Thiol surface complexation on growing CdS clusters

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

Swayambunathan, V.; Hayes, D.; Schmidt, K.H.

1990-05-09

The growth of small CdS colloidal particles has been initiated by pulse radiolytic release of sulfide from thiol (3-mercapto-1,2-propanediol, RSH) in the presence of Cd{sup 2+} ions. The kinetics and stoichiometry of the ensuring reactions were followed by conductivity, absorption spectroscopy, and light-scattering techniques. The final CdS product has been identified by electron diffraction. The formation of Cd-thiolate complexes at the surface of the particles is indicated by conductivity and by energy dispersive analysis of X-ray (EDAX) results. The rate of formation of CdS clusters is strongly pH dependent due to the pH effect on the stability of Dd{sup 2+}/HS{supmore » {minus}} complexes. At low pHs (4.0-5.3) the growth mechanism is proposed to be primarily a cluster-molecule process. At this pH range Cd{sup 2+} ions at the CdS particle surface complex with thiolate ions stronger than in the bulk of the solution. The size control of the particles by thiols is proposed to result from a competition of thiolate ions with HS{sup {minus}} ions for cadmium ions at the surface of the growing particles.« less

Investigation of interaction between the Pt(II) ions and aminosilane-modified silica surface in heterogeneous system

NASA Astrophysics Data System (ADS)

Nowicki, Waldemar; Gąsowska, Anna; Kirszensztejn, Piotr

2016-05-01

UV-vis spectroscopy measurements confirmed the reaction in heterogeneous system between Pt(II) ions and ethylenediamine type ligand, n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, immobilized at the silica surface. The formation of complexes is a consequence of interaction between the amine groups from the ligand grafted onto SiO2 and ions of platinum. A potentiometric titration technique was to determine the stability constants of complexes of Pt(II) with immobilized insoluble ligand (SG-L), on the silica gel. The results show the formation of three surface complexes of the same type (PtHSG-L, Pt(HSG-L)2, PtSG-L) with SG-L ligand, in a wide range of pH for different Debye length. The concentration distribution of the complexes in a heterogeneous system is evaluated.

Effect of alkali ions (Na+, K+, Cs+) on reaction mechanism of CZTS nano-particles synthesis

NASA Astrophysics Data System (ADS)

Kumar, Suresh; Altosaar, Mare; Grossberg, Maarja; Mikli, Valdek

2018-04-01

The control of morphology, elemental composition and phase composition of Cu2ZnSnS4 (CZTS) nano-crystals depends on the control of complex formation and surface stabilization of nano-particles in solution-based synthesis in oleylamine. At temperatures ≥280 °C, the control of nano-crystal's morphology and homogenous growth is difficult because of fast poly-nuclear growth occurring at higher temperatures. In the present work the effect of oleylamine complex formation with different alkali ions (Na+, K+ and Cs+) on nano-crystals growth at synthesis temperature of 280 °C was studied. It was found that nano-powders synthesized in the presence of Na+ and K+ ions showed the formation of crystals of different sizes - small nano-particles (18 nm-30 nm), large aggregated crystals (few nm to 1 μm) and large single crystals (1 μm - 4 μm). The presence of Cs+ ions in the nano-powder synthesis in oleylamine-metal precursor-CsOH solution promoted growth of nano-crystals of homogenous size. It is proposed that the formed oleylamine-Cs complexes a) enhance the formation and stabilization of oleylamine-metal (Cu, Zn and Sn) complexes before the injection of sulphur precursor into the oleylamine-metal precursor solution and b) after addition of sulphur stabilize the fast nucleated nano-particles and promote diffusion limited growth.

Visualization of complex DNA double-strand breaks in a tumor treated with carbon ion radiotherapy

PubMed Central

Oike, Takahiro; Niimi, Atsuko; Okonogi, Noriyuki; Murata, Kazutoshi; Matsumura, Akihiko; Noda, Shin-Ei; Kobayashi, Daijiro; Iwanaga, Mototaro; Tsuchida, Keisuke; Kanai, Tatsuaki; Ohno, Tatsuya; Shibata, Atsushi; Nakano, Takashi

2016-01-01

Carbon ion radiotherapy shows great potential as a cure for X-ray-resistant tumors. Basic research suggests that the strong cell-killing effect induced by carbon ions is based on their ability to cause complex DNA double-strand breaks (DSBs). However, evidence supporting the formation of complex DSBs in actual patients is lacking. Here, we used advanced high-resolution microscopy with deconvolution to show that complex DSBs are formed in a human tumor clinically treated with carbon ion radiotherapy, but not in a tumor treated with X-ray radiotherapy. Furthermore, analysis using a physics model suggested that the complexity of radiotherapy-induced DSBs is related to linear energy transfer, which is much higher for carbon ion beams than for X-rays. Visualization of complex DSBs in clinical specimens will help us to understand the anti-tumor effects of carbon ion radiotherapy. PMID:26925533

The influence of projectile ion induced chemistry on surface pattern formation

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

Karmakar, Prasanta, E-mail: prasantak@vecc.gov.in; Satpati, Biswarup

We report the critical role of projectile induced chemical inhomogeneity on surface nanostructure formation. Experimental inconsistency is common for low energy ion beam induced nanostructure formation in the presence of uncontrolled and complex contamination. To explore the precise role of contamination on such structure formation during low energy ion bombardment, a simple and clean experimental study is performed by selecting mono-element semiconductors as the target and chemically inert or reactive ion beams as the projectile as well as the source of controlled contamination. It is shown by Atomic Force Microscopy, Cross-sectional Transmission Electron Microscopy, and Electron Energy Loss Spectroscopy measurementsmore » that bombardment of nitrogen-like reactive ions on Silicon and Germanium surfaces forms a chemical compound at impact zones. Continuous bombardment of the same ions generates surface instability due to unequal sputtering and non-uniform re-arrangement of the elemental atom and compound. This instability leads to ripple formation during ion bombardment. For Argon-like chemically inert ion bombardment, the chemical inhomogeneity induced boost is absent; as a result, no ripples are observed in the same ion energy and fluence.« less

Aqueous photochemical reactions of chloride, bromide, and iodide ions in a diode-array spectrophotometer. Autoinhibition in the photolysis of iodide ions.

PubMed

Kalmár, József; Dóka, Éva; Lente, Gábor; Fábián, István

2014-03-28

The aqueous photoreactions of three halide ions (chloride, bromide and iodide) were studied using a diode array spectrophotometer to drive and detect the process at the same time. The concentration and pH dependences of the halogen formation rates were studied in detail. The experimental data were interpreted by improving earlier models where the cage complex of a halogen atom and an electron has a central role. The triiodide ion was shown to exert a strong inhibiting effect on the reaction sequence leading to its own formation. An assumed chemical reaction between the triiodide ion and the cage complex interpreted the strong autoinhibition effect. It is shown that there is a real danger of unwanted interference from the photoreactions of halide ions when halide salts are used as supporting electrolytes in spectrophotometric experiments using a relatively high intensity UV light source.

Ion pair particles at the air–water interface

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Francisco, Joseph S.

2017-11-01

Although the role of methanesulfonic acid (HMSA) in particle formation in the gas phase has been extensively studied, the details of the HMSA-induced ion pair particle formation at the air–water interface are yet to be examined. In this work, we have performed Born–Oppenheimer molecular dynamics simulations and density functional theory calculations to investigate the ion pair particle formation from HMSA and (R1)(R2)NH (for NH3, R1 = R2 = H; for CH3NH2, R1 = H and R2 = CH3; and for CH3NH2, R1 = R2 = CH3) at the air–water interface. The results show that, at the air–water interface, HMSA deprotonates within a few picoseconds and results in the formation of methanesulfonate ion (MSA‑)ṡṡH3O+ ion pair. However, this ion pair decomposes immediately, explaining why HMSA and water alone are not sufficient for forming stable particles in atmosphere. Interestingly, the particle formation from the gas-phase hydrogen-bonded complexes of HMSA with (R1)(R2)NH on the water droplet is observed with a few femtoseconds, suggesting a mechanism for the gas to particle conversion in aqueous environments. The reaction involves a direct proton transfer between HMSA and (R1)(R2)NH, and the resulting MSA‑ṡṡ(R1)(R2)NH2+ complex is bound by one to four interfacial water molecules. The mechanistic insights gained from this study may serve as useful leads for understanding about the ion pair particle formation from other precursors in forested and polluted urban environments.

Effects of calcium, magnesium, and sodium on alleviating cadmium toxicity to Hyalella azteca

USGS Publications Warehouse

Jackson, B.P.; Lasier, P.J.; Miller, W.P.; Winger, P.V.

2000-01-01

Toxicity of trace metal ions to aquatic organisms, arising through either anthropogenic inputs or acidification of surface waters, continues to be both a regulatory and environmental problem. It is generally accepted that the free metal ion is the major toxic species (Florence et a1.,1992) and that inorganic or organic complexation renders the metal ion non-bioavailable (Meador, 1991, Galvez and Wood, 1997). However, water chemistry parameters such as alkalinity, hardness, dissolved organic carbon and pH influence metal ion toxicity either directly by lowering free metal ion concentration or indirectly through synergistic or antagonistic effects. Alkalinity and salinity can affect the speciation of metal ions by increasing ion-pair formation, thus decreasing free metal ion concentration. For example, Cu was found to be less toxic to rainbow trout in waters of high alkalinity (Miller and Mackay, 1980), due to formation of CuCO3 ion pair, and corresponding reduction in free Cu2+ concentration. The influence of salinity on the toxicity of cadmium to various organisms has been demonstrated in a number of studies (Bervoets et al., 1995, Hall et al., 1995, Lin and Dunson, 1993, Blust et al., 1992). In all these studies the apparent toxicity of cadmium was lowered as salinity was increased due to increased formation of CdC1+ and CDCl2 aqueous complexes that are non-toxic or of much lower toxicity than the free Cd2+ ion. Changes in pH exert both a biological and chemical effect on metal ion toxicity (Campbell and Stokes, 1985). Low pH favors greater metal ion solubility, and, in the absence of complexing ions, reduced speciation of the metal ion, which tends to increase toxicity compared to higher pH. However, Iow pH also enhances competition between H+ and metal ion for cell surface binding sites, which tends to decrease metal ion toxicity.

Hair dye-incorporated poly-γ-glutamic acid/glycol chitosan nanoparticles based on ion-complex formation.

PubMed

Lee, Hye-Young; Jeong, Young-Il; Choi, Ki-Choon

2011-01-01

p-Phenylenediamine (PDA) or its related chemicals are used more extensively than oxidative hair dyes. However, permanent hair dyes such as PDA are known to have potent contact allergy reactions in humans, and severe allergic reactions are problematic. PDA-incorporated nanoparticles were prepared based on ion-complex formation between the cationic groups of PDA and the anionic groups of poly(γ-glutamic acid) (PGA). To reinforce PDA/PGA ion complexes, glycol chitosan (GC) was added. PDA-incorporated nanoparticles were characterized using field-emission scanning electron microscopy, Fourier- transform infrared (FT-IR) spectroscopy, dynamic light scattering, and powder X-ray diffractometry (XRD). Nanoparticles were formed by ion-complex formation between the amine groups of PDA and the carboxyl groups of PGA. PDA-incorporated nanoparticles are small in size (<100 nm), and morphological observations showed spherical shapes. FT-IR spectra results showed that the carboxylic acid peak of PGA decreased with increasing PDA content, indicating that the ion complexes were formed between the carboxyl groups of PGA and the amine groups of PDA. Furthermore, the intrinsic peak of the carboxyl groups of PGA was also decreased by the addition of GC. Intrinsic crystalline peaks of PDA were observed by XRD. This crystalline peak of PDA was completely nonexistent when nanoparticles were formed by ion complex between PDA, PGA, and GC, indicating that PDA was complexed with PGA and no free drug existed in the formulation. During the drug-release experiment, an initial burst release of PDA was observed, and then PDA was continuously released over 1 week. Cytotoxicity testing against HaCaT human skin keratinocyte cells showed PDA-incorporated nanoparticles had lower toxicity than PDA itself. Furthermore, PDA-incorporated nanoparticles showed reduced apoptosis and necrosis reaction at HaCaT cells. The authors suggest that these microparticles are ideal candidates for a vehicle for decreasing side effects of hair dye.

Synthesis, characterization, spectroscopic and antioxidation studies of Cu(II)-morin complex

NASA Astrophysics Data System (ADS)

Panhwar, Qadeer Khan; Memon, Shahabuddin; Bhanger, M. I.

2010-04-01

Complex formation between copper (II) sulfate and morin (3,5,7,2',4'-pentahydroxyflavone) have been studied in methanol. Structure of the complex was determined through various analytical techniques including UV-vis, IR, 1H NMR, thermal, gravimetric and elemental analyses. The stoichiometric ratio for the reaction between the flavonoid and the metal ion in methanol has been determined by Job's method and elemental analysis for metal content of complex by titration with EDTA, which confirm that morin forms a 1:1 metal:ligand complex. 1H NMR study reveals that, 3OH and 4CO groups of morin take part in complexation with a copper ion. Individual stress was given to the site of central ion and composition of the complex. Antioxidant activity of the complex was evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method, which showed that the antioxidant activity of complexed morin has higher value as compared to the free morin. Moreover, it was observed that the metal complex is sufficiently stable as well as the data indicates the spontaneous formation of complex (-Δ G) that is exothermic in nature (-Δ H) and entropically unfavourable (-Δ S).

Improvement of drug loading onto ion exchange resin by cyclodextrin inclusion complex.

PubMed

Samprasit, Wipada; Rojanarata, Theerasak; Akkaramongkolporn, Prasert; Ngawhirunpat, Tanasait; Sila-on, Warisada; Opanasopit, Praneet

2013-11-01

Ion exchange resins have ability to exchange their counter ions for ionized drug in the surrounding medium, yielding "drug resin complex." Cyclodextrin can be applied for enhancement of drug solubility and stability. Cyclodextrin inclusion complex of poorly water-soluble NSAIDs, i.e. meloxicam and piroxicam, was characterized and its novel application for improving drug loading onto an anionic exchange resin, i.e. Dowex® 1×2, was investigated. β-Cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrin (HP-β-CD) were used for the preparation of inclusion complex with drugs in solution state at various pH. The inclusion complex was characterized by phase solubility, continuous variation, spectroscopic and electrochemistry methods. Then, the drug with and without cyclodextrin were equilibrated with resin at 1:1 and 1:2 weight ratio of drug and resin. Solubility of the drugs was found to increase with increasing cyclodextrin concentration and pH. The increased solubility was explained predominantly due to the formation of inclusion complex at low pH and the increased ionization of drug at high pH. According to characterization studies, the inclusion complex was successfully formed with a 1:1 stoichiometry. The presence of cyclodextrin in the loading solution resulted in the improvement of drug loading onto resin. Enhancing drug loading onto ion-exchange resin via the formation of cyclodextrin inclusion complex is usable in the development of ion-exchange based drug delivery systems, which will beneficially reduce the use of harmful acidic or basic and organic chemicals.

Interaction of metal ions and amino acids - Possible mechanisms for the adsorption of amino acids on homoionic smectite clays

NASA Technical Reports Server (NTRS)

Gupta, A.; Loew, G. H.; Lawless, J.

1983-01-01

A semiempirical molecular orbital method is used to characterize the binding of amino acids to hexahydrated Cu(2+) and Ni(2+), a process presumed to occur when they are adsorbed in the interlamellar space of homoionic smectite clays. Five alpha-amino acids, beta-alanine, and gamma-aminobutyric acid were used to investigate the metal ion and amino acid specificity in binding. It was assumed that the alpha, beta, and gamma-amino acids would bind as bidentate anionic ligands, forming either 1:1 or 1:2 six-coordinated five, six, and seven-membered-ring chelate complexes, respectively. Energies of complex formation, optimized geometries, and electron and spin distribution were determined; and steric constraints of binding of the amino acids to the ion-exchanged cations in the interlamellar spacing of a clay were examined. Results indicate that hexahydrated Cu(2+) forms more stable complexes than hexahydrated Ni(2+) with all the amino acids studied. However, among these amino acids, complex formation does not favor the adsorption of the biological subset. Calculated energetics of complex formation and steric constraints are shown to predict that 1:1 rather than 1:2 metal-amino acid complexes are generally favored in the clay.

Complexation of lanthanides and actinides by acetohydroxamic acid

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

Taylor, R.J.; Sinkov, S.I.; Choppin, G.R.

2008-07-01

Acetohydroxamic acid (AHA) has been proposed as a suitable reagent for the complexant-based, as opposed to reductive, stripping of plutonium and neptunium ions from the tributylphosphate solvent phase in advanced PUREX or UREX processes designed for future nuclear-fuel reprocessing. Stripping is achieved by the formation of strong hydrophilic complexes with the tetravalent actinides in nitric acid solutions. To underpin such applications, knowledge of the complexation constants of AHA with all relevant actinide (5f) and lanthanide (4f) ions is therefore important. This paper reports the determination of stability constants of AHA with the heavier lanthanide ions (Dy-Yb) and also U(IV) andmore » Th(IV) ions. Comparisons with our previously published AHA stability-constant data for 4f and 5f ions are made. (authors)« less

In Praise of Thiosulfate.

ERIC Educational Resources Information Center

Tykodi, R. J.

1990-01-01

The use of the thiosulfate ion in teaching the concepts of gas formation, precipitate formation, complex formation, acid-base interaction, redox interaction, time evolution of chemical processes, catalysis, and stoichiometry is discussed. Several demonstrations and activities are detailed. (CW)

A comparison of complexation of Li+ ion with macrocyclic ligands 15-crown-5 and 12-crown-4 in binary nitromethane-acetonitrile mixtures by using lithium-7 NMR technique and ab initio calculation.

PubMed

Alizadeh, Nina

2011-01-01

Lithium-7 NMR measurements were used to investigate the stoichiometry and stability of Li+ complexes with 15-crown-5 (15C5), benzo-15-crown-5 (B15C5), dibenzo-15-crown-5 (DB15C5) and 12-crown-4 (12C4) in a number of nitromethane (NM)-acetonitrile (AN) binary mixtures. In all cases, the exchange between the free and complexed lithium ion was fast on the NMR time scale and a single population average resonance was observed. While all crown ethers form 1:1 complexes with Li+ ion in the binary mixtures used, both 1:1 and 2:1 (sandwich) complexes were observed between lithium ion and 12C4 in pure nitromethane solution. Stepwise formation constants of the 1:1 and 2:1 (ligand/metal) complexes were evaluated from computer fitting of the NMR-mole ratio data to equations which relate the observed metal ion chemical shifts to formation constants. There is an inverse linear relationship between the logarithms of the stability constants and the mole fraction of acetonitrile in the solvent mixtures. The stability order of the 1:1 complexes was found to be 15C5·Li+>B15C5·Li+>DB15C5·Li+>12C4·Li+. The optimized structures of the free ligands and their 1:1 and 2:1 complexes with Li+ ion were predicted by ab initio theoretical calculations using the Gaussian 98 software, and the results are discussed. Copyright © 2010 Elsevier B.V. All rights reserved.

Chansporter complexes in cell signaling.

PubMed

Abbott, Geoffrey W

2017-09-01

Ion channels facilitate diffusion of ions across cell membranes for such diverse purposes as neuronal signaling, muscular contraction, and fluid homeostasis. Solute transporters often utilize ionic gradients to move aqueous solutes up their concentration gradient, also fulfilling a wide variety of tasks. Recently, an increasing number of ion channel-transporter ('chansporter') complexes have been discovered. Chansporter complex formation may overcome what could otherwise be considerable spatial barriers to rapid signal integration and feedback between channels and transporters, the ions and other substrates they transport, and environmental factors to which they must respond. Here, current knowledge in this field is summarized, covering both heterologous expression structure/function findings and potential mechanisms by which chansporter complexes fulfill contrasting roles in cell signaling in vivo. © 2017 Federation of European Biochemical Societies.

Isolation and Characterization of FORMATE/NI(CYCLAM)^{2+} Complexes with Cryogenic Ion Vibrational Predissociation

NASA Astrophysics Data System (ADS)

Wolk, Arron B.; Fournier, Joseph A.; Wolke, Conrad T.; Johnson, Mark A.

2013-06-01

Transition metal-based organometallic catalysts are a promising means of converting CO_{2} to transportable fuels. Ni(cyclam)^{2+}(cyclam = 1,4,8,11-tetraazacyclotetradecane), a Ni^{II} complex ligated by four nitrogen centers, has shown promise as a catalyst selective for CO_{2} reduction in aqueous solutions. The cyclam ligand has four NH hydrogen bond donors that can adopt five conformations, each offering distinct binding motifs for coordination of CO_{2} close to the metal center. To probe the ligand conformation and the role of hydrogen bonding in adduct binding, we extract Ni(cyclam)^{2+} complexes with the formate anion and some of its analogs from solution using electrospray ionization, and characterize their structures using cryogenic ion vibrational predissociation spectroscopy. Using the signature vibrational features of the embedded carboxylate anion and the NH groups as reporters, we compare the binding motifs of oxalate, benzoate, and formate anions to the Ni(cyclam)^{2+} framework. Finally, we comment on possible routes to generate the singly charged Ni(cyclam)^{+} complex, a key intermediate that has been invoked in the catalytic CO_{2} reduction cycle, but has never been isolated through ion processing techniques.

Making the invisible visible: improved electrospray ion formation of metalloporphyrins/-phthalocyanines by attachment of the formate anion (HCOO(-)).

PubMed

Hitzenberger, Jakob Felix; Dammann, Claudia; Lang, Nina; Lungerich, Dominik; García-Iglesias, Miguel; Bottari, Giovanni; Torres, Tomás; Jux, Norbert; Drewello, Thomas

2016-02-21

A protocol is developed for the coordination of the formate anion (HCOO(-)) to neutral metalloporphyrins (Pors) and -phthalocyanines (Pcs) containing divalent metals as a means to improve their ion formation in electrospray ionization (ESI). This method is particularly useful when the oxidation of the neutral metallomacrocycle fails. While focusing on Zn(II)Pors and Zn(II)Pcs, we show that formate is also readily attached to Mn(II), Mg(II) and Co(II)Pcs. However, for the Co(II)Pc secondary reactions can be observed. Upon collision-induced dissociation (CID), Zn(II)Por/Pc·formate supramolecular complexes can undergo the loss of CO2 in combination with transfer of a hydride anion (H(-)) to the zinc metal center. Further dissociation leads to electron transfer and hydrogen atom loss, generating a route to the radical anion of the Zn(II)Por/Pc without the need for electrochemical reduction, although the Zn(II)Por/Pc may have a too low electron affinity to allow electron transfer directly from the formate anion. In addition to single Por molecules, multi Por arrays were successfully analyzed by this method. In this case, multiple addition of formate occurs, giving rise to multiply charged species. In these multi Por arrays, complexation of the formate anion occurs by two surrounding Por units (sandwich). Therefore, the maximum attainment of formate anions in these arrays corresponds to the number of such sandwich complexes rather than the number of porphyrin moieties. The same bonding motif leads to dimers of the composition [(Zn(II)Por/Pc)2·HCOO](-). In these, the formate anion can act as a structural probe, allowing the distinction of isomeric ions with the formate bridging two macrocycles or being attached to a dimer of directly connected macrocycles.

Using Gas-Phase Guest-Host Chemistry to Probe the Structures of b Ions of Peptides

NASA Astrophysics Data System (ADS)

Somogyi, Árpád; Harrison, Alex G.; Paizs, Béla

2012-12-01

Middle-sized b n ( n ≥ 5) fragments of protonated peptides undergo selective complex formation with ammonia under experimental conditions typically used to probe hydrogen-deuterium exchange in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Other usual peptide fragments like y, a, a*, etc., and small b n ( n ≤ 4) fragments do not form stable ammonia adducts. We propose that complex formation of b n ions with ammonia is characteristic to macrocyclic isomers of these fragments. Experiments on a protonated cyclic peptide and N-terminal acetylated peptides fully support this hypothesis; the protonated cyclic peptide does form ammonia adducts while linear b n ions of acetylated peptides do not undergo complexation. Density functional theory (DFT) calculations on the proton-bound dimers of all-Ala b 4 , b 5 , and b 7 ions and ammonia indicate that the ionizing proton initially located on the peptide fragment transfers to ammonia upon adduct formation. The ammonium ion is then solvated by N+-H…O H-bonds; this stabilization is much stronger for macrocyclic b n isomers due to the stable cage-like structure formed and entropy effects. The present study demonstrates that gas-phase guest-host chemistry can be used to selectively probe structural features (i.e., macrocyclic or linear) of fragments of protonated peptides. Stable ammonia adducts of b 9 , b 9 -A, and b 9 -2A of A8YA, and b 13 of A20YVFL are observed indicating that even these large b-type ions form macrocyclic structures.

Gas Phase Reactions of Ions Derived from Anionic Uranyl Formate and Uranyl Acetate Complexes.

PubMed

Perez, Evan; Hanley, Cassandra; Koehler, Stephen; Pestok, Jordan; Polonsky, Nevo; Van Stipdonk, Michael

2016-12-01

The speciation and reactivity of uranium are topics of sustained interest because of their importance to the development of nuclear fuel processing methods, and a more complete understanding of the factors that govern the mobility and fate of the element in the environment. Tandem mass spectrometry can be used to examine the intrinsic reactivity (i.e., free from influence of solvent and other condensed phase effects) of a wide range of metal ion complexes in a species-specific fashion. Here, electrospray ionization, collision-induced dissociation, and gas-phase ion-molecule reactions were used to create and characterize ions derived from precursors composed of uranyl cation (U VI O 2 2+ ) coordinated by formate or acetate ligands. Anionic complexes containing U VI O 2 2+ and formate ligands fragment by decarboxylation and elimination of CH 2 =O, ultimately to produce an oxo-hydride species [U VI O 2 (O)(H)] - . Cationic species ultimately dissociate to make [U VI O 2 (OH)] + . Anionic complexes containing acetate ligands exhibit an initial loss of acetyloxyl radical, CH 3 CO 2 •, with associated reduction of uranyl to U V O 2 + . Subsequent CID steps cause elimination of CO 2 and CH 4 , ultimately to produce [U V O 2 (O)] - . Loss of CH 4 occurs by an intra-complex H + transfer process that leaves U V O 2 + coordinated by acetate and acetate enolate ligands. A subsequent dissociation step causes elimination of CH 2 =C=O to leave [U V O 2 (O)] - . Elimination of CH 4 is also observed as a result of hydrolysis caused by ion-molecule reaction with H 2 O. The reactions of other anionic species with gas-phase H 2 O create hydroxyl products, presumably through the elimination of H 2 . Graphical Abstract ᅟ.

Gas Phase Reactions of Ions Derived from Anionic Uranyl Formate and Uranyl Acetate Complexes

NASA Astrophysics Data System (ADS)

Perez, Evan; Hanley, Cassandra; Koehler, Stephen; Pestok, Jordan; Polonsky, Nevo; Van Stipdonk, Michael

2016-12-01

The speciation and reactivity of uranium are topics of sustained interest because of their importance to the development of nuclear fuel processing methods, and a more complete understanding of the factors that govern the mobility and fate of the element in the environment. Tandem mass spectrometry can be used to examine the intrinsic reactivity (i.e., free from influence of solvent and other condensed phase effects) of a wide range of metal ion complexes in a species-specific fashion. Here, electrospray ionization, collision-induced dissociation, and gas-phase ion-molecule reactions were used to create and characterize ions derived from precursors composed of uranyl cation (UVIO2 2+) coordinated by formate or acetate ligands. Anionic complexes containing UVIO2 2+ and formate ligands fragment by decarboxylation and elimination of CH2=O, ultimately to produce an oxo-hydride species [UVIO2(O)(H)]-. Cationic species ultimately dissociate to make [UVIO2(OH)]+. Anionic complexes containing acetate ligands exhibit an initial loss of acetyloxyl radical, CH3CO2•, with associated reduction of uranyl to UVO2 +. Subsequent CID steps cause elimination of CO2 and CH4, ultimately to produce [UVO2(O)]-. Loss of CH4 occurs by an intra-complex H+ transfer process that leaves UVO2 + coordinated by acetate and acetate enolate ligands. A subsequent dissociation step causes elimination of CH2=C=O to leave [UVO2(O)]-. Elimination of CH4 is also observed as a result of hydrolysis caused by ion-molecule reaction with H2O. The reactions of other anionic species with gas-phase H2O create hydroxyl products, presumably through the elimination of H2.

Voltammetry of ion transfer across a polarized room-temperature ionic liquid membrane facilitated by valinomycin: theoretical aspects and application.

PubMed

Langmaier, Jan; Samec, Zdenek

2009-08-01

Cyclic voltammetry is used to investigate the transfer of alkali-metal cations, protons, and ammonium ions facilitated by the complex formation with valinomycin at the interface between an aqueous electrolyte solution and a room-temperature ionic liquid (RTIL) membrane. The membrane is made of a thin (approximately 112 microm) microporous filter impregnated with an RTIL that is composed of tridodecylmethylammonium cations and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anions. An extension of the existing theory of voltammetry of ion transfer across polarized liquid membranes makes it possible to evaluate the standard ion-transfer potentials for the hydrophilic cations studied, as well as the stability constants (K(i)) of their 1:1 complexes with valinomycin, as log K(i) = 9.0 (H(+)), 11.1 (Li(+)), 12.8 (Na(+)), 17.2 (K(+)), 15.7 (Rb(+)), 15.1 (Cs(+)), and 14.7 (NH(4)(+)). These data point to the remarkably enhanced stability of the valinomycin complexes within RTIL, and to the enhanced selectivity of valinomycin for K(+) over all other univalent ions studied, compared to the conventional K(+) ion-selective liquid-membrane electrodes. Selective complex formation allows one to resolve voltammetric responses of K(+) and Na(+) in the presence of an excess of Mg(2+) or Ca(2+), which is demonstrated by determination of K(+) and Na(+) in the table and tap water samples.

Triggers for β-sheet formation at the hydrophobic-hydrophilic interface: high concentration, in-plane orientational order, and metal ion complexation.

PubMed

Hoernke, Maria; Falenski, Jessica A; Schwieger, Christian; Koksch, Beate; Brezesinski, Gerald

2011-12-06

Amyloid formation plays a causative role in neurodegenerative diseases such as Alzheimer's disease or Parkinson's disease. Soluble peptides form β-sheets that subsequently rearrange into fibrils and deposit as amyloid plaques. Many parameters trigger and influence the onset of the β-sheet formation. Early stages are recently discussed to be cell-toxic. Aiming at understanding various triggers such as interactions with hydrophobic-hydrophilic interfaces and metal ion complexation and their interplay, we investigated a set of model peptides at the air-water interface. We are using a general approach to a variety of diseases such as Alzheimer's disease, Parkinson's disease, and type II diabetes that are connected to amyloid formation. Surface sensitive techniques combined with film balance measurements have been used to assess the conformation of the peptides and their orientation at the air-water interface (IR reflection-absorption spectroscopy). Additionally, the structures of the peptide layers were characterized by grazing incidence X-ray diffraction and X-ray reflectivity. The peptides adsorb to the air-water interface and immediately adopt an α-helical conformation. This helical intermediate transforms into β-sheets upon further triggering. The factors that result in β-sheet formation are dependent on the peptide sequence. In general, the interface has the strongest effect on peptide conformation compared to high concentrations or metal ions. Metal ions are able to prevent aggregation in bulk but not at the interface. At the interface, metal ion complexation has only minor effects on the peptide secondary structure, influencing the in-plane structure that is formed in two dimensions. At the air-water interface, increased concentrations or a parallel arrangement of the α-helical intermediates are the most effective triggers. This study reveals the role of various triggers for β-sheet formation and their complex interplay. Our main finding is that the hydrophobic-hydrophilic interface largely governs the conformation of peptides. Therefore, the present study implies that special care is needed when interpreting data that may be affected by different amounts or types of interfaces during experimentation. © 2011 American Chemical Society

Composition and chemistry of Titan's thermosphere and ionosphere.

PubMed

Vuitton, V; Yelle, R V; Lavvas, P

2009-02-28

Titan has long been known to harbour the richest atmospheric chemistry in the Solar System. Until recently, it had been believed that complex hydrocarbons and nitriles were produced through neutral chemistry that would eventually lead to the formation of micrometre sized organic aerosols. However, recent measurements by the Cassini spacecraft are drastically changing our understanding of Titan's chemistry. The Ion and Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) revealed an extraordinary complex ionospheric composition. INMS detected roughly 50 positive ions with m/z<100 and a density higher than 0.1cm-3. CAPS provided evidence for heavy (up to 350amu) positively and negatively charged (up to 4000amu) ions. These observations all indicate that Titan's ionospheric chemistry is incredibly complex and that molecular growth starts in the upper atmosphere rather than at lower altitude. Here, we review the recent progress made on ionospheric chemistry. The presence of heavy neutrals in the upper atmosphere has been inferred as a direct consequence of the presence of complex positive ions. Benzene (C6H6) is created by ion chemistry at high altitudes and its main photolysis product, the phenyl radical (C6H5), is at the origin of the formation of aromatic species at lower altitude.

Vibrational spectroscopic study of nickel (II) formate, Ni(HCO 2) 2, and its aqueous solution

NASA Astrophysics Data System (ADS)

Edwards, H. G. M.; Knowles, A.

1992-04-01

A vibrational spectroscopic study of nickel (II) formate and its aqueous solution has been made. The vibrations characteristic of a formato—nickel complex have been assigned and it is concluded that the species Ni(HCO 2) +(HCO 2) - exists in the solid state, with monodentate ligand-to-metal bonding. The Raman spectrum of an aqueous solution of nickel (II) formate indicates that complete dissociation of the formato—nickel (II) species occurs to formate ions and nickel (II) hexa-aquo ions. Comparisons are made with other nickel (II) carboxylates.

Coordinating properties of uridine 5'-monophosphate with selected Ln(3+) ions in ionic micellar media.

PubMed

Sudhiranjan Singh, M; Homendra, Naorem; Lonibala, R K

2012-12-01

Coordinating properties of uridine 5'-monophosphate (UMP) towards trivalent La, Pr, Nd, Sm, Eu and Gd ions in presence of cationic and anionic micelles have been investigated by potentiometric pH-titration and spectroscopic methods. Stability constants of the 2:1 complexes have been determined and the change in free energy, enthalpy and entropy associated with the complexation are also calculated. Nd(III) complexes isolated from aqueous and aqueous-micellar media do not show any significant structural difference. Formation of Ln(III) complexes in all cases completes below pH 7.5 showing that UMP best interacts with Ln(3+) ions at the physiological pH range 7.3-7.5. The nucleobase is not involved in the complexation and the metal ion coordination of UMP is through the phosphate moiety only. Coordinating tendency of UMP with lanthanides, Nd(III) ion in particular, at different pH is also discussed. Luminescent properties of Eu(III) complex and its decay lifetime are also presented. This information may prove helpful regarding the use of lanthanides as biological probes for calcium/magnesium ions.

ESI-MS measurements for the equilibrium constants of copper(II)-insulin complexes.

PubMed

Gülfen, Mustafa; Özdemir, Abdil; Lin, Jung-Lee; Chen, Chung-Hsuan

2018-06-01

Trace elements regulate many biological reactions in the body. Copper(II) is known as one of trace elements and capable of binding to proteins. Insulin is a blood glucose-lowering peptide hormone and it is secreted by the pancreatic β-cells. In this study, Cu(II)-insulin complexes were investigated by using ESI-MS method. Insulin molecule gives ESI-MS peaks at +4, +5, +6 and +7 charged states. Cu(II)-insulin complexes can be monitored and quantified on the ESI-MS spectra as the shifted peaks according to insulin peaks. The solutions of Cu(II)-insulin complexes at different pHs and mole ratios of Cu(II) ions to insulin molecule were measured on the ESI-MS. The highest complex formation ratio for Cu(II)-insulin were found at pH 7. The multiple bindings of Cu(II) ions to insulin molecule was observed. The formation equilibrium constants of Cu(II)-insulin complexes were calculated as Kf 1 : 3.34 × 10 4 , Kf 2 : 2.99 × 10 4 , Kf 3 : 7.00 × 10 3 and Kf 4 :2.86 × 10 3 . The specific binding property of Cu(II) ions was controlled by using different spray ion sources including electrospray and nano-electrospray. The binding property of Cu(II) also investigated by MS/MS fragmentation. It was concluded from the ESI-MS measurements that Cu(II) ion has a high affinity to insulin molecules to form stable complexes. Copyright © 2018 Elsevier B.V. All rights reserved.

Aqueous citrato-oxovanadate(IV) precursor solutions for VO2: synthesis, spectroscopic investigation and thermal analysis.

PubMed

Peys, Nick; Adriaensens, Peter; Van Doorslaer, Sabine; Gielis, Sven; Peeters, Ellen; De Dobbelaere, Christopher; De Gendt, Stefan; Hardy, An; Van Bael, Marlies K

2014-09-07

An aqueous precursor solution, containing citrato-VO(2+) complexes, is synthesized for the formation of monoclinic VO2. With regard to the decomposition of the VO(2+) complexes towards vanadium oxide formation, it is important to gain insights into the chemical structure and transformations of the precursor during synthesis and thermal treatment. Hence, the conversion of the cyclic [V4O12](4-) ion to the VO(2+) ion in aqueous solution, using oxalic acid as an acidifier and a reducing agent, is studied by (51)Vanadium nuclear magnetic resonance spectroscopy. The citrate complexation of this VO(2+) ion and the differentiation between a solution containing citrato-oxalato-VO(2+) and citrato-VO(2+) complexes are studied by electron paramagnetic resonance and Fourier transform infra-red spectroscopy. In both solutions, the VO(2+) containing complex is mononuclear and has a distorted octahedral geometry with a fourfold R-CO2(-) ligation at the equatorial positions and likely a fifth R-CO2(-) ligation at the axial position. Small differences in the thermal decomposition pathway between the gel containing citrato-oxalato-VO(2+) complexes and the oxalate-free gel containing citrato-VO(2+) complexes are observed between 150 and 200 °C in air and are assigned to the presence of (NH4)2C2O4 in the citrato-oxalato-VO(2+) solution. Both precursor solutions are successfully used for the formation of crystalline vanadium oxide nanostructures on SiO2, after thermal annealing at 500 °C in a 0.1% O2 atmosphere. However, the citrato-oxalato-VO(2+) and the oxalate-free citrato-VO(2+) solution result in the formation of monoclinic V6O13 and monoclinic VO2, respectively.

[Partitioning of taxifolin-iron ions complexes in octanol-water system].

PubMed

Shatalin, Iu V; Shubina, V S

2014-01-01

The composition of taxifolin-iron ions complexes in an octanol-water biphasic system was studied using the method of absorption spectrophotometry. It was found that at pH 5.0 in an aqueous biphasic system the complex of [Tf2 x Fe x (OH)k(H2O)8-k] is present, but at pH 7.0 and 9.0 the complexes of [Tf2 x Fe x (OH)k(H2O)2-k] and [Tf x Fe x OH)k(H2O)4-k] are predominantly observed. The formation of a stable [Tf3 x Fe] complex occurred in octanol phase. The charged iron ion of this complex is surrounded by taxifolin molecules, which shield the iron ion from lipophilic solvent. During transition from water to octanol phase the changes of the composition of complexes are accompanied by reciprocal changes in portion of taxifolin and iron ions in these phases. It was shown that the portion of taxifolin in aqueous solution in the presence of iron ions is increased at high pH values, and the portion of iron ions is minimal at pH 7.0. In addition, the parameters of solubility limits of taxifolin-iron ions complexes in an aqueous solution were determined. The data obtained gain a better understanding of the role of complexation of polyphenol with metal of variable valency in passive transport of flavonoids and metal ions across lipid membranes.

Ellagic acid inhibits iron-mediated free radical formation

NASA Astrophysics Data System (ADS)

Dalvi, Luana T.; Moreira, Daniel C.; Andrade, Roberto; Ginani, Janini; Alonso, Antonio; Hermes-Lima, Marcelo

2017-02-01

Polyphenols are reported to have some health benefits, which are link to their antioxidant properties. In the case of ellagic acid (EA), there is evidence that it has free radical scavenger properties and that it is able to form complexes with metal ions. However, information on a possible link between the formation of iron-EA complexes and their interference in Haber-Weiss/Fenton reactions was not yet determined. Thus, the present study investigated the in vitro antioxidant mechanism of EA in a system containing ascorbate, Fe(III) and different iron ligands (EDTA, citrate and NTA). Iron-mediated oxidative degradation of 2-deoxyribose was poorly inhibited (by 12%) in the presence of EA (50 μM) and EDTA. When citrate or NTA - which form weak iron complexes - were used, the 2-deoxyribose protection increased to 89-97% and 45%, respectively. EA also presented equivalent inhibitory effects on iron-mediated oxygen uptake and ascorbyl radical formation. Spectral analyses of iron-EA complexes show that EA removes Fe(III) from EDTA within hours, and from citrate within 1 min. This difference in the rate of iron-EA complex formation may explain the antioxidant effects of EA. Furthermore, the EA antioxidant effectiveness was inversely proportional to the Fe(III) concentration, suggesting a competition with EDTA. In conclusion, the results indicate that EA may prevent in vitro free radical formation when it forms a complex with iron ions.

Potentiometric study of binary complexes of 3-[(1 R)-1-hydroxy-2-(methylamino)ethyl]phenol hydrochloride with some lanthanide ions in aqueous and mixed solutions

NASA Astrophysics Data System (ADS)

Sharma, S. S.; Kadia, M. V.

2014-12-01

The complexation of lanthanide ions (Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Gd3+, Tb3+, and Dy3+) with 3-[(1 R)-1-hydroxy-2-(methylamino)ethyl]phenol hydrochloride was studied at different temperatures and different ionic strengths in aqueous solutions by Irving-Rossotti pH titration technique. Stepwise calculation, PKAS and BEST Fortran IV computer programs were used for determination of proton-ligand and metal-ligand stability constants. The formation of species like MA, MA2, and MA(OH) is considered in SPEPLOT. Thermodynamic parameters of complex formation (Δ G, Δ H, and Δ S) are also evaluated. Negative Δ G and Δ H values indicate that complex formation is favourable in these experimental conditions. The stability of complexes is also studied at in different solvent-aqueous (vol/vol). The stability series of lanthanide complexes has shown to have the "gadolinium break." Stability of complexes decreases with increase in ionic strength and temperature. Effect of systematic errors like effect of dissolved carbon dioxide, concentration of alkali, concentration of acid, concentration of ligand and concentration of metal have also been explained.

Formation of crystalline nanoparticles by iron binding to pentapeptide (Asp-His-Thr-Lys-Glu) from egg white hydrolysates.

PubMed

Sun, Na; Cui, Pengbo; Li, Dongmei; Jin, Ziqi; Zhang, Shuyu; Lin, Songyi

2017-09-20

A novel peptide from egg white, Asp-His-Thr-Lys-Glu (DHTKE), contains specific amino acids associated with iron binding. The present study aims to better understand the molecular basis of interactions between the DHTKE peptide and iron ions. The ultraviolet-visible and fluorescence spectra indicate an interaction between the DHTKE peptide and iron ions, which leads to the formation of a DHTKE-iron complex. Notably, Asp, Glu, His, and Lys in the DHTKE peptide play crucial roles in the formation of the DHTKE-iron complex, and the iron-binding site of the DHTKE peptide corresponds primarily to the amide and carboxyl groups. The DHTKE peptide can bind iron ions in a 1 : 2 ratio with a binding constant of 1.312 × 10 5 M -1 . Moreover, the DHTKE-iron complex belongs to thermodynamically stable nanoparticles that are present in the crystalline structure, which might be attributed to peptide folding induced by iron binding. Meanwhile, the DHTKE-iron complex exhibits a relatively high iron-releasing percentage and exerts excellent solubility in the human gastrointestinal tract in vitro. This suggests a potential application of peptides containing Asp, Glu, His, or Lys residues as potential iron supplements.

Positive and negative ion mode comparison for the determination of DNA/peptide noncovalent binding sites through the formation of "three-body" noncovalent fragment ions.

PubMed

Brahim, Bessem; Tabet, Jean-Claude; Alves, Sandra

2018-02-01

Gas-phase fragmentation of single strand DNA-peptide noncovalent complexes is investigated in positive and negative electrospray ionization modes.Collision-induced dissociation experiments, performed on the positively charged noncovalent complex precursor ions, have confirmed the trend previously observed in negative ion mode, i.e. a high stability of noncovalent complexes containing very basic peptidic residues (i.e. R > K) and acidic nucleotide units (i.e. Thy units), certainly incoming from the existence of salt bridge interactions. Independent of the ion polarity, stable noncovalent complex precursor ions were found to dissociate preferentially through covalent bond cleavages of the partners without disrupting noncovalent interactions. The resulting DNA fragment ions were found to be still noncovalently linked to the peptides. Additionally, the losses of an internal nucleic fragment producing "three-body" noncovalent fragment ions were also observed in both ion polarities, demonstrating the spectacular salt bridge interaction stability. The identical fragmentation patterns (regardless of the relative fragment ion abundances) observed in both polarities have shown a common location of salt bridge interaction certainly preserved from solution. Nonetheless, most abundant noncovalent fragment ions (and particularly three-body ones) are observed from positively charged noncovalent complexes. Therefore, we assume that, independent of the preexisting salt bridge interaction and zwitterion structures, multiple covalent bond cleavages from single-stranded DNA/peptide complexes rely on an excess of positive charges in both electrospray ionization ion polarities.

3D-structured illumination microscopy reveals clustered DNA double-strand break formation in widespread γH2AX foci after high LET heavy-ion particle radiation.

PubMed

Hagiwara, Yoshihiko; Niimi, Atsuko; Isono, Mayu; Yamauchi, Motohiro; Yasuhara, Takaaki; Limsirichaikul, Siripan; Oike, Takahiro; Sato, Hiro; Held, Kathryn D; Nakano, Takashi; Shibata, Atsushi

2017-12-12

DNA double-strand breaks (DSBs) induced by ionising radiation are considered the major cause of genotoxic mutations and cell death. While DSBs are dispersed throughout chromatin after X-rays or γ-irradiation, multiple types of DNA damage including DSBs, single-strand breaks and base damage can be generated within 1-2 helical DNA turns, defined as a complex DNA lesion, after high Linear Energy Transfer (LET) particle irradiation. In addition to the formation of complex DNA lesions, recent evidence suggests that multiple DSBs can be closely generated along the tracks of high LET particle irradiation. Herein, by using three dimensional (3D)-structured illumination microscopy, we identified the formation of 3D widespread γH2AX foci after high LET carbon-ion irradiation. The large γH2AX foci in G 2 -phase cells encompassed multiple foci of replication protein A (RPA), a marker of DSBs undergoing resection during homologous recombination. Furthermore, we demonstrated by 3D analysis that the distance between two individual RPA foci within γH2AX foci was approximately 700 nm. Together, our findings suggest that high LET heavy-ion particles induce clustered DSB formation on a scale of approximately 1 μm 3 . These closely localised DSBs are considered to be a risk for the formation of chromosomal rearrangement after heavy-ion irradiation.

Modified Extraction-Free Ion-Pair Methods for the Determination of Flunarizine Dihydrochloride in Bulk Drug, Tablets, and Human Urine

NASA Astrophysics Data System (ADS)

Prashanth, K. N.; Basavaiah, K.

2018-01-01

Two simple and sensitive extraction-free spectrophotometric methods are described for the determination of flunarizine dihydrochloride. The methods are based on the ion-pair complex formation between the nitrogenous compound flunarizine (FNZ), converted from flunarizine dihydrochloride (FNH), and the acidic dye phenol red (PR), in which experimental variables were circumvented. The first method (method A) is based on the formation of a yellow-colored ion-pair complex (1:1 drug:dye) between FNZ and PR in chloroform, which is measured at 415 nm. In the second method (method B), the formed drug-dye ion-pair complex is treated with ethanolic potassium hydroxide in an ethanolic medium, and the resulting base form of the dye is measured at 580 nm. The stoichiometry of the formed ion-pair complex between the drug and dye (1:1) is determined by Job's continuous variations method, and the stability constant of the complex is also calculated. These methods quantify FNZ over the concentration ranges 5.0-70.0 in method A and 0.5-7.0 μg/mL in method B. The calculated molar absorptivities are 6.17 × 103 and 5.5 × 104 L/mol·cm-1 for method A and method B, respectively, with corresponding Sandell sensitivity values of 0.0655 and 0.0074 μg/cm2. The methods are applied to the determination of FNZ in pure drug and human urine.

Rapid assessment of human amylin aggregation and its inhibition by copper(II) ions by laser ablation electrospray ionization mass spectrometry with ion mobility separation

DOE PAGES

Li, Hang; Ha, Emmeline; Donaldson, Robert P.; ...

2015-09-09

Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreasmore » that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. In this paper, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin–copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the —HSSNN– residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin–copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of amylin oligomerization and fibril formation. Finally and more generally, this rapid technique opens the door for high-throughput screening of potential inhibitors of amyloid protein aggregation.« less

Thermodynamics and Kinetics of Na+/K+-Formate Ion Pairs Association in Polarizable Water: A Molecular Dynamics Study

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

Nguyen, Phuong T.; Nguyen, Van T.; Annapureddy, Harsha V.

2012-12-03

To elevate our understanding of ion specific activity in biological systems, the potential of mean force approach was utilized to study solvent effects on interactions between two alkali cations (Na+ and K+) with a formate anion in water. A very complex free energy landscape was observed, much more so than alkali-halide ion pairs. Furthermore, stronger binding between the Na+-formate pair was found in comparison to the K+-formate pair in water, a finding that agrees with experimental and theoretical studies of these systems. The kinetics of ion-pair interconversions were studied using transition rate theory, along with a variety of theoretical approachesmore » such as the Kramers and Grote Hynes theories. These rate results were used to predict solvent effects on dynamical features of contact ion-pair association, in which faster dynamics were found for K+-formate pairs than for Na+-formate pairs. This work was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated for DOE by Battelle.« less

Density functional theory-based prediction of the formation constants of complexes of ammonia in aqueous solution: indications of the role of relativistic effects in the solution chemistry of gold(I).

PubMed

Hancock, Robert D; Bartolotti, Libero J

2005-10-03

A prediction of the formation constants (log K1) for complexes of metal ions with a single NH3 ligand in aqueous solution, using quantum mechanical calculations, is reported. DeltaG values at 298 K in the gas phase for eq 1 (DeltaG(DFT)) were calculated for 34 metal ions using density functional theory (DFT), with the expectation that these would correlate with the free energy of complex formation in aqueous solution (DeltaG(aq)). [M(H2O)6]n+(g) + NH(3)(g) = [M(H2O)5NH3]n+(g) + H2O(g) (eq 1). The DeltaG(aq) values include the effects of complex changes in solvation on complex formation, which are not included in eq 1. It was anticipated that such changes in solvation would be constant or vary systematically with changes in the log K(1) value for different metal ions; therefore, simple correlations between DeltaG(DFT) and DeltaG(aq) were sought. The bulk of the log K1(NH3) values used to calculate DeltaG(aq) were not experimental, but estimated previously (Hancock 1978, 1980) from a variety of empirical correlations. Separate linear correlations between DeltaG(DFT) and DeltaG(aq) for metal ions of different charges (M2+, M3+, and M4+) were found. In plots of DeltaG(DFT) versus DeltaG(aq), the slopes ranged from 2.201 for M2+ ions down to 1.076 for M4+ ions, with intercepts increasing from M2+ to M4+ ions. Two separate correlations occurred for the M3+ ions, which appeared to correspond to small metal ions with a coordination number (CN) of 6 and to large metal ions with a higher CN in the vicinity of 7-9. The good correlation coefficients (R) in the range of 0.97-0.99 for all these separate correlations suggest that the approach used here may be the basis for future predictions of aqueous phase chemistry that would otherwise be experimentally inaccessible. Thus, the log K1(NH3) value for the transuranic Lr3+, which has a half-life of 3.6 h in its most stable isotope, is predicted to be 1.46. These calculations should also lead to a greater insight into the factors governing complex formation in aqueous solution. All of the above DFT calculations involved corrections for scalar relativistic effects (RE). Au has been described (Koltsoyannis 1997) as a "relativistic element". The chief effect of RE for group 11 ions is to favor linear coordination geometry and greatly increase covalence in the M-L bond. The correlation for M+ ions (H+, Cu+, Ag+, Au+) involved the preferred linear coordination of the [M(H2O)2]+ complexes, so that the DFT calculations of DeltaG for the gas-phase reaction in eq 2 were carried out for M = H+, Cu+, Ag+, and Au+. [M(H2O)2]+(g) + NH3(g) = [M(H2O)NH3]+(g) + H2O(g) (eq 2). Additional DFT calculations for eq 2 were carried out omitting corrections for RE. These indicated, in the absence of RE, virtually no change in the log K1(NH3) value for H+, a small decrease for Cu+, and a larger decrease for Ag+. There would, however, be a very large decrease in the log K1(NH3) value for Au(I) from 9.8 (RE included) to 1.6 (RE omitted). These results suggest that much of "soft" acid behavior in aqueous solution in the hard and soft acid-base classification of Pearson may be the result of RE in the elements close to Au in the periodic table.

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

Li, Hang; Ha, Emmeline; Donaldson, Robert P.

Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreasmore » that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. In this paper, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin–copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the —HSSNN– residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin–copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of amylin oligomerization and fibril formation. Finally and more generally, this rapid technique opens the door for high-throughput screening of potential inhibitors of amyloid protein aggregation.« less

A Photoluminescence Study of the Changes Induced in the Zinc White Pigment by Formation of Zinc Complexes

PubMed Central

Artesani, Alessia; Gherardi, Francesca; Nevin, Austin; Valentini, Gianluca; Comelli, Daniela

2017-01-01

It is known that oil paintings containing zinc white are subject to rapid degradation. This is caused by the interaction between the active groups of binder and the metal ions of the pigment, which gives rise to the formation of new zinc complexes (metal soaps). Ongoing studies on zinc white paints have been limited to the chemical mechanisms that lead to the formation of zinc complexes. On the contrary, little is known of the photo-physical changes induced in the zinc oxide crystal structure following this interaction. Time-resolved photoluminescence spectroscopy has been applied to follow modifications in the luminescent zinc white pigment when mixed with binder. Significant changes in trap state photoluminescence emissions have been detected: the enhancement of a blue emission combined with a change of the decay kinetic of the well-known green emission. Complementary data from molecular analysis of paints using Fourier transform infrared spectroscopy confirms the formation of zinc carboxylates and corroborates the mechanism for zinc complexes formation. We support the hypothesis that zinc ions migrate into binder creating novel vacancies, affecting the photoluminescence intensity and lifetime properties of zinc oxide. Here, we further demonstrate the advantages of a time-resolved photoluminescence approach for studying defects in semiconductor pigments. PMID:28772700

Observation of CO2 and solvent adduct ions during negative mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of monohydric alcohols.

PubMed

Zhou, Xibin; Zhang, Yahe; Zhao, Suoqi; Hsu, Chang Samuel; Shi, Quan

2013-12-15

Monohydric alcohols are common in natural products, bio-oils, and medicine. We have found that monohydric alcohols can form O3 (ions containing three oxygen atoms) and O4 adduct ions in negative electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), which would significantly affect the composition analysis of alcohols, especially in a complex mixture. It is necessary to study the reaction pathways and the method to eliminate or reduce the 'artifact' adducts. Octadecanol, cholesterol, squalanol and two complex monohydric alcohol mixtures were selected as model compounds. These samples were subjected to negative ion ESI FT-ICR MS analysis. The composition and formation mechanism of adducts were studied by the ultrahigh-resolution accurate mass measurement for elemental composition, along with the MS(2) isolation and collision-induced dissociation (CID) experiments for structural determination. The reaction pathway of O3 adduct formation is the coupling of a monohydric alcohol ion with a CO2 to form a stable O3 ionic species by likely a covalent bond (source of CO2 is not clear). The O4 species are formed by O3 ionic species adducted with an alcohol molecule of the solvent, such as methanol or ethanol, by likely a hydrogen bond. These adduct ions could be eliminated or reduced by increasing collision energy. However, excessive collision energy would fragment monohydric alcohol ions. The formation mechanisms of O3 and O4 adducts from monohydric alcohols in negative ion ESI FT-ICR MS were proposed. The solvent adduction effects can be eliminated or reduced by optimizing the collision energy of CID in FT-ICR MS. Copyright © 2013 John Wiley & Sons, Ltd.

Effect of ultrasonic waves on the water turbidity during the oxidation of phenol. Formation of (hydro)peroxo complexes.

PubMed

Villota, Natalia; Lomas, Jose M; Camarero, Luis M

2017-11-01

Analysis of the kinetics of aqueous phenol oxidation by a sono-Fenton process reveals that the via involving ortho-substituted intermediates prevails: catechol (25.0%), hydroquinone (7.7%) and resorcinol (0.6%). During the oxidation, water rapidly acquires color that reaches its maximum intensity at the maximum concentration of p-benzoquinone. Turbidity formation occurs at a slower rate. Oxidant dosage determines the nature of the intermediates, being trihydroxylated benzenes (pyrogallol, hydroxyhydroquinone) and muconic acid the main precursors causing turbidity. It is found that the concentration of iron species and ultrasonic waves affects the intensity of the turbidity. The pathway of (hydro)peroxo-iron(II) complexes formation is proposed. Operating with 20.0-27.8mgFe 2+ /kW rates leads to formation of (hydro)peroxo-iron(II) complexes, which induce high turbidity levels. These species would dissociate into ZZ-muconic acid and ferrous ions. Applying relationships around 13.9mgFe 2+ /kW, the formation of (hydro)peroxo-iron(III) complexes would occur, which could react with carboxylic acids (2,5-dioxo-3-hexenedioic acid). That reaction induces turbidity slower. This is due to the organic substrate reacting with two molecules of the (hydro)peroxo complex. Therefore, it is necessary to accelerate the iron regeneration, intensifying the ultrasonic irradiation. Afterwards, this complex would dissociate into maleic acid and ferric ions. Copyright © 2017 Elsevier B.V. All rights reserved.

Uptake of Au(III) Ions by Aluminum Hydroxide and Their Spontaneous Reduction to Elemental Gold (Au(0)).

PubMed

Yokoyama; Matsukado; Uchida; Motomura; Watanabe; Izawa

2001-01-01

The behavior of AuCl(4)(-) ions during the formation of aluminum hydroxide at pH 6 was examined. With an increase in NaCl concentration, the content of gold taken up by aluminum hydroxide decreased, suggesting that chloro-hydroxy complexes of Au(III) ion were taken up due to the formation of Al-O-Au bonds. It was found unexpectedly that the Au(III) ions taken up were spontaneously reduced to elemental gold without addition of a specific reducing reagent and then colloidal gold particles were formed. The mechanisms for the uptake of Au(III) ions by aluminum hydroxide and for their spontaneous reduction are discussed. Copyright 2001 Academic Press.

Quantification of trace metals in water using complexation and filter concentration.

PubMed

Dolgin, Bella; Bulatov, Valery; Japarov, Julia; Elish, Eyal; Edri, Elad; Schechter, Israel

2010-06-15

Various metals undergo complexation with organic reagents, resulting in colored products. In practice, their molar absorptivities allow for quantification in the ppm range. However, a proper pre-concentration of the colored complex on paper filter lowers the quantification limit to the low ppb range. In this study, several pre-concentration techniques have been examined and compared: filtering the already complexed mixture, complexation on filter, and dipping of dye-covered filter in solution. The best quantification has been based on the ratio of filter reflectance at a certain wavelength to that at zero metal concentration. The studied complex formations (Ni ions with TAN and Cd ions with PAN) involve production of nanoparticle suspensions, which are associated with complicated kinetics. The kinetics of the complexation of Ni ions with TAN has been investigated and optimum timing could be found. Kinetic optimization in regard to some interferences has also been suggested.

A Simple Qualitative Analysis Scheme for Several Environmentally Important Elements

ERIC Educational Resources Information Center

Lambert, Jack L.; Meloan, Clifton E.

1977-01-01

Describes a scheme that uses precipitation, gas evolution, complex ion formation, and flame tests to analyze for the following ions: Hg(I), Hg(II), Sb(III), Cr(III), Pb(II), Sr(II), Cu(II), Cd(II), As(III), chloride, nitrate, and sulfate. (MLH)

Study on the mechanism of copper-ammonia complex decomposition in struvite formation process and enhanced ammonia and copper removal.

PubMed

Peng, Cong; Chai, Liyuan; Tang, Chongjian; Min, Xiaobo; Song, Yuxia; Duan, Chengshan; Yu, Cheng

2017-01-01

Heavy metals and ammonia are difficult to remove from wastewater, as they easily combine into refractory complexes. The struvite formation method (SFM) was applied for the complex decomposition and simultaneous removal of heavy metal and ammonia. The results indicated that ammonia deprivation by SFM was the key factor leading to the decomposition of the copper-ammonia complex ion. Ammonia was separated from solution as crystalline struvite, and the copper mainly co-precipitated as copper hydroxide together with struvite. Hydrogen bonding and electrostatic attraction were considered to be the main surface interactions between struvite and copper hydroxide. Hydrogen bonding was concluded to be the key factor leading to the co-precipitation. In addition, incorporation of copper ions into the struvite crystal also occurred during the treatment process. Copyright © 2016. Published by Elsevier B.V.

Chemometric analysis of voltammetric data on metal ion binding by selenocystine.

PubMed

Gusmão, Rui; Díaz-Cruz, José Manuel; Ariño, Cristina; Esteban, Miquel

2012-06-28

The behavior of selenocystine (SeCyst) alone or in the presence of various metal ions (Bi(3+), Cd(2+), Co(2+), Cu(2+), Cr(3+), Ni(2+), Pb(2+), and Zn(2+)) was studied using differential pulse voltammetry (DPV) over a wide pH range. Voltammetric data matrices were analyzed using chemometric tools recently developed for nonlinear data: pHfit and Gaussian Peak Adjustment (GPA). Under the experimental conditions tested, no evidence was found for the formation of metal complexes with Bi(3+), Cu(2+), Cr(3+), and Pb(2+). In contrast, SeCyst formed electroinactive complexes with Co(2+) and Ni(2+) and kinetically inert but electroactive complexes with Cd(2+) and Zn(2+). Titrations with Cd(2+), Co(2+), Ni(2+), and Zn(2+) produced data that were reasonably consistent with the formation of stable 1:1 M(SeCyst) complexes.

Non-covalent and coordination interactions in Cu(II) systems with uridine, uridine 5'-monophosphate and triamine or tetramine as biogenic amine analogues in aqueous solutions.

PubMed

Łomozik, Lechosław; Jastrzab, Renata

2003-10-01

Reactions of metallation and non-covalent interactions have been studied in ternary systems of Cu(II) ions with uridine, uridine 5'-monophosphate and diamines or triamines. It has been found that in metal-free systems the reaction centres of the nucleoside with the polyamine are the donor nitrogen atoms N(3) and protonated -NH(x) groups of the amines. In comparison to systems with adenosine or cytidine, the pH range of complex formation is shifted towards higher values. It is a consequence of significantly higher basicity of uridine and in agreement with the ion-ion, ion-dipole interaction model assumed. Formation of molecular complexes of uridine 5'-monophosphate with polyamines at a low pH is the result of activity of the phosphate group which plays the role of a negatively charged reaction site. Non-covalent interactions interfere in processes of bioligand metallation. Centres of weak interactions are simultaneously binding sites of metal ions. In protonated Cu(Urd)(PA)H(x) complexes, coordination has been found to involve the N(3) atom from the nucleoside and two donor nitrogen atoms from the polyamine (PA). In the heteroligand species Cu(Urd)(PA), despite deprotonation of all amine groups, one of these groups is located outside the inner coordination sphere. In complexes with uridine-5'-monophosphate, the phosphate group is active in metallation. Moreover, in certain coordination compounds this group is engaged in non-covalent interactions with PA molecules, despite binding Cu ions, as has been shown on the basis of equilibrium and spectral studies.

3D-structured illumination microscopy reveals clustered DNA double-strand break formation in widespread γH2AX foci after high LET heavy-ion particle radiation

PubMed Central

Hagiwara, Yoshihiko; Niimi, Atsuko; Isono, Mayu; Yamauchi, Motohiro; Yasuhara, Takaaki; Limsirichaikul, Siripan; Oike, Takahiro; Sato, Hiro; Held, Kathryn D.; Nakano, Takashi; Shibata, Atsushi

2017-01-01

DNA double-strand breaks (DSBs) induced by ionising radiation are considered the major cause of genotoxic mutations and cell death. While DSBs are dispersed throughout chromatin after X-rays or γ-irradiation, multiple types of DNA damage including DSBs, single-strand breaks and base damage can be generated within 1–2 helical DNA turns, defined as a complex DNA lesion, after high Linear Energy Transfer (LET) particle irradiation. In addition to the formation of complex DNA lesions, recent evidence suggests that multiple DSBs can be closely generated along the tracks of high LET particle irradiation. Herein, by using three dimensional (3D)-structured illumination microscopy, we identified the formation of 3D widespread γH2AX foci after high LET carbon-ion irradiation. The large γH2AX foci in G2-phase cells encompassed multiple foci of replication protein A (RPA), a marker of DSBs undergoing resection during homologous recombination. Furthermore, we demonstrated by 3D analysis that the distance between two individual RPA foci within γH2AX foci was approximately 700 nm. Together, our findings suggest that high LET heavy-ion particles induce clustered DSB formation on a scale of approximately 1 μm3. These closely localised DSBs are considered to be a risk for the formation of chromosomal rearrangement after heavy-ion irradiation. PMID:29312614

An ion-pair principle for enantioseparations of basic analytes by nonaqueous capillary electrophoresis using the di-n-butyl L-tartrate-boric acid complex as chiral selector.

PubMed

Wang, Li-Juan; Liu, Xiu-Feng; Lu, Qie-Nan; Yang, Geng-Liang; Chen, Xing-Guo

2013-04-05

A chiral recognition mechanism of ion-pair principle has been proposed in this study. It rationalized the enantioseparations of some basic analytes using the complex of di-n-butyl l-tartrate and boric acid as the chiral selector in methanolic background electrolytes (BGEs) by nonaqueous capillary electrophoresis (NACE). An approach of mass spectrometer (MS) directly confirmed that triethylamine promoted the formation of negatively charged di-n-butyl l-tartrate-boric acid complex chiral counter ion with a complex ratio of 2:1. And the negatively charged counter ion was the real chiral selector in the ion-pair principle enantioseparations. It was assumed that triethylamine should play its role by adjusting the apparent acidity (pH*) of the running buffer to a higher value. Consequently, the effects of various basic electrolytes including inorganic and organic ones on the enantioseparations in NACE were investigated. The results showed that most of the basic electrolytes tested were favorable for the enantioseparations of basic analytes using di-n-butyl l-tartrate-boric acid complex as the chiral ion-pair selector. Copyright © 2013 Elsevier B.V. All rights reserved.

Linked supramolecular building blocks for enhanced cluster formation

DOE PAGES

McLellan, Ross; Palacios, Maria A.; Beavers, Christine M.; ...

2015-01-09

Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]arenes and transition metal ions or 3d-4f combinations display characteristic features of the analogous calix[4]arene supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures.

Phosphorylation-Dependent Regulation of Ryanodine Receptors

PubMed Central

Marx, Steven O.; Reiken, Steven; Hisamatsu, Yuji; Gaburjakova, Marta; Gaburjakova, Jana; Yang, Yi-Ming; Rosemblit, Nora; Marks, Andrew R.

2001-01-01

Ryanodine receptors (RyRs), intracellular calcium release channels required for cardiac and skeletal muscle contraction, are macromolecular complexes that include kinases and phosphatases. Phosphorylation/dephosphorylation plays a key role in regulating the function of many ion channels, including RyRs. However, the mechanism by which kinases and phosphatases are targeted to ion channels is not well understood. We have identified a novel mechanism involved in the formation of ion channel macromolecular complexes: kinase and phosphatase targeting proteins binding to ion channels via leucine/isoleucine zipper (LZ) motifs. Activation of kinases and phosphatases bound to RyR2 via LZs regulates phosphorylation of the channel, and disruption of kinase binding via LZ motifs prevents phosphorylation of RyR2. Elucidation of this new role for LZs in ion channel macromolecular complexes now permits: (a) rapid mapping of kinase and phosphatase targeting protein binding sites on ion channels; (b) predicting which kinases and phosphatases are likely to regulate a given ion channel; (c) rapid identification of novel kinase and phosphatase targeting proteins; and (d) tools for dissecting the role of kinases and phosphatases as modulators of ion channel function. PMID:11352932

Serum albumin forms a lactoferrin-like soluble iron-binding complex in presence of hydrogen carbonate ions.

PubMed

Ueno, Hiroshi M; Urazono, Hiroshi; Kobayashi, Toshiya

2014-02-15

The iron-lactoferrin complex is a common food ingredient because of its iron-solubilizing capability in the presence of hydrogen carbonate ions. However, it is unclear whether the formation of a stable iron-binding complex is limited to lactoferrin. In this study, we investigated the effects of bovine serum albumin (BSA) on iron solubility and iron-catalyzed lipid oxidation in the presence of hydrogen carbonate ions. BSA could solubilize >100-fold molar equivalents of iron at neutral pH, exceeding the specific metal-binding property of BSA. This iron-solubilizing capability of BSA was impaired by thermally denaturing BSA at ≥ 70 °C for 10 min at pH 8.5. The resulting iron-BSA complex inhibited iron-catalyzed oxidation of soybean oil in a water-in-oil emulsion measured using the Rancimat test. Our study is the first to show that BSA, like lactoferrin, forms a soluble iron-binding complex in the presence of hydrogen carbonate ions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Biomimetic fabrication of materials: the minimalist approach

NASA Astrophysics Data System (ADS)

Lahiri, Joydeep; Xu, Guofeng; Lee, Tu; Dabbs, Daniel M.; Yao, Nan; Aksay, Ilhan A.; Groves, John T.

1996-02-01

The interfacial chemistry between inorganic ceramics and defined organic surfaces is the focus of intense investigation. Partially compressed Langmuir-Blodgett monolayers of anionic porphyrins have been used as modified nucleation sites for calcium carbonate. The porphyrin monolayer has an ordered array of carboxylates, and hence the system serves as a minimalist template for the modeling of complex biogenic acidic glycoproteins for biomineralization. The initial results suggest the formation of calcite with morphologically distinct calcitic rhombs with truncated, 3-edged corners and intricately articulated facial cavities. Stearic acid monolayers yield distinctly different calcite crystals, indicative that the geometrically defined carboxylate array is probably important. Phosphatidylcholine vesicles have been used as a tool for the formation of membrane encapsulated iron-oxides. Gramicindin A ion channels have been embedded in vesicles to kinetically alter the formation and growth of iron oxides, starting with intravesicular ferrous chloride. The results indicate that the presence of ion channels lead to the formation of magnetite vis-a-vis maghemite formation in vesicles lacking the ion channels. The use of ion channels has important implications in probable signal transduction processes during biomineralization pathways.

The Formation and Thermochemical Properties of Multiligand Complexes

DTIC Science & Technology

1987-08-25

SUBJECT TERMS (Continue on revers, if necessary and identify by block numoer) FIELD GROUP SUB-GROUP Ion-molecule reactions, clusters, multiligand...mercaptans, and phosphonates for which the results may be useful in the development of detection techniques that employ ion mobility analyzers or... field involve the use of ion mobility and mass spectrometers. Detection of a species by such instruments in an atmospheric environment requires that the

Stability of coordination compounds of Ni2+ and Co2+ ions with succinic acid anion in water-ethanol solvents

NASA Astrophysics Data System (ADS)

Tukumova, N. V.; Dieu Thuan, Tran Thi; Usacheva, T. R.; Koryshev, N. E.; Sharnin, V. A.

2017-04-01

Stability constants of the coordination compounds of nickel(II) and cobalt(II) ions with succinic acid anion in water-ethanol solvents are determined via potentiometric titration at ionic strength of 0.1 and at T = 298.15 K. It is found that logβ values of monoligand complexes of these ions and succinic acid anions rise along with the content of ethanol in solution ( X EtOH = 0-0.7 mole fractions). Based on an analysis of the thermodynamic characteristics of the solvation of the reagents involved in complex formation, it is found that the increased stability of succinate complexes of nickel(II) and cobalt(II) ions in water-ethanol solvents is mainly determined by the weakening of the solvation of succinic acid anion (Y2-).

Microemulsions and Aggregation Formation in Extraction Processes for Used Nuclear Fuel: Thermodynamic and Structural Studies

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

Nilsson, Mikael

Advanced nuclear fuel cycles rely on successful chemical separation of various elements in the used fuel. Numerous solvent extraction (SX) processes have been developed for the recovery and purification of metal ions from this used material. However, the predictability of process operations has been challenged by the lack of a fundamental understanding of the chemical interactions in several of these separation systems. For example, gaps in the thermodynamic description of the mechanism and the complexes formed will make predictions very challenging. Recent studies of certain extraction systems under development and a number of more established SX processes have suggested thatmore » aggregate formation in the organic phase results in a transformation of its selectivity and efficiency. Aggregation phenomena have consistently been interfering in SX process development, and have, over the years, become synonymous with an undesirable effect that must be prevented. This multiyear, multicollaborative research effort was carried out to study solvation and self-organization in non-aqueous solutions at conditions promoting aggregation phenomena. Our approach to this challenging topic was to investigate extraction systems comprising more than one extraction reagent where synergy of the metal ion could be observed. These systems were probed for the existence of stable microemulsions in the organic phase, and a number of high-end characterization tools were employed to elucidate the role of the aggregates in metal ion extraction. The ultimate goal was to find connections between synergy of metal ion extraction and reverse micellar formation. Our main accomplishment for this project was the expansion of the understanding of metal ion complexation in the extraction system combining tributyl phosphate (TBP) and dibutyl phosphoric acid (HDBP). We have found that for this system no direct correlation exists for the metal ion extraction and the formation of aggregates, meaning that the metal ion is not solubilized in a reverse micelle core. Rather we have found solid evidence that the metal ions are extracted and coordinated by the organic ligands as suggested by classic SX theories. However, we have challenged the existence of mixed complexes that have been suggested to exist in this particular extraction system. Most importantly we have generated a wealth of information and trained students on important lab techniques and strengthened the collaboration between the DOE national laboratories and US educational institution involved in this work.« less

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

From a Dy(III) single molecule magnet (SMM) to a ferromagnetic [Mn(II)Dy(III)Mn(II)] trinuclear complex.

PubMed

Bhunia, Asamanjoy; Gamer, Michael T; Ungur, Liviu; Chibotaru, Liviu F; Powell, Annie K; Lan, Yanhua; Roesky, Peter W; Menges, Fabian; Riehn, Christoph; Niedner-Schatteburg, Gereon

2012-09-17

The Schiff base compound 2,2'-{[(2-aminoethyl)imino]bis[2,1-ethanediyl-nitriloethylidyne]}bis-2-hydroxy-benzoic acid (H(4)L) as a proligand was prepared in situ. This proligand has three potential coordination pockets which make it possible to accommodate from one to three metal ions allowing for the possible formation of mono-, di-, and trinuclear complexes. Reaction of in situ prepared H(4)L with Dy(NO(3))(3)·5H(2)O resulted in the formation of a mononuclear complex [Dy(H(3)L)(2)](NO(3))·(EtOH)·8(H(2)O) (1), which shows SMM behavior. In contrast, reaction of in situ prepared H(4)L with Mn(ClO(4))(2)·6H(2)O and Dy(NO(3))(3)·5H(2)O in the presence of a base resulted in a trinuclear mixed 3d-4f complex (NHEt(3))(2)[Dy{Mn(L)}(2)](ClO(4))·2(H(2)O) (2). At low temperatures, compound 2 is a weak ferromagnet. Thus, the SMM behavior of compound 1 can be switched off by incorporating two Mn(II) ions in close proximity either side of the Dy(III). This quenching behavior is ascribed to the presence of the weak ferromagnetic interactions between the Mn(II) and Dy(III) ions, which at T > 2 K act as a fluctuating field causing the reversal of magnetization on the dysprosium ion. Mass spectrometric ion signals related to compounds 1 and 2 were both detected in positive and negative ion modes via electrospray ionization mass spectrometry. Hydrogen/deuterium exchange (HDX) reactions with ND(3) were performed in a FT-ICR Penning-trap mass spectrometer.

Efficient Covalent Bond Formation in Gas-Phase Peptide-Peptide Ion Complexes with the Photoleucine Stapler

NASA Astrophysics Data System (ADS)

Shaffer, Christopher J.; Andrikopoulos, Prokopis C.; Řezáč, Jan; Rulíšek, Lubomír; Tureček, František

2016-04-01

Noncovalent complexes of hydrophobic peptides GLLLG and GLLLK with photoleucine (L*) tagged peptides G(L* n L m )K (n = 1,3, m = 2,0) were generated as singly charged ions in the gas phase and probed by photodissociation at 355 nm. Carbene intermediates produced by photodissociative loss of N2 from the L* diazirine rings underwent insertion into X-H bonds of the target peptide moiety, forming covalent adducts with yields reaching 30%. Gas-phase sequencing of the covalent adducts revealed preferred bond formation at the C-terminal residue of the target peptide. Site-selective carbene insertion was achieved by placing the L* residue in different positions along the photopeptide chain, and the residues in the target peptide undergoing carbene insertion were identified by gas-phase ion sequencing that was aided by specific 13C labeling. Density functional theory calculations indicated that noncovalent binding to GL*L*L*K resulted in substantial changes of the (GLLLK + H)+ ground state conformation. The peptide moieties in [GL*L*LK + GLLLK + H]+ ion complexes were held together by hydrogen bonds, whereas dispersion interactions of the nonpolar groups were only secondary in ground-state 0 K structures. Born-Oppenheimer molecular dynamics for 100 ps trajectories of several different conformers at the 310 K laboratory temperature showed that noncovalent complexes developed multiple, residue-specific contacts between the diazirine carbons and GLLLK residues. The calculations pointed to the substantial fluidity of the nonpolar side chains in the complexes. Diazirine photochemistry in combination with Born-Oppenheimer molecular dynamics is a promising tool for investigations of peptide-peptide ion interactions in the gas phase.

