential of the ferricinium/ferrocene system (Fe{sup +}/Fc) is used as a reference of potential. It appears as a general trend that when the concentration of salt increases from 1 to 14 M, the potentials of the systems vary slightly, indicating weak interactions between these solutes and the salt. The examined ions can be classified into two groups: those that are less solvated as the concentration of NH{sub 4}NO{sub 3} increases (CU{sup 2+}, Cd{sup 2+}, Zn{sup 2+}, Cl{sup {minus}}, Br{sup {minus}}, I{sup {minus}}) and those that are more solvated, (Pb{sup 2+}, Ag{sup +}, Hg{sup 2+}, Sn{sup 2+}). The solubility constants of the AgX salts in the H{sub 2}O + NH{sub 4}NO{sub 3} mixtures are also calculated.

  3. The regulation of ammonium translocation in plants.

    PubMed

    Schjoerring, J K; Husted, S; Mäck, G; Mattsson, M

    2002-04-01

    Much controversy exists about whether or not NH(+)(4) is translocated in the xylem from roots to shoots. In this paper it is shown that such translocation can indeed take place, but that interference from other metabolites such as amino acids and amines may give rise to large uncertainties about the magnitude of xylem NH(+)(4) concentrations. Elimination of interference requires sample stabilization by, for instance, formic acid or methanol. Subsequent quantification of NH(+)(4) should be done by the OPA-fluorometric method at neutral pH with 2-mercaptoethanol as the reducing agent since this method is sensitive and reliable. Colorimetric methods based on the Berthelot reaction should never be used, as they are prone to give erroneous results. Significant concentrations of NH(+)(4), exceeding 1 mM, were measured in both xylem sap and leaf apoplastic solution of oilseed rape and tomato plants growing with NO(-)(3) as the sole N source. When NO(-)(3) was replaced by NH(+)(4), xylem sap NH(+)(4) concentrations increased with increasing external concentrations and with time of exposure to NH(+)(4). Up to 11% of the translocated N was constituted by NH(+)(4). Glutamine synthetase (GS) incorporates NH(+)(4) into glutamine, but root GS activity and expression were repressed when high levels of NH(+)(4) were supplied. Ammonium concentrations measured in xylem sap sampled just above the stem base were highly correlated with NH(+)(4) concentrations in apoplastic solution from the leaves. Young leaves tended to have higher apoplastic NH(+)(4) concentrations than older non-senescing leaves. The flux of NH(+)(4) (concentration multiplied by transpirational water flow) increased with temperature despite a decline in xylem NH(+)(4) concentration. Retrieval of leaf apoplastic NH(+)(4) involves both high and low affinity transporters in the plasma membrane of mesophyll cells. Current knowledge about these transporters and their regulation is discussed.

  4. Crystal structure of cyclo-hexyl-ammonium thio-cyanate.

    PubMed

    Bagabas, Abdulaziz A; Alhoshan, Sultan B; Ghabbour, Hazem A; Chidan Kumar, C S; Fun, Hoong-Kun

    2015-01-01

    In the title salt, C6H11NH3 (+)·SCN(-), the cyclo-hexyl-ammonium ring adopts a slightly distorted chair conformation. The ammonium group occupies an equatorial position to minimize 1,3 and 1,5 diaxial inter-actions. In the crystal, the components are linked by N-H⋯N and N-H⋯S hydrogen-bonding inter-actions, resulting in a three-dimensional network.

  5. Safety assessment of ammonium hectorites as used in cosmetics.

    PubMed

    Becker, Lillian C; Bergfeld, Wilma F; Belsito, Donald V; Hill, Ronald A; Klaassen, Curtis D; Liebler, Daniel C; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

    2013-01-01

    The Cosmetic Ingredient Review Expert Panel (Panel) reviewed the safety of 4 ammonium hectorite compounds used in cosmetics: disteardimonium hectorite, dihydrogenated tallow benzylmonium hectorite, stearalkonium hectorite, and quaternium-18 hectorite. These ingredients function in cosmetics mainly as nonsurfactant suspending agents. The Panel reviewed available animal and human data and concluded that these ammonium hectorite compounds were safe as cosmetic ingredients in the practices of use and concentration as given in this safety assessment.

  6. Localized corrosion of stainless steels in ammonium chloride solutions

    SciTech Connect

    Forsen, O.; Aromaa, J.; Tavi, M.; Virtanen, J.

    1997-05-01

    Ammonium chloride deposition is a well-known problem in oil refining. When these deposits form in a moist environment, they are corrosive to carbon steel. When unexpected corrosion problems are faced, the material is often changed to alloys like stainless steels (SS). Electrochemical measurements were used to study the corrosion resistance of SS in ammonium chloride environments with different chloride contents and at different temperatures.

  7. Thermal storage in ammonium alum/ammonium nitrate eutectic for solar space heating

    SciTech Connect

    Goswami, D.Y.; Jotshi, C.K.; Klausner, J.F.; Hsieh, C.K.; Srinivasan, N.

    1995-10-01

    Ammonium alum and ammonium nitrate in the weight ratio of 1:1 forms a eutectic that melts at 53 C and crystallizes at 48 C. The latent heat of fusion of this eutectic was found to be 215 kJ/kg. Its enthalpy as measured by drop calorimetry was found to be 287 kJ/kg in the temperature range of 24--65 C, which is 1.67 times greater than water (172.2 kJ/kg) and 8.75 times greater than rock (32.8 kJ/kg). Upon several heating/cooling cycles, phase separation was observed. However, by adding 5% attapulgite clay to this eutectic mixture, phase separation was prevented. This eutectic was encapsulated in 0.0254m diameter HDPE hollow balls and subjected to about 1,100 heating/cooling cycles in the temperature range between 25 and 65 C. At the end of these cycles, the decrease in enthalpy was found to be 5%. A scale model of the heat storage unit was fabricated to investigate the heat transfer characteristics of this eutectic encapsulated in HDPE balls. The thermal extraction efficiency of the system was measured with the recirculation of hot air during charging and was found to be in the range of 85--98%.

  8. Sorption of aromatic ionizable organic compounds to montmorillonites modified by hexadecyltrimethyl ammonium and polydiallyldimethyl ammonium.

    PubMed

    Xu, Huaizhou; Wan, Yuqiu; Li, Hui; Zheng, Shourong; Zhu, Dongqiang

    2011-01-01

    Environmental residues of aromatic ionizable organic compounds (AIOCs) have received considerable attention due to their potential human health and ecological risks. The main objective of this study was to investigate the key factors and mechanisms controlling sorption of a series of anionic and zwitterionic AIOCs (two aromatic sulfonates, 4-methyl-2,6-dinitrophenol, tetracycline, sulfamethoxazole, and tannic acid) to montmorillonites modified with hexadecyltrimethyl ammonium (HDTMA) and polydiallyldimethyl ammonium (PDADMA). Compared with naphthalene (a nonpolar and nonionic solute), all AIOCs showed stronger sorption (the sorbent-to-solution distribution coefficient was in the order of 10-10 L kg) to the two organoclays in spite of the much lower hydrophobicity, indicating the predominance of electrostatic interaction in sorption. The proposed electrostatic mechanism of the tested AIOCs was supported by the pH dependency of sorption to the two organoclays. The two organoclays manifested weaker sorption affinity but faster sorption kinetics for bulky AIOCs than commercial activated carbon, resulting from the high accessibility of sorption sites in the open, ordered clay interlayer. The findings of this study highlight the potential of using HDTMA- and PDADMA-exchanged montmorillonites as effective sorbents for AIOCs in water and wastewater treatments.

  9. Thermal Decomposition Behavior of Ammonium Perchlorate and of an Ammonium-Perchlorate-Based Composite Propellant

    NASA Technical Reports Server (NTRS)

    Behrens, R.; Minier, L.

    1998-01-01

    The thermal decomposition of ammonium perchlorate (AP) and ammonium-perchlorate-based composite propellants is studied using the simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) technique. The main objective of the present work is to evaluate whether the STMBMS can provide new data on these materials that will have sufficient detail on the reaction mechanisms and associated reaction kinetics to permit creation of a detailed model of the thermal decomposition process. Such a model is a necessary ingredient to engineering models of ignition and slow-cookoff for these AP-based composite propellants. Results show that the decomposition of pure AP is controlled by two processes. One occurs at lower temperatures (240 to 270 C), produces mainly H2O, O2, Cl2, N2O and HCl, and is shown to occur in the solid phase within the AP particles. 200(micro) diameter AP particles undergo 25% decomposition in the solid phase, whereas 20(micro) diameter AP particles undergo only 13% decomposition. The second process is dissociative sublimation of AP to NH3 + HClO4 followed by the decomposition of, and reaction between, these two products in the gas phase. The dissociative sublimation process occurs over the entire temperature range of AP decomposition, but only becomes dominant at temperatures above those for the solid-phase decomposition. AP-based composite propellants are used extensively in both small tactical rocket motors and large strategic rocket systems.

  10. The thermal decomposition behavior of ammonium perchlorate and of an ammonium-perchlorate-based composite propellant

    SciTech Connect

    Behrens, R.; Minier, L.

    1998-03-24

    The thermal decomposition of ammonium perchlorate (AP) and ammonium-perchlorate-based composite propellants is studied using the simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) technique. The main objective of the present work is to evaluate whether the STMBMS can provide new data on these materials that will have sufficient detail on the reaction mechanisms and associated reaction kinetics to permit creation of a detailed model of the thermal decomposition process. Such a model is a necessary ingredient to engineering models of ignition and slow-cookoff for these AP-based composite propellants. Results show that the decomposition of pure AP is controlled by two processes. One occurs at lower temperatures (240 to 270 C), produces mainly H{sub 2}O, O{sub 2}, Cl{sub 2}, N{sub 2}O and HCl, and is shown to occur in the solid phase within the AP particles. 200{micro} diameter AP particles undergo 25% decomposition in the solid phase, whereas 20{micro} diameter AP particles undergo only 13% decomposition. The second process is dissociative sublimation of AP to NH{sub 3} + HClO{sub 4} followed by the decomposition of, and reaction between, these two products in the gas phase. The dissociative sublimation process occurs over the entire temperature range of AP decomposition, but only becomes dominant at temperatures above those for the solid-phase decomposition. AP-based composite propellants are used extensively in both small tactical rocket motors and large strategic rocket systems.

