Sample records for conserved hydrophobic tetrad

  1. Conservation laws for vacuum tetrad gravity

    Energy Technology Data Exchange (ETDEWEB)

    Estabrook, Frank B [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)


    Ten conservation laws in useful polynomial form are derived from a Cartan form and exterior differential system (EDS) for the tetrad equations of vacuum general relativity. The Noether construction of conservation laws for well-posed EDSs is introduced first, and an illustration given, deriving 15 conservation laws of the free field Maxwell equations from symmetries of its EDS. The Maxwell EDS and tetrad gravity EDS have parallel structures, with their numbers of dependent variables, numbers of generating 2-forms and generating 3-forms, and Cartan character tables all in the ratio of 1 to 4. They have ten corresponding symmetries with the same Lorentz algebra and ten corresponding conservation laws.

  2. Follicular occlusion tetrad

    Directory of Open Access Journals (Sweden)

    Vani Vasanth


    Full Text Available Follicular occlusion tetrad is a symptom complex consisting of four conditions having a similar pathophysiology. It includes Hidradenitis suppurativa, acne conglobata, dissecting cellulitis of the scalp and pilonidal sinus. The exact pathogenesis of this group of disease is unknown but evidence suggests that they share the same pathological process initiated by follicular occlusion in apocrine gland bearing areas. Though each of these conditions is commonly encountered singly, follicular occlusion tetrad as a symptom complex has been rarely reported in the literature.

  3. Conservation of Hydrophobic and Hydrophilic Residues in Four-Helix Bundle

    Institute of Scientific and Technical Information of China (English)

    秦猛; 王骏; 王炜


    The conservation of the hydrophobic and the hydrophilic residue sites obtained from 1000 designed sequences with the Z-score method for a four-helix bundle has been studied. The folding dynamic and thermodynamic features of the designed sequences and their different mutations are also studied. It is found that this conservation is related to the stability and the fast folding of the model proteins. Our results are consistent with the experimental results.

  4. Conformal transformation of tetrads and spin connection

    CERN Document Server

    Chakrabarty, Subhasish


    We investigate the conformal transformation of vierbein-Einstein-Palatini (VEP) action in terms of tetrads $e^I_\\mu$ and spin connection $A^{IJ}_\\mu$. The transformation of tetrads is obtained from that of the spacetime metric whereas that of the spin connection is not unique off-shell. When the connection can be completely expressed in terms of the tetrads, its transformation follows from that of the tetrads. We also construct the conformally invariant scalar field in the VEP formalism.

  5. A conserved patch of hydrophobic amino acids modulates Myb activity by mediating protein-protein interactions. (United States)

    Dukare, Sandeep; Klempnauer, Karl-Heinz


    The transcription factor c-Myb plays a key role in the control of proliferation and differentiation in hematopoietic progenitor cells and has been implicated in the development of leukemia and certain non-hematopoietic tumors. c-Myb activity is highly dependent on the interaction with the coactivator p300 which is mediated by the transactivation domain of c-Myb and the KIX domain of p300. We have previously observed that conservative valine-to-isoleucine amino acid substitutions in a conserved stretch of hydrophobic amino acids have a profound effect on Myb activity. Here, we have explored the function of the hydrophobic region as a mediator of protein-protein interactions. We show that the hydrophobic region facilitates Myb self-interaction and binding of the histone acetyl transferase Tip60, a previously identified Myb interacting protein. We show that these interactions are affected by the valine-to-isoleucine amino acid substitutions and suppress Myb activity by interfering with the interaction of Myb and the KIX domain of p300. Taken together, our work identifies the hydrophobic region in the Myb transactivation domain as a binding site for homo- and heteromeric protein interactions and leads to a picture of the c-Myb transactivation domain as a composite protein binding region that facilitates interdependent protein-protein interactions of Myb with regulatory proteins.

  6. Critical role of conserved hydrophobic residues within the major homology region in mature retroviral capsid assembly. (United States)

    Purdy, John G; Flanagan, John M; Ropson, Ira J; Rennoll-Bankert, Kristen E; Craven, Rebecca C


    During retroviral maturation, the CA protein undergoes dramatic structural changes and establishes unique intermolecular interfaces in the mature capsid shell that are different from those that existed in the immature precursor. The most conserved region of CA, the major homology region (MHR), has been implicated in both immature and mature assembly, although the precise contribution of the MHR residues to each event has been largely undefined. To test the roles of specific MHR residues in mature capsid assembly, an in vitro system was developed that allowed for the first-time formation of Rous sarcoma virus CA into structures resembling authentic capsids. The ability of CA to assemble organized structures was destroyed by substitutions of two conserved hydrophobic MHR residues and restored by second-site suppressors, demonstrating that these MHR residues are required for the proper assembly of mature capsids in addition to any role that these amino acids may play in immature particle assembly. The defect caused by the MHR mutations was identified as an early step in the capsid assembly process. The results provide strong evidence for a model in which the hydrophobic residues of the MHR control a conformational reorganization of CA that is needed to initiate capsid assembly and suggest that the formation of an interdomain interaction occurs early during maturation.

  7. Distantly related lipocalins share two conserved clusters of hydrophobic residues: use in homology modeling

    Directory of Open Access Journals (Sweden)

    Brasseur Robert


    Full Text Available Abstract Background Lipocalins are widely distributed in nature and are found in bacteria, plants, arthropoda and vertebra. In hematophagous arthropods, they are implicated in the successful accomplishment of the blood meal, interfering with platelet aggregation, blood coagulation and inflammation and in the transmission of disease parasites such as Trypanosoma cruzi and Borrelia burgdorferi. The pairwise sequence identity is low among this family, often below 30%, despite a well conserved tertiary structure. Under the 30% identity threshold, alignment methods do not correctly assign and align proteins. The only safe way to assign a sequence to that family is by experimental determination. However, these procedures are long and costly and cannot always be applied. A way to circumvent the experimental approach is sequence and structure analyze. To further help in that task, the residues implicated in the stabilisation of the lipocalin fold were determined. This was done by analyzing the conserved interactions for ten lipocalins having a maximum pairwise identity of 28% and various functions. Results It was determined that two hydrophobic clusters of residues are conserved by analysing the ten lipocalin structures and sequences. One cluster is internal to the barrel, involving all strands and the 310 helix. The other is external, involving four strands and the helix lying parallel to the barrel surface. These clusters are also present in RaHBP2, a unusual "outlier" lipocalin from tick Rhipicephalus appendiculatus. This information was used to assess assignment of LIR2 a protein from Ixodes ricinus and to build a 3D model that helps to predict function. FTIR data support the lipocalin fold for this protein. Conclusion By sequence and structural analyzes, two conserved clusters of hydrophobic residues in interactions have been identified in lipocalins. Since the residues implicated are not conserved for function, they should provide the minimal

  8. Structural adaptation of extreme halophilic proteins through decrease of conserved hydrophobic contact surface

    Directory of Open Access Journals (Sweden)

    Siglioccolo Alessandro


    Full Text Available Abstract Background Halophiles are extremophilic microorganisms growing optimally at high salt concentrations. There are two strategies used by halophiles to maintain proper osmotic pressure in their cytoplasm: accumulation of molar concentrations of potassium and chloride with extensive adaptation of the intracellular macromolecules ("salt-in" strategy or biosynthesis and/or accumulation of organic osmotic solutes ("osmolyte" strategy. Our work was aimed at contributing to the understanding of the shared molecular mechanisms of protein haloadaptation through a detailed and systematic comparison of a sample of several three-dimensional structures of halophilic and non-halophilic proteins. Structural differences observed between the "salt-in" and the mesophilic homologous proteins were contrasted to those observed between the "osmolyte" and mesophilic pairs. Results The results suggest that haloadaptation strategy in the presence of molar salt concentration, but not of osmolytes, necessitates a weakening of the hydrophobic interactions, in particular at the level of conserved hydrophobic contacts. Weakening of these interactions counterbalances their strengthening by the presence of salts in solution and may help the structure preventing aggregation and/or loss of function in hypersaline environments. Conclusions Considering the significant increase of biotechnology applications of halophiles, the understanding of halophilicity can provide the theoretical basis for the engineering of proteins of great interest because stable at concentrations of salts that cause the denaturation or aggregation of the majority of macromolecules.

  9. A conserved hydrophobic surface of the LARG pleckstrin homology domain is critical for RhoA activation in cells. (United States)

    Aittaleb, Mohamed; Gao, Guang; Evelyn, Chris R; Neubig, Richard R; Tesmer, John J G


    Leukemia associated Rho guanine nucleotide exchange factor (LARG) activates RhoA in response to signals received by specific classes of cell surface receptors. The catalytic core of LARG is a Dbl homology (DH) domain whose activity is modulated by an adjacent pleckstrin homology (PH) domain. In this study, we used a transcriptional assay and confocal microscopy to examine the roles of several novel structural features of the LARG DH/PH domains, including a conserved and exposed hydrophobic patch on the PH domain that mediates protein-protein interactions in crystal structures of LARG and its close homolog PDZ-RhoGEF. Mutation of the hydrophobic patch has no effect on nucleotide exchange activity in vitro, but abolished the ability of LARG to activate RhoA and to induce stress fiber formation in cultured cells. The activity of these mutants could be rescued by fusion with exogenous membrane-targeting domains. However, because membrane recruitment by activated G alpha(13) subunits was not sufficient to rescue activity of a hydrophobic patch mutant, the LARG PH domain cannot solely contribute to membrane targeting. Instead, it seems likely that the domain is involved in regulatory interactions with other proteins near the membrane surface. We also show that the hydrophobic patch of the PH domain is likely important for the activity of all Lbc subfamily RhoGEFs.

  10. Critical Role of Conserved Hydrophobic Residues within the Major Homology Region in Mature Retroviral Capsid Assembly ▿ (United States)

    Purdy, John G.; Flanagan, John M.; Ropson, Ira J.; Rennoll-Bankert, Kristen E.; Craven, Rebecca C.


    During retroviral maturation, the CA protein undergoes dramatic structural changes and establishes unique intermolecular interfaces in the mature capsid shell that are different from those that existed in the immature precursor. The most conserved region of CA, the major homology region (MHR), has been implicated in both immature and mature assembly, although the precise contribution of the MHR residues to each event has been largely undefined. To test the roles of specific MHR residues in mature capsid assembly, an in vitro system was developed that allowed for the first-time formation of Rous sarcoma virus CA into structures resembling authentic capsids. The ability of CA to assemble organized structures was destroyed by substitutions of two conserved hydrophobic MHR residues and restored by second-site suppressors, demonstrating that these MHR residues are required for the proper assembly of mature capsids in addition to any role that these amino acids may play in immature particle assembly. The defect caused by the MHR mutations was identified as an early step in the capsid assembly process. The results provide strong evidence for a model in which the hydrophobic residues of the MHR control a conformational reorganization of CA that is needed to initiate capsid assembly and suggest that the formation of an interdomain interaction occurs early during maturation. PMID:18400856

  11. Molecular dynamics analysis of conserved hydrophobic and hydrophilic bond-interaction networks in ErbB family kinases. (United States)

    Shih, Andrew J; Telesco, Shannon E; Choi, Sung-Hee; Lemmon, Mark A; Radhakrishnan, Ravi


    The EGFR (epidermal growth factor receptor)/ErbB/HER (human EGFR) family of kinases contains four homologous receptor tyrosine kinases that are important regulatory elements in key signalling pathways. To elucidate the atomistic mechanisms of dimerization-dependent activation in the ErbB family, we have performed molecular dynamics simulations of the intracellular kinase domains of three members of the ErbB family (those with known kinase activity), namely EGFR, ErbB2 (HER2) and ErbB4 (HER4), in different molecular contexts: monomer against dimer and wild-type against mutant. Using bioinformatics and fluctuation analyses of the molecular dynamics trajectories, we relate sequence similarities to correspondence of specific bond-interaction networks and collective dynamical modes. We find that in the active conformation of the ErbB kinases, key subdomain motions are co-ordinated through conserved hydrophilic interactions: activating bond-networks consisting of hydrogen bonds and salt bridges. The inactive conformations also demonstrate conserved bonding patterns (albeit less extensive) that sequester key residues and disrupt the activating bond network. Both conformational states have distinct hydrophobic advantages through context-specific hydrophobic interactions. We show that the functional (activating) asymmetric kinase dimer interface forces a corresponding change in the hydrophobic and hydrophilic interactions that characterize the inactivating bond network, resulting in motion of the αC-helix through allostery. Several of the clinically identified activating kinase mutations of EGFR act in a similar fashion to disrupt the inactivating bond network. The present molecular dynamics study reveals a fundamental difference in the sequence of events in EGFR activation compared with that described for the Src kinase Hck.

  12. The Vanishing Tetrad Test: Another Test of Model Misspecification (United States)

    Roos, J. Micah


    The Vanishing Tetrad Test (VTT) (Bollen, Lennox, & Dahly, 2009; Bollen & Ting, 2000; Hipp, Bauer, & Bollen, 2005) is an extension of the Confirmatory Tetrad Analysis (CTA) proposed by Bollen and Ting (Bollen & Ting, 1993). VTT is a powerful tool for detecting model misspecification and can be particularly useful in cases in which…

  13. The Vanishing Tetrad Test: Another Test of Model Misspecification (United States)

    Roos, J. Micah


    The Vanishing Tetrad Test (VTT) (Bollen, Lennox, & Dahly, 2009; Bollen & Ting, 2000; Hipp, Bauer, & Bollen, 2005) is an extension of the Confirmatory Tetrad Analysis (CTA) proposed by Bollen and Ting (Bollen & Ting, 1993). VTT is a powerful tool for detecting model misspecification and can be particularly useful in cases in which…

  14. Canonical Noncommutativity Algebra for the Tetrad Field in General Relativity

    CERN Document Server

    Kober, Martin


    General relativity under the assumption of noncommuting components of the tetrad field is considered in this paper. Since the algebraic properties of the tetrad field representing the gravitational field are assumed to correspond to the noncommutativity algebra of the coordinates in the canonical case of noncommutative geometry, this idea is closely related to noncommutative geometry as well as to canonical quantization of gravity. According to this presupposition there are derived generalized field equations for general relativity which are obtained by replacing the usual tetrad field by the tetrad field operator within the actions and then building expectation values of the corresponding field equations between coherent states. These coherent states refer to creation and annihilation operators created from the components of the tetrad field operator. In this sense the obtained theory could be regarded as a kind of semiclassical approximation of a complete quantum description of gravity. The consideration pr...

  15. Structure of an IgNAR-AMA1 complex: targeting a conserved hydrophobic cleft broadens malarial strain recognition. (United States)

    Henderson, Kylie A; Streltsov, Victor A; Coley, Andrew M; Dolezal, Olan; Hudson, Peter J; Batchelor, Adrian H; Gupta, Aditi; Bai, Tao; Murphy, Vincent J; Anders, Robin F; Foley, Michael; Nuttall, Stewart D


    Apical membrane antigen 1 (AMA1) is essential for invasion of erythrocytes and hepatocytes by Plasmodium parasites and is a leading malarial vaccine candidate. Although conventional antibodies to AMA1 can prevent such invasion, extensive polymorphisms within surface-exposed loops may limit the ability of these AMA1-induced antibodies to protect against all parasite genotypes. Using an AMA1-specific IgNAR single-variable-domain antibody, we performed targeted mutagenesis and selection against AMA1 from three P. falciparum strains. We present cocrystal structures of two antibody-AMA1 complexes which reveal extended IgNAR CDR3 loops penetrating deep into a hydrophobic cleft on the antigen surface and contacting residues conserved across parasite species. Comparison of a series of affinity-enhancing mutations allowed dissection of their relative contributions to binding kinetics and correlation with inhibition of erythrocyte invasion. These findings provide insights into mechanisms of single-domain antibody binding, and may enable design of reagents targeting otherwise cryptic epitopes in pathogen antigens.

  16. Spore analysis and tetrad dissection of Schizosaccharomyces pombe

    DEFF Research Database (Denmark)

    Ekwall, Karl; Thon, Genevieve


    Here we describe the processing of Schizosaccharomyces pombe spores in batches (random spore analysis) or through tetrad dissections. Spores are usually prepared from matings between haploid strains (producing zygotic asci) or from sporulating diploids (producing azygotic asci). In random spore...... analysis, a snail enzyme preparation is used to digest the walls of asci to release free spores that are diluted and plated to form colonies. In tetrad dissection, a needle attached to a micromanipulator is used to pick asci and separate spores. Tetrad dissection has traditionally been the method of choice...

  17. Is Asp-His-Ser/Thr-Trp tetrad hydrogen-bond network important to WD40-repeat proteins: a statistical and theoretical study. (United States)

    Wu, Xian-Hui; Zhang, Hui; Wu, Yun-Dong


    WD40-repeat proteins are abundant and play important roles in forming protein complexes. The domain usually has seven WD40 repeats, which folds into a seven beta-sheet propeller with each beta-sheet in a four-strand structure. An analysis of 20 available WD40-repeat proteins in Protein Data Bank reveals that each protein has at least one Asp-His-Ser/Thr-Trp (D-H-S/T-W) hydrogen-bonded tetrad, and some proteins have up to six or seven such tetrads. The relative positions of the four residues in the tetrads are also found to be conserved. A sequence alignment analysis of 560 WD40-repeat protein sequences in human reveals very similar features, indicating that such tetrad may be a general feature of WD40-repeat proteins. We carried out density functional theory and found that these tetrads can lead to significant stabilization including hydrogen-bonding cooperativity. The hydrogen bond involving Trp is significant. These results lead us to propose that the tetrads may be critical to the stability and the mechanism of folding of these proteins.

  18. Relativistic rotating Boltzmann gas using the tetrad formalism

    CERN Document Server

    Ambrus, Victor E


    We consider an application of the tetrad formalism introduced by Cardall et al. [Phys. Rev. D 88 (2013) 023011] to the problem of a rigidly rotating relativistic gas in thermal equilibrium and discuss the possible applications of this formalism to relativistic lattice Boltzmann simulations. We present in detail the transformation to the comoving frame, the choice of tetrad, as well as the explicit calculation and analysis of the components of the equilibrium particle flow four-vector and of the equilibrium stress-energy tensor.

  19. The Use of Tetrads in the Analysis of Arts-Based Media (United States)

    Gouzouasis, Peter; LaMonde, Anne-Marie


    In this article, we chose the musical form of a sonata to examine tetrads, a simple four-fold structure that Marshall McLuhan coined and employed to describe various technologies. Tetrads, as cognitive models, are used to refine, focus, or discover entities in cultures and technologies, which are hidden from view in the psyche. Tetradic logic…

  20. A Conserved Hydrophobic Core in Gαi1 Regulates G Protein Activation and Release from Activated Receptor. (United States)

    Kaya, Ali I; Lokits, Alyssa D; Gilbert, James A; Iverson, T M; Meiler, Jens; Hamm, Heidi E


    G protein-coupled receptor-mediated heterotrimeric G protein activation is a major mode of signal transduction in the cell. Previously, we and other groups reported that the α5 helix of Gαi1, especially the hydrophobic interactions in this region, plays a key role during nucleotide release and G protein activation. To further investigate the effect of this hydrophobic core, we disrupted it in Gαi1 by inserting 4 alanine amino acids into the α5 helix between residues Gln(333) and Phe(334) (Ins4A). This extends the length of the α5 helix without disturbing the β6-α5 loop interactions. This mutant has high basal nucleotide exchange activity yet no receptor-mediated activation of nucleotide exchange. By using structural approaches, we show that this mutant loses critical hydrophobic interactions, leading to significant rearrangements of side chain residues His(57), Phe(189), Phe(191), and Phe(336); it also disturbs the rotation of the α5 helix and the π-π interaction between His(57) and Phe(189) In addition, the insertion mutant abolishes G protein release from the activated receptor after nucleotide binding. Our biochemical and computational data indicate that the interactions between α5, α1, and β2-β3 are not only vital for GDP release during G protein activation, but they are also necessary for proper GTP binding (or GDP rebinding). Thus, our studies suggest that this hydrophobic interface is critical for accurate rearrangement of the α5 helix for G protein release from the receptor after GTP binding.

