Femtosecond study of the effects of ions and hydrophobes on the dynamics of water.

Science.gov (United States)

van der Post, Sietse T; Tielrooij, Klaas-Jan; Hunger, Johannes; Backus, Ellen H G; Bakker, Huib J

2013-01-01

We study the effects of ions and hydrophobic molecular groups on the orientational dynamics of water using THz dielectric relaxation (THz-DR) and polarization-resolved femtosecond infrared (fs-IR) pump-probe spectroscopy. We measure the dynamics of water in solutions of NaI, NaCl, CsCl, guanidinium chloride (GndCl) and tetramethyl guanidinium chloride (TMGndCl) of different the static dipoles of their surrounding water molecules. With fs-IR we find that concentrations. With THz-DR we observe that strongly hydrated cations align the OD groups that form hydrogen bonds to halide anions reorient with two distinct time constants of 2 +/- 0.3 ps and 9 +/- 1 ps. The fast process is assigned to a wobbling motion of the OD group that keeps the hydrogen bond with the anion intact. The amplitude of this wobbling motion depends on the nature of both the anion and the counter cation. The replacement of four of the six hydrogen atoms of the weakly hydrated cation guanidinium by hydrophobic methyl groups leads to an exceptionally strong slowing down of the water dynamics. Hydrophobic groups thus appear to have a much stronger effect on the dynamics of water than ions. These findings give new insights in the mechanism of protein denaturation by GndCl and TMGndCl.

Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions

Science.gov (United States)

Yaremko, Z. M.; Fedushinskaya, L. B.; Burka, O. A.; Soltys, M. N.

2014-09-01

The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and pH of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant. It is found that the inflection point on the dependence of the difference between the pH values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of pH of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.

Ion Transfer Voltammetry Associated with Two Polarizable Interfaces Within Water and Moderately Hydrophobic Ionic Liquid Systems

DEFF Research Database (Denmark)

Gan, Shiyu; Zhou, Min; Zhang, Jingdong

2013-01-01

An electrochemical system composed of two polarizable interfaces (the metallic electrode|water and water|ionic liquid interfaces), namely two‐polarized‐interface (TPI) technique, has been proposed to explore the ion transfer processes between water and moderately hydrophobic ionic liquids (W...... to an extremely narrow polarized potential window (ppw) caused by these moderately hydrophobic ionic components. In this article, we show that TPI technique has virtually eliminated the ppw limitation based on a controlling step of concentration polarization at the electrode|water interface. With the aid...

Premicellar interaction of PEO-PPO-PEO triblock copolymers with partially hydrophobic alcohols: NMR study

Czech Academy of Sciences Publication Activity Database

Kříž, Jaroslav; Dybal, Jiří

2013-01-01

Roč. 51, č. 5 (2013), s. 275-282 ISSN 0749-1581 R&D Projects: GA ČR GAP205/11/1657; GA ČR GA203/09/1478 Institutional support: RVO:61389013 Keywords : pluronics * hydrophobic interaction * hydrophobic alcohols Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.559, year: 2013

Hydrophobic Interaction Chromatography for Bottom-Up Proteomics Analysis of Single Proteins and Protein Complexes.

Science.gov (United States)

Rackiewicz, Michal; Große-Hovest, Ludger; Alpert, Andrew J; Zarei, Mostafa; Dengjel, Jörn

2017-06-02

Hydrophobic interaction chromatography (HIC) is a robust standard analytical method to purify proteins while preserving their biological activity. It is widely used to study post-translational modifications of proteins and drug-protein interactions. In the current manuscript we employed HIC to separate proteins, followed by bottom-up LC-MS/MS experiments. We used this approach to fractionate antibody species followed by comprehensive peptide mapping as well as to study protein complexes in human cells. HIC-reversed-phase chromatography (RPC)-mass spectrometry (MS) is a powerful alternative to fractionate proteins for bottom-up proteomics experiments making use of their distinct hydrophobic properties.

Purification of tracer for somatomedin C radioimmunoassay by hydrophobic interaction chromatography

Energy Technology Data Exchange (ETDEWEB)

Baxter, R.C.; Brown, A.S.

1982-03-01

A tracer for use in the somatomedin C radiommunoassay by hydrophobic interaction chromatography was purified. Material showing greatest immunoreactivity binds to Octyl Sepharose CL-4B (Pharmacia) in a buffer mixture consisting of 130 mL of acetonitrile and 870 mL of 0.1 mol/L NH/sub 4/HCO/sub 3/, pH 7.8, but is eluted by increasing the acetonitrile content to 180 mL/L. As compared with tracer purified by binding to specific antiserum in liquid phase, precipitating the complex with second antibody, and then dissociating by gel chromatography at acid pH, this tracer shows equal immunoreactivity against specific somatomedin C antiserum. Either preparation allows excellent discrimination between extracts of normal, acromegalic, and hypopituitary plasma samples; thus either is suitable for use in the somatomedin C radioimmunoassay. Tracer purification by hydrophobic interaction chromatography is rapid and inexpensive. It may be useful in preparing highly immunoreactive tracers for other peptide radioimmunoassays.

Molecular-Level Thermodynamic Switch Controls Chemical Equilibrium in Sequence-Specific Hydrophobic Interaction of 35 Dipeptide Pairs

OpenAIRE

Chun, Paul W.

2003-01-01

Applying the Planck-Benzinger methodology, the sequence-specific hydrophobic interactions of 35 dipeptide pairs were examined over a temperature range of 273–333 K, based on data reported by Nemethy and Scheraga in 1962. The hydrophobic interaction in these sequence-specific dipeptide pairs is highly similar in its thermodynamic behavior to that of other biological systems. The results imply that the negative Gibbs free energy change minimum at a well-defined stable temperature, 〈Ts〉, where t...

Preferential hydrophobic interactions are responsible for a preference of D-amino acids in the aminoacylation of 5'-AMP with hydrophobic amino acids

Science.gov (United States)

Lacey, J. C. Jr; Wickramasinghe, N. S.; Sabatini, R. S.

1992-01-01

We have studied the chemistry of aminoacyl AMP to model reactions at the 3' terminus of aminoacyl tRNA for the purpose of understanding the origin of protein synthesis. The present studies relate to the D, L preference in the esterification of 5'-AMP. All N-acetyl amino acids we studied showed faster reaction of the D-isomer, with a generally decreasing preference for D-isomer as the hydrophobicity of the amino acid decreased. The beta-branched amino acids, Ile and Val, showed an extreme preference for D-isomer. Ac-Leu, the gamma-branched amino acid, showed a slightly low D/L ratio relative to its hydrophobicity. The molecular basis for these preferences for D-isomer is understandable in the light of our previous studies and seems to be due to preferential hydrophobic interaction of the D-isomer with adenine. The preference for hydrophobic D-amino acids can be decreased by addition of an organic solvent to the reaction medium. Conversely, peptidylation with Ac-PhePhe shows a preference for the LL isomer over the DD isomer.

Dewetting and Hydrophobic Interaction in Physical and Biological Systems

Science.gov (United States)

Berne, Bruce J.; Weeks, John D.; Zhou, Ruhong

2013-01-01

Hydrophobicity manifests itself differently on large and small length scales. This review focuses on large length scale hydrophobicity, particularly on dewetting at single hydrophobic surfaces and drying in regions bounded on two or more sides by hydrophobic surfaces. We review applicable theories, simulations and experiments pertaining to large scale hydrophobicity in physical and biomoleclar systems and clarify some of the critical issues pertaining to this subject. Given space constraints, we could not review all of the significant and interesting work in this very active field. PMID:18928403

Thermodynamic Molecular Switch in Sequence-Specific Hydrophobic Interaction: Two Computational Models Compared

Directory of Open Access Journals (Sweden)

Paul Chun

2003-01-01

Full Text Available We have shown in our published work the existence of a thermodynamic switch in biological systems wherein a change of sign in ΔCp°(Treaction leads to a true negative minimum in the Gibbs free energy change of reaction, and hence, a maximum in the related Keq. We have examined 35 pair-wise, sequence-specific hydrophobic interactions over the temperature range of 273–333 K, based on data reported by Nemethy and Scheraga in 1962. A closer look at a single example, the pair-wise hydrophobic interaction of leucine-isoleucine, will demonstrate the significant differences when the data are analyzed using the Nemethy-Scheraga model or treated by the Planck-Benzinger methodology which we have developed. The change in inherent chemical bond energy at 0 K, ΔH°(T0 is 7.53 kcal mol-1 compared with 2.4 kcal mol-1, while ‹ts› is 365 K as compared with 355 K, for the Nemethy-Scheraga and Planck-Benzinger model, respectively. At ‹tm›, the thermal agitation energy is about five times greater than ΔH°(T0 in the Planck-Benzinger model, that is 465 K compared to 497 K in the Nemethy-Scheraga model. The results imply that the negative Gibbs free energy minimum at a well-defined ‹ts›, where TΔS° = 0 at about 355 K, has its origin in the sequence-specific hydrophobic interactions, which are highly dependent on details of molecular structure. The Nemethy-Scheraga model shows no evidence of the thermodynamic molecular switch that we have found to be a universal feature of biological interactions. The Planck-Benzinger method is the best known for evaluating the innate temperature-invariant enthalpy, ΔH°(T0, and provides for better understanding of the heat of reaction for biological molecules.

Review: Milk Proteins as Nanocarrier Systems for Hydrophobic Nutraceuticals.

Science.gov (United States)

Kimpel, Florian; Schmitt, Joachim J

2015-11-01

Milk proteins and milk protein aggregates are among the most important nanovehicles in food technology. Milk proteins have various functional properties that facilitate their ability to carry hydrophobic nutraceutical substances. The main functional transport properties that were examined in the reviewed studies are binding of molecules or ions, surface activity, aggregation, gelation, and interaction with other polymers. Hydrophobic binding has been investigated using caseins and isolated β-casein as well as whey proteins. Surface activity of caseins has been used to create emulsion-based carrier systems. Furthermore, caseins are able to self-assemble into micelles, which can incorporate molecules. Gelation and interaction with other polymers can be used to encapsulate molecules into protein networks. The release of transported substances mainly depends on pH and swelling behavior of the proteins. The targeted use of nanocarrier systems requires specific knowledge about the binding mechanisms between the proteins and the carried substances in a certain food matrix. © 2015 Institute of Food Technologists®

Reference interaction site model with hydrophobicity induced density inhomogeneity: An analytical theory to compute solvation properties of large hydrophobic solutes in the mixture of polyatomic solvent molecules

International Nuclear Information System (INIS)

Cao, Siqin; Sheong, Fu Kit; Huang, Xuhui

2015-01-01

Reference interaction site model (RISM) has recently become a popular approach in the study of thermodynamical and structural properties of the solvent around macromolecules. On the other hand, it was widely suggested that there exists water density depletion around large hydrophobic solutes (>1 nm), and this may pose a great challenge to the RISM theory. In this paper, we develop a new analytical theory, the Reference Interaction Site Model with Hydrophobicity induced density Inhomogeneity (RISM-HI), to compute solvent radial distribution function (RDF) around large hydrophobic solute in water as well as its mixture with other polyatomic organic solvents. To achieve this, we have explicitly considered the density inhomogeneity at the solute-solvent interface using the framework of the Yvon-Born-Green hierarchy, and the RISM theory is used to obtain the solute-solvent pair correlation. In order to efficiently solve the relevant equations while maintaining reasonable accuracy, we have also developed a new closure called the D2 closure. With this new theory, the solvent RDFs around a large hydrophobic particle in water and different water-acetonitrile mixtures could be computed, which agree well with the results of the molecular dynamics simulations. Furthermore, we show that our RISM-HI theory can also efficiently compute the solvation free energy of solute with a wide range of hydrophobicity in various water-acetonitrile solvent mixtures with a reasonable accuracy. We anticipate that our theory could be widely applied to compute the thermodynamic and structural properties for the solvation of hydrophobic solute

Epitope mapping of imidazolium cations in ionic liquid-protein interactions unveils the balance between hydrophobicity and electrostatics towards protein destabilisation.

Science.gov (United States)

Silva, Micael; Figueiredo, Angelo Miguel; Cabrita, Eurico J

2014-11-14

We investigated imidazolium-based ionic liquid (IL) interactions with human serum albumin (HSA) to discern the level of cation interactions towards protein stability. STD-NMR spectroscopy was used to observe the imidazolium IL protons involved in direct binding and to identify the interactions responsible for changes in Tm as accessed by differential scanning calorimetry (DSC). Cations influence protein stability less than anions but still significantly. It was found that longer alkyl side chains of imidazolium-based ILs (more hydrophobic) are associated with a higher destabilisation effect on HSA than short-alkyl groups (less hydrophobic). The reason for such destabilisation lies on the increased surface contact area of the cation with the protein, particularly on the hydrophobic contacts promoted by the terminus of the alkyl chain. The relevance of the hydrophobic contacts is clearly demonstrated by the introduction of a polar moiety in the alkyl chain: a methoxy or alcohol group. Such structural modification reduces the degree of hydrophobic contacts with HSA explaining the lesser extent of protein destabilisation when compared to longer alkyl side chain groups: above [C2mim](+). Competition STD-NMR experiments using [C2mim](+), [C4mim](+) and [C2OHmim](+) also validate the importance of the hydrophobic interactions. The combined effect of cation and anion interactions was explored using (35)Cl NMR. Such experiments show that the nature of the cation has no influence on the anion-protein contacts, still the nature of the anion modulates the cation-protein interaction. Herein we propose that more destabilising anions are likely to be a result of a partial contribution from the cation as a direct consequence of the different levels of interaction (cation-anion pair and cation-protein).

Ion mobilities and ion-atom interaction potentials

International Nuclear Information System (INIS)

Gatland, I.R.

1982-01-01

The techniques for measuring the mobilities of ions in gases, relating interaction potentials to mobilities, and determining potentials from experimental mobilities are reviewed. Applications are presented for positive alkali ions and negative halogen ions in inert gases. (Auth.)

Hydrophobic core substitutions in calbindin D9k

DEFF Research Database (Denmark)

Kragelund, B B; Jönsson, M; Bifulco, G

1998-01-01

Hydrophobic core residues have a marked influence on the Ca2+-binding properties of calbindin D9k, even though there are no direct contacts between these residues and the bound Ca2+ ions. Eleven different mutants with substitutions in the hydrophobic core were produced, and their equilibrium Ca2+...... that the hydrophobic core residues promote Ca2+ binding both by contributing to the preformation of the Ca2+ sites in the apo state and by preferentially stabilizing the Ca2+-bound state.......Hydrophobic core residues have a marked influence on the Ca2+-binding properties of calbindin D9k, even though there are no direct contacts between these residues and the bound Ca2+ ions. Eleven different mutants with substitutions in the hydrophobic core were produced, and their equilibrium Ca2...... that the mutation causes only very minimal perturbations in the immediate vicinity of residue 61. Substitutions of alanines or glycines for bulky residues in the center of the core were found to have significant effects on both Ca2+ affinity and dissociation rates. These substitutions caused a reduction in affinity...

Interactions between nano-TiO2 and the oral cavity: Impact of nanomaterial surface hydrophilicity/hydrophobicity

International Nuclear Information System (INIS)

Teubl, Birgit J.; Schimpel, Christa; Leitinger, Gerd; Bauer, Bettina; Fröhlich, Eleonore; Zimmer, Andreas; Roblegg, Eva

2015-01-01

Highlights: • Hydrophilic as well as hydrophobic TiO 2 NPs agglomerated under oral physiological conditions. • Particles penetrated the upper and lower buccal epithelium, independent on the degree of hydrophilicity. • Most of the hydrophobic particles were found in vesicular structures, while hydrophilic particles were freely distributed in the cytoplasm. • Hydrophilic particles had a higher potential to trigger toxic effects (e.g., ROS) than hydrophobic particles. - Abstract: Titanium dioxide (TiO 2 ) nanoparticles are available in a variety of oral applications, such as food additives and cosmetic products. Thus, questions about their potential impact on the oro-gastrointestinal route rise. The oral cavity represents the first portal of entry and is known to rapidly interact with nanoparticles. Surface charge and size contribute actively to the particle–cell interactions, but the influence of surface hydrophilicity/hydrophobicity has never been shown before. This study addresses the biological impact of hydrophilic (NM 103, rutile, 20 nm) and hydrophobic (NM 104, rutile, 20 nm) TiO 2 particles within the buccal mucosa. Particle characterization was addressed with dynamic light scattering and laser diffraction. Despite a high agglomeration tendency, 10% of the particles/agglomerates were present in the nanosized range and penetrated into the mucosa, independent of the surface properties. However, significant differences were observed in intracellular particle localization. NM 104 particles were found freely distributed in the cytoplasm, whereas their hydrophobic counterparts were engulfed in vesicular structures. Although cell viability/membrane integrity was not affected negatively, screening assays demonstrated that NM 104 particles showed a higher potential to decrease the physiological mitochondrial membrane potential than NM 103, resulting in a pronounced generation of reactive oxygen species

Towards understanding hydrophobic recovery of plasma treated polymers: Storing in high polarity liquids suppresses hydrophobic recovery

International Nuclear Information System (INIS)

Bormashenko, Edward; Chaniel, Gilad; Grynyov, Roman

2013-01-01

The phenomenon of hydrophobic recovery was studied for cold air plasma treated polyethylene films. Plasma-treated polymer films were immersed into liquids with very different polarities such as ethanol, acetone, carbon tetrachloride, benzene and carbon disulphide. Hydrophobic recovery was studied by measurement of contact angles. Immersion into high polarity liquids slows markedly the hydrophobic recovery. We relate this slowing to dipole–dipole interaction of polar groups of the polymer with those of the liquids. This kind of interaction becomes decisive when polar groups of polymer chains are at least partially spatially fixed.

Influence of nonelectrostatic ion-ion interactions on double-layer capacitance

Science.gov (United States)

Zhao, Hui

2012-11-01

Recently a Poisson-Helmholtz-Boltzmann (PHB) model [Bohinc , Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.031130 85, 031130 (2012)] was developed by accounting for solvent-mediated nonelectrostatic ion-ion interactions. Nonelectrostatic interactions are described by a Yukawa-like pair potential. In the present work, we modify the PHB model by adding steric effects (finite ion size) into the free energy to derive governing equations. The modified PHB model is capable of capturing both ion specificity and ion crowding. This modified model is then employed to study the capacitance of the double layer. More specifically, we focus on the influence of nonelectrostatic ion-ion interactions on charging a double layer near a flat surface in the presence of steric effects. We numerically compute the differential capacitance as a function of the voltage under various conditions. At small voltages and low salt concentrations (dilute solution), we find out that the predictions from the modified PHB model are the same as those from the classical Poisson-Boltzmann theory, indicating that nonelectrostatic ion-ion interactions and steric effects are negligible. At moderate voltages, nonelectrostatic ion-ion interactions play an important role in determining the differential capacitance. Generally speaking, nonelectrostatic interactions decrease the capacitance because of additional nonelectrostatic repulsion among excess counterions inside the double layer. However, increasing the voltage gradually favors steric effects, which induce a condensed layer with crowding of counterions near the electrode. Accordingly, the predictions from the modified PHB model collapse onto those computed by the modified Poisson-Boltzmann theory considering steric effects alone. Finally, theoretical predictions are compared and favorably agree with experimental data, in particular, in concentrated solutions, leading one to conclude that the modified PHB model adequately predicts the diffuse

Interactions between nano-TiO{sub 2} and the oral cavity: Impact of nanomaterial surface hydrophilicity/hydrophobicity

Energy Technology Data Exchange (ETDEWEB)

Teubl, Birgit J.; Schimpel, Christa [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Leitinger, Gerd [Institute of Cell Biology, Histology and Embryology, Research Unit Electron Microscopic Techniques, Medical University of Graz, 8010 (Austria); Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Bauer, Bettina [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); Fröhlich, Eleonore [Center for Medical Research, Medical University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Zimmer, Andreas [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria); Roblegg, Eva, E-mail: eva.roblegg@uni-graz.at [Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, 8010 (Austria); BioTechMed, Graz 8010 (Austria)

2015-04-09

Highlights: • Hydrophilic as well as hydrophobic TiO{sub 2} NPs agglomerated under oral physiological conditions. • Particles penetrated the upper and lower buccal epithelium, independent on the degree of hydrophilicity. • Most of the hydrophobic particles were found in vesicular structures, while hydrophilic particles were freely distributed in the cytoplasm. • Hydrophilic particles had a higher potential to trigger toxic effects (e.g., ROS) than hydrophobic particles. - Abstract: Titanium dioxide (TiO{sub 2}) nanoparticles are available in a variety of oral applications, such as food additives and cosmetic products. Thus, questions about their potential impact on the oro-gastrointestinal route rise. The oral cavity represents the first portal of entry and is known to rapidly interact with nanoparticles. Surface charge and size contribute actively to the particle–cell interactions, but the influence of surface hydrophilicity/hydrophobicity has never been shown before. This study addresses the biological impact of hydrophilic (NM 103, rutile, 20 nm) and hydrophobic (NM 104, rutile, 20 nm) TiO{sub 2} particles within the buccal mucosa. Particle characterization was addressed with dynamic light scattering and laser diffraction. Despite a high agglomeration tendency, 10% of the particles/agglomerates were present in the nanosized range and penetrated into the mucosa, independent of the surface properties. However, significant differences were observed in intracellular particle localization. NM 104 particles were found freely distributed in the cytoplasm, whereas their hydrophobic counterparts were engulfed in vesicular structures. Although cell viability/membrane integrity was not affected negatively, screening assays demonstrated that NM 104 particles showed a higher potential to decrease the physiological mitochondrial membrane potential than NM 103, resulting in a pronounced generation of reactive oxygen species.

Hydrophobic interaction chromatography in dual salt system increases protein binding capacity.

Science.gov (United States)

Senczuk, Anna M; Klinke, Ralph; Arakawa, Tsutomu; Vedantham, Ganesh; Yigzaw, Yinges

2009-08-01

Hydrophobic interaction chromatography (HIC) uses weakly hydrophobic resins and requires a salting-out salt to promote protein-resin interaction. The salting-out effects increase with protein and salt concentration. Dynamic binding capacity (DBC) is dependent on the binding constant, as well as on the flow characteristics during sample loading. DBC increases with the salt concentration but decreases with increasing flow rate. Dynamic and operational binding capacity have a major raw material cost/processing time impact on commercial scale production of monoclonal antibodies. In order to maximize DBC the highest salt concentration without causing precipitation is used. We report here a novel method to maintain protein solubility while increasing the DBC by using a combination of two salting-out salts (referred to as dual salt). In a series of experiments, we explored the dynamic capacity of a HIC resin (TosoBioscience Butyl 650M) with combinations of salts. Using a model antibody, we developed a system allowing us to increase the dynamic capacity up to twofold using the dual salt system over traditional, single salt system. We also investigated the application of this novel approach to several other proteins and salt combinations, and noted a similar protein solubility and DBC increase. The observed increase in DBC in the dual salt system was maintained at different linear flow rates and did not impact selectivity.

Hydrophobically modified polyelectrolytes : synthesis, properties and interactions with surfactants

NARCIS (Netherlands)

Nieuwkerk, A.C.

1998-01-01

Hydrophobically modified polyelectrolytes can form micelle-like aggregates, so-called microdomains, in aqueous solution. The hydrophobic side chains constitute the apolar inner part of these microdomains and the hydrophilic groups on the polyelectrolyte backbone are at the surface of the

Electronic structures in ion-surface interactions

International Nuclear Information System (INIS)

Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.

1997-01-01

A chemical bond generated by the interaction between low energy ion and base was investigated by ab initio molecular orbital method. The effects of ion charge were studied by calculation of this method. When carbon ion approached to graphite base (C 24 H 12 ), the positive ion and the neutral atom covalently bonded, but the negative ion did not combine with it. When carbon ion was injected into h-BN base (B 12 N 12 H 12 , hexagonal system boron nitride), the positive ion and the neutron atom formed covalent bond and the van der Waals binding, and the negative ion interacted statically with it. (S.Y.)

Characterization of Hydrophobic Interactions of Polymers with Water and Phospholipid Membranes Using Molecular Dynamics Simulations

Science.gov (United States)

Drenscko, Mihaela

Polymers and lipid membranes are both essential soft materials. The structure and hydrophobicity/hydrophilicity of polymers, as well as the solvent they are embedded in, ultimately determines their size and shape. Understating the variation of shape of the polymer as well as its interactions with model biological membranes can assist in understanding the biocompatibility of the polymer itself. Computer simulations, in particular molecular dynamics, can aid in characterization of the interaction of polymers with solvent, as well as polymers with model membranes. In this thesis, molecular dynamics serve to describe polymer interactions with a solvent (water) and with a lipid membrane. To begin with, we characterize the hydrophobic collapse of single polystyrene chains in water using molecular dynamics simulations. Specifically, we calculate the potential of mean force for the collapse of a single polystyrene chain in water using metadynamics, comparing the results between all atomistic with coarse-grained molecular simulation. We next explore the scaling behavior of the collapsed globular shape at the minimum energy configuration, characterized by the radius of gyration, as a function of chain length. The exponent is close to one third, consistent with that predicted for a polymer chain in bad solvent. We also explore the scaling behavior of the Solvent Accessible Surface Area (SASA) as a function of chain length, finding a similar exponent for both all-atomistic and coarse-grained simulations. Furthermore, calculation of the local water density as a function of chain length near the minimum energy configuration suggests that intermediate chain lengths are more likely to form dewetted states, as compared to shorter or longer chain lengths. Next, in order to investigate the molecular interactions between single hydrophobic polymer chains and lipids in biological membranes and at lipid membrane/solvent interface, we perform a series of molecular dynamics simulations of

Toward engineering intra-receptor interactions into bis(crown ethers).

Science.gov (United States)

Krause, Martin R; Kubik, Stefan

2012-03-01

A synthetic receptor was designed in which cooperative binding of two crown ether moieties to an alkali metal ion simultaneously causes two hydrophobic substituents not involved in direct host-guest interactions to converge. Hydrophobic interactions between these substituents can be expected to contribute to the overall complex stability. Independent binding studies involving two diastereoisomers of this bis(crown ether), one in which intra-receptor interactions between the substituents are potentially possible and one in which they are not, using isothermal titration calorimetry showed that both isomers bind potassium ions in different solvent mixtures with the same overall affinity. Profound differences were observed for each isomer, however, in the enthalpies and entropies of binding, which are consistent with intra-receptor interactions in one compound. These interactions are counteracted by enthalpy-entropy compensation so that no overall improvement in cation affinity could be observed.

Application of perfluorinated acids as ion-pairing reagents for reversed-phase chromatography and retention-hydrophobicity relationships studies of selected beta-blockers.

Science.gov (United States)

Flieger, J

2010-01-22

The addition of the homologous series of perfluorinated acids-trifluoroacetic acid (TFAA), pentafluoropropionic acid (PFPA), heptafluorobutyric acid (HFBA) to mobile phases for reversed-phase high-performance liquid chromatography (RP-HPLC) of beta-blockers was tested. Acidic modifiers were responsible for acidification of mobile phase (pH 3) ensuring the protonation of the beta-blockers and further ion pairs creation. The effect of the type and concentration of mobile phase additives on retention parameters, the efficiency of the peaks, their symmetry and separation selectivity of the beta-blockers mixture were all studied. It appeared that at increasing acid concentration, the retention factor, for all compounds investigated, increased to varying degrees. It should be stressed that the presence of acids more significantly affected the retention of the most hydrophobic beta-blockers. Differences in hydrophobicity of drugs can be maximized through variation of the hydrophobicity of additives. Thus, the relative increase in the retention depends on either concentration and hydrophobicity of the anionic mobile phase additive or hydrophobicity of analytes. According to QSRR (quantitative structure retention relationship) methodology, chromatographic lipophilicity parameters: isocratic log k and log k(w) values (extrapolated retention to pure water) were correlated with the molecular (log P(o/w)) and apparent (log P(app)) octanol-water partition coefficients obtained experimentally by countercurrent chromatography (CCC) or predicted by Pallas software. The obtained, satisfactory retention-hydrophobicity correlations indicate that, in the case of the basic drugs examined in RP-HPLC systems modified with perfluorinated acids, the retention is mainly governed by their hydrophobicity. Copyright 2009 Elsevier B.V. All rights reserved.

Protein-induced bilayer Perturbations: Lipid ordering and hydrophobic coupling

DEFF Research Database (Denmark)

Petersen, Frederic Nicolas Rønne; Laursen, Ib; Bohr, Henrik

2009-01-01

The host lipid bilayer is increasingly being recognized as an important non-specific regulator of membrane protein function. Despite considerable progress the interplay between hydrophobic coupling and lipid ordering is still elusive. We use electron spin resonance (ESR) to study the interaction...... between the model protein gramicidin and lipid bilayers of varying thickness. The free energy of the interaction is up to −6 kJ/mol; thus not strongly favored over lipid–lipid interactions. Incorporation of gramicidin results in increased order parameters with increased protein concentration...... and hydrophobic mismatch. Our findings also show that at high protein:lipid ratios the lipids are motionally restricted but not completely immobilized. Both exchange on and off rate values for the lipid ↔ gramicidin interaction are lowest at optimal hydrophobic matching. Hydrophobic mismatch of few Å results...

Effects of copper ions on the characteristics of egg white gel induced by strong alkali.

Science.gov (United States)

Shao, Yaoyao; Zhao, Yan; Xu, Mingsheng; Chen, Zhangyi; Wang, Shuzhen; Tu, Yonggang

2017-09-01

This study investigated the effects of copper ions on egg white (EW) gel induced by strong alkali. Changes in gel characteristics were examined through texture profile analysis, scanning electron microscopy (SEM), and chemical methods. The value of gel strength reached its maximum when 0.1% copper ions was added. However, the lowest cohesiveness values were observed at 0.1%. The springiness of gel without copper ions was significantly greater than the gel with copper ions added. SEM results illustrated that the low concentration of copper ions contributes to a dense and uniform gel network, and an open matrix was formed at 0.4%. The free and total sulphhydryl group content in the egg white protein gel significantly decreased with the increased copper. The increase of copper ions left the contents of ionic and hydrogen bonds basically unchanged, hydrophobic interaction presented an increasing trend, and the disulfide bond exhibited a completely opposite change. The change of surface hydrophobicity proved that the main binding force of copper induced gel was hydrophobic interaction. However, copper ions had no effect on the protein component of the gels. Generally, a low level of copper ions facilitates protein-protein association, which is involved in the characteristics of gels. Instead, high ionic strength had a negative effect on gels induced by strong alkali. © 2017 Poultry Science Association Inc.

Numerical simulation of ion-surface interactions

International Nuclear Information System (INIS)

Hou, M.

1994-01-01

This paper, based on examples from the author's contribution, aims to illustrate the role of ballistic simulations of the interaction between an ion beam and a surface in the characterization of surface properties. Several aspects of the ion-surface interaction have been modelled to various levels of sophistication by computer simulation. Particular emphasis is given to the ion scattering in the impact mode, in the multiple scattering regime and at grazing incidence, as well as to the Auger emission resulting from electronic excitation. Some examples are then given in order to illustrate the use of the combination between simulation and experiment to study the ion-surface interaction and surface properties. Ion-induced Auger emission, the determination of potentials and of overlay structures are discusse. The possibility to tackle dynamical surface properties by menas of a combination between molecular dynamics, ballistic simulations and ion scattering measurements in then briefly discussed. (orig.)

Interactions between nano-TiO2 and the oral cavity: impact of nanomaterial surface hydrophilicity/hydrophobicity.

Science.gov (United States)

Teubl, Birgit J; Schimpel, Christa; Leitinger, Gerd; Bauer, Bettina; Fröhlich, Eleonore; Zimmer, Andreas; Roblegg, Eva

2015-04-09

Titanium dioxide (TiO2) nanoparticles are available in a variety of oral applications, such as food additives and cosmetic products. Thus, questions about their potential impact on the oro-gastrointestinal route rise. The oral cavity represents the first portal of entry and is known to rapidly interact with nanoparticles. Surface charge and size contribute actively to the particle-cell interactions, but the influence of surface hydrophilicity/hydrophobicity has never been shown before. This study addresses the biological impact of hydrophilic (NM 103, rutile, 20 nm) and hydrophobic (NM 104, rutile, 20 nm) TiO2 particles within the buccal mucosa. Particle characterization was addressed with dynamic light scattering and laser diffraction. Despite a high agglomeration tendency, 10% of the particles/agglomerates were present in the nanosized range and penetrated into the mucosa, independent of the surface properties. However, significant differences were observed in intracellular particle localization. NM 104 particles were found freely distributed in the cytoplasm, whereas their hydrophobic counterparts were engulfed in vesicular structures. Although cell viability/membrane integrity was not affected negatively, screening assays demonstrated that NM 104 particles showed a higher potential to decrease the physiological mitochondrial membrane potential than NM 103, resulting in a pronounced generation of reactive oxygen species. Copyright © 2015 Elsevier B.V. All rights reserved.

3DRISM-HI-D2MSA: an improved analytic theory to compute solvent structure around hydrophobic solutes with proper treatment of solute–solvent electrostatic interactions

KAUST Repository

Cao, Siqin

2017-12-22

The 3D reference interaction site model (3DRISM) is a powerful tool to study the thermodynamic and structural properties of liquids. However, for hydrophobic solutes, the inhomogeneity of the solvent density around them poses a great challenge to the 3DRISM theory. To address this issue, we have previously introduced the hydrophobic-induced density inhomogeneity theory (HI) for purely hydrophobic solutes. To further consider the complex hydrophobic solutes containing partial charges, here we propose the D2MSA closure to incorporate the short-range and long-range interactions with the D2 closure and the mean spherical approximation, respectively. We demonstrate that our new theory can compute the solvent distributions around real hydrophobic solutes in water and complex organic solvents that agree well with the explicit solvent molecular dynamics simulations.

3DRISM-HI-D2MSA: an improved analytic theory to compute solvent structure around hydrophobic solutes with proper treatment of solute–solvent electrostatic interactions

KAUST Repository

Cao, Siqin; Zhu, Lizhe; Huang, Xuhui

2017-01-01

The 3D reference interaction site model (3DRISM) is a powerful tool to study the thermodynamic and structural properties of liquids. However, for hydrophobic solutes, the inhomogeneity of the solvent density around them poses a great challenge to the 3DRISM theory. To address this issue, we have previously introduced the hydrophobic-induced density inhomogeneity theory (HI) for purely hydrophobic solutes. To further consider the complex hydrophobic solutes containing partial charges, here we propose the D2MSA closure to incorporate the short-range and long-range interactions with the D2 closure and the mean spherical approximation, respectively. We demonstrate that our new theory can compute the solvent distributions around real hydrophobic solutes in water and complex organic solvents that agree well with the explicit solvent molecular dynamics simulations.

3DRISM-HI-D2MSA: an improved analytic theory to compute solvent structure around hydrophobic solutes with proper treatment of solute–solvent electrostatic interactions

Science.gov (United States)

Cao, Siqin; Zhu, Lizhe; Huang, Xuhui

2018-04-01

The 3D reference interaction site model (3DRISM) is a powerful tool to study the thermodynamic and structural properties of liquids. However, for hydrophobic solutes, the inhomogeneity of the solvent density around them poses a great challenge to the 3DRISM theory. To address this issue, we have previously introduced the hydrophobic-induced density inhomogeneity theory (HI) for purely hydrophobic solutes. To further consider the complex hydrophobic solutes containing partial charges, here we propose the D2MSA closure to incorporate the short-range and long-range interactions with the D2 closure and the mean spherical approximation, respectively. We demonstrate that our new theory can compute the solvent distributions around real hydrophobic solutes in water and complex organic solvents that agree well with the explicit solvent molecular dynamics simulations.

Preparation of a novel dual-function strong cation exchange/hydrophobic interaction chromatography stationary phase for protein separation.

Science.gov (United States)

Zhao, Kailou; Yang, Li; Wang, Xuejiao; Bai, Quan; Yang, Fan; Wang, Fei

2012-08-30

We have explored a novel dual-function stationary phase which combines both strong cation exchange (SCX) and hydrophobic interaction chromatography (HIC) characteristics. The novel dual-function stationary phase is based on porous and spherical silica gel functionalized with ligand containing sulfonic and benzyl groups capable of electrostatic and hydrophobic interaction functionalities, which displays HIC character in a high salt concentration, and IEC character in a low salt concentration in mobile phase employed. As a result, it can be employed to separate proteins with SCX and HIC modes, respectively. The resolution and selectivity of the dual-function stationary phase were evaluated under both HIC and SCX modes with standard proteins and can be comparable to that of conventional IEC and HIC columns. More than 96% of mass and bioactivity recoveries of proteins can be achieved in both HIC and SCX modes, respectively. The results indicated that the novel dual-function column could replace two individual SCX and HIC columns for protein separation. Mixed retention mechanism of proteins on this dual-function column based on stoichiometric displacement theory (SDT) in LC was investigated to find the optimal balance of the magnitude of electrostatic and hydrophobic interactions between protein and the ligand on the silica surface in order to obtain high resolution and selectivity for protein separation. In addition, the effects of the hydrophobicity of the ligand of the dual-function packings and pH of the mobile phase used on protein separation were also investigated in detail. The results show that the ligand with suitable hydrophobicity to match the electrostatic interaction is very important to prepare the dual-function stationary phase, and a better resolution and selectivity can be obtained at pH 6.5 in SCX mode. Therefore, the dual-function column can replace two individual SCX and HIC columns for protein separation and be used to set up two-dimensional liquid

Optimization of linear and branched alkane interactions with water to simulate hydrophobic hydration

Science.gov (United States)

Ashbaugh, Henry S.; Liu, Lixin; Surampudi, Lalitanand N.

2011-08-01

Previous studies of simple gas hydration have demonstrated that the accuracy of molecular simulations at capturing the thermodynamic signatures of hydrophobic hydration is linked both to the fidelity of the water model at replicating the experimental liquid density at ambient pressure and an accounting of polarization interactions between the solute and water. We extend those studies to examine alkane hydration using the transferable potentials for phase equilibria united-atom model for linear and branched alkanes, developed to reproduce alkane phase behavior, and the TIP4P/2005 model for water, which provides one of the best descriptions of liquid water for the available fixed-point charge models. Alkane site/water oxygen Lennard-Jones cross interactions were optimized to reproduce the experimental alkane hydration free energies over a range of temperatures. The optimized model reproduces the hydration free energies of the fitted alkanes with a root mean square difference between simulation and experiment of 0.06 kcal/mol over a wide temperature range, compared to 0.44 kcal/mol for the parent model. The optimized model accurately reproduces the temperature dependence of hydrophobic hydration, as characterized by the hydration enthalpies, entropies, and heat capacities, as well as the pressure response, as characterized by partial molar volumes.

Ion Selectivity Mechanism in a Bacterial Pentameric Ligand-Gated Ion Channel

International Nuclear Information System (INIS)

Wang, Hailong; Cheng, Xiaolin

2011-01-01

The proton-gated ion channel from Gloeobacter violaceus (GLIC) is a prokaryotic homolog of the eukaryotic nicotinic acetylcholine receptor (nAChR) that responds to the binding of neurotransmitter acetylcholine and mediates fast signal transmission. Recent emergence of a high resolution crystal structure of GLIC captured in a potentially open state allowed detailed, atomic-level insight into ion conduction and selectivity mechanisms in these channels. Herein, we have examined the barriers to ion conduction and origins of ion selectivity in the GLIC channel by the construction of potential of mean force (PMF) profiles for sodium and chloride ions inside the transmembrane region. Our calculations reveal that the GLIC channel is open for a sodium ion to transport, but presents a ∼10 kcal/mol free energy barrier for a chloride ion, which arises primarily from the unfavorable interactions with a ring of negatively charged glutamate residues (E-2) at the intracellular end and a ring of hydrophobic residues (I9) in the middle of the transmembrane domain. Our collective findings further suggest that the charge selection mechanism can, to a large extent, be attributed to the narrow intracellular end and a ring of glutamate residues in this position their strong negative electrostatics and ability to bind cations. By contrast, E19 at the extracellular entrance only plays a minor role in ion selectivity of GLIC. In addition to electrostatics, both ion hydration and protein dynamics are found to be crucial for ion conduction as well, which explains why a chloride ion experiences a much greater barrier than a sodium ion in the hydrophobic region of the pore.

Immobilization of molecular cobalt electrocatalyst by hydrophobic interaction with hematite photoanode for highly stable oxygen evolution

KAUST Repository

Joya, Khurram

2015-07-15

A unique modification of a hematite photoanode with perfluorinated Co-phthalocyanine (CoFPc) by strong binding associated with hydrophobic interaction is demonstrated. The resultant molecular electrocatalyst – hematite photoanode hybrid material showed significant onset shift and high stability for photoelectrochemical oxidation evolution reaction (OER).

Immobilization of molecular cobalt electrocatalyst by hydrophobic interaction with hematite photoanode for highly stable oxygen evolution

KAUST Repository

Joya, Khurram; Morlanes, Natalia; Maloney, Edward; Rodionov, Valentin; Takanabe, Kazuhiro

2015-01-01

A unique modification of a hematite photoanode with perfluorinated Co-phthalocyanine (CoFPc) by strong binding associated with hydrophobic interaction is demonstrated. The resultant molecular electrocatalyst – hematite photoanode hybrid material showed significant onset shift and high stability for photoelectrochemical oxidation evolution reaction (OER).

Key aromatic/hydrophobic amino acids controlling a cross-amyloid peptide interaction versus amyloid self-assembly.

Science.gov (United States)

Bakou, Maria; Hille, Kathleen; Kracklauer, Michael; Spanopoulou, Anna; Frost, Christina V; Malideli, Eleni; Yan, Li-Mei; Caporale, Andrea; Zacharias, Martin; Kapurniotu, Aphrodite

2017-09-01

The interaction of the intrinsically disordered polypeptide islet amyloid polypeptide (IAPP), which is associated with type 2 diabetes (T2D), with the Alzheimer's disease amyloid-β (Aβ) peptide modulates their self-assembly into amyloid fibrils and may link the pathogeneses of these two cell-degenerative diseases. However, the molecular determinants of this interaction remain elusive. Using a systematic alanine scan approach, fluorescence spectroscopy, and other biophysical methods, including heterocomplex pulldown assays, far-UV CD spectroscopy, the thioflavin T binding assay, transmission EM, and molecular dynamics simulations, here we identified single aromatic/hydrophobic residues within the amyloid core IAPP region as hot spots or key residues of its cross-interaction with Aβ40(42) peptide. Importantly, we also find that none of these residues in isolation plays a key role in IAPP self-assembly, whereas simultaneous substitution of four aromatic/hydrophobic residues with Ala dramatically impairs both IAPP self-assembly and hetero-assembly with Aβ40(42). Furthermore, our experiments yielded several novel IAPP analogs, whose sequences are highly similar to that of IAPP but have distinct amyloid self- or cross-interaction potentials. The identified similarities and major differences controlling IAPP cross-peptide interaction with Aβ40(42) versus its amyloid self-assembly offer a molecular basis for understanding the underlying mechanisms. We propose that these insights will aid in designing intervention strategies and novel IAPP analogs for the management of type 2 diabetes, Alzheimer's disease, or other diseases related to IAPP dysfunction or cross-amyloid interactions. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Ion beam modification of solids ion-solid interaction and radiation damage

CERN Document Server

Wesch, Werner

2016-01-01

This book presents the method of ion beam modification of solids in realization, theory and applications in a comprehensive way. It provides a review of the physical basics of ion-solid interaction and on ion-beam induced structural modifications of solids. Ion beams are widely used to modify the physical properties of materials. A complete theory of ion stopping in matter and the calculation of the energy loss due to nuclear and electronic interactions are presented including the effect of ion channeling. To explain structural modifications due to high electronic excitations, different concepts are presented with special emphasis on the thermal spike model. Furthermore, general concepts of damage evolution as a function of ion mass, ion fluence, ion flux and temperature are described in detail and their limits and applicability are discussed. The effect of nuclear and electronic energy loss on structural modifications of solids such as damage formation, phase transitions and amorphization is reviewed for ins...

Ion-solid interactions for materials modification and processing

International Nuclear Information System (INIS)

Poker, D.B.; Ila, D.; Cheng, Y.T.; Harriott, L.R.; Sigmon, T.W.

1996-01-01

Topics ranged from the very fundamental ion-solid interactions to the highly device-oriented semiconductor applications. Highlights of the symposium featured in this volume include: nanocrystals in insulators, plasma immersion ion implantation. Focused ion beams, molecular dynamics simulations of ion-surface interactions, ion-beam mixing of insulators, GeV ion irradiation, electro-optical materials, polymers, tribological materials, and semiconductor processing. Separate abstracts were prepared for most papers in this volume

The H2A-H2B dimeric kinetic intermediate is stabilized by widespread hydrophobic burial with few fully native interactions.

Science.gov (United States)

Guyett, Paul J; Gloss, Lisa M

2012-01-20

The H2A-H2B histone heterodimer folds via monomeric and dimeric kinetic intermediates. Within ∼5 ms, the H2A and H2B polypeptides associate in a nearly diffusion limited reaction to form a dimeric ensemble, denoted I₂ and I₂*, the latter being a subpopulation characterized by a higher content of nonnative structure (NNS). The I₂ ensemble folds to the native heterodimer, N₂, through an observable, first-order kinetic phase. To determine the regions of structure in the I₂ ensemble, we characterized 26 Ala mutants of buried hydrophobic residues, spanning the three helices of the canonical histone folds of H2A and H2B and the H2B C-terminal helix. All but one targeted residue contributed significantly to the stability of I₂, the transition state and N₂; however, only residues in the hydrophobic core of the dimer interface perturbed the I₂* population. Destabilization of I₂* correlated with slower folding rates, implying that NNS is not a kinetic trap but rather accelerates folding. The pattern of Φ values indicated that residues forming intramolecular interactions in the peripheral helices contributed similar stability to I₂ and N₂, but residues involved in intermolecular interactions in the hydrophobic core are only partially folded in I₂. These findings suggest a dimerize-then-rearrange model. Residues throughout the histone fold contribute to the stability of I₂, but after the rapid dimerization reaction, the hydrophobic core of the dimer interface has few fully native interactions. In the transition state leading to N₂, more native-like interactions are developed and nonnative interactions are rearranged. Copyright © 2011 Elsevier Ltd. All rights reserved.

The role of hydrophobic interactions in positioning of peripheral proteins in membranes

Directory of Open Access Journals (Sweden)

Lomize Mikhail A

2007-06-01

Full Text Available Abstract Background Three-dimensional (3D structures of numerous peripheral membrane proteins have been determined. Biological activity, stability, and conformations of these proteins depend on their spatial positions with respect to the lipid bilayer. However, these positions are usually undetermined. Results We report the first large-scale computational study of monotopic/peripheral proteins with known 3D structures. The optimal translational and rotational positions of 476 proteins are determined by minimizing energy of protein transfer from water to the lipid bilayer, which is approximated by a hydrocarbon slab with a decadiene-like polarity and interfacial regions characterized by water-permeation profiles. Predicted membrane-binding sites, protein tilt angles and membrane penetration depths are consistent with spin-labeling, chemical modification, fluorescence, NMR, mutagenesis, and other experimental studies of 53 peripheral proteins and peptides. Experimental membrane binding affinities of peripheral proteins were reproduced in cases that did not involve a helix-coil transition, specific binding of lipids, or a predominantly electrostatic association. Coordinates of all examined peripheral proteins and peptides with the calculated hydrophobic membrane boundaries, subcellular localization, topology, structural classification, and experimental references are available through the Orientations of Proteins in Membranes (OPM database. Conclusion Positions of diverse peripheral proteins and peptides in the lipid bilayer can be accurately predicted using their 3D structures that represent a proper membrane-bound conformation and oligomeric state, and have membrane binding elements present. The success of the implicit solvation model suggests that hydrophobic interactions are usually sufficient to determine the spatial position of a protein in the membrane, even when electrostatic interactions or specific binding of lipids are substantial. Our

Structure dependent hydrophobic and hydrophilic interactions between nickel(II) Schiff base complexes and serum albumins: Spectroscopic and docking studies

Energy Technology Data Exchange (ETDEWEB)

Koley Seth, Banabithi; Ray, Aurkie; Banerjee, Mousumi; Bhattacharyya, Teerna [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Bhattacharyya, Dhananjay [Computational Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Basu, Samita, E-mail: samita.basu@saha.ac.in [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

2016-03-15

A systematic and comparative binding study between serum-albumins (SA) and a series of monomeric nickel(II)-Schiff-base-complexes (NSCs), which might be imperative to investigate the function of SA behind nickel allergy, has been carried out through docking and different spectroscopic techniques. The initial docking studies indicate structure-dependent selective hydrophobic and hydrophilic interactions. The pyridine and phenyl containing NSCs, which are more aromatic, show better π–π staking compared to pyrrole one. Again all the NSCs bind with BSA though amino acid residues of IB domain affecting local environment of the Trp-134 surrounded by both hydrophobic and hydrophilic residues instead of the hydrophobically buried Trp-212. In HSA the hydophobically buried Trp-214 is influenced by NSCs. The experimental results nicely support the docking outcomes. The changes in Gibbs free energy, binding affinity and the nature of hydrophilic/hydrophobic interactions of NSC–SA systems indicate greater accessibility of N{sub 2}O{sub 2} donor set complex compared to N{sub 4} one towards SA. Quantum chemical structure optimizations support the better planarity of NSC with N{sub 2}O{sub 2} which provides better binding. Therefore the structural variation of N{sub 2}O{sub 2} donor set complexes becomes much more useful compared to N{sub 4} one to search out the most compatible NSC towards SAs.

The interaction between fluid flow and ultra-hydrophobic surface in mini channel

Directory of Open Access Journals (Sweden)

Jasikova Darina

2017-01-01

Full Text Available Interaction of liquid with ultra-hydrophobic surface is accompanied by creation of layer of air. The effect of the air film has a potential of use in industry in many applications. The quality of the surface is influenced by matrix roughness, the character of physical or chemical cover. There was developed a method for analysis of the liquid flow and the air film using the lighting in volume, visualization with CCD camera and long distance microscope, and optical filters. There were prepared four stainless steel samples of inner channel of dimensions (80 × 8 × 8 mm and initial surface roughness Ra 0.33, Ra 1.0, Ra 2.0, and Ra 2.2. The inner channel was treated with plasma and commercial hydrophobic coating Greblon (WEILBURGER Coatings GmbH. There was realized study focused on the liquid flow velocity profile close to the air film. There are present results for laminar, transient and turbulent flows. The study also estimated the air film thickness depending on the Re number. The knowledge of the air film behaviour helps applied suitable degree of processing and cover for the target application.

The role of hydrophobic interactions for the formation of gas hydrates

Energy Technology Data Exchange (ETDEWEB)

Yoon, R.H.; Wang, J.; Eriksson, J.C. [Virginia Polytech Inst. and State Univ., Blacksburg, VA (United States). Center for Advanced Separation Technologies; Sum, A.K. [Colorado School of Mines, Golden, CO (United States). Dept. of Chemical Engineering

2008-07-01

The process of hydrate formation remains largely unexplained due to a lack of evidence for the water molecules around the hydrophobic solute such as methane, and the nucleation process leading to the clustering that induces hydrate growth. However, the water structure is known to play a major role in the mechanism for hydrate nucleation. This paper presented evidence that hydrophobic solutes promote the structuring of water. Water molecules at room temperature tend to form ice structures around the hydrocarbon chains of surfactant molecules dissolved in water. An atomic force microscope (AFM) was used in this study to measure the surface forces between thiolated gold surfaces. The purpose was to better understand the structure of the thin films of water between hydrophobic surfaces. The water molecules tended to reorganize themselves to form ordered structures, which may be related to the nucleation of hydrates. The entropy reduction associated with the ice structure can be considered as the net driving force for self-assembly. Recent studies have revealed that long-range attractive forces exist between hydrophobic surfaces, which are likely to result from structuring of the water molecules in the vicinity of the hydrophobic surfaces. Similarly, the hydrophobic nature of most gas hydrate formers may induce ordering of water molecules in the vicinity of dissolved solutes. It was concluded that the results of this study may be used to develop a new mechanism for the formation of gas hydrates, including methane. 20 refs., 2 figs.

The use of dielectric spectroscopy for the characterisation of the precipitation of hydrophobically modified poly(acrylic-acid) with divalent barium ions

DEFF Research Database (Denmark)

Christensen, Peter Vittrup; Keiding, Kristian

2009-01-01

The use of dielectric spectroscopy as a monitor for coagulation processes was investigated. Hydrophobically modified poly(acrylic-acid) polymers were used as model macromolecules and coagulated with barium ions. The coagulation process was quantified using a photometric dispersion analyser, thereby...... serving as a point of reference for the dielectric spectroscopy. It was found that the hydrophobic modification increased the dosage of barium needed to obtain complete coagulation, whereas the dosage required to initiate coagulation was lowered. The coagulation of the polymer samples caused...... the relaxation time of the measured dielectric dispersion to increase, and this parameter was found to be a good indicator of the formation of polymer aggregates. The magnitude of the dielectric dispersion decreased as a function of barium dosage, but when coagulation was initiated an increase was observed...

Divalent Ion Parameterization Strongly Affects Conformation and Interactions of an Anionic Biomimetic Polymer

Energy Technology Data Exchange (ETDEWEB)

Daily, Michael D.; Baer, Marcel D.; Mundy, Christopher J.

2016-03-10

The description of peptides and the use of molecular dynamics simulations to refine structures and investigate the dynamics on an atomistic scale are well developed. Through a consensus in this community over multiple decades, parameters were developed for molecular interactions that only require the sequence of amino-acids and an initial guess for the three-dimensional structure. The recent discovery of peptoids will require a retooling of the currently available interaction potentials in order to have the same level of confidence in the predicted structures and pathways as there is presently in the peptide counterparts. Here we present modeling of peptoids using a combination of ab initio molecular dynamics (AIMD) and atomistic resolution classical forcefield (FF) to span the relevant time and length scales. To properly account for the dominant forces that stabilize ordered structures of peptoids, namely steric-, electrostatic, and hydrophobic interactions mediated through sidechain-sidechain interactions in the FF model, those have to be first mapped out using high fidelity atomistic representations. A key feature here is not only to use gas phase quantum chemistry tools, but also account for solvation effects in the condensed phase through AIMD. One major challenge is to elucidate ion binding to charged or polar regions of the peptoid and its concomitant role in the creation of local order. Here, similar to proteins, a specific ion effect is observed suggesting that both the net charge and the precise chemical nature of the ion will need to be described. MDD was supported by MS3 (Materials Synthesis and Simulation Across Scales) Initiative at Pacific Northwest National Laboratory. Research was funded by the Laboratory Directed Research and Development program at Pacific Northwest National Laboratory. MDB acknowledges support from US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Material & Engineering. CJM acknowledges

Basic atomic interactions of accelerated heavy ions in matter atomic interactions of heavy ions

CERN Document Server

Tolstikhina, Inga; Winckler, Nicolas; Shevelko, Viacheslav

2018-01-01

This book provides an overview of the recent experimental and theoretical results on interactions of heavy ions with gaseous, solid and plasma targets from the perspective of atomic physics. The topics discussed comprise stopping power, multiple-electron loss and capture processes, equilibrium and non-equilibrium charge-state fractions in penetration of fast ion beams through matter including relativistic domain. It also addresses mean charge-states and equilibrium target thickness in ion-beam penetrations, isotope effects in low-energy electron capture, lifetimes of heavy ion beams, semi-empirical formulae for effective cross sections. The book is intended for researchers and graduate students working in atomic, plasma and accelerator physics.

Influence of mixed electrolytes and pH on adsorption of bovine serum albumin in hydrophobic interaction chromatography.

Science.gov (United States)

Hackemann, Eva; Hasse, Hans

2017-10-27

Using salt mixtures instead of single salts can be beneficial for hydrophobic interaction chromatography (HIC). The effect of electrolytes on the adsorption of proteins, however, depends on the pH. Little is known on that dependence for mixed electrolytes. Therefore, the effect of the pH on protein adsorption from aqueous solutions containing mixed salts is systematically studied in the present work for a model system: the adsorption of bovine serum albumin (BSA) on the mildly hydrophobic resin Toyopearl PPG-600M. The pH is adjusted to 4.0, 4.7 or 7.0 using 25mM sodium phosphate or sodium citrate buffer. Binary and ternary salt mixtures of sodium chloride, ammonium chloride, sodium sulfate and ammonium sulfate as well as the pure salts are used at overall ionic strengths between 1500 and 4200mM. The temperature is always 25°C. The influence of the mixed electrolytes on the adsorption behavior of BSA changes completely with varying pH. Positive as well as negative cooperative effects of the mixed electrolytes are observed. The results are analyzed using a mathematical model which was recently introduced by our group. In that model the influence of the electrolytes is described by a Taylor series expansion in the individual ion molarities. After suitable parametrization using a subset of the data determined in the present work, the model successfully predicts the influence of mixed electrolytes on the protein adsorption. Furthermore, results for BSA from the present study are compared to literature data for lysozyme, which are available for the same adsorbent, temperature and salts. By calculating the ratio of the loading of the adsorbent for both proteins particularly favorable separation conditions can be selected. Hence, a model-based optimization of solvents for protein separation is possible. Copyright © 2017 Elsevier B.V. All rights reserved.

The new view of hydrophobic free energy.

Science.gov (United States)

Baldwin, Robert L

2013-04-17

In the new view, hydrophobic free energy is measured by the work of solute transfer of hydrocarbon gases from vapor to aqueous solution. Reasons are given for believing that older values, measured by solute transfer from a reference solvent to water, are not quantitatively correct. The hydrophobic free energy from gas-liquid transfer is the sum of two opposing quantities, the cavity work (unfavorable) and the solute-solvent interaction energy (favorable). Values of the interaction energy have been found by simulation for linear alkanes and are used here to find the cavity work, which scales linearly with molar volume, not accessible surface area. The hydrophobic free energy is the dominant factor driving folding as judged by the heat capacity change for transfer, which agrees with values for solvating hydrocarbon gases. There is an apparent conflict with earlier values of hydrophobic free energy from studies of large-to-small mutations and an explanation is given. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Characterisation of nanomaterial hydrophobicity using engineered surfaces

Energy Technology Data Exchange (ETDEWEB)

Desmet, Cloé; Valsesia, Andrea; Oddo, Arianna; Ceccone, Giacomo; Spampinato, Valentina; Rossi, François; Colpo, Pascal, E-mail: pascal.colpo@ec.europa.eu [Directorate Health, Consumer and Reference Materials, Consumer Products Safety Unit (Italy)

2017-03-15

Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current physico-chemical characterisation techniques. In this work, we developed a method for the direct characterisation of NM hydrophobicity. The determination of the nanomaterial hydrophobic character is carried out by the direct measurement of the affinity of the NMs for different collectors. Each collector is an engineered surface designed in order to present specific surface charge and hydrophobicity degrees. Being thus characterised by a combination of surface energy components, the collectors enable the NM immobilisation with surface coverage in relation to their hydrophobicity. The experimental results are explained by using the extended DLVO theory, which takes into account the hydrophobic forces acting between NMs and collectors.