Experimental evidence for the participation of deep eutectic solvents in silver chloride crystal formation at low temperature

NASA Astrophysics Data System (ADS)

Bhatt, Jitkumar; Mondal, Dibyendu; Prasad, Kamalesh

2016-05-01

Deep eutectic solvents (DESs) obtained by the complexation of choline chloride (ChoCl) as hydrogen bond acceptor and hydrogen bond donors such as ethylene glycol (ChoCl-EG 1:2) and glycerol (ChoCl-Gly 1:2) were used as media for the formation of AgCl crystals. Although formation of AgCl crystals was observed in both the solvents but the rate of formation of crystals was faster in ChoCl-EG 1:2 at low temperature (4-5 °C). In the crystals, cholinium cations were found to be present with chloride ions bridged with Ag ions resulting generation of 1D network of AgCl2 anions.

Solvent-coordinate free-energy landscape view of water-mediated ion-pair dissociation

NASA Astrophysics Data System (ADS)

Yonetani, Yoshiteru

2017-12-01

Water-mediated ion-pair dissociation is studied by molecular dynamics simulations of NaCl in water. Multidimensional free-energy analysis clarifies the relation between two essential solvent coordinates: the water coordination number and water-bridge formation. These two are related in a complex way. Both are necessary to describe ion-pair dissociation. The mechanism constructed with both solvent variables clearly shows the individual roles. The water coordination number is critical for starting ion-pair dissociation. Water-bridge formation is also important because it increases the likelihood of ion-pair dissociation by reducing the dissociation free-energy barrier. Additional Ca-Cl and NH4-Cl calculations show that these conclusions are unaffected by changes in the ion charge and shape. The present results will contribute to future explorations of many other molecular events such as surface water exchange and protein-ligand dissociation because the same mechanism is involved in such events.

Self-templated formation of uniform NiCo2O4 hollow spheres with complex interior structures for lithium-ion batteries and supercapacitors.

PubMed

Shen, Laifa; Yu, Le; Yu, Xin-Yao; Zhang, Xiaogang; Lou, Xiong Wen David

2015-02-02

Despite the significant advancement in preparing metal oxide hollow structures, most approaches rely on template-based multistep procedures for tailoring the interior structure. In this work, we develop a new generally applicable strategy toward the synthesis of mixed-metal-oxide complex hollow spheres. Starting with metal glycerate solid spheres, we show that subsequent thermal annealing in air leads to the formation of complex hollow spheres of the resulting metal oxide. We demonstrate the concept by synthesizing highly uniform NiCo2O4 hollow spheres with a complex interior structure. With the small primary building nanoparticles, high structural integrity, complex interior architectures, and enlarged surface area, these unique NiCo2O4 hollow spheres exhibit superior electrochemical performances as advanced electrode materials for both lithium-ion batteries and supercapacitors. This approach can be an efficient self-templated strategy for the preparation of mixed-metal-oxide hollow spheres with complex interior structures and functionalities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemodynamics of aquatic metal complexes: from small ligands to colloids.

PubMed

Van Leeuwen, Herman P; Buffle, Jacques

2009-10-01

Recent progress in understanding the formation/dissociation kinetics of aquatic metal complexes with complexants in different size ranges is evaluated and put in perspective, with suggestions for further studies. The elementary steps in the Eigen mechanism, i.e., diffusion and dehydration of the metal ion, are reviewed and further developed. The (de)protonation of both the ligand and the coordinating metal ion is reconsidered in terms of the consequences for dehydration rates and stabilities of the various outer-sphere complexes. In the nanoparticulate size range, special attention is given to the case of fulvic ligands, for which the impact of electrostatic interactions is especially large. In complexation with colloidal ligands (hard, soft, and combination thereof) the diffusive transport of metal ions is generally a slower step than in the case of complexation with small ligands in a homogeneous solution. The ensuing consequences for the chemodynamics of colloidal complexes are discussed in detail and placed in a generic framework, encompassing the complete range of ligand sizes.

Understanding the mechanism of DNA deactivation in ion therapy of cancer cells: hydrogen peroxide action*

NASA Astrophysics Data System (ADS)

Piatnytskyi, Dmytro V.; Zdorevskyi, Oleksiy O.; Perepelytsya, Sergiy M.; Volkov, Sergey N.

2015-11-01

Changes in the medium of biological cells under ion beam irradiation has been considered as a possible cause of cell function disruption in the living body. The interaction of hydrogen peroxide, a long-lived molecular product of water radiolysis, with active sites of DNA macromolecule was studied, and the formation of stable DNA-peroxide complexes was considered. The phosphate groups of the macromolecule backbone were picked out among the atomic groups of DNA double helix as a probable target for interaction with hydrogen peroxide molecules. Complexes consisting of combinations including: the DNA phosphate group, H2O2 and H2O molecules, and Na+ counterion, were considered. The counterions have been taken into consideration insofar as under the natural conditions they neutralise DNA sugar-phosphate backbone. The energy of the complexes have been determined by considering the electrostatic and the Van der Waals interactions within the framework of atom-atom potential functions. As a result, the stability of various configurations of molecular complexes was estimated. It was shown that DNA phosphate groups and counterions can form stable complexes with hydrogen peroxide molecules, which are as stable as the complexes with water molecules. It has been demonstrated that the formation of stable complexes of H2O2-Na+-PO4- may be detected experimentally by observing specific vibrations in the low-frequency Raman spectra. The interaction of H2O2 molecule with phosphate group of the double helix backbone can disrupt DNA biological function and induce the deactivation of the cell genetic apparatus. Thus, the production of hydrogen peroxide molecules in the nucleus of living cells can be considered as an additional mechanism by which high-energy ion beams destroy tumour cells during ion beam therapy. Contribution to the Topical Issue "COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy", edited by Andrey Solov'yov, Nigel Mason, Gustavo García, Eugene Surdutovich.

Evidence of Multi-Component Ion Exchange in Dolomite Formation during Low Salinity Waterflooding

NASA Astrophysics Data System (ADS)

Srisuriyachai, Falan; Meekangwal, Suthida

2017-12-01

Low salinity waterflooding is a technique performed in many oil reservoirs around the globe. The technique is simply implemented by injecting water with very low ionic activity compared to formation water into an injection well. The injected water will increase reservoir pressure that is compulsory to drive oil moving toward production well. More than just maintaining reservoir pressure as obtained from conventional waterflooding, low salinity water creates shifting of surface condition, resulting in additional amount of liberated oil. Nevertheless, exact oil recovery mechanisms are still discussed. Among these proposed mechanisms, Multi-component Ion Exchange (MIE) together with wettability alteration is believed to be a major mechanism leading to higher oil recovery compared to conventional waterflooding. In this study, detection of calcium and magnesium ions which are Potential Determining Ions (PDI) for carbonate reservoirs are detected during the coreflood experiment. Dolomite rock sample is used to represent carbonate formation and detection of previously mentioned ions is performed by complexometric titration of the effluents. From the study, it is observed that during conventional waterflooding and low salinity waterflooding at low temperature of 30 degrees Celsius, calcium and magnesium ions in the produced water is increased compared to the amount of these ions in the injected water. This incremental of ions can be explained by the dissolution of calcium and magnesium from dolomite which is chemically composed of calcium magnesium carbonate. At this temperature, the portion of calcium ion is always less than magnesium ion even though the amount of calcium ion is higher than magnesium ion in injected water. However, at higher temperatures which are 50 and 70 degrees Celsius, ratio of calcium and magnesium ions in injected and produced water is reversed. Disappearance of magnesium ion in the effluent is more obvious especially at 70 degrees Celsius and by low salinity waterflooding. This can be explained that at lower temperature, calcium ion disappears to form of calcium carboxylate complex with oil and at higher temperature, magnesium ion disappears as magnesium can start to form magnesium carboxylate complex with oil and hence, the amount of both calcium and magnesium ions is decreased compared to lower temperature. In dolomite reservoir, since both calcium ions and magnesium ions are provided from dissolution mechanism, the benefit from multi-component ion exchange will occur at high temperature as both calcium and magnesium ions will be consumed for oil recovery mechanism.

Femtosecond-picosecond laser photolysis studies on the dynamics of excited charge-transfer complexes: Aromatic hydrocarbon-acid anhydride, -tetracyanoethylene, and -tetracyanoquinodimethane systems in acetonitrile solutions

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

Asahi, Tsuyoshi; Mataga, Noboru

1991-03-07

Formation processes of contact ion pairs (CIP) from the excited Franck-Condon (FC) state of charge-transfer (CT) complexes of aromatic hydrocarbons with acid anhydride as well as cyano compound acceptors in acetonitrile solution and charge recombination (CR) rates (k{sub CR}{sup CIP}) of produced CIP states have been investigated by femtosecond and picosecond laser phototlysis and time-resolved absorption spectral measurements covering a wide range of free energy gap-{Delta}G{degree}{sub ip} between the ion pair and the ground state. It has been confirmed that the CIP formation becomes faster and k{sub CR}{sup CIP} of the produced CIP increases with increase of the strengths ofmore » the electron donor (D) and acceptor (A) in the complex, i.e., with decrease of the {minus}{Delta}G{degree}{sub ip} value. This peculiar energy gap dependence of k{sub CR}{sup CIP}, quite different from the bell-shaped one observed in the case of the solvent-separated ion pairs (SSIP) or loose ion pairs (LIP) formed by encounter between fluorescer and quencher in the fluoresence quenching reaction, has been interpreted by assuming the change of electronic and geometrical structures of CIP depending on the strengths of D and A.« less

Thermodynamics of the formation of Cu2+-glycyl-glycyl-glycine complex in water-ethanol solutions at 298 K

NASA Astrophysics Data System (ADS)

Pham Thi, L.; Usacheva, T. R.; Tukumova, N. V.; Koryshev, N. E.; Khrenova, T. M.; Sharnin, V. A.

2016-10-01

The stability constants of monoligand complexes of copper(II) ions with glycyl-glycyl-glycine zwitterions (triglycine, HL±) and triglycinate ions (L-) in a water-ethanol solvent with 0.0, 0.1, 0.3, and 0.5 mole fractions of ethanol at an ionic strength of 0.1 created by sodium perchlorate and temperature T = 298.15 K are determined by means of potentiometric titration. It is found that an increase of ethanol content improves the stability of the investigated complexes, due mainly to the resolvation of ligands.

HI and Low Metal Ions at the Intersection of Galaxies and the CGM

NASA Astrophysics Data System (ADS)

Oppenheimer, Benjamin

2017-08-01

Over 1000 COS orbits have revealed a surprisingly complex picture of circumgalactic gas flows surrounding the diversity of galaxies in the evolved Universe. Cosmological hydrodynamic simulations have only begun to confront the vast amount of galaxy formation physics, chemistry, and dynamics revealed in the multi-ion CGM datasets. We propose the next generation of EAGLE zoom simulations, called EAGLE Cosmic Origins, to model HI and low metal ions (C II, Mg II, & Si II) throughout not just the CGM but also within the galaxies themselves. We will employ a novel, new chemistry solver, CHIMES, to follow time-dependent ionization, chemistry, and cooling of 157 ionic and molecular species, and include multiple ionization sources from the extra-galactic background, episodic AGN, and star formation. Our aim is to understand the complete baryon cycle of inflows, outflows, and gas recycling traced over 10 decades of HI column densities as well as the complex kinematic information encoded low ion absorption spectroscopy. This simulation project represents a pilot program for a larger suite of zoom simulations, which will be publicly released and lead to additional publications.

Facial and meridional isomers of holmium-nitrate N-tert-butylacetamide complexes

NASA Astrophysics Data System (ADS)

Chang, Ye-Di; Xue, Jun-Hui; Kang, Xiao-Yan; Yang, Li-Min; Li, Wei-Hong; Xu, Yi-Zhuang; Zhao, Guo-Zhong; Zhang, Gao-Hui; Liu, Ke-Xin; Chen, Jia-Er; Wu, Jin-Guang

2018-06-01

Two Ho(C6H13NO)3(NO3)3 complexes formed by holmium nitrate and N-tert-butylacetamide (NtBA) (Ho-NtBA(I) in a Cc space group, and Ho-NtBA(II) in a P21/c space group) are reported here to investigate the coordination of lanthanide ions with amide groups. Using X-ray single crystal diffraction, FTIR, Raman, FIR and THz methods the structures of the two complexes were identified, in which Ho3+ is 9-coordinated to three carbonyl oxygen atoms provided by three NtBA ligands and three bidentate nitrate ions to form the "facial" and "meridional" isomers. Their FTIR and Raman spectra indicate the formation of two holmium complexes, the variations of NtBA after holmium coordination and the spectra are similar for the isomers in some extent. Their FIR and THz spectroscopic results show the coordination of holmium ions and THz maybe more sensitive to isomers. The results demonstrate the coordination behaviors of holmium ions and NtBA ligand.

Molecular dynamics study of thermodynamic stability and dynamics of [Li(glyme)]+ complex in lithium-glyme solvate ionic liquids

NASA Astrophysics Data System (ADS)

Shinoda, Wataru; Hatanaka, Yuta; Hirakawa, Masashi; Okazaki, Susumu; Tsuzuki, Seiji; Ueno, Kazuhide; Watanabe, Masayoshi

2018-05-01

Equimolar mixtures of glymes and organic lithium salts are known to produce solvate ionic liquids, in which the stability of the [Li(glyme)]+ complex plays an important role in determining the ionic dynamics. Since these mixtures have attractive physicochemical properties for application as electrolytes, it is important to understand the dependence of the stability of the [Li(glyme)]+ complex on the ion dynamics. A series of microsecond molecular dynamics simulations has been conducted to investigate the dynamic properties of these solvate ionic liquids. Successful solvate ionic liquids with high stability of the [Li(glyme)]+ complex have been shown to have enhanced ion dynamics. Li-glyme pair exchange rarely occurs: its characteristic time is longer than that of ion diffusion by one or two orders of magnitude. Li-glyme pair exchange most likely occurs through cluster formation involving multiple [Li(glyme)]+ pairs. In this process, multiple exchanges likely take place in a concerted manner without the production of energetically unfavorable free glyme or free Li+ ions.

Phosphodiester Cleavage in Ribonuclease H Occurs via an Associative Two-Metal-Aided Catalytic Mechanism

PubMed Central

De Vivo, Marco; Dal Peraro, Matteo; Klein, Michael L.

2009-01-01

Ribonuclease H (RNase H) belongs to the nucleotidyl-transferase (NT) superfamily and hydrolyzes the phosphodiester linkages that form the backbone of the RNA strand in RNA·DNA hybrids. This enzyme is implicated in replication initiation and DNA topology restoration and represents a very promising target for anti-HIV drug design. Structural information has been provided by high-resolution crystal structures of the complex RNase H/RNA·DNA from Bacillus halodurans (Bh), which reveals that two metal ions are required for formation of a catalytic active complex. Here, we use classical force field-based and quantum mechanics/molecular mechanics calculations for modeling the nucleotidyl transfer reaction in RNase H, clarifying the role of the metal ions and the nature of the nucleophile (water versus hydroxide ion). During the catalysis, the two metal ions act cooperatively, facilitating nucleophile formation and stabilizing both transition state and leaving group. Importantly, the two Mg2+ metals also support the formation of a meta-stable phosphorane intermediate along the reaction, which resembles the phosphorane intermediate structure obtained only in the debated β-phosphoglucomutase crystal. The nucleophile formation (i.e., water deprotonation) can be achieved in situ, after migration of one proton from the water to the scissile phosphate in the transition state. This proton transfer is actually mediated by solvation water molecules. Due to the highly conserved nature of the enzymatic bimetal motif, these results might also be relevant for structurally similar enzymes belonging to the NT superfamily. PMID:18662000

Evidence of zinc superoxide formation in the gas phase: comparisons in behaviour between ligated Zn(I/II) and Cu(I/II) with regard to the attachment of O2 or H2O.

PubMed

Cox, Hazel; Norris, Caroline; Wu, Guohua; Guan, Jingang; Hessey, Stephen; Stace, Anthony J

2011-11-14

Singly and doubly charged atomic ions of zinc and copper have been complexed with pyridine and held in an ion trap. Complexes involving Zn(II) and Cu(I) (3d(10)) display a strong tendency to bind with H(2)O, whilst the Zn(I) (3d(10)4s(1)) complexes exhibit a strong preference for the attachment of O(2). DFT calculations show that this latter result can be interpreted as internal oxidation leading to the formation of superoxide complexes, [Zn(II)O(2)(-)](pyridine)(n), in the gas phase. The calculations also show that the oxidation of Zn(I) to form Zn(II)O(2)(-) is promoted by a mixing of the occupied 4s and vacant 4p orbitals on the metal cation, and that this process is facilitated by the presence of the pyridine ligands.

Defect states of complexes involving a vacancy on the boron site in boronitrene

NASA Astrophysics Data System (ADS)

Ngwenya, T. B.; Ukpong, A. M.; Chetty, N.

2011-12-01

First principles calculations have been performed to investigate the ground state properties of freestanding monolayer hexagonal boronitrene (h-BN). We have considered monolayers that contain native point defects and their complexes, which form when the point defects bind with the boron vacancy on the nearest-neighbor position. The changes in the electronic structure are analyzed to show the extent of localization of the defect-induced midgap states. The variations in formation energies suggest that defective h-BN monolayers that contain carbon substitutional impurities are the most stable structures, irrespective of the changes in growth conditions. The high energies of formation of the boron vacancy complexes suggest that they are less stable, and their creation by ion bombardment would require high-energy ions compared to point defects. Using the relative positions of the derived midgap levels for the double vacancy complex, it is shown that the quasi-donor-acceptor pair interpretation of optical transitions is consistent with stimulated transitions between electron and hole states in boronitrene.

Influence of ionic strength and OH(-) ion concentration on the Cu(II) complex formation with EDTA in alkaline solutions.

PubMed

Norkus, E; Vaskelis, A; Zakaite, I

1996-03-01

D.c. polarographic data show that the complex formation of copper ions with EDTA depends markedly on the ionic strength of the solution at pH 8-10. This is primarily associated with the dependence of the fourth deprotonization constant of EDTA on the solution ionic strength: when it increases from 0.4 to 3.4, the pK(a4) value decreases from 9.5 to 8.2. According to polarographic and spectrophotometric data the degree of Cu(II) complexation increases at pH>10 due to transformation of the complex CuY(2-) to the more stable CuY(OH)(3-) (Y(4-), a fully deprotonized anion of EDTA), but it decreases with increase in alkalinity in a highly alkaline solution (pH>13.5). The latter result could be explained by the decrease in the EDTA anion activity. The calculated values of the activity coefficient are lower than 0.05 at pH>14.

Inorganic and organic structures as interleavers among [bis(1-methyl-3-(p-carboxylatephenyl)triazenide 1-oxide)Ni(II)] complexes to form supramolecular arrangements

NASA Astrophysics Data System (ADS)

Santos, Aline Joana Rolina Wohlmuth Alves; dos Santos Hackbart, Helen Cristina; Giacomini, Gabriela Xavier; Bersch, Patrícia; Paraginski, Gustavo Luiz; Hörner, Manfredo

2016-12-01

Alternative compounds to capture metal ions are triazenes 1-oxide since they are basic compounds O(N) with negative charge in the deprotonated form. The proximity of both coordination sites (O and N) enables these compounds to have good chelating ability and a tendency to stabilize in the formation of rings with soft and hard transition metal ions. The structure analysis by single crystal X-ray diffraction of compounds (1) and (2) demonstrate the formation of 3D supramolecular arrangements through ion-ion, ion-dipolo and dipolo-dipolo interactions. In one of them, there are [(H2O)2(CH3CH3SO)K2]2+ as linkers of polymerization and, in another complex, there are [(H2O)(CH3CH3SO)Ni(H2O)6]2+ as a linker of polymerization. These linkers act in the polymerization of the novel mononuclear complex [bis(1-methyl (p-carboxylatephenyl) triazenide 1-oxide) NiII] (3). The crystallography analysis of (1) and (2) showed distorted quadratic geometry for Ni (II), thus, there are two axial positions available in Ni (II) to be used in catalysis studies and as sensor or biosensor. In addition, this study shows the support of this novel mononuclear complex of Ni (II) (3) on protonated chitosan chains (4). The compounds (3) and (4) were characterized by spectroscopic analysis, infrared (IR) and energy dispersive X-ray detector (EDS), and by differential scanning calorimetry analysis (DSC). The specificity of ligand 1-methyl (p-carboxyphenyl) triazene 1-oxide to capture potassium and nickel ions will be tested at different pH values, as well as the capacity of the triazenide 1-oxide of Ni (II) complex, supported on chitosan polymer, or not, to act as a catalyst for organic reactions and biomimetic organic reactions.

Fe(2+) substrate transport through ferritin protein cage ion channels influences enzyme activity and biomineralization.

PubMed

Behera, Rabindra K; Torres, Rodrigo; Tosha, Takehiko; Bradley, Justin M; Goulding, Celia W; Theil, Elizabeth C

2015-09-01

Ferritins, complex protein nanocages, form internal iron-oxy minerals (Fe2O3·H2O), by moving cytoplasmic Fe(2+) through intracage ion channels to cage-embedded enzyme (2Fe(2+)/O2 oxidoreductase) sites where ferritin biomineralization is initiated. The products of ferritin enzyme activity are diferric oxy complexes that are mineral precursors. Conserved, carboxylate amino acid side chains of D127 from each of three cage subunits project into ferritin ion channels near the interior ion channel exits and, thus, could direct Fe(2+) movement to the internal enzyme sites. Ferritin D127E was designed and analyzed to probe properties of ion channel size and carboxylate crowding near the internal ion channel opening. Glu side chains are chemically equivalent to, but longer by one -CH2 than Asp, side chains. Ferritin D127E assembled into normal protein cages, but diferric peroxo formation (enzyme activity) was not observed, when measured at 650 nm (DFP λ max). The caged biomineral formation, measured at 350 nm in the middle of the broad, nonspecific Fe(3+)-O absorption band, was slower. Structural differences (protein X-ray crystallography), between ion channels in wild type and ferritin D127E, which correlate with the inhibition of ferritin D127E enzyme activity include: (1) narrower interior ion channel openings/pores; (2) increased numbers of ion channel protein-metal binding sites, and (3) a change in ion channel electrostatics due to carboxylate crowding. The contributions of ion channel size and structure to ferritin activity reflect metal ion transport in ion channels are precisely regulated both in ferritin protein nanocages and membranes of living cells.

Fe2+ Substrate Transport through Ferritin Protein Cage Ion Channels Influences Enzyme Activity and Biomineralization

PubMed Central

Behera, Rabindra K.; Torres, Rodrigo; Tosha, Takehiko; Bradley, Justin M.; Goulding, Celia W.; Theil, Elizabeth C.

2015-01-01

Ferritins, complex protein nanocages, form internal iron-oxy minerals (Fe2O3.H2O), by moving cytoplasmic Fe2+ through intracage ion channels to cage-embedded enzyme (2Fe2+/O2 oxidoreductase) sites where ferritin biomineralization is initiated. The products of ferritin enzyme activity are diferric oxy complexes that are mineral precursors. Conserved, carboxylate amino acid side chains of D127 from each of three cage subunits project into ferritin ion channels near the interior ion channel exits and, thus, could direct Fe2+ movement to the internal enzyme sites. Ferritin D127E was designed and analyzed to probe properties of ion channel size and carboxylate crowding near the internal ion channel opening. Glu side chains are chemically equivalent to, but longer by one – CH2 than Asp, side chains. Ferritin D127E assembled into normal protein cages, but diferric peroxo formation (enzyme activity) was not observed, when measured at 650nm (DFP λmax). The caged biomineral formation, measured at 350 nm in the middle of the broad, nonspecific Fe3+-O absorption band, was slower. Structural differences (protein X-ray crystallography), between ion channels in wild type and ferritin D127E, which correlate with the inhibition of ferritin D127E enzyme activity include: 1. narrower interior ion channel openings/pores, 2. increased numbers of ion channel protein-metal binding sites, and 3. a change in ion channel electrostatics due to carboxylate crowding. The contributions of ion channel size and structure to ferritin activity reflect metal ion transport in ion channels are precisely regulated both in ferritin protein nanocages and membranes of living cells. PMID:26202907

Dielectric response and transport properties of alkylammonium formate ionic liquids

NASA Astrophysics Data System (ADS)

Nazet, Andreas; Buchner, Richard

2018-05-01

Dielectric relaxation spectra of three members of the alkylammonium formate family of protic ionic liquids (PILs), namely, ethylammonium formate (EAF), n-butylammonium formate (BuAF), and n-pentylammonium formate (PeAF), as well as the pseudo-PIL triethylamine + formic acid (molar ratio 1:2; TEAF) have been studied over a wide frequency (50 MHz to 89 GHz) and temperature range (5-65 °C), complemented by measurements of their density, viscosity, and conductivity. It turned out that the dominating relaxation of EAF, BuAF, and PeAF arises from both cation and anion reorientations which are synchronized in their dynamics due to hydrogen bonding. Amplitudes and relaxation times of this mode reflect the—compared to nitrate—different nature of H bonding between the formate anion and ethylammonium cation, as well as increasing segregation of the PIL structure into polar and non-polar domains. The TEAF data suggest that its dominating relaxation is due to the rotation of the complex triethylamineṡ(formic acid)2 in which no significant proton transfer to an ion pair occurred. Weak dissociation of this complex into ions was postulated to account for the high conductivity of TEAF.

Structure and magnetic properties of an unprecedented syn-anti μ-nitrito-1κO:2κO' bridged Mn(III)-salen complex and its isoelectronic and isostructural formate analogue.

PubMed

Kar, Paramita; Biswas, Rituparna; Drew, Michael G B; Ida, Yumi; Ishida, Takayuki; Ghosh, Ashutosh

2011-04-07

The preparation, crystal structures and magnetic properties of two new isoelectronic and isomorphous formate- and nitrite-bridged 1D chains of Mn(III)-salen complexes, [Mn(salen)(HCOO)](n) (1) and [Mn(salen)(NO(2))](n) (2), where salen is the dianion of N,N'-bis(salicylidene)-1,2-diaminoethane, are presented. The structures show that the salen ligand coordinates to the four equatorial sites of the metal ion and the formate or nitrite ions coordinate to the axial positions to bridge the Mn(III)-salen units through a syn-antiμ-1κO:2κO' coordination mode. Such a bridging mode is unprecedented in Mn(III) for formate and in any transition metal ion for nitrite. Variable-temperature magnetic susceptibility measurements of complexes 1 and 2 indicate the presence of ferromagnetic exchange interactions with J values of 0.0607 cm(-1) (for 1) and 0.0883 cm(-1) (for 2). The ac measurements indicate negligible frequency dependence for 1 whereas compound 2 exhibits a decrease of χ(ac)' and a concomitant increase of χ(ac)'' on elevating frequency around 2 K. This finding is an indication of slow magnetization reversal characteristic of single-chain magnets or spin-glasses. The μ-nitrito-1κO:2κO' bridge seems to be a potentially superior magnetic coupler to the formate bridge for the construction of single-molecule/-chain magnets as its coupling constant is greater and the χ(ac)' and χ(ac)'' show frequency dependence. © The Royal Society of Chemistry 2011

Further aspects of ochratoxin A-cation interactions: complex formation with zinc ions and a novel analytical application of ochratoxin A-magnesium interaction in the HPLC-FLD system.

PubMed

Poór, Miklós; Kuzma, Mónika; Matisz, Gergely; Li, Yin; Perjési, Pál; Kunsági-Máté, Sándor; Kőszegi, Tamás

2014-04-10

Ochratoxin A (OTA) is a mycotoxin produced by different Aspergillus and Penicillium species. Since its mechanism of action is not fully understood yet, it is important to gain further insight into different interactions of OTA at the molecular level. OTA is found worldwide in many foods and drinks. Moreover, it can also be detected in human and animal tissues and body fluids, as well. Therefore, the development of highly sensitive quantitative methods for the determination of OTA is of utmost importance. OTA most likely forms complexes with divalent cations, both in cells and body fluids. In the present study, the OTA-zinc interaction was investigated and compared to OTA-magnesium complex formation using fluorescence spectroscopy and molecular modeling. Our results show that zinc(II) ion forms a two-fold higher stable complex with OTA than magnesium(II) ion. In addition, based on the enhanced fluorescence emission of OTA in its magnesium-bound form, a novel RP-HPLC-fluorescence detector (FLD) method was also established. Our results highlight that the application of magnesium chloride in alkaline eluents results in an approximately two-fold increase in sensitivity using the HPLC-FLD technique.

Formation of methyl formate in comets by irradiation of methanol-bearing ices

NASA Astrophysics Data System (ADS)

Modica, P.; Palumbo, M. E.; Strazzulla, G.

2012-12-01

Methyl formate is a complex organic molecule considered potentially relevant as precursor of biologically active molecules. It has been observed in several astrophysical environments, such as hot cores, hot corinos, and comets. The processes that drive the formation of molecules in cometary ices are poorly understood. In particular it is not yet clear if molecules are directly accreted from the pre-solar nebula to form comets or are formed after accretion. The present work analyzes the possible role of cosmic ion irradiation and radioactive decay in methyl formate formation in methanol-bearing ices. The results indicate that cosmic ion irradiation can account for about 12% of the methyl formate observed in comet Hale-Bopp, while radioactive decay can account for about 6% of this amount. The need of new data coming from earth based and space observational projects as well as from laboratory experiments is outlined.

Focused Ion Beam Microscopy of ALH84001 Carbonate Disks

NASA Technical Reports Server (NTRS)

Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Vali, Hojatollah; Gibson, Everett K., Jr.; Romanek, Christopher S.

2005-01-01

Our aim is to understand the mechanism(s) of formation of carbonate assemblages in ALH84001. A prerequisite is that a detailed characterization of the chemical and physical properties of the carbonate be established. We present here analyses by transmission electron microscopy (TEM) of carbonate thin sections produced by both focused ion beam (FIB) sectioning and ultramicrotomy. Our results suggest that the formation of ALH84001 carbonate assemblages were produced by considerably more complex process(es) than simple aqueous precipitation followed by partial thermal decomposition as proposed by other investigators [e.g., 1-3].

Spectroscopic studies on the interaction of cimetidine drug with biologically significant σ- and π-acceptors

NASA Astrophysics Data System (ADS)

Pandeeswaran, M.; Elango, K. P.

2010-05-01

Spectroscopic studies revealed that the interaction of cimetidine drug with electron acceptors iodine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) resulted through the initial formation of ionic intermediate to charge transfer (CT) complex. The CT-complexes of the interactions have been characterized using UV-vis, 1H NMR, FT-IR and GC-MS techniques. The formation of triiodide ion, I 3-, is further confirmed by the observation of the characteristic bands in the far IR spectrum for non-linear I 3- ion with C s symmetry at 156 and 131 cm -1 assigned to νas(I-I) and νs(I-I) of the I-I bond and at 73 cm -1 due to bending δ(I 3-). The rate of formation of the CT-complexes has been measured and discussed as a function of relative permittivity of solvent and temperature. The influence of relative permittivity of the medium on the rate indicated that the intermediate is more polar than the reactants and this observation was further supported by spectral studies. Based on the spectroscopic results plausible mechanisms for the interaction of the drug with the chosen acceptors were proposed and discussed and the point of attachment of the multifunctional cimetidine drug with these acceptors during the formation of CT-complex has been established.

Lewis acid properties of alumina based catalysts: study by paramagnetic complexes of probe molecules

NASA Astrophysics Data System (ADS)

Fionov, Alexander V.

2002-06-01

Lewis acid properties of LiAl 5O 8/Al 2O 3 (2 wt.% Li) and MgAl 2O 4/Al 2O 3 (3 wt.% Mg) catalysts were studied by EPR of adsorbed probe molecules--anthraquinone and 2,2,6,6-tetramethylpiperidine- N-oxyl (TEMPO). The lesser (in comparison with γ-Al 2O 3) concentration and the strength of Lewis acid sites (LAS) formed on the surface of aluminate layer has been shown. The stability of this layer plays important role in the change of Lewis acid properties during the calcination of modified alumina. The lithium aluminate layer was stable at used calcination temperature, 773 K, meanwhile magnesium aluminate layer observed only at calcination temperature below 723 K. The increase of the calcination temperature to 773 K caused the segregation of MgAl 2O 4 on the surface resulted in the release of alumina surface and recovery of the Lewis acid properties. The differences in the LAS manifestations towards TEMPO and anthraquinone was discussed. The mechanism of the formation of anthraquinone paramagnetic complexes with LAS--three-coordinated aluminum ions--was proposed. This mechanism includes the formation of anthrasemiquinone, and then--anthrasemiquinone ion pair or triple ion. Fragments like -O-Al +-O- play the role of cations in these ion pairs and triple ions. Proposed mechanism can also be applied for the consideration of similar anthraquinone paramagnetic complexes on the surface of gallium oxide containing systems.

Simple method for determining binding energies of fullerene and complex atomic negative ions

NASA Astrophysics Data System (ADS)

Felfli, Zineb; Msezane, Alfred

2017-04-01

A robust potential which embeds fully the vital core polarization interaction has been used in the Regge pole method to explore low-energy electron scattering from C60, Eu and Nb through the total cross sections (TCSs) calculations. From the characteristic dramatically sharp resonances in the TCSs manifesting negative ion formation in these systems, we extracted the binding energies for the C60, Euand Nbanions they are found to be in outstanding agreement with the measured electron affinities of C60, Eu and Nb. Common among these considered systems, including the standard atomic Au is the formation of their ground state negative ions at the second Ramsauer-Townsend (R-T) minima of their TCSs. Indeed, this is a signature of all the fullerenes and complex atoms considered thus far. Shape resonances, R-T minima and binding energies of the resultant anions are presented. This work was supported by U.S. DOE, Basic Energy Sciences, Office of Energy Research.

Complexation of Nickel Ions by Boric Acid or (Poly)borates.

PubMed

Graff, Anais; Barrez, Etienne; Baranek, Philippe; Bachet, Martin; Bénézeth, Pascale

2017-01-01

An experiment based on electrochemical reactions and pH monitoring was performed in which nickel ions were gradually formed by oxidation of a nickel metal electrode in a solution of boric acid. Based on the experimental results and aqueous speciation modeling, the evolution of pH showed the existence of significant nickel-boron complexation. A triborate nickel complex was postulated at high boric acid concentrations when polyborates are present, and the equilibrium constants were determined at 25, 50 and 70 °C. The calculated enthalpy and entropy at 25 °C for the formation of the complex from boric acid and Ni 2+ ions are respectively equal to (65.6 ± 3.1) kJ·mol -1 and (0.5 ± 11.1) J·K -1 ·mol -1 . The results of this study suggest that complexation of nickel ions by borates can significantly enhance the solubility of nickel metal and nickel oxide depending on the concentration of boric acid and pH. First principles calculations were investigated and tend to show that the complex is thermodynamically stable and the nickel cation in solution should interact more strongly with the [Formula: see text] than with boric acid.

Reagent Anions for Charge Inversion of Polypeptide/Protein Cations in the Gas Phase

PubMed Central

He, Min; Emory, Joshua F.; McLuckey, Scott A.

2005-01-01

Various reagent anions capable of converting polypeptide cations to anions via ion/ion reactions have been investigated. The major charge inversion reaction channels include multiple proton transfer and adduct formation. Dianions composed of sulfonate groups as the negative charge carriers show essentially exclusive adduct formation in converting protonated peptides and proteins to anions. Dianions composed of carboxylate groups, on the other hand, show far more charge inversion via multiple proton transfer, with the degree of adduct formation dependent upon both the size of the polypeptide and the spacings between carboxylate groups in the dianion. More highly charged carboxylate-containing anions, such as those derived from carboxylate-terminated polyamidoamine half-generation dendrimers show charge inversion to give anion charges as high in magnitude as −4, with the degree of adduct formation being inversely related to dendrimer generation. All observations can be interpreted on the basis of charge inversion taking place via a long-lived chemical complex. The lifetime of this complex is related to the strengths and numbers of the interactions of the reactants in the complex. Calculations with model systems are fully consistent with sulfonate groups giving rise to more stable complexes. The kinetic stability of the complex can also be affected by the presence of electrostatic repulsion if it is multiply charged. In general, this situation destabilizes the complex and reduces the likelihood for observation of adducts. The findings highlight the characteristics of multiply charged anions that play roles in determining the nature of charge inversion products associated with protonated peptides and proteins. PMID:15889906

On the protein crystal formation as an interface-controlled process with prototype ion-channeling effect.

PubMed

Siódmiak, Jacek; Uher, Jan J; Santamaría-Holek, Ivan; Kruszewska, Natalia; Gadomski, Adam

2007-08-01

A superdiffusive random-walk action in the depletion zone around a growing protein crystal is considered. It stands for a dynamic boundary condition of the growth process and competes steadily with a quasistatic, curvature-involving (thermodynamic) free boundary condition, both of them contributing to interpret the (mainly late-stage) growth process in terms of a prototype ion-channeling effect. An overall diffusion function contains quantitative signatures of both boundary conditions mentioned and indicates whether the new phase grows as an orderly phase or a converse scenario occurs. This situation can be treated in a quite versatile way both numerically and analytically, within a generalized Smoluchowski framework. This study can help in (1) elucidating some dynamic puzzles of a complex crystal formation vs biomolecular aggregation, also those concerning ion-channel formation, and (2) seeing how ion-channel-type dynamics of non-Markovian nature may set properly the pace of model (dis)ordered protein aggregation.

Secondary ion mass spectra of gold super clusters up to 140000 Dalton

NASA Astrophysics Data System (ADS)

Feld, H.; Leute, A.; Rading, D.; Benninghoven, A.; Schmid, G.

1990-03-01

The bombardment of a two-shell gold complex (Au55(PPh3)12Cl6) with 10 keV Xe+-ions results in the formation of secondary ion masses up to 140000 u. These are by far the largest secondary ions observed under primary particle bombardment. The detection and identification of these ions with a Time-Of-Flight Secondary Ion Mass Spectrometer (TOF-SIMS) gives important information about the behavior of naked full-shell clusters. Au13 particles, generated from the Au55 cluster, serve as building blocks for a series of super-clusters up to (Au13)55. The results for keV-ion bombardment are compared to those for MeV-ion bombardment.

Inhibition of precipitation of carbonate apatite by trisodium citrate analysed in base of the formation of chemical complexes in growth solution

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

Prywer, Jolanta, E-mail: jolanta.prywer@p.lodz.pl; Olszynski, Marcin; Mielniczek-Brzóska, Ewa

2015-11-15

Effect of trisodium citrate on the precipitation of carbonate apatite is studied. The experimental series are performed in the solution of artificial urine. The investigations are related to infectious urinary stones formation as carbonate apatite is one of the main components of this kind of stones. To mimic a real infection in urinary tract the aqueous ammonia solution was added to the solution of artificial urine. The spectrophotometric results demonstrate that trisodium citrate increases induction time with respect to carbonate apatite formation and decreases the efficiency of carbonate apatite precipitation. The inhibitory effect of trisodium citrate on the precipitation ofmore » carbonate apatite is explained in base of chemical speciation analysis. Such an analysis demonstrates that the inhibitory effect is mainly related with the fact that trisodium citrate binds Ca{sup 2+} ions and causes the formation of CaCit{sup −} and Ca{sub 10}(PO{sub 4}){sub 6}CO{sub 3} complexes. Trisodium citrate binds Ca{sup 2+} ions in the range of pH from 6 to 9.5 for which carbonate apatite is favored to be formed. - Highlights: • Trisodium citrate (TC) increases induction time of carbonate apatite (CA) formation. • TC decreases the efficiency of CA precipitation. • The inhibitory effect of TC is explained in base of chemical speciation analysis. • The inhibitory effect is mainly related with the fact that TC binds Ca{sup 2+} ions. • TC binds Ca{sup 2+} ions in the range of pH from 6 to 9.5 for which CA is formed.« less

Ultrafast fluxional exchange dynamics in electrolyte solvation sheath of lithium ion battery

PubMed Central

Lee, Kyung-Koo; Park, Kwanghee; Lee, Hochan; Noh, Yohan; Kossowska, Dorota; Kwak, Kyungwon; Cho, Minhaeng

2017-01-01

Lithium cation is the charge carrier in lithium-ion battery. Electrolyte solution in lithium-ion battery is usually based on mixed solvents consisting of polar carbonates with different aliphatic chains. Despite various experimental evidences indicating that lithium ion forms a rigid and stable solvation sheath through electrostatic interactions with polar carbonates, both the lithium solvation structure and more importantly fluctuation dynamics and functional role of carbonate solvent molecules have not been fully elucidated yet with femtosecond vibrational spectroscopic methods. Here we investigate the ultrafast carbonate solvent exchange dynamics around lithium ions in electrolyte solutions with coherent two-dimensional infrared spectroscopy and find that the time constants of the formation and dissociation of lithium-ion···carbonate complex in solvation sheaths are on a picosecond timescale. We anticipate that such ultrafast microscopic fluxional processes in lithium-solvent complexes could provide an important clue to understanding macroscopic mobility of lithium cation in lithium-ion battery on a molecular level. PMID:28272396

Ultrafast fluxional exchange dynamics in electrolyte solvation sheath of lithium ion battery

NASA Astrophysics Data System (ADS)

Lee, Kyung-Koo; Park, Kwanghee; Lee, Hochan; Noh, Yohan; Kossowska, Dorota; Kwak, Kyungwon; Cho, Minhaeng

2017-03-01

Lithium cation is the charge carrier in lithium-ion battery. Electrolyte solution in lithium-ion battery is usually based on mixed solvents consisting of polar carbonates with different aliphatic chains. Despite various experimental evidences indicating that lithium ion forms a rigid and stable solvation sheath through electrostatic interactions with polar carbonates, both the lithium solvation structure and more importantly fluctuation dynamics and functional role of carbonate solvent molecules have not been fully elucidated yet with femtosecond vibrational spectroscopic methods. Here we investigate the ultrafast carbonate solvent exchange dynamics around lithium ions in electrolyte solutions with coherent two-dimensional infrared spectroscopy and find that the time constants of the formation and dissociation of lithium-ion...carbonate complex in solvation sheaths are on a picosecond timescale. We anticipate that such ultrafast microscopic fluxional processes in lithium-solvent complexes could provide an important clue to understanding macroscopic mobility of lithium cation in lithium-ion battery on a molecular level.

Ultrafast fluxional exchange dynamics in electrolyte solvation sheath of lithium ion battery.

PubMed

Lee, Kyung-Koo; Park, Kwanghee; Lee, Hochan; Noh, Yohan; Kossowska, Dorota; Kwak, Kyungwon; Cho, Minhaeng

2017-03-08

Lithium cation is the charge carrier in lithium-ion battery. Electrolyte solution in lithium-ion battery is usually based on mixed solvents consisting of polar carbonates with different aliphatic chains. Despite various experimental evidences indicating that lithium ion forms a rigid and stable solvation sheath through electrostatic interactions with polar carbonates, both the lithium solvation structure and more importantly fluctuation dynamics and functional role of carbonate solvent molecules have not been fully elucidated yet with femtosecond vibrational spectroscopic methods. Here we investigate the ultrafast carbonate solvent exchange dynamics around lithium ions in electrolyte solutions with coherent two-dimensional infrared spectroscopy and find that the time constants of the formation and dissociation of lithium-ion···carbonate complex in solvation sheaths are on a picosecond timescale. We anticipate that such ultrafast microscopic fluxional processes in lithium-solvent complexes could provide an important clue to understanding macroscopic mobility of lithium cation in lithium-ion battery on a molecular level.

Structural, microstructural and electrochemical properties of dispersed-type polymer nanocomposite films

NASA Astrophysics Data System (ADS)

Arya, Anil; Sharma, A. L.

2018-01-01

Free-standing solid polymer nanocomposite (PEO-PVC)  +  LiPF6-TiO2 films have been prepared through a standard solution-cast technique. The improvement in structural, microstructural and electrochemical properties has been observed on the dispersion of nanofiller in polymer salt complex. X-ray diffraction studies clearly reflect the formation of complex formation, as no corresponding salt peak appeared in the diffractograms. The Fourier transform infrared analysis suggested clear and convincing evidence of polymer-ion, ion-ion and polymer-ion-nanofiller interaction. The highest ionic conductivity of the prepared solid polymer electrolyte (SPE) films is ~5  ×  10-5 S cm-1 for 7 wt.% TiO2. The linear sweep voltammetry provides the electrochemical stability window of the prepared SPE films, about ~3.5 V. The ion transference number has been estimated, t ion  =  0.99 through the DC polarization technique. Dielectric spectroscopic studies were performed to understand the ion transport process in polymer electrolytes. All solid polymer electrolytes possess good thermal stability up to 300 °C. Differential scanning calorimetry analysis confirms the decrease of the melting temperature and signal of glass transition temperature with the addition of nanofiller, which indicates the decrease of crystallinity of the polymer matrix. An absolute correlation between diffusion coefficient (D), ion mobility (µ), number density (n), double-layer capacitance (C dl), glass transition temperature, melting temperature (T m), free ion area (%) and conductivity (σ) has been observed. A convincing model to study the role of nanofiller in a polymer salt complex has been proposed, which supports the experimental findings. The prepared polymer electrolyte system with significant ionic conductivity, high ionic transference number, and good thermal and voltage stability could be suggested as a potential candidate as electrolyte cum separator for the fabrication of a rechargeable lithium-ion battery system.

alpha-Lactalbumin species variation, HAMLET formation, and tumor cell death.

PubMed

Pettersson, Jenny; Mossberg, Ann-Kristin; Svanborg, Catharina

2006-06-23

HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a tumoricidal complex of apo alpha-lactalbumin and oleic acid, formed in casein after low pH treatment of human milk. This study examined if HAMLET-like complexes are present in casein from different species and if isolated alpha-lactalbumin from those species can form such complexes with oleic acid. Casein from human, bovine, equine, and porcine milk was separated by ion exchange chromatography and active complexes were only found in human casein. This was not explained by alpha-lactalbumin sequence variation, as purified bovine, equine, porcine, and caprine alpha-lactalbumins formed complexes with oleic acid with biological activity similar to HAMLET. We conclude that structural variation of alpha-lactalbumins does not preclude the formation of HAMLET-like complexes and that natural HAMLET formation in casein was unique to human milk, which also showed the highest oleic acid content.

Studying of kinetics of rear earth ion (REI) nanoscale complex formation by resonant energy transfer

NASA Astrophysics Data System (ADS)

Ignatova, Tetyana; Pristinski, Denis; Rotkin, Slava V.

2011-03-01

We observed formation of nanoscale complexes between multivalent REIs (Tb and Eu) and negatively charged DNA wrapped SWNTs, ionized in the water solution. Foerster Resonance Energy Transfer (FRET) was found to be an ideal method to confirm the complex formation. Because of its high sensitivity and non-destructive characterization approach FRET can be used to trace the kinetics of the complex formation. Strong dependence of SWNT photoluminescence (PL) on the REI concentration was detected and interpreted as a competition between the REI absorption on the SWNTs and subsequent FRET enhanced PL and the SWNT agglomeration followed by PL quenching. We measured the distance between REI and SWNT which appears to be much shorter than the one from their relative concentration in solution. We speculate that Manning condensation of the REIs on the SWNT/DNA surface happens thereby significantly reducing their spacing and making FRET possible.

Thermodynamic Characteristics of Reactions of the Formation of Complexes between Triglycine and Ni2+ Ions in Aqueous Solution

NASA Astrophysics Data System (ADS)

Gorboletova, G. G.; Metlin, A. A.; Bychkova, S. A.

2018-05-01

Thermal effects of reactions of the formation of complexes between Ni(II) and triglycine are determined via direct calorimetry in aqueous solutions at 298.15 K and ionic strengths of 0.2, 0.5, and 1.0 (KNO3). Standard thermodynamic characteristics (Δr H°, Δr G°, Δr S°) of complexing processes in the investigated systems are calculated. The structures of triglycinate complexes NiL+, NiH-1L, NiL2, NiH-2L2- 2, NiL- 3, and NiH-3L4- 3 are introduced to compare the obtained values and data on the thermodynamics of triglycinate complexes of Ni(II).

Equilibrium constant for calcium ion and ascorbate ion.

PubMed

Tsao, C S

1984-02-15

The combination of calcium and ascorbic acid in water at 25 degrees C has been examined by measuring the change of free calcium ion concentration as ascorbate was added in small increment to a solution of calcium. The data show clearly that complex formation between calcium ion and ascorbate ion occurred. At ionic strength mu = 0.1-0.2, the equilibrium constant of Ca++ and the singly-charged ascorbate ion has been measured to be 2.1 M-1. The precision of the result is better than 5% and the accuracy is estimated to be better than 20%. The application of the equilibrium constants is discussed.

Steric and Electronic Effects of Bidentate Phosphine Ligands on Ruthenium(II)-Catalyzed Hydrogenation of Carbon Dioxide.

PubMed

Zhang, Pan; Ni, Shao-Fei; Dang, Li

2016-09-20

The reactivity difference between the hydrogenation of CO2 catalyzed by various ruthenium bidentate phosphine complexes was explored by DFT. In addition to the ligand dmpe (Me2 PCH2 CH2 PMe2 ), which was studied experimentally previously, a more bulky diphosphine ligand, dmpp (Me2 PCH2 CH2 CH2 PMe2 ), together with a more electron-withdrawing diphosphine ligand, PN(Me) P (Me2 PCH2 N(Me) CH2 PMe2 ), have been studied theoretically to analyze the steric and electronic effects on these catalyzed reactions. Results show that all of the most favorable pathways for the hydrogenation of CO2 catalyzed by bidentate phosphine ruthenium dihydride complexes undergo three major steps: cis-trans isomerization of ruthenium dihydride complex, CO2 insertion into the Ru-H bond, and H2 insertion into the ruthenium formate ion. Of these steps, CO2 insertion into the Ru-H bond has the lowest barrier compared with the other two steps in each preferred pathway. For the hydrogenation of CO2 catalyzed by ruthenium complexes of dmpe and dmpp, cis-trans isomerization of ruthenium dihydride complex has a similar barrier to that of H2 insertion into the ruthenium formate ion. However, in the reaction catalyzed by the PN(Me) PRu complex, cis-trans isomerization of the ruthenium dihydride complex has a lower barrier than H2 insertion into the ruthenium formate ion. These results suggest that the steric effect caused by the change of the outer sphere of the diphosphine ligand on the reaction is not clear, although the electronic effect is significant to cis-trans isomerization and H2 insertion. This finding refreshes understanding of the mechanism and provides necessary insights for ligand design in transition-metal-catalyzed CO2 transformation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Divergent Coordination Chemistry: Parallel Synthesis of [2×2] Iron(II) Grid-Complex Tauto-Conformers.

PubMed

Schäfer, Bernhard; Greisch, Jean-François; Faus, Isabelle; Bodenstein, Tilmann; Šalitroš, Ivan; Fuhr, Olaf; Fink, Karin; Schünemann, Volker; Kappes, Manfred M; Ruben, Mario

2016-08-26

The coordination of iron(II) ions by a homoditopic ligand L with two tridentate chelates leads to the tautomerism-driven emergence of complexity, with isomeric tetramers and trimers as the coordination products. The structures of the two dominant [Fe(II) 4 L4 ](8+) complexes were determined by X-ray diffraction, and the distinctness of the products was confirmed by ion-mobility mass spectrometry. Moreover, these two isomers display contrasting magnetic properties (Fe(II) spin crossover vs. a blocked Fe(II) high-spin state). These results demonstrate how the coordination of a metal ion to a ligand that can undergo tautomerization can increase, at a higher hierarchical level, complexity, here expressed by the formation of isomeric molecular assemblies with distinct physical properties. Such results are of importance for improving our understanding of the emergence of complexity in chemistry and biology. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

General Synthesis of Transition-Metal Oxide Hollow Nanospheres/Nitrogen-Doped Graphene Hybrids by Metal-Ammine Complex Chemistry for High-Performance Lithium-Ion Batteries.

PubMed

Chen, Jiayuan; Wu, Xiaofeng; Gong, Yan; Wang, Pengfei; Li, Wenhui; Mo, Shengpeng; Peng, Shengpan; Tan, Qiangqiang; Chen, Yunfa

2018-02-09

We present a general and facile synthesis strategy, on the basis of metal-ammine complex chemistry, for synthesizing hollow transition-metal oxides (Co 3 O 4 , NiO, CuO-Cu 2 O, and ZnO)/nitrogen-doped graphene hybrids, potentially applied in high-performance lithium-ion batteries. The oxygen-containing functional groups of graphene oxide play a prerequisite role in the formation of hollow transition-metal oxides on graphene nanosheets, and a significant hollowing process occurs only when forming metal (Co 2+ , Ni 2+ , Cu 2+ , or Zn 2+ )-ammine complex ions. Moreover, the hollowing process is well correlated with the complexing capacity between metal ions and NH 3 molecules. The significant hollowing process occurs for strong metal-ammine complex ions including Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ ions, and no hollow structures formed for weak and/or noncomplex Mn 2+ and Fe 3+ ions. Simultaneously, this novel strategy can also achieve the direct doping of nitrogen atoms into the graphene framework. The electrochemical performance of two typical hollow Co 3 O 4 or NiO/nitrogen-doped graphene hybrids was evaluated by their use as anodic materials. It was demonstrated that these unique nanostructured hybrids, in contrast with the bare counterparts, solid transition-metal oxides/nitrogen-doped graphene hybrids, perform with significantly improved specific capacity, superior rate capability, and excellent capacity retention. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inhibition of precipitation of carbonate apatite by trisodium citrate analysed in base of the formation of chemical complexes in growth solution

NASA Astrophysics Data System (ADS)

Prywer, Jolanta; Olszynski, Marcin; Mielniczek-Brzóska, Ewa

2015-11-01

Effect of trisodium citrate on the precipitation of carbonate apatite is studied. The experimental series are performed in the solution of artificial urine. The investigations are related to infectious urinary stones formation as carbonate apatite is one of the main components of this kind of stones. To mimic a real infection in urinary tract the aqueous ammonia solution was added to the solution of artificial urine. The spectrophotometric results demonstrate that trisodium citrate increases induction time with respect to carbonate apatite formation and decreases the efficiency of carbonate apatite precipitation. The inhibitory effect of trisodium citrate on the precipitation of carbonate apatite is explained in base of chemical speciation analysis. Such an analysis demonstrates that the inhibitory effect is mainly related with the fact that trisodium citrate binds Ca2+ ions and causes the formation of CaCit- and Ca10(PO4)6CO3 complexes. Trisodium citrate binds Ca2+ ions in the range of pH from 6 to 9.5 for which carbonate apatite is favored to be formed.

Coprecipitation of gold(III) complex ions with manganese(II) hydroxide and their stoichiometric reduction to atomic gold (Au(0)): analysis by Mössbauer spectroscopy and XPS.

PubMed

Yamashita, Mamiko; Ohashi, Hironori; Kobayashi, Yasuhiro; Okaue, Yoshihiro; Kurisaki, Tsutomu; Wakita, Hisanobu; Yokoyama, Takushi

2008-03-01

To elucidate the formation process of precursor of gold-supported manganese dioxide (MnO2), the coprecipitation behavior of [AuCl4-n(OH)n](-) (n=0-4) (Au(III)) complex ions with manganese(II) hydroxide (Mn(OH)2 and the change in their chemical state were examined. The Au(III) complex ions were rapidly and effectively coprecipitated with Mn(OH)(2) at pH 9. According to the Mössbauer spectra for gold (Au) coprecipitated with Mn(OH)2, below an Au content of 60 wt% in the coprecipitates, all of the coprecipitated Au existed in the atomic state (Au(0)), while, above an Au content of 65 wt%, part of the gold existed in the Au(III) state, and the proportion increased with increasing coprecipitated Au content. Based on the results of X-ray photoelectron spectroscopy, Mn(II) in Mn(OH)2 converted to Mn(IV) in conjunction with coprecipitation of Au(III) complex ions. These results indicate that the rapid stoichiometric reduction of Au(III) to Au(0) is caused by electron transfer from Mn(II) in Mn(OH)2 to the Au(III) complex ion through an Mn-O-Au bond.

A peroxynitrite complex of copper: formation from a copper-nitrosyl complex, transformation to nitrite and exogenous phenol oxidative coupling or nitration.

PubMed

Park, Ga Young; Deepalatha, Subramanian; Puiu, Simona C; Lee, Dong-Heon; Mondal, Biplab; Narducci Sarjeant, Amy A; del Rio, Diego; Pau, Monita Y M; Solomon, Edward I; Karlin, Kenneth D

2009-11-01

Reaction of nitrogen monoxide with a copper(I) complex possessing a tridentate alkylamine ligand gives a Cu(I)-(*NO) adduct, which when exposed to dioxygen generates a peroxynitrite (O=NOO(-))-Cu(II) species. This undergoes thermal transformation to produce a copper(II) nitrito (NO(2) (-)) complex and 0.5 mol equiv O(2). In the presence of a substituted phenol, the peroxynitrite complex effects oxidative coupling, whereas addition of chloride ion to dissociate the peroxynitrite moiety instead leads to phenol ortho nitration. Discussions include the structures (including electronic description) of the copper-nitrosyl and copper-peroxynitrite complexes and the formation of the latter, based on density functional theory calculations and accompanying spectroscopic data.

Metal ion influence on eumelanin fluorescence and structure.

PubMed

Sutter, Jens-Uwe; Birch, David J S

2014-04-10

Melanin has long been thought to have an unworkably weak and complex fluorescence, but here we study its intrinsic fluorescence in order to demonstrate how metal ions can be used to control the rate of formation, constituents and structure of eumelanin formed from the well-known laboratory auto-oxidation of 3,4-dihydroxy-L-phenylalanine (L-DOPA). The effect on eumelanin absorption and fluorescence of a range of solvated metal ions is reported including Cu, Zn, Ni, Na and K. Monovalent cations and Zn have little effect, but the effect of transition metal cations can be considerable. For example, at pH 10, copper ions are shown to accelerate the onset of eumelanin formation, but not the rate of formation once it commences, and simplify the usual complex structure and intrinsic fluorescence of eumelanin in a way that is consistent with an increased abundance of 5,5-dihydroxyindole-2-carboxylic acid (DHICA). The presence of a dominant 6 ns fluorescence decay time at 480 nm, when excited at 450 nm describes a distinct photophysical species, which we tentatively assign to small oligomers. Copper is well-known to normally quench fluorescence, but increasing amounts of copper surprisingly leads to an increase in the fluorescence decay time of eumelanin, while reducing the fluorescence intensity, suggesting copper modification of the excited state. Such results have bearing on diverse areas. The most accepted morphology for melanin is that of a graphite-like sheet structure, and one which readily binds metal ions, an interaction that is thought to have an important, though as yet unclear bearing on several areas of medicine including neurology. There is also increasing interest in bio-mimicry by preparing and labelling sheet structures with metal ions for new electronic and photonic materials.

Metal ion influence on eumelanin fluorescence and structure

NASA Astrophysics Data System (ADS)

Sutter, Jens-Uwe; Birch, David J. S.

2014-06-01

Melanin has long been thought to have an unworkably weak and complex fluorescence, but here we study its intrinsic fluorescence in order to demonstrate how metal ions can be used to control the rate of formation, constituents and structure of eumelanin formed from the well-known laboratory auto-oxidation of 3,4-dihydroxy-L-phenylalanine (L-DOPA). The effect on eumelanin absorption and fluorescence of a range of solvated metal ions is reported including Cu, Zn, Ni, Na and K. Monovalent cations and Zn have little effect, but the effect of transition metal cations can be considerable. For example, at pH 10, copper ions are shown to accelerate the onset of eumelanin formation, but not the rate of formation once it commences, and simplify the usual complex structure and intrinsic fluorescence of eumelanin in a way that is consistent with an increased abundance of 5,5-dihydroxyindole-2-carboxylic acid (DHICA). The presence of a dominant 6 ns fluorescence decay time at 480 nm, when excited at 450 nm describes a distinct photophysical species, which we tentatively assign to small oligomers. Copper is well-known to normally quench fluorescence, but increasing amounts of copper surprisingly leads to an increase in the fluorescence decay time of eumelanin, while reducing the fluorescence intensity, suggesting copper modification of the excited state. Such results have bearing on diverse areas. The most accepted morphology for melanin is that of a graphite-like sheet structure, and one which readily binds metal ions, an interaction that is thought to have an important, though as yet unclear bearing on several areas of medicine including neurology. There is also increasing interest in bio-mimicry by preparing and labelling sheet structures with metal ions for new electronic and photonic materials.

Formation of Wear Resistant Steel Surfaces by Plasma Immersion Ion Implantation

NASA Astrophysics Data System (ADS)

Mändl, S.; Rauschenbach, B.

2003-08-01

Plasma immersion ion implantation (PIII) is a versatile and fast method for implanting energetic ions into large and complex shaped three-dimensional objects where the ions are accelerated by applying negative high voltage pulses to a substrate immersed in a plasma. As the line-of-sight restrictions of conventional implanters are circumvented, it results in a fast and cost-effective technology. Implantation of nitrogen at 30 - 40 keV at moderate temperatures of 200 - 400 °C into steel circumvents the diminishing thermal nitrogen activation encountered, e.g., in plasma nitriding in this temperature regime, thus enabling nitriding of additional steel grades. Nitride formation and improvement of the mechanical properties after PIII are presented for several steel grades, including AISI 316Ti (food industry), AISI D2 (used for bending tools) and AISI 1095 (with applications in the textile industry).

Extractive Spectrophotometric Methods for the Determination of Zolmitriptan in Bulk Drug and Pharmaceutical Formulation Using Bromocresol Green

NASA Astrophysics Data System (ADS)

Prashanth, K. N.; Swamy, N.; Basavaiah, K.

2013-11-01

Considering the basic property of zolmitriptan (ZMT) to generate ion-pairs with sulfonephthalein dyes two methods have been developed for its assay in bulk drug and dosage form. The first method (method A) is based on the formation of a colored ion-pair complex (1:1 drug:dye) of ZMT with bromocresol green (BCG) at pH 4.20 ± 0.01 and extraction of the complex into chloroform followed by measurement of the yellow ion-pair complex at 435 nm. In the second method (method B), the drug-dye ion-pair complex was treated with ethanolic potassium hydroxide in ethanolic medium and the resulting base form of the dye was measured at 630 nm. Beer's law was obeyed in the concentration range of 0.8-18.0 and 0.08-1.4 μg/ml for method A and B, respectively, and the corresponding molar absorptivity values were 1.50ṡ104 and 1.52ṡ105 l/(molṡcm). The Sandell sensitivity values were 0.0191 and 0.0019 μg/cm2 for method A and method B, respectively. The stoichiometry of the ion-pair complex formed between the drug and dye (1:1) was determined by Job's continuous variation method and the stability constant of the complex was also calculated. The proposed method was successfully extended to dosage form (tablets).

Studies on the weak interactions and CT complex formations between chloranilic acid, 2,3-dichloro-5,6-dicyano-p-benzoquinone, tetracyanoethylene and papaverine in acetonitrile and their thermodynamic properties, theoretically, spectrophotometrically aided by FTIR

NASA Astrophysics Data System (ADS)

Datta, Asim Sagar; (Chattaraj), Seema Bagchi; Chakrabortty, Ashutosh; Lahiri, Sujit Chandra

2015-07-01

Spectrophotometric, FTIR and theoretical studies of the charge-transfer complexes between mild narcotic drug papaverine and the acceptors chloranilic acid (Cl-A), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and tetracyanoethylene (TCNE) in acetonitrile, their association constants, thermodynamic (ΔG0, ΔH0 and ΔS0) and other related properties had been described. Papaverine was found to form colored charge-transfer complexes with Cl-A, DDQ and TCNE in acetonitrile. The absorption maxima of the complexes were 518.5, 584.0 and 464.0 nm for Cl-A complex, DDQ complex, and TCNE complex respectively. The compositions of the papaverine complexes were determined to be 1:1 from Job's method of continuous variation. Solid complexes formed between papaverine and the acceptors were isolated. Comparison of the FTIR spectra of the solid complexes between papaverine and the acceptors and their constituents showed considerable shift in absorption peaks, changes in intensities of the peaks and formation of the new bands on complexation. However, no attempt has been made to purify the complexes and study the detailed spectra both theoretically and experimentally. The energies hνCT of the charge-transfer complexes were compared with the theoretical values of hνCT of the complexes obtained from HOMO and LUMO of the donor and the acceptors. The reasons for the differences in hνCT values were explained. Density function theory was used for calculation. hνCT (experimental) values of the transition energies of the complexes in acetonitrile differed from hνCT (theoretical) values. IDV value of papaverine was calculated. Charge-transfer complexes were assumed to be partial electrovalent compounds with organic dative ions D+ and A- (in the excited state) and attempts had been made to correlate the energy changes for the formation of the complexes with the energy changes for the formation of electrovalent compounds between M+ and X- ions.

Ion energy/momentum effects during ion assisted growth of niobium nitride films

NASA Astrophysics Data System (ADS)

Klingenberg, Melissa L.

The research described herein was performed to better understand and discern ion energy vs. ion momentum effects during ion beam assisted (IBAD) film growth and their effects on residual stress, crystalline structure, morphology, and composition, which influence film tribological properties. NbxN y was chosen for this research because it is a refractory material that can possess a large number of crystalline structures, and it has been found to have good tribological properties. To separate the effects of momentum transfer per arriving atom (p/a), which considers bombarding species mass, energy, and ion-to-atom transport ratio, from those of energy deposition per arriving atom (E/a), a mass independent parameter, different inert ion beams (krypton, argon, and neon) were used to create a matrix of coatings formed using similar energy deposition, but different momentum transfer and vice versa. Deposition was conducted in a research-scale IBAD system using electron beam evaporation, a radio frequency ion source, and a neutral nitrogen gas backfill. Films were characterized using x-ray diffraction, atomic force microscopy, Rutherford backscattering spectrometry, and residual stress analysis. Direct and quantifiable effects of bombardment were observed; however, energy deposition and momentum transfer effects could not be completely separated, confirming that thin film processes are complex. Complexities arose from ion-specific interactions (ion size, recoil energy, per cent reflected neutrals, Penning ionization, etc.) and chemistry effects that are not considered by the simple models. Overall, it can be stated that bombardment promoted nitride formation, nanocrystallinity, and compressive stress formation; influenced morphology (which influenced post-deposition oxygen uptake) and stress evolution; increased lattice parameter; modified crystalline phase and texture; and led to inert gas incorporation. High stress levels correlated strongly with material disorder and closed-structured morphologies.

Cd(II) and Pb(II) complexes of the polyether ionophorous antibiotic salinomycin

PubMed Central

2011-01-01

Background The natural polyether ionophorous antibiotics are used for the treatment of coccidiosis in poultry and ruminants. They are effective agents against infections caused by Gram-positive microorganisms. On the other hand, it was found that some of these compounds selectively bind lead(II) ions in in vivo experiments, despite so far no Pb(II)-containing compounds of defined composition have been isolated and characterized. To assess the potential of polyether ionophores as possible antidotes in the agriculture, a detailed study on their in vitro complexation with toxic metal ions is required. In the present paper we report for the first time the preparation and the structure elucidation of salinomycin complexes with ions of cadmium(II) and lead(II). Results New metal(II) complexes of the polyether ionophorous antibiotic salinomycin with Cd(II) and Pb(II) ions were prepared and structurally characterized by IR, FAB-MS and NMR techniques. The spectroscopic information and elemental analysis data reveal that sodium salinomycin (SalNa) undergoes a reaction with heavy metal(II) ions to form [Cd(Sal)2(H2O)2] (1) and [Pb(Sal)(NO3)] (2), respectively. Abstraction of sodium ions from the cavity of the antibiotic is occurring during the complexation reaction. Salinomycin coordinates with cadmium(II) ions as a bidentate monoanionic ligand through the deprotonated carboxylic moiety and one of the hydroxyl groups to yield 1. Two salinomycin anions occupy the equatorial plane of the Cd(II) center, while two water molecules take the axial positions of the inner coordination sphere of the metal(II) cation. Complex 2 consists of monoanionic salinomycin acting in polydentate coordination mode in a molar ratio of 1: 1 to the metal ion with one nitrate ion for charge compensation. Conclusion The formation of the salinomycin heavy metal(II) complexes indicates a possible antidote activity of the ligand in case of chronic/acute intoxications likely to occur in the stock farming. PMID:21906282

Zeolite-encapsulated Co(II), Mn(II), Cu(II) and Cr(III) salen complexes as catalysts for efficient selective oxidation of benzyl alcohol

NASA Astrophysics Data System (ADS)

Li, F. H.; Bi, H.; Huang, D. X.; Zhang, M.; Song, Y. B.

2018-01-01

Co(II), Mn(II), Cu(II) and Cr(III) salen type complexes were synthesized in situ in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. Data of characterization indicates the formation of metal salen complexes in the pores without affecting the zeolite framework structure, the absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activity results show that Cosalcyen Y exhibited higher catalytic activity in the water phase selective oxidation of benzyl alcohol, which could be attributed to their geometry and the steric environment of the metal actives sites.

Inhibitory effect of phosphates on magnesium lactate efflorescence formation in dry-fermented sausages.

PubMed

Walz, Felix H; Gibis, Monika; Schrey, Pia; Herrmann, Kurt; Reichert, Corina L; Hinrichs, Jörg; Weiss, Jochen

2017-10-01

This study aimed to prevent the phenomena of efflorescence formation on the surface of dry fermented sausages due to the complexation of efflorescence forming cations with phosphates. Efflorescence formation is a critical issue constituting a major quality defect, especially of dry fermented sausages. Different phosphates (di- and hexametaphosphate) were added (3.0g/kg) to the sausage batter. As a hypothesis, these additives should complex with one of the main efflorescence-causing substances such as magnesium. The formation of efflorescences was determined for dry fermented sausages without phosphate addition, with diphosphate, or hexametaphosphate addition during 8weeks of storage under modified atmosphere. The visual analyses of the sausage surface revealed high amounts of efflorescences for the control (42.2%) and for the sausages with added diphosphate (40.9%), whereas the sausages containing hexametaphosphate had significantly reduced amounts of efflorescence formation, showing only 11.9% efflorescences after 8weeks of storage. This inhibition was a result of strong complexation of hexametaphosphate with magnesium ions, thus preventing the diffusion of magnesium towards the sausage surface. This can be explained by the magnesium content on the sausage surface that increased by 163.9, 127.8, and 52.8% for the sausages without phosphate, diphosphate, and hexametaphosphate addition, respectively. The mass transport of lactate and creatine was not affected by phosphate addition. Isothermal titration calorimetry confirmed that, theoretically, 4.5g/kg of diphosphate or 2.8g/kg hexametaphosphate are required to complex 0.2g/kg magnesium ions naturally occurring in dry fermented sausages and, thus, the chosen overall phosphate concentration of 3.0g/kg was enough when adding hexametaphosphate, but not for diphosphate, to inhibit the efflorescence formation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of variable chemical conditions on EDTA-enhanced transport of metal ions in mildly acidic groundwater

USGS Publications Warehouse

Kent, D.B.; Davis, J.A.; Joye, J.L.; Curtis, G.P.

2008-01-01

Adsorption of Ni and Pb on aquifer sediments from Cape Cod, Massachusetts, USA increased with increasing pH and metal-ion concentration. Adsorption could be described quantitatively using a semi-mechanistic surface complexation model (SCM), in which adsorption is described using chemical reactions between metal ions and adsorption sites. Equilibrium reactive transport simulations incorporating the SCMs, formation of metal-ion-EDTA complexes, and either Fe(III)-oxyhydroxide solubility or Zn desorption from sediments identified important factors responsible for trends observed during transport experiments conducted with EDTA complexes of Ni, Zn, and Pb in the Cape Cod aquifer. Dissociation of Pb-EDTA by Fe(III) is more favorable than Ni-EDTA because of differences in Ni- and Pb-adsorption to the sediments. Dissociation of Ni-EDTA becomes more favorable with decreasing Ni-EDTA concentration and decreasing pH. In contrast to Ni, Pb-EDTA can be dissociated by Zn desorbed from the aquifer sediments. Variability in adsorbed Zn concentrations has a large impact on Pb-EDTA dissociation.

Radiochemical study of reactions of alkyl cations with amines. I. Reactions of methyl and sec-butyl cations with diethylamine

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

Ignat`ev, I.S.; Kochina, T.A.; Nefedov, V.D.

1995-08-10

Ion-molecular gas-phase reactions of free methyl and sec-butyl cations with diethylamine were studied. These reactions proceed via two competing pathways involving formation of a condensation complex or a proton-transfer complex, the latter process predominating. 32 refs., 1 tab.

Struvite formation and decomposition characteristics for ammonia and phosphorus recovery: A review of magnesium-ammonia-phosphate interactions.

PubMed

Tansel, Berrin; Lunn, Griffin; Monje, Oscar

2018-03-01

Struvite (MgNH 4 PO 4 ·6H 2 O) forms in aqueous systems with high ammonia and phosphate concentrations. However, conditions that result into struvite formation are highly dependent on the ionic compositions, temperature, pH, and ion speciation characteristics. The primary ions involved in struvite formation have complex interactions and can form different crystals depending on the ionic levels, pH and temperature. Struvite as well as struvite analogues (with substitution of monovalent cations for NH 4 + or divalent cations for Mg 2+ ) as well as other crystals can form simultaneously and result in changes in crystal morphology during crystal growth. This review provides the results from experimental and theoretical studies on struvite formation and decomposition studies. Characteristics of NH 4 + or divalent cations for Mg 2+ were evaluated in comparison to monovalent and divalent ions for formation of struvite and its analogues. Struvite crystals forming in wastewater systems are likely to contain crystals other than struvite due to ionic interactions, pH changes, temperature effects and clustering of ions during nucleation and crystal growth. Decomposition of struvite occurs following a series of reactions depending on the rate of heating, temperature and availability of water during heating. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evidence for the dissolution of molybdenum during tribocorrosion of CoCrMo hip implants in the presence of serum protein.

PubMed

Simoes, Thiago A; Bryant, Michael G; Brown, Andy P; Milne, Steven J; Ryan, Mary; Neville, Anne; Brydson, Rik

2016-11-01

We have characterized CoCrMo, Metal-on-Metal (MoM) implant, wear debris particles and their dissolution following cycling in a hip simulator, and have related the results to the tribocorrosion of synthetic wear debris produced by milling CoCrMo powders in solutions representative of environments in the human body. Importantly, we have employed a modified ICP-MS sample preparation procedure to measure the release of ions from CoCrMo alloys during wear simulation in different media; this involved use of nano-porous ultrafilters which allowed complete separation of particles from free ions and complexes in solution. As a result, we present a new perspective on the release of metal ions and formation of metal complexes from CoCrMo implants. The new methodology enables the mass balance of ions relative to complexes and particles during tribocorrosion in hip simulators to be determined. A much higher release of molybdenum ions relative to cobalt and chromium has been measured. The molybdenum dissolution was enhanced by the presence of bovine serum albumin (BSA), possibly due to the formation of metal-protein complexes. Overall, we believe that the results could have significant implications for the analysis and interpretation of metal ion levels in fluids extracted from hip arthroplasty patients; we suggest that metal levels, including molybdenum, be analysed in these fluids using the protocol described here. We have developed an important new protocol for the analysis of metal ion levels in fluids extracted from hip implant patients and also hip simulators. Using this procedure, we present a new perspective on the release of metal ions from CoCrMo alloy implants, revealing significantly lower levels of metal ion release during tribocorrosion in hip simulators than previously thought, combined with the release of much higher percentages of molybdenum ions relative to cobalt and chromium. This work is of relevance, both from the perspective of the fundamental science and study of metal-protein interactions, enabling understanding of the ongoing problem associated with the biotribocorrosion and the link to inflammation associated with Metal-on-Metal (MoM) hip implants made from CoCrMo alloys. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Dependence of the enthalpies of formation of glycylglycinate complexes of nickel(II) on the composition of a mixed water-dimethylsulfoxide solvent

NASA Astrophysics Data System (ADS)

Naumov, V. V.; Kovaleva, Yu. A.; Isaeva, V. A.; Usacheva, T. R.; Sharnin, V. A.

2014-06-01

The heat effects of the complexation reactions of nickel(II) with a glycylglycinate ion in a water-dimethylsulfoxide solvent in a range of compositions of 0.00-0.60 molar parts of dimethylsulfoxide (DMSO) (an ionic strength of 0.1 was maintained using sodium perchlorate) were determined by means of calorimetry at 298.15 K. It is established that the exothermicity of complexation reactions rises by the first two steps and falls upon the addition of a third glycylglycinate anion with an increase in the concentration of DMSO. It is shown that the formation of mono- and bis-glycylglycinate complexes of nickel(II) in a water-DMSO solvent is determined mostly by the enthalpic contribution. It is concluded that the formation of tris-ligand complexes is more associated with the entropic contribution.

Synthesis and characterization of the tetranuclear iron(III) complex of a new asymmetric multidentate ligand. A structural model for purple acid phosphatases.

PubMed

Boudalis, Athanassios K; Aston, Robyn E; Smith, Sarah J; Mirams, Ruth E; Riley, Mark J; Schenk, Gerhard; Blackman, Allan G; Hanton, Lyall R; Gahan, Lawrence R

2007-11-28

The ligand, 2-((2-hydroxy-5-methyl-3-((pyridin-2-ylmethylamino)methyl)benzyl)(2-hydroxybenzyl)amino)acetic acid (H(3)HPBA), which contains a donor atom set that mimics that of the active site of purple acid phosphatase is described. Reaction of H(3)HPBA with iron(III) or iron(II) salts results in formation of the tetranuclear complex, [Fe(4)(HPBA)(2)(OAc)(2)(mu-O)(mu-OH)(OH(2))(2)]ClO(4) x 5H(2)O. X-Ray structural analysis reveals the cation consists of four iron(III) ions, two HPBA(3-) ligands, two bridging acetate ligands, a bridging oxide ion and a bridging hydroxide ion. Each binucleating HPBA(3-) ligand coordinates two structurally distinct hexacoordinate iron(III) ions. The two metal ions coordinated to a HPBA(3-) ligand are linked to the two iron(III) metal ions of a second, similar binuclear unit by intramolecular oxide and hydroxide bridging moieties to form a tetramer. The complex has been further characterised by elemental analysis, mass spectrometry, UV-vis and MCD spectroscopy, X-ray crystallography, magnetic susceptibility measurements and variable-temperature Mössbauer spectroscopy.