  1. Symmetries in tetrad theories. [of gravitational fields and general relativity (United States)

    Chinea, F. J.


    The isometry conditions for gravitational fields are given directly at the tetrad level, rather than in terms of the metric. As an illustration, an analysis of the curvature collineations and Killing fields for a twisting type-N vacuum gravitational field is made.

  2. Total conserved charges of Kerr-NUT spacetimes using Poincare version of teleparallel equivalent of general relativity

    Energy Technology Data Exchange (ETDEWEB)

    Nashed, Gamal G.L. [King Faisal University, Mathematics Department, Faculty of Science, Al-Ahsaa (Saudi Arabia); Ain Shams University, Mathematics Department, Faculty of Science, Cairo (Egypt); British University of Egypt, Center for Theoretical Physics, Sherouk City (Egypt)


    Total conserved charges of several axially symmetric tetrad spacetimes generating Kerr-NUT metric are calculated by using the approach of invariant conserved currents. Certain tetrads give the known values, while others give unusual charges and divergent quantities. Therefore, regularized expressions are employed to get the known form of conserved charges. (orig.)

  3. An attempted analysis of the tetrads in the complex heterozygote species of the sub-genus Oenothera. (United States)

    Jean, R


    The statistical parameters of a pollen population of Oenothera purpurata in which the mendelian factor of pollen lethality segregates, showed that the pollen population analysed at anthesis in the Oenothera sub-genus quite faithfully conserves the segregation indicated in the tetrads. Following on this fact, the segregation "active grains, inactive grains, empty grains" was analysed in the pollen of the complex heterozygotes. The large standard deviation of the percentages of the three pollen classes and the value of the correlation between the percentages of grain classes taken two by two signify that the segregation of the three potential classes of microspore differs from one tetrad to another. By superimposing the correlation coefficient estimated between the percentage of the three grain classes of a bifactorial segregation of corn pollen on the correlation coefficient of the three classes of Oenothera pollen, it is possible to know with certainty the distribution of the potentially active, inactive and empty microspores in the tetrads. This distribution, which is different depending on whether the species is heterogamous or isogamous, allows us to confirm that the empty grains carry the recombined complexes which become lethal as a result of this recombination.

  4. On the Hamiltonian formalism of the tetrad-gravity

    CERN Document Server

    Lagraa, Meriem Hadjer; Touhami, Nabila


    We present a detailed analysis of the Hamiltonian constraints of the d-dimensional tetrad-gravity where the non-dynamical part of the spatial connection is fixed to zero. This new action depending on the co-tetrad and the dynamical part of the spatial connection leads to Lorentz, scalar and vectorial first-class polynomial constraints obeying a closed algebra in terms of Poisson brackets. This algebra closes on the structure constants instead of structure functions resulting from the Hamiltonian formalisms based on the A.D.M. decomposition. The same algebra of the reduced first-class constraints defined on the reduced phase-space, where the second-class constraints are solved, is obtained in terms of Dirac brackets. PACS numbers: 04.20.Cv, 04.20.Fy, 11.10.Ef, 11.30.Cp

  5. Examples of tetrad effect in lanthanides in natural systems

    Directory of Open Access Journals (Sweden)

    Lauro Valentim Stoll Nardi


    Full Text Available The irregular patterns of rare earth elements, caused by the tetrad effect are revised and discussed in this work, covering its concept and subdivision into M and W types, quantification and the mechanisms that led to its occurrence in magmatic-hydrothermal and biological systems. M type patterns are more frequent in highly differentiated magmatic-hydrothermal systems, where volatile oversaturation and high activities of F are registered. M and W type patterns are registered in plants mostly as result of complexes absorption in the rhizosphere (W type, free-ions absorption by the plant (M type, or due to the pH variation and mineralogy of the soil. Examples of tetrad effects in plants, soils, minerals, and rocks are discussed in different geological contexts in the Pitinga Mine region, Amazonia, and in southernmost Brazil.

  6. Null-Tetradic treatment of the Relativistic Dynamics (II) (United States)

    Gottlieb, I.; Maftei, Gh.

    The authors apply the Null-tetradic formalism as was given in the book by Kramer, Stephani, Herlt, Mac-Callum, Exact Solutions (1980) to some of the chapters of General Relativity which were not examined in the book above and such a way make a connection with another classic book in General Relativity: that of Landau and Lifchitz, Theorie des champs, Ed. Mir, Moscou (1989).

  7. New solutions in pure gravity with degenerate tetrads

    CERN Document Server

    Kaul, Romesh K


    In first order formulation of pure gravity, we find a new class of solutions to the equations of motion represented by degenerate four-geometries. These configurations are described by non- invertible tetrads with two zero eigenvalues and admit non-vanishing torsion. The homogeneous ones among these infinitely many degenerate solutions admit a geometric classification provided by the three fundamental geometries that a closed two-surface can accomodate, namely, E^2 , S^2 and H^2.

  8. Pollen tetrad-based visual assay for meiotic recombination in Arabidopsis (United States)

    Francis, Kirk E.; Lam, Sandy Y.; Harrison, Benjamin D.; Bey, Alexandra L.; Berchowitz, Luke E.; Copenhaver, Gregory P.


    Recombination, in the form of cross-overs (COs) and gene conversion (GC), is a highly conserved feature of meiosis from fungi to mammals. Recombination helps ensure chromosome segregation and promotes allelic diversity. Lesions in the recombination machinery are often catastrophic for meiosis, resulting in sterility. We have developed a visual assay capable of detecting Cos and GCs and measuring CO interference in Arabidopsis thaliana. This flexible assay utilizes transgene constructs encoding pollen-expressed fluorescent proteins of three different colors in the qrt1 mutant background. By observing the segregation of the fluorescent alleles in 92,489 pollen tetrads, we demonstrate (i) a correlation between developmental position and CO frequency, (ii) a temperature dependence for CO frequency, (iii) the ability to detect meiotic GC events, and (iv) the ability to rapidly assess CO interference. PMID:17360452

  9. Energy and momentum of rotating frames in tetrad gravity

    Institute of Scientific and Technical Information of China (English)

    Gamal G L Nashed


    Within the framework of the tetrad formulation of general relativity theory,we compute the total energy and momentum of four rotating frames using the gravitational energy-momentum 3-form.We show how the effect of inertia always makes the total energy divergent.We use a natural regularization method to obtain physical values for the total energy of the system and show how it works on a number of explicit examples.We also show by calculation that inertia has no effect on the momentum components.

  10. Micronucleus assays with Tradescantia pollen tetrads: an update. (United States)

    Misík, M; Ma, T-H; Nersesyan, A; Monarca, S; Kim, J K; Knasmueller, S


    Micronucleus (MN) assays with early pollen tetrad cells of Tradescantia (Trad-MN assays) are at present the most widely used bioassays with plants for the detection of genotoxins in the environment. So far, ∼ 160 chemicals have been tested and ∼ 100 articles that concern complex environmental mixtures were published. This article summarises the results of Trad-MN studies, which have been carried out during the last 15 years with individual compounds and investigations concerning the pollution of environmental compartments (soil, water and air). The evaluation shows that the effects of certain genotoxins such as heavy metals, radionuclides, pesticides and air pollutants can be easily detected with this test. Comparisons with results obtained in MN studies with mitotic (root tip) cells indicate that meiotic tetrad cells are in general more sensitive. Important issues for future research concern the evaluation of the suitability of wildlife Tradescantia species that are sometimes used instead of specific clones (such as #4430 for which standardised protocols have been developed) as well as the assessment of the predictive value of Trad-MN results in regard to the prediction of cancer hazards in humans and adverse effects at the ecosystem level. The fact that the genotoxic effects of certain compound such as metals, which can be detected with plant bioassays, in particular with the Trad-MN assay but not in other commonly used bioassays (e.g. in bacterial tests) makes them an essential element in the batteries for environmental monitoring.

  11. Emergence of a catalytic tetrad during evolution of a highly active artificial aldolase (United States)

    Obexer, Richard; Godina, Alexei; Garrabou, Xavier; Mittl, Peer R. E.; Baker, David; Griffiths, Andrew D.; Hilvert, Donald


    Designing catalysts that achieve the rates and selectivities of natural enzymes is a long-standing goal in protein chemistry. Here, we show that an ultrahigh-throughput droplet-based microfluidic screening platform can be used to improve a previously optimized artificial aldolase by an additional factor of 30 to give a >109 rate enhancement that rivals the efficiency of class I aldolases. The resulting enzyme catalyses a reversible aldol reaction with high stereoselectivity and tolerates a broad range of substrates. Biochemical and structural studies show that catalysis depends on a Lys-Tyr-Asn-Tyr tetrad that emerged adjacent to a computationally designed hydrophobic pocket during directed evolution. This constellation of residues is poised to activate the substrate by Schiff base formation, promote mechanistically important proton transfers and stabilize multiple transition states along a complex reaction coordinate. The emergence of such a sophisticated catalytic centre shows that there is nothing magical about the catalytic activities or mechanisms of naturally occurring enzymes, or the evolutionary process that gave rise to them.

  12. Re(I) bridged porphyrin dyads, triads and tetrads

    Indian Academy of Sciences (India)

    M Yedukondalu; M Ravikanth


    Porphyrin rings containing two meso-pyridyl groups either in cis or trans fashion can be used to construct Re(I) bridged multiporphyrin assemblies. The cis-dipyridyl porphyrins with various porphyrin cores such as N4, N3O, N3S, N2S2 have been used to react with Re(CO)5Cl in THF at refluxing temperature and constructed planar Re(I) bridged porphyrin dyads containing either one type of porphyrin subunit or two types of porphyrin subunits. The trans-dipyridyl porphyrins have been used to construct Re(I) bridged porphyrin squares. The porphyrin dyads have been explored for singlet-singlet energy transfer studies and porphyrin squares have been used for catalysis, chemical sensing, molecular sieving and photocurrent production studies. An overview of synthesis of Re(I) bridged porphyrin dyads, triads and tetrads and their interesting photophysical properties are highlighted in this paper.

  13. The lanthanide tetrad effect in granitoid of the Alvand Intrusive Complex, Hamedan

    Directory of Open Access Journals (Sweden)

    Farhad Aliani


    Full Text Available The Alvand Intrusive Complex (AIC is located in an area between Hamedan and Tuyserkan cities, and crops out over an area 400 km2 intruding the Sanandaj-Sirjan plutono-metamorphic belt. The emplacement age of the AIC is constrained to Upper to Middle Jurassic, based on U–Pb zircon geochronogic data. Lanthanide tetrad effects are often observed in REE patterns in the granites of the Alvand. The degree of the tetrad effect (TE1,3 is estimated and plotted vs. K/Rb, Sr/Eu, Eu/Eu*,Y/Ho, and Zr/Hf. The diagrams reveal that the tetrad effect develops parallel to granite evolution, and significant tetrad effects are strictly confined to highly differentiated samples. The strong decrease of Eu concentrations in highly evolved rocks suggests that Eu fractionates between the residual melt and a coexisting aqueous high-temperature fluid.

  14. Comparing Hamiltonians of a spinning test particle for different tetrad fields

    CERN Document Server

    Kunst, Daniela; Lukes-Gerakopoulos, Georgios; Seyrich, Jonathan


    This work is concerned with suitable choices of tetrad fields and coordinate systems for the Hamiltonian formalism of a spinning particle derived in [E. Barausse, E. Racine, and A. Buonanno, A., Phys. Rev. D 80, 104025 (2009)]. After demonstrating that with the originally proposed tetrad field the components of the total angular momentum are not preserved in the Schwarzschild limit, we analyze other hitherto proposed tetrad choices. Then, we introduce and thoroughly test two new tetrad fields in the horizon penetrating Kerr--Schild coordinates. Moreover, we show that for the Schwarzschild spacetime background the Hamiltonian linearized in spin corresponds to an integrable system, while for the Kerr spacetime we find chaos which suggests a nonintegrable system.

  15. Regular Charged Solutions in Mφller's Tetrad Theory of Gravitation

    Institute of Scientific and Technical Information of China (English)

    Gamal G. L. Nashed


    We find the most general tetrads which give a regular charged spacetime in tetrad theory of gravitation. The metric is a static one and it includes the Schwarzschild and Reissner Nordstr(o)m black holes. The energy content contained in a sphere of radius R is calculated using the superpotential given by Mφller in the context of Weitzenb(o)ck spacetime.

  16. Recognition and rehabilitation of the female athlete triad/tetrad: a multidisciplinary approach. (United States)

    Temme, Kate E; Hoch, Anne Z


    While the benefits of physical activity are numerous, the female athlete triad poses a significant health risk to young athletes. Emerging research links the triad to endothelial dysfunction--a sentinel event in cardiovascular disease--suggesting that this complex interplay of metabolic and endocrine factors may be described more accurately as a tetrad. Effective treatment of the triad/tetrad requires a multidisciplinary approach. Emphasis must be placed on prevention, recognition, and treatment of triad for the promotion of healthy nutritional and activity profiles in female athletes across their lifespans.

  17. A study of redundancy management strategy for tetrad strap-down inertial systems. [error detection codes (United States)

    Hruby, R. J.; Bjorkman, W. S.; Schmidt, S. F.; Carestia, R. A.


    Algorithms were developed that attempt to identify which sensor in a tetrad configuration has experienced a step failure. An algorithm is also described that provides a measure of the confidence with which the correct identification was made. Experimental results are presented from real-time tests conducted on a three-axis motion facility utilizing an ortho-skew tetrad strapdown inertial sensor package. The effects of prediction errors and of quantization on correct failure identification are discussed as well as an algorithm for detecting second failures through prediction.

  18. Total Conserved Charges of Kerr-Newman Spacetimes in Gravity Theory Using a Poincaré Gauge Version of the Teleparallel Equivalent of General Relativity

    Directory of Open Access Journals (Sweden)

    Gamal G. L. Nashed


    Full Text Available The total conserved charges of several tetrad spacetimes, generating the Kerr-Newman (KN metric, are calculated using the approach of invariant conserved currents generated by an arbitrary vector field that reproduces a diffeomorphism on the spacetime. The accompanying charges of some tetrads give the known value of energy and angular momentum, while those of other tetrads give, in addition to the unknown format charges, a divergent entity. Therefore, regularized expressions are considered also to get the commonly known form of conserved charges of KN.

  19. Two-dimensional metric and tetrad gravities as constrained second order systems

    CERN Document Server

    Kiriushcheva, N; Ghalati, R N


    Using the Gitman-Lyakhovich-Tyutin generalization of the Ostrogradsky method for analyzing singular systems, we consider the Hamiltonian formulation of metric and tetrad gravities in two-dimensional Riemannian spacetime treating them as constrained higher-derivative theories. The algebraic structure of the Poisson brackets of the constraints and the corresponding gauge transformations are investigated in both cases.

  20. Thermal properties of Lense-Thirring spacetime in tetrad theory of gravity

    Institute of Scientific and Technical Information of China (English)

    Gamal G. L. Nashed


    Using the divergence term appearing in the Lagrangian of the teleparallel equivalent of general relativity (TEGR),we calculate the thermodynamic quantities of four tetrads' spacetime reproducing Lense-Thirring (LT) metric.We also investigate the first law of thermodynamics and the quantum statistical relation.

  1. Spinning particles in vacuum spacetimes of different curvature types: Natural reference tetrads, and massless particles

    CERN Document Server

    Semerák, Oldřich


    In a previous paper, we considered the motion of massive spinning test particles in the "pole-dipole" approximation, as described by the Mathisson--Papapetrou--Dixon (MPD) equations, and examined its properties in dependence on the spin supplementary condition. We decomposed the equations in the orthonormal tetrad based on the time-like vector fixing the spin condition and on the corresponding spin, while representing the curvature in terms of the Weyl scalars obtained in the Newman--Penrose (NP) null tetrad naturally associated with the orthonormal one; the projections thus obtained did not contain the Weyl scalars $\\Psi_0$ and $\\Psi_4$. In the present paper, we choose the interpretation tetrad in a different way, attaching it to the tangent $u^\\mu$ of the world-line representing the history of the spinning body. Actually {\\em two} tetrads are suggested, both given "intrinsically" by the problem and each of them incompatible with one specific spin condition. The decomposition of the MPD equation, again suppl...

  2. The Hydrophobic Effect. (United States)

    Huque, Entazul M.


    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)

  3. Tetrad currents in the Einstein-Cartan theory (United States)

    Polishchuk, Rostislav F.


    Local and non-local integral conservation laws in the Riemann-Cartan spaces are given. Hypothesis of the friedmons as dark matter particles is proposed. The friedmon mass is about 109 GeV, and thesymmetry group is dual for SU(2) one.

  4. Assaying genome-wide recombination and centromere functions with Arabidopsis tetrads (United States)

    Copenhaver, Gregory P.; Browne, William E.; Preuss, Daphne


    During meiosis, crossover events generate new allelic combinations, yet the abundance of these genetic exchanges in individual cells has not been measured previously on a genomic level. To perform a genome-wide analysis of recombination, we monitored the assortment of genetic markers in meiotic tetrads from Arabidopsis. By determining the number and distribution of crossovers in individual meiotic cells, we demonstrated (i) surprisingly precise regulation of crossover number in each meiosis, (ii) considerably reduced recombination along chromosomes carrying ribosomal DNA arrays, and (iii) an inversely proportional relationship between recombination frequencies and chromosome size. This use of tetrad analysis also achieved precise mapping of all five Arabidopsis centromeres, localizing centromere functions in the intact chromosomes of a higher eukaryote. PMID:9419361

  5. Photoinitiated electron transfer in multichromophoric species: Synthetic tetrads and pentads featuring diquinone moieties

    Energy Technology Data Exchange (ETDEWEB)


    This project involves the design, synthesis and photophysical study of complex molecular systems engineered to achieve long lived charge separated states by a biomimetic, photoinitiated multistep electron transfer process. The use of these artificial systems to investigate different electron and energy transfer strategies will allow the evolution of more efficient molecular devices for the gathering of light energy and its transformation into chemical potential energy. The three major aspects of the work emphasized in the initial proposal are: design and synthesis of molecular devices incorporating new quinone moieties, synthesis and spectroscopic studies of molecular tetrads and pentads featuring modified porphyrin-diquinone linkages, and new photochemical and photophysical investigations of tetrads and pentads, including the development of methods for harvesting the energy stored in long-lived charge separated states.

  6. Photoinitiated electron transfer in multichromophoric species: Synthetic tetrads and pentads

    Energy Technology Data Exchange (ETDEWEB)



    This project involves the design, synthesis and study of molecules which mimic some of the important aspects of photosynthetic electron and energy transfer. This research project is leading to a better understanding of the energy conserving steps of photosynthesis via the study of synthetic model systems which abstract features of the natural photosynthetic apparatus. The knowledge gained from these studies will aid in the design of artificial photosynthetic reaction centers which employ the basic chemistry and physics of photosynthesis to help meet mankind`s energy needs. The approach to artificial photosynthesis employed in this project is to use synthetic pigments, electron donors, and electron acceptors similar to those found in biological reaction centers, but to replace the protein component with covalent bonds. These chemical linkages determine the electronic coupling between the various moieties by controlling separation, relative orientation, and overlap of electronic orbitals. The model systems are designed to mimic the following aspects of natural photosynthetic electron transfer: electron donation from a tetrapyrrole excited single state, electron transfer between tetrapyrroles, electron transfer from tetrapyrroles to quinones, and electron transfer between quinones with different redox properties. In addition, they mimic carotenoid antenna function in photosynthesis (singlet-singlet energy transfer from carotenoid polyenes to chlorophyll) and carotenoid photoprotection from singlet oxygen damage (triplet-triplet energy transfer from chlorophyll to carotenoids).