  11. Optogenetic techniques for the study of native potassium channels

    PubMed Central

    Sandoz, Guillaume; Levitz, Joshua

    2013-01-01

    Optogenetic tools were originally designed to target specific neurons for remote control of their activity by light and have largely been built around opsin-based channels and pumps. These naturally photosensitive opsins are microbial in origin and are unable to mimic the properties of native neuronal receptors and channels. Over the last 8 years, photoswitchable tethered ligands (PTLs) have enabled fast and reversible control of mammalian ion channels, allowing optical control of neuronal activity. One such PTL, maleimide-azobenzene-quaternary ammonium (MAQ), contains a maleimide (M) to tether the molecule to a genetically engineered cysteine, a photoisomerizable azobenzene (A) linker and a pore-blocking quaternary ammonium group (Q). MAQ was originally used to photocontrol SPARK, an engineered light-gated potassium channel derived from Shaker. Potassium channel photoblock by MAQ has recently been extended to a diverse set of mammalian potassium channels including channels in the voltage-gated and K2P families. Photoswitchable potassium channels, which maintain native properties, pave the way for the optical control of specific aspects of neuronal function and for high precision probing of a specific channel’s physiological functions. To extend optical control to natively expressed channels, without overexpression, one possibility is to develop a knock-in mouse in which the wild-type channel gene is replaced by its light-gated version. Alternatively, the recently developed photoswitchable conditional subunit technique provides photocontrol of the channel of interest by molecular replacement of wild-type complexes. Finally, photochromic ligands also allow photocontrol of potassium channels without genetic manipulation using soluble compounds. In this review we discuss different techniques for optical control of native potassium channels and their associated advantages and disadvantages. PMID:23596388

  12. Nitric oxide controls nitrate and ammonium assimilation in Chlamydomonas reinhardtii.

    PubMed

    Sanz-Luque, Emanuel; Ocaña-Calahorro, Francisco; Llamas, Angel; Galvan, Aurora; Fernandez, Emilio

    2013-08-01

    Nitrate and ammonium are major inorganic nitrogen sources for plants and algae. These compounds are assimilated by means of finely regulated processes at transcriptional and post-translational levels. In Chlamydomonas, the expression of several genes involved in high-affinity ammonium (AMT1.1, AMT1.2) and nitrate transport (NRT2.1) as well as nitrate reduction (NIA1) are downregulated by ammonium through a nitric oxide (NO)-dependent mechanism. At the post-translational level, nitrate/nitrite uptake and nitrate reductase (NR) are also inhibited by ammonium, but the mechanisms implicated in this regulation are scarcely known. In this work, the effect of NO on nitrate assimilation and the high-affinity ammonium uptake was addressed. NO inhibited the high-affinity uptake of ammonium and nitrate/nitrite, as well as the NR activity, in a reversible form. In contrast, nitrite reductase and glutamine synthetase activities were not affected. The in vivo and in vitro studies suggested that NR enzyme is inhibited by NO in a mediated process that requires the cell integrity. These data highlight a role of NO in inorganic nitrogen assimilation and suggest that this signalling molecule is an important regulator for the first steps of the pathway.

  13. The ground water ammonium sorption onto Croatian and Serbian clinoptilolite.

    PubMed

    Siljeg, Mario; Foglar, Lucija; Kukucka, Miroslav

    2010-06-15

    The removal of ammonium from the Valpovo region ground water (VGW) with the use of natural clinoptilolite samples from the Donje Jesenje deposit (Croatia) and the Zlatokop deposit in Vranjska Banja (Serbia) was studied. The natural Serbian (SZ) and Croatian zeolites (CZ) were transformed to the Na-form (Na-CZ and Na-SZ) in order to increase the exchange capacity of zeolite. The CZ and SZ theoretic ammonium sorption capacities were 24.24 mg NH(4)(+)/g CZ and 32.55 mg NH(4)(+)/g SZ, respectively. The application of natural and Na-form of clinoptilolite for efficient removal of ammonium ions from VGW was further investigated. For that purpose, the four "filter guard" vessels filled with zeolite samples were set in parallel in the ground water purification pilot plant. The complete ammonium removal, with the use of SZ and Na-SZ was achieved during 20 h. After having observed saturation of clinoptilolite, the samples were regenerated with the use of 2 mol/L NaCl, and reused for determination of ammonium sorption efficiency. The regenerated samples showed to be still very efficient for NH(4)(+) removal and, in addition, the SZ was shown as superior for ammonium removal in comparison to the CZ.

  14. Removal of ammonium from municipal landfill leachate using natural zeolites.

    PubMed

    Ye, Zhihong; Wang, Jiawen; Sun, Lingyu; Zhang, Daobin; Zhang, Hui

    2015-01-01

    Ammonium ion-exchange performance of the natural zeolite was investigated in both batch and column studies. The effects of zeolite dosage, contact time, stirring speed and pH on ammonium removal were investigated in batch experiments. The result showed that ammonium removal efficiency increased with an increase in zeolite dosage from 25 to 150 g/L, and an increase in stirring speed from 200 to 250 r/min. But further increase in zeolite dosage and stirring speed would result in an unpronounced increase of ammonium removal. The optimal pH for the removal of ammonium was found as 7.1. In the column studies, the effect of flow rate was investigated, and the total ammonium removal percentage during 180 min operation time decreased with the flow rate though the ion-exchange capacity varied to a very small extent with the flow rate ranging from 4 to 9 mL/min. The spent zeolite was regenerated by sodium chloride solution and the ammonia removal capacity of zeolite changed little or even increased after three regeneration cycles.

  15. Source regions of ammonium nitrate, ammonium sulfate, and natural silicates in the surface aerosols of Moscow oblast

    NASA Astrophysics Data System (ADS)

    Shukurov, K. A.; Shukurova, L. M.

    2017-05-01

    Maps of potential source regions of ammonium nitrate, ammonium sulfate, and natural silicates in the surface aerosols in 2002-2005, 2010, and 2012-2015 are obtained based on measurements of the optical depth of 1-2 μm surface aerosol samples and the analysis results of backward trajectories of air parcels at the Zvenigorod scientific station (ZSS) of the A. M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. The most likely potential source regions of ammonium nitrate are in western and central Europe; those of ammonium sulfate are in southern Ukraine, southern Russia, and northwest Kazakhstan; and those of natural silicates are in the Caspian and Aral regions. The maps of potential source regions are consistent with EMEP fields of surface concentrations of nitrates and sulfates and natural aerosol concentration in PM2.5.

  16. 76 FR 39847 - Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation; Final Results of the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-07

    ... International Trade Administration Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation; Final... investigation on solid fertilizer grade ammonium nitrate (``ammonium nitrate'') from the Russian Federation...: Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation, 64 FR 45236 (August 19, 1999)....

  17. Synthesis and structure-activity study of quaternary ammonium functionalized beta-cyclodextrin-carboxymethylcellulose polymers.

    PubMed

    Bonenfant, Danielle; Bourgeois, François-René; Mimeault, Murielle; Monette, Frédéric; Niquette, Patrick; Hausler, Robert

    2011-01-01

    Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment.

  18. English Channel

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The cloud covered earthscape of Northern Europe demonstrates the difficulty of photographing this elusive subject from space. The English Channel (51.0N, 1.5E) separating the British Islands from Europe is in the center of the scene. The white cliffs of Dover on the SE coast of the UK, the Thames River estuary and a partial view of the city of London can be seen on the north side of the Channel while the Normandy coast of France is to the south.

  19. English Channel

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The cloud covered earthscape of Northern Europe demonstrates the difficulty of photographing this elusive subject from space. The English Channel (51.0N, 1.5E) separating the British Islands from Europe is in the center of the scene. The white cliffs of Dover on the SE coast of the UK, the Thames River estuary and a partial view of the city of London can be seen on the north side of the Channel while the Normandy coast of France is to the south.

  20. The different ecological niches of enterotoxigenic E scherichia coli

    PubMed Central

    Gonzales‐Siles, Lucia

    2015-01-01

    Summary Enterotoxigenic E scherichia coli (ETEC) is a water and food‐borne pathogen that infects the small intestine of the human gut and causes diarrhoea. Enterotoxigenic E. coli adheres to the epithelium by means of colonization factors and secretes two enterotoxins, the heat labile toxin and/or the heat stable toxin that both deregulate ion channels and cause secretory diarrhoea. Enterotoxigenic E. coli as all E. coli, is a versatile organism able to survive and grow in different environments. During transmission and infection, ETEC is exposed to various environmental cues that have an impact on survivability and virulence. The ability to cope with exposure to different stressful habitats is probably shaping the pool of virulent ETEC strains that cause both endemic and epidemic infections. This review will focus on the ecology of ETEC in its different habitats and interactions with other organisms as well as abiotic factors. PMID:26522129

  1. E. Coli and Pregnancy

    MedlinePlus

    ... best live chat Live Help Fact Sheets Share E. coli and Pregnancy Thursday, 20 November 2014 In ... pregnancy and while breastfeeding. Donate Sign Up For E-Newsletter Full Name * Email Address * Enter The Code: ...

  2. E. Coli Infections

    MedlinePlus

    ... type causes travelers' diarrhea. The worst type of E. coli causes bloody diarrhea, and can sometimes cause kidney failure and even death. These problems are most likely to occur in children and ...

  3. Early metabolic effects and mechanism of ammonium transport in yeast

    SciTech Connect

    Pena, A.; Pardo, J.P.; Ramirez, J.

    1987-03-01

    Studies were performed to define the effects and mechanism of NH+4 transport in yeast. The following results were obtained. Glucose was a better facilitator than ethanol-H/sub 2/O/sub 2/ for ammonium transport; low concentrations of uncouplers or respiratory inhibitors could inhibit the transport with ethanol as the substrate. With glucose, respiratory inhibitors showed only small inhibitory effects, and only high concentrations of azide or trifluoromethoxy carbonylcyanide phenylhydrazone could inhibit ammonium transport. Ammonium in the free state could be concentrated approximately 200-fold by the cells. Also, the addition of ammonium produced stimulation of both respiration and fermentation; an increased rate of H+ extrusion and an alkalinization of the interior of the cell; a decrease of the membrane potential, as monitored by fluorescent cyanine; an immediate decrease of the levels of ATP and an increase of ADP, which may account for the stimulation of both fermentation and respiration; and an increase of the levels of inorganic phosphate. Ammonium was found to inhibit 86Rb+ transport much less than K+. Also, while K+ produced a competitive type of inhibition, that produced by NH4+ was of the noncompetitive type. From the distribution ratio of ammonium and the pH gradient, an electrochemical potential gradient of around -180 mV was calculated. The results indicate that ammonium is transported in yeast by a mechanism similar to that of monovalent alkaline cations, driven by a membrane potential. The immediate metabolic effects of this cation seem to be due to an increased (H+)ATPase, to which its transport is coupled. However, the carriers seem to be different. The transport system studied in this work was that of low affinity.

  4. Clinoptilolite: a possible support material for nitrifying biofilms for effective control of ammonium effluent quality?

    PubMed

    Inan, H; Beler Baykal, B

    2005-01-01

    Ammonium selective natural zeolite clinoptilolite is suggested as a possible support material for nitrifying biofilms to help improve effluent ammonium quality through its high capacity of ammonium removal in the process of ion exchange. This will especially be helpful in cases where the biofilter receives peak or variable loads routinely or occasionally. At the time of peak loads or shocks of ammonium, ion exchange capacity will provide a buffer for the effluent ammonium quality. Data to support this suggestion is presented.