The role of the ion-molecule and molecule-molecule interactions in the formation of the two-ion average force interaction potential

CERN Document Server

Ajrian, E A; Sidorenko, S N

2002-01-01

The effect of the ion-molecule and intermolecular interactions on the formation of inter-ion average force potentials is investigated within the framework of a classical ion-dipole model of electrolyte solutions. These potentials are shown to possess the Coulomb asymptotics at large distances while in the region of mean distances they reveal creation and disintegration of solvent-shared ion pairs. The calculation results provide a qualitatively authentic physical picture which is experimentally observed in strong electrolytes solutions. In particular, an increased interaction between an ion and a molecule enhances formation of ion pairs in which the ions are separated by one solvent molecule

Polymer-surfactant interactions studied by titration microcalorimetry : Influence of polymer hydrophobicity, electrostatic forces, and surfactant aggregational state

NARCIS (Netherlands)

Kevelam, J; van Breemen, J.F.L.; Blokzijl, W.; Engberts, J.B.F.N.

1996-01-01

Isothermal titration microcalorimetry has been applied to investigate the interactions between hydrophobically-modified water-soluble polymers and surfactants. The following polymers were used in this study: poly(sodium acrylate-co-n-alkyl methacrylate) (A), where n-alkyl = C9H19, C12H25, and C18H37

Nuclear import of cutaneous beta genus HPV8 E7 oncoprotein is mediated by hydrophobic interactions between its zinc-binding domain and FG nucleoporins

Energy Technology Data Exchange (ETDEWEB)

Onder, Zeynep; Moroianu, Junona, E-mail: moroianu@bc.edu

2014-01-20

We have previously discovered and characterized the nuclear import pathways for the E7 oncoproteins of mucosal alpha genus HPVs, type 16 and 11. Here we investigated the nuclear import of cutaneous beta genus HPV8 E7 protein using confocal microscopy after transfections of HeLa cells with EGFP-8E7 and mutant plasmids and nuclear import assays in digitonin-permeabilized HeLa cells. We determined that HPV8 E7 contains a nuclear localization signal (NLS) within its zinc-binding domain that mediates its nuclear import. Furthermore, we discovered that a mostly hydrophobic patch {sub 65}LRLFV{sub 69} within the zinc-binding domain is essential for the nuclear import and localization of HPV8 E7 via hydrophobic interactions with the FG nucleoporins Nup62 and Nup153. Substitution of the hydrophobic residues within the {sub 65}LRLFV{sub 69} patch to alanines, and not R66A mutation, disrupt the interactions between the 8E7 zinc-binding domain and Nup62 and Nup153 and consequently inhibit nuclear import of HPV8 E7. - Highlights: • HPV8 E7 has a cNLS within its zinc-binding domain that mediates its nuclear import. • Discovery of a hydrophobic patch that is critical for the nuclear import of HPV8 E7. • HPV8 E7 nuclear import is mediated by hydrophobic interactions with FG-Nups, Nup62 and Nup153.

Ion-ion interactions in the denatured state contribute to the stabilization of CutA1 proteins.

Science.gov (United States)

Yutani, Katsuhide; Matsuura, Yoshinori; Naitow, Hisashi; Joti, Yasumasa

2018-05-16

In order to elucidate features of the denatured state ensembles that exist in equilibrium with the native state under physiological conditions, we performed 1.4-μs molecular dynamics (MD) simulations at 400 K and 450 K using the monomer subunits of three CutA1 mutants from Escherichia coli: an SH-free mutant (Ec0SH) with denaturation temperature (T d ) = 85.6 °C, a hydrophobic mutant (Ec0VV) with T d  = 113.3 °C, and an ionic mutant (Ec0VV_6) with T d  = 136.8 °C. The occupancy of salt bridges by the six substituted charged residues in Ec0VV_6 was 140.1% at 300 K and 89.5% at 450 K, indicating that even in the denatured state, salt bridge occupancy was high, approximately 60% of that at 300 K. From these results, we can infer that proteins from hyperthermophiles with a high ratio of charged residues are stabilized by a decrease in conformational entropy due to ion-ion interactions in the denatured state. The mechanism must be comparable to the stabilization conferred by disulfide bonds within a protein. This suggests that introduction of charged residues, to promote formation of salt bridges in the denatured state, would be a simple way to rationally design stability-enhanced mutants.

Isolation of soy bean protein P34 from oil bodies using hydrophobic interaction chromatography

OpenAIRE

Sewekow, E.; Keßler, L.; Seidel-Morgenstern, A.; Rothkoetter, H.

2008-01-01

Abstract Background Soybeans play a prominent role in allergologic research due to the high incidence of allergic reactions. For detailed studies on specific proteins it is necessary to have access to a large amount of pure substance. Results In this contribution, a method for purifying soybean (Glycine max) protein P34 (also called Gly m Bd 30 K or Gly m 1) using hydrophobic interaction chromatography is presented. After screening experiments using 1 mL HiTrap columns, Butyl Sepharose 4 FF w...

Construction of ion accelerator for ion-surface interaction research

International Nuclear Information System (INIS)

Obara, Kenziro; Ohtsuka, Hidewo; Yamada, Rayji; Abe, Tetsuya; Sone, Kazuho

1977-09-01

A Cockcroft-Walton type ion accelerator for ion-surface interaction research was installed at Plasma Engineering Laboratory, Division of Thermonuclear Fusion Research, JAERI, in March 1977. Its maximum accelerating voltage is 400 kV. The accelerator has some outstanding features compared with the conventional type. Described are setup of the accelerator specification of the major components, safety system and performance. (auth.)

Hydrophobicity study of kaolinite from La Unión, Antioquia

Directory of Open Access Journals (Sweden)

Liliana M. Usuga-Manco

2015-07-01

Full Text Available In this research three methodologies to convert the hydrophilic surface of kaolinite into a hydrophobic surface are proposed, this condition is required to recover this mineral by means of froth flotation. Taking into account the anisotropy, zeta potential and complex surface electrical properties of the kaolinite, three surface chemical treatments based on the interacting and absorption of anionic collectors onto the mineral surface, causing an increase in the contact angle and thus increased hydrophobicity of kaolinite were applied. The methodologies proposed were interactions of kaolinite particles with: sodium dodecyl sulfate solutions with concentration 1x10-3M, 1x10-4M, 1x10-5M; sodium dodecyl sulfate solutions 1x10-3M, 1x10-4M, 1x10-5M with further interaction with kerosene solutions 127000 ppm; and oleic acid solutions 1x10-3M, 1x10-4M, 1x10-5M, each one with a five minutes of interaction. The experimental results obtained by zeta potential and contact angle of the kaolinite before and after applying chemical treatments indicate that larger the chain length of the collector and its concentration, bigger the contact angle and so, more hydrophobic the surface (edge or face. In order to optimize, control and understand this solid-liquid interaction phenomenon is suggested to find out about the hydrophobization mechanism of kaolinite with oleic acid and its percentage of hydrophobization.

The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

DEFF Research Database (Denmark)

Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

2004-01-01

Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding......-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time...

Fundamentals of ion-solid interaction. A compact introduction

International Nuclear Information System (INIS)

Moeller, Wolfhard

2017-01-01

Since Rutherford's famous paper which first described the scattering of α-particles in matter, the field of ion-solid interaction has matured by now during one entire century. First theoretical concepts addressing particle penetration of solids were given by Thomson and Bohr. Quantum theory entered the field in treatments of ion stopping by Born and Bethe. Still on classical grounds, transport theory was first introduced in a paper on multiple scattering by Bothe. The discovery of nuclear fission launched theoretical studies by Bohr on the scattering and stopping of fission products. A further milestone in the understanding of particle penetration phenomena is the 1948 paper by Bohr. On this basis, the theoretical understanding was enhanced in the early 1960's in particular by a series of papers by Lindhard. Simultaneously, an increasing amount of experimental studies on ion stopping and scattering were launched in connection with the development of ion acceleration devices and corresponding equipment for particle detection. During this period, also first computer simulation studies came up which later proved to be an utmost efficient tool for the description of collisional phenomena in ion-solid interaction. The relevance for numerous applications became evident, such as for the compositional and structural analysis of thin films and near-surface layers, for semiconductor technology, and nuclear fission and fusion technology. This caused increasing interest not only in the penetration and the scattering of the impinging ions, but also in the modification of the irradiated material due to ion implantation, radiation damage and surface erosion by sputtering. Consequently, ion-solid interaction established around 1970 internationally as a quickly expanding field at the intersection of solid-state physics and nuclear physics. Numerous reviews and textbooks are available which cover the fundamentals of ion-solid interaction. Torrens reviewed the knowledge about

Fundamentals of ion-solid interaction. A compact introduction

Energy Technology Data Exchange (ETDEWEB)

Moeller, Wolfhard [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany). Inst. of Ion Beam Physics and Materials Research

2017-09-01

Since Rutherford's famous paper which first described the scattering of α-particles in matter, the field of ion-solid interaction has matured by now during one entire century. First theoretical concepts addressing particle penetration of solids were given by Thomson and Bohr. Quantum theory entered the field in treatments of ion stopping by Born and Bethe. Still on classical grounds, transport theory was first introduced in a paper on multiple scattering by Bothe. The discovery of nuclear fission launched theoretical studies by Bohr on the scattering and stopping of fission products. A further milestone in the understanding of particle penetration phenomena is the 1948 paper by Bohr. On this basis, the theoretical understanding was enhanced in the early 1960's in particular by a series of papers by Lindhard. Simultaneously, an increasing amount of experimental studies on ion stopping and scattering were launched in connection with the development of ion acceleration devices and corresponding equipment for particle detection. During this period, also first computer simulation studies came up which later proved to be an utmost efficient tool for the description of collisional phenomena in ion-solid interaction. The relevance for numerous applications became evident, such as for the compositional and structural analysis of thin films and near-surface layers, for semiconductor technology, and nuclear fission and fusion technology. This caused increasing interest not only in the penetration and the scattering of the impinging ions, but also in the modification of the irradiated material due to ion implantation, radiation damage and surface erosion by sputtering. Consequently, ion-solid interaction established around 1970 internationally as a quickly expanding field at the intersection of solid-state physics and nuclear physics. Numerous reviews and textbooks are available which cover the fundamentals of ion-solid interaction. Torrens reviewed the knowledge

Thermodynamics of the interactions of a homologous series of some amino acids with trimethylamine N-oxide: Volumetric, compressibility, and calorimetric studies

International Nuclear Information System (INIS)

Choudhary, Sinjan; Kishore, Nand

2011-01-01

Highlights: → Thermodynamics of interaction of amino acids with trimethy N-oxide (TMAO) studied. → Partial molar properties in aqueous osmolyte provide interaction details. → Volumes, compressibilites, enthalpies indicate predominant hydrophobic interactions. → TMAO exerts its effect both by preferential hydration and hydrophobic interactions. → Results suggest hydrophobic interactions lead to destabilization of the protein. - Abstract: The values of apparent molar volume V 2,φ and apparent molar compressibility K S,2,φ of glycine, L-alanine, DL-α-amino-n-butyric acid, L-valine, and L-leucine have been determined in the aqueous solution of 1 mol . kg -1 and 2 mol . kg -1 trimethylamine N-oxide (TMAO) solutions by density and sound velocity measurements. Isothermal titration calorimetry has been employed to determine the values of heats of dilution q of the aqueous solutions of these amino acids in TMAO at temperatures from T = 288.15 K to T = 308.15 K. These data have been used to calculate values of the infinite dilution standard partial molar volume (V 2,m 0 ), standard partial molar isentropic compressibility (K S,2,m 0 ) and limiting enthalpy of dilution (Δ dil H o ) of the amino acids in aqueous TMAO solutions. The standard partial molar volumes of transfer (Δ tr V 2,m 0 ), isentropic compressibility of transfer (Δ tr K S,2,m 0 ), and enthalpy of dilution of transfer (Δ tr Δ dil H o ) of amino acids from water to aqueous TMAO solutions have been calculated from the measured quantities for these thermodynamic quantities. The linear correlation of V 2,m 0 for a homologous series of amino acids has been utilized to calculate the contribution of the charged end groups (NH 3 + , COO - ), CH 2 groups, and the other alkyl chains of the amino acids to V 2,m 0 . The results for the partial molar properties of transfer from water to aqueous TMAO solutions have been interpreted in terms of ion-ion, ion-polar, hydrophilic-hydrophobic, and hydrophobic-hydrophobic

Ion-ion interaction and energy transfer of 4+ transuranium ions in cerium tetrafluoride

International Nuclear Information System (INIS)

Liu, G.K.; Beitz, J.V.

1990-01-01

Dynamics of excited 5f electron states of the transuranium ions Cm 4+ and Bk 4+ in CeF 4 are compared. Based on time- and wavelength-resolved laser-induced fluorescence, excitation energy transfer processes have been probed. Depending on concentration and electronic energy level structure of the studied 4+ transuranium ion, the dominant energy transfer mechanisms were identified as cross relaxation, exciton-exciton annihilation, and trapping. Energy transfer rates derived from the fitting of the observed fluorescence decays to theoretical models, based on electric multipolar ion-ion interactions, are contrasted with prior studies of 4f states of 3+ lanthanide and 3d states of transition metal ions. 16 refs., 1 tab

Different assembly of type IV collagen on hydrophilic and hydrophobic substrata alters endothelial cells interaction

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NM Coelho

2010-06-01

Full Text Available Considering the structural role of type IV collagen (Col IV in the assembly of the basement membrane (BM and the perspective of mimicking its organization for vascular tissue engineering purposes, we studied the adsorption pattern of this protein on model hydrophilic (clean glass and hydrophobic trichloro(octadecylsilane (ODS surfaces known to strongly affect the behavior of other matrix proteins. The amount of fluorescently labeled Col IV was quantified showing saturation of the surface for concentration of the adsorbing solution of about 50μg/ml, but with approximately twice more adsorbed protein on ODS. AFM studies revealed a fine – nearly single molecular size – network arrangement of Col IV on hydrophilic glass, which turns into a prominent and growing polygonal network consisting of molecular aggregates on hydrophobic ODS. The protein layer forms within minutes in a concentration-dependent manner. We further found that human umbilical vein endothelial cells (HUVEC attach less efficiently to the aggregated Col IV (on ODS, as judged by the significantly altered cell spreading, focal adhesions formation and the development of actin cytoskeleton. Conversely, the immunofluorescence studies for integrins revealed that the fine Col IV network formed on hydrophilic substrata is better recognized by the cells via both α1 and α2 heterodimers which support cellular interaction, apart from these on hydrophobic ODS where almost no clustering of integrins was observed.

Ion-materials interactions and their application

International Nuclear Information System (INIS)

Whitlow, H.J.

1998-01-01

The interaction of energetic ions and other charged particles with solid matter leads to a wealth of physical processes. This thesis comprises a collection of papers and an introductory commentary, which explore some aspects of how these interactions may be used for: (i) Characterisation of thin surface layers of material, (ii) characterisation of energetic charged particles, and (iii) modification of materials by ion bombardment. In (i) Elastic Recoil Detection using a detector system for measurement of Time of Flight and kinetic energy of recoiling target atoms has been developed as a quantitative method for elemental depth profiling of thin (0.5-1 μm) surface layers. This method has been applied to the study of reactions of metal/III-V structures, which are of importance for the semiconductor industry. (ii) MeV-ion - materials interactions have been used as the basis for developing Si p-i-n detectors for the CHICSi programme which will undertake experimental studies of heavy ion collisions at intermediate energies. This involved development and testing of extremely thin (10-12 μm) Si ΔE detectors for characterising light- and intermediate mass charged particles as well as calibration of Si p-i-n detectors and their susceptibility to radiation damage. (iii) Nuclear Reaction Analysis (NRA) with resonant nuclear reactions has been used to study modification of material with ion beams. In the first study, the accumulation of fluorine in BF 2 + ion implanted WSi 2 solid diffusion sources was investigated. The second study investigated if there was a correlation between photoluminescence and segregation of hydrogen to buried heterojunctions in plasma-etched III-V quantum-well structures. The ion bombardment in this case was during etching in an Ar+CH 4 plasma using an Electron Cyclotron Resonance (ECR) source. (author)

Ion sensing method

Science.gov (United States)

Smith, Richard Harding; Martin, Glenn Brian

2004-05-18

The present invention allows the determination of trace levels of ionic substances in a sample solution (ions, metal ions, and other electrically charged molecules) by coupling a separation method, such as liquid chromatography, with ion selective electrodes (ISE) prepared so as to allow detection at activities below 10.sup.-6 M. The separation method distributes constituent molecules into fractions due to unique chemical and physical properties, such as charge, hydrophobicity, specific binding interactions, or movement in an electrical field. The separated fractions are detected by means of the ISE(s). These ISEs can be used singly or in an array. Accordingly, modifications in the ISEs are used to permit detection of low activities, specifically, below 10.sup.-6 M, by using low activities of the primary analyte (the molecular species which is specifically detected) in the inner filling solution of the ISE. Arrays constructed in various ways allow flow-through sensing for multiple ions.

Oligopeptidase B from Serratia proteamaculans. III. Inhibition analysis. Specific interactions with metalloproteinase inhibitors.

Science.gov (United States)

Mikhailova, A G; Khairullin, R F; Kolomijtseva, G Ya; Rumsh, L D

2012-03-01

Inhibition of the novel oligopeptidase B from Serratia proteamaculans (PSP) by basic pancreatic trypsin inhibitor, Zn2+ ions, and o- and m-phenanthroline was investigated. A pronounced effect of calcium ions on the interaction of PSP with inhibitors was demonstrated. Inversion voltamperometry and atomic absorption spectrometry revealed no zinc ions in the PSP molecule. Hydrophobic nature of the enzyme inhibition by o- and m-phenanthroline was established.

Interaction of langmuir and ion acoustic waves

International Nuclear Information System (INIS)

Lee, Hee Jae

1991-01-01

Interaction of Langmuir and ion acoustic waves in a plasma is described by Landau-Ginzburg type of equation when the group velocity of the Langmuir wave is equal to the wave velocity of ion acoustic wave. (Author)

The influence of salt chaotropicity, column hydrophobicity and analytes' molecular properties on the retention of pramipexole and its impurities.

Science.gov (United States)

Vemić, Ana; Kalinić, Marko; Erić, Slavica; Malenović, Anđelija; Medenica, Mirjana

2015-03-20

The aim of this study was to examine the interaction of the chaotropic salts of different position in Hofmeister series (CF3COONa, NaClO4, NaPF6) added to the mobile phase with the stationary phases of different hydrophobicity (C8 and C18 XTerra(®) columns), as well as their common influence on the retention behavior of pramipexole and its structurally related impurities. The extended thermodynamic approach enabled the understanding of the underlying separation mechanism. Comparing six different column-salt systems it was observed that general system hydrophobicity presented by salt chaotropicity and column hydrophobicity favors stationary phase ion-pairing over the ion-pair formation in the eluent. Further, an attempt was made to describe the influence of analytes' nature on their retention behavior in such chromatographic systems. An analysis is performed in order to select and elucidate the molecular descriptors (electrostatical, quantum-chemical, geometrical, topological, and constitutional) that best explain the experimental evidence and findings obtained by the thermodynamic approach. The results of this analysis suggest that analytes' charge distribution and its complementarity to the structure of the electric double layer formed on the surface of the stationary phase upon the addition of chaotropic additives can be useful for understanding the differences in retention of structurally related analytes. These findings provide a novel understanding of the interactions between all the components of the chromatographic system containing chaotropic additive and a good basis for further investigations suggesting the development of generally applicable predictors in structure-retention relationship studies in related chromatographic systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Evaporation rate of water in hydrophobic confinement.

Science.gov (United States)

Sharma, Sumit; Debenedetti, Pablo G

2012-03-20

The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14 Å and surface areas between 1 and 9 nm(2)), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14 Å. The computed free energy barriers are of the order of 50 kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm(2)) than by the smaller (1 nm(2)) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube.

Ion - biomolecule interactions and radiation damage

International Nuclear Information System (INIS)

Schlathoelter, T.

2004-01-01

Full text: The biological effects of ionizing radiation in living cells are not a mere result of the direct impact of high energy quanta of radiation. Secondary particles such as low energy electrons, radicals and (multiply charged) ions are formed within the track. The interaction of these secondary particles with biologically relevant molecules is responsible for a large fraction of biological radiation damage to a cell, as well. Singly and multiply charged ions can be of importance as both, primary and secondary particles, and are known to cause severe biological damage. For instance, in heavy ion therapy and proton therapy the pronounced Bragg peak of fast (typically a few 100 MeV/u) ions in biological tissue is utilized. The Bragg peak is located at a depth, where the ions (mostly C q+ or protons) are slowed down to about 100 keV/u and have their maximum linear energy transfer (LET) to the medium. This depth is reasonably well defined and depends on the initial ion kinetic energy. Since the ions are rapidly stopped in this energy range, penetration beyond the Bragg peak is weak and it is thus possible to 'scan' the Bragg peak through a malignant tumour without excessive damage of the surrounding tissue by mere variation of the ion kinetic energy (i.e. the penetration depth). Severe biological damage is almost only possible, when the track of a primary quantum of ionizing radiation crosses the nucleus of a cell. Particularly the induction of double strand breaks of DNA or clustered DNA lesions is potentially lethal or mutagenic. A primary particle interacting with individual molecules within this environment leads to molecular excitation, ionization and fragmentation. In the process, the primary particle looses energy and slow secondary electrons and ions are formed, which might induce further damage. For a deep understanding of biological radiation damage on the level of individual molecules it is thus important to quantify excitation, ionization and

Fluoroalkyl and Alkyl Chains Have Similar Hydrophobicities in Binding to the “Hydrophobic Wall” of Carbonic Anhydrase

Energy Technology Data Exchange (ETDEWEB)

J Mecinovic; P Snyder; K Mirica; S Bai; E Mack; R Kwant; D Moustakas; A Heroux; G Whitesides

2011-12-31

entropic contributions to the hydrophobic effect in this representative system of protein and ligand: hydrophobic interactions, here, seem to comprise approximately equal contributions from enthalpy (plausibly from strengthening networks of hydrogen bonds among molecules of water) and entropy (from release of water from configurationally restricted positions).

Interaction of the Yersinia pestis type III regulatory proteins LcrG and LcrV occurs at a hydrophobic interface

Directory of Open Access Journals (Sweden)

Nilles Matthew L

2002-06-01

Full Text Available Abstract Background Secretion of anti-host proteins by Yersinia pestis via a type III mechanism is not constitutive. The process is tightly regulated and secretion occurs only after an appropriate signal is received. The interaction of LcrG and LcrV has been demonstrated to play a pivotal role in secretion control. Previous work has shown that when LcrG is incapable of interacting with LcrV, secretion of anti-host proteins is prevented. Therefore, an understanding of how LcrG interacts with LcrV is required to evaluate how this interaction regulates the type III secretion system of Y. pestis. Additionally, information about structure-function relationships within LcrG is necessary to fully understand the role of this key regulatory protein. Results In this study we demonstrate that the N-terminus of LcrG is required for interaction with LcrV. The interaction likely occurs within a predicted amphipathic coiled-coil domain within LcrG. Our results demonstrate that the hydrophobic face of the putative helix is required for LcrV interaction. Additionally, we demonstrate that the LcrG homolog, PcrG, is incapable of blocking type III secretion in Y. pestis. A genetic selection was utilized to obtain a PcrG variant capable of blocking secretion. This PcrG variant allowed us to locate a region of LcrG involved in secretion blocking. Conclusion Our results demonstrate that LcrG interacts with LcrV via hydrophobic interactions located in the N-terminus of LcrG within a predicted coiled-coil motif. We also obtained preliminary evidence that the secretion blocking activity of LcrG is located between amino acids 39 and 53.

Interaction of energetic ions with high-density plasmas

International Nuclear Information System (INIS)

Gericke, D.O.; Edie, D.; Grinenko, A.; Vorberger, J.

2010-01-01

Complete text of publication follows. The talk will review the importance of energetic ions in different inertial confinement fusion scenarios: i) heavy ion beams are very efficient drivers that can deliver the energy for compression in indirect as well as direct drive approaches; ii) the interaction of α-particles, that are created in a burning plasma, with the surrounding cold plasma is essential for creating a burn wave; iii) laser-produced ion beams are also a strong candidate to create the hot spot needed for fast ignition. In all applications the ions interact with dense matter that is characterized by strongly coupled ions and (possibly) partially degenerate electrons. Moreover, the coupling between beam ions and target electrons can be strong as well. Under these conditions, standard approaches for the beam-plasma interactions process are known to fail. The presentation will demonstrate how advanced models for the energy loss of ions in dense plasmas can resolve the issues mentioned above. These models are largely built on quantum kinetic theory that is able to describe degeneracy and strong coupling in a systematic way. In particular, strong interactions require a quantum description for electron-ion collisions in dense plasma environments, which is done by direct solutions of the Schroedinger equation. Degeneracy and collective excitations can be included via the Lenard-Balescu description where strong interactions may be included via a pseudo-potential approach. Finally, results are shown for all three fusion applications described above. The effects related to strong coupling and degeneracy mainly concern the end of the stopping range where the beam ion dose not have enough energy to excite all possible degrees of freedom and, thus, certain processes are frozen out. However, we also find a significant reduction of the range for swift heavy ions in the GeV-range when stopping in dense matter is considered. The stopping range of α-particles in the

MICROBIAL CELL-SURFACE HYDROPHOBICITY - THE INVOLVEMENT OF ELECTROSTATIC INTERACTIONS IN MICROBIAL ADHESION TO HYDROCARBONS (MATH)

NARCIS (Netherlands)

GEERTSEMADOORNBUSCH, GI; VANDERMEI, HC; BUSSCHER, HJ

Microbial adhesion to hydrocarbons (MATH) is the most commonly used method to determine microbial cell surface hydrophobicity. Since, however, the assay is based on adhesion, it is questionable whether the results reflect only the cell surface hydrophobicity or an interplay of hydrophobicity and

INTERACTION OF NEUTRAL BEAM INJECTED FAST IONS WITH ION CYCLOTRON RESONANCE FREQUENCY WAVES

International Nuclear Information System (INIS)

CHOI, M.; CHAN, V.S.; CHIU, S.C.; OMELCHENKO, Y.A.; SENTOKU, Y.; STJOH, H.E.

2003-01-01

OAK B202 INTERACTION OF NEUTRAL BEAM INJECTED FAST IONS WITH CYCLOTRON RESONANCE FREQUENCY WAVES. Existing tokamaks such as DIII-D and future experiments like ITER employ both NB injection (NBI) and ion-cyclotron resonance heating (ICRH) for auxiliary heating and current drive. The presence of energetic particles produced by NBI can result in absorption of the Ion cyclotron radio frequency (ICRF) power. ICRF can also interact with the energetic beam ions to alter the characteristics of NBI momentum deposition and resultant impact on current drive and plasma rotation. To study the synergism between NBI and ICRF, a simple physical model for the slowing-down of NB injected fast ions is implemented in a Monte-Carlo rf orbit code. This paper presents the first results. The velocity space distributions of energetic ions generated by ICRF and NBI are calculated and compared. The change in mechanical momentum of the beam and an estimate of its impact on the NB-driven current are presented and compared with ONETWO simulation results

Influence of hydrophobic modification in alginate-based hydrogels for biomedical applications

Science.gov (United States)

Choudhary, Soumitra

Alginate has been exploited commercially for decades in foods, textiles, paper, pharmaceutical industries, and also as a detoxifier for removing heavy metals. Alginate is also popular in cell encapsulation because of its relatively mild gelation protocol and simple chemistry with which biological active entities can be immobilized. Surface modification of alginate gels has been explored to induce desired cell interactions with the gel matrix. These modifications alter the bulk properties, which strongly determine on how cells feel and response to the three-dimensional microenvironment. However, there is a need to develop strategies to engineer functionalities into bulk alginate hydrogels that not only preserve their inherent qualities but are also less toxic. In this thesis, our main focus was to optimize the mechanical properties of alginate-based hydrogels, and by doing so control the performance of the biomaterials. In the first scheme, we used alginate and hydrophobically modified ethyl hydroxy ethyl cellulose as components in interpenetrating polymer network (IPN) gels. The second network was used to control gelation time and rheological properties. We believe these experiments also may provide insight into the mechanical and structural properties of more complex biopolymer gels and naturally-occurring IPNs. Next, we worked on incorporating a hydrophobic moiety directly into the alginate chain, resulting in materials for extended release of hydrophobic drugs. We successfully synthesized hydrophobically modified alginate (HMA) by attaching octylamine groups onto the alginate backbone by standard carbodiimide based amide coupling reaction. Solubility of several model hydrophobic drugs in dilute HMA solutions was found to be increased by more than an order of magnitude. HMA hydrogels, prepared by crosslinking the alginate chains with calcium ions, were found to exhibit excellent mechanical properties (modulus ˜100 kPa) with release extended upto 5 days. Ability

Interaction between a hydrophobic rigid face and a flexible alkyl tail: Thermodynamics of self-assembling of sodium cholate and SDS

International Nuclear Information System (INIS)

Bai, Guangyue; Sheng, Jianhui; Wang, Yujie; Wu, Hui; Zhao, Yang; Zhuo, Kelei; Bastos, Margarida

2016-01-01

Highlights: • Critical concentrations and enthalpy changes for stepwise aggregation are obtained by ITC. • ITC allowed the thermodynamic characterization for NaCA/SDS self-assembling. • Steroid face-to-alkyl chain hydrophobic interaction tends to be saturated at molar ratio 1:1.5. • Alkyl-steroid interaction favors micellization of NaCA/SDS and the mixture shows nonideal behavior. • Intermolecular interaction and excess enthalpies were discussed according to Rubingh’s model. - Abstract: The thermodynamics of molecular self-assembling of an anionic biosurfactant, sodium cholate (NaCA) and its mixtures with sodium dodecyl sulfate (SDS) in aqueous solution have been investigated by isothermal titration calorimetry (ITC), along with fluorescence and conductivity measurements. Different critical concentrations were obtained by these three techniques – critical pre-micelle concentration (cmc_p_r_e) and critical micelle concentration (cmc) for pure NaCA, and critical micelle concentrations (cmc_m_i_x) for the mixed systems with differently initial SDS concentrations. Importantly, ITC allowed us to directly measure the enthalpy changes of pre-micelle formation (ΔH_p_r_e_m_i_c = (−0.28 ± 0.02) kJ·mol"−"1) and of micelle formation (ΔH_m_i_c = (−1.76 ± 0.05) kJ·mol"−"1) for pure NaCA as well as the enthalpies for micellization for the mixed systems NaCA/SDS. The non-ideality of the mixed surfactant solution was evaluated in terms of interaction parameters and excess enthalpies that were calculated in the light of Clint’s and Rubingh’s models. It was found that there is an obvious synergistic effect in the NaCA/SDS mixed system. From all these results we can ascribe the strong interaction between the same charge surfactants NaCA and SDS to the structural difference in their hydrophobic moieties. In fact, the flexible alkyl chains of SDS and the non-planar hydrophobic β-faces of NaCA tend to have a more compact packing than pure NaCA.

Characterization of Hydrophobic Peptides in the Presence of Detergent by Photoionization Mass Spectrometry

Science.gov (United States)

Bagag, Aïcha; Jault, Jean-Michel; Sidahmed-Adrar, Nazha; Réfrégiers, Matthieu; Giuliani, Alexandre; Le Naour, François

2013-01-01

The characterization of membrane proteins is still challenging. The major issue is the high hydrophobicity of membrane proteins that necessitates the use of detergents for their extraction and solubilization. The very poor compatibility of mass spectrometry with detergents remains a tremendous obstacle in studies of membrane proteins. Here, we investigated the potential of atmospheric pressure photoionization (APPI) for mass spectrometry study of membrane proteins. This work was focused on the tetraspanin CD9 and the multidrug transporter BmrA. A set of peptides from CD9, exhibiting a broad range of hydropathicity, was investigated using APPI as compared to electrospray ionization (ESI). Mass spectrometry experiments revealed that the most hydrophobic peptides were hardly ionized by ESI whereas all peptides, including the highly hydrophobic one that corresponds to the full sequence of the first transmembrane domain of CD9, were easily ionized by APPI. The native protein BmrA purified in the presence of the non-ionic detergent beta-D-dodecyl maltoside (DDM) was digested in-solution using trypsin. The resulting peptides were investigated by flow injection analysis of the mixture followed by mass spectrometry. Upon ESI, only detergent ions were detected and the ionic signals from the peptides were totally suppressed. In contrast, APPI allowed many peptides distributed along the sequence of the protein to be detected. Furthermore, the parent ion corresponding to the first transmembrane domain of the protein BmrA was detected under APPI conditions. Careful examination of the APPI mass spectrum revealed a-, b-, c- and y- fragment ions generated by in-source fragmentation. Those fragment ions allowed unambiguous structural characterization of the transmembrane domain. In conclusion, APPI–MS appears as a versatile method allowing the ionization and fragmentation of hydrophobic peptides in the presence of detergent. PMID:24236085

Characterization of hydrophobic peptides in the presence of detergent by photoionization mass spectrometry.

Directory of Open Access Journals (Sweden)

Aïcha Bagag

Full Text Available The characterization of membrane proteins is still challenging. The major issue is the high hydrophobicity of membrane proteins that necessitates the use of detergents for their extraction and solubilization. The very poor compatibility of mass spectrometry with detergents remains a tremendous obstacle in studies of membrane proteins. Here, we investigated the potential of atmospheric pressure photoionization (APPI for mass spectrometry study of membrane proteins. This work was focused on the tetraspanin CD9 and the multidrug transporter BmrA. A set of peptides from CD9, exhibiting a broad range of hydropathicity, was investigated using APPI as compared to electrospray ionization (ESI. Mass spectrometry experiments revealed that the most hydrophobic peptides were hardly ionized by ESI whereas all peptides, including the highly hydrophobic one that corresponds to the full sequence of the first transmembrane domain of CD9, were easily ionized by APPI. The native protein BmrA purified in the presence of the non-ionic detergent beta-D-dodecyl maltoside (DDM was digested in-solution using trypsin. The resulting peptides were investigated by flow injection analysis of the mixture followed by mass spectrometry. Upon ESI, only detergent ions were detected and the ionic signals from the peptides were totally suppressed. In contrast, APPI allowed many peptides distributed along the sequence of the protein to be detected. Furthermore, the parent ion corresponding to the first transmembrane domain of the protein BmrA was detected under APPI conditions. Careful examination of the APPI mass spectrum revealed a-, b-, c- and y- fragment ions generated by in-source fragmentation. Those fragment ions allowed unambiguous structural characterization of the transmembrane domain. In conclusion, APPI-MS appears as a versatile method allowing the ionization and fragmentation of hydrophobic peptides in the presence of detergent.

Arginine side chain interactions and the role of arginine as a gating charge carrier in voltage sensitive ion channels

Science.gov (United States)

Armstrong, Craig T.; Mason, Philip E.; Anderson, J. L. Ross; Dempsey, Christopher E.

2016-02-01

Gating charges in voltage-sensing domains (VSD) of voltage-sensitive ion channels and enzymes are carried on arginine side chains rather than lysine. This arginine preference may result from the unique hydration properties of the side chain guanidinium group which facilitates its movement through a hydrophobic plug that seals the center of the VSD, as suggested by molecular dynamics simulations. To test for side chain interactions implicit in this model we inspected interactions of the side chains of arginine and lysine with each of the 19 non-glycine amino acids in proteins in the protein data bank. The arginine guanidinium interacts with non-polar aromatic and aliphatic side chains above and below the guanidinium plane while hydrogen bonding with polar side chains is restricted to in-plane positions. In contrast, non-polar side chains interact largely with the aliphatic part of the lysine side chain. The hydration properties of arginine and lysine are strongly reflected in their respective interactions with non-polar and polar side chains as observed in protein structures and in molecular dynamics simulations, and likely underlie the preference for arginine as a mobile charge carrier in VSD.

The Non-Specific Binding of Fluorescent-Labeled MiRNAs on Cell Surface by Hydrophobic Interaction.

Science.gov (United States)

Lu, Ting; Lin, Zongwei; Ren, Jianwei; Yao, Peng; Wang, Xiaowei; Wang, Zhe; Zhang, Qunye

2016-01-01

MicroRNAs are small noncoding RNAs about 22 nt long that play key roles in almost all biological processes and diseases. The fluorescent labeling and lipofection are two common methods for changing the levels and locating the position of cellular miRNAs. Despite many studies about the mechanism of DNA/RNA lipofection, little is known about the characteristics, mechanisms and specificity of lipofection of fluorescent-labeled miRNAs. Therefore, miRNAs labeled with different fluorescent dyes were transfected into adherent and suspension cells using lipofection reagent. Then, the non-specific binding and its mechanism were investigated by flow cytometer and laser confocal microscopy. The results showed that miRNAs labeled with Cy5 (cyanine fluorescent dye) could firmly bind to the surface of adherent cells (Hela) and suspended cells (K562) even without lipofection reagent. The binding of miRNAs labeled with FAM (carboxyl fluorescein) to K562 cells was obvious, but it was not significant in Hela cells. After lipofectamine reagent was added, most of the fluorescently labeled miRNAs binding to the surface of Hela cells were transfected into intra-cell because of the high transfection efficiency, however, most of them were still binding to the surface of K562 cells. Moreover, the high-salt buffer which could destroy the electrostatic interactions did not affect the above-mentioned non-specific binding, but the organic solvent which could destroy the hydrophobic interactions eliminated it. These results implied that the fluorescent-labeled miRNAs could non-specifically bind to the cell surface by hydrophobic interaction. It would lead to significant errors in the estimation of transfection efficiency only according to the cellular fluorescence intensity. Therefore, other methods to evaluate the transfection efficiency and more appropriate fluorescent dyes should be used according to the cell types for the accuracy of results.

The Non-Specific Binding of Fluorescent-Labeled MiRNAs on Cell Surface by Hydrophobic Interaction.

Directory of Open Access Journals (Sweden)

Ting Lu

Full Text Available MicroRNAs are small noncoding RNAs about 22 nt long that play key roles in almost all biological processes and diseases. The fluorescent labeling and lipofection are two common methods for changing the levels and locating the position of cellular miRNAs. Despite many studies about the mechanism of DNA/RNA lipofection, little is known about the characteristics, mechanisms and specificity of lipofection of fluorescent-labeled miRNAs.Therefore, miRNAs labeled with different fluorescent dyes were transfected into adherent and suspension cells using lipofection reagent. Then, the non-specific binding and its mechanism were investigated by flow cytometer and laser confocal microscopy. The results showed that miRNAs labeled with Cy5 (cyanine fluorescent dye could firmly bind to the surface of adherent cells (Hela and suspended cells (K562 even without lipofection reagent. The binding of miRNAs labeled with FAM (carboxyl fluorescein to K562 cells was obvious, but it was not significant in Hela cells. After lipofectamine reagent was added, most of the fluorescently labeled miRNAs binding to the surface of Hela cells were transfected into intra-cell because of the high transfection efficiency, however, most of them were still binding to the surface of K562 cells. Moreover, the high-salt buffer which could destroy the electrostatic interactions did not affect the above-mentioned non-specific binding, but the organic solvent which could destroy the hydrophobic interactions eliminated it.These results implied that the fluorescent-labeled miRNAs could non-specifically bind to the cell surface by hydrophobic interaction. It would lead to significant errors in the estimation of transfection efficiency only according to the cellular fluorescence intensity. Therefore, other methods to evaluate the transfection efficiency and more appropriate fluorescent dyes should be used according to the cell types for the accuracy of results.

Coumarins as new matrices for matrix-assisted laser-desorption/ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of hydrophobic compounds

Energy Technology Data Exchange (ETDEWEB)

Wang, Hang, E-mail: hangwang@sjtu.edu.cn [Instrumental Analysis Center, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240 (China); Dai, Bona [Instrumental Analysis Center, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240 (China); Liu, Bin [Key Laboratory of Kidney Disease Pathogenesis and Intervention of Hubei Province, College of Medicine, Hubei Polytechnic University, Huangshi, Hubei 435003 (China); Lu, Han [Department of Anesthesiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine (SJTU-SM), 197, Rui Jin Er Road, Shanghai 200025 (China)

2015-07-02

Highlights: • Coumarins were used as new MALDI matrices. • Coumarins were used for MALDI-FT ICR MS detection of hydrophobic compounds. • DCA had improvement in detection sensitivity, stability, selectivity and reproducibility. • DCA was applied to sterols detection in yeast cells. - Abstract: Hydrophobic compounds with hydroxyl, aldehyde or ketone groups are generally difficult to detect using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), because these compounds have low proton affinity and are poorly ionized by MALDI. Herein, coumarins have been used as new matrices for MALDI-MS analysis of a variety of hydrophobic compounds with low ionization efficiency, including steroids, coenzyme Q10, a cyclic lipopeptide and cholesterol oleate. Five coumarins, including coumarin, umbelliferone, esculetin, 7-hydroxycoumarin-3-carboxylic acid (HCA) and 6,7-dihydroxycoumarin-3-carboxylic acid (DCA), were compared with the conventional matrices of 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA). Coumarins with hydroxyl or carboxylic acid groups enabled detection. Taking DCA as an example, this matrix proved to be superior to DHB or CHCA in detection sensitivity, stability, spot-to-spot and sample-to-sample reproducibility, and accuracy. DCA increased the stability of the target compounds and decreased the loss of water. The [M + Na]{sup +} peaks were observed for all target compounds by adding NaCl as an additive, and the [M − H{sub 2}O + H]{sup +} and [M + H]{sup +} peaks decreased. DCA was selected for the identification of sterols in yeast cells, and thirteen sterols were detected by Fourier transform ion cyclotron resonance (FT ICR) mass spectrometry. This work demonstrates the potential of DCA as a new matrix for detection of hydrophobic molecules by MALDI-MS and provides an alternative tool for screening sterols in antifungal research.

Fabrication of a novel hydrophobic/ion-exchange mixed-mode adsorbent for the dispersive solid-phase extraction of chlorophenols from environmental water samples.

Science.gov (United States)

Gao, Li; Wei, Yinmao

2016-08-01

A novel mixed-mode adsorbent was prepared by functionalizing silica with tris(2-aminoethyl)amine and 3-phenoxybenzaldehyde as the main mixed-mode scaffold due to the presence of the plentiful amino groups and benzene rings in their molecules. The adsorption mechanism was probed with acidic, natural and basic compounds, and the mixed hydrophobic and ion-exchange interactions were found to be responsible for the adsorption of analytes. The suitability of dispersive solid-phase extraction was demonstrated in the determination of chlorophenols in environmental water. Several parameters, including sample pH, desorption solvent, ionic strength, adsorbent dose, and extraction time were optimized. Under the optimal extraction conditions, the proposed dispersive solid-phase extraction coupled with high-performance liquid chromatography showed good linearity range and acceptable limits of detection (0.22∽0.54 ng/mL) for five chlorophenols. Notably, the higher extraction recoveries (88.7∽109.7%) for five chlorophenols were obtained with smaller adsorbent dose (10 mg) and shorter extraction time (15 min) compared with the reported methods. The proposed method might be potentially applied in the determination of trace chlorophenols in real water samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interactions of heavy ions with biomolecules: a dynamical microscopic approach

International Nuclear Information System (INIS)

Zhang Fengshou; Beijing Radiation Center, Beijing; National Laboratory of Heavy Ion Accelerator of Lanzhou, Lanzhou

2006-01-01

The status of studying biology system therapy with X-rays, γ-rays, neutron, proton, and heavy ions is reviewed. The depth dose profile, called Bragg profile, makes heavy ion an ideal tool for radiotherapy. The physical process of therapy with heavy ions is analyzed and a 3-step interaction processes of heavy ions with biomolecules is proposed, that is, nuclear fragmentation in nuclear interaction, electron excitation in Coulomb interaction, and the biomolecules relaxation in surroundings, finally leads to a new structure of biomolecule. Since this physical process is the base of the following chemical process and biological process, a dynamical microscopic approach is strongly demanded to be built. (authors)

Ionic Liquids as Extraction Media for Metal Ions

Science.gov (United States)

Hirayama, Naoki

In solvent extraction separation of metal ions, recently, many researchers have investigated possible use of hydrophobic ionic liquids as extraction media instead of organic solvents. Ionic liquids are salts of liquid state around room temperature and can act not only as solvents but also as ion-exchangers. Therefore, the extraction mechanism of metal ions into ionic liquids is complicated. This review presents current overview and perspective on evaluation of nature of hydrophobic ionic liquids as extraction media for metal ions.

Robust cross-links in molluscan adhesive gels: testing for contributions from hydrophobic and electrostatic interactions.

Science.gov (United States)

Smith, A M; Robinson, T M; Salt, M D; Hamilton, K S; Silvia, B E; Blasiak, R

2009-02-01

The cross-linking interactions that provide cohesive strength to molluscan adhesive gels were investigated. Metal-based interactions have been shown to play an important role in the glue of the slug Arion subfuscus (Draparnaud), but other types of interactions may also contribute to the glue's strength and their role has not been investigated. This study shows that treatments that normally disrupt hydrophobic or electrostatic interactions have little to no effect on the slug glue. High salt concentrations and non-ionic detergent do not affect the solubility of the proteins in the glue or the ability of the glue proteins to stiffen gels. In contrast, metal chelation markedly disrupts the gel. Experiments with gel filtration chromatography identify a 40 kDa protein that is a central component of the cross-links in the glue. This 40 kDa protein forms robust macromolecular aggregations that are stable even in the presence of high concentrations of salt, non-ionic detergent, urea or metal chelators. Metal chelation during glue secretion, however, may block some of these cross-links. Such robust, non-specific interactions in an aqueous environment are highly unusual for hydrogels and reflect an intriguing cross-linking mechanism.

Fabrication of Super-Hydrophobic Microchannels via Strain-Recovery Deformations of Polystyrene and Oxygen Reactive Ion Etch.

Science.gov (United States)

Chakraborty, Anirban; Xiang, Mingming; Luo, Cheng

2013-08-19

In this article, we report a simple approach to generate micropillars (whose top portions are covered by sub-micron wrinkles) on the inner surfaces of polystyrene (PS) microchannels, as well as on the top surface of the PS substrate, based on strain-recovery deformations of the PS and oxygen reactive ion etch (ORIE). Using this approach, two types of micropillar-covered microchannels are fabricated. Their widths range from 118 μm to 132 μm, depths vary from 40 μm to 44 μm, and the inclined angles of their sidewalls are from 53° to 64°. The micropillars enable these microchannels to have super-hydrophobic properties. The contact angles observed on the channel-structured surfaces are above 162°, and the tilt angles to make water drops roll off from these channel-structured substrates can be as small as 1°.

Fabrication of Super-Hydrophobic Microchannels via Strain-Recovery Deformations of Polystyrene and Oxygen Reactive Ion Etch

Directory of Open Access Journals (Sweden)

Anirban Chakraborty

2013-08-01

Full Text Available In this article, we report a simple approach to generate micropillars (whose top portions are covered by sub-micron wrinkles on the inner surfaces of polystyrene (PS microchannels, as well as on the top surface of the PS substrate, based on strain-recovery deformations of the PS and oxygen reactive ion etch (ORIE. Using this approach, two types of micropillar-covered microchannels are fabricated. Their widths range from 118 μm to 132 μm, depths vary from 40 μm to 44 μm, and the inclined angles of their sidewalls are from 53° to 64°. The micropillars enable these microchannels to have super-hydrophobic properties. The contact angles observed on the channel-structured surfaces are above 162°, and the tilt angles to make water drops roll off from these channel-structured substrates can be as small as 1°.

Ion-ion and ion-solvent interactions in lithium imidazolide electrolytes studied by Raman spectroscopy and DFT models.

Science.gov (United States)

Scheers, Johan; Niedzicki, Leszek; Zukowska, Grażyna Z; Johansson, Patrik; Wieczorek, Władysław; Jacobsson, Per

2011-06-21

Molecular level interactions are of crucial importance for the transport properties and overall performance of ion conducting electrolytes. In this work we explore ion-ion and ion-solvent interactions in liquid and solid polymer electrolytes of lithium 4,5-dicyano-(2-trifluoromethyl)imidazolide (LiTDI)-a promising salt for lithium battery applications-using Raman spectroscopy and density functional theory calculations. High concentrations of ion associates are found in LiTDI:acetonitrile electrolytes, the vibrational signatures of which are transferable to PEO-based LiTDI electrolytes. The origins of the spectroscopic changes are interpreted by comparing experimental spectra with simulated Raman spectra of model structures. Simple ion pair models in vacuum identify the imidazole nitrogen atom of the TDI anion to be the most important coordination site for Li(+), however, including implicit or explicit solvent effects lead to qualitative changes in the coordination geometry and improved correlation of experimental and simulated Raman spectra. To model larger aggregates, solvent effects are found to be crucial, and we finally suggest possible triplet and dimer ionic structures in the investigated electrolytes. In addition, the effects of introducing water into the electrolytes-via a hydrate form of LiTDI-are discussed.

Super-Hydrophobic Green Corrosion Inhibitor On Carbon Steel

Science.gov (United States)

Hassan, H.; Ismail, A.; Ahmad, S.; Soon, C. F.

2017-06-01

There are many examples of organic coatings used for corrosion protection. In particular, hydrophobic and super-hydrophobic coatings are shown to give good protection because of their enhanced ability to slow down transport of water and ions through the coating. The purpose of this research is to develop water repellent coating to avoid direct contact between metal and environment corrosive and mitigate corrosion attack at pipeline system. This water repellent characteristic on super-hydrophobic coating was coated by electrodeposition method. Wettability of carbon steel with super-hydrophobic coating (cerium chloride and myristic acid) and oxidized surface was investigated through contact angle and inhibitor performance test. The inhibitor performance was studied in 25% tannin acid corrosion test at 30°C and 3.5% sodium chloride (NaCl). The water contact angle test was determined by placing a 4-μL water droplet of distilled water. It shows that the wettability of contact angle super-hydrophobic with an angle of 151.60° at zero minute can be classified as super-hydrophobic characteristic. By added tannin acid as inhibitor the corrosion protection on carbon steel becomes more consistent. This reveals that the ability of the coating to withstand with the corrosion attack in the seawater at different period of immersions. The results elucidate that the weight loss increased as the time of exposure increased. However, the corrosion rates for uncoated carbon steel is high compared to coated carbon steel. As a conclusion, from both samples it can be seen that the coated carbon steel has less corrosion rated compared to uncoated carbon steel and addition of inhibitor to the seawater provides more protection to resist corrosion attack on carbon steel.

Interaction between human BAP31 and respiratory syncytial virus small hydrophobic (SH) protein

International Nuclear Information System (INIS)

Li, Yan; Jain, Neeraj; Limpanawat, Suweeraya; To, Janet; Quistgaard, Esben M.; Nordlund, Par; Thanabalu, Thirumaran; Torres, Jaume

2015-01-01

The small hydrophobic (SH) protein is a short channel-forming polypeptide encoded by the human respiratory syncytial virus (hRSV). Deletion of SH protein leads to the viral attenuation in mice and primates, and delayed apoptosis in infected cells. We have used a membrane-based yeast two-hybrid system (MbY2H) and a library from human lung cDNA to detect proteins that bind SH protein. This led to the identification of a membrane protein, B-cell associated protein 31 (BAP31). Transfected SH protein co-localizes with transfected BAP31 in cells, and pulls down endogenous BAP31. Titration of purified C-terminal endodomain of BAP31 against isotopically labeled SH protein in detergent micelles suggests direct interaction between the two proteins. Given the key role of BAP31 in protein trafficking and its critical involvement in pro- and anti-apoptotic pathways, this novel interaction may constitute a potential drug target. - Highlights: • A yeast two-hybrid system (MbY2H) detected BAP31 as a binder of RSV SH protein. • Transfected SH and BAP31 co-localize in lung epithelial cells. • Endogenous BAP31 is pulled down by RSV SH protein. • BAP31 endodomain interacts with the N-terminal α-helix of SH protein in micelles. • This interaction is proposed to be a potential drug target

Interaction between human BAP31 and respiratory syncytial virus small hydrophobic (SH) protein

Energy Technology Data Exchange (ETDEWEB)

Li, Yan; Jain, Neeraj; Limpanawat, Suweeraya; To, Janet [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore); Quistgaard, Esben M. [Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm (Sweden); Nordlund, Par [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore); Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm (Sweden); Thanabalu, Thirumaran [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore); Torres, Jaume, E-mail: jtorres@ntu.edu.sg [School of Biological Sciences, Nanyang Technological University, 637551 (Singapore)

2015-08-15

The small hydrophobic (SH) protein is a short channel-forming polypeptide encoded by the human respiratory syncytial virus (hRSV). Deletion of SH protein leads to the viral attenuation in mice and primates, and delayed apoptosis in infected cells. We have used a membrane-based yeast two-hybrid system (MbY2H) and a library from human lung cDNA to detect proteins that bind SH protein. This led to the identification of a membrane protein, B-cell associated protein 31 (BAP31). Transfected SH protein co-localizes with transfected BAP31 in cells, and pulls down endogenous BAP31. Titration of purified C-terminal endodomain of BAP31 against isotopically labeled SH protein in detergent micelles suggests direct interaction between the two proteins. Given the key role of BAP31 in protein trafficking and its critical involvement in pro- and anti-apoptotic pathways, this novel interaction may constitute a potential drug target. - Highlights: • A yeast two-hybrid system (MbY2H) detected BAP31 as a binder of RSV SH protein. • Transfected SH and BAP31 co-localize in lung epithelial cells. • Endogenous BAP31 is pulled down by RSV SH protein. • BAP31 endodomain interacts with the N-terminal α-helix of SH protein in micelles. • This interaction is proposed to be a potential drug target.

APIPIS: the Atomic Physics Ion-Photon Interaction System

International Nuclear Information System (INIS)

Johnson, B.M.; Jones, K.W.; Meron, M.; Kostroun, V.O.

1985-01-01

A proposed new facility for the study of highly charged heavy ions is described. The basic elements of APIPIS, the Atomic Physics Ion-Photon Interaction System, are: (1) a source of multiply-charged ions; (2) a linear accelerator; (3) a synchrotron storage ring; and (4) a source of high brightness x rays. The placement of a heavy ion storage ring at the x-ray ring of the National Synchrotron Light Source will provide unique opportunities for the study of photo-excitation of heavy ions

Microphase Separation in Oil-Water Mixtures Containing Hydrophilic and Hydrophobic Ions

NARCIS (Netherlands)

Tasios, Nikos; Samin, Sela; van Roij, Rene; Dijkstra, Marjolein

2017-01-01

We develop a lattice-based Monte Carlo simulation method for charged mixtures capable of treating dielectric heterogeneities. Using this method, we study oil-water mixtures containing an antagonistic salt, with hydrophilic cations and hydrophobic anions. Our simulations reveal several phases with a

Nonlinear interaction of an ion flux with plasma

International Nuclear Information System (INIS)

Ivanov, A.A.; Krasheninnikov, S.I.; Pistunovich, V.I.; Soboleva, T.K.; Yushamanov, P.N.

The present report discusses the interaction of an ion beam, formed during the charge exchange of injected neutral atoms, with a plasma. Methods of analytical study by means of quasi-linear equations as well as two-dimensional numerical modelling are used. It is shown that at a beam velocity U 0 /C/sub s/ approximately less than 1 / 2 , the relaxation process may be described by using the theory of quasi-linear relaxation of electron beams, at U 0 /C/sub s/ approximately greater than 10; one can neglect the slowing down of the ion beam and consider only the angular spread. An analytical dependence of the spread angle on time was obtained. On the basis of the ion beam relaxation theory evolved, experiments on charge exchange of plasma fluxes on a gas target are analyzed. It is shown that the anomalous scattering of the plasma flux observed in a series of experiments may be explained by the interaction of ions of the flux with ion-acoustic oscillations of the target plasma. Consideration of damping of ion-acoustic noise by the plasma electrons and ions leads to a limitation of the relaxation of the angular distribution function. The relationships obtained are in good agreement with the experimental results

Screened ion-ion interaction in mercury-chain compounds: Single chain

International Nuclear Information System (INIS)

Mohan, M.M.; Griffin, A.

1985-01-01

At room temperature, the mercury chains in Hg/sub 3-delta/AsF 6 exhibit phonons characteristic of a one-dimensional lattice. We calculate the screening of the Hg ion-ion interaction in a single chain by electrons moving in a cylindrical potential of finite radius, within the random-phase approximation. The resulting Bohm-Staver-type expression for the phonon velocity is (Z 2 mN/sub I//MN/sub e/)/sup 1/2/v/sub F/, where Z is the Hg ionic charge and N/sub I/ (N/sub e/) is the number of ions (electrons) per unit length. Use of the Tomonaga-Luttinger solution for the electronic response function (keeping only the small-momentum scattering processes) just renormalizes the Fermi velocity in this expression

Influence of the interaction of ions-dust grains on ion acoustic wave and dust acoustic wave

International Nuclear Information System (INIS)

Hua Jianjun; Liu Jinyuan; Ma Tengcai

2004-01-01

Based on a set of hydrodynamic equations and a linear time-dependent perturbation theory, the influence of the interaction of ions-dust grains on ion acoustic wave IAW and dust acoustic wave DAW in dusty plasma is analyzed. The results show that the interaction makes IAW more stable and DAW less stable

The cation-π interaction.

Science.gov (United States)

Dougherty, Dennis A

2013-04-16

The chemistry community now recognizes the cation-π interaction as a major force for molecular recognition, joining the hydrophobic effect, the hydrogen bond, and the ion pair in determining macromolecular structure and drug-receptor interactions. This Account provides the author's perspective on the intellectual origins and fundamental nature of the cation-π interaction. Early studies on cyclophanes established that water-soluble, cationic molecules would forego aqueous solvation to enter a hydrophobic cavity if that cavity was lined with π systems. Important gas phase studies established the fundamental nature of the cation-π interaction. The strength of the cation-π interaction (Li(+) binds to benzene with 38 kcal/mol of binding energy; NH4(+) with 19 kcal/mol) distinguishes it from the weaker polar-π interactions observed in the benzene dimer or water-benzene complexes. In addition to the substantial intrinsic strength of the cation-π interaction in gas phase studies, the cation-π interaction remains energetically significant in aqueous media and under biological conditions. Many studies have shown that cation-π interactions can enhance binding energies by 2-5 kcal/mol, making them competitive with hydrogen bonds and ion pairs in drug-receptor and protein-protein interactions. As with other noncovalent interactions involving aromatic systems, the cation-π interaction includes a substantial electrostatic component. The six (four) C(δ-)-H(δ+) bond dipoles of a molecule like benzene (ethylene) combine to produce a region of negative electrostatic potential on the face of the π system. Simple electrostatics facilitate a natural attraction of cations to the surface. The trend for (gas phase) binding energies is Li(+) > Na(+) > K(+) > Rb(+): as the ion gets larger the charge is dispersed over a larger sphere and binding interactions weaken, a classical electrostatic effect. On other hand, polarizability does not define these interactions. Cyclohexane is

Electron emission during multicharged ion-metal surface interactions

International Nuclear Information System (INIS)

Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Hughes, I.G.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M.; Meyer, F.W.