  7. Monazite and xenotime solubility in granitic melts and the origin of the lanthanide tetrad effect (United States)

    Duc-Tin, Quach; Keppler, Hans


    The solubility of synthetic, pure rare earth phosphates with monazite or xenotime structure (LaPO4 to LuPO4) in hydrous haplogranitic melts was measured at 2 kbar and 800-1,100 °C. Experiments were run for up to 2 months to attain equilibrium. Monazite and xenotime solubility decreases with increasing phosphorus concentration in the melt. Published equations for monazite solubility in felsic melts, which do not explicitly include phosphorus concentration in the melt, should therefore be treated with caution. The effect of phosphorus can be quantitatively modeled if one assumes that monazite partially dissolves as ionic and molecular species in the melt (REE3+ and REEPO4). Equilibrium constants for the dissolution reactions as well as quantitative data on speciation were derived from the solubility data. Monazite and xenotime solubility strongly increases with the peralkalinity of the melt. This effect is mostly due to an increase in the solubility of the ionic species, which are probably stabilized by non-bridging oxygen atoms in the melt. In peraluminous melts, the solubility of monazite and xenotime is nearly constant. Fluorine has no major effect on monazite and xenotime solubility; in fact, the solubility appears to slightly decrease with increasing fluorine content. The solubility of rare earth phosphates is not a simple continuous function of atomic number or ionic radius. Rather, the solubility shows a "tetrad"-like pattern with several local maxima of solubility at individual rare earth elements. The solubilities of neighboring rare earth elements sometimes differ by more than a factor of two; these effects are far outside any analytical error. The tetrad pattern is particularly clearly seen in some of the peralkaline melts and in the fluorine-rich metaluminous melts. Some features, however, such as a solubility maximum at ytterbium, are seen in virtually all melts. The lanthanide tetrad effect in some highly evolved granites may therefore be a result of

  8. Xanthine and 8-oxoguanine in G-quadruplexes: formation of a G·G·X·O tetrad. (United States)

    Cheong, Vee Vee; Heddi, Brahim; Lech, Christopher Jacques; Phan, Anh Tuân


    G-quadruplexes are four-stranded structures built from stacked G-tetrads (G·G·G·G), which are planar cyclical assemblies of four guanine bases interacting through Hoogsteen hydrogen bonds. A G-quadruplex containing a single guanine analog substitution, such as 8-oxoguanine (O) or xanthine (X), would suffer from a loss of a Hoogsteen hydrogen bond within a G-tetrad and/or potential steric hindrance. We show that a proper arrangement of O and X bases can reestablish the hydrogen-bond pattern within a G·G·X·O tetrad. Rational incorporation of G·G·X·O tetrads in a (3+1) G-quadruplex demonstrated a similar folding topology and thermal stability to that of the unmodified G-quadruplex. pH titration conducted on X·O-modified G-quadruplexes indicated a protonation-deprotonation equilibrium of X with a pKa ∼6.7. The solution structure of a G-quadruplex containing a G·G·X·O tetrad was determined, displaying the same folding topology in both the protonated and deprotonated states. A G-quadruplex containing a deprotonated X·O pair was shown to exhibit a more electronegative groove compared to that of the unmodified one. These differences are likely to manifest in the electronic properties of G-quadruplexes and may have important implications for drug targeting and DNA-protein interactions.

  9. A geometrically motivated coordinate system for exploring spacetime dynamics in numerical-relativity simulations using a quasi-Kinnersley tetrad

    CERN Document Server

    Zhang, Fan; Szilágyi, Béla; Lovelace, Geoffrey


    We investigate the suitability and properties of a quasi-Kinnersley tetrad and a geometrically motivated coordinate system as tools for quantifying both strong-field and wave-zone effects in numerical relativity (NR) simulations. We fix the radial and latitudinal coordinate degrees of freedom of the metric, using the Coulomb potential associated with the quasi-Kinnersley transverse frame. These coordinates are invariants of the spacetime and can be used to unambiguously fix the outstanding spin-boost freedom associated with the quasi-Kinnersley frame (resulting in a preferred quasi-Kinnersley tetrad (QKT)). In the limit of small perturbations about a Kerr spacetime, these coordinates and QKT reduce to Boyer-Lindquist coordinates and the Kinnersley tetrad, irrespective of the simulation gauge choice. We explore the properties of this construction both analytically and numerically, and we gain insights regarding the propagation of radiation described by a super-Poynting vector. We also quantify in detail the pe...

  10. Hydrophobic Forces in Flotation


    Pazhianur, Rajesh R


    An atomic force microscope (AFM) has been used to conduct force measurements to better understand the role of hydrophobic forces in flotation. The force measurements were conducted between a flat mineral substrate and a hydrophobic glass sphere in aqueous solutions. It is assumed that the hydrophobic glass sphere may simulate the behavior of air bubbles during flotation. The results may provide information relevant to the bubble-particle interactions occurring during flotation. The glass ...

  11. Preparation of hydrophobic coatings (United States)

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


    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 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.

  12. Prediction of coal hydrophobicity

    Energy Technology Data Exchange (ETDEWEB)

    Labuschagne, B.C.J. [Council for Scientific and Industrial Research, Pretoria (South Africa). Div. of Energy Technology; Wheelock, T.D.; Guo, R.K.; David, H.T. [Iowa State Univ. of Science and Technology, Ames, IA (United States); Markuszewski, R. [Ames Lab., IA (United States)


    Many coals exhibit a certain degree of native hydrophobicity. The more hydrophobic coals (the higher-rank coals) are easily beneficiated by froth flotation or oil agglomeration, while the more hydrophilic coals (the lower-rank coals) are floated or agglomerated with difficulty. Coals of different ranks and often even of the same rank sometimes differ greatly in hydrophobicity as measured by contact angle or natural floatability. Although the degree of hydrophobicity of a coal is related to its rank and has been correlated with other surface properties of the coal , the known information is still not sufficient to allow a good estimation to be made of the hydrophobicity of a given coal and does not explain the variation of coal hydrophobicity as a function of rank. A statistical analysis of previously published data, as well as newly acquired data, shows that coal hydrophobicity correlates better with moisture content than with carbon content, and better with the moisture/carbon molar ratio than with the hydrogen/carbon or oxygen/carbon atomic ratios. These findings indicate that there is a strong association between hydrophobicity and coal moisture content.

  13. Maxwell equations in Duffin - Kemmer tetrad form, spherical waves in Riemann space S_3

    CERN Document Server

    Bogush, A A; Red'kov, V M


    The Duffin-Kemmer form of massless vector field (Maxwell field) is extended to the case of arbitrary pseudo-Riemannian space-time in accordance with the tetrad recipe of Tetrode-Weyl-Fock-Ivanenko. In this approach, the Maxwell equations are solved exactly on the background of simplest static cosmological model, space of constant curvature of Riemann parameterized by spherical coordinates. Separation of variables is realized in the basis of Schr\\"odinger- Pauli type, description of angular dependence in electromagnetic filed functions is given in terms of Wigner D-functions. A discrete frequency spectrum for electromagnetic modes depending on the curvature radius of space and three discrete parameters is found. 4-potentials for spherical electro- magnetic waves of magnetic and electric type have been constructed.

  14. Energy and spatial momentum of charged rotating frames in tetrad gravity

    Institute of Scientific and Technical Information of China (English)

    Gamal G.L. Nashed


    We compute the total energy and the spatial momentum of four charged rotating (Kerr-Newman) frames by using the gravitational energy-momentum 3-form within the framework of the tetrad formulation of the general relativity theory.We show how the effect of the inertial always makes the total energy divergent.We use a natural regularization method,which yields the physical value for the total energy of the system.We show how the regularization method works on a number of different rotating frames that are related to each other by the local Lorentz transformation.We also show that the inertial has no effect on the spatial momentum components.

  15. Energy of the Universe in Bianchi-type I Models in Moller's Tetrad Theory of Gravity

    CERN Document Server

    Aydogdu, O; Aydogdu, Oktay; Salti, Mustafa


    In this paper, using the energy definition in Moller's tetrad theory of gravity we calculate the total energy of the universe in Bianchi-type I cosmological models which includes both the matter and gravitational fields. The total energy is found to be zero and this result agrees with a previous works of Banerjee-Sen who investigated this problem using the general relativity version of the Einstein energy-momentum complex and Xulu who investigated same problem using the general relativity versions of the Landau-lifshitz, Papapetrou and Weinberg's energy-momentum complexes. The result that total energy of the universe in Bianchi-type I universes is zero supports the viewpoint of Tryon.


    Directory of Open Access Journals (Sweden)

    Héctor Torres-Silva


    Full Text Available Every metric tensor can be expressed by the inner product of tetrad fields. We prove that Einstein's equations for these fields have the same form as the stress-energy tensor of electromagnetism if the total external current . Using the Evans' unified field theory, we show that the true unification of gravity and electromagnetism is with source-free Maxwell equations.Todo tensor métrico puede ser expresado por el producto interno de campos tetrados. Se prueba que las ecuaciones de Einstein para esos campos tienen la misma forma que el tensor electromagnético de momento-energía si la corriente externa total es igual a cero. Usando la teoría de campo unificado de Evans se muestra que la verdadera unificación de la gravedad y el electromagnetismo es con las ecuaciones de Maxwell sin fuentes.

  17. A Static Cosmological Model Based on the Group of Conservative Transformations

    CERN Document Server

    Green, Edward Lee


    The group of Conservative transformations is an enlargement of the group of diffeomorphisms which leads to a richer geometry than that of general relativity. The field variables of the theory are the usual orthonormal tetrads and also internal space tetrads. Using the fundamental geometric object which is the curvature vector, an appropriate Lagrangian has been defined for both free-field and fields with sources. Solutions to the corresponding field equations have been developed. In this paper we use the static spherically symmetric tetrad field with sources to model the universe. Our foundational assumption is that the total density comprised of both ordinary and dark matter should be constant. The resulting model with one adjustable parameter predicts that ordinary matter is approximately 77\\% of the total mass content, but this percentage is near 0\\% for regions near the center of the universe. The space is approximately isotropic for $r$ near zero. The radial and tangential pressures are negative and uneq...

  18. Maxwell-Juttner distribution for rigidly-rotating flows in spherically symmetric spacetimes using the tetrad formalism

    CERN Document Server

    Ambrus, Victor E


    We consider rigidly rotating states in thermal equilibrium on static spherically symmetric spacetimes. Using the Maxwell-Juttner equilibrium distribution function, onstructed as a solution of the relativistic Boltzmann equation, the equilibrium particle flow four-vector, stress-energy tensor and the transport coefficients in the Marle model are computed. Their properties are discussed in view of the topology of the speed-of-light surface induced by the rotation for two classes of spacetimes: maximally symmetric (Minkowski, de Sitter and anti-de Sitter) and charged (Reissner-Nordstrom) black-hole spacetimes. To facilitate our analysis, we employ a non-holonomic comoving tetrad field, obtained unambiguously by applying a Lorentz boost on a fixed background tetrad.

  19. Retro-causal Holographic Dark Energy Coherent Vacuum Super-Solid Tetrad Emergent Gravity (United States)

    Sarfatti, Jack


    Frictionless irrotational flow in superfluid helium comes from the gradient of a single Goldstone phase in the spontaneous broken U1 symmetry ground state, so too the four gravity tetrad and six spin connection Einstein-Cartan 1-form fields come from eight SU3 Goldstone phases of the post-inflation macro-quantum coherent 4D super-solid ``world crystal lattice'' QCD vacuum superconductor. Wheeler-Feynman's advanced potential, Hoyle-Narlikar's future influence functional, Cramer's ``transaction'' and Aharonov's pre-selection history/post-selection destiny double quantum state vector lead to the hologram idea that our interior bulk accelerating comoving spacelike slice 3D cosmological metric expansion rate in conformal time is a dynamical 3D back-from-the-future (final cause) retro-causal holographic image of 2D surface fractional quantum statistical anyonic qubit patterns on our observer-dependent thermal future de Sitter (dS) event horizon whose asymptotically constant area/entropy is the reciprocal dark energy density.

  20. Reissner-Nordstr\\"om Spacetime in the Tetrad Theory of Gravitation

    CERN Document Server

    Nashed, Gamal G L


    We give two classes of spherically symmetric exact solutions of the couple gravitational and electromagnetic fields with charged source in the tetrad theory of gravitation. The first solution depends on an arbitrary function $H({R},t)$. The second solution depends on a constant parameter $\\eta$. These solutions reproduce the same metric, i.e., the Reissner--Nordstr$\\ddot{o}$m metric. If the arbitrary function which characterizes the first solution and the arbitrary constant of the second solution are set to be zero, then the two exact solutions will coincide with each other. We then calculate the energy content associated with these analytic solutions using the superpotential method. In particular, we examine whether these solutions meet the condition which M{\\o}ller required for a consistent energy-momentum complex: Namely, we check whether the total four-momentum of an isolated system behaves as a four-vector under Lorentz transformations. It is then found that the arbitrary function should decrease faster ...

  1. The Lazarus project. II. Spacelike extraction with the quasi-Kinnersley tetrad (United States)

    Campanelli, Manuela; Kelly, Bernard; Lousto, Carlos O.


    The Lazarus project was designed to make the most of limited 3D binary black-hole simulations, through the identification of perturbations at late times, and subsequent evolution of the Weyl scalar Ψ4 via the Teukolsky formulation. Here we report on new developments, employing the concept of the “quasi-Kinnersley” (transverse) frame, valid in the full nonlinear regime, to analyze late-time numerical space-times that should differ only slightly from Kerr. This allows us to extract the essential information about the background Kerr solution, and through this, to identify the radiation present. We explicitly test this procedure with full-numerical evolutions of Bowen-York data for single spinning black holes, head-on and orbiting black holes near the ISCO regime. These techniques can be compared with previous Lazarus results, providing a measure of the numerical-tetrad errors intrinsic to the method, and giving as a by-product a more robust wave extraction method for numerical elativity.

  2. Hydrophobic, Porous Battery Boxes (United States)

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


    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.

  3. Hydrophobic treatment of concrete

    NARCIS (Netherlands)

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


    As part of the maintenance policy of the Dutch Ministry of Transport, Civil Engineering Division, hydrophobic treatment of concrete was considered as an additional protective measure against penetration of aggressive substances, for instance deicing salts in bridge decks. A set of tests was designed

  4. Hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Vries,; Polder, R.B.


    As part of the maintenance policy of the dutch Ministry of Transport, Civil Engineering Division, hydrophobic treatment of concrete was considered as an additional protective measure against penetration of aggressive substances, for instance deicing salts in bridge decks. A set of tests was designed

  5. Hydrophobic interactions and chemical reactivity

    NARCIS (Netherlands)

    Otto, Sijbren; Engberts, Jan B.F.N.


    This perspective describes how kinetic studies of organic reactions can be used to increase our understanding of hydrophobic interactions. In turn, our understanding of hydrophobic interactions can be used as a tool to influence chemical reactions.

  6. Hydrophobic interactions and chemical reactivity

    NARCIS (Netherlands)

    Otto, Sijbren; Engberts, Jan B.F.N.


    This perspective describes how kinetic studies of organic reactions can be used to increase our understanding of hydrophobic interactions. In turn, our understanding of hydrophobic interactions can be used as a tool to influence chemical reactions.

  7. Hydrophobic sugar holograms (United States)

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


    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%.

  8. Microsatellite-centromere mapping in Japanese scallop ( Patinopecten yessoensis) through half-tetrad analysis in gynogenetic diploid families (United States)

    Li, Qi; Qi, Mingjun; Nie, Hongtao; Kong, Lingfeng; Yu, Hong


    Gene-centromere mapping is an essential prerequisite for understanding the composition and structure of genomes. Half-tetrad analysis is a powerful tool for mapping genes and understanding chromosomal behavior during meiosis. The Japanese scallop ( Patinopecten yessoensis), a cold-tolerant species inhabiting the northwestern Pacific coast, is a commercially important marine bivalve in Asian countries. In this study, inheritance of 32 informative microsatellite loci was examined in 70-h D-shaped larvae of three induced meiogynogenetic diploid families of P. yessoensis for centromere mapping using half-tetrad analysis. The ratio of gynogenetic diploids was proven to be 100%, 100% and 96% in the three families, respectively. Inheritance analysis in the control crosses showed that 51 of the 53 genotypic ratios observed were in accordance with Mendelian expectations at the 5% level after Bonferroni correction. Seven of the 32 microsatellite loci showed the existence of null alleles in control crosses. The second division segregation frequency ( y) of the microsatellite loci ranged from 0.07 to 0.85 with a mean of 0.38, suggesting the existence of positive interference after a single chiasma formation in some chromosomes in the scallop. Microsatellite-centromere distances ranged from 4 cM to 42 cM under the assumption of complete interference. Information on the positions of centromeres in relation to the microsatellite loci will represent a contribution towards the assembly of genetic maps in the commercially important scallop species.

  9. Hydrogels with micellar hydrophobic (nanodomains

    Directory of Open Access Journals (Sweden)

    Miloslav ePekař


    Full Text Available Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  10. Hydrophobic encapsulation of hydrocarbon gases. (United States)

    Leontiev, Alexander V; Saleh, Anas W; Rudkevich, Dmitry M


    [reaction: see text] Encapsulation data for hydrophobic hydrocarbon gases within a water-soluble hemicarcerand in aqueous solution are reported. It is concluded that hydrophobic interactions serve as the primary driving force for the encapsulation, which can be used for the design of gas-separating polymers with intrinsic inner cavities.

  11. Changing water affinity from hydrophobic to hydrophilic in hydrophobic channels. (United States)

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


    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.

  12. [A simple method to correct genetic distance between linked genes and a correction of calculating data in tetrad analysis in Neurospora crassa]. (United States)

    Li, You-Yong; Zhao, Yuan-Zeng


    The present paper is dealing with a simple method to correct the distance of linked genes in tetrad analysis in Neurospora crassa. It is suggested that the data of 4-thread double crossing over should be added in two single crossing over respectively in centromere maping when calculating crossover value of the two genes locating across the centromere.

  13. Use of thermolytic protective groups to prevent G-tetrad formation in CpG ODN type D: structural studies and immunomodulatory activity in primates. (United States)

    Puig, Montserrat; Grajkowski, Andrzej; Boczkowska, Malgorzata; Ausín, Cristina; Beaucage, Serge L; Verthelyi, Daniela


    CpG oligodeoxynucleotides (ODN) show promise as immunoprotective agents and vaccine adjuvants. CpG ODN type D were shown to improve clinical outcome in rhesus macaques challenged with Leishmania major. These ODN have a self-complementary core sequence and a 3' end poly(G) track that favors G-tetrad formation leading to multimerization. Although multimerization appears necessary for localization to early endosomes and signaling via Toll-like receptor 9 (TLR-9), it can result in product polymorphisms, aggregation and precipitation, thereby hampering their clinical applications. This study shows that functionalizing the poly(G) track of D ODN with thermolytic 2-(N-formyl-N-methyl)aminoethyl (fma) phosphate/thiophosphate protecting groups (pro-D ODN) reduces G-tetrad formation in solution, while allowing tetrad formation inside the cell where the potassium concentration is higher. Temperature-dependent cleavage of the fma groups over time further promoted formation of stable G-tetrads. Peripheral blood cells internalized pro-D ODN efficiently, inducing high levels of IFNalpha, IL-6, IFNgamma and IP-10 and triggering dendritic cell maturation. Administration of pro-D35 to macaques challenged with L.major significantly increased the number of antigen-specific IFNgamma-secreting PBMC and reduced the severity of the skin lesions demonstrating immunoprotective activity of pro-D ODN in vivo. This technology fosters the development of more efficient immunotherapeutic oligonucleotide formulations for the treatment of allergies, cancer and infectious diseases.

