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Sample records for hydrophobic molecule separations

  1. Bile salt surfactants in micellar electrokinetic capillary chromatography: Application to hydrophobic molecule separations

    SciTech Connect

    Cole, R.O.; Sepaniak, M.J. . Dept. of Chemistry); Hinze, W.L. . Dept. of Chemistry); Gorse, J.; Oldiges, K. . Dept. of Chemistry)

    1990-01-01

    Bile Salt surfactants are used in the micellar electrokinetic capillary chromatography (MECC) separation of various hydrophobic compounds. The use of methanol in the mobile phase allows the separation of previously intractable compounds including polyaromatic hydrocarbons. The effects of methanol on critical micelle concentration is investigated for sodium dodecyl sulfate (SDS) and the bile salt sodium cholate. It is determined that the unique structure of the bile salt micelle is much more tolerant to the addition of organic solvents than SDS, thereby increasing the scope of applications of MECC to include hydrophobic compounds. 30 refs., 9 figs.

  2. Selective on site separation and detection of molecules in diluted solutions with super-hydrophobic clusters of plasmonic nanoparticles

    NASA Astrophysics Data System (ADS)

    Gentile, Francesco; Coluccio, Maria Laura; Zaccaria, Remo Proietti; Francardi, Marco; Cojoc, Gheorghe; Perozziello, Gerardo; Raimondo, Raffaella; Candeloro, Patrizio; di Fabrizio, Enzo

    2014-06-01

    Super-hydrophobic surfaces are bio-inspired interfaces with a superficial texture that, in its most common evolution, is formed by a periodic lattice of silicon micro-pillars. Similar surfaces reveal superior properties compared to conventional flat surfaces, including very low friction coefficients. In this work, we modified meso-porous silicon micro-pillars to incorporate networks of metal nano-particles into the porous matrix. In doing so, we obtained a multifunctional-hierarchical system in which (i) at a larger micrometric scale, the super-hydrophobic pillars bring the molecules dissolved in an ultralow-concentration droplet to the active sites of the device, (ii) at an intermediate meso-scale, the meso-porous silicon film adsorbs the low molecular weight content of the solution and, (iii) at a smaller nanometric scale, the aggregates of silver nano-particles would measure the target molecules with unprecedented sensitivity. In the results, we demonstrated how this scheme can be utilized to isolate and detect small molecules in a diluted solution in very low abundance ranges. The presented platform, coupled to Raman or other spectroscopy techniques, is a realistic candidate for the protein expression profiling of biological fluids.Super-hydrophobic surfaces are bio-inspired interfaces with a superficial texture that, in its most common evolution, is formed by a periodic lattice of silicon micro-pillars. Similar surfaces reveal superior properties compared to conventional flat surfaces, including very low friction coefficients. In this work, we modified meso-porous silicon micro-pillars to incorporate networks of metal nano-particles into the porous matrix. In doing so, we obtained a multifunctional-hierarchical system in which (i) at a larger micrometric scale, the super-hydrophobic pillars bring the molecules dissolved in an ultralow-concentration droplet to the active sites of the device, (ii) at an intermediate meso-scale, the meso-porous silicon film

  3. Selective on site separation and detection of molecules in diluted solutions with super-hydrophobic clusters of plasmonic nanoparticles.

    PubMed

    Gentile, Francesco; Coluccio, Maria Laura; Zaccaria, Remo Proietti; Francardi, Marco; Cojoc, Gheorghe; Perozziello, Gerardo; Raimondo, Raffaella; Candeloro, Patrizio; Di Fabrizio, Enzo

    2014-07-21

    Super-hydrophobic surfaces are bio-inspired interfaces with a superficial texture that, in its most common evolution, is formed by a periodic lattice of silicon micro-pillars. Similar surfaces reveal superior properties compared to conventional flat surfaces, including very low friction coefficients. In this work, we modified meso-porous silicon micro-pillars to incorporate networks of metal nano-particles into the porous matrix. In doing so, we obtained a multifunctional-hierarchical system in which (i) at a larger micrometric scale, the super-hydrophobic pillars bring the molecules dissolved in an ultralow-concentration droplet to the active sites of the device, (ii) at an intermediate meso-scale, the meso-porous silicon film adsorbs the low molecular weight content of the solution and, (iii) at a smaller nanometric scale, the aggregates of silver nano-particles would measure the target molecules with unprecedented sensitivity. In the results, we demonstrated how this scheme can be utilized to isolate and detect small molecules in a diluted solution in very low abundance ranges. The presented platform, coupled to Raman or other spectroscopy techniques, is a realistic candidate for the protein expression profiling of biological fluids.

  4. Size selective hydrophobic adsorbent for organic molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Hickey, Gregory S. (Inventor)

    1997-01-01

    The present invention relates to an adsorbent formed by the pyrolysis of a hydrophobic silica with a pore size greater than 5 .ANG., such as SILICALITE.TM., with a molecular sieving polymer precursor such as polyfurfuryl alcohol, polyacrylonitrile, polyvinylidene chloride, phenol-formaldehyde resin, polyvinylidene difluoride and mixtures thereof. Polyfurfuryl alcohol is the most preferred. The adsorbent produced by the pyrolysis has a silicon to carbon mole ratio of between about 10:1 and 1:3, and preferably about 2:1 to 1:2, most preferably 1:1. The pyrolysis is performed as a ramped temperature program between about 100.degree. and 800.degree. C., and preferably between about 100.degree. and 600.degree. C. The present invention also relates to a method for selectively adsorbing organic molecules having a molecular size (mean molecular diameter) of between about 3 and 6 .ANG. comprising contacting a vapor containing the small organic molecules to be adsorbed with the adsorbent composition of the present invention.

  5. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  6. Intercalation of small hydrophobic molecules in lipid bilayers containing cholesterol

    SciTech Connect

    Worcester, D.L.; Hamacher, K.; Kaiser, H.; Kulasekere, R.; Torbet, J.

    1994-12-31

    Partitioning of small hydrophobic molecules into lipid bilayers containing cholesterol has been studied using the 2XC diffractometer at the University of Missouri Research Reactor. Locations of the compounds were determined by Fourier difference methods with data from both deuterated and undeuterated compounds introduced into the bilayers from the vapor phase. Data fitting procedures were developed for determining how well the compounds were localized. The compounds were found to be localized in a narrow region at the center of the hydrophobic layer, between the two halves of the bilayer. The structures are therefore intercalated structures with the long axis of the molecules in the plane of the bilayer.

  7. Fast rotational motion of water molecules increases ordering of hydrophobes in solutions and may cause hydrophobic chains to collapse.

    PubMed

    Mohorič, Tomaž; Bren, Urban; Vlachy, Vojko

    2015-12-28

    Using the molecular dynamics simulations with separate thermostats for translational and rotational degrees of freedom, we investigate the effects of water's rotational motion on the interaction among Lennard-Jones solutes. The situation with rotational temperature higher than the translational one (TR > TT) is mimicking the effects of microwaves on model solutions. Molecular dynamics simulations suggest that solutions of Lennard-Jones solutes become increasingly more structured with the rise in TR, while keeping the TT constant. This is evidenced by an increase of the first and the second peak of the solute-solute radial distribution function. In addition, the first peak moves toward slightly larger distances; the effect seems to be caused by the destabilization of water molecules in the first hydration shell around hydrophobic solutes. More evidence of strong effects of the rotationally excited water is provided by the simulations of short hydrophobic polymers, which upon an increase in TR assume more compact conformations. In these simulations, we see the re-distribution of water molecules, which escape from hydrophobic "pockets" to better solvate the solvent exposed monomers.

  8. Fast rotational motion of water molecules increases ordering of hydrophobes in solutions and may cause hydrophobic chains to collapse

    NASA Astrophysics Data System (ADS)

    Mohorič, Tomaž; Bren, Urban; Vlachy, Vojko

    2015-12-01

    Using the molecular dynamics simulations with separate thermostats for translational and rotational degrees of freedom, we investigate the effects of water's rotational motion on the interaction among Lennard-Jones solutes. The situation with rotational temperature higher than the translational one (TR > TT) is mimicking the effects of microwaves on model solutions. Molecular dynamics simulations suggest that solutions of Lennard-Jones solutes become increasingly more structured with the rise in TR, while keeping the TT constant. This is evidenced by an increase of the first and the second peak of the solute-solute radial distribution function. In addition, the first peak moves toward slightly larger distances; the effect seems to be caused by the destabilization of water molecules in the first hydration shell around hydrophobic solutes. More evidence of strong effects of the rotationally excited water is provided by the simulations of short hydrophobic polymers, which upon an increase in TR assume more compact conformations. In these simulations, we see the re-distribution of water molecules, which escape from hydrophobic "pockets" to better solvate the solvent exposed monomers.

  9. A New Hydrophobic Catalyst for Tritium Separation from Nuclear Effluents

    SciTech Connect

    Popescu, I.; Ionita, Gh.; Stefanescu, I.; Kitamoto, A.

    2005-07-15

    The hydrophobic catalysts were originally conceived in Canada for the deuterium enrichment and tritium separation by hydrogen-liquid water isotopic exchange in nuclear field. Unlike the conventional hydrophilic catalysts, which becomes inefficient to direct contact with liquid water, the hydrophobic catalysts kept a high catalytic activity and stability, even under the direct contact with liquid water or in presence of humid gas. 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 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 asses and to find a new procedure for preparation of a new improved hydrophobic catalyst. From reviewed references we consider that platinum remains the most active and efficient catalytic metal and the TEFLON is the best wetproofing agent. A new improved hydrophobic Pt-catalyst has been proposed and is now underway. The main steps and experimental conditions of preparation are largely discussed. A new wet-proofing agent and a new binding agents (titanium oxide, cerium oxide, zirconium oxide) with catalytic role are proposed and tested. The physico-structural parameters of new improved catalyst have been determined and are discussed in details. The new proposal is a promising idea to improve the performances of conventional hydrophobic Pt-catalysts.

  10. Hydration properties of small hydrophobic molecules by Brillouin light scattering

    NASA Astrophysics Data System (ADS)

    Comez, L.; Lupi, L.; Paolantoni, M.; Picchiò, F.; Fioretto, D.

    2012-09-01

    We study the relaxation of water molecules next to hydrophobic solutes with different functional groups by Brillouin light scattering. Evidence is given for (i) water activation energy in trimethylamine-N-oxide, proline and t-butyl alcohol diluted solutions which is comparable to that of neat water, almost independent from solute mole fraction and (ii) moderate slowdown of relaxation time of proximal water compared to the bulk, which is consistent with excluded volume models. Assuming that the main contribution to viscosity comes from bulk and hydration water, a rationale is given of the phenomenological Arrhenius' laws for the viscosity of diluted aqueous solutions.

  11. Separations method for polar molecules

    DOEpatents

    Thoma, Steven G.; Bonhomme, Francois R.

    2004-07-27

    A method for separating at least one compound from a liquid mixture containing different compounds where anew crystalline manganese phosphate composition with the formula Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O) is dispersed in the liquid mixture, selectively intercalating one or more compounds into the crystalline structure of the Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O).

  12. Separation of hydrophobic polymer additives by microemulsion electrokinetic chromatography.

    PubMed

    Hilder, E F; Klampfl, C W; Buchberger, W; Haddad, P R

    2001-07-13

    Microemulsion electrokinetic chromatography (MEEKC) has been applied to the separation of some phenolic antioxidants [Irganox 1024, Irganox 1035, Irganox 1076, Irganox 1010, Irganox 1330, Irgafos 138, Irganox 168 and 2,6-di-tert.-butyl-4-methylphenol (BHT)]. Due to the extremely hydrophobic nature of these analytes, they could not be separated using standard MEEKC conditions and two alternative approaches were investigated. Using an acidic buffer (phosphate, pH 2.5) to effectively suppress the electroosmotic flow, the addition of 2-propanol to the aqueous phase of the microemulsion buffer to improve partitioning of the analytes, and a negative separation voltage, separation of five of the analytes in under 10 min was possible. The second approach, using a basic buffer (borate, pH 9.2) and a positive separation voltage resulted in complete resolution of all eight analytes. A mixed surfactant system comprising the anionic sodium dodecyl sulfate (SDS) and neutral Brij 35 was used to reduce the overall charge and with it the mobility of the droplets, and hence the separation time. Using an optimised MEEKC buffer consisting of 2.25% (w/w) SDS, 0.75% (w/w) Brij 35, 0.8% (w/w) n-octane, 6.6% (w/w) 1-butanol, 25% (w/w) 2-propanol and 64.6% (w/w) 10 mM borate buffer (pH 9.2) the eight target analytes were baseline separated in under 25 min. For these analytes, MEEKC was found to be superior to micellar electrokinetic chromatography in every respect. Specifically, the solubility of the analytes was better, the selectivity was more favourable, the analysis time was shorter and the separation efficiency was up to 72% higher when using the MEEKC method. Detection limits from 5.4 to 26 microg/ml were obtained and the calibration plot was linear over more than one order of magnitude. The optimised method could be applied to the determination of Irganox 1330 and Irganox 1010 in polypropylene.

  13. Roles of Interleaflet Coupling and Hydrophobic Mismatch in Lipid Membrane Phase-Separation Kinetics.

    PubMed

    Fowler, Philip W; Williamson, John J; Sansom, Mark S P; Olmsted, Peter D

    2016-09-14

    Characterizing the nanoscale dynamic organization within lipid bilayer membranes is central to our understanding of cell membranes at a molecular level. We investigate phase separation and communication across leaflets in ternary lipid bilayers, including saturated lipids with between 12 and 20 carbons per tail. Coarse-grained molecular dynamics simulations reveal a novel two-step kinetics due to hydrophobic mismatch, in which the initial response of the apposed leaflets upon quenching is to increase local asymmetry (antiregistration), followed by dominance of symmetry (registration) as the bilayer equilibrates. Antiregistration can become thermodynamically preferred if domain size is restricted below ∼20 nm, with implications for the symmetry of rafts and nanoclusters in cell membranes, which have similar reported sizes. We relate our findings to theory derived from a semimicroscopic model in which the leaflets experience a "direct" area-dependent coupling, and an "indirect" coupling that arises from hydrophobic mismatch and is most important at domain boundaries. Registered phases differ in composition from antiregistered phases, consistent with a direct coupling between the leaflets. Increased hydrophobic mismatch purifies the phases, suggesting that it contributes to the molecule-level lipid immiscibility. Our results demonstrate an interplay of competing interleaflet couplings that affect phase compositions and kinetics, and lead to a length scale that can influence lateral and transverse bilayer organization within cells. PMID:27574865

  14. Roles of Interleaflet Coupling and Hydrophobic Mismatch in Lipid Membrane Phase-Separation Kinetics

    PubMed Central

    2016-01-01

    Characterizing the nanoscale dynamic organization within lipid bilayer membranes is central to our understanding of cell membranes at a molecular level. We investigate phase separation and communication across leaflets in ternary lipid bilayers, including saturated lipids with between 12 and 20 carbons per tail. Coarse-grained molecular dynamics simulations reveal a novel two-step kinetics due to hydrophobic mismatch, in which the initial response of the apposed leaflets upon quenching is to increase local asymmetry (antiregistration), followed by dominance of symmetry (registration) as the bilayer equilibrates. Antiregistration can become thermodynamically preferred if domain size is restricted below ∼20 nm, with implications for the symmetry of rafts and nanoclusters in cell membranes, which have similar reported sizes. We relate our findings to theory derived from a semimicroscopic model in which the leaflets experience a “direct” area-dependent coupling, and an “indirect” coupling that arises from hydrophobic mismatch and is most important at domain boundaries. Registered phases differ in composition from antiregistered phases, consistent with a direct coupling between the leaflets. Increased hydrophobic mismatch purifies the phases, suggesting that it contributes to the molecule-level lipid immiscibility. Our results demonstrate an interplay of competing interleaflet couplings that affect phase compositions and kinetics, and lead to a length scale that can influence lateral and transverse bilayer organization within cells. PMID:27574865

  15. Coat thickness dependent adsorption of hydrophobic molecules at polymer brushes

    NASA Astrophysics Data System (ADS)

    Smiatek, Jens; Heuer, Andreas; Wagner, Hendrik; Studer, Armido; Hentschel, Carsten; Chi, Lifeng

    2013-01-01

    We study the adsorption properties of hydrophobic test particles at polymer brushes with different coat thicknesses via mesoscopic dissipative particle dynamics simulations. Our findings indicate stronger free energies of adsorption at thin polymer brushes. The reason for this difference is mainly given by entropic contributions due to different elastic deformations of the coatings. The numerical findings are supported by analytical calculations and are in good qualitative agreement to experimental fluorescence intensity results.

  16. DNA micelles as nanoreactors: efficient DNA functionalization with hydrophobic organic molecules.

    PubMed

    Trinh, Tuan; Chidchob, Pongphak; Bazzi, Hassan S; Sleiman, Hanadi F

    2016-09-18

    We report a micelle-templated method to enhance the reactivity of DNA with highly hydrophobic molecules. Lipids, chromophores and polymers can be conjugated to DNA in high yield and under mild conditions. This method expands the range of DNA-templated reactions for DNA-encoded libraries, oligonucleotide and drug delivery, nanopore mimetics and DNA nanotechnology.

  17. Dependence of the number of hydrogen bonds per water molecule on its distance to a hydrophobic surface and a thereupon-based model for hydrophobic attraction.

    PubMed

    Djikaev, Y S; Ruckenstein, Eli

    2010-11-21

    A water molecule in the vicinity of a hydrophobic surface forms fewer hydrogen bonds than a bulk molecule because the surface restricts the space available for other water molecules necessary for its hydrogen-bonding. In this vicinity, the number of hydrogen bonds per water molecule depends on its distance to the surface. Considering the number of hydrogen bonds per bulk water molecule (available experimentally) as the only reference quantity, we propose an improved probabilistic approach to water hydrogen-bonding that allows one to obtain an analytic expression for this dependence. (The original version of this approach [Y. S. Djikaev and E. Ruckenstein, J. Chem. Phys. 130, 124713 (2009)] provides the number of hydrogen bonds per water molecule in the vicinity of a hydrophobic surface as an average over all possible locations and orientations of the molecule.) This function (the number of hydrogen bonds per water molecule versus its distance to a hydrophobic surface) can be used to develop analytic models for the effect of hydrogen-bonding on the hydration of hydrophobic particles and their solvent-mediated interaction. Presenting a model for the latter, we also examine the temperature effect on the solvent-mediated interaction of two parallel hydrophobic plates.

  18. Separation and counting of single molecules through nanofluidics, programmable electrophoresis, and nanoelectrode-gated tunneling and dielectric detection

    DOEpatents

    Lee, James W.; Thundat, Thomas G.

    2006-04-25

    An apparatus for carrying out the separation, detection, and/or counting of single molecules at nanometer scale. Molecular separation is achieved by driving single molecules through a microfluidic or nanofluidic medium using programmable and coordinated electric fields. In various embodiments, the fluidic medium is a strip of hydrophilic material on nonconductive hydrophobic surface, a trough produced by parallel strips of hydrophobic nonconductive material on a hydrophilic base, or a covered passageway produced by parallel strips of hydrophobic nonconductive material on a hydrophilic base together with a nonconductive cover on the parallel strips of hydrophobic nonconductive material. The molecules are detected and counted using nanoelectrode-gated electron tunneling methods, dielectric monitoring, and other methods.

  19. A Novel Separation Method of Microthrix parvicella Filaments from Activated Sludge by a Hydrophobic Plate.

    PubMed

    Fei, Xuening; Li, Songya; Cao, Lingyun; Yan, Weiguo; Ma, Huaji; Jia, Guozhi

    2015-10-01

    The aim of this paper is to develop a novel method to separate Microthrix parvicella (M. parvicella) filaments from activated sludge easily and quickly, as there are a few difficulties in the isolation of M. parvicella filaments, such as complicated isolation process, time consuming, etc. In this work, a series of hydrophobic plate with and without microchannels have been prepared for the separation of M. parvicella filaments. The results showed that the presence of microchannels and hydrophobic property of the hydrophobic plates affected the separation efficiency of M. parvicella significantly. The scanning electron microscope and Keyence Digital Microscope analysis results showed that the diameter of microchannels was similar to the width of M. parvicella filament, which was beneficial for the fastening of M. parvicella filaments on the plate. The hydrophobic property of the prepared plates was tested by contact angle of water droplets, and the results displayed that the polydimethylsiloxane (PDMS) plate possessed the highest contact angle compared with that of other plates, like polymethylmethacrylate, polystyrene plate, and PDMS plate with no hydrophobic microchannels. Thus, it was concluded that the high separation efficiency of PDMS plates to M. parvicella filaments was due to its best hydrophobic property.

  20. Morphology and phase separation of hydrophobic clusters of soy globular protein polymers.

    PubMed

    Sun, Xiuzhi Susan; Wang, Donghai; Zhang, Lu; Mo, Xiaoqun; Zhu, Li; Bolye, Dan

    2008-04-01

    Protein hydrophobic interaction has been considered the most important factor dominating protein folding, aggregation, gelling, self-assembly, adhesion, and cohesion properties. In this paper, morphology and phase separation of hydrophobic clusters, networks, and aggregates of soy globular protein polymers, induced by using a reducing agent (NaHSO3), are studied using microscopic instruments. The morphology and phase separation of these hydrophobic clusters are sensitive to protein structure and composition, pH, and ionic-strength (I(m)). Most of the clusters are in spherical-shape architecture and mainly consist of hydrophobic polypeptides. Rod-shape clusters were also observed at higher ionic strength, and mainly consist of hydrophilic polypeptides. The ratio of hydrophobic/hydrophilic (HB/HL) polypeptides is important to facilitate the formation of clusters in an environment with a certain pH value and ionic strength. At HB/HL 0.8, uniform spherical clusters were observed and diameters ranged from 30 to 70 nm. At HB/HL <0.8, large spherical clusters were formed with diameters ranging from 100 to 1,000 nm, and at HB/HL >or=1.8, large hydrophobic aggregates formed, and size of aggregates can be up to 2 500 nm. When solid content increased from 3% to 38%, at I(m) or= 0.115 mol x L(-1), HB/HL ratio >or=1.8, the large aggregates became very cohesive and viscoelastic. Clear phase separation was observed during curing between hydrophobic and hydrophilic protein polymers. Phase-separation degree increased as HB/HL ratio increased.

  1. Microsphere adsorption method to study interaction of DNA with hydrophobic molecules

    NASA Astrophysics Data System (ADS)

    Carr, Aaron C.; Crockett, Harriet; Krishnan, Rajagopal; Little, Kevin; Nordlund, Thomas M.

    2003-03-01

    Polystyrene microspheres are reproducible in size, material, and surface character, and can have surfaces that adsorb hydrophobic molecules such as the sunscreens octyl methoxycinnamate and octyl salicylate. Inclusion of 220-nm polystyrene microspheres increases the amount of optically-observed octyl salicylate injected and then vortex-mixed in a buffer suspension by 30 times or more compared to the same buffer without microspheres. Addition of a roughly equal amount of DNA to the salicylate/microsphere preparation caused a 40sunscreen fluorescence. The microsphere technique is thus effective both in adsorbing significant amounts of hydrophobic sunscreen and in showing interaction with DNA. The most straightforward interpretation of these results is that 40fluorescence quenching only indicates the energy leaves the sunscreen. The DNA may cause this energy movement, but the final location of the energy, on the DNA or dissipated into solution, is unknown. Addition of DNA appropriately labeled with an energy acceptor will settle the issue.

  2. Controlled supramolecular oligomerization of C3-symmetrical molecules in water: the impact of hydrophobic shielding.

    PubMed

    Besenius, Pol; van den Hout, Kelly P; Albers, Harald M H G; de Greef, Tom F A; Olijve, Luuk L C; Hermans, Thomas M; de Waal, Bas F M; Bomans, Paul H H; Sommerdijk, Nico A J M; Portale, Giuseppe; Palmans, Anja R A; van Genderen, Marcel H P; Vekemans, Jef A J M; Meijer, E W

    2011-04-26

    The supramolecular oligomerization of three water-soluble C(3)-symmetrical discotic molecules is reported. The compounds all possess benzene-1,3,5-tricarboxamide cores and peripheral Gd(III)-DTPA (diethylene triamine pentaacetic acid) moieties, but differ in their linker units and thus in their propensity to undergo secondary interactions in H(2)O. The self-assembly behavior of these molecules was studied in solution using circular dichroism, UV/Vis spectroscopy, nuclear magnetic resonance, and cryogenic transmission electron microscopy. The aggregation concentration of these molecules depends on the number of secondary interactions and on the solvophobic character of the polymerizing moieties. Hydrophobic shielding of the hydrogen-bonding motif in the core of the discotic is of paramount importance for yielding stable, helical aggregates that are designed to be restricted in size through anti-cooperative, electrostatic, repulsive interactions.

  3. Spin Hall separation of ultracold atom-molecule mixed gases

    NASA Astrophysics Data System (ADS)

    Ye, Chong; Fu, Li-Bin; Liu, Jie

    2016-05-01

    We propose a theoretical scheme to separate a molecular cloud from atoms in analogy to the spin Hall effect and to completely transfer Feshbach molecules to the ground state by applying a spatially modulated laser field to an atom-molecule mixed gas. In particular, the laser-molecule interaction induces a synthetic U(1) gauge potential for the dressed molecular dark state. Through numerical simulation, we demonstrate that such a gauge field leads to a spin Hall separation of atoms and molecules. In such a process, molecules can be transformed into the ground state completely.

  4. Modulation by small hydrophobic molecules of valinomycin-mediated potassium transport across phospholipid vesicle membranes

    SciTech Connect

    Clement, N.R.; Gould, J.M.

    1981-01-01

    The effects of small hydrophobic molecules on valinonycin-mediated K/sup +/ transport in small unilamellar soybean phospholipid vesicles have been studied by using a vesicle-entrapped pH-sensitive hydropholic fluorescence probe to monitor counterion-limited, passive H/sup +/ diffusion into vesicles after an abrupt decrease in external pH. Under conditions where, even in the absence of valinomycin, transmembrane K/sup +/ movement represented the primary and limiting counterion flux, <1 valinomycin molecule/vesicle was sufficient to accelerate the rate of H/sup +/ entry into all of the vesicles. Incorporation of the bulkily substituted molecules butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and p-di-tert-butylbenzene into soybean lipid bilayers had no effect upon K/sup +/ diffusion in the absence of valinomycin. However, the presence of these hydrophobic molecules increased the apparent efficacy for K/sup +/ transport of a given valinomycin concentration by as much as 4-6 fold. The less bulky membrane perturbants tert-butyl alcohol, phenol, and heptane showed very much less dramatic effects. While the rate of valinomycin-mediated K/sup +/ transport (in the presence or absence of BHT) was very sensitive to temperature-induced changes in membrane fluidity, the degree of synergistic interaction between valinomycin and BHT was independent of temperature. Furthermore, BHT, BHA, and p-di-tert-butylbenzene, at levels which alter valinomycin-mediated K/sup +/ transport, did not by themselves induce changes in membrane fluidity. It is postulated that changes in phospholipid head-group packing and/or surface charge density brought about by the presence of bulky perturber molecules leads to changes in partitioning of valinomycin or the valinomycin-K/sup +/ complex between the aqueous and membrane phases.

  5. pH-Triggered Release of Hydrophobic Molecules from Self-Assembling Hybrid Nanoscaffolds.

    PubMed

    Lu, Lei; Unsworth, Larry D

    2016-04-11

    Self-assembling peptide based hydrogels have a wide range of applications in the field of tissue repair and tissue regeneration. Because of its physicochemical properties, (RADA)4 has been studied as a potential platform for 3D cell culture, drug delivery, and tissue engineering. Despite some small molecule and protein release studies with this system, there is a lack of work investigating the controlled release of hydrophobic compounds (i.e., anti-inflammatory, anticancer, antibacterial drugs, etc.) that are important for many clinical therapies. Attempts to incorporate hydrophobic compounds into self-assembling matrices usually inhibited nanofiber formation, rather resulting in a peptide-drug complex or microcrystal formation. Herein, a self-assembling chitosan/carboxymethyl-β-cyclodextrin nanoparticle system was used to load dexamethasone, which formed within a self-assembling (RADA)4 nanoscaffold matrix. Nanoparticles dispersed within the matrix were stabilized by the nanofibers within. The in vitro release of dexamethasone from the hybrid system was observed to be pH sensitive. At pH 7, release was observed for more than 8 days, with three distinct kinetic domains in the first 6 days. Data suggest that the deprotonation of chitosan at a solution pH > 6.8 leads to nanoparticle dissociation and ultimately the release of dexamethasone from the hybrid system. This system has the potential to form a multifunctional scaffold that can self-assemble with the ability to control the release of hydrophobic drugs for a wide variety of applications. PMID:26938197

  6. A new anion-exchange/hydrophobic monolith as stationary phase for nano liquid chromatography of small organic molecules and inorganic anions.

    PubMed

    Aydoğan, Cemil

    2015-05-01

    In this study, an anion-exchange/hydrophobic polymethacrylate-based stationary phase was prepared for nano-liquid chromatography of small organic molecules and inorganic anions. The stationary phase was synthesized by in situ polymerization of 3-chloro-2-hydroxypropylmethacrylate and ethylene dimethacrylate inside silanized 100 μm i.d. fused silica capillary. The porogen mixture consisted of toluene and dodecanol. The pore size distrubution profiles of the resulting monolith were determined by mercury intrusion porosimetry and the morphology of the prepared monolith was investigated by scanning electron microscope. Good permeability, stability and column efficiency were observed on the monolithic column with nano flow. The produced monolithic column, which contains reactive chloro groups, was then modified by reaction with N,N-dimethyl-N-dodecylamine to obtain an anion-exchange/hydrophobic monolithic stationary phase. The functionalized monolith contained ionizable amine groups and hydrophobic groups that are useful of anion-exchange/hydrophobic mixed-mode chromatography. The final monolithic column performance with respect to anion-exchange and hydrophobic interactions was assesed by the separation of alkylbenzene derivatives, phenolic compounds and inorganic anions, respectively. Theoretical plate numbers up to 23,000 plates/m were successfully achieved in the separation of inorganic anions.

  7. Hydrophobic fluorescent probes introduce artifacts into single molecule tracking experiments due to non-specific binding.

    PubMed

    Zanetti-Domingues, Laura C; Tynan, Christopher J; Rolfe, Daniel J; Clarke, David T; Martin-Fernandez, Marisa

    2013-01-01

    Single-molecule techniques are powerful tools to investigate the structure and dynamics of macromolecular complexes; however, data quality can suffer because of weak specific signal, background noise and dye bleaching and blinking. It is less well-known, but equally important, that non-specific binding of probe to substrates results in a large number of immobile fluorescent molecules, introducing significant artifacts in live cell experiments. Following from our previous work in which we investigated glass coating substrates and demonstrated that the main contribution to this non-specific probe adhesion comes from the dye, we carried out a systematic investigation of how different dye chemistries influence the behaviour of spectrally similar fluorescent probes. Single-molecule brightness, bleaching and probe mobility on the surface of live breast cancer cells cultured on a non-adhesive substrate were assessed for anti-EGFR affibody conjugates with 14 different dyes from 5 different manufacturers, belonging to 3 spectrally homogeneous bands (491 nm, 561 nm and 638 nm laser lines excitation). Our results indicate that, as well as influencing their photophysical properties, dye chemistry has a strong influence on the propensity of dye-protein conjugates to adhere non-specifically to the substrate. In particular, hydrophobicity has a strong influence on interactions with the substrate, with hydrophobic dyes showing much greater levels of binding. Crucially, high levels of non-specific substrate binding result in calculated diffusion coefficients significantly lower than the true values. We conclude that the physic-chemical properties of the dyes should be considered carefully when planning single-molecule experiments. Favourable dye characteristics such as photostability and brightness can be offset by the propensity of a conjugate for non-specific adhesion. PMID:24066121

  8. How To Functionalize Ceramics by Perfluoroalkylsilanes for Membrane Separation Process? Properties and Application of Hydrophobized Ceramic Membranes.

    PubMed

    Kujawa, Joanna; Cerneaux, Sophie; Kujawski, Wojciech; Bryjak, Marek; Kujawski, Jan

    2016-03-23

    The combination of microscopic (atomic force microscopy and scanning electron microscopy) and goniometric (static and dynamic measurements) techniques, and surface characterization (surface free energy determination, critical surface tension, liquid entry pressure, hydraulic permeability) was implemented to discuss the influence of perfluoroalkylsilanes structure and grafting time on the physicochemistry of the created hydrophobic surfaces on the titania ceramic membranes of 5 kD and 300 kD. The impact of molecular structure of perfluoroalkylsilanes modifiers (possessing from 6 to 12 carbon atoms in the fluorinated part of the alkyl chain) and the time of the functionalization process in the range of 5 to 35 h was studied. Based on the scanning electron microscopy with energy-dispersive X-ray spectroscopy, it was found that the localization of grafting molecules depends on the membrane pore size (5 kD or 300 kD). In the case of 5 kD titania membranes, modifiers are attached mainly on the surface and only partially inside the membrane pores, whereas, for 300 kD membranes, the perfluoroalkylsilanes molecules are present within the whole porous structure of the membranes. The application of 4 various types of PFAS molecules enabled for interesting observations and remarks. It was explained how to obtain ceramic membrane surfaces with controlled material (contact angle, roughness, contact angle hysteresis) and separation properties. Highly hydrophobic surfaces with low values of contact angle hysteresis and low roughness were obtained. These surfaces possessed also low values of critical surface tension, which means that surfaces are highly resistant to wetting. This finding is crucial in membrane applicability in separation processes. The obtained and characterized hydrophobic membranes were subsequently applied in air-gap membrane distillation processes. All membranes were very efficient in MD processes, showing good transport and selective properties (∼99% of Na

  9. How To Functionalize Ceramics by Perfluoroalkylsilanes for Membrane Separation Process? Properties and Application of Hydrophobized Ceramic Membranes.

    PubMed

    Kujawa, Joanna; Cerneaux, Sophie; Kujawski, Wojciech; Bryjak, Marek; Kujawski, Jan

    2016-03-23

    The combination of microscopic (atomic force microscopy and scanning electron microscopy) and goniometric (static and dynamic measurements) techniques, and surface characterization (surface free energy determination, critical surface tension, liquid entry pressure, hydraulic permeability) was implemented to discuss the influence of perfluoroalkylsilanes structure and grafting time on the physicochemistry of the created hydrophobic surfaces on the titania ceramic membranes of 5 kD and 300 kD. The impact of molecular structure of perfluoroalkylsilanes modifiers (possessing from 6 to 12 carbon atoms in the fluorinated part of the alkyl chain) and the time of the functionalization process in the range of 5 to 35 h was studied. Based on the scanning electron microscopy with energy-dispersive X-ray spectroscopy, it was found that the localization of grafting molecules depends on the membrane pore size (5 kD or 300 kD). In the case of 5 kD titania membranes, modifiers are attached mainly on the surface and only partially inside the membrane pores, whereas, for 300 kD membranes, the perfluoroalkylsilanes molecules are present within the whole porous structure of the membranes. The application of 4 various types of PFAS molecules enabled for interesting observations and remarks. It was explained how to obtain ceramic membrane surfaces with controlled material (contact angle, roughness, contact angle hysteresis) and separation properties. Highly hydrophobic surfaces with low values of contact angle hysteresis and low roughness were obtained. These surfaces possessed also low values of critical surface tension, which means that surfaces are highly resistant to wetting. This finding is crucial in membrane applicability in separation processes. The obtained and characterized hydrophobic membranes were subsequently applied in air-gap membrane distillation processes. All membranes were very efficient in MD processes, showing good transport and selective properties (∼99% of Na

  10. PEGylated protein separation using different hydrophobic interaction supports: Conventional and monolithic supports.

    PubMed

    Mayolo-Deloisa, Karla; González-Valdez, José; Rito-Palomares, Marco

    2016-05-01

    Protein hydrophobicity can be modified after a PEGylation process. However, hydrophobic interaction chromatography (HIC) has been used to separate PEGylation reaction products less frequently than other techniques. In this context, chromatographic monoliths represent a good alternative to continue exploring the separation of PEGylated proteins with HIC. In this work, the separation of PEGylated proteins using C4 A monolith as well as Toyopearl Butyl 650C and Butyl Sepharose was analyzed. Three proteins were used as models: RNase A, β-lactoglobulin, and lysozyme. All proteins were PEGylated in the N-terminal amino groups with 20 kDa methoxy poly(ethylene glycol) propionaldehyde. The concentration of ammonium sulfate (1 M) used was the same for all stationary phases. The results obtained demonstrated that the C4 A monolith could better resolve all protein PEGylation reaction mixtures, since the peaks of mono- and di-PEGylated proteins can be clearly distinguished in the chromatographic profiles. On the contrary, while using Butyl Sepharose media only the PEGylation reaction mixtures of RNase A could be partially separated at 35 and 45 CVs. PEGylated proteins of β-lactoglobulin and lysozyme could not be resolved when Toyopearl Butyl 650C and Butyl Sepharose were used. It is then clear that monoliths are an excellent choice to explore the purification process of PEGylated proteins exploiting the advantages of HIC. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:702-707, 2016. PMID:26918888

  11. Stimuli-responsive HBPS-g-PDMAEMA and its application as nanocarrier in loading hydrophobic molecules.

    PubMed

    Chen, Yongsheng; Wang, Li; Yu, Haojie; Zain-Ul-Abdin; Sun, Ruoli; Jing, Guanghui; Tong, Rongbai; Deng, Zheng

    2016-01-01

    The topic of stimuli-responsive nanocarriers for loading guest molecules is dynamic. It has been widely studied in applications including drug controlled release, smart sensing, catalysis, and modeling. In this paper, a graft copolymer (hyperbranched polystyrene)-g-poly[2-(dimethylamino)ethyl methacrylate] (HBPS-g-PDMAEMA) was synthesized and characterized by (1)H NMR and GPC. It was observed that the star-like HBPS-g-PDMAEMA formed aggregates in aqueous solution. The influence of polymer concentration, ionic strength and pH value on the aggregates in aqueous solution was investigated by using UV-vis spectroscopy and DLS analysis. The results showed that size of aggregates was affected by a corresponding stimulus. In addition, the loading ability of HBPS-g-PDMAEMA aggregates was investigated by using pyrene or Nile red as the model guest molecules by using UV-vis and fluorescence spectroscopy. The results showed that HBPS-g-PDMAEMA aggregates were capable to encapsulate small hydrophobic molecules. These newly prepared HBPS-g-PDMAEMA nanocarriers might be used in, e.g., medicine or catalysis.

  12. Stimuli-responsive HBPS-g-PDMAEMA and its application as nanocarrier in loading hydrophobic molecules

    PubMed Central

    Chen, Yongsheng; Zain-Ul-Abdin; Sun, Ruoli; Jing, Guanghui; Tong, Rongbai; Deng, Zheng

    2016-01-01

    Summary The topic of stimuli-responsive nanocarriers for loading guest molecules is dynamic. It has been widely studied in applications including drug controlled release, smart sensing, catalysis, and modeling. In this paper, a graft copolymer (hyperbranched polystyrene)-g-poly[2-(dimethylamino)ethyl methacrylate] (HBPS-g-PDMAEMA) was synthesized and characterized by 1H NMR and GPC. It was observed that the star-like HBPS-g-PDMAEMA formed aggregates in aqueous solution. The influence of polymer concentration, ionic strength and pH value on the aggregates in aqueous solution was investigated by using UV–vis spectroscopy and DLS analysis. The results showed that size of aggregates was affected by a corresponding stimulus. In addition, the loading ability of HBPS-g-PDMAEMA aggregates was investigated by using pyrene or Nile red as the model guest molecules by using UV–vis and fluorescence spectroscopy. The results showed that HBPS-g-PDMAEMA aggregates were capable to encapsulate small hydrophobic molecules. These newly prepared HBPS-g-PDMAEMA nanocarriers might be used in, e.g., medicine or catalysis. PMID:27340484

  13. Temperature dependence of the transport of single-file water molecules through a hydrophobic channel.

    PubMed

    Su, Jiaye; Yang, Keda

    2016-05-01

    Although great effort has been made on the transport properties of water molecules through nanometer channels, our understanding on the effect of some basic parameters are still rather poor. In this article, we use molecular dynamics simulations to study the temperature effect on the transport of single-file water molecules through a hydrophobic channel. Of particular interest is that the water flow and average translocation time both exhibit exponential relations with the temperature. Based on the continuous-time random-walk model and Arrhenius equation, we explore some new physical insights on these exponential behaviors. With the increase of temperature, the water dipoles flip more frequently, since the estimated flipping barrier is less than 2 kB T. Specifically, the flipping frequency also shows an exponential relation with the temperature. Furthermore, the water-water interaction and water occupancy demonstrate linear relations with the temperature, and the water density profiles along the channel axis can be slightly affected by the temperature. These results not only enhance our knowledge about the temperature effect on the single-file water transport, but also have potential implications for the design of controllable nanofluidic machines.

  14. Isotope separation by photodissociation of Van der Waal's molecules

    DOEpatents

    Lee, Yuan T.

    1977-01-01

    A method of separating isotopes based on the dissociation of a Van der Waal's complex. A beam of molecules of a Van der Waal's complex containing, as one partner of the complex, a molecular species in which an element is present in a plurality of isotopes is subjected to radiation from a source tuned to a frequency which will selectively excite vibrational motion by a vibrational transition or through electronic transition of those complexed molecules of the molecular species which contain a desired isotope. Since the Van der Waal's binding energy is much smaller than the excitational energy of vibrational motion, the thus excited Van der Waal's complex dissociate into molecular components enriched in the desired isotope. The recoil velocity associated with vibrational to translational and rotational relaxation will send the separated molecules away from the beam whereupon the product enriched in the desired isotope can be separated from the constituents of the beam.

  15. Efficient Catalytic Electrode for CO2 Reduction Realized by Physisorbing Ni(cyclam) Molecules with Hydrophobicity Based on Hansen's Theory.

    PubMed

    Murase, Masakazu; Kitahara, Gaku; Suzuki, Tomiko M; Ohta, Riichiro

    2016-09-21

    An electrochemical electrode physisorbed with Ni(cyclam) complex molecules containing tetraphenylborate ions (BPh4(-)) as counteranions shows catalytic activity for the reduction reaction of CO2 to CO in an aqueous electrolyte, superior to that of an electrode physisorbed with conventional [Ni(cyclam)]Cl2 complex molecules. The BPh4(-)-containing Ni(cyclam) is inferred as having high hydrophobicity based on its Hansen solubility parameter (HSP), with an interaction sphere excluding HSPs of water in a three-dimensional vector space. The high hydrophobicity of BPh4(-)-containing Ni(cyclam) molecules inhibits their dissolution into aqueous electrolyte and retains their immobilization onto the electrode surface, which we believe to result in the improved catalytic activity of the electrode physisorbed with them. HSP analysis also provides an optimized mixing ratio of solvents dissolving BPh4(-)-containing Ni(cyclam) molecules. PMID:27606702

  16. Temperature dependence of local solubility of hydrophobic molecules in the liquid-vapor interface of water.

    PubMed

    Abe, Kiharu; Sumi, Tomonari; Koga, Kenichiro

    2014-11-14

    One important aspect of the hydrophobic effect is that solubility of small, nonpolar molecules in liquid water decreases with increasing temperature. We investigate here how the characteristic temperature dependence in liquid water persists or changes in the vicinity of the liquid-vapor interface. From the molecular dynamics simulation and the test-particle insertion method, the local solubility Σ of methane in the liquid-vapor interface of water as well as Σ of nonpolar solutes in the interface of simple liquids are calculated as a function of the distance z from the interface. We then examine the temperature dependence of Σ under two conditions: variation of Σ at fixed position z and that at fixed local solvent density around the solute molecule. It is found that the temperature dependence of Σ at fixed z depends on the position z and the system, whereas Σ at fixed local density decreases with increasing temperature for all the model solutions at any fixed density between vapor and liquid phases. The monotonic decrease of Σ under the fixed-density condition in the liquid-vapor interface is in accord with what we know for the solubility of nonpolar molecules in bulk liquid water under the fixed-volume condition but it is much robust since the solvent density to be fixed can be anything between the coexisting vapor and liquid phases. A unique feature found in the water interface is that there is a minimum in the local solubility profile Σ(z) on the liquid side of the interface. We find that with decreasing temperature the minimum of Σ grows and at the same time the first peak in the oscillatory density profile of water develops. It is likely that the minimum of Σ is due to the layering structure of the free interface of water.

  17. Separation of proteins from human plasma by sample displacement chromatography in hydrophobic interaction mode

    PubMed Central

    Josic, Djuro; Breen, Lucas; Clifton, James; Gajdosik, Martina Srajer; Gaso-Sokac, Dajana; Rucevic, Marijana; Müller, Egbert

    2013-01-01

    Sample displacement chromatography (SDC) in reversed-phase and ion-exchange modes was introduced approximately twenty years ago. This method was first used for the preparative purification of peptides and proteins. Recently, SDC in ion-exchange mode was also successfully used for enrichment of low abundance proteins from human plasma. In this paper, the use of SDC for the separation of plasma proteins in hydrophobic interaction mode is demonstrated. By use of two or more columns coupled in series during sample application, and subsequent elution of detached columns in parallel, additional separation of bound proteins was achieved. Further low-abundance, physiologically active proteins could be highly enriched and detected by ESI-MS/MS. PMID:22740472

  18. Separation of proteins from human plasma by sample displacement chromatography in hydrophobic interaction mode.

    PubMed

    Josic, Djuro; Breen, Lucas; Clifton, James; Gajdosik, Martina Srajer; Gaso-Sokac, Dajana; Rucevic, Marijana; Müller, Egbert

    2012-07-01

    Sample displacement chromatography (SDC) in reversed-phase and ion-exchange modes was introduced approximately 20 years ago. This method was first used for the preparative purification of peptides and proteins. Recently, SDC in ion-exchange mode was also successfully used for enrichment of low-abundance proteins from human plasma. In this paper, the use of SDC for the separation of plasma proteins in hydrophobic interaction mode is demonstrated. By use of two or more columns coupled in series during sample application, and subsequent elution of detached columns in parallel, additional separation of bound proteins was achieved. Further low-abundance, physiologically active proteins could be highly enriched and detected by ESI-MS/MS.

  19. Hydrophobic asymmetric ultrafiltration PVDF membranes: an alternative separator for VFB with excellent stability.

    PubMed

    Wei, Wenping; Zhang, Huamin; Li, Xianfeng; Zhang, Hongzhang; Li, Yun; Vankelecom, Ivo

    2013-02-14

    Polyvinylidene fluoride (PVDF) ultrafiltration membranes were investigated for the first time in vanadium redox flow battery (VFB) applications. Surprisingly, PVDF ultrafiltration membranes with hydrophobic pore walls and relatively large pore sizes of several tens of nanometers proved able to separate vanadium ions and protons efficiently, thus being suitable as a VFB separator. The ion selectivity of this new type of VFB membrane could be tuned readily by controlling the membrane morphology via changes in the composition of the membrane casting solution, and the casting thickness. The results showed that the PVDF membranes offered good performances and excellent stability in VFB applications, where it could, performance-wise, truly substitute Nafion in VFB applications, but at a much lower cost. PMID:23223708

  20. Hydrophobic asymmetric ultrafiltration PVDF membranes: an alternative separator for VFB with excellent stability.

    PubMed

    Wei, Wenping; Zhang, Huamin; Li, Xianfeng; Zhang, Hongzhang; Li, Yun; Vankelecom, Ivo

    2013-02-14

    Polyvinylidene fluoride (PVDF) ultrafiltration membranes were investigated for the first time in vanadium redox flow battery (VFB) applications. Surprisingly, PVDF ultrafiltration membranes with hydrophobic pore walls and relatively large pore sizes of several tens of nanometers proved able to separate vanadium ions and protons efficiently, thus being suitable as a VFB separator. The ion selectivity of this new type of VFB membrane could be tuned readily by controlling the membrane morphology via changes in the composition of the membrane casting solution, and the casting thickness. The results showed that the PVDF membranes offered good performances and excellent stability in VFB applications, where it could, performance-wise, truly substitute Nafion in VFB applications, but at a much lower cost.

  1. Cu mesh's super-hydrophobic and oleophobic properties with variations in gravitational pressure and surface components for oil/water separation applications

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Zhang, Qin; Xiao, Haibo; Xu, Jie; Li, Qintao; Pan, Xiaohui; Huang, Zhiyong

    2014-09-01

    The super-hydrophobic and super-oleophilic properties of various materials have been utilized to separate oil from water. These properties induce both oil penetration and water slide off. This research demonstrates that the mesh with both super-hydrophobic and oleophobic properties, with a water contact angle (WCA) higher than 150° and oil contact angle (OCA) near 140°, can also be used to separate oil from. Oil has a higher probability than water of entering into the interstice of the Cu mesh surface and passing through it due to the capillarity effect, van der Waals attractions and the effects of gravitational pressure. The modified mesh surface can easily adsorb the oil, which then forms a film, due to the very strong adhesion properties of the oil molecules. The oil film then contributes to the water sliding off. These properties can be used to separate oil from water with separation efficiencies reaching 99.3%. Additionally, the separation of an oil/water mixture using sand permeated with oil yielded separation efficiencies exceeding 90%.

  2. Structural Order of Water Molecules around Hydrophobic Solutes: Length-Scale Dependence and Solute-Solvent Coupling.

    PubMed

    Hande, Vrushali R; Chakrabarty, Suman

    2015-08-27

    It has been suggested that the structure and thermodynamics of the water molecules in the hydration layer of simple hydrophobic solutes undergo an order-disorder transition around a nanometer length-scale of the solute size. Using extensive atomistic molecular dynamics (MD) and replica exchange molecular dynamics (REMD) simulation studies, we have probed this order-disorder transition around model hydrophobic solutes of varying size and shape (spherical, planar, and linear), as well as flexible hydrophobic homopolymer chains (n-alkanes), where the conformational fluctuations are likely to create both spatial and temporal heterogeneity on the solvent accessible surface. We have explored the structural response of the water molecules in the hydration shell due to the local variations of the length-scale (or curvature) upon hydrophobic collapse and/or local conformational changes of these polymers. We have shown that the tetrahedral order of the water molecules in the hydration shell is practically independent of the polymer size in the extended state of the polymer due to the availability of a subnanometer cross-sectional length-scale, allowing the water molecules to form hydrogen bonds around the polymer chain. Beyond a certain length of the polymer chains, the collapsed states (associated with larger solute length-scale) start to induce disorder in the surface water molecules. We demonstrate that the local structure (both local number density and tetrahedral order) of the hydration layer is dynamically coupled to the local topology of the polymer. Thus, we envisage that in a flexible (bio)polymer, the hydration shell properties will be sensitive to the local conformational state of the molecule (both spatially and temporally), and the overall observed water structure and dynamics will be dependent on the topological/chemical heterogeneity, and the time-scale of fluctuations in the local curvature (length-scale) of the solvent accessible surface. Moreover, we have

  3. Nanometric molecular separation measurements by single molecule photobleaching.

    PubMed

    Webb, Stephen E D; Hirsch, Michael; Needham, Sarah R; Coles, Benjamin C; Scherer, Kathrin M; Roberts, Selene K; Zanetti-Domingues, Laura C; Tynan, Christopher J; Martin-Fernandez, Marisa L; Rolfe, Daniel J

    2015-10-15

    Although considerable progress has been made in imaging distances in cells below the diffraction limit using FRET and super-resolution microscopy, methods for determining the separation of macromolecules in the 10-50 nm range have been elusive. We have developed fluorophore localisation imaging with photobleaching (FLImP), based on the quantised bleaching of individual protein-bound dye molecules, to quantitate the molecular separations in oligomers and nanoscale clusters. We demonstrate the benefits of using our method in studying the nanometric organisation of the epidermal growth factor receptor in cells.

  4. Effect of time and of precursor molecule on the deposition of hydrophobic nanolayers on ethyelene tetrafluoroethylene-silicon oxide substrates

    NASA Astrophysics Data System (ADS)

    Rossi, Gabriella; Castellano, Piera; Incarnato, Loredana

    2016-01-01

    A method was developed for generating transparent and hydrophobic nanolayers chemisorbed onto flexible substrates of ethylene tetrafluoroethylene-silicon oxide (ETFE-SiOx). In particular, the effect of the deposition time and of the precursor molecule on the nanocoating process was analyzed with the aim of pursuing an optimization of the above method in an industrial application perspective. It was found that precursor molecule of triethoxysilane allowed to obtain better hydrophobic properties on the SiOx surface in shorter times compared to trichlorosilane, reaching the 92 % of final contact angle (CA) value of 106° after only 1 h of deposition. The optical properties and surface morphology were also assessed in function of time, revealing that an initial transparency reduction is followed by a subsequent transmittance increase during the self assembly of fluoroalkylsilanes on the SiOx surface, coherently with the surface roughness analysis data. Encouraging results were also obtained in terms of oleophobic properties improvement of the nanocoated surfaces.

  5. Effect of time and of precursor molecule on the deposition of hydrophobic nanolayers on ethyelene tetrafluoroethylene-silicon oxide substrates

    NASA Astrophysics Data System (ADS)

    Rossi, Gabriella; Castellano, Piera; Incarnato, Loredana

    2016-10-01

    A method was developed for generating transparent and hydrophobic nanolayers chemisorbed onto flexible substrates of ethylene tetrafluoroethylene-silicon oxide (ETFE-SiOx). In particular, the effect of the deposition time and of the precursor molecule on the nanocoating process was analyzed with the aim of pursuing an optimization of the above method in an industrial application perspective. It was found that precursor molecule of triethoxysilane allowed to obtain better hydrophobic properties on the SiOx surface in shorter times compared to trichlorosilane, reaching the 92 % of final contact angle (CA) value of 106° after only 1 h of deposition. The optical properties and surface morphology were also assessed in function of time, revealing that an initial transparency reduction is followed by a subsequent transmittance increase during the self assembly of fluoroalkylsilanes on the SiOx surface, coherently with the surface roughness analysis data. Encouraging results were also obtained in terms of oleophobic properties improvement of the nanocoated surfaces.

  6. Ultrafast molecule separation through layered WS(2) nanosheet membranes.

    PubMed

    Sun, Luwei; Ying, Yulong; Huang, Hubiao; Song, Zhigong; Mao, Yiyin; Xu, Zhiping; Peng, Xinsheng

    2014-06-24

    Two-dimensional layered materials have joined in the family of size-selective separation membranes recently. Here, chemically exfoliated tungsten disulfide (WS2) nanosheets are assembled into lamellar thin films and explored as an ultrafast separation membrane for small molecules with size of about 3 nm. Layered WS2 membranes exhibit 5- and 2-fold enhancement in water permeance of graphene oxide membranes and MoS2 laminar membranes with similar rejection, respectively. To further increase the water permeance, ultrathin nanostrands are used as templates to generate more fluidic channel networks in the WS2 membrane. The water permeation behavior and separation performance in the pressure loading-unloading process reveal that the channels created by the ultrathin nanostrands are cracked under high pressure and result in a further 2-fold increase of the flux without significantly degrading the rejection for 3 nm molecules. This is supported by finite-element-based mechanical simulation. These layered WS2 membranes demonstrate up to 2 orders of magnitude higher separation performance than that of commercial membranes with similar rejections and hold the promising potential for water purification. PMID:24853383

  7. Beta-cyclodextrins conjugated magnetic Fe3O4 colloidal nanoclusters for the loading and release of hydrophobic molecule

    NASA Astrophysics Data System (ADS)

    Lv, Shaonan; Song, Yubei; Song, Yaya; Zhao, Zhigang; Cheng, Changjing

    2014-06-01

    Herein, we report a facile method to prepare beta-cyclodextrin (β-CD)-conjugated magnetic Fe3O4 colloidal nanocrystal clusters (Fe3O4@GLY-CD) using (3-glycidyloxypropyl) trimethoxysilane (GLY) as the intermediate linker. The resulting Fe3O4@GLY-CD was characterized by several methods including Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). In addition, the loading and release properties of the synthesized Fe3O4@GLY-CD for the hydrophobic molecule 8-anilino-1-naphthalenesulfonic acid ammonium salt (ANS) were also investigated. The results show that the Fe3O4@GLY-CD has a spherical structure with an average diameter of 186 nm and high saturated magnetism of 51.2 emu/g. The grafting of β-CD onto Fe3O4 colloidal nanocrystal clusters can markedly increase the loading capacity of ANS because of β-CD/ANS inclusion complex formation. The in vitro delivery profile shows that the release of ANS from the Fe3O4@GLY-CD nanosystem exhibits an initial burst followed by a slow and steady release. Moreover, Fe3O4@GLY-CD also demonstrates a temperature-dependent release behavior for ANS owing to the effect of temperature on the association constants of β-CD/ANS inclusion complexes. The developed magnetic hybrid nanomaterial is expected to find potential applications in several fields including separation science and biomedicine.

  8. [Beaded molecule imprinted polymer for stereo isomer separation].

    PubMed

    Meng, Z; Wang, J; Zhou, L; Wang, Q; Zhu, D

    1999-07-01

    Beaded molecule imprinted polymer (MIP) was made by suspension polymerization. Particles with the size of 50-70 microns in diameter were collected and evaluated in HPLC mode to separate stereo isomers. Stereo isomers cinchonine and cinchonidine were successfully discriminated with selectivity factor of 2.89 and resolution factor of 0.76. Stereo selectivity of the MIP was found to come from both the interaction between the analyte and carboxyl group on the MIP and the similarity between the stereo structure of imprinted molecule and the MIP. The thermal analysis results showed that the MIP had high thermal stability with initial thermal decomposition temperature of 320 degrees C. The pore volume of the MIP was 0.1849 mL/g, the specific surface area was 126.84 sqm/g and the average pore diameter was 5.8 nanometer. Scanning electron microscopy showed that MIP had perfect spherical morphology.

  9. New shell crosslinked micelles from dextran with hydrophobic end groups and their interaction with bioactive molecules.

    PubMed

    Mocanu, Georgeta; Nichifor, Marieta; Stanciu, Magdalena C

    2015-03-30

    Micelles formed in aqueous solution by dextran with hydrophobic (alkyl) end-groups were stabilized through divinyl sulfone crosslinking of the dextran shell. The efficacy of the crosslinking reaction was influenced by the divinyl sulfone amount, the pH and micelle concentration. Crosslinked micelles with a moderate crosslinking degree were further functionalized by attachment of 10 and 17 moles% N-(2-hydroxypropyl)-N,N-dimethyl-N-benzylammonium chloride groups along the dextran chain. The size and shape of both crosslinked micelles and their cationic derivatives were analyzed by DLS and TEM. The prepared micelles were able to bind anionic diclofenac (60-370 mg/g), hydrophobic anionic indometacin (70-120 mg/g), and hydrophobic alpha-tocopherol (170-220 mg/g) or ergocalciferol (90-110 mg/g) by hydrophobic or/and electrostatic forces. The release experiments and the antioxidant activity of bound alpha-tocopherol highlighted the potential of the new nano-sized micelles mainly as carriers for prolonged and controlled delivery of hydrophobic drugs.

  10. Superhydrophobic silica wool—a facile route to separating oil and hydrophobic solvents from water

    NASA Astrophysics Data System (ADS)

    Crick, Colin R.; Bhachu, Davinder S.; Parkin, Ivan P.

    2014-12-01

    Silica microfiber wool was systematically functionalized in order to provide an extremely water repellent and oleophilic material. This was carried out using a two-step functionalization that was shown to be a highly effective method for generating an intense water repulsion and attraction for oil. A demonstration of the silica wools application is shown through the highly efficient separation of oils and hydrophobic solvents from water. Water is confined to the extremities of the material, while oil is absorbed into the voids within the wool. The effect of surface functionalization is monitored though observing the interaction of the material with both oils and water, in addition to scanning electron microscope images, x-ray photoelectron spectroscopy and energy dispersive x-ray analysis. The material can be readily utilized in many applications, including the cleaning of oil spills and filtering during industrial processes, as well as further water purification tasks—while not suffering the losses of efficiency observed in current leading polymeric materials.

  11. Mercedes-Benz water molecules near hydrophobic wall: integral equation theories vs Monte Carlo simulations.

    PubMed

    Urbic, T; Holovko, M F

    2011-10-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes-Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied.

  12. Mercedes–Benz water molecules near hydrophobic wall: Integral equation theories vs Monte Carlo simulations

    PubMed Central

    Urbic, T.; Holovko, M. F.

    2011-01-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes–Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied. PMID:21992334

  13. Mercedes-Benz water molecules near hydrophobic wall: Integral equation theories vs Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Urbic, T.; Holovko, M. F.

    2011-10-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes-Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied.

  14. Mercedes-Benz water molecules near hydrophobic wall: integral equation theories vs Monte Carlo simulations.

    PubMed

    Urbic, T; Holovko, M F

    2011-10-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes-Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied. PMID:21992334

  15. Single-molecule methods to quantify adsorptive separations (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Landes, Christy

    2015-08-01

    Interfacial adsorption and transport are the chemical and physical processes that underlie separations. Although separations technology accounts for hundreds of billions of dollars in the global economy, the process is not well-understood at the mechanistic level and instead is almost always optimized empirically. One of the reasons is that access to the underlying molecular phenomena has only been available recently via single-molecule methods. There are still interesting challenges because adsorption, desorption, and transport are all dynamic processes, whereas much of the advances in super-resolution imaging have focused on imaging static materials. Our lab has focused in recent years on developing and optimizing data analysis methods for quantifying the dynamics of adsorption and transport in porous materials at nanometer-resolution spatial scales. Our methods include maximizing information content in dynamic single-molecule data and developing methods to detect change-points in binned data. My talk will outline these methods, and will address how and when they can be applied to extract dynamic details in heterogeneous materials such as porous membranes.

  16. Glyconanosomes: disk-shaped nanomaterials for the water solubilization and delivery of hydrophobic molecules.

    PubMed

    Assali, Mohyeddin; Cid, Juan-José; Pernía-Leal, Manuel; Muñoz-Bravo, Miguel; Fernández, Inmaculada; Wellinger, Ralf E; Khiar, Noureddine

    2013-03-26

    Herein, we describe the first report on a new class of disk-shaped and quite monodisperse water-soluble nanomaterials that we named glyconanosomes (GNS). GNSs were obtained by sliding out the cylindrical structures formed upon self-organization and photopolymerization of glycolipid 1 on single-walled carbon nanotube (SWCNT) sidewalls. GNSs present a sheltered hydrophobic inner cavity formed by the carbonated tails, surrounded by PEG and lactose moieties. The amphiphilic character of GNSs allows the water solubility of insoluble hydrophobic cargos such as a perylene-bisimide derivative, [60]fullerene, or the anti-carcinogenic drug camptothecin (CPT). GNS/C60 inclusion complexes are able to establish specific interactions between peanut agglutinin (PNA) lectin and the lactose moiety surrounding the complexes, while CPT solubilized by GNS shows higher cytotoxicity toward MCF7-type breast cancer cells than CPT alone. Thus, GNS represents an attractive extension of nanoparticle-based drug delivery systems.

  17. Super-hydrophobic fluorine containing aerogels

    DOEpatents

    Coronado, Paul R.; Poco, John F.; Hrubesh, Lawrence W.

    2007-05-01

    An aerogel material with surfaces containing fluorine atoms which exhibits exceptional hydrophobicity, or the ability to repel liquid water. Hydrophobic aerogels are efficient absorbers of solvents from water. Solvents miscible with water are separated from it because the solvents are more volatile than water and they enter the porous aerogel as a vapor across the liquid water/solid interface. Solvents that are immisicble with water are separated from it by selectively wetting the aerogel. The hydrophobic property is achieved by formulating the aerogel using fluorine containing molecules either directly by addition in the sol-gel process, or by treating a standard dried aerogel using the vapor of fluorine containing molecules.

  18. Entropically favored adsorption of cellulosic molecules onto carbon materials through hydrophobic functionalities.

    PubMed

    Yabushita, Mizuho; Kobayashi, Hirokazu; Hasegawa, Jun-Ya; Hara, Kenji; Fukuoka, Atsushi

    2014-05-01

    Carbon-based materials have attracted interest as high-performance catalysts for the aqueous-phase conversion of cellulose. The adsorption of β-glucans plays a crucial role in the catalytic performance of carbons, although the primary driving force and details of the adsorption process remain unclear. This study demonstrates that adsorption occurs at hydrophobic sites on the carbon surface and that hydrophilic groups are not involved. Analysis of adsorption temperature dependence also reveals that the entropy change associated with adsorption is positive. Our results indicate that adsorption occurs by entropically driven hydrophobic interactions in addition to CH-π hydrogen bonding. These same CH-π hydrogen bonds are also confirmed by DFT calculations. The adsorption of β-glucans on carbons is significantly stronger than the affinity between β-glucans. The adsorption equilibrium constants of β-glucans on carbons increase exponentially with increasing degrees of polymerization, which supports the theory of strong interactions between the carbon and the long β-glucans found in cellulose. PMID:24644071

  19. Co-delivery of a hydrophobic small molecule and a hydrophilic peptide by porous silicon nanoparticles.

    PubMed

    Liu, Dongfei; Bimbo, Luis M; Mäkilä, Ermei; Villanova, Francesca; Kaasalainen, Martti; Herranz-Blanco, Barbara; Caramella, Carla M; Lehto, Vesa-Pekka; Salonen, Jarno; Herzig, Karl-Heinz; Hirvonen, Jouni; Santos, Hélder A

    2013-09-10

    Nanoparticulate drug delivery systems offer remarkable opportunities for clinical treatment. However, there are several challenges when they are employed to deliver multiple cargos/payloads, particularly concerning the synchronous delivery of small molecular weight drugs and relatively larger peptides. Since porous silicon (PSi) nanoparticles (NPs) can easily contain high payloads of drugs with various properties, we evaluated their carrier potential in multi-drug delivery for co-loading of the hydrophobic drug indomethacin and the hydrophilic human peptide YY3-36 (PYY3-36). Sequential loading of these two drugs into the PSi NPs enhanced the drug release rate of each drug and also their amount permeated across Caco-2 and Caco-2/HT29 cell monolayers. Regardless of the loading approach used, dual or single, the drug permeation profiles were in good correlation with their drug release behaviour. Furthermore, the permeation studies indicated the critical role of the mucus intestinal layer and the paracellular resistance in the permeation of the therapeutic compounds across the intestinal wall. Loading with PYY3-36 also greatly improved the cytocompatibility of the PSi NPs. Conformational analysis indicated that the PYY3-36 could still display biological activity after release from the PSi NPs and permeation across the intestinal cell monolayers. These results are the first demonstration of the promising potential of PSi NPs for simultaneous multi-drug delivery of both hydrophobic and hydrophilic compounds.

  20. Entropically favored adsorption of cellulosic molecules onto carbon materials through hydrophobic functionalities.

    PubMed

    Yabushita, Mizuho; Kobayashi, Hirokazu; Hasegawa, Jun-Ya; Hara, Kenji; Fukuoka, Atsushi

    2014-05-01

    Carbon-based materials have attracted interest as high-performance catalysts for the aqueous-phase conversion of cellulose. The adsorption of β-glucans plays a crucial role in the catalytic performance of carbons, although the primary driving force and details of the adsorption process remain unclear. This study demonstrates that adsorption occurs at hydrophobic sites on the carbon surface and that hydrophilic groups are not involved. Analysis of adsorption temperature dependence also reveals that the entropy change associated with adsorption is positive. Our results indicate that adsorption occurs by entropically driven hydrophobic interactions in addition to CH-π hydrogen bonding. These same CH-π hydrogen bonds are also confirmed by DFT calculations. The adsorption of β-glucans on carbons is significantly stronger than the affinity between β-glucans. The adsorption equilibrium constants of β-glucans on carbons increase exponentially with increasing degrees of polymerization, which supports the theory of strong interactions between the carbon and the long β-glucans found in cellulose.

  1. Separation of hydrophobic metabolites using monolithic silica column in high-performance liquid chromatography and supercritical fluid chromatography.

    PubMed

    Bamba, Takeshi; Fukusaki, Eiichiro

    2009-08-01

    Monolithic silica columns have very low back-pressures and offer several advantages over conventional columns packed with spherical particles, such as high separation efficiency and rapid analysis. In this review, we report the applicability of monolithic silica columns for the analysis of complex hydrophobic metabolites. We have used monolithic columns in HPLC and developed a separation technique for the high-speed and high-resolution analysis of the geometric analogs of natural polyprenols. We also used monolithic columns in supercritical fluid chromatography for the successful separation of the structural isomers of carotenoids after deciding the analytical conditions that were suitable for this separation and have developed a method for profiling biological samples containing complex matrices. We have proved that excellent resolution can be obtained by connecting a number of monolithic columns in series.

  2. Adsorption behavior of some aromatic compounds on hydrophobic magnetite for magnetic separation.

    PubMed

    Sasaki, Takahiro; Tanaka, Shunitz

    2011-11-30

    In this study, a hydrophobic magnetite coated with an alkyl chain or a phenyl group on the surface was prepared and used as an adsorbent to investigate the adsorption behavior of aromatic compounds having various values of log P(ow) (phenol 1.46, benzonitrile 1.56, nitrobenzene 1.86, benzene 2.13, toluene 2.73, chlorobenzene 2.84 and o-dichlorobenzene 3.38) onto hydrophobic magnetite. The hydrophobic magnetites were modified with stearic acid and phenyltrimethoxysilane, and the modification amounts were 9.84 × 10(-3) and 4.17 × 10(-2)mmol/g, respectively. The aromatic compounds used in this study were divided into 3 groups depending on the log P(ow): 1hydrophobicity of aromatic compounds. The adsorption mechanism for 2hydrophobic interaction and that for 1

  3. Miniaturized monolithic columns for the electrochromatographic separation and SERS detection of molecules of exobiological interest

    NASA Astrophysics Data System (ADS)

    Carbonnier, Benjamin; Guerrouache, Mohamed

    elegant strategy for preparing multifunctional monoliths through spatially controlled surface functionalization.[9] Photochemical initiation affords spatial control over the reaction site, i.e. site-specific immobilization of ligands on the pore surface of the monolith. Hydrophobic and hydrophilic molecular entities were successfully grafted and the obtained monoliths were applied to electrochromatographic separation application under reversed-phase and hydrophilic interaction electrochromatography modes, respectively. The panel of successfully analyzed analytes ranges from hydrophobic polycyclic aromatic hydrocarbons to life markers such as amino acids and peptides. Our approach was extended to the local design of chelating interface for the site-specific immobilisation of gold nanoparticles. Taking advantage of the unique properties of supported nano-gold, it was possible to perform surface enhanced Raman spectroscopy (SERS) sensing of organic molecules at the sub-nanomolar level. This work is funded by the French Space Agency (CNES) References [1] M.C. Pietrogrande, M.G. Zampolli, F. Dondi, C. Szopa, R. Sternberg, A. Buch, J.F. Raulin, J. Chromatogr. A 1071 (2005) 255. [2] A. M. Stockton, T.M. Chiesl, J.M. Scherer, R. A. Mathies, Anal. Chem. 81 (2009) 790 [3] B. Carbonnier, M. Guerrouache, R. Denoyel, M. C. Millot, J. Sep. Sci. 30 (2007) 3000. [4] J.k. Liu, C.F. Chen, C.W. Chang, D.L. DeVoe, Biosensors Bioelectron. 26 (2010) 182. [5] J. Krenkova, F. Svec, J. Sep. Sci. 32 (2009) 706. [6] F. Svec, J. Chromatogr. B 841 (2004) 52 [7] M. Guerrouache, M. C. Millot, B. Carbonnier, Macromol. Rapid. Commun, 30 (2009) 109. [8] M. Guerrouache, B. Carbonnier, C. Vidal-Madjar, M.C. Millot, J. Chromatogr A, 1149 (2007) 368. [9] M. Guerrouache, S. Mahouche Chergui, M.M. Chehimi, B. Carbonnier. Chem. Commun. 48 (2012) 7486.

  4. Synthesis and characterisation of immunogens for the production of antibodies against small hydrophobic molecules with biosignature properties.