1992-01-01

The electron emission during multicharged ion-metal surface interactions will be discussed. The interactions lead to the emission of a significant number of electrons. Most of these electrons have energies below 30 eV. For incident ions with innershell vacancies the emission of Auger electrons that fill these vacancies has been found to occur mainly below the surface. We will present recently measured electron energy distributions which will be used to discuss the mechanisms that lead to the emission of Auger and of low-energy electrons

Plasma-surface interaction in negative hydrogen ion sources

Science.gov (United States)

Wada, Motoi

2018-05-01

A negative hydrogen ion source delivers more beam current when Cs is introduced to the discharge, but a continuous operation of the source reduces the beam current until more Cs is added to the source. This behavior can be explained by adsorption and ion induced desorption of Cs atoms on the plasma grid surface of the ion source. The interaction between the ion source plasma and the plasma grid surface of a negative hydrogen ion source is discussed in correlation to the Cs consumption of the ion source. The results show that operation with deuterium instead of hydrogen should require more Cs consumption and the presence of medium mass impurities as well as ions of the source wall materials in the arc discharge enlarges the Cs removal rate during an ion source discharge.

Electro-osmosis over inhomogeneously charged surfaces in presence of non-electrostatic ion-ion interactions

Science.gov (United States)

Ghosh, Uddipta; Chakraborty, Suman

2016-06-01

In this study, we attempt to bring out a generalized formulation for electro-osmotic flows over inhomogeneously charged surfaces in presence of non-electrostatic ion-ion interactions. To this end, we start with modified electro-chemical potential of the individual species and subsequently use it to derive modified Nernst-Planck equation accounting for the ionic fluxes generated because of the presence of non-electrostatic potential. We establish what we refer to as the Poisson-Helmholtz-Nernst-Planck equations, coupled with the Navier-Stokes equations, to describe the complete transport process. Our analysis shows that the presence of non-electrostatic interactions between the ions results in an excess body force on the fluid, and modifies the osmotic pressure as well, which has hitherto remained unexplored. We further apply our analysis to a simple geometry, in an effort to work out the Smoluchowski slip velocity for thin electrical double layer limits. To this end, we employ singular perturbation and develop a general framework for the asymptotic analysis. Our calculations reveal that the final expression for slip velocity remains the same as that without accounting for non-electrostatic interactions. However, the presence of non-electrostatic interactions along with ion specificity can significantly change the quantitative behavior of Smoluchowski slip velocity. We subsequently demonstrate that the presence of non-electrostatic interactions may significantly alter the effective interfacial potential, also termed as the "Zeta potential." Our analysis can potentially act as a guide towards the prediction and possibly quantitative determination of the implications associated with the existence of non-electrostatic potential, in an electrokinetic transport process.

Is Br2 hydration hydrophobic?

Science.gov (United States)

Alcaraz-Torres, A; Gamboa-Suárez, A; Bernal-Uruchurtu, M I

2017-02-28

The spectroscopic properties of bromine in aqueous systems suggest it can behave as either hydrophilic or hydrophobic solute. In small water clusters, the halogen bond and the hydrogen-halogen interaction are responsible for its specific way of binding. In water hydrates, it is efficiently hosted by two different cages forming the crystal structure and it has been frequently assumed that there is little or no interaction between the guest and the host. Bromine in liquid solution poses a challenging question due to its non-negligible solubility and the large blue shift measured in its absorption spectra. Using a refined semi-empirical force field, PM3-PIF, we performed a Born-Oppenheimer molecular dynamics study of bromine in liquid water. Here we present a detailed study in which we retrieved the most representative hydration structures in terms of the most frequent positions around bromine and the most common water orientations. Albeit being an approximate description of the total hydration phenomenon, it captures the contribution of the leading molecular interactions in form of the recurrent structures. Our findings confirm that the spectroscopic signature is mainly caused by the closest neighbors. The dynamics of the whole first hydration shell strongly suggests that the external molecules in that structure effectively isolate the bulk from the presence of bromine. The solvation structure fluctuates from a hydrophilic to a hydrophobic-like environment along the studied trajectory.

Selective Binding, Self-Assembly and Nanopatterning of the Creutz-Taube Ion on Surfaces

Directory of Open Access Journals (Sweden)

Qingling Hang

2009-02-01

Full Text Available The surface attachment properties of the Creutz-Taube ion, i.e., [(NH35Ru(pyrazineRu(NH35]5+, on both hydrophilic and hydrophobic types of surfaces were investigated using X-ray photoelectron spectroscopy (XPS. The results indicated that the Creutz-Taube ions only bound to hydrophilic surfaces, such as SiO2 and –OH terminated organic SAMs on gold substrates. No attachment of the ions on hydrophobic surfaces such as –CH3 terminated organic SAMs and poly(methylmethacrylate (PMMA thin films covered gold or SiO2 substrates was observed. Further ellipsometric, atomic force microscopy (AFM and time-dependent XPS studies suggested that the attached cations could form an inorganic analog of the self-assembled monolayer on SiO2 substrate with a “lying-down” orientation. The strong electrostatic interaction between the highly charged cations and the anionic SiO2 surface was believed to account for these observations. Based on its selective binding property, patterning of wide (~200 nm and narrow (~35 nm lines of the Creutz-Taube ions on SiO2 surface were demonstrated through PMMA electron resist masks written by electron beam lithography (EBL.

Cation–Anion Interactions within the Nucleic Acid Ion Atmosphere Revealed by Ion Counting

Science.gov (United States)

Gebala, Magdalena; Giambasu, George M.; Lipfert, Jan; Bisaria, Namita; Bonilla, Steve; Li, Guangchao; York, Darrin M.; Herschlag, Daniel

2016-01-01

The ion atmosphere is a critical structural, dynamic, and energetic component of nucleic acids that profoundly affects their interactions with proteins and ligands. Experimental methods that “count” the number of ions thermodynamically associated with the ion atmosphere allow dissection of energetic properties of the ion atmosphere, and thus provide direct comparison to theoretical results. Previous experiments have focused primarily on the cations that are attracted to nucleic acid polyanions, but have also showed that anions are excluded from the ion atmosphere. Herein, we have systematically explored the properties of anion exclusion, testing the zeroth-order model that anions of different identity are equally excluded due to electrostatic repulsion. Using a series of monovalent salts, we find, surprisingly, that the extent of anion exclusion and cation inclusion significantly depends on salt identity. The differences are prominent at higher concentrations and mirror trends in mean activity coefficients of the electrolyte solutions. Salts with lower activity coefficients exhibit greater accumulation of both cations and anions within the ion atmosphere, strongly suggesting that cation–anion correlation effects are present in the ion atmosphere and need to be accounted for to understand electrostatic interactions of nucleic acids. To test whether the effects of cation–anion correlations extend to nucleic acid kinetics and thermodynamics, we followed the folding of P4–P6, a domain of the Tetrahymena group I ribozyme, via single-molecule fluorescence resonance energy transfer in solutions with different salts. Solutions of identical concentration but lower activity gave slower and less favorable folding. Our results reveal hitherto unknown properties of the ion atmosphere and suggest possible roles of oriented ion pairs or anion-bridged cations in the ion atmosphere for electrolyte solutions of salts with reduced activity. Consideration of these new

Ion-atom interactions probed by photofragment spectroscopy

International Nuclear Information System (INIS)

Helm, H.

1984-01-01

Photofragment spectroscopy studies energetic and dynamical properties of molecular states interacting with dissociation continuum. So far, data for eighteen diatomic molecular ions have been gathered by this technique. This paper is a review of these investigations, introduced by a discussion of the experimental methods used. The wealth of information accessible by ion photofragment spectroscopy challenges the experimentalist in the application of innovative techniques and the theoretician for less approximate accounts of the Hamiltonian. (Auth.)

Does an electronic continuum correction improve effective short-range ion-ion interactions in aqueous solution?

Science.gov (United States)

Bruce, Ellen E.; van der Vegt, Nico F. A.

2018-06-01

Non-polarizable force fields for hydrated ions not always accurately describe short-range ion-ion interactions, frequently leading to artificial ion clustering in bulk aqueous solutions. This can be avoided by adjusting the nonbonded anion-cation or cation-water Lennard-Jones parameters. This approach has been successfully applied to different systems, but the parameterization is demanding owing to the necessity of separate investigations of each ion pair. Alternatively, polarization effects may effectively be accounted for using the electronic continuum correction (ECC) of Leontyev et al. [J. Chem. Phys. 119, 8024 (2003)], which involves scaling the ionic charges with the inverse square-root of the water high-frequency dielectric permittivity. ECC has proven to perform well for monovalent salts as well as for divalent salts in water. Its performance, however, for multivalent salts with higher valency remains unexplored. The present work illustrates the applicability of the ECC model to trivalent K3PO4 and divalent K2HPO4 in water. We demonstrate that the ECC models, without additional tuning of force field parameters, provide an accurate description of water-mediated interactions between salt ions. This results in predictions of the osmotic coefficients of aqueous K3PO4 and K2HPO4 solutions in good agreement with experimental data. Analysis of ion pairing thermodynamics in terms of contact ion pair (CIP), solvent-separated ion pair, and double solvent-separated ion pair contributions shows that potassium-phosphate CIP formation is stronger with trivalent than with divalent phosphate ions.

Coulomb interaction rules timescales in potassium ion channel tunneling

Science.gov (United States)

De March, N.; Prado, S. D.; Brunnet, L. G.

2018-06-01

Assuming the selectivity filter of KcsA potassium ion channel may exhibit quantum coherence, we extend a previous model by Vaziri and Plenio (2010 New J. Phys. 12 085001) to take into account Coulomb repulsion between potassium ions. We show that typical ion transit timescales are determined by this interaction, which imposes optimal input/output parameter ranges. Also, as observed in other examples of quantum tunneling in biological systems, the addition of moderate noise helps coherent ion transport.

Temperature effects on the hydrophobic force between two ...

Indian Academy of Sciences (India)

TUHIN SAMANTA

2018-03-02

Mar 2, 2018 ... We perform the molecular dynamics simulations to investigate ... molecular assemblies and in the formation of protein complexes.1–7 One of the important manifestations of the hydrophobic interactions is observed in oil-water.

Preparation and use of polymeric materials containing hydrophobic anions and plasticizers for separation of cesium and strontium

International Nuclear Information System (INIS)

Abney, K.D.; Kinkead, S.A.; Mason, C.F.V.; Rais, J.

1997-01-01

Preparation and use is described for polymeric materials containing hydrophobic anions and plasticizers for extraction of cesium and strontium. The use of polymeric materials containing plasticizers which are solvents for hydrophobic anions such as derivatives of cobalt dicarbollide or tetraphenylborate which are capable of extracting cesium and strontium ions from aqueous solutions in contact with the polymeric materials, is described. The polymeric material may also include a synergistic agent for a given ion like polyethylene glycol or a crown ether, for removal of radioactive isotopes of cesium and strontium from solutions of diverse composition and, in particular, for solutions containing large excess of sodium nitrate

Nuclear import of high risk HPV16 E7 oncoprotein is mediated by its zinc-binding domain via hydrophobic interactions with Nup62

Energy Technology Data Exchange (ETDEWEB)

Eberhard, Jeremy; Onder, Zeynep; Moroianu, Junona, E-mail: moroianu@bc.edu

2013-11-15

We previously discovered that nuclear import of high risk HPV16 E7 is mediated by a cNLS located within the zinc-binding domain via a pathway that is independent of karyopherins/importins (Angeline et al., 2003; Knapp et al., 2009). In this study we continued our characterization of the cNLS and nuclear import pathway of HPV16 E7. We find that an intact zinc-binding domain is essential for the cNLS function in mediating nuclear import of HPV16 E7. Mutagenesis of cysteine residues to alanine in each of the two CysXXCys motifs involved in zinc-binding changes the nuclear localization of the EGFP-16E7 and 2xEGFP-16E7 mutants. We further discover that a patch of hydrophobic residues, {sub 65}LRLCV{sub 69}, within the zinc-binding domain of HPV16 E7 mediates its nuclear import via hydrophobic interactions with the FG domain of the central channel nucleoporin Nup62. - Highlights: • An intact zinc-binding domain is essential for the nuclear localization of HPV16 E7. • Identification of a hydrophobic patch that is critical for the nuclear import of HPV16 E7. • HPV16 E7 interacts via its zinc-binding domain with the FG domain of Nup62.

Four faces of the interaction between ions and aromatic rings.

Science.gov (United States)

Papp, Dóra; Rovó, Petra; Jákli, Imre; Császár, Attila G; Perczel, András

2017-07-15

Non-covalent interactions between ions and aromatic rings play an important role in the stabilization of macromolecular complexes; of particular interest are peptides and proteins containing aromatic side chains (Phe, Trp, and Tyr) interacting with negatively (Asp and Glu) and positively (Arg and Lys) charged amino acid residues. The structures of the ion-aromatic-ring complexes are the result of an interaction between the large quadrupole moment of the ring and the charge of the ion. Four attractive interaction types are proposed to be distinguished based on the position of the ion with respect to the plane of the ring: perpendicular cation-π (CP ⊥ ), co-planar cation-π (CP ∥ ), perpendicular anion-π (AP ⊥ ), and co-planar anion-π (AP ∥ ). To understand more than the basic features of these four interaction types, a systematic, high-level quantum chemical study is performed, using the X -  + C 6 H 6 , M +  + C 6 H 6 , X -  + C 6 F 6 , and M +  + C 6 F 6 model systems with X -  = H - , F - , Cl - , HCOO - , CH 3 COO - and M +  = H + , Li + , Na + , NH4+, CH 3 NH3+, whereby C 6 H 6 and C 6 F 6 represent an electron-rich and an electron-deficient π system, respectively. Benchmark-quality interaction energies with small uncertainties, obtained via the so-called focal-point analysis (FPA) technique, are reported for the four interaction types. The computations reveal that the interactions lead to significant stabilization, and that the interaction energy order, given in kcal mol -1 in parentheses, is CP ⊥ (23-37) > AP ⊥ (14-21) > CP ∥ (9-22) > AP ∥ (6-16). A natural bond orbital analysis performed leads to a deeper qualitative understanding of the four interaction types. To facilitate the future quantum chemical characterization of ion-aromatic-ring interactions in large biomolecules, the performance of three density functional theory methods, B3LYP, BHandHLYP, and M06-2X, is tested against the FPA benchmarks

Proton-ion collisions: behind the scenes of an exotic interaction

CERN Multimedia

Antonella Del Rosso

2012-01-01

Protons to the right, ions to the left: the basic principle of proton-ion collisions at the LHC might seem straightforward. However, this is an almost unprecedented mode of collider operation, certainly unique at the energy provided by the LHC. In addition to being a remarkable technical achievement, this interaction between a proton and an ion can potentially contribute a lot to the understanding of the properties of matter in its primordial state.   Prior to last week, the LHC had only collided protons with protons and lead ions with lead ions. These were indeed the two operational schemes the LHC was designed for. However, since science can often evolve in directions that were not necessarily expected at the beginning of a project, over the years the scientific community has become more and more interested in the hybrid type of interaction – that between protons and ions. Last week’s collisions were only a test for the teams involved in the operation of the LHC, in prepara...

Rational design of viscosity reducing mutants of a monoclonal antibody: hydrophobic versus electrostatic inter-molecular interactions.

Science.gov (United States)

Nichols, Pilarin; Li, Li; Kumar, Sandeep; Buck, Patrick M; Singh, Satish K; Goswami, Sumit; Balthazor, Bryan; Conley, Tami R; Sek, David; Allen, Martin J

2015-01-01

High viscosity of monoclonal antibody formulations at concentrations ≥100 mg/mL can impede their development as products suitable for subcutaneous delivery. The effects of hydrophobic and electrostatic intermolecular interactions on the solution behavior of MAB 1, which becomes unacceptably viscous at high concentrations, was studied by testing 5 single point mutants. The mutations were designed to reduce viscosity by disrupting either an aggregation prone region (APR), which also participates in 2 hydrophobic surface patches, or a negatively charged surface patch in the variable region. The disruption of an APR that lies at the interface of light and heavy chain variable domains, VH and VL, via L45K mutation destabilized MAB 1 and abolished antigen binding. However, mutation at the preceding residue (V44K), which also lies in the same APR, increased apparent solubility and reduced viscosity of MAB 1 without sacrificing antigen binding or thermal stability. Neutralizing the negatively charged surface patch (E59Y) also increased apparent solubility and reduced viscosity of MAB 1, but charge reversal at the same position (E59K/R) caused destabilization, decreased solubility and led to difficulties in sample manipulation that precluded their viscosity measurements at high concentrations. Both V44K and E59Y mutations showed similar increase in apparent solubility. However, the viscosity profile of E59Y was considerably better than that of the V44K, providing evidence that inter-molecular interactions in MAB 1 are electrostatically driven. In conclusion, neutralizing negatively charged surface patches may be more beneficial toward reducing viscosity of highly concentrated antibody solutions than charge reversal or aggregation prone motif disruption.

Heating and reduction affect the reaction with tannins of wine protein fractions differing in hydrophobicity.

Science.gov (United States)

Marangon, Matteo; Vincenzi, Simone; Lucchetta, Marco; Curioni, Andrea

2010-02-15

During the storage, bottled white wines can manifest haziness due to the insolubilisation of the grape proteins that may 'survive' in the fermentation process. Although the exact mechanism of this occurrence is not fully understood, proteins and tannins are considered two of the key factors involved in wine hazing, since their aggregation leads to the formation of insoluble particles. To better understand this complex interaction, proteins and tannins from the same unfined Pinot grigio wine were separated. Wine proteins were then fractionated by hydrophobic interaction chromatography (HIC). A significant correlation between hydrophobicity of the wine protein fractions and the haze formed after reacting with wine tannins was found, with the most reactive fractions revealing (by SDS-PAGE and RP-HPLC analyses) the predominant presence of thaumatin-like proteins. Moreover, the effects of both protein heating and disulfide bonds reduction (with dithiotreithol) on haze formation in the presence of tannins were assessed. These treatments generally resulted in an improved reactivity with tannins, and this phenomenon was related to both the surface hydrophobicity and composition of the protein fractions. Therefore, haze formation in wines seems to be related to hydrophobic interactions occurring among proteins and tannins. These interactions should occur on hydrophobic tannin-binding sites, whose exposition on the proteins can depend on both protein heating and reduction. Copyright 2009 Elsevier B.V. All rights reserved.

Hydrophobizing coatings for cultural heritage. A detailed study of resin/stone surface interaction

Science.gov (United States)

Fermo, P.; Cappelletti, G.; Cozzi, N.; Padeletti, G.; Kaciulis, S.; Brucale, M.; Merlini, M.

2014-07-01

Conservation of historical buildings is an important issue and the environmental conditions seriously affect the monument's stones. The protection of cultural heritage buildings and monuments by surface treatment with polymers is a common practice due to their ability to form a protective layer on the monument's surface as well as to control the transport of different fluids from the surface to the monument's interior. In this work, three different substrates were used: Carrara marble, Botticino limestone, and Angera stone. A commercially available Si-based resin (Alpha®SI30) was used as protective agent to improve the hydrophobicity features of the different tested materials. The surface properties of the coating and the relative interaction with the adopted stones were studied using different techniques such as contact angle measurements, electron microscope coupled with an energy dispersive spectrometer, X-ray photoelectron spectroscopy, atomic force microscopy, and attenuated total reflection infrared spectroscopy.

Rheological Properties in Aqueous Solution for Hydrophobically Modified Polyacrylamides Prepared in Inverse Emulsion Polymerization

Directory of Open Access Journals (Sweden)

Shirley Carro

2017-01-01

Full Text Available Inverse emulsion polymerization technique was employed to synthesize hydrophobically modified polyacrylamide polymers with hydrophobe contents near to feed composition. Three different structures were obtained: multisticker, telechelic, and combined. N-Dimethyl-acrylamide (DMAM, n-dodecylacrylamide (DAM, and n-hexadecylacrylamide (HDAM were used as hydrophobic comonomers. The effect of the hydrophobe length of comonomer, the initial monomer, and surfactant concentrations on shear viscosity was studied. Results show that the molecular weight of copolymer increases with initial monomer concentration and by increasing emulsifier concentration it remained almost constant. Shear viscosity measurements results show that the length of the hydrophobic comonomer augments the hydrophobic interactions causing an increase in viscosity and that the polymer thickening ability is higher for combined polymers.

Solvent effects on ion-receptor interactions in the presence of an external electric field.

Science.gov (United States)

Novák, Martin; Foroutan-Nejad, Cina; Marek, Radek

2016-11-09

In this work we investigated the influence of an external electric field on the arrangement of the solvent shells around ions interacting with a carbon-based receptor. Our survey reveals that the mechanism of interaction between a monoatomic ion and a π-type ion receptor varies by the variation in the solvent polarity, the nature of the ion, and the strength of the external field. The characteristics of the ion-surface interaction in nonpolar solvents are similar to those observed in a vacuum. However, in water, we identified two mechanisms. Soft and polarizable ions preferentially interact with the π-receptor. In contrast, two bonded states were found for hard ions. A fully solvated ion, weakly interacting with the receptor at weak field, and a strong π-complex at the strong-field regime were identified. An abrupt variation in the potential energy surface (PES) associated with the rearrangement of the solvation shell on the surface of the receptor induced by an external field was observed both in implicit and explicit solvent environments. The electric field at which the solvation shell breaks is proportional to the hardness of the ion as has been suggested recently based on experimental observations.

Diels-Alder reactions in water : Enforced hydrophobic interaction and hydrogen bonding

NARCIS (Netherlands)

Engberts, Jan B.F.N.

1995-01-01

Second-order rate constants have been measured for the Diels-Alder (DA) reactions of cyclopentadiene with dienophiles of varying hydrophobicity and hydrogen-bond acceptor capacity in water, in a series of organic solvents and in alcohol-water mixtures. The intramolecular DA reaction of

DIELS-ALDER REACTIONS IN WATER - ENFORCED HYDROPHOBIC INTERACTION AND HYDROGEN-BONDING

NARCIS (Netherlands)

Engberts, J.B.F.N.

Second-order rate constants have been measured for the Diels-Alder (DA) reactions of cyclopentadiene with dienophiles of varying hydrophobicity and hydrogen-bond acceptor capacity in water, in a series of organic solvents and in alcohol-water mixtures. The intramolecular DA reaction of

Unravelling the hydrophobicity of urea in water using thermodiffusion: implications for protein denaturation.

Science.gov (United States)

Niether, Doreen; Di Lecce, Silvia; Bresme, Fernando; Wiegand, Simone

2018-01-03

Urea is widely used as a protein denaturant in aqueous solutions. Experimental and computer simulation studies have shown that it dissolves in water almost ideally at high concentrations, introducing little disruption in the water hydrogen bonded structure. However, at concentrations of the order of 5 M or higher, urea induces denaturation in a wide range of proteins. The origin of this behaviour is not completely understood, but it is believed to stem from a balance between urea-protein and urea-water interactions, with urea becoming possibly hydrophobic at a specific concentration range. The small changes observed in the water structure make it difficult to connect the denaturation effects to the solvation properties. Here we show that the exquisite sensitivity of thermodiffusion to solute-water interactions allows the identification of the onset of hydrophobicity of urea-water mixtures. The hydrophobic behaviour is reflected in a sign reversal of the temperature dependent slope of the Soret coefficient, which is observed, both in experiments and non-equilibrium computer simulations at ∼5 M concentration of urea in water. This concentration regime corresponds to the one where abrupt changes in the denaturation of proteins are commonly observed. We show that the onset of hydrophobicity is intrinsically connected to the urea-water interactions. Our results allow us to identify correlations between the Soret coefficient and the partition coefficient, log P, hence establishing the thermodiffusion technique as a powerful approach to study hydrophobicity.

Non-invasive high throughput approach for protein hydrophobicity determination based on surface tension.

Science.gov (United States)

Amrhein, Sven; Bauer, Katharina Christin; Galm, Lara; Hubbuch, Jürgen

2015-12-01

The surface hydrophobicity of a protein is an important factor for its interactions in solution and thus the outcome of its production process. Yet most of the methods are not able to evaluate the influence of these hydrophobic interactions under natural conditions. In the present work we have established a high resolution stalagmometric method for surface tension determination on a liquid handling station, which can cope with accuracy as well as high throughput requirements. Surface tensions could be derived with a low sample consumption (800 μL) and a high reproducibility (content. The protein influence on the solutions' surface tension was correlated to the hydrophobicity of lysozyme, human lysozyme, BSA, and α-lactalbumin. Differences in proteins' hydrophobic character depending on pH and species could be resolved. Within this work we have developed a pH dependent hydrophobicity ranking, which was found to be in good agreement with literature. For the studied pH range of 3-9 lysozyme from chicken egg white was identified to be the most hydrophilic. α-lactalbumin at pH 3 exhibited the most pronounced hydrophobic character. The stalagmometric method occurred to outclass the widely used spectrophotometric method with bromophenol blue sodium salt as it gave reasonable results without restrictions on pH and protein species. © 2015 Wiley Periodicals, Inc.

Functional bacterial amyloid increases Pseudomonas biofilm hydrophobicity and stiffness

DEFF Research Database (Denmark)

Zeng, Guanghong; Vad, Brian S; Dueholm, Morten S

2015-01-01

The success of Pseudomonas species as opportunistic pathogens derives in great part from their ability to form stable biofilms that offer protection against chemical and mechanical attack. The extracellular matrix of biofilms contains numerous biomolecules, and it has recently been discovered...... that in Pseudomonas one of the components includes β-sheet rich amyloid fibrils (functional amyloid) produced by the fap operon. However, the role of the functional amyloid within the biofilm has not yet been investigated in detail. Here we investigate how the fap-based amyloid produced by Pseudomonas affects biofilm...... hydrophobicity and mechanical properties. Using atomic force microscopy imaging and force spectroscopy, we show that the amyloid renders individual cells more resistant to drying and alters their interactions with hydrophobic probes. Importantly, amyloid makes Pseudomonas more hydrophobic and increases biofilm...

Cationic flocculants carrying hydrophobic functionalities: applications for solid/liquid separation.

Science.gov (United States)

Schwarz, S; Jaeger, W; Paulke, B-R; Bratskaya, S; Smolka, N; Bohrisch, J

2007-07-26

The flocculation behaviors of three series of polycations with narrow molecular weight distributions carrying hydrophobic substituents on their backbones [poly(N-vinylbenzyl-N,N,N-trimethylammonium chloride), poly(N-vinylbenzyl-N,N-dimethyl-N-butylammonium chloride), and poly(N-vinylbenzylpyridinium chloride)] were investigated in dispersions of monodisperse polystyrene latexes and kaolin. Apparently, the charge density of the polycations decreases with increasing substituent hydrophobicity and increasing molecular weight of the polyelectrolytes. The necessary amount of flocculant for phase separation in dispersions with high substrate surface charge densities increases with increasing hydrophobicity of the polyelectrolyte. Nevertheless, the introduction of hydrophobic functionalities is beneficial, resulting in a substantial broadening of the range between the minimum and maximum amounts of flocculant necessary for efficient flocculation (flocculation window). An increase in ionic strength supports this effect. When the substrate has a low charge density, the hydrophobic interactions play a much more significant role in the flocculation process. Here, the minimum efficient doses remained the same for all three polyelectrolytes investigated, but the width of the flocculation window increased as the polycation hydrophobicity and the molecular weight increased. The necessary amount of flocculant increased with an increase in particle size at constant solid content of the dispersion, as well as with a decreasing number of particles at a constant particle size.

Investigation of Ion-Solvent Interactions in Nonaqueous Electrolytes Using in Situ Liquid SIMS

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yanyan; Su, Mao; Yu, Xiaofei; Zhou, Yufan; Wang, Jungang; Cao, Ruiguo; Xu, Wu; Wang, Chongmin; Baer, Donald R.; Borodin, Oleg; Xu, Kang; Wang, Yanting; Wang, Xue-Lin; Xu, Zhijie; Wang, Fuyi; Zhu, Zihua

2018-02-06

Ion-solvent interactions in non-aqueous electrolytes are of fundamental interest and practical importance, yet debates regarding ion preferential solvation and coordination numbers persist. In this work, in situ liquid SIMS was used to examine ion-solvent interactions in three representative electrolytes, i.e., lithium hexafluorophosphate (LiPF6) at 1.0 M in ethylene carbonate (EC)-dimethyl carbonate (DMC), and lithium bis(fluorosulfonyl)imide (LiFSI) at both low (1.0 M) and high (4.0 M) concentrations in 1,2-dimethoxyethane (DME). In the positive ion mode, solid molecular evidence strongly supports the preferential solvation of Li+ by EC. Besides, from the negative spectra, we also found that PF6- forms association with EC, which has been neglected by previous studies due to the relatively weak interaction. While in both LiFSI in DME electrolytes, no evidence shows that FSI- is associated with DME. Furthermore, strong salt ion cluster signals were observed in the 1.0 M LiPF6 in EC-DMC electrolyte, suggesting that a significant amount of Li+ ions stay in vicinity of anions. In sharp comparison, weak ion cluster signals were detected in dilute LiFSI in DME electrolyte, suggesting most ions are well separated, in agreement with our molecular dynamics (MD) simulation results. These findings indicate that with virtues of little bias on detecting positive and negative ions and the capability of directly analyzing concentrated electrolytes, in situ liquid SIMS is a powerful tool that can provide key evidence for improved understanding on the ion-solvent interactions in non-aqueous electrolytes. Therefore, we anticipate wide applications of in situ liquid SIMS on investigations of various ion-solvent interactions in the near future.

Slow, target associated particles produced in ultrarelativistic heavy-ion interactions

Energy Technology Data Exchange (ETDEWEB)

Adamovich, M I; Aggarwal, M M; Alexandrov, Y A; Andreeva, N P; Anson, Z V; Arora, R; Avetyan, F A; Badyal, S K; Basova, E; Bhalla, K B; Bhasin, A; Bhatia, V S; Bogdanov, V G; Bubnov, V I; Burnett, T H; Cai, X; Chasnikov, I Y; Chernova, L P; Chernyavsky, M M; Dressel, B; Eligbaeva, G Z; Eremenko, L E; Friedlander, E M; Gaitinov, A S; Ganssauge, E R; Garpman, S; Gerassimov, S G; Grote, J; Gulamov, K G; Gupta, S K; Gupta, V; Heckman, H H; Huang, H; Jakobsson, B; Judek, B; Kachroo, S; Kadyrov, F G; Kalyachkina, G S; Kanygina, E K; Karabova, M; Kaul, G L; Kaur, M; Kharlamov, S P; Koss, Y; Krasnov,; Kumar,; Lal, P; Larionova,; Lepetan,; Lindstrom,; Liu,; Lokanathan, S; Lord, J; Lukicheva, N S; Luo, S B; Mangotra, L K; Marutyan,; Maslennikova, N V; Mittra, I S; Mookerjee, S; Mueller, C; Nasrulaeva, H; Nasyrov, S H; Navotny, V S; Orlova, G I; Otterlund, I; Palsania, H S; Peresadko, N G; Petrov, N V; Plyushchev, V A; Qian, W Y; Raniwala,; EMU01 Collaboration

1991-06-20

The slow, target associated particles produced in ultrarelativistic heavy-ion interactions are a quantitative probe of the cascading processes in the spectator parts of the target nucleus. These processes are directly influenced by the proper timescale for the formation of hadronic matter. In this letter we show experimental data on singly and multiply charged particles, with velocities smaller than 0.7c, produced in ultrarelativistic heavy-ion interactions in nuclear emulsion. (orig.).

Two dimensional simulation of ion beam-plasm interaction | Echi ...

African Journals Online (AJOL)

Hybrid plasma simulation is a model in which different components of the plasma are treated differently. In this work the ions are treated as particles while the electrons are treated as a neutralizing background fluid through which electric signals may propagate. Deuterium ion beams incident on the tritium plasma interact ...

Light ions and ozone - generation and interactions with living organisms

International Nuclear Information System (INIS)

Kriha, V.; Aubrecht, L.

2005-01-01

With directly in the living organism born ions exception, LNI coming through three phases: ionisation, attachment by the electronegative molecules and the clusters formation due to local electrostatic interactions. The quantitative analysis of physical parameters leads to conclusion that we cannot find any physical property (till known) explaining the positive affect of LNI on living organisms. Analysis of possible mechanism produces several hypotheses of LNI-organism interaction. A simplified semi-quantitative model of respiratory tract was developed for estimation of ions and ozone interaction with living organisms. A formation of oxygen radicals and products of their chain-reactions in intrinsic conditions is discussed

Gradient elution behavior of proteins in hydrophobic interaction chromatography with U-shaped retention factor curves.

Science.gov (United States)

Creasy, Arch; Lomino, Joseph; Barker, Gregory; Khetan, Anurag; Carta, Giorgio

2018-04-27

Protein retention in hydrophobic interaction chromatography is described by the solvophobic theory as a function of the kosmostropic salt concentration. In general, an increase in salt concentration drives protein partitioning to the hydrophobic surface while a decrease reduces it. In some cases, however, protein retention also increases at low salt concentrations resulting in a U-shaped retention factor curve. During gradient elution the salt concentration is gradually decreased from a high value thereby reducing the retention factor and increasing the protein chromatographic velocity. For these conditions, a steep gradient can overtake the protein in the column, causing it to rebind. Two dynamic models, one based on the local equilibrium theory and the other based on the linear driving force approximation, are presented. We show that the normalized gradient slope determines whether the protein elutes in the gradient, partially elutes, or is trapped in the column. Experimental results are presented for two different monoclonal antibodies and for lysozyme on Capto Phenyl (High Sub) resin. One of the mAbs and lysozyme exhibit U-shaped retention factor curves and for each, we determine the critical gradient slope beyond which 100% recovery is no longer possible. Elution with a reverse gradient is also demonstrated at low salt concentrations for these proteins. Understanding this behavior has implications in the design of gradient elution since the gradient slope impacts protein recovery. Copyright © 2018 Elsevier B.V. All rights reserved.

Defining process design space for a hydrophobic interaction chromatography (HIC) purification step: application of quality by design (QbD) principles.

Science.gov (United States)

Jiang, Canping; Flansburg, Lisa; Ghose, Sanchayita; Jorjorian, Paul; Shukla, Abhinav A

2010-12-15

The concept of design space has been taking root under the quality by design paradigm as a foundation of in-process control strategies for biopharmaceutical manufacturing processes. This paper outlines the development of a design space for a hydrophobic interaction chromatography (HIC) process step. The design space included the impact of raw material lot-to-lot variability and variations in the feed stream from cell culture. A failure modes and effects analysis was employed as the basis for the process characterization exercise. During mapping of the process design space, the multi-dimensional combination of operational variables were studied to quantify the impact on process performance in terms of yield and product quality. Variability in resin hydrophobicity was found to have a significant influence on step yield and high-molecular weight aggregate clearance through the HIC step. A robust operating window was identified for this process step that enabled a higher step yield while ensuring acceptable product quality. © 2010 Wiley Periodicals, Inc.

Molecular Studies of Complex Soil Organic Matter Interactions with Metal Ions and Mineral Surfaces using Classical Molecular Dynamics and Quantum Chemistry Methods

Science.gov (United States)

Andersen, A.; Govind, N.; Laskin, A.

2017-12-01

Mineral surfaces have been implicated as potential protectors of soil organic matter (SOM) against decomposition and ultimate mineralization to small molecules which can provide nutrients for plants and soil microbes and can also contribute to the Earth's elemental cycles. SOM is a complex mixture of organic molecules of biological origin at varying degrees of decomposition and can, itself, self-assemble in such a way as to expose some biomolecule types to biotic and abiotic attack while protecting other biomolecule types. The organization of SOM and SOM with mineral surfaces and solvated metal ions is driven by an interplay of van der Waals and electrostatic interactions leading to partitioning of hydrophilic (e.g. sugars) and hydrophobic (e.g., lipids) SOM components that can be bridged with amphiphilic molecules (e.g., proteins). Classical molecular dynamics simulations can shed light on assemblies of organic molecules alone or complexation with mineral surfaces. The role of chemical reactions is also an important consideration in potential chemical changes of the organic species such as oxidation/reduction, degradation, chemisorption to mineral surfaces, and complexation with solvated metal ions to form organometallic systems. For the study of chemical reactivity, quantum chemistry methods can be employed and combined with structural insight provided by classical MD simulations. Moreover, quantum chemistry can also simulate spectroscopic signatures based on chemical structure and is a valuable tool in interpreting spectra from, notably, x-ray absorption spectroscopy (XAS). In this presentation, we will discuss our classical MD and quantum chemistry findings on a model SOM system interacting with mineral surfaces and solvated metal ions.

Role of long- and short-range hydrophobic, hydrophilic and charged residues contact network in protein’s structural organization

Directory of Open Access Journals (Sweden)

Sengupta Dhriti

2012-06-01

Full Text Available Abstract Background The three-dimensional structure of a protein can be described as a graph where nodes represent residues and the strength of non-covalent interactions between them are edges. These protein contact networks can be separated into long and short-range interactions networks depending on the positions of amino acids in primary structure. Long-range interactions play a distinct role in determining the tertiary structure of a protein while short-range interactions could largely contribute to the secondary structure formations. In addition, physico chemical properties and the linear arrangement of amino acids of the primary structure of a protein determines its three dimensional structure. Here, we present an extensive analysis of protein contact subnetworks based on the London van der Waals interactions of amino acids at different length scales. We further subdivided those networks in hydrophobic, hydrophilic and charged residues networks and have tried to correlate their influence in the overall topology and organization of a protein. Results The largest connected component (LCC of long (LRN-, short (SRN- and all-range (ARN networks within proteins exhibit a transition behaviour when plotted against different interaction strengths of edges among amino acid nodes. While short-range networks having chain like structures exhibit highly cooperative transition; long- and all-range networks, which are more similar to each other, have non-chain like structures and show less cooperativity. Further, the hydrophobic residues subnetworks in long- and all-range networks have similar transition behaviours with all residues all-range networks, but the hydrophilic and charged residues networks don’t. While the nature of transitions of LCC’s sizes is same in SRNs for thermophiles and mesophiles, there exists a clear difference in LRNs. The presence of larger size of interconnected long-range interactions in thermophiles than mesophiles, even at

Enhancement of hydrophobicity and tensile strength of muga silk fiber by radiofrequency Ar plasma discharge

International Nuclear Information System (INIS)

Gogoi, D.; Choudhury, A.J.; Chutia, J.; Pal, A.R.; Dass, N.N.; Devi, D.; Patil, D.S.

2011-01-01

The hydrophobicity and tensile strength of muga silk fiber are investigated using radiofrequency (RF) Ar plasma treatment at various RF powers (10-30 W) and treatment times (5-20 min). The Ar plasma is characterized using self-compensated Langmuir and emissive probe. The ion energy is observed to play an important role in determining the tensile strength and hydrophobicity of the plasma treated fibers. The chemical compositions of the fibers are observed to be affected by the increase in RF power rather than treatment time. XPS study reveals that the ions that are impinging on the substrates are mainly responsible for the cleavage of peptide bond and side chain of amino acid groups at the surface of the fibers. The observed properties (tensile strength and hydrophobicity) of the treated fibers are found to be dependent on their variation in atomic concentration and functional composition at the surfaces. All the treated muga fibers exhibit almost similar thermal behavior as compared to the virgin one. At RF power of 10 W and treatment time range of 5-20 min, the treated fibers exhibit properties similar to that of the virgin one. Higher RF power (30 W) and the increase in treatment time deteriorate the properties of the fibers due to incorporation of more surface roughness caused by sufficiently high energetic ion bombardment. The properties of the plasma treated fibers are attempted to correlate with the XPS analysis and their surface morphologies.

Influence of Hydrophobicity on Polyelectrolyte Complexation

Energy Technology Data Exchange (ETDEWEB)

Sadman, Kazi [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Wang, Qifeng [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Chen, Yaoyao [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States; Keshavarz, Bavand [Department; Jiang, Zhang [X-ray; Shull, Kenneth R. [Department; amp, Engineering, Northwestern University, Evanston, Illinois 60208, United States

2017-11-16

Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) with methyl, ethyl and propyl substituents– thereby increasing the hydrophobicity with increasing side chain length– and complexing them with a common anionic polyelectrolyte, poly(styrene sulfonate). The mechanical 1 ACS Paragon Plus Environment behavior of these complexes is compared to the more hydrophilic system of poly(styrene sulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling-modulus master curves that are quantified in this work. The rheological behavior of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.

Study of highly charged ion production by electron cyclotron resonance ion source. Interactions of Argon 17+ ions with metallic surface at grazing incidence

International Nuclear Information System (INIS)

Ban, G.

1992-04-01

In this thesis divided in 2 parts, the author first presents the operating of MiniMafios 16/18 GHz ECR ion sources and methods of extracted multicharged ion identification and then, studies the highly charged ion interactions with a metallic surface and the formation of 'hollow atoms'. 556 figs., 17 tabs

ENERGETIC PHOTON AND ELECTRON INTERACTIONS WITH POSITIVE IONS

Energy Technology Data Exchange (ETDEWEB)

Phaneuf, Ronald A. [UNR

2013-07-01

The objective of this research is a deeper understanding of the complex multi-electron interactions that govern inelastic processes involving positive ions in plasma environments, such as those occurring in stellar cares and atmospheres, x-ray lasers, thermonuclear fusion reactors and materials-processing discharges. In addition to precision data on ionic structure and transition probabilities, high resolution quantitative measurements of ionization test the theoretical methods that provide critical input to computer codes used for plasma modeling and photon opacity calculations. Steadily increasing computational power and a corresponding emphasis on simulations gives heightened relevance to precise and accurate benchmark data. Photons provide a highly selective probe of the internal electronic structure of atomic and molecular systems, and a powerful means to better understand more complex electron-ion interactions.

Structure and Dynamics of Ionic Liquid [MMIM][Br] Confined in Hydrophobic and Hydrophilic Porous Matrices: A Molecular Dynamics Simulation Study.

Science.gov (United States)

Sharma, Anirban; Ghorai, Pradip Kr

2016-11-17

The effects of confinement on the structural and dynamical properties of the ionic liquid (IL) 1,3-dimethylimidazolium bromide ([MMIM][Br]) have been investigated by molecular dynamics simulations. We used zeolite faujasite (NaY) as a hydrophilic confinement and dealuminated faujasite (DAY) as a hydrophobic confinement. The presence of an extra framework cation, [Na + ], in NaY makes the host hydrophilic, whereas DAY, with no extra framework cation, is hydrophobic. Although both NaY and DAY have almost similar structures, the IL showed markedly different structural and dynamical properties in these confinements and in bulk. In the confinements, the cation-cation radial distribution function, which strongly depends on temperature, exhibits a layer-like structure, whereas in bulk, it shows a liquid-like structure that hardly depends on temperature. Although the interaction between [MMIM] + and Br - in DAY is stronger than that in both NaY and bulk, the strength of the interaction between them is almost invariant with temperature. Both [MMIM] + and Br - strongly interact with Na + of the host, and their interaction strongly depends on temperature, whereas the interaction of the IL with Si and O is very weak and invariant with temperature. In bulk, the self-diffusion coefficient, [D], of both [MMIM] + and Br - increases exponentially with temperature, and the D of the cation is slightly higher than that of the anion at all studied temperatures, whereas in the confinements, [MMIM] + moves much faster than Br - . For example, in the hydrophilic confinement, the D of the cation is 20-30 times higher than that of the anion. The D of both the ions decreases significantly in the confinements as compared to that in bulk. During diffusion, [MMIM] + diffuses closer to the inner surface in the hydrophilic confinement than that in the hydrophobic confinement. The diffusion pathway imperceptibly depends on temperature but strongly depends on the nature of the confinement. The self

RKKY interaction between Ce ions in CexLa1-xB6

International Nuclear Information System (INIS)

Schlottmann, P.

2000-01-01

Ce ions in (Ce x La 1-x )B 6 have a Γ 8 ground multiplet, which is fourfold degenerate and has orbital and spin content. The interaction between Ce ions is of the Ruderman-Kittel-Kasuya-Yosida (RKKY) type, which competes with the Kondo screening. The conduction states of the compound are described by three approximately ellipsoidal pockets centered at the X points of the cubic lattice. The RKKY interaction is calculated considering the interference of the three pockets. The interaction strength strongly depends on the relative position of the ions, as well as on the relative orientation of the line joining two ions to the cubic crystalline field axis. The sixteen states of a pair of Ce ions are split by the RKKY interaction into a singlet, a triplet, and a twelvefold degenerate level. The ground state is always either a singlet or a triplet, depending on the sign of the interaction. Using the exact Bethe ansatz solution of a model for a pair of interacting impurities with Γ 8 ground multiplet, we calculate the occupation of the levels, the magnetic-field susceptibility, the specific-heat γ coefficient, and the Wilson ratio for the ground state as a function of the ratio of the RKKY coupling strength to the Kondo temperature along the main crystallographic directions. As a consequence of the RKKY splitting a pair of impurities always has a quadrupolar moment. The implication of the interactions on the quadrupolar order of CeB 6 is also discussed

Fabrication of hydrophobic/super-hydrophobic nanofilms on magnesium alloys by polymer plating

Energy Technology Data Exchange (ETDEWEB)

Kang Zhixin, E-mail: zxkang@scut.edu.cn; Lai Xiaoming; Sang Jing; Li Yuanyuan

2011-11-01

Hydrophobic/super-hydrophobic nanofilms with improved corrosion resistance were fabricated on the surfaces of Mg-Mn-Ce magnesium alloy by a surface modification technique, named as polymer plating, which has been developed to modify superficial characteristics of magnesium alloys with polymeric nanofilms through synthesized organic compounds of triazine dithiol containing functional groups. The nanofilms were prepared by the electrochemical and polymerization reactions during polymer plating analyzed from characteristics of Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy and scanning electron microscopy. The fabricated nanofilms changed the surface wettability of blank magnesium alloy from hydrophilic to hydrophobic with contact angle 119.0 Degree-Sign of distilled water with lower surface free energy of 20.59 mJ/m{sup 2} and even super-hydrophobic with contact angle 158.3 Degree-Sign with lowest surface free energy of 4.68 mJ/m{sup 2} by different functional nanofilms on their surfaces. Alteration of wettability from hydrophilic to hydrophobic and super-hydrophobic resulted from their low surface free energy and surface morphology with micro- and nano-rough structures. The corrosion behaviors from potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that the super-hydrophobic nanofilm has higher corrosion resistance and stability in 0.1 mol/L NaCl solution and lower corrosion current density (I{sub corr}) with R{sub ct} increasing two orders of magnitude of 16,500 {Omega}{center_dot}cm{sup 2} compared to that obtained for blank of 485 {Omega}{center_dot}cm{sup 2}.

Fabrication of hydrophobic/super-hydrophobic nanofilms on magnesium alloys by polymer plating

International Nuclear Information System (INIS)

Kang Zhixin; Lai Xiaoming; Sang Jing; Li Yuanyuan

2011-01-01

Hydrophobic/super-hydrophobic nanofilms with improved corrosion resistance were fabricated on the surfaces of Mg–Mn–Ce magnesium alloy by a surface modification technique, named as polymer plating, which has been developed to modify superficial characteristics of magnesium alloys with polymeric nanofilms through synthesized organic compounds of triazine dithiol containing functional groups. The nanofilms were prepared by the electrochemical and polymerization reactions during polymer plating analyzed from characteristics of Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy and scanning electron microscopy. The fabricated nanofilms changed the surface wettability of blank magnesium alloy from hydrophilic to hydrophobic with contact angle 119.0° of distilled water with lower surface free energy of 20.59 mJ/m 2 and even super-hydrophobic with contact angle 158.3° with lowest surface free energy of 4.68 mJ/m 2 by different functional nanofilms on their surfaces. Alteration of wettability from hydrophilic to hydrophobic and super-hydrophobic resulted from their low surface free energy and surface morphology with micro- and nano-rough structures. The corrosion behaviors from potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that the super-hydrophobic nanofilm has higher corrosion resistance and stability in 0.1 mol/L NaCl solution and lower corrosion current density (I corr ) with R ct increasing two orders of magnitude of 16,500 Ω·cm 2 compared to that obtained for blank of 485 Ω·cm 2 .

Effects on Ion Cyclotron Emission of the Orbit Topology Changes from the Wave-Particle Interactions

International Nuclear Information System (INIS)

Hellsten, T.; Holmstroem, K.; Johnson, T.; Bergkvist, T.; Laxaback, M.

2006-01-01

It is known that non-relaxed distribution functions can give rise to excitation of magnetosonic waves by ion cyclotron interactions when the distribution function increases with respect to the perpendicular velocity. We have found that in a toroidal plasma also collisional relaxed distribution functions of central peaked high-energy ions can destabilise magnetosonic eigenmodes by ion cyclotron interactions, due to the change in localisation of the orbits establishing inverted distribution functions with respect to energy along the characteristics describing the cyclotron interactions. This can take place by interactions with barely co-passing and marginally trapped high-energy ions at the plasma boundary. The interactions are enhanced by tangential interactions, which can also prevent the interactions to reach the stable part of the characteristics where they interact with more deeply trapped orbits. (author)

How to separate ionic liquids: Use of Hydrophilic Interaction Liquid Chromatography and mixed mode phases

International Nuclear Information System (INIS)

Lamouroux, C.

2011-01-01

This chromatographic study deals with the development of a convenient and versatile method to separate Room Temperature Ionic Liquids. Different modes of chromatography were studied. The study attempts to answer the following question: 'what were the most important interactions for the separation of ionic liquids?'. The results show that the essential interactions to assure a good retention of RTILs are the ionic ones and that hydrophobic interactions play a role in the selectivity of the separation. The separation of five imidazolium salt with a traditional dial columns in Hydrophilic Interaction Chromatography (HILIC) was demonstrated. It shows that neutral diol grafted column allows an important retention that we assume is due to the capability of diol to develop a thick layer of water. Furthermore, stationary phase based on mixed interaction associating ion exchange and hydrophobic properties were studied. Firstly, it will be argued that it is possible to separate RTILs with a convenient retention and resolution according to a reverse phase elution with the Primesep columns made of a brush type long alkyl chain with an embedded negatively charged functional group. Secondly, a successful separation of RTILs in HILIC mode with a mixed phase column containing a cationic exchanger and a hydrophobic octyl chain length will be demonstrated. (author)

Investigation on degradation mechanism of ion exchange membrane immersed in highly concentrated tritiated water under the Broader Approach Activities

Energy Technology Data Exchange (ETDEWEB)

Iwai, Yasunori, E-mail: iwai.yasunori@jaea.go.jp; Sato, Katsumi; Yamanishi, Toshihiko

2014-10-15

Highlights: • Endurance of Nafion ion exchange membrane immersed into 1.38 × 10{sup 12} Bq/kg of highly concentrated tritiated water has been demonstrated. • The formation of free hydrophobic free products by reactions between radicals on the membrane and oxygen caused the decrease in ionic conductivity. • From the {sup 19}F NMR spectrum, no distinctive degradation in the membrane structure by interaction with tritium was measured. - Abstract: The ion exchange membrane is a key material for electrolysis cells of the water detritiation system. Durability of ion exchange membrane has been demonstrated under the Broader Approach Activities. Long-term exposure of Nafion{sup ®} ion exchange membrane in 1.38 × 10{sup 12} Bq/kg of tritiated water was conducted at room temperature for up to 2 years. The ionic conductivity of Nafion{sup ®} membrane after immersed in tritiated water was changed. The change in color of membrane from colorless to yellowish was caused by reactions of radicals on the polymer and oxygen molecules in air. Infrared Fourier transform spectrum of a yellowish membrane revealed a small peak for bending vibration of C-H situated at 1437 cm{sup −1}, demonstrating the formation of hydrophobic functional group in the membrane. The hydrophilic network in Nafion{sup ®} membrane was partially obstructed by the hydrophobic free products. This caused the decrease in ionic conductivity. The peak for bending vibration was clearly eliminated in the spectrum of the membrane after treatment by acid for removal of free products. The high-resolution solid state {sup 19}F NMR spectrum of a membrane after immersed in tritiated water was similar to that of a membrane irradiated with gamma-rays. From the {sup 19}F NMR spectrum, no distinctive degradation in the membrane structure by interaction with tritium was measured.

Investigation on degradation mechanism of ion exchange membrane immersed in highly concentrated tritiated water under the Broader Approach Activities

International Nuclear Information System (INIS)

Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko

2014-01-01

Highlights: • Endurance of Nafion ion exchange membrane immersed into 1.38 × 10 12 Bq/kg of highly concentrated tritiated water has been demonstrated. • The formation of free hydrophobic free products by reactions between radicals on the membrane and oxygen caused the decrease in ionic conductivity. • From the 19 F NMR spectrum, no distinctive degradation in the membrane structure by interaction with tritium was measured. - Abstract: The ion exchange membrane is a key material for electrolysis cells of the water detritiation system. Durability of ion exchange membrane has been demonstrated under the Broader Approach Activities. Long-term exposure of Nafion ® ion exchange membrane in 1.38 × 10 12 Bq/kg of tritiated water was conducted at room temperature for up to 2 years. The ionic conductivity of Nafion ® membrane after immersed in tritiated water was changed. The change in color of membrane from colorless to yellowish was caused by reactions of radicals on the polymer and oxygen molecules in air. Infrared Fourier transform spectrum of a yellowish membrane revealed a small peak for bending vibration of C-H situated at 1437 cm −1 , demonstrating the formation of hydrophobic functional group in the membrane. The hydrophilic network in Nafion ® membrane was partially obstructed by the hydrophobic free products. This caused the decrease in ionic conductivity. The peak for bending vibration was clearly eliminated in the spectrum of the membrane after treatment by acid for removal of free products. The high-resolution solid state 19 F NMR spectrum of a membrane after immersed in tritiated water was similar to that of a membrane irradiated with gamma-rays. From the 19 F NMR spectrum, no distinctive degradation in the membrane structure by interaction with tritium was measured

Preparation of composite micro/nano structure on the silicon surface by reactive ion etching: Enhanced anti-reflective and hydrophobic properties

Science.gov (United States)

Zeng, Yu; Fan, Xiaoli; Chen, Jiajia; He, Siyu; Yi, Zao; Ye, Xin; Yi, Yougen

2018-05-01

A silicon substrate with micro-pyramid structure (black silicon) is prepared by wet chemical etching and then subjected to reactive ion etching (RIE) in the mixed gas condition of SF6, CHF3 and He. We systematically study the impacts of flow rates of SF6, CHF3 and He, the etching pressure and the etching time on the surface morphology and reflectivity through various characterizations. Meanwhile, we explore and obtain the optimal combination of parameters for the preparation of composite structure that match the RIE process based on the basis of micro-pyramid silicon substrate. The composite sample prepared under the optimum parameters exhibits excellent anti-reflective performance, hydrophobic, self-cleaning and anti-corrosive properties. Based on the above characteristics, the composite micro/nano structure can be applied to solar cells, photodetectors, LEDs, outdoor devices and other important fields.

Tensor interaction in heavy-ion scattering. Pt. 1

International Nuclear Information System (INIS)

Nishioka, H.; Johnson, R.C.

1985-01-01

The Heidelberg shape-effect model for heavy-ion tensor interactions is reformulated and generalized using the Hooton-Johnson formulation. The generalized semiclassical model (the turning-point model) predicts that the components of the tensor analysing power anti Tsub(2q) have certain relations with each other for each type of tensor interaction (Tsub(R), Tsub(P) and Tsub(L) types). The predicted relations between the anti Tsub(2q) are very simple and have a direct connection with the properties of the tensor interaction at the turning point. The model predictions are satisfied in quantum-mechanical calculations for 7 Li and 23 Na elastic scattering from 58 Ni in the Fresnel-diffraction energy region. As a consequence of this model, it becomes possible to single out effects from a Tsub(P)- or Tsub(L)-type tensor interaction in polarized heavy-ion scattering. The presence of a Tsub(P)-type tensor interaction is suggested by measured anti T 20 /anti T 22 ratios for 7 Li + 58 Ni scattering. In the turning-point model the three types of tensor operator are not independent, and this is found to be true also in a quantum-mechanical calculation. The model also predicts relations between the components of higher-rank tensor analysing power in the presence of a higher-rank tensor interaction. The rank-3 tensor case is discussed in detail. (orig.)

Novel wave/ion beam interaction approach to isotope separation

International Nuclear Information System (INIS)

Post, R.F.; Lowder, R.S.; Schwager, L.A.; Barr, W.L.; Warner, B.E.

1993-02-01

Numerical simulations and experimental studies have been made related to the possibility of employing an externally imposed electrostatic potential wave to separate isotopes. This wave/ion interaction is a sensitive function of the wave/ion difference velocity and for the appropriate wave amplitude and wave speed, a lighter faster isotope will be reflected by the wave to a higher energy while leaving heavier, slower isotopes virtually undisturbed in energy -- allowing subsequent ion separation by simple energy discrimination. In these experiments, a set of some 200 individual, electrodes, which surrounded a microamp beam of neon ions, was used to generate the wave. Measurements of the wave amplitudes needed for ion reflection and measurements of the final energies of those reflected ions are consistent with values expected from simple kinetic arguments and with the more detailed results of numeric simulations

Synthesis of silver nanocubes in a hydrophobic binary organic solvent.

Energy Technology Data Exchange (ETDEWEB)

Peng, S.; Sun, Y. (Center for Nanoscale Materials)

2010-01-01

Synthesis of metal nanoparticles with controlled shapes in hydrophobic solvents is challenging because homogeneous nucleation with high rate in these solvents is favorable for the formation of multiply twinned (MT) nanoparticles with spherical morphology. In this work, we report an inhomogeneous nucleation strategy in a binary hydrophobic solvent mediated by dimethyldistearylammonium chloride (DDAC), resulting in the coexistence of single-crystalline Ag polyhedrons and MT Ag quasi-spheres at the beginning of the reaction. In the consequent step, the MT Ag nanoparticles are selectively etched and dissolved through oxidation by NO{sub 3}{sup -} ions (from the Ag precursor, AgNO{sub 3}) with the assistance of Cl{sup -} ions (from DDAC). The dissolved Ag species are then reduced and deposited on the more stable single-crystalline polyhedrons to form Ag nanocubes. Synergy of the oxidative etching of MT particles and growth of single-crystalline particles leads to Ag nanocubes with high purity when the ripening time is long enough. For example, refluxing a mixing solvent of octyl ether and oleylamine containing AgNO{sub 3} (0.02 M) and DDAC (0.03 M) at 260 C for 1 h results in Ag nanocubes with an average edge length of 34 nm and a purity higher than 95%.

