Mechanism of Pd(NHC)-catalyzed transfer hydrogenation of alkynes.

PubMed

Hauwert, Peter; Boerleider, Romilda; Warsink, Stefan; Weigand, Jan J; Elsevier, Cornelis J

2010-12-01

The transfer semihydrogenation of alkynes to (Z)-alkenes shows excellent chemo- and stereoselectivity when using a zerovalent palladium(NHC)(maleic anhydride)-complex as precatalyst and triethylammonium formate as hydrogen donor. Studies on the kinetics under reaction conditions showed a broken positive order in substrate and first order in catalyst and hydrogen donor. Deuterium-labeling studies on the hydrogen donor showed that both hydrogens of formic acid display a primary kinetic isotope effect, indicating that proton and hydride transfers are separate rate-determining steps. By monitoring the reaction with NMR, we observed the presence of a coordinated formate anion and found that part of the maleic anhydride remains coordinated during the reaction. From these observations, we propose a mechanism in which hydrogen transfer from coordinated formate anion to zerovalent palladium(NHC)(MA)(alkyne)-complex is followed by migratory insertion of hydride, after which the product alkene is liberated by proton transfer from the triethylammonium cation. The explanation for the high selectivity observed lies in the competition between strongly coordinating solvent and alkyne for a Pd(alkene)-intermediate.

Anionized and cationized hemeundecapeptides as probes for cell surface charge and permeability studies: differentiated labeling of endothelial plasmalemmal vesicles

PubMed Central

1985-01-01

To obtain small membrane markers easily accessible to the charged groups of the cell surface, we prepared, from hemeundecapeptide (HUP), three derivatives that maintain the peroxidatic activity: the anionized hemeundecapeptide, Mr 1,963, estimated diameter 1.68 nm, pl 3.5, for the detection of basic groups; and both a cationized hemeundecapeptide containing predominantly tertiary amino groups, Mr 2,215, estimated diameter 1.75 nm, pl 9.0, and a cationized hemeundecapeptide containing only primary amino groups, Mr 2,271, estimated diameter 1.75 nm, pl 10.6, for labeling acidic residues. The markers were perfused in situ in mice to label the luminal surface of fenestrated endothelium of pancreatic capillaries. Specimens were processed through the cytochemical reaction for peroxidatic activity and examined by electron microscopy. The anionized HUP and HUP (pl 4.85) marked the plasmalemma proper, the coated pits, and the membrane and diaphragms of plasmalemmal vesicles and transendothelial channels. The cationized HUP containing predominantly tertiary amino groups (pl 9.0) decorated all cell surface components with the exception of plasmalemmal vesicles and channels; the latter were, however, labeled by the cationized HUP containing only primary groups (pl 10.6), which suggests that these structures contain on their luminal surface very weak acidic residues of high pKa values. The fact that the membrane of plasmalemmal vesicles can discriminate against permeant cationic macromolecules only up to a pl of approximately 9.0 indicates that in the electrostatic restriction there is a charge limit. In the case of fenestrated capillary endothelium, the upper charge limit seems to be a pl of approximately 9.0. In these vessels, the charge discrimination is effective for molecules as small as 2 nm. PMID:3968182

Anionized and cationized hemeundecapeptides as probes for cell surface charge and permeability studies: differentiated labeling of endothelial plasmalemmal vesicles.

PubMed

Ghinea, N; Simionescu, N

1985-02-01

To obtain small membrane markers easily accessible to the charged groups of the cell surface, we prepared, from hemeundecapeptide (HUP), three derivatives that maintain the peroxidatic activity: the anionized hemeundecapeptide, Mr 1,963, estimated diameter 1.68 nm, pl 3.5, for the detection of basic groups; and both a cationized hemeundecapeptide containing predominantly tertiary amino groups, Mr 2,215, estimated diameter 1.75 nm, pl 9.0, and a cationized hemeundecapeptide containing only primary amino groups, Mr 2,271, estimated diameter 1.75 nm, pl 10.6, for labeling acidic residues. The markers were perfused in situ in mice to label the luminal surface of fenestrated endothelium of pancreatic capillaries. Specimens were processed through the cytochemical reaction for peroxidatic activity and examined by electron microscopy. The anionized HUP and HUP (pl 4.85) marked the plasmalemma proper, the coated pits, and the membrane and diaphragms of plasmalemmal vesicles and transendothelial channels. The cationized HUP containing predominantly tertiary amino groups (pl 9.0) decorated all cell surface components with the exception of plasmalemmal vesicles and channels; the latter were, however, labeled by the cationized HUP containing only primary groups (pl 10.6), which suggests that these structures contain on their luminal surface very weak acidic residues of high pKa values. The fact that the membrane of plasmalemmal vesicles can discriminate against permeant cationic macromolecules only up to a pl of approximately 9.0 indicates that in the electrostatic restriction there is a charge limit. In the case of fenestrated capillary endothelium, the upper charge limit seems to be a pl of approximately 9.0. In these vessels, the charge discrimination is effective for molecules as small as 2 nm.

Bis-ureidoquinoline as a selective fluoride anion sensor through hydrogen-bond interactions.

PubMed

Jo, Yunhee; Chidalla, Nagesh; Cho, Dong-Gyu

2014-10-03

Bis-ureidoquinoline shows a characteristic UV-vis absorbance and turn-on fluorescence changes in the presence of the fluoride anion. Such selective changes probably originate from the hydrogen-bond interactions, as shown by the (1)H NMR titration and DFT calculations. Bis-ureidoquinoline can be used as a fluoride-selective sensor for the detection of fluoride anions under illumination from a laboratory hand-held UV lamp.

Anion transport and supramolecular medicinal chemistry

DOE PAGES

Gale, Philip A.; Davis, Jeffery T.; Quesada, Roberto

2017-04-05

New approaches to the transmembrane transport of anions are discussed in this review. Advances in the design of small molecule anion carriers are reviewed in addition to advances in the design of synthetic anion channels. The application of anion transporters to the potential future treatment of disease is discussed in the context of recent findings on the selectivity of anion transporters.

Anion transport and supramolecular medicinal chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gale, Philip A.; Davis, Jeffery T.; Quesada, Roberto

New approaches to the transmembrane transport of anions are discussed in this review. Advances in the design of small molecule anion carriers are reviewed in addition to advances in the design of synthetic anion channels. The application of anion transporters to the potential future treatment of disease is discussed in the context of recent findings on the selectivity of anion transporters.

N-acetylglyoxylic amide bearing a nitrophenyl group as anion receptors: NMR and X-ray investigations on anion binding and selectivity

NASA Astrophysics Data System (ADS)

Suryanti, Venty; Bhadbhade, Mohan; Black, David StC; Kumar, Naresh

2017-10-01

N-Nitrophenylglyoxylic amides 1 and 2 in presence of tetrabutylammonium cation (TBA) act as receptors for anions HSO4-, Cl-, Br- and NO3- as investigated by NMR studies. The receptors formed 1:1 host-guest complexes in solution. X-ray structure of 1 along with TBA that bind a chloride anion is reported. Molecule 1 showed the highest selectivity for HSO4- anion over others measured. X-ray structure of the bound Cl- revealed a pocket containing the anion making strong (Nsbnd H⋯Cl) and weak hydrogen bonds (Csbnd H⋯Cl) that contribute to the recognition of the chloride anion. Nsbnd H and Csbnd H hydrogen bonds resulted in a relatively strong binding for chloride ions.

New Gel-Like Polymers as Selective Weak-Base Anion Exchangers

PubMed Central

Gierczyk, Błażej; Cegłowski, Michał; Zalas, Maciej

2015-01-01

A group of new anion exchangers, based on polyamine podands and of excellent ion-binding capacity, were synthesized. The materials were obtained in reactions between various poly(ethyleneamines) with glycidyl derivatives of cyclotetrasiloxane. The final polymeric, strongly cross-linked materials form gel-like solids. Their structures and interactions with anions adsorbed were studied by spectroscopic methods (CP-MAS NMR, FR-IR, UV-Vis). The sorption isotherms and kinetic parameters were determined for 29 anions. Materials studied show high ion capacity and selectivity towards some important anions, e.g., selenate(VI) or perrhenate. PMID:25946220

Application of a macrocyclic compound, bambus[6]uril, in tailor-made liquid membranes for highly selective electromembrane extractions of inorganic anions.

PubMed

Šlampová, Andrea; Šindelář, Vladimír; Kubáň, Pavel

2017-01-15

A tailor-made liquid membrane consisting of a resistive organic solvent (nitrobenzene, NB) and a highly selective non-ionic macrocyclic compound (bambus[6]uril, BU6) was employed for electromembrane extraction (EME) of inorganic anions. BU6 facilitates strong host-guest interactions of its internal cavity with selected inorganic anions only and its presence in the liquid membrane ensured excellent selectivity of the EME process. EME transfers were directly related to association constants between BU6 and inorganic anions and nearly absolute selectivity was achieved for EMEs of iodide, bromide and perchlorate. Major inorganic anions (chloride, nitrate, sulphate and carbonate), which exhibit low interactions with BU6 cavity, were efficiently eliminated from the EME transfer. No interferences were observed for EMEs of target analytes from samples containing up to 100.000-fold higher concentrations of the major anions. Addition of species-specific macrocyclic modifiers to free and supported liquid membranes might thus open new directions in fine-tuning of EME selectivity. At optimized EME conditions (polypropylene hollow fiber impregnated with NB + 3% (w/w) BU6, extraction voltage 25 V, extraction time 15 min, deionized water as acceptor solution) perchlorate was selectively extracted from tap water at concentrations below the guideline value recommended by United States Environmental Protection Agency. Excellent selectivity of the tailor-made liquid membrane was further demonstrated by EME of bromide from sea water. Copyright © 2016 Elsevier B.V. All rights reserved.

Temperature dependence of chloride, bromide, iodide, thiocyanate and salicylate transport in human red cells

PubMed Central

Dalmark, Mads; Wieth, Jens Otto

1972-01-01

1. The temperature dependence of the steady-state self-exchange of chloride between human red cells and a plasma-like electrolyte medium has been studied by measuring the rate of 36Cl- efflux from radioactively labelled cells. Between 0 and 10° C the rate increased by a factor of eight corresponding to an Arrhenius activation energy of 33 kcal/mole. 2. The rate of chloride exchange decreased significantly in experiments where 95% of the chloride ions in cells and medium were replaced by other monovalent anions of a lyotropic series. The rate of chloride self-exchange was increasingly reduced by bromide, bicarbonate, nitrate, iodide, thiocyanate, and salicylate. The latter aromatic anion was by far the most potent inhibitor, reducing the rate of chloride self-exchange to 0·2% of the value found in a chloride medium. 3. The temperature sensitivity of the chloride self-exchange was not affected significantly by the anionic inhibitors. The Arrhenius activation energies of chloride exchange were between 30 and 40 kcal/mole in the presence of the six inhibitory anions mentioned above. 4. The rate of self-exchange of bromide, thiocyanate, and iodide between human red cells and media was determined after washing and labelling cells in media containing 120 mM bromide, thiocyanate, or iodide respectively. The rate of self-exchange of the three anions were 12, 3, and 0·4% of the rate of chloride self-exchange found in the chloride medium. 5. The Arrhenius activation energies of the self-exchange of bromide, iodide, and thiocyanate were all between 29 and 37 kcal/mole, the same magnitude as found for the self-exchange of chloride. 6. Although approximately 40% of the intracellular iodide and salicylate ions appeared to be adsorbed to intracellular proteins, the rate of tracer anion efflux followed first order kinetics until at least 98% of the intracellular anions had been exchanged. 7. The self-exchange of salicylate across the human red cell membrane occurred by a different mechanism than the one utilized by the inorganic monovalent anions. The activation energy of salicylate exchange (13·2 kcal/mole) was significantly lower than that of inorganic anion exchange. Salicylate exchange increased with decreasing pH in contrast to the exchange of chloride, which decreases when pH is lowered. PMID:5071931

Herbicide-Intercalated Zinc Layered Hydroxide Nanohybrid for a Dual-Guest Controlled Release Formulation

PubMed Central

Hussein, Mohd Zobir; Rahman, Nor Shazlirah Shazlyn Abdul; Sarijo, Siti H.; Zainal, Zulkarnain

2012-01-01

Herbicides, namely 4-(2,4-dichlorophenoxy) butyrate (DPBA) and 2-(3-chlorophenoxy) propionate (CPPA), were intercalated simultaneously into the interlayers of zinc layered hydroxide (ZLH) by direct reaction of zinc oxide with both anions under aqueous environment to form a new nanohybrid containing both herbicides labeled as ZCDX. Successful intercalation of both anions simultaneously into the interlayer gallery space of ZLH was studied by PXRD, with basal spacing of 28.7 Å and supported by FTIR, TGA/DTG and UV-visible studies. Simultaneous release of both CPPA and DPBA anions into the release media was found to be governed by a pseudo second-order equation. The loading and percentage release of the DPBA is higher than the CPPA anion, which indicates that the DPBA anion was preferentially intercalated into and released from the ZLH interlayer galleries. This work shows that layered single metal hydroxide, particularly ZLH, is a suitable host for the controlled release formulation of two herbicides simultaneously. PMID:22837696

Phosphatidylinositol anchor of HeLa cell alkaline phosphatase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jemmerson, R.; Low, M.G.

1987-09-08

Alkaline phosphatase from cancer cells, HeLa TCRC-1, was biosynthetically labeled with either /sup 3/H-fatty acids or (/sup 3/H)ethanolamine as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography of immunoprecipitated material. Phosphatidylinositol-specific phospholipase C (PI-PLC) released a substantial proportion of the /sup 3/H-fatty acid label from immunoaffinity-purified alkaline phosphatase but had no effect on the radioactivity of (/sup 3/H)ethanolamine-labeled material. PI-PLC also liberated catalytically active alkaline phosphatase from viable cells, and this could be selectively blocked by monoclonal antibodies to alkaline phosphatase. However, the alkaline phosphatase released from /sup 3/H-fatty acid labeled cells by PI-PLC was not radioactive. By contrast,more » treatment with bromelain removed both the /sup 3/H-fatty acid and the (/sup 3/H)ethanolamine label from purified alkaline phosphatase. Subtilisin was also able to remove the (/sup 3/H)ethanolamine label from the purified alkaline phosphatase. The /sup 3/H radioactivity in alkaline phosphatase purified from (/sup 3/H)ethanolamine-labeled cells comigrated with authentic (/sup 3/H)ethanolamine by anion-exchange chromatography after acid hydrolysis. The data suggest that the /sup 3/H-fatty acid and (/sup 3/H)ethanolamine are covalently attached to the carboxyl-terminal segment since bromelain and subtilisin both release alkaline phosphatase from the membrane by cleavage at that end of the polypeptide chain. The data are consistent with findings for other proteins recently shown to be anchored in the membrane through a glycosylphosphatidylinositol structure and indicate that a similar structure contributes to the membrane anchoring of alkaline phosphatase.« less

Method for preparing radionuclide-labeled chelating agent-ligand complexes

DOEpatents

Meares, Claude F.; Li, Min; DeNardo, Sally J.

1999-01-01

Radionuclide-labeled chelating agent-ligand complexes that are useful in medical diagnosis or therapy are prepared by reacting a radionuclide, such as .sup.90 Y or .sup.111 In, with a polyfunctional chelating agent to form a radionuclide chelate that is electrically neutral; purifying the chelate by anion exchange chromatography; and reacting the purified chelate with a targeting molecule, such as a monoclonal antibody, to form the complex.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J.Y.

Serial experiments were performed in order to understand and explore the Na/sup +/ transport system. In order to test possible covariation of cation and anion permeabilities, we applied inhibitors of cation or anion transport. Sulfonamide loop diuretics, furosemide and bumetanide, suppress 22/sub Na/sup +// influx into high permeability (HP) red cells but less into low permeability (LP) erythrocytes. These drugs also inhibit SO/sub 4/ = transport about 70% in both types of RBC. RBC pretreated with impermeant polyanions also show significantly decreased Na/sup +/ influx into HP but not LP RBC. However,a potent inhibitor of RBC anion transport, diisothiocyanostilbene disulfonatemore » (DIDS), has no influence on Na/sup +/ transport. Since the glucose channel is another transmembrane protein in erythrocyte membranes, the effects of the potent glucose transport inhibitors, phlorizin and phloretinyl-3'-benzylazide (PBAz), were measured. Both chemicals effect reduction of Na/sup +/ flux. Because radioactive PBAz is not available, we employed another potent Na/sup +/ channel blocker, /sup 32/P-8-azido-ATP, in an attempt to label HP and LP RBC membranes. Autoradiograms showed that /sup 32/P labels only band 4.2 and external iodination with /sup 125/I yields similar results.« less

Anion channels in the sea urchin sperm plasma membrane.

PubMed

Morales, E; de la Torre, L; Moy, G W; Vacquier, V D; Darszon, A

1993-10-01

Ionic fluxes in sea urchin sperm plasma membrane regulate cell motility and the acrosome reaction (AR). Although cationic channels mediate some of the ionic movements, little is known about anion channels in these cells. The fusion of sperm plasma membranes into lipid bilayers allowed identification of a 150 pS anion channel. This anion channel was enriched from detergent-solubilized sperm plasma membranes using a wheat germ agglutinin Sepharose column. Vesicles formed from this preparation were fused into black lipid membranes (BLM), yielding single channel anion-selective activity with the properties of those found in the sperm membranes. The following anion selectivity sequence was found: NO3- > CNS- > Br- > Cl-. This anion channel has a high open probability at the holding potentials tested, it is partially blocked by 4,4'-diisothiocyano-2,2'-stilbendisulfonic acid (DIDS), and it often displays substates. The sperm AR was also inhibited by DIDS.

Strapped Calix[4]pyrroles Bearing an 1,3-Indanedione at a β-Pyrrolic Position: Chemodosimeters for the Cyanide Anion

PubMed Central

Kim, Sook-Hee; Hong, Seong-Jin; Yoo, Jaeduk; Kim, Sung Kuk; Sessler, Janathan L.; Lee, Chang-Hee

2014-01-01

A strapped calix[4]pyrrole bearing an 1,3-indanedione group at a β-pyrrolic position has been synthesized and studied as a ratiometric cyanide selective chemosensor. A concentration-dependent bleaching of the initial yellow color was observed upon addition of the cyanide anion. The bleaching, which was observed exclusively with the cyanide anion, occurred even in the presence of other anions. Spectroscopic studies provides support for a mechanistic interpretation wherein the cyanide anion forms a complex with the receptor (K = 2.78 × 104 M-1) through a fast equilibrium, which is followed by slow nucleophilic addition to the β-position of the 1,3-indanedione group. A minimum inhibitory effect from other anions was observed, a feature that could be beneficial in the selective sensing of the cyanide anion. PMID:19639968

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strittmatter, S.M.

(/sup 3/H)Captopril binds to angiotensin converting enzyme (ACE) in rat tissue homogenates. The pharmacology, regional distribution and copurification of (/sup 3/H)captopril binding with enzymatic activity demonstrate the selectivity of (/sup 3/H)captopril labeling of ACE. (/sup 3/H)Captopril binding to purified ACE reveals differences in cationic dependence and anionic regulation between substrate catalysis and inhibitor recognition. (/sup 3/H)Captopril association with ACE is entropically driven. The selectivity of (/sup 3/H)captopril binding permits autoradiographic localization of the ACE in the brain, male reproductive system, pituitary gland and adrenal gland. In the brain, ACE is visualized in a striatonigral neuronal pathway which develops between 1more » and 7 d after birth. In the male reproductive system, (/sup 3/H)captopril associated silver grains are found over spermatid heads and in the lumen of seminiferous tubules in stages I-VIII and XII-XIV. In the pituitary gland, ACE is localized to the posterior lobe and patches of the anterior lobe. The adrenal medulla contains moderate ACE levels while low levels are found in the adrenal cortex. Adrenal medullary ACE is increased after hypophysectomy and after reserpine treatment. The general of ligand binding techniques for the study of enzymes is demonstrated by the specific labeling of another enzyme, enkephaline convertase, in crude tissue homogenates by the inhibitor (/sup 3/H)GEMSA.« less

Semithiobambus[6]uril is a transmembrane anion transporter.

PubMed

Lang, Chao; Mohite, Amar; Deng, Xiaoli; Yang, Feihu; Dong, Zeyuan; Xu, Jiayun; Liu, Junqiu; Keinan, Ehud; Reany, Ofer

2017-07-04

Semithiobambus[6]uril is shown to be an efficient transmembrane anion transporter. Although all bambusuril analogs (having either O, S or N atoms in their portals) are excellent anion binders, only the sulfur analog is also an effective anion transporter capable of polarizing lipid membranes through selective anion uniport. This notable divergence reflects significant differences in the lipophilic character of the bambusuril analogs.

Purification and labeling strategies for (68)Ga from (68)Ge/ (68)Ga generator eluate.

PubMed

Mueller, Dirk; Klette, Ingo; Baum, Richard P

2013-01-01

For successful labeling, (68)Ge/(68)Ga generator eluate has to be concentrated (from 10 mL or more to less than 1 mL) and to be purified of metallic impurities, especially Fe(III), and (68)Ge breakthrough. Anionic, cationic and fractional elution methods are well known. We describe two new methods: (1) a combined cationic-anionic purification and (2) an easy-to-use and reliable cationic purification with NaCl solution. Using the first method, (68)Ga from 10 mL generator eluate was collected on a SCX cartridge, then eluted with 1.0 mL 5.5 M HCl directly on an anion exchanger (30 mg AG1X8). After drying with a stream of helium, (68)Ga was eluted with 0.4 mL water into the reaction vial. We provide as an example labeling of BPAMD. Using the second method, (68)Ga from 10 mL generator eluate was collected on a SCX cartridge, then eluted with a hydrochloric solution of sodium chloride (0.5 mL 5 M NaCl, 12.5 μL 5.5 M HCl) into the reaction vial, containing 40 μg DOTATOC and 0.5 mL 1 M ammonium acetate buffer pH 4.5. After heating for 7 min at 90°C, the reaction was finished. Radiochemical purity was higher than 95% without further purification. No (68)Ge breakthrough was found in the final product.

Anion-π Catalysis on Fullerenes.

PubMed

López-Andarias, Javier; Frontera, Antonio; Matile, Stefan

2017-09-27

Anion-π interactions on fullerenes are about as poorly explored as the use of fullerenes in catalysis. However, strong exchange-correlation contributions and the localized π holes on their surface promise unique selectivities. To elaborate on this promise, tertiary amines are attached nearby. Dependent on their positioning, the resulting stabilization of anionic transition states on fullerenes is shown to accelerate disfavored enolate addition and exo Diels-Alder reactions enantioselectively. The found selectivities are consistent with computational simulations, particularly concerning the discrimination of differently planarized and charge-delocalized enolate tautomers by anion-π interactions. Enolate-π interactions on fullerenes are much shorter than standard π-π interactions and anion-π interactions on planar surfaces, and alternative cation-π interactions are not observed. These findings open new perspectives with regard to anion-π interactions in general and the use of carbon allotropes in catalysis.

Bifunctional anion-exchange resins with improved selectivity and exchange kinetics

DOEpatents

Alexandratos, Spiro D.; Brown, Gilbert M.; Bonnesen, Peter V.; Moyer, Bruce A.

2000-01-01

Disclosed herein are a class of anion exchange resins containing two different exchange sites with improved selectivity and sorptive capability for chemical species in solution, such as heptavalent technetium (as pertechnetate anion, TcO.sub.4.sup.-). The resins are prepared by first reacting haloalkylated crosslinked copolymer beads with a large tertiary amine in a solvent in which the resin beads can swell, followed by reaction with a second, smaller, tertiary amine to more fully complete the functionalization of the resin. The resins have enhanced selectivity, capacity, and exchange kinetics.

RP-UHPLC-UV-ESI-MS/MS analysis of LPMO generated C4-oxidized gluco-oligosaccharides after non-reductive labeling with 2-aminobenzamide.

PubMed

Frommhagen, Matthias; van Erven, Gijs; Sanders, Mark; van Berkel, Willem J H; Kabel, Mirjam A; Gruppen, Harry

2017-08-07

Lytic polysaccharide monooxygenases (LPMOs) are able to cleave recalcitrant polysaccharides, such as cellulose, by oxidizing the C1 and/or C4 atoms. The analysis of the resulting products requires a variety of analytical techniques. Up to now, these techniques mainly focused on the identification of non-oxidized and C1-oxidized oligosaccharides. The analysis of C4-oxidized gluco-oligosaccharides is mostly performed by using high pressure anion exchange chromatography (HPAEC). However, the alkaline conditions used during HPAEC analysis lead to tautomerization of C4-oxidized gluco-oligosaccharides, which limits the use of this technique. Here, we describe the use of reverse phase-ultra high performance liquid chromatography (RP-UHPLC) in combination with non-reductive 2-aminobenzamide (2-AB) labeling. Non-reductive 2-AB labeling enabled separation of C4-oxidized gluco-oligosaccharides from their non-oxidized counterparts. Moreover, RP-UHPLC does not require buffered mobile phases, which reduce mass spectrometry (MS) sensitivity. The latter is seen as an advantage over other techniques such as hydrophilic interaction liquid chromatography and porous graphitized carbon coupled to MS. RP-UHPLC coupled to UV detection and mass spectrometry allowed the identification of both labeled non-oxidized and C4-oxidized oligosaccharides. Non-reductive labeling kept the ketone at the C4-position of LPMO oxidized oligosaccharides intact, while selective reducing agents such as sodium triacetoxyborohydride (STAB) reduced this ketone group. Our results show that RP-UHPLC-UV-ESI-MS in combination with non-reductively 2-AB labeling is a suitable technique for the separation and identification of LPMO-generated C4-oxidized gluco-oligosaccharides. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Selective Nitrate Recognition by a Halogen-Bonding Four-Station [3]Rotaxane Molecular Shuttle.

PubMed

Barendt, Timothy A; Docker, Andrew; Marques, Igor; Félix, Vítor; Beer, Paul D

2016-09-05

The synthesis of the first halogen bonding [3]rotaxane host system containing a bis-iodo triazolium-bis-naphthalene diimide four station axle component is reported. Proton NMR anion binding titration experiments revealed the halogen bonding rotaxane is selective for nitrate over the more basic acetate, hydrogen carbonate and dihydrogen phosphate oxoanions and chloride, and exhibits enhanced recognition of anions relative to a hydrogen bonding analogue. This elaborate interlocked anion receptor functions via a novel dynamic pincer mechanism where upon nitrate anion binding, both macrocycles shuttle from the naphthalene diimide stations at the periphery of the axle to the central halogen bonding iodo-triazolium station anion recognition sites to form a unique 1:1 stoichiometric nitrate anion-rotaxane sandwich complex. Molecular dynamics simulations carried out on the nitrate and chloride halogen bonding [3]rotaxane complexes corroborate the (1) H NMR anion binding results. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Selective Nitrate Recognition by a Halogen‐Bonding Four‐Station [3]Rotaxane Molecular Shuttle

PubMed Central

Barendt, Timothy A.; Docker, Andrew; Marques, Igor; Félix, Vítor

2016-01-01

Abstract The synthesis of the first halogen bonding [3]rotaxane host system containing a bis‐iodo triazolium‐bis‐naphthalene diimide four station axle component is reported. Proton NMR anion binding titration experiments revealed the halogen bonding rotaxane is selective for nitrate over the more basic acetate, hydrogen carbonate and dihydrogen phosphate oxoanions and chloride, and exhibits enhanced recognition of anions relative to a hydrogen bonding analogue. This elaborate interlocked anion receptor functions via a novel dynamic pincer mechanism where upon nitrate anion binding, both macrocycles shuttle from the naphthalene diimide stations at the periphery of the axle to the central halogen bonding iodo‐triazolium station anion recognition sites to form a unique 1:1 stoichiometric nitrate anion–rotaxane sandwich complex. Molecular dynamics simulations carried out on the nitrate and chloride halogen bonding [3]rotaxane complexes corroborate the 1H NMR anion binding results. PMID:27436297

Bipolar membranes with fluid distribution passages

NASA Technical Reports Server (NTRS)

Hitchens, G. Duncan (Inventor); Archer, Shivaun (Inventor); Tennakoon, Charles L. (Inventor); Gonzalez-Martin, Anuncia (Inventor); Cisar, Alan J. (Inventor)

1999-01-01

The present invention provides a bipolar membrane and methods for making and using the membrane. The bipolar membrane comprises a cation-selective region, an anion-selective region, an interfacial region between the anion-selective region and the cation-selective region, and means for delivering fluid directly into the interfacial region. The means for delivering fluid includes passages that may comprise a fluid-permeable material, a wicking material, an open passage disposed within the membrane or some combination thereof. The passages may be provided in many shapes, sizes and configurations, but preferably deliver fluid directly to the interfacial region so that the rate of electrodialysis is no longer limited by the diffusion of fluid through the cation- or anion-selective regions to the interfacial region.

Simultaneous separation of inorganic anions and metal-citrate complexes on a zwitterionic stationary phase with on-column complexation.

PubMed

Nesterenko, Ekaterina P; Nesterenko, Pavel N; Paull, Brett

2008-12-05

The retention and separation selectivity of inorganic anions and on-column derivatised negatively charged citrate or oxalate metal complexes on reversed-phase stationary phases dynamically coated with N-(dodecyl-N,N-dimethylammonio)undecanoate (DDMAU) has been investigated. The retention mechanism for the metal-citrate complexes was predominantly anion exchange, although the amphoteric/zwitterionic nature of the stationary phase coating undoubtedly also contributed to the unusual separation selectivity shown. A mixture of 10 inorganic anions and metal cations was achieved using a 20 cm monolithic DDMAU modified column and a 1 mM citrate eluent, pH 4.0, flow rate equal to 0.8 mL/min. Selectivity was found to be strongly pH dependent, allowing additional scope for manipulation of solute retention, and thus application to complex samples. This is illustrated with the analysis of an acidic mine drainage sample with a range of inorganic anions and transition metal cations, varying significantly in their concentrations levels.

Loss of benzene to generate an enolate anion by a site-specific double-hydrogen transfer during CID fragmentation of o-alkyl ethers of ortho-hydroxybenzoic acids.

PubMed

Attygalle, Athula B; Bialecki, Jason B; Nishshanka, Upul; Weisbecker, Carl S; Ruzicka, Josef

2008-09-01

Collision-induced dissociation of anions derived from ortho-alkyloxybenzoic acids provides a facile way of producing gaseous enolate anions. The alkyloxyphenyl anion produced after an initial loss of CO(2) undergoes elimination of a benzene molecule by a double-hydrogen transfer mechanism, unique to the ortho isomer, to form an enolate anion. Deuterium labeling studies confirmed that the two hydrogen atoms transferred in the benzene loss originate from positions 1 and 2 of the alkyl chain. An initial transfer of a hydrogen atom from the C-1 position forms a phenyl anion and a carbonyl compound, both of which remain closely associated as an ion/neutral complex. The complex breaks either directly to give the phenyl anion by eliminating the neutral carbonyl compound, or to form an enolate anion by transferring a hydrogen atom from the C-2 position and eliminating a benzene molecule in the process. The pronounced primary kinetic isotope effect observed when a deuterium atom is transferred from the C-1 position, compared to the weak effect seen for the transfer from the C-2 position, indicates that the first transfer is the rate determining step. Quantum mechanical calculations showed that the neutral loss of benzene is a thermodynamically favorable process. Under the conditions used, only the spectra from ortho isomers showed peaks at m/z 77 for the phenyl anion and m/z 93 for the phenoxyl anion, in addition to that for the ortho-specific enolate anion. Under high collision energy, the ortho isomers also produce a peak at m/z 137 for an alkene loss. The spectra of meta and para compounds show a peak at m/z 92 for the distonic anion produced by the homolysis of the O-C bond. Moreover, a small peak at m/z 136 for a distonic anion originating from an alkyl radical loss allows the differentiation of para compounds from meta isomers.

A highly sensitive and selective fluorescent sensor for detection of sulfide anion based on the steric hindrance effect

NASA Astrophysics Data System (ADS)

Chen, Guanfan; Tang, Mengzhuo; Fu, Xiufang; Cheng, Fenmin; Zou, Xianghua; Wang, Jingpei; Zeng, Rongjin

2018-01-01

Sulfide anions are not only generated as a byproduct from industrial processes but also as a crucial kind of element in biological systems. Therefore, fluorescent probes for detecting sulfide anion with sensitive and selective characters are highly popular. In this study, we report a highly sensitive and selective fluorescent sensor M1 for detection of sulfide anion based on the steric hindrance effect, where the recognition unit, dinitrobenzenesulfonate ester group is linked to aromatic ortho-position in the porphyrin, and correspondingly the fluorescence of fluorescein is efficiently quenched. Compared with the sensors with recognition unit linked to the other aromatic positions, the fluorescent sensor M1 has a lower fluorescence background. Furthermore, the corresponding fluorescence responses (F/F0) of M1 for mercapto amino-acid GSH, Hcy and Cys, were all far lower than the relative fluorescence ratio F/F0 values for S2-. It means that M1 is sensitive and selective to detection of S2-, and has an anti-disturbance ability to the biologically-relevant thiols, GSH, Hcy and Cys, and has the prospect of application in the exact detection of sulfide anions in living organisms. This approach offers some useful insights for realizing sensitive and selective fluorescent turn-on sensing in the detection assays for other analytes.

A Cr(VI) selective probe based on a quinoline-amide calix[4]arene

NASA Astrophysics Data System (ADS)

Ferreira, Juliane F.; Bagatin, Izilda A.

2018-01-01

A new quinoline-amide calix[4]arene 3-receptor for detection of hazardous anions and cations have been synthesized. The 3-receptor was examined for its sensing properties towards several different anions (Cr2O72 -, SCN-, F-, Cl-, NO3-) and metal ions (Hg2+, Cd2+, Ag+) by UV-vis and fluorescence spectroscopies. It was detected that the 3-receptor has only sensing ability for Cr2O72 - and Hg2+ ions, resulting in the association constants higher for Cr2O72 - than to the Hg2+ ions. High selectivity towards Cr2O72 - were also observed by fluorescence measurement among other ions (F-, Cl-, SCN-, Hg2+, Cd2+, Ag+) with a low limit of detection (7.36 × 10-6 mol dm-3). Proton NMR anion-binding investigations revealed a strong interaction of Cr2O72 - anion with NH and CH groups of the receptor, showing that the combination with hydrogen-bonds donor groups strengthened the anion receptor association. Furthermore, remarkable association constants for dichromate anion obtained by all techniques strongly suggest the 3-receptor as a selective Cr(VI) sensor.

A Cr(VI) selective probe based on a quinoline-amide calix[4]arene.

PubMed

Ferreira, Juliane F; Bagatin, Izilda A

2018-01-15

A new quinoline-amide calix[4]arene 3-receptor for detection of hazardous anions and cations have been synthesized. The 3-receptor was examined for its sensing properties towards several different anions (Cr 2 O 7 2- , SCN - , F - , Cl - , NO 3 - ) and metal ions (Hg 2+ , Cd 2+ , Ag + ) by UV-vis and fluorescence spectroscopies. It was detected that the 3-receptor has only sensing ability for Cr 2 O 7 2- and Hg 2+ ions, resulting in the association constants higher for Cr 2 O 7 2- than to the Hg 2+ ions. High selectivity towards Cr 2 O 7 2- were also observed by fluorescence measurement among other ions (F - , Cl - , SCN - , Hg 2+ , Cd 2+ , Ag + ) with a low limit of detection (7.36×10 -6 moldm -3 ). Proton NMR anion-binding investigations revealed a strong interaction of Cr 2 O 7 2- anion with NH and CH groups of the receptor, showing that the combination with hydrogen-bonds donor groups strengthened the anion receptor association. Furthermore, remarkable association constants for dichromate anion obtained by all techniques strongly suggest the 3-receptor as a selective Cr(VI) sensor. Copyright © 2017 Elsevier B.V. All rights reserved.

Simultaneous Analysis of Monovalent Anions and Cations with a Sub-Microliter Dead-Volume Flow-Through Potentiometric Detector for Ion Chromatography

PubMed Central

Dumanli, Rukiye; Attar, Azade; Erci, Vildan; Isildak, Ibrahim

2016-01-01

A microliter dead-volume flow-through cell as a potentiometric detector is described in this article for sensitive, selective and simultaneous detection of common monovalent anions and cations in single column ion chromatography for the first time. The detection cell consisted of less selective anion- and cation-selective composite membrane electrodes together with a solid-state composite matrix reference electrode. The simultaneous separation and sensitive detection of sodium (Na+), potassium (K+), ammonium (NH4+), chloride (Cl−) and nitrate (NO3−) in a single run was achieved by using 98% 1.5 mM MgSO4 and 2% acetonitrile eluent with a mixed-bed ion-exchange separation column without suppressor column system. The separation and simultaneous detection of the anions and cations were completed in 6 min at the eluent flow-rate of 0.8 mL/min. Detection limits, at S/N = 3, were ranged from 0.2 to 1.0 µM for the anions and 0.3 to 3.0 µM for the cations, respectively. The developed method was successfully applied to the simultaneous determination of monovalent anions and cations in several environmental and biological samples. PMID:26786906

Cationizable lipid micelles as vehicles for intraarterial glioma treatment.

PubMed

Nguyen, Juliane; Cooke, Johann R N; Ellis, Jason A; Deci, Michael; Emala, Charles W; Bruce, Jeffrey N; Bigio, Irving J; Straubinger, Robert M; Joshi, Shailendra

2016-05-01

The relative abundance of anionic lipids on the surface of endothelia and on glioma cells suggests a workable strategy for selective drug delivery by utilizing cationic nanoparticles. Furthermore, the extracellular pH of gliomas is relatively acidic suggesting that tumor selectivity could be further enhanced if nanoparticles can be designed to cationize in such an environment. With these motivating hypotheses the objective of this study was to determine whether nanoparticulate (20 nm) micelles could be designed to improve their deposition within gliomas in an animal model. To test this, we performed intra-arterial injection of micelles labeled with an optically quantifiable dye. We observed significantly greater deposition (end-tissue concentration) of cationizable micelles as compared to non-ionizable micelles in the ipsilateral hemisphere of normal brains. More importantly, we noted enhanced deposition of cationizable as compared to non-ionizable micelles in glioma tissue as judged by semiquantitative fluorescence analysis. Micelles were generally able to penetrate to the core of the gliomas tested. Thus we conclude that cationizable micelles may be constructed as vehicles for facilitating glioma-selective delivery of compounds after intraarterial injection.

8-Hydroxyquinoline based push-pull azo dye: Novel colorimetric chemosensor for anion detection

NASA Astrophysics Data System (ADS)

Arslan, Ömer; Aydıner, Burcu; Yalçın, Ergin; Babür, Banu; Seferoğlu, Nurgül; Seferoğlu, Zeynel

2017-12-01

A novel colorimetric chemosensor based on push-pull dye (8HQA) was synthesized and characterized by using IR, 1H/13C NMR and HRMS for the purpose of recognition of anions and cations in DMSO. The absorption maxima of the chemosensor were determined in different solvents. The selectivity and sensitivity of 8HQA to anions were determined with spectrophotometric and 1H NMR titration techniques. The selectivity of 8HQA for studied anions (CN-, F-, Cl-, I-, AcO-, HSO4- and H2PO4-) was determined in DMSO. There is no selectivity between competing anions such as CN-, F- AcO- and H2PO4- at the stoichiometric ratio of 1:1 in UV-vis titrations experiments however, it was observed different color changes upon addition of CN-, F-, AcO- and H2PO4- to the DMSO solution. In addition, the chemosensor showed no colorimetric response for the following anions; Cl-, I- and HSO4- in DMSO. The colorimetric sensing ability of 8HQA was studied in the presence of chloride salts of different cations such as Ca2+, Mg2+, Cu2+, Co2+, Sn2+, Ni2+, Cd2+ and Hg2+. Upon the addition of 4 equiv of each of the cations showed bathochromic shifts except for Ca2+and Cu2+. Interestingly, no selectivity was observed in interaction with metal cations. In addition, the molecular and electronic structures of 8HQA, as well as the molecular complexes of 8HQA, formed with the anions, were obtained theoretically and confirmed by DFT and TD-DFT calculations.

A coumarin-pyrazolone based fluorescent probe for selective colorimetric and fluorimetric fluoride detection: Synthesis, spectroscopic properties and DFT calculations

NASA Astrophysics Data System (ADS)

Babür, Banu; Seferoğlu, Nurgül; Seferoğlu, Zeynel

2018-06-01

A novel coumarin based fluorescence anion chemosensor (P-1) bearing pyrazolone as a receptoric part was synthesized and characterized by using FT-IR, 1H/13C NMR and HRMS for the purpose of recognition of anions in DMSO. P-1 has four tautomeric structures and the most stable tautomeric form of P-1 was determined experimentally and theoretically. The chemosensor P-1 consists two receptoric parts as free amide Nsbnd H and enamine Nsbnd H which is stabilized intramolecular H-bonding with coumarin carbonyl oxygen. P-1 interacts selectively with fluoride anion via amide Nsbnd H. The selectivity and sensitivity of probe to various anions were determined with spectrophotometric and 1H NMR titration techniques as experimentally and all results were also explained by theoretical calculations.

Effect of the electronegativity on the electrosorption selectivity of anions during capacitive deionization.

PubMed

Sun, Zhumei; Chai, Liyuan; Liu, Mingshi; Shu, Yude; Li, Qingzhu; Wang, Yunyan; Qiu, Dingfan

2018-03-01

The effect of electronegativity on the electrosorption selectivity of anions during capacitive deionization was investigated via a combination of experimental and theoretical studies. A model was developed based on chemical thermodynamics and the classic Stern's model to reveal the role of the anode potential and to describe electrosorption selectivity behavior during capacitive deionization. The effects of the anode potential on the adsorption of Cl - and ReO 4 - were studied and the obtained data were used to validate the model. Using the validated model, the effects of the anode potential and electronegativity of various anions, including Cl - , ReO 4 - , SO 4 2- and NO 3 - were assessed. The experimental results for the electrosorption of Cl - and ReO 4 - corresponded well with the developed model. The electrosorption capacity demonstrates a logarithmic relationship with the anode potential. The model showed that the electronegativity significantly affects the selectivity. In a mixed Cl - , ReO 4 - , SO 4 2- and NO 3 - solution, ReO 4 - was preferentially adsorbed over the other three anions, and the following selectivity was exhibited: ReO 4 -  > NO 3 -  > Cl -  > SO 4 2- . The results showed that the effect of flow rates on the electrosorption selectivity can be considered negligible when the flow rates are higher than 112 mL min -1 . The anions selectivity can be further enhanced by increasing the anode potential, and electrosorption selectivity is no appreciable decline after 6 experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Surfactants, not size or zeta-potential influence blood-brain barrier passage of polymeric nanoparticles.

PubMed

Voigt, Nadine; Henrich-Noack, Petra; Kockentiedt, Sarah; Hintz, Werner; Tomas, Jürgen; Sabel, Bernhard A

2014-05-01

Nanoparticles (NP) can deliver drugs across the blood-brain barrier (BBB), but little is known which of the factors surfactant, size and zeta-potential are essential for allowing BBB passage. To this end we designed purpose-built fluorescent polybutylcyanoacrylate (PBCA) NP and imaged the NP's passage over the blood-retina barrier - which is a model of the BBB - in live animals. Rats received intravenous injections of fluorescent PBCA-NP fabricated by mini-emulsion polymerisation to obtain various NP's compositions that varied in surfactants (non-ionic, anionic, cationic), size (67-464nm) and zeta-potential. Real-time imaging of retinal blood vessels and retinal tissue was carried out with in vivo confocal neuroimaging (ICON) before, during and after NP's injection. Successful BBB passage with subsequent cellular labelling was achieved if NP were fabricated with non-ionic surfactants or cationic stabilizers but not when anionic compounds were added. NP's size and charge had no influence on BBB passage and cell labelling. This transport was not caused by an unspecific opening of the BBB because control experiments with injections of unlabelled NP and fluorescent dye (to test a "door-opener" effect) did not lead to parenchymal labelling. Thus, neither NP's size nor chemo-electric charge, but particle surface is the key factor determining BBB passage. This result has important implications for NP engineering in medicine: depending on the surfactant, NP can serve one of two opposite functions: while non-ionic tensides enhance brain up-take, addition of anionic tensides prevents it. NP can now be designed to specifically enhance drug delivery to the brain or, alternatively, to prevent brain penetration so to reduce unwanted psychoactive effects of drugs or prevent environmental nanoparticles from entering tissue of the central nervous system. Copyright © 2014 Elsevier B.V. All rights reserved.

CLAG3 Self-Associates in Malaria Parasites and Quantitatively Determines Nutrient Uptake Channels at the Host Membrane

PubMed Central

Gupta, Ankit; Balabaskaran-Nina, Praveen; Nguitragool, Wang; Saggu, Gagandeep S.; Schureck, Marc A.

2018-01-01

ABSTRACT Malaria parasites increase host erythrocyte permeability to ions and nutrients via a broad-selectivity channel known as the plasmodial surface anion channel (PSAC), linked to parasite-encoded CLAG3 and two associated proteins. These proteins lack the multiple transmembrane domains typically present in channel-forming proteins, raising doubts about their precise roles. Using the virulent human Plasmodium falciparum parasite, we report that CLAG3 undergoes self-association and that this protein’s expression determines channel phenotype quantitatively. We overcame epigenetic silencing of clag3 paralogs and engineered parasites that express two CLAG3 isoforms simultaneously. Stoichiometric expression of these isoforms yielded intermediate channel phenotypes, in agreement with observed trafficking of both proteins to the host membrane. Coimmunoprecipitation and surface labeling revealed formation of CLAG3 oligomers. In vitro selections applied to these transfectant lines yielded distinct mutants with correlated changes in channel activity. These findings support involvement of the identified oligomers in PSAC formation and parasite nutrient acquisition. PMID:29739907

Hybrid capacitive deionization with anion-exchange membranes for lithium extraction

NASA Astrophysics Data System (ADS)

Siekierka, Anna; Bryjak, Marek

2017-11-01

Lithium is considered to be a critical material for various industrial fields. We present our studies on extraction lithium from diluted aqueous solution by novel hybrid system based on a membrane capacitive deionization and batteries desalination. Hybrid CDI is comprised by a lithium selective adsorbent, activated carbon electrode and anion-exchange membranes. Here, we demonstrated implication of various type of anion-exchange membranes and influence their properties on effective capacity and energy requirements in charge/discharge steps. We described a configuration with anion-exchange membrane characterized by adsorption capacity of 35 mg/g of Li+ with 0.08Wh/g and removal efficiency of 60 % of lithium ions, using novel selective desalination technique.

The electrostatics of VDAC: implications for selectivity and gating.

PubMed

Choudhary, Om P; Ujwal, Rachna; Kowallis, William; Coalson, Rob; Abramson, Jeff; Grabe, Michael

2010-02-26

The voltage-dependent anion channel (VDAC) is the major pathway mediating the transfer of metabolites and ions across the mitochondrial outer membrane. Two hallmarks of the channel in the open state are high metabolite flux and anion selectivity, while the partially closed state blocks metabolites and is cation selective. Here we report the results from electrostatics calculations carried out on the recently determined high-resolution structure of murine VDAC1 (mVDAC1). Poisson-Boltzmann calculations show that the ion transfer free energy through the channel is favorable for anions, suggesting that mVDAC1 represents the open state. This claim is buttressed by Poisson-Nernst-Planck calculations that predict a high single-channel conductance indicative of the open state and an anion selectivity of 1.75--nearly a twofold selectivity for anions over cations. These calculations were repeated on mutant channels and gave selectivity changes in accord with experimental observations. We were then able to engineer an in silico mutant channel with three point mutations that converted mVDAC1 into a channel with a preference for cations. Finally, we investigated two proposals for how the channel gates between the open and the closed state. Both models involve the movement of the N-terminal helix, but neither motion produced the observed voltage sensitivity, nor did either model result in a cation-selective channel, which is observed experimentally. Thus, we were able to rule out certain models for channel gating, but the true motion has yet to be determined. Copyright (c) 2009. Elsevier Ltd. All rights reserved.

Polymeric Optical Sensors for Selective and Sensitive Nitrite Detection Using Cobalt(III) Corrole and Rh(III) Porphyrin as Ionophores

PubMed Central

Yang, Si; Wo, Yaqi; Meyerhoff, Mark E.

2014-01-01

Cobalt(III) 5, 10, 15-tris(4-tert-butylphenyl) corrole with a triphenylphosphine axial ligand and rhodium(III) 5,10,15,20-tetra(p-tert-butylphenyl)porphyrin are incorporated into plasticized poly(vinyl chloride) films to fabricate nitrite-selective bulk optodes via absorbance measurements. The resulting films yield sensitive, fast and fully reversible response toward nitrite with significantly enhanced nitrite selectivity over other anions including lipophilic anions such as thiocyanate and perchlorate. The selectivity patterns differ greatly from the Hofmeister series based on anion lipophilicity and are consistent with selectivity obtained with potentiometric sensors based on the same ionophores. The optical nitrite sensors are shown to be useful for detecting rates of emission of nitric oxide (NO) from NO releasing polymers containing S-nitroso-N-acetyl-penicillamine. PMID:25150700

Highly selective and sensitive macrocycle-based dinuclear foldamer for fluorometric and colorimetric sensing of citrate in water.

PubMed

Rhaman, Md Mhahabubur; Hasan, Mohammad H; Alamgir, Azmain; Xu, Lihua; Powell, Douglas R; Wong, Bryan M; Tandon, Ritesh; Hossain, Md Alamgir

2018-01-10

The selective detection of citrate anions is essential for various biological functions in living systems. A quantitative assessment of citrate is required for the diagnosis of various diseases in the human body; however, it is extremely challenging to develop efficient fluorescence and color-detecting molecular probes for sensing citrate in water. Herein, we report a macrocycle-based dinuclear foldamer (1) assembled with eosin Y (EY) that has been studied for anion binding by fluorescence and colorimetric techniques in water at neutral pH. Results from the fluorescence titrations reveal that the 1·EY ensemble strongly binds citrate anions, showing remarkable selectivity over a wide range of inorganic and carboxylate anions. The addition of citrate anions to the 1·EY adduct led to a large fluorescence enhancement, displaying a detectable color change under both visible and UV light in water up to 2 μmol. The biocompatibility of 1·EY as an intracellular carrier in a biological system was evaluated on primary human foreskin fibroblast (HF) cells, showing an excellent cell viability. The strong binding properties of the ensemble allow it to be used as a highly sensitive, detective probe for biologically relevant citrate anions in various applications.

Analyses of sulfonamide antibiotics by a successive anion- and cation-selective injection coupled to microemulsion electrokinetic chromatography.

PubMed

Lin, Yun-Ta; Liu, Yu-Wei; Cheng, Yi-Jie; Huang, Hsi-Ya

2010-07-01

In this study, an MEEKC was used to detect and analyze nine sulfonamide antibiotics. Owing to an insufficient sensitivity of on-column UV detection, a field-amplified sample injection, successive anion- and cation-selective injection, was used for the on-line concentration of the nine antibiotics. In the successive anion- and cation-selective injection mode, a leading water plug was introduced prior to anion injection, and then an acidic plug followed by a terminal water plug had to be used before subsequent cation injection. The results indicated some sulfonamides (sulfamonomethoxine, sulfamethazine, sulfamerazine and sulfadiazine) were determined as split signals in pairs, and this was likely due to the use of a longer acid plug (360 s) which caused the sulfonamide anions and cations to be stacked in two distinct zones of the leading water and acid plugs. Meanwhile, all the sulfonamides that were introduced either by anion or cation injection were stacked within the leading water plug when a shorter acid plug (210 s) was used. As a result, the nine sulfonamides were determined as single and symmetrical peaks with low LODs (0.9-4.2 microg/L). Furthermore, the MEEKC method was successfully applied for the detection of trace sulfonamide residues in several food and water samples.

The benzil-cyanide reaction and its application to the development of a selective cyanide anion indicator.

PubMed

Cho, Dong-Gyu; Kim, Jong Hoon; Sessler, Jonathan L

2008-09-10

The benzil-cyanide reaction is a cyanide-specific reaction that has been exploited to produce a colorimetric indicator for this toxic anion. This was done by producing a pi-extended analogue of benzil, 7, which is soluble in a 70:30 (v/v) mixture of methanol-water. In this medium, dilute solutions of 7 are yellow but produce colorless products when exposed to low concentrations of cyanide anion (> or = 1.7 microM; added as an aqueous NaCN solution), but no other common anions (e.g., OH(-), F(-), N3(-), benzoate(-), and H2PO4(-)). On the basis of these observations and supporting mechanistic analyses, it is concluded that the modified benzil system 7 is a promising cyanide anion indicator that is attractive in terms of its selectivity, ease-of-use, water compatibility, and the low, naked-eye discernible cyanide detection limit it provides.

On the role of methacrylic acid copolymers in the intracellular delivery of antisense oligonucleotides.

PubMed

Yessine, Marie-Andrée; Meier, Christian; Petereit, Hans-Ulrich; Leroux, Jean-Christophe

2006-05-01

The delivery of active biomacromolecules to the cytoplasm is a major challenge as it is generally hindered by the endosomal/lysosomal barrier. Synthetic titratable polyanions can overcome this barrier by destabilizing membrane bilayers at pH values typically found in endosomes. This study investigates how anionic polyelectrolytes can enhance the cytoplasmic delivery of an antisense oligonucleotide (ODN). Novel methacrylic acid (MAA) copolymers were examined for their pH-sensitive properties and ability to destabilize cell membranes in a pH-dependent manner. Ternary complex formulations prepared with the ODN, a cationic lipid and a MAA copolymer were systematically characterized with respect to their size, zeta potential, antisense activity, cytotoxicity and cellular uptake using the A549 human lung carcinoma cell line. The MAA copolymer substantially increased the activity of the antisense ODN in inhibiting the expression of protein kinase C-alpha. Uptake, cytotoxicity and antisense activity were strongly dependent on copolymer concentration. Metabolic inhibitors demonstrated that endocytosis was the major internalization pathway of the complexes, and that endosomal acidification was essential for ODN activity. Confocal microscopy analysis of cells incubated with fluorescently-labeled complexes revealed selective delivery of the ODN, but not of the copolymer, to the cytoplasm/nucleus. This study provides new insight into the mechanisms of intracellular delivery of macromolecular drugs, using synthetic anionic polyelectrolytes.

Purification and Characterization of Two Voltage-Dependent Anion Channel Isoforms from Plant Seeds1

PubMed Central

Abrecht, Helge; Wattiez, Ruddy; Ruysschaert, Jean-Marie; Homblé, Fabrice

2000-01-01

Mitochondria were isolated from imbibed seeds of lentil (Lens culinaris) and Phaseolus vulgaris. We copurified two voltage-dependent anion channel from detergent solubilized mitochondria in a single purification step using hydroxyapatite. The two isoforms from P. vulgaris were separated by chromatofocusing chromatography in 4 m urea without any loss of channel activity. Channel activity of each isoform was characterized upon reconstitution into diphytanoyl phosphatidylcholine planar lipid bilayers. Both isoforms form large conductance channels that are slightly anion selective and display cation selective substates. PMID:11080295

Simple guanidinium motif for the selective binding and extraction of sulfate

DOE PAGES

Seipp, Charles A.; Williams, Neil J.; Bryantsev, Vyacheslav S.; ...

2017-06-30

A simple bidentate anion receptor, shown previously to adopt a rigid pseudobicyclic conformation while binding anions in the solid state, selectively binds sulfate in aqueous solutions with logK1 and logK2 values of 3.78 ± 0.12 M-1 and 2.10 ± 0.23 M-1, respectively. This anion receptor has little to no affinity for nitrate and chloride in the same solutions. A lipophilic derivative was synthesized in four steps to yield an extractant that is capable of partitioning sulfate into 1,2 dichloroethane from water in the presence of large excesses of chloride. This extractant demonstrated D values as high as 2.5 with onlymore » 30 mM of anion receptor.« less

Simple guanidinium motif for the selective binding and extraction of sulfate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seipp, Charles A.; Williams, Neil J.; Bryantsev, Vyacheslav S.

A simple bidentate anion receptor, shown previously to adopt a rigid pseudobicyclic conformation while binding anions in the solid state, selectively binds sulfate in aqueous solutions with logK1 and logK2 values of 3.78 ± 0.12 M-1 and 2.10 ± 0.23 M-1, respectively. This anion receptor has little to no affinity for nitrate and chloride in the same solutions. A lipophilic derivative was synthesized in four steps to yield an extractant that is capable of partitioning sulfate into 1,2 dichloroethane from water in the presence of large excesses of chloride. This extractant demonstrated D values as high as 2.5 with onlymore » 30 mM of anion receptor.« less

Electrochemical Quartz Crystal Microbalance Monitoring of the Cyclic Voltammetric Deposition of Polyaniline

ERIC Educational Resources Information Center

Xie, Qingji; Li, Zhili; Deng, Chunyan; Liu, Meiling; Zhang, Youyu; Ma, Ming; Xia, Shaoxi; Xiao, Xiaoming; Yin, Dulin; Yao, Shouzhuo

2007-01-01

A real-time, labeled-free and nanogram-sensitive mass sensor, electrochemical quartz crystal microbalance (EQCM) is used to monitor a cyclic voltammetric deposition of polyaniline (PANI). The results determined that the efficiency for PANI deposition and the anion-doping ratio is calculated in one single cyclic voltammetric.

Engineering Considerations for Hydroxide Treatment of Training Ranges

DTIC Science & Technology

2007-06-01

solutions were compared to the untreated controls. [14C] labeled samples were counted on a Packard Instruments liquid scin - tillation counter (Model...and the soil was removed to a scin - tillation vial. Unlabeled flasks had the soil and liquid analyzed for TOC and the liquid analyzed for anion content

Low-energy electron-induced dissociation in gas-phase nicotine, pyridine, and methyl-pyrrolidine

NASA Astrophysics Data System (ADS)

Ryszka, Michal; Alizadeh, Elahe; Li, Zhou; Ptasińska, Sylwia

2017-09-01

Dissociative electron attachment to nicotine, pyridine, and N-methyl-pyrrolidine was studied in the gas phase in order to assess their stability with respect to low-energy electron interactions. Anion yield curves for different products at electron energies ranging from zero to 15 eV were measured, and the molecular fragmentation pathways were proposed. Nicotine does not form a stable parent anion or a dehydrogenated anion, contrary to other biological systems. However, we have observed complex dissociation pathways involving fragmentation at the pyrrolidine side accompanied by isomerization mechanisms. Combining structure optimization and enthalpy calculations, performed with the Gaussian09 package, with the comparison with a deuterium-labeled N-methyl-d3-pyrrolidine allowed for the determination of the fragmentation pathways. In contrast to nicotine and N-methylpyrrolidine, the dominant pathway in dissociative electron attachment to pyridine is the loss of hydrogen, leading to the formation of an [M—H]- anion. The presented results provide important new information about the stability of nicotine and its constituent parts and contribute to a better understanding of the fragmentation mechanisms and their effects on the biological environment.

Locating the Anion-selectivity Filter of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Chloride Channel

PubMed Central

Cheung, Min; Akabas, Myles H.

1997-01-01

The cystic fibrosis transmembrane conductance regulator forms an anion-selective channel; the site and mechanism of charge selectivity is unknown. We previously reported that cysteines substituted, one at a time, for Ile331, Leu333, Arg334, Lys335, Phe337, Ser341, Ile344, Arg347, Thr351, Arg352, and Gln353, in and flanking the sixth membrane-spanning segment (M6), reacted with charged, sulfhydryl-specific, methanethiosulfonate (MTS) reagents. We inferred that these residues are on the water-accessible surface of the protein and may line the ion channel. We have now measured the voltage-dependence of the reaction rates of the MTS reagents with the accessible, engineered cysteines. By comparing the reaction rates of negatively and positively charged MTS reagents with these cysteines, we measured the extent of anion selectivity from the extracellular end of the channel to eight of the accessible residues. We show that the major site determining anion vs. cation selectivity is near the cytoplasmic end of the channel; it favors anions by ∼25-fold and may involve the residues Arg347 and Arg352. From the voltage dependence of the reaction rates, we calculated the electrical distance to the accessible residues. For the residues from Leu333 to Ser341 the electrical distance is not significantly different than zero; it is significantly different than zero for the residues Thr351 to Gln353. The maximum electrical distance measured was 0.6 suggesting that the channel extends more cytoplasmically and may include residues flanking the cytoplasmic end of the M6 segment. Furthermore, the electrical distance calculations indicate that R352C is closer to the extracellular end of the channel than either of the adjacent residues. We speculate that the cytoplasmic end of the M6 segment may loop back into the channel narrowing the lumen and thereby forming both the major resistance to current flow and the anion-selectivity filter. PMID:9089437

Comprehensive and accurate tracking of carbon origin of LC-tandem mass spectrometry collisional fragments for 13C-MFA.

PubMed

Kappelmann, Jannick; Klein, Bianca; Geilenkirchen, Petra; Noack, Stephan

2017-03-01

In recent years the benefit of measuring positionally resolved 13 C-labeling enrichment from tandem mass spectrometry (MS/MS) collisional fragments for improved precision of 13 C-Metabolic Flux Analysis ( 13 C-MFA) has become evident. However, the usage of positional labeling information for 13 C-MFA faces two challenges: (1) The mass spectrometric acquisition of a large number of potentially interfering mass transitions may hamper accuracy and sensitivity. (2) The positional identity of carbon atoms of product ions needs to be known. The present contribution addresses the latter challenge by deducing the maximal positional labeling information contained in LC-ESI-MS/MS spectra of product anions of central metabolism as well as product cations of amino acids. For this purpose, we draw on accurate mass spectrometry, selectively labeled standards, and published fragmentation pathways to structurally annotate all dominant mass peaks of a large collection of metabolites, some of which with a complete fragmentation pathway. Compiling all available information, we arrive at the most detailed map of carbon atom fate of LC-ESI-MS/MS collisional fragments yet, comprising 170 intense and structurally annotated product ions with unique carbon origin from 76 precursor ions of 72 metabolites. Our 13 C-data proof that heuristic fragmentation rules often fail to yield correct fragment structures and we expose common pitfalls in the structural annotation of product ions. We show that the positionally resolved 13 C-label information contained in the product ions that we structurally annotated allows to infer the entire isotopomer distribution of several central metabolism intermediates, which is experimentally demonstrated for malate using quadrupole-time-of-flight MS technology. Finally, the inclusion of the label information from a subset of these fragments improves flux precision in a Corynebacterium glutamicum model of the central carbon metabolism.

A new method for the labelling of proteins with radioactive arsenic isotopes

NASA Astrophysics Data System (ADS)

Jennewein, M.; Hermanne, A.; Mason, R. P.; Thorpe, P. E.; Rösch, F.

2006-12-01

Radioarsenic labelled radiopharmaceuticals could be a valuable asset to positron emission tomography. In particular, the long half-lives of 72As ( T=26 h) and 74As ( T=17.8 d) allow to investigate slow physiological or metabolical processes, like the enrichment and distribution of monoclonal antibodies (mab) in tumour tissue. In this work, a new method for the labelling of proteins with various radioactive arsenic isotopes was developed. For this purpose, two proteins, namely a chimeric IgG 3 monoclonal antibody, ch3G4, directed against anionic phospholipids, and Rituxan (Rituximab), were labelled as a proof of principle with no-carrier-added radioarsenic isotopes ( 74As and 77As). The developed labelling chemistry gives high yields (>99.9%), is reliable and could easily be transferred to automated labelling systems in a clinical environment. At least for the mab used in this work, this route of radioarsenic labelling does not affect the immunoreactivity of the product. The arsenic label stays stable for up to 72 h at the molecular mass of the monoclonal antibody, which is in particular relevant to follow the pharmacology and pharmacokinetics of the labelled mab for several days.

A selective optical sensor based on [9]mercuracarborand-3, a new type of ionophore with a chloride complexing cavity

NASA Technical Reports Server (NTRS)

Badr, I. H.; Johnson, R. D.; Diaz, M.; Hawthorne, M. F.; Bachas, L. G.; Daunert, S. (Principal Investigator)

2000-01-01

A highly selective optical sensor for chloride, based on the multidentate Lewis acid ionophore [9]mercuracarborand-3, is described herein. This sensor is constructed by embedding the mercuracarborand ionophore, a suitable pH-sensitive lipophilic dye, and lipophilic cationic sites in a plasticized polymeric membrane. The multiple complementary interactions offered by the preorganized complexing cavity of [9]mercuracarborand-3 is shown to control the anion selectivity pattern of the optical film. The film exhibits a significantly enhanced selectivity for chloride over a variety of lipophilic anions such as perchlorate, nitrate, salicylate, and thiocyanate. Furthermore, the optical selectivity coefficients obtained for chloride over other biologically relevant anions are shown to meet the selectivity requirements for the determination of chloride in physiological fluids, unlike previously reported chloride optical sensors. In addition, the optical film responds to chloride reversibly over a wide dynamic range (16 microM-136 mM) with fast response and recovery times.

A simple and efficient anionic chromogenic chemosensor based on 2,4-dinitrodiphenylamine in dimethyl sulfoxide and in dimethyl sulfoxide-water mixtures

NASA Astrophysics Data System (ADS)

Marini, Vanderléia Gava; Zimmermann, Lizandra Maria; Machado, Vanderlei Gageiro

2010-02-01

Solutions of 2,4-dinitrodiphenylamine ( 1) in dimethylsulfoxide (DMSO) are colorless but upon deprotonation they become red. Addition of various anionic species (HSO 4-, H 2PO 4-, NO 3-, CN -, CH 3COO -, F -, Cl -, Br -, and I -) to solutions of 1 revealed that only CN -, F -, CH 3COO -, and H 2PO 4- led to the appearance of the red color in solution. The presence of increasing amounts of water in solutions containing 1 made it progressively selective toward CN - and the system with the addition of 4.3% (v/v) of water was highly selective for CN - among all anions studied. The experimental data collected indicated that proton transfer from 1 to the anion occurs, and a model was used to explain the experimental results, which considers two 1:anion stoichiometries, 1:1 and 1:2. For the latter, the data suggest that the anion forms firstly a hydrogen-bonded complex with a second anion equivalent necessary for the abstraction of the proton, with the formation of a [HA 2] - complex. The study performed here demonstrates the important role of the environment of the anion and 1 for the efficiency of the chromogenic chemosensor. Besides the different affinities of each anion for water, the solvation of both the anion and 1 is responsible for reducing the interaction between these species. In small amounts, water or hydrogen-bonded DMSO-water complexes are able to stabilize the conjugated base of 1 through hydrogen bonding, making 1 more acidic, which explains the change from 1:1 and 1:2 toward 1:1 1:anion stoichiometry upon addition of water. In addition, water is able to solvate the anion and also 1, which hinders the formation of 1:1 hydrogen-bonded 1:anion complexes prior to the abstraction of the proton.

A simple and efficient anionic chromogenic chemosensor based on 2,4-dinitrodiphenylamine in dimethyl sulfoxide and in dimethyl sulfoxide-water mixtures.

PubMed

Marini, Vanderléia Gava; Zimmermann, Lizandra Maria; Machado, Vanderlei Gageiro

2010-02-01

Solutions of 2,4-dinitrodiphenylamine (1) in dimethylsulfoxide (DMSO) are colorless but upon deprotonation they become red. Addition of various anionic species (HSO(4)(-), H(2)PO(4)(-), NO(3)(-), CN(-), CH(3)COO(-), F(-), Cl(-), Br(-), and I(-)) to solutions of 1 revealed that only CN(-), F(-), CH(3)COO(-), and H(2)PO(4)(-) led to the appearance of the red color in solution. The presence of increasing amounts of water in solutions containing 1 made it progressively selective toward CN(-) and the system with the addition of 4.3% (v/v) of water was highly selective for CN(-) among all anions studied. The experimental data collected indicated that proton transfer from 1 to the anion occurs, and a model was used to explain the experimental results, which considers two 1:anion stoichiometries, 1:1 and 1:2. For the latter, the data suggest that the anion forms firstly a hydrogen-bonded complex with a second anion equivalent necessary for the abstraction of the proton, with the formation of a [HA(2)](-) complex. The study performed here demonstrates the important role of the environment of the anion and 1 for the efficiency of the chromogenic chemosensor. Besides the different affinities of each anion for water, the solvation of both the anion and 1 is responsible for reducing the interaction between these species. In small amounts, water or hydrogen-bonded DMSO-water complexes are able to stabilize the conjugated base of 1 through hydrogen bonding, making 1 more acidic, which explains the change from 1:1 and 1:2 toward 1:1 1:anion stoichiometry upon addition of water. In addition, water is able to solvate the anion and also 1, which hinders the formation of 1:1 hydrogen-bonded 1:anion complexes prior to the abstraction of the proton. Copyright (c) 2009 Elsevier B.V. All rights reserved.

A highly selective and turn-on fluorescence sensor for detection of cyanide.

PubMed

Jhong, Yi; Hsieh, Wei Hsun; Chir, Jiun-Ly; Wu, An-Tai

2014-11-01

2-Hydroxy-1-naphthaldehyde (receptor 1) serves as a selective chemosensor for cyanide anion (CN(-)). In the presence of CN(-), an enhanced fluorescent intensity and red shift were observed. The observed complexation between receptor 1 and CN(-) may cause from a formation of phenoxide anion by nucleophilic addition of the CN(-) to carbonyl group.

Covalent Polymers Containing Discrete Heterocyclic Anion Receptors

PubMed Central

Rambo, Brett M.; Silver, Eric S.; Bielawski, Christopher W.; Sessler, Jonathan L.

2010-01-01

This chapter covers recent advances in the development of polymeric materials containing discrete heterocyclic anion receptors, and focuses on advances in anion binding and chemosensor chemistry. The development of polymers specific for anionic species is a relatively new and flourishing area of materials chemistry. The incorporation of heterocyclic receptors capable of complexing anions through non-covalent interactions (e.g., hydrogen bonding and electrostatic interactions) provides a route to not only sensitive but also selective polymer materials. Furthermore, these systems have been utilized in the development of polymers capable of extracting anionic species from aqueous environments. These latter materials may lead to advances in water purification and treatment of diseases resulting from surplus ions. PMID:20871791

Distinct regions that control ion selectivity and calcium-dependent activation in the bestrophin ion channel.

PubMed

Vaisey, George; Miller, Alexandria N; Long, Stephen B

2016-11-22

Cytoplasmic calcium (Ca 2+ ) activates the bestrophin anion channel, allowing chloride ions to flow down their electrochemical gradient. Mutations in bestrophin 1 (BEST1) cause macular degenerative disorders. Previously, we determined an X-ray structure of chicken BEST1 that revealed the architecture of the channel. Here, we present electrophysiological studies of purified wild-type and mutant BEST1 channels and an X-ray structure of a Ca 2+ -independent mutant. From these experiments, we identify regions of BEST1 responsible for Ca 2+ activation and ion selectivity. A "Ca 2+ clasp" within the channel's intracellular region acts as a sensor of cytoplasmic Ca 2+ . Alanine substitutions within a hydrophobic "neck" of the pore, which widen it, cause the channel to be constitutively active, irrespective of Ca 2+ . We conclude that the primary function of the neck is as a "gate" that controls chloride permeation in a Ca 2+ -dependent manner. In contrast to what others have proposed, we find that the neck is not a major contributor to the channel's ion selectivity. We find that mutation of a cytosolic "aperture" of the pore does not perturb the Ca 2+ dependence of the channel or its preference for anions over cations, but its mutation dramatically alters relative permeabilities among anions. The data suggest that the aperture functions as a size-selective filter that permits the passage of small entities such as partially dehydrated chloride ions while excluding larger molecules such as amino acids. Thus, unlike ion channels that have a single "selectivity filter," in bestrophin, distinct regions of the pore govern anion-vs.-cation selectivity and the relative permeabilities among anions.

Rotaxane and catenane host structures for sensing charged guest species.

PubMed

Langton, Matthew J; Beer, Paul D

2014-07-15

CONSPECTUS: The promise of mechanically interlocked architectures, such as rotaxanes and catenanes, as prototypical molecular switches and shuttles for nanotechnological applications, has stimulated an ever increasing interest in their synthesis and function. The elaborate host cavities of interlocked structures, however, can also offer a novel approach toward molecular recognition: this Account describes the use of rotaxane and catenane host systems for binding charged guest species, and for providing sensing capability through an integrated optical or electrochemical reporter group. Particular attention is drawn to the exploitation of the unusual dynamic properties of interlocked molecules, such as guest-induced shuttling or conformational switching, as a sophisticated means of achieving a selective and functional sensor response. We initially survey interlocked host systems capable of sensing cationic guests, before focusing on our accomplishments in synthesizing rotaxanes and catenanes designed for the more challenging task of selective anion sensing. In our group, we have developed the use of discrete anionic templation to prepare mechanically interlocked structures for anion recognition applications. Removal of the anion template reveals an interlocked host system, possessing a unique three-dimensional geometrically restrained binding cavity formed between the interlocked components, which exhibits impressive selectivity toward complementary anionic guest species. By incorporating reporter groups within such systems, we have developed both electrochemical and optical anion sensors which can achieve highly selective sensing of anionic guests. Transition metals, lanthanides, and organic fluorophores integrated within the mechanically bonded structural framework of the receptor are perturbed by the binding of the guest, with a concomitant change in the emission profile. We have also exploited the unique dynamics of interlocked hosts by demonstrating that an anion-induced conformational change can be used as a means of signal transduction. Electrochemical sensing has been realized by integration of the redox-active ferrocene functionality within a range of rotaxane and catenanes; binding of an anion perturbs the metallocene, leading to a cathodic shift in the ferrocene/ferrocenium redox couple. In order to obtain practical sensors for target charged guest species, confinement of receptors at a surface is necessary in order to develop robust, reuseable devices. Surface confinement also offers advantages over solution based receptors, including amplification of signal, enhanced guest binding thermodynamics and the negation of solubility problems. We have fabricated anion-templated rotaxanes and catenanes on gold electrode surfaces and demonstrated that the resulting mechanically bonded self-assembled monolayers are electrochemically responsive to the binding of anions, a crucial first step toward the advancement of sophisticated, highly selective, anion sensory devices. Rotaxane and catenane host molecules may be engineered to offer a superior level of molecular recognition, and the incorporation of optical or electrochemical reporter groups within these interlocked frameworks can allow for guest sensing. Advances in synthetic templation strategies has facilitated the synthesis of interlocked architectures and widened their interest as prototype molecular machines. However, their unique host-guest properties are only now beginning to be exploited as a sophisticated approach to chemical sensing. The development of functional host-guest sensory systems such as these is of great interest to the interdisciplinary field of supramolecular chemistry.

Novel salicylic acid-oriented thiourea-type receptors as colorimetric chemosensor: Synthesis, characterizations and selective naked-eye recognition properties

NASA Astrophysics Data System (ADS)

Li, Shaowei; Cao, Xiufang; Chen, Changshui; Ke, Shaoyong

2012-10-01

Based on the salicylic acid backbone, three highly sensitive and selective colorimetric chemosensors with an acylthiourea binding unit have been designed, synthesized and characterized. These chemosensors have been utilized for selective recognition of fluoride anions in dry DMSO solution by typical spectroscopic titration techniques. Furthermore, the obtained chemosensors AR1-3 have shown naked-eye sensitivity for detection of biologically important fluoride ion over other anions in solution.

Novel heterocyclic thiosemicarbazones derivatives as colorimetric and "turn on" fluorescent sensors for fluoride anion sensing employing hydrogen bonding.

PubMed

Ashok Kumar, S L; Saravana Kumar, M; Sreeja, P B; Sreekanth, A

2013-09-01

Two novel heterocyclic thiosemicarbazone derivatives have been synthesized, and characterized, by means of spectroscopic and single crystal X-ray diffraction methods. Their chromophoric-fluorogenic response towards anions in competing solvent dimethyl sulfoxide (DMSO) was studied. The receptor shows selective recognition towards fluoride anion. The binding affinity of the receptors with fluoride anion was calculated using UV-visible and fluorescence spectroscopic techniques. Copyright © 2013 Elsevier B.V. All rights reserved.

Suppression of H-/O2- exchange by incorporated nitride anions in the perovskite lattice

NASA Astrophysics Data System (ADS)

Takeiri, Fumitaka; Yajima, Takeshi; Yamamoto, Takafumi; Kobayashi, Yoji; Matsui, Toshiaki; Hester, James; Kageyama, Hiroshi

2017-12-01

We investigate the low temperature anion exchange behavior of hydride and oxide in perovskite oxynitrides. CaH2 reduction of (Sr1-xLax)Ti(O3-xNx) (0

A versatile tripodal amide receptor for the encapsulation of anions or hydrated anions via formation of dimeric capsules.