  5. Ammonium excretion in two benthic cnidarians: Alcyonium digitatum (Linnaeus, 1758) and Urticina felina (Linnaeus, 1767)

    NASA Astrophysics Data System (ADS)

    Migné, A.; Davoult, D.

    1997-05-01

    As part of an evaluation of nitrogen fluxes between the water column and a macrobenthic community of the Strait of Dover (eastern English Channel), ammonium excretion was measured throughout the year in two common cnidarians (the octocoral Alcyonium digitatum and the sea anemone Urticina felina) which together accounted for 37% of the biomass. Mean ammonium excretion rates were 6.48 (±2.44 s.d.) μg N g -1 h -1 (ash-free dry weight) for A. digitatum and 4.12 (±l.38 s.d.) μg N g -1 h -1 for U. felina. Seasonal variations were observed in the excretion of A. digitatum, whereas such variations were less pronounced in U. felina. These trends are discussed in relation to temperature, food availability, nutritional state and nutritional habits of the two species. The results of this and a previous study indicate a nitrogen production of 18.9 g N m -2 y -1 for the entire benthic community.

  6. Recurrent Escherichia coli bacteremia.

    PubMed Central

    Maslow, J N; Mulligan, M E; Arbeit, R D

    1994-01-01

    Escherichia coli is the most common gram-negative organism associated with bacteremia. While recurrent E. coli urinary tract infections are well-described, recurrent E. coli bacteremia appears to be uncommon, with no episodes noted in multiple series of patients with gram-negative bacteremias. We report on 5 patients with recurrent bloodstream infections identified from a series of 163 patients with E. coli bacteremia. For each patient, the isolates from each episode were analyzed by pulsed-field gel electrophoresis (PFGE) and ribotyping and for the presence of E. coli virulence factors. For each of four patients, the index and recurrent episodes of bacteremia represented the same strain as defined by PFGE, and the strains were found to carry one or more virulence factors. The remaining patient, with two episodes of bloodstream infection separated by a 4-year interval, was infected with two isolates that did not carry any virulence factors and that were clonally related by ribotype analysis but differed by PFGE. All five patients had either a local host defense defect (three patients) or impaired systemic defenses (one patient) or both (one patient). Thus, recurrent E. coli bacteremia is likely to represent a multifactorial process that occurs in patients with impaired host defenses who are infected with virulent isolates. Images PMID:7910828

  7. Ammonium Removal from Synthetic Stormwater using Clinoptilolite and Hydroaluminosilicate Columns.

    PubMed

    Khorsha, Golnaz; Davis, Allen P

    2017-06-01

    Ammonium can enter stormwater control measures (SCMs) with the influent, but is also the intermediate product between organic nitrogen and nitrate, and it is important to retain and treat ammonium within the SCM. In this study the use of aluminosilicate aggregates (CA) and clinoptilolite zeolite (ZT) was investigated under SCM (column) conditions. ZT was found to have the highest capacity (0.45 mg -N/g ZT vis-à-vis 0.33 mg -N/g CA) at 2.5 mg NH4-N/L. The presence of Ca2+ and K+ was found to reduce the capacity of the media significantly. Increasing the contact time from 10 minutes to 47 minutes enhanced the removal efficiency of the system by 70% for CA and 23% for ZT, respectively. Finally, changes in the influent ammonium concentration resulted in successful removal during concentration increases, but desorption of ammonium for sudden concentration reduction. The use of ZT in media-based SCMs is recommended for ammonium removal.

  8. Electrospray ionization tandem mass spectrometry of ammonium cationized polyethers.

    PubMed

    Nasioudis, Andreas; Heeren, Ron M A; van Doormalen, Irene; de Wijs-Rot, Nicolette; van den Brink, Oscar F

    2011-05-01

    Quaternary ammonium salts (Quats) and amines are known to facilitate the MS analysis of high molar mass polyethers by forming low charge state adduct ions. The formation, stability, and behavior upon collision-induced dissociation (CID) of adduct ions of polyethers with a variety of Quats and amines were studied by electrospray ionization quadrupole time-of-flight, quadrupole ion trap, and linear ion trap tandem mass spectrometry (MS/MS). The linear ion trap instrument was part of an Orbitrap hybrid mass spectrometer that allowed accurate mass MS/MS measurements. The Quats and amines studied were of different degree of substitution, structure, and size. The stability of the adduct ions was related to the structure of the cation, especially the amine's degree of substitution. CID of singly/doubly charged primary and tertiary ammonium cationized polymers resulted in the neutral loss of the amine followed by fragmentation of the protonated product ions. The latter reveals information about the monomer unit, polymer sequence, and endgroup structure. In addition, the detection of product ions retaining the ammonium ion was observed. The predominant process in the CID of singly charged quaternary ammonium cationized polymers was cation detachment, whereas their doubly charged adduct ions provided the same information as the primary and tertiary ammonium cationized adduct ions. This study shows the potential of specific amines as tools for the structural elucidation of high molar mass polyethers.

  9. Electrospray Ionization Tandem Mass Spectrometry of Ammonium Cationized Polyethers

    NASA Astrophysics Data System (ADS)

    Nasioudis, Andreas; Heeren, Ron M. A.; van Doormalen, Irene; de Wijs-Rot, Nicolette; van den Brink, Oscar F.

    2011-05-01

    Quaternary ammonium salts (Quats) and amines are known to facilitate the MS analysis of high molar mass polyethers by forming low charge state adduct ions. The formation, stability, and behavior upon collision-induced dissociation (CID) of adduct ions of polyethers with a variety of Quats and amines were studied by electrospray ionization quadrupole time-of-flight, quadrupole ion trap, and linear ion trap tandem mass spectrometry (MS/MS). The linear ion trap instrument was part of an Orbitrap hybrid mass spectrometer that allowed accurate mass MS/MS measurements. The Quats and amines studied were of different degree of substitution, structure, and size. The stability of the adduct ions was related to the structure of the cation, especially the amine's degree of substitution. CID of singly/doubly charged primary and tertiary ammonium cationized polymers resulted in the neutral loss of the amine followed by fragmentation of the protonated product ions. The latter reveals information about the monomer unit, polymer sequence, and endgroup structure. In addition, the detection of product ions retaining the ammonium ion was observed. The predominant process in the CID of singly charged quaternary ammonium cationized polymers was cation detachment, whereas their doubly charged adduct ions provided the same information as the primary and tertiary ammonium cationized adduct ions. This study shows the potential of specific amines as tools for the structural elucidation of high molar mass polyethers.

  10. Loss of Fine Particle Ammonium from Denuded Nylon Filters

    SciTech Connect

    Yu, Xiao-Ying; Lee, Taehyoung; Ayres, Benjamin; Kreidenweis, Sonia M.; Malm, William C.; Collett, Jeffrey L.

    2006-08-01

    Ammonium is an important constituent of fine particulate mass in the atmosphere, but can be difficult to quantify due to possible sampling artifacts. Losses of semivolatile species such as NH4NO3 can be particularly problematic. In order to evaluate ammonium losses from aerosol particles collected on filters, a series of field experiments was conducted using denuded nylon and Teflon filters at Bondville, Illinois (February 2003), San Gorgonio, California (April 2003 and July 2004), Grand Canyon National Park, Arizona (May, 2003), Brigantine, New Jersey (November 2003), and Great Smoky Mountains National Park (NP), Tennessee (July–August 2004). Samples were collected over 24-hr periods. Losses from denuded nylon filters ranged from 10% (monthly average) in Bondville, Illinois to 28% in San Gorgonio, California in summer. Losses on individual sample days ranged from 1% to 65%. Losses tended to increase with increasing diurnal temperature and relative humidity changes and with the fraction of ambient total N(--III) (particulate NH4+ plus gaseous NH3) present as gaseous NH3. The amount of ammonium lost at most sites could be explained by the amount of NH4NO3 present in the sampled aerosol. Ammonium losses at Great Smoky Mountains NP, however, significantly exceeded the amount of NH4NO3 collected. Ammoniated organic salts are suggested as additional important contributors to observed ammonium loss at this location.

  11. Modeling of alkyl quaternary ammonium cations intercalated into montmorillonite lattice

    SciTech Connect

    Daoudi, El Mehdi; Boughaleb, Yahia; El Gaini, Layla; Meghea, Irina; Bakasse, Mina

    2013-05-15

    Highlights: ► The modification of montmorillonites by three surfactants increases the basal spacing. ► The model proposed show a bilayer conformation for the surfactant ODTMA. ► The DODMA and TOMA surfactants adopt a paraffin type arrangement. ► Behavior of surfactants in interlayer space was confirmed by TGA and ATR analysis. - Abstract: The objective of this work was to study the conformation of the quaternary ammonium cations viz., octadecyl trimethyl ammonium (ODTMA), dioctadecyl dimethyl ammonium (DMDOA) and trioctadecyl methyl ammonium (TOMA) intercalated within montmorillonite. The modified montmorillonite was characterized by X-ray diffraction in small angle (SAXS), thermal analysis (TGA) and infrared spectroscopy of attenuated total reflection (ATR). The modification of organophilic montmorillonites by the three surfactants ODTMA, DMDOA and TOMA increases the basal spacing from their respective intercalated distances of 1.9 nm, 2.6 nm and 3.4 nm respectively. The increase in the spacing due to the basic organic modification was confirmed by the results of thermal analysis (TGA) and infrared spectroscopy (ATR), and also supported by theoretical calculations of longitudinal and transversal chain sizes of these alkyl quaternary ammonium cations.

  12. Loss of fine particle ammonium from denuded nylon filters

    NASA Astrophysics Data System (ADS)

    Yu, Xiao-Ying; Lee, Taehyoung; Ayres, Benjamin; Kreidenweis, Sonia M.; Malm, William; Collett, Jeffrey L.

    Ammonium is an important constituent of fine particulate mass in the atmosphere, but can be difficult to quantify due to possible sampling artifacts. Losses of semivolatile species such as NH 4NO 3 can be particularly problematic. In order to evaluate ammonium losses from aerosol particles collected on filters, a series of field experiments was conducted using denuded nylon and Teflon filters at Bondville, IL (February 2003), San Gorgonio, CA (April 2003 and July 2004), Grand Canyon NP, AZ (May, 2003), Brigantine, NJ (November 2003), and Great Smoky Mountains National Park (NP), TN (July-August 2004). Samples were collected over 24 h periods. Losses from denuded nylon filters ranged from 10% (monthly average) in Bondville, IL to 28% in San Gorgonio, CA in summer. Losses on individual sample days ranged from 1% to 65%. Losses tended to increase with increasing diurnal temperature and relative humidity changes and with the fraction of ambient total N(-III) (particulate NH 4++gaseous NH 3) present as gaseous NH 3. The amount of ammonium lost at most sites could be explained by the amount of NH 4NO 3 present in the sampled aerosol. Ammonium losses at Great Smoky Mountains NP, however, significantly exceeded the amount of NH 4NO 3 collected. Ammoniated organic salts are suggested as additional important contributors to observed ammonium loss at this location.