Characterization of Actinides Complexed to Nuclear Fuel Constituents Using ESI-MS.

PubMed

McDonald, Luther W; Campbell, James A; Vercouter, Thomas; Clark, Sue B

2016-03-01

Electrospray ionization-mass spectrometry (ESI-MS) was tested for its use in monitoring spent nuclear fuel (SNF) constituents including U, Pu, dibutyl phosphate (DBP), and tributyl phosphate (TBP). Both positive and negative ion modes were used to evaluate the speciation of U and Pu with TBP and DBP. Furthermore, apparent stability constants were determined for U complexed to TBP and DBP. In positive ion mode, TBP produced a strong signal with and without complexation to U or Pu, but, in negative ion mode, no TBP, U-TBP, or Pu-TBP complexes were observed. Apparent stability constants were determined for [UO2(NO3)2(TBP)2], [UO2(NO3)2(H2O)(TBP)2], and [UO2(NO3)2(TBP)3]. In contrast DBP, U-DBP, and Pu-DBP complexes were observed in both positive and negative ion modes. Apparent stability constants were determined for the species [UO2(DBP)], [UO2(DBP)3], and [UO2(DBP)4]. Analyzing mixtures of U or Pu with TBP and DBP yielded the formation of ternary complexes whose stoichiometry was directly related to the ratio of TBP to DBP. The ESI-MS protocols used in this study will further demonstrate the utility of ESI-MS and its applicability to process control monitoring in SNF reprocessing facilities.

Complex chromatid-isochromatid exchanges following irradiation with heavy ions?

PubMed

Loucas, B D; Eberle, R L; Durante, M; Cornforth, M N

2004-01-01

We describe a peculiar and relatively rare type of chromosomal rearrangement induced in human peripheral lymphocytes that were ostensibly irradiated in G(0) phase of the cell cycle by accelerated heavy ions, and which, to the best of our knowledge, have not been previously described. The novel rearrangements which were detected using mFISH following exposure to 500 MeV/nucleon and 5 GeV/n 56Fe particles, but were not induced by either 137Cs gamma rays or 238Pu alpha particles, can alternatively be described as either complex chromatid-isochromatid or complex chromatid-chromosome exchanges. Different mechanisms potentially responsible for their formation are discussed. Copyright 2003 S. Karger AG, Basel

A GAS-PHASE FORMATION ROUTE TO INTERSTELLAR TRANS-METHYL FORMATE

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

Cole, Callie A.; Wehres, Nadine; Yang Zhibo

2012-07-20

The abundance of methyl formate in the interstellar medium has previously been underpredicted by chemical models. Additionally, grain surface chemistry cannot account for the relative abundance of the cis- and trans-conformers of methyl formate, and the trans-conformer is not even formed at detectable abundance on these surfaces. This highlights the importance of studying formation pathways to methyl formate in the gas phase. The rate constant and branching fractions are reported for the gas-phase reaction between protonated methanol and formic acid to form protonated trans-methyl formate and water as well as adduct ion: Rate constants were experimentally determined using a flowingmore » afterglow-selected ion flow tube apparatus at 300 K and a pressure of 530 mTorr helium. The results indicate a moderate overall rate constant of (3.19 {+-} 0.39) Multiplication-Sign 10{sup -10} cm{sup 3} s{sup -1} ({+-} 1{sigma}) and an average branching fraction of 0.05 {+-} 0.04 for protonated trans-methyl formate and 0.95 {+-} 0.04 for the adduct ion. These experimental results are reinforced by ab initio calculations at the MP2(full)/aug-cc-pVTZ level of theory to examine the reaction coordinate and complement previous density functional theory calculations. This study underscores the need for continued observational studies of trans-methyl formate and for the exploration of other gas-phase formation routes to complex organic molecules.« less

Sensitive and selective spectrophotometric assay of piroxicam in pure form, capsule and human blood serum samples via ion-pair complex formation.

PubMed

Alizadeh, Nina; Keyhanian, Fereshteh

2014-09-15

A simple, accurate and highly sensitive spectrophotometric method has been developed for the rapid determination of piroxicam (PX) in pure and pharmaceutical formulations. The proposed method involves formation of stable yellow colored ion-pair complexes of the amino derivative (basic nitrogen) of PX with three sulphonphthalein acid dyes namely; bromocresol green (BCG), bromothymol blue (BTB), bromophenol blue (BPB) in acidic medium. The colored species exhibited absorption maxima at 438, 429 and 432 nm with molar absorptivity values of 9.400×10(3), 1.218×10(3) and 1.02×10(4) L mol(-1) cm(-1) for PX-BCG, PX-BTB and PX-BPB complexes, respectively. The effect of optimum conditions via acidity, reagent concentration, time and solvent were studied. The reactions were extremely rapid at room temperature and the absorbance values remained constant for 48h. Beer's law was obeyed with a good correlation coefficient in the concentration ranges 1-100 μg mL(-1) for BCG, BTB complexes and 1-95 μg mL(-1) for BPB complex. The composition ratio of the ion-pair complexes were found to be 1:1 in all cases as established by Job's method. No interference was observed from common additives and excipients which may be present in the pharmaceutical preparations. The proposed method was successfully applied for the determination of PX in capsule and human blood serum samples with good accuracy and precision. Copyright © 2014 Elsevier B.V. All rights reserved.

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with Fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry.

PubMed

Pasilis, Sofie; Somogyi, Arpád; Herrmann, Kristin; Pemberton, Jeanne E

2006-02-01

Electrospray ionization (ESI) of uranyl nitrate solutions generates a wide variety of positively and negatively charged ions, including complex adducts of uranyl ions with methoxy, hydroxy, and nitrate ligands. In the positive ion mode, ions detected by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry are sensitive to instrumental tuning parameters such as quadrupole operating frequency and trapping time. Positive ions correspond to oligomeric uranyl nitrate species that can be characterized as having a general formula of [(UO(2))(n)(A)(m)(CH(3)OH)(s)](+) or [(UO(2))(n)(O)(A)(m)(CH(3)OH)(s)](+) with n = 1-4, m = 1-7, s = 0 or 1, and A = OH, NO(3), CH(3)O or a combination of these, although the formation of NO(3)-containing species is preferred. In the negative ion mode, complexes of the form [(UO(2))(NO(3))(m)](-) (m = 1-3) are detected, although the formation of the oxo-containing ions [(UO(2))(O)(n)(NO(3))(m)](-) (n = 1-2, m = 1-2) and the hydroxy-containing ions [(UO(2))(OH)(n)(NO(3))(m)](-) (n = 1-2, m = 0-1) are also observed. The extent of coordinative unsaturation of both positive and negative ions can be determined by ligand association/exchange and H/D exchange experiments using D(2)O and CD(3)OD as neutral reaction partners in the gas-phase. Positive ions are of varying stability and reactivity and may fragment extensively upon collision with D(2)O, CD(3)OD and N(2) in sustained off-resonance irradiation/collision-induced dissociation (SORI-CID) experiments. Electron-transfer reactions, presumably occurring during electrospray ionization but also in SORI-CID, can result in reduction of U(VI) to U(V) and perhaps even U(IV).

The kinetics of lanthanide complexation by EDTA and DTPA in lactate media.

PubMed

Nash, K L; Brigham, D; Shehee, T C; Martin, A

2012-12-28

The interaction of trivalent lanthanide and actinide cations with polyaminopolycarboxylic acid complexing agents in lactic acid buffer systems is an important feature of the chemistry of the TALSPEAK process for the separation of trivalent actinides from lanthanides. To improve understanding of metal ion coordination chemistry in this process, the results of an investigation of the kinetics of lanthanide complexation by ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) and diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA) in 0.3 M lactic acid/0.3 M ionic strength solution are reported. Progress of the reaction was monitored using the distinctive visible spectral changes attendant to lanthanide complexation by the colorimetric indicator ligand Arsenazo III, which enables the experiment but plays no mechanistic role. Under the conditions of these experiments, the reactions occur in a time regime suitable for study by stopped-flow spectrophotometric techniques. Experiments have been conducted as a function of EDTA/DTPA ligand concentration, total lactic acid concentration, and pH. The equilibrium perturbation reaction proceeds as a first order approach to equilibrium over a wide range of conditions, allowing the simultaneous determination of complex formation and dissociation rate constants. The rate of the complexation reaction has been determined for the entire lanthanide series (except Pm(3+)). The predominant pathway for lanthanide-EDTA and lanthanide-DTPA dissociation is inversely dependent on the total lactate concentration; the complex formation reaction demonstrates a direct dependence on [H(+)]. Unexpectedly, the rate of the complex formation reaction is seen in both ligand systems to be fastest for Gd(3+). Correlation of these results indicates that in 0.3 M lactate solutions the exchange of lanthanide ions between lactate complexes and the polyaminopolycarboxylate govern the process.

Characterization of surface complexes in enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Roy, D.; Furtak, T. E.

1984-11-01

An indicator molecule, para-nitrosodimethylanaline (p-NDMA), has been used to study the chemical nature of surface complexes involving the active site for SERS in the electrochemical environment. We present evidence for positively charged Ag atoms stabilized by coadsorbed Cl- ions as the primary sites which are produced during the oxidation reduction cycle treatment of an Ag electrode. Depending on the relative number of Cl- ions which influence the Ag site the active site demonstrates a greater or lesser electron accepting character toward p-NDMA. This character is influenced by the applied voltage and by the presence of Tl+ ions in the bulk of the solution near the surface. As in previously studied systems p-NDMA/Cl-/Ag complexes demonstrate charge transfer excitation which in this case is from the p-NDMA to the Ag site. These results further solidify the importance of complex formation in electrochemical SERS and suggest that caution should be applied when using SERS as a quantitative measure of surface coverage.

Unusual Complex Formation and Chemical Reaction of Haloacetate Anion on the Exterior Surface of Cucurbit[6]uril in the Gas Phase

NASA Astrophysics Data System (ADS)

Choi, Tae Su; Ko, Jae Yoon; Heo, Sung Woo; Ko, Young Ho; Kim, Kimoon; Kim, Hugh I.

2012-10-01

Noncovalent interactions of cucurbit[6]uril (CB[6]) with haloacetate and halide anions are investigated in the gas phase using electrospray ionization ion mobility mass spectrometry. Strong noncovalent interactions of monoiodoacetate, monobromoacetate, monochloroacetate, dichloroacetate, and trichloroacetate on the exterior surface of CB[6] are observed in the negative mode electrospray ionization mass spectra. The strong binding energy of the complex allows intramolecular SN2 reaction of haloacetate, which yields externally bound CB[6]-halide complex, by collisional activation. Utilizing ion mobility technique, structures of exteriorly bound CB[6] complexes of haloacetate and halide anions are confirmed. Theoretically determined low energy structures using density functional theory (DFT) further support results from ion mobility studies. The DFT calculation reveals that the binding energy and conformation of haloacetate on the CB[6] surface affect the efficiency of the intramolecular SN2 reaction of haloacetate, which correlate well with the experimental observation.

Ground-State Structure of the Proton-Bound Formate Dimer by Cold-Ion Infrared Action Spectroscopy.

PubMed

Thomas, Daniel; Marianski, Mateusz; Mucha, Eike; Meijer, Gerard; Johnson, Mark A; von Helden, Gert

2018-06-19

The proton-bound dicarboxylate motif, RCOO-·H+·-OOCR, is a prevalent chemical configuration found in many condensed phase systems. We study the archetypal proton-bound formate dimer, HCOO-·H+·-OOCH, utilizing cold-ion infrared action spectroscopy in the photon energy range of 400-1800 cm-1. The spectrum obtained at ~0.4 K utilizing action spectroscopy of ions captured in helium nanodroplets is compared to that measured at ~10 K by photodissociation of Ar-ion complexes. Similar band patterns are obtained by the two techniques that are consistent with calculations for a C2 symmetry structure with a proton shared equally between the two formate moieties. Isotopic substitution experiments point to the nominal parallel stretch of the bridging proton appearing as a sharp, dominant feature near 600 cm-1. Multidimensional anharmonic calculations, however, reveal that the bridging proton motion is strongly coupled to the flanking -COO- framework, an effect that is qualitatively in line with the expected change in -C=O bond rehybridization upon protonation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gas-Phase Amidation of Carboxylic Acids with Woodward’s Reagent K Ions

PubMed Central

Peng, Zhou; Pilo, Alice L.; Luongo, Carl A.; McLuckey, Scott A.

2015-01-01

Gas-phase amidation of carboxylic acids in multiply-charged peptides is demonstrated via ion/ion reactions with Woodward’s reagent K (wrk) in both positive and negative mode. Woodward’s reagent K, N-ethyl-3-phenylisoxazolium-3′-sulfonate, is a commonly used reagent that activates carboxylates to form amide bonds with amines in solution. Here, we demonstrate that the analogous gas-phase chemistry occurs upon reaction of the wrk ions and doubly protonated (or doubly deprotonated) peptide ions containing the carboxylic acid functionality. The reaction involves the formation of the enol ester intermediate in the electrostatic complex. Upon collisional activation, the ethyl amine on the reagent is transferred to the activated carbonyl carbon on the peptide, resulting in the formation of an ethyl amide (addition of 27 Da to the peptide) with loss of a neutral ketene derivative. Further collision-induced dissociation (CID) of the products and comparison with solution-phase amidation product confirms the structure of the ethyl amide. PMID:26122523

Features of the complexation of octadecane-2,4-dione and lanthanide ions in Langmuir monolayers

NASA Astrophysics Data System (ADS)

Sokolov, M. E.; Repina, I. N.; Raitman, O. A.; Kolokolov, F. A.; Panyushkin, V. T.

2016-05-01

Monolayers of octadecane-2,4-dione on the surfaces of EuCl3 and TbCl3 solutions in the concentration range of 1 × 10-4 to 5 × 10-3 M at pH 5.8 are studied. It is found that the limiting area of octadecane-2,4-dione molecule in a monolayer dependence on Eu3+ and Tb3+ concentration is of extreme nature. The formation of complex compounds in the ligand monolayer is postulated, and structures are proposed for these compounds at different concentrations of metal ions.

Slow positron beam study of hydrogen ion implanted ZnO thin films

NASA Astrophysics Data System (ADS)

Hu, Yi; Xue, Xudong; Wu, Yichu

2014-08-01

The effects of hydrogen related defect on the microstructure and optical property of ZnO thin films were investigated by slow positron beam, in combination with x-ray diffraction, infrared and photoluminescence spectroscopy. The defects were introduced by 90 keV proton irradiation with doses of 1×1015 and 1×1016 ions cm-2. Zn vacancy and OH bonding (VZn+OH) defect complex were identified in hydrogen implanted ZnO film by positron annihilation and infrared spectroscopy. The formation of these complexes led to lattice disorder in hydrogen implanted ZnO film and suppressed the luminescence process.

β-Lactam antibiotics. Spectroscopy and molecular orbital (MO) calculations . Part I: IR studies of complexation in penicillin-transition metal ion systems and semi-empirical PM3 calculations on simple model compounds

NASA Astrophysics Data System (ADS)

Kupka, Teobald

1997-12-01

IR studies were preformed to determine possible transition metal ion binding sites of penicillin. the observed changes in spectral position and shape of characteristic IR bands of cloxacillin in the presence of transition metal ions (both in solutions and in the solid state) indicate formation of M-L complexes with engagement of -COO - and/or -CONH- functional groups. The small shift of νCO towards higher frequencies rules out direct M-L interaction via β-lactam carbonyl. PM3 calculations on simple model compounds (substituted formamide, cyclic ketones, lactams and substituted monocyclic β-lactams) have been performed. All structures were fully optimized and the calculated bond lengths, angles, heats of formation and CO stretching frequencies were discussed to determine the β-lactam binding sites and to explain its susceptibility towards nucleophilic attack (hydrolysis in vitro) and biological activity. The relative changes of calculated values were critically compared with available experimental data and same correlation between structural parameters and in vivo activity was shown.

Engineering of a calcium-ion binding site into the RC-LH1-PufX complex of Rhodobacter sphaeroides to enable ion-dependent spectral red-shifting.

PubMed

Swainsbury, David J K; Martin, Elizabeth C; Vasilev, Cvetelin; Parkes-Loach, Pamela S; Loach, Paul A; Neil Hunter, C

2017-11-01

The reaction centre-light harvesting 1 (RC-LH1) complex of Thermochromatium (Tch.) tepidum has a unique calcium-ion binding site that enhances thermal stability and red-shifts the absorption of LH1 from 880nm to 915nm in the presence of calcium-ions. The LH1 antenna of mesophilic species of phototrophic bacteria such as Rhodobacter (Rba.) sphaeroides does not possess such properties. We have engineered calcium-ion binding into the LH1 antenna of Rba. sphaeroides by progressively modifying the native LH1 polypeptides with sequences from Tch. tepidum. We show that acquisition of the C-terminal domains from LH1 α and β of Tch. tepidum is sufficient to activate calcium-ion binding and the extent of red-shifting increases with the proportion of Tch. tepidum sequence incorporated. However, full exchange of the LH1 polypeptides with those of Tch. tepidum results in misassembled core complexes. Isolated α and β polypeptides from our most successful mutant were reconstituted in vitro with BChl a to form an LH1-type complex, which was stabilised 3-fold by calcium-ions. Additionally, carotenoid specificity was changed from spheroidene found in Rba. sphaeroides to spirilloxanthin found in Tch. tepidum, with the latter enhancing in vitro formation of LH1. These data show that the C-terminal LH1 α/β domains of Tch. tepidum behave autonomously, and are able to transmit calcium-ion induced conformational changes to BChls bound to the rest of a foreign antenna complex. Thus, elements of foreign antenna complexes, such as calcium-ion binding and blue/red switching of absorption, can be ported into Rhodobacter sphaeroides using careful design processes. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

Radiation induced deposition of copper nanoparticles inside the nanochannels of poly(acrylic acid)-grafted poly(ethylene terephthalate) track-etched membranes

NASA Astrophysics Data System (ADS)

Korolkov, Ilya V.; Güven, Olgun; Mashentseva, Anastassiya A.; Atıcı, Ayse Bakar; Gorin, Yevgeniy G.; Zdorovets, Maxim V.; Taltenov, Abzal A.

2017-01-01

Poly(ethylene terephthalate) PET, track-etched membranes (TeMs) with 400 nm average pore size were UV-grafted with poly(acrylic acid) (PAA) after oxidation of inner surfaces by H2O2/UV system. Carboxylate groups of grafted PAA chains were easily complexed with Cu2+ ions in aqueous solutions. These ions were converted into metallic copper nanoparticles (NPs) by radiation-induced reduction of copper ions in aqueous-alcohol solution by gamma rays in the dose range of 46-250 kGy. Copper ions chelating with -COOH groups of PAA chains grafted on PET TeMs form polymer-metal ion complex that prevent the formation of agglomerates during reduction of copper ions to metallic nanoparticles. The detailed analysis by X-Ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) confirmed the deposition of copper nanoparticles with the average size of 70 nm on the inner surface of nanochannels of PET TeMs. Samples were also investigated by FTIR, ESR spectroscopies to follow copper ion reduction.

Transformation of [M + 2H](2+) Peptide Cations to [M - H](+), [M + H + O](+), and M(+•) Cations via Ion/Ion Reactions: Reagent Anions Derived from Persulfate.

PubMed

Pilo, Alice L; Bu, Jiexun; McLuckey, Scott A

2015-07-01

The gas-phase oxidation of doubly protonated peptides is demonstrated here using ion/ion reactions with a suite of reagents derived from persulfate. Intact persulfate anion (HS2O8(-)), peroxymonosulfate anion (HSO5(-)), and sulfate radical anion (SO4(-•)) are all either observed directly upon negative nanoelectrospray ionization (nESI) or easily obtained via beam-type collisional activation of persulfate into the mass spectrometer. Ion/ion reactions between each of these reagents and doubly protonated peptides result in the formation of a long-lived complex. Collisional activation of the complex containing a peroxymonosulfate anion results in oxygen transfer from the reagent to the peptide to generate the [M + H + O](+) species. Activation of the complex containing intact persulfate anion either results in oxygen transfer to generate the [M + H + O](+) species or abstraction of two hydrogen atoms and a proton to generate the [M - H](+) species. Activation of the complex containing sulfate radical anion results in abstraction of one hydrogen atom and a proton to form the peptide radical cation, [M](+•). This suite of reagents allows for the facile transformation of the multiply protonated peptides obtained via nESI into a variety of oxidized species capable of providing complementary information about the sequence and structure of the peptide.

Highly Manufacturable Deep (Sub-Millimeter) Etching Enabled High Aspect Ratio Complex Geometry Lego-Like Silicon Electronics.

PubMed

Ghoneim, Mohamed Tarek; Hussain, Muhammad Mustafa

2017-04-01

A highly manufacturable deep reactive ion etching based process involving a hybrid soft/hard mask process technology shows high aspect ratio complex geometry Lego-like silicon electronics formation enabling free-form (physically flexible, stretchable, and reconfigurable) electronic systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Advances in Understanding of Swift Heavy-Ion Tracks in Complex Ceramics

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

Lang, Maik; Devanathan, Ram; Toulemonde, Marcel

2015-02-01

Tracks produced by swift heavy ions in ceramics are of interest for fundamental science as well as for applications covering different fields such as nanotechnology or fission-track dating of minerals. In the case of pyrochlores with general formula A2B2O7, the track structure and radiation sensitivity shows a clear dependence on the composition. Ion irradiated Gd2Zr2O7, e.g., retains its crystallinity while amorphous tracks are produced in Gd2Ti2O7. Tracks in Ti-containing compositions have a complex morphology consisting of an amorphous core surrounded by a shell of a disordered, defect-fluorite phase. The size of the amorphous core decreases with decreasing energy loss andmore » with increasing Zr content, while the shell thickness seems to be similar over a wide range of energy loss values. The large data set and the complex track structure has made pyrochlore an interesting model system for a general theoretical description of track formation including thermal spike calculations (providing the spatial and temporal evolution of temperature around the ion trajectory) and molecular dynamics (MD) simulations (describing the response of the atomic system).Recent MD advances consider the sudden temperature increase by inserting data from the thermal spike. The combination allows the reproduction of the core-shell track characteristic and sheds light on the early stages of track formation including recrystallization of the molten material produced by the thermal spike.« less

Simulating the dynamics of complex plasmas.

PubMed

Schwabe, M; Graves, D B

2013-08-01

Complex plasmas are low-temperature plasmas that contain micrometer-size particles in addition to the neutral gas particles and the ions and electrons that make up the plasma. The microparticles interact strongly and display a wealth of collective effects. Here we report on linked numerical simulations that reproduce many of the experimental results of complex plasmas. We model a capacitively coupled plasma with a fluid code written for the commercial package comsol. The output of this model is used to calculate forces on microparticles. The microparticles are modeled using the molecular dynamics package lammps, which we extended to include the forces from the plasma. Using this method, we are able to reproduce void formation, the separation of particles of different sizes into layers, lane formation, vortex formation, and other effects.

IBiSA_Tools: A Computational Toolkit for Ion-Binding State Analysis in Molecular Dynamics Trajectories of Ion Channels.

PubMed

Kasahara, Kota; Kinoshita, Kengo

2016-01-01

Ion conduction mechanisms of ion channels are a long-standing conundrum. Although the molecular dynamics (MD) method has been extensively used to simulate ion conduction dynamics at the atomic level, analysis and interpretation of MD results are not straightforward due to complexity of the dynamics. In our previous reports, we proposed an analytical method called ion-binding state analysis to scrutinize and summarize ion conduction mechanisms by taking advantage of a variety of analytical protocols, e.g., the complex network analysis, sequence alignment, and hierarchical clustering. This approach effectively revealed the ion conduction mechanisms and their dependence on the conditions, i.e., ion concentration and membrane voltage. Here, we present an easy-to-use computational toolkit for ion-binding state analysis, called IBiSA_tools. This toolkit consists of a C++ program and a series of Python and R scripts. From the trajectory file of MD simulations and a structure file, users can generate several images and statistics of ion conduction processes. A complex network named ion-binding state graph is generated in a standard graph format (graph modeling language; GML), which can be visualized by standard network analyzers such as Cytoscape. As a tutorial, a trajectory of a 50 ns MD simulation of the Kv1.2 channel is also distributed with the toolkit. Users can trace the entire process of ion-binding state analysis step by step. The novel method for analysis of ion conduction mechanisms of ion channels can be easily used by means of IBiSA_tools. This software is distributed under an open source license at the following URL: http://www.ritsumei.ac.jp/~ktkshr/ibisa_tools/.

Magnetite solubility and phase stability in alkaline media at elevated temperatures

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

Ziemniak, S.E.; Jones, M.E.; Combs, K.E.S.

Magnetite, Fe{sub 3}O{sub 4}, is the dominant oxide constituent of the indigenous corrosion layers that form on iron base alloys in high purity, high temperature water. The apparent simultaneous stability of two distinct oxidation states of iron in this metal oxide is responsible for its unique solubility behavior. The present work was undertaken to extend the experimental and theoretical bases for estimating solubilities of an iron corrosion product (Fe{sub 3}O{sub 4}/Fe(OH){sub 2}) over a broader temperature range and in the presence of complexing, pH-controlling reagents. These results indicate that a surface layer of ferrous hydroxide controls magnetite solubility behavior atmore » low temperatures in much the same manner as a surface layer of nickel(II) hydroxide was previously reported to control the low temperature solubility behavior of NiO. The importance of Fe(III) ion complexes implies not only that most previously-derived thermodynamic properties of the Fe(OH){sub 3}{sup {minus}} ion are incorrect, but that magnetite phase stability probably shifts to favor a sodium ferric hydroxyphosphate compound in alkaline sodium phosphate solutions at elevated temperatures. The test methodology involved pumping alkaline solutions of known composition through a bed of Fe{sub 3}O{sub 4} granules and analyzing the emerging solution for Fe. Two pH-controlling reagents were tested: sodium phosphate and ammonia. Equilibria for the following reactions were described in thermodynamic terms: (a) Fe(OH){sub 2}/Fe{sub 3}O{sub 4} dissolution and transformation, (b) Fe(II) and Fe(III) ion hydroxocomplex formation (hydrolysis), (c) Fe(II) ion amminocomplex formation, and (d) Fe(II) and Fe(III) ion phosphatocomplex formation. 36 refs.« less

Electrospray ionization of uranyl-citrate complexes

NASA Astrophysics Data System (ADS)

Somogyi, Árpád; Pasilis, Sofie P.; Pemberton, Jeanne E.

2007-09-01

Results presented here demonstrate the usefulness of electrospray ionization and gas-phase ion-molecule reactions to predict structural and electronic differences in complex inorganic ions. Electrospray ionization of uranyl citrate solutions generates positively and negatively charged ions that participate in further ion-molecule reactions in 3D ion trap and FT-ICR mass analyzers. Most ions observed are derived from the major solution uranyl-citrate complexes and involve species of {(UO2)2Cit2}2-, (UO2)3Cit2, and {(UO2)3Cit3}3-, where Cit indicates the citrate trianion, C6H5O73-. In a 3D ion trap operated at relatively high pressure, complex adducts containing solvent molecules, alkali and ammonium cations, and nitrate or chloride anions are dominant, and proton/alkali cation (Na+, K+) exchange is observed for up to six exchangeable protons in an excess of alkali cations. Adduct formation in a FT-ICR cell that is operated at lower pressures is less dominant, and direct detection of positive and negative ions of the major solution complexes is possible. Multiply charged ions are also detected, suggesting the presence of uranium in different oxidation states. Changes in uranium oxidation state are detected by He-CID and SORI-CID fragmentation, and certain fragments undergo association reactions in trapping analyzers, forming "exotic" species such as [(UO2)4O3]-, [(UO2)4O4]-, and [(UO2)4O5]-. Ion-molecule reactions with D2O in the FT-ICR cell indicate substantial differences in H/D exchange rate and D2O accommodation for different ion structures and charge states. Most notably, the positively charged ions [H2(UO2)2Cit2(H)]+ and [(UO2)2(Cit)]+ accommodate two and three D2O molecules, respectively, which reflects well the structural differences, i.e., tighter uranyl-citrate coordination in the former ion than in the latter. The corresponding negatively charged ions accommodate zero or two D2O molecules, which can be rationalized using suggested solution phase structures and charge state distributions.

Reactions in 1,1,1-trifluoroacetone triggered by low energy electrons (0-10 eV): from simple bond cleavages to complex unimolecular reactions.

PubMed

Illenberger, Eugen; Meinke, Martina C

2014-08-21

The impact of low energy electrons (0-10 eV) to 1,1,1-trifluoroacetone yields a variety of fragment anions which are formed via dissociative electron attachment (DEA) through three pronounced resonances located at 0.8 eV, near 4 eV, and in the energy range 8-9 eV. The fragment ions arise from different reactions ranging from the direct cleavage of one single or double bond (formation of F(-), CF3(-), O(-), (M-H)(-), and M-F)(-)) to remarkably complex unimolecular reactions associated with substantial geometric and electronic rearrangement in the transitory intermediate (formation of OH(-), FHF(-), (M-HF)(-), CCH(-), and HCCO(-). The ion CCH(-), for example, is formed by an excision of unit from the target molecule through the concerted cleavage of four bonds and recombination to H2O within the neutral component of the reaction.

Dinitrosyl iron complexes and S-nitrosothiols are two possible forms for stabilization and transport of nitric oxide in biological systems.

PubMed

Vanin, A F

1998-07-01

The physicochemical properties, mechanisms of synthesis and decomposition of dinitrosyl iron complexes (DNICs) with thiol-containing ligands and of S-nitrosothiols (RS-NO), and the potential role of these compounds in storage and transport of NO in biological systems are reviewed. Special attention is given to the phenomenon of mutual transformation of DNIC and RS-NO catalyzed by Fe2+. Each Fe2+ binds two neutral NO molecules in the DNICs, catalyzes their mutual oxidation--reduction with formation of nitrous oxide and nitrosonium ions appearing in the DNICs. These ions S-nitrosate thiol-compounds with RS-NO formation. Fe2+ binds two RS-NO molecules and catalyzes their mutual oxidation--reduction followed by decomposition of the resulting molecules. Mutual conversion of DNICs and RS-NO regulated by iron, thiol, and NO levels is suggested to provide NO transport in cells and tissues.

Interrogating viral capsid assembly with ion mobility-mass spectrometry

NASA Astrophysics Data System (ADS)

Uetrecht, Charlotte; Barbu, Ioana M.; Shoemaker, Glen K.; van Duijn, Esther; Heck, Albert J. R.

2011-02-01

Most proteins fulfil their function as part of large protein complexes. Surprisingly, little is known about the pathways and regulation of protein assembly. Several viral coat proteins can spontaneously assemble into capsids in vitro with morphologies identical to the native virion and thus resemble ideal model systems for studying protein complex formation. Even for these systems, the mechanism for self-assembly is still poorly understood, although it is generally thought that smaller oligomeric structures form key intermediates. This assembly nucleus and larger viral assembly intermediates are typically low abundant and difficult to monitor. Here, we characterised small oligomers of Hepatitis B virus (HBV) and norovirus under equilibrium conditions using native ion mobility mass spectrometry. This data in conjunction with computational modelling enabled us to elucidate structural features of these oligomers. Instead of more globular shapes, the intermediates exhibit sheet-like structures suggesting that they are assembly competent. We propose pathways for the formation of both capsids.

CARBONATE METHOD OF SEPARATION OF TETRAVALENT PLUTONIUM FROM FISSION PRODUCT VALUES

DOEpatents

Duffield, R.B.; Stoughton, R.W.

1959-02-01

It has been found that plutonium forms an insoluble precipitate with carbonate ion when the carbonate ion is present in stoichiometric proportions, while an excess of the carbonate ion complexes plutonium and renders it soluble. A method for separating tetravalent plutonium from lanthanum-group rare earths has been based on this discovery, since these rare earths form insoluble carbonates in approximately neutral solutions. According to the process the pH is adjusted to between 5 and 7, and approximately stoichiometric amounts of carbonate ion are added to the solution causing the formation of a precipitate of plutonium carbonate and the lanthanum-group rare earth carbonates. The precipitate is then separated from the solution and contacted with a carbonate solution of a concentration between 1 M and 3 M to complex and redissolve the plutonium precipitate, and thus separate it from the insoluble rare earth precipitate.

A study of the vacancy loop formation probability in Ni-Cu and Ag-Pd alloys. [50-keV Kr sup + ions

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

Smalinskas, K.; Chen, Gengsheng; Haworth, J.

1992-04-01

The molten-zone model of vacancy loop formation from a displacement cascade predicts that the loop formation probability should scale with the melting temperature. To investigate this possibility the vacancy loop formation probability has been determined in a series of Cu-Ni and Ag-Pd alloys. The irradiations were performed at room temperature with 50 keV Kr+ ions and the resulting damage structure was examined by using transmission electron microscopy. In the Cu-Ni alloy series, the change in loop formation probability with increasing Ni concentration was complex, and at low- and high- nickel concentrations, the defect yield did not change in the predictedmore » manner. The defect yield was higher in the Cu-rich alloys than in the Ni-rich alloys. In the Ag-Pd alloy the change in the loop formation probability followed more closely the change in melting temperature, but no simple relationship was determined.« less

Atomistic origin of superior performance of ionic liquid electrolytes for Al-ion batteries.

PubMed

Kamath, Ganesh; Narayanan, Badri; Sankaranarayanan, Subramanian K R S

2014-10-14

Encouraged by recent experimental findings, here we report on an in silico investigation to probe the atomistic origin behind the superior performance of ionic liquids (ILs) over traditional carbonate electrolytes for Al-ion batteries. Fundamental insights from computationally derived thermodynamic and kinetic considerations coupled with an atomistic-level description of the solvation dynamics is used to elucidate the performance improvements. The formation of low-stability ion-solvent complexes in ILs facilitates rapid Al-ion solvation-desolvation and translates into favorable transport properties (viscosity and ionic conductivity). Our results offer encouraging prospects for this approach in the a priori prediction of optimal IL formulations for Al-ion batteries.

Temporal evolution of ion spectral structures during a geomagnetic storm: Observations and modeling

NASA Astrophysics Data System (ADS)

Ferradas, C.; Zhang, J.; Spence, H. E.; Kistler, L. M.; Larsen, B.; Reeves, G. D.; Skoug, R. M.; Funsten, H. O.

2016-12-01

During the last decades several missions have recorded the presence of dynamic spectral features of energetic ions in the inner magnetosphere. We present a case study of the temporal evolution of H+, He+, and O+ spectral structures throughout the geomagnetic storm of 2 October 2013. We use data from the Helium, Oxygen, Proton, and Electron (HOPE) mass spectrometer onboard Van Allen Probe A to analyze the spectral structures in the energy range of 1- 50 keV. We find that the characteristics of the ion structures follow a cyclic pattern, the observed features changing dramatically as the storm starts and then returning to its initial pre-storm state. Quiet, pre-storm times are characterized by multiple and often complex flux structures at narrow energy bands. During the storm main phase, the observed features become simple, with no nose structures or only one nose structure present in the energy-time spectrograms. As the inner magnetosphere recovers from the storm, more complex structures appear once again. Additionally, the heavy ion spectral features are generally more complex than the H+ features, with multiple noses being observed more often in the heavy ion spectra. We use a model of ion drift and losses due to charge exchange to understand the formation of the spectral features and their species dependence.

The Role of Oxygen in the Formation of TNT Product Ions in Ion Mobility Spectrometry

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

Daum, Keith Alvin; Atkinson, David Alan; Ewing, Robert Gordon

2002-03-01

The atmospheric pressure ionization of 2,4,6-trinitrotoluene (TNT) in air yields the (TNT-H)- product ion. It is generally accepted that this product ion is formed by the direct proton abstraction of neutral TNT by O2- reactant ions. Data presented here demonstrate the reaction involves the formation of an intermediate (TNT·O2)-, from the association of either TNT+O2- or TNT-+O2. This intermediate has two subsequent reaction branches. One of these branches involves simple dissociation of the intermediate to TNT-; the other branch is a terminal reaction that forms the typically observed (TNT-H)- ion via proton abstraction. The dissociation reaction involving electron transfer tomore » TNT- appeared to be kinetically favored and prevailed at low concentrations of oxygen (less than 2%). The presence of significant amounts of oxygen, however, resulted in the predominant formation of the (TNT-H)- ion by the terminal reaction branch. With TNT- in the system, either from direct electron attachment or by simple dissociation of the intermediate, increasing levels of oxygen in the system will continue to reform the intermediate, allowing the cycle to continue until proton abstraction occurs. Key to understanding this complex reaction pathway is that O2- was observed to transfer an electron directly to neutral TNT to form the TNT-. At oxygen levels of less than 2%, the TNT- ion intensity increased with increasing levels of oxygen (and O2-) and was larger than the (TNT-H)- ion intensity. As the oxygen level increased from 2 to 10%, the (TNT-H)- product ion became predominant. The potential reaction mechanisms were investigated with an ion mobility spectrometer, which was configured to independently evaluate the ionization pathways.« less

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.

Polymer-Supported Optically Active fac(S)-Tris(thiotato)rhodium(III) Complex for Sulfur-Bridging Reaction With Precious Metal Ions.

PubMed

Aizawa, Sen-Ichi; Tsubosaka, Soshi

2016-01-01

The optically active mixed-ligand fac(S)-tris(thiolato)rhodium(III) complexes, ΔL -fac(S)-[Rh(aet)2 (L-cys-N,S)](-) (aet = 2-aminoethanethiolate, L-cys = L-cysteinate) () and ΔLL -fac(S)-[Rh(aet)(L-cys-N,S)2 ](2-) were newly prepared by the equatorial preference of the carboxyl group in the coordinated L-cys ligand. The amide formation reaction of with 1,10-diaminodecane and polyallylamine gave the diamine-bridged dinuclear Rh(III) complex and the single-chain polymer-supported Rh(III) complex with retention of the ΔL configuration of , respectively. These Rh(III) complexes reacted with Co(III) or Co(II) to give the linear-type trinuclear structure with the S-bridged Co(III) center and the two Δ-Rh(III) terminal moieties. The polymer-supported Rh(III) complex was applied not only to the CD spectropolarimetric detection and determination of a trace of precious metal ions such as Au(III), Pt(II), and Pd(II) but also to concentration and extraction of these metal ions into the solid polymer phase. Chirality 28:85-91, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Characterization of Actinides Complexed to Nuclear Fuel Constituents Using ESI-MS

DOE PAGES

McDonald, Luther W.; Campbell, James A.; Vercouter, Thomas; ...

2016-03-01

Electrospray ionization-mass spectrometry (ESI-MS) was tested for its use in monitoring spent nuclear fuel (SNF) constituents including U, Pu, dibutyl phosphate (DBP), and tributyl phosphate (TBP). Both positive and negative ion modes were used to evaluate the speciation of U and Pu with TBP and DBP. Furthermore, apparent stability constants were determined for U complexed to TBP and DBP. In positive ion mode, TBP produced a strong signal with and without complexation to U or Pu, but, in negative ion mode, no TBP, U-TBP, or Pu-TBP complexes were observed. Apparent stability constants were determined for [UO 2(NO 3) 2(TBP) 2],more » [UO 2(NO 3) 2(H 2O)(TBP) 2], and [UO 2(NO 3) 2(TBP) 3]. In contrast DBP, U-DBP, and Pu-DBP complexes were observed in both positive and negative ion modes. Apparent stability constants were determined for the species [UO 2(DBP)], [UO 2(DBP) 3], and [UO 2(DBP) 4]. Analyzing mixtures of U or Pu with TBP and DBP yielded the formation of ternary complexes whose stoichiometry was directly related to the ratio of TBP to DBP. The ESI-MS protocols used in this study will further demonstrate the utility of ESI-MS and its applicability to process control monitoring in SNF reprocessing facilities.« less

Host-guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V.

PubMed

Begel, Svetlana; Puchta, Ralph; van Eldik, Rudi

2013-01-01

The selectivity of the cryptands [2.2.bpy] and [2.bpy.bpy] for the endohedral complexation of alkali, alkaline-earth and earth metal ions was predicted on the basis of the DFT (B3LYP/LANL2DZp) calculated structures and complex-formation energies. The cavity size in both cryptands lay between that for [2.2.2] and [bpy.bpy.bpy], such that the complexation of K(+), Sr(2+) and Tl(3+) is most favorable. While the [2.2.bpy] is moderately larger, preferring Rb(+) complexation and demonstrating equal priority for Sr(2+) and Ba(2+), the slightly smaller [2.bpy.bpy] yields more stable cryptates with Na(+) and Ca(2+). Although the CH2-units containing molecular bars fixed at the bridgehead nitrogen atoms determine the flexibility of the cryptands, the twist angles associated with the bipyridine and glycol building blocks also contribute considerably.

Ionization of doped helium nanodroplets: Complexes of C60 with water clusters

NASA Astrophysics Data System (ADS)

Denifl, S.; Zappa, F.; Mähr, I.; Mauracher, A.; Probst, M.; Urban, J.; Mach, P.; Bacher, A.; Bohme, D. K.; Echt, O.; Märk, T. D.; Scheier, P.

2010-06-01

Water clusters are known to undergo an autoprotonation reaction upon ionization by photons or electron impact, resulting in the formation of (H2O)nH3O+. Ejection of OH cannot be quenched by near-threshold ionization; it is only partly quenched when clusters are complexed with inert gas atoms. Mass spectra recorded by electron ionization of water-doped helium droplets show that the helium matrix also fails to quench OH loss. The situation changes drastically when helium droplets are codoped with C60. Charged C60-water complexes are predominantly unprotonated; C60(H2O)4+ and (C60)2(H2O)4+ appear with enhanced abundance. Another intense ion series is due to C60(H2O)nOH+; dehydrogenation is proposed to be initiated by charge transfer between the primary He+ ion and C60. The resulting electronically excited C60+∗ leads to the formation of a doubly charged C60-water complex either via emission of an Auger electron from C60+∗, or internal Penning ionization of the attached water complex, followed by charge separation within {C60(H2O)n}2+. This mechanism would also explain previous observations of dehydrogenation reactions in doped helium droplets. Mass-analyzed ion kinetic energy scans reveal spontaneous (unimolecular) dissociation of C60(H2O)n+. In addition to the loss of single water molecules, a prominent reaction channel yields bare C60+ for sizes n=3, 4, or 6. Ab initio Hartree-Fock calculations for C60-water complexes reveal negligible charge transfer within neutral complexes. Cationic complexes are well described as water clusters weakly bound to C60+. For n=3, 4, or 6, fissionlike desorption of the entire water complex from C60(H2O)n+ energetically competes with the evaporation of a single water molecule.

Complexation equilibria and spectrophotometric determination of iron(III) with 1-amino-4-hydroxyanthraquinone.

PubMed

Abu-Bakr, M S; Sedaira, H; Hashem, E Y

1994-10-01

The complex equilibria of iron(III) with 1-amino-4-hydroxyanthraquinone (AMHA) were studied spectrophotometrically in 40% (v/v) ethanol and an ionic strength of 0.1M (NaClO(4)). The complexation reactions were demonstrated and characterized using graphical logarithmic analysis of the absorbance-pH graphs. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of Fe(III) is developed based on the formation of Fe(AMHA) complex at pH 2.5 (lambda(max) = 640 nm, epsilon approximately = 2.1 x 10(4) L. mol(-1) . cm(-1)) in the presence of a large number of foreign ions. Interferences caused by palladium(II) was masked by the addition of cyanide ions. The method has been applied to the determination of iron in some synthetic samples and polymetallic iron ores.

A rationale on the role of intermediate Au(III)-vitamin C complexation in the production of gold nanoparticles

NASA Astrophysics Data System (ADS)

Zümreoglu-Karan, B.

2009-07-01

Preparation of gold nanoparticles, particularly gold nanorods, by wet chemistry processes involves gold seeds, an Au(III) salt, structure directing surfactants, and metal ion additives in the growth solution into which a weak reducing agent is added. The most commonly employed weak reducing agent is l-ascorbic acid (vitamin C) which is known to reduce many metal ions in the solution phase and form complexes with relatively low stability constants. A purple-gray gold-ascorbate compound, obtained from the reaction of sodium tetrachloroaurate(III) with sodium ascorbate, is now reported. The compound possesses the expected structural features of vitamin C-metal complexes as verified by its 13C CP-MAS NMR spectrum. A discussion is also presented on the possibility of gold-ascorbate complexation operating in gold nanoparticle formation.

Influence of complex impurity centres on radiation damage in wide-gap metal oxides

NASA Astrophysics Data System (ADS)

Lushchik, A.; Lushchik, Ch.; Popov, A. I.; Schwartz, K.; Shablonin, E.; Vasil'chenko, E.

2016-05-01

Different mechanisms of radiation damage of wide-gap metal oxides as well as a dual influence of impurity ions on the efficiency of radiation damage have been considered on the example of binary ionic MgO and complex ionic-covalent Lu3Al5O12 single crystals. Particular emphasis has been placed on irradiation with ∼2 GeV heavy ions (197Au, 209Bi, 238U, fluence of 1012 ions/cm2) providing extremely high density of electronic excitations within ion tracks. Besides knock-out mechanism for Frenkel pair formation, the additional mechanism through the collapse of mobile discrete breathers at certain lattice places (e.g., complex impurity centres) leads to the creation of complex defects that involve a large number of host atoms. The experimental manifestations of the radiation creation of intrinsic and impurity antisite defects (Lu|Al or Ce|Al - a heavy ion in a wrong cation site) have been detected in LuAG and LuAG:Ce3+ single crystals. Light doping of LuAG causes a small enhancement of radiation resistance, while pair impurity centres (for instance, Ce|Lu-Ce|Al or Cr3+-Cr3+ in MgO) are formed with a rise of impurity concentration. These complex impurity centres as well as radiation-induced intrinsic antisite defects (Lu|Al strongly interacting with Lu in a regular site) tentatively serve as the places for breathers collapse, thus decreasing the material resistance against dense irradiation.

Solar wind ion impacts into ice surfaces: A molecular-dynamics study using the REAX force field

NASA Astrophysics Data System (ADS)

Anders, Christian; Urbassek, Herbert M.

2017-01-01

Molecular dynamics simulation is used to study the effects of solar-wind ion irradiation on an ice target, focusing on the effects of nuclear energy deposition. A reactive force field (REAX) interatomic interaction potential is employed that allows us to model the breaking and formation of molecular bonds and hence to follow the chemistry occurring in the target. As ions we study H and He ions as typical constituents of the solar wind, and Ne as an example of a heavier ion; they impact at the speed of maximum flux in the solar wind, 400 km/s. The ice consists of a mixture of H2O, CO2, CH3OH and NH3. We find that molecular dissociations occur within 0.2 ps after ion impact and new products are formed up to a time of 1 ps; only water has a slower dynamics, due to highly mobile H atoms allowing for late recombinations. The number of dissociations, and hence also of product molecules increases from H over He to Ne ion projectiles and can be quantified by the amount of energy deposited in the target by these ions. The most abundant products formed include CO, OH and NH2. Reaction products are most complex for Ne impact, and include H3O, formaldehyde (H2CO), HO2, and NO. Formaldehyde is important as it is formed relatively frequently and is known as a precursor in the formation of sugars. In addition, molecules containing all CHON elements are formed, among which are CH2NO, CONH, methanolamine (CH5NO), and ethyne (C2H2). Repeated impacts generate novel, and more complex product species; we found CN, CH4, CH3NO, methylamine (CH3NH2), and acetamide (CH3CONH2), among others; the complex species are formed less frequently than the simple fragments. Sputtering occurs for all projectiles, even H. The ejecta are either original molecules - in particular CO2 - or simple fragments; only few product molecules are emitted.

Solvation-controlled lithium-ion complexes in a nonflammable solvent containing ethylene carbonate: structural and electrochemical aspects.

PubMed

Sogawa, Michiru; Kawanoue, Hikaru; Todorov, Yanko Marinov; Hirayama, Daisuke; Mimura, Hideyuki; Yoshimoto, Nobuko; Morita, Masayuki; Fujii, Kenta

2018-02-28

The structural and electrochemical properties of lithium-ion solvation complexes in a nonflammable organic solvent, tris(2,2,2-trifluoroethyl)phosphate (TFEP) containing ethylene carbonate (EC), were investigated using vibrational spectroscopic and electrochemical measurements. Based on quantitative Raman and infrared (IR) spectral analysis of the Li bis(trifluoromethanesulfonyl)amide (TFSA) salt in TFEP + EC electrolytes, we successfully evaluated the individual solvation numbers of EC (n EC ), TFEP (n TFEP ), and TFSA - (n TFSA ) in the first solvation sphere of the Li-ion. We found that the n EC value linearly increased with increasing EC mole fraction (x EC ), whereas the n TFEP and n TFSA values gradually decreased with increasing n EC . The ionic conductivity and viscosity (Walden plots) indicated that mainly Li + TFSA - ion pairs formed in neat TFEP (x EC = 0). This ion pair gradually dissociated into positively charged Li-ion complexes as x EC increased, which was consistent with the Raman/IR spectroscopy results. The redox reaction corresponding to an insertion/desertion of Li-ion into/from the graphite electrode occurred in the LiTFSA/TFEP + EC system at x EC ≥ 0.25. The same was not observed in the lower x EC cases. We discussed the relation between Li-ion solvation and electrode reaction behaviors at the molecular level and proposed that n EC plays a crucial role in the electrode reaction, particularly in terms of solid electrolyte interphase formation on the graphite electrode.

A DFT based analysis of adsorption of Hg2+ ion on chitosan monomer and its citralidene and salicylidene derivatives: Prior to the removal of Hg toxicity.

PubMed

Hassan, Basila; Rajan, Vijisha K; Mujeeb, V M Abdul; K, Muraleedharan

2017-06-01

A Density functional theory based study of adsorption of the toxic metal Hg (II) ion by chitosan monomer and two of its derivatives; citralidene and salicylidene chitosan, has been performed. The effect of structural features on the stability of studied complexes has been analyzed by using Gaussian03 software package. All the possible conformations of these adsorbents were studied using the global minimum geometries. All the adsorbing sites were studied by placing the metal ion on the centroid of the atoms and the stable conformer of the adsorbent-metal ion complex was identified. Interaction between Hg (II) and the adsorbents is found to be electrostatic. Metal ion binding with nitrogen atom is stronger than that with oxygen atoms in all the cases as the charge density of nitrogen is enhanced on Schiff base formation. The advantage of derivatives over chitosan monomer is their stability in acidic media. ΔE value of the complexes are in the order SC-Hg (II)>chitosan-Hg (II)>CC-Hg (II) which indicates that the stability of complexes increases with increase in energy gap. The study reveals that aromatic Schiff base derivatives of chitosan is better for Hg(II) intake than aliphatic derivatives. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Ion Streaming on Diffusion of Dust Grains in Dissipative System

NASA Astrophysics Data System (ADS)

Begum, M.; Das, N.

2018-01-01

The presence of strong electric fields in the sheath region of laboratory complex plasma induces an ion drift and perturbs the field around dust grains. The downstream focusing of ions leads to the formation of oscillatory kind of attractive wake potential which superimpose with the normal Debye-Hückel (DH) potential. The structural properties of complex plasma and diffusion coefficient of dust grains in the presence of such a wake potential have been investigated using Langevin dynamics simulation in the subsonic regime of ion flow. The study reveals that the diffusion of dust grains is strongly affected by the ion flow, so that the diffusion changes its character in the wake potential to the DH potential dominant regimes. The dependence of the diffusion coefficient on the parameters, such as the neutral pressure, dust grain size, ion flow velocity, and Coulomb coupling parameter, have been calculated for the subsonic regime by using the Green-Kubo expression, which is based on the integrated velocity autocorrelation function. It is found that the diffusion and the structural property of the system is intimately connected with the interaction potential and significantly get affected in the presence of ion flow in the subsonic regime.

Influence of complexation with chloride on the responses of a lux-marked bacteria bioassay to cadmium, copper, lead, and mercury

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

Sarin, C.; Hall, J.M.; Cotter-Howells, J.

2000-02-01

The toxicity of a heavy metal in solution to a microorganism depends not only on its concentration but also on pH and the concentrations of any aqueous complexing ligands in the microorganism's environment. This paper reports on the use of different inorganic resuscitation media and effect of the chloride ion, Cl{sup {minus}}, on the bioluminescence response of a bacterial biosensor, Escherichia coli HB101 (pUCD607), to four metals: Cd, Cu, Hg, and Pb. The toxicity tests were conducted at pH 4, using 0.1 M KNO{sub 3} as resuscitation medium and adding KCl to investigate effect of Cl{sup {minus}} concentration. The speciesmore » distributions of metals as a function of Cl{sup {minus}} concentration were calculated using GeoChem-PC. Resuscitation in 0.1 M KCl gave significantly higher light output than that in 0.1 M KNO{sub 3}, demonstrating that Cl{sup {minus}} ions increased the toxicity of Hg, apparently because of the formation of HgCl{sub 3}{sup {minus}}, and increased the toxicity of Pb because of PbCl{sup +} formation. The toxicity of Cu decreased at high Cl{sup {minus}} concentrations as free Cu{sup 2+} decreased, in accordance with the free ion model. Concentrations of Cl{sup {minus}} had no significant effect on the toxicity of Cd. This study clearly demonstrates that the chloro-complexes of some heavy metals can be toxic and, for Pb and Hg, more toxic than the free ion.« less

Precursor Ion–Ion Aggregation in the Brust–Schiffrin Synthesis of Alkanethiol Nanoparticles

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

Graham, Trent R.; Renslow, Ryan; Govind, Niranjan

Tetraoctylammonium bromide is used in the Brust-Schiffrin nanoparticle synthesis to phase-transfer chloroaurate ions from the aqueous phase to the organic phase. While it is established that the quaternary ammonium complex self-associates in the organic phase, the actual self-assembled structure is debated. We have confirmed the presence of ion-ion aggregates through quantitative 1H Nuclear Magnetic Resonance spectroscopy (NMR), pulsed field gradient, diffusion-ordered NMR (DOSY-NMR) and density functional theory (DFT) based NMR shift calculations. Tetraoctylammonium complexes (TOA-X, where X = Br, Cl, AuCl4-xBrx, AuBr4/Br and AuCl4-xBrx/Br) were investigated to measure the extraction of water into the organic phase. 1H NMR and DFTmore » based NMR shielding calculations indicated that deshielding of water is due to hydration of the anion and not the formation of the aqueous core of a reverse micelle. DOSYNMR results were consistent with the formation of small aggregates at typical Brust-Schiffrin synthesis concentrations. The extent of aggregation correlated with the size and electronegativity of the anion and was analyzed with a modified, isodesmic, indefinite aggregation model. The substitution of bromoauric acid for chlororoauric acid at conditions emulating the Brust-Schiffrin synthesis increased the aggregation of the quaternary ammonium complex. The increase in aggregation corresponded with an increase in the size of the produced nanoparticles from 4.3 to 4.6 nm. Understanding the selfassembly and supramolecular structure of precursors in the Brust-Schiffrin synthesis will enable further refinement of models that predict the growth of noble metal nanoparticles.« less

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

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

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

DOE PAGES

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.; ...

2017-11-17

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

Interaction of the alpha-subunit of Escherichia coli RNA polymerase with DNA: rigid body nature of the protein-DNA contact.

PubMed

Heyduk, E; Baichoo, N; Heyduk, T

2001-11-30

The alpha-subunit of Escherichia coli RNA polymerase plays an important role in the activity of many promoters by providing a direct protein-DNA contact with a specific sequence (UP element) located upstream of the core promoter sequence. To obtain insight into the nature of thermodynamic forces involved in the formation of this protein-DNA contact, the binding of the alpha-subunit of E. coli RNA polymerase to a fluorochrome-labeled DNA fragment containing the rrnB P1 promoter UP element sequence was quantitatively studied using fluorescence polarization. The alpha dimer and DNA formed a 1:1 complex in solution. Complex formation at 25 degrees C was enthalpy-driven, the binding was accompanied by a net release of 1-2 ions, and no significant specific ion effects were observed. The van't Hoff plot of temperature dependence of binding was linear suggesting that the heat capacity change (Deltac(p)) was close to zero. Protein footprinting with hydroxyradicals showed that the protein did not change its conformation upon protein-DNA contact formation. No conformational changes in the DNA molecule were detected by CD spectroscopy upon protein-DNA complex formation. The thermodynamic characteristics of the binding together with the lack of significant conformational changes in the protein and in the DNA suggested that the alpha-subunit formed a rigid body-like contact with the DNA in which a tight complementary recognition interface between alpha-subunit and DNA was not formed.

Deprotonated Dicarboxylic Acid Homodimers: Hydrogen Bonds and Atmospheric Implications

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

Hou, Gao-Lei; Valiev, Marat; Wang, Xue-Bin

Dicarboxylic acids represent an important class of water-soluble organic compounds found in the atmosphere. In this work we are studying properties of dicarboxylic acid homodimer complexes (HO 2(CH 2) nCO 2 -[HO 2(CH 2) nCO 2H], n = 0-12), as potentially important intermediates in aerosol formation processes. Our approach is based on experimental data from negative ion photoelectron spectra of the dimer complexes combined with updated measurements of the corresponding monomer species. These results are analyzed with quantum-mechanical calculations, which provide further information about equilibrium structures, thermochemical parameters associated with the complex formation, and evaporation rates. We find that uponmore » formation of the dimer complexes the electron binding energies increase by 1.3–1.7 eV (30.0–39.2 kcal/mol), indicating increased stability of the dimerized complexes. Calculations indicate that these dimer complexes are characterized by the presence of strong intermolecular hydrogen bonds with high binding energies and are thermodynamically favorable to form with low evaporation rates. Comparison with previously studied HSO 4 -[HO 2(CH 2) 2CO 2H] complex (J. Phys. Chem. Lett. 2013, 4, 779-785) shows that HO 2(CH 2) 2CO 2 -[HO 2(CH 2) 2CO 2H] has very similar thermochemical properties. These results imply that dicarboxylic acids not only can contribute to the heterogeneous complexes formation involving sulfuric acid and dicarboxylic acids, but also can promote the formation of homogenous complexes by involving dicarboxylic acids themselves.« less

A new dual fluorogenic and chromogenic "turn-on" chemosensor for Cu²⁺/F⁻ ions.

PubMed

Yu, Hyungwook; Lee, Jae-Young; Angupillai, Satheshkumar; Wang, Sheng; Feng, Shuhang; Matsumoto, Shinya; Son, Young-A

2015-01-01

Turn "off-on" chemosensor 2-(-2-((3',6'-bis(diethylamino)-3-oxospiro[isoindoline-1,9'-xanthen]-2-yl)imino)ethylidene)-N-phenylhydrazine-1-carbothioamide (RBS) was designed and synthesized. Using the naked eye, RBS showed favorable observation characteristics with both Cu(2+) and F(-) ions. The various modes of sensitivity shown by RBS toward the Cu(2+) and F(-) ions were investigated by spectral techniques, including UV-Vis, fluorescence and (1)H NMR spectroscopy. The Job's plot indicated the formation of 1:1 complex between RBS and Cu(2+)/F(-). The binding constant of the RBS-guest(-) complexes were found to be 1.3×10(4) and 6.2×10(3)M(-1) for the RBS-Cu(2+) and RBS-F(-), respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

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

Laskin, Julia

In this work, resonant ejection coupled with surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer is used to examine fragmentation kinetics of two singly protonated hexapeptides, RYGGFL and KYGGFL, containing the basic arginine residue and less basic lysine residue at the N-terminus. The kinetics of individual reaction channels at different collision energies are probed by applying a short ejection pulse (1 ms) in resonance with the cyclotron frequency of a selected fragment ion and varying the delay time between ion-surface collision and resonant ejection while keeping total reaction delay time constant. Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of themore » experimental data provides accurate threshold energies and activation entropies of individual reaction channels. Substitution of arginine with less basic lysine has a pronounced effect on the observed fragmentation kinetics of several pathways, including the b2 ion formation, but has little or no effect on formation of the b5+H2O fragment ion. The combination of resonant ejection SID, time- and collision energy-resolved SID, and RRKM modeling of both types of experimental data provides a detailed mechanistic understanding of the primary dissociation pathways of complex gaseous ions.« less

Infrared Multiple-Photon Dissociation spectroscopy of group II metal complexes with salicylate

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

Ryan P. Dain; Gary Gresham; Gary S. Groenewold

2011-07-01

Ion-trap tandem mass spectrometry with collision-induced dissociation, and the combination of infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations were used to characterize singly-charged, 1:1 complexes of Ca2+, Sr2+ and Ba2+ with salicylate. For each metal-salicylate complex, the CID pathways are: (a) elimination of CO2 and (b) formation of [MOH]+ where M=Ca2+, Sr2+ or Ba2+. DFT calculations predict three minima for the cation-salicylate complexes which differ in the mode of metal binding. In the first, the metal ion is coordinated by O atoms of the (neutral) phenol and carboxylate groups of salicylate. In the second, the cationmore » is coordinated by phenoxide and (neutral) carboxylic acid groups. The third mode involves coordination by the carboxylate group alone. The infrared spectrum for the metal-salicylate complexes contains a number of absorptions between 1000 – 1650 cm-1, and the best correlation between theoretical and experimental spectra for the structure that features coordination of the metal ion by phenoxide and the carbonyl group of the carboxylic acid group, consistent with calculated energies for the respective species.« less

Infrared multiple-photon dissociation spectroscopy of group II metal complexes with salicylate.

PubMed

Dain, Ryan P; Gresham, Gary; Groenewold, Gary S; Steill, Jeffrey D; Oomens, Jos; van Stipdonk, Michael J

2011-07-15

Ion trap tandem mass spectrometry with collision-induced dissociation, and the combination of infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations, were used to characterize singly charged, 1:1 complexes of Ca(2+), Sr(2+) and Ba(2+) with salicylate. For each metal-salicylate complex, the CID pathways are: (a) elimination of CO(2) and (b) formation of [MOH](+) where M = Ca(2+), Sr(2+) or Ba(2+). DFT calculations predict three minima for the cation-salicylate complexes which differ in the mode of metal binding. In the first, the metal ion is coordinated by O atoms of the (neutral) phenol and carboxylate groups of salicylate. In the second, the cation is coordinated by phenoxide and (neutral) carboxylic acid groups. The third mode involves coordination by the carboxylate group alone. The infrared spectrum for the metal-salicylate complexes contains a number of absorptions between 1000 and 1650 cm(-1), and the best correlation between theoretical and experimental spectra is found for the structure that features coordination of the metal ion by phenoxide and the carbonyl O of the carboxylic acid group, consistent with the calculated energies for the respective species. Copyright © 2011 John Wiley & Sons, Ltd.

Thermodynamic Investigation and Mixed Ligand Complex Formation of 1,4-Bis-(3-aminopropyl)-piperazine and Biorelevant Ligands.

PubMed

El-Sherif, Ahmed A; Shehata, Mohamed R; Shoukry, Mohamed M; Barakat, Mohammad H

2012-01-01

Thermodynamic parameters for protonation of 1,4-bis(3-aminopropyl)-piperazine (BAPP) and its metal complexation with some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1 M NaNO(3)) using a potentiometric technique. The order of -ΔG(0) and -ΔH(0) was found to obey Co(2+) < Ni(2+) < Cu(2+) > Zn(2+), in accordance with the Irving-Williams order. The formation equilibria of zinc (II) complexes and the ternary complexes Zn(BAPP)L, where L = amino acid, amides, or DNA constituents), have been investigated. Ternary complexes are formed by a simultaneous mechanism. The concentration distribution of the complexes in solution was evaluated as a function of pH. Stoichiometry and stability constants for the complexes formed are reported and discussed. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameter Δlog K.

Thermodynamic Investigation and Mixed Ligand Complex Formation of 1,4-Bis-(3-aminopropyl)-piperazine and Biorelevant Ligands

PubMed Central

El-Sherif, Ahmed A.; Shehata, Mohamed R.; Shoukry, Mohamed M.; Barakat, Mohammad H.

2012-01-01

Thermodynamic parameters for protonation of 1,4-bis(3-aminopropyl)-piperazine (BAPP) and its metal complexation with some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1 M NaNO3) using a potentiometric technique. The order of –ΔG0 and –ΔH0 was found to obey Co2+ < Ni2+ < Cu2+ > Zn2+, in accordance with the Irving-Williams order. The formation equilibria of zinc (II) complexes and the ternary complexes Zn(BAPP)L, where L = amino acid, amides, or DNA constituents), have been investigated. Ternary complexes are formed by a simultaneous mechanism. The concentration distribution of the complexes in solution was evaluated as a function of pH. Stoichiometry and stability constants for the complexes formed are reported and discussed. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameter Δlog K. PMID:23226992

A unique substituted Co(II)-formate coordination framework exhibits weak ferromagnetic single-chain-magnet like behavior.

PubMed

Zhao, Jiong-Peng; Yang, Qian; Liu, Zhong-Yi; Zhao, Ran; Hu, Bo-Wen; Du, Miao; Chang, Ze; Bu, Xian-He

2012-07-04

A magnetic isolated chain-based substituted cobalt-formate framework was obtained with isonicotine as a spacer. In the chain, canted antiferromagnetic interactions exist in between the Co(II) ions, and slow magnetic relaxation is detected at low temperature. For the block effects of the isonicotine ligands, the complex could be considered as a peculiar example of a weak ferromagnetic single-chain-magnet.

Spectrophotometric complexation of cephalosporins with palladium (II) chloride in aqueous and non-aqueous solvents

NASA Astrophysics Data System (ADS)

Bagheri Gh., A.; Yosefi rad, A.; Rezvani, M.; Roshanzamir, S.

2012-04-01

The complexation reaction of cephalosporins namely cefotaxime (CTX), cefuroxime (CRX), and cefazolin (CEFAZ) with palladium (II) ions have been studied in water and DMF in 25 °C by the spectrophotometric methods. The method is based on the formation of yellow to yellowish brown complex between palladium (II) chloride and the investigated cephalosporins in the presence of sodium lauryl sulfate (SLS) as surfactant. The complexation process was optimized in terms of pH, temperature and contact time. The stoichiometry of all the complexes was found to be 2:1 (metal ion/ligand) for CTX, CRX, and 1:2 for CEFAZ. The stoichiometry of palladium (II)-cephalosporins was estimated by mole ratio and continuous variation methods and emphasized by the KINFIT program. These drugs could be determined by measuring the absorbance of each complex at its specific λmax. The results obtained are in good agreement with those obtained using the official methods. The proposed method was successfully applied for the determination of these compounds in their dosage forms.

Nuclear magnetic resonance studies of formyltetrahydrofolate synthetase interactions with formate and methylammonium ion.

PubMed

Wendland, M F; Stevens, T H; Buttlaire, D H; Everett, G W; Himes, R H

1983-02-15

Using nuclear magnetic resonance techniques, we have measured the internuclear distances separating the nucleotide-bound metal from the carbon and hydrogen nuclei of formate as well as the carbon of methylammonium cation when bound to formyltetrahydrofolate synthetase. Measurements were made of the paramagnetic effect on the spin-lattice relaxation rates (1/T1) of 13C and 1H nuclei arising from the replacement of Mg2+ with Mn2+, which binds to the enzyme in the form of a metal-nucleotide complex. Distances from Mn2+ to the formate carbon and proton were found to be 6.3 and 7.4 A, respectively, in the E . ATP . Mn2+ . formate complex and 6.0 and 7.1 A, respectively, in the E . ADP . Mn2+ . formate complex. When tetrahydrofolate was added to the latter complex, the exchange of formate was greatly reduced and became rate limiting for relaxation. These results are consistent with substantial conformational effects produced by the binding of the cofactor. The distance from Mn2+ to the methylammonium carbon in the E . ADP . Mn2+ . CH3NH+3, E . ADP . Mn2+ . formate . CH3NH3+, and E . ADP . Mn2+ . tetrahydrofolate . CH3NH3+ complexes was estimated to be in the range of 7.4-12 A. However, in the E . ADP . Mn2+ formate . tetrahydrofolate . CH3NH3+ complex, the data suggest that exchange of cation contributes significantly to relaxation. These results, combined with other known features of the enzyme, suggest that there may be a monovalent cation site within the active site of the enzyme.

Role of second-sphere coordination in anion binding: Synthesis, characterization and X-ray structure of hexaamminecobalt(III) chloride hydrogen phthalate trihydrate and sodium hexaamminecobalt(III) benzoate monohydrate

NASA Astrophysics Data System (ADS)

Sharma, Raj Pal; Bala, Ritu; Sharma, Rajni; Kariuki, B. M.; Rychlewska, Urszula; Warżajtis, Beata

2005-06-01

In an effort to utilize [Co(NH 3) 6] 3+cation as a new host for carboxylate ions, orange coloured crystalline solids of composition [Co(NH 3) 6]Cl(C 8H 5O 4) 2·3H 2O ( 1) and Na[Co(NH 3) 6](C 7H 5O 2) 4·H 2O ( 2) were obtained by reacting hot aqueous solutions of hexaamminecobalt(III) chloride with potassium hydrogen phthalate and sodium benzoate in 1:3 molar ratio, respectively. The title complex salts were characterized by elemental analyses and spectroscopic studies (IR, UV/Visible and NMR). Single crystal X-ray structure determinations revealed the formation of second-sphere coordination complexes based on hydrogen bond interactions. In complex salt 1 only two out of three ionisable chloride ions present in [Co(NH 3) 6]Cl 3 were replaced by two CHO4- ions whereas in complex salt 2 all the three ionisable chloride ions present in [Co(NH 3) 6]Cl 3 were replaced and the final product was an adduct with another mole of sodium benzoate in solid state. The crystal lattice is stabilized by electrostatic forces of attraction and predominantly N-H⋯O interactions.

Study of microstructural characterization and ionic conductivity of a chemical-covalent polyether-siloxane hybrid doped with LiClO4.

PubMed

Liang, Wuu-Jyh; Chen, Ying-Pin; Wu, Chien-Pang; Kuo, Ping-Lin

2005-12-29

The chemical-covalent polyether-siloxane hybrids (EDS) doped with various amounts of LiClO4 salt were characterized by FT-IR, DSC, TGA, and solid-state NMR spectra as well as impedance measurements. These observations indicate that different types of complexes by the interactions of Li+ and ClO4- ions are formed within the hybrid host, and the formation of transient cross-links between Li+ ions and ether oxygens results in the increase in T(g) of polyether segments and the decrease in thermal stability of hybrid electrolyte. Initially a cation complexation dominated by the oxirane-cleaved cross-link site and PEO block is present, and after the salt-doped level of O/Li+ = 20, the complexation through the PPO block becomes more prominent. Moreover, a significant degree of ionic association is examined in the polymer-salt complexes at higher salt uptakes. A VTF-like temperature dependence of ionic conductivity is observed in all of the investigated salt concentrations, implying that the diffusion of charge carrier is assisted by the segmental motions of the polymer chains. The behavior of ion transport in these hybrid electrolytes is further correlated with the interactions between ions and polymer host.

Crystallization Pathways in Biomineralization

NASA Astrophysics Data System (ADS)

Weiner, Steve; Addadi, Lia

2011-08-01

A crystallization pathway describes the movement of ions from their source to the final product. Cells are intimately involved in biological crystallization pathways. In many pathways the cells utilize a unique strategy: They temporarily concentrate ions in intracellular membrane-bound vesicles in the form of a highly disordered solid phase. This phase is then transported to the final mineralization site, where it is destabilized and crystallizes. We present four case studies, each of which demonstrates specific aspects of biological crystallization pathways: seawater uptake by foraminifera, calcite spicule formation by sea urchin larvae, goethite formation in the teeth of limpets, and guanine crystal formation in fish skin and spider cuticles. Three representative crystallization pathways are described, and aspects of the different stages of crystallization are discussed. An in-depth understanding of these complex processes can lead to new ideas for synthetic crystallization processes of interest to materials science.

Assembly of Multi-Phthalocyanines on a Porphyrin Template by Fourfold Rotaxane Formation.

PubMed

Yamada, Yasuyuki; Kato, Tatsuhisa; Tanaka, Kentaro

2016-08-22

A stacked assembly composed of a porphyrin and two phthalocyanines was prepared through fourfold rotaxane formation. Two phthalocyanine molecules, bearing four 24-crown-8 units, were assembled onto a porphyrin template incorporating four sidechains with two dialkylammonium ions each through pseudorotaxane formation between crown ether units and ammonium ions. The Staudinger phosphite reaction, as the stoppering reaction, resulted in the formation of the stacked heterotrimer composed of a porphyrin and two phthalocyanines connected through a fourfold rotaxane structure. UV/Vis spectroscopic and electrochemical studies of the heterotrimer indicated that there is a significant electronic interaction between the two phthalocyanine units due to the close stacking. The electrochemical oxidation process of the stacked heterotrimer was studied by cyclic voltammetry and spectroelectrochemistry. Electron paramagnetic resonance (EPR) spectroscopy of a dinuclear Cu(II) complex, in which two Cu(II) phthalocyanines were assembled on a metal-free porphyrin template, revealed that two Cu(II) phthalocyanines were located within the stacking distance, which resulted in an antiferromagnetic interaction between the two S=1/2 spins in the ground state of the Cu(2+) ions in the heterotrimer. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gadolinium substitution induced defect restructuring in multiferroic BiFeO3: case study by positron annihilation spectroscopy

NASA Astrophysics Data System (ADS)

Mukherjee, A.; Banerjee, M.; Basu, S.; Nambissan, P. M. G.; Pal, M.

2013-12-01

Positron annihilation spectroscopy (PAS) comprising of the measurements of positron lifetime and coincidence Doppler broadening spectra has been carried out to understand and monitor the evolution of the vacancy-type defects arising from the ionic deficiencies at lattice points of the multiferroic perovskite bismuth ferrite (BiFeO3) doped with 1, 5 and 10 at% gadolinium (Gd3+) ions. Negatively charged defects in the form of Bi3+ monovacancies (V_{Bi}^{3-} ) were present in the undoped nanocrystallites, which strongly trapped positrons. During the successive doping by Gd3+ ions, the positron trapping efficiency decreased while the doped ions combined with the vacancies to form complexes, which became neutral. A fraction of the positrons got annihilated at the crystallite surfaces too, being evident from the very large positron lifetimes obtained and confirming the nano-size-specific characteristics of the samples. Further, the intercrystallite regions provided favourable sites for orthopositronium formation, although in minute concentrations. The dopant ion-complex formation was also depicted clearly by the defect characteristic S-W plot. Also, the large change of electrical resistivity with Gd concentration has been explained nicely by invoking the defect information from the PAS study. The study has demonstrated the usefulness of an excellent method of defect identification in such a novel material system, which is vital information for exploiting them for further technological applications.

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid-Liquid Extraction

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

Wintergerst, Mr. Matthieu; Levitskaia, Tatiana G.; Moyer, Bruce A

Solvent extraction studies provide confirming evidence that meso-octamethylcalix[4]pyrrole acts as an ion-pair receptor for cesium chloride and cesium bromide in nitrobenzene solution. The stoichiometry of the interaction under extraction conditions from water to nitrobenzene was determined from plots of the cesium distribution ratios vs. cesium salt and receptor concentration, indicating the formation of an ion-paired 1:1:1 cesium:calix[4]pyrrole:halide complex. The extraction results were modeled to evaluate the equilibria inherent to the solvent extraction system, either with chloride or bromide. The binding energy between the halide anion and the calix[4]pyrrole was found to be about 7 kJ/mol larger for cesium chloride thanmore » for the cesium bromide. The ion-pairing free energies between the calix[4]pyrrole-halide complex and the cesium cation are nearly the same within experimental uncertainty for either halide, consistent with a structural model in which the Cs+ cation resides in the calix bowl. These results are unexpected since nitrobenzene is a very polar solvent that generally leads to dissociated complexes in the organic phase when used as a diluent in extraction studies of univalent ions. Control studies involving nitrate revealed no evidence of ion-pairing for CsNO3 under conditions identical to those where it is observed for CsCl and CsBr.« less

On the role of Fe ions on magnetic properties of doped TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Tolea, F.; Grecu, M. N.; Kuncser, V.; Constantinescu, S. Gr.; Ghica, D.

2015-04-01

The role of iron doping on magnetic properties of hydrothermal anatase TiO2:57Fe (0-1 at. %) nanoparticles is investigated by combining superconducting quantum interference device magnetometry with Mössbauer and electron paramagnetic resonance techniques. The results on both as-prepared and thermally treated samples in reduced air atmosphere reveal complexity of magnetic interactions, in connection to certain iron ion electron configurations and defects (oxygen vacancies, F-center, and Ti3+ ions). The distribution of iron ions is predominantly at nanoparticle surface layers. Formation of weak ferromagnetic domains up to 380 K is mainly related to defects, supporting the bound magnetic polaron model.

Solvent-induced assembly of two helical Eu(III) metal-organic frameworks and fluorescence sensing activities towards nitrobenzene and Cu2+ ions

NASA Astrophysics Data System (ADS)

Ma, Ranran; Chen, Zhiwei; Wang, Suna; Yao, Qingxia; Li, Yunwu; Lu, Jing; Li, Dacheng; Dou, Jianmin

2017-08-01

Two helical Eu(III) metal-organic frameworks, namely, {[Eu(L)(DMF)(H2O)]·0.5DMF}n (1) and [Eu(L)(DEF)(H2O)]n (2) (H3L=3,5-bis(2-carboxylphenoxy)benzoic acid, DMF=N,N-dimethylformamide, DEF=N,N-diethylformamide), have been solvothermally synthesized in different solvents, respectively. Both complexes possess helical structures through the connectivity of Eu atoms and phenolic-oxygen containing branches of the flexible multicarboxylate ligand. Based on different helices, these two complexes exhibited hexagonal and tetragonal channels, respectively. Both complexes possess (3,6)-connected (4.62)2(42.610.83) topology but with different long Schlafli symbol. The solvent plays an important role in the formation of the final frameworks. Both complexes can sensitively and selectively detect nitrobenzene and Cu2+ ions.