PubMed

Arunachalam, M; Ghosh, Pradyut

2010-02-01

A bowl-shaped tripodal receptor with an appropriately positioned amide functionality on the benzene platform and electron-withdrawing p-nitrophenyl terminals (L(1)) has been designed, synthesized, and studied for the anion binding properties. The single-crystal X-ray crystallographic analysis on crystals of L(1) with tetrabutylammonium salts of nitrate (1), acetate (2), fluoride (3), and chloride (4) obtained in moist dioxane medium showed encapsulation of two NO(3)(-), [(AcO)(2)(H(2)O)(4)](2-), [F(2)(H(2)O)(6)](2-), and [Cl(2)(H(2)O)(4)](2-) respectively as the anionic guests inside the staggered dimeric capsular assembly of L(1). The p-nitro substitution in the aryl terminals assisted the formation of dimeric capsular assembly of L(1) exclusively upon binding/encapsulating above different guests. Though L(1) demonstrates capsule formation upon anion or hydrated anion complexation for all of the anions studied here, its positional isomer with the o-nitro-substituted tripodal triamide receptor L(2) selectively formed the dimeric capsular assembly upon encapsulation of [F(2)(H(2)O)(6)](2-) and noncapsular aggregates in the cases of other anions such as Cl(-), NO(3)(-), and AcO(-). Interestingly, structural investigations upon anion exchange of the complexes revealed that both isomers have selectivity toward the formation of a [F(2)(H(2)O)(6)](2-) encapsulated dimeric capsule. In contrast, solution-state (1)H NMR titration studies of L(1) and L(2) in DMSO-d(6) with AcO(-) indicated 1:3 (host:guest) binding.

Effective charge measurements reveal selective and preferential accumulation of anions, but not cations, at the protein surface in dilute salt solutions

PubMed Central

Gokarn, Yatin R; Fesinmeyer, R Matthew; Saluja, Atul; Razinkov, Vladimir; Chase, Susan F; Laue, Thomas M; Brems, David N

2011-01-01

Specific-ion effects are ubiquitous in nature; however, their underlying mechanisms remain elusive. Although Hofmeister-ion effects on proteins are observed at higher (>0.3M) salt concentrations, in dilute (<0.1M) salt solutions nonspecific electrostatic screening is considered to be dominant. Here, using effective charge (Q*) measurements of hen-egg white lysozyme (HEWL) as a direct and differential measure of ion-association, we experimentally show that anions selectively and preferentially accumulate at the protein surface even at low (<100 mM) salt concentrations. At a given ion normality (50 mN), the HEWL Q* was dependent on anion, but not cation (Li+, Na+, K+, Rb+, Cs+, GdnH+, and Ca2+), identity. The Q* decreased in the order F− > Cl− > Br− > NO3− ∼ I− > SCN− > ClO4− ≫ SO42−, demonstrating progressively greater binding of the monovalent anions to HEWL and also show that the SO42− anion, despite being strongly hydrated, interacts directly with the HEWL surface. Under our experimental conditions, we observe a remarkable asymmetry between anions and cations in their interactions with the HEWL surface. PMID:21432935

Preparation of ⁶⁸Ga-labelled DOTA-peptides using a manual labelling approach for small-animal PET imaging.

PubMed

Romero, Eduardo; Martínez, Alfonso; Oteo, Marta; García, Angel; Morcillo, Miguel Angel

2016-01-01

(68)Ga-DOTA-peptides are a promising PET radiotracers used in the detection of different tumours types due to their ability for binding specifically receptors overexpressed in these. Furthermore, (68)Ga can be produced by a (68)Ge/(68)Ga generator on site which is a very good alternative to cyclotron-based PET isotopes. Here, we describe a manual labelling approach for the synthesis of (68)Ga-labelled DOTA-peptides based on concentration and purification of the commercial (68)Ga/(68)Ga generator eluate using an anion exchange-cartridge. (68)Ga-DOTA-TATE was used to image a pheochromocytoma xenograft mouse model by a microPET/CT scanner. The method described provides satisfactory results, allowing the subsequent (68)Ga use to label DOTA-peptides. The simplicity of the method along with its implementation reduced cost, makes it useful in preclinical PET studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mimicking the cell membrane: bio-inspired simultaneous functions with monovalent anion selectivity and antifouling properties of anion exchange membrane

PubMed Central

Zhao, Yan; Liu, Huimin; Tang, Kaini; Jin, Yali; Pan, Jiefeng; der Bruggen, Bart Van; Shen, Jiangnan; Gao, Congjie

2016-01-01

A new bio-inspired method was applied in this study to simultaneously improve the monovalent anion selectivity and antifouling properties of anion exchange membranes (AEMs). Three-layer architecture was developed by deposition of polydopamine (PDA) and electro-deposition of N-O-sulfonic acid benzyl chitosan (NSBC). The innermost and outermost layers were PDA with different deposition time. The middle layer was prepared by NSBC. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that PDA and NSBC were successfully modified on the surfaces of AEMs. The contact angle of the membranes indicated an improved hydrophilicity of the modified membranes. A series of electrodialysis experiments in which Cl−/SO42− separation was studied, demonstrating the monovalent anion selectivity of the samples. The Cl−/SO42− permselectivity of the modified membranes can reach up to 2.20, higher than that of the commercial membrane (only 0.78) during 90 minutes in electrodialysis (ED). The increase value of the resistance of the membranes was also measured to evaluate the antifouling properties. Sodium dodecyl benzene sulfonate (SDBS) was used as the fouling material in the ED process and the membrane area resistance of modified membrane increase value of was only 0.08 Ωcm2 30 minutes later. PMID:27853255

Mimicking the cell membrane: bio-inspired simultaneous functions with monovalent anion selectivity and antifouling properties of anion exchange membrane.

PubMed

Zhao, Yan; Liu, Huimin; Tang, Kaini; Jin, Yali; Pan, Jiefeng; der Bruggen, Bart Van; Shen, Jiangnan; Gao, Congjie

2016-11-17

A new bio-inspired method was applied in this study to simultaneously improve the monovalent anion selectivity and antifouling properties of anion exchange membranes (AEMs). Three-layer architecture was developed by deposition of polydopamine (PDA) and electro-deposition of N-O-sulfonic acid benzyl chitosan (NSBC). The innermost and outermost layers were PDA with different deposition time. The middle layer was prepared by NSBC. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that PDA and NSBC were successfully modified on the surfaces of AEMs. The contact angle of the membranes indicated an improved hydrophilicity of the modified membranes. A series of electrodialysis experiments in which Cl - /SO 4 2- separation was studied, demonstrating the monovalent anion selectivity of the samples. The Cl - /SO 4 2- permselectivity of the modified membranes can reach up to 2.20, higher than that of the commercial membrane (only 0.78) during 90 minutes in electrodialysis (ED). The increase value of the resistance of the membranes was also measured to evaluate the antifouling properties. Sodium dodecyl benzene sulfonate (SDBS) was used as the fouling material in the ED process and the membrane area resistance of modified membrane increase value of was only 0.08 Ωcm 2 30 minutes later.

Mimicking the cell membrane: bio-inspired simultaneous functions with monovalent anion selectivity and antifouling properties of anion exchange membrane

NASA Astrophysics Data System (ADS)

Zhao, Yan; Liu, Huimin; Tang, Kaini; Jin, Yali; Pan, Jiefeng; der Bruggen, Bart Van; Shen, Jiangnan; Gao, Congjie

2016-11-01

A new bio-inspired method was applied in this study to simultaneously improve the monovalent anion selectivity and antifouling properties of anion exchange membranes (AEMs). Three-layer architecture was developed by deposition of polydopamine (PDA) and electro-deposition of N-O-sulfonic acid benzyl chitosan (NSBC). The innermost and outermost layers were PDA with different deposition time. The middle layer was prepared by NSBC. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that PDA and NSBC were successfully modified on the surfaces of AEMs. The contact angle of the membranes indicated an improved hydrophilicity of the modified membranes. A series of electrodialysis experiments in which Cl-/SO42- separation was studied, demonstrating the monovalent anion selectivity of the samples. The Cl-/SO42- permselectivity of the modified membranes can reach up to 2.20, higher than that of the commercial membrane (only 0.78) during 90 minutes in electrodialysis (ED). The increase value of the resistance of the membranes was also measured to evaluate the antifouling properties. Sodium dodecyl benzene sulfonate (SDBS) was used as the fouling material in the ED process and the membrane area resistance of modified membrane increase value of was only 0.08 Ωcm2 30 minutes later.

Targeted drug delivery of Sunitinib Malate to tumor blood vessels by cRGD-chiotosan-gold nanoparticles.

PubMed

Saber, Mohaddeseh Mahmoudi; Bahrainian, Sara; Dinarvand, Rassoul; Atyabi, Fatemeh

2017-01-30

The unique characteristics of tumor vasculature represent an attractive strategy for targeted delivery of antitumor and antiangiogenic agents to the tumor. The purpose of this study was to prepare c(RGDfK) labeled chitosan capped gold nanoparticles [cRGD(CS-Au) NPs] as a carrier for selective intracellular delivery of Sunitinib Malate (STB) to the tumor vasculature. cRGD(CS-Au) NPs was formed by electrostatic interaction between cationic CS and anionic AuNPs. cRGD modified CS-Au NPs had a spherical shape with a narrow size distribution. The entrapment efficiency of sunitinib molecule was found to be 45.2%±2.05. Confocal microscopy showed enhanced and selective uptake of cRGD(CS-Au) NPs into MCF-7 and HUVEC cells compared with non-targeted CS-Au NPs. Our results suggest that it may be possible to use cRGD(CS-Au) NPs as a carrier for delivery of anticancer drugs, genes and biomolecules for inhibiting tumor vasculature. Copyright © 2016. Published by Elsevier B.V.

Development of anion-selective membranes. [for energy storage

NASA Technical Reports Server (NTRS)

Lacey, R. E.; Cowsar, D. R.

1975-01-01

Methods were studied of preparing anion-exchange membranes that would have low resistance, high selectivity, and physical and chemical stability when used in acidic media in a redox energy storage system. Of the twelve systems selected for study, only the system that was based on crosslinked poly-4-vinylpyridinium chloride produced physically strong membranes when equilibrated in l M HCl. The resistivity of the best membrane was 12 ohm-cm, and the transference number for chloride ions was 0.81.

Endocytosis and interaction of poly (amidoamine) dendrimers with Caco-2 cells.

PubMed

Kitchens, Kelly M; Foraker, Amy B; Kolhatkar, Rohit B; Swaan, Peter W; Ghandehari, Hamidreza

2007-11-01

To investigate the internalization and subcellular trafficking of fluorescently labeled poly (amidoamine) (PAMAM) dendrimers in intestinal cell monolayers. PAMAM dendrimers with positive or negative surface charge were conjugated to fluorescein isothiocyanate (FITC) and visualized for colocalization with endocytosis markers using confocal microscopy. Effect of concentration, generation and charge on the morphology of microvilli was observed using transmission electron microscopy. Both cationic and anionic PAMAM dendrimers internalized within 20 min, and differentially colocalized with endocytosis markers clathrin, EEA-1, and LAMP-1. Transmission electron microscopy analysis showed a concentration-, generation- and surface charge-dependent effect on microvilli morphology. These studies provide visual evidence that endocytic mechanism(s) contribute to the internalization and subcellular trafficking of PAMAM dendrimers across the intestinal cells, and that appropriate selection of PAMAM dendrimers based on surface charge, concentration and generation number allows the application of these polymers for oral drug delivery.

ANION EXCHANGE METHOD FOR SEPARATION OF METAL VALUES

DOEpatents

Hyde, E.K.; Raby, B.A.

1959-02-10

A method is described for selectively separating radium, bismuth, poloniums and lead values from a metallic mixture of thc same. The mixture is dissolved in aqueous hydrochloric acid and the acidity is adjusted to between 1 to 2M in hydrochloric acid to form the anionic polychloro complexes of polonium and bismuth. The solution is contacted with a first anion exchange resin such as strong base quaternary ammonia type to selectively absorb the polonium and bismuth leaving the radium and lead in the effluent. The effluent, after treatment in hydrochloric acid to increase the hydrochloric acid concentration to 6M is contacted with a second anion exchange iesin of the same type as the above to selectively adsorb the lead leaving the radium in the effluent. Radium is separately recovered from the effluent from the second exchange column. Lead is stripped from the loaded resin of the second column by treatment with 3M hydrochloric acid solution. The loaded resin of the first column is washed with 8M hydrochloric acid solution to recover bismuth and then treated with strong nitric acid solution to recover polonium.

The selective determination of sulfates, sulfonates, and phosphates in urine by capillary electrophoresis/mass spectrometry.

PubMed

Bunz, Svenja-Catharina; Neusüß, Christian

2013-01-01

Metabolite identification and metabolite profiling are of major importance in the pharmaceutical and clinical context. However, anions of biological relevance such as sulfates, sulfonates, and phosphates are rarely included in common techniques for metabolite studies. In this protocol, we demonstrate a unique method to selectively determine these anions. The method comprises a capillary electrophoresis separation using an acidic background electrolyte (pH ≤ 2) and anodic detection by mass spectrometry via negative electrospray ionization. In this way, only anions of strong acids like sulfates are determined. The selectivity for sulfur-containing species is proved based on the specific isotopic ratios. In conjunction with the accurate mass from the time-of-flight mass spectrometer, the presented method is well suited for clinical and pharmaceutical applications to identify possible metabolites and to quantify known metabolites.

Fluoride-selective colorimetric sensor based on thiourea binding site and anthraquinone reporter.

PubMed

Wu, Fang-ying; Hu, Mei-hua; Wu, Yu-mei; Tan, Xiao-fang; Zhao, Yong-qiang; Ji, Zhao-jun

2006-11-01

A structurally simple colorimetric sensor, N-4-nitrobenzene-N'-1'-anthraquinone-thiourea (1), for anions was synthesized and characterized by (1)H NMR, ESI mass and IR methods. In acetonitrile, the addition of F(-) changed 1 solution from colorless to yellow. In the presence of other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-), however, the absorption spectrum of 1 was slightly red shifted with no obvious color changes observed. The association constants of anionic complexes followed the order of F(-)>CH(3)CO(2)(-)>H(2)PO(4)(-)>HSO(4)(-)>Cl(-)>Br(-), which was different from the order of anion basicity. AM1 calculation results indicated that the most stable configuration of 1 existed in the Z-E-conformation with a six-membered ring via intramolecular hydrogen bond. This made thiourea moiety of 1 in an unfavorable conformation to bond with oxygen-anionic substrates such as CH(3)CO(2)(-) and H(2)PO(4)(-), thus leading to a high selectivity and sensitivity for the detection of F(-).

Colorimetric chemosensors based on diketopyrrolopyrrole for selective and reversible recognition of fluoride ions

NASA Astrophysics Data System (ADS)

Zhang, Yan; Yang, Xiaofeng; Sun, Guoxin; Zhang, Hao; Liu, Xiaolei; Zhu, Fengqiao; Qin, Shuchun; Zhao, Ziqi; Cui, Yu

2018-06-01

A series of colorimetric and reversible receptors for fluoride anions based on diketopyrrolopyrrole (DPP) were designed and synthesized successfully. The position of nitro substituent on the phenylhydrazide affected the alteration of photophysical properties to varying degrees. While the photoluminescence intensity of receptor 1 was weaker than that of receptor 2 and receptor 3 on account of the formation of intramolecular hydrogen bond deriving from oxygen atom of nitro substituent and hydrogen atom of hydrazide. The receptor 2 was a preferable chemosensor for responding fluoride anions. The fluorescence was quenched in the presence of fluoride anion resulted from the photo-induced electron transfer (PET) effect from the amide. The formation of deprotonation species, which produced by hydrazide Nsbnd H moiety and F- was answerable for the spectral changes. Especially, the spectral and color responses of receptors could be switched back and forth successively by adding F- and HSO4- anions in DMSO solution. These receptors could response fluoride anion sensitively, visually and selectively in a manner of reversible with a low determination.

An Anion-Induced Hydrothermal Oriented-Explosive Strategy for the Synthesis of Porous Upconversion Nanocrystals

PubMed Central

Qiu, Peiyu; Sun, Rongjin; Gao, Guo; Zhang, Chunlei; Chen, Bin; Yan, Naishun; Yin, Ting; Liu, Yanlei; Zhang, Jingjing; Yang, Yao; Cui, Daxiang

2015-01-01

Rare-earth (RE)-doped upconversion nanocrystals (UCNCs) are deemed as the promising candidates of luminescent nanoprobe for biological imaging and labeling. A number of methods have been used for the fabrication of UCNCs, but their assembly into porous architectures with desired size, shape and crystallographic phase remains a long-term challenging task. Here we report a facile, anion-induced hydrothermal oriented-explosive method to simultaneously control size, shape and phase of porous UCNCs. Our results confirmed the anion-induced hydrothermal oriented-explosion porous structure, size and phase transition for the cubic/hexagonal phase of NaLuF4 and NaGdF4 nanocrystals with various sizes and shapes. This general method is very important not only for successfully preparing lanthanide doped porous UCNCs, but also for clarifying the formation process of porous UCNCs in the hydrothermal system. The synthesized UCNCs were used for in vitro and in vivo CT imaging, and could be acted as the potential CT contrast agents. PMID:25767613

Organic solvent and temperature-enhanced ion chromatography-high resolution mass spectrometry for the determination of low molecular weight organic and inorganic anions.

PubMed

Gilchrist, Elizabeth S; Nesterenko, Pavel N; Smith, Norman W; Barron, Leon P

2015-03-20

There has recently been increased interest in coupling ion chromatography (IC) to high resolution mass spectrometry (HRMS) to enable highly sensitive and selective analysis. Herein, the first comprehensive study focusing on the direct coupling of suppressed IC to HRMS without the need for post-suppressor organic solvent modification is presented. Chromatographic selectivity and added HRMS sensitivity offered by organic solvent-modified IC eluents on a modern hyper-crosslinked polymeric anion-exchange resin (IonPac AS18) are shown using isocratic eluents containing 5-50 mM hydroxide with 0-80% methanol or acetonitrile for a range of low molecular weight anions (<165 Da). Comprehensive experiments on IC thermodynamics over a temperature range between 20-45 °C with the eluent containing up to 60% of acetonitrile or methanol revealed markedly different retention behaviour and selectivity for the selected analytes on the same polymer based ion-exchange resin. Optimised sensitivity with HRMS was achieved with as low as 30-40% organic eluent content. Analytical performance characteristics are presented and compared with other IC-MS based works. This study also presents the first application of IC-HRMS to forensic detection of trace low-order anionic explosive residues in latent human fingermarks. Copyright © 2015 Elsevier B.V. All rights reserved.

The selectivity of water-based pyrophosphate recognition is tuned by metal substitution in dimetallic receptors.

PubMed

Svane, Simon; Kjeldsen, Frank; McKee, Vickie; McKenzie, Christine J

2015-07-14

The three dimetallic compounds [Ga2(bpbp)(OH)2(H2O)2](ClO4)3, [In2(bpbp)(CH3CO2)2](ClO4)3 and [Zn2(bpbp)(HCO2)2](ClO4) (bpbp(-) = 2,6-bis((N,N'-bis(2-picolyl)amino)methyl)-4-tertbutylphenolate) were evaluated as stable solid state precursors for reactive solution state receptors to use for the recognition of the biologically important anion pyrophosphate in water at neutral pH. Indicator displacement assays using in situ generated complex-pyrocatechol violet adducts, {M2(bpbp)(HxPV)}(n+) M = Ga(3+), In(3+), Zn(2+), were tested for selectivity in their reactions with a series of common anions: pyrophosphate, phosphate, ATP, arsenate, nitrate, perchlorate, chloride, sulfate, formate, carbonate and acetate. The receptor employing Ga(3+) showed a slow but visually detectable response (blue to yellow) in the presence of one equivalent of pyrophosphate but no response to any other anion, even when they were present in much higher concentrations. The systems based on In(3+) or Zn(2+) show less selectivity in accord with visibly discernible responses to several of the anions. These results demonstrate a facile method for increasing anion selectivity without modification of an organic dinucleating ligand scaffold. The comfortable supramolecular recognition of pyrophosphate by the dimetallic complexes is demonstrated by the single crystal X-ray structure of [Ga2(bpbp)(HP2O7)](ClO4)2 in which the pyrophosphate is coordinated to the two gallium ions via four of its oxygen atoms.

Preparation of a surface-grafted imprinted ceramic membrane for selective separation of molybdate anion from water solutions.

PubMed

Zeng, Jianxian; Dong, Zhihui; Zhang, Zhe; Liu, Yuan

2017-07-05

A surface-grafted imprinted ceramic membrane (IIP-PVI/CM) for recognizing molybdate (Mo(VI)) anion was prepared by surface-initiated graft-polymerization. Firstly, raw alumina ceramic membrane (CM) was deposited with SiO 2 active layer by situ hydrolysis deposition method. Subsequently, γ-methacryloxy propyl trimethoxyl silane (MPS) was used as a coupling agent to introduce double bonds onto the SiO 2 layer (MPS-CM). Then, 1-vinylimidazole (VI) was employed as a functional monomer to graft-polymerization onto the MPS-CM (PVI-CM). During the graft-polymerization, the influence factors of grafting degree of PVI were investigated in detail. Under optimum conditions (monomer concentration 20wt%, temperature 70°C, initiator amount 1.1wt% and reaction time 8h), the grafting degree of 20.39g/100g was obtained. Further, Mo(VI) anion was used as a template to imprint in the PVI-CM by employing 1,6-dibromohexane as a cross-linking agent, and then Mo(VI) was removed, obtaining the IIP-PVI/CM with many imprinted cavities for Mo(VI). Thereafter, static adsorption and dynamic separation properties of IIP-PVI/CM for Mo(VI) were studied. Results indicate that IIP-PVI/CM shows a specific selectivity for Mo(VI) with the adsorption capacity of 0.69mmol/100g, and the selectivity coefficient of IIP-PVI/CM is 7.48 for molybdate to tungstate anions. During the dynamic separation, IIP-PVI/CM has also good selectivity for separation of Mo(VI) and W(VI) anions. Copyright © 2017 Elsevier B.V. All rights reserved.

Laboratory Anion Chemistry: Implications for the DIBs, and a Potential Formation Mechanism for a Known Interstellar Molecule

NASA Technical Reports Server (NTRS)

Eichelberger, B.; Barckholtz, C.; Stepanovic, M.; Bierbaum, V.; Snow, T.

2002-01-01

Due to recent interest in molecular anions as possible interstellar species, we have carried out several laboratory studies of anion chemistry. The reactions of the series C(sub n)(sup -); and C(sub n)H(sup -) with H and H2 were studied to address the viability of such species in the diffuse interstellar medium and to address their ability to be carriers of the diffuse interstellar bands (DIBs). These same molecules were also reacted with N and O to show possible heteroatomic products. C(sub m)N(sup - was a particularly stable product from the reaction of C(sub n)(sup -) + N. C3N(sup -) was further reacted with H to study chemistry that could produce HC3N, a known interstellar species. The reactions were done in a flowing afterglow selected ion flow tube apparatus (FA-SIFT). The anions were generated in an electron impact or cold cathode discharge source and the anion of interest was then selected by a quadrupole mass filter. The selected ion was then reacted with the atomic or molecular species in the flow tube and products were detected by another quadrupole. While the C(sub n)(sup -) species do not appear to be viable DIB carriers, their possible presence could provide a mechanism for the formation of known heteroatomic neutral molecules detected in the interstellar medium (ISM).

Perrhenate incorporation into binary mixed sodalites: The role of anion size and implications for technetium-99 sequestration

DOE PAGES

Dickson, Johnbull O.; Harsh, James B.; Lukens, Wayne W.; ...

2014-12-20

Perrhenate (ReO 4 -), as a TcO 4 - analogue, was incorporated into mixed-anion sodalites from binary solutions containing ReO 4 - and a competing anion X n- (Cl -, CO 3 2-, SO 4 2-, MnO 4 -, or WO 4 2-). For this study, our objective was to determine the extent of solid solution formation and the dependence of competing ion selectivity on ion size. Using equivalent aqueous concentrations of the anions (ReO 4 -/X n- molar ratio = 1:1), we synthesized mixed-anion sodalites from zeolite and NaOH at 90 °C for 96 h. The resulting solids weremore » characterized by bulk chemical analysis, powder X-ray diffraction, scanning electron microscopy, and X-ray absorption near edge structure (XANES) spectroscopy to determine crystal structure, chemical composition, morphology, and rhenium (Re) oxidation state. Rhenium in the solid phase occurred predominately as Re(VII)O 4 - in the sodalites, which have a primitive cubic pattern in the space group P43n. The refined unit-cell parameters of the mixed sodalites ranged from 8.88 to 9.15 Å and showed a linear dependence on the size and mole fraction of the incorporated anion(s). The ReO 4 - selectivity, represented by its distribution coefficient (K d), increased in the following order: Cl - < NO 3 - < MnO 4 - and CO 3 2- < SO 4 2- < WO 4 2- for the monovalent and divalent anions, respectively. The relationship between the ReO 4 - distribution coefficient and competing anion size was nonlinear. When the difference in ionic radius (DIR) between ReO 4 - and X n - (n = 1 or 2) was greater than ~ 12%, then ReO 4 - incorporation into sodalite was insignificant. The results imply that anion size is the major factor that determines sodalite anion compositions. Given the similarity in chemical behavior and anion size, ReO 4 - serves as a suitable analogue for TcO 4 - under oxidizing conditions where both elements are expected to remain as oxyanions in the + 7 oxidation state.« less

Delivery of cyclodextrin polymers to bacterial biofilms - An exploratory study using rhodamine labelled cyclodextrins and multiphoton microscopy.

PubMed

Thomsen, Hanna; Benkovics, Gábor; Fenyvesi, Éva; Farewell, Anne; Malanga, Milo; Ericson, Marica B

2017-10-15

Cyclodextrin (CD) polymers are interesting nanoparticulate systems for pharmaceutical delivery; however, knowledge regarding their applications towards delivery into complex microbial biofilm structures is so far limited. The challenge is to demonstrate penetration and transport through the biofilm and its exopolysaccharide matrix. The ideal functionalization for penetration into mature biofilms is unexplored. In this paper, we present a novel set of rhodamine labelled βCD-polymers, with different charge moieties, i.e., neutral, anionic, and cationic, and explore their potential delivery into mature Staphylococcus epidermidis biofilms using multiphoton laser scanning microscopy (MPM). The S. epidermidis biofilms, being a medically relevant model organism, were stained with SYTO9. By using MPM, three-dimensional imaging and spectral investigation of the distribution of the βCD-polymers could be obtained. It was found that the cationic βCD-polymers showed significantly higher integration into the biofilms, compared to neutral and anionic functionalized βCDs. None of the carriers presented any inherent toxicity to the biofilms, meaning that the addition of rhodamine moiety does not affect the inertness of the delivery system. Taken together, this study demonstrates a novel approach by which delivery of fluorescently labelled CD nanoparticles to bacterial biofilms can be explored using MPM. Future studies should be undertaken investigating the potential in using cationic functionalization of CD based delivery systems for targeting anti-microbial effects in biofilms. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Synthetic Ubiquinones Specifically Bind to Mitochondrial Voltage-Dependent Anion Channel 1 (VDAC1) in Saccharomyces cerevisiae Mitochondria.

PubMed

Murai, Masatoshi; Okuda, Ayaka; Yamamoto, Takenori; Shinohara, Yasuo; Miyoshi, Hideto

2017-01-31

The role of the voltage-dependent anion channel (VDAC) as a metabolic gate of the mitochondrial outer membrane has been firmly established; however, its involvement in the regulation of mitochondrial permeability transition (PT) remains extremely controversial. Although some low-molecular-weight chemicals have been proposed to modulate the regulatory role of VDAC in the induction of PT, direct binding between these chemicals and VDAC has not yet been demonstrated. In the present study, we investigated whether the ubiquinone molecule directly binds to VDAC in Saccharomyces cerevisiae mitochondria through a photoaffinity labeling technique using two photoreactive ubiquinones (PUQ-1 and PUQ-2). The results of the labeling experiments demonstrated that PUQ-1 and PUQ-2 specifically bind to VDAC1 and that the labeled position is located in the C-terminal region Phe221-Lys234, connecting the 15th and 16th β-strand sheets. Mutations introduced in this region (R224A, Y225A, D228A, and Y225A/D228A) hardly affected the binding affinity of PUQ-1. PUQ-1 and PUQ-2 both significantly suppressed the Ca 2+ -induced mitochondrial PT (monitored by mitochondrial swelling) at the one digit μM level. Thus, the results of the present study provided, for the first time to our knowledge, direct evidence indicating that the ubiquinone molecule specifically binds to VDAC1 through its quinone-head ring.

High-throughput bioconjugation for enhanced 193 nm photodissociation via droplet phase initiated ion/ion chemistry using a front-end dual spray reactor.

PubMed

Cotham, Victoria C; Shaw, Jared B; Brodbelt, Jennifer S

2015-09-15

Fast online chemical derivatization of peptides with an aromatic label for enhanced 193 nm ultraviolet photodissociation (UVPD) is demonstrated using a dual electrospray reactor implemented on the front-end of a linear ion trap (LIT) mass spectrometer. The reactor facilitates the intersection of protonated peptides with a second population of chromogenic 4-formyl-1,3-benzenedisulfonic acid (FBDSA) anions to promote real-time formation of ion/ion complexes at atmospheric pressure. Subsequent collisional activation of the ion/ion intermediate results in Schiff base formation generated via reaction between a primary amine in the peptide cation and the aldehyde moiety of the FBDSA anion. Utilizing 193 nm UVPD as the subsequent activation step in the MS(3) workflow results in acquisition of greater primary sequence information relative to conventional collision induced dissociation (CID). Furthermore, Schiff-base-modified peptides exhibit on average a 20% increase in UVPD efficiency compared to their unmodified counterparts. Due to the efficiency of covalent labeling achieved with the dual spray reactor, we demonstrate that this strategy can be integrated into a high-throughput LC-MS(n) workflow for rapid derivatization of peptide mixtures.

Anion-Cation Permeability Correlates with Hydrated Counterion Size in Glycine Receptor Channels

PubMed Central

Sugiharto, Silas; Lewis, Trevor M.; Moorhouse, Andrew J.; Schofield, Peter R.; Barry, Peter H.

2008-01-01

The functional role of ligand-gated ion channels depends critically on whether they are predominantly permeable to cations or anions. However, these, and other ion channels, are not perfectly selective, allowing some counterions to also permeate. To address the mechanisms by which such counterion permeation occurs, we measured the anion-cation permeabilities of different alkali cations, Li+ Na+, and Cs+, relative to either Cl− or \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\usepackage[Euler]{upgreek} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{NO}}_{3}^{-}\\end{equation*}\\end{document} anions in both a wild-type glycine receptor channel (GlyR) and a mutant GlyR with a wider pore diameter. We hypothesized and showed that counterion permeation in anionic channels correlated inversely with an equivalent or effective hydrated size of the cation relative to the channel pore radius, with larger counterion permeabilities being observed in the wider pore channel. We also showed that the anion component of conductance was independent of the nature of the cation. We suggest that anions and counterion cations can permeate through the pore as neutral ion pairs, to allow the cations to overcome the large energy barriers resulting from the positively charged selectivity filter in small GlyR channels, with the permeability of such ion pairs being dependent on the effective hydrated diameter of the ion pair relative to the pore diameter. PMID:18708455

Capped Mesoporous Silica Nanoparticles for the Selective and Sensitive Detection of Cyanide.

PubMed

Sayed, Sameh El; Licchelli, Maurizio; Martínez-Máñez, Ramón; Sancenón, Félix

2017-10-18

The development of easy and affordable methods for the detection of cyanide is of great significance due to the high toxicity of this anion and the potential risks associated with its pollution. Herein, optical detection of cyanide in water has been achieved by using a hybrid organic-inorganic nanomaterial. Mesoporous silica nanoparticles were loaded with [Ru(bipy) 3 ] 2+ , functionalized with macrocyclic nickel(II) complex subunits, and capped with a sterically hindering anion (hexametaphosphate). Cyanide selectively induces demetallation of nickel(II) complexes and the removal of capping anions from the silica surface, allowing the release of the dye and the consequent increase in fluorescence intensity. The response of the capped nanoparticles in aqueous solution is highly selective and sensitive towards cyanide with a limit of detection of 2 μm. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

New reagent for extraction photomeric determination of anionic surface-active substances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chernova, R.K.; Yastrebova, N.I.; Pankratov, A.N.

1995-02-01

The new reagent 2,6-diphenyl-4-(4-dimethylamino)styrylpyryl chloride is suggested for extraction photometric determination of anionic surface-active substances (SAS). This reagent possesses high sensitivity and selectivity, and can be used for the determination of both individual SAS of any kind and the total amount of anionic SAS. The reagent was used in analysis of highly mineralized statal waters and for the determination of sulfated products in polyoxyethylated alkylphenols.

The Ion Permeability Induced in Thin Lipid Membranes by the Polyene Antibiotics Nystatin and Amphotericin B

PubMed Central

Cass, Albert; Finkelstein, Alan; Krespi, Vivian

1970-01-01

Characteristics of nystatin and amphotericin B action on thin (<100 A) lipid membranes are: (a) micromolar amounts increase membrane conductance from 10-8 to over 10-2 Ω-1 cm-2; (b) such membranes are (non-ideally) anion selective and discriminate among anions on the basis of size; (c) membrane sterol is required for action; (d) antibiotic presence on both sides of membrane strongly favors action; (e) conductance is proportional to a large power of antibiotic concentration; (f) conductance decreases ∼104 times for a 10°C temperature rise; (g) kinetics of antibiotic action are also very temperature sensitive; (h) ion selectivity is pH independent between 3 and 10, but (i) activity is reversibly lost at high pH; (j) methyl ester derivatives are fully active; N-acetyl and N-succinyl derivatives are inactive; (k) current-voltage characteristic is nonlinear when membrane separates nonidentical salt solutions. These characteristics are contrasted with those of valinomycin. Observations (a)–(g) suggest that aggregates of polyene and sterol from opposite sides of the membrane interact to create aqueous pores; these pores are not static, but break up (melt) and reform continuously. Mechanism of anion selectivity is obscure. Observations (h)–(j) suggest—NH3 + is important for activity; it is probably not responsible for selectivity, particularly since four polyene antibiotics, each containing two—NH3 + groups, induce ideal cation selectivity. Possibly the many hydroxyl groups in nystatin and amphotericin B are responsible for anion selectivity. The effects of polyene antibiotics on thin lipid membranes are consistent with their action on biological membranes. PMID:5514157

Ionic liquid containing hydroxamate and N-alkyl sulfamate ions

DOEpatents

Friesen, Cody A.; Wolfe, Derek; Johnson, Paul Bryan

2016-03-15

Embodiments of the invention are related to ionic liquids and more specifically to ionic liquids used in electrochemical metal-air cells in which the ionic liquid includes a cation and an anion selected from hydroxamate and/or N-alkyl sulfamate anions.

Influence of hydrogen bond accepting ability of anions on the adsorption performance of ionic liquid surface molecularly imprinted polymers.

PubMed

Zhu, Guifen; Gao, Xia; Wang, Xiaolong; Wang, Jianji; Fan, Jing

2018-01-12

To illuminate the influence mechanism of anionic structure of ionic liquids (ILs) on the adsorption performance of surface molecularly imprinted polymers (MIPs), in this work, six newly designed MIPs were prepared on the surface of amino-poly(styrene-divinylbenzene) particles by using imidazolium ILs with the same cation [C 4 mim] + but different anions (Cl, CH 3 SO 3 , PF 6 , BF 4 , C 4 F 7 O 2 , C 4 F 9 SO 3 ) as template molecules, methacrylic acid as functional monomer, and ethylene dimethacrylate as cross-linker. The resulting MIP materials were characterized by IR and SEM, and the influence of hydrogen bond accepting ability of anions on the adsorption performance of the MIPs for the ILs was investigated in acetonitrile. It was found that adsorption capacity of the MIPs towards the ILs decreased in the order MIP [C4mim][Cl]  > MIP [C4mim][C4F7O2]  ≥ MIP [C4mim][BF4] and MIP [C4mim][CH3SO3]  > MIP [C4mim][C4F9SO3]  > MIP [C4mim][PF6] , which is in good agreement with the ability of anions of the ILs to form hydrogen bonds. Ultraviolet, 1 H-NMR and 35 Cl-NMR spectroscopy was then used to study the interactions of anions of the ILs with the functional monomer. It was found that the hydrogen bond interaction between anions of the ILs and acidic proton of the functional monomer was the main driving force for the high adsorption selectivity of the imprinted polymers, and the stronger hydrogen bond interaction indicates higher binding capacity and higher selectivity of the polymers towards the ILs. It was also verified that the ILs with stronger hydrogen bond accepting ability of anions could be selectively extracted by the corresponding IL-MIPs. These results may provide new insight into the recognition mechanism of MIPs for ILs, and are also useful for the rational design of this new class of imprinting materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Corrosion protection of copper by polypyrrole film studied by electrochemical impedance spectroscopy and the electrochemical quartz microbalance

NASA Astrophysics Data System (ADS)

Lei, Yanhua; Ohtsuka, Toshiaki; Sheng, Nan

2015-12-01

Polypyrrole (PPy) films were synthesized on copper in solution of sodium di-hydrogen phosphate and phytate for corrosion protection. The protection properties of PPy films were comparatively investigated in NaCl solution. During two months immersion, the PPy film doped with phytate anions, working as a cationic perm-selective membrane, inhibited the dissolution of copper to 1% of bare copper. Differently, the PPy film doped with di-hydrogen phosphate anions, possessing anionic perm-selectivity, was gradually reduced, and inhibited the dissolution to 7.8% of bare copper. Degradation of the PPy films was studied by comparing the electrochemical impedance spectroscopy change at different immersion time and Raman spectra change after immersion.

Label-free fluorescent detection of protein kinase activity based on the aggregation behavior of unmodified quantum dots.

PubMed

Xu, Xiahong; Liu, Xin; Nie, Zhou; Pan, Yuliang; Guo, Manli; Yao, Shouzhuo

2011-01-01

Herein, we present a novel label-free fluorescent assay for monitoring the activity and inhibition of protein kinases based on the aggregation behavior of unmodified CdTe quantum dots (QDs). In this assay, cationic substrate peptides induce the selective aggregation of unmodified QDs with anionic surface charge, whereas phosphorylated peptides do not. Phosphorylation by kinase alters the net charge of peptides and subsequently inhibits the aggregation of unmodified QDs, causing an enhanced fluorescence with a 45 nm blue-shift in emission and a yellow-to-green emission color change. Hence the fluorescence response allows this QD-based method to easily probe kinase activity by a spectrometer or even by the naked eye. The feasibility of the method has been demonstrated by sensitive measurement of the activity of cAMP-dependent protein kinase (PKA) with a low detection limit (0.47 mU μL(-1)). On the basis of the fluorescence response of QDs on the concentration of PKA inhibitor H-89, the IC(50) value, the half maximal inhibitory concentration, was estimated, which was in agreement with the literature value. Moreover, the system can be applicable to detect the Forskolin/3-isobutyl-1-methylxantine (IBMX)-stimulated activation of PKA in cell lysate. Unlike the existing QD-based enzyme activity assays in which the modification process of QDs is essential, this method relies on unmodified QDs without the requirement of peptide labeling and QDs' modification, presenting a promising candidate for cost-effective kinase activity and inhibitor screening assays.

C2 Domain of Protein Kinase Cα: Elucidation of the Membrane Docking Surface by Site-Directed Fluorescence and Spin Labeling†

PubMed Central

Kohout, Susy C.; Corbalán-García, Senena; Gómez-Fernández, Juan C.; Falke, Joseph J.

2013-01-01

The C2 domain is a conserved signaling motif that triggers membrane docking in a Ca2+-dependent manner, but the membrane docking surfaces of many C2 domains have not yet been identified. Two extreme models can be proposed for the docking of the protein kinase Cα (PKCα) C2 domain to membranes. In the parallel model, the membrane-docking surface includes the Ca2+ binding loops and an anion binding site on β-strands 3–4, such that the β-strands are oriented parallel to the membrane. In the perpendicular model, the docking surface is localized to the Ca2+ binding loops and the β-strands are oriented perpendicular to the membrane surface. The present study utilizes site-directed fluorescence and spin-labeling to map out the membrane docking surface of the PKCα C2 domain. Single cysteine residues were engineered into 18 locations scattered over all regions of the protein surface, and were used as attachment sites for spectroscopic probes. The environmentally sensitive fluorescein probe identified positions where Ca2+ activation or membrane docking trigger measurable fluorescence changes. Ca2+ binding was found to initiate a global conformational change, while membrane docking triggered the largest fluorescein environmental changes at labeling positions on the three Ca2+ binding loops (CBL), thereby localizing these loops to the membrane docking surface. Complementary EPR power saturation measurements were carried out using a nitroxide spin probe to determine a membrane depth parameter, Φ, for each spin-labeled mutant. Positive membrane depth parameters indicative of membrane insertion were found for three positions, all located on the Ca2+ binding loops: N189 on CBL 1, and both R249 and R252 on CBL 3. In addition, EPR power saturation revealed that five positions near the anion binding site are partially protected from collisions with an aqueous paramagnetic probe, indicating that the anion binding site lies at or near the surface of the headgroup layer. Together, the fluorescence and EPR results indicate that the Ca2+ first and third Ca2+ binding loops insert directly into the lipid headgroup region of the membrane, and that the anion binding site on β-strands 3–4 lies near the headgroups. The data support a model in which the β-strands are tilted toward the parallel orientation relative to the membrane surface. PMID:12564928

Anion-π Catalysts with Axial Chirality.

PubMed

Wang, Chao; Matile, Stefan

2017-09-04

The idea of anion-π catalysis is to stabilize anionic transition states by anion-π interactions on aromatic surfaces. For asymmetric anion-π catalysis, π-acidic surfaces have been surrounded with stereogenic centers. This manuscript introduces the first anion-π catalysts that operate with axial chirality. Bifunctional catalysts with tertiary amine bases next to π-acidic naphthalenediimide planes are equipped with a bulky aromatic substituent in the imide position to produce separable atropisomers. The addition of malonic acid half thioesters to enolate acceptors is used for evaluation. In the presence of a chiral axis, the selective acceleration of the disfavored but relevant enolate addition was much better than with point chirality, and enantioselectivity could be observed for the first time for this reaction with small-molecule anion-π catalysts. Enantioselectivity increased with the π acidity of the π surface, whereas the addition of stereogenic centers around the aromatic plane did not cause further improvements. These results identify axial chirality of the active aromatic plane generated by atropisomerism as an attractive strategy for asymmetric anion-π catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Methods development for separation of inorganic anions, organic acids and bases, and neutral organic compounds by ion chromatography and capillary electrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jie

1999-04-01

A novel anion-exchange resin containing three amine groups was prepared by reaction of a chloromethylated polystyrene-divinylbenzene (PS-DVB) resin with diethylenetriamine. After being protonated by contact with an aqueous acid, this resin can be used for ion chromatographic separation of anions. The charge on the resins can be varied from +1 to +3 by changing the mobile phase pH. The selectivity of the new ion exchangers for various inorganic anions was quite different from that of conventional anion exchangers. The performance of this new anion exchanger was studied by changing the pH and the concentration of the eluent, and several differentmore » eluents were used with some common anions as testing analytes. Conductivity detection and UV-visible detection were applied to detect the anions after separation. The new resin can also be used for HPLC separation of neutral organic compounds. Alkylphenols and alkylbenzenes were separated with this new polymeric resin, and excellent separations were obtained under simple conditions. This report contains Chapter 1: General introduction and Chapter 6: General conclusions.« less

An anionic Na(i)-organic framework platform: separation of organic dyes and post-modification for highly sensitive detection of picric acid.

PubMed

Chen, Di-Ming; Tian, Jia-Yue; Wang, Zhuo-Wei; Liu, Chun-Sen; Chen, Min; Du, Miao

2017-09-26

A cage-based anionic Na(i)-organic framework with a unique Na 9 cluster-based secondary building unit and a cage-in-cage structure was constructed. The selective separation of dyes with different charges and sizes was investigated. Furthermore, the Rh6G@MOF composite could be applied as a recyclable fluorescent sensor for detecting picric acid (PA) with high sensitivity and selectivity.

Cytochemical analysis of alkaline phosphatase and esterase activities and of lectin-binding and anionic sites in rat and mouse Peyer's patch M cells.

PubMed

Owen, R L; Bhalla, D K

1983-10-01

M cells in Peyer's patch follicle epithelium endocytose and transport luminal materials to intraepithelial lymphocytes. We examined (1) enzymatic characteristics of the epithelium covering mouse and rat Peyer's patches by using cytochemical techniques, (2) distribution of lectin-binding sites by peroxidase-labeled lectins, and (3) anionic site distribution by using cationized ferritin to develop a profile of M cell surface properties. Alkaline phosphatase activity resulted in deposits of dense reaction product over follicle surfaces but was markedly reduced over M cells, unlike esterase which formed equivalent or greater product over M cells. Concanavalin A, ricinus communis agglutinin, wheat germ agglutinin and peanut agglutinin reacted equally with M cells and with surrounding enterocytes over follicle surfaces. Cationized ferritin distributed in a random fashion along microvillus membranes of both M cells and enterocytes, indicating equivalent anionic site distribution. Staining for alkaline phosphatase activity provides a new approach for distinguishing M cells from enterocytes at the light microscopic level. Identical binding of lectins indicates that M cells and enterocytes share common glycoconjugates even though molecular groupings may differ. Lectin binding and anionic charge similarities of M cells and enterocytes may facilitate antigen sampling by M cells of particles and compounds that adhere to intestinal surfaces in non-Peyer's patch areas.

A modular synthesis of dithiocarbamate pendant unnatural α-amino acids

EPA Science Inventory

Unnatural α-amino acids containing dithiocarbamate side chains were synthesized by a one-pot reaction of in-situ generated dithiocarbamate anions with sulfamidates. A wide range of these anions participated in the highly regio- and stereo-selective ring opening of sulfamidates to...

Improved Steroids Detection and Evidence for Their Regiospecific Decompositions Using Anion Attachment Mass Spectrometry.

PubMed

Dumont, Quentin; Bárcenas, Mariana; Dossmann, Héloïse; Bailloux, Isabelle; Buisson, Corinne; Mechin, Nathalie; Molina, Adeline; Lasne, Françoise; Rannulu, Nalaka S; Cole, Richard B

2016-04-05

Nonpolar anabolic steroids are doping agents that typically do not provide strong signals by electrospray ionization-mass spectrometry (ESI-MS) owing especially to the low polarity of the functional groups present. We have investigated the addition of anions, in ammonium salt form, to anabolic steroid samples as ionization enhancers and have confirmed that lower instrumental limits of detection (as low as 10 ng/mL for fluoxymesterone-M) are obtained by fluoride anion attachment mass spectrometry, as compared to ESI(+)/(-) or atmospheric pressure photoionization (APPI)(+). Moreover, collision-induced decomposition (CID) spectra of precursor fluoride adducts of the bifunctional steroid "reduced pregnenolone" (containing two hydroxyl groups) and its d4-analogue provide evidence of regiospecific decompositions after attachment of fluoride anion to a specific hydroxyl group of the steroid. This type of charting of specific CID reaction pathways can offer value to selected reaction monitoring experiments (SRM) as it may result in a gain in selectivity in detection as well as in improvements in quantification.

Electrodialysis potential for fractionation of multicomponent aqueous solutions

NASA Astrophysics Data System (ADS)

Grzegorzek, Martyna; Majewska-Nowak, Katarzyna

2017-11-01

The paper aimed at the evaluation of the batch electrodialysis (ED) run in the course of treatment and desalination of various aqueous mixtures containing both mineral (sodium fluoride, sodium chloride) and organic substances (dyes or humic acids). The commercial ED stack (PCCell Bed) equipped with standard anion-exchange and cation-exchange membranes or monovalent selective anion-exchange membranes was used. The ED experiments were performed at a constant current density (1.56 or 1.72 mA/cm2). The mechanism of ion migration as well as membrane deposition for variable solution composition and various membrane types was analyzed The calculated mass balance and electrical energy demand for each ED run were helpful in evaluating the membrane fouling intensity. It was found that the presence of organic substances in the treated solution had a minor impact on energy consumption, but rather strongly affected chloride flux. The extent of organics deposition was significantly lower for monovalent selective anion-exchange membranes than for classic anion-exchange membranes.

Evidence for halogen bond covalency in acyclic and interlocked halogen-bonding receptor anion recognition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Sean W.; Mustoe, Chantal L.; White, Nicholas G.

The synthesis and anion binding properties of novel halogen-bonding (XB) bis-iodotriazole-pyridinium-containing acyclic and [2]catenane anion host systems are described. The XB acyclic receptor displays selectivity for acetate over halides with enhanced anion recognition properties compared to the analogous hydrogen-bonding (HB) acyclic receptor. A reversal in halide selectivity is observed in the XB [2]catenane, in comparison to the acyclic XB receptor, due to the interlocked host’s unique three-dimensional binding cavity, and no binding is observed for oxoanions. Notable halide anion association constant values determined for the [2]catenane in competitive organic–aqueous solvent mixtures demonstrate considerable enhancement of anion recognition as compared tomore » the HB catenane analogue. X-ray crystallographic analysis of a series of halide catenane complexes reveal strong XB interactions in the solid state. These interactions were studied using Cl and Br K-edge X-ray Absorption Spectroscopy (XAS) indicating intense pre-edge features characteristic of charge transfer from the halide to its bonding partner (σ AX←X–* ← X1s), and providing a direct measure of the degree of covalency in the halogen bond(s). Lastly, the data reveal that the degree of covalency is similar to that which is observed in transition metal coordinate covalent bonds. These results are supported by DFT results, which correlate well with the experimental data.« less

Evidence for halogen bond covalency in acyclic and interlocked halogen-bonding receptor anion recognition

DOE PAGES

Robinson, Sean W.; Mustoe, Chantal L.; White, Nicholas G.; ...

2014-12-05

The synthesis and anion binding properties of novel halogen-bonding (XB) bis-iodotriazole-pyridinium-containing acyclic and [2]catenane anion host systems are described. The XB acyclic receptor displays selectivity for acetate over halides with enhanced anion recognition properties compared to the analogous hydrogen-bonding (HB) acyclic receptor. A reversal in halide selectivity is observed in the XB [2]catenane, in comparison to the acyclic XB receptor, due to the interlocked host’s unique three-dimensional binding cavity, and no binding is observed for oxoanions. Notable halide anion association constant values determined for the [2]catenane in competitive organic–aqueous solvent mixtures demonstrate considerable enhancement of anion recognition as compared tomore » the HB catenane analogue. X-ray crystallographic analysis of a series of halide catenane complexes reveal strong XB interactions in the solid state. These interactions were studied using Cl and Br K-edge X-ray Absorption Spectroscopy (XAS) indicating intense pre-edge features characteristic of charge transfer from the halide to its bonding partner (σ AX←X–* ← X1s), and providing a direct measure of the degree of covalency in the halogen bond(s). Lastly, the data reveal that the degree of covalency is similar to that which is observed in transition metal coordinate covalent bonds. These results are supported by DFT results, which correlate well with the experimental data.« less

Coumarin-indole conjugate donor-acceptor system: Synthesis, photophysical properties, anion sensing ability, theoretical and biological activity studies of two coumarin-indole based push-pull dyes

NASA Astrophysics Data System (ADS)

Aksungur, Tuğçe; Aydıner, Burcu; Seferoğlu, Nurgül; Özkütük, Müjgan; Arslan, Leyla; Reis, Yasemin; Açık, Leyla; Seferoğlu, Zeynel

2017-11-01

Two coumarin-indole conjugate fluorescent dyes having donor-acceptor-donor (D-A-D) (CI-1 and CI-2) were synthesized, and characterized using IR, 1H/13C NMR and HRMS. The absorption and emission properties of the dyes were determined in different solvents. The anion sensitivity and selectivity of the dyes were studied with some anions (CN-, F-, AcO-, Cl-, Br-, I-, HSO4- and H2PO4-) in DMSO, and their interaction mechanisms were evaluated by spectrophotometric and 1H NMR titration techniques. In addition, the molecular and electronic structures of CI-1, as well as the molecular complexes of CI-1, formed with the anions (F- and AcO-), were obtained theoretically and confirmed by DFT and TD-DFT calculations. CI-1 behaves as a colorimetric chemosensor for selective and sensitive detection of CN- in DMSO/H2O (9:1) over other competing anions such as F- and AcO-. However, only CN- interacts with chromophore CI-2 via Michael addition and the main absorption maxima shifts hypsochromically with an observed distinctive color change from orange to yellow. For using as a optic dye, the thermal stability properties of the dyes was determined by TGA (Thermal Gravimetric Analysis). Antimicrobial, antifungal and DNA-ligand interaction studies of the dyes were also examined. The dyes cause conformational changes on DNA and selectively bind to nucleotides of A/A and G/G.

Understanding Anion, Water, and Methanol Transport in a Polyethylene- b -poly(vinylbenzyl trimethylammonium) Copolymer Anion-Exchange Membrane for Electrochemical Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarode, Himanshu N.; Yang, Yuan; Motz, Andrew R.

Herein, we report the anion and water transport properties of an anion-exchange membrane (AEM) comprising a block copolymer of polyethylene and poly- (vinylbenzyl trimethylammonium) (PE-b-PVBTMA) with an ion-exchange capacity (IEC) of 1.08 mequiv/g. The conductivity varied little among the anions CO3 2-, HCO3 -, and F-, with a value of Ea ≈ 20 kJ/mol and a maximum fluoride conductivity of 34 mS/cm at 90 °C and 95% relative humidity. The Br- conductivity showed a transition at 60 °C. Pulsed gradient stimulated spin echo nuclear magnetic resonance (PGSE NMR) experiments showed that water diffusion in this AEM is heterogeneous and ismore » affected by the anion present, being fastest in the presence of F-. We determined the methanol self-diffusion in this membrane and observed that it is lower than that in Nafion 117, because of the lower water uptake. This article reports the first measurements of 13C-labeled bicarbonate self-diffusion in an AEM using PGSE NMR spectrometry, which was found to be significantly slower than F- self-diffusion. Back-calculation of the bicarbonate conductivity using the Nernst-Einstein equation gave a value that was significantly lower than the measured value, implying that bicarbonate transport involves OH- in the transport mechanism. Fourier transform infrared spectroscopy, PGSE NMR spectrometry, and small-angle X-ray scattering (SAXS) indicated the presence of different types of waters present in the membrane at different length scales. The SAXS data indicated that there is a water-rich region within the hydrophilic domains of the polymer that has a temperature dependence in intensity at 95% relative humidity (RH).« less

Low-energy collision-induced fragmentation of negative ions derived from ortho-, meta-, and para-hydroxyphenyl carbaldehydes, ketones, and related compounds.

PubMed

Attygalle, Athula B; Ruzicka, Josef; Varughese, Deepu; Bialecki, Jason B; Jafri, Sayed

2007-09-01

Collision-induced dissociation (CID) mass spectra of anions derived from several hydroxyphenyl carbaldehydes and ketones were recorded and mechanistically rationalized. For example, the spectrum of m/z 121 ion of deprotonated ortho-hydroxybenzaldehyde shows an intense peak at m/z 93 for a loss of carbon monoxide attributable to an ortho-effect mediated by a charge-directed heterolytic fragmentation mechanism. In contrast, the m/z 121 ion derived from meta and para isomers undergoes a charge-remote homolytic cleavage to eliminate an *H and form a distonic anion radical, which eventually loses CO to produce a peak at m/z 92. In fact, for the para isomer, this two-step homolytic mechanism is the most dominant fragmentation pathway. The spectrum of the meta isomer on the other hand, shows two predominant peaks at m/z 92 and 93 representing both homolytic and heterolytic fragmentations, respectively. (18)O-isotope-labeling studies confirmed that the oxygen in the CO molecule that is eliminated from the anion of meta-hydroxybenzaldehyde originates from either the aldehydic or the phenolic group. In contrast, anions of ortho-hydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde, both of which show two consecutive CO eliminations, specifically lose the carbonyl oxygen first, followed by that of the phenolic group. Anions from 2-hydroxyphenyl alkyl ketones lose a ketene by a hydrogen transfer predominantly from the alpha position. Interestingly, a very significant charge-remote 1,4-elimination of a H(2) molecule was observed from the anion derived from 2,4-dihydroxybenzaldehyde. For this mechanism to operate, a labile hydrogen atom should be available on the hydroxyl group adjacent to the carbaldehyde functionality.

Development of (99m)Tc-labeled asymmetric urea derivatives that target prostate-specific membrane antigen for single-photon emission computed tomography imaging.

PubMed

Kimura, Hiroyuki; Sampei, Sotaro; Matsuoka, Daiko; Harada, Naoya; Watanabe, Hiroyuki; Arimitsu, Kenji; Ono, Masahiro; Saji, Hideo

2016-05-15

Prostate-specific membrane antigen (PSMA) is expressed strongly in prostate cancers and is, therefore, an attractive diagnostic and radioimmunotherapeutic target. In contrast to previous reports of PMSA-targeting (99m)Tc-tricarbonyl complexes that are cationic or lack a charge, no anionic (99m)Tc-tricarbonyl complexes have been reported. Notably, the hydrophilicity conferred by both cationic and anionic charges leads to rapid hepatobiliary clearance, whereas an anionic charge might better enhance renal clearance relative to a cationic charge. Therefore, an improvement in rapid clearance would be expected with either cationic or anionic charges, particularly anionic charges. In this study, we designed and synthesized a novel anionic (99m)Tc-tricarbonyl complex ([(99m)Tc]TMCE) and evaluated its use as a single-photon emission computed tomography (SPECT) imaging probe for PSMA detection. Direct synthesis of [(99m)Tc]TMCE from dimethyl iminodiacetate, which contains both the asymmetric urea and succinimidyl moiety important for PSMA binding, was performed using our microwave-assisted one-pot procedure. The chelate formation was successfully achieved even though the precursor included a complicated bioactive moiety. The radiochemical yield of [(99m)Tc]TMCE was 12-17%, with a radiochemical purity greater than 98% after HPLC purification. [(99m)Tc]TMCE showed high affinity in vitro, with high accumulation in LNCaP tumors and low hepatic retention in biodistribution and SPECT/CT studies. These findings warrant further evaluation of [(99m)Tc]TMCE as an imaging agent and support the benefit of this strategy for the design of other PSMA imaging probes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Properties of the anion-binding site of pharaonis Halorhodopsin studied by ultrafast pump-probe spectroscopy and low-temperature FTIR spectroscopy.

PubMed

Nakashima, Keisuke; Nakamura, Takumi; Takeuchi, Satoshi; Shibata, Mikihiro; Demura, Makoto; Tahara, Tahei; Kandori, Hideki

2009-06-18

Halorhodopsin (HR) is a light-driven chloride pump. Cl(-) is bound in the Schiff base region of the retinal chromophore, and unidirectional Cl(-) transport is probably enforced by the specific hydrogen-bonding interaction with the protonated Schiff base and internal water molecules. It is known that HR from Natronobacterium pharaonis (pHR) also pumps NO(3)(-) with similar efficiency, suggesting that NO(3)(-) binds to the Cl(-)-binding site. In the present study, we investigated the properties of the anion-binding site by means of ultrafast pump-probe spectroscopy and low-temperature FTIR spectroscopy. The obtained data were surprisingly similar between pHR-NO(3)(-) and pHR-Cl(-), even though the shapes and sizes of the two anions are quite different. Femtosecond pump-probe spectroscopy showed very similar excited-state dynamics between pHR-NO(3)(-) and pHR-Cl(-). Low-temperature FTIR spectroscopy of unlabeled and [zeta-(15)N]Lys-labeled pHR revealed almost identical hydrogen-bonding strengths of the protonated retinal Schiff base between pHR-NO(3)(-) and pHR-Cl(-), which is similarly strengthened after retinal isomerization. There were spectral variations for water stretching vibrations between pHR-NO(3)(-) and pHR-Cl(-), suggesting that the water molecules hydrate each anion. Nevertheless, the overall spectral features were similar for the two species. These observations strongly suggest that the anion-binding site has a flexible structure and that the interaction between retinal and the anions is weak, despite the presence of an electrostatic interaction. Such a flexible hydrogen-bonding network in the Schiff base region in HR appears to be in remarkable contrast to that in light-driven proton-pumping proteins.

Temporary anion states of selected amino acids

NASA Astrophysics Data System (ADS)

Aflatooni, K.; Hitt, B.; Gallup, G. A.; Burrow, P. D.

2001-10-01

Vertical attachment energies for the formation of low-lying temporary anion states of glycine, alanine, phenylalanine, tryptophan, and proline in the gas phase are reported using electron transmission spectroscopy. Electron attachment into the empty π* orbital of the -COOH group was observed in all the compounds. Temporary anion states associated with the side groups in phenylalanine and tryptophan are found to be stabilized with respect to those in the reference compounds toluene and indole, respectively, by approximately 0.2 eV. We attribute this to electrostatic effects and explore, using simple theoretical models, the extent to which such anion states could be further stabilized if these amino acids were in zwitterionic form.

Use of the Oak Ridge National Laboratory tungsten-188/rhenium-188 generator for preparation of the rhenium-188 HDD/lipiodol complex for trans-arterial liver cancer therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, J M; Knapp Jr, Russ F

2008-01-01

This work describes the installation, use, and quality control (QC) of the alumina-based tungsten-188 ({sup 188}W)/rhenium-188 ({sup 188}Re) generators provided by the Oak Ridge National Laboratory (ORNL). In addition, methods used for concentration of the {sup 188}Re-perrhenate bolus and preparation of {sup 188}Re-labeled HDD (4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol) for trans-arterial administration for therapy of nonresectable liver cancer also are described. The {sup 188}W/{sup 188}Re generator has a long useful shelf-life of several months and is a convenient on-site {sup 188}Re production system. {sup 188}Re has excellent therapeutic and imaging properties (T{sub 1/2} 16.9 hours; E{sub {beta}max} 2.12 MeV; 155-keV gamma ray, 15%) andmore » is cost effectively obtained on demand by saline elution of the generator. The clinical efficacy of a variety of {sup 188}Re-labeled agents has been demonstrated for several therapeutic applications. Because of the favorable physical properties of {sup 188}Re, several {sup 188}Re-labeled agents are being developed and evaluated for the treatment of nonresectable/refractory liver cancer. {sup 188}Re-labeled HDD has been the most widely studied of these agents for this application and has been introduced into clinical trials at a number of institutions. The trans-arterial administration of {sup 188}Re-labeled agents for treatment of inoperable liver cancer requires use of high-level (1-2 Ci) {sup 188}W/{sup 188}Re generators. The handling of such high levels of {sup 188}Re imposes radiological precautions normally not encountered in a radiopharmacy and adequate care and ALARA (i.e., 'As Low As Reasonably Achievable') principles must be followed. The ORNL generator provides consistently high {sup 188}Re yields (>75%) and low {sup 188}W parent breakthrough (<10{sup -3}%) over an extended shelf-life of several months. However, the high elution volumes (20-40 mL for 1-2 Ci generators) can require concentration of the {sup 188}Re bolus by postelution passage through silver cation chloride trapping columns used in the cost-effective tandem cation/anion column system. The silver column removes the high levels of chloride anion as insoluble AgCl, thus allowing subsequent specific trapping of the perrhenate anion on the small (QMA SeaPak) anion column. This method permits subsequent elution of {sup 188}Re-perrhenate with a small volume of saline, providing a very high activity-concentration solution. Because the {sup 188}Re-specific volume-activity concentration continually decreases with time, the tandem system is especially effective method for extending the useful generator shelf-life. Low elution flow rates (<1 mL/min) minimize any high back pressure which may be encountered during generator/tandem column elution when using tightly packed, small-particle-size commercial columns. In-house preparation of silver cation columns is recommended since the chloride trapping capacity is essentially unlimited, it is inexpensive and not limited in availability to any one supplier, and back pressure can be eliminated by the use of larger particles. Methods for the preparation of {sup 188}Re-HDD have been optimized and this agent can be obtained in high yield (80%).« less

Use of the ORNL Tungsten-188/Rhenium-188 Generator for Preparation of the Rhenium-188 HDD/Lipiodol Complex for Transarterial Liver Cancer Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knapp Jr, Russ F; Jeong, J M

2008-01-01

This work describes the installation, use, and quality control (QC) of the alumina-based tungsten-188 ({sup 188}W)/rhenium-188 ({sup 188}Re) generators provided by the Oak Ridge National Laboratory (ORNL). In addition, methods used for concentration of the {sup 188}Re-perrhenate bolus and preparation of {sup 188}Re-labeled HDD (4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol) for trans-arterial administration for therapy of nonresectable liver cancer also are described. The {sup 188}W/{sup 188}Re generator has a long useful shelf-life of several months and is a convenient on-site {sup 188}Re production system. {sup 188}Re has excellent therapeutic and imaging properties (T{sub 1/2} 16.9 hours; E{beta}{sub max} 2.12 MeV; 155-keV gamma ray, 15%) andmore » is cost effectively obtained on demand by saline elution of the generator. The clinical efficacy of a variety of {sup 188}Re-labeled agents has been demonstrated for several therapeutic applications. Because of the favorable physical properties of {sup 188}Re, several {sup 188}Re-labeled agents are being developed and evaluated for the treatment of nonresectable/refractory liver cancer. {sup 188}Re-labeled HDD has been the most widely studied of these agents for this application and has been introduced into clinical trials at a number of institutions. The trans-arterial administration of {sup 188}Re-labeled agents for treatment of inoperable liver cancer requires use of high-level (1-2 Ci) {sup 188}W/{sup 188}Re generators. The handling of such high levels of {sup 188}Re imposes radiological precautions normally not encountered in a radiopharmacy and adequate care and ALARA (ie, 'As Low As Reasonably Achievable') principles must be followed. The ORNL generator provides consistently high {sup 188}Re yields (>75%) and low {sup 188}W parent breakthrough (<10{sup -3}%) over an extended shelf-life of several months. However, the high elution volumes (20-40 mL for 1-2 Ci generators) can require concentration of the {sup 188}Re bolus by postelution passage through silver cation chloride trapping columns used in the cost-effective tandem cation/anion column system. The silver column removes the high levels of chloride anion as insoluble AgCl, thus allowing subsequent specific trapping of the perrhenate anion on the small (QMA SeaPak) anion column. This method permits subsequent elution of {sup 188}Re-perrhenate with a small volume of saline, providing a very high activity-concentration solution. Because the {sup 188}Re-specific volume-activity concentration continually decreases with time, the tandem system is especially effective method for extending the useful generator shelf-life. Low elution flow rates (<1 mL/min) minimize any high back pressure which may be encountered during generator/tandem column elution when using tightly packed, small-particle-size commercial columns. In-house preparation of silver cation columns is recommended since the chloride trapping capacity is essentially unlimited, it is inexpensive and not limited in availability to any one supplier, and back pressure can be eliminated by the use of larger particles. Methods for the preparation of {sup 188}Re-HDD have been optimized and this agent can be obtained in high yield (80%).« less

Construction of a Nano Biosensor for Cyanide Anion Detection and Its Application in Environmental and Biological Systems.

PubMed

Dong, Zhen-Zhen; Yang, Chao; Vellaisamy, Kasipandi; Li, Guodong; Leung, Chung-Hang; Ma, Dik-Lung

2017-10-27

We have developed a Ag@Au core-shell nanoparticle (NP)/iridium(III) complex-based sensing platform for the sensitive luminescence "turn-on" sensing of cyanide ions, an acutely toxic pollutant. The assay is based on the quenching effect of Ag@Au NPs on the emission of complex 1, but luminescence is restored after the addition of cyanide anions due to their ability to dissolve the Au shell. Our sensing platform exhibited a high sensitivity toward cyanide anions with a detection limit of 0.036 μM, and also showed high selectivity for cyanide over 10-fold excess amounts of other anions. The sensing platform was also successfully applied to monitor cyanide anions in drinking water and in living cells.

Use of anionic surfactants for selective polishing of silicon dioxide over silicon nitride films using colloidal silica-based slurries

NASA Astrophysics Data System (ADS)

Penta, Naresh K.; Amanapu, H. P.; Peethala, B. C.; Babu, S. V.

2013-10-01

Four different anionic surfactants, sodium dodecyl sulfate, dodecyl benzene sulfonic acid (DBSA), dodecyl phosphate and Sodium lauroyl sarcosine, selected from the sulfate, phosphate, and carboxylic family, were investigated as additives in silica dispersions for selective polishing of silicon dioxide over silicon nitride films. We found that all these anionic surfactants suppress the nitride removal rates (RR) for pH ≤4 while more or less maintaining the oxide RRs, resulting in high oxide-to-nitride RR selectivity. The RR data obtained as a function of pH were explained based on pH dependent distributions of surfactant species, change in the zeta potentials of oxide and nitride surfaces, and thermogravimetric data. It appears that the negatively charged surfactant species preferentially adsorb on the positively charged nitride surface below IEP through its electrostatic interactions and form a bilayer adsorption, resulting in the suppression of nitride RRs. In contrast to the surfactants, K2SO4 interacts only weakly with the nitride surface and hence cannot suppress its RR.

Switch on or switch off: an optical DNA sensor based on poly(p-phenylenevinylene) grafted magnetic beads.

PubMed

Srinivas, Anupama R Gulur; Peng, Hui; Barker, David; Travas-Sejdic, Jadranka

2012-05-15

There has been an enormous demand for commercial label-free DNA sensors in a diverse range of fields including pre-emptive medicine, diagnostics, environmental monitoring, and food industry. Addressing the need for sensitive, selective and facile DNA sensors, we demonstrate a novel switch on/off sensor design that utilizes sandwich hybridization between photoluminescent anionic conjugated polyelectrolyte (CPE) bound captureprobe coated onto magnetic beads, target and the signaling probe. The hybridization-readout in our sensor was monitored by either fluorescence resonance energy transfer (FRET, switch-on) or superquenching (switch-off) depending on the type of signaling probe used. Moreover recent designs that utilize beads for sensing DNA have been limited towards using electrostatic interactions or intercalation of dyes to observe FRET. To our knowledge this is the first report of a switch on/off sensor utilizing either FRET or superquenching thus providing flexibility for future development of such rapid, facile and sensitive DNA sensors. The FRET-based sensor was investigated by optimizing the reaction parameters and selectivity. A low detection limit of 240 fmol in 2 mL of SSC buffer was achieved. Copyright © 2012 Elsevier B.V. All rights reserved.

Concave Reagents. 20. Sterically Shielded m-Terphenyls as Selective Agents in General Protonations(1).

PubMed

Lüning, U.; Baumgartner, H.; Manthey, C.; Meynhardt, B.

1996-11-01

New m-terphenyls with acidic substituents in the 2'-position have been used in general protonations leading to reagent-controlled selectivity enhancements: up to 96:4 for the gamma/alpha-protonation of unsymmetrically substituted allyl anions, up to 97:3 for the protonation of cyclohexyl anions generating preferentially the thermodynamically less stable cis-products. In order to allow a general, reagent-controlled protonation the acidity of the protonating agent should be as low as possible.

A core-substituted naphthalene diimide fluoride sensor.

PubMed

Bhosale, Sheshanath V; Bhosale, Sidhanath V; Kalyankar, Mohan B; Langford, Steven J

2009-12-03

The synthesis and characterization of a highly fluorescent core-substituted naphthalene diimide sensor (varphi = 0.34) bearing a bis-sulfonamide group is described. The compound shows a unique selectivity and reactivity for the fluoride ion over other anions in CHCl(3) by a two-stage deprotonation process leading to a colorimetric response. In DMSO solution, the sensor is shown to be highly selective for fluoride (K(a) approximately 10(6) M(-1)) over other anions with more pronounced changes in absorption characteristics.

Heterologous expression and solution structure of defensin from lentil Lens culinaris

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shenkarev, Zakhar O.; Gizatullina, Albina K.; Moscow Institute of Physics and Technology

2014-08-22

Highlights: • Lentil defensin Lc-def and its {sup 15}N-labeled analog were overexpressed in E. coli. • Lc-def is active against fungi, but does not inhibit growth of G+ and G− bacteria. • Lc-def spatial structure involves triple-stranded β-sheet and α-helix (CSαβ motif). • Lc-def is able to bind to anionic lipid vesicles under low-salt conditions. • NMR data revealed significant μs–ms mobility in the loops 1 and 3 of Lc-def. - Abstract: A new defensin Lc-def, isolated from germinated seeds of the lentil Lens culinaris, has molecular mass 5440.4 Da and consists of 47 amino acid residues. Lc-def and itsmore » {sup 15}N-labeled analog were overexpressed in Escherichia coli. Antimicrobial activity of the recombinant protein was examined, and its spatial structure, dynamics, and interaction with lipid vesicles were studied by NMR spectroscopy. It was shown that Lc-def is active against fungi, but does not inhibit the growth of Gram-positive and Gram-negative bacteria. The peptide is monomeric in aqueous solution and contains one α-helix and triple-stranded β-sheet, which form cysteine-stabilized αβ motif (CSαβ) previously found in other plant defensins. The sterically neighboring loop1 and loop3 protrude from the defensin core and demonstrate significant mobility on the μs–ms timescale. Lc-def does not bind to the zwitterionic lipid (POPC) vesicles but interacts with the partially anionic (POPC/DOPG, 7:3) membranes under low-salt conditions. The Lc-def antifungal activity might be mediated through electrostatic interaction with anionic lipid components of fungal membranes.« less

A G-quadruplex based fluorescent oligonucleotide turn-on probe towards iodides detection in real samples.

PubMed

Li, Qian; Li, Shuaihua; Chen, Xiu; Bian, Liujiao

2017-09-01

A basket-type G-quadruplex (GQ) fluorescent oligonucleotide (OND) probe is designed to detect iodides dependent on thymine-Hg(II)-thymine (T-Hg(II)-T) base pairs and the intrinsic fluorescence quenching capacity of GQ. In the presence of Hg(II) ions (Hg 2+ ), the two hexachloro-fluorescein-labeled ONDs form a hairpin structure and the fluorophores are dragged close to the GQ, leading to fluorescence quenching of the probe due to photoinduced electron transfer. Upon addition of iodide anions, Hg 2+ are extracted from T-Hg(II)-T complexes which attributes to the stronger binding with iodide anions, resulting in the fluorescence recovery. Through performing the fluorescence quenching and recovery processes, this probe developed a fluorescence turn-on sensor for iodide anions determination over a linear range of 20-200nmol/L with a limit of detection of 5nmol/L. The practical use of the turn-on technology was demonstrated by its application in determination of iodides in water, food, pharmaceutical products and biological samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

A newly synthesized thiazole derivative as a fluoride ion chemosensor: naked-eye, spectroscopic, electrochemical and NMR studies.

PubMed

Sarıgüney, Ahmet Burak; Saf, Ahmet Özgür; Coşkun, Ahmet

2014-07-15

2,3-Indoledione 3-thiosemicarbazone (TSCI) and a novel compound 3-(2-(4-(4-phenoxyphenyl)thiazol-2-yl)hydrazono)indolin-2-one (FTHI) were synthesized with high yield and characterized by spectroscopic techniques. The complexation behaviors of TSCI and FTHI for various anionic species (F(-), Cl(-), Br(-), I(-), NO2(-), NO3(-), BzO(-), HSO4(-), ClO4(-)) in CH3CN were investigated and compared by UV-vis spectroscopy, cyclic voltammetry and (1)H NMR titration techniques. FTHI showed high degree of selectivity for fluoride over other anions. This selectivity could be easily observed by the naked eye, indicating that FTHI is potential colorimetric sensor for fluoride anion. Copyright © 2014 Elsevier B.V. All rights reserved.

Cysteine Scanning Mutagenesis of Transmembrane Domain 10 in Organic Anion Transporting Polypeptide 1B1

PubMed Central

2015-01-01

Organic anion transporting polypeptide (OATP) 1B1 is an important drug transporter expressed in human hepatocytes. Previous studies have indicated that transmembrane (TM) domain 2, 6, 8, 9, and in particular 10 might be part of the substrate binding site/translocation pathway. To explore which amino acids in TM10 are important for substrate transport, we mutated 34 amino acids individually to cysteines, expressed them in HEK293 cells, and determined their surface expression. Transport activity of the two model substrates estrone-3-sulfate and estradiol-17β-glucuronide as well as of the drug substrate valsartan for selected mutants was measured. Except for F534C and F537C, all mutants were expressed at the plasma membrane of HEK293 cells. Mutants Q541C and A549C did not transport estradiol-17β-glucuronide and showed negligible estrone-3-sulfate transport. However, A549C showed normal valsartan transport. Pretreatment with the anionic and cell impermeable sodium (2-sulfonatoethyl)methanethiosulfonate (MTSES) affected the transport of each substrate differently. Pretreatment of L545C abolished estrone-3-sulfate uptake almost completely, while it stimulated estradiol-17β-glucuronide uptake. Further analyses revealed that mutant L545C in the absence of MTSES showed biphasic kinetics for estrone-3-sulfate that was converted to monophasic kinetics with a decreased apparent affinity, explaining the previously seen inhibition. In contrast, the apparent affinity for estradiol-17β-glucuronide was not changed by MTSES treatment, but the Vmax value was increased about 4-fold, explaining the previously seen stimulation. Maleimide labeling of L545C was affected by preincubation with estrone-3-sulfate but not with estradiol-17β-glucuronide. These results strongly suggest that L545C is part of the estrone-3-sulfate binding site/translocation pathway but is not directly involved in binding/translocation of estradiol-17β-glucuronide. PMID:24673529

Halogenation of cobalt dicarbollide

DOEpatents

Hurlburt, P.K.; Abney, K.D.; Kinkead, S.A.