    PubMed

    Sathe, Manisha; Derveni, Mariliza; Broadbent, Gillian; Bodlenner, Anne; Charlton, Keith; Ravi, Bindu; Rohmer, Michel; Sims, Mark R; Cullen, David C

    2011-12-01

    In the present study, five different classes of small hydrophobic molecular targets, atypical for antibody generation, were structurally modified in order to introduce suitable reactive functionalities and/or spacers which allow covalent coupling to a carrier protein resulting in a stable carrier-hapten complex. These targets were chosen to serve as markers of extant and/or extinct life in the context of the development of the Life Marker Chip (LMC), an antibody-based instrument, which is being developed by a UK-led international consortium for flight to Mars on board the joint ESA/NASA Mars exploration ExoMars mission. The hapten-protein conjugates were designed to be used as immunogens for antibody generation and immunoassay reagents in subsequent stages of the LMC development. The extent of protein modification due to covalent attachment of hapten was determined by two independent methods, i.e. trinitrobenzenesulfonic acid (TNBSA) titrations of remaining protein reactive groups and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of the resultant hapten-protein conjugates. In a further quality validation step, the conjugates were presented to an animal's immune system and polyclonal antibody titres with moderate specificity were obtained. These results suggest that conjugates synthesized as described herein can successfully be used in the generation of antibodies targeting small hydrophobic molecules. PMID:22093350

  5. Preparation of a weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography stationary phase for protein separation using click chemistry.

    PubMed

    Zhao, Kailou; Yang, Fan; Xia, Hongjun; Wang, Fei; Song, Qingguo; Bai, Quan

    2015-03-01

    In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h.

  6. Hydrophobic modification on surface of chitin sponges for highly effective separation of oil.

    PubMed

    Duan, Bo; Gao, Huimin; He, Meng; Zhang, Lina

    2014-11-26

    A highly hydrophobic and oleophilic chitin sponge was synthesized, for the first time, via a freeze-dried method and then by using a thermal chemical vapor deposition of methyltrichlorosilane (MTCS) at different relative humidity. Fourier-transform infrared, energy-dispersive X-ray spectra, and scanning electron microscopy confirmed that the silanization occurred on the pore wall surface of the chitin sponge. The MTCS-coated chitin sponge had interconnected open-cell structures with the average pore size from 20 to 50 μm, and the MTCS nanofilaments immobilized on the chitin matrix, leading to the high hydrophobicity, as a result of the existence of a solid/air composite rough surface. Cyclic compression test indicated that the hydrophobic chitin sponges exhibited excellent elasticity and high mechanical durability. The sponges could efficiently collect organics both on the surface and bottom from the water with the highest 58 times of their own weight absorption capacities through the combination of the particular wettability and great porosity. Furthermore, the biodegradation kinetics of the chitin sponge forecasted that the chitin could be completely biodegraded within 32 days by the microorganisms in the soil. This work provided a new pathway to prepare the chitin-based materials for highly effective removal of oil from water, showing potential application in the pollutant remediation field. PMID:25347002

  7. Hydrophobic modification on surface of chitin sponges for highly effective separation of oil.

    PubMed

    Duan, Bo; Gao, Huimin; He, Meng; Zhang, Lina

    2014-11-26

    A highly hydrophobic and oleophilic chitin sponge was synthesized, for the first time, via a freeze-dried method and then by using a thermal chemical vapor deposition of methyltrichlorosilane (MTCS) at different relative humidity. Fourier-transform infrared, energy-dispersive X-ray spectra, and scanning electron microscopy confirmed that the silanization occurred on the pore wall surface of the chitin sponge. The MTCS-coated chitin sponge had interconnected open-cell structures with the average pore size from 20 to 50 μm, and the MTCS nanofilaments immobilized on the chitin matrix, leading to the high hydrophobicity, as a result of the existence of a solid/air composite rough surface. Cyclic compression test indicated that the hydrophobic chitin sponges exhibited excellent elasticity and high mechanical durability. The sponges could efficiently collect organics both on the surface and bottom from the water with the highest 58 times of their own weight absorption capacities through the combination of the particular wettability and great porosity. Furthermore, the biodegradation kinetics of the chitin sponge forecasted that the chitin could be completely biodegraded within 32 days by the microorganisms in the soil. This work provided a new pathway to prepare the chitin-based materials for highly effective removal of oil from water, showing potential application in the pollutant remediation field.

  8. Unified Effect of Hydrophobic Hydration on the Dynamics and the Structure of Water Molecules in Lower Alcohol Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Nakada, Masaru; Maruyama, Kenji; Yamamuro, Osamu; Kikuchi, Tatsuya; Misawa, Masakatsu

    2011-04-01

    After the analysis of the quasi-elastic neutron scattering (QENS) spectra of lower alcoholic aqueous solutions, we found that the parameter α, which is the number fraction of hydrophobic hydrating water molecules, has an important role in describing the dynamics and other properties of these solutions. The diffusion coefficient D was obtained from QENS spectra using the relaxing cage model, and D was found to have the same linear relation against α for ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and t-butyl alcohol (with a small deviation) aqueous solutions. The excess molar volume and average hydration number of these solutions could also be expressed with common parameters, which are independent of the alcohol species.

  9. Ultrasound driven assembly of lignin into microcapsules for storage and delivery of hydrophobic molecules.

    PubMed

    Tortora, Mariarosaria; Cavalieri, Francesca; Mosesso, Pasquale; Ciaffardini, Flavia; Melone, Federica; Crestini, Claudia

    2014-05-12

    Oil-filled microcapsules of kraft lignin were synthesized by first creating an oil in water emulsion followed by a high-intensity, ultrasound-assisted cross-linking of lignin at the water/oil interface. The rationale behind our approach is based on promoting documented lignin hydrophobic interactions within the oil phase, followed by locking the resulting spherical microsystems by covalent cross-linking using a high intensity ultrasound treatment. As further evidence in support of our rationale, confocal and optical microscopies demonstrated the uniformly spherical morphology of the created lignin microparticles. The detailed elucidation of the cross-linking processes was carried out using gel permeation chromatography (GPC) and quantitative (31)P NMR analyses. The ability of lignin microcapsules to incorporate and release Coumarin-6 was evaluated in detail. In vitro studies and confocal laser scanning microscopy analysis were carried out to assess the internalization of capsules into Chinese hamster ovary (CHO) cells. This part of our work demonstrated that the lignin microcapsules are not cytotoxic and readily incorporated in the CHO cells.

  10. Biodegradable Janus nanoparticles for local pulmonary delivery of hydrophilic and hydrophobic molecules to the lungs.

    PubMed

    Garbuzenko, Olga B; Winkler, Jennifer; Tomassone, M Silvina; Minko, Tamara

    2014-11-01

    The aim of the present work is to synthesize, characterize, and test self-assembled anisotropic or Janus particles designed to load anticancer drugs for lung cancer treatment by inhalation. The particles were synthesized using binary mixtures of biodegradable and biocompatible materials. The particles did not demonstrate cyto- and genotoxic effects. Janus particles were internalized by cancer cells and accumulated both in the cytoplasm and nuclei. After inhalation delivery, nanoparticles accumulated preferentially in the lungs of mice and retained there for at least 24 h. Two drugs or other biologically active components with substantially different aqueous solubility can be simultaneously loaded in two-phases (polymer-lipid) of these nanoparticles. In the present proof-of-concept investigation, the particles were loaded with two anticancer drugs: doxorubicin and curcumin as model anticancer drugs with relatively high and low aqueous solubility, respectively. However, there are no obstacles for loading any hydrophobic or hydrophilic chemical agents. Nanoparticles with dual load were used for their local inhalation delivery directly to the lungs of mice with orthotopic model of human lung cancer. In vivo experiments showed that the selected nanoparticles with two anticancer drugs with different mechanisms of action prevented progression of lung tumors. It should be stressed that anticancer effects of the combined treatment with two anticancer drugs loaded in the same nanoparticle significantly exceeded the effect of either drug loaded in similar nanoparticles alone.

  11. 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

    SciTech Connect

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

    2015-08-07

    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.

  12. Adsorption and transport of charged vs. neutral hydrophobic molecules at the membrane of murine erythroleukemia (MEL) cells.

    PubMed

    Zeng, Jia; Eckenrode, Heather M; Dai, Hai-Lung; Wilhelm, Michael J

    2015-03-01

    The adsorption and transport of hydrophobic molecules at the membrane surface of pre- and post-DMSO induced differentiated murine erythroleukemia (MEL) cells were examined by time- and wavelength-resolved second harmonic light scattering. Two medium (<600 Da) hydrophobic molecules, cationic malachite green (MG) and neutral bromocresol purple (BCP), were investigated. While it was observed that the MG cation adsorbs onto the surface of the MEL cell, neutral BCP does not. It is suggested that an electrostatic interaction between the opposite charges of the cation and the MEL cell surface is the primary driving force for adsorption. Comparisons of adsorption density and free energy, measured at different pH and cell morphology, indicate that the interaction is predominantly through sialic acid carboxyl groups. MG cation adsorption densities have been determined as (0.6±0.3)×10(6) μm(-2) on the surface of undifferentiated MEL cells, and (1.8±0.5)×10(7) μm(-2) on differentiated MEL cells, while the deduced adsorption free energies are effectively identical (ca. -10.9±0.1 and -10.8±0.1 kcal mol(-1), respectively). The measured MG densities indicate that the total number of surface carboxyl groups is largely conserved following differentiation, and therefore the density of carboxylic groups is much larger on the differentiated cell surface than the undifferentiated one. Finally, in contrast to synthetic liposomes and bacterial membranes, surface adsorbed MG cations are unable to traverse the MEL cell membrane. PMID:25660095

  13. The hydrophobic adsorption of charged molecules to bilayer membranes: a test of the applicability of the stern equation.

    PubMed

    McLaughlin, S; Harary, H

    1976-05-01

    To describe the hydrophobic adsorption of charged molecules to bilayer membranes, one must recognize that the adsorption produces a change in the electrostatic potential at the surface of the membrane. The surface potential produced by the adsorption of the charged molecules can be described most simply by the Gouy equation from the theory of the diffuse double layer. This potential will tend to lower the concentration of the adsorbing ions in the aqueous phase immediately adjacent to the membrane, a phenomenon which can be described by the Boltzmann relation. The number of adsorbed ions is, in turn, a function of the aqueous concentration of these ions at the membrane solution interface and can be described, in the simplest case, by a Langmuir adsorption isotherm. If the ions are regarded as point charges, the combination of the Gouy, Boltzmann, and Langmuir relations may be considered a simplified Stern equation. To test experimentally the applicability of this equation, one should measure both the charge density and surface potential as a function of the concentration of adsorbing molecules in the bulk aqueous phases. Direct, accurate measurements of one of these parameters, the number of moles of 2, 6-toluidinylnaphthalenesulfonate ions bound to vesicles formed from phosphatidylcholine, are available in the literature (Huang, C., and Charlton, J.P. (1972), Biochemistry 11, 735). We estimated the change in the surface potential in two independent ways; by means of conductance measurements with "probe" molecules on planar black lipid membranes and by means of electrophoresis measurements on multilaminar unsonicated vesicles. The two estimates agreed with one another and all of the data could be adequately described by the Stern equation, assuming, at 25 degrees C, a dissociation constant of 2 X 10(-4) M and a maximum number of binding sites of 1/70 A2.

  14. Application of neutral hydrophobic hypercrosslinked polystyrene to the separation of inorganic anions by ion chromatography.

    PubMed

    Penner, N A; Nesterenko, P N

    2000-07-01

    Neutral hydrophobic hypercrosslinked polystyrene was shown to exhibit anion-exchange properties in the pH range 2.6-4.3 that can be attributed to the presence of protonated carbonyls in the framework of the polymer. This resin does not contain any other heteroatoms, except oxygen, responsible for the occurrence of positive charge at the surface. The anion-exchange selectivity of MN-200 and monosized spherical hypercrosslinked polystyrene to inorganic anions with diluted perchloric, nitric and sulfuric acid solutions as eluent was studied and the selectivity was found to be different from that observed for the common anion-exchangers. The main features of hypercrosslinked polystyrene are weak retention of sulphate and comparatively strong retention of nitrite that can be useful in practical ion chromatography. The influence of column temperature on the retention was investigated. Calculated adsorption heats are in the range from -2 to 19 kJ/mol. The retention mechanism of inorganic anions on neutral hypercrosslinked polystyrene includes both ion-exchange and hydrophobic interactions.

  15. An effective strategy to increase hydroxide-ion conductivity through microphase separation induced by hydrophobic-side chains

    NASA Astrophysics Data System (ADS)

    Zeng, L.; Zhao, T. S.

    2016-01-01

    A highly conductive and durable anion exchange membrane (AEM) is an essential component for alkaline electrochemical conversion and storage systems. Contrary to the conventional wisdom that the ionic conductivity can be improved by increasing the ion exchange capacity (IEC) through a cross-linking process, in this work, a new approach to improve the ionic conductivity by enhancing the ionic mobility is adopted. The microstructure of quaternary ammonia poly (2, 6-dimethyl-1, 4-phenylene oxide) (QAPPO) is manipulated through grafting with hydrophobic side chains, which will drive the well-established hydrophilic/hydrophobic domains and nano-phase separated, well-connected ionic channels. As a result, the local hydroxide concentration is enhanced by the novel microstructure, thereby improving the ionic conductivity of the as-prepared ionomers. The as-prepared ionomers, denoted as self-aggregated QAPPO-CF, with an intermediate IEC value achieved an ionic conductivity of 65 mS cm-1 at 80 °C, outperforming the QAPPO with an even higher IEC value. This result suggests that the microphase separation is an effective approach to enhance the ionic conductivity.

  16. Separation of rare gases and chiral molecules by selective binding in porous organic cages.

    PubMed

    Chen, Linjiang; Reiss, Paul S; Chong, Samantha Y; Holden, Daniel; Jelfs, Kim E; Hasell, Tom; Little, Marc A; Kewley, Adam; Briggs, Michael E; Stephenson, Andrew; Thomas, K Mark; Armstrong, Jayne A; Bell, Jon; Busto, Jose; Noel, Raymond; Liu, Jian; Strachan, Denis M; Thallapally, Praveen K; Cooper, Andrew I

    2014-10-01

    The separation of molecules with similar size and shape is an important technological challenge. For example, rare gases can pose either an economic opportunity or an environmental hazard and there is a need to separate these spherical molecules selectively at low concentrations in air. Likewise, chiral molecules are important building blocks for pharmaceuticals, but chiral enantiomers, by definition, have identical size and shape, and their separation can be challenging. Here we show that a porous organic cage molecule has unprecedented performance in the solid state for the separation of rare gases, such as krypton and xenon. The selectivity arises from a precise size match between the rare gas and the organic cage cavity, as predicted by molecular simulations. Breakthrough experiments demonstrate real practical potential for the separation of krypton, xenon and radon from air at concentrations of only a few parts per million. We also demonstrate selective binding of chiral organic molecules such as 1-phenylethanol, suggesting applications in enantioselective separation. PMID:25038731

  17. Separation of rare gases and chiral molecules by selective binding in porous organic cages

    NASA Astrophysics Data System (ADS)

    Chen, Linjiang; Reiss, Paul S.; Chong, Samantha Y.; Holden, Daniel; Jelfs, Kim E.; Hasell, Tom; Little, Marc A.; Kewley, Adam; Briggs, Michael E.; Stephenson, Andrew; Thomas, K. Mark; Armstrong, Jayne A.; Bell, Jon; Busto, Jose; Noel, Raymond; Liu, Jian; Strachan, Denis M.; Thallapally, Praveen K.; Cooper, Andrew I.

    2014-10-01

    The separation of molecules with similar size and shape is an important technological challenge. For example, rare gases can pose either an economic opportunity or an environmental hazard and there is a need to separate these spherical molecules selectively at low concentrations in air. Likewise, chiral molecules are important building blocks for pharmaceuticals, but chiral enantiomers, by definition, have identical size and shape, and their separation can be challenging. Here we show that a porous organic cage molecule has unprecedented performance in the solid state for the separation of rare gases, such as krypton and xenon. The selectivity arises from a precise size match between the rare gas and the organic cage cavity, as predicted by molecular simulations. Breakthrough experiments demonstrate real practical potential for the separation of krypton, xenon and radon from air at concentrations of only a few parts per million. We also demonstrate selective binding of chiral organic molecules such as 1-phenylethanol, suggesting applications in enantioselective separation.

  18. Demonstrating Electrophoretic Separation in a Straight Paper Channel Delimited by a Hydrophobic Wax Barrier

    ERIC Educational Resources Information Center

    Xu, Chunxiu; Lin, Wanqi; Cai, Longfei

    2016-01-01

    A demonstration is described of electrophoretic separation of carmine and sunset yellow with a paper-based device. The channel in the paper device was fabricated by hand with a wax pen. Electrophoretic separation of carmine and sunset yellow was achieved within a few minutes by applying potential on the channel using a simple and inexpensive power…

  19. Microphase separation in copolymers of hydrophilic PEG blocks and hydrophobic tyrosine-derived segments using simultaneous SAXS/WAXS/DSC

    SciTech Connect

    Murthy, N.S.; Wang, W.; Kohn, J.

    2010-10-22

    Hydration- and temperature-induced microphase separations were investigated by simultaneous small- and wide-angle X-ray scattering (SAXS and WAXS) and differential scanning calorimetry (DSC) in a family of copolymers in which hydrophilic poly(ethylene glycol) (PEG) blocks are inserted randomly into a hydrophobic polymer made of either desaminotyrosyl-tyrosine ethyl ester (DTE) or iodinated I{sub 2}DTE segments. Iodination of the tyrosine rings in I{sub 2}DTE increased the X-ray contrast between the hydrophobic and hydrophilic segments in addition to facilitating the study of the effect of iodination on microphase separation. The formation of phase-separated, hydrated PEG domains is of considerable significance as it profoundly affects the polymer properties. The copolymers of DTE (or I{sub 2}DTE) and PEG are a useful model system, and the findings presented here may be applicable to other PEG-containing random copolymers. In copolymers of PEG and DTE and I{sub 2}DTE, the presence of PEG depressed the glass transition temperature (T{sub g}) of the copolymer relative to the homopolymer, poly(DTE carbonate), and the DTE/I{sub 2}DTE segments hindered the crystallization of the PEG segments. In the dry state, at large PEG fractions (>70 vol%), the PEG domains self-assembled into an ordered structure with 14-18 nm distance between the domains. These domains gave rise to a SAXS peak at all temperatures in the iodinated polymers, but only above the T{sub g} in non-iodinated polymers, due to the unexpected contrast-match between the crystalline PEG domains and the glassy DTE segments. Irrespective of whether PEG was crystalline or not, immersion of these copolymers in water resulted in the formation of hydrated PEG domains that were 10-20 nm apart. Since both water and the polymer chains must be mobile for the phase separation to occur, the PEG domains disappeared when the water froze, and reappeared as the ice began to melt. This transformation was reversible, and showed

  20. Adsorption and Gas Separation of Molecules by Carbon Nanohorns.

    PubMed

    Gatica, Silvina M; Nekhai, Anton; Scrivener, Adam

    2016-05-19

    In this paper, we report the results of Monte Carlo simulations of the adsorption of neon, argon, methane and carbon dioxide in carbon nanohorns. We model the nanohorns as an array of carbon cones and obtained adsorption isotherms and isosteric heats. The main sites of adsorption are inside the cones and in the interstices between three cones. We also calculated the selectivity of carbon dioxide/methane, finding that nanohorns are a suitable substrate for gas separation. Our simulations are compared to available experimental data.

  1. Adsorption and Gas Separation of Molecules by Carbon Nanohorns.

    PubMed

    Gatica, Silvina M; Nekhai, Anton; Scrivener, Adam

    2016-01-01

    In this paper, we report the results of Monte Carlo simulations of the adsorption of neon, argon, methane and carbon dioxide in carbon nanohorns. We model the nanohorns as an array of carbon cones and obtained adsorption isotherms and isosteric heats. The main sites of adsorption are inside the cones and in the interstices between three cones. We also calculated the selectivity of carbon dioxide/methane, finding that nanohorns are a suitable substrate for gas separation. Our simulations are compared to available experimental data. PMID:27213313

  2. Nonempirical range-separated hybrid functionals for solids and molecules

    NASA Astrophysics Data System (ADS)

    Skone, Jonathan H.; Govoni, Marco; Galli, Giulia

    2016-06-01

    Dielectric-dependent hybrid (DDH) functionals were recently shown to yield accurate energy gaps and dielectric constants for a wide variety of solids, at a computational cost considerably less than that of GW calculations. The fraction of exact exchange included in the definition of DDH functionals depends (self-consistently) on the dielectric constant of the material. Here we introduce a range-separated (RS) version of DDH functionals where short- and long-range components are matched using system-dependent, nonempirical parameters. We show that RS-DDHs yield accurate electronic properties of inorganic and organic solids, including energy gaps and absolute ionization potentials. Furthermore we show that these functionals may be generalized to finite systems.

  3. The Crystal Structure of OprG from Pseudomonas aeruginosa a Potential Channel for Transport of Hydrophobic Molecules across the Outer Membrane

    SciTech Connect

    D Touw; D Patel; b van den Berg

    2011-12-31

    The outer membrane (OM) of Gram-negative bacteria provides a barrier to the passage of hydrophobic and hydrophilic compounds into the cell. The OM has embedded proteins that serve important functions in signal transduction and in the transport of molecules into the periplasm. The OmpW family of OM proteins, of which P. aeruginosa OprG is a member, is widespread in Gram-negative bacteria. The biological functions of OprG and other OmpW family members are still unclear. The outer membrane (OM) of Gram-negative bacteria provides a barrier to the passage of hydrophobic and hydrophilic compounds into the cell. The OM has embedded proteins that serve important functions in signal transduction and in the transport of molecules into the periplasm. The OmpW family of OM proteins, of which P. aeruginosa OprG is a member, is widespread in Gram-negative bacteria. The biological functions of OprG and other OmpW family members are still unclear. The crystal structure, together with recent biochemical data, suggests that OprG and other OmpW family members form channels that mediate the diffusion of small hydrophobic molecules across the OM by a lateral diffusion mechanism similar to that of E. coli FadL.

  4. Investigation of localization of DNA molecules using triangular metal electrodes with varying separation

    NASA Astrophysics Data System (ADS)

    Prasad, D. Nagendra; Ghonge, Sudarshan; Banerjee, Souri

    2016-04-01

    In this paper we investigate the effect of separation of triangular metal electrodes with both convex and concave geometries, on the localization of suspended DNA molecules under the combined effect of dielectrophoresis and AC electro-osmosis through simulations using COMSOL Multiphysics. Trapping points are realized within the electrodes which are found to vary with the separation of the electrodes.

  5. Effects of exposure time on variations in the structure and hydrophobicity of polyvinylidene fluoride membranes prepared via vapor-induced phase separation

    NASA Astrophysics Data System (ADS)

    Peng, Yuelian; Fan, Hongwei; Dong, Yajun; Song, Yanna; Han, Hua

    2012-08-01

    The present investigation revealed how the surface morphology and hydrophobicity of polyvinylidene fluoride (PVDF) membranes, which were prepared via a vapor-induced phase separation (VIPS) method, were affected by the exposure time. The mass variation of the cast film was recorded. Membrane morphologies were observed by scanning electron microscopy (SEM) and thermal behaviors of membranes were examined by differential scanning calorimetry (DSC). Wide angle X-ray diffraction (WAXD) was employed to analyze the crystalline structures of the overall membranes and the surface layers. The results showed that different membrane morphologies and hydrophobicities could be obtained by changing the exposure time. A long exposure time facilitated the crystallization process, resulting in the formation of a porous skin and particle morphology, which increased the hydrophobicity of the surface. A short exposure time favored the formation of a digitate macrovoid and dense skin resulting from liquid-liquid phase separation in the immersion process, which reduced surface hydrophobicity. The water permeate flux in vacuum membrane distillation was greatly affected by the membrane porosity and surface hydrophobicity.

  6. Rigid porous polyacrylamide-based monolithic columns containing butyl methacrylate as a separation medium for the rapid hydrophobic interaction chromatography of proteins.

    PubMed

    Xie, S; Svec, F; Fréchet, J M

    1997-07-18

    Macroporous poly(acrylamide-co-butyl methacrylate-co-N,N'-methylenebisacrylamide) monoliths containing up to 15% butyl methacrylate units have been prepared by direct polymerization within the confines of HPLC columns. The hydrodynamic and chromatographic properties of these 50 mm x 8 mm I.D. columns-such as back pressure at different flow-rates, effect of percentage of hydrophobic component in the polymerization mixture, effect of salt concentration on the retention of proteins, dynamic loading capacity, and recovery-were determined under conditions typical of hydrophobic interaction chromatography. Using the monolithic column, five proteins were easily separated within only 3 min.

  7. Single-molecule analysis enables free solution hydrodynamic separation using yoctomole levels of DNA.

    PubMed

    Liu, Kelvin J; Rane, Tushar D; Zhang, Yi; Wang, Tza-Huei

    2011-05-11

    Single-molecule free solution hydrodynamic separation (SML-FSHS) cohesively integrates cylindrical illumination confocal spectroscopy with free solution hydrodynamic separation. This technique enables single-molecule analysis of size separated DNA with 100% mass detection efficiency, high sizing resolution and wide dynamic range, surpassing the performance of single molecule capillary electrophoresis. Furthermore, SML-FSHS required only a bare fused silica microcapillary and simple pressure control rather than complex high voltage power supplies, sieving matrices, and wall coatings. The wide dynamic range and high sizing resolution of SML-FSHS was demonstrated by separating both large DNA (23 vs 27 kbp) and small DNA (100 vs 200 bp) under identical conditions. Separations were successfully performed with near zero sample consumption using as little as 5 pL of sample and 240 yoctomoles (∼150 molecules) of DNA. Quantitative accuracy was predominantly limited by molecular shot noise. Furthermore, the ability of this method to analyze of single molecule nanosensors was investigated. SML-FSHS was used to examine the thermodynamic equilibrium between stochastically open molecular beacon and target-bound molecular beacon in the detection of E. coli 16s rRNA targets.

  8. Molecular Orbital Study of the Formation of Intramolecular Hydrogen Bonding of a Ligand Molecule in a Protein Aromatic Hydrophobic Pocket.

    PubMed

    Koseki, Jun; Gouda, Hiroaki; Hirono, Shuichi

    2016-01-01

    The natural product argadin is a cyclopentapeptide chitinase inhibitor that binds to chitinase B (ChiB) from the pathogenic bacteria Serratia marcescens. N(ω)-Acetyl-L-arginine and L-aminoadipic acid of argadin form intramolecular ionic hydrogen bonds in the aromatic hydrophobic pocket of ChiB. We performed ab initio molecular orbital and density functional theory calculations to elucidate the role of this intramolecular hydrogen bonding on intermolecular interactions between argadin and ChiB. We found that argadin accrues large stabilization energies from the van der Waals dispersion interactions, such as CH-π, π-π, and π-lone pair interactions, in the aromatic hydrophobic pocket of ChiB, although intramolecular hydrogen bonding within argadin might result in loss of entropy. The intramolecular ionic hydrogen bonding formation canceled local molecular charges and provided good van der Waals interactions with surrounding aromatic residues.

  9. Single molecule fluorescence burst detection of DNA separated by capillary electrophoresis

    NASA Astrophysics Data System (ADS)

    Haab, Brian B.; Mathies, Richard A.

    1996-03-01

    A method has been developed for detecting DNA separated by capillary gel electrophoresis using single molecule photon burst counting. A confocal fluorescence microscope was used to observe the fluorescence bursts from single molecules of DNA multiply labeled with a thiazole orange derivative as they passed through the approximately 2 micrometer diameter focused laser beam. Amplified photoelectron pulses from the photomultiplier are grouped into bins of from 360 - 450 microseconds in duration, and the resulting histogram stored in a computer for analysis. Solutions of M13 DNA were first flowed through the capillary at various concentrations, and the resulting data were used to optimize the parameters for digital filtering using a low-pass Fourier filter, selecting a discriminator level for peak detection, and applying a peak-calling algorithm. The optimized single molecule counting method was then used to detect a separation of pBR 322 DNA from pRL 277 DNA. Clusters of discrete fluorescence bursts were observed at the expected appearance time of each DNA band. These separations were easily detected when only 50 to 100 molecules of DNA per band traveled through the detection region. This new detection technology should lead to the routine analysis of DNA in capillary columns with an on-column sensitivity of approximately 100 DNA molecules per band or better.

  10. Three-dimensional Nanowire Structures for Ultra-Fast Separation of DNA, Protein and RNA Molecules

    PubMed Central

    Rahong, Sakon; Yasui, Takao; Yanagida, Takeshi; Nagashima, Kazuki; Kanai, Masaki; Meng, Gang; He, Yong; Zhuge, Fuwei; Kaji, Noritada; Kawai, Tomoji; Baba, Yoshinobu

    2015-01-01

    Separation and analysis of biomolecules represent crucial processes for biological and biomedical engineering development; however, separation resolution and speed for biomolecules analysis still require improvements. To achieve separation and analysis of biomolecules in a short time, the use of highly-ordered nanostructures fabricated by top-down or bottom-up approaches have been proposed. Here, we reported on the use of three-dimensional (3D) nanowire structures embedded in microchannels fabricated by a bottom-up approach for ultrafast separation of small biomolecules, such as DNA, protein, and RNA molecules. The 3D nanowire structures could analyze a mixture of DNA molecules (50–1000 bp) within 50 s, a mixture of protein molecules (20–340 kDa) within 5 s, and a mixture of RNA molecules (100–1000 bases) within 25 s. And, we could observe the electrophoretic mobility difference of biomolecules as a function of molecular size in the 3D nanowire structures. Since the present methodology allows users to control the pore size of sieving materials by varying the number of cycles for nanowire growth, the 3D nanowire structures have a good potential for use as alternatives for other sieving materials. PMID:26073192

  11. Qualitative and Quantitative Study of the Potential of Lipid Nanocapsules of One Hundred Twenty Nanometers for the Topical Administration of Hydrophobic Molecules.

    PubMed

    Nguyen, Hoang Truc Phuong; Munnier, Emilie; Perse, Xavier; Vial, Francis; Yvergnaux, Florent; Perrier, Thomas; Soucé, Martin; Chourpa, Igor

    2016-10-01

    In this study, we evaluated the potential of lipid nanocapsules (LNC) of 120 nm as drug nanocarriers to treat skin diseases. As a model molecule, we encapsulated the fluorescent dye curcumin, which also is an antioxidant. Curcumin-loaded LNC showed interesting antioxidant properties and a low toxicity on human skin cells. The penetration of curcumin in the skin was determined by 2 complementary methods: high performance liquid chromatography was used to measure total curcumin accumulation in the skin, whereas fluorescence confocal spectral imaging of skin sections showed that curcumin preferentially accumulates in the stratum corneum and the viable epidermis. These results confirm that LNC of a size above 100 nm can vectorize hydrophobic compounds to the keratinocytes without transdermal delivery. They also demonstrate the interest of combining 2 analytical methods when studying the skin penetration of nanovectorized molecules.

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

    DOEpatents

    Abney, Kent D.; Kinkead, Scott A.; Mason, Caroline F. V.; Rais, Jiri

    1997-01-01

    Preparation and use of 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.

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

    DOEpatents

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

    1997-09-09

    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.

  14. Single molecule fluorescence burst detection of DNA fragments separated by capillary electrophoresis

    SciTech Connect

    Haab, B.B.; Mathies, R.A.

    1995-09-15

    A method has been developed for detecting DNA separated by capillary gel electrophoresis (CGE) using single molecule photon burst counting. A confocal fluorescence microscope was used to observe the fluorescence bursts from single molecules of DNA multiply labeled with the thiazole orange derivative TO6 as they passed through the nearly 2-{mu}m diameter focused laser beam. Amplified photo-electron pulses from the photomultiplier are grouped into bins of 360-450 {mu}s in duration, and the resulting histogram is stored in a computer for analysis. Solutions of M13 DNA were first flowed through the capillary at various concentrations, and the resulting data were used to optimize the parameters for digital filtering using a low-pass Fourier filter, selecting a discriminator level for peak detection, and applying a peak-calling algorithm. The optimized single molecule counting method was then applied to an electrophoretic separation of M13 DNA and to a separation of pBR 322 DNA from pRL 277 DNA. Clusters of discreet fluorescence bursts were observed at the expected appearance time of each DNA band. The auto-correlation function of these data indicated transit times that were consistent with the observed electrophoretic velocity. These separations were easily detected when only 50-100 molecules of DNA per band traveled through the detection region. This new detection technology should lead to the routine analysis of DNA in capillary columns with an on-column sensitivity of nearly 100 DNA molecules/band or better. 45 refs., 10 figs.

  15. Accurate thermochemistry for larger molecules : gaussian-2 theory with bond separation energies.

    SciTech Connect

    Raghavachari, K.; Stefanov, B. B.; Curtiss, L. A.; Lucent Tech.

    1997-04-22

    Gaussian-2 (G2) theory is combined with isodesmic bond separation reaction energies to yield accurate thermochemistry for larger molecules. For a test set of 40 molecules composed of H, C, O, and N, our method yields enthalpies of formation, {Delta}H{sub f}{sup 0}(298 K), with a mean absolute deviation from experiment of only 0.5 kcal/mol. This is an improvement of a factor of three over the deviation of 1.5 kcal/mol seen in standard G2 theory.

  16. Property evaluations and application for separation of small molecules of a nanodiamond-polymer composite monolithic column.

    PubMed

    Wang, Fengqing; Wei, Aile; Wang, Xixi; Liu, Haiyan; Bai, Ligai; Yan, Hongyuan

    2016-07-01

    A nanodiamond-polymer composite monolithic column was first prepared successfully with modified nanodiamond (ND) as monomer, ethylene glycol dimethacrylate (EDMA) as cross-linker, 1-dodecanol as porogenic agent and benzoyl peroxide/dimethylacetamide (BPO/DMA) as initiator at 35°C for 2.5h. There was a sharp increase of specific surface area with ND added about 22 times from 0mg (3.90m(2)/g) to 7mg (81.2m(2)/g) determined with BET. Characterizations including scanning electron microscopy (SEM), fourier-transform infrared spectra (FIRT) and mercury intrusion porosimetry (MIP) were used to determine the microstructure, group composition, pore size distribution (≃1.56μm) and porosity (≃0.7484μm) of the monolith. An excellent column stability was confirmed by permeability (1.258x10(-10)cm(2)) and good linearity (R(2)=0.998) corresponding to backpressures measured at different flow rates. The highest swelling ability of the composite was about (5%) and classical RPLC of the column obtained occurred with the acetonitrile concentration increasing from 20% to 85% in the mobile phase, above which another retention model of normal-phase chromatography appeared. The items of the eddy dispersion and the absorption-release kinetics were the decisional factors of the composite column compared with the factors of longitudinal diffusion, and the skeleton-eluent mass transfer resistance due to the finite diffusivity. Good separation of neutral and basic small molecules was obtained (24,350 plates/m for neutral molecules and 22,300 plates/m for basic ones) with the hydrophobicity retention mechanism, but not for the acidic ones except to regulate the pH of the mobile phase. PMID:27154670

  17. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    NASA Astrophysics Data System (ADS)

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-02-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures.

  18. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    PubMed Central

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-01-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures. PMID:26891851

  19. Nanofluidic single-molecule sorting of DNA: a new concept in separation and analysis of biomolecules towards ultimate level performance

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takatoki; Fujii, Teruo

    2010-10-01

    Separation and separation-based analysis of biomolecules are fundamentally important techniques in the field of biotechnology. These techniques, however, depend on stochastic processes that intrinsically involve uncertainty, and thus it is not possible to achieve 100% separation accuracy. Theoretically, the ultimate resolution and sensitivity should be realized in a single-molecule system because of the deterministic nature of single-molecule manipulation. Here, we have proposed and experimentally demonstrated the concept of a 'single-molecule sorter' that detects and correctly identifies individual single molecules, realizing the ultimate level of resolution and sensitivity for any separation-based technology. The single-molecule sorter was created using a nanofluidic network consisting of a single inlet channel that branches off into multiple outlet channels. It includes two major functional elements, namely a single-molecule detection and identification element and a flow path switching element to accurately separate single molecules. With this system we have successfully demonstrated the world's first single-molecule sorting using DNA as a sample molecule. In the future, we hope to expand the application of such devices to comprehensive sorting of single-proteins from a single cell. We also believe that in addition to the single-molecule sorting method reported here, other types of single-molecule based processes will emerge and find use in a wide variety of applications.

  20. Calculations on Isotope Separation by Laser Induced Photodissociation of Polyatomic Molecules. Final Report

    DOE R&D Accomplishments Database

    Lamb, W. E. Jr.

    1978-11-01

    This report describes research on the theory of isotope separation produced by the illumination of polyatomic molecules by intense infrared laser radiation. Newton`s equations of motion were integrated for the atoms of the SF{sub 6} molecule including the laser field interaction. The first year`s work has been largely dedicated to obtaining a suitable interatomic potential valid for arbitrary configurations of the seven particles. This potential gives the correct symmetry of the molecule, the equilibrium configuration, the frequencies of the six distinct normal modes of oscillation and the correct (or assumed) value of the total potential energy of the molecule. Other conditions can easily be imposed in order to obtain a more refined potential energy function, for example, by making allowance for anharmonicity data. A suitable expression was also obtained for the interaction energy between a laser field and the polyatomic molecule. The electromagnetic field is treated classically, and it would be easily possible to treat the cases of time dependent pulses, frequency modulation and noise.

  1. Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation.

    PubMed

    Yap, R K L; Whittaker, M; Diao, M; Stuetz, R M; Jefferson, B; Bulmus, V; Peirson, W L; Nguyen, A V; Henderson, R K

    2014-09-15

    Dissolved air flotation (DAF), an effective treatment method for clarifying algae/cyanobacteria-laden water, is highly dependent on coagulation-flocculation. Treatment of algae can be problematic due to unpredictable coagulant demand during blooms. To eliminate the need for coagulation-flocculation, the use of commercial polymers or surfactants to alter bubble charge in DAF has shown potential, termed the PosiDAF process. When using surfactants, poor removal was obtained but good bubble adherence was observed. Conversely, when using polymers, effective cell removal was obtained, attributed to polymer bridging, but polymers did not adhere well to the bubble surface, resulting in a cationic clarified effluent that was indicative of high polymer concentrations. In order to combine the attributes of both polymers (bridging ability) and surfactants (hydrophobicity), in this study, a commercially-available cationic polymer, poly(dimethylaminoethyl methacrylate) (polyDMAEMA), was functionalised with hydrophobic pendant groups of various carbon chain lengths to improve adherence of polymer to a bubble surface. Its performance in PosiDAF was contrasted against commercially-available poly(diallyl dimethyl ammonium chloride) (polyDADMAC). All synthesised polymers used for bubble surface modification were found to produce positively charged bubbles. When applying these cationic micro-bubbles in PosiDAF, in the absence of coagulation-flocculation, cell removals in excess of 90% were obtained, reaching a maximum of 99% cell removal and thus demonstrating process viability. Of the synthesised polymers, the polymer containing the largest hydrophobic functionality resulted in highly anionic treated effluent, suggesting stronger adherence of polymers to bubble surfaces and reduced residual polymer concentrations.

  2. Separation of toxic metal ions, hydrophilic hydrocarbons, hydrophobic fuel and halogenated hydrocarbons and recovery of ethanol from a process stream

    DOEpatents

    Kansa, E.J.; Anderson, B.L.; Wijesinghe, A.M.; Viani, B.E.

    1999-05-25

    This invention provides a process to tremendously reduce the bulk volume of contaminants obtained from an effluent stream produced subsurface remediation. The chemicals used for the subsurface remediation are reclaimed for recycling to the remediation process. Additional reductions in contaminant bulk volume are achieved by the ultra-violet light destruction of halogenated hydrocarbons, and the complete oxidation of hydrophobic fuel hydrocarbons and hydrophilic hydrocarbons. The contaminated bulk volume will arise primarily from the disposal of the toxic metal ions. The entire process is modular, so if there are any technological breakthroughs in one or more of the component process modules, such modules can be readily replaced. 3 figs.

  3. Separation of toxic metal ions, hydrophilic hydrocarbons, hydrophobic fuel and halogenated hydrocarbons and recovery of ethanol from a process stream

    DOEpatents

    Kansa, Edward J.; Anderson, Brian L.; Wijesinghe, Ananda M.; Viani, Brian E.

    1999-01-01

    This invention provides a process to tremendously reduce the bulk volume of contaminants obtained from an effluent stream produced subsurface remediation. The chemicals used for the subsurface remediation are reclaimed for recycling to the remediation process. Additional reductions in contaminant bulk volume are achieved by the ultra-violet light destruction of halogenated hydrocarbons, and the complete oxidation of hydrophobic fuel hydrocarbons and hydrophilic hydrocarbons. The contaminated bulk volume will arise primarily from the disposal of the toxic metal ions. The entire process is modular, so if there are any technological breakthroughs in one or more of the component process modules, such modules can be readily replaced.

  4. Preparation of porous polymer monolithic column using functionalized graphene oxide as a functional crosslinker for high performance liquid chromatography separation of small molecules.

    PubMed

    Li, Yaping; Qi, Li; Ma, Huimin

    2013-09-21

    A newly developed porous polymer monolith was prepared through copolymerization of 3-(trimethoxysilyl)propylmethacrylate modified graphene oxide with glycidyl methacrylate and ethylene dimethacrylate as a functional crosslinker, which was synthesized through silanization reaction of graphene oxide prepared by Hummers method with 3-(trimethoxysilyl)propylmethacrylate. The monolith was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, mercury intrusion porosimetry and nitrogen adsorption measurement. The monolith column was applied as the stationary phase of high performance liquid chromatography and its chromatographic performance was evaluated by separation of small molecules in the isocratic reversed-phase mode. The chromatograms of hydrophobic steroids and polar aromatic amines on the prepared monolith displayed the enhanced separation performance over those on the parent monolith. The reproducibility of the column was less than 3.5% in terms of relative standard deviation of retention time. The results demonstrate that copolymerization of functionalized graphene oxide into porous polymer monolith was an effective tool for chromatography separation enhancement of small molecules in an isocratic mode. PMID:23884304

  5. Symmetry of extremely floppy molecules: Molecular states beyond rotation-vibration separation

    NASA Astrophysics Data System (ADS)

    Schmiedt, Hanno; Schlemmer, Stephan; Jensen, Per

    2015-10-01

    Traditionally, molecules are theoretically described as near-static structures rotating in space. Vibrational motion causing small structural deformations induces a perturbative treatment of the rotation-vibration interaction, which fails in highly fluxional molecules, where all vibrational motions have amplitudes comparable in size to the linear dimensions of the molecule. An example is protonated methane (CH 5+ ) [P. Kumar and D. Marx, Phys. Chem. Chem. Phys. 8, 573 (2006); Z. Jin et al., J. Phys. Chem. A 110, 1569 (2006); and A. S. Petit et al., J. Phys. Chem. A 118, 7206 (2014)]. For these molecules, customary theory fails to simulate reliably even the low-energy spectrum [T. Oka, Science 347, 1313-1314 (2015) and O. Asvany et al., Science 347, 1346-1349 (2015)]. Within the traditional view of rotation and vibration being near-separable, rotational and vibrational wavefunctions can be symmetry classified separately in the molecular symmetry (MS) group [P. Bunker and P. Jensen, Molecular Symmetry and Spectroscopy, NRC Monograph Publishing Program (NRC Research Press, 2006)]. In this article, we discuss a fundamental group theoretical approach to the problem of determining the symmetries of molecular rotation-vibration states. We will show that all MS groups discussed so far are isomorphic to subgroups of the special orthogonal group in three dimensions SO(3). This leads to a group theoretical foundation of the technique of equivalent rotations [H. Longuet-Higgins, Mol. Phys. 6, 445 (1963)]. The group G240 (the MS group of protonated methane) represents, to the best of our knowledge, the first example of a MS group which is not isomorphic to a subgroup of SO(3) (nor of O(3) or of SU(2)). Because of this, a separate symmetry classification of vibrational and rotational wavefunctions becomes impossible in this MS group, consistent with the fact that a decoupling of vibrational and rotational motion is impossible. We discuss here the consequences of this. In

  6. Symmetry of extremely floppy molecules: Molecular states beyond rotation-vibration separation.

    PubMed

    Schmiedt, Hanno; Schlemmer, Stephan; Jensen, Per

    2015-10-21

    Traditionally, molecules are theoretically described as near-static structures rotating in space. Vibrational motion causing small structural deformations induces a perturbative treatment of the rotation-vibration interaction, which fails in highly fluxional molecules, where all vibrational motions have amplitudes comparable in size to the linear dimensions of the molecule. An example is protonated methane (CH5(+)) [P. Kumar and D. Marx, Phys. Chem. Chem. Phys. 8, 573 (2006); Z. Jin et al., J. Phys. Chem. A 110, 1569 (2006); and A. S. Petit et al., J. Phys. Chem. A 118, 7206 (2014)]. For these molecules, customary theory fails to simulate reliably even the low-energy spectrum [T. Oka, Science 347, 1313-1314 (2015) and O. Asvany et al., Science 347, 1346-1349 (2015)]. Within the traditional view of rotation and vibration being near-separable, rotational and vibrational wavefunctions can be symmetry classified separately in the molecular symmetry (MS) group [P. Bunker and P. Jensen, Molecular Symmetry and Spectroscopy, NRC Monograph Publishing Program (NRC Research Press, 2006)]. In this article, we discuss a fundamental group theoretical approach to the problem of determining the symmetries of molecular rotation-vibration states. We will show that all MS groups discussed so far are isomorphic to subgroups of the special orthogonal group in three dimensions SO(3). This leads to a group theoretical foundation of the technique of equivalent rotations [H. Longuet-Higgins, Mol. Phys. 6, 445 (1963)]. The group G240 (the MS group of protonated methane) represents, to the best of our knowledge, the first example of a MS group which is not isomorphic to a subgroup of SO(3) (nor of O(3) or of SU(2)). Because of this, a separate symmetry classification of vibrational and rotational wavefunctions becomes impossible in this MS group, consistent with the fact that a decoupling of vibrational and rotational motion is impossible. We discuss here the consequences of this. In

  7. Hydrophobic interaction ligand selection and scale-up of an expanded bed separation of an intracellular enzyme from Saccharomyces cerevisiae.

    PubMed

    Smith, M P; Bulmer, M A; Hjorth, R; Titchener-Hooker, N J

    2002-08-30

    A prototype Streamline-Phenyl matrix was evaluated in a hydrophobic interaction mode for the direct recovery of alcohol dehydrogenase (ADH) from yeast cell homogenate. At 5% breakthrough of ADH, a yield of 100% was obtained for a dynamic expanded bed capacity of 240 U(ADH)/ml matrix with a purification factor of 9.2. This compared with a dynamic capacity of 3013 U(ADH)/ml matrix for the packed bed equivalent and a purification factor of 18. In both systems the purification factor was found to increase simultaneously with a decrease in yield as the load of homogenate or breakthrough of ADH was increased. The expanded bed mode of operation conferred considerable robustness with respect to process fouling. No loss in yield was seen over five cycles of repeat loading with an unclarified homogenate. By contrast the packed bed media showed a decrease in yield from 86 to 56% over the same period. Successful scale up of the expanded bed protocol for a 20% breakthrough was demonstrated over a fourfold increase in column diameter. The application of hydrophobic interaction chromatography mediated expanded bed adsorption and its scale-up is discussed in the context of large-scale operations.

  8. The separation between the 5′-3′ ends in long RNA molecules is short and nearly constant

    PubMed Central

    Leija-Martínez, Nehemías; Casas-Flores, Sergio; Cadena-Nava, Rubén D.; Roca, Joan A.; Mendez-Cabañas, José A.; Gomez, Eduardo; Ruiz-Garcia, Jaime

    2014-01-01

    RNA molecules play different roles in coding, decoding and gene expression regulation. Such roles are often associated to the RNA secondary or tertiary structures. The folding dynamics lead to multiple secondary structures of long RNA molecules, since an RNA molecule might fold into multiple distinct native states. Despite an ensemble of different structures, it has been theoretically proposed that the separation between the 5′ and 3′ ends of long single-stranded RNA molecules (ssRNA) remains constant, independent of their base content and length. Here, we present the first experimental measurements of the end-to-end separation in long ssRNA molecules. To determine this separation, we use single molecule Fluorescence Resonance Energy Transfer of fluorescently end-labeled ssRNA molecules ranging from 500 to 5500 nucleotides in length, obtained from two viruses and a fungus. We found that the end-to-end separation is indeed short, within 5–9 nm. It is remarkable that the separation of the ends of all RNA molecules studied remains small and similar, despite the origin, length and differences in their secondary structure. This implies that the ssRNA molecules are ‘effectively circularized’ something that might be a general feature of RNAs, and could result in fine-tuning for translation and gene expression regulation. PMID:25428360

  9. The separation between the 5'-3' ends in long RNA molecules is short and nearly constant.

    PubMed

    Leija-Martínez, Nehemías; Casas-Flores, Sergio; Cadena-Nava, Rubén D; Roca, Joan A; Mendez-Cabañas, José A; Gomez, Eduardo; Ruiz-Garcia, Jaime

    2014-12-16

    RNA molecules play different roles in coding, decoding and gene expression regulation. Such roles are often associated to the RNA secondary or tertiary structures. The folding dynamics lead to multiple secondary structures of long RNA molecules, since an RNA molecule might fold into multiple distinct native states. Despite an ensemble of different structures, it has been theoretically proposed that the separation between the 5' and 3' ends of long single-stranded RNA molecules (ssRNA) remains constant, independent of their base content and length. Here, we present the first experimental measurements of the end-to-end separation in long ssRNA molecules. To determine this separation, we use single molecule Fluorescence Resonance Energy Transfer of fluorescently end-labeled ssRNA molecules ranging from 500 to 5500 nucleotides in length, obtained from two viruses and a fungus. We found that the end-to-end separation is indeed short, within 5-9 nm. It is remarkable that the separation of the ends of all RNA molecules studied remains small and similar, despite the origin, length and differences in their secondary structure. This implies that the ssRNA molecules are 'effectively circularized' something that might be a general feature of RNAs, and could result in fine-tuning for translation and gene expression regulation. PMID:25428360

  10. Pulsed-field electrophoresis: application of a computer model to the separation of large DNA molecules.

    PubMed Central

    Lalande, M; Noolandi, J; Turmel, C; Rousseau, J; Slater, G W

    1987-01-01

    The biased reptation theory has been applied to the pulsed-field electrophoresis of DNA in agarose gels. A computer simulation of the theoretical model that calculates the mobility of large DNA molecules as a function of agarose pore size, DNA chain properties, and electric field conditions has been used to generate mobility curves for DNA molecules in the size range of the larger yeast chromosomes. Pulsed-field electrophoresis experiments resulting in the establishment of an electrophoretic karyotype for yeast, where the mobility of the DNA fragments is a monotonic function of molecular size for the entire size range that is resolved (200-2200 kilobase pairs), has been compared to the theoretical mobility curves generated by the computer model. The various physical mechanisms and experimental conditions responsible for band inversion and improved electrophoretic separation are identified and discussed in the framework of the model. Images PMID:3317398

  11. Synthesis and characterization of a porous and hydrophobic cellulose-based composite for efficient and fast oil-water separation.

    PubMed

    Wang, Xiangyun; Xu, Shimei; Tan, Yun; Du, Juan; Wang, Jide

    2016-04-20

    Oily wastewater is generated in diverse industrial processes, and its treatment has become crucial due to increasing environmental concerns. Herein, silanized cellulose was prepared by sol-gel reaction between microcrystalline cellulose (MCC) and hexadecyltrimethoxysilane (HDTMS) using for oil-water separation. The silanized cellulose was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). A higher mass ratio of HDTMS to MCC made silanized cellulose become looser, and showed lower water absorbency. The silanized cellulose exhibited specific separation performance towards vegetable oil-water mixture (not for mineral oil-water mixture) with separation efficiency of 99.93%. Moreover, the separation was fast with a water flux of 4628.5Lm(-2)h(-1). The separation efficiency still remained at 99.77% even after recycling for 10 times. PMID:26876843

  12. Separation of a group of N-phenylpyrazole derivatives by micellar electrokinetic chromatography: application to the determination of solute-micelle association constants and estimation of the hydrophobicity.

    PubMed

    García-Ruiz, C; García, M A; Marina, M L

    2000-07-01

    Micellar electrokinetic chromatography (MEKC) was applied to the separation of a group of N-phenylpyrazole derivatives. Sodium dodecyl sulfate (SDS) as micellar system and 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) as separation buffer (pH 10) were employed in the absence and presence of different percentages of medium chain alcohols (n-propanol or n-butanol). The separation of multicomponent mixtures of the solutes studied enabled the rapid determination of their retention factors which, in turn, allowed the study of the separation selectivity of compounds and the determination of their solute-micelle association constants (from the linear variation of the retention factors as a function of the total surfactant concentration in the separation buffer). Separation selectivity was studied according to the elution range and number of solutes separated in all the electrolyte solutions employed (45 micellar phases). The effect of the buffer concentration (0.05, 0.08 and 0.10 M), the alcohol nature (n-propanol or n-butanol) and the alcohol percentage (1, 3 or 5%) of the values obtained for the solute-micelle association constants was also studied. The best separation (12 solutes) was performed when a 0.08 M CHES buffer, pH 10, 0.02 M SDS modified by 5% n-butanol was used. The possibilities of using MEKC for evaluating the hydrophobicity of compounds was investigated through the study of the correlation between the logarithm of the retention factors of N-phenylpyrazole derivatives and their logarithm of the octanol-water distribution coefficients estimated by high performance liquid chromatography (HPLC).

  13. Separation of large DNA molecules by size exclusion chromatography-based microchip with on-chip concentration structure

    NASA Astrophysics Data System (ADS)

    Azuma, Naoki; Itoh, Shintaro; Fukuzawa, Kenji; Zhang, Hedong

    2016-06-01

    The separation of DNA molecules according to their size represents a fundamental bioanalytical procedure. Here, we report the development of a chip-sized device, consisting of micrometer-sized fence structures fabricated in a microchannel, for the separation of large DNA molecules (over 10 kbp) based on the principle of size exclusion chromatography (SEC). In order to achieve separation, two approaches were utilized: first, the DNA samples were concentrated immediately prior to separation using nanoslit structures, with the aim of improving the resolution. Second, a theoretical model of SEC-based separation was established and applied in order to predict the optimal voltage range for separation. In this study, we achieved separation of λ DNA (48.5 kbp) and T4 DNA (166 kbp) using the present SEC-based microchip.

  14. Magnetic solid sulfonic acid decorated with hydrophobic regulators: a combinatorial and magnetically separable catalyst for the synthesis of α-aminonitriles.

    PubMed

    Mobaraki, Akbar; Movassagh, Barahman; Karimi, Babak

    2014-07-14

    A three-component, Strecker reaction of a series of aldehydes or ketones, amines, and trimethylsilyl cyanide for the synthesis of α-aminonitriles in the presence of a catalytic amount of a magnetic solid sulfonic acid catalyst, Fe3O4@SiO2@Me&Et-PhSO3H under solvent-free conditions have been investigated. This catalyst, with a combination of hydrophobicity and acidity on the Fe3O4@SiO2 core-shell of the magnetic nanobeads, as well as its water-resistant property, enabled easy mass transfer and catalytic activity in the Strecker reaction. The catalyst was easily separated by an external magnet and the recovered catalyst was reused in 6 successive reaction cycles without any significant loss of activity.

  15. Separation of chromosomal DNA molecules from yeast by orthogonal-field-alternation gel electrophoresis.

    PubMed Central

    Carle, G F; Olson, M V

    1984-01-01

    A simple agarose-gel apparatus has been developed that allows the separation of DNA molecules in the size range from 50 kb to well over 750 kb, the largest size for which size standards were available. The apparatus is based on the recent discovery that large DNA molecules are readily fractionated on agarose gels if they are alternately subjected to two approximately orthogonal electric fields. The switching time, which was on the order of 20-50 sec in our experiments, can be adjusted to optimize fractionation in a given size range. The resolution of the technique is sufficient to allow the fractionation of a sample of self-ligated lambda DNA into a ladder of approximately 15 bands, spaced at 50 kb intervals. We have applied the technique to the fractionation of yeast DNA into 11 distinct bands, several of which have been shown by DNA-DNA hybridization to hybridize uniquely to different chromosome-specific hybridization probes. In this paper, we describe the design of the apparatus, the electrophoretic protocol, and the sample-handling procedures that we have employed. Images PMID:6379602

  16. Hydrophobic Compounds Reshape Membrane Domains

    PubMed Central

    Barnoud, Jonathan; Rossi, Giulia; Marrink, Siewert J.; Monticelli, Luca

    2014-01-01

    Cell membranes have a complex lateral organization featuring domains with distinct composition, also known as rafts, which play an essential role in cellular processes such as signal transduction and protein trafficking. In vivo, perturbations of membrane domains (e.g., by drugs or lipophilic compounds) have major effects on the activity of raft-associated proteins and on signaling pathways, but they are difficult to characterize because of the small size of the domains, typically below optical resolution. Model membranes, instead, can show macroscopic phase separation between liquid-ordered and liquid-disordered domains, and they are often used to investigate the driving forces of membrane lateral organization. Studies in model membranes have shown that some lipophilic compounds perturb membrane domains, but it is not clear which chemical and physical properties determine domain perturbation. The mechanisms of domain stabilization and destabilization are also unknown. Here we describe the effect of six simple hydrophobic compounds on the lateral organization of phase-separated model membranes consisting of saturated and unsaturated phospholipids and cholesterol. Using molecular simulations, we identify two groups of molecules with distinct behavior: aliphatic compounds promote lipid mixing by distributing at the interface between liquid-ordered and liquid-disordered domains; aromatic compounds, instead, stabilize phase separation by partitioning into liquid-disordered domains and excluding cholesterol from the disordered domains. We predict that relatively small concentrations of hydrophobic species can have a broad impact on domain stability in model systems, which suggests possible mechanisms of action for hydrophobic compounds in vivo. PMID:25299598

  17. Towards long-term colloidal stability of silica-based nanocarriers for hydrophobic molecules: beyond the Stöber method.

    PubMed

    Paula, Amauri J; Montoro, Luciano A; Filho, Antonio G Souza; Alves, Oswaldo L

    2012-01-14

    The highly uniform micro- and mesoporous SiO(2) nanoparticles (40-70 nm) are hierarchically functionalized with antagonistic groups: hydrophobic (phenyl) on the internal pores and hydrophilic (methyl-phosphonate) on the external surface. Considering the large hydrophobic internal coating and the long-term colloidal stability, these systems are suitable nanocarriers by using the host-guest approach.

  18. Multistep photochemical charge separation in rod-like molecules based on aromatic insides and diimides

    SciTech Connect

    Greenfield, S.R.; Svec, W.A.; Gosztola, D.; Wasielewski, M.R. |

    1996-07-17

    A series of intramolecular triads with linear, rod-like structures has been developed that undergo very efficient two-step electron transfer following direct excitation of a chromophore possessing a charge transfer (CT) excited state. The CT state of 4-aminonaphthalene-1,8-imide (ANI), produced by direct excitation of the chromophore, has about 70% of a negative charge transferred from the amine to the imide. Attachment of aniline (AN) and p-methoxyaniline (MeOAn) donors to ANI by means of a piperazine bridge results in linear dyads. An-ANI and MeOAn-ANI, that undergo rapid electron transfer in about 10{sup -11} s to give a >99% yield of the ion pairs, An{sup +}-ANI{sup -} and MeOAn{sup +}-ANI{sup -}, in which the charges are separated by 7.7 A. Further attachment of a 1,8:4,5-naphthalene-dimide (NI) electron acceptor to the imide group of ANI using a 2,5-dimethyphenyl spacer results in triads An-ANI-NI and MeOAn-ANI-NI. Excitation of the CT state of ANI within these triads results in the same high yield charge separation step observed in the corresponding dyads followed by a subnanosecond charge shift reaction to yield the giant dipole states An{sup +}-ANI-NI{sup -} and MeOAn{sup +}-ANI-NI{sup -} in 72% and 92% yield, respectively, in toluene. The lifetime of MeOAn{sup +}-ANI-NI{sup -} is 310 ns. These triad molecules make explicit use of a CT excited state to initiate a multistep electron transfer process. 67 refs., 10 figs., 4 tabs.

  19. Creation of quantum entanglement with two separate diamond nitrogen vacancy centers coupled to a photonic molecule

    SciTech Connect

    Liu, Siping; Yu, Rong; Li, Jiahua; Wu, Ying

    2013-12-28

    We explore the entanglement generation and the corresponding dynamics between two separate nitrogen-vacancy (NV) centers in diamond nanocrystal coupled to a photonic molecule consisting of a pair of coupled photonic crystal (PC) cavities. By calculating the entanglement concurrence with readily available experimental parameters, it is found that the entanglement degree strongly depends on the cavity-cavity hopping strength and the NV-center-cavity detuning. High concurrence peak and long-lived entanglement plateau can be achieved by properly adjusting practical system parameters. Meanwhile, we also discuss the influence of the coupling strength between the NV centers and the cavity modes on the behavior of the concurrence. Such a PC-NV system can be employed for quantum entanglement generation and represents a building block for an integrated nanophotonic network in a solid-state cavity quantum electrodynamics platform. In addition, the present theory can also be applied to other similar systems, such as two single quantum emitters positioned close to a microtoroidal resonator with the whispering-gallery-mode fields propagating inside the resonator.

  20. Interaction of gas molecules with crystalline polymer separation membranes: Atomic-scale modeling and first-principles calculations

    SciTech Connect

    Sergey N. Rashkeev; Eric S. Peterson

    2011-11-01

    Carbon dioxide (CO2)-induced plasticization can significantly decrease the gas separation performance of membranes in high-temperature or high pressure conditions, such as industrial methane (CH4) separations. In this paper, we investigated the crystalline phase of three polymers (polybenzimidazole (PBI), Bis(isobutylcarboxy)polybenzimidazole (PBI-Butyl), and KaptonTM) and interactions between gas molecules (CO2 and N2) and these polymers. A novel, molecular dynamics (MD) based, computational technique was employed to find unknown crystalline structures of these polymer materials. The interaction of CO2 and N2 gases with these crystals was studied by first-principles calculations and by classical MD simulations. The results showed that the packing structure and the interlayer coupling in polymer crystals determine the permeability and diffusivity of gas molecules. This methodology also allows prediction of plastic swelling in these materials caused by gas molecules absorbed in the polymer matrix.

  1. Fabrication of zeolitic imidazolate framework-8-methacrylate monolith composite capillary columns for fast gas chromatographic separation of small molecules.

    PubMed

    Yusuf, Kareem; Badjah-Hadj-Ahmed, Ahmed Yacine; Aqel, Ahmad; ALOthman, Zeid Abdullah

    2015-08-01

    A composite zeolitic imidazolate framework-8 (ZIF-8) with a butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250μm i.d.) was fabricated to enhance the separation efficiency of methacrylate monoliths toward small molecules using conventional low-pressure gas chromatography in comparison with a neat butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250μm i.d.). The addition of 10mgmL(-1) ZIF-8 micro-particles increased the BET surface area of BuMA-co-EDMA by 3.4-fold. A fast separation of five linear alkanes in 36s with high resolution (Rs≥1.3) was performed using temperature program. Isothermal separation of the same sample also showed a high efficiency (3315platesm(-1) for octane) at 0.89min. Moreover, the column was able to separate skeletal isomers, such as iso-octane/octane and 2-methyl octane/nonane. In addition, an iso-butane/iso-butylene gas mixture was separated at ambient temperature. Comparison with an open tubular TR-5MS column (30m long×250μm i.d.) revealed the superiority of the composite column in separating the five-membered linear alkane mixture with 4-5 times increase in efficiency and a total separation time of 0.89min instead of 4.67min. A paint thinner sample was fully separated using the composite column in 2.43min with a good resolution (Rs≥0.89). The perfect combination between the polymeric monolith, with its high permeability, and ZIF-8, with its high surface area and flexible 0.34nm pore openings, led to the fast separation of small molecules with high efficiency and opened a new horizon in GC applications.

  2. Fabrication of zeolitic imidazolate framework-8-methacrylate monolith composite capillary columns for fast gas chromatographic separation of small molecules.

    PubMed

    Yusuf, Kareem; Badjah-Hadj-Ahmed, Ahmed Yacine; Aqel, Ahmad; ALOthman, Zeid Abdullah

    2015-08-01

    A composite zeolitic imidazolate framework-8 (ZIF-8) with a butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250μm i.d.) was fabricated to enhance the separation efficiency of methacrylate monoliths toward small molecules using conventional low-pressure gas chromatography in comparison with a neat butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250μm i.d.). The addition of 10mgmL(-1) ZIF-8 micro-particles increased the BET surface area of BuMA-co-EDMA by 3.4-fold. A fast separation of five linear alkanes in 36s with high resolution (Rs≥1.3) was performed using temperature program. Isothermal separation of the same sample also showed a high efficiency (3315platesm(-1) for octane) at 0.89min. Moreover, the column was able to separate skeletal isomers, such as iso-octane/octane and 2-methyl octane/nonane. In addition, an iso-butane/iso-butylene gas mixture was separated at ambient temperature. Comparison with an open tubular TR-5MS column (30m long×250μm i.d.) revealed the superiority of the composite column in separating the five-membered linear alkane mixture with 4-5 times increase in efficiency and a total separation time of 0.89min instead of 4.67min. A paint thinner sample was fully separated using the composite column in 2.43min with a good resolution (Rs≥0.89). The perfect combination between the polymeric monolith, with its high permeability, and ZIF-8, with its high surface area and flexible 0.34nm pore openings, led to the fast separation of small molecules with high efficiency and opened a new horizon in GC applications. PMID:26141277

  3. Laser-induced shockwave chromatography: a separation and analysis method for nanometer-sized particles and molecules.

    PubMed

    Nagahara, Tetsuhiko; Ichinose, Nobuyuki; Nakamura, Shinpei

    2011-04-01

    A microscopic chromatography has been developed where nanometer-size molecules or particles are separated according to their size by the laser-induced shockwave in a water-filled capillary. As the shockwave passed through the mixture of molecules/particles in solution, they move to the direction of the propagation of the shockwave. The distance from the point of shockwave generation depends on the particle size or molecular weight. This technique has some advantages compared to conventional chromatography, in terms of quick analysis of molecular weight and applicability to sticky and adsorbing polymers. Experimental results obtained for proteins, their aggregates, and inorganic nanoparticles are presented.

  4. On the separability of the extended molecule: Constructing the best localized molecular orbitals for an organic molecule bridging two model electrodes

    SciTech Connect

    Moreira, Rodrigo A.; Melo, Celso P. de

    2014-09-28

    Based on a quantum chemical valence formalism that allows the rigorous construction of best-localized molecular orbitals on specific parts of an extended system, we examined the separability of individual components of model systems relevant to the description of electron transport in molecular devices. We started by examining how to construct the maximally localized electronic density at the tip of a realistic model of a gold electrode. By varying the number of gold atoms included in the local region where to project the total electronic density, we quantitatively assess how many molecular orbitals are entirely localized in that region. We then considered a 1,4-benzene-di-thiol molecule connected to two model gold electrodes and examined how to localize the electronic density of the total system in the extended molecule, a fractional entity comprising the organic molecule plus an increasing number of the closest metal atoms. We were able to identify in a rigorous manner the existence of three physically different electronic populations, each one corresponding to a distinct set of molecular orbitals. First, there are those entirely localized in the extended molecule, then there is a second group of those completely distributed in the gold atoms external to that region, and, finally, there are those delocalized over the entire system. This latter group can be associated to the shared electronic population between the extended molecule and the rest of the system. We suggest that the treatment here presented could be useful in the theoretical analysis of the electronic transport in nanodevices whenever the use of localized molecular states are required by the physics of the specific problem, such as in cases of weak coupling and super-exchange limits.

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

    PubMed

    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.

  6. Polydimethysiloxane Modified Silica Nanochannel Membrane for Hydrophobicity-Based Molecular Filtration and Detection.

    PubMed

    Lin, Xingyu; Zhang, Bowen; Yang, Qian; Yan, Fei; Hua, Xin; Su, Bin

    2016-08-01

    We report in this work the fabrication of ultrathin silica nanochannel membranes inhomogeneously modified by polydimethysiloxane (PDMS), designated as PDMS-SNM, for hydrophobicity-based molecular filtration and detection. The modification was accomplished by spatially selective evaporation of hydrophobic PDMS oligomers onto the top surface of the membrane and orifice of silica nanochannels. Thanks to this hydrophobic ultrathin layer and beneath ultrasmall channels (2-3 nm in diameter), only small hydrophobic molecules are able to transport through the PDMS-SNM, whereas hydrophilic and large ones are remarkably inhibited. We first employed this PDMS-SNM as the molecular sieving matrix for selective electrochemical detection of hydrophobic organophosphates (OPs) in milk samples without pretreatment. The PDMS-SNM modified electrode displayed an excellent analytical performance and antifouling/anti-interference ability. We also prepared the free-standing PDMS-SNM consisting of perforated channels, which could filtrate molecules based on their hydrophobicity with an excellent selectivity. As demonstrated, 2,4,6-trinitrotoluene and dopamine could be separated with a selectivity coefficient as high as 335. Moreover, because of the inhomogeneous nanochannel structure and ultrasmall thickness, a remarkably high flux of hydrophobic molecules across the PDMS-SNM was obtained, which was 3-4 orders of magnitude higher than that reported previously. PMID:27414252

  7. Hydrophobicity of rare-earth oxide ceramics.

    PubMed

    Azimi, Gisele; Dhiman, Rajeev; Kwon, Hyuk-Min; Paxson, Adam T; Varanasi, Kripa K

    2013-04-01

    Hydrophobic materials that are robust to harsh environments are needed in a broad range of applications. Although durable materials such as metals and ceramics, which are generally hydrophilic, can be rendered hydrophobic by polymeric modifiers, these deteriorate in harsh environments. Here we show that a class of ceramics comprising the entire lanthanide oxide series, ranging from ceria to lutecia, is intrinsically hydrophobic. We attribute their hydrophobicity to their unique electronic structure, which inhibits hydrogen bonding with interfacial water molecules. We also show with surface-energy measurements that polar interactions are minimized at these surfaces and with Fourier transform infrared/grazing-angle attenuated total reflection that interfacial water molecules are oriented in the hydrophobic hydration structure. Moreover, we demonstrate that these ceramic materials promote dropwise condensation, repel impinging water droplets, and sustain hydrophobicity even after exposure to harsh environments. Rare-earth oxide ceramics should find widespread applicability as robust hydrophobic surfaces.

  8. Hydrophobicity of rare-earth oxide ceramics

    NASA Astrophysics Data System (ADS)

    Azimi, Gisele; Dhiman, Rajeev; Kwon, Hyuk-Min; Paxson, Adam T.; Varanasi, Kripa K.

    2013-04-01

    Hydrophobic materials that are robust to harsh environments are needed in a broad range of applications. Although durable materials such as metals and ceramics, which are generally hydrophilic, can be rendered hydrophobic by polymeric modifiers, these deteriorate in harsh environments. Here we show that a class of ceramics comprising the entire lanthanide oxide series, ranging from ceria to lutecia, is intrinsically hydrophobic. We attribute their hydrophobicity to their unique electronic structure, which inhibits hydrogen bonding with interfacial water molecules. We also show with surface-energy measurements that polar interactions are minimized at these surfaces and with Fourier transform infrared/grazing-angle attenuated total reflection that interfacial water molecules are oriented in the hydrophobic hydration structure. Moreover, we demonstrate that these ceramic materials promote dropwise condensation, repel impinging water droplets, and sustain hydrophobicity even after exposure to harsh environments. Rare-earth oxide ceramics should find widespread applicability as robust hydrophobic surfaces.

  9. Simulation of dynamic behavior of surfactants on a hydrophobic surface using periodic-shell boundary molecular dynamics.