Thermodynamics of the complex formation of copper(II) with L-phenylalanine in aqueous ethanol solutions

NASA Astrophysics Data System (ADS)

Burov, D. M.; Ledenkov, S. F.; Vandyshev, V. N.

2013-05-01

Constants of the acid dissociation and complexation of L-phenylalanine (HPhe) with copper(II) ions are determined by potentiometry in aqueous ethanol solutions containing 0 to 0.7 molar fraction of alcohol. Changes in the Gibbs energy for the transfer from water to a binary solvent of L-phenylalanine, Phe- anion, and [CuPhe]+ complex are calculated. It is found that the weakening of solvation of the ligand donor groups in solvents with high ethanol contents is accompanied by an increase in the stability of [CuPhe]+ complex.

VUV Dissociative Photoionization of Quinoline in the 7-26 eV Photon Energy Range

NASA Astrophysics Data System (ADS)

Leach, Sydney; Jochims, Hans-Werner; Baumgärtel, Helmut; Champion, Norbert

2018-05-01

The dissociative photoionization of quinoline was studied by photoionization mass spectrometry and ion yield measurements over a synchrotron photon excitation energy range 7-26 eV. The ionic and neutral products were identified with the aid of thermochemical calculations that, in some cases, led to deeper understanding of photodissociation pathways and the determination of upper limits of heats of formation of ionic and neutral dissociation products. A detailed comparison between the 20 eV photon excitation and 70 eV electron impact mass spectra, coupled with estimation of thermochemical appearance energies, leads to assignment of the dissociative ionization cation and neutral products for each detected ion. Reaction schemes for formation of these products are proposed in a number of cases. Ion intensities in the photon and electron impact mass spectra were used to consider extending a rule of charge retention in simple bond cleavage to more complex cases of dissociative ionization.

Green synthesis of ZnO nanoparticles via complex formation by using Curcuma longa extract

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

Fatimah, Is, E-mail: isfatimah@uii.ac.id; Yudha, Septian P.; Mutiara, Nur Afisa Lintang

Synthesis of ZnO nanoparticles(NPs) were conducted via Zn(II) complex formation by using Curcuma longa extract as template. Curcuma longa extract has the ability to form zinc ions complex with curcumin as ligating agent. Study on synthesis was conducted by monitoring thermal degradation of the material. Successful formation of zinc oxide nanoparticles was confirmed by employing x-ray diffraction, surface area analysis and transmission electron microscopy(TEM) studies. From the XRD analysis it is denoted that ZnO in hexagonal wurtzite phase was formed and particle size was varied as varied temperature. The data are also confirmed by TEM analysis which shows the particlemore » sie at the range 20-80nm. The NPs exhibited excelent photocatalytic activity for methylene blue degradation and also significant antibacterial activity for Eschericia coli. The activity in methylene blue degradation was also confirmed from fast chemical oxygen demand (COD) reduction.« less

Green synthesis of ZnO nanoparticles via complex formation by using Curcuma longa extract

NASA Astrophysics Data System (ADS)

Fatimah, Is; Yudha, Septian P.; Mutiara, Nur Afisa Lintang

2016-02-01

Synthesis of ZnO nanoparticles(NPs) were conducted via Zn(II) complex formation by using Curcuma longa extract as template. Curcuma longa extract has the ability to form zinc ions complex with curcumin as ligating agent. Study on synthesis was conducted by monitoring thermal degradation of the material. Successful formation of zinc oxide nanoparticles was confirmed by employing x-ray diffraction, surface area analysis and transmission electron microscopy(TEM) studies. From the XRD analysis it is denoted that ZnO in hexagonal wurtzite phase was formed and particle size was varied as varied temperature. The data are also confirmed by TEM analysis which shows the particle sie at the range 20-80nm. The NPs exhibited excelent photocatalytic activity for methylene blue degradation and also significant antibacterial activity for Eschericia coli. The activity in methylene blue degradation was also confirmed from fast chemical oxygen demand (COD) reduction.

Interaction of palladium ions with the skin.

PubMed

Santucci, B; Cristaudo, A; Cannistraci, C; Picardo, M

1995-08-01

87 subjects sensitive to both nickel sulfate and palladium-chloride pet., were contemporaneously patch retested to nickel sulfate 5% pet., metallic palladium chloride 1% pet. and to palladium chloride 1% aq. Whilst all subjects reacted to nickel sulfate and palladium chloride pet., only 3 reacted to palladium chloride aq. No positive reactions were found to metallic palladium. The negative results to palladium chloride aq. are probably due to the formation of a new palladium ion (PdCl4)2-, achieved on adding an amount of hydrocloric acid to the aqueous solution of PdCl2. The findings seem to demonstrate that the allergic reaction to palladium depends on the arrangement of the metal electrons. The sensitization to palladium does not seem to be dependent on the element itself but on the complexes formed by the different compounds. The concomitant reactions to nickel and palladium ions could be dependent on the generation of similar complexes between the ions and the skin proteins.

A turn-on fluorescent chemosensor for Zn2+ ion: X-ray structure and application in cell imaging study

NASA Astrophysics Data System (ADS)

Ghosh, Koushik; Dey, Sudipto; Halder, Shibashis; Bhattacharjee, Aradhita; Rizzoli, Corrado; Roy, Partha

2016-08-01

The selective fluorescence zinc(II) sensing properties of a Schiff-base compound, 2-methoxy-6-(2-morpholinoethyliminomethyl)phenol (HL) have been explored. The emission intensity of HL in the presence of one equivalent of Zn2+ ion increases by about 25 times. Several other metal ions, except Cd2+ and Ni2+, have not been able to increase the emission intensity of HL significantly. The quantum yield and life-time of HL have also been increased in the presence of Zn2+ ions. The enhancement in fluorescence intensity of HL is mainly due to the restriction of ESIPT, CHEF and PET on complex formation. HL forms a complex with Zn2+ in 1:1 ratio as evidenced by Job's plot analysis and X-ray single crystal structure determination. Some theoretical calculations have been performed to get a better view on the nature of the observed electronic transitions. The probe has been applied for imaging of DLD-1, human colorectal adenocarcinoma cell.

Theoretical study of ethylbenzenium ions: the mechanism for splitting off ethene, and the formation of a pi complex of ethene and the benzenium ion.

PubMed

Kolboe, Stein; Svelle, Stian; Arstad, Bjørnar

2009-02-05

Structures and energies of protonated ethylbenzene and 2,6-dimethylethylbenzene have been studied by quantum chemical calculations. The main goal is to study the mechanism for splitting off ethene from protonated ethylbenzene. Data are reported for the four ethylbenzenium isomers arising depending on the position of the proton on the benzene ring: a pi complex where ethene is weakly bonded to a benzenium ion and two transition states connected with the cleavage of the ethylbenzenium ion. The larger part of the data that are reported has been obtained at the B3LYP/cc-pVTZ level of theory. Energies obtained by the Gaussian-3 G3B3 composite method are also given. Computations have also been carried out at the MP2/6-311++G(d,p) level of theory. The calculated results can be reconciled with published experimental observations, and they give information about the reaction system that is not obtained by experimental techniques.

Synthesis of Copper Oxide/Graphite Composite for High-Performance Rechargeable Battery Anode.

PubMed

Cho, Sanghun; Ahn, Yong-Keon; Yin, Zhenxing; You, Duck-Jae; Kim, Hyunjin; Piao, Yuanzhe; Yoo, Jeeyoung; Kim, Youn Sang

2017-08-25

A novel copper oxide/graphite composite (GCuO) anode with high capacity and long cycle stability is proposed. A simple, one-step synthesis method is used to prepare the GCuO, through heat treatment of the Cu ion complex and pristine graphite. The gases generated during thermal decomposition of the Cu ion complex (H 2 and CO 2 ) induce interlayer expansion of the graphite planes, which assists effective ion intercalation. Copper oxide is formed simultaneously as a high-capacity anode material through thermal reduction of the Cu ion complex. Material analyses reveal the formation of Cu oxide nanoparticles and the expansion of the gaps between the graphite layers from 0.34 to 0.40 nm, which is enough to alleviate layer stress for reversible ion intercalation for Li or Na batteries. The GCuO cell exhibits excellent Li-ion battery half-cell performance, with a capacity of 532 mAh g -1 at 0.2 C (C-rate) and capacity retention of 83 % after 250 cycles. Moreover, the LiFePO 4 /GCuO full cell is fabricated to verify the high performance of GCuO in practical applications. This cell has a capacity of 70 mAh g -1 and a coulombic efficiency of 99 %. The GCuO composite is therefore a promising candidate for use as an anode material in advanced Li- or Na-ion batteries. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detection of Threat Materials Using Terahertz Waveguides and Long Pathlength Terahertz Spectroscopy

DTIC Science & Technology

2015-05-01

intramolecular modes. Therefore a complex spectrum is anticipated. In the range between 0.2 THz and 3.0 THz there have been several free space THz...narrowing. A more complex underlying spectrum is only suggested, but not resolved. A PETN layer was formed on an Au-coated PPWG surface by drop casting...structure of the analyte, or complex formation where metal ions incorporate into the lattice of the analyte. In each of these cases the resulting THz

Synthesis of aqueous suspensions of magnetic nanoparticles with the co-precipitation of iron ions in the presence of aspartic acid

NASA Astrophysics Data System (ADS)

Pušnik, Klementina; Goršak, Tanja; Drofenik, Miha; Makovec, Darko

2016-09-01

There is increasing demand for the production of large quantities of aqueous suspensions of magnetic iron-oxide nanoparticles. Amino acids are one possible type of inexpensive, nontoxic, and biocompatible molecules that can be used as the surfactants for the preparation of stable suspensions. This preparation can be conducted in a simple, one-step process based on the co-precipitation of Fe3+/Fe2+ ions in the presence of the amino acid. However, the presence of this amino acid changes the mechanism of the magnetic nanoparticles' formation. In this investigation we analyzed the influence of aspartic amino acid (Asp) on the formation of magnetic iron-oxide nanoparticles during the co-precipitation. The process of the nanoparticles' formation was followed using a combination of TEM, x-ray diffractometry, magnetic measurements, in-situ FT-IR spectroscopy, and chemical analysis, and compared with the formation of nanoparticles without the Asp. The Asp forms a coordination complex with the Fe3+ ions, which impedes the formation of the intermediate iron oxyhydroxide phase and suppresses the growth of the final magnetic iron-oxide nanoparticles. Slower reaction kinetics can lead to the formation of nonmagnetic secondary phases. The aspartic-acid-absorbed nanoparticles can be dispersed to form relatively concentrated aqueous suspensions displaying a good colloidal stability at an increased pH.

Label-free histamine detection with nanofluidic diodes through metal ion displacement mechanism.

PubMed

Ali, Mubarak; Ramirez, Patricio; Duznovic, Ivana; Nasir, Saima; Mafe, Salvador; Ensinger, Wolfgang

2017-02-01

We design and characterize a nanofluidic device for the label-free specific detection of histamine neurotransmitter based on a metal ion displacement mechanism. The sensor consists of an asymmetric polymer nanopore fabricated via ion track-etching technique. The nanopore sensor surface having metal-nitrilotriacetic (NTA-Ni 2+ ) chelates is obtained by covalent coupling of native carboxylic acid groups with N α ,N α -bis(carboxymethyl)-l-lysine (BCML), followed by exposure to Ni 2+ ion solution. The BCML immobilization and subsequent Ni 2+ ion complexation with NTA moieties change the surface charge concentration, which has a significant impact on the current-voltage (I-V) curve after chemical modification of the nanopore. The sensing mechanism is based on the displacement of the metal ion from the NTA-Ni 2+ chelates. When the modified pore is exposed to histamine solution, the Ni 2+ ion in NTA-Ni 2+ chelate recognizes histamine through a metal ion coordination displacement process and formation of stable Ni-histamine complexes, leading to the regeneration of metal-free NTA groups on the pore surface, as shown in the current-voltage characteristics. Nanomolar concentrations of the histamine in the working electrolyte can be detected. On the contrary, other neurotransmitters such as glycine, serotonin, gamma-aminobutyric acid, and dopamine do not provoke significant changes in the nanopore electronic signal due to their inability to displace the metal ion and form a stable complex with Ni 2+ ion. The nanofluidic sensor exhibits high sensitivity, specificity and reusability towards histamine detection and can then be used to monitor the concentration of biological important neurotransmitters. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of a C3-symmetric benzohydroxamate tripod: Trimetallic complexation with Fe(III), Cr(III) and Al(III)

NASA Astrophysics Data System (ADS)

Baral, Minati; Gupta, Amit; Kanungo, B. K.

2016-06-01

The design, synthesis and physicochemical characterization of a C3-symmetry Benzene-1,3,5-tricarbonylhydroxamate tripod, noted here as BTHA, are described. The chelator was built from a benzene as an anchor, symmetrically extended by three hydroxamate as ligating moieties, each bearing O, O donor sites. A combination of absorption spectrophotometry, potentiometry and theoretical investigations are used to explore the complexation behavior of the ligand with some trivalent metal ions: Fe(III), Cr(III), and Al(III). Three protonation constants were calculated for the ligand in a pH range of 2-11 in a highly aqueous medium (9:1 H2O: DMSO). A high rigidity in the molecular structure restricts the formation of 1:1 (M/L) metal encapsulation but shows a high binding efficiency for a 3:1 metal ligand stoichiometry giving formation constant (in β unit) 28.73, 26.13 and 19.69 for [M3L]; Mdbnd Fe(III), Al(III) and Cr(III) respectively, and may be considered as an efficient Fe-carrier. The spectrophotometric study reveals of interesting electronic transitions occurred during the complexation. BTHA exhibits a peak at 238 nm in acidic pH and with the increase of pH, a new peak appeared at 270 nm. A substantial shifting in both of the peaks in presence of the metal ions implicates a s coordination between ligand and metal ions. Moreover, complexation of BTHA with iron shows three distinct colors, violet, reddish orange and yellow in different pH, enables the ligand to be considered for the use as colorimetric sensor.

Designing molecular complexes using free-energy derivatives from liquid-state integral equation theory

NASA Astrophysics Data System (ADS)

Mrugalla, Florian; Kast, Stefan M.

2016-09-01

Complex formation between molecules in solution is the key process by which molecular interactions are translated into functional systems. These processes are governed by the binding or free energy of association which depends on both direct molecular interactions and the solvation contribution. A design goal frequently addressed in pharmaceutical sciences is the optimization of chemical properties of the complex partners in the sense of minimizing their binding free energy with respect to a change in chemical structure. Here, we demonstrate that liquid-state theory in the form of the solute-solute equation of the reference interaction site model provides all necessary information for such a task with high efficiency. In particular, computing derivatives of the potential of mean force (PMF), which defines the free-energy surface of complex formation, with respect to potential parameters can be viewed as a means to define a direction in chemical space toward better binders. We illustrate the methodology in the benchmark case of alkali ion binding to the crown ether 18-crown-6 in aqueous solution. In order to examine the validity of the underlying solute-solute theory, we first compare PMFs computed by different approaches, including explicit free-energy molecular dynamics simulations as a reference. Predictions of an optimally binding ion radius based on free-energy derivatives are then shown to yield consistent results for different ion parameter sets and to compare well with earlier, orders-of-magnitude more costly explicit simulation results. This proof-of-principle study, therefore, demonstrates the potential of liquid-state theory for molecular design problems.

Designing molecular complexes using free-energy derivatives from liquid-state integral equation theory.

PubMed

Mrugalla, Florian; Kast, Stefan M

2016-09-01

Complex formation between molecules in solution is the key process by which molecular interactions are translated into functional systems. These processes are governed by the binding or free energy of association which depends on both direct molecular interactions and the solvation contribution. A design goal frequently addressed in pharmaceutical sciences is the optimization of chemical properties of the complex partners in the sense of minimizing their binding free energy with respect to a change in chemical structure. Here, we demonstrate that liquid-state theory in the form of the solute-solute equation of the reference interaction site model provides all necessary information for such a task with high efficiency. In particular, computing derivatives of the potential of mean force (PMF), which defines the free-energy surface of complex formation, with respect to potential parameters can be viewed as a means to define a direction in chemical space toward better binders. We illustrate the methodology in the benchmark case of alkali ion binding to the crown ether 18-crown-6 in aqueous solution. In order to examine the validity of the underlying solute-solute theory, we first compare PMFs computed by different approaches, including explicit free-energy molecular dynamics simulations as a reference. Predictions of an optimally binding ion radius based on free-energy derivatives are then shown to yield consistent results for different ion parameter sets and to compare well with earlier, orders-of-magnitude more costly explicit simulation results. This proof-of-principle study, therefore, demonstrates the potential of liquid-state theory for molecular design problems.

Impurity-defect complexes in non-implanted aluminum

NASA Astrophysics Data System (ADS)

Pedersen, F. T.; Grann, H.; Weyer, G.

1986-02-01

The formation of impurity-defect complexes in ion-implanted aluminum has been studied in the temperature interval 100 400K. Radioactive119In isotopes have been implanted. Mössbauer spectra have been measured for the 24 keV γ-radiation emitted after the decay to119Sn. The spectra could be analysed satisfactorily with two lines, one of which is known to be due to substitutional Sn. A second line, which has a higher isomer shift and lower Debye temperature, is tentatively assigned to vacancy-associated Sn, formed by trapping of thermally mobile (multi-)vacancies. Comparison to similar DPAC experiments suggests that cubic Sn-V4 complexes are formed. Some indication (˜15%) for an athermal formation of impurity defects below 175K is obtained.

Hydride-Meisenheimer Complex Formation and Protonation as Key Reactions of 2,4,6-Trinitrophenol Biodegradation by Rhodococcus erythropolis

PubMed Central

Rieger, Paul-Gerhard; Sinnwell, Volker; Preuß, Andrea; Francke, Wittko; Knackmuss, Hans-Joachim

1999-01-01

Biodegradation of 2,4,6-trinitrophenol (picric acid) by Rhodococcus erythropolis HLPM-1 proceeds via initial hydrogenation of the aromatic ring system. Here we present evidence for the formation of a hydride-Meisenheimer complex (anionic ς-complex) of picric acid and its protonated form under physiological conditions. These complexes are key intermediates of denitration and productive microbial degradation of picric acid. For comparative spectroscopic identification of the hydride complex, it was necessary to synthesize this complex for the first time. Spectroscopic data revealed the initial addition of a hydride ion at position 3 of picric acid. This hydride complex readily picks up a proton at position 2, thus forming a reactive species for the elimination of nitrite. Cell extracts of R. erythropolis HLPM-1 transform the chemically synthesized hydride complex into 2,4-dinitrophenol. Picric acid is used as the sole carbon, nitrogen, and energy source by R. erythropolis HLPM-1. PMID:9973345

DEVELOPMENT OF AN ELECTROSPRAY MASS SPECTROMETRIC METHOD FOR DETERMINING PERCHLORATE IN FERTILIZERS

EPA Science Inventory

An electrospray mass spectrometric method has been developed for application to agricultural and horticultural fertilizers to determine perchlorate. After fertilizers are leached or dissolved in water, the method relies on the formation of stable ion pair complex of the perchlor...

Photoinduced Charge Shifts and Electron Transfer in Viologen-Tetraphenylborate Complexes: Push-Pull Character of the Exciplex.

PubMed

Santos, Willy G; Budkina, Darya S; Deflon, Victor M; Tarnovsky, Alexander N; Cardoso, Daniel R; Forbes, Malcolm D E

2017-06-14

Viologen-tetraarylborate ion-pair complexes were prepared and investigated by steady-state and time-resolved spectroscopic techniques such as fluorescence and femtosecond transient absorption. The results highlight a charge transfer transition that leads to changes in the viologen structure in the excited singlet state. Femtosecond transient absorption reveals the formation of excited-state absorption and stimulated emission bands assigned to the planar (k obs < 10 12 s -1 ) and twisted (k obs ∼ 10 10 s -1 ) structures between two pyridinium groups in the viologen ion. An efficient photoinduced electron transfer from the tetraphenylborate anionic moiety to the viologen dication was observed less than 1 μs after excitation. This is a consequence of the push-pull character of the electron donor twisted viologen structure, which helps formation of the borate triplet state. The borate triplet state is deactivated further via a second electron transfer process, generating viologen cation radical (V •+ ).

Theoretical study of the coordination behavior of formate and formamidoximate with dioxovanadium( v ) cation: implications for selectivity towards uranyl

DOE PAGES

Mehio, Nada; Johnson, J. Casey; Dai, Sheng; ...

2015-10-28

Poly(acrylamidoxime)-based fibers bearing random mixtures of carboxylate and amidoxime groups are the most widely utilized materials for extracting uranium from seawater. However, the competition between uranyl (UO 2 2+) and vanadium ions poses a significant challenge to the industrial mining of uranium from seawater using the current generation of adsorbents. To design more selective adsorbents, a detailed understanding of how major competing ions interact with carboxylate and amidoxime ligands is required. In this work, we employ density functional theory (DFT) and wave-function methods to investigate potential binding motifs of the dioxovanadium ion, VO 2 +, with water, formate, and formamidoximatemore » ligands. Employing higher level of theory calculations (CCSD(T)) resolve the existing controversy between the experimental results and previous DFT calculations for the structure of the hydrated VO 2 + ion. Consistent with the EXAFS data, CCSD(T) calculations predict higher stability of the distorted octahedral geometry of VO 2 +(H 2O) 4 compared to the five-coordinate complex with a single water molecule in the second hydration shell, while all seven tested DFT methods yield the reverse stability of the two conformations. Analysis of the relative stabilities of formate-VO 2 + complexes indicates that both monodentate and bidentate forms may coexist in thermodynamic equilibrium in solution, with the equilibrium balance leaning more towards the formation of monodentate species. Investigations of VO 2 + coordination with the formamidoximate anion has revealed the existence of seven possible binding motifs, four of which are within ~ 4.0 kcal/mol of each other. Calculations establish that the most stable binding motif entails the coordination of oxime oxygen and amide nitrogen atoms via a tautomeric rearrangement of amidoxime to imino hydroxylamine. Lastly, the difference in the most stable VO 2 + and UO 2 2+ binding conformation has important implications for the design of more selective UO 2 2+ ligands.« less

Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

PubMed

Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

2015-05-21

Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

Structural and magnetic conformation of a cerocene [Ce(COT'')2]- exhibiting a uniconfigurational f1 ground state and slow-magnetic relaxation.

PubMed

Le Roy, Jennifer J; Korobkov, Ilia; Kim, Jee Eon; Schelter, Eric J; Murugesu, Muralee

2014-02-21

Magnet-like behaviour, in the form of slow relaxation of the magnetization, was observed for a monometallic cerium(III) sandwich complex. The use of trimethylsilyl substituted COT ligands (COT'') led to the formation of a staggered COT'' arrangement in the cerocene-type sandwich complex with a well-defined oxidation state of +3 for the Ce ion.

Comparative solution equilibrium studies on pentamethylcyclopentadienyl rhodium complexes of 2,2'-bipyridine and ethylenediamine and their interaction with human serum albumin.

PubMed

Enyedy, Éva A; Mészáros, János P; Dömötör, Orsolya; Hackl, Carmen M; Roller, Alexander; Keppler, Bernhard K; Kandioller, Wolfgang

2015-11-01

Complex formation equilibrium processes of the (N,N) donor containing 2,2'-bipyridine (bpy) and ethylenediamine (en) with (η(5)-pentamethylcyclopentadienyl)rhodium(III) were investigated in aqueous solution via pH-potentiometry, (1)H NMR spectroscopy, and UV-vis spectrophotometry in the absence and presence of chloride ions. The structure of [RhCp*(en)Cl]ClO4 (Cp*, pentamethylcyclopentadienyl) was also studied by single-crystal X-ray diffraction. pKa values of 8.56 and 9.58 were determined for [RhCp*(bpy)(H2O)](2+) and [RhCp*(en)(H2O)](2+), respectively resulting in the formation of negligible amount of mixed hydroxido complexes at pH 7.4. Stability and the H2O/Cl(-) co-ligand exchange constants of bpy and en complexes considerably exceed those of the bidentate O-donor deferiprone. The strong affinity of the bpy and en complexes to chloride ions most probably contributes to their low antiproliferative effect. Interactions between human serum albumin (HSA) and [RhCp*(H2O)3](2+), its complexes formed with deferiprone, bpy and en were also monitored by (1)H NMR spectroscopy, ultrafiltration/UV-vis and spectrofluorometry. Numerous binding sites (≥ 8) are available for [RhCp*(H2O)3](2+); and the interaction takes place most probably via covalent bonds through the imidazole nitrogen of His. According to the various fluorescence studies [RhCp*(H2O)3](2+) binds on sites I and II, and coordination of surface side chain donor atoms of the protein is also feasible. The binding of the bpy and en complex is weaker and slower compared to that of [RhCp*(H2O)3](2+), and formation of ternary HSA-RhCp*-ligand adducts was proved. In the case of the deferiprone complex, the RhCp* fragment is cleaved off when HSA is loaded with low equivalents of the compound.

Molecular recognition of organic ammonium ions in solution using synthetic receptors

PubMed Central

Späth, Andreas

2010-01-01

Summary Ammonium ions are ubiquitous in chemistry and molecular biology. Considerable efforts have been undertaken to develop synthetic receptors for their selective molecular recognition. The type of host compounds for organic ammonium ion binding span a wide range from crown ethers to calixarenes to metal complexes. Typical intermolecular interactions are hydrogen bonds, electrostatic and cation–π interactions, hydrophobic interactions or reversible covalent bond formation. In this review we discuss the different classes of synthetic receptors for organic ammonium ion recognition and illustrate the scope and limitations of each class with selected examples from the recent literature. The molecular recognition of ammonium ions in amino acids is included and the enantioselective binding of chiral ammonium ions by synthetic receptors is also covered. In our conclusion we compare the strengths and weaknesses of the different types of ammonium ion receptors which may help to select the best approach for specific applications. PMID:20502608

The role of metals in production and scavenging of reactive oxygen species in photosystem II.

PubMed

Pospíšil, Pavel

2014-07-01

Metal ions play a crucial role in enzymatic reactions in all photosynthetic organisms such as cyanobacteria, algae and plants. It well known that metal ions maintain the binding of substrate in the active site of the metalloenzymes and control the redox activity of the metalloenzyme in the enzymatic reaction. A large pigment-protein complex, PSII, known to serve as a water-plastoquinone oxidoreductase, contains three metal centers comprising non-heme iron, heme iron of Cyt b559 and the water-splitting manganese complex. Metal ions bound to PSII proteins maintain the electron transport from water to plastoquinone and regulate the pro-oxidant and antioxidant activity in PSII. In this review, attention is focused on the role of PSII metal centers in (i) the formation of superoxide anion and hydroxyl radicals by sequential one-electron reduction of molecular oxygen and the formation of hydrogen peroxide by incomplete two-electron oxidation of water; and (ii) the elimination of superoxide anion radical by one-electron oxidation and reduction (superoxide dismutase activity) and of hydrogen peroxide by two-electron oxidation and reduction (catalase activity). The balance between the formation and elimination of reactive oxygen species by PSII metal centers is discussed as an important aspect in the prevention of photo-oxidative damage of PSII proteins and lipids. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Curcumin based chemosensor for selective detection of fluoride and cyanide anions in aqueous media.

PubMed

Ponnuvel, Kandasamy; Santhiya, Kuppusamy; Padmini, Vediappen

2016-11-30

The conjugate N,N-dimethyl curcumin analogue fluorophore dye 1 has been synthesized and its performance as a sensor was demonstrated. As a fluoride and cyanide sensor it enabled visual detection, and showed changes in UV-vis and fluorescence spectra in the presence of fluoride and cyanide ions in aqueous medium. The Job's plot indicated that the formation of a complex between dye-1 fluoride ions has a 1 : 1 stoichiometric ratio.

[Advances in the research of function of Merkel cells in tactile formation of skin].

PubMed

You, X; Wei, Z R

2018-01-20

Skin is the largest sense organ of human, with many mechanoreceptor cells under epidermis or dermis of skin and Merkel cell is one of them. It has been confirmed that Merkel cells play an important role in the process of mechanical transmission of mammalian soft tactile stimulation. Researches showed that Merkel cells had close relation to tactile formation and functioned by Merkel cell-neurite complexes and ion channels Piezo2. This article reviews Merkel cells and the function, problem and prospect of Merkel cells in tactile formation.

Identifying precursors and aqueous organic aerosol formation pathways during the SOAS campaign

NASA Astrophysics Data System (ADS)

Sareen, Neha; Carlton, Annmarie G.; Surratt, Jason D.; Gold, Avram; Lee, Ben; Lopez-Hilfiker, Felipe D.; Mohr, Claudia; Thornton, Joel A.; Zhang, Zhenfa; Lim, Yong B.; Turpin, Barbara J.

2016-11-01

Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized, low-volatility organic aerosol and, in some cases, light-absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, and health. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented, forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols), leading to the formation of secondary organic aerosol (SOAAQ). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOAAQ. The goal of this work is to identify additional precursors and products that may be atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere into water at Brent, Alabama, during the 2013 Southern Oxidant and Aerosol Study (SOAS). Hydroxyl (OH⚫) radical oxidation experiments were conducted with the aqueous mixtures collected from SOAS to better understand the formation of SOA through gas-phase followed by aqueous-phase chemistry. Total aqueous-phase organic carbon concentrations for these mixtures ranged from 92 to 179 µM-C, relevant for cloud and fog waters. Aqueous OH-reactive compounds were primarily observed as odd ions in the positive ion mode by electrospray ionization mass spectrometry (ESI-MS). Ultra high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) spectra and tandem MS (MS-MS) fragmentation of these ions were consistent with the presence of carbonyls and tetrols. Products were observed in the negative ion mode and included pyruvate and oxalate, which were confirmed by ion chromatography. Pyruvate and oxalate have been found in the particle phase in many locations (as salts and complexes). Thus, formation of pyruvate/oxalate suggests the potential for aqueous processing of these ambient mixtures to form SOAAQ.

Raman spectroscopic studies of the interaction of oxalic acid and sodium oxalate used as corrosion inhibitors with copper

NASA Astrophysics Data System (ADS)

Jeziorowski, H.; Moser, B.

1985-09-01

The Raman spectra of the liquid-solid interface recorded in situ show the formation of a salt complex of the inhibitor molecules and the copper ions. This suggests that this chemisorbed surface species produces the protective layer.

The Ionic Building Blocks of Life: Exploring Astrochemistry through Mass Spectrometry

NASA Astrophysics Data System (ADS)

Cole, Callie A.

The first polyatomic molecule was discovered in interstellar space in 1968, catalyzing the growth of a new scientific field called astrochemistry. Since its inception, collaborations among laboratory chemists, astrophysical modelers, and observational astronomers in this field have led to the detection of nearly 200 molecules in the interstellar medium (ISM). Similarly, detections of complex biomolecules in cometary dust and meteorites have sparked theories of the origin of terrestrial life, a central focus of the recently-established field of astrobiology. Chemical processing occurs in a variety of environments within our galaxy. The purpose of this work is to explore the chemistry of ions and molecules that are pertinent to a multitude of these regions including nebulae, prestellar cores, and the atmosphere of Saturn's moon, Titan. This thesis presents mass spectrometric investigations of gas-phase ion chemistry that contribute to the fields of both astrochemistry and astrobiology. Many gas-phase chemical reactions are initiated by ions due to the attractive forces induced by their charge on a reacting partner. This attraction often lowers the barriers of ion-neutral reactions, and can lead to high reaction rates even at low temperatures. The ions examined herein increase in complexity starting with simple species (CN-) and concluding with larger biomolecules, the deprotonated nucleobases. This work begins with a series of Flowing Afterglow-Selected Ion Flow Tube (FA-SIFT) experiments exploring nitrogen-containing carbanion (C xNy-) chemistry and the formation of interstellar propene and methyl formate (Chapters 3 and 4). Reactions between CxN y- and H atoms reveal pathways for destruction of several CxN- and CxN2 - anions, but no reactions are observed for CxN3 - species. Two previously-proposed reactions between organic cations and H2 are shown to be immeasurably slow and unlikely to produce propene. Lastly, a reaction pathway producing protonated trans-methyl formate is experimentally and computationally verified. The later chapters describe studies of heterocyclic biomolecules performed using a modified ion trap apparatus. These ions include deprotonated azoles, pyrimidines, and purines (Chapters 5-7). In addition to their reactivity, the dissociation processes and fragments of these anions provide clues to potential precursors and abiotic syntheses. Notably, nearly all fragments observed are detected interstellar species.

Effect of point defects on the amorphization of metallic alloys during ion implantation. [NiTi

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

Pedraza, D.F.; Mansur, L.K.

1985-01-01

A theoretical model of radiation-induced amorphization of ordered intermetallic compounds is developed. The mechanism is proposed to be the buildup of lattice defects to very high concentrations, which destabilizes the crystalline structure. Because simple point defects do not normally reach such levels during irradiation, a new defect complex containing a vacancy and an interstitial is hypothesized. Crucial properties of the complex are that the interstitial sees a local chemical environment similar to that of an atom in the ordered lattice, that the formation of the complex prevents mutual recombination and that the complex is immobile. The evolution of a disordermore » based on complexes is not accompanied by like point defect aggregation. The latter leads to the development of a sink microstructure in alloys that do not become amorphous. For electron irradiation, the complexes form by diffusional encounters. For ion irradiation, complexes are also formed directly in cascades. The possibility of direct amorphization in cascades is also included. Calculations for the compound NiTi show reasonable agreement with measured amorphization kinetics.« less

Bioinorganic Chemistry of Parkinson's Disease: Affinity and Structural Features of Cu(I) Binding to the Full-Length β-Synuclein Protein.

PubMed

Miotto, Marco C; Pavese, Mayra D; Quintanar, Liliana; Zweckstetter, Markus; Griesinger, Christian; Fernández, Claudio O

2017-09-05

Alterations in the levels of copper in brain tissue and formation of α-synuclein (αS)-copper complexes might play a key role in the amyloid aggregation of αS and the onset of Parkinson's disease (PD). Recently, we demonstrated that formation of the high-affinity Cu(I) complex with the N-terminally acetylated form of the protein αS substantially increases and stabilizes local conformations with α-helical secondary structure and restricted motility. In this work, we performed a detailed NMR-based structural characterization of the Cu(I) complexes with the full-length acetylated form of its homologue β-synuclein (βS), which is colocalized with αS in vivo and can bind copper ions. Our results show that, similarly to αS, the N-terminal region of βS constitutes the preferential binding interface for Cu(I) ions, encompassing two independent and noninteractive Cu(I) binding sites. According to these results, βS binds the metal ion with higher affinity than αS, in a coordination environment that involves the participation of Met-1, Met-5, and Met-10 residues (site 1). Compared to αS, the shift of His from position 50 to 65 in the N-terminal region of βS does not change the Cu(I) affinity features at that site (site 2). Interestingly, the formation of the high-affinity βS-Cu(I) complex at site 1 in the N-terminus promotes a short α-helix conformation that is restricted to the 1-5 segment of the AcβS sequence, which differs with the substantial increase in α-helix conformations seen for N-terminally acetylated αS upon Cu(I) complexation. Our NMR data demonstrate conclusively that the differences observed in the conformational transitions triggered by Cu(I) binding to AcαS and AcβS find a correlation at the level of their backbone dynamic properties; added to the potential biological implications of these findings, this fact opens new avenues of investigations into the bioinorganic chemistry of PD.

Vibrational spectra of carboxylato complexes—III. Trinuclear 'basic' acetates and formates of chromium(III), iron(III) and other transition metals

NASA Astrophysics Data System (ADS)

Johnson, M. K.; Powell, D. B.; Cannon, R. D.

The i.r. and Raman spectra of a series of complexes [M III3O(OOCR) 6L 3]X· xH 2O (M = Cr, Fe, Mn, Ru, Rh; L = H 2O, pyridine, γ-picoline; X = Cl, Br, I, NO 3, ClO 3, ClO 4, BF 4) have been analysed in detail. The vibrational modes of the central M 3O and the three surrounding MO 4 units, are identified. The metal—nitrogen stretching vibrations and the MOH 2 modes are assigned. The 'basic' chromium(III) formate is shown to be [Cr 3O(OOCH) 6(OH 2) 2(OOCH)] xH 2O, containing monodentate, inner-sphere coordinated formate ion. The use of the symmetric and asymmetric OCO stretching frequencies in characterizing bridging carboxylate ions is discussed.

Investigations on caesium-free alternatives for H{sup −} formation at ion source relevant parameters

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

Kurutz, U.; Fantz, U.; AG Experimentelle Plasmaphysik, Institut für Physik, Universität Augsburg, 86135 Augsburg

2015-04-08

Negative hydrogen ions are efficiently produced in ion sources by the application of caesium. Due to a thereby induced lowering of the work function of a converter surface a direct conversion of impinging hydrogen atoms and positive ions into negative ions is maintained. However, due to the complex caesium chemistry and dynamics a long-term behaviour is inherent for the application of caesium that affects the stability and reliability of negative ion sources. To overcome these drawbacks caesium-free alternatives for efficient negative ion formation are investigated at the flexible laboratory setup HOMER (HOMogenous Electron cyclotron Resonance plasma). By the usage ofmore » a meshed grid the tandem principle is applied allowing for investigations on material induced negative ion formation under plasma parameters relevant for ion source operation. The effect of different sample materials on the ratio of the negative ion density to the electron density n{sub H{sup −}} /n{sub e} is compared to the effect of a stainless steel reference sample and investigated by means of laser photodetachment in a pressure range from 0.3 to 3 Pa. For the stainless steel sample no surface induced effect on the negative ion density is present and the measured negative ion densities are resulting from pure volume formation and destruction processes. In a first step the dependency of n{sub H{sup −}} /n{sub e} on the sample distance has been investigated for a caesiated stainless steel sample. At a distance of 0.5 cm at 0.3 Pa the density ratio is 3 times enhanced compared to the reference sample confirming the surface production of negative ions. In contrast for the caesium-free material samples, tantalum and tungsten, the same dependency on pressure and distance n{sub H{sup −}} /n{sub e} like for the stainless steel reference sample were obtained within the error margins: A density ratio of around 14.5% is measured at 4.5 cm sample distance and 0.3 Pa, linearly decreasing with decreasing distance to 7% at 1.5 cm. Thus, tantalum and tungsten do not significantly affect the negative ion density. First measurements conducted with LaB{sub 6} as well as with two types of diamond like carbon (DLC) n{sub H{sup −}} /n{sub e} of about 15% at 1 Pa were measured, which is comparable to the density ratio obtained for the stainless steel reference sample. At HOMER a surface induced enhancement of n{sub H{sup −}} is only observed when it exceeds the volume formation of H{sup −} which is also realistic for negative hydrogen ion sources.« less

Laboratory Simulation of Frozen Methanol Under X-ray Radiation Field: Relevancies to Astrophysical Ices

NASA Astrophysics Data System (ADS)

Andrade, Diana; Rocco, Maria Luiza M.; Boechat-Roberty, Heloisa Maria

The origin of complex organic molecules detected in comets, meteorites, star-forming regions and other environments are currently subject of discussion. Depending on the environment, it is dominated by X-rays, UV photons as well as by charged particles, electrons and ions with high or low energies. Every particle will promote a different fragmentation in the molecule and different phenomena in the ice, favoring the formation of an ion species rather than another. To predict the chemical evolution and to quantify the complex organics incorporated into grains or desorbed to the gas phase, it is necessary to establish the main formation route, which can be tested in the laboratories. In this way, the study of the effects of different ionization agents on the ices becomes crucial. Methanol (CH3 OH), the simplest organic alcohol, is an important precursor of more complex prebiotic species and is found abundantly in icy mantles on interstellar and protostellar dust grains. This molecule has been detected through infrared spectroscopy in some astrophysics environments as W33A and RAFGL 7009. Additionally, methanol has been found in comets, as Hale-Bopp, and other solar system bodies, such as the centaur 5145 Pholus. All of these astronomical environments are subjected to some form of ionizing agents such as cosmic rays, electrons and photons (e.g. stellar radiation field). In this work, synchrotron radiation from the Brazilian Synchrotron Light Laboratory at the O 1s-edge was employed to perform desorption experiments on the frozen methanol. The desorp-tion rates (desorbed ion per incident photon) of the most intense ions desorbed from methanol due soft X-ray bombardment are estimated. The desorption rates are critical parameters for modeling the chemistry of interstellar clouds. Moreover, a comparison among our results and literature using different ionization agents and different phases (photons at 292 eV and elec-trons at 70 eV in gaseous phase and heavy ions around 65 MeV on methanol ice) is given and discussed.

Structural dependence of flavonoid interactions with Cu2+ ions: implications for their antioxidant properties.

PubMed Central

Brown, J E; Khodr, H; Hider, R C; Rice-Evans, C A

1998-01-01

The flavonoids constitute a large group of polyphenolic phytochemicals with antioxidant properties in vitro. The interactions of four structurally related flavonoids (quercetin, kaempferol, rutin and luteolin) with Cu2+ ions were investigated in terms of the extent to which they undergo complex formation through chelation or modification through oxidation, as well as in their structural dependence. The ortho 3',4'-dihydroxy substitution in the B ring is shown to be important for Cu2+-chelate formation, thereby influencing the antioxidant activity. The presence of a 3-hydroxy group in the flavonoid structure enhances the oxidation of quercetin and kaempferol, whereas luteolin and rutin, each lacking the 3-hydroxy group, do not oxidize as readily in the presence of Cu2+ ions. The results also demonstrate that the reactivities of the flavonoids in protecting low-density lipoprotein (LDL) against Cu2+ ion-induced oxidation are dependent on their structural properties in terms of the response of the particular flavonoid to Cu2+ ions, whether chelation or oxidation, their partitioning abilities between the aqueous compartment and the lipophilic environment within the LDL particle, and their hydrogen-donating antioxidant properties. PMID:9494082

Photosynthesis. Electronic structure of the oxygen-evolving complex in photosystem II prior to O-O bond formation.

PubMed

Cox, Nicholas; Retegan, Marius; Neese, Frank; Pantazis, Dimitrios A; Boussac, Alain; Lubitz, Wolfgang

2014-08-15

The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived from quantum chemical modeling is consistent with all magnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximal manganese-bound oxygens in the transition state of the cofactor. Copyright © 2014, American Association for the Advancement of Science.

Copper-phospholipid interaction at cell membrane model hydrophobic surfaces.

PubMed

Mlakar, Marina; Cuculić, Vlado; Frka, Sanja; Gašparović, Blaženka

2018-04-01

Detailed investigation of Cu (II) binding with natural lipid phosphatidylglycerol (PG) in aqueous solution was carried out by voltammetric measurements at the mercury drop electrode, complemented by monolayer studies in a Langmuir trough and electrophoretic measurements, all used as models for hydrophobic cell membranes. Penetration of copper ions into the PG layer was facilitated by the formation of hydrophilic Cu-Phenanthroline (Phen) complex in the subphase, followed by the mixed ligand Cu-Phen-PG complex formation at the hydrophobic interface. Electrophoretic measurements indicated a comparatively low abundance of the formed mixed ligand complex within the PG vesicles, resulting it the zeta potential change of +0.83mV, while monolayer studies confirmed their co-existence at the interface. The Cu-Phen-PG complex was identified in the pH range from 6 to 9. The stoichiometry of the complex ([PhenCuOHPG]), as well as its stability and kinetics of formation, were determined at the mercury drop electrode. Cu-Phen-PG reduces quasireversibly at about -0.7V vs. Ag/AgCl including reactant adsorption, followed by irreversible mixed complex dissociation, indicating a two-electron transfer - chemical reaction (EC mechanism). Consequently, the surface concentration (γ) of the adsorbed [PhenCuOHPG] complex at the hydrophobic electrode surface was calculated to be (3.35±0.67)×10 -11 molcm -2 . Information on the mechanism of Cu (II) - lipid complex formation is a significant contribution to the understanding of complex processes at natural cell membranes. Copyright © 2017 Elsevier B.V. All rights reserved.

Liesegang banding and multiple precipitate formation in cobalt phosphate systems

NASA Astrophysics Data System (ADS)

Karam, Tony; El-Rassy, Houssam; Zaknoun, Farah; Moussa, Zeinab; Sultan, Rabih

2012-02-01

We study a cobalt phosphate Liesegang pattern from cobalt(II) and phosphate ions in a 1D tube. The system yields a complex, multi-component pattern. Characterization of the different precipitates by FTIR, SEM and XRD reveals that they are cobalt phosphate polymorphs with different degrees of hydration.

Mixed system of Eudragit s-100 with a designed amphipathic peptide: control of interfacial elasticity by solution composition.

PubMed

Dexter, Annette F; Malcolm, Andrew S; Zeng, Biyun; Kennedy, Debora; Middelberg, Anton P J

2008-04-01

We report an interfacially active system based on an informational peptide surfactant mixed with an oppositely charged polyelectrolyte. The 21-residue cationic peptide, AM1, has previously been shown to respond reversibly to pH and metal ions at fluid interfaces, forming elastic films that can be rapidly switched to collapse foams or emulsions on demand. Here we report the reversible association of AM1 with the methacrylate-based anionic polymer Eudragit S-100. The strength of the association, in bulk aqueous solution, is modulated by added metal ions and by ionic strength. Addition of zinc ions to the peptide-polymer system promotes complex formation and phase separation, while addition of a chelating agent reverses the association. The addition of salt weakens peptide-polymer interactions in the presence or absence of zinc. At the air-water interface, Eudragit S-100 forms an elastic mixed film with AM1 in the absence of metal, under conditions where the peptide alone does not show interfacial elasticity. When zinc is present, the elasticity of the mixed film is increased, but the rate of interfacial adsorption slows due to formation of peptide-polymer complexes in bulk solution. An understanding of these interactions can be used to identify favorable foam-forming conditions in the mixed system.

Supramolecular structures on silica surfaces and their adsorptive properties.

PubMed

Belyakov, Vladimir N; Belyakova, Lyudmila A; Varvarin, Anatoly M; Khora, Olexandra V; Vasilyuk, Sergei L; Kazdobin, Konstantin A; Maltseva, Tetyana V; Kotvitskyy, Alexey G; Danil de Namor, Angela F

2005-05-01

The study of adsorptive and chemical immobilization of beta-cyclodextrin on a surface of hydroxylated silicas with various porous structure is described. Using IR spectroscopy, thermal gravimetrical analysis with a programmed heating, and chemical analysis of the silica surface, it is shown that the process of adsorption-desorption of beta-cyclodextrin depends on the porous structure of the silica. The reaction of esterification was used for chemical grafting of beta-cyclodextrin on the surface of hydroxylated silicas. Hydrolytic stability of silicas chemically modified by beta-cyclodextrin apparently is explained by simultaneous formation of chemical and hydrogen bonds between surface silanol groups and hydroxyl groups of beta-cyclodextrin. The uptake of the cations Cu(II), Cd(II), and Pb(II) and the anions Cr(VI) and As(V) by silicas modified with beta-cyclodextrin is investigated as a function of equilibrium ion concentrations. The increase of ion uptake and selectivity of ion extraction in comparison with starting silicas is established. It is due to the formation of surface inclusion complexes of the "host-guest" type in which one molecule of beta-cyclodextrin interacts simultaneously with several ions.

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte.

PubMed

Arya, Anil; Sharma, A L

2018-04-25

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO 8 -NaPF 6 +  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ([Formula: see text]) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ([Formula: see text]) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole-Cole plot ([Formula: see text]) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Effect of phospholipase A treatment of low density lipoproteins on the dextran sulfate--lipoprotein interaction.

PubMed

Nishida, T

1968-09-01

The effect of phospholipase A on the interaction of low density lipoproteins of the S(f) 0-10 class with dextran sulfate was studied in phosphate buffer of pH 7.4, ionic strength 0.1, by chemical, spectrophotometric, and centrifugal methods. When low density lipoproteins that had been treated with phospholipase A were substituted for untreated lipoproteins, the amount of insoluble dextran sulfate-lipoprotein complex formed was greatly reduced. Hydrolysis of over 20% of the lecithin and phosphatidyl ethanolamine constituents of the lipoproteins prevented the formation of insoluble complex. However, even the lipoproteins in which almost all the phosphoglycerides were hydrolyzed produced soluble complex, which was converted to insoluble complex upon addition of magnesium sulfate. It is apparent that the lipoproteins altered extensively by treatment with phospholipase A retain many characteristic properties of native low density lipoproteins. Fatty acids, but not lysolecithin, released by the action of phospholipase A interfered with the formation of insoluble complex; this interference was due to association of the fatty acids with the lipoproteins. With increases in the concentration of the associated fatty acids, the amounts of magnesium ion required for the conversion of soluble complex to insoluble complex increased progressively. Charge interaction is evidently of paramount importance in the formation of sulfated polysaccharide-lipoprotein complexes.

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid-Liquid Extraction

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

Wintergerst, Mr. Matthieu; Levitskaia, Tatiana G.; Moyer, Bruce A

Solvent-extraction studies provide confirming evidence that meso-octamethylcalix[4]pyrrole acts as an ion-pair receptor for cesium chloride and cesium bromide in nitrobenzene solution. The stoichiometry of the interaction under extraction conditions from water to nitrobenzene was determined from plots of the cesium distribution ratios vs cesium salt and receptor concentration, indicating the formation of an ionpaired 1:1:1 cesium:calix[4]pyrrole:halide complex. The extraction results were modeled to evaluate the equilibria inherent to the solvent-extraction system, with either chloride or bromide. The binding energy between the halide anion and the calix[4]pyrrole was found to be about 7 kJ/mol larger for cesium chloride than for themore » cesium bromide. The ion-pairing free energies between the calix[4]pyrrole-halide complex and the cesium cation are nearly the same within experimental uncertainty for either halide, consistent with a structural model in which the Cs+ cation resides in the calix bowl. These results are unexpected since nitrobenzene is a polar solvent that generally leads to dissociated complexes in the organic phase when used as a diluent in extraction studies of univalent ions. Control studies involving nitrate revealed no evidence of ion pairing for CsNO3 under conditions identical to those where it is observed for CsCl and CsBr.« less

Complexation-induced supramolecular assembly drives metal-ion extraction.

PubMed

Ellis, Ross J; Meridiano, Yannick; Muller, Julie; Berthon, Laurence; Guilbaud, Philippe; Zorz, Nicole; Antonio, Mark R; Demars, Thomas; Zemb, Thomas

2014-09-26

Combining experiment with theory reveals the role of self-assembly and complexation in metal-ion transfer through the water-oil interface. The coordinating metal salt Eu(NO3)3 was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X-ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long-range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu(3+)-3(NO3(-)) ion pairs involves incorporation of the "hard" metal complex into the core of "soft" aggregates. This seeds the formation of reverse micelles that draw the water and "free" amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod-shaped polynuclear Eu(III) -containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O-donor ligands and anions, provide improved Eu(III) solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu(III) partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal-ion coordination with nanoscale structure to reveal the free-energy balance that drives the phase transfer of neutral metal salts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solar Ion Processing of Itokawa Grains: Reconciling Model Predictions with Sample Observations

NASA Technical Reports Server (NTRS)

Christoffersen, Roy; Keller, L. P.

2014-01-01

Analytical TEM observations of Itokawa grains reported to date show complex solar wind ion processing effects in the outer 30-100 nm of pyroxene and olivine grains. The effects include loss of long-range structural order, formation of isolated interval cavities or "bubbles", and other nanoscale compositional/microstructural variations. None of the effects so far described have, however, included complete ion-induced amorphization. To link the array of observed relationships to grain surface exposure times, we have adapted our previous numerical model for progressive solar ion processing effects in lunar regolith grains to the Itokawa samples. The model uses SRIM ion collision damage and implantation calculations within a framework of a constant-deposited-energy model for amorphization. Inputs include experimentally-measured amorphization fluences, a Pi steradian variable ion incidence geometry required for a rotating asteroid, and a numerical flux-versus-velocity solar wind spectrum.

Relationships between nitric oxide, nitroxyl ion, nitrosonium cation and peroxynitrite.

PubMed

Hughes, M N

1999-05-05

This review is concerned mainly with the three redox-related, but chemically distinct, species NO-, NO. and NO+, with greatest emphasis being placed on the chemistry and biology of the nitroxyl ion. Biochemical routes for the formation of nitroxyl ion and methods for showing the intermediacy of this species are discussed, together with chemical methods for generating nitroxyl ion in solution. Reactions of nitroxyl ion with NO., thiols, iron centres in haem and with dioxygen are reviewed The significance of the reaction between NO- and dioxygen as a source of peroxynitrite is assessed, and attention drawn to the possible significance of the spin state of the nitroxyl ion in this context. The biological significance of nitrosation and the importance of S-nitrosothiols and certain metal nitrosyl complexes as carriers of NO+ at physiological pH is stressed. Some features in the chemistry of peroxynitrite are noted.

Formation of p-type ZnO thin film through co-implantation

NASA Astrophysics Data System (ADS)

Chuang, Yao-Teng; Liou, Jhe-Wei; Woon, Wei-Yen

2017-01-01

We present a study on the formation of p-type ZnO thin film through ion implantation. Group V dopants (N, P) with different ionic radii are implanted into chemical vapor deposition grown ZnO thin film on GaN/sapphire substrates prior to thermal activation. It is found that mono-doped ZnO by N+ implantation results in n-type conductivity under thermal activation. Dual-doped ZnO film with a N:P ion implantation dose ratio of 4:1 is found to be p-type under certain thermal activation conditions. Higher p-type activation levels (1019 cm-3) under a wider thermal activation range are found for the N/P dual-doped ZnO film co-implanted by additional oxygen ions. From high resolution x-ray diffraction and x-ray photoelectron spectroscopy it is concluded that the observed p-type conductivities are a result of the promoted formation of PZn-4NO complex defects via the concurrent substitution of nitrogen at oxygen sites and phosphorus at zinc sites. The enhanced solubility and stability of acceptor defects in oxygen co-implanted dual-doped ZnO film are related to the reduction of oxygen vacancy defects at the surface. Our study demonstrates the prospect of the formation of stable p-type ZnO film through co-implantation.

Structure of the Ni(II) complex of Escherichia coli peptide deformylase and suggestions on deformylase activities depending on different metal(II) centres.

PubMed

Yen, Ngo Thi Hai; Bogdanović, Xenia; Palm, Gottfried J; Kühl, Olaf; Hinrichs, Winfried

2010-02-01

Crystal structures of polypeptide deformylase (PDF) of Escherichia coli with nickel(II) replacing the native iron(II) have been solved with chloride and formate as metal ligands. The chloro complex is a model for the correct protonation state of the hydrolytic hydroxo ligand and the protonated status of the Glu133 side chain as part of the hydrolytic mechanism. The ambiguity that recently some PDFs have been identified with Zn(2+) ion as the active-site centre whereas others are only active with Fe(2+) (or Co(2+), Ni(2+) is discussed with respect to Lewis acid criteria of the metal ion and substrate activation by the CD loop.

Direct two-photon excitation of Sm3+, Eu3+, Tb3+, Tb.DOTA-, and Tb.propargylDO3A in solution

NASA Astrophysics Data System (ADS)

Sørensen, Thomas Just; Blackburn, Octavia A.; Tropiano, Manuel; Faulkner, Stephen

2012-07-01

We have observed direct two-photon excitation of samarium, europium and terbium ions in solution upon near IR excitation using a tuneable pulsed light source, and have also studied two-photon processes in a pair of related terbium complexes, namely [Tb.DOTA]- and Tb.propargylDO3A. Direct two-photon excitation of lanthanides is observed in simple systems in the absence of sensitizing chromophores. Where even simple chromophores such as a triple bond are present in the complex, then single and two-photon excitation of chromophore excited states competes with direct two-photon excitation of the ions and is the dominant pathway for sensitizing formation of the lanthanide excited state.

Target-induced formation of gold amalgamation on DNA-based sensing platform for electrochemical monitoring of mercury ion coupling with cycling signal amplification strategy.

PubMed

Chen, Jinfeng; Tang, Juan; Zhou, Jun; Zhang, Lan; Chen, Guonan; Tang, Dianping

2014-01-31

Heavy metal ion pollution poses severe risks in human health and environmental pollutant, because of the likelihood of bioaccumulation and toxicity. Driven by the requirement to monitor trace-level mercury ion (Hg(2+)), herein we construct a new DNA-based sensor for sensitive electrochemical monitoring of Hg(2+) by coupling target-induced formation of gold amalgamation on DNA-based sensing platform with gold amalgamation-catalyzed cycling signal amplification strategy. The sensor was simply prepared by covalent conjugation of aminated poly-T(25) oligonucleotide onto the glassy carbon electrode by typical carbodiimide coupling. Upon introduction of target analyte, Hg(2+) ion was intercalated into the DNA polyion complex membrane based on T-Hg(2+)-T coordination chemistry. The chelated Hg(2+) ion could induce the formation of gold amalgamation, which could catalyze the p-nitrophenol with the aid of NaBH4 and Ru(NH3)6(3+) for cycling signal amplification. Experimental results indicated that the electronic signal of our system increased with the increasing Hg(2+) level in the sample, and has a detection limit of 0.02nM with a dynamic range of up to 1000nM Hg(2+). The strategy afforded exquisite selectivity for Hg(2+) against other environmentally related metal ions. In addition, the methodology was evaluated for the analysis of Hg(2+) in spiked tap-water samples, and the recovery was 87.9-113.8%. Copyright © 2013 Elsevier B.V. All rights reserved.

Gas-Phase Analysis of the Complex of Fibroblast GrowthFactor 1 with Heparan Sulfate: A Traveling Wave Ion Mobility Spectrometry (TWIMS) and Molecular Modeling Study

NASA Astrophysics Data System (ADS)

Zhao, Yuejie; Singh, Arunima; Xu, Yongmei; Zong, Chengli; Zhang, Fuming; Boons, Geert-Jan; Liu, Jian; Linhardt, Robert J.; Woods, Robert J.; Amster, I. Jonathan

2017-01-01

Fibroblast growth factors (FGFs) regulate several cellular developmental processes by interacting with cell surface heparan proteoglycans and transmembrane cell surface receptors (FGFR). The interaction of FGF with heparan sulfate (HS) is known to induce protein oligomerization, increase the affinity of FGF towards its receptor FGFR, promoting the formation of the HS-FGF-FGFR signaling complex. Although the role of HS in the signaling pathways is well recognized, the details of FGF oligomerization and formation of the ternary signaling complex are still not clear, with several conflicting models proposed in literature. Here, we examine the effect of size and sulfation pattern of HS upon FGF1 oligomerization, binding stoichiometry and conformational stability, through a combination of ion mobility (IM) and theoretical modeling approaches. Ion mobility-mass spectrometry (IMMS) of FGF1 in the presence of several HS fragments ranging from tetrasaccharide (dp4) to dodecasaccharide (dp12) in length was performed. A comparison of the binding stoichiometry of variably sulfated dp4 HS to FGF1 confirmed the significance of the previously known high-affinity binding motif in FGF1 dimerization, and demonstrated that certain tetrasaccharide-length fragments are also capable of inducing dimerization of FGF1. The degree of oligomerization was found to increase in the presence of dp12 HS, and a general lack of specificity for longer HS was observed. Additionally, collision cross-sections (CCSs) of several FGF1-HS complexes were calculated, and were found to be in close agreement with experimental results. Based on the (CCSs) a number of plausible binding modes of 2:1 and 3:1 FGF1-HS are proposed.

Spectrophotometric study of the charge-transfer and ion-pair complexation of methamphetamine with some acceptors

NASA Astrophysics Data System (ADS)

Shahdousti, Parvin; Aghamohammadi, Mohammad; Alizadeh, Naader

2008-04-01

The charge-transfer (CT) complexes of methamphetamine (MPA) as a n-donor with several acceptors including bromocresolgreen (BCG), bromocresolpurple (BCP), chlorophenolred (CPR), picric acid (PIC), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been studied spectrophotometrically in chloroform solutions in order to obtain some information about their stoichiometry and stability of complexation. The oscillator strengths, transition dipole moments and resonance energy of the complex in the ground state for all complexes have been calculated. Vertical ionization potential of MPA and electron affinity of acceptors were determined by ab initio calculation. The acceptors were also used to utilize a simple and sensitive extraction-spectrophotometric method for the determination of MPA. The method is based on the formation of 1:1 ion-pair association complexes of MPA with BCG, BCP and PIC in chloroform medium. Beer's plots were obeyed in a general concentration range of 0.24-22 μg ml -1 for the investigated drug with different acceptors. The proposed methods were applied successfully for the determination of MAP in pure and abuse drug with good accuracy and precision.

Pyrazolate-based copper(II) and nickel(II) [2 x 2] grid complexes: protonation-dependent self-assembly, structures and properties.

PubMed

Klingele, Julia; Prikhod'ko, Alexander I; Leibeling, Guido; Demeshko, Serhiy; Dechert, Sebastian; Meyer, Franc

2007-05-28

The pyrazole-based diamide ligand N,N'-bis(2-pyridylmethyl)pyrazole-3,5-dicarboxamide (H(3)L) has been structurally characterised and successfully employed in the preparation of [2 x 2] grid-type complexes. Thus, the reaction of H(3)L with Cu(ClO(4))2.6H(2)O or Ni(ClO(4))2.6H(2)O in the presence of added base (NaOH) affords the tetranuclear complexes [M(4)(HL(4))].8H(2)O (1: M = Cu, 2: M = Ni). Employment of a mixture of the two metal salts under otherwise identical reaction conditions leads to the formation of the mixed-metal species [Cu(x)Ni(4-x)(HL)(4)].8H(2)O (x

Properties of Prussian blue materials manifested in molecular complexes: observation of cyanide linkage isomerism and spin-crossover behavior in pentanuclear cyanide clusters.

PubMed

Shatruk, Mikhail; Dragulescu-Andrasi, Alina; Chambers, Kristen E; Stoian, Sebastian A; Bominaar, Emile L; Achim, Catalina; Dunbar, Kim R

2007-05-16

Pentanuclear, cyanide-bridged clusters [M(tmphen)2]3[M'(CN)6]2 (M/M' = Zn/Cr (1), Zn/Fe (2), Fe/Fe (3), Fe/Co (4), and Fe/Cr (5); tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) were prepared by combining [M'III(CN)6]3- anions with mononuclear complexes of MII ions with two capping tmphen ligands. The clusters consist of a trigonal bipyramidal (TBP) core with three MII ions in the equatorial positions and two M'III ions in the axial positions. Compounds 1-4 are isostructural and crystallize in the monoclinic space group P21/c. Complex 5 crystallizes in the enantiomorphic space group P3221. The magnetic properties of compounds 1 and 2 reflect the contributions of the individual [CrIII(CN)6]3- and [FeIII(CN)6]3- ions. The FeII ions in compounds 3 and 4 exhibit a gradual, temperature-induced spin transition between high spin (HS) and low spin (LS), as determined by the combination of Mössbauer spectroscopy, magnetic measurements, and single-crystal X-ray studies. The investigation of compound 5 by these methods and by IR spectroscopy indicates that cyanide linkage isomerism occurs during cluster formation. The magnetic behavior of 5 is determined by weak ferromagnetic coupling between the axial CrIII centers mediated by the equatorial diamagnetic FeII ions. Mössbauer spectra collected in the presence of a high applied field have allowed, for the first time, the direct experimental observation of uncompensated spin density at diamagnetic metal ions that bridge paramagnetic metal ions.

Investigation of metal ions sorption of brown peat moss powder

NASA Astrophysics Data System (ADS)

Kelus, Nadezhda; Blokhina, Elena; Novikov, Dmitry; Novikova, Yaroslavna; Chuchalin, Vladimir

2017-11-01

For regularities research of sorptive extraction of heavy metal ions by cellulose and its derivates from aquatic solution of electrolytes it is necessary to find possible mechanism of sorption process and to choice a model describing this process. The present article investigates the regularities of aliovalent metals sorption on brown peat moss powder. The results show that sorption isotherm of Al3+ ions is described by Freundlich isotherm and sorption isotherms of Na+ i Ni2+ are described by Langmuir isotherm. To identify the mechanisms of brown peat moss powder sorption the IR-spectra of the initial brown peat moss powder samples and brown peat moss powder samples after Ni (II) sorption were studied. Metal ion binding mechanisms by brown peat moss powder points to ion exchange, physical adsorption, and complex formation with hydroxyl and carboxyl groups.

Lipophilic ternary complexes in liquid-liquid extraction of trivalent lanthanides

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

Lumetta, Gregg J.; Levitskaia, Tatiana G.; Latesky, Stanley

2012-03-01

The formation of ternary complexes between lanthanide ions [Nd(III) or Eu(III)], octyl(phenyl)-N,N-diisobutyl-carbamoylmethylphosphine oxide (CMPO), and bis-(2-ethylhexyl)phosphoric acid (HDEHP) was probed by liquid-liquid extraction and spectroscopic techniques. Equilibrium modeling of data for the extraction of Nd(III) or Eu(III) from lactic acid media into n-dodecane solutions of CMPO and HDEHP indicates the predominant extracted species are of the type [Ln(AHA){sub 2}(A)] and [Ln(CMPO)(AHA){sub 2}(A)], where Ln = Nd or Eu and A represents the DEHP{sup -} anion. FTIR (for both Eu and Nd) and visible spectrophotometry (in the case of Nd) indicate the formation of the [Ln(CMPO)(A){sup 3}] complexes when CMPO ismore » added to n-dodecane solutions of the LnA{sub 3} compounds. Both techniques indicate a stronger propensity of CMPO to complex Nd(III) versus Eu(III).« less

The Effect of Salt on the Complex Coacervation of Vinyl Polyelectrolytes

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

Perry, Sarah; Li, Yue; Priftis, Dimitrios

2014-06-01

Complex coacervation is an electrostatically-driven phase separation phenomenon that is utilized in a wide range of everyday applications and is of great interest for the creation of self-assembled materials. Here, we utilized turbidity to characterize the effect of salt type on coacervate formation using two vinyl polyelectrolytes, poly(acrylic acid sodium salt) (pAA) and poly(allylamine hydrochloride) (pAH), as simple models for industrial and biological coacervates. We confirmed the dominant role of salt valence on the extent of coacervate formation, while demonstrating the presence of significant secondary effects, which can be described by Hofmeister-like behavior. These results revealed the importance of ion-specificmore » interactions, which are crucial for the informed design of coacervate-based materials for use in complex ionic environments, and can enable more detailed theoretical investigations on the role of subtle electrostatic and thermodynamic effects in complex coacervation.« less

Complexation studies with lanthanides and humic acid analyzed by ultrafiltration and capillary electrophoresis-inductively coupled plasma mass spectrometry.

PubMed

Kautenburger, Ralf; Beck, Horst Philipp

2007-08-03

For the long-term storage of radioactive waste, detailed information about geo-chemical behavior of radioactive and toxic metal ions under environmental conditions is necessary. Humic acid (HA) can play an important role in the immobilisation or mobilisation of metal ions due to complexation and colloid formation. Therefore, we investigate the complexation behavior of HA and its influence on the migration or retardation of selected lanthanides (europium and gadolinium as homologues of the actinides americium and curium). Two independent speciation techniques, ultrafiltration and capillary electrophoresis coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS) have been compared for the study of Eu and Gd interaction with (purified Aldrich) HA. The degree of complexation of Eu and Gd in 25 mg l(-1) Aldrich HA solutions was determined with a broad range of metal loading (Eu and Gd total concentration between 10(-6) and 10(-4) mol l(-1)), ionic strength of 10 mM (NaClO4) and different pH-values. From the CE-ICP-MS electropherograms, additional information on the charge of the Eu species was obtained by the use of 1-bromopropane as neutral marker. To detect HA in the ICP-MS and separate between HA complexed and non complexed metal ions in the CE-ICP-MS, we have halogenated the HA with iodine as ICP-MS marker.

Carbonic acid ionization and the stability of sodium bicarbonate and carbonate ion pairs to 200 °C - A potentiometric and spectrophotometric study

NASA Astrophysics Data System (ADS)

Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

2013-11-01

Carbonic acid ionization and sodium bicarbonate and carbonate ion pair formation constants have been experimentally determined in dilute hydrothermal solutions to 200 °C. Two experimental approaches were applied, potentiometric acid-base titrations at 10-60 °C and spectrophotometric pH measurements using the pH indicators, 2-napthol and 4-nitrophenol, at 25-200 °C. At a given temperature, the first and second ionization constants of carbonic acid (K1, K2) and the ion pair formation constants for NaHCO(aq)(K) and NaCO3-(aq)(K) were simultaneously fitted to the data. Results of this study compare well with previously determined values of K1 and K2. The NaHCO(aq) and NaCO3-(aq) ion pair formation constants vary between 25 and 200 °C having values of logK=-0.18 to 0.58 and logK=1.01 to 2.21, respectively. These ion pairs are weak at low-temperatures but become increasingly important with increasing temperature under neutral to alkaline conditions in moderately dilute to concentrated NaCl solutions, with NaCO3-(aq) predominating over CO32-(aq) in ⩾0.1 M NaCl solution at temperatures above 100 °C. The results demonstrate that NaCl cannot be considered as an inert (non-complexing) electrolyte in aqueous carbon dioxide containing solutions at elevated temperatures.

Why can a gold salt react as a base?

PubMed

Anania, Mariarosa; Jašíková, Lucie; Jašík, Juraj; Roithová, Jana

2017-09-26

This study shows that gold salts [(L)AuX] (L = PMe 3 , PPh 3 , JohnPhos, IPr; X = SbF 6 , PF 6 , BF 4 , TfO, Tf 2 N) act as bases in aqueous solutions and can transform acetone to digold acetonyl complexes [(L) 2 Au 2 (CH 2 COCH 3 )] + without any additional base present in solution. The key step is the formation of digold hydroxide complexes [(L) 2 Au 2 (OH)] + . The kinetics of the formation of the digold complexes and their mutual transformation is studied by electrospray ionization mass spectrometry and the delayed reactant labelling method. We show that the formation of digold hydroxide is the essential first step towards the formation of the digold acetonyl complex, the reaction is favoured by more polar solvents, and the effect of counter ions is negligible. DFT calculations suggest that digold hydroxide and digold acetonyl complexes can exist in solution only due to the stabilization by the interaction with two gold atoms. The reaction between the digold hydroxide and acetone proceeds towards the dimer {[(L)Au(OH)]·[(L)Au(CH 3 COCH 3 )] + }. The monomeric units interact at the gold atoms in the perpendicular arrangement typical of the gold clusters bound by the aurophilic interaction. The hydrogen is transferred within the dimer and the reaction continues towards the digold acetonyl complex and water.

Titan's Complex Chemistry: Insights from the Lab

NASA Astrophysics Data System (ADS)

Horst, Sarah

2018-06-01

The Cassini-Huygens mission revealed Titan to be a complex world with physical processes reminiscent of other terrestrial planets, but chemistry that is unlike anywhere else in the Solar System. Titan's complex atmospheric chemistry converts N2 and CH4 into numerous, abundant organic molecules ranging from relatively simple hydrocarbons to ions with mass to charge ratios up to 10,000 amu/q. The molecules eventually settle to the surface where they can participate in and be modified by geological processes such as aeolian and fluvial erosion or undergo subsequent chemistry in Titan's lakes and seas or impact craters and potential cryovolcanic flows. From the processes leading to massive ion formation in the atmosphere to the behavior of saltating organic sands on the surface, laboratory experiments are playing a pivotal role in understanding Titan and expanding our understanding of planetary processes into new, exciting phase space.

Coinage metal complexes of 2-diphenylphosphino-3-methylindole.

PubMed

Koshevoy, Igor O; Shakirova, Julia R; Melnikov, Alexei S; Haukka, Matti; Tunik, Sergey P; Pakkanen, Tapani A

2011-08-21

Coordination of P,N indolyl-phosphine ligands to Au(I), Ag(I) and Cu(I) metal ions under weakly basic conditions results in easy deprotonation of the indolyl N-H function and effective formation of a family of homo- and heterobimetallic complexes MM'(PPh(2)C(9)H(7)N)(2) (M = M' = Au (2), Ag (5); M = Au, M' = Cu (3), Ag (4)). The latter (4) exists as an inseparable mixture of four different complexes, which are in equilibrium driven by slow dynamics. The reaction of silver(I) and copper(I) ions with PPh(2)(C(9)H(8)N) affords a rare tetranuclear Z-shaped cluster Ag(2)Cu(2)(PPh(2)C(9)H(7)N)(4) (6), which exhibits red luminescence in solid state (650 nm) and a weak dual emission in solution with the main component in the near-IR region (746 nm). This journal is © The Royal Society of Chemistry 2011

Vanadium(IV/V) complexes of Triapine and related thiosemicarbazones: Synthesis, solution equilibrium and bioactivity.

PubMed

Kowol, Christian R; Nagy, Nóra V; Jakusch, Tamás; Roller, Alexander; Heffeter, Petra; Keppler, Bernhard K; Enyedy, Éva A

2015-11-01

The stoichiometry and thermodynamic stability of vanadium(IV/V) complexes of Triapine and two related α(N)-heterocyclic thiosemicarbazones (TSCs) with potential antitumor activity have been determined by pH-potentiometry, EPR and (51)V NMR spectroscopy in 30% (w/w) dimethyl sulfoxide/water solvent mixtures. In all cases, mono-ligand complexes in different protonation states were identified. Dimethylation of the terminal amino group resulted in the formation of vanadium(IV/V) complexes with considerably higher stability. Three of the most stable complexes were also synthesized in solid state and comprehensively characterized. The biological evaluation of the synthesized vanadium complexes in comparison to the metal-free ligands in different human cancer cell lines revealed only minimal influence of the metal ion. Thus, in addition the coordination ability of salicylaldehyde thiosemicarbazone (STSC) to vanadium(IV/V) ions was investigated. The exchange of the pyridine nitrogen of the α(N)-heterocyclic TSCs to a phenolate oxygen in STSC significantly increased the stability of the complexes in solution. Finally, this also resulted in increased cytotoxicity activity of a vanadium(V) complex of STSC compared to the metal-free ligand. Copyright © 2015 Elsevier Inc. All rights reserved.

A dye-binding assay for measurement of the binding of Cu(II) to proteins.

PubMed

Wilkinson-White, Lorna E; Easterbrook-Smith, Simon B

2008-10-01

We analysed the theory of the coupled equilibria between a metal ion, a metal ion-binding dye and a metal ion-binding protein in order to develop a procedure for estimating the apparent affinity constant of a metal ion:protein complex. This can be done by analysing from measurements of the change in the concentration of the metal ion:dye complex with variation in the concentration of either the metal ion or the protein. Using experimentally determined values for the affinity constant of Cu(II) for the dye, 2-(5-bromo-2-pyridylaxo)-5-(N-propyl-N-sulfopropylamino) aniline (5-Br-PSAA), this procedure was used to estimate the apparent affinity constants for formation of Cu(II):transthyretin, yielding values which were in agreement with literature values. An apparent affinity constant for Cu(II) binding to alpha-synuclein of approximately 1 x 10(9)M(-1) was obtained from measurements of tyrosine fluorescence quenching by Cu(II). This value was in good agreement with that obtained using 5-Br-PSAA. Our analysis and data therefore show that measurement of changes in the equilibria between Cu(II) and 5-Br-PSAA by Cu(II)-binding proteins provides a general procedure for estimating the affinities of proteins for Cu(II).

Silver ions-mediated conformational switch: facile design of structure-controllable nucleic acid probes.

PubMed

Wang, Yongxiang; Li, Jishan; Wang, Hao; Jin, Jianyu; Liu, Jinhua; Wang, Kemin; Tan, Weihong; Yang, Ronghua

2010-08-01

Conformationally constraint nucleic acid probes were usually designed by forming an intramolecular duplex based on Watson-Crick hydrogen bonds. The disadvantages of these approaches are the inflexibility and instability in complex environment of the Watson-Crick-based duplex. We report that this hydrogen bonding pattern can be replaced by metal-ligation between specific metal ions and the natural bases. To demonstrate the feasibility of this principle, two linear oligonucleotides and silver ions were examined as models for DNA hybridization assay and adenosine triphosphate detection. The both nucleic acids contain target binding sequences in the middle and cytosine (C)-rich sequences at the lateral portions. The strong interaction between Ag(+) ions and cytosines forms stable C-Ag(+)-C structures, which promises the oligonucleotides to form conformationally constraint formations. In the presence of its target, interaction between the loop sequences and the target unfolds the C-Ag(+)-C structures, and the corresponding probes unfolding can be detected by a change in their fluorescence emission. We discuss the thermodynamic and kinetic opportunities that are provided by using Ag(+) ion complexes instead of traditional Watson-Crick-based duplex. In particular, the intrinsic feature of the metal-ligation motif facilitates the design of functional nucleic acids probes by independently varying the concentration of Ag(+) ions in the medium.

Cation Distribution and Local Configuration of Fe 2+ Ions in Structurally Nonequivalent Lattice Sites of Heterometallic Fe(II)/ M(II) ( M = Mn, Co, Ni, Cu, Zn) Diaquadiformato Complexes

NASA Astrophysics Data System (ADS)

Devillers, M.; Ladrière, J.

1993-03-01

57Fe Mössbauer investigations are carried out on a wide series of heterometallic diaquadiformato Fe(II)/ M(II) complexes with M = Mn, Co, Ni, Cu, and Zn to provide a local picture of the coordination environment of the 57Fe 2+ ions as a function of (i) the nature of the host cation and (ii) the relative amounts of both metals in the matrix (between 50 and 0.25 at.% Fe). Information is obtained on the quantitative distribution of both metals between the two structurally nonequivalent lattice sites and on the local geometry around the dopant atom in each crystal site. In the mixed Fe-Cu complexes. Fe 2+ ions are preferentially incorporated in the tetrahydrated site; in Cu-rich Fe xCu 1- x(HCO 2) 2· 2H 2O, the 57Fe 2+ ions located in the hexaformato-coordinated site are surrounded by an axially compressed octahedron of formate ligands which contrasts with the elongated configuration observed in the pure iron compound and in the other mixed systems. Semiquantitative estimations of the tetragonal field splitting and of the extent of metal-ligand interactions are proposed from the temperature dependence of the quadrupole splitting values.

Bismuth generator method

DOEpatents

Bray, Lane Allan; DesChane, Jaquetta R.