  13. Climate impact of solid ammonium sulfate aerosols as ice nuclei

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Penner, J.

    2016-12-01

    Laboratory experiments show that solid ammonium sulfate aerosols can act as heterogeneous ice nuclei particles (INPs) in the deposition mode. In this study we used the coupled IMPACT/CAM5 model to track the efflorescence and deliquescence of ammonium sulfate. Liquid pure ammonium sulfate particles effloresce when RHw is below 34% and dissolve when RHw is above 79%. About 1/3 of the total simulated sulfate aerosol mass is in the solid state. When 0.1% of these solid ammonium sulfate aerosols are assumed to be efficient ice nuclei, they act to reduce the bias in simulated ice particle number concentration in cirrus clouds by reducing ice particle number in cold cirrus clouds (T<205 K) and increasing ice particle number in warm cirrus clouds (T>215K). The increased ice particles in warm cirrus clouds lead to an increase in the IWP and a net global warming effect as large as 3 W/m2. The magnitude of the warming effect can vary if a different efficiency of solid ammonium sulfate aerosols acting as ice nuclei particles is assumed.

  14. Removing ammonium from water using modified corncob-biochar.

    PubMed

    Vu, Thi Mai; Trinh, Van Tuyen; Doan, Dinh Phuong; Van, Huu Tap; Nguyen, Tien Vinh; Vigneswaran, Saravanamuthu; Ngo, Huu Hao

    2017-02-01

    Ammonium pollution in groundwater and surface water is of major concern in many parts of the world due to the danger it poses to the environment and people's health. This study focuses on the development of a low cost adsorbent, specifically a modified biochar prepared from corncob. Evaluated here is the efficiency of this new material for removing ammonium from synthetic water (ammonium concentration from 10 to 100mg/L). The characteristics of the modified biochar were determined by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). It was found that ammonium adsorption on modified biochar strongly depended on pH. Adsorption kinetics of NH4(+)-N using modified biochar followed the pseudo-second order kinetic model. Both Langmuir and Sips adsorption isotherm models could simulate well the adsorption behavior of ammonium on modificated biochar. The highest adsorption capacity of 22.6mg NH4(+)-N/g modified biochar was obtained when the biochar was modified by soaking it in HNO3 6M and NaOH 0.3M for 8h and 24h, respectively. The high adsorption capacity of the modified biochar suggested that it is a promising adsorbent for NH4(+)-N remediation from water.

  15. Fractionation of bamboo hemicelluloses by graded saturated ammonium sulphate.

    PubMed

    Guan, Ying; Zhang, Bing; Qi, Xian-Ming; Peng, Feng; Yao, Chun-Li; Sun, Run-Cang

    2015-09-20

    The hemicelluloses were isolated with 10% KOH at 25°C from dewaxed and delignified bamboo powder. The alkali-soluble hemicelluloses from Sinocalamus affinis were fractionated by ammonium sulphate precipitation method. The bamboo alkali-soluble hemicelluloses yielded seven hemicellulosic fractions obtained at 0, 5, 15, 25, 40, 55, and 70% saturation with ammonium sulphate. It was found that the more branched hemicelluloses were precipitated at higher ammonium sulphate concentrations (55 and 70%), the more linear hemicelluloses were precipitated at lower ammonium sulphate concentrations (0, 5, 15, 25, and 40%). The molecular weights of hemicellulosic fractions become lower from 35,270 (H0) to 18,680 (H70)gmol(-1) with the increasing concentrations of saturated ammonium sulphate from 0 to 70%. Based on the FT-IR, (1)H, (13)C and 2D HSQC NMR studies, the alkali-soluble hemicelluloses were 4-O-methyl-glucuronoarabinoxylans composed of the (1→4)-linked β-d-xylopyranosyl backbone with branches at O-3 of α-L-arabinofuranosyl or at O-2 of 4-O-methyl-α-d-glucuronic acid.

  16. Simultaneous removal of ammonium and suspended solids in multipurpose filters.

    PubMed

    Alkas, Deniz; Baykal, Bilsen Beler; Kinaci, Cumali

    2012-06-01

    A multipurpose filter in which sand and clinoptilolite are used together as filter material is suggested for the simultaneous removal of suspended solids and ammonium in one single unit. The capacity of the clinoptilolite used was determined as 10.4 mg/g for 20 mg/l initial ammonium concentration. In addition, a packed column ion exchanger with clinoptilolite and a classical sand filter were also investigated for comparison. Ammonium and suspended solids removal rates were observed and compared for all columns. The results of the column analysis have revealed that the ammonium removal rate, which was only 20% in the sand column, was increased to 100% by replacing 50% of the sand with clinoptilolite; similarly, the suspended solids removal, which was only 17% in the clinoptilolite column, was increased to 75% by replacing 50% of the clinoptilolite with sand. As such, when ion exchange and filtration processes were carried out in a multipurpose column, high removals for both parameters could be obtained simultaneously. Multipurpose columns could be an alternative both for the upgrading of existing treatment plants or for new plants for simultaneous removal of ammonium and suspended solids, giving considerable savings in terms of land requirements.

  17. Effects of bisphenol A on ammonium assimilation in soybean roots.

    PubMed

    Sun, Hai; Wang, Li Hong; Zhou, Qing; Huang, Xiao Hua

    2013-12-01

    Bisphenol A (BPA), which is ubiquitous in the environment, is an example of an endocrine-disrupting compound (EDC). Ammonium assimilation has an important function in plant growth and development. However, insufficient information on the potential effect of BPA on ammonium assimilation in plants is available. In this study, the effects of BPA on ammonium assimilation in roots of soybean seedlings were investigated. During the stress period, 1.5 mg L(-1) of BPA improved glutamine synthetase (GS)/glutamate synthase (GOGAT) cycle and glutamate dehydrogenase (GDH) pathway in ammonium assimilation. The amino acid and the soluble protein contents increased in the soybeans. At 17.2 and 50.0 mg L(-1) of BPA, the GS/GOGAT cycle was inhibited and the GDH pathway was promoted. The amino acid content increased and the soluble protein content decreased. During the recovery period, the GS/GOGAT cycle and the GDH pathway recovered at 1.5 and 17.2 mg L(-1) of BPA but not at 50.0 mg L(-1) of BPA. The amino acid content continuously increased and the soluble protein content decreased compared with those in the control treatment. In summary, BPA treatment could affect the contents of soluble protein and amino acid in the soybean roots by regulating ammonium assimilation.

  18. Anomalous neutron Compton scattering cross sections in ammonium hexachlorometallates

    NASA Astrophysics Data System (ADS)

    Krzystyniak, M.; Chatzidimitriou-Dreismann, C. A.; Lerch, M.; Lalowicz, Z. T.; Szymocha, A.

    2007-03-01

    The authors have performed neutron Compton scattering measurements on ammonium hexachloropalladate (NH4)2PdCl6 and ammonium hexachlorotellurate (NH4)2TeCl6. Both substances belong to the family of ammonium metallates. The aim of the experiment was to investigate the possible role of electronic environment of a proton on the anomaly of the neutron scattering intensity. The quantity of interest that was subject to experimental test was the reduction factor of the neutron scattering intensities. In both samples, the reduction factor was found to be smaller than unity, thus indicating the anomalous neutron Compton scattering from protons. Interestingly, the anomaly decreases with decreasing scattering angle and disappears at the lowest scattering angle (longest scattering time). The dependence of the amount of the anomaly on the scattering angle (scattering time) is the same in both substances (within experimental error). Also, the measured widths of proton momentum distributions are equal in both metallates. This is consistent with the fact that the attosecond proton dynamics of ammonium cations is fairly well decoupled from the dynamics of the sublattice of the octahedral anions PdCl62- and TeCl62-, respectively. The hypothesis is put forward that proton-electron decoherence processes are responsible for the considered effect. Decoherence processes may have to do rather with the direct electronic environment of ammonium protons and not with the electronic structure of the metal-chlorine bond.

  19. The channels of Mars

    NASA Technical Reports Server (NTRS)

    Baker, Victor R.

    1988-01-01

    The geomorphology of Mars is discussed, focusing on the Martian channels. The great flood channels of Mars, the processes of channel erosion, and dendritic channel networks, are examined. The topography of the Channeled Scabland region of the northwestern U.S. is described and compared to the Martian channels. The importance of water in the evolution of the channel systems is considered.

  20. The channels of Mars

    NASA Technical Reports Server (NTRS)

    Baker, Victor R.

    1988-01-01

    The geomorphology of Mars is discussed, focusing on the Martian channels. The great flood channels of Mars, the processes of channel erosion, and dendritic channel networks, are examined. The topography of the Channeled Scabland region of the northwestern U.S. is described and compared to the Martian channels. The importance of water in the evolution of the channel systems is considered.

  1. Expression-dependent pharmacology of transient receptor potential vanilloid subtype 1 channels in Xenopus laevis oocytes

    PubMed Central

    Rivera-Acevedo, Ricardo E.; Pless, Stephan A.; Schwarz, Stephan K.W.; Ahern, Christopher A.