  14. A note on classification of proper teleparallel conformal symmetries of spherically symmetric static space-times in the teleparallel theory of gravitation using diagonal tetrads

    CERN Document Server

    Qureshi, Muhammad Amer; Mahomed, K S


    A study of proper teleparallel conformal vector field in spherically symmetric static space-times is given using the direct integration technique and diagonal tetrads. In this study we show that the above space-times do not admit proper teleparallel conformal vector fields.

  15. Force-free Currents and the Newman-Penrose Tetrad of a Kerr Black Hole: Exact Local Solutions

    CERN Document Server

    Menon, Govind


    In a previous article we derived a class of solutions to the force-free magnetosphere in a Kerr background. Here, the streaming surface, defined by constant values of the toriodal component of the electromagnetic vector potential $A$, were generated by constant values of $\\theta$. The electromagnetic current vector flowed along the in-falling principle null geodesic vector of the geometry. Subsequently, we generalized this to obtain an out-going principle null geodesic vector as well. In this article, we derive solutions that are complimentary to the above mentioned criteria. Namely, here the solution has a streaming surface generated by spheres of constant radial coordinate $r$, and the current vector is generated by linear combinations of $m$ and $m^\\star$, the remaining bases vectors in the Newman-Penrose null tetrad.

  16. Comprehensive lipid tetrad index, atherogenic index and lipid peroxidation: Surrogate markers for increased cardiovascular risk in psoriasis

    Directory of Open Access Journals (Sweden)

    S Sunitha


    Full Text Available Background and Objectives: Recently, the concept of "psoriatic march" has come to the fore, in which chronic cutaneous inflammation in psoriasis leads to systemic inflammation which, in conjunction with increased oxidative stress, triggers a cascade of events resulting in increased cardiovascular risk in patients with severe psoriasis. We, therefore, decided to study the levels of some biochemical cardiovascular risk markers: lipid peroxidation (malondialdehyde, lipoprotein (a, lipid indices and atherogenic index, in patients with psoriasis and their association with disease severity. Methods: Fortyfive patients with psoriasis and 45 age and gender-matched healthy controls were included in this cross-sectional study. Disease severity was assessed by the Psoriasis Area Severity Index (PASI. Serum malondialdehyde, lipoprotein (a and fasting lipid profile were estimated in all study subjects. Lipoprotein ratios were computed using standard formulae. Atherogenic index was calculated as ratio of lipoprotein (a/high-density lipoprotein. Results: In psoriasis, we observed significantly higher levels of malondialdehyde, total cholesterol, low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, lipoprotein (a, lipid ratios, atherogenic index and comprehensive lipid tetrad index, compared to controls. These levels were directly proportional to disease severity. Serum levels of malondialdehyde correlated positively with serum lipoprotein (a, comprehensive lipid tetrad index and atherogenic index. Limitations: Different morphological types of psoriasis were not included and follow-up post-therapy was not done. A larger sample size would have validated the results further. Conclusion: Our results indicate that psoriasis, especially the severe variants, are associated with increased oxidative stress and dyslipidemia, which correlate positively with atherogenic index and hence, an increased cardiovascular risk.

  17. Method for producing hydrophobic aerogels (United States)

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


    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.

  18. A Natural Based Method for Hydrophobic Treatment of Natural Fiber Material. (United States)

    Kick, Thomas; Grethe, Thomas; Mahltig, Boris


    A treatment for hydrophobic functionalization of natural fiber materials is developed. This hydrophobic treatment is based mainly on natural products. As hydrophobic component the natural Tung Oil is used, which is originally a compound used for wood conservation purposes. The application on textile is done in a padding process under presence of an oxidative agent. For the current investigations a fiber felt from linen was used. The hydrophobic effect is determined by the concentration of Tung Oil and the duration of a thermal drying process. The hydrophobic effect is investigated by capillary rise tests and contact angle measurements. Scanning electron microscopy SEM is used to investigate the surface topography of the fiber material and the deposited hydrophobic material. Altogether, an interesting and promising method for hydrophobisation of natural fibers is developed, which could especially be used as part of a production process of a fiber reinforced composite material, mainly based on natural products.

  19. 21 CFR 584.700 - Hydrophobic silicas. (United States)


    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRINKING WATER OF ANIMALS Listing of Specific Substances Affirmed as GRAS § 584.700 Hydrophobic silicas. (a) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No....

  20. Photoinitiated electron transfer in multichromophoric species: Synthetic tetrads and pentads featuring diquinone moieties. Technical progress report, September 1, 1991--30 April 1992

    Energy Technology Data Exchange (ETDEWEB)


    This project involves the design, synthesis and photophysical study of complex molecular systems engineered to achieve long lived charge separated states by a biomimetic, photoinitiated multistep electron transfer process. The use of these artificial systems to investigate different electron and energy transfer strategies will allow the evolution of more efficient molecular devices for the gathering of light energy and its transformation into chemical potential energy. The three major aspects of the work emphasized in the initial proposal are: design and synthesis of molecular devices incorporating new quinone moieties, synthesis and spectroscopic studies of molecular tetrads and pentads featuring modified porphyrin-diquinone linkages, and new photochemical and photophysical investigations of tetrads and pentads, including the development of methods for harvesting the energy stored in long-lived charge separated states.

  1. Hydrophobic aggregation of ultrafine kaolinite

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-ping; HU Yue-hua; LIU Run-Qing


    The hydrophobic aggregation of ultrafine kaolinite in cationic surfactant suspension was investigated by sedimentation test, zeta potential measurement and SEM observation. SEM images reveal that kaolinite particles show the self-aggregation of edge-face in acidic media, the aggregation of edge-face and edge-edge in neutral media, and the dispersion in alkaline media due to electrostatic repulsion. In the presence of the dodecylammonium acetate cationic surfactant and in neutral and alkaline suspension, the hydrophobic aggregation of face-face is demonstrated. The zeta potential of kaolinite increases with increasing the concentration of cationic surfactant. The small and loose aggregation at a low concentration but big and tight aggregation at a high concentration is presented At pH=7 alkyl quarterly amine salt CTAB has the best hydrophobic aggregation among three cationic surfactants, namely, dodecylammonium acetate, alkyl quarterly amine salts 1227 and CTAB.

  2. Extended Electron-Transfer in Animal Cryptochromes Mediated by a Tetrad of Aromatic Amino Acids. (United States)

    Nohr, Daniel; Franz, Sophie; Rodriguez, Ryan; Paulus, Bernd; Essen, Lars-Oliver; Weber, Stefan; Schleicher, Erik


    The cryptochrome/photolyase protein family possesses a conserved triad of tryptophans that may act as a molecular wire to transport electrons from the protein surface to the FAD cofactor for activation and/or signaling-state formation. Members from the animal (and animal-like) cryptochrome subclade use this process in a light-induced fashion in a number of exciting responses, such as the (re-)setting of circadian rhythms or magnetoreception; however, electron-transfer pathways have not been explored in detail yet. Therefore, we present an in-depth time-resolved optical and electron-paramagnetic resonance spectroscopic study of two cryptochromes from Chlamydomonas reinhardtii and Drosophila melanogaster. The results do not only reveal the existence of a fourth, more distant aromatic amino acid that serves as a terminal electron donor in both proteins, but also show that a tyrosine is able to fulfill this very role in Chlamydomonas reinhardtii cryptochrome. Additionally, exchange of the respective fourth aromatic amino acid to redox-inactive phenylalanines still leads to light-induced radical pair formation; however, the lifetimes of these species are drastically reduced from the ms- to the μs-range. The results presented in this study open up a new chapter, to our knowledge, in the diversity of electron-transfer pathways in cryptochromes. Moreover, they could explain unique functions of animal cryptochromes, in particular their potential roles in magnetoreception because magnetic-field effects of light-induced radical pairs strongly depend on distance and orientation parameters.

  3. Hydrophobic patches on protein surfaces

    NARCIS (Netherlands)

    Lijnzaad, P.


    Hydrophobicity is a prime determinant of the structure and function of proteins. It is the driving force behind the folding of soluble proteins, and when exposed on the surface, it is frequently involved in recognition and binding of ligands and other proteins. The energetic cost of exposing hydroph

  4. Hydrophobic Solvation: Aqueous Methane Solutions (United States)

    Konrod, Oliver; Lankau, Timm


    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.

  5. Hydrophobic Solvation: Aqueous Methane Solutions (United States)

    Konrod, Oliver; Lankau, Timm


    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.


    NARCIS (Netherlands)



    Hydrophobins are small secreted fungal proteins rich in hydrophobic amino acids with a characteristic hydropathy pattern and conserved location of eight cysteine residues. It was previously shown that purified SC3p hydrophobin of Schizophyllum commune self-assembles at hydrophilic/hydrophobic interf

  7. Intrinsic Hydrophobicity of Rammed Earth (United States)

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


    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.

  8. Hydrophobic effect at aqueous interfaces (United States)

    Pohorille, Andrew


    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.

  9. A Heuristic Molecular Model of Hydrophobic Interactions

    CERN Document Server

    Hummer, G; García, A E; Pohorille, A; Pratt, L R


    Hydrophobic interactions provide driving forces for protein folding, membrane formation, and oil-water separation. Motivated by information theory, the poorly understood nonpolar solute interactions in water are investigated. A simple heuristic model of hydrophobic effects in terms of density fluctuations is developed. This model accounts quantitatively for the central hydrophobic phenomena of cavity formation and association of inert gas solutes; it therefore clarifies the underlying physics of hydrophobic effects and permits important applications to conformational equilibria of nonpolar solutes and hydrophobic residues in biopolymers.

  10. Cell-surface hydrophobicity of Staphylococcus saprophyticus. (United States)

    Schneider, P. F.; Riley, T. V.


    The cell-surface hydrophobicity of 100 urinary isolates of Staphylococcus saprophyticus, cultured from symptomatic females in the general population, was assessed using a two-phase aqueous:hydrocarbon system. Relatively strong cell-surface hydrophobicity was exhibited by 79 isolates using the criteria employed, while only 2 of the remaining 21 isolates failed to demonstrate any detectable hydrophobicity. Cell-surface hydrophobicity may be a virulence factor of S. saprophyticus, important in adherence of the organism to uroepithelia. Additionally, the data support the concept that cell-surface hydrophobicity may be a useful predictor of clinical significance of coagulase-negative staphylococci isolated from clinical sources. PMID:1993454

  11. Hydrophobic-Core Microcapsules and Their Formation (United States)

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


    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.

  12. Hydrophobicity of rare-earth oxide ceramics (United States)

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


    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.

  13. Inhibitory effect of super-hydrophobicity on silver release and antibacterial properties of super-hydrophobic Ag/TiO2 nanotubes. (United States)

    Zhang, Licheng; Zhang, Lihai; Yang, Yun; Zhang, Wei; Lv, Houchen; Yang, Fei; Lin, Changjian; Tang, Peifu


    The antibacterial properties of super-hydrophobic silver (Ag) on implant surface have not yet to be fully illuminated. In our study, we investigate the protective effects of super-hydrophobic coating of silver/titanium dioxide (Ag/TiO2 ) nanotubes against bacterial pathogens, as well as its pattern of Ag release. Ag/TiO2 nanotubes are prepared by a combination of electrochemical anodization and pulse electrodeposition. The super-hydrophobic coating is prepared by modifying the surface of Ag/TiO2 nanotubes with 1H, 1H, 2H, 2H-perfluorooctyl-triethoxysilane (PTES). Surface features and Ag release are examined by SEM, X-ray photoelectron spectroscopy, contact-angle measurement, and inductively coupled plasma-mass spectrometry (ICP-MS). The antibacterial activity of super-hydrophobic coating Ag/TiO2 nanotubes is investigated both in vitro and in vivo. Consequently, the super-hydrophobic coating on Ag/TiO2 nanotubes shows a regularly arranged structure; and nano-Ag particles (10-30 nm) are evenly distributed on the surface or inside the nanotubes. The contact angles of water on the super-hydrophobic coating Ag/TiO2 nanotubes are all above 150°. In addition, the super-hydrophobic character displays a certain conserved effect that contributes to the sustained release of Ag. The super-hydrophobic Ag/TiO2 nanotubes are also effective in inhibiting bacterial adhesion, killing the adhering bacteria and preventing postoperative infection in rabbits. Therefore, it is expected that the super-hydrophobic Ag/TiO2 nanotubes which can contain the release of Ag, leading to stable release, may show a consistent surface antibacterial capability. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1004-1012, 2016.

  14. Drying Induced Hydrophobic Polymer Collapse


    ten Wolde, Pieter Rein; Chandler, David


    We have used computer simulation to study the collapse of a hydrophobic chain in water. We find that the mechanism of collapse is much like that of a first-order phase transition. The evaporation of water in the vicinity of the polymer provides the driving force for collapse, and the rate limiting step is the nucleation of a sufficiently large vapor bubble. The study is made possible through the application of transition path sampling and a coarse-grained treatment of liquid water. Relevance ...

  15. Dropwise Condensation on Hydrophobic Cylinders

    CERN Document Server

    Park, Kyoo-Chul; Hoang, Michelle; McManus, Brendan; Aizenberg, Joanna


    In this work, we studied the effect of the diameter of horizontal hydrophobic cylinders on droplet growth. We postulate that the concentration gradient created by natural convection around a horizontal circular cylinder is related to the droplet growth on the cylinder by condensation. We derive a simple scaling law of droplet growth and compare it with experimental results. The predicted negative exponent of drop diameter (d) as a function of cylinder diameter (D) at different time points is similar to the general trend of experimental data. Further, this effect of cylinder diameter on droplet growth is observed to be stronger than the supersaturation conditions created by different surface temperatures.

  16. Preparation of hydrophobic organic aeorgels (United States)

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


    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.

  17. Characterisation of nanomaterial hydrophobicity using engineered surfaces (United States)

    Desmet, Cloé; Valsesia, Andrea; Oddo, Arianna; Ceccone, Giacomo; Spampinato, Valentina; Rossi, François; Colpo, Pascal


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

  18. A Heuristic Molecular Model of Hydrophobic Interactions


    Hummer, G; Garde, S; Garcia, A.E.; Pohorille, A; Pratt, L.R.


    Hydrophobic interactions provide driving forces for protein folding, membrane formation, and oil-water separation. Motivated by information theory, the poorly understood nonpolar solute interactions in water are investigated. A simple heuristic model of hydrophobic effects in terms of density fluctuations is developed. This model accounts quantitatively for the central hydrophobic phenomena of cavity formation and association of inert gas solutes; it therefore clarifies the underlying physics...

  19. How specific halide adsorption varies hydrophobic interactions. (United States)

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


    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.

  20. How fast is protein hydrophobic collapse?


    Sadqi, Mourad; Lapidus, Lisa J.; Muñoz, Victor


    One of the most recurring questions in protein folding refers to the interplay between formation of secondary structure and hydrophobic collapse. In contrast with secondary structure, it is hard to isolate hydrophobic collapse from other folding events. We have directly measured the dynamics of protein hydrophobic collapse in the absence of competing processes. Collapse was triggered with laser-induced temperature jumps in the acid-denatured form of a simple protein and monitored by fluoresce...

  1. The physical origin of hydrophobic effects (United States)

    Sun, Qiang


    From the structural studies on water and air/water interface, hydration free energy is derived, and used to investigate the origin of hydrophobic effects. As a solute is dissolved into water, hydration free energy increases, and is divided into initial and hydrophobic solvation processes. In the initial process, hydration free energy is dominated by hydrogen bonding in interfacial water (topmost water layer at solute/water interface). For hydrophobic process, hydration free energy is related to the hydrogen bonding in bulk and interfacial water. Therefore, hydrophobic effects originate from the structural competition between hydrogen bonding in bulk water and that in interfacial water.

  2. Method for making nanoporous hydrophobic coatings (United States)

    Fan, Hongyou; Sun, Zaicheng


    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. Hydrophobic Interactions Involved in Attachment of a Baculovirus to Hydrophobic Surfaces


    Small, Deirdre A.; Moore, Norman F.; Entwistle, Philip F.


    The hydrophobic interactions of Trichoplusia ni nuclear polyhedrosis virus were characterized by hydrophobic interaction chromatography. The determination of the hydrophobic force and some of the factors that influence its size is discussed in relation to the attachment to leaf surfaces of polyhedra during their use as biological control agents against insect pests.

  4. Hydrophobicity of peritoneal tissues in the rat

    NARCIS (Netherlands)

    Gomez-Suarez, C; Bruinsma, GM; Rakhorst, G; van der Mei, HC; Busscher, HJ


    In this study, an inventory of the hydrophobicity of peritoneal tissues in the living rat was made. Peritoneal tissues were divided into mesentery (i.e., omentum) and parietal and visceral peritoneum and their hydrophobicity was determined by the sessile drop method. All peritoneal tissues were hydr

  5. Hydrogels with Micellar Hydrophobic (Nano)Domains


    Pekař, Miloslav


    Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  6. Hydrogels with micellar hydrophobic (nano)domains


    Miloslav ePekař


    Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  7. Hydrogels with micellar hydrophobic (nano)domains (United States)

    Pekař, Miloslav


    Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  8. Durability of hydrophobic treatment of concrete

    NARCIS (Netherlands)

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


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

  9. Durability of hydrophobic treatment of concrete

    NARCIS (Netherlands)

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


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

  10. Composite, nanostructured, super-hydrophobic material (United States)

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


    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.


    Institute of Scientific and Technical Information of China (English)

    Zhi-min Zheng; Cai-hong Xu; Jian Jiang; Chang-yu Ren; Wei Gao; Ze-min Xie


    Silicone rubber (SIR) shows superior performance when used outdoors, but its surface can be transformed frominherently hydrophobic to hydrophilic by the adsorption of contaminants. Al(OH)3, Al2O3, quartz powder and active carbonwere selected as authentic contaminants. Hydrophobicity of the surface was determined using contact angle measurement.The results indicate that the adsorbability of the contaminants can strongly affect the hydrophobicity of contaminated SIRsurface. The increasing rate of contact angle of specimens contaminated by Al(OH)3 was much faster than that by Al2O3 andquartz due to the adsorption of migrated low molecular weight (LMW) polydimethylsiloxanes. Specimens contaminated byactive carbon could achieve surface hydrophobicity within 15 min because active carbon has high adsorbability. Surfaces ofcontaminated ultrapure SIR, polytetrafluoroethylene (PTFE) and glass remain hydrophilic because they contain no mobileLMW components. The addition of oligomeric polydimethylsiloxanes has little effect on the hydrophobicity of contaminantscovered on SIR surface.

  12. Solution properties of hydrophobically modified

    Directory of Open Access Journals (Sweden)

    A.M. Al-Sabagh


    Full Text Available We tested nine hydrophobically modified polyacrylamides with molecular weights situated between 1.58 and 0.89 × 106 g/mol for enhanced oil recovery applications. Their solution properties were investigated in the distilled water, brine solution, formation water and sea water. Their critical association concentrations were determined from the relationship between their concentrations and the corresponding apparent viscosities (ηapp at 30 °C at shear rate 6 s−1. They were between 0.4 and 0.5 g/dl. The brine solutions of 0.5 g/dl of HM-PAMs were investigated at different conditions regarding their apparent viscosities. Such conditions were mono and divalent cations, temperature ranging from 30 to 90 °C, the shear rate ranging from 6 to 30 s−1 and the aging time for 45 days. The surface and interfacial tensions for the HM-PAMs were measured for concentration range from 0.01 to 1 g/dl brine solutions at 30 °C and their emulsification efficiencies were investigated for 7 days. The discrepancy in the properties and efficiencies of the tested copolymers was discussed in the light of their chemical structure.

  13. Novel hydrophobically associative polyacrylamide with tunable viscosity

    Institute of Scientific and Technical Information of China (English)

    Xu Feng Zhang; Wen Hui Wu


    Hydrophobically associative polyacrylamide (HAPAM) were prepared in aqueous solution by radical copolymerization of novel cationic surface-active monomer, dimethylhexadecyl(3-acrylamidopropyl)ammonium bromide (DMHAB), with acrylarnide (AM) in the presence of DMHAB/CTAB mixed micelles. The length of hydrophobic microblock (N_H) in HAPAM is controlled by the molar fraction of DMHAB in mixed micelles, which can be mediated by the ratio of CTAB to DMHAB. The results of steady-state fluorescence probe and viscometry experiments showed the ability of HAPAM association was determined by the length of the hydrophobic microblock. HAPAM with tunable association ability are promising materials for thickening agent.