1998-01-01

A method for separating .sup.213 Bi from a solution of radionuclides wherein the solution contains a concentration of the chloride ions and hydrogen ions adjusted to allow the formation of a chloride complex. The solution is then brought into contact with an anion exchange resin, whereupon .sup.213 Bi is absorbed from the solution and adhered onto the anion exchange resin in the chloride complex. Other non-absorbing radionuclides such as .sup.225 Ra, .sup.225 Ac, and .sup.221 Fr, along with HCl are removed from the anion exchange resin with a scrub solution. The .sup.213 Bi is removed from the anion exchange resin by washing the anion exchange resin with a stripping solution free of chloride ions and with a reduced hydrogen ion concentration which breaks the chloride anionic complex, releasing the .sup.213 Bi as a cation. In a preferred embodiment of the present invention, the anion exchange resin is provided as a thin membrane, allowing for extremely rapid adherence and stripping of the .sup.213 Bi. A preferred stripping solution for purification of .sup.213 Bi for use in medical applications includes sodium acetate, pH 5.5. A protein conjugated with bifunctional chelating agents in vivo with the NaOAc, to receive the .sup.213 Bi as it is being released from the anion exchange resin.

Bismuth generator method

DOEpatents

Bray, L.A.; DesChane, J.R.

1998-05-05

A method is described for separating {sup 213}Bi from a solution of radionuclides wherein the solution contains a concentration of the chloride ions and hydrogen ions adjusted to allow the formation of a chloride complex. The solution is then brought into contact with an anion exchange resin, whereupon {sup 213}Bi is absorbed from the solution and adhered onto the anion exchange resin in the chloride complex. Other non-absorbing radionuclides such as {sup 225}Ra, {sup 225}Ac, and {sup 221}Fr, along with HCl are removed from the anion exchange resin with a scrub solution. The {sup 213}Bi is removed from the anion exchange resin by washing the anion exchange resin with a stripping solution free of chloride ions and with a reduced hydrogen ion concentration which breaks the chloride anionic complex, releasing the {sup 213}Bi as a cation. In a preferred embodiment of the present invention, the anion exchange resin is provided as a thin membrane, allowing for extremely rapid adherence and stripping of the {sup 213}Bi. A preferred stripping solution for purification of {sup 213}Bi for use in medical applications includes sodium acetate, pH 5.5. A protein conjugated with bifunctional chelating agents in vivo with the NaOAc receives the {sup 213}Bi as it is being released from the anion exchange resin. 10 figs.

Colorimetric and atomic absorption spectrometric determination of mucolytic drug ambroxol through ion-pair formation with iron and thiocyanate.

PubMed

Levent, Abdulkadir; Sentürk, Zühre

2010-09-01

Colorimetric and atomic absorption spectrometric methods have been developed for the determination of mucolytic drug Ambroxol. These procedures depend upon the reaction of iron(III) metal ion with the drug in the presence of thiocyanate ion to form stable ion-pair complex which extractable chloroform. The red-coloured complex was determined either colorimetrically at 510 nm or by indirect atomic absorption spectrometry (AAS) via the determination of the iron content in the formed complex. The optimum experimental conditions for pH, concentrations of Fe(3+) and SCN(-), shaking time, phase ratio, and the number of extractions were determined. Under the proposed conditions, linearity was obeyed in the concentration ranges 4.1x10(-6) - 5.7x10(-5) M (1.7-23.6 µg mL(-1)) using both methods, with detection limits of 4.6x10(-7) M (0.19 µg mL(-1)) for colorimetry and 1.1x10(-6) M (0.46 µg mL(-1)) for AAS. The proposed methods were applied for the determination of Ambroxol in tablet dosage forms. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection.

Composition and stability of complexes of maleic and succinic acids with Cu2+ ions in water-ethanol solutions at 298 K

NASA Astrophysics Data System (ADS)

Tukumova, N. V.; Usacheva, T. R.; Thuan, Tran Thi Dieu; Sharnin, V. A.

2014-10-01

The composition and stability of coordination compounds of the anions of maleic (H2L) and succinic (H2Y) acids with copper(II) ions in water-ethanol solutions is studied by means of potentiometric titration at a sodium perchlorate ionic strength of 0.1 and a temperature of 298.15 K. The composition of the water-ethanol solvent was varied from 0 to 0.7 molar parts of ethanol for maleic acid and from 0 to 0.4 molar parts for succinic acid. The stability of monoligand complexes of copper ions with the anions of maleic and succinic acids grows with increase of ethanol concentration from 3.86 to 6.62 for logβCuL and from 2.98 to 6.01 for logβCuY. It is shown that a monotonic rise in stability upon an increase in the content of ethanol in solution is observed, while the values of logβCuL change more sharply. The succinic acid anion forms a stronger complex with copper ions than maleic acid anions do at an ethanol content of 0.4 molar parts. The possibility of the formation of a protonated CuHY+ particle is established.

Flame Atmospheric Pressure Chemical Ionization Coupled with Negative Electrospray Ionization Mass Spectrometry for Ion Molecule Reactions

NASA Astrophysics Data System (ADS)

Cheng, Sy-Chyi; Bhat, Suhail Muzaffar; Shiea, Jentaie

2017-07-01

Flame atmospheric pressure chemical ionization (FAPCI) combined with negative electrospray ionization (ESI) mass spectrometry was developed to detect the ion/molecule reactions (IMRs) products between nitric acid (HNO3) and negatively charged amino acid, angiotensin I (AI) and angiotensin II (AII), and insulin ions. Nitrate and HNO3-nitrate ions were detected in the oxyacetylene flame, suggesting that a large quantity of nitric acid (HNO3) was produced in the flame. The HNO3 and negatively charged analyte ions produced by a negative ESI source were delivered into each arm of a Y-shaped stainless steel tube where they merged and reacted. The products were subsequently characterized with an ion trap mass analyzer attached to the exit of the Y-tube. HNO3 showed the strongest affinity to histidine and formed (Mhistidine-H+HNO3)- complex ions, whereas some amino acids did not react with HNO3 at all. Reactions between HNO3 and histidine residues in AI and AII resulted in the formation of dominant [MAI-H+(HNO3)]- and [MAII-H+(HNO3)]- ions. Results from analyses of AAs and insulin indicated that HNO3 could not only react with basic amino acid residues, but also with disulfide bonds to form [M-3H+(HNO3)n]3- complex ions. This approach is useful for obtaining information about the number of basic amino acid residues and disulfide bonds in peptides and proteins.

Flame Atmospheric Pressure Chemical Ionization Coupled with Negative Electrospray Ionization Mass Spectrometry for Ion Molecule Reactions.

PubMed

Cheng, Sy-Chyi; Bhat, Suhail Muzaffar; Shiea, Jentaie

2017-07-01

Flame atmospheric pressure chemical ionization (FAPCI) combined with negative electrospray ionization (ESI) mass spectrometry was developed to detect the ion/molecule reactions (IMRs) products between nitric acid (HNO 3 ) and negatively charged amino acid, angiotensin I (AI) and angiotensin II (AII), and insulin ions. Nitrate and HNO 3 -nitrate ions were detected in the oxyacetylene flame, suggesting that a large quantity of nitric acid (HNO 3 ) was produced in the flame. The HNO 3 and negatively charged analyte ions produced by a negative ESI source were delivered into each arm of a Y-shaped stainless steel tube where they merged and reacted. The products were subsequently characterized with an ion trap mass analyzer attached to the exit of the Y-tube. HNO 3 showed the strongest affinity to histidine and formed (M histidine -H+HNO 3 ) - complex ions, whereas some amino acids did not react with HNO 3 at all. Reactions between HNO 3 and histidine residues in AI and AII resulted in the formation of dominant [M AI -H+(HNO 3 )] - and [M AII -H+(HNO 3 )] - ions. Results from analyses of AAs and insulin indicated that HNO 3 could not only react with basic amino acid residues, but also with disulfide bonds to form [M-3H+(HNO 3 ) n ] 3- complex ions. This approach is useful for obtaining information about the number of basic amino acid residues and disulfide bonds in peptides and proteins. Graphical Abstract ᅟ.

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

Moutanabbir, O.; Scholz, R.; Goesele, U.

We present a detailed study of the thermal evolution of H ion-induced vacancy related complexes and voids in bulk GaN implanted under ion-cut conditions. By using transmission electron microscopy, we found that the damage band in as-implanted GaN is decorated with a high density of nanobubbles of approx1-2 nm in diameter. Variable energy Doppler broadening spectroscopy showed that this band contains vacancy clusters and voids. In addition to vacancy clusters, the presence of V{sub Ga}, V{sub Ga}-H{sub 2}, and V{sub Ga}V{sub N} complexes was evidenced by pulsed low-energy positron lifetime spectroscopy. Subtle changes upon annealing in these vacancy complexes weremore » also investigated. As a general trend, a growth in open-volume defects is detected in parallel to an increase in both size and density of nanobubbles. The observed vacancy complexes appear to be stable during annealing. However, for temperatures above 450 deg. C, unusually large lifetimes were measured. These lifetimes are attributed to the formation of positronium in GaN. Since the formation of positronium is not possible in a dense semiconductor, our finding demonstrates the presence of sufficiently large open-volume defects in this temperature range. Based on the Tao-Eldrup model, the average lattice opening during thermal annealing was quantified. We found that a void diameter of 0.4 nm is induced by annealing at 600 deg. C. The role of these complexes in the subsurface microcracking is discussed.« less

Complexes of carboxyl-containing polymer and monosubstituted bipyridinium salts

NASA Astrophysics Data System (ADS)

Merekalova, N. D.; Bondarenko, G. N.; Krylsky, D. W.; Zakirov, M. I.; Talroze, R. V.

2013-09-01

Semi-empirical PM3 method for the quantum calculations of molecular electronic structure based on NDDO integral approximation is used to investigate the complex formation of monosubstituted 4,4‧-bipyridinium salts BpyR (Hal) containing a halide anion interacting with the quaternary nitrogen atom and carboxylic group of the two-units construct. Significant effect of the BpyR (Hal) electronic structure is unveiled that contributes in two different structures of these salts, namely, partial charge transfer complex and ion pair structure, both having stable energy minima. We demonstrate that (i) the structure of the N-substituent modulates the energy and electronic characteristics of monosubstituted salts BpyR with chlorine and bromine anions and (ii) the coulomb interactions between quaternary N-atom, halogen anion, and the proton of carboxylic group stimulate the transformation of the charge transfer complex into the ion pair structure. Results of calculations are compared with the experimental FTIR spectra of blends of BpyR(Hal) with Eudragit copolymer.

Rapid Screening of Carboxylic Acids from Waste and Surface Waters by ESI-MS/MS Using Barium Ion Chemistry and On-Line Membrane Sampling.

PubMed

Duncan, Kyle D; Volmer, Dietrich A; Gill, Chris G; Krogh, Erik T

2016-03-01

Negative ion tandem mass spectrometric analysis of aliphatic carboxylic acids often yields only non-diagnostic ([M - H](-)) ions with limited selective fragmentation. However, carboxylates cationized with Ba(2+) have demonstrated efficient dissociation in positive ion mode, providing structurally diagnostic product ions. We report the application of barium adducts followed by collision induced dissociation (CID), to improve selectivity for rapid screening of carboxylic acids in complex aqueous samples. The quantitative MS/MS method presented utilizes common product ions of [M - H + Ba](+) precursor ions. The mechanism of product ion formation is investigated using isotopically labeled standards and a series of structurally related carboxylic acids. The results suggest that hydrogen atoms in the β and γ positions yield common product ions ([BaH](+) and [BaOH](+)). Furthermore, the diagnostic product ion at m/z 196 serves as a qualifying ion for carboxylate species. This methodology has been successfully used in conjunction with condensed phase membrane introduction mass spectrometry (CP-MIMS), with barium acetate added directly to the methanol acceptor phase. The combination enables rapid screening of carboxylic acids directly from acidified water samples (wastewater effluent, spiked natural waters) using a capillary hollow fiber PDMS membrane immersion probe. We have applied this technique for the direct analysis of complex naphthenic acid mixtures spiked into natural surface waters using CP-MIMS. Selectivity at the ionization and tandem mass spectrometry level eliminate isobaric interferences from hydroxylated species present within the samples, which have been observed in negative electrospray ionization.

Identification of Ion-Pair Structures in Solution by Vibrational Stark Effects.

PubMed

Hack, John; Grills, David C; Miller, John R; Mani, Tomoyasu

2016-02-18

Ion pairing is a fundamental consideration in many areas of chemistry and has implications in a wide range of sciences and technologies that include batteries and organic photovoltaics. Ions in solution are known to inhabit multiple possible states, including free ions (FI), contact ion pairs (CIP), and solvent-separated ion pairs (SSIP). However, in solutions of organic radicals and nonmetal electrolytes, it is often difficult to distinguish between these states. In the first part of this work, we report evidence for the formation of SSIPs in low-polarity solvents and distinct measurements of CIP, SSIP, and FI, by using the ν(C≡N) infrared (IR) band of a nitrile-substituted fluorene radical anion. Use of time-resolved IR detection following pulse radiolysis allowed us to unambiguously assign the peak of the FI. In the presence of nonmetal electrolytes, two distinct red-shifted peaks were observed and assigned to the CIP and SSIP. The assignments are interpreted in the framework of the vibrational Stark effect (VSE) and are supported by (1) the solvent dependence of ion-pair populations, (2) the observation of a cryptand-separated sodium ion pair that mimics the formation of SSIPs, and (3) electronic structure calculations. In the second part of this work, we show that a blue-shift of the ν(C≡N) IR band due to the VSE can be induced in a nitrile-substituted fluorene radical anion by covalently tethering it to a metal-chelating ligand that forms an intramolecular ion pair upon reduction and complexation with sodium ion. This adds support to the conclusion that the shift in IR absorptions by ion pairing originates from the VSE. These results combined show that we can identify ion-pair structures by using the VSE, including the existence of SSIPs in a low-polarity solvent.

Structure of UreG/UreF/UreH Complex Reveals How Urease Accessory Proteins Facilitate Maturation of Helicobacter pylori Urease

PubMed Central

Fong, Yu Hang; Wong, Ho Chun; Yuen, Man Hon; Lau, Pak Ho; Chen, Yu Wai; Wong, Kam-Bo

2013-01-01

Urease is a metalloenzyme essential for the survival of Helicobacter pylori in acidic gastric environment. Maturation of urease involves carbamylation of Lys219 and insertion of two nickel ions at its active site. This process requires GTP hydrolysis and the formation of a preactivation complex consisting of apo-urease and urease accessory proteins UreF, UreH, and UreG. UreF and UreH form a complex to recruit UreG, which is a SIMIBI class GTPase, to the preactivation complex. We report here the crystal structure of the UreG/UreF/UreH complex, which illustrates how UreF and UreH facilitate dimerization of UreG, and assembles its metal binding site by juxtaposing two invariant Cys66-Pro67-His68 metal binding motif at the interface to form the (UreG/UreF/UreH)2 complex. Interaction studies revealed that addition of nickel and GTP to the UreG/UreF/UreH complex releases a UreG dimer that binds a nickel ion at the dimeric interface. Substitution of Cys66 and His68 with alanine abolishes the formation of the nickel-charged UreG dimer. This nickel-charged UreG dimer can activate urease in vitro in the presence of the UreF/UreH complex. Static light scattering and atomic absorption spectroscopy measurements demonstrated that the nickel-charged UreG dimer, upon GTP hydrolysis, reverts to its monomeric form and releases nickel to urease. Based on our results, we propose a mechanism on how urease accessory proteins facilitate maturation of urease. PMID:24115911

Crystal structure and solution species of Ce(III) and Ce(IV) formates: from mononuclear to hexanuclear complexes.

PubMed

Hennig, Christoph; Ikeda-Ohno, Atsushi; Kraus, Werner; Weiss, Stephan; Pattison, Philip; Emerich, Hermann; Abdala, Paula M; Scheinost, Andreas C

2013-10-21

Cerium(III) and cerium(IV) both form formate complexes. However, their species in aqueous solution and the solid-state structures are surprisingly different. The species in aqueous solutions were investigated with Ce K-edge EXAFS spectroscopy. Ce(III) formate shows only mononuclear complexes, which is in agreement with the predicted mononuclear species of Ce(HCOO)(2+) and Ce(HCOO)2(+). In contrast, Ce(IV) formate forms in aqueous solution a stable hexanuclear complex of [Ce6(μ3-O)4(μ3-OH)4(HCOO)x(NO3)y](12-x-y). The structural differences reflect the different influence of hydrolysis, which is weak for Ce(III) and strong for Ce(IV). Hydrolysis of Ce(IV) ions causes initial polymerization while complexation through HCOO(-) results in 12 chelate rings stabilizing the hexanuclear Ce(IV) complex. Crystals were grown from the above-mentioned solutions. Two crystal structures of Ce(IV) formate were determined. Both form a hexanuclear complex with a [Ce6(μ3-O)4(μ3-OH)4](12+) core in aqueous HNO3/HCOOH solution. The pH titration with NaOH resulted in a structure with the composition [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)2(H2O)3]·(H2O)9.5, while the pH adjustment with NH3 resulted in [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)4]·(NO3)3(NH4)5(H2O)5. Furthermore, the crystal structure of Ce(III) formate, Ce(HCOO)3, was determined. The coordination polyhedron is a tricapped trigonal prism which is formed exclusively by nine HCOO(-) ligands. The hexanuclear Ce(IV) formate species from aqueous solution is widely preserved in the crystal structure, whereas the mononuclear solution species of Ce(III) formate undergoes a polymerization during the crystallization process.

Ferric ion as a scavenging agent in a solvent extraction process

DOEpatents

Bruns, Lester E.; Martin, Earl C.

1976-01-01

Ferric ions are added into the aqueous feed of a plutonium scrap recovery process that employs a tributyl phosphate extractant. Radiolytic degradation products of tributyl phosphate such as dibutyl phosphate form a solid precipitate with iron and are removed from the extraction stages via the waste stream. Consequently, the solvent extraction characteristics are improved, particularly in respect to minimizing the formation of nonstrippable plutonium complexes in the stripping stages. The method is expected to be also applicable to the partitioning of plutonium and uranium in a scrap recovery process.

Factors affecting catalysis of copper corrosion products in NDMA formation from DMA in simulated premise plumbing.

PubMed

Zhang, Hong; Andrews, Susan A

2013-11-01

This study investigated the effects of corrosion products of copper, a metal commonly employed in household plumbing systems, on N-nitrosodimethylamine (NDMA) formation from a known NDMA precursor, dimethylamine (DMA). Copper-catalyzed NDMA formation increased with increasing copper concentrations, DMA concentrations, alkalinity and hardness, but decreased with increasing natural organic matter (NOM) concentration. pH influenced the speciation of chloramine and the interactions of copper with DMA. The transformation of monochloramine (NH2Cl) to dichloramine and complexation of copper with DMA were involved in elevating the formation of NDMA by copper at pH 7.0. The inhibiting effect of NOM on copper catalysis was attributed to the rapid consumption of NH2Cl by NOM and/or the competitive complexation of NOM with copper to limit the formation of DMA-copper complexes. Hardness ions, as represented by Ca(2+), also competed with copper for binding sites on NOM, thereby weakening the inhibitory effect of NOM on NDMA formation. Common copper corrosion products also participated in these reactions but in different ways. Aqueous copper released from malachite [Cu2CO3(OH)2] was shown to promote NDMA formation while NDMA formation decreased in the presence of CuO, most likely due to the adsorption of DMA. Copyright © 2013 Elsevier Ltd. All rights reserved.

Spectrophotometric determination of trazodone, amineptine and amitriptyline hydrochlorides through ion-pair formation with molybdenum and thiocyanate

NASA Astrophysics Data System (ADS)

Mohamed, Gehad G.; Nour El-Dien, F. A.; Khalil, S. M.; Mohamed, Nehad A.

2006-12-01

Extraction spectrophotometric method has been developed for the determination of tricyclic drugs such as trazodone (TZH), amineptine (APH) and amitriptyline (ATPH) hydrochlorides in pure form and in the dosage forms coming from different Egyptian markets. The method based on the formation of ion-pairs between these drugs under investigation and inorganic complex of Mo(V)-thiocyanate followed by its extraction with methylene chloride. The optimum conditions for the ion-pairs formation are established. The method permits the determination of TZH, APH and ATPH over the concentration range of 2-28, 2-32 and 1-30 μg ml -1, respectively. The Sandell sensitivity ( S) is found to be 0.105, 0.138 and 0.118 g cm -2 for TZH, APH and ATPH, respectively. The SD is found to be 0.16-0.377, 0.12-0.259 and 0.091-0.286 and the R.S.D. are 0.14-0.55, 0.12-0.399 and 0.095-0.485 for TZH, APH and ATPH, respectively. The method is applicable for the assay of the investigated drugs in different dosage forms and the results are in good agreement with those obtained by the official method.

Lipid domains in zwitterionic-anionic lipid mixtures induced by combined effect of monovalent and divalent ions

NASA Astrophysics Data System (ADS)

Xu, Hongcheng; Ganesan, Sai; Matysiak, Silvina

Lipid domain formation is an important process for many cellular processes. In experiment, the effects of Ba2+, Sr2+, Ca2+ and Mg2+ in inducing lateral phase separation in the binary phosphatidylcholine-phosphatidylserine (PC-PS) bilayer are quite different, of which the molecular mechanism remains to be understood. We have explored the effect of monovalent (MI) and divalent (MII) cationic radii on lipid domain formation in mixed zwitterionic-anionic lipid bilayers. We propose a mechanism for the formation of divalent-cation-induced lipid domains based on MD simulations with our Water-Explicit Polarizable MEMbrane (WEPMEM) coarse-grained model, which uses PC as the model for zwitterionic and PS for anionic lipids. Lipid aggregation only occurs with limited range of monovalent and divalent ion sizes in agreement with experimental observations. More ordering and closer packing of the lipids are noted within the domains, which correlate with bilayer thickness, curvature and lipid asymmetry. The results of the simulations reveal that the lipid domain consists of MII-mediated anionic lipid dimer/trimer complexes bridged by monovalent ions MI and provide a stereochemical insight in understanding the experimentally observed calcium-induced phase separation.

Inorganic Geochemistry of Flowback Water from the Montney Formation: Potential Sources of Elevated Ion Concentrations

NASA Astrophysics Data System (ADS)

Owen, J.; Bustin, R.

2016-12-01

An inorganic geochemical analysis was conducted on flowback water from hydraulically fractured oil and gas wells of the Montney Formation of varying thermal maturity and stratigraphy in the Western Canadian Sedimentary Basin. The results of this study provide insight into potential sources of the elevated ion concentrations and can be used to assist with wastewater management and blending of water for reuse. Samples were obtained from 31 wells across the Montney and include wells completed in the lower, middle, and upper units. Selected fluid samples from each well were analyzed using ICP-OES, ICP-MS, and IC. Oxygen and hydrogen isotope analysis was performed using a liquid-water isotope analyzer. The flowback waters are classified as sodium-chloride type. In addition to Na and Cl, calcium, potassium, magnesium, and strontium are elevated and increase during the flowback period. Barium, iron, and lithium are also elevated at some locations. The early flowback water chemistry varies within the formation: higher initial TDS values of approximately 50,000mg/L in Upper Montney flowback water relative to the initial TDS from both Middle and Lower Montney wells (<25,000mg/L and <15,000mg/L, respectively). However, overall, the maximum TDS attained later in the flowback period does not show a consistent stratigraphic trend (range: 55,000 - 130,000mg/L) except for one region in the Middle Montney where the maximum TDS remains consistently lower than other areas (<50,000mg/L). Barium is notable in Montney flowback due to its high variability, with the lowest concentrations occurring in Middle Montney flowback and the highest in Lower Montney flowback. Comparing closely spaced wells completed on the same pad and in the same zone, the flowback waters generally have similar ion concentrations and consistent ion ratios. The increasing ion concentrations as well as the stable water isotopes support mixing between the hydraulic fracturing fluid, which has relatively low ion concentrations, and more saline connate formation water. Geochemical modeling indicates the ion concentrations in the flowback water are a complex product of mineral precipitation/dissolution, ion exchange with the reservoir, geochemistry of the connate water and water saturation of the reservoir.

Interaction of NaOH solutions with silica surfaces

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

Rimsza, Jessica M.; Jones, Reese E.; Criscenti, Louise J.

Sodium adsorption on silica surfaces depends on the solution counter-ion. Here, we use NaOH solutions to investigate basic environments. Sodium adsorption on hydroxylated silica surfaces from NaOH solutions were investigated through molecular dynamics with a dissociative force field, allowing for the development of secondary molecular species. Furthermore, across the NaOH concentrations (0.01 M – 1.0 M), ~50% of the Na + ions were concentrated in the surface region, developing silica surface charges between –0.01 C/m 2 (0.01 M NaOH) and –0.76 C/m 2 (1.0 M NaOH) due to surface site deprotonation. Five inner-sphere adsorption complexes were identified, including monodentate, bidentate,more » and tridentate configurations and two additional structures, with Na + ions coordinated by bridging oxygen and hydroxyl groups or water molecules. Coordination of Na + ions by bridging oxygen atoms indicates partial or complete incorporation of Na + ions into the silica surface. Residence time analysis identified that Na + ions coordinated by bridging oxygen atoms stayed adsorbed onto the surface four times longer than the mono/bi/tridentate species, indicating formation of relatively stable and persistent Na + ion adsorption structures. Such inner-sphere complexes form only at NaOH concentrations of > 0.5 M. Na + adsorption and lifetimes have implications for the stability of silica surfaces.« less

Interaction of NaOH solutions with silica surfaces

DOE PAGES

Rimsza, Jessica M.; Jones, Reese E.; Criscenti, Louise J.

2018-01-16

Sodium adsorption on silica surfaces depends on the solution counter-ion. Here, we use NaOH solutions to investigate basic environments. Sodium adsorption on hydroxylated silica surfaces from NaOH solutions were investigated through molecular dynamics with a dissociative force field, allowing for the development of secondary molecular species. Furthermore, across the NaOH concentrations (0.01 M – 1.0 M), ~50% of the Na + ions were concentrated in the surface region, developing silica surface charges between –0.01 C/m 2 (0.01 M NaOH) and –0.76 C/m 2 (1.0 M NaOH) due to surface site deprotonation. Five inner-sphere adsorption complexes were identified, including monodentate, bidentate,more » and tridentate configurations and two additional structures, with Na + ions coordinated by bridging oxygen and hydroxyl groups or water molecules. Coordination of Na + ions by bridging oxygen atoms indicates partial or complete incorporation of Na + ions into the silica surface. Residence time analysis identified that Na + ions coordinated by bridging oxygen atoms stayed adsorbed onto the surface four times longer than the mono/bi/tridentate species, indicating formation of relatively stable and persistent Na + ion adsorption structures. Such inner-sphere complexes form only at NaOH concentrations of > 0.5 M. Na + adsorption and lifetimes have implications for the stability of silica surfaces.« less

Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

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

MacDonald, Margaret G.; Palmer, Michael R.; Suchomel, Matthew R.

To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K +, Zn 2+, Pb 2+) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic-inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm -1 for Pb(II) and ca. 1580 cm -1 for Zn(II) are consistentmore » with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. Finally, these complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.« less

Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

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

MacDonald, Margaret G.; Palmer, Michael R.; Suchomel, Matthew R.

To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K +, Zn 2+, Pb 2+) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic–inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm –1 for Pb(II) and ca. 1580 cm –1 for Zn(II) are consistentmore » with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. These complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.« less

Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

DOE PAGES

MacDonald, Margaret G.; Palmer, Michael R.; Suchomel, Matthew R.; ...

2016-09-07

To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K +, Zn 2+, Pb 2+) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic-inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm -1 for Pb(II) and ca. 1580 cm -1 for Zn(II) are consistentmore » with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. Finally, these complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.« less

Solubility enhancement of seven metal contaminants using carboxymethyl-β-cyclodextrin (CMCD)

NASA Astrophysics Data System (ADS)

Skold, Magnus E.; Thyne, Geoffrey D.; Drexler, John W.; McCray, John E.

2009-07-01

Carboxymethyl-β-cyclodextrin (CMCD) has been suggested as a complexing agent for remediation of sites co-contaminated with metals and organic pollutants. As part of an attempt to construct a geochemical complexation model for metal-CMCD interactions, conditional formation constants for the complexes between CMCD and 7 metal ions (Ba, Ca, Cd, Ni, Pb, Sr, and Zn) are estimated from experimental data. Stable metal concentrations were reached after approximately 1 day and estimated logarithmic conditional formation constants range from - 3.2 to - 5.1 with confidence intervals within ± 0.08 log units. Experiments performed at 10 °C and 25 °C show that temperature affects the solubility of the metal salts but the strength of CMCD-metal complexes are not affected by this temperature variation. The conditional stability constants and complexation model presented in this work can be used to screen CMCD as a potential remediation agent for clean-up of contaminated soil and groundwater.

Chemical sporulation and germination: cytoprotective nanocoating of individual mammalian cells with a degradable tannic acid-FeIII complex

NASA Astrophysics Data System (ADS)

Lee, Juno; Cho, Hyeoncheol; Choi, Jinsu; Kim, Doyeon; Hong, Daewha; Park, Ji Hun; Yang, Sung Ho; Choi, Insung S.

2015-11-01

Individual mammalian cells were coated with cytoprotective and degradable films by cytocompatible processes maintaining the cell viability. Three types of mammalian cells (HeLa, NIH 3T3, and Jurkat cells) were coated with a metal-organic complex of tannic acid (TA) and ferric ion, and the TA-FeIII nanocoat effectively protected the coated mammalian cells against UV-C irradiation and a toxic compound. More importantly, the cell proliferation was controlled by programmed formation and degradation of the TA-FeIII nanocoat, mimicking the sporulation and germination processes found in nature.Individual mammalian cells were coated with cytoprotective and degradable films by cytocompatible processes maintaining the cell viability. Three types of mammalian cells (HeLa, NIH 3T3, and Jurkat cells) were coated with a metal-organic complex of tannic acid (TA) and ferric ion, and the TA-FeIII nanocoat effectively protected the coated mammalian cells against UV-C irradiation and a toxic compound. More importantly, the cell proliferation was controlled by programmed formation and degradation of the TA-FeIII nanocoat, mimicking the sporulation and germination processes found in nature. Electronic supplementary information (ESI) available: Experimental details, LSCM images, and SEM and TEM images. See DOI: 10.1039/c5nr05573c

A fluorescence turn-on sensor for iodide based on a thymine-Hg(II)-thymine complex.

PubMed

Ma, Boling; Zeng, Fang; Zheng, Fangyuan; Wu, Shuizhu

2011-12-23

Iodide plays a vital role in many biological processes, including neurological activity and thyroid function. Due to its physiological relevance, a method for the rapid, sensitive, and selective detection of iodide in food, pharmaceutical products, and biological samples such as urine is of great importance. Herein, we demonstrate a novel and facile strategy for constructing a fluorescence turn-on sensor for iodide based on a T-Hg(II)-T complex (T=thymine). A fluorescent anthracene-thymine dyad (An-T) was synthesized, the binding of which to a mercury(II) ion lead to the formation of a An-T-Hg(II)-T-An complex, thereby quenching the fluorescent emission of this dyad. In this respect, the dyad An-T constituted a fluorescence turn-off sensor for mercury(II) ions in aqueous media. More importantly, it was found that upon addition of iodide, the mercury(II) ion was extracted from the complex due to the even stronger binding between mercury(II) ions and iodide, leading to the release of the free dyad and restoration of the fluorescence. By virtue of this fluorescence quenching and recovery process, the An-T-Hg(II)-T-An complex constitutes a fluorescence turn-on sensor for iodide with a detection limit of 126 nM. Moreover, this sensor is highly selective for iodide over other common anions, and can be used in the determination of iodide in drinking water and biological samples such as urine. This strategy may provide a new approach for sensing some other anions. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Autocatalytic formation of an iron(IV)-oxo complex via scandium ion-promoted radical chain autoxidation of an iron(II) complex with dioxygen and tetraphenylborate.

PubMed

Nishida, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Fukuzumi, Shunichi

2014-06-04

A non-heme iron(IV)-oxo complex, [(TMC)Fe(IV)(O)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), was formed by oxidation of an iron(II) complex ([(TMC)Fe(II)](2+)) with dioxygen (O2) and tetraphenylborate (BPh4(-)) in the presence of scandium triflate (Sc(OTf)3) in acetonitrile at 298 K via autocatalytic radical chain reactions rather than by a direct O2 activation pathway. The autocatalytic radical chain reaction is initiated by scandium ion-promoted electron transfer from BPh4(-) to [(TMC)Fe(IV)(O)](2+) to produce phenyl radical (Ph(•)). The chain propagation step is composed of the addition of O2 to Ph(•) and the reduction of the resulting phenylperoxyl radical (PhOO(•)) by scandium ion-promoted electron transfer from BPh4(-) to PhOO(•) to produce phenyl hydroperoxide (PhOOH), accompanied by regeneration of phenyl radical. PhOOH reacts with [(TMC)Fe(II)](2+) to yield phenol (PhOH) and [(TMC)Fe(IV)(O)](2+). Biphenyl (Ph-Ph) was formed via the radical chain autoxidation of BPh3 by O2. The induction period of the autocatalytic radical chain reactions was shortened by addition of a catalytic amount of [(TMC)Fe(IV)(O)](2+), whereas addition of a catalytic amount of ferrocene that can reduce [(TMC)Fe(IV)(O)](2+) resulted in elongation of the induction period. Radical chain autoxidation of BPh4(-) by O2 also occurred in the presence of Sc(OTf)3 without [(TMC)Fe(IV)(O)](2+), initiating the autocatalytic oxidation of [(TMC)Fe(II)](2+) with O2 and BPh4(-) to yield [(TMC)Fe(IV)(O)](2+). Thus, the general view for formation of non-heme iron(IV)-oxo complexes via O2-binding iron species (e.g., Fe(III)(O2(•-))) without contribution of autocatalytic radical chain reactions should be viewed with caution.

Methylenediphosphonotetrathioate: synthesis, characterization, and chemical properties.

PubMed

Amir, Aviran; Sayer, Alon Haim; Ezra, Alon; Fischer, Bilha

2013-03-18

Metal chelators are potential therapeutic agents for treating diseases such as Wilson's and Alzheimer's where the pathology involves an excess of metal-ions (Cu(II) and Zn(II)/Cu(II)/Fe(II/III), respectively). In addition to the high affinity of the metal-ion to the chelators, metal selectivity of the chelators is essential to achieve the therapeutic goal, that is, the successful removal of excess of harmful metal-ions in a physiological extracellular medium rich in alkali and alkali earth metal-ions. For this purpose, we synthesized a novel chelator, methylenediphosphonotetrathioate (MDPT) which is the tetrathio analogue of methylenediphosphonic acid (MDP). MDPT was synthesized from bis-methylene(phosphonicdichloride) in a 3-step synthesis and a 31% overall yield. MDPT formed a stable complex with Zn(II) (log K = 10.84), which is 10(7) times more stable than the corresponding Ca(II) complex. Moreover, the MDPT-Zn(II) complex was 50-fold more stable than the MDP-Zn(II) complex. In addition, MDPT was found to inhibit the Cu(I)-catalyzed Fenton reaction (IC50 26 μM) 2.5 times more potently than a Fe(II)-catalyzed Fenton reaction, and 2.5 times more potently than EDTA (IC50 64 μM) in the Cu(I)/H2O2 system, as monitored by electron spin resonance (ESR). Furthermore, MDPT was found to be relatively stable in both acidic (pD 1.9, t(½) = 71.5 h) and basic media (pD 12.4, t(½) = 81 h) as monitored by (31)P/(1)H NMR. However, MDPT was not stable in air because of intramolecular oxidation and disulfide formation (33% oxidation after 27 h). In conclusion, MDPT was found to be a water-soluble chelator showing a clear preference to soft/borderline metal-ions and a remarkable selectivity to those metal-ions vs Ca(II) ions. The relative sensitivity of MDPT to oxidation may limit its use; however, the application of MDPT in acidic or basic media will increase its lifetime.

Ligational behavior of clioquinol antifungal drug towards Ag(I), Hg(II), Cr(III) and Fe(III) metal ions: Synthesis, spectroscopic, thermal, morphological and antimicrobial studies

NASA Astrophysics Data System (ADS)

El-Megharbel, Samy M.; Refat, Moamen S.

2015-04-01

This article presents a synthesis, characterization, theoretical and biological (anti-bacterial, and anti-fugal) evaluation studies of Ag(I), Hg(II), Cr(III) and Fe(III) complexes of clioquinol (CQ) drug ligand. Structures of the titled complexes cited herein were discussed using elemental analyses and spectral measurements e.g., IR, 1H NMR, and electronic studies. The results confirmed the formation of the clioquinol complexes by three molar ratios (1:1) for Ag(I), (1:2) for Hg(II) and (1:3) for both Cr(III) and Fe(III) metal ions. The clioquinol reacts as a bidentate chelate bound to all respected metal ions through the oxygen and nitrogen of quinoline-8-ol. The metal(II) ions coordinated to clioquinol ligand through deprotonation of sbnd OH terminal group. Infrared and 1H NMR spectral data confirm that coordination is via the oxygen of phenolic group and nitrogen atom of quinoline moiety. The molar conductance measurements of the CQ complexes in DMSO correspond to be non-electrolyte nature. Thus, these complexes may be formulated as [Ag(CQ)(H2O)2] H2O, [Hg(CQ)2]ṡ2H2O, [Cr(CQ)3] and [Fe(CQ)3]H2O. The Coats-Redfern method, the kinetic thermodynamic parameters like activation energies (E∗), entropies (ΔS∗), enthalpies (ΔH∗), and Gibbs free energies (ΔG∗) of the thermal decomposition reactions have been deduced from thermogravimetric curves (TG) with helpful of differential thermo gravimetric (DTG) curves. The narrow size distribution in nano-scale range for the clioquinol complexes have been discussed using X-ray powder diffraction (XRD), scanning electron microscope (SEM), and X-ray energy dispersive spectrometer (EDX) analyzer.

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Arya, Anil; Sharma, A. L.

2018-04-01

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO8-NaPF6+  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ({{τ }{{\\varepsilon \\prime}}}>~{{τ }tanδ }>{{τ }z}>{{τ }m} ) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ({{σ }\\prime\\prime}~versus~{{σ }\\prime} ) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole–Cole plot ({{\\varepsilon }\\prime\\prime}~versus~{{\\varepsilon }\\prime} ) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Saturated fatty acid determination method using paired ion electrospray ionization mass spectrometry coupled with capillary electrophoresis.

PubMed

Lee, Ji-Hyun; Kim, Su-Jin; Lee, Sul; Rhee, Jin-Kyu; Lee, Soo Young; Na, Yun-Cheol

2017-09-01

A sensitive and selective capillary electrophoresis-mass spectrometry (CE-MS) method for determination of saturated fatty acids (FAs) was developed by using dicationic ion-pairing reagents forming singly charged complexes with anionic FAs. For negative ESI detection, 21 anionic FAs at pH 10 were separated using ammonium formate buffer containing 40% acetonitrile modifier in normal polarity mode in CE by optimizing various parameters. This method showed good separation efficiency, but the sensitivity of the method to short-chain fatty acids was quite low, causing acetic and propionic acids to be undetectable even at 100 mgL -1 in negative ESI-MS detection. Out of the four dicationic ion-pairing reagents tested, N,N'-dibutyl 1,1'-pentylenedipyrrolidium infused through a sheath-liquid ion source during CE separation was the best reagent regarding improved sensitivity and favorably complexed with anionic FAs for detection in positive ion ESI-MS. The monovalent complex showed improved ionization efficiency, providing the limits of detection (LODs) for 15 FAs ranging from 0.13 to 2.88 μg/mL and good linearity (R 2  > 0.99) up to 150 μg/mL. Compared to the negative detection results, the effect was remarkable for the detection of short- and medium-chain fatty acids. The optimized CE-paired ion electrospray (PIESI)-MS method was utilized for the determination of FAs in cheese and coffee with simple pretreatment. This method may be extended for sensitive analysis of unsaturated fatty acids. Copyright © 2017 Elsevier B.V. All rights reserved.

Structural investigations of transition metal (II) tetracyanonickelate complexes of 3-chloropyridine using Fourier transform-infrared and laser Raman spectroscopy

NASA Astrophysics Data System (ADS)

Akyüz, Sevim; Akyüz, Tanil; Eric, J.; Davies, D.

1992-01-01

The FT-IR and laser-Raman spectra of five new complexes of the formula ML 2Ni(CN) 4 (where MMn, Fe, Ni, Zn or Cd; L3-chloropyridine) are reported. The complexes are shown to have a structure consisting of two dimensional polymeric layers formed with Ni(CN) 4 ions bridged by ML 2 cations. For a given series of isomorphous complexes, the effects of metal ligand bond formation on the ligand vibrational modes are examined and the metal-sensitivity sequence of the ligand frequencies is found to be Mn≈Cd

Interaction of Cu(+) with cytosine and formation of i-motif-like C-M(+)-C complexes: alkali versus coinage metals.

PubMed

Gao, Juehan; Berden, Giel; Rodgers, M T; Oomens, Jos

2016-03-14

The Watson-Crick structure of DNA is among the most well-known molecular structures of our time. However, alternative base-pairing motifs are also known to occur, often depending on base sequence, pH, or the presence of cations. Pairing of cytosine (C) bases induced by the sharing of a single proton (C-H(+)-C) may give rise to the so-called i-motif, which occurs primarily in expanded trinucleotide repeats and the telomeric region of DNA, particularly at low pH. At physiological pH, silver cations were recently found to stabilize C dimers in a C-Ag(+)-C structure analogous to the hemiprotonated C-dimer. Here we use infrared ion spectroscopy in combination with density functional theory calculations at the B3LYP/6-311G+(2df,2p) level to show that copper in the 1+ oxidation state induces an analogous formation of C-Cu(+)-C structures. In contrast to protons and these transition metal ions, alkali metal ions induce a different dimer structure, where each ligand coordinates the alkali metal ion in a bidentate fashion in which the N3 and O2 atoms of both cytosine ligands coordinate to the metal ion, sacrificing hydrogen-bonding interactions between the ligands for improved chelation of the metal cation.

Cyclodextrin–polysaccharide-based, in situ-gelled system for ocular antifungal delivery

PubMed Central

Fernández-Ferreiro, Anxo; Fernández Bargiela, Noelia; Varela, María Santiago; Martínez, Maria Gil; Pardo, Maria; Piñeiro Ces, Antonio; Méndez, José Blanco; Barcia, Miguel González; Lamas, Maria Jesus

2014-01-01

Summary Fluconazole was studied with two different hydrophilic cyclodextrins (hydroxypropyl-β-cyclodextrin (HPBCD) and sulfobutyl ether-β-cyclodextrin (SBECD)) for the formation of inclusion complexes. HPBCD and SBECD showed low cell cytotoxicity in human keratocytes as assessed by the label-free xCELLigence system for real-time monitoring. The fluconazole–HPBCD complex was incorporated into an ion-sensitive ophthalmic gel composed of the natural polysaccharides gellan gum and κ-carrageenan. This system showed good bioadhesive properties and effective control of fluconazole release. PMID:25550757

Growth of large zeolite crystals in space

NASA Technical Reports Server (NTRS)

Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

1988-01-01

Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species fo not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

Characterization of helium-vacancy complexes in He-ions implanted Fe9Cr by using positron annihilation spectroscopy

NASA Astrophysics Data System (ADS)

Zhu, Te; Jin, Shuoxue; Zhang, Peng; Song, Ligang; Lian, Xiangyu; Fan, Ping; Zhang, Qiaoli; Yuan, Daqing; Wu, Haibiao; Yu, Runsheng; Cao, Xingzhong; Xu, Qiu; Wang, Baoyi

2018-07-01

The formation of helium bubble precursors, i.e., helium-vacancy complexes, was investigated for Fe9Cr alloy, which was uniformly irradiated by using 100 keV helium ions with fluences up to 5 × 1016 ions/cm2 at RT, 523, 623, 723, and 873 K. Helium-irradiation-induced microstructures in the alloy were probed by positron annihilation technique. The results show that the ratio of helium atom to vacancy (m/n) in the irradiation induced HemVn clusters is affected by the irradiation temperature. Irradiated at room temperature, there is a coexistence of large amounts of HemV1 and mono-vacancies in the sample. However, the overpressured HemVn (m > n) clusters or helium bubbles are easily formed by the helium-filled vacancy clusters (HemV1 and HemVn (m ≈ n)) absorbing helium atoms when irradiated at 523 K and 823 K. The results also show that void swelling of the alloy is the largest under 723 K irradiation.

Selective time-resolved binding of copper(II) by pyropheophorbide-a methyl ester.

PubMed

Ghosh, Indrajit; Saleh, Na'il; Nau, Werner M

2010-05-01

The complexation behavior of pyropheophorbide-a methyl ester (PPME) with transition metal ions as well as other biologically relevant metal ions has been investigated in water-DMF (2 : 1 v/v) solution. PPME was found to selectively complex Cu(2+) ions, which leads to a distinct change in its absorption spectrum as well as efficient fluorescence quenching. The degree of fluorescence quenching by Cu(2+) depended on concentration and time. Upon addition of Cu(2+), the fluorescence showed a time-resolved decay on the time scale of minutes to hours, with the decay rate being dependent on the cation concentration. Fitting according to a bimolecular reaction rate law provided a rate constant of 650 +/- 90 M(-1) s(-1) at 298 K for metallochlorin formation. The potential implications of Cu(2+) binding for the use of PPME in photodynamic therapy are discussed, along with its use as a fluorescent sensor for detection of micromolar concentrations of Cu(2+).

Hepatitis E virus ORF3 is a functional ion channel required for release of infectious particles.

PubMed

Ding, Qiang; Heller, Brigitte; Capuccino, Juan M V; Song, Bokai; Nimgaonkar, Ila; Hrebikova, Gabriela; Contreras, Jorge E; Ploss, Alexander

2017-01-31

Hepatitis E virus (HEV) is the leading cause of enterically transmitted viral hepatitis globally. Of HEV's three ORFs, the function of ORF3 has remained elusive. Here, we demonstrate that via homophilic interactions ORF3 forms multimeric complexes associated with intracellular endoplasmic reticulum (ER)-derived membranes. HEV ORF3 shares several structural features with class I viroporins, and the function of HEV ORF3 can be maintained by replacing it with the well-characterized viroporin influenza A virus (IAV) matrix-2 protein. ORF3's ion channel function is further evidenced by its ability to mediate ionic currents when expressed in Xenopus laevis oocytes. Furthermore, we identified several positions in ORF3 critical for its formation of multimeric complexes, ion channel activity, and, ultimately, release of infectious particles. Collectively, our data demonstrate a previously undescribed function of HEV ORF3 as a viroporin, which may serve as an attractive target in developing direct-acting antivirals.

The influence of vegetation on the hydrodynamics and geomorphology of a tree island in Everglades National Park (Florida, United States)

USGS Publications Warehouse

Sullivan, Pamela L.; Engel, Victor C.; Ross, Michael S.; Price, René M.

2013-01-01

Transpiration-driven nutrient accumulation has been identified as a potential mechanism governing the creation and maintenance of wetland vegetation patterning. This process may contribute to the formation of nutrient-rich tree islands within the expansive oligotrophic marshes of the Everglades (Florida, United States). This study presents hydrogeochemical data indicating that tree root water uptake is a primary driver of groundwater ion accumulation across one of these islands. Sap flow, soil moisture, water level, water chemistry, and rainfall were measured to identify the relationships between climate, transpiration, and groundwater uptake by phreatophytes and to examine the effect this uptake has on groundwater chemistry and mineral formation in three woody plant communities of differing elevations. During the dry season, trees relied more on groundwater for transpiration, which led to a depressed water table and the advective movement of groundwater and dissolved ions, including phosphorus, from the surrounding marsh towards the centre of the island. Ion exclusion during root water uptake led to elevated concentrations of all major dissolved ions in the tree island groundwater compared with the adjacent marsh. Groundwater was predominately supersaturated with respect to aragonite and calcite in the lower-elevation woody communities, indicating the potential for soil formation. Elevated groundwater phosphorous concentrations detected in the highest-elevation woody community were associated with the leaching of inorganic sediments (i.e. hydroxyapatite) in the vadose zone. Understanding the complex feedback mechanisms regulating plant/groundwater/surface water interactions, nutrient dynamics, and potential soil formation is necessary to manage and restore patterned wetlands such as the Everglades.

Characterization of the interaction between the heavy and light chains of bovine factor Va.

PubMed

Walker, F J

1992-10-05

Bovine factor Va has been previously been shown to consist of heavy (M(r) = 94,000) and light chains (M(r) = 81,000), that interact in a manner dependent upon the presence of either calcium or manganese ions. In an attempt to understand the mechanism of subunit interaction we have studied the effects of temperature and ions on factor Va stability. The rates of formation of factor Va from isolated chains and dissociation were temperature-dependent with an energy of activation of 6.2 and 1.3 kcal mol-1, respectively. The yield of factor Va from isolated chains was inversely related to the amount of time the chains were incubated at 4 degrees C. Incubation of individual chains revealed that the heavy chain is cold-labile, an effect that is reversible. Manganese ion was observed to prevent the conversion to the inactive form. High salt tends to stabilize the two-chain structure of factor Va, but is inhibitory to its formation from isolated chains. High concentrations of either manganese or calcium ions also inhibited reconstitution of activity. The light chain, in particular, was sensitive to the presence of manganese or calcium ion. Heavy chain that had been cleaved by activated protein C had a weakened interaction with the light chain, and the resulting complex had no procoagulant activity. Cooling of the heavy chain to 4 degrees C enhanced its intrinsic fluorescence. Manganese ion prevented some of this enhancement. The heavy chain fluorescence returned to the room temperature value with a half-life of approximately 10 min. In the presence of manganese ion relaxation was accelerated. The intrinsic fluorescence of activated protein C-cleaved heavy chain was not increased when the temperature was decreased. These data suggest that the heavy chain can exist in two forms. Elevated temperature converts it to a form that can bind ions and have a productive interaction with the light chain. However, conditions that prevent the heavy chain from combining with the light chain also stabilize the two subunit structure, suggesting that the high affinity of the complex is due to conformational changes that occur after chain interaction.

Dehydrogenation of formic acid catalyzed by magnesium hydride anions, HMgL2- (L = Cl and HCO2)

NASA Astrophysics Data System (ADS)

Khairallah, George N.; O'Hair, Richard A. J.

2006-08-01

A two step gas-phase catalytic cycle for the dehydrogenation of formic acid was established using a combination of experiments carried out on a quadrupole ion trap mass spectrometer and DFT calculations. The catalysts are the magnesium hydride anions HMgL2- (L = Cl and HCO2), which are formed from the formate complexes, HCO2MgL2-, via elimination of carbon dioxide under conditions of collision induced dissociation. This is followed by an ion-molecule reaction between HMgL2- and formic acid, which yields hydrogen and also reforms the formate complex, HCO2MgL2-. A kinetic isotope effect in the range 2.3-2.9 was estimated for the rate determining decarboxylation step by carrying out CID on the (HCO2)(DCO2)MgCl2- and subjecting the resultant mixture of (H)(DCO2)MgCl2- and (HCO2)(D)MgCl2- ions at m/z 106 to ion-molecule reactions. DFT calculations (at the B3LYP/6-31 + G* level of theory) were carried out on the HMgCl2- system and revealed that: (i) the decarboxylation of HCO2MgCl2- is endothermic by 47.8 kcal mol-1, consistent with the need to carry out CID to form the HMgCl2-; (ii) HMgCl2- can react with formic acid via either a four centred transition state or a six centred transition state. The former reaction is favoured by 7.8 kcal mol-1.

Novel fragmentation pathways of anionic adducts of steroids formed by electrospray anion attachment involving regioselective attachment, regiospecific decompositions, charge-induced pathways, and ion-dipole complex intermediates.

PubMed

Rannulu, Nalaka S; Cole, Richard B

2012-09-01

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion](-) adducts of these steroids revealed that fluoride adduct [M + F](-) precursors first lose HF to produce [M - H](-) and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d(4)-pregnenolone, are also discussed.

Novel Fragmentation Pathways of Anionic Adducts of Steroids Formed by Electrospray Anion Attachment Involving Regioselective Attachment, Regiospecific Decompositions, Charge-Induced Pathways, and Ion-Dipole Complex Intermediates

NASA Astrophysics Data System (ADS)

Rannulu, Nalaka S.; Cole, Richard B.

2012-09-01

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion]- adducts of these steroids revealed that fluoride adduct [M + F]- precursors first lose HF to produce [M - H]- and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d4-pregnenolone, are also discussed.

Structure of 3,4-dihydroxy-2-butanone 4-phosphate synthase from Methanococcus jannaschii in complex with divalent metal ions and the substrate ribulose 5-phosphate: implications for the catalytic mechanism.

PubMed

Steinbacher, Stefan; Schiffmann, Susanne; Richter, Gerald; Huber, Robert; Bacher, Adelbert; Fischer, Markus

2003-10-24

Skeletal rearrangements of carbohydrates are crucial for many biosynthetic pathways. In riboflavin biosynthesis ribulose 5-phosphate is converted into 3,4-dihydroxy-2-butanone 4-phosphate while its C4 atom is released as formate in a sequence of metal-dependent reactions. Here, we present the crystal structure of Methanococcus jannaschii 3,4-dihydroxy-2-butanone 4-phosphate synthase in complex with the substrate ribulose 5-phosphate at a dimetal center presumably consisting of non-catalytic zinc and calcium ions at 1.7-A resolution. The carbonyl group (O2) and two out of three free hydroxyl groups (OH3 and OH4) of the substrate are metal-coordinated. We correlate previous mutational studies on this enzyme with the present structural results. Residues of the first coordination sphere involved in metal binding are indispensable for catalytic activity. Only Glu-185 of the second coordination sphere cannot be replaced without complete loss of activity. It contacts the C3 hydrogen atom directly and probably initiates enediol formation in concert with both metal ions to start the reaction sequence. Mechanistic similarities to Rubisco acting on the similar substrate ribulose 1,5-diphosphate in carbon dioxide fixation as well as other carbohydrate (reducto-) isomerases are discussed.

Interactions in ion pairs of protic ionic liquids: Comparison with aprotic ionic liquids

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

Tsuzuki, Seiji, E-mail: s.tsuzuki@aist.go.jp; Shinoda, Wataru; Miran, Md. Shah

2013-11-07

The stabilization energies for the formation (E{sub form}) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G{sup **} level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E{sub form} for the [dema][CF{sub 3}SO{sub 3}] and [dmpa][CF{sub 3}SO{sub 3}] complexes (−95.6 and −96.4 kcal/mol, respectively) are significantly larger (more negative)more » than that for the [etma][CF{sub 3}SO{sub 3}] complex (−81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl{sup −}, BF{sub 4}{sup −}, TFSA{sup −} anions. The anion has contact with the N–H bond of the dema{sup +} or dmpa{sup +} cations in the most stable geometries of the dema{sup +} and dmpa{sup +} complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0–18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E{sub form} for the less stable geometries for the dema{sup +} and dmpa{sup +} complexes are close to those for the most stable etma{sup +} complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N–H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA{sup −} anion, while the strong directionality of the interactions was not suggested from the simulation of the [etma][CF{sub 3}SO{sub 3}] ionic liquid.« less

Differential Deformability of the DNA Minor Groove and Altered BI/BII Backbone Conformational Equilibrium by the Monovalent Ions Li+, Na+, K+ and Rb+ via Water-Mediated Hydrogen Bonding

PubMed Central

Savelyev, Alexey; MacKerell, Alexander D.

2015-01-01

Recently, we reported the differential impact of the monovalent cations Li+, Na+, K+ and Rb+ on DNA conformational properties. These were identified from variations in the calculated solution-state X-ray DNA spectra as a function of the ion type in the solvation buffer in MD simulations using our recently developed polarizable force field based on the classical Drude oscillator. Changes in the DNA structure were found to mainly involve variations in the minor groove width. Because minor groove dimensions vary significantly in protein-DNA complexes and have been shown to play a critical role in both specific and nonspecific DNA readout, understanding the origins of the observed differential DNA modulation by the first-group monovalent ions is of great biological importance. In the present study we show that the primary microscopic mechanism for the phenomenon is the formation of the water-mediated hydrogen bonds between solvated cations located inside the minor groove and simultaneously to two DNA strands, a process whose intensity and impact on DNA structure depends on both the type of the ion and DNA sequence. Additionally, it is shown that formation of such ion-DNA hydrogen bond complexes appreciably modulates the conformation of the backbone by increasing the population of the BII substate. Notably, the differential impact of the ions on DNA conformational behavior is only predicted by the Drude polarizable model for DNA, with virtually no effect observed from MD simulations utilizing the additive CHARMM36 model. Analysis of dipole moments of the water shows the Drude SWM4 model to possess high sensitivity to changes in the local environment, which indicates the important role of electronic polarization in the salt-dependent conformational properties. This also suggests that inclusion of polarization effects is required to model even relatively simple biological systems such as DNA in various ionic solutions. PMID:26575937

Colorimetric assay for lead ions based on the leaching of gold nanoparticles.

PubMed

Chen, Yi-You; Chang, Huan-Tsung; Shiang, Yen-Chun; Hung, Yu-Lun; Chiang, Cheng-Kang; Huang, Chih-Ching

2009-11-15

A colorimetric, label-free, and nonaggregation-based gold nanoparticles (Au NPs) probe has been developed for the detection of Pb(2+) in aqueous solution, based on the fact that Pb(2+) ions accelerate the leaching rate of Au NPs by thiosulfate (S(2)O(3)(2-)) and 2-mercaptoethanol (2-ME). Au NPs reacted with S(2)O(3)(2-) ions in solution to form Au(S(2)O(3))(2)(3-) complexes on the Au NP surfaces, leading to slight decreases in their surface plasmon resonance (SPR) absorption. Surface-assisted laser desorption/ionization time-of-flight ionization mass spectrometry (SALDI-TOF MS) data reveals the formation of Pb-Au alloys on the surfaces of the Au NPs in the presence of Pb(2+) ions and 2-ME. The formation of Pb-Au alloys accelerated the Au NPs rapidly dissolved into solution, leading to dramatic decreases in the SPR absorption. The 2-ME/S(2)O(3)(2-)-Au NP probe is highly sensitive (LOD = 0.5 nM) and selective (by at least 1000-fold over other metal ions) toward Pb(2+) ions, with a linear detection range (2.5 nM-10 muM) over nearly 4 orders of magnitude. The cost-effective probe allows rapid and simple determination of the concentrations of Pb(2+) ions in environmental samples (Montana soil and river), with results showing its great practicality for the detection of lead in real samples.

Achieving One-Electron Oxidation of a Mononuclear Nonheme Iron(V)-Imido Complex

DOE PAGES

Hong, Seungwoo; Lu, Xiaoyan; Lee, Yong -Min; ...

2017-09-29

Here, a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [Fe V(NTs)(TAML)] – (1), was oxidized by one-electron oxidants, affording formation of an iron(V)-imido TAML cation radical species, [Fe V(NTs)(TAML +•)] (2); 2 is a diamagnetic (S = 0) complex, resulting from the antiferromagnetic coupling of the low-spin iron(V) ion (S = 1/2) with the one-electron oxidized ligand (TAML +•). 2 is a competent oxidant in C–H bond functionalization and nitrene transfer reaction, showing that the reactivity of 2 is greater than that of 1.

Assembly and Properties of Heterobimetallic CoII/III/CaII Complexes with Aquo and Hydroxo Ligands

PubMed Central

Lacy, David C.; Park, Young Jun; Ziller, Joseph W.; Yano, Junko; Borovik, A. S.

2012-01-01

The use of water as a reagent in redox-driven reactions is advantageous because it is abundant and environmentally compatible. The conversion of water to dioxygen in photosynthesis illustrates one example, in which a redox-inactive CaII ion and four manganese ions are required for function. In this report we describe the stepwise formation of two new heterobimetallic complexes containing CoII/III and CaII ions, and either hydroxo or aquo ligands. The preparation of a 4-coordinate CoII synthon was achieved with the tripodal ligand, N,N′,N″-[2,2′,2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido, [MST]3−. Water binds to [CoIIMST]− to form the 5-coordinate [CoIIMST(OH2)]− complex that was used to prepare the CoII/CaII complex [CoIIMST(μ-OH2)CaII⊂15-crown-5(OH2)]+ ([CoII(μ-OH2)CaIIOH2]+). [CoII(μ-OH2)CaOH2]+ contained two aquo ligands, one bonded to the CaII ion and one bridging between the two metal ions and thus represents an unusual example of a heterobimetallic complex containing 2 aquo ligands spanning different metal ions. Both aquo ligands formed intramolecular hydrogen bonds with the [MST]3− ligand. [CoIIMST(OH2)]− was oxidized to form [CoIIIMST(OH2)] that was further converted to [CoIIIMST(μ-OH)CaII⊂15-crown-5]+ ([CoIII(μ-OH)CaII]+) in the presence of base and CaIIOTf2/15-crown-5. [CoIII(μ-OH)CaII]+ was also synthesized from the oxidation of [CoIIMST]− with PhIO in the presence of CaIIOTf2/15-crown-5. Allowing [CoIII(μ-OH)CaII]+ to react with diphenylhydrazine afforded [CoII(μ-OH2)CaIIOH2]+ and azobenzene. Additionally, the characterization of [CoIII(μ-OH)CaII]+ provides another formulation for the previously reported CoIV–oxo complex, [(TMG3tren)CoIV(μ-O)ScIII(OTf)3]2+ to one that instead could contain a CoIII–OH unit. PMID:22998407

A fluorescent nanosensor based on graphene quantum dots-aptamer probe and graphene oxide platform for detection of lead (II) ion.

PubMed

Qian, Zhao Sheng; Shan, Xiao Yue; Chai, Lu Jing; Chen, Jian Rong; Feng, Hui

2015-06-15

The sensitive detection of heavy metal ions in the organism and aquatic ecosystem using nanosensors based on environment friendly and biocompatible materials still remains a challenge. A fluorescent turn-on nanosensor for lead (II) detection based on biocompatible graphene quantum dots and graphene oxide by employment of Pb(2+)-induced G-quadruplex formation was reported. Graphene quantum dots with high quantum yield, good biocompatibility were prepared and served as the fluorophore of Pb(2+) probe. Fluorescence turn-off of graphene quantum dots is easily achieved through efficient photoinduced electron transfer between graphene quantum dots and graphene oxide, and subsequent fluorescence turn-on process is due to the formation of G-quadraplex aptamer-Pb(2+) complex triggered by the addition of Pb(2+). This nanosensor can distinguish Pb(2+) ion from other ions with high sensitivity and good reproducibility. The detection method based on this nanosensor possesses a fast response time of one minute, a broad linear span of up to 400.0 nM and ultralow detection limit of 0.6 nM. Copyright © 2015 Elsevier B.V. All rights reserved.

Formation of gold and silver nanostructures within polyvinylpyrollidone (PVP) gel

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

Kan Caixia, E-mail: cxkan@nuaa.edu.c; Wang Changshun; Zhu Jiejun

2010-04-15

Study on reduction of Au(III) and Ag(I) and the formation of Au and Ag nanostructures was performed on the gels of metal precursor and PVP polymer mixture. Some comparing samples were prepared for better understanding the role of reactants on the reduction of metal ions and further growth of nanocrystals. The results suggest that, in addition to its function of generating stable colloids, PVP not only has a reducing effect on metal ions, but also acts as a crystal growth modifier. At low temperatures, the reducing effect of PVP is strong on Ag(I) ions in AgNO{sub 3}, while the reductionmore » of complex Au(III) ions in HAuCl{sub 4} is slow, involving two steps of Au(III)->Au(I)->Au. In the study of temperature disturbance on crystal growth, Au nanoplates of new and well-defined star shape were observed. The differences in the size and shape of nanoparticles are discussed from the colloid chemistry. - Graphical abstract: If a temperature difference was introduced to the gel of Au{sup 3+}(H{sub 2}O)-PVP, large sized Au nanoplates with new and well-defined star shape were observed.« less

Regioselectivity in the gas-phase reactions of the O- radical anion with ([eta]5-cyclopentadienyl)tricarbonylmanganese(I) and ([eta]5-methylcyclopentadienyl)tricarbonylmanganese(I): formation and structure of C5H5MnO-n and C6H7MnO-n (n = 1, 2) ions

NASA Astrophysics Data System (ADS)

van den Berg, Klaas Jan; Ingemann, Steen; Nibbering, Nico M. M.

1994-06-01

The gas-phase reactions of the O- ion with ([eta]5-cyclopentadienyl)tricarbonylmanganese(I), CpMn(CO)3, and ([eta]5-methylcyclopentadienyl)tricarbonylmanganese(I), CH3CpMn(CO)3, have been studied with Fourier transform ion cyclotron resonance. The main reactions are (i) proton abstraction, (ii) loss of CO2, and (iii) expulsion of two or three CO molecules from the collision complex. Initial attack on a CO ligand is the main process as indicated by experiments with 18O- and the ion/molecule reactions of the product ions resulting from the loss of three CO molecules with water, aliphatic alcohols, methanethiol and SO2. The attack on a CO ligand followed by loss of three CO molecules is suggested to yield C5H5MnO- ions with a (cyclopentadienone)MnH- structure in the reaction with CpMn(CO)3 and (methylcyclopentadienone)MnH- ions if CH3CpMn(CO)3 is the substrate. A possible mechanism for the process leading to the indicated transformation of the Cp and CH3Cp ligands into C5H4O and CH3C5H3O ligands, respectively, is discussed together with the formation of (fulvene)Mn(OH)- ions following attack of O- on CH3CpMn(CO)3. The (cyclopentadienone)MnH- and (methylcyclopentadienone)MnH- ions react with N2O by oxygen atom abstraction to form C5H5MnO-2 and C6H7MnO-2 ions, respectively.

Anaerobic Formate and Hydrogen Metabolism.

PubMed

Pinske, Constanze; Sawers, R Gary

2016-10-01

Numerous recent developments in the biochemistry, molecular biology, and physiology of formate and H2 metabolism and of the [NiFe]-hydrogenase (Hyd) cofactor biosynthetic machinery are highlighted. Formate export and import by the aquaporin-like pentameric formate channel FocA is governed by interaction with pyruvate formate-lyase, the enzyme that generates formate. Formate is disproportionated by the reversible formate hydrogenlyase (FHL) complex, which has been isolated, allowing biochemical dissection of evolutionary parallels with complex I of the respiratory chain. A recently identified sulfido-ligand attached to Mo in the active site of formate dehydrogenases led to the proposal of a modified catalytic mechanism. Structural analysis of the homologous, H2-oxidizing Hyd-1 and Hyd-5 identified a novel proximal [4Fe-3S] cluster in the small subunit involved in conferring oxygen tolerance to the enzymes. Synthesis of Salmonella Typhimurium Hyd-5 occurs aerobically, which is novel for an enterobacterial Hyd. The O2-sensitive Hyd-2 enzyme has been shown to be reversible: it presumably acts as a conformational proton pump in the H2-oxidizing mode and is capable of coupling reverse electron transport to drive H2 release. The structural characterization of all the Hyp maturation proteins has given new impulse to studies on the biosynthesis of the Fe(CN)2CO moiety of the [NiFe] cofactor. It is synthesized on a Hyp-scaffold complex, mainly comprising HypC and HypD, before insertion into the apo-large subunit. Finally, clear evidence now exists indicating that Escherichia coli can mature Hyd enzymes differentially, depending on metal ion availability and the prevailing metabolic state. Notably, Hyd-3 of the FHL complex takes precedence over the H2-oxidizing enzymes.

Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques

NASA Technical Reports Server (NTRS)

Borsdorf, H.; Nazarov, E. G.; Eiceman, G. A.

2002-01-01

The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization. c. 2002 American Society for Mass Spectrometry.

Calcium ion binding to a soil fulvic acid using a donnan potential model

USGS Publications Warehouse

Marinsky, J.A.; Mathuthu, A.; Ephraim, J.H.; Reddy, M.M.

1999-01-01

Calcium ion binding to a soil fulvic acid (Armadale Bh Horizon) was evaluated over a range of calcium ion concentrations, from pH 3.8 to 7.3, using potentiometric titrations and calcium ion electrode measurements. Fulvic acid concentration was constant (100 milligrams per liter) and calcium ion concentration varied up to 8 X 10-4 moles per liter. Experiments discussed here included: (1) titrations of fulvic acid-calcium ion containing solutions with sodium hydroxide; and (2) titrations of fully neutralized fulvic acid with calcium chloride solutions. Apparent binding constants (expressed as the logarithm of the value, log ??app) vary with solution pH, calcium ion concentration, degree of acid dissociation, and ionic strength (from log ??app = 2.5 to 3.9) and are similar to those reported by others. Fulvic acid charge, and the associated Donnan Potential, influences calcium ion-fulvic acid ion pair formation. A Donnan Potential corrrection term allowed calculation of intrinsic calcium ion-fulvic acid binding constants. Intrinsic binding constants vary from 1.2 to 2.5 (the average value is about log??= 1.6) and are similar to, but somewhat higher than, stability constants for calcium ion-carboxylic acid monodentate complexes. ?? by Oldenbourg Wissenschaftsverlag, Mu??nchen.

Core-Shell Coating Silicon Anode Interfaces with Coordination Complex for Stable Lithium-Ion Batteries.

PubMed

Zhou, Jinqiu; Qian, Tao; Wang, Mengfan; Xu, Na; Zhang, Qi; Li, Qun; Yan, Chenglin

2016-03-02

In situ core-shell coating was used to improve the electrochemical performance of Si-based anodes with polypyrrole-Fe coordination complex. The vast functional groups in the organometallic coordination complex easily formed hydrogen bonds when in situ modifying commercial Si nanoparticles. The incorporation of polypyrrole-Fe resulted in the conformal conductive coating surrounding each Si nanoparticle, not only providing good electrical connection to the particles but also promoting the formation of a stable solid-electrolyte-interface layer on the Si electrode surface, enhancing the cycling properties. As an anode material for Li-ion batteries, modified silicon powders exhibited high reversible capacity (3567 mAh/g at 0.3 A/g), good rate property (549.12 mAh/g at 12 A/g), and excellent cycling performance (reversible capacity of 1500 mAh/g after 800 cycles at 1.2 A/g). The constructed novel concept of core-shell coating Si particles presented a promising route for facile and large-scale production of Si-based anodes for extremely durable Li-ion batteries, which provided a wide range of applications in the field of energy storage of the renewable energy derived from the solar energy, hydropower, tidal energy, and geothermal heat.

Synthesis of Tb{sub 4}O{sub 7} complexed with reduced graphene oxide for Rhodamine-B absorption

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

Gao, Hui, E-mail: hope@lzu.edu.cn; Zhou, Yang; Chen, Keqin

2016-05-15

Highlights: • Tb–rGO composite was fabricated via a facile thermally reduction process. • The green and blue emissions were both observed in the composite. • The composite exhibited efficient absorption capability for Rhodamine-B. - Abstract: Tb{sub 4}O{sub 7} complexed with reduced graphene oxide composite (Tb–rGO) had been designed and fabricated by a facile thermal reduction method. The formation of Tb{sub 4}O{sub 7} particles and reduction of graphene oxide (GO) occurred simultaneously, and partial terbium ions would be complexed with rGO via oxygen-containing function groups on rGO sheets. Introducing of terbium ions could effectively tune the photoluminescence properties of rGO, andmore » the composite exhibited the typical green emission of terbium ions as well as the blue self-luminescence of graphene entered at 440 nm. Moreover, Tb–rGO had demonstrated its high capability as an organic dye (Rhodamine-B) scavenger with high speed and efficiency. The findings showed the promising applications for large-scale removal of organic dye contaminants, especially in the field of waste water treatment.« less

Structural changes at the metal ion binding site during the phosphoglucomutase reaction.

PubMed

Ray, W J; Post, C B; Liu, Y; Rhyu, G I

1993-01-12

An electron density map of the reactive, Cd2+ form of crystalline phosphoglucomutase from X-ray diffraction studies shows that the enzymic phosphate donates a nonbridging oxygen to the ligand sphere of the bound metal ion, which appears to be tetracoordinate. 31P and 113Cd NMR spectroscopy are used to assess changes in the properties of bound Cd2+ produced by substrate/product and by substrate/product analog inhibitors. The approximately 50 ppm downfield shift of the 113Cd resonance on formation of the complex of dephosphoenzyme and glucose 1,6-bisphosphate is associated with the initial sugar-phosphate binding step and likely involves a change in the geometry of the coordinating ligands. This interpretation is supported by spectral studies involving various complexes of the active Co2+ and Ni(2+)-enzyme. In addition, there is a loss of the 31P-113Cd J coupling that characterizes the monophosphate complexes of the Cd2+ enzyme either during or immediately after the PO3- transfer step that produces the bisphosphate complex, indicating a further change at the metal binding site. The implications of these observations with respect to the PO3- transfer process in the phosphoglucomutase reaction are considered. The apparent plasticity of the ligand sphere of the active site metal ion in this system may allow a single metal ion to act as a chaperone for a nonbridging oxygen during PO3- transfer or to allow a change in metal ion coordination during catalysis. A general NMR line shape/chemical-exchange analysis for evaluating binding in protein-ligand systems when exchange is intermediate to fast on the NMR time scale is described. Its application to the present system involves multiple exchange sites that depend on a single binding rate, thereby adding further constraints to the analysis.

Structural and Biochemical Studies on the Regulation of Biotin Carboxylase by Substrate Inhibition and Dimerization

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

C Chou; L Tong

2011-12-31

Biotin carboxylase (BC) activity is shared among biotin-dependent carboxylases and catalyzes the Mg-ATP-dependent carboxylation of biotin using bicarbonate as the CO{sub 2} donor. BC has been studied extensively over the years by structural, kinetic, and mutagenesis analyses. Here we report three new crystal structures of Escherichia coli BC at up to 1.9 {angstrom} resolution, complexed with different ligands. Two structures are wild-type BC in complex with two ADP molecules and two Ca{sup 2+} ions or two ADP molecules and one Mg{sup 2+} ion. One ADP molecule is in the position normally taken by the ATP substrate, whereas the other ADPmore » molecule occupies the binding sites of bicarbonate and biotin. One Ca{sup 2+} ion and the Mg{sup 2+} ion are associated with the ADP molecule in the active site, and the other Ca{sup 2+} ion is coordinated by Glu-87, Glu-288, and Asn-290. Our kinetic studies confirm that ATP shows substrate inhibition and that this inhibition is competitive against bicarbonate. The third structure is on the R16E mutant in complex with bicarbonate and Mg-ADP. Arg-16 is located near the dimer interface. The R16E mutant has only a 2-fold loss in catalytic activity compared with the wild-type enzyme. Analytical ultracentrifugation experiments showed that the mutation significantly destabilized the dimer, although the presence of substrates can induce dimer formation. The binding modes of bicarbonate and Mg-ADP are essentially the same as those to the wild-type enzyme. However, the mutation greatly disrupted the dimer interface and caused a large re-organization of the dimer. The structures of these new complexes have implications for the catalysis by BC.« less

Structural and Biochemical Studies on the Regulation of Biotin Carboxylase by Substrate Inhibition and Dimerization

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

Chou, Chi-Yuan; Tong, Liang

2012-06-19

Biotin carboxylase (BC) activity is shared among biotin-dependent carboxylases and catalyzes the Mg-ATP-dependent carboxylation of biotin using bicarbonate as the CO{sub 2} donor. BC has been studied extensively over the years by structural, kinetic, and mutagenesis analyses. Here we report three new crystal structures of Escherichia coli BC at up to 1.9 {angstrom} resolution, complexed with different ligands. Two structures are wild-type BC in complex with two ADP molecules and two Ca{sup 2+} ions or two ADP molecules and one Mg{sup 2+} ion. One ADP molecule is in the position normally taken by the ATP substrate, whereas the other ADPmore » molecule occupies the binding sites of bicarbonate and biotin. One Ca{sup 2+} ion and the Mg{sup 2+} ion are associated with the ADP molecule in the active site, and the other Ca{sup 2+} ion is coordinated by Glu-87, Glu-288, and Asn-290. Our kinetic studies confirm that ATP shows substrate inhibition and that this inhibition is competitive against bicarbonate. The third structure is on the R16E mutant in complex with bicarbonate and Mg-ADP. Arg-16 is located near the dimer interface. The R16E mutant has only a 2-fold loss in catalytic activity compared with the wild-type enzyme. Analytical ultracentrifugation experiments showed that the mutation significantly destabilized the dimer, although the presence of substrates can induce dimer formation. The binding modes of bicarbonate and Mg-ADP are essentially the same as those to the wild-type enzyme. However, the mutation greatly disrupted the dimer interface and caused a large re-organization of the dimer. The structures of these new complexes have implications for the catalysis by BC.« less

Hydration and ion pair formation in aqueous Y(3+)-salt solutions.

PubMed

Rudolph, Wolfram W; Irmer, Gert

2015-11-14

Raman spectra of aqueous yttrium perchlorate, triflate (trifluoromethanesulfonate), chloride and nitrate solutions were measured over a broad concentration range (0.198-3.252 mol L(-1)). The spectra range from low wavenumbers to 4200 cm(-1). A very weak mode at 384 cm(-1) with a full width at half height at 50 cm(-1) in the isotropic spectrum suggests that the Y(3+)- octa-aqua ion is thermodynamically stable in dilute perchlorate solutions (∼0.5 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The octa-hydrate, [Y(OH2)8](3+) was also detected in a 1.10 mol L(-1) aqueous Y(CF3SO3)3 solution. Furthermore, very weak and broad depolarized modes could be detected which are assigned to [Y(OH2)8](3+)(aq) at 100, 166, 234 and 320 cm(-1) confirming that a hexa-hydrate is not compatible with the hydrated species in solution. In yttrium chloride solutions contact ion pair formation was detected over the measured concentration range from 0.479-3.212 mol L(-1). The contact ion pairs in YCl3(aq) are fairly weak and disappear with dilution. At a concentration <0.2 mol L(-1) almost all complexes have disappeared. In YCl3 solutions, with additional HCl, chloro-complexes of the type [Y(OH2)8-nCln](+3-n) (n = 1,2) are formed. The Y(NO3)3(aq) spectra were compared with a spectrum of a dilute NaNO3 solution and it was concluded that in Y(NO3)3(aq) over the concentration range from 2.035-0.198 mol L(-1) nitrato-complexes [Y(OH2)8-n(NO3)ln](+3-n) (n = 1,2) are formed. The nitrato-complexes are weak and disappear with dilution <0.1 mol L(-1). DFT geometry optimizations and frequency calculations are reported for both the yttrium-water cluster in the gas phase and the cluster within a polarizable continuum model in order to implicitly describe the presence of the bulk solvent. The bond distance and angle for the square antiprismatic cluster geometry of [Y(OH2)8](3+) with the polarizable dielectric continuum is in good agreement with data from recent structural experimental measurements. The DFT frequency of the Y-O stretching mode of the [Y(OH2)8](3+) cluster, in a polarizable continuum, is at 372 cm(-1) in satisfactory agreement with the experimental value.