Quantifying high-affinity binding of hydrophobic ligands by isothermal titration calorimetry.

Science.gov (United States)

Krainer, Georg; Broecker, Jana; Vargas, Carolyn; Fanghänel, Jörg; Keller, Sandro

2012-12-18

A fast and reliable quantification of the binding thermodynamics of hydrophobic high-affinity ligands employing a new calorimetric competition experiment is described. Although isothermal titration calorimetry is the method of choice for a quantitative characterization of intermolecular interactions in solution, a reliable determination of a dissociation constant (K(D)) is typically limited to the range 100 μM > K(D) > 1 nM. Interactions displaying higher or lower K(D) values can be assessed indirectly, provided that a suitable competing ligand is available whose K(D) falls within the directly accessible affinity window. This established displacement assay, however, requires the high-affinity ligand to be soluble at high concentrations in aqueous buffer and, consequently, poses serious problems in the study of protein binding involving small-molecule ligands dissolved in organic solvents--a familiar case in many drug-discovery projects relying on compound libraries. The calorimetric competition assay introduced here overcomes this limitation, thus allowing for a detailed thermodynamic description of high-affinity receptor-ligand interactions involving poorly water-soluble compounds. Based on a single titration of receptor into a dilute mixture of the two competing ligands, this competition assay provides accurate and precise values for the dissociation constants and binding enthalpies of both high- and moderate-affinity ligands. We discuss the theoretical background underlying the approach, demonstrate its practical application to metal ion chelation and high-affinity protein-inhibitor interactions, and explore its potential and limitations with the aid of simulations and statistical analyses.

Hydrophobic Interactions Are a Key to MDM2 Inhibition by Polyphenols as Revealed by Molecular Dynamics Simulations and MM/PBSA Free Energy Calculations.

Directory of Open Access Journals (Sweden)

Sharad Verma

Full Text Available p53, a tumor suppressor protein, has been proven to regulate the cell cycle, apoptosis, and DNA repair to prevent malignant transformation. MDM2 regulates activity of p53 and inhibits its binding to DNA. In the present study, we elucidated the MDM2 inhibition potential of polyphenols (Apigenin, Fisetin, Galangin and Luteolin by MD simulation and MM/PBSA free energy calculations. All polyphenols bind to hydrophobic groove of MDM2 and the binding was found to be stable throughout MD simulation. Luteolin showed the highest negative binding free energy value of -173.80 kJ/mol followed by Fisetin with value of -172.25 kJ/mol. It was found by free energy calculations, that hydrophobic interactions (vdW energy have major contribution in binding free energy.

Mapping Hydrophobicity on the Protein Molecular Surface at Atom-Level Resolution

Science.gov (United States)

Nicolau Jr., Dan V.; Paszek, Ewa; Fulga, Florin; Nicolau, Dan V.

2014-01-01

A precise representation of the spatial distribution of hydrophobicity, hydrophilicity and charges on the molecular surface of proteins is critical for the understanding of the interaction with small molecules and larger systems. The representation of hydrophobicity is rarely done at atom-level, as this property is generally assigned to residues. A new methodology for the derivation of atomic hydrophobicity from any amino acid-based hydrophobicity scale was used to derive 8 sets of atomic hydrophobicities, one of which was used to generate the molecular surfaces for 35 proteins with convex structures, 5 of which, i.e., lysozyme, ribonuclease, hemoglobin, albumin and IgG, have been analyzed in more detail. Sets of the molecular surfaces of the model proteins have been constructed using spherical probes with increasingly large radii, from 1.4 to 20 Å, followed by the quantification of (i) the surface hydrophobicity; (ii) their respective molecular surface areas, i.e., total, hydrophilic and hydrophobic area; and (iii) their relative densities, i.e., divided by the total molecular area; or specific densities, i.e., divided by property-specific area. Compared with the amino acid-based formalism, the atom-level description reveals molecular surfaces which (i) present an approximately two times more hydrophilic areas; with (ii) less extended, but between 2 to 5 times more intense hydrophilic patches; and (iii) 3 to 20 times more extended hydrophobic areas. The hydrophobic areas are also approximately 2 times more hydrophobicity-intense. This, more pronounced “leopard skin”-like, design of the protein molecular surface has been confirmed by comparing the results for a restricted set of homologous proteins, i.e., hemoglobins diverging by only one residue (Trp37). These results suggest that the representation of hydrophobicity on the protein molecular surfaces at atom-level resolution, coupled with the probing of the molecular surface at different geometric resolutions

Preparation and purification of Flavobacterium heparinum chondroitinases AC and B by hydrophobic interaction chromatography

Directory of Open Access Journals (Sweden)

Aguiar J.A.K.

1999-01-01

Full Text Available Flavobacterium heparinum is a soil bacterium that produces several mucopolysaccharidases such as heparinase, heparitinases I and II, and chondroitinases AC, B, C and ABC. The purpose of the present study was to optimize the preparation of F. heparinum chondroitinases, which are very useful tools for the identification and structural characterization of chondroitin and dermatan sulfates. We observed that during the routine procedure for cell disruption (ultrasound, 100 kHz, 5 min some of the chondroitinase B activity was lost. Using milder conditions (2 min, most of the chondroitinase B and AC protein was solubilized and the enzyme activities were preserved. Tryptic soy broth without glucose was the best culture medium both for bacterial growth and enzyme induction. Chondroitinases AC and B were separated from each other and also from glucuronidases and sulfatases by hydrophobic interaction chromatography on HP Phenyl-Sepharose. A rapid method for screening of the column fractions was also developed based on the metachromatic shift of the color of dimethylmethylene blue.

Spacecraft-plasma-debris interaction in an ion beam shepherd mission

Science.gov (United States)

Cichocki, Filippo; Merino, Mario; Ahedo, Eduardo

2018-05-01

This paper presents a study of the interaction between a spacecraft, a plasma thruster plume and a free floating object, in the context of an active space debris removal mission based on the ion beam shepherd concept. The analysis is performed with the EP2PLUS hybrid code and includes the evaluation of the transferred force and torque to the target debris, its surface sputtering due to the impinging hypersonic ions, and the equivalent electric circuit of the spacecraft-plasma-debris interaction. The electric potential difference that builds up between the spacecraft and the debris, the ion backscattering and the backsputtering contamination of the shepherd satellite are evaluated for a nominal scenario. A sensitivity analysis is carried out to evaluate quantitatively the effects of electron thermodynamics, ambient plasma, heavy species collisions, and debris position.

Ultra-relativistic ion acceleration in the laser-plasma interactions

Energy Technology Data Exchange (ETDEWEB)

Huang Yongsheng; Wang Naiyan; Tang Xiuzhang; Shi Yijin [China Institute of Atomic Energy, Beijing 102413 (China); Xueqing Yan [Institute of Heavy Ion Physics, Peking University, Beijing 100871 (China)

2012-09-15

An analytical relativistic model is proposed to describe the relativistic ion acceleration in the interaction of ultra-intense laser pulses with thin-foil plasmas. It is found that there is a critical value of the ion momentum to make sure that the ions are trapped by the light sail and accelerated in the radiation pressure acceleration (RPA) region. If the initial ion momentum is smaller than the critical value, that is in the classical case of RPA, the potential has a deep well and traps the ions to be accelerated, as the same described before by simulation results [Eliasson et al., New J. Phys. 11, 073006 (2009)]. There is a new ion acceleration region different from RPA, called ultra-relativistic acceleration, if the ion momentum exceeds the critical value. In this case, ions will experience a potential downhill. The dependence of the ion momentum and the self-similar variable at the ion front on the acceleration time has been obtained. In the ultra-relativistic limit, the ion momentum at the ion front is proportional to t{sup 4/5}, where t is the acceleration time. In our analytical hydrodynamical model, it is naturally predicted that the ion distribution from RPA is not monoenergetic, although the phase-stable acceleration mechanism is effective. The critical conditions of the laser and plasma parameters which identify the two acceleration modes have been achieved.

Ultra-relativistic ion acceleration in the laser-plasma interactions

International Nuclear Information System (INIS)

Huang Yongsheng; Wang Naiyan; Tang Xiuzhang; Shi Yijin; Xueqing Yan

2012-01-01

An analytical relativistic model is proposed to describe the relativistic ion acceleration in the interaction of ultra-intense laser pulses with thin-foil plasmas. It is found that there is a critical value of the ion momentum to make sure that the ions are trapped by the light sail and accelerated in the radiation pressure acceleration (RPA) region. If the initial ion momentum is smaller than the critical value, that is in the classical case of RPA, the potential has a deep well and traps the ions to be accelerated, as the same described before by simulation results [Eliasson et al., New J. Phys. 11, 073006 (2009)]. There is a new ion acceleration region different from RPA, called ultra-relativistic acceleration, if the ion momentum exceeds the critical value. In this case, ions will experience a potential downhill. The dependence of the ion momentum and the self-similar variable at the ion front on the acceleration time has been obtained. In the ultra-relativistic limit, the ion momentum at the ion front is proportional to t 4/5 , where t is the acceleration time. In our analytical hydrodynamical model, it is naturally predicted that the ion distribution from RPA is not monoenergetic, although the phase-stable acceleration mechanism is effective. The critical conditions of the laser and plasma parameters which identify the two acceleration modes have been achieved.

Improved gel electrophoresis matrix for hydrophobic protein separation and identification.

Science.gov (United States)

Tokarski, Caroline; Fillet, Marianne; Rolando, Christian

2011-03-01

We propose an improved acrylamide gel for the separation of hydrophobic proteins. The separation strategy is based on the incorporation of N-alkylated and N,N'-dialkylated acrylamide monomers in the gel composition in order to increase hydrophobic interactions between the gel matrix and the membrane proteins. Focusing on the most efficient monomer, N,N'-dimethylacrylamide, the potentiality of the new matrix was evaluated on membrane proteins of the human colon HCT-116 cell line. Protein analysis was performed using an adapted analytical strategy based on FT-ICR tandem mass spectrometry. As a result of this comparative study, including advanced reproducibility experiments, more hydrophobic proteins were identified in the new gel (average GRAVY: -0.085) than in the classical gel (average GRAVY: -0.411). Highly hydrophobic peptides were identified reaching a GRAVY value up to 1.450, therefore indicating their probable locations in the membrane. Focusing on predicted transmembrane domains, it can be pointed out that 27 proteins were identified in the hydrophobic gel containing up to 11 transmembrane domains; in the classical gel, only 5 proteins containing 1 transmembrane domain were successfully identified. For example, multiple ionic channels and receptors were characterized in the hydrophobic gel such as the sodium/potassium channel and the glutamate or the transferrin receptors whereas they are traditionally detected using specific enrichment techniques such as immunoprecipitation. In total, membrane proteins identified in the classical gel are well documented in the literature, while most of the membrane proteins only identified on the hydrophobic gel have rarely or never been described using a proteomic-based approach. 2010 Elsevier Inc. All rights reserved.

Structural Analysis of DNA Interactions with Magnesium Ion Studied by Raman Spectroscopy

OpenAIRE

S. Ponkumar; P. Duraisamy; N. Iyandurai

2011-01-01

Problem statement: In the present study, FT Raman spectroscopy had been used to extend our knowledge about Magnesium ion - DNA interactions at various volume ratios (1:50, 1:20, 1:10 and 1:5). Approach: The analysis of FT Raman data supported the existence of structural specificities in the interaction and also the stability of DNA secondary structure. Results: Results from the Raman spectra clearly indicate that the interaction of Magnesium ion with DNA is mainly through the phosphate groups...

Ion-surface interaction: simulation of plasma-wall interaction (ITER)

International Nuclear Information System (INIS)

Salou, Pierre

2013-01-01

The wall materials of magnetic confinement in fusion machines are exposed to an aggressive environment; the reactor blanket is bombarded with a high flux of particles extracted from the plasma, leading to the sputtering of surface material. This sputtering causes wall erosion as well as plasma contamination problems. In order to control fusion reactions in complex reactors, it is thus imperative to well understand the plasma-wall interactions. This work proposes the study of the sputtering of fusion relevant materials. We propose to simulate the charged particles influx by few keV single-charged ion beams. This study is based on the catcher method; to avoid any problem of pollution (especially in the case of carbon) we designed a new setup allowing an in situ Auger electron spectroscopy analysis. The results provide the evolution of the angular distribution of the sputtering yield as a function of the ion mass (from helium to xenon) and its energy (from 3 keV to 9 keV). (author) [fr

Temperature dependence of the evaporation lengthscale for water confined between two hydrophobic plates.

Science.gov (United States)

Djikaev, Yuri S; Ruckenstein, Eli

2015-07-01

Liquid water in a hydrophobic confinement is the object of high interest in physicochemical sciences. Confined between two macroscopic hydrophobic surfaces, liquid water transforms into vapor if the distance between surfaces is smaller than a critical separation, referred to as the evaporation lengthscale. To investigate the temperature dependence of the evaporation lengthscale of water confined between two hydrophobic parallel plates, we use the combination of the density functional theory (DFT) with the probabilistic hydrogen bond (PHB) model for water-water hydrogen bonding. The PHB model provides an analytic expression for the average number of hydrogen bonds per water molecule as a function of its distance to a hydrophobic surface and its curvature. Knowing this expression, one can implement the effect of hydrogen bonding between water molecules on their interaction with the hydrophobe into DFT, which is then employed to determine the distribution of water molecules between two macroscopic hydrophobic plates at various interplate distances and various temperatures. For water confined between hydrophobic plates, our results suggest the evaporation lengthscale to be of the order of several nanometers and a linearly increasing function of temperature from T=293 K to T=333 K, qualitatively consistent with previous results. Copyright © 2015 Elsevier Inc. All rights reserved.

Fundamental aspects of laser and ion-beam interactions with solid surfaces

International Nuclear Information System (INIS)

Wang, Z.L.

1982-01-01

In the first part of the thesis laser-beam interactions with solid surfaces are discussed. In the second part ion-beam interactions with solid surfaces are discussed and mainly the mixing of atoms due to ion bombardment. A study of ion-beam mixing of Cu-Au and Cu-W systems is described in order to illustrate the mechanism for ion beam mixing. As Cu-Au are miscible whereas Cu-W systems are not, and both systems have comparable mass numbers, comparison provides a test for current theories on ion-beam mixing. The results of experiments where 300 keV Kr 4+ ion-bombardment at a dose of 5x10 15 cm -2 has been applied to initiate mixing of a single layer structure and sandwich samples for both systems are described. Room temperature irradiations with a dose of 5x10 15 cm -2 show that Cu-Au mix readily, whereas a small mixing effect is observed for Cu-W systems. A comparable amount of mixing for Cu-Au induced by laser or ion beams is found whereas no mixing of Cu-W induced by laser irradiation is observed, which is in agreement with the criteria for formation of metastable solid solutions due to pulsed laser treatment. (Auth.)

Metal Enhanced Fluorescence on Super-Hydrophobic Clusters of Gold Nanoparticles

KAUST Repository

Battista, Edmondo; Coluccio, Maria Laura; Alabastri, Alessandro; Barberio, Marianna; Causa, Filippo; Netti, Paolo Antonio; Di Fabrizio, Enzo M.; Gentile, Francesco

2016-01-01

We used optical lithography, electroless deposition and deep reactive ion etching techniques to realize arrays of super-hydrophobic gold nanoparticles arranged in a hierarchical structure. At the micro-scale, silicon-micro pillars in the chip permit to manipulate and concentrate biological solutions, at the nano-scale, gold nanoparticles enable metal enhanced fluorescence (MEF) effects, whereby fluorescence signal of fluorophores in close proximity to a rough metal surface is amplified by orders of magnitude. Here, we demonstrated the device in the analysis of fluorescein derived gold-binding peptides (GBP-FITC). While super-hydrophobic schemes and MEF effects have been heretofore used in isolation, their integration in a platform may advance the current state of fluorescence-based sensing technology in medical diagnostics and biotechnology. This scheme may be employed in protein microarrays where the increased sensitivity of the device may enable the early detection of cancer biomarkers or other proteins of biomedical interest.

Metal Enhanced Fluorescence on Super-Hydrophobic Clusters of Gold Nanoparticles

KAUST Repository

Battista, Edmondo

2016-12-15

We used optical lithography, electroless deposition and deep reactive ion etching techniques to realize arrays of super-hydrophobic gold nanoparticles arranged in a hierarchical structure. At the micro-scale, silicon-micro pillars in the chip permit to manipulate and concentrate biological solutions, at the nano-scale, gold nanoparticles enable metal enhanced fluorescence (MEF) effects, whereby fluorescence signal of fluorophores in close proximity to a rough metal surface is amplified by orders of magnitude. Here, we demonstrated the device in the analysis of fluorescein derived gold-binding peptides (GBP-FITC). While super-hydrophobic schemes and MEF effects have been heretofore used in isolation, their integration in a platform may advance the current state of fluorescence-based sensing technology in medical diagnostics and biotechnology. This scheme may be employed in protein microarrays where the increased sensitivity of the device may enable the early detection of cancer biomarkers or other proteins of biomedical interest.

Gel properties and interactions of Mesona blumes polysaccharide-soy protein isolates mixed gel: The effect of salt addition.

Science.gov (United States)

Wang, Wenjie; Shen, Mingyue; Liu, Suchen; Jiang, Lian; Song, Qianqian; Xie, Jianhua

2018-07-15

Effect of different salt ions on the gel properties and microstructure of Mesona blumes polysaccharide (MBP)-soy protein isolates (SPI) mixed gels were investigated. Sodium and calcium ions were chosen to explore their effects on the rheological behavior and gel properties of MBP-SPI mixed gels were evaluated by using rheological, X-ray diffraction, protein solubility determination, and microstructure analysis. Results showed that the addition of salt ions change the crystalline state of gels system, the crystal of gel was enhanced at low ion concentrations (0.005-0.01 M). The two peaks of gel characteristic at 8.9° and 19.9° almost disappeared at high salt ions concentrations (0.015-0.02 M), and new crystallization peaks appeared at around 30° and 45°. The elasticity, viscosity, gel strength, water holding capacity, and thermal stability of gel were increased at low ion concentration. Results showed that the main interactions which promoted gel formation and maintain the three-dimensional structure of the gel were electrostatic interactions, hydrophobic interactions, and disulfide interactions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Novel lanthanide doped micro- and mesoporous solids. Characterization of ion-host-interactions, species distribution and luminescence properties using time-resolved luminescence spectroscopy

International Nuclear Information System (INIS)

Gessner, Andre

2010-12-01

easily accessible for water and thus show shorter luminescence decay times and a more symmetrical coordination sphere, which is mostly made up by water molecules. Another investigated aspect was the influence of surface modifications on the luminescence behavior of the lanthanide ions inside the material. Here we could show, that surface modifications hydrophobize the material and thus are able to protect the lanthanide ions from water, which is important for the conservation of the luminescence properties. Concerning the mesoporous silicates, again a heterogeneous distribution of the lanthanide ions in the pore system was found. A part of the lanthanide ions interacts with the pore wall, while the other part is located in the aqueous phase inside the pores. Surface modification led to a interaction of the lanthanide ions with the modification. This was reflected in the luminescence properties depending on the structure of the modification and the surface loading.

Effects of hydrophobic drug-polyesteric core interactions on drug loading and release properties of poly(ethylene glycol)-polyester-poly(ethylene glycol) triblock core-shell nanoparticles

International Nuclear Information System (INIS)

Khoee, Sepideh; Hassanzadeh, Salman; Goliaie, Bahram

2007-01-01

BAB amphiphilic triblock copolymers consisting of poly(ethylene glycol) (B) (PEG) as the hydrophilic segment and different polyesters (A) as the hydrophobic block were prepared by a polycondensation reaction as efficient model core-shell nanoparticles to assay the effect of interactions between the hydrophobic drug and the polyesteric core in terms of drug loading content and release profile. PEG-poly(hexylene adipate)-PEG (PEG-PHA-PEG) and PEG-poly(butylene adipate)-PEG (PEG-PBA-PEG) to PEG-poly(ethylene adipate)-PEG (PEG-PEA-PEG) core-shell type nanoparticles entrapping quercetin (an anticarcinogenic, allergy inhibitor and antibacterial agent), were prepared by a nanoprecipitation method and characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and x-ray diffraction (XRD) techniques. It was found that the obtained nanoparticles showed a smooth surface and spherical shape with controllable sizes in the range of 64-74 nm, while drug loading varied from 7.24% to 19% depending on the copolymer composition and the preparation conditions. The in vitro release behaviour exhibited a sustained release and was affected by the polymer-drug interactions. UV studies revealed the presence of hydrogen bonding as the main existing interaction between quercetin and polyesters in the nanosphere cores

In vitro evaluation of tissue adhesives composed of hydrophobically modified gelatins and disuccinimidyl tartrate

Directory of Open Access Journals (Sweden)

Miyuki Matsuda

2012-01-01

Full Text Available The effect of the hydrophobic group content in gelatin on the bonding strength of novel tissue–penetrating tissue adhesives was evaluated. The hydrophobic groups introduced into gelatin were the saturated hexanoyl, palmitoyl, and stearoyl groups, and the unsaturated oleoyl group. A collagen casing was employed as an adherend to model soft tissue for the in vitro determination of bonding strength of tissue adhesives composed of various hydrophobically modified gelatins and disuccinimidyl tartrate. The adhesive composed of stearoyl-modified gelatin (7.4% stearoyl; 10Ste and disuccinimidyl tartrate showed the highest bonding strength. The bonding strength of the adhesives decreased as the degree of substitution of the hydrophobic groups increased. Cell culture experiments demonstrated that fluorescein isothiocyanate-labeled 10Ste was integrated onto the surface of smooth muscle cells and showed no cytotoxicity. These results suggest that 10Ste interacted with the hydrophobic domains of collagen casings, such as hydrophobic amino acid residues and cell membranes. Therefore, 10Ste–disuccinimidyl tartrate is a promising adhesive for use in aortic dissection.

Effect of surface hydrophobicity on the dynamics of water at the nanoscale confinement: A molecular dynamics simulation study

International Nuclear Information System (INIS)

Choudhury, Niharendu

2013-01-01

Highlights: • We present atomistic MD simulation of water confined between two paraffin-like plates. • Effect of plate hydrophobicity on the confined water dynamics is investigated. • Diffusivity of confined water is calculated from mean squared displacements. • Rotational dynamics of the confined water has bimodal nature of relaxation. • Monotonic dependence of translational and rotational dynamics on hydrophobicity. - Abstract: We present detailed molecular dynamics simulations of water in and around a pair of plates immersed in water to investigate the effect of degree of hydrophobicity or hydrophilicity of the plates on dynamics of water confined between the two plates. The nature of the plate has been tuned from hydrophobic to hydrophilic and vice versa by varying plate-water dispersion interaction. Analyses of the translational dynamics as performed by calculating mean squared displacements of the confined water reveal a monotonically decreasing trend of the diffusivity with increasing hydrophilicity of the plates. Orientational dynamics of the confined water also follows the same monotonic trend. Although orientational time constant almost does not change with the increase of plate-water dispersion interaction in the hydrophobic regime corresponding to the smaller plate-water attraction, it changes considerably in the hydrophilic regime corresponding to larger plate-water dispersion interactions

Hydrophobic interaction between contiguous residues in the S6 transmembrane segment acts as a stimuli integration node in the BK channel

Science.gov (United States)

Carrasquel-Ursulaez, Willy; Contreras, Gustavo F.; Sepúlveda, Romina V.; Aguayo, Daniel; González-Nilo, Fernando

2015-01-01

Large-conductance Ca2+- and voltage-activated K+ channel (BK) open probability is enhanced by depolarization, increasing Ca2+ concentration, or both. These stimuli activate modular voltage and Ca2+ sensors that are allosterically coupled to channel gating. Here, we report a point mutation of a phenylalanine (F380A) in the S6 transmembrane helix that, in the absence of internal Ca2+, profoundly hinders channel opening while showing only minor effects on the voltage sensor active–resting equilibrium. Interpretation of these results using an allosteric model suggests that the F380A mutation greatly increases the free energy difference between open and closed states and uncouples Ca2+ binding from voltage sensor activation and voltage sensor activation from channel opening. However, the presence of a bulky and more hydrophobic amino acid in the F380 position (F380W) increases the intrinsic open–closed equilibrium, weakening the coupling between both sensors with the pore domain. Based on these functional experiments and molecular dynamics simulations, we propose that F380 interacts with another S6 hydrophobic residue (L377) in contiguous subunits. This pair forms a hydrophobic ring important in determining the open–closed equilibrium and, like an integration node, participates in the communication between sensors and between the sensors and pore. Moreover, because of its effects on open probabilities, the F380A mutant can be used for detailed voltage sensor experiments in the presence of permeant cations. PMID:25548136

Elementary processes in plasma-surface interactions with emphasis on ions

International Nuclear Information System (INIS)

Zalm, P.C.

1985-01-01

Elementary processes occurring at solid surfaces immersed in low pressure plasmas are reviewed. In particular mechanisms leading to anisotropic or directional etching are discussed. The crucial role of ion bombardment is emphasized. First a brief summary of the interaction of (excited) neutrals, ions and electrons with targets is given. Next various aspects of sputter-etching with noble gas and reactive ions are surveyed. Finally it will be argued that synergistic effects, invoked by ion bombardment of a surface under simultaneous exposure to a reactive gas flux, are foremost important in explaining anisotropic plasma etching. It is shown that the role of the ions is not merely to stimulate the chemical reaction path but rather that the active gas flow chemically enhances the sputtering. (author)

Are N-methyl groups of Tetramethylurea (TMU) Hydrophobic? A ...

Indian Academy of Sciences (India)

of three dimensional tetrahedral H-bond network to two dimensional zig-zag chain-like structure often found in alcohols. A comparison to ... All these results indicate hydrophobic interaction-induced aggregation of TMU in dilute aqueous solutions which .... off by gently blowing hot air around the outer surface of the cuvette.

A 2-100 keV, UHV ion impact spectrometer for ion-solid interaction studies

International Nuclear Information System (INIS)

Berg, J.A. Van den; Armour, D.G.; Verheij, L.K.

1978-01-01

A 2 to 100 keV ion accelerator has been constructed as part of an ion impact spectrometer in which a number of analytical techniques have been combined to allow a comprehensive study of the interaction of low- and medium-energy ions with solids to be carried out under carefully controlled conditions. The overall requirements of the ion beam system in terms of ion species, beam purity, uniformity, energy spread and intensity were dictated by the interest in carrying out low-energy ion scattering, Rutherford back-scattering and thermal desorption experiments. The accelerator design utilises the principle of low-energy extraction and mass analysis, and post-acceleration up to the required high energy. The ions are produced in a duoplasmatron ion source and a parallel beam is obtained after mass selection, utilising a quadrupole triplet lens in conjunction with a 60 0 stigmatic focusing magnetic analyser. Proton and rare gas ion beams of 1 to 100 nA are routinely obtained on target. The 54 cm diameter, UHV target chamber is pumped by a 270 1 s -1 turbo-molecular pump in conjunction with an in-line titanium sublimator, and typical base pressures of 1 to 4 x 10 -11 Torr are achieved. The target is supported in a precision, three-axis goniometer and the detection system, at present comprising a 90 mm mean diameter hemispherical energy analyser and channel electron multiplier, is mounted on a two-axis manipulator. Preliminary measurements using the system have employed the low-energy ion scattering technique to study the oxidation of a Ni(110) surface. (author)

Interactions between poly(acrylic acid) and sodium dodecyl sulfate: isothermal titration calorimetric and surfactant ion-selective electrode studies.

Science.gov (United States)

Wang, C; Tam, K C

2005-03-24

Interaction between a monodispersed poly(acrylic acid) (PAA) (M(W) = 5670 g/mol, M(w)/M(n) = 1.02) with sodium dodecyl sulfate (SDS) was investigated using isothermal titration calorimetry (ITC), ion-selective electrode (ISE), and dynamic light scattering measurements. Contrary to previous studies, we report for the first time evidence of interaction between SDS and PAA when the degree of neutralization (alpha) of PAA is lower than 0.2. Hydrocarbon chains of SDS cooperatively bind to apolar segments of PAA driven by hydrophobic interaction. The interaction is both enthalpy and entropy favored (deltaH is negative but deltaS is positive). In 0.05 wt % PAA solution, the SDS concentration corresponding to the onset of binding (i.e., CAC) is approximately 2.4 mM and the saturation concentration (i.e., C(S)) is approximately 13.3 mM when alpha = 0. When PAA was neutralized and ionized, the binding was hindered by the enhanced electrostatic repulsion between negatively charged SDS and PAA chains and improved solubility of the polymer. With increasing alpha to 0.2, CAC increases to approximately 6.2 mM, C(S) drops to 8.6 mM, and the interaction is significantly weakened where the amount of bound SDS on PAA is reduced considerably. The values of CAC and C(S) derived from different techniques are in good agreement. The binding results in the formation of mixed micelles on apolar PAA coils, which then expands and dissociates into single PAA chains. The majority of unneutralized PAA molecules exist as single polymer chains stabilized by bound SDS micelles in solution after the saturation concentration.

Adsorption of hydrophobin on different self-assembled monolayers: the role of the hydrophobic dipole and the electric dipole.

Science.gov (United States)

Peng, Chunwang; Liu, Jie; Zhao, Daohui; Zhou, Jian

2014-09-30

In this work, the adsorptions of hydrophobin (HFBI) on four different self-assembled monolayers (SAMs) (i.e., CH3-SAM, OH-SAM, COOH-SAM, and NH2-SAM) were investigated by parallel tempering Monte Carlo and molecular dynamics simulations. Simulation results indicate that the orientation of HFBI adsorbed on neutral surfaces is dominated by a hydrophobic dipole. HFBI adsorbs on the hydrophobic CH3-SAM through its hydrophobic patch and adopts a nearly vertical hydrophobic dipole relative to the surface, while it is nearly horizontal when adsorbed on the hydrophilic OH-SAM. For charged SAM surfaces, HFBI adopts a nearly vertical electric dipole relative to the surface. HFBI has the narrowest orientation distribution on the CH3-SAM, and thus can form an ordered monolayer and reverse the wettability of the surface. For HFBI adsorption on charged SAMs, the adsorption strength weakens as the surface charge density increases. Compared with those on other SAMs, a larger area of the hydrophobic patch is exposed to the solution when HFBI adsorbs on the NH2-SAM. This leads to an increase of the hydrophobicity of the surface, which is consistent with the experimental results. The binding of HFBI to the CH3-SAM is mainly through hydrophobic interactions, while it is mediated through a hydration water layer near the surface for the OH-SAM. For the charged SAM surfaces, the adsorption is mainly induced by electrostatic interactions between the charged surfaces and the oppositely charged residues. The effect of a hydrophobic dipole on protein adsorption onto hydrophobic surfaces is similar to that of an electric dipole for charged surfaces. Therefore, the hydrophobic dipole may be applied to predict the probable orientations of protein adsorbed on hydrophobic surfaces.

Unified superresolution experiments and stochastic theory provide mechanistic insight into protein ion-exchange adsorptive separations.

Science.gov (United States)

Kisley, Lydia; Chen, Jixin; Mansur, Andrea P; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Chen, Wen-Hsiang; Dhamane, Sagar; Willson, Richard C; Landes, Christy F

2014-02-11

Chromatographic protein separations, immunoassays, and biosensing all typically involve the adsorption of proteins to surfaces decorated with charged, hydrophobic, or affinity ligands. Despite increasingly widespread use throughout the pharmaceutical industry, mechanistic detail about the interactions of proteins with individual chromatographic adsorbent sites is available only via inference from ensemble measurements such as binding isotherms, calorimetry, and chromatography. In this work, we present the direct superresolution mapping and kinetic characterization of functional sites on ion-exchange ligands based on agarose, a support matrix routinely used in protein chromatography. By quantifying the interactions of single proteins with individual charged ligands, we demonstrate that clusters of charges are necessary to create detectable adsorption sites and that even chemically identical ligands create adsorption sites of varying kinetic properties that depend on steric availability at the interface. Additionally, we relate experimental results to the stochastic theory of chromatography. Simulated elution profiles calculated from the molecular-scale data suggest that, if it were possible to engineer uniform optimal interactions into ion-exchange systems, separation efficiencies could be improved by as much as a factor of five by deliberately exploiting clustered interactions that currently dominate the ion-exchange process only accidentally.

Relativistic ion acceleration by ultraintense laser interactions

International Nuclear Information System (INIS)

Nakajima, K.; Koga, J.K.; Nakagawa, K.

2001-01-01

There has been a great interest in relativistic particle generation by ultraintense laser interactions with matter. We propose the use of relativistically self-focused laser pulses for the acceleration of ions. Two dimensional PIC simulations are performed, which show the formation of a large positive electrostatic field near the front of a relativistically self-focused laser pulse. Several factors contribute to the acceleration including self-focusing distance, pulse depletion, and plasma density. Ultraintense laser-plasma interactions are capable of generating enormous electrostatic fields of ∼3 TV/m for acceleration of protons with relativistic energies exceeding 1 GeV

Investigation of the mechanism of interaction of Lithium 6 ions on Beryllium 9

International Nuclear Information System (INIS)

Coste, Mireille

1962-01-01

The objective of this research on the interaction of Lithium 6 and Beryllium 9 ions is to obtain new indications on the mode of interaction of these heavy ions, and on the configuration of target nuclei and projectile nuclei. In a first part, the author presents and describes the experimental conditions which comprise a Van de Graaff accelerator, a source, a stripper, and a target. He reports the study of α particles emitted by the reaction between the Lithium and Beryllium ions: description of the experimental installation (irradiation chamber and method), presentation and interpretation of experimental results. In the next part, he reports the study of Lithium 7 and Beryllium 10 nuclides emitted by disintegration of Beryllium 11: description of experimental conditions, variations of cross sections, variation of the cross section rate, and interpretation. The author then addresses the study of the intervention of the mode of interaction by 15 N compound nucleus in the reactions between lithium and beryllium ions: study of intensities of the different spectrum lines, measurement of the Doppler effect produced of the 479 keV line, interpretation of results. In conclusion, the author analyses the mechanism of interaction between lithium and beryllium ions, and discusses different theories: the Newns and Glendenning theories, and the Leigh theory

Images of Complex Interactions of an Intense Ion Beam with Plasma Electrons

International Nuclear Information System (INIS)

Kaganovich, Igor D.; Startsev, Edward; Davidson, Ronald C.

2004-01-01

Ion beam propagation in a background plasma is an important scientific issue for many practical applications. The process of ion beam charge and current neutralization is complex because plasma electrons move in strong electric and magnetic fields of the beam. Computer simulation images of plasma interaction with an intense ion beam pulse are presented

Predicting hot spots in protein interfaces based on protrusion index, pseudo hydrophobicity and electron-ion interaction pseudopotential features

Science.gov (United States)

Xia, Junfeng; Yue, Zhenyu; Di, Yunqiang; Zhu, Xiaolei; Zheng, Chun-Hou

2016-01-01

The identification of hot spots, a small subset of protein interfaces that accounts for the majority of binding free energy, is becoming more important for the research of drug design and cancer development. Based on our previous methods (APIS and KFC2), here we proposed a novel hot spot prediction method. For each hot spot residue, we firstly constructed a wide variety of 108 sequence, structural, and neighborhood features to characterize potential hot spot residues, including conventional ones and new one (pseudo hydrophobicity) exploited in this study. We then selected 3 top-ranking features that contribute the most in the classification by a two-step feature selection process consisting of minimal-redundancy-maximal-relevance algorithm and an exhaustive search method. We used support vector machines to build our final prediction model. When testing our model on an independent test set, our method showed the highest F1-score of 0.70 and MCC of 0.46 comparing with the existing state-of-the-art hot spot prediction methods. Our results indicate that these features are more effective than the conventional features considered previously, and that the combination of our and traditional features may support the creation of a discriminative feature set for efficient prediction of hot spots in protein interfaces. PMID:26934646

Ion Acceleration by Laser Plasma Interaction from Cryogenic Microjets

Energy Technology Data Exchange (ETDEWEB)

Propp, Adrienne [Harvard Univ., Cambridge, MA (United States)

2015-08-16

Processes that occur in extreme conditions, such as in the center of stars and large planets, can be simulated in the laboratory using facilities such as SLAC National Accelerator Laboratory and the Jupiter Laser Facility (JLF) at Lawrence Livermore National Laboratory (LLNL). These facilities allow scientists to investigate the properties of matter by observing their interactions with high-power lasers. Ion acceleration from laser plasma interaction is gaining greater attention today due to its widespread potential applications, including proton beam cancer therapy and fast ignition for energy production. Typically, ion acceleration is achieved by focusing a high power laser on thin foil targets through a mechanism called Target Normal Sheath Acceleration. However, this mechanism is not ideal for creating the high-energy proton beams needed for future applications. Based on research and recent experiments, we hypothesized that a pure liquid cryogenic jet would be an ideal target for exploring new regimes of ion acceleration. Furthermore, it would provide a continuous, pure target, unlike metal foils which are consumed in the interaction and easily contaminated. In an effort to test this hypothesis, we used the 527 nm split beam, frequency-doubled TITAN laser at JLF. Data from the cryogenic jets was limited due to the flow of current up the jet into the nozzle during the interaction, heating the jet and damaging the orifice. However, we achieved a pure proton beam with evidence of a monoenergetic feature. Furthermore, data from gold and carbon wires showed surprising and interesting results. Preliminary analysis of data from two ion emission diagnostics, Thomson parabola spectrometers (TPs) and radio chromic films (RCFs), suggests that shockwave acceleration occurred rather than target normal sheath acceleration, the standard mechanism of ion acceleration. Upon completion of the experiment at TITAN, I researched the possibility of transforming our liquid cryogenic

Ion Acceleration by Laser Plasma Interaction from Cryogenic Microjets

International Nuclear Information System (INIS)

Propp, Adrienne

2015-01-01

Processes that occur in extreme conditions, such as in the center of stars and large planets, can be simulated in the laboratory using facilities such as SLAC National Accelerator Laboratory and the Jupiter Laser Facility (JLF) at Lawrence Livermore National Laboratory (LLNL). These facilities allow scientists to investigate the properties of matter by observing their interactions with high-power lasers. Ion acceleration from laser plasma interaction is gaining greater attention today due to its widespread potential applications, including proton beam cancer therapy and fast ignition for energy production. Typically, ion acceleration is achieved by focusing a high power laser on thin foil targets through a mechanism called Target Normal Sheath Acceleration. However, this mechanism is not ideal for creating the high-energy proton beams needed for future applications. Based on research and recent experiments, we hypothesized that a pure liquid cryogenic jet would be an ideal target for exploring new regimes of ion acceleration. Furthermore, it would provide a continuous, pure target, unlike metal foils which are consumed in the interaction and easily contaminated. In an effort to test this hypothesis, we used the 527 nm split beam, frequency-doubled TITAN laser at JLF. Data from the cryogenic jets was limited due to the flow of current up the jet into the nozzle during the interaction, heating the jet and damaging the orifice. However, we achieved a pure proton beam with evidence of a monoenergetic feature. Furthermore, data from gold and carbon wires showed surprising and interesting results. Preliminary analysis of data from two ion emission diagnostics, Thomson parabola spectrometers (TPs) and radio chromic films (RCFs), suggests that shockwave acceleration occurred rather than target normal sheath acceleration, the standard mechanism of ion acceleration. Upon completion of the experiment at TITAN, I researched the possibility of transforming our liquid cryogenic

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

International Nuclear Information System (INIS)

Tsuzuki, Seiji; Shinoda, Wataru; Miran, Md. Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi

2013-01-01

The stabilization energies for the formation (E form ) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G ** 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 form for the [dema][CF 3 SO 3 ] and [dmpa][CF 3 SO 3 ] complexes (−95.6 and −96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF 3 SO 3 ] complex (−81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl − , BF 4 − , TFSA − anions. The anion has contact with the N–H bond of the dema + or dmpa + cations in the most stable geometries of the dema + and dmpa + 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 form for the less stable geometries for the dema + and dmpa + complexes are close to those for the most stable etma + 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 − anion, while the strong directionality of the interactions was not suggested from the simulation of the [etma][CF 3 SO 3 ] ionic liquid

The Role of Hydrophobicity and Surface Receptors at Hyphae of Lyophyllum sp. Strain Karsten in the Interaction with Burkholderia terrae BS001 – Implications for Interactions in Soil

Science.gov (United States)

Vila, Taissa; Nazir, Rashid; Rozental, Sonia; dos Santos, Giulia M. P.; Calixto, Renata O. R.; Barreto-Bergter, Eliana; Wick, Lukas Y.; van Elsas, Jan Dirk

2016-01-01

The soil bacterium Burkholderia terrae strain BS001 can interact with varying soil fungi, using mechanisms that range from the utilization of carbon/energy sources such as glycerol to the ability to reach novel territories in soil via co-migration with growing fungal mycelia. Here, we investigate the intrinsic properties of the B. terrae BS001 interaction with the basidiomycetous soil fungus Lyophyllum sp. strain Karsten. In some experiments, the ascomycetous Trichoderma asperellum 302 was also used. The hyphae of Lyophyllum sp. strain Karsten were largely hydrophilic on water-containing media versus hydrophobic when aerial, as evidenced by contact angle analyses (CA). Co-migration of B. terrae strain BS001 cells with the hyphae of the two fungi occurred preferentially along the - presumably hydrophilic - soil-dwelling hyphae, whereas aerial hyphae did not allow efficient migration, due to reduced thickness of their surrounding mucous films. Moreover, the cell numbers over the length of the hyphae in soil showed an uneven distribution, i.e., the CFU numbers increased from minima at the inoculation point to maximal numbers in the middle of the extended hyphae, then decreasing toward the terminal side. Microscopic analyses of the strain BS001 associations with the Lyophyllum sp. strain Karsten hyphae in the microcosms confirmed the presence of B. terrae BS001 cells on the mucous matter that was present at the hyphal surfaces of the fungi used. Cell agglomerates were found to accumulate at defined sites on the hyphal surfaces, which were coined ‘fungal-interactive’ hot spots. Evidence was further obtained for the contention that receptors for a physical bacterium-fungus interaction occur at the Lyophyllum sp. strain Karsten hyphal surface, in which the specific glycosphingolipid ceramide monohexoside (CMH) plays an important role. Thus, bacterial adherence may be mediated by heterogeneously distributed fungal-specific receptors, implying the CMH moieties. This

Transferability of polarizable models for ion-water electrostatic interaction

International Nuclear Information System (INIS)

Masia, Marco

2009-01-01

Studies of ion-water systems at condensed phase and at interfaces have pointed out that molecular and ionic polarization plays an important role for many phenomena ranging from hydrogen bond dynamics to water interfaces' structure. Classical and ab initio Molecular Dynamics simulations reveal that induced dipole moments at interfaces (e.g. air-water and water-protein) are usually high, hinting that polarizable models to be implemented in classical force fields should be very accurate in reproducing the electrostatic properties of the system. In this paper the electrostatic properties of three classical polarizable models for ion-water interaction are compared with ab initio results both at gas and condensed phase. For Li + - water and Cl - -water dimers the reproducibility of total dipole moments obtained with high level quantum chemical calculations is studied; for the same ions in liquid water, Car-Parrinello Molecular Dynamics simulations are used to compute the time evolution of ionic and molecular dipole moments, which are compared with the classical models. The PD2-H2O model developed by the author and coworkers [Masia et al. J. Chem. Phys. 2004, 121, 7362] together with the gaussian intermolecular damping for ion-water interaction [Masia et al. J. Chem. Phys. 2005, 123, 164505] showed to be the fittest in reproducing the ab initio results from gas to condensed phase, allowing for force field transferability.

Ion Motion in a Plasma Interacting with Strong Magnetic Fields

International Nuclear Information System (INIS)

Weingarten, A.; Grabowski, C.; Chakrabarti, N.; Maron, Y.; Fruchtmant, A.

1999-01-01

The interaction of a plasma with strong magnetic fields takes place in many laboratory experiments and astrophysical plasmas. Applying a strong magnetic field to the plasma may result in plasma displacement, magnetization, or the formation of instabilities. Important phenomena in plasma, such as the energy transport and the momentum balance, take a different form in each case. We study this interaction in a plasma that carries a short-duration (80-ns) current pulse, generating a magnetic field of up to 17 kG. The evolution of the magnetic field, plasma density, ion velocities, and electric fields are determined before and during the current pulse. The dependence of the plasma limiting current on the plasma density and composition are studied and compared to theoretical models based on the different phenomena. When the plasma collisionality is low, three typical velocities should be taken into consideration: the proton and heavier-ion Alfven velocities (v A p and v A h , respectively) and the EMHD magnetic-field penetration velocity into the plasma (v EMHD ). If both Alfven velocities are larger than v EMHD the plasma is pushed ahead of the magnetic piston and the magnetic field energy is dissipated into ion kinetic energy. If v EMHD is the largest of three velocities, the plasma become magnetized and the ions acquire a small axial momentum only. Different ion species may drift in different directions along the current lines. In this case, the magnetic field energy is probably dissipated into electron thermal energy. When vs > V EMHD > vi, as in the case of one of our experiments, ion mass separation occurs. The protons are pushed ahead of the piston while the heavier-ions become magnetized. Since the plasma electrons are unmagnetized they cannot cross the piston, and the heavy ions are probably charge-neutralized by electrons originating from the cathode that are 'born' magnetized

Possible mechanisms for the interaction of polymeric composite resins with Cu(II) ions in aqueous solution

International Nuclear Information System (INIS)

El-Zahhhar, A.A.; Abdel-Aziz, H.M.; Siyam, T.

2005-01-01

The interaction between the active groups of polymeric composite resins such as Poly(acrylamide-acrylic acid)-ethylenediaminetetra acetic acid disodium salt P(AM-AA)EDTANa 2 , Poly(acrylamide-acrylic acid)- montmorillonite P(AM-AA)-montmorillonite, and Poly(acrylamide-acrylic acid)-potassium nickel hexacyanoferrate P(AM-AA)-KNiHCF, with copper sulfate as a test ion has been studied. The spectroscopic studies show that the mechanism of interaction between polymeric composite resins and copper sulfate is a bond formation between the active groups of polymeric chains and copper ion. The bond formation depends on nature of polymeric chains. It was also found that the amide groups form complexes with hydrated cations, while carboxylate group interact by ion exchange mechanism through complex formation. Montmorillonite and hexacyanoferrate of the resins interact with metal ions by ion exchange mechanism

Water-based adhesives with tailored hydrophobic association: dilution resistance and improved setting behavior.

Science.gov (United States)

Dundua, Alexander; Landfester, Katharina; Taden, Andreas

2014-11-01

Hydrophobic association and stimuli-responsiveness is a powerful tool towards water-based adhesives with strongly improved properties, which is demonstrated based on the example of hydrophobically modified alkali-soluble latexes (HASE) with modulated association. Their rheological properties are highly tunable due to the hydrophobic domains that act as physical crosslinking sites of adjustable interaction strength. Ethanol, propanol, and butanol are used as water-soluble model additives with different hydrophobicity in order to specifically target the association sites and impact the viscoelastic properties and stimuli-responsiveness. The rheological and mechanical property response upon dilution with water can be tailored, and dilution-resistant or even dilution-thickening systems are obtained. The investigations are of high importance for water-based adhesives, as our findings provide insight into general structure-property relationships to improve their setting behavior, especially upon contact with wet substrates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrophobic-Core Microcapsules and Their Formation

Science.gov (United States)

Calle, Luz M. (Inventor); Li, Wenyan (Inventor); Buhrow, Jerry W. (Inventor); Jolley, Scott T. (Inventor)

2016-01-01

Hydrophobic-core microcapsules and methods of their formation are provided. A hydrophobic-core microcapsule may include a shell that encapsulates a hydrophobic substance with a core substance, such as dye, corrosion indicator, corrosion inhibitor, and/or healing agent, dissolved or dispersed therein. The hydrophobic-core microcapsules may be formed from an emulsion having hydrophobic-phase droplets, e.g., containing the core substance and shell-forming compound, dispersed in a hydrophilic phase. The shells of the microcapsules may be capable of being broken down in response to being contacted by an alkali, e.g., produced during corrosion, contacting the shell.

Modelling the interaction of high energy ions with inert matter, living matter, and moving matter

International Nuclear Information System (INIS)

Beuve, Michael

2007-01-01

In this report for accreditation to supervise research (HDR), the author proposes a synthetic (and however relatively detailed) overview of his research works in the fields of physics and radiology. The first part addresses works in the field of interaction between ions and inert matter (Monte Carlo simulation of emission induced by ion-solid interaction, simulation by molecular dynamics of pulverization). The second part addresses the interaction between ions and living matter: research strategy, principle of the Local Effect Model (LEM) and influence of its main parameters, LEM experimental assessment, LEM theoretical analysis, role of the cell oxidizing and anti-oxidizing system. The next part addresses the interaction of ions with moving matter: research strategy, lung mechanics modelling and clinical assessments, chest wall mechanics, transformation of movements simulated in 4D scanner imagery

[Noncovalent cation-π interactions--their role in nature].

Science.gov (United States)

Fink, Krzysztof; Boratyński, Janusz

2014-11-07

Non-covalent interactions play an extremely important role in organisms. The main non-covalent interactions in nature are: ion-ion interactions, dipole-dipole interactions, hydrogen bonds, and van der Waals interactions. A new kind of intermolecular interactions--cation-π interactions--is gaining increasing attention. These interactions occur between a cation and a π system. The main contributors to cation-π interactions are electrostatic, polarization and, to a lesser extent, dispersion interactions. At first, cation-π interactions were studied in a gas phase, with metal cation-aromatic system complexes. The characteristics of these complexes are as follows: an increase of cation atomic number leads to a decrease of interaction energy, and an increase of cation charge leads to an increase of interaction energy. Aromatic amino acids bind with metal cations mainly through interactions with their main chain. Nevertheless, cation-π interaction with a hydrophobic side chain significantly enhances binding energy. In water solutions most cations preferentially interact with water molecules rather than aromatic systems. Cation-π interactions occur in environments with lower accessibility to a polar solvent. Cation-π interactions can have a stabilizing role on the secondary, tertiary and quaternary structure of proteins. These interactions play an important role in substrate or ligand binding sites in many proteins, which should be taken into consideration when the screening of effective inhibitors for these proteins is carried out. Cation-π interactions are abundant and play an important role in many biological processes.

Ion interactions with solids and plasma

International Nuclear Information System (INIS)

Arista, N.R.

1987-01-01

The models developed for studying processing of energy losses in dense medium, in particular some recent results for atomic systems confined in solids and in partially degenerated medium are described. Applications of these models to some cases of ion interaction with thin metallic foils and with dense plasmas are described. The processes of excitation and energy losses in the case of a degenerated electron gas, and in the general case of a plasma with arbitrary degenerescency are considered. (M.C.K.) [pt

Interactions of relativistic heavy ions in thick heavy element targets and some unresolved problems

International Nuclear Information System (INIS)

Brandt, R.; Ditlov, V.A.; Pozharova, E.A.; Smirnitskij, V.A.

2005-01-01

Interactions of relativistic heavy ions with total energies above 30 GeV in thick Cu and Pb targets (≥2 cm) have been studied with various techniques. Radiochemical irradiation experiments using thick Cu targets, both in a compact form or as diluted '2π-Cu targets' have been carried out with several relativistic heavy ions, such as 44 GeV 12 C (JINR, Dubna) and 72 GeV 40 Ar (LBL, Berkeley, USA). Neutron measuring experiments using thick targets irradiated with various relativistic heavy ions up to 44 GeV 12 C have been performed at JINR. In addition, the number of 'black prongs' in nuclear interactions (due to protons with energies less than 30 MeV and emitted from the target-like interaction partner at rest) produced with 72 GeV 22 Ne ions in nuclear emulsion plates has been measured in the first nuclear interaction of the primary 22 Ne ion and in the following second nuclear interaction of the secondary heavy (Z>1) ion. Some essential results have been obtained. 1) Spallation products produced by relativistic secondary fragments in interactions ([44 GeV 12 C or 72 GeV 40 Ar]+Cu) within thick copper yield less products close to the target and much more products far away from the target as compared to primary beam interactions. This applies also to secondary particles emitted into large angles (Θ>10deg). 2) The neutron production of 44 GeV 12 C within thick Cu and Pb targets is beyond the estimated yield as based on experiments with 12 GeV 12 C. These rather independent experimental results cannot be understood with well-accepted nuclear reaction models. They appear to present unresolved problems

Nanocarriers from GRAS Zein Proteins to Encapsulate Hydrophobic Actives.

Science.gov (United States)

Weissmueller, Nikolas T; Lu, Hoang D; Hurley, Amanda; Prud'homme, Robert K

2016-11-14

One factor limiting the expansion of nanomedicines has been the high cost of the materials and processes required for their production. We present a continuous, scalable, low cost nanoencapsulation process, Flash Nanoprecipitation (FNP) that enables the production of nanocarriers (NCs) with a narrow size distribution using zein corn proteins. Zein is a low cost, GRAS protein (having the FDA status of "Generally Regarded as Safe") currently used in food applications, which acts as an effective encapsulant for hydrophobic compounds using FNP. The four-stream FNP configuration allows the encapsulation of very hydrophobic compounds in a way that is not possible with previous precipitation processes. We present the encapsulation of several model active compounds with as high as 45 wt % drug loading with respect to zein concentration into ∼100 nm nanocarriers. Three examples are presented: (1) the pro-drug antioxidant, vitamin E-acetate, (2) an anticholera quorum-sensing modulator CAI-1 ((S)-3-hydroxytridecan-4-one; CAI-1 that reduces Vibrio cholerae virulence by modulating cellular communication), and (3) hydrophobic fluorescent dyes with a range of hydrophobicities. The specific interaction between zein and the milk protein, sodium caseinate, provides stabilization of the NCs in PBS, LB medium, and in pH 2 solutions. The stability and size changes in the three media provide information on the mechanism of assembly of the zein/active/casein NC.

Medium dependent dual turn on/turn off fluorescence sensing for Cu2 + ions using AMI/SDS assemblies

Science.gov (United States)

Gujar, Varsha B.; Ottoor, Divya

2017-02-01

Behavior of Amiloride (AMI) as a metal ion sensor in anionic surfactant assemblies of varying concentrations at different pH is depicted in this work. From a non-sensor fluorophore, AMI has been transformed in to a tunable fluorosensor for Cu2 + ions in various SDS concentrations. At premicellar concentration of SDS, ion-pair complex is expected to be formed between AMI and SDS due to electrostatic interactions between them. However at CMC concentrations of SDS, fluorescence intensity of AMI is greatly enhanced with red shift in emission, due to the incorporation of AMI molecule in the hydrophobic micellar interface. The behavior of metal sensing by AMI-SDS assemblies gives rise to several interesting observations. Micellation of SDS has been greatly enhanced by increasing copper ion concentrations, as these counter ions screens the charge on monomers of SDS which lead to the aggregation at premicellar concentrations only. Concentrations and pH dependent discrete trends of interactions between SDS-AMI and SDS-Cu2 + ions, have given tunable fluorescence responses (fluorescence turn on/turn off) of AMI for added Cu2 + ions. The electrostatic interaction between the metal cations and the anionic surfactants is the driving force for bringing the metal ions near to the vicinity of micelle where AMI resides. Thus, a comprehensive understanding of the mechanism related to the 'turn on-turn off' fluorescence response of AMI with respect to pH and SDS concentration for effective Cu2 + ion sensing is illustrated in this work.

Water on a Hydrophobic surface

Science.gov (United States)

Scruggs, Ryan; Zhu, Mengjue; Poynor, Adele

2012-02-01

Hydrophobicity, meaning literally fear of water, is exhibited on the surfaces of non-stick cooking pans and water resistant clothing, on the leaves of the lotus plan, or even during the protein folding process in our bodies. Hydrophobicity is directly measured by determining a contact angle between water and an objects surface. Associated with a hydrophobic surface is the depletion layer, a low density region approximately 0.2 nm thick. We study this region by comparing data found in lab using surface plasmon resonance techniques to theoretical calculations. Experiments use gold slides coated in ODT and Mercapto solutions to model both hydrophobic and hydrophilic surfaces respectively.

Hydrophobic Calcium Carbonate for Cement Surface

Directory of Open Access Journals (Sweden)

Shashi B. Atla

2017-12-01

Full Text Available This report describes a novel way to generate a highly effective hydrophobic cement surface via a carbonation route using sodium stearate. Carbonation reaction was carried out at different temperatures to investigate the hydrophobicity and morphology of the calcium carbonate formed with this process. With increasing temperatures, the particles changed from irregular shapes to more uniform rod-like structures and then aggregated to form a plate-like formation. The contact angle against water was found to increase with increasing temperature; after 90 °C there was no further increase. The maximum contact angle of 129° was obtained at the temperature of 60 °C. It was also found that carbonation increased the micro hardness of the cement material. The micro hardness was found to be dependent on the morphology of the CaCO3 particles. The rod like structures which caused increased mineral filler produced a material with enhanced strength. The 13C cross polarization magic-angle spinning NMR spectra gave plausible explanation of the interaction of organic-inorganic moieties.

Interaction of a finite-length ion beam with a background plasma: Reflected ions at the quasi-parallel bow shock

International Nuclear Information System (INIS)

Onsager, T.G.; Winske, D.; Thomsen, M.F.