1997-05-20

A method for selectively adding chlorine, bromine, or iodine to cobalt dicarbollide anions by means of electrophilic substitution reactions. Halogens are added only to the B10 and B10{prime} positions of the anion. The process involves use of hypohalous acid or N-halosuccinimide or gaseous chlorine in the presence of iron. 1 fig.

Halogenation of cobalt dicarbollide

DOEpatents

Hurlburt, Paul K.; Abney, Kent D.; Kinkead, Scott A.

1997-01-01

A method for selectively adding chlorine, bromine, or iodine to cobalt dicarbollide anions by means of electrophilic substitution reactions. Halogens are added only to the B10 and B10' positions of the anion. The process involves use of hypohalous acid or N-halosuccinimide or gaseous chlorine in the presence of iron.

Development of poly-l-lysine-coated calcium-alginate microspheres encapsulating fluorescein-labeled dextrans

NASA Astrophysics Data System (ADS)

Charron, Luc; Harmer, Andrea; Lilge, Lothar

2005-09-01

A technique to produce fluorescent cell phantom standards based on calcium alginate microspheres with encapsulated fluorescein-labeled dextrans is presented. An electrostatic ionotropic gelation method is used to create the microspheres which are then exposed to an encapsulation method using poly-l-lysine to trap the dextrans inside. Both procedures were examined in detail to find the optimal parameters producing cell phantoms meeting our requirements. Size distributions favoring 10-20 microns microspheres were obtained by varying the high voltage and needle size parameters. Typical size distributions of the samples were centered at 150 μm diameter. Neither the molecular weight nor the charge of the dextrans had a significant effect on their retention in the microspheres, though anionic dextrans were chosen to help in future capillary electrophoresis work. Increasing the exposure time of the microspheres to the poly-l-lysine solution decreased the leakage rates of fluorescein-labeled dextrans.

Quantification of isotope-labelled and unlabelled folates in plasma, ileostomy and food samples.

PubMed

Büttner, Barbara E; Öhrvik, Veronica E; Witthöft, Cornelia M; Rychlik, Michael

2011-01-01

New stable isotope dilution assays were developed for the simultaneous quantitation of [(13)C(5)]-labelled and unlabelled 5-methyltetrahydrofolic acid, 5-formyltetrahydrofolic acid, folic acid along with unlabelled tetrahydrofolic acid and 10-formylfolic acid in clinical samples deriving from human bioavailability studies, i.e. plasma, ileostomy samples, and food. The methods were based on clean-up by strong anion exchange followed by LC-MS/MS detection. Deuterated analogues of the folates were applied as the internal standards in the stable isotope dilution assays. Assay sensitivity was sufficient to detect all relevant folates in the respective samples as their limits of detection were below 0.62 nmol/L in plasma and below 0.73 μg/100 g in food or ileostomy samples. Quantification of the [(13)C(5)]-label in clinical samples offers the possibility to differentiate between folate from endogenous body pools and the administered dose when executing bioavailability trials.

Intercalation of IR absorber into layered double hydroxides: Preparation, thermal stability and selective IR absorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Haifeng; Tang, Pinggui; Feng, Yongjun, E-mail: yjfeng@mail.buct.edu.cn

2012-03-15

Highlights: Black-Right-Pointing-Pointer PMIDA anions were intercalated into Mg{sub 2}Al-NO{sub 3} LDH by anion-exchange method. Black-Right-Pointing-Pointer The prepared material has highly selective IR absorption property in 9-11 {mu}m. Black-Right-Pointing-Pointer The obtained material has practical applications as heat-retaining additive. -- Abstract: N-phosphonomethyl aminodiacetic acid (PMIDA) was intercalated into the interlayer spacing of layered double hydroxides (LDH) by an anion-exchange method. The intercalated LDHs were characterized by various techniques such as powder X-ray diffraction (XRD), FT-IR spectroscopy, elemental analysis and simultaneous thermogravimetric and mass spectrometry (TG-MS) in details. The results show the formation of Mg{sub 2}Al-PMIDA LDH based on the expansion of d-spacingmore » from 0.89 nm to 1.22 nm and the disappearance of the characteristic IR absorption band at 1384 cm{sup -1} for NO{sub 3}{sup -} anions. The incorporation of Mg{sub 2}Al-PMIDA LDH into the low density polyethylene (LDPE) as an additive enhances the selectivity of IR absorption in the main wavelength region 9-11 {mu}m for radiant heat loss at night. Mg{sub 2}Al-PMIDA LDH as a heat-retaining additive has practical application in agricultural plastic films.« less

Electrochemically Switchable Polymeric Membrane Ion-Selective Electrodes.

PubMed

Zdrachek, Elena; Bakker, Eric

2018-06-07

We present here for the first time a solid contact ion-selective electrode suitable for the simultaneous sensing of cations (tetrabutylammonium) and anions (hexafluorophosphate), achieved by electrochemical switching. The membrane is based on a thin plasticized polyurethane membrane deposited on poly(3-octylthiophene) (POT) and contains a cation exchanger and lipophilic electrolyte (ETH 500). The cation exchanger is initially in excess; the ion-selective electrode exhibits an initial potentiometric response to cations. During an oxidative current pulse, POT is converted into POT + , which results in the expulsion of cations from the membrane followed by the extraction of anions from the sample solution to fulfill the electroneutrality condition. This creates a defined excess of lipophilic cation in the membrane, resulting in a potentiometric anion response. A reductive current pulse restores the original cation response by triggering the conversion of POT + back into POT, which is accompanied by the expulsion of anions from the membrane and the extraction of cations from the sample solution. Various current pulse magnitudes and durations are explored, and the best results in terms of response slope values and signal stability were observed with an oxidation current pulse of 140 μA cm -2 applied for 8 s and a reduction current pulse of -71 μA cm -2 applied for 8 s.

A novel, environmentally friendly sodium lauryl ether sulfate-, cocamidopropyl betaine-, cocamide monoethanolamine-containing buffer for MEKC on microfluidic devices.

PubMed

Hoeman, Kurt W; Culbertson, Christopher T

2008-12-01

A new buffer has been developed for fast, high-efficiency separations of amino acids by MEKC. This buffer was more environmentally friendly than the most commonly used surfactant-containing buffers for MEKC separations. It used a commercially available dishwashing soap by Seventh Generation (Burlington, VT, USA), which contained three micelle-forming agents. The mixed micelles were composed of sodium lauryl ether sulfate (anionic), cocamidopropyl betaine (zwitterionic), and cocamide monoethanolamine (non-ionic). The optimized buffer contained 5.0% w/w Seventh Generation Free & Clear dishwashing soap, 10 mM sodium borate, and was completely void of organics. The lack of organics and the biodegradability of the surfactant molecules made this buffer more environmentally friendly than typical SDS-containing buffers. This new buffer also had a different selectivity and provided faster separations with higher separation efficiencies than SDS-based buffers. Fast separations of BODIPY FL labeled amino acids yielded peaks with separation efficiencies greater than 100,000 in less than 20 s.

Microfluidic integration of parallel solid-phase liquid chromatography.

PubMed

Huft, Jens; Haynes, Charles A; Hansen, Carl L

2013-03-05

We report the development of a fully integrated microfluidic chromatography system based on a recently developed column geometry that allows for robust packing of high-performance separation columns in poly(dimethylsiloxane) microfluidic devices having integrated valves made by multilayer soft lithography (MSL). The combination of parallel high-performance separation columns and on-chip plumbing was used to achieve a fully integrated system for on-chip chromatography, including all steps of automated sample loading, programmable gradient generation, separation, fluorescent detection, and sample recovery. We demonstrate this system in the separation of fluorescently labeled DNA and parallel purification of reverse transcription polymerase chain reaction (RT-PCR) amplified variable regions of mouse immunoglobulin genes using a strong anion exchange (AEX) resin. Parallel sample recovery in an immiscible oil stream offers the advantage of low sample dilution and high recovery rates. The ability to perform nucleic acid size selection and recovery on subnanogram samples of DNA holds promise for on-chip genomics applications including sequencing library preparation, cloning, and sample fractionation for diagnostics.

Evaluating Varied Label Designs for Use with Medical Devices: Optimized Labels Outperform Existing Labels in the Correct Selection of Devices and Time to Select.

PubMed

Bix, Laura; Seo, Do Chan; Ladoni, Moslem; Brunk, Eric; Becker, Mark W

2016-01-01

Effective standardization of medical device labels requires objective study of varied designs. Insufficient empirical evidence exists regarding how practitioners utilize and view labeling. Measure the effect of graphic elements (boxing information, grouping information, symbol use and color-coding) to optimize a label for comparison with those typical of commercial medical devices. Participants viewed 54 trials on a computer screen. Trials were comprised of two labels that were identical with regard to graphics, but differed in one aspect of information (e.g., one had latex, the other did not). Participants were instructed to select the label along a given criteria (e.g., latex containing) as quickly as possible. Dependent variables were binary (correct selection) and continuous (time to correct selection). Eighty-nine healthcare professionals were recruited at Association of Surgical Technologists (AST) conferences, and using a targeted e-mail of AST members. Symbol presence, color coding and grouping critical pieces of information all significantly improved selection rates and sped time to correct selection (α = 0.05). Conversely, when critical information was graphically boxed, probability of correct selection and time to selection were impaired (α = 0.05). Subsequently, responses from trials containing optimal treatments (color coded, critical information grouped with symbols) were compared to two labels created based on a review of those commercially available. Optimal labels yielded a significant positive benefit regarding the probability of correct choice ((P<0.0001) LSM; UCL, LCL: 97.3%; 98.4%, 95.5%)), as compared to the two labels we created based on commercial designs (92.0%; 94.7%, 87.9% and 89.8%; 93.0%, 85.3%) and time to selection. Our study provides data regarding design factors, namely: color coding, symbol use and grouping of critical information that can be used to significantly enhance the performance of medical device labels.

Surface-active ionic liquids in micellar catalysis: impact of anion selection on reaction rates in nucleophilic substitutions† †Electronic supplementary information (ESI) available: Formulae for calculating aggregation parameters and fitting of kinetic constants and copies of NMR spectra. See DOI: 10.1039/c6cp00493h Click here for additional data file.

PubMed Central

Cognigni, Alice; Gaertner, Peter; Zirbs, Ronald; Peterlik, Herwig; Prochazka, Katharina; Schröder, Christian

2016-01-01

A series of surface-active ionic liquids based on the 1-dodecyl-3-methylimidazolium cation and different anions such as halides and alkylsulfates was synthesized. The aggregation behavior of these ionic liquids in water was characterized by surface tension, conductivity measurements and UV-Vis spectroscopy in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. The determination of surface activity and aggregation properties of amphiphilic ionic liquids was accompanied by SAXS studies on selected surface-active ionic liquids. The application of these surface-active ionic liquids with different anions was tested in nucleophilic substitution reactions for the degradation of organophosphorus compounds. Kinetic studies via UV-Vis spectrophotometry showed a strong acceleration of the reaction in the micellar system compared to pure water. In addition, an influence of the anion was observed, resulting in a correlation between the anion binding to the micelle and the reaction rate constants, indicating that the careful choice of the surface-active ionic liquid can considerably affect the outcome of reactions. PMID:27121134

Carbon-dot-based fluorescent turn-on sensor for selectively detecting sulfide anions in totally aqueous media and imaging inside live cells.

PubMed

Hou, Xianfeng; Zeng, Fang; Du, Fangkai; Wu, Shuizhu

2013-08-23

Sulfide anions are generated not only as a byproduct from industrial processes but also in biosystems. Hence, robust fluorescent sensors for detecting sulfide anions which are fast-responding, water soluble and biocompatible are highly desirable. Herein, we report a carbon-dot-based fluorescent sensor, which features excellent water solubility, low cytotoxicity and a short response time. This sensor is based on the ligand/Cu(II) approach so as to achieve fast sensing of sulfide anions. The carbon dot (CD) serves as the fluorophore as well as the anchoring site for the ligands which bind with copper ions. For this CD-based system, as copper ions bind with the ligands which reside on the surface of the CD, the paramagnetic copper ions efficiently quench the fluorescence of the CD, affording the system a turn-off sensor for copper ions. More importantly, the subsequently added sulfide anions can extract Cu(2+) from the system and form very stable CuS with Cu(2+), resulting in fluorescence enhancement and affording the system a turn-on sensor for sulfide anions. This fast-responding and selective sensor can operate in totally aqueous solution or in physiological milieu with a low detection limit of 0.78 μM. It displays good biocompatibility, and excellent cell membrane permeability, and can be used to monitor S(2-) levels in running water and living cells.

Intrinsic electrophilic properties of nucleosides: Photoelectron spectroscopy of their parent anions

NASA Astrophysics Data System (ADS)

Stokes, Sarah T.; Li, Xiang; Grubisic, Andrej; Ko, Yeon Jae; Bowen, Kit H.

2007-08-01

The nucleoside parent anions 2'-deoxythymidine-, 2'-deoxycytidine-, 2'-deoxyadenosine-, uridine-, cytidine-, adenosine-, and guanosine- were generated in a novel source, employing a combination of infrared desorption, electron photoemission, and a gas jet expansion. Once mass selected, the anion photoelectron spectrum of each of these was recorded. In the three cases in which comparisons were possible, the vertical detachment energies and likely adiabatic electron affinities extracted from these spectra agreed well with the values calculated both by Richardson et al. [J. Am. Chem. Soc. 126, 4404 (2004)] and by Li et al. [Radiat. Res. 165, 721 (2006)]. Through the combination of our experimental results and their theoretical calculations, several implications emerge. (1) With the possible exception of dG-, the parent anions of nucleosides exist, and they are stable. (2) These nucleoside anions are valence anions, and in most cases the negative charge is closely associated with the nucleobase moiety. (3) The nucleoside parent anions we have generated and studied are the negative ions of canonical, neutral nucleosides, similar to those found in DNA.

Intrinsic electrophilic properties of nucleosides: photoelectron spectroscopy of their parent anions.

PubMed

Stokes, Sarah T; Li, Xiang; Grubisic, Andrej; Ko, Yeon Jae; Bowen, Kit H

2007-08-28

The nucleoside parent anions 2(')-deoxythymidine(-), 2(')-deoxycytidine(-), 2(')-deoxyadenosine(-), uridine(-), cytidine(-), adenosine(-), and guanosine(-) were generated in a novel source, employing a combination of infrared desorption, electron photoemission, and a gas jet expansion. Once mass selected, the anion photoelectron spectrum of each of these was recorded. In the three cases in which comparisons were possible, the vertical detachment energies and likely adiabatic electron affinities extracted from these spectra agreed well with the values calculated both by Richardson et al. [J. Am. Chem. Soc. 126, 4404 (2004)] and by Li et al. [Radiat. Res. 165, 721 (2006)]. Through the combination of our experimental results and their theoretical calculations, several implications emerge. (1) With the possible exception of dG(-), the parent anions of nucleosides exist, and they are stable. (2) These nucleoside anions are valence anions, and in most cases the negative charge is closely associated with the nucleobase moiety. (3) The nucleoside parent anions we have generated and studied are the negative ions of canonical, neutral nucleosides, similar to those found in DNA.

Matrix influences on the determination of common ions by using ion chromatography part 1--determination of inorganic anions.

PubMed

Michalski, Rajmund; Lyko, Aleksandra; Kurzyca, Iwona

2012-07-01

Ion chromatography is the most popular instrumental analytical method used for the determination of anions and cations in water and wastewater. Isocratic ion chromatography with suppressed conductivity detection is frequently used in laboratories carrying out routine analyses of inorganic anions. The paper presents the results of the research into the influence of selected inorganic anions dominant in environmental samples (Cl(-), NO(3)(-), SO(4)(2-)) on the possibility of simultaneous determination of F(-), Cl(-), NO(2)(-), NO(3)(-), PO(4)(3-) and SO(4)(2-) with the application of this most popular ion chromatography type in standard separation conditions. Four Dionex and four Metrohm anion-exchange columns were tested in standard separation conditions recommended by their manufacturers with both standard solutions and environmental samples with complex matrix.

Isolation and partial characterization of gypsy moth BTR-270, an anionic brush border membrane glycoconjugate that binds Bacillus thuringiensis Cry1A toxins with high affinity

Treesearch

Algimantas P. Valaitis; Jeremy L. Jenkins; Mi Kyong Lee; Donald H. Dean; Karen J. Garner

2001-01-01

BTR-270, a gypsy moth (Lymantria dispar) brush border membrane molecule that binds Bacillus thuringiensis (Bt) Cry1A toxins with high affinity, was purified by preparative gel electrophoresis. Rabbit antibodies specific for the Bt toxin-binding molecule were raised. Attempts to label BTR-270 by protein-directed techniques were...

Short-range order in the Ca sub 1-x La sub x F sub 2+x solid solution: 1:0:3 or 1:0:4 clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laval, J.P.; Abaouz, A.; Frit, B.

1989-08-01

The defect structure of the Ca{sub 1-x}La{sub x}F{sub 2+x} solid solution (0 {le} x {le} 0.38) has been examined at room temperature by powder neutron diffraction. Two kinds of (xxx) interstitial anions, whose respective numbers increase linearly with increasing dopant cation concentration, have been found: one labeled F{sup 0} (x {approx} 0.41) is a true interstitial; the other labeled F{sup {prime}{double prime}} (x {approx} 0.31) can be considered a relaxed normal anion. Two 1:0:n defect clusters are compatible, within the experimental errors, with these results: the 1:0:3 (1V{sub F}, OF{prime}, 3F{sup {double prime}}, 2 La{sup 3+}) and the 1:0:4 (1V{submore » F}, OF{prime}, 4F{sup {double prime}}, 3La{sup 3+}) clusters. Charge balance considerations and comparisons with the homologous Ca{sub 1-x}M{sub x}{sup IV}F{sub 2+2x} solid solutions (M{sup IV} = Th, U) allow us to think that the less dense 1:0:3 cluster is present for the whole domain of both kinds of solid solutions.« less

Anion-selective interaction and colorimeter by an optical metalloreceptor based on ruthenium(II) 2,2'-biimidazole: hydrogen bonding and proton transfer.

PubMed

Cui, Ying; Mo, Hao-Jun; Chen, Jin-Can; Niu, Yan-Li; Zhong, Yong-Rui; Zheng, Kang-Cheng; Ye, Bao-Hui

2007-08-06

A new anion sensor [Ru(bpy)2(H2biim)](PF6)2 (1) (bpy = 2,2'-bipyridine and H2biim = 2,2'-biimidazole) has been developed, in which the Ru(II)-bpy moiety acts as a chromophore and the H2biim ligand as an anion receptor via hydrogen bonding. A systematic investigation shows that 1 is an eligible sensor for various anions. It donates protons for hydrogen bonding to Cl-, Br-, I-, NO3-, HSO4-, H2PO4-, and OAc- anions and further actualizes monoproton transfer to the OAc- anion, changing color from yellow to orange brown. The fluoride ion has a high affinity toward the N-H group of the H2biim ligand for proton transfer, rather than hydrogen bonding, because of the formation of the highly stable HF2- anion, resulting in stepwise deprotonation of the two N-H fragments. These processes are signaled by vivid color changes from yellow to orange brown and then to violet because of second-sphere donor-acceptor interactions between Ru(II)-H2biim and the anions. The significant color changes can be distinguished visually. The processes are not only determined by the basicity of anion but also by the strength of hydrogen bonding and the stability of the anion-receptor complexes. The design strategy and remarkable photophysical properties of sensor 1 help to extend the development of anion sensors.

Final Technical Report: Targeting DOE-Relevant Ions with Supramolecular Strategies, DE-SC0010555

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowman-James, Kristin

The effectiveness of three popular supramolecular strategies to selectively target negatively charged ions (anions) was evaluated. Ions of interest included oxo anions, particularly sulfate, that hamper nuclear waste remediation. Three objectives were pursued using a simple building block strategies and by strategically placing anion-binding sites at appropriate positions on organic host molecules. The goal of the first objective was to assess the influence of secondary, tertiary and quaternized amines on binding tetrahedral anions using mixed amide/amine macrocyclic and urea/amine hosts containing aromatic or heteroaromatic spacers. Objective 2 focused on the design of ion pair hosts, using mixed macrocyclic anion hostsmore » joined through polyether linkages. Objective 3 was to explore the synthesis of new metal-linked extended macrocyclic frameworks to leverage anion binding. Key findings were that smaller 24-membered macrocycles provided the most complementary binding for sulfate ion and mixed urea/amine chelates showed enhanced binding over amide corollaries in addition to being highly selective for SO 4 2- in the presence of small quantities of water. In addition to obtaining prototype metal-linked macrocyclic anion hosts, a new dipincer ligand was designed that can be used to link macrocyclic or other supramolecular hosts in extended frameworks. When the tetraamide-based pincers are bound to two metal ions, an interesting phenomenon occurs. Upon deprotonation of the amides, two new protons appear between adjacent carbonyl pairs on the ligand, which may modify the chemistry, and metal-metal interactions in the complexes. Gel formation occurred for some of these extended hosts, and the physical properties are currently under investigation. The new tetracarboxamide-based pincers can also provide basic frameworks for double macrocycles capable of binding ion pairs as well as for binding metal ions and exploring intermetallic interactions through the pyrazine π system. Additionally appendages capable of influencing solvation effects can be introduced, and a number of other potential applications can be realized in areas such as soft materials chemistry, catalysis, sensing, and proton switches, the latter for binding and release of targeted guests. These findings provide a better foundation for understanding the selective binding of anions by targeted placement of hydrogen binding sites, and the strengths and weaknesses of various functional groups, that will allow for more the design of more effective anion sequestering agents. Our design strategy also used simple, cost-effective building blocks for host synthesis to allow for scale-up should real-world applications be forthcoming.« less

One-step selective electrokinetic removal of inorganic anions from small volumes and its application as sample clean-up for mass spectrometric techniques.

PubMed

Tubaon, Ria Marni; Haddad, Paul R; Quirino, Joselito P

2017-03-10

The presence of inorganic anions in a sample interferes with mass spectrometric (MS) analysis. Here, a simple method to remove these ions from a liquid sample in one-step is described. The inorganic anions present in a 50μL sample were extracted into a low pH solution inside a 200μm i.d.×33cm long capillary by the use of an electric field. The selective removal of unwanted anions and retention of target analytes was accomplished by control of the apparent electrophoretic velocities of anions and analytes at a boundary that separated the sample and extraction solution. No physical barrier (e.g., membrane) was required and with the boundary situated at the tip of the capillary, efficient removal of inorganic anions (e.g., >80% removal) and good recovery of target analytes (e.g., >80% recovery) were achieved. The time required for removal of the inorganic anions was found to depend on their initial concentrations. The removal process was investigated using different concentrations of bromide and nitrate (as potassium salts) and negatively chargeable drugs as target analytes. This micro-sample clean-up technique used no organic solvents and little consumables and was studied to the determination of 0.6μg/L arsenic and 8.3μg/L vanadium in 500mg/L sodium chloride using inductively coupled plasma MS and 50μM angiotensin I in 1000mg/L sodium chloride using electrospray ionisation MS. Micro-sample clean-up was performed for 45min at 3kV in both demonstrations. The calculated recoveries for the metals at trace levels were 110-130%, and for the peptide was 103.8%. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluating of arsenic(V) removal from water by weak-base anion exchange adsorbents.

PubMed

Awual, M Rabiul; Hossain, M Amran; Shenashen, M A; Yaita, Tsuyoshi; Suzuki, Shinichi; Jyo, Akinori

2013-01-01

Arsenic contamination of groundwater has been called the largest mass poisoning calamity in human history and creates severe health problems. The effective adsorbents are imperative in response to the widespread removal of toxic arsenic exposure through drinking water. Evaluation of arsenic(V) removal from water by weak-base anion exchange adsorbents was studied in this paper, aiming at the determination of the effects of pH, competing anions, and feed flow rates to improvement on remediation. Two types of weak-base adsorbents were used to evaluate arsenic(V) removal efficiency both in batch and column approaches. Anion selectivity was determined by both adsorbents in batch method as equilibrium As(V) adsorption capacities. Column studies were performed in fixed-bed experiments using both adsorbent packed columns, and kinetic performance was dependent on the feed flow rate and competing anions. The weak-base adsorbents clarified that these are selective to arsenic(V) over competition of chloride, nitrate, and sulfate anions. The solution pH played an important role in arsenic(V) removal, and a higher pH can cause lower adsorption capacities. A low concentration level of arsenic(V) was also removed by these adsorbents even at a high flow rate of 250-350 h(-1). Adsorbed arsenic(V) was quantitatively eluted with 1 M HCl acid and regenerated into hydrochloride form simultaneously for the next adsorption operation after rinsing with water. The weak-base anion exchange adsorbents are to be an effective means to remove arsenic(V) from drinking water. The fast adsorption rate and the excellent adsorption capacity in the neutral pH range will render this removal technique attractive in practical use in chemical industry.

Selections from 2017: Discoveries in Titan's Atmosphere

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

Editors note:In these last two weeks of 2017, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume in January.Carbon Chain Anions and the Growth of Complex Organic Molecules in Titans IonospherePublished July2017Main takeaway:Graphic depicting some of the chemical reactions taking place in Titans atmosphere, leading to the generation of organic haze particles. [ESA]In a recently published study led by Ravi Desai (University College London), scientists used data from the Cassini mission to identify negatively charged molecules known as carbon chain anions in the atmosphere of Saturns largest moon, Titan.Why its interesting:Carbon chain anions are the building blocks ofmore complex molecules, and Titans thick nitrogen and methane atmosphere mightmimic the atmosphere of earlyEarth. This first unambiguous detection of carbon chain anions in a planet-like atmosphere might therefore teach us about the conditions and chemical reactions that eventually led to the development of life on Earth. And ifwe can use Titan to learn about how complex molecules grow from these anion chains, we may be able to identify auniversal pathway towards the ingredients for life.What weve learned so far:Cassini measured fewer and fewer lower-mass anions the deeper in Titans ionosphere that it looked and at the same time,an increase in the number of precursors to larger aerosol molecules further down. This tradeoff strongly suggests that the anions are indeed involved in building up the more complex molecules, seeding their eventual growth into the complex organic haze of Titans lower atmosphere.CitationR. T. Desai et al 2017 ApJL 844 L18. doi:10.3847/2041-8213/aa7851

Pattern-based detection of anion pollutants in water with DNA polyfluorophores† †Electronic supplementary information (ESI) available: Additional figures and tables and experimental details. See DOI: 10.1039/c4sc03992k Click here for additional data file.

PubMed Central

Kwon, Hyukin; Jiang, Wei

2015-01-01

Many existing irrigation, industrial and chemical storage sites are currently introducing hazardous anions into groundwater, making the monitoring of such sites a high priority. Detecting and quantifying anions in water samples typically requires complex instrumentation, adding cost and delaying analysis. Here we address these challenges by development of an optical molecular method to detect and discriminate a broad range of anionic contaminants with DNA-based fluorescent sensors. A library of 1296 tetrameric-length oligodeoxyfluorosides (ODFs) composed of metal ligand and fluorescence modulating monomers was constructed with a DNA synthesizer on PEG-polystyrene microbeads. These oligomers on beads were incubated with YIII or ZnII ions to provide affinity and responsiveness to anions. Seventeen anions were screened with the library under an epifluorescence microscope, ultimately yielding eight chemosensors that could discriminate 250 μM solutions of all 17 anions in buffered water using their patterns of response. This sensor set was able to identify two unknown anion samples from ten closely-responding anions and could also function quantitatively, determining unknown concentrations of anions such as cyanide (as low as 1 mM) and selenate (as low as 50 μM). Further studies with calibration curves established detection limits of selected anions including thiocyanate (detection limit ∼300 μM) and arsenate (∼800 μM). The results demonstrate DNA-like fluorescent chemosensors as versatile tools for optically analyzing environmentally hazardous anions in aqueous environments. PMID:26146537

A novel reaction-based colorimetric and ratiometric fluorescent sensor for cyanide anion with a large emission shift and high selectivity.

PubMed

Wang, Shaodan; Fei, Xiaoliang; Guo, Jing; Yang, Qingbiao; Li, Yaoxian; Song, Yan

2016-01-01

A hybrid carbazole-hemicyanine dye (Cac) has been developed as a novel colorimetric and ratiometric fluorescent sensor for cyanide detection. Upon treatment with cyanide, Cac displayed a remarkable fluorescence ratiometric response, with the emission wavelength displaying a very large emission shift (214 nm). The detection of cyanide was performed via the nucleophilic addition of cyanide anion to the indolium group of the sensor, which resulted in the blocking of the intramolecular charge transfer (ICT) process in the sensor, inducing a ratiometric fluorescence change and simultaneously an obvious color change. Furthermore, competitive anions did not showed any significant changes both in color and emission intensity ratio (I381/I595), indicating the high selectivity of the sensor to CN(-). Copyright © 2015 Elsevier B.V. All rights reserved.

Rationally designed fluorescently labeled sulfate-binding protein mutants: evaluation in the development of a sensing system for sulfate

NASA Technical Reports Server (NTRS)

Shrestha, Suresh; Salins, Lyndon L E.; Mark Ensor, C.; Daunert, Sylvia

2002-01-01

Periplasmic binding proteins from E. coli undergo large conformational changes upon binding their respective ligands. By attaching a fluorescent probe at rationally selected unique sites on the protein, these conformational changes in the protein can be monitored by measuring the changes in fluorescence intensity of the probe which allow the development of reagentless sensing systems for their corresponding ligands. In this work, we evaluated several sites on bacterial periplasmic sulfate-binding protein (SBP) for attachment of a fluorescent probe and rationally designed a reagentless sensing system for sulfate. Eight different mutants of SBP were prepared by employing the polymerase chain reaction (PCR) to introduce a unique cysteine residue at a specific location on the protein. The sites Gly55, Ser90, Ser129, Ala140, Leu145, Ser171, Val181, and Gly186 were chosen for mutagenesis by studying the three-dimensional X-ray crystal structure of SBP. An environment-sensitive fluorescent probe (MDCC) was then attached site-specifically to the protein through the sulfhydryl group of the unique cysteine residue introduced. Each fluorescent probe-conjugated SBP mutant was characterized in terms of its fluorescence properties and Ser171 was determined to be the best site for the attachment of the fluorescent probe that would allow for the development of a reagentless sensing system for sulfate. Three different environment-sensitive fluorescent probes (1,5-IAEDANS, MDCC, and acylodan) were studied with the SBP171 mutant protein. A calibration curve for sulfate was constructed using the labeled protein and relating the change in the fluorescence intensity with the amount of sulfate present in the sample. The detection limit for sulfate was found to be in the submicromolar range using this system. The selectivity of the sensing system was demonstrated by evaluating its response to other anions. A fast and selective sensing system with detection limits for sulfate in the submicromolar range was developed. Copyright 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 517-526, 2002.

A Cross-Sectional Study of the Relationship between Nutrition Label Use and Food Selection, Servings, and Consumption in a University Dining Setting.

PubMed

Christoph, Mary J; Ellison, Brenna

2017-10-01

Nutrition labels at the point of purchase are recommended to improve food choice, yet food choice does not always translate into food consumption. It is important to understand the relationship between label use, food selection, servings, and consumption. Previous research, which has relied on self-reported intake or inferred label use or intake based on sales data, has not adequately answered this question. To combine survey and meal photographic data to compare food selection, servings, and consumption between label users and nonusers. Diners were surveyed in two cross-sectional waves during the fall 2014 semester. Food selections were recorded, and pre- and postmeal photographs were taken of diners' plate. Photographs were coded to identify the selection, servings, and consumption of MyPlate food categories. Convenience sample of 1,069 diners (39% women, 53% freshman) in two university dining halls. Students had to be older than age 18 years and just beginning their meal to participate. Selection, servings, and consumption of MyPlate food categories for label users and nonusers. Differences in food selection were tested via χ 2 tests, and differences in adjusted least squares means for servings and consumption were tested via t tests. A greater proportion of nutrition label users selected fruits, vegetables, and beans and fewer selected potatoes compared with nonusers. In addition, fewer label users selected fried foods and foods with added sugars (all P values <0.05). Label users served themselves and consumed more vegetables and fewer potatoes and refined grains compared with nonusers (all P values <0.05). Our results suggest label users behave differently compared with nonusers. Based on the meals observed, these differences appear more qualitative in nature (selecting different foods) than quantitative (selecting more or less food). Copyright © 2017 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Continuous real-time measurement of aqueous cyanide

DOEpatents

Rosentreter, Jeffrey J.; Gering, Kevin L.

2007-03-06

This invention provides a method and system capable of the continuous, real-time measurement of low concentrations of aqueous free cyanide (CN) using an on-line, flow through system. The system is based on the selective reactivity of cyanide anions and the characteristically nonreactive nature of metallic gold films, wherein this selective reactivity is exploited as an indirect measurement for aqueous cyanide. In the present invention the dissolution of gold, due to the solubilization reaction with the analyte cyanide anion, is monitored using a piezoelectric microbalance contained within a flow cell.

Selective Metal Cation Capture by Soft Anionic Metal-Organic Frameworks via Drastic Single-Crystal-to-Single-Crystal Transformations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Jian; Saraf, Laxmikant V.; Schwenzer, Birgit

2012-05-25

Flexible anionic metal-organic frameworks transform to neutral heterobimetallic systems via single-crystal-to-single-crystal processes invoked by cation insertion. These transformations are directed by cooperative bond breakage and formation, resulting in expansion or contraction of the 3D framework by up to 33% due to the flexible nature of the organic linker. These MOFs displays highly selective uptake of divalent transition metal cations (Co2+ and Ni2+ for example) over alkali metal cations (Li+ and Na+).

Characteristics of SnO2-based 68Ge/68Ga generator and aspects of radiolabelling DOTA-peptides.

PubMed

de Blois, Erik; Sze Chan, Ho; Naidoo, Clive; Prince, Deidre; Krenning, Eric P; Breeman, Wouter A P

2011-02-01

PET scintigraphy with (68)Ga-labelled analogs is of increasing interest in Nuclear Medicine and performed all over the world. Here we report the characteristics of the eluate of SnO(2)-based (68)Ge/(68)Ga generators prepared by iThemba LABS (Somerset West, South Africa). Three purification and concentration techniques of the eluate for labelling DOTA-TATE and concordant SPE purifications were investigated. Characteristics of 4 SnO(2)-based generators (range 0.4-1 GBq (68)Ga in the eluate) and several concentration techniques of the eluate (HCl) were evaluated. The elution profiles of SnO(2)-based (68)Ge/(68)Ga generators were monitored, while [HCl] of the eluens was varied from 0.3-1.0 M. Metal ions and sterility of the eluate were determined by ICP. Fractionated elution and concentration of the (68)Ga eluate were performed using anion and cation exchange. Concentrated (68)Ga eluate, using all three concentration techniques, was used for labelling of DOTA-TATE. (68)Ga-DOTA-TATE-containing solution was purified and RNP increased by SPE, therefore also 11 commercially available SPE columns were investigated. The amount of elutable (68)Ga activity varies when the concentration of the eluens, HCl, was varied, while (68)Ge activity remains virtually constant. SnO(2)-based (68)Ge/(68)Ga generator elutes at 0.6 M HCl >100% of the (68)Ga activity at calibration time and ±75% after 300 days. Eluate at discharge was sterile and Endotoxins were <0.5 EU/mL, RNP was always <0.01%. Metal ions in the eluate were <10 ppm (in total). Highest desorption for anion purification was obtained with the 30 mg Oasis WAX column (>80%). Highest desorption for cation purification was obtained using a solution containing 90% acetone at increasing molarity of HCl, resulted in a (68)Ga desorption of 68±8%. With all (68)Ge/(68)Ga generators and for all 3 purification methods a SA up to 50 MBq/nmol with >95% incorporation (ITLC) and RCP (radiochemical purity) by HPLC ±90% could be achieved. Purification and concentration of the eluate with anion exchange has the benefit of more elutable (68)Ga with 1 M HCl as eluens. The additional washing step of the anion column with NaCl and ethanol, resulted in a lower and less variable [H(+)] in the eluate, and, as a result the pH in the reaction vial is better controlled, more constant, and less addition of buffer is required and concordant smaller reaction volumes. Desorption of (68)Ga-DOTA-TATE of SPE columns varied, highest desorption was obtained with Baker C(18) 100 mg (84%). Purification of (68)Ga-DOTA-TATE by SPE resulted in an RNP of <10(-4)%. Eluate of SnO(2)-based (68)Ge/(68)Ga generator, either by fractionated elution as by ion exchange can be used for labelling DOTA-peptides with (68)Ga at a SA of 50 MBq/nmol at >95% incorporation and a RCP of ±90%. SPE columns are very effective to increase RNP. Copyright © 2010 Elsevier Ltd. All rights reserved.

Fluoride-selective optical sensor based on aluminum(III)-octaethylporphyrin in thin polymeric film: further characterization and practical application.

PubMed

Badr, Ibrahim H A; Meyerhoff, Mark E

2005-10-15

More detailed analytical studies of a new fluoride-selective optical sensor based on the use of aluminum(III)-octaethylporphyrin and a lipophilic pH indicator (4',5'-dibromofluorescein octadecyl ester; ETH-7075) within a thin plasticized poly(vinyl chloride) film are reported. The sensor exhibits extraordinary optical selectivity for fluoride over a wide range of other anions, including anions with far more positive free energies of hydration (e.g., perchlorate, thiocyanate, nitrate, etc.). UV-visible spectrophotometric studies of the sensing films indicate that fluoride interacts with the Al(III) center of the porphyrin structure, yielding both a change in the Soret band lambda(max) of the porphyrin and a change in the protonation state of the pH indicator within the film. The same change in spectral properties of the metalloporphyrin occurs in the absence of added pH indicator or with added tetraphenylborate derivative anionic sites, but optical responses to fluoride in these cases are shown to be irreversible. The presence of the pH indicator and the simultaneous fluoride/proton coextraction equilibrium chemistry is shown to greatly enhance the reversibility of fluoride binding to the Al(III) porphyrin. Optical response toward fluoride can be observed in the range of 0.1 microM-1.6 mM. Optical selectivity coefficients of <10(-6) for common anions (e.g., sulfate, chloride, nitrate, etc.) and <10(-4) for perchlorate and thiocyanate are obtained. Measurements of fluoride in drinking water via the new optical sensor are shown to correlate well with values obtained for the same samples using a classical LaF3-based fluoride ion-selective electrode method.

Fluoride Selective Optical Sensor Based on Aluminum(III)-Octaethylporphyrin in Thin Polymeric Film: Further Characterization and Practical Application

PubMed Central

Badr, Ibrahim H. A.; Meyerhoff, Mark E.

2008-01-01

More detailed analytical studies of a new fluoride selective optical sensor based on the use of aluminum(III)-octaethylporphyrin and a lipophilic pH indicator (4′,5′-dibromofluorescein octadecyl ester; ETH-7075) within a thin plasticized poly(vinyl chloride) film are reported. The sensor exhibits extraordinary optical selectivity for fluoride over a wide range of other anions, including anions with far more positive free energies of hydration (e.g., perchlorate, thiocyanate, nitrate, etc.). UV-VIS spectrophotometric studies of the sensing films indicate that fluoride interacts with the Al(III) center of the porphyrin structure, yielding both a change in the Soret band λmax of the porphyrin as well as a change in the protonation state of the pH indicator within the film. The same change in spectral properties of the metalloporphyrin occurs in the absence of added pH indicator or with added tetraphenylborate derivative anionic sites, but optical responses to fluoride in these cases are shown to be irreversible. The presence of the pH indicator and the simultaneous fluoride/proton coextraction equilibrium chemistry is shown to greatly enhance the reversibility of fluoride binding to the Al(III) porphyrin. Optical response toward fluoride can be observed in the range of 0.1 μM to 1.6 mM. Optical selectivity coefficients of < 10−6 for common anions (e.g., sulfate, chloride, nitrate etc.) and < 10−4 for perchlorate and thiocyanate are obtained. Measurements of fluoride in drinking water via the new optical sensor are shown to correlate well with values obtained for the same samples using a classical LaF3 based fluoride ion-selective electrode method. PMID:16223262

Terahertz-visible two-photon rotational spectroscopy of cold OD-

NASA Astrophysics Data System (ADS)

Lee, Seunghyun; Hauser, Daniel; Lakhmanskaya, Olga; Spieler, Steffen; Endres, Eric S.; Geistlinger, Katharina; Kumar, Sunil S.; Wester, Roland

2016-03-01

We present a method to measure rotational transitions of molecular anions in the terahertz domain by sequential two-photon absorption. Ion excitation by bound-bound terahertz absorption is probed by absorption in the visible on a bound-free transition. The visible frequency is tuned to a state-selective photodetachment transition of the excited anions. This provides a terahertz action spectrum for just a few hundred molecular ions. To demonstrate this we measure the two lowest rotational transitions, J =1 ←0 and J =2 ←1 of OD- anions in a cryogenic 22-pole trap. We obtain rotational transition frequencies of 598 596.08(19) MHz for J =1 ←0 and 1 196 791.57(27) MHz for J =2 ←1 of OD-, in good agreement with their only previous measurement. This two-photon scheme opens up terahertz rovibrational spectroscopy for a range of molecular anions, in particular for polyatomic and cluster anions.

Detection of anions by normal Raman spectroscopy and surface-enhanced Raman spectroscopy of cationic-coated substrates.

PubMed

Mosier-Boss, P A; Lieberman, S H

2003-09-01

The use of normal Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) of cationic-coated silver and gold substrates to detect polyatomic anions in aqueous environments is examined. For normal Raman spectroscopy, using near-infrared excitation, linear concentration responses were observed. Detection limits varied from 84 ppm for perchlorate to 2600 ppm for phosphate. In general, detection limits in the ppb to ppm concentration range for the polyatomic anions were achieved using cationic-coated SERS substrates. Adsorption of the polyatomic anions on the cationic-coated SERS substrates was described by a Frumkin isotherm. The SERS technique could not be used to detect dichromate, as this anion reacted with the coatings to form thiol esters. A competitive complexation method was used to evaluate the interaction of chloride ion with the cationic coatings. Hydrogen bonding and pi-pi interactions play significant roles in the selectivity of the cationic coatings.

Long-chain alkylimidazolium ionic liquids, a new class of cationic surfactants coated on ODS columns for anion-exchange chromatography.

PubMed

Qiu, Hongdeng; Zhang, Qinghua; Chen, Limei; Liu, Xia; Jiang, Shengxiang

2008-08-01

Separations of common inorganic anions were carried out on ODS columns coated with two long-chain alkylimidazolium ionic liquids ([C(12)MIm]Br and [C(14)MIm]Br) as new cationic surfactants for ion chromatography. With phthalate buffer solution as the mobile phases and non-suppressed conductivity detection, high column efficiencies and excellent selectivity were obtained in the separation of inorganic anions. Chromatographic parameters are calculated and the results show that the coated column possesses significant potential for the analysis of some inorganic anions such as CH(3)COO(-), IO(3)(-), Cl(-), BrO(3)(-), NO(2)(-), Br(-), NO(3)(-), SO(4)(2-), I(-), BF(4)(-), and SCN(-). The effect of eluent pH values on the separation of anions has been studied on the column coated with [C(12)MIm]Br. The stability of the coated columns was also examined.

Application of a taste evaluation system to the monitoring of Kimchi fermentation.

PubMed

Kim, Namsoo; Park, Kyung-Rim; Park, In-Seon; Cho, Yong-Jin; Bae, Young Min

2005-05-15

As an objective method, taste evaluation with an instrument is able to supplement the subjective sensory evaluation and to be applied to the optimization of food processing. Kimchi, a Korean traditional pickle fermented with lactic acid bacteria, is expanding its consumption worldwide. The fermentation control of it has been routinely done by measuring titratable acidity and pH. In this study, an eight-channel taste evaluation system was prepared, followed by an application to the monitoring of Kimchi fermentation. Eight polymer membranes which individually responded to cationic or anionic substances were prepared by mixing electroactive materials such as tri-n-octylmethylammonium chloride, bis(2-ethylhexyl)sebacate as the plasticizer and polyvinyl chloride in the ratio of 1:66:33. Each membrane prepared was separately installed onto the sensitive area of an ion-selective electrode to produce the respective taste sensor. The eight-channel sensor array and a double junction reference electrode were connected to a 16-channel high input impedance amplifier. The amplified sensor signals were stored to a personal computer via a multi-channel A/D converter. Two sensor groups composed of the cation-selective and anion-selective polymer membrane electrodes showed characteristic concentration-dependency to various artificial taste substances. As a whole, the response potentials of the sensor array increased during the fermentation period at 4, 10 and 25 degrees C. Even the response potentials of the anion-selective taste sensors slightly increased possibly due to the protonation of anions by liberated H+ ions, thereby leading to a decrease in the anion concentration. When the signal data were interpreted by principal component analysis (PCA), the first PC at 4 degrees C explained most of the total data variance. A close correlation was found between the values of titratable acidity and the first PC, which indicated a possible applicability of the multi-channel taste sensor of this study to the process monitoring of various pickle.

A new ratiometric and colorimetric chemosensor for cyanide anion based on coumarin-hemicyanine hybrid.

PubMed

Yang, Zhenghao; Liu, Zhipeng; Chen, Yuncong; Wang, Xiaoqing; He, Weijiang; Lu, Yi

2012-07-14

A hybrid coumarin-hemicyanine dye, Cou-BT, was developed as a new ratiometric and colorimetric sensor for cyanide with a sensing mechanism via nucleophilic addition of cyanide anion to the benzothiolium group. Cou-BT shows high sensitivity and selectivity for cyanide detection over other common anion species in aqueous acetonitrile solution. The calculated pseudo-first-order rate constant for cyanide anion addition was (2.13 ± 0.08) × 10(-2) s(-1) at 298 K, and the detection limit was estimated to be 0.64 μM. The DFT and TDDFT calculation results suggest that the ratiometric and colorimetric sensing behavior of Cou-BT upon its reaction with cyanide was due to the interrupted π-conjugation and blocked ICT progress.

Enhanced anion exchange for selective sulfate extraction: overcoming the Hofmeister bias.

PubMed

Fowler, Christopher J; Haverlock, Tamara J; Moyer, Bruce A; Shriver, James A; Gross, Dustin E; Marquez, Manuel; Sessler, Jonathan L; Hossain, Md Alamgir; Bowman-James, Kristin

2008-11-05

In this communication, a new approach to enhancing the efficacy of liquid-liquid anion exchange is demonstrated. It involves the concurrent use of appropriately chosen hydrogen-bond-donating (HBD) anion receptors in combination with a traditional quaternary ammonium extractant. The fluorinated calixpyrroles 1 and 2 and the tetraamide macrocycle 4 were found to be particularly effective receptors. Specifically, their use allowed the extraction of sulfate by tricaprylmethylammonium nitrate to be effected in the presence of excess nitrate. As such, the present work provides a rare demonstration of overcoming the Hofmeister bias in a competitive environment and the first to the authors' knowledge wherein this difficult-to-achieve objective is attained using a neutral HBD-based anion binding agent under conditions of solvent extraction.

Fast oxygen diffusion in bismuth oxide probed by quasielastic neutron scattering

DOE PAGES

Mamontov, Eugene

2016-09-24

In this paper, we present the first, to our knowledge, study of solid state oxygen translational diffusion by quasielastic neutron scattering. Such studies in the past might have been precluded by relatively low diffusivities of oxygen anions in the temperature range amenable to neutron scattering experiments. To explore the potential of the quasielastic scattering technique, which can deduce atomic diffusion jump length of oxygen anions through the momentum transfer dependence of the scattering signal, we have selected the fastest known oxygen conductor, bismuth oxide. Finally, we have found the oxygen anion jump length in excellent agreement with the nearest oxygen-vacancymore » distance in the anion sublattice of the fluorite-related structure of bismuth oxide.« less

Fluoride-driven 'turn on' ESPT in the binding with a novel benzimidazole-based sensor.

PubMed

Liu, Kai; Zhao, Xiaojun; Liu, Qingxiang; Huo, Jianzhong; Zhu, Bolin; Diao, Shihua

2015-01-01

A novel fluorescence sensor (BIP) bearing NH and OH subunits displayed a highly selective and sensitive recognition property for fluoride over other anions. Fluoride-driven ESPT, poorly used in anion recognition and sensing, was suggested to be responsible for the fluorescence enhancement with a blue shift of 35 nm in the emission spectrum.

Glomerular disease augments kidney accumulation of synthetic anionic polymers.

PubMed

Liu, Gary W; Prossnitz, Alexander N; Eng, Diana G; Cheng, Yilong; Subrahmanyam, Nithya; Pippin, Jeffrey W; Lamm, Robert J; Ngambenjawong, Chayanon; Ghandehari, Hamidreza; Shankland, Stuart J; Pun, Suzie H

2018-06-02

Polymeric drug carriers can alter the pharmacokinetics of their drug cargoes, thereby improving drug therapeutic index and reducing side effects. Understanding and controlling polymer properties that drive tissue-specific accumulation is critical in engineering targeted drug delivery systems. For kidney disease applications, targeted drug delivery to renal cells that reside beyond the charge- and size-selective glomerular filtration barrier could have clinical potential. However, there are limited reports on polymer properties that might enhance kidney accumulation. Here, we studied the effects of molecular weight and charge on the in vivo kidney accumulation of polymers in health and disease. We synthesized a panel of well-defined polymers by atom transfer radical polymerization to answer several questions. First, the biodistribution of low molecular weight (23-27 kDa) polymers composed of various ratios of neutral:anionic monomers (1:0, 1:1, 1:4) in normal mice was determined. Then, highly anionic (1:4 monomer ratio) low molecular and high molecular weight (47 kDa) polymers were tested in both normal and experimental focal segmental glomerulosclerosis (FSGS) mice, a model that results in loss of glomerular filtration selectivity. Through these studies, we observed that kidney-specific polymer accumulation increases with anionic monomer content, but not molecular weight; experimental FSGS increases kidney accumulation of anionic polymers; and anionic polymers accumulate predominantly in proximal tubule cells, with some distribution in kidney glomeruli. These findings can be applied to the design of polymeric drug carriers to enhance or mitigate kidney accumulation. Copyright © 2018 Elsevier Ltd. All rights reserved.

C(3i)-symmetric octanuclear cadmium cages: double-anion-templated synthesis, formation mechanism, and properties.

PubMed

Sun, Jie; Sun, Di; Yuan, Shuai; Tian, Dongxu; Zhang, Liangliang; Wang, Xingpo; Sun, Daofeng

2012-12-14

A series of C(3i)-symmetric bicapped trigonal antiprismatic Cd(8) cages [2X@Cd(8)L(6)(H(2)O)(6)]⋅n Y⋅solvents (X = Cl(-), Y = NO(3)(-), n = 2: MOCC-4; X = Br(-), Y = NO(3)(-), n = 2: MOCC-5; X = NO(3)(-), Y = NO(3)(-), n = 2: MOCC-6; X = NO(3)(-), Y = BF(4)(-), n = 2: MOCC-7; X = NO(3)(-), Y = ClO(4)(-), n = 2: MOCC-8; X = CO(3)(2-), n = 0: MOCC-9), doubly anion templated by different anions, were solvothermally synthesized by means of a flexible ligand. Interestingly, the CO(3)(2-) template for MOCC-9 was generated in situ by two-step decomposition of DMF solvent. For other MOCCs, spherical or trigonal monovalent anions could also play the role of template in their formation. The template abilities of these anions in the formation of the cages were experimentally studied and are discussed for the first time. Anion exchange of MOCC-8 was carried out and showed anion-size selectivity. All of the cage-like compounds emit strong luminescence at room temperature. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of explained v. unexplained front-of-package nutrition labels on parent and child food choices: a randomized trial.

PubMed

Graham, Dan J; Lucas-Thompson, Rachel G; Mueller, Megan P; Jaeb, Melanie; Harnack, Lisa

2017-04-01

The present study investigated whether parent/child pairs would select more healthful foods when: (i) products were labelled with front-of-package (FOP) nutrition labels relative to packages without labels; (ii) products were labelled with colour-coded Multiple Traffic Light (MTL) FOP labels relative to monochromatic Facts up Front (FuF) FOP labels; and (iii) FOP labels were explained via in-aisle signage v. unexplained. Participants were randomly assigned to one of five conditions: (i) FuF labels with in-aisle signs explaining the labels; (ii) FuF labels, no signage; (iii) MTL labels with in-aisle signage; (iv) MTL labels, no signage; (v) control group, no labels/signage. Saturated fat, sodium, sugar and energy (calorie) content were compared across conditions. The study took place in a laboratory grocery aisle. Parent/child pairs (n 153) completed the study. Results did not support the hypothesis that MTL labels would lead to more healthful choices than FuF labels. The presence of FOP labels did little to improve the healthfulness of selected foods, with few exceptions (participants with v. without access to FOP labels selected lower-calorie cereals, participants with access to both FOP labels and in-aisle explanatory signage selected products with less saturated fat v. participants without explanatory signage). Neither MTL nor FuF FOP labels led to food choices with significantly lower saturated fat, sodium or sugar. In-aisle signs explaining the FOP labels were somewhat helpful to consumers in making more healthful dietary decisions. New FOP labelling programmes could benefit from campaigns to increase consumer awareness and understanding of the labels.

Anionic Lanthanide MOFs as a Platform for Iron-Selective Sensing, Systematic Color Tuning, and Efficient Nanoparticle Catalysis.

PubMed

Wu, Ya-Pan; Xu, Guo-Wang; Dong, Wen-Wen; Zhao, Jun; Li, Dong-Sheng; Zhang, Jian; Bu, Xianhui

2017-02-06

New porous anionic Ln-MOFs, namely, [Me 2 NH 2 ][Ln(CPA) 2 (H 2 O) 2 ] (Ln = Eu, Gd), have been prepared through the self-assembly of 5-(4-carboxy phenyl)picolinic acid (H 2 CPA) and lanthanide ions. They feature open anionic frameworks with 1-D hydrophilic channels and exchangeable dimethylamine ions. The Eu phase could detect Fe 3+ ions with high selectivity and sensitivity in either aqueous solution or biological condition. The ratios of lanthanide ions on this structure platform could be rationally tuned to not only achieve dichromatic emission colors with linear correlation but also attain three primary colors (RGB) and even white light with favorable correlated color temperature. Furthermore, the Ag(I)-exchanged phases can be readily reduced to afford Ag nanoparticles. The as-prepared Ag@Ln-MOFs composite shows highly efficient catalytic performance for the reduction of 4-nitrophenol.

A novel coumarin-pyrazole-triazine based fluorescence chemosensor for fluoride detection via deprotonation process: Experimental and theoretical studies

NASA Astrophysics Data System (ADS)

Yalçın, Ergin; Alkış, Meltem; Seferoğlu, Nurgül; Seferoğlu, Zeynel

2018-03-01

A novel fluorescence coumarin-pyrazole-triazine based chemosensor (CPT) bearing 5-hydroxypyrazole as a receptoric part was synthesized and characterized by using IR, 1H/13C NMR and HRMS for the purpose of recognition of anions in DMSO. The most stable tautomeric form of CPT was determined by experimental techniques and theoretical calculations. The selectivity and sensitivity of CPT towards anions (CN-, F-, Cl-, Br-, I-, AcO-, HSO4-, H2PO4- and ClO4-) were determined using spectrophotometric and 1H NMR titration techniques as the experimental approach, and the results were explained by employing theoretical calculations. It was found to be suitable for the selective detection of F- in the presence of CN- and AcO- as competing anions. In addition, CPT exhibits significant "light-up" effect after interaction with TFA in CH2Cl2.

A highly selective fluorescent chemosensor for CN- based on a novel bis(salamo)-type tetraoxime ligand

NASA Astrophysics Data System (ADS)

Wang, Fei; Gao, Lei; Zhao, Qing; Zhang, Yang; Dong, Wen-Kui; Ding, Yu-Jie

2018-02-01

The optical properties of a novel chemosensor for cyanide anions based on a symmetric bis(salamo)-type ligand (H3L) were investigated by UV-Vis and fluorescence spectroscopy in MeOH/H2O (1:1 v/v) solution. Sensor H3L can selectively sense CN- based on prominent color changes among other anions. The chemosensor exhibits an apparent fluorescence enhancement at 482 nm to CN- which because cyanide ions interact with Cdbnd N bonds. Combining the corrected Benesi-Hildebrand formula, the binding constant of the formed host-guest complex was calculated as 2.42 × 105 M- 1. Meanwhile, the detection limit of the sensor toward CN- was 8.91 × 10- 7 M. It is worth noting that the designed sensor can be used for rapid detection of cyanide anions in basic pH range, and has great practical value.

Preparation of a Highly Fluorophilic Phosphonium Salt and its Use in a Fluorous Anion-Exchanger Membrane with High Selectivity for Perfluorinated Acids

PubMed Central

Boswell, Paul G.; Anfang, Alyce C.; Bühlmann, Philippe

2008-01-01

Fluorous solvents are the most nonpolar, nonpolarizable phases known, whereas ions are inherently polar. This makes it difficult to create salts that are soluble in a fluorous solvent. Here we present the synthesis and characterization of a new fluorophilic phosphonium salt, tris{3,5-bis[(perfluorooctyl)propyl]phenyl}methylphosphonium methyl sulfate. The salt has a solubility of at least 14 mM in perfluoro(perhydrophenanthrene), perfluoro(methylcyclohexane), and perfluorohexanes. It also shows immediate potential for use as a phase-transfer catalyst in fluorous biphasic catalysis, but in this work it is used as an anion exchanger site in the first potentiometric fluorous-membrane anion-selective electrode. The membrane sensor exhibited the exceptional selectivity of 3.9 × 1010 to 1 for perfluorooctanesulfonate over chloride, and of 2.5 × 107 to 1 for perfluorooctanoate over chloride. With improvements to the sensor’s detection limit and lifetime, it has the potential to be an attractive alternative to the expensive, time-consuming methods currently employed for measurement of perfluorinated acids. PMID:22072222

Novel colorimetric sensors for cyanide based on azo-hydrazone tautomeric skeletons.

PubMed

Adegoke, Olajire A; Adesuji, Temitope E; Thomas, Olusegun E

2014-07-15

The monoazo dyes, 4-carboxyl-2, 6-dinitrophenylazohydroxynaphthalenes dyes (AZ-01, AZ-03 and AZ-04), were evaluated as a highly selective colorimetric chemosensor for cyanide ion. The recognition of cyanide ion gave an obvious colour change from light yellow to brownish red and upon dilution with acetone produced a purple to lilac colour. Optimum conditions for the reaction between the azo dyes and cyanide ion were established at 30°C for 5 min, and different variables affecting the reaction were carefully studied and optimised. Under the optimum conditions, linear relationships between the CN(-) concentrations and light absorption were established. Using these azo-hydrazone molecular switch entities, excellent selectivity towards the detection of CN(-) in aqueous solution over miscellaneous competitive anions was observed. Such selectivity mainly results from the possibility of nucleophilic attack on the azo-hydrazone chemosensors by cyanide anions in aqueous system, which is not afforded by other competing anions. The cyanide chemosensor method described here should have potential application as a new family probes for detecting cyanide in aqueous solution. Copyright © 2014 Elsevier B.V. All rights reserved.

Combined experimental and theoretical studies on selective sensing of zinc and pyrophosphate ions by rational design of compartmental chemosensor probe: Dual sensing behaviour via secondary recognition approach and cell imaging studies.

PubMed

Mawai, Kiran; Nathani, Sandip; Roy, Partha; Singh, U P; Ghosh, Kaushik

2018-05-08

A compartmental chemosensor probe HL has been designed and synthesized for the selective recognition of zinc ions over other transition metal ions via fluorescence "ON" strategy. The chemosensing behaviour of HL was demonstrated through fluorescence, absorption and NMR spectroscopic techniques. The molecular structure of the zinc complex derived from HL was determined by X-ray crystallography. A probable mechanism of this selective sensing behavior was described on the basis of spectroscopic results and theoretical studies by density functional theory (DFT). The biological applicability of the chemosensor HL was examined via cell imaging on HeLa cells. The HL-zinc complex served as a secondary fluorescent probe responding to the pyrophosphate anion specifically over other anions. The fluorescence enhancement of HL in association with Zn2+ ions was quenched in the presence of pyrophosphate (PPi). Thus, a dual response was established based on "OFF-ON-OFF" strategy for detection of both cation and anion. This phenomenon was utilized in the construction of a "INHIBIT" logic gate.

Using Ensemble Decisions and Active Selection to Improve Low-Cost Labeling for Multi-View Data

NASA Technical Reports Server (NTRS)

Rebbapragada, Umaa; Wagstaff, Kiri L.

2011-01-01

This paper seeks to improve low-cost labeling in terms of training set reliability (the fraction of correctly labeled training items) and test set performance for multi-view learning methods. Co-training is a popular multiview learning method that combines high-confidence example selection with low-cost (self) labeling. However, co-training with certain base learning algorithms significantly reduces training set reliability, causing an associated drop in prediction accuracy. We propose the use of ensemble labeling to improve reliability in such cases. We also discuss and show promising results on combining low-cost ensemble labeling with active (low-confidence) example selection. We unify these example selection and labeling strategies under collaborative learning, a family of techniques for multi-view learning that we are developing for distributed, sensor-network environments.

College Students Must Overcome Barriers to Use Calorie Labels in Fast-Food Restaurants.

PubMed

Stran, Kimberly A; Knol, Linda L; Turner, Lori W; Severt, Kimberly; McCallum, Debra M; Lawrence, Jeannine C

2016-02-01

To explore predictors of intention of college students to use calorie labels on fast-food menus and differences in calories ordered after viewing calorie information. Quasi-experimental design. Participants selected a meal from a menu without calorie labels, selected a meal from the same menu with calorie labels, and completed a survey that assessed demographics, dietary habits, Theory of Planned Behavior constructs, and potential barriers to use of calorie labeling. A southern university. Undergraduate university students (n = 97). Predictors of intention to use calorie labels and whether calories selected from the nonlabeled menu differed from the labeled menu. Confirmatory factor analysis, exploratory factor analysis, multiple regression, and paired t tests. Participants ordered significantly fewer calories (P = .02) when selecting from the labeled menu vs the menu without labels. Attitudes (P = .006), subjective norms (P < .001), and perceived behavioral control (P = .01) predicted intention to use calorie information but did not predict a difference in the calories ordered. Hunger (P = .03) and cost (P = .04) were barriers to using the calorie information. If students can overcome barriers, calorie labeling could provide information that college students need to select lower-calorie items at fast-food restaurants. Copyright © 2016 Society for Nutrition Education and Behavior. Published by Elsevier Inc. All rights reserved.

Determination of "net carbohydrates" using high-performance anion exchange chromatography.

PubMed

Lilla, Zach; Sullivan, Darryl; Ellefson, Wayne; Welton, Kevin; Crowley, Rick

2005-01-01

For labeling purposes, the carbohydrate content of foods has traditionally been determined by difference. This value includes sugars, starches, fiber, dextrins, sugar alcohols, polydextrose, and various other organic compounds. In some cases, the current method may lack sufficient specificity, precision, and accuracy. These are subsequently quantitated by high performance anion exchange chromatography with pulsed amperometric detection and expressed as total nonfiber saccharides or percent "net carbohydrates." In this research, a new method was developed to address this need. The method consists of enzyme digestions to convert starches, dextrins, sugars, and polysaccharides to their respective monosaccharide components. These are subsequently quantified by high-performance anion exchange chromatography with pulsed amperometric detector and expressed as total nonfiber saccharides or percent "net carbohydrates." Hydrolyzed end products of various novel fibers and similar carbohydrates have been evaluated to ensure that they do not register as false positives in the new test method. The data generated using the "net carbohydrate" method were, in many cases, significantly different than the values produced using the traditional methodology. The recoveries obtained in a fortified drink matrix ranged from 94.9 to 105%. The coefficient of variation was 3.3%.

Cell-selective metabolic labeling of biomolecules with bioorthogonal functionalities.

PubMed

Xie, Ran; Hong, Senlian; Chen, Xing

2013-10-01

Metabolic labeling of biomolecules with bioorthogonal functionalities enables visualization, enrichment, and analysis of the biomolecules of interest in their physiological environments. This versatile strategy has found utility in probing various classes of biomolecules in a broad range of biological processes. On the other hand, metabolic labeling is nonselective with respect to cell type, which imposes limitations for studies performed in complex biological systems. Herein, we review the recent methodological developments aiming to endow metabolic labeling strategies with cell-type selectivity. The cell-selective metabolic labeling strategies have emerged from protein and glycan labeling. We envision that these strategies can be readily extended to labeling of other classes of biomolecules. Copyright © 2013 Elsevier Ltd. All rights reserved.

Recognition of anions using urea and thiourea substituted calixarenes: A density functional theory study of non-covalent interactions

NASA Astrophysics Data System (ADS)

Athar, Mohd; Lone, Mohsin Y.; Jha, Prakash C.

2018-02-01

Designing of new calixarene receptors for the selective binding of anions is an age-old concept; even though expected outcomes from this field are at premature stage. Herein, we have performed quantum chemical calculations to provide structural basis of anion binding with urea and thiourea substituted calixarenes (1, 2, and 3). In particular, spherical halides (F-, Cl-, Br-) and linear anions (CN-, N3-, SCN-) were modelled for calculating binding energies with receptor 1, 2 and 3 followed by their marked IR vibrations; taking the available experimental information into account. We found that the thiourea substitutions have better capability to stabilize the anions. Results have suggested that the structural behaviour of macrocyclic motifs were responsible for displaying the anion binding potentials. Moreover, second order "charge transfer" interactions of n-σ∗NH and n-σ∗OH type along the H-bond axis played critical role in developing hydrogen bonds. The present work also examines the role of non-covalent interactions (NCI) and their effects on thermodynamic and chemical-reactivity descriptors.

Gas-Phase Anionic σ-Adduct (Trans)formations in Heteroaromatic Systems1

NASA Astrophysics Data System (ADS)

Zimnicka, Magdalena; Danikiewicz, Witold

2015-07-01

Anions of nitroderivatives of thiophene and furan were subjected to the reactions with selected C-H acids in the gas phase. Various structures and reaction pathways were proposed for the observed ionic products. In general, the reactions of heteroaromatic anions with C-H acids may be divided into three groups, depending on the proton affinity difference between C-H acid's conjugate base and heteroaromatic anion (ΔPA). The proton transfer from C-H acid to heteroaromatic anion is a dominant process in the reactions for which ΔPA < 0 kcal mol-1, whereas the reactions with high ΔPA (ΔPA > 16 kcal mol-1) do not lead to any ionic products. The formation of σ-adducts and products of their further transformations according to the VNS, SNAr, cine, and tele substitution mechanisms have been proposed for reactions with moderate ΔPA. The other possible mechanisms as SN2 reaction, nucleophilic addition to the cyano group, ring-opening pathway, and halogenophilic reaction have also been discussed to contribute in the reactions between heteroaromatic anions and C-H acids.

Electron anions and the glass transition temperature.

PubMed

Johnson, Lewis E; Sushko, Peter V; Tomota, Yudai; Hosono, Hideo

2016-09-06

Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca12Al14O32](2+) ⋅ (e(-))2, we demonstrate that electron anions in this system behave as glass modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. The concentration of such electron anions is a consequential control parameter: It invokes materials evolution pathways and properties not available in conventional glasses, which opens a unique avenue in rational materials design.

Electron anions and the glass transition temperature

DOE PAGES

Johnson, Lewis E.; Sushko, Peter V.; Tomota, Yudai; ...

2016-08-24

Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca 12Al 14O 32] 2+ ∙ (e –) 2, we demonstrate that electron anions in this system behave as glass-modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. Concentration of such electron anions is a consequential control parameter: it invokes materials evolution pathways and properties not available in conventional glasses, which opens a new avenue in rational materials design.

Selective detection of pyrophosphate anion by a simple Cd(II) based terpyridine complex

NASA Astrophysics Data System (ADS)

Purohit, Aditya Kumar; Ghosh, Biswa Nath; Kar, Pravin Kumar

2018-01-01

A simple ratiometric terpyridine-Cd(ll) complex was synthesized by the treatment of CdCl2 with terpyridine ligand 4‧-(4-N,N‧-dimethylaminophenyl)-2,2‧:6‧,2″-terpyridine. The synthesized complex was found to act as a selective fluorescent chemosensor for pyrophosphate P2O74 - (PPi) over other anions like F-, Cl-, Br-, CO32 -, SO32 -, AcO-, NO2-, and H2PO4-. Furthermore, the receptor probe was also successfully employed in HeLa cell for PPi detection, which indicates this can be used as a chemosensor for cells.

Arylethynyl receptors for neutral molecules and anions: emerging applications in cellular imaging.

PubMed

Carroll, Calden N; Naleway, John J; Haley, Michael M; Johnson, Darren W

2010-10-01

This critical review will focus on the application of shape-persistent receptors for anions that derive their rigidity and optoelectronic properties from the inclusion of arylethynyl linkages. It will highlight a few of the design strategies involved in engineering selective and sensitive fluorescent probes and how arylacetylenes can offer a design pathway to some of the more desirable properties of a selective sensor. Additionally, knowledge gained in the study of these receptors in organic media often leads to improved receptor design and the production of chromogenic and fluorogenic probes capable of detecting specific substrates among the multitude of ions present in biological systems. In this ocean of potential targets exists a large number of geometrically distinct anions, which present their own problems to the design of receptors with complementary binding for each preferred coordination geometry. Our interest in targeting charged substrates, specifically how previous work on receptors for cations or neutral guests can be adapted to anions, will be addressed. Additionally, we will focus on the design and development of supramolecular arylethynyl systems, their shape-persistence and fluorogenic or chromogenic optoelectronic responses to complexation. We will also examine briefly how the "chemistry in the cuvet" translates into biological media (125 references).

Chiral recognition and selection during the self-assembly process of protein-mimic macroanions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, Panchao; Zhang, Zhi-Ming; Lv, Hongjin

The research on chiral recognition and chiral selection is not only fundamental in resolving the puzzle of homochirality, but also instructive in chiral separation and stereoselective catalysis. Here we report the chiral recognition and chiral selection during the self-assembly process of two enantiomeric wheel-shaped macroanions, [Fe28(μ3-O)8(Tart)16(HCOO)24]20- (Tart=D- or L-tartaric acid tetra-anion). The enantiomers are observed to remain self-sorted and self-assemble into their individual assemblies in their racemic mixture solution. The addition of chiral co-anions can selectively suppress the self-assembly process of the enantiomeric macroanions, which is further used to separate the two enantiomers from their mixtures on the basis ofmore » the size difference between the monomers and the assemblies. We believe that delicate long-range electrostatic interactions could be responsible for such high-level chiral recognition and selection.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mirjankar, Nikhil S.; Fraga, Carlos G.; Carman, April J.

Chemical attribution signatures (CAS) for chemical threat agents (CTAs) are being investigated to provide an evidentiary link between CTAs and specific sources to support criminal investigations and prosecutions. In a previous study, anionic impurity profiles developed using high performance ion chromatography (HPIC) were demonstrated as CAS for matching samples from eight potassium cyanide (KCN) stocks to their reported countries of origin. Herein, a larger number of solid KCN stocks (n = 13) and, for the first time, solid sodium cyanide (NaCN) stocks (n = 15) were examined to determine what additional sourcing information can be obtained through anion, carbon stablemore » isotope, and elemental analyses of cyanide stocks by HPIC, isotope ratio mass spectrometry (IRMS), and inductively coupled plasma optical emission spectroscopy (ICP-OES), respectively. The HPIC anion data was evaluated using the variable selection methods of Fisher-ratio (F-ratio), interval partial least squares (iPLS), and genetic algorithm-based partial least squares (GAPLS) and the classification methods of partial least squares discriminate analysis (PLSDA), K nearest neighbors (KNN), and support vector machines discriminate analysis (SVMDA). In summary, hierarchical cluster analysis (HCA) of anion impurity profiles from multiple cyanide stocks from six reported country of origins resulted in cyanide samples clustering into three groups: Czech Republic, Germany, and United States, independent of the associated alkali metal (K or Na). The three country groups were independently corroborated by HCA of cyanide elemental profiles and corresponded to countries with known solid cyanide factories. Both the anion and elemental CAS are believed to originate from the aqueous alkali hydroxides used in cyanide manufacture. Carbon stable isotope measurements resulted in two clusters: Germany and United States (the single Czech stock grouped with United States stocks). The carbon isotope CAS is believed to originate from the carbon source and process used to make the HCN utilized in cyanide synthesis. Classification errors for two validation studies using anion impurity profiles collected over five years on different instruments were as low as zero for KNN and SVMDA, demonstrating the excellent reliability (so far) of using anion impurities for matching a cyanide sample to its country of manufacture (i.e., factory). Variable selection reduced errors for those classification methods having errors greater than zero with iPLS-forward selection, and F-ratio typically providing the lowest errors. Finally, using anion profiles to match cyanides to a specific stock or stock group resulted in cross-validation errors ranging from zero to 5.3%.« less

Recognition-driven chemical labeling of endogenous proteins in multi-molecular crowding in live cells.

PubMed

Amaike, Kazuma; Tamura, Tomonori; Hamachi, Itaru

2017-11-14

Endogenous protein labeling is one of the most invaluable methods for studying the bona fide functions of proteins in live cells. However, multi-molecular crowding conditions, such as those that occur in live cells, hamper the highly selective chemical labeling of a protein of interest (POI). We herein describe how the efficient coupling of molecular recognition with a chemical reaction is crucial for selective protein labeling. Recognition-driven protein labeling is carried out by a synthetic labeling reagent containing a protein (recognition) ligand, a reporter tag, and a reactive moiety. The molecular recognition of a POI can be used to greatly enhance the reaction kinetics and protein selectivity, even under live cell conditions. In this review, we also briefly discuss how such selective chemical labeling of an endogenous protein can have a variety of applications at the interface of chemistry and biology.

The effects of non-ionic polymeric surfactants on the cleaning of biofouled hydrogel materials.

PubMed

Guan, Allan; Li, Zhenyu; Phillips, K Scott

2015-01-01

Block co-polymer surfactants have been used for cleaning hydrogel medical devices that contact the body (e.g., contact lenses) because of their biocompatibility. This work examined the relationship between concentration and detergency of two non-ionic polymeric surfactants (Pluronic F127 and Triton X-100) for cleaning protein soil, with anionic surfactants (sodium dodecyl sulfate and sodium laureth sulfate) as positive controls. Surface plasmon resonance was used to quantify removal of simulated tear soil from self-assembled monolayer surfaces, and a microplate format was used to study the removal of fluorescently labeled soil proteins from contact lenses. While detergency increased as a function of concentration for anionic surfactants, it decreased with concentration for the two polymeric surfactants. The fact that the protein detergency of some non-ionic polymeric surfactants did not increase with concentration above the critical micelle concentration could have implications for optimizing the tradeoff between detergency and biocompatibility.

A simple colorimetric chemosensor bearing a carboxylic acid group with high selectivity for CN-

NASA Astrophysics Data System (ADS)

Park, Gyeong Jin; Choi, Ye Won; Lee, Dongkuk; Kim, Cheal

2014-11-01

A new simple ‘naked eye' chemosensor 1 (sodium (E)-2-((2-(3-hydroxy-2-naphthoyl)hydrazono)methyl)benzoate) has been synthesized for detection of CN- in a mixture of DMF/H2O (9:1). The sensor 1 comprises of a naphthoic hydrazide as efficient hydrogen bonding donor group and a benzoic acid as the moiety with the water solubility. The receptor 1 showed high selectivity toward cyanide ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to yellow for CN- over other anions. Therefore, receptor 1 could be useful for cyanide detection in aqueous environment, displaying a high distinguishable selectivity from hydrogen bonded anions and being clearly visible to the naked eye.

Characterisation of gunshot residue from three ammunition types using suppressed anion exchange chromatography.

PubMed

Gilchrist, Elizabeth; Jongekrijg, Fleur; Harvey, Laura; Smith, Norman; Barron, Leon

2012-09-10

Gunshot residue (GSR) is commonly analysed in forensic casework using either scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) or gas chromatography-mass spectrometry (GC-MS). Relatively little work has been reported on the post-discharge GSR content of non-metallic inorganic or low molecular weight organic anions to distinguish between different ammunition types. The development of an analytical method using suppressed micro-bore anion exchange chromatography (IC) is presented for the analysis of GSR. A hydroxide gradient was optimised for the separation of 19 forensically relevant organic and inorganic anions in <23min and sensitivities of the order of 0.12-3.52ng of anion detected for all species were achieved. Along with an optimised extraction procedure, this method was applied to the analysis of post-ignition residues from three selected ammunition types. By profiling and comparing the anionic content in each ammunition residue, the possibility to distinguish between each type using their anionic profiles and absolute weight is presented. The potential for interference is also discussed with respect to sample types which are typically problematic in the analysis of GSR using SEM-EDX and GC-MS. To the best of our knowledge this represents the first study on the analysis of inorganic anions in GSR using suppressed ion chromatography. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

A preference for edgewise interactions between aromatic rings and carboxylate anions: the biological relevance of anion-quadrupole interactions.