The Effects of Trivalent Lanthanide Cationization on the Electron Transfer Dissociation of Acidic Fibrinopeptide B and its Analogs

NASA Astrophysics Data System (ADS)

Commodore, Juliette J.; Cassady, Carolyn J.

2016-09-01

Electrospray ionization (ESI) on mixtures of acidic fibrinopeptide B and two peptide analogs with trivalent lanthanide salts generates [M + Met + H]4+, [M + Met]3+, and [M + Met -H]2+, where M = peptide and Met = metal (except radioactive promethium). These ions undergo extensive and highly efficient electron transfer dissociation (ETD) to form metallated and non-metallated c- and z-ions. All metal adducted product ions contain at least two acidic sites, which suggest attachment of the lanthanide cation at the side chains of one or more acidic residues. The three peptides undergo similar fragmentation. ETD on [M + Met + H]4+ leads to cleavage at every residue; the presence of both a metal ion and an extra proton is very effective in promoting sequence-informative fragmentation. Backbone dissociation of [M + Met]3+ is also extensive, although cleavage does not always occur between adjacent glutamic acid residues. For [M + Met - H ]2+, a more limited range of product ions form. All lanthanide metal peptide complexes display similar fragmentation except for europium (Eu). ETD on [M + Eu - H]2+ and [M + Eu]3+ yields a limited amount of peptide backbone cleavage; however, [M + Eu + H]4+ dissociates extensively with cleavage at every residue. With the exception of the results for Eu(III), metallated peptide ion formation by ESI, ETD fragmentation efficiencies, and product ion formation are unaffected by the identity of the lanthanide cation. Adduction with trivalent lanthanide metal ions is a promising tool for sequence analysis of acidic peptides by ETD.

An empirical model for ion formation from polymer surfaces during analysis by secondary ion mass spectrometry

NASA Astrophysics Data System (ADS)

Leggett, Graham J.; Vickerman, John C.

1992-12-01

Some of the models that have been proposed to account for ion formation during sputtering are reviewed. Particular attention is paid to models describing polyatomic ion formation. Aspects of these models that are relevant to ion formation from molecular materials are discussed. Reports describing the sputtering of polymeric materials are reviewed, and the bearing of recent tandem studies on attempts to formulate a model for ion formation from polymer materials is discussed. Some of the characteristics that a suitable model would possess are identified from the experimental data.

Sensitized green emission of terbium with dibenzoylmethane and 1, 10 phenanthroline in polyvinyl alcohol and polyvinyl pyrrolidone blends

NASA Astrophysics Data System (ADS)

Kumar, Brijesh; Kaur, Gagandeep; Rai, S. B.

2017-12-01

Tb doped polyvinyl alcohol: polyvinyl pyrrolidone blends with dibenzoylmethane (DBM) and 1, 10 Phenanthroline (Phen) have been prepared by solution cast technique. Bond formation amongst the ligands and Tb3 + ions in the doped polymer has been confirmed employing Fourier Transform Infrared (FTIR) techniques. Optical properties of the Tb3 + ions have been investigated using UV-Vis absorption, excitation and fluorescence studies excited by different radiations. Addition of dimethylbenzoate and 1, 10 Phenanthroline to the polymer blend increases the luminescence from Tb3 + ions along with energy transfer from the polymer blend itself. Luminescence decay curve analysis affirms the non-radiative energy transfer from DBM and Phen to Tb3 + ions, which is identified as the reason behind this enhancement. The fluorescence decay time of PVA-PVP host decreases from 6.02 ns to 2.31 ns showing an evidence of energy transfer from the host blend to the complexed Tb ions. Similarly the lifetime of DBM and Phen and both in the blend reduces in the complexed system showing the feasibility of energy transfer from these excited DBM and Phen to Tb3 + and is proposed as the cause of the above observations. These entire phenomena have been explained by the energy level diagram.

Potentiometric and spectroscopic study of the interaction of 3d transition metal ions with inositol hexakisphosphate

NASA Astrophysics Data System (ADS)

Veiga, Nicolás; Macho, Israel; Gómez, Kerman; González, Gabriel; Kremer, Carlos; Torres, Julia

2015-10-01

Among myo-inositol phosphates, the most abundant in nature is the myo-inositol hexakisphosphate, InsP6. Although it is known to be vital to cell functioning, the biochemical research into its metabolism needs chemical and structural analysis of all the protonation, complexation and precipitation processes that it undergoes in the biological media. In view of its high negative charge at physiological level, our group has been leading a thorough research into the InsP6 chemical and structural behavior in the presence of the alkali and alkaline earth metal ions essential for life. The aim of this article is to extend these studies, dealing with the chemical and structural features of the InsP6 interaction with biologically relevant 3d transition metal ions (Fe(II), Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)), in a non-interacting medium and under simulated physiological conditions. The metal-complex stability constants were determined by potentiometry, showing under ligand-excess conditions the formation of mononuclear species in different protonation states. Under metal ion excess, polymetallic species were detected for Fe(II), Fe(III), Zn(II) and Cu(II). Additionally, the 31P NMR and UV-vis spectroscopic studies provided interesting structural aspects of the strong metal ion-InsP6 interaction.

Effects of Charge State on Fragmentation Pathways, Dynamics, and Activation Energies of Ubiquitin Ions Measured by Blackbody Infrared Radiative Dissociation

PubMed Central

Jockusch, Rebecca A.; Schnier, Paul D.; Price, William D.; Strittmatter, Eric. F.; Demirev, Plamen A.; Williams*, Evan R.

2005-01-01

Blackbody infrared radiative dissociation spectra of the (M + 5H)5+ through (M + 11H)11+ ions of the protein ubiquitin (8.6 kDa) formed by electrospray ionization were measured in a Fourier-transform mass spectrometer. The 5+ ion dissociates exclusively by loss of water and/or ammonia, whereas the 11+ charge state dissociates only by formation of complementary y and b ions. These two processes are competitive for intermediate charge state ions, with the formation of y and b ions increasingly favored for the higher charge states. The y and b ions are formed by cleavage of the backbone amide bond on the C-terminal side of acidic residues exclusively, with cleavage adjacent to aspartic acid favored. Thermal unimolecular dissociation rate constants for the dissociation of each of these charge states were measured. From the temperature dependence of these rates, Arrhenius activation parameters in the rapid energy exchange limit are obtained. The activation energies (Ea) and preexponential factors (A) for the 5+, 8+, and 9+ ions are 1.2 eV and 1012 s−1, respectively. These values for the 6+ and 7+ ions are 0.9–1.0 eV and 109 s−1, and those for the 10+ and 11+ ions are 1.6 eV and 1016–1017 s−1. Thus, with the exception of the 5+ ion, the higher charge states of ubiquitin have larger dissociation activation energies than the lower charge states. The different A factors observed for production of y and b ions from different precursor charge states indicate that they are formed by different mechanisms, ranging from relatively complex rearrangements to direct bond cleavages. These results clearly demonstrate that the relative dissociation rates of large biomolecule ions by themselves are not necessarily a reliable indicator of their relative dissociation energies, even when similar fragment ions are formed. PMID:9075403

Effects of charge state on fragmentation pathways, dynamics, and activation energies of ubiquitin ions measured by blackbody infrared radiative dissociation.

PubMed

Jockusch, R A; Schnier, P D; Price, W D; Strittmatter, E F; Demirev, P A; Williams, E R

1997-03-15

Blackbody infrared radiative dissociation spectra of the (M + 5H)5+ through (M + 11H)11+ ions of the protein ubiquitin (8.6 kDa) formed by electrospray ionization were measured in a Fourier-transform mass spectrometer. The 5+ ion dissociates exclusively by loss of water and/or ammonia, whereas the 11+ charge state dissociates only by formation of complementary y and b ions. These two processes are competitive for intermediate charge state ions, with the formation of y and b ions increasingly favored for the higher charge states. The y and b ions are formed by cleavage of the backbone amide bond on the C-terminal side of acidic residues exclusively, with cleavage adjacent to aspartic acid favored. Thermal unimolecular dissociation rate constants for the dissociation of each of these charge states were measured. From the temperature dependence of these rates, Arrhenius activation parameters in the rapid energy exchange limit are obtained. The activation energies (Ea) and preexponential factors (A) for the 5+, 8+, and 9+ ions are 1.2 eV and 10(12) s-1, respectively. These values for the 6+ and 7+ ions are 0.9-1.0 eV and 10(9) s-1, and those for the 10+ and 11+ ions are 1.6 eV and 10(16)-10(17) s-1. Thus, with the exception of the 5+ ion, the higher charge states of ubiquitin have larger dissociation activation energies than the lower charge states. The different A factors observed for production of y and b ions from different precursor charge states indicate that they are formed by different mechanisms, ranging from relatively complex rearrangements to direct bond cleavages. These results clearly demonstrate that the relative dissociation rates of large biomolecule ions by themselves are not necessarily a reliable indicator of their relative dissociation energies, even when similar fragment ions are formed.

Investigation of corrosion caused by constituents of refinery wastewater effluent used as circulating cooling water.

PubMed

Zhang, Zhongzhi; Song, Shaofu; Huang, Jie; Ji, Lin; Wu, Fangyun

2003-01-01

The corrosion rate of steel plate using single-factor, multifactor, and complex water systems was investigated via refinery wastewater effluents used as circulating cooling water. The results show that the primary corrosion factors of steel depend on the characteristics of the ions, the formation of the oxidized coating, the diffusion of dissolved oxygen, and other complex factors, although ions such as chloride, calcium, and carbonate play an important role. The corrosion rate of carbon steel exhibits two trends: The corrosion rate is high at low conductivity, increases to a maximum, and then decreases and becomes stable with increasing conductivity, as is the case with chloride, sulfate, nitrate and calcium ions. On the other hand, the corrosion rate is highest at low conductivity and then decreases and becomes stable with increasing conductivity, as is the case with carbonate, silicate, and sodium nitrate ions. Research results indicate that the anticorrosive ability is minimal at low conductivity; but is excellent at high conductivity. Pretreatment of low-conductivity water using air flotation and clarification to decrease the concentrations of chloride, calcium, and carbonate ions to a suitable level to satisfy the anticorrosion requirements is required. However, it is not necessary to significantly reduce the salt concentration or conductivity of the water by osmosis or ion exchange to obtain an anticorrosion effect when reusing wastewater effluents as circulating cooling water.

SK3/TRPC1/Orai1 complex regulates SOCE-dependent colon cancer cell migration: a novel opportunity to modulate anti-EGFR mAb action by the alkyl-lipid Ohmline

PubMed Central

Guéguinou, Maxime; Harnois, Thomas; Crottes, David; Uguen, Arnaud; Deliot, Nadine; Gambade, Audrey; Chantôme, Aurélie; Haelters, Jean Pierre; Jaffrès, Paul Alain; Jourdan, Marie Lise; Weber, Günther; Soriani, Olivier; Bougnoux, Philippe; Mignen, Olivier; Bourmeyster, Nicolas; Constantin, Bruno; Lecomte, Thierry

2016-01-01

Background Barely 10-20% of patients with metastatic colorectal cancer (mCRC) receive a clinical benefit from the use of anti-EGFR monoclonal antibodies (mAbs). We hypothesized that this could depends on their efficiency to reduce Store Operated Calcium Entry (SOCE) that are known to enhance cancer cells. Results In the present study, we demonstrate that SOCE promotes migration of colon cancer cell following the formation of a lipid raft ion channel complex composed of TRPC1/Orai1 and SK3 channels. Formation of this complex is stimulated by the phosphorylation of the reticular protein STIM1 by EGF and activation of the Akt pathway. Our data show that, in a positive feedback loop SOCE activates both Akt pathway and SK3 channel activity which lead to SOCE amplification. This amplification occurs through the activation of Rac1/Calpain mediated by Akt. We also show that Anti-EGFR mAbs can modulate SOCE and cancer cell migration through the Akt pathway. Interestingly, the alkyl-lipid Ohmline, which we previously showed to be an inhibitor of SK3 channel, can dissociated the lipid raft ion channel complex through decreased phosphorylation of Akt and modulation of mAbs action. Conclusions This study demonstrates that the inhibition of the SOCE-dependent colon cancer cell migration trough SK3/TRPC1/Orai1 channel complex by the alkyl-lipid Ohmline may be a novel strategy to modulate Anti-EGFR mAb action in mCRC. PMID:27102434

Siderophores in Cloud Waters and Potential Impact on Atmospheric Chemistry: Photoreactivity of Iron Complexes under Sun-Simulated Conditions.

PubMed

Passananti, Monica; Vinatier, Virginie; Delort, Anne-Marie; Mailhot, Gilles; Brigante, Marcello

2016-09-06

In the present work, the photoreactivity of a mixture of iron(III)–pyoverdin (Fe(III)–Pyo) complexes was investigated under simulated cloud conditions. Pyoverdins are expected to complex ferric ions naturally present in cloudwater, thus modifying their availability and photoreactivity. The spectroscopic properties and photoreactivity of Fe(III)-Pyo were investigated, with particular attention to their fate under solar irradiation, also studied through simulations. The photolysis of the Fe(III)–Pyo complex leads to the generation of Fe(II), with rates of formation (RFe(II)f) of 6.98 and 3.96 × 10–9 M s–1 at pH 4.0 and 6.0, respectively. Interestingly, acetate formation was observed during the iron-complex photolysis, suggesting that fragmentation can occur after the ligand-to-metal charge transfer (LMCT) via a complex reaction mechanism. Moreover, photogenerated Fe(II) represent an important source of hydroxyl radical via the Fenton reaction in cloudwater. This reactivity might be relevant for the estimation of the rates of formation and steady-state concentrations of the hydroxyl radical by cloud chemistry models and for organic matter speciation in the cloud aqueous phase. In fact, the conventional models, which describe the iron photoreactivity in terms of iron–aqua and oxalate complexes, are not in accordance with our results.

The role of metals in protein conformational disorders - The case of prion protein and Aβ -peptide

NASA Astrophysics Data System (ADS)

De Santis, E.; Minicozzi, V.; Morante, S.; Rossi, G. C.; Stellato, F.

2016-02-01

Protein conformational disorders are members of a vast class of pathologies in which endogenous proteins or peptides undergo a misfolding process by switching from the physiological soluble configuration to a pathological fibrillar insoluble state. An important, but not yet fully elucidated, role in the process appears to be played by transition metal ions, mainly copper and zinc. X-ray absorption spectroscopy is one of the most suitable techniques for the structural characterization of biological molecules in complex with metal. Owing to its chemical selectivity and sensitivity to the local atomic geometry around the absorber, it can be successfully used to study the environment of metal ions in complex with proteins and peptides in physiological conditions. In this paper we present X-ray absorption spectroscopy studies of the metal ions coordination modes in systems where metals are complexed with specific amyloidogenic proteins and peptides. In particular, we show results concerning the Amyloid β peptide, that is involved in Alzheimer's disease, and the Prion protein, that is responsible for the Transmissible Spongiform Encephalopathy. Our findings suggest that the copper and zinc ions may play a crucial role in the aggregation and fibril formation process of these two biomolecules. Elucidating this kind of interaction could be a key preliminary step before any viable therapy can be conceived or designed.

On the origin of red and blue shifts of X-H and C-H stretching vibrations in formic acid (formate ion) and proton donor complexes.

PubMed

Tâme Parreira, Renato Luis; Galembeck, Sérgio Emanuel; Hobza, Pavel

2007-01-08

Complexes between formic acid or formate anion and various proton donors (HF, H(2)O, NH(3), and CH(4)) are studied by the MP2 and B3LYP methods with the 6-311++G(3df,3pd) basis set. Formation of a complex is characterized by electron-density transfer from electron donor to ligands. This transfer is much larger with the formate anion, for which it exceeds 0.1 e. Electron-density transfer from electron lone pairs of the electron donor is directed into sigma* antibonding orbitals of X--H bonds of the electron acceptor and leads to elongation of the bond and a red shift of the X--H stretching frequency (standard H-bonding). However, pronounced electron-density transfer from electron lone pairs of the electron donor also leads to reorganization of the electron density in the electron donor, which results in changes in geometry and vibrational frequency. These changes are largest for the C--H bonds of formic acid and formate anion, which do not participate in H-bonding. The resulting blue shift of this stretching frequency is substantial and amounts to almost 35 and 170 cm(-1), respectively.

Role of ammonium ion and transition metals in the formation of secondary organic aerosol and metallo-organic complex within fog processed ambient deliquescent submicron particles collected in central part of Indo-Gangetic Plain.

PubMed

Singh, Dharmendra Kumar; Gupta, Tarun

2017-08-01

In this study we observed the role of ammonium ion (NH 4 + ) and transition metals (Fe, Mn, Cr, and Cu) present in ambient submicron particles in stabilizing and enhancing the yield of water soluble organic carbon (WSOC). A good correlation of WSOC with transition metals and NH 4 + was found (R 2  = 0.87 and 0.71), respectively within foggy episode collected ambient PM 1 (particles having aerodynamic diameter ≤1.0 μm) suggesting plausibleness of alternate oxidation (primarily various carbonyls into their respective organic acids, esters and other derivatives.) and aging mechanisms. Molar concentration of ammonium ion was observed to be exceeded over and above to require in neutralizing the sulphate and nitrate which further hints its role in the neutralization, stabilization and enhancement of subset of WSOC such as water soluble organic acids. Transition metals were further apportioned using enrichment factor analysis. The source of Fe, Mn, and Cr was found to be crustal and Cu was tagged to anthropogenic origin. This study also described the plausible role of significant predictors (Fe and Cu) in the secondary organic aerosol (SOA) formation through effect of Fenton chemistry. Mass-to-charge ratio of identified oxalic acid from our published recent field study (carried out from same sampling location) was used for understanding the possible metallo-organic complex with Fe supports the substantial role of Fe in SOA formation in the deliquescent submicron particles facilitated by aqueous-phase chemistry. Copyright © 2017 Elsevier Ltd. All rights reserved.

Studies on the mechanism of action of 6-mercaptopurine. Interaction with copper and xanthine oxidase.

PubMed

Kela, U; Vijayvargiya, R

1981-03-01

Interaction between 6-mercaptopurine, Cu2+ and the enzyme xanthine oxidase (EC 1.2.3.2.) was examined. Whereas Cu2+ was found to inhibit the enzyme, 6-mercaptopurine could protect as well as reverse the enzyme inhibition produced by the metal ion. The formation of a complex between 6-mercaptopurine and Cu2+ seems to be responsible for the observed effect. Job's [(1928) Ann. Chem. 9, 113] method has shown the composition of the complex to be 1:1. The apparent stability constant (log K value), as determined by Subhrama Rao & Raghav Rao's [(1955) J. Sci. Chem. Ind. Res. 143, 278], method is found to be 6.74. It is suggested that the formation of a stable complex between 6-mercaptopurine molecules and Cu2+ may be an additional mechanism of action of 6-mercaptopurine, particularly with reference to its anti-inflammatory properties.

Hexahomotrioxacalix[3]arene derivatives as ionophores for molecular recognition of dopamine, serotonin and phenylethylamine.

PubMed

Ni, Xin-Long; Rahman, Shofiur; Wang, Shi; Jin, Cheng-Cheng; Zeng, Xi; Hughes, David L; Redshaw, Carl; Yamato, Takehiko

2012-06-21

The lower rim functionalized hexahomotrioxacalix[3]arene derivatives cone-3 and cone-5 bearing three benzyl and three N,N-diethyl-2-aminoethoxy groups, respectively, were synthesized from triol 1. Their complexation with 2-(3,4-dihydroxyphenyl)ethylamine (dopamine), 5-hydroxytryptamine (serotonin), and 2-phenylethylamine (phenethylamine), which have biologically important activities, has been studied by (1)H-NMR spectroscopy. The chemical shifts of the aromatic protons of the host and guest molecules and the up-field shifts of the ethyl protons of the guest molecules strongly suggest the formation of inclusion complexes in solution. The formation of the host-guest complexes is assisted by a hydrogen bond and/or an electrostatic interaction between the host and ammonium ion (RNH(3)(+)) of the guest. The structures of receptors cone-3 and cone-5 have been determined by X-ray crystallography.

Studies on the mechanism of action of 6-mercaptopurine. Interaction with copper and xanthine oxidase.

PubMed Central

Kela, U; Vijayvargiya, R

1981-01-01

Interaction between 6-mercaptopurine, Cu2+ and the enzyme xanthine oxidase (EC 1.2.3.2.) was examined. Whereas Cu2+ was found to inhibit the enzyme, 6-mercaptopurine could protect as well as reverse the enzyme inhibition produced by the metal ion. The formation of a complex between 6-mercaptopurine and Cu2+ seems to be responsible for the observed effect. Job's [(1928) Ann. Chem. 9, 113] method has shown the composition of the complex to be 1:1. The apparent stability constant (log K value), as determined by Subhrama Rao & Raghav Rao's [(1955) J. Sci. Chem. Ind. Res. 143, 278], method is found to be 6.74. It is suggested that the formation of a stable complex between 6-mercaptopurine molecules and Cu2+ may be an additional mechanism of action of 6-mercaptopurine, particularly with reference to its anti-inflammatory properties. PMID:6895465

Polymorphism in the nitrate salt of the [Mn(acetylacetonate)2(H2O)2]+ ion.

PubMed

Biju, A R; Rajasekharan, M V

2010-06-01

The crystallization of [Mn(acac)(2)(H(2)O)(2)](+) from solutions containing excess nitrate leads to the formation of four polymorphs. All polymorphs contain two different types of complex ions, one containing essentially coplanar acac ligands and the other in which the two acac ligands together assume a chair conformation. Molecular modelling using DFT (density-functional theory) calculations shows that the coplanar conformation is the electronically stable one. The hydrogen bonding between the trans-water molecules and the nitrate ion produces a one-dimensional chain of 12-membered rings, which are further organized into a two-dimensional network via a lattice water molecule. Lattice-energy calculations have been carried out to compare the stabilities of the four polymorphs.

A reversible fluorescence "off-on-off" sensor for sequential detection of aluminum and acetate/fluoride ions.

PubMed

Gupta, Vinod Kumar; Mergu, Naveen; Kumawat, Lokesh Kumar; Singh, Ashok Kumar

2015-11-01

A new rhodamine functionalized fluorogenic Schiff base CS was synthesized and its colorimetric and fluorescence responses toward various metal ions were explored. The sensor exhibited highly selective and sensitive colorimetric and "off-on" fluorescence response towards Al(3+) in the presence of other competing metal ions. These spectral changes are large enough in the visible region of the spectrum and thus enable naked-eye detection. Studies proved that the formation of CS-Al(3+) complex is fully reversible and can sense to AcO(-)/F(-) via dissociation. The results revealed that the sensor provides fluorescence "off-on-off" strategy for the sequential detection of Al(3+) and AcO(-)/F(-). Copyright © 2015 Elsevier B.V. All rights reserved.

Indirect consequences of exciplex states on the phosphorescence lifetime of phenazine-based 1,2,3-triazole luminescent probes.

PubMed

Costa, Bárbara B A; Jardim, Guilherme A M; Santos, Paloma L; Calado, Hállen D R; Monkman, Andrew P; Dias, Fernando B; da Silva Júnior, Eufrânio N; Cury, Luiz A

2017-02-01

The optical properties of phenazine derivative probe solutions involving intersystem crossing from singlet to triplet states were investigated by time resolved spectroscopy. The room temperature phosphorescence emission presented different time responses when Cd 2+ ions were bound to the probe chemical structure. The complex exciplex formation observed to occur in this case was not directly responsible for the change in the phosphorescence lifetime. This was more influenced by the new molecular conformation and modified spin-orbit coupling imposed by the binding of the Cd 2+ ions to the phenazine molecules.

Reactions in trifluoroacetic acid (CF 3COOH) induced by low energy electron attachment

NASA Astrophysics Data System (ADS)

Langer, Judith; Stano, Michal; Gohlke, Sascha; Foltin, Victor; Matejcik, Stefan; Illenberger, Eugen

2006-02-01

Dissociative electron attachment to trifluoroacetic acid (CF 3COOH) is characterized by an intense low energy shape resonance located near 1 eV and a comparatively weaker core excited resonance located near 7 eV. The shape resonance decomposes into the fragment ions CF 3COO -, CF 2COO -, and CF2-. The underlying reactions include simple bond cleavage but also more complex sequences involving multiple bond cleavages, rearrangement in the precursor ion and formation of new molecules (HF, CO 2). The core excited resonance additionally decomposes into F -, CF3- and probably metastable CO2-.

Synthesis and characterization of UO(2)(2+)-ion imprinted polymer for selective extraction of UO(2)(2+).

PubMed

Singh, Dhruv K; Mishra, Shraddha

2009-06-30

Ion-imprinted polymers (IIPs) were prepared for uranyl ion (imprint ion) by formation of binary (salicylaldoxime (SALO) or 4-vinylpyridine (VP)) or ternary (salicylaldoxime and 4-vinylpyridine) complex in 2-methoxy ethanol (porogen) following copolymerization with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking monomer using 2,2'-azobisisobutyronitrile as initiator. Control polymers (CPs) were also prepared under identical experimental conditions without using imprint ion. The above synthesized polymers were characterized by surface area measurement, microanalysis and FT-IR analysis techniques. The imprinted polymer formed with ternary complex of UO(2)(2+)-SALO-VP (1:2:2, IIP3) showed quantitative enrichment of uranyl ion from dilute aqueous solution and hence was chosen for detailed studies. The optimal pH for quantitative enrichment is 3.5-6.5. The adsorbed UO(2)(2+) was completely eluted with 10 mL of 1.0 M HCl. The retention capacity of IIP3 was found to be 0.559 mmol g(-1). Further, the distribution ratio and selectivity coefficients of uranium and other selected inorganic ions were also evaluated. Five replicate determinations of 25 microg L(-1) of uranium(VI) gave a mean absorbance of 0.032 with a relative standard deviation of 2.20%. The detection limit corresponding to three times the standard deviation of the blank was found to be 5 microg L(-1). IIP3 was tested for preconcentration of uranium(VI) from ground, river and sea water samples.

Effect of iron ion on doxycycline photocatalytic and Fenton-based autocatatalytic decomposition.

PubMed

Bolobajev, Juri; Trapido, Marina; Goi, Anna

2016-06-01

Doxycycline plays a key role in Fe(III)-to-Fe(II) redox cycling and therefore in controlling the overall reaction rate of the Fenton-based process (H2O2/Fe(III)). This highlights the autocatalytic profile of doxycycline degradation. Ferric iron reduction in the presence of doxycycline relied on doxycycline-to-Fe(III) complex formation with an ensuing reductive release of Fe(II). The lower ratio of OH-to-contaminant in an initial H2O2/Fe(III) oxidation step than in that of classical Fenton (H2O2/Fe(II)) decreased the doxycycline degradation rate. The quantum yield of doxycycline in direct UV-C photolysis was 3.1 × 10(-3) M E(-1). In spite of doxycycline-Fe(III) complexes could produce the adverse effect on the doxycycline degradation in the UV/Fe(III) system some acceleration of the rate was observed upon irradiation of the Fe(III)-hydroxy complex. Acidic reaction media (pH 3.0) and the molar ratio of DC/Fe(III) = 2/1 favored the complex formation. Doxycycline close degradation rates and complete mineralization achieved for 120 min (Table 1) with both UV/H2O2 and UV/H2O2/Fe(III) indicated the unsubstantial role of the reduction of Fe(III) to Fe(II) in UV/H2O2/Fe(III) system efficacy. Thus, factors such as doxycycline's ability to form complexes with ferric iron and the ability of complexes to participate in a reductive pathway should be considered at a technological level in process optimization, with chemistry based on iron ion catalysis to enhance the doxycycline oxidative pathway. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interaction of metallo- and free base meso-tetrakis(N-methylpyridium-4-yl)porphyrin with a G-quadruplex: effect of the central metal ions.

PubMed

Kim, Yun-Hwa; Lee, Changyun; Kim, Seog K; Jeoung, Sae Chae

2014-06-01

The effects of the central metal ion on complex formation between meso-tetrakis(N-methylpyridium-4-yl)porphyrin (TMPyP) and the thrombin-binding aptamer G-quadruplex, 5'G2T2G2TGTG2T2G2, were examined in this study. The central metal ions were vanadium and zinc. At a [porphyrin]/[G-quadruplex] ratio of less than one, the absorption and CD spectra were unaffected by the mixing ratio for all three porphyrins, suggesting that the binding mode is homogeneous. Relatively small changes in the absorption spectrum when forming the complexes with the G-quadruplex, the positive CD signal, and the large accessibility of the I(-) quencher, suggested that all these porphyrins are not intercalated between the G-quartet. Stabilization of the G-quadruplex by ZnTMPyP was most effective. The effect of VOTMPyP on G-quadruplex stabilization was moderate, whereas TMPyP slightly destabilized G-quadruplex. From this observation, the involvement of the ligation of one G-quartet component to the central metal ion in G-quadruplex stabilization by metallo-TMPyP is suggested. Copyright © 2014 Elsevier B.V. All rights reserved.

Methylene-bis[(aminomethyl)phosphinic acids]: synthesis, acid-base and coordination properties.

PubMed

David, Tomáš; Procházková, Soňa; Havlíčková, Jana; Kotek, Jan; Kubíček, Vojtěch; Hermann, Petr; Lukeš, Ivan

2013-02-21

Three symmetrical methylene-bis[(aminomethyl)phosphinic acids] bearing different substituents on the central carbon atom, (NH(2)CH(2))PO(2)H-C(R(1))(R(2))-PO(2)H(CH(2)NH(2)) where R(1) = OH, R(2) = Me (H(2)L(1)), R(1) = OH, R(2) = Ph (H(2)L(2)) and R(1),R(2) = H (H(2)L(3)), were synthesized. Acid-base and complexing properties of the ligands were studied in solution as well as in the solid state. The ligands show unusually high basicity of the nitrogen atoms (log K(1) = 9.5-10, log K(2) = 8.5-9) if compared with simple (aminomethyl)phosphinic acids and, consequently, high stability constants of the complexes with studied divalent metal ions. The study showed the important role of the hydroxo group attached to the central carbon atom of the geminal bis(phosphinate) moiety. Deprotonation of the hydroxo group yields the alcoholate anion which tends to play the role of a bridging ligand and induces formation of polynuclear complexes. Solid-state structures of complexes [H(2)N=C(NH(2))(2)][Cu(2)(H(-1)L(2))(2)]CO(3)·10H(2)O and Li(2)[Co(4)(H(-1)L(1))(3)(OH)]·17.5H(2)O were determined by X-ray diffraction. The complexes show unexpected geometries forming dinuclear and cubane-like structures, respectively. The dinuclear copper(II) complex contains a bridging μ(2)-alcoholate group with the (-)O-P(=O)-CH(2)-NH(2) fragments of each ligand molecule chelated to the different central ion. In the cubane cobalt(II) complex, one μ(3)-hydroxide and three μ(3)-alcoholate anions are located in the cube vertices and both phosphinate groups of one ligand molecule are chelating the same cobalt(II) ion while each of its amino groups are bound to different neighbouring metal ions. All such three metal ions are bridged by the alcoholate group of a given ligand.

Determination of Tetracycline in Pharmaceutical Preparation by Molecular and Atomic Absorption Spectrophotometry and High Performance Liquid Chromatography via Complex Formation with Au(III) and Hg(II) Ions in Solutions

PubMed Central

Abdulghani, Ahlam Jameel; Jasim, Hadi Hassan; Hassan, Abbas Shebeeb

2013-01-01

UV-visible and atomic spectrophotometry and HPLC techniques were applied for the determination of tetracycline (TC) in pharmaceutical preparations via complexation of the drug with Au(III) and Hg(II) ions in solutions. The mole ratio of TC to metal ions was 1 : 1. Maximum peak absorption at λ 425 and 320 nm for the two ions, respectively, was optimized at heating temperature 75°C for 15 minutes at pH = 4 followed by the extraction with ethyl acetate. The percentage of extraction and stability constants for the two complexes was 95.247, 95.335% and 2.518 × 104, 1.162 × 105 M−1, respectively. HPLC method was applied without extraction process. The analytical data obtained from direct calibration curves of UV-visible absorption, FAAS, and HPLC for Au(III) complexes were recovery (100.78, 104.85, and 101.777%, resp.); detection limits (0.7403, 0.0997, and 2.647 μg/ml, resp.); linearity (5–70, 5–30, and 10–150 μg/ml, resp.), and correlation coefficient (0.9991, 0.9967, and 0.9986, resp.). The analytical data obtained from direct calibration curves for Hg(II) complexes by UV-visible spectrophotometry and HPLC were recovery (100.95 and 102.000%, resp.); detection limits (0.5867 and 2.532 μg/ml, resp.); linearity (5–70 and 10–150 μg/ml, resp.); and correlation coefficients (0.9989 and 0.9997, resp.). PMID:23853607

Calcium ion binding properties of Medicago truncatula calcium/calmodulin-dependent protein kinase.

PubMed

Swainsbury, David J K; Zhou, Liang; Oldroyd, Giles E D; Bornemann, Stephen

2012-09-04

A calcium/calmodulin-dependent protein kinase (CCaMK) is essential in the interpretation of calcium oscillations in plant root cells for the establishment of symbiotic relationships with rhizobia and mycorrhizal fungi. Some of its properties have been studied in detail, but its calcium ion binding properties and subsequent conformational change have not. A biophysical approach was taken with constructs comprising either the visinin-like domain of Medicago truncatula CCaMK, which contains EF-hand motifs, or this domain together with the autoinhibitory domain. The visinin-like domain binds three calcium ions, leading to a conformational change involving the exposure of hydrophobic surfaces and a change in tertiary but not net secondary or quaternary structure. The affinity for calcium ions of visinin-like domain EF-hands 1 and 2 (K(d) = 200 ± 50 nM) was appropriate for the interpretation of calcium oscillations (~125-850 nM), while that of EF-hand 3 (K(d) ≤ 20 nM) implied occupancy at basal calcium ion levels. Calcium dissociation rate constants were determined for the visinin-like domain of CCaMK, M. truncatula calmodulin 1, and the complex between these two proteins (the slowest of which was 0.123 ± 0.002 s(-1)), suggesting the corresponding calcium association rate constants were at or near the diffusion-limited rate. In addition, the dissociation of calmodulin from the protein complex was shown to be on the same time scale as the dissociation of calcium ions. These observations suggest that the formation and dissociation of the complex between calmodulin and CCaMK would substantially mirror calcium oscillations, which typically have a 90 s periodicity.

Force field inside the void in complex plasmas under microgravity conditions

NASA Astrophysics Data System (ADS)

Kretschmer, M.; Khrapak, S. A.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E.; Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Ivanov, A. I.; Turin, M. V.

2005-05-01

Observations of complex plasmas under microgravity conditions onboard the International Space Station performed with the Plasma-Kristall experiment-Nefedov facility are reported. A weak instability of the boundary between the central void (region free of microparticles) and the microparticle cloud is observed at low gas pressures. The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called the “trampoline effect”). The trajectories of injected particles are analyzed providing information on the force field inside the void. The experimental results are compared with theory which assumes that the most important forces inside the void are the electric and the ion drag forces. Good agreement is found clearly indicating that under conditions investigated the void formation is caused by the ion drag force.

Iron catalyzed conversion of NO into nitrosonium (NO+) and nitroxyl (HNO/NO-) species.

PubMed

Stojanović, Srdjan; Stanić, Dragana; Nikolić, Milan; Spasić, Mihailo; Niketić, Vesna

2004-11-01

The conversion of NO into its congeners, nitrosonium (NO+) and nitroxyl (HNO/NO-) species, has important consequences in NO metabolism. Dinitrosyl iron complex (DNIC) combined with thiol ligands was shown to catalyze the conversion of NO into NO+, resulting in the synthesis of S-nitrosothiols (RSNO) both in vitro and in vivo. The formation mechanism of DNIC was proposed to involve the intermediate release of nitroxyl. Since the detection of hydroxylamine (as the product of a rapid reaction of HNO/NO- with thiols) is taken as the evidence for nitroxyl generation, we examined the formation of hydroxylamine, RSNO, and nitrite (the product of a rapid reaction of NO+ with water) in neutral solutions containing iron ions and thiols exposed to NO under anaerobic conditions. Hydroxylamine was detected in NO treated solutions of iron ions in the presence of cysteine, but not glutathione (GSH). The addition of urate, a major "free" iron-binding agent in humans, to solutions of GSH and iron ions, and the subsequent treatment of these solutions with NO increased the synthesis of GSNO and resulted in the formation of hydroxylamine. This caused a loss of urate and yielded a novel nitrosative/nitration product. GSH attenuated the urate decomposition to such a degree that it could be reflected as the function of GSH:urate. Results described here contribute to the understanding of the role of iron ions in catalyzing the conversion of NO into HNO/NO- and point to the role of uric acid not previously described.

Kinetics and its accompanying thermodynamics studies on simultaneous complexation of heterobimetallic neodymium (III) with zinc (II) and L-tryptophan in aquated DMF using 4f-4f absorption spectra.

PubMed

Huidrom, Bimola; Singh, N Rajmuhon

2014-01-24

The 4f-4f absorption spectra of the simultaneous heterobimetallic complexation of trivalent neodymium ion with l-tryptophan and divalent zinc ion in aquated DMF (50%, v/v) at pH 6.0 was recorded at the time interval of 1h. From the observed absorption spectra, the values of intensity parameters such as oscillator strength (P) and Judd-Ofelt intensity (Tλ) parameters, kinetics and thermodynamics parameters were evaluated. The rate constant increases with an increase in the temperature along with the oscillator strengths and Judd-Ofelt intensity parameters. The positive values of the change in the standard enthalpy (ΔH°) and entropy (ΔS°) indicate that the complexation is endothermic. The negative values of the change in the standard free energy (ΔG°) in the range from 293.15 K to 308.15 K, indicate that the reaction occurs spontaneously and hence the formation of heterobimetallic complex in the solution is favored kinetically and thermodynamically. Copyright © 2013 Elsevier B.V. All rights reserved.

Kinetics and its accompanying thermodynamics studies on simultaneous complexation of heterobimetallic neodymium (III) with zinc (II) and L-tryptophan in aquated DMF using 4f-4f absorption spectra

NASA Astrophysics Data System (ADS)

Huidrom, Bimola; Rajmuhon Singh, N.

2014-01-01

The 4f-4f absorption spectra of the simultaneous heterobimetallic complexation of trivalent neodymium ion with L-tryptophan and divalent zinc ion in aquated DMF (50%, v/v) at pH 6.0 was recorded at the time interval of 1 h. From the observed absorption spectra, the values of intensity parameters such as oscillator strength (P) and Judd-Ofelt intensity (Tλ) parameters, kinetics and thermodynamics parameters were evaluated. The rate constant increases with an increase in the temperature along with the oscillator strengths and Judd-Ofelt intensity parameters. The positive values of the change in the standard enthalpy (ΔH°) and entropy (ΔS°) indicate that the complexation is endothermic. The negative values of the change in the standard free energy (ΔG°) in the range from 293.15 K to 308.15 K, indicate that the reaction occurs spontaneously and hence the formation of heterobimetallic complex in the solution is favored kinetically and thermodynamically.

Development of an ELISA assay for screening inhibitors against divalent metal ion dependent alphavirus capping enzyme.

PubMed

Kaur, Ramanjit; Mudgal, Rajat; Narwal, Manju; Tomar, Shailly

2018-06-26

Alphavirus non-structural protein, nsP1 has a distinct molecular mechanism of capping the viral RNAs than the conventional capping mechanism of host. Thus, alphavirus capping enzyme nsP1 is a potential drug target. nsP1 catalyzes the methylation of guanosine triphosphate (GTP) by transferring the methyl group from S-adenosylmethionine (SAM) to a GTP molecule at its N7 position with the help of nsP1 methyltransferase (MTase) followed by guanylylation (GT) reaction which involves the formation of m 7 GMP-nsP1 covalent complex by nsP1 guanylyltransferase (GTase). In subsequent reactions, m 7 GMP moiety is added to the 5' end of the viral ppRNA by nsP1 GTase resulting in the formation of cap0 structure. In the present study, chikungunya virus (CHIKV) nsP1 MTase and GT reactions were confirmed by an indirect non-radioactive colorimetric assay and western blot assay using an antibody specific for the m 7 G cap, respectively. The purified recombinant CHIKV nsP1 has been used for the development of a rapid and sensitive non-radioactive enzyme linked immunosorbent assay (ELISA) to identify the inhibitors of CHIKV nsP1. The MTase reaction is followed by GT reaction and resulted in m 7 GMP-nsP1 covalent complex formation. The developed ELISA nsP1 assay measures this m 7 GMP-nsP1 complex by utilizing anti-m 7 G cap monoclonal antibody. The mutation of a conserved residue Asp63 to Ala revealed its role in nsP1 enzyme reaction. Inductively coupled plasma mass spectroscopy (ICP-MS) was used to determine the presence of magnesium ions (Mg 2+ ) in the purified nsP1 protein. The divalent metal ion selectivity and investigation show preference for Mg 2+ ion by CHIKV nsP1. Additionally, using the developed ELISA nsP1 assay, the inhibitory effects of sinefungin, aurintricarboxylic acid (ATA) and ribavirin were determined and the IC 50 values were estimated to be 2.69 µM, 5.72 µM and 1.18 mM, respectively. Copyright © 2018. Published by Elsevier B.V.

Effects of low-energy electron irradiation on formation of nitrogen–vacancy centers in single-crystal diamond

DOE PAGES

Schwartz, J.; Aloni, S.; Ogletree, D. F.; ...

2012-04-20

Exposure to beams of low-energy electrons (2-30 keV) in a scanning electron microscope locally induces formation of NV-centers without thermal annealing in diamonds that have been implanted with nitrogen ions. In this study, we find that non-thermal, electron-beam-induced NV-formation is about four times less efficient than thermal annealing. But NV-center formation in a consecutive thermal annealing step (800°C) following exposure to low-energy electrons increases by a factor of up to 1.8 compared to thermal annealing alone. Finally, these observations point to reconstruction of nitrogen-vacancy complexes induced by electronic excitations from low-energy electrons as an NV-center formation mechanism and identify localmore » electronic excitations as a means for spatially controlled room-temperature NV-center formation.« less

Transient increase in the levels of gamma-tubulin complex in reorientation of cortical microtubules by gravity in azuki bean epicotyls

NASA Astrophysics Data System (ADS)

Soga, Kouichi; Kotake, Toshihisa; Wakabayashi, Kazuyuki; Kamisaka, Seiichiro; Hoson, Takayuki

Azuki bean (Vigna angularis Ohwi et Ohashi) seedlings were exposed to centrifugal hypergravity, and the changes in the orientation of cortical microtubules and the expression of genes cording γ-tubulin complex (VaTUBG and VaSpc98p) were examined. By 300 g treatment, the percentage of cells with transverse microtubules was decreased, while that with longitudinal microtubules was increased in epicotyls. Hypergravity increased the expression of VaTUBG and VaSpc98p transiently. Also, the expression of both genes was increased transiently by removal of hypergravity stimulus. Lanthanum and gadolinium ions, potential blockers of mechanosensitive calcium ion-permeable channels (mechanoreceptors), nullified reorientation of microtubules as well as up-regulation of expression of VaTUBG and VaSpc98p by hypergravity. These results suggest that mechanoreceptors on the plasma membrane may perceive the gravity signal, which leads to reorientation of cortical microtubules by transiently stimulating the formation of γ-tubulin complex.

Synthesis, spectral, thermal and structural characterization of two complexes containing [N-(2-hydroxyethyl)-ethylenediamine] with carboxylate

NASA Astrophysics Data System (ADS)

Aycan, Tuǧba; Paşaoǧlu, Hümeyra

2018-02-01

Compounds based on the [Zn(hydet-en)2].(tpht).(H2O) (1) (tpht=dianion of terephthalic acid, hydet-en=N-(2-hydroxyethyl)ethylenediamine) has been synthesized which is characterized by single crystal X-ray determination, IR and thermal analysis. In 1, the Zinc(II) ion is six-coordinated that sandwiched by two hydet-en ligands which lies each hydeten ligand adopts a tripodal conformation and acts as tridentate ligand, carboxylate is uncoordinated. The coordination monomer is connected by C(13) chains and linear chains are connected by O-H...O H-bonds formed by DA:AD type 4 organization of aqua ligands and tpa2- ions resulting in R44(12 ) synthons to 3D structure. The FT-IR investigation of the complex were performed within the mid-IR region, mainly focusing on the characteristic vibrations of its free state and ligand behaviour in the case of complex formation. Thermal behaviours of 1 were followed using TG, DTA and DTG techniques.

Mononuclear Ni(II) complexes of Schiff base ligands formed from unsymmetrical tripodal amines of differing arm lengths: Spectral, X-ray crystal structural, antimicrobial and DNA cleavage activity

NASA Astrophysics Data System (ADS)

Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Dhers, Sébastien; Küp, Fatma Öztürk; Güllü, Mithat; Ng, Seikweng

2017-11-01

The synthesis of two unsymmetrical N-capped tripodal amines, 2-((4-aminobutyl)(pyridin-2-ylmethyl)amino)ethanol (3) and 3-((2-aminoethyl)(pyridin-2-ylmethyl)amino)propan-1-ol (4) is reported. They feature a longer, 3-hydroxypropyl or butylamino arm than that in the analogues previously employed. All four tripodal amines, 1-4, are equipped with a 2-methylpyridyl-arm, and either an ethylamino-arm (1 and 4), propylamino-arm (2) or butylamino-arm (3). The amines, 3 and 4, have been employed in one pot condensation reactions with salicylaldehyde and its derivatives in the presence of Ni(II) metal ion. A series of new mononuclear complexes, [NiIILaldi](ClO4) or [NiIILaldi(solvent)](ClO4) with different geometry, of Schiff base ligands were generated. X-ray crystal structure determinations of [NiIILOMe3(H2O)](ClO4)·2H2O and [NiIILOMe4](ClO4) revealed them to be mononuclear. The Ni(II) ion in [NiIILOMe4](ClO4) complex is in a distorted square-planar environment whilst this ion is in distorted octahedral environment in [NiIILOMe3(H2O)](ClO4)·2H2O complex despite the longer arm length of L3. While, in related systems in our previous work, they had led to dimeric complexes. These results clearly showed that the variation of the arm lengths of the ligands and metal ions has a remarkable impact on the formation and structure of the complexes. The cleavage of DNA by all synthesised complexes was examined using gel electrophoresis experiments. Also, the antibacterial effects of components were determined against the three Gram-positive bacteria, and against the three Gram-negative bacteria and against the three yeast Candida albicans ATCC 10231, Candida krusei ATCC 1424 and Candida tropicalis ATCC 13803.

Molecular Designs for Controlling the Local Environments around Metal Ions

PubMed Central

Cook, Sarah A.; Borovik, A.S.

2015-01-01

CONSPECTUS The functions of metal complexes are directly linked to the local environment in which they are housed; modifications to the local environment (or secondary coordination sphere) are known to produce changes in key properties of the metal centers that can affect reactivity. Non-covalent interactions are the most common and influential forces that regulate the properties of secondary coordination spheres, which leads to complexities in structure that are often difficult to achieve in synthetic systems. Using key architectural features from the active sites of metalloproteins as inspiration, we have developed molecular systems that enforce intramolecular hydrogen bonds (H-bonds) around a metal center via incorporation of H-bond donors and acceptors into rigid ligand scaffolds. We have utilized these molecular species to probe mechanistic aspects of biological dioxygen activation and water oxidation. This Account describes the stabilization and characterization of unusual M–oxo and heterobimetallic complexes. These types of species have been implicated in a range of oxidative processes in biology but are often difficult to study because of their inherent reactivity. Our H-bonding ligand systems allowed us to prepare an FeIII–oxo species directly from the activation of O2 that was subsequently oxidized to form a monomeric FeIV–oxo species with an S = 2 spin state, similar to those species proposed as key intermediates in non-heme monooxygenases. We also demonstrated that a single MnIII–oxo center that was prepared from water could be converted to a high spin MnV–oxo species via stepwise oxidation—a process that mimics the oxidative charging of the oxygen-evolving complex (OEC) of photosystem II. Current mechanisms for photosynthetic O–O bond formation invoke a MnIV–oxyl species rather than the isoelectronic MnV–oxo system as the key oxidant based on computational studies. However, there is no experimental information to support the existence of an Mn–oxyl radical. We therefore probed the amount of spin density on the oxido ligand of our complexes using EPR spectroscopy in conjunction with oxygen-17 labeling. Our findings showed that there is a significant amount of spin on the oxido ligand, yet the M–oxo bonds are best described as highly covalent and there is no indication that an oxyl radical is formed. These results offer the intriguing possibility that high spin M–oxo complexes are involved in O–O bond formation in biology. Ligand redesign to incorporate H-bond accepting units (sulfonamido groups) simultaneously provided a metal ion binding pocket, adjacent H-bond acceptors, and an auxiliary binding site for a second metal ion. These properties allowed us to isolate a series of heterobimetallic complexes of FeIII and MnIII in which a group II metal ion was coordinated within the secondary coordination sphere. Examination of the influence of the second metal ion on the electron transfer properties of the primary metal center revealed unexpected similarities between CaII and SrII ions—a result with relevance to the OEC. In addition, the presence of a second metal ion was found to prevent intramolecular oxidation of the ligand with an O-atom transfer reagent. PMID:26181849

Atorvastatin affects negatively respiratory function of isolated endothelial mitochondria.

PubMed

Broniarek, Izabela; Jarmuszkiewicz, Wieslawa

2018-01-01

The purpose of this research was to elucidate the direct effects of two popular blood cholesterol-lowering drugs used to treat cardiovascular diseases, atorvastatin and pravastatin, on respiratory function, membrane potential, and reactive oxygen species formation in mitochondria isolated from human umbilical vein endothelial cells (EA.hy926 cell line). Hydrophilic pravastatin did not significantly affect endothelial mitochondria function. In contrast, hydrophobic calcium-containing atorvastatin induced a loss of outer mitochondrial membrane integrity, an increase in hydrogen peroxide formation, and reductions in maximal (phosphorylating or uncoupled) respiratory rate, membrane potential and oxidative phosphorylation efficiency. The atorvastatin-induced changes indicate an impairment of mitochondrial function at the level of ATP synthesis and at the level of the respiratory chain, likely at complex I and complex III. The atorvastatin action on endothelial mitochondria was highly dependent on calcium ions and led to a disturbance in mitochondrial calcium homeostasis. Uptake of calcium ions included in atorvastatin molecule induced mitochondrial uncoupling that enhanced the inhibition of the mitochondrial respiratory chain by atorvastatin. Our results indicate that hydrophobic calcium-containing atorvastatin, widely used as anti-atherosclerotic agent, has a direct negative action on isolated endothelial mitochondria. Copyright © 2017. Published by Elsevier Inc.

Curcumin derivatives as metal-chelating agents with potential multifunctional activity for pharmaceutical applications.

PubMed

Ferrari, Erika; Benassi, Rois; Sacchi, Stefania; Pignedoli, Francesca; Asti, Mattia; Saladini, Monica

2014-10-01

Curcuminoids represent new perspectives for the development of novel therapeutics for Alzheimer's disease (AD), one probable mechanism of action is related to their metal complexing ability. In this work we examined the metal complexing ability of substituted curcuminoids to propose new chelating molecules with biological properties comparable with curcumin but with improved stability as new potential AD therapeutic agents. The K2T derivatives originate from the insertion of a -CH2COOC(CH3)3 group on the central atom of the diketonic moiety of curcumin. They retain the diketo-ketoenol tautomerism which is solvent dependent. In aqueous solution the prevalent form is the diketo one but the addition of metal ion (Ga(3+), Cu(2+)) causes the dissociation of the enolic proton creating chelate complexes and shifting the tautomeric equilibrium towards the keto-enol form. The formation of metal complexes is followed by both NMR and UV-vis spectroscopy. The density functional theory (DFT) calculations on K2T21 complexes with Ga(3+) and Cu(2+) are performed and compared with those on curcumin complexes. [Ga(K2T21)2(H2O)2](+) was found more stable than curcumin one. Good agreement is detected between calculated and experimental (1)H and (13)C NMR data. The calculated OH bond dissociation energy (BDE) and the OH proton dissociation enthalpy (PDE), allowed to predict the radical scavenging ability of the metal ion complexed with K2T21, while the calculated electronic affinity (EA) and ionization potential (IP) represent yardsticks of antioxidant properties. Eventually theoretical calculations suggest that the proton-transfer-associated superoxide-scavenging activity is enhanced after binding metal ions, and that Ga(3+) complexes display possible superoxide dismutase (SOD)-like activity. Copyright © 2014 Elsevier Inc. All rights reserved.

Self-organized surface ripple pattern formation by ion implantation

NASA Astrophysics Data System (ADS)

Hofsäss, Hans; Zhang, Kun; Bobes, Omar

2016-10-01

Ion induced ripple pattern formation on solid surfaces has been extensively studied in the past and the theories describing curvature dependent ion erosion as well as redistribution of recoil atoms have been very successful in explaining many features of the pattern formation. Since most experimental studies use noble gas ion irradiation, the incorporation of the ions into the films is usually neglected. In this work we show that the incorporation or implantation of non-volatile ions also leads to a curvature dependent term in the equation of motion of a surface height profile. The implantation of ions can be interpreted as a negative sputter yield; and therefore, the effect of ion implantation is opposite to the one of ion erosion. For angles up to about 50°, implantation of ions stabilizes the surface, whereas above 50°, ion implantation contributes to the destabilization of the surface. We present simulations of the curvature coefficients using the crater function formalism and we compare the simulation results to the experimental data on the ion induced pattern formation using non-volatile ions. We present several model cases, where the incorporation of ions is a crucial requirement for the pattern formation.

Adenosine/guanosine-3',5'-bis-phosphates as biocompatible and selective Zn2+-ion chelators. Characterization and comparison with adenosine/guanosine-5'-di-phosphate.

PubMed

Sayer, Alon Haim; Blum, Eliav; Major, Dan Thomas; Vardi-Kilshtain, Alexandra; Levi Hevroni, Bosmat; Fischer, Bilha

2015-04-28

Although involved in various physiological functions, nucleoside bis-phosphate analogues and their metal-ion complexes have been scarcely studied. Hence, here, we explored the solution conformation of 2′-deoxyadenosine- and 2′-deoxyguanosine-3′,5′-bisphosphates, 3 and 4, d(pNp), as well as their Zn(2+)/Mg(2+) binding sites and binding-modes (i.e. inner- vs. outer-sphere coordination), acidity constants, stability constants of their Zn(2+)/Mg(2+) complexes, and their species distribution. Analogues 3 and 4, in solution, adopted a predominant Southern ribose conformer (ca. 84%), gg conformation around C4'-C5' and C5'-O5' bonds, and glycosidic angle in the anti-region (213-270°). (1)H- and (31)P-NMR experiments indicated that Zn(2+)/Mg(2+) ions coordinated to P5' and P3' groups of 3 and 4 but not to N7 nitrogen atom. Analogues 3 and 4 formed ca. 100-fold more stable complexes with Zn(2+)vs. Mg(2+)-ions. Complexes of 3 and 4 with Mg(2+) at physiological pH were formed in minute amounts (11% and 8%, respectively) vs. Zn(2+) complexes (46% and 44%). Stability constants of Zn(2+)/Mg(2+) complexes of analogues 3 and 4 (log KML(M) = 4.65-4.75/2.63-2.79, respectively) were similar to those of the corresponding complexes of ADP and GDP (log KML(M) = 4.72-5.10/2.95-3.16, respectively). Based on the above findings, we hypothesized that the unexpectedly low log K values of Zn(2+)-d(pNp) as compared to Zn(2+)-NDP complexes, are possibly due to formation of outer-sphere coordination in the Zn(2+)-d(pNp) complex vs. inner-sphere in the NDP-Zn(2+) complex, in addition to loss of chelation to N7 nitrogen atom in Zn(2+)-d(pNp). Indeed, explicit solvent molecular dynamics simulations of 1 and 3 for 100 ns supported this hypothesis.

Host-guest complexes between cucurbit[n]urils and acetanilides having aminopropyl units.

PubMed

Buaki-Sogo, Mireia; Montes-Navajas, Pedro; Alvaro, Mercedes; Garcia, Hermenegildo

2013-06-01

2-(Propylamino)acetamide of aniline (1a), and bis-2-(propylamino)acetamide of ortho- (1b) and para-(1c) phenylenediamine form host-guest complexes with CB[6], CB[7] and CB[8] as evidenced by the variations in the (1)H NMR spectroscopy chemical shifts and observation in MALDI-TOF-MS and ESI-MS of ions at the corresponding mass. Binding constants for the 1:1 complexes were estimated from fluorescence titrations and were in the range 10(5)-10(6)M(-1). Models based on molecular mechanics for these supramolecular complexes are provided. In spite of the different geometries arising from the ortho- or para-substitution, phenylenediamides form complexes of similar strength in which the hydrophobic alkyl chains are accommodated inside the host cavity. Formation of these host-guest complexes in the solid state was also achieved by modifying an aminopropyl silica with chloroacetanilides and preparing three silica having analogues of compounds 1a-c anchored to the solid particles. Titrations showed, however, that these solids can adsorb a large percentage of CBs by unselective interactions that are not related to the formation of inclusion complexes. Copyright © 2013 Elsevier Inc. All rights reserved.

Chemometrics-assisted spectrophotometric method for simultaneous determination of Pb²⁺ and Cu²⁺ ions in different foodstuffs, soil and water samples using 2-benzylspiro [isoindoline-1,5'-oxazolidine]-2',3,4'-trione using continuous wavelet transformation and partial least squares - calculation of pKf of complexes with rank annihilation factor analysis.

PubMed

Abbasi Tarighat, Maryam; Nabavi, Masoume; Mohammadizadeh, Mohammad Reza

2015-06-15

A new multi-component analysis method based on zero-crossing point-continuous wavelet transformation (CWT) was developed for simultaneous spectrophotometric determination of Cu(2+) and Pb(2+) ions based on the complex formation with 2-benzyl espiro[isoindoline-1,5 oxasolidine]-2,3,4 trione (BSIIOT). The absorption spectra were evaluated with respect to synthetic ligand concentration, time of complexation and pH. Therefore according the absorbance values, 0.015 mmol L(-1) BSIIOT, 10 min after mixing and pH 8.0 were used as optimum values. The complex formation between BSIIOT ligand and the cations Cu(2+) and Pb(2+) by application of rank annihilation factor analysis (RAFA) were investigated. Daubechies-4 (db4), discrete Meyer (dmey), Morlet (morl) and Symlet-8 (sym8) continuous wavelet transforms for signal treatments were found to be suitable among the wavelet families. The applicability of new synthetic ligand and selected mother wavelets were used for the simultaneous determination of strongly overlapped spectra of species without using any pre-chemical treatment. Therefore, CWT signals together with zero crossing technique were directly applied to the overlapping absorption spectra of Cu(2+) and Pb(2+). The calibration graphs for estimation of Pb(2+) and Cu (2+)were obtained by measuring the CWT amplitudes at zero crossing points for Cu(2+) and Pb(2+) at the wavelet domain, respectively. The proposed method was validated by simultaneous determination of Cu(2+) and Pb(2+) ions in red beans, walnut, rice, tea and soil samples. The obtained results of samples with proposed method have been compared with those predicted by partial least squares (PLS) and flame atomic absorption spectrophotometry (FAAS). Copyright © 2015 Elsevier B.V. All rights reserved.

Identification of ion-pair structures in solution by vibrational stark effects

DOE PAGES

Hack, John; Mani, Tomoyasu; Grills, David C.; ...

2016-01-25

Here, ion pairing is a fundamental consideration in many areas of chemistry and has implications in a wide range of sciences and technologies that include batteries and organic photovoltaics. Ions in solution are known to inhabit multiple possible states, including free ions (FI), contact ion pairs (CIP), and solvent-separated ion pairs (SSIP). However, in solutions of organic radicals and nonmetal electrolytes, it is often difficult to distinguish between these states. In the first part of this work, we report evidence for the formation of SSIPs in low-polarity solvents and distinct measurements of CIP, SSIP, and FI, by using the ν(C≡N)more » infrared (IR) band of a nitrile-substituted fluorene radical anion. Use of time-resolved IR detection following pulse radiolysis allowed us to unambiguously assign the peak of the FI. In the presence of nonmetal electrolytes, two distinct red-shifted peaks were observed and assigned to the CIP and SSIP. The assignments are interpreted in the framework of the vibrational Stark effect (VSE) and are supported by (1) the solvent dependence of ion-pair populations, (2) the observation of a cryptand-separated sodium ion pair that mimics the formation of SSIPs, and (3) electronic structure calculations. In the second part of this work, we show that a blue-shift of the ν(C≡N) IR band due to the VSE can be induced in a nitrile-substituted fluorene radical anion by covalently tethering it to a metal-chelating ligand that forms an intramolecular ion pair upon reduction and complexation with sodium ion. This adds support to the conclusion that the shift in IR absorptions by ion pairing originates from the VSE. These results combined show that we can identify ion-pair structures by using the VSE, including the existence of SSIPs in a low-polarity solvent.« less

Identification of ion-pair structures in solution by vibrational stark effects

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

Hack, John; Mani, Tomoyasu; Grills, David C.

Here, ion pairing is a fundamental consideration in many areas of chemistry and has implications in a wide range of sciences and technologies that include batteries and organic photovoltaics. Ions in solution are known to inhabit multiple possible states, including free ions (FI), contact ion pairs (CIP), and solvent-separated ion pairs (SSIP). However, in solutions of organic radicals and nonmetal electrolytes, it is often difficult to distinguish between these states. In the first part of this work, we report evidence for the formation of SSIPs in low-polarity solvents and distinct measurements of CIP, SSIP, and FI, by using the ν(C≡N)more » infrared (IR) band of a nitrile-substituted fluorene radical anion. Use of time-resolved IR detection following pulse radiolysis allowed us to unambiguously assign the peak of the FI. In the presence of nonmetal electrolytes, two distinct red-shifted peaks were observed and assigned to the CIP and SSIP. The assignments are interpreted in the framework of the vibrational Stark effect (VSE) and are supported by (1) the solvent dependence of ion-pair populations, (2) the observation of a cryptand-separated sodium ion pair that mimics the formation of SSIPs, and (3) electronic structure calculations. In the second part of this work, we show that a blue-shift of the ν(C≡N) IR band due to the VSE can be induced in a nitrile-substituted fluorene radical anion by covalently tethering it to a metal-chelating ligand that forms an intramolecular ion pair upon reduction and complexation with sodium ion. This adds support to the conclusion that the shift in IR absorptions by ion pairing originates from the VSE. These results combined show that we can identify ion-pair structures by using the VSE, including the existence of SSIPs in a low-polarity solvent.« less

Nanomechanical and thermophoretic analyses of the nucleotide-dependent interactions between the AAA + subunits of magnesium chelatase

DOE PAGES

Adams, Nathan B. P.; Vasilev, Cvetelin; Brindley, Amanda A.; ...

2016-04-30

In chlorophyll biosynthesis, the magnesium chelatase enzyme complex catalyzes the insertion of a Mg 2+ ion into protoporphyrin IX. Prior to this event, two of the three subunits, the AAA + proteins ChlI and ChlD, form a ChlID–MgATP complex. We used microscale thermophoresis to directly determine dissociation constants for the I-D subunits from Synechocystis, and to show that the formation of a ChlID–MgADP complex, mediated by the arginine finger and the sensor II domain on ChlD, is necessary for the assembly of the catalytically active ChlHID–MgATP complex. The N-terminal AAA + domain of ChlD is essential for complex formation, butmore » some stability is preserved in the absence of the C-terminal integrin domain of ChlD, particularly if the intervening polyproline linker region is retained. Single molecule force spectroscopy (SMFS) was used to determine the factors that stabilize formation of the ChlID–MgADP complex at the single molecule level; ChlD was attached to an atomic force microscope (AFM) probe in two different orientations, and the ChlI subunits were tethered to a silica surface; the probability of subunits interacting more than doubled in the presence of MgADP, and we show that the N-terminal AAA + domain of ChlD mediates this process, in agreement with the microscale thermophoresis data. Analysis of the unbinding data revealed a most probable interaction force of around 109 pN for formation of single ChlID–MgADP complexes. Finally, these experiments provide a quantitative basis for understanding the assembly and function of the Mg chelatase complex.« less

Evaluation of the stability of uranyl peroxo-carbonato complex ions in carbonate media at different temperatures.

PubMed

Kim, Kwang-Wook; Lee, Keun-Young; Chung, Dong-Yong; Lee, Eil-Hee; Moon, Jei-Kwon; Shin, Dong-Woo

2012-09-30

This work studied the stability of peroxide in uranyl peroxo carbonato complex ions in a carbonate solution with hydrogen peroxide using absorption and Raman spectroscopies, and evaluated the temperature dependence of the decomposition characteristics of uranyl peroxo carbonato complex ions in the solution. The uranyl peroxo carbonato complex ions self-decomposed more rapidly into uranyl tris-carbonato complex ions in higher temperature carbonate solutions. The concentration of peroxide in the solution without free hydrogen peroxide represents the concentration of uranyl peroxo carbonato complex ions in a mixture of uranyl peroxo carbonato complex and uranyl tris-carbonato complex ions. The self-decomposition of the uranyl peroxo carbonato complex ions was a first order reaction, and its activation energy was evaluated to be 7.144×10(3) J mol(-1). The precipitation of sodium uranium oxide hydroxide occurred when the amount of uranyl tris-carbonato complex ions generated from the decomposition of the uranyl peroxo carbonato complex ions exceeded the solubility of uranyl tris-carbonato ions in the solution at the solution temperature. Copyright © 2012 Elsevier B.V. All rights reserved.

Formation and Recondensation of Complex Organic Molecules During Protostellar Luminosity Outbursts

NASA Technical Reports Server (NTRS)

Taquet, Vianney; Wirstrom, Eva S.; Charnley, Steven B.

2016-01-01

During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion-molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude.

Formation and Recondensation of Complex Organic Molecules during Protostellar Luminosity Outbursts

NASA Astrophysics Data System (ADS)

Taquet, Vianney; Wirström, Eva S.; Charnley, Steven B.

2016-04-01

During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion-molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude.

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations.

PubMed

Hassan, Wafaa S; El-Henawee, Magda M; Gouda, Ayman A

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at lambda(max) 470nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70microgmL(-1) for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

The adsorption behavior of U(VI) on granite.

PubMed

Fan, Q H; Hao, L M; Wang, C L; Zheng, Z; Liu, C L; Wu, W S

2014-03-01

The effects of pH, counter ions and temperature on the adsorption of U(VI) on Beishan granite (BsG) were investigated in the presence and absence of fulvic acid (FA) and humic acid (HA). The adsorption edge of U(VI) on BsG suggested that U(VI) adsorption was mainly controlled by ion exchange and outer-sphere complexation at low pH, whereas inner-sphere complex was the dominant adsorption species in the pH range of 4.0-9.0. Above pH 9.0, Na2U2O7 might play an important role in the rise of U(VI) adsorption again. Counter ions such as Cl(-), SO4(2-) and PO4(3-) can provoke U(VI) adsorption on BsG to some extent, which was directly correlated to the complexing ability of U(VI)-ligand. More noticeably, the large enhancement of U(VI) adsorption in the presence of phosphate can be attributed to the ternary complex formation (BsG-PO4-UO2), precipitation ((UO2)3(PO4)2(s)) and secondary phase (Na-autunite). Both FA and HA can slightly increase U(VI) adsorption at low pH, whereas they strongly inhibited U(VI) adsorption at high pH range. Artificial synthesized granite (AsG) prepared in the laboratory is impossible to use as an analogue of natural granite because of the large difference in the adsorption and surface properties.

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations

NASA Astrophysics Data System (ADS)

Hassan, Wafaa S.; El-Henawee, Magda M.; Gouda, Ayman A.

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at λmax 470 nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426 nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70 μg mL -1 for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

Preparation of metal/zeolite catalysts: Formation of palladium aquocomplexes in the precursor of palladium-mordenite catalysts

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

Not Available

1993-09-01

Previous research has revealed that the catalytic performance of metal/zeolite catalysts can be significantly modified by exposing the catalyst precursor to H[sub 2]O vapor during the period after calcination, but before reduction. For bimetallic PdCo/NaY catalysts used for CO hydrogenation, the selectivity was changed from predominant production of oxygenates to predominant production of higher hydrocarbons. For Pt/H-mordenite catalysts, this water treatment has been reported to improve the alkane isomerization activity. Although it is certain that Lewis sites are transformed to Bronsted sites by reaction with H[sub 2]O, the activity of the catalyst is affected most when the water is addedmore » after calcination, when the noble metal is present as ligand-free ions. This observation led to the hypothesis that complexation of transition metal ions with water might be instrumental for the observed effects. In zeolites containing cages, such as Y, the formation of metal-ligand complex ions appears to incite their migration from small to large cages. In cageless zeolites such as mordenite, however, it is not clear, a priori, whether hydration of transition metal ions will increase or decrease their reducibility and whether it will ultimately result in higher or lower metal dispersion. The authors have therefore undertaken research to clarify these issues. Palladium supported in H-mordenite (Pd/HMor) or Na-mordenite (Pd/Na-Mor) has been tested using methylcyclopentane as a probe reaction; temperature-programmed reduction (TPR), desorption (TPD), and extended X-ray absorption fine structure (EXAFS) spectroscopy have been used to characterize the effects of water treatment on the samples.« less

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

Hong, Seungwoo; Lu, Xiaoyan; Lee, Yong -Min

Here, a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [Fe V(NTs)(TAML)] – (1), was oxidized by one-electron oxidants, affording formation of an iron(V)-imido TAML cation radical species, [Fe V(NTs)(TAML +•)] (2); 2 is a diamagnetic (S = 0) complex, resulting from the antiferromagnetic coupling of the low-spin iron(V) ion (S = 1/2) with the one-electron oxidized ligand (TAML +•). 2 is a competent oxidant in C–H bond functionalization and nitrene transfer reaction, showing that the reactivity of 2 is greater than that of 1.

Method of separating thorium from plutonium

DOEpatents

Clifton, David G.; Blum, Thomas W.

1984-01-01

A method of chemically separating plutonium from thorium. Plutonium and thorium to be separated are dissolved in an aqueous feed solution, preferably as the nitrate salts. The feed solution is acidified and sodium nitrite is added to the solution to adjust the valence of the plutonium to the +4 state. A chloride salt, preferably sodium chloride, is then added to the solution to induce formation of an anionic plutonium chloride complex. The anionic plutonium chloride complex and the thorium in solution are then separated by ion exchange on a strong base anion exchange column.

Method of separating thorium from plutonium

DOEpatents

Clifton, D.G.; Blum, T.W.

A method of chemically separating plutonium from thorium is claimed. Plutonium and thorium to be separated are dissolved in an aqueous feed solution, preferably as the nitrate salts. The feed solution is acidified and sodium nitrite is added to the solution to adjust the valence of the plutonium to the +4 state. A chloride salt, preferably sodium chloride, is then added to the solution to induce formation of an anionic plutonium chloride complex. The anionic plutonium chloride complex and the thorium in solution are then separated by ion exchange on a strong base anion exchange column.

Method of separating thorium from plutonium

DOEpatents

Clifton, D.G.; Blum, T.W.

1984-07-10

A method is described for chemically separating plutonium from thorium. Plutonium and thorium to be separated are dissolved in an aqueous feed solution, preferably as the nitrate salts. The feed solution is acidified and sodium nitrite is added to the solution to adjust the valence of the plutonium to the +4 state. A chloride salt, preferably sodium chloride, is then added to the solution to induce formation of an anionic plutonium chloride complex. The anionic plutonium chloride complex and the thorium in solution are then separated by ion exchange on a strong base anion exchange column.

Synthesis, characterization and biological assay of Salicylaldehyde Schiff base Cu(II) complexes and their precursors

NASA Astrophysics Data System (ADS)

Iftikhar, Bushra; Javed, Kanwal; Khan, Muhammad Saif Ullah; Akhter, Zareen; Mirza, Bushra; Mckee, Vickie

2018-03-01

Three new Schiff base ligands were synthesized by the reaction of Salicylaldehyde with semi-aromatic diamines, prepared by the reduction of corresponding dinitro-compounds, and were further used for the formation of complexes with Cu(II) metal ion. The structural features of the synthesized compounds were confirmed by their physical properties and infrared, electronic and NMR spectroscopic techniques. The studies revealed that the synthesized Schiff bases existed as tetradentate ligands and bonded to the metal ion through the phenolic oxygen and azomethine nitrogen. One of the dinitro precursors was also analyzed by single crystal X-ray crystallography, which showed that it crystallizes in monoclinic system with space group P2/n. The thermal behavior of the Cu(II) complexes was determined by thermogravimetric analysis (TGA) and kinetic parameters were evaluated from the data. Schiff base ligands, their precursors and metal complexes were also screened for antibacterial, antifungal, antitumor, Brine shrimp lethality, DPPH free radical scavenging and DNA damage assays. The results of these analyses indicated the substantial potential of the synthesized Schiff bases, their precursors and Cu(II) complexes in biological field as future drugs.

A 3D complex containing novel 2D Cu{sup II}-azido layers: Structure, magnetic properties and effects of 'Non-innocent' reagent

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

Gao, Xue-Miao; Guo, Qian; Zhao, Jiong-Peng, E-mail: horryzhao@yahoo.com

A novel copper-azido coordination polymer, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with 'Non-innocent' reagent in the aqueous solution. In the reaction system, Cu{sup II} ions are avoided to reduce to Cu{sup I} ions due to the existence of Nd{sup III}. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron Cu{sup II} ions, in which the azide ligands take on EO and {mu}{sub 1,1,3} mode to form Cu{sup II}-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D frameworkmore » with the Schlaefli symbol of {l_brace}4;6{sup 2}{r_brace}4{l_brace}4{sup 2};6{sup 12};8{sup 10};10{sup 4}{r_brace}{l_brace}4{sup 2};6{sup 4}{r_brace}. Magnetic studies revealed that the interactions between the Cu{sup II} ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98 Degree-Sign , while the interactions between the trimmer and octahedron Cu{sup II} ion are antiferromgantic and result in an antiferromagnetic state. - Graphical abstract: A 3D complex containing novel 2D Cu{sup II}-azido layers, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (HL=pyrazine-2-carboxylic acid), was synthesized by hydrothermal reaction and exhibit interesting structure and magnetic properties. Highlights: Black-Right-Pointing-Pointer 'Non-innocent' reagents plays a key role in the process of formation of this complex. Black-Right-Pointing-Pointer 2D layer is formed only by Cu{sup II} ions and azido ligands. Black-Right-Pointing-Pointer Pyrazine-2-carboxylate ligands reinforce 2D layers and pillar them into an infinite 3D framework. Black-Right-Pointing-Pointer Magnetic study indicates that alternating FM-AF coupling exists in the complex.« less

Structural and electronic transport properties of compound forming HgPb liquid alloy using ab-initio pseudopotential

NASA Astrophysics Data System (ADS)

Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

2013-02-01

The electrical resistivity of compound forming liquid alloy HgPb is studied as a function of concentration. Hard sphere diameters of Hg and Pb are obtained through the inter-ionic pair potential evaluated using Troullier and Martins ab initio pseudopotential, which have been used to calculate partial structure factors. Considering the liquid alloy to be a ternary mixture Ziman's formula for calculating the resistivity of binary liquid alloys, modified for complex formation, has been used. The concentration dependence in resistivity occurs due to preferential ordering of unlike atoms as nearest neighbours with help of complex formation model. Though the compound HgiPbi as per structure peaks is found to be less stable. However it contributes significantly to resistivity as compared to bare ions.

Structure and stability of hexa-aqua V(III) cations in vanadium redox flow battery electrolytes.

PubMed

Vijayakumar, M; Li, Liyu; Nie, Zimin; Yang, Zhenguo; Hu, JianZhi

2012-08-07

The vanadium(III) cation structure in mixed acid based electrolyte solution from vanadium redox flow batteries is studied by (17)O and (35/37)Cl nuclear magnetic resonance (NMR) spectroscopy, electronic spectroscopy and density functional theory (DFT) based computational modelling. Both computational and experimental results reveal that the V(III) species can complex with counter anions (sulfate/chlorine) depending on the composition of its solvation sphere. By analyzing the powder precipitate it was found that the formation of sulfate complexed V(III) species is the crucial process in the precipitation reaction. The precipitation occurs through nucleation of neutral species formed through deprotonation and ion-pair formation process. However, the powder precipitate shows a multiphase nature which warrants multiple reaction pathways for precipitation reaction.

H passivation of Li on Zn-site in ZnO: Positron annihilation spectroscopy and secondary ion mass spectrometry

NASA Astrophysics Data System (ADS)

Johansen, K. M.; Zubiaga, A.; Tuomisto, F.; Monakhov, E. V.; Kuznetsov, A. Yu.; Svensson, B. G.

2011-09-01

The interaction of hydrogen (H) with lithium (Li) and zinc vacancies (VZn) in hydrothermally grown n-type zinc oxide (ZnO) has been investigated by positron annihilation spectroscopy (PAS) and secondary ion mass spectrometry. Li on Zn-site (LiZn) is found to be the dominant trap for migrating H atoms, while the trapping efficiency of VZn is considerably smaller. After hydrogenation, where the LiZn acceptor is passivated via formation of neutral LiZn-H pairs, VZn occurs as the prime PAS signature and with a concentration similar to that observed in nonhydrogenated Li-poor samples. Despite a low efficiency as an H trap, the apparent concentration of VZn in Li-poor samples decreases after hydrogenation, as detected by PAS, and evidence for formation of the neutral VZnH2 complex is presented.