    PubMed

    Minami, Daiki; Horikoshi, Satoshi; Sakai, Kenichi; Sakai, Hideki; Abe, Masahiko

    2011-01-01

    The adsorption and aggregation behaviors of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) on a hydrophobic graphite surface were examined using a novel molecular dynamics (MD) simulation with the periodic-shell boundary condition (PSBC). Differences in the adsorption behavior of SDS and CTAB molecules were clearly shown on the hydrophobic surface. Unexpectedly, the SDS molecules approached the graphite surface with their hydrophilic head groups. This unexpected approach mode was thought to be due to the aqueous layer on the graphite surface. The hydrophobic moiety of SDS molecules repeatedly adsorbed and desorbed on the graphite surface. In addition, SDS molecules kept moving on the graphite surface; thus, they did not form a stable adsorption layer. In contrast to SDS, the hydrophobic moiety of CTAB molecules approached the graphite surface at the primary step of adsorption. The hydrophobic moieties of CTAB molecules came close to each other, whereas the hydrophilic groups separated from one another. This result suggests that the CTAB molecules form molecular assemblies with a curved structure. The simulation results were consistent with the experimental observations. A clear difference between the adsorption behavior of SDS and CTAB molecules was revealed by MD simulations with PSBC.

  10. Separation of rare gases and chiral molecules by selective binding in porous organic cages

    SciTech Connect

    Chen, Linjiang; Reiss, Paul S.; Chong, Samantha Y.; Holden, Daniel; Jelfs, Kim E.; Hasell, Tom; Little, Marc A.; Kewley, Adam; Briggs, Michael E.; Stephenson, Andrew; Thomas, K. M.; Armstrong, Jayne A.; Bell, Jon; Busto, Jose; Noel, Raymond; Liu, Jian; Strachan, Denis M.; Thallapally, Praveen K.; Cooper, Andrew I.

    2014-10-31

    Abstract: The rare gases krypton, xenon, and radon pose both an economic opportunity and a potential environmental hazard. Xenon is used in commercial lighting, medical imaging, and anesthesia, and can sell for $5,000 per kilogram. Radon, by contrast, Is naturally radioactive and the second largest cause of lung cancer, and radioactive xenon, 133Xe, was a major pollutant released In the Fukushima Daiichi Nuclear Power Plant disaster. We describe an organic cage molecule that can capture xenon and radon with unprecedented selectivity, suggesting new technologies for environmental monitoring, removal of pollutants, or the recovery of rare, valuable elements from air.

  11. Interference effects in above-threshold ionization from diatomic molecules: Determining the internuclear separation

    SciTech Connect

    Hetzheim, H.; Figueira de Morisson Faria, C.; Becker, W.

    2007-08-15

    We calculate angle-resolved above-threshold ionization spectra for diatomic molecules in linearly polarized laser fields, employing the strong-field approximation. The interference structure resulting from the individual contributions of the different scattering scenarios is discussed in detail, with respect to the dependence on the internuclear distance and molecular orientation. We show that, in general, the contributions from the processes in which the electron is freed at one center and rescatters off the other obscure the interference maxima and minima obtained from single-center processes. However, around the boundary of the energy regions for which rescattering has a classical counterpart, such processes play a negligible role and very clear interference patterns are observed. In such energy regions, one is able to infer the internuclear distance from the energy difference between adjacent interference minima.

  12. Optimization of a pre-MEKC separation SPE procedure for steroid molecules in human urine samples.

    PubMed

    Olędzka, Ilona; Kowalski, Piotr; Dziomba, Szymon; Szmudanowski, Piotr; Bączek, Tomasz

    2013-01-01

    Many steroid hormones can be considered as potential biomarkers and their determination in body fluids can create opportunities for the rapid diagnosis of many diseases and disorders of the human body. Most existing methods for the determination of steroids are usually time- and labor-consuming and quite costly. Therefore, the aim of analytical laboratories is to develop a new, relatively low-cost and rapid implementation methodology for their determination in biological samples. Due to the fact that there is little literature data on concentrations of steroid hormones in urine samples, we have made attempts at the electrophoretic determination of these compounds. For this purpose, an extraction procedure for the optimized separation and simultaneous determination of seven steroid hormones in urine samples has been investigated. The isolation of analytes from biological samples was performed by liquid-liquid extraction (LLE) with dichloromethane and compared to solid phase extraction (SPE) with C18 and hydrophilic-lipophilic balance (HLB) columns. To separate all the analytes a micellar electrokinetic capillary chromatography (MECK) technique was employed. For full separation of all the analytes a running buffer (pH 9.2), composed of 10 mM sodium tetraborate decahydrate (borax), 50 mM sodium dodecyl sulfate (SDS), and 10% methanol was selected. The methodology developed in this work for the determination of steroid hormones meets all the requirements of analytical methods. The applicability of the method has been confirmed for the analysis of urine samples collected from volunteers--both men and women (students, amateur bodybuilders, using and not applying steroid doping). The data obtained during this work can be successfully used for further research on the determination of steroid hormones in urine samples. PMID:24232737

  13. The Hydrophobic Effect.

    ERIC Educational Resources Information Center

    Huque, Entazul M.

    1989-01-01

    Discusses the physical basis and current understanding of hydrophobic effects. The thermodynamic background of the effects, hydrophobic hydration, and hydrophobic interactions are described. Four existing controversies are outlined. (YP)

  14. Water-Mediated Hydrophobic Interactions

    NASA Astrophysics Data System (ADS)

    Ben-Amotz, Dor

    2016-05-01

    Hydrophobic interactions are driven by the combined influence of the direct attraction between oily solutes and an additional water-mediated interaction whose magnitude (and sign) depends sensitively on both solute size and attraction. The resulting delicate balance can lead to a slightly repulsive water-mediated interaction that drives oily molecules apart rather than pushing them together and thus opposes their direct (van der Waals) attraction for each other. As a consequence, competing solute size-dependent crossovers weaken hydrophobic interactions sufficiently that they are only expected to significantly exceed random thermal energy fluctuations for processes that bury more than ˜1 nm2 of water-exposed area.

  15. Water-COOH Composite Structure with Enhanced Hydrophobicity Formed by Water Molecules Embedded into Carboxyl-Terminated Self-Assembled Monolayers

    NASA Astrophysics Data System (ADS)

    Guo, Pan; Tu, Yusong; Yang, Jinrong; Wang, Chunlei; Sheng, Nan; Fang, Haiping

    2015-10-01

    By combining molecular dynamics simulations and quantum mechanics calculations, we show the formation of a composite structure composed of embedded water molecules and the COOH matrix on carboxyl-terminated self-assembled monolayers (COOH SAMs) with appropriate packing densities. This composite structure with an integrated hydrogen bond network inside reduces the hydrogen bonds with the water above. This explains the seeming contradiction on the stability of the surface water on COOH SAMs observed in experiments. The existence of the composite structure at appropriate packing densities results in the two-step distribution of contact angles of water droplets on COOH SAMs, around 0° and 35°, which compares favorably to the experimental measurements of contact angles collected from forty research articles over the past 25 years. These findings provide a molecular-level understanding of water on surfaces (including surfaces on biomolecules) with hydrophilic functional groups.

  16. Water-COOH Composite Structure with Enhanced Hydrophobicity Formed by Water Molecules Embedded into Carboxyl-Terminated Self-Assembled Monolayers.

    PubMed

    Guo, Pan; Tu, Yusong; Yang, Jinrong; Wang, Chunlei; Sheng, Nan; Fang, Haiping

    2015-10-30

    By combining molecular dynamics simulations and quantum mechanics calculations, we show the formation of a composite structure composed of embedded water molecules and the COOH matrix on carboxyl-terminated self-assembled monolayers (COOH SAMs) with appropriate packing densities. This composite structure with an integrated hydrogen bond network inside reduces the hydrogen bonds with the water above. This explains the seeming contradiction on the stability of the surface water on COOH SAMs observed in experiments. The existence of the composite structure at appropriate packing densities results in the two-step distribution of contact angles of water droplets on COOH SAMs, around 0° and 35°, which compares favorably to the experimental measurements of contact angles collected from forty research articles over the past 25 years. These findings provide a molecular-level understanding of water on surfaces (including surfaces on biomolecules) with hydrophilic functional groups.

  17. Enthalpic and Entropic Contributions to Hydrophobicity.

    PubMed

    Schauperl, Michael; Podewitz, Maren; Waldner, Birgit J; Liedl, Klaus R

    2016-09-13

    Hydrophobic hydration plays a key role in a vast variety of biological processes, ranging from the formation of cells to protein folding and ligand binding. Hydrophobicity scales simplify the complex process of hydration by assigning a value describing the averaged hydrophobic character to each amino acid. Previously published scales were not able to calculate the enthalpic and entropic contributions to the hydrophobicity directly. We present a new method, based on Molecular Dynamics simulations and Grid Inhomogeneous Solvation Theory, that calculates hydrophobicity from enthalpic and entropic contributions. Instead of deriving these quantities from the temperature dependence of the free energy of hydration or as residual of the free energy and the enthalpy, we directly obtain these values from the phase space occupied by water molecules. Additionally, our method is able to identify regions with specific enthalpic and entropic properties, allowing to identify so-called "unhappy water" molecules, which are characterized by weak enthalpic interactions and unfavorable entropic constraints. PMID:27442443

  18. Enthalpic and Entropic Contributions to Hydrophobicity

    PubMed Central

    2016-01-01

    Hydrophobic hydration plays a key role in a vast variety of biological processes, ranging from the formation of cells to protein folding and ligand binding. Hydrophobicity scales simplify the complex process of hydration by assigning a value describing the averaged hydrophobic character to each amino acid. Previously published scales were not able to calculate the enthalpic and entropic contributions to the hydrophobicity directly. We present a new method, based on Molecular Dynamics simulations and Grid Inhomogeneous Solvation Theory, that calculates hydrophobicity from enthalpic and entropic contributions. Instead of deriving these quantities from the temperature dependence of the free energy of hydration or as residual of the free energy and the enthalpy, we directly obtain these values from the phase space occupied by water molecules. Additionally, our method is able to identify regions with specific enthalpic and entropic properties, allowing to identify so-called “unhappy water” molecules, which are characterized by weak enthalpic interactions and unfavorable entropic constraints. PMID:27442443

  19. Buffer system for the separation of neutral and charged small molecules using micellar electrokinetic chromatography with mass spectrometric detection.

    PubMed

    Goetzinger, Wolfgang K; Cai, Hong

    2005-06-24

    An organic buffer system will be discussed that is suitable for the separation of neutral as well as charged molecules be means of micellar electrokinetic chromatography (MEKC). The buffers are based on the combination of a long chain alkyl acid, such as lauric acid with ammonium hydroxide or an organic base such as tris-hydroxymethylaminomethane (Tris). The resulting buffer system is able to separate neutral compounds based on its micellar properties. These buffers exhibit much reduced conductivity compared to traditional MEKC buffers, such as sodium dodecylsulfate (SDS), which contain inorganic salts. They also have inherent buffer capacity at high pH resulting from the basic buffer component, which in our studies had pK values from about 8-11. The separations that were observed showed high efficiency with plate counts in many cases above 500,000 plates per meter. The reduced conductivity allowed for the application of much higher electric fields, resulting in very fast analysis times. Alternatively, an increase in detection sensitivity could be achieved, as the reduced conductivity allowed for the use of capillaries with lager internal diameters. Combinations of different alkyl acids and organic bases provided for significant flexibility in selectivity tuning. Finally, the fact that the organic micellar buffer systems discussed here do not contain inorganic ions, allows for coupling with mass spectrometric (MS) detection. The possibility of MS detection combined with the high speed in analysis that can be obtained using these organic buffer systems, could make this approach an interesting option for high throughput analysis of combinatorial libraries. PMID:16038325

  20. Interconnection of salt-induced hydrophobic compaction and secondary structure formation depends on solution conditions: revisiting early events of protein folding at single molecule resolution.

    PubMed

    Haldar, Shubhasis; Chattopadhyay, Krishnananda

    2012-03-30

    What happens in the early stage of protein folding remains an interesting unsolved problem. Rapid kinetics measurements with cytochrome c using submillisecond continuous flow mixing devices suggest simultaneous formation of a compact collapsed state and secondary structure. These data seem to indicate that collapse formation is guided by specific short and long range interactions (heteropolymer collapse). A contrasting interpretation also has been proposed, which suggests that the collapse formation is rapid, nonspecific, and a trivial solvent related compaction, which could as well be observed by a homopolymer (homopolymer collapse). We address this controversy using fluorescence correlation spectroscopy (FCS), which enables us to monitor the salt-induced compaction accompanying collapse formation and the associated time constant directly at single molecule resolution. In addition, we follow the formation of secondary structure using far UV CD. The data presented here suggest that both these models (homopolymer and heteropolymer) could be applicable depending on the solution conditions. For example, the formation of secondary structure and compact state is not simultaneous in aqueous buffer. In aqueous buffer, formation of the compact state occurs through a two-state co-operative transition following heteropolymer formalism, whereas secondary structure formation takes place gradually. In contrast, in the presence of urea, a compaction of the protein radius occurs gradually over an extended range of salt concentration following homopolymer formalism. The salt-induced compaction and the formation of secondary structure take place simultaneously in the presence of urea.

  1. Practical method development for the separation of monoclonal antibodies and antibody-drug-conjugate species in hydrophobic interaction chromatography, part 1: optimization of the mobile phase.

    PubMed

    Rodriguez-Aller, Marta; Guillarme, Davy; Beck, Alain; Fekete, Szabolcs

    2016-01-25

    The goal of this work is to provide some recommendations for method development in HIC using monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) as model drug candidates. The effects of gradient steepness, mobile phase pH, salt concentration and type, as well as organic modifier were evaluated for tuning selectivity and retention in HIC. Except the nature of the stationary phase, which was not discussed in this study, the most important parameter for modifying selectivity was the gradient steepness. The addition of organic solvent (up to 15% isopropanol) in the mobile phase was also found to be useful for mAbs analysis, since it could provide some changes in elution order, in some cases. On the contrary, isopropanol was not beneficial with ADCs, since the most hydrophobic DAR species (DAR6 and DAR8) cannot be eluted from the stationary phase under these conditions. This study also illustrates the possibility to perform HIC method development using optimization software, such as Drylab. The optimum conditions suggested by the software were tested using therapeutic mAbs and commercial cysteine linked ADC (brentuximab-vedotin) and the average retention time errors between predicted and experimental retention times were ∼ 1%.

  2. Method for making nanoporous hydrophobic coatings

    DOEpatents

    Fan, Hongyou; Sun, Zaicheng

    2013-04-23

    A simple coating method is used to form nanoporous hydrophobic films that can be used as optical coatings. The method uses evaporation-induced self-assembly of materials. The coating method starts with a homogeneous solution comprising a hydrophobic polymer and a surfactant polymer in a selective solvent. The solution is coated onto a substrate. The surfactant polymer forms micelles with the hydrophobic polymer residing in the particle core when the coating is dried. The surfactant polymer can be dissolved and selectively removed from the separated phases by washing with a polar solvent to form the nanoporous hydrophobic film.

  3. Probabilistic approach to the length-scale dependence of the effect of water hydrogen bonding on hydrophobic hydration.

    PubMed

    Djikaev, Y S; Ruckenstein, E

    2013-06-13

    We present a probabilistic approach to water-water hydrogen bonding that allows one to obtain an analytic expression for the number of bonds per water molecule as a function of both its distance to a hydrophobic particle and hydrophobe radius. This approach can be used in density functional theory (DFT) and computer simulations to examine particle size effects on the hydration of particles and on their solvent-mediated interaction. For example, it allows one to explicitly identify a water hydrogen bond contribution to the external potential, whereto a water molecule is subjected near a hydrophobe. The DFT implementation of the model predicts the hydration free energy per unit area of a spherical hydrophobe to be sharply sensitive to the hydrophobe radius for small radii and weakly sensitive thereto for large ones; this corroborates the vision of the hydration of small and large length-scale particles as occurring via different mechanisms. On the other hand, the model predicts that the hydration of even apolar particles of small enough radii may become thermodynamically favorable owing to the interplay of the energies of pairwise (dispersion) water-water and water-hydrophobe interactions. This sheds light on previous counterintuitive observations (both theoretical and simulational) that two inert gas molecules would prefer to form a solvent-separated pair rather than a contact one.

  4. Online Capillary IsoElectric Focusing-ElectroSpray Ionization Mass Spectrometry (CIEF-ESI MS) in Glycerol-Water Media for the Separation and Characterization of Hydrophilic and Hydrophobic Proteins.

    PubMed

    Mokaddem, Meriem; d'Orlyé, Fanny; Varenne, Anne

    2016-01-01

    Capillary isoelectric focusing (CIEF) is a high-resolution technique for the separation of ampholytes, such as proteins, according to their isoelectric point. CIEF coupled online with MS is regarded as a promising alternative to 2-D PAGE for fast proteome analysis with high-resolving capabilities and enhanced structural information without the drawbacks of conventional slab-gel electrophoresis. However, online coupling has been rarely described, as it presents some difficulties. A new methodology for the online coupling of CIEF with electrospray ionization mass spectrometry (ESI-MS) has been developed in glycerol-water media. This new integrated methodology provides a mean for the characterization of a large number of hydrophilic and hydrophobic proteins. PMID:27473481

  5. Apparatus and process for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles

    DOEpatents

    Yoon, R.H.; Adel, G.T.; Luttrell, G.H.

    1998-09-29

    A method and apparatus are disclosed for the microbubble flotation separation of very fine and coarse particles, especially coal and minerals, so as to produce high purity and high recovery efficiency. This is accomplished through the use of a flotation column, microbubbles, recycling of the flotation pulp, and countercurrent wash water to gently wash the froth. Also disclosed are unique processes and apparatus for generating microbubbles for flotation in a highly efficient and inexpensive manner using either a porous tube or in-line static generators. 14 figs.

  6. Apparatus and process for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles

    DOEpatents

    Yoon, Roe-Hoan; Adel, Gregory T.; Luttrell, Gerald H.

    1992-01-01

    A method and apparatus are disclosed for the microbubble flotation separation of very fine and coarse particles, especially coal and minerals, so as to produce high purity and high recovery efficiency. This is accomplished through the use of a flotation column, microbubbles, recycling of the flotation pulp, and countercurrent wash water to gently wash the froth. Also disclosed are unique processes and apparatus for generating microbubbles for flotation in a highly efficient and inexpensive manner using either a porous tube or in-line static generators.

  7. Apparatus and process for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles

    DOEpatents

    Yoon, Roe-Hoan; Adel, Gregory T.; Luttrell, Gerald H.

    1998-01-01

    A method and apparatus are disclosed for the microbubble flotation separation of very fine and coarse particles, especially coal and minerals, so as to produce high purity and high recovery efficiency. This is accomplished through the use of a flotation column, microbubbles, recycling of the flotation pulp, and countercurrent wash water to gently wash the froth. Also disclosed are unique processes and apparatus for generating microbubbles for flotation in a highly efficient and inexpensive manner using either a porous tube or in-line static generators.

  8. Apparatus for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles

    DOEpatents

    Yoon, Roe-Hoan; Adel, Gregory T.; Luttrell, Gerald H.

    1995-01-01

    An apparatus is disclosed for the microbubble flotation separation of very fine and coarse particles, especially coal, and minerals so as to produce high purity and high recovery efficiency. This is accomplished through the use of a flotation column, microbubbles, recycling of the flotation pulp, and countercurrent wash water to gently wash the froth. Also disclosed are unique processes and apparatus for generating microbubbles for flotation in a highly efficient and inexpensive manner using either a porous tube or in-line static generators.

  9. Apparatus for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles

    DOEpatents

    Yoon, R.H.; Adel, G.T.; Luttrell, G.H.

    1995-03-14

    An apparatus is disclosed for the microbubble flotation separation of very fine and coarse particles, especially coal, and minerals so as to produce high purity and high recovery efficiency. This is accomplished through the use of a flotation column, microbubbles, recycling of the flotation pulp, and countercurrent wash water to gently wash the froth. Also disclosed are unique processes and apparatus for generating microbubbles for flotation in a highly efficient and inexpensive manner using either a porous tube or in-line static generators. 14 figs.

  10. Apparatus and process for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles

    DOEpatents

    Yoon, R.H.; Adel, G.T.; Luttrell, G.H.

    1992-12-01

    A method and apparatus are disclosed for the microbubble flotation separation of very fine and coarse particles, especially coal and minerals, so as to produce high purity and high recovery efficiency. This is accomplished through the use of a flotation column, microbubbles, recycling of the flotation pulp, and countercurrent wash water to gently wash the froth. Also disclosed are unique processes and apparatus for generating microbubbles for flotation in a highly efficient and inexpensive manner using either a porous tube or in-line static generators. 14 figs.

  11. Incorporation of ionic liquid into porous polymer monoliths to enhance the separation of small molecules in reversed-phase high-performance liquid chromatography.

    PubMed

    Wang, Jiafei; Bai, Ligai; Wei, Zhen; Qin, Junxiao; Ma, Yamin; Liu, Haiyan

    2015-06-01

    An ionic liquid was incorporated into the porous polymer monoliths to afford stationary phases with enhanced chromatographic performance for small molecules in reversed-phase high-performance liquid chromatography. The effect of the ionic liquid in the polymerization mixture on the performance of the monoliths was studied in detail. While monoliths without ionic liquid exhibited poor resolution and low efficiency, the addition of ionic liquid to the polymerization mixture provides highly increased resolution and high efficiency. The chromatographic performances of the monoliths were demonstrated by the separations of various small molecules including aromatic hydrocarbons, isomers, and homologues using a binary polar mobile phase. The present column efficiency reached 27 000 plates/m, which showed that the ionic liquid monoliths are alternative stationary phases in the separation of small molecules by high-performance liquid chromatography.

  12. Detection of chemical substances in water using an oxide nanowire transistor covered with a hydrophobic nanoparticle thin film as a liquid-vapour separation filter

    NASA Astrophysics Data System (ADS)

    Lim, Taekyung; Lee, Jonghun; Ju, Sanghyun

    2016-08-01

    We have developed a method to detect the presence of small amounts of chemical substances in water, using a Al2O3 nanoparticle thin film covered with phosphonic acid (HDF-PA) self-assembled monolayer. The HDF-PA self-assembled Al2O3 nanoparticle thin film acts as a liquid-vapour separation filter, allowing the passage of chemical vapour while blocking liquids. Prevention of the liquid from contacting the SnO2 nanowire and source-drain electrodes is required in order to avoid abnormal operation. Using this characteristic, the concentration of chemical substances in water could be evaluated by measuring the current changes in the SnO2 nanowire transistor covered with the HDF-PA self-assembled Al2O3 nanoparticle thin film.

  13. Preparation of low flow-resistant methacrylate-based monolithic stationary phases of different hydrophobicity and the application to rapid reversed-phase liquid chromatographic separation of alkylbenzenes at high flow rate and elevated temperature.

    PubMed

    Ueki, Yuji; Umemura, Tomonari; Iwashita, Yoshikazu; Odake, Tamao; Haraguchi, Hiroki; Tsunoda, Kin-ichi

    2006-02-17

    Low flow-resistant alkyl methacrylate-based monolithic stationary phases of different hydrophobicity were constructed for reversed-phase capillary liquid chromatography by thermally initiated radical polymerization of respective methacrylate ester monomer with different alkyl chain (C2, C4, C6, C12, C18) and ethylene glycol dimethacrylate (EDMA) in a 250 microm i.d. fused silica capillary. The hydrophobicity was basically controlled by changing the length and/or the density of the alkyl-chain, while the composition and the ratio of porogenic solvent were adjusted to obtain highly permeable rigid monoliths with adequate column efficiency. Among the prepared monolithic stationary phases, C18-methacrylate monoliths polymerized from a binary porogenic solvent of isoamyl alcohol and 1,4-buthandiol exhibited the most promising performance in terms of hydraulic resistance and column efficiency. The pressure drops of 20-cm long monolithic columns were below approximately 0.4 MPa at a normal linear velocity of 1mm/s (a flow rate of 3 microL/min), and the numbers of theoretical plates for alkylbenzenes mostly exceeded 3000 plates/20 cm. The produced monolithic columns had good mechanical strength for high pressure and temperature, and could be properly operated even at a temperature of 80 degrees C and at a pressure of at least 33 MPa. At 80 degrees C, the theoretical plate numbers reached 6000 plates/20 cm because of the enhanced mass transfer. Due to the novel hydraulic resistance and mechanical strength, the separation time could be reduced 120-fold simply by raising the flow rate and column temperature.

  14. Molecular Shape and the Hydrophobic Effect

    NASA Astrophysics Data System (ADS)

    Hillyer, Matthew B.; Gibb, Bruce C.

    2016-05-01

    This review focuses on papers published since 2000 on the topic of the properties of solutes in water. More specifically, it evaluates the state of the art of our understanding of the complex relationship between the shape of a hydrophobe and the hydrophobic effect. To highlight this, we present a selection of references covering both empirical and molecular dynamics studies of small (molecular-scale) solutes. These include empirical studies of small molecules, synthetic hosts, crystalline monolayers, and proteins, as well as in silico investigations of entities such as idealized hard and soft spheres, small solutes, hydrophobic plates, artificial concavity, molecular hosts, carbon nanotubes and spheres, and proteins.

  15. ARTICLES: Isotope separation by multiphoton dissociation of molecules using high-power CO2 laser radiation. Scaling of the process for carbon isotopes

    NASA Astrophysics Data System (ADS)

    Abdushelishvili, G. I.; Avatkov, O. N.; Bagratashvili, Viktor N.; Baranov, V. Yu; Bakhtadze, A. B.; Velikhov, E. P.; Vetsko, V. M.; Gverdtsiteli, I. G.; Dolzhikov, V. S.; Esadze, G. G.; Kazakov, S. A.; Kolomiĭskiĭ, Yu R.; Letokhov, V. S.; Pigul'skiĭ, S. V.; Pis'mennyĭ, V. D.; Ryabov, Evgenii A.; Tkeshelashvili, G. I.

    1982-04-01

    Data are presented on multiphoton dissociation of halogenated methanes, CF3I and CF3Br, in a pulsed CO2 laser field in the single-pulse irradiation regime. It is shown that the high parameters of an elementary separation event (dissociation yield and selectivity, quantum efficiency) for these molecules can be used to achieve efficient laser separation of the carbon isotopes 12C and 13C. An analysis is made of problems involved in organizing the chemical cycle when the process is scaled up. A description is given of an apparatus for scaled-up laser isotope separation, including a pulse-periodic CO2 laser with a kilowatt average power, and a laser separation cell. Experiments carried out using this apparatus showed that the high parameters obtained in the single-pulse regime can also be achieved using this design and a yield rate comparable with that of traditional separation systems can be achieved for fairly low energy losses. These results make it possible to develop a commercial system for laser isotope separation using multiphoton dissociation of molecules.

  16. Hydrophobic effect at aqueous interfaces

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew

    2005-01-01

    Conceptual basis for hydrophobic effects in bulk water and at aqueous interfaces have similar conceptual basis but often manifests itself differently. Using a wide range of computer simulations as the basis, I will review different forms of hydrophobic effects at a variety of interfaces starting from simple liquid-vapor and water-oil interfaces and progressing to water-membrane interfaces. I will start with discussing how water is organized at different interfaces, stressing both similarities and differences. The main thread is that, as in the bulk liquid, hydrophobic effects have profound influence on conformational equilibria and organization of both small molecules and macromolecules, but the result of this influence is quite different. Specifically, it will be shown that many small, but not necessarily amphiphilic molecules tend to accumulate at the interface and, and this tendency will be explained. Furthermore, I will show that many short peptides that are disordered in water spontaneously fold into well-defined structures in the interfacial environment. Biological implications of this self-organizing effect will be discussed.

  17. Isotope separation

    DOEpatents

    Bartlett, Rodney J.; Morrey, John R.

    1978-01-01

    A method and apparatus is described for separating gas molecules containing one isotope of an element from gas molecules containing other isotopes of the same element in which all of the molecules of the gas are at the same electronic state in their ground state. Gas molecules in a gas stream containing one of the isotopes are selectively excited to a different electronic state while leaving the other gas molecules in their original ground state. Gas molecules containing one of the isotopes are then deflected from the other gas molecules in the stream and thus physically separated.

  18. Hydrophobic pocket targeting probes for enteroviruses

    NASA Astrophysics Data System (ADS)

    Martikainen, Mari; Salorinne, Kirsi; Lahtinen, Tanja; Malola, Sami; Permi, Perttu; Häkkinen, Hannu; Marjomäki, Varpu

    2015-10-01

    onwards. Remarkably, before and during the time of replication, the fluorescent probe was seen to leak from the virus-positive endosomes and thus separate from the capsid proteins that were left in the endosomes. These results suggest that, like the physiological hydrophobic content, the probe may be released upon virus uncoating. Our results collectively thus show that the gold and fluorescently labeled probes may be used to track and visualize the studied enteroviruses during the early phases of infection opening new avenues to follow virus uncoating in cells. Electronic supplementary information (ESI) available: Details of the synthesis of the probes, UV-Vis absorption spectra of the probe (2), PAGE separation and the absorption spectra of the gold labeled probe (3), details of the NMR experiments, determination of the cytotoxicity of the studied molecules, TEM micrographs of the gold labeled probe (3) with enteroviruses, live cell imaging of the fluorescent probe (4) in cells, and additional details of modeling of the hydrophobic pockets. See DOI: 10.1039/c5nr04139b

  19. Water transport through functionalized nanotubes with tunable hydrophobicity

    SciTech Connect

    Moskowitz, Ian; Snyder, Mark A.; Mittal, Jeetain

    2014-11-14

    Molecular dynamics simulations are used to study the occupancy and flow of water through nanotubes comprised of hydrophobic and hydrophilic atoms, which are arranged on a honeycomb lattice to mimic functionalized carbon nanotubes (CNTs). We consider single-file motion of TIP3P water through narrow channels of (6,6) CNTs with varying fractions (f) of hydrophilic atoms. Various arrangements of hydrophilic atoms are used to create heterogeneous nanotubes with separate hydrophobic/hydrophilic domains along the tube as well as random mixtures of the two types of atoms. The water occupancy inside the nanotube channel is found to vary nonlinearly as a function of f, and a small fraction of hydrophilic atoms (f ≈ 0.4) are sufficient to induce spontaneous and continuous filling of the nanotube. Interestingly, the average number of water molecules inside the channel and water flux through the nanotube are less sensitive to the specific arrangement of hydrophilic atoms than to the fraction, f. Two different regimes are observed for the water flux dependence on f – an approximately linear increase in flux as a function of f for f < 0.4, and almost no change in flux for higher f values, similar to the change in water occupancy. We are able to define an effective interaction strength between nanotube atoms and water's oxygen, based on a linear combination of interaction strengths between hydrophobic and hydrophilic nanotube atoms and water, that can quantitatively capture the observed behavior.

  20. Water transport through functionalized nanotubes with tunable hydrophobicity

    NASA Astrophysics Data System (ADS)

    Moskowitz, Ian; Snyder, Mark A.; Mittal, Jeetain

    2014-11-01

    Molecular dynamics simulations are used to study the occupancy and flow of water through nanotubes comprised of hydrophobic and hydrophilic atoms, which are arranged on a honeycomb lattice to mimic functionalized carbon nanotubes (CNTs). We consider single-file motion of TIP3P water through narrow channels of (6,6) CNTs with varying fractions (f) of hydrophilic atoms. Various arrangements of hydrophilic atoms are used to create heterogeneous nanotubes with separate hydrophobic/hydrophilic domains along the tube as well as random mixtures of the two types of atoms. The water occupancy inside the nanotube channel is found to vary nonlinearly as a function of f, and a small fraction of hydrophilic atoms (f ≈ 0.4) are sufficient to induce spontaneous and continuous filling of the nanotube. Interestingly, the average number of water molecules inside the channel and water flux through the nanotube are less sensitive to the specific arrangement of hydrophilic atoms than to the fraction, f. Two different regimes are observed for the water flux dependence on f - an approximately linear increase in flux as a function of f for f < 0.4, and almost no change in flux for higher f values, similar to the change in water occupancy. We are able to define an effective interaction strength between nanotube atoms and water's oxygen, based on a linear combination of interaction strengths between hydrophobic and hydrophilic nanotube atoms and water, that can quantitatively capture the observed behavior.

  1. Preparation of hydrophobic coatings

    DOEpatents

    Branson, Eric D.; Shah, Pratik B.; Singh, Seema; Brinker, C. Jeffrey

    2009-02-03

    A method for preparing a hydrophobic coating by preparing a precursor sol comprising a metal alkoxide, a solvent, a basic catalyst, a fluoroalkyl compound and water, depositing the precursor sol as a film onto a surface, such as a substrate or a pipe, heating, the film and exposing the film to a hydrophobic silane compound to form a hydrophobic coating with a contact angle greater than approximately 150.degree.. The contact angle of the film can be controlled by exposure to ultraviolet radiation to reduce the contact angle and subsequent exposure to a hydrophobic silane compound to increase the contact angle.

  2. A probabilistic approach to the effect of hydrogen bonding on the hydrophobic attraction.

    PubMed

    Djikaev, Y S; Ruckenstein, Eli

    2009-03-28

    Water molecules, belonging to the first hydration shell around a hydrophobic particle, form fewer hydrogen bonds than bulk molecules. On the other hand, the former (boundary) bonds may be slightly stronger than the latter. When two hydrophobic particles are sufficiently close to each other, the disruption of water-water hydrogen bonds in their first hydration layers can give rise to an additional contribution to their overall interaction potential. Here we present a probabilistic approach to studying this phenomenon. The proposed method allows one to determine the average number of hydrogen bonds per water molecule in the first hydration shell. Numerical evaluations show that in the interplay between a decrease in the number of boundary bonds per water molecule and the enhancement of such a bond the former effect is clearly predominant. As a result, the disruption of boundary hydrogen bonds, which occurs when the first two hydration shells of two particles overlap, leads to an attractive contribution to the overall particle interaction. This contribution is naturally short range, appearing only when the separation between the two particles becomes smaller than four lengths of a hydrogen bond. It is greater than the overall van der Waals interaction potential of the same hydrophobic particles (with typical Hamaker constants) by at least an order of magnitude.

  3. Facile Surface Functionalization of Hydrophobic Magnetic Nanoparticles

    PubMed Central

    2015-01-01

    Nonpolar phase synthesized hydrophobic nanocrystals show attractive properties and have demonstrated prominent potential in biomedical applications. However, the preparation of biocompatible nanocrystals is made difficult by the presence of hydrophobic surfactant stabilizer on their surfaces. To address this limitation, we have developed a facile, high efficiency, single-phase and low-cost method to convert hydrophobic magnetic nanoparticles (MNPs) to an aqueous phase using tetrahydrofuran, NaOH and 3,4-dihydroxyhydrocinnamic acid without any complicated organic synthesis. The as-transferred hydrophilic MNPs are water-soluble over a wide pH range (pH = 3–12), and the solubility is pH-controllable. Furthermore, the as-transferred MNPs with carboxylate can be readily adapted with further surface functionalization, varying from small molecule dyes to oligonucleotides and enzymes. Finally, the strategy developed here can easily be extended to other types of hydrophobic nanoparticles to facilitate biomedical applications of nanomaterials. PMID:25140614

  4. Hydrophobic and moisture-stable metal–organic frameworks

    SciTech Connect

    Fernandez, Carlos A.; Nune, Satish K.; Annapureddy, Harsha V.; Dang, Liem X.; McGrail, B. Peter; Zheng, Feng; Polikarpov, Evgueni; King, David L.; Freeman, Charles J.; Brooks, Kriston P.

    2015-08-15

    Metal-organic frameworks (MOFs) have proved to be very attractive for applications including gas storage, separation, sensing and catalysis. In particular, CO2 separation from flue gas in post-combustion processes is one of the main focuses of research among the scientific community. One of the major issues that are preventing the successful commercialization of these novel materials (e.g., MgDOBDC and NiDOBDC) is their high affinity towards water that not only compromises gas sorption capacity but also the chemical stability. In this paper, we demonstrate a novel post-synthesis modification approach to modify MOFs towards increasing hydrophobic behavior and chemical stability against moisture without compromising CO2 sorption capacity. Our approach consists of incorporating hydrophobic moieties on the external surface of the MOFs via physical adsorption. The rationale behind this concept is to increase the surface hydrophobicity in the porous materials without the need of introducing bulky functionalities inside the pore which compromises the sorption capacity toward other gases. This allows MOF interaction/sorption of CO2 molecules comparable to unmodified MOFs. We herein report preliminary results on three routinely studied MOF materials [MIL-101(Cr), MgDOBDC and NiDOBDC] demonstrating that the polymer-modified MOFs retain CO2 sorption capacity while reducing the water adsorption up to three times, respect to the un-modified materials, via an equilibrium effect. Furthermore, the water stability of the polymer-functionalized MOFs is significantly higher than the water stability of the bare material. Molecular dynamic simulations demonstrated that this equilibrium effect implies a fundamental and permanent change in the water sorption capacity of MOFs. This approach can also be employed to render moisture stability and selectivity to MOFs that find applications in gas separations, catalysis and sensing where water plays a critical role in compromising MOF

  5. Entangled microwaves as a resource for entangling spatially separate solid-state qubits: Superconducting qubits, nitrogen-vacancy centers, and magnetic molecules

    NASA Astrophysics Data System (ADS)

    Gómez, Angela Viviana; Rodríguez, Ferney Javier; Quiroga, Luis; García-Ripoll, Juan José

    2016-06-01

    Quantum correlations present in a broadband two-line squeezed microwave state can induce entanglement in a spatially separated bipartite system consisting of either two single qubits or two-qubit ensembles. By using an appropriate master equation for a bipartite quantum system in contact with two separate but entangled baths, the generating entanglement process in spatially separated quantum systems is thoroughly characterized. Decoherence thermal effects on the entanglement transfer are also discussed. Our results provide evidence that this entanglement transfer by dissipation is feasible, yielding to a steady-state amount of entanglement in the bipartite quantum system which can be optimized for a wide range of realistic physical systems that include state-of-the-art experiments with nitrogen-vacancy centers in diamond, superconducting qubits, or even magnetic molecules embedded in a crystalline matrix.

  6. Water on hydrophobic surfaces: Mechanistic modeling of hydrophobic interaction chromatography.

    PubMed

    Wang, Gang; Hahn, Tobias; Hubbuch, Jürgen

    2016-09-23

    Mechanistic models are successfully used for protein purification process development as shown for ion-exchange column chromatography (IEX). Modeling and simulation of hydrophobic interaction chromatography (HIC) in the column mode has been seldom reported. As a combination of these two techniques is often encountered in biopharmaceutical purification steps, accurate modeling of protein adsorption in HIC is a core issue for applying holistic model-based process development, especially in the light of the Quality by Design (QbD) approach. In this work, a new mechanistic isotherm model for HIC is derived by consideration of an equilibrium between well-ordered water molecules and bulk-like ordered water molecules on the hydrophobic surfaces of protein and ligand. The model's capability of describing column chromatography experiments is demonstrated with glucose oxidase, bovine serum albumin (BSA), and lysozyme on Capto™ Phenyl (high sub) as model system. After model calibration from chromatograms of bind-and-elute experiments, results were validated with batch isotherms and prediction of further gradient elution chromatograms. PMID:27575919

  7. Towards porous polymer monoliths for the efficient, retention-independent performance in the isocratic separation of small molecules by means of nano-liquid chromatography.

    PubMed

    Nischang, Ivo; Teasdale, Ian; Brüggemann, Oliver

    2010-11-26

    We have investigated the free-radical copolymerization dynamics of styrene and divinylbenzene in the presence of micro- and macro-porogenic diluents in 100 μm I.D. sized molds under conditions of slow thermal initiation leading to (macro)porous poly(styrene-co-divinylbenzene) monolithic scaffolds. These specifically designed experiments allowed the quantitative determination of monomer specific conversion against polymerization time to derive the porous polymer scaffold composition at each desirable copolymerization stage after phase separation. This was carried out over a time scale of 3h up to 48 h polymerization time, enabling the efficient and repeatable termination of the polymerization reactions. In parallel, the porous and hydrodynamic properties of the derived monolithic columns were thoroughly studied in isocratic nano-LC mode for the reversed-phase separation of a homologous series of small retained molecules. At the optimized initiator concentration, polymerization temperature and time, the macroporous poly(styrene-co-divinylbenzene) monoliths show a permanent mesoporous pore space, which was readily observable by electron microscopy and indicated by nitrogen adsorption experiments. Under these conditions, we consistently find a polymer scaffold composition which suggests a high degree of cross-linking and thus minimum amount of gel porosity. These columns reveal a retention-insensitive plate height in the separation of small retained molecules which only slightly decreases at increased linear mobile phase velocity. As the polymerization progresses, a build-up of less-densely cross-linked material occurs, which is directly reflected in the observed consistent increase in retention and plate heights. This leads to a significant deterioration in overall isocratic separation performance. The decrease in performance is ascribed in particular to the increased mass transfer resistance governing the monoliths' performance over the whole linear chromatographic

  8. Magnetically separable nanocomposites with photocatalytic activity under visible light for the selective transformation of biomass-derived platform molecules

    EPA Science Inventory

    Novel magnetically separable TiO2-guanidine-(Ni,Co)Fe2O4 nanomaterials were prepared and characterised by a series of techniques including XRD, SEM, TEM, N2 physisorption as well as XPS and subsequently tested for their photocatalytic activities in the selective transformation of...

  9. Hypercrosslinking: New approach to porous polymer monolithic capillary columns with large surface area for the highly efficient separation of small molecules

    PubMed Central

    Urban, Jiri; Svec, Frantisek; Fréchet, Jean M.J.

    2010-01-01

    Monolithic polymers with an unprecedented surface area of over 600 m2/g have been prepared from a poly(styrene-co-vinylbenzyl chloride-co-divinylbenzene) precursor monolith that was swollen in 1,2-dichloroethane and hypercrosslinked via Friedel-Crafts reaction catalyzed by ferric chloride. Both the composition of the reaction mixture used for the preparation of the precursor monolith and the conditions of the hypercrosslinking reaction have been varied using mathematical design of experiments and the optimized system validated. Hypercrosslinked monolithic capillary columns contain an array of small pores that make the column ideally suited for the high efficiency isocratic separations of small molecules such as uracil and alkylbenzenes with column efficiencies reproducibly exceeding 60,000 plates/m for retained compounds. The separation process could be accelerated while also improving peak shape through the use of higher temperatures and a ternary mobile phase consisting of acetonitrile, tetrahydrofuran, and water. As a result, seven compounds were well separated in less than 2 min. These columns also facilitate separations of peptide mixtures such as a tryptic digest of cytochrome c using a gradient elution mode which affords a sequence coverage of 93%. A 65 cm long hypercrosslinked capillary column used in size exclusion mode with tetrahydrofuran as the mobile phase afforded almost baseline separation of toluene and five polystyrene standards. PMID:21092973

  10. Development of a membrane-less dynamic field gradient focusing device for the separation of low-molecular-weight molecules.

    PubMed

    Burke, Jeffrey M; Smith, Colin D; Ivory, Cornelius F

    2010-03-01

    Dynamic field gradient focusing uses an electric field gradient generated by controlling the voltage profile of an electrode array to separate and concentrate charged analytes according to their individual electrophoretic mobilities. This study describes a new instrument in which the electrodes have been placed within the separation channel. The major challenge faced with this device is that when applied voltages to the electrodes are larger than the redox potential of water, electrolysis will occur, producing hydrogen ions (H+) plus oxygen gas on the anodes and hydroxide (OH(-)) plus hydrogen gas on the cathodes. The resulting gas bubbles and pH excursions can cause problems with system performance and reproducibility. An on-column, degassing system that can remove gas bubbles "on-the-fly" is described. In addition, the use of a high capacity, low-conductivity buffer to address the problem of the pH shift that occurs due to the production of H+ on the anodes is illustrated. Finally, the successful separation of three, low-molecular-weight dyes (amaranth, bromophenol blue and methyl red) is described.

  11. Development of a membrane-less dynamic field gradient focusing device for the separation of low-molecular-weight molecules

    PubMed Central

    Burke, Jeffrey M.; Smith, Colin D.; Ivory, Cornelius F.

    2010-01-01

    Dynamic field gradient focusing uses an electric field gradient generated by controlling the voltage profile of an electrode array to separate and concentrate charged analytes according to their individual electrophoretic mobilities. This study describes a new instrument in which the electrodes have been placed within the separation channel. The major challenge faced with this device is that when applied voltages to the electrodes are larger than the redox potential of water, electrolysis will occur, producing hydrogen ions (H+) plus oxygen gas on the anodes and hydroxide (OH−) plus hydrogen gas on the cathodes. The resulting gas bubbles and pH excursions can cause problems with system performance and reproducibility. An on-column, degassing system that can remove gas bubbles “on-the-fly” is described. In addition, the use of a high capacity, low-conductivity buffer to address the problem of the pH shift that occurs due to the production of H+ on the anodes is illustrated. Finally, the successful separation of three, low-molecular-weight dyes (amaranth, bromophenol blue and methyl red) is described. PMID:20191553

  12. Quest for organic polymer-based monolithic columns affording enhanced efficiency in high performance liquid chromatography separations of small molecules in isocratic mode.

    PubMed

    Svec, Frantisek

    2012-03-01

    The separations of small molecules using columns containing porous polymer monoliths invented two decades ago went a long way from the very modest beginnings to the current capillary columns with efficiencies approaching those featured by their silica-based counterparts. This review article presents a variety of techniques that have been used to form capillary formats of monolithic columns with enhanced separation performance in isocratic elutions. The following text first describes the traditional approaches used for the preparation of efficient monoliths comprising variations in polymerization conditions including temperature as well as composition of monomers and porogenic solvents. Encouraging results of these experiments fueled research of completely new preparation methods such as polymerization to an incomplete conversion, use of single crosslinker, hypercrosslinking, and incorporation of carbon nanotubes that are described in the second part of the text. PMID:21816401

  13. Electrohydrodynamics Near Hydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Maduar, S. R.; Belyaev, A. V.; Lobaskin, V.; Vinogradova, O. I.

    2015-03-01

    We show that an electro-osmotic flow near the slippery hydrophobic surface depends strongly on the mobility of surface charges, which are balanced by counterions of the electrostatic diffuse layer. For a hydrophobic surface with immobile charges, the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges, it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this, we formulate electrohydrodynamic boundary conditions at the slipping interface, which should be applied to quantify electro-osmotic flows instead of hydrodynamic boundary conditions. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new interpretation of zeta potential of hydrophobic surfaces.

  14. Electrohydrodynamics near hydrophobic surfaces.

    PubMed

    Maduar, S R; Belyaev, A V; Lobaskin, V; Vinogradova, O I

    2015-03-20

    We show that an electro-osmotic flow near the slippery hydrophobic surface depends strongly on the mobility of surface charges, which are balanced by counterions of the electrostatic diffuse layer. For a hydrophobic surface with immobile charges, the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges, it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this, we formulate electrohydrodynamic boundary conditions at the slipping interface, which should be applied to quantify electro-osmotic flows instead of hydrodynamic boundary conditions. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new interpretation of zeta potential of hydrophobic surfaces.

  15. Oleic and docosahexaenoic acid differentially phase separate from lipid raft molecules: a comparative NMR, DSC, AFM, and detergent extraction study.

    PubMed

    Shaikh, Saame Raza; Dumaual, Alfred C; Castillo, Alicia; LoCascio, Daniel; Siddiqui, Rafat A; Stillwell, William; Wassall, Stephen R

    2004-09-01

    We have previously suggested that the omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA) may in part function by enhancing membrane lipid phase separation into lipid rafts. Here we further tested for differences in the molecular interactions of an oleic (OA) versus DHA-containing phospholipid with sphingomyelin (SM) and cholesterol (CHOL) utilizing (2)H NMR spectroscopy, differential scanning calorimetry, atomic force microscopy, and detergent extractions in model bilayer membranes. (2)H NMR and DSC (differential scanning calorimetry) established the phase behavior of the OA-containing 1-[(2)H(31)]palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (16:0-18:1PE-d(31))/SM (1:1) and the DHA-containing 1-[(2)H(31)]palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (16:0-22:6PE-d(31))/SM (1:1) in the absence and presence of equimolar CHOL. CHOL was observed to affect the OA-containing phosphatidylethanolamine (PE) more than the DHA-containing PE, as exemplified by >2 x greater increase in order measured for the perdeuterated palmitic chain in 16:0-18:1PE-d(31)/SM (1:1) compared to 16:0-22:6PE-d(31)/SM (1:1) bilayers in the liquid crystalline phase. Atomic force microscopy (AFM) experiments showed less lateral phase separation between 16:0-18:1PE-rich and SM/CHOL-rich raft domains in 16:0-18:1PE/SM/CHOL (1:1:1) bilayers than was observed when 16:0-22:6PE replaced 16:0-18:1PE. Differences in the molecular interaction of 16:0-18:1PE and 16:0-22:6PE with SM/CHOL were also found using biochemical detergent extractions. In the presence of equimolar SM/CHOL, 16:0-18:1PE showed decreased solubilization in comparison to 16:0-22:6PE, indicating greater phase separation with the DHA-PE. Detergent experiments were also conducted with cardiomyocytes fed radiolabeled OA or DHA. Although both OA and DHA were found to be largely detergent solubilized, the amount of OA that was found to be associated with raft-rich detergent-resistant membranes exceeded DHA by

  16. Optically controllable dual-gate organic transistor produced via phase separation between polymer semiconductor and photochromic spiropyran molecules.

    PubMed

    Ishiguro, Yasushi; Hayakawa, Ryoma; Chikyow, Toyohiro; Wakayama, Yutaka

    2014-07-01

    We produced an optically controllable dual-gate organic field-effect transistor by a simple one-step spin-coating of a mixed solution of photochromic spiropyran (SP) and poly(3-hexylthiophene) (P3HT). Postannealing enhanced polymer chain ordering of P3HT to induce phase separation into an SP-rich lower layer and an SP-free upper layer. These layers worked independently as transistor channels with distinct optical responsivity. The top channel was optically inactive, but the bottom channel was optically active, because of the photoisomerization of SP. These results demonstrate the potential of our technique to produce a multifunctional photoactive organic transistor by a simple process.

  17. Formation and properties of magnetic chains for 100 nm nanoparticles used in separations of molecules and cells

    PubMed Central

    Wilson, Robert J.; Hu, Wei; Fu, Cheryl Wong Po; Koh, Ai Leen; Gaster, Richard S.; Earhart, Christopher M.; Fu, Aihua; Heilshorn, Sarah C.; Sinclair, Robert; Wang, Shan X.

    2009-01-01

    Optical observations of 100 nm metallic magnetic nanoparticles are used to study their magnetic field induced self assembly. Chains with lengths of tens of microns are observed to form within minutes at nanoparticle concentrations of 1010 per mL. Chain rotation and magnetophoresis are readily observed, and SEM reveals that long chains are not simple single particle filaments. Similar chains are detected for several 100 nm commercial bio-separation nanoparticles. We demonstrate the staged magnetic condensation of different types of nanoparticles into composite structures and show that magnetic chains bind to immunomagnetically labeled cells, serving as temporary handles which allow novel magnetic cell manipulations. PMID:20161001

  18. Incorporation of graphene oxide nanosheets into boronate-functionalized polymeric monolith to enhance the electrochromatographic separation of small molecules.

    PubMed

    Lin, Zian; Wang, Juan; Yu, Ruifang; Yin, Xiaofei; He, Yu

    2015-02-01

    Graphene oxide (GO) nanosheets were incorporated into an organic polymer monolith containing 3-acrylamidophenylboronic acid (AAPBA) and pentaerythritol triacrylate (PETA) to form a novel monolithic stationary phase for CEC. The effects of the mass ratio of AAPBA/PETA, the amount of GO, and the volume of porogen on the morphology, permeability and pore properties of the prepared poly(AAPBA-GO-PETA) monoliths were investigated. A series of test compounds including amides, alkylbenzenes, polycyclic aromatics, phenols, and anilines were used to evaluate and compare the separation performances of the poly(AAPBA-GO-PETA) and the parent poly(AAPBA-co-PETA) monoliths. The results indicated that incorporation of GO into monolithic column exhibited much higher resolutions (>1.5) and column efficiency (62,000 ∼ 110,000 plates/m for toluene, DMF, formamide, and thiourea) than the poly(AAPBA-co-PETA). The successful application in isocratic separation of peptides suggests the potential of the GO incorporated monolithic column in complex sample analysis. In addition, the reproducibility and stability of the prepared poly(AAPBA-GO-PETA) monolith was assessed. The run-to-run, column-to-column and batch-to-batch reproducibilities of this monolith for alkylbenzenes' retention were satisfactory with the RSDs less than 1.8% (n = 5), 3.7% and 5.6% (n = 3), respectively, indicating the effectiveness and practicability of the proposed method.

  19. Incorporation of graphene oxide nanosheets into boronate-functionalized polymeric monolith to enhance the electrochromatographic separation of small molecules.

    PubMed

    Lin, Zian; Wang, Juan; Yu, Ruifang; Yin, Xiaofei; He, Yu

    2015-02-01

    Graphene oxide (GO) nanosheets were incorporated into an organic polymer monolith containing 3-acrylamidophenylboronic acid (AAPBA) and pentaerythritol triacrylate (PETA) to form a novel monolithic stationary phase for CEC. The effects of the mass ratio of AAPBA/PETA, the amount of GO, and the volume of porogen on the morphology, permeability and pore properties of the prepared poly(AAPBA-GO-PETA) monoliths were investigated. A series of test compounds including amides, alkylbenzenes, polycyclic aromatics, phenols, and anilines were used to evaluate and compare the separation performances of the poly(AAPBA-GO-PETA) and the parent poly(AAPBA-co-PETA) monoliths. The results indicated that incorporation of GO into monolithic column exhibited much higher resolutions (>1.5) and column efficiency (62,000 ∼ 110,000 plates/m for toluene, DMF, formamide, and thiourea) than the poly(AAPBA-co-PETA). The successful application in isocratic separation of peptides suggests the potential of the GO incorporated monolithic column in complex sample analysis. In addition, the reproducibility and stability of the prepared poly(AAPBA-GO-PETA) monolith was assessed. The run-to-run, column-to-column and batch-to-batch reproducibilities of this monolith for alkylbenzenes' retention were satisfactory with the RSDs less than 1.8% (n = 5), 3.7% and 5.6% (n = 3), respectively, indicating the effectiveness and practicability of the proposed method. PMID:25395232

  20. Surface analysis of selected hydrophobic materials

    NASA Astrophysics Data System (ADS)

    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

  1. Statistical Analyses of Hydrophobic Interactions: A Mini-Review.

    PubMed

    Pratt, Lawrence R; Chaudhari, Mangesh I; Rempe, Susan B

    2016-07-14

    This review focuses on the striking recent progress in solving for hydrophobic interactions between small inert molecules. We discuss several new understandings. First, the inverse temperature phenomenology of hydrophobic interactions, i.e., strengthening of hydrophobic bonds with increasing temperature, is decisively exhibited by hydrophobic interactions between atomic-scale hard sphere solutes in water. Second, inclusion of attractive interactions associated with atomic-size hydrophobic reference cases leads to substantial, nontrivial corrections to reference results for purely repulsive solutes. Hydrophobic bonds are weakened by adding solute dispersion forces to treatment of reference cases. The classic statistical mechanical theory for those corrections is not accurate in this application, but molecular quasi-chemical theory shows promise. Finally, because of the masking roles of excluded volume and attractive interactions, comparisons that do not discriminate the different possibilities face an interpretive danger. PMID:27258151

  2. Antagonistic effects between magnetite nanoparticles and a hydrophobic surfactant in highly concentrated Pickering emulsions.

    PubMed

    Vílchez, Alejandro; Rodríguez-Abreu, Carlos; Menner, Angelika; Bismarck, Alexander; Esquena, Jordi

    2014-05-13

    Herein we present a systematic study of the antagonistic interaction between magnetite nanoparticles (Fe3O4) and nonionic hydrophobic surfactant in Pickering highly concentrated emulsions. Interfacial tension measurements, phase behavior, and emulsion stability studies, combined with electron microscopy observations in polymerized systems and magnetometry, are used to support the discussion. First, stable W/O highly concentrated emulsions were obtained using partially hydrophobized magnetite nanoparticles. These emulsions experienced phase separation when surfactant is added at concentrations as low as 0.05 wt %. Such phase separation arises from the preferential affinity of the surfactant for the nanoparticle surfaces, which remarkably enhances their hydrophobicity, leading to a gradual desorption of nanoparticles from the interface. W/O emulsions were obtained at higher surfactant concentrations, but in this case, these emulsions were mainly stabilized by surfactant molecules. Therefore, stable emulsions could be prepared in two separate ranges of surfactant concentrations. After polymerization, low-density macroporous polymers were obtained, and the adsorption and aggregation of nanoparticles was analyzed by transmission electron microscopy. The progressive displacement of the nanoparticles was revealed: from the oil-water interface, in which aggregated nanoparticles were adsorbed, forming dense layers, to the continuous phase of the emulsions, where small nanoparticle aggregates were randomly dispersed. Interestingly, the results also show that the blocking temperature of the iron oxide superparamagnetic nanoparticles embedded in the macroporous polymers could be modulated by appropriate control of the concentrations of both surfactant and nanoparticles. PMID:24738961

  3. Antagonistic effects between magnetite nanoparticles and a hydrophobic surfactant in highly concentrated Pickering emulsions.

    PubMed

    Vílchez, Alejandro; Rodríguez-Abreu, Carlos; Menner, Angelika; Bismarck, Alexander; Esquena, Jordi

    2014-05-13

    Herein we present a systematic study of the antagonistic interaction between magnetite nanoparticles (Fe3O4) and nonionic hydrophobic surfactant in Pickering highly concentrated emulsions. Interfacial tension measurements, phase behavior, and emulsion stability studies, combined with electron microscopy observations in polymerized systems and magnetometry, are used to support the discussion. First, stable W/O highly concentrated emulsions were obtained using partially hydrophobized magnetite nanoparticles. These emulsions experienced phase separation when surfactant is added at concentrations as low as 0.05 wt %. Such phase separation arises from the preferential affinity of the surfactant for the nanoparticle surfaces, which remarkably enhances their hydrophobicity, leading to a gradual desorption of nanoparticles from the interface. W/O emulsions were obtained at higher surfactant concentrations, but in this case, these emulsions were mainly stabilized by surfactant molecules. Therefore, stable emulsions could be prepared in two separate ranges of surfactant concentrations. After polymerization, low-density macroporous polymers were obtained, and the adsorption and aggregation of nanoparticles was analyzed by transmission electron microscopy. The progressive displacement of the nanoparticles was revealed: from the oil-water interface, in which aggregated nanoparticles were adsorbed, forming dense layers, to the continuous phase of the emulsions, where small nanoparticle aggregates were randomly dispersed. Interestingly, the results also show that the blocking temperature of the iron oxide superparamagnetic nanoparticles embedded in the macroporous polymers could be modulated by appropriate control of the concentrations of both surfactant and nanoparticles.

  4. Small molecule pinocytosis and clathrin-dependent endocytosis at the intestinal brush border: Two separate pathways into the enterocyte.

    PubMed

    Michael Danielsen, E; Hansen, Gert H

    2016-02-01

    Pinocytosis at the small intestinal brush border was studied in postweaned porcine cultured mucosal explants, using the fluorescent polar probes Alexa hydrazide (AH, MW 570), Texas red dextran (TRD, MW ~ 3000), and Cascade blue dextran (CBD, MW ~ 10,000). Within 1 h, AH appeared in a string of subapical punctae in enterocytes, indicative of an ongoing constitutive pinocytosis. By comparison, TRD was taken up less efficiently into the same compartment, and no intracellular labeling of CBD was detectable, indicating that only small molecules are pinocytosed from the postweaned gut lumen. AH remained in the terminal web region in EEA-1-positive endosomes (“TWEEs”) for at least 2 h, implying that the pinocytic uptake does not proceed towards a transcytic pathway. Like AH, cholera toxin B subunit (CTB) was readily internalized, but the two probes appeared in completely non-overlapping subapical compartments, indicating the existence of two different uptake mechanisms operating simultaneously at the brush border. CTB is internalized by clathrin-dependent receptor mediated endocytosis, but surprisingly the toxin also caused a rapid disappearance from the apical cell surface of two major brush border enzymes, alkaline phosphatase and aminopeptidase N, demonstrating the disruptive effect of this pathway. By immunofluorescence, caveolin-1 was hardly detectable in enterocytes, arguing against a caveolae-mediated uptake of AH, whereas the pinocytosis/phagocytosis inhibitors dimethyl amiloride and cytochalasin D both arrested AH uptake. We propose that the constitutive pinocytic mechanism visualized by AH contributes to maintenance of membrane homeostasis and to enrich the contents of lipid raft constituents at the brush border.

  5. Intermolecular Vibrations of Hydrophobic Amino Acids

    NASA Astrophysics Data System (ADS)

    Williams, Michael Roy Casselman

    Hydrophobic amino acids interact with their chemical environment through a combination of electrostatic, hydrogen bonding, dipole, induced dipole, and dispersion forces. These interactions all have their own characteristic energy scale and distance dependence. The low-frequency (0.1-5 THz, 5-150 cm-1) vibrational modes of amino acids in the solid state are a direct indicator of the interactions between the molecules, which include interactions between an amino acid functional group and its surroundings. This information is central to understanding the dynamics and morphology of proteins. The alpha-carbon is a chiral center for all of the hydrophobic amino acids, meaning that they exist in two forms, traditionally referred to as L- and D-enantiomers. This nomenclature indicates which direction the molecule rotates plane-polarized visible light (levorotory and dextrorotory). Chiral a-amino acids in proteins are exclusively the L-variety In the solid state, the crystal lattice of the pure L-enantiomer is the mirror image of the D-enantiomer crystal lattice. These solids are energetically identical. Enantiomers also have identical spectroscopic properties except when the measurement is polarization sensitive. A mixture of equal amounts D- and L-amino acid enantiomers can crystallize into a racemic (DL-) structure that is different from that of the pure enantiomers. Whether a solution of both enantiomers will crystallize into a racemic form or spontaneously resolve into a mixture of separate D- and L-crystals largely depends on the interactions between molecules available in the various possible configurations. This is an active area of research. Low-frequency vibrations with intermolecular character are very sensitive to changes in lattice geometry, and consequently the vibrational spectra of racemic crystals are usually quite distinct from the spectra of the crystals of the corresponding pure enantiomers in the far-infrared (far-IR). THz time-domain spectroscopy (THz

  6. Hydrophobically modified polyelectrolytes: Characterization, aggregation and adsorption

    NASA Astrophysics Data System (ADS)

    Islam, Mohammad Ferdous

    The focus of our work was to experimentally study the aggregation and adsorption behavior of model HM polyelectrolytes. Hydrophobically modified alkali soluble emulsions (HASE), the model HM polyelectrolytes, were chosen because they had complex architecture yet possessed key variables for systematic study. The HASE polymers have methacrylic acid (MAA) and ethyl acrylate (EA) in the backbone with pendent hydrophobic groups. Characterization of a single molecule is an important first step in understanding the aggregation and adsorption of these polymers. However, characterizations of the HASE polymers using conventional techniques such as gel permeation chromatography or static light scattering were difficult because of the hydrophobic association. In this study, two different approaches have been taken to prevent the hydrophobic association in aqueous solution: (1) hydrolyze the polymer to cleave the hydrophobic constituents, and (2) use methyl beta-cyclodextrin that has a hydrophobic cavity and a hydrophilic outer shell, to shield the hydrophobes from associating. By taking these two approaches and using gel permeation chromatography (GPC), dynamic (DLS) and static (SLS) light scattering techniques, the molecular weight, hydrodynamic radius and radius of gyration of a single molecule were determined. Except for one chemical site, we were able to determine that branching or grafting did not occur in the polymer chain during synthesis. Our aggregation studies showed that, in aqueous solutions, the HASE polymers formed small aggregates (presumably single micelles of single or a few chains) and large aggregates (presumably formed by bridging between micelles). The radii and masses of the larger aggregates, measured using DLS and SLS, were found to increase with an increase in the polymer concentration, indicating an open association process for the HASE polymers. Our SLS results also showed that, at high salt concentration, the aggregates of the HASE polymer with

  7. Ultra-fast Laser Synthesis of Nanopore Arrays in Silicon for Bio-molecule Separation and Detection

    SciTech Connect

    Tringe, J W; Ileri, N; Letant, S E; Stroeve, P; Shirk, M; Zaidi, S; Balhorn, R L; Siders, C W

    2008-02-07

    We demonstrate that interference of ultra-fast pulses of laser light can create regular patterns in thin silicon membranes that are compatible with the formation of a uniform array of nanopores. The spacing and size of these pores can be tuned by changing the laser energy, wavelength and number of ultra-short pulses. Short pulses and wavelengths ({approx}550 nm and smaller) are needed to define controllable nanoscale features in silicon. Energy must be localized in time and space to produce the etching, ablation or amorphization effects over the {approx}100 nm length scales appropriate for definition of single pores. Although in this brief study pattern uniformity was limited by laser beam quality, a complementary demonstration reported here used continuous-wave interferometric laser exposure of photoresist to show the promise of the ultra-fast approach for producing uniform pore arrays. The diameters of these interferometrically-defined features are significantly more uniform than the diameters of pores in state-of-the-art polycarbonate track etch membranes widely used for molecular separations.

  8. Single water entropy: hydrophobic crossover and application to drug binding.

    PubMed

    Sasikala, Wilbee D; Mukherjee, Arnab

    2014-09-11

    Entropy of water plays an important role in both chemical and biological processes e.g. hydrophobic effect, molecular recognition etc. Here we use a new approach to calculate translational and rotational entropy of the individual water molecules around different hydrophobic and charged solutes. We show that for small hydrophobic solutes, the translational and rotational entropies of each water molecule increase as a function of its distance from the solute reaching finally to a constant bulk value. As the size of the solute increases (0.746 nm), the behavior of the translational entropy is opposite; water molecules closest to the solute have higher entropy that reduces with distance from the solute. This indicates that there is a crossover in translational entropy of water molecules around hydrophobic solutes from negative to positive values as the size of the solute is increased. Rotational entropy of water molecules around hydrophobic solutes for all sizes increases with distance from the solute, indicating the absence of crossover in rotational entropy. This makes the crossover in total entropy (translation + rotation) of water molecule happen at much larger size (>1.5 nm) for hydrophobic solutes. Translational entropy of single water molecule scales logarithmically (Str(QH) = C + kB ln V), with the volume V obtained from the ellipsoid of inertia. We further discuss the origin of higher entropy of water around water and show the possibility of recovering the entropy loss of some hypothetical solutes. The results obtained are helpful to understand water entropy behavior around various hydrophobic and charged environments within biomolecules. Finally, we show how our approach can be used to calculate the entropy of the individual water molecules in a protein cavity that may be replaced during ligand binding.

  9. Friction and adsorption of aqueous polyoxyethylene (Tween) surfactants at hydrophobic surfaces.

    PubMed

    Graca, Malgorzata; Bongaerts, Jeroen H H; Stokes, Jason R; Granick, Steve

    2007-11-15

    The nanotribological responses of a series of nonionic polyoxyethylene surfactants (Tween 20, Tween 40, Tween 60, and Tween 80) were investigated after they were adsorbed from aqueous solution onto atomically smooth hydrophobic substrates. The hydrophobic surfaces were composed of a condensed monolayer of octadecyltriethoxysilane (OTE; contact angle theta>110 degrees ). The nanorheological measurements were performed using a modified surface forces apparatus after coating atomically smooth mica with these OTE monolayers, while adsorption measurements were performed using phase-modulated ellipsometry on silicon wafers coated with these same monolayers. The minimum surface-surface separation observed under high load in friction studies agreed quantitatively with the thickness obtained from ellipsometry. For Tweens 20, 40, and 60, the thickness of the adsorbed film increases with increasing alkyl chain length. Systematic investigations of the nanorheological response showed that there is a "solid-like" elastic response from confined surfactant layers, which is the case for the smallest separations to separations up to slightly larger than twice the adsorbed film thickness. In kinetic friction, these confined layers are characterized by a shear stress of approximately 3 MPa with minimal dependence on shear rate. The magnitude of the sliding shear stress is the same as the apparent yield stress at approximately 3 MPa; it is independent of alkyl chain length within the Tween family of surfactants and corresponds to a nominal friction coefficient of mu approximately 1. A similar friction coefficient is observed for boundary lubrication on the macroscopic scale in a tribometer utilizing hydrophobic surfaces and mu approximately 1.1 for Tweens 20, 40, and 60. These results suggest that while Tween molecules adsorb onto hydrophobic surfaces to form a robust separating layer, the lubricating properties of these layers are dominated by a highly dissipative slip plane, the same

  10. Temperature, stability, and the hydrophobic interaction.

    PubMed Central

    Schellman, J A

    1997-01-01

    Changes in free energy are normally used to track the effect of temperature on the stability of proteins and hydrophobic interactions. Use of this procedure on the aqueous solubility of hydrocarbons, a standard representation of the hydrophobic effect, leads to the conclusion that the hydrophobic effect increases in strength as the temperature is raised to approximately 140 degrees C. Acceptance of this interpretation leads to a number of far-reaching conclusions that are at variance with the original conception of the hydrophobic effect and add considerably to the complexity of interpretation. There are two legitimate thermodynamic functions that can be used to look at stability as a function of temperature: the standard Gibbs free energy change, deltaG degrees, and deltaG degrees/T. The latter is proportional to the log of the equilibrium constant and is sometimes called the Massieu-Planck function. Arguments are presented for using deltaG degrees/T rather than deltaG degrees for variations in stability with temperature. This makes a considerable difference in the interpretation of the hydrophobic interaction, but makes little change in the stability profile of proteins. Protein unfolding and the aqueous solubility of benzene are given as examples. The contrast between protein unfolding and the hydration of nonpolar molecules provides a rough estimate of the contribution of other factors that stabilize and destabilize protein structure. PMID:9414210

  11. Hydrophobic, Porous Battery Boxes

    NASA Technical Reports Server (NTRS)

    Bragg, Bobby J.; Casey, John E., Jr.

    1995-01-01

    Boxes made of porous, hydrophobic polymers developed to contain aqueous potassium hydroxide electrolyte solutions of zinc/air batteries while allowing air to diffuse in as needed for operation. Used on other types of batteries for in-cabin use in which electrolytes aqueous and from which gases generated during operation must be vented without allowing electrolytes to leak out.

  12. Modulation of hydrophobic interactions by proximally immobilized ions.

    PubMed

    Ma, C Derek; Wang, Chenxuan; Acevedo-Vélez, Claribel; Gellman, Samuel H; Abbott, Nicholas L

    2015-01-15

    The structure of water near non-polar molecular fragments or surfaces mediates the hydrophobic interactions that underlie a broad range of interfacial, colloidal and biophysical phenomena. Substantial progress over the past decade has improved our understanding of hydrophobic interactions in simple model systems, but most biologically and technologically relevant structures contain non-polar domains in close proximity to polar and charged functional groups. Theories and simulations exploring such nanometre-scale chemical heterogeneity find it can have an important effect, but the influence of this heterogeneity on hydrophobic interactions has not been tested experimentally. Here we report chemical force microscopy measurements on alkyl-functionalized surfaces that reveal a dramatic change in the surfaces' hydrophobic interaction strengths on co-immobilization of amine or guanidine groups. Protonation of amine groups doubles the strength of hydrophobic interactions, and guanidinium groups eliminate measurable hydrophobic interactions in all pH ranges investigated. We see these divergent effects of proximally immobilized cations also in single-molecule measurements on conformationally stable β-peptides with non-polar subunits located one nanometre from either amine- or guanidine-bearing subunits. Our results demonstrate the importance of nanometre-scale chemical heterogeneity, with hydrophobicity not an intrinsic property of any given non-polar domain but strongly modulated by functional groups located as far away as one nanometre. The judicious placing of charged groups near hydrophobic domains thus provides a strategy for tuning hydrophobic driving forces to optimize molecular recognition or self-assembly processes.