    2013-01-01

    Transient receptor potential vanilloid subfamily member 1 channels are polymodal sensors of noxious stimuli and integral players in thermosensation, inflammation and pain signaling. It has been shown previously that under prolonged stimulation, these channels show dynamic pore dilation, providing a pathway for large and otherwise relatively impermeant molecules. Further, we have shown recently that these nonselective cation channels, when activated by capsaicin, are potently and reversibly blocked by external application of quaternary ammonium compounds and local anesthetics. Here we describe a novel phenomenon in transient receptor potential channel pharmacology whereby their expression levels in Xenopus laevis oocytes, as assessed by the magnitude of macroscopic currents, are negatively correlated with extracellular blocker affinity: small current densities give rise to nanomolar blockade by quaternary ammoniums and this affinity decreases linearly as current density increases. Possible mechanisms to explain these data are discussed in light of similar observations in other channels and receptors. PMID:23428812

  2. The Kinetics and the Permeation Properties of Piezo Channels.

    PubMed

    Gnanasambandam, R; Gottlieb, P A; Sachs, F

    2017-01-01

    Piezo channels are eukaryotic, cation-selective mechanosensitive channels (MSCs), which show rapid activation and voltage-dependent inactivation. The kinetics of these channels are largely consistent across multiple cell types and different stimulation paradigms with some minor variability. No accessory subunits that associate with Piezo channels have been reported. They are homotrimers and each ∼300kD monomer has an N-terminal propeller blade-like mechanosensing module, which can confer mechanosensing capabilities on ASIC-1 (the trimeric non-MSC, acid-sensing ion channel-1) and a C-terminal pore module, which influences conductance, selectivity, and channel inactivation. Repeated stimulation can cause domain fracture and diffusion of these channels leading to synchronous loss of inactivation. The reconstituted channels spontaneously open only in asymmetric bilayers but lack inactivation. Mutations that cause hereditary xerocytosis alter PIEZO1 kinetics. The kinetics of the wild-type PIEZO1 and alterations thereof in mutants (M2225R, R2456K, and DhPIEZO1) are summarized in the form of a quantitative model and hosted online. The pore is permeable to alkali ions although Li(+) permeates poorly. Divalent cations, notably Ca(2+), traverse the channel and inhibit the flux of monovalents. The large monovalent organic cations such as tetramethyl ammonium and tetraethyl ammonium can traverse the channel, but slowly, suggesting a pore diameter of ∼8Å, and the estimated in-plane area change upon opening is around 6-20nm(2). Ruthenium red can enter the channel only from the extracellular side and seems to bind in a pocket close to residue 2496. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Inverted Channels

    NASA Technical Reports Server (NTRS)

    2006-01-01

    23 June 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sinuous ridges and other landforms exposed by erosion in the Aeolis region of Mars. The ridges in this scene indicate the locations of ancient channels in a fan of sediment deposited in this region. Over time, wind erosion has removed surrounding materials and left the channels, which had been filled by sediment, standing as ridges.

    Location near: 4.5oS, 205.2oW Image width: 2 km (1.2 mi) Illumination from: upper left Season: Southern Autumn

  4. Starburst Channels

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Figure 1

    Translucent carbon dioxide ice covers the polar regions of Mars seasonally. It is warmed and sublimates (evaporates) from below, and escaping gas carves a numerous channel morphologies.

    In this example (figure 1) the channels form a 'starburst' pattern, radiating out into feathery extensions. The center of the pattern is being buried with dust and new darker dust fans ring the outer edges. This may be an example of an expanding morphology, where new channels are formed as the older ones fill and are no longer efficiently channeling the subliming gas out.

    Observation Geometry Image PSP_003443_0980 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 21-Apr-2007. The complete image is centered at -81.8 degrees latitude, 76.2 degrees East longitude. The range to the target site was 247.1 km (154.4 miles). At this distance the image scale is 24.7 cm/pixel (with 1 x 1 binning) so objects 74 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel. The image was taken at a local Mars time of 04:52 PM and the scene is illuminated from the west with a solar incidence angle of 71 degrees, thus the sun was about 19 degrees above the horizon. At a solar longitude of 223.4 degrees, the season on Mars is Northern Autumn.

  5. Starburst Channels

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Figure 1

    Translucent carbon dioxide ice covers the polar regions of Mars seasonally. It is warmed and sublimates (evaporates) from below, and escaping gas carves a numerous channel morphologies.

    In this example (figure 1) the channels form a 'starburst' pattern, radiating out into feathery extensions. The center of the pattern is being buried with dust and new darker dust fans ring the outer edges. This may be an example of an expanding morphology, where new channels are formed as the older ones fill and are no longer efficiently channeling the subliming gas out.

    Observation Geometry Image PSP_003443_0980 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 21-Apr-2007. The complete image is centered at -81.8 degrees latitude, 76.2 degrees East longitude. The range to the target site was 247.1 km (154.4 miles). At this distance the image scale is 24.7 cm/pixel (with 1 x 1 binning) so objects 74 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel. The image was taken at a local Mars time of 04:52 PM and the scene is illuminated from the west with a solar incidence angle of 71 degrees, thus the sun was about 19 degrees above the horizon. At a solar longitude of 223.4 degrees, the season on Mars is Northern Autumn.

  6. Cetyltrimethyl ammonium bromide assisted hydrothermal growth of hematite hollow cubes

    SciTech Connect

    Wang, Wei-Wei; Yao, Jia-Liang

    2010-11-15

    Hematite hollow cubes have been prepared by forced hydrolysis of ferric chloride solutions under hydrothermal conditions. The effects of reaction time, reaction temperature and cetyltrimethyl ammonium bromide on the transformation process from akageneite to hematite were investigated in detail. The products were characterized by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. It is found that cetyltrimethyl ammonium bromide was a critical factor influencing the phase transformation process of akageneite and the final morphology of the as-prepared products. With cetyltrimethyl ammonium bromide, hematite hollow cubes and porous spheres were obtained. Otherwise only dense cubes were observed even prolonging reaction time or increasing reaction temperature. The mechanism was proposed.

  7. Exposure to common quaternary ammonium disinfectants decreases fertility in mice

    PubMed Central

    Melin, Vanessa E.; Potineni, Haritha; Hunt, Patricia; Griswold, Jodi; Siems, Bill; Werre, Stephen R.; Hrubec, Terry C.

    2014-01-01

    Quaternary ammonium compounds (QACs) are antimicrobial disinfectants commonly used in commercial and household settings. Extensive use of QACs results in ubiquitous human exposure, yet reproductive toxicity has not been evaluated. Decreased reproductive performance in laboratory mice coincided with the introduction of a disinfectant containing both alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyl dimethyl ammonium chloride (DDAC). QACs were detected in caging material over a period of several months following cessation of disinfectant use. Breeding pairs exposed for six months to a QAC disinfectant exhibited decreases in fertility and fecundity: increased time to first litter, longer pregnancy intervals, fewer pups per litter and fewer pregnancies. Significant morbidity in near term dams was also observed. In summary, exposure to a common QAC disinfectant mixture significantly impaired reproductive health in mice. This study illustrates the importance of assessing mixture toxicity of commonly used products whose components have only been evaluated individually. PMID:25483128

  8. Effect of temperature on ammonium removal in Scenedesmus sp.

    PubMed

    Ruiz-Martínez, A; Serralta, J; Seco, A; Ferrer, J

    2015-09-01

    The effect of temperature on microalgal ammonium uptake was investigated by carrying out four batch experiments in which a mixed culture of microalgae, composed mainly of Scenedesmus sp., was cultivated under different temperatures within the usual temperature working range in Mediterranean climate (15-34 °C). Ammonium removal rates increased with temperature up to 26 °C and stabilized thereafter. Ratkowsky and Cardinal temperatures models successfully reproduced the experimental data. Optimum (31.3 °C), minimum (8.8 °C) and maximum (46.1 °C) temperatures for ammonium removal by Scenedesmus sp. under the studied conditions were obtained as model parameters. These temperature-related parameters constitute very useful information for designing and operating wastewater treatment systems using these microalgae.

  9. Study on mechanism of isomerization between ammonium thiocyanate and thiourea

    NASA Astrophysics Data System (ADS)

    Zhang, Chao-Zhi; Niu, Meng-Xiao

    2016-12-01

    Application of ammonium thiocyanate that can be separated from wastewater in coking plant is limited. It may isomerize to thiourea which has widely applied in industry. However, the isomerization yield is low. Moreover, the isomerization temperature is more than 145 °C. In this paper, the isomerization was investigated. The mechanism of the isomerization was supposed based on quantum chemistry calculations. Ammonia was employed as a catalyst to lower isomerization temperature and improved the yield of thiourea in the isomerization reaction. Results of quantum chemical calculation and experiments support the supposed mechanism. The mechanism can be applied in production of thiourea from isomerization of ammonium thiocyanate. The paper suggests a useful way of resourcizing ammonium thiocyanate in wastewater.

  10. Exposure to common quaternary ammonium disinfectants decreases fertility in mice.

    PubMed

    Melin, Vanessa E; Potineni, Haritha; Hunt, Patricia; Griswold, Jodi; Siems, Bill; Werre, Stephen R; Hrubec, Terry C

    2014-12-01

    Quaternary ammonium compounds (QACs) are antimicrobial disinfectants commonly used in commercial and household settings. Extensive use of QACs results in ubiquitous human exposure, yet reproductive toxicity has not been evaluated. Decreased reproductive performance in laboratory mice coincided with the introduction of a disinfectant containing both alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyl dimethyl ammonium chloride (DDAC). QACs were detected in caging material over a period of several months following cessation of disinfectant use. Breeding pairs exposed for six months to a QAC disinfectant exhibited decreases in fertility and fecundity: increased time to first litter, longer pregnancy intervals, fewer pups per litter and fewer pregnancies. Significant morbidity in near term dams was also observed. In summary, exposure to a common QAC disinfectant mixture significantly impaired reproductive health in mice. This study illustrates the importance of assessing mixture toxicity of commonly used products whose components have only been evaluated individually. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Ammonium as a sustainable proton shuttle in bioelectrochemical systems.

    PubMed

    Cord-Ruwisch, Ralf; Law, Yingyu; Cheng, Ka Yu

    2011-10-01

    This work examines a pH control method using ammonium (NH(4)(+)) as a sustainable proton shuttle in a CEM-equipped BES. Current generation was sustained by adding NH(3) or ammonium hydroxide (NH(4)OH) to the anolyte, controlling its pH at 7. Ammonium ion migration maintained the catholyte pH at approximately 9.25. Such NH(4)(+)/NH(3) migration accounted for 90±10% of the ionic flux in the BES. Reintroducing the volatilized NH(3) from the cathode into the anolyte maintained a suitable anolyte pH for sustained microbial-driven current generation. Hence, NH(4)(+)/NH(3) acted as a proton shuttle that is not consumed in the process.

  12. Ammonium and sulfate ion release of histamine from lung fragments.

    PubMed

    Charles, J M; Menzel, D B

    1975-06-01

    In vitro studies with guinea pig lung fragments incubated with 10- to 200-mM concentrations of ammonium ion demonstrated the release of substanial quantities of histamine. Of the anions tested with ammonium ion, sulfate was the most potent, while nitrate and acetate ions were of intermediate potency and chloride was less potent. An osmotic effect is unlikely since equal concentrations of sodium chloride failed to release histamine. Isoproterenol, known to decrease anaphylactic histamine release, and acetycholine, known to increase histamine release, had no effect on the ammonium sulfate-mediated release of histamine. N-6 2'-O-Dibutyryladenosine 3',5' monophosphate (dibutyryl c-AMP) was also ineffective. These studies suggest that the inhalation irritation associated with certain sulfate and other salts, may be a function of their ability to release histamine in the presence of amonium ion.