  14. Super-hydrophobic fluorine containing aerogels (United States)

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


    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.

  15. Hydrophobic interactions increase attachment of gum Arabic- and PVP-coated Ag nanoparticles to hydrophobic surfaces. (United States)

    Song, Jee Eun; Phenrat, Tanapon; Marinakos, Stella; Xiao, Yao; Liu, Jie; Wiesner, Mark R; Tilton, Robert D; Lowry, Gregory V


    A fundamental understanding of attachment of surface-coated nanoparticles (NPs) is essential to predict the distribution and potential risks of NPs in the environment. Column deposition studies were used to examine the effect of surface-coating hydrophobicity on NP attachment to collector surfaces in mixtures with varying ratios of octadecylichlorosilane (OTS)-coated (hydrophobic) glass beads and clean silica (hydrophilic) glass beads. Silver nanoparticles (AgNPs) coated with organic coatings of varying hydrophobicity, including citrate, polyvinylpyrrolidone (PVP), and gum arabic (GA), were used. The attachment efficiencies of GA and PVP AgNPs increased by 2- and 4-fold, respectively, for OTS-coated glass beads compared to clean glass beads. Citrate AgNPs showed no substantial change in attachment efficiency for hydrophobic compared to hydrophilic surfaces. The attachment efficiency of PVP-, GA-, and citrate-coated AgNPs to hydrophobic collector surfaces correlated with the relative hydrophobicity of the coatings. The differences in the observed attachment efficiencies among AgNPs could not be explained by classical DLVO, suggesting that hydrophobic interactions between AgNPs and OTS-coated glass beads were responsible for the increase in attachment of surface-coated AgNPs with greater hydrophobicity. This study indicates that the overall attachment efficiency of AgNPs will be influenced by the hydrophobicity of the NP coating and the fraction of hydrophobic surfaces in the environment.

  16. Using Profiles Based on Nucleotide Hydrophobicity to Define Essential Regions for Splicing

    Directory of Open Access Journals (Sweden)

    Galina Boldina, Anatoly Ivashchenko, Mireille Régnier


    Full Text Available The splice-site sequences of U2-type introns are highly degenerate, so many different sequences can function as U2-type splice sites. Using our new profiles based on hydrophobicity properties we pointed out specific properties for regions surrounding splice sites. We built a set T of flanking regions of genes with 1-3 introns from 21st and 22nd chromosomes extracted from GenBank to define positions having conserved properties, namely hydrophobicity, that are potentially essential for recognition by spliceosome. GT–AG introns exist in U2 and U12-types. Therefore, intron type cannot be simply determined by the dinucleotide termini. We attempted to distinguish U2 and U12-types introns with help of hydrophobicity profiles on sets of spice sites for U2 or U12-type introns extracted from SpliceRack database. The positions given by our method, which may be important for recognition by spliceosome, were compared to the nucleotide consensus provided by a classical method, Pictogram. We showed that there is a similarity of hydrophobicity profiles inside intron types. On one hand, GT–AG and GC–AG introns belonging to U2-type have resembling hydrophobicity profiles as well as AT–AC and GT–AG introns belonging to U12-type. On the other hand, hydrophobicity profiles of U2 and U12-types GT–AG introns are completely different. We suggest that hydrophobicity profiles facilitate definition of intron type, distinguishing U2 and U12 intron types and can be used to build programs to search splice site and to evaluate their strength. Therefore, our study proves that hydrophobicity profiles are informative method providing insights into mechanisms of splice sites recognition.

  17. The physical origin of hydrophobic effects

    CERN Document Server

    Sun, Qiang


    Because the strength of hydrogen bonding in water is stronger than that of van der Waals Interaction, water should play an important role in the process of hydrophobic effects. According to our recent structural studies on bulk water and air/water interface, the hydrophobic solutes mainly affect the structure of the topmost water layer (interfacial water) at solute/water interface. In reference with bulk water, due to truncations of hydrogen bonding at the interface, the effects of solutes on water structure are ascribed to the loss of tetrahedral hydrogen bonding in interfacial water. From this, the hydration free energy is derived, and utilized to investigate the dissolved behaviors of hydrophobic solutes. With increasing the size of solutes, this leads to the increase of hydration free energy, which can be divided into the initial solvation and hydrophobic solvation processes, respectively. In the initial solvation process, the hydration free energy is dominated by the hydrogen bonding in interfacial water...

  18. Electro-hydrodynamics near Hydrophobic Surfaces

    CERN Document Server

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


    We show that the dynamics of the electrostatic diffuse layer at the slippery hydrophobic surface depends strongly on the mobility of surface charges. 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 electro-hydrodynamic boundary conditions at the slipping interface, which are applied to quantify electro-osmotic flows. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new general concept of zeta-potential of hydrophobic surfaces.

  19. Surface analysis of selected hydrophobic materials (United States)

    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

  20. Conservative management. (United States)

    Kruis, W; Leifeld, L; Pfützer, R


    Treatment of diverticulitis comprises at least two options: conservative or surgical management. There is a recent trend to limit surgical treatment of acute diverticulitis and to favor conservative management. This review addresses general aspects of conservative patient care with special focus on the treatment of patients with a first attack of diverticulitis. The presentation does not include a discussion of specific drugs which is given in other sections of this issue.

  1. Characterization of surface hydrophobicity of engineered nanoparticles. (United States)

    Xiao, Yao; Wiesner, Mark R


    The surface chemistry of nanoparticles, including their hydrophobicity, is a key determinant of their fate, transport and toxicity. Engineered NPs often have surface coatings that control the surface chemistry of NPs and may dominate the effects of the nanoparticle core. Suitable characterization methods for surface hydrophobicity at the nano-scale are needed. Three types of methods, surface adsorption, affinity coefficient and contact angle, were investigated in this study with seven carbon and metal based NPs with and without coatings. The adsorption of hydrophobic molecules, Rose Bengal dye and naphthalene, on NPs was used as one measure of hydrophobicity and was compared with the relative affinity of NPs for octanol or water phases, analogous to the determination of octanol-water partition coefficients for organic molecules. The sessile drop method was adapted for measuring contact angle of a thin film of NPs. Results for these three methods were qualitatively in agreement. Aqueous-nC(60) and tetrahydrofuran-nC(60) were observed to be more hydrophobic than nano-Ag coated with polyvinylpyrrolidone or gum arabic, followed by nano-Ag or nano-Au with citrate-functionalized surfaces. Fullerol was shown to be the least hydrophobic of seven NPs tested. The advantages and limitations of each method were also discussed.

  2. Evaporation-induced failure of hydrophobicity (United States)

    Luo, H.; Liu, T.; Ma, J.; Wang, P.; Wang, Y.; Leprince-Wang, Y.; Jing, G.


    Hydrophobic coatings have tremendous applications in many fields of industries, and their robustness is an important subject of investigation. Here we experimentally demonstrate the detachment of hydrophobic coating and the formation of the residual deposit resulting from an evaporating drop of water. A hydrophobic octadecanethiol (ODT) coating is employed to enhance the hydrophobicity of ZnO nanowire arrays (advancing and receding contact angle of 165° and 128°, respectively). Being a model system of the unique bonding interaction between ODT and ZnO, water drop drying on the structure of ODT/ZnO is examined. Our experimental results showed the significant depression and even failure of the hydrophobicity on this composite surface resulting from collecting the deposits of ODT molecules during the drop drying. By analyzing energy criterion and force balance, surface tension at the moving contact line is identified as a dominating destructive force to unstick the coating molecules. Interestingly, a normal rinsing stream does not damage this coating to alter its hydrophobicity, but rather is overshadowed by the evaporation of the tinny water drop. The drops of rain or condensed water outdoor may thus play the same role to damage the functional coatings after their evaporation. Our findings indicate that more delicate designs are needed to prevent the destructive effects of drop evaporation on superhydrophobic surfaces.

  3. Hydrophobicity of silver surfaces with microparticle geometry (United States)

    Macko, Ján; Oriňaková, Renáta; Oriňak, Andrej; Kovaľ, Karol; Kupková, Miriam; Erdélyi, Branislav; Kostecká, Zuzana; Smith, Roger M.


    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.

  4. Hydrophobically modified polyelectrolytes: Characterization, aggregation and adsorption (United States)

    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

  5. Effect of morphology of hydrophobic surfaces on cavitation kinetics

    Energy Technology Data Exchange (ETDEWEB)



    Cavitation has been suggested to be a possible source of long range interactions between mesoscopic hydrophobic surfaces. While evaporation is predicted by thermodynamics, little is known about its kinetics. Glauber dynamics Monte Carlo simulations of a lattice gas close to liquid-gas coexistence and confined between partially drying surfaces are used to model the effect of water confinement on the dynamics of surface-induced phase transition. Specifically, they examine how kinetics of induced evaporation change as the texture of hydrophobic surfaces is varied. Evaporation rates are considerably slowed with relatively small amount of hydrophilic coverage. However, the distribution of hydrophilic patches is found to be crucial, with the homogeneous one being much more effective in slowing the formation of vapor tubes which triggers the evaporation process. They estimate the free energy barrier of vapor tube formation via transition state theory, using a constrained forward-backward umbrella sampling technique applied to the metastable, confined liquid. Furthermore, to relate simulation rates to experimental ones, they perform simulations using the mass-conserving Kawasaki algorithm. They predict evaporation time scales that range from hundreds of picoseconds in the case of mesoscopic surfaces {approximately} 10{sup 4} nm{sup 2} to tens of nanoseconds for smaller surfaces {approximately} 40 nm{sup 2}, when the two surfaces are {approximately} 10 solvent layers apart. The present study demonstrates that cavitation is kinetically viable in real systems and should be considered in studies of processes at confined geometry.

  6. Highly evolved juvenile granites with tetrad REE patterns: the Woduhe and Baerzhe granites from the Great Xing'an Mountains in NE China (United States)

    Jahn, Bor-ming; Wu, Fuyuan; Capdevila, R.; Martineau, F.; Zhao, Zhenhua; Wang, Yixian


    In NE China, voluminous granitoids were emplaced in late Paleozoic and Mesozoic times. We report here Sr-Nd-O isotopic and elemental abundance data for two highly evolved granitic plutons, Woduhe and Baerzhe, from the Great Xing'an Mountains. They show a rather "juvenile" Sr-Nd isotopic signature and a spectacular tetrad effect in their REE distribution patterns as well as non-CHARAC (charge-and-radius-controlled) trace element behavior. The emplacement ages are constrained at 130±4 Ma for the Woduhe and 122±5 Ma for the Baerzhe granites by Rb-Sr and Sm-Nd isotope analyses. Both granites are also characterized by low but imprecise initial 87Sr/ 86Sr ratios of about 0.703. The Nd-Sr isotope data argue for their generation by melting of dominantly juvenile mantle component with subordinate recycled ancient crust. This is largely compatible with the general scenario for much of the Phanerozoic granitoids emplaced in the Central Asian Orogenic Belt. The parental magmas for both the Woduhe and Baerzhe granites have undergone extensive magmatic differentiation, during which intense interaction of the residual melts with aqueous hydrothermal fluids (probably rich in F and Cl) resulted in the non-CHARAC trace element behavior and the tetrad effect of REE distribution. Both the Woduhe and Baerzhe granites show the characteristic trace element patterns of rare-metal granites, but their absolute abundances differ by as much as two orders of magnitude. The oxygen isotope compositions of the two granites have been severely disturbed. Significant 18O depletion in feldspar, but not so much in quartz, suggests that the hydrothermal alteration took place in a temperature condition of 300-500 °C. This subsolidus hydrothermal alteration is decoupled from the late-stage magma-fluid interaction at higher temperatures. Despite the two distinct and intense events of "water-rock" interaction, the Rb-Sr and Sm-Nd geochronological systems seem to have maintained closed, hence, suggesting

  7. Biogeochemistry of REE elements and tetrad effect in the soil-plant system: a study on volcanic rock covers in southernmost Brazil

    Directory of Open Access Journals (Sweden)

    Maria do Carmo Lima e Cunha


    Full Text Available This paper deals with the distribution of REE in rock, soil and plant in an area of monzonitic rocks from southernmost Brazil. The REE patterns in Schinus lensticifolius show a negative-Ce anomaly and a prominent tetrad effect, characterized as W-type that are not present in rock and soil samples. The REE patterns in the soils and rocks sampled are very similar and there is no fractionation of REE during the processes of soil formation. The W-type patterns are interpreted as indicating that REE were absorved by S. lentiscifolius as simple ions rather than as complex ions, or, alternatively, that the transport of REE in the plant metabolic processes was as free ions. The recognition of tetrads, either, M- or W-type patterns, is an additional tool for understanding the biogeochemistry of REE and can contribute to the study of monitoring processes of contaminated environment or to mineral prospecting.Este trabalho trata da distribuição dos ETR na rocha, solo e planta em área de ocorrência de rochas monzoníticas do extremo sul do Brasil. O padrão dos ETR em Schinus lentiscifolius apresenta anomalia negativa de Ce e significativo efeito tétrade, do tipo W, ausente no padrão da rocha e do solo. A configuração das curvas da rocha e do solo é similar e sem fracionamento das ETR durante a pedogênese. O padrão em W é interpretado como decorrente da absorção dos ETR pela planta na forma de íons livres e não complexados, ou, alternativamente, que o transporte das ETR nos processos metabólicos foi na forma de íons livres. O reconhecimento de tétrades, seja do tipo W ou M, é uma ferramenta adicional na compreensão da biogeoquímica dos ETR e pode contribuir para o estudo de processos de monitoramento de ambientes contaminados ou para pesquisas em prospecção mineral.

  8. Droplet Transport Mechanism on Horizontal Hydrophilic/Hydrophobic Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Myong, Hyon Kook [Kookmin University, Seoul (Korea, Republic of)


    A fluid transport technique is a key issue for the development of microfluidic systems. In this study, the movement of a droplet on horizontal hydrophilic/hydrophobic surfaces, which is a new concept to transport droplets without external power sources that was recently proposed by the author, was simulated using an in-house solution code(PowerCFD). This code employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The droplet transport mechanism is examined through numerical results that include velocity vectors, pressure contours, and total kinetic energy inside and around the droplet.

  9. Reshaping conservation

    DEFF Research Database (Denmark)

    Funder, Mikkel; Danielsen, Finn; Ngaga, Yonika


    members strengthen the monitoring practices to their advantage, and to some extent move them beyond the reach of government agencies and conservation and development practitioners. This has led to outcomes that are of greater social and strategic value to communities than the original 'planned' benefits......, although the monitoring scheme has also to some extent become dominated by local 'conservation elites' who negotiate the terrain between the state and other community members. Our findings suggest that we need to move beyond simplistic assumptions of community strategies and incentives in participatory...... conservation and allow for more adaptive and politically explicit governance spaces in protected area management....

  10. Selective isolation of bacteria from soil with hydrophobic materials


    Oku, Shota; Nishiyama, Masaya; Takao, Yuji


    Bacterial strains having a hydrophobic cell surface have often been considered as degraders of hydrophobic organic pollutants in soil. In this study, bacterial strains were isolated using hydrophobic materials from 12 soil samples, and their cell surface hydrophobicity was determined by evaluating their adherence to n-hexane. Bacterial strains isolated using polytetrafluoroethylene (PTFE) membrane were more hydrophobic on an average than those isolated with styrene-divinylbenzene (DVB) partic...

  11. Research progress on theultra hydrophobic surface topography effect

    Institute of Scientific and Technical Information of China (English)

    WANG Jiadao; YU Ying; CHEN Darong


    Ultra hydrophobic surfaces take on better hydrophobicity and exhibit a water contact angle larger than 150°. In this paper the ultra hydrophobicity is analyzed and common fabrication methods are summarized in detail. The applications of micro topography in both the fabrication of hydrophobic surface and the experiments of drag reduction are addressed. Finally, the development trend and foreground of ultra hydrophobic surface are discussed.

  12. On gel electrophoresis of dielectric charged particles with hydrophobic surface: A combined theoretical and numerical study. (United States)

    Majee, Partha Sarathi; Bhattacharyya, Somnath; Gopmandal, Partha Pratim; Ohshima, Hiroyuki


    A theoretical study on the gel electrophoresis of a charged particle incorporating the effects of dielectric polarization and surface hydrophobicity at the particle-liquid interface is made. A simplified model based on the weak applied field and low charge density assumption is also presented and compared with the full numerical model for a nonpolarizable particle to elucidate the nonlinear effects such as double layer polarization and relaxation as well as surface conduction. The main motivation of this study is to analyze the electrophoresis of the surface functionalized nanoparticle with tunable hydrophobicity or charged fluid drop in gel medium by considering the electrokinetic effects and hydrodynamic interactions between the particle and the gel medium. An effective medium approach, in which the transport in the electrolyte saturated hydrogel medium is governed by the Brinkman equation, is adopted in the present analysis. The governing electrokinetic equations based on the conservation principles is solved numerically. The Navier-slip boundary condition along with the continuity condition of dielectric displacement are imposed on the surface of the hydrophobic polarizable particle. The impact of the slip length on the electrophoresis is profound for a thinner Debye layer, however, surface conduction effect also becomes significant for a hydrophobic particle. Impact of hydrophobicity and relaxation effects are higher for a larger particle. Dielectric polarization creates a reduction in its electrophoretic propulsion and has negligible impact at the thinner Debye length as well as lower gel screening length. This article is protected by copyright. All rights reserved.

  13. Biosurfactant-enhanced bioremediation of hydrophobic pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Cameotra, S.S.; Makkar, R.S. [Inst. of Microbial Technology, Chandigarh (India)


    Biosurfactants are surface-active compounds synthesized by a wide variety of microorganisms. They are molecules that have both hydrophobic and - philic domains and are capable of lowering the surface tension and the interfacial tension of the growth medium. Biosurfactants possess different chemical structures-lipopeptides, glycolipids, neutral lipids, and fatty acids. They are nontoxic biomolecules that are biodegradable. Biosurfactants also exhibit strong emulsification of hydrophobic compounds and form stable emulsions. Polycyclic aromatic hydrocarbons (PAHs), crude on sludge, and pesticides call be toxic, mutagenic, and carcinogenic compounds that pollute the environment. They are released into the environment as a result of oil spillage and by-products of coal treatment processes. The low water solubility of these compounds limits their availability to microorganisms, which is a potential problem for bioremediation of contaminated sites. Microbially produced surfactants enhance the bioavailability of these hydrophobic compounds for bioremediation. Therefore, biosurfactant-enhanced solubility of pollutants has potential hioremediation applications.

  14. Wildlife Conservation


    Clive L. Spash; Aldred, Jonathan


    In this paper we consider how conservation has arisen as a key aspect of the reaction to human-initiated degradation and disappearance of ecosystems, wild lands. and wildlife. Concern over species extinction is given an historical perspective which shows the way in which pressure on wild and natural aspects of global ecology have changed in recent centuries. The role of conservation in the struggle to protect the environment is then analysed using underlying ethical arguments behind the econo...