  13. Modulation of hydrophobic interactions by proximally immobilized ions

    NASA Astrophysics Data System (ADS)

    Ma, C. Derek; Wang, Chenxuan; Acevedo-Vélez, Claribel; Gellman, Samuel H.; Abbott, Nicholas L.

    2015-01-01

    The structure of water near non-polar molecular fragments or surfaces mediates the hydrophobic interactions that underlie a broad range of interfacial, colloidal and biophysical phenomena. Substantial progress over the past decade has improved our understanding of hydrophobic interactions in simple model systems, but most biologically and technologically relevant structures contain non-polar domains in close proximity to polar and charged functional groups. Theories and simulations exploring such nanometre-scale chemical heterogeneity find it can have an important effect, but the influence of this heterogeneity on hydrophobic interactions has not been tested experimentally. Here we report chemical force microscopy measurements on alkyl-functionalized surfaces that reveal a dramatic change in the surfaces' hydrophobic interaction strengths on co-immobilization of amine or guanidine groups. Protonation of amine groups doubles the strength of hydrophobic interactions, and guanidinium groups eliminate measurable hydrophobic interactions in all pH ranges investigated. We see these divergent effects of proximally immobilized cations also in single-molecule measurements on conformationally stable β-peptides with non-polar subunits located one nanometre from either amine- or guanidine-bearing subunits. Our results demonstrate the importance of nanometre-scale chemical heterogeneity, with hydrophobicity not an intrinsic property of any given non-polar domain but strongly modulated by functional groups located as far away as one nanometre. The judicious placing of charged groups near hydrophobic domains thus provides a strategy for tuning hydrophobic driving forces to optimize molecular recognition or self-assembly processes.

  14. Preparation and evaluation of monolithic poly(N-vinylcarbazole-co-1,4-divinylbenzene) capillary columns for the separation of small molecules.

    PubMed

    Koeck, Rainer; Fischnaller, Martin; Bakry, Rania; Tessadri, Richard; Bonn, Guenther K

    2014-09-01

    Short-term polymerization or the so-called low-conversion polymerization was applied for the preparation of N-vinylcarbazole (NVC) and 1,4-divinylbenzene (DVB) monolithic capillary columns. The synthesis was carried out by thermally initiated free radical copolymerization under the influence of inert micro- (toluene) and macroporogen (1-decanol) and α,α'-azoisobutyronitrile (AIBN) as radical initiator. The morphological and porous properties were studied by scanning electron microscopy (SEM), nitrogen adsorption, and mercury intrusion porosimetry (MIP). The copolymerization process was studied by monomer conversion measurements. This approach led to increased porosity and specific surface area. A specific surface area above 400 m(2)/g of the monolith and a distinct bimodal pore size distribution were obtained. The chromatographic performance was determined in terms of theoretical plate heights and number of theoretical plates. The lowest plate height value was found to be 3.9 μm (corresponding to ≈256,000 plates per meter) applying methylparaben utilizing an 80 mm × 0.2 mm i.d. monolithic capillary. The developed NVC/DVB monolithic supports showed high separation efficiency towards small molecules, which was exemplified applying reversed-phase (RP) separation of alkylbenzenes, beta-blockers, flavanoids, parabens, and phenones. The loading capacity was analyzed for isocratic separation of seven alkylbenzenes and was found to be up to 77 ng total mass of alkylbenzenes. Furthermore, a long-term stability test of 1,000 consecutive runs was performed and resulted in a maximum variance of 0.97, 0.85, and 0.16 % RSD for resolution, peak width at half height, and retention times, respectively. The material was proven to have a high permeability of 1.11E-14 m(2), applying water as a mobile phase. PMID:25056873

  15. Water's hydrogen bonds in the hydrophobic effect: a simple model.

    PubMed

    Xu, Huafeng; Dill, Ken A

    2005-12-15

    We propose a simple analytical model to account for water's hydrogen bonds in the hydrophobic effect. It is based on computing a mean-field partition function for a water molecule in the first solvation shell around a solute molecule. The model treats the orientational restrictions from hydrogen bonding, and utilizes quantities that can be obtained from bulk water simulations. We illustrate the principles in a 2-dimensional Mercedes-Benz-like model. Our model gives good predictions for the heat capacity of hydrophobic solvation, reproduces the solvation energies and entropies at different temperatures with only one fitting parameter, and accounts for the solute size dependence of the hydrophobic effect. Our model supports the view that water's hydrogen bonding propensity determines the temperature dependence of the hydrophobic effect. It explains the puzzling experimental observation that dissolving a nonpolar solute in hot water has positive entropy.

  16. Water's hydrogen bonds in the hydrophobic effect: a simple model.

    PubMed

    Xu, Huafeng; Dill, Ken A

    2005-12-15

    We propose a simple analytical model to account for water's hydrogen bonds in the hydrophobic effect. It is based on computing a mean-field partition function for a water molecule in the first solvation shell around a solute molecule. The model treats the orientational restrictions from hydrogen bonding, and utilizes quantities that can be obtained from bulk water simulations. We illustrate the principles in a 2-dimensional Mercedes-Benz-like model. Our model gives good predictions for the heat capacity of hydrophobic solvation, reproduces the solvation energies and entropies at different temperatures with only one fitting parameter, and accounts for the solute size dependence of the hydrophobic effect. Our model supports the view that water's hydrogen bonding propensity determines the temperature dependence of the hydrophobic effect. It explains the puzzling experimental observation that dissolving a nonpolar solute in hot water has positive entropy. PMID:16375338

  17. Hydrophobic sugar holograms

    NASA Astrophysics Data System (ADS)

    Mejias-Brizuela, N. Y.; Olivares-Pérez, A.; Páez-Trujillo, G.; Hernández-Garay, M. P.; Fontanilla-Urdaneta, R.; Fuentes-Tapia, I.

    2008-02-01

    The sugar matrix is used to record of phase holograms; it was modified with the purpose of obtaining a hydrophobic material to improve the stability of the registered image and to stimulate the photosensitivity of the sugar. The new material is formed by a sugar, pectin and vanillin dissolution. The diffraction efficiency parameter increases in comparison with only the sugar matrix, obtaining already of 10%.

  18. Multifunctional polypeptide-PEO nanoreactors via the hydrophobic switch.

    PubMed

    Wu, Yuzhou; Wang, Tao; Ng, David Y W; Weil, Tanja

    2012-09-14

    We prepare various protein-derived amphiphilic polymers. By modifying the polypeptide backbone with a few (5-8) hydrophilic or lipophilic substituents, we are able to switch the hydrophobicity of the polymer and control the formation of stable nano-sized micelles. In the hydrophobic interior of these micelles, ethynyl groups are introduced to provide a nanoreactor environment for click reactions with lipophilic cargo molecules, such as 3-azidocoumarin, a hydrophobic fluorophore, and the anti-cancer drug doxorubicin. These protein-derived amphiphilic polymers reported herein offer a promising potential to design a delivery platform for biomedical applications.

  19. Potential of mean force of association of large hydrophobic particles: toward the nanoscale limit.

    PubMed

    Makowski, Mariusz; Czaplewski, Cezary; Liwo, Adam; Scheraga, Harold A

    2010-01-21

    The potentials of mean force (PMFs) were determined, in both water with the TIP3P water model and in vacuo, for systems involving formation of nonpolar dimers composed of bicyclooctane, adamantane (both an all-atom model and a sphere with the radius of 3.4 A representing adamantane), and fullerene, respectively. A series of umbrella-sampling molecular dynamics simulations with the AMBER force field were carried out for each pair under both environmental conditions. The PMFs were calculated by using the weighted histogram analysis method. The results were compared with our previously determined PMF for neopentane. The shape of the PMFs for dimers of all four nonpolar molecules is characteristic of hydrophobic interactions with contact and solvent-separated minima and desolvation maxima. The positions of all these minima and maxima change with the size of the nonpolar molecule; for larger molecules they shift toward larger distances. Comparison of the PMFs of the bicyclooctane, adamantane, and fullerene dimers in water and in vacuo shows that hydrophobic interactions in each dimer are different from that for the dimer of neopentane. Interactions in the bicyclooctane, adamantane, and fullerene dimers are stronger in vacuo than in water. These dimers cannot be treated as classical, spherical, hydrophobic objects. The solvent contribution to the PMF was also computed by subtracting the PMF determined in vacuo from that in explicit solvent. The solvent contribution to the PMFs of bicyclooctane, adamantane, and fullerene is positive, as opposed to that of neopentane. The water molecules in the first solvation sphere of both adamantane and neopentane dimers are more ordered as compared to bulk water, with their dipole moments pointing away from the surface of the dimers. The average number of hydrogen bonds per water molecule in the first hydration shell of adamantane is smaller compared to that in bulk water, but this shell is thicker for all-atom adamantane than for

  20. The search for the hydrophobic force law.

    PubMed

    Hammer, Malte U; Anderson, Travers H; Chaimovich, Aviel; Shell, M Scott; Israelachvili, Jacob

    2010-01-01

    After nearly 30 years of research on the hydrophobic interaction, the search for the hydrophobic force law is still continuing. Indeed, there are more questions than answers, and the experimental data are often quite different for nominally similar conditions, as well as, apparently, for nano-, micro-, and macroscopic surfaces. This has led to the conclusion that the experimentally observed force-distance relationships are either a combination of different 'fundamental' interactions, or that the hydrophobic force-law, if there is one, is complex--depending on numerous parameters. The only unexpectedly strong attractive force measured in all experiments so far has a range of D approximately 100-200 angstroms, increasing roughly exponentially down to approximately 10-20 angstroms and then more steeply down to adhesive contact at D = 0 or, for power-law potentials, effectively at D approximately 2 angstroms. The measured forces in this regime (100-200 angstroms) and especially the adhesive forces are much stronger, and have a different distance-dependence from the continuum VDW force (Lifshitz theory) for non-conducting dielectric media. We suggest a three-regime force-law for the forces observed between hydrophobic surfaces: In the first, from 100-200 angstroms to thousands of angstroms, the dominating force is created by complementary electrostatic domains or patches on the apposing surfaces and/or bridging vapour cavities; a 'pure' but still not well-understood 'long-range hydrophobic force' dominates the second regime from approximately 150 to approximately 15 angstroms, possibly due to an enhanced Hamaker constant associated with the 'proton-hopping' polarizability of water; while below approximately 10-15 anstroms to contact there is another 'pure short-range hydrophobic force' related to water structuring effects associated with surface-induced changes in the orientation and/or density of water molecules and H-bonds at the water-hydrophobic interface. We

  1. Diameter-dependent hydrophobicity in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kyakuno, Haruka; Fukasawa, Mamoru; Ichimura, Ryota; Matsuda, Kazuyuki; Nakai, Yusuke; Miyata, Yasumitsu; Saito, Takeshi; Maniwa, Yutaka

    2016-08-01

    Single-wall carbon nanotubes (SWCNTs) are a good model system that provides atomically smooth nanocavities. It has been reported that water-SWCNTs exhibit hydrophobicity depending on the temperature T and the SWCNT diameter D. SWCNTs adsorb water molecules spontaneously in their cylindrical pores around room temperature, whereas they exhibit a hydrophilic-hydrophobic transition or wet-dry transition (WDT) at a critical temperature Twd ≈ 220-230 K and above a critical diameter Dc ≈ 1.4-1.6 nm. However, details of the WDT phenomenon and its mechanism remain unknown. Here, we report a systematic experimental study involving X-ray diffraction, optical microscopy, and differential scanning calorimetry. It is found that water molecules inside thick SWCNTs (D > Dc) evaporate and condense into ice Ih outside the SWCNTs at Twd upon cooling, and the ice Ih evaporates and condenses inside the SWCNTs upon heating. On the other hand, residual water trapped inside the SWCNTs below Twd freezes. Molecular dynamics simulations indicate that upon lowering T, the hydrophobicity of thick SWCNTs increases without any structural transition, while the water inside thin SWCNTs (D < Dc) exhibits a structural transition, forming an ordered ice. This ice has a well-developed hydrogen bonding network adapting to the cylindrical pores of the SWCNTs. Thus, the unusual diameter dependence of the WDT is attributed to the adaptability of the structure of water to the pore dimension and shape.

  2. Generation of a multi-qubit W entangled state through spatially separated semiconductor quantum-dot-molecules in cavity-quantum electrodynamics arrays

    SciTech Connect

    Liu, Siping; Yu, Rong; Li, Jiahua; Wu, Ying

    2014-04-07

    Generating entangled states attract tremendous interest as the most vivid manifestation of nonlocality of quantum mechanics and also for emerging applications in quantum information processing (QIP). Here, we propose theoretically a scheme for the deterministic generation of a three-qubit W sate with three semiconductor quantum-dot-molecules (QDMs) trapped in spatially separated cavities connected by optical fibers. The proposed scheme takes full advantage of the voltage-controlled tunnelling effects in QDMs, which induces the quantum coherence and further controls the generation of the W entangled state. The influences of the system parameters and various decoherence processes including spontaneous decay and photon leakage on the fidelity of the W state are discussed in details. Numerical results indicate that our scheme is not only robust against these decoherence factors but also insensitive to the deviation of the system parameters from the ideal conditions. Furthermore, the present scheme can be directly extended to realize an N-qubit W state. Also, this scheme can be generically transferred to other physical systems, including circuit quantum electrodynamics and photonic crystal cavities. The results obtained here may be useful in real experiments for realizing QIP in a solid-state platform.

  3. Separators and organics for lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Böhnstedt, Werner

    This review discusses various interactions between organic compounds, brought into the lead-acid battery via the separator, and their subsequent effect on battery performance. Historically, the interrelationship started with certain 'expander' actions on the lead morphology due to lignins, which leached out of the wooden separators of that time. Synthetic separator materials did not show this effect, but gained acceptance as they were far more stable in the hostile battery environment. The partially hydrophobic character of synthetic separators has been overcome by organic surfactants. Other organic compounds have been found to improve further the stability of separators against oxidation. Special organic molecules, namely aldehydes and ketones, have been identified to retard, or even suppress, the adverse effects of metals such as antimony, and thus prolong the cycle-life of traction batteries in heavy-duty applications or reduce water loss from automotive batteries. Knowledge about these interactions has opened ways to improve separators.

  4. Exploring Hydrophobic Binding Surfaces Using Comfa and Flexible Hydrophobic Ligands

    NASA Astrophysics Data System (ADS)

    Thakkar, Shraddha; Sanchez, Rosa. I.; Bhuveneswaran, Chidambaram; Compadre, Cesar M.

    2011-06-01

    Cysteine proteinases are a very important group of enzymes involved in a variety of physiological and pathological processes including cancer metastasis and rheumatoid arthritis. In this investigation we used 3D-Quantitative Structure Activity Relationships (3D-QSAR) techniques to model the binding of a variety of substrates to two cysteine proteinases, papain, and cathepsin B. The analysis was performed using Comparative Molecular Field Analysis (CoMFA). The molecules were constructed using standard bond angles and lengths, minimized and aligned. Charges were calculated using the PM3 method in MOPAC. The CoMFA models derived for the binding of the studied substrates to the two proteinases were compared with the expected results from the experimental X-ray crystal structures of the same proteinases. The results showed the value of CoMFA modeling of flexible hydrophobic ligands to analyze ligand binding to protein receptors, and could also serve as the basis to design specific inhibitors of cysteine proteinases with potential therapeutic value.

  5. Investigation on hydrophobic films from a hydrophobic powder

    NASA Astrophysics Data System (ADS)

    Zhu, Liqun; Hao, Guofang; Chen, Yuan; Chen, Yizhi

    2012-11-01

    A hydrophobic powder was prepared based mainly on an organosiloxane and a corrosion inhibitor with the addition of a reaction promoter. Structure and thermal stability of the hydrophobic powder were characterized by FTIR and TG/DSC, respectively. Hydrophobic property and corrosion resistance of the hydrophobic film formed on phosphatized steel by immersion in 3 wt% NaCl aqueous solution were evaluated together with the electrochemical behavior. Results showed that the skeleton of the hydrophobic powder was composed mainly of sbnd Sisbnd Osbnd Sisbnd which comprises longer and more hydrophobic groups of sbnd Sisbnd R compared with the conventional BH-102 water-repellent agent. A thin hydrophobic film with a thickness of 15-20 μm was formed on surface of the phosphatized steel after immersion in the solution of 5 g/L of the hydrophobic powder in ethanol for 5 min. The hydrophobic film exhibited excellent stability at a temperature below 135 °C. Water contact angle on the film is about 117-132° and it was until 30 h later when a corrosion spot occurred on the film covered on steel which revealed better water-repellent and corrosion resistant properties compared to that of the BH-102.

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

    SciTech Connect

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

    2011-12-31

    The hydrophobic effect, the free-energetically favorable association of nonpolar solutes in water, makes a dominant contribution to binding of many systems of ligands and proteins. The objective of this study was to examine the hydrophobic effect in biomolecular recognition using two chemically different but structurally similar hydrophobic groups, aliphatic hydrocarbons and aliphatic fluorocarbons, and to determine whether the hydrophobicity of the two groups could be distinguished by thermodynamic and biostructural analysis. This paper uses isothermal titration calorimetry (ITC) to examine the thermodynamics of binding of benzenesulfonamides substituted in the para position with alkyl and fluoroalkyl chains (H{sub 2}NSO{sub 2}C{sub 6}H{sub 4}-CONHCH{sub 2}(CX{sub 2}){sub n}CX{sub 3}, n = 0-4, X = H, F) to human carbonic anhydrase II (HCA II). Both alkyl and fluoroalkyl substituents contribute favorably to the enthalpy and the entropy of binding; these contributions increase as the length of chain of the hydrophobic substituent increases. Crystallography of the protein-ligand complexes indicates that the benzenesulfonamide groups of all ligands examined bind with similar geometry, that the tail groups associate with the hydrophobic wall of HCA II (which is made up of the side chains of residues Phe131, Val135, Pro202, and Leu204), and that the structure of the protein is indistinguishable for all but one of the complexes (the longest member of the fluoroalkyl series). Analysis of the thermodynamics of binding as a function of structure is compatible with the hypothesis that hydrophobic binding of both alkyl and fluoroalkyl chains to hydrophobic surface of carbonic anhydrase is due primarily to the release of nonoptimally hydrogen-bonded water molecules that hydrate the binding cavity (including the hydrophobic wall) of HCA II and to the release of water molecules that surround the hydrophobic chain of the ligands. This study defines the balance of enthalpic and

  7. Hydrophobic Association in Mixed Urea-TMAO Solutions.

    PubMed

    Ganguly, Pritam; van der Vegt, Nico F A; Shea, Joan-Emma

    2016-08-01

    The formation of a hydrophobic core is key to the folding and resulting function of most proteins in the cell. In several organisms, as well as in many in vitro experiments, protein folding is modulated by the presence of osmolytes, but the mechanism by which hydrophobic association occurs is not well understood. We present a study of the solvation thermodynamics of hydrophobic self-association in mixed-osmolyte urea-TMAO solutions, with neopentane as a model hydrophobic molecule. Using molecular dynamics simulations and the Kirkwood-Buff theory of solutions, we show that a sensitive balance between the TMAO-water and the TMAO-urea interactions governs the osmolyte-induced changes in hydrophobic association in mixed urea-TMAO solutions. This balance must be correctly incorporated in force-field parametrization because hydrophobic association can be either enhanced or prevented all together by slightly increasing or decreasing the osmolyte-water affinity and osmolyte-osmolyte self-affinity of TMAO molecules. PMID:27440555

  8. Effect of temperature on the structure and phase behavior of water confined by hydrophobic, hydrophilic, and heterogeneous surfaces.

    PubMed

    Giovambattista, Nicolas; Rossky, Peter J; Debenedetti, Pablo G

    2009-10-22

    We perform molecular dynamics simulations of water confined between atomically detailed hydrophobic, hydrophilic, and heterogeneous (patchy) nanoscale plates. We study the effects of temperature 220 separations 0.5 hydrophobic plates can form vapor, liquid, or crystal (bilayer ice) phases, depending on the values of P and d. The P-d phase diagrams at T = 300 K and T = 220 K show that cooling suppresses the vapor phase and stabilizes the liquid and crystal phases. The critical separation d(c)(P), below which vapor forms, shifts to lower values of d and P upon cooling. The density profiles show that, upon cooling, water approaches the hydrophobic plates. Hence, the effective hydrophobicity of the plate decreases as T decreases, consistent with the suppression of the vapor phase upon cooling. However, both the orientation of water's molecules at the interface and the water contact angle on the hydrophobic surface show practically no temperature dependence. Simulations of water confined by heterogeneous plates decorated with hydrophobic and hydrophilic patches reveal that cooling leads to appreciable blurring of the differences between water densities at hydrophobic and hydrophilic surfaces. This observation, together with remarkable similarities in confined water's response to isobaric cooling and to isothermal

  9. Water on a Hydrophobic surface

    NASA Astrophysics Data System (ADS)

    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.

  10. Pathways to dewetting in hydrophobic confinement

    PubMed Central

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

    2015-01-01

    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. PMID:26100866

  11. Thermodynamics of hydrophobic interaction between silica surfaces coated with octadecyltrichlorosilane.

    PubMed

    Li, Zuoli; Yoon, Roe-Hoan

    2013-02-15

    Surface force measurements conducted with thiolated gold surfaces showed previously that hydrophobic interaction entails a decrease in excess film entropy, suggesting that hydrophobic force originates from changes in the structure of the medium (water) confined between hydrophobic surfaces. As a follow-up work, surface force measurements have been conducted in the present work using an atomic force microscope (AFM) with silica surfaces coated with octadecyltrichlorosilane (OTS) at temperatures in the range of 10-40°C. A thermodynamic analysis of the results show that both the excess film entropy (ΔS(f)) and excess film enthalpy (ΔH(f)) decrease with decreasing thickness of the water films between the hydrophobic surfaces. It has been found also that |ΔH(f)|>|TΔS(f)|, which represents a necessary condition for the excess free energy change (ΔG(f)) to be negative and hence the hydrophobic interaction be attractive. Thus, the results obtained with both the thiolated and silylated surfaces show that hydrophobic forces originate from the structural changes in the medium. It is believed that the water molecules in the thin liquid films (TLFs) of water form clusters as a means to reduce the free energy when they cannot form H-bonds to neighboring hydrophobic surfaces. PMID:23127878

  12. Cellobiohydrolase Hydrolyzes Crystalline Cellulose on Hydrophobic Faces*

    PubMed Central

    Liu, Yu-San; Baker, John O.; Zeng, Yining; Himmel, Michael E.; Haas, Thomas; Ding, Shi-You

    2011-01-01

    Biodegradation of plant biomass is a slow process in nature, and hydrolysis of cellulose is also widely considered to be a rate-limiting step in the proposed industrial process of converting lignocellulosic materials to biofuels. It is generally known that a team of enzymes including endo- and exocellulases as well as cellobiases are required to act synergistically to hydrolyze cellulose to glucose. The detailed molecular mechanisms of these enzymes have yet to be convincingly elucidated. In this report, atomic force microscopy (AFM) is used to image in real-time the structural changes in Valonia cellulose crystals acted upon by the exocellulase cellobiohydrolase I (CBH I) from Trichoderma reesei. Under AFM, single enzyme molecules could be observed binding only to one face of the cellulose crystal, apparently the hydrophobic face. The surface roughness of cellulose began increasing after adding CBH I, and the overall size of cellulose crystals decreased during an 11-h period. Interestingly, this size reduction apparently occurred only in the width of the crystal, whereas the height remained relatively constant. In addition, the measured cross-section shape of cellulose crystal changed from asymmetric to nearly symmetric. These observed changes brought about by CBH I action may constitute the first direct visualization supporting the idea that the exocellulase selectively hydrolyzes the hydrophobic faces of cellulose. The limited accessibility of the hydrophobic faces in native cellulose may contribute significantly to the rate-limiting slowness of cellulose hydrolysis. PMID:21282110

  13. Voltage-Gated Hydrophobic Nanopores

    SciTech Connect

    Lavrik, Nickolay V

    2011-01-01

    Hydrophobicity is a fundamental property that is responsible for numerous physical and biophysical aspects of molecular interactions in water. Peculiar behavior is expected for water in the vicinity of hydrophobic structures, such as nanopores. Indeed, hydrophobic nanopores can be found in two distinct states, dry and wet, even though the latter is thermodynamically unstable. Transitions between these two states are kinetically hindered in long pores but can be much faster in shorter pores. As it is demonstrated for the first time in this paper, these transitions can be induced by applying a voltage across a membrane with a single hydrophobic nanopore. Such voltage-induced gating in single nanopores can be realized in a reversible manner through electrowetting of inner walls of the nanopores. The resulting I-V curves of such artificial hydrophobic nanopores mimic biological voltage-gated channels.

  14. Molecular simulation study of cooperativity in hydrophobic association.

    PubMed Central

    Czaplewski, C.; Rodziewicz-Motowidło, S.; Liwo, A.; Ripoll, D. R.; Wawak, R. J.; Scheraga, H. A.

    2000-01-01

    To investigate the cooperativity of hydrophobic interactions, the potential of mean force of two- and three-molecule methane clusters in water was determined by molecular dynamics simulations using two methods: umbrella-sampling with the weighted histogram analysis method and thermodynamic integration. Two water models, TIP3P and TIP4P, were used, while each methane molecule was modeled as a united atom. It was found that the three-body potential of mean force is not additive, i.e., it cannot be calculated as a sum of two-body contributions, but requires an additional three-body cooperative term. The cooperative term, which amounts to only about 10% of the total hydrophobic association free energy, was found to increase the strength of hydrophobic association; this finding differs from the results of earlier Monte Carlo studies with the free energy perturbation method of Rank and Baker (1997). As in the work of Rank and Baker, the solvent contribution to the potential of mean force was found to be well approximated by the molecular surface of two methane molecules. Moreover, we also found that the cooperative term is well represented by the difference between the molecular surface of the three-methane cluster and those of all three pairs of methane molecules. In addition, it was found that, while there is a cooperative contribution to the hydrophobic association free energy albeit a small one, the errors associated with the use of pairwise potentials are comparable to or larger than this contribution. PMID:10892816

  15. Changing water affinity from hydrophobic to hydrophilic in hydrophobic channels.

    PubMed

    Ohba, Tomonori; Yamamoto, Shotaro; Kodaira, Tetsuya; Hata, Kenji

    2015-01-27

    The behavior of water at hydrophobic interfaces can play a significant role in determining chemical reaction outcomes and physical properties. Carbon nanotubes and aluminophosphate materials have one-dimensional hydrophobic channels, which are entirely surrounded by hydrophobic interfaces. Unique water behavior was observed in such hydrophobic channels. In this article, changes in the water affinity in one-dimensional hydrophobic channels were assessed using water vapor adsorption isotherms at 303 K and grand canonical Monte Carlo simulations. Hydrophobic behavior of water adsorbed in channels wider than 3 nm was observed for both adsorption and desorption processes, owing to the hydrophobic environment. However, water showed hydrophilic properties in both adsorption and desorption processes in channels narrower than 1 nm. In intermediate-sized channels, the hydrophobic properties of water during the adsorption process were seen to transition to hydrophilic behavior during the desorption process. Hydrophilic properties in the narrow channels for both adsorption and desorption processes are a result of the relatively strong water-channel interactions (10-15 kJ mol(-1)). In the 2-3 nm channels, the water-channel interaction energy of 4-5 kJ mol(-1) was comparable to the thermal translational energy. The cohesive water interaction was approximately 35 kJ mol(-1), which was larger than the others. Thus, the water affinity change in the 2-3 nm channels for the adsorption and desorption processes was attributed to weak water-channel interactions and strong cohesive interactions. These results are inherently important to control the properties of water in hydrophobic environments.

  16. Subtle Balance Between Length Scale of Phase Separation and Domain Purification in Small-Molecule Bulk-Heterojunction Blends under Solvent Vapor Treatment.

    PubMed

    Li, Miaomiao; Liu, Feng; Wan, Xiangjian; Ni, Wang; Kan, Bin; Feng, Huanran; Zhang, Qian; Yang, Xuan; Wang, Yunchuang; Zhang, Yamin; Shen, Yan; Russell, Thomas P; Chen, Yongsheng

    2015-10-28

    A series of solvents with different solubilities for DR3TBDTT and PC71 BM, and different boiling points, is used for solvent vapor annealing (SVA) treatment to systematically investigate the solvent-morphology-performance relationship. The presence of solvent molecules inside bulk-heterojunction (BHJ) thin films promotes the mobility of both donor and acceptor molecules, leading to crystallization and aggregation, which are important in modulating morphology. PMID:26333172

  17. Air agglomeration of hydrophobic particles

    SciTech Connect

    Drzymala, J.; Wheelock, T.D.

    1995-12-31

    The agglomeration of hydrophobic particles in an aqueous suspension was accomplished by introducing small amounts of air into the suspension while it was agitated vigorously. The extent of aggregation was proportional both to the air to solids ratio and to the hydrophobicity of the solids. For a given air/solids ratio, the extent of aggregation of different materials increased in the following order: graphite, gilsonite, coal coated with heptane, and Teflon. The structure of agglomerates produced from coarse Teflon particles differed noticeably from the structure of bubble-particle aggregates produced from smaller, less hydrophobic particles.

  18. Mechanisms for Enhanced Hydrophobicity by Atomic-Scale Roughness

    PubMed Central

    Katasho, Yumi; Liang, Yunfeng; Murata, Sumihiko; Fukunaka, Yasuhiro; Matsuoka, Toshifumi; Takahashi, Satoru

    2015-01-01

    It is well known that the close-packed CF3-terminated solid surface is among the most hydrophobic surfaces in nature. Molecular dynamic simulations show that this hydrophobicity can be further enhanced by the atomic-scale roughness. Consequently, the hydrophobic gap width is enlarged to about 0.6 nm for roughened CF3-terminated solid surfaces. In contrast, the hydrophobic gap width does not increase too much for a rough CH3-terminated solid surface. We show that the CF3-terminated surface exists in a microscopic Cassie–Baxter state, whereas the CH3-terminated surface exists as a microscopic Wenzel state. This finding elucidates the underlying mechanism for the different widths of the observed hydrophobic gap. The cage structure of the water molecules (with integrated hydrogen bonds) around CH3 terminal assemblies on the solid surface provides an explanation for the mechanism by which the CH3-terminated surface is less hydrophobic than the CF3-terminated surface. PMID:26337567

  19. Review: Milk Proteins as Nanocarrier Systems for Hydrophobic Nutraceuticals.

    PubMed

    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. PMID:26467442

  20. Hydrophobic ionic liquids

    DOEpatents

    Koch, Victor R.; Nanjundiah, Chenniah; Carlin, Richard T.

    1998-01-01

    Ionic liquids having improved properties for application in non-aqueous batteries, electrochemical capacitors, electroplating, catalysis and chemical separations are disclosed. Exemplary compounds have one of the following formulas: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are either H; F; separate alkyl groups of from 1 to 4 carbon atoms, respectively, or joined together to constitute a unitary alkylene radical of from 2 to 4 carbon atoms forming a ring structure converging on N; or separate phenyl groups; and wherein the alkyl groups, alkylene radicals or phenyl groups may be substituted with electron withdrawing groups, preferably F--, Cl--, CF.sub.3 --, SF.sub.5 --, CF.sub.3 S--, (CF.sub.3).sub.2 CHS-- or (CF.sub.3).sub.3 CS--; and X.sup.- is a non-Lewis acid-containing polyatomic anion having a van der Waals volume exceeding 100 .ANG..sup.3.

  1. Hydrophobic ionic liquids

    DOEpatents

    Koch, V.R.; Nanjundiah, C.; Carlin, R.T.

    1998-10-27

    Ionic liquids having improved properties for application in non-aqueous batteries, electrochemical capacitors, electroplating, catalysis and chemical separations are disclosed. Exemplary compounds have one of the following formulas shown in a diagram wherein R{sub 1}, R{sub 2}, R{sub 3}, R{sub 4}, R{sub 5}, and R{sub 6} are either H; F; separate alkyl groups of from 1 to 4 carbon atoms, respectively, or joined together to constitute a unitary alkylene radical of from 2 to 4 carbon atoms forming a ring structure converging on N; or separate phenyl groups; and wherein the alkyl groups, alkylene radicals or phenyl groups may be substituted with electron withdrawing groups, preferably F-, Cl-, CF{sub 3}-, SF{sub 5}-, CF{sub 3}S-, (CF{sub 3}){sub 2}CHS- or (CF{sub 3}){sub 3}CS-; and X{sup {minus}} is a non-Lewis acid-containing polyatomic anion having a van der Waals volume exceeding 100 {angstrom}{sup 3}. 4 figs.

  2. Estimation of atomic hydrophobicities using molecular dynamics simulation of peptides

    NASA Astrophysics Data System (ADS)

    Held, Marie; Nicolau, Dan V.

    2007-12-01

    The hydrophobic force is one of the main driving forces in protein folding and binding. However, its nature is not yet well understood and consequently there are more than 80 different scales published trying to quantify it. Most of the hydrophobicity scales are amino acid-based, but the interaction between the molecular surface of the proteins (and DNA) and surfaces they are immobilized on, e.g., on biomedical micro/nanodevices, occurs on fractions of, rather than whole amino acids. This fragmented structure of the biomolecular surface requires the derivation of atom-level hydrophobicity. Most attempts for the evaluation of atomic hydrophobicities are derived from amino acid-based values, which ignore dynamic and steric factors. This contribution reports on the Molecular Dynamics simulations that aim to overcome this simplification. The calculations examine various tripeptides in an aqueous solution and the analysis focuses on the distance of the nearest water molecules to the individual atoms in the peptides. Different environments result in a variation of average distances for similar atoms in different tripeptides. Comparison with the atomic hydrophobicities derived from the amino acid-based hydrophobicity obtained from peptide partition in water-octanol (Dgoct) and transport through the membrane interface (Dgwif) shows a similar trend to the calculated distances. The variations are likely due to the steric differences of similar types of atoms in different geometric contexts. Therefore, Molecular Dynamics simulations proved convenient for the evaluation of atomic hydrophobicities and open new research avenues. The atomic hydrophobicities can be used to design surfaces that mimic the biomolecular surfaces and therefore elicit an expected biomolecular activity from the immobilized biomolecules.

  3. Method for producing hydrophobic aerogels

    DOEpatents

    Hrubesh, Lawrence W.; Poco, John F.; Coronado, Paul R.

    1999-01-01

    A method for treating a dried monolithic aerogel containing non-dispersed particles, with an organometallic surface modifying agent to produce hydrophobic aerogels. The dried, porous hydrophobic aerogels contain a protective layer of alkyl groups, such as methyl groups, on the modified surfaces of the pores of the aerogel. The alkyl groups at the aerogel surface typically contain at least one carbon-metal bond per group.

  4. Geometrical Patterning of Super-Hydrophobic Biosensing Transistors Enables Space and Time Resolved Analysis of Biological Mixtures

    PubMed Central

    Gentile, Francesco; Ferrara, Lorenzo; Villani, Marco; Bettelli, Manuele; Iannotta, Salvatore; Zappettini, Andrea; Cesarelli, Mario; Di Fabrizio, Enzo; Coppedè, Nicola

    2016-01-01

    PEDOT:PSS is a conductive polymer that can be integrated into last generation Organic Electrochemical Transistor (OECT) devices for biological inspection, identification and analysis. While a variety of reports in literature demonstrated the chemical and biological sensitivity of these devices, still their ability in resolving complex mixtures remains controversial. Similar OECT devices display good time dynamics behavior but lack spatial resolution. In this work, we integrated PEDOT:PSS with patterns of super-hydrophobic pillars in which a finite number of those pillars is independently controlled for site-selective measurement of a solution. We obtained a multifunctional, hierarchical OECT device that bridges the micro- to the nano-scales for specific, combined time and space resolved analysis of the sample. Due to super-hydrophobic surface properties, the biological species in the drop are driven by convection, diffusion, and the externally applied electric field: the balance/unbalance between these forces will cause the molecules to be transported differently within its volume depending on particle size thus realizing a size-selective separation. Within this framework, the separation and identification of two different molecules, namely Cetyl Trimethyl Ammonium Bromid (CTAB) and adrenaline, in a biological mixture have been demonstrated, showing that geometrical control at the micro-nano scale impart unprecedented selectivity to the devices. PMID:26753611

  5. Sticking polydisperse hydrophobic magnetite nanoparticles to lipid membranes.

    PubMed

    Paulus, Michael; Degen, Patrick; Brenner, Thorsten; Tiemeyer, Sebastian; Struth, Bernd; Tolan, Metin; Rehage, Heinz

    2010-10-19

    The formation of a layer of hydrophobic magnetite (Fe(3)O(4)) nanoparticles stabilized by lauric acid is analyzed by in situ X-ray reflectivity measurements. The data analysis shows that the nanoparticles partially disperse their hydrophobic coating. Consequently, a Langmuir layer was formed by lauric acid molecules that can be compressed into an untilted condensed phase. A majority of the nanoparticles are attached to the Langmuir film integrating lauric acid residue on their surface into the Langmuir film. Hence, the particles at the liquid-gas interface can be identified as so-called Janus beads, which are amphiphilic solids having two sides with different functionality.

  6. Sticking polydisperse hydrophobic magnetite nanoparticles to lipid membranes.

    PubMed

    Paulus, Michael; Degen, Patrick; Brenner, Thorsten; Tiemeyer, Sebastian; Struth, Bernd; Tolan, Metin; Rehage, Heinz

    2010-10-19

    The formation of a layer of hydrophobic magnetite (Fe(3)O(4)) nanoparticles stabilized by lauric acid is analyzed by in situ X-ray reflectivity measurements. The data analysis shows that the nanoparticles partially disperse their hydrophobic coating. Consequently, a Langmuir layer was formed by lauric acid molecules that can be compressed into an untilted condensed phase. A majority of the nanoparticles are attached to the Langmuir film integrating lauric acid residue on their surface into the Langmuir film. Hence, the particles at the liquid-gas interface can be identified as so-called Janus beads, which are amphiphilic solids having two sides with different functionality. PMID:20873726

  7. Development of the selective hydrophobic coagulation process

    SciTech Connect

    Yoon, R.H.; Luttrell, G.H.

    1992-01-01

    A novel technique for selectively coagulating and separating coal from dispersed mineral matter has been developed at Virginia Tech. The process, Selective Hydrophobic Coagulation (SHC), has been studied since 1986 under the sponsorship of the US Department of Energy. The SHC process differs from oil agglomeration, shear or polymer flocculation, and electrolytic coagulation processes in that it does not require reagents or additives to induce the formation of coagula. In most cases, simple pH control is all that is required to (i) induce the coagulation of coal particles and (ii) effectively disperse particles of mineral matter. If the coal is oxidized, a small dosage of reagents can be used to enhance the process. The technical work program was initiated on July 1, 1992. Force-distance curves were generated for DDOA Br-coated mica surfaces in water and used to calculate hydrophobicity constants and decay lengths for this system; and a new device for the measurement of water contact angles, similar to the Wilhelmy plate balance, has been built 225 kg samples of Pittsburgh No. 8 and Elkhom No. 3 seam coals were obtained; a static mixer test facility for the study of coagula growth was set up and was undergoing shakedown tests at the end of the quarter; a bench-scale lamella thickener was being constructed; and preliminary coagula/ mineral separation tests were being conducted in a bench-scale continuous drum filter.

  8. Simplex and duplex polymerase chain reaction analysis of Herculex RW (59122) maize based on one reference molecule including separated fragments of 5' integration site and endogenous gene.

    PubMed

    Li, Xiang; Yang, Litao; Zhang, Jianzhong; Wang, Shu; Shen, Kailin; Pan, Liangwen; Zhang, Dabing

    2009-01-01

    Reference molecules, as positive controls and calibrators, have been recently developed in genetically modified organism analysis as a potential substitute for reference materials derived from plant raw materials. In this study, a novel reference molecule p59122, including the revealed 5' integration sequence of maize Herculex RW (59122), was constructed that was suitable for simplex and duplex event-specific qualitative and quantitative PCR detections. The LOD values were 10 copies both for simplex and duplex qualitative PCR when p59122 was used as the calibrator. These values were comparable to those of using genomic DNA samples with 0.01 and 0.05%, approximately 5 and 25 hyploid genomic DNA copies, respectively. The absolute LOD and LOQ values were confirmed to be as low as 10 and 25 copies of p59122 DNA both in simplex and duplex quantitative systems. Furthermore, ideal quantification data with low bias, SD and RSD values were obtained from the practical samples analyses in simplex and duplex real-time PCR systems using the reference molecule p59122 as a calibrator. All these results suggested that the developed reference molecule p59122 and the qualitative and quantitative PCR detection methods are suitable for identification and quantification of GM maize 59122 and its derived products. PMID:19916386

  9. Simplex and duplex polymerase chain reaction analysis of Herculex RW (59122) maize based on one reference molecule including separated fragments of 5' integration site and endogenous gene.

    PubMed

    Li, Xiang; Yang, Litao; Zhang, Jianzhong; Wang, Shu; Shen, Kailin; Pan, Liangwen; Zhang, Dabing

    2009-01-01

    Reference molecules, as positive controls and calibrators, have been recently developed in genetically modified organism analysis as a potential substitute for reference materials derived from plant raw materials. In this study, a novel reference molecule p59122, including the revealed 5' integration sequence of maize Herculex RW (59122), was constructed that was suitable for simplex and duplex event-specific qualitative and quantitative PCR detections. The LOD values were 10 copies both for simplex and duplex qualitative PCR when p59122 was used as the calibrator. These values were comparable to those of using genomic DNA samples with 0.01 and 0.05%, approximately 5 and 25 hyploid genomic DNA copies, respectively. The absolute LOD and LOQ values were confirmed to be as low as 10 and 25 copies of p59122 DNA both in simplex and duplex quantitative systems. Furthermore, ideal quantification data with low bias, SD and RSD values were obtained from the practical samples analyses in simplex and duplex real-time PCR systems using the reference molecule p59122 as a calibrator. All these results suggested that the developed reference molecule p59122 and the qualitative and quantitative PCR detection methods are suitable for identification and quantification of GM maize 59122 and its derived products.

  10. Separation of very hydrophobic analytes by micellar electrokinetic chromatography. I. Optimization of the composition of the sample solution for the determination of the aromatic ingredients of sassafras and other essential oils of forensic interest.

    PubMed

    Huhn, Carolin; Pütz, Michael; Holthausen, Ivie; Pyell, Ute

    2008-01-01

    A micellar electrokinetic chromatographic method using UV and (UV)LIF detection in-line was developed for the determination of aromatic constituents, mainly allylbenzenes in essential oils. The method optimization included the optimization of the composition of the separation electrolyte using ACN and urea to reduce retention factors and CaCl(2) to widen the migration time window. In addition, it was necessary to optimize the composition of the sample solution which included the addition of a neutral surfactant at high concentration. With the optimized method, the determination of minor constituents in essential oils was possible despite of the presence of a structurally related compound being in a molar ratio excess of 1000:1. The use of UV and LIF-detection in-line enabled the direct comparison of the two detection traces using an electrophoretic mobility x-axis instead of the normal time-based scale. This simplifies the assignment of signals and enhances repeatability. The method developed was successfully applied to the determination of minor and major constituents in herbal essential oils, some of them being forensically relevant as sources of precursors for synthetic drugs.

  11. Novel conduction behavior in nanopores coated with hydrophobic molecules

    NASA Astrophysics Data System (ADS)

    Balagurusamy, Venkat; Stolovitzky, Gustavo; Afzali-Ardakani, Ali

    2015-03-01

    We obtain (Bi0.7Pb0.3)Sr2Ca2Cu3O10 nano-crystals by sol-gel improved with acrylamide and microwaves, not reported in the literature. TGA gives an idea of the reaction temperatures (200-550 ° C) for the formation of binary, ternary and unknown materials. SEM and TEM shows morphology and crystal size 30-33 nm. We studied the thermodynamic and kinetic stability of the gel quenching, by varying the temperature and time according to a previous thermal analysis. Starting compounds (bismuth oxide, strontium carbonate, copper acetate, lead nitrate and calcium sulfate) were analyzed by XRD. By AFM we observed the dehydrated gel surface absorbed water from the environment. From the micrographs we measured the size of the fibers, grains and nano-crystals. We found at 560 ° C Bi1.6Pb0.4Sr2Ca2Cu3Ox compound with tetragonal crystal structure, corresponding to the 2:2:2:3 compound, with Tc 110 K. At 860 ° C seen a shift of some reflections corresponding to two phases. Xerogel magnetic measurement shows antiferromagnetic behavior at 63 K.

  12. Stereoisomers Separation

    NASA Astrophysics Data System (ADS)

    Wieczorek, Piotr

    The use of capillary electrophoresis for enantiomer separation and optical purity determination is presented. The contents start with basic information about the nature of stereoizomers and the mechanism of enantioseparation using capillary electrophoresis techniques. The molecules to be separated show identical chemical structure and electrochemical behavior. Therefore, the chiral recognition of enantiomers is possible only by bonding to chiral selector and the separation based on very small differences in complexation energies of diastereomer complexes formed. This method is useful for this purpose due to the fact that different compounds can be used as chiral selectors. The mostly used chiral selectors like cyclodextrins, crown ethers, chiral surfactants, macrocyclic antibiotics, transition metal complexes, natural, and synthetic polymers and their application for this purpose is also discussed. Finally, examples of practical applications of electromigration techniques for enantiomers separation and determination are presented.

  13. Separation of isotopes of carbon upon the multiphoton single-frequency dissociation of chlorodifluoromethane molecules in the presence of hydrogen iodine

    SciTech Connect

    Velichko, A.M.; Nadeikin, A.A.; Nikitin, A.I.; Pimenova, N.V.; Tal'roze, V.L.

    1987-11-01

    Chlorodifluoromethane (CF/sub 2/HCl) is considered to be one of the the promising substances for setting up the industrial process of the laser separation /sup 12/C and /sup 13/C isotopes. The secondary chemical processes accompanying the multiphoton dissociation of chlorodifluoromethane in the presence of hydrogen iodide have been investigated. The values of the separation coefficients of the isotopes of carbon in the products CF/sub 2/HI and CF/sub 2/H/sub 2/ have been obtained.

  14. 1.9 μm superficially porous packing material with radially oriented pores and tailored pore size for ultra-fast separation of small molecules and biomolecules.

    PubMed

    Min, Yi; Jiang, Bo; Wu, Ci; Xia, Simin; Zhang, Xiaodan; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

    2014-08-22

    In this work, 1.9 μm reversed-phase packing materials with superficially porous structure were prepared to achieve the rapid and high efficient separation of peptides and proteins. The silica particles were synthesized via three steps, nonporous silica particle preparation by a modified seeded growth method, mesoporous shell formation by a one pot templated dissolution and redeposition strategy, and pore size expansion via acid-refluxing. By such a method, 1.9 μm superficially porous materials with 0.18 μm shell thickness and tailored pore diameter (10 nm, 15 nm) were obtained. After pore enlargement, the formerly dense arrays of mesoporous structure changed, the radially oriented pores dominated the superficially porous structure. The chromatographic performance of such particles was investigated after C18 derivatization. For packing materials with 1.9 μm diameter and 10 nm pore size, the column efficiency could reach 211,300 plates per m for naphthalene. To achieve the high resolution separation of peptides and proteins, particles with pore diameter of 15 nm were tailored, by which the baseline separation of 5 peptides and 5 intact proteins could be respectively achieved within 1 min, demonstrating the superiority in the high efficiency and high throughput analysis of biomolecules. Furthermore, BSA digests were well separated with peak capacity of 120 in 30 min on a 15 cm-long column. Finally, we compared our columns with a 1.7 μm Kinetex C18 column under the same conditions, our particles with 10nm pore size demonstrated similar performance for separation of the large intact proteins. Moreover, the particles with 15 nm pore size showed more symmetrical peaks for the separation of large proteins (BSA, OVA and IgG) and provided rapid separation of protein extracts from Escherichia coli in 5 min. All these results indicated that the synthesized 1.9 μm superficially porous silica packing materials would be promising in the ultra-fast and high

  15. Wetting in hydrophobic nanochannels: a challenge of classical capillarity.

    PubMed

    Helmy, Roy; Kazakevich, Yuri; Ni, Chaoying; Fadeev, Alexander Y

    2005-09-14

    We report an investigation of the water-hydrophobic interface in well-defined nanochannels (R approximately 2-4 nm). Wetting in these systems cannot be described by classical (macroscopic) capillary theory: (1) water occupies only a fraction ( approximately 60%) of the pore volume, and (2) the capillary pressures are approximately 60-90% greater than predicted by the Laplace equation. The results suggest the presence of approximately 0.6 nm layer of low-density fluid (vapor) separating water from the hydrophobic solid.

  16. Hydrophobic pocket targeting probes for enteroviruses

    NASA Astrophysics Data System (ADS)

    Martikainen, Mari; Salorinne, Kirsi; Lahtinen, Tanja; Malola, Sami; Permi, Perttu; Häkkinen, Hannu; Marjomäki, Varpu

    2015-10-01

    Visualization and tracking of viruses without compromising their functionality is crucial in order to understand virus targeting to cells and tissues, and to understand the subsequent subcellular steps leading to virus uncoating and replication. Enteroviruses are important human pathogens causing a vast number of acute infections, and are also suggested to contribute to the development of chronic diseases like type I diabetes. Here, we demonstrate a novel method to target site-specifically the hydrophobic pocket of enteroviruses. A probe, a derivative of Pleconaril, was developed and conjugated to various labels that enabled the visualization of enteroviruses under light and electron microscopes. The probe mildly stabilized the virus particle by increasing the melting temperature by 1-3 degrees, and caused a delay in the uncoating of the virus in the cellular endosomes, but could not however inhibit the receptor binding, cellular entry or infectivity of the virus. The hydrophobic pocket binding moiety of the probe was shown to bind to echovirus 1 particle by STD and tr-NOESY NMR methods. Furthermore, binding to echovirus 1 and Coxsackievirus A9, and to a lesser extent to Coxsackie virus B3 was verified by using a gold nanocluster labeled probe by TEM analysis. Molecular modelling suggested that the probe fits the hydrophobic pockets of EV1 and CVA9, but not of CVB3 as expected, correlating well with the variations in the infectivity and stability of the virus particles. EV1 conjugated to the fluorescent dye labeled probe was efficiently internalized into the cells. The virus-fluorescent probe conjugate accumulated in the cytoplasmic endosomes and caused infection starting from 6 hours onwards. Remarkably, before and during the time of replication, the fluorescent probe was seen to leak from the virus-positive endosomes and thus separate from the capsid proteins that were left in the endosomes. These results suggest that, like the physiological hydrophobic content

  17. Recent experimental advances on hydrophobic interactions at solid/water and fluid/water interfaces.

    PubMed

    Zeng, Hongbo; Shi, Chen; Huang, Jun; Li, Lin; Liu, Guangyi; Zhong, Hong

    2016-03-01

    Hydrophobic effects play important roles in a wide range of natural phenomena and engineering processes such as coalescence of oil droplets in water, air flotation of mineral particles, and folding and assembly of proteins and biomembranes. In this work, the authors highlight recent experimental attempts to reveal the physical origin of hydrophobic effects by directly quantifying the hydrophobic interaction on both solid/water and fluid/water interfaces using state-of-art nanomechanical techniques such as surface forces apparatus and atomic force microscopy (AFM). For solid hydrophobic surfaces of different hydrophobicity, the range of hydrophobic interaction was reported to vary from ∼10 to >100 nm. With various characterization techniques, the very long-ranged attraction (>100 nm) has been demonstrated to be mainly attributed to nonhydrophobic interaction mechanisms such as pre-existing nanobubbles and molecular rearrangement. By ruling out these factors, intrinsic hydrophobic interaction was measured to follow an exponential law with decay length of 1-2 nm with effective range less than 20 nm. On the other hand, hydrophobic interaction measured at fluid interfaces using AFM droplet/bubble probe technique was found to decay with a much shorter length of ∼0.3 nm. This discrepancy of measured decay lengths is proposed to be attributed to inherent physical distinction between solid and fluid interfaces, which impacts the structure of interface-adjacent water molecules. Direct measurement of hydrophobic interaction on a broader range of interfaces and characterization of interfacial water molecular structure using spectroscopic techniques are anticipated to help unravel the origin of this rigidity-related mismatch of hydrophobic interaction and hold promise to uncover the physical nature of hydrophobic effects. With improved understanding of hydrophobic interaction, intrinsic interaction mechanisms of many biological and chemical pathways can be better

  18. A novel polymeric monolith prepared with multi-acrylate crosslinker for retention-independent efficient separation of small molecules in capillary liquid chromatography.

    PubMed

    Zhang, Haiyang; Ou, Junjie; Wei, Yinmao; Wang, Hongwei; Liu, Zhongshan; Chen, Lianfang; Zou, Hanfa

    2015-07-01

    Low column efficiency for small molecules in reversed-phase chromatography is a major problem commonly encountered in polymer-based monoliths. Herein, a novel highly crosslinked porous polymeric monolith was in situ prepared by using a multi-acrylate monomer, dipentaerythritol penta-/hexa-acrylate (DPEPA), as crosslinker, which copolymerized with lauryl methacrylate (LMA) as functional monomer in a UV-transparent fused-silica capillary via photo-initiated free-radical polymerization within 5 min. The mechanical stability and permeability of the resulting poly(LMA-co-DPEPA) monolith were characterized in detail. One series of highly crosslinked poly(LMA-co-DPEPA) columns were prepared with relatively higher content of crosslinker (63.3%) in the precursor. Although they exhibited lower permeability, high column efficiency for alkylbenzenes was acquired in cLC, and the minimum plate height (column B) was in the range of 6.04-9.00 μm, corresponding to 111,000-165,000 N m(-1). Meanwhile, another series of poly(LMA-co-DPEPA) columns prepared with relatively lower content of crosslinker (52.7%) in the precursor exhibited higher permeability, but the minimum plate height (column E) was relatively low in the range of 10.75-20.04 μm for alkylbenzenes, corresponding to 50,000-93,000 N m(-1). Compared with common poly(LMA-co-EDMA) columns previously reported, the highly crosslinked poly(LMA-co-DPEPA) columns using a multi-acrylate monomer as crosslinker possessed remarkably high column efficiency for small molecules in cLC. By plotting of plate height (H) of alkylbenzenes versus the linear velocity (u) of mobile phase, the results revealed a retention-independent efficient performance of small molecules in the isocratic elution, indicating that the use of multi-functional crosslinker possibly prevents the generation of gel-like micropores in the poly(LMA-co-DPEPA) monolith, reducing the mass transfer resistance (C-term).

  19. Wet foams hydrophobized by amphiphiles to give Al2O3 porous ceramics

    NASA Astrophysics Data System (ADS)

    Pokhrel, Ashish; Park, Jung Gyu; Kim, Ik Jin

    2012-05-01

    Wet chemical method to prepare ceramic foams with antecedent stability using inorganic particles (Al2O3,SiO2 etc.) which are in situ hydrophobized upon adsorption of short-chain amphiphilic molecules in the wet state and heightened mechanical property in the sintered state was developed. These wet foams are stable over several days and show no bubble coarsening nor drainage or creaming. This long-term stability is achieved through the irreversible adsorption of partially hydrophobized colloidal particles to the air-water interface using short-chain amphiphiles to in situ modify the wetting behavior of the particle surface based on the observations of Pickering emulsions. As a result, the suspension is foamed homogeneously throughout its entire volume and porous bulk materials can be produced upon drying and sintering. Wet foams featuring average bubble sizes between 30 and 300μm and sintered foams with porosity from 50 to 85% were obtained by adjusting the amphiphile - particle concentration, and additives in the initial suspension. Cells were mostly closed with an average size of approximately 150 μm. Single cells were separated by walls with minimum thicknesses of 1-3 μm.

  20. Mechanism of formation of humus coatings on mineral surfaces 2. Attenuated total reflectance spectra of hydrophobic and hydrophilic fractions of organic acids from compost leachate on alumina

    USGS Publications Warehouse

    Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.; Sperline, R.P.; Song, Y.

    1996-01-01

    Hydrophobic and hydrophilic fractions were isolated from a compost leachate. The adsorption isotherms of both fractions on alumina were measured by attenuated total reflectance infrared spectroscopy. The shapes of the adsorption isotherms of the two fractions were different. The isotherms for the hydrophilic fraction showed little change in surface excess with increasing solution concentration above 4 mg L-1. The isotherms for the hydrophobic fraction, on the other hand, displayed a marked increase in surface excess with increasing solution concentration. This increase is evidence for the formation of aggregates (admicelles or hemimicelles) on the alumina surface. Linear dichroism calculations indicated that more of the carboxylate groups in the adsorbed hydrophobic molecules than in the absorbed hydrophilic fraction were free to rotate. The hindered rotation of the carboxylate groups in the adsorbed hydrophilic-fraction molecules probably indicates that these groups are bound to surface aluminum ions by a bidentate mechanism in which the two oxygen atoms of a single carboxylate group bind to separate aluminum ions.

  1. Development of the Selective Hydrophobic Coagulation process

    SciTech Connect

    Yoon, R.H.; Luttrell, G.H.

    1992-01-01

    A novel technique for selectively coagulating and separating coal from dispersed mineral matter has been developed at Virginia Tech. The process, Selective Hydrophobic Coagulation (SHC), has been studied since 1986 under the sponsorship of the US Department of Energy (Contracts AC22-86PC91221 and AC22-90PC90174). The SHC process differs from oil agglomeration, shear or polymer flocculation, and electrolytic coagulation processes in that it does not require reagents or additives to induce the formation of coagula. In most cases, simple pH control is all that is required to (1) induce the coagulation of coal particles and (2) effectively disperse particles of mineral matter. If the coal is oxidized, a small dosage of reagents can be used to enhance the process. During the quarter, the Anutech Mark IV surface force apparatus was used to generate surface force-distance data for the mica/dodecylamine hydrochloride system (Task 2.1.1). Work to characterize the hydrophobicity of this system and the mica/DDOA[sup [minus

  2. Hydrophobic Solvation: Aqueous Methane Solutions

    ERIC Educational Resources Information Center

    Konrod, Oliver; Lankau, Timm

    2007-01-01

    A basic introduction to concept of a solvation shell around an apolar solute as well as its detection is presented. The hydrophobic solvation of toluene is found to be a good teaching example which connects macroscopic, phenomenological thermodynamic results with an atomistic point of view.

  3. Research Directed at Developing a Classical Theory to Describe Isotope Separation of Polyatomic Molecules Illuminated by Intense Infrared Radiation. Final Report for period May 7, 1979 to September 30, 1979; Extension December 31, 1997

    DOE R&D Accomplishments Database

    Lamb, W. E. Jr.

    1981-12-01

    This final report describes research on the theory of isotope separation produced by the illumination of polyatomic molecules by intense infrared laser radiation. This process is investigated by treating the molecule, sulfur hexafluoride, as a system of seven classical particles that obey the Newtonian equations of motion. A minicomputer is used to integrate these differential equations. The particles are acted on by interatomic forces, and by the time-dependent electric field of the laser. We have a very satisfactory expression for the interaction of the laser and the molecule which is compatible with infrared absorption and spectroscopic data. The interatomic potential is capable of improvement, and progress on this problem is still being made. We have made several computer runs of the dynamical behavior of the molecule using a reasonably good model for the interatomic force law. For the laser parameters chosen, we find that typically the molecule passes quickly through the resonance region into the quasi-continuum and even well into the real continuum before dissociation actually occurs. When viewed on a display terminal, the motions are exceedingly complex. As an aid to the visualization of the process, we have made a number of 16 mm movies depicting a three-dimensional representation of the motion of the seven particles. These show even more clearly the enormous complexity of the motions, and make clear the desirability of finding ways of characterizing the motion in simple ways without giving all of the numerical detail. One of the ways to do this is to introduce statistical parameters such as a temperature associated with the distribution of kinetic energies of the single particle. We have made such an analysis of our data runs, and have found favorable indications that such methods will prove useful in keeping track of the dynamical histories.

  4. Preparative-scale isoelectric trapping separations in methanol-water mixtures.

    PubMed

    Shave, Evan; Vigh, Gyula

    2004-05-14

    The typically low aqueous solubilities of small, hydrophobic organic ampholytic molecules limit the production rates that can be achieved in their isoelectric trapping (IET) separations and call for the use of hydro-organic mixtures as solvents. The compatibility of methanol-water mixtures and poly(ethylene terephthalate) substrate-supported isoelectric polyacrylamide hydrogels, developed for binary IET separations in a Gradiflow BF200IET unit, was investigated. The isoelectric polyacrylamide-based hydrogels retained their functional and mechanical integrities when the methanol concentration in the hydro-organic solvent mixture was kept at or below 25% (v/v). The utility of the hydro-organic media was demonstrated in the purification of a hydrophobic ampholytic compound, technical grade 4-hydroxy-3-(morpholinomethyl) benzoic acid. Production rates as high as 7 mg/h were achieved using small, 15 cm2 active surface area isoelectric membranes.

  5. Preparative-scale isoelectric trapping separations in methanol-water mixtures.

    PubMed

    Shave, Evan; Vigh, Gyula

    2004-05-14

    The typically low aqueous solubilities of small, hydrophobic organic ampholytic molecules limit the production rates that can be achieved in their isoelectric trapping (IET) separations and call for the use of hydro-organic mixtures as solvents. The compatibility of methanol-water mixtures and poly(ethylene terephthalate) substrate-supported isoelectric polyacrylamide hydrogels, developed for binary IET separations in a Gradiflow BF200IET unit, was investigated. The isoelectric polyacrylamide-based hydrogels retained their functional and mechanical integrities when the methanol concentration in the hydro-organic solvent mixture was kept at or below 25% (v/v). The utility of the hydro-organic media was demonstrated in the purification of a hydrophobic ampholytic compound, technical grade 4-hydroxy-3-(morpholinomethyl) benzoic acid. Production rates as high as 7 mg/h were achieved using small, 15 cm2 active surface area isoelectric membranes. PMID:15139407

  6. Fabrication of an ionic liquid-based macroporous polymer monolithic column via atom transfer radical polymerization for the separation of small molecules.

    PubMed

    Zhang, Hang; Bai, Ligai; Wei, Zhen; Liu, Sha; Liu, Haiyan; Yan, Hongyuan

    2016-03-01

    A polymer monolithic column was prepared in a stainless steel column (50×4.6mm i.d.) via atom transfer radical polymerization technique using triallyl isocyanurate and ionic liquid (1-allyl-3-methylimidazolium chloride) as co-monomers, ethylene dimethacrylate as cross linking agent, polyethylene glycol 200, 1,4-butanediol, and N, N- dimethylformamide as porogen system, CCl4 as initiator, and FeCl2 as catalyst. The optimized polymer columns were characterized by scanning electron microscope, nitrogen adsorption-desorption instrument, mercury intrusion porosimetry, infrared spectrometer, and thermogravimetric analysis technique. Respectively, all of these factors above could illustrate that the optimized columns had relative uniform macroporous structure and high thermal stability. A series of basic and acidic small molecules, isomers, and homologues were used to evaluate the performance of these monoliths and enhanced column efficiency was obtained. PMID:26717814

  7. Hydrophobic pocket targeting probes for enteroviruses.

    PubMed

    Martikainen, Mari; Salorinne, Kirsi; Lahtinen, Tanja; Malola, Sami; Permi, Perttu; Häkkinen, Hannu; Marjomäki, Varpu

    2015-11-01

    Visualization and tracking of viruses without compromising their functionality is crucial in order to understand virus targeting to cells and tissues, and to understand the subsequent subcellular steps leading to virus uncoating and replication. Enteroviruses are important human pathogens causing a vast number of acute infections, and are also suggested to contribute to the development of chronic diseases like type I diabetes. Here, we demonstrate a novel method to target site-specifically the hydrophobic pocket of enteroviruses. A probe, a derivative of Pleconaril, was developed and conjugated to various labels that enabled the visualization of enteroviruses under light and electron microscopes. The probe mildly stabilized the virus particle by increasing the melting temperature by 1-3 degrees, and caused a delay in the uncoating of the virus in the cellular endosomes, but could not however inhibit the receptor binding, cellular entry or infectivity of the virus. The hydrophobic pocket binding moiety of the probe was shown to bind to echovirus 1 particle by STD and tr-NOESY NMR methods. Furthermore, binding to echovirus 1 and Coxsackievirus A9, and to a lesser extent to Coxsackie virus B3 was verified by using a gold nanocluster labeled probe by TEM analysis. Molecular modelling suggested that the probe fits the hydrophobic pockets of EV1 and CVA9, but not of CVB3 as expected, correlating well with the variations in the infectivity and stability of the virus particles. EV1 conjugated to the fluorescent dye labeled probe was efficiently internalized into the cells. The virus-fluorescent probe conjugate accumulated in the cytoplasmic endosomes and caused infection starting from 6 hours onwards. Remarkably, before and during the time of replication, the fluorescent probe was seen to leak from the virus-positive endosomes and thus separate from the capsid proteins that were left in the endosomes. These results suggest that, like the physiological hydrophobic content

  8. Enhancement of hydrophobic chromophore fluorescence by adsorption to nanospheres

    NASA Astrophysics Data System (ADS)

    Blair, Elizabeth; Carr, Aaron; Krishnan, Rajagopal; Nordlund, Thomas M.

    2003-11-01

    Optical properties of hydrophobic molecules are usually studied in solvents of low dielectric constant. However, biologically or medically important molecules often exist in a mixed hydrophobic/ aqueous environment, e.g., in emulsions or membranes. In order to study optical processes occurring in oily sunscreen agents, octyl salicylate and octyl methoxycinnamate, in a model aqueous/hydrophobic environment, we dispersed the agents in suspensions of polystyrene nanospheres, ranging in diameter from 30 to 1500 nm. The spheres had sulfate functional groups and a low negative charge on the surface. Adsorption of salicylate resulted in a fluorescence intensity enhancement of 6 +/- 0.5 compared to a solution in methanol. The enhancement was independent of sphere diameter. Cinnamate had a much lower enhancement, about 1.5. The enhancement correlates with fluorescence yield vs. dielectric constant in organic solvents: the adsorbed chromophore acts as if it were surrounded by a material of dielectric constant less than 2, in spite of the presence of neighboring water molecules.

  9. Surfactant Facilitated Spreading of Aqueous Drops on Hydrophobic Surfaces

    NASA Technical Reports Server (NTRS)

    Kumar, Nitin; Couzis, Alex; Maldarelli, Charles; Singh, Bhim S. (Technical Monitor)

    2000-01-01

    Microgravity technologies often require aqueous phases to spread over nonwetting hydrophobic solid/surfaces. At a hydrophobic surface, the air/hydrophobic solid tension is low, and the solid/aqueous tension is high. A large contact angle forms as the aqueous/air tension acts together with the solid/air tension to balance the large solid/aqueous tension. The aqueous phase, instead of spreading, is held in a meniscus by the large angle. Surfactants facilitate the wetting of water on hydrophobic surfaces by adsorbing on the water/air and hydrophobic solid/water interfaces and lowering the surface tensions of these interfaces. The tension reductions decrease the contact angle, which increases the equilibrium wetted area. Hydrocarbon surfactants (i.e. amphiphiles with a hydrophobic chain of methylene groups attached to a large polar group to give aqueous solubility) do not reduce significantly the contact angles of the very hydrophobic surfaces such as parafilm or polyethylene. Trisiloxane surfactants (amphiphiles with a hydrophobe consisting of methyl groups linked to a trisiloxane backbone in the form of a disk ((CH3)3-Si-O-Si-O-Si(CH3)3)) and an extended ethoxylate (-(OCH2CH2)n-) polar group in the form of a chain with seven or eight units) can significantly reduce the contact angle of water on a very hydrophobic surface and cause rapid and complete (or nearly complete) spreading (lermed superspreading). The overall goal of the research described in this proposal is to establish and verify a theory for how trisiloxanes cause superspreading, and then use this knowledge as a guide to developing more general hydrocarbon based surfactant systems which superspread and can be used in microgravity. We propose that the trisiloxane surfactants superspread when the siloxane adsorbs, the hydrophobic disk parts of the molecule adsorb onto the surface removing the surface water. Since the cross sectional area of the disk is larger than that of the extended ethoxylate chain, the

  10. Isotope separation by photochromatography

    DOEpatents

    Suslick, K.S.

    1975-10-03

    A photochromatographic method for isotope separation is described. An isotopically mixed molecular species is adsorbed on an adsorptive surface, and the adsorbed molecules are irradiated with radiation of a predetermined wavelength which will selectively excite desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thus separate them from the undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes. (BLM)

  11. Isotope separation by photochromatography

    DOEpatents

    Suslick, Kenneth S.

    1977-01-01

    An isotope separation method which comprises physically adsorbing an isotopically mixed molecular species on an adsorptive surface and irradiating the adsorbed molecules with radiation of a predetermined wavelength which will selectively excite a desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thereby separate them from the unexcited undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes.

  12. Hydrophobic liquid/gas separator for heat pipes

    NASA Technical Reports Server (NTRS)

    Marcus, B. D.

    1972-01-01

    Perforated nonwetting plug of material such as polytetrafluoroethylene is mounted in gas reservoir feed tube, preferably at end which extends into heat pipe condenser section, to prevent liquid from entering gas reservoir of passively controlled heat pipe.

  13. Dry layer formation? Solvent polarity at hydrophobic solid-liquid surfaces

    NASA Astrophysics Data System (ADS)

    Walker, Robert; Zhang, Xiaoyi; Esenturk, Okan

    2002-03-01

    From low-wear, "friction-free" materials to reverse phase chromatography columns to specific protein domains, hydrophobic surfaces are ubiquitous in physics, chemistry and biology. Our efforts to understand how hydrophobic surfaces influence the solvating properties of an adjacent solvent have led us to investigate solvent polarity at a number of weakly associating, solid-liquid interfaces. Second-order nonlinear optical spectroscopy enables experiments to probe the solvent-sensitive excitation energies of adsorbed probe molecules. Comparisons to probe behavior in bulk solution allow us to infer how hydrophobic surfaces have altered properties inside of the solute cavity. Boundaries formed between hydrophobic surfaces and associating or hydrogen bonding solvents show significantly reduced solvent polarity, consistent with proposed models of dry-layer formation. Polar, aprotic liquid-hydrophobic solid interfaces show no evidence of this effect. We can understand this behavior based on the relative imbalance in forces between the solid and liquid phases.

  14. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  15. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  16. Thermodynamics of water entry in hydrophobic channels of carbon nanotubes.

    PubMed

    Kumar, Hemant; Mukherjee, Biswaroop; Lin, Shiang-Tai; Dasgupta, Chandan; Sood, A K; Maiti, Prabal K

    2011-03-28

    Experiments and computer simulations demonstrate that water spontaneously fills the hydrophobic cavity of a carbon nanotube. To gain a quantitative thermodynamic understanding of this phenomenon, we use the recently developed two phase thermodynamics method to compute translational and rotational entropies of confined water molecules inside single-walled carbon nanotubes and show that the increase in energy of a water molecule inside the nanotube is compensated by the gain in its rotational entropy. The confined water is in equilibrium with the bulk water and the Helmholtz free energy per water molecule of confined water is the same as that in the bulk within the accuracy of the simulation results. A comparison of translational and rotational spectra of water molecules confined in carbon nanotubes with that of bulk water shows significant shifts in the positions of the spectral peaks that are directly related to the tube radius.

  17. Behavior of aqueous solutions in hydrophobic confinement studied using molecular simulations

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit

    Biological processes, such as formation of cell membranes, vesicles and folding of protein molecules, entail formation of a predominantly hydrophobic interior devoid of water. These processes occur in crowded aqueous environments comprising of amino acids, carbohydrates, ionic species, protein molecules, etc. Kinetics of these processes involve drying of hydrophobic pockets. Previous studies reveal that the kinetics of evaporation of water in hydrophobic confinement significantly slow down as the confinement gap increases. Presumably, the constituents of aqueous environment in biological systems modulate the kinetics of evaporation of confined water. In this work, we employ forward flux sampling in molecular dynamics simulations to study the role of solutes at different concentrations in modulating the kinetics and mechanism of evaporation of water under hydrophobic confinement. The results of these simulations will be useful for understanding optimum conditions for protein folding and other biological self-assembly processes.