  13. Handling of Ammonium Nitrate Mother-Liquid Radiochemical Production - 13089

    SciTech Connect

    Zherebtsov, Alexander; Dvoeglazov, Konstantine; Volk, Vladimir; Zagumenov, Vladimir; Zverev, Dmitriy; Tinin, Vasiliy; Kozyrev, Anatoly; Shamin, Dladimir; Tvilenev, Konstantin

    2013-07-01

    The aim of the work is to develop a basic technology of decomposition of ammonium nitrate stock solutions produced in radiochemical enterprises engaged in the reprocessing of irradiated nuclear fuel and fabrication of fresh fuel. It was necessary to work out how to conduct a one-step thermal decomposition of ammonium nitrate, select and test the catalysts for this process and to prepare proposals for recycling condensation. Necessary accessories were added to a laboratory equipment installation decomposition of ammonium nitrate. It is tested several types of reducing agents and two types of catalyst to neutralize the nitrogen oxides. It is conducted testing of modes of the process to produce condensation, suitable for use in the conversion of a new technological scheme of production. It is studied the structure of the catalysts before and after their use in a laboratory setting. It is tested the selected catalyst in the optimal range for 48 hours of continuous operation. (authors)

  14. Ferric ammonium citrate decomposition--a taxonomic tool for gram-negative bacteria.

    PubMed

    Szentmihályi, A; Lányi, B

    1986-01-01

    The iron uptake test of Szabó and Vandra has been modified and used for the differentiation of Gram-negative bacteria. Nutrient agar containing 20 g per litre of ferric ammonium citrate was distributed into narrow tubes and solidified so as to form butts and slants. Considering the localization of the rusty-brown coloration produced after seeding and incubation, 2367 strains were classified into four groups. (1) Unchanged medium: Escherichia coli, Shigella spp., Yersinia spp., Hafnia alvei and Morganella morganii 100% each, Klebsiella spp., 50%, Enterobacter cloacae 37%, Proteus vulgaris 59%, Acinetobacter spp. 42%, Pseudomonas fluorescens 19%, some other bacteria 2-12%. (2) Rusty-brown slant, unchanged butt: Salmonella subgenera II, III and IV 98%, Citrobacter freundii 65%, E. cloacae 55%, P. vulgaris 41%, Proteus mirabilis 98%, Providencia rettgeri 100%, urease-negative Providencia 96%, Acinetobacter spp. 58%, Pseudomonas aeruginosa 100%, P. fluorescens 81%, UFP (unclassified fluorescent pseudomonads) 100%, other Pseudomonas spp. 55%. (3) Unchanged slant, brown butt: S. typhi 88%, Salmonella subgenus I 3%, Klebsiella spp. 31%, some other bacteria 2-3%. (4) Rusty-brown slant, brown butt: Salmonella subgenus I 75%, C. freundii 20%, Klebsiella spp. 12%, some other bacteria 1-5%. Colour reactions in ferric ammonium citrate agar are associated with the accumulation of ferric hydroxide: bacteria giving positive reactions on the slant took up as an average, 63 times more iron than those with negative test. The localization of colour reaction correlated partly with aerobic and anaerobic citrate utilization or decomposition in Simmons' minimal and in Kauffmann's peptone water medium.

  15. Optogenetic photochemical control of designer K+ channels in mammalian neurons

    PubMed Central

    Fortin, Doris L.; Dunn, Timothy W.; Fedorchak, Alexis; Allen, Duane; Montpetit, Rachel; Banghart, Matthew R.; Trauner, Dirk; Adelman, John P.

    2011-01-01

    Currently available optogenetic tools, including microbial light-activated ion channels and transporters, are transforming systems neuroscience by enabling precise remote control of neuronal firing, but they tell us little about the role of indigenous ion channels in controlling neuronal function. Here, we employ a chemical-genetic strategy to engineer light sensitivity into several mammalian K+ channels that have different gating and modulation properties. These channels provide the means for photoregulating diverse electrophysiological functions. Photosensitivity is conferred on a channel by a tethered ligand photoswitch that contains a cysteine-reactive maleimide (M), a photoisomerizable azobenzene (A), and a quaternary ammonium (Q), a K+ channel pore blocker. Using mutagenesis, we identify the optimal extracellular cysteine attachment site where MAQ conjugation results in pore blockade when the azobenzene moiety is in the trans but not cis configuration. With this strategy, we have conferred photosensitivity on channels containing Kv1.3 subunits (which control axonal action potential repolarization), Kv3.1 subunits (which contribute to rapid-firing properties of brain neurons), Kv7.2 subunits (which underlie “M-current”), and SK2 subunits (which are Ca2+-activated K+ channels that contribute to synaptic responses). These light-regulated channels may be overexpressed in genetically targeted neurons or substituted for native channels with gene knockin technology to enable precise optopharmacological manipulation of channel function. PMID:21525363

  16. Nonlinear channelizer.

    PubMed

    In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D; Leung, Daniel; Liu, Norman; Meadows, Brian K; Gordon, Frank; Bulsara, Adi R; Palacios, Antonio

    2012-12-01

    The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.

  17. Nonlinear channelizer

    NASA Astrophysics Data System (ADS)

    In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D.; Leung, Daniel; Liu, Norman; Meadows, Brian K.; Gordon, Frank; Bulsara, Adi R.; Palacios, Antonio

    2012-12-01

    The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.

  18. Selectivity filter gating in large-conductance Ca(2+)-activated K+ channels.

    PubMed

    Thompson, Jill; Begenisich, Ted

    2012-03-01

    Membrane voltage controls the passage of ions through voltage-gated K (K(v)) channels, and many studies have demonstrated that this is accomplished by a physical gate located at the cytoplasmic end of the pore. Critical to this determination were the findings that quaternary ammonium ions and certain peptides have access to their internal pore-blocking sites only when the channel gates are open, and that large blocking ions interfere with channel closing. Although an intracellular location for the physical gate of K(v) channels is well established, it is not clear if such a cytoplasmic gate exists in all K(+) channels. Some studies on large-conductance, voltage- and Ca(2+)-activated K(+) (BK) channels suggest a cytoplasmic location for the gate, but other findings question this conclusion and, instead, support the concept that BK channels are gated by the pore selectivity filter. If the BK channel is gated by the selectivity filter, the interactions between the blocking ions and channel gating should be influenced by the permeant ion. Thus, we tested tetrabutyl ammonium (TBA) and the Shaker "ball" peptide (BP) on BK channels with either K(+) or Rb(+) as the permeant ion. When tested in K(+) solutions, both TBA and the BP acted as open-channel blockers of BK channels, and the BP interfered with channel closing. In contrast, when Rb(+) replaced K(+) as the permeant ion, TBA and the BP blocked both closed and open BK channels, and the BP no longer interfered with channel closing. We also tested the cytoplasmically gated Shaker K channels and found the opposite behavior: the interactions of TBA and the BP with these K(v) channels were independent of the permeant ion. Our results add significantly to the evidence against a cytoplasmic gate in BK channels and represent a positive test for selectivity filter gating.

  19. Selectivity filter gating in large-conductance Ca2+-activated K+ channels

    PubMed Central

    Thompson, Jill

    2012-01-01

    Membrane voltage controls the passage of ions through voltage-gated K (Kv) channels, and many studies have demonstrated that this is accomplished by a physical gate located at the cytoplasmic end of the pore. Critical to this determination were the findings that quaternary ammonium ions and certain peptides have access to their internal pore-blocking sites only when the channel gates are open, and that large blocking ions interfere with channel closing. Although an intracellular location for the physical gate of Kv channels is well established, it is not clear if such a cytoplasmic gate exists in all K+ channels. Some studies on large-conductance, voltage- and Ca2+-activated K+ (BK) channels suggest a cytoplasmic location for the gate, but other findings question this conclusion and, instead, support the concept that BK channels are gated by the pore selectivity filter. If the BK channel is gated by the selectivity filter, the interactions between the blocking ions and channel gating should be influenced by the permeant ion. Thus, we tested tetrabutyl ammonium (TBA) and the Shaker “ball” peptide (BP) on BK channels with either K+ or Rb+ as the permeant ion. When tested in K+ solutions, both TBA and the BP acted as open-channel blockers of BK channels, and the BP interfered with channel closing. In contrast, when Rb+ replaced K+ as the permeant ion, TBA and the BP blocked both closed and open BK channels, and the BP no longer interfered with channel closing. We also tested the cytoplasmically gated Shaker K channels and found the opposite behavior: the interactions of TBA and the BP with these Kv channels were independent of the permeant ion. Our results add significantly to the evidence against a cytoplasmic gate in BK channels and represent a positive test for selectivity filter gating. PMID:22371364

  20. Mutagenic activity of quaternary ammonium salt derivatives of carbohydrates

    PubMed Central

    Sikora, Karol; Woziwodzka, Anna; Piosik, Jacek; Podgórska, Beata

    2016-01-01

    Summary This paper presents a study on a series of quaternary ammonium salt (QAS) derivatives of glucopyranosides with an elongated hydrophobic hydrocarbon chain. The new N-[6-(β-D-glucopyranosyloxy)hexyl]ammonium bromides and their O-acetyl derivatives were analyzed via 1H and 13C NMR spectroscopy. The mutagenic activity of the newly synthesized QAS was investigated using two different techniques: The Vibrio harveyi luminescence assay and the Ames test. The obtained results support previous findings contesting QAS safety and indicate that QAS, specifically pyridinium derivatives, might be mutagenic. PMID:27559394

  1. Construction techniques for adiabatic demagnetization refrigerators using ferric ammonium alum

    NASA Astrophysics Data System (ADS)

    Wilson, Grant W.; Timbie, Peter T.

    1999-07-01

    We describe techniques used to fabricate the cold stage of an adiabatic demagnetization refrigerator that uses the paramagnetic salt ferric ammonium alum. We discuss the design of a leak-tight housing for the salt as well as a technique for growing ferric ammonium alum crystals that results in a housing filled with >98% refrigerant. These techniques have proven to be reliable in creating robust single-stage refrigerators. Similar techniques can be used for the second stage of a dual-stage adiabatic demagnetization refrigerator.

  2. Precipitation of phenyl and phenoxypenicillin from solutions using ammonium sulfate.

    PubMed

    Luengo, J M

    1985-09-01

    An easy, rapid, and available method for separating 6-aminopenicillanic acid (6-APA), benzylpenicillin (penicillin G), and other related molecules from aqueous solutions or complex industrial broths is described. A high concentration of ammonium sulphate induces partially or totally the precipitation of the penicillin present in the solutions, while 6-APA, phenylacetic, and phenoxyacetic acid always remain in the supernatant. The filtration through No. 4 Pyrex glass-fiber filter or Whatman 3MM paper permits the separation of the compounds present in the supernatant from the other ones precipitated. The precipitated product was identified, in all cases, as ammonium penicillin. This method is described here for the first time.

  3. Effects of Ammonium and Non-Ammonium Salt Additions on Methane Oxidation by Methylosinus trichosporium OB3b and Maine Forest Soils.