PubMed

Jackson, Michael R; Beahm, Robert; Duvvuru, Suman; Narasimhan, Chandrasegara; Wu, Jun; Wang, Hsin-Neng; Philip, Vivek M; Hinde, Robert J; Howell, Elizabeth E

2007-07-19

Noncovalent interactions are quite important in biological structure-function relationships. To study the pairwise interaction of aromatic amino acids (phenylalanine, tyrosine, tryptophan) with anionic amino acids (aspartic and glutamic acids), small molecule mimics (benzene, phenol or indole interacting with formate) were used at the MP2 level of theory. The overall energy associated with an anion-quadrupole interaction is substantial (-9.5 kcal/mol for a benzene-formate planar dimer at van der Waals contact distance), indicating the electropositive ring edge of an aromatic group can interact with an anion. Deconvolution of the long-range coplanar interaction energy into fractional contributions from charge-quadrupole interactions, higher-order electrostatic interactions, and polarization terms was achieved. The charge-quadrupole term contributes between 30 to 45% of the total MP2 benzene-formate interaction; most of the rest of the interaction arises from polarization contributions. Additional studies of the Protein Data Bank (PDB Select) show that nearly planar aromatic-anionic amino acid pairs occur more often than expected from a random angular distribution, while axial aromatic-anionic pairs occur less often than expected; this demonstrates the biological relevance of the anion-quadrupole interaction. While water may mitigate the strength of these interactions, they may be numerous in a typical protein structure, so their cumulative effect could be substantial.

Selectivity and stoichiometry boosting of beta-cyclodextrin in cationic/anionic surfactant systems: when host-guest equilibrium meets biased aggregation equilibrium.

PubMed

Jiang, Lingxiang; Yu, Caifang; Deng, Manli; Jin, Changwen; Wang, Yilin; Yan, Yun; Huang, Jianbin

2010-02-18

Cationic surfactant/anionic surfactant/beta-CD ternary aqueous systems provide a platform for the coexistence of the host-guest (beta-CD/surfactant) equilibrium and the biased aggregation (monomeric/aggregated surfactants) equilibrium. We report here that the interplay between the two equilibria dominates the systems as follows. (1) The biased aggregation equilibrium imposes an apparent selectivity on the host-guest equilibrium, namely, beta-CD has to always selectively bind the major surfactant (molar fraction > 0.5) even if binding constants of beta-CD to the pair of surfactants are quite similar. (2) In return, the host-guest equilibrium amplifies the bias of the aggregation equilibrium, that is, the selective binding partly removes the major surfactant from the aggregates and leaves the aggregate composition approaching the electroneutral mixing stoichiometry. (3) This composition variation enhances electrostatic attractions between oppositely charged surfactant head groups, thus resulting in less-curved aggregates. In particular, the present apparent host-guest selectivity is of remarkably high values, and the selectivity stems from the bias of the aggregation equilibrium rather than the difference in binding constants. Moreover, beta-CD is defined as a "stoichiometry booster" for the whole class of cationic/anionic surfactant systems, which provides an additional degree of freedom to directly adjust aggregate compositions of the systems. The stoichiometry boosting of the compositions can in turn affect or even determine microstructures and macroproperties of the systems.

78 FR 53773 - Select Updates for Non-Clinical Engineering Tests and Recommended Labeling for Intravascular...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-30

...] Select Updates for Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and... Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems.'' FDA has developed this guidance to inform the coronary and peripheral stent industry about selected updates to FDA's...

Label Design Affects Medication Safety in an Operating Room Crisis: A Controlled Simulation Study.

PubMed

Estock, Jamie L; Murray, Andrew W; Mizah, Margaret T; Mangione, Michael P; Goode, Joseph S; Eibling, David E

2018-06-01

Several factors contribute to medication errors in clinical practice settings, including the design of medication labels. The objective of this study was to quantify the impact of label design on medication safety in a realistic, high-stress clinical situation. Ninety-six anesthesia trainee participants were randomly assigned to either the redesigned or the current label condition. Participants were blinded to the study's focus on medication label design and their assigned label condition. Each participant was the sole anesthesia provider in a simulated operating room scenario involving an unexpected vascular injury. The surgeon asked the participant to administer hetastarch to the simulated patient because of hemodynamic instability. The fluid drawer of the anesthesia cart contained three 500-ml intravenous bags of hetastarch and one 500-ml intravenous bag of lidocaine. We hypothesized that redesigned labels would help participants correctly select hetastarch from the cart. If the participants incorrectly selected lidocaine from the cart, we hypothesized that the redesigned labels would help participants detect the lidocaine before administration. The percentage of participants who correctly selected hetastarch from the cart was significantly higher for the redesigned labels than the current labels (63% versus 40%; odds ratio, 2.61 [95% confidence interval, 1.1-6.1]; P = 0.03). Of the participants who incorrectly selected lidocaine from the cart, the percentage who detected the lidocaine before administration did not differ by label condition. The redesigned labels helped participants correctly select hetastarch from the cart, thus preventing some potentially catastrophic medication errors from reaching the simulated patient.

Transesterification of propylene glycol methyl ether in chromatographic reactors using anion exchange resin as a catalyst.

PubMed

Oh, Jungmin; Sreedhar, Balamurali; Donaldson, Megan E; Frank, Timothy C; Schultz, Alfred K; Bommarius, Andreas S; Kawajiri, Yoshiaki

2016-09-30

Reactive chromatography using an anion exchange resin is proposed for a transesterification reaction of propylene glycol methyl ether (DOWANOL™ PM) with ethyl acetate to produce propylene glycol methyl ether acetate (DOWANOL™ PMA). This reaction is studied in batch and chromatographic reactors catalyzed by an anion exchange resin. Several anion exchange resins are tested and compared based on the performance of resin as an adsorbent and a catalyst. A chromatographic column is packed with a selected catalyst, AMBERLITE™ IRA904, and both reaction and chromatographic elution are studied at different temperatures and feed concentrations. The resulting chromatograms are fitted to a mathematical model to obtain adsorption equilibrium and reaction kinetic parameters by the inverse method. Compared to esterification investigated in a previous study, transesterification has advantages such as a higher conversion at lower temperature and easy removal of the byproduct which may lead to higher productivity. Deactivation of anion exchange resins is observed and potential solutions are suggested. Copyright © 2016 Elsevier B.V. All rights reserved.

Self-organizing layers from complex molecular anions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warneke, Jonas; McBriarty, Martin E.; Riechers, Shawn L.

Ions are promising building blocks for tunable self-organizing materials with advanced technological applications. However, because of strong Coulomb attraction with counterions, the intrinsic properties of ions are difficult to exploit for preparation of bulk materials. Here, we report the precisely-controlled preparation of macroscopic surface layers by soft landing of mass selected complex anions which determine the self organization of the layers with their molecular properties. The family of halogenated dodecaborates [B12X12]2- (X = F, Cl, Br, I), in which the internal charge distribution between core and shell regions of the molecular ions systematically vary, was deposited on different self assembledmore » monolayer surfaces (SAMs) on gold at high coverage. Layers of anions were found to be stabilized by accumulation of neutral molecules. Different phases, self-organization mechanisms and optical properties were observed to depend upon the internal charge distribution of the deposited anions, the underlying surface and the coadsorbed molecules. This demonstrates rational control of the properties of anion based layers.« less

Gallium based low-interaction anions

DOEpatents

King, Wayne A.; Kubas, Gregory J.

2000-01-01

The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

Ion-Gated Gas Separation through Porous Graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Ziqi; Mahurin, Shannon M.; Dai, Sheng

Porous graphene holds great promise as an atom-thin, high-permeance membrane for gas separation, but to precisely control the pore size at three to five angstroms proves challenging. Here we propose an ion-gated graphene membrane comprising a monolayer of ionic liquid coated porous graphene to dynamically modulate the pore size to achieve selective gas separation. This approach enables the otherwise non-selective large pores on the order of 1 nm in size to be selective for gases whose diameters range from three to four angstroms. We show from molecular dynamics simulations that CO 2, N 2 and CH 4 all can permeatemore » through a 1-nm pore in graphene without any selectivity. But when a monolayer of [emim][BF 4] is deposited on the porous graphene, CO 2 has much higher permeance than the other two gases. We find that the anion dynamically modulates the pore size by hovering above the pore and provides affinity for CO 2 while the larger cation (which cannot go through the pore) holds the anion in place via electrostatic attraction. This composite membrane is especially promising for CO 2/CH 4 separation, with a CO 2/CH 4 selectivity of about 42 and CO 2 permeance ~105 GPU (gas permeation unit). We further demonstrate that selectivity and permeance can be tuned by the anion size. The present work points toward a promising direction of using the atom-thin ionic-liquid/porous-graphene hybrid membrane for high-permeance, selective gas separation that allows a greater flexibility in substrate pore size control.« less

Ion-Gated Gas Separation through Porous Graphene

DOE PAGES

Tian, Ziqi; Mahurin, Shannon M.; Dai, Sheng; ...

2017-02-10

Porous graphene holds great promise as an atom-thin, high-permeance membrane for gas separation, but to precisely control the pore size at three to five angstroms proves challenging. Here we propose an ion-gated graphene membrane comprising a monolayer of ionic liquid coated porous graphene to dynamically modulate the pore size to achieve selective gas separation. This approach enables the otherwise non-selective large pores on the order of 1 nm in size to be selective for gases whose diameters range from three to four angstroms. We show from molecular dynamics simulations that CO 2, N 2 and CH 4 all can permeatemore » through a 1-nm pore in graphene without any selectivity. But when a monolayer of [emim][BF 4] is deposited on the porous graphene, CO 2 has much higher permeance than the other two gases. We find that the anion dynamically modulates the pore size by hovering above the pore and provides affinity for CO 2 while the larger cation (which cannot go through the pore) holds the anion in place via electrostatic attraction. This composite membrane is especially promising for CO 2/CH 4 separation, with a CO 2/CH 4 selectivity of about 42 and CO 2 permeance ~105 GPU (gas permeation unit). We further demonstrate that selectivity and permeance can be tuned by the anion size. The present work points toward a promising direction of using the atom-thin ionic-liquid/porous-graphene hybrid membrane for high-permeance, selective gas separation that allows a greater flexibility in substrate pore size control.« less

Biasing hydrogen bond donating host systems towards chemical warfare agent recognition.

PubMed

Hiscock, Jennifer R; Wells, Neil J; Ede, Jayne A; Gale, Philip A; Sambrook, Mark R

2016-10-12

A series of neutral ditopic and negatively charged, monotopic host molecules have been evaluated for their ability to bind chloride and dihydrogen phosphate anions, and neutral organophosphorus species dimethyl methylphosphonate (DMMP), pinacolyl methylphosphonate (PMP) and the chemical warfare agent (CWA) pinacolyl methylphosphonofluoridate (GD, soman) in organic solvent via hydrogen bonding. Urea, thiourea and boronic acid groups are shown to bind anions and neutral guests through the formation of hydrogen bonds, with the urea and thiourea groups typically exhibiting higher affinity interactions. The introduction of a negative charge on the host structure is shown to decrease anion affinity, whilst still allowing for high stability host-GD complex formation. Importantly, the affinity of the host for the neutral CWA GD is greater than for anionic guests, thus demonstrating the potential for selectivity reversal based on charge repulsion.

Apparatus for purifying arsine, phosphine, ammonia, and inert gases to remove Lewis acid and oxidant impurities therefrom

DOEpatents

Tom, Glenn M.; Brown, Duncan W.

1991-01-08

An apparatus for purifying a gaseous mixture comprising arsine, phosphine, ammonia, and/or inert gases, to remove Lewis acid and/or oxidant impurities therefrom, comprising a vessel containing a bed of a scavenger, the scavenger including a support having associated therewith an anion which is effective to remove such impurities, such anion being selected from one or more members of the group consisting of: (i) carbanions whose corresponding protonated compounds have a pK.sub.a value of from about 22 to about 36; and (ii) anions formed by reaction of such carbanions with the primary component of the mixture.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dekan, G.; Farquhar, M.G.; Gabel, C.

Podocalyxin is the major sialoprotein of the rat glomerulus. Its function is to maintain the filtration slits of the glomerular epithelium open by virtue of its high net negative charge. The authors have used biosynthetic labeling and oligosaccharide analysis to characterize the anionic-charge-carrying moieties on this protein. Kidney slices from 2-day-old rats were biosynthetically labeled with ({sup 35}S)Cys, ({sup 3}H)Man, ({sup 3}H)GlcN, and {sup 35}SO{sub 4}, after which podocalyxin was immunoprecipitated and purified by SDS/PAGE. All these labels were incorporated into podocalyxin. Immunoprecipitates were subjected to digestion with specific glycosidases or digested with Pronase followed by chromatographic analysis of themore » released glycopeptides. Analysis of the {sup 35}SO{sub 4}-labeled glycopeptides indicated that both the N- and O-linked structures were sulfated. They conclude that in newborn rat kidney (i) podocalyxin contains both O- and N-linked oligosaccharides (ii) podocalyxin is sulfated, and (iii) sulfate is located on both O-linked oligosaccharides and on glycopeptides carrying tri- or tetrantennary N-linked structures. These results indicate that the net negative charge of podocalyxin is most likely derived from sulfate as well as from sialic acid residues.« less

Electron Spin Resonance Studies of Carbonic Anhydrase: Transition Metal Ions and Spin-Labeled Sulfonamides*

PubMed Central

Taylor, June S.; Mushak, Paul; Coleman, Joseph E.

1970-01-01

Electron spin resonance (esr) spectra of Cu(II) and Co(II) carbonic anhydrase, and a spin-labeled sulfonamide complex of the Zn(II) enzyme, are reported. The coordination geometry of Cu(II) bound in the enzyme appears to have approximately axial symmetry. Esr spectra of enzyme complexes with metal-binding anions also show axial symmetry and greater covalency, in the order ethoxzolamide < SH- < N3- ≤ CN-. Well-resolved superhyperfine structure in the spectrum of the cyanide complex suggests the presence of two, and probably three, equivalent nitrogen ligands from the protein. Esr spectra of the Co(II) enzyme and its complexes show two types of Co(II) environment, one typical of the native enzyme and the 1:1 CN- complex, and one typical of a 2:1 CN- complex. Co(II) in the 2:1 complex appears to be low-spin and probably has a coordination number of 5. Binding of a spin-labeled sulfonamide to the active center immobilizes the free radical. The similarity of the esr spectra of spin-labeled Zn(II) and Co(II) carbonic anhydrases suggests that the conformation at the active center is similar in the two metal derivatives. PMID:4320976

Probes for anionic cell surface detection

DOEpatents

Smith, Bradley D.

2013-03-05

Embodiments of the present invention are generally directed to compositions comprising a class of molecular probes for detecting the presence of anionic cell surfaces. Embodiments include compositions that are enriched for these compositions and preparations, particularly preparations suitable for use as laboratory/clinical reagents and diagnostic indicators, either alone or as part of a kit. An embodiment of the invention provides for a highly selective agent useful in the discernment and identification of dead or dying cells, such as apoptotic cells, in a relatively calcium-free environment. An embodiment of the invention provides a selective agent for the identification of bacteria in a mixed population of bacterial cells and nonbacterial cells.

Determination of Multiple φ-Torsion Angles in Proteins by Selective and Extensive 13C Labeling and Two-Dimensional Solid-State NMR

NASA Astrophysics Data System (ADS)

Hong, Mei

1999-08-01

We describe an approach to efficiently determine the backbone conformation of solid proteins that utilizes selective and extensive 13C labeling in conjunction with two-dimensional magic-angle-spinning NMR. The selective 13C labeling approach aims to reduce line broadening and other multispin complications encountered in solid-state NMR of uniformly labeled proteins while still enhancing the sensitivity of NMR spectra. It is achieved by using specifically labeled glucose or glycerol as the sole carbon source in the protein expression medium. For amino acids synthesized in the linear part of the biosynthetic pathways, [1-13C]glucose preferentially labels the ends of the side chains, while [2-13C]glycerol labels the Cα of these residues. Amino acids produced from the citric-acid cycle are labeled in a more complex manner. Information on the secondary structure of such a labeled protein was obtained by measuring multiple backbone torsion angles φ simultaneously, using an isotropic-anisotropic 2D correlation technique, the HNCH experiment. Initial experiments for resonance assignment of a selectively 13C labeled protein were performed using 15N-13C 2D correlation spectroscopy. From the time dependence of the 15N-13C dipolar coherence transfer, both intraresidue and interresidue connectivities can be observed, thus yielding partial sequential assignment. We demonstrate the selective 13C labeling and these 2D NMR experiments on a 8.5-kDa model protein, ubiquitin. This isotope-edited NMR approach is expected to facilitate the structure determination of proteins in the solid state.

Highly selective and sensitive nanoprobes for cyanide based on gold nanoclusters with red fluorescence emission

NASA Astrophysics Data System (ADS)

Zhang, Guomei; Qiao, Yunyun; Xu, Ting; Zhang, Caihong; Zhang, Yan; Shi, Lihong; Shuang, Shaomin; Dong, Chuan

2015-07-01

We report a novel and environmentally friendly fluorescent probe for detecting the cyanide ion (CN-) using l-amino acid oxidase (LAAOx)-protected Au nanoclusters (LAAOx@AuNCs) with red emission. The fluorescence-based sensing behaviour of LAAOx@AuNCs towards anions was investigated in buffered aqueous media. Among the anions studied, CN- was found to effectively quench the fluorescence emission of AuNCs based on CN- induced Au core decomposition. Excellent sensitivity and selectivity toward the detection of CN- in aqueous solution were observed. The CN- detection limit was determined to be approximately 180 nM, which is 15 times lower than the maximum level (2700 nM) of CN- in drinking water permitted by the World Health Organization (WHO). A linear relationship between the fluorescence intensity and CN- concentration was observed in two ranges of CN- concentration, including 3.2 × 10-6 to 3.4 × 10-5 mol L-1 and 3.81 × 10-5 to 1.04 × 10-4 mol L-1. The high sensitivity and selectivity to CN- among the 17 types of anions make the AuNCs good candidates for use in fluorescent nanoprobes of CN-.

Extracellular determinants of anion discrimination of the Cl-/H+ antiporter protein CLC-5.

PubMed

De Stefano, Silvia; Pusch, Michael; Zifarelli, Giovanni

2011-12-23

Mammalian CLC proteins comprise both Cl- channels and Cl-/H+ antiporters that carry out fundamental physiological tasks by transporting Cl- across plasma membrane and intracellular compartments. The NO3- over Cl- preference of a plant CLC transporter has been pinpointed to a conserved serine residue located at Scen and it is generally assumed that the other two binding sites of CLCs, Sext and Sin, do not substantially contribute to anion selectivity. Here we show for the Cl-/H+ antiporter CLC-5 that the conserved and extracellularly exposed Lys210 residue is critical to determine the anion specificity for transport activity. In particular, mutations that neutralize or invert the charge at this position reverse the NO3- over Cl- preference of WT CLC-5 at a concentration of 100 mm, but do not modify the coupling stoichiometry with H+. The importance of the electrical charge is shown by chemical modification of K210C with positively charged cysteine-reactive compounds that reintroduce the WT preference for Cl-. At saturating extracellular anion concentrations, neutralization of Lys210 is of little impact on the anion preference, suggesting an important role of Lys210 on the association rate of extracellular anions to Sext.

Vanadium Uptake by Plants

PubMed Central

Welch, Ross M.

1973-01-01

The kinetics of vanadium absorption by excised barley (Hordeum vulgare L., cv. Eire) roots were investigated with respect to ionic species of V in solution, time and concentration dependence, Ca sensitivity, and interaction with various anions, cations, and pH levels. The role of metabolism in V absorption was also studied using anaerobic treatment (N2 gas) and chemical inhibitors (NaN3, KCN, or 2,4-dinitrophenol). Approximately one-third of the labeled V initially taken up by excised roots was desorbed to a constant level after 45 min in unlabeled V solutions. The rate of absorption of labeled V from 5 μm NH4VO3 solutions containing 0.5 mm CaSO4 was constant for at least 3 hours. Omission of Ca resulted in a 72% reduction in V uptake when compared to controls with 0.5 mm CaSO4. The rate of uptake of V was highest at pH 4 but dropped to a very low level at pH 10. It was relatively constant between the pH levels of 5 and 8 at which the VO3− ion is the predominant ionic species in solution. The rate of absorption of V was followed as a function of concentrations from 0.5 to 100 μm NH4VO3. It was found to be a linear function of concentration and did not follow saturation kinetics. Absorption experiments carried out with labeled V from either NaVO3 or NH4VO3 sources gave similar results. No anion studied (i.e. HPO42−, HAsO42−, MoO42−, SeO42−, SeO32−, CrO42−, BO33−, No3−, and Cl−) interfered appreciably (i.e. less than 30% inhibition) with the absorption of labeled V. Anaerobic treatment of absorption solution with N2 gas did not inhibit V absorption by excised roots. The results obtained using chemical inhibitors were not consistent. It was concluded that V is not actively absorbed by excised barley roots. PMID:16658421

Production of sodium-22 from proton irradiated aluminum

DOEpatents

Taylor, Wayne A.; Heaton, Richard C.; Jamriska, David J.

1996-01-01

A process for selective separation of sodium-22 from a proton irradiated minum target including dissolving a proton irradiated aluminum target in hydrochloric acid to form a first solution including aluminum ions and sodium ions, separating a portion of the aluminum ions from the first solution by crystallization of an aluminum salt, contacting the remaining first solution with an anion exchange resin whereby ions selected from the group consisting of iron and copper are selectively absorbed by the anion exchange resin while aluminum ions and sodium ions remain in solution, contacting the solution with an cation exchange resin whereby aluminum ions and sodium ions are adsorbed by the cation exchange resin, and, contacting the cation exchange resin with an acid solution capable of selectively separating the adsorbed sodium ions from the cation exchange resin while aluminum ions remain adsorbed on the cation exchange resin is disclosed.

A new method based on the Butler-Volmer formalism to evaluate voltammetric cation and anion sensors.

PubMed

Cano, Manuel; Rodríguez-Amaro, Rafael; Fernández Romero, Antonio J

2008-12-11

A new method based on the Butler-Volmer formalism is applied to assess the capability of two voltammetric ion sensors based on polypyrrole films: PPy/DBS and PPy/ClO4 modified electrodes were studied as voltammetric cation and anion sensors, respectively. The reversible potential versus electrolyte concentrations semilogarithm plots provided positive calibration slopes for PPy/DBS and negative ones for PPy/ClO4, as was expected from the proposed method and that based on the Nernst equation. The slope expressions deduced from Butler-Volmer include the electron-transfer coefficient, which allows slope values different from the ideal Nernstian value to be explained. Both polymeric films exhibited a degree of ion-selectivity when they were immersed in mixed-analyte solutions. Selectivity coefficients for the two proposed voltammetric cation and anion sensors were obtained by several experimental methods, including the separated solution method (SSM) and matched potential method (MPM). The K values acquired by the different methods were very close for both polymeric sensors.

Fluoride resistance and transport by riboswitch-controlled CLC antiporters

PubMed Central

Stockbridge, Randy B.; Lim, Hyun-Ho; Otten, Renee; Williams, Carole; Shane, Tania; Weinberg, Zasha; Miller, Christopher

2012-01-01

A subclass of bacterial CLC anion-transporting proteins, phylogenetically distant from long-studied CLCs, was recently shown to be specifically up-regulated by F-. We establish here that a set of randomly selected representatives from this “CLCF” clade protect Escherichia coli from F- toxicity, and that the purified proteins catalyze transport of F- in liposomes. Sequence alignments and membrane transport experiments using 19F NMR, osmotic response assays, and planar lipid bilayer recordings reveal four mechanistic traits that set CLCF proteins apart from all other known CLCs. First, CLCFs lack conserved residues that form the anion binding site in canonical CLCs. Second, CLCFs exhibit high anion selectivity for F- over Cl-. Third, at a residue thought to distinguish CLC channels and transporters, CLCFs bear a channel-like valine rather than a transporter-like glutamate, and yet are F-/H+ antiporters. Finally, F-/H+ exchange occurs with 1∶1 stoichiometry, in contrast to the usual value of 2∶1. PMID:22949689

Fluoride resistance and transport by riboswitch-controlled CLC antiporters.

PubMed

Stockbridge, Randy B; Lim, Hyun-Ho; Otten, Renee; Williams, Carole; Shane, Tania; Weinberg, Zasha; Miller, Christopher

2012-09-18

A subclass of bacterial CLC anion-transporting proteins, phylogenetically distant from long-studied CLCs, was recently shown to be specifically up-regulated by F(-). We establish here that a set of randomly selected representatives from this "CLC(F)" clade protect Escherichia coli from F(-) toxicity, and that the purified proteins catalyze transport of F(-) in liposomes. Sequence alignments and membrane transport experiments using (19)F NMR, osmotic response assays, and planar lipid bilayer recordings reveal four mechanistic traits that set CLC(F) proteins apart from all other known CLCs. First, CLC(F)s lack conserved residues that form the anion binding site in canonical CLCs. Second, CLC(F)s exhibit high anion selectivity for F(-) over Cl(-). Third, at a residue thought to distinguish CLC channels and transporters, CLC(F)s bear a channel-like valine rather than a transporter-like glutamate, and yet are F(-)/H(+) antiporters. Finally, F(-)/H(+) exchange occurs with 1:1 stoichiometry, in contrast to the usual value of 2:1.

A quinoline-based Cu2 + ion complex fluorescence probe for selective detection of inorganic phosphate anion in aqueous solution and its application to living cells

NASA Astrophysics Data System (ADS)

Dai, Yanpeng; Wang, Peng; Fu, Jiaxin; Yao, Kun; Xu, Kuoxi; Pang, Xiaobin

2017-08-01

A quinaldine functionalized probe QP has been designed and synthesized. It exhibited selective turn-off fluorescence response toward Cu2 + ion over most of the biologically important ions at physiological pH. The binding ratio of the probe QP and Cu2 + ion was determined to be 1:1 through fluorescence titration, Job's plot and ESI-MS. The binding constant (K) of Cu2 + to probe QP was found to be 2.12 × 104 M- 1. Further, the Cu2 + ensemble of probe QP was found to respond H2PO4- and HPO42 - among other important biological anions via fluorescence turn-on response at physiological pH. Fluorescence microscopy imaging using living Hela cells showed that probe QP could be used as an effective fluorescent probe for detecting Cu2 + cation and H2PO4- and HPO42 - anions in living cells.

A quinoline-based Cu2+ ion complex fluorescence probe for selective detection of inorganic phosphate anion in aqueous solution and its application to living cells.

PubMed

Dai, Yanpeng; Wang, Peng; Fu, Jiaxin; Yao, Kun; Xu, Kuoxi; Pang, Xiaobin

2017-08-05

A quinaldine functionalized probe QP has been designed and synthesized. It exhibited selective turn-off fluorescence response toward Cu 2+ ion over most of the biologically important ions at physiological pH. The binding ratio of the probe QP and Cu 2+ ion was determined to be 1:1 through fluorescence titration, Job's plot and ESI-MS. The binding constant (K) of Cu 2+ to probe QP was found to be 2.12×10 4 M -1 . Further, the Cu 2+ ensemble of probe QP was found to respond H 2 PO 4 - and HPO 4 2- among other important biological anions via fluorescence turn-on response at physiological pH. Fluorescence microscopy imaging using living Hela cells showed that probe QP could be used as an effective fluorescent probe for detecting Cu 2+ cation and H 2 PO 4 - and HPO 4 2- anions in living cells. Copyright © 2017 Elsevier B.V. All rights reserved.

A micrometer-sized europium(iii)-organic framework for selective sensing of the Cr2O72- anion and picric acid in water systems.

PubMed

He, Hongming; Chen, Si-Hang; Zhang, De-Yu; Hao, Rui; Zhang, Chao; Yang, En-Cui; Zhao, Xiao-Jun

2017-10-10

A micrometer-sized europium(iii)-organic framework with asymmetric binuclear metal subunits extended by 4,5-dichlorophthalaten (DCPA), [Eu 2 (H 2 O)(DCPA) 3 ] n , was easily obtained using a reverse microemulsion method. The framework exhibits good dispersibility, excellent thermal and environmental stability and easy regeneration ability. More importantly, the complex displays strong red emission and can selectively and sensitively detect both inorganic Cr 2 O 7 2- anions (K sv = 8.7 × 10 3 M -1 ) and organic picric acid contaminants (K sv = 1.07 × 10 4 M -1 ) in water systems through fluorescence quenching. A luminescent film of 1 was further prepared and successfully used to detect the Cr 2 O 7 2- anion in an aqueous system. These interesting results indicate that the well-dispersed europium(iii)-organic framework can serve as a promising dual-responsive luminescent sensor for environmental pollutant monitoring.

Active Learning by Querying Informative and Representative Examples.

PubMed

Huang, Sheng-Jun; Jin, Rong; Zhou, Zhi-Hua

2014-10-01

Active learning reduces the labeling cost by iteratively selecting the most valuable data to query their labels. It has attracted a lot of interests given the abundance of unlabeled data and the high cost of labeling. Most active learning approaches select either informative or representative unlabeled instances to query their labels, which could significantly limit their performance. Although several active learning algorithms were proposed to combine the two query selection criteria, they are usually ad hoc in finding unlabeled instances that are both informative and representative. We address this limitation by developing a principled approach, termed QUIRE, based on the min-max view of active learning. The proposed approach provides a systematic way for measuring and combining the informativeness and representativeness of an unlabeled instance. Further, by incorporating the correlation among labels, we extend the QUIRE approach to multi-label learning by actively querying instance-label pairs. Extensive experimental results show that the proposed QUIRE approach outperforms several state-of-the-art active learning approaches in both single-label and multi-label learning.

Factors associated with nutrition label use among female college students applying the theory of planned behavior.

PubMed

Lim, Hyun Jeong; Kim, Min Ju; Kim, Kyung Won

2015-02-01

Use of nutrition labels in food selection is recommended for consumers. The aim of this study is to examine factors, mainly beliefs explaining nutrition label use in female college students based on the Theory of Planned Behavior (TPB). The subjects were female college students from a university in Seoul, Korea. The survey questionnaire was composed of items examining general characteristics, nutrition label use, behavioral beliefs, normative beliefs, corresponding motivation to comply, and control beliefs. The subjects (n = 300) responded to the questionnaire by self-report, and data from 275 students were analyzed using t-test or χ(2)-test. The results showed that 37.8% of subjects were nutrition label users. Three out of 15 behavioral beliefs differed significantly by nutrition label use. Nutrition label users agreed more strongly on the benefits of using nutrition labels including 'comparing and selecting better foods' (P < 0.001), 'selecting healthy foods' (P < 0.05). The negative belief of 'annoying' was stronger in non-users than in users (P < 0.001). Three out of 7 sources (parents, siblings, best friend) were important in nutrition label use. Twelve out of 15 control beliefs differed significantly by nutrition label use. These included beliefs regarding constraints of using nutrition labels (e.g., time, spending money for healthy foods) and lack of nutrition knowledge (P < 0.001). Perceived confidence in understanding and applying the specifics of nutrition labels in food selection was also significantly related to nutrition label use (P < 0.001). This study found that the beliefs, especially control beliefs, suggested in the TPB were important in explaining nutrition label use. To promote nutrition label use, nutrition education might focus on increasing perceived control over constraints of using nutrition labels, acquiring skills for checking nutrition labels, as well as the benefits of using nutrition labels and receiving support from significant others for nutrition label use.

Factors associated with nutrition label use among female college students applying the theory of planned behavior

PubMed Central

Lim, Hyun Jeong; Kim, Min Ju

2015-01-01

BACKGROUND/OBJECTIVES Use of nutrition labels in food selection is recommended for consumers. The aim of this study is to examine factors, mainly beliefs explaining nutrition label use in female college students based on the Theory of Planned Behavior (TPB). SUBJECTS/METHODS The subjects were female college students from a university in Seoul, Korea. The survey questionnaire was composed of items examining general characteristics, nutrition label use, behavioral beliefs, normative beliefs, corresponding motivation to comply, and control beliefs. The subjects (n = 300) responded to the questionnaire by self-report, and data from 275 students were analyzed using t-test or χ2-test. RESULTS The results showed that 37.8% of subjects were nutrition label users. Three out of 15 behavioral beliefs differed significantly by nutrition label use. Nutrition label users agreed more strongly on the benefits of using nutrition labels including 'comparing and selecting better foods' (P < 0.001), 'selecting healthy foods' (P < 0.05). The negative belief of 'annoying' was stronger in non-users than in users (P < 0.001). Three out of 7 sources (parents, siblings, best friend) were important in nutrition label use. Twelve out of 15 control beliefs differed significantly by nutrition label use. These included beliefs regarding constraints of using nutrition labels (e.g., time, spending money for healthy foods) and lack of nutrition knowledge (P < 0.001). Perceived confidence in understanding and applying the specifics of nutrition labels in food selection was also significantly related to nutrition label use (P < 0.001). CONCLUSIONS This study found that the beliefs, especially control beliefs, suggested in the TPB were important in explaining nutrition label use. To promote nutrition label use, nutrition education might focus on increasing perceived control over constraints of using nutrition labels, acquiring skills for checking nutrition labels, as well as the benefits of using nutrition labels and receiving support from significant others for nutrition label use. PMID:25671070

Interactions between selected bile salts and Triton X-100 or sodium lauryl ether sulfate.

PubMed

Cirin, Dejan M; Poša, Mihalj M; Krstonošić, Veljko S

2011-12-29

In order to develop colloidal drug carriers with desired properties, it is important to determine physico-chemical characteristics of these systems. Bile salt mixed micelles are extensively studied as novel drug delivery systems. The objective of the present investigation is to develop and characterize mixed micelles of nonionic (Triton X-100) or anionic (sodium lauryl ether sulfate) surfactant having oxyethylene groups in the polar head and following bile salts: cholate, deoxycholate and 7-oxodeoxycholate. The micellization behaviour of binary anionic-nonionic and anionic-anionic surfactant mixtures was investigated by conductivity and surface tension measurements. The results of the study have been analyzed using Clint's, Rubingh's, and Motomura's theories for mixed binary systems. The negative values of the interaction parameter indicate synergism between micelle building units. It was noticed that Triton X-100 and sodium lauryl ether sulfate generate the weakest synergistic interactions with sodium deoxycholate, while 7-oxodeoxycholate creates the strongest attractive interaction with investigated co-surfactants. It was concluded that increased synergistic interactions can be attributed to the larger number of hydrophilic groups at α side of the bile salts. Additionally, 7-oxo group of 7-oxodeoxycholate enhance attractive interactions with selected co-surfactants more than 7-hydroxyl group of sodium cholate.

Interactions between selected bile salts and Triton X-100 or sodium lauryl ether sulfate

PubMed Central

2011-01-01

Background In order to develop colloidal drug carriers with desired properties, it is important to determine physico-chemical characteristics of these systems. Bile salt mixed micelles are extensively studied as novel drug delivery systems. The objective of the present investigation is to develop and characterize mixed micelles of nonionic (Triton X-100) or anionic (sodium lauryl ether sulfate) surfactant having oxyethylene groups in the polar head and following bile salts: cholate, deoxycholate and 7-oxodeoxycholate. Results The micellization behaviour of binary anionic-nonionic and anionic-anionic surfactant mixtures was investigated by conductivity and surface tension measurements. The results of the study have been analyzed using Clint's, Rubingh's, and Motomura's theories for mixed binary systems. The negative values of the interaction parameter indicate synergism between micelle building units. It was noticed that Triton X-100 and sodium lauryl ether sulfate generate the weakest synergistic interactions with sodium deoxycholate, while 7-oxodeoxycholate creates the strongest attractive interaction with investigated co-surfactants. Conclusion It was concluded that increased synergistic interactions can be attributed to the larger number of hydrophilic groups at α side of the bile salts. Additionally, 7-oxo group of 7-oxodeoxycholate enhance attractive interactions with selected co-surfactants more than 7-hydroxyl group of sodium cholate. PMID:22206681

Engineering the electrochemical capacitive properties of graphene sheets in ionic-liquid electrolytes by correct selection of anions.

PubMed

Shi, Minjie; Kou, Shengzhong; Yan, Xingbin

2014-11-01

Graphene sheet (GS)-ionic liquid (IL) supercapacitors are receiving intense interest because their specific energy density far exceeds that of GS-aqueous electrolytes supercapacitors. The electrochemical properties of ILs mainly depend on their diverse ions, especially anions. Therefore, identifying suitable IL electrolytes for GSs is currently one of the most important tasks. The electrochemical behavior of GSs in a series of ILs composed of 1-ethyl-3-methylimidazolium cation (EMIM(+)) with different anions is systematically studied. Combined with the formula derivation and building models, it is shown that the viscosity, ion size, and molecular weight of ILs affect the electrical conductivity of ILs, and thus, determine the electrochemical performances of GSs. Because the EMIM-dicyanamide IL has the lowest viscosity, ion size, and molecular weight, GSs in it exhibit the highest specific capacitance, smallest resistance, and best rate capability. In addition, because the tetrafluoroborate anion (BF4(-)) has the best electrochemical stability, the GS-[EMIM][BF4] supercapacitor has the widest potential window, and thus, displays the largest energy density. These results may provide valuable information for selecting appropriate ILs and designing high-performance GS-IL supercapacitors to meet different needs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anion-Regulated Selective Generation of Cobalt Sites in Carbon: Toward Superior Bifunctional Electrocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, Gang; Yang, Ce; Zhao, Wanpeng

The introduction of active transition metal sites (TMSs) in carbon enables the synthesis of noble-metal-free electrocatalysts for clean energy conversion applications, however, there are often multiple existing forms of TMSs, which are of different natures and catalytic models. Regulating the evolution of distinctive TMSs is highly desirable but remains challenging to date. Anions, as essential elements involved in the synthesis, have been totally neglected previously in the construction of TMSs. Herein, the effects of anions on the creation of different types of TMSs is investigated for the first time. It is found that the active cobalt-nitrogen sites tend to bemore » selectively constructed on the surface of N-doped carbon by using chloride, while metallic cobalt nanoparticles encased in protective graphite layers are the dominant forms of cobalt species with nitrate ions. The obtained catalysts demonstrate cobalt-sites-dependent activity for ORR and HER in acidic media. And the remarkably enhanced catalytic activities approaching that of benchmark Pt/C in acidic medium has been obtained on the catalyst dominated with cobalt-nitrogen sites, confirmed by the advanced spectroscopic . Our finding demonstrates a general paradigm of anion-regulated evolution of distinctive TMSs, providing a new pathway for enhancing performances of various targeted reactions related with TMSs.« less

A novel porous anionic metal–organic framework with pillared double-layer structure for selective adsorption of dyes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Shu-Nan; Han, Yi; Wang, Bin

2016-01-15

A novel porous anionic metal–organic framework, (Me{sub 2}NH{sub 2}){sub 2}[Zn{sub 2}L{sub 1.5}bpy]·2DMF (BUT-201; H{sub 4}L=4,8-disulfonaphthalene-2,6-dicarboxylic acid; bpy=4,4-bipyridine; DMF=N,N-dimethylformamide), with pillared double-layer structure has been synthesized through the reaction of a sulfonated carboxylic acid ligand and Zn(NO{sub 3}){sub 2}·6H{sub 2}O with 4,4-bipyridine as a co-ligand. It is found that BUT-201 can rapidly adsorb cationic dyes with a smaller size such as Methylene Blue (MB) and Acriflavine Hydrochloride (AH) by substitution of guest (CH{sub 3}){sub 2}NH{sub 2}{sup +}, but has no adsorption towards the cationic dyes with a lager size such as Methylene Violet (MV), the anionic dyes like C. I. Acidmore » Yellow 1 (AY1) and neutral dyes like C. I. Solvent Yellow 7 (SY7), respectively. The results show that the adsorption behavior of BUT-201 relates not only to the charge but also to the size/shape of dyes. Furthermore, the adsorbed dyes can be gradually released in the methanol solution of LiNO{sub 3}. - Graphical abstract: A porous anionic metal–organic framework (BUT-201) can selectively adsorb the cationic dyes by cationic guest molecule substitution, and the adsorbed dyes can be gradually released in the methanol solution of LiNO{sub 3}. - Highlights: • An anionic metal-organic framework (BUT-201) has been synthesized and characterized. • BUT-201 has a three-dimensional (3D) pillared double-layer structure. • BUT-201 can selectively and rapidly adsorb cationic dyes. • The adsorbed dyes can be gradually released in the methanol solution of LiNO{sub 3}.« less

Synthetic cation-selective nanotube: permeant cations chaperoned by anions.

PubMed

Hilder, Tamsyn A; Gordon, Dan; Chung, Shin-Ho

2011-01-28

The ability to design ion-selective, synthetic nanotubes which mimic biological ion channels may have significant implications for the future treatment of bacteria, diseases, and as ultrasensitive biosensors. We present the design of a synthetic nanotube made from carbon atoms that selectively allows monovalent cations to move across and rejects all anions. The cation-selective nanotube mimics some of the salient properties of biological ion channels. Before practical nanodevices are successfully fabricated it is vital that proof-of-concept computational studies are performed. With this in mind we use molecular and stochastic dynamics simulations to characterize the dynamics of ion permeation across a single-walled (10, 10), 36 Å long, carbon nanotube terminated with carboxylic acid with an effective radius of 5.08 Å. Although cations encounter a high energy barrier of 7 kT, its height is drastically reduced by a chloride ion in the nanotube. The presence of a chloride ion near the pore entrance thus enables a cation to enter the pore and, once in the pore, it is chaperoned by the resident counterion across the narrow pore. The moment the chaperoned cation transits the pore, the counterion moves back to the entrance to ferry another ion. The synthetic nanotube has a high sodium conductance of 124 pS and shows linear current-voltage and current-concentration profiles. The cation-anion selectivity ratio ranges from 8 to 25, depending on the ionic concentrations in the reservoirs.

Ion transport and selectivity in biomimetic nanopores with pH-tunable zwitterionic polyelectrolyte brushes.

PubMed

Zeng, Zhenping; Yeh, Li-Hsien; Zhang, Mingkan; Qian, Shizhi

2015-10-28

Inspired by nature, functionalized nanopores with biomimetic structures have attracted growing interests in using them as novel platforms for applications of regulating ion and nanoparticle transport. To improve these emerging applications, we study theoretically for the first time the ion transport and selectivity in short nanopores functionalized with pH tunable, zwitterionic polyelectrolyte (PE) brushes. In addition to background salt ions, the study takes into account the presence of H(+) and OH(-) ions along with the chemistry reactions between functional groups on PE chains and protons. Due to ion concentration polarization, the charge density of PE layers is not homogeneously distributed and depends significantly on the background salt concentration, pH, grafting density of PE chains, and applied voltage bias, thereby resulting in many interesting and unexpected ion transport phenomena in the nanopore. For example, the ion selectivity of the biomimetic nanopore can be regulated from anion-selective (cation-selective) to cation-selective (anion-selective) by diminishing (raising) the solution pH when a sufficiently small grafting density of PE chains, large voltage bias, and low background salt concentration are applied.

Influence of bidentate ligand donor types on the formation and stability in 2 + 1 fac-[MI(CO)3]+ (M = Re, 99mTc) complexes.

PubMed

Hayes, Thomas R; Bottorff, Shalina C; Slocumb, Winston S; Barnes, Charles L; Clark, Aurora E; Benny, Paul D

2017-01-24

In the last two decades, a number of chelate strategies have been proposed for the fac-[M I (CO) 3 ] + (M = Re, 99m Tc) core in radiopharmaceutical applications. However, the development of new ligands/complexes with improved function and in vivo performance has been limited in recent years. Expanding on our previous studies using the 2 + 1 labeling strategy, a series of bidentate ligands (neutral vs. anionic) containing an aromatic amine in combination with monodentate pyridine analogs or imidazole were explored to determine the influence of the bidentate and monodentate ligands on the formation and stability of the respective complexes. The 2 + 1 complexes with Re and 99m Tc were synthesized in two steps and characterized by standard radio/chemical methods. X-ray characterization and density functional theory analysis of the Re 2 + 1 complexes with the complete bidentate series with 4-dimethylaminopyridine were conducted, indicating enhanced ligand binding energies of the neutral over anionic ligands. In the 99m Tc studies, anionic bidentate ligands had significantly higher formation yields of the 2 + 1 product, but neutral ligands appear to have increased stability in an amino acid challenge assay. Both bidentate series exhibited improved stability by increasing the basicity of the pyridine ligands.

Influence of Bidentate Ligand Donor Types on the Formation and Stability in 2+1 fac-[MI(CO)3]+ (M = Re, 99mTc) Complexes

PubMed Central

Hayes, Thomas R.; Bottorff, Shalina C.; Slocumb, Winston S.; Barnes, Charles L.; Clark, Aurora E.; Benny, Paul D.

2017-01-01

In the last two decades, a number of chelate strategies have been proposed for the fac-[MI(CO)3]+ (M = Re, 99mTc) core in radiopharmaceutical applications. However, the development of new ligands/complexes with improved function and in vivo performance has been limited in recent years. Expanding on our previous studies using the 2+1 labeling strategy, a series of bidentate ligands (neutral vs. anionic) containing an aromatic amine in combination with monodentate pyridine analogs or imidazole were explored to determine the influence of the bidentate and monodentate ligands on the formation and stability of the respective complexes. The 2+1 complexes with Re and 99mTc were synthesized in two steps and characterized by standard radio/chemical methods. X-ray characterization and density functional theory analysis of the Re 2+1 complexes with the complete bidentate series with 4-dimethylaminopyridine were conducted, indicating enhanced ligand binding energies of the neutral over anionic ligands. In the 99mTc studies, anionic bidentate ligands had significantly higher formation yields of the 2+1 product, but neutral ligands appear to have increased stability in an amino acid challenge assay. Both bidentate series exhibited improved stability by increasing the basicity of the pyridine ligands. PMID:28045466

Selective removal of arsenic and monovalent ions from brackish water reverse osmosis concentrate.

PubMed

Xu, Pei; Capito, Marissa; Cath, Tzahi Y

2013-09-15

Concentrate disposal and management is a considerable challenge for the implementation of desalination technologies, especially for inland applications where concentrate disposal options are limited. This study has focused on selective removal of arsenic and monovalent ions from brackish groundwater reverse osmosis (RO) concentrate for beneficial use and safe environmental disposal using in situ and pre-formed hydrous ferric oxides/hydroxides adsorption, and electrodialysis (ED) with monovalent permselective membranes. Coagulation with ferric salts is highly efficient at removing arsenic from RO concentrate to meet a drinking water standard of 10 μg/L. The chemical demand for ferric chloride however is much lower than ferric sulfate as coagulant. An alternative method using ferric sludge from surface water treatment plant is demonstrated as an efficient adsorbent to remove arsenic from RO concentrate, providing a promising low cost, "waste treat waste" approach. The monovalent permselective anion exchange membranes exhibit high selectivity in removing monovalent anions over di- and multi-valent anions. The transport of sulfate and phosphate through the anion exchange membranes was negligible over a broad range of electrical current density. However, the transport of divalent cations such as calcium and magnesium increases through monovalent permselective cation exchange membranes with increasing current density. Higher overall salt concentration reduction is achieved around limiting current density while higher normalized salt removal rate in terms of mass of salt per membrane area and applied energy is attained at lower current density because the energy unitization efficiency decreases at higher current density. Copyright © 2013 Elsevier B.V. All rights reserved.

Fractionation of whey proteins with high-capacity superparamagnetic ion-exchangers.

PubMed

Heebøll-Nielsen, Anders; Justesen, Sune F L; Thomas, Owen R T

2004-09-30

In this study we describe the design, preparation and testing of superparamagnetic anion-exchangers, and their use together with cation-exchangers in the fractionation of bovine whey proteins as a model study for high-gradient magnetic fishing. Adsorbents prepared by attachment of trimethyl amine to particles activated in sequential reactions with allyl bromide and N-bromosuccinimide yielded a maximum bovine serum albumin binding capacity of 156 mg g(-1) combined with a dissociation constant of 0.60 microM, whereas ion-exchangers created by linking polyethylene imine through superficial aldehydes bound up to 337 mg g(-1) with a dissociation constant of 0.042 microM. The latter anion-exchanger was selected for studies of whey protein fractionation. In these, crude bovine whey was treated with a superparamagnetic cation-exchanger to adsorb basic protein species, and the supernatant arising from this treatment was then contacted with the anion-exchanger. For both adsorbent classes of ion-exchanger, desorption selectivity was subsequently studied by sequentially increasing the concentration of NaCl in the elution buffer. In the initial cation-exchange step quantitative removal of lactoferrin (LF) and lactoperoxidase (LPO) was achieved with some simultaneous binding of immunoglobulins (Ig). The immunoglobulins were separated from the other two proteins by desorbing with a low concentration of NaCl (< or = 0.4 M), whereas lactoferrin and lactoperoxidase were co-eluted in significantly purer form, e.g. lactoperoxidase was purified 28-fold over the starting material, when the NaCl concentration was increased to 0.4-1 M. The anion-exchanger adsorbed beta-lactoglobulin (beta-LG) selectively allowing separation from the remaining protein.

Infrared spectroscopy of hydrated naphthalene cluster anions.

PubMed

Knurr, Benjamin J; Adams, Christopher L; Weber, J Mathias

2012-09-14

We present infrared spectra of mass-selected C(10)H(8)(-)·(H(2)O)(n)·Ar(m) cluster anions (n = 1-6) obtained by Ar predissociation spectroscopy. The experimental spectra are compared with predicted spectra from density functional theory calculations. The OH groups of the water ligands are involved in H-bonds to other water molecules or to the π system of the naphthalene anion, which accommodates the excess electron. The interactions in the water network are generally found to be more important than those between water molecules and the ion. For 2 ≤ n ≤ 4 the water molecules form single layer water networks on one side of the naphthalene anion, while for n = 5 and 6, cage and multilayer structures become more energetically favorable. For cluster sizes with more than 3 water molecules, multiple conformers are likely to be responsible for the experimental spectra.

Specific anion binding to sulfobetaine micelles and kinetics of nucleophilic reactions.

PubMed

Marte, Luisa; Beber, Rosane C; Farrukh, M Akhyar; Micke, Gustavo A; Costa, Ana C O; Gillitt, Nicholas D; Bunton, Clifford A; Di Profio, Pietro; Savelli, Gianfranco; Nome, Faruk

2007-08-23

With fully micellar bound substrates reactions of OH- with benzoic anhydride, Bz(2)O, and of Br- with methyl naphthalene-2-sulfonate, MeONs, in micellized sulfobetaines are strongly inhibited by NaClO4 which displaces the nucleophilic anions from the micellar pseudophases. Micellar incorporations of ClO4- and Br- are estimated with an ion-selective electrode and by electrophoresis, and partitioning of Br- between water and micelles is related to changes in NMR spectral (79)Br- line widths. Extents of inhibition by ClO4- of these nucleophilic reactions in the micellar pseudophase are related to quantitative displacement of the reactive anions from the micelles by ClO4-. The kinetic data are correlated with physical evidence on the strong interactions between sulfobetaines and ClO4-, which turn sulfobetaine micelles anionic and effectively provoke displacement of OH- and Br-.

A high selective anion colorimetric sensor based on salicylaldehyde for fluoride in aqueous media.

PubMed

Li, Jianwei; Lin, Hai; Cai, Zunsheng; Lin, Huakuan

2009-06-01

A new and simple salicylaldehyde-based sensor 1 designed for fluoride sensing has been investigated in DMSO and even in the 9/1 DMSO/H(2)O (v/v) mixtures. The affinity constants of receptor 1 for anionic species in the 9/1 DMSO/H(2)O (v/v) reveal that it is sensitive to F. Also, the color changes induced by anions can provide a way of detection by 'naked-eye'. These result can be substantiated by the spectrum changes upon the addition of 25equiv. anions to 1 in the 9/1 DMSO/H(2)O solution. The further insights to the nature of interactions between the sensor 1 and F(-) were investigated by (1)H NMR titration experiments in 9/1 DMSO-d(6)/H(2)O (v/v). In addition, the proposed binding mode between 1 and F(-) was suggested.

Acrosome reaction inducers impose alterations in repulsive strain and hydration barrier in human sperm membranes.

PubMed

Purohit, S B; Laloraya, M; Kumar, G P

1998-06-01

Spin labeling studies of the lipophilic domains of human spermatozoa during capacitation and during acrosome reaction (AR) under the influence of selected AR-inducers were performed. Significantly enhanced rotational function of molecules was obvious during capacitation, with no significant changes in membrane packaging or the lateral diffusion of molecules. The AR inducers appeared to restrict the rotational freedom of molecules, dramatically enhancing the lateral diffusion and ordering coefficients. A significant decrease in superoxide anion generation was observed in the acrosome reacted groups when compared to the non-acrosome reacted groups. A high level of superoxide anion radical (O2.-) level maintained in capacitated spermatozoa would add to the Van der Waal's repulsive forces at the polar head of phospholipids, holding the membrane in strain where the molecular enjoy little freedom for lateral motion. A sudden drop in the levels of O2.- in spermatozoa upon addition of AR inducers could abruptly release the local hydrophobic repulsive strain within the membrane. This loss of hydration barrier explains the observed enhancement in lateral diffusion profiles of lipids and the packaging of molecules. It is reasonable to assume that these phenomena could be amplified further by interplay of Ca2+ by modifying the local charge aggregation. Thus, we would conclude that AR inducers release the oxyradical load in capacitated spermatozoa, which would modify the repulsive strain and hydration barrier forces in the lipophilic domains permitting vesiculation of the membranes. It appears that various acrosome reaction inducers act as effectors of grossly similar physical alterations in sperm membranes and that the resulting signal cascades proceed through intercalating biochemical sequences.

Optimized anion exchange column isolation of zirconium-89 ( 89 Zr) from yttrium cyclotron target: Method development and implementation on an automated fluidic platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Hara, Matthew J.; Murray, Nathaniel J.; Carter, Jennifer C.

Zirconium-89 (89Zr), produced by the (p,n) reaction from naturally monoisotopic yttrium (natY), is a promising positron emitting isotope for immunoPET imaging. Its long half-life of 78.4 h is sufficient for evaluating slow physiological processes. A prototype automated fluidic system, coupled to on-line and in-line detectors, has been constructed to facilitate development of new 89Zr purification methodologies. The highly reproducible reagent delivery platform and near-real time monitoring of column effluents allows for efficient method optimization. The separation of Zr from dissolved Y metal targets was evaluated using several anion exchange resins. Each resin was evaluated against its ability to quantitatively capturemore » Zr from a load solution that is high in dissolved Y. The most appropriate anion exchange resin for this application was identified, and the separation method was optimized. The method is capable of a high Y decontamination factor (>105) and has been shown to separate Fe, an abundant contaminant in Y foils, from the 89Zr elution fraction. Finally, the performance of the method was evaluated using cyclotron bombarded Y foil targets. The separation method was shown to achieve >95% recovery of the 89Zr present in the foils. The 89Zr eluent, however, was in a chemical matrix not immediately conducive to labeling onto proteins. The main intent of this study was to develop a tandem column 89Zr purification process, wherein the anion exchange column method described here is the first separation in a dual-column purification process.« less

Specific in vivo labeling with GFP retroviruses, lentiviruses, and adenoviruses for imaging

NASA Astrophysics Data System (ADS)

Hoffman, Robert M.; Kishimoto, Hiroyuki; Fujiwara, Toshiyoshi

2008-02-01

Fluorescent proteins have revolutionized the field of imaging. Our laboratory pioneered in vivo imaging with fluorescent proteins. Fluorescent proteins have enabled imaging at the subcellular level in mice. We review here the use of different vectors carrying fluorescent proteins to selectively label normal and tumor tissue in vivo. We show that a GFP retrovirus and telomerase-driven GFP adenovirus can selectively label tumors in mice. We also show that a GFP lentivirus can selectively label the liver in mice. The practical application of these results are discussed.

Selection Rule of Preferred Doping Site for n-Type Oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, C.; Li, J.; Li, S. S.

2012-06-25

Using first-principles calculations and analysis, we show that to create shallow n-type dopants in oxides, anion site doping is preferred for more covalent oxides such as SnO{sub 2} and cation site doping is preferred for more ionic oxides such as ZnO. This is because for more ionic oxides, the conduction band minimum (CBM) state actually contains a considerable amount of O 3s orbitals, thus anion site doping can cause large perturbation on the CBM and consequently produces deeper donor levels. We also show that whether it is cation site doping or anion site doping, the oxygen-poor condition should always bemore » used.« less

Mixed mode HILIC/anion exchange separations on latex coated silica monoliths.

PubMed

Ibrahim, Mohammed E A; Lucy, Charles A

2012-10-15

Bare silica monoliths do not possess anion exchange sites hence they show low retention for anions. Moreover, bare silica monoliths show low retention in hydrophilic interaction liquid chromatography (HILIC). Coating the silica surface with cationic nanoparticles e.g. AS9-SC (latex A), AS12A (latex B) and DNApac (latex C) increases the thickness of the water layer on the Onyx silica monolith 8-10 times enabling HILIC retention when a high % acetonitrile (ACN) mobile phase is used. The formed water layer by itself is not sufficient to perform good separation of the studied anions (acetate, formate, nitrate, bromate, thiocyanate and iodide). On the other hand, the latex nanoparticles introduce positively charged sites, making anion exchange chromatography possible, with the anion exchange capacity varying with the latex adsorbed (44.1 ± 0.2, 4.4 ± 0.1 and 14.0 ± 0.7 μeq/column for latex A, B and C, respectively). Latex A nanoparticles which provided the highest ion exchange capacity separated all tested anions with reasonable resolution. Fast separation (2.5 min) of acetate, formate, nitrate, bromate, thiocyanate and iodide was performed using the latex A coated silica monolith. The obtained efficiencies are 13,000-50,000 plates/m at 3 mL/min with a minimum resolution of 0.85. Retention is mixed mode under HILIC conditions with HILIC dominating for the kosmotropic anions and ion exchange dominating for the chaotropic anions. The two different brands of silica monoliths (Merck Chromolith and Phenomenex Onyx) coated with the same latex A nanoparticles displayed similar water layer volumes, ion exchange capacity and selectivity. Copyright © 2012 Elsevier B.V. All rights reserved.

Electroactive Self-Assembled Monolayers Detect Micelle Formation.

PubMed

Dionne, Eric R; Badia, Antonella

2017-02-15

The interfacial electrochemistry of self-assembled monolayers (SAMs) of ferrocenyldodecanethiolate on gold (FcC 12 SAu) electrodes is applied to detect the micellization of some common anionic surfactants, sodium n-alkyl sulfates, sodium n-alkyl sulfonates, sodium diamyl sulfosuccinate, and sodium dodecanoate, in aqueous solution by cyclic voltammetry. The apparent formal redox potential (E°' SAM ) of the FcC 12 SAu SAM is used to track changes in the concentration of the unaggregated surfactant anions and determine the critical micelle concentration (cmc). The effect of added salt (NaF) on the sodium alkyl sulfate concentration dependence of E°' SAM is also investigated. Weakly hydrated anions, such as ClO 4 - , pair with the electrogenerated SAM-bound ferroceniums to neutralize the excess positive charge created at the SAM/electrolyte solution interface and stabilize the oxidized cations. E°' SAM exhibits a Nernstian-type dependence on the anion activity in solution. Aggregation of the surfactant anions into micelles above the cmc causes the free surfactant anion activity to deviate from the molar concentration of added surfactant, resulting in a break in the plot of E°' SAM versus the logarithm of the concentration of anionic surfactant. The concentration at which this deviation occurs is in good agreement with literature or experimentally determined values of the cmc. The effects of Ohmic potential drop, liquid junction potential, and surfactant adsorption behavior on E°' SAM are addressed. Ultimately, the E°' SAM response as a function of the anionic surfactant concentration exhibits the same features reported using potentiometry and surfactant ion-selective electrodes, which provide a direct measure of the free surfactant anion activity, thus making FcC 12 SAu SAM electrodes useful for the detection of surfactant aggregation and micelle formation.

Nuclear Forensic Lab Interoperability and Criminal Investigation

DTIC Science & Technology

2014-08-01

34 Hydrometallurgy (3-4): 175-180 13. Kolodynska, D., H. Hubicka, et al. (2008). " Sorption of heavy metal ions from aqueous solutions in the presence of...EDTA on monodisperse anion exchangers." Desalination (1-3): 150-166 14. Kolodynska, D. (2009). "Polyacrylate anion exchangers in sorption of heavy...F. D. and A. H. Martins (2004). "Selective sorption of nickel and cobalt from sulphate solutions using chelating resins." International Journal of

Squarylium-based chromogenic anion sensors

NASA Astrophysics Data System (ADS)

Lee, Eun-Mi; Gwon, Seon-Yeong; Son, Young-A.; Kim, Sung-Hoon

2012-09-01

A squarylium (SQ) dye was synthesized by the reaction between squaric acid and 2,3,3-trimethylindolenine and its anion sensing properties were investigated using absorption and emission spectroscopy. This chemosensor exhibited high selectivity for CN- as compared with F-, CHCO2-, Br-, HPO4-, Cl-, and NO3- in acetonitrile, which was attributed to the formation of a 1:1 squarylium:CN- coordination complex, the formation of which was supported by the calculated geometry of the complex.

Optical Imaging of Mammary and Prostate Tumors in Living Animals using a Synthetic Near Infrared Zinc(II)-Dipicolylamine Probe for Anionic Cell Surfaces

PubMed Central

Smith, Bryan A.; Akers, Walter J.; Leevy, W. Matthew; Lampkins, Andrew J.; Xiao, Shuzhang; Wolter, William; Suckow, Mark A.; Achilefu, Samuel; Smith, Bradley D.

2009-01-01

In vivo optical imaging shows that a fluorescent imaging probe, comprised of a near-infrared fluorophore attached to an affinity group containing two zinc(II)-dipicolylamine (Zn-DPA) units, targets prostate and mammary tumors in two different xenograft animal models. The tumor selectivity is absent with control fluorophores whose structures do not have appended Zn-DPA targeting ligands. Ex vivo biodistribution and histological analyses indicate that the probe is targeting the necrotic regions of the tumors, which is consistent with in vitro microscopy showing selective targeting of the anionic membrane surfaces of dead and dying cells. PMID:20014845

Preparation and regulating cell adhesion of anion-exchangeable layered double hydroxide micropatterned arrays.

PubMed

Yao, Feng; Hu, Hao; Xu, Sailong; Huo, Ruijie; Zhao, Zhiping; Zhang, Fazhi; Xu, Fujian

2015-02-25

We describe a reliable preparation of MgAl-layered double hydroxide (MgAl-LDH) micropatterned arrays on gold substrate by combining SO3(-)-terminated self-assembly monolayer and photolithography. The synthesis route is readily extended to prepare LDH arrays on the SO3(-)-terminated polymer-bonded glass substrate amenable for cell imaging. The anion-exchangeable MgAl-LDH micropattern can act both as bioadhesive region for selective cell adhesion and as nanocarrier for drug molecules to regulate cell behaviors. Quantitative analysis of cell adhesion shows that selective HepG2 cell adhesion and spreading are promoted by the micropatterned MgAl-LDH, and also suppressed by methotrexate drug released from the LDH interlayer galleries.

Anion permselective membrane

NASA Technical Reports Server (NTRS)

Alexander, S.; Hodgdon, R. B.

1977-01-01

The objective of NAS 3-20108 was the development and evaluation of improved anion selective membranes useful as efficient separators in a redox power storage cell system being constructed. The program was divided into three parts, (a) optimization of the selected candidate membrane systems, (b) investigation of alternative membrane/polymer systems, and (c) characterization of candidate membranes. The major synthesis effort was aimed at improving and optimizing as far as possible each candidate system with respect to three critical membrane properties essential for good redox cell performance. Substantial improvements were made in 5 candidate membrane systems. The critical synthesis variables of cross-link density, monomer ratio, and solvent composition were examined over a wide range. In addition, eight alternative polymer systems were investigated, two of which attained candidate status. Three other alternatives showed potential but required further research and development. Each candidate system was optimized for selectivity.

A bifunctional luminescent Tb(III)-metal-organic framework by a tetracarboxylate ligand for highly selective detection of Fe3+ cation and Cr2O72- anion

NASA Astrophysics Data System (ADS)

Yu, Li; Wang, Chao; Hu, Chang-Jiang; Dong, Wen-Wen; Wu, Ya-Pan; Li, Dong-Sheng; Zhao, Jun

2018-06-01

Reaction of Tb3+ ions with p-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4ptptc) in a mixed solvent system has afforded a new metal-organic framework formulated as [Tb2(ptptc)1.5(H2O)2]n (1). Compound 1 displays a 3D (5,6,8)-connected framework with fascinating one-dimensional triangle open channels. The luminescence explorations demonstrated that 1 exhibits highly selective and sensitive response to Fe3+ in DMF solution and biological system through luminescence quenching effects. In addition, 1 also shows high detection for the Cr2O72-, making it a promising dual functional materials for detecting Fe3+ cation and Cr2O72- anion with high sensitivity and selectivity.

Solvent effect on the synthesis of clarithromycin: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Duran, Dilek; Aviyente, Viktorya; Baysal, Canan

2004-02-01

Clarithromycin (6- O-methylerythromycin A) is a 14-membered macrolide antibiotic which is active in vitro against clinically important gram-positive and gram-negative bacteria. The selectivity of the methylation of the C-6 OH group is studied on erythromycin A derivatives. To understand the effect of the solvent on the methylation process, detailed molecular dynamics (MD) simulations are performed in pure DMSO, pure THF and DMSO:THF (1:1) mixture by using the anions at the C-6, C-11 and C-12 positions of 2',4''-[ O-bis(TMS)]erythromycin A 9-[ O-(dimethylthexylsilyl)oxime] under the assumption that the anions are stable on the sub-nanosecond time scale. The conformations of the anions are not affected by the presence of the solvent mixture. The radial distribution functions are computed for the distribution of different solvent molecules around the `O-' of the anions. At distances shorter than 5 Å, DMSO molecules are found to cluster around the C-11 anion, whereas the anion at the C-12 position is surrounded by the THF molecules. The anion at the C-6 position is not blocked by the solvent molecules. The results are consistent with the experimental finding that the methylation yield at the latter position is increased in the presence of a DMSO:THF (1:1) solvent mixture. Thus, the effect of the solvent in enhancing the yield during the synthesis is not by changing the conformational properties of the anions, but rather by creating a suitable environment for methylation at the C-6 position.

Extracellular Determinants of Anion Discrimination of the Cl−/H+ Antiporter Protein CLC-5*

PubMed Central

De Stefano, Silvia; Pusch, Michael; Zifarelli, Giovanni

2011-01-01

Mammalian CLC proteins comprise both Cl− channels and Cl−/H+ antiporters that carry out fundamental physiological tasks by transporting Cl− across plasma membrane and intracellular compartments. The NO3− over Cl− preference of a plant CLC transporter has been pinpointed to a conserved serine residue located at Scen and it is generally assumed that the other two binding sites of CLCs, Sext and Sin, do not substantially contribute to anion selectivity. Here we show for the Cl−/H+ antiporter CLC-5 that the conserved and extracellularly exposed Lys210 residue is critical to determine the anion specificity for transport activity. In particular, mutations that neutralize or invert the charge at this position reverse the NO3− over Cl− preference of WT CLC-5 at a concentration of 100 mm, but do not modify the coupling stoichiometry with H+. The importance of the electrical charge is shown by chemical modification of K210C with positively charged cysteine-reactive compounds that reintroduce the WT preference for Cl−. At saturating extracellular anion concentrations, neutralization of Lys210 is of little impact on the anion preference, suggesting an important role of Lys210 on the association rate of extracellular anions to Sext. PMID:21921031

Inulin determination for food labeling.

PubMed

Zuleta, A; Sambucetti, M E

2001-10-01

Inulin and oligofructose exhibit valuable nutritional and functional attributes, so they are used as supplements as soluble fiber or as macronutrient substitutes. As classic analytical methods for dietary fiber measurement are not effective, several specific methods have been proposed. These methods measure total fructans and are based on one or more enzymatic sample treatments and determination of released sugars. To determine inulin for labeling purposes, we developed an easy and rapid anion-exchange high-performance liquid chromatography (HPLC) method following water extraction of inulin. HPLC conditions included an Aminex HPX- 87C column (Bio-Rad), deionized water at 85 degrees C as the mobile phase and a refractive index detector. The tested foods included tailor-made food products containing known amounts of inulin and commercial products (cookies, milk, ice creams, cheese, and cereal bars). The average recovery was 97%, and the coefficient of variation ranged from 1.1 to 5% in the food matrixes. The obtained results showed that this method provides an easier, faster and cheaper alternative than previous techniques for determining inulin with enough accuracy and precision for routine labeling purposes by direct determination of inulin by HPLC with refractive index detection.

Selective Chemical Labeling of Proteins with Small Fluorescent Molecules Based on Metal-Chelation Methodology

PubMed Central

Soh, Nobuaki

2008-01-01

Site-specific chemical labeling utilizing small fluorescent molecules is a powerful and attractive technique for in vivo and in vitro analysis of cellular proteins, which can circumvent some problems in genetic encoding labeling by large fluorescent proteins. In particular, affinity labeling based on metal-chelation, advantageous due to the high selectivity/simplicity and the small tag-size, is promising, as well as enzymatic covalent labeling, thereby a variety of novel methods have been studied in recent years. This review describes the advances in chemical labeling of proteins, especially highlighting the metal-chelation methodology. PMID:27879749

Source Attribution of Cyanides Using Anionic Impurity Profiling, Stable Isotope Ratios, Trace Elemental Analysis and Chemometrics.

PubMed

Mirjankar, Nikhil S; Fraga, Carlos G; Carman, April J; Moran, James J

2016-02-02

Chemical attribution signatures (CAS) for chemical threat agents (CTAs), such as cyanides, are being investigated to provide an evidentiary link between CTAs and specific sources to support criminal investigations and prosecutions. Herein, stocks of KCN and NaCN were analyzed for trace anions by high performance ion chromatography (HPIC), carbon stable isotope ratio (δ(13)C) by isotope ratio mass spectrometry (IRMS), and trace elements by inductively coupled plasma optical emission spectroscopy (ICP-OES). The collected analytical data were evaluated using hierarchical cluster analysis (HCA), Fisher-ratio (F-ratio), interval partial least-squares (iPLS), genetic algorithm-based partial least-squares (GAPLS), partial least-squares discriminant analysis (PLSDA), K nearest neighbors (KNN), and support vector machines discriminant analysis (SVMDA). HCA of anion impurity profiles from multiple cyanide stocks from six reported countries of origin resulted in cyanide samples clustering into three groups, independent of the associated alkali metal (K or Na). The three groups were independently corroborated by HCA of cyanide elemental profiles and corresponded to countries each having one known solid cyanide factory: Czech Republic, Germany, and United States. Carbon stable isotope measurements resulted in two clusters: Germany and United States (the single Czech stock grouped with United States stocks). Classification errors for two validation studies using anion impurity profiles collected over five years on different instruments were as low as zero for KNN and SVMDA, demonstrating the excellent reliability associated with using anion impurities for matching a cyanide sample to its factory using our current cyanide stocks. Variable selection methods reduced errors for those classification methods having errors greater than zero; iPLS-forward selection and F-ratio typically provided the lowest errors. Finally, using anion profiles to classify cyanides to a specific stock or stock group for a subset of United States stocks resulted in cross-validation errors ranging from 0 to 5.3%.

Tetrel Bonding as a Vehicle for Strong and Selective Anion Binding.

PubMed

Scheiner, Steve

2018-05-11

Tetrel atoms T (T = Si, Ge, Sn, and Pb) can engage in very strong noncovalent interactions with nucleophiles, which are commonly referred to as tetrel bonds. The ability of such bonds to bind various anions is assessed with a goal of designing an optimal receptor. The Sn atom seems to form the strongest bonds within the tetrel family. It is most effective in the context of a -SnF₃ group and a further enhancement is observed when a positive charge is placed on the receptor. Connection of the -SnF₃ group to either an imidazolium or triazolium provides a strong halide receptor, which can be improved if its point of attachment is changed from the C to an N atom of either ring. Aromaticity of the ring offers no advantage nor is a cyclic system superior to a simple alkyl amine of any chain length. Placing a pair of -SnF₃ groups on a single molecule to form a bipodal dicationic receptor with two tetrel bonds enhances the binding, but falls short of a simple doubling. These two tetrel groups can be placed on opposite ends of an alkyl diamine chain of any length although SnF₃⁺NH₂(CH₂) n NH₂SnF₃⁺ with n between 2 and 4 seems to offer the strongest halide binding. Of the various anions tested, OH − binds most strongly: OH − > F − > Cl − > Br − > I − . The binding energy of the larger NO₃ − and HCO₃ − anions is more dependent upon the charge of the receptor. This pattern translates into very strong selectivity of binding one anion over another. The tetrel-bonding receptors bind far more strongly to each anion than an equivalent number of K⁺ counterions, which leads to equilibrium ratios in favor of the former of many orders of magnitude.

What do we know about the effects of exposure to 'Low alcohol' and equivalent product labelling on the amounts of alcohol, food and tobacco people select and consume? A systematic review.

PubMed

Shemilt, Ian; Hendry, Vivien; Marteau, Theresa M

2017-01-12

Explicit labelling of lower strength alcohol products could reduce alcohol consumption by attracting more people to buy and drink such products instead of higher strength ones. Alternatively, it may lead to more consumption due to a 'self-licensing' mechanism. Equivalent labelling of food or tobacco (for example "Low fat" or "Low tar") could influence consumption of those products by similar mechanisms. This systematic review examined the effects of 'Low alcohol' and equivalent labelling of alcohol, food and tobacco products on selection, consumption, and perceptions of products among adults. A systematic review was conducted based on Cochrane methods. Electronic and snowball searches identified 26 eligible studies. Evidence from 12 randomised controlled trials (all on food) was assessed for risk of bias, synthesised using random effects meta-analysis, and interpreted in conjunction with evidence from 14 non-randomised studies (one on alcohol, seven on food and six on tobacco). Outcomes assessed were: quantities of the product (i) selected or (ii) consumed (primary outcomes - behaviours), (iii) intentions to select or consume the product, (iv) beliefs associated with it consumption, (v) product appeal, and (vi) understanding of the label (secondary outcomes - cognitions). Evidence for impacts on the primary outcomes (i.e. amounts selected or consumed) was overall of very low quality, showing mixed effects, likely to vary by specific label descriptors, products and population characteristics. Overall very low quality evidence suggested that exposure to 'Low alcohol' and equivalent labelling on alcohol, food and tobacco products can shift consumer perceptions of products, with the potential to 'self-licence' excess consumption. Considerable uncertainty remains about the effects of labels denoting low alcohol, and equivalent labels, on alcohol, food and tobacco selection and consumption. Independent, high-quality studies are urgently needed to inform policies on labelling regulations.

Tandem mass spectrometry measurement of the collision products of carbamate anions derived from CO2 capture sorbents: paving the way for accurate quantitation.

PubMed

Jackson, Phil; Fisher, Keith J; Attalla, Moetaz Ibrahim

2011-08-01

The reaction between CO(2) and aqueous amines to produce a charged carbamate product plays a crucial role in post-combustion capture chemistry when primary and secondary amines are used. In this paper, we report the low energy negative-ion CID results for several anionic carbamates derived from primary and secondary amines commonly used as post-combustion capture solvents. The study was performed using the modern equivalent of a triple quadrupole instrument equipped with a T-wave collision cell. Deuterium labeling of 2-aminoethanol (1,1,2,2,-d(4)-2-aminoethanol) and computations at the M06-2X/6-311++G(d,p) level were used to confirm the identity of the fragmentation products for 2-hydroxyethylcarbamate (derived from 2-aminoethanol), in particular the ions CN(-), NCO(-) and facile neutral losses of CO(2) and water; there is precedent for the latter in condensed phase isocyanate chemistry. The fragmentations of 2-hydroxyethylcarbamate were generalized for carbamate anions derived from other capture amines, including ethylenediamine, diethanolamine, and piperazine. We also report unequivocal evidence for the existence of carbamate anions derived from sterically hindered amines (Tris(2-hydroxymethyl)aminomethane and 2-methyl-2-aminopropanol). For the suite of carbamates investigated, diagnostic losses include the decarboxylation product (-CO(2), 44 mass units), loss of 46 mass units and the fragments NCO(-) (m/z 42) and CN(-) (m/z 26). We also report low energy CID results for the dicarbamate dianion ((-)O(2)CNHC(2)H(4)NHCO(2)(-)) commonly encountered in CO(2) capture solution utilizing ethylenediamine. Finally, we demonstrate a promising ion chromatography-MS based procedure for the separation and quantitation of aqueous anionic carbamates, which is based on the reported CID findings. The availability of accurate quantitation methods for ionic CO(2) capture products could lead to dynamic operational tuning of CO(2) capture-plants and, thus, cost-savings via real-time manipulation of solvent regeneration energies.

Parents' meal choices for their children at fast food and family restaurants with different menu labeling presentations.