Counteranion Driven Homochiral Assembly of a Cationic C3-Symmetric Gelator through Ion-Pair Assisted Hydrogen Bond.

PubMed

Maity, Arunava; Gangopadhyay, Monalisa; Basu, Arghya; Aute, Sunil; Babu, Sukumaran Santhosh; Das, Amitava

2016-09-07

The helical handedness in achiral self-assemblies is mostly complex due to spontaneous symmetry breaking or kinetically controlled random assembly formation. Here an attempt has been made to address this issue through chiral anion exchange. A new class of cationic achiral C3-symmetric gelator devoid of any conventional gelation assisting functional units is found to form both right- and left-handed helical structures. A chiral counteranion exchange-assisted approach is successfully introduced to control the chirality sign and thereby to obtain preferred homochiral assemblies. Formation of anion-assisted chiral assembly was confirmed by circular dichroism (CD) spectroscopy, microscopic images, and crystal structure. The X-ray crystal structure reveals the construction of helical assemblies with opposite handedness for (+)- and (-)-chiral anion reformed gelators. The appropriate counteranion driven ion-pair-assisted hydrogen-bonding interactions are found responsible for the helical bias control in this C3-symmetric gelator.

Upconversion luminescence from Er-N codoped of ZnO nanowires prepared by ion implantation method

NASA Astrophysics Data System (ADS)

Zhong, Kun; Xu, Jie; Su, Jing; Chen, Yu lin

2011-02-01

Nitrogen and erbium co-doped of ZnO nanowires (NWs) are fabricated by ion implantation and subsequent annealing in air. The incorporation of Er3+ and N+ ions is verified by energy dispersive X-ray spectroscopy (EDS) and Raman spectra. The samples exhibit upconversion photoluminescence around ∼550 nm and ∼660 nm under an excitation at 980 nm. It is discovered that the N-doped can drastically increase the upconversion photoluminescence intensity by modifying the local structure around Er3+ in ZnO matrix. The enhancement of the PL intensity by the N-doped is caused by the formation of ErO6-xNx octahedron complexes. With the increase of the annealing temperature (Ta), the Er3+ ions diffuse towards the surface of the NWs, which benefits the red emission and evokes the variation of intensity ratio owing to the existence of some organic groups.

Formation of iron complexs from trifluoroacetic acid based liquid chromatography mobile phases as interference ions in liquid chromatography/electrospray ionization mass spectrometric analysis

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

Shukla, Anil K.; Zhang, Rui; Orton, Daniel J.

Two unexpected singly charged ions at m/z 1103 and 944 have been observed in mass spectra obtained from electrospray ionization-mass spectrometric analysis of liquid chromatography effluents with mobile phases containing trifluoroacetic acid. Accurate mass measurement and tandem mass spectrometry studies revealed that these two ions are not due to any contamination from solvents and chemicals used for mobile and stationary phases or from the laboratory atmospheric environment. Instead these ions are clusters of trifluoroacetic acid formed in association with acetonitrile, water and iron from the stainless steel union used to connect the column with the electrospray tip and to applymore » high voltage; the molecular formulae are Fe+((OH)(H2O)2)9(CF3COOH)5 and Fe+((OH)(H2O)2)6 (CF3COOH)5.« less

Entropy and charge in molecular evolution--the case of phosphate

NASA Technical Reports Server (NTRS)

Arrhenius, G.; Sales, B.; Mojzsis, S.; Lee, T.; Bada, J. L. (Principal Investigator)

1997-01-01

Biopoesis, the creation of life, implies molecular evolution from simple components, randomly distributed and in a dilute state, to form highly organized, concentrated systems capable of metabolism, replication and mutation. This chain of events must involve environmental processes that can locally lower entropy in several steps; by specific selection from an indiscriminate mixture, by concentration from dilute solution, and in the case of the mineral-induced processes, by particular effectiveness in ordering and selective reaction, directed toward formation of functional biomolecules. Numerous circumstances provide support for the notion that negatively charged molecules were functionally required and geochemically available for biopoesis. Sulfite ion may have been important in bisulfite complex formation with simple aldehydes, facilitating the initial concentration by sorption of aldehydes in positively charged surface active minerals. Borate ion may have played a similar, albeit less investigated role in forming charged sugar complexes. Among anionic species, oligophosphate ions and charged phosphate esters are likely to have been of even more wide ranging importance, reflected in the continued need for phosphate in a proposed RNA world, and extending its central role to evolved biochemistry. Phosphorylation is shown to result in selective concentration by surface sorption of compounds, otherwise too dilute to support condensation reactions. It provides protection against rapid hydrolysis of sugars and, by selective concentration, induces the oligomerization of aldehydes. As a manifestation of life arisen, phosphate already appears in an organic context in the oldest preserved sedimentary record.

Method for ion implantation induced embedded particle formation via reduction

DOEpatents

Hampikian, Janet M; Hunt, Eden M

2001-01-01

A method for ion implantation induced embedded particle formation via reduction with the steps of ion implantation with an ion/element that will chemically reduce the chosen substrate material, implantation of the ion/element to a sufficient concentration and at a sufficient energy for particle formation, and control of the temperature of the substrate during implantation. A preferred embodiment includes the formation of particles which are nano-dimensional (<100 m-n in size). The phase of the particles may be affected by control of the substrate temperature during and/or after the ion implantation process.

Efficiency of Cs-free materials for negative ion production in H2 and D2 plasmas

NASA Astrophysics Data System (ADS)

Friedl, R.; Kurutz, U.; Fantz, U.

2017-08-01

High power negative ion sources use caesium to reduce the work function of the converter surface which significantly increases the negative ion yield. Caesium, however, is a very reactive alkali-metal and shows complex redistribution dynamics in consequence of plasma-surface-interaction. Thus, maintaining a stable and homogenous low work function surface is a demanding task, which is not easily compatible with the RAMI issues (reliability, availability, maintainability, inspectability) for a future DEMO fusion reactor. Hence, Cs-free alternative materials for efficient negative ion formation are desirable. At the laboratory experiment HOMER materials which are referred to as promising are investigated under identical and ion source relevant parameters: the refractory metals Ta and W, non-doped and boron-doped diamond as well as materials with inherent low work function (lanthanum-doped molybdenum, MoLa and lanthanum hexaboride, LaB6). The results are compared to the effect of in-situ caesiation, which at HOMER leads to a maximal increase of the negative ion density by a factor of 2.5. Among the examined samples low work function materials are most efficient. In particular, MoLa leads to an increase of almost 50 % compared to pure volume formation. The difference to a caesiated surface can be attributed to the still higher work function of MoLa, which is expected to be slightly below 3 eV. Using deuterium instead of hydrogen leads to increased atomic and positive ion densities, while comparable negative ion densities are achieved. In contrast to the low work function materials, bulk samples of the refractory metals as well as carbon based materials have no enhancing effect on H-, where the latter materials furthermore show severe erosion due to the hydrogen plasma.

Azide and acetate complexes plus two iron-depleted crystal structures of the di-iron enzyme delta9 stearoyl-acyl carrier protein desaturase. Implications for oxygen activation and catalytic intermediates.

PubMed

Moche, Martin; Shanklin, John; Ghoshal, Alokesh; Lindqvist, Ylva

2003-07-04

Delta9 stearoyl-acyl carrier protein (ACP) desaturase is a mu-oxo-bridged di-iron enzyme, which belongs to the structural class I of large helix bundle proteins and that catalyzes the NADPH and O2-dependent formation of a cis-double bond in stearoyl-ACP. The crystal structures of complexes with azide and acetate, respectively, as well as the apoand single-iron forms of Delta9 stearoyl-ACP desaturase from Ricinus communis have been determined. In the azide complex, the ligand forms a mu-1,3-bridge between the two iron ions in the active site, replacing a loosely bound water molecule. The structure of the acetate complex is similar, with acetate bridging the di-iron center in the same orientation with respect to the di-iron center. However, in this complex, the iron ligand Glu196 has changed its coordination mode from bidentate to monodentate, the first crystallographic observation of a carboxylate shift in Delta9 stearoyl-ACP desaturase. The two complexes are proposed to mimic a mu-1,2 peroxo intermediate present during catalytic turnover. There are striking structural similarities between the di-iron center in the Delta9 stearoyl-ACP desaturase-azide complex and in the reduced rubrerythrin-azide complex. This suggests that Delta9 stearoyl-ACP desaturase might catalyze the formation of water from exogenous hydrogen peroxide at a low rate. From the similarity in iron center structure, we propose that the mu-oxo-bridge in oxidized desaturase is bound to the di-iron center as in rubrerythrin and not as reported for the R2 subunit of ribonucleotide reductase and the hydroxylase subunit of methane monooxygenase. The crystal structure of the one-iron depleted desaturase species demonstrates that the affinities for the two iron ions comprising the di-iron center are not equivalent, Fe1 being the higher affinity site and Fe2 being the lower affinity site.

Preferential Solvation of an Asymmetric Redox Molecule

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

Han, Kee Sung; Rajput, Nav Nidhi; Vijayakumar, M.

2016-12-15

The fundamental correlations between inter-molecular interactions, solvation structure and functionality of electrolytes are in many cases unknown, particularly for multi-component liquid systems. In this work, we explore such correlations by investigating the complex interplay between solubility and solvation structure for the electrolyte system comprising N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium bistrifluoromethylsulfonimide (Fc1N112-TFSI) dissolved in a ternary carbonate solvent mixture using combined NMR relaxation and computational analyses. Probing the evolution of the solvent-solvent, ion-solvent and ion-ion interactions with an increase in solute concentration provides a molecular level understanding of the solubility limit of the Fc1N112-TFSI system. An increase in solute con-centration leads to pronounced Fc1N112-TFSI contact-ionmore » pair formation by diminishing solvent-solvent and ion-solvent type interactions. At the solubility limit, the precipitation of solute is initiated through agglomeration of contact-ion pairs due to overlapping solvation shells.« less

A newly developed highly selective Zn2+-AcO- ion-pair sensor through partner preference: equal efficiency under solitary and colonial situation.

PubMed

Karar, Monaj; Paul, Suvendu; Biswas, Bhaskar; Majumdar, Tapas; Mallick, Arabinda

2018-05-10

Unusual self-sorting of an ion-pair under highly crowded conditions driven by a synthesized intelligent molecule 2-((E)-(3-((E)-2-hydroxy-3-methoxybenzylideneamino)-2-hydroxypropyl imino)methyl)-6-methoxyphenol, hereafter HBP, is described. When a mixture of various metal salts was allowed to react with HBP, only a specific ion-pair ZnII/AcO- in the solution simultaneously reacted, resulting in high-fidelity ion-pair recognition of HBP. This phenomenon was evidenced by significant changes in the absorption spectra and huge enhancement in emission intensity of HBP. The property that one molecule preferring one particular cation-anion pair over others is a rare but interesting phenomenon. Thus, the potential to interact selectively with the targeted ion-pair resulting in the formation of a specific complex recognized HBP as a new class of molecule that might find future applications in real time and on-site monitoring and separation of new molecules.

What dictates which ion, I- or Br-, mediates the growth of cubic Pd nanocrystals?

PubMed

Wang, Ze-Hong; Wu, Ya-Jiao; Xue, Huan-Huan; Zhou, Lin-Nan; Geng, Wen-Chao; Yi, Hai-Bo; Li, Yong-Jun

2018-04-25

Cubic Pd nanocrystals (CPNCs) as one of typical nanostructures are generally fabricated using I- or Br- as capping ions. However, which ion, I- or Br-, exclusively mediates the growth of CPNCs in a given reaction system is not well understood. Herein, regardless of I- or Br- as the capping ion, we successfully achieved CPNCs in the same reaction system simply by adjusting the pH. Based on the Finke-Watzky kinetic model, an increase in pH accelerates the overall reduction rate of Pd2+, and the formation of CPNCs only occurs over the range of specific solution reduction rate constants (k1). This kinetically illuminates that the reduction rate of Pd2+ is the physicochemical parameter that determines which ion, I- or Br-, dictates the growth of CPNCs. Also, density functional theory (DFT) calculations further elucidate the dependence of the reduction rate of Pd2+ on pH and the configuration of the activated Pd2+ complex.

A newly developed highly selective ratiometric fluoride ion sensor: spectroscopic, NMR and density functional studies.

PubMed

Mallick, Arabinda; Roy, Ujjal Kanti; Haldar, Basudeb; Pratihar, Sanjay

2012-03-07

A new easy-to-synthesize chemosensor, 3,3'-bis(indolyl)-4-chlorophenylmethane (hereafter S), was designed, synthesized and employed as a selective optical chemosensor for fluoride ions.(1)H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between S and X(-) (X = inorganic anions) responsible for the significant fluoride-induced changes in the absorption properties of S. The experimental results reveal that abstraction of an acidic proton of S by the fluoride ion, leading to the formation of anionic species, is responsible for the spectral changes. These changes allow signaling for the fluoride ion to detect and estimate the concentration of fluoride ion present even at the submicromolar level, accurate up to 2 μM. Calculations of the transition energies of S, S(-), and S···F(-) (hydrogen bonded complex) show that only S(-) is responsible for the long-wavelength absorption band in the presence of F(-).

Interactions of diamines with adenosine-5'-triphosphate (ATP) in the systems including copper(II) ions.

PubMed

Bregier-Jarzebowska, R; Gasowska, A; Hoffmann, S K; Lomozik, L

2016-09-01

Interactions were studied in the systems ATP/tn and ATP/Put (tn=1,3-diaminopropane, Put=putrescine) whereas the complexation reactions in ternary systems Cu(II)/ATP/tn and Cu(II)/ATP/Put. Results of the potentiometric and spectroscopic studies evidenced the formation of adducts of the type (ATP)H x (PA), where PA=diamine. The thermodynamic stability of the complexes and the mode of interactions were determined. On the basis of analysis of changes in the positions of NMR signals, in the pH range of (ATP)H 3 (Put) formation, the preferred centres of the interaction between ATP and Put are the endocyclic nitrogen atoms from the nucleotide. On the other hand, the shorter diamine tn in the entire pH range reacts with the phosphate groups from ATP. The positive centres of noncovalent interactions are the protonated NH x + groups from amines. In both complexes Cu(ATP)H 2 (tn) and Cu(ATP)H 3 (Put) formed in ternary systems at pH<6.5, the amines are in the outer sphere of coordination with the noncovalent interaction with anchoring Cu(ATP). Only the phosphate groups from the nucleotide take part in metalation. At higher pH in the range of Cu(ATP)(PA) complex formation, significant differences in the reactions of the two amines appear. The shorter one (tn) binds Cu(II) ions with two nitrogen atoms, while putrescine coordinates in the monofunctional mode, which is undoubtedly related to the differences in lengths of methylene chain. This explains the considerable differences in the stability of Cu(ATP)(tn) and Cu(ATP)(Put). In both complexes the nucleotide is coordinated through phosphate groups. As a result of noncovalent interactions ATP forms molecular complexes with 1,3-diaminopropane and 1,4-diaminobutane (putrescine). Significant differences in the mode of interactions between the two diamines were observed in ATP/diamine binary systems and in ternary systems Cu(II)/ATP/diamine, at high pH. Copyright © 2016 Elsevier Inc. All rights reserved.

In situ formation of heterobimetallic salen complexes containing titanium and/or vanadium ions.

PubMed

Belokon, Yuri N; Harrington, Ross W; North, Michael; Young, Carl

2008-05-05

A combination of high-resolution electrospray mass spectrometry and (1)H NMR spectroscopy has been used to prove that when a mixture of [(salen)TiO]2 complexes containing two different salen ligands (salen and salen') is formed, an equilibrium is established between the homodimers and the heterodimer [(salen)TiO2Ti(salen')]. Depending upon the structure and stereochemistry of the two salen ligands, the equilibrium may favor either the homodimers or the heterodimer. Extension of this process to mixtures of titanium(salen) complexes [(salen)TiO]2 and vanadium (V)(salen') complexes [(salen')VO] (+)Cl (-) allowed the in situ formation of the heterobimetallic complex [(salen)TiO2V(salen')] (+)X (-) to be confirmed for all combinations of salen ligands studied except when the salen ligand attached to titanium contained highly electron-withdrawing nitro-groups. The rate of equilibration between heterobimetallic complexes is faster than that between two titanium complexes as determined by line broadening in the (1)H NMR spectra. These structural results explain the strong rate-inhibiting effect of vanadium (V)(salen) complexes in asymmetric cyanohydrin synthesis catalyzed by [(salen)TiO]2 complexes. It has also been demonstrated for the first time that the titanium and vanadium complexes can undergo exchange of salen ligands and that this is catalyzed by protic solvents. However, the ligand exchange is relatively slow (occurring on a time scale of days at room temperature) and so does not complicate studies aimed at using heterobimetallic titanium and vanadium salen complexes as asymmetric catalysts. Attempts to obtain a crystal structure of a heterobimetallic salen complex led instead to the isolation of a trinuclear titanium(salen) complex, the formation of which is also consistent with the catalytic results obtained previously.

Ion Chemistry in Atmospheric and Astrophysical Plasmas

NASA Technical Reports Server (NTRS)

Dalgarno, A.; Fox, J. L.

1994-01-01

There are many differences and also remarkable similarities between the ion chemistry and physics of planetary ionospheres and the ion chemistry and physics of astronomical environments beyond the solar system. In the early Universe, an expanded cooling gas of hydrogen and helium was embedded in the cosmic background radiation field and ionized by it. As the Universe cooled by adiabatic expansion, recombination occurred and molecular formation was driven by catalytic reactions involving the relict electrons and protons. Similar chemical processes are effective in the ionized zones of gaseous and planetary nebulae and in stellar winds where the ionization is due to radiation from the central stars, in the envelopes of supernovae where the ionization is initiated by the deposition of gamma-rays, in dissociative shocks where the ionization arises from electron impacts in a hot gas and in quasar broad-line region clouds where the quasar is responsible for the ionization. At high altitudes in the atmospheres of the Jovian planets, the main constituents are hydrogen and helium and the ion chemistry and physics is determined by the same processes, the source of the ionization being solar ultraviolet radiation and cosmic rays. After the collapse of the first distinct astronomical entities to emerge from the uniform flow, heavy elements were created by nuclear burning in the cores of the collapsed objects and distributed throughout the Universe by winds and explosions. The chemistry and physics became more complicated. Over 90 distinct molecular species have been identified in interstellar clouds where they are ionized globally by cosmic ray impacts and locally by radiation and shocks associated with star formation and evolution. Complex molecules have also been found in circumstellar shells of evolved stars. At intermediate and low altitudes in the Jovian atmospheres, the ion chemistry is complicated by the increasing abundance of heavy elements such as carbon, and an extensive array of complex molecules has been predicted. Reactions involving heavy elements dominate the structure of the ionspheres of the terrestrial planets and the satellites Titan and Triton.

Dissolution behaviour of ferric pyrophosphate and its mixtures with soluble pyrophosphates: Potential strategy for increasing iron bioavailability.

PubMed

Tian, Tian; Blanco, Elena; Smoukov, Stoyan K; Velev, Orlin D; Velikov, Krassimir P

2016-10-01

Ferric pyrophosphate (FePP) is a widely used iron source in food fortification and in nutritional supplements, due to its white colour, that is very uncommon for insoluble Fe salts. Although its dissolution is an important determinant of Fe adsorption in human body, the solubility characteristics of FePP are complex and not well understood. This report is a study on the solubility of FePP as a function of pH and excess of pyrophosphate ions. FePP powder is sparingly soluble in the pH range of 3-6 but slightly soluble at pH<2 and pH>8. In the presence of pyrophosphate ions the solubility of FePP strongly increases at pH 5-8.5 due to formation a soluble complex between Fe(III) and pyrophosphate ions, which leads to an 8-10-fold increase in the total ionic iron concentration. This finding is beneficial for enhancing iron bioavailability, which important for the design of fortified food, beverages, and nutraceutical products. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optical activity and defect/dopant evolution in ZnO implanted with Er

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

Azarov, Alexander; Galeckas, Augustinas; Kuznetsov, Andrej

2015-09-28

The effects of annealing on the optical properties and defect/dopant evolution in wurtzite (0001) ZnO single crystals implanted with Er ions are studied using a combination of Rutherford backscattering/channeling spectrometry and photoluminescence measurements. The results suggest a lattice recovery behavior dependent on ion dose and involving formation/evolution of an anomalous multipeak defect distribution, thermal stability of optically active Er complexes, and Er outdiffusion. An intermediate defect band occurring between the surface and ion-induced defects in the bulk is stable up to 900 °C and has a photoluminescence signature around 420 nm well corresponding to Zn interstitials. The optical activity of the Ermore » atoms reaches a maximum after annealing at 700 °C but is not directly associated to the ideal Zn site configuration, since the Er substitutional fraction is maximal already in the as-implanted state. In its turn, annealing at temperatures above 700 °C leads to dissociation of the optically active Er complexes with subsequent outdiffusion of Er accompanied by the efficient lattice recovery.« less

Electrical conductivity of In2O3 and Ga2O3 after low temperature ion irradiation; implications for instrinsic defect formation and charge neutrality level.

PubMed

Vines, L; Bhoodoo, C; von Wenckstern, H; Grundmann, M

2017-12-13

The evolution of sheet resistance of n-type In 2 O 3 and Ga 2 O 3 exposed to bombardment with MeV 12 C and 28 Si ions at 35 K is studied in situ. While the sheet resistance of Ga 2 O 3 increased by more than eight orders of magnitude as a result of ion irradiation, In 2 O 3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga 2 O 3 remained highly resistive, while In 2 O 3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to [Formula: see text] cm -2 . A model where larger defect complexes preferentially produce donor like defects in In 2 O 3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

Electrical conductivity of In2O3 and Ga2O3 after low temperature ion irradiation; implications for instrinsic defect formation and charge neutrality level

NASA Astrophysics Data System (ADS)

Vines, L.; Bhoodoo, C.; von Wenckstern, H.; Grundmann, M.

2018-01-01

The evolution of sheet resistance of n-type In2O3 and Ga2O3 exposed to bombardment with MeV 12C and 28Si ions at 35 K is studied in situ. While the sheet resistance of Ga2O3 increased by more than eight orders of magnitude as a result of ion irradiation, In2O3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga2O3 remained highly resistive, while In2O3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to 2 × 1012 cm-2. A model where larger defect complexes preferentially produce donor like defects in In2O3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

In situ formation of the amino sugars 1-amino-1-deoxy-fructose and 2-amino-2-deoxy-glucose under Maillard reaction conditions in the absence of ammonia.

PubMed

Nashalian, Ossanna; Yaylayan, Varoujan A

2016-04-15

Replacing amino acids with their binary metal complexes during the Maillard reaction can initiate various processes, including the oxidative degradation of their glucose conjugates, generating 1-amino-1-deoxy-fructose and its derivatives. These reactive amino sugars are not easily accessible under Maillard reaction conditions and are only formed in the presence of ammonia. To explore the generality of this observation and to study in particular the ability of fructose to generate glucosamine, the amino acid-metal complexes were heated in aqueous solutions with three aldohexoses and two ketohexoses at 110°C for 2 h and the dry residues were analysed by ESI/qTOF/MS/MS. All the sugars generated relatively intense ions at [M+H](+) 180 (C6H14NO5); those ions originating from ketohexoses exhibited MS/MS fragmentations identical to glucosamine and those originating form aldohexoses showed ions identical to fructosamine. Furthermore, the amino sugars were found to form fructosazine, react with other sugars and undergo dehydration reactions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Chemical Properties of Elements 99 and 100 [Einsteinium and Fermium

DOE R&D Accomplishments Database

Seaborg, G. T.; Thompson, S. G.; Harvey, B. G.; Choppin, G. R.

1954-07-23

A description of some of the chemical properties and of the methods used in the separations of elements 99 [Einsteinium] and 100 [Fermium] are given. The new elements exhibit the properties expected for the tenth and eleventh actinide elements. Attempts to produce an oxidation state greater than III of element 99 have been unsuccessful. In normal aqueous media only the III state of element 100 appears to exist. The relative spacings of the elution peaks of the new elements in some separations with ion exchange resin columns are the same as the relative spacings of the homologous lanthanide elements. The results of experiments involving cation exchange resins with very concentrated hydrochloric acid eluant show that the new elements, like the earlier actinides, are more strongly complexed than the lanthanides. The new elements also exist partially as anions in concentrated hydrochloric acid, as do earlier actinide elements, and they may be partially separated from each other by means of ion exchange resins. With some eluants interesting reversals of elution positions are observed in the region Bk-Cf-99-100, indicating complex ion formation involving unusual factors.

Molecular dynamics simulations of electrostatics and hydration distributions around RNA and DNA motifs

NASA Astrophysics Data System (ADS)

Marlowe, Ashley E.; Singh, Abhishek; Semichaevsky, Andrey V.; Yingling, Yaroslava G.

2009-03-01

Nucleic acid nanoparticles can self-assembly through the formation of complementary loop-loop interactions or stem-stem interactions. Presence and concentration of ions can significantly affect the self-assembly process and the stability of the nanostructure. In this presentation we use explicit molecular dynamics simulations to examine the variations in cationic distributions and hydration environment around DNA and RNA helices and loop-loop interactions. Our simulations show that the potassium and sodium ionic distributions are different around RNA and DNA motifs which could be indicative of ion mediated relative stability of loop-loop complexes. Moreover in RNA loop-loop motifs ions are consistently present and exchanged through a distinct electronegative channel. We will also show how we used the specific RNA loop-loop motif to design a RNA hexagonal nanoparticle.

Naphthaldimine-based simple glucose derivative as a highly selective sensor for colorimetric detection of Cu2+ ion in aqueous media

NASA Astrophysics Data System (ADS)

Dolai, Bholanath; Bhaumik, Atanu; Pramanik, Nabakumar; Ghosh, Kalyan Sundar; Atta, Ananta Kumar

2018-07-01

Naphthaldimine-based glucose derivatives 1 and 3 have been designed, synthesized and characterized. In aqueous media, glucose derivative 1, exhibited high selectivity and sensitivity towards Cu2+ ion in comparison with various cations and anions. In presence of Cu2+, sensor 1 has provided significant naked-eye detectable color change. The formation of 1-Cu2+ complex has been analyzed by UV-vis spectroscopy, 1H NMR titration experiments, mass spectrometry and DFT (density functional theory) calculations. Limit of detection of 1 as a colorimetric sensor for Cu2+ ion is found to be 0.23 μM, much lower than recommended value of World Health Organization (WHO), which makes to Cu2+ sensor 1 more effective and useful.

Spectrophotometric determination of some anti-tussive and anti-spasmodic drugs through ion-pair complex formation with thiocyanate and cobalt(II) or molybdenum(V)

NASA Astrophysics Data System (ADS)

El-Shiekh, Ragaa; Zahran, Faten; El-Fetouh Gouda, Ayman Abou

2007-04-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of anti-tussive drugs, e.g., dextromethorphan hydrobromide (DEX) and pipazethate hydrochloride (PiCl) and anti-spasmodic drugs, e.g., drotaverine hydrochloride (DvCl) and trimebutine maleate (TM) in bulk and in their pharmaceutical formulations. The proposed methods depend upon the reaction of cobalt(II)-thiocyanate (method A) and molybdenum(V)-thiocyanate ions (method B) with the cited drugs to form stable ion-pair complexes which extractable with an n-butnol-dichloromethane solvent mixture (3.5:6.5) and methylene chloride for methods A and B, respectively. The blue and orange red color complexes are determined either colorimetrically at λmax 625 nm (using method A) and 467 or 470 nm for (DEX and PiCl) or (DvCl and TM), respectively (using method B). The concentration range is 20-400 and 2.5-50 μg mL -1 for methods A and B, respectively. The proposed method was successfully applied for the determination of the studied drugs in pure and in pharmaceutical formulations applying the standard additions technique and the results obtained in good agreement well with those obtained by the official method.

mer, fac, and Bidentate Coordination of an Alkyl-POP Ligand in the Chemistry of Nonclassical Osmium Hydrides.

PubMed

Esteruelas, Miguel A; García-Yebra, Cristina; Martín, Jaime; Oñate, Enrique

2017-01-03

Nonclassical and classical osmium polyhydrides containing the diphosphine 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(P i Pr 2 ) 2 ), coordinated in κ 3 -mer, κ 3 -fac, and κ 2 -P,P fashions, have been isolated during the cyclic formation of H 2 by means of the sequential addition of H + and H - or H - and H + to the classical trihydride OsH 3 Cl{xant(P i Pr 2 ) 2 } (1). This complex adds H + to form the compressed dihydride dihydrogen complex [OsCl(H···H)(η 2 -H 2 ){xant(P i Pr 2 ) 2 }] + (2). Under argon, cation 2 loses H 2 and the resulting unsaturated fragment dimerizes to give [(Os(H···H){xant(P i Pr 2 ) 2 }) 2 (μ-Cl) 2 ] 2+ (3). During the transformation the phosphine changes its coordination mode from mer to fac. The benzofuran counterpart of 1, OsH 3 Cl{dbf(P i Pr 2 ) 2 } (4; dbf(P i Pr 2 ) 2 = 4,6-bis(diisopropylphosphino)dibenzofuran), also adds H + to afford the benzofuran counterpart of 2, [OsCl(H···H)(η 2 -H 2 ){xant(P i Pr 2 ) 2 }] + (5), which in contrast to the latter is stable and does not dimerize. Acetonitrile breaks the chloride bridge of 3 to form the dihydrogen [OsCl(η 2 -H 2 )(CH 3 CN){xant(P i Pr 2 ) 2 }] + (6), regenerating the mer coordination of the diphosphine. The hydride ion also breaks the chloride bridge of 3. The addition of KH to 3 leads to 1, closing a cycle for the formation of H 2 . Complex 1 reacts with a second hydride ion to give OsH 4 {xant(P i Pr 2 ) 2 } (7) as consequence of the displacement of the chloride. Similarly to the latter, the oxygen atom of the mer-coordinated diphosphine of 7 has a tendency to be displaced by the hydride ion. Thus, the addition of KH to 7 yields [OsH 5 {xant(P i Pr 2 ) 2 }] - (8), containing a κ 2 -P,P-diphosphine. Complex 8 is easily protonated to afford OsH 6 {xant(P i Pr 2 ) 2 } (9), which releases H 2 to regenerate 7, closing a second cycle for the formation of molecular hydrogen.

Influence of memory effect on the state-of-charge estimation of large-format Li-ion batteries based on LiFePO4 cathode

NASA Astrophysics Data System (ADS)

Shi, Wei; Wang, Jiulin; Zheng, Jianming; Jiang, Jiuchun; Viswanathan, Vilayanur; Zhang, Ji-Guang

2016-04-01

In this work, we systematically investigated the influence of the memory effect of LiFePO4 cathodes in large-format full batteries. The electrochemical performance of the electrodes used in these batteries was also investigated separately in half-cells to reveal their intrinsic properties. We noticed that the memory effect of LiFePO4/graphite cells depends not only on the maximum state of charge reached during the memory writing process, but is also affected by the depth of discharge reached during the memory writing process. In addition, the voltage deviation in a LiFePO4/graphite full battery is more complex than in a LiFePO4/Li half-cell, especially for a large-format battery, which exhibits a significant current variation in the region near its terminals. Therefore, the memory effect should be taken into account in advanced battery management systems to further extend the long-term cycling stabilities of Li-ion batteries using LiFePO4 cathodes.

Fast detection of narcotics by single photon ionization mass spectrometry and laser ion mobility spectrometry

NASA Astrophysics Data System (ADS)

Laudien, Robert; Schultze, Rainer; Wieser, Jochen

2010-10-01

In this contribution two analytical devices for the fast detection of security-relevant substances like narcotics and explosives are presented. One system is based on an ion trap mass spectrometer (ITMS) with single photon ionization (SPI). This soft ionization technique, unlike electron impact ionization (EI), reduces unwanted fragment ions in the mass spectra allowing the clear determination of characteristic (usually molecular) ions. Their enrichment in the ion trap and identification by tandem MS investigations (MS/MS) enables the detection of the target substances in complex matrices at low concentrations without time-consuming sample preparation. For SPI an electron beam pumped excimer light source of own fabrication (E-Lux) is used. The SPI-ITMS system was characterized by the analytical study of different drugs like cannabis, heroin, cocaine, amphetamines, and some precursors. Additionally, it was successfully tested on-site in a closed illegal drug laboratory, where low quantities of MDMA could be directly detected in samples from floors, walls and lab equipments. The second analytical system is based on an ion mobility (IM) spectrometer with resonant multiphoton ionization (REMPI). With the frequency quadrupled Nd:YAG laser (266 nm), used for ionization, a selective and sensitive detection of aromatic compounds is possible. By application of suited aromatic dopants, in addition, also non-aromatic polar compounds are accessible by ion molecule reactions like proton transfer or complex formation. Selected drug precursors could be successfully detected with this device as well, qualifying it to a lower-priced alternative or useful supplement of the SPI-ITMS system for security analysis.

Competitive Binding to Cuprous Ions of Protein and BCA in the Bicinchoninic Acid Protein Assay

PubMed Central

Huang, Tao; Long, Mian; Huo, Bo

2010-01-01

Although Bicinchoninic acid (BCA) has been widely used to determine protein concentration, the mechanism of interaction between protein, copper ion and BCA in this assay is still not well known. Using the Micro BCA protein assay kit (Pierce Company), we measured the absorbance at 562 nm of BSA solutions with different concentrations of protein, and also varied the BCA concentration. When the concentration of protein was increased, the absorbance exhibited the known linear and nonlinear increase, and then reached an unexpected plateau followed by a gradual decrease. We introduced a model in which peptide chains competed with BCA for binding to cuprous ions. Formation of the well-known chromogenic complex of BCA-Cu1+-BCA was competed with the binding of two peptide bonds (NTPB) to cuprous ion, and there is the possibility of the existence of two new complexes. A simple equilibrium equation was established to describe the correlations between the substances in solution at equilibrium, and an empirical exponential function was introduced to describe the reduction reaction. Theoretical predictions of absorbance from the model were in good agreement with the measurements, which not only validated the competitive binding model, but also predicted a new complex of BCA-Cu1+-NTPB that might exist in the final solution. This work provides a new insight into understanding the chemical bases of the BCA protein assay and might extend the assay to higher protein concentration. PMID:21625379

Two-stage DNA compaction induced by silver ions suggests a cooperative binding mechanism

NASA Astrophysics Data System (ADS)

Jiang, Wen-Yan; Ran, Shi-Yong

2018-05-01

The interaction between silver ions and DNA plays an important role in the therapeutic use of silver ions and in related technologies such as DNA sensors. However, the underlying mechanism has not been fully understood. In this study, the dynamics of Ag+-DNA interaction at a single-molecule level was studied using magnetic tweezers. AgNO3 solutions with concentrations ranging from 1 μM to 20 μM led to a 1.4-1.8 μm decrease in length of a single λ-DNA molecule, indicating that Ag+ has a strong binding with DNA, causing the DNA conformational change. The compaction process comprises one linear declining stage and another sigmoid-shaped stage, which can be attributed to the interaction mechanism. Considering the cooperative effect, the sigmoid trend was well explained using a phenomenological model. By contrast, addition of silver nanoparticle solution induced no detectable transition of DNA. The dependence of the interaction on ionic strength and DNA concentration was examined via morphology characterization and particle size distribution measurement. The size of the Ag+-DNA complex decreased with an increase in Ag+ ionic strength ranging from 1 μM to 1 mM. Morphology characterization confirmed that silver ions induced DNA to adopt a compacted globular conformation. At a fixed [AgNO3]:[DNA base pairs] ratio, increasing DNA concentration led to increased sizes of the complexes. Intermolecular interaction is believed to affect the Ag+-DNA complex formation to a large extent.

Particle size and shape modification of hydroxyapatite nanostructures synthesized via a complexing agent-assisted route.

PubMed

Mohandes, Fatemeh; Salavati-Niasari, Masoud

2014-07-01

In this work, hydroxyapatite (HAP), Ca10(PO4)6(OH)2, nanostructures including nanorods, nanobundles and nanoparticles have been prepared via a simple precipitation method. In the present method, Ca(NO3)2·4H2O and (NH4)2HPO4 were used as calcium and phosphorus precursors, respectively. Besides, the Schiff bases derived from 2-hydroxyacetophenone and different diamines were used as complexing agents for the in situ formation of Ca(2+) complexes. The formation mechanism of 0-D and 1-D nanostructures of HAP was also considered. When the complexing agents could coordinate to the Ca(2+) ions through N and O atoms to form the [CaN2O2](2+) complexes, HAP nanoparticles were generated. On the other hand, nanorods and nanobundles of HAP were obtained by forming the [CaN2](2+) as well as [CaO2](2+) complexes in the reaction solution. This work is the first successful synthesis of pure HAP nanostructures in the presence of Schiff bases instead of using the common surfactants. Copyright © 2014 Elsevier B.V. All rights reserved.

Spectroscopic and theoretical studies of charge-transfer interaction of 1-(2-pyridylazo)-2-napthol with nitroaromatics

NASA Astrophysics Data System (ADS)

Karmakar, Animesh; Singh, Bula

2017-05-01

1-(2-Pyridylazo)-2-napthol (hereafter 1Q) is widely used as a chelating ligand applied in chelatometric, spectrophotometric analysis of metal ions. It appeared from the literature survey that no inclusion complex of 1Q was reported with nitroaromatics. The formation of charge-transfer complex gives an opportunity to improve the physico-chemical properties of different donors. So the complex of 1Q with 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP), picric acid (PA), and 3,5-dinitrosalicylic acid (3,5-DNSA) was described in this work in methanol medium. The ground and excited state binding constants and other spectroscopic data have been determined using UV-vis and fluorescence spectroscopic studies. All the complexes have been synthesized and characterized using FT-IR, 1H NMR, and elemental analysis. Spectroscopic data reveal that 1Q joins by a N+sbnd Hsbnd O- type hydrogen bond with nitroaromatics. Job's plot of the continuous variation of absorbance indicates that stoichiometry of CT-complex was 1:1. Thermal stability of the synthesized complex has determined by TGA-DTA analysis. Energy-minimization DFT calculation further supported the formation of the H-bonded charge-transfer adduct.

Functional Groups and Structural Insights of Water-Soluble Organic Carbon using Ultrahigh Resolution FT-ICR Tandem Mass Spectrometry

NASA Astrophysics Data System (ADS)

Mazzoleni, L. R.; Habib, D.; Zhao, Y.; Dalbec, M.; Samburova, V.; Hallar, G.; Zielinska, B.; Lowenthal, D.

2013-12-01

Water-soluble organic carbon (WSOC) is a complex mixture of thousands of organic compounds which may have significant influence on the climate-relevant properties of atmospheric aerosols. An improved understanding of the molecular composition of WSOC is needed to evaluate the effect of aerosol composition upon aerosol physical properties. Products of gas phase, aqueous phase and particle phase reactions contribute to pre-existing aerosol organic mass or nucleate new aerosol particles. Thus, ambient aerosols carry a complex array of WSOC components with variable chemical signatures depending upon its origin and aerosol life-cycle processes. In this work, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize aerosol WSOC collected during the summer of 2010 at the Storm Peak Laboratory (3210 m a.s.l.) near Steamboat Springs, CO. Approximately 4000 molecular formulas were assigned in the mass range of m/z 100-800 after negative-ion electrospray ionization. The observed trends indicate significant non-oxidative accretion reaction pathways for the formation of high molecular weight WSOC components closely associated with terpene ozonolysis secondary organic aerosol (SOA). The aerosol WSOC was further characterized using ultrahigh resolution tandem MS analysis with infrared multiphoton dissociation to determine the functional groups and structural properties of 1700 WSOC species up to m/z 600. Due to the complex nature of the WSOC, multiple precursor ions were simultaneously fragmented. The exact mass measurements of the precursor and product ions facilitated molecular formula assignments and matching of neutral losses. The most important neutral losses are CO2, H2O, CH3OH, HNO3, CH3NO3, SO3 and SO4. The presence and frequency of these losses indicate the type of functional groups contained in the precursor structures. Consistent with the acidic nature of WSOC compounds, the most frequently observed losses were CO2 (~65%), H2O (~60%) and CH3OH (~40%). Several of the studied precursors had two or more losses associated with them and combinations of neutral losses such as, H4O2, CH2O3, C2H4O3 and C2O4. These neutral losses clearly indicate a multifunctional nature of the studied aerosol WSOC. Analysis of the fragment ions which were not associated with typical neutral losses indicates an overall aliphatic SOA-like structure with regular differences of 14 Da and 18 Da between low molecular weight fragment ions. Many of the fragment ions were observed in 85% or more of the MS2 spectra. The patterns observed in the low molecular weight fragment ions were very consistent over all of the mass spectra providing evidence for the significance of the non-oxidative accretion formation pathways.

Alignment and Imaging of the CS2 Dimer Inside Helium Nanodroplets

NASA Astrophysics Data System (ADS)

Pickering, James D.; Shepperson, Benjamin; Hübschmann, Bjarke A. K.; Thorning, Frederik; Stapelfeldt, Henrik

2018-03-01

The carbon disulphide (CS2) dimer is formed inside He nanodroplets and identified using fs laser-induced Coulomb explosion, by observing the CS2+ ion recoil velocity. It is then shown that a 160 ps moderately intense laser pulse can align the dimer in advantageous spatial orientations which allow us to determine the cross-shaped structure of the dimer by analysis of the correlations between the emission angles of the nascent CS2+ and S+ ions, following the explosion process. Our method will enable fs time-resolved structural imaging of weakly bound molecular complexes during conformational isomerization, including formation of exciplexes.

The radiation chemistry of nuclear reactor decontaminating reagents

NASA Astrophysics Data System (ADS)

Sellers, Robin M.

Processes involved in the radiation chemistry of some typical nuclear reactor decontaminating reagents including complexing, reducing and oxidising agents are described. It is concluded that radiation-induced decomposition is only likely to be a problem with dilute formulations, and/or with minor additives such as corrosion inhibitors which are not protected from attack by the other constituents. Addition of a "sacrificial" compound may be necessary to overcome this. The importance of considering loss of function, rather than the decomposition rate of the starting material, is emphasised. Reagents based on low oxidation state metal ions (LOMI) can be regenerated by the radiation field in the presence of formate ion.

MRMer, an interactive open source and cross-platform system for data extraction and visualization of multiple reaction monitoring experiments.

PubMed

Martin, Daniel B; Holzman, Ted; May, Damon; Peterson, Amelia; Eastham, Ashley; Eng, Jimmy; McIntosh, Martin

2008-11-01

Multiple reaction monitoring (MRM) mass spectrometry identifies and quantifies specific peptides in a complex mixture with very high sensitivity and speed and thus has promise for the high throughput screening of clinical samples for candidate biomarkers. We have developed an interactive software platform, called MRMer, for managing highly complex MRM-MS experiments, including quantitative analyses using heavy/light isotopic peptide pairs. MRMer parses and extracts information from MS files encoded in the platform-independent mzXML data format. It extracts and infers precursor-product ion transition pairings, computes integrated ion intensities, and permits rapid visual curation for analyses exceeding 1000 precursor-product pairs. Results can be easily output for quantitative comparison of consecutive runs. Additionally MRMer incorporates features that permit the quantitative analysis experiments including heavy and light isotopic peptide pairs. MRMer is open source and provided under the Apache 2.0 license.

Supramolecular metallogels with complex of phosphonate substituted carbazole derivative and aluminum(III) ion as gelator.

PubMed

Ding, Zicheng; Chen, Bo; Ding, Junqiao; Wang, Lixiang; Han, Yanchun

2014-07-01

Supramolecular metallogels can be gained from the phosphonate substituted 4,4'-bis(N-carbazolyl)biphenyl (PCBP) in the presence of aluminum chloride in alcohols, which can donate oxygen to aid proton transfer in the aluminum organophosphorus complexes. Inside the metallogels, three-dimensional fiber networks with nanofibers entangling and intersecting with each other inside are formed. The nanofibers show layered structures with a period thickness of 0.82 nm. As the content of aluminum(III) increases, the size of the fibers becomes smaller and the fibers pack more densely. It makes the transparent gel become turbid but nevertheless improves the stability of the metallogels. NMR, FT-IR and fluorescence spectroscopy show that the coordination interactions between the phosphonate groups of PCBP molecules and aluminum(III) ions as well as the π-π interactions among PCBP molecules are involved during the gel formation process. Copyright © 2014 Elsevier Inc. All rights reserved.

Modified Ion-Conducting Ceramics Based on Lanthanum Gallate: Synthesis, Structure, and Properties

NASA Astrophysics Data System (ADS)

Kaleva, G. M.; Politova, E. D.; Mosunov, A. V.; Sadovskaya, N. V.

2018-06-01

A review is presented of the synthesis and complex investigation of modified ion-conducting ceramics based on heterosubstituted lanthanum gallate as a promising electrolyte material for solid oxide fuel cells. The effect the composition of multicomponent complex oxides has on the structure, microstructure, and electrophysical properties of ceramics is examined. Samples of ceramics with new compositions are produced via solid-state synthesis and modified with lithium fluoride. A drop is observed in the sintering temperature of the ceramics, caused by the liquid phase mechanism of sintering as a result of the low-melting superstoichiometric quantities of the additive. The effect lithium fluoride has on the process of phase formation, microstructure, and conductivity of the ceramics is investigated. It is found that samples modified with lithium fluoride display high density, dense grain packing, and high values of electrical conductivity at high temperatures.

Study of ion-ion plasma formation in negative ion sources by a three-dimensional in real space and three-dimensional in velocity space particle in cell model

NASA Astrophysics Data System (ADS)

Nishioka, S.; Goto, I.; Miyamoto, K.; Hatayama, A.; Fukano, A.

2016-01-01

Recently, in large-scale hydrogen negative ion sources, the experimental results have shown that ion-ion plasma is formed in the vicinity of the extraction hole under the surface negative ion production case. The purpose of this paper is to clarify the mechanism of the ion-ion plasma formation by our three dimensional particle-in-cell simulation. In the present model, the electron loss along the magnetic filter field is taken into account by the " √{τ///τ⊥ } model." The simulation results show that the ion-ion plasma formation is due to the electron loss along the magnetic filter field. Moreover, the potential profile for the ion-ion plasma case has been looked into carefully in order to discuss the ion-ion plasma formation. Our present results show that the potential drop of the virtual cathode in front of the plasma grid is large when the ion-ion plasma is formed. This tendency has been explained by a relationship between the virtual cathode depth and the net particle flux density at the virtual cathode.

Oligomerisation of Synaptobrevin-2 Studied by Native Mass Spectrometry and Chemical Cross-Linking

NASA Astrophysics Data System (ADS)

Wittig, Sabine; Haupt, Caroline; Hoffmann, Waldemar; Kostmann, Susann; Pagel, Kevin; Schmidt, Carla

2018-06-01

Synaptobrevin-2 is a key player in signal transmission in neurons. It forms, together with SNAP25 and Syntaxin-1A, the neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex and mediates exocytosis of synaptic vesicles with the pre-synaptic membrane. While Synaptobrevin-2 is part of a four-helix bundle in this SNARE complex, it is natively unstructured in the absence of lipids or other SNARE proteins. Partially folded segments, presumably SNARE complex formation intermediates, as well as formation of Synaptobrevin-2 dimers and oligomers, were identified in previous studies. Here, we employ three Synaptobrevin-2 variants—the full-length protein Syb(1-116), the soluble, cytosolic variant Syb(1-96) as well as a shorter version Syb(49-96) containing structured segments but omitting a trigger site for SNARE complex formation—to study oligomerisation in the absence of interaction partners or when incorporated into the lipid bilayer of liposomes. Combining native mass spectrometry with chemical cross-linking, we find that the truncated versions show increased oligomerisation. Our findings from both techniques agree well and confirm the presence of oligomers in solution while membrane-bound Synaptobrevin-2 is mostly monomeric. Using ion mobility mass spectrometry, we could further show that lower charge states of Syb(49-96) oligomers, which most likely represent solution structures, follow an isotropic growth curve suggesting that they are intrinsically disordered. From a technical point of view, we show that the combination of native ion mobility mass spectrometry with chemical cross-linking is well-suited for the analysis of protein homo-oligomers. [Figure not available: see fulltext.

Anionic Palladium(0) and Palladium(II) Ate Complexes.

PubMed

Kolter, Marlene; Böck, Katharina; Karaghiosoff, Konstantin; Koszinowski, Konrad

2017-10-16

Palladium ate complexes are frequently invoked as important intermediates in Heck and cross-coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray-ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron-poor catalyst [L 3 Pd] (L=tris[3,5-bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br - ions to afford the anionic, zero-valent ate complex [L 3 PdBr] - . In contrast, more-electron-rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L 3 Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the Pd II ate complex [L 2 Pd(Ar)I 2 ] - . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Argon ion beam induced surface pattern formation on Si

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

Hofsäss, H.; Bobes, O.; Zhang, K.

The development of self-organized surface patterns on Si due to noble gas ion irradiation has been studied extensively in the past. In particular, Ar ions are commonly used and the pattern formation was analyzed as function of ion incidence angle, ion fluence, and ion energies between 250 eV and 140 keV. Very few results exist for the energy regime between 1.5 keV and 10 keV and it appears that pattern formation is completely absent for these ion energies. In this work, we present experimental data on pattern formation for Ar ion irradiation between 1 keV and 10 keV and ion incidence angles between 50° and 75°.more » We confirm the absence of patterns at least for ion fluences up to 10{sup 18} ions/cm{sup 2}. Using the crater function formalism and Monte Carlo simulations, we calculate curvature coefficients of linear continuum models of pattern formation, taking into account contribution due to ion erosion and recoil redistribution. The calculations consider the recently introduced curvature dependence of the erosion crater function as well as the dynamic behavior of the thickness of the ion irradiated layer. Only when taking into account these additional contributions to the linear theory, our simulations clearly show that that pattern formation is strongly suppressed between about 1.5 keV and 10 keV, most pronounced at 3 keV. Furthermore, our simulations are now able to predict whether or not parallel oriented ripple patterns are formed, and in case of ripple formation the corresponding critical angles for the whole experimentally studied energies range between 250 eV and 140 keV.« less

Adsorption of aliphatic polyhydroxy carboxylic acids on gibbsite: pH dependency and importance of adsorbate structure.

PubMed

Schneckenburger, Tatjana; Riefstahl, Jens; Fischer, Klaus

2018-01-01

Aliphatic (poly)hydroxy carboxylic acids [(P)HCA] occur in natural, e.g. soils, and in technical (waste disposal sites, nuclear waste repositories) compartments . Their distribution, mobility and chemical reactivity, e.g. complex formation with metal ions and radionuclides, depend, among others, on their adsorption onto mineral surfaces. Aluminium hydroxides, e.g. gibbsite [α-Al(OH) 3 ], are common constituents of related solid materials and mimic the molecular surface properties of clay minerals. Thus, the study was pursued to characterize the adsorption of glycolic, threonic, tartaric, gluconic, and glucaric acids onto gibbsite over a wide pH and (P)HCA concentration range. To consider specific conditions occurring in radioactive wastes, adsorption applying an artificial cement pore water (pH 13.3) as solution phase was investigated additionally. The sorption of gluconic acid at pH 4, 7, 9, and 12 was best described by the "two-site" Langmuir isotherm, combining "high affinity" sorption sites (adsorption affinity constants [Formula: see text] > 1 L mmol -1 , adsorption capacities < 6.5 mmol kg -1 ) with "low affinity" sites ([Formula: see text] < 0.1 L mmol -1 , adsorption capacities ≥ 19 mmol kg -1 ). The total adsorption capacities at pH 9 and 12 were roughly tenfold of that at pH 4 and 7. The S-shaped pH sorption edge of gluconic acid was modelled applying a constant capacitance model, considering electrostatic interactions, hydrogen bonding, surface complex formation, and formation of solved polynuclear complexes between Al 3+ ions and gluconic acid. A Pearson and Spearman rank correlation between (P)HCA molecular properties and adsorption parameters revealed the high importance of the size and the charge of the adsorbates. The adsorption behaviour of (P)HCAs is best described by a combination of adsorption properties of carboxylic acids at acidic pH and of polyols at alkaline pH. Depending on the molecular properties of the adsorbates and on pH, electrostatic interactions, hydrogen bonding, and ternary surface complexation contribute in varying degrees to the adsorption process. Linear distribution coefficients K d between 8.7 and 60.5 L kg -1 (1 mmol L -1 initial PHCA concentration) indicate a considerable mineral surface affinity at very high pH, thus lowering the PHCA fraction available for the complexation of metal ions including radionuclides in solution and their subsequent mobilization.

The potential of at-home prediction of the formation of urolithiasis by simple multi-frequency electrical conductivity of the urine and the comparison of its performance with urine ion-related indices, color and specific gravity.

PubMed

Silverio, Angelito A; Chung, Wen-Yaw; Cheng, Cheanyeh; Wang, Hai-Lung; Kung, Chien-Min; Chen, Jun; Tsai, Vincent F S

2016-04-01

It is important to control daily diet, water intake and life style as well as monitor the quality of urine for urolithiasis prevention. For decades, many ion-related indices have been developed for predicting the formation of urinary stones or urolithiasis, such as EQUILs, relative supersaturation (RSS), Tiselius indices (TI), Robertson risk factor algorithms (RRFA) and more recently, the Bonn risk index. However, they mostly demand robust laboratory analysis, are work-intensive, and even require complex computational programs to get the concentration patterns of several urine analytes. A simple and fast platform for measuring multi-frequency electrical conductivity (MFEC) of morning spot urine (random urine) to predict the onset of urolithiasis was implemented in this study. The performance thereof was compared to ion-related indices, urine color and specific gravity. The concentrations of relevant ions, color, specific gravity (SG) and MFEC (MFEC tested at 1, 10, 100, 5001 KHz and 1 MHz) of 80 random urine samples were examined after collection. Then, the urine samples were stored at 4 °C for 24 h to determine whether sedimentation would occur or not. Ion-activity product index of calcium oxalate (AP(CaOx) EQ2) was calculated. The correlation between AP(CaOx) EQ2, urine color, SG and MFEC were analyzed. AP(CaOx) EQ2, urine color and MFEC (at 5 frequencies) all demonstrated good prediction (p = 0.01, 0.01, 0.01, respectively) for stone formation. The positive correlation between AP(CaOx) EQ2 and MFEC is also significant (p = 0.01). MFEC provides a good metric for predicting the onset of urolithiasis, which is comparable to conventional ion-related indices and urine color. This technology can be implemented with much ease for objectively monitoring the quality of urine at points-of-care or at home.

Deprotonation effect of tetrahydrofuran-2-carbonitrile buffer gas dopant in ion mobility spectrometry.

PubMed

Fernandez-Maestre, Roberto; Meza-Morelos, Dairo; Wu, Ching

2016-06-15

When dopants are introduced into the buffer gas of an ion mobility spectrometer, spectra are simplified due to charge competition. We used electrospray ionization to inject tetrahydrofuran-2-carbonitrile (F, 2-furonitrile or 2-furancarbonitrile) as a buffer gas dopant into an ion mobility spectrometer coupled to a quadrupole mass spectrometer. Density functional theory was used for theoretical calculations of dopant-ion interaction energies and proton affinities, using the hybrid functional X3LYP/6-311++(d,p) with the Gaussian 09 program that accounts for the basis set superposition error; analytes structures and theoretical calculations with Gaussian were used to explain the behavior of the analytes upon interaction with F. When F was used as a dopant at concentrations below 1.5 mmol m(-3) in the buffer gas, ions were not observed for α-amino acids due to charge competition with the dopant; this deprotonation capability arises from the production of a dimer with a high formation energy that stabilized the positive charge and created steric hindrance that deterred the equilibrium with analyte ions. F could not completely strip other compounds of their charge because they either showed steric hindrance at the charge site that deterred the approach of the dopant (2,4-lutidine, and DTBP), formed intramolecular bonds that stabilized the positive charge (atenolol), had high proton affinity (2,4-lutidine, DTBP, valinol and atenolol), or were inherently ionic (tetraalkylammonium ions). This selective deprotonation suggests the use of F to simplify spectra of complex mixtures in ion mobility and mass spectrometry in metabolomics, proteomics and other studies that generate complex spectra with thousands of peaks. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Density functional theory and RRKM calculations of decompositions of the metastable E-2,4-pentadienal molecular ions.

PubMed

Solano Espinoza, Eduardo A; Vallejo Narváez, Wilmer E

2010-07-01

The potential energy profiles for the fragmentations that lead to [C(5)H(5)O](+) and [C(4)H(6)](+*) ions from the molecular ions [C(5)H(6)O](+*) of E-2,4-pentadienal were obtained from calculations at the UB3LYP/6-311G + + (3df,3pd)//UB3LYP/6-31G(d,p) level of theory. Kinetic barriers and harmonic frequencies obtained by the density functional method were then employed in Rice-Ramsperger-Kassel-Marcus calculations of individual rate coefficients for a large number of reaction steps. The pre-equilibrium and rate-controlling step approximations were applied to different regions of the complex potential energy surface, allowing the overall rate of decomposition to be calculated and discriminated between three rival pathways: C-H bond cleavage, decarbonylation and cyclization. These processes should have to compete for an equilibrated mixture of four conformers of the E-2,4-pentadienal ions. The direct dissociation, however, can only become important in the high-energy regime. In contrast, loss of CO and cyclization are observable processes in the metastable kinetic window. The former involves a slow 1,2-hydrogen shift from the carbonyl group that is immediately followed by the formation of an ion-neutral complex which, in turn, decomposes rapidly to the s-trans-1,3-butadiene ion [C(4)H(6)](+*). The predominating metastable channel is the second one, that is, a multi-step ring closure which starts with a rate-limiting cis-trans isomerization. This process yields a mixture of interconverting pyran ions that dissociates to the pyrylium ions [C(5)H(5)O](+). These results can be used to rationalize the CID mass spectrum of E-2,4-pentadienal in a low-energy regime. 2010 John Wiley & Sons, Ltd.

Chemical speciation and recovery of gold(I, III) from wastewater and silver by liquid-liquid extraction with the ion-pair reagent amiloride mono hydrochloride and AAS determination.

PubMed

El-Shahawi, M S; Bashammakh, A S; Bahaffi, S O

2007-06-15

A novel and low cost liquid-liquid extraction procedure for the separation of gold(III) at trace level from aqueous medium of pH 5-9 has been developed. The method has been based upon the formation of a yellow colored ternary complex ion associate of tetrachloro gold(III) complex anion, AuCl(4)(-) with the ion-pair reagent 1-(3,5-diamino-6-chloropyrazinecarboxyl) guanidine hydrochloride monohydrate, namely amiloride, DPG(+).Cl(-). The effect of various parameters, e.g. pH, organic solvent, shaking time, etc. on the preconcentration of gold(III) from the aqueous media by the DPG(+).Cl(-) reagent has been investigated. The colored gold species was quantitatively extracted into 4-methyl pentan-2-one. The chemical composition of the ion associate of DPG(+).Cl(-) with AuCl(4)(-) in the organic solvent has been determined by the Job's method. The molar absorptivity (2.19x10(4)Lmol(-1)cm(-1)) of the associate DPG(+).AuCl(4)(-) at 362nm enabled a convenient application of the developed extraction procedure for the separation and AAS determination of traces of aurate ions. Mono-valence gold ions after oxidation to gold(III) with bromine water in HCl (1.0molL(-1)) media have been also extracted quantitatively from the aqueous media by the developed procedure. The chemical speciation of mono- and/or tri-valence gold species spiked to fresh and industrial wastewater samples has been achieved. The method has been also applied successfully from the separation of gold(I) and gold(III) species from metallic ions and silver. The developed method has also the advantage of freedom from most diverse ions.

Struvite crystal growth inhibition by trisodium citrate and the formation of chemical complexes in growth solution

NASA Astrophysics Data System (ADS)

Prywer, Jolanta; Mielniczek-Brzóska, Ewa; Olszynski, Marcin

2015-05-01

Effect of trisodium citrate on the crystallization of struvite was studied. To evaluate such an effect an experiment of struvite growth from artificial urine was performed. The investigations are related to infectious urinary stones formation. The crystallization process was induced by the addition of aqueous ammonia solution to mimic the bacterial activity. The spectrophotometric results demonstrate that trisodium citrate increases induction time with respect to struvite formation and decreases the growth efficiency of struvite. The inhibitory effect of trisodium citrate on the nucleation and growth of struvite is explained in base of chemical speciation analysis. Such an analysis demonstrates that the inhibitory effect is related with the fact that trisodium citrate binds NH4 + and Mg2+ ions in the range of pH from 7 to 9.5 characteristic for struvite precipitation. The most important is the MgCit- complex whose concentration strongly depends on an increase in pH rather than on an increase in citrate concentrations.

The linear and non-linear characterization of dust ion acoustic mode in complex plasma in presence of dynamical charging of dust

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

Bhattacharjee, Saurav, E-mail: sauravtsk.bhattacharjee@gmail.com; Das, Nilakshi

2015-10-15

A systematic theoretical investigation has been carried out on the role of dust charging dynamics on the nature and stability of DIA (Dust Ion Acoustic) mode in complex plasma. The study has been made for both linear and non-linear scale regime of DIA mode. The observed results have been characterized in terms of background plasma responses towards dust surface responsible for dust charge fluctuation, invoking important dusty plasma parameters, especially the ion flow speed and dust size. The linear analyses confirm the nature of instability in DIA mode in presence of dust charge fluctuation. The instability shows a damping ofmore » DIA mode in subsonic flow regime followed by a gradual growth in instability in supersonic limit of ion flow. The strength of non-linearity and their existence domain is found to be driven by different dusty plasma parameters. As dust is ubiquitous in interstellar medium with plasma background, the study also addresses the possible effect of dust charging dynamics in gravito-electrostatic characterization and the stability of dust molecular clouds especially in proto-planetary disc. The observations are influential and interesting towards the understanding of dust settling mechanism and formation of dust environments in different regions in space.« less

Combining the Power of Irmpd with Ion-Molecule Reactions: the Structure and Reactivity of Radical Ions of Cysteine and its Derivatives

NASA Astrophysics Data System (ADS)

Lesslie, Michael; Osburn, Sandra; Berden, Giel; Oomens, J.; Ryzhov, Victor

2015-06-01

Most of the work on peptide radical cations has involved protons as the source of charge. Nonetheless, using metal ions as charge sources often offers advantages like stabilization of the structure via multidentate coordination and the elimination of the "mobile proton". Moreover, characterization of metal-bound amino acids is of general interest as the interaction of peptide side chains with metal ions in biological systems is known to occur extensively. In the current study, we generate thiyl radicals of cysteine and homocysteine in the gas phase complexed to alkali metal ions. Subsequently, we utilize infrared multiple-photon dissociation (IRMPD) and ion-molecule reactions (IMR) to characterize the structure and reactivity of these radical ions. Our group has worked extensively with the cysteine-based radical cations and anions, characterizing the gas-phase reactivity and rearrangement of the amino acid and several of its derivatives. In a continuation of this work, we are perusing the effects of metal ions as the charge bearing species on the reactivity of the sulfur radical. Our S-nitroso chemistry can easily be used in conjunction with metal ion coordination to produce initial S-based radicals in peptide radical-metal ion complexes. In all cases we have been able to achieve radical formation with significant yield to study reactivity. Ion-molecule reactions of metallated radicals with allyl iodide, dimethyl disulfide, and allyl bromide have all shown decreasing reactivity going down group 1A. Recently, we determined the experimental IR spectra for the homocysteine radical cation with Li+, Na+, and K+ as the charge bearing species at the FELIX facility. For comparison, the protonated IR spectrum of homocysteine has previously been obtained by our group. A preliminary match of the IR spectra has been confirmed. Finally, calculations are underway to determine the bond distances of all the metal adduct structures.

DOTA analogues with a phosphinate-iminodiacetate pendant arm: modification of the complex formation rate with a strongly chelating pendant.

PubMed

Procházková, Soňa; Kubíček, Vojtěch; Böhmová, Zuzana; Holá, Kateřina; Kotek, Jan; Hermann, Petr

2017-08-08

The new ligand H 6 do3aP ida combines the macrocyclic DOTA-like cavity and the open-chain iminodiacetate group connected through a coordinating phosphinate spacer. Its acid-base and coordination properties in solution were studied by potentiometry. Thermodynamic coordination characteristics of both chelating units are similar to those reported for H 4 dota and iminodiacetic acid themselves, respectively, so, macrocyclic and iminodiacetate units behave independently. The formation kinetics of the Ce(iii)-H 6 do3aP ida complex was studied by UV-Vis spectrophotometry. Various out-of-cage intermediates were identified with 1 : 1, 1 : 2 and 2 : 1 ligand-to-metal ratios. The presence of the strongly coordinating iminodiacetate group significantly slows down the metal ion transfer into the macrocyclic cavity and, so, the formation of the in-cage complex is two orders of magnitude slower than that reported for the Ce(iii)-H 4 dota system. The kinetic inertness of the [Ce(do3aP ida )] 3- complex towards acid-assisted dissociation is comparable to that of the [Ce(dota)] - complex. The coordination modes of the ligand are demonstrated in the solid-state structure of [Cu 4 (do3aP ida )(OH)(H 2 O) 4 ]Cl·7.5H 2 O.

Formation and Fragmentation Chemistry of Tripositive Ln(TMGA)33+ Complexes in the Gas Phase.

PubMed

Chen, Xiuting; Li, Qingnuan; Gong, Yu

2017-08-01

Electrospray ionization (ESI) of LnCl 3 (Ln = La-Lu except Pm) and TMGA (tetramethyl glutaramide) mixtures resulted in the formation of gas-phase Ln(TMGA) 3 3+ complexes, where tripositive lanthanide cation was coordinated by three neutral TMGA ligands. Collision induced dissociation (CID) was employed to investigate the fragmentation chemistry of these tripositive complexes. Ln(TMGA) 2 (TMGA- 45) 3+ resulting from C carbonyl -N bond cleavage of TMGA and hydrogen transfer is the major CID product for all Ln(TMGA) 3 3+ except Eu(TMGA) 3 3+ which predominantly forms divalent Eu II (TMGA) 2 2+ complex via loss of TMGA + . Analogous Yb II (TMGA) 2 2+ and Sm II (TMGA) 2 2+ complexes arising from charge reduction were also observed, in competition with the formation of charge conserving Yb III (TMGA)(TMGA-H) 2+ and Sm III (TMGA)(TMGA-H) 2+ products. The yield of these charge reducing products follows their reduction potentials in condensed phase. In addition to Ln(TMGA) 3 3+ , tripositive ions such as Ln(TMGA) 4 3+ and Ln(TMGA) 2 3+ were experimentally identified as well. While the former was observed along with Ln(TMGA) 3 3+ during ESI, the latter was observed upon CID of Ln(TMGA) 3 3+ , suggesting two TMGA molecules can stabilize Ln 3+ in the gas phase. Graphical Abstract ᅟ.

Orthogonal projection approach and continuous wavelet transform-feed forward neural networks for simultaneous spectrophotometric determination of some heavy metals in diet samples.

PubMed

Abbasi Tarighat, Maryam

2016-02-01

Simultaneous spectrophotometric determination of a mixture of overlapped complexes of Fe(3+), Mn(2+), Cu(2+), and Zn(2+) ions with 2-(3-hydroxy-1-phenyl-but-2-enylideneamino) pyridine-3-ol(HPEP) by orthogonal projection approach-feed forward neural network (OPA-FFNN) and continuous wavelet transform-feed forward neural network (CWT-FFNN) is discussed. Ionic complexes HPEP were formulated with varying reagent concentration, pH and time of color formation for completion of complexation reactions. It was found that, at 5.0 × 10(-4) mol L(-1) of HPEP, pH 9.5 and 10 min after mixing the complexation reactions were completed. The spectral data were analyzed using partial response plots, and identified non-linearity modeled using FFNN. Reducing the number of OPA-FFNN and CWT-FFNN inputs were simplified using dissimilarity pure spectra of OPA and selected wavelet coefficients. Once the pure dissimilarity plots ad optimal wavelet coefficients are selected, different ANN models were employed for the calculation of the final calibration models. The performance of these two approaches were tested with regard to root mean square errors of prediction (RMSE %) values, using synthetic solutions. Under the working conditions, the proposed methods were successfully applied to the simultaneous determination of metal ions in different vegetable and foodstuff samples. The results show that, OPA-FFNN and CWT-FFNN were effective in simultaneously determining Fe(3+), Mn(2+), Cu(2+), and Zn(2+) concentration. Also, concentrations of metal ions in the samples were determined by flame atomic absorption spectrometry (FAAS). The amounts of metal ions obtained by the proposed methods were in good agreement with those obtained by FAAS. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sculpting Nanoscale Functional Channels in Complex Oxides Using Energetic Ions and Electrons

DOE PAGES

Sachan, Ritesh; Zarkadoula, Eva; Ou, Xin; ...

2018-04-26

The formation of metastable phases has attracted significant attention because of their unique properties and potential functionalities. In the present study, we demonstrate the phase conversion of energetic-ion-induced amorphous nanochannels/tracks into a metastable defect fluorite in A 2B 2O 7 structured complex oxides by electron irradiation. Through in situ electron irradiation experiments in a scanning transmission electron microscope, we observe electron-induced epitaxial crystallization of the amorphous nanochannels in Yb 2Ti 2O 7 into the defect fluorite. This energetic-electron-induced phase transformation is attributed to the coupled effect of ionization-induced electronic excitations and local heating, along with subthreshold elastic energy transfers. Wemore » also show the role of ionic radii of A-site cations (A = Yb, Gd, and Sm) and B-site cations (Ti and Zr) in facilitating the electron-beam-induced crystallization of the amorphous phase to the defect-fluorite structure. The formation of the defect-fluorite structure is eased by the decrease in the difference between ionic radii of A- and B-site cations in the lattice. Molecular dynamics simulations of thermal annealing of the amorphous phase nanochannels in A 2B 2O 7 draw parallels to the electron-irradiation-induced crystallization and confirm the role of ionic radii in lowering the barrier for crystallization. Furthermore, these results suggest that employing guided electron irradiation with atomic precision is a useful technique for selected area phase formation in nanoscale printed devices.« less

Sculpting Nanoscale Functional Channels in Complex Oxides Using Energetic Ions and Electrons

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

Sachan, Ritesh; Zarkadoula, Eva; Ou, Xin

The formation of metastable phases has attracted significant attention because of their unique properties and potential functionalities. In the present study, we demonstrate the phase conversion of energetic-ion-induced amorphous nanochannels/tracks into a metastable defect fluorite in A 2B 2O 7 structured complex oxides by electron irradiation. Through in situ electron irradiation experiments in a scanning transmission electron microscope, we observe electron-induced epitaxial crystallization of the amorphous nanochannels in Yb 2Ti 2O 7 into the defect fluorite. This energetic-electron-induced phase transformation is attributed to the coupled effect of ionization-induced electronic excitations and local heating, along with subthreshold elastic energy transfers. Wemore » also show the role of ionic radii of A-site cations (A = Yb, Gd, and Sm) and B-site cations (Ti and Zr) in facilitating the electron-beam-induced crystallization of the amorphous phase to the defect-fluorite structure. The formation of the defect-fluorite structure is eased by the decrease in the difference between ionic radii of A- and B-site cations in the lattice. Molecular dynamics simulations of thermal annealing of the amorphous phase nanochannels in A 2B 2O 7 draw parallels to the electron-irradiation-induced crystallization and confirm the role of ionic radii in lowering the barrier for crystallization. Furthermore, these results suggest that employing guided electron irradiation with atomic precision is a useful technique for selected area phase formation in nanoscale printed devices.« less

Synergism of Saturn, Enceladus and Titan and Formation of HCNO Prebiotic Molecules

NASA Technical Reports Server (NTRS)

Sittler, Edward C.; Cooper, John F.

2011-01-01

Saturn as a system has two very exotic moons Titan and Enceladus. Titan, taking in energy from Saturn's magnetosphere, solar UV irradiation, and cosmic rays, can make HCN based molecules as discussed in earlier paper by Raulin and Owen. Space radiation effects at both moons, and as coupled by the Saturn magnetosphere, could cause an unexpected series of events potentially leading to prebiotic chemical evolution at Titan with HCNO from magnetospheric oxygen as the new ingredient. The "Old Faithful" model suggests that Enceladus, highly irradiated by Saturn magnetospheric electrons and thus having a source of chemical energy from radiolytic gas production, has episodic ejections of water vapor, carbon dioxide, and various hydrocarbons into Saturn's magnetosphere. The hydrocarbons do not survive transport through the plasma environment, but oxygen ions from Enceladus water molecules become the dominant ion species in the outer magnetosphere. At Titan, Cassini discovered that 1) keV oxygen ions, evidently from Enceladus, are bombarding Titan's upper atmosphere and 2) heavy positive and negative ions exist in significant abundances within Titan's upper atmosphere. Initial models of heavy ion formation in Titan's upper atmosphere invoked polymerization of aromatics such as benzenes and their radicals to make polycyclic aromatic hydrocarbons (PAH) , while a more recent model by Sittler et al., has raised the possibility of carbon chains forming from the polymerization of acetylene and its radicals to make fullerenes. Laboratory measurements indicate that fullerenes, which are hollow carbon shells, can trap keV oxygen ions. Clustering of the fullerenes with aerosol mixtures from PAHs and the dominant nitrogen molecules could form larger aerosols enriched in trapped oxygen. Aerosol precipitation could then convey these chemically complex structures deeper into the atmosphere and to the moon surface. Ionizing solar UV, magnetospheric electron, and galactic cosmic ray irradiation would provide further energy for processing into more complex organic forms. Further ionizing irradiation from cosmic rays deep in the atmosphere "tho lin" molecules are produced with all the molecular components present from which prebiotic organic molecules can form. This synergy of Saturn system, exogenic irradiation, and molecular processes provides a potential pathway for accumulation of prebiotic chemistry on the surface of Titan. Since fullerenes are also thought to exist in interstellar space, similar processes may also occur there to seed molecular clouds with prebiotic chemical species. We will also discuss possible future laboratory experiments that could be done to investigate fullerene formation at Titan and the trapping of oxygen in fullerenes.

Elucidation of metal-ion accumulation induced by hydrogen bonds on protein surfaces by using porous lysozyme crystals containing Rh(III) ions as the model surfaces.

PubMed

Ueno, Takafumi; Abe, Satoshi; Koshiyama, Tomomi; Ohki, Takahiro; Hikage, Tatsuo; Watanabe, Yoshihito

2010-03-01

Metal-ion accumulation on protein surfaces is a crucial step in the initiation of small-metal clusters and the formation of inorganic materials in nature. This event is expected to control the nucleation, growth, and position of the materials. There remain many unknowns, as to how proteins affect the initial process at the atomic level, although multistep assembly processes of the materials formation by both native and model systems have been clarified at the macroscopic level. Herein the cooperative effects of amino acids and hydrogen bonds promoting metal accumulation reactions are clarified by using porous hen egg white lysozyme (HEWL) crystals containing Rh(III) ions, as model protein surfaces for the reactions. The experimental results reveal noteworthy implications for initiation of metal accumulation, which involve highly cooperative dynamics of amino acids and hydrogen bonds: i) Disruption of hydrogen bonds can induce conformational changes of amino-acid residues to capture Rh(III) ions. ii) Water molecules pre-organized by hydrogen bonds can stabilize Rh(III) coordination as aqua ligands. iii) Water molecules participating in hydrogen bonds with amino-acid residues can be replaced by Rh(III) ions to form polynuclear structures with the residues. iv) Rh(III) aqua complexes are retained on amino-acid residues through stabilizing hydrogen bonds even at low pH (approximately 2). These metal-protein interactions including hydrogen bonds may promote native metal accumulation reactions and also may be useful in the preparation of new inorganic materials that incorporate proteins.

Possible steric control of the relative strength of chelation enhanced fluorescence for zinc(II) compared to cadmium(II): metal ion complexing properties of tris(2-quinolylmethyl)amine, a crystallographic, UV-visible, and fluorometric study.

PubMed

Williams, Neil J; Gan, Wei; Reibenspies, Joseph H; Hancock, Robert D

2009-02-16

The idea is examined that steric crowding in ligands can lead to diminution of the chelation enhanced fluorescence (CHEF) effect in complexes of the small Zn(II) ion as compared to the larger Cd(II) ion. Steric crowding is less severe for the larger ion and for the smaller Zn(II) ion leads to Zn-N bond length distortion, which allows some quenching of fluorescence by the photoinduced electron transfer (PET) mechanism. Some metal ion complexing properties of the ligand tris(2-quinolylmethyl)amine (TQA) are presented in support of the idea that more sterically efficient ligands, which lead to less M-N bond length distortion with the small Zn(II) ion, will lead to a greater CHEF effect with Zn(II) than Cd(II). The structures of [Zn(TQA)H(2)O](ClO(4))(2).1.5 H(2)O (1), ([Pb(TQA)(NO(3))(2)].C(2)H(5)OH) (2), ([Ag(TQA)(ClO(4))]) (3), and (TQA).C(2)H(5)OH (4) are reported. In 1, the Zn(II) is 5-coordinate, with four N-donors from the ligand and a water molecule making up the coordination sphere. The Zn-N bonds are all of normal length, showing that the level of steric crowding in 1 is not sufficient to cause significant Zn-N bond length distortion. This leads to the observation that, as expected, the CHEF effect in the Zn(II)/TQA complex is much stronger than that in the Cd(II)/TQA complex, in contrast to similar but more sterically crowded ligands, where the CHEF effect is stronger in the Cd(II) complex. The CHEF effect for TQA with the metal ions examined varies as Zn(II) > Cd(II) > Ni(II) > Pb(II) > Hg(II) > Cu(II). The structure of 2 shows an 8-coordinate Pb(II), with evidence of a stereochemically active lone pair, and normal Pb-N bond lengths. In 3, the Ag(I) is 5-coordinate, with four N-donors from the TQA and an oxygen from the perchlorate. The Ag(I) shows no distortion toward linear 2-coordinate geometry, and the Ag-N bonds fall slightly into the upper range for Ag-N bonds in 5-coordinate complexes. The structure of 4 shows the TQA ligand to be involved in pi-stacking between quinolyl groups from adjacent TQA molecules. Formation constants determined by UV-visible spectroscopy are reported in 0.1 M NaClO(4) at 25 degrees C for TQA with Zn(II), Cd(II), and Pb(II). When compared with other similar ligands, one sees that, as the level of steric crowding increases, the stability decreases most with the small Zn(II) ion and least with the large Pb(II) ion. This is in accordance with the idea that TQA has a moderate level of steric crowding and that steric crowding increases for TQA analogs tris(2-pyridylmethyl)amine (TPyA) < TQA < tris(6-methyl-2-pyridyl)amine (TMPyA).