    PubMed

    King, G M; Schnell, S

    1998-01-01

    Additions of ammonium and non-ammonium salts inhibit atmospheric methane consumption by soil at salt concentrations that do not significantly affect the soil water potential. The response of soils to non-ammonium salts has previously raised questions about the mechanism of ammonium inhibition. Results presented here show that inhibition of methane consumption by non-ammonium salts can be explained in part by ion-exchange reactions: cations desorb ammonium, with the level of desorption varying as a function of both the cation and anion added; differential desorption results in differential inhibition levels. Differences in the extent of inhibition among ammonium salts can also be explained in part by the effects of anions on ammonium exchange. In contrast, only minimal effects of cations and anions are observed in liquid cultures of Methylosinus trichosporium OB3b. The comparable level of inhibition by equinormal concentrations of NH(4)Cl and (NH(4))(2)SO(4) and the insensitivity of salt inhibition to increasing methane concentrations (from 10 to 100 ppm) are of particular interest, since both of these patterns are in contrast to results for soils. The greater inhibition of methane consumption for NH(4)Cl than (NH(4))(2)SO(4) in soils can be attributed to increased ammonium adsorption by sulfate; increasing inhibition by non-ammonium salts with increasing methane concentrations can be attributed to desorbed ammonium and a physiological mechanism proposed previously for pure cultures.

  4. Effects of Ammonium and Non-Ammonium Salt Additions on Methane Oxidation by Methylosinus trichosporium OB3b and Maine Forest Soils†

    PubMed Central

    King, G. M.; Schnell, S.

    1998-01-01

    Additions of ammonium and non-ammonium salts inhibit atmospheric methane consumption by soil at salt concentrations that do not significantly affect the soil water potential. The response of soils to non-ammonium salts has previously raised questions about the mechanism of ammonium inhibition. Results presented here show that inhibition of methane consumption by non-ammonium salts can be explained in part by ion-exchange reactions: cations desorb ammonium, with the level of desorption varying as a function of both the cation and anion added; differential desorption results in differential inhibition levels. Differences in the extent of inhibition among ammonium salts can also be explained in part by the effects of anions on ammonium exchange. In contrast, only minimal effects of cations and anions are observed in liquid cultures of Methylosinus trichosporium OB3b. The comparable level of inhibition by equinormal concentrations of NH4Cl and (NH4)2SO4 and the insensitivity of salt inhibition to increasing methane concentrations (from 10 to 100 ppm) are of particular interest, since both of these patterns are in contrast to results for soils. The greater inhibition of methane consumption for NH4Cl than (NH4)2SO4 in soils can be attributed to increased ammonium adsorption by sulfate; increasing inhibition by non-ammonium salts with increasing methane concentrations can be attributed to desorbed ammonium and a physiological mechanism proposed previously for pure cultures. PMID:16349485

  5. Dynamic Channel Allocation

    DTIC Science & Technology

    2003-09-01

    7 1 . Fixed Channel Allocation (FCA) ........................................................7 2. Dynamic Channel ...19 7. CSMA/CD-Based Multiple Network Lines .....................................20 8. Hybrid Channel Allocation in Wireless Networks...28 1 . Channel Allocation

  6. Destruction of 2,4,6-trinitrotoluene using ammonium peroxydisulfate

    SciTech Connect

    Cooper, J.F.; Wang, F.; Shell, T.; King, K.

    1996-07-01

    TNT was destroyed in a small batch reactor, using uncatalyzed 4 N ammonium peroxydisulfate at 95 {degrees}C. The material was destroyed below limit of detection in less that 15 minutes, indicating a formal order rate constant of 0.06 min{sup -1}. A crude estimate of scaleup rates indicates a throughput of 1 tonne/m{sup 3}-day.

  7. 21 CFR 573.560 - Iron ammonium citrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Iron ammonium citrate. 573.560 Section 573.560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  8. 21 CFR 573.560 - Iron ammonium citrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Iron ammonium citrate. 573.560 Section 573.560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  9. 21 CFR 573.560 - Iron ammonium citrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Iron ammonium citrate. 573.560 Section 573.560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  10. 21 CFR 573.560 - Iron ammonium citrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Iron ammonium citrate. 573.560 Section 573.560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  11. Calorimetry Studies of Ammonia, Nitric Acid, and Ammonium Nitrate

    DTIC Science & Technology

    1979-10-01

    block nmmber) Calorimetry Heat of reaction Ammonium nitrate Heat capacity Nitric acid Heat of solution • Amonia 20. ABSTRACT r(Cmrtfe m,.re a N "no•a.•r sd...identical to the literature spectrum of W NO3. Anhydrous nitric acid was prepared by distillation of 90% HNO 3 from fuming sulfuric acid (oxides of nitrogen

  12. 21 CFR 573.560 - Iron ammonium citrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Iron ammonium citrate. 573.560 Section 573.560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  13. Nitrate, Nitrite, and Ammonium Variability in Drinking Water Distribution Systems.

    PubMed

    Schullehner, Jörg; Stayner, Leslie; Hansen, Birgitte

    2017-03-09

    Accurate assessments of exposure to nitrate in drinking water is a crucial part of epidemiological studies investigating long-term adverse human health effects. However, since drinking water nitrate measurements are usually collected for regulatory purposes, assumptions on (1) the intra-distribution system variability and (2) short-term (seasonal) concentration variability have to be made. We assess concentration variability in the distribution system of nitrate, nitrite, and ammonium, and seasonal variability in all Danish public waterworks from 2007 to 2016. Nitrate concentrations at the exit of the waterworks are highly correlated with nitrate concentrations within the distribution net or at the consumers' taps, while nitrite and ammonium concentrations are generally lower within the net compared with the exit of the waterworks due to nitrification. However, nitrification of nitrite and ammonium in the distribution systems only results in a relatively small increase in nitrate concentrations. No seasonal variation for nitrate, nitrite, or ammonium was observed. We conclude that nitrate measurements taken at the exit of the waterworks are suitable to calculate exposures for all consumers connected to that waterworks and that sampling frequencies in the national monitoring programme are sufficient to describe temporal variations in longitudinal studies.

  14. Growth rate dispersion of small ammonium alum crystals

    NASA Astrophysics Data System (ADS)

    Teodossiev, N.

    1987-01-01

    The growth rates of small (below 60 μm) and large (about 1 mm) crystals of ammonium alum was measured during batch crystallization from aqueous solutions. The growth rate distribution of small crystals is close to normal. With increasing supersaturation the growth rate of the large crystals increases more rapidly than that of small crystals.

  15. Electrodeposition of Californium Using Isobutanol and Aqueous Ammonium Acetate

    NASA Astrophysics Data System (ADS)

    Matoš, Milan; Boll, Rose A.; Phelps, Clarice E.; Torrico, Matthew N.; van Cleve, Shelley M.; Lewis, Benjamin E.

    2013-10-01

    Californium sources and targets are used in many applications in research and industry. Molecular deposition (commonly referred to as electrodeposition) is an experimental technique suitable for production of californium thin films. We are investigating molecular depositions using isobutanol and aqueous ammonium acetate solvents at various conditions to optimize for the best deposition efficiency and repeatability. Results of those tests will be presented.

  16. 21 CFR 184.1296 - Ferric ammonium citrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... FOR HUMAN CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE... brown or garnet red scales or granules or as a brownish-yellowish powder. (2) Ferric ammonium citrate... occurs as thin transparent green scales, as granules, as a powder, or as transparent green crystals....

  17. 21 CFR 184.1296 - Ferric ammonium citrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... FOR HUMAN CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE... brown or garnet red scales or granules or as a brownish-yellowish powder. (2) Ferric ammonium citrate... occurs as thin transparent green scales, as granules, as a powder, or as transparent green crystals....

  18. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... clarification when further processing of the sugar cane juice must be delayed. (d) The additive is applied to... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR... additive, quaternary ammonium chloride combination, may be safely used in food in accordance with the...

  19. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... clarification when further processing of the sugar cane juice must be delayed. (d) The additive is applied to... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR... additive, quaternary ammonium chloride combination, may be safely used in food in accordance with the...

  20. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... clarification when further processing of the sugar cane juice must be delayed. (d) The additive is applied to... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR... additive, quaternary ammonium chloride combination, may be safely used in food in accordance with the...

  1. Semiautomated Microbiological Method for the Assay of Quaternary Ammonium Compounds

    PubMed Central

    Berg, T. M.

    1975-01-01

    A semiautomated method has been developed for quantitatively assaying the activity of detergent disinfectants. Automation permitted a high level of reproducibility, which in turn allowed a meaningful comparison between the activities of some types of quaternary ammonium compounds. Images PMID:808163

  2. A potentiometric tattoo sensor for monitoring ammonium in sweat.

    PubMed

    Guinovart, Tomàs; Bandodkar, Amay J; Windmiller, Joshua R; Andrade, Francisco J; Wang, Joseph

    2013-11-21

    The development and analytical characterization of a novel ion-selective potentiometric cell in a temporary-transfer tattoo platform for monitoring ammonium levels in sweat is presented. The fabrication of this skin-worn sensor, which is based on a screen-printed design, incorporates all-solid-state potentiometric sensor technology for both the working and reference electrodes, in connection to ammonium-selective polymeric membrane based on the nonactin ionophore. The resulting tattooed potentiometric sensor exhibits a working range between 10(-4) M to 0.1 M, well within the physiological levels of ammonium in sweat. Testing under stringent mechanical stress expected on the epidermis shows that the analytical performance is not affected by factors such as stretching or bending. Since the levels of ammonium are related to the breakdown of proteins, the new wearable potentiometric tattoo sensor offers considerable promise for monitoring sport performance or detecting metabolic disorders in healthcare. Such combination of the epidermal integration, screen-printed technology and potentiometric sensing represents an attractive path towards non-invasive monitoring of a variety of electrolytes in human perspiration.

  3. INVESTIGATION OF SENSITIVITY OF FERTILIZER GRADE AMMONIUM NITRATE TO EXPLOSION

    DTIC Science & Technology

    In order to determine the probable cause and mechanism of the explosion of cargoes of fertilizer grade ammonium nitrate on shipboard at Texas City...undergo explosion and in turn initiate the explosion of unconsumed nitrate fertilizer . A hypothesis of the mechanism of the Texas City disaster was established on this basis. (Author)

  4. 40 CFR 180.473 - Glufosinate ammonium; tolerances for residues.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 2-amino-4-(hydroxymethylphosphinyl)butanoic acid, in or on the commodity. Commodity Parts per... ammonium, 2-amino-4-(hydroxymethylphosphinyl)butanoic acid monoammonium salt, and its metabolite, 3-(hydroxymethylphosphinyl)propionic acid, calculated as the stoichiometric equivalent of 2-amino-4-(hydroxymethylphosphinyl...

  5. 40 CFR 180.473 - Glufosinate ammonium; tolerances for residues.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 2-amino-4-(hydroxymethylphosphinyl)butanoic acid, in or on the commodity. Commodity Parts per... ammonium, 2-amino-4-(hydroxymethylphosphinyl)butanoic acid monoammonium salt, and its metabolite, 3-(hydroxymethylphosphinyl)propionic acid, calculated as the stoichiometric equivalent of 2-amino-4-(hydroxymethylphosphinyl...