PubMed

Lee, Kiwon; Lee, Youngmi

2018-06-01

This study examined the effect of nutrition labeling formats on parents' food choices for their children at different restaurant types. An online survey was conducted with 1,980 parents of children aged 3-12 years. Participants were randomly assigned to fast food or family restaurant scenarios, and one of four menu stimuli conditions: no labeling, low-calorie symbol (symbol), numeric value (numeric), and both low-calorie symbol and numeric value (symbol + numeric). Participants selected menu items for their children. Menu choices and total calories were compared by nutrition labeling formats in each type of the restaurant. Low-calorie item selections were scored and a two-way analysis of variance (ANOVA) was conducted for an interaction effect between restaurant and labeling type. In the fast food restaurant group, parents presented with low-calorie symbols selected the lowest calorie items more often than those not presented with the format. Parents in the symbol + numeric condition selected significantly fewer calories (653 kcal) than those in the no labeling (677 kcal) or numeric conditions (674 kcal) ( P = 0.006). In the family restaurant group, no significant difference were observed among different labeling conditions. A significant interaction between restaurant and labeling type on low-calorie selection score (F = 6.03, P < 0.01) suggests that the effect of nutrition labeling format interplays with restaurant type to jointly affect parents' food choices for their children. The provision of easily interpretable nutritional information format at fast food restaurants may encourage healthier food choices of parents for their children; however, the effects were negligible at family restaurants.

Comprehensive clinical approach to renal tubular acidosis.

PubMed

Sharma, Sonia; Gupta, Ankur; Saxena, Sanjiv

2015-08-01

Renal tubular acidosis (RTA) is essentially characterized by normal anion gap and hyperchloremic metabolic acidosis. It is important to understand that despite knowing the disease for 60-70 years, complexities in the laboratory tests and their interpretation still make clinicians cautious to diagnose and label types of tubular disorder. Hence, we are writing this mini-review to emphasize on the step wise approach to RTA with some understanding on its basic etiopathogenesis. This will definitely help to have an accurate interpretation of urine and blood reports in correlation with the clinical condition. RTA can be a primary or secondary defect and results either due to abnormality in bicarbonate ion absorption or hydrogen ion secretion. Primary defects are common in children due to gene mutation or idiopathic nature while secondary forms are more common in adults. We are focusing and explaining here in this review all the clinical and laboratory parameters which are essential for making the diagnosis of RTA and excluding the extrarenal causes of hyperchloremic, normal anion gap metabolic acidosis.

Impact of food labelling systems on food choices and eating behaviours: a systematic review and meta-analysis of randomized studies.

PubMed

Cecchini, M; Warin, L

2016-03-01

Food labels are considered a crucial component of strategies tackling unhealthy diets and obesity. This study aims at assessing the effectiveness of food labelling in increasing the selection of healthier products and in reducing calorie intake. In addition, this study compares the relative effectiveness of traffic light schemes, Guideline Daily Amount and other food labelling schemes. A comprehensive set of databases were searched to identify randomized studies. Studies reporting homogeneous outcomes were pooled together and analysed through meta-analyses. Publication bias was evaluated with a funnel plot. Food labelling would increase the amount of people selecting a healthier food product by about 17.95% (confidence interval: +11.24% to +24.66%). Food labelling would also decrease calorie intake/choice by about 3.59% (confidence interval: -8.90% to +1.72%), but results are not statistically significant. Traffic light schemes are marginally more effective in increasing the selection of healthier options. Other food labels and Guideline Daily Amount follow. The available evidence did not allow studying the effects of single labelling schemes on calorie intake/choice. Findings of this study suggest that nutrition labelling may be an effective approach to empowering consumers in choosing healthier products. Interpretive labels, as traffic light labels, may be more effective. © 2015 World Obesity.

Anionic deep cavitands enable the adhesion of unmodified proteins at a membrane bilayer.

PubMed

Ghang, Yoo-Jin; Perez, Lizeth; Morgan, Melissa A; Si, Fang; Hamdy, Omar M; Beecher, Consuelo N; Larive, Cynthia K; Julian, Ryan R; Zhong, Wenwan; Cheng, Quan; Hooley, Richard J

2014-12-28

An anionic self-folding deep cavitand is capable of immobilizing unmodified proteins and enzymes at a supported lipid bilayer interface, providing a simple, soft bioreactive surface that allows enzymatic function under mild conditions. The adhesion is based on complementary charge interactions, and the hosts are capable of binding enzymes such as trypsin at the bilayer interface: the catalytic activity is retained upon adhesion, allowing selective reactions to be performed at the membrane surface.

Synthetic oligonucleotide separations by mixed-mode reversed-phase/weak anion-exchange liquid chromatography.

PubMed

Zimmermann, Aleksandra; Greco, Roberto; Walker, Isabel; Horak, Jeannie; Cavazzini, Alberto; Lämmerhofer, Michael

2014-08-08

Synthetic oligonucleotides gain increasing importance in new therapeutic concepts and as probes in biological sciences. If pharmaceutical-grade purities are required, chromatographic purification using ion-pair reversed-phase chromatography is commonly carried out. However, separation selectivity for structurally closely related impurities is often insufficient, especially at high sample loads. In this study, a "mixed-mode" reversed-phase/weak anion exchanger stationary phase has been investigated as an alternative tool for chromatographic separation of synthetic oligonucleotides with minor sequence variations. The employed mixed-mode phase shows great flexibility in method development. It has been run in various gradient elution modes, viz. one, two or three parameter (mixed) gradients (altering buffer pH, buffer concentration, and organic modifier) to find optimal elution conditions and gain further insight into retention mechanisms. Compared to ion-pair reversed-phase and mere anion-exchange separation, enhanced selectivities were observed with the mixed-mode phase for 20-23 nucleotide (nt) long oligonucleotides with similar sequences. Oligonucleotides differing by 1, 2 or 3 nucleotides in length could be readily resolved and separation factors for single nucleotide replacements declined in the order Cytosine (C)/Guanine (G)>Adenine (A)/Guanine∼Guanine/Thymine (T)>Adenine/Cytosine∼Cytosine/Thymine>Adenine/Thymine. Selectivities were larger when the modification was at the 3' terminal-end, declined when it was in the middle of the sequence and was smallest when it was located at the 5' terminus. Due to the lower surface area of the 200Å pore size mixed-mode stationary phase compared to the corresponding 100Å material, lower retention times with equal selectivities under milder elution conditions were achievable. Considering high sample loading capacities of the mixed-mode anion-exchanger phase, it should have great potential for chromatographic oligonucleotide separation and purification. Copyright © 2014 Elsevier B.V. All rights reserved.

Study of surface-bonded dicationic ionic liquids as stationary phases for hydrophilic interaction chromatography.

PubMed

Qiao, Lizhen; Li, Hua; Shan, Yuanhong; Wang, Shuangyuan; Shi, Xianzhe; Lu, Xin; Xu, Guowang

2014-02-21

In the present study, several geminal dicationic ionic liquids based on 1,4-bis(3-allylimidazolium)butane and 1,8-bis(3-allylimidazolium)octane in combination with different anions bromide and bis(trifluoromethanesulphonyl)imide were prepared and then bonded to the surface of 3-mercaptopropyl modified silica materials through the "thiol-ene" click chemistry as stationary phases for hydrophilic interaction chromatography (HILIC). Compared with their monocationic analogues, the dicationic ionic liquids stationary phases presented effective retention and good selectivity for typical hydrophilic compounds under HILIC mode with the column efficiency as high as 130,000 plates/m. Moreover, the influence of different alkyl chain spacer between dications and combined anions on the retention behavior and selectivity of the dicationic ionic liquids stationary phases under HILIC mode was displayed. The results indicated that the longer linkage chain would decrease the hydrophilicity and retention on the dicationic ionic liquid stationary phase, and while differently combined anions had no difference due to the exchangeability under the common HILIC mobile phase with buffer salt. Finally, the retention mechanism was investigated by evaluating the effect of chromatographic factors on retention, including the water content in the mobile phase, the mobile phase pH and buffer salt concentration. The results showed that the dicationic ionic liquids stationary phases presented a mixed-mode retention behavior with HILIC mechanism and anion exchange. Copyright © 2014 Elsevier B.V. All rights reserved.

Selective Anion Binding by a Cofacial Binuclear Zinc Complex of a Schiff-Base Pyrrole Macrocycle

PubMed Central

Devoille, Aline M. J.; Richardson, Patricia; Bill, Nathan; Sessler, Jonathan L.; Love, Jason B.

2011-01-01

The synthesis of the new cofacial binuclear zinc complex [Zn2(L)] of a Schiff-base pyrrole macrocycle is reported. It was discovered that the binuclear microenvironment between the two metals of [Zn2(L)] is suited for the encapsulation of anions, leading to the formation of [K(THF)6][Zn2(μ-Cl)(L)].2THF and [Bun4N][Zn2(μ-OH)(L)] which were characterized by X-ray crystallography. Unusually obtuse Zn-X-Zn angles (X=Cl: 150.54(9)° and OH: 157.4(3)°) illustrate the weak character of these interactions and the importance of the cleft pre-organization to stabilize the host. In the absence of added anion, aggregation of [Zn2(L)] was inferred and investigated by successive dilutions and by the addition of coordinating solvents to [Zn2(L)] solutions using NMR spectroscopy as well as isothermal microcalorimetry (ITC). On anion addition, evidence for de-aggregation of [Zn2(L)], combined with the formation of the 1:1 host-guest complex, was observed by NMR spectroscopy and ITC titrations. Furthermore, [Zn2(L)] binds to Cl− selectively in THF as deduced from the ITC analyses, while other halides induce only de-aggregation. These conclusions were reinforced by DFT calculations, which indicated that the binding energies of OH− and Cl− were significantly greater than for the other halides. PMID:21391550

P39-T Analysis of Oligosaccharides by Capillary-Scale High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection (CHPAEC-PAD) and On-Line Electrospray-Ionization Ion-Trap Mass Spectrometry (CHPAEC-ITMS)

PubMed Central

Bruggink, C.; Koeleman, C.; Barreto, V.; Lui, Y.; Pohl, C.; Ingendoh, A.; Wuhrer, M.; Hokke, C.; Deelder, A.

2007-01-01

High-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) is an established technique for selective separation and analysis of underivatized carbohydrates. The miniaturization of chromatographic techniques by means of capillary columns, and on-line coupling to mass spectrometry are critical to the further development of glycan analysis methods that are compatible with the current requirements in clinical settings. A system has been developed based on the Dionex BioLC equipped with a microbore gradient pump with PEEK flow splitter, a FAMOS micro autosampler, a modified electrochemical cell for on-line capillary PAD, and a capillary column (380 μm i.d.) packed with a new type of anion-exchange resin. This system operates with sensitivity in the low femtomol range. In addition, an on-line capillary desalter has been developed to allow direct coupling to the Bruker Esquire 3000 ion-trap mass spectrometer with electrospray ionization interface (ESI-IT-MS). Both systems have been evaluated using oligosaccharide standards as well as urine samples exhibiting various lysosomal oligosaccharide storage diseases. Initial data indicate that the robust and selective anion-exchange system, in combination with ESI-IT-MS for structure confirmation and analysis, provides a powerful platform that complements existing nano/capillary LC-MS methods for analytical determination of oligosaccharides in biological matrices.

The impact of price and nutrition labelling on sugary drink purchases: Results from an experimental marketplace study.

PubMed

Acton, Rachel B; Hammond, David

2018-02-01

To examine the effect of front-of-package (FOP) nutrition labelling and sugary drink taxation on consumer beverage purchases. A total of 675 respondents aged 16 years and older participated in an experimental marketplace study using a 4 × 5 within-between group design. Participants were randomised to one of four labelling conditions (no label; star rating; high sugar symbol; health warning) and completed five within-subject purchase tasks. Beverage prices in each task corresponded to 'tax' conditions: 0%, 10%, 20%, 30% and a variable tax proportional to free sugar level. In each task, participants selected from 20 commercially available beverages; upon conclusion, one of five selections was randomly chosen for purchase. As price increased, participants were significantly less likely to select a sugary drink, and selected drinks with fewer calories and less free sugar (p < 0.001 for all). The overall effect of labelling was not statistically significant, although there was a trend for the 'high sugar' label to reduce the likelihood of selecting a sugary drink (p = 0.11) and encouraging participants to select drinks with less free sugar (p = 0.11). Increasing price was associated with reduced sugary drink purchases. Enhanced FOP labelling results highlight the need for further research to investigate their potential impact. The study adds empirical support for taxation to reduce sugary drink consumption. Copyright © 2017 Elsevier Ltd. All rights reserved.

Legionella phosphatase hydrolyzes phosphatidylinositol 4,5-bisphosphate and inosital triphosphate in human neutrophils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowling, J.N.; Saha, A.K.; Glew, R.H.

1987-05-01

Legionella are facultative intracellular bacterial pathogens which multiply in host phagocytes. L. micdadei cells contain an acid phosphatase (ACP) that blocks superoxide anion production by human neutrophils stimulated with the formylated peptide, fMLP. The possibility that ACP acts by interefering with polyphosphoinositide metabolism and the production of the intracellular second messenger, inositol triphosphate (IP3) was explored. When neutrophil phosphoinositides were labeled with TSP, incubation of the cells with ACP caused an 85% loss of the labeled phosphatidylinositol-4,5-bisphosphate (PIP2) over 2 h. Treatment of (TH)inositol-labeled neutrophils with ACP for 30 min resulted in a 20% decrease of labeled PIP2. Following fMLPmore » stimulation, the fractional reduction in PIP2 and the fractional increase in IP3 was the same in ACP-treated and untreated neutrophils, but the total quantity of IP3 was reduced by ACP pre-treatment. The reduction in IP3 generated following fMLP stimulation seems to be due primarily to the decreased amount of PIP2 available for hydrolysis. However, some loss of IP3 due to direct hydrolysis by ACP cannot be ruled out. The Legionella phosphatase may compromise neutrophil response to the bacteria by hydrolyzing PIP2, the prognitor of IP3, and by hydrolyzing IP3 itself.« less

The evaluation of new and isotopically labeled isoindoline nitroxides and an azaphenalene nitroxide for EPR oximetry

PubMed Central

Khan, Nadeem; Blinco, James P.; Bottle, Steven E.; Hosokawa, Kazuyuki; Swartz, Harold M.; Micallef, Aaron S.

2011-01-01

Isoindoline nitroxides are potentially useful probes for viable biological systems, exhibiting low cytotoxicity, moderate rates of biological reduction and favorable Electron Paramagnetic Resonance (EPR) characteristics. We have evaluated the anionic (5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl; CTMIO), cationic (5-(N,N,N-trimethylammonio)-1,1,3,3-tetramethylisoindolin-2-yloxyl iodide, QATMIO) and neutral (1,1,3,3-tetramethylisoindolin-2-yloxyl; TMIO) nitroxides and their isotopically labeled analogues (2H12- and/or 2H12-15N-labeled) as potential EPR oximetry probes. An active ester analogue of CTMIO, designed to localize intracellularly, and the azaphenalene nitroxide 1,1,3,3-tetramethyl-2,3-dihydro-2-azaphenalen-2-yloxyl (TMAO) were also studied. While the EPR spectra of the unlabeled nitroxides exhibit high sensitivity to O2 concentration, deuteration resulted in a loss of superhyperfine features and a subsequent reduction in O2 sensitivity. Labeling the nitroxides with 15N increased the signal intensity and this may be useful in decreasing the detection limits for in vivo measurements. The active ester nitroxide showed approximately 6% intracellular localization and low cytotoxicity. The EPR spectra of TMAO nitroxide indicated an increased rigidity in the nitroxide ring, due to dibenzo-annulation. PMID:21665499

Electrolyte system strategies for anionic ITP with ESI-MS detection. 3. The ITP spacer technique in moving-boundary systems and configurations with two self-maintained ITP subsystems.

PubMed

Gebauer, Petr; Malá, Zdena; Boček, Petr

2014-03-01

This contribution is the third part of the project on strategies used in the selection and tuning of electrolyte systems for anionic ITP with ESI-MS detection. The strategy presented here is based on the creation of self-maintained ITP subsystems in moving-boundary systems and describes two new principal approaches offering physical separation of analyte zones from their common ITP stack and/or simultaneous selective stacking of two different analyte groups. Both strategic directions are based on extending the number of components forming the electrolyte system by adding a third suitable anion. The first method is the application of the spacer technique to moving-boundary anionic ITP systems, the second method is a technique utilizing a moving-boundary ITP system in which two ITP subsystems exist and move with mutually different velocities. It is essential for ESI detection that both methods can be based on electrolyte systems containing only several simple chemicals, such as simple volatile organic acids (formic and acetic) and their ammonium salts. The properties of both techniques are defined theoretically and discussed from the viewpoint of their applicability to trace analysis by ITP-ESI-MS. Examples of system design for selected model separations of preservatives and pharmaceuticals illustrate the validity of the theoretical model and application potential of the proposed techniques by both computer simulations and experiments. Both new methods enhance the application range of ITP-MS and may be beneficial particularly for complex multicomponent samples or for analytes with identical molecular mass. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A PEGylated fluorescent turn-on sensor for detecting fluoride ions in totally aqueous media and its imaging in live cells.

PubMed

Zheng, Fangyuan; Zeng, Fang; Yu, Changmin; Hou, Xianfeng; Wu, Shuizhu

2013-01-14

Owing to the considerable significance of fluoride anions for health and environmental issues, it is of great importance to develop methods that can rapidly, sensitively and selectively detect the fluoride anion in aqueous media and biological samples. Herein, we demonstrate a robust fluorescent turn-on sensor for detecting the fluoride ion in a totally aqueous solution. In this study, a biocompatible hydrophilic polymer poly(ethylene glycol) (PEG) is incorporated into the sensing system to ensure water solubility and to enhance biocompatibility. tert-Butyldiphenylsilyl (TBDPS) groups were then covalently introduced onto the fluorescein moiety, which effectively quenched the fluorescence of the sensor. Upon addition of fluoride ion, the selective fluoride-mediated cleavage of the Si-O bond leads to the recovery of the fluorescein moiety, resulting in a dramatic increase in fluorescence intensity under visible light excitation. The sensor is responsive and highly selective for the fluoride anion over other common anions; it also exhibits a very low detection limit of 19 ppb. In addition, this sensor is operative in some real samples such as running water, urine, and serum and can accurately detect fluoride ions in these samples. The cytotoxicity of the sensor was determined to be Grade I toxicity according to United States Pharmacopoeia and ISO 10993-5, suggesting the very low cytotoxicity of the sensor. Moreover, it was found that the senor could be readily internalized by both HeLa and L929 cells and the sensor could be utilized to track fluoride level changes inside the cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Revealing mechanisms of selective, concentration-dependent potentials of 4-hydroxy-2-nonenal to induce apoptosis in cancer cells through inactivation of membrane-associated catalase.

PubMed

Bauer, Georg; Zarkovic, Neven

2015-04-01

Tumor cells generate extracellular superoxide anions and are protected against superoxide anion-mediated intercellular apoptosis-inducing signaling by the expression of membrane-associated catalase. 4-Hydroxy-2-nonenal (4-HNE), a versatile second messenger generated during lipid peroxidation, has been shown to induce apoptosis selectively in malignant cells. The findings described in this paper reveal the strong, concentration-dependent potential of 4-HNE to specifically inactivate extracellular catalase of tumor cells both indirectly and directly and to consequently trigger apoptosis in malignant cells through superoxide anion-mediated intercellular apoptosis-inducing signaling. Namely, 4-HNE caused apoptosis selectively in NOX1-expressing tumor cells through inactivation of their membrane-associated catalase, thus reactivating subsequent intercellular signaling through the NO/peroxynitrite and HOCl pathways, followed by the mitochondrial pathway of apoptosis. Concentrations of 4-HNE of 1.2 µM and higher directly inactivated membrane-associated catalase of tumor cells, whereas at lower concentrations, 4-HNE triggered a complex amplificatory pathway based on initial singlet oxygen formation through H2O2 and peroxynitrite interaction. Singlet-oxygen-dependent activation of the FAS receptor and caspase-8 increased superoxide anion generation by NOX1 and amplification of singlet oxygen generation, which allowed singlet-oxygen-dependent inactivation of catalase. 4-HNE and singlet oxygen cooperate in complex autoamplificatory loops during this process. The finding of these novel anticancer pathways may be useful for understanding the role of 4-HNE in the control of malignant cells and for the optimization of ROS-dependent therapeutic approaches including antioxidant treatments. Copyright © 2015 Elsevier Inc. All rights reserved.

Selective capture of iodide from solutions by microrosette-like δ-Bi₂O₃.

PubMed

Liu, Long; Liu, Wei; Zhao, Xiaoliang; Chen, Daimei; Cai, Rongsheng; Yang, Weiyou; Komarneni, Sridhar; Yang, Dongjiang

2014-09-24

Radioactive iodine isotopes that are produced in nuclear power plants and used in medical research institutes could be a serious threat to the health of many people if accidentally released to the environment because the thyroid gland can absorb and concentrate them from a liquid. For this reason, uptake of iodide anions was investigated on microrosette-like δ-Bi2O3 (MR-δ-Bi2O3). The MR-δ-Bi2O3 adsorbent showed a very high uptake capacity of 1.44 mmol g(-1) by forming insoluble Bi4I2O5 phase. The MR-δ-Bi2O3 also displayed fast uptake kinetics and could be easily separated from a liquid after use because of its novel morphology. In addition, the adsorbent showed excellent selectivity for I(-) anions in the presence of large concentrations of competitive anions such as Cl(-) and CO3(2-), and could work in a wide pH range of 4-11. This study led to a new and highly efficient Bi-based adsorbent for iodide capture from solutions.

Direct and Quantitative Characterization of Dynamic Ligand Exchange between Coordination-Driven Self-Assembled Supramolecular Polygons

PubMed Central

Zheng, Yao-Rong; Stang, Peter J.

2009-01-01

The direct observation of dynamic ligand exchange beween Pt-N coordination-driven self-assembled supramolecular polygons (triangles and rectangles) has been achieved using stable isotope labeling (1H/2D) of the pyridyl donors and electrospray ionization mass spectrometry (ESI-MS) together with NMR spectroscopy. Both the thermodynamic and kinetic aspects of such exchange processes have been established based on quantitative mass spectral results. Further investigation showed that the exchange is highly dependent on experimental conditions such as temperature, solvent, and the counter anions. PMID:19243144

Selective labeling of a single organelle by using two-photon conversion of a photoconvertible fluorescent protein

NASA Astrophysics Data System (ADS)

Watanabe, Wataru; Shimada, Tomoko; Matsunaga, Sachihiro; Kurihara, Daisuke; Arimura, Shin-ichi; Tsutsumi, Nobuhiro; Fukui, Kiichi; Itoh, Kazuyoshi

2008-02-01

We present space-selective labeling of organelles by using two-photon conversion of a photoconvertible fluorescent protein with near-infrared femtosecond laser pulses. Two-photon excitation of photoconvertible fluorescent-protein, Kaede, enables space-selective labeling of organelles. We alter the fluorescence of target mitochondria in a tobacco BY-2 cell from green to red by focusing femtosecond laser pulses with a wavelength of 750 nm.

Tuning a Protein-Labeling Reaction to Achieve Highly Site Selective Lysine Conjugation.

PubMed

Pham, Grace H; Ou, Weijia; Bursulaya, Badry; DiDonato, Michael; Herath, Ananda; Jin, Yunho; Hao, Xueshi; Loren, Jon; Spraggon, Glen; Brock, Ansgar; Uno, Tetsuo; Geierstanger, Bernhard H; Cellitti, Susan E

2018-04-16

Activated esters are widely used to label proteins at lysine side chains and N termini. These reagents are useful for labeling virtually any protein, but robust reactivity toward primary amines generally precludes site-selective modification. In a unique case, fluorophenyl esters are shown to preferentially label human kappa antibodies at a single lysine (Lys188) within the light-chain constant domain. Neighboring residues His189 and Asp151 contribute to the accelerated rate of labeling at Lys188 relative to the ≈40 other lysine sites. Enriched Lys188 labeling can be enhanced from 50-70 % to >95 % by any of these approaches: lowering reaction temperature, applying flow chemistry, or mutagenesis of specific residues in the surrounding protein environment. Our results demonstrated that activated esters with fluoro-substituted aromatic leaving groups, including a fluoronaphthyl ester, can be generally useful reagents for site-selective lysine labeling of antibodies and other immunoglobulin-type proteins. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrically Driven Ion Separations in Permeable Membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruening, Merlin

2017-04-21

Membranes are attractive for a wide range of separations due to their low energy costs and continuous operation. To achieve practical fluxes, most membranes consist of a thin, selective skin on a highly permeable substrate that provides mechanical strength. Thus, this project focused on creating new methods for forming highly selective ultrathin skins as well as modeling transport through these coatings to better understand their unprecedented selectivities. The research explored both gas and ion separations, and the latter included transport due to concentration, pressure and electrical potential gradients. This report describes a series of highlights of the research and thenmore » provides a complete list of publications supported by the grant. These publications have been cited more than 4000 times. Perhaps the most stunning finding is the recent discovery of monovalent/divalent cation and anion selectivities around 1000 when modifying cation- and anion-exchange membranes with polyelectrolyte multilayers (PEMs). This discovery builds on many years of exciting research. (Citation numbers refer to the journal articles in the bibliography.)« less

Relationships among grocery nutrition label users and consumers' attitudes and behavior toward restaurant menu labeling.

PubMed

Roseman, Mary G; Mathe-Soulek, Kimberly; Higgins, Joseph A

2013-12-01

In the United States (US), based on the 2010 Affordable Care Act, restaurant chains and similar retail food establishments with 20 or more locations are required to begin implementing calorie information on their menus. As enacting of the law begins, it is important to understand its potential for improving consumers' healthful behaviors. Therefore, the objective of this study was to explore relationships among users of grocery nutrition labels and attitudes toward restaurant menu labeling, along with the caloric content of their restaurant menu selection. Study participants were surveyed and then provided identical mock restaurant menus with or without calories. Results found that participants who used grocery nutrition labels and believed they would make healthy menu selections with nutrition labels on restaurant menus made healthier menu selections, regardless of whether the menu displayed calories or not. Consumers' nutrition knowledge and behaviors gained from using grocery nutrition labels and consumers' desire for restaurants to provide nutrition menu labels have a positive effect on their choosing healthful restaurant menu items. Copyright © 2013 Elsevier Ltd. All rights reserved.

Simultaneous determination of inorganic anions and cations by supercritical fluid chromatography using evaporative light scattering detection.

PubMed

Foulon, Catherine; Di Giulio, Pauline; Lecoeur, Marie

2018-01-26

Supercritical fluid chromatography (SFC) is commonly used for the analysis of non-polar compounds, but remains poorly explored for the separation of polar and ionized molecules. In this paper, SFC has been investigated for the separation of 14 inorganic ions sampled in aqueous solutions. Four polar stationary phases were first screened using CO 2 -methanol-based mobile phases containing water or different acidic or basic additives, in order to select the most efficient conditions for the simultaneous retention of inorganic cations and anions and to favor their detection using evaporative light scattering detector (ELSD). Orthogonal selectivity was obtained depending on the stationary phase used: whereas anions are less retained on HILIC stationary phase, 2-ethylpyridine (2-EP) stationary phase exhibits strong interaction for anions. Best results were obtained under gradient elution mode using a 2-EP stationary phase and by adding 0.2% triethylamine in the CO 2 -methanol-based mobile phase. The composition of the injection solvent was also investigated. The results showed that a methanolic sample containing a percentage of water not exceeding 20% does not affect the analytical performances obtained on 2-EP. Moreover, the presence of triethylamine in the injection solvent contributes to eliminate peaks shoulders. Among the 14 inorganic ions tested, three cations (Li + , Ca 2+ and Mg 2+ ) and five anions (Cl - , Br - , NO 3 - , I - , SCN - ) were totally resolved in 15 min. NO 3 - and NO 2 - still coeluted in the final optimized conditions. The other investigated ions were either strongly retained on the stationary phase or not detected by the ELSD. Copyright © 2017 Elsevier B.V. All rights reserved.

Identification of inorganic ions in post-blast explosive residues using portable CE instrumentation and capacitively coupled contactless conductivity detection.

PubMed

Hutchinson, Joseph P; Johns, Cameron; Breadmore, Michael C; Hilder, Emily F; Guijt, Rosanne M; Lennard, Chris; Dicinoski, Greg; Haddad, Paul R

2008-11-01

Novel CE methods have been developed on portable instrumentation adapted to accommodate a capacitively coupled contactless conductivity detector for the separation and sensitive detection of inorganic anions and cations in post-blast explosive residues from homemade inorganic explosive devices. The methods presented combine sensitivity and speed of analysis for the wide range of inorganic ions used in this study. Separate methods were employed for the separation of anions and cations. The anion separation method utilised a low conductivity 70 mM Tris/70 mM CHES aqueous electrolyte (pH 8.6) with a 90 cm capillary coated with hexadimethrine bromide to reverse the EOF. Fifteen anions could be baseline separated in 7 min with detection limits in the range 27-240 microg/L. A selection of ten anions deemed most important in this application could be separated in 45 s on a shorter capillary (30.6 cm) using the same electrolyte. The cation separation method was performed on a 73 cm length of fused-silica capillary using an electrolyte system composed of 10 mM histidine and 50 mM acetic acid, at pH 4.2. The addition of the complexants, 1 mM hydroxyisobutyric acid and 0.7 mM 18-crown-6 ether, enhanced selectivity and allowed the separation of eleven inorganic cations in under 7 min with detection limits in the range 31-240 microg/L. The developed methods were successfully field tested on post-blast residues obtained from the controlled detonation of homemade explosive devices. Results were verified using ion chromatographic analyses of the same samples.

Controlling the Charge State and Redox Properties of Supported Polyoxometalates via Soft Landing of Mass Selected Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunaratne, Kalupathirannehelage Don D.; Johnson, Grant E.; Andersen, Amity

2014-12-04

We investigate the controlled deposition of Keggin polyoxometalate (POM) anions, PMo12O403- and PMo12O402-, onto different self-assembled monolayer (SAM) surfaces via soft landing of mass-selected ions. Utilizing in situ infrared reflection absorption spectroscopy (IRRAS), ex situ cyclic voltammetry (CV) and electronic structure calculations, we examine the structure and charge retention of supported multiply-charged POM anions and characterize the redox properties of the modified surfaces. SAMs of alkylthiol (HSAM), perfluorinated alkylthiol (FSAM), and alkylthiol terminated with NH3+ functional groups (NH3+SAM) are chosen as model substrates for soft landing to examine the factors which influence the immobilization and charge retention of multiply chargedmore » anionic molecules. The distribution of charge states of POMs on different SAM surfaces are determined by comparing the IRRAS spectra with vibrational spectra calculated using density functional theory (DFT). In contrast to the results obtained previously for multiply charged cations, soft landed anions are found to retain charge on all three SAM surfaces. This charge retention is attributed to the substantial electron binding energy of the POM anions. Investigation of redox properties by CV reveals that, while surfaces prepared by soft landing exhibit similar features to those prepared by adsorption of POM from solution, the soft landed POM2- has a pronounced shift in oxidation potential compared to POM3- for one of the redox couples. These results demonstrate that ion soft landing is uniquely suited for precisely controlled preparation of substrates with specific electronic and chemical properties that cannot be achieved using conventional deposition techniques.« less

Conformation-selective resonant photoelectron imaging from dipole-bound states of cold 3-hydroxyphenoxide

NASA Astrophysics Data System (ADS)

Zhu, Guo-Zhu; Huang, Dao-Ling; Wang, Lai-Sheng

2017-07-01

We report a photoelectron imaging and photodetachment study of cryogenically cooled 3-hydroxyphenoxide (3HOP) anions, m-HO(C6H4)O-. In a previous preliminary study, two conformations of the cold 3HOP anions with different dipole bound states were observed [D. L. Huang et al., J. Phys. Chem. Lett. 6, 2153 (2015)]. Five near-threshold vibrational resonances were revealed in the photodetachment spectrum from the dipole-bound excited states of the two conformations. Here, we report a more extensive investigation of the two conformers with observation of thirty above-threshold vibrational resonances in a wide spectral range between 18 850 and 19 920 cm-1 (˜1000 cm-1 above the detachment thresholds). By tuning the detachment laser to the vibrational resonances in the photodetachment spectrum, high-resolution conformation-selective resonant photoelectron images are obtained. Using information of the autodetachment channels and theoretical vibrational frequencies, we are able to assign the resonant peaks in the photodetachment spectrum: seventeen are assigned to vibrational levels of anti-3HOP, eight to syn-3HOP, and five to overlapping vibrational levels of both conformers. From the photodetachment spectrum and the conformation-selective resonant photoelectron spectra, we have obtained fourteen fundamental vibrational frequencies for the neutral syn- and anti-m-HO(C6H4)Oṡ radicals. The possibility to produce conformation-selected neutral beams using resonant photodetachment via dipole-bound excited states of anions is discussed.

Advances in stable isotope assisted labeling strategies with information science.

PubMed

Kigawa, Takanori

2017-08-15

Stable-isotope (SI) labeling of proteins is an essential technique to investigate their structures, interactions or dynamics by nuclear magnetic resonance (NMR) spectroscopy. The assignment of the main-chain signals, which is the fundamental first step in these analyses, is usually achieved by a sequential assignment method based on triple resonance experiments. Independently of the triple resonance experiment-based sequential assignment, amino acid-selective SI labeling is beneficial for discriminating the amino acid type of each signal; therefore, it is especially useful for the signal assignment of difficult targets. Various combinatorial selective labeling schemes have been developed as more sophisticated labeling strategies. In these strategies, amino acids are represented by combinations of SI labeled samples, rather than simply assigning one amino acid to one SI labeled sample as in the case of conventional amino acid-selective labeling. These strategies have proven to be useful for NMR analyses of difficult proteins, such as those in large complex systems, in living cells, attached or integrated into membranes, or with poor solubility. In this review, recent advances in stable isotope assisted labeling strategies will be discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

Nanomolar colorimetric quantitative detection of Fe3 + and PPi with high selectivity

NASA Astrophysics Data System (ADS)

Li, Zhanxian; Li, Haixia; Shi, Caixia; Yu, Mingming; Wei, Liuhe; Ni, Zhonghai

2016-04-01

A novel rhodamine and 8-hydroxyquinoline-based derivative was synthesized, which is shown to act as a colorimetric chemosensor for Fe3 + in aqueous solution with high selectivity over various environmentally and biologically relevant metal ions and anions with a distinct color change from colorless to pink in very fast response time (< 1 min). Fe3 + can be detected quantitatively in the concentration range from 6.7 to 16 μM and the detection limit (LOD) on UV-vis response of the sensor can be as low as 15 nM. The 'in situ' prepared Fe3 + complex (1 ṡ Fe) showed high selectivity toward PPi against many common anions, and sensitivity (the LOD can be as low as 71 nM). In addition, both the chemosensor and the 'in situ' prepared Fe3 + complex are reusable for the detection of Fe3 + and PPi respectively.

Parents' meal choices for their children at fast food and family restaurants with different menu labeling presentations

PubMed Central

2018-01-01

BACKGROUND/OBJECTIVES This study examined the effect of nutrition labeling formats on parents' food choices for their children at different restaurant types. SUBJECTS/METHODS An online survey was conducted with 1,980 parents of children aged 3–12 years. Participants were randomly assigned to fast food or family restaurant scenarios, and one of four menu stimuli conditions: no labeling, low-calorie symbol (symbol), numeric value (numeric), and both low-calorie symbol and numeric value (symbol + numeric). Participants selected menu items for their children. Menu choices and total calories were compared by nutrition labeling formats in each type of the restaurant. RESULTS Low-calorie item selections were scored and a two-way analysis of variance (ANOVA) was conducted for an interaction effect between restaurant and labeling type. In the fast food restaurant group, parents presented with low-calorie symbols selected the lowest calorie items more often than those not presented with the format. Parents in the symbol + numeric condition selected significantly fewer calories (653 kcal) than those in the no labeling (677 kcal) or numeric conditions (674 kcal) (P = 0.006). In the family restaurant group, no significant difference were observed among different labeling conditions. A significant interaction between restaurant and labeling type on low-calorie selection score (F = 6.03, P < 0.01) suggests that the effect of nutrition labeling format interplays with restaurant type to jointly affect parents' food choices for their children. CONCLUSIONS The provision of easily interpretable nutritional information format at fast food restaurants may encourage healthier food choices of parents for their children; however, the effects were negligible at family restaurants. PMID:29854330

Glutamate transporter-associated anion channels adjust intracellular chloride concentrations during glial maturation.

PubMed

Untiet, Verena; Kovermann, Peter; Gerkau, Niklas J; Gensch, Thomas; Rose, Christine R; Fahlke, Christoph

2017-02-01

Astrocytic volume regulation and neurotransmitter uptake are critically dependent on the intracellular anion concentration, but little is known about the mechanisms controlling internal anion homeostasis in these cells. Here we used fluorescence lifetime imaging microscopy (FLIM) with the chloride-sensitive dye MQAE to measure intracellular chloride concentrations in murine Bergmann glial cells in acute cerebellar slices. We found Bergmann glial [Cl - ] int to be controlled by two opposing transport processes: chloride is actively accumulated by the Na + -K + -2Cl - cotransporter NKCC1, and chloride efflux through anion channels associated with excitatory amino acid transporters (EAATs) reduces [Cl - ] int to values that vary upon changes in expression levels or activity of these channels. EAATs transiently form anion-selective channels during glutamate transport, and thus represent a class of ligand-gated anion channels. Age-dependent upregulation of EAATs results in a developmental chloride switch from high internal chloride concentrations (51.6 ± 2.2 mM, mean ± 95% confidence interval) during early development to adult levels (35.3 ± 0.3 mM). Simultaneous blockade of EAAT1/GLAST and EAAT2/GLT-1 increased [Cl - ] int in adult glia to neonatal values. Moreover, EAAT activation by synaptic stimulations rapidly decreased [Cl - ] int . Other tested chloride channels or chloride transporters do not contribute to [Cl - ] int under our experimental conditions. Neither genetic removal of ClC-2 nor pharmacological block of K + -Cl - cotransporter change resting Bergmann glial [Cl - ] int in acute cerebellar slices. We conclude that EAAT anion channels play an important and unexpected role in adjusting glial intracellular anion concentration during maturation and in response to cerebellar activity. GLIA 2017;65:388-400. © 2016 Wiley Periodicals, Inc.

Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors

PubMed Central

Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz; Riahi, Siavash

2008-01-01

Ionophore incorporated PVC membrane sensors are well-established analytical tools routinely used for the selective and direct measurement of a wide variety of different ions in complex biological and environmental samples. Potentiometric sensors have some outstanding advantages including simple design and operation, wide linear dynamic range, relatively fast response and rational selectivity. The vital component of such plasticized PVC members is the ionophore involved, defining the selectivity of the electrodes' complex formation. Molecular recognition causes the formation of many different supramolecules. Different types of supramolecules, like calixarenes, cyclodextrins and podands, have been used as a sensing material in the construction of ion selective sensors. Schiff's bases and crown ethers, which feature prominently in supramolecular chemistry, can be used as sensing materials in the construction of potentiometric ion selective electrodes. Up to now, more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anion complexes will be described. Liquid membrane sensors based on Schiff's bases and crown ethers will then be discussed. PMID:27879786

A pyrophosphate-responsive gadolinium(III) MRI contrast agent.

PubMed

Surman, Andrew J; Bonnet, Célia S; Lowe, Mark P; Kenny, Gavin D; Bell, Jimmy D; Tóth, Eva; Vilar, Ramon

2011-01-03

This study shows that the relaxivity and optical properties of functionalised lanthanide-DTPA-bis-amide complexes (lanthanide=Gd(3+) and Eu(3+) , DTPA=diethylene triamine pentaacetic acid) can be successfully modulated by addition of specific anions, without direct Ln(3+) /anion coordination. Zinc(II)-dipicolylamine moieties, which are known to bind strongly to phosphates, were introduced in the amide "arms" of these ligands, and the interaction of the resulting Gd-Zn(2) complexes with a range of anions was screened by using indicator displacement assays (IDAs). Considerable selectivity for polyphosphorylated species (such as pyrophosphate and adenosine-5'-triphosphate (ATP)) over a range of other anions (including monophosphorylated anions) was apparent. In addition, we show that pyrophosphate modulates the relaxivity of the gadolinium(III) complex, this modulation being sufficiently large to be observed in imaging experiments. To establish the binding mode of the pyrophosphate and gain insight into the origin of the relaxometric modulation, a series of studies including UV/Vis and emission spectroscopy, luminescence lifetime measurements in H(2) O and D(2) O, (17) O and (31) P NMR spectroscopy and nuclear magnetic resonance dispersion (NMRD) studies were carried out. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced liquid-liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate-nitrate exchange selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moyer, Bruce A; Sloop Jr, Frederick; Fowler, Christopher J

2010-01-01

When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and -decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1more » receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.« less

Can collision-induced negative-ion fragmentations of [M-H](-) anions be used to identify phosphorylation sites in peptides?

PubMed

Tran, T T Nha; Wang, Tianfang; Hack, Sandra; Hoffmann, Peter; Bowie, John H

2011-12-15

A joint experimental and theoretical investigation of the fragmentation behaviour of energised [M-H](-) anions from selected phosphorylated peptides has confirmed some of the most complex rearrangement processes yet to be reported for peptide negative ions. In particular: pSer and pThr (like pTyr) may transfer phosphate groups to C-terminal carboxyl anions and to the carboxyl anion side chains of Asp and Glu, and characteristic nucleophilic/cleavage reactions accompany or follow these rearrangements. pTyr may transfer phosphate to the side chains of Ser and Thr. The reverse reaction, namely transfer of a phosphate group from pSer or pThr to Tyr, is energetically unfavourable in comparison. pSer can transfer phosphate to a non-phosphorylated Ser. The non-rearranged [M-H](-) species yields more abundant product anions than its rearranged counterpart. If a peptide containing any or all of Ser, Thr and Tyr is not completely phosphorylated, negative-ion cleavages can determine the number of phosphated residues, and normally the positions of Ser, Thr and Tyr, but not which specific residues are phosphorylated. This is in accord with comments made earlier by Lehmann and coworkers. Copyright © 2011 John Wiley & Sons, Ltd.

Synthesis and selective IR absorption properties of iminodiacetic-acid intercalated MgAl-layered double hydroxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Lijing; Xu Xiangyu; Evans, David G.

2010-05-15

An MgAl-NO{sub 3}-layered double hydroxide (LDH) precursor has been prepared by a method involving separate nucleation and aging steps (SNAS). Reaction with iminodiacetic acid (IDA) under weakly acidic conditions led to the replacement of the interlayer nitrate anions by iminodiacetic acid anions. The product was characterized by XRD, FT-IR, TG-DTA, ICP, elemental analysis and SEM. The results show that the original interlayer nitrate anions of LDHs precursor were replaced by iminodiacetic acid anions and that the resulting intercalation product MgAl-IDA-LDH has an ordered crystalline structure. MgAl-IDA-LDH was mixed with low density polyethylene (LDPE) using a masterbatch method. LDPE films filledmore » with MgAl-IDA-LDH showed a higher mid to far infrared absorption than films filled with MgAl-CO{sub 3}-LDH in the 7-25 {mu}m range, particularly in the key 9-11 {mu}m range required for application in agricultural plastic films. - Graphical abstract: Intercalation of iminodiacetic acid (IDA) anions in a MgAl-NO{sub 3}-layered double hydroxide host leads to an enhancement of its infrared absorbing ability for application in agricultural plastic films.« less

Electron interaction with phosphate cytidine oligomer dCpdC: base-centered radical anions and their electronic spectra.

PubMed

Gu, Jiande; Wang, Jing; Leszczynski, Jerzy

2014-01-30

Computational chemistry approach was applied to explore the nature of electron attachment to cytosine-rich DNA single strands. An oligomer dinucleoside phosphate deoxycytidylyl-3',5'-deoxycytidine (dCpdC) was selected as a model system for investigations by density functional theory. Electron distribution patterns for the radical anions of dCpdC in aqueous solution were explored. The excess electron may reside on the nucleobase at the 5' position (dC(•-)pdC) or at the 3' position (dCpdC(•-)). From comparison with electron attachment to the cytosine related DNA fragments, the electron affinity for the formation of the cytosine-centered radical anion in DNA is estimated to be around 2.2 eV. Electron attachment to cytosine sites in DNA single strands might cause perturbations of local structural characteristics. Visible absorption spectroscopy may be applied to validate computational results and determine experimentally the existence of the base-centered radical anion. The time-dependent DFT study shows the absorption around 550-600 nm for the cytosine-centered radical anions of DNA oligomers. This indicates that if such species are detected experimentally they would be characterized by a distinctive color.

Elusive anion growth in Titan's atmosphere: Low temperature kinetics of the C3N- + HC3N reaction

NASA Astrophysics Data System (ADS)

Bourgalais, Jérémy; Jamal-Eddine, Nour; Joalland, Baptiste; Capron, Michael; Balaganesh, Muthiah; Guillemin, Jean-Claude; Le Picard, Sébastien D.; Faure, Alexandre; Carles, Sophie; Biennier, Ludovic

2016-06-01

Ion chemistry appears to be deeply involved in the formation of heavy molecules in the upper atmosphere of Titan. These large species form the seeds of the organic aerosols responsible for the opaque haze surrounding the biggest satellite of Saturn. The chemical pathways involving individual anions remain however mostly unknown. The determination of the rates of the elementary reactions with ions and the identification of the products are essential to the progress in our understanding of Titan's upper atmosphere. We have taken steps in that direction through the investigation of the low temperature reactivity of C3N- , which was tentatively identified in the spectra measured by the CAPS-ELS instrument of the Cassini spacecraft during its high altitude flybys. The reaction of this anion with HC3N, one of the most abundant trace organics in the atmosphere, has been studied over the 49-294 K temperature range in uniform supersonic flows using the CRESU technique. The proton transfer is found to be the main exit channel (>91%) of the C315N- + HC3N reaction. It remains however indistinguishable with the non-isotopically labeled C314N- reactant. The T - 1 / 2 temperature dependence of this proton transfer reaction and its global rate are reasonably well reproduced theoretically using an average dipole orientation model. A minor exit channel, reactive detachment (< 9%), has also been uncovered, although the nature of the neutral products has not been determined. It is concluded that the C314N- + HC3N reaction cannot contribute to the growth of molecular anions in the upper atmosphere of Titan. Due to the low branching into the neutral exit channel, it cannot contribute either to the growth of neutrals even assuming a complete mass transfer.

High CO2 absorption capacity by chemisorption at cations and anions in choline-based ionic liquids.

PubMed

Bhattacharyya, Shubhankar; Filippov, Andrei; Shah, Faiz Ullah

2017-11-29

The effect of CO 2 absorption on the aromaticity and hydrogen bonding in ionic liquids is investigated. Five different ionic liquids with choline based cations and aprotic N-heterocyclic anions were synthesized. Purity and structures of the synthesized ionic liquids were characterized by 1 H and 13 C NMR spectroscopy. CO 2 capture performance was studied at 20 °C and 40 °C under three different pressures (1, 3, 6 bar). The IL [N 1,1,6,2OH ][4-Triz] showed the highest CO 2 capture capacity (28.6 wt%, 1.57 mol of CO 2 per mol of the IL, 6.48 mol of CO 2 per kg of the ionic liquid) at 20 °C and 1 bar. The high CO 2 capture capacity of the [N 1,1,6,2OH ][4-Triz] IL is due to the formation of carbonic acid (-OCO 2 H) together with carbamate by participation of the -OH group of the [N 1,1,6,2OH ] + cation in the CO 2 capture process. The structure of the adduct formed by CO 2 reaction with the IL [N 1,1,6,2OH ][4-Triz] was probed by using IR, 13 C NMR and 1 H- 13 C HMBC NMR experiments utilizing 13 C labeled CO 2 gas. 1 H and 13 C PFG NMR studies were performed before and after CO 2 absorption to explore the effect of cation-anion structures on the microscopic ion dynamics in ILs. The ionic mobility was significantly increased after CO 2 reaction due to lowering of aromaticity in the case of ILs with aromatic N-heterocyclic anions.

Nanoengineered field induced charge separation membranes manufacture thereof

DOEpatents

O'Brien, Kevin C.; Haslam, Jeffery J.; Bourcier, William L.; Floyd, III, William Clary

2016-08-02

A device according to one embodiment includes a porous membrane having a surface charge and pore configuration characterized by a double layer overlap effect being present in pores of the membrane, where the porous membrane includes functional groups that preferentially interact with either cations or anions. A device according to another embodiment includes a porous membrane having a surface charge in pores thereof sufficient to impart anion or cation selectivity in the pores. Additional devices, systems and methods are also presented.

Aqueous Sulfate Separation by Sequestration of [(SO 4) 2(H 2O) 4] 4 Clusters within Highly Insoluble Imine-Linked Bis-Guanidinium Crystals

DOE PAGES

Custelcean, Radu; Williams, Neil J.; Seipp, Charles A.; ...

2015-12-18

Quantitative removal of sulfate from seawater was achieved by selective crystallization of the anion with a bis(guanidinium) ligand self-assembled in situ through imine condensation of simple components. The resulting crystalline salt has an exceptionally low aqueous solubility, on a par with BaSO 4. Single-crystal X-ray diffraction analysis revealed pairs of sulfate anions clustered together with four water molecules within the crystals.

Removal of Pertechnetate-Related Oxyanions from Solution Using Functionalized Hierarchical Porous Frameworks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Debasis; Elsaidi, Sameh K.; Aguila, Briana

2016-10-20

Efficient and cost-effective removal of radioactive pertechnetate anions from nuclear waste is a key challenge to mitigate long-term nuclear waste storage issues. Traditional materials such as resins and layered double hydroxides (LDHs) were evaluated for their pertechnetate or perrhenate (the non-radioactive surrogate) removal capacity, but there is room for improvement in terms of capacity, selectivity and kinetics. A series of functionalized hierarchical porous frameworks were evaluated for their perrhenate removal capacity in the presence of other competing anions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yan; Dyck, Jeffrey; Graham, Todd

Oil-soluble phosphonium-based ionic liquids (ILs) have recently been reported as potential ashless lubricant additives. This study is to expand the IL chemistry envelope and to achieve fundamental correlations between the ion structures and ILs’ physiochemical and tribological properties. Here we present eight ILs containing two different phosphonium cations and seven different anions from three groups: organophosphate, carboxylate, and sulfonate. The oil solubility of ILs seems largely governed by the IL molecule size and structure complexity. When used as oil additives, the ranking of effectiveness in wear protection for the anions are: organophosphate > carboxylate > sulfonate. All selected ILs outperformedmore » a commercial ashless anti-wear additive. Surface characterization from the top and the cross-section revealed the nanostructures and compositions of the tribo-films formed by the ILs. Some fundamental insights were achieved: branched and long alkyls improve the IL’s oil solubility, anions of a phosphonium-phosphate IL contribute most phosphorus in the tribofilm, and carboxylate anions, though free of P, S, N, or halogen, can promote the formation of an anti-wear tribofilm.« less

New turn-on fluorescent and colorimetric probe for cyanide detection based on BODIPY-salicylaldehyde and its application in cell imaging.

PubMed

Sukato, Rangsarit; Sangpetch, Nuanphan; Palaga, Tanapat; Jantra, Suthikorn; Vchirawongkwin, Viwat; Jongwohan, Chanantida; Sukwattanasinitt, Mongkol; Wacharasindhu, Sumrit

2016-08-15

Development of cyanide sensor is important as the anion is harmful to human health and the environment. Herein, a new colorimetric and fluorescent probe GSB based on boron dipyrrole-methene (BODIPY) containing salicylaldehyde group for cyanide detection has been reported. GSB undergoes exclusive colorimetric change from orange to colorless and exhibits selective fluorescence turn-on at 504nm upon the addition of cyanide. Other 13 anions give almost no interference under physiological condition. Detection limit of the new cyanide-sensing GSB is 0.88μM, which is below World Health Organization (WHO) recommended level in drinking water. A calculation by density functional theory (DFT) shows suppression of photoinduced electron transfer (PET) mechanism along with the interruption of π-conjugation between salicylaldehyde and BODIPY core by cyanide anion. Cell imaging studies demonstrated that GSB is compatible and capable of sensing cyanide anion in living cells. Copyright © 2016 Elsevier B.V. All rights reserved.

Does lipophilicity affect the effectiveness of a transmembrane anion transporter? Insight from squaramido-functionalized bis(choloyl) conjugates.

PubMed

Li, Zhi; Deng, Li-Qun; Chen, Jin-Xiang; Zhou, Chun-Qiong; Chen, Wen-Hua

2015-12-28

Six squaramido-functionalized bis(choloyl) conjugates were synthesized and fully characterized on the basis of NMR ((1)H and (13)C) and ESI MS (LR and HR) data. Their transmembrane anionophoric activity was investigated in detail by means of chloride ion selective electrode technique and pyranine assay. The data indicate that this set of compounds is capable of promoting the transmembrane transport of anions presumably via proton/anion symport and anion exchange processes, and that lipophilicity in terms of clog P from 3.90 to 8.32 affects the apparent ion transport rate in a concentration-dependent fashion. Detailed kinetic analysis on the data obtained from both the chloride efflux and pH discharge experiments reveals that there may exist an optimum clog P range for the intrinsic ion transport rate. However, lipophilicity exhibits little effect on the effectiveness of this set of compounds in terms of either k2/Kdiss or EC50 values.

Hyperthermal (1-100 eV) nitrogen ion scattering damage to D-ribose and 2-deoxy-D-ribose films.

PubMed

Deng, Zongwu; Bald, Ilko; Illenberger, Eugen; Huels, Michael A

2007-10-14

Highly charged heavy ion traversal of a biological medium can produce energetic secondary fragment ions. These fragment ions can in turn cause collisional and reactive scattering damage to DNA. Here we report hyperthermal (1-100 eV) scattering of one such fragment ion (N(+)) from biologically relevant sugar molecules D-ribose and 2-deoxy-D-ribose condensed on polycrystalline Pt substrate. The results indicate that N(+) ion scattering at kinetic energies down to 10 eV induces effective decomposition of both sugar molecules and leads to the desorption of abundant cation and anion fragments. Use of isotope-labeled molecules (5-(13)C D-ribose and 1-D D-ribose) partly reveals some site specificity of the fragment origin. Several scattering reactions are also observed. Both ionic and neutral nitrogen atoms abstract carbon from the molecules to form CN(-) anion at energies down to approximately 5 eV. N(+) ions also abstract hydrogen from hydroxyl groups of the molecules to form NH(-) and NH(2) (-) anions. A fraction of OO(-) fragments abstract hydrogen to form OH(-). The formation of H(3)O(+) ions also involves hydrogen abstraction as well as intramolecular proton transfer. These findings suggest a variety of severe damaging pathways to DNA molecules which occur on the picosecond time scale following heavy ion irradiation of a cell, and prior to the late diffusion-limited homogeneous chemical processes.

Characterization of inositol phosphates in carrot (Daucus carota L. ) cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rincon, M.; Chen, Q.; Boss, W.F.

1989-01-01

We have shown previously that inositol-1,4,5-trisphosphate (IP{sub 3}) stimulates an efflux of {sup 45}Ca{sup 2+} from fusogenic carrot protoplasts. In light of these results, we suggested that IP{sub 3} might serve as a second messenger for the mobilization of intracellular Ca{sup 2+} in higher plant cells. To determine whether or not IP{sub 3} and other inositol phosphates were present in the carrot cells, the cells were labeled with myo-(2-{sup 3}H)inositol for 18 hours and extracted with ice-cold 10% trichloroacetic acid. The inositol metabolites were separated by anion exchange chromatography and by paper electrophoresis. We found that ({sup 3}H)inositol metabolites coelutedmore » with inositol bisphosphate (IP{sub 2}) and IP{sub 3} when separated by anion exchange chromatography. However, we could not detect IP{sub 2} or IP{sub 3} when the inositol metabolites were analyzed by paper electrophoresis even though the polyphosphoinositides, which are the source of IP{sub 2} and IP{sub 3}, were present in these cells. Thus, ({sup 3}H)inositol metabolites other than IP{sub 2} and IP{sub 3} had coeluted on the anion exchange columns. The data indicate that either IP{sub 3} is rapidly metabolized or that it is not present at a detectable level in the carrot cells.« less

Selective in vivo metabolic cell-labeling-mediated cancer targeting

PubMed Central

Wang, Hua; Wang, Ruibo; Cai, Kaimin; He, Hua; Liu, Yang; Yen, Jonathan; Wang, Zhiyu; Xu, Ming; Sun, Yiwen; Zhou, Xin; Yin, Qian; Tang, Li; Dobrucki, Iwona T; Dobrucki, Lawrence W; Chaney, Eric J; Boppart, Stephen A; Fan, Timothy M; Lezmi, Stéphane; Chen, Xuesi; Yin, Lichen; Cheng, Jianjun

2017-01-01

Distinguishing cancer cells from normal cells through surface receptors is vital for cancer diagnosis and targeted therapy. Metabolic glycoengineering of unnatural sugars provides a powerful tool to manually introduce chemical receptors onto the cell surface; however, cancer-selective labeling still remains a great challenge. Herein we report the design of sugars that can selectively label cancer cells both in vitro and in vivo. Specifically, we inhibit the cell-labeling activity of tetraacetyl-N-azidoacetylmannosamine (Ac4ManAz) by converting its anomeric acetyl group to a caged ether bond that can be selectively cleaved by cancer-overexpressed enzymes and thus enables the overexpression of azido groups on the surface of cancer cells. Histone deacetylase and cathepsin L-responsive acetylated azidomannosamine, one such enzymatically activatable Ac4ManAz analog developed, mediated cancer-selective labeling in vivo, which enhanced tumor accumulation of a dibenzocyclooctyne–doxorubicin conjugate via click chemistry and enabled targeted therapy against LS174T colon cancer, MDA-MB-231 triple-negative breast cancer and 4T1 metastatic breast cancer in mice. PMID:28192414

Joint Feature Selection and Classification for Multilabel Learning.

PubMed

Huang, Jun; Li, Guorong; Huang, Qingming; Wu, Xindong

2018-03-01

Multilabel learning deals with examples having multiple class labels simultaneously. It has been applied to a variety of applications, such as text categorization and image annotation. A large number of algorithms have been proposed for multilabel learning, most of which concentrate on multilabel classification problems and only a few of them are feature selection algorithms. Current multilabel classification models are mainly built on a single data representation composed of all the features which are shared by all the class labels. Since each class label might be decided by some specific features of its own, and the problems of classification and feature selection are often addressed independently, in this paper, we propose a novel method which can perform joint feature selection and classification for multilabel learning, named JFSC. Different from many existing methods, JFSC learns both shared features and label-specific features by considering pairwise label correlations, and builds the multilabel classifier on the learned low-dimensional data representations simultaneously. A comparative study with state-of-the-art approaches manifests a competitive performance of our proposed method both in classification and feature selection for multilabel learning.

A perspective on tritium versus carbon-14: ensuring optimal label selection in pharmaceutical research and development.

PubMed

Krauser, Joel A

2013-01-01

Tritium ((3) H) and carbon-14 ((14) C) labels applied in pharmaceutical research and development each offer their own distinctive advantages and disadvantages coupled with benefits and risks. The advantages of (3) H have a higher specific activity, shorter half-life that allows more manageable waste remediation, lower material costs, and often more direct synthetic routes. The advantages of (14) C offer certain analytical benefits and less potential for label loss. Although (3) H labels offer several advantages, they might be overlooked as a viable option because of the concerns about its drawbacks. A main drawback often challenged is metabolic liability. These drawbacks, in some cases, might be overstated leading to underutilization of a perfectly viable option. As a consequence, label selection may automatically default to (14) C, which is a more conservative approach. To challenge this '(14) C-by-default' approach, pharmaceutical agents with strategically selected (3) H-labeling positions based on non-labeled metabolism data have been successfully implemented and evaluated for (3) H loss. From in-house results, the long term success of projects clearly would benefit from a thorough, objective, and balanced assessment regarding label selection ((3) H or (14) C). This assessment should be based on available project information and scientific knowledge. Important considerations are project applicability (preclinical and clinical phases), synthetic feasibility, costs, and timelines. Copyright © 2013 John Wiley & Sons, Ltd.

Energy and traffic light labelling have no impact on parent and child fast food selection.

PubMed

Dodds, Pennie; Wolfenden, Luke; Chapman, Kathy; Wellard, Lyndal; Hughes, Clare; Wiggers, John

2013-10-25

Labelling of food from fast food restaurants at point-of-purchase has been suggested as one strategy to reduce population energy consumption and contribute to reductions in obesity prevalence. The aim of this study was to examine the effects of energy and single traffic light labelling systems on the energy content of child and adult intended food purchases. The study employed a randomised controlled trial design. English speaking parents of children aged between three and 12 years were recruited from an existing research cohort. Participants were mailed one of three hypothetical fast food menus. Menus differed in their labelling technique- either energy labels, single traffic light labels, or a no-label control. Participants then completed a telephone survey which assessed intended food purchases for both adult and child. The primary trial outcome was total energy of intended food purchase. A total of 329 participants completed the follow-up telephone interview. Eighty-two percent of the energy labelling group and 96% of the single traffic light labelling group reported noticing labelling information on their menu. There were no significant differences in total energy of intended purchases of parents, or intended purchases made by parents for children, between the menu labelling groups, or between menu labelling groups by socio-demographic subgroups. This study provided no evidence to suggest that energy labelling or single traffic light labelling alone were effective in reducing the energy of fast food items selected from hypothetical fast food menus for purchase. Additional complementary public health initiatives promoting the consumption of healthier foods identified by labelling, and which target other key drivers of menu item selection in this setting may be required. Copyright © 2013. Published by Elsevier Ltd.

The effect of energy and traffic light labelling on parent and child fast food selection: a randomised controlled trial.

PubMed

Dodds, Pennie; Wolfenden, Luke; Chapman, Kathy; Wellard, Lyndal; Hughes, Clare; Wiggers, John

2014-02-01

Labelling of food from fast food restaurants at point-of-purchase has been suggested as one strategy to reduce population energy consumption and contribute to reductions in obesity prevalence. The aim of this study was to examine the effects of energy and single traffic light labelling systems on the energy content of child and adult intended food purchases. The study employed a randomised controlled trial design. English speaking parents of children aged between three and 12 years were recruited from an existing research cohort. Participants were mailed one of three hypothetical fast food menus. Menus differed in their labelling technique – either energy labels, single traffic light labels, or a no-label control. Participants then completed a telephone survey which assessed intended food purchases for both adult and child. The primary trial outcome was total energy of intended food purchase. A total of 329 participants completed the follow-up telephone interview. Eighty-two percent of the energy labelling group and 96% of the single traffic light labelling group reported noticing labelling information on their menu. There were no significant differences in total energy of intended purchases of parents, or intended purchases made by parents for children, between the menu labelling groups, or between menu labelling groups by socio-demographic subgroups. This study provided no evidence to suggest that energy labelling or single traffic light labelling alone were effective in reducing the energy of fast food items selected from hypothetical fast food menus for purchase. Additional complementary public health initiatives promoting the consumption of healthier foods identified by labelling, and which target other key drivers of menu item selection in this setting may be required.

Redox responsive nanotubes from organometallic polymers by template assisted layer by layer fabrication

NASA Astrophysics Data System (ADS)

Song, Jing; Jańczewski, Dominik; Guo, Yuanyuan; Xu, Jianwei; Vancso, G. Julius

2013-11-01

Redox responsive nanotubes were fabricated by the template assisted layer-by-layer (LbL) assembly method and employed as platforms for molecular payload release. Positively and negatively charged organometallic poly(ferrocenylsilane)s (PFS) were used to construct the nanotubes, in combination with other polyions. During fabrication, multilayers of these polyions were deposited onto the inner pores of template porous membranes, followed by subsequent removal of the template. Anodized porous alumina and track-etched polycarbonate membranes were used as templates. The morphology, electrochemistry, composition and other properties of the obtained tubular structure were characterized by fluorescence microscopy, scanning (SEM) and transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) spectroscopy. Composite nanotubes, consisting of poly(acrylic acid) anions with PFS+ and nanoparticles including fluorophore labelled dextran and decorated quantum dots, with PFS polyelectrolytes were also fabricated, broadening the scope of the structures. Cyclic voltammograms of PFS containing nanotubes showed similar redox responsive behaviour to thin LbL assembled films. Redox triggered release of labelled macromolecules from these tubular structures demonstrated application potential in controlled molecular delivery.Redox responsive nanotubes were fabricated by the template assisted layer-by-layer (LbL) assembly method and employed as platforms for molecular payload release. Positively and negatively charged organometallic poly(ferrocenylsilane)s (PFS) were used to construct the nanotubes, in combination with other polyions. During fabrication, multilayers of these polyions were deposited onto the inner pores of template porous membranes, followed by subsequent removal of the template. Anodized porous alumina and track-etched polycarbonate membranes were used as templates. The morphology, electrochemistry, composition and other properties of the obtained tubular structure were characterized by fluorescence microscopy, scanning (SEM) and transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) spectroscopy. Composite nanotubes, consisting of poly(acrylic acid) anions with PFS+ and nanoparticles including fluorophore labelled dextran and decorated quantum dots, with PFS polyelectrolytes were also fabricated, broadening the scope of the structures. Cyclic voltammograms of PFS containing nanotubes showed similar redox responsive behaviour to thin LbL assembled films. Redox triggered release of labelled macromolecules from these tubular structures demonstrated application potential in controlled molecular delivery. Electronic supplementary information (ESI) available: Nanotube wall thickness determination protocol. See DOI: 10.1039/c3nr03927g

Octamethyl-octaundecylcyclo[8]pyrrole: A Promising Sulfate Anion Extractant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eller, Leah R; Stepien, Marcin; Fowler, Christopher J

The diprotonated form of an organic-solubilized cyclo[8]pyrrole derivative, bearing eight undecyl chains on the {beta}-pyrrolic positions, was found to extract sulfate anion effectively from neutral aqueous media into a toluene organic phase. The kinetics of sulfate anion exchange between the two phases were found to be exceedingly slow in the absence of the phase-transfer catalyst, Aliquat 336-nitrate (A336N), but appreciable in its presence. The bisnitrate anion bound form of this cyclo[8]pyrrole could be generated in situ by subjecting the toluene phase containing initially 0.5 mM of the sulfate anion bound form and 0.1 mM trioctylamine (TOA) to successive equilibrations withmore » aqueous 0.1 M HNO{sub 3} until sulfate was no longer detected in the aqueous phase. This bisnitrate complex, when studied as a 0.5 mM solution in toluene in the presence of 0.1 mM (TOAH){sup +}(NO{sub 3}{sup -}), was also found to be an effective extractant for sulfate anion. D{sub SO4} values of 0.001 and 1000 were observed at 1 M NaNO{sub 3}(aq) and 0.3 mM NaNO{sub 3}(aq), respectively, and the logarithm of the conditional exchange constant, log(K{prime}{sub exch}), was calculated to be 4.9 {+-} 0.4. The present cyclo[8]pyrrole system is thus noteworthy as being the first synthetic receptor that displays a high selectivity for sulfate anion in the presence of excess nitrate under conditions of solvent extraction.« less

Ultrahigh and Selective SO2 Uptake in Inorganic Anion-Pillared Hybrid Porous Materials.

PubMed

Cui, Xili; Yang, Qiwei; Yang, Lifeng; Krishna, Rajamani; Zhang, Zhiguo; Bao, Zongbi; Wu, Hui; Ren, Qilong; Zhou, Wei; Chen, Banglin; Xing, Huabin

2017-07-01

The efficient capture of SO 2 is of great significance in gas-purification processes including flue-gas desulfurization and natural-gas purification, but the design of porous materials with high adsorption capacity and selectivity of SO 2 remains very challenging. Herein, the selective recognition and dense packing of SO 2 clusters through multiple synergistic host-guest and guest-guest interactions by controlling the pore chemistry and size in inorganic anion (SiF 6 2- , SIFSIX) pillared metal-organic frameworks is reported. The binding sites of anions and aromatic rings in SIFSIX materials grasp every atom of SO 2 firmly via S δ+ ···F δ- electrostatic interactions and O δ- ···H δ+ dipole-dipole interactions, while the guest-guest interactions between SO 2 molecules further promote gas trapping within the pore space, which is elucidated by first-principles density functional theory calculations and powder X-ray diffraction experiments. These interactions afford new benchmarks for the highly efficient removal of SO 2 from other gases, even if at a very low SO 2 concentration. Exceptionally high SO 2 capacity of 11.01 mmol g -1 is achieved at atmosphere pressure by SIFSIX-1-Cu, and unprecedented low-pressure SO 2 capacity is obtained in SIFSIX-2-Cu-i (4.16 mmol g -1 SO 2 at 0.01 bar and 2.31 mmol g -1 at 0.002 bar). More importantly, record SO 2 /CO 2 selectivity (86-89) and excellent SO 2 /N 2 selectivity (1285-3145) are also achieved. Experimental breakthrough curves further demonstrate the excellent performance of these hybrid porous materials in removing low-concentration SO 2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of a flame retardant hydrolysis product in human urine by SPE and LC-MS. Comparison of molecularly imprinted solid-phase extraction with a mixed-mode anion exchanger.

PubMed

Möller, Kristina; Crescenzi, Carlo; Nilsson, Ulrika

2004-01-01

Diphenyl phosphate is a hydrolysis product and possible metabolite of the flame retardant and plasticiser additive triphenyl phosphate. A molecularly imprinted polymer solid-phase extraction (MISPE) method for extracting diphenyl phosphate from aqueous solutions has been developed and compared with SPE using a commercially available mixed-mode anion exchanger. The imprinted polymer was prepared using 2-vinylpyridine (2-Vpy) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and a structural analogue of the analyte as the template molecule. The imprinted polymer was evaluated for use as a SPE sorbent, in tests with both aqueous standards and spiked urine samples, by comparing recovery and breakthrough data obtained using the imprinted form of the polymer and a non-imprinted form (NIP). Extraction from aqueous solutions resulted in more than 80% recovery. Adsorption by the molecularly imprinted polymer (MIP) was non-selective, but selectivity was achieved by selective desorption in the wash steps. Diphenyl phosphate could also be selectively extracted from urine samples, although the urine matrix reduced the capacity of the MISPE cartridges. Recoveries from urine extraction were higher than 70%. It was important to control pH during sample loading. The MISPE method was found to yield a less complex LC-ESI-MS chromatogram of the urine extracts compared with the mixed-mode anion-exchanger method. An LC-ESI-MS method using a Hypercarb LC column with a graphitised carbon stationary phase was also evaluated for organophosphate diesters. LC-ESI-MS using negative-ion detection in selected ion monitoring (SIM) mode was shown to be linear for diphenyl phosphate in the range 0.08-20 ng microL(-1).

A new fluorescent enhanced probe based on (E)-9-(2-nitrovinyl)-anthracene for the detection of bisulfite anions and its practical application

NASA Astrophysics Data System (ADS)

Chao, Jianbin; Liu, Yuhong; Zhang, Yan; Zhang, Yongbin; Huo, Fangjun; Yin, Caixia; Wang, Yu; Qin, Liping

2015-07-01

A new fluorescent enhanced probe based on (E)-9-(2-nitrovinyl)-anthracene is developed, which shows high selectivity and sensitivity for the detection of bisulfite anions at Na2HPO4 citric acid buffer solutions (pH 5.0). When addition of HSO3-, the fluorescence intensity is significantly enhanced and the probe displays apparent fluorescence color changes from non-fluorescence to blue under a UV lamp illumination, the solution color also changes from yellow to colorless. The detection limit is determined to be as low as 6.30 μM. This offers another specific colorimetric and fluorescent probe for bisulfite anions detection, furthermore it is applied in detecting the level of bisulfite in sugar samples.

Ionic liquids containing symmetric quaternary phosphonium cations and phosphorus-containing anions, and their use as lubricant additives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Jun; Luo, Huimin

An ionic liquid composition having the following generic structural formula: ##STR00001## wherein R 1, R 2, R 3, and R 4 are equivalent and selected from hydrocarbon groups containing at least three carbon atoms, and X - is a phosphorus-containing anion, particularly an organophosphate, organophosphonate, or organophosphinate anion, or a thio-substituted analog thereof containing hydrocarbon groups with at least three carbon atoms. Also described are lubricant compositions comprising the above ionic liquid and a base oil, wherein the ionic liquid is dissolved in the base oil. Further described are methods for applying the ionic liquid or lubricant composition onto amore » mechanical device for which lubrication is beneficial, with resulting improvement in friction reduction, wear rate, and/or corrosion inhibition.« less

Selective Gas Capture Ability of Gas-Adsorbent-Incorporated Cellulose Nanofiber Films.

PubMed

Shah, Kinjal J; Imae, Toyoko

2016-05-09

The 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized cellulose nanofibers (TOCNF) were hybridized with cation and anion-exchange organoclays, where poly(amido amine) dendrimers were loaded to enhance the functionality of gas adsorption, since dendrimers have the high adsorbability and the enough selectivity on the gas adsorption. The thin films were prepared from the organoclay-TOCNF hybrids and supplied to the gas adsorption. The adsorption of CO2 and NH3 gases increased with an increasing amount of organoclays in TOCNF films, but the behavior of the increase depended on gases, clays, and dendrimers. The hydrotalcite organoclay-TOCNF films displayed the highest adsorption of both gases, but the desorption of CO2 gas from hydrotalcite organoclay-TOCNF films was drastically high in comparison with the other systems. While the CO2 gas is adsorbed and remained on cationic dendrimer sites in cation-exchange organoclay-TOCNF films, the CO2 gas is adsorbed on cationic clay sites in anion exchange organoclay-TOCNF films, and it is easily desorbed from the films. The NH3 adsorption is inversive to the CO2 adsorption. Then the CO2 molecules adsorbed on the cationic dendrimers and the NH3 molecules adsorbed on the anionic dendrimers are preferably captured in these adsorbents. The present research incorporated dendrimers will be contributing to the development of gas-specialized adsorbents, which are selectively storable only in particular gases.

One-pot fabrication of FRET-based fluorescent probe for detecting copper ion and sulfide anion in 100% aqueous media

NASA Astrophysics Data System (ADS)

Lv, Kun; Chen, Jian; Wang, Hong; Zhang, Peisheng; Yu, Maolin; Long, Yunfei; Yi, Pinggui

2017-04-01

The design of effective tools for detecting copper ion (Cu2 +) and sulfide anion (S2 -) is of great importance due to the abnormal level of Cu2 + and S2 - has been associated with an increase in risk of many diseases. Herein, we report on the fabrication of fluorescence resonance energy transfer (FRET) based fluorescent probe PF (PEI-FITC) for detecting Cu2 + and S2 - in 100% aqueous media via a facile one-pot method by covalent linking fluorescein isothiocyanate (FITC) with branched-polyethylenimine (b-PEI). PF could selectively coordinate with Cu2 + among 10 metal ions to form PF-Cu2 + complex, resulting in fluorescence quenching through FRET mechanism. Furthermore, the in situ generated PF-Cu2 + complex can be used to selectively detect S2 - based on the displacement approach, resulting in an off-on type sensing. There is no obvious interference from other anions, such as Cl-, NO3-, ClO4-, SO42 -, HCO3-, CO32 -, Br-, HPO42 -, F- and S2O32 -. In addition, PF was successfully used to determine Cu2 + and S2 - in human serum and tap water samples. Therefore, the FRET-based probe PF may provide a new method for selective detection of multifarious analysts in biological and environmental applications, and even hold promise for application in more complicated systems.

A strategy to modulate the electrophoretic behavior in plastic microchips using sodium polystyrene sulfonate.

PubMed

Guo, Jinxiu; Chen, Yu; Zhao, Lizhi; Sun, Ping; Li, Hongli; Zhou, Lei; Wang, Xiayan; Pu, Qiaosheng

2016-12-16

Plastic microchips have been broadly used as disposable microfluidic devices, but the poorly defined surface properties limit their application. Herein, we proved that an anionic polymer could be used as the background electrolyte (BGE) to provide a strong and stable cathodic electroosmotic flow (EOF) and modulate the electrophoretic behavior for efficient separation in relative thicker microchannels (∼75μm id). A cathodic EOF of ∼3.3×10 -4 cm 2 V -1 s -1 was maintained using sodium polystyrene sulfonate (PSSNa) with a molecular weight of 5×10 5 as the BGE, which ensured fluorescein isothiocyanate labeled biogenic amines (BAs) appeared ahead of other components in the electropherograms obtained with microchips of cyclic olefin copolymer. Four selected BAs appeared within 50s and theoretical plate numbers of 8.0×10 5 /m were achieved. The role of PSSNa was evaluated with streaming potential, dynamic light scattering, contact angle and atomic force microscopy. Its functionalities as surface modifier, viscosity regulator and pseudostationary phase were also confirmed. The proposed electrophoretic method was applied in the fast determination of BAs in fish meat samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Nutrition Label Viewing during a Food-Selection Task: Front-of-Package Labels vs Nutrition Facts Labels.