Formation of ion-pairs in aqueous solutions of diclofenac salts.

PubMed

Fini, A; Fazio, G; Gonzalez-Rodriguez, M; Cavallari, C; Passerini, N; Rodriguez, L

1999-10-05

In this work we studied the ability of the diclofenac anion to form ion-pairs in aqueous solution in the presence of organic and inorganic cations: ion-pairs have a polarity and hydrophobicity more suitable to the partition than each ion considered separately and can be extracted by a lipid phase. The cations considered were those of the organic bases diethylamine, diethanolamine, pyrrolidine, N-(2-hydroxyethyl) pyrrolidine and N-(2-hydroxyethyl) piperidine; the inorganic cations studied were Li(+), Na(+), K(+), Rb(+), Cs(+). Related to each cation we determined the equilibrium constant (K(XD)) for the ion-pair formation with the diclofenac anion in aqueous solution and the water/n-octanol partition coefficient (P(XD)) for each type of ion-pair formed. Among the alkali metal cations, only Li(+) shows some interaction with the diclofenac anion, in agreement with its physiological behaviour of increasing clearance during the administration of diclofenac. The influence of the ionic radius and desolvation enthalpy of the alkali metal cations on the ion-pair formation and partition was briefly discussed. Organic cations promote the formation of ion-pairs with the diclofenac anion better than the inorganic ones, and improve the partition of the ion-pair according to their hydrophobicity. The values of the equilibrium parameters for the formation and partition of ion-pairs are not high enough to allow the direct detection of their presence in the aqueous solution. Their formation can be appreciated in the presence of a lipid phase that continuously extracts the ion-pair. Extraction constants (E(XD)=P(XD) times K(XD)) increase passing from inorga to organic cations. This study could help to clarify the mechanism of the percutaneous absorption of diclofenac in the form of a salt, a route where the formation of ion-pairs appears to play an important role.

Engineering electron metabolism to increase ethanol production in Clostridium thermocellum.

PubMed

Lo, Jonathan; Olson, Daniel G; Murphy, Sean Jean-Loup; Tian, Liang; Hon, Shuen; Lanahan, Anthony; Guss, Adam M; Lynd, Lee R

2017-01-01

The NfnAB (NADH-dependent reduced ferredoxin: NADP + oxidoreductase) and Rnf (ion-translocating reduced ferredoxin: NAD + oxidoreductase) complexes are thought to catalyze electron transfer between reduced ferredoxin and NAD(P) + . Efficient electron flux is critical for engineering fuel production pathways, but little is known about the relative importance of these enzymes in vivo. In this study we investigate the importance of the NfnAB and Rnf complexes in Clostridium thermocellum for growth on cellobiose and Avicel using gene deletion, enzyme assays, and fermentation product analysis. The NfnAB complex does not seem to play a major role in metabolism, since deletion of nfnAB genes had little effect on the distribution of fermentation products. By contrast, the Rnf complex appears to play an important role in ethanol formation. Deletion of rnf genes resulted in a decrease in ethanol formation. Overexpression of rnf genes resulted in an increase in ethanol production of about 30%, but only in strains where the hydG hydrogenase maturation gene was also deleted. Copyright © 2016 International Metabolic Engineering Society. All rights reserved.

Ionization dynamics of the water trimer: A direct ab initio MD study

NASA Astrophysics Data System (ADS)

Tachikawa, Hiroto; Takada, Tomoya

2013-03-01

Ionization dynamics of the cyclic water trimer (H2O)3 have been investigated by means of direct ab initio molecular dynamics (AIMD) method. Two reaction channels, complex formation and OH dissociation, were found following the ionization of (H2O)3. In both channels, first, a proton was rapidly transferred from H2O+ to H2O (time scale is ˜15 fs after the ionization). In complex channel, an ion-radical contact pair (H3O+-OH) solvated by the third water molecule was formed as a long-lived H3O+(OH)H2O complex. In OH dissociation channel, the second proton transfer further takes place from H3O+(OH) to H2O (time scale is 50-100 fs) and the OH radical is separated from the H3O+. At the same time, the OH dissociation takes place when the excess energy is efficiently transferred into the kinetic energy of OH radical. The OH dissociation channel is significantly minor, and almost all product channels were the complex formation. The reaction mechanism was discussed on the basis of theoretical results.

Designing functionality in perovskite thin films using ion implantation techniques: Assessment and insights from first-principles calculations

DOE PAGES

Sharma, Vinit K.; Herklotz, Andreas; Ward, Thomas Zac; ...

2017-09-11

Ion implantation has been widely used in the semiconductor industry for decades to selectively control electron/hole doping for device applications. Recently, experimental studies on ion implantation into more structurally and electronically complex materials have been undertaken in which defect generation has been used to control a variety of functional phenomena. Of particular interest, are recent findings demonstrating that low doses of low energy helium ions into single crystal films can be used to tailor the structural properties. These initial experimental studies have shown that crystal symmetry can be continuously controlled by applying increasingly large doses of He ions into amore » crystal. The observed changes in lattice structure were then observed to correlate with functional changes, such as metal-insulator transition temperature2 and optical bandgap3. In these preliminary experimental studies, changes to lattice expansion was proposed to be the direct result of chemical pressure originating predominantly from the implanted He applying chemical pressure at interstitial sites. However, the influence of possible secondary knock-on damage arising from the He atoms transferring energy to the lattice through nuclear-nuclear collision with the crystal lattice remains largely unaddressed. In this work, we focus on a SrRuO3 model system to provide a comprehensive examination of the impact of common defects on structural and electronic properties, obtain calculated defect formation energies, and define defect migration barriers. Our model indicates that, while interstitial He can modify the crystal properties, a dose significantly larger than those reported in experimental studies would be required. The true origin of the observed structural changes is likely the result of a combination of secondary defects created during He implantation. Of particular importance, we observe that different defect types can generate greatly varied local electronic structures and that the formation energies and migration energy barriers vary by defect type. Thus, we may have identified a new method of selectively inducing controlled defect complexes into single crystal materials. Development of this approach would have a broad impact on both our ability to probe specific defect contributions in fundamental studies and allow a new level of control over functional properties driven by specific defect complexes.« less

Synthesis, crystal structure and DFT studies of a novel dinuclear copper(I) complex with triphenylphosphine and 2-mercaptonicotinic acid

NASA Astrophysics Data System (ADS)

Ahmad, Tayyaba; Mahmood, Rashid; Georgieva, Ivelina; Zahariev, Tsvetan; Tahir, Muhammad Nawaz; Shaheen, Muhammad Ashraf; Gilani, Mazhar Amjad; Ahmad, Saeed

2018-02-01

A novel dinuclear copper(I) complex, {[Cu2(Mnt)2(PPh3)2Cl2].2H2O.CH3CN}2 (1) (Mnt = Mercaptonicotinic acid, PPh3 = triphenylphosphine) was prepared and its structure was determined by X-ray crystallography. The complex 1 consists of two dinuclear molecules and in each molecule, the two copper atoms are bridged by S atoms of N-protonated mercaptonicotinic acid forming a four-membered ring. The planar Cu2S2 core is characterized by significant cuprophilic interactions (Cusbnd Cu distance = 2.7671(8), 2.8471(8) Å). Each copper atom in 1 is coordinated by two sulfur atoms of Mnt, one phosphorus atom of PPh3 and a chloride ion adopting a tetrahedral geometry. The calculated Gibbs energies for reaction in CH3CN supported the experimental structure and predicted more favorable formation of dinuclear Cu(I) complex as compared to the mononuclear Cu(I) complex. The dinuclear complex is stabilized by 65.98 kJ mol-1 by coupling of two mononuclear Cu(I) complexes. The IR spectra of 1 and Mnt ligand were reliably interpreted and the Mnt vibrations, which are sensitive to the ligand coordination to Cu(I) ion in 1 were selected with the help of DFT/ωB97XD calculations.

Synthesis, spectral, DFT modeling, cytotoxicity and microbial studies of novel Zr(IV), Ce(IV) and U(VI) piroxicam complexes

NASA Astrophysics Data System (ADS)

El-Shwiniy, Walaa H.; Zordok, Wael A.

2018-06-01

The Zr(IV), Ce(IV) and U(VI) piroxicam anti-inflammatory drug complexes were prepared and characterized using elemental analyses, conductance, IR, UV-Vis, magnetic moment, IHNMR and thermal analysis. The ratio of metal: Pir is found to be 1:2 in all complexes estimated by using molar ratio method. The conductance data reveal that Zr(IV) and U(VI) chelates are non-electrolytes except Ce(IV) complex is electrolyte. Infrared spectroscopic confirm that the Pir behaves as a bidentate ligand co-ordinated to the metal ions via the oxygen and nitrogen atoms of ν(Cdbnd O)carbonyl and ν(Cdbnd N)pyridyl, respectively. The kinetic parameters of thermogravimetric and its differential, such as activation energy, entropy of activation, enthalpy of activation, and Gibbs free energy evaluated using Coats-Redfern and Horowitz-Metzger equations for Pir and complexes. The geometry of the piroxicam drug in the Free State differs significantly from that in the metal complex. In the time of metal ion-drug bond formation the drug switches-on from the closed structure (equilibrium geometry) to the open one. The antimicrobial tests were assessed towards some types of bacteria and fungi. The in vitro cell cytotoxicity of the complexes in comparison with Pir against colon carcinoma (HCT-116) cell line was measured. Optimized geometrical structure of piroxicam ligand by using DFT calculations.

The separation distance distribution in electron-donor-acceptor systems and the wavelength dependence of free ion yields

NASA Astrophysics Data System (ADS)

Zhou, Jinwei; Findley, Bret R.; Braun, Charles L.; Sutin, Norman

2001-06-01

We recently reported that free radical ion quantum yields for electron-donor-acceptor (EDA) systems of alkylbenzenes-tetracyanoethylene (TCNE) exhibit a remarkable wavelength dependence in dichloromethane, a medium polarity solvent. We proposed that weak absorption by long-distance, unassociated or "random" D⋯A pairs is mainly responsible for the free radical ion yield. Here a model for the wavelength dependence of the free ion yield is developed for four systems in which differing degrees of EDA complex formation are present: 1,3,5-tri-tert-butylbenzene-TCNE in which only random pairs exist due to the bulky groups on the electron donor, and toluene—TCNE, 1,3,5-triethylbenzene-TCNE and 1,3,5-trimethylbenzene-TCNE. Mulliken-Hush theory is used to determine the excitation distance distribution of unassociated, random pairs at different wavelengths. For each absorption distribution, free radical ion yields at different wavelengths are then calculated using Onsager's result for the ion separation probability. Encouraging agreement between the calculated yields and our experimental results is obtained. As far as we are aware, this is the first time that photoexcitation of unassociated donor/acceptor pairs has been invoked as the source of separated radical ion pairs.

High fluorescence emission of carboxylic acid functionalized polystyrene/BaTiO{sub 3} nanocomposites and rare earth metal complexes: Preparation and characterization

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

Cao, X. T.; Showkat, A. M.; Wang, Z.

2015-03-30

Noble fluorescence nanocomposite compound based on barium titanate nanoparticles (BTO), polystyrene (PSt), and terbium ion (Tb{sup 3+}) was synthesized by a combination of surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization, Friedel-Crafts alkylation reaction and coordinate chemistry. Initially, a modification of surface of BTO was conducted by an exchange process with S-benzyl S’-trimethoxysilylpropyltrithiocarbonate to create macro-initiator for polymerization of styrene. Subsequently, aryl carboxylic acid functionalized polystyrene grafted barium titanate (BTO-g-PSt-COOH) was generated by substitution reaction between 4-(Chloromethyl) benzoic acid and PSt chains. The coordination of the nanohybrids with Tb{sup 3+} ions afforded fluorescent Tb{sup 3+} tagged aryl carboxylic acid functionalized polystyrenemore » grafted barium titanate (BTO-g-PSt-Tb{sup 3+}) complexes. Structure, morphology, and fluorescence properties of nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR and SEM analyses confirmed the formation of BTO-g-PSt-Tb{sup 3+}nanohybrids. Furthermore, TGA profiles demonstrated the grafting of aryl carboxylic acid functionalized polystyrene on BTO surface. Optical properties of BTO-g-PSt-Tb{sup 3+} complexes were investigated by fluorescence spectroscopy.« less

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation

NASA Astrophysics Data System (ADS)

Ragab, Gamal H.; Amin, Alaa S.

2004-03-01

Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at λmax 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 μg ml -1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15±1.15, 99.30±1.40, 99.60±1.50, and 99.00±1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

Examination of the effect of the annealing cation on higher order structures containing guanine or isoguanine repeats

PubMed Central

Pierce, Sarah E.; Wang, Junmei; Jayawickramarajah, Janarthanan; Hamilton, Andrew D.; Brodbelt, Jennifer S.

2010-01-01

Isoguanine (2-oxo-6-amino-guanine), a natural but non-standard base, exhibits unique self-association properties compared to its isomer, guanine, and results in formation of different higher order DNA structures. In this work, the higher order structures formed by oligonucleotides containing guanine repeats or isoguanine repeats after annealing in solutions containing various cations are evaluated by electrospray ionization mass spectrometry (ESI-MS) and circular dichroism (CD) spectroscopy. The guanine-containing strand (G9) consistently formed quadruplexes upon annealing, whereas the isoguanine strand (Ig9) formed both pentaplexes and quadruplexes depending on the annealing cation. Quadruplex formation with G9 showed some dependence on the identity of the cation present during annealing with high relative quadruplex formation detected with six of ten cations. Analogous annealing experiments with Ig9 resulted in complex formation with all ten cations, and the majority of the resulting complexes were pentaplexes. CD results indicated most of the original complexes survived the desalting process necessary for ESI-MS analysis. In addition, several complexes, especially the pentaplexes, were found to be capable of cation exchange with ammonium ions. Ab initio calculations were conducted for isoguanine tetrads and pentads coordinated with all ten cations to predict the most energetically stable structures of the complexes in the gas phase. The observed preference of forming quadruplexes versus pentaplexes as a function of the coordinated cation can be interpreted by the calculated reaction energies of both the tetrads and pentads in combination with the distortion energies of tetrads. PMID:19746468

In situ synthesis, photometric and spectroscopic studies of chelating system during the 1,4,7,10,13,16-hexaoxacyclooctadecane charge transfer reaction with different acceptors

NASA Astrophysics Data System (ADS)

Hossan, Aisha S. M.; Abou-Melha, Hanaa M.; Refat, Moamen S.

2011-08-01

Electron donor acceptor complexes (EDA) of the 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) as a rich donor were spectrophotometrically discussed and synthesized in solid form according the interactions with different nine of usual π-acceptors like 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione (p-chloranil; p-CHL), tetrachloro-1,2-benzoquinone (o-chloranil; o-CHL), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetracyanoquinodimethane (TCNQ), 2,6-dichloroquinone-4-chloroimide (DCQ), 2,6-dibromoquinone-4-chloroimide (DBQ), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid; CLA), N-bromosuccinimide (NBS), 2,4,6-trinitrophenol (picric acid; PA). Spectroscopic and physical data such as formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ G°), oscillator strength ( f), transition dipole moment ( μ), resonance energy ( RN) and ionization potential ( Ip) were estimated in chloroform or methanol at 25 °C. Based on the elemental analysis and photometric titrations the CT-complexes were formed indicated the formation of 1:1 charge-transfer complexes for the o-CHL, TCNQ, DCQ, DBQ and NBS acceptors but 1:3 ratio for p-CHL, DDQ, CLA and PA, respectively. The charge-transfer interactions were interpretative according to the formation of dative ion pairs [18C6 rad +, A rad -], where A is acceptor. All of the resulting charge transfer complexes were isolated in amorphous form and the complexes formations on IR and 1H NMR spectra were discussed.

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.

Photochemically stable fluorescent heteroditopic ligands for zinc ion.

PubMed

Zhang, Lu; Zhu, Lei

2008-11-07

Photochemically stable fluorescent heteroditopic ligands (9 and 10) for zinc ion were prepared and studied. Two independent metal coordination-driven photophysical processes, chelation-enhanced fluorescence (CHEF) and internal (or intramolecular) charge transfer (ICT), were designed into our heteroditopic ligand framework. This strategy successfully relates three coordination states of a ligand, non-, mono-, and dicoordinated, to three fluorescence states, fluorescence OFF, ON at one wavelength, and ON at another wavelength. This ligand platform has provided chemical foundation for applications such as the quantification of zinc concentration over broad ranges (Zhang, L.; Clark, R. J.; Zhu, L. Chem.-Eur. J. 2008, 14, 2894-2903) and molecular logic functions (Zhang, L.; Whitfield, W. A.; Zhu, L. Chem. Commun. 2008, 1880-1882). The binding stoichiometries of dipicolylamino and 2,2'-bipyridyl, the two binding sites featured in heteroditopic ligands 7-10, were studied in acetonitrile using both Job's method of continuous variation and isothermal titration calorimetry (ITC). The fluorescence enhancement of 7-10 upon the formation of monozinc complexes (defined as the fluorescence quantum yield ratio of monozinc complex and free ligand) is qualitatively related to the highest occupied molecular orbital (HOMO) energy levels of their fluorophores. This is consistent with our hypothesis on the thermodynamics of the coordination-driven photophysical processes embodied in the designed heteroditopic system, which was supported by cyclic voltammetry studies. In conclusion, compounds 9 and 10 not only possess better photochemical stability but also display a higher degree of fluorescence turn-on upon formation of monozinc complexes than their vinyl counterparts 7 and 8.

Electron-molecule chemistry and charging processes on organic ices and Titan's icy aerosol surrogates

NASA Astrophysics Data System (ADS)

Pirim, C.; Gann, R. D.; McLain, J. L.; Orlando, T. M.

2015-09-01

Electron-induced polymerization processes and charging events that can occur within Titan's atmosphere or on its surface were simulated using electron irradiation and dissociative electron attachment (DEA) studies of nitrogen-containing organic condensates. The DEA studies probe the desorption of H- from hydrogen cyanide (HCN), acetonitrile (CH3CN), and aminoacetonitrile (NH2CH2CN) ices, as well as from synthesized tholin materials condensed or deposited onto a graphite substrate maintained at low temperature (90-130 K). The peak cross sections for H- desorption during low-energy (3-15 eV) electron irradiation were measured and range from 3 × 10-21 to 2 × 10-18 cm2. Chemical and structural transformations of HCN ice upon 2 keV electron irradiation were investigated using X-ray photoelectron and Fourier-transform infrared spectroscopy techniques. The electron-beam processed materials displayed optical properties very similar to tholins produced by conventional discharge methods. Electron and negative ion trapping lead to 1011 charges cm-2 on a flat surface which, assuming a radius of 0.05 μm for Titan aerosols, is ∼628 charges/radius (in μm). The facile charge trapping indicates that electron interactions with nitriles and complex tholin-like molecules could affect the conductivity of Titan's atmosphere due to the formation of large negative ion complexes. These negatively charged complexes can also precipitate onto Titan's surface and possibly contribute to surface reactions and the formation of dunes.

Copper(II) Thiosemicarbazone Complexes and Their Proligands upon UVA Irradiation: An EPR and Spectrophotometric Steady-State Study.

PubMed

Hricovíni, Michal; Mazúr, Milan; Sîrbu, Angela; Palamarciuc, Oleg; Arion, Vladimir B; Brezová, Vlasta

2018-03-21

X- and Q-band electron paramagnetic resonance (EPR) spectroscopy was used to characterize polycrystalline Cu(II) complexes that contained sodium 5-sulfonate salicylaldehyde thiosemicarbazones possessing a hydrogen, methyl, ethyl, or phenyl substituent at the terminal nitrogen. The ability of thiosemicarbazone proligands to generate superoxide radical anions and hydroxyl radicals upon their exposure to UVA irradiation in aerated aqueous solutions was evidenced by the EPR spin trapping technique. The UVA irradiation of proligands in neutral or alkaline solutions and dimethylsulfoxide (DMSO) caused a significant decrease in the absorption bands of aldimine and phenolic chromophores. Mixing of proligand solutions with the equimolar amount of copper(II) ions resulted in the formation of 1:1 Cu(II)-to-ligand complex, with the EPR and UV-Vis spectra fully compatible with those obtained for the dissolved Cu(II) thiosemicarbazone complexes. The formation of the complexes fully inhibited the photoinduced generation of reactive oxygen species, and only subtle changes were found in the electronic absorption spectra of the complexes in aqueous and DMSO solutions upon UVA steady-state irradiation. The dark redox activity of copper(II) complexes and proligand/Cu(II) aqueous solutions towards hydrogen peroxide which resulted in the generation of hydroxyl radicals, was confirmed by spin trapping experiments.

Experimental and theoretical studies of the products of reaction between Ln(hfa) 3 and Cu(acac) 2 (Ln = La, Y; acac = acetylacetonate, hfa = hexafluoroacetylacetonate)

NASA Astrophysics Data System (ADS)

Rogachev, Andrey Yu.; Mironov, Andrey V.; Nemukhin, Alexander V.

2007-04-01

The new unusual heterobimetallic complex [La(hfa) 3Cu(acac) 2(H 2O)] ( I) was obtained in the reaction La(hfa) 3·2H 2O with Cu(acac) 2 in CHCl 3. This is the first example of such type of heterobimetallic complexes based on the Cu(acac) 2 species. According to the X-ray single crystal analysis, complex I crystallizes in the monoclinic space group P2 1/c, with a = 12.516(3) Å, b = 17.757(4) Å, c = 17.446(4) Å, β = 93.90(3)° and Z = 4. The structure consists of isolated heterobinuclear molecules with the coordination number of La being 9. The molecules are further assembled into dimers via hydrogen bonds. The theoretical modeling of the structure and the properties of parent monometallic complexes Ln(hfa) 3 (Ln = La, Y) and Cu(acac) 2 is described. The comparative theoretical study of lanthanide complexes indicates relations in formation of a heterobimetallic complex to the Lewis acidity of original monometallic complexes. In particular, the Lewis acidity and charge of the central metal ion in Ln(hfa) 3 are the key parameters accounting for the formation of [Ln(hfa) 3Cu(acac) 2].

Projection structure of a ClC-type chloride channel at 6.5Å resolution

NASA Astrophysics Data System (ADS)

Mindell, Joseph A.; Maduke, Merritt; Miller, Christopher; Grigorieff, Nikolaus

2001-01-01

Virtually all cells in all eukaryotic organisms express ion channels of the ClC type, the only known molecular family of chloride-ion-selective channels. The diversity of ClC channels highlights the multitude and range of functions served by gated chloride-ion conduction in biological membranes, such as controlling electrical excitability in skeletal muscle, maintaining systemic blood pressure, acidifying endosomal compartments, and regulating electrical responses of GABA (γ-aminobutyric acid)-containing interneurons in the central nervous system. Previously, we expressed and purified a prokaryotic ClC channel homologue. Here we report the formation of two-dimensional crystals of this ClC channel protein reconstituted into phospholipid bilayer membranes. Cryo-electron microscopic analysis of these crystals yields a projection structure at 6.5Å resolution, which shows off-axis water-filled pores within the dimeric channel complex.

Post-Self-Assembly Cross-Linking to Integrate Molecular Nanofibers with Copolymers in Oscillatory Hydrogels

DTIC Science & Technology

2013-05-09

The BZ reaction provides a model system to mimic a variety of complex processes, such as biological morphogenesis, in monodisperse microemulsions .15...surfaces, ion-exchange resins, membranes, and microemulsions . For example, in addition to minimizing the hydrodynamic effects and formation of bubbles...Reaction-Diffusion Microemulsions Reveals Three-Dimensional Tu- ring Patterns. Science (Washington, DC, U.S.) 2011, 331, 1309−1312. (16) Agladze, K. I

Effect of drug Piper nigrum on magnesium chloride at varying concentration and temperature through ultrasonic method: A thermoacoustic study

NASA Astrophysics Data System (ADS)

Nalle, Pallavi B.; Deshmukh, S. S.; Dorik, R. G.; Jadhav, K. M.

2016-12-01

The ultrasonic velocity (U), density (ρ), and viscosity (η) of an ethanolic extract of drug Piper nigrum with MgCl2 (metal ions) have been measured as a function of the number of moles n = (0.7009, 1.4018, 2.1027, 2.8036 and 3.5045) at 303.15, 308.15, 313.15 and 318.15 K temperature. Various thermoacoustic and their excess values such as adiabatic compressibilities (β), intermolecular free lengths (Lf), excess adiabatic compressibility (βE), excess intermolecular free length (?) have been computed using values of ultrasonic velocity (U), density (ρ), and viscosity (η). The excess values of ultrasonic velocity, specific acoustic impedance are positive, whereas isentropic compressibility and intermolecular free lengths are negative over the entire composition range of MgCl2 + P. nigrum which indicates the presence of specific interactions between unlike molecules. Molecular association is reflected by ultrasonic investigation. This may be interpreted due to the of complex formation. The chemical interaction may involve the association due to the solute-solvent and ion-solvent interaction and due to the formation of charge-transfer complexes, which is useful to understand the mechanism of their metabolism in living systems. The results obtained from these studies are helpful for pharmacological applications of drugs, transport of drugs across biological membranes.

Triacylglycerol estolides, a new class of mammalian lipids, in the paracloacal gland of the brushtail possum (Trichosurus vulpecula).

PubMed

McLean, Stuart; Davies, Noel W; Nichols, David S; Mcleod, Bernie J

2015-06-01

The paracloacal glands are the most prevalent scent glands in marsupials, and previous investigation of their secretions in the brushtail possum (Trichosurus vulpecula) has identified many odorous compounds together with large amounts of neutral lipids. We have examined the lipids by LC-MS, generating ammonium adducts of acylglycerols by electrospray ionisation. Chromatograms showed a complex mixture of coeluting acylglycerols, with m/z from about 404 to 1048. Plots of single [M + NH4](+) ions showed three groups of lipids clearly separated by retention time. MS-MS enabled triacylglycerols and diacylglycerol ethers to be identified from neutral losses and formation of diacylglycerols and other product ions. The earliest-eluting lipids were found to be triacylglycerol estolides, in which a fourth fatty acid forms an ester link with a hydroxy fatty acid attached to the glycerol chain. This is the first report of triacylglycerol estolides in animals. They form a complex mixture with the triacylglycerols and diacylglycerol ethers of lipids with short- and long-chain fatty acids with varying degrees of unsaturation. This complexity suggests a functional role, possibly in social communication.

Synthesis, crystal structure, theoretical calculations and antimicrobial properties of [Pt(tetramethylthiourea)4] [Pt(CN)4]·4H2O

NASA Astrophysics Data System (ADS)

Sadaf, Haseeba; Isab, Anvarhusein A.; Ahmad, Saeed; Espinosa, Arturo; Mas-Montoya, Míriam; Khan, Islam Ullah; Ejaz; Rehman, Seerat-ur; Ali, Muhammad Akhtar Javed; Saleem, Muhammad; Ruiz, José; Janiak, Christoph

2015-04-01

A new platinum(II) complex, [Pt(Tmtu)4][Pt(CN)4]·4H2O (1) was synthesized by reaction of K2[PtCl4], KCN and tetramethylthiourea (Tmtu). Its structure was determined by X-ray crystallography. The [Pt(CN)4]2- anion shows regular square planar geometry at platinum, while in the [Pt(Tmtu)4]2+ cation the geometry at platinum is somewhat distorted. Hydrogen bonding between water molecules and the cyanide nitrogen of [Pt(CN)4]2- ions stabilizes the structure and leads to a supramolecular 2D network. DFT calculations support the experimentally found dinuclear (homocoordinated) ion-pair structure 1 as the most stable in comparison to noncovalent dimer [Pt(CN)2(Tmtu)2]222 that could, in turn, be involved in the formation sequence of 1. Antimicrobial activities of the complex were evaluated by minimum inhibitory concentration and the results showed that the complex exhibited moderate activities against gram-negative bacteria (Escherichiacoli, Pseudomonas aeruginosa) and molds (Aspergillus niger,Penicilliumcitrinum).

Characterization of ternary bivalent metal complexes with bis(2-hydroxyethyl)iminotris(hydroxymethy)methane (Bis?Tris) and the comparison of five crystal structures of Bis?Tris complexes*1

NASA Astrophysics Data System (ADS)

Inomata, Yoshie; Gochou, Yoshihiro; Nogami, Masanobu; Howell, F. Scott; Takeuchi, Toshio

2004-09-01

Eleven bivalent metal complexes with bis(2-hydroxyethyl)iminotris(hydroxymethy)methane (Bis-Tris:hihm): [M(hihm)(H 2O)]SO 4· nH 2O (M: Co, Ni, Cu, Zn), [MCl(hihm)]Cl· nH 2O (M: Co, Ni, Cu), and [M(HCOO)(hihm)](HCOO) (M: Co, Ni, Cu, Zn) have been prepared and characterized by using their infrared absorption and powder diffuse reflection spectra, magnetic susceptibility, thermal analysis and powder X-ray diffraction analysis. The crystal structures of [Ni(hihm)(H 2O)]SO 4·H 2O ( 2), [Cu(hihm)(H 2O)]SO 4 ( 3), [NiCl(hihm)]Cl·H 2O ( 6), [CuCl(hihm)]Cl ( 7) and [Co(HCOO)(hihm)](HCOO) ( 8) have been determined by single crystal X-ray diffraction analysis. The crystals of [Ni(hihm)(H 2O)]SO 4·H 2O ( 2) and [Cu(hihm)(H 2O)]SO 4 ( 3) are each orthorhombic with the space group P2 12 12 1 and Pna2 1. For both complexes, the metal atom is in a distorted octahedral geometry, ligated by four hydroxyl oxygen atoms, a nitrogen atom and a water molecule. [NiCl(hihm)]Cl·H 2O ( 6) is monoclinic with the space group P2 1/ n. For complex ( 6), the nickel atom is in a distorted octahedral geometry, ligated by four hydroxyl oxygen atoms, a nitrogen atom and a chloride ion. [CuCl(hihm)]Cl ( 7) is orthorhombic with the space group P2 12 12 1. Although in this copper(II) complex the copper atom is ligated by six atoms, it is more reasonable to think that the copper atom is in a trigonal bipyramidal geometry coordinated with five atoms: three hydroxyl oxygen atoms, a nitrogen atom and a chloride ion if the bond distances and angles surrounding the copper atom are taken into consideration. [Co(HCOO)(hihm)](HCOO) ( 8) is monoclinic with the space group P2 1. In cobalt(II) complex ( 8), the cobalt atom is in a distorted octahedral geometry, ligated by four hydroxyl oxygen atoms, a nitrogen atom and an oxygen atom of a formate ion. The structure of complex ( 8) is the same as the structure of [NiCl(hihm)]Cl·H 2O ( 6) except for the formate ion coordinating instead of the chloride ion. [M(hihm)(H 2O)]SO 4·H 2O (M: Co, Zn) ( 1, 4), [CoCl(hihm)]Cl·H 2O ( 5) and [M(HCOO)(hihm)](HCOO) (M: Ni, Cu, Zn) ( 9- 11) seem to have the same structures as the structures of [Ni(hihm)(H 2O)]SO 4·H 2O ( 2), [NiCl(hihm)]Cl·H 2O ( 6) and [Co(HCOO)(hihm)](HCOO) ( 8), respectively, judging by the results of IR and powder diffuse reflection spectra and powder X-ray diffraction analysis. Bis-Tris has coordinated to the metal atoms as a pentadentate ligand in all complexes of which the structures have been determined by single crystal X-ray diffraction analysis in this work.

Structural Evidence for the Tetrameric Assembly of Chemokine CCL11 and the Glycosaminoglycan Arixtra™

PubMed Central

Dykstra, Andrew B.; Sweeney, Matt D.; Leary, Julie A.

2013-01-01

Understanding chemokine interactions with glycosaminoglycans (GAG) is critical as these interactions have been linked to a number of inflammatory medical conditions, such as arthritis and asthma. To better characterize in vivo protein function, comprehensive knowledge of multimeric species, formed by chemokines under native conditions, is necessary. Herein is the first report of a tetrameric assembly of the human chemokine CCL11, which was shown bound to the GAG Arixtra™. Isothermal titration calorimetry data indicated that CCL11 interacts with Arixtra, and ion mobility mass spectrometry (IM-MS) was used to identify ions corresponding to the CCL11 tetrameric species bound to Arixtra. Collisional cross sections (CCS) of the CCL11 tetramer-Arixtra noncovalent complex were compared to theoretical CCS values calculated using a preliminary structure of the complex deduced using X-ray crystallography. Experimental CCS values were in agreement with theoretical values, strengthening the IM-MS evidence for the formation of the noncovalent complex. Tandem mass spectrometry data of the complex indicated that the tetramer-GAG complex dissociates into a monomer and a trimer-GAG species, suggesting that two CC-like dimers are bridged by Arixtra. As development of chemokine inhibitors is of utmost importance to treatment of medical inflammatory conditions, these results provide vital insights into chemokine-GAG interactions. PMID:24970196

Structural Evidence for the Tetrameric Assembly of Chemokine CCL11 and the Glycosaminoglycan Arixtra™.

PubMed

Dykstra, Andrew B; Sweeney, Matt D; Leary, Julie A

2013-11-06

Understanding chemokine interactions with glycosaminoglycans (GAG) is critical as these interactions have been linked to a number of inflammatory medical conditions, such as arthritis and asthma. To better characterize in vivo protein function, comprehensive knowledge of multimeric species, formed by chemokines under native conditions, is necessary. Herein is the first report of a tetrameric assembly of the human chemokine CCL11, which was shown bound to the GAG Arixtra™. Isothermal titration calorimetry data indicated that CCL11 interacts with Arixtra, and ion mobility mass spectrometry (IM-MS) was used to identify ions corresponding to the CCL11 tetrameric species bound to Arixtra. Collisional cross sections (CCS) of the CCL11 tetramer-Arixtra noncovalent complex were compared to theoretical CCS values calculated using a preliminary structure of the complex deduced using X-ray crystallography. Experimental CCS values were in agreement with theoretical values, strengthening the IM-MS evidence for the formation of the noncovalent complex. Tandem mass spectrometry data of the complex indicated that the tetramer-GAG complex dissociates into a monomer and a trimer-GAG species, suggesting that two CC-like dimers are bridged by Arixtra. As development of chemokine inhibitors is of utmost importance to treatment of medical inflammatory conditions, these results provide vital insights into chemokine-GAG interactions.

On the formation and structure of rare-earth element complexes in aqueous solutions under hydrothermal conditions with new data on gadolinium aqua and chloro complexes

USGS Publications Warehouse

Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

2007-01-01

Synchrotron X-ray spectroscopy experiments were made on the Gd(III) aqua and chloro complexes in low pH aqueous solutions at temperatures ranging from 25 to 500????C and at pressures up to 480??MPa using a hydrothermal diamond anvil cell. Analysis of fluorescence Gd L3-edge X-ray absorption fine structure (XAFS) spectra measured from a 0.006m Gd/0.16m HNO3 aqueous solution at temperatures up to 500????C and at pressures up to 260??MPa shows that the Gd-O distance of the Gd3+ aqua ion decreases steadily at a rate of ??? 0.007??A??/100????C whereas the number of coordinated H2O molecules decreases from 9.0 ?? 0.5 to 7.0 ?? 0.4. The loss of water molecules in the Gd3+ aqua ion inner hydration shell over this temperature range (a 22% reduction) is smaller than exhibited by the Yb3+ aqua ion (42% reduction) indicating that the former is significantly more stable than the later. We conjecture that the anomalous enrichment of Gd reported from measurement of REE concentrations in ocean waters may be attributed to the enhanced stability of the Gd3+ aqua ion relative to other REEs. Gd L3-edge XAFS measurements of 0.006m and 0.1m GdCl3 aqueous solutions at temperatures up to 500????C and pressures up to 480??MPa reveal that the onset of significant Gd3+-Cl- association occurs around 300????C. Partially-hydrated stepwise inner-sphere complexes most likely of the type Gd(H2O)??-nCln+3-n occur in the chloride solutions at higher temperatures, where ?? ??? 8 at 300????C decreasing slightly to an intermediate value between 7 and 8 upon approaching 500????C. This is the first direct evidence for the occurrence of partially-hydrated REE Gd (this study) and Yb [Mayanovic, R.A., Jayanetti, S., Anderson, A.J., Bassett, W.A., Chou, I-M., 2002a. The structure of Yb3+ aquo ion and chloro complexes in aqueous solutions at up to 500 ??C and 270 MPa. J. Phys. Chem. A 106, 6591-6599.] chloro complexes in hydrothermal solutions. The number of chlorides (n) of the partially-hydrated Gd(III) chloro complexes increases steadily with temperature from 0.4 ?? 0.2 to 1.7 ?? 0.3 in the 0.006m chloride solution and from 0.9 ?? 0.7 to 1.8 ?? 0.7 in the 0.1m GdCl3 aqueous solution in the 300-500????C range. Conversely, the number of H2O ligands of Gd(H2O)??-nCln+3-n complexes decreases steadily from 8.9 ?? 0.4 to 5.8 ?? 0.7 in the 0.006m GdCl3 aqueous solution and from 9.0 ?? 0.5 to 5.3 ?? 1.0 in the 0.1m GdCl3 aqueous solution at temperatures from 25 to 500????C. Analysis of our results shows that the chloride ions partially displace the inner-shell water molecules during Gd(III) complex formation under hydrothermal conditions. The Gd-OH2 bond of the partially-hydrated Gd(III) chloro complexes exhibits slightly smaller rates of length contraction (??? 0.005??A??/100????C) for both solutions. The structural aspects of chloride speciation of Gd(III) as measured from this study and of Yb(III) as measured from our previous experiments are consistent with the solubility of these and other REE in deep-sea hydrothermal fluids. ?? 2006 Elsevier B.V. All rights reserved.

Molybdenum(V) complexes with formate: Geometric isomerism of the [Mo2O4Cl2(Py)2(HCOO)]- ion

NASA Astrophysics Data System (ADS)

Modec, Barbara; Dolenc, Darko

2013-11-01

Reactions of (PyH)5[MoOCl4(H2O)]3Cl2 with formate resulted in trans-{(Py)2H}[Mo2O4Cl2(Py)2(HCOO)] (1) and cis-(PyH)[Mo2O4Cl2(Py)2(HCOO)] (2), whereas the bromide starting material (PyH)[MoOBr4], yielded (PyH)3[Mo2O4Br4(HCOO)]·2CH3CN (3) and cis-(PyH)[Mo2O4Br2(Py)2(HCOO)] (4) (where Py stands for pyridine, PyH+ for pyridinium cation and (Py)2H+ for a hydrogen-bonded PyH+⋯Py ion). In all, the dinuclear metal-metal bonded { core may be recognized with its six coordination sites distributed among halides, pyridine ligands and formate. The latter is coordinated via both oxygen atoms, with each to a different metal ion. The [Mo2O4Cl2(Py)2(HCOO)]- ion exhibits geometric isomerism: the pyridine ligands, on each metal ion one, are either trans or cis to each other. The trans isomer crystallized with (Py)2H+ countercations, whereas the cis isomer as a PyH+ salt. In the crystal lattice of cis-(PyH)[Mo2O4Cl2(Py)2(HCOO)] (2), as confirmed by the X-ray structure analysis, pyridinium cation forms a hydrogen bond with the doubly-bridging oxide of the cis-[Mo2O4Cl2(Py)2(HCOO)]- ion. The countercations of trans-{(Py)2H}[Mo2O4Cl2(Py)2(HCOO)] (1) cannot participate in hydrogen-bonding. The DFT calculations on the isomers of the [Mo2O4Cl2(Py)2(HCOO)]- ion show the trans isomer to be by ca. 15 kJ/mol more stable than the cis isomer. The calculations on the hydrogen-bonded PyH+⋯[Mo2O4Cl2(Py)2(HCOO)]- ion-pairs show a reversed order of stability. Hydrogen-bonding and weak Csbnd H⋯Cl interactions between PyH+ cations and the cis-[Mo2O4Cl2(Py)2(HCOO)]- ion increase the stability of the cis compound.

Next generation multi-scale biophysical characterization of high precision cancer particle radiotherapy using clinical proton, helium-, carbon- and oxygen ion beams

PubMed Central

Niklas, Martin; Zimmermann, Ferdinand; Chaudhri, Naved; Krunic, Damir; Tessonnier, Thomas; Ferrari, Alfredo; Parodi, Katia; Jäkel, Oliver; Debus, Jürgen; Haberer, Thomas; Abdollahi, Amir

2016-01-01

The growing number of particle therapy facilities worldwide landmarks a novel era of precision oncology. Implementation of robust biophysical readouts is urgently needed to assess the efficacy of different radiation qualities. This is the first report on biophysical evaluation of Monte Carlo simulated predictive models of prescribed dose for four particle qualities i.e., proton, helium-, carbon- or oxygen ions using raster-scanning technology and clinical therapy settings at HIT. A high level of agreement was found between the in silico simulations, the physical dosimetry and the clonogenic tumor cell survival. The cell fluorescence ion track hybrid detector (Cell-Fit-HD) technology was employed to detect particle traverse per cell nucleus. Across a panel of radiobiological surrogates studied such as late ROS accumulation and apoptosis (caspase 3/7 activation), the relative biological effectiveness (RBE) chiefly correlated with the radiation species-specific spatio-temporal pattern of DNA double strand break (DSB) formation and repair kinetic. The size and the number of residual nuclear γ-H2AX foci increased as a function of linear energy transfer (LET) and RBE, reminiscent of enhanced DNA-damage complexity and accumulation of non-repairable DSB. These data confirm the high relevance of complex DSB formation as a central determinant of cell fate and reliable biological surrogates for cell survival/RBE. The multi-scale simulation, physical and radiobiological characterization of novel clinical quality beams presented here constitutes a first step towards development of high precision biologically individualized radiotherapy. PMID:27494855

The formation and dissipation of electrostatic shock waves: the role of ion–ion acoustic instabilities

NASA Astrophysics Data System (ADS)

Zhang, Wen-shuai; Cai, Hong-bo; Zhu, Shao-ping

2018-05-01

The role of ion–ion acoustic instabilities in the formation and dissipation of collisionless electrostatic shock waves driven by counter-streaming supersonic plasma flows has been investigated via two-dimensional particle-in-cell simulations. The nonlinear evolution of unstable waves and ion velocity distributions has been analyzed in detail. It is found that for electrostatic shocks driven by moderate-velocity flows, longitudinal and oblique ion–ion acoustic instabilities can be excited in the downstream and upstream regions, which lead to thermalization of the transmitted and reflected ions, respectively. For high-velocity flows, oblique ion–ion acoustic instabilities can develop in the overlap layer during the shock formation process and impede the shock formation.

Local formation of nitrogen-vacancy centers in diamond by swift heavy ions

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

Schwartz, J.; Aloni, S.; Ogletree, D. F.

2014-12-03

In this paper, we exposed nitrogen-implanted diamonds to beams of swift heavy ions (~1 GeV, ~4 MeV/u) and find that these irradiations lead directly to the formation of nitrogen vacancy (NV) centers, without thermal annealing. We compare the photoluminescence intensities of swift heavy ion activated NV - centers to those formed by irradiation with low-energy electrons and by thermal annealing. NV - yields from irradiations with swift heavy ions are 0.1 of yields from low energy electrons and 0.02 of yields from thermal annealing. We discuss possible mechanisms of NV center formation by swift heavy ions such as electronic excitationsmore » and thermal spikes. While forming NV centers with low efficiency, swift heavy ions could enable the formation of three dimensional NV - assemblies over relatively large distances of tens of micrometers. Finally and further, our results show that NV center formation is a local probe of (partial) lattice damage relaxation induced by electronic excitations from swift heavy ions in diamond.« less

Chemistry and Chemical Equilibrium Dynamics of BMAA and Its Carbamate Adducts

PubMed Central

Diaz-parga, Pedro

2018-01-01

Beta-N-methylamino-L-alanine (BMAA) has been demonstrated to contribute to the onset of the ALS/Parkinsonism-dementia complex (ALS/PDC) and is implicated in the progression of other neurodegenerative diseases. While the role of BMAA in these diseases is still debated, one of the suggested mechanisms involves the activation of excitatory glutamate receptors. In particular, the excitatory effects of BMAA are shown to be dependent on the presence of bicarbonate ions, which in turn forms carbamate adducts in physiological conditions. The formation of carbamate adducts from BMAA and bicarbonate is similar to the formation of carbamate adducts from non-proteinogenic amino acids. Structural, chemical, and biological information related to non-proteinogenic amino acids provide insight into the formation of and possible neurological action of BMAA. This article reviews the carbamate formation of BMAA in the presence of bicarbonate ions, with a particular focus on how the chemical equilibrium of BMAA carbamate adducts may affect the molecular mechanism of its function. Highlights of nuclear magnetic resonance (NMR)-based studies on the equilibrium process between free BMAA and its adducts are presented. The role of divalent metals on the equilibrium process is also explored. The formation and the equilibrium process of carbamate adducts of BMAA may answer questions on their neuroactive potency and provide strong motivation for further investigations into other toxic mechanisms. PMID:28921378

Chemistry and Chemical Equilibrium Dynamics of BMAA and Its Carbamate Adducts.

PubMed

Diaz-Parga, Pedro; Goto, Joy J; Krishnan, V V

2018-01-01

Beta-N-methylamino-L-alanine (BMAA) has been demonstrated to contribute to the onset of the ALS/Parkinsonism-dementia complex (ALS/PDC) and is implicated in the progression of other neurodegenerative diseases. While the role of BMAA in these diseases is still debated, one of the suggested mechanisms involves the activation of excitatory glutamate receptors. In particular, the excitatory effects of BMAA are shown to be dependent on the presence of bicarbonate ions, which in turn forms carbamate adducts in physiological conditions. The formation of carbamate adducts from BMAA and bicarbonate is similar to the formation of carbamate adducts from non-proteinogenic amino acids. Structural, chemical, and biological information related to non-proteinogenic amino acids provide insight into the formation of and possible neurological action of BMAA. This article reviews the carbamate formation of BMAA in the presence of bicarbonate ions, with a particular focus on how the chemical equilibrium of BMAA carbamate adducts may affect the molecular mechanism of its function. Highlights of nuclear magnetic resonance (NMR)-based studies on the equilibrium process between free BMAA and its adducts are presented. The role of divalent metals on the equilibrium process is also explored. The formation and the equilibrium process of carbamate adducts of BMAA may answer questions on their neuroactive potency and provide strong motivation for further investigations into other toxic mechanisms.

Monitoring dediazoniation product formation by high-performance liquid chromatography after derivatization.

PubMed

Bravo-Díaz, Carlos; González-Romero, Elisa

2003-03-14

A derivatization protocol that exploits the rapid reaction between arenediazonium ions and a suitable coupling agent followed by high-performance liquid chromatography analyses of the reaction mixture was employed to determine the product distribution, the rate constants for product formation and the association constant of 4-nitrobenzenediazonium, PNBD, ion with beta-cyclodextrin, beta-CD. The derivatization of PNBD with the coupling agent leads to the formation of a stable azo dye that prevents by-side reactions of PNBD with the solvents of the mobile phase, including water, or the metallic parts of the chromatographic system that would eventually lead to erroneous identification and quantification of dediazoniation products. The results show that in the presence of beta-CD, nitrobenzene is formed at the expense of 4-nitrophenol, which is the major product in its absence. The observed rate constants for the interaction between PNBD and beta-CD increase upon increasing [beta-CD] showing a saturation profile indicative of the formation of an inclusion complex between PNBD and beta-CD. By fitting the experimental data to a simplified Lineaweaver-Burk equation, the corresponding association constant and the maximum acceleration rate of beta-CD towards PNBD were estimated. The protocol is applicable under a variety of experimental conditions provided that the rate of the coupling reaction is much faster than that of dediazoniation.

Solution and Gas-Phase H/D Exchange of Protein-Small-Molecule Complexes: Cex and Its Inhibitors

NASA Astrophysics Data System (ADS)

Kang, Yang; Terrier, Peran; Ding, Chuanfan; Douglas, D. J.

2012-01-01

The properties of noncovalent complexes of the enzyme exo-1,4-β-D-glycanase ("Cex") with three aza-sugar inhibitors, deoxynojirimycin (X2DNJ), isofagomine lactam (X2IL), and isofagomine (X2IF), have been studied with solution and gas-phase hydrogen deuterium exchange (H/Dx) and measurements of collision cross sections of gas-phase ions. In solution, complexes have lower H/Dx levels than free Cex because binding the inhibitors blocks some sites from H/Dx and reduces fluctuations of the protein. In mass spectra of complexes, abundant Cex ions are seen, which mostly are formed by dissociation of complexes in the ion sampling interface. Both complex ions and Cex ions formed from a solution containing complexes have lower cross sections than Cex ions from a solution of Cex alone. This suggests the Cex ions formed by dissociation "remember" their solution conformations. For a given charge, ions of the complexes have greater gas-phase H/Dx levels than ions of Cex. Unlike cross sections, H/Dx levels of the complexes do not correlate with the relative gas-phase binding strengths measured by MS/MS. Cex ions from solutions with or without inhibitors, which have different cross sections, show the same H/Dx level after 15 s, indicating the ions may fold or unfold on the seconds time scale of the H/Dx experiment. Thus, cross sections show that complexes have more compact conformations than free protein ions on the time scale of ca. 1 ms. The gas-phase H/Dx measurements show that at least some complexes retain different conformations from the Cex ions on a time scale of seconds.

Complexes of silver(I) ions and silver phosphate nanoparticles with hyaluronic acid and/or chitosan as promising antimicrobial agents for vascular grafts.

PubMed

Chudobova, Dagmar; Nejdl, Lukas; Gumulec, Jaromir; Krystofova, Olga; Rodrigo, Miguel Angel Merlos; Kynicky, Jindrich; Ruttkay-Nedecky, Branislav; Kopel, Pavel; Babula, Petr; Adam, Vojtech; Kizek, Rene

2013-06-28

Polymers are currently widely used to replace a variety of natural materials with respect to their favourable physical and chemical properties, and due to their economic advantage. One of the most important branches of application of polymers is the production of different products for medical use. In this case, it is necessary to face a significant disadvantage of polymer products due to possible and very common colonization of the surface by various microorganisms that can pose a potential danger to the patient. One of the possible solutions is to prepare polymer with antibacterial/antimicrobial properties that is resistant to bacterial colonization. The aim of this study was to contribute to the development of antimicrobial polymeric material ideal for covering vascular implants with subsequent use in transplant surgery. Therefore, the complexes of polymeric substances (hyaluronic acid and chitosan) with silver nitrate or silver phosphate nanoparticles were created, and their effects on gram-positive bacterial culture of Staphylococcus aureus were monitored. Stages of formation of complexes of silver nitrate and silver phosphate nanoparticles with polymeric compounds were characterized using electrochemical and spectrophotometric methods. Furthermore, the antimicrobial activity of complexes was determined using the methods of determination of growth curves and zones of inhibition. The results of this study revealed that the complex of chitosan, with silver phosphate nanoparticles, was the most suitable in order to have an antibacterial effect on bacterial culture of Staphylococcus aureus. Formation of this complex was under way at low concentrations of chitosan. The results of electrochemical determination corresponded with the results of spectrophotometric methods and verified good interaction and formation of the complex. The complex has an outstanding antibacterial effect and this effect was of several orders higher compared to other investigated complexes.

Complexes of Silver(I) Ions and Silver Phosphate Nanoparticles with Hyaluronic Acid and/or Chitosan as Promising Antimicrobial Agents for Vascular Grafts

PubMed Central

Chudobova, Dagmar; Nejdl, Lukas; Gumulec, Jaromir; Krystofova, Olga; Rodrigo, Miguel Angel Merlos; Kynicky, Jindrich; Ruttkay-Nedecky, Branislav; Kopel, Pavel; Babula, Petr; Adam, Vojtech; Kizek, Rene

2013-01-01

Polymers are currently widely used to replace a variety of natural materials with respect to their favourable physical and chemical properties, and due to their economic advantage. One of the most important branches of application of polymers is the production of different products for medical use. In this case, it is necessary to face a significant disadvantage of polymer products due to possible and very common colonization of the surface by various microorganisms that can pose a potential danger to the patient. One of the possible solutions is to prepare polymer with antibacterial/antimicrobial properties that is resistant to bacterial colonization. The aim of this study was to contribute to the development of antimicrobial polymeric material ideal for covering vascular implants with subsequent use in transplant surgery. Therefore, the complexes of polymeric substances (hyaluronic acid and chitosan) with silver nitrate or silver phosphate nanoparticles were created, and their effects on gram-positive bacterial culture of Staphylococcus aureus were monitored. Stages of formation of complexes of silver nitrate and silver phosphate nanoparticles with polymeric compounds were characterized using electrochemical and spectrophotometric methods. Furthermore, the antimicrobial activity of complexes was determined using the methods of determination of growth curves and zones of inhibition. The results of this study revealed that the complex of chitosan, with silver phosphate nanoparticles, was the most suitable in order to have an antibacterial effect on bacterial culture of Staphylococcus aureus. Formation of this complex was under way at low concentrations of chitosan. The results of electrochemical determination corresponded with the results of spectrophotometric methods and verified good interaction and formation of the complex. The complex has an outstanding antibacterial effect and this effect was of several orders higher compared to other investigated complexes. PMID:23812079

Carbonate ions and arsenic dissolution by groundwater

USGS Publications Warehouse

Kim, M.-J.; Nriagu, J.; Haack, S.

2000-01-01

Samples of Marshall Sandstone, a major source of groundwater with elevated arsenic levels in southeast Michigan, were exposed to bicarbonate ion under controlled chemical conditions. In particular, effects of pH and redox conditions on arsenic release were evaluated. The release of arsenic from the aquifer rock was strongly related to the bicarbonate concentration in the leaching solution. The results obtained suggest that the carbonation of arsenic sulfide minerals, including orpiment (As2S3) and realgar (As2S2), is an important process in leaching arsenic into groundwater under anaerobic conditions. The arseno-carbonate complexes formed, believed to be As(CO3)2-, As(CO3)(OH)2-, and AsCO3+, are stable in groundwater. The reaction of ferrous ion with the thioarsenite from carbonation process can result in the formation of arsenopyrite which is a common mineral in arsenic-rich aquifers.Samples of Marshall Sandstone, a major source of groundwater with elevated arsenic levels in southeast Michigan, were exposed to bicarbonate ion under controlled chemical conditions. In particular, effects of pH and redox conditions on arsenic release were evaluated. The release of arsenic from the aquifer rock was strongly related to the bicarbonate concentration in the leaching solution. The results obtained suggest that the carbonation of arsenic sulfide minerals, including orpiment (As2S3) and realgar (As2S2), is an important process in leaching arsenic into groundwater under anaerobic conditions. The arseno-carbonate complexes formed, believed to be As(CO3)2-, As(CO3)(OH)2-, and AsCO3+, are stable in groundwater. The reaction of ferrous ion with the thioarsenite from carbonation process can result in the formation of arsenopyrite which is a common mineral in arsenic-rich aquifers.The role of bicarbonate in leaching arsenic into groundwater was investigated by conducting batch experiments using core samples of Marshall Sandstone from southeast Michigan and different bicarbonate solutions. The effects of pH and redox conditions on As dissolution were examined. Results showed that As was not leached significantly out of the Marshall Sandstone samples after 3 d using either deionized water or groundwater, but As was leached efficiently by sodium bicarbonate, potassium bicarbonate, and ferric chloride solutions. The leaching rate with sodium bicarbonate was about 25% higher than that with potassium bicarbonate. The data indicated that bicarbonate ion was involved primarily in As dissolution and that hydroxyl radical ion did not affect As dissolution to any significant degree. The amount of As leached was dependent upon the sodium bicarbonate concentration, increasing with reaction time for each concentration. Significant As leaching was found in the extreme pH ranges of <1.9 and 8.0-10.4. The resulting arseno-carbonate complexes formed were stable in groundwater.

EFFECT OF CADMIUM(II) ON FREE RADICALS IN DOPA-MELANIN TESTED BY EPR SPECTROSCOPY.

PubMed

Zdybel, Magdalena; Pilawa, Barbara; Chodurek, Ewa

2015-01-01

Electron paramagnetic resonance (EPR) spectroscopy may be applied to examine interactions of melanin with metal ions and drugs. In this work EPR method was used to examination of changes in free radical system of DOPA-melanin--the model eumelanin after complexing with diamagnetic cadmium(II) ions. Cadmium(II) may affect free radicals in melanin and drugs binding by this polymer, so the knowledge of modification of properties and free radical concentration in melanin is important to pharmacy. The effect of cadmium(II) in different concentrations on free radicals in DOPA-melanin was determined. EPR spectra of DOPA-melanin, and DOPA-melanin complexes with cadmium(II) were measured by an X-band (9.3 GHz) EPR spectrometer produced by Radiopan (Poznań, Poland) and the Rapid Scan Unit from Jagmar (Krak6w, Poland). The DOPA (3,4-dihydroxyphenylalanine) to metal ions molar ratios in the reaction mixtures were 2:1, 1:1, and 1: 2. High concentrations of o-semiquinone (g ~2.0040) free radicals (~10(21)-10(22) spin/g) characterize DOPA-melanin and its complexes with cadmium(II). Formation of melanin complexes with cadmium(II) increase free radical concentration in DOPA-melanin. The highest free radical concentration was obtained for DOPA-melanin-cadmium(II) (1:1) complexes. Broad EPR lines with linewidths: 0.37-0.73 mT, were measured. Linewidths increase after binding of cadmium(II) to melanin. Changes of integral intensities and linewidths with increasing microwave power indicate the homogeneous broadening of EPR lines, independently on the metal ion concentration. Slow spin-lattice relaxation processes existed in all the tested samples, their EPR lines saturated at low microwave powers. Cadmium(II) causes fastening of spin-lattice relaxation processes in DOPA-melanin. The EPR results bring to light the effect of cadmium(II) on free radicals in melanin, and probably as the consequence on drug binding to eumelanin.

Technological applications arising from the interactions of DNA bases with metal ions.

PubMed

Park, Ki Soo; Park, Hyun Gyu

2014-08-01

An intense interest has grown in the unique interactions of nucleic acids with metal ions, which lead to the formation of metal-base pairs and the generation of fluorescent nanomaterials. In this review, different types of metal-base pairs, especially those formed from naturally occurring nucleosides, are described with emphasis also being given to recent advances made in employing these complexes to govern enzymatic reactions. The review also contains a comprehensive description of DNA-templated inorganic nanomaterials such as silver nanoclusters which possess excellent fluorescence properties. Finally, a summary is given about how these materials have led to recent advances in the field of nanobiotechnology. Copyright © 2013 Elsevier Ltd. All rights reserved.

Surface aspects of pitting and stress corrosion cracking

NASA Technical Reports Server (NTRS)

Truhan, J. S., Jr.; Hehemann, R. F.

1977-01-01

The pitting and stress corrosion cracking of a stable austenitic stainless steel in aqueous chloride environments were investigated using a secondary ion mass spectrometer as the primary experimental technique. The surface concentration of hydrogen, oxygen, the hydroxide, and chloride ion, magnesium or sodium, chromium and nickel were measured as a function of potential in both aqueous sodium chloride and magnesium chloride environments at room temperature and boiling temperatures. It was found that, under anodic conditions, a sharp increase in the chloride concentration was observed to occur for all environmental conditions. The increase may be associated with the formation of an iron chloride complex. Higher localized chloride concentrations at pits and cracks were also detected with an electron microprobe.

Bioastrophysical aspects of low energy ion irradiation of frozen anthracene containing water.

PubMed

Tuleta, M; Gabła, L; Madej, J

2001-08-13

The origin of life on Earth remains a fascinating mystery in spite of many theories existing on this subject. However, it seems that simple prebiotic molecules could play an essential role in the formation of more complex organisms. In our experiment, we synthesized a class of these molecules (quinones) bombarding frozen anthracene containing water with low energy hydrogen ions. This experiment roughly simulated the astrophysical conditions which one can find in the solar system. Thus, we can hypothesize that prebiotic molecules could be created by interaction of the solar wind with interplanetary dust grains. The delivery of these molecules to early Earth may have contributed to the generation of life on our planet.

Complementary experimental-simulational study of surfactant micellar phase in the extraction process of metallic ions: Effects of temperature and salt concentration

NASA Astrophysics Data System (ADS)

Soto-Ángeles, Alan Gustavo; Rodríguez-Hidalgo, María del Rosario; Soto-Figueroa, César; Vicente, Luis

2018-02-01

The thermoresponsive micellar phase behaviour that exhibits the Triton-X-100 micelles by temperature effect and addition of salt in the extraction process of metallic ions was explored from mesoscopic and experimental points. In the theoretical study, we analyse the formation of Triton-X-100 micelles, load and stabilization of dithizone molecules and metallic ions extraction inside the micellar core at room temperature; finally, a thermal analysis is presented. In the experimental study, the spectrophotometric outcomes confirm the solubility of the copper-dithizone complex in the micellar core, as well as the extraction of metallic ions of aqueous environment via a cloud-point at 332.2 K. The micellar solutions with salt present a low absorbance value compared with the micellar solutions without salt. The decrease in the absorbance value is attributed to a change in the size of hydrophobic region of colloidal micelles. All transitory stages of extraction process are discussed and analysed in this document.

Bridging the gap between ionic liquids and molten salts: group 1 metal salts of the bistriflamide anion in the gas phase.

PubMed

Leal, João P; da Piedade, Manuel E Minas; Canongia Lopes, José N; Tomaszowska, Alina A; Esperança, José M S S; Rebelo, Luís Paulo N; Seddon, Kenneth R

2009-03-19

Fourier transform ion cyclotron resonance mass spectrometry experiments showed that liquid Group 1 metal salts of the bistriflamide anion undergoing reduced-pressure distillation exhibit a remarkable behavior that is in transition between that of the vapor-liquid equilibrium characteristics of aprotic ionic liquids and that of the Group 1 metal halides: the unperturbed vapors resemble those of aprotic ionic liquids, in the sense that they are essentially composed of discrete ion pairs. However, the formation of large aggregates through a succession of ion-molecule reactions is closer to what might be expected for Group 1 metal halides. Similar experiments were also carried out with bis{(trifluoromethyl)sulfonyl}amine to investigate the effect of H(+), which despite being the smallest Group 1 cation, is generally regarded as a nonmetal species. In this case, instead of the complex ion-molecule reaction pattern found for the vapors of Group 1 metal salts, an equilibrium similar to those observed for aprotic ionic liquids was observed.

Study of zinc-induced changes in lymphocyte membranes using atomic force microscopy, luminescence, and light scattering methods

NASA Astrophysics Data System (ADS)

Filimonenko, D. S.; Khairullina, A. Ya.; Yasinskii, V. M.; Kozlova, N. M.; Zubritskaja, G. P.; Slobozhanina, E. I.

2011-07-01

Changes in the surface structure of lymphocyte membranes exposed to various concentrations of zinc ions are studied. It is found by atomic force microscopy that increasing the concentration of zinc ions leads to a reduction in the correlation length of the autocorrelation function of the roughness profile of a lymphocyte compared to control samples; this may indicate the existence of fine structure in the membrane surface. Fluorescence markers are used to observe a reduction in the microviscosity of the lipids in the outer monolayer of the lipid bilayer after lymphocytes are exposed to Zn ions, as well as the exposure of phosphatidylserine on the surface membrane, and the oxidation of HS-groups of membrane proteins. Calculations of the absorption coefficients of lymphocytes modified with zinc reveal the existence of absorption bands owing to the formation of metal-protein complexes and zinc oxide nanoparticles. These results indicate significant changes in the structural and functional state of lymphocyte membranes exposed to zinc ions.

Synthesis, spectroscopic and thermal studies of transition metal complexes derived from benzil and diethylenetriamine

NASA Astrophysics Data System (ADS)

Khan, Sadaf; Nami, Shahab A. A.; Siddiqi, K. S.

2007-10-01

A macrocyclic ligand, bdta (where bdta = 3,6,9,12,15,18-hexaaza-1,2,10,11-tetraphenyl-2,9,11,18-tetraenecyclododecane) has been prepared by cyclocondensation of benzil with diethylenetriamine which efficiently encapsulates transition as well as pseudo-transition metal ions leading to the formation of M(bdta)Cl 2 type complexes [where M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)]. The analytical, spectroscopic and magnetic moment data suggests an octahedral geometry for all the complexes. EPR spectra of Mn(II) and Cu(II) show considerable exchange interaction in the complex. They are non-conducting in DMSO. The TGA profile of the ligand and its complexes are identical and consists of two discreet stages. The voltammogram of Cu-complex exhibits a quasi-reversible one-electron transfer wave for Cu(II)/Cu(I) couple.

Synthesis, spectroscopic and thermal studies of transition metal complexes derived from benzil and diethylenetriamine.

PubMed

Khan, Sadaf; Nami, Shahab A A; Siddiqi, K S

2007-10-01

A macrocyclic ligand, bdta (where bdta=3,6,9,12,15,18-hexaaza-1,2,10,11-tetraphenyl-2,9,11,18-tetraenecyclododecane) has been prepared by cyclocondensation of benzil with diethylenetriamine which efficiently encapsulates transition as well as pseudo-transition metal ions leading to the formation of M(bdta)Cl2 type complexes [where M=Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)]. The analytical, spectroscopic and magnetic moment data suggests an octahedral geometry for all the complexes. EPR spectra of Mn(II) and Cu(II) show considerable exchange interaction in the complex. They are non-conducting in DMSO. The TGA profile of the ligand and its complexes are identical and consists of two discreet stages. The voltammogram of Cu-complex exhibits a quasi-reversible one-electron transfer wave for Cu(II)/Cu(I) couple.

Space Plasma Ion Processing of the Lunar Soil: Modeling of Radiation-Damaged Rim Widths on Lunar Grains

NASA Technical Reports Server (NTRS)

Chamberlin, S.; Christoffersen, R.; Keller, L.

2007-01-01

Chemically and microstructurally complex altered rims around grains in the finest size fraction (<20 micron) of the lunar regolith are the result of multi-stage processes involving both solar ion radiation damage and nanoscale deposition of impact or sputter-derived vapors. The formation of the rims is an important part of the space weathering process, and is closely linked to key changes in optical reflectance and other bulk properties of the lunar surface. Recent application of field-emission scanning transmission electron microscope techniques, including energy dispersive X-ray spectral imaging, is making it easier to unravel the "nano-stratigraphy" of grain rims, and to delineate the portions of rims that represent Radiation-Amorphized (RA) host grain from overlying amorphous material that represents vapor/sputter deposits. For the portion of rims formed by host grain amorphization (henceforth called RA rims), we have been investigating the feasibility of using Monte Carlo-type ion-atom collision models, combined with experimental ion irradiation data, to derive predictive numerical models linking the width of RA rims to the grain s integrated solar ion radiation exposure time.

Engineering an FMN-based iLOV protein for the detection of arsenic ions.

PubMed

Ravikumar, Yuvaraj; Nadarajan, Saravanan Prabhu; Lee, Chong-Soon; Yun, Hyungdon

2017-05-15

Over the past few decades, genetically encoded fluorescent proteins have been widely used as efficient probes to explore and investigate the roles of metal ions in biological processes. The discovery of small FMN-based fluorescent proteins, such as iLOV and FbFP, has enabled researchers to exploit these fluorescent reporter proteins for metal-sensing applications. In this study, we report the inherent binding properties of iLOV towards arsenic ions. The fluorescence quenching of iLOV was linearly related to the concentration of arsenic ions, and engineered proteins showed better sensitivity than the wild-type protein. Engineering key residues around the chromophore converted the iLOV protein into a highly sensitive sensor for As 3+ ions. iLOV N468S exhibited an improved binding affinity with a dissociation constant of 1.5 μM. Furthermore, the circular dichroism spectra indicated that the fluorescence quenching mechanism might be related to arsenic-protein complex formation. Thus, the reagentless sensing of arsenic can potentially be exploited to determine intracellular or environmental arsenic using a genetically encoded biosensing approach. Copyright © 2017 Elsevier Inc. All rights reserved.

PC-ANN assisted to the determination of Vanadium (IV) ion using an optical sensor based on immobilization of Eriochorome Cyanine R on a triacetylcellulose film.

PubMed

Bordbar, Mohammad Mahdi; Khajehsharifi, Habibollah; Solhjoo, Aida

2015-01-01

More detailed analytical studies of an optical sensor based on immobilization of Eriochorome Cyanine R (ECR) on a triacetylcellulose film have been described to determine Vanadium (IV) ions in some real samples. The sensor based on complex formation between Vanadium (IV) ions and ECR in acidic media caused the color of the film to change from violet to blue along with the appearance of a strong peak appears at 595 nm. At the optimal conditions, the calibration curve showed a linear range of 9.90×10(-7)-8.25×10(-5)mol L(-1). Vanadium (IV) ions can be detected with a detection limit of 1.03×10(-7)mol L(-1) within 15 min depending on its concentration. Also, the working range was improved by using PC-ANN algorithm. The sensor could regenerate with dilute acetic acid solution and could be completely reversible. The proposed sensor was successfully applied for determining V (IV) ions in environmental water and tea leaves. Copyright © 2015 Elsevier B.V. All rights reserved.

Computing the complex : Dusty plasmas in the presence of magnetic fields and UV radiation

NASA Astrophysics Data System (ADS)

Land, V.

2007-12-01

About 90% of the visible universe is plasma. Interstellar clouds, stellar cores and atmospheres, the Solar wind, the Earth's ionosphere, polar lights, and lightning are all plasma; ionized gases, consisting of electrons, ions, and neutrals. Not only many industries, like the microchip and solar cell industry, but also future fusion power stations, rely heavily on the use of plasma. More and more, home appliances include plasma technologies, like compact fluorescent light sources, and plasma screens. Dust particles, which can disrupt plasma processes, enter these plasmas, through chemical reactions in the plasma, or through interactions between plasma and walls. For instance, during microchip fabrication, dust particles can destroy the tiny, nanometre-sized structures on the surface of these chips. On the other hand, dust particles orbiting Young Stellar Objects coagulate and form the seeds of planets. In order to understand fundamental processes, such as planet formation, or to optimize industrial plasma processes, a thorough description of dusty plasma is necessary. Dust particles immersed in plasma collect ions and electrons from the plasma and charge up electrically. Therefore, the presence of dust changes plasma, while at the same time many forces start acting on the dust. Therefore, the dust and plasma become coupled, making dusty plasma a very complex medium to describe, in which many length and time scales play a role, from the Debye length to the length of the electrodes, and from the inverse plasma frequencies to the dust transport times. Using a self-consistent fluid model, we simulate these multi-scale dusty plasmas in radio frequency discharges under micro-gravity. We show that moderate non-linear scattering of ions by the dust particles is the most important aspect in the calculation of the ion drag force. This force is also responsible for the formation of a dust-free 'void' in dusty plasma under micro-gravity, caused by ions moving from the centre of the void towards the outside of the discharge. The void thus requires electron-impact ionizations inside the void. The electrons gain the energy for these ionizations inside the dust cloud surrounding the void, however. We show that a growing electron temperature gradient is responsible for the transport of electron energy from the surrounding dust cloud into the void. An axial magnetic field in the discharge magnetizes the electrons. This changes the ambipolar flux of ions through the bulk of the discharge. The ion drag force changes, resulting in a differently shaped void and faster void formation. Experiments in a direct current discharge, show a response of both dust and plasma in the E?B direction, when a magnetic field is applied. The dust response consists of two phases: an initial fast phase, and a later, slow phase. Using a Particle-In-Cell plus Monte Carlo model, we show that the dust charge can be reduced by adding a flux of ultraviolet radiation. A source of ultraviolet light can thus serve as a tool to manipulate dusty plasmas, but might also be important for the coagulation of dust particles around young stars and planet formation in general.

Sustained release of antibiotic complexed by multivalent ion: in vitro and in vivo study for the treatment of peritonitis.

PubMed

Na, Seung Yeon; Oh, Se Heang; Kim, Tae Ho; Yoon, Jin A; Lee, In Soo; Lee, Jin Ho

2014-12-10

The main aims of this study are (i) the development of an antibiotic complexed with multivalent ion, which can allow sustained release of the antibiotic without any additional matrix or difficult process and (ii) the feasibility study of the ion-complexed antibiotic as a therapeutic technique for peritonitis treatment. An ion-complexed antibiotic is prepared by simple mixing of two aqueous solutions containing an ionized (water-soluble) drug (tetracycline) and a multivalent counter ionic compound. The ion-complexed antibiotic shows a continuous release of the antibiotic up to 21 days, and thus prolonged anti-bacterial effect by gradual ionic exchange between the multivalent ions in the complex and same-charged monovalent ions in surrounding medium. From the in vivo animal study using a cecum perforated peritonitis mouse model, the ion-complexed antibiotic group shows sufficient anti-bacterial effect and thus effectively treat the peritonitis because of the extermination of the contaminated enteric bacteria in the peritoneum during wound healing of injury cecum (by the sustained release of antibiotic from the ion complex). These results suggest that the ion-complexed antibiotic system may be promising for the effective treatment of the peritonitis caused by frequent gastrointestinal defect in clinical fields. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and characterization of a novel aminopolycarboxylate complexant for efficient trivalent f-element differentiation: N-butyl-2-acetamide-diethylenetriamine- N, N', N", N"-tetraacetic acid

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

Heathman, Colt R.; Grimes, Travis S.; Jansone-Popova, Santa

The novel metal ion complexant N-butyl-2-acetamide-diethylenetriamine-N,N',N",N"-tetraacetic acid (DTTA-BuA) uses an amide functionalization to increase the total ligand acidity and attain efficient 4f/5f differentiation in low pH conditions. The amide, when located on the diethylenetriamine platform containing four acetate pendant arms maintains the octadentate coordination sphere for all investigated trivalent f-elements. This compact coordination environment inhibits the protonation of LnL- complexes, as indicated by lower K 111 constants relative to the corresponding protonation site of the free ligand. For actinide ions, the enhanced stability of AnL- lowers the K 111 for americium and curium beyond the aptitude of potentiometric detection. Densitymore » functional theory computations indicate the difference in the back-donation ability of Am 3+ and Eu 3+ f-orbitals is mainly responsible for stronger proton affinity of EuL- compared to AmL-. The measured stability constants for the formation of AmL- and CmL- complexes are consistently higher, relative to ML- complexes with lanthanides of similar charge density. When compared with the conventional aminopolycarboxylate diethylenetriamine pentaacetic acid (DTPA), the modified DTTA-BuA complexant features higher ligand acidity and the important An 3+/Ln 3+ differentiation when deployed on a liquid–liquid distribution platform.« less

Synthesis and binding properties of arylethyne-linked porphyrin-zinc complexes for organic electronics applications.

PubMed

Reainthippayasakul, W; Paosawatyanyong, B; Bhanthumnavin, W

2013-05-01

Conjugated meso-alkynyl 5,15-dimesitylporphyrin metal complexes have been synthesized by Sonogashira coupling reaction in good yields. Alkynyl groups were chosen as a link at the meso positions in order to extend the pi-conjugated length of porphyrin rings. These synthesized porphyrin derivatives were characterized by 1H NMR spectroscopy and MALDI-TOF mass spectrometry. Moreover, UV-visible spectroscopy and fluorescence spectroscopy were also used to investigate their photophysical properties. It has been demonstrated that central metal ions as well as meso substituents on porphyrin rings affected the electronic absorption and emission spectra of the compounds. Spectroscopic results revealed that alkyne-linked porphyrin metal complexes showed higher pi-conjugation compared with porphyrin building blocks resulting in red shifts in both absorption and emission spectra. Coordination properties of synthesized porphyrins were preliminarily investigated by UV-visible absorption and fluorescence emission spectroscopic titration with pyridine as axial ligand. The formation of porphyrin-pyridine complexes resulted in significant red shifts in absorption spectra and decrease of fluorescence intensity in emission spectra. Moreover, the 1H NMR titration experiments suggested that central metal ions play an important role to coordinate with pyridine and the coordination of porphyrin zinc(II) complex with pyridine occur in a 1:1 ratio. From these spectroscopic results, alkyne-linked porphyrin metal complexes offer potential applications as materials for optical organic nanosensors.

Influence of metal ions on flavonoid protection against asbestos-induced cell injury.

PubMed

Kostyuk, V A; Potapovich, A I; Vladykovskaya, E N; Korkina, L G; Afanas'ev, I B

2001-01-01

Influence of metal ions (Fe2+, Fe3+, Cu2+, Zn2+) on the protective effect of rutin, dihydroquercetin, and green tea epicatechins against in vitro asbestos-induced cell injury was studied. Metals have been found to increase the capacity of rutin and dihydroquercetin to protect peritoneal macrophages against chrysotile asbestos-induced injury. The data presented here show that this effect is due to the formation of flavonoid metal complexes, which turned out to be more effective radical scavengers than uncomplexed flavonoids. At the same time epicatechins and their metal complexes have similar antiradical properties and protective capacities against the asbestos induced injury of macrophages. Metal complexes of all flavonoids were found to be considerably more potent than parent flavonoids in protecting red blood cells against asbestos-induced injury. It was also found that the metal complexes of all flavonoids were absorbed by chrysotile asbestos fibers considerably better than uncomplexed compounds and probably for this reason flavonoid metal complexes have better protective properties against asbestos induced hemolysis. Thus, the results of the present study show that flavonoid metal complexes may be effective therapy for the inflammatory response associated with the inhalation of asbestos fiber. The advantage of their application could be the strong increase in ROS scavenging by flavonoids and finally a better cell protection under the conditions of cellular oxidative stress.