  18. Hydrophobic and hydrophilic interactions in aqueous mixtures of alcohols at a hydrophobic surface.

    PubMed

    Ballal, Deepti; Chapman, Walter G

    2013-09-21

    Aqueous solutions of alcohols are interesting because of their anomalous behavior that is believed to be due to the molecular structuring of water and alcohol around each other in solution. The interfacial structuring and properties are significant for application in alcohol purification processes and biomolecular structure. Here we study aqueous mixtures of short alcohols (methanol, ethanol, 1-propanol, and 2-propanol) at a hydrophobic surface using interfacial statistical associating fluid theory which is a perturbation density functional theory. The addition of a small amount of alcohol decreases the interfacial tension of water drastically. This trend in interfacial tension can be explained by the structure of water and alcohol next to the surface. The hydrophobic group of an added alcohol preferentially goes to the surface preserving the structure of water in the bulk. For a given bulk alcohol concentration, water mixed with the different alcohols has different interfacial tensions with propanol having a lower interfacial tension than methanol and ethanol. 2-propanol is not as effective in decreasing the interfacial tension as 1-propanol because it partitions poorly to the surface due to its larger excluded volume. But for a given surface alcohol mole fraction, all the alcohol mixtures give similar values for interfacial tension. For separation of alcohol from water, methods that take advantage of the high surface mole fraction of alcohol have advantages compared to separation using the vapor in equilibrium with a water-alcohol liquid.

  19. Intrinsic Hydrophobicity of Rammed Earth

    NASA Astrophysics Data System (ADS)

    Holub, M.; Stone, C.; Balintova, M.; Grul, R.

    2015-11-01

    Rammed earth is well known for its vapour diffusion properties, its ability to regulate humidity within the built environment. Rammed earth is also an aesthetically iconic material such as marble or granite and therefore is preferably left exposed. However exposed rammed earth is often coated with silane/siloxane water repellents or the structure is modified architecturally (large roof overhangs) to accommodate for the hydrophilic nature of the material. This paper sets out to find out optimal hydrophobicity for rammed earth based on natural composite fibres and surface coating without adversely affecting the vapour diffusivity of the material. The material is not required to be waterproof, but should resist at least driving rain. In order to evaluate different approaches to increase hydrophobicity of rammed earth surface, peat fibres and four types of repellents were used.

  20. Nanodisks: hydrophobic drug delivery vehicles.

    PubMed

    Ryan, Robert O

    2008-03-01

    Members of the class of exchangeable apolipoproteins possess the unique capacity to transform phospholipid vesicle substrates into nanoscale disk-shaped bilayers. This reaction can proceed in the presence of exogenous hydrophobic biomolecules, resulting in the formation of novel transport vehicles termed nanodisks (NDs). The objective of this study is to describe the structural organization of NDs and evaluate the utility of these complexes as hydrophobic biomolecule transport vehicles. The topics presented focus on two distinct water insoluble drugs, amphotericin B (AMB) and all trans retinoic acid (ATRA). In vitro and in vivo studies reveal that AMB-ND display potent anti-fungal and anti-protozoal activity, while ATRA-ND show promise in the treatment of cancer. The versatility conferred by the presence of a polypeptide component provides opportunities for targeted delivery of ND to cells.

  1. Preparation and characterization of poly(triallyl isocyanurate-co-trimethylolpropane triacrylate) monolith and its applications in the separation of small molecules by liquid chromatography.

    PubMed

    Zhong, Jing; Hao, Mengbei; Li, Ruo; Bai, Ligai; Yang, Gengliang

    2014-03-14

    A new polymeric monolith was prepared in stainless-steel column and fused-silica capillary, respectively, by atom transfer radical polymerization technique. In the polymerization, triallyl isocyanurate (TAIC) was used as the functional monomer; trimethylolpropane triacrylate (TMPTA) as the crosslinking agent; polyethylene glycol 200 and 1,2-propanediol as the co-porogens; carbon tetrachloride as the initiator and ferrous chloride as the catalyst. The conditions of polymerization were optimized. Morphology of the prepared poly(TAIC-co-TMPTA) monolith was investigated by scanning electron microscopy; pore properties were assayed by mercury porosimetry and nitrogen adsorption. The characterization indicated that the prepared reversed-phase monolith possessed uniform structure, good permeability and mechanical stability. The column was used as the stationary phase of reversed phase high performance liquid chromatography (RP-HPLC) and capillary liquid chromatography (CLC) to separate the mixture of aromatic compounds. The new column performed around 125,000 theoretical plates per meter. The column showed good reproducibility: the relative standard deviation values of the retention factor values for aromatic compounds were less than 1.52% (n=7, column-to-column).

  2. Preparation and characterization of poly(triallyl isocyanurate-co-trimethylolpropane triacrylate) monolith and its applications in the separation of small molecules by liquid chromatography.

    PubMed

    Zhong, Jing; Hao, Mengbei; Li, Ruo; Bai, Ligai; Yang, Gengliang

    2014-03-14

    A new polymeric monolith was prepared in stainless-steel column and fused-silica capillary, respectively, by atom transfer radical polymerization technique. In the polymerization, triallyl isocyanurate (TAIC) was used as the functional monomer; trimethylolpropane triacrylate (TMPTA) as the crosslinking agent; polyethylene glycol 200 and 1,2-propanediol as the co-porogens; carbon tetrachloride as the initiator and ferrous chloride as the catalyst. The conditions of polymerization were optimized. Morphology of the prepared poly(TAIC-co-TMPTA) monolith was investigated by scanning electron microscopy; pore properties were assayed by mercury porosimetry and nitrogen adsorption. The characterization indicated that the prepared reversed-phase monolith possessed uniform structure, good permeability and mechanical stability. The column was used as the stationary phase of reversed phase high performance liquid chromatography (RP-HPLC) and capillary liquid chromatography (CLC) to separate the mixture of aromatic compounds. The new column performed around 125,000 theoretical plates per meter. The column showed good reproducibility: the relative standard deviation values of the retention factor values for aromatic compounds were less than 1.52% (n=7, column-to-column). PMID:24556171

  3. The fabrication of monolithic capillary column based on poly (bisphenol A epoxy vinyl ester resin-co-ethylene glycol dimethacrylate) and its applications for the separation of small molecules in high performance liquid chromatography.

    PubMed

    Niu, Wenjing; Wang, Lijuan; Bai, Ligai; Yang, Gengliang

    2013-07-01

    A new polymeric monolith was synthesized in fused-silica capillary by in situ polymerization technique. In the polymerization, bisphenol A epoxy vinyl ester resin (VER) was used as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the crosslinking monomer, 1,4-butanediol, 1-propanol and water as the co-porogens, and azobisisobutyronitrile (AIBN) as the initiator. The conditions of polymerization have been optimized. Morphology of the prepared poly (VER-co-EDMA) monolith was investigated by the scanning electron microscopy (SEM); pore properties were assayed by mercury porosimetry and nitrogen adsorption. The optimized poly (VER-co-EDMA) monolith showed a uniform structure, good permeability and mechanical stability. Then, the column was used as the stationary phase of high performance liquid chromatography (HPLC) to separate the mixture of benzene derivatives. The best column efficiency achieved for phenol was 235790 theoretical plates per meter. Baseline separations of benzene derivatives and halogenated benzene compounds under optimized isocratic mode conditions were achieved with high column efficiency. The column showed good reproducibility: the relative standard deviation (RSD) values based on the retention times (n=3) for run-to-run, column-to-column and batch-to-batch were less than 0.98, 1.68, 5.48%, respectively. Compared with poly (BMA-co-EDMA) monolithic column, the proposed monolith exhibited more efficiency in the separation of small molecules. PMID:23726080

  4. I. Hydrophobic nanoporous silica particles for biomedical applications II. Novel approaches to two-dimensional correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Brumaru, Claudiu Stelian

    Many highly effective drugs display serious side-effects. To limit them, one can contain the drug in tiny containers, which are subsequently delivered toward targets inside the body. The entrapment of drug molecules prevents them from coming in contact with and thus causing damage to normal cells. Inherently, it is difficult to reach 100% efficiency of drug trapping and release when employing physical caps to seal the vehicles. Instead, we propose drug trapping inside the nanopores of hydrophobic silica particles by "hydrophobic trapping". This phenomenon is associated with the repulsive "force field" generated inside nanometer-sized hydrophobic channels that completely prevents aqueous solutions from entering the channels. We demonstrate the excellent trapping efficiency using C18-modified silica particles with 10 nm pores and the anticancer drug doxorubicin. The major challenge in using hydrophobic particles in biological applications is their tendency to cluster in aqueous media. To overcome it, we use surfactants as solubilization means. We have developed protocols that effectively solubilize the outer surface of the particles while preventing surfactant micelles from entering nanopores. Consequently, particles become well-dispersible in aqueous solutions, with the pre-loaded drug safely contained inside nanopores. Nanomaterials exhibit heterogeneity on their surfaces that impact their functional applications. Although techniques such as atomic force microscopy are great tools for studying nanomaterials with their excellent spatial resolution, they cannot probe the inner surface of porous structures. We have established a method of single-molecule ratiometric imaging that is currently the only technique able to provide the nanopolarity of adsorption sites located on the pore surface. We analyze the polarity distribution of adsorptions events for the solvatochromic probe Nile Red at the C18/acetonitrile interface and discover at least two different populations

  5. Biomimetic solution against dewetting in a highly hydrophobic nanopore.

    PubMed

    Picaud, Fabien; Paris, Guillaume; Gharbi, Tijani; Balme, Sébastien; Lepoitevin, Mathilde; Tangaraj, Vidhyadevi; Bechelany, Mikhael; Janot, Jean Marc; Balanzat, Emmanuel; Henn, François

    2016-06-14

    A water molecule is the foundation of life and is the primary compound in every living system. While many of its properties are understood in a bulk solvent, its behavior in a small hydrophobic nanopore still raises fundamental questions. For instance, a wetting/dewetting transition in a hydrophobic solid-state or a polymer nanopore occurs stochastically and can only be prevented by external physical stimuli. Controlling these transitions would be a primary requirement to improve many applications. Some biological channels, such as gramicidin A (gA) proteins, show a high rate of water and ion diffusion in their central subnanochannel while their external surface is highly hydrophobic. The diameter of this channel is significantly smaller than the inner size of the lowest artificial nanopore in which water drying occurs (i.e. 1.4 nm). In this paper, we propose an innovative idea to generate nanopore wetting as a result of which the application of an external field is no longer required. In a nanopore, the drying or wetting of the inner walls occurs randomly (in experiments and in simulations). However, we have shown how the confinement of gA, in a dried hydrophobic nanopore, rapidly generates a stable wetting of the latter. We believe that this simple idea, based on biomimetism, could represent a real breakthrough that could help to improve and develop new nanoscale applications.

  6. Highly efficient hydrophobic titania ceramic membranes for water desalination.

    PubMed

    Kujawa, Joanna; Cerneaux, Sophie; Koter, Stanisław; Kujawski, Wojciech

    2014-08-27

    Hydrophobic titania ceramic membranes (300 kD) were prepared by grafting of C6F13C2H4Si(OC2H5)3 and C12F25C2H4Si(OC2H5)3 molecules and thus applied in membrane distillation (MD) process of NaCl solutions. Grafting efficiency and hydrophobicity were evaluated by contact angle measurement, atomic force microscopy, scanning electron microscopy, nitrogen adsorption/desorption, and liquid entry pressure measurement of water. Desalination of NaCl solutions was performed using the modified hydrophobic membranes in air gap MD (AGMD) and direct contact MD (DCMD) processes in various operating conditions. High values of NaCl retention coefficient (>99%) were reached. The permeate fluxes were in the range 231-3692 g·h(-1)·m(-2), depending on applied experimental conditions. AGMD mode appeared to be more efficient showing higher fluxes and selectivity in desalination. Overall mass transfer coefficients (K) for membranes tested in AGMD were constant over the investigated temperature range. However, K values in DCMD increased at elevated temperature. The hydrophobic layer was also stable after 4 years of exposure to open air. PMID:25084346

  7. Water repellency in hydrophobic nanocapsules--molecular view on dewetting.

    PubMed

    Müller, Achim; Garai, Somenath; Schäffer, Christian; Merca, Alice; Bögge, Hartmut; Al-Karawi, Ahmed Jasim M; Prasad, Thazhe Kootteri

    2014-05-26

    The hydrophobic effect plays a major role in a variety of important phenomena in chemistry, materials science and biology, for instance in protein folding and protein-ligand interactions. Studies--performed within cavities of the unique metal oxide based porous capsules of the type {(pentagon)12(linker)30}≡{(W)W5}12{Mo2(ligand)}30 with different acetate/water ligand ratios--have provided unprecedented results revealing segregation/repellency of the encapsulated "water" from the internal hydrophobic ligand walls of the capsules, while the disordered water molecules, interacting strongly with each other via hydrogen bonding, form in all investigated cases the same type of spherical shell. The present results can be (formally) compared--but only regarding the repellency effect--with the amazing "action" of the (super)hydrophobic Lotus (Nelumbo) leaves, which are self-cleaning based on water repellency resulting in the formation of water droplets picking up dirt. The present results were obtained by constructing deliberately suitable hydrophobic interiors within the mentioned capsules. PMID:24782303

  8. Water repellency in hydrophobic nanocapsules--molecular view on dewetting.

    PubMed

    Müller, Achim; Garai, Somenath; Schäffer, Christian; Merca, Alice; Bögge, Hartmut; Al-Karawi, Ahmed Jasim M; Prasad, Thazhe Kootteri

    2014-05-26

    The hydrophobic effect plays a major role in a variety of important phenomena in chemistry, materials science and biology, for instance in protein folding and protein-ligand interactions. Studies--performed within cavities of the unique metal oxide based porous capsules of the type {(pentagon)12(linker)30}≡{(W)W5}12{Mo2(ligand)}30 with different acetate/water ligand ratios--have provided unprecedented results revealing segregation/repellency of the encapsulated "water" from the internal hydrophobic ligand walls of the capsules, while the disordered water molecules, interacting strongly with each other via hydrogen bonding, form in all investigated cases the same type of spherical shell. The present results can be (formally) compared--but only regarding the repellency effect--with the amazing "action" of the (super)hydrophobic Lotus (Nelumbo) leaves, which are self-cleaning based on water repellency resulting in the formation of water droplets picking up dirt. The present results were obtained by constructing deliberately suitable hydrophobic interiors within the mentioned capsules.

  9. Profile of the Interface between a Hydrophobic Surface and Water

    NASA Astrophysics Data System (ADS)

    Perez-Salas, Ursula; Stalgren, Johan; Majkrzak, Charles; Heinrich, Frank; Toney, Michael; Vanderah, David

    2008-03-01

    Aqueous interfaces are ubiquitous and play a fundamental role in biology, chemistry, and geology. The structure of water near interfaces is of the utmost importance, including chemical reactivity and macromolecular function. Theoretical work by Chandler et al. on polar-apolar interfaces predicts that a water depletion layer exists between a hydrophobic surface and bulk water for hydrophobes larger than ˜20nm2 (a ˜4A in radius apolar molecule). Until now, what the interface really looks like remains in dispute since recent experiments give conflicting results: from complete wetting (no water depletion layer) to a water depletion layer. Those experiments that have found a water depletion layer report 40-70% water in the depletion zone: 40 -70% and a width of ˜3A. However, an alternative interpretation to the profiles exists where no depletion layer is required. By studying hydrophobic SAM surfaces against several water mixtures we obtained the hydrophobic/water profile by phase sensitive neutron reflectivity. With this model independent technique we observe a 2 times wider and drier depletion water layer: 6A thick and 0-25% water. Given the level of disagreement, I will review the topic of immiscible interfaces and show how phase sensitive reflectometry is unique in obtaining nm resolution profiles without fitting bias.

  10. Highly efficient hydrophobic titania ceramic membranes for water desalination.

    PubMed

    Kujawa, Joanna; Cerneaux, Sophie; Koter, Stanisław; Kujawski, Wojciech

    2014-08-27

    Hydrophobic titania ceramic membranes (300 kD) were prepared by grafting of C6F13C2H4Si(OC2H5)3 and C12F25C2H4Si(OC2H5)3 molecules and thus applied in membrane distillation (MD) process of NaCl solutions. Grafting efficiency and hydrophobicity were evaluated by contact angle measurement, atomic force microscopy, scanning electron microscopy, nitrogen adsorption/desorption, and liquid entry pressure measurement of water. Desalination of NaCl solutions was performed using the modified hydrophobic membranes in air gap MD (AGMD) and direct contact MD (DCMD) processes in various operating conditions. High values of NaCl retention coefficient (>99%) were reached. The permeate fluxes were in the range 231-3692 g·h(-1)·m(-2), depending on applied experimental conditions. AGMD mode appeared to be more efficient showing higher fluxes and selectivity in desalination. Overall mass transfer coefficients (K) for membranes tested in AGMD were constant over the investigated temperature range. However, K values in DCMD increased at elevated temperature. The hydrophobic layer was also stable after 4 years of exposure to open air.

  11. Raman Spectroscopic Studies of Clathrate Hydrate Formation in the Presence of Hydrophobized Particles.

    PubMed

    Li, Huijuan; Stanwix, Paul; Aman, Zachary; Johns, Michael; May, Eric; Wang, Liguang

    2016-01-28

    In the present work, Raman spectroscopy was used to study the structure of water molecules in the vicinity of glass particles with different hydrophobicity, immersed in water and in tetrahydrofuran and cyclopentane hydrates. The glass particle surfaces were clean (hydrophilic), coated with N,N-dimethyl-N-octadecyl-3-aminopropyl trimethoxysilyl chloride (partially hydrophobic), or coated with octadecyltrichlorosilane (hydrophobic). The Raman spectra indicate that, prior to nucleation, water molecules in the vicinity of hydrophobic surfaces are more ice-like ordered than those in the bulk liquid or near either hydrophilic or partially hydrophobic surfaces. Furthermore, the degree of hydrogen-bond ordering of water observed prior to hydrate nucleation, as measured by the ratio of the inter- and intramolecular Raman OH bands, was found to have an inverse relationship with the mean induction time for hydrate formation. Following hydration formation, no significant difference in the water molecule structure was observed in the hydrate phase based on their Raman OH bands, irrespective of surface hydrophobicity. These observations made with Raman spectroscopy provide the foundations for a quantitative link between hydrate nucleation promotion and water-ordering near solid surfaces, which could enable direct comparisons with results from corresponding molecular dynamics simulations. PMID:26731126

  12. Hydrophobic-Core Microcapsules and Their Formation

    NASA Technical Reports Server (NTRS)

    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.

  13. Dehydration-Driven Solvent Exposure of Hydrophobic Surfaces as a Driving Force in Peptide Folding

    SciTech Connect

    Daidone, Isabella; Ulmschneider, Martin; DiNola, Alfredo; Amadei, Andrea; Smith, Jeremy C

    2007-09-01

    Recent work has shown that the nature of hydration of pure hydrophobic surfaces changes with the length scale considered: water hydrogen-bonding networks adapt to small exposed hydrophobic species, hydrating or 'wetting' them at relatively high densities, whereas larger hydrophobic areas are 'dewetted' [Chandler D (2005), Nature 29:640-647]. Here we determine whether this effect is also present in peptides by examining the folding of a {beta}-hairpin (the 14-residue amyloidogenic prion protein H1 peptide), using microsecond time-scale molecular dynamics simulations. Two simulation models are compared, one explicitly including the water molecules, which may thus adapt locally to peptide configurations, and the other using a popular continuum approximation, the generalized Born/surface area implicit solvent model. The results obtained show that, in explicit solvent, peptide conformers with high solvent-accessible hydrophobic surface area indeed also have low hydration density around hydrophobic residues, whereas a concomitant higher hydration density around hydrophilic residues is observed. This dewetting effect stabilizes the fully folded {beta}-hairpin state found experimentally. In contrast, the implicit solvent model destabilizes the fully folded hairpin, tending to cluster hydrophobic residues regardless of the size of the exposed hydrophobic surface. Furthermore, the rate of the conformational transitions in the implicit solvent simulation is almost doubled with respect to that of the explicit solvent. The results suggest that dehydration-driven solvent exposure of hydrophobic surfaces may be a significant factor determining peptide conformational equilibria.

  14. Phenylalanine functionalized zwitterionic monolith for hydrophobic interaction electrochromatography.

    PubMed

    Wang, Jiabin; Jia, Wenchao; Lin, Xucong; Wu, Xiaoping; Xie, Zenghong

    2013-12-01

    A novel phenylalanine (Phe) functionalized zwitterionic monolith for hydrophobic electrochromatography was prepared by a two-step procedure involving the synthesis of glycidyl methacrylate based polymer monolith and subsequent on-column chemical modification with Phe via ring-opening reaction of epoxides. Benefitting from the hydrophobicity of both methacrylate-based matrix and aromatic group of Phe, this monolith could exhibit good hydrophobic interaction for the separation. Typical RP chromatographic behavior was observed toward various solutes. The well-controlled cathodic or anodic EOF of the prepared column could be facilely switched by altering the pH values of running buffers. The separation mechanism of this Phe functionalized zwitterionic monolith is discussed in detail. Two mixed-mode mechanisms of RP/cation exchange and RP/anion exchange could be further realized on the same monolith in different pH condition of the mobile phase. Versatile separation capabilities of neutral, basic, and acidic analytes have been successfully achieved in this zwitterionic monolith by CEC method.

  15. Direct Biofluid Analysis Using Hydrophobic Paper Spray Mass Spectrometry.

    PubMed

    Damon, Deidre E; Davis, Kathryn M; Moreira, Camila R; Capone, Patricia; Cruttenden, Riley; Badu-Tawiah, Abraham K

    2016-02-01

    Ambient electrostatic paper spray ionization from a hydrophobic paper occurs when a DC potential is applied to the dry paper triangle. Online liquid/liquid extraction of small organic compounds from a drop of biological fluid present on the dry hydrophobic paper is achieved with an organic spray solvent in under 1 min and utilizes in situ electrostatic-spray ionization for more efficient detection of extracted molecules. Direct analysis of small volumes of biofluids with no sample pretreatment is possible, which is applicable in point-of-care analyses. High sensitivity and quantitative accuracy was achieved for the direct analysis of illicit drugs in 4 μL of raw blood, serum, and whole urine. The study was extended to monitor the activity of alanine transaminase enzyme, a key biomarker for the detection of liver injury in patients (with HIV and tuberculosis) who typically take several medications at once.

  16. A comprehensive study to protein retention in hydrophobic interaction chromatography.

    PubMed

    Baca, Martyna; De Vos, Jelle; Bruylants, Gilles; Bartik, Kristin; Liu, Xiaodong; Cook, Ken; Eeltink, Sebastiaan

    2016-10-01

    The effect of different kosmotropic/chaotropic salt systems on retention characteristics of intact proteins has been examined in hydrophobic interaction chromatography (HIC). The performance was assessed using different column chemistries, i.e., polyalkylamide, alkylamine incorporating hydrophobic moieties, and a butyl chemistry. Selectivity in HIC is mainly governed by the salt concentration and by the molal surface tension increment of the salt. Typically, a linear relationship between the natural logarithm of the retention factor and the salt concentration is obtained. Using a 250mm long column packed with 5μm polyalkylamide functionalized silica particles and applying a 30min linear salt gradient, a peak capacity of 78 was achieved, allowing the baseline separation of seven intact proteins. The hydrophobicity index appeared to be a good indicator to predict the elution order of intact proteins in HIC mode. Furthermore, the effect of adding additives in the mobile phase, such as calcium chloride (stabilizing the 3D conformation of α-lactalbumin) and isopropanol, on retention properties has been assessed. Results indicate that HIC retention is also governed by conformational in the proteins which affect the number of accessible hydrophobic moieties. PMID:27237734

  17. Reversible Hydrophobic to Hydrophilic Transition in Graphene via Water Splitting Induced by UV Irradiation

    PubMed Central

    Xu, Zhemi; Ao, Zhimin; Chu, Dewei; Younis, Adnan; Li, Chang Ming; Li, Sean

    2014-01-01

    Although the reversible wettability transition between hydrophobic and hydrophilic graphene under ultraviolet (UV) irradiation has been observed, the mechanism for this phenomenon remains unclear. In this work, experimental and theoretical investigations demonstrate that the H2O molecules are split into hydrogen and hydroxyl radicals, which are then captured by the graphene surface through chemical binding in an ambient environment under UV irradiation. The dissociative adsorption of H2O molecules induces the wettability transition in graphene from hydrophobic to hydrophilic. Our discovery may hold promise for the potential application of graphene in water splitting. PMID:25245110

  18. Hydrophobic regions on protein surfaces: definition based on hydration shell structure and a quick method for their computation.

    PubMed

    Eisenhaber, F; Argos, P

    1996-12-01

    The hydrophobic part of the solvent-accessible surface of a typical monomeric globular protein consists of a single, large interconnected region formed from faces of apolar atoms and constituting approximately 60% of the solvent-accessible surface area. Therefore, the direct delineation of the hydrophobic surface patches on an atom-wise basis is impossible. Experimental data indicate that, in a two-state hydration model, a protein can be considered to be unified with its first hydration shell in its interaction with bulk water. We show that, if the surface area occupied by water molecules bound at polar protein atoms as generated by AUTOSOL is removed, only about two-thirds of the hydrophobic part of the protein surface remains accessible to bulk solvent. Moreover, the organization of the hydrophobic part of the solvent-accessible surface experiences a drastic change, such that the single interconnected hydrophobic region disintegrates into many smaller patches, i.e. the physical definition of a hydrophobic surface region as unoccupied by first hydration shell water molecules can distinguish between hydrophobic surface clusters and small interconnecting channels. It is these remaining hydrophobic surface pieces that probably play an important role in intra- and intermolecular recognition processes such as ligand binding, protein folding and protein-protein association in solution conditions. These observations have led to the development of an accurate and quick analytical technique for the automatic determination of hydrophobic surface patches of proteins. This technique is not aggravated by the limiting assumptions of the methods for generating explicit water hydration positions. Formation of the hydrophobic surface regions owing to the structure of the first hydration shell can be computationally simulated by a small radial increment in solvent-accessible polar atoms, followed by calculation of the remaining exposed hydrophobic patches. We demonstrate that a

  19. Deuterium isotope effects on hydrophobic interactions: the importance of dispersion interactions in the hydrophobic phase.

    PubMed

    Turowski, Maciej; Yamakawa, Naoki; Meller, Jaroslaw; Kimata, Kazuhiro; Ikegami, Tohru; Hosoya, Ken; Tanaka, Nobuo; Thornton, Edward R

    2003-11-12

    Hydrogen/deuterium isotope effects on hydrophobic binding were examined by means of reversed-phase chromatographic separation of protiated and deuterated isotopologue pairs for a set of 10 nonpolar and low-polarity compounds with 10 stationary phases having alkyl and aryl groups bonded to the silica surface. It was found that protiated compounds bind to nonpolar moieties attached to silica more strongly than deuterated ones, demonstrating that the CH/CD bonds of the solutes are weakened or have less restricted motions when bound in the stationary phase compared with the aqueous solvent (mobile phase). The interactions responsible for binding have been further characterized by studies of the effects of changes in mobile phase composition, temperature dependence of binding, and QSRR (quantitative structure-chromatographic retention relationship) analysis, demonstrating the importance of enthalpic effects in binding and differentiation between the isotopologues. To explain our results showing the active role of the hydrophobic (stationary) phase we propose a plausible model that includes specific contributions from aromatic edge-to-face attractive interactions and attractive interactions of aliphatic groups with the pi clouds of aromatic groups present as the solute or in the stationary phase.

  20. Production of hydrophobic amino acids from biobased resources: wheat gluten and rubber seed proteins.

    PubMed

    Widyarani; Sari, Yessie W; Ratnaningsih, Enny; Sanders, Johan P M; Bruins, Marieke E

    2016-09-01

    Protein hydrolysis enables production of peptides and free amino acids that are suitable for usage in food and feed or can be used as precursors for bulk chemicals. Several essential amino acids for food and feed have hydrophobic side chains; this property may also be exploited for subsequent separation. Here, we present methods for selective production of hydrophobic amino acids from proteins. Selectivity can be achieved by selection of starting material, selection of hydrolysis conditions, and separation of achieved hydrolysate. Several protease combinations were applied for hydrolysis of rubber seed protein concentrate, wheat gluten, and bovine serum albumin (BSA). High degree of hydrolysis (>50 %) could be achieved. Hydrophobic selectivity was influenced by the combination of proteases and by the extent of hydrolysis. Combination of Pronase and Peptidase R showed the highest selectivity towards hydrophobic amino acids, roughly doubling the content of hydrophobic amino acids in the products compared to the original substrates. Hydrophobic selectivity of 0.6 mol-hydrophobic/mol-total free amino acids was observed after 6 h hydrolysis of wheat gluten and 24 h hydrolysis of rubber seed proteins and BSA. The results of experiments with rubber seed proteins and wheat gluten suggest that this process can be applied to agro-industrial residues.

  1. Preparation of hydrophobic organic aeorgels

    DOEpatents

    Baumann, Theodore F.; Satcher, Jr., Joe H.; Gash, Alexander E.

    2004-10-19

    Synthetic methods for the preparation of hydrophobic organics aerogels. One method involves the sol-gel polymerization of 1,3-dimethoxybenzene or 1,3,5-trimethoxybenzene with formaldehyde in non-aqueous solvents. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be dried using either supercritical solvent extraction to generate the new organic aerogels or air dried to produce an xerogel. Other methods involve the sol-gel polymerization of 1,3,5 trihydroxy benzene (phloroglucinol) or 1,3 dihydroxy benzene (resorcinol) and various aldehydes in non-aqueous solvents. These methods use a procedure analogous to the one-step base and two-step base/acid catalyzed polycondensation of phloroglucinol and formaldehyde, but the base catalyst used is triethylamine. These methods can be applied to a variety of other sol-gel precursors and solvent systems. These hydrophobic organics aerogels have numerous application potentials in the field of material absorbers and water-proof insulation.

  2. Preparation of hydrophobic organic aeorgels

    DOEpatents

    Baumann, Theodore F.; Satcher, Jr., Joe H.; Gash, Alexander E.

    2007-11-06

    Synthetic methods for the preparation of hydrophobic organics aerogels. One method involves the sol-gel polymerization of 1,3-dimethoxybenzene or 1,3,5-trimethoxybenzene with formaldehyde in non-aqueous solvents. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be dried using either supercritical solvent extraction to generate the new organic aerogels or air dried to produce an xerogel. Other methods involve the sol-gel polymerization of 1,3,5 trihydroxy benzene (phloroglucinol) or 1,3 dihydroxy benzene (resorcinol) and various aldehydes in non-aqueous solvents. These methods use a procedure analogous to the one-step base and two-step base/acid catalyzed polycondensation of phloroglucinol and formaldehyde, but the base catalyst used is triethylamine. These methods can be applied to a variety of other sol-gel precursors and solvent systems. These hydrophobic organics aerogels have numerous application potentials in the field of material absorbers and water-proof insulation.

  3. Order and correlation contributions to the entropy of hydrophobic solvation

    SciTech Connect

    Liu, Maoyuan; Besford, Quinn Alexander; Mulvaney, Thomas; Gray-Weale, Angus

    2015-03-21

    The entropy of hydrophobic solvation has been explained as the result of ordered solvation structures, of hydrogen bonds, of the small size of the water molecule, of dispersion forces, and of solvent density fluctuations. We report a new approach to the calculation of the entropy of hydrophobic solvation, along with tests of and comparisons to several other methods. The methods are assessed in the light of the available thermodynamic and spectroscopic information on the effects of temperature on hydrophobic solvation. Five model hydrophobes in SPC/E water give benchmark solvation entropies via Widom’s test-particle insertion method, and other methods and models are tested against these particle-insertion results. Entropies associated with distributions of tetrahedral order, of electric field, and of solvent dipole orientations are examined. We find these contributions are small compared to the benchmark particle-insertion entropy. Competitive with or better than other theories in accuracy, but with no free parameters, is the new estimate of the entropy contributed by correlations between dipole moments. Dipole correlations account for most of the hydrophobic solvation entropy for all models studied and capture the distinctive temperature dependence seen in thermodynamic and spectroscopic experiments. Entropies based on pair and many-body correlations in number density approach the correct magnitudes but fail to describe temperature and size dependences, respectively. Hydrogen-bond definitions and free energies that best reproduce entropies from simulations are reported, but it is difficult to choose one hydrogen bond model that fits a variety of experiments. The use of information theory, scaled-particle theory, and related methods is discussed briefly. Our results provide a test of the Frank-Evans hypothesis that the negative solvation entropy is due to structured water near the solute, complement the spectroscopic detection of that solvation structure by

  4. Order and correlation contributions to the entropy of hydrophobic solvation

    NASA Astrophysics Data System (ADS)

    Liu, Maoyuan; Besford, Quinn Alexander; Mulvaney, Thomas; Gray-Weale, Angus

    2015-03-01

    The entropy of hydrophobic solvation has been explained as the result of ordered solvation structures, of hydrogen bonds, of the small size of the water molecule, of dispersion forces, and of solvent density fluctuations. We report a new approach to the calculation of the entropy of hydrophobic solvation, along with tests of and comparisons to several other methods. The methods are assessed in the light of the available thermodynamic and spectroscopic information on the effects of temperature on hydrophobic solvation. Five model hydrophobes in SPC/E water give benchmark solvation entropies via Widom's test-particle insertion method, and other methods and models are tested against these particle-insertion results. Entropies associated with distributions of tetrahedral order, of electric field, and of solvent dipole orientations are examined. We find these contributions are small compared to the benchmark particle-insertion entropy. Competitive with or better than other theories in accuracy, but with no free parameters, is the new estimate of the entropy contributed by correlations between dipole moments. Dipole correlations account for most of the hydrophobic solvation entropy for all models studied and capture the distinctive temperature dependence seen in thermodynamic and spectroscopic experiments. Entropies based on pair and many-body correlations in number density approach the correct magnitudes but fail to describe temperature and size dependences, respectively. Hydrogen-bond definitions and free energies that best reproduce entropies from simulations are reported, but it is difficult to choose one hydrogen bond model that fits a variety of experiments. The use of information theory, scaled-particle theory, and related methods is discussed briefly. Our results provide a test of the Frank-Evans hypothesis that the negative solvation entropy is due to structured water near the solute, complement the spectroscopic detection of that solvation structure by

  5. Molecule nanoweaver

    DOEpatents

    Gerald, II; Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2009-03-10

    A method, apparatus, and system for constructing uniform macroscopic films with tailored geometric assemblies of molecules on the nanometer scale. The method, apparatus, and system include providing starting molecules of selected character, applying one or more force fields to the molecules to cause them to order and condense with NMR spectra and images being used to monitor progress in creating the desired geometrical assembly and functionality of molecules that comprise the films.

  6. Surfactant Facilitated Spreading of Aqueous Drops on Hydrophobic Surfaces

    NASA Technical Reports Server (NTRS)

    Kumar, Nitin; Couzis, Alex; Maldareili, Charles; Singh, Bhim (Technical Monitor)

    2001-01-01

    Microgravity technologies often require aqueous phases to spread over nonwetting hydrophobic solid surfaces. Surfactants facilitate the wetting of water on hydrophobic surfaces by adsorbing on the water/air and hydrophobic solid/water interfaces and lowering the surface tensions of these interfaces. The tension reductions decrease the contact angle, which increases the equilibrium wetted area. Hydrocarbon surfactants; (i.e., amphiphiles with a hydrophobic moiety consisting of an extended chain of (aliphatic) methylene -CH2- groups attached to a large polar group to give aqueous solubility) are capable of reducing the contact angles on surfaces which are not very hydrophobic, but do not reduce significantly the contact angles of the very hydrophobic surfaces such as parafilm, polyethylene or self assembled monolayers. Trisiloxane surfactants (amphiphiles with a hydrophobe consisting of methyl groups linked to a trisiloxane backbone in the form of a disk ((CH3)3-Si-O-Si-O-Si(CH3)3) and an extended ethoxylate (-(OCH2CH2)a-) polar group in the form of a chain with four or eight units) can significantly reduce the contact angle of water on a very hydrophobic surface and cause rapid and complete (or nearly complete) spreading (termed superspreading). The overall goal of the research described in this proposal is to establish and verify a theory for how trisiloxanes cause superspreading, and then use this knowledge as a guide to developing more general hydrocarbon based surfactant systems which superspread. We propose that the trisiloxane surfactants superspread because their structure allows them to strongly lower the high hydrophobic solid/aqueous tension when they adsorb to the solid surface. When the siloxane adsorbs, the hydrophobic disk parts of the molecule adsorb onto the surface removing the surface water. Since the cross-sectional area of the disk is larger than that of the extended ethoxylate chain, the disks can form a space-filling mat on the surface which

  7. Effect of water-water hydrogen bonding on the hydrophobic hydration of large-scale particles and its temperature dependence.

    PubMed

    Djikaev, Y S; Ruckenstein, E

    2012-03-01

    We present a theoretical model for the effect of water hydrogen bonding on the thermodynamics of hydrophobic hydration. The model is based on a combination of the classical density functional theory with the recently developed probabilistic approach to water hydrogen bonding near a hydrophobic surface. This combination allows one to determine the distribution of water molecules in the vicinity of a hydrophobic particle and calculate the thermodynamic quantities of hydrophobic hydration as well as their temperature dependence. The probabilistic approach allows one to implement the effect of the hydrogen bonding ability of water molecules on their interaction with the hydrophobic surface into the formalism of density functional theory. This effect arises because the number and energy of hydrogen bonds that a water molecule forms near a hydrophobic surface differ from their bulk values. Such alteration gives rise to a hydrogen bond contribution to the external potential field whereto a water molecule is subjected in that vicinity. This contribution is shown to play a dominant role in the interaction of a water molecule with the surface. Our approach predicts that in the temperature range from 293 to 333 K: (a) the free energy of hydration of a planar hydrophobic surface in a model liquid water increases with increasing temperature (although its ratio to the temperature decreases); (b) the hydration process is unfavorable both enthalpically and entropically; (c) the entropic contribution to the hydration free energy is much smaller than the enthalpic one and decreases with increasing temperature, potentially becoming negative. The latter is indirectly supported by the experimental observation that under some conditions the hydration of a molecular hydrophobe is entropically favorable as well as by the molecular dynamics simulations predicting positive hydration entropy for sufficiently large hydrophobes.

  8. Stability of proteins inside a hydrophobic cavity

    NASA Astrophysics Data System (ADS)

    Radhakrishna, Mithun; Sharma, Sumit; Kumar, Sanat K.

    2011-03-01

    Previous studies have shown that enclosing a protein in an athermal cavity stabilizes the protein against reversible unfolding by virtue of eliminating many open chain conformations. Examples of such confined spaces include pores in chromatographic columns, Anfinsen's cage in Chaperonins, interiors of Ribosomes or regions of steric occlusion inside cells. However, the situation is more complex inside a hydrophobic cavity. The protein has a tendency to adsorb on the surface of the hydrophobic cavity, but at the same time it loses conformational entropy because of confinement. We study this system using a simple Hydrophobic Polar (HP) lattice protein model. Canonical Monte Carlo (MC) simulations at different temperatures and surface hydrophobicity show that proteins are stabilized at low and moderate hydrophobicity upon adsorption. The range of surface hydrophobicity over which a protein is stable increases with a decrease in radius of the cavity.

  9. How specific halide adsorption varies hydrophobic interactions.

    PubMed

    Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus

    2016-03-11

    Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

  10. Hydrophobic coatings for MEMS applications

    NASA Astrophysics Data System (ADS)

    Doms, M.; Feindt, H.; Kuipers, W. J.; Shewtanasoontorn, D.; Matar, A. S.; Brinkhues, S.; Welton, R. H.; Mueller, J.

    2008-05-01

    Different kinds of thin-film coatings were investigated with regard to their applicability as hydrophobic coatings for MEMS. The films were deposited onto silicon and borosilicate glass substrates by spincoating of Dyneon™ PTFE and PFA, plasmapolymerization of HMDS-N and C4F8 as well as liquid-phase and vapor-phase coating of SAMs from DDMS, FDTS, FOTS and Geleste Aquaphobe™ CM. The layer properties were analyzed using profilometry, FTIR, SEM and contact angle measurements. Furthermore, the adhesion of the layers to the substrates was determined in an acetone ultrasonic bath. The influence of various deposition process parameters on the properties of the films was investigated. As these layers can be used in microfluidic systems, as water-repellent layers and as anti-stiction coatings, they are suited for versatile fields of application.

  11. Infrared spectral marker bands characterizing a transient water wire inside a hydrophobic membrane protein

    SciTech Connect

    Wolf, Steffen; Gerwert, Klaus; Freier, Erik; Cui, Qiang

    2014-12-14

    Proton conduction along protein-bound “water wires” is an essential feature in membrane proteins. Here, we analyze in detail a transient water wire, which conducts protons via a hydrophobic barrier within a membrane protein to create a proton gradient. It is formed only for a millisecond out of three water molecules distributed at inactive positions in a polar environment in the ground state. The movement into a hydrophobic environment causes characteristic shifts of the water bands reflecting their different chemical properties. These band shifts are identified by time-resolved Fourier Transform Infrared difference spectroscopy and analyzed by biomolecular Quantum Mechanical/Molecular Mechanical simulations. A non-hydrogen bonded (“dangling”) O–H stretching vibration band and a broad continuum absorbance caused by a combined vibration along the water wire are identified as characteristic marker bands of such water wires in a hydrophobic environment. The results provide a basic understanding of water wires in hydrophobic environments.

  12. Enhancement of Water Evaporation on Solid Surfaces with Nanoscale Hydrophobic-Hydrophilic Patterns.

    PubMed

    Wan, Rongzheng; Wang, Chunlei; Lei, Xiaoling; Zhou, Guoquan; Fang, Haiping

    2015-11-01

    Using molecular dynamics simulations, we show that the evaporation of nanoscale water on hydrophobic-hydrophilic patterned surfaces is unexpectedly faster than that on any surfaces with uniform wettability. The key to this phenomenon is that, on the patterned surface, the evaporation rate from the hydrophilic region only slightly decreases due to the correspondingly increased water thickness; meanwhile, a considerable number of water molecules evaporate from the hydrophobic region despite the lack of water film. Most of the evaporated water from the hydrophobic region originates from the hydrophilic region by diffusing across the contact lines. Further analysis shows that the evaporation rate from the hydrophobic region is approximately proportional to the total length of the contact lines.

  13. Molecular simulation studies of hydrophobic gating in nanopores and ion channels.

    PubMed

    Trick, Jemma L; Aryal, Prafulla; Tucker, Stephen J; Sansom, Mark S P

    2015-04-01

    Gating in channels and nanopores plays a key role in regulating flow of ions across membranes. Molecular simulations provide a 'computational microscope' which enables us to examine the physical nature of gating mechanisms at the level of the single channel molecule. Water enclosed within the confines of a nanoscale pore may exhibit unexpected behaviour. In particular, if the molecular surfaces lining the pore are hydrophobic this promotes de-wetting of the pore. De-wetting is observed as stochastic liquid-vapour transitions within a pore, and may lead to functional closure of a pore to the flow of ions and/or water. Such behaviour was first observed in simulations of simple model nanopores and referred to as 'hydrophobic gating'. Simulations of both the nicotinic acetylcholine receptor and of TWIK-1 potassium channels (the latter alongside experimental studies) suggest hydrophobic gating may occur in some biological ion channels. Current studies are focused on designing hydrophobic gates into biomimetic nanopores.

  14. Hydrophobic core/hydrophilic shell structured mesoporous silica nanospheres: enhanced adsorption of organic compounds from water.

    PubMed

    Li, Shuru; Jiao, Xuan; Yang, Hengquan

    2013-01-29

    Inspired by the structure features of micelle, we attempt to synthesize a novel functionalized mesoporous silica nanosphere consisting of a hydrophobic core and a hydrophilic shell. The obtained solid materials were structurally confirmed by N(2) sorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Their compositions were characterized by Fourier transfer infrared spectroscopy (FT-IR), solid state NMR, X-ray photoelectron spectroscopy (XPS), and elemental analysis. Its fundamental properties such as dispersibility in water or organic phase, wettability, and adsorption ability toward hydrophobic organics in water were investigated. It was revealed that these important properties could be facilely adjusted through varying structure and composition. In particular, these materials showed much better adsorption ability toward hydrophobic organic molecules in water than conventional monofunctionalized mesoporous materials, owing to possessing the hydrophobic/hydrophilic domain-segregated and hierarchically functionalized mesoporous structures. The intriguing properties would make mesoporous materials more accessible to many important applications, especially in aqueous systems.

  15. Three-phase microemulsion/sol-gel system for aqueous catalysis with hydrophobic chemicals.

    PubMed

    Abu-Reziq, Raed; Blum, Jochanan; Avnir, David

    2004-02-20

    A facile three-phase transport process is described that allows to carry out catalytic reactions in water, whereby all components are hydrophobic. According to this process a hydrophobic substrate is microemulsified in water and subjected to an organometallic catalyst, which is entrapped within a partially hydrophobized sol-gel matrix. The surfactant molecules, which carry the hydrophobic substrate, adsorb/desorb reversibly on the surface of the sol-gel matrix breaking the micellar structure, spilling their substrate load into the porous medium that contains the catalyst. A catalytic reaction then takes place within the ceramic material to form the desired products that are extracted by the desorbing surfactant, carrying the emulsified product back into the solution. The method is general and versatile and has been demonstrated with the catalytic hydrogenations of alkenes, alkynes, aromatic C=C bonds, and nitro and cyano groups.

  16. Self-degrading niosomes for encapsulation of hydrophilic and hydrophobic drugs: An efficient carrier for cancer multi-drug delivery.

    PubMed

    Sharma, Varsha; Anandhakumar, Sundaramurthy; Sasidharan, Manickam

    2015-11-01

    In this study, we have examined the encapsulation and release of hydrophilic and hydrophobic drugs in self-degrading niosomes as a unique method for anticancer therapy. Niosomes were prepared by amphiphilic self-assembly of Tween 80 and cholesterol through film hydration method. Encapsulation studies with two active molecules curcumin and doxorubicin hydrochloride (Dox) showed that curcumin is supposed to accumulate in the shell whereas Dox accumulates in the inner aqueous core of the niosome. Confocal studies indicated that nile red adsorbs preferentially to the head group of the Tween 80 and forms two separate layers in the shell. It was also seen that the niosomes undergo self-degradation in PBS through a sequential process, forming interconnected pores followed by complete collapse after 1week. The release profile shows two phases: i) initial Dox release in the first two days, followed by ii) curcumin release over 7days. Enhanced (synergistic) cytotoxicity was observed for dual-drug loaded niosomes against HeLa cell lines. Thus these niosomes are shown to offer a promising delivery system for hydrophobic and hydrophilic drugs collectively.

  17. Phase Transfer of Polystyrene- b-poly(ethylene oxide) Polymersomes from a Hydrophobic Ionic Liquid to Water

    NASA Astrophysics Data System (ADS)

    So, Soonyong; Lodge, Timothy

    2015-03-01

    The phase transfer of molecules and supramolecular assemblies from one phase to the other in a biphasic system is desirable for various applications such as catalysis, separation, and delivery. Herein, we describe the phase transfer of polystyrene- b-poly(ethylene oxide) (PS-PEO) polymersomes from a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]), into water. The phase transfer behavior of PS-PEO polymersomes was studied systematically by varying the molecular weight of PS and the PEO volume fraction of the PS-PEO. We demonstrate a general boundary for the phase transfer in terms of a reduced tethering density for PEO, which is independent of the molecular weight of the hydrophobic PS. The tethering density can be increased by increasing the block length of PEO and the size of the polymersomes, and the increased tethering density induces the phase transfer. This phase transfer were also analyzed thermodynamically with the free energy difference of the polymersomes in [EMIM][TFSI] and water. Higher grafting density can reduce the interfacial tension between PS and water, and leads the polymersomes to transfer from [EMIM][TFSI] to water at room temperature.

  18. Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene.

    PubMed

    Strong, Steven E; Eaves, Joel D

    2016-05-19

    Mirroring their role in electrical and optical physics, two-dimensional crystals are emerging as novel platforms for fluid separations and water desalination, which are hydrodynamic processes that occur in nanoscale environments. For numerical simulation to play a predictive and descriptive role, one must have theoretically sound methods that span orders of magnitude in physical scales, from the atomistic motions of particles inside the channels to the large-scale hydrodynamic gradients that drive transport. Here, we use constraint dynamics to derive a nonequilibrium molecular dynamics method for simulating steady-state mass flow of a fluid moving through the nanoscopic spaces of a porous solid. After validating our method on a model system, we use it to study the hydrophobic effect of water moving through pores of electrically doped single-layer graphene. The trend in permeability that we calculate does not follow the hydrophobicity of the membrane but is instead governed by a crossover between two competing molecular transport mechanisms.

  19. Cononsolvency behavior of hydrophobes in water + methanol mixtures.

    PubMed

    Mochizuki, Kenji; Koga, Kenichiro

    2016-06-28

    The molecular origin of cononsolvency behavior is explored using molecular dynamics simulations. Cononsolvency behavior in aggregations of methane molecules and conformational changes of those clusters dissolved in water + methanol mixtures are confirmed by re-entrant changes in the solvent-mediated interactions with increasing methanol concentration. The results indicate that the cononsolvency behavior arises from the solute-solute hydrophobic interactions rather than other interactions such as solute-solvent hydrophilic interactions. Furthermore, we show that even the van der Waals interaction is not necessary to induce the cononsolvency behavior by investigating the dimerization process of repulsive cavities. The non-monotonic change of the solvent-mediated interaction results from the difference in the concentration dependencies of excess chemical potentials between an isolated methane and methane clusters. The concentration dependencies of the excess chemical potentials are decomposed into contributions from various intermolecular effective interactions through the framework of the Kirkwood-Buff theory, and then we show that the change of the relative magnitude between hydrophobe-methanol and hydrophobe-water effective interactions with increasing methanol concentration is responsible for the cononsolvency behavior. PMID:27251342

  20. Droplet nucleation on a well-defined hydrophilic-hydrophobic surface of 10 nm order resolution.

    PubMed

    Yamada, Yutaka; Ikuta, Tatsuya; Nishiyama, Takashi; Takahashi, Koji; Takata, Yasuyuki

    2014-12-01

    Water condensation on a hybrid hydrophilic-hydrophobic surface was investigated to reveal nucleation mechanisms at the microscale. Focused ion beam (FIB) irradiation was used to change the wettability of the hydrophobic surface with 10 nm order spatial resolution. Condensation experiments were conducted using environmental scanning electron microscopy; droplets, with a minimum diameter of 800 nm, lined up on the FIB-irradiated hydrophilic lines. The heterogeneous nucleation theory was extended to consider the water molecules attracted to the hydrophilic area, thereby enabling explanation of the nucleation mechanism under unsaturated conditions. Our results showed that the effective surface coverage of the water molecules on the hydrophilic region was 0.1-1.1 at 0.0 °C and 560 Pa and was dependent on the width of the FIB-irradiated hydrophilic lines and hydrophobic area. The droplet nucleation mechanism unveiled in this work would enable the design of new surfaces with enhanced dropwise condensation heat transfer.

  1. Hydrophobic drug delivery by self-assembling triblock copolymer-derived nanospheres.

    PubMed

    Sheihet, Larisa; Dubin, Robert A; Devore, David; Kohn, Joachim

    2005-01-01

    We describe the synthesis and characterization of a family of biocompatible ABA-triblock copolymers that comprised of hydrophilic A-blocks of poly(ethylene glycol) and hydrophobic B-blocks of oligomers of suberic acid and desaminotyrosyl-tyrosine esters. The triblock copolymers spontaneously self-assemble in aqueous solution into nanospheres, with hydrodynamic diameters between 40 and 70 nm, that do not dissociate under chromatographic and ultracentrifugation conditions. These nanospheres form strong complexes with hydrophobic molecules, including the fluorescent dye 5-dodecanoylaminofluorescein (DAF) and the antitumor drug, paclitaxel, but not with hydrophilic molecules such as fluorescein and Oregon Green. The nanosphere-paclitaxel complexes retain in vitro the high antiproliferative activity of paclitaxel, demonstrating that these nanospheres may be useful for delivery of the hydrophobic drugs.

  2. Composite, nanostructured, super-hydrophobic material

    DOEpatents

    D'Urso, Brian R.; Simpson, John T.

    2007-08-21

    A hydrophobic disordered composite material having a protrusive surface feature includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wherein the protrusive phase protrudes from the surface to form a protrusive surface feature, the protrusive feature being hydrophobic.

  3. Single-point mutation detection in RNA extracts using gold nanoparticles modified with hydrophobic molecular beacon-like structures.

    PubMed

    Latorre, Alfonso; Posch, Christian; Garcimartín, Yolanda; Ortiz-Urda, Susana; Somoza, Álvaro

    2014-03-21

    Gold nanoparticles functionalized with oligonucleotides that bear a cholesterol group are used as gene sensors. The hydrophobic molecule is buried inside the nanostructure but when the complementary RNA sequence is present the structure unfolds exposing the cholesterol group to the water molecules. This rearrangement leads to the aggregation of the nanostructures.

  4. Dynamics of Wetting of Ultra Hydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    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.

  5. Understanding the mutual impact of interaction between hydrophobic nanoparticles and pulmonary surfactant monolayer.

    PubMed

    Sachan, Amit K; Galla, Hans-Joachim

    2014-03-26

    Interaction between hydrophobic nanoparticles (NPs) and a pulmonary surfactant (PS) film leads to a shift in molecular packing of surfactant molecules in the PS film around the interacting NPs. The resultant structural arrangement of surfactants around the NPs may be a potential structural factor responsible for their high retention ability within the film. Moreover, during this interaction, surfactant molecules coat the NPs and change their surface properties.

  6. Hydration and hydrogen bond network of water around hydrophobic surface investigated by terahertz spectroscopy.

    PubMed

    Shiraga, K; Suzuki, T; Kondo, N; Ogawa, Y

    2014-12-21

    Water conformation around hydrophobic side chains of four amino acids (glycine, L-alanine, L-aminobutyric acid, and L-norvaline) was investigated via changes in complex dielectric constant in the terahertz (THz) region. Each of these amino acids has the same hydrophilic backbone, with successive additions of hydrophobic straight methylene groups (-CH2-) to the side chain. Changes in the degree of hydration (number of dynamically retarded water molecules relative to bulk water) and the structural conformation of the water hydrogen bond (HB) network related to the number of methylene groups were quantitatively measured. Since dielectric responses in the THz region represent water relaxations and water HB vibrations at a sub-picosecond and picosecond timescale, these measurements characterized the water relaxations and HB vibrations perturbed by the methylene apolar groups. We found each successive straight -CH2- group on the side chain restrained approximately two hydrophobic hydration water molecules. Additionally, the number of non-hydrogen-bonded (NHB) water molecules increased slightly around these hydrophobic side chains. The latter result seems to contradict the iceberg model proposed by Frank and Evans, where water molecules are said to be more ordered around apolar surfaces. Furthermore, we compared the water-hydrophilic interactions of the hydrophilic amino acid backbone with those with the water-hydrophobic interactions around the side chains. As the hydrophobicity of the side chain increased, the ordering of the surrounding water HB network was altered from that surrounding the hydrophilic amino acid backbone, thereby diminishing the fraction of NHB water and ordering the surrounding tetrahedral water HB network.

  7. Hydration and hydrogen bond network of water around hydrophobic surface investigated by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Shiraga, K.; Suzuki, T.; Kondo, N.; Ogawa, Y.

    2014-12-01

    Water conformation around hydrophobic side chains of four amino acids (glycine, L-alanine, L-aminobutyric acid, and L-norvaline) was investigated via changes in complex dielectric constant in the terahertz (THz) region. Each of these amino acids has the same hydrophilic backbone, with successive additions of hydrophobic straight methylene groups (-CH2-) to the side chain. Changes in the degree of hydration (number of dynamically retarded water molecules relative to bulk water) and the structural conformation of the water hydrogen bond (HB) network related to the number of methylene groups were quantitatively measured. Since dielectric responses in the THz region represent water relaxations and water HB vibrations at a sub-picosecond and picosecond timescale, these measurements characterized the water relaxations and HB vibrations perturbed by the methylene apolar groups. We found each successive straight -CH2- group on the side chain restrained approximately two hydrophobic hydration water molecules. Additionally, the number of non-hydrogen-bonded (NHB) water molecules increased slightly around these hydrophobic side chains. The latter result seems to contradict the iceberg model proposed by Frank and Evans, where water molecules are said to be more ordered around apolar surfaces. Furthermore, we compared the water-hydrophilic interactions of the hydrophilic amino acid backbone with those with the water-hydrophobic interactions around the side chains. As the hydrophobicity of the side chain increased, the ordering of the surrounding water HB network was altered from that surrounding the hydrophilic amino acid backbone, thereby diminishing the fraction of NHB water and ordering the surrounding tetrahedral water HB network.

  8. Transport properties of simple organic molecules in a transmembrane cyclic peptide nanotube.

    PubMed

    Xu, Jian; Fan, Jian Fen; Zhang, Ming Ming; Weng, Pei Pei; Lin, Hui Fang

    2016-05-01

    Multiple molecular dynamics simulations have been performed to explore the transport properties of single methane, methanol, and ethanol molecules through the water-filled transmembrane cyclic peptide nanotube (CPNT) of 8 × (WL)₄-POPE, as well as the potential application of this CPNT in the separation of an alcohol/water mixture. Molecular size and hydrophilicity/hydrophobicity were found to significantly influence molecular diffusion behavior in the channel. Methane and ethanol display more explicit distributions in midplane regions, while methanol mainly occurs in α-plane zones. Methane and ethanol drift faster near an α-plane zone, whereas methanol diffuses uniformly throughout the whole transmembrane region. The dipole orientation of channel methanol is significantly affected by the bare carbonyl groups at the tube mouths and flips mainly in gap 4, whereas the rotation of ethanol is blocked. Ball-shaped hydrophobic methane experiences more flips in gap 4. The PMF (potential of mean force) profiles of the three organic molecules disclose their different diffusion behaviors in the CPNT. Amphiphilic alcohols are able to form direct H-bonds with channel water and the tube. Both single and double water bridges with the tube were observed in the methanol and ethanol systems. The different adsorption behaviors of the alcohols and water in the dehydrated CPNT may lead to the potential application of the CPNT as a means of separating alcohols from water. PMID:27083567

  9. Controlling wetting and self-assembly dynamics by tailored hydrophobic and oleophobic surfaces.

    PubMed

    Miele, Ermanno; Malerba, Mario; Dipalo, Michele; Rondanina, Eliana; Toma, Andrea; De Angelis, Francesco

    2014-06-25

    Tailored hydrophobic and oleophobic surfaces are exploited for controlling the wetting behaviour and evaporation process of solution dropped on them. This enables molecules and nano-objects that are dissolved in water or organic solvents to be delivered and arranged in a well-defined 2D layout. PMID:24711259

  10. Controlling wetting and self-assembly dynamics by tailored hydrophobic and oleophobic surfaces.

    PubMed

    Miele, Ermanno; Malerba, Mario; Dipalo, Michele; Rondanina, Eliana; Toma, Andrea; De Angelis, Francesco

    2014-06-25

    Tailored hydrophobic and oleophobic surfaces are exploited for controlling the wetting behaviour and evaporation process of solution dropped on them. This enables molecules and nano-objects that are dissolved in water or organic solvents to be delivered and arranged in a well-defined 2D layout.

  11. Hydrophobic and moisture-stable metal-organic frameworks.

    PubMed

    Fernandez, Carlos A; Nune, Satish K; Annapureddy, Harsha V; Dang, Liem X; McGrail, B Peter; Zheng, Feng; Polikarpov, Evgueni; King, David L; Freeman, Charles; Brooks, Kriston P

    2015-08-14

    Metal-organic frameworks (MOFs) have proved to be very attractive for applications including gas storage, separation, sensing and catalysis. In particular, CO(2) separation from flue gas in post-combustion processes is one of the main focuses of research among the scientific community. One of the major issues that are preventing the successful commercialization of these novel materials is their high affinity towards water that not only compromises gas sorption capacity but also the chemical stability. In this paper, we demonstrate a novel post-synthesis modification approach to modify MOFs towards increasing hydrophobic behaviour and chemical stability against moisture without compromising CO(2) sorption capacity. Our approach consists of incorporating hydrophobic moieties on the external surface of the MOFs via physical adsorption. The rationale behind this concept is to increase the surface hydrophobicity in the porous materials without the need of introducing bulky functionalities inside the pore which compromises the sorption capacity toward other gases. We herein report preliminary results on routinely studied MOF materials [MIL-101(Cr) and NiDOBDC] demonstrating that the polymer-modified MOFs retain CO(2) sorption capacity while reducing the water adsorption up to three times, with respect to the un-modified materials, via an equilibrium effect. Furthermore, the water stability of the polymer-functionalized MOFs is significantly higher than the water stability of the bare material. Molecular dynamic simulations demonstrated that this equilibrium effect implies a fundamental and permanent change in the water sorption capacity of MOFs. This approach can also be employed to render moisture stability and selectivity to MOFs that find applications in gas separations, catalysis and sensing where water plays a critical role in compromising MOF performance and recyclability. PMID:25970023

  12. Characterization of hydrophobic nanoporous particle liquids for energy absorption

    NASA Astrophysics Data System (ADS)

    Hsu, Yi; Liu, Yingtao

    2016-04-01

    Recently, the development of hydrophobic nanoporous technologies has drawn increased attention, especially for the applications of energy absorption and impact protection. Although significant amount of research has been conducted to synthesis and characterize materials to protect structures from impact damage, the tradition methods focused on converting kinetic energy to other forms, such as heat and cell buckling. Due to their high energy absorption efficiency, hydrophobic nanoporous particle liquids (NPLs) are one of the most attractive impact mitigation materials. During impact, such particles directly trap liquid molecules inside the non-wetting surface of nanopores in the particles. The captured impact energy is simply stored temporarily and isolated from the original energy transmission path. In this paper we will investigate the energy absorption efficiency of combinations of silica nanoporous particles and with multiple liquids. Inorganic particles, such as nanoporous silica, are characterized using scanning electron microscopy. Small molecule promoters, such as methanol and ethanol, are introduced to the prepared NPLs. Their effects on the energy absorption efficiency are studied in this paper. NPLs are prepared by dispersing the studied materials in deionized water. Energy absorption efficiency of these liquids are experimentally characterized using an Instron mechanical testing frame and in-house develop stainless steel hydraulic cylinder system.

  13. Quantification of hydrophobic interaction affinity of colloids

    NASA Astrophysics Data System (ADS)

    Saini, G.; Nasholm, N.; Wood, B. D.

    2009-12-01

    Colloids play an important role in a wide variety of disciplines, including water and wastewater treatment, subsurface transport of metals and organic contaminants, migration of fines in oil reservoirs, biocolloid (virus and bacteria) transport in subsurface, and are integral to laboratory transport studies. Although the role of hydrophobicity in adhesion and transport of colloids, particularly bacteria, is well known; there is scarcity of literature regarding hydrophobicity measurement of non-bacterial colloids and other micron-sized particles. Here we detail an experimental approach based on differential partitioning of colloids between two liquid phases (hydrocarbon and buffer) as a measure of the hydrophobic interaction affinity of colloids. This assay, known as Microbial adhesion to hydrocarbons or MATH, is frequently used in microbiology and bacteriology for quantifying the hydrophobicity of microbes. Monodispersed colloids and particles, with sizes ranging from 1 micron to 33 micron, were used for the experiments. A range of hydrophobicity values were observed for different particles. The hydrophobicity results are also verified against water contact angle measurements of these particles. This liquid-liquid partitioning assay is quick, easy-to-perform and requires minimal instrumentation. Estimation of the hydrophobic interaction affinity of colloids would lead to a better understanding of their adhesion to different surfaces and subsequent transport in porous media.

  14. Exploring the dewetting transition in the hydrophobic collapse of melittin

    NASA Astrophysics Data System (ADS)

    Varilly, Patrick; Patel, Amish J.; Chandler, David

    2011-03-01

    We present our recent results on understanding the hydrophobic collapse of melittin dimers. Melittin dimers have large, complementary hydrophobic patches, and the dimer collapse mechanism involves a dewetting transition [Liu, Huang, Zhou and Berne, Nature 437, 159--162 (2005)]. As a result, melittin has become a model system for studying dewetting transitions in proteins. We apply our recently- developed tools for probing density fluctuations in water [Patel, Varilly and Chandler, JPCB 114, 1632--1637 (2010)] to understand this dewetting transition in terms of free energy surfaces, their bistability and their barrier heights. We show how the hydrophobic character of melittin's tetramerization surface results in an enhanced probability of density depletion next to that surface. When two dimers come together, the density depletion is further enhanced, so that even at large separations, there is a metastable dry phase in the region between the dimers. As the dimers come together, the dry phase is stabilized and eventually the wet phase is destabilized, leading to the collapse of the dimers. We explore how mutations that have been observed to suppress the dewetting transition affect the corresponding free energy surfaces and discuss our ongoing efforts to fully map out the reaction coordinate of melittin collapse.

  15. Effects of Molecular Size and Surface Hydrophobicity on Oligonucleotide Interfacial Dynamics

    PubMed Central

    Monserud, Jon H.; Schwartz, Daniel K.

    2012-01-01

    Single-molecule total internal reflection fluorescence microscopy was used to observe the dynamic behavior of (poly)-cytosine ssDNA (1–50 nucleotides long) at the interface between aqueous solution and hydrophilic (oligoethylene oxide-modified fused silica, OEG) and hydrophobic (octadecyltriethoxysilane-modified fused silica, OTES) solid surfaces. High throughput molecular tracking was used to determine >75,000 molecular trajectories for each molecular length, which were then used to calculate surface residence time and squared displacement (i.e. “step-size”) distributions. On hydrophilic OEG surfaces, the surface residence time increased systematically with ssDNA chain length, as expected due to increasing molecule-surface interactions. Interestingly, the residence time decreased with increasing ssDNA length on the hydrophobic OTES surface, particularly for longer chains. Similarly, the interfacial mobility of polynucleotides slowed with increasing chain length on OEG, but became faster on OTES. On OTES surfaces, the rates associated with desorption and surface diffusion exhibited the distinctive anomalous temperature dependence that is characteristic of hydrophobic interactions for short chain species but not for longer chains. These combined observations suggest that long oligonucleotides adopt conformations minimizing hydrophobic interactions, e.g. by internal sequestration of hydrophobic nucleobases. PMID:23127250

  16. The association of low-molecular-weight hydrophobic compounds with native casein micelles in bovine milk.

    PubMed

    Cheema, M; Mohan, M S; Campagna, S R; Jurat-Fuentes, J L; Harte, F M

    2015-08-01

    The agreed biological function of the casein micelles in milk is to carry minerals (calcium, magnesium, and phosphorus) from mother to young along with amino acids for growth and development. Recently, native and modified casein micelles were used as encapsulating and delivery agents for various hydrophobic low-molecular-weight probes. The ability of modified casein micelles to bind certain probes may derive from the binding affinity of native casein micelles. Hence, a study with milk from single cows was conducted to further elucidate the association of hydrophobic molecules into native casein micelles and further understand their biological function. Hydrophobic and hydrophilic extraction followed by ultraperformance liquid chromatography-high resolution mass spectrometry analysis were performed over protein fractions obtained from size exclusion fractionation of raw skim milk. Hydrophobic compounds, including phosphatidylcholine, lyso-phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin, showed strong association exclusively to casein micelles as compared with whey proteins, whereas hydrophilic compounds did not display any preference for their association among milk proteins. Further analysis using liquid chromatography-tandem mass spectrometry detected 42 compounds associated solely with the casein-micelles fraction. Mass fragments in tandem mass spectrometry identified 4 of these compounds as phosphatidylcholine with fatty acid composition of 16:0/18:1, 14:0/16:0, 16:0/16:0, and 18:1/18:0. These results support that transporting low-molecular-weight hydrophobic molecules is also a biological function of the casein micelles in milk.

  17. A hydrophobic dye-encapsulated nano-hybrid as an efficient fluorescent probe for living cell imaging.

    PubMed

    Chang, Shu; Wu, Xumeng; Li, Yongsheng; Niu, Dechao; Ma, Zhi; Zhao, Wenru; Gu, Jinlou; Dong, Wenjie; Ding, Feng; Zhu, Weihong; Shi, Jianlin

    2012-07-01

    Water-soluble hydrophobic-dye@nano-hybrids (DPN@NHs) with extraordinarily enhanced fluorescent performance were fabricated by encapsulating the hydrophobic dye molecules into the core of the hybrid nanospheres based on the self-assembly of amphiphilic block copolymers followed by shell cross-linking using 3-mercaptopropyltrimethoxy-silane. The DPN@NHs are 50 nm in size, are monodispersed in aqueous solution and have a quantum yield enhanced by 30 times.

  18. Mobius Molecules

    ERIC Educational Resources Information Center

    Eckert, J. M.

    1973-01-01

    Discusses formation of chemical molecules via Mobius strip intermediates, and concludes that many special physics-chemical properties of the fully closed circular form (1) of polyoma DNA are explainable by this topological feature. (CC)

  19. Interstellar Molecules

    ERIC Educational Resources Information Center

    Solomon, Philip M.

    1973-01-01

    Radioastronomy reveals that clouds between the stars, once believed to consist of simple atoms, contain molecules as complex as seven atoms and may be the most massive objects in our Galaxy. (Author/DF)

  20. Interstellar molecules

    NASA Astrophysics Data System (ADS)

    Smith, D.

    1987-09-01

    Some 70 different molecular species have so far been detected variously in diffuse interstellar clouds, dense interstellar clouds, and circumstellar shells. Only simple (diatomic and triatomic) species exist in diffuse clouds because of the penetration of destructive UV radiations, whereas more complex (polyatomic) molecules survive in dense clouds as a result of the shielding against this UV radiation provided by dust grains. A current list of interstellar molecules is given together with a few other molecular species that have so far been detected only in circumstellar shells. Also listed are those interstellar species that contain rare isotopes of several elements. The gas phase ion chemistry is outlined via which the observed molecules are synthesized, and the process by which enrichment of the rare isotopes occurs in some interstellar molecules is described.

  1. Modeling Molecules

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The molecule modeling method known as Multibody Order (N) Dynamics, or MBO(N)D, was developed by Moldyn, Inc. at Goddard Space Flight Center through funding provided by the SBIR program. The software can model the dynamics of molecules through technology which stimulates low-frequency molecular motions and properties, such as movements among a molecule's constituent parts. With MBO(N)D, a molecule is substructured into a set of interconnected rigid and flexible bodies. These bodies replace the computation burden of mapping individual atoms. Moldyn's technology cuts computation time while increasing accuracy. The MBO(N)D technology is available as Insight II 97.0 from Molecular Simulations, Inc. Currently the technology is used to account for forces on spacecraft parts and to perform molecular analyses for pharmaceutical purposes. It permits the solution of molecular dynamics problems on a moderate workstation, as opposed to on a supercomputer.

  2. Rho-associated kinase (ROCK) inhibition reverses low cell activity on hydrophobic surfaces

    SciTech Connect

    Tian, Yu Shun; Kim, Hyun Jung; Kim, Hyun-Man

    2009-08-28

    Hydrophobic polymers do not offer an adequate scaffold surface for cells to attach, migrate, proliferate, and differentiate. Thus, hydrophobic scaffolds for tissue engineering have traditionally been physicochemically modified to enhance cellular activity. However, modifying the surface by chemical or physical treatment requires supplementary engineering procedures. In the present study, regulation of a cell signal transduction pathway reversed the low cellular activity on a hydrophobic surface without surface modification. Inhibition of Rho-associated kinase (ROCK) by Y-27632 markedly enhanced adhesion, migration, and proliferation of osteoblastic cells cultured on a hydrophobic polystyrene surface. ROCK inhibition regulated cell-cycle-related molecules on the hydrophobic surface. This inhibition also decreased expression of the inhibitors of cyclin-dependent kinases such as p21{sup cip1} and p27{sup kip1} and increased expression of cyclin A and D. These results indicate that defective cellular activity on the hydrophobic surface can be reversed by the control of a cell signal transduction pathway without physicochemical surface modification.