PubMed

Graham, Dan J; Heidrick, Charles; Hodgin, Katie

2015-10-01

Earlier research has identified consumer characteristics associated with viewing Nutrition Facts labels; however, little is known about those who view front-of-package nutrition labels. Front-of-package nutrition labels might appeal to more consumers than do Nutrition Facts labels, but it might be necessary to provide consumers with information about how to locate and use these labels. This study quantifies Nutrition Facts and front-of-package nutrition label viewing among American adult consumers. Attention to nutrition information was measured during a food-selection task. One hundred and twenty-three parents (mean age=38 years, mean body mass index [calculated as kg/m(2)]=28) and one of their children (aged 6 to 9 years) selected six foods from a university laboratory-turned-grocery aisle. Participants were randomized to conditions in which front-of-package nutrition labels were present or absent, and signage explaining front-of-package nutrition labels was present or absent. Adults' visual attention to Nutrition Facts labels and front-of-package nutrition labels was objectively measured via eye-tracking glasses. To examine whether there were significant differences in the percentages of participants who viewed Nutrition Facts labels vs front-of-package nutrition labels, McNemar's tests were conducted across all participants, as well as within various sociodemographic categories. To determine whether hypothesized factors, such as health literacy and education, had stronger relationships with front-of-package nutrition label vs Nutrition Facts label viewing, linear regression assessed the magnitude of relationships between theoretically and empirically derived factors and each type of label viewing. Overall, front-of-package nutrition labels were more likely to be viewed than Nutrition Facts labels; however, for all subgroups, higher rates of front-of-package nutrition label viewership occurred only when signage was present drawing attention to the presence and meaning of front-of-package nutrition labels. Consumers should receive education about the availability and use of new nutrition labels. Copyright © 2015 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Determination of selected anions in water by ion chromatography

USGS Publications Warehouse

Fishman, Marvin J.; Pyen, Grace

1979-01-01

Ion chromatography is a rapid, sensitive, precise, and accurate method for the determination of major anions in rain water and surface waters. Simultaneous analyses of a single sample for bromide, chloride, fluoride, nitrate, nitrite, orthophosphate, and sulfate require approximately 20 minutes to obtain a chromatogram.Minimum detection limits range from 0.01 milligrams per liter for fluoride to 0.20 milligrams per liter for chloride and sulfate. Percent relative standard deviations were less than nine percent for all anions except nitrite in Standard Reference Water Samples. Only one reference sample contained nitrite and its concentration was near the minimum level of detection. Similar precision was found for chloride, nitrate, and sulfate at concentrations less than 5 milligrams per liter in rainfall samples. Precision for fluoride ranged from 12 to 22 percent, but is attributed to the low concentrations in these samples. The other anions were not detected.To determine accuracy of results, several samples were spiked with known concentrations of fluoride, chloride, nitrate, and sulfate; recoveries ranged from 96 to 103 percent. Known amounts of bromide and phosphate were added, separately, to several other waters, which contained bromide or phosphate. Recovery of added bromide and phosphate ranged from approximately 95 to 104 percent. No recovery data were obtained for nitrite.Chloride, nitrate, nitrite, orthophosphate, and sulfate, in several samples, were also determined independently by automated colorimetric procedures. An automated ion-selective electrode method was used to determine fluoride. Results are in agreement with results obtained by ion chromatography.

Chemical Composition and Labeling of Substances Marketed as Selective Androgen Receptor Modulators and Sold via the Internet.

PubMed

Van Wagoner, Ryan M; Eichner, Amy; Bhasin, Shalender; Deuster, Patricia A; Eichner, Daniel

2017-11-28

Recent reports have described the increasing use of nonsteroidal selective androgen receptor modulators, which have not been approved by the US Food and Drug Administration (FDA), to enhance appearance and performance. The composition and purity of such products is not known. To determine the chemical identity and the amounts of ingredients in dietary supplements and products marketed and sold through the internet as selective androgen receptor modulators and compare the analyzed contents with product labels. Web-based searches were performed from February 18, 2016, to March 25, 2016, using the Google search engine on the Chrome and Internet Explorer web browsers to identify suppliers selling selective androgen receptor modulators. The products were purchased and the identities of the compounds and their amounts were determined from April to August 2016 using chain-of-custody and World Anti-Doping Association-approved analytical procedures. Analytical findings were compared against the label information. Products marketed and sold as selective androgen receptor modulators. Chemical identities and the amount of ingredients in each product marketed and sold as selective androgen receptor modulators. Among 44 products marketed and sold as selective androgen receptor modulators, only 23 (52%) contained 1 or more selective androgen receptor modulators (Ostarine, LGD-4033, or Andarine). An additional 17 products (39%) contained another unapproved drug, including the growth hormone secretagogue ibutamoren, the peroxisome proliferator-activated receptor-δ agonist GW501516, and the Rev-ErbA agonist SR9009. Of the 44 tested products, no active compound was detected in 4 (9%) and substances not listed on the label were contained in 11 (25%). In only 18 of the 44 products (41%), the amount of active compound in the product matched that listed on the label. The amount of the compounds listed on the label differed substantially from that found by analysis in 26 of 44 products (59%). In this limited investigation involving chemical analyses of 44 products marketed as selective androgen receptor modulators and sold via the internet, most products contained unapproved drugs and substances. Only 52% contained selective androgen receptor modulators and many were inaccurately labeled.

Use of food labels by adolescents to make healthier choices on snacks: a cross-sectional study from Sri Lanka.

PubMed

Talagala, Ishanka A; Arambepola, Carukshi

2016-08-08

Unhealthy snacking is commonly seen among adolescents. Therefore, use of food labels is promoted for making healthier choices on packaged snacks. This study was conducted to assess the use of food labels in making choices on packaged snack and its associated factors among adolescents. A cross-sectional study was conducted in 2012 among 542 Grade 12 students in Sri Lanka. Eight classes were selected as 'clusters' for the study (two classes each from two schools that were selected randomly from each list of 'Girls only' and 'Boys only' schools in Colombo district). A self-administered questionnaire assessed their socio-demography, snacking behaviour, attitudes and nutrition knowledge related to food labels. Adolescents' use of labels was assessed by three practices (label reading frequency, attention paid to label contents and correct interpretation of six hypothetical labels of snacks). Based on total scores obtained for the three practices, 'satisfactory' (score ≥75(th) percentile mark) and 'unsatisfactory' (score <75(th) percentile mark) label users were identified. Using SPSS, associations were assessed at 0.05 significance level using Chi-square-test. Of the participants, 51 % were males; 61 % spent their pocket money at least once/week on packaged snacks; predominantly on biscuits (85 %) and cola-drinks (77 %) and 88 % selected snacks on their own. The majority (74.5 %) was frequent ('always' or 'most often') label readers with female predominance (p < 0.05). Over 74 % paid attention frequently to the brand name (75 %), price (85 %) and nutrition panel (81 %). Over 64 % were able to select the better food label when given a choice between two snacks, although some did it for reasons such as attractive label (63 %). The majority (84 %) had good knowledge (obtaining more than the 75(th) percentile mark) on interpreting labels. Although not statistically significant, 'unsatisfactory' label use was higher among males (73 %), purchasing power (70.4 %) and unhealthy snacking behaviour (73 %). In contrast, among the marketing strategies, identifying known brands (73.2 %) and imported products (75.8 %) as 'good' products were significantly associated with 'unsatisfactory' label use (p < 0.05). Despite having good knowledge and positive attitudes, food label use is unsatisfactory among adolescents. Skills in reading labels should be addressed in the 'School canteen policy' in Sri Lanka.

Anton permselective membrane

NASA Technical Reports Server (NTRS)

Alexander, S. S.; Hodgdon, R. B.; Waite, W. A.

1979-01-01

Experimental composite membranes were synthesized on a lab scale consisting of a thin layer of anion permselective resin supported by and bonded to a porous physically strong and conductive substrate film. These showed good selectivity and also substantially lower electrical resistivities than the homogenous candidate membranes optimized in the previous contract. A wide range of resin porosities were examined for three candidate membrane systems, CDIL, CP4L, and A3L to identify the formulation giving the best overall redox cell performance. Candidate anion membranes showed large increases in resistivity after a short time of immersion in concentrated FeCl/HCl solution. Largely on the basis of resistance stability the CDIL formulation was selected as prime candidate and about thirty-five membranes (one foot square) were produced for experimental static and dynamic evaluation.

A triarylmethyl spin label for long-range distance measurement at physiological temperatures using T1 relaxation enhancement

NASA Astrophysics Data System (ADS)

Yang, Zhongyu; Bridges, Michael D.; López, Carlos J.; Rogozhnikova, Olga Yu.; Trukhin, Dmitry V.; Brooks, Evan K.; Tormyshev, Victor; Halpern, Howard J.; Hubbell, Wayne L.

2016-08-01

Site-directed spin labeling (SDSL) in combination with electron paramagnetic resonance (EPR) spectroscopy has become an important tool for measuring distances in proteins on the order of a few nm. For this purpose pairs of spin labels, most commonly nitroxides, are site-selectively introduced into the protein. Recent efforts to develop new spin labels are focused on tailoring the intrinsic properties of the label to either extend the upper limit of measurable distances at physiological temperature, or to provide a unique spectral lineshape so that selective pairwise distances can be measured in a protein or complex containing multiple spin label species. Triarylmethyl (TAM) radicals are the foundation for a new class of spin labels that promise to provide both capabilities. Here we report a new methanethiosulfonate derivative of a TAM radical that reacts rapidly and selectively with an engineered cysteine residue to generate a TAM containing side chain (TAM1) in high yield. With a TAM1 residue and Cu2+ bound to an engineered Cu2+ binding site, enhanced T1 relaxation of TAM should enable measurement of interspin distances up to 50 Å at physiological temperature. To achieve favorable TAM1-labeled protein concentrations without aggregation, proteins are tethered to a solid support either site-selectively using an unnatural amino acid or via native lysine residues. The methodology is general and readily extendable to complex systems, including membrane proteins.

Anion recognition using newly synthesized hydrogen bonding disubstituted phenylhydrazone-based receptors: poly(vinyl chloride)-based sensor for acetate.

PubMed

Gupta, Vinod K; Goyal, Rajendra N; Sharma, Ram A

2008-08-15

A potentiometric acetate-selective sensor, based on the use of butane-2,3-dione,bis[(2,4-dinitrophenyl)hydrazone] (BDH) as a neutral carrier in poly(vinyl chloride) (PVC) matrix, is reported. Effect of various plasticizers and cation excluder, cetryaltrimethylammonium bromide (CTAB) was studied. The best performance was obtained with a membrane composition of PVC:BDH:CTAB ratio (w/w; mg) of 160:8:8. The sensor exhibits significantly enhanced selectivity toward acetate ions over a wide concentration range 5.0 x 10(-6) to 1.0 x 10(-1)M with a lower detection limit of 1.2 x 10(-6)M within pH range 6.5-7.5 with a response time of <15s and a Nernstian slope of 60.3+/-0.3 mV decade(-1) of activity. Influences of the membrane composition, and possible interfering anions were investigated on the response properties of the electrode. Fast and stable response, good reproducibility and long-term stability are demonstrated. The sensor has a response time of 15s and can be used for at least 65 days without any considerable divergence in their potential response. Selectivity coefficients determined with the separate solution method (SSM) and fixed interference method (FIM) indicate that high selectivity for acetate ion. The proposed electrode shows fairly good discrimination of acetate from several inorganic and organic anions. It was successfully applied to direct determination of acetate within food preservatives. Total concentration of acetic acid in vinegar samples were determined by direct potentiometry and the values agreed with those mentioned by the manufacturers.

Quantum chemical investigation on photodegradation mechanisms of sulfamethoxypyridazine with dissolved inorganic matter and hydroxyl radical.

PubMed

Shah, Shaheen; Hao, Ce

2017-07-01

Sulfamethoxypyridazine (SMP) is one of the commonly used sulfonamide antibiotics (SAs). SAs are mainly studied to undergo triplet-sensitized photodegradation in water under natural sunlight with other coexisting aquatic environmental organic pollutants. In this work, SMP was selected as a representative of SAs. We studied the mechanisms of triplet-sensitized photodegradation of SMP and the influence of selected dissolved inorganic matter, i.e., anions (Br - , Cl - , and NO 3 - ) and cations ions (Ca 2+ , Mg 2+ , and Zn 2+ ) on SMP photodegradation mechanism by quantum chemical methods. In addition, the degradation mechanisms of SMP by hydroxyl radical (OH) were also investigated. The creation of SO 2 extrusion product was accessed with two different energy pathways (pathway-1 and pathway-2) by following two steps (step-I and step-II) in the triplet-sensitized photodegradation of SMP. Due to low activation energy, the pathway-1 was considered as the main pathway to obtain SO 2 extrusion product. Step-II of pathway-1 was measured to be the rate-limiting step (RLS) of SMP photodegradation mechanism and the effect of the selected anions and cations was estimated for this step. All selected anions and cations promoted photodegradation of SMP by dropping the activation energy of pathway-1. The estimated low activation energies of different degradation pathways of SMP with OH radical indicate that OH radical is a very powerful oxidizing agent for SMP degradation via attack through benzene derivative and pyridazine derivative ring. Copyright © 2016. Published by Elsevier B.V.

Molecules for materials: germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeHn/GeHn- (n = 0-4) and Ge2Hn/Ge2Hn(-) (n = 0-6).

PubMed

Li, Qian-Shu; Lü, Rui-Hua; Xie, Yaoming; Schaefer, Henry F

2002-12-01

The GeH(n) (n = 0-4) and Ge(2)H(n) (n = 0-6) systems have been studied systematically by five different density functional methods. The basis sets employed are of double-zeta plus polarization quality with additional s- and p-type diffuse functions, labeled DZP++. For each compound plausible energetically low-lying structures were optimized. The methods used have been calibrated against a comprehensive tabulation of experimental electron affinities (Chemical Reviews 102, 231, 2002). The geometries predicted in this work include yet unknown anionic species, such as Ge(2)H(-), Ge(2)H(2)(-), Ge(2)H(3)(-), Ge(2)H(4)(-), and Ge(2)H(5)(-). In general, the BHLYP method predicts the geometries closest to the few available experimental structures. A number of structures rather different from the analogous well-characterized hydrocarbon radicals and anions are predicted. For example, a vinylidene-like GeGeH(2) (-) structure is the global minimum of Ge(2)H(2) (-). For neutral Ge(2)H(4), a methylcarbene-like HGë-GeH(3) is neally degenerate with the trans-bent H(2)Ge=GeH(2) structure. For the Ge(2)H(4) (-) anion, the methylcarbene-like system is the global minimum. The three different neutral-anion energy differences reported in this research are: the adiabatic electron affinity (EA(ad)), the vertical electron affinity (EA(vert)), and the vertical detachment energy (VDE). For this family of molecules the B3LYP method appears to predict the most reliable electron affinities. The adiabatic electron affinities after the ZPVE correction are predicted to be 2.02 (Ge(2)), 2.05 (Ge(2)H), 1.25 (Ge(2)H(2)), 2.09 (Ge(2)H(3)), 1.71 (Ge(2)H(4)), 2.17 (Ge(2)H(5)), and -0.02 (Ge(2)H(6)) eV. We also reported the dissociation energies for the GeH(n) (n = 1-4) and Ge(2)H(n) (n = 1-6) systems, as well as those for their anionic counterparts. Our theoretical predictions provide strong motivation for the further experimental study of these important germanium hydrides. Copyright 2002 Wiley Periodicals, Inc.

Diagnostic labels assigned to patients with orthopedic conditions and the influence of the label on selection of interventions: a qualitative study of orthopaedic clinical specialists.

PubMed

Miller-Spoto, Marcia; Gombatto, Sara P

2014-06-01

A variety of diagnostic classification systems are used by physical therapists, but little information about how therapists assign diagnostic labels and how the labels are used to direct intervention is available. The purposes of this study were: (1) to examine the diagnostic labels assigned to patient problems by physical therapists who are board-certified Orthopaedic Clinical Specialists (OCSs) and (2) to determine whether the label influences selection of interventions. A cross-sectional survey was conducted. Two written cases were developed for patients with low back and shoulder pain. A survey was used to evaluate the diagnostic label assigned and the interventions considered important for each case. The cases and survey were sent to therapists who are board-certified OCSs. Respondents assigned a diagnostic label and rated the importance of intervention categories for each case. Each diagnostic label was coded based on the construct it represented. Percentage responses for each diagnostic label code and intervention category were calculated. Relative importance of intervention category based on diagnostic label was examined. For the low back pain and shoulder pain cases, respectively, "Combination" (48.5%, 34.9%) and "Pathology/Pathophysiology" (32.7%, 57.3%) diagnostic labels were most common. Strengthening (85.9%, 98.1%), stretching (86.8%, 84.9%), neuromuscular re-education (87.6%, 93.4%), functional training (91.4%, 88.6%), and mobilization/manipulation (85.1%, 86.8%) were considered the most important interventions. Relative importance of interventions did not differ based on diagnostic label (χ2=0.050-1.263, P=.261-.824). The low response rate may limit the generalizability of the findings. Also, examples provided for labels may have influenced responses, and some of the label codes may have represented overlapping constructs. There is little consistency with which OCS therapists assign diagnostic labels, and the label does not seem to influence selection of interventions. © 2014 American Physical Therapy Association.

Do nutrition labels improve dietary outcomes?

PubMed

Variyam, Jayachandran N

2008-06-01

The disclosure of nutritional characteristics of most packaged foods became mandatory in the United States with the implementation of the Nutrition Labeling and Education Act (NLEA) in 1994. Under the NLEA regulations, a 'Nutrition Facts' panel displays information on nutrients such as calories, total and saturated fats, cholesterol, and sodium in a standardized format. By providing nutrition information in a credible, distinctive, and easy-to-read format, the new label was expected to help consumers choose healthier, more nutritious diets. This paper examines whether the disclosure of nutrition information through the mandatory labels impacted consumer diets. Assessing the dietary effects of labeling is problematic due to the confounding of the label effect with unobserved label user characteristics. This self-selection problem is addressed by exploiting the fact that the NLEA exempts away-from-home foods from mandatory labeling. Difference-in-differences models that account for zero away-from-home intakes suggest that the labels increase fiber and iron intakes of label users compared with label nonusers. In comparison, a model that does not account for self-selection implies significant label effects for all but two of the 13 nutrients that are listed on the label.

Interface behaviors of acetylene and ethylene molecules with 1-butyl-3-methylimidazolium acetate ionic liquid: a combined quantum chemistry calculation and molecular dynamics simulation study.

PubMed

Xu, Hao; Han, Zhe; Zhang, Dongju; Zhan, Jinhua

2012-12-01

Although imidazolium-based ionic liquids (ILs) combined with oxygen-containing anions were proposed as the potential solvents for the selective separation of acetylene (C(2)H(2)) and ethylene (C(2)H(4)), the detailed mechanism at the molecular level is still not well understood. The present work focuses on a most effective IL for removing C(2)H(2) from a C(2)H(4) stream, 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]), aiming at understanding the first steps of the adsorption process of the molecules at the IL surface. We present a combined quantum mechanical (QM) calculation and molecular dynamics (MD) simulation study on the structure and property of the IL as well as its interaction with C(2)H(2) and C(2)H(4) molecules. The calculated results indicate that C(2)H(2) presents a stronger interaction with the IL than C(2)H(4) and the anion of the IL is mainly responsible for the stronger interaction. QM calculations show a stronger hydrogen-binding linkage between an acidic proton of C(2)H(2)/C(2)H(4) and the basic oxygen atom in [OAc](-) anion, in contrast to the relative weaker association via the C-H···π interaction between C(2)H(2)/C(2)H(4) and the cation. From MD simulations, it is observed that in the interfacial region, the butyl chain of cations and methyl of anions point into the vapor phase. The coming molecules on the IL surface may be initially wrapped by the extensive butyl chain and then devolved to the interface or caught into the bulk by the anion of IL. The introduction of guest molecules significantly influences the anion distribution and orientation on the interface, but the cations are not disturbed because of their larger volume and relatively weaker interaction with the changes in the guest molecules. The theoretical results provide insight into the molecular mechanism of the observed selective separation of C(2)H(2) form a C(2)H(4) stream by ILs.

Fluorescent Photo-conversion: A second chance to label unique cells.

PubMed

Mellott, Adam J; Shinogle, Heather E; Moore, David S; Detamore, Michael S

2015-03-01

Not all cells behave uniformly after treatment in tissue engineering studies. In fact, some treated cells display no signs of treatment or show unique characteristics not consistent with other treated cells. What if the "unique" cells could be isolated from a treated population, and further studied? Photo-convertible reporter proteins, such as Dendra2 , allow for the ability to selectively identify unique cells with a secondary label within a primary labeled treated population. In the current study, select cells were identified and labeled through photo-conversion of Dendra2 -transfected human Wharton's Jelly cells (hWJCs) for the first time. Robust photo-conversion of green-to-red fluorescence was achieved consistently in arbitrarily selected cells, allowing for precise cell identification of select hWJCs. The current study demonstrates a method that offers investigators the opportunity to selectively label and identify unique cells within a treated population for further study or isolation from the treatment population. Photo-convertible reporter proteins, such as Dendra2 , offer the ability over non-photo-convertible reporter proteins, such as green fluorescent protein, to analyze unique individual cells within a treated population, which allows investigators to gain more meaningful information on how a treatment affects all cells within a target population.

Efficient colorimetric and fluorescent detection of fluoride in DMSO-water mixtures with arylaldoximes.

PubMed

Rosen, Christian B; Hansen, Dennis J; Gothelf, Kurt V

2013-12-07

Fluoride detection through hydrogen bonding or deprotonation is most commonly achieved using amide, urea or pyrrole derivatives. The sensor molecules are often complex constructs and several synthetic steps are required for their preparation. Here we report the discovery that simple arylaldoximes have remarkable properties as fluoride anion sensors, providing distinct colorimetric or fluorescent readouts, depending on the structure of the arylaldoxime. The oximes showed exceptional selectivity towards fluoride over other typical anions, and low detection limits for fluoride in both DMSO and DMSO-water mixtures were obtained.

Pyrrole based Schiff bases as colorimetric and fluorescent chemosensors for fluoride and hydroxide anions.

PubMed

Velmathi, Sivan; Reena, Vijayaraghavan; Suganya, Sivalingam; Anandan, Sambandam

2012-01-01

An efficient colorimetric sensor with pyrrole-NH moiety as binding site and nitro group as a signaling unit has been synthesized by a one step procedure and characterized by spectroscopic techniques, which displays excellent selectivity and sensitivity for fluoride and hydroxide ions. The hydrogen bonding with these anions provides remarkable colorimetric responses. (1)H NMR and FT IR studies has been carried out to confirm the hydrogen bonding. UV-vis and fluorescence spectral changes can be exploited for real time and on site application.

Squarylium-based chromogenic anion sensors.

PubMed

Lee, Eun-Mi; Gwon, Seon-Yeong; Son, Young-A; Kim, Sung-Hoon

2012-09-01

A squarylium (SQ) dye was synthesized by the reaction between squaric acid and 2,3,3-trimethylindolenine and its anion sensing properties were investigated using absorption and emission spectroscopy. This chemosensor exhibited high selectivity for CN(-) as compared with F(-), CH(3)CO(2)(-), Br(-), H(2)PO(4)(-), Cl(-), and NO(3)(-) in acetonitrile, which was attributed to the formation of a 1:1 squarylium:CN(-) coordination complex, the formation of which was supported by the calculated geometry of the complex. Copyright © 2012 Elsevier B.V. All rights reserved.

The benzil rearrangement reaction: trapping of a hitherto minor product and its application to the development of a selective cyanide anion indicator.

PubMed

Sessler, Jonathan L; Cho, Dong-Gyu

2008-01-03

The isolation and characterization of an intermediate from the benzil-cyanide reaction is reported. The use of this trapping chemistry to produce a chemical indicator for the cyanide anion is described. It relies on the synthesis and reaction of a pi-extended analogue of benzil. Addition of tetrabutylammonium cyanide to organic solutions of this species, referred to as compound 3 in the text, gives rise to a dramatic change in both color and fluorescence properties.

Selective binding of choline by a phosphate-coordination-based triple helicate featuring an aromatic box.

PubMed

Jia, Chuandong; Zuo, Wei; Yang, Dong; Chen, Yanming; Cao, Liping; Custelcean, Radu; Hostaš, Jiří; Hobza, Pavel; Glaser, Robert; Wang, Yao-Yu; Yang, Xiao-Juan; Wu, Biao

2017-10-16

In nature, proteins have evolved sophisticated cavities tailored for capturing target guests selectively among competitors of similar size, shape, and charge. The fundamental principles guiding the molecular recognition, such as self-assembly and complementarity, have inspired the development of biomimetic receptors. In the current work, we report a self-assembled triple anion helicate (host 2) featuring a cavity resembling that of the choline-binding protein ChoX, as revealed by crystal and density functional theory (DFT)-optimized structures, which binds choline in a unique dual-site-binding mode. This similarity in structure leads to a similarly high selectivity of host 2 for choline over its derivatives, as demonstrated by the NMR and fluorescence competition experiments. Furthermore, host 2 is able to act as a fluorescence displacement sensor for discriminating choline, acetylcholine, L-carnitine, and glycine betaine effectively.The choline-binding protein ChoX exhibits a synergistic dual-site binding mode that allows it to discriminate choline over structural analogues. Here, the authors design a biomimetic triple anion helicate receptor whose selectivity for choline arises from a similar binding mechanism.

Effect of the Anion Activity on the Stability of Li Metal Anodes in Lithium-Sulfur Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Ruiguo; Chen, Junzheng; Han, Kee Sung

2016-03-29

With the significant progress made in the development of cathodes in lithium-sulfur (Li-S) batteries, the stability of Li metal anodes becomes a more urgent challenge in these batteries. Here we report the systematic investigation of the stability of the anode/electrolyte interface in Li-S batteries with concentrated electrolytes containing various lithium salts. It is found that Li-S batteries using LiTFSI-based electrolytes are more stable than those using LiFSI-based electrolytes. The decreased stability is because the N-S bond in the FSI- anion is fairly weak and the scission of this bond leads to the formation of lithium sulfate (LiSOx) in the presencemore » of polysulfide species. In contrast, even the weakest bond (C-S) in the TFSI- anion is stronger than the N-S bond in the FSI- anion. In the LiTFSI-based electrolyte, the lithium metal anode tends to react with polysulfide to form lithium sulfide (LiSx) which is more reversible than LiSOx formed in the LiTFSI-based electrolyte. This fundamental difference in the bond strength of the salt anions in the presence of polysulfide species leads to a large difference in the stability of the anode-electrolyte interface and performance of the Li-S batteries with electrolytes composed of these salts. Therefore, anion selection is one of the key parameters in the search for new electrolytes for stable operation of Li-S batteries.« less

Ultrathin self-assembled anionic polymer membranes for superfast size-selective separation

NASA Astrophysics Data System (ADS)

Deng, Chao; Zhang, Qiu Gen; Han, Guang Lu; Gong, Yi; Zhu, Ai Mei; Liu, Qing Lin

2013-10-01

Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5-12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m-2 h-1 bar-1) that is an order of magnitude larger than commercial membranes, and can highly efficiently separate 5 and 15 nm gold nanoparticles from their mixtures. The newly developed nanoporous membranes have a wide application in separation and purification of biomacromolecules and nanoparticles.Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5-12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m-2 h-1 bar-1) that is an order of magnitude larger than commercial membranes, and can highly efficiently separate 5 and 15 nm gold nanoparticles from their mixtures. The newly developed nanoporous membranes have a wide application in separation and purification of biomacromolecules and nanoparticles. Electronic supplementary information (ESI) available: Synthesis and characterization of SPEK-C; effect of the sulfonation degree on membrane formation; structure and properties of the self-assembled membranes; separation of cyt.c by the self-assembled membranes; size-selective separation of gold nanoparticles by the self-assembled membranes; comparison with commercial flat sheet ultrafiltration membranes. See DOI: 10.1039/c3nr03362g

A Joint Gaussian Process Model for Active Visual Recognition with Expertise Estimation in Crowdsourcing

PubMed Central

Long, Chengjiang; Hua, Gang; Kapoor, Ashish

2015-01-01

We present a noise resilient probabilistic model for active learning of a Gaussian process classifier from crowds, i.e., a set of noisy labelers. It explicitly models both the overall label noise and the expertise level of each individual labeler with two levels of flip models. Expectation propagation is adopted for efficient approximate Bayesian inference of our probabilistic model for classification, based on which, a generalized EM algorithm is derived to estimate both the global label noise and the expertise of each individual labeler. The probabilistic nature of our model immediately allows the adoption of the prediction entropy for active selection of data samples to be labeled, and active selection of high quality labelers based on their estimated expertise to label the data. We apply the proposed model for four visual recognition tasks, i.e., object category recognition, multi-modal activity recognition, gender recognition, and fine-grained classification, on four datasets with real crowd-sourced labels from the Amazon Mechanical Turk. The experiments clearly demonstrate the efficacy of the proposed model. In addition, we extend the proposed model with the Predictive Active Set Selection Method to speed up the active learning system, whose efficacy is verified by conducting experiments on the first three datasets. The results show our extended model can not only preserve a higher accuracy, but also achieve a higher efficiency. PMID:26924892

How to Select a Good Training-data Subset for Transcription: Submodular Active Selection for Sequences

DTIC Science & Technology

2009-01-01

selection and uncertainty sampling signif- icantly. Index Terms: Transcription, labeling, submodularity, submod- ular selection, active learning , sequence...name of batch active learning , where a subset of data that is most informative and represen- tative of the whole is selected for labeling. Often...representative subset. Note that our Fisher ker- nel is over an unsupervised generative model, which enables us to bootstrap our active learning approach

Biophysical characterization of OprB, a glucose-inducible porin of Pseudomonas aeruginosa.

PubMed

Wylie, J L; Bernegger-Egli, C; O'Neil, J D; Worobec, E A

1993-10-01

OprB, a glucose-inducible porin of P. aeruginosa, was characterized by black lipid bilayer analysis and circular dichroism spectroscopy. Black lipid bilayer analysis of OprB revealed a single-channel conductance of 25 pS, the presence of a glucose binding site with a Ks for glucose of 380 +/- 40 mM, and the formation of channels with a strong selection for anions. Analysis of P. aeruginosa OprB circular dichroism spectra revealed a high beta sheet content (40%) which is within the range of that determined for other porins. Values obtained from black lipid bilayer analysis were compared to those previously obtained for OprB of P. putida [Saravolac et al. (1991). J. Bacteriol. 173, 4970-4976] and indicated extensive similarities in the single-channel conductance and glucose-binding properties of these two porins. Immunological and amino terminal sequence analysis revealed a high degree of homology. Of the first 14 amino terminal residues, 12 were identical. A major difference between the two porins was found in their ion selectivity. Whereas P. aeruginosa OprB is anion selective, P. putida OprB and other carbohydrate selective porins are known to be cation selective.

Synthesis and anion binding studies of tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors: Proton transfer-induced selectivity for hydrogen sulfate over sulfate.

PubMed

Khansari, Maryam Emami; Johnson, Corey R; Basaran, Ismet; Nafis, Aemal; Wang, Jing; Leszczynski, Jerzy; Hossain, Md Alamgir

2015-01-01

Tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors, tris([(4-cyanophenyl)amino]propyl)urea ( L1 ) and tris([(4-cyanophenyl)amino]propyl)thiourea ( L2 ), have been synthesized and their anion binding properties have been investigated for halides and oxoanions. As investigated by 1 H NMR titrations, each receptor binds an anion with a 1:1 stoichiometry via hydrogen-bonding interactions (NH⋯anion), showing the binding trend in the order of F - > H 2 PO 4 - > HCO 3 - > HSO 4 - > CH 3 COO - > SO 4 2- > Cl - > Br - > I in DMSO- d 6 . The interactions of the receptors were further studied by 2D NOESY, showing the loss of NOESY contacts of two NH resonances for the complexes of F - , H 2 PO 4 - , HCO 3 - , HSO 4 - or CH 3 COO - due to the strong NH⋯anion interactions. The observed higher binding affinity for HSO 4 - than SO 4 2- is attributed to the proton transfer from HSO 4 - to the central nitrogen of L1 or L2 which was also supported by the DFT calculations, leading to the secondary acid-base interactions. The thiourea receptor L2 has a general trend to show a higher affinity for an anion as compared to the urea receptor L1 for the corresponding anion in DMSO- d 6 . In addition, the compound L2 has been exploited for its extraction properties for fluoride in water using a liquid-liquid extraction technique, and the results indicate that the receptor effectively extracts fluoride from water showing ca. 99% efficiency (based on L2 ).

Synthesis and anion binding studies of tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors: Proton transfer-induced selectivity for hydrogen sulfate over sulfate

PubMed Central

Khansari, Maryam Emami; Johnson, Corey R.; Basaran, Ismet; Nafis, Aemal; Wang, Jing

2015-01-01

Tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors, tris([(4-cyanophenyl)amino]propyl)urea (L1) and tris([(4-cyanophenyl)amino]propyl)thiourea (L2), have been synthesized and their anion binding properties have been investigated for halides and oxoanions. As investigated by 1H NMR titrations, each receptor binds an anion with a 1:1 stoichiometry via hydrogen-bonding interactions (NH⋯anion), showing the binding trend in the order of F− > H2PO4− > HCO3− > HSO4− > CH3COO− > SO42− > Cl− > Br− > I in DMSO-d6. The interactions of the receptors were further studied by 2D NOESY, showing the loss of NOESY contacts of two NH resonances for the complexes of F−, H2PO4−, HCO3−, HSO4− or CH3COO− due to the strong NH⋯anion interactions. The observed higher binding affinity for HSO4− than SO42− is attributed to the proton transfer from HSO4− to the central nitrogen of L1 or L2 which was also supported by the DFT calculations, leading to the secondary acid-base interactions. The thiourea receptor L2 has a general trend to show a higher affinity for an anion as compared to the urea receptor L1 for the corresponding anion in DMSO-d6. In addition, the compound L2 has been exploited for its extraction properties for fluoride in water using a liquid-liquid extraction technique, and the results indicate that the receptor effectively extracts fluoride from water showing ca. 99% efficiency (based on L2). PMID:28184300

MitoTracker Green labeling of mitochondrial proteins and their subsequent analysis by capillary electrophoresis with laser-induced fluorescence detection.

PubMed

Presley, Andrew D; Fuller, Kathryn M; Arriaga, Edgar A

2003-08-05

MitoTracker Green (MTG) is a mitochondrial-selective fluorescent label commonly used in confocal microscopy and flow cytometry. It is expected that this dye selectively accumulates in the mitochondrial matrix where it covalently binds to mitochondrial proteins by reacting with free thiol groups of cysteine residues. Here we demonstrate that MTG can be used as a protein labeling reagent that is compatible with a subsequent analysis by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). Although the MTG-labeled proteins and MTG do not seem to electrophoretically separate, an enhancement in fluorescence intensity of the product indicates that only proteins with free thiol groups are capable of reacting with MTG. In addition we propose that MTG is a partially selective label towards some mitochondrial proteins. This selectivity stems from the high MTG concentration in the mitochondrial matrix that favors alkylation of the available thiol groups in this subcellular compartment. To that effect we treated mitochondria-enriched fractions that had been prepared by differential centrifugation of an NS-1 cell lysate. This fraction was solubilized with an SDS-containing buffer and analyzed by CE-LIF. The presence of a band with fluorescence stronger than MTG alone also indicated the presence of an MTG-protein product. Confirming that MTG is labeling mitochondrial proteins was done by treating the solubilized mitochondrial fraction with 5-furoylquinoline-3-carboxaldehyde (FQ), a fluorogenic reagent that reacts with primary amino groups, and analysis by CE-LIF using two separate detection channels: 520 nm for MTG-labeled species and 635 nm for FQ-labeled species. In addition, these results indicate that MTG labels only a subset of proteins in the mitochondria-enriched fraction.

Formation and identification of borane radical anions isolated in solid argon

NASA Astrophysics Data System (ADS)

Lin, Meng-Yeh; Huang, Tzu-Ping; Chin, Chih-Hao; Wu, Yu-Jong

2018-02-01

The infrared (IR) spectrum of borane(3) anions (BH3-) isolated in solid Ar was recorded; two vibrational modes were observed at 2259.4 and 606.6 cm-1, which were assigned to the BH2 stretching (ν3) and out-of-plane large-amplitude (ν2) modes, respectively. These anions were produced by the electron bombardment of an Ar matrix sample containing a small proportion of B2H6 and H2 during matrix deposition or by the photolysis of single-bridged-B2H5- in an Ar matrix with the selected ultraviolet light. The band positions, relative intensity ratios, isotopic splitting pattern, and isotopic shift ratios of the observed IR features of BH3- are generally in good agreement with those predicted by the B2PLYP/aug-cc-pVTZ method.

Relocation of the disulfonic stilbene sites of AE1 (band 3) on the basis of fluorescence energy transfer measurements.

PubMed

Knauf, Philip A; Law, Foon-Yee; Leung, Tze-Wah Vivian; Atherton, Stephen J

2004-09-28

Previous fluorescence resonance energy transfer (FRET) measurements, using BIDS (4-benzamido-4'-isothiocyanostilbene-2,2'-disulfonate) as a label for the disulfonic stilbene site and FM (fluorescein-5-maleimide) as a label for the cytoplasmic SH groups on band 3 (AE1), combined with data showing that the cytoplasmic SH groups lie about 40 A from the cytoplasmic surface of the lipid bilayer, would place the BIDS sites very near the membrane's inner surface, a location that seems to be inconsistent with current models of AE1 structure and mechanism. We reinvestigated the BIDS-FM distance, using laser single photon counting techniques as well as steady-state fluorescence of AE1, in its native membrane environment. Both techniques agree that there is very little energy transfer from BIDS to FM. The mean energy transfer (E), based on three-exponential fits to the fluorescence decay data, is 2.5 +/- 0.7% (SEM, N = 12). Steady-state fluorescence measurements also indicate <3% energy transfer from BIDS to FM. These data indicate that the BIDS sites are probably over 63 A from the cytoplasmic SH groups, placing them near the middle or the external half of the lipid bilayer. This relocation of the BIDS sites fits with other evidence that the disulfonic stilbene sites are located farther toward the external membrane surface than Glu-681, a residue near the inner membrane surface whose modification affects the pH dependence and anion selectivity of band 3. The involvement of two relatively distant parts of the AE1 protein in transport function suggests that the transport mechanism requires coordinated large-scale conformational changes in the band 3 protein.

Imidazolium- and Triazine-Based Porous Organic Polymers for Heterogeneous Catalytic Conversion of CO2 into Cyclic Carbonates.

PubMed

Zhong, Hong; Su, Yanqing; Chen, Xingwei; Li, Xiaoju; Wang, Ruihu

2017-12-22

CO 2 adsorption and concomitant catalytic conversion into useful chemicals are promising approaches to alleviate the energy crisis and effects of global warming. This is highly desirable for developing new types of heterogeneous catalytic materials containing CO 2 -philic groups and catalytic active sites for CO 2 chemical transformation. Here, we present an imidazolium- and triazine-based porous organic polymer with counter chloride anion (IT-POP-1). The porosity and CO 2 affinity of IT-POP-1 may be modulated at the molecular level through a facile anion-exchange strategy. Compared with the post-modified polymers with iodide and hexafluorophosphate anions, IT-POP-1 possesses the highest surface area and the best CO 2 uptake capacity with excellent adsorption selectivity over N 2 . The roles of the task-specific components such as triazine, imidazolium, hydroxyl, and counter anions in CO 2 absorption and catalytic performance were illustrated. IT-POP-1 exhibits the highest catalytic activity and excellent recyclability in solvent- and additive-free cycloaddition reaction of CO 2 with epoxides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zirconium-Based Metal–Organic Framework for Removal of Perrhenate from Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Debasis; Xu, Wenqian; Nie, Zimin

2016-09-06

Efficient removal of pertechnetate (TcO4-) anions from liquid waste or melter off-gas solution for alternative treatment is one of the promising options to manage 99Tc in legacy nuclear waste. Safe immobilization of 99Tc is of major importance due to its long half-life (t1/2= 2.13 × 105 yrs) and environmental mobility. Different types of inorganic and solid state ion-exchange materials such as layered double hydroxides have been shown to absorb TcO4- anions from water. However, both high capacity and selectivity have yet to be achieved in a single material. Herein, we show that a protonated version of an ultra-stable zirconium basedmore » metal-organic framework can adsorb perrhenate (ReO4-) anions, a non-radioactive sur-rogate for TcO4-, from water even in the presence of other common anions. Synchrotron based powder X-ray diffraction and molecular simulations were used to identify the position of the adsorbed ReO4- (surrogate for TcO4-) molecule within the framework.« less

Charge-functionalized and mechanically durable composite cryogels from Q-NFC and CS for highly selective removal of anionic dyes.

PubMed

Chen, Yufei; Ru, Jing; Geng, Biyao; Wang, Haiying; Tong, Congcong; Du, Chungui; Wu, Shengchun; Liu, Hongzhi

2017-10-15

A composite cryogel was prepared from quaternized nanofibrillated cellulose (Q-NFC) and chitosan (CS) through a combination of freeze-drying and cross-linking with epichlorohydrin. The specific surface area of the composite cryogel was approximately two times that of Q-NFC cryogel. And the composite cryogel exhibited superior adsorption properties of anionic dyes than either the Q-NFC or CS cryogel controls. The adsorption isotherm well fitted the Langmuir model with the maximum theoretical adsorption capacity up to 473.9mg/g. The adsorption behavior was found to follow pseudo second-order kinetic model, indicating the chemisorption nature. Notably, the composite cryogel could effectively separate the cationic dye from anionic one. Furthermore, the composite cryogel displayed excellent reusability, evidenced by the removal percentage of Acid red 88 still as high as 96% even after five adsorption-desorption cycles. These advantages would make it an environmentally friendly candidate for the use in the separation and efficient removal of anionic dyes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adaptive self-assembly and induced-fit transformations of anion-binding metal-organic macrocycles

NASA Astrophysics Data System (ADS)

Zhang, Ting; Zhou, Li-Peng; Guo, Xiao-Qing; Cai, Li-Xuan; Sun, Qing-Fu

2017-06-01

Container-molecules are attractive to chemists due to their unique structural characteristics comparable to enzymes and receptors in nature. We report here a family of artificial self-assembled macrocyclic containers that feature induced-fit transformations in response to different anionic guests. Five metal-organic macrocycles with empirical formula of MnL2n (M=Metal L=Ligand n=3, 4, 5, 6, 7) are selectively obtained starting from one simple benzimidazole-based ligand and square-planar palladium(II) ions, either by direct anion-adaptive self-assembly or induced-fit transformations. Hydrogen-bonding interactions between the inner surface of the macrocycles and the anionic guests dictate the shape and size of the product. A comprehensive induced-fit transformation map across all the MnL2n species is drawn, with a representative reconstitution process from Pd7L14 to Pd3L6 traced in detail, revealing a gradual ring-shrinking mechanism. We envisage that these macrocyclic molecules with adjustable well-defined hydrogen-bonding pockets will find wide applications in molecular sensing or catalysis.

Effect of Anions on Nanofiber Formation of β-sheet Propensity Amphiphile Peptide

NASA Astrophysics Data System (ADS)

Shamsudeen, H.; Tan, H. L.; Eshak, Z.

2018-05-01

Peptide self-assembly forms different nanostructures under simple alteration in the solution environment. Understanding the mechanism of the assembly will help us to control and tailor functional nanomaterials. This study aims to investigate the influence of anions on the self-assembly morphology and shape using a synthetic peptide of FFFFKK. Circular Dichoism (CD) and Environmental Scanning Electron Microscope (ESEM) were used to determine the secondary structure and self-assembly morphology, while Image J imaging software was used to measure diameter size. In the absence of anion, FFFFKK formed anti-parallel β-sheet that adopted sizeable fibrillar structure with a minimal increment over the first 7 hours of assembly. Irregular structure was observed in the presence of Iodide ion (I-) with a less stable secondary structure such as β-turn and β-loop. In the presence of perchlorate ion (ClO4 -), needle-like structure was observed with predominantly β-sheet structure. Our study showed that peptide morphology can be controlled by using different anions with careful selection of amino acid residues in peptide sequence.

Synthesis of a dimeric 3α-hydroxy-7α,12α-diamino-5β-cholan-24-oate conjugate and its derivatives, and the effect of lipophilicity on their anion transport efficacy.

PubMed

Li, Zhi; Chen, Yun; Yuan, De-Qi; Chen, Wen-Hua

2017-03-28

A dimeric 3α-hydroxy-7α,12α-diamino-5β-cholan-24-oate conjugate and its derivatives having alkyl chains of varying length from methyl to n-pentyl groups on the amido bonds were synthesized and fully characterized on the basis of NMR ( 1 H and 13 C) and ESI MS (LR and HR) data. Their transmembrane anion transport activities were investigated in detail by means of a chloride ion selective electrode technique and the pyranine assay. The data indicate that this set of compounds is capable of promoting the transmembrane transport of anions, presumably via an anion exchange process and a mobile carrier mechanism. Detailed kinetic analysis on the data obtained from both chloride efflux and pH discharge experiments reveals that an optimum log P range may exist for the transport effectiveness in terms of both k 2 /K diss and EC 50 values. The present finding highlights the importance of high anionophoric activity in clarifying the effect of lipophilicity on ion-transport effectiveness.

Ionic liquids composed of phosphonium cations and organophosphate, carboxylate, and sulfonate as lubricant antiwear additives

DOE PAGES

Zhou, Yan; Dyck, Jeffrey; Graham, Todd; ...

2014-10-20

Oil-soluble phosphonium-based ionic liquids (ILs) have recently been reported as potential ashless lubricant additives. This study is to expand the IL chemistry envelope and to achieve fundamental correlations between the ion structures and ILs’ physiochemical and tribological properties. Here we present eight ILs containing two different phosphonium cations and seven different anions from three groups: organophosphate, carboxylate, and sulfonate. The oil solubility of ILs seems largely governed by the IL molecule size and structure complexity. When used as oil additives, the ranking of effectiveness in wear protection for the anions are: organophosphate > carboxylate > sulfonate. All selected ILs outperformedmore » a commercial ashless anti-wear additive. Surface characterization from the top and the cross-section revealed the nanostructures and compositions of the tribo-films formed by the ILs. Some fundamental insights were achieved: branched and long alkyls improve the IL’s oil solubility, anions of a phosphonium-phosphate IL contribute most phosphorus in the tribofilm, and carboxylate anions, though free of P, S, N, or halogen, can promote the formation of an anti-wear tribofilm.« less

Thermoelectric materials ternary penta telluride and selenide compounds

DOEpatents

Sharp, Jeffrey W.

2001-01-01

Ternary tellurium compounds and ternary selenium compounds may be used in fabricating thermoelectric devices with a thermoelectric figure of merit (ZT) of 1.5 or greater. Examples of such compounds include Tl.sub.2 SnTe.sub.5, Tl.sub.2 GeTe.sub.5, K.sub.2 SnTe.sub.5 and Rb.sub.2 SnTe.sub.5. These compounds have similar types of crystal lattice structures which include a first substructure with a (Sn, Ge) Te.sub.5 composition and a second substructure with chains of selected cation atoms. The second substructure includes selected cation atoms which interact with selected anion atoms to maintain a desired separation between the chains of the first substructure. The cation atoms which maintain the desired separation between the chains occupy relatively large electropositive sites in the resulting crystal lattice structure which results in a relatively low value for the lattice component of thermal conductivity (.kappa..sub.g). The first substructure of anion chains indicates significant anisotropy in the thermoelectric characteristics of the resulting semiconductor materials.

Thermoelectric materials: ternary penta telluride and selenide compounds

DOEpatents

Sharp, Jeffrey W.

2002-06-04

Ternary tellurium compounds and ternary selenium compounds may be used in fabricating thermoelectric devices with a thermoelectric figure of merit (ZT) of 1.5 or greater. Examples of such compounds include Tl.sub.2 SnTe.sub.5, Tl.sub.2 GeTe.sub.5, K.sub.2 SnTe.sub.5 and Rb.sub.2 SnTe.sub.5. These compounds have similar types of crystal lattice structures which include a first substructure with a (Sn, Ge) Te.sub.5 composition and a second substructure with chains of selected cation atoms. The second substructure includes selected cation atoms which interact with selected anion atoms to maintain a desired separation between the chains of the first substructure. The cation atoms which maintain the desired separation between the chains occupy relatively large electropositive sites in the resulting crystal lattice structure which results in a relatively low value for the lattice component of thermal conductivity (.kappa..sub.g). The first substructure of anion chains indicates significant anisotropy in the thermoelectric characteristics of the resulting semiconductor materials.

A Change in the Ion Selectivity of Ligand-Gated Ion Channels Provides a Mechanism to Switch Behavior.

PubMed

Pirri, Jennifer K; Rayes, Diego; Alkema, Mark J

2015-01-01

Behavioral output of neural networks depends on a delicate balance between excitatory and inhibitory synaptic connections. However, it is not known whether network formation and stability is constrained by the sign of synaptic connections between neurons within the network. Here we show that switching the sign of a synapse within a neural circuit can reverse the behavioral output. The inhibitory tyramine-gated chloride channel, LGC-55, induces head relaxation and inhibits forward locomotion during the Caenorhabditis elegans escape response. We switched the ion selectivity of an inhibitory LGC-55 anion channel to an excitatory LGC-55 cation channel. The engineered cation channel is properly trafficked in the native neural circuit and results in behavioral responses that are opposite to those produced by activation of the LGC-55 anion channel. Our findings indicate that switches in ion selectivity of ligand-gated ion channels (LGICs) do not affect network connectivity or stability and may provide an evolutionary and a synthetic mechanism to change behavior.

Influence of Inner Transducer Properties on EMF Response and Stability of Solid-Contact Anion Selective Membrane Electrodes Based on Metalloporphyrin Ionophores

PubMed Central

Górski, Łukasz; Matusevich, Alexey; Pietrzak, Mariusz; Wang, Lin; Meyerhoff, Mark E.; Malinowska, Elżbieta

2010-01-01

The performance of solid-contact/coated wire type electrodes with plasticized PVC membranes containing metalloporphyrins as anion selective ionophores is reported. The membranes are deposited on transducers based on graphite pastes and graphite rods. The hydrophobicity of the underlying conductive transducer surface is found to be a key factor that influences the formation of an aqueous layer beneath the polymer film. Elimination of this ill-defined water layer greatly improves the electrochemical properties of the ion-sensors, such as EMF stability and life-time. Only highly lipophilic electrode substrates, namely graphite paste with mineral oil, were shown to prevent the formation of aqueous layer underneath the ion-sensing membrane. The possibility of employing Co(III)-tetraphenylporphyrin both as NO2− selective ionophore and as electron/ion conducting species to ensure ion-to-electron translation was also discussed based on the results of preliminary experiments. PMID:20357903

13C metabolic flux analysis: optimal design of isotopic labeling experiments.

PubMed

Antoniewicz, Maciek R

2013-12-01

Measuring fluxes by 13C metabolic flux analysis (13C-MFA) has become a key activity in chemical and pharmaceutical biotechnology. Optimal design of isotopic labeling experiments is of central importance to 13C-MFA as it determines the precision with which fluxes can be estimated. Traditional methods for selecting isotopic tracers and labeling measurements did not fully utilize the power of 13C-MFA. Recently, new approaches were developed for optimal design of isotopic labeling experiments based on parallel labeling experiments and algorithms for rational selection of tracers. In addition, advanced isotopic labeling measurements were developed based on tandem mass spectrometry. Combined, these approaches can dramatically improve the quality of 13C-MFA results with important applications in metabolic engineering and biotechnology. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fluorescent humanized anti-CEA antibody specifically labels metastatic pancreatic cancer in a patient-derived orthotopic xenograft (PDOX) mouse model

NASA Astrophysics Data System (ADS)

Lwin, Thinzar M.; Miyake, Kentaro; Murakami, Takashi; DeLong, Jonathan C.; Yazaki, Paul J.; Shivley, John E.; Clary, Bryan; Hoffman, Robert M.; Bouvet, Michael

2018-03-01

Specific tumor targeting can result in selective labeling of cancer in vivo for surgical navigation. In the present study, we show that the use of an anti-CEA antibody conjugated to the near-infrared (NIR) fluorescent dye, IRDye800CW, can selectively target and label pancreatic cancer and its metastases in a clinically relevant patient derived xenograft mouse model.

Accurate, precise, and efficient theoretical methods to calculate anion-π interaction energies in model structures.

PubMed

Mezei, Pál D; Csonka, Gábor I; Ruzsinszky, Adrienn; Sun, Jianwei

2015-01-13

A correct description of the anion-π interaction is essential for the design of selective anion receptors and channels and important for advances in the field of supramolecular chemistry. However, it is challenging to do accurate, precise, and efficient calculations of this interaction, which are lacking in the literature. In this article, by testing sets of 20 binary anion-π complexes of fluoride, chloride, bromide, nitrate, or carbonate ions with hexafluorobenzene, 1,3,5-trifluorobenzene, 2,4,6-trifluoro-1,3,5-triazine, or 1,3,5-triazine and 30 ternary π-anion-π' sandwich complexes composed from the same monomers, we suggest domain-based local-pair natural orbital coupled cluster energies extrapolated to the complete basis-set limit as reference values. We give a detailed explanation of the origin of anion-π interactions, using the permanent quadrupole moments, static dipole polarizabilities, and electrostatic potential maps. We use symmetry-adapted perturbation theory (SAPT) to calculate the components of the anion-π interaction energies. We examine the performance of the direct random phase approximation (dRPA), the second-order screened exchange (SOSEX), local-pair natural-orbital (LPNO) coupled electron pair approximation (CEPA), and several dispersion-corrected density functionals (including generalized gradient approximation (GGA), meta-GGA, and double hybrid density functional). The LPNO-CEPA/1 results show the best agreement with the reference results. The dRPA method is only slightly less accurate and precise than the LPNO-CEPA/1, but it is considerably more efficient (6-17 times faster) for the binary complexes studied in this paper. For 30 ternary π-anion-π' sandwich complexes, we give dRPA interaction energies as reference values. The double hybrid functionals are much more efficient but less accurate and precise than dRPA. The dispersion-corrected double hybrid PWPB95-D3(BJ) and B2PLYP-D3(BJ) functionals perform better than the GGA and meta-GGA functionals for the present test set.

Dynamic map labeling.

PubMed

Been, Ken; Daiches, Eli; Yap, Chee

2006-01-01

We address the problem of filtering, selecting and placing labels on a dynamic map, which is characterized by continuous zooming and panning capabilities. This consists of two interrelated issues. The first is to avoid label popping and other artifacts that cause confusion and interrupt navigation, and the second is to label at interactive speed. In most formulations the static map labeling problem is NP-hard, and a fast approximation might have O(nlogn) complexity. Even this is too slow during interaction, when the number of labels shown can be several orders of magnitude less than the number in the map. In this paper we introduce a set of desiderata for "consistent" dynamic map labeling, which has qualities desirable for navigation. We develop a new framework for dynamic labeling that achieves the desiderata and allows for fast interactive display by moving all of the selection and placement decisions into the preprocessing phase. This framework is general enough to accommodate a variety of selection and placement algorithms. It does not appear possible to achieve our desiderata using previous frameworks. Prior to this paper, there were no formal models of dynamic maps or of dynamic labels; our paper introduces both. We formulate a general optimization problem for dynamic map labeling and give a solution to a simple version of the problem. The simple version is based on label priorities and a versatile and intuitive class of dynamic label placements we call "invariant point placements". Despite these restrictions, our approach gives a useful and practical solution. Our implementation is incorporated into the G-Vis system which is a full-detail dynamic map of the continental USA. This demo is available through any browser.

Ammonium boranes for the selective complexation of cyanide or fluoride ions in water.

PubMed

Hudnall, Todd W; Gabbaï, François P

2007-10-03

With the recognition of aqueous fluoride and cyanide ions as an objective, we have investigated the anion binding properties of two isomeric ammonium boranes, namely [p-(Mes2B)C6H4(NMe3)]+ ([1]+) and [o-(Mes2B)C6H4(NMe3)]+ ([2]+). These cationic boranes, which could be obtained by reaction of the known 4- and 2-dimesitylboryl-N,N-dimethylaniline with MeOTf, have been investigated both experimentally and computationally. They both react with fluoride and cyanide ions in organic solvents to afford the corresponding fluoroborate/ or cyanoborate/ammonium zwitterions 1F, 1CN, 2F, and 2CN. In aqueous solution, however, these cationic boranes behave as remarkably selective receptors. Indeed, [1]+ only complexes cyanide ions while [2]+ only complexes fluoride ions. In H2O/DMSO 60:40 vol (HEPES 6 mM, pH 7), the cyanide binding constant of [1]+ and the fluoride binding constant of [2]+ are respectively equal to 3.9 (+/-0.1) x 108 and 910 (+/-50) M-1. Structural and computational studies indicate that both steric and electronic effects contribute to the unusual selectivity displayed by these cationic boranes. Owing to favorable Coulombic effects, the para-derivative [1]+ has a very high affinity for cyanide; yet these effects are not sufficiently intense to allow complexation of the more efficiently hydrated and less basic fluoride anion. In the case of the ortho-derivative [2]+, the proximity of the ammonium moiety leads to an increase in the Lewis acidity of the boron center thus making fluoride binding possible. However, steric effects prevent cyanide coordination to the boron center of [2]+. Finally, cation [1]+ and [2]+ bind their dedicated anions reversibly and show a negligible response in the presence of other common anions including Cl-, Br-, I-, NO3-, OAc-, H2PO4-, and HSO4-.

Comparison of capillary electrophoresis-mass spectrometry and hydrophilic interaction chromatography-mass spectrometry for anionic metabolic profiling of urine.

PubMed

Kok, Miranda G M; Somsen, Govert W; de Jong, Gerhardus J

2015-01-01

In order to assess the utility of a recently developed capillary electrophoresis-mass spectrometry (CE-MS) method for the study of anionic metabolites in urine, a comparison was made with hydrophilic interaction chromatography-MS (HILIC-MS) using negative electrospray ionization. After optimization of the HILIC conditions, a gradient employing 10mM ammonium acetate (pH 6.8) in acetonitrile-water (5 min 90% acetonitrile followed by 90%-50% acetonitrile in 10 min) was selected, providing baseline separation of five representative anionic test metabolites. Relative standard deviations (RSDs) for HILIC retention times and peak areas were below 0.2% and 7.7%, respectively, and detection limits were in the range 0.04-2.21 μM. Metabolites in rat urine could also be analysed in a reproducible way with retention time and peak area RSDs below 0.6% and 13.6%, respectively. The CE-MS and HILIC-MS methods were compared in terms of reproducibility, sensitivity, selectivity and coverage of the anionic urinary metabolome. In general, peak area RSDs were similar whereas HILIC-MS yielded better retention-time repeatability and up to 80 times lower detection limits (expressed in injected concentration) for test metabolites as compared to CE-MS. Rat urine analysis by HILIC-MS provided detection of 1360 molecular features compared to 347 molecular features revealed with CE-MS. Of these, a number of 144 molecular features were found with both HILIC-MS and CE-MS, which showed on average 10 times higher peak areas in HILIC-MS. The HILIC retention and CE migration times of the common features were clearly not correlated. The HILIC and CE behavior of the test metabolites and 16 putatively identified common features were evaluated involving their physicochemical properties, indicating a markedly different separation selectivity, and thus significant degree of orthogonality of HILIC and CE. Copyright © 2014 Elsevier B.V. All rights reserved.

Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li0.2Ni0.2Mn0.6]O2.

PubMed

Luo, Kun; Roberts, Matthew R; Guerrini, Niccoló; Tapia-Ruiz, Nuria; Hao, Rong; Massel, Felix; Pickup, David M; Ramos, Silvia; Liu, Yi-Sheng; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

2016-09-07

Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn(3+/4+) in LiMn2O4, and this limits the energy storage of Li-ion batteries. Compounds such as Li[Li0.2Ni0.2Mn0.6]O2 exhibit a capacity to store charge in excess of the transition metal redox reactions. The additional capacity occurs at and above 4.5 V versus Li(+)/Li. The capacity at 4.5 V is dominated by oxidation of the O(2-) anions accounting for ∼0.43 e(-)/formula unit, with an additional 0.06 e(-)/formula unit being associated with O loss from the lattice. In contrast, the capacity above 4.5 V is mainly O loss, ∼0.08 e(-)/formula. The O redox reaction involves the formation of localized hole states on O during charge, which are located on O coordinated by (Mn(4+)/Li(+)). The results have been obtained by combining operando electrochemical mass spec on (18)O labeled Li[Li0.2Ni0.2Mn0.6]O2 with XANES, soft X-ray spectroscopy, resonant inelastic X-ray spectroscopy, and Raman spectroscopy. Finally the general features of O redox are described with discussion about the role of comparatively ionic (less covalent) 3d metal-oxygen interaction on anion redox in lithium rich cathode materials.

Absence of Proton Channels in COS-7 Cells Expressing Functional NADPH Oxidase Components

PubMed Central

Morgan, Deri; Cherny, Vladimir V.; Price, Marianne O.; Dinauer, Mary C.; DeCoursey, Thomas E.

2002-01-01

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is an enzyme of phagocytes that produces bactericidal superoxide anion (O2 −) via an electrogenic process. Proton efflux compensates for the charge movement across the cell membrane. The proton channel responsible for the H+ efflux was thought to be contained within the gp91phox subunit of NADPH oxidase, but recent data do not support this idea (DeCoursey, T.E., V.V. Cherny, D. Morgan, B.Z. Katz, and M.C. Dinauer. 2001. J. Biol. Chem. 276:36063–36066). In this study, we investigated electrophysiological properties and superoxide production of COS-7 cells transfected with all NADPH oxidase components required for enzyme function (COSphox). The 7D5 antibody, which detects an extracellular epitope of the gp91phox protein, labeled 96–98% of COSphox cells. NADPH oxidase was functional because COSphox (but not COSWT) cells stimulated by phorbol myristate acetate (PMA) or arachidonic acid (AA) produced superoxide anion. No proton currents were detected in either wild-type COS-7 cells (COSWT) or COSphox cells studied at pHo 7.0 and pHi 5.5 or 7.0. Anion currents that decayed at voltages positive to 40 mV were the only currents observed. PMA or AA did not elicit detectable H+ current in COSWT or COSphox cells. Therefore, gp91phox does not function as a proton channel in unstimulated cells or in activated cells with a demonstrably functional oxidase. PMID:12034764

Absence of proton channels in COS-7 cells expressing functional NADPH oxidase components.

PubMed

Morgan, Deri; Cherny, Vladimir V; Price, Marianne O; Dinauer, Mary C; DeCoursey, Thomas E

2002-06-01

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is an enzyme of phagocytes that produces bactericidal superoxide anion (O(2)(-)) via an electrogenic process. Proton efflux compensates for the charge movement across the cell membrane. The proton channel responsible for the H(+) efflux was thought to be contained within the gp91(phox) subunit of NADPH oxidase, but recent data do not support this idea (DeCoursey, T.E., V.V. Cherny, D. Morgan, B.Z. Katz, and M.C. Dinauer. 2001. J. Biol. Chem. 276:36063-36066). In this study, we investigated electrophysiological properties and superoxide production of COS-7 cells transfected with all NADPH oxidase components required for enzyme function (COS(phox)). The 7D5 antibody, which detects an extracellular epitope of the gp91(phox) protein, labeled 96-98% of COS(phox) cells. NADPH oxidase was functional because COS(phox) (but not COS(WT)) cells stimulated by phorbol myristate acetate (PMA) or arachidonic acid (AA) produced superoxide anion. No proton currents were detected in either wild-type COS-7 cells (COS(WT)) or COS(phox) cells studied at pH(o) 7.0 and pH(i) 5.5 or 7.0. Anion currents that decayed at voltages positive to 40 mV were the only currents observed. PMA or AA did not elicit detectable H(+) current in COS(WT) or COS(phox) cells. Therefore, gp91(phox) does not function as a proton channel in unstimulated cells or in activated cells with a demonstrably functional oxidase.

The mechanism and thermodynamics of transesterification of acetate-ester enolates in the gas phase

NASA Astrophysics Data System (ADS)

Haas, George W.; Giblin, Daryl E.; Gross, Michael L.

1998-01-01

In solution, base-catalyzed hydrolysis and transesterification of esters are initiated by hydroxide- or alkoxide-ion attack at the carbonyl carbon. At low pressures in the gas phase, however, transesterification proceeds by an attack of the enolate anion of an acetate ester on an alcohol. Fourier transform mass spectrometry (FTMS) indicates that the reaction is the second-order process: -CH2-CO2-R + R'-OH --> - CH2-CO2-R' + R-OH and there is little to no detectable production of either alkoxide anion. Labeling studies show that the product and reactant enolate anion esters undergo exchange of hydrogens located [alpha] to the carbonyl carbon with the deuterium of R'-OD. The extent of the H/D exchange increases with reaction time, pointing to a short-lived intermediate. The alcoholysis reaction rate constants increase with increasing acidity of the primary, straight-chained alkyl alcohols, whereas steric effects associated with branched alcohols cause the rate constants to decrease. Equilibrium constants, which were determined directly from measurements at equilibrium and which were calculated from the forward and reverse rate constants, are near unity and show internal consistency. In the absence of steric effects, the larger enolate is always the favored product at equilibrium. The intermediate for the transesterification reaction, which can be generated at a few tenths of a torr in a tandem mass spectrometer, is tetrahedral, but other adducts that are collisionally stabilized under these conditions are principally loosely bound complexes.

Volume-dependent ATP-conductive large-conductance anion channel as a pathway for swelling-induced ATP release.

PubMed

Sabirov, R Z; Dutta, A K; Okada, Y

2001-09-01

In mouse mammary C127i cells, during whole-cell clamp, osmotic cell swelling activated an anion channel current, when the phloretin-sensitive, volume-activated outwardly rectifying Cl(-) channel was eliminated. This current exhibited time-dependent inactivation at positive and negative voltages greater than around +/-25 mV. The whole-cell current was selective for anions and sensitive to Gd(3)+. In on-cell patches, single-channel events appeared with a lag period of approximately 15 min after a hypotonic challenge. Under isotonic conditions, cell-attached patches were silent, but patch excision led to activation of currents that consisted of multiple large-conductance unitary steps. The current displayed voltage- and time-dependent inactivation similar to that of whole-cell current. Voltage-dependent activation profile was bell-shaped with the maximum open probability at -20 to 0 mV. The channel in inside-out patches had the unitary conductance of approximately 400 pS, a linear current-voltage relationship, and anion selectivity. The outward (but not inward) single-channel conductance was suppressed by extracellular ATP with an IC(50) of 12.3 mM and an electric distance (delta) of 0.47, whereas the inward (but not outward) conductance was inhibited by intracellular ATP with an IC(50) of 12.9 mM and delta of 0.40. Despite the open channel block by ATP, the channel was ATP-conductive with P(ATP)/P(Cl) of 0.09. The single-channel activity was sensitive to Gd(3)+, SITS, and NPPB, but insensitive to phloretin, niflumic acid, and glibenclamide. The same pharmacological pattern was found in swelling-induced ATP release. Thus, it is concluded that the volume- and voltage-dependent ATP-conductive large-conductance anion channel serves as a conductive pathway for the swelling-induced ATP release in C127i cells.

Methodology of analysis of very weak acids by isotachophoresis with electrospray-ionization mass-spectrometric detection: Anionic electrolyte systems for the medium-alkaline pH range.

PubMed

Malá, Zdena; Gebauer, Petr

2018-01-15

This work describes for the first time a functional electrolyte system setup for anionic isotachophoresis (ITP) with electrospray-ionization mass-spectrometric (ESI-MS) detection in the neutral to medium-alkaline pH range. So far no application was published on the analysis of very weak acids by anionic ITP-MS although there is a broad spectrum of potential analytes with pK a values in the range 5-10, where application of this technique promises interesting gains in both sensitivity and specificity. The problem so far was the lack of anionic ESI-compatible ITP systems in the mentioned pH range as all typical volatile anionic system components are fully ionized at neutral and alkaline pH and thus too fast to suit as terminators. We propose an original solution of the problem based on the combination of two ITP methods: (i) use of the hydroxyl ion as a natural and ESI-compatible terminator, and (ii) use of configurations based on moving-boundary ITP. The former method ensures effective stacking of analytes by an alkaline terminator of sufficiently low mobility and the latter offers increased flexibility for tuning of the separation window and selectivity according to actual needs. A theoretical description of the proposed model is presented and applied to the design of very simple functional electrolyte configurations. The properties of example systems are demonstrated by both computer simulation and experiments with a group of model analytes. Potential effects of carbon dioxide present in the solutions are demonstrated for particular systems. Experimental results confirm that the proposed methodology is well capable of performing sensitive and selective ITP-MS analyses of very weak acidic analytes (e.g. sulfonamides or chlorophenols). Copyright © 2017 Elsevier B.V. All rights reserved.

Reported Influences on Restaurant-Type Food Selection Decision Making in a Grocery Store Chain.

PubMed

Bachman, Jessica Lynne; Arigo, Danielle

2018-06-01

To examine food decision-making priorities for restaurant-type foods at grocery stores and determine whether adding calorie information, as required by federal menu labeling laws, affected decision-making priorities. Natural experiment: intervention and control groups with baseline and follow-up. Regional grocery store chain with 9 locations. Participants (n = 393; mean age, 54.8 ± 15.1 years) were primarily women (71%) and Caucasian (95%). Data were collected before and after calorie information was added to restaurant-type foods at 4 intervention locations. Primary influencers of food selection decision making for restaurant-type foods and frequency of use of nutrition information. Quantitative analysis examined the top 3 influencers of food selections and chi-square goodness of fit test determined whether the calorie labeling intervention changed food decision-making priorities. Qualitative data were used to describe responses. Taste, cost, and convenience were the most frequently reported influencers of restaurant-type food selections; 20% of participants rated calories as influential. Calorie labeling did not affect food selection decision making; 16% of participants in intervention stores noticed calorie labels. Qualitative explanations confirmed these findings. Menu labeling laws increase access to calorie information; however, use of this information is limited. Additional interventions are needed to encourage healthier restaurant-type food selections in grocery stores. Copyright © 2018 Society for Nutrition Education and Behavior. Published by Elsevier Inc. All rights reserved.

Selective oxoanion separation using a tripodal ligand

DOEpatents

Custelcean, Radu; Moyer, Bruce A.; Rajbanshi, Arbin

2016-02-16

The present invention relates to urea-functionalized crystalline capsules self-assembled by sodium or potassium cation coordination and by hydrogen-bonding water bridges to selectively encapsulate tetrahedral divalent oxoanions from highly competitive aqueous alkaline solutions and methods using this system for selective anion separations from industrial solutions. The method involves competitive crystallizations using a tripodal tris(urea) functionalized ligand and, in particular, provides a viable approach to sulfate separation from nuclear wastes.

Effect of Chloride Anions on the Synthesis and Enhanced Catalytic Activity of Silver Nanocoral Electrodes for CO 2 Electroreduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, Yu-Chi; Senanayake, Sanjaya D.; Zhang, Yu

2015-09-04

Metallic silver (Ag) is known as an efficient electrocatalyst for the conversion of carbon dioxide (CO 2) to carbon monoxide (CO) in aqueous or nonaqueous electrolytes. However, polycrystalline silver electrocatalysts require significant overpotentials in order to achieve high selectivity toward CO 2 reduction, as compared to the side reaction of hydrogen evolution. Here we report a high-surface-area Ag nanocoral catalyst, fabricated by an oxidation–reduction method in the presence of chloride anions in an aqueous medium, for the electro-reduction of CO 2 to CO with a current efficiency of 95% at the low overpotential of 0.37 V and the current densitymore » of 2 mA cm –2. A lower limit of TOF of 0.4 s –1 and TON > 8.8 × 10 4 (over 72 h) was estimated for the Ag nanocoral catalyst at an overpotential of 0.49 V. The Ag nanocoral catalyst demonstrated a 32-fold enhancement in surface-area-normalized activity, at an overpotential of 0.49 V, as compared to Ag foil. We found that, in addition to the effect on nanomorphology, the adsorbed chloride anions play a critical role in the observed enhanced activity and selectivity of the Ag nanocoral electrocatalyst toward CO 2 reduction. Synchrotron X-ray photoelectron spectroscopy (XPS) studies along with a series of control experiments suggest that the chloride anions, remaining adsorbed on the catalyst surface under electrocatalytic conditions, can effectively inhibit the side reaction of hydrogen evolution and enhance the catalytic performance for CO 2 reduction.« less

Meningococcal X polysaccharide quantification by high-performance anion-exchange chromatography using synthetic N-acetylglucosamine-4-phosphate as standard.

PubMed

Micoli, F; Adamo, R; Proietti, D; Gavini, M; Romano, M R; MacLennan, C A; Costantino, P; Berti, F

2013-11-15

A method for meningococcal X (MenX) polysaccharide quantification by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) is described. The polysaccharide is hydrolyzed by strong acidic treatment, and the peak of glucosamine-4-phosphate (4P-GlcN) is detected and measured after chromatography. In the selected conditions of hydrolysis, 4P-GlcN is the prevalent species formed, with GlcN detected for less than 5% in moles. As standard for the analysis, the monomeric unit of MenX polysaccharide, N-acetylglucosamine-4-phosphate (4P-GlcNAc), was used. This method for MenX quantification is highly selective and sensitive, and it constitutes an important analytical tool for the development of a conjugate vaccine against MenX. Copyright © 2013 Elsevier Inc. All rights reserved.

Complete Transmetalation in a Metal-Organic Framework by Metal Ion Metathesis in a Single Crystal for Selective Sensing of Phosphate Ions in Aqueous Media.

PubMed

Asha, K S; Bhattacharjee, Rameswar; Mandal, Sukhendu

2016-09-12

A complete transmetalation has been achieved on a barium metal-organic framework (MOF), leading to the isolation of a new Tb-MOF in a single-crystal (SC) to single-crystal (SC) fashion. It leads to the transformation of an anionic framework with cations in the pore to one that is neutral. The mechanistic studies proposed a core-shell metal exchange through dissociation of metal-ligand bonds. This Tb-MOF exhibits enhanced photoluminescence and acts as a selective sensor for phosphate anion in aqueous medium. Thus, this work not only provides a method to functionalize a MOF that can have potential application in sensing but also elucidates the formation mechanism of the resulting MOF. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical sensing of hydrogen sulphate using rhodamine 6G hydrazide from aqueous medium

NASA Astrophysics Data System (ADS)

Upadhyay, Yachana; Bothra, Shilpa; Kumar, Rajender; Choi, Heung-Jin; Sahoo, Suban K.

2017-06-01

This communication reports the application of rhodamine 6G hydrazide (L) for the selective colorimetric and turn-on fluorescent sensing of hydrogen sulphate ions from aqueous medium. The ring opening of the colourless spirocyclic form of L was selectively triggered in the presence of HSO4- among the other tested anions (F-, Cl-, Br-, I-, AcO-, H2PO4-, NO3-, ClO4-, CN-, HO-, AsO33 - and SO42 -), which gives rise to a pink colour and strong fluorescence in the visible region. Sensor L showed a detection limit down to micromolar range without any interference from the other tested competitive anions. Sensor L was applied for the construction of two inputs (HO- and HSO4-) INHIBIT type molecular logic gate and naked-eye detection of HSO4- using test paper strips.

Anion mediated polytype selectivity among the basic salts of Co(II)

NASA Astrophysics Data System (ADS)

Ramesh, T. N.; Rajamathi, Michael; Vishnu Kamath, P.

2006-08-01

Basic salts of Co(II) crystallize in the rhombohedral structure. Two different polytypes, 3R 1 and 3R 2, with distinct stacking sequences of the metal hydroxide slabs, are possible within the rhombohedral structure. These polytypes are generated by simple translation of successive layers by (2/3, 1/3, z) or (1/3, 2/3, z). The symmetry of the anion and the mode of coordination influences polytype selection. Cobalt hydroxynitrate crystallizes in the structure of the 3R 2 polytype while the hydroxytartarate, hydroxychloride and α-cobalt hydroxide crystallize in the structure of the 3R 1 polytype. Cobalt hydroxysulfate is turbostratically disordered. The turbostratic disorder is a direct consequence of the mismatch between the crystallographically defined interlayer sites generated within the crystal and the tetrahedral symmetry of the SO 42- ions.

Toward the use of surface modified activated carbon in speciation: selective preconcentration of selenite and selenate in environmental waters.

PubMed

Tsoi, Yeuk-Ki; Leung, Kelvin Sze-Yin

2011-04-22

This paper describes a novel application of tetrabutylammonium hydroxide-modified activated carbon (AC-TBAH) to the speciation of ultra-trace Se(IV) and Se(VI) using LC-ICP-DRC-MS. The anion exchange functionality was immobilized onto the AC surface enables selective preconcentration of inorganic Se anions in a wide range of working pHs. Simultaneous retention and elution of both analytes, followed by subsequent analysis with LC-ICP-DRC-MS, allows to accomplish speciation analysis in natural samples without complicated redox pre-treatment. The laboratory-made column of immobilized AC (0.4 g of sorbent packed in a 6 mL syringe barrel) has achieved analyte enrichment factors of 76 and 93, respectively, for Se(IV) and Se(VI), thus proving its superior preconcentration efficiency and selectivity over common AC. The considerable enhancement in sensitivity achieved by using the preconcentration column has improved the method's detection limits to 1.9-2.2 ng L(-1), which is a 100-fold improvement compared with direct injection. The analyte recoveries from heavily polluted river matrix were between 95.3 and 107.7% with less than 5.0% RSD. The robustness of the preconcentration and speciation method was validated by analysis of natural waters collected from rivers and reservoirs in Hong Kong. The modified AC material is hence presented as a low-cost yet robust substitute for conventional anion exchange resins for routine applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Harvesting polysulfides by sealing the sulfur electrode in a composite ion-selective net

NASA Astrophysics Data System (ADS)

Chen, Yazhou; Li, Zhong; Li, Xuekui; Zeng, Danli; Xu, Guodong; Zhang, Yunfeng; Sun, Yubao; Ke, Hanzhong; Cheng, Hansong

2017-11-01

A cathode was prepared by sealing a carbon supported sulfur electrode inside a composite ion-selective net made of carbon, binder and lithiated ionomer to restrict shuttling of polysulfide anionic species. As a result, the soluble polysulfide anions become unable to escape from the composite ion-selective films due to the electrostatic repulsion between the immobilized single ion conducting ionomers and the polysulfides with no dead angles. Experimentally, lithiated 4,4‧-difluoro bis(benzene sulfonyl)imide and PEG200 were copolymerized to form a polyether based single ion conducting polymer. The ionic conductivity of the blend film made of ionomer and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) at a mass ratio of 1:1 is 0.57 mS cm-1 at room temperature. The battery capacity with the sealed sulfur electrode is 1412 mAh g-1 at 0.5 C, 1041 mAh g-1 at 1.0 C, 873 mAh g-1 at 2.0 C and 614 mAh g-1 at 5.0 C, significantly better than the results with lithiated Nafion especially at high C rates. In addition, a long cycling test at 2 C for 500 cycles gives rise to a stable capacity of 800 mAh g-1. The intrinsic electrostatic repulsion between polysulfide anions and the negatively charged electrolyte film, together with the overall sealed electrode configuration, is responsible for blocking the shuttling of polysulfides effectively.