  15. Metagenomic characterization of 'Candidatus Defluviicoccus tetraformis strain TFO71', a tetrad-forming organism, predominant in an anaerobic-aerobic membrane bioreactor with deteriorated biological phosphorus removal. (United States)

    Nobu, Masaru K; Tamaki, Hideyuki; Kubota, Kengo; Liu, Wen-Tso


    In an acetate-fed anaerobic-aerobic membrane bioreactor with deteriorated enhanced biological phosphorus removal (EBPR), Defluviicoccus-related tetrad-forming organisms (DTFO) were observed to predominate in the microbial community. Using metagenomics, a partial genome of the predominant DTFO, 'Candidatus Defluviicoccus tetraformis strain TFO71', was successfully constructed and characterized. Examining the genome confirmed the presence of genes related to the synthesis and degradation of glycogen and polyhydroxyalkanoate (PHA), which function as energy and carbon storage compounds. TFO71 and 'Candidatus Accumulibacter phosphatis' (CAP) UW-1 and CAP UW-2, representative polyphosphate-accumulating organisms (PAO), have PHA metabolism-related genes with high homology, but TFO71 has unique genes for PHA synthesis, gene regulation and granule management. We further discovered genes encoding DTFO polyphosphate (polyP) synthesis, suggesting that TFO71 may synthesize polyP under untested conditions. However, TFO71 may not activate these genes under EBPR conditions because the retrieved genome does not contain all inorganic phosphate transporters that are characteristic of PAOs (CAP UW-1, CAP UW-2, Microlunatus phosphovorus NM-1 and Tetrasphaera species). As a first step in characterizing EBPR-associated DTFO metabolism, this study identifies important differences between DTFO and PAO that may contribute to EBPR community competition and deterioration. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

  16. Practical application of the vanishing tetrad test for causal indicator measurement models: an example from health-related quality of life. (United States)

    Bollen, Kenneth A; Lennox, Richard D; Dahly, Darren L


    Researchers are often faced with the task of trying to measure abstract concepts. The most common approach is to use multiple indicators that reflect an underlying latent variable. However, this 'effect indicator' measurement model is not always appropriate; sometimes the indicators instead cause the construct of interest. While the notion of 'causal indicators' has been known for some time, it is still too often ignored. However, there are limited means to determine whether a possible indicator should be treated as a cause or an effect of the latent construct of interest. Perhaps the best empirical way is to use the vanishing tetrad test (VTT), yet this method is still often overlooked. We speculate that one reason for this is the lack of published examples of its use in practice, written for an audience without extensive statistical training. The goal of this paper was to help fill this gap in the literature-to provide a basic example of how to use the VTT. We illustrated the VTT by looking at multiple items from a health related quality of life instrument that seem more likely to cause the latent variable rather than the other way around.

  17. Multilocus half-tetrad analysis and centromere mapping in citrus: evidence of SDR mechanism for 2n megagametophyte production and partial chiasma interference in mandarin cv 'Fortune'. (United States)

    Cuenca, J; Froelicher, Y; Aleza, P; Juárez, J; Navarro, L; Ollitrault, P


    The genetic structure of 2n gametes and, particularly, the parental heterozygosity restitution at each locus depends on the meiotic process by which they originated, with first-division restitution and second-division restitution (SDR) being the two major mechanisms. The origin of 2n gametes in citrus is still controversial, although sexual polyploidisation is widely used for triploid seedless cultivar development. In this study, we report the analysis of 2n gametes of mandarin cv 'Fortune' by genotyping 171 triploid hybrids with 35 simple sequence repeat markers. The microsatellite DNA allele counting-peak ratios method for allele-dosage evaluation proved highly efficient in segregating triploid progenies and allowed half-tetrad analysis (HTA) by inferring the 2n gamete allelic configuration. All 2n gametes arose from the female genitor. The observed maternal heterozygosity restitution varied between 10 and 82%, depending on the locus, thus SDR appears to be the mechanism underlying 2n gamete production in mandarin cv 'Fortune'. A new method to locate the centromere, based on the best fit between observed heterozygosity restitution within a linkage group and theoretical functions under either partial or no chiasmata interference hypotheses was successfully applied to linkage group II. The maximum value of heterozygosity restitution and the pattern of restitution along this linkage group would suggest there is partial chiasma interference. The implications of such a restitution mechanism for citrus breeding are discussed.

  18. The Einstein-Maxwell-Particle System in the York Canonical Basis of ADM Tetrad Gravity: I) The Equations of Motion in Arbitrary Schwinger Time Gauges

    CERN Document Server

    Alba, David


    We study the coupling of N charged scalar particles plus the electro-magnetic field to ADM tetrad gravity and its canonical formulation in asymptotically Minkowskian space-times without super-translations. We make the canonical transformation to the York canonical basis, where there is a separation between the {\\it inertial} (gauge) variables and the {\\it tidal} ones inside the gravitational field and a special role of the Eulerian observers associated to the 3+1 splitting of space-time. The Dirac Hamiltonian is weakly equal to the weak ADM energy. The Hamilton equations in Schwinger time gauges are given explicitly. In the York basis they are naturally divided in four sets: a) the contracted Bianchi identities; b) the equations for the inertial gauge variables; c) the equations for the tidal ones; d) the equations for matter. Finally we give the restriction of the Hamilton equations and of the constraints to the family of {\\it non-harmonic 3-orthogonal} gauges, in which the instantaneous Riemannian 3-spaces ...

  19. Distance-dependent hydrophobic-hydrophobic contacts in protein folding simulations. (United States)

    Onofrio, Angelo; Parisi, Giovanni; Punzi, Giuseppe; Todisco, Simona; Di Noia, Maria Antonietta; Bossis, Fabrizio; Turi, Antonio; De Grassi, Anna; Pierri, Ciro Leonardo


    Successful prediction of protein folding from an amino acid sequence is a challenge in computational biology. In order to reveal the geometric constraints that drive protein folding, highlight those constraints kept or missed by distinct lattices and for establishing which class of intra- and inter-secondary structure element interactions is the most relevant for the correct folding of proteins, we have calculated inter-alpha carbon distances in a set of 42 crystal structures consisting of mainly helix, sheet or mixed conformations. The inter-alpha carbon distances were also calculated in several lattice "hydrophobic-polar" models built from the same protein set. We found that helix structures are more prone to form "hydrophobic-hydrophobic" contacts than beta-sheet structures. At a distance lower than or equal to 3.8 Å (very short-range interactions), "hydrophobic-hydrophobic" contacts are almost absent in the native structures, while they are frequent in all the analyzed lattice models. At distances in-between 3.8 and 9.5 Å (short-/medium-range interactions), the best performing lattice for reproducing mainly helix structures is the body-centered-cubic lattice. If protein structures contain sheet portions, lattice performances get worse, with few exceptions observed for double-tetrahedral and body-centered-cubic lattices. Finally, we can observe that ab initio protein folding algorithms, i.e. those based on the employment of lattices and Monte Carlo simulated annealings, can be improved simply and effectively by preventing the generation of "hydrophobic-hydrophobic" contacts shorter than 3.8 Å, by monitoring the "hydrophobic-hydrophobic/polar-polar" contact ratio in short-/medium distance ranges and by using preferentially a body-centered-cubic lattice.

  20. Fluoroalkyl and alkyl chains have similar hydrophobicities in binding to the "hydrophobic wall" of carbonic anhydrase. (United States)

    Mecinović, Jasmin; Snyder, Phillip W; Mirica, Katherine A; Bai, Serena; Mack, Eric T; Kwant, Richard L; Moustakas, Demetri T; Héroux, Annie; Whitesides, George M


    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(2)NSO(2)C(6)H(4)-CONHCH(2)(CX(2))(n)CX(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 entropic contributions to the

  1. A method for detecting hydrophobic patches protein

    NARCIS (Netherlands)

    Lijnzaad, P.; Berendsen, H.J.C.; Argos, P.


    A method for the detection of hydrophobic patches on the surfaces of protein tertiary structures is presented, it delineates explicit contiguous pieces of surface of arbitrary size and shape that consist solely of carbon and sulphur atoms using a dot representation of the solvent-accessible surface,

  2. Binding Hydrated Anions with Hydrophobic Pockets. (United States)

    Sokkalingam, Punidha; Shraberg, Joshua; Rick, Steven W; Gibb, Bruce C


    Using a combination of isothermal titration calorimetry and quantum and molecular dynamics calculations, we demonstrate that relatively soft anions have an affinity for hydrophobic concavity. The results are consistent with the anions remaining partially hydrated upon binding, and suggest a novel strategy for anion recognition.

  3. Deposition and Investigation of Hydrophobic Coatings

    Directory of Open Access Journals (Sweden)

    Safonov Aleksey


    Full Text Available The fluoropolymer coatings of different morphologies are deposited by the HWCVD (Hot Wire CVD method. The effect of activator filament temperature on the structure of fluoropolymer coating is shown. The results of studying the hydrophobic fluoropolymer coatings with different structures, deposited by the HWCVD method, are presented.

  4. A method for detecting hydrophobic patches protein

    NARCIS (Netherlands)

    Lijnzaad, P.; Berendsen, H.J.C.; Argos, P.


    A method for the detection of hydrophobic patches on the surfaces of protein tertiary structures is presented, it delineates explicit contiguous pieces of surface of arbitrary size and shape that consist solely of carbon and sulphur atoms using a dot representation of the solvent-accessible surface,

  5. Conservation endocrinology (United States)

    McCormick, Stephen; Romero, Michael


    Endocrinologists can make significant contributions to conservation biology by helping to understand the mechanisms by which organisms cope with changing environments. Field endocrine techniques have advanced rapidly in recent years and can provide substantial information on the growth, stress, and reproductive status of individual animals, thereby providing insight into current and future responses of populations to changes in the environment. Environmental stressors and reproductive status can be detected nonlethally by measuring a number of endocrine-related endpoints, including steroids in plasma, living and nonliving tissue, urine, and feces. Information on the environmental or endocrine requirements of individual species for normal growth, development, and reproduction will provide critical information for species and ecosystem conservation. For many taxa, basic information on endocrinology is lacking, and advances in conservation endocrinology will require approaches that are both “basic” and “applied” and include integration of laboratory and field approaches.

  6. Colorful Conservation (United States)

    Skophammer, Karen


    Some people only think about conservation on Earth Day. Being in the "art business" however, this author is always conscious of the many products she thinks get wasted when they could be reused, recycled, and restored--especially in a school building and art room. In this article, she describes an art lesson that allows students to paint…

  7. [Conservation Units. (United States)

    Texas Education Agency, Austin.

    Each of the six instructional units deals with one aspect of conservation: forests, water, rangeland, minerals (petroleum), and soil. The area of the elementary school curriculum with which each correlates is indicated. Lists of general and specific objectives are followed by suggested teaching procedures, including ideas for introducing the…

  8. [Conservation Units. (United States)

    Texas Education Agency, Austin.

    Instructional units deal with each aspect of conservation: forests, wildlife, rangelands, water, minerals, and soil. The area of the secondary school curriculum with which each is correlated is indicated. Lists of general and specific objectives are followed by suggested teaching procedures, including ideas for introducing the topic, questions to…

  9. Gel formation driven by tunable hydrophobic domain: design of acrylamide macromonomer with oligo hydrophobic segment. (United States)

    Nitta, Kyohei; Miyake, Junpei; Watanabe, Junji; Ikeda, Yoshiyuki


    Nowadays, biomaterials with amphiphilic properties are undergoing remarkable development. Here, we present one such development, in which we prepared amphiphilic graft copolymers, with a main chain composed of hydroxyethyl acrylamide (HEAA), to introduce hydrophilicity, and a side chain composed of poly(trimethylene carbonate) (PTMC) to introduce tunable hydrophobicity. These macromonomers were created with a novel molecular design, which introduced a ring-opening polymerization by the hydroxyl end group of HEAA in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, and were analyzed by (1)H NMR and gel permeation chromatography. The amphiphilic graft copolymers were shown to form a hydrogel, the swelling ratio of which was greatly influenced by the number of trimethylene carbonate units. These copolymers also exhibited the Tyndall phenomenon in aqueous solution; they aggregated spontaneously due to hydrogen bonding and hydrophobic interactions, and a sodium 8-anilino-1-naphthalenesulfonate (ANS) fluorescence probe was introduced into the hydrophobic domain. The solution property of ANS in the polymer solution was analyzed by fluorescence measurement and (1)H NMR. The maximum fluorescence wavelength of ANS shifted to shorter wavelengths as the degree of polymerization of the hydrophobic PTMC, the composition of the macromonomer, and the concentration of the copolymer increased. The resulting copolymer formed a polymer micelle structure due to the tunable hydrophobic domain formation in selected solvents. Therefore, these amphiphilic graft copolymers containing a PTMC segment are excellent candidates for use as hydrophobic drug delivery carriers.

  10. Brain-mind dyad, human experience, the consciousness tetrad and lattice of mental operations: And further, The need to integrate knowledge from diverse disciplines

    Directory of Open Access Journals (Sweden)

    Ajai R Singh


    Full Text Available Brain, Mind and Consciousness are the research concerns of psychiatrists, psychologists, neurologists, cognitive neuroscientists and philosophers. All of them are working in different and important ways to understand the workings of the brain, the mysteries of the mind and to grasp that elusive concept called consciousness. Although they are all justified in forwarding their respective researches, it is also necessary to integrate these diverse appearing understandings and try and get a comprehensive perspective that is, hopefully, more than the sum of their parts. There is also the need to understand what each one is doing, and by the other, to understand each other's basic and fundamental ideological and foundational underpinnings. This must be followed by a comprehensive and critical dialogue between the respective disciplines. Moreover, the concept of mind and consciousness in Indian thought needs careful delineation and critical/evidential enquiry to make it internationally relevant. The brain-mind dyad must be understood, with brain as the structural correlate of the mind, and mind as the functional correlate of the brain. To understand human experience, we need a triad of external environment, internal environment and a consciousness that makes sense of both. We need to evolve a consensus on the definition of consciousness, for which a working definition in the form of a Consciousness Tetrad of Default, Aware, Operational and Evolved Consciousness is presented. It is equally necessary to understand the connection between physical changes in the brain and mental operations, and thereby untangle and comprehend the lattice of mental operations. Interdisciplinary work and knowledge sharing, in an atmosphere of healthy give and take of ideas, and with a view to understand the significance of each other's work, and also to critically evaluate the present corpus of knowledge from these diverse appearing fields, and then carry forward from there

  11. Brain-Mind Dyad, Human Experience, the Consciousness Tetrad and Lattice of Mental Operations: And Further, The Need to Integrate Knowledge from Diverse Disciplines (United States)

    Singh, Ajai R.; Singh, Shakuntala A.


    Brain, Mind and Consciousness are the research concerns of psychiatrists, psychologists, neurologists, cognitive neuroscientists and philosophers. All of them are working in different and important ways to understand the workings of the brain, the mysteries of the mind and to grasp that elusive concept called consciousness. Although they are all justified in forwarding their respective researches, it is also necessary to integrate these diverse appearing understandings and try and get a comprehensive perspective that is, hopefully, more than the sum of their parts. There is also the need to understand what each one is doing, and by the other, to understand each other’s basic and fundamental ideological and foundational underpinnings. This must be followed by a comprehensive and critical dialogue between the respective disciplines. Moreover, the concept of mind and consciousness in Indian thought needs careful delineation and critical/evidential enquiry to make it internationally relevant. The brain-mind dyad must be understood, with brain as the structural correlate of the mind, and mind as the functional correlate of the brain. To understand human experience, we need a triad of external environment, internal environment and a consciousness that makes sense of both. We need to evolve a consensus on the definition of consciousness, for which a working definition in the form of a Consciousness Tetrad of Default, Aware, Operational and Evolved Consciousness is presented. It is equally necessary to understand the connection between physical changes in the brain and mental operations, and thereby untangle and comprehend the lattice of mental operations. Interdisciplinary work and knowledge sharing, in an atmosphere of healthy give and take of ideas, and with a view to understand the significance of each other’s work, and also to critically evaluate the present corpus of knowledge from these diverse appearing fields, and then carry forward from there in a spirit of

  12. Brain-mind dyad, human experience, the consciousness tetrad and lattice of mental operations: and further, the need to integrate knowledge from diverse disciplines. (United States)

    Singh, Ajai R; Singh, Shakuntala A


    Brain, Mind and Consciousness are the research concerns of psychiatrists, psychologists, neurologists, cognitive neuroscientists and philosophers. All of them are working in different and important ways to understand the workings of the brain, the mysteries of the mind and to grasp that elusive concept called consciousness. Although they are all justified in forwarding their respective researches, it is also necessary to integrate these diverse appearing understandings and try and get a comprehensive perspective that is, hopefully, more than the sum of their parts. There is also the need to understand what each one is doing, and by the other, to understand each other's basic and fundamental ideological and foundational underpinnings. This must be followed by a comprehensive and critical dialogue between the respective disciplines. Moreover, the concept of mind and consciousness in Indian thought needs careful delineation and critical/evidential enquiry to make it internationally relevant. The brain-mind dyad must be understood, with brain as the structural correlate of the mind, and mind as the functional correlate of the brain. To understand human experience, we need a triad of external environment, internal environment and a consciousness that makes sense of both. We need to evolve a consensus on the definition of consciousness, for which a working definition in the form of a Consciousness Tetrad of Default, Aware, Operational and Evolved Consciousness is presented. It is equally necessary to understand the connection between physical changes in the brain and mental operations, and thereby untangle and comprehend the lattice of mental operations. Interdisciplinary work and knowledge sharing, in an atmosphere of healthy give and take of ideas, and with a view to understand the significance of each other's work, and also to critically evaluate the present corpus of knowledge from these diverse appearing fields, and then carry forward from there in a spirit of

  13. Hydrophobic Core Variations Provide a Structural Framework for Tyrosine Kinase Evolution and Functional Specialization. (United States)

    Mohanty, Smita; Oruganty, Krishnadev; Kwon, Annie; Byrne, Dominic P; Ferries, Samantha; Ruan, Zheng; Hanold, Laura E; Katiyar, Samiksha; Kennedy, Eileen J; Eyers, Patrick A; Kannan, Natarajan


    Protein tyrosine kinases (PTKs) are a group of closely related enzymes that have evolutionarily diverged from serine/threonine kinases (STKs) to regulate pathways associated with multi-cellularity. Evolutionary divergence of PTKs from STKs has occurred through accumulation of mutations in the active site as well as in the commonly conserved hydrophobic core. While the functional significance of active site variations is well understood, relatively little is known about how hydrophobic core variations contribute to PTK evolutionary divergence. Here, using a combination of statistical sequence comparisons, molecular dynamics simulations, mutational analysis and in vitro thermostability and kinase assays, we investigate the structural and functional significance of key PTK-specific variations in the kinase core. We find that the nature of residues and interactions in the hydrophobic core of PTKs is strikingly different from other protein kinases, and PTK-specific variations in the core contribute to functional divergence by altering the stability and dynamics of the kinase domain. In particular, a functionally critical STK-conserved histidine that stabilizes the regulatory spine in STKs is selectively mutated to an alanine, serine or glutamate in PTKs, and this loss-of-function mutation is accommodated, in part, through compensatory PTK-specific interactions in the core. In particular, a PTK-conserved phenylalanine in the I-helix appears to structurally and functionally compensate for the loss of STK-histidine by interacting with the regulatory spine, which has far-reaching effects on enzyme activity, inhibitor sensing, and stability. We propose that hydrophobic core variations provide a selective advantage during PTK evolution by increasing the conformational flexibility, and therefore the allosteric potential of the kinase domain. Our studies also suggest that Tyrosine Kinase Like kinases such as RAF are intermediates in PTK evolutionary divergence inasmuch as they

  14. Hydrophobic sponge structure-based triboelectric nanogenerator. (United States)

    Lee, Keun Young; Chun, Jinsung; Lee, Ju-Hyuck; Kim, Kyeong Nam; Kang, Na-Ri; Kim, Ju-Young; Kim, Myung Hwa; Shin, Kyung-Sik; Gupta, Manoj Kumar; Baik, Jeong Min; Kim, Sang-Woo


    Hydrophobic sponge structure-based triboelectric nanogenerators using an inverse opal structured film for sustainable energy harvesting over a wide range of humid atmosphere have been successfully demonstrated. The output voltage and current density reach a record value of 130 V and 0.10 mA cm(-2) , respectively, giving over 10-fold power enhancement, compared with the flat film-based triboelectric nanogenerator. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Hydrophobic Solvation : A 2D IR Spectroscopic Inquest

    NARCIS (Netherlands)

    Bakulin, Artem A.; Liang, Chungwen; Jansen, Thomas La Cour; Wiersma, Douwe A.; Bakker, Huib J.; Pshenichnikov, Maxim S.