  6. Glufosinate and Ammonium Sulfate Inhibits Atrazine Degradation in Adapted Soils

    USDA-ARS?s Scientific Manuscript database

    The co-application of glufosinate with nitrogen fertilizers may alter atrazine co-metabolism, thereby extending the herbicide’s residual weed control in adapted soils. The objective of this study was to assess the effects of glufosinate, ammonium sulfate, and the combination of glufosinate and ammo...

  7. 21 CFR 73.1025 - Ferric ammonium citrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Ferric ammonium citrate. 73.1025 Section 73.1025 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF... general and ophthalmic surgery subject to the following conditions: (1) The dyed suture shall conform...

  8. 21 CFR 73.1025 - Ferric ammonium citrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Ferric ammonium citrate. 73.1025 Section 73.1025 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF... general and ophthalmic surgery subject to the following conditions: (1) The dyed suture shall conform...

  9. 21 CFR 73.1025 - Ferric ammonium citrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Ferric ammonium citrate. 73.1025 Section 73.1025 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF... general and ophthalmic surgery subject to the following conditions: (1) The dyed suture shall conform...

  10. 21 CFR 73.1025 - Ferric ammonium citrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Ferric ammonium citrate. 73.1025 Section 73.1025 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF... general and ophthalmic surgery subject to the following conditions: (1) The dyed suture shall conform...

  11. Global modeling of nitrate and ammonium aerosols using EQSAM3

    NASA Astrophysics Data System (ADS)

    Xu, L.; Penner, J. E.

    2009-12-01

    Atmospheric aerosols, particles suspending in air, are important as they affect human health, air quality, and visibility as well as climate. Sulfate, nitrate, ammonium, chloride and sodium are among the most important inorganic aerosol species in the atmosphere. These compounds are hygroscopic and absorb water under almost all ambient environmental conditions. The uptake of water alters the aerosol size, and causes water to become the constituent with the largest atmospheric aerosol mass, especially when the aerosols grow into fog, haze or clouds. Furthermore, several global model studies have demonstrated that rapid increases in nitrogen emissions could produce enough nitrate in aerosols to offset the expected decline in sulfate forcing by 2100 for the extreme IPCC A2 scenario (Bauer et al., 2007). Although nitrate and ammonium were identified as significant anthropogenic sources of aerosols by a number of modeling studies, most global aerosol models still exclude ammonium-nitrate when the direct aerosol forcing is studied. In this study, the computationally efficient equilibrium model, EQSAM3, is incorporated into the UMICH-IMPACT-nitrate model using the hybrid dynamical solution method (Feng and Penner, 2007). The partitioning of nitrate and ammonium along with the corresponding water uptake is evaluated by comparing the model to the EQUISOLVE II method used in Feng and Penner (2007). The model is also evaluated by comparison with the AERONET data base and satellite-based aerosol optical depths.

  12. Producing ammonium sulfate from flue gas desulfurization by-products

    USGS Publications Warehouse

    Chou, I.-Ming; Bruinius, J.A.; Benig, V.; Chou, S.-F.J.; Carty, R.H.

    2005-01-01

    Emission control technologies using flue gas desulfurization (FGD) have been widely adopted by utilities burning high-sulfur fuels. However, these technologies require additional equipment, greater operating expenses, and increased costs for landfill disposal of the solid by-products produced. The financial burdens would be reduced if successful high-volume commercial applications of the FGD solid by-products were developed. In this study, the technical feasibility of producing ammonium sulfate from FGD residues by allowing it to react with ammonium carbonate in an aqueous solution was preliminarily assessed. Reaction temperatures of 60, 70, and 80??C and residence times of 4 and 6 hours were tested to determine the optimal conversion condition and final product evaluations. High yields (up to 83%) of ammonium sulfate with up to 99% purity were achieved under relatively mild conditions. The optimal conversion condition was observed at 60??C and a 4-hour residence time. The results of this study indicate the technical feasibility of producing ammonium sulfate fertilizer from an FGD by-product. Copyright ?? Taylor & Francis Inc.

  13. Simultaneous Nitrite-Dependent Anaerobic Methane and Ammonium Oxidation Processes▿

    PubMed Central

    Luesken, Francisca A.; Sánchez, Jaime; van Alen, Theo A.; Sanabria, Janeth; Op den Camp, Huub J. M.; Jetten, Mike S. M.; Kartal, Boran

    2011-01-01

    Nitrite-dependent anaerobic oxidation of methane (n-damo) and ammonium (anammox) are two recently discovered processes in the nitrogen cycle that are catalyzed by n-damo bacteria, including “Candidatus Methylomirabilis oxyfera,” and anammox bacteria, respectively. The feasibility of coculturing anammox and n-damo bacteria is important for implementation in wastewater treatment systems that contain substantial amounts of both methane and ammonium. Here we tested this possible coexistence experimentally. To obtain such a coculture, ammonium was fed to a stable enrichment culture of n-damo bacteria that still contained some residual anammox bacteria. The ammonium supplied to the reactor was consumed rapidly and could be gradually increased from 1 to 20 mM/day. The enriched coculture was monitored by fluorescence in situ hybridization and 16S rRNA and pmoA gene clone libraries and activity measurements. After 161 days, a coculture with about equal amounts of n-damo and anammox bacteria was established that converted nitrite at a rate of 0.1 kg-N/m3/day (17.2 mmol day−1). This indicated that the application of such a coculture for nitrogen removal may be feasible in the near future. PMID:21841030

  14. 21 CFR 184.1141a - Ammonium phosphate, monobasic.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium phosphate, monobasic. 184.1141a Section 184.1141a Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific Substances...

  15. 21 CFR 184.1141b - Ammonium phosphate, dibasic.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ammonium phosphate, dibasic. 184.1141b Section 184.1141b Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific Substances Affirmed...

  16. Salmonella enterica Strains with Reduced Susceptibility to Quarternary Ammonium Compounds

    USDA-ARS?s Scientific Manuscript database

    Background: Salmonella spp. are responsible for 76 million illnesses per year in the U.S. Quaternary ammonium compounds (QAC) are commonly used antimicrobial agents. Reduced susceptibility to these compounds by a broad spectrum of organisms is a concern. Methods: Salmonella enterica strains with r...

  17. Nitrate, Nitrite, and Ammonium Variability in Drinking Water Distribution Systems

    PubMed Central

    Schullehner, Jörg; Stayner, Leslie; Hansen, Birgitte

    2017-01-01

    Accurate assessments of exposure to nitrate in drinking water is a crucial part of epidemiological studies investigating long-term adverse human health effects. However, since drinking water nitrate measurements are usually collected for regulatory purposes, assumptions on (1) the intra-distribution system variability and (2) short-term (seasonal) concentration variability have to be made. We assess concentration variability in the distribution system of nitrate, nitrite, and ammonium, and seasonal variability in all Danish public waterworks from 2007 to 2016. Nitrate concentrations at the exit of the waterworks are highly correlated with nitrate concentrations within the distribution net or at the consumers’ taps, while nitrite and ammonium concentrations are generally lower within the net compared with the exit of the waterworks due to nitrification. However, nitrification of nitrite and ammonium in the distribution systems only results in a relatively small increase in nitrate concentrations. No seasonal variation for nitrate, nitrite, or ammonium was observed. We conclude that nitrate measurements taken at the exit of the waterworks are suitable to calculate exposures for all consumers connected to that waterworks and that sampling frequencies in the national monitoring programme are sufficient to describe temporal variations in longitudinal studies. PMID:28282914

  18. Structures of KcsA in Complex with Symmetrical Quaternary Ammonium Compounds Reveal a Hydrophobic Binding Site

    PubMed Central

    2015-01-01

    Potassium channels allow for the passive movement of potassium ions across the cell membrane and are instrumental in controlling the membrane potential in all cell types. Quaternary ammonium (QA) compounds block potassium channels and have long been used to study the functional and structural properties of these channels. Here we describe the interaction between three symmetrical hydrophobic QAs and the prokaryotic potassium channel KcsA. The structures demonstrate the presence of a hydrophobic pocket between the inner helices of KcsA and provide insight into the binding site and blocking mechanism of hydrophobic QAs. The structures also reveal a structurally hidden pathway between the central cavity and the outside membrane environment reminiscent of the lateral fenestration observed in sodium channels that can be accessed through small conformational changes in the pore wall. We propose that the hydrophobic binding pocket stabilizes the alkyl chains of long-chain QA molecules and may play a key role in hydrophobic drug binding in general. PMID:25093676

  19. Calcium ions open a selectivity filter gate during activation of the MthK potassium channel.

    PubMed

    Posson, David J; Rusinova, Radda; Andersen, Olaf S; Nimigean, Crina M

    2015-09-23

    Ion channel opening and closing are fundamental to cellular signalling and homeostasis. Gates that control K(+) channel activity were found both at an intracellular pore constriction and within the selectivity filter near the extracellular side but the specific location of the gate that opens Ca(2+)-activated K(+) channels has remained elusive. Using the Methanobacterium thermoautotrophicum homologue (MthK) and a stopped-flow fluorometric assay for fast channel activation, we show that intracellular quaternary ammonium blockers bind to closed MthK channels. Since the blockers are known to bind inside a central channel cavity, past the intracellular entryway, the gate must be within the selectivity filter. Furthermore, the blockers access the closed channel slower than the open channel, suggesting that the intracellular entryway narrows upon pore closure, without preventing access of either the blockers or the smaller K(+). Thus, Ca(2+)-dependent gating in MthK occurs at the selectivity filter with coupled movement of the intracellular helices.

  20. Calcium ions open a selectivity filter gate during activation of the MthK potassium channel

    NASA Astrophysics Data System (ADS)

    Posson, David J.; Rusinova, Radda; Andersen, Olaf S.; Nimigean, Crina M.

    2015-09-01

    Ion channel opening and closing are fundamental to cellular signalling and homeostasis. Gates that control K+ channel activity were found both at an intracellular pore constriction and within the selectivity filter near the extracellular side but the specific location of the gate that opens Ca2+-activated K+ channels has remained elusive. Using the Methanobacterium thermoautotrophicum homologue (MthK) and a stopped-flow fluorometric assay for fast channel activation, we show that intracellular quaternary ammonium blockers bind to closed MthK channels. Since the blockers are known to bind inside a central channel cavity, past the intracellular entryway, the gate must be within the selectivity filter. Furthermore, the blockers access the closed channel slower than the open channel, suggesting that the intracellular entryway narrows upon pore closure, without preventing access of either the blockers or the smaller K+. Thus, Ca2+-dependent gating in MthK occurs at the selectivity filter with coupled movement of the intracellular helices.