Portion Size Labeling and Intended Soft Drink Consumption: The Impact of Labeling Format and Size Portfolio

ERIC Educational Resources Information Center

Vermeer, Willemijn M.; Steenhuis, Ingrid H. M.; Leeuwis, Franca H.; Bos, Arjan E. R.; de Boer, Michiel; Seidell, Jacob C.

2010-01-01

Objective: To assess what portion size labeling "format" is most promising in helping consumers selecting appropriate soft drink sizes, and whether labeling impact depends on the size portfolio. Methods: An experimental study was conducted in fast-food restaurants in which 2 labeling formats (ie, reference portion size and small/medium/large…

Fluorescent Photo-conversion: A second chance to label unique cells

PubMed Central

Mellott, Adam J.; Shinogle, Heather E.; Moore, David S.; Detamore, Michael S.

2014-01-01

Not all cells behave uniformly after treatment in tissue engineering studies. In fact, some treated cells display no signs of treatment or show unique characteristics not consistent with other treated cells. What if the “unique” cells could be isolated from a treated population, and further studied? Photo-convertible reporter proteins, such as Dendra2, allow for the ability to selectively identify unique cells with a secondary label within a primary labeled treated population. In the current study, select cells were identified and labeled through photo-conversion of Dendra2-transfected human Wharton's Jelly cells (hWJCs) for the first time. Robust photo-conversion of green-to-red fluorescence was achieved consistently in arbitrarily selected cells, allowing for precise cell identification of select hWJCs. The current study demonstrates a method that offers investigators the opportunity to selectively label and identify unique cells within a treated population for further study or isolation from the treatment population. Photo-convertible reporter proteins, such as Dendra2, offer the ability over non-photo-convertible reporter proteins, such as green fluorescent protein, to analyze unique individual cells within a treated population, which allows investigators to gain more meaningful information on how a treatment affects all cells within a target population. PMID:25914756

Ionic liquid-capped graphene quantum dots as label-free fluorescent probe for direct detection of ferricyanide.

PubMed

Sun, Xue; Qian, Yuting; Jiao, Yajie; Liu, Jiyang; Xi, Fengna; Dong, Xiaoping

2017-04-01

Despite complex molecular and atomic doping, efficient post-functionalization strategies for graphene quantum dots (GQDs) are of key importance to control the physicochemical properties and broaden the practical applications. With ionic liquid as specific modification agents, herein, the preparation of ionic liquid-capped GQDs (IL-GQDs) and its application as label-free fluorescent probe for direct detection of anion were reported. Hydroxyl-functionalized GQDs that could be easily gram-scale synthesized and possessed single-crystalline were chosen as the model GQDs. Also, the most commonly used ionic liquids, water-soluble 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF 4 ) was chosen as the model IL. Under the ultrasonic treatment, BMIMBF 4 easily composited with GQDs to form IL-GQDs. The synthesized IL-GQDs were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and fluorescence (FL) spectrum. After successful combination with IL, the excitation-independent photoluminescence behavior of GQDs presented almost no change, whereas, the anion responsiveness of IL-GQDs drastically improved, which afforded the IL-GQDs a sensitive response to Fe(CN) 6 3- . Based on the strong fluorescence quench, a facile and sensitive detection of Fe(CN) 6 3- was achieved. A wide linear range of 1.0×10 -7 to 2.5×10 -3 moll -1 with a low detection limit of 40 nmol l -1 was obtained. As the composition and properties of IL and GQDs could be easily tuned by varying the structure, ionic liquids-capped GQDs might present promising potential for their applications in sensing and catalysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of anion exchange resins Tulsion A-30 and Indion-930A by application of radioanalytical technique

NASA Astrophysics Data System (ADS)

Singare, P. U.

2014-07-01

Radioanalytical technique using 131I and 82Br was employed to evaluate organic based anion exchange resins Tulsion A-30 and Indion-930A. The evaluation was based on performance of these resins during iodide and bromide ion-isotopic exchange reactions. It was observed that for iodide ion-isotopic exchange reaction by using Tulsion A-30 resin, the values of specific reaction rate (min-1), amount of iodide ion exchanged (mmol), initial rate of iodide ion exchange (mmol/min) and log K d were 0.238, 0.477, 0.114, and 11.0, respectively, which was higher than 0.155, 0.360, 0.056, and 7.3, respectively as that obtained by using Indion-930A resins under identical experimental conditions of 40.0°C, 1.000 g of ion exchange resins and 0.003 M labeled iodide ion solution. Also at a constant temperature of 40.0°C, as the concentration of labeled iodide ion solution increases 0.001 to 0.004 M, for Tulsion A-30 resins the percentage of iodide ions exchanged increases from 59.0 to 65.1%, and from 46.4 to 48.8% for Indion-930A resins under identical experimental conditions. The identical trend was observed for both the resins during bromide ion-isotopic exchange reactions. The overall results indicate that under identical experimental conditions, Tulsion A-30 show superior performance over Indion-930A resins. The results of present experimental work have demonstrated that the radioanalytical technique used here can be successfully applied for characterization of different ion exchange resins so as to evaluate their performance under various process parameters.

UXO Discrimination Study Former Spencer Artillery Range

DTIC Science & Technology

2013-04-01

tested . This approach uses one of three models labeled: aggressive, intermediate and conservative. The choice of model depends on an a...anomalies will be selected for labeling using NMAL. The goal at this step is to maximize the information gain from new labels requested from the set of ...number of false alarms (nFA) is lower for the classifier where feature selection was used . 9 Complexity of a site is measured using an information

Microfabricated capillary electrophoresis chip and method for simultaneously detecting multiple redox labels

DOEpatents

Mathies, Richard A.; Singhal, Pankaj; Xie, Jin; Glazer, Alexander N.

2002-01-01

This invention relates to a microfabricated capillary electrophoresis chip for detecting multiple redox-active labels simultaneously using a matrix coding scheme and to a method of selectively labeling analytes for simultaneous electrochemical detection of multiple label-analyte conjugates after electrophoretic or chromatographic separation.

Role of the electric field in selective ion filtration in nanostructures.

PubMed

Park, Yong; Kim, Sueon; Jang, In Hyuk; Nam, Young Suk; Hong, Hiki; Choi, Dukhyun; Lee, Won Gu

2016-02-21

Nafion has received great attention as a proton conductor that can block negative ions. Here, we report the effect of a Nafion coating on an anodic aluminium oxide (AAO) nanoporous membrane on its function of ion rejection and filtering depending on the electric field. In our experiments, Nafion, once coated, was used to repel the negative ions (anions) from the coated surface, and then selectively allowed positive ions (cations) to pass through the nanopores in the presence of an electric field. To demonstrate the proof-of-concept validation, we coated Nafion solution onto the surface of AAO membranes with 20 nm nanopores average diameter at different solution concentration levels. Vacuum filtration methods for Nafion coating were vertically applied to the plane of an AAO membrane. An electric field was then applied to the upper surface of the Nafion-coated AAO membrane to investigate if ion rejection and filtering was affected by the presence of the electric field. Both anions and cations could pass through the AAO nanopores without an electric field applied. However, only cations could well pass through the AAO nanopores under an electric field, thus effectively blocking anions from passing through the nanopores. This result shows that ion filtration of electrons has been selectively performed while the system also works as a vital catalyst in reactivating Nafion via electrolysis. A saturated viscosity ratio of Nafion solution for the coating was also determined. We believe that this approach is potentially beneficial for better understanding the fundamentals of selective ion filtration in nanostructures and for promoting the use of nanostructures in potential applications such as ion-based water purification and desalination system at the nanoscale in a massively electrically integrated format.

Pitavastatin is a more sensitive and selective organic anion-transporting polypeptide 1B clinical probe than rosuvastatin

PubMed Central

Prueksaritanont, Thomayant; Chu, Xiaoyan; Evers, Raymond; Klopfer, Stephanie O; Caro, Luzelena; Kothare, Prajakti A; Dempsey, Cynthia; Rasmussen, Scott; Houle, Robert; Chan, Grace; Cai, Xiaoxin; Valesky, Robert; Fraser, Iain P; Stoch, S Aubrey

2014-01-01

Aims Rosuvastatin and pitavastatin have been proposed as probe substrates for the organic anion-transporting polypeptide (OATP) 1B, but clinical data on their relative sensitivity and selectivity to OATP1B inhibitors are lacking. A clinical study was therefore conducted to determine their relative suitability as OATP1B probes using single oral (PO) and intravenous (IV) doses of the OATP1B inhibitor rifampicin, accompanied by a comprehensive in vitro assessment of rifampicin inhibitory potential on statin transporters. Methods The clinical study comprised of two separate panels of eight healthy subjects. In each panel, subjects were randomized to receive a single oral dose of rosuvastatin (5 mg) or pitavastatin (1 mg) administered alone, concomitantly with rifampicin (600 mg) PO or IV. The in vitro transporter studies were performed using hepatocytes and recombinant expression systems. Results Rifampicin markedly increased exposures of both statins, with greater differential increases after PO vs. IV rifampicin only for rosuvastatin. The magnitudes of the increases in area under the plasma concentration–time curve were 5.7- and 7.6-fold for pitavastatin and 4.4- and 3.3-fold for rosuvastatin, after PO and IV rifampicin, respectively. In vitro studies showed that rifampicin was an inhibitor of OATP1B1 and OATP1B3, breast cancer resistance protein and multidrug resistance protein 2, but not of organic anion transporter 3. Conclusions The results indicate that pitavastatin is a more sensitive and selective and thus preferred clinical OATP1B probe substrate than rosuvastatin, and that a single IV dose of rifampicin is a more selective OATP1B inhibitor than a PO dose. PMID:24617605

Characterization of an alkaline protease associated with a granulosis virus of Plodia interpunctella.

PubMed

Tweeten, K A; Bulla, L A; Consigli, R A

1978-06-01

An alkaline protease was found to be associated with the granulosis virus of the Indian meal moth. Plodia interpunctella. The protease was located within the protein matrix of the occluded virus and hydrolyzed the major constituent of this matrix, a 28,000-dalton protein (granulin), to a mixture of polypeptides ranging in molecular weight from 10,000 to 27,000. A rapid, sensitive assay for the protease was developed using radioactively labeled granulosis virus as substrate. With this assay, the proteolytic activity could be detected by measuring the release of acid-soluble peptides from the labeled virus. The protease had a pH optimum of 10.5 and a temperature optimum of 40 degrees C and was inhibited by diisopropyl phosphorofluoridate, phenylmethylsulfonyl fluoride, and L-(1-tosylamido-2-phenyl) ethyl chloromethyl ketone. Purification of the protease from matrix protein was achieved by anion-exchange and gel permeation chromatography. The molecular weight of the isolated protease, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, was approximately 14,000.

The effects of restaurant menu calorie labeling on hypothetical meal choices of females with disordered eating.

PubMed

Haynos, Ann F; Roberto, Christina A

2017-03-01

Concerns have been raised that obesity public policy measures may have harmful effects on individuals with eating disorders. However, little research has investigated this topic. We examined the impact of a popular obesity public policy, menu calorie labeling, on hypothetical food choices of women with disordered eating. Seven hundred sixteen adult females completed an online survey in which they were randomly assigned to receive a restaurant menu with or without calorie information listed. Participants selected foods representative of a meal they would choose to consume and answered questions on restaurant ordering and menu labeling. Participants completed the Eating Disorder Examination Questionnaire (Fairburn & Beglin, ) to assess global eating pathology. Diagnoses of anorexia nervosa (AN), bulimia nervosa (BN), and binge-eating disorder (BED) were also derived from this measure. Generalized linear modeling examined the impact of menu label condition, disordered eating, and the menu label by disordered eating interaction on hypothetical food selection and related variables. When disordered eating was examined continuously, menu labeling did not differentially affect food selections of those with elevated disordered eating (p = .45). However, when examined by eating disorder diagnosis, participants with AN or BN ordered significantly fewer (p < .001) and participants with BED ordered significantly more (p = .001) calories in the menu label versus no label condition. Menu labeling may decrease the calories ordered among individuals with AN or BN and increase calories ordered among individuals with BED. © 2017 Wiley Periodicals, Inc.

The effect of sugar-sweetened beverage front-of-pack labels on drink selection, health knowledge and awareness: An online randomised controlled trial.

PubMed

Billich, Natassja; Blake, Miranda R; Backholer, Kathryn; Cobcroft, Megan; Li, Vincy; Peeters, Anna

2018-06-04

Sugar-sweetened beverages (SSBs) provide little nutritional value and are associated with an increased risk of diet-related diseases. Despite this, SSB consumption is high globally. One emerging strategy aimed at reducing SSB consumption involves the use of front-of-pack (FOP) labels that clearly identify the risks associated with SSB consumption. The aim of this research study was to determine whether FOP labels with a graphic warning, text warning, sugar information (with the number of teaspoons of added sugar) or Health Star Rating (HSR) reduces intended choice of a SSB in an online choice experiment with young Australian adults. 994 participants were recruited and completed the online choice experiment. Compared to the control group who were not exposed to a label, the graphic warning, text warning, sugar information and HSR labels all significantly reduced selection of a SSB in the choice scenario. The magnitude of effect was greatest for the graphic warning label (OR 0.22 95% CI 0.14-0.35). Compared to the control group, only the HSR label significantly increased selections of the high HSR drinks (OR 2.18 95% CI 1.20-3.97). FOP labels, particularly those with graphic warnings, have the potential to reduce intended SSB purchases. Labels that also identify healthier alternatives may influence consumers to substitute SSBs with healthier drinks. Copyright © 2018. Published by Elsevier Ltd.

The effects of restaurant menu calorie labeling on hypothetical meal choices of females with disordered eating

PubMed Central

Haynos, Ann F.; Roberto, Christina A.

2017-01-01

Objective Concerns have been raised that obesity public policy measures may have harmful effects on individuals with eating disorders. However, little research has investigated this topic. We examined the impact of a popular obesity public policy, menu calorie labeling, on hypothetical food choices of women with disordered eating. Methods 716 adult females completed an online survey in which they were randomly assigned to receive a restaurant menu with or without calorie information listed. Participants selected foods representative of a meal they would choose to consume and answered questions on restaurant ordering and menu labeling. Participants completed the Eating Disorder Examination Questionnaire (Fairburn & Beglin, 1994) to assess global eating pathology. Diagnoses of anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED) were also derived from this measure. Generalized linear modeling examined the impact of menu label condition, disordered eating, and the menu label by disordered eating interaction on hypothetical food selection and related variables. Results When disordered eating was examined continuously, menu labeling did not differentially affect food selections of those with elevated disordered eating (p = .45). However, when examined by eating disorder diagnosis, participants with AN or BN ordered significantly fewer (p < .001) and participants with BED ordered significantly more (p = .001) calories in the menu label versus no label condition. Discussion Menu labeling may decrease the calories ordered among individuals with AN or BN and increase calories ordered among individuals with BED. PMID:28130796

Nutrition labelling, marketing techniques, nutrition claims and health claims on chip and biscuit packages from sixteen countries.

PubMed

Mayhew, Alexandra J; Lock, Karen; Kelishadi, Roya; Swaminathan, Sumathi; Marcilio, Claudia S; Iqbal, Romaina; Dehghan, Mahshid; Yusuf, Salim; Chow, Clara K

2016-04-01

Food packages were objectively assessed to explore differences in nutrition labelling, selected promotional marketing techniques and health and nutrition claims between countries, in comparison to national regulations. Cross-sectional. Chip and sweet biscuit packages were collected from sixteen countries at different levels of economic development in the EPOCH (Environmental Profile of a Community's Health) study between 2008 and 2010. Seven hundred and thirty-seven food packages were systematically evaluated for nutrition labelling, selected promotional marketing techniques relevant to nutrition and health, and health and nutrition claims. We compared pack labelling in countries with labelling regulations, with voluntary regulations and no regulations. Overall 86 % of the packages had nutrition labels, 30 % had health or nutrition claims and 87 % displayed selected marketing techniques. On average, each package displayed two marketing techniques and one health or nutrition claim. In countries with mandatory nutrition labelling a greater proportion of packages displayed nutrition labels, had more of the seven required nutrients present, more total nutrients listed and higher readability compared with those with voluntary or no regulations. Countries with no health or nutrition claim regulations had fewer claims per package compared with countries with regulations. Nutrition label regulations were associated with increased prevalence and quality of nutrition labels. Health and nutrition claim regulations were unexpectedly associated with increased use of claims, suggesting that current regulations may not have the desired effect of protecting consumers. Of concern, lack of regulation was associated with increased promotional marketing techniques directed at children and misleadingly promoting broad concepts of health.

Label fusion based brain MR image segmentation via a latent selective model

NASA Astrophysics Data System (ADS)

Liu, Gang; Guo, Xiantang; Zhu, Kai; Liao, Hengxu

2018-04-01

Multi-atlas segmentation is an effective approach and increasingly popular for automatically labeling objects of interest in medical images. Recently, segmentation methods based on generative models and patch-based techniques have become the two principal branches of label fusion. However, these generative models and patch-based techniques are only loosely related, and the requirement for higher accuracy, faster segmentation, and robustness is always a great challenge. In this paper, we propose novel algorithm that combines the two branches using global weighted fusion strategy based on a patch latent selective model to perform segmentation of specific anatomical structures for human brain magnetic resonance (MR) images. In establishing this probabilistic model of label fusion between the target patch and patch dictionary, we explored the Kronecker delta function in the label prior, which is more suitable than other models, and designed a latent selective model as a membership prior to determine from which training patch the intensity and label of the target patch are generated at each spatial location. Because the image background is an equally important factor for segmentation, it is analyzed in label fusion procedure and we regard it as an isolated label to keep the same privilege between the background and the regions of interest. During label fusion with the global weighted fusion scheme, we use Bayesian inference and expectation maximization algorithm to estimate the labels of the target scan to produce the segmentation map. Experimental results indicate that the proposed algorithm is more accurate and robust than the other segmentation methods.

Eu(III) complexes as Anion-responsive Luminescent Sensors and PARACEST Agents

PubMed Central

Hammell, Jacob; Buttarazzi, Leandro; Huang, Ching-Hui; Morrow, Janet R.

2011-01-01

The Eu(III) complex of (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (S-THP) is studied as a sensor for biologically relevant anions. Anion interactions produce changes in the luminescence emission spectrum of the Eu(III) complex, in the 1H NMR spectrum, and correspondingly, in the PARACEST spectrum of the complex (PARACEST = paramagnetic chemical exchange saturation transfer). Direct excitation spectroscopy and luminescence lifetime studies of Eu(S-THP) give information about the speciation and nature of anion interactions including carbonate, acetate, lactate, citrate, phosphate and methylphosphate at pH 7.2. Data is consistent with the formation of both innersphere and outersphere complexes of Eu(S-THP) with acetate, lactate and carbonate. These anions have weak dissociation constants that range from 19–38 mM. Citrate binding to Eu(S-THP) is predominantly innersphere with a dissociation constant of 17 μM. Luminescence emission peak changes upon addition of anion to Eu(S-THP) show that there are two distinct binding events for phosphate and methylphosphate with dissociation constants of 0.3 mM and 3.0 mM for phosphate and 0.6 mM and 9.8 mM for methyl phosphate. Eu(THPC) contains an appended carbostyril derivative as an antenna to sensitize Eu(III) luminescence. Eu(THPC) binds phosphate and citrate with dissociation constants that are 10-fold less than that of the Eu(S-THP) parent, suggesting that functionalization through a pendent group disrupts the anion binding site. Eu(S-THP) functions as an anion responsive PARACEST agent through exchange of the alcohol protons with bulk water. The alcohol proton resonances of Eu(S-THP) shift downfield in the presence of acetate, lactate, citrate and methylphosphate, giving rise to distinct PARACEST peaks. In contrast, phosphate binds to Eu(S-THP) to suppress the PARACEST alcohol OH peak and carbonate does not markedly change the alcohol peak at 5 mM Eu(S-THP), 15 mM carbonate at pH 6.5 or 7.2. This work shows that the Eu(S-THP) complex has unique selectivity toward binding of biologically relevant anions and that anion binding results in changes in both the luminescence and PARACEST spectra of the complex. PMID:21548563

Eu(III) complexes as anion-responsive luminescent sensors and paramagnetic chemical exchange saturation transfer agents.

PubMed

Hammell, Jacob; Buttarazzi, Leandro; Huang, Ching-Hui; Morrow, Janet R

2011-06-06

The Eu(III) complex of (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (S-THP) is studied as a sensor for biologically relevant anions. Anion interactions produce changes in the luminescence emission spectrum of the Eu(III) complex, in the (1)H NMR spectrum, and correspondingly, in the PARACEST spectrum of the complex (PARACEST = paramagnetic chemical exchange saturation transfer). Direct excitation spectroscopy and luminescence lifetime studies of Eu(S-THP) give information about the speciation and nature of anion interactions including carbonate, acetate, lactate, citrate, phosphate, and methylphosphate at pH 7.2. Data is consistent with the formation of both innersphere and outersphere complexes of Eu(S-THP) with acetate, lactate, and carbonate. These anions have weak dissociation constants that range from 19 to 38 mM. Citrate binding to Eu(S-THP) is predominantly innersphere with a dissociation constant of 17 μM. Luminescence emission peak changes upon addition of anion to Eu(S-THP) show that there are two distinct binding events for phosphate and methylphosphate with dissociation constants of 0.3 mM and 3.0 mM for phosphate and 0.6 mM and 9.8 mM for methyl phosphate. Eu(THPC) contains an appended carbostyril derivative as an antenna to sensitize Eu(III) luminescence. Eu(THPC) binds phosphate and citrate with dissociation constants that are 10-fold less than that of the Eu(S-THP) parent, suggesting that functionalization through a pendent group disrupts the anion binding site. Eu(S-THP) functions as an anion responsive PARACEST agent through exchange of the alcohol protons with bulk water. The alcohol proton resonances of Eu(S-THP) shift downfield in the presence of acetate, lactate, citrate, and methylphosphate, giving rise to distinct PARACEST peaks. In contrast, phosphate binds to Eu(S-THP) to suppress the PARACEST alcohol OH peak and carbonate does not markedly change the alcohol peak at 5 mM Eu(S-THP), 15 mM carbonate at pH 6.5 or 7.2. This work shows that the Eu(S-THP) complex has unique selectivity toward binding of biologically relevant anions and that anion binding results in changes in both the luminescence and the PARACEST spectra of the complex. © 2011 American Chemical Society

Five-year-olds are willing, but 4-year-olds refuse, to trust informants who offer new and unfamiliar labels for parts of the body.

PubMed

Luu, Betty; Rosnay, Marc de; Harris, Paul L

2013-10-01

This study employed the selective trust paradigm to examine how children interpret novel labels when compared with labels they already know to be accurate or inaccurate within the biological domain. The participants--3-, 4-, and 5-year-olds (N=144)--were allocated to one of three conditions. In the accurate versus inaccurate condition, one informant labeled body parts correctly, whereas the other labeled them incorrectly (e.g., calling an eye an "arm"). In the accurate versus novel condition, one informant labeled body parts accurately, whereas the other provided novel labels (e.g., calling an eye a "roke"). Finally, in the inaccurate versus novel condition, one informant labeled body parts incorrectly, whereas the other offered novel labels. In subsequent test trials, the two informants provided conflicting labels for unfamiliar internal organs. In the accurate versus inaccurate condition, children sought and endorsed labels from the accurate informant. In the accurate versus novel condition, only 4- and 5-year-olds preferred the accurate informant, whereas 3-year-olds did not selectively prefer either informant. In the inaccurate versus novel condition, only 5-year-olds preferred the novel informant, whereas 3- and 4-year-olds did not demonstrate a selective preference. Results are supportive of previous studies suggesting that 3-year-olds are sensitive to inaccuracy and that 4-year-olds privilege accuracy. However, 3- and 4-year-olds appear to be unsure as to how the novel informant should be construed. In contrast, 5-year-olds appreciate that speakers offering new information are more trustworthy than those offering inaccurate information, but they are cautious in judging such informants as being "better" at providing that information. Copyright © 2013 Elsevier Inc. All rights reserved.

Automated selected reaction monitoring software for accurate label-free protein quantification.

PubMed

Teleman, Johan; Karlsson, Christofer; Waldemarson, Sofia; Hansson, Karin; James, Peter; Malmström, Johan; Levander, Fredrik

2012-07-06

Selected reaction monitoring (SRM) is a mass spectrometry method with documented ability to quantify proteins accurately and reproducibly using labeled reference peptides. However, the use of labeled reference peptides becomes impractical if large numbers of peptides are targeted and when high flexibility is desired when selecting peptides. We have developed a label-free quantitative SRM workflow that relies on a new automated algorithm, Anubis, for accurate peak detection. Anubis efficiently removes interfering signals from contaminating peptides to estimate the true signal of the targeted peptides. We evaluated the algorithm on a published multisite data set and achieved results in line with manual data analysis. In complex peptide mixtures from whole proteome digests of Streptococcus pyogenes we achieved a technical variability across the entire proteome abundance range of 6.5-19.2%, which was considerably below the total variation across biological samples. Our results show that the label-free SRM workflow with automated data analysis is feasible for large-scale biological studies, opening up new possibilities for quantitative proteomics and systems biology.

SK-N-MC cell death occurs by distinct molecular mechanisms in response to hydrogen peroxide and superoxide anions: involvements of JAK2-STAT3, JNK, and p38 MAP kinases pathways.

PubMed

Moslehi, Maryam; Yazdanparast, Razieh

2013-07-01

Oxidative stress plays a vital role in the pathogenesis of neurodegenerative diseases. Nerve cells are incessantly exposed to environmental stresses leading to overproduction of some harmful species like reactive oxygen species (ROS). ROS including hydrogen peroxide and superoxide anion are potent inducers of various signaling pathways encompassing MAPKs and JAK-STAT pathways. In the current study, we scrutinized the effects of hydrogen peroxide and/or menadione (superoxide anion generator) on JNK/p38-MAPKs and JAK2-STAT3 pathways to elucidate the mechanism(s) by which each oxidant modulated the above-mentioned pathways leading to SK-N-MC cell death. Our results delineated that hydrogen peroxide and superoxide anion radical induced distinct responses as we showed that STAT3 and p38 were activated in response to hydrogen peroxide, but not superoxide anion radicals indicating the specificity in ROS-induced signaling pathways activations and behaviors. We also observed that menadione induced JNK-dependent p53 expression and apoptotic death in SK-N-MC cells while H2O2-induced JNK activation was p53 independent. Thus, we declare that ROS type has a key role in selective instigation of JNK/p38-MAPKs and JAK2-STAT3 pathways in SK-N-MC cells. Identifying these differential behaviors and mechanisms of hydrogen peroxide and superoxide anion functions illuminates the possible therapeutic targets in the prevention or treatment of ROS-induced neurodegenerative diseases such as Alzheimer's disease.

Electrochemical separation and concentration of hydrogen sulfide from gas mixtures

DOEpatents

Winnick, Jack; Sather, Norman F.; Huang, Hann S.

1984-10-30

A method of removing sulfur oxides of H.sub.2 S from high temperature gas mixtures (150.degree.-1000.degree. C.) is the subject of the present invention. An electrochemical cell is employed. The cell is provided with inert electrodes and an electrolyte which will provide anions compatible with the sulfur containing anions formed at the anode. The electrolyte is also selected to provide inert stable cations at the temperatures encountered. The gas mixture is passed by the cathode where the sulfur gases are converted to SO.sub.4 -- or, in the case of H.sub.2 S, to S--. The anions migrate to the anode where they are converted to a stable gaseous form at much greater concentration levels (>10X). Current flow may be effected by utilizing an external source of electrical energy or by passing a reducing gas such as hydrogen past the anode.

ELECTROCHEMICAL SEPARATION AND CONCENTRATION OF HYDROGEN SULFIDE FROM GAS MIXTURES

DOEpatents

Winnick, Jack; Sather, Norman F.; Huang, Hann S.

1984-10-30

A method of removing sulfur oxides of H.sub.2 S from high temperature gas mixtures (150.degree.-1000.degree. C.) is the subject of the present invention. An electrochemical cell is employed. The cell is provided with inert electrodes and an electrolyte which will provide anions compatible with the sulfur containing anions formed at the anode. The electrolyte is also selected to provide inert stable cations at the temperatures encountered. The gas mixture is passed by the cathode where the sulfur gases are converted to SO.sub.4 -- or, in the case of H.sub.2 S, to S--. The anions migrate to the anode where they are converted to a stable gaseous form at much greater concentration levels (>10X). Current flow may be effected by utilizing an external source of electrical energy or by passing a reducing gas such as hydrogen past the anode.

Electrochemical separation and concentration of sulfur containing gases from gas mixtures

DOEpatents

Winnick, Jack

1981-01-01

A method of removing sulfur oxides of H.sub.2 S from high temperature gas mixtures (150.degree.-1000.degree. C.) is the subject of the present invention. An electrochemical cell is employed. The cell is provided with inert electrodes and an electrolyte which will provide anions compatible with the sulfur containing anions formed at the anode. The electrolyte is also selected to provide inert stable cations at the temperatures encountered. The gas mixture is passed by the cathode where the sulfur gases are converted to SO.sub.4.sup.= or, in the case of H.sub.2 S, to S.sup.=. The anions migrate to the anode where they are converted to a stable gaseous form at much greater concentration levels (>10X). Current flow may be effected by utilizing an external source of electrical energy or by passing a reducing gas such as hydrogen past the anode.

(-)-Xanthienopyran, a new inhibitor of superoxide anion generation by activated neutrophils, and further constituents of the seeds of Xanthium strumarium.

PubMed

Lee, Chia-Lin; Huang, Po-Ching; Hsieh, Pei-Wen; Hwang, Tsong-Long; Hou, Yu-Yi; Chang, Fang-Rong; Wu, Yang-Chang

2008-08-01

The dried seeds of XANTHIUM STRUMARIUM (Asteraceae) are used after thorough stir-frying as an ingredient in traditional Chinese medicines for relieving allergy. Two new compounds, xanthialdehyde ( 2) and (-)-xanthienopyran ( 7), as well as 26 known compounds were isolated in the present study. The structures of the isolates were elucidated by spectroscopic methods. Among them, compound 7 exhibited significant selective inhibition of superoxide anion generation by human neutrophils induced by formyl- L-methionyl- L-leucyl- L-phenylalanine, with an IC50 value of 1.72 microg/mL.

Synthesis of 1,8-naphthyridines and their application in the development of anionic fluorogenic chemosensors.

PubMed

Nicoleti, Celso R; Garcia, Diogo N; da Silva, Luiz E; Begnini, Iêda M; Rebelo, Ricardo A; Joussef, Antonio C; Machado, Vanderlei G

2012-07-01

Two 1,8-naphthyridines were synthesized and found to be fluorescent in solution. These compounds were studied in the presence of Cu(+) and Cu(2+) ions and it was verified that the metal causes the quenching of their fluorescence emission, due to the formation of complexes between the naphthyridine and the metal. A displacement assay was carried out in a DMSO-water mixture with the addition of various anions to the solutions of the complexes, and it was observed that these systems have a high capacity to selectively detect cyanide.

Synthesis and anion recognition studies of novel bis (4-hydroxycoumarin) methane azo dyes

NASA Astrophysics Data System (ADS)

Panitsiri, Amorn; Tongkhan, Sukanya; Radchatawedchakoon, Widchaya; Sakee, Uthai

2016-03-01

Four new bis (4-hydroxycoumarin) methane azo dyes were synthesized by the condensation of 4-hydroxycoumarin with four different azo salicylaldehydes and their structures were characterized by FT-IR, 1H NMR, 13C NMR, HRMS. Anion binding ability in dimethyl sulfoxide (DMSO) solutions with tetrabutylammonium (TBA) salts (F-, Cl-, Br-, I-, AcO- and H2PO4-) was investigated by the naked eye, as well as UV-visible spectroscopy. The sensor shows selective recognition towards fluoride and acetate. The binding affinity of the sensors with fluoride and acetate was calculated using UV-visible spectroscopic technique.

Ratiometric detection of adenosine triphosphate (ATP) in water and real-time monitoring of apyrase activity with a tripodal zinc complex.

PubMed

Butler, Stephen J

2014-11-24

Two tripodal fluorescent probes Zn⋅L(1,2) have been synthesised, and their anion-binding capabilities were examined by using fluorescence spectroscopy. Probe Zn⋅L(1) allows the selective and ratiometric detection of adenosine triphosphate (ATP) at physiological pH, even in the presence of several competing anions, such as ADP, phosphate and bicarbonate. The probe was applied to the real-time monitoring of the apyrase-catalysed hydrolysis of ATP, in a medium that mimics an extracellular fluid. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective conversion of {Mo132} Keplerate ion into 4-electron reduced crown-capped Keggin derivative [Te5Mo15O57](8-). A key intermediate to single-phase M1 multielement MoVTeO light-alkanes oxidation catalyst.

PubMed

Canioni, Romain; Marchal-Roch, Catherine; Leclerc-Laronze, Nathalie; Haouas, Mohamed; Taulèlle, Francis; Marrot, Jérôme; Paul, Sebastien; Lamonier, Carole; Paul, Jean-François; Loridant, Stéphane; Millet, Jean-Marc M; Cadot, Emmanuel

2011-06-14

{Mo(132)} Keplerate anion reacts with tellurites to give a soluble precursor to produce in hydrothermal conditions single-phase M1 MoVTeO light-alkanes oxidation catalyst. Characterization of this Te-containing intermediate by single-crystal X-ray diffraction, (125)Te NMR, UV-visible and redox titration reveals a molybdotellurite anion as a crown-capped Keggin derivative. This journal is © The Royal Society of Chemistry 2011

Salt taste inhibition by cathodal current.

PubMed

Hettinger, Thomas P; Frank, Marion E

2009-09-28

Effects of cathodal current, which draws cations away from the tongue and drives anions toward the tongue, depend on the ionic content of electrolytes through which the current is passed. To address the role of cations and anions in human salt tastes, cathodal currents of -40 microA to -80 microA were applied to human subjects' tongues through supra-threshold salt solutions. The salts were sodium chloride, sodium bromide, potassium chloride, ammonium chloride, calcium chloride, sodium nitrate, sodium sulfate, sodium saccharin, sodium acetate and sodium benzoate, which taken together encompass salty, bitter, sour and sweet taste qualities. The taste of NaCl, the salty and bitter tastes of the other chloride salts and the taste of NaNO(3) was inhibited, suggesting the current displaced stimulatory cations from salty and bitter receptors. However, bitter tastes of non-halide sodium salts were not inhibited, likely because other bitter receptors respond to anions. A discharge current at cathode-off ubiquitously evoked a metallic taste reminiscent of anodal taste used in clinical electrogustometry. Analogous effects on ambient NaCl responses were recorded from the hamster chorda tympani nerve. Increases in tastes of the saccharin and benzoate anions were not evoked during current flow, suggesting that cathodal current does not carry stimulatory anions to sweet receptors. Cathodal current may selectively inhibit salty and bitter-salty tastes for which proximal stimuli are cations.

Contribution of attendant anions on cadmium toxicity to soil enzymes.

PubMed

Tian, Haixia; Kong, Long; Megharaj, Mallavarapu; He, Wenxiang

2017-11-01

Sorption and desorption are critical processes to control the mobility and biotoxicity of cadmium (Cd) in soils. It is known that attendant anion species of heavy metals could affect metal adsorption on soils and might further alter their biotoxicity. However, for Cd, the influence of attendant anions on its sorption in soils and subsequent toxicity on soil enzymes are still unknown. In this work, four Cd compounds with different salt anions (SO 4 2- , NO 3 - , Cl - , and Ac - ) were selected to investigate their impact of on the sorption, soil dehydrogenase activity (DHA) and alkaline phosphatase activity (ALP). Thus, a series of simulated Cd pollution batch experiments including measuring adsorption-desorption behavior of Cd on soils and soil enzyme activities were carried out. Results showed that CdSO 4 exhibited highest sorption capacity among the tested soils except in Hunan soil. The Cd sorption with NO 3 - displayed a similar behavior with Cl - on all tested soils. Compared with soil properties, all four kinds of anions on Cd sorption played a more significant role affecting Cd ecological toxicity to soil DHA and ALP. Cd in acetate or nitrate form appears more sensitive towards DHA than sulphate and chloride, while the later pair is more toxic towards ALP than the former. These results have important implications for evaluation of Cd contamination using soil enzyme as bioindicator. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of an ODS column modified with zwitterionic/nonionic mixed surfactants and its application to direct injection determination of inorganic anions.

PubMed

Hasegawa, Takuya; Umemura, Tomonari; Koide, Akira; Chiba, Koichi; Ueki, Yuji; Tsunoda, Kin-ichi; Haraguchi, Hiroki

2005-08-01

An octadecylsilica (ODS) column modified with zwitterionic/nonionic mixed surfactants was evaluated for the direct injection determination of inorganic anions in biological fluids by ion chromatography. A zwitterionic surfactant (sulfobetaine-type) and a nonionic surfactant (polyoxyethylene-type) were used for a stationary-phase modification. When aqueous electrolyte solutions with concentrations of sub-mM to several mM were used as a mobile phase, the zwitterionic surfactant coated on the ODS surface exhibited unique separation selectivity for ionic species, while the nonionic surfactant coated on the ODS might have formed a hydrophilic network over the ODS surface and restricted matrix proteins from adsorbing on the stationary phase. Consequently, the mixed surfactant-modified column system allowed an efficient ion chromatographic separation of inorganic anions as well as a size-exclusive removal of column-fouling proteins. This separation system was applied to the direct injection determination of UV-absorbing anions in human saliva. The detection limits for nitrite, nitrate, iodide and thiocyanate were 3.1, 2.7, 4.5 and 25 microM, respectively, with UV detection at 210 nm (injection volume; 20 microl), and their relative standard deviations for 5 replicate measurements of saliva samples spiked with 100 microM each of those anions were 1.4, 0.9, 2.2 and 5.5%, respectively.

Effects of inorganic electrolyte anions on enrichment of Cu(II) ions with aminated Fe3O4/graphene oxide: Cu(II) speciation prediction and surface charge measurement.

PubMed

Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; Wang, Hui; You, Shao-hong; Hu, Xi; Tan, Xiao-fei; Chen, An-wei; Guo, Fang-ying

2015-05-01

The present work evaluated the effects of six inorganic electrolyte anions on Cu(II) removal using aminated Fe3O4/graphene oxide (AMGO) in single- and multi-ion systems. A 2(6-2) fractional factorial design (FFD) was employed for assessing the effects of multiple anions on the adsorption process. The results indicated that the Cu(II) adsorption was strongly dependent on pH and could be significantly affected by inorganic electrolyte anions due to the changes in Cu(II) speciation and surface charge of AMGO. In the single-ion systems, the presence of monovalent anions (Cl(-), ClO4(-), and NO3(-)) slightly increased the Cu(II) adsorption onto AMGO at low pH, while the Cu(II) adsorption was largely enhanced by the presence of SO4(2-), CO3(2-), and HPO4(2-). Based on the estimates of major effects and interactions from FFD, the factorial effects of the six selected species on Cu(II) adsorption in multi-ion system were in the following sequence: HPO4(2-)>CO3(2-)>Cl(-)>SO4(2-)>NO3(-)=ClO4(-), and the combined factors of AD (Cl(-)×SO4(2-)) and EF (Cl(-)×SO4(2-)) had significant effects on Cu(II) removal. Copyright © 2015 Elsevier Ltd. All rights reserved.

Probing the interactions between ionic liquids and water: experimental and quantum chemical approach.

PubMed

Khan, Imran; Kurnia, Kiki A; Mutelet, Fabrice; Pinho, Simão P; Coutinho, João A P

2014-02-20

For an adequate choice or design of ionic liquids, the knowledge of their interaction with other solutes and solvents is an essential feature for predicting the reactivity and selectivity of systems involving these compounds. In this work, the activity coefficient of water in several imidazolium-based ionic liquids with the common cation 1-butyl-3-methylimidazolium was measured at 298.2 K. To contribute to a deeper insight into the interaction between ionic liquids and water, COSMO-RS was used to predict the activity coefficient of water in the studied ionic liquids along with the excess enthalpies. The results showed good agreement between experimental and predicted activity coefficient of water in ionic liquids and that the interaction of water and ionic liquids was strongly influenced by the hydrogen bonding of the anion with water. Accordingly, the intensity of interaction of the anions with water can be ranked as the following: [CF3SO3](-) < [SCN](-) < [TFA](-) < Br(-) < [TOS](-) < Cl(-) < [CH3SO3](-) [DMP](-) < [Ac](-). In addition, fluorination and aromatization of anions are shown to reduce their interaction with water. The effect of temperature on the activity coefficient of water at infinite dilution was measured by inverse gas chromatography and predicted by COSMO-RS. Further analysis based on COSMO-RS provided information on the nature of hydrogen bonding between water and anion as well as the possibility of anion-water complex formation.

Synthesis, characterization, and reactivity of arylpalladium cyanoalkyl complexes: selection of catalysts for the alpha-arylation of nitriles.

PubMed

Culkin, Darcy A; Hartwig, John F

2002-08-14

A new coupling process, the palladium-catalyzed alpha-arylation of nitriles, was developed by exploring the structure and reactivity of arylpalladium cyanoalkyl complexes. Complexes of 1,2-bis(diphenylphosphino)benzene (DPPBz), 1,1'-bis(di-i-propylphosphino)ferrocene (D(i)()PrPF), racemic-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), and diphenylethylphosphine (PPh(2)Et) were prepared. Coordination to palladium through the alpha-carbon was observed for DPPBz-ligated complexes and for complexes of primary and benzylic nitrile anions. However, the anion of isobutyronitrile was coordinated to palladium through the cyano-nitrogen when the complex was ligated by D(i)()PrPF. The isobutyronitrile anion displaced a phosphine ligand to form a C,N-bridged dimer when generated from PPh(2)Et-ligated palladium. These results suggest that the nitrile anion preferentially coordinates to palladium through the carbon atom in the absence of steric effects. Thermolysis of the arylpalladium cyanoalkyl complexes led to reductive elimination that formed alpha-aryl nitriles. The high yields and short reaction times observed for BINAP-ligated complexes suggested that BINAP-ligated palladium catalysts might be appropriate for the arylation of nitriles. Initial results on a palladium-catalyzed process for the direct coupling of aryl bromides and primary, benzylic, and secondary nitrile anions to form alpha-aryl nitriles in good yields are reported.

Electrodialytic extraction of anionic pharmaceutical compounds from a single drop of whole blood using a supported liquid membrane.

PubMed

Imoto, Yurika; Nishiyama, Hiroka; Nakamura, Yukihide; Ohira, Shin-Ichi; Toda, Kei

2018-05-01

A method to introduce target analytes to a chromatograph from a single drop of whole blood was investigated for minimally invasive monitoring of anionic pharmaceuticals. In this work, salicylate and loxoprofen were examined as organic anions. A micro ion extractor (MIE) has been developed for extraction of inorganic trace anions from whole blood, but this device is not suitable for extraction of pharmaceuticals. In the present study, we improved and optimized the MIE device for organic anion extraction. Various supported liquid membranes were evaluated for use as the ion transfer membrane, with each membrane placed between a droplet sample (donor) and an acceptor solution. A supported liquid membrane of porous polypropylene impregnated with 1-butanol was selected. In addition, the methods for electric field creation and electrode contact were examined to improve the characteristics of the MIE device. The current and extraction time were also optimized. With the optimized method, salicylate and loxoprofen were successfully extracted from a single drop of whole blood. Changes in the concentrations of these pharmaceuticals in blood over time were monitored after administration. As only 25μL of whole blood was required for analysis, repeat measurements could be conducted to monitor changes in the concentrations. This MIE will be useful for monitoring pharmaceutical concentrations in blood. Copyright © 2018 Elsevier B.V. All rights reserved.

An interference-free glucose biosensor based on an anionic redox polymer-mediated enzymatic oxidation of glucose.

PubMed

Deng, Huimin; Shen, Wei; Gao, Zhiqiang

2013-07-22

Herein a novel strategy for the construction of an amperometric biosensor for highly sensitive and selective determination of glucose is described. The biosensor is made of a biocomposite membrane of glucose oxidase (GOx) and an Os(bpy)2 (bpy=2,2'-bipyridine)-based anionic redox polymer (Os-RP) mediator. The biosensor is fabricated through the co-immobilization of GOx and the Os-RP on the surface of a glassy carbon electrode by a simple one-step chemical crosslinking process. The crosslinked Os-RP/GOx composite membrane shows excellent catalytic activity toward the oxidation of glucose. Under optimal experimental conditions, a linear correlation between the oxidation current of glucose in amperometry at 0.25 V (vs. Ag/AgCl) and glucose concentration up to 10 mM with a sensitivity of 16.5 μA mM(-1) cm(-2) and a response time <5 s. Due to the presence of anionic sulfonic acid groups in the backbone of the redox polymer, the biosensor exhibits excellent selectivity to glucose in the presence of ascorbic acid and uric acid. The low hydrophobicity of the composite membrane also effectively retards the transport of molecular oxygen within the membrane. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Overview of As(V) adsorption on Zr-functionalized activated carbon for aqueous streams remediation.

PubMed

Velazquez-Jimenez, Litza Halla; Arcibar-Orozco, Javier Antonio; Rangel-Mendez, Jose Rene

2018-04-15

The present work introduces a simple methodology of carbon modification with zirconium, using an organic complexing ligand, as efficient media for selective As(V) removal. It is hypothesized that the incorporation of Zr-nanoparticles improves the attraction of anionic species such as arsenates (HAsO 4 2- /H 2 AsO 4 - ) making the material highly selective. The effects of pH (3-11) and temperature (15, 25 and 35 °C) were studied. Furthermore, potentiometric titrations, the effect of competing anions, thermodynamics, and adsorption kinetics were evaluated in order to clarify the rate-controlling process and the adsorption mechanism for arsenic removal. Results demonstrated that OH and COOH groups play an important role during the arsenic adsorption process; a small amount of Zr(IV) species (0.77%) increased the adsorption capacity of activated carbon in about a 43%. Thermodynamic analysis showed the spontaneous exothermic nature of the adsorption process was favored at lower temperatures. The presence of anions, such as chloride, sulfate, carbonate, nitrate and phosphate, did not affect the adsorption capacity, while kinetic studies demonstrated that the arsenic adsorption process in Zr-modified activated carbon is not exclusively controlled by intraparticle diffusion. Copyright © 2018 Elsevier Ltd. All rights reserved.

Assimilation efficiency for sediment-sorbed benzo(a)pyrene by Diporeia spp.

USGS Publications Warehouse

Lydy, M.J.; Landrum, P.F.

1993-01-01

Two methods are currently available for determining contaminant assimilation efficiencies (AE) from ingested material in benthic invertebrates. These methods were compared using the Great Lakes amphipod Diporeia spp. and [14C]benzo(a)pyrene (BaP) sorbed to Florissant sediment (< 63 µm). The first approach, the direct measurement method, uses total organic carbon as a tracer and yielded AE values ranging from 45.9~50.4%. The second approach, the dual-labeled method, uses 51Cr as a non-assimilated tracer and did not yield AE values for our data. The inability of the dual-labeled approach to estimate AEs was due, in part, to the selective feeding by Diporeia resulting in a failure of the non-assimilated tracer (51Cr) to track with the assimilated tracer ([14C]BaP). The failure of the dual-labeled approach was not a result of an uneven distribution of the labels among particle size classes, but more likely resulted from differential sorption of the two isotopically labeled materials to particles of differing composition. The [14C]BaP apparently sorbs to organic particles that are selectively ingested, while the 51Cr apparently sorbs to particles which are selectively excluded by Diporeia. The dual-labeled approach would be a viable and easier experimental approach for determining AE values if the characteristics that govern selective feeding can be determined.

H-Bonding Assisted Self-Assembly of Anionic and Neutral Ligand on Metal: A Comprehensive Strategy To Mimic Ditopic Ligands in Olefin Polymerization.

PubMed

Mote, Nilesh R; Patel, Ketan; Shinde, Dinesh R; Gaikwad, Shahaji R; Koshti, Vijay S; Gonnade, Rajesh G; Chikkali, Samir H

2017-10-16

Self-assembly of two neutral ligands on a metal to mimic bidentate ligand coordination has been frequently encountered in the recent past, but self-assembly of an anionic ligand on a metal template alongside a neutral ligand remains an elusive target. Such a self-assembly is hampered by additional complexity, wherein a highly negatively charged anion can form intermolecular hydrogen bonding with the supramolecular motif, leaving no scope for self-assembly with neutral ligand. Presented here is the self-association of anionic ligand 3-ureidobenzoic acid (2a) and neutral ligand 1-(3-(diphenylphosphanyl)phenyl)urea (1a) on a metal template to yield metal complex [{COOC 6 H 4 NH(CO)NH 2 }{Ph 2 PC 6 H 4 NH(CO)NH 2 }PdMeDMSO] (4a). The identity of 4a was established by NMR and mass spectroscopy. Along the same lines, 3-(3-phenylureido)benzoic acid (2b) and 1-(3-(diphenylphosphanyl)phenyl)-3-phenylurea (1b) self-assemble on a metal template to produce palladium complex [{COOC 6 H 4 NH(CO)NHPh}{Ph 2 PC 6 H 4 NH(CO)NHPh}PdMePy] (5c). The existence of 5c was confirmed by Job plot, 1-2D NMR spectroscopy, deuterium labeling, IR spectroscopy, UV-vis spectroscopy, model complex synthesis, and DFT calculations. These solution and gas phase investigations authenticated the presence of intramolecular hydrogen bonding between hydrogen's of 1b and carbonyl oxygen of 2b. The generality of the supramolecular approach has been validated by preparing six complexes from four monodentate ligands, and their synthetic utility was demonstrated in ethylene polymerization. Complex 4a was found to be the most active, leading to the production of highly branched polyethylene with a molecular weight of 55700 g/mol and melting temperature of 112 °C.

Phosphate binding protein as the biorecognition element in a biosensor for phosphate

NASA Technical Reports Server (NTRS)

Salins, Lyndon L E.; Deo, Sapna K.; Daunert, Sylvia

2004-01-01

This work explores the potential use of a member of the periplasmic family of binding proteins, the phosphate binding protein (PBP), as the biorecognition element in a sensing scheme for the detection of inorganic phosphate (Pi). The selectivity of this protein originates from its natural role which, in Escherichia coli, is to serve as the initial receptor for the highly specific translocation of Pi to the cytoplasm. The single polypeptide chain of PBP is folded into two similar domains connected by three short peptide linkages that serve as a hinge. The Pi binding site is located deep within the cleft between the two domains. In the presence of the ligand, the two globular domains engulf the former in a hinge-like manner. The resultant conformational change constitutes the basis of the sensor development. A mutant of PBP (MPBP), where an alanine was replaced by a cysteine residue, was prepared by site-directed mutagenesis using the polymerase chain reaction (PCR). The mutant was expressed, from plasmid pSD501, in the periplasmic space of E. coli and purified in a single chromatographic step on a perfusion anion-exchange column. Site-specific labeling was achieved by attaching the fluorophore, N-[2-(1-maleimidyl)ethyl]-7-(diethylamino)coumarin-3-carboxamide (MDCC), to the protein through the sulfhydryl group of the cysteine moiety. Steady-state fluorescence studies of the MPBP-MDCC conjugate showed a change in the intensity of the signal upon addition of Pi. Calibration curves for Pi were constructed by relating the intensity of the fluorescence signal with the amount of analyte present in the sample. The sensing system was first developed and optimized on a spectrofluorometer using ml volumes of sample. It was then adapted to be used on a microtiter plate arrangement with microliter sample volumes. The system's versatility was finally proven by developing a fiber optic fluorescence-based sensor for monitoring Pi. In all three cases the detection limits for the analyte were in the sub-microMolar range. It was also demonstrated that the sensing system was selective for phosphate over other structurally-similar anions, paving the way for the design and development of a new family of biosensors utilizing the specific binding properties of periplasmic proteins. c2003 Elsevier B.V. All rights reserved.

ANIONIC EXCHANGE PROCESS FOR THE RECOVERY OF URANIUM AND VANADIUM FROM CARBONATE SOLUTIONS

DOEpatents

Bailes, R.H.; Ellis, D.A.; Long, R.S.

1958-12-16

Uranium and vanadium can be economically purified and recovered from non- salt roast carbonate leach liquors by adsorption on a strongly basic anionic exchange resin and subsequent selective elution by one of three alternative methods. Method 1 comprises selectively eluting uranium from the resin with an ammonium sulfate solution followed by eluting vanadium from the resin with either 5 M NaCl, saturated (NH/sub 4/)/sub 2/CO/sub 3/, saturated NaHCO/sub 3/, 1 M NaOH, or saturated S0/sub 2/ solutions. Method II comprises selectively eluting vanadium from the resin with either concentrated NaCl or S0/sub 2/ solutions subsequent to pretreatment of the column with either S0/sub 2/ gas, 1 N HCl, or 0.1 N H/sub 2/8O/sub 4/ followed by eluting uranium from the resin with solutions containing 0.9 M NH/sub 4/Cl or NaCl and 0.1 Cl. Method III comprises flowing the carbonate leac solutlon through a first column of a strongly basic anlonlc exchange resin untll vanadium breakthrough occurs, so that the effluent solution is enriched ln uranium content and the vanadium is chiefly retalned by the resln, absorbing the uranlum from the enriched effluent solution on a second column of a strongly basic anionic exchange resin, pretreating the first column with either 0.1 N HCl, 0.1 H/sub 2/SO/sub 4/, C0/sub 2/ gas, or ammonium sulfate, selectively eluting the vanadlum from the column with saturated S0/sub 2/ solution, pretreatlng the second column with either 0.1 N HCl or S0/sub 2/ gas, selectively eluting residual vanadium from the column with saturated S0/sub 2/ solution, and then eluting the uranium from the column with either 0.1 N HCl and 1 N NaCl orO.l N HCl and 1 N NH/sub 4/Cl.

Heterologous expression of Cenchritis muricatus protease inhibitor II (CmPI-II) in Pichia pastoris system: Purification, isotopic labeling and preliminary characterization.

PubMed

Cabrera-Muñoz, Aymara; Rojas, Laritza; Gil, Dayrom F; González-González, Yamile; Mansur, Manuel; Camejo, Ayamey; Pires, José R; Alonso-Del-Rivero Antigua, Maday

2016-10-01

Cenchritis muricatus protease inhibitor II (CmPI-II) is a tight-binding serine protease inhibitor of the Kazal family with an atypical broad specificity, being active against several proteases such as bovine pancreatic trypsin, human neutrophil elastase and subtilisin A. CmPI-II 3D structures are necessary for understanding the molecular basis of its activity. In the present work, we describe an efficient and straightforward recombinant expression strategy, as well as a cost-effective procedure for isotope labeling for NMR structure determination purposes. The vector pCM101 containing the CmPI-II gene, under the control of Pichia pastoris AOX1 promoter was constructed. Methylotrophic Pichia pastoris strain KM71H was then transformed with the plasmid and the recombinant protein (rCmPI-II) was expressed in benchtop fermenter in unlabeled or (15)N-labeled forms using ammonium chloride ((15)N, 99%) as the sole nitrogen source. Protein purification was accomplished by sequential cation exchange chromatography in STREAMLINE DirectHST, anion exchange chromatography on Hitrap Q-Sepharose FF and gel filtration on Superdex 75 10/30, yielding high quantities of pure rCmPI-II and (15)N rCmPI-II. Recombinant proteins displayed similar functional features as compared to the natural inhibitor and NMR spectra indicated folded and homogeneously labeled samples, suitable for further studies of structure and protease-inhibitor interactions. Copyright © 2016 Elsevier Inc. All rights reserved.

Sensing site-specific structural characteristics and chirality using vibrational circular dichroism of isotope labeled peptides.

PubMed

Keiderling, Timothy A

2017-12-01

Isotope labeling has a long history in chemistry as a tool for probing structure, offering enhanced sensitivity, or enabling site selection with a wide range of spectroscopic tools. Chirality sensitive methods such as electronic circular dichroism are global structural tools and have intrinsically low resolution. Consequently, they are generally insensitive to modifications to enhance site selectivity. The use of isotope labeling to modify vibrational spectra with unique resolvable frequency shifts can provide useful site-specific sensitivity, and these methods have been recently more widely expanded in biopolymer studies. While the spectral shifts resulting from changes in isotopic mass can provide resolution of modes from specific parts of the molecule and can allow detection of local change in structure with perturbation, these shifts alone do not directly indicate structure or chirality. With vibrational circular dichroism (VCD), the shifted bands and their resultant sign patterns can be used to indicate local conformations in labeled biopolymers, particularly if multiple labels are used and if their coupling is theoretically modeled. This mini-review discusses selected examples of the use of labeling specific amides in peptides to develop local structural insight with VCD spectra. © 2017 Wiley Periodicals, Inc.

Air breathing lithium power cells

DOEpatents

Farmer, Joseph C.

2014-07-15

A cell suitable for use in a battery according to one embodiment includes a catalytic oxygen cathode; a stabilized zirconia electrolyte for selective oxygen anion transport; a molten salt electrolyte; and a lithium-based anode. A cell suitable for use in a battery according to another embodiment includes a catalytic oxygen cathode; an electrolyte; a membrane selective to molecular oxygen; and a lithium-based anode.

A cobalt(II) bis(salicylate)-based ionic liquid that shows thermoresponsive and selective water coordination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohno, Y; Cowan, MG; Masuda, M

2014-01-01

A metal-containing ionic liquid (MCIL) has been prepared in which the [CoII(salicylate)(2)](2-) anion is able to selectively coordinate two water molecules with a visible colour change, even in the presence of alcohols. Upon moderate heating or placement in vacuo, the hydrated MCIL undergoes reversible thermochromism by releasing the bound water molecules.

Porous anionic indium-organic framework with enhanced gas and vapor adsorption and separation ability.

PubMed

Huang, Yuanbiao; Lin, Zujin; Fu, Hongru; Wang, Fei; Shen, Min; Wang, Xusheng; Cao, Rong

2014-09-01

A three-dimensional microporous anionic metal-organic framework (MOF) (Et4N)3[In3(TATB)4] (FJI-C1, H3TATB=4,4',4''-s-triazine-2,4,6-triyltribenzoic acid) with large unit cell volume has been synthesized. Assisted by the organic cation group Et4N in the pores of the compound, FJI-C1 not only shows high adsorption uptakes of C2 and C3 hydrocarbons, but also exhibits highly selective separation of propane, acetylene, ethane, and ethylene from methane at room temperature. Furthermore, it also exhibits high separation selectivity for propane over C2 hydrocarbons and acetylene can be readily separated from their C2 hydrocarbons mixtures at low pressure due to the high selectivity for C2H2 in comparison to C2H4 and C2H6. In addition, FJI-C1 with hydrophilic internal pores surfaces shows highly efficient adsorption separation of polar molecules from nonpolar molecules. Notably, it exhibits high separation selectivity for benzene over cyclohexane due to the π-π interactions between benzene molecules and s-triazine rings of the porous MOF. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mapping of Residues Forming the Voltage Sensor of the Voltage-Dependent Anion-Selective Channel

NASA Astrophysics Data System (ADS)

Thomas, Lorie; Blachly-Dyson, Elizabeth; Colombini, Marco; Forte, Michael

1993-06-01

Voltage-gated ion-channel proteins contain "voltage-sensing" domains that drive the conformational transitions between open and closed states in response to changes in transmembrane voltage. We have used site-directed mutagenesis to identify residues affecting the voltage sensitivity of a mitochondrial channel, the voltage-dependent anion-selective channel (VDAC). Although charge changes at many sites had no effect, at other sites substitutions that increased positive charge also increased the steepness of voltage dependance and substitutions that decreased positive charge decreased voltage dependance by an appropriate amount. In contrast to the plasma membrane K^+ and Na^+ channels, these residues are distributed over large parts of the VDAC protein. These results have been used to define the conformational transitions that accompany voltage gating of an ion channel. This gating mechanism requires the movement of large portions of the VDAC protein through the membrane.

Evaluation of capillary electrophoresis for in-flight ionic contaminant monitoring of SSF potable water

NASA Technical Reports Server (NTRS)

Mudgett, Paul D.; Schultz, John R.; Sauer, Richard L.

1992-01-01

Until 1989, ion chromatography (IC) was the baseline technology selected for the Specific Ion Analyzer, an in-flight inorganic water quality monitor being designed for Space Station Freedom. Recent developments in capillary electrophoresis (CE) may offer significant savings of consumables, power consumption, and weight/volume allocation, relative to IC technology. A thorough evaluation of CE's analytical capability, however, is necessary before one of the two techniques is chosen. Unfortunately, analytical methods currently available for inorganic CE are unproven for NASA's target list of anions and cations. Thus, CE electrolyte chemistry and methods to measure the target contaminants must be first identified and optimized. This paper reports the status of a study to evaluate CE's capability with regard to inorganic and carboxylate anions, alkali and alkaline earth cations, and transition metal cations. Preliminary results indicate that CE has an impressive selectivity and trace sensitivity, although considerable methods development remains to be performed.

New dendritic gelator bearing carbazole in each branching unit: selected response to fluoride ion in gel phase.

PubMed

Xu, Defang; Liu, Xingliang; Lu, Ran; Xue, Pengchong; Zhang, Xiaofei; Zhou, Huipeng; Jia, Junhui

2011-03-07

A new dendritic gelator with carbazole as the building block (HBCD) was synthesized. It was found that H-bonding between the amide groups and π-π interaction between the aromatic rings played predominant roles in the gel formation. Meanwhile, significant aggregation-induced emission enhancement was observed in the gel state due to the formation of J-aggregates and the restricted molecular motion. Notably, the gel state of HBCD can be destroyed upon addition of F(-), accompanied by fluorescence enhancement on account of the formation of N-HF(-), which could further lead to the increased coplanarity of HBCD. The sensory capability of HBCD exhibited a high selectivity towards F(-) instead of the Cl(-), Br(-), I(-) and AcO(-) anions, which could be explained by the fact that the steric hindrance of the dendrimer would go against the interactions between the larger anions and HBCD.

An easy prepared dual-channel chemosensor for selective and instant detection of fluoride based on double Schiff-base

NASA Astrophysics Data System (ADS)

Leng, Yan-Li; Zhang, Jian-Hui; Li, Qiao; Zhang, You-Ming; Lin, Qi; Yao, Hong; Wei, Tai-Bao

2016-10-01

A colorimetric and fluorescent dual-channel fluoride chemosensor N,N‧-bis (4-diethylaminosalicylidene) hydrazine (sensor S) bearing two imine groups has been designed and synthesized. This structurally simple probe displays rapid response and high selectivity for fluoride over other common anions (Cl-, Br-, I-, AcO-, H2PO4-, HSO4-, ClO4-, CN- and SCN-) in a highly polar aqueous DMSO solution. Mechanism studies suggested that the sensor firstly combined with F- through hydrogen bonds and then experienced the deprotonation process at higher concentrations of F- anion to the two Ar-OH groups. The detection limit was 5.78 × 10- 7 M of F-, which points to the high detection sensitivity. Test strips based on sensor S were fabricated, which could act as a convenient and efficient F- test kit to detect F- for ;in-the-field; measurement.

Incorporation of isotopic, fluorescent, and heavy-atom-modified nucleotides into RNAs by position-selective labeling of RNA.

PubMed

Liu, Yu; Holmstrom, Erik; Yu, Ping; Tan, Kemin; Zuo, Xiaobing; Nesbitt, David J; Sousa, Rui; Stagno, Jason R; Wang, Yun-Xing

2018-05-01

Site-specific incorporation of labeled nucleotides is an extremely useful synthetic tool for many structural studies (e.g., NMR, electron paramagnetic resonance (EPR), fluorescence resonance energy transfer (FRET), and X-ray crystallography) of RNA. However, specific-position-labeled RNAs >60 nt are not commercially available on a milligram scale. Position-selective labeling of RNA (PLOR) has been applied to prepare large RNAs labeled at desired positions, and all the required reagents are commercially available. Here, we present a step-by-step protocol for the solid-liquid hybrid phase method PLOR to synthesize 71-nt RNA samples with three different modification applications, containing (i) a 13 C 15 N-labeled segment; (ii) discrete residues modified with Cy3, Cy5, or biotin; or (iii) two iodo-U residues. The flexible procedure enables a wide range of downstream biophysical analyses using precisely localized functionalized nucleotides. All three RNAs were obtained in <2 d, excluding time for preparing reagents and optimizing experimental conditions. With optimization, the protocol can be applied to other RNAs with various labeling schemes, such as ligation of segmentally labeled fragments.

Rapid synthesis of maleimide functionalized fluorine-18 labeled prosthetic group using "radio-fluorination on the Sep-Pak" method.

PubMed

Basuli, Falguni; Zhang, Xiang; Jagoda, Elaine M; Choyke, Peter L; Swenson, Rolf E

2018-06-30

Following our recently published fluorine-18 labeling method, "Radio-fluorination on the Sep-Pak", we have successfully synthesized 6-[ 18 F]fluoronicotinaldehyde by passing a solution (1:4 acetonitrile: t-butanol) of its quaternary ammonium salt precursor, 6-(N,N,N-trimethylamino)nicotinaldehyde trifluoromethanesulfonate (2), through a fluorine-18 containing anion exchange cartridge (PS-HCO 3 ). Over 80% radiochemical conversion was observed using 10 mg of precursor within 1 minute. The [ 18 F]fluoronicotinaldehyde ([ 18 F]5) was then conjugated with 1-(6-(aminooxy)hexyl)-1H-pyrrole-2,5-dione to prepare the fluorine-18 labeled maleimide functionalized prosthetic group, 6-[ 18 F]fluoronicotinaldehyde O-(6-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)hexyl) oxime, 6-[ 18 F]FPyMHO ([ 18 F]6). The current Sep-Pak method not only improves the overall radiochemical yield (50 ± 9%, decay-corrected, n = 9) but also significantly reduces the synthesis time (from 60-90 minutes to 30 minutes) when compared with literature methods for the synthesis of similar prosthetic groups. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Characterization of carbohydrates using highly fluorescent 2-aminobenzoic acid tag following gel electrophoresis of glycoproteins.

PubMed

Anumula, K R; Du, P

1999-11-15

Application of the most sensitive fluorescent label 2-aminobenzoic acid (anthranilic acid, AA) for characterization of carbohydrates from the glycoproteins ( approximately 15 pmol) separated by polyacrylamide gel electrophoresis is described. AA label is used for the determination of both monosaccharide composition and oligosaccharide map. For the monosaccharide determination, bands containing the glycoprotein of interest are excised from the polyvinylidene fluoride (PVDF) membrane blots, hydrolyzed in 20% trifluoroacetic acid, derivatized, and analyzed by C-18 reversed-phase high-performance liquid chromatography. For the oligosaccharide mapping, bands were digested with peptide N-glycosidase F (PNGase F) in order to release the N-linked oligosaccharides, derivatized, and analyzed by normal-phase anion-exchange chromatography. For convenience, the PNGase F digestion was performed in 1:100 diluted ammonium hydroxide overnight. The oligosaccharide yield from ammonium hydroxide-PNGase F digestion was better or equal to all the other reported procedures, and the presumed "oligosaccharide-amine" product formed in the reaction mixture did not interfere with labeling of the oligosaccharides under the conditions used for derivatization. Sequencing of oligosaccharides can be performed using the same mapping method following treatment with an array of glycosidases. In addition, the mapping method is useful for determining the relative and simultaneous distribution of sialic acid and fucose. Copyright 1999 Academic Press.

A novel dichromate-sensitive fluorescent nano-chemosensor using new functionalized SBA-15.

PubMed

Hosseini, Morteza; Gupta, Vinod Kumar; Ganjali, Mohammad Reza; Rafiei-Sarmazdeh, Zahra; Faridbod, Farnoush; Goldooz, Hassan; Badiei, Ali Reza; Norouzi, Parviz

2012-02-17

A novel fluorescence nano-chemosensor for Cr(2)O(7)(2-) anion has been developed by assembly of fluorescent aluminum complex of 8-hydroxyquinoline (AlQ(x)) within the channels of modified SBA-15. SBA-SPS-AlQ(x) shows a fluorescence emission at 486 nm. The observed remarkable fluorescence of SBA-SPS-AlQ(x) quenches in presence of Cr(2)O(7)(2-) anion. The results showed that this fluorescent nano-material can be a useful chemo-sensor for determination of dichromate anions in aqueous solutions. The linear detecting range of fluorescent nano-chemosensor for Cr(2)O(7)(2-) anion was 0.16-2.9 μmol L(-1). The lowest limit of detection (LDL) was also found to be 0.2 ng mL(-1) in aqueous solutions. SBA-SPS-AlQ(x) showed selectively and sensitively fluorescent quenching response toward Cr(2)O(7)(2-) ion in comparison with I(3)(-), NO(3)(-), CN(-), CO(3)(2-), Br(-), Cl(-), F(-), H(2)PO(4)(-) and SO(4)(2-) ions, which was because of the higher stability of its inorganic complex with dichromate ion. Copyright © 2011 Elsevier B.V. All rights reserved.

Do TFSA anions slither? Pressure exposes the role of TFSA conformational exchange in self-diffusion

DOE PAGES

Suarez, Sophia N.; Wishart, James F.; Rua, Armando; ...

2015-10-28

Multi-nuclear ( 1H, 2H, and 19F) magnetic resonance spectroscopy techniques as functions of temperature and pressure were applied to the study of selectively deuterated 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMIM TFSA) ionic liquid isotopologues and related ionic liquids. For EMIM TFSA, temperature-dependent 2H T 1 data indicate stronger electric field gradients in the alkyl chain region compared to the imidazolium ring. Most significantly, the pressure dependences of the EMIM and TFSA self-diffusion coefficients revealed that the displacements of the cations and anions are independent, with diffusion of the TFSA anions being slowed much more by increasing pressure than for the EMIM cations, asmore » shown by their respective activation volumes (28.8 ± 2.5 cm³/mol for TFSA vs. 14.6 ± 1.3 cm³/mol for EMIM). Increasing pressure may lower the mobility of the TFSA anion by hindering its interconversion between trans and cis conformers, a process that is coupled to diffusion according to published molecular dynamics simulations. Measured activation volumes (ΔV ‡) for ion self-diffusion in EMIM bis(fluoromethylsulfonyl)amide and EMIM tetrafluoroborate support this hypothesis.« less

Do TFSA anions slither? Pressure exposes the role of TFSA conformational exchange in self-diffusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suarez, Sophia N.; Wishart, James F.; Rua, Armando

Multi-nuclear ( 1H, 2H, and 19F) magnetic resonance spectroscopy techniques as functions of temperature and pressure were applied to the study of selectively deuterated 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMIM TFSA) ionic liquid isotopologues and related ionic liquids. For EMIM TFSA, temperature-dependent 2H T 1 data indicate stronger electric field gradients in the alkyl chain region compared to the imidazolium ring. Most significantly, the pressure dependences of the EMIM and TFSA self-diffusion coefficients revealed that the displacements of the cations and anions are independent, with diffusion of the TFSA anions being slowed much more by increasing pressure than for the EMIM cations, asmore » shown by their respective activation volumes (28.8 ± 2.5 cm³/mol for TFSA vs. 14.6 ± 1.3 cm³/mol for EMIM). Increasing pressure may lower the mobility of the TFSA anion by hindering its interconversion between trans and cis conformers, a process that is coupled to diffusion according to published molecular dynamics simulations. Measured activation volumes (ΔV ‡) for ion self-diffusion in EMIM bis(fluoromethylsulfonyl)amide and EMIM tetrafluoroborate support this hypothesis.« less

Impact of front-of-pack 'traffic-light' nutrition labelling on consumer food purchases in the UK.

PubMed

Sacks, Gary; Rayner, Mike; Swinburn, Boyd

2009-12-01

Front-of-pack 'traffic-light' nutrition labelling has been widely proposed as a tool to improve public health nutrition. This study examined changes to consumer food purchases after the introduction of traffic-light labels with the aim of assessing the impact of the labels on the 'healthiness' of foods purchased. The study examined sales data from a major UK retailer in 2007. We analysed products in two categories ('ready meals' and sandwiches), investigating the percentage change in sales 4 weeks before and after traffic-light labels were introduced, and taking into account seasonality, product promotions and product life-cycle. We investigated whether changes in sales were related to the healthiness of products. All products that were not new and not on promotion immediately before or after the introduction of traffic-light labels were selected for the analysis (n = 6 for ready meals and n = 12 for sandwiches). For the selected ready-meals, sales increased (by 2.4% of category sales) in the 4 weeks after the introduction of traffic-light labels, whereas sales of the selected sandwiches did not change significantly. Critically, there was no association between changes in product sales and the healthiness of the products. This short-term study based on a small number of ready meals and sandwiches found that the introduction of a system of four traffic-light labels had no discernable effect on the relative healthiness of consumer purchases. Further research on the influence of nutrition signposting will be needed before this labelling format can be considered a promising public health intervention.

Toxicity evaluation of selected ammonium-based ionic liquid forms with MCPP and dicamba moieties on Pseudomonas putida.

PubMed

Piotrowska, Aleksandra; Syguda, Anna; Wyrwas, Bogdan; Chrzanowski, Łukasz; Heipieper, Hermann J

2017-01-01

Combination of the hydrophilic herbicidal anion with hydrophobic, antimicrobial ammonium cation allows to obtain compounds in ionic liquid form with better properties then conventional herbicides. Both cation and anion can be modified by selection of herbicide and the length of alkyl chains in cation structure. However the knowledge of their potential toxic effects are still limited. Furthermore, the relation between hydrophobicity associated with the length of alkyl chains and toxicity for ionic liquids has not been thoroughly studied. Therefore we investigated toxic effects of herbicidal ionic liquid forms on growth inhibition, given as EC 50, of the common soil bacterium Pseudomonas putida. We thereby concentrated on quaternary ammonium salts. Analyzed compounds were composed of dicamba or MCPP moieties and cation with various alkyl chain lengths (n = 6,8,10) We compared them with commercial herbicides, and ammonium-based ionic liquids with neutral anion (Br - ). In addition, cis-trans isomerisation of unsaturated membrane fatty acids in Pseudomonas putida was applied as the proxy for toxicity and membrane activity. We showed that toxicity increased with the length of alkyl chains. However, this correlation is only valid for six and eight carbon atom in alkyl chains, where for n = 10 the EC 50 values rise by one order of magnitude. In our studies, the herbicidal ionic liquids [C 10 ,C 10 ,C 1 ,C 1 N][MCPP] and [C 10 ,C 10 ,C 1 ,C 1 N][dicamba] showed the lowest toxicity among analyzed quaternary ammonium salts and comparable toxicity with corresponding herbicides. No clear increase in toxicity could be followed by changing the anion moieties for ammonium-based ionic liquid forms. Copyright © 2016 Elsevier Ltd. All rights reserved.

Extraction behaviour and mechanism of Pt(iv) and Pd(ii) by liquid-liquid extraction with an ionic liquid [HBBIm]Br.

PubMed

Liu, Wenhui; Wang, Qi; Zheng, Yan; Wang, Shubin; Yan, Yan; Yang, Yanzhao

2017-06-06

In this study, a method of one-step separation and recycling of high purity Pd(ii) and Pt(iv) using an ionic liquid, 1-butyl-3-benzimidazolium bromate ([HBBIm]Br), was investigated. The effects of [HBBIm]Br concentration, initial metal concentration, and loading capacity of [HBBIm]Br were examined in detail. It was observed that [HBBIm]Br was a very effective extractant for selectively extracting Pd(ii) and precipitating Pt(iv). Through selectively extracting Pd(ii) and precipitating Pt(iv), each metal with high purity was separately obtained from mixed Pd(ii) and Pt(iv) multi-metal solution. The method of one-step separation of Pd(ii) and Pt(iv) is simple and convenient. The anion exchange mechanism between [HBBIm]Br and Pt(iv) was proven through Job's method and FTIR and 1 H NMR spectroscopies. The coordination mechanism between [HBBIm]Br and Pd(ii) was demonstrated via single X-ray diffraction and was found to be robust and distinct, as supported by the ab initio quantum-chemical studies. The crystals of the [PdBr 2 ·2BBIm] complex were formed first. Moreover, the influence of the concentrations of hydrochloric acid, sodium chloride, and sodium nitrate on the precipitation of Pt(iv) and extraction of Pd(ii) was studied herein. It was found that only the concentration of H + could inhibit the separation of Pt(iv) because H + could attract the anion PtCl 6 2- ; thus, the exchange (anion exchange mechanism) between the anions PtCl 6 2- and Br - was prevented. However, both the concentration of H + and Cl - can obviously inhibit the extraction of Pd(ii) because H + and Cl - are the reaction products and increasing their concentration can inhibit the progress of the reaction (coordination mechanism).