  3. Rho-associated kinase (ROCK) inhibition reverses low cell activity on hydrophobic surfaces.

    PubMed

    Tian, Yu Shun; Kim, Hyun Jung; Kim, Hyun-Man

    2009-08-28

    Hydrophobic polymers do not offer an adequate scaffold surface for cells to attach, migrate, proliferate, and differentiate. Thus, hydrophobic scaffolds for tissue engineering have traditionally been physicochemically modified to enhance cellular activity. However, modifying the surface by chemical or physical treatment requires supplementary engineering procedures. In the present study, regulation of a cell signal transduction pathway reversed the low cellular activity on a hydrophobic surface without surface modification. Inhibition of Rho-associated kinase (ROCK) by Y-27632 markedly enhanced adhesion, migration, and proliferation of osteoblastic cells cultured on a hydrophobic polystyrene surface. ROCK inhibition regulated cell-cycle-related molecules on the hydrophobic surface. This inhibition also decreased expression of the inhibitors of cyclin-dependent kinases such as p21(cip1) and p27(kip1) and increased expression of cyclin A and D. These results indicate that defective cellular activity on the hydrophobic surface can be reversed by the control of a cell signal transduction pathway without physicochemical surface modification.

  4. Enumerating molecules.

    SciTech Connect

    Visco, Donald Patrick, Jr.; Faulon, Jean-Loup Michel; Roe, Diana C.

    2004-04-01

    This report is a comprehensive review of the field of molecular enumeration from early isomer counting theories to evolutionary algorithms that design molecules in silico. The core of the review is a detail account on how molecules are counted, enumerated, and sampled. The practical applications of molecular enumeration are also reviewed for chemical information, structure elucidation, molecular design, and combinatorial library design purposes. This review is to appear as a chapter in Reviews in Computational Chemistry volume 21 edited by Kenny B. Lipkowitz.

  5. 3D hydrophobic moment vectors as a tool to characterize the surface polarity of amphiphilic peptides.

    PubMed

    Reißer, Sabine; Strandberg, Erik; Steinbrecher, Thomas; Ulrich, Anne S

    2014-06-01

    The interaction of membranes with peptides and proteins is largely determined by their amphiphilic character. Hydrophobic moments of helical segments are commonly derived from their two-dimensional helical wheel projections, and the same is true for β-sheets. However, to the best of our knowledge, there exists no method to describe structures in three dimensions or molecules with irregular shape. Here, we define the hydrophobic moment of a molecule as a vector in three dimensions by evaluating the surface distribution of all hydrophilic and lipophilic regions over any given shape. The electrostatic potential on the molecular surface is calculated based on the atomic point charges. The resulting hydrophobic moment vector is specific for the instantaneous conformation, and it takes into account all structural characteristics of the molecule, e.g., partial unfolding, bending, and side-chain torsion angles. Extended all-atom molecular dynamics simulations are then used to calculate the equilibrium hydrophobic moments for two antimicrobial peptides, gramicidin S and PGLa, under different conditions. We show that their effective hydrophobic moment vectors reflect the distribution of polar and nonpolar patches on the molecular surface and the calculated electrostatic surface potential. A comparison of simulations in solution and in lipid membranes shows how the peptides undergo internal conformational rearrangement upon binding to the bilayer surface. A good correlation with solid-state NMR data indicates that the hydrophobic moment vector can be used to predict the membrane binding geometry of peptides. This method is available as a web application on http://www.ibg.kit.edu/HM/. PMID:24896117

  6. Single-molecule insights into retention at a reversed-phase chromatographic interface.

    PubMed

    Mabry, Joshua N; Skaug, Michael J; Schwartz, Daniel K

    2014-10-01

    The efficiency of chromatographic separations decreases markedly when peaks exhibit asymmetry (e.g., "peak tailing"). Theoretically, these effects can arise from heterogeneous adsorption kinetics. To investigate the nature and consequences of such heterogeneity, we used a combination of single-molecule imaging and reversed-phase liquid chromatography (RPLC). In both single-molecule and macroscopic RPLC experiments, the stationary phase was hydrophobic end-capped (trimethylsilyl-functionalized) silica, which we exposed to different methanol/water solutions (50%-62% methanol), containing a fluorescent fatty acid analyte. Super-resolution maps based on single-molecule observations revealed rare, strong adsorption sites with activity that varied significantly with methanol concentration. The adsorption and desorption kinetics on the strong sites were heterogeneous and positively correlated, suggesting a broad underlying distribution of site binding energies. Adsorption equilibrium on the strong sites was more sensitive to solution conditions than overall retention measured in RPLC experiments, suggesting that the effect of strong sites on the overall adsorption kinetics should change with solution conditions. Interestingly, in RPLC experiments, peak tailing had a nonmonotonic dependence on methanol concentration within the range studied. Using the stochastic model of chromatography, we showed quantitatively that our single-molecule kinetic results were consistent with this macroscopic trend. This approach to identifying and quantifying adsorption sites should be useful for designing better chromatographic separations and for identifying the role of heterogeneous surface chemistry in molecular dynamics. PMID:25188676

  7. Erosion and flow of hydrophobic granular materials

    NASA Astrophysics Data System (ADS)

    Utter, Brian; Benns, Thomas; Foltz, Benjamin; Mahler, Joseph

    2015-03-01

    We experimentally investigate submerged granular flows of hydrophobic and hydrophilic grains both in a rotating drum geometry and under erosion by a surface water flow. While slurry and suspension flows are common in nature and industry, effects of surface chemistry on flow behavior have received relatively little attention. In the rotating drum, we use varying concentrations of hydrophobic and hydrophilic grains of sand submerged in water rotated at a constant angular velocity. Sequential images of the resulting avalanches are taken and analyzed. High concentrations of hydrophobic grains result in an effectively cohesive interaction between the grains forming aggregates, with aggregate size and repose angle increasing with hydrophobic concentration. However, the formation and nature of the aggregates depends significantly on the presence of air in the system. We present results from a related experiment on erosion by a surface water flow designed to characterize the effects of heterogeneous granular surfaces on channelization and erosion.

  8. Erosion and flow of hydrophobic granular materials

    NASA Astrophysics Data System (ADS)

    Utter, Brian; Benns, Thomas; Mahler, Joseph

    2013-11-01

    We experimentally investigate submerged granular flows of hydrophobic and hydrophilic grains both in a rotating drum geometry and under erosion by a surface water flow. While slurry and suspension flows are common in nature and industry, effects of surface chemistry on flow behavior have received relatively little attention. In the rotating drum , we use varying concentrations of hydrophobic and hydrophilic grains of sand submerged in water rotated at a constant angular velocity. Sequential images of the resulting avalanches are taken and analyzed. High concentrations of hydrophobic grains result in an effectively cohesive interaction between the grains forming aggregates, with aggregate size and repose angle increasing with hydrophobic concentration. However, the formation and nature of the aggregates depends significantly on the presence of air in the system. We present results from a related experiment on erosion by a surface water flow designed to characterize the effects of heterogeneous granular surfaces on channelization and erosion. Supported by NSF CBET Award 1067598.

  9. Hydrophobic gating in single and multiple nanopores

    NASA Astrophysics Data System (ADS)

    Innes, Laura Michele

    The ion transport properties of hydrophobic conical nanopores in polymer films in the presence of a salt solution were studied. The purpose of this study was to develop a hydrophobic gating mechanism similar to those seen in biological channels. Current-voltage curves were measured to determine if the gating behavior was present in hydrophobic modified nanopores, which would be seen as a zero ion current for small voltages and a finite ion current for larger voltages. It is shown, that for a single nanopore to gate water, it must be partially modified such that there are hydrophobic and hydrophilic islands on the pore walls. Similar experiments were also done with 105 pores/cm2 mutlipore samples.

  10. Why Hydrophilic Water can Permeate Hydrophobic Interior of Lipid Membranes

    NASA Astrophysics Data System (ADS)

    Qiao, Baofu; Olvera de La Cruz, Monica

    2014-03-01

    Water molecules as well as some small molecules have long been found to be able to diffuse across lipid membranes. Such permeation is of significant biological and biotechnological importance. For instance, the permeation of water across lipid membrane plays a important role in regulating ionic concentrations inside of cells. Such water permeation without the assistance of proteins embedded in membranes has been found to be a energetically unfavorable process. We, for the first time, explicitly depict the driving force for such an energetically unfavorable process. Atomistic molecular dynamics simulations are employed to investigate water diffusion in both liquid-crystalline and ordered gel phases of membranes containing zwitterionic DPPC or anionic DLPS lipid. The membrane conformation is calculated to have a critical role in water permeation, regardless of the type of lipid. The fluctuations in the potential energy are found to have a significant, if not the exclusive, role in the transportation of water across lipid membranes. Our results are also informative for the diffusion of small molecules of CO2, O2 and drug molecules, the absence of diffusion of ions, and the diffusion of water into the hydrophobic pores of carbon nanotubes. The authors acknowledge the support from the Office of the Director of Defense Research and Engineering (DDR & E) under Award No. FA9550-10-1-0167.

  11. How osmolytes influence hydrophobic polymer conformations: A unified view from experiment and theory.

    PubMed

    Mondal, Jagannath; Halverson, Duncan; Li, Isaac T S; Stirnemann, Guillaume; Walker, Gilbert C; Berne, Bruce J

    2015-07-28

    It is currently the consensus belief that protective osmolytes such as trimethylamine N-oxide (TMAO) favor protein folding by being excluded from the vicinity of a protein, whereas denaturing osmolytes such as urea lead to protein unfolding by strongly binding to the surface. Despite there being consensus on how TMAO and urea affect proteins as a whole, very little is known as to their effects on the individual mechanisms responsible for protein structure formation, especially hydrophobic association. In the present study, we use single-molecule atomic force microscopy and molecular dynamics simulations to investigate the effects of TMAO and urea on the unfolding of the hydrophobic homopolymer polystyrene. Incorporated with interfacial energy measurements, our results show that TMAO and urea act on polystyrene as a protectant and a denaturant, respectively, while complying with Tanford-Wyman preferential binding theory. We provide a molecular explanation suggesting that TMAO molecules have a greater thermodynamic binding affinity with the collapsed conformation of polystyrene than with the extended conformation, while the reverse is true for urea molecules. Results presented here from both experiment and simulation are in line with earlier predictions on a model Lennard-Jones polymer while also demonstrating the distinction in the mechanism of osmolyte action between protein and hydrophobic polymer. This marks, to our knowledge, the first experimental observation of TMAO-induced hydrophobic collapse in a ternary aqueous system. PMID:26170324

  12. Hydrophilization and hydrophobic recovery in polymers obtained by casting of polymer solutions on water surface.

    PubMed

    Bormashenko, Edward; Chaniel, Gilad; Gendelman, Oleg

    2014-12-01

    We demonstrate the possibility of hydrophilization of polymer films in situ under the process of their preparation. The polymer surface is hydrophilized when the polymer solution is spread on the water surface and the solvent is evaporated. Essential hydrophilization of the polymer surface is achieved under this process. We relate the observed hydrophilization of polymer films to the dipole-dipole interaction of the polar moieties of polymer chains with highly polar water molecules. The dipole-dipole interaction between water molecules and polar groups of polymer chains, orienting the polar groups of a polymer, may prevail over the London dispersion forces. The process, reported in the paper, allows to manufacture the films in which the hydrophilic moieties of the polymer molecule are oriented toward the polymer/air interface. It is demonstrated that even such traditionally extremely hydrophobic polymers as polydimethylsiloxane can be markedly hydrophilized. This hydrophilization, however, does not persist forever. After removal from the water surface, hydrophobic recovery was observed, i.e. polymer films restored their hydrophobicity with time. The characteristic time of the hydrophobic recovery is on the order of magnitude of hours.

  13. Reduction of graphene oxide/alginate composite hydrogels for enhanced adsorption of hydrophobic compounds.

    PubMed

    Kim, Semin; Yoo, Youngjae; Kim, Hanbit; Lee, Eunju; Lee, Jae Young

    2015-10-01

    Carbon-based materials, consisting of graphene oxide (GO) or reduced GO (rGO), possess unique abilities to interact with various molecules. In particular, rGO materials hold great promise for adsorption and delivery applications of hydrophobic molecules. However, conventional production and/or usage of rGO in aqueous solution often causes severe aggregation due to its low water solubility and thus difficulties in handling and applications. In our study, to prevent the severe aggregation of GO during reduction and to achieve a high adsorption capacity with hydrophobic compounds, GO/alginate composite hydrogels were first prepared and then reduced in an aqueous ascorbic acid solution at 37 °C. Adsorption studies with a model hydrophobic substance, rhodamine B, revealed that the reduced composite hydrogels are more highly absorbent than the unreduced hydrogels. In addition, the adsorption properties of the composite hydrogels, which are consequences of hydrophobic and ionic interactions, could be modulated by controlling the degree of reduction for the adsorption of different molecules. The composite hydrogels embedding rGO can be very useful in applications related to drug delivery, waste treatment, and biosensing.

  14. Multicompartmental Microcapsules with Orthogonal Programmable Two-Way Sequencing of Hydrophobic and Hydrophilic Cargo Release.

    PubMed

    Xu, Weinan; Ledin, Petr A; Iatridi, Zacharoula; Tsitsilianis, Constantinos; Tsukruk, Vladimir V

    2016-04-11

    Multicompartmental responsive microstructures with the capability for the pre-programmed sequential release of multiple target molecules of opposite solubility (hydrophobic and hydrophilic) in a controlled manner have been fabricated. Star block copolymers with dual-responsive blocks (temperature for poly(N-isopropylacrylamide) chains and pH for poly(acrylic acid) and poly(2-vinylpyridine) arms) and unimolecular micellar structures serve as nanocarriers for hydrophobic molecules in the microcapsule shell. The interior of the microcapsule can be loaded with water-soluble hydrophilic macromolecules. For these dual-loaded microcapsules, a programmable and sequential release of hydrophobic and hydrophilic molecules from the shell and core, respectively, can be triggered independently by temperature and pH variations. These stimuli affect the hydrophobicity and chain conformation of the star block copolymers to initiate out-of-shell release (elevated temperature), or change the overall star conformation and interlayer interactions to trigger increased permeability of the shell and out-of-core release (pH). Reversing stimulus order completely alters the release process.

  15. Reduction of graphene oxide/alginate composite hydrogels for enhanced adsorption of hydrophobic compounds

    NASA Astrophysics Data System (ADS)

    Kim, Semin; Yoo, Youngjae; Kim, Hanbit; Lee, Eunju; Lee, Jae Young

    2015-10-01

    Carbon-based materials, consisting of graphene oxide (GO) or reduced GO (rGO), possess unique abilities to interact with various molecules. In particular, rGO materials hold great promise for adsorption and delivery applications of hydrophobic molecules. However, conventional production and/or usage of rGO in aqueous solution often causes severe aggregation due to its low water solubility and thus difficulties in handling and applications. In our study, to prevent the severe aggregation of GO during reduction and to achieve a high adsorption capacity with hydrophobic compounds, GO/alginate composite hydrogels were first prepared and then reduced in an aqueous ascorbic acid solution at 37 °C. Adsorption studies with a model hydrophobic substance, rhodamine B, revealed that the reduced composite hydrogels are more highly absorbent than the unreduced hydrogels. In addition, the adsorption properties of the composite hydrogels, which are consequences of hydrophobic and ionic interactions, could be modulated by controlling the degree of reduction for the adsorption of different molecules. The composite hydrogels embedding rGO can be very useful in applications related to drug delivery, waste treatment, and biosensing.

  16. Modeling of the hydrophobic microenvironment of water-soluble molybdoenzymes in an aqueous micellar solution.

    PubMed

    Hasenaka, Yuki; Okamura, Taka-aki; Onitsuka, Kiyotaka

    2015-07-28

    A toluene-soluble molybdenum(vi) complex containing a bulky hydrophobic substituent, (Et4N)2[Mo(VI)O2{1,2-S2-3,6-(RCONH)2C6H2}2] (R = (4-(t)BuC6H4)3C), was dissolved in the hydrophobic core of a micelle in an aqueous medium and catalyzed the biomimetic reduction of an amine N-oxide by an NADH analog. The kinetic isotope effect of solvent water clearly indicates that water molecules are essential for catalysis and are involved in the rate-determining step. PMID:26076318

  17. Method for separating boron isotopes

    DOEpatents

    Rockwood, Stephen D.

    1978-01-01

    A method of separating boron isotopes .sup.10 B and .sup.11 B by laser-induced selective excitation and photodissociation of BCl.sub.3 molecules containing a particular boron isotope. The photodissociation products react with an appropriate chemical scavenger and the reaction products may readily be separated from undissociated BCl.sub.3, thus effecting the desired separation of the boron isotopes.

  18. Hydrophobicity of silver surfaces with microparticle geometry

    NASA Astrophysics Data System (ADS)

    Macko, Ján; Oriňaková, Renáta; Oriňak, Andrej; Kovaľ, Karol; Kupková, Miriam; Erdélyi, Branislav; Kostecká, Zuzana; Smith, Roger M.

    2016-11-01

    The effect of the duration of the current deposition cycle and the number of current pulses on the geometry of silver microstructured surfaces and on the free surface energy, polarizability, hydrophobicity and thus adhesion force of the silver surfaces has been investigated. The changes in surface hydrophobicity were entirely dependent on the size and density of the microparticles on the surface. The results showed that formation of the silver microparticles was related to number of current pulses, while the duration of one current pulse played only a minor effect on the final surface microparticle geometry and thus on the surface tension and hydrophobicity. The conventional geometry of the silver particles has been transformed to the fractal dimension D. The surface hydrophobicity depended predominantly on the length of the dendrites not on their width. The highest silver surface hydrophobicity was observed on a surface prepared by 30 current pulses with a pulse duration of 1 s, the lowest one when deposition was performed by 10 current pulses with a duration of 0.1 s. The partial surface tension coefficients γDS and polarizability kS of the silver surfaces were calculated. Both parameters can be applied in future applications in living cells adhesion prediction and spectral method selection. Silver films with microparticle geometry showed a lower variability in final surface hydrophobicity when compared to nanostructured surfaces. The comparisons could be used to modify surfaces and to modulate human cells and bacterial adhesion on body implants, surgery instruments and clean surfaces.

  19. Designing a hydrophobic barrier within biomimetic nanopores.

    PubMed

    Trick, Jemma L; Wallace, E Jayne; Bayley, Hagan; Sansom, Mark S P

    2014-11-25

    Nanopores in membranes have a range of potential applications. Biomimetic design of nanopores aims to mimic key functions of biological pores within a stable template structure. Molecular dynamics simulations have been used to test whether a simple β-barrel protein nanopore can be modified to incorporate a hydrophobic barrier to permeation. Simulations have been used to evaluate functional properties of such nanopores, using water flux as a proxy for ionic conductance. The behavior of these model pores has been characterized as a function of pore size and of the hydrophobicity of the amino acid side chains lining the narrow central constriction of the pore. Potential of mean force calculations have been used to calculate free energy landscapes for water and for ion permeation in selected models. These studies demonstrate that a hydrophobic barrier can indeed be designed into a β-barrel protein nanopore, and that the height of the barrier can be adjusted by modifying the number of consecutive rings of hydrophobic side chains. A hydrophobic barrier prevents both water and ion permeation even though the pore is sterically unoccluded. These results both provide insights into the nature of hydrophobic gating in biological pores and channels, and furthermore demonstrate that simple design features may be computationally transplanted into β-barrel membrane proteins to generate functionally complex nanopores.

  20. Positive charges of translocating polypeptide chain retrieve an upstream marginal hydrophobic segment from the endoplasmic reticulum lumen to the translocon.

    PubMed

    Fujita, Hidenobu; Kida, Yuichiro; Hagiwara, Masatoshi; Morimoto, Fumiko; Sakaguchi, Masao

    2010-06-15

    Positively charged amino acid residues are well recognized topology determinants of membrane proteins. They contribute to the stop-translocation of a polypeptide translocating through the translocon and to determine the orientation of signal sequences penetrating the membrane. Here we analyzed the function of these positively charged residues during stop-translocation in vitro. Surprisingly, the positive charges facilitated membrane spanning of a marginally hydrophobic segment, even when separated from the hydrophobic segment by 70 residues. In this case, the hydrophobic segment was exposed to the lumen, and then the downstream positive charges triggered the segment to slide back into the membrane. The marginally hydrophobic segment spanned the membrane, but maintained access to the water environment. The positive charges not only fix the hydrophobic segment in the membrane at its flanking position, but also have a much more dynamic action than previously realized. PMID:20427573

  1. Primordial oil slick and the formation of hydrophobic tetrapyrrole macrocycles.

    PubMed

    Soares, Ana R M; Taniguchi, Masahiko; Chandrashaker, Vanampally; Lindsey, Jonathan S

    2012-11-01

    The functional end products of the extant biosynthesis of tetrapyrrole macrocycles in photosynthetic organisms are hydrophobic: chlorophylls and bacteriochlorophylls. A model for the possible prebiogenesis of hydrophobic analogues of nature's photosynthetic pigments was investigated by reaction of acyclic reactants in five media: aqueous solution (pH 7, 60°C, 24 h); aqueous solution containing 0.1 M decanoic acid (which forms a turbid suspension of vesicles); or aqueous solution accompanied by dodecane, mesitylene, or a five-component organic mixture (each of which forms a phase-separated organic layer). The organic mixture was composed of equimolar quantities of decanoic acid, dodecane, mesitylene, naphthalene, and pentyl acetate. The reaction of 1,5-dimethoxy-3-methylpentan-2,4-dione and 1-aminobutan-2-one to give etioporphyrinogens was enhanced in the presence of decanoic acid, affording (following chemical oxidation) etioporphyrins (tetraethyltetramethylporphyrins) in yields of 1.4-10.8% across the concentration range of 3.75-120 mM. The yield of etioporphyrins was greater in the presence of the five-component organic mixture (6.6% at 120 mM) versus that with dodecane or mesitylene (2.1% or 2.9%, respectively). The reaction in aqueous solution with no added oil-slick constituents resulted in phase separation-where the organic reactants themselves form an upper organic layer-and the yield of etioporphyrins was 0.5-2.6%. Analogous reactions leading to uroporphyrins (hydrophilic, eight carboxylic acids) or coproporphyrins (four carboxylic acids) were unaffected by the presence of decanoic acid or dodecane, and all yields were at most ∼2% or ∼8%, respectively. Taken together, the results indicate a facile means for the formation of highly hydrophobic constituents of potential value for prebiotic photosynthesis. PMID:23095096

  2. Dynamics of hydrophobic organic contaminants in the Baltic proper pelagial

    SciTech Connect

    Axelman, J.; Broman, D.; Naef, C.; Pettersen, H.

    1995-12-31

    Hydrophobic organic contaminants occur in different forms in natural water. Apart from being truly dissolved in water they partition into dissolved organic carbon (DOC) and particles of different sizes including pelagic bacteria, phytoplankton and zooplankton. The distribution between the different forms is dependent on carbon turnover rates in and transport between the different compartments and on the physical and chemical properties of the compound in focus. The water phase, the DOC-phase and two particle size fractions, 0.2--2pm and 2--20 pm representing the base of the pelagic food web, were analyzed for their content of PCBs and PAHs during summer and winter conditions in the open sea in the Baltic proper. New methods for separating truly dissolved from DOC-bound compounds have been developed using a high capacity perfusion adsorbent and large scale gas sparging. The small particle size fraction was sampled using high volume tangential flow filtration. The possibility to separate between these four different compartments has given a more detailed picture of the short term dynamics of hydrophobic organic compounds in the important base of the pelagial food web.

  3. 'Escentric' molecules.

    PubMed

    Schön, Geza

    2008-06-01

    Can a fragrance be revolutionary? In this commentary, the creation of two unusual, extravagant fine fragrances, 'escentric01' and 'molecule01', is described. In response to the fantasy components found in release notes of many recent perfume launches, both center around a single real fragrance raw material, the transparent woody aroma chemical 'Iso E Super' (1+2). The perfume 'escentric01' contains 65% of it, accompanied by Trisamber (3), red pepper, lime oil, incense and musks, while 'molecule01' consists exclusively of 'Iso E Super' (1+2). The elegant woody note lives here its own eccentric life--the revolution starts.

  4. Hydrophobic properties of Candida spp. under the influence of selected essential oils.

    PubMed

    Rajkowska, Katarzyna; Kunicka-Styczyńska, Alina; Pęczek, Marlena

    2015-01-01

    Processes of colonization of biotic and abiotic surfaces and biofilm formation depend inter alia on hydrophobic properties of Candida spp. The aim of this research was to determine the effect of tea tree, thyme and clove essential oils on hydrophobic properties of environmental and clinical Candida isolates. The relative cell surface hydrophobicity of strains tested was high, and ranged from 68.7% to 91.2%, with the highest value for a C. rugosa food-borne strain. The effectiveness of essential oils was diversified and depended on the type of essential oil, concentration and yeast strain. Statistically significant decrease of hydrophobicity indexes was observed after application of tea tree oil for C. krusei, clove oil for C. albicans reference strain, and all essential oils tested for C. rugosa. Only in the case of C. famata food-borne strain and C. albicans clinical isolate, solely used essential oils did not affect their hydrophobic properties. To determine the interactions of essential oils, their mixtures (1 MIC:1 MIC, 1 MIC:2 MIC and 2 MIC:1 MIC) were applied. Generally, essential oils used in combinations influenced yeast's hydrophobic properties much more than applied separately. The essential oils' mixtures reduced hydrophobicity of Candida yeasts in the range of 8.2 to 45.1%, depending on combination and strain. The interaction indexes of essential oils used in combinations predominantly indicate their additive effect. The application of tea tree, thyme and clove essential oils, especially in combinations, decreases hydrophobicity of the tested Candida isolates with implications of a probable advantageous limitation of their ability to colonize the food production industry environment.

  5. Hydrophobic properties of Candida spp. under the influence of selected essential oils.

    PubMed

    Rajkowska, Katarzyna; Kunicka-Styczyńska, Alina; Pęczek, Marlena

    2015-01-01

    Processes of colonization of biotic and abiotic surfaces and biofilm formation depend inter alia on hydrophobic properties of Candida spp. The aim of this research was to determine the effect of tea tree, thyme and clove essential oils on hydrophobic properties of environmental and clinical Candida isolates. The relative cell surface hydrophobicity of strains tested was high, and ranged from 68.7% to 91.2%, with the highest value for a C. rugosa food-borne strain. The effectiveness of essential oils was diversified and depended on the type of essential oil, concentration and yeast strain. Statistically significant decrease of hydrophobicity indexes was observed after application of tea tree oil for C. krusei, clove oil for C. albicans reference strain, and all essential oils tested for C. rugosa. Only in the case of C. famata food-borne strain and C. albicans clinical isolate, solely used essential oils did not affect their hydrophobic properties. To determine the interactions of essential oils, their mixtures (1 MIC:1 MIC, 1 MIC:2 MIC and 2 MIC:1 MIC) were applied. Generally, essential oils used in combinations influenced yeast's hydrophobic properties much more than applied separately. The essential oils' mixtures reduced hydrophobicity of Candida yeasts in the range of 8.2 to 45.1%, depending on combination and strain. The interaction indexes of essential oils used in combinations predominantly indicate their additive effect. The application of tea tree, thyme and clove essential oils, especially in combinations, decreases hydrophobicity of the tested Candida isolates with implications of a probable advantageous limitation of their ability to colonize the food production industry environment. PMID:26601324

  6. Aptamers in Affinity Separations: Stationary Separation

    NASA Astrophysics Data System (ADS)

    Ravelet, Corinne; Peyrin, Eric

    The use of DNA or RNA aptamers as tools in analytical chemistry is a very promising field of research because of their capabilities to bind specifically the target molecules with an affinity similar to that of antibodies. Notably, they appear to be of great interest as target-specific ligands for the separation and capture of various analytes in affinity chromatography and related affinity-based methods such as magnetic bead technology. In this chapter, the recent developments of these aptamer-based separation/capture approaches are addressed.

  7. Effect of surfactant hydrophobicity on the pathway for unfolding of ubiquitin.

    PubMed

    Shaw, Bryan F; Schneider, Grégory F; Whitesides, George M

    2012-11-14

    This paper describes the interaction between ubiquitin (UBI) and three sodium n-alkyl sulfates (SC(n)S) that have the same charge (Z = -1) but different hydrophobicity (n = 10, 12, or 14). Increasing the hydrophobicity of the n-alkyl sulfate resulted in (i) an increase in the number of distinct intermediates (that is, complexes of UBI and surfactant) that form along the pathway of unfolding, (ii) a decrease in the minimum concentrations of surfactant at which intermediates begin to form (i.e., a more negative ΔG(binding) of surfactant for UBI), and (iii) an increase in the number of surfactant molecules bound to UBI in each intermediate or complex. These results demonstrate that small changes in the hydrophobicity of a surfactant can significantly alter the binding interactions with a folded or unfolded cytosolic protein.

  8. Evaluation of biocompatible stabilised gelled soya bean oil nanoparticles as new hydrophobic reservoirs.

    PubMed

    Boudier, Ariane; Kirilov, Plamen; Franceschi-Messant, Sophie; Belkhelfa, Haouaria; Hadioui, Laila; Roques, Christine; Perez, Emile; Rico-Lattes, Isabelle

    2010-01-01

    Based on the organogel concept, in which an oil is trapped in a network of low-molecular-mass organic gelator fibres creating a gel, a formulation of gelled soya bean oil nanoparticles was evaluated for its capacity to form biocompatible hydrophobic reservoirs. The aqueous dispersions of nanoparticles were prepared by hot emulsification (T° > Tgel) and cooling at room temperature in the presence of polyethyleneimine (PEI). The dispersions were stabilised by the electrostatic interactions between the positively charged amino groups of the PEI and the negatively charged carboxylates of the gelator fibres present at the surface of the particles. The aqueous dispersions were highly stable (several months) and the gelled particles were able to entrap a hydrophobic fluorescent model molecule (Nile red), allowing testing in cells. The gelled oil nanoparticles were found to be biocompatible with the tested cells (keratinocytes) and had the ability to become rapidly internalised. Thus, organogel-based nanoparticles are a promising hydrophobic drug delivery system.

  9. Cavity-containing supramolecular gels as a crystallization tool for hydrophobic pharmaceuticals.

    PubMed

    Kaufmann, Lena; Kennedy, Stuart R; Jones, Christopher D; Steed, Jonathan W

    2016-08-01

    We present two approaches to low-molecular-weight supramolecular gels bearing hydrophobic cavities based on calixarene-containing building blocks. Gels are formed by a calixarene based tetrahydrazide gelator or a co-gel of a calixarene diammonium salt and a bis-crown ether. The calixarene hydrophobic cavity enables the complexation of hydrophobic drug molecules in a generic fashion thus providing an anchor site on the surface of the gel fibre to initiate drug crystal nucleation and growth. This technique potentially represents a route to growth of hard-to-nucleate polymorphic modifications. The co-gel comprising two components holding together by non-covalent ammonium-crown ether interaction can be easily switched back to the sol state by adding competitive binding cations.

  10. Supramolecular Complex Antioxidant Consisting of Vitamins C, E and Hydrophilic-Hydrophobic Silica Nanoparticles

    NASA Astrophysics Data System (ADS)

    Laguta, I. V.; Kuzema, P. O.; Stavinskaya, O. N.; Kazakova, O. A.

    Samples with varied amount of surface trimethylsilyl groups were obtained via gas-phase chemical modification of silica nanoparticles. The biocompatibility tests conducted in erythrocyte suspension have shown that hydrophobization of silica decreases its damaging effect to the cells. Being wettable in aqueous media, partially silylated silicas have higher affinity to hydrophobic bioactive molecules in comparison with the initial silica. Novel antioxidant consisting of vitamins C and E and silica with 40% of surface trimethylsilyl groups was formulated. It was found that supramolecular complexes are formed on the silica surface due to the affinity of water- and fat-soluble antioxidants to hydrophilic silanol and hydrophobic trimethylsilyl groups, respectively. Test reactions (total phenolic index determination, DPPH test) and in vitro studies (spectral analysis of erythrocyte suspensions undergoing UV irradiation) revealed the correlation between antioxidant activity of the complex antioxidant and the vitamins’ content. The antioxidant remained active during long-term storage under standard conditions.

  11. Supramolecular Complex Antioxidant Consisting of Vitamins C, E and Hydrophilic-Hydrophobic Silica Nanoparticles

    NASA Astrophysics Data System (ADS)

    Laguta, I. V.; Kuzema, P. O.; Stavinskaya, O. N.; Kazakova, O. A.

    Samples with varied amount of surface trimethylsilyl groups were obtained via gas-phase chemical modification of silica nanoparticles. The biocompatibility tests conducted in erythrocyte suspension have shown that hydrophobization of silica decreases its damaging effect to the cells. Being wettable in aqueous media, partially silylated silicas have higher affinity to hydrophobic bioactive molecules in comparison with the initial silica. Novel antioxidant consisting of vitamins C and E and silica with 40% of surface trimethylsilyl groups was formulated. It was found that supramolecular complexes are formed on the silica surface due to the affinity of water- and fat-soluble antioxidants to hydrophilic silanol and hydrophobic trimethylsilyl groups, respectively. Test reactions (total phenolic index determination, DPPH test) and in vitro studies (spectral analysis of erythrocyte suspensions undergoing UV irradiation) revealed the correlation between antioxidant activity of the complex antioxidant and the vitamins' content. The antioxidant remained active during long-term storage under standard conditions.

  12. Influence of a Neighboring Charged Group on Hydrophobic Hydration Shell Structure.

    PubMed

    Davis, Joel G; Zukowski, Samual R; Rankin, Blake M; Ben-Amotz, Dor

    2015-07-23

    Raman multivariate curve resolution (Raman-MCR), as well as quantum and classical calculations, are used to probe water structural changes in the hydration shells of carboxylic acids and tetraalkyl ammonium ions with various aliphatic chain lengths. The results reveal that water molecules in the hydration shell around the hydrophobic chains undergo a temperature and chain length dependent structural transformation resembling that previously observed in aqueous solutions of n-alcohols. Deprotonation of the carboxylic acid headgroup (at pH ∼ 7) is found to suppress the onset of the hydration-shell structural transformation around the nearest aliphatic methylene group. Tetraalkyl ammonium cations are found to more strongly suppress the water structural transformation, perhaps reflecting the greater intramolecular charge delocalization and suppression of dangling OH defects in water's tetrahedral H-bond network. The observed coupling between ionic and hydrophobic groups, as well as the associated charge asymmetry, may influence the hydrophobicity of proteins and other materials.

  13. Switchable Hydrophobic-Hydrophilic Surfaces

    SciTech Connect

    BUNKER, BRUCE C.; HUBER, DALE L.; KENT, MICHAEL S.; YIM, HYUN; CURRO, JOHN G.; LOPEZ, GABRIEL P.; KUSHMERICK, JAMES G.; MANGINELL, RONALD P.; MENDEZ, SERGIO

    2002-12-01

    Tethered films of poly n-isopropylacrylamide (PNIPAM) films have been developed as materials that can be used to switch the chemistry of a surface in response to thermal activation. In water, PNIPAM exhibits a thermally-activated phase transition that is accompanied by significant changes in polymer volume, water contact angle, and protein adsorption characteristics. New synthesis routes have been developed to prepare PNIPAM films via in-situ polymerization on self-assembled monolayers. Swelling transitions in tethered films have been characterized using a wide range of techniques including surface plasmon resonance, attenuated total reflectance infrared spectroscopy, interfacial force microscopy, neutron reflectivity, and theoretical modeling. PNIPAM films have been deployed in integrated microfluidic systems. Switchable PNIPAM films have been investigated for a range of fluidic applications including fluid pumping via surface energy switching and switchable protein traps for pre-concentrating and separating proteins on microfluidic chips.

  14. Top-down mass spectrometry of hybrid materials with hydrophobic peptide and hydrophilic or hydrophobic polymer blocks.

    PubMed

    Alalwiat, Ahlam; Grieshaber, Sarah E; Paik, Bradford A; Kiick, Kristi L; Jia, Xinqiao; Wesdemiotis, Chrys

    2015-11-21

    A multidimensional mass spectrometry (MS) methodology is introduced for the molecular level characterization of polymer-peptide (or polymer-protein) copolymers that cannot be crystallized or chromatographically purified. It encompasses electrospray ionization (ESI) or matrix-assisted laser desorption ionization (MALDI) coupled with mass analysis, tandem mass spectrometry (MS(2)) and gas-phase separation by ion mobility mass spectrometry (IM-MS). The entire analysis is performed in the mass spectrometer ("top-down" approach) within milliseconds and with high sensitivity, as demonstrated for hybrid materials composed of hydrophobic poly(tert-butyl acrylate) (PtBA) or hydrophilic poly(acrylic acid) (PAA) blocks tethered to the hydrophobic decapeptide VPGVGVPGVG (VG2) via triazole linkages. The composition of the major products can be rapidly surveyed by MALDI-MS and MS(2). For a more comprehensive characterization, the ESI-IM-MS (and MS(2)) combination is more suitable, as it separates the hybrid materials based on their unique charges and shapes from unconjugated polymer and partially hydrolyzed products. Such separation is essential for reducing spectral congestion, deconvoluting overlapping compositions and enabling straightforward structural assignments, both for the hybrid copolymers as well as the polymer and peptide reactants. The IM dimension also permits the measurement of collision cross-sections (CCSs), which reveal molecular architecture. The MS and MS(2) spectra of the mobility separated ions conclusively showed that [PtBA-VG2]m and [PAA-VG2]m chains with the expected compositions and sequences were formed. Single and double copolymer blocks (m = 1-2) could be detected. Further, the CCSs of the hybrids, which were prepared via azide/alkyne cycloadditions, confirmed the formation of macrocyclic structures. The top-down methodology described would be particularly useful for the detection and identification of peptide/protein-polymer conjugates which are

  15. Top-down mass spectrometry of hybrid materials with hydrophobic peptide and hydrophilic or hydrophobic polymer blocks.

    PubMed

    Alalwiat, Ahlam; Grieshaber, Sarah E; Paik, Bradford A; Kiick, Kristi L; Jia, Xinqiao; Wesdemiotis, Chrys

    2015-11-21

    A multidimensional mass spectrometry (MS) methodology is introduced for the molecular level characterization of polymer-peptide (or polymer-protein) copolymers that cannot be crystallized or chromatographically purified. It encompasses electrospray ionization (ESI) or matrix-assisted laser desorption ionization (MALDI) coupled with mass analysis, tandem mass spectrometry (MS(2)) and gas-phase separation by ion mobility mass spectrometry (IM-MS). The entire analysis is performed in the mass spectrometer ("top-down" approach) within milliseconds and with high sensitivity, as demonstrated for hybrid materials composed of hydrophobic poly(tert-butyl acrylate) (PtBA) or hydrophilic poly(acrylic acid) (PAA) blocks tethered to the hydrophobic decapeptide VPGVGVPGVG (VG2) via triazole linkages. The composition of the major products can be rapidly surveyed by MALDI-MS and MS(2). For a more comprehensive characterization, the ESI-IM-MS (and MS(2)) combination is more suitable, as it separates the hybrid materials based on their unique charges and shapes from unconjugated polymer and partially hydrolyzed products. Such separation is essential for reducing spectral congestion, deconvoluting overlapping compositions and enabling straightforward structural assignments, both for the hybrid copolymers as well as the polymer and peptide reactants. The IM dimension also permits the measurement of collision cross-sections (CCSs), which reveal molecular architecture. The MS and MS(2) spectra of the mobility separated ions conclusively showed that [PtBA-VG2]m and [PAA-VG2]m chains with the expected compositions and sequences were formed. Single and double copolymer blocks (m = 1-2) could be detected. Further, the CCSs of the hybrids, which were prepared via azide/alkyne cycloadditions, confirmed the formation of macrocyclic structures. The top-down methodology described would be particularly useful for the detection and identification of peptide/protein-polymer conjugates which are

  16. Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface, and intrapeptide forces.

    PubMed

    Horinek, D; Serr, A; Geisler, M; Pirzer, T; Slotta, U; Lud, S Q; Garrido, J A; Scheibel, T; Hugel, T; Netz, R R

    2008-02-26

    The hydrophobic effect, i.e., the poor solvation of nonpolar parts of molecules, plays a key role in protein folding and more generally for molecular self-assembly and aggregation in aqueous media. The perturbation of the water structure accounts for many aspects of protein hydrophobicity. However, to what extent the dispersion interaction between molecular entities themselves contributes has remained unclear. This is so because in peptide folding interactions and structural changes occur on all length scales and make disentangling various contributions impossible. We address this issue both experimentally and theoretically by looking at the force necessary to peel a mildly hydrophobic single peptide molecule from a flat hydrophobic diamond surface in the presence of water. This setup avoids problems caused by bubble adsorption, cavitation, and slow equilibration that complicate the much-studied geometry with two macroscopic surfaces. Using atomic-force spectroscopy, we determine the mean desorption force of a single spider-silk peptide chain as F = 58 +/- 8 pN, which corresponds to a desorption free energy of approximately 5 k(B)T per amino acid. Our all-atomistic molecular dynamics simulation including explicit water correspondingly yields the desorption force F = 54 +/- 15 pN. This observation demonstrates that standard nonpolarizable force fields used in classical simulations are capable of resolving the fine details of the hydrophobic attraction of peptides. The analysis of the involved energetics shows that water-structure effects and dispersive interactions give contributions of comparable magnitude that largely cancel out. It follows that the correct modeling of peptide hydrophobicity must take the intimate coupling of solvation and dispersive effects into account.

  17. Cyclodextrin-polyhydrazine degradable gels for hydrophobic drug delivery.

    PubMed

    Jalalvandi, Esmat; Cabral, Jaydee; Hanton, Lyall R; Moratti, Stephen C

    2016-12-01

    An injectable and biocompatible hydrogel system was designed for hydrophobic drug delivery. This hydrogel consisted of degradable polymers with cyclodextrin (CD) moieties. CD groups were used to increase the solubility of a hydrophobic molecule (nicardipine) in an aqueous solution through the formation of the inclusion complex. Two sets of gels were prepared by mixing oxidized dextran (DA) and CD functionalized polyhydrazine (PH) at physiological conditions and different level of crosslinking via hydrazone bonds. Cytotoxicity studies on the gels and their components confirmed the biocompatibility of these materials. Gel-30 with higher crosslinking density showed a two week degradation period whereas this period was 10days for gel-10, with lower crosslinking density, to complete degradation. The results from swelling tests and rheological measurements were also found to be dependent on crosslinking density of the hydrogels. Release profile of the hydrogel displayed a sustained release of nicardipin up to 6days for gel-30 and a 4day release with initial burst release for gel-10. PMID:27612699

  18. Hydrophobicity and thermodynamic response for aqueous solutions of amphiphiles

    NASA Astrophysics Data System (ADS)

    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.

  19. Modification of deeply buried hydrophobic interfaces by ionic surfactants.

    PubMed

    Tamam, Lilach; Pontoni, Diego; Sapir, Zvi; Yefet, Shai; Sloutskin, Eli; Ocko, Benjamin M; Reichert, Harald; Deutsch, Moshe

    2011-04-01

    Hydrophobicity, the spontaneous segregation of oil and water, can be modified by surfactants. The way this modification occurs is studied at the oil-water interface for a range of alkanes and two ionic surfactants. A liquid interfacial monolayer, consisting of a mixture of alkane molecules and surfactant tails, is found. Upon cooling, it freezes at T(s), well above the alkane's bulk freezing temperature, T(b). The monolayer's phase diagram, derived by surface tensiometry, is accounted for by a mixtures-based theory. The monolayer's structure is measured by high-energy X-ray reflectivity above and below T(s). A solid-solid transition in the frozen monolayer, occurring approximately 3 °C below T(s), is discovered and tentatively suggested to be a rotator-to-crystal transition.

  20. Intermolecular vibrations in hydrophobic amino acid crystals: experiments and calculations.

    PubMed

    Williams, Michael R C; Aschaffenburg, Daniel J; Ofori-Okai, Benjamin K; Schmuttenmaer, Charles A

    2013-09-12

    Intermolecular vibrations of amino acid crystals occur in the THz, or far-infrared, region of the electromagnetic spectrum. We have measured the THz and Raman spectra of DL-leucine as well as two polymorphs of DL-valine, the spectroscopic properties of which have not previously been compared. Theoretical modeling of intermolecular vibrations in hydrophobic amino acids is challenging because the van der Waals interactions between molecules are not accounted for in standard density functional theory. Therefore, to calculate the vibrational modes, we used a recently developed approach that includes these nonlocal electron correlation forces. We discuss methods for comparing results from different theoretical models using metrics other than calculated vibrational frequency and intensity, and we also report a new approach enabling concise comparison of vibrational modes that involve complicated mixtures of inter- and intramolecular displacements.

  1. Modification of deeply buried hydrophobic interfaces by ionic surfactants.

    PubMed

    Tamam, Lilach; Pontoni, Diego; Sapir, Zvi; Yefet, Shai; Sloutskin, Eli; Ocko, Benjamin M; Reichert, Harald; Deutsch, Moshe

    2011-04-01

    Hydrophobicity, the spontaneous segregation of oil and water, can be modified by surfactants. The way this modification occurs is studied at the oil-water interface for a range of alkanes and two ionic surfactants. A liquid interfacial monolayer, consisting of a mixture of alkane molecules and surfactant tails, is found. Upon cooling, it freezes at T(s), well above the alkane's bulk freezing temperature, T(b). The monolayer's phase diagram, derived by surface tensiometry, is accounted for by a mixtures-based theory. The monolayer's structure is measured by high-energy X-ray reflectivity above and below T(s). A solid-solid transition in the frozen monolayer, occurring approximately 3 °C below T(s), is discovered and tentatively suggested to be a rotator-to-crystal transition. PMID:21422287

  2. Collapse of a hydrophobic polymer in a mixture of denaturants.

    PubMed

    Das, Payel; Xia, Zhen; Zhou, Ruhong

    2013-04-16

    The solvent quality of an aqueous mixture of two good solvents, urea and guanidinium chloride (GdmCl), for a hydrophobic polymer was investigated using atomistic molecular dynamics simulations. A counterintuitive collapse of the polymer was found, suggesting that mixing the two denaturants reduces the solvent quality. This cononsolvency of the polymer in the urea + GdmCl mixture is found to be caused by the preferential adsorption of urea on the polymer. The polymer collapses as a result of indirect long-range interactions between monomers resulting from the presence of urea clouds surrounding them. Surprisingly, urea behaves as the better solvent in the mixture not because there exists a stronger affinity of the polymer for urea. Instead, attractive interactions between two unlike denaturant molecules combined with the direct dispersion interactions of the polymer with both denaturants determine the solvent quality of the mixture.

  3. Modification of Deeply Buried Hydrophobic Interfaces by Ionic Surfactants

    SciTech Connect

    L Tamam; D Pontoni Z Sapir; S Yefet; S Sloutskin; B Ocko; H Reichert; M Deutsch

    2011-12-31

    Hydrophobicity, the spontaneous segregation of oil and water, can be modified by surfactants. The way this modification occurs is studied at the oil-water interface for a range of alkanes and two ionic surfactants. A liquid interfacial monolayer, consisting of a mixture of alkane molecules and surfactant tails, is found. Upon cooling, it freezes at T{sub s}, well above the alkane's bulk freezing temperature, T{sub b}. The monolayer's phase diagram, derived by surface tensiometry, is accounted for by a mixtures-based theory. The monolayer's structure is measured by high-energy X-ray reflectivity above and below T{sub s}. A solid-solid transition in the frozen monolayer, occurring approximately 3 C below T{sub s}, is discovered and tentatively suggested to be a rotator-to-crystal transition.

  4. Modification of Deeply Buried Hydrophobic Interfaces by Ionic Surfactants

    SciTech Connect

    Ocko, B.M.; Tamam, L.; Pontoni, D.; Sapir, Z.; Yefet, S.; Sloutskin, E.; Reichert, H.; Deutsch, M.

    2011-04-05

    Hydrophobicity, the spontaneous segregation of oil and water, can be modified by surfactants. The way this modification occurs is studied at the oil-water interface for a range of alkanes and two ionic surfactants. A liquid interfacial monolayer, consisting of a mixture of alkane molecules and surfactant tails, is found. Upon cooling, it freezes at T{sub s}, well above the alkane's bulk freezing temperature, T{sub b}. The monolayer's phase diagram, derived by surface tensiometry, is accounted for by a mixtures-based theory. The monolayer's structure is measured by high-energy X-ray reflectivity above and below T{sub s}. A solid-solid transition in the frozen monolayer, occurring approximately 3 C below T{sub s}, is discovered and tentatively suggested to be a rotator-to-crystal transition.

  5. Effects of polarity, hydrophobicity, and density of ionic liquids on cellulose solubility.

    PubMed

    Abe, Mitsuru; Kuroda, Kosuke; Sato, Daiki; Kunimura, Haruhito; Ohno, Hiroyuki

    2015-12-28

    We have synthesised novel ionic liquids (ILs) to show both cellulose dissolution ability and LCST-type phase transition after mixing with water. To realise both polar and hydrophobic properties, tetraalkylphosphonium cations and a series of carboxylate anions were employed to assume hydrophobic and highly polar properties, respectively. Effects of their alkyl chain length on the water compatibility and cellulose solubility of the corresponding ILs were systematically examined. We succeeded in synthesising novel ILs which dissolve cellulose and separable with water at moderate temperature. Through the present study, we have clarified that not only polarity but also density of ILs is an important factor in designing the ILs for cellulose dissolution. PMID:26583649

  6. Potential of mean force between two hydrophobic solutes in water.

    PubMed

    Southall, Noel T; Dill, Ken A

    2002-12-10

    We study the potential of mean force between two nonpolar solutes in the Mercedes Benz model of water. Using NPT Monte Carlo simulations, we find that the solute size determines the relative preference of two solute molecules to come into contact ('contact minimum') or to be separated by a single layer of water ('solvent-separated minimum'). Larger solutes more strongly prefer the contacting state, while smaller solutes have more tendency to become solvent-separated, particularly in cold water. The thermal driving forces oscillate with solute separation. Contacts are stabilized by entropy, whereas solvent-separated solute pairing is stabilized by enthalpy. The free energy of interaction for small solutes is well-approximated by scaled-particle theory.

  7. Potential of mean force between two hydrophobic solutes in water.

    PubMed

    Southall, Noel T; Dill, Ken A

    2002-12-10

    We study the potential of mean force between two nonpolar solutes in the Mercedes Benz model of water. Using NPT Monte Carlo simulations, we find that the solute size determines the relative preference of two solute molecules to come into contact ('contact minimum') or to be separated by a single layer of water ('solvent-separated minimum'). Larger solutes more strongly prefer the contacting state, while smaller solutes have more tendency to become solvent-separated, particularly in cold water. The thermal driving forces oscillate with solute separation. Contacts are stabilized by entropy, whereas solvent-separated solute pairing is stabilized by enthalpy. The free energy of interaction for small solutes is well-approximated by scaled-particle theory. PMID:12488009

  8. Surfactant Facilitated Spreading of Aqueous Drops on Hydrophobic Surfaces

    NASA Technical Reports Server (NTRS)

    Kumar, Nitin; Couzis, Alex; Maldareili, Charles; Singh, Bhim (Technical Monitor)

    2001-01-01

    Microgravity technologies often require aqueous phases to spread over nonwetting hydrophobic solid surfaces. Surfactants facilitate the wetting of water on hydrophobic surfaces by adsorbing on the water/air and hydrophobic solid/water interfaces and lowering the surface tensions of these interfaces. The tension reductions decrease the contact angle, which increases the equilibrium wetted area. Hydrocarbon surfactants; (i.e., amphiphiles with a hydrophobic moiety consisting of an extended chain of (aliphatic) methylene -CH2- groups attached to a large polar group to give aqueous solubility) are capable of reducing the contact angles on surfaces which are not very hydrophobic, but do not reduce significantly the contact angles of the very hydrophobic surfaces such as parafilm, polyethylene or self assembled monolayers. Trisiloxane surfactants (amphiphiles with a hydrophobe consisting of methyl groups linked to a trisiloxane backbone in the form of a disk ((CH3)3-Si-O-Si-O-Si(CH3)3) and an extended ethoxylate (-(OCH2CH2)a-) polar group in the form of a chain with four or eight units) can significantly reduce the contact angle of water on a very hydrophobic surface and cause rapid and complete (or nearly complete) spreading (termed superspreading). The overall goal of the research described in this proposal is to establish and verify a theory for how trisiloxanes cause superspreading, and then use this knowledge as a guide to developing more general hydrocarbon based surfactant systems which superspread. We propose that the trisiloxane surfactants superspread because their structure allows them to strongly lower the high hydrophobic solid/aqueous tension when they adsorb to the solid surface. When the siloxane adsorbs, the hydrophobic disk parts of the molecule adsorb onto the surface removing the surface water. Since the cross-sectional area of the disk is larger than that of the extended ethoxylate chain, the disks can form a space-filling mat on the surface which

  9. Properties of hydrophobic free energy found by gas-liquid transfer.

    PubMed

    Baldwin, Robert L

    2013-01-29

    The hydrophobic free energy in current use is based on transfer of alkane solutes from liquid alkanes to water, and it has been argued recently that these values are incorrect and should be based instead on gas-liquid transfer data. Hydrophobic free energy is measured here by gas-liquid transfer of hydrocarbon gases from vapor to water. The new definition reduces more than twofold the values of the apparent hydrophobic free energy. Nevertheless, the newly defined hydrophobic free energy is still the dominant factor that drives protein folding as judged by ΔCp, the change in heat capacity, found from the free energy change for heat-induced protein unfolding. The ΔCp for protein unfolding agrees with ΔCp values for solvating hydrocarbon gases and disagrees with ΔCp for breaking peptide hydrogen bonds, which has the opposite sign. The ΔCp values for the enthalpy of liquid-liquid and gas-liquid transfer are similar. The plot of free energy against the apparent solvent-exposed surface area is given for linear alkanes, but only for a single conformation, the extended conformation, of these flexible-chain molecules. The ability of the gas-liquid hydrophobic factor to predict protein stability is tested and reasonable agreement is found, using published data for the dependences on temperature of the unfolding enthalpy of ribonuclease T1 and the solvation enthalpies of the nonpolar and polar groups.

  10. Ultracapacitor separator

    DOEpatents

    Wei, Chang; Jerabek, Elihu Calvin; LeBlanc, Jr., Oliver Harris

    2001-03-06

    An ultracapacitor includes two solid, nonporous current collectors, two porous electrodes separating the collectors, a porous separator between the electrodes and an electrolyte occupying the pores in the electrodes and separator. The electrolyte is a polar aprotic organic solvent and a salt. The porous separator comprises a wet laid cellulosic material.

  11. Self-Assemblies of novel molecules, VECAR

    NASA Astrophysics Data System (ADS)

    Shrestha, Bijay; Kim, Hye-Young; Lee, Soojin; Novak, Brian; Moldovan, Dorel

    2015-03-01

    VECAR is a newly synthesized molecule, which is an amphiphilic antioxidant molecule that consists of two molecular groups, vitamin-E and Carnosine, linked by a hydrocarbon chain. The hydrocarbon chain is hydrophobic and both vitamin-E and Carnosine ends are hydrophilic. In the synthesis process, the length of the hydrophobic chain of VECAR molecules can vary from the shortest (n =0) to the longest (n =18), where n indicates the number of carbon atoms in the chain. We conducted MD simulation studies of self-assembly of VECAR molecules in water using GROMACS on LONI HPC resources. Our study shows that there is a strong correlation between the shape and atomistic structure of the self-assembled nano-structures (SANs) and the chain-length (n) of VECAR molecules. We will report the results of data analyses including the atomistic structure of each SANs and the dynamic and energetic mechanisms of their formation as function of time. In summary, both VECAR molecules of chain-length n =18 and 9 form worm-like micelles, which may be used as a drug delivery system. This research is supported by the Louisiana Board of Regents-RCS Grant (LEQSF(2012-15)-RD-A-19).

  12. Hydrophobic surface functionalization of lignocellulosic jute fabrics by enzymatic grafting of octadecylamine.

    PubMed

    Dong, Aixue; Fan, Xuerong; Wang, Qiang; Yu, Yuanyuan; Cavaco-Paulo, Artur

    2015-08-01

    Enzymatic grafting of synthetic molecules onto lignins provides a mild and eco-friendly alternative for the functionalization of lignocellulosic materials. In this study, laccase-mediated grafting of octadecylamine (OA) onto lignin-rich jute fabrics was investigated for enhancing the surface hydrophobicity. First, the lignins in jute fabrics were isolated and analyzed in the macromolecular level by MALDI-TOF MS, (1)H NMR, (13)C NMR, and HSQC-NMR. Then, the surface of jute fabrics was characterized by FT-IR, XPS, and SEM. Subsequently, the nitrogen content of jute fabrics was determined by the micro-Kjeldahl method, and the grafting percentage (Gp) and grafting efficiency (GE) of the enzymatic reaction were calculated. Finally, the surface hydrophobicity of the jute fabrics was estimated by contact angle and wetting time measurements. The results indicate that the OA monomers were successfully grafted onto the lignin moieties on the jute fiber surface by laccase with Gp and GE values of 0.712% and 10.571%, respectively. Moreover, the modified jute fabrics via OA-grafting showed an increased wetting time of 18.5 min and a contact angle of 116.72°, indicating that the surface hydrophobicity of the jute fabrics increased after the enzymatic grafting modification with hydrophobic OA molecules.

  13. Hydrophobic surface functionalization of lignocellulosic jute fabrics by enzymatic grafting of octadecylamine.

    PubMed

    Dong, Aixue; Fan, Xuerong; Wang, Qiang; Yu, Yuanyuan; Cavaco-Paulo, Artur

    2015-08-01

    Enzymatic grafting of synthetic molecules onto lignins provides a mild and eco-friendly alternative for the functionalization of lignocellulosic materials. In this study, laccase-mediated grafting of octadecylamine (OA) onto lignin-rich jute fabrics was investigated for enhancing the surface hydrophobicity. First, the lignins in jute fabrics were isolated and analyzed in the macromolecular level by MALDI-TOF MS, (1)H NMR, (13)C NMR, and HSQC-NMR. Then, the surface of jute fabrics was characterized by FT-IR, XPS, and SEM. Subsequently, the nitrogen content of jute fabrics was determined by the micro-Kjeldahl method, and the grafting percentage (Gp) and grafting efficiency (GE) of the enzymatic reaction were calculated. Finally, the surface hydrophobicity of the jute fabrics was estimated by contact angle and wetting time measurements. The results indicate that the OA monomers were successfully grafted onto the lignin moieties on the jute fiber surface by laccase with Gp and GE values of 0.712% and 10.571%, respectively. Moreover, the modified jute fabrics via OA-grafting showed an increased wetting time of 18.5 min and a contact angle of 116.72°, indicating that the surface hydrophobicity of the jute fabrics increased after the enzymatic grafting modification with hydrophobic OA molecules. PMID:25987460

  14. Friction Force Microscopy of Lubricin and Hyaluronic Acid between Hydrophobic and Hydrophilic Surfaces

    PubMed Central

    Chang, Debby P.; Abu-Lail, Nehal I.; Coles, Jeffrey M.; Guilak, Farshid; Jay, Gregory D.; Zauscher, Stefan

    2010-01-01

    Lubricin and hyaluronic acid (HA), molecular constituents of synovial fluid, have long been theorized to play a role in joint lubrication and wear protection. While lubricin has been shown to function as a boundary lubricant, conflicting evidence exists as to the boundary lubricating ability of hyaluronic acid. Here, we use colloidal force microscopy to explore the friction behavior of these two molecules on the microscale between chemically uniform hydrophilic (hydroxyl-terminated) and hydrophobic (methyl-terminated) surfaces in physiological buffer solution. Behaviors on both surfaces are physiologically relevant since the heterogeneous articular cartilage surface contains both hydrophilic and hydrophobic elements. Friction between hydrophobic surfaces was initially high (μ=1.1, at 100nN of applied normal load) and was significantly reduced by lubricin addition while friction between hydrophilic surfaces was initially low (μ=0.1) and was slightly increased by lubricin addition. At lubricin concentrations above 200 µg/ml, friction behavior on the two surfaces was similar (μ=0.2) indicating that nearly all interaction between the two surfaces was between adsorbed lubricin molecules rather than between the surfaces themselves. In contrast, addition of HA did not appreciably alter the frictional behavior between the model surfaces. No synergistic effect on friction behavior was seen in a physiological mixture of lubricin and HA. Lubricin can equally mediate the frictional response between both hydrophilic and hydrophobic surfaces, likely fully preventing direct surface-to-surface contact at sufficient concentrations, whereas HA provides considerably less boundary lubrication. PMID:20936046

  15. [Separation of purines, pyrimidines, pterins and flavonoids on magnolol-bonded silica gel stationary phase by high performance liquid chromatography].

    PubMed

    Chen, Hong; Li, Laishen; Zhang, Yang; Zhou, Rendan

    2012-10-01

    A new magnolol-bonded silica gel stationary phase (MSP) was used to separate the basic drugs including four purines, eight pyrimidines, four pterins and five flavonoids as polar representative samples by high performance liquid chromatography (HPLC). To clarify the separation mechanism, a commercial ODS column was also tested under the same chromatographic conditions. The high selectivities and fast baseline separations of the above drugs were achieved by using simple mobile phases on MSP. Although there is no end-caped treatment, the peak shapes of basic drugs containing nitrogen such as purines, pyrimidines and pterins were rather symmetrical on MSP, which indicated the the magnolol as ligand with multi-sites could shield the side effect of residual silanol groups on the surface of silica gel. Although somewhat different in the separation resolution, it was found that the elution orders of some drugs were generally similar on both MSP and ODS. The hydrophobic interaction should play a significant role in the separations of the above basic drugs, which was attributed to their reversed-phase property in the nature. However, MSP could provide the additional sites for many polar solutes, which was a rational explanation for the high selectivity of MSP. For example, in the separation of purines, pyrimidines and pterins on MSP, hydrogen-bonding and dipole-dipole interactions played leading roles besides hydrophobic interaction. Some solute molecules (such as mercaptopurine, vitexicarpin) and MSP can form the strong pi-pi stacking in the separation process. All enhanced the retention and improved the separation selectivity of MSP, which facilitated the separation of the basic drugs.

  16. Molecular separation method and apparatus

    DOEpatents

    Villa-Aleman, Eliel

    1996-01-01

    A method and apparatus for separating a gaseous mixture of chemically identical but physically different molecules based on their polarities. The gaseous mixture of molecules is introduced in discrete quantities into the proximal end of a porous glass molecular. The molecular sieve is exposed to microwaves to excite the molecules to a higher energy state from a lower energy state, those having a higher dipole moment being excited more than those with a lower energy state. The temperature of the sieve kept cold by a flow of liquid nitrogen through a cooling jacket so that the heat generated by the molecules colliding with the material is transferred away from the material. The molecules thus alternate between a higher energy state and a lower one, with the portion of molecules having the higher dipole moment favored over the others. The former portion can then be extracted separately from the distal end of the molecular sieve.

  17. Molecular separation method and apparatus

    DOEpatents

    Villa-Aleman, E.

    1996-04-09

    A method and apparatus are disclosed for separating a gaseous mixture of chemically identical but physically different molecules based on their polarities. The gaseous mixture of molecules is introduced in discrete quantities into the proximal end of a porous glass molecular sieve. The molecular sieve is exposed to microwaves to excite the molecules to a higher energy state from a lower energy state, those having a higher dipole moment being excited more than those with a lower energy state. The temperature of the sieve kept cold by a flow of liquid nitrogen through a cooling jacket so that the heat generated by the molecules colliding with the material is transferred away from the material. The molecules thus alternate between a higher energy state and a lower one, with the portion of molecules having the higher dipole moment favored over the others. The former portion can then be extracted separately from the distal end of the molecular sieve. 2 figs.

  18. Primordial Oil Slick and the Formation of Hydrophobic Tetrapyrrole Macrocycles

    PubMed Central

    Soares, Ana R. M.; Taniguchi, Masahiko; Chandrashaker, Vanampally

    2012-01-01

    Abstract The functional end products of the extant biosynthesis of tetrapyrrole macrocycles in photosynthetic organisms are hydrophobic: chlorophylls and bacteriochlorophylls. A model for the possible prebiogenesis of hydrophobic analogues of nature's photosynthetic pigments was investigated by reaction of acyclic reactants in five media: aqueous solution (pH 7, 60°C, 24 h); aqueous solution containing 0.1 M decanoic acid (which forms a turbid suspension of vesicles); or aqueous solution accompanied by dodecane, mesitylene, or a five-component organic mixture (each of which forms a phase-separated organic layer). The organic mixture was composed of equimolar quantities of decanoic acid, dodecane, mesitylene, naphthalene, and pentyl acetate. The reaction of 1,5-dimethoxy-3-methylpentan-2,4-dione and 1-aminobutan-2-one to give etioporphyrinogens was enhanced in the presence of decanoic acid, affording (following chemical oxidation) etioporphyrins (tetraethyltetramethylporphyrins) in yields of 1.4–10.8% across the concentration range of 3.75–120 mM. The yield of etioporphyrins was greater in the presence of the five-component organic mixture (6.6% at 120 mM) versus that with dodecane or mesitylene (2.1% or 2.9%, respectively). The reaction in aqueous solution with no added oil-slick constituents resulted in phase separation—where the organic reactants themselves form an upper organic layer—and the yield of etioporphyrins was 0.5–2.6%. Analogous reactions leading to uroporphyrins (hydrophilic, eight carboxylic acids) or coproporphyrins (four carboxylic acids) were unaffected by the presence of decanoic acid or dodecane, and all yields were at most ∼2% or ∼8%, respectively. Taken together, the results indicate a facile means for the formation of highly hydrophobic constituents of potential value for prebiotic photosynthesis. Key Words: Origin of life—Prebiotic—Oil slick—Porphyrinogen—Porphyrin—Pyrrole—Partition. Astrobiology 12, 1055

  19. Staphylococcus epidermidis adhesion on hydrophobic and hydrophilic textured biomaterial surfaces.

    PubMed

    Xu, Li-Chong; Siedlecki, Christopher A

    2014-06-01

    It is of great interest to use nano- or micro-structured surfaces to inhibit microbial adhesion and biofilm formation and thereby to prevent biomaterial-associated infection, without modification of the surface chemistry or bulk properties of the materials and without use of the drugs. Our previous study showed that a submicron textured polyurethane surface can inhibit staphylococcal bacterial adhesion and biofilm formation. To further understand the effect of the geometry of textures on bacterial adhesion as well as the underlying mechanism, in this study, submicron and micron textured polyurethane surfaces featuring ordered arrays of pillars were fabricated and modified to have different wettabilities. All the textured surfaces were originally hydrophobic and showed significant reductions in Staphylococcus epidermidis RP62A adhesion in phosphate buffered saline or 25% platelet poor plasma solutions under shear, as compared to smooth surfaces. After being subjected to an air glow discharge plasma treatment, all polyurethane surfaces were modified to hydrophilic, and reductions in bacterial adhesion on surfaces were subsequently found to be dependent on the size of the patterns. The submicron patterned surfaces reduced bacterial adhesion, while the micron patterned surfaces led to increased bacterial adhesion. The extracellular polymeric substances (EPS) from the S. epidermidis cell surfaces were extracted and purified, and were coated on a glass colloidal surface so that the adhesion force and separation energy in interactions of the EPS and the surface could be measured by colloidal probe atomic force microscopy. These results were consistent with the bacterial adhesion observations. Overall, the data suggest that the increased surface hydrophobicity and the decreased availability of the contact area contributes to a reduction in bacterial adhesion to the hydrophobic textured surfaces, while the availability of the contact area is the primary determinant factor

  20. Tunable integration of absorption-membrane-adsorption for efficiently separating low boiling gas mixtures near normal temperature

    PubMed Central

    Liu, Huang; Pan, Yong; Liu, Bei; Sun, Changyu; Guo, Ping; Gao, Xueteng; Yang, Lanying; Ma, Qinglan; Chen, Guangjin

    2016-01-01

    Separation of low boiling gas mixtures is widely concerned in process industries. Now their separations heavily rely upon energy-intensive cryogenic processes. Here, we report a pseudo-absorption process for separating low boiling gas mixtures near normal temperature. In this process, absorption-membrane-adsorption is integrated by suspending suitable porous ZIF material in suitable solvent and forming selectively permeable liquid membrane around ZIF particles. Green solvents like water and glycol were used to form ZIF-8 slurry and tune the permeability of liquid membrane surrounding ZIF-8 particles. We found glycol molecules form tighter membrane while water molecules form looser membrane because of the hydrophobicity of ZIF-8. When using mixing solvents composed of glycol and water, the permeability of liquid membrane becomes tunable. It is shown that ZIF-8/water slurry always manifests remarkable higher separation selectivity than solid ZIF-8 and it could be tuned to further enhance the capture of light hydrocarbons by adding suitable quantity of glycol to water. Because of its lower viscosity and higher sorption/desorption rate, tunable ZIF-8/water-glycol slurry could be readily used as liquid absorbent to separate different kinds of low boiling gas mixtures by applying a multistage separation process in one traditional absorption tower, especially for the capture of light hydrocarbons. PMID:26892255

  1. Tunable integration of absorption-membrane-adsorption for efficiently separating low boiling gas mixtures near normal temperature.

    PubMed

    Liu, Huang; Pan, Yong; Liu, Bei; Sun, Changyu; Guo, Ping; Gao, Xueteng; Yang, Lanying; Ma, Qinglan; Chen, Guangjin

    2016-02-19

    Separation of low boiling gas mixtures is widely concerned in process industries. Now their separations heavily rely upon energy-intensive cryogenic processes. Here, we report a pseudo-absorption process for separating low boiling gas mixtures near normal temperature. In this process, absorption-membrane-adsorption is integrated by suspending suitable porous ZIF material in suitable solvent and forming selectively permeable liquid membrane around ZIF particles. Green solvents like water and glycol were used to form ZIF-8 slurry and tune the permeability of liquid membrane surrounding ZIF-8 particles. We found glycol molecules form tighter membrane while water molecules form looser membrane because of the hydrophobicity of ZIF-8. When using mixing solvents composed of glycol and water, the permeability of liquid membrane becomes tunable. It is shown that ZIF-8/water slurry always manifests remarkable higher separation selectivity than solid ZIF-8 and it could be tuned to further enhance the capture of light hydrocarbons by adding suitable quantity of glycol to water. Because of its lower viscosity and higher sorption/desorption rate, tunable ZIF-8/water-glycol slurry could be readily used as liquid absorbent to separate different kinds of low boiling gas mixtures by applying a multistage separation process in one traditional absorption tower, especially for the capture of light hydrocarbons.

  2. The enhanced SERS effect of Ag/ZnO nanoparticles through surface hydrophobic modification

    NASA Astrophysics Data System (ADS)

    Li, Zhenjiang; Zhu, Kaixing; Zhao, Qian; Meng, Alan

    2016-07-01

    Ag/ZnO nanocomposites modified by a mixture of stearic acid (SA) and polyvinylpyrrolidone (PVP) were obtained using a heating reflux method. Fourier transform infrared spectroscopy (FT-IR) suggests that organic SA/PVP was bonded onto the surface of Ag/ZnO nanocrystals, converting the wettability property of the nanostructures from hydrophilic to hydrophobic. The modified Ag/ZnO nanostructures were confirmed as effective Raman substrates, with a 3-fold signal enhancement compared to the ordinary hydrophilic Ag/ZnO substrate for detecting Rh B molecules due to the hydrophobic condensation effect. It is expected that the modified Ag/ZnO nanoparticles have potential for SERS-based rapid detection of molecules.