1991-01-01

The coupling of a finite-length, field-aligned, ion beam with a uniform background plasma is investigated using one-dimensional hybrid computer simulations. The finite-length beam is used to study the interaction between the incident solar wind and ions reflected from the Earth's quasi-parallel bow shock, where the reflection process may vary with time. The coupling between the reflected ions and the solar wind is relevant to ion heating at the bow shock and possibly to the formation of hot, flow anomalies and re-formation of the shock itself. The authors find that although there are many similarities between the instabilities driven by the finite-length beam and those predicted by linear theory for an infinite, homogeneous beam, there are also some important differences. Consistent with linear theory, the waves which dominate the interaction are the electromagnetic right-hand polarized resonant and nonresonant modes. However, in addition to the instability growth rates, the length of time that the waves are in contact with the beam is also an important factor in determining which wave mode will dominate the interaction. Whereas linear theory predicts the nonresonant mode to have the larger growth rate for the parameters they investigate, with finite-length beam they find that both the nonresonant and resonant modes contribute to the interaction. They find that the interaction will result in strong coupling, where a significant fraction of the available free energy is converted into thermal energy in a short time, provided the beam is sufficiently dense or sufficiently long

Interaction of antihypertensive drug amiloride with metal ions in micellar medium using fluorescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Gujar, Varsha; Pundge, Vijaykumar; Ottoor, Divya, E-mail: divya@chem.unipune.ac.in

2015-05-15

Steady state and life time fluorescence spectroscopy have been employed to study the interaction of antihypertensive drug amiloride with biologically important metal ions i.e. Cu{sup 2+}, Fe{sup 2+}, Ni{sup 2+} and Zn{sup 2+} in various micellar media (anionic SDS (sodium dodecyl sulfate), nonionic TX-100 (triton X-100) and cationic CTAB (cetyl trimethyl ammonium bromide)). It was observed that fluorescence properties of drug remain unaltered in the absence of micellar media with increasing concentration of metal ions. However, addition of Cu{sup 2+}, Fe{sup 2+} and Ni{sup 2+} caused fluorescence quenching of amiloride in the presence of anionic micelle, SDS. Binding of drug with metal ions at the charged micellar interface could be the possible reason for this pH-dependent metal-mediated fluorescence quenching. There were no remarkable changes observed due to metal ions addition when drug was present in cationic and nonionic micellar medium. The binding constant and bimolecular quenching constant were evaluated and compared for the drug–metal complexes using Stern–Volmer equation and fluorescence lifetime values. - Highlights: • Interaction of amiloride with biologically important metal ions, Fe{sup 2+}, Cu{sup 2+}, Ni{sup 2+} and Zn{sup 2+}. • Monitoring the interaction in various micelle at different pH by fluorescence spectroscopy. • Micelles acts as receptor, amiloride as transducer and metal ions as analyte in the present system. • Interaction study provides pH dependent quenching and binding mechanism of drug with metal ions.

Interaction of antihypertensive drug amiloride with metal ions in micellar medium using fluorescence spectroscopy

International Nuclear Information System (INIS)

Gujar, Varsha; Pundge, Vijaykumar; Ottoor, Divya

2015-01-01

Steady state and life time fluorescence spectroscopy have been employed to study the interaction of antihypertensive drug amiloride with biologically important metal ions i.e. Cu 2+ , Fe 2+ , Ni 2+ and Zn 2+ in various micellar media (anionic SDS (sodium dodecyl sulfate), nonionic TX-100 (triton X-100) and cationic CTAB (cetyl trimethyl ammonium bromide)). It was observed that fluorescence properties of drug remain unaltered in the absence of micellar media with increasing concentration of metal ions. However, addition of Cu 2+ , Fe 2+ and Ni 2+ caused fluorescence quenching of amiloride in the presence of anionic micelle, SDS. Binding of drug with metal ions at the charged micellar interface could be the possible reason for this pH-dependent metal-mediated fluorescence quenching. There were no remarkable changes observed due to metal ions addition when drug was present in cationic and nonionic micellar medium. The binding constant and bimolecular quenching constant were evaluated and compared for the drug–metal complexes using Stern–Volmer equation and fluorescence lifetime values. - Highlights: • Interaction of amiloride with biologically important metal ions, Fe 2+ , Cu 2+ , Ni 2+ and Zn 2+ . • Monitoring the interaction in various micelle at different pH by fluorescence spectroscopy. • Micelles acts as receptor, amiloride as transducer and metal ions as analyte in the present system. • Interaction study provides pH dependent quenching and binding mechanism of drug with metal ions

Interactions of Na+, K+, Mg2+, and Ca 2+ with benzene self-assembled monolayers

DEFF Research Database (Denmark)

Pedersen, Morten Rimmen; Matthiesen, Jesper; Bovet, Nicolas Emile

2014-01-01

that are most common in the natural world, namely, Na+, K+, Mg 2+, and Ca2+. Specifically, we investigated how these ions affect the interactions between surfaces covered by self-Assembled monolayers (SAMs) terminated with benzene molecules. We used a flat oxidized silicon substrate and an atomic force...... from X-ray photoelectron spectroscopy (XPS) allowed us to conclude that K+ binds in the benzene layers, creating a positive surface charge on the benzene-covered surfaces, thus leading to lower adhesion in KCl solutions than in pure water. Evidence suggested that Ca2+ does not bind to the surfaces...... measurements. The results of our studies clearly show that even a nonpolar, hydrophobic molecule, such as benzene, has a role to play in the behavior of aqueous solutions and that it interacts differently depending on which ions are present. Even ions from the same column in the periodic table behave...

Extraction of highly charged ions from the Berlin Electron Beam Ion Trap for interactions with a gas target

International Nuclear Information System (INIS)

Allen, F.I.; Biedermann, C.; Radtke, R.; Fussmann, G.

2006-01-01

Highly charged ions are extracted from the Berlin Electron Beam Ion Trap for investigations of charge exchange with a gas target. The classical over-the-barrier model for slow highly charged ions describes this process, whereby one or more electrons are captured from the target into Rydberg states of the ion. The excited state relaxes via a radiative cascade of the electron to ground energy. The cascade spectra are characteristic of the capture state. We investigate x-ray photons emitted as a result of interactions between Ar 17+ ions at energies ≤5q keV with Ar atoms. Of particular interest is the velocity dependence of the angular momentum capture state l c

Hydrophobic ion pairing of a minocycline/Ca(2+)/AOT complex for preparation of drug-loaded PLGA nanoparticles with improved sustained release.

Science.gov (United States)

Holmkvist, Alexander Dontsios; Friberg, Annika; Nilsson, Ulf J; Schouenborg, Jens

2016-02-29

Polymeric nanoparticles is an established and efficient means to achieve controlled release of drugs. Incorporation of minocycline, an antibiotic with anti-inflammatory and neuroprotective properties, into biodegradable nanoparticles may therefore provide an efficient means to combat foreign body reactions to implanted electrodes in the brain. However, minocycline is commonly associated with poor encapsulation efficiencies and/or fast release rates due to its high solubility in water. Moreover, minocycline is unstable under conditions of low and high pH, heat and exposure to light, which exacerbate the challenges of encapsulation. In this work drug loaded PLGA nanoparticles were prepared by a modified emulsification-solvent-diffusion technique and characterized for size, drug encapsulation and in vitro drug release. A novel hydrophobic ion pair complex of minocycline, Ca(2+) ions and the anionic surfactant AOT was developed to protect minocycline from degradation and prolong its release. The optimized formulation resulted in particle sizes around 220 nm with an entrapment efficiency of 43% and showed drug release over 30 days in artificial cerebrospinal fluid. The present results constitute a substantial increase in release time compared to what has hitherto been achieved for minocycline and indicate that such particles might provide useful for sustained drug delivery in the CNS. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Porous Materials to Support Bilayer Lipid Membranes for Ion Channel Biosensors

Directory of Open Access Journals (Sweden)

Thai Phung

2011-01-01

Full Text Available To identify materials suitable as membrane supports for ion channel biosensors, six filter materials of varying hydrophobicity, tortuosity, and thickness were examined for their ability to support bilayer lipid membranes as determined by electrical impedance spectroscopy. Bilayers supported by hydrophobic materials (PTFE, polycarbonate, nylon, and silanised silver had optimal resistance (14–19 GΩ and capacitance (0.8–1.6 μF values whereas those with low hydrophobicity did not form BLMs (PVDF or were short-lived (unsilanised silver. The ability of ion channels to function in BLMs was assessed using a method recently reported to improve the efficiency of proteoliposome incorporation into PTFE-supported bilayers. Voltage-gated sodium channel activation by veratridine and inhibition by saxitoxin showed activity for PTFE, nylon, and silanised silver, but not polycarbonate. Bilayers on thicker, more tortuous, and hydrophobic materials produced higher current levels. Bilayers that self-assembled on PTFE filters were the longest lived and produced the most channel activity using this method.

Ion beam profiling from the interaction with a freestanding 2D layer

Directory of Open Access Journals (Sweden)

Ivan Shorubalko

2017-03-01

Full Text Available Recent years have seen a great potential of the focused ion beam (FIB technology for the nanometer-scale patterning of a freestanding two-dimensional (2D layer. Experimentally determined sputtering yields of the perforation process can be quantitatively explained using the binary collision theory. The main peculiarity of the interaction between the ion beams and the suspended 2D material lies in the absence of collision cascades, featured by no interaction volume. Thus, the patterning resolution is directly set by the beam diameters. Here, we demonstrate pattern resolution beyond the beam size and precise profiling of the focused ion beams. We find out that FIB exposure time of individual pixels can influence the resultant pore diameter. In return, the pore dimension as a function of the exposure dose brings out the ion beam profiles. Using this method of determining an ion-beam point spread function, we verify a Gaussian profile of focused gallium ion beams. Graphene sputtering yield is extracted from the normalization of the measured Gaussian profiles, given a total beam current. Interestingly, profiling of unbeknown helium ion beams in this way results in asymmetry of the profile. Even triangular beam shapes are observed at certain helium FIB conditions, possibly attributable to the trimer nature of the beam source. Our method of profiling ion beams with 2D-layer perforation provides more information on ion beam profiles than the conventional sharp-edge scan method does.

Interaction of low-energy highly charged ions with matter

International Nuclear Information System (INIS)

Ginzel, Rainer

2010-01-01

The thesis presented herein deals with experimental studies of the interaction between highly charged ions and neutral matter at low collision energies. The energy range investigated is of great interest for the understanding of both charge exchange reactions between ions comprising the solar wind and various astrophysical gases, as well as the creation of near-surface nanostructures. Over the course of this thesis an experimental setup was constructed, capable of reducing the kinetic energy of incoming ions by two orders of magnitude and finally focussing the decelerated ion beam onto a solid or gaseous target. A coincidence method was employed for the simultaneous detection of photons emitted during the charge exchange process together with the corresponding projectile ions. In this manner, it was possible to separate reaction channels, whose superposition presumably propagated large uncertainties and systematic errors in previous measurements. This work has unveiled unexpectedly strong contributions of slow radiative decay channels and clear evidence of previously only postulated decay processes in charge exchange-induced X-ray spectra. (orig.)

Single Molecule Sensors to Study Hydrophobic Phenomena

OpenAIRE

Geisler, Michael

2010-01-01

The nature and magnitude of the hydrophobic interaction is crucial for many technical and biological processes. In the current study a molecular probe was developed which consists of a single polymer that is bound onto the tip of an AFM cantilever in order to study these effects on the molecular scale. In the following, equilibrium forces are measured and factors of influence such as temperature, cosolvents and chemical composition are varied. Thereby, the system under investigation is so sma...

Double folded Yukawa interaction potential between two heavy ions

International Nuclear Information System (INIS)

Bulgac, A.; Carstoiu, F.; Dumitrescu, O.

1980-02-01

A simple semi-analytical formula for the heavy ion interaction potential within the double-folding model approximation is obtained. The folded interaction is assumed to be expressed in Yukawa terms or the derivatives of them. The densities used can be both experimental or theoretical (of simple ''step-wise'', ''Fermi-Saxon-Woods'' or complicated ''shell model'' structure) densities. A way of inserting the exchange terms is discussed. Numerical calculations for some colliding partners are reported. (author)

Direct observation of interaction between plasma ions and grid-excited pulses in a Q-machine

DEFF Research Database (Denmark)

Andersen, S.A.; Jensen, Vagn Orla; Michelsen, Poul

1970-01-01

The change in velocity-distribution function caused by interaction between ions and density pulses in a Q-machine is observed experimentally.......The change in velocity-distribution function caused by interaction between ions and density pulses in a Q-machine is observed experimentally....

Metal ion interaction with phosphorylated tyrosine analogue monolayers on gold.

Science.gov (United States)

Petoral, Rodrigo M; Björefors, Fredrik; Uvdal, Kajsa

2006-11-23

Phosphorylated tyrosine analogue molecules (pTyr-PT) were assembled onto gold substrates, and the resulting monolayers were used for metal ion interaction studies. The monolayers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), both prior to and after exposure to metal ions. XPS verified the elemental composition of the molecular adsorbate and the presence of metal ions coordinated to the phosphate groups. Both the angle-dependent XPS and IRAS results were consistent with the change in the structural orientation of the pTyr-PT monolayer upon exposure to metal ions. The differential capacitance of the monolayers upon coordination of the metal ions was evaluated using EIS. These metal ions were found to significantly change the capacitance of the pTyr-PT monolayers in contrast to the nonphosphorylated tyrosine analogue (TPT). CV results showed reduced electrochemical blocking capabilities of the phosphorylated analogue monolayer when exposed to metal ions, supporting the change in the structure of the monolayer observed by XPS and IRAS. The largest change in the structure and interfacial capacitance was observed for aluminum ions, compared to calcium, magnesium, and chromium ions. This type of monolayer shows an excellent capability to coordinate metal ions and has a high potential for use as sensing layers in biochip applications to monitor the presence of metal ions.

Observation of large-amplitude ion acoustic wave in microwave-plasma interaction experiments

International Nuclear Information System (INIS)

Yugami, Noboru; Nishida, Yasushi

1997-01-01

Large amplitude ion acoustic wave, which is not satisfied with a linear dispersion relationship of ion acoustic wave, is observed in microwave-plasma interaction experiments. This ion acoustic wave is excited around critical density layer and begins to propagate to underdense region with a phase velocity one order faster than sound velocity C s , which is predicted by the linear theory, the phase velocity and the wave length of the wave decreases as it propagates. Finally, it converges to C s and strongly dumps. Diagnostic by the Faraday cup indicates that this ion acoustic wave is accompanied with a hot ion beam. (author)

Mechanism of ion adsorption to aqueous interfaces: Graphene/water vs. air/water.

Science.gov (United States)

McCaffrey, Debra L; Nguyen, Son C; Cox, Stephen J; Weller, Horst; Alivisatos, A Paul; Geissler, Phillip L; Saykally, Richard J

2017-12-19

The adsorption of ions to aqueous interfaces is a phenomenon that profoundly influences vital processes in many areas of science, including biology, atmospheric chemistry, electrical energy storage, and water process engineering. Although classical electrostatics theory predicts that ions are repelled from water/hydrophobe (e.g., air/water) interfaces, both computer simulations and experiments have shown that chaotropic ions actually exhibit enhanced concentrations at the air/water interface. Although mechanistic pictures have been developed to explain this counterintuitive observation, their general applicability, particularly in the presence of material substrates, remains unclear. Here we investigate ion adsorption to the model interface formed by water and graphene. Deep UV second harmonic generation measurements of the SCN - ion, a prototypical chaotrope, determined a free energy of adsorption within error of that for air/water. Unlike for the air/water interface, wherein repartitioning of the solvent energy drives ion adsorption, our computer simulations reveal that direct ion/graphene interactions dominate the favorable enthalpy change. Moreover, the graphene sheets dampen capillary waves such that rotational anisotropy of the solute, if present, is the dominant entropy contribution, in contrast to the air/water interface.

Biophysical aspects of heavy ion interactions in matter

International Nuclear Information System (INIS)

Schimmerling, W.; Wong, M.; Ludewigt, B.; Phillips, M.; Alpen, E.L.; Powers-Risius, P.; DeGuzman, R.J.; Townsend, L.W.; Wilson, J.W.

1989-01-01

The biological effects of high energy, high charge nuclei (HZE particles) occupy a central role in the management of space radiation hazards due to galactic cosmic rays. For the energy range of interest, the mean free path for nuclear interactions of these heavy ions is comparable to the thickness of the material traversed, and a significant fraction of stopping particles will undergo a nuclear reaction with the nuclei of the stopping material. Transport methods for HZE particles are dependent on models of the interaction of man-made systems with the space environment to an even greater extent than methods used for other types of radiation. Hence, there is a major need to validate these transport codes by comparison with experimental data. The basic physical properties of HZE particles will be reviewed and illustrated with the results of nuclear fragmentation experiments performed with 670A MeV neon ions incident on a water absorber and with measurements of multiple Coulomb scattering of uranium beams in copper. Finally, the extent to which physical measurements yield radiobiological predictions is illustrated for the example of neon

Hydrophobization by Means of Nanotechnology on Greek Sandstones Used as Building Facades

Directory of Open Access Journals (Sweden)

Georgios Karagiannis

2013-01-01

Full Text Available Modern sustainable architecture indicates the use of local natural stones for building. Greek sandstones from Epirus (Demati, Greece, EN 12440 used as building facades meet aesthetic and have high mechanical properties, but the inevitable interaction between stone materials and natural or anthropogenic weathering factors controls the type, and extent of stone damages. In the present paper, samples of sandstone were treated with a conventional hydrophobic product and four solutions of the same product, enriched with nanosilica of different concentrations. The properties of the treated samples, such as porosity and pore size distribution, microstructure, static contact angle of a water droplet, and durability to deterioration cycles (freeze-thaw were recorded and conclusions were drawn. The research indicates the increased hydrophobic properties in nanosilica solutions but also the optimum content in nanoparticles that provides hydrophobicity without altering the properties of the stone.

Isolation of soybean protein P34 from oil bodies using hydrophobic interaction chromatography

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Seidel-Morgenstern Andreas

2008-03-01

Full Text Available Abstract Background Soybeans play a prominent role in allergologic research due to the high incidence of allergic reactions. For detailed studies on specific proteins it is necessary to have access to a large amount of pure substance. Results In this contribution, a method for purifying soybean (Glycine max protein P34 (also called Gly m Bd 30 K or Gly m 1 using hydrophobic interaction chromatography is presented. After screening experiments using 1 mL HiTrap columns, Butyl Sepharose 4 FF was selected for further systematic investigations. With this stationary phase, suitable operation conditions for two-step gradient elution using ammonium sulphate were determined experimentally. The separation conditions obtained in a small column could be scaled up successfully to column volumes of 7.5 and 75 mL, allowing for high product purities of almost 100% with a yield of 27% for the chromatographic separation step. Conditions could be simplified further using a onestep gradient, which gave comparable purification in a shorter process time. The identity of the purified protein was verified using in-gel digestion and mass spectrometry as well as immunological techniques. Conclusion With the technique presented it is possible to produce, within a short timeframe, pure P34, suitable for further studies where an example antigen is needed.

Modelling interaction cross sections for intermediate and low energy ions

International Nuclear Information System (INIS)

Toburen, L.H.; Shinpaugh, J.L.; Justiniano, E.L.B.

2002-01-01

When charged particles slow in tissue they undergo electron capture and loss processes than can have profound effects on subsequent interaction cross sections. Although a large amount of data exists for the interaction of bare charged particles with atoms and molecules, few experiments have been reported for these 'dressed' particles. Projectile electrons contribute to an impact-parameter-dependent screening of the projectile charge that precludes straightforward scaling of energy loss cross sections from those of bare charged particles. The objective of this work is to develop an analytical model for the energy-loss-dependent effects of screening on differential ionisation cross sections that can be used in track structure calculations for high LET ions. As a first step a model of differential ionisation cross sections for bare ions has been combined with a simple screening model to explore cross sections for intermediate and low energy dressed ions in collisions with atomic and molecular gas targets. The model is described briefly and preliminary results compared to measured electron energy spectra. (author)

Study of interaction between protein and main active components in Citrus aurantium L. by optical spectroscopy

International Nuclear Information System (INIS)

Sun Yantao; Zhang Haitao; Sun Ye; Zhang Yupu; Liu He; Cheng Jianhua; Bi Shuyun; Zhang Hanqi

2010-01-01

The interaction between flavonoids and proteins was investigated by fluorescence and absorption spectroscopy. The binding parameters of drugs with proteins were obtained according to the corrected fluorescence data by an improved calculation method. The ΔH, ΔS and ΔG obtained indicate that the van der Waals or hydrogen bond, electrostatic force and hydrophobic forces all play a role in the interaction of drugs with proteins. Based on Foerster's theory, the binding average distance r between the protein and drug was evaluated and found to be less than 3 nm. The interaction of drug-metal ion complexes and proteins was also investigated.

Chemotherapy drugs form ion pores in membranes due to physical interactions with lipids.

Science.gov (United States)

Ashrafuzzaman, Mohammad; Tseng, Chih-Yuan; Duszyk, Marek; Tuszynski, Jack A

2012-12-01

We demonstrate the effects on membrane of the tubulin-binding chemotherapy drugs: thiocolchicoside and taxol. Electrophysiology recordings across lipid membranes in aqueous phases containing drugs were used to investigate the drug effects on membrane conductance. Molecular dynamics simulation of the chemotherapy drug-lipid complexes was used to elucidate the mechanism at an atomistic level. Both drugs are observed to induce stable ion-flowing pores across membranes. Discrete pore current-time plots exhibit triangular conductance events in contrast to rectangular ones found for ion channels. Molecular dynamics simulations indicate that drugs and lipids experience electrostatic and van der Waals interactions for short periods of time when found within each other's proximity. The energies from these two interactions are found to be similar to the energies derived theoretically using the screened Coulomb and the van der Waals interactions between peptides and lipids due to mainly their charge properties while forming peptide-induced ion channels in lipid bilayers. Experimental and in silico studies together suggest that the chemotherapy drugs induce ion pores inside lipid membranes due to drug-lipid physical interactions. The findings reveal cytotoxic effects of drugs on the cell membrane, which may aid in novel drug development for treatment of cancer and other diseases. © 2012 John Wiley & Sons A/S.

21 CFR 584.700 - Hydrophobic silicas.

Science.gov (United States)

2010-04-01

...) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No. 68611-0944... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRUGS, FEEDS, AND RELATED PRODUCTS FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE IN FEED AND...

Adsorption of Hydrophobically Modified Polyelectrolytes on Hydrophobic Substrates Adsorption de polyélectrolytes modifiés hydrophobiquement sur les substrats hydrophobes

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Mays J. W.

2006-12-01

Full Text Available A series of diblock copolymers, poly (tert-butyl styrene-sodium poly (styrene sulfonate with different molecular weight and percentage of sulfonation have been used to study the effect of polymer structure on its adsorption behavior onto hydrophobically modified silicon wafers. The percentage of the hydrophobic block varies from 3. 6-8. 9%. Previous studies show that salt concentration is very important for the adsorption of such polyelectrolytes onto silica surfaces. Octadecyltriethoxysilane (OTE has been used to modify the silicon wafer which changes the water contact angle from 50° on unmodified silica to 100° to 120°. On this hydrophobic surface, we found that the adsorption of these slightly hydrophobically modified polyelectrolytes is close to the 4/23rd power of salt concentration predicted by a recent model. The grafting density is also consistent with a dependence on the length of the hydrophobic block to the -12/23rd power, and the length of the polyelectrolyte block to the -6/23rd power, predicted by this model. Une série de copolymères à diblocs poly (tert-butyle styrène-sodium (sulfonate de polystyrène de masses moléculaires et pourcentages de sulfonation différents ont été utilisés pour étudier les effets de la structure du polymère sur son pouvoir d'adsorption sur des surfaces de silicium modifiées hydrophobiquement. Le pourcentage du bloc hydrophobe varie de 3,6 à 8,9%. Les études antérieures montrent que la concentration saline est très importante pour l'adsorption de ces polyélectrolytes sur les surfaces de silice. Nous avons utilisé l'octadecyltriéthoxysilane (OTE pour modifier la surface de silicium qui change l'angle de contact de l'eau de 50° sur la silice non modifiée à une valeur comprise entre 100° et 120° sur la silice modifiée. Sur cette surface hydrophobe, nous constatons que l'adsorption de ces polyélectrolytes légèrement modifiés hydrophobiquement est proche de la loi puissance 4

Mutation of exposed hydrophobic amino acids to arginine to increase protein stability

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Czaplicki Jerzy

2004-07-01

Full Text Available Abstract Background One strategy to increase the stability of proteins is to reduce the area of water-accessible hydrophobic surface. Results In order to test it, we replaced 14 solvent-exposed hydrophobic residues of acetylcholinesterase by arginine. The stabilities of the resulting proteins were tested using denaturation by high temperature, organic solvents, urea and by proteolytic digestion. Conclusion Altough the mutational effects were rather small, this strategy proved to be successful since half of the mutants showed an increased stability. This stability may originate from the suppression of unfavorable interactions of nonpolar residues with water or from addition of new hydrogen bonds with the solvent. Other mechanisms may also contribute to the increased stability observed with some mutants. For example, introduction of a charge at the surface of the protein may provide a new coulombic interaction on the protein surface.

Surface analysis of selected hydrophobic materials

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Wisniewska, Sylwia Katarzyna

This dissertation contains a series of studies on hydrophobic surfaces by various surface sensitive techniques such as contact angle measurements, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Hydrophobic surfaces have been classified as mineral surfaces, organic synthetic surfaces, or natural biological surfaces. As a model hydrophobic mineral surface, elemental sulfur has been selected. The sulfur surface has been characterized for selected allotropic forms of sulfur such as rhombic, monoclinic, plastic, and cyclohexasulfur. Additionally, dextrin adsorption at the sulfur surface was measured. The structure of a dextrin molecule showing hydrophobic sites has been presented to support the proposed hydrophobic bonding nature of dextrin adsorption at the sulfur surface. As a model organic hydrophobic surface, primary fatty amines such as dodecylamine, hexadecylamine, and octadecylamine were chosen. An increase of hydrophobicity, significant changes of infrared bands, and surface topographical changes with time were observed for each amine. Based on the results it was concluded that hydrocarbon chain rearrangement associated with recrystallization took place at the surface during contact with air. A barley straw surface was selected as a model of biological hydrophobic surfaces. The differences in the contact angles for various straw surfaces were explained by the presence of a wax layer. SEM images confirmed the heterogeneity and complexity of the wax crystal structure. AFM measurements provided additional structural details including a measure of surface roughness. Additionally, straw degradation as a result of conditioning in an aqueous environment was studied. Significant contact angle changes were observed as soon as one day after conditioning. FTIR studies showed a gradual wax layer removal due to straw surface decomposition. SEM and AFM images revealed topographical changes and biological

Structural Characteristics of Homogeneous Hydrophobic Ionic Liquid-HNO3-H2O Ternary System: Experimental Studies and Molecular Dynamics Simulations.

Science.gov (United States)

Fu, Jing; Yang, Y Isaac; Zhang, Jun; Chen, Qingde; Shen, Xinghai; Gao, Yi Qin

2016-06-16

The solubility of water in the hydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) increases significantly in the presence of HNO3. [C2mim][NTf2] is completely miscible with HNO3 but immiscible with water. The triangular phase diagram of the ternary system [C2mim][NTf2]-HNO3-H2O was determined at 300.1 K. The homogeneous [C2mim][NTf2]-HNO3-H2O phase is thermodynamically stable, while it can be separated into two phases with an increase of water content. Experiments (electrospray ionization mass spectrometry, Fourier transform infrared spectrometry, and (1)H-nuclear magnetic resonance spectrometry) and molecular dynamics simulations were carried out to investigate the interaction between [C2mim][NTf2], HNO3, and water in the homogeneous phase. It was found that NO3(-) ions interact with both C2mim(+) and water via H-bonding and act as a "bridge" to induce a large amount of water to be dissolved in the hydrophobic IL phase. This confirms that the complexes [C2mim-NTf2-C2mim](+) and [NTf2-C2mim-NTf2](-) exist in the homogeneous [C2mim][NTf2]-HNO3-H2O system at the concentration of HNO3 up to 27.01 wt % and of water as high as 20.74 wt %.

Comparison of the Fouling Release Properties of Hydrophobic Fluorinated and Hydrophilic PEGylated Block Copolymer Surfaces

International Nuclear Information System (INIS)

Krishnan, S.; Wang, N.; Ober, C.; Finlay, J.; Callow, M.; Callow, J.; Hexemer, A.; Sohn, K.; Kramer, E.; Fischer, D.

2006-01-01

To understand the role of surface wettability in adhesion of cells, the attachment of two different marine algae was studied on hydrophobic and hydrophilic polymer surfaces. Adhesion of cells of the diatom Navicula and sporelings (young plants) of the green macroalga Ulva to an underwater surface is mainly by interactions between the surface and the adhesive exopolymers, which the cells secrete upon settlement and during subsequent colonization and growth. Two types of block copolymers, one with poly(ethylene glycol) side-chains and the other with liquid crystalline, fluorinated side-chains, were used to prepare the hydrophilic and hydrophobic surfaces, respectively. The formation of a liquid crystalline smectic phase in the latter inhibited molecular reorganization at the surface, which is generally an issue when a highly hydrophobic surface is in contact with water. The adhesion strength was assessed by the fraction of settled cells (Navicula) or biomass (Ulva) that detached from the surface in a water flow channel with a wall shear stress of 53 Pa. The two species exhibited opposite adhesion behavior on the same sets of surfaces. While Navicula cells released more easily from hydrophilic surfaces, Ulva sporelings showed higher removal from hydrophobic surfaces. This highlights the importance of differences in cell-surface interactions in determining the strength of adhesion of cells to substrates

Ion beam-plasma interactions. Final report, September 1, 1983-August 31, 1984

International Nuclear Information System (INIS)

DeGroot, J.S.

1985-01-01

The purpose of this study was to design experiments that model the fast ion plasma interaction region in a heavy ion driven inertial confinement fusion (HIF) pellet. The effort consisted of (1) construction and testing of the experimental device and (2) preliminary experiments. The results of this work are reported

Design and synthesis of an amphiphilic graft hydrogel having a hydrophobic domain formed by multiple interactions

Energy Technology Data Exchange (ETDEWEB)

Nitta, Kyohei [Department of Life and Functional Material Science, Graduate School of Natural Science, Konan University, 8-9-1 Okamoto, Higashinada, Kobe 658-8501 (Japan); Japan Society for the Promotion of Science (DC1), Ichibancho, Chiyoda, Tokyo 102-8471 (Japan); Kimoto, Atsushi [Department of Chemistry of Functional Molecules, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada, Kobe 658-8501 (Japan); Watanabe, Junji, E-mail: junjiknd@konan-u.ac.jp [Department of Chemistry of Functional Molecules, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada, Kobe 658-8501 (Japan)

2016-11-01

A novel hydrogel having hydrophobic oligo segments and hydrophilic poly(acrylamidoglycolic acid) (PAGA) as pH responsive polymer segments was designed and synthesized to be used as a soft biomaterial. Poly(trimethylene carbonate) (PTMC) as the side chain, for which the degrees of polymerization were 9, 19, and 49, and the composition ratios were 1, 5, and 10 mol%, was used as the oligo segment in the hydrogel. The swelling ratio of the hydrogel was investigated under various changes in conditions such as pH, temperature, and hydrogen bonding upon urea addition. Under pH 2–11 conditions, the graft gel reversibly swelled and shrank due to the effect of PAGA main chain. The interior morphology and skin layer of the hydrogel was observed by a scanning electron microscope. The hydrogel composed of PAGA as the hydrophilic polymer backbone had a sponge-like structure, with a pore size of approximately 100 μm. On the other hand, upon increasing the ratio of trimethylene carbonate (TMC) units in the hydrogel, the pores became smaller or disappeared. Moreover, thickness of the skin layer significantly increased with the swelling ratio depended on the incorporation ratios of the PTMC macromonomer. Molecular incorporation in the hydrogel was evaluated using a dye as a model drug molecule. These features would play an important role in drug loading. Increasing the ratio of TMC units favored the adsorption of the dye and activation of the incorporation behavior. - Highlights: • Hydrogen bonding and hydrophobic interaction are dominant factor for forming hydrogels. • Hydrogel properties were tuned by changing in graft length and macromonomer content in feed. • The resulting graft gel could encapsulate and retain organic dye in the hydrogel. • Poly(trimethylene carbonate) segment in the hydrogel was dominant unit for hydrogel.

Design and synthesis of an amphiphilic graft hydrogel having a hydrophobic domain formed by multiple interactions

International Nuclear Information System (INIS)

Nitta, Kyohei; Kimoto, Atsushi; Watanabe, Junji

2016-01-01

A novel hydrogel having hydrophobic oligo segments and hydrophilic poly(acrylamidoglycolic acid) (PAGA) as pH responsive polymer segments was designed and synthesized to be used as a soft biomaterial. Poly(trimethylene carbonate) (PTMC) as the side chain, for which the degrees of polymerization were 9, 19, and 49, and the composition ratios were 1, 5, and 10 mol%, was used as the oligo segment in the hydrogel. The swelling ratio of the hydrogel was investigated under various changes in conditions such as pH, temperature, and hydrogen bonding upon urea addition. Under pH 2–11 conditions, the graft gel reversibly swelled and shrank due to the effect of PAGA main chain. The interior morphology and skin layer of the hydrogel was observed by a scanning electron microscope. The hydrogel composed of PAGA as the hydrophilic polymer backbone had a sponge-like structure, with a pore size of approximately 100 μm. On the other hand, upon increasing the ratio of trimethylene carbonate (TMC) units in the hydrogel, the pores became smaller or disappeared. Moreover, thickness of the skin layer significantly increased with the swelling ratio depended on the incorporation ratios of the PTMC macromonomer. Molecular incorporation in the hydrogel was evaluated using a dye as a model drug molecule. These features would play an important role in drug loading. Increasing the ratio of TMC units favored the adsorption of the dye and activation of the incorporation behavior. - Highlights: • Hydrogen bonding and hydrophobic interaction are dominant factor for forming hydrogels. • Hydrogel properties were tuned by changing in graft length and macromonomer content in feed. • The resulting graft gel could encapsulate and retain organic dye in the hydrogel. • Poly(trimethylene carbonate) segment in the hydrogel was dominant unit for hydrogel.

Transparent Hydrophobic Coating by Sol Gel Method

International Nuclear Information System (INIS)

Mohd Hamzah Harun; Nik Ghazali Nik Salleh; Mahathir Mohamed; Mohd Sofian Alias

2016-01-01

Transparent hydrophobic coating of inorganic based tetra orthosilicate (TEOS) was prepared by sol gel method by varying fluoroalkylsilane (FAS) content which works as hydrophobic agent. Surface contact angle, transmittance degree and surface morphology were characterized for each sample. All samples show good transparency which was confirmed by UV visible spectroscopy. The hydrophobicity obtained increases with FAS content indicates that FAS is best candidate to induce hydrophobicity for inorganic coating. (author)

Porphyrin-phospholipid interaction and ring metallation depending on the phospholipid polar head type.

Science.gov (United States)

Ramos, Ana P; Pavani, Christiane; Iamamoto, Yassuko; Zaniquelli, Maria E D

2010-10-01

The interaction between a hydrophobically modified 5,10,15,20-tetrakis(4-N-tetradecyl-pyridyl) porphyrin and three phospholipids: two negatively charged, DMPA (the sodium salt of dimyristoyl-sn-glycero-phosphatidyl acid) and DMPG (the sodium salt of 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)]) and a zwitterionic DMPC (dimyristoyl-sn-glycero-phosphatidylcholine), were studied by means of surface pressure isotherms and spectroscopic methods. The interaction results in partial or total metallation of the porphyrin with zinc ions in the presence of negatively charged phospholipids, as attested by UV-vis and luminescence spectroscopy of the transferred films. In the presence of the zwitterionic phospholipid no insertion of zinc ion in the porphyrin ring is detected. These results are relevant for the understanding of photosensitizer-lipid-carrier binding for use in photodynamic therapy. Copyright 2010 Elsevier Inc. All rights reserved.

Modulation and interactions of charged biomimetic membranes with bivalent ions

Science.gov (United States)

Kazadi Badiambile, Adolphe

The biological membrane of an eukaryotic cell is a two-dimensional structure of mostly phospholipids with embedded proteins. This two-dimensional structure plays many key roles in the life of a cell. Transmembrane proteins, for example, play the role of a gate for different ions (such as Ca2+). Also found are peripheral proteins that are used as enzymes for different purposes in the inner leaflet of the plasma membrane. Phospholipids, in particular play three key roles. Firstly, some members of this group are used to store energy. Secondly, the hydrophobic and hydrophilic properties inherent to phospholipids enable them to be used as building blocks of the cell membrane by forming an asymmetric bilayer. This provides a shielding protection against the outer environment while at the same time keeping the organelles and cytosol from leaking out of the cell. Finally lipids are involved in regulating the aggregation of proteins in the membrane. In addition, some subspecies such as phosphatidylinositol (PtdIns) are second messenger molecules in their own right, thus playing an important role in cellular signaling events. In my work presented in this thesis, I am focusing on the role of some phospholipids as signaling molecules and in particular the physicochemical underpinnings that could be used in their spatiotemporal organization in the cellular plasma membrane. I am specifically concerned with the important family of phosphatidylinositol lipids. PtdIns are very well known for their role as signaling molecules in numerous cell events. They are located in the inner leaflet of the plasma membrane as well as part of the membrane of other organelles. Studies of these signaling molecules in their in vivo environment present many challenges: Firstly, the complexity of interactions due to the numerous entities present in eukaryotic cell membranes makes it difficult to establish clear cause and effect relationships. Secondly, due to their size, our inability to probe these

Contribution of hydrophobic effect to the sorption of phenanthrene, 9-phenanthrol and 9, 10-phenanthrenequinone on carbon nanotubes.

Science.gov (United States)

Peng, Hongbo; Zhang, Di; Pan, Bo; Peng, Jinhui

2017-02-01

Polycyclic aromatic hydrocarbons (PAHs), with diverse sources and acute toxicity, are categorized as priority pollutants. Previous studies have stated that the hydrophobic effect controls PAH sorption, but no study has been conducted to quantify the exact contribution of the hydrophobic effect. Considering the well-defined structure of carbon nanotubes and their stable chemical composition in organic solvents, three multi-walled carbon nanotubes (MWCNTs) were selected as a model adsorbent. Phenanthrene (PHE) and its degradation intermediates 9-phenanthrol (PTR) and 9, 10-phenanthrenequinone (PQN) were used as model adsorbates. To quantify the contribution of the hydrophobic effect for these three chemicals, the effect of organic solvent (methanol and hexadecane) was investigated. Adsorption isotherms for PHE, PTR and PQN were well fitted by the Freundlich isotherm model. A positive relationship between adsorption affinities of these three chemicals and specific surface area (SSA) was observed in hexadecane but not in water or methanol. Other factors should be included other than SSA. Adsorption of PQN on MWCNTs with oxygen functional groups was higher than that on pristine MWCNTs due to π-π EDA interactions. The contribution of hydrophobic effect was 50%-85% for PHE, suggesting that hydrophobic effect was the predominant mechanism. This contribution was lower than 30% for PTR/PQN on functionalized MWCNTs. Hydrogen bonds control the adsorption of PTR, and π-π bonding interactions control PQN sorption after screening out the hydrophobic effect in hexadecane. Hydrophobic effect is the control mechanism for nonpolar chemicals, while functional groups of CNTs and solvent types control the adsorption of polar compounds. Extended work on quantifying the relationship between chemical structure and the contribution of the hydrophobic effect will provide a useful technique for PAH fate modeling. Copyright © 2016 Elsevier Ltd. All rights reserved.

Resonance interaction of heavy ions in radar scattering

International Nuclear Information System (INIS)

Strutinskij, V.M.

1983-01-01

Resonances on back angles in the process of scatterina of heavy ions are investigated. Comprehensive investigation into possible sources of irregular structure of angular distribution during elastic scattering (ES) on wide angles are compated with an experiment. The first source is a two-component interference and the second one is a resonance structure connected with the process of formation of definite nucleon states in strongly deformed intermediate nucleus. Comparison of radar cross section calculations (back scattering cross section) with angular ES distributions of hydrogen on silicon testifies a possibility to interpret an anomalous scattering on wide angles in some reactions with heavy ions as a result of modulation of partial amplitudes by resonances of the input state typein the initial state of interaction of two nuclei

Molecular origin of urea driven hydrophobic polymer collapse and unfolding depending on side chain chemistry.

Science.gov (United States)

Nayar, Divya; Folberth, Angelina; van der Vegt, Nico F A

2017-07-19

Osmolytes affect hydrophobic collapse and protein folding equilibria. The underlying mechanisms are, however, not well understood. We report large-scale conformational sampling of two hydrophobic polymers with secondary and tertiary amide side chains using extensive molecular dynamics simulations. The calculated free energy of unfolding increases with urea for the secondary amide, yet decreases for the tertiary amide, in agreement with experiment. The underlying mechanism is rooted in opposing entropic driving forces: while urea screens the hydrophobic macromolecular interface and drives unfolding of the tertiary amide, urea's concomitant loss in configurational entropy drives collapse of the secondary amide. Only at sufficiently high urea concentrations bivalent urea hydrogen bonding interactions with the secondary amide lead to further stabilisation of its collapsed state. The observations provide a new angle on the interplay between side chain chemistry, urea hydrogen bonding, and the role of urea in attenuating or strengthening the hydrophobic effect.

Interaction of slow highly-charged ions with metals and insulators

International Nuclear Information System (INIS)

Yamazaki, Y.

2007-01-01

Interaction of slow highly charged ions with insulator as well as metallic surfaces is discussed. In addition to the usual flat surface targets, studies with thin foils having a multitude of straight holes of ∼100 nm in diameter (micro-capillary foil) are introduced, which provide various unique information on the above surface interaction. In the case of an insulator micro-capillary foil, a so-called guiding effect was observed, where slow highly charged ions can transmit through the capillary tunnel keeping their initial charge state even when the capillary axis is tilted against the incident beam. A similar guiding effect has recently been found for slow highly-charged ions transmitted through a single tapered glass capillary. In both cases, the guiding effects are expected to be governed by a self-organized charging and discharging of the inner-wall of the insulator capillary. One of the prominent features of this guiding effect with the tapered capillary is the formation of a nano-size beam, which can be applied in various fields of science including surface nano-modification/analysis, nano-surgery of living cells, etc

Production of ultrahigh ion current densities at skin-layer subrelativistic laser-plasma interaction

Energy Technology Data Exchange (ETDEWEB)

Badziak, J [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Glowacz, S [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Jablonski, S [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Parys, P [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Wolowski, J [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Hora, H [Department of Theoretical Physics, University of New South Wales, Sydney (Australia); Krasa, J [Institute of Physics, ASCR, Prague (Czech Republic); Laska, L [Institute of Physics, ASCR, Prague (Czech Republic); Rohlena, K [Institute of Physics, ASCR, Prague (Czech Republic)

2004-12-01

Some applications of fast ions driven by a short ({<=}1 ps) laser pulse (e.g. fast ignition of ICF targets, x-ray laser pumping, laboratory astrophysics research or some nuclear physics experiments) require ion beams of picosecond (or shorter) time durations and of very high ion current densities ({approx}10{sup 10} A cm{sup -2} or higher). A possible way of producing ion beams with such extreme parameters is ballistic focusing of fast ions generated by a target normal sheath acceleration (TNSA) mechanism at relativistic laser intensities. In this paper we discuss another method, where the production of short-pulse ion beams of ultrahigh current densities is possible in a planar geometry at subrelativistic laser intensities and at a low energy ({<=}1 J) of the laser pulse. This method-referred to as skin-layer ponderomotive acceleration (S-LPA)-uses strong ponderomotive forces induced at the skin-layer interaction of a short laser pulse with a proper preplasma layer in front of a solid target. The basic features of the high-current ion generation by S-LPA were investigated using a simplified theory, numerical hydrodynamic simulations and measurements. The experiments were performed with subjoule 1 ps laser pulses interacting with massive or thin foil targets at intensities of up to 2 x 10{sup 17} W cm{sup -2}. It was found that both in the backward and forward directions highly collimated high-density ion beams (plasma blocks) with current densities at the ion source (close to the target) approaching 10{sup 10} A cm{sup -2} are produced, in accordance with the theory and numerical calculations. These ion current densities were found to be comparable to (or even higher than) those estimated from recent short-pulse TNSA experiments with relativistic laser intensities. Apart from the simpler physics of the laser-plasma interaction, the advantage of the considered method is the low energy of the driving laser pulses allowing the production of ultrahigh

A novel method to survey parameters of an ion beam and its interaction with a target

Science.gov (United States)

Long, J. D.; Yang, Z.; Li, J.; Wang, X. H.; Wang, T.; Lan, C. H.; Dong, P.; Li, X.; He, J. L.; Zheng, L.; Liu, P.

2017-09-01

Beam profile and composition of the pulsed ion beam from a vacuum arc source are valuable information for designing a high-intensity deuterium-tritium neutron generator. Traditional methods are notoriously difficult to obtain the information at the same time. A novel off-line diagnostic method is presented, which can obtain the transverse beam profile with high resolution as well as species of the ions in the beam. The method is using a silicon target with high purity to interact with the ion beam, and then use secondary ion mass spectrometry (SIMS) to analyze the interaction zone of the target to get the beam information. More information on beam-target interaction could get simultaneously. Proof-of-principle simulation and experimental works have demonstrated this method is practical.

The interaction of uranyl ions with inorganic pyrophosphatase from baker's yeast

International Nuclear Information System (INIS)

Bienwald, B.; Heitmann, P.

1978-01-01

The interaction of uranyl ions with inorganic pyrophosphatase from baker's yeast was investigated by measurement of their effect on the protein fluorescence. Fluorescence titrations of the native enzyme with uranyl nitrate show that there is a specific binding of uranyl ions to the enzyme. It was deduced that each subunit of the enzyme binds one uranyl ion. The binding constant was estimated to be in the order of 10 7 M -1 . The enzyme which contains a small number of chemically modified carboxyl groups was not able to bind uranyl ions specifically. The modification of carboxyl groups was carried out by use of a water soluble carbodiimide and the nucleophilic reagent N-(2,4-dinitro-phenyl)-hexamethylenediamine. The substrate analogue calcium pyrophosphate displaced the uranyl ions from their binding sites at the enzyme From the results it is concluded that carboxyl groups of the active site are the ligands for the binding of uranyl ions. (author)

Novel lanthanide doped micro- and mesoporous solids. Characterization of ion-host-interactions, species distribution and luminescence properties using time-resolved luminescence spectroscopy; Neuartige Lanthanoid-dotierte mikro- und mesoporoese Feststoffe. Charakterisierung von Ion-Wirt-Wechselwirkungen, Speziesverteilung und Lumineszenzeigenschaften mittels zeitaufgeloester Lumineszenzspektroskopie

Energy Technology Data Exchange (ETDEWEB)

Gessner, Andre

2010-12-15

mesopores. Lanthanide ions located here, are easily accessible for water and thus show shorter luminescence decay times and a more symmetrical coordination sphere, which is mostly made up by water molecules. Another investigated aspect was the influence of surface modifications on the luminescence behavior of the lanthanide ions inside the material. Here we could show, that surface modifications hydrophobize the material and thus are able to protect the lanthanide ions from water, which is important for the conservation of the luminescence properties. Concerning the mesoporous silicates, again a heterogeneous distribution of the lanthanide ions in the pore system was found. A part of the lanthanide ions interacts with the pore wall, while the other part is located in the aqueous phase inside the pores. Surface modification led to a interaction of the lanthanide ions with the modification. This was reflected in the luminescence properties depending on the structure of the modification and the surface loading.

Rice Starch Particle Interactions at Air/Aqueous Interfaces—Effect of Particle Hydrophobicity and Solution Ionic Strength

Science.gov (United States)

McNamee, Cathy E.; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-01-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film. PMID:29868551

Colorimetric Detection of Some Highly Hydrophobic Flavonoids Using Polydiacetylene Liposomes Containing Pentacosa-10,12-diynoyl Succinoglycan Monomers

Science.gov (United States)

Yun, Deokgyu; Jeong, Daham; Cho, Eunae; Jung, Seunho

2015-01-01

Flavonoids are a group of plant secondary metabolites including polyphenolic molecules, and they are well known for antioxidant, anti-allergic, anti-inflammatory and anti-viral propertied. In general, flavonoids are detected with various non-colorimetric detection methods such as column liquid chromatography, thin-layer chromatography, and electrochemical analysis. For the first time, we developed a straightforward colorimetric detection system allowing recognition of some highly hydrophobic flavonoids such as alpha-naphthoflavone and beta-naphthoflavone, visually using 10,12-pentacosadiynoic acid (PCDA) derivatized with succinoglycan monomers isolated from Sinorhizobium meliloti. Besides changes in visible spectrum, we also demonstrate fluorescence changes using our detection system in the presence of those flavonoids. The succinoglycan monomers attached to PCDA molecules may function as an unstructured molecular capturer for some highly hydrophobic flavonoids by hydrophobic interactions, and transmit their molecular interactions as a color change throughout the PCDA liposome. PMID:26600071

Synthesis and toxicity evaluation of hydrophobic ionic liquids for volatile organic compounds biodegradation in a two-phase partitioning bioreactor

International Nuclear Information System (INIS)

Rodriguez Castillo, Alfredo Santiago; Guihéneuf, Solène; Le Guével, Rémy; Biard, Pierre-François

2016-01-01

Highlights: • Description of a VOC depollution system suitable with industrial processes, TPPB. • Novel association of TPPB and hydrophobic ionic liquids. • Synthesis of several hydrophobic ionic liquids designed to fit desired properties. • Toxicity evaluation of these ILs towards cells, animals and bacteria. - Abstract: Synthesis of several hydrophobic ionic liquids (ILs), which might be selected as good candidates for degradation of hydrophobic volatile organic compounds in a two-phase partitioning bioreactor (TPPB), were carried out. Several bioassays were also realized, such as toxicity evaluation on activated sludge and zebrafish, cytotoxicity, fluoride release in aqueous phase and biodegradability in order to verify their possible effects in case of discharge in the aquatic environment and/or human contact during industrial manipulation. The synthesized compounds consist of alkylimidazoliums, functionalized imidazoliums, isoqinoliniums, triazoliums, sulfoniums, pyrrolidiniums and morpholiniums and various counter-ions such as: PF_6"−, NTf_2"− and NfO"−. Toxicity evaluation on activated sludge of each compound (5% v/v of IL) was assessed by using a glucose uptake inhibition test. Toxicity against zebrafish and cytotoxicity were evaluated by the ImPACCell platform of Rennes (France). Fluoride release in water was estimated by regular measurements using ion chromatography equipment. IL biodegradability was determined by measuring BOD_2_8 of aqueous samples (compound concentration,1 mM). All ILs tested were not biodegradable; while some of them were toxic toward activated sludge. Isoquinolinium ILs were toxic to human cancerous cell lines. Nevertheless no toxicity was found against zebrafish Danio rerio. Only one IL released fluoride after long-time agitation.

Calculation of ion storage in electron beams with account of ion-ion interactions

International Nuclear Information System (INIS)

Perel'shtejn, Eh.A.; Shirkov, G.D.

1979-01-01

Ion storage in relativistic electron beams was calculated taking account of ion-ion charge exchange and ionization. The calculations were made for nitrogen ion storage from residual gas during the compression of electron rings in the adhezator of the JINR heavy ion accelerator. The calculations were made for rings of various parameters and for various pressures of the residual gas. The results are compared with analogous calculations made without account of ion-ion processes. It is shown that at heavy loading of a ring by ions ion-ion collisions play a significant part, and they should be taken into account while calculating ion storage

The ion–aerosol interactions from the ion mobility and aerosol ...

Indian Academy of Sciences (India)

2005-02-18

aerosol interactions from the ion mobility and aerosol particle size distribution measurements on January 17 and February 18, 2005 at Maitri, Antarctica – A case study. Devendraa Siingh Vimlesh Pant A K Kamra. Volume 120 Issue 4 August ...

Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

International Nuclear Information System (INIS)

Naus, Dan J.; Mattus, Catherine H.; Dole, Leslie Robert

2007-01-01

The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a 'primer' on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a 'bench-scale' laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the 'primer,' a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures

Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

Energy Technology Data Exchange (ETDEWEB)

Naus, Dan J [ORNL; Mattus, Catherine H [ORNL; Dole, Leslie Robert [ORNL

2007-06-01

The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a "primer" on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a "bench-scale" laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the "primer," a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures.

Effect of whey goat milk kefir on hydrophobicity of E. coli O157:H7, S. typhi bacteria and C. albicans

Directory of Open Access Journals (Sweden)

Dedi Fardiaz

2012-03-01

Full Text Available The hydrophobicity of bacteria. was determined using BATH (Bacteria adhesion to hydrocarbon test. All bacteria showed that 0,9 ml n-octane exposure gave a positive response and indicating that E. coli O157:H7 was categorized as moderate hydrophobic bacteria,  while S.  typhi  and C. albicans were catagorized as  highly hydrophobic bacteria. Goat Milk Kefir increased hydrophobicity of E.  coli O157:H7 by 24.40, however, decreased hydrophobicity of S. typhi by 47.56  and C. albicans by 70.14 percent, respectively. This finding showed that one of the inhibition mechanism may be caused by  an interaction  of  organic acid and peptide  compounds with cell membrane, in which hydrophobic sites of component  modified the hydrophobicity of the bacteria cell surface. The hydrophobicity modification in bacterial  cell wall might result inhibition of adhetion bacteria at cell host. Key words : Enterophatogenic bacteria, hidrophobisitas bacteria

Liposomes coated with hydrophobically modified hydroxyethyl cellulose: Influence of hydrophobic chain length and degree of modification.

Science.gov (United States)

Smistad, Gro; Nyström, Bo; Zhu, Kaizheng; Grønvold, Marthe Karoline; Røv-Johnsen, Anne; Hiorth, Marianne

2017-08-01

Nanoparticulate systems with an uncharged hydrophilic surface may have a great potential in mucosal drug delivery. In the present study liposomes were coated with hydrophobically modified hydroxyethyl cellulose (HM-HEC) to create a sterically stabilized liposomal system with an uncharged surface. The aim was to clarify the influence of the amount of hydrophobic modification of HEC and the length of the hydrophobic moiety, on the stability of the system and on the release properties. HM-HEC with different degrees of hydrophobic modification (1 and 2mol%) and hydrophobic groups with different chain lengths (C8, C12, C16) were included in the study, as well as fluid phase and gel phase liposomes. Both types of liposomes were successfully coated with HM-HEC containing 1mol% of hydrophobic groups, while 2mol% did not work for the intended pharmaceutical applications. The polymer coated gel phase liposomes were stable (size, zeta potential, leakage) for 24 weeks at 4°C, with no differences between the C8 and C16 HM-HEC coating. For the fluid phase liposomes a size increase was observed after 24 weeks at 4°C for all formulations; the C8 HM-HEC coated liposomes increased the most. No differences in the leakage during storage at 4°C or in the release at 35°C were observed between the fluid phase formulations. To conclude; HM-HEC with a shorter hydrophobic chain length resulted in a less stable product for the fluid phase liposomes, while no influence of the chain length was observed for the gel phase liposomes (1mol% HM). Copyright © 2017 Elsevier B.V. All rights reserved.

Interaction of ion clusters with fusion plasmas: Scaling laws

International Nuclear Information System (INIS)

Arista, N.R.; Bringa, E.M.

1997-01-01

The interaction between large ion clusters or very intense ion beams with fusion plasma is studied using the dielectric function formalism with appropriate quantum corrections. The contributions from individual and collective modes to the energy loss are calculated. The general properties of the interference effects are characterized in terms of the relevant parameters, and simple scaling laws are obtained. In particular, the conditions for a maximum enhancement in the energy deposition are derived. The study provides a unified view and a general formulation of collective effects in the energy loss for low and high velocities of the beam particles. copyright 1997 The American Physical Society

Applications of ion implantation for modifying the interactions between metals and hydrogen gas

Science.gov (United States)

Musket, R. G.

1989-04-01

Ion implantations into metals have been shown recently to either reduce or enhance interactions with gaseous hydrogen. Published studies concerned with modifications of these interactions are reviewed and discussed in terms of the mechanisms postulated to explain the observed changes. The interactions are hydrogenation, hydrogen permeation, and hydrogen embrittlement. In particular, the results of the reviewed studies are (a) uranium hydriding suppressed by implantation of oxygen and carbon, (b) hydrogen gettered in iron and nickel using implantation of titanium, (c) hydriding of titanium catalyzed by implanted palladium, (d) tritium permeation of 304L stainless steel reduced using selective oxidation of implanted aluminum, and (e) hydrogen attack of a low-alloy steel accelerated by implantation of helium. These studies revealed ion implantation to be an effective method for modifying the interactions of hydrogen gas with metals.

Adsorption of hydrophobic organic compounds onto a hydrophobic carbonaceous geosorbent in the presence of surfactants.

Science.gov (United States)

Wang, Peng; Keller, Arturo A

2008-06-01

The adsorption of hydrophobic organic compounds (HOCs; atrazine and diuron) onto lampblack was studied in the presence of nonionic, cationic, and anionic surfactants (Triton(R) X-100), benzalkonium chloride [BC], and linear alkylbenzene sulfonate [LAS]) to determine the effect of the surfactant on HOC adsorption onto a hydrophobic carbonaceous geosorbent. Linear alkylbenzene sulfonate showed an adsorption capacity higher than that of BC but similar to that of Triton X-100, implying the charge property of a surfactant is not a useful indicator for predicting the surfactant's adsorption onto a hydrophobic medium. The results also indicated that the octanol-water partition coefficient (K(OW)) of a surfactant is not a good predictor of that surfactant's sorption onto a hydrophobic medium. Under subsaturation adsorption conditions (i.e., before sorption saturation is reached), surfactant adsorption reduced HOC adsorption to a significant extent, with the reduction in HOC adsorption increasing monotonically with the amount of surfactant adsorbed. Among the three surfactants, Triton X-100 was the most effective in reducing HOC adsorption, whereas BC and LAS showed similar effectiveness in this regard. Under the same amount of the surfactant sorbed, the reduction in atrazine adsorption was consistently greater than that for diuron because of atrazine's lower hydrophobicity. No significant difference was observed in the amount of the HOC adsorbed under different adsorption sequences. Our results showed that the presence of surfactant can significantly decrease HOC adsorption onto hydrophobic environmental media and, thus, is important in predicting HOC fate and transport in the environment.

Event Generators for Simulating Heavy Ion Interactions of Interest in Evaluating Risks in Human Spaceflight

Science.gov (United States)

Wilson, Thomas L.; Pinsky, Lawrence; Andersen, Victor; Empl, Anton; Lee, Kerry; Smirmov, Georgi; Zapp, Neal; Ferrari, Alfredo; Tsoulou, Katerina; Roesler, Stefan;

Cluster ion-surface interactions: from meV to MeV energies

Energy Technology Data Exchange (ETDEWEB)

Nordlund, Kai; Meinander, Kristoffer; Jaervi, Tommi T.; Peltola, Jarkko; Samela, Juha [Accelerator Laboratory, University of Helsinki (Finland)

2008-07-01

The nature of cluster ion-surface interactions changes dramatically with the kinetic energy of the incoming cluster species. In this talk I review some of our recent work on the nature of cluster-surface interactions spanning an energy range from a few MeV/cluster to about 1 MeV/cluster and cluster sizes in the range of 10 - 1000 atoms/cluster. In the energy range of a few MeV/cluster ion, the kinetic energy of the incoming ion is insignificant compared to the energy gained when the surface potential energy at the cluster-surface interface is released and partly translated into kinetic energy. Even in this energy regime I show that surprisingly drastic effects can occur. When the energy of the incoming cluster is raised to a few eV/atom, the kinetic energy of the incoming cluster starts to affect the deposition. It will cause the cluster to entirely reform on impact. When the energy is raised to the range of keV's/cluster, the clusters start to penetrate the sample, fairly similar to conventional ion implantation. However, in dense targets the cluster ions may stick close to each other long enough to cause a significant enhancement of the heat spike in the material. Finally, I show that at kinetic energies around 1 MeV/cluster the cluster enhancement of the heat spike may lead to dramatic surface effects.