An in vitro examination of the antioxidant and anti-inflammatory properties of buckwheat honey.

PubMed

van den Berg, A J J; van den Worm, E; van Ufford, H C Quarles; Halkes, S B A; Hoekstra, M J; Beukelman, C J

2008-04-01

Hydroxyl radical and hypochlorite anion formed at the wound site from superoxide anion produced by activated polymorphonuclear neutrophils (PMNs) are considered important factors in impaired wound healing. Superoxide anion may also react with nitric oxide produced by macrophages to form peroxynitrite, a third strong oxidant that damages surrounding tissue. In order to select honey for use in wound-healing products, different samples were compared for their capacity to reduce levels of reactive oxygen species (ROS) in vitro. Honey samples were tested in assays for inhibition of ROS production by activated human PMNs, antioxidant activity (scavenging of superoxide anion in a cell-free system) and inhibition of human complement (reducing levels of ROS by limiting formation of complement factors that attract and stimulate PMNs). For buckwheat honey (NewYork, US), moisture and free acid content were determined by refractive index measurement and potentiometric titration respectively. Honey constituents other than sugars were investigated by thin layer chromatography, using natural product reagent to detect phenolic compounds. Constituents with antioxidant properties were detected by spraying the chromatogram with DPPH. Although most honey samples were shown to be active, significant differences were observed, with the highly active honey exceeding the activities of samples with minor effects by factors of 4 to 30. Most pronounced activities were found for American buckwheat honey from the state of NewYork. Phenolic constituents of buckwheat honey were shown to have antioxidant activity. As buckwheat honey was most effective in reducing ROS levels, it was selected for use in wound-healing products. The major antioxidant properties in buckwheat honey derive from its phenolic constituents, which are present in relatively large amounts. Its phenolic compounds may also exert antibacterial activity, whereas its low pH and high free acid content may assist wound healing.

Charge retention of soft-landed phosphotungstate Keggin anions on self-assembled monolayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunaratne, K. Don D.; Prabhakaran, Venkateshkumar; Andersen, Amity

Soft landing of mass-selected ions onto surfaces often results in partial loss of charge that may affect the structure and reactivity of deposited species. In this study, Keggin phosphotungstate anions in two selected charge states, PW12O403- (WPOM3-) and PW12O402- (WPOM2-), were soft-landed onto different self-assembled monolayer (SAM) surfaces and examined using in situ infrared reflection absorption spectroscopy (IRRAS) and density functional theory (DFT) calculations. Partial retention of the 3- charge was observed when WPOM3- was soft-landed onto the fluorinated SAM (FSAM), while the charge state distribution was dominated by the 2- charge after both WPOM3- and WPOM2- were deposited ontomore » a hydrophilic alkylthiol SAM terminated with cationic NH3+ functional groups (NH3+SAM). We found that during the course of the soft landing of WPOM3-, the relative abundance of WPOM3- on FSAM decreased while that of WPOM2- increased. We propose that the higher stability of immobilized WPOM2- in comparison with WPOM3- makes it the preferred charge state of WPOM on both the FSAM and NH3+SAM. We also observe weaker binding of WPOM anions to SAMs in comparison with phosphomolybdate ions (MoPOM) reported previously (J. Phys. Chem. C 2014, 118, 27611–27622). The weaker binding of WPOM to SAMs is attributed to the lower reactivity of WPOM reported in the literature. This study demonstrates that both the charge retention and the reactivity of deposited anionic POM clusters on surfaces are determined by the type of addenda metal atoms in the cluster.« less

Theoretical calculations on the electron absorption spectra of selected Polycyclic Aromatic Hydrocarbons (PAH) and derivatives

NASA Technical Reports Server (NTRS)

Du, Ping

1993-01-01

As a theoretical component of the joint effort with the laboratory of Dr. Lou Allamandola to search for potential candidates for interstellar organic carbon compound that are responsible for the visible diffuse interstellar absorption bands (DIB's), quantum mechanical calculations were performed on the electron absorption spectra of selected polycyclic aromatic hydrocarbons (PAH) and derivatives. In the completed project, 15 different species of naphthalene, its hydrogen abstraction and addition derivatives, and corresponding cations and anions were studied. Using semiempirical quantum mechanical method INDO/S, the ground electronic state of each species was evaluated with restricted Hartree-Fock scheme and limited configuration interaction. The lowest energy spin state for each species was used for electron absorption calculations. Results indicate that these calculations are accurate enough to reproduce the spectra of naphthalene cation and anion observed in neon matrix. The spectral pattern of the hydrogen abstraction and addition derivatives predicted based on these results indicate that the electron configuration of the pi orbitals of these species is the dominant determinant. A combined list of 19 absorptions calculated from 4500 A to 10,400 A were compiled and suggested as potential candidates that are relevant for the DIB's absorptions. Continued studies on pyrene and derivatives revealed the ground state symmetries and multiplicities of its neutral, anionic, and cationic species. Spectral calculations show that the cation (B(sub 3g)-2) and the anion (A(sub u)-2) are more likely to have low energy absorptions in the regions between 10 kK and 20 kK, similar to naphthalene. These absorptions, together with those to be determined from the hydrogen abstraction and addition derivatives of pyrene, can be used to provide additional candidates and suggest experimental work in the search for interstellar compounds that are responsible for DIB's.

Increased Ca++ uptake by erythrocytes infected with malaria parasites: Evidence for exported proteins and novel inhibitors.

PubMed

Kushwaha, Ambuj K; Apolis, Liana; Ito, Daisuke; Desai, Sanjay A

2018-05-03

Malaria parasites export many proteins into their host erythrocytes and increase membrane permeability to diverse solutes. Although most solutes use a broad-selectivity channel known as the plasmodial surface anion channel, increased Ca ++ uptake is mediated by a distinct, poorly characterised mechanism that appears to be essential for the intracellular parasite. Here, we examined infected cell Ca ++ uptake with a kinetic fluorescence assay and the virulent human pathogen, Plasmodium falciparum. Cell surface labelling with N-hydroxysulfosuccinimide esters revealed differing effects on transport into infected and uninfected cells, indicating that Ca ++ uptake at the infected cell surface is mediated by new or altered proteins at the host membrane. Conditional knockdown of PTEX, a translocon for export of parasite proteins into the host cell, significantly reduced infected cell Ca ++ permeability, suggesting involvement of parasite-encoded proteins trafficked to the host membrane. A high-throughput chemical screen identified the first Ca ++ transport inhibitors active against Plasmodium-infected cells. These novel chemical scaffolds inhibit both uptake and parasite growth; improved in vitro potency at reduced free [Ca ++ ] is consistent with parasite killing specifically via action on one or more Ca ++ transporters. These inhibitors should provide mechanistic insights into malaria parasite Ca ++ transport and may be starting points for new antimalarial drugs. © 2018 John Wiley & Sons Ltd.

New Fluorescent and Colorimetric Chemosensor for Detection of Cyanide with High Selectivity and Sensitivity in Aqueous Media.

PubMed

Zali-Boeini, Hassan; Zareh Jonaghani, Mohammad

2017-05-01

A fluorescent and colorimetric chemosensor for detection of cyanide ion based on a styryl quinoline derivative has been designed and synthesized. The chemosensor (E)-2-(4-mercaptostyryl)quinolin-8-ol L showed high selectivity for detection of cyanide over other anions such as F¯, Cl¯, Br¯, I¯, NO 3 ¯, SCN¯, N 3 ¯, ClO 4 ¯, H 2 PO 4 ¯, AcO¯, HCO 3 ¯, SO 4 2 ¯ and HSO 4 ¯in aqueous solution. The chemosensor L displayed an immediate visible and fluorescence changes from nearly colorless to orange and greenish-blue to brick-red upon addition of cyanide ion respectively. It is more likely, these distinct changes can be attributed to hydrogen bonding interaction between phenol group and cyanide anion leading to a 1:1 binding stoichiometry following with deprotonation of phenol group. The detection limit for chemosensor L toward CN¯ was 2.73× 10 -8  M. Thus, the chemosensor can be used efficiently and selectively for detection and monitoring of small amounts of cyanide ion in aqueous media.

Molecular recognition principles and stationary-phase characteristics of topoisomer-selective chemoaffinity materials for chromatographic separation of circular plasmid DNA topoisomers.

PubMed

Mahut, Marek; Lindner, Wolfgang; Lämmerhofer, Michael

2012-01-18

We recently discovered the molecular recognition capability of a quinine carbamate ligand attached to silica as a powerful chemoaffinity material for the chromatographic separation of circular plasmid topoisomers of different linking numbers. In this paper we develop structure-selectivity relationship studies to figure out the essential structural features for topoisomer recognition. By varying different moieties of the original cinchonan-derived selector, it was shown that intercalation by the quinoline moiety of the ligand as assumed initially as the working hypothesis is not an essential feature for topoisomer recognition during chromatography. We found that the key elements for topoisomer selectivity are the presence of a rigid weak anion-exchange site and a H-donor site separated from each other in a defined distance by a 4-atom spacer. Additionally, incorporation of the weak anion-exchange site into a cyclic ring structure provides greater rigidity of the ligand molecule and turned out to be advantageous, if not mandatory, for (close to) baseline separation. © 2011 American Chemical Society

Selective inclusion of PO4(3-) within persistent dimeric capsules of a tris(thiourea) receptor and evidence of cation/solvent sealed unimolecular capsules.

PubMed

Dey, Sandeep Kumar; Das, Gopal

2012-08-07

A tren-based tris(thiourea) receptor, L with electron-withdrawing p-nitrophenyl terminals has been established as a competent hydrogen-bonding scaffold that can selectively encapsulate PO(4)(3-) within persistent and rigid dimeric capsules, assembled by aromatic π-stacking interactions between the receptor side-arms. A quaternary ammonium salt of PO(4)(3-) capsules (complexes 1 and 1b, 2:1 host-guest) can reproducibly be obtained in quantitative yields by a solution-state deprotonation of [HL](+) moieties and a bound HPO(4)(2-) anion of complex 1a (HPO(4)(2-) complex of protonated L, 2:1 host-guest), induced by the presence of a large excess of anions such as HCO(3)(-), CH(3)CO(2)(-), and F(-). Qualitative as well as quantitative (1)H and (31)P NMR experiments (DMSO-d(6)) have been carried out in detail to demonstrate the selective and preferential inclusion of PO(4)(3-) by L in solution-states. Competitive crystallization experiments performed in the presence of an excess of anions such as HCO(3)(-), HSO(4)(-), CH(3)CO(2)(-), NO(3)(-) and halides (F(-) and Cl(-)) further establish the phenomenon of selective PO(4)(3-) encapsulation as confirmed by (1)H NMR, (31)P NMR, FT-IR and powder X-ray diffraction patterns of the isolated crystals. X-ray structural analyses and (31)P NMR studies of the isolated crystals of phosphate complexes (1, 1a and 1b) provide evidence of the binding discrepancy of inorganic phosphates with protonated and neutral form of L. Furthermore, extensive studies have been carried out with other anions of different sizes and dimensions in solid- and solution-states (complexes 2a, 3, 4 and 5). Crystal structure elucidation revealed the formation of a solvent (DMSO) sealed unimolecular capsule in the F(-) encapsulated complex, 2a (1:1 host-guest), a CO(3)(2-) encapsulated centrosymmetric molecular capsule in 3 (2:1 host-guest) and a cation (tetrabutylammonium) sealed SO(4)(2-) encapsulated unimolecular capsule in 4 (1:1 host-guest). 2D-NOESY NMR experiments carried out on these capsule complexes further confirm the relevant binding stoichiometry of complexes (2a-4) except for the PO(4)(3-)-encapsulated complex (1b) which showed a 1:1 host-guest stoichiometry in solution.

[C–H···anion] interactions mediate the templation and anion binding properties of topologically non-trivial metal–organic structures in aqueous solutions† †Electronic supplementary information (ESI) available: For general methods, further details of synthesis and characterization, anions binding, and DFT and PM6 calculations. CCDC 1409618. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc04246a Click here for additional data file. Click here for additional data file.

PubMed Central

Bilbeisi, Rana A.; Prakasam, Thirumurugan; Lusi, Matteo; El Khoury, Roberto; Platas-Iglesias, Carlos; Charbonnière, Loïc J.; Olsen, John-Carl

2016-01-01

Two synthetic approaches—temperature variation and anion templation—allowed for the selective formation of a [2]catenane ([2]C4+) or a trefoil knot (TK6+), or for the enhanced formation of a Solomon link (SL8+), all from a simple set of starting materials (Zn(ii) acetate, diformylpyridine (DFP) and a diamino-2,2′-bipyridine (DAB)) in mixed aqueous solutions. The catenane formed exclusively at 90 °C in a 1 : 1 mixed solvent of D2O and MeOD. In the presence of bromide ion as template, TK6+ formed exclusively at 50 °C in the same solvent. In the solid state, TK6+ hosts two bromide ions in its central cavity by forming six Csp2–H hydrogen bonds. In D2O, TK6+, which was originally prepared as a trifluoroacetate (TFA) salt, was found to exchange two TFA counterions for two monovalent anions of different sizes and shapes, which lodged within the knot's central cavity. In contrast to bromide, the larger triflate anion (CF3SO3 –) promoted the formation of SL8+, which was characterized by 1H NMR spectroscopy and mass spectrometry. Two dimensional heteronuclear 19F-1H-HOSEY NMR experiments detected CH···F interactions inside the cavity of SL8+. Thus, the product distribution of this dynamic link forming system is sensitive to temperature and the size and shape of the anion template, and one of the products, TK6+, is capable of binding a variety of monovalent anions in D2O with high affinity (with log β 2 values of 4 to 6 being typical). PMID:28660022

Fluoride ion recognition by chelating and cationic boranes.

PubMed

Hudnall, Todd W; Chiu, Ching-Wen; Gabbaï, François P

2009-02-17

Because of the ubiquity of fluoride ions and their potential toxicity at high doses, researchers would like to design receptors that selectively detect this anion. Fluoride is found in drinking water, toothpaste, and osteoporosis drugs. In addition, fluoride ions also can be detected as an indicator of uranium enrichment (via hydrolysis of UF(6)) or of the chemical warfare agent sarin, which releases the ion upon hydrolysis. However, because of its high hydration enthalpy, the fluoride anion is one of the most challenging targets for anion recognition. Among the various recognition strategies that are available, researchers have focused a great deal of attention on Lewis acidic boron compounds. These molecules typically interact with fluoride anions to form the corresponding fluoroborate species. In the case of simple triarylboranes, the fluoroborates are formed in organic solvents but not in water. To overcome this limitation, this Account examines various methods we have pursued to increase the fluoride-binding properties of boron-based receptors. We first considered the use of bifunctional boranes, which chelate the fluoride anion, such as 1,8-diborylnaphthalenes or heteronuclear 1-boryl-8-mercurio-naphthalenes. In these molecules, the neighboring Lewis acidic atoms can cooperatively interact with the anionic guest. Although the fluoride binding constants of the bifunctional compounds exceed those of neutral monofunctional boranes by several orders of magnitude, the incompatibility of these systems with aqueous media limits their utility. More recently, we have examined simple triarylboranes whose ligands are decorated by cationic ammonium or phosphonium groups. These cationic groups increase the electrophilic character of these boranes, and unlike their neutral analogs, they are able to complex fluoride in aqueous media. We have also considered cationic boranes, which form chelate complexes with fluoride anions. Our work demonstrates that Coulombic and chelate effects are additive and can be combined to boost the anion affinity of Lewis acidic hosts. The boron compounds that we have investigated present a set of photophysical and electrochemical properties that can serve to signal the fluoride-binding event. We can also apply this approach to cyanide complexation and are continuing our investigations in that area.

Cl- channels of the gastric parietal cell that are active at low pH.

PubMed

Cuppoletti, J; Baker, A M; Malinowska, D H

1993-06-01

HCl secretion across mammalian gastric parietal cell apical membrane may involve Cl- channels. H(+)-K(+)-ATPase-containing membranes isolated from gastric mucosa of histamine-stimulated rabbits were fused to planar lipid bilayers. Channels were recorded with symmetric 800 mM CsCl solutions, pH 7.4. A linear current-voltage (I-V) relationship was obtained, and conductance was 28 +/- 1 pS at 800 mM CsCl. Conductance was 6.9 +/- 2 pS at 150 mM CsCl. Reversal potential was +22 mV with a fivefold cis-trans CsCl concentration gradient, indicating that the channel was anion selective with a discrimination ratio of 6:1 for Cl- over Cs+. Anion selectivity of the channel was I- > Cl- > or = Br- > NO3-, and gluconate was impermeant. Channels obtained at pH 7.4 persisted when pH of medium bathing the trans side of the bilayer (pHtrans) was reduced to pH 3, without a change in conductance, linearity of I-V relationship, or ion selectivity. In contrast, asymmetric reduction of pH of medium bathing the cis side of the bilayer from 7.4 to 3 always resulted in loss of channel activity. At pH 7.4, open probability (Po) of the channel was voltage dependent, i.e., predominantly open at +80 mV but mainly closed at -80 mV. In contrast, with low pHtrans, channel Po at -80 mV was increased 3.5-fold. The Cl- channel was Ca2+ indifferent. In absence of ionophores, ion selectivity for support of H(+)-K(+)-ATPase activity and H+ transport was consistent with that exhibited by the channel and could be limited by substitution with NO3-, whereas maximal H(+)-K(+)-ATPase activity was indifferent to anion present, demonstrating that anion transport can be rate limiting. Cl- channels with similar characteristics (conductance, linear I-V relationship, and ion selectivity) were also present in H(+)-K(+)-ATPase-containing vesicles isolated from resting (cimetidine-treated) gastric mucosa, exhibiting at -80 mV a pH-independent approximately 3.5-fold lower Po than stimulated vesicle channels. At -80 mV, reduction of pHtrans increased Po of both resting and stimulated Cl- channels by five- to sixfold. Changing membrane potential from 0 to -80 mV across stimulated vesicles increased Cl- channel activity an additional 10-fold.(ABSTRACT TRUNCATED AT 400 WORDS)

Hyperthermal (1-100 eV) nitrogen ion scattering damage to D-ribose and 2-deoxy-D-ribose films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng Zongwu; Bald, Ilko; Illenberger, Eugen

2007-10-14

Highly charged heavy ion traversal of a biological medium can produce energetic secondary fragment ions. These fragment ions can in turn cause collisional and reactive scattering damage to DNA. Here we report hyperthermal (1-100 eV) scattering of one such fragment ion (N{sup +}) from biologically relevant sugar molecules D-ribose and 2-deoxy-D-ribose condensed on polycrystalline Pt substrate. The results indicate that N{sup +} ion scattering at kinetic energies down to 10 eV induces effective decomposition of both sugar molecules and leads to the desorption of abundant cation and anion fragments. Use of isotope-labeled molecules (5-{sup 13}C D-ribose and 1-D D-ribose) partlymore » reveals some site specificity of the fragment origin. Several scattering reactions are also observed. Both ionic and neutral nitrogen atoms abstract carbon from the molecules to form CN{sup -} anion at energies down to {approx}5 eV. N{sup +} ions also abstract hydrogen from hydroxyl groups of the molecules to form NH{sup -} and NH{sub 2}{sup -} anions. A fraction of O/O{sup -} fragments abstract hydrogen to form OH{sup -}. The formation of H{sub 3}O{sup +} ions also involves hydrogen abstraction as well as intramolecular proton transfer. These findings suggest a variety of severe damaging pathways to DNA molecules which occur on the picosecond time scale following heavy ion irradiation of a cell, and prior to the late diffusion-limited homogeneous chemical processes.« less

Erratum to "The mechanism and thermodynamics of transesterification of acetate-ester enolates in the gas phase" : [Int. J. Mass Spectrom. Ion Process. 172 (1998) 25

NASA Astrophysics Data System (ADS)

Haas, George W.; Giblin, Daryl E.; Gross, Michael L.

1998-02-01

In solution, base-catalyzed hydrolysis and transesterification of esters are initiated by hydroxide- or alkoxide-ion attack at the carbonyl carbon. At low pressures in the gas phase, however, transesterification proceeds by an attack of the enolate anion of an acetate ester on an alcohol. Fourier transform mass spectrometry (FTMS) indicates that the reaction is the second-order process: -CH2-CO2-R+R'-OH-->-CH2-CO2-R'+R-OH and there is little to no detectable production of either alkoxide anion. Labeling studies show that the product and reactant enolate anion esters undergo exchange of hydrogens located [alpha] to the carbonyl carbon with the deuterium of R'--OD. The extent of the H/D exchange increases with reaction time, pointing to a short-lived intermediate. The alcoholysis reaction rate constants increase with increasing acidity of the primary, straight-chained alkyl alcohols, whereas steric effects associated with branched alcohols cause the rate constants to decrease. Equilibrium constants, which were determined directly from measurements at equilibrium and which were calculated from the forward and reverse rate constants, are near unity and show internal consistency. In the absence of steric effects, the larger enolate is always the favored product at equilibrium. The intermediate for the transesterification reaction, which can be generated at a few tenths of a torr in a tandem mass spectrometer, is tetrahedral, but other adducts that are collisionally stabilized under these conditions are principally loosely bound complexes.

Theoretical study of native point defects in strained-layer superlattice systems

NASA Astrophysics Data System (ADS)

Krishnamurthy, S.; Yu, Zhi Gang

2018-04-01

We developed a theoretical approach that employs first-principles Hamiltonians, tight-binding Hamiltonians, and Green's function techniques to obtain energy levels arising from native point defects (NPDs) in InAs-GaSb and InAs-InAs1-xSbx strained layer superlattice (SLS) systems. In InAs and GaSb regions, we considered four types of NPDs—anion vacancy, cation vacancy, anion anti-site, and cation anti-site—as well as isoelectronic substitution at anion sites (Sb at the As site and As at the Sb site). Additionally, we considered three types of defects—the cation at the second anion site, the second anion at the cation site, and second anion vacancy—in the InAs1-xSbx alloy region of the SLS. For a selected few designs, we studied NPDs both in the bulk region and near the interfaces of the SLS. We have considered 12 designs of InAs-GaSb systems and two designs of InAs-InAs0.7Sb0.3 systems lattice-matched to the GaSb substrate. The calculated defect levels not only agreed well with available measurements, but also revealed the connection between mid-gap levels and specific NPDs. We further calculated defect formation energies both in compounds and in all superlattices considered above. Since the absolute value of defect formation energy depends considerably on growth conditions, we evaluated the formation energies in SLS with respect to their value in the corresponding bulk or alloy. The calculated defect formation energies, together with defect energy level results, allow us to identify a few promising SLS designs for high-performing photodetectors.

Synergistic Anion-(π) n-π Catalysis on π-Stacked Foldamers.

PubMed

Bornhof, Anna-Bea; Bauzá, Antonio; Aster, Alexander; Pupier, Marion; Frontera, Antonio; Vauthey, Eric; Sakai, Naomi; Matile, Stefan

2018-04-11

In this report, we demonstrate that synergistic effects between π-π stacking and anion-π interactions in π-stacked foldamers provide access to unprecedented catalytic activity. To elaborate on anion-(π) n -π catalysis, we have designed, synthesized and evaluated a series of novel covalent oligomers with up to four face-to-face stacked naphthalenediimides (NDIs). NMR analysis including DOSY confirms folding into π stacks, cyclic voltammetry, steady-state and transient absorption spectroscopy the electronic communication within the π stacks. Catalytic activity, assessed by chemoselective catalysis of the intrinsically disfavored but biologically relevant addition reaction of malonate half thioesters to enolate acceptors, increases linearly with the length of the stacks to reach values that are otherwise beyond reach. This linear increase violates the sublinear power laws of oligomer chemistry. The comparison of catalytic activity with ratiometric changes in absorption and decreasing energy of the LUMO thus results in superlinearity, that is synergistic amplification of anion-π catalysis by remote control over the entire stack. In computational models, increasing length of the π-stacked foldamers correlates sublinearly with changes in surface potentials, chloride binding energies, and the distances between chloride and π surface and within the π stack. Computational evidence is presented that the selective acceleration of disfavored but relevant enolate chemistry by anion-π catalysis indeed originates from the discrimination of planar and bent tautomers with delocalized and localized charges, respectively, on π-acidic surfaces. Computed binding energies of keto and enol intermediates of the addition reaction as well as their difference increase with increasing length of the π stack and thus reflect experimental trends correctly. These results demonstrate that anion-(π) n -π interactions exist and matter, ready for use as a unique new tool in catalysis and beyond.

Differential processing of the two subunits of human choriogonadotropin (hCG) by granulosa cells. I. Preparation and characterization of selectively labeled hCG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landefeld, T.D.; Byrne, M.D.; Campbell, K.L.

1981-12-01

The alpha- and beta-subunits of hCG were radioiodinated and recombined with unlabeled complementary subunits. The resultant recombined hormones, selectively labeled in either the alpha- or beta-subunit, were separated from unrecombined subunit by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, extracted with Triton X-100, and characterized by binding analysis. The estimates of maximum binding (active fraction) of the two resultant selectively labeled, recombined hCG preparations, determined with excess receptor were 0.41 and 0.59. These values are similar to those obtained when hCG is labeled as an intact molecule. The specific activities of the recombined preparations were estimated by four different methods, and themore » resulting values were used in combination with the active fraction estimates to determine the concentrations of active free and bound hormone. Binding analyses were run using varying concentrations of both labeled and unlabeled hormone. Estimates of the equilibrium dissociation binding constant (Kd) and receptor capacity were calculated in three different ways. The mean estimates of capacity (52.6 and 52.7 fmol/mg tissue) and Kd (66.6 and 65.7 pM) for the two preparations were indistinguishable. Additionally, these values were similar to values reported previously for hCG radioiodinated as an intact molecule. The availability of well characterized, selectively labeled hCG preparations provides new tools for studying the mechanism of action and the target cell processing of the subunits of this hormone.« less

Selective disulfide reduction for labeling and enhancement of Fab antibody fragments.

PubMed

Kirley, Terence L; Greis, Kenneth D; Norman, Andrew B

2016-11-25

Many methods have been developed for chemical labeling and enhancement of the properties of antibodies and their common fragments, including the Fab and F(ab') 2 fragments. Somewhat selective reduction of some antibody disulfide bonds has been previously achieved, yielding antibodies and antibody fragments that can be labeled at defined sites, enhancing their utility and properties. Selective reduction of the two hinge disulfide bonds present in F(ab') 2 fragments using mild reduction has been useful. However, such reduction is often not quantitative and results in the reduction of multiple disulfide bonds, and therefore subsequent multiple labeling or conjugation sites are neither homogenous nor stoichiometric. Here, a simple and efficient selective reduction of the single disulfide bond linking the partial heavy chain and the intact light chain which compose the Fab fragment is accomplished utilizing tris(2-carboxyethyl)phosphine (TCEP) immobilized on agarose beads. The resultant reduced cysteine residues were labeled with several cysteine-selective fluorescent reagents, as well as by cysteine-directed PEGylation. These two cysteine residues can also be re-ligated by means of a bifunctional cysteine cross-linking agent, dibromobimane, thereby both restoring a covalent linkage between the heavy and light chains at this site, far removed from the antigen binding site, and also introducing a fluorescent probe. There are many other research and clinical uses for these selectively partially reduced Fab fragments, including biotinylation, toxin and drug conjugation, and incorporation of radioisotopes, and this technique enables simple generation of very useful Fab fragment derivatives with many potential applications. Copyright © 2016 Elsevier Inc. All rights reserved.

Label-aligned Multi-task Feature Learning for Multimodal Classification of Alzheimer’s Disease and Mild Cognitive Impairment

PubMed Central

Zu, Chen; Jie, Biao; Liu, Mingxia; Chen, Songcan

2015-01-01

Multimodal classification methods using different modalities of imaging and non-imaging data have recently shown great advantages over traditional single-modality-based ones for diagnosis and prognosis of Alzheimer’s disease (AD), as well as its prodromal stage, i.e., mild cognitive impairment (MCI). However, to the best of our knowledge, most existing methods focus on mining the relationship across multiple modalities of the same subjects, while ignoring the potentially useful relationship across different subjects. Accordingly, in this paper, we propose a novel learning method for multimodal classification of AD/MCI, by fully exploring the relationships across both modalities and subjects. Specifically, our proposed method includes two subsequent components, i.e., label-aligned multi-task feature selection and multimodal classification. In the first step, the feature selection learning from multiple modalities are treated as different learning tasks and a group sparsity regularizer is imposed to jointly select a subset of relevant features. Furthermore, to utilize the discriminative information among labeled subjects, a new label-aligned regularization term is added into the objective function of standard multi-task feature selection, where label-alignment means that all multi-modality subjects with the same class labels should be closer in the new feature-reduced space. In the second step, a multi-kernel support vector machine (SVM) is adopted to fuse the selected features from multi-modality data for final classification. To validate our method, we perform experiments on the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database using baseline MRI and FDG-PET imaging data. The experimental results demonstrate that our proposed method achieves better classification performance compared with several state-of-the-art methods for multimodal classification of AD/MCI. PMID:26572145

Calculation and mitigation of isotopic interferences in liquid chromatography-mass spectrometry/mass spectrometry assays and its application in supporting microdose absolute bioavailability studies.

PubMed

Gu, Huidong; Wang, Jian; Aubry, Anne-Françoise; Jiang, Hao; Zeng, Jianing; Easter, John; Wang, Jun-sheng; Dockens, Randy; Bifano, Marc; Burrell, Richard; Arnold, Mark E

2012-06-05

A methodology for the accurate calculation and mitigation of isotopic interferences in liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) assays and its application in supporting microdose absolute bioavailability studies are reported for the first time. For simplicity, this calculation methodology and the strategy to minimize the isotopic interference are demonstrated using a simple molecule entity, then applied to actual development drugs. The exact isotopic interferences calculated with this methodology were often much less than the traditionally used, overestimated isotopic interferences simply based on the molecular isotope abundance. One application of the methodology is the selection of a stable isotopically labeled internal standard (SIL-IS) for an LC-MS/MS bioanalytical assay. The second application is the selection of an SIL analogue for use in intravenous (i.v.) microdosing for the determination of absolute bioavailability. In the case of microdosing, the traditional approach of calculating isotopic interferences can result in selecting a labeling scheme that overlabels the i.v.-dosed drug or leads to incorrect conclusions on the feasibility of using an SIL drug and analysis by LC-MS/MS. The methodology presented here can guide the synthesis by accurately calculating the isotopic interferences when labeling at different positions, using different selective reaction monitoring (SRM) transitions or adding more labeling positions. This methodology has been successfully applied to the selection of the labeled i.v.-dosed drugs for use in two microdose absolute bioavailability studies, before initiating the chemical synthesis. With this methodology, significant time and cost saving can be achieved in supporting microdose absolute bioavailability studies with stable labeled drugs.

Direct modulation of the outer mitochondrial membrane channel, voltage-dependent anion channel 1 (VDAC1) by cannabidiol: a novel mechanism for cannabinoid-induced cell death

PubMed Central

Rimmerman, N; Ben-Hail, D; Porat, Z; Juknat, A; Kozela, E; Daniels, M P; Connelly, P S; Leishman, E; Bradshaw, H B; Shoshan-Barmatz, V; Vogel, Z

2013-01-01

Cannabidiol (CBD) is a non-psychoactive plant cannabinoid that inhibits cell proliferation and induces cell death of cancer cells and activated immune cells. It is not an agonist of the classical CB1/CB2 cannabinoid receptors and the mechanism by which it functions is unknown. Here, we studied the effects of CBD on various mitochondrial functions in BV-2 microglial cells. Our findings indicate that CBD treatment leads to a biphasic increase in intracellular calcium levels and to changes in mitochondrial function and morphology leading to cell death. Density gradient fractionation analysis by mass spectrometry and western blotting showed colocalization of CBD with protein markers of mitochondria. Single-channel recordings of the outer-mitochondrial membrane protein, the voltage-dependent anion channel 1 (VDAC1) functioning in cell energy, metabolic homeostasis and apoptosis revealed that CBD markedly decreases channel conductance. Finally, using microscale thermophoresis, we showed a direct interaction between purified fluorescently labeled VDAC1 and CBD. Thus, VDAC1 seems to serve as a novel mitochondrial target for CBD. The inhibition of VDAC1 by CBD may be responsible for the immunosuppressive and anticancer effects of CBD. PMID:24309936

Asparagine-linked oligosaccharides on lutropin, follitropin, and thyrotropin: structural elucidation of the sulfated and sialylated oligosaccharides on bovine, ovine, and human pituitary glycoprotein hormones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, E.D.; Baenziger, J.U.

1988-01-05

The authors have elucidated the structures of the anionic asparagine-linked oligosaccharides present on the glycoprotein hormones lutropin (luteinizing hormone), follitropin (follicle-stimulating hormone), and thyrotropin (thyroid-stimulating hormone). Purified hormones, isolated from bovine, ovine, and human pituitaries, were digested with N-glycanase, and the released oligosaccharides were reduced with NaB(/sup 3/H)/sub 4/. The /sup 3/H-labeled oligosaccharides from each hormone were then fractionated by anion-exchange high performance liquid chromatography (HPLC) into populations differing in the number of sulfate and/or sialic acid moieties. The sulfated, sialylated, and sulfated/sialylated structures, which together comprised 67-90% of the asparagine-linked oligosaccharides on the pituitary glycoprotein hormones, were highly heterogeneousmore » and displayed hormone- as well as animal species-specific features. A previously uncharacterized dibranched oligosaccharide, bearing one residue each of sulfate and sialic acid, was found on all of the hormones except bovine lutropin. In this study, they describe the purification and detailed structural characterizations of the sulfated, sialylated, and sulfated/sialylated oligosaccharides found on lutropin, follitropin, and thyrotropin from several animal species.« less

Attitude and Behavior Factors Associated with Front-of-Package Label Use with Label Users Making Accurate Product Nutrition Assessments.

PubMed

Roseman, Mary G; Joung, Hyun-Woo; Littlejohn, Emily I

2018-05-01

Front-of-package (FOP) labels are increasing in popularity on retail products. Reductive FOP labels provide nutrient-specific information, whereas evaluative FOP labels summarize nutrient information through icons. Better understanding of consumer behavior regarding FOP labels is beneficial to increasing consumer use of nutrition labeling when making grocery purchasing decisions. We aimed to determine FOP label format effectiveness in aiding consumers at assessing nutrient density of food products. In addition, we sought to determine relationships between FOP label use and attitude toward healthy eating, diet self-assessment, self-reported health and nutrition knowledge, and label and shopping behaviors. A between-subjects experimental design was employed. Participants were randomly assigned to one of four label conditions: Facts Up Front, Facts Up Front Extended, a binary symbol, and no-label control. One hundred sixty-one US primary grocery shoppers, aged 18 to 69 years. Participants were randomly invited to the online study. Participants in one of four label condition groups viewed three product categories (cereal, dairy, and snacks) with corresponding questions. Adults' nutrition assessment of food products based on different FOP label formats, along with label use and attitude toward healthy eating, diet self-assessment, self-reported health and nutrition knowledge, and label and shopping behaviors. Data analyses included descriptive statistics, χ 2 tests, and logistical regression. Significant outcomes were set to α=.05. Participants selected the more nutrient-dense product in the snack food category when it contained an FOP label. Subjective health and nutrition knowledge and frequency of selecting food for healthful reasons were associated with FOP label use (P<0.01 and P<0.05, respectively). Both Facts Up Front (reductive) and binary (evaluative) FOP labels appear effective for nutrition assessment of snack products compared with no label. Specific attitude and behavior factors were associated with label use. Copyright © 2018 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Supramolecular organization of calix[4]pyrrole with a methyl-trialkylammonium anion exchanger leads to remarkable reversal of selectivity for sulfate extraction vs. nitrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borman, Christopher J.; Custelcean, Radu; Hay, Ben P.

Here, meso-Octamethylcalix[4]pyrrole (C4P) enhances sulfate selectivity in solvent extraction by Aliquat 336N, an effect ascribed to the supramolecular preorganization and thermodynamic stability imparted by insertion of the methyl group of the Aliquat cation into the cup of C4P in its cone conformation.

Highly selective optical fluoride ion sensor with submicromolar detection limit based on aluminum(III) octaethylporphyrin in thin polymeric film.

PubMed

Badr, Ibrahim H A; Meyerhoff, Mark E

2005-04-20

A highly selective, sensitive, and reversible fluoride optical sensing film based on aluminum(III)octaethylporphyrin as a fluoride ionophore and a lipophilic pH indicator as the optical transducer is described. The fluoride optical sensing films exhibit a submicromolar detection limit and high discrimination for fluoride over several lipophilic anions such as nitrate, perchlorate, and thiocyanate.

Ionene polymers for selectively inhibiting the vitro growth of malignant cells

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor)

1977-01-01

Ionene polymers of the structure ##STR1## WHERE X AND Y ARE INTEGERS FROM 3 TO 16, Z.sup.- is an anion such as a halogen and n is an integer from 50 to 150 are found to bind negatively charged mammalian cells such as malignant cells and can be utilized to selectively inhibit the growth of malignant cells in vitro.

Amino Acid Selective 13C Labeling and 13C Scrambling Profile Analysis of Protein α and Side-Chain Carbons in Escherichia coli Utilized for Protein Nuclear Magnetic Resonance.

PubMed

Sugiki, Toshihiko; Furuita, Kyoko; Fujiwara, Toshimichi; Kojima, Chojiro

2018-06-20

Amino acid selective isotope labeling is an important nuclear magnetic resonance technique, especially for larger proteins, providing strong bases for the unambiguous resonance assignments and information concerning the structure, dynamics, and intermolecular interactions. Amino acid selective 15 N labeling suffers from isotope dilution caused by metabolic interconversion of the amino acids, resulting in isotope scrambling within the target protein. Carbonyl 13 C atoms experience less isotope scrambling than the main-chain 15 N atoms do. However, little is known about the side-chain 13 C atoms. Here, the 13 C scrambling profiles of the Cα and side-chain carbons were investigated for 15 N scrambling-prone amino acids, such as Leu, Ile, Tyr, Phe, Thr, Val, and Ala. The level of isotope scrambling was substantially lower in 13 Cα and 13 C side-chain labeling than in 15 N labeling. We utilized this reduced scrambling-prone character of 13 C as a simple and efficient method for amino acid selective 13 C labeling using an Escherichia coli cold-shock expression system and high-cell density fermentation. Using this method, the 13 C labeling efficiency was >80% for Leu and Ile, ∼60% for Tyr and Phe, ∼50% for Thr, ∼40% for Val, and 30-40% for Ala. 1 H- 15 N heteronuclear single-quantum coherence signals of the 15 N scrambling-prone amino acid were also easily filtered using 15 N-{ 13 Cα} spin-echo difference experiments. Our method could be applied to the assignment of the 55 kDa protein.

TREATMENT FOR IMPROVING THE OPERATION OF STRONG BASE ANION EXCHANGE RESINS

DOEpatents

Stevenson, P.C.

1960-11-29

A process is offered for improving quaternary ammonium type strongly basic anion exchange resins so that centain zinc and cadmium residues, which normally stick to and "poison" this type of resin, can be removed by elution. Specifically, the resin as obtained commercially is treated with an aqueous solution of sodium hydroxide of about 1 to 4 M concentration by heating therein and periodically adding small amounts of oxidizing agent selected from hydrogen peroxide, sodium peroxide and hypochlorite. Zinc and cadmium values may then be adsorbed onto the resin from a 0.1 to 3 M HCl and thereafter eluted therefrom with very dilute HCl solutions.

Titanate-based adsorbents for radioactive ions entrapment from water.

PubMed

Yang, Dongjiang; Liu, Hongwei; Zheng, Zhanfeng; Sarina, Sarina; Zhu, Huaiyong

2013-03-21

This feature article reviews some titanate-based adsorbents for the removal of radioactive wastes (cations and anions) from water. At the beginning, we discuss the development of the conventional ion-exchangeable titanate powders for the entrapment of radioactive cations, such as crystalline silicotitanate (CST), monosodium titanate (MST), peroxotitanate (PT). Then, we specially emphasize the recent progress in the uptake of radioactive ions by one-dimensional (1D) sodium titanate nanofibers and nanotubes, which includes the synthesis and phase transformation of the 1D nanomaterials, adsorption ability (capacity, selectivity, kinetics, etc.) of radioactive cations and anions, and the structural evolution during the adsorption process.

Widespread genetic switches and toxicity resistance proteins for fluoride.

PubMed

Baker, Jenny L; Sudarsan, Narasimhan; Weinberg, Zasha; Roth, Adam; Stockbridge, Randy B; Breaker, Ronald R

2012-01-13

Most riboswitches are metabolite-binding RNA structures located in bacterial messenger RNAs where they control gene expression. We have discovered a riboswitch class in many bacterial and archaeal species whose members are selectively triggered by fluoride but reject other small anions, including chloride. These fluoride riboswitches activate expression of genes that encode putative fluoride transporters, enzymes that are known to be inhibited by fluoride, and additional proteins of unknown function. Our findings indicate that most organisms are naturally exposed to toxic levels of fluoride and that many species use fluoride-sensing RNAs to control the expression of proteins that alleviate the deleterious effects of this anion.

Widespread Genetic Switches and Toxicity Resistance Proteins for Fluoride

PubMed Central

Weinberg, Zasha; Roth, Adam; Stockbridge, Randy B.; Breaker, Ronald R.

2014-01-01

Most riboswitches are metabolite-binding RNA structures located in bacterial messenger RNAs where they control gene expression. We have discovered a riboswitch class in many bacterial and archaeal species whose members are selectively triggered by fluoride but reject other small anions, including chloride. These fluoride riboswitches activate expression of genes that encode putative fluoride transporters, enzymes that are known to be inhibited by fluoride, and additional proteins of unknown function. Our findings indicate that most organisms are naturally exposed to toxic levels of fluoride and that many species use fluoride-sensing RNAs to control the expression of proteins that alleviate the deleterious effects of this anion. PMID:22194412

Thiourea based novel chromogenic sensor for selective detection of fluoride and cyanide anions in organic and aqueous media.

PubMed

Kumar, Vinod; Kaushik, M P; Srivastava, A K; Pratap, Ajay; Thiruvenkatam, V; Row, T N Guru

2010-03-17

Novel chromogenic thiourea based sensors 4,4'-bis-[3-(4-nitrophenyl) thiourea] diphenyl ether 1 and 4,4'-bis-[3-(4-nitrophenyl) thiourea] diphenyl methane 2 having nitrophenyl group as signaling unit have been synthesized and characterized by spectroscopic techniques and X-ray crystallography. The both sensors show visual detection, UV-vis and NMR spectral changes in presence of fluoride and cyanide anions in organic solvent as well as in aqueous medium. The absorption spectra indicated the formation of complex between host and guest is in 1:2 stoichiometric ratios. Copyright 2010 Elsevier B.V. All rights reserved.

Detection of irradiation induced reactive oxygen species production in live cells

NASA Astrophysics Data System (ADS)

Gao, Bo; Zhu, Debin

2006-09-01

Reactive oxygen species (ROS) is thought to play an important role in cell signaling of apoptosis, necrosis, and proliferation. Light irradiation increases mitochondrial reactive oxygen species (ROS) production and mediates its intracellular signaling by adjusting the redox potential in tumor cells. Mitochondria are the main source of ROS in the living cell. Superoxide anions (0 II - are likely the first ROS generated in the mitochondria following radiation damage, and then convert to hydrogen peroxide (H II0 II), hydroxyl radical (•OH), and singlet oxygen (10 II), etc. Conventional methods for research ROS production in mitochondria mostly use isolated mitochondria rather than mitochondria in living cells. In this study, a highly selective probe to detect mitochondrial 0 II - in live cells, MitoSOX TM Red, was applied to quantify the mitochondrial ROS production in human lung adenocarcinoma cells (ASTC-a-1) with laser scanning microscope (LSM) after ultraviolet C (UVC) and He-Ne laser irradiation. Dichiorodihydrofluoresein diacetate (DCFHDA), a common used fluorescent probe for ROS detection without specificity, were used as a comparison to image the ROS production. The fluorescent image of MItoSOX TM Red counterstained with MitoTracker Deep Red 633, a mitochondria selective probe, shows that the mitochondrial ROS production increases distinctly after UVC and He-Ne laser irradiation. DCFH-DA diffuses labeling throughout the cell though its fluorescence increases markedly too. In conclusion, the fluorescent method with MitoSOX TM Red reagent is proved to be a promising technique to research the role of ROS in radiation induced apoptosis.

Effect of calorie or exercise labels on menus on calories and macronutrients ordered and calories from specific foods in Hispanic participants: a randomized study.

PubMed

Shah, Meena; Bouza, Brooke; Adams-Huet, Beverley; Jaffery, Manall; Esposito, Phil; Dart, Lyn

2016-12-01

The effect of menu labels on food choices is unknown in Hispanics. This study evaluated the impact of menu labels on calories and macronutrients ordered in Hispanics. 372 Hispanics (18-65 years) were randomly assigned to menus with no labels (NL) (n=127), rank-ordered calorie labels plus a statement on energy needs per meal (CL) (n=123), or rank-ordered exercise labels showing minutes of brisk walking necessary to burn the food calories (EL) (n=122). The menus had identical food choices. Participants were instructed to select foods from the assigned menu as if having lunch in a fast food restaurant. One-way analysis of variance found no difference in calories ordered (median (25th and 75th centiles)) by menu condition (NL: 785.0 (465.0, 1010.0) kcal; CL: 790.0 (510.0, 1020.0) kcal; EL: 752.5 (520.0, 1033.8) kcal; p=0.75). Calories from specific foods and macronutrient intake were not different by menu condition. Menu label use was 26.8% in the CL and 25.4% in the EL condition. Calories ordered were not different between those who used and those who did not use the labels. Regression analysis showed that perception of being overweight (p=0.02), selecting foods based on health value (p<0.0001), and meeting exercise guidelines (p<0.0001) were associated with fewer calories ordered. Logistic regression showed that selecting foods based on health value (p=0.01) was associated with higher food label use. Menu labels did not affect food choices in Hispanic participants. Future studies should determine if nutrition, exercise, and weight perception counseling prior to menu labels intervention would result in better food choices. NCT02804503; post-results. Copyright © 2016 American Federation for Medical Research.

Phospholipid analogues of Porphyromonas gingivalis.

PubMed

Tavana, A M; Korachi, M; Boote, V; Hull, P S; Love, D N; Drucker, D B

2000-05-01

Porphyromonas has lipids containing hydroxy acids and C16:0 and iso-C15:0 major monocarboxylic acids among others. Nothing is known of its individual phospholipid molecular species. The aim of this study was to determine molecular weights and putative identities of individual phospholipid molecular species extracted from Porphyromonas gingivalis (seven strains), P. asaccharolytica (one strain) and P. endodontalis (two strains). Cultures on Blood-Fastidious Anaerobe Agar were harvested, washed and freeze-dried. Phospholipids were extracted and separated by fast atom bombardment mass spectrometry (FAB MS) in negative-ion mode. Phospholipid classes were also separated by thin layer chromatography (TLC). The major anions in the range m/z 209-299 were consistent with the presence of the C13: 0, C15: 0, C16: 0 and C18: 3 mono-carboxylate anions. Major polar lipid anion peaks in the range m/z 618-961 were consistent with the presence of molecular species of phosphatidylethanolamine, phosphatidylglycerol and with unidentified lipid analogues. Porphyromonas gingivalis differed from comparison strains of other species by having major anions with m/z 932, 946 and 960. Unusually, a feline strain of P. gingivalis had a major peak of m/z 736. Selected anions were studied by tandem FAB MS which revealed that peaks with m/z 653 and 946 did not correspond to commonly occurring classes of polar lipids. They were however, glycerophosphates. It is concluded that the polar lipid analogue profiles obtained with Porphyromonas are quite different from those of the genera Prevotella and Bacteroides but reveal heterogeneity within P. gingivalis.

Analysis of quaternary ammonium and phosphonium ionic liquids by reversed-phase high-performance liquid chromatography with charged aerosol detection and unified calibration.

PubMed

Stojanovic, Anja; Lämmerhofer, Michael; Kogelnig, Daniel; Schiesel, Simone; Sturm, Martin; Galanski, Markus; Krachler, Regina; Keppler, Bernhard K; Lindner, Wolfgang

2008-10-31

Several hydrophobic ionic liquids (ILs) based on long-chain aliphatic ammonium- and phosphonium cations and selected aromatic anions were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) employing trifluoroacetic acid as ion-pairing additive to the acetonitrile-containing mobile phase and adopting a step-gradient elution mode. The coupling of charged aerosol detection (CAD) for the non-chromophoric aliphatic cations with diode array detection (DAD) for the aromatic anions allowed their simultaneous analysis in a set of new ILs derived from either tricaprylmethylammonium chloride (Aliquat 336) and trihexyltetradecylphosphonium chloride as precursors. Aliquat 336 is a mix of ammonium cations with distinct aliphatic chain lengths. In the course of the studies it turned out that CAD generates an identical detection response for all the distinct aliphatic cations. Due to lack of single component standards of the individual Aliquat 336 cation species, a unified calibration function was established for the quantitative analysis of the quaternary ammonium cations of the ILs. The developed method was validated according to ICH guidelines, which confirmed the validity of the unified calibration. The application of the method revealed molar ratios of cation to anion close to 1 indicating a quantitative exchange of the chloride ions of the precursors by the various aromatic anions in the course of the synthesis of new ILs. Anomalies of CAD observed for the detection of some aromatic anions (thiosalicylate and benzoate) are discussed.

In-Situ 13C-Labeling of Microbial Phospholipid Fatty Acids: Tracing Substrate Assimilation in a Petroleum-Contaminated Aquifer

NASA Astrophysics Data System (ADS)

Pombo, S. A.; Schroth, M. H.; Pelz, O.; Zeyer, J.

2001-12-01

Stable isotope analysis of phospholipid-derived fatty acids (PLFA) is a novel tool to trace assimilation of organic carbon in microbial communities. The 13C-labeling of biomarker fatty acids allows the identification of specific microbial populations involved in the metabolism of particular substrates, supplemented in 13C-labeled form. The goal of this study was to investigate the feasibility of 13C-labeling of PLFA and produced dissolved inorganic carbon (DIC) in a petroleum hydrocarbon (PHC)-contaminated aquifer during an in-situ experiment. To this end, we performed a single-well "push-pull" test in a monitoring well located in the denitrifying zone of a PHC-contaminated aquifer in Studen, Switzerland. During the experiment, we injected 500 L of site groundwater that was amended with 13C-labeled acetate (50% [2-13C]) and nitrate as reactants, and bromide as conservative tracer. Following the injection, we extracted a total of 1000 L of test solution/groundwater mixture after 4, 23 and 46 h from the same location. Concentrations of anions were measured in samples collected during the extraction. From these data, we computed first order rate coefficients for consumption of acetate (0.70 +/- 0.05 1/d) and nitrate (0.63 +/- 0.08 1/d). In addition, we extracted and identified PLFA, and measured \\delta13C values of PLFA and DIC. After only 4 h of incubation, we detected 13C-enrichment of certain PLFA in suspended biomass of extracted groundwater. After 46 h, we measured enrichments of up to 5000 per mil in certain PLFA (e.g. 16:1ω 7c), and up to 1500 per mil in the produced DIC. Our results demonstrate the feasibility of in-situ 13C-labeling of PLFA and DIC using push-pull tests to determine microbial activities in-situ in a natural ecosystem.

Cross-cultural measurement equivalence of the EQ-5D-5L items for English-speaking Asians in Singapore.

PubMed

Luo, N; Wang, Y; How, C H; Wong, K Y; Shen, L; Tay, E G; Thumboo, J; Herdman, M

2015-06-01

To investigate how the response labels of the 5-level EQ-5D (EQ-5D-5L) items are interpreted and used by English-speaking Chinese and non-Chinese Singaporeans, as a means to assessing whether those items are cross-culturally equivalent health-status measures in this Asian population. In face-to-face interviews, Chinese, Malay and Indian visitors to a primary care institution in Singapore were asked to rate the relative severity conveyed by EQ-5D-5L response labels, each containing the keyword of 'no(t),' 'slight(ly),' 'moderate(ly),' 'severe(ly),' or 'unable'/'extreme(ly),' using a 0-100 numerical rating scale. Participants were also asked to describe 25 hypothetical health states using the EQ-5D-5L response labels. Differences between Chinese and Malay/Indian participants in label interpretation and selection were examined using multivariate regression analysis to adjust for participant characteristics. The differences in adjusted mean severity scores for individual EQ-5D-5L labels between Chinese (n = 148) and non-Chinese (Malay: n = 53; Indian: n = 56) participants ranged from 0.0 to 9.0. The relative severity of the labels to the participants supported the ordinality of the EQ-5D-5L response labels and was similar across ethnic groups. Chinese and non-Chinese participants selected similar response labels to describe each hypothetical health state, with the adjusted odds ratios of selecting any type of the five response labels for non-Chinese versus Chinese participants ranging from 0.92 to 1.15 (p > 0.05 for all). The EQ-5D-5L items are likely to generate equivalent health outcomes between English-speaking Chinese and non-Chinese Singaporeans.

Hematopoietic stem cell-specific GFP-expressing transgenic mice generated by genetic excision of a pan-hematopoietic reporter gene.

PubMed

Perez-Cunningham, Jessica; Boyer, Scott W; Landon, Mark; Forsberg, E Camilla

2016-08-01

Selective labeling of specific cell types by expression of green fluorescent protein (GFP) within the hematopoietic system would have great utility in identifying, localizing, and tracking different cell populations in flow cytometry, microscopy, lineage tracing, and transplantation assays. In this report, we describe the generation and characterization of a new transgenic mouse line with specific GFP labeling of all nucleated hematopoietic cells and platelets. This new "Vav-GFP" mouse line labels the vast majority of hematopoietic cells with GFP during both embryonic development and adulthood, with particularly high expression in hematopoietic stem and progenitor cells (HSPCs). With the exception of transient labeling of fetal endothelial cells, GFP expression is highly selective for hematopoietic cells and persists in donor-derived progeny after transplantation of HSPCs. Finally, we also demonstrate that the loxP-flanked reporter allows for specific GFP labeling of different hematopoietic cell subsets when crossed to various Cre reporter lines. By crossing Vav-GFP mice to Flk2-Cre mice, we obtained robust and highly selective GFP expression in hematopoietic stem cells (HSCs). These data describe a new mouse model capable of directing GFP labeling exclusively of hematopoietic cells or exclusively of HSCs. Copyright © 2016 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc. All rights reserved.

DEMONSTRATION BULLETIN: FORAGER™ SPONGE TECHNOLOGY - DYNAPHORE, INC.

EPA Science Inventory

The Forager™ Sponge is an open-celled cellulose sponge incorporating an amine-containing chelating polymer that has selective affinity for dissolved heavy metals in both cationic and anionic states. The Forager™ Sponge technology can be utilized to remove and concentrate heavy me...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christopher M. Leavitt; Garold L. Gresham; Michael T. Benson

Diphenyldithiophosphinate (DTP) ligands modified with electron-withdrawing trifluoromethyl (TFM) substitutents are of high interest because they have demonstrated potential for exceptional separation of Am3+ from lanthanide3+ cations. Specifically, the bis(ortho-TFM) (L1-) and (ortho-TFM)(meta-TFM) (L2-) derivatives have shown excellent separation selectivity, while the bis(meta-TFM) (L3)- and unmodified DTP (Lu-) did not. Factors responsible for selective coordination have been investigated using density functional theory (DFT) calculations in concert with competitive dissociation reactions in the gas phase. To evaluate the role of (DTP+H) acidity, density functional calculations were used to predict pKa values, which followed the trend of L3 < L2 < L1 L1- > L2- > L3-.« less

Identifying the elusive link between amino acid sequence and charge selectivity in pentameric ligand-gated ion channels.

PubMed

Cymes, Gisela D; Grosman, Claudio

2016-10-10

Among neurotransmitter-gated ion channels, the superfamily of pentameric ligand-gated ion channels (pLGICs) is unique in that its members display opposite permeant-ion charge selectivities despite sharing the same structural fold. Although much effort has been devoted to the identification of the mechanism underlying the cation-versus-anion selectivity of these channels, a careful analysis of past work reveals that discrepancies exist, that different explanations for the same phenomenon have often been put forth, and that no consensus view has yet been reached. To elucidate the molecular basis of charge selectivity for the superfamily as a whole, we performed extensive mutagenesis and electrophysiological recordings on six different cation-selective and anion-selective homologs from vertebrate, invertebrate, and bacterial origin. We present compelling evidence for the critical involvement of ionized side chains-whether pore-facing or buried-rather than backbone atoms and propose a mechanism whereby not only their charge sign but also their conformation determines charge selectivity. Insertions, deletions, and residue-to-residue mutations involving nonionizable residues in the intracellular end of the pore seem to affect charge selectivity by changing the rotamer preferences of the ionized side chains in the first turn of the M2 α-helices. We also found that, upon neutralization of the charged residues in the first turn of M2, the control of charge selectivity is handed over to the many other ionized side chains that decorate the pore. This explains the long-standing puzzle as to why the neutralization of the intracellular-mouth glutamates affects charge selectivity to markedly different extents in different cation-selective pLGICs.

9 CFR 317.5 - Generically approved labeling.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Section 317.5 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE..., without such labeling being submitted for approval to the Food Safety and Inspection Service in Washington... particular. (2) The Food Safety and Inspection Service shall select samples of generically approved labeling...

Carbon "Quantum" Dots for Fluorescence Labeling of Cells.

PubMed

Liu, Jia-Hui; Cao, Li; LeCroy, Gregory E; Wang, Ping; Meziani, Mohammed J; Dong, Yiyang; Liu, Yuanfang; Luo, Pengju G; Sun, Ya-Ping

2015-09-02

The specifically synthesized and selected carbon dots of relatively high fluorescence quantum yields were evaluated in their fluorescence labeling of cells. For the cancer cell lines, the cellular uptake of the carbon dots was generally efficient, resulting in the labeling of the cells with bright fluorescence emissions for both one- and two-photon excitations from predominantly the cell membrane and cytoplasm. In the exploration on labeling the live stem cells, the cellular uptake of the carbon dots was relatively less efficient, though fluorescence emissions could still be adequately detected in the labeled cells, with the emissions again predominantly from the cell membrane and cytoplasm. This combined with the observed more efficient internalization of the same carbon dots by the fixed stem cells might suggest some significant selectivity of the stem cells toward surface functionalities of the carbon dots. The needs and possible strategies for more systematic and comparative studies on the fluorescence labeling of different cells, including especially live stem cells, by carbon dots as a new class of brightly fluorescent probes are discussed.

View the label before you view the movie: A field experiment into the impact of Portion size and Guideline Daily Amounts labelling on soft drinks in cinemas

PubMed Central

2011-01-01

Background Large soft drink sizes increase consumption, and thereby contribute to obesity. Portion size labelling may help consumers to select more appropriate food portions. This study aimed to assess the effectiveness of portion size and caloric Guidelines for Daily Amounts (GDA) labelling on consumers' portion size choices and consumption of regular soft drinks. Methods A field experiment that took place on two subsequent evenings in a Dutch cinema. Participants (n = 101) were asked to select one of five different portion sizes of a soft drink. Consumers were provided with either portion size and caloric GDA labelling (experimental condition) or with millilitre information (control condition). Results Labelling neither stimulated participants to choose small portion sizes (OR = .75, p = .61, CI: .25 - 2.25), nor did labelling dissuade participants to choose large portion sizes (OR = .51, p = .36, CI: .12 - 2.15). Conclusions Portion size and caloric GDA labelling were found to have no effect on soft drink intake. Further research among a larger group of participants combined with pricing strategies is required. The results of this study are relevant for the current public health debate on food labelling. PMID:21645373

Examining Interpretations of Graphic Cigarette Warning Labels Among U.S. Youth and Adults.

PubMed

McQueen, Amy; Waters, Erika A; Kaphingst, Kimberly A; Caburnay, Charlene A; Sanders Thompson, Vetta L; Boyum, Sonia; Kreuter, Matthew W

2016-08-01

Few studies have examined how diverse populations interpret warning labels. This study examined interpretations of 9 graphic cigarette warning labels (image plus text) proposed by the U.S. Food and Drug Administration among a convenience sample of youth (ages 13-17) and adults (18+) across the United States. Participants (N = 1,571) completed a cross-sectional survey. Participants were asked to select 1 of 3 plausible interpretations (1 preferred vs. 2 alternative) created by the research team about the particular consequence of smoking addressed in each warning label. Participants also rated each label for novelty, counterarguing, perceived effectiveness, and harm. Smokers reported their thoughts of quitting, self-efficacy, and motivation to quit. Although at least 70% of the sample chose the preferred interpretation for 7 of 9 labels, only 13% of participants chose all 9 preferred interpretations. The odds of selecting the preferred interpretation were lower among African Americans, among those with less education, and for labels perceived as being more novel. Smokers reported greater counterarguing and less perceived effectiveness and harms than nonsmokers, but results were not consistent across all labels and interpretations. The alternative interpretations of cigarette warning labels were associated with lower perceived effectiveness and lower perceived harms of smoking, both of which are important for motivating quit attempts.

Dynamics in a Water Interfacial Boundary Layer Investigated with IR Polarization-Selective Pump-Probe Experiments.

PubMed

Yuan, Rongfeng; Yan, Chang; Nishida, Jun; Fayer, Michael D

2017-05-04

The dynamics of water molecules near the surfactant interface in large Aerosol-OT reverse micelles (RMs) (w 0 = 16-25) was investigated with IR polarization-selective pump-probe experiments using the SeCN - anion as a vibrational probe. Linear absorption spectra of RMs (w 0 = 25-2) can be decomposed into the weighted sum of the SeCN - spectra in bulk water and the spectrum of the SeCN - anion interacting with the interfacial sulfonate head groups (w 0 = 1). The spectra of the large RMs, w 0 ≥ 16, are overwhelmingly dominated by the bulk water component. Anisotropy decays (orientational relaxation) of the anion for w 0 ≥ 16 displayed bulk water relaxation (1.4 and 4.5 ps) plus an additional slow decay with a time constant of ∼13 ps. The amplitude of the slow decay was too large to be associated with SeCN - in contact with the interface on the basis of the linear spectrum decomposition. The results indicate that the observed slow components arise from SeCN - in a water boundary layer, in which water molecules are perturbed by the interface but are not directly associated with it. This layer is the transition between water in direct contact with the interface and bulk water in the large RM cores. In the boundary layer, the water dynamics is slow compared to that in bulk water.

Reversal of Ion Charge Selectivity Renders the Pentameric Ligand-Gated Ion Channel GLIC Insensitive to Anesthetics

PubMed Central

Tillman, Tommy; Cheng, Mary H.; Chen, Qiang; Tang, Pei; Xu, Yan

2014-01-01

Pentameric ligand gated ion channels (pLGICs) are a family of structurally homologous cationic and anionic channels involved in neurotransmission. Cationic members of the pLGIC family are typically inhibited by general anesthetics, while anionic members are potentiated. GLIC is a prokaryotic cationic pLGIC and can be inhibited by clinical concentrations of general anesthetics. The introduction of three mutations, Y221A (Y–3′A), E222P (E–2′P) and N224R (N0′R), at the selectivity filter and one, A237T (A13′T), at the hydrophobic gate, converted GLIC to an anion channel. The mutated GLIC (GLIC4) became insensitive to the anesthetics propofol and etomidate as well as the channel blocker picrotoxin. Molecular dynamics (MD) simulations revealed changes in the structure and dynamics of GLIC4 in comparison to GLIC, particularly in the tilting angles of the pore-lining helix (TM2) that consequently resulted in different pore radius and hydration profiles. Propofol binding to an intra-subunit site of GLIC shifted the tilting angles of TM2 towards closure at the hydrophobic gate region, consistent with propofol inhibition of GLIC. In contrast, the pore of GLIC4 was much more resilient to perturbation from propofol binding. This study underscores the importance of pore dynamics and conformation to anesthetic effects on channel functions. PMID:22978431

Iodination of Escherichia coli with chloramine T: selective labeling of the outer membrane lipoprotein.

PubMed Central

Munford, R S; Gotschlich, E C

1977-01-01

Iodination of Escherichia coli cells with chloramine T preferentially labels the free and murein-bound forms of the outer membrane lipoprotein. Iodination for 15 s at 15 degrees C labels the two forms of the lipoprotein almost exclusively, whereas iodination for 60 s at 25 degrees C also labels the other major outer membrane proteins. Chloramine T iodination is a rapid, simple technique for labeling the outer membrane lipoprotein. PMID:400793

Exploring enhanced menu labels' influence on fast food selections and exercise-related attitudes, perceptions, and intentions.

PubMed

Lee, Morgan S; Thompson, Joel Kevin

2016-10-01

Labeling restaurant menus with calorie counts is a popular public health intervention, but research shows these labels have small, inconsistent effects on behavior. Supplementing calorie counts with physical activity equivalents may produce stronger results, but few studies of these enhanced labels have been conducted, and the labels' potential to influence exercise-related outcomes remains unexplored. This online study evaluated the impact of no information, calories-only, and calories plus equivalent miles of walking labels on fast food item selection and exercise-related attitudes, perceptions, and intentions. Participants (N = 643) were randomly assigned to a labeling condition and completed a menu ordering task followed by measures of exercise-related outcomes. The labels had little effect on ordering behavior, with no significant differences in total calories ordered and counterintuitive increases in calories ordered in the two informational conditions in some item categories. The labels also had little impact on the exercise-related outcomes, though participants in the two informational conditions perceived exercise as less enjoyable than did participants in the no information condition, and trends following the same pattern were found for other exercise-related outcomes. The present findings concur with literature demonstrating small, inconsistent effects of current menu labeling strategies and suggest that alternatives such as traffic light systems should be explored. Copyright © 2016 Elsevier Ltd. All rights reserved.

On the Extraction of Aromatic Compounds from Hydrocarbons by Imidazolium Ionic Liquids

PubMed Central

Cassol, Cláudia C.; Umpierre, Alexandre P.; Ebeling, Günter; Ferrera, Bauer; Chiaro, Sandra S. X.; Dupont, Jairton

2007-01-01

The liquid-liquid equilibrium for the ternary system formed by n-octane and aromatic (alkylbenzenes) and heteroaromatic compounds (nitrogen and sulfur containing heterocyles) and 1-alkyl-3-methylimidazolium ionic liquids (ILs) associated with various anions has been investigated. The selectivity on the extraction of a specific aromatic compound is influenced by anion volume, hydrogen bond strength between the anion and the imidazolium cation and the length of the 1-methyl-3-alkylimidazolium alkyl side chain. The interaction of alkylbenzenes and sulfur heterocyles with the IL is preferentially through CH-π hydrogen bonds and the quantity of these aromatics in the IL phase decreases with the increase of the steric hindrance imposed by the substituents on the aromatic nucleus. In the case of nitrogen heterocycles the interaction occurs preferentially through N(heteroaromatic)-H(imidazolium) hydrogen bonds and the extraction process is largely controlled by the nitrogen heterocycle pKa. Competitive extraction experiments suggest that benzene, pyridine and dibenzothiophene do not compete for the same hydrogen bond sites of the IL.

Investigation of Anion-Exchange and Immunoaffinity Particle-Loaded Membranes for the Isolation of Charged Organic Analytes from Water

USGS Publications Warehouse

Dombrowski, T.R.; Wilson, G.S.; Thurman, E.M.

1998-01-01

Anion-exchange and immunoaffinity particle loaded membranes (PLMs) were investigated as a mechanism for the isolation of charged organic analytes from water. Kinetic properties determined theoretically included dynamic capacity, pressure drop (??P), residence and diffusion times (Tr, Td), and total membrane porosity (???T). These properties were confirmed through experimental evaluation, and the PLM method showed significant improvement over conventional solid-phase extraction (SPE) and ion-exchange formats. Recoveries of more than 90% were observed for a variety of test compounds at flow rates up to 70 mL/min (equipment-limited maximum flow rate). A fast-flow immunoaffinity column was developed using antibodies (Abs) attached to the PLMs. Reproducible recoveries (88% ?? 4%) were observed at flow rates up to 70 mL/min for the antibody (Ab)-loaded PLMs. Findings indicate increased selectivity over anion-exchange PLMs and conventional SPE or ion-exchange methods and rapid Ab-antigen binding rates given the excellent mass-transfer characteristics of the PLMs.

The effect of varying the anion of an ionic liquid on the solvent effects on a nucleophilic aromatic substitution reaction.

PubMed

Hawker, Rebecca R; Haines, Ronald S; Harper, Jason B

2018-05-09

A variety of ionic liquids, each containing the same cation but a different anion, were examined as solvents for a nucleophilic aromatic substitution reaction. Varying the proportion of ionic liquid was found to increase the rate constant as the mole fraction of ionic liquid increased demonstrating that the reaction outcome could be controlled through varying the ionic liquid. The solvent effects were correlated with the hydrogen bond accepting ability (β) of the ionic liquid anion allowing for qualitative prediction of the effect of changing this component of the solute. To determine the microscopic origins of the solvent effects, activation parameters were determined through temperature-dependent kinetic analyses and shown to be consistent with previous studies. With the knowledge of the microscopic interactions in solution, an ionic liquid was rationally chosen to maximise rate enhancement demonstrating that an ionic solvent can be selected to control reaction outcome for this reaction type.

NH2- in a cold ion trap with He buffer gas: Ab initio quantum modeling of the interaction potential and of state-changing multichannel dynamics

NASA Astrophysics Data System (ADS)

Hernández Vera, Mario; Yurtsever, Ersin; Wester, Roland; Gianturco, Franco A.

2018-05-01

We present an extensive range of accurate ab initio calculations, which map in detail the spatial electronic potential energy surface that describes the interaction between the molecular anion NH2 - (1A1) in its ground electronic state and the He atom. The time-independent close-coupling method is employed to generate the corresponding rotationally inelastic cross sections, and then the state-changing rates over a range of temperatures from 10 to 30 K, which is expected to realistically represent the experimental trapping conditions for this ion in a radio frequency ion trap filled with helium buffer gas. The overall evolutionary kinetics of the rotational level population involving the molecular anion in the cold trap is also modelled during a photodetachment experiment and analyzed using the computed rates. The present results clearly indicate the possibility of selectively detecting differences in behavior between the ortho- and para-anions undergoing photodetachment in the trap.

GABA signalling modulates plant growth by directly regulating the activity of plant-specific anion transporters.

PubMed

Ramesh, Sunita A; Tyerman, Stephen D; Xu, Bo; Bose, Jayakumar; Kaur, Satwinder; Conn, Vanessa; Domingos, Patricia; Ullah, Sana; Wege, Stefanie; Shabala, Sergey; Feijó, José A; Ryan, Peter R; Gilliham, Matthew; Gillham, Matthew

2015-07-29

The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.

GABA signalling modulates plant growth by directly regulating the activity of plant-specific anion transporters

PubMed Central

Ramesh, Sunita A.; Tyerman, Stephen D.; Xu, Bo; Bose, Jayakumar; Kaur, Satwinder; Conn, Vanessa; Domingos, Patricia; Ullah, Sana; Wege, Stefanie; Shabala, Sergey; Feijó, José A.; Ryan, Peter R.; Gillham, Matthew

2015-01-01

The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms. PMID:26219411

Chemical Reactions Triggered Using Electrons Photodetached from "Clean" Distributions of Anions Deposited in Cryogenic Matrices via Counterion Codeposition.

PubMed

Ludwig, Ryan M; Moore, David T

2014-09-04

Application of matrix isolation spectroscopy to ionic species is typically complicated by the presence of neutral contaminants during matrix deposition. Herein we demonstrate that simultaneous deposition of balanced currents of counterions with mass-selected ions of interest generates "clean" distributions of matrix-isolated metal carbonyl anions, where the only bands appearing in the CO-stretching region of the vibrational spectrum arise from ions. (Neutrals are initially absent.) Photodetachment by mild irradiation with visible light leads to complete conversion of the anions into their corresponding neutral species. The photodetached electrons, in turn, initiate covalent chemistry, inducing C-C bond formation following electron-capture by CO van der Waals dimers to produce trans-OCCO(-). The initial clean distribution of ions enables clear connections to be drawn between the spectral changes occurring at each experimental step, thus demonstrating the potential of the counterion codeposition technique to facilitate detailed studies of chemistry involving ions and electron transfer in cryogenic matrices.

A specific chemodosimeter for fluoride ion based on a pyrene derivative with trimethylsilylethynyl groups.

PubMed

Lu, Hua; Wang, Qiuhong; Li, Zhifang; Lai, Guoqiao; Jiang, Jianxiong; Shen, Zhen

2011-06-21

Pyrene derivative 1 containing four trimethylsilylethynyl substituents was synthesized and investigated as a chromogenic and fluorescent chemodosimeter sensor for fluoride ions. 1 showed a high sensitivity and specific selectivity over a rapid response time toward fluoride anions compared to other anions, such as Cl(-), Br(-), ClO(4)(-), H(2)PO(4)(-) and HPO(4)(2-). TD-DFT calculations showed that the delocalization of the σ-electrons of the silicon destabilized the HOMO energy level of 1, thus red shifting both its absorption and emission spectrum. The addition of F(-) removed the trimethylsilyl substituents and resulted in a blue shift of both the absorption and fluorescent spectra of 1, which could be monitored by the color change with the naked-eye. Moreover, an easy to prepare test paper, which was obtained by immersing a filter paper into a THF solution of 1, could be utilized to detect and estimate the concentration of fluoride anions in water.

Homologue Structure of the SLAC1 Anion Channel for Closing Stomata in Leaves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Y Chen; L Hu; M Punta

2011-12-31

The plant SLAC1 anion channel controls turgor pressure in the aperture-defining guard cells of plant stomata, thereby regulating the exchange of water vapour and photosynthetic gases in response to environmental signals such as drought or high levels of carbon dioxide. Here we determine the crystal structure of a bacterial homologue (Haemophilus influenzae) of SLAC1 at 1.20 {angstrom} resolution, and use structure-inspired mutagenesis to analyse the conductance properties of SLAC1 channels. SLAC1 is a symmetrical trimer composed from quasi-symmetrical subunits, each having ten transmembrane helices arranged from helical hairpin pairs to form a central five-helix transmembrane pore that is gated bymore » an extremely conserved phenylalanine residue. Conformational features indicate a mechanism for control of gating by kinase activation, and electrostatic features of the pore coupled with electrophysiological characteristics indicate that selectivity among different anions is largely a function of the energetic cost of ion dehydration.« less

A Multi-responsive Regenerable Europium-Organic Framework Luminescent Sensor for Fe3+ , CrVI Anions, and Picric Acid.

PubMed

Liu, Wei; Huang, Xin; Xu, Cong; Chen, Chunyang; Yang, Lizi; Dou, Wei; Chen, Wanmin; Yang, Huan; Liu, Weisheng

2016-12-23

A novel luminescent microporous lanthanide metal-organic framework (Ln-MOF) based on a urea-containing ligand has been successfully assembled. Structural analysis revealed that the framework features two types of 1D channels, with urea N-H bonds projecting into the pores. Luminescence studies have revealed that the Ln-MOF exhibits high sensitivity, good selectivity, and a fast luminescence quenching response towards Fe 3+ , Cr VI anions, and picric acid. In particular, in the detection of Cr 2 O 7 2- and picric acid, the Ln-MOF can be simply and quickly regenerated, thus exhibiting excellent recyclability. To the best of our knowledge, this is the first example of a multi-responsive luminescent Ln-MOF sensor for Fe 3+ , Cr VI anions, and picric acid based on a urea derivative. This Ln-MOF may potentially be used as a multi-responsive regenerable luminescent sensor for the quantitative detection of toxic and harmful substances. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anion permselective membrane

NASA Technical Reports Server (NTRS)

Hodgdon, R. B.; Waite, W. A.

1982-01-01

The synthesis and fabrication of polymeric anion permselective membranes for redox systems are discussed. Variations of the prime candidate anion membrane formulation to achieve better resistance and/or lower permeability were explored. Processing parameters were evaluated to lower cost and fabricate larger sizes. The processing techniques to produce more membranes per batch were successfully integrated with the fabrication of larger membranes. Membranes of about 107 cm x 51 cm were made in excellent yield. Several measurements were made on the larger sample membranes. Among the data developed were water transport and transference numbers for these prime candidate membranes at 20 C. Other work done on this system included characterization of a number of specimens of candidate membranes which had been returned after service lives of up to sixteen months. Work with new polymer constituents, with new N.P.'s, catalysts and backing fabrics is discussed. Some work was also done to evaluate other proportions of the ingredients of the prime candidate system. The adoption of a flow selectivity test at elevated temperature was explored.