    For decades, the enigma of the hydrophobic force has captured the imagination of scientists. in particular, Frank and Evans' idea that the hydrophobic effect was mainly due to some kind of "iceberg" formation around a hydrophobic solute stimulated many experiments and molecular dynamics simulation s

  16. Hydrophobic treatment of concrete as protection against chloride penetration

    NARCIS (Netherlands)

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


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

  17. Phenylalanine containing hydrophobic nanospheres for antibody purification. (United States)

    Türkmen, Deniz; Denizli, Adil; Oztürk, Nevra; Akgöl, Sinan; Elkak, Assem


    In this study, novel hydrophobic nanospheres with an average size of 158 nm utilizing N-methacryloyl-(L)-phenylalanine methyl ester (MAPA) as a hydrophobic monomer were produced by surfactant free emulsion polymerization of 2-hydroxyethyl methacrylate (HEMA) and MAPA conducted in an aqueous dispersion medium. MAPA was synthesized using methacryloyl chloride and L-phenylalanine methyl ester. Specific surface area of the nonporous nanospheres was found to be 1874 m2/g. Poly(HEMA-MAPA) nanospheres were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Average particle size, size distribution, and surface charge measurements were also performed. Elemental analysis of MAPA for nitrogen was estimated as 0.42 mmol/g polymer. Then, poly(HEMA-MAPA) nanospheres were used in the adsorption of immunoglobulin G (IgG) in batch system. Higher adsorption values (780 mg/g) were obtained when the poly (HEMA-MAPA) nanospheres were used from both aqueous solutions and human plasma. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that IgG could be repeatedly adsorbed and desorbed without significant loss in adsorption amount. These findings show considerable promise for this material as a hydrophobic support in industrial processes.

  18. Magnetic hydrophobic nanocomposites: Silica aerogel/maghemite

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza Zelis, P. [Departamento de Fisica-IFLP, Universidad Nacional de La Plata-CONICET (Argentina); Fernandez van Raap, M.B., E-mail: [Departamento de Fisica-IFLP, Universidad Nacional de La Plata-CONICET (Argentina); Socolovsky, L.M. [Laboratorio de Solidos Amorfos, INTECIN, Universidad de Buenos Aires-CONICET (Argentina); Leyva, A.G. [Div. Materia condensada, CNEA- ECyT-UNSAM, Buenos Aires (Argentina); Sanchez, F.H. [Departamento de Fisica-IFLP, Universidad Nacional de La Plata-CONICET (Argentina)


    Magnetic hydrophobic aerogels (MHA) in the form of nanocomposites of silica and maghemite ({gamma}-Fe{sub 2}O{sub 3}) were prepared by one step sol-gel procedure followed by supercritical solvent extraction. Silica alcogels were obtained from TEOS, MTMS, methanol and H{sub 2}O, and Fe(III) nitrate as magnetic precursor. The hydrophobic property was achieved using the methytrimethoxysilane (MTMS) as co-precursor for surface modification. The so produced nanocomposite aerogels are monolithic, hydrophobic and magnetic. The interconnected porous structure hosts {approx}6 nm size {gamma}-Fe{sub 2}O{sub 3} particles, has a mean pore diameter of 5 nm, and a specific surface area (SSA) of 698 m Superscript-Two /g. Medium range structure of MHA is determined by SAXS, which displays the typical fractal power law behavior with primary particle radius of {approx}1 nm. Magnetic properties of the nanoparticle ensembles hosted in them are studied by means of dc-magnetometry.

  19. Nonflammable, Hydrophobic Aerogel Composites for Insulation (United States)

    Redouane, Begag


    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)

  20. Heron conservation (United States)

    Kushlan, J.A.; Hafner, H.


    Herons are large, popular and, in many cases, spectacular birds found in wetlands world-wide, both tropical and temperate, natural and man-made. Some populations are very small and localized, some have decreased, some have expanded their ranges, and a few are pests of human activities. In the fifteen years since the publication of the latest monographic treatment of the family, The Herons Handbook, there has been a tremendous increase in our knowledge of heron status and conservation requirements, set against a backdrop of increasing concern about the future of the world?s wetland habitats. This book provides a comprehensive update following two distinct threads. The status and conservation needs of herons are first presented on a regional basis, in a series of chapters set at a continental or subcontinental scale. Over 200 biologists and heron conservationists have contributed to the data summarized here, and the very latest census and survey results provide the most up-to-date and detailed picture of heron populations currently available. Chapters discussing several critical issues in heron conservation follow, tending to focus on the international nature of the problems.

  1. Flocculation, hydrophobic agglomeration and filtration of ultrafine coal

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Z. [University of British Columbia, Vancouver, BC (Canada). Department of Mineral and Mineral Process Engineering


    Selective flocculation tests were run on three types of coal and three additives in tests on a new hydrophobic agglomeration process using hydrophobic latices. The coals differed widely in surface wettability. The additives were hydrophobic latexes, a semi-hydrophobic flocculant, and a typical hydrophilic polyelectrolyte. The results show that coal wettability is very important in selective flocculation. UBC-1 hydrophobic latex flocculated hydrophobic coal particles only, while the polyelectrolyte flocculated all the coal samples and minerals that were tested. Tests of oil agglomeration using kerosene emulsified with surfactants of various ionic properties show that even oxidized coals can be agglomerated, if cationic surfactants are used to emulsify the oil. The hydrophobic latex and emulsified oils also significantly increase filtration rate and reduce filter cake moisture content.

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

    DEFF Research Database (Denmark)

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


    experimental data from x-ray reflectivity measurements, reveal a uniform weak de-wetting characteristic for the extended hydrophobic surface, while the hydrophilic surface is weakly wetted. These microscopic data are consistent with macroscopic contact angle measurements. Specific water orientation is present......-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together......Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding...

  3. Responsive gelation of hydrophobized linear polymer

    DEFF Research Database (Denmark)

    Madsen, Claus Greve; Toeth, Joachim; Jørgensen, Lene;

    In this study we present the rheological properties of a physically linked polymer network, composed of linear hydrophilic chains, modified with hydrophobic moieties in each end. Solutions of the polymer in ethanol-water mixtures showed Newtonian behaviour up to about 99 % ethanol, with the highest...... viscosity observed in a 1:1 mixture of ethanol and water. In pure ethanol, the polymer forms a thermo-responsive, non-Newtonian gel, which collapses upon addition of as little as 1 % water or heating to about 40 °C....

  4. Hydrophobic silica aerogel production at KEK

    CERN Document Server

    Tabata, Makoto; Kawai, Hideyuki; Sumiyoshi, Takayuki; Yokogawa, Hiroshi


    We present herein a characterization of a standard method used at the High Energy Accelerator Research Organization (KEK) to produce hydrophobic silica aerogels and expand this method to obtain a wide range of refractive index (n = 1.006-1.14). We describe in detail the entire production process and explain the methods used to measure the characteristic parameters of aerogels, namely the refractive index, transmittance, and density. We use a small-angle X-ray scattering (SAXS) technique to relate the transparency to the fine structure of aerogels.

  5. Aggregate size distributions in hydrophobic flocculation

    Directory of Open Access Journals (Sweden)

    Chairoj Rattanakawin


    Full Text Available The evolution of aggregate (floc size distributions resulting from hydrophobic flocculation has been investigated using a laser light scattering technique. By measuring floc size distributions it is possible to distinguish clearly among floc formation, growth and breakage. Hydrophobic flocculation of hematite suspensions with sodium oleate under a variety of agitating conditions produces uni-modal size distributions. The size distribution of the primary particles is shifted to larger floc sizes when the dispersed suspension is coagulated by pH adjustment. By adding sodium oleate to the pre-coagulated suspension, the distribution progresses further to the larger size. However, prolonged agitation degrades the formed flocs, regressing the distribution to the smaller size. Median floc size derived from the distribution is also used as performance criterion. The median floc size increases rapidly at the initial stage of the flocculation, and decreases with the extended agitation time and intensity. Relatively weak flocs are produced which may be due to the low dosage of sodium oleate used in this flocculation study. It is suggested that further investigation should focus on optimum reagent dosage and non-polar oil addition to strengthen these weak flocs.

  6. Hydrophobic effects on partial molar volume (United States)

    Imai, Takashi; Hirata, Fumio


    The hydrophobic effects on partial molar volume (PMV) are investigated as a PMV change in the transfer of a benzenelike nonpolar solute from the nonpolar solvent to water, using an integral equation theory of liquids. The volume change is divided into two effects. One is the "packing" effect in the transfer from the nonpolar solvent to hypothetical "nonpolar water" without hydrogen bonding networks. The other is the "iceberg" effect in the transfer from nonpolar water to water. The results indicate that the packing effect is negative and a half compensated by the positive iceberg effect. The packing effect is explained by the difference in the solvent compressibility. Further investigation shows that the sign and magnitude of the volume change depend on the solute size and the solvent compressibility. The finding gives a significant implication that the exposure of a hydrophobic residue caused by protein denaturation can either increase or decrease the PMV of protein depending on the size of the residue and the fluctuation of its surroundings.

  7. Nanostructured coatings for super hydrophobic textiles

    Indian Academy of Sciences (India)

    M Joshi; A Bhattacharyya; N Agarwal; S Parmar


    The promising aspects of nanocomposite coatings to mimic the nano roughened self cleaning surface of lotus leaf is explored in this paper. A detailed study on nanosilica and clay based nanocomposite coatings using dip coating and layer by layer self assembly (L–b–L) is being described where lotus leaf effect has been mimicked on the cotton fabric surface using these particles as they develop nanosized surface roughness which helps to produce a super-hydrophobic surface. Nanosilica performs better in creating nano roughness on cotton fabric wherein the contact angle is >150°. The water contact angle of 2 wt% fluoro emulsion (Nuva HPU) treated cotton fabric increases from 115° to 155° when the fabric is pretreated with 0.5 wt% nanosilica emulsion. The water repellency rating of fabric treated with 0.16 wt% nanosilica along with 2 wt% Nuva HPU is comparable to that of 4 wt% Nuva HPU treated cotton fabric. On the other hand, 40 bilayers of nanosilica need to be applied on cotton fabric surface through L–b–L technique to create uniform nano roughening and gives a water repellency rating of 4. The air permeability of L–b–L nanocoated cotton fabric is not adversely affected by the super-hydrophobic nanostructured coating.

  8. Statistical analyses of hydrophobic interactions: A mini-review

    CERN Document Server

    Pratt, L R; Rempe, Susan B


    This review focuses on the striking recent progress in solving for hydrophobic interactions between small inert molecules. We discuss several new understandings. Firstly, 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. Secondly, inclusion of attractive interactions associated with atomic-size hydrophobic reference cases leads to substantial, non-trivial 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...

  9. Contacts Between Alcohols in Water Are Random Rather than Hydrophobic. (United States)

    Rankin, Blake M; Ben-Amotz, Dor; van der Post, Sietse T; Bakker, Huib J


    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.

  10. The hydrophobic motif of ROCK2 requires association with the N-terminal extension for kinase activity. (United States)

    Couzens, Amber L; Saridakis, Vivian; Scheid, Michael P


    ROCK (Rho-associated coiled-coil kinase) 2 is a member of the AGC kinase family that plays an essential role downstream of Rho in actin cytoskeleton assembly and contractility. The process of ROCK2 activation is complex and requires suppression of an autoinhibitory mechanism that is facilitated by Rho binding. ROCK2 harbours a C-terminal extension within the kinase domain that contains a hydrophobic cluster of phenylalanine and tyrosine residues surrounding a key threonine residue. In growth-factor-stimulated AGC kinases, the hydrophobic motif is important for the transition of the kinase from inactive to active complex and requires phosphorylation of the conserved serine/threonine residue. Less is understood about the contribution that the hydrophobic motif plays in the activation of ROCK, and the role of the hydrophobic motif threonine at position 405. In the present study, we show that this residue of ROCK is essential for substrate phosphorylation and kinase domain dimerization. However, in contrast with the growth-factor-activated AGC kinases, a phosphomimetic residue at position 405 was inhibitory for ROCK2 activity and dimerization. A soluble hydrophobic motif peptide allosterically activated ROCK2 In vitro, but not the equivalent peptide with Asp(405) substitution. Mechanistically, both ROCK2 activity and dimerization were dependent upon the interaction between Thr(405) of the hydrophobic motif and Asp(39) of the N-terminal extension. The reciprocal exchange of these residues was permissive for kinase activity, but dimerization was lost. These results support the rationale for development of small-molecule inhibitors designed to block ROCK activation by selectively interfering with hydrophobic motif-mediated activation-state transition and dimer formation.

  11. New Hydrophobic IOL Materials and Understanding the Science of Glistenings. (United States)

    Tetz, Manfred; Jorgensen, Matthew R


    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.

  12. Hydrophobic Interactions Modulate Self-Assembly of Nanoparticles


    Sánchez-Iglesias, Ana; Grzelczak, Marek; Altantzis, Thomas; Goris, Bart; Pérez-Juste, Jorge; Bals, Sara; Van Tendeloo, Gustaaf; Donaldson, Stephen H.; Chmelka, Bradley F.; Israelachvili, Jacob N.; Liz-Marzán, Luis M.


    Abstract: Hydrophobic interactions constitute one of the most important types of nonspecific interactions in biological systems, which emerge when water molecules rearrange as two hydrophobic species come close to each other. The prediction of hydrophobic interactions at the level of nanoparticles (Brownian objects) remains challenging because of uncontrolled diffusive motion of the particles. We describe here a general methodology for solvent-induced, reversible self-assembly of gold nanopar...

  13. On the thermodynamics and kinetics of hydrophobic interactions at interfaces. (United States)

    Vembanur, Srivathsan; Patel, Amish J; Sarupria, Sapna; Garde, Shekhar


    We have studied how primitive hydrophobic interactions between two or more small nonpolar solutes are affected by the presence of surfaces. We show that the desolvation barriers present in the potential of mean force between the solutes in bulk water are significantly reduced near an extended hydrophobic surface. Correspondingly, the kinetics of hydrophobic contact formation and breakage are faster near a hydrophobic surface than near a hydrophilic surface or in the bulk. We propose that the reduction in the desolvation barrier is a consequence of the fact that water near extended hydrophobic surfaces is akin to that at a liquid-vapor interface and is easily displaced. We support this proposal with three independent observations. First, when small hydrophobic solutes are brought near a hydrophobic surface, they induce local dewetting, thereby facilitating the reduction of desolvation barriers. Second, our results and those of Patel et al. (Proc. Natl. Acad. Sci. U.S.A. 2011, 108, 17678-17683) show that, whereas the association of small solutes in bulk water is driven by entropy, that near hydrophobic surfaces is driven by enthalpy, suggesting that the physics of interface deformation is important. Third, moving water away from its vapor-liquid coexistence, by applying hydrostatic pressure, leads to recovery of bulklike signatures (e.g., the presence of a desolvation barrier and an entropic driving force) in the association of solutes. These observations for simple solutes also translate to end-to-end contact formation in a model peptide with hydrophobic end groups, for which lowering of the desolvation barrier and acceleration of contact formation are observed near a hydrophobic surface. Our results suggest that extended hydrophobic surfaces, such as air-water or hydrocarbon-water surfaces, could serve as excellent platforms for catalyzing hydrophobically driven assembly.

  14. Thermally stable hydrophobicity in electrospun silica/polydimethylsiloxane hybrid fibers (United States)

    Wei, Zhonglin; Li, Jianjun; Wang, Chao; Cao, Jungang; Yao, Yongtao; Lu, Haibao; Li, Yibin; He, Xiaodong


    In order to improve practical performances of silica-based inorganic/organic hybrid fibers, silica/polydimethylsiloxane hydrophobic fibers were successfully prepared by electrospinning. Silica sol and polydimethylsiloxane can be mixed homogeneously and become stable precursor solution in dichloromethane, which allows the transformation of silica/polydimethylsiloxane precursor solution into ultrafine fibers. Flame can ignite organic groups in polydimethylsiloxane directly and destroy the hydrophobicity of hybrid fibers, but hydrophobic feature may survive if electrospun hybrid membrane is combined with thin stainless-steel-304 gauze of 150 meshes due to its thermally stable hydrophobicity (>600 °C).

  15. Modulation of hydrophobic interactions by proximally immobilized ions. (United States)

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


    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.

  16. High performance hydrophobic solvent, carbon dioxide capture

    Energy Technology Data Exchange (ETDEWEB)

    Nulwala, Hunaid; Luebke, David


    Methods and compositions useful, for example, for physical solvent carbon capture. A method comprising: contacting at least one first composition comprising carbon dioxide with at least one second composition to at least partially dissolve the carbon dioxide of the first composition in the second composition, wherein the second composition comprises at least one siloxane compound which is covalently modified with at least one non-siloxane group comprising at least one heteroatom. Polydimethylsiloxane (PDMS) materials and ethylene-glycol based materials have high carbon dioxide solubility but suffer from various problems. PDMS is hydrophobic but suffers from low selectivity. Ethylene-glycol based systems have good solubility and selectivity, but suffer from high affinity to water. Solvents were developed which keep the desired combinations of properties, and result in a simplified, overall process for carbon dioxide removal from a mixed gas stream.

  17. Intermolecular Vibrations of Hydrophobic Amino Acids (United States)

    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

  18. Floating behavior of hydrophobic glass spheres. (United States)

    Liu, Xinjie; Wang, Xiaolong; Liang, Yongmin; Zhou, Feng


    When a hydrophobic solid sphere is floating on water or salt solutions with different concentrations, it is at equilibrium under the impact of gravity, buoyancy force, and curvature force, the component of surface tension in the vertical direction. We have changed the diameters of the spheres and the concentrations of the two selected salts, NaCl and NaNO(3), to study the floating behaviors of these spheres and the contributions of surface tension and buoyancy force to their floatation. Generally speaking, the surface tension plays a more important role than the buoyancy force when the gravity is small, but the buoyancy force plays an identical or a more important role when the spheres are big enough. The wettability of the spheres significantly influences the height below the contact perimeter especially in salt solutions. The theoretical calculation meniscus slope angles at the sphere three-phase contact line are in agreement with experimental results.

  19. Droplet Impact Dynamics on Micropillared Hydrophobic Surfaces

    CERN Document Server

    Patil, Nagesh D; Sharma, Atul


    The effect of pitch of the pillars and impact velocity are studied for the impact dynamics of a microliter water droplet on a micropillared hydrophobic surface. The results are presented qualitatively by the high-speed photography and quantitatively by the temporal variation of wetted diameter and droplet height. A characterization of the transient quantitative results is a novel aspect of our work. Three distinct regimes, namely, non-bouncing, complete bouncing and partial bouncing are presented. A critical pitch as well as impact velocity exists for the transition from one regime to another. This is explained with a demonstration of Cassie to Wenzel wetting transition in which the liquid penetrates in the grooves between the pillars at larger pitch or impact velocity. The regimes are demarcated on a map of pitch and impact velocity. A good agreement is reported between the present measurements and published analytical models.

  20. Relative Stabilities of Conserved and Non-Conserved Structures in the OB-Fold Superfamily

    Directory of Open Access Journals (Sweden)

    Andrei T. Alexandrescu


    Full Text Available The OB-fold is a diverse structure superfamily based on a β-barrel motif that is often supplemented with additional non-conserved secondary structures. Previous deletion mutagenesis and NMR hydrogen exchange studies of three OB-fold proteins showed that the structural stabilities of sites within the conserved β-barrels were larger than sites in non-conserved segments. In this work we examined a database of 80 representative domain structures currently classified as OB-folds, to establish the basis of this effect. Residue-specific values were obtained for the number of Cα-Cα distance contacts, sequence hydrophobicities, crystallographic B-factors, and theoretical B-factors calculated from a Gaussian Network Model. All four parameters point to a larger average flexibility for the non-conserved structures compared to the conserved β-barrels. The theoretical B-factors and contact densities show the highest sensitivity.Our results suggest a model of protein structure evolution in which novel structural features develop at the periphery of conserved motifs. Core residues are more resistant to structural changes during evolution since their substitution would disrupt a larger number of interactions. Similar factors are likely to account for the differences in stability to unfolding between conserved and non-conserved structures.