Selective layer-free blood serum ionogram based on ion-specific interactions with a nanotransistor

Science.gov (United States)

Sivakumarasamy, R.; Hartkamp, R.; Siboulet, B.; Dufrêche, J.-F.; Nishiguchi, K.; Fujiwara, A.; Clément, N.

2018-05-01

Despite being ubiquitous in the fields of chemistry and biology, the ion-specific effects of electrolytes pose major challenges for researchers. A lack of understanding about ion-specific surface interactions has hampered the development and application of materials for (bio-)chemical sensor applications. Here, we show that scaling a silicon nanotransistor sensor down to 25 nm provides a unique opportunity to understand and exploit ion-specific surface interactions, yielding a surface that is highly sensitive to cations and inert to pH. The unprecedented sensitivity of these devices to Na+ and divalent ions can be attributed to an overscreening effect via molecular dynamics. The surface potential of multi-ion solutions is well described by the sum of the electrochemical potentials of each cation, enabling selective measurements of a target ion concentration without requiring a selective organic layer. We use these features to construct a blood serum ionogram for Na+, K+, Ca2+ and Mg2+, in an important step towards the development of a versatile, durable and mobile chemical or blood diagnostic tool.

Ion-exchange selectivity of diclofenac, ibuprofen, ketoprofen, and naproxen in ureolyzed human urine.

Science.gov (United States)

Landry, Kelly A; Sun, Peizhe; Huang, Ching-Hua; Boyer, Treavor H

2015-01-01

This research advances the knowledge of ion-exchange of four non-steroidal anti-inflammatory drugs (NSAIDs) - diclofenac (DCF), ibuprofen (IBP), ketoprofen (KTP), and naproxen (NPX) - and one analgesic drug-paracetamol (PCM) - by strong-base anion exchange resin (AER) in synthetic ureolyzed urine. Freundlich, Langmuir, Dubinin-Astakhov, and Dubinin-Radushkevich isotherm models were fit to experimental equilibrium data using nonlinear least squares method. Favorable ion-exchange was observed for DCF, KTP, and NPX, whereas unfavorable ion-exchange was observed for IBP and PCM. The ion-exchange selectivity of the AER was enhanced by van der Waals interactions between the pharmaceutical and AER as well as the hydrophobicity of the pharmaceutical. For instance, the high selectivity of the AER for DCF was due to the combination of Coulombic interactions between quaternary ammonium functional group of resin and carboxylate functional group of DCF, van der Waals interactions between polystyrene resin matrix and benzene rings of DCF, and possibly hydrogen bonding between dimethylethanol amine functional group side chain and carboxylate and amine functional groups of DCF. Based on analysis of covariance, the presence of multiple pharmaceuticals did not have a significant effect on ion-exchange removal when the NSAIDs were combined in solution. The AER reached saturation of the pharmaceuticals in a continuous-flow column at varying bed volumes following a decreasing order of DCF > NPX ≈ KTP > IBP. Complete regeneration of the column was achieved using a 5% (m/m) NaCl, equal-volume water-methanol solution. Results from multiple treatment and regeneration cycles provide insight into the practical application of pharmaceutical ion-exchange in ureolyzed urine using AER.

Super-hydrophobic surfaces of SiO₂-coated SiC nanowires: fabrication, mechanism and ultraviolet-durable super-hydrophobicity.

Science.gov (United States)

Zhao, Jian; Li, Zhenjiang; Zhang, Meng; Meng, Alan

2015-04-15

The interest in highly water-repellent surfaces of SiO2-coated SiC nanowires has grown in recent years due to the desire for self-cleaning and anticorrosive surfaces. It is imperative that a simple chemical treatment with fluoroalkylsilane (FAS, CF3(CF2)7CH2CH2Si(OC2H5)3) in ethanol solution at room temperature resulted in super-hydrophobic surfaces of SiO2-coated SiC nanowires. The static water contact angle of SiO2-coated SiC nanowires surfaces was changed from 0° to 153° and the morphology, microstructure and crystal phase of the products were almost no transformation before and after super-hydrophobic treatment. Moreover, a mechanism was expounded reasonably, which could elucidate the reasons for their super-hydrophobic behavior. It is important that the super-hydrophobic surfaces of SiO2-coated SiC nanowires possessed ultraviolet-durable (UV-durable) super-hydrophobicity. Copyright © 2014 Elsevier Inc. All rights reserved.

Possible mechanisms for interaction of poly electrolytes with ions in aqueous solution

International Nuclear Information System (INIS)

Siyam, T.

1995-01-01

The interaction between the active groups of water soluble poly electrolytes such as polyacrylamide 'neutral polymers PAM', poly sodium acrylate 'anionic polymer PAANA', polyacrylamide-diallyamine-hydrochloride 'cationic polymer PAM-DAA-HCl and polyacrylamide-diallylethylamine-hydrochloride 'cationic polymer PAM-DAEA-HCl' with copper sulphate has been carried out under different experimental conditions. Spectroscopic studies show that the mechanism of the flock formation due to interaction between the polymer and copper sulphate is a bond formation between the active group of polymeric chains and copper sulphate. This bond formation depends on the nature of polymer chain. It was also found that the amide groups form complexes with hydrated cations, while both carboxylate-and ammonium groups interact by ion-exchange mechanism. The same studies were applied on polyacrylamideacrylic acid resin 'PAM-AA' resin and copper sulphate. The obtained results show that the resin interacts by the same mechanism, where the amide groups form a complex with hydrated cations, while the carboxylic group interacts by ion-exchange mechanism. 1 fig., 1 tab

Some physicochemical aspects of water-soluble mineral flotation.

Science.gov (United States)

Wu, Zhijian; Wang, Xuming; Liu, Haining; Zhang, Huifang; Miller, Jan D

2016-09-01

Some physicochemical aspects of water-soluble mineral flotation including hydration phenomena, associations and interactions between collectors, air bubbles, and water-soluble mineral particles are presented. Flotation carried out in saturated salt solutions, and a wide range of collector concentrations for effective flotation of different salts are two basic aspects of water-soluble mineral flotation. Hydration of salt ions, mineral particle surfaces, collector molecules or ions, and collector aggregates play an important role in water-soluble mineral flotation. The adsorption of collectors onto bubble surfaces is suggested to be the precondition for the association of mineral particles with bubbles. The association of collectors with water-soluble minerals is a complicated process, which may include the adsorption of collector molecules or ions onto such surfaces, and/or the attachment of collector precipitates or crystals onto the mineral surfaces. The interactions between the collectors and the minerals include electrostatic and hydrophobic interactions, hydrogen bonding, and specific interactions, with electrostatic and hydrophobic interactions being the common mechanisms. For the association of ionic collectors with minerals with an opposite charge, electrostatic and hydrophobic interactions could have a synergistic effect, with the hydrophobic interactions between the hydrophobic groups of the previously associated collectors and the hydrophobic groups of oncoming collectors being an important attractive force. Association between solid particles and air bubbles is the key to froth flotation, which is affected by hydrophobicity of the mineral particle surfaces, surface charges of mineral particles and bubbles, mineral particle size and shape, temperature, bubble size, etc. The use of a collector together with a frother and the use of mixed surfactants as collectors are suggested to improve flotation. Copyright © 2016 Elsevier B.V. All rights reserved.

Defect-impurity interactions in ion-implanted metals

International Nuclear Information System (INIS)

Turos, A.

1986-01-01

An overview of defect-impurity interactions in metals is presented. When point defects become mobile they migrate towards the sinks and on the way can be captured by impurity atoms forming stable associations so-called complexes. In some metallic systems complexes can also be formed athermally during ion implantation by trapping point defects already in the collision cascade. An association of a point defect with an impurity atom leads to its displacement from the lattice site. The structure and stability of complexes are strongly temperature dependent. With increasing temperature they dissociate or grow by multiple defect trapping. The appearance of freely migrating point defects at elevated temperatures, due to ion bombardment or thermal annealing, causes via coupling with defect fluxes, important impurity redistribution. Because of the sensitivity of many metal-in-metal implanted systems to radiation damage the understanding of this processes is essential for a proper interpretation of the lattice occupancy measurements and the optimization of implantation conditions. (author)

Combined effects of potassium chloride and ethanol as mobile phase modulators on hydrophobic interaction and reversed-phase chromatography of three insulin variants.

Science.gov (United States)

Johansson, Karolina; Frederiksen, Søren S; Degerman, Marcus; Breil, Martin P; Mollerup, Jørgen M; Nilsson, Bernt

2015-02-13

The two main chromatographic modes based on hydrophobicity, hydrophobic interaction chromatography (HIC) and reversed-phase chromatography (RPC), are widely used for both analytical and preparative chromatography of proteins in the pharmaceutical industry. Despite the extensive application of these separation methods, and the vast amount of studies performed on HIC and RPC over the decades, the underlying phenomena remain elusive. As part of a systematic study of the influence of mobile phase modulators in hydrophobicity-based chromatography, we have investigated the effects of both KCl and ethanol on the retention of three insulin variants on two HIC adsorbents and two RPC adsorbents. The focus was on the linear adsorption range, separating the modulator effects from the capacity effects, but some complementary experiments at higher load were included to further investigate observed phenomena. The results show that the modulators have the same effect on the two RPC adsorbents in the linear range, indicating that the modulator concentration only affects the activity of the solute in the mobile phase, and not that of the solute-ligand complex, or that of the ligand. Unfortunately, the HIC adsorbents did not show the same behavior. However, the insulin variants displayed a strong tendency toward self-association on both HIC adsorbents; on one in particular. Since this causes peak fronting, the retention is affected, and this could probably explain the lack of congruity. This conclusion was supported by the results from the non-linear range experiments which were indicative of double-layer adsorption on the HIC adsorbents, while the RPC adsorbents gave the anticipated increased tailing at higher load. Copyright © 2015 Elsevier B.V. All rights reserved.

Mixed micelles of 7,12-dioxolithocholic acid and selected hydrophobic bile acids: interaction parameter, partition coefficient of nitrazepam and mixed micelles haemolytic potential.

Science.gov (United States)

Poša, Mihalj; Tepavčević, Vesna

2011-09-01

The formation of mixed micelles built of 7,12-dioxolithocholic and the following hydrophobic bile acids was examined by conductometric method: cholic (C), deoxycholic (D), chenodeoxycholic (CD), 12-oxolithocholic (12-oxoL), 7-oxolithocholic (7-oxoL), ursodeoxycholic (UD) and hiodeoxycholic (HD). Interaction parameter (β) in the studied binary mixed micelles had negative value, suggesting synergism between micelle building units. Based on β value, the hydrophobic bile acids formed two groups: group I (C, D and CD) and group II (12-oxoL, 7-oxoL, UD and HD). Bile acids from group II had more negative β values than bile acids from group I. Also, bile acids from group II formed intermolecular hydrogen bonds in aggregates with both smaller (2) and higher (4) aggregation numbers, according to the analysis of their stereochemical (conformational) structures and possible structures of mixed micelles built of these bile acids and 7,12-dioxolithocholic acid. Haemolytic potential and partition coefficient of nitrazepam were higher in mixed micelles built of the more hydrophobic bile acids (C, D, CD) and 7,12-dioxolithocholic acid than in micelles built only of 7,12-dioxolithocholic acid. On the other hand, these mixed micelles still had lower values of haemolytic potential than micelles built of C, D or CD. The mixed micelles that included bile acids: 12-oxoL, 7-oxoL, UD or HD did not significantly differ from the micelles of 7,12-dioxolithocholic acid, observing the values of their haemolytic potential. Copyright © 2011 Elsevier B.V. All rights reserved.

Intra-chain organisation of hydrophobic residues controls inter-chain aggregation rates of amphiphilic polymers

Science.gov (United States)

Varilly, Patrick; Willard, Adam P.; Kirkegaard, Julius B.; Knowles, Tuomas P. J.; Chandler, David

2017-04-01

Aggregation of amphiphiles through the action of hydrophobic interactions is a common feature in soft condensed matter systems and is of particular importance in the context of biophysics as it underlies both the generation of functional biological machinery as well as the formation of pathological misassembled states of proteins. Here we explore the aggregation behaviour of amphiphilic polymers using lattice Monte Carlo calculations and show that the distribution of hydrophobic residues within the polymer sequence determines the facility with which dry/wet interfaces can be created and that such interfaces drive the aggregation process.

Hyperfine interaction studies with pulsed heavy-ion beams

International Nuclear Information System (INIS)

Raghavan, P.

1985-01-01

Heavy-ion reactions using pulsed beams have had a strong impact on the study of hyperfine interactions. Unique advantages offered by this technique have considerably extended the scope, detail and systematic range of its applications beyond that possible with radioactivity or light-ion reaction. This survey will cover a brief description of the methodological aspects of the field and recent applications to selected problems in nuclear and solid state physiscs illustrating its role. These include measurements of nuclear magnetic and electric quadrupole moments of high spin isomers, measurements of hyperfine magnetic fields at impurities in 3d and rare-earths ferromagnetic hosts, studies of paramagnetic systems, especially those exhibiting valence instabilities, and investigations of electric field gradients of impurities in noncubic metals. Future prospects of this technique will be briefly assessed. (orig.)

Modelling oral up-take of hydrophobic and super-hydrophobic chemicals in fish.

Science.gov (United States)

Larisch, Wolfgang; Goss, Kai-Uwe

2018-01-24

We have extended a recently published toxicokinetic model for fish (TK-fish) towards the oral up-take of contaminants. Validation with hydrophobic chemicals revealed that diffusive transport through aqueous boundary layers in the gastro-intestinal tract and in the blood is the limiting process. This process can only be modelled correctly if facilitated transport by albumin or bile micelles through these boundary layers is accounted for. In a case study we have investigated the up-take of a super hydrophobic chemical, Dechlorane Plus. Our results suggest that there is no indication of a hydrophobicity or size cut-off in the bioconcentration of this chemical. Based on an extremely high, but mechanistically sound facilitation factor we received model results in good agreement with experimental values from the literature. The results also indicate that established experimental procedures for BCF determination cannot cover the very slow up-take and clearance kinetics that are to be expected for such a chemical.

Dynamics of Wetting of Ultra Hydrophobic Surfaces

Science.gov (United States)

Mohammad Karim, Alireza; Kim, Jeong-Hyun; Rothstein, Jonathan; Kavehpour, Pirouz; Mechanical and Industrial Engineering, University of Massachusetts, Amherst Collaboration

2013-11-01

Controlling the surface wettability of hydrophobic and super hydrophobic surfaces has extensive industrial applications ranging from coating, painting and printing technology and waterproof clothing to efficiency increase in power and water plants. This requires enhancing the knowledge about the dynamics of wetting on these hydrophobic surfaces. We have done experimental investigation on the dynamics of wetting on hydrophobic surfaces by looking deeply in to the dependency of the dynamic contact angles both advancing and receding on the velocity of the three-phase boundary (Solid/Liquid/Gas interface) using the Wilhelmy plate method with different ultra-hydrophobic surfaces. Several fluids with different surface tension and viscosity are used to study the effect of physical properties of liquids on the governing laws.

Getting the ion-protein interactions right in molecular dynamics simulations

Czech Academy of Sciences Publication Activity Database

Duboué-Dijon, Elise; Mason, Philip E.; Jungwirth, Pavel

2017-01-01

Roč. 46, Suppl 1 (2017), S66 ISSN 0175-7571. [IUPAB congress /19./ and EBSA congress /11./. 16.07.2017-20.07.2017, Edinburgh] Institutional support: RVO:61388963 Keywords : ion-protein interaction * molecular dynamics simulations * neutron scattering * insulin Subject RIV: BO - Biophysics

Native Hydrophobic Binding Interactions at the Transition State for Association between the TAZ1 Domain of CBP and the Disordered TAD-STAT2 Are Not a Requirement.

Science.gov (United States)

Lindström, Ida; Dogan, Jakob

2017-08-15

A significant fraction of the eukaryotic proteome consists of proteins that are either partially or completely disordered under native-like conditions. Intrinsically disordered proteins (IDPs) are common in protein-protein interactions and are involved in numerous cellular processes. Although many proteins have been identified as disordered, much less is known about the binding mechanisms of the coupled binding and folding reactions involving IDPs. Here we have analyzed the rate-limiting transition state for binding between the TAZ1 domain of CREB binding protein and the intrinsically disordered transactivation domain of STAT2 (TAD-STAT2) by site-directed mutagenesis and kinetic experiments (Φ-value analysis) and found that the native protein-protein binding interface is not formed at the transition state for binding. Instead, native hydrophobic binding interactions form late, after the rate-limiting barrier has been crossed. The association rate constant in the absence of electrostatic enhancement was determined to be rather high. This is consistent with the Φ-value analysis, which showed that there are few or no obligatory native contacts. Also, linear free energy relationships clearly demonstrate that native interactions are cooperatively formed, a scenario that has usually been observed for proteins that fold according to the so-called nucleation-condensation mechanism. Thus, native hydrophobic binding interactions at the rate-limiting transition state for association between TAD-STAT2 and TAZ1 are not a requirement, which is generally in agreement with previous findings on other IDP systems and might be a common mechanism for IDPs.

Characterization of molecular determinants of the conformational stability of macrophage migration inhibitory factor: leucine 46 hydrophobic pocket.

Directory of Open Access Journals (Sweden)

Farah El-Turk

Full Text Available Macrophage Migration Inhibitory Factor (MIF is a key mediator of inflammatory responses and innate immunity and has been implicated in the pathogenesis of several inflammatory and autoimmune diseases. The oligomerization of MIF, more specifically trimer formation, is essential for its keto-enol tautomerase activity and probably mediates several of its interactions and biological activities, including its binding to its receptor CD74 and activation of certain signaling pathways. Therefore, understanding the molecular factors governing the oligomerization of MIF and the role of quaternary structure in modulating its structural stability and multifunctional properties is crucial for understanding the function of MIF in health and disease. Herein, we describe highly conserved intersubunit interactions involving the hydrophobic packing of the side chain of Leu46 onto the β-strand β3 of one monomer within a hydrophobic pocket from the adjacent monomer constituted by residues Arg11, Val14, Phe18, Leu19, Val39, His40, Val41, Val42, and Pro43. To elucidate the structural significance of these intersubunit interactions and their relative contribution to MIF's trimerization, structural stability and catalytic activity, we generated three point mutations where Leu46 was replaced by glycine (L46G, alanine (L46A and phenylalanine (L46F, and their structural properties, stability, oligomerization state, and catalytic activity were characterized using a battery of biophysical methods and X-ray crystallography. Our findings provide new insights into the role of the Leu46 hydrophobic pocket in stabilizing the conformational state of MIF in solution. Disrupting the Leu46 hydrophobic interaction perturbs the secondary and tertiary structure of the protein but has no effect on its oligomerization state.

Improving Hydrophobicity of Glass Surface Using Dielectric Barrier Discharge Treatment in Atmospheric Air

International Nuclear Information System (INIS)

Fang Zhi; Qiu Yuchang; Wang Hui; Kuffel, E

2007-01-01

Non-thermal plasmas under atmospheric pressure are of great interest in industrial applications, especially in material surface treatment. In this paper, the treatment of a glass surface for improving hydrophobicity using the non-thermal plasma generated by dielectric barrier discharge (DBD) at atmospheric pressure in ambient air is conducted, and the surface properties of the glass before and after the DBD treatment are studied by using contact angle measurement, surface resistance measurement and wet flashover voltage tests. The effects of the applied voltage and time duration of DBD on the surface modification are studied, and the optimal conditions for the treatment are obtained. It is found that a layer of hydrophobic coating is formed on the glass surface after spraying a thin layer of silicone oil and undergoing the DBD treatment, and the improvement of hydrophobicity depends on DBD voltage and treating time. It seems that there exists an optimum treating time for a certain applied voltage of DBD during the surface treatment. The test results of thermal aging and chemical aging show that the hydrophobic layer has quite stable characteristics. The interaction mechanism between the DBD plasma and the glass surface is discussed. It is concluded that CH 3 and large molecule radicals can react with the radicals in the glass surface to replace OH, and the hydrophobicity of the glass surface is improved accordingly

Breakup Behavior of a Capillary Bridge on a Hydrophobic Stripe Separating Two Hydrophilic Stripes

Science.gov (United States)

Hartmann, Maximilian; Hardt, Steffen

2017-11-01

The breakup dynamics of a capillary bridge on a hydrophobic area between two liquid filaments occupying two parallel hydrophilic stripes is studied experimentally. In addition calculations with the finite-element software Surface Evolver are performed to obtain the corresponding stable minimal surfaces. Droplets of de-ionized water are placed on substrates with alternating hydrophilic and hydrophobic stripes of different width. Their volume decreases by evaporation. This results in a droplet shaped as the letter ``H'' covering two hydrophilic stripes separated by one hydrophobic stripe. The width of the capillary bridge d(t) on the hydrophobic stripe during the breakup process is observed using a high-speed camera mounted on a bright-field microscope. The results of the experiments and the numerical studies show that the critical width dcrit, indicating the point where the capillary bridge becomes unstable, mainly depends on the width ratio of the hydrophilic and hydrophobic stripes. It is found that the time derivative of d(t) first decreases after dcrit has been reached. The final breakup dynamics then follows a t 2 / 3 scaling. We kindly acknowledge the financial support by the German Research Foundation (DFG) within the Collaborative Research Centre 1194 ``Interaction of Transport and Wetting Processes'', Project A02a.

Surface characterization of hydrophobic thin films deposited by inductively coupled and pulsed plasmas

International Nuclear Information System (INIS)

Kim, Youngsoo; Lee, Ji-Hye; Kim, Kang-Jin; Lee, Yeonhee

2009-01-01

Different fluorocarbon thin films were deposited on Si substrates using a plasma-polymerization method. Fluorine-containing hydrophobic thin films were obtained by inductively coupled plasma (ICP) and pulsed plasma (PP) with a mixture of fluorocarbon precursors C 2 F 6 , C 3 F 8 , and c-C 4 F 8 and the unsaturated hydrocarbons of C 2 H 2 . The influence on the fluorocarbon surfaces of the process parameters for plasma polymerization, including the gas ratio and the plasma power, were investigated under two plasma-polymerized techniques with different fluorocarbon gas precursors. The hydrophobic properties, surface morphologies, and chemical compositions were elucidated using water contact angle measurements, field emission-scanning electron microscope, x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). In this study, the ICP technique provides coarser grained films and more hydrophobic surfaces as well as a higher deposition rate compared to the PP technique. XPS, FT-IR, and TOF-SIMS analyses indicated that the ICP technique produced more fluorine-related functional groups, including CF 2 and CF 3 , on the surface. From the curve-fitted XPS results, fluorocarbon films grown under ICP technique exhibited less degree of cross-linking and higher CF 2 concentrations than those grown under PP technique.

Applications of ion implantation for modifying the interactions between metals and hydrogen gas

International Nuclear Information System (INIS)

Musket, R.G.

1989-01-01

Ion implantations into metals have been shown recently to either reduce or enhance interactions with gaseous hydrogen. Published studies concerned with modifications of these interactions are reviewed and discussed in terms of the mechanisms postulated to explain the observed changes. The interactions are hydrogenation, hydrogen permeation and hydrogen embrittlement. In particular, the results of the reviewed studies are 1. uranium hydriding suppressed by implantation of oxygen and carbon, 2. hydrogen gettered in iron and nickel using implantation of titanium, 3. hydriding of titanium catalyzed by implanted palladium, 4. tritium permeation of 304L stainless steel reduced using selective oxidation of implanted aluminum, and 5. hydrogen attack of a low-alloy steel accelerated by implantation of helium. These studies revealed ion implantation to be an effective method for modifying the interactions of hydrogen gas with metals. (orig.)

RF plasma based selective modification of hydrophilic regions on super hydrophobic surface

Energy Technology Data Exchange (ETDEWEB)

Lee, Jaehyun; Hwang, Sangyeon; Cho, Dae-Hyun [Department of Mechanical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Hong, Jungwoo [Department of Mechanical Engineering, Graduate of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141 (Korea, Republic of); Shin, Jennifer H., E-mail: j_shin@kaist.ac.kr [Department of Mechanical Engineering, Graduate of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141 (Korea, Republic of); Byun, Doyoung, E-mail: dybyun@skku.edu [Department of Mechanical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of)

2017-02-01

Highlights: • Simple and amenable reforming method for a substrate with disparate patterns of hydrophilic dots on super-hydrophobic surfaces is proposed. • Wettability characteristics and modification mechanism for the surfaces are conducted and revealed through SEM, AFM, WSI, and SIMS. • Several representative materials for various applications are successfully deposited. - Abstract: Selective modification and regional alterations of the surface property have gained a great deal of attention to many engineers. In this paper, we present a simple, a cost-effective, and amendable reforming method for disparate patterns of hydrophilic regions on super-hydrophobic surfaces. Uniform super-hydrophobic layer (Contact angle; CA > 150°, root mean square (RMS) roughness ∼0.28 nm) can be formed using the atmospheric radio frequency (RF) plasma on top of the selective hydrophilic (CA ∼ 70°, RMS roughness ∼0.34 nm) patterns imprinted by electrohydrodynamic (EHD) jet printing technology with polar alcohols (butyl carbitol or ethanol). The wettability of the modified surface was investigated qualitatively utilizing scanning electron microscopy (SEM), atomic force microscopy (AFM), and wavelength scanning interferometer (WSI). Secondary ion mass spectroscopy (SIMS) analysis showed that the alcohol addiction reaction changed the types of radicals on the super-hydrophobic surface. The wettability was found to depend sensitively on chemical radicals on the surface, not on surface morphology (particle size and surface roughness). Furthermore, three different kinds of representative hydrophilic samples (polystyrene nano-particle aqueous solution, Salmonella bacteria medium, and poly(3,4-ethylenediocythiophene) ink) were tested for uniform deposition onto the desired hydrophilic regions. This simple strategy would have broad applications in various research fields that require selective deposition of target materials.

RF plasma based selective modification of hydrophilic regions on super hydrophobic surface

International Nuclear Information System (INIS)

Lee, Jaehyun; Hwang, Sangyeon; Cho, Dae-Hyun; Hong, Jungwoo; Shin, Jennifer H.; Byun, Doyoung

2017-01-01

Highlights: • Simple and amenable reforming method for a substrate with disparate patterns of hydrophilic dots on super-hydrophobic surfaces is proposed. • Wettability characteristics and modification mechanism for the surfaces are conducted and revealed through SEM, AFM, WSI, and SIMS. • Several representative materials for various applications are successfully deposited. - Abstract: Selective modification and regional alterations of the surface property have gained a great deal of attention to many engineers. In this paper, we present a simple, a cost-effective, and amendable reforming method for disparate patterns of hydrophilic regions on super-hydrophobic surfaces. Uniform super-hydrophobic layer (Contact angle; CA > 150°, root mean square (RMS) roughness ∼0.28 nm) can be formed using the atmospheric radio frequency (RF) plasma on top of the selective hydrophilic (CA ∼ 70°, RMS roughness ∼0.34 nm) patterns imprinted by electrohydrodynamic (EHD) jet printing technology with polar alcohols (butyl carbitol or ethanol). The wettability of the modified surface was investigated qualitatively utilizing scanning electron microscopy (SEM), atomic force microscopy (AFM), and wavelength scanning interferometer (WSI). Secondary ion mass spectroscopy (SIMS) analysis showed that the alcohol addiction reaction changed the types of radicals on the super-hydrophobic surface. The wettability was found to depend sensitively on chemical radicals on the surface, not on surface morphology (particle size and surface roughness). Furthermore, three different kinds of representative hydrophilic samples (polystyrene nano-particle aqueous solution, Salmonella bacteria medium, and poly(3,4-ethylenediocythiophene) ink) were tested for uniform deposition onto the desired hydrophilic regions. This simple strategy would have broad applications in various research fields that require selective deposition of target materials.

Studies on polyurethane adhesives and surface modification of hydrophobic substrates

Science.gov (United States)

Krishnamoorthy, Jayaraman

studies involved making functionalized, thickness-controlled, wettability-controlled multilayers on hydrophobic substrates and the adsorption of carboxylic acid-terminated poly(styrene-b-isoprene) on alumina/silica substrates. Poly(vinyl alcohol) has been shown to adsorb onto hydrophobic surfaces irreversibly due to hydrophobic interactions. This thin semicrystalline coating is chemically modified using acid chlorides, butyl isocyanate and butanal to form thicker and hydrophobic coatings. The products of the modification reactions allow adsorption of a subsequent layer of poly(vinyl alcohol) that could subsequently be hydrophobized. This 2-step (adsorption/chemical modification) allows layer-by-layer deposition to prepare coatings with thickness, chemical structure and wettability control on any hydrophobic surface. Research on adsorption characteristics of carboxylic acid-terminated poly(styrene-b-isoprene) involved syntheses of block copolymers with the functional group present at specific ends. Comparative adsorption studies for carboxylic acid-terminated and hydrogen-terminated block copolymers was carried out on alumina and silica substrates.

Ion-solid interaction at low energies: principles and application of quantitative ISS

International Nuclear Information System (INIS)

Niehus, H.; Spitzl, R.

1991-01-01

Quantitative surface analysis with low-energy (500-5000 eV) ion scattering spectroscopy is known to be difficult, most often because of strong charge transfer and multiple scattering effects occurring during ion-surface interaction. In order to avoid neutralization problems, either alkali primary ions or noble gas ions in combination with the detection of all scattered particles was applied. Multiple scattering occurs predominantly at forward scattering and might confound the analysis. Backward scattering (i.e. 180 o impact collision ion scattering) bypasses strongly the multiple scattering complication and has been used successfully for the analysis of a number of surface structures for metals, semiconductors and binary alloys. A simple triangulation concept gives access to mass-selective qualitative surface crystallography. Quantitative surface structures were determined by comparison with computer simulations. (author)

Construction of Hydrophobic Wood Surface and Mechanical Property of Wood Cell Wall on Nanoscale Modified by Dimethyldichlorosilane

Science.gov (United States)

Yang, Rui; Wang, Siqun; Zhou, Dingguo; Zhang, Jie; Lan, Ping; Jia, Chong

2018-01-01

Dimethyldichlorosilane was used to improve the hydrophobicity of wood surface. The water contact angle of the treated wood surface increased from 85° to 143°, which indicated increased hydrophobicity. The nanomechanical properties of the wood cell wall were evaluated using a nanoindentation test to analyse the hydrophobic mechanism on the nano scale. The elastic modulus of the cell wall was significantly affected by the concentration but the influence of treatment time is insignificant. The hardness of the cell wall for treated samples was significantly affected by both treatment time and concentration. The interaction between treatment time and concentration was extremely significant for the elastic modulus of the wood cell wall.

Control of ion beam generation in intense short pulse laser target interaction

International Nuclear Information System (INIS)

Nagashima, T.; Izumiyama, T.; Barada, D.; Kawata, S.; Gu, Y.J.; Wang, W.M.; Ma, Y.Y.; Kong, Q.

2013-01-01

In intense laser plasma interaction, several issues still remain to be solved for future laser particle acceleration. In this paper we focus on a control of generation of high-energy ions. In this study, near-critical density plasmas are employed and are illuminated by high intensity short laser pulses; we have successfully generated high-energy ions, and also controlled ion energy and the ion energy spectrum by multiple-stages acceleration. We performed particle-in-cell simulations in this paper. The first near-critical plasma target is illuminated by a laser pulse, and the ions accelerated are transferred to the next target. The next identical target is also illuminated by another identical large pulse, and the ion beam introduced is further accelerated and controlled. In this study four stages are employed, and finally a few hundreds of MeV of protons are realized. A quasi-monoenergetic energy spectrum is also obtained. (author)

Effects of urea, metal ions and surfactants on the binding of baicalein with bovine serum albumin

Directory of Open Access Journals (Sweden)

Atanu Singha Roy

2016-08-01

Full Text Available The interaction of baicalein with bovine serum albumin (BSA was investigated with the help of spectroscopic and molecular docking studies. The binding affinity of baicalein towards BSA was estimated to be in order of 105 M−1 from fluorescence quenching studies. Negative ΔH° (−5.66±0.14 kJ/mol and positive (ΔS° (+79.96±0.65 J/mol K indicate the presence of electrostatic interactions along with the hydrophobic forces that result in a positive ΔS°. The hydrophobic association of baicalein with BSA diminishes in the presence of sodium dodecyl sulfate (SDS due to probable hydrophobic association of baicalein with SDS, resulting in a negative ΔS° (−40.65±0.87 J/mol K. Matrix-assisted laser desorption ionization/time of flight (MALDI--TOF experiments indicate a 1:1 complexation between baicalein and BSA. The unfolding and refolding phenomena of BSA were investigated in the absence and presence of baicalein using steady-state and fluorescence lifetime measurements. It was observed that the presence of urea ruptured the non-covalent interaction between baicalein and BSA. The presence of metal ions (Ag+, Mg2+, Ni2+, Mn2+, Co2+and Zn2+ increased the binding affinity of ligand towards BSA. The changes in conformational aspects of BSA after ligand binding were also investigated using circular dichroism (CD and Fourier transform infrared (FT-IR spectroscopic techniques. Site selectivity studies following molecular docking analyses indicated the binding of baicalein to site 1 (subdomain IIA of BSA.

Experimental evidence of beam-foil plasma creation during ion-solid interaction

Energy Technology Data Exchange (ETDEWEB)

Sharma, Prashant, E-mail: prashant@iuac.res.in; Nandi, Tapan [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

2016-08-15

Charge state evolution of the energetic projectile ions during the passage through thin carbon foils has been revisited using the X-ray spectroscopy technique. Contributions from the bulk and the solid surface in the charge changing processes have been segregated by measuring the charge state distribution of the projectile ions in the bulk of the target during the ion–solid interaction. Interestingly, the charge state distribution measured in the bulk exhibits Lorentzian profile in contrast to the well-known Gaussian structure observed using the electromagnetic methods and the theoretical predictions. The occurrence of such behavior is a direct consequence of the imbalance between charge changing processes, which has been seen in various cases of the laboratory plasma. It suggests that the ion-solid collisions constitute high-density, localized plasma in the bulk of the solid target, called the beam-foil plasma. This condensed beam-foil plasma is similar to the high-density solar and stellar plasma which may have practical implementations in various fields, in particular, plasma physics and nuclear astrophysics. The present work suggests further modification in the theoretical charge state distribution calculations by incorporating the plasma coupling effects during the ion–solid interactions. Moreover, the multi-electron capture from the target exit surface has been confirmed through comparison between experimentally measured and theoretically predicted values of the mean charge state of the projectile ions.

Switchable Super-Hydrophilic/Hydrophobic Indium Tin Oxide (ITO) Film Surfaces on Reactive Ion Etching (RIE) Textured Si Wafer.

Science.gov (United States)

Kim, Hwa-Min; Litao, Yao; Kim, Bonghwan

2015-11-01

We have developed a surface texturing process for pyramidal surface features along with an indium tin oxide (ITO) coating process to fabricate super-hydrophilic conductive surfaces. The contact angle of a water droplet was less than 5 degrees, which means that an extremely high wettability is achievable on super-hydrophilic surfaces. We have also fabricated a super-hydrophobic conductive surface using an additional coating of polytetrafluoroethylene (PTFE) on the ITO layer coated on the textured Si surface; the ITO and PTFE films were deposited by using a conventional sputtering method. We found that a super-hydrophilic conductive surface is produced by ITO coated on the pyramidal Si surface (ITO/Si), with contact angles of approximately 0 degrees and a resistivity of 3 x 10(-4) Ω x cm. These values are highly dependent on the substrate temperature during the sputtering process. We also found that the super-hydrophobic conductive surface produced by the additional coating of PTFE on the pyramidal Si surface with an ITO layer (PTFE/ITO/Si) has a contact angle of almost 160 degrees and a resistivity of 3 x 10(-4) Ω x cm, with a reflectance lower than 9%. Therefore, these processes can be used to fabricate multifunctional features of ITO films for switchable super-hydrophilic and super-hydrophobic surfaces.

Synthesis and toxicity evaluation of hydrophobic ionic liquids for volatile organic compounds biodegradation in a two-phase partitioning bioreactor

Energy Technology Data Exchange (ETDEWEB)

Rodriguez Castillo, Alfredo Santiago [Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7 (France); Université européenne de Bretagne (France); Guihéneuf, Solène, E-mail: solene.guiheneuf@wanadoo.fr [Université européenne de Bretagne, Université de Rennes 1, Sciences Chimiques de Rennes, UMR, CNRS 6226, Groupe Ingénierie Chimique & Molécules Pour le Vivant (ICMV), Bât. 10A, Campus de Beaulieu, Avenue du Général Leclerc, CS 74205, 35042 Rennes cedex (France); Le Guével, Rémy [Plate-forme ImPACcell Structure Fédérative de Recherche BIOSIT Université de Rennes 1, Bat. 8, Campus de Villejean, 2 Avenue du Pr. Leon Bernard, CS 34317, 35043 Rennes Cedex (France); Biard, Pierre-François [Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7 (France); Université européenne de Bretagne (France); and others

2016-04-15

Highlights: • Description of a VOC depollution system suitable with industrial processes, TPPB. • Novel association of TPPB and hydrophobic ionic liquids. • Synthesis of several hydrophobic ionic liquids designed to fit desired properties. • Toxicity evaluation of these ILs towards cells, animals and bacteria. - Abstract: Synthesis of several hydrophobic ionic liquids (ILs), which might be selected as good candidates for degradation of hydrophobic volatile organic compounds in a two-phase partitioning bioreactor (TPPB), were carried out. Several bioassays were also realized, such as toxicity evaluation on activated sludge and zebrafish, cytotoxicity, fluoride release in aqueous phase and biodegradability in order to verify their possible effects in case of discharge in the aquatic environment and/or human contact during industrial manipulation. The synthesized compounds consist of alkylimidazoliums, functionalized imidazoliums, isoqinoliniums, triazoliums, sulfoniums, pyrrolidiniums and morpholiniums and various counter-ions such as: PF{sub 6}{sup −}, NTf{sub 2}{sup −} and NfO{sup −}. Toxicity evaluation on activated sludge of each compound (5% v/v of IL) was assessed by using a glucose uptake inhibition test. Toxicity against zebrafish and cytotoxicity were evaluated by the ImPACCell platform of Rennes (France). Fluoride release in water was estimated by regular measurements using ion chromatography equipment. IL biodegradability was determined by measuring BOD{sub 28} of aqueous samples (compound concentration,1 mM). All ILs tested were not biodegradable; while some of them were toxic toward activated sludge. Isoquinolinium ILs were toxic to human cancerous cell lines. Nevertheless no toxicity was found against zebrafish Danio rerio. Only one IL released fluoride after long-time agitation.

Evaluation of hydrophobicity in PAH-contaminated soils during phytoremediation

International Nuclear Information System (INIS)

Cofield, Naressa; Banks, M. Katherine; Schwab, A. Paul

2007-01-01

The impact of recalcitrant organic compounds on soil hydrophobicity was evaluated in contaminated soil from a manufactured gas plant site following 12 months of phytoremediation. Significant reduction in soil wetting and water retention was observed in contaminated soil compared to an uncontaminated control. Phytoremediation was effective at reducing total PAHs by 69% with corresponding changes in soil classification from extremely hydrophobic (initial sample) to moderately-strongly hydrophobic (planted) and hydrophilic-very hydrophilic (unplanted) after 12 months. The greatest reduction in soil hydrophobicity was observed in the unplanted, unfertilized treatments that had the lowest removal rate of PAHs. The presence of plants may contribute to hydrophobicity in contaminated soil. - The presence of recalcitrant hydrophobic organic pollutants may enhance soil hydrophobicity

Ion-molecule interactions in crossed-beams

International Nuclear Information System (INIS)

Hansen, S.G.

1980-09-01

Interactions of the ions N + , F + , and CO 2 + with H 2 and/or its isotopes were examined using the crossed-beam technique in the low ( + ( 3 P) + H 2 → NH + + H, complex formation dominates up to 1.9 eV and a substantial interaction occurs between all collision partners up to 3.6 eV. The distribution of N + scattered nonreactively from H 2 also showed a long-lived complex channel below 1.9 eV. The reaction F + ( 3 P) + H 2 →FH + + H proceeded by a direct reaction mechanism at 0.20 to 1.07 eV. The reaction CO 2 + + D 2 → DCO 2 + + D gives asymmetric product distributions at 0.27 eV and above, indicating a direct reaction mechanism. Results indicated that there are probably barriers in the exit channels for DCO 2 + , DCO + , and D 2 O + products. The electronic state distributions of the N + , F + , and CO 2 + beams was investigated using beam attenuation and total luminescence techniques

Interaction of aluminium(3) with uranyl ions in the course of joint hydrolysis

International Nuclear Information System (INIS)

Yusov, A.B.; Budantseva, N.A.; Fedoseev, A.M.; Astafurova, L.N.

2001-01-01

By means of spectrophotometry, luminescence and IR-spectroscopy one studied interaction of uranyl ions with Al 3+ ions in solutions at pH≥2 and in precipitates at pH≥5. It is shown that within 3-4 pH range the uranyl hydrolyzed forms interact with these of aluminium. Mixed hydroxoaquacomplexes are likely to be formed in solution with U:Al = 1:1 molar ratio. Large-size mixed polymers may be formed with pH increase. Varying of precipitation pH from 5 up to 14 does not minimize the importance of the oligomer mixed compounds for precipitation formation [ru

Wave–particle interactions in a resonant system of photons and ion-solvated water

Energy Technology Data Exchange (ETDEWEB)

Konishi, Eiji, E-mail: konishi.eiji.27c@st.kyoto-u.ac.jp

2017-02-26

Highlights: • We consider a QED model of rotating water molecules with ion solvation effects. • The equations of motion are cast in terms of a conventional free electron laser. • We offer a new quantum coherence mechanism induced by collective instability. - Abstract: We investigate a laser model for a resonant system of photons and ion cluster-solvated rotating water molecules in which ions in the cluster are identical and have very low, non-relativistic velocities and direction of motion parallel to a static electric field induced in a single direction. This model combines Dicke superradiation with wave–particle interaction. As the result, we find that the equations of motion of the system are expressed in terms of a conventional free electron laser system. This result leads to a mechanism for dynamical coherence, induced by collective instability in the wave–particle interaction.

Three Dimensional Explicit Model for Cometary Tail Ions Interactions with Solar Wind

Science.gov (United States)

Al Bermani, M. J. F.; Alhamed, S. A.; Khalaf, S. Z.; Ali, H. Sh.; Selman, A. A.

2009-06-01

The different interactions between cometary tail and solar wind ions are studied in the present paper based on three-dimensional Lax explicit method. The model used in this research is based on the continuity equations describing the cometary tail-solar wind interactions. Three dimensional system was considered in this paper. Simulation of the physical system was achieved using computer code written using Matlab 7.0. The parameters studied here assumed Halley comet type and include the particle density rho, the particles velocity v, the magnetic field strength B, dynamic pressure p and internal energy E. The results of the present research showed that the interaction near the cometary nucleus is mainly affected by the new ions added to the plasma of the solar wind, which increases the average molecular weight and result in many unique characteristics of the cometary tail. These characteristics were explained in the presence of the IMF.

Salt effects on hydrophobic interaction and charge screening in the folding of a negatively charged peptide to a coiled coil (leucine zipper).

Science.gov (United States)

Jelesarov, I; Dürr, E; Thomas, R M; Bosshard, H R

1998-05-19

The stability of a coiled coil or leucine zipper is controlled by hydrophobic interactions and electrostatic forces between the constituent helices. We have designed a 30-residue peptide with the repeating seven-residue pattern of a coiled coil, (abcdefg)n, and with Glu in positions e and g of each heptad. The glutamate side chains prevented folding at pH values above 6 because of electrostatic repulsion across the helix dimer interface as well as within the individual helices. Protonation of the carboxylates changed the conformation from a random coil monomer to a coiled coil dimer. Folding at alkaline pH where the peptide had a net charge of -7e was promoted by the addition of salts. The nature of the charge screening cation was less important than that of the anion. The high salt concentrations (>1 M) necessary to induce folding indicated that the salt-induced folding resulted from alterations in the protein-water interaction. Folding was promoted by the kosmotropic anions sulfate and fluoride and to a lesser extent by the weak kosmotrope formate, whereas chloride and the strong chaotrope perchlorate were ineffective. Kosmotropes are excluded from the protein surface, which is preferentially hydrated, and this promotes folding by strengthening hydrophobic interactions at the coiled coil interface. Although charge neutralization also contributed to folding, it was effective only when the screening cation was partnered by a good kosmotropic anion. Folding conformed to a two-state transition from random coil monomer to coiled coil dimer and was enthalpy driven and characterized by a change in the heat capacity of unfolding of 3.9 +/- 1.2 kJ mol-1 K-1. The rate of folding was analyzed by fluorescence stopped-flow measurements. Folding occurred in a biphasic reaction in which the rapid formation of an initial dimer (kf = 2 x 10(7) M-1 s-1) was followed by an equally rapid concentration-independent rearrangement to the folded dimer (k > 100 s-1).

Nonlinear correlations in the hydrophobicity and average flexibility along the glycolytic enzymes sequences

Energy Technology Data Exchange (ETDEWEB)

Ciorsac, Alecu, E-mail: aleciorsac@yahoo.co [Politehnica University of Timisoara, Department of Physical Education and Sport, 2 P-ta Victoriei, 300006, Timisoara (Romania); Craciun, Dana, E-mail: craciundana@gmail.co [Teacher Training Department, West University of Timisoara, 4 Boulevard V. Pirvan, Timisoara, 300223 (Romania); Ostafe, Vasile, E-mail: vostafe@cbg.uvt.r [Department of Chemistry, West University of Timisoara, 16 Pestallozi, 300115, Timisoara (Romania); Laboratory of Advanced Researches in Environmental Protection, Nicholas Georgescu-Roegen Interdisciplinary Research and Formation Platform, 4 Oituz, Timisoara, 300086 (Romania); Isvoran, Adriana, E-mail: aisvoran@cbg.uvt.r [Department of Chemistry, West University of Timisoara, 16 Pestallozi, 300115, Timisoara (Romania); Laboratory of Advanced Researches in Environmental Protection, Nicholas Georgescu-Roegen Interdisciplinary Research and Formation Platform, 4 Oituz, Timisoara, 300086 (Romania)

2011-04-15

Research highlights: lights: We focus our study on the glycolytic enzymes. We reveal correlation of hydrophobicity and flexibility along their chains. We also reveal fractal aspects of the glycolytic enzymes structures and surfaces. The glycolytic enzyme sequences are not random. Creation of fractal structures requires the operation of nonlinear dynamics. - Abstract: Nonlinear methods widely used for time series analysis were applied to glycolytic enzyme sequences to derive information concerning the correlation of hydrophobicity and average flexibility along their chains. The 20 sequences of different types of the 10 human glycolytic enzymes were considered as spatial series and were analyzed by spectral analysis, detrended fluctuations analysis and Hurst coefficient calculation. The results agreed that there are both short range and long range correlations of hydrophobicity and average flexibility within investigated sequences, the short range correlations being stronger and indicating that local interactions are the most important for the protein folding. This correlation is also reflected by the fractal nature of the structures of investigated proteins.

Deciphering the perturbation effect of urea on the supramolecular host-guest interaction of biologically active hydrophobic molecule inside the nanocavity of cyclodextrins

Energy Technology Data Exchange (ETDEWEB)

Maity, Banibrata; Chatterjee, Aninda; Ahmed, Sayeed Ashique; Seth, Debabrata, E-mail: debabrata@iitp.ac.in

2017-03-15

The present work articulates the supramolecular interaction and the formation of host-guest complex between the biologically active hydrophobic coumarin derivative and cyclodextrins by using several spectroscopic, calorimetric and microscopic techniques. All the studies clearly revealed that in presence of cyclodextrins (CDs), coumarin forms 1:1 stoichiometric complex. From all the study, we have found that with gradual increasing the cavity diameter of the hosts, the binding efficiency of the complexes gradually increases. The small population of the non emissive twisted intramolecular charge transfer (TICT) state of coumarin molecule turns into highly emissive in presence of γ-CD owing to its greater cavity diameter. The emissive TICT band is not found in β-CD complex due to its comparative small hydrophilic exterior and less polar environment. The present finding also interpret the perturbation effect of urea on host-guest complexes. In the presence of urea, the TICT emissive band of γ-CD is completely diminished. From, {sup 1}H NMR study it was observed that –NEt{sub 2} moiety of 7-DCCAE molecule is deeply buried inside the hydrophobic cavity of the CDs and forms host-guest complexes. Isothermal titration calorimetry measurement also indicates the formation of 1:1 host-guest complexes.

Interaction of relativistic H- ions with thin foils

International Nuclear Information System (INIS)

Mohagheghi, A.H.

1990-09-01

The response of relativistic H - ions to thin carbon foils was investigated for beam energies ranging from 226 MeV to 800 MeV. For the foil thicknesses we have studied, ranging from 15 to 300 μg/cm 2 , an appreciable fraction of the H - beam survives intact, some H - ions are stripped down to protons, and the remainder is distributed over the states of H 0 . This experiment is different from the low energy studies in that the projectile velocity is comparable to the speed of light, leading to an interaction time of typically less than a femtosecond. The present results challenge the theoretical understanding of the interaction mechanisms. An electron spectrometer was used to selectively field-ionize the Rydberg states, 9 < n < 17, at beam energies of 581 MeV and 800 MeV. The yield of low-lying states were measured by Doppler tuning a Nd:YAG laser to excite transitions to a Rydberg state which was then field-ionized and detected. A simple model is developed to fit the yield of each state as a function of foil thickness. The simple model is successful in predicting the general features of the yield data. However, the data are suggestive of a more complex structure in the yield curves. The yield of a given state depends strongly on the foil thickness, demonstrating that the excited states are formed during the passage of the ions through a foil. The optimum thickness to produce a given state increases with the principal quantum number of the state suggesting an excitation process which is at least pratially stepwise. The results of a Monte Carlo simulation are compared with the experimental data to estimate the distribution of the excited states coming out of a foil. The distributions of the excited states and their dependence on foil thickness are discussed

Electron-electron interaction and transfer ionization in fast ion-atom collisions

International Nuclear Information System (INIS)

Voitkiv, A B

2008-01-01

Recently it was pointed out that electron capture occurring in fast ion-atom collisions can proceed via a mechanism which earlier was not considered. In the present paper we study this mechanism in more detail. Similarly as in radiative capture, where the electron transfer occurs due to the interaction with the radiation field and proceeds via emission of a photon, within this mechanism the electron capture is caused by the interaction with another atomic electron leading mainly to the emission of the latter. In contrast to the electron-electron Thomas capture, this electron-electron (E-E) mechanism is basically a first-order one having similarities to the kinematic and radiative capture channels. It also possesses important differences with the latter two. Leading to transfer ionization, this first-order capture mechanism results in the electron emission mainly in the direction opposite to the motion of the projectile ion. The same, although less pronounced, feature is also characteristic for the momenta of the target recoil ions produced via this mechanism. It is also shown that the action of the E-E mechanism is clearly seen in recent experimental data on the transfer ionization in fast proton-helium collisions.

FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions

Science.gov (United States)

Gerbino, E.; Mobili, P.; Tymczyszyn, E.; Fausto, R.; Gómez-Zavaglia, A.

2011-02-01

FTIR spectroscopy was used to structurally characterize the interaction of S-layer proteins extracted from two strains of Lactobacillus kefir (the aggregating CIDCA 8348 and the non-aggregating JCM 5818) with metal ions (Cd +2, Zn +2, Pb +2 and Ni +2). The infrared spectra indicate that the metal/protein interaction occurs mainly through the carboxylate groups of the side chains of Asp and Glut residues, with some contribution of the NH groups belonging to the peptide backbone. The frequency separation between the νCOO - anti-symmetric and symmetric stretching vibrations in the spectra of the S-layers in presence of the metal ions was found to be ca. 190 cm -1 for S-layer CIDCA 8348 and ca. 170 cm -1 for JCM 5818, denoting an unidentate coordination in both cases. Changes in the secondary structures of the S-layers induced by the interaction with the metal ions were also noticed: a general trend to increase the amount of β-sheet structures and to reduce the amount of α-helices was observed. These changes allow the proteins to adjust their structure to the presence of the metal ions at minimum energy expense, and accordingly, these adjustments were found to be more important for the bigger ions.

Application of retention modelling to the simulation of separation of organic anions in suppressed ion chromatography.

Science.gov (United States)

Zakaria, Philip; Dicinoski, Greg W; Ng, Boon Khing; Shellie, Robert A; Hanna-Brown, Melissa; Haddad, Paul R

2009-09-18

The ion-exchange separation of organic anions of varying molecular mass has been demonstrated using ion chromatography with isocratic, gradient and multi-step eluent profiles on commercially available columns with UV detection. A retention model derived previously for inorganic ions and based solely on electrostatic interactions between the analytes and the stationary phase was applied. This model was found to accurately describe the observed elution of all the anions under isocratic, gradient and multi-step eluent conditions. Hydrophobic interactions, although likely to be present to varying degrees, did not limit the applicability of the ion-exchange retention model. Various instrumental configurations were investigated to overcome problems associated with the use of organic modifiers in the eluent which caused compatibility issues with the electrolytically derived, and subsequently suppressed, eluent. The preferred configuration allowed the organic modifier stream to bypass the eluent generator, followed by subsequent mixing before entering the injection valve and column. Accurate elution prediction was achieved even when using 5-step eluent profiles with errors in retention time generally being less than 1% relative standard deviation (RSD) and all being less than 5% RSD. Peak widths for linear gradient separations were also modelled and showed good agreement with experimentally determined values.

Durability of hydrophobic treatment of concrete

NARCIS (Netherlands)

Vries, J. de; Polder, R.B.; Borsje, H.

1998-01-01

The subject of this study was the performance of hydrophobic treatment to protect concrete against chloride penetration from de-icing salts. Hydrophobic treatment makes a concrete surface absorb less water and less chloride. Test methods and requirements for commercial products were established. In

Interaction of singly and multiply charged ions with a lithium-fluoride surface

International Nuclear Information System (INIS)

Wirtz, L.

2001-10-01

Charge transfer between slow ions and an ionic crystal surface still poses a considerable challenge to theory due to the intrinsic many-body character of the system. For the neutralization of multiply charged ions in front of metal surfaces, the Classical Over the Barrier (COB) model is a widely used tool. We present an extension of this model to ionic crystal surfaces where the localization of valence electrons at the anion sites and the lack of cylindrical symmetry of the ion-surface system impede a simple analytical estimate of electron transfer rates. We use a classical trajectory Monte Carlo approach to calculate electron transfer rates for different charge states of the projectile ion. With these rates we perform a Monte Carlo simulation of the neutralization of slow Ne10+ ions in vertical incidence on an LiF surface. Capture of one or several electrons may lead to a local positive charge up of the surface. The projectile dynamics depends on the balance between the repulsion due to this charge and the attraction due to the self-image potential. In a simulation that treats electronic and nuclear dynamics simultaneously, we show that the image attraction dominates over the repulsive force. Backscattering of very slow multiply charged projectiles high above the surface without touching it ('trampoline effect') does not take place. Instead, the projectile ion penetrates into the surface or is reflected due to close binary collision with surface ions. The case of a singly charged ion in front of an LiF surface is within the reach of ab-initio calculations. We use a multi-configuration self consistent field (MCSCF) and a multi-reference configuration interaction (MR-CI) method to calculate adiabatic potential energy curves for a system consisting of the projectile ion and an embedded cluster of surface ions. With increasing cluster size, the energy levels of the embedded cluster converge towards the band structure of the infinitely extended solid. Due to

Electromagnetic Waves Dispersion and Interaction of an Annular Beam-Ion Channel System in Plasma Waveguide

Directory of Open Access Journals (Sweden)

Jixiong Xiao

2017-01-01

Full Text Available A linear theory for the electromagnetic properties and interactions of an annular beam-ion channel system in plasma waveguide is presented. The dispersion relations for two families of propagating modes, including the electrostatic and transverse magnetic modes, are derived. The dependencies of the dispersion behavior and interaction for different wave modes on the thickness of the annular beam and betatron oscillation frequency are studied in detail by numerical calculations. The results show that the inner and outer radii of the beam have different influences on propagation properties of the electrostatic and electromagnetic modes with different betatron oscillation parameters. In the weak ion channel situation, the two types of electrostatic waves, that is, space charge and betatron modes, have no interaction with the transverse magnetic modes. However, in the strong ion channel situation, the transverse magnetic modes will have two branches and a low frequency mode emerged as the new branch. In this case, compared with the solid beam case, the betatron modes not only can interact with the high frequency branch at small wavenumber but also can interact with the low frequency branch at large wavenumber.

Experiments on the interaction of heavy ions with dense plasma at GSI-Darmstadt

International Nuclear Information System (INIS)

Stoeckl, C.; Boine-Frankenheim, O.; Geissel, M.; Roth, M.; Wetzler, H.; Seelig, W.; Iwase, O.; Spiller, P.; Bock, R.; Suess, W.; Hoffmann, D.H.H.

1998-01-01

One of the main objectives of the experimental plasma physics activities at the Gesellschaft fuer Schwerionenforschung (GSI) are the interaction processes of heavy ions with dense ionized matter. Gas-discharge plasma targets were used for energy loss and charge state measurements in a regime of electron density and temperature up to 10 19 cm -3 and 20 eV, respectively. An improved model of the charge exchange processes in fully ionized hydrogen plasma, taking into account multiple excited electronic configurations which subsequently ionize, has removed the discrepancies of previous theoretical descriptions. The energy loss of the ion beam in partially ionized plasmas such as argon was found to agree very well with our simple theoretical model based on the modified Bethe-Bloch theory. A new setup with a 100 J/5 GW Nd-glass laser now provides access to density ranges up to 10 21 cm -3 and temperatures of up to 100 eV. First results of interaction experiments with laser-produced plasma are presented. To fully exploit the experimental possibilities of the new laser-plasma setup both improved charge state detection systems and better plasma diagnostics are indispensable. Present developments and future possibilities in these fields are presented. This paper summarizes the following contributions: Interaction of heavy-ion beams with laser plasma by C. Stoeckl et al. Energy loss of heavy ions in a laser-produced plasma by M. Roth et al. Charge state measurements of heavy ions passing a laser produced plasma with high time resolution by W. Suess et al. Plasma diagnostics for laser-produced plasma by O. Iwase et al. Future possibilities of plasma diagnostics at GSI by M. Geissel et al. (orig.)