  3. Walking molecules.

    PubMed

    von Delius, Max; Leigh, David A

    2011-07-01

    Movement is intrinsic to life. Biologists have established that most forms of directed nanoscopic, microscopic and, ultimately, macroscopic movements are powered by molecular motors from the dynein, myosin and kinesin superfamilies. These motor proteins literally walk, step by step, along polymeric filaments, carrying out essential tasks such as organelle transport. In the last few years biological molecular walkers have inspired the development of artificial systems that mimic aspects of their dynamics. Several DNA-based molecular walkers have been synthesised and shown to walk directionally along a track upon sequential addition of appropriate chemical fuels. In other studies, autonomous operation--i.e. DNA-walker migration that continues as long as a complex DNA fuel is present--has been demonstrated and sophisticated tasks performed, such as moving gold nanoparticles from place-to-place and assistance in sequential chemical synthesis. Small-molecule systems, an order of magnitude smaller in each dimension and 1000× smaller in molecular weight than biological motor proteins or the walker systems constructed from DNA, have also been designed and operated such that molecular fragments can be progressively transported directionally along short molecular tracks. The small-molecule systems can be powered by light or chemical fuels. In this critical review the biological motor proteins from the kinesin, myosin and dynein families are analysed as systems from which the designers of synthetic systems can learn, ratchet concepts for transporting Brownian substrates are discussed as the mechanisms by which molecular motors need to operate, and the progress made with synthetic DNA and small-molecule walker systems reviewed (142 references). PMID:21416072

  4. Bioluminescence assay for estimating the hydrophobic properties of bacteria as revealed by hydrophobic interaction chromatography.

    PubMed Central

    Mafu, A A; Roy, D; Savoie, L; Goulet, J

    1991-01-01

    The luciferin-luciferase bioluminescence method was used to estimate the number of bacteria retained in neutral and amphiphilic gels and those in the eluate to determine the hydrophobic surface properties of bacteria by using hydrophobic interaction chromatography. Good correlations were found between viable counts and ATP content for Escherichia coli, Pseudomonas fragi, and Listeria monocytogenes. ATP determination was more rapid than viable counts for characterizing the relative hydrophobicity of L. monocytogenes. Quantitative estimations of adsorption of L. monocytogenes on octyl-Sepharose indicate that this microorganism is hydrophilic. PMID:1908207

  5. Drag Reduction for Flow Past a Perfectly Hydrophobic Surface

    NASA Astrophysics Data System (ADS)

    McHale, Glen; Newton, Michael I.; Flynn, Morris R.; Gruncell, Brian R. K.; Sandham, Neil D.; Busse, Angela

    2014-11-01

    We consider drag reduction for flow past a perfectly hydrophobic sphere (i.e. a vanishing Cassie solid surface fraction or with a Leidenfrost layer). At small Re number an exact analytical model for drag can be constructed for a sphere encapsulated in a layer of a gas (a ``plastron''). This predicts an optimum thickness for the gas layer for maximum drag reduction due to a competition between increased lubrication of the flow and increased cross-section for drag by the compound object (the solid plus its surface-retained layer of gas). Using numerical simulations for a perfectly hydrophobic solid sphere in water we show that the maximum drag reduction increases from 19% to 50% as the Re number increases to 100; this is due to suppression of flow separation and a narrower wake. Introducing roughness into the simulations to model a superhydrophobic surface with a finite Cassie fraction results in less drag reduction because the vortex regime is no longer fully suppressed. Finally, we describe an analytical model of flow resistance through tubes or channels using similar boundary conditions to the flow past a gas-encapsulated sphere. We acknowledge funding from the UK EPSRC (EP/G058318/1, EP/G069581/1 and EP/L026899/1) and the Canadian NSERC.

  6. Sorption of hydrophobic organic compounds (HOC) in rapeseed oil bodies.

    PubMed

    Boucher, J; Cengelli, F; Trumbic, D; Marison, I W

    2008-02-01

    Oil-bodies are minute plant organelles (0.5-2.0microm diameter) consisting of an oil core surrounded by a phospholipid monolayer/proteinaceous membrane. Oil-bodies have been isolated from rapeseed seeds and demonstrated to constitute a novel type of micro-capsule suitable for the extraction of hydrophobic organic compounds from aqueous environments. Three hydrophobic pesticides: atrazine (2-chlor-4-ethyl-amino-6-isopropylamino-1,3,5-triazine), carbaryl (1-naphthyl methylcarbamate) and parathion (O,O-diethyl O-(4-nitrophenyl) phosphorothioate), as well as naphthalene and 2-phenylethanol were successfully extracted from aqueous solutions, with absorption in the inner oily core of OB as sorption mechanism. The OB membrane does not represent a barrier for the mass transfer of the compound towards the inner oily core of OB. Moreover, due to very high surface area to volume ratio, oil-bodies exhibit very good mass transfer properties compared with larger synthetic microcapsules or two-phase liquid-liquid extraction (LLE) techniques, which diminishes the need for strong agitation and avoids the formation of difficult to separate stable emulsions.

  7. Vapor transport through short hydrophobic nanopores for desalination

    NASA Astrophysics Data System (ADS)

    Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Rahman, Faizur; Karnik, Rohit

    2011-11-01

    We propose a concept for desalination of water by reverse osmosis (RO) using a vapor-trapping membrane composed of short hydrophobic nanopores and separates the salt water (feed) and the fresh water (permeate) on each side. The feed water is vaporized by applied pressure and the water vapor condenses on the permeate side accompanied by recovery of latent heat. A probabilistic model based on rarified gas conditions predicted 3-5 times larger mass flux by the proposed membrane than conventional RO membranes at temperatures in the range of 30-50C. To realize the short hydrophobic nanopores, gold was deposited at the entrance of alumina pores followed by SAM formation. The fraction of leaking pores was confirmed to be less than 0.2% using a calcium ion indicator (Fluo-4). Finally, a microfluidic flow cell was fabricated for characterizing the transport properties of the membranes. The authors would like to thank the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia, for funding the research reported in this paper through the Center for Clean Water and Clean Energy at MIT and KFUPM.

  8. Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene.

    PubMed

    Strong, Steven E; Eaves, Joel D

    2016-05-19

    Mirroring their role in electrical and optical physics, two-dimensional crystals are emerging as novel platforms for fluid separations and water desalination, which are hydrodynamic processes that occur in nanoscale environments. For numerical simulation to play a predictive and descriptive role, one must have theoretically sound methods that span orders of magnitude in physical scales, from the atomistic motions of particles inside the channels to the large-scale hydrodynamic gradients that drive transport. Here, we use constraint dynamics to derive a nonequilibrium molecular dynamics method for simulating steady-state mass flow of a fluid moving through the nanoscopic spaces of a porous solid. After validating our method on a model system, we use it to study the hydrophobic effect of water moving through pores of electrically doped single-layer graphene. The trend in permeability that we calculate does not follow the hydrophobicity of the membrane but is instead governed by a crossover between two competing molecular transport mechanisms. PMID:27139634

  9. Hydrophobic flocculation flotation for beneficiating fine coal and minerals

    SciTech Connect

    Song, S.; Valdivieso, A.L.

    1998-06-01

    It is shown that hydrophobic flocculation flotation (HFF) is an effective process to treat finely ground ores and slimes so as to concentrate coal and mineral values at a fine size range. The process is based on first dispersing the fine particles suspension, followed by flocculation of fine mineral values or coal in the form of hydrophobic surfaces either induced by specifically adsorbed surfactants or from nature at the conditioning of the slurry with the shear field of sufficient magnitude. The flocculation is intensified by the addition of a small amount of nonpolar oil. finely ground coals, ilmenite slimes, and gold finely disseminated in a slag have been treated by this process. Results are presented indicating that cleaned coal with low ash and sulfur remaining and high Btu recovery can be obtained, and the refractory ores of ilmenite slimes and fine gold-bearing slag can be reasonably concentrated, leading to better beneficiation results than other separation techniques. In addition, the main operating parameters affecting the HFF process are discussed.

  10. Energy Conversion over Super-hydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Hui; Zhai, Shengjie

    2015-11-01

    The streaming potential generated by a pressure-driven flow over a charged slip-stick surface with an arbitrary double layer thickness is both theoretically and experimentally studied. To understand the impact of the slip, the streaming potential is compared against that over a homogenously charged smooth surface. Our results indicate that the streaming potential over a super-hydrophobic surface only can be enhanced under certain conditions. In addition, the Onsager relation which directly relates the magnitude of electro-osmotic effect to that of the streaming current effect has been explicitly proved to be valid for thin and thick double layers and homogeneously charged super-hydrophobic surfaces. Comparisons between the streaming current and electro-osmotic mobility for an arbitrary electric double layer thickness under various conditions indicate that the Onsager relation seems applicable for arbitrary weakly charged super-hydrophobic surfaces though there is no general proof. Knowledge of the streaming potential over a slip-stick surface can provide guidance for designing novel and efficient microfluidic energy-conversion devices using super-hydrophobic surfaces. The work was supported by the NSF Grant No. ECCS-1509866.

  11. COSOLVENCY AND SOPRTION OF HYDROPHOBIC ORGANIC CHEMICALS

    EPA Science Inventory

    Sorption of hydrophobic organic chemicals (HOCs) by two soils was measured from mixed solvents containing water plus completely miscible organic solvents (CMOSs) and partially miscible organic solvents (PMOSs). The utility of the log-linear cosolvency model for predicting HOC sor...

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

    PubMed Central

    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

  13. Iontophoretic transport of a homologous series of ionized and nonionized model compounds: influence of hydrophobicity and mechanistic interpretation.

    PubMed

    Del Terzo, S; Behl, C R; Nash, R A

    1989-01-01

    An in vitro study was carried out to elucidate the mechanisms controlling iontophoretic transport. The investigation focused on three areas, including the nature of the permeant (state of ionization and hydrophobicity), skin structures (hair follicle distribution and stratum corneum), and various parameters influencing iontophoresis (current, permeant concentration, and competitive ion effects). The data indicate that iontophoretic-facilitated transport is essentially pore mediated and that the transport of ionized and nonionized molecules may be enhanced through the pore-type pathway. The data presented show that iontophoresis has a detrimental effect on the lipoidal transport pathway and that the transport of more hydrophobic nonionized molecules is decreased compared with passive diffusion. The iontophoretic enhancement values decreased linearly with increasing alkyl chain length of n-alkanols. The iontophoretic permeability coefficients of ionized n-alkanoic acids was shown to decrease with increasing permeant hydrophobicity.

  14. Hydrophobic and hydrophilic control in polyphosphazene materials

    NASA Astrophysics Data System (ADS)

    Steely, Lee Brent

    This thesis is the culmination of several recent studies focused on the surface characterization of polyphosphazenes specifically the properties of water repellency or hydrophobicity. Chapter 1 is a background account of polyphosphazene chemistry and the hydrophobicity of polyphosphazenes. Chapter 2 provides an examination of the role of surface morphology on hydrophobicity. This study deals in depth with the electrospinning of poly[bis(2,2,2-trifluoroethoxy)phosphazene] in tetrahydrofuran. This process yields fiber mats or bead and fiber mats which exhibit roughness in continuous contact with the water droplet (fiber mats) or discontinuous contact (bead and fiber mats). These surface roughness types are compared to spun cast films using water contact angles to measure the air-water-polymer interface. The influence of aromatic moieties and fluorine content on the air-water-polymer interface is examined in Chapter 3. This study examines the influence of fluorine content and aryloxy groups on the hydrophobicity of a polyphosphazene surface via static water contact angle measurements on a goniometer. Polymer surfaces of spun cast and electrospun mats were probed with advancing, receeding, and static water contact angle and dip coated slides of the same materials were also examined with a Langmuir-Blogett trough. Chapter 4 is a description of the environmental plasma surface treatments of polyphosphazenes as a method of functionalizing solid polymer surfaces. The treatment procedure of functionalizing spun cast and electrospun poly[bis(2,2,2-trifluoroethoxy)phosphazene] surfaces with plasma gases of oxygen, nitrogen, methane, and tetrafluoromethane is detailed. The resulting functionalization of the surface is examined with XPS and water contact angle data. In Chapter 5 fluoroalkoxy polyphosphazenes were processed with liquid carbon dioxide into foams. The foams were then tested for flame retardance and hydrophobicity. Appendixes A-C contain studies on moisture

  15. Charges in the hydrophobic interior of proteins.

    PubMed

    Isom, Daniel G; Castañeda, Carlos A; Cannon, Brian R; Velu, Priya D; García-Moreno E, Bertrand

    2010-09-14

    Charges are inherently incompatible with hydrophobic environments. Presumably for this reason, ionizable residues are usually excluded from the hydrophobic interior of proteins and are found instead at the surface, where they can interact with bulk water. Paradoxically, ionizable groups buried in the hydrophobic interior of proteins play essential roles, especially in biological energy transduction. To examine the unusual properties of internal ionizable groups we measured the pK(a) of glutamic acid residues at 25 internal positions in a stable form of staphylococcal nuclease. Two of 25 Glu residues titrated with normal pK(a) near 4.5; the other 23 titrated with elevated pK(a) values ranging from 5.2-9.4, with an average value of 7.7. Trp fluorescence and far-UV circular dichroism were used to monitor the effects of internal charges on conformation. These data demonstrate that although charges buried in proteins are indeed destabilizing, charged side chains can be buried readily in the hydrophobic core of stable proteins without the need for specialized structural adaptations to stabilize them, and without inducing any major conformational reorganization. The apparent dielectric effect experienced by the internal charges is considerably higher than the low dielectric constants of hydrophobic matter used to represent the protein interior in electrostatic continuum models of proteins. The high thermodynamic stability required for proteins to withstand the presence of buried charges suggests a pathway for the evolution of enzymes, and it underscores the need to mind thermodynamic stability in any strategy for engineering novel or altered enzymatic active sites in proteins. PMID:20798341

  16. The [BMI][Tf2N] ionic liquid/water binary system: a molecular dynamics study of phase separation and of the liquid-liquid interface.

    PubMed

    Sieffert, N; Wipff, G

    2006-07-01

    We report molecular dynamics (MD) simulations of the aqueous interface of the hydrophobic [BMI][Tf2N] ionic liquid (IL), composed of 1-butyl-3-methylimidazolium cations (BMI+) and bis(trifluoromethylsulfonyl)imide anions (Tf2N-). The questions of water/IL phase separation and properties of the neat interface are addressed, comparing different liquid models (TIP3P vs TIP5P water and +1.0/-1.0 vs +0.9/-0.9 charged IL ions), the Ewald vs the reaction field treatments of the long range electrostatics, and different starting conditions. With the different models, the "randomly" mixed liquids separate much more slowly (in 20 to 40 ns) than classical water-oil mixtures do (typically, in less than 1 ns), finally leading to distinct nanoscopic phases separated by an interface, as in simulations which started with a preformed interface, but the IL phase is more humid. The final state of water in the IL thus depends on the protocol and relates to IL heterogeneities and viscosity. Water mainly fluctuates in hydrophilic basins (rich in O(Tf2N) and aromatic CH(BMI) groups), separated by more hydrophobic domains (rich in CF3(Tf2N) and alkyl(BMI) groups), in the form of monomers and dimers in the weakly humid IL phase, and as higher aggregates when the IL phase is more humid. There is more water in the IL than IL in water, to different extents, depending on the model. The interface is sharper and narrower (approximately 10 A) than with the less hydrophobic [BMI][PF6] IL and is overall neutral, with isotropically oriented molecules, as in the bulk phases. The results allow us to better understand the analogies and differences of aqueous interfaces with hydrophobic (but hygroscopic) ILs, compared to classical organic liquids.

  17. Potentiometric responses of polymeric liquid membranes based on hydrophobic chelating agents to metal ions.

    PubMed

    Itoh, Y; Ueda, Y; Hirano, A; Sugawara, M; Tohda, K; Akaiwa, H; Umezawa, Y

    2001-05-01

    The effect of hydrophobicity of acidic chelating agents as sensing materials on the potentiometric responses of polymeric liquid membranes was investigated. The chelating agents tested were 8-quinolinol (HOx), dithizone (HDz), 1-(2-pyridylazo)-2-naphthol (PAN) and their alkylated analogues, 5-octyloxymethyl-8-quinolinol (HO8Q), di(phexylphenyl)thiocarbazone (C6HDz), 7-pentadecyloxy-1-(2-pyridylazo)-2-naphthol (C15PAN) and a series of N-alkylcarbonyl-N-phenylhydroxylamines (CnPHA, n = 3, 6, 9, 12). The distribution coefficients between membrane solvent and water were determined to evaluate the hydrophobicity of the agents. The potential-pH profiles of the membranes containing hydrophobic chelating agents demonstrated the generation of potentiometric responses, while less hydrophobic agents gave no response. A possible model for the generation of membrane potential is proposed. The charge separation is attained by the permselective uptake of metal cations by the chelating agent anion at membrane/solution interface, where the high hydrophobicity of the agent enables the anionic or deprotonated form of the agents to remain at the membrane/solution interface.

  18. Proline-poor hydrophobic domains modulate the assembly and material properties of polymeric elastin.

    PubMed

    Muiznieks, Lisa D; Reichheld, Sean E; Sitarz, Eva E; Miao, Ming; Keeley, Fred W

    2015-10-01

    Elastin is a self-assembling extracellular matrix protein that provides elasticity to tissues. For entropic elastomers such as elastin, conformational disorder of the monomer building block, even in the polymeric form, is essential for elastomeric recoil. The highly hydrophobic monomer employs a range of strategies for maintaining disorder and flexibility within hydrophobic domains, particularly involving a minimum compositional threshold of proline and glycine residues. However, the native sequence of hydrophobic elastin domain 30 is uncharacteristically proline-poor and, as an isolated polypeptide, is susceptible to formation of amyloid-like structures comprised of stacked β-sheet. Here we investigated the biophysical and mechanical properties of multiple sets of elastin-like polypeptides designed with different numbers of proline-poor domain 30 from human or rat tropoelastins. We compared the contributions of these proline-poor hydrophobic sequences to self-assembly through characterization of phase separation, and to the tensile properties of cross-linked, polymeric materials. We demonstrate that length of hydrophobic domains and propensity to form β-structure, both affecting polypeptide chain flexibility and cross-link density, play key roles in modulating elastin mechanical properties. This study advances the understanding of elastin sequence-structure-function relationships, and provides new insights that will directly support rational approaches to the design of biomaterials with defined suites of mechanical properties.

  19. Prediction of Water's Mobility and Disorder in Protein Crystals Using Novel Local Hydrophobic Descriptors.

    PubMed

    Pan, Yuzhu; Lv, Fenglin; Tian, Feifei; Luo, Xiaoli; Kong, Xiangjun; Li, Yuanchao; Yang, Qingwu

    2010-03-15

    The B-factors of crystal structures reflect the atomic fluctuations about their average positions and provide important information about molecular dynamics. Although numerous works have been addressed on theoretical and computational studies of B-factor profile of protein atoms, the methods used for predicting B-factor values of water molecules in protein crystals still remain unexploited. In this article, we describe a new approach that we named local hydrophobic descriptors (LHDs) to characterize the hydrophobic landscapes of protein hydration sites. Using this approach coupled with partial least squares (PLS) regression and least-squares squares support vector machine (LSSVM), we perform a systematic investigation on the linear and nonlinear relationships between the LHDs and water B-factors. Based upon an elaborately selected, large-scale dataset of crystal water molecules, our method predicts B-factor profile with coefficient of determination rpred of 0.554. We demonstrate that (i) the dynamics of water molecules is primarily governed by the local features of hydrophobic potential landscapes, and (ii) the accuracy of predicted B-factor values depends on water packing density.

  20. An experimental study on the effects of rough hydrophobic surfaces on the flow around a circular cylinder

    NASA Astrophysics Data System (ADS)

    Kim, Nayoung; Kim, Hyunseok; Park, Hyungmin

    2015-08-01

    The present study investigates the effect that rough hydrophobic (or superhydrophobic) surfaces have on the flow separation and subsequent vortex structures in a turbulent wake behind a circular cylinder. The velocity fields were measured using two-dimensional particle image velocimetry in a water tunnel with Reynolds numbers of 0.7-2.3 × 104. The spray-coating of hydrophobic nanoparticles and roughened Teflon was used to produce the rough hydrophobic surfaces, and sandpapers with two different grit sizes were used to sand the Teflon into streamwise and spanwise directions, respectively, in order to examine the effect of the slip direction. The rough hydrophobic surface was found to enhance the turbulence in the flows above the circular cylinder and along the separating shear layers, resulting in a delay of the flow separation and early vortex roll-up in the wake. As a result, the size of the recirculation bubble in the wake was reduced by up to 40%, while the drag reduction of less than 10% is estimated from a wake survey. However, these effects are reversed as the Reynolds number increases. The surface texture normal to the flow direction (spanwise slip) was found to be more effective than that aligned to the flow (streamwise slip), supporting the suggested mechanism. In addition, the superhydrophobic surface is locally applied by varying the installation angle and that applied around the separation point is most effective, indicating that the rough hydrophobic surface directly affects the boundary layer at flow separation. In order to control the flow around a circular cylinder using rough hydrophobic surfaces, it is suggested to have a smaller roughness width, which can stably retain air pockets. In addition, a higher gas fraction and a more uniform distribution of the roughness size are helpful to enhance the performance such as the separation delay and drag reduction.

  1. Chemotactic separation of enzymes.

    PubMed

    Dey, Krishna Kanti; Das, Sambeeta; Poyton, Matthew F; Sengupta, Samudra; Butler, Peter J; Cremer, Paul S; Sen, Ayusman

    2014-12-23

    We demonstrate a procedure for the separation of enzymes based on their chemotactic response toward an imposed substrate concentration gradient. The separation is observed within a two-inlet, five-outlet microfluidic network, designed to allow mixtures of active (ones that catalyze substrate turnover) and inactive (ones that do not catalyze substrate turnover) enzymes, labeled with different fluorophores, to flow through one of the inlets. Substrate solution prepared in phosphate buffer was introduced through the other inlet of the device at the same flow rate. The steady-state concentration profiles of the enzymes were obtained at specific positions within the outlets of the microchannel using fluorescence microscopy. In the presence of a substrate concentration gradient, active enzyme molecules migrated preferentially toward the substrate channel. The excess migration of the active enzyme molecules was quantified in terms of an enrichment coefficient. Experiments were carried out with different pairs of enzymes. Coupling the physics of laminar flow of liquid and molecular diffusion, multiphysics simulations were carried out to estimate the extent of the chemotactic separation. Our results show that, with appropriate microfluidic arrangement, molecular chemotaxis leads to spontaneous separation of active enzyme molecules from their inactive counterparts of similar charge and size.

  2. Competition of electrostatic and hydrophobic interactions between small hydrophobes and model enclosures

    PubMed Central

    Wang, Lingle; Friesner, Richard A.; Berne, B.J.

    2010-01-01

    The binding affinity between a probe hydrophobic particle and model hydrophobic plates with different charge (or dipole) densities in water was investigated through molecular dynamics simulations free-energy perturbation calculations. We observed a reduced binding affinity when the plates are charged, in agreement with previous findings. With increased charge density, the plates can change from “hydrophobic like” (pulling the particle into the interplate region) to “hydrophilic like” (ejecting the particle out of the interplate region), demonstrating the competition between hydrophobic and electrostatic interactions. The reduction of the binding affinity is quadratically dependent on the magnitude of the charge for symmetric systems, but linear and cubic terms also make a contribution for asymmetric systems. Statistical perturbation theory explains these results and shows when and why implicit solvent models fail. PMID:20443643

  3. Separation of molybdenum and technetium

    NASA Astrophysics Data System (ADS)

    Andersson, J. D.; Gagnon, K.; Wilson, J. S.; Romaniuk, J.; Abrams, D. N.; McQuarrie, S. A.

    2012-12-01

    After the production of 99mTc via the 100Mo(p,2n)99mTc reaction, there is a requirement for separating 99mTc from bulk 100Mo. Although a number of separation methods have been demonstrated, the possibility of using a cartridge-based system is particularly attractive for routine use in a good manufacturing practice (GMP) regulatory environment. This study confirmed that hydrophobic interaction chromatography (HIC) solid phase extraction (SPE) with PEG as stationary phase is an efficient and easily automated method for separating molybdate and pertechnetate, and that PEG degradation in the conditions used does not affect the performance of the resin. In addition, reversed phase SPE using Waters Oasis® HLB shows promise for successful separation of molybdenum and technetium and work continues to extend this technology to readily available commercial SPE cartridges.

  4. Isotope separation apparatus and method

    DOEpatents

    Feldman, Barry J.

    1985-01-01

    The invention relates to an improved method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferably substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. Because the molecules in the beam occupy various degenerate energy levels, if the laser beam comprises chirped pulses comprising selected wavelengths, the laser beam will very efficiently excite substantially all unexcited molecules and will cause stimulated emission of substantially all excited molecules of a selected one of the isotopes in the beam which such pulses encounter. Excitation caused by first direction chirped pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning chirped pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement of essentially all the molecules containing the one isotope is accomplished by a large number of chirped pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam.

  5. Interplay of metalloligand and organic ligand to tune micropores within isostructural mixed-metal organic frameworks (M'MOFs) for their highly selective separation of chiral and achiral small molecules.

    PubMed

    Das, Madhab C; Guo, Qunsheng; He, Yabing; Kim, Jaheon; Zhao, Cong-Gui; Hong, Kunlun; Xiang, Shengchang; Zhang, Zhangjing; Thomas, K Mark; Krishna, Rajamani; Chen, Banglin

    2012-05-23

    Four porous isostructural mixed-metal-organic frameworks (M'MOFs) have been synthesized and structurally characterized. The pores within these M'MOFs are systematically tuned by the interplay of both the metalloligands and organic ligands which have enabled us not only to direct their highly selective separation of chiral alcohols 1-phenylethanol (PEA), 2-butanol (BUT), and 2-pentanol (2-PEN) with the highest ee up to 82.4% but also to lead highly selective separation of achiral C(2)H(2)/C(2)H(4) separation. The potential application of these M'MOFs for the fixed bed pressure swing adsorption (PSA) separation of C(2)H(2)/C(2)H(4) has been further examined and compared by the transient breakthrough simulations in which the purity requirement of 40 ppm in the outlet gas can be readily fulfilled by the fixed bed M'MOF-4a adsorber at ambient conditions.

  6. Apparatus for molecular weight separation

    DOEpatents

    Smith, Richard D.; Liu, Chuanliang

    2001-01-01

    The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, (4) conducting a two-stage separation or (5) any combination of (1), (2), (3) and (4).

  7. Water properties inside nanoscopic hydrophobic pocket studied by computer simulations

    NASA Astrophysics Data System (ADS)

    Setny, Piotr; Geller, Maciej

    2006-10-01

    The structure and dynamics of water in the vicinity of the hemispherical hydrophobic pocket of 8Å radius were examined via molecular dynamics simulations in NVT ensemble. Density, hydrogen bonding properties, and residence times of water molecules were projected on two-dimensional planes providing a spatial description of water behavior. We found that the average water density is significantly depleted relative to bulk value. A detailed analysis of pocket occupancy revealed fluctuations between states of completely empty pocket and a pocket filled with a bulklike fluid, which seem to result from collective behavior of water molecules. Free energy differences accompanying these fluctuations are rather small, suggesting that the given pocket radius is close to the critical one for transition between gas and liquid phases in the considered system. We show that the situation is different in the case of a simple Lennard-Jones fluid. These results indicate that changing the surface curvature from flat to concave may lead to qualitative difference in water behavior in its vicinity. We think that our studies may also put some light on binding site desolvation process which is necessary to understand to make correct predictions of binding energies.

  8. Recovering Magnetic Fe3O4-ZnO Nanocomposites from Algal Biomass Based on Hydrophobicity Shift under UV Irradiation.

    PubMed

    Ge, Shijian; Agbakpe, Michael; Zhang, Wen; Kuang, Liyuan; Wu, Zhiyi; Wang, Xianqin

    2015-06-01

    Magnetic separation, one of the promising bioseparation technologies, faces the challenges in recovery and reuse of magnetic agents during algal harvesting for biofuel extraction. This study synthesized a steric acid (SA)-coated Fe3O4-ZnO nanocomposite that could shift hydrophobicity under UV365 irradiation. Our results showed that with the transition of surface hydrophobicity under UV365 irradiation, magnetic nanocomposites detached from the concentrated algal biomass. The detachment was partially induced by the oxidation of SA coating layers due to the generation of radicals (e.g., •OH) by ZnO under UV365 illumination. Consequently, the nanocomposite surface shifted from hydrophobic to hydrophilic, which significantly reduced the adhesion between magnetic particles and algae as predicted by the extended Derjaguin and Landau, Verwey, and Overbeek (EDLVO) theory. Such unique hydrophobicity shift may also find many other potential applications that require recovery, recycle, and reuse of valuable nanomaterials to increase sustainability and economically viability.

  9. Determining drug release rates of hydrophobic compounds from nanocarriers.

    PubMed

    D'Addio, Suzanne M; Bukari, Abdallah A; Dawoud, Mohammed; Bunjes, Heike; Rinaldi, Carlos; Prud'homme, Robert K

    2016-07-28

    Obtaining meaningful drug release profiles for drug formulations is essential prior to in vivo testing and for ensuring consistent quality. The release kinetics of hydrophobic drugs from nanocarriers (NCs) are not well understood because the standard protocols for maintaining sink conditions and sampling are not valid owing to mass transfer and solubility limitations. In this work, a new in vitroassay protocol based on 'lipid sinks' and magnetic separation produces release conditions that mimic the concentrations of lipid membranes and lipoproteins in vivo, facilitates separation, and thus allows determination of intrinsic release rates of drugs from NCs. The assay protocol is validated by (i) determining the magnetic separation efficiency, (ii) demonstrating that sink condition requirements are met, and (iii) accounting for drug by completing a mass balance. NCs of itraconazole and cyclosporine A (CsA) were prepared and the drug release profiles were determined. This release protocol has been used to compare the drug release from a polymer stabilized NC of CsA to a solid drug NP of CsA alone. These data have led to the finding that stabilizing block copolymer layers have a retarding effect on drug release from NCs, reducing the rate of CsA release fourfold compared with the nanoparticle without a polymer coating.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

  10. Sustained release of hydrophobic drugs by the microfluidic assembly of multistage microgel/poly (lactic-co-glycolic acid) nanoparticle composites

    PubMed Central

    Hsu, Myat Noe; Luo, Rongcong; Kwek, Kerwin Zeming; Por, Yong Chen; Zhang, Yong; Chen, Chia-Hung

    2015-01-01

    The poor solubility of many newly discovered drugs has resulted in numerous challenges for the time-controlled release of therapeutics. In this study, an advanced drug delivery platform to encapsulate and deliver hydrophobic drugs, consisting of poly (lactic-co-glycolic acid) (PLGA) nanoparticles incorporated within poly (ethylene glycol) (PEG) microgels, was developed. PLGA nanoparticles were used as the hydrophobic drug carrier, while the PEG matrix functioned to slow down the drug release. Encapsulation of the hydrophobic agents was characterized by fluorescence detection of the hydrophobic dye Nile Red within the microgels. In addition, the microcomposites prepared via the droplet-based microfluidic technology showed size tunability and a monodisperse size distribution, along with improved release kinetics of the loaded cargo compared with bare PLGA nanoparticles. This composite system has potential as a universal delivery platform for a variety of hydrophobic molecules. PMID:25825623

  11. Size separation of analytes using monomeric surfactants

    DOEpatents

    Yeung, Edward S.; Wei, Wei

    2005-04-12

    A sieving medium for use in the separation of analytes in a sample containing at least one such analyte comprises a monomeric non-ionic surfactant of the of the general formula, B-A, wherein A is a hydrophilic moiety and B is a hydrophobic moiety, present in a solvent at a concentration forming a self-assembled micelle configuration under selected conditions and having an aggregation number providing an equivalent weight capable of effecting the size separation of the sample solution so as to resolve a target analyte(s) in a solution containing the same, the size separation taking place in a chromatography or electrophoresis separation system.

  12. Thermal conductance of hydrophilic and hydrophobic interfaces.

    PubMed

    Ge, Zhenbin; Cahill, David G; Braun, Paul V

    2006-05-12

    Using time-domain thermoreflectance, we have measured the transport of thermally excited vibrational energy across planar interfaces between water and solids that have been chemically functionalized with a self-assembled monolayer (SAM). The Kapitza length--i.e., the thermal conductivity of water divided by the thermal conductance per unit area of the interface--is analogous to the "slip length" for water flowing tangentially past a solid surface. We find that the Kapitza length at hydrophobic interfaces (10-12 nm) is a factor of 2-3 larger than the Kapitza length at hydrophilic interfaces (3-6 nm). If a vapor layer is present at the hydrophobic interface, and this vapor layer has a thermal conductivity that is comparable to bulk water vapor, then our experimental results constrain the thickness of the vapor layer to be less than 0.25 nm.

  13. Biodegradable, hydrophobic coatings based on crosslinked polycaprolactone

    SciTech Connect

    Koenig, M.F.

    1993-12-31

    Crosslinked poly(caprolactone) (PCL) has been explored as a hydrophobic and biodegradable coating for hydrophilic substrates. Crosslinking of PCL is known to retard its degradation rate, but does not affect its biodegradability. The cross-linking efficiencies of several organic peroxides have been determined for PCL. This has been accomplished by calculating the crosslink density (M{sub c} from dynamic mechanical data) for a given molar concentration of organic peroxide. Various thicknesses of crosslinked PCL have been coated on several different hydrophilic substrates, including paper, MaterBi (regsign), and PCL/starch composites. The hydrophobicity of the coating has been measured by following the weight gain of the coated samples upon exposure to water and a high relative humidity for various lengths of time. Results show that a coating as thin as 10 {mu}m reduces water absorption of paper by a factor of five, and thicker coatings (0.25 mm) by more than two orders of magnitude.

  14. Preparation of a thermoresponsive polymer grafted polystyrene monolithic capillary for the separation of bioactive compounds.

    PubMed

    Koriyama, Takuya; Asoh, Taka-Aki; Kikuchi, Akihiko

    2016-11-01

    To develop aqueous microseparation columns for bioactive compounds, a thermoresponsive polymer grafted polymer monolith was prepared inside silica capillaries having an I.D. of 100μm by polymerization of styrene (St) with m/p-divinylbenzene (DVB) in the presence of polydimethylsiloxane as porogen, followed by surface-initiated atom transfer radical polymerization (SI-ATRP) of N-isopropylacrylamide (NIPAAm). SEM analysis indicated that the resulting poly(N-isopropylacrylamide) (PNIPAAm) grafted polystyrene monolith had a consecutive three-dimensionally interconnected structure and through-pores, similar to the base polystyrene (PSt) monolith. The elution behavior of steroids with different hydrophobicity was evaluated using micro-high-performance liquid chromatography in sole aqueous mobile phase. Temperature dependent interaction changes were observed between steroids and the PNIPAAm modified surfaces. Furthermore, the interaction between bioactive compounds and the PNIPAAm grafted PSt surfaces was controlled and eventually separate these molecules with different hydrophobicities by simple temperature modulation in aqueous environment. The PNIPAAm grafted PSt monolithic capillary showed improved separation properties of bioactive compounds, compared with a PNIPAAm grafted hollow capillary in aqueous environment. PMID:27559999

  15. Preparation of a thermoresponsive polymer grafted polystyrene monolithic capillary for the separation of bioactive compounds.

    PubMed

    Koriyama, Takuya; Asoh, Taka-Aki; Kikuchi, Akihiko

    2016-11-01

    To develop aqueous microseparation columns for bioactive compounds, a thermoresponsive polymer grafted polymer monolith was prepared inside silica capillaries having an I.D. of 100μm by polymerization of styrene (St) with m/p-divinylbenzene (DVB) in the presence of polydimethylsiloxane as porogen, followed by surface-initiated atom transfer radical polymerization (SI-ATRP) of N-isopropylacrylamide (NIPAAm). SEM analysis indicated that the resulting poly(N-isopropylacrylamide) (PNIPAAm) grafted polystyrene monolith had a consecutive three-dimensionally interconnected structure and through-pores, similar to the base polystyrene (PSt) monolith. The elution behavior of steroids with different hydrophobicity was evaluated using micro-high-performance liquid chromatography in sole aqueous mobile phase. Temperature dependent interaction changes were observed between steroids and the PNIPAAm modified surfaces. Furthermore, the interaction between bioactive compounds and the PNIPAAm grafted PSt surfaces was controlled and eventually separate these molecules with different hydrophobicities by simple temperature modulation in aqueous environment. The PNIPAAm grafted PSt monolithic capillary showed improved separation properties of bioactive compounds, compared with a PNIPAAm grafted hollow capillary in aqueous environment.

  16. Stability and phase separation in mixed monopolar lipid/bolalipid layers.

    PubMed

    Longo, Gabriel S; Thompson, David H; Szleifer, I

    2007-10-15

    The phase stability of a fluid lipid layer that is a mixture of conventional monopolar lipids and C20 bipolar bolalipids was studied using a mean field theory that explicitly includes molecular details and configurational properties of the lipid molecules. The effect of changing the fraction of bolalipids, as well as the length of the hydrocarbon chain of the monopolar lipids, was probed. A phase separation between two liquid lipid phases was found when a mismatch exists in the optimal hydrophobic thicknesses of the pure bolalipid and monopolar lipid layers. The lipid mixture phase separates into a thin bolalipid-rich layer and a thicker monopolar-rich layer. The thin membrane phase is mainly composed of transmembrane bolalipid molecules whose polar heads are positioned at opposite membrane-water interfaces. In the monopolar lipid-rich phase, bolalipids are the minor component and most of them assume a looping configuration where both headgroups are present at the same membrane-water interface. For mixed layers that form a single lipid phase across all bolalipid concentrations, the hairpin-transmembrane ratio strongly depends on the hydrocarbon chain length of the monopolar lipid and the bolalipid concentration. The C-D bond order parameters of the different species have been calculated. Our findings suggest that the concentration-dependent phase transition should be experimentally observable by measuring of the order parameters through quadrupolar splitting experiments. The driving force for the phase separation in the monopolar lipid/bolalipid mixture is the packing mismatch between hydrophobic regions of the monopolar lipid hydrocarbon chains and the membrane-spanning bolalipid chains. The results from the molecular theory may be useful in the design of stable lipid layers for integral membrane protein sensing.

  17. Nonflammable, Hydrophobic Aerogel Composites for Insulation

    NASA Technical Reports Server (NTRS)

    Redouane, Begag

    2005-01-01

    Aerogel composites that are both nonflammable and hydrophobic have been developed for use as lightweight thermal- insulation materials for cryogenic systems. Aerogels are well known in the industry for their effectiveness as thermal insulators under cryogenic conditions, but the treatments used heretofore to render them hydrophobic also make them flammable. Nonflammability would make it safer to use aerogel insulation, especially in oxygen-rich environments and on cryogenic systems that contain liquid oxygen. A composite of this type is a silica aerogel reinforced with fibers. In comparison with unreinforced aerogels, the aerogel composite is about ten times as stiff and strong, better able to withstand handling, and more amenable to machining to required shapes. The composite can be made hydrophobic and nonflammable by appropriate design of a sol-gel process used to synthesize the aerogel component. In addition to very low thermal conductivity needed for insulation, aerogel composites of this type have been found to exhibit high resistance to moisture and nonflammability in oxygen-rich atmospheres: Samples floating on water for months gained no weight and showed no signs of deterioration. Samples were found to be nonflammable, even in pure oxygen at atmospheric pressure [14.7 psia (0.10 MPa)

  18. How to move an amphipathic molecule across a lipid bilayer: different mechanisms for different ABC transporters?

    PubMed Central

    Theodoulou, Frederica L.; Carrier, David J.; Schaedler, Theresia A.; Baldwin, Stephen A.; Baker, Alison

    2016-01-01

    Import of β-oxidation substrates into peroxisomes is mediated by ATP binding cassette (ABC) transporters belonging to subfamily D. In order to enter the β-oxidation pathway, fatty acids are activated by conversion to fatty acyl-CoA esters, a reaction which is catalysed by acyl-CoA synthetases (ACSs). Here, we present evidence for an unusual transport mechanism, in which fatty acyl-CoA substrates are accepted by ABC subclass D protein (ABCD) transporters, cleaved by the transporters during transit across the lipid bilayer to release CoA, and ultimately re-esterified in the peroxisome lumen by ACSs which interact with the transporter. We propose that this solves the biophysical problem of moving an amphipathic molecule across the peroxisomal membrane, since the intrinsic thioesterase activity of the transporter permits separate membrane translocation pathways for the hydrophobic fatty acid moiety and the polar CoA moiety. The cleavage/re-esterification mechanism also has the potential to control entry of disparate substrates into the β-oxidation pathway when coupled with distinct peroxisomal ACSs. A different solution to the movement of amphipathic molecules across a lipid bilayer is deployed by the bacterial lipid-linked oligosaccharide (LLO) flippase, PglK, in which the hydrophilic head group and the hydrophobic polyprenyl tail of the substrate are proposed to have distinct translocation pathways but are not chemically separated during transport. We discuss a speculative alternating access model for ABCD proteins based on the mammalian ABC transporter associated with antigen processing (TAP) and compare it to the novel mechanism suggested by the recent PglK crystal structures and biochemical data. PMID:27284041

  19. How to move an amphipathic molecule across a lipid bilayer: different mechanisms for different ABC transporters?

    PubMed

    Theodoulou, Frederica L; Carrier, David J; Schaedler, Theresia A; Baldwin, Stephen A; Baker, Alison

    2016-06-15

    Import of β-oxidation substrates into peroxisomes is mediated by ATP binding cassette (ABC) transporters belonging to subfamily D. In order to enter the β-oxidation pathway, fatty acids are activated by conversion to fatty acyl-CoA esters, a reaction which is catalysed by acyl-CoA synthetases (ACSs). Here, we present evidence for an unusual transport mechanism, in which fatty acyl-CoA substrates are accepted by ABC subclass D protein (ABCD) transporters, cleaved by the transporters during transit across the lipid bilayer to release CoA, and ultimately re-esterified in the peroxisome lumen by ACSs which interact with the transporter. We propose that this solves the biophysical problem of moving an amphipathic molecule across the peroxisomal membrane, since the intrinsic thioesterase activity of the transporter permits separate membrane translocation pathways for the hydrophobic fatty acid moiety and the polar CoA moiety. The cleavage/re-esterification mechanism also has the potential to control entry of disparate substrates into the β-oxidation pathway when coupled with distinct peroxisomal ACSs. A different solution to the movement of amphipathic molecules across a lipid bilayer is deployed by the bacterial lipid-linked oligosaccharide (LLO) flippase, PglK, in which the hydrophilic head group and the hydrophobic polyprenyl tail of the substrate are proposed to have distinct translocation pathways but are not chemically separated during transport. We discuss a speculative alternating access model for ABCD proteins based on the mammalian ABC transporter associated with antigen processing (TAP) and compare it to the novel mechanism suggested by the recent PglK crystal structures and biochemical data. PMID:27284041

  20. Water anomalous thermodynamics, attraction, repulsion, and hydrophobic hydration.

    PubMed

    Cerdeiriña, Claudio A; Debenedetti, Pablo G

    2016-04-28

    A model composed of van der Waals-like and hydrogen bonding contributions that simulates the low-temperature anomalous thermodynamics of pure water while exhibiting a second, liquid-liquid critical point [P. H. Poole et al., Phys. Rev. Lett. 73, 1632 (1994)] is extended to dilute solutions of nonionic species. Critical lines emanating from such second critical point are calculated. While one infers that the smallness of the water molecule may be a relevant factor for those critical lines to move towards experimentally accessible regions, attention is mainly focused on the picture our model draws for the hydration thermodynamics of purely hydrophobic and amphiphilic non-electrolyte solutes. We first focus on differentiating solvation at constant volume from the corresponding isobaric process. Both processes provide the same viewpoint for the low solubility of hydrophobic solutes: it originates from the combination of weak solute-solvent attractive interactions and the specific excluded-volume effects associated with the small molecular size of water. However, a sharp distinction is found when exploring the temperature dependence of hydration phenomena since, in contrast to the situation for the constant-V process, the properties of pure water play a crucial role at isobaric conditions. Specifically, the solubility minimum as well as enthalpy and entropy convergence phenomena, exclusively ascribed to isobaric solvation, are closely related to water's density maximum. Furthermore, the behavior of the partial molecular volume and the partial molecular isobaric heat capacity highlights the interplay between water anomalies, attraction, and repulsion. The overall picture presented here is supported by experimental observations, simulations, and previous theoretical results. PMID:27131551

  1. Water anomalous thermodynamics, attraction, repulsion, and hydrophobic hydration

    NASA Astrophysics Data System (ADS)

    Cerdeiriña, Claudio A.; Debenedetti, Pablo G.

    2016-04-01

    A model composed of van der Waals-like and hydrogen bonding contributions that simulates the low-temperature anomalous thermodynamics of pure water while exhibiting a second, liquid-liquid critical point [P. H. Poole et al., Phys. Rev. Lett. 73, 1632 (1994)] is extended to dilute solutions of nonionic species. Critical lines emanating from such second critical point are calculated. While one infers that the smallness of the water molecule may be a relevant factor for those critical lines to move towards experimentally accessible regions, attention is mainly focused on the picture our model draws for the hydration thermodynamics of purely hydrophobic and amphiphilic non-electrolyte solutes. We first focus on differentiating solvation at constant volume from the corresponding isobaric process. Both processes provide the same viewpoint for the low solubility of hydrophobic solutes: it originates from the combination of weak solute-solvent attractive interactions and the specific excluded-volume effects associated with the small molecular size of water. However, a sharp distinction is found when exploring the temperature dependence of hydration phenomena since, in contrast to the situation for the constant-V process, the properties of pure water play a crucial role at isobaric conditions. Specifically, the solubility minimum as well as enthalpy and entropy convergence phenomena, exclusively ascribed to isobaric solvation, are closely related to water's density maximum. Furthermore, the behavior of the partial molecular volume and the partial molecular isobaric heat capacity highlights the interplay between water anomalies, attraction, and repulsion. The overall picture presented here is supported by experimental observations, simulations, and previous theoretical results.

  2. Water anomalous thermodynamics, attraction, repulsion, and hydrophobic hydration.

    PubMed

    Cerdeiriña, Claudio A; Debenedetti, Pablo G

    2016-04-28

    A model composed of van der Waals-like and hydrogen bonding contributions that simulates the low-temperature anomalous thermodynamics of pure water while exhibiting a second, liquid-liquid critical point [P. H. Poole et al., Phys. Rev. Lett. 73, 1632 (1994)] is extended to dilute solutions of nonionic species. Critical lines emanating from such second critical point are calculated. While one infers that the smallness of the water molecule may be a relevant factor for those critical lines to move towards experimentally accessible regions, attention is mainly focused on the picture our model draws for the hydration thermodynamics of purely hydrophobic and amphiphilic non-electrolyte solutes. We first focus on differentiating solvation at constant volume from the corresponding isobaric process. Both processes provide the same viewpoint for the low solubility of hydrophobic solutes: it originates from the combination of weak solute-solvent attractive interactions and the specific excluded-volume effects associated with the small molecular size of water. However, a sharp distinction is found when exploring the temperature dependence of hydration phenomena since, in contrast to the situation for the constant-V process, the properties of pure water play a crucial role at isobaric conditions. Specifically, the solubility minimum as well as enthalpy and entropy convergence phenomena, exclusively ascribed to isobaric solvation, are closely related to water's density maximum. Furthermore, the behavior of the partial molecular volume and the partial molecular isobaric heat capacity highlights the interplay between water anomalies, attraction, and repulsion. The overall picture presented here is supported by experimental observations, simulations, and previous theoretical results.

  3. Long-range and short-range mechanisms of hydrophobic attraction and hydrophilic repulsion in specific and aspecific interactions.

    PubMed

    van Oss, Carel Jan

    2003-01-01

    Among the three different non-covalent forces acting in aqueous media, i.e. Lifshitz-van der Waals (LW), Lewis acid-base (AB) and electrical double layer (EL) forces, the AB forces or electron-acceptor/electron-donor interactions are quantitatively by far the predominant ones. A subset of the AB forces acting in water causes the hydrophobic effect, which is the attraction caused by the hydrogen-bonding (AB) free energy of cohesion between the water molecules which surround all apolar as well as polar molecules and particles when they are immersed in water. As the polar energy of cohesion among water molecules is an innate property of water, the hydrophobic attraction (due to the hydrophobic effect) is unavoidably always present in aqueous media and has a value of DeltaG(hydrophobic) = -102 mJ/m(2), at 20 degrees C, being equal to the AB free energy of cohesion between the water molecules at that temperature. The strong underlying hydrophobic attraction due to this effect can, however, be surmounted by very hydrophilic molecules and particles that attract water molecules more strongly than the free energy of attraction of these molecules or particles for one another, plus the hydrogen-bonding free energy of cohesion between the water molecules, thus resulting in a net non-electrical double layer repulsion. Each of the three non-covalent forces, LW, AB or EL, any of which can be independently attractive or repulsive, decays, dependent on the circumstances, as a function of distance according to different rules. These rules, following an extended DLVO (XDLVO) approach, are given, as well as the measurement methods for the LW, AB and EL surface thermodynamic properties, determined at "contact". The implications of the resulting hydrophobic attractive and hydrophilic repulsive free energies, as a function of distance, are discussed with respect to specific and aspecific interactions in biological systems. The discussion furnishes a description of the manner by which

  4. Water around fullerene shape amphiphiles: A molecular dynamics simulation study of hydrophobic hydration

    SciTech Connect

    Varanasi, S. R. E-mail: guskova@ipfdd.de; John, A.; Guskova, O. A. E-mail: guskova@ipfdd.de; Sommer, J.-U.

    2015-06-14

    Fullerene C{sub 60} sub-colloidal particle with diameter ∼1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C{sub 60} fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent molecules—water retardation—in the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and the “dangling” –OH groups that represent surface defects in water network are monitored. The fraction of such defect structures is increased near the hydrophobic cap of fullerenes. Some “dry” regions of C{sub 60} are observed which can be considered as signatures of surface dewetting. In an effort to provide molecular level insight into the thermodynamics of hydration, the free energy of solvation is determined for a family of fullerene particles using thermodynamic integration technique.

  5. Hydrophobic ion interactions with membranes. Thermodynamic analysis of tetraphenylphosphonium binding to vesicles.

    PubMed Central

    Flewelling, R F; Hubbell, W L

    1986-01-01

    The thermodynamic properties for the interaction of the hydrophobic ion tetraphenylphosphonium (TPP+) with egg phosphatidylcholine vesicles were studied in detail by equilibrium dialysis and spin label techniques. A partition coefficient of beta = 4.2 + 0.4 x 10(-6) cm (K congruent to 100) was determined. Electrostatic saturation sets in at approximately 600 microM (about one absorbed TPP+ molecule per 100 lipids), and is not screened by salt. The temperature dependence of binding was determined, which reveals that the binding is entropy-driven with a positive (repulsive) enthalpy of binding, a result to be compared with hydrophobic anions in which the binding enthalpy is negative. The membrane dipole potential may be responsible for this binding difference. Activity coefficients are determined and shown to be significantly different from those of most common salts, an important result that should be considered in all hydrophobic ion studies. Comparison of the TPP+ results with those of its anionic structural analogue, tetraphenylboron (TPB-), permits a general analysis of hydrophobic ion interactions with membranes. A theoretical model consistent with the entire set of data is developed in an accompanying article. PMID:3006814

  6. Interplay of Metalloligand and Organic Ligand to Tune Micropores within Isostructural Mixed-Metal Organic Frameworks (M MOFs) for Their Highly Selective Separation of Chiral and Achiral Small Molecules

    SciTech Connect

    Madhab, Das; He, Yabing; Kim, Jaheon; Guo, Qunsheng; Zhao, Cong-Gui; Hong, Kunlun; Xiang, Sheng-Chang; Zhang, Zhangjing; Thomas, K Mark; Krishna, Rajamani; Chen, Banglin

    2012-01-01

    Four porous isostructural mixed-metal-organic frameworks (M'MOFs) have been synthesized and structurally characterized. The pores within these M'MOFs are systematically tuned by the interplay of both the metalloligands and organic ligands which have enabled us not only to direct their highly selective separation of chiral alcohols 1-phenylethanol (PEA), 2-butanol (BUT), and 2-pentanol (2-PEN) with the highest ee up to 82.4% but also to lead highly selective separation of achiral C{sub 2}H{sub 2}/C{sub 2}H{sub 4} separation. The potential application of these M'MOFs for the fixed bed pressure swing adsorption (PSA) separation of C{sub 2}H{sub 2}/C{sub 2}H{sub 4} has been further examined and compared by the transient breakthrough simulations in which the purity requirement of 40 ppm in the outlet gas can be readily fulfilled by the fixed bed M'MOF-4a adsorber at ambient conditions.

  7. Enhanced oil recovery process using a hydrophobic associative composition containing a hydrophilic/hydrophobic polymer

    SciTech Connect

    Evani, S.

    1989-03-21

    An enhanced oil recovery process is described, which comprises forcing an aqueous flooding medium from an injection well through a subterranean formation toward a producing well wherein the flooding medium contains a mobility control agent which is soluble in an aqueous flooding medium. The agent consists of a hydrophilic/hydrophobic polymer having hydrophobic moieties and a water-dispersible, nonionic surfactant having hydrophobic groups that are capable of associating with the hydrophobic moieties of the polymer wherein the proportion of the polymer and the surfactant is such that, at ambient conditions, water containing 0.5 weight percent of the agent has a viscosity at least twice the viscosity of water. The agent is prepared by carrying out the polymerization to form the polymer in the presence of the nonionic surfactant, the ratio of the surfactant to the polymer in the agent being sufficient to provide a viscosity at least twice that of an aqueous solution containing only the polymer, the hydrophobic polymer being a copolymer of a hydrophilic/water-soluble monomer and a water-insoluble monomer selected from the group consisting of higher alkyl ester of ..cap alpha..,..beta..-ethylenically unsaturated carboxylic acids wherein alkyl has from 8 to 20 carbons, alkylaryl esters of ethylenically unsaturated carboxylic acids, N-alkylethylenically unsaturated amides wherein alkyl has from 8 to 20 carbon atoms; vinyl alkylates wherein alkyl has at least 8 carbons and ar-alkyl styrenes wherein alkyl has at least 4 carbons.

  8. Low proliferation and high apoptosis of osteoblastic cells on hydrophobic surface are associated with defective Ras signaling

    SciTech Connect

    Chang, Eun-Ju; Kim, Hong-Hee; Huh, Jung-Eun; Kim, In-Ae; Seung Ko, Jea; Chung, Chong-Pyoung; Kim, Hyun-Man . E-mail: hyunmkim@plaza.snu.ac.kr

    2005-02-01

    The hydrophobic (HPB) nature of most polymeric biomaterials has been a major obstacle in using those materials in vivo due to low compatibility with cells. However, there is little knowledge of the molecular detail to explain how surface hydrophobicity affects cell responses. In this study, we compared the proliferation and apoptosis of human osteoblastic MG63 cells adhered to hydrophilic (HPL) and hydrophobic surfaces. On the hydrophobic surface, less formation of focal contacts and actin stress fibers, a delay in cell cycle progression, and an increase in apoptosis were observed. By using fibroblast growth factor 1 (FGF1) as a model growth factor, we also investigated intracellular signaling pathways on hydrophilic and hydrophobic surfaces. The activation of Ras, Akt, and ERK by FGF1 was impaired in MG63 cells on the hydrophobic surface. The overexpression of constitutively active form of Ras and Akt rescued those cells from apoptosis and recovered cell cycle progression. Furthermore, their overexpression also restored the actin cytoskeletal organization on the hydrophobic surface. Finally, the proliferative, antiapoptotic, and cytoskeletal effects of constitutively active Ras in MG63 cells on the hydrophobic surface were blocked by wortmannin and PD98059 that inhibit Akt and ERK activation, respectively. Therefore, our results suggest that the activation of Ras and its downstream molecules Akt and ERK to an appropriate level is one of crucial elements in the determination of osteoblast cell responses. The Ras pathway may represent a cell biological target that should be considered for successful surface modification of biomaterials to induce adequate cell responses in the bone tissue.

  9. Difference of carboxybetaine and oligo(ethylene glycol) moieties in altering hydrophobic interactions: a molecular simulation study.

    PubMed

    Shao, Qing; White, Andrew D; Jiang, Shaoyi

    2014-01-01

    Polycarboxybetaine and poly(ethylene glycol) materials resist nonspecific protein adsorption but differ in influencing biological functions such as enzymatic activity. To investigate this difference, we studied the influence of carboxybetaine and oligo(ethylene glycol) moieties on hydrophobic interactions using molecular simulations. We employed a model system composed of two non-polar plates and studied the potential of mean force of plate-plate association in carboxybetaine, (ethylene glycol)4, and (ethylene glycol)2 solutions using well-tempered metadynamics simulations. Water, trimethylamine N-oxide, and urea solutions were used as reference systems. We analyzed the variation of the potential of mean force in various solutions to study how carboxybetaine and oligo(ethylene glycol) moieties influence the hydrophobic interactions. To study the origin of their influence, we analyzed the normalized distributions of moieties and water molecules using molecular dynamics simulations. The simulation results showed that oligo(ethylene glycol) moieties repel water molecules away from the non-polar plates and weaken the hydrophobic interactions. Carboxybetaine moieties do not repel water molecules away from the plates and therefore do not influence the hydrophobic interactions.

  10. Towards a structural biology of the hydrophobic effect in protein folding

    PubMed Central

    Camilloni, Carlo; Bonetti, Daniela; Morrone, Angela; Giri, Rajanish; Dobson, Christopher M.; Brunori, Maurizio; Gianni, Stefano; Vendruscolo, Michele

    2016-01-01

    The hydrophobic effect is a major driving force in protein folding. A complete understanding of this effect requires the description of the conformational states of water and protein molecules at different temperatures. Towards this goal, we characterise the cold and hot denatured states of a protein by modelling NMR chemical shifts using restrained molecular dynamics simulations. A detailed analysis of the resulting structures reveals that water molecules in the bulk and at the protein interface form on average the same number of hydrogen bonds. Thus, even if proteins are ‘large’ particles (in terms of the hydrophobic effect, i.e. larger than 1 nm), because of the presence of complex surface patterns of polar and non-polar residues their behaviour can be compared to that of ‘small’ particles (i.e. smaller than 1 nm). We thus find that the hot denatured state is more compact and richer in secondary structure than the cold denatured state, since water at lower temperatures can form more hydrogen bonds than at high temperatures. Then, using Φ-value analysis we show that the structural differences between the hot and cold denatured states result in two alternative folding mechanisms. These findings thus illustrate how the analysis of water-protein hydrogen bonds can reveal the molecular origins of protein behaviours associated with the hydrophobic effect. PMID:27461719

  11. Fluorinated carbide-derived carbon: more hydrophilic, yet apparently more hydrophobic.

    PubMed

    Farmahini, Amir H; Sholl, David S; Bhatia, Suresh K

    2015-05-13

    We explore the effect of fluorine doping on hydrophobicity of nanoporous silicon carbide-derived carbon (SiCDC), and investigate the underlying barriers for adsorption and diffusion of water vapor and CO2 in the fluorinated and nonfluorinated structures. We develop atomistic models of fluorine-doped SiCDC at three different levels of fluorination, based on a hybrid reverse Monte Carlo constructed model of SiCDC, and develop a novel first-principles force field for the simulation of adsorption and transport of water and CO2 in the fluorine-doped carbon materials. We demonstrate an apparent dual effect of fluorination, showing that while fluorination generates more hydrophilic carbon surfaces, they actually act as more hydrophobic structures due to enhanced energy barriers in the disordered network of microporous carbon. While an increase in adsorption energy and in water uptake is seen for fluorine-doped carbon, large internal free energy barriers as well as the results of MD simulations demonstrate that the increased adsorption is kinetically limited and not experimentally observable on practical time scales. We show that an increase in apparent hydrophobicity due to fluorination is mediated by larger free energy barriers arising from stronger binding of fluid molecules inside the pore network, as opposed to repulsion or steric hindrance to the diffusion of molecules through narrow pore entries. For carbon dioxide, adsorption enthalpies and activation energy barriers are both decreased on fluorination, indicating weakened solid-fluid binding energies in the fluorinated systems.

  12. Shaping Nanoparticles with Hydrophilic Compositions and Hydrophobic Properties as Nanocarriers for Antibiotic Delivery

    PubMed Central

    2015-01-01

    Inspired by the lotus effect in nature, surface roughness engineering has led to novel materials and applications in many fields. Despite the rapid progress in superhydrophobic and superoleophobic materials, this concept of Mother Nature’s choice is yet to be applied in the design of advanced nanocarriers for drug delivery. Pioneering work has emerged in the development of nanoparticles with rough surfaces for gene delivery; however, the preparation of nanoparticles with hydrophilic compositions but with enhanced hydrophobic property at the nanoscale level employing surface topology engineering remains a challenge. Herein we report for the first time the unique properties of mesoporous hollow silica (MHS) nanospheres with controlled surface roughness. Compared to MHS with a smooth surface, rough mesoporous hollow silica (RMHS) nanoparticles with the same hydrophilic composition show unusual hydrophobicity, leading to higher adsorption of a range of hydrophobic molecules and controlled release of hydrophilic molecules. RMHS loaded with vancomycin exhibits an enhanced antibacterial effect. Our strategy provides a new pathway in the design of novel nanocarriers for diverse bioapplications. PMID:27162988

  13. Shaping Nanoparticles with Hydrophilic Compositions and Hydrophobic Properties as Nanocarriers for Antibiotic Delivery.

    PubMed

    Ahmad Nor, Yusilawati; Niu, Yuting; Karmakar, Surajit; Zhou, Liang; Xu, Chun; Zhang, Jun; Zhang, Hongwei; Yu, Meihua; Mahony, Donna; Mitter, Neena; Cooper, Matthew A; Yu, Chengzhong

    2015-09-23

    Inspired by the lotus effect in nature, surface roughness engineering has led to novel materials and applications in many fields. Despite the rapid progress in superhydrophobic and superoleophobic materials, this concept of Mother Nature's choice is yet to be applied in the design of advanced nanocarriers for drug delivery. Pioneering work has emerged in the development of nanoparticles with rough surfaces for gene delivery; however, the preparation of nanoparticles with hydrophilic compositions but with enhanced hydrophobic property at the nanoscale level employing surface topology engineering remains a challenge. Herein we report for the first time the unique properties of mesoporous hollow silica (MHS) nanospheres with controlled surface roughness. Compared to MHS with a smooth surface, rough mesoporous hollow silica (RMHS) nanoparticles with the same hydrophilic composition show unusual hydrophobicity, leading to higher adsorption of a range of hydrophobic molecules and controlled release of hydrophilic molecules. RMHS loaded with vancomycin exhibits an enhanced antibacterial effect. Our strategy provides a new pathway in the design of novel nanocarriers for diverse bioapplications. PMID:27162988

  14. Interfacial water at hydrophobic and hydrophilic surfaces: slip, viscosity, and diffusion.

    PubMed

    Sendner, Christian; Horinek, Dominik; Bocquet, Lyderic; Netz, Roland R

    2009-09-15

    The dynamics and structure of water at hydrophobic and hydrophilic diamond surfaces is examined via non-equilibrium Molecular Dynamics simulations. For hydrophobic surfaces under shearing conditions, the general hydrodynamic boundary condition involves a finite surface slip. The value of the slip length depends sensitively on the surface water interaction strength and the surface roughness; heuristic scaling relations between slip length, contact angle, and depletion layer thickness are proposed. Inert gas in the aqueous phase exhibits pronounced surface activity but only mildly increases the slip length. On polar hydrophilic surfaces, in contrast, slip is absent, but the water viscosity is found to be increased within a thin surface layer. The viscosity and the thickness of this surface layer depend on the density of polar surface groups. The dynamics of single water molecules in the surface layer exhibits a similar distinction: on hydrophobic surfaces the dynamics is purely diffusive, while close to a hydrophilic surface transient binding or trapping of water molecules over times of the order of hundreds of picoseconds occurs. We also discuss in detail the effect of the Lennard-Jones cutoff length on the interfacial properties.

  15. Evaluation of magnetic particles modified with a hydrophobic charge-induction ligand for antibody capture.

    PubMed

    Gu, Jia-Li; Tong, Hong-Fei; Lin, Dong-Qiang

    2016-08-19

    Magnetic particles modified with 5-amino-benzimidazole (ABI), a ligand for hydrophobic charge-induction chromatography, were prepared and used for antibody capture. In this study, with IgG as the model target, and bovine serum albumin (BSA) as the model impurity, the separation mechanism and process of IgG was investigated. The adsorption isotherms of IgG and BSA were measured, and the effects of pH were investigated in the range of pH 4.0-8.0. The maximum adsorption capacity of IgG on the particles was 180mg/ml at pH 7.0, while low adsorption capacity of BSA (64mg/ml) was found at pH 7.0, resulting in good selectivity. The protein-ligand interactions were elucidated by adding NaCl and glycerol. The results indicated the hydrophobic interactions were the main forces for IgG-ligand association. Moreover, the batch uptake and desorption experiments demonstrated the fast adsorption and desorption processes for IgG separation. The purity of IgG separated from mimetic serum could reach 98.6%, and the purity of monoclonal antibody (mAb) from a cell culture supernatant was 97.1%. Magnetic particles with hydrophobic charge-induction ligands showed a robust performance and could purify antibody directly from the complicated feedstock without clarification, which would improve the efficiency of antibody purification. PMID:27439357

  16. Evaluation of magnetic particles modified with a hydrophobic charge-induction ligand for antibody capture.

    PubMed

    Gu, Jia-Li; Tong, Hong-Fei; Lin, Dong-Qiang

    2016-08-19

    Magnetic particles modified with 5-amino-benzimidazole (ABI), a ligand for hydrophobic charge-induction chromatography, were prepared and used for antibody capture. In this study, with IgG as the model target, and bovine serum albumin (BSA) as the model impurity, the separation mechanism and process of IgG was investigated. The adsorption isotherms of IgG and BSA were measured, and the effects of pH were investigated in the range of pH 4.0-8.0. The maximum adsorption capacity of IgG on the particles was 180mg/ml at pH 7.0, while low adsorption capacity of BSA (64mg/ml) was found at pH 7.0, resulting in good selectivity. The protein-ligand interactions were elucidated by adding NaCl and glycerol. The results indicated the hydrophobic interactions were the main forces for IgG-ligand association. Moreover, the batch uptake and desorption experiments demonstrated the fast adsorption and desorption processes for IgG separation. The purity of IgG separated from mimetic serum could reach 98.6%, and the purity of monoclonal antibody (mAb) from a cell culture supernatant was 97.1%. Magnetic particles with hydrophobic charge-induction ligands showed a robust performance and could purify antibody directly from the complicated feedstock without clarification, which would improve the efficiency of antibody purification.

  17. Sweeping Gas Membrane Desalination Using Commercial Hydrophobic Hollow Fiber Membranes

    SciTech Connect

    EVANS, LINDSEY; MILLER, JAMES E.

    2002-01-01

    Water shortages affect 88 developing countries that are home to half of the world's population. In these places, 80-90% of all diseases and 30% of all deaths result from poor water quality. Furthermore, over the next 25 years, the number of people affected by severe water shortages is expected to increase fourfold. Low cost methods of purifying freshwater, and desalting seawater are required to contend with this destabilizing trend. Membrane distillation (MD) is an emerging technology for separations that are traditionally accomplished via conventional distillation or reverse osmosis. As applied to desalination, MD involves the transport of water vapor from a saline solution through the pores of a hydrophobic membrane. In sweeping gas MD, a flowing gas stream is used to flush the water vapor from the permeate side of the membrane, thereby maintaining the vapor pressure gradient necessary for mass transfer. Since liquid does not penetrate the hydrophobic membrane, dissolved ions are completely rejected by the membrane. MD has a number of potential advantages over conventional desalination including low temperature and pressure operation, reduced membrane strength requirements, compact size, and 100% rejection of non-volatiles. The present work evaluated the suitability of commercially available technology for sweeping gas membrane desalination. Evaluations were conducted with Celgard Liqui-Cel{reg_sign} Extra-Flow 2.5X8 membrane contactors with X-30 and X-40 hydrophobic hollow fiber membranes. Our results show that sweeping gas membrane desalination systems are capable of producing low total dissolved solids (TDS) water, typically 10 ppm or less, from seawater, using low grade heat. However, there are several barriers that currently prevent sweeping gas MD from being a viable desalination technology. The primary problem is that large air flows are required to achieve significant water yields, and the costs associated with transporting this air are prohibitive. To

  18. Temperature effects on the hydrophobic interaction of parallel plates in the framework of the probabilistic approach to hydrogen bonding.

    PubMed

    Djikaev, Y S; Ruckenstein, Eli

    2010-03-15

    Recently, we have proposed a probabilistic approach to examine the effect of water-water hydrogen bond networks around two foreign hydrophobic particles (immersed in water) on their interaction. Because of the proximity to a particle, a water molecule in the first hydration shell around it forms a smaller number of hydrogen bonds compared to a bulk molecule. The probabilistic approach allows one to analytically evaluate the former number if the latter is known (which is usually the case). On the other hand, the former bonds may be slightly (energetically) enhanced compared to the latter if at least one of the two bonded molecules lie in the first hydration shell and does not form a bond with a nearest neighbor site on the particle surface. When two hydrophobic particles are sufficiently close to each other, the overlap of boundary water-water hydrogen bond networks gives rise to an additional attractive force between them. In this paper we use the probabilistic approach to examine the effect of solvent temperature on the solvent-mediated interaction of two hydrophobic particles. Their hydrophobic attraction is affected by the solvent (water) temperature because the density of the solvent, strength of a hydrogen bonds, and number of hydrogen bonds per molecule are sensitive thereto (the pressure effects are not considered here). The probabilistic approach predicts that the solvent-mediated attraction of hydrophobic solutes is driven by the favorable entropic component ("-temperature x entropy") of the potential of mean force that dominates the unfavorable energetic component. This attraction decreases as the temperature increases.

  19. Water-Mediated Interactions between Hydrophilic and Hydrophobic Surfaces.

    PubMed

    Kanduč, Matej; Schlaich, Alexander; Schneck, Emanuel; Netz, Roland R

    2016-09-01

    All surfaces in water experience at short separations hydration repulsion or hydrophobic attraction, depending on the surface polarity. These interactions dominate the more long-ranged electrostatic and van der Waals interactions and are ubiquitous in biological and colloidal systems. Despite their importance in all scenarios where the surface separation is in the nanometer range, the origin of these hydration interactions is still unclear. Using atomistic solvent-explicit molecular dynamics simulations, we analyze the interaction free energies of charge-neutral model surfaces with different elastic and water-binding properties. The surface polarity is shown to be the most important parameter that not only determines the hydration properties and thereby the water contact angle of a single surface but also the surface-surface interaction and whether two surfaces attract or repel. Elastic properties of the surfaces are less important. On the basis of surface contact angles and surface-surface binding affinities, we construct a universal interaction diagram featuring three different interaction regimes-hydration repulsion, cavitation-induced attraction-and for intermediate surface polarities-dry adhesion. On the basis of scaling arguments and perturbation theory, we establish simple combination rules that predict the interaction behavior for combinations of dissimilar surfaces. PMID:27487420

  20. Superporous agarose beads as a hydrophobic interaction chromatography support.

    PubMed

    Gustavsson, P E; Axelsson, A; Larsson, P O

    1999-01-15

    Superporous agarose beads were used as a support for hydrophobic interaction chromatography. These beads have large connecting flow pores in addition to their normal diffusion pores. The flow pores, which are approximately one fifth of the overall diameter of the superporous agarose beads, were earlier shown to give the beads improved mass transfer properties relative to homogeneous agarose beads (Gustavsson and Larsson, J. Chromatogr. A, 734 (1996) 231-240). Superporous agarose beads and homogeneous agarose beads of the same particle size range (106-180 microns) were derivatized with phenyl groups. The properties of the superporous beads were then compared with the homogeneous beads in the separation of a mixture of three model proteins (ribonuclease A, lysozyme and bovine serum albumin) at various superficial flow velocities from 30 to 600 cm/h. The superporous beads gave satisfactory separation at flow velocities five times higher than was possible for homogeneous beads. The performance of the two types of beads was also compared in the purification of lactate dehydrogenase from a beef heart extract at a superficial flow velocity of 150 cm/h. The superporous beads performed considerably better, leading to twice the purification factor and twice the concentration of the desired product. The results were interpreted using the theoretical treatment given by Carta and Rodrigues (Carta and Rodrigues, Chem. Eng. Sci., 48 (1993) 3927).