Nanomechanical probing of soft matter through hydrophobic AFM tips fabricated by two-photon polymerization

International Nuclear Information System (INIS)

Suriano, Raffaella; De Marco, Carmela; Turri, Stefano; Zandrini, Tommaso; Osellame, Roberto; Bragheri, Francesca

2016-01-01

Atomic force microscopy (AFM) nanoindentation of soft materials is a powerful tool for probing mechanical properties of biomaterials. Though many results have been reported in this field over the last decade, adhesion forces between the tip and the sample hinder the elastic modulus measurement when hydrophilic soft samples are investigated. Here, two-photon polymerization (2PP) technology was used to fabricate hydrophobic perfluoropolyether-based AFM tips. The hydrophobic 2PP tips allowed us to overcome the limitations of commercial and functionalized tips as well as to successfully measure the elastic modulus of medically relevant soft materials in air. Our results obtained in the characterization of poly(dimethyl siloxane) and polyethylene glycol hydrogels showed lower adhesion forces over a larger measurement range when compared to measurements performed with commercial tips. The elastic moduli measured by means of hydrophobic 2PP AFM tips were also found to be comparable to those obtained using conventional techniques for macroscopic samples. We successfully showed that the hydrophobic AFM tips developed by this highly versatile technology enable the study of mechanical properties of soft matter, benefiting from reduced sample–tip interactions, and a custom-made shape and dimension of the tips. (paper)

Durability of hydrophobic treatment of concrete

NARCIS (Netherlands)

Vries, J. de; Polder, R.B.; Borsje, H.

1998-01-01

The subject of this study was the performance of hydrophobic treatment to protect concrete against chloride penetration from de-icing salts. Hydrophobic treatment makes a concrete surface absorb less water and less chloride. Several types of tests were carried out to study the performance of

Hydrophobic Modification of Layered Clays and Compatibility for Epoxy Nanocomposites

Directory of Open Access Journals (Sweden)

Jiang-Jen Lin

2010-04-01

Full Text Available Recent studies on the intercalation and exfoliation of layered clays with polymeric intercalating agents involving poly(oxypropylene-amines and the particular uses for epoxy nanocomposites are reviewed. For intercalation, counter-ionic exchange reactions of clays including cationic layered silicates and anionic Al-Mg layered double hydroxide (LDH with polymeric organic ions afforded organoclays led to spatial interlayer expansion from 12 to 92 Å (X-ray diffraction as well as hydrophobic property. The inorganic clays of layered structure could be modified by the poly(oxypropyleneamine-salts as the intercalating agents with molecular weights ranging from 230 to 5,000 g/mol. Furthermore, natural montmorillonite (MMT clay could be exfoliated into thin layer silicate platelets (ca. 1 nm thickness in one step by using polymeric types of exfoliating agents. Different lateral dimensions of MMT, synthetic fluorinated Mica and LDH clays had been cured into epoxy nanocomposites. The hydrophobic amine-salt modification resulting in high spacing of layered or exfoliation of individual clay platelets is the most important factor for gaining significant improvements of properties. In particular, these modified clays were reported to gain significant improvements such as reduced coefficient of thermal expansion (CTE, enhanced thermal stability, and hardness. The utilization of these layered clays for initiating the epoxy self-polymerization was also reported to have a unique compatibility between clay and organic resin matrix. However, the matrix domain lacks of covalently bonded crosslink and leads to the isolation of powder material. It is generally concluded that the hydrophobic expansion of the clay inter-gallery spacing is the crucial step for enhancing the compatibility and the ultimate preparation of the advanced epoxy materials.

Hydrophobic Modification of Layered Clays and Compatibility for Epoxy Nanocomposites

Science.gov (United States)

Lin, Jiang-Jen; Chan, Ying-Nan; Lan, Yi-Fen

2010-01-01

Recent studies on the intercalation and exfoliation of layered clays with polymeric intercalating agents involving poly(oxypropylene)-amines and the particular uses for epoxy nanocomposites are reviewed. For intercalation, counter-ionic exchange reactions of clays including cationic layered silicates and anionic Al-Mg layered double hydroxide (LDH) with polymeric organic ions afforded organoclays led to spatial interlayer expansion from 12 to 92 Å (X-ray diffraction) as well as hydrophobic property. The inorganic clays of layered structure could be modified by the poly(oxypropylene)amine-salts as the intercalating agents with molecular weights ranging from 230 to 5,000 g/mol. Furthermore, natural montmorillonite (MMT) clay could be exfoliated into thin layer silicate platelets (ca. 1 nm thickness) in one step by using polymeric types of exfoliating agents. Different lateral dimensions of MMT, synthetic fluorinated Mica and LDH clays had been cured into epoxy nanocomposites. The hydrophobic amine-salt modification resulting in high spacing of layered or exfoliation of individual clay platelets is the most important factor for gaining significant improvements of properties. In particular, these modified clays were reported to gain significant improvements such as reduced coefficient of thermal expansion (CTE), enhanced thermal stability, and hardness. The utilization of these layered clays for initiating the epoxy self-polymerization was also reported to have a unique compatibility between clay and organic resin matrix. However, the matrix domain lacks of covalently bonded crosslink and leads to the isolation of powder material. It is generally concluded that the hydrophobic expansion of the clay inter-gallery spacing is the crucial step for enhancing the compatibility and the ultimate preparation of the advanced epoxy materials.

Interplay of Electrostatics and Hydrophobic Effects in the Metamorphic Protein Human Lymphotactin.

Science.gov (United States)

Korkmaz, Elif Nihal; Volkman, Brian F; Cui, Qiang

2015-07-30

The human lymphotactin (hLtn) is a protein that features two native states both of which are physiologically relevant: it is a monomer (hLtn10) at 10 °C with 200 mM salt and a dimer (hLtn40) at 40 °C and without salt. Here we focus on the networks of electrostatic and hydrophobic interactions that display substantial changes upon the conversion from hLtn10 to hLtn40 since they are expected to modulate the relative stability of the two folds. In addition to the Arg 23-Arg 43 interaction discussed in previous work, we find several other like-charge pairs that are likely important to the stability of hLtn10. Free energy perturbation calculations are carried out to explicitly evaluate the contribution of the Arg 23-Arg 43 interaction to the hLtn10 stability. hLtn40 features a larger number of salt bridges, and a set of hydrophobic residues undergo major changes in the solvent accessible surface area between hLtn10 and hLtn40, pointing to their importance to the relative stability of the two folds. We also discuss the use of explicit and implicit solvent simulations for characterizing the conformational ensembles under different solution conditions.

Mechanistic insights into the interaction between energetic oxygen ions and nanosized ZnFe2O4: XAS-XMCD investigations.

Science.gov (United States)

Singh, Jitendra Pal; Kaur, Baljeet; Sharma, Aditya; Kim, So Hee; Gautam, Sanjeev; Srivastava, Ramesh Chandra; Goyal, Navdeep; Lim, Weol Cheol; Lin, H-J; Chen, J M; Asokan, K; Kanjilal, D; Won, Sung Ok; Lee, Ik-Jae; Chae, Keun Hwa

2018-04-20

The interactions of energetic ions with multi-cation compounds and their consequences in terms of changes in the local electronic structure, which may facilitate intriguing hybridization between O 2p and metal d orbitals and magnetic ordering, are the subject of debate and require a deep understanding of energy transfer processes and magnetic exchange mechanisms. In this study, nanocrystals of ZnFe2O4 were exposed to O7+ ions with an energy of 100 MeV to understand, qualitatively and quantitatively, the metal-ligand field interactions, cation migration and magnetic exchange interactions by employing X-ray absorption fine structure measurements and X-ray magnetic circular dichroism to get deeper mechanistic insights. Nanosized zinc ferrite nanoparticles (NPs) with a size of ∼16 nm synthesized in the cubic spinel phase exhibited deterioration of the crystalline phase when 100 MeV O7+ ions passed through them. However, the size of these NPs remained almost the same. The behaviour of crystal deterioration is associated with the confinement of heat in this interaction. The energy confined inside the nanoparticles promotes cation redistribution as well as the modification of the local electronic structure. Prior to this interaction, almost 42% of Zn2+ ions occupied AO4 tetrahedra; however, this value increased to 63% after the interaction. An inverse effect was observed for metal ion occupancies in BO6 octahedra. The L-edge spectra of Fe and Zn reveal that the spin and valence states of the metal ions were not affected by this interaction. This effect is also supported by K-edge measurements for Fe and Zn. The t2g/eg intensity ratio in the O K-edge spectra decreased after this interaction, which is associated with detachment of Zn2+ ions from the lattice. The extent of hybridization, as estimated from the ratio of the post-edge to the pre-edge region of the O K-edge spectra, decreased after this interaction. The metal-oxygen and metal-metal bond lengths were modified

Interaction between counter-streaming ion-acoustic solitons and the Langmuir waves

International Nuclear Information System (INIS)

Basovich, A.Ya.; Gromov, E.M.; Talanov, V.I.

1984-01-01

The interaction between strong counter-streaming ion-acoustic solitons and the Langmuir waves is considered. At first the Langmuir waves spectrum transformation by counter-streaming ion-acoustic solutions of a preset amplitude e has been found. An increase in the frequency and number of the Langmuir waves due to the Doppler effect in the course of multiple reflection from the f front soliton slope has been determined and the wave number range in which the confinement of the Langmuir waves by counter-streaning solitons is possible has s been found. It is shown that the time of the Langmuir wave transformation into the short-wave region under the effect of the counter-streaming soliton may y be short as compared with the time of the Langmuir wave diffusion into the Landau damping region under the effect of random fields of ion-acoustic waves. In the adiabatic fpproximation changes in the counter-streaming ion acoustic parameters of solitons owing to the Langmuir waves have been

Interactions between electrons in the field of a positive ion

International Nuclear Information System (INIS)

Heideman, A.G.M.; Eck, J. van.

1976-01-01

Recent studies on the (auto)ionization of atoms by means of electron-atom collisions reveal the existence of phenomena probably brought about by post-collision interactions in the vicinity of a positive ion. In this article, a review of the subject is given in relation to the research program of the Utrecht atomic physics group

Membrane interactions of ionic liquids and imidazolium salts.

Science.gov (United States)

Wang, Da; Galla, Hans-Joachim; Drücker, Patrick

2018-06-01

Room-temperature ionic liquids (RTILs) have attracted considerable attention in recent years due to their versatile properties such as negligible volatility, inflammability, high extractive selectivity and thermal stability. In general, RTILs are organic salts with a melting point below ~100 °C determined by the asymmetry of at least one of their ions. Due to their amphiphilic character, strong interactions with biological materials can be expected. However, rising attention has appeared towards their similarity and interaction with biomolecules. By employing structural modifications, the biochemical properties of RTILs can be designed to mimic lipid structures and to tune their hydrophobicity towards a lipophilic behavior. This is evident for the interaction with lipid-membranes where some of these compounds present membrane-disturbing effects or cellular toxicity. Moreover, they can form micelles or lipid-like bilayer structures by themselves. Both aspects, cellular effects and membrane-forming capacities, of a novel class of lipophilic imidazolium salts will be discussed.

Surface Hydrophobicity Causes SO2 Tolerance in Lichens

Science.gov (United States)

Hauck, Markus; Jürgens, Sascha-René; Brinkmann, Martin; Herminghaus, Stephan

2008-01-01

Background and Aims The superhydrophobicity of the thallus surface in one of the most SO2-tolerant lichen species, Lecanora conizaeoides, suggests that surface hydrophobicity could be a general feature of lichen symbioses controlling their tolerance to SO2. The study described here tests this hypothesis. Methods Water droplets of the size of a raindrop were placed on the surface of air-dry thalli in 50 lichen species of known SO2 tolerance and contact angles were measured to quantify hydrophobicity. Key Results The wettability of lichen thalli ranges from strongly hydrophobic to strongly hydrophilic. SO2 tolerance of the studied lichen species increased with increasing hydrophobicity of the thallus surface. Extraction of extracellular lichen secondary metabolites with acetone reduced, but did not abolish the hydrophobicity of lichen thalli. Conclusions Surface hydrophobicity is the main factor controlling SO2 tolerance in lichens. It presumably originally evolved as an adaptation to wet habitats preventing the depression of net photosynthesis due to supersaturation of the thallus with water. Hydrophilicity of lichen thalli is an adaptation to dry or humid, but not directly rain-exposed habitats. The crucial role of surface hydrophobicity in SO2 also explains why many markedly SO2-tolerant species are additionally tolerant to other (chemically unrelated) toxic substances including heavy metals. PMID:18077467

Hypothetical interaction mechanisms for heavy-ion collisions between 20 and 50 MeV/u

International Nuclear Information System (INIS)

Ngo, C.; Dalili, D.; Lucas, R.

1985-01-01

A brief survey of some aspects of heavy-ion interaction mechanisms, at bombarding energies between 20 and 50 MeV/u is presented. The maximum energy content of a nuclear system, the most probable linear momentum transfer and the possible existence of a ''calefaction'' phenomenon in heavy-ion collisions have also been investigated

Motion of the plasma critical layer during relativistic-electron laser interaction with immobile and comoving ion plasma for ion acceleration

International Nuclear Information System (INIS)

Sahai, Aakash A.

2014-01-01

We analyze the motion of the plasma critical layer by two different processes in the relativistic-electron laser-plasma interaction regime (a 0 >1). The differences are highlighted when the critical layer ions are stationary in contrast to when they move with it. Controlling the speed of the plasma critical layer in this regime is essential for creating low-β traveling acceleration structures of sufficient laser-excited potential for laser ion accelerators. In Relativistically Induced Transparency Acceleration (RITA) scheme, the heavy plasma-ions are fixed and only trace-density light-ions are accelerated. The relativistic critical layer and the acceleration structure move longitudinally forward by laser inducing transparency through apparent relativistic increase in electron mass. In the Radiation Pressure Acceleration (RPA) scheme, the whole plasma is longitudinally pushed forward under the action of the laser radiation pressure, possible only when plasma ions co-propagate with the laser front. In RPA, the acceleration structure velocity critically depends upon plasma-ion mass in addition to the laser intensity and plasma density. In RITA, mass of the heavy immobile plasma-ions does not affect the speed of the critical layer. Inertia of the bared immobile ions in RITA excites the charge separation potential, whereas RPA is not possible when ions are stationary

Yeast enolase: mechanism of activation by metal ions.

Science.gov (United States)

Brewer, J M

1981-01-01

Yeast enolase as prepared by current procedures is inherently chemically homogeneous, though deamidation and partial denaturation can produce electrophoretically distinct forms. A true isozyme of the enzyme exists but does not survive the purification procedure. The chemical sequence for both has been established. The enzyme behaves in solution like a compact, nearly spherical molecule of moderate hydration. Strong intramolecular forces maintain the structure of the individual subunits. The enzyme as isolated is dimeric. If dissociated in the presence of magnesium ions and substrate, then the subunits are active, but if the dissociation occurs in the absence of metal ions, they are inactive until they have reassociated and undergone a first order "annealing" process. Magnesium (II) enhances association. The interaction between the subunits is hydrophobic in character. The enzyme can bind up to 2 mol of most metal ions in "conformational" sites which then allows up to 2 mol of substrate or some substrate analogue to bind. This is not sufficient for catalysis, but conformational metal ions do more than just allow substrate binding. A change in the environment of the metal ions occurs on substrate or substrate analogue binding. There is an absolute correlation between the occurrence of a structural change undergone by the 3-amino analogue of phosphoenolpyruvate and whether the metal ions produce any level of enzymatic activity. For catalysis, two more moles of metal ions, called "catalytic", must bind. There is evidence that the enzymatic reaction involves a carbanion mechanism. It is likely that two more moles of metal ion can bind which inhibit the reaction. The requirement for 2 mol of metal ion per subunit which contribute in different ways to catalysis is exhibited by a number of other enzymes.

Modeling, investigation and formulation of hydrophobic coatings for potential self-cleaning applications

Science.gov (United States)

Rios, Pablo Fabian

Self-cleaning surfaces have received a great deal of attention, both in research and commercial applications. Transparent and non-transparent self-cleaning surfaces are highly desired. The Lotus flower is a symbol of purity in Asian cultures, even when rising from muddy waters it stays clean and untouched by dirt. The Lotus leaf "self-cleaning" surface is hydrophobic and rough, showing a two-layer morphology. While hydrophobicity produces a high contact angle, surface morphology reduces the adhesion of dirt and water to the surface, thus water drops slide easily across the leaf carrying the dirt particles with them. Nature example in the Lotus-effect and extensive scientific research on related fields have rooted wide acceptance that high hydrophobicity can be obtained only by a proper combination of surface chemistry and roughness. Most researchers relate hydrophobicity to a high contact angle. However, the contact angle is not the only parameter that defines liquid-solid interactions. An additional parameter, the sliding angle, related to the adhesion between the liquid drop and the solid surface is also important in cases where liquid sliding is involved, such as self-cleaning applications. In this work, it is postulated that wetting which is related to the contact angle, and interfacial adhesion, which is related to the sliding angle, are interdependent phenomena and have to be considered simultaneously. A variety of models that relate the sliding angle to forces developed along the contact line between a liquid drop and a solid surface have been proposed in the literature. A new model is proposed here that quantifies the drop sliding phenomenon, based also on the interfacial adhesion across the contact area of the liquid/solid interface. The effects of roughness and chemical composition on the contact and sliding angles of hydrophobic smooth and rough surfaces were studied theoretically and experimentally. The validity of the proposed model was investigated

Heat-resistant hydrophobic-oleophobic coatings

OpenAIRE

Uyanik, Mehmet; Arpac, Ertugrul; Schmidt, Helmut K.; Akarsu, Murat; Sayilkan, Funda; Sayilkan, Hikmet

2006-01-01

Thermally and chemically durable hydrophobic oleophobic coatings, containing different ceramic particles such as SiO2, SiC, Al 2O3, which can be alternative instead of Teflon, have been developed and applied on the aluminum substrates by spin-coating method. Polyimides, which are high-thermal resistant heteroaromatic polymers, were synthesized, and fluor oligomers were added to these polymers to obtain hydrophobic-oleophobic properties. After coating, Al surface was subjected to Taber-abrasio...

Interaction of intersteller pick-up ions with the solar wind

International Nuclear Information System (INIS)

Mobius, E.; Klecker, B.; Hovestadt, D.; Scholer, M.

1988-01-01

The interaction of interstellar pick-up ions with the solar wind is studied by comparing a model for the velocity distribution function of pick-up ions with actual measurements of He + ions in the solar wind. The model includes the effects of pitch-angle diffusion due to interplanetary Alfven waves, adiabatic deceleration in the expanding solar wind and the radial variation of the source function. It is demonstrated that the scattering mean free path is in the range ≤0.1 AU and that energy diffusion can be neglected as compared with adiabatic deceleration. The effects of adiabatic focusing, of the radial variation of the neutral density and of an variation of the solar wind velocity with distance from the Sun are investigated. With the correct choice of these parameters the authors can model the measured energy spectra of the pick-up ions does not vary with the solar wind velocity and the direction of the interplanetary magnetic field for a given local neutral gas density and ionization rate. Therefore, the comparison of the model distributions with the measurements leads to a quantitative determination of the local interstellar gas density

Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity

Directory of Open Access Journals (Sweden)

Adewale Adewuyi

2017-09-01

Full Text Available Cellulose (SC isolated from sesame seed (SS was surface modified with the introduction of an ester functional group via a simple reaction to produce the modified product (SA. SS, SC and SA were characterized using Fourier transform infrared (FTIR, X-ray diffraction (XRD, thermogravimetric analysis (TG, particle size distribution (PSD, zeta potential and scanning electron microscopy (SEM. SC and SA were evaluated for their water holding capacity (WC, oil holding capacity (OC, swelling capacity (SW and their ability to adsorb heavy metals. The FTIR revealed peaks corresponding to the formation of the ester functional group at the surface of SA. The crystallinity of SC was 28.02% but after the modification, it increased to 77.03% in SA. The PSD of SC and SA was both monomodal with sizes of 10.1305 μm in SC and 10.2511 μm in SA. The adsorption capacity of SC towards Pb (II and Cu (II ions was higher than that of SA. However, SA was unable to adsorb Cu (II ions. SA exhibited the lower WC and SW values as compared to SC which suggested an improved hydrophobicity after the modification. This study has shown that hydrophobicity can be improved in cellulose via surface modification.

Fish skin bacteria: Colonial and cellular hydrophobicity.

Science.gov (United States)

Sar, N; Rosenberg, E

1987-05-01

Bacteria were desorbed from the skin of healthy, fast-swimming fish by several procedures, including brief exposure to sonic oscillation and treatment with nontoxic surface active agents. The surface properties of these bacteria were studied by measuring their adhesion to hexadecane, as well as by a newly developed, simple method for studying the hydrophobicity of bacterial lawns. This method, referred to as the "Direction of Spreading" (DOS) method, consists of recording the direction to which a water drop spreads when introduced at the border between bacterial lawns and other surfaces. Of the 13 fish skin isolates examined, two strains were as hydrophobic as polystyrene by the DOS method. Suspended cells of one of these strains adhered strongly to hexadecane (84%), whereas cells of the other strain adhered poorly (13%). Another strain which was almost as hydrophobic as polystyrene by the DOS method did not adhere to hexadecane at all. Similarly, lawns of three other strains were more hydrophobic than glass by the DOS method, but cell suspensions prepared from these colonies showed little or no adhesion to hexadecane. The high colonial but relatively low cellular hydrophobicity could be due to a hydrophobic slime that is removed during the suspension and washing procedures. The possibility that specific bacteria assist in fish locomotion by changing the surface properties of the fish skin and by producing drag-reducing polymers is discussed.

DFT study of the interaction between DOTA chelator and competitive alkali metal ions.

Science.gov (United States)

Frimpong, E; Skelton, A A; Honarparvar, B

2017-09-01

1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetracetic acid (DOTA) is an important chelator for radiolabeling of pharmaceuticals. The ability of alkali metals found in the body to complex with DOTA and compete with radio metal ions can alter the radiolabeling process. Non-covalent interactions between DOTA complexed with alkali metals Li + , Na + , K + and Rb + , are investigated with density functional theory using B3LYP and ωB97XD functionals. Conformational possibilities of DOTA were explored with a varying number of carboxylic pendant arms of DOTA in close proximity to the ions. It is found that the case in which four arms of DOTA are interacting with ions is more stable than other conformations. The objective of this study is to explore the electronic structure properties upon complexation of alkali metals Li + Na + , K + and Rb + with a DOTA chelator. Interaction energies, relaxation energies, entropies, Gibbs free energies and enthalpies show that the stability of DOTA, complexed with alkali metals decreases down the group of the periodic table. Implicit water solvation affects the complexation of DOTA-ions leading to decreases in the stability of the complexes. NBO analysis through the natural population charges and the second order perturbation theory, revealed a charge transfer between DOTA and alkali metals. Conceptual DFT-based properties such as HOMO/LUMO energies, ΔE HOMO-LUMO and chemical hardness and softness indicated a decrease in the chemical stability of DOTA-alkali metal complexes down the alkali metal series. This study serves as a guide to researchers in the field of organometallic chelators, particularly, radiopharmaceuticals in finding the efficient optimal match between chelators and various metal ions. Copyright © 2017 Elsevier Inc. All rights reserved.

The Manipulation of Hydrophobicity in Catalyst Design for Applications of Aerobic Alcohols Oxidation and Electrocatalytic Water Oxidation

KAUST Repository

Chen, Batian

2016-05-17

Hydrophobicity is the generalized characteristic of non-polar substances that brings about their exclusion from aqueous phases. This property, entropic in its nature, drives key self-assembly and phase separation processes in water. Protein folding, the formation of DNA double helix, the existence of lipid bilayers and the wetting properties of leaf surfaces are all due to hydrophobic interactions. Inspired by Nature, we aimed to use hydrophobicity for creating novel and improved catalytic systems. (I) A number of fluorous amphiphilic star block-copolymers containing a tris(benzyltriazolylmethyl)amine motif have been prepared. These polymers assembled into well-defined nanostructures in water, and their mode of assembly could be controlled by changing the composition of the polymer. The polymers were used for enzyme-inspired catalysis of alcohol oxidation. (II) An enzyme-inspired catalytic system based on a rationally designed multifunctional surfactant was developed. The resulting micelles feature metal-binding sites and stable free radical moieties as well as fluorous pockets that attract and preconcentrate molecular oxygen. In the presence of copper ions, the micelles effect chemoselective aerobic alcohol oxidation under ambient conditions in water, a transformation that is challenging to achieve nonenzymatically. (III) Development of a facile means of photo/electrocatalytic water splitting is one of the main barriers to establishing of a solar hydrogen economy. Of the two half-reactions involved in splitting water into O2 and H2, water oxidation presents the most challenge due to its mechanistic complexity. A practical water oxidation catalyst must be highly active, yet inexpensive and indefinitely stable under harsh oxidative conditions. Here, I shall describe the synthesis of a library of molecular water oxidation catalysts based on the Co complex of tris(2-benzimidazolylmethyl)amine, (BimH)3. A wide range of catalysts differing in their electronic properties

Water flow in carbon-based nanoporous membranes impacted by interactions between hydrated ions and aromatic rings.

Science.gov (United States)

Liu, Jian; Shi, Guosheng; Fang, Haiping

2017-02-24

Carbon-based nanoporous membranes, such as carbon nanotubes (CNTs), graphene/graphene oxide and graphyne, have shown great potential in water desalination and purification, gas and ion separation, biosensors, and lithium-based batteries, etc. A deep understanding of the interaction between hydrated ions in an aqueous solution and the graphitic surface in systems composed of water, ions and a graphitic surface is essential for applications with carbon-based nanoporous membrane platforms. In this review, we describe the recent progress of the interaction between hydrated ions and aromatic ring structures on the carbon-based surface and its applications in the water flow in a carbon nanotube. We expect that these works can be extended to the understanding of water flow in other nanoporous membranes, such as nanoporous graphene, graphyne and stacked sheets of graphene oxide.

Charged patchy particle models in explicit salt: Ion distributions, electrostatic potentials, and effective interactions.

Science.gov (United States)

Yigit, Cemil; Heyda, Jan; Dzubiella, Joachim

2015-08-14

We introduce a set of charged patchy particle models (CPPMs) in order to systematically study the influence of electrostatic charge patchiness and multipolarity on macromolecular interactions by means of implicit-solvent, explicit-ion Langevin dynamics simulations employing the Gromacs software. We consider well-defined zero-, one-, and two-patched spherical globules each of the same net charge and (nanometer) size which are composed of discrete atoms. The studied mono- and multipole moments of the CPPMs are comparable to those of globular proteins with similar size. We first characterize ion distributions and electrostatic potentials around a single CPPM. Although angle-resolved radial distribution functions reveal the expected local accumulation and depletion of counter- and co-ions around the patches, respectively, the orientation-averaged electrostatic potential shows only a small variation among the various CPPMs due to space charge cancellations. Furthermore, we study the orientation-averaged potential of mean force (PMF), the number of accumulated ions on the patches, as well as the CPPM orientations along the center-to-center distance of a pair of CPPMs. We compare the PMFs to the classical Derjaguin-Verwey-Landau-Overbeek theory and previously introduced orientation-averaged Debye-Hückel pair potentials including dipolar interactions. Our simulations confirm the adequacy of the theories in their respective regimes of validity, while low salt concentrations and large multipolar interactions remain a challenge for tractable theoretical descriptions.

Hydrophobicity-induced drying transition in alkanethiol self ...

Indian Academy of Sciences (India)

Raman Research Institute, C.V. Raman Avenue, Bangalore 560 080, India ... Hydrophobicity; hydrophobic gap; self-assembled monolayer; length scale dependent .... From our work, we find that when the alkanethiol SAM is prepared from a.

Tailoring the surface chemical bond states of the NbN films by doping Ag: Achieving hard hydrophobic surface

Energy Technology Data Exchange (ETDEWEB)

Ren, Ping; Zhang, Kan; Du, Suxuan [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Meng, Qingnan [College of Construction Engineering, Jilin University, Changchun, 130026 (China); He, Xin [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Wang, Shuo [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Wen, Mao, E-mail: wenmao225@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Zheng, Weitao, E-mail: WTZheng@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China)

2017-06-15

Highlights: • Intrinsically hydrophilic NbN films can transfer to hydrophobic Nb-Ag-N films by doping Ag atoms into NbN sublattice. • Solute Ag can promote that the hydrophobic Ag{sub 2}O groups formed on the Nb-Ag-N film surface through self-oxidation. • The present work may provide a straightforward approach for the production of robust hydrophobic ceramic surfaces. - Abstract: Robust hydrophobic surfaces based on ceramics capable of withstanding harsh conditions such as abrasion, erosion and high temperature, are required in a broad range of applications. The metal cations with coordinative saturation or low electronegativity are commonly chosen to achieve the intrinsically hydrophobic ceramic by reducing Lewis acidity, and thus the ceramic systems are limited. In this work, we present a different picture that robust hydrophobic surface with high hardness (≥20 GPa) can be fabricated through doping Ag atoms into intrinsically hydrophilic ceramic film NbN by reactive co-sputtering. The transition of wettability from hydrophilic to hydrophobic of Nb-Ag-N films induced by Ag doping results from the appearance of Ag{sub 2}O groups on the films surfaces through self-oxidation, because Ag cations (Ag{sup +}) in Ag{sub 2}O are the filled-shell (4d{sup 10}5S{sup 0}) electronic structure with coordinative saturation that have no tendency to interact with water. The results show that surface Ag{sub 2}O benefited for hydrophobicity comes from the solute Ag atoms rather than precipitate metal Ag, in which the more Ag atoms incorporated into Nb-sublattice are able to further improve the hydrophobicity, whereas the precipitation of Ag nanoclusters would worsen it. The present work opens a window for fabricating robust hydrophobic surface through tailoring surface chemical bond states by doping Ag into transition metal nitrides.

Nonlinear correlations in the hydrophobicity and average flexibility along the glycolytic enzymes sequences

International Nuclear Information System (INIS)

Ciorsac, Alecu; Craciun, Dana; Ostafe, Vasile; Isvoran, Adriana

2011-01-01

Research highlights: → We focus our study on the glycolytic enzymes. → We reveal correlation of hydrophobicity and flexibility along their chains. → We also reveal fractal aspects of the glycolytic enzymes structures and surfaces. → The glycolytic enzyme sequences are not random. → Creation of fractal structures requires the operation of nonlinear dynamics. - Abstract: Nonlinear methods widely used for time series analysis were applied to glycolytic enzyme sequences to derive information concerning the correlation of hydrophobicity and average flexibility along their chains. The 20 sequences of different types of the 10 human glycolytic enzymes were considered as spatial series and were analyzed by spectral analysis, detrended fluctuations analysis and Hurst coefficient calculation. The results agreed that there are both short range and long range correlations of hydrophobicity and average flexibility within investigated sequences, the short range correlations being stronger and indicating that local interactions are the most important for the protein folding. This correlation is also reflected by the fractal nature of the structures of investigated proteins.

23Na-NMR-studies on the detection of the interaction of phospholipids with sodium ions

International Nuclear Information System (INIS)

Arnold, K.; Pausch, R.; Frenzel, J.; Winkler, E.

1975-01-01

The 23 Na-NMR-relaxation times have been measured in different sonicated phospholipid dispersions in dependence on the NaCl concentration. In an egg lecithin dispersion and a DPPC dispersion the relaxation rates are independent of the sodium concentration. In both systems there is no interaction between sodium ions and phospholipids. However, in a phosphatidylethanolamine dispersion a concentration dependence may be observed. Its interpretation is only possible for a stoichiometric ratio of 3:1 of the lecithin-ion-complex. The association constant is found to be k=65,0 l/Mol. For the case of an equimolar egg lecithin/phosphatidylethanolamine dispersion a stronger interaction is measured. The addition of CaCl 2 results in a complete inhibition of the binding of sodium ions at phosphatidylethanolamine

The effect of enhancing the hydrophobicity of OMMT on the characteristics of PMMA/OMMT nanocomposites

International Nuclear Information System (INIS)

Yamagata, Shuichi; Hamba, Yusuke; Akasaka, Tsukasa; Ushijima, Natsumi; Uo, Motohiro; Iida, Junichiro; Watari, Fumio

2012-01-01

Highlights: ► PMMA/OMMT nanocomposites were fabricated using a solution intercalation method. ► The silicate platelets were largely well dispersed independent of the hydrophobicity. ► The partially exfoliation of the silicate layers were observed. ► The flexural modulus of the nanocomposites increased favorably. ► The strain at breakage of the nanocomposites remained suitable for our use. - Abstract: Transparent poly(methyl methacrylate)/organically modified montmorillonite (PMMA/OMMT) nanocomposites were fabricated using a solution intercalation method. Two grades of OMMT modified with quaternary alkylammonium ions and containing different amounts of organic matter, NZ70 and NX, were used. X-ray diffraction patterns showed that the peaks regarded as a (0 0 1) d-spacing and a second peak were shifted toward lower 2θ values, implying the expansion or the partial exfoliation of the silicate layers, respectively. TEM images showed that the silicate platelets were largely well dispersed independent of the hydrophobicity, although some aggregates were observed. The flexural modulus of the PMMA/OMMT nanocomposites increased favorably with an increasing amount of OMMT of either grade. However, only the NX displayed comparable strain at breakage to that of the PMMA. These results suggest that the highly hydrophobic grade NX shows great promise for use in nanocomposites made via solution intercalation.

Hydrophobic perfluoro-silane functionalization of porous silicon photoluminescent films and particles

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, C.; Laplace, P.; Gallach-Pérez, D.; Pellacani, P.; Martín-Palma, R.J. [Departamento de Física Aplicada e Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, 28049, Madrid (Spain); Torres-Costa, V. [Departamento de Física Aplicada e Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, 28049, Madrid (Spain); Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, 28049, Madrid (Spain); Ceccone, G. [European Commission, Joint Research Centre, Institute for Health and Consumer Protection, 21020, Ispra (Italy); Manso Silván, M., E-mail: miguel.manso@uam.es [Departamento de Física Aplicada e Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, 28049, Madrid (Spain)

2016-09-01

Highlights: • Hydrophobic functionalization of porous silicon structures. • Perfluorooctyl group binding confirmed by XPS. • Improved stability face to extreme oxidation conditions. • Perfluorooctyl functionalization compatible with photoluminescence of porous silicon particles. - Abstract: Luminescent structures based on semiconductor quantum dots (QDs) are increasingly used in biomolecular assays, cell tracking systems, and in-vivo diagnostics devices. In this work we have carried out the functionalization of porous silicon (PSi) luminescent structures by a perfluorosilane (Perfluoro-octyltriethoxysilane, PFOS) self assembly. The PFOS surface binding (traced by X-ray photoelectron spectroscopy) and photoluminescence efficiency were analyzed on flat model PSi. Maximal photoluminescence intensity was obtained from PSi layers anodized at 110 mA/cm{sup 2}. Resistance to hydroxylation was assayed in H{sub 2}O{sub 2}:ethanol solutions and evidenced by water contact angle (WCA) measurements. PFOS-functionalized PSi presented systematically higher WCA than untreated PSi. The PFOS functionalization was found to slightly improve the aging of the PSi particles in water giving rise to particles with longer luminescent life. Confirmation of PFOS binding to PSi particles was derived from FTIR spectra and the preservation of luminescence was observed by fluorescence microscopy. Such functionalization opens the possibility of promoting hydrophobic-hydrophobic interactions between biomolecules and fluorescent QD structures, which may enlarge their biomedical applications catalogue.

Soil hydrophobicity: comparative study of usual determination methods

Directory of Open Access Journals (Sweden)

Eduardo Saldanha Vogelmann

2015-02-01

Full Text Available Hydrophobic or water repellent soils slowly absorb water because of the low wett ability of the soil particles which are coated with hydrophobic organic substances. These pose significant effects on plant growth, water infiltration and retention, surface runoff and erosion. The objective of this study was to compare the performance of tension micro-infiltrometer(TMI and the water drop penetration time (WDPT methods in the determination of the hydrophobicity index of eighteen soils from southern Brazil. Soil samples were collected from the 0-5cm soil layer to determine particle size distribution, organic matter content, hydrophobicity index of soil aggregates and droplet penetration time of disaggregated and sieved soil samples. For the TMI method the soil samples were subjected to minor changes due to the use of macroaggregates to preserve the distribution of solid constituents in the soil. Due to the homogeneity of the soil samples the WDPT method gave smaller coefficients of variation unlike the TMI method where the soil structure is preserved. However, both methods had low coefficients of variation, and are thus effective for determining the soil hydrophobicity, especially when the log hydrophobicity index or log WDPT is >1.

Protein Stabilization and Enzyme Activation in Ionic Liquids: Specific Ion Effects

Science.gov (United States)

Zhao, Hua

2015-01-01

There are still debates on whether the hydration of ions perturbs the water structure, and what is the degree of such disturbance; therefore, the origin of Hofmeister effect on protein stabilization continues being questioned. For this reason, it is suggested to use the ‘specific ion effect’ instead of other misleading terms such as Hofmeister effect, Hofmeister series, lyotropic effect, and lyotropic series. In this review, we firstly discuss the controversial aspect of inorganic ion effects on water structures, and several possible contributors to the specific ion effect of protein stability. Due to recent overwhelming attraction of ionic liquids (ILs) as benign solvents in many enzymatic reactions, we further evaluate the structural properties and molecular-level interactions in neat ILs and their aqueous solutions. Next, we systematically compare the specific ion effects of ILs on enzyme stability and activity, and conclude that (a) the specificity of many enzymatic systems in diluted aqueous IL solutions is roughly in line with the traditional Hofmeister series albeit some exceptions; (b) however, the specificity follows a different track in concentrated or neat ILs because other factors (such as hydrogen-bond basicity, nucelophilicity, and hydrophobicity, etc) are playing leading roles. In addition, we demonstrate some examples of biocatalytic reactions in IL systems that are guided by the empirical specificity rule. PMID:26949281

Stabilization of liquid crystal dispersion by nonionic surfactant/acrylamide copolymer containing hydrophobic moieties

Energy Technology Data Exchange (ETDEWEB)

Park, S.J.; Kim, M.H.; Lee, J.R. [Korea Research Institute of Chemical Technology, Taejon (Korea)

1999-07-01

The effect of nonionic surfactant (H(OCH){sub 2}-OC{sub 6}H{sub 4}-C{sub 9}H{sub 19}, NP-8) and acrylamide copolymer containing nonylphenyl groups as hydrophobic moieties on the stabilization of liquid crystal (LC)-in-water dispersion has been studied. According to cloud point and adsorption measurements, the hydrophobically strong interaction between NP-8 and the nonylphenol moieties is formed. And the addition of surfactant increases the stability of LC dispersion and improve the electrooptical properties of the nematic curvilinear aligned phase (NCAP) composite film. It is due to the presence of surfactant which allows the formation of nonpolar microenvironment in the round of LC droplet and finally reduces the anchoring effect between LC and the polymeric wall. 21 refs., 8 figs.

Origins of protein denatured state compactness and hydrophobic clustering in aqueous urea: inferences from nonpolar potentials of mean force.

Science.gov (United States)

Shimizu, Seishi; Chan, Hue Sun

2002-12-01

Free energies of pairwise hydrophobic association are simulated in aqueous solutions of urea at concentrations ranging from 0-8 M. Consistent with the expectation that hydrophobic interactions are weakened by urea, the association of relatively large nonpolar solutes is destabilized by urea. However, the association of two small methane-sized nonpolar solutes in water has the opposite tendency of being slightly strengthened by the addition of urea. Such size effects and the dependence of urea-induced stability changes on the configuration of nonpolar solutes are not predicted by solvent accessible surface area approaches based on energetic parameters derived from bulk-phase solubilities of model compounds. Thus, to understand hydrophobic interactions in proteins, it is not sufficient to rely solely on transfer experiment data that effectively characterize a single nonpolar solute in an aqueous environment but not the solvent-mediated interactions among two or more nonpolar solutes. We find that the m-values for the rate of change of two-methane association free energy with respect to urea concentration is a dramatically nonmonotonic function of the spatial separation between the two methanes, with a distance-dependent profile similar to the corresponding two-methane heat capacity of association in pure water. Our results rationalize the persistence of residual hydrophobic contacts in some proteins at high urea concentrations and explain why the heat capacity signature (DeltaC(P)) of a compact denatured state can be similar to DeltaC(P) values calculated by assuming an open random-coil-like unfolded state. Copyright 2002 Wiley-Liss, Inc.

Hydrophobic treatment of concrete as protection against chloride penetration

NARCIS (Netherlands)

Vries, J. de; Polder, R.B.; Borsje, H.

1996-01-01

Hydrophobic treatment makes a concrete surface absorb less water and less chloride. Hydrophobic treatment was studied as a protection agninst chloride penetration from deicing salts. Test methods were designed. Nine hydrophobic products were tested, of which three complied to the requirements on

The Molecular Basis of Polyunsaturated Fatty Acid Interactions with the Shaker Voltage-Gated Potassium Channel.

Directory of Open Access Journals (Sweden)

Samira Yazdi

2016-01-01

Full Text Available Voltage-gated potassium (KV channels are membrane proteins that respond to changes in membrane potential by enabling K+ ion flux across the membrane. Polyunsaturated fatty acids (PUFAs induce channel opening by modulating the voltage-sensitivity, which can provide effective treatment against refractory epilepsy by means of a ketogenic diet. While PUFAs have been reported to influence the gating mechanism by electrostatic interactions to the voltage-sensor domain (VSD, the exact PUFA-protein interactions are still elusive. In this study, we report on the interactions between the Shaker KV channel in open and closed states and a PUFA-enriched lipid bilayer using microsecond molecular dynamics simulations. We determined a putative PUFA binding site in the open state of the channel located at the protein-lipid interface in the vicinity of the extracellular halves of the S3 and S4 helices of the VSD. In particular, the lipophilic PUFA tail covered a wide range of non-specific hydrophobic interactions in the hydrophobic central core of the protein-lipid interface, while the carboxylic head group displayed more specific interactions to polar/charged residues at the extracellular regions of the S3 and S4 helices, encompassing the S3-S4 linker. Moreover, by studying the interactions between saturated fatty acids (SFA and the Shaker KV channel, our study confirmed an increased conformational flexibility in the polyunsaturated carbon tails compared to saturated carbon chains, which may explain the specificity of PUFA action on channel proteins.

Enantioselective Crystallization of Sodium Chlorate in the Presence of Racemic Hydrophobic Amino Acids and Static Magnetic Fields

Directory of Open Access Journals (Sweden)

María-Paz Zorzano

2014-06-01

Full Text Available We study the bias induced by a weak (200 mT external magnetic field on the preferred handedness of sodium chlorate crystals obtained by slow evaporation at ambient conditions of its saturated saline solution with 20 ppm of added racemic (dl hydrophobic amino acids. By applying the Fisher test to pairs of experiments with opposing magnetic field orientation we conclude, with a confidence level of 99.7%, that at the water-air interface of this saline solution there is an enantioselective magnetic interaction that acts upon racemic mixtures of hydrophobic chiral amino acids. This interaction has been observed with the three tested racemic hydrophobic amino acids: dl-Phe, dl-Try and dl-Trp, at ambient conditions and in spite of the ubiquitous chiral organic contamination. This enantioselective magnetic dependence is not observed when there is only one handedness of added chiral amino-acid, if the added amino acid is not chiral or if there is no additive. This effect has been confirmed with a double blind test. This novel experimental observation may have implications for our view of plausible initial prebiotic scenarios and of the roles of the geomagnetic field in homochirality in the biosphere.

Transferred hyperfine interaction between the rare-earth ions and the fluorine nuclei in rare-earth trifluorides

DEFF Research Database (Denmark)

Hansen, P. E.; Nevald, Rolf; Guggenheim, H. G.

1978-01-01

The isotropic and anisotropic transferred hyperfine interactions between F ions in the two chemically inequivalent sites and the rare-earth ions (R) have been derived from 19F NMR measurements in the temperature region 100-300 K on single crystals of TbF3 and DyF3. The isotropic interactions are ...... to vary only slightly with temperature. They are further assigned to definite R's in the unit cell, which cannot be done from macroscopic magnetic measurements....

Ion-ion collisions and ion storage rings

International Nuclear Information System (INIS)

Mowat, J.R.

1988-01-01

Improved understanding of fundamental ion-ion interactions is expected to emerge from research carried out with ion storage rings. In this short survey the significant advantages and unique features that make stored ions useful targets for collision experiments are reviewed and discussed. It is pointed out that improvements to existing ion-ion experiments, as well as qualitatively new experiments, should occur over the next few years as ion storage rings become available for atomic physics. Some new experiments are suggested which are difficult if not impossible with present-day technology, but which seem feasible at storage rings facilities. (orig.)

Interaction of human endothelial cells and nickel-titanium materials modified with silicon ions

Energy Technology Data Exchange (ETDEWEB)

Lotkov, Aleksandr I., E-mail: lotkov@ispms.tsc.ru; Kashin, Oleg A., E-mail: okashin@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Kudryavtseva, Yuliya A., E-mail: yulia-k1970@mail.ru; Antonova, Larisa V., E-mail: antonova.la@mail.ru; Matveeva, Vera G., E-mail: matveeva-vg@mail.ru; Sergeeva, Evgeniya A., E-mail: sergeewa.ew@yandex.ru [Research Institute for Complex Issues of Cardiovascular Diseases, Kemerovo, 650002 (Russian Federation); Kudryashov, Andrey N., E-mail: kudryashov@angioline.ru [Angioline Interventional Device Ltd, Novosibirsk, 630090 (Russian Federation)

2015-10-27

The paper studies the influence of chemical and phase compositions of NiTi surface layers modified with Si ions by plasma immersion implantation on their interaction with endothelial cells. It is shown that certain technological modes of Si ion implantation enhance the adhesion, proliferation, and viability of endothelial cells. It is found that the Si-modified NiTi surface is capable of stimulating the formation of capillary-like structures in the cell culture.

Imaging and structural studies of DNA–protein complexes and membrane ion channels

KAUST Repository

Marini, Monica; Limongi, Tania; Falqui, Andrea; Genovese, Alessandro; Allione, Marco; Moretti, Manola; Lopatin, Sergei; Tirinato, Luca; Das, Gobind; Torre, Bruno; Giugni, Andrea; Cesca, F.; Benfenati, F.; Di Fabrizio, Enzo M.

2017-01-01

In bio-imaging by electron microscopy, damage of the sample and limited contrast are the two main hurdles for reaching high image quality. We extend a new preparation method based on nanofabrication and super-hydrophobicity to the imaging and structural studies of nucleic acids, nucleic acid-protein complexes (DNA/Rad51 repair protein complex) and neuronal ion channels (gap-junction, K+ and GABA(A) channels) as paradigms of biological significance and increasing complexity. The preparation method is based on the liquid phase and is compatible with physiological conditions. Only in the very last stage, samples are dried for TEM analysis. Conventional TEM and high-resolution TEM (HRTEM) were used to achieve a resolution of 3.3 and 1.5 angstrom, respectively. The EM dataset quality allows the determination of relevant structural and metrological information on the DNA structure, DNA-protein interactions and ion channels, allowing the identification of specific macromolecules and their structure.

Imaging and structural studies of DNA–protein complexes and membrane ion channels

KAUST Repository

Marini, Monica

2017-01-17

In bio-imaging by electron microscopy, damage of the sample and limited contrast are the two main hurdles for reaching high image quality. We extend a new preparation method based on nanofabrication and super-hydrophobicity to the imaging and structural studies of nucleic acids, nucleic acid-protein complexes (DNA/Rad51 repair protein complex) and neuronal ion channels (gap-junction, K+ and GABA(A) channels) as paradigms of biological significance and increasing complexity. The preparation method is based on the liquid phase and is compatible with physiological conditions. Only in the very last stage, samples are dried for TEM analysis. Conventional TEM and high-resolution TEM (HRTEM) were used to achieve a resolution of 3.3 and 1.5 angstrom, respectively. The EM dataset quality allows the determination of relevant structural and metrological information on the DNA structure, DNA-protein interactions and ion channels, allowing the identification of specific macromolecules and their structure.

Thz Spectroscopy and DFT Modeling of Intermolecular Vibrations in Hydrophobic Amino Acids

Science.gov (United States)

Williams, michael R. C.; Aschaffenburg, Daniel J.; Schmuttenmaer, Charles A.

2013-06-01

Vibrations that involve intermolecular displacements occur in molecular crystals at frequencies in the 0.5-5 THz range (˜15-165 cm^{-1}), and these motions are direct indicators of the interaction potential between the molecules. The intermolecular potential energy surface of crystalline hydrophobic amino acids is inherently interesting simply because of the wide variety of forces (electrostatic, dipole-dipole, hydrogen-bonding, van der Waals) that are present. Furthermore, an understanding of these particular interactions is immediately relevant to important topics like protein conformation and pharmaceutical polymorphism. We measured the low-frequency absorption spectra of several polycrystalline hydrophobic amino acids using THz time-domain spectroscopy, and in addition we carried out DFT calculations using periodic boundary conditions and an exchange-correlation functional that accounts for van der Waals dispersion forces. We chose to investigate a series of similar amino acids with closely analogous unit cells (leucine, isoleucine, and allo-isoleucine, in racemic or pseudo-racemic mixtures). This allows us to consider trends in the vibrational spectra as a function of small changes in molecular arrangement and/or crystal geometry. In this way, we gain confidence that peak assignments are not based on serendipitous similarities between calculated and observed features.

Investigation of ion acceleration mechanism through laser-matter interaction in femtosecond domain

Energy Technology Data Exchange (ETDEWEB)

Altana, C., E-mail: altana@lns.infn.it [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, Via S. Sofia 64, 95123 Catania (Italy); Muoio, A. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Messina, Viale F.S. D’Alcontres 31, 98166 Messina (Italy); Lanzalone, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Università degli Studi di Enna “Kore”, Via delle Olimpiadi, 94100 Enna (Italy); Tudisco, S. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Brandi, F. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Cirrone, G.A.P. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Cristoforetti, G. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Fazzi, A. [Energy Department, Polytechnic of Milan and INFN, Milan (Italy); Ferrara, P.; Fulgentini, L. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Giove, D. [Energy Department, Polytechnic of Milan and INFN, Milan (Italy); Koester, P. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Labate, L. [CNR, Intense Laser Irradiation Laboratory, Via G. Moruzzi 1, 56124 Pisa (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); and others

2016-09-01

An experimental campaign aiming to investigate the ion acceleration mechanisms through laser-matter interaction in the femtosecond domain has been carried out at the ILIL facility at a laser intensity of up to 2×10{sup 19} W/cm{sup 2}. A Thomson Parabola Spectrometer was used to identify different ion species and measure the energy spectra and the corresponding temperature parameters. We discuss the dependence of the protons spectra upon the structural characteristics of the targets (thickness and atomic mass) and the role of surface versus target bulk during acceleration process. - Highlights: • Ion acceleration mechanism in TNSA regime was investigated. • The energy spectra and the corresponding temperature parameters were measured. • Dependence of the spectra upon the target structural characteristics was discussed.

Molecular dynamics and brownian dynamics investigation of ion permeation and anesthetic halothane effects on a proton-gated ion channel.

Science.gov (United States)

Cheng, Mary Hongying; Coalson, Rob D; Tang, Pei

2010-11-24

Bacterial Gloeobacter violaceus pentameric ligand-gated ion channel (GLIC) is activated to cation permeation upon lowering the solution pH. Its function can be modulated by anesthetic halothane. In the present work, we integrate molecular dynamics (MD) and Brownian dynamics (BD) simulations to elucidate the ion conduction, charge selectivity, and halothane modulation mechanisms in GLIC, based on recently resolved X-ray crystal structures of the open-channel GLIC. MD calculations of the potential of mean force (PMF) for a Na(+) revealed two energy barriers in the extracellular domain (R109 and K38) and at the hydrophobic gate of transmembrane domain (I233), respectively. An energy well for Na(+) was near the intracellular entrance: the depth of this energy well was modulated strongly by the protonation state of E222. The energy barrier for Cl(-) was found to be 3-4 times higher than that for Na(+). Ion permeation characteristics were determined through BD simulations using a hybrid MD/continuum electrostatics approach to evaluate the energy profiles governing the ion movement. The resultant channel conductance and a near-zero permeability ratio (P(Cl)/P(Na)) were comparable to experimental data. On the basis of these calculations, we suggest that a ring of five E222 residues may act as an electrostatic gate. In addition, the hydrophobic gate region may play a role in charge selectivity due to a higher dehydration energy barrier for Cl(-) ions. The effect of halothane on the Na(+) PMF was also evaluated. Halothane was found to perturb salt bridges in GLIC that may be crucial for channel gating and open-channel stability, but had no significant impact on the single ion PMF profiles.

Tri- and tetra-substituted cyclen based lanthanide(III) ion complexes as ribonuclease mimics: a study into the effect of log Ka, hydration and hydrophobicity on phosphodiester hydrolysis of the RNA-model 2-hydroxypropyl-4-nitrophenyl phosphate (HPNP).

Science.gov (United States)

Fanning, Ann-Marie; Plush, Sally E; Gunnlaugsson, Thorfinnur

2015-05-28

A series of tetra-substituted 'pseudo' dipeptide ligands of cyclen (1,4,7,10,-tetraazacyclododecane) and a tri-substituted 3'-pyridine ligand of cyclen, and the corresponding lanthanide(III) complexes were synthesised and characterised as metallo-ribonuclease mimics. All complexes were shown to promote hydrolysis of the phosphodiester bond of 2-hydroxypropyl-4-nitrophenyl phosphate (HPNP, τ1/2 = 5.87 × 10(3) h), a well known RNA mimic. The La(III) and Eu(III) tri-substituted 3'-pyridine lanthanide(III) complexes being the most efficient in promoting such hydrolysis at pH 7.4 and at 37 °C; with τ1/2 = 1.67 h for La(III) and 1.74 h for Eu(III). The series was developed to provide the opportunity to investigate the consequences of altering the lanthanide(III) ion, coordination ability and hydrophobicity of a metallo-cavity on the rate of hydrolysis using the model phosphodiester, HPNP, at 37 °C. To further provide information on the role that the log Ka of the metal bound water plays in phosphodiester hydrolysis the protonation constants and the metal ion stability constants of both a tri and tetra-substituted 3'pyridine complex were determined. Our results highlighted several key features for the design of lanthanide(III) ribonucelase mimics; the presence of two metal bound water molecules are vital for pH dependent rate constants for Eu(III) complexes, optimal pH activity approximating physiological pH (∼7.4) may be achieved if the log Ka values for both MLOH and ML(OH)2 species occur in this region, small changes to hydrophobicity within the metallo cavity influence the rate of hydrolysis greatly and an amide adjacent to the metal ion capable of forming hydrogen bonds with the substrate is required for achieving fast hydrolysis.

Design of textured surfaces for super-hydrophobicity

Indian Academy of Sciences (India)

Prithvi Raj Jelia

2017-11-11

Nov 11, 2017 ... as silicon wafer [1, 10, 11]. Yoon et al [12] used a modified ... The explanation for the increase in the contact angle or hydrophobicity on the ... water droplets on super-hydrophobic surfaces that exhibit large contact angles are ...

Preparation of hydrophobic Pt-catalysts for decontamination of nuclear effluents

International Nuclear Information System (INIS)

Ionita, Gh.; Popescu, I.; Retegan, T.; Stefanescu, I.

2005-01-01

Based on the long experience of the authors, in the preparation, testing and evaluation of the performances of hydrophobic catalysts, and based on the reviewed references, this paper presents up-to-date R and D activities on the preparation methods and applications of the hydrophobic catalysts, in deuterium and tritium separation. The objectives of the paper are: (1) to provide a database for selection of the most appropriate catalyst and catalytic packing for above mentioned processes, (2) to evaluate the potentiality of hydrophobic Pt-catalysts in the deuterium and tritium separation (3) to asses and to find a new procedure for preparation a new improved hydrophobic catalyst. The merits of the hydrophobic catalysts are shown in comparison to hydrophilic catalysts. As results of the review some general conclusions about the applications of hydrophobic catalysts in environmental field are as follow: (1) the hydrophobic Pt-catalysts packed in the trickle bed reactors showed a high catalytic activity and long stability; (2) the utilization of the hydrophobic Pt-catalysts for tritium removal from liquid and gaseous effluent in nuclear field was entirely confirmed on industrial scale; (3) the extension of the utilization of the hydrophobic Pt-catalysts in other new processes, which take place in presence of liquid water or high humidity are subjected to testing. (author)

Preparation of hydrophobic Pt-catalysts for decontamination of nuclear effluents

International Nuclear Information System (INIS)

Ionita, Gh.; Popescu, I.; Retegan, T.; Stefanescu, I.

2004-01-01

Based on the long experience of the authors, in the preparation, testing and evaluation of the performances of hydrophobic catalysts, and based on the reviewed references, this paper presents up-to-date R and D activities on the preparation methods and applications of the hydrophobic catalysts, in deuterium and tritium separation. The objectives of the paper are: - to provide a database for selection of the most appropriate catalyst and catalytic packing for above mentioned processes; - to evaluate the potentiality of hydrophobic Pt-catalysts in the deuterium and tritium separation; - to assess and to find a new procedure for preparation a new improved hydrophobic catalyst. The merits of the hydrophobic catalysts are shown in comparison to hydrophilic catalysts. As results of the review some general conclusions about the applications of hydrophobic catalysts in environmental field are as follows: - the hydrophobic Pt-catalysts packed in the trickle bed reactors showed a high catalytic activity and long stability; - the utilization of the hydrophobic Pt-catalysts for tritium removal from liquid and gaseous effluent in nuclear field was entirely confirmed on industrial scale; - the extension of the utilization of the hydrophobic Pt-catalysts in other new processes, which take place in presence of liquid water or high humidity are subject to testing. (authors)

Kinetics of interaction from low-energy-ion bombardment of surfaces

International Nuclear Information System (INIS)

Horton, C.C.

1988-01-01

The kinetics of interaction from low energy oxygen ion bombardment of carbon and Teflon surfaces have been investigated. The surfaces were bombarded with 4.5 to 93 eV oxygen ions and emitted species were observed with a mass spectrometer. To obtain the kinetic information, the ion beam was square pulse modulated and reaction products were observed as a function of time. The kinetic information is contained in the response of the emitted species to the pulsed ion beam. Oxygen bombardment of carbon produced CO in three parallel branches with each following an adsorption-desorption process. The fast branch, with a rate constants of 12,000/sec, appeared to be sputter induced an was absent below about 19 eV. The medium and slow branches, with rate constants of 850/sec and 45/sec respectively, has little energy dependence and appeared to be due to chemical sputtering from two sites. The ratio of the fraction of the medium branch to that of the slow was constant at 1:3. The bombardment of Teflon produced CF in two parallel branches, with one following a series process and the other an adsorb-desorb process. The rate constant of the other branch were 22,000/sec and 7,000/sec and the rate constant of the other branch was 90/sec. The total signal fell monotonically with decreasing ion energy with the fraction for each branch holding constant at 71% for the series and 29% for the adsorb-desorb

Architecture of the hydrophobic and hydrophilic layers as found from crystal structure analysis of N-benzyl-N,N-dimethylalkylammonium bromides.