  1. Water-Mediated Interactions between Hydrophilic and Hydrophobic Surfaces.

    PubMed

    Kanduč, Matej; Schlaich, Alexander; Schneck, Emanuel; Netz, Roland R

    2016-09-01

    All surfaces in water experience at short separations hydration repulsion or hydrophobic attraction, depending on the surface polarity. These interactions dominate the more long-ranged electrostatic and van der Waals interactions and are ubiquitous in biological and colloidal systems. Despite their importance in all scenarios where the surface separation is in the nanometer range, the origin of these hydration interactions is still unclear. Using atomistic solvent-explicit molecular dynamics simulations, we analyze the interaction free energies of charge-neutral model surfaces with different elastic and water-binding properties. The surface polarity is shown to be the most important parameter that not only determines the hydration properties and thereby the water contact angle of a single surface but also the surface-surface interaction and whether two surfaces attract or repel. Elastic properties of the surfaces are less important. On the basis of surface contact angles and surface-surface binding affinities, we construct a universal interaction diagram featuring three different interaction regimes-hydration repulsion, cavitation-induced attraction-and for intermediate surface polarities-dry adhesion. On the basis of scaling arguments and perturbation theory, we establish simple combination rules that predict the interaction behavior for combinations of dissimilar surfaces.

  2. Interaction of engineered nanomaterials with hydrophobic organic pollutants

    NASA Astrophysics Data System (ADS)

    Sahle-Demessie, E.; Han, Changseok; Zhao, Amy; Hahn, Bill; Grecsek, Heidi

    2016-07-01

    As nanomaterials become an increasing part of everyday consumer products, it is imperative to monitor their potential release during production, use and disposal, and to assess their impact on the health of humans and the ecosystem. This necessitates research to better understand how the properties of engineered nanomaterials (ENMs) lead to their accumulation and redistribution in the environment, and to assess whether they could become novel pollutants or if they can affect the mobility and bioavailability of other toxins. This study focuses on understanding the influence of nanostructured-TiO2 and the interaction of multi-walled carbon nanotubes with organic pollutants in water. We studied the adsorption and water phase dispersion of model pollutants with relatively small water solubility (i.e., two- and three-ring polyaromatic hydrocarbons and insecticides) with respect to ENMs. The sorption of pollutants was measured based on water phase analysis, and by separating suspended particles from the water phase and analyzing dried samples using integrated thermal-chromatographic-mass spectroscopic (TGA/GC/MS) techniques. Solid phase analysis using a combination of TGA/GC/MS is a novel technique that can provide real-time quantitative analysis and which helps to understand the interaction of hydrophobic organic pollutants and ENMs. The adsorption of these contaminants to nanomaterials increased the concentration of the contaminants in the aqueous phase as compared to the ‘real’ partitioning due to the octanol-water partitioning. The study showed that ENMs can significantly influence the adsorption and dispersion of hydrophobic/low water soluble contaminants. The type of ENM, the exposure to light, and the water pH have a significant influence on the partitioning of pollutants.

  3. Interaction of engineered nanomaterials with hydrophobic organic pollutants.

    PubMed

    Sahle-Demessie, E; Han, Changseok; Zhao, Amy; Hahn, Bill; Grecsek, Heidi

    2016-07-15

    As nanomaterials become an increasing part of everyday consumer products, it is imperative to monitor their potential release during production, use and disposal, and to assess their impact on the health of humans and the ecosystem. This necessitates research to better understand how the properties of engineered nanomaterials (ENMs) lead to their accumulation and redistribution in the environment, and to assess whether they could become novel pollutants or if they can affect the mobility and bioavailability of other toxins. This study focuses on understanding the influence of nanostructured-TiO2 and the interaction of multi-walled carbon nanotubes with organic pollutants in water. We studied the adsorption and water phase dispersion of model pollutants with relatively small water solubility (i.e., two- and three-ring polyaromatic hydrocarbons and insecticides) with respect to ENMs. The sorption of pollutants was measured based on water phase analysis, and by separating suspended particles from the water phase and analyzing dried samples using integrated thermal-chromatographic-mass spectroscopic (TGA/GC/MS) techniques. Solid phase analysis using a combination of TGA/GC/MS is a novel technique that can provide real-time quantitative analysis and which helps to understand the interaction of hydrophobic organic pollutants and ENMs. The adsorption of these contaminants to nanomaterials increased the concentration of the contaminants in the aqueous phase as compared to the 'real' partitioning due to the octanol-water partitioning. The study showed that ENMs can significantly influence the adsorption and dispersion of hydrophobic/low water soluble contaminants. The type of ENM, the exposure to light, and the water pH have a significant influence on the partitioning of pollutants. PMID:27265536

  4. Bioaccumulation of hydrophobic xenobiotics via gill and gut

    SciTech Connect

    Qiao, P.; Farrell, A.P.

    1995-12-31

    The authors demonstrated that the uptake of three hydrophobic chemicals, 1,2,4-trichlorobenzene (TCB), 1,2,3,4,5-pentachlorobenzene (PeCB), and 2,2{prime},4,4{prime},6,6{prime}-hexachlorobiphenyl (HCB), from water laden with sediments from the Fraser River was just as rapid and to at least the same level in juvenile rainbow trout with pharynx blocked as compared with control, unfed fish. Furthermore, a chemical mass balance analysis revealed that the quantity of PECB and HCB dissolved in water could not account by itself for the quantity of these compounds that had appeared in the fish after 6 days of exposure. Thus, the authors conclude that hydrophobic chemicals such as these with log K{sub ow} values of 5--7 are bioavailable for gill uptake from water laden with sediments from the Fraser River. In a separate experiment, the appearance of TCB, PeCB and HCB in fish eating contaminated food at 2% body mass/day was measured over 12 days. Although the chemical concentrations in the food were 5,000 to 65,000 times higher than the concentrations in the water plus suspended sediments of the earlier experiment, the concentrations of xenobiotics in fish tissues were not significantly higher than in the unfed fish of the earlier experiment. The authors conclude that the bioavailability via the gill of high K{sub ow} compounds from Fraser River sediments is very significant in juvenile rainbow trout. Data also showed that metabolism of TCB, but not PeCB and HCB, was significant.

  5. Interaction of engineered nanomaterials with hydrophobic organic pollutants

    NASA Astrophysics Data System (ADS)

    Sahle-Demessie, E.; Han, Changseok; Zhao, Amy; Hahn, Bill; Grecsek, Heidi

    2016-07-01

    As nanomaterials become an increasing part of everyday consumer products, it is imperative to monitor their potential release during production, use and disposal, and to assess their impact on the health of humans and the ecosystem. This necessitates research to better understand how the properties of engineered nanomaterials (ENMs) lead to their accumulation and redistribution in the environment, and to assess whether they could become novel pollutants or if they can affect the mobility and bioavailability of other toxins. This study focuses on understanding the influence of nanostructured-TiO2 and the interaction of multi-walled carbon nanotubes with organic pollutants in water. We studied the adsorption and water phase dispersion of model pollutants with relatively small water solubility (i.e., two- and three-ring polyaromatic hydrocarbons and insecticides) with respect to ENMs. The sorption of pollutants was measured based on water phase analysis, and by separating suspended particles from the water phase and analyzing dried samples using integrated thermal–chromatographic–mass spectroscopic (TGA/GC/MS) techniques. Solid phase analysis using a combination of TGA/GC/MS is a novel technique that can provide real-time quantitative analysis and which helps to understand the interaction of hydrophobic organic pollutants and ENMs. The adsorption of these contaminants to nanomaterials increased the concentration of the contaminants in the aqueous phase as compared to the ‘real’ partitioning due to the octanol–water partitioning. The study showed that ENMs can significantly influence the adsorption and dispersion of hydrophobic/low water soluble contaminants. The type of ENM, the exposure to light, and the water pH have a significant influence on the partitioning of pollutants.

  6. Isotope separation apparatus and method

    DOEpatents

    Cotter, Theodore P.

    1982-12-28

    The invention relates to a method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferable substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. The laser beam comprises .pi.-pulses of a selected wavelength which excite unexcited molecules, or cause stimulated emission of excited molecules of one of the isotopes. Excitation caused by first direction .pi.-pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning .pi.-pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement is accomplished by a large number of .pi.-pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam.

  7. Synthesis of novel lanthanide acylpyrazolonato ligands with long aliphatic chains and immobilization of the Tb complex on the surface of silica pre-modified via hydrophobic interactions.

    PubMed

    Pettinari, C; Marchetti, F; Pettinari, R; Belousov, Y A; Taydakov, I V; Krasnobrov, V D; Petukhov, D I; Drozdov, A A

    2015-09-01

    Five new complexes Ln(Q(C17))3(H2O)(Solv) (Ln = Y, Solv = H2O, Ln = Tb, Dy, Sm or Eu, Solv = EtOH) were synthesized with the acylpyrazolonato ligand Q(C17) bearing a long aliphatic C17H35 chain in the acyl moiety, and the crystal structure of Y(Q(C17))3(H2O)2 shows the three aliphatic chains from the coordinated ligands positioned in the same direction, affording plane layers built by Y(Q(C17))3(H2O)2 molecules connected through H-bonding interactions. The layers are stitched to each other like in "hook & loop" tapes. Luminescence of complexes was determined and the complex Tb(Q(C17))3(H2O)(EtOH) was immobilized on the surface of silica preprocessed using a C17H35CONH(CH2)3Si(OEt)3 reagent via hydrophobic interactions of long aliphatic chains. Luminescent properties and micromorphology of the obtained hybrid particles and hybrid films were investigated. Intensive green emission of the complex retains after grafting onto the silica surface. Inclusion of the complex on the surface of silica materials occurs as separate molecules, after the disruption of the H-bonding network present in the crystalline phase of the pure terbium sample.

  8. Gadolinium speciation with Tetradentate, N-donor extractants for minor actinide/lanthanide separation: an XRD, mass spectrometry and EPR study

    SciTech Connect

    Whittaker, D.M.; Sharrad, C.A.; Sproules, S.

    2013-07-01

    The hydrophobic organic molecules CyMe{sub 4}-BTPhen (1) and CyMe{sub 4}-BTBP (2) have been developed and tuned over many years to be able to separate the trivalent actinides from the trivalent lanthanides (Ln) selectively in bi-phasic solvent extraction processes for the separation of the long-lived radio-toxic minor actinides from spent nuclear fuel. The ability of these N-donor ligands to perform this separation is poorly understood, as is their speciation with the metal ions when extracted into the organic phase. Our previous work has shown Ln{sup 3+} speciation to be largely 1:2 Ln:L in nature with another small molecule, either water or nitrate, occupying a cavity between the tetradentate bound N-donor ligands. The identity of the small molecule changes across the lanthanide series, and here we continue investigations into this speciation. Complexes of these N-donor ligands with Gd{sup 3+} have been synthesised and characterised by X-ray crystallography, mass spectrometry and EPR spectroscopy. We show that the N-donor ligands have no effect on the electronic configuration of Gd{sup 3+} and that the lanthanide contraction with the steric rigidity of the N-donor ligand appears to determine the size of the cavity between the coordinated ligands. This in turn appears to control the identity of the small molecule on the ninth site in the 1:2 Gd:L species. (authors)

  9. Char separator

    DOEpatents

    Matthews, Francis T.

    1979-01-01

    Particulates removed from the flue gases produced in a fluidized-bed furnace are separated into high-and low-density portions. The low-density portion is predominantly char, and it is returned to the furnace or burned in a separate carbon burnup cell. The high-density portion, which is predominantly limestone products and ash, is discarded or reprocessed. According to another version, the material drained from the bed is separated, the resulting high-and low-density portions being treated in a manner similar to that in which the flue-gas particulates are treated.

  10. CENTRIFUGAL SEPARATORS

    DOEpatents

    Skarstrom, C.

    1959-03-10

    A centrifugal separator is described for separating gaseous mixtures where the temperature gradients both longitudinally and radially of the centrifuge may be controlled effectively to produce a maximum separation of the process gases flowing through. Tbe invention provides for the balancing of increases and decreases in temperature in various zones of the centrifuge chamber as the result of compression and expansions respectively, of process gases and may be employed effectively both to neutralize harmful temperature gradients and to utilize beneficial temperaturc gradients within the centrifuge.

  11. Engineering the hydrophobic residues of a GH11 xylanase impacts its adsorption onto lignin and its thermostability.

    PubMed

    Rakotoarivonina, Harivony; Hermant, Béatrice; Aubry, Nathalie; Rémond, Caroline

    2015-12-01

    This study aimed to characterise the parameters governing the non-specific adsorption of a xylanase from Thermobacillus xylanilyticus (Tx-Xyn11) onto lignin isolated from maize stems. Such adsorption may be due to hydrophobic interactions between Tx-Xyn11 and lignin. Our strategy was to mutate hydrophobic residues present on the surface of Tx- Xyn11 into non-hydrophobic residues. Three mutants (P1, P2, and P3) with altered hydrophobic regions were produced and characterised. The thermostability of the P1 mutant was largely decreased compared with the thermostable Tx-Xyn11. The rate of adsorbed enzyme onto lignin was reduced to a similar extent for the P1 and P2 mutants, whereas the adsorption of the P3 mutant was less affected compared with that of Tx-Xyn11. When considered separately, the hydrophobic residues did not affect xylanase adsorption onto lignin. The addition of Tween 20 also led to the decreased adsorption of Tx-Xyn11 onto lignin. These results suggest that hydrophobic interactions are a key parameter in the interaction of Tx-Xyn11 with isolated lignin.

  12. Measuring forces and spatiotemporal evolution of thin water films between an air bubble and solid surfaces of different hydrophobicity.

    PubMed

    Shi, Chen; Cui, Xin; Xie, Lei; Liu, Qingxia; Chan, Derek Y C; Israelachvili, Jacob N; Zeng, Hongbo

    2015-01-27

    A combination of atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM) was used to measure simultaneously the interaction force and the spatiotemporal evolution of the thin water film between a bubble in water and mica surfaces with varying degrees of hydrophobicity. Stable films, supported by the repulsive van der Waals-Casimir-Lifshitz force were always observed between air bubble and hydrophilic mica surfaces (water contact angle, θ(w) < 5°) whereas bubble attachment occurred on hydrophobized mica surfaces. A theoretical model, based on the Reynolds lubrication theory and the augmented Young-Laplace equation including the effects of disjoining pressure, provided excellent agreement with experiment results, indicating the essential physics involved in the interaction between air bubble and solid surfaces can be elucidated. A hydrophobic interaction free energy per unit area of the form: WH(h) = -γ(1 - cos θ(w))exp(-h/D(H)) can be used to quantify the attraction between bubble and hydrophobized solid substrate at separation, h, with γ being the surface tension of water. For surfaces with water contact angle in the range 45° < θ(w) < 90°, the decay length DH varied between 0.8 and 1.0 nm. This study quantified the hydrophobic interaction in asymmetric system between air bubble and hydrophobic surfaces, and provided a feasible method for synchronous measurements of the interaction forces with sub-nN resolution and the drainage dynamics of thin films down to nm thickness.

  13. Measuring forces and spatiotemporal evolution of thin water films between an air bubble and solid surfaces of different hydrophobicity.

    PubMed

    Shi, Chen; Cui, Xin; Xie, Lei; Liu, Qingxia; Chan, Derek Y C; Israelachvili, Jacob N; Zeng, Hongbo

    2015-01-27

    A combination of atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM) was used to measure simultaneously the interaction force and the spatiotemporal evolution of the thin water film between a bubble in water and mica surfaces with varying degrees of hydrophobicity. Stable films, supported by the repulsive van der Waals-Casimir-Lifshitz force were always observed between air bubble and hydrophilic mica surfaces (water contact angle, θ(w) < 5°) whereas bubble attachment occurred on hydrophobized mica surfaces. A theoretical model, based on the Reynolds lubrication theory and the augmented Young-Laplace equation including the effects of disjoining pressure, provided excellent agreement with experiment results, indicating the essential physics involved in the interaction between air bubble and solid surfaces can be elucidated. A hydrophobic interaction free energy per unit area of the form: WH(h) = -γ(1 - cos θ(w))exp(-h/D(H)) can be used to quantify the attraction between bubble and hydrophobized solid substrate at separation, h, with γ being the surface tension of water. For surfaces with water contact angle in the range 45° < θ(w) < 90°, the decay length DH varied between 0.8 and 1.0 nm. This study quantified the hydrophobic interaction in asymmetric system between air bubble and hydrophobic surfaces, and provided a feasible method for synchronous measurements of the interaction forces with sub-nN resolution and the drainage dynamics of thin films down to nm thickness. PMID:25514470

  14. Soil hydrophobicity - relating effects at atomic, molecular, core and national scales

    NASA Astrophysics Data System (ADS)

    Matthews, Peter; Doerr, Stefan; Van Keulen, Geertje; Dudley, Ed; Francis, Lewis; Whalley, Richard; Gazze, Andrea; Hallin, Ingrid; Quinn, Gerry; Sinclair, Kat; Ashton, Rhys

    2016-04-01

    The detrimental impacts of soil hydrophobicity include increased runoff, erosion and flooding, reduced biomass production, inefficient use of irrigation water and preferential leaching of pollutants. Its impacts may exacerbate flood risk associated with more extreme drought and precipitation events predicted with UK climate change scenarios. The UK's Natural Environment Research Council (NERC) has therefore funded a major research programme to investigate soil hydrophobicity over length scales ranging from atomic through molecular, core and landscape scale. This presentation gives an overview of the findings to date. The programme is predicated on the hypothesis that changes in soil protein abundance and localization, induced by variations in soil moisture and temperature, are crucial driving forces for transitions between hydrophobic and hydrophilic conditions at soil particle surfaces. Three soils were chosen based on the severity of hydrophobicity that can be achieved in the field: severe to extreme (Cefn Bryn, Gower, Wales), intermediate to severe (National Botanical Garden, Wales), and subcritical (Park Grass, Rothamsted Research near London). The latter is already highly characterised so was also used as a control. Hydrophobic/ hydrophilic transitions were measured from water droplet penetration times. Scientific advances in the following five areas will be described: (i) the identification of these soil proteins by proteomic methods, using a novel separation method which reduces interference by humic acids, and allows identification by ESI and MALDI TOF mass spectrometry and database searches, (ii) the examination of such proteins, which form ordered hydrophobic ridges, and measurement of their elasticity, stickiness and hydrophobicity at nano- to microscale using atomic force microscopy adapted for the rough surfaces of soil particles, (iii) the novel use of a picoliter goniometer to show hydrophobic effects at a 1 micron diameter droplet level, which

  15. "Clickable" Polymeric Nanofibers through Hydrophilic-Hydrophobic Balance: Fabrication of Robust Biomolecular Immobilization Platforms.

    PubMed

    Kalaoglu-Altan, Ozlem I; Sanyal, Rana; Sanyal, Amitav

    2015-05-11

    Fabrication of hydrophilic polymeric nanofibers that undergo facile and selective functionalization through metal catalyst-free Diels-Alder "click" reaction in aqueous environment is outlined. Electrospinning of copolymers containing an electron-rich furan moiety, hydrophobic methyl methacrylate units and hydrophilic poly(ethylene glycol)s as side chains provide specifically functionalizable yet antibiofouling fibers that remain stable in aqueous media due to appropriate hydrophobic hydrophilic balance. Efficient functionalization of these nanofibers is accomplished through the Diels-Alder reaction by exposing them to maleimide-containing molecules and ligands. Diels-Alder conjugation based functionalization is demonstrated through attachment of fluorescein-maleimide and a maleimide tethered biotin ligand. Biotinylated nanofibers were utilized to mediate immobilization of the protein streptavidin, as well as streptavidin coated quantum dots. Facile fabrication from readily available polymers and their effective functionalization under mild and reagent-free conditions in aqueous media make these "clickable" nanofibers attractive candidates as functionalizable scaffolds for various biomedical applications.

  16. Comparative study of laterite and bentonite based organoclays: implications of hydrophobic compounds remediation from aqueous solutions.

    PubMed

    Nafees, Muhammad; Waseem, Amir; Khan, Abdur Rehman

    2013-01-01

    Four cost effective organoclays were synthesized, characterized, and studied for the sorption of hydrophobic compounds (edible oil/grease and hydrocarbon oil) from aqueous solutions. Organoclays were prepared by cation exchange reaction of lattice ions (present onto the surface of laterite and bentonite clay minerals) with two surfactants, hexadecyl trimethyl ammonium chloride (HDTMA-Cl) and tetradecyl trimethyl ammonium bromide (TDTMA-Br). Fourier transform infrared spectroscopy and scanning electron microscopy were used for the characterization of synthesized organoclays. It was found that the amount of surfactant loading and the nature of the surfactant molecules used in the syntheses of organoclay strongly affect the sorption capacity of the clay mineral. Further, it was found that both the laterite and bentonite based organoclays efficiently removed the edible and hydrocarbon oil content from lab prepared emulsions; however, the adsorption capacity of clay mineral was greatly influenced by the nature of hydrophobic compounds as well. PMID:24302867

  17. N-(L-2-aminopentanoyl)-L-phenylalanine dihydrate, a hydrophobic dipeptide with a nonproteinogenic residue.

    PubMed

    Görbitz, Carl Henrik; Yadav, Vitthal N

    2013-09-01

    The title dipeptide, better known as L-norvalyl-L-phenylalanine {systematic name: (S)-2-[(S)-2-aminopentanamido]-3-phenylpropanoic acid dihydrate}, C14H20N2O3·2H2O, has a nonproteinogenic N-terminal residue. In the solid state, it takes on a molecular conformation typical for one of the three classes of nanoporous dipeptides, but like two related compounds with a hydrophobic N-terminal residue and a C-terminal L-phenylalanine, it fails to form channels or pores. Instead, the crystal structure is divided into distinct hydrophobic and hydrophilic layers, the latter encompassing cocrystallized water molecules connecting the charged N- and C-terminal groups.

  18. Preparation of lipase-coated, stabilized, hydrophobic magnetic particles for reversible conjugation of biomacromolecules.

    PubMed

    Marciello, Marzia; Bolivar, Juan M; Filice, Marco; Mateo, Cesar; Guisan, Jose M

    2013-03-11

    This Communication presents the development of a novel strategy for the easy conjugation of biomolecules to hydrophobic magnetic microparticles via reversible coating with previously functionalized lipase molecules. First, the ability of lipase to be strongly adsorbed onto hydrophobic surfaces was exploited for the stabilization of microparticles in aqueous medium by the creation of a hydrophilic surface. Second, the surface amino acids of lipase can be tailored to suit biomolecule conjugation. This approach has been demonstrated by amino-epoxy activation of lipase, enabling the conjugation of different biomolecules to the magnetic particle's surface. For example, it was possible to immobilize 70% of Escherichia coli proteins on the recovered particles. Furthermore, this strategy could be extended to other lipase chemical modification protocols, enabling fine control of biomolecule coupling. These conjugation techniques constitute a modular methodology that also permits the recycling of the magnetic carrier following use.

  19. Comparative Study of Laterite and Bentonite Based Organoclays: Implications of Hydrophobic Compounds Remediation from Aqueous Solutions

    PubMed Central

    Nafees, Muhammad; Waseem, Amir; Khan, Abdur Rehman

    2013-01-01

    Four cost effective organoclays were synthesized, characterized, and studied for the sorption of hydrophobic compounds (edible oil/grease and hydrocarbon oil) from aqueous solutions. Organoclays were prepared by cation exchange reaction of lattice ions (present onto the surface of laterite and bentonite clay minerals) with two surfactants, hexadecyl trimethyl ammonium chloride (HDTMA-Cl) and tetradecyl trimethyl ammonium bromide (TDTMA-Br). Fourier transform infrared spectroscopy and scanning electron microscopy were used for the characterization of synthesized organoclays. It was found that the amount of surfactant loading and the nature of the surfactant molecules used in the syntheses of organoclay strongly affect the sorption capacity of the clay mineral. Further, it was found that both the laterite and bentonite based organoclays efficiently removed the edible and hydrocarbon oil content from lab prepared emulsions; however, the adsorption capacity of clay mineral was greatly influenced by the nature of hydrophobic compounds as well. PMID:24302867

  20. Comparative study of laterite and bentonite based organoclays: implications of hydrophobic compounds remediation from aqueous solutions.

    PubMed

    Nafees, Muhammad; Waseem, Amir; Khan, Abdur Rehman

    2013-01-01

    Four cost effective organoclays were synthesized, characterized, and studied for the sorption of hydrophobic compounds (edible oil/grease and hydrocarbon oil) from aqueous solutions. Organoclays were prepared by cation exchange reaction of lattice ions (present onto the surface of laterite and bentonite clay minerals) with two surfactants, hexadecyl trimethyl ammonium chloride (HDTMA-Cl) and tetradecyl trimethyl ammonium bromide (TDTMA-Br). Fourier transform infrared spectroscopy and scanning electron microscopy were used for the characterization of synthesized organoclays. It was found that the amount of surfactant loading and the nature of the surfactant molecules used in the syntheses of organoclay strongly affect the sorption capacity of the clay mineral. Further, it was found that both the laterite and bentonite based organoclays efficiently removed the edible and hydrocarbon oil content from lab prepared emulsions; however, the adsorption capacity of clay mineral was greatly influenced by the nature of hydrophobic compounds as well.

  1. Analysis of Toxoplasma gondii proteins after Triton X-114 solubilization and hydrophobic chromatography.

    PubMed

    De Simone, S G; Guedes, H C; Bendet, I

    1988-01-01

    The distribution of the surface proteins of Toxoplasma gondii radiodinated were studied using the phase separation technique and ability of binding in the phenyl-Sepharose column. Eight polypeptides with Mr 22 to 180 distributed exclusively in the detergent rich-phase, while six polypeptides with mol. wt. 15,000 to 76,000 distributed exclusively in the detergent poor-phase. Two polypeptides with 15,000 and 70,000 distributed in both phase. All the polypeptides present in the detergent rich-phase binding in the phenyl-Sepharose column, and can be isolated in two peak according with their relative hydrophobicities. Two polypeptides hydrophobic with Mr 60 and 66 recognized by human serum were isolated by the association of the two technique. Our result showed that the surface proteins of T. gondii present different degrees of hydrophobicity and that the use of hydrophobic interaction chromatography after Triton X-114 extraction may be an important isolation method of membrane proteins.

  2. Hydrophobic, electrostatic, and dynamic polymer forces at silicone surfaces modified with long-chain bolaform surfactants.

    PubMed

    Rapp, Michael V; Donaldson, Stephen H; Gebbie, Matthew A; Das, Saurabh; Kaufman, Yair; Gizaw, Yonas; Koenig, Peter; Roiter, Yuri; Israelachvili, Jacob N

    2015-05-01

    Surfactant self-assembly on surfaces is an effective way to tailor the complex forces at and between hydrophobic-water interfaces. Here, the range of structures and forces that are possible at surfactant-adsorbed hydrophobic surfaces are demonstrated: certain long-chain bolaform surfactants-containing a polydimethylsiloxane (PDMS) mid-block domain and two cationic α, ω-quarternary ammonium end-groups-readily adsorb onto thin PDMS films and form dynamically fluctuating nanostructures. Through measurements with the surface forces apparatus (SFA), it is found that these soft protruding nanostructures display polymer-like exploration behavior at the PDMS surface and give rise to a long-ranged, temperature- and rate-dependent attractive bridging force (not due to viscous forces) on approach to a hydrophilic bare mica surface. Coulombic interactions between the cationic surfactant end-groups and negatively-charged mica result in a rate-dependent polymer bridging force during separation as the hydrophobic surfactant mid-blocks are pulled out from the PDMS interface, yielding strong adhesion energies. Thus, (i) the versatile array of surfactant structures that may form at hydrophobic surfaces is highlighted, (ii) the need to consider the interaction dynamics of such self-assembled polymer layers is emphasized, and (iii) it is shown that long-chain surfactants can promote robust adhesion in aqueous solutions. PMID:25504803

  3. Temperature effect on the small-to-large crossover lengthscale of hydrophobic hydration

    SciTech Connect

    Djikaev, Y. S. Ruckenstein, E.

    2013-11-14

    The thermodynamics of hydration is expected to change gradually from entropic for small solutes to enthalpic for large ones. The small-to-large crossover lengthscale of hydrophobic hydration depends on the thermodynamic conditions of the solvent such as temperature, pressure, presence of additives, etc. We attempt to shed some light on the temperature dependence of the crossover lengthscale by using a probabilistic approach to water hydrogen bonding that allows one to obtain an analytic expression for the number of bonds per water molecule as a function of both its distance to a solute and solute radius. Incorporating that approach into the density functional theory, one can examine the solute size effects on its hydration over the entire small-to-large lengthscale range at a series of different temperatures. Knowing the dependence of the hydration free energy on the temperature and solute size, one can also obtain its enthalpic and entropic contributions as functions of both temperature and solute size. These functions can provide some interesting insight into the temperature dependence of the crossover lengthscale of hydrophobic hydration. The model was applied to the hydration of spherical particles of various radii in water in the temperature range from T = 293.15 K to T = 333.15 K. The model predictions for the temperature dependence of the hydration free energy of small hydrophobes are consistent with the experimental and simulational data on the hydration of simple molecular solutes. Three alternative definitions for the small-to-large crossover length-scale of hydrophobic hydration are proposed, and their temperature dependence is obtained. Depending on the definition and temperature, the small-to-large crossover in the hydration mechanism is predicted to occur for hydrophobes of radii from one to several nanometers. Independent of its definition, the crossover length-scale is predicted to decrease with increasing temperature.

  4. Temperature effect on the small-to-large crossover lengthscale of hydrophobic hydration.

    PubMed

    Djikaev, Y S; Ruckenstein, E

    2013-11-14

    The thermodynamics of hydration is expected to change gradually from entropic for small solutes to enthalpic for large ones. The small-to-large crossover lengthscale of hydrophobic hydration depends on the thermodynamic conditions of the solvent such as temperature, pressure, presence of additives, etc. We attempt to shed some light on the temperature dependence of the crossover lengthscale by using a probabilistic approach to water hydrogen bonding that allows one to obtain an analytic expression for the number of bonds per water molecule as a function of both its distance to a solute and solute radius. Incorporating that approach into the density functional theory, one can examine the solute size effects on its hydration over the entire small-to-large lengthscale range at a series of different temperatures. Knowing the dependence of the hydration free energy on the temperature and solute size, one can also obtain its enthalpic and entropic contributions as functions of both temperature and solute size. These functions can provide some interesting insight into the temperature dependence of the crossover lengthscale of hydrophobic hydration. The model was applied to the hydration of spherical particles of various radii in water in the temperature range from T = 293.15 K to T = 333.15 K. The model predictions for the temperature dependence of the hydration free energy of small hydrophobes are consistent with the experimental and simulational data on the hydration of simple molecular solutes. Three alternative definitions for the small-to-large crossover length-scale of hydrophobic hydration are proposed, and their temperature dependence is obtained. Depending on the definition and temperature, the small-to-large crossover in the hydration mechanism is predicted to occur for hydrophobes of radii from one to several nanometers. Independent of its definition, the crossover length-scale is predicted to decrease with increasing temperature.

  5. Product separator

    DOEpatents

    Welsh, Robert A.; Deurbrouck, Albert W.

    1976-01-20

    A secondary light sensitive photoelectric product separator for use with a primary product separator that concentrates a material so that it is visually distinguishable from adjacent materials. The concentrate separation is accomplished first by feeding the material onto a vibratory inclined surface with a liquid flow, such as a wet concentrating table. Vibrations generally perpendicular to the stream direction of flow cause the concentrate to separate from its mixture according to its color. When the concentrate and its surrounding stream reach the recovery end of the table, a detecting device notes the line of color demarcation and triggers a signal if it differs from a normal condition. If no difference is noted nothing moves on the second separator. However, if a difference is detected in the constant monitoring of the color line's location, a product splitter and recovery unit normally positioned near the color line at the recovery end, moves to a new position. In this manner the selected separated concentrate is recovered at a maximum rate regardless of variations in the flow stream or other conditions present.

  6. The Use ofa Hydrophobic Binding Peptide Modified Lipid Nanocarrier Improving Tumor Distribution and Antitumor Efficacy.

    PubMed

    Gao, Wei; Yang, Xiucong; Lin, Zhiqiang; Gao, Shanyun; He, Bing; Mei, Bong; Wang, Dan; Yuan, Lan; Zhang, Hua; Dai, Wenbing; Wang, Xueqing; Wang, Jiancheng; Zhang, Xuan; Zhang, Qiang

    2016-06-01

    In addition to showing the specific interaction between a generalized ligand and its receptor and the electrostatic effect between positive cell-penetrating peptides and negative cell membranes, our last study demonstrated the hydrophobic interactivity between a hydrophobic binding peptide (HBP) and biomembranes to be favorable in drug delivery. To yield more evidence for this new strategy and to find more effective HBPs, here we designed and established a novel nanomedicine associated with cyclosporin A (CsA) because this peptide is electrically neutral, highly hydrophobic, very stable in vivo and safe at the given dose. First, isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) studies showed a strong hydrophobic interaction between the CsA molecules and the lipid membrane. The lactate dehydrogenase release assay proved that CsA exhibited low toxicity to cell membranes. These facts encouraged us to explore the potential application of CsA as an HBP to actualize intracellular delivery of nanomedicines for tumor therapy. When conjugated to lipid nanocarriers, CsA significantly enhanced their binding with cells and,. consequently, increased the internalization of recoded nanomedicines into cells. The in vivo experiments further showed that the CsA-associated nanocarriers could achieve better delivery to tumor tissues and improve the tumor therapy of doxorubicin (DOX) compared to the nonmodified control; these findings were identical to the observations-in cell studies. In conclusion, CsA, a readily obtainable molecule with favorable characteristics, is indeed a good candidate for an HBP, and this study provides solid, novel evidence for the use of HBP-based nanocarriers as effective antitumor drug delivery systems.

  7. The Use ofa Hydrophobic Binding Peptide Modified Lipid Nanocarrier Improving Tumor Distribution and Antitumor Efficacy.

    PubMed

    Gao, Wei; Yang, Xiucong; Lin, Zhiqiang; Gao, Shanyun; He, Bing; Mei, Bong; Wang, Dan; Yuan, Lan; Zhang, Hua; Dai, Wenbing; Wang, Xueqing; Wang, Jiancheng; Zhang, Xuan; Zhang, Qiang

    2016-06-01

    In addition to showing the specific interaction between a generalized ligand and its receptor and the electrostatic effect between positive cell-penetrating peptides and negative cell membranes, our last study demonstrated the hydrophobic interactivity between a hydrophobic binding peptide (HBP) and biomembranes to be favorable in drug delivery. To yield more evidence for this new strategy and to find more effective HBPs, here we designed and established a novel nanomedicine associated with cyclosporin A (CsA) because this peptide is electrically neutral, highly hydrophobic, very stable in vivo and safe at the given dose. First, isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) studies showed a strong hydrophobic interaction between the CsA molecules and the lipid membrane. The lactate dehydrogenase release assay proved that CsA exhibited low toxicity to cell membranes. These facts encouraged us to explore the potential application of CsA as an HBP to actualize intracellular delivery of nanomedicines for tumor therapy. When conjugated to lipid nanocarriers, CsA significantly enhanced their binding with cells and,. consequently, increased the internalization of recoded nanomedicines into cells. The in vivo experiments further showed that the CsA-associated nanocarriers could achieve better delivery to tumor tissues and improve the tumor therapy of doxorubicin (DOX) compared to the nonmodified control; these findings were identical to the observations-in cell studies. In conclusion, CsA, a readily obtainable molecule with favorable characteristics, is indeed a good candidate for an HBP, and this study provides solid, novel evidence for the use of HBP-based nanocarriers as effective antitumor drug delivery systems. PMID:27319213

  8. A simple water model in the presence of inert Lennard-Jones obstacles II: the hydrophobic effect

    NASA Astrophysics Data System (ADS)

    Kurtjak, Mario; Urbic, Tomaz

    2015-04-01

    Using Monte Carlo computer simulations, hydrophobic effect for a non-polar particle with the diameter of a water molecule was studied in water, confined within a disordered matrix. Freely mobile two-dimensional Mercedes-Benz water was put in a disordered, but fixed, matrix of Lennard-Jones disks. Influence of temperature and matrix properties on the thermodynamic quantities of a non-polar solute solvation was studied. The hydrophobic effect is changed by the presence of the obstacles. Smaller matrix particles change the solute-water structure and thermodynamics drastically, as it was also observed for the properties of pure confined water. The study is bringing new scientific important observations in understanding the role of hydrophobic forces under confinement.

  9. Chemical hydrophobicity and uptake by plant roots.

    PubMed

    Dettenmaier, Erik M; Doucette, William J; Bugbee, Bruce

    2009-01-15

    The transpiration stream concentration factor (TSCF), the ratio between a compound's concentration in the xylem to that in the solution adjacent to the roots, is commonly used to describe the relative ability of an organic compound to be passively transported from root to shoot. Widely cited bell-shaped curves relating TSCFto the octanol/water partition coefficient (log Kow) imply that significant root uptake and transfer into shoot tissues occurs only for compounds falling within an intermediate hydrophobicity range. However, recent laboratory and field data for relatively water soluble compounds such as sulfolane, methyl tert-butyl ether (MTBE), and 1,4-dioxane suggest that these relationships are not universally applicable, especiallyfor nonionizable, highly polar, water soluble organics. To re-evaluate the relationship between root uptake and chemical hydrophobicity, TSCFs were measured for 25 organic chemicals ranging in log Kow from -0.8 to 5 using a pressure chamber technique. Using the TSCF values measured in this study, a new empirical relationship between TSCF (0 and 1) and log Kow (-0.8 to 5) is presented that indicates that nonionizable, polar, highly water soluble organic compounds are most likely to be taken up by plant roots and translocated to shoot tissue.

  10. Hydrophobic and Basic Domains Target Proteins to Lipid Droplets

    PubMed Central

    Ingelmo-Torres, Mercedes; González-Moreno, Elena; Kassan, Adam; Hanzal-Bayer, Michael; Tebar, Francesc; Herms, Albert; Grewal, Thomas; Hancock, John F.; Enrich, Carlos; Bosch, Marta; Gross, Steven P.; Parton, Robert G.; Pol, Albert

    2010-01-01

    In recent years, progress in the study of the lateral organization of the plasma membrane has led to the proposal that mammalian cells use two different organelles to store lipids: intracellular lipid droplets (LDs) and plasma membrane caveolae. Experimental evidence suggests that caveolin (CAV) may act as a sensitive lipid-organizing molecule that physically connects these two lipid-storing organelles. Here, we determine the sequences necessary for efficient sorting of CAV to LDs. We show that targeting is a process cooperatively mediated by two motifs. CAV's central hydrophobic domain (Hyd) anchors CAV to the endoplasmic reticulum (ER). Next, positively charged sequences (Pos-Seqs) mediate sorting of CAVs into LDs. Our findings were confirmed by identifying an equivalent, non-conserved but functionally interchangeable Pos-Seq in ALDI, a bona fide LD-resident protein. Using this information, we were able to retarget a cytosolic protein and convert it to an LD-resident protein. Further studies suggest three requirements for targeting via this mechanism: the positive charge of the Pos-Seq, physical proximity between Pos-Seq and Hyd and a precise spatial orientation between both motifs. The study uncovers remarkable similarities with the signals that target proteins to the membrane of mitochondria and peroxisomes PMID:19874557

  11. Aggregation of a hydrophobically modified poly(propylene imine) dendrimer

    NASA Astrophysics Data System (ADS)

    Tan, Susheng; Su, Aihua; Ford, Warren T.

    2008-10-01

    The poly(propylene imine) dendrimer DAB-dendr- (NH2)8 was hydrophobically modified with dodecanoyl end groups. The modified dendrimer was deposited onto mica by adsorption from solution and observed by atomic force microscopy. With the decrease of adsorption time, the modified dendrimer varied from continuous film to scattered islands. For the adsorption time of 20s the dendrimer formed a sub-monolayer thin film that contained many fractal aggregates of fractal dimension 1.80 that were > 1 μm in diameter and no more than 0.8nm thick. After 5 months at 1#1 , the initial fractal aggregates transformed into disks and other less-branched shapes with average heights of the domains of 0.6nm and 0.4nm, respectively. Formation of the fractal aggregates is explained by diffusion-limited aggregation. The slow reorganization of dendrimer molecules in the fractal aggregates occurs at a temperature well above the Tg of the dendrimer.

  12. [Effect of relative molecular mass distribution and hydrophilicity/ hydrophobicity of NOM on membrane fouling in MF-combined process].

    PubMed

    Hu, Meng-Liu; Lin, Jie; Xu, Guang-Hong; Dong, Bing-Zhi

    2013-01-01

    This study investigated the reversible and irreversible foulants in a submerged microfiltration (MF) with pretreatments (coagulation/powdered activated carbon (PAC)/potassium permanganate) in a pilot scale treatment of water from Taihu Lake. The study focused on the effect of relative molecular mass (M(r)) distribution and hydrophilicity/hydrophobicity on membrane fouling using high performance size-exclusion chromatography (HPSEC) with UV and TOC detectors and three dimension fluorescence excitation-emission matrix (3DEEM). HPSEC analyses showed that pretreatments could almost completely remove the macro molecules (M(r) > 10 x 10(3)), but only eliminate part of medium (10 x 10(3)) > M(r) > 1 x 10(3)) and micro molecules (M(r) < 1 x 10(3)). A majority of medium and micro molecules were found in chemical cleaning solutions, indicating that medium and micro molecules were the main foulants that contributed to irreversible membrane fouling. In addition, it was also found that the content of strong hydrophobic acids (SHA) and neutral hydrophilic (Neut) fractions in chemical solutions were far higher than that of weakly hydrophobic acids (WHA) and charged hydrophilic (Char), which suggested that both organic fractions were responsible for irreversible fouling. 3DEEM fluorescence demonstrated that aromatic proteins and soluble microbial products were the main contributors to irreversible membrane fouling. PMID:23487934

  13. Influence of self-assembling redox mediators on charge transfer at hydrophobic electrodes.

    PubMed

    Smith, Timothy J; Wang, Chenxuan; Abbott, Nicholas L

    2015-10-01

    We report an investigation of the influence of reversible self-assembly of amphiphilic redox-mediators on interfacial charge transfer at chemically functionalized electrodes. Specifically, we employed (11-ferrocenylundecyl)-trimethylammonium bromide (FTMA) as a model self-assembling redox mediator and alkanethiol-modified gold films as hydrophobic electrodes. By performing cyclic voltammetry (CV, 10 mV/s) in aqueous solutions containing FTMA above its critical micellar concentration (CMC), we measured anodic (Ia) and cathodic (Ic) peak current densities of 18 ± 3 and 1.1 ± 0.1 μA/cm(2), respectively, revealing substantial current rectification (Ia/Ic= 17) at the hydrophobic electrodes. In contrast, hydroxymethyl ferrocene (a non-self-assembling redox mediator) at hydrophobic electrodes and FTMA at bare gold electrodes, yielded relatively low levels of rectification (Ia/Ic= 1.7 and 2.3, respectively). Scan-rate-dependent measurements revealed Ia of FTMA to arise largely from the diffusion of FTMA from bulk solution to the hydrophobic electrode whereas Ic was dominated by adsorbed FTMA, leading to the proposal that current rectification observed with FTMA is mediated by interfacial assemblies of reduced FTMA that block access of oxidized FTMA to the hydrophobic electrode. Support for this proposal was obtained by using atomic force microscopy and quartz crystal microbalance measurements to confirm the existence of interfacial assemblies of reduced FTMA (1.56 ± 0.2 molecules/nm(2)). Additional characterization of a mixed surfactant system containing FTMA and dodecyltrimethylammonium bromide (DTAB) revealed that interfacial assemblies of DTAB also block access of oxidized FTMA to hydrophobic electrodes; this system exhibited Ia/Ic > 80. These results and others reported in this paper suggest that current rectification occurs in this system because oxidized FTMA does not mix with interfacial assemblies of reduced FTMA or DTAB formed at hydrophobic electrodes. More

  14. Map Separates

    USGS Publications Warehouse

    ,

    2001-01-01

    U.S. Geological Survey (USGS) topographic maps are printed using up to six colors (black, blue, green, red, brown, and purple). To prepare your own maps or artwork based on maps, you can order separate black-and-white film positives or negatives for any color printed on a USGS topographic map, or for one or more of the groups of related features printed in the same color on the map (such as drainage and drainage names from the blue plate.) In this document, examples are shown with appropriate ink color to illustrate the various separates. When purchased, separates are black-and-white film negatives or positives. After you receive a film separate or composite from the USGS, you can crop, enlarge or reduce, and edit to add or remove details to suit your special needs. For example, you can adapt the separates for making regional and local planning maps or for doing many kinds of studies or promotions by using the features you select and then printing them in colors of your choice.

  15. Contacts Between Alcohols in Water Are Random Rather than Hydrophobic.

    PubMed

    Rankin, Blake M; Ben-Amotz, Dor; van der Post, Sietse T; Bakker, Huib J

    2015-02-19

    Given the importance of water-mediated hydrophobic interactions in a wide range of biological and synthetic self-assembly processes, it is remarkable that both the sign and the magnitude of the hydrophobic interactions between simple amphiphiles, such as alcohols, remain unresolved. To address this question, we have performed Raman hydration-shell vibrational spectroscopy and polarization-resolved femtosecond infrared experiments, as well as random mixing and molecular dynamics simulations. Our results indicate that there are no more hydrophobic contacts in aqueous solutions of alcohols ranging from methanol to tertiary butyl alcohol than in random mixtures of the same concentration. This implies that the interaction between small hydrophobic groups is weaker than thermal energy fluctuations. Thus, the corresponding water-mediated hydrophobic interaction must be repulsive, with a magnitude sufficient to negate the attractive direct van der Waals interaction between the hydrophobic groups.

  16. Contacts Between Alcohols in Water Are Random Rather than Hydrophobic.

    PubMed

    Rankin, Blake M; Ben-Amotz, Dor; van der Post, Sietse T; Bakker, Huib J

    2015-02-19

    Given the importance of water-mediated hydrophobic interactions in a wide range of biological and synthetic self-assembly processes, it is remarkable that both the sign and the magnitude of the hydrophobic interactions between simple amphiphiles, such as alcohols, remain unresolved. To address this question, we have performed Raman hydration-shell vibrational spectroscopy and polarization-resolved femtosecond infrared experiments, as well as random mixing and molecular dynamics simulations. Our results indicate that there are no more hydrophobic contacts in aqueous solutions of alcohols ranging from methanol to tertiary butyl alcohol than in random mixtures of the same concentration. This implies that the interaction between small hydrophobic groups is weaker than thermal energy fluctuations. Thus, the corresponding water-mediated hydrophobic interaction must be repulsive, with a magnitude sufficient to negate the attractive direct van der Waals interaction between the hydrophobic groups. PMID:26262487

  17. Evidence of water molecules--a statistical evaluation of water molecules based on electron density.

    PubMed

    Nittinger, Eva; Schneider, Nadine; Lange, Gudrun; Rarey, Matthias

    2015-04-27

    Water molecules play important roles in many biological processes, especially when mediating protein-ligand interactions. Dehydration and the hydrophobic effect are of central importance for estimating binding affinities. Due to the specific geometric characteristics of hydrogen bond functions of water molecules, meaning two acceptor and two donor functions in a tetrahedral arrangement, they have to be modeled accurately. Despite many attempts in the past years, accurate prediction of water molecules-structurally as well as energetically-remains a grand challenge. One reason is certainly the lack of experimental data, since energetic contributions of water molecules can only be measured indirectly. However, on the structural side, the electron density clearly shows the positions of stable water molecules. This information has the potential to improve models on water structure and energy in proteins and protein interfaces. On the basis of a high-resolution subset of the Protein Data Bank, we have conducted an extensive statistical analysis of 2.3 million water molecules, discriminating those water molecules that are well resolved and those without much evidence of electron density. In order to perform this classification, we introduce a new measurement of electron density around an individual atom enabling the automatic quantification of experimental support. On the basis of this measurement, we present an analysis of water molecules with a detailed profile of geometric and structural features. This data, which is freely available, can be applied to not only modeling and validation of new water models in structural biology but also in molecular design.

  18. New Hydrophobic IOL Materials and Understanding the Science of Glistenings.

    PubMed

    Tetz, Manfred; Jorgensen, Matthew R

    2015-01-01

    An introduction to the history of intraocular lenses (IOLs) is given, leading up to modern hydrophobic examples. The roles of hydrophobicity, hygroscopy, materials chemistry, and edge design are discussed in the context of IOLs. The four major types of IOL materials are compared in terms of their chemistry and biocompatibility. An example of a modern "hydrophobic" acrylic polymer with higher water content is discussed in detail.

  19. Conductive hydrophobic hybrid textiles modified with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kowalczyk, D.; Brzeziński, S.; Makowski, T.; Fortuniak, W.

    2015-12-01

    The paper presents the results of modifying and testing modern hybrid polyester-cotton woven fabrics with deposited multi-wall carbon nanotubes and imparted hydrophobicity. The effect of the carbon nanotubes deposited on these fabrics on their conductive properties and hydrophobicity has been assessed. The electro-conductive and hydrophobic composite fabrics obtained in this way, being light, elastic and resistant to mechanical effects, make it possible to be widely used in various industrial fields.

  20. Adsorption behavior of human plasma fibronectin on hydrophobic and hydrophilic Ti6Al4V substrata and its influence on bacterial adhesion and detachment.

    PubMed

    Vadillo-Rodríguez, Virginia; Pacha-Olivenza, Miguel A; Gónzalez-Martín, M Luisa; Bruque, José M; Gallardo-Moreno, Amparo M

    2013-05-01

    Biomaterial implant-associated infections, a common cause of medical devices' failure, are initiated by bacterial adhesion to an adsorbed protein layer on the implant material surface. In this study, the influence of protein surface orientation on bacterial adhesion has been examined using three clinically relevant bacterial strains known to express specific binding sites for human plasma fibronectin (HFN). HFN was allowed to adsorb on hydrophobic Ti6Al4V and physically modified hydrophilic Ti6Al4V substrata. Ellipsometric data reveal that the characteristics of the adsorbed protein layers primary depend on solid surface tension and the initial protein concentration in solution. In particular, HFN molecules adopt a more extended conformation on hydrophobic than hydrophilic surfaces, an effect that is more pronounced at low than at high initial protein concentrations. Moreover, the extended conformation of the protein molecules on these surfaces likely facilitates the exposure of specific sites for adhesion, resulting in the higher bacterial-cell attachment observed regardless of the strain considered. Contact angle measurements and the analysis of the number of remaining adhering cells after being subjected to external forces further suggest that both specific and nonspecific (hydrophobic) interactions play an important role on bacterial attachment. This study is the first one to evaluate the influence of surface hydrophobicity on protein adsorption and its subsequent effect on bacterial adhesion using a material whose hydrophobicity was not modified using chemical treatments that potentially led to surface properties changes other than hydrophobicity.

  1. Sialyltransferase inhibitors: consideration of molecular shape and charge/hydrophobic interactions.

    PubMed

    Kumar, Rishi; Nasi, Ravindranath; Bhasin, Milan; Huan Khieu, Nam; Hsieh, Margaret; Gilbert, Michel; Jarrell, Harold; Zou, Wei; Jennings, Harold J

    2013-08-30

    In order to evaluate the importance of molecular shape of inhibitor molecules and the charge/H-bond and hydrophobic interactions, we synthesized three types of molecules and tested them against a sialyltransferase. The first type of compounds were designed as substrate mimics in which the phosphate in CMP-Neu5NAc was replaced by a non-hydrolysable, uncharged 1,2,3-triazole moiety. The second type of compound contained a 2-deoxy-2,3-dehydro-acetylneuraminic moiety which was linked to cytidine through its carboxylic acid and amide linkers. In the third type of compound the sialyl phosphate was substituted by an aryl sulfonamide which was then linked to cytidine. Inhibition study of these cytidine conjugates against Campylobacter jejuni sialyltransferase Cst 06 showed that the first type of molecules are competitive inhibitors, whereas the other two could only inhibit the enzyme non-competitively. The results indicate that although the binding specificity may be guided by molecular shape and H-bond interaction, the charge and hydrophobic interactions contributed most to the binding affinity.

  2. Water dynamics in aqueous solutions of tetra-n-alkylammonium salts: hydrophobic and Coulomb interactions disentangled.

    PubMed

    van der Post, Sietse T; Scheidelaar, Stefan; Bakker, Huib J

    2013-12-01

    We studied the effects of tetra-n-alkylammonium bromide (N(C(n)H(2n+1))(4)(+)Br(-)) salts on the dynamics of water using polarization-resolved femtosecond infrared spectroscopy. With this technique, we are capable of distinguishing the response of water solvating the hydrophobic cations from that of water solvating the bromide anion. We observe that both types of ions slow down the orientational dynamics of the water molecules in their solvation shells. However, the nature of this slowdown is different for both ions. For the hydrophobic cation, we find an increasing number of retarded water molecules, scaling with the alkyl chain length. Water in the bromide solvation shell experiences a partial decay of its orientation by a fast wobbling motion, after which the remaining anisotropy decays much slower. The dynamics of the wobbling motion are observed to be dependent on the nature of the cation. For Me(4)NBr, the slow reorientation time is not concentration-dependent, and no aggregation is observed. This is in contrast to the tetra-n-alkylammonium salts with longer alkyl chains, for which the slow reorientation time of bromide-bound water molecules increases dramatically with concentration, and clusters of cations and anions appear to be formed. PMID:24228939

  3. Orientational order as the origin of the long-range hydrophobic effect.

    PubMed

    Banerjee, Saikat; Singh, Rakesh S; Bagchi, Biman

    2015-04-01

    The long range attractive force between two hydrophobic surfaces immersed in water is observed to decrease exponentially with their separation-this distance-dependence of effective force is known as the hydrophobic force law (HFL). We explore the microscopic origin of HFL by studying distance-dependent attraction between two parallel rods immersed in 2D Mercedes Benz model of water. This model is found to exhibit a well-defined HFL. Although the phenomenon is conventionally explained by density-dependent theories, we identify orientation, rather than density, as the relevant order parameter. The range of density variation is noticeably shorter than that of orientational heterogeneity. The latter is comparable to the observed distances of hydrophobic force. At large separation, attraction between the rods arises primarily from a destructive interference among the inwardly propagating oppositely oriented heterogeneity generated in water by the two rods. As the rods are brought closer, the interference increases leading to a decrease in heterogeneity and concomitant decrease in free energy of the system, giving rise to the effective attraction. We notice formation of hexagonal ice-like structures at the onset of attractive region which suggests that metastable free energy minimum may play a role in the origin of HFL.

  4. [Development of the Selective Hydrophobic Coagulation process]. [Quarterly report, January 1, 1993--March 31, 1993

    SciTech Connect

    Not Available

    1993-08-01

    A novel technique for selectively coagulating and separating mineral matter has been developed at Virginia Tech. The process, known as Selective Hydrophobic Coagulation (SHC), has been studied under the sponsorship of the US Department of Energy since 1986 (Contracts DE-AC22-86PC91221 and DE-AC22-90PC90174). The SHC process differs from oil agglomeration, shear flocculation, polymer flocculation, and electrolytic coagulation processes in that it does not require reagents or additives to induce the formation of coagula. Often, simple pH control is all that is required to (1) induce the coagulation of coal particles and (2) effectively disperse particles of mineral matter. When the coal is superficially oxidized, a small dosage of reagents may be used to promote coagulation. During the last quarter, work was completed on the collection of the surface force and hydrophobicity data required for the estimation of the parameters in the hydrophobic interaction energy function. The estimation of these parameters will be completed in May, and the development of the extended DLVO equation for coal should be completed by the end of the next quarter. In Task 3, the mixing/coagulation characteristics of in-line mixers have been established and work with the ultrasonic horn has begun. The study of the recovery of coagula by column flotation will be completed in early May, and work on the remaining sub-tasks of Advanced Separation Methods has been accelerated in an effort to complete this task on schedule.

  5. Orientational order as the origin of the long-range hydrophobic effect.

    PubMed

    Banerjee, Saikat; Singh, Rakesh S; Bagchi, Biman

    2015-04-01

    The long range attractive force between two hydrophobic surfaces immersed in water is observed to decrease exponentially with their separation-this distance-dependence of effective force is known as the hydrophobic force law (HFL). We explore the microscopic origin of HFL by studying distance-dependent attraction between two parallel rods immersed in 2D Mercedes Benz model of water. This model is found to exhibit a well-defined HFL. Although the phenomenon is conventionally explained by density-dependent theories, we identify orientation, rather than density, as the relevant order parameter. The range of density variation is noticeably shorter than that of orientational heterogeneity. The latter is comparable to the observed distances of hydrophobic force. At large separation, attraction between the rods arises primarily from a destructive interference among the inwardly propagating oppositely oriented heterogeneity generated in water by the two rods. As the rods are brought closer, the interference increases leading to a decrease in heterogeneity and concomitant decrease in free energy of the system, giving rise to the effective attraction. We notice formation of hexagonal ice-like structures at the onset of attractive region which suggests that metastable free energy minimum may play a role in the origin of HFL. PMID:25854251

  6. ISOTOPE SEPARATORS

    DOEpatents

    Bacon, C.G.

    1958-08-26

    An improvement is presented in the structure of an isotope separation apparatus and, in particular, is concerned with a magnetically operated shutter associated with a window which is provided for the purpose of enabling the operator to view the processes going on within the interior of the apparatus. The shutier is mounted to close under the force of gravity in the absence of any other force. By closing an electrical circuit to a coil mouated on the shutter the magnetic field of the isotope separating apparatus coacts with the magnetic field of the coil to force the shutter to the open position.

  7. Mussel inspired modification of polypropylene separators by catechol/polyamine for Li-ion batteries.

    PubMed

    Wang, Hao; Wu, Junjie; Cai, Chao; Guo, Jing; Fan, Haosen; Zhu, Caizhen; Dong, Haixia; Zhao, Ning; Xu, Jian

    2014-04-23

    Inspired by the remarkable adhesion of mussel, dopamine, a mimicking adhesive molecule, has been widely used for surface modification of various materials ranging from organic to inorganic. However, dopamine and its derivatives are expensive which impede their application in large scale. Herein, we replaced dopamine with low-cost catechol and polyamine (only 8% of the cost of dopamine), which could be polymerized in an alkaline solution and deposited on the surfaces of various materials. By using this cheap and simple modification method, polypropylene (PP) separator could be transformed from hydrophobic to hydrophilic, while the pore structure and mechanical property of the separator remained intact. The uptake of electrolyte increased from 80% to 270% after the hydrophilic modification. Electrochemical studies demonstrated that battery with the modified PP separator had a better Coulombic efficiency (80.9% to 85.3%) during the first cycle at a current density of 0.1 C, while the discharging current density increased to 15 C and the discharge capacity increased by 1.4 times compared to the battery using the bare PP separator. Additionally, the modification allowed excellent stability during manifold cycles. This study provides new insights into utilizing low-cost chemicals to mimic the mussel adhesion and has potential practical application in many fields. PMID:24684271

  8. Mussel inspired modification of polypropylene separators by catechol/polyamine for Li-ion batteries.

    PubMed

    Wang, Hao; Wu, Junjie; Cai, Chao; Guo, Jing; Fan, Haosen; Zhu, Caizhen; Dong, Haixia; Zhao, Ning; Xu, Jian

    2014-04-23

    Inspired by the remarkable adhesion of mussel, dopamine, a mimicking adhesive molecule, has been widely used for surface modification of various materials ranging from organic to inorganic. However, dopamine and its derivatives are expensive which impede their application in large scale. Herein, we replaced dopamine with low-cost catechol and polyamine (only 8% of the cost of dopamine), which could be polymerized in an alkaline solution and deposited on the surfaces of various materials. By using this cheap and simple modification method, polypropylene (PP) separator could be transformed from hydrophobic to hydrophilic, while the pore structure and mechanical property of the separator remained intact. The uptake of electrolyte increased from 80% to 270% after the hydrophilic modification. Electrochemical studies demonstrated that battery with the modified PP separator had a better Coulombic efficiency (80.9% to 85.3%) during the first cycle at a current density of 0.1 C, while the discharging current density increased to 15 C and the discharge capacity increased by 1.4 times compared to the battery using the bare PP separator. Additionally, the modification allowed excellent stability during manifold cycles. This study provides new insights into utilizing low-cost chemicals to mimic the mussel adhesion and has potential practical application in many fields.

  9. Hydrogen isotope separation from water

    DOEpatents

    Jensen, R.J.

    1975-09-01

    A process for separating tritium from tritium-containing water or deuterium enrichment from water is described. The process involves selective, laser-induced two-photon excitation and photodissociation of those water molecules containing deuterium or tritium followed by immediate reaction of the photodissociation products with a scavenger gas which does not substantially absorb the laser light. The reaction products are then separated from the undissociated water. (auth)

  10. Structures of KcsA in Complex with Symmetrical Quaternary Ammonium Compounds Reveal a Hydrophobic Binding Site

    PubMed Central

    2015-01-01

    Potassium channels allow for the passive movement of potassium ions across the cell membrane and are instrumental in controlling the membrane potential in all cell types. Quaternary ammonium (QA) compounds block potassium channels and have long been used to study the functional and structural properties of these channels. Here we describe the interaction between three symmetrical hydrophobic QAs and the prokaryotic potassium channel KcsA. The structures demonstrate the presence of a hydrophobic pocket between the inner helices of KcsA and provide insight into the binding site and blocking mechanism of hydrophobic QAs. The structures also reveal a structurally hidden pathway between the central cavity and the outside membrane environment reminiscent of the lateral fenestration observed in sodium channels that can be accessed through small conformational changes in the pore wall. We propose that the hydrophobic binding pocket stabilizes the alkyl chains of long-chain QA molecules and may play a key role in hydrophobic drug binding in general. PMID:25093676

  11. Combined hydrophobicity and mechanical durability through surface nanoengineering

    SciTech Connect

    Elliott, Paul R.; Stagon, Stephen P.; Huang, Hanchen; Furrer, David U.; Burlatsky, Sergei F.; Filburn, Thomas P.

    2015-04-08

    This paper reports combined hydrophobicity and mechanical durability through the nanoscale engineering of surfaces in the form of nanorod-polymer composites. Specifically, the hydrophobicity derives from nanoscale features of mechanically hard ZnO nanorods and the mechanical durability derives from the composite structure of a hard ZnO nanorod core and soft polymer shell. Experimental characterization correlates the morphology of the nanoengineered surfaces with the combined hydrophobicity and mechanical durability, and reveals the responsible mechanisms. Such surfaces may find use in applications, such as boat hulls, that benefit from hydrophobicity and require mechanical durability.

  12. Combined Hydrophobicity and Mechanical Durability through Surface Nanoengineering

    PubMed Central

    Elliott, Paul R.; Stagon, Stephen P.; Huang, Hanchen; Furrer, David U.; Burlatsky, Sergei F.; Filburn, Thomas P.

    2015-01-01

    This paper reports combined hydrophobicity and mechanical durability through the nanoscale engineering of surfaces in the form of nanorod-polymer composites. Specifically, the hydrophobicity derives from nanoscale features of mechanically hard ZnO nanorods and the mechanical durability derives from the composite structure of a hard ZnO nanorod core and soft polymer shell. Experimental characterization correlates the morphology of the nanoengineered surfaces with the combined hydrophobicity and mechanical durability, and reveals the responsible mechanisms. Such surfaces may find use in applications, such as boat hulls, that benefit from hydrophobicity and require mechanical durability. PMID:25851026

  13. The Role of Hydrophobic Surfaces in Altering Water-Mediated Peptide-Peptide Interactions in an Aqueous Environment

    SciTech Connect

    Yoo, Soohaeng; Xantheas, Sotiris S

    2011-06-16

    Using Born-Oppenheimer molecular dynamics within the density functional framework, we calculated the effective force acting on water-mediated peptide-peptide interaction between antiparallel β-sheets in an aqueous environment and also in the vicinity of a hydrophobic surface. From the magnitude of the effective force (corresponding to the slope of the free energy as a function of the inter-peptide distance) and its sign (a negative value indicating an effective attraction whereas a positive value an effective repulsion) we can elucidate the fundamental differences of the water-mediated peptide-peptide interactions in those two environments. The computed effective forces indicate that the water-mediated interaction between peptides in an aqueous environment is attractive in the range of inter-peptide distance d=7-8 Å when hydrophobic surfaces are not nearby. Due to the stabilization of the water molecules bridging between the two β-sheets, a free energy barrier exists between the direct and indirect (water-mediated) inter-peptide interactions. However, when the peptides are in the proximity of hydrophobic surfaces, this free energy barrier decreases because the hydrophobic surfaces enhance the inter-peptide attraction by the destabilization and ease-to-libration of the bridging water molecules between them. This work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, US Department of Energy. Battelle operates the Pacific Northwest National Laboratory for the U.S. Department of Energy.

  14. Effect of hydrophobic interactions on the folding mechanism of β-hairpins.

    PubMed

    Popp, Alexander; Wu, Ling; Keiderling, Timothy A; Hauser, Karin

    2014-12-11

    Hydrophobic interactions are essential in stabilizing protein structures. How they affect the folding pathway and kinetics, however, is less clear. We used time-resolved infrared spectroscopy to study the dynamics of hydrophobic interactions of β-hairpin variants of the sequence Trpzip2 (SWTWENGKWTWK-NH2) that is stabilized by two cross-strand Trp-Trp pairs. The hydrophobicity strength was varied by substituting the tryptophans pairwise by either tyrosines or valines. Relaxation dynamics were induced by a laser-excited temperature jump, which separately probed for the loss of the cross-strand β-hairpin interaction and the rise of the disordered structure. All substitutions tested result in reduced thermal stability, lower transition temperatures, and faster dynamics compared to Trpzip2. However, the changes in folding dynamics depend on the amino acid substituted for Trp. The aromatic substitution of Tyr for Trp results in the same kinetics for the unfolding of sheet and growth of disorder, with similar activation energies, independent of the substitution position. Substitution of Trp with a solely hydrophobic Val results in even faster kinetics than substitution with Tyr but is additionally site-dependent. If the hairpin has a Val pair close to its termini, the rate constants for loss of sheet and gain of disorder are the same, but if the pair is close to the turn, the sheet and disorder components show different relaxation kinetics. The Trp → Val substitutions reveal that hydrophobic interactions alone weakly stabilize the hairpin structure, but adding edge-to-face aromatic interaction strengthens it, and both modify the complex folding process.

  15. Asymmetric electrostatic and hydrophobic-hydrophilic interaction forces between mica surfaces and silicone polymer thin films.

    PubMed

    Donaldson, Stephen H; Das, Saurabh; Gebbie, Matthew A; Rapp, Michael; Jones, Louis C; Roiter, Yuri; Koenig, Peter H; Gizaw, Yonas; Israelachvili, Jacob N

    2013-11-26

    We have synthesized model hydrophobic silicone thin films on gold surfaces by a two-step covalent grafting procedure. An amino-functionalized gold surface reacts with monoepoxy-terminated polydimethylsiloxane (PDMS) via a click reaction, resulting in a covalently attached nanoscale thin film of PDMS, and the click chemistry synthesis route provides great selectivity, reproducibility, and stability in the resulting model hydrophobic silicone thin films. The asymmetric interaction forces between the PDMS thin films and mica surfaces were measured with the surface forces apparatus in aqueous sodium chloride solutions. At an acidic pH of 3, attractive interactions are measured, resulting in instabilities during both approach (jump-in) and separation (jump-out from adhesive contact). Quantitative analysis of the results indicates that the Derjaguin-Landau-Verwey-Overbeek theory alone, i.e., the combination of electrostatic repulsion and van der Waals attraction, cannot fully describe the measured forces and that the additional measured adhesion is likely due to hydrophobic interactions. The surface interactions are highly pH-dependent, and a basic pH of 10 results in fully repulsive interactions at all distances, due to repulsive electrostatic and steric-hydration interactions, indicating that the PDMS is negatively charged at high pH. We describe an interaction potential with a parameter, known as the Hydra parameter, that can account for the extra attraction (low pH) due to hydrophobicity as well as the extra repulsion (high pH) due to hydrophilic (steric-hydration) interactions. The interaction potential is general and provides a quantitative measure of interfacial hydrophobicity/hydrophilicity for any set of interacting surfaces in aqueous solution.

  16. Configurations of the amphiphilic molecules in micelles

    SciTech Connect

    Dill, K.A.

    1982-04-29

    Several theoretic models aim to account for the properties of micelles in terms of the configurations of the constituent amphiphilic chain molecules. Recent /sup 13/C NMR measurement of one property of the configuration distribution of the the hydrocarbon chain segments allows critical evaluation of these theories. It is concluded that the interphase and singly-bent chain theories, which fully account for chain continuity and for intermolecular constraints imposed by hydrophobic and steric forces, give a more satisfactory description of micellar molecular organization than models in which chains are ordered and radially aligned, or in which they have the complete disorder characteristic of an amorphous hydrocarbon liquid.

  17. Penetration of surfactant solutions into hydrophobic capillaries.

    PubMed

    Bain, Colin D

    2005-08-21

    The initial rise velocity of surfactant solutions in hydrophobic capillaries is independent of time (F. Tiberg, B. Zhmud, K. Hallstensson and M. von Bahr, Phys. Chem. Chem. Phys., 2000, 2, 5189). By analogy with the hydrodynamics of an overflowing cylinder, we present a steady-state solution for capillary penetration in which the velocity is determined by the adsorption kinetics at the air-water interface. Good agreement between the model predictions and experimental data of Tiberg and coworkers is obtained for the non-ionic surfactant C10E6 under the assumption of diffusion-controlled adsorption. The longer chain homologue, C14E6, shows evidence of kinetic barriers to adsorption.

  18. SEPARATION PROCESS

    DOEpatents

    Stoughton, R.W.

    1961-10-24

    A process for separating tetravalent plutonium from aqueous solutions and from niobium and zirconium by precipitation on lanthanum oxalate is described. The oxalate ions of the precipitate may be decomposed by heating in the presence of an oxidizing agent, forming a plutonium compound readily soluble in acid. (AEC)

  19. Plasma separation

    NASA Technical Reports Server (NTRS)

    Steurer, Wolfgang

    1992-01-01

    This process employs a thermal plasma for the separation and production of oxygen and metals. It is a continuous process that requires no consumables and relies entirely on space resources. The almost complete absence of waste renders it relatively clean. It can be turned on or off without any undesirable side effects or residues. The prime disadvantage is its high power consumption.

  20. Hydrophobicity within the three-dimensional Mercedes-Benz model: Potential of mean force

    NASA Astrophysics Data System (ADS)

    Dias, Cristiano L.; Hynninen, Teemu; Ala-Nissila, Tapio; Foster, Adam S.; Karttunen, Mikko

    2011-02-01

    We use the three-dimensional Mercedes-Benz model for water and Monte Carlo simulations to study the structure and thermodynamics of the hydrophobic interaction. Radial distribution functions are used to classify different cases of the interaction, namely, contact configurations, solvent separated configurations, and desolvation configurations. The temperature dependence of these cases is shown to be in qualitative agreement with atomistic models of water. In particular, while the energy for the formation of contact configurations is favored by entropy, its strengthening with increasing temperature is accounted for by enthalpy. This is consistent with our simulated heat capacity. An important feature of the model is that it can be used to account for well-converged thermodynamics quantities, e.g., the heat capacity of transfer. Microscopic mechanisms for the temperature dependence of the hydrophobic interaction are discussed at the molecular level based on the conceptual simplicity of the model.