Science.gov (United States)

Hodorowicz, Maciej; Stadnicka, Katarzyna; Czapkiewicz, Jan

2005-10-01

The molecular and crystal structures of N-benzyl-N,N-dimethylalkylammonium bromides monohydrates with chain length n=8-10 have been determined. The crystals are isostructural with the N-benzyl-N,N-dimethyldodecylammonium bromide monohydrate. The structures consist of alternated hydrophobic and hydrophilic layers perpendicular to [001]. The attraction between N+ of the cation head-groups and Br- anions is achieved through weak C_H...Br interactions. The water molecules incorporated into ionic layers are donors for two O_H...Br hydrogen bonds and serve as the acceptors in two weak interactions of C_H...O type. The methylene chains, with the slightly curved general shape, have the extended all-trans conformation. The mutual packing of the chains in the hydrophobic layers is governed by weak C_H...pi interactions.

Harvesting electrostatic energy using super-hydrophobic surfaces

Science.gov (United States)

Pociecha, Dominik; Zylka, Pawel

2016-11-01

Almost all environments are now being extensively populated by miniaturized, nano-powered electronic sensor devices communicated together through wireless sensor networks building Internet of Things (IoT). Various energy harvesting techniques are being more and more frequently proposed for battery-less powering of such remote, unattended, implantable or wearable sensors or other low-power electronic gadgets. Energy harvesting relays on extracting energy from the ambient sources readily accessible at the sensor location and converting it into electrical power. The paper exploits possibility of generating electric energy safely accessible for nano-power electronics using tribo-electric and electrostatic induction phenomena displayed at super-hydrophobic surfaces impinged by water droplets. Mechanism of such interaction is discussed and illustrated by experimental results.

Fast ion beam-laser interactions

International Nuclear Information System (INIS)

Berry, H.G.; Young, L.; Engstroem, L.; Hardis, J.E.; Somerville, L.P.; Ray, W.J.; Kurtz, C.

1985-01-01

The authors are using collinear laser excitation of fast ion beams to study a number of atomic structure problems. The problems include the determination of fine and hyperfine structure in light positive and negative ions, plus measurements of absolute wavelengths of light from two-electron ions. In addition the authors intend to use a similar experimental arrangement to study excitation and decay of high Rydberg states first in the absence of fields and then in crossed electric and magnetic fields

Influence of the Coulomb interaction in the final state on the cross section of single-electron capture by fast ions

International Nuclear Information System (INIS)

Novikov, N.V.; Teplova, Ya.A.

2011-01-01

It is shown that the Coulomb interaction of ions in the final state must be taken into account in the estimation of the cross section of electron capture by fast ions. The cross section of electron capture decreases considerably, and the dependence of the cross section on the collision energy becomes close to the experimental one if the interaction of charged particles after collision is taken into account. -- Highlights: → Coulomb interaction of ions in the final state must be taken into account. → This interaction leads to a considerable decrease in the cross section. → The dependence on energy close to the experimental one.

Structuring unbreakable hydrophobic barriers in paper

Science.gov (United States)

Nargang, Tobias M.; Kotz, Frederik; Rapp, Bastian E.

2018-02-01

Hydrophobic barriers are one of the key elements of microfluidic paper based analytical devices (μPADs).μPADs are simple and cost efficient and they can be carried out without the need of high standard laboratories. To carry out such a test a method is needed to create stable hydrophobic barriers. Commonly used methods like printing wax or polystyrene have the major drawback that these barriers are stiff and break if bended which means they will no longer be able to retain a liquid sample. Here we present silanes to structure hydrophobic barriers via polycondensation and show a silanization method which combines the advantages of flexible silane/siloxane layers with the short processing times of UV-light based structuring. The barriers are created by using methoxy silanes which are mixed with a photo acid generator (PAG) as photoinitiator. Also a photosensitizer was given to the mixture to increase the effectiveness of the PAG. After the PAG is activated by UV-light the silane is hydrolyzed and coupled to the cellulose via polycondensation. The created hydrophobic barriers are highly stable and do not break if being bended.

A Comment on Interaction of Lower Hybrid Waves with the Current-Driven Ion-Acoustic Instability

DEFF Research Database (Denmark)

Schrittwieser, R.; Juul Rasmussen, Jens

1985-01-01

Majeski et al. (1984) have investigated the interaction between the current-driven 'ion-acoustic' instability and high frequency lower hybrid waves. The 'ion-acoustic' instability was excited by drawing an electron current through the plasma column of a single-ended Q-machine by means...... of a positively biased cold plate. Schmittwieser et al. do not believe that the observed instability is of the ion-acoustic type but that it is rather the so-called potential relaxation instability....

The interactions of high-energy, highly charged Xe ions with buckyballs

International Nuclear Information System (INIS)

Ali, R.; Berry, H.G.; Cheng, S.

1994-01-01

Ionization and fragmentation have been measured for C 60 molecules bombarded by highly charged (up to 35+) xenon ions with energies ranging up to 625 MeV. The observed mass distribution of positively charged fragments is explained in terms of a theoretical model indicating that the total interaction cross section contains roughly equal contributions from (a) excitation of the giant plasmon resonance, and (b) large-energy-transfer processes that lead to multiple fragmentation of the molecule. Preliminary results of measurements on VUV photons emitted in these interactions are also presented

Interaction of supra-thermal ions with turbulence in a magnetized toroidal plasma

International Nuclear Information System (INIS)

Plyushchev, G.

2009-01-01

This thesis addresses the interaction of a supra-thermal ion beam with turbulence in the simple magnetized toroidal plasma of TORPEX. The first part of the Thesis deals with the ohmic assisted discharges on TORPEX. The aim of these discharges is the investigation of the open to closed magnetic field line transition. The relevant magnetic diagnostics were developed. Ohmic assisted discharges with a maximum plasma current up to 1 kA are routinely obtained. The equilibrium conditions on the vacuum magnetic field configuration were investigated. In the second part of the Thesis, the design of the fast ion source and detector are discussed. The accelerating electric field needed for the fast ion source was optimized. The fast ion source was constructed and commissioned. To detect the fast ions a specially designed gridded energy analyzer was used. The electron energy distribution function was obtained to demonstrate the efficiency of the detector. The experiments with the fast ion beam were conducted in different plasma regions of TORPEX. In the third part of the Thesis, numerical simulations are used to interpret the measured fast ion beam behavior. It is shown that a simple single particle equation of motion explains the beam behavior in the experiments in the absence of plasma. To explain the fast ion beam experiments with the plasma a turbulent electric field must be used. The model that takes into account this turbulent electrical field qualitatively explains the shape of the fast ion current density profile in the different plasma regions of TORPEX. The vertically elongated fast ion current density profiles are explained by a spread in the fast ion velocity distribution. The theoretically predicted radial fast ion beam spreading due to the turbulent electric field was observed in the experiment. (author)

Pathways to dewetting in hydrophobic confinement.

Science.gov (United States)

Remsing, Richard C; Xi, Erte; Vembanur, Srivathsan; Sharma, Sumit; Debenedetti, Pablo G; Garde, Shekhar; Patel, Amish J

2015-07-07

Liquid water can become metastable with respect to its vapor in hydrophobic confinement. The resulting dewetting transitions are often impeded by large kinetic barriers. According to macroscopic theory, such barriers arise from the free energy required to nucleate a critical vapor tube that spans the region between two hydrophobic surfaces--tubes with smaller radii collapse, whereas larger ones grow to dry the entire confined region. Using extensive molecular simulations of water between two nanoscopic hydrophobic surfaces, in conjunction with advanced sampling techniques, here we show that for intersurface separations that thermodynamically favor dewetting, the barrier to dewetting does not correspond to the formation of a (classical) critical vapor tube. Instead, it corresponds to an abrupt transition from an isolated cavity adjacent to one of the confining surfaces to a gap-spanning vapor tube that is already larger than the critical vapor tube anticipated by macroscopic theory. Correspondingly, the barrier to dewetting is also smaller than the classical expectation. We show that the peculiar nature of water density fluctuations adjacent to extended hydrophobic surfaces--namely, the enhanced likelihood of observing low-density fluctuations relative to Gaussian statistics--facilitates this nonclassical behavior. By stabilizing isolated cavities relative to vapor tubes, enhanced water density fluctuations thus stabilize novel pathways, which circumvent the classical barriers and offer diminished resistance to dewetting. Our results thus suggest a key role for fluctuations in speeding up the kinetics of numerous phenomena ranging from Cassie-Wenzel transitions on superhydrophobic surfaces, to hydrophobically driven biomolecular folding and assembly.

Relativistic configuration-interaction calculation of the correlation energies of heliumlike ions. Revision 1

International Nuclear Information System (INIS)

Cheng, K.T.; Chen, M.H.; Johnson, W.R.

1994-04-01

A new relativistic configuration-interaction (CI) method using B-spline basis functions has been developed to study the correlation energies of two-electron heliumlike ions. Based on the relativistic no-pair Hamiltonian, the CI equation leads to a symmetric eigenvalue problem involving large, dense matrices. Davidson's method is used to obtain the lowest few eigenenergies and eigenfunctions. Results on transition energies and finite structure splittings for heliumlike ions are in very good agreement with experiment throughout the periodic table

Structural study of surfactant-dependent interaction with protein

Energy Technology Data Exchange (ETDEWEB)

Mehan, Sumit; Aswal, Vinod K., E-mail: vkaswal@barc.gov.in [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kohlbrecher, Joachim [Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 PSI Villigen (Switzerland)

2015-06-24

Small-angle neutron scattering (SANS) has been used to study the complex structure of anionic BSA protein with three different (cationic DTAB, anionic SDS and non-ionic C12E10) surfactants. These systems form very different surfactant-dependent complexes. We show that the structure of protein-surfactant complex is initiated by the site-specific electrostatic interaction between the components, followed by the hydrophobic interaction at high surfactant concentrations. It is also found that hydrophobic interaction is preferred over the electrostatic interaction in deciding the resultant structure of protein-surfactant complexes.

Influence of the inter-ion interaction on the phase diagrams of the 1D Falicov-Kimball system

Science.gov (United States)

Gajek, Z.; Lemański, R.

2004-05-01

A model of itinerant, spinless electrons interacting with ions via the on-site Coulomb potential U, modified by the inter-ionic nearest-neighbour interaction V, is studied on the one-dimensional infinite lattice. Only periodical configurations of the ions with a limited number of lattice sites in a unit cell and their mixtures are taken into account. Phases whose energies reach minimum values for given electron and ion chemical potentials are selected and depicted for a set of model parameters. Then the results are translated into the ion density-electron density canonical phase diagrams and summarized in the electrondensity-U plane. The diagrams clearly show how various kinds of charge ordering evolve with V, starting from V=0 case, that represents the standard Falicov-Kimball model discussed previously.

Influence of the inter-ion interaction on the phase diagrams of the 1D Falicov-Kimball system

International Nuclear Information System (INIS)

Gajek, Z.; Lemanski, R.

2004-01-01

A model of itinerant, spinless electrons interacting with ions via the on-site Coulomb potential U, modified by the inter-ionic nearest-neighbour interaction V, is studied on the one-dimensional infinite lattice. Only periodical configurations of the ions with a limited number of lattice sites in a unit cell and their mixtures are taken into account. Phases whose energies reach minimum values for given electron and ion chemical potentials are selected and depicted for a set of model parameters. Then the results are translated into the ion density-electron density canonical phase diagrams and summarized in the electron density-U plane. The diagrams clearly show how various kinds of charge ordering evolve with V, starting from V=0 case, that represents the standard Falicov-Kimball model discussed previously

Influence of the inter-ion interaction on the phase diagrams of the 1D Falicov-Kimball system

Energy Technology Data Exchange (ETDEWEB)

Gajek, Z. E-mail: gajek@int.pan.wroc.pl; Lemanski, R

2004-05-01

A model of itinerant, spinless electrons interacting with ions via the on-site Coulomb potential U, modified by the inter-ionic nearest-neighbour interaction V, is studied on the one-dimensional infinite lattice. Only periodical configurations of the ions with a limited number of lattice sites in a unit cell and their mixtures are taken into account. Phases whose energies reach minimum values for given electron and ion chemical potentials are selected and depicted for a set of model parameters. Then the results are translated into the ion density-electron density canonical phase diagrams and summarized in the electron density-U plane. The diagrams clearly show how various kinds of charge ordering evolve with V, starting from V=0 case, that represents the standard Falicov-Kimball model discussed previously.

Preparation of inorganic hydrophobic catalysts

International Nuclear Information System (INIS)

Yang, Yong; Wang, Heyi; Du, Yang

2009-04-01

In order to catalyse the oxidation of tritium gas, two inorganic hydrophobic catalysts are prepared. Under room temperature, the catalysed oxidation ratio of 0.3%-1% (V/V) hydrogen gas in air is higher than 95%. Pt-II inorganic hydrophobic catalysts has obviously better catalysing ability than Pt-PTFE and lower ability than Pt-SDB in H 2 -HTO isotopic exchange, because the pressure resistence of Pt-II is much higher than Pt-SDB, it can be used to the CECE cell of heavy water detritium system. (authors)

Enhanced water transport and salt rejection through hydrophobic zeolite pores

Science.gov (United States)

Humplik, Thomas; Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N.

2017-12-01

The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

Enhanced water transport and salt rejection through hydrophobic zeolite pores.

Science.gov (United States)

Humplik, Thomas; Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N

2017-12-15

The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

Hydrophobic mismatch in gramicidin A'/lecithin systems

International Nuclear Information System (INIS)

Watnick, P.I.; Chan, S.I.; Dea, P.

1990-01-01

Gramicidin A' (GA') has been added to three lipid systems of varying hydrophobic thickness: dimyristoyllecithin (DML), dipalmitoyllecithin (DPL), and distearoyllecithin (DSL). The similarity in length between the hydrophobic portion of GA' and the hydrocarbon chains of the lipid bilayers has been studied by using 31 P and 2 H NMR. Hydrophobic mismatch has been found to be most severe in the DML bilayer system and minimal in the case of DSL. In addition, the effects of hydrophobic mismatch on the cooperative properties of the bilayer have been obtained from 2 H NMR relaxation measurements. The results indicate that incorporation of the peptide into the bilayer disrupts the cooperative director fluctuations characteristic of pure multilamellar lipid dispersions. Finally, the GA'/lecithin ratio at which the well-known transformation from bilayer to reverse hexagonal (H II ) phase occurs is shown to depend on the acyl chain length of the phospholipid. A rationale is proposed for this chain length dependence

Formation of hydrophobic coating on glass surface using atmospheric pressure non-thermal plasma in ambient air

International Nuclear Information System (INIS)

Fang, Z; Qiu, Y; Kuffel, E

2004-01-01

Non-thermal plasmas under atmospheric pressure are of great interest in material surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of a glass surface for improving hydrophobicity using a non-thermal plasma generated by a dielectric barrier corona discharge (DBCD) with a needle array-to-plane electrode arrangement in atmospheric air is conducted, and the surface properties of the glass before and after the DBCD treatment are studied using contact angle measurement, surface resistance measurement and the wet flashover voltage test. The effects of the plasma dose (the product of average discharge power and treatment time) of DBCD on the surface modification are studied, and the mechanism of interaction between the plasma and glass surface is discussed. It is found that a layer of hydrophobic coating is formed on the glass surface through DBCD treatment, and the improvement of hydrophobicity depends on the plasma dose of the DBCD. It seems that there is an optimum plasma dose for the surface treatment. The test results of thermal ageing and chemical ageing show that the hydrophobic layer has quite stable characteristics

Non-Native Metal Ion Reveals the Role of Electrostatics in Synaptotagmin 1-Membrane Interactions.

Science.gov (United States)

Katti, Sachin; Nyenhuis, Sarah B; Her, Bin; Srivastava, Atul K; Taylor, Alexander B; Hart, P John; Cafiso, David S; Igumenova, Tatyana I

2017-06-27

C2 domains are independently folded modules that often target their host proteins to anionic membranes in a Ca 2+ -dependent manner. In these cases, membrane association is triggered by Ca 2+ binding to the negatively charged loop region of the C2 domain. Here, we used a non-native metal ion, Cd 2+ , in lieu of Ca 2+ to gain insight into the contributions made by long-range Coulombic interactions and direct metal ion-lipid bridging to membrane binding. Using X-ray crystallography, NMR, Förster resonance energy transfer, and vesicle cosedimentation assays, we demonstrate that, although Cd 2+ binds to the loop region of C2A/B domains of synaptotagmin 1 with high affinity, long-range Coulombic interactions are too weak to support membrane binding of individual domains. We attribute this behavior to two factors: the stoichiometry of Cd 2+ binding to the loop regions of the C2A and C2B domains and the impaired ability of Cd 2+ to directly coordinate the lipids. In contrast, electron paramagnetic resonance experiments revealed that Cd 2+ does support membrane binding of the C2 domains in full-length synaptotagmin 1, where the high local lipid concentrations that result from membrane tethering can partially compensate for lack of a full complement of divalent metal ions and specific lipid coordination in Cd 2+ -complexed C2A/B domains. Our data suggest that long-range Coulombic interactions alone can drive the initial association of C2A/B with anionic membranes and that Ca 2+ further augments membrane binding by the formation of metal ion-lipid coordination bonds and additional Ca 2+ ion binding to the C2 domain loop regions.

The interaction of a nanoscale coherent helium-ion probe with a crystal

International Nuclear Information System (INIS)

D'Alfonso, A.J.; Forbes, B.D.; Allen, L.J.

2013-01-01

Thickness fringing was recently observed in helium ion microscopy (HIM) when imaging magnesium oxide cubes using a 40 keV convergent probe in scanning transmission mode. Thickness fringing is also observed in electron microscopy and is due to quantum mechanical, coherent, multiple elastic scattering attenuated by inelastic phonon excitation (thermal scattering). A quantum mechanical model for elastic scattering and phonon excitation correctly models the thickness fringes formed by the helium ions. However, unlike the electron case, the signal in the diffraction plane is due mainly to the channeling of ions which have first undergone inelastic thermal scattering in the first few atomic layers so that the origin of the thickness fringes is not due to coherent interference effects. This quantum mechanical model affords insight into the interaction of a nanoscale, focused coherent ion probe with the specimen and allows us to elucidate precisely what is needed to achieve atomic resolution HIM. - Highlights: • Thickness fringing has recently been observed imaging MgO cubes using helium ion microscopy. • A quantum mechanical model for elastic scattering and phonon excitation models the fringes. • The signal is due mainly to the coherent scattering of ions after inelastic thermal scattering. • We elucidate precisely what is needed to achieve atomic resolution HIM

Ab initio calculation atomics ground state wave function for interactions Ion- Atom

International Nuclear Information System (INIS)

Shojaee, F.; Bolori zadeh, M. A.

2007-01-01

Ab initio calculation atomics ground state wave function for interactions Ion- Atom Atomic wave function expressed in a Slater - type basis obtained within Roothaan- Hartree - Fock for the ground state of the atoms He through B. The total energy is given for each atom.

Interactions of Native Cyclodextrins with Metal Ions and Inorganic Nanoparticles: Fertile Landscape for Chemistry and Materials Science.

Science.gov (United States)

Prochowicz, Daniel; Kornowicz, Arkadiusz; Lewiński, Janusz

2017-11-22

Readily available cyclodextrins (CDs) with an inherent hydrophobic internal cavity and hydrophilic external surface are macrocyclic entities that display a combination of molecular recognition and complexation properties with vital implications for host-guest supramolecular chemistry. While the host-guest chemistry of CDs has been widely recognized and led to their exploitation in a variety of important functions over the last five decades, these naturally occurring macrocyclic systems have emerged only recently as promising macrocyclic molecules to fabricate environmentally benign functional nanomaterials. This review surveys the development in the field paying special attention to the synthesis and emerging uses of various unmodified CD-metal complexes and CD-inorganic nanoparticle systems and identifies possible future directions. The association of a hydrophobic cavity of CDs with metal ions or various inorganic nanoparticles is a very appealing strategy for controlling the inorganic subunits properties in the very competitive water environment. In this review we provide the most prominent examples of unmodified CDs' inclusion complexes with organometallic guests and update the research in this field from the past decade. We discuss also the coordination flexibility of native CDs to metal ions in CD-based metal complexes and summarize the progress in the synthesis and characterization of CD-metal complexes and their use in catalysis and sensing as well as construction of molecular magnets. Then we provide a comprehensive overview of emerging applications of native CDs in materials science and nanotechnology. Remarkably, in the past few years CDs have appeared as attractive building units for the synthesis of carbohydrate metal-organic frameworks (CD-MOFs) in a combination of alkali-metal cations. The preparation of this new class of highly porous materials and their applications in the separation of small molecules, the loading of drug molecules, as well as

Thermodynamics of interactions between organic ammonium ions and sulfonatocalixarenes

Energy Technology Data Exchange (ETDEWEB)

Wang Lihua [Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071 (China); Guo Dongsheng [Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071 (China); Chen Yong [Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071 (China); Liu Yu [Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071 (China)]. E-mail: yuliu@nankai.edu.cn

2006-04-01

Calorimetric titration and NMR experiments in aqueous phosphate buffer (pH 7.2) at 298.15 K have been done to determine the binding mode, complex stability constants and thermodynamics ({delta}G{sup o}, {delta}H{sup o}, and T{delta}S{sup o}) for 1:1 inclusion complexation of water-soluble calix[n]arenesulfonates (CnAS, n = 4 and 6) and thiacalix[4]arene tetrasulfonate (TCAS) with acethylcholine, carnitine, betaine and benzyltrimethylammonium ion. The results show the inclusion complexations are driven by enthalpy ({delta}H{sup o} < 0), accompanied by negative entropic changes ({delta}S{sup o} < 0). The binding affinities (C4AS > C6AS > TCAS) are discussed from the viewpoint of CH-{pi}/{pi}-{pi} interactions, electrostatic interactions and size/shape-fit relationship between host and guest.

Measuring baryon-(anti-)baryon interaction cross-sections with femtoscopy in Heavy-Ion Collisions

Energy Technology Data Exchange (ETDEWEB)

Kisiel, A.

2016-12-15

Two-particle correlations at low relative momentum (femtoscopy) are used to study the space-time dynamics of the source created in heavy-ion collisions. The same method can be used in a novel way to study the Final State Interaction potential for various particle pairs. The parameters are also directly related to the relevant interaction cross-sections. Of special interest are correlations of baryons, where the strong interaction often dominates. The femtoscopic technique offers a unique opportunity to study this interaction in such systems. In this work we discuss the similarities and differences of such measurement for baryon-baryon and baryon-antibaryon pairs.

Bound water at protein-protein interfaces: partners, roles and hydrophobic bubbles as a conserved motif.

Directory of Open Access Journals (Sweden)

Mostafa H Ahmed

Full Text Available There is a great interest in understanding and exploiting protein-protein associations as new routes for treating human disease. However, these associations are difficult to structurally characterize or model although the number of X-ray structures for protein-protein complexes is expanding. One feature of these complexes that has received little attention is the role of water molecules in the interfacial region.A data set of 4741 water molecules abstracted from 179 high-resolution (≤ 2.30 Å X-ray crystal structures of protein-protein complexes was analyzed with a suite of modeling tools based on the HINT forcefield and hydrogen-bonding geometry. A metric termed Relevance was used to classify the general roles of the water molecules.The water molecules were found to be involved in: a (bridging interactions with both proteins (21%, b favorable interactions with only one protein (53%, and c no interactions with either protein (26%. This trend is shown to be independent of the crystallographic resolution. Interactions with residue backbones are consistent for all classes and account for 21.5% of all interactions. Interactions with polar residues are significantly more common for the first group and interactions with non-polar residues dominate the last group. Waters interacting with both proteins stabilize on average the proteins' interaction (-0.46 kcal mol(-1, but the overall average contribution of a single water to the protein-protein interaction energy is unfavorable (+0.03 kcal mol(-1. Analysis of the waters without favorable interactions with either protein suggests that this is a conserved phenomenon: 42% of these waters have SASA ≤ 10 Å(2 and are thus largely buried, and 69% of these are within predominantly hydrophobic environments or "hydrophobic bubbles". Such water molecules may have an important biological purpose in mediating protein-protein interactions.

Direct Detection of the Ion Pair to Free Ions Transformation upon Complexation with an Ion Receptor in Non-Polar Solvents by using Conductometry.

Science.gov (United States)

Iseda, Kazuya; Kokado, Kenta; Sada, Kazuki

2018-03-01

In this study, we performed conductometry in various organic solvents to directly detect the transformation from tetrabutylammonium chloride ( TBACl ) ion-pair salt to the free ions through complexation with meso -octamethylcalix[4]pyrrole ( CP ), which is a well-known receptor for chloride anions. In the presence of CP , the conductivity of TBACl increases in various non-polar solvents, indicating that complexation with CP enhances the ionic dissociation of TBACl in such non-polar solvents. In other words, CP recognizes chloride as an ion-paired salt as well as a free anion in non-polar solvents. Additionally, the TBA(CP - Cl ) complex exhibited a considerably lower ion-pairing constant ( K ip ) than TBACl in non-polar solvents, resulting in enhanced conductivity. Based on these findings, we can conclude that complexation of an anion with a hydrophobic anion receptor will be useful for creating functional and stimuli-responsive soft materials in organic solvents using coulombic forces.

Controllable picoliter pipetting using hydrophobic microfluidic valves

Science.gov (United States)

Zhang, M.; Huang, J.; Qian, X.; Mi, S.; Wang, X.

2017-06-01

A picoliter pipetting technique using the microfluidic method is presented. Utilizing the hydrophobic self-assembled monolayer films patterned in microchannels as pressure-controlled valves, a small volume of liquid can be separated by a designed channel trap and then ejected from the channel end at a higher pressure. The liquid trap section is composed of a T-shaped channel junction and a hydrophobic patch. The liquid volume can be precisely controlled by varying the distance of the hydrophobic patch from the T-junction. By this means, liquid less than 100 pl can be separated and pipetted. The developed device is potentially useful for sample dispensing in biological, medical, and chemical applications.

Early time interaction of lithium ions with the solar wind in the AMPTE mission

International Nuclear Information System (INIS)

Lui, A.T.Y.; Goodrich, C.C.; Mankofsky, A.; Papadopoulos, K.

1986-01-01

The early time interaction of an artificially injected lithium cloud with the solar wind is simulated with a one-dimensional hybrid code. Simulation results indicate that the lithium cloud presents an obstacle to the solar wind flow, forming a shock-like interaction region. Several notable features are found: (1) The magnetic field is enhanced up to a factor of about 6 followed by a magnetic cavity downstream. (2) Solar wind ions are slowed down inside the lithium cloud, with substantial upstream reflection. (3) Most of the lithium ions gradually pick up the velocity of the solar wind and move downstream. (4) Intense and short-wavelength electric fields exist ahead of the interaction region. (5) Strong electron heating occurs within the lithium clouds. (6) The convection electric field in the in the solar wind is modulated in the interaction region. The simulation results are in remarkable agreement with in situ spacecraft measurements made during lithium releases in the solar wind by the AMPTE (Active magnetospheric Particle Tracer Explorers) Program

The effect of enhancing the hydrophobicity of OMMT on the characteristics of PMMA/OMMT nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Yamagata, Shuichi, E-mail: shuic@den.hokudai.ac.jp [Department of Orthodontics, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Hamba, Yusuke [Department of Orthodontics, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Akasaka, Tsukasa [Department of Biomedical Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Ushijima, Natsumi [Support Section for Education and Research, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Uo, Motohiro [Advanced Biomaterials, Department of Restorative Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549 (Japan); Iida, Junichiro [Department of Orthodontics, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Watari, Fumio [Department of Biomedical Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan)

2012-12-01

Highlights: Black-Right-Pointing-Pointer PMMA/OMMT nanocomposites were fabricated using a solution intercalation method. Black-Right-Pointing-Pointer The silicate platelets were largely well dispersed independent of the hydrophobicity. Black-Right-Pointing-Pointer The partially exfoliation of the silicate layers were observed. Black-Right-Pointing-Pointer The flexural modulus of the nanocomposites increased favorably. Black-Right-Pointing-Pointer The strain at breakage of the nanocomposites remained suitable for our use. - Abstract: Transparent poly(methyl methacrylate)/organically modified montmorillonite (PMMA/OMMT) nanocomposites were fabricated using a solution intercalation method. Two grades of OMMT modified with quaternary alkylammonium ions and containing different amounts of organic matter, NZ70 and NX, were used. X-ray diffraction patterns showed that the peaks regarded as a (0 0 1) d-spacing and a second peak were shifted toward lower 2{theta} values, implying the expansion or the partial exfoliation of the silicate layers, respectively. TEM images showed that the silicate platelets were largely well dispersed independent of the hydrophobicity, although some aggregates were observed. The flexural modulus of the PMMA/OMMT nanocomposites increased favorably with an increasing amount of OMMT of either grade. However, only the NX displayed comparable strain at breakage to that of the PMMA. These results suggest that the highly hydrophobic grade NX shows great promise for use in nanocomposites made via solution intercalation.

Interaction between crystal lattice and mobile ions in copper selenides studied by EXAFS spectroscopy

International Nuclear Information System (INIS)

Asylgushina, G.N.; Bikkulova, N.N.; Titova, S.G.; Kochubey, D.I.

2005-01-01

Interaction between crystal lattice and mobile Cu ions has been studied in Cu 2- x Se in superionic and in normal state using EXAFS-spectroscopy. It has been found that the transition from normal to superionic state and change of mobile Cu ion concentration practically do not have an influence on local state of Cu atoms, but change of both these parameters is accompanied by a change of Se-sublattice state

Hydrophobicity and thermodynamic response for aqueous solutions of amphiphiles

Science.gov (United States)

Zemánková, Katerina; Troncoso, Jacobo; Cerdeiriña, Claudio A.; Romaní, Luis; Anisimov, Mikhail A.

2016-06-01

The anomalous behavior of aqueous solutions of amphiphiles in the water-rich region is analyzed via a phenomenological approach that utilizes the isobaric heat capacity Cp as an experimental probe. We report extensive data for solutions of 14 amphiphiles as a function of temperature at atmospheric pressure. Beyond that, Cp data but also isobaric thermal expansivities and isothermal compressibilities for three solutions of tert-butanol as a function of both temperature and pressure are presented. Results rule out the possibility that the observed phenomenology is associated with the anomalous thermodynamics of pure water. Indeed, our Cp data, quantitatively consistent with recent spectroscopic analyses, suggest that water-mediated interactions between the nonpolar parts of amphiphiles are at the origin of anomalies, with the effects of such "hydrophobic aggregation" being observed at mole fractions as small as 0.01. Physicochemical details like the size, the electronic charge distribution and the geometry of amphiphile molecules as well as third-order derivatives of the Gibbs energy and the associated Koga lines support the above claims while they further contribute to characterizing the role of hydrophobicity in these phenomena. Progress with a view to gain a deeper, more concrete understanding remains.

Binding of ferric ions is essential for the biological activity of glycine-extended gastrin

International Nuclear Information System (INIS)

Baldwin, G.S.; Pannequin, J.; Hollande, F.; Shulkes, A.

2002-01-01

Full text: Non-amidated gastrins, such as glycine-extended gastrin17 (Ggly), are now known to be biologically active. Ggly stimulates cell proliferation and migration, and was recently shown to bind two ferric ions with high affinity. The objective of the present work was to define the structure of Ggly for the first time, and to investigate the role of ferric ions in biological activity. Methods: The structure of Ggly, and the identity of the ammo acids that act as ferric ion ligands, were determined by NMR and fluorescence spectroscopy. The effect on the gastric epithelial cell line IMGE-5 of Ggly fragments, and of Ggy mutants with some or all of the five consecutive glutamate residues replaced by alanine, was measured in terms of cell proliferation, cell migration and phosphorylation of focal adhesion kinase. Results: Ggly adopts a well-defined loop stabilised by hydrophobic interactions between Leu5, Tyrl2, Trp 14 and Phe17. Studies with Ggly fragments indicated that ferric ions bind via the pentaglutamate sequence, which is necessary but not sufficient for full activity Selective replacement of some or all of the glutamates results in a reduction in ferric ion binding, and complete loss of biological activity. Conclusion: Our results are consistent with the hypothesis that ferric ion binding is necessary for biological activity

Intra-pulse transition between ion acceleration mechanisms in intense laser-foil interactions

Energy Technology Data Exchange (ETDEWEB)

Padda, H.; King, M.; Gray, R. J.; Powell, H. W.; Gonzalez-Izquierdo, B.; Wilson, R.; Dance, R. J.; MacLellan, D. A.; Butler, N. M. H.; Capdessus, R.; McKenna, P., E-mail: paul.mckenna@strath.ac.uk [SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Stockhausen, L. C. [Centro de Laseres Pulsados (CLPU), Parque Cientifico, Calle del Adaja s/n. 37185 Villamayor, Salamanca (Spain); Carroll, D. C. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Yuan, X. H. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240 (China); Borghesi, M. [Centre for Plasma Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Neely, D. [SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom)

2016-06-15

Multiple ion acceleration mechanisms can occur when an ultrathin foil is irradiated with an intense laser pulse, with the dominant mechanism changing over the course of the interaction. Measurement of the spatial-intensity distribution of the beam of energetic protons is used to investigate the transition from radiation pressure acceleration to transparency-driven processes. It is shown numerically that radiation pressure drives an increased expansion of the target ions within the spatial extent of the laser focal spot, which induces a radial deflection of relatively low energy sheath-accelerated protons to form an annular distribution. Through variation of the target foil thickness, the opening angle of the ring is shown to be correlated to the point in time transparency occurs during the interaction and is maximized when it occurs at the peak of the laser intensity profile. Corresponding experimental measurements of the ring size variation with target thickness exhibit the same trends and provide insight into the intra-pulse laser-plasma evolution.

Electron emission induced by resonant coherent ion-surface interaction at grazing incidence

International Nuclear Information System (INIS)

Garcia de Abajo, F.J.; Ponce, V.H.; Echenique, P.M.

1992-01-01

A new spectroscopy based on the resonant coherently induced electron loss to the continuum in ion-surface scattering under grazing incidence is proposed. A series of peaks, corresponding to the energy differences determined by the resonant interaction with the rows of atoms in the surface, is predicted to appear in the energy distribution of electrons emitted from electronic states bound to the probe. Calculations for MeV He + ions scattered at a W(001) surface along the left-angle 100 right-angle direction with a glancing angle of 0--2 mrad show a total yield close to 1

Potentiometric and spectroscopic study of the interaction of 3d transition metal ions with inositol hexakisphosphate

Science.gov (United States)

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.

Breakout character of islet amyloid polypeptide hydrophobic mutations at the onset of type-2 diabetes

Science.gov (United States)

Frigori, Rafael B.

2014-11-01

Toxic fibrillar aggregates of islet amyloid polypeptide (IAPP) appear as the physical outcome of a peptidic phase transition signaling the onset of type-2 diabetes mellitus in different mammalian species. In particular, experimentally verified mutations on the amyloidogenic segment 20-29 in humans, cats, and rats are highly correlated with the molecular aggregation propensities. Through a microcanonical analysis of the aggregation of IAPP20 -29 isoforms, we show that a minimalist one-bead hydrophobic-polar continuum model for protein interactions properly quantifies those propensities from free-energy barriers. Our results highlight the central role of sequence-dependent hydrophobic mutations on hot spots for stabilization, and thus for the engineering, of such biological peptides.

Cu(I)/Cu(II) mixed-valence surface complexes of S-[(2-hydroxyamino)-2-oxoethyl]-N,N-dibutyldithiocarbamate: Hydrophobic mechanism to malachite flotation.

Science.gov (United States)

Liu, Sheng; Zhong, Hong; Liu, Guangyi; Xu, Zhenghe

2018-02-15

Hydroxamate and sulfhydryl surfactants are effective collectors for flotation of copper minerals. The combination application of hydroxamate and sulfhydryl collectors has been proved to be an effective approach for improving the flotation recovery of non-sulfide copper minerals. A surfactant owing both hydroxamate and dithiocarbamate groups might exhibit strong affinity to non-sulfide copper minerals through double sites adsorption, rendering an enhanced hydrophobization to non-sulfide copper minerals flotation. The flotation performance of S-[(2-hydroxyamino)-2-oxoethyl]- N,N-dibutyldithiocarbamate (HABTC) to malachite, calcite and quartz were first evaluated through systematic micro-flotation experiments. HABTC's hydrophobic mechanism to malachite was further investigated and analyzed by zeta potential, Fourier transform infrared spectroscopy (FTIR), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The micro-flotation results demonstrated HABTC was an excellent collector for malachite flotation and exhibited favorable selectivity for flotation separation of malachite from quartz or calcite under pH 8.5-10.3. Zeta potential and FTIR implied that HABTC might bond with the surface copper atoms of malachite, with releasing the H + ions of its hydroxamate group into pulp. ToF-SIMS provided clear evidences that the Cu-hydroxamate and Cu-dithiocarbamate groups were formed on malachite surfaces after HABTC adsorption. XPS revealed that Cu(I)/Cu(II) mixed-valence surface complexes of HABTC anchored on malachite through formation of Cu(I)S and Cu(II)O bonds, accompanying with reduction of partial surface Cu(II) to Cu(I). The Cu(I)/Cu(II) mixed-valence double chelating character and "chair"-shape N,N-dibutyldithiocarbamate hydrophobic group, resulting in an enhanced affinity and hydrophobization of HABTC to malachite flotation. Copyright © 2017 Elsevier Inc. All rights reserved.

Coulombic interactions during advection-dominated transport of ions in porous media

DEFF Research Database (Denmark)

Muniruzzaman, Muhammad; Stolze, Lucien; Rolle, Massimo

2017-01-01

bench-scale experiments and numerical simulations. The investigation aims at quantifying the key role of small-scale electrostatic interactions in flow-through systems, especially when advection is the dominant mass-transfer process. Considering dilute solutions of strong electrolytes (e.g., MgCl2......Solute transport of charged species in porous media is significantly affected by the electrochemical migration term resulting from the charge-induced interactions among dissolved ions and with solid surfaces. Therefore, the characterization of such Coulombic interactions and their effect...... on multicomponent ionic transport is of critical importance for assessing the fate of charged solutes in porous media. In this work we present a detailed investigation of the electrochemical effects during conservative multicomponent ionic transport in homogeneous and heterogeneous domains by means of laboratory...

The Outer Membrane Protein OmpW Forms an Eight-Stranded beta-Barrel with a Hydrophobic Channel

International Nuclear Information System (INIS)

Hong, H.; Patel, D.; Tamm, L.; van den Berg, B.

2006-01-01

Escherichia coli OmpW belongs to a family of small outer membrane (OM) proteins that are widespread in Gram-negative bacteria. Their functions are unknown, but recent data suggest that they may be involved in the protection of bacteria against various forms of environmental stress. In order to gain insight into the function of these proteins we have determined the crystal structure of Escherichia coli OmpW to 2.7 Angstroms resolution. The structure shows that OmpW forms an eight-stranded beta-barrel with a long and narrow hydrophobic channel that contains a bound LDAO detergent molecule. Single channel conductance experiments show that OmpW functions as an ion channel in planar lipid bilayers. The channel activity can be blocked by the addition of LDAO. Taken together, the data suggest that members of the OmpW family could be involved in the transport of small hydrophobic molecules across the bacterial OM

Interchannel interactions in high-energetic radiationless transitions of neon-like ions

International Nuclear Information System (INIS)

Fritzsche, S.; Zschornack, G.; Musiol, G.; Soff, G.

1990-07-01

Relativistic K-LL Auger transition rates in intermediate coupling including interchannel interactions are presented for nine ions in the neon-isoelectronic sequence up to uranium. For neutral neon a comparison with experimental data is given. We demonstrate for the first time, that intercontinuum interactions result in a remarkable redistribution of individual transition rates even in high-energetic transitions. For instance, channel mixing shifts the K-L 1 L 1 rate by about 4% and the K-L 3 L 3 (J = 0) rate by about 11% in neon-like uranium, while total Auger rates are almost not affected. (orig.)

The operator technique in the theory of the rare earth ion interaction with ligand nuclei

International Nuclear Information System (INIS)

Anikeenok, O.A.; Eremin, M.V.; Khutsishvili, O.G.

1986-01-01

The tensor structure of the operator of rare earth ion interaction with nuclei of close ligands conditioned by virtual processes of charge transport is established. It is taken into account that virtual processes of electron transport from the ligand can take place to the non-filled 4f-, void 5d- and 6s- and preliminarily excited 5p-shells of the rare earth ion. Effects of 4f- and 5d-state mixing by the odd crystal field are considered for the first time. In contrast to the usual multipole-dipole interaction the given one is characterized by anomalously greater significance of highest multipole momenta of the rare earth ion and in the common case it does not have axial symmetry. The theory is compared with data on double electron-nuclear resonance and radiofrequency discrete saturation, taking CaF 2 :Ce 3+ impurity centers as an example

Ion-beam Plasma Neutralization Interaction Images

Energy Technology Data Exchange (ETDEWEB)

Igor D. Kaganovich; Edward Startsev; S. Klasky; Ronald C. Davidson

2002-04-09

Neutralization of the ion beam charge and current is an important scientific issue for many practical applications. The process of ion beam charge and current neutralization is complex because the excitation of nonlinear plasma waves may occur. Computer simulation images of plasma neutralization of the ion beam pulse are presented.

Ion-beam Plasma Neutralization Interaction Images

International Nuclear Information System (INIS)

Igor D. Kaganovich; Edward Startsev; S. Klasky; Ronald C. Davidson

2002-04-01

Neutralization of the ion beam charge and current is an important scientific issue for many practical applications. The process of ion beam charge and current neutralization is complex because the excitation of nonlinear plasma waves may occur. Computer simulation images of plasma neutralization of the ion beam pulse are presented

A new viscosupplement based on partially hydrophobic hyaluronic acid: a comparative study.

Science.gov (United States)

Finelli, Ivana; Chiessi, Ester; Galesso, Devis; Renier, Davide; Paradossi, Gaio

2011-01-01

A novel partially hydrophobized derivative of hyaluronic acid (HYADD® 4), containing a low number of C16 side-chains per polysaccharide backbone, provides injectable hydrogels stabilized by side-chain hydrophobic interactions. The rheological properties of Hymovis®, a physical hydrogel based on the hyaluronic acid derivative HYADD® 4, were evaluated using as reference a solution of the parent natural polysaccharide, hyaluronic acid. The rheological measurements were performed both in flow and oscillation regimes at the physiological frequency values of the knee, typically spanning the range from 0.5 Hz (walking frequency) to 3 Hz (running frequency). Moreover, the viscoelastic features of Hymovis® were compared with the market-available viscosupplementation products in view of its use in joint diseases.The different behavior of the investigated materials in crossover frequency measurements and in structure recovery experiments can be explained on the basis of the structural and dynamic properties of the polymeric systems.

Why are ionic liquid ions mainly associated in water? A Car-Parrinello study of 1-ethyl-3-methyl-imidazolium chloride water mixture

Science.gov (United States)

Spickermann, C.; Thar, J.; Lehmann, S. B. C.; Zahn, S.; Hunger, J.; Buchner, R.; Hunt, P. A.; Welton, T.; Kirchner, B.

2008-09-01

In this study we present the results of a first principles molecular dynamics simulation of a single 1-ethyl-3-methyl-imidazolium chloride [C2C1im][Cl] ion pair dissolved in 60 water molecules. We observe a preference of the in plane chloride coordination with respect to the cation ring plane as compared to the energetic slightly more demanding on top coordination. Evaluation of the different radial distribution functions demonstrates that the structure of the hydration shell around the ion pair differs significantly from bulk water and that no true ion pair dissociation in terms of completely autonomous solvation shells takes place on the timescale of the simulation. In addition, dipole moment distributions of the solvent in distinct solvation shells around different functional parts of the [C2C1im][Cl] ion pair are calculated from maximally localized Wannier functions. The analysis of these distributions gives evidence for a depolarization of water molecules close to the hydrophobic parts of the cation as well as close to the anion. Examination of the angular distribution of different OH(H2O )-X angles in turn shows a linear coordination of chloride accompanied by a tangential orientation of water molecules around the hydrophobic groups, being a typical feature of hydrophobic hydration. Based on these orientational aspects, a structural model for the obvious preference of ion pair association is developed, which justifies the associating behavior of solvated [C2C1im][Cl] ions in terms of an energetically favorable interface between the solvation shells of the anion and the hydrophobic parts of the cation.

Effect and interactions of commercial additives and chloride ion in copper electrowinning

Science.gov (United States)

Cui, Wenyuan

This thesis is to understand and compare the effects and interactions of modified polysaccharide (HydroStar), polyacrylamide (Cyquest N-900) and chloride ion on copper electrowinning. A study of the nucleation and growth was conducted in a synthetic electrolyte (40 g/L Cu, 160 g/L H2SO 4, 20 mg/L Cl-) with the addition of HydroStar or Cyquest N-900 using potential step measurements. The current responses generated were compared to theoretical models of nucleation and growth mechanisms. The nucleation and growth mechanism changed as function of potential and the presence of organic additives. The nucleation and growth mechanisms were confirmed using scanning electron microscopy (SEM). At low overpotentials, electrodeposition from the electrolyte without additives proceeded by progressive nucleation with three-dimensional (3-D) growth. The addition of HydroStar produced smaller nuclei and changed the mechanism to progressive nucleation and 2-D growth. Cyquest N-900 used there appeared to be progressive nucleation with 2-D growth and polarize the cathodes. In addition, instantaneous nucleation under diffusion control occurred at high overpotentials. Chloride ion and its interaction with HydroStar and Cyquest N-900 were further characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The trends observed from Nyquist plots and equivalent circuit models were consistent with the CV results. Chloride, on its own, depolarized copper electrodeposition, while chloride ion associated with Cyquest N-900 inhibited the reaction. It is proposed that Cl- acted as a bridging ligand between copper and Cyquest N-900. The addition of HydroStar depolarized copper deposition, but it did not interact with.

High hydrostatic pressure inactivation of Lactobacillus plantarum cells in (O/W)-emulsions is independent from cell surface hydrophobicity and lipid phase parameters

Science.gov (United States)

Kafka, T. A.; Reitermayer, D.; Lenz, C. A.; Vogel, R. F.

2017-07-01

Inactivation efficiency of high hydrostatic pressure (HHP) processing of food is strongly affected by food matrix composition. We investigated effects of fat on HHP inactivation of spoilage-associated Lactobacillus (L.) plantarum strains using defined oil-in-water (O/W)-emulsion model systems. Since fat-mediated effects on HHP inactivation could be dependent on interactions between lipid phase and microbial cells, three major factors possibly influencing such interactions were considered, that is, cell surface hydrophobicity, presence and type of surfactants, and oil droplet size. Pressure tolerance varied noticeably among L. plantarum strains and was independent of cell surface hydrophobicity. We showed that HHP inactivation of all strains tended to be more effective in presence of fat. The observation in both, surfactant-stabilized and surfactant-free (O/W)-emulsion, indicates that cell surface hydrophobicity is no intrinsic pressure resistance factor. In contrast to the presence of fat per se, surfactant type and oil droplet size did not affect inactivation efficiency.

Prediction of Hydrophobic Cores of Proteins Using Wavelet Analysis.

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Hirakawa; Kuhara

1997-01-01

Information concerning the secondary structures, flexibility, epitope and hydrophobic regions of amino acid sequences can be extracted by assigning physicochemical indices to each amino acid residue, and information on structure can be derived using the sliding window averaging technique, which is in wide use for smoothing out raw functions. Wavelet analysis has shown great potential and applicability in many fields, such as astronomy, radar, earthquake prediction, and signal or image processing. This approach is efficient for removing noise from various functions. Here we employed wavelet analysis to smooth out a plot assigned to a hydrophobicity index for amino acid sequences. We then used the resulting function to predict hydrophobic cores in globular proteins. We calculated the prediction accuracy for the hydrophobic cores of 88 representative set of proteins. Use of wavelet analysis made feasible the prediction of hydrophobic cores at 6.13% greater accuracy than the sliding window averaging technique.

Twisted-Light-Ion Interaction: The Role of Longitudinal Fields

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Quinteiro, G. F.; Schmidt-Kaler, Ferdinand; Schmiegelow, Christian T.

2017-12-01

The propagation of light beams is well described using the paraxial approximation, where field components along the propagation direction are usually neglected. For strongly inhomogeneous or shaped light fields, however, this approximation may fail, leading to intriguing variations of the light-matter interaction. This is the case of twisted light having opposite orbital and spin angular momenta. We compare experimental data for the excitation of a quadrupole transition in a single trapped 40Ca+ ion from Schmiegelow et al. [Nat. Commun. 7, 12998 (2016), 10.1038/ncomms12998] with a complete model where longitudinal components of the electric field are taken into account. Our model matches the experimental data and excludes by 11 standard deviations the approximation of a complete transverse field. This demonstrates the relevance of all field components for the interaction of twisted light with matter.

A simple model for low energy ion-solid interactions

International Nuclear Information System (INIS)

Mohajerzadeh, S.; Selvakumar, C.R.

1997-01-01

A simple analytical model for ion-solid interactions, suitable for low energy beam depositions, is reported. An approximation for the nuclear stopping power is used to obtain the analytic solution for the deposited energy in the solid. The ratio of the deposited energy in the bulk to the energy deposited in the surface yields a ceiling for the beam energy above which more defects are generated in the bulk resulting in defective films. The numerical evaluations agree with the existing results in the literature. copyright 1997 American Institute of Physics

Multi-spectroscopic characterization of bovine serum albumin upon interaction with atomoxetine

Directory of Open Access Journals (Sweden)

Arunkumar T. Buddanavar

2017-06-01

Full Text Available The quenching interaction of atomoxetine (ATX with bovine serum albumin (BSA was studied in vitro under optimal physiological condition (pH=7.4 by multi-spectroscopic techniques. The mechanism of ATX-BSA system was a dynamic quenching process and was confirmed by the fluorescence spectra and lifetime measurements. The number of binding sites, binding constants and other binding characteristics were computed. Thermodynamic parameters ∆H° and ∆S° indicated that intermolecular hydrophobic forces predominantly stabilized the drug-protein system. The average binding distance between BSA and ATX was studied by Försters theory. UV-absorption, Fourier transform infrared spectroscopy (FT-IR, circular dichroism (CD, synchronous spectra and three-dimensional (3D fluorescence spectral results revealed the changes in micro-environment of secondary structure of protein upon the interaction with ATX. Displacement of site probes and the effects of some common metal ions on the binding of ATX with BSA interaction were also studied.

Accelerator-Based Studies of Heavy Ion Interactions Relevant to Space Biomedicine

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Miller, J.; Heilbronn, L.; Zeitlin, C.

1999-01-01

Evaluation of the effects of space radiation on the crews of long duration space missions must take into account the interactions of high energy atomic nuclei in spacecraft and planetary habitat shielding and in the bodies of the astronauts. These heavy ions (i.e. heavier than hydrogen), while relatively small in number compared to the total galactic cosmic ray (GCR) charged particle flux, can produce disproportionately large effects by virtue of their high local energy deposition: a single traversal by a heavy charged particle can kill or, what may be worse, severely damage a cell. Research into the pertinent physics and biology of heavy ion interactions has consequently been assigned a high priority in a recent report by a task group of the National Research Council. Fragmentation of the incident heavy ions in shielding or in the human body will modify an initially well known radiation field and thereby complicate both spacecraft shielding design and the evaluation of potential radiation hazards. Since it is impractical to empirically test the radiation transport properties of each possible shielding material and configuration, a great deal of effort is going into the development of models of charged particle fragmentation and transport. Accurate nuclear fragmentation cross sections (probabilities), either in the form of measurements with thin targets or theoretical calculations, are needed for input to the transport models, and fluence measurements (numbers of fragments produced by interactions in thick targets) are needed both to validate the models and to test specific shielding materials and designs. Fluence data are also needed to characterize the incident radiation field in accelerator radiobiology experiments. For a number of years, nuclear fragmentation measurements at GCR-like energies have been carried out at heavy ion accelerators including the LBL Bevalac, Saturne (France), the Synchrophasotron and Nuklotron (Dubna, Russia), SIS-18 (GSI, Germany), the

New insights into the interactions between cork chemical components and pesticides. The contribution of π-π interactions, hydrogen bonding and hydrophobic effect.

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Olivella, M À; Bazzicalupi, C; Bianchi, A; Fiol, N; Villaescusa, I

2015-01-01

The role of chemical components of cork in the sorption of several pesticides has been investigated. For this purpose raw cork and three cork extracted fractions (i.e. cork free of aliphatic extractives, cork free of all extractives and cork free of all extractives and suberin) were used as sorbent of three ionic pesticides (propazine, 2,4-dichlorophenoxy acetic acid (2,4-D) and alachlor) and five non-ionic pesticides (chlorpyrifos, isoproturon, metamitron, methomyl and oxamyl) with a logKow within the range -0.47 to 4.92. The effect of cations on the ionic pesticides, propazine and 2,4-D sorption was also analyzed. Results indicated that the highest yields were obtained for chlorpyrifos and alachlor sorption onto raw cork (>55%). After removal of aliphatic extractives sorption of all pesticides increased that ranged from 3% for propazine to 31% for alachlor. In contrast, removal of phenolic extractives caused a sorption decrease. Low sorption yields were obtained for hydrophobic pesticides such as metamitron, oxamyl and methomyl (cork fractions and extremely low when using raw cork (cork toward aromatic pesticides. Results presented in this paper gain insights into the cork affinities for pesticides and the interactions involved in the sorption process and also enables to envisage sorption affinity of cork for other organic pollutants. Copyright © 2014 Elsevier Ltd. All rights reserved.

Molecular models of alginic acid: Interactions with calcium ions and calcite surfaces

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Perry, Thomas D.; Cygan, Randall T.; Mitchell, Ralph

2006-07-01

Cation binding by polysaccharides is observed in many environments and is important for predictive environmental modeling, and numerous industrial and food technology applications. The complexities of these cation-organic interactions are well suited for predictive molecular modeling and the analysis of conformation and configuration of polysaccharides and their influence on cation binding. In this study, alginic acid was chosen as a model polymer system and representative disaccharide and polysaccharide subunits were developed. Molecular dynamics simulation of the torsion angles of the ether linkage between various monomeric subunits identified local and global energy minima for selected disaccharides. The simulations indicate stable disaccharide configurations and a common global energy minimum for all disaccharide models at Φ = 274 ± 7°, Ψ = 227 ± 5°, where Φ and Ψ are the torsion angles about the ether linkage. The ability of disaccharide subunits to bind calcium ions and to associate with the (101¯4) surface of calcite was also investigated. Molecular models of disaccharide interactions with calcite provide binding energy differences for conformations that are related to the proximity and residence densities of the electron-donating moieties with calcium ions on the calcite surface, which are controlled, in part, by the torsion of the ether linkage between monosaccharide units. Dynamically optimized configurations for polymer alginate models with calcium ions were also derived.

Studies of Interactions of Positive Helium Ions with Small Neutrals at Temperatures Below 50K

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Schauer, Martin Michael

1990-01-01

Interactions of He^+ ions with small neutrals are important because of their fundamental nature and applicability to other areas of research. In the past, very little work has been done on such systems at very low temperatures (T Boehringer and Arnold (1986) and Johnsen, Chen, and Biondi (1980). A new method of detecting the ions in the trap was also developed and implemented. The Fourier Transform Ion Z-resonance (FTIZR) technique took advantage of an induced coherence in the oscillations of the ions in the trap. This method allowed for measurement of faster ion -neutral reactions. This method was demonstrated by studying the non -resonant charge transfer process ^3He ^+{+}^4He{toatop >=ts}^3He{+}^4He^+. These measurements confirmed that the forward reaction is endothermic by about 1.1 meV.

Electron emission induced by resonant coherent interaction in ion-surface scattering at grazing incidence

International Nuclear Information System (INIS)

Garcia de Abajo, F.J.; Ponce, V.H.; Echenique, P.M.

1994-01-01

The resonant coherent interaction of an ion with an oriented crystal surface, under grazing-incidence conditions with respect to a special direction of the crystal, gives rise to electron loss to the continuum from electronic bound states of the ion. The calculations presented below predict large probabilities for electron emission due to this mechanism. The electrons are emitted with well defined energies, expressed in terms of the condition of resonance. Furthermore, the emission takes place around certain preferential directions, which are determined by both the latter condition and the symmetry of the surface lattice. Our calculations for MeV He + ions scattered at a W(001) surface along the left-angle 100 right-angle direction with glancing angle of 0--2 mrad indicate a yield of emission close to 1. Using heavier projectiles, one obtains smaller yields, but still large enough to be measurable in some cases (e.g., ∼0.9 for 53 MeV B 4+ and an angle of incidence of 1 mrad). Besides, the initial bound state is energy shifted due to the interaction with both the crystal potential and the velocity-dependent image potential. This results in a slight shift of the peaks of emission, which suggests a possible spectroscopy for analyzing the dynamical interaction of electronic bound states with solid surfaces

Role of air bubbles overlooked in the adsorption of perfluorooctanesulfonate on hydrophobic carbonaceous adsorbents.

Science.gov (United States)

Meng, Pingping; Deng, Shubo; Lu, Xinyu; Du, Ziwen; Wang, Bin; Huang, Jun; Wang, Yujue; Yu, Gang; Xing, Baoshan

2014-12-02

Hydrophobic interaction has been considered to be responsible for adsorption of perfluorooctanesulfonate (PFOS) on the surface of hydrophobic adsorbents, but the long C-F chain in PFOS is not only hydrophobic but also oleophobic. In this study, for the first time we propose that air bubbles on the surface of hydrophobic carbonaceous adsorbents play an important role in the adsorption of PFOS. The level of adsorption of PFOS on carbon nanotubes (CNTs), graphite (GI), graphene (GE), and powdered activated carbon (PAC) decreases after vacuum degassing. Vacuum degassing time and pressure significantly affect the removal of PFOS by these adsorbents. After vacuum degassing at 0.01 atm for 36 h, the extent of removal of PFOS by the pristine CNTs and GI decreases 79% and 74%, respectively, indicating the main contribution of air bubbles to PFOS adsorption. When the degassed solution is recontacted with air during the adsorption process, the removal of PFOS recovers to the value obtained without vacuum degassing, further verifying the key role of air bubbles in PFOS adsorption. By theoretical calculation, the distribution of PFOS in air bubbles on the adsorbent surfaces is discussed, and a new schematic sorption model of PFOS on carbonaceous adsorbents in the presence of air bubbles is proposed. The accumulation of PFOS at the interface of air bubbles on the adsorbents is primarily responsible for its adsorption, providing a new mechanistic insight into the transport, fate, and removal of PFOS.

Tarantula toxins use common surfaces for interacting with Kv and ASIC ion channels.