  1. Prevention of reinforcement corrosion by hydrophobic treatment of concrete

    NARCIS (Netherlands)

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


    Corrosion of reinforcement in concrete bridge decks may occur due to penetration of de-icing salts, even in the presence of an asphalt overlay. This paper reports a laboratory study into additional protection of concrete by hydrophobic treatment. It was found that hydrophobic treatment strongly redu

  2. Responses of Transmembrane Peptide and Lipid Chains to Hydrophobic Mismatch

    Institute of Scientific and Technical Information of China (English)

    YANG Lei; LI Jian-tao; QI Hai-yan; LI Fei


    Hydrophobic mismatch between the hydrophobic length of membrane proteins and hydrophobic thickness of membranes is a crucial factor in controlling protein function and assembly.We combined fluorescence with circular dichroism(CD) and attenuated total reflection infrared(ATR-IR) spectroscopic methods to investigate the behaviors of the peptide and lipids under hydrophobic mismatch using a model peptide from the fourth transmembrane domain of natural resistance-associated macrophage protein 1 (Nramp 1),the phosphatidylcholines(PCs) and phosphatidylglycerols(PGs) with different lengths of acyl chains(14:0,16:0 and 18:0).In all PG lipid membranes,the peptide forms stable α-helix structure,and the helix axis is parallel to lipid chains.The helical span and orientation hardly change in varying thickness of PG membranes,while the lipid chains can deform to accommodate to the hydrophobic surface of embedded peptide.By comparison,the helical structures of the model peptide in PC lipid membranes are less stable.Upon incorporation with PC lipid membranes,the peptide can deform itself to accommodate to the hydrophobic thickness of lipid membranes in response to hydrophobic mismatch.In addition,hydrophobic mismatch can increase the aggregation propensity of the peptide in both PC and PG lipid membranes and the peptide in PC membranes has more aggregation tendency than that in PG membranes.

  3. Hydrophobically modified polyelectrolytes : synthesis, properties and interactions with surfactants

    NARCIS (Netherlands)

    Nieuwkerk, A.C.


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

  4. Corrosion protection of reinforcement by hydrophobic treatment of concrete

    NARCIS (Netherlands)

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


    Penetration of de-icing salts into concrete bridge decks may cause corrosion of reinforcement. Hydrophobic treatment of concrete was studied as additional protection. It was shown that hydrophobic treatment strongly reduces chloride ingress, during semi-permanent contact and in wetting/drying situat

  5. Developing a general interaction potential for hydrophobic and hydrophilic interactions. (United States)

    Donaldson, Stephen H; Røyne, Anja; Kristiansen, Kai; Rapp, Michael V; Das, Saurabh; Gebbie, Matthew A; Lee, Dong Woog; Stock, Philipp; Valtiner, Markus; Israelachvili, Jacob


    We review direct force measurements on a broad class of hydrophobic and hydrophilic surfaces. These measurements have enabled the development of a general interaction potential per unit area, W(D) = -2γ(i)Hy exp(-D/D(H)) in terms of a nondimensional Hydra parameter, Hy, that applies to both hydrophobic and hydrophilic interactions between extended surfaces. This potential allows one to quantitatively account for additional attractions and repulsions not included in the well-known combination of electrostatic double layer and van der Waals theories, the so-called Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The interaction energy is exponentially decaying with decay length D(H) ≈ 0.3-2 nm for both hydrophobic and hydrophilic interactions, with the exact value of D(H) depending on the precise system and conditions. The pre-exponential factor depends on the interfacial tension, γ(i), of the interacting surfaces and Hy. For Hy > 0, the interaction potential describes interactions between partially hydrophobic surfaces, with the maximum hydrophobic interaction (i.e., two fully hydrophobic surfaces) corresponding to Hy = 1. Hydrophobic interactions between hydrophobic monolayer surfaces measured with the surface forces apparatus (SFA) are shown to be well described by the proposed interaction potential. The potential becomes repulsive for Hy < 0, corresponding to partially hydrophilic (hydrated) interfaces. Hydrated surfaces such as mica, silica, and lipid bilayers are discussed and reviewed in the context of the values of Hy appropriate for each system.

  6. Hydroglyphics: Demonstration of Selective Wetting on Hydrophilic and Hydrophobic Surfaces (United States)

    Kim, Philseok; Alvarenga, Jack; Aizenberg, Joanna; Sleeper, Raymond S.


    A visual demonstration of the difference between hydrophilic and hydrophobic surfaces has been developed. It involves placing a shadow mask on an optically clear hydrophobic plastic dish, corona treating the surface with a modified Tesla coil, removing the shadow mask, and visualizing the otherwise invisible message or pattern by applying water,…

  7. The effect of heterogeneity and surface roughness on soil hydrophobicity (United States)

    Hallin, I.; Bryant, R.; Doerr, S. H.; Douglas, P.


    Soil water repellency, or hydrophobicity, can develop under both natural and anthropogenic conditions. Forest fires, vegetation decomposition, microbial activity and oil spills can all promote hydrophobic behaviour in surrounding soils. Hydrophobicity can stabilize soil organic matter pools and decrease evapotranspiration, but there are many negative impacts of hydrophobicity as well: increased erosion of topsoil, an increasingly scarce resource; increased runoff, which can lead to flooding; and decreased infiltration, which directly affects plant health. The degree of hydrophobicity expressed by soil can vary greatly within a small area, depending partly on the type and severity of the disturbance as well as on temporal factors such as water content and microbial activity. To date, many laboratory investigations into soil hydrophobicity have focused on smooth particle surfaces. As a result, our understanding of how hydrophobicity develops on rough surfaces of macro, micro and nano-particulates is limited; we are unable to predict with certainty how these soil particles will behave on contact with water. Surface chemistry is the main consideration when predicting hydrophobic behaviour of smooth solids, but for particles with rough surfaces, hydrophobicity is believed to develop as a combination of surface chemistry and topography. Topography may reflect both the arrangement (aggregation) of soil particles and the distribution of materials adsorbed on particulate surfaces. Patch-wise or complete coverage of rough soil particles by hydrophobic material may result in solid/water contact angles ≥150° , at which point the soil may be classified as super-hydrophobic. Here we present a critical review of the research to date on the effects of heterogeneity and surface roughness on soil hydrophobicity in which we discuss recent advances, current trends, and future research areas. References: Callies, M., Y. Chen, F. Marty, A. Pépin and D. Quéré. 2005. Microfabricated

  8. Plasma-induced polymerization for enhancing paper hydrophobicity. (United States)

    Song, Zhaoping; Tang, Jiebin; Li, Junrong; Xiao, Huining


    Hydrophobic modification of cellulose fibers was conducted via plasma-induced polymerization in an attempt to graft the hydrophobic polymer chains on paper surface, this increasing the hydrophobicity of paper. Two hydrophobic monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA), were grafted on cellulose fibers, induced by atmospheric cold plasma. Various influencing factors associated with the plasma-induced grafting were investigated. Contact-angle measurement, Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used to ascertain the occurrence of the grafting and characterized the changes of the cellulose fiber after modification. The results showed that the hydrophobicity of the modified paper sheet was improved significantly after the plasma-induced grafting. The water contact angle on the paper surface reached up to 130°. The morphological differences between modified and unmodified samples were also revealed by SEM observation. The resulting paper is promising as a green-based packaging material.

  9. Protein-induced bilayer Perturbations: Lipid ordering and hydrophobic coupling

    DEFF Research Database (Denmark)

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


    The host lipid bilayer is increasingly being recognized as an important non-specific regulator of membrane protein function. Despite considerable progress the interplay between hydrophobic coupling and lipid ordering is still elusive. We use electron spin resonance (ESR) to study the interaction...... and hydrophobic mismatch. Our findings also show that at high protein:lipid ratios the lipids are motionally restricted but not completely immobilized. Both exchange on and off rate values for the lipid ↔ gramicidin interaction are lowest at optimal hydrophobic matching. Hydrophobic mismatch of few Å results...... in up to 10-fold increased exchange rates as compared to the ‘optimal’ match situation pointing to the regulatory role of hydrophobic coupling in lipid–protein interactions....

  10. Hydrophobic plug functions as a gate in voltage-gated proton channels. (United States)

    Chamberlin, Adam; Qiu, Feng; Rebolledo, Santiago; Wang, Yibo; Noskov, Sergei Y; Larsson, H Peter


    Voltage-gated proton (Hv1) channels play important roles in the respiratory burst, in pH regulation, in spermatozoa, in apoptosis, and in cancer metastasis. Unlike other voltage-gated cation channels, the Hv1 channel lacks a centrally located pore formed by the assembly of subunits. Instead, the proton permeation pathway in the Hv1 channel is within the voltage-sensing domain of each subunit. The gating mechanism of this pathway is still unclear. Mutagenic and fluorescence studies suggest that the fourth transmembrane (TM) segment (S4) functions as a voltage sensor and that there is an outward movement of S4 during channel activation. Using thermodynamic mutant cycle analysis, we find that the conserved positively charged residues in S4 are stabilized by countercharges in the other TM segments both in the closed and open states. We constructed models of both the closed and open states of Hv1 channels that are consistent with the mutant cycle analysis. These structural models suggest that electrostatic interactions between TM segments in the closed state pull hydrophobic residues together to form a hydrophobic plug in the center of the voltage-sensing domain. Outward S4 movement during channel activation induces conformational changes that remove this hydrophobic plug and instead insert protonatable residues in the center of the channel that, together with water molecules, can form a hydrogen bond chain across the channel for proton permeation. This suggests that salt bridge networks and the hydrophobic plug function as the gate in Hv1 channels and that outward movement of S4 leads to the opening of this gate.

  11. Analysis of GTPases carrying hydrophobic amino acid substitutions in lieu of the catalytic glutamine: implications for GTP hydrolysis. (United States)

    Mishra, Rajeev; Gara, Sudheer Kumar; Mishra, Shambhavi; Prakash, Balaji


    Ras superfamily GTP-binding proteins regulate important signaling events in the cell. Ras, which often serves as a prototype, efficiently hydrolyzes GTP in conjunction with its regulator GAP. A conserved glutamine plays a vital role in GTP hydrolysis in most GTP-binding proteins. Mutating this glutamine in Ras has oncogenic effects, since it disrupts GTP hydrolysis. The analysis presented here is of GTP-binding proteins that are a paradox to oncogenic Ras, since they have the catalytic glutamine (Glncat) substituted by a hydrophobic amino acid, yet can hydrolyze GTP efficiently. We term these proteins HAS-GTPases. Analysis of the amino acid sequences of HAS-GTPases reveals prominent presence of insertions around the GTP-binding pocket. Homology modeling studies suggest an interesting means to achieve catalysis despite the drastic hydrophobic substitution replacing the key Glncat of Ras-like GTPases. The substituted hydrophobic residue adopts a "retracted conformation," where it is positioned away from the GTP, as its role in catalysis would be unproductive. This conformation is further stabilized by interactions with hydrophobic residues in its vicinity. These interacting residues are strongly conserved and hydrophobic in all HAS-GTPases, and correspond to residues Asp92 and Tyr96 of Ras. An experimental support for the "retracted conformation" of Switch II arises from the crystal structures of Ylqf and hGBP1. This conformation allows us to hypothesize that, unlike in classical GTPases, catalytic residues could be supplied by regions other than the Switch II (i.e., either the insertions or a neighboring domain).

  12. Hydrophobic Interactions Are Key To Drive the Association of Tapasin with Peptide Transporter Subunit TAP2. (United States)

    Rufer, Elke; Kägebein, Danny; Leonhardt, Ralf M; Knittler, Michael R


    The transporter associated with Ag processing (TAP) translocates proteasomally derived cytosolic peptides into the endoplasmic reticulum. TAP is a central component of the peptide-loading complex (PLC), to which tapasin (TPN) recruits MHC class I (MHC I) and accessory chaperones. The PLC functions to facilitate and optimize MHC I-mediated Ag presentation. The heterodimeric peptide transporter consists of two homologous subunits, TAP1 and TAP2, each of which contains an N-terminal domain (N-domain) in addition to a conserved transmembrane (TM) core segment. Each N-domain binds to the TM region of a single TPN molecule, which recruits one MHC I molecule to TAP1 and/or TAP2. Although both N-domains act as TPN-docking sites, various studies suggest a functional asymmetry within the PLC resulting in greater significance of the TAP2/TPN interaction for MHC loading. In this study, we demonstrate that the leucine-rich hydrophobic sequence stretches (with the central leucine residues L20 and L66) in the first and second TM helix of TAP2 form a functional unit acting as a docking site for optimal TPN/MHC I recruitment, whereas three distinct highly conserved arginine and/or aspartate residues inside or flanking these TM helices are dispensable. Moreover, we show that the physical interaction between TAP2 and TPN is disrupted by benzene, a compound known to interfere with hydrophobic interactions, such as those between pairing leucine zippers. No such effects were observed for the TAP1/TAP2 interaction or the complex formation between TPN and MHC I. We propose that TAP/TPN complex formation is driven by hydrophobic interactions via leucine zipper-like motifs.

  13. Adsorption of hydrophobically modified polyacrylic acid on a hydrophobic surface : hysteresis caused by an electrostatic adsorption barrier

    NARCIS (Netherlands)

    Göbel, J.G.; Besseling, N.A.M.; Cohen Stuart, M.A.; Poncet, C.


    The adsorption of hydrophobically modified polyacrylic acid (HM-PAAc) has been compared to the adsorption of unmodified polymers by means of reflectometry. The polymers were adsorbed onto a noncharged hydrophobic polystyrene surface. The adsorption kinetics of both types of polymer is the same until

  14. Rheological Properties of Hydrophobically Associating Polyacrylamide Solution

    Institute of Scientific and Technical Information of China (English)


    A temperature-resistant, salt-tolerant polyacrylamide, hydrophobically associating polymer (HAP), was synthesized in the State Key Laboratory of Heavy Oil Processing. The rheological behavior of HAP solution was investigated by means of flow experiments in porous media and by using a HAAKE RS600 rheometer. The results of Nuclepore membrane filtration showed that filtration time increased sharply when the critical association concentration was reached. Shear rate had a greater impact on viscosity and shear stress with increasing HAP concentration. The HAP solution with a concentration of 100 mg/L (salinity 32,868 mg/L) exhibited negative thixotropy. However, at the same salinity the HAP solution showed thixotropy and its viscosity became greater when the polymer concentration increased to 1,500 mg/L.The flow experiments in cemented core samples indicated that the resistance factor and residual resistance factor of the HAP solution were 31.8 and 12 when polymer concentration and salinity were 1,500 mg/L, 32,868 mg/L at 85℃ respectively,which is favorable for flooding application. Such factors of partially hydrolyzed polyacrylamide 3530S were merely 3.14 and 1.71, so it could not be applied to polymer flooding in the oilfield with high temperature and high salinity.

  15. Sequestration of hydrophobic organic contaminants by geosorbents (United States)

    Luthy, Richard G.; Aiken, George R.; Brusseau, Mark L.; Cunningham, Scott D.; Gschwend, Philip M.; Pignatello, Joseph J.; Reinhard, Martin; Traina, Samuel J.; Weber, Walter J.; Westall, John C.


    The chemical interactions of hydrophobic organic contaminants (HOCs) with soils and sediments (geosorbents) may result in strong binding and slow subsequent release rates that significantly affect remediation rates and endpoints. The underlying physical and chemical phenomena potentially responsible for this apparent sequestration of HOCs by geosorbents are not well understood. This challenges our concepts for assessing exposure and toxicity and for setting environmental quality criteria. Currently there are no direct observational data revealing the molecular-scale locations in which nonpolar organic compounds accumulate when associated with natural soils or sediments. Hence macroscopic observations are used to make inferences about sorption mechanisms and the chemical factors affecting the sequestration of HOCs by geosorbents. Recent observations suggest that HOC interactions with geosorbents comprise different inorganic and organic surfaces and matrices, and distinctions may be drawn along these lines, particularly with regard to the roles of inorganic micropores, natural sorbent organic matter components, combustion residue particulate carbon, and spilled organic liquids. Certain manipulations of sorbates or sorbent media may help reveal sorption mechanisms, but mixed sorption phenomena complicate the interpretation of macroscopic data regarding diffusion of HOCs into and out of different matrices and the hysteretic sorption and aging effects commonly observed for geosorbents. Analytical characterizations at the microscale, and mechanistic models derived therefrom, are needed to advance scientific knowledge of HOC sequestration, release, and environmental risk.

  16. Size selective hydrophobic adsorbent for organic molecules (United States)

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


    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 and C., and preferably between about and 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.

  17. Solubilization of Hydrophobic Dyes in Surfactant Solutions

    Directory of Open Access Journals (Sweden)

    Ali Reza Tehrani-Bagha


    Full Text Available In this paper, the use of surfactants for solubilization of hydrophobic organic dyes (mainly solvent and disperse dyes has been reviewed. The effect of parameters such as the chemical structures of the surfactant and the dye, addition of salt and of polyelectrolytes, pH, and temperature on dye solubilization has been discussed. Surfactant self-assemble into micelles in aqueous solution and below the concentration where this occurs—the critical micelle concentration (CMC—there is no solubilization. Above the CMC, the amount of solubilized dye increases linearly with the increase in surfactant concentration. It is demonstrated that different surfactants work best for different dyes. In general, nonionic surfactants have higher solubilization power than anionic and cationic surfactants. It is likely that the reason for the good performance of nonionic surfactants is that they allow dyes to be accommodated not only in the inner, hydrocarbon part of the micelle but also in the headgroup shell. It is demonstrated that the location of a dye in a surfactant micelle can be assessed from the absorption spectrum of the dye-containing micellar solution.

  18. Functional analysis of the conserved hydrophobic gate region of the magnesium transporter CorA. (United States)

    Svidová, Soňa; Sponder, Gerhard; Schweyen, Rudolf J; Djinović-Carugo, Kristina


    The Leu294 residue in the cytoplasmic neck of Thermotoga maritima CorA is considered to be the main gate for Mg2+ transport. We created three site-directed mutants at this position: in the Leu294Asp and Leu294Gly mutants we observed a defect in closing of the pore, while in the Leu294Arg mutant not only gating, but also the regulation of Mg2+ uptake was affected. Our results confirmed the importance of the Leu294 for gating of Mg2+ transport and in addition revealed the influence of the charge and structural features of the amino acid residues on the gating mechanism. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Surface Hydrophobicity Causes SO2 Tolerance in Lichens (United States)

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


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

  20. Electrokinetic Instability near Charge-Selective Hydrophobic Surfaces

    CERN Document Server

    Shelistov, V S; Ganchenko, G S


    The influence of the texture of a hydrophobic surface on the electro-osmotic slip of the second kind and the electrokinetic instability near charge-selective surfaces (permselective membranes, electrodes, or systems of micro- and nanochannels) is investigated theoretically using a simple model based on the Rubinstein-Zaltzman approach. A simple formula is derived to evaluate the decrease in the instability threshold due to hydrophobicity. The study is complemented by numerical investigations both of linear and nonlinear instabilities near a hydrophobic membrane surface. Theory predicts a significant enhancement of the ion flux to the surface and shows a good qualitative agreement with the available experimental data.

  1. Hydrophobic and hydrophilic interactions in aqueous mixtures of alcohols at a hydrophobic surface. (United States)

    Ballal, Deepti; Chapman, Walter G


    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.

  2. Surface hydrophobization by electrostatic deposition of hydrophobically modified poly(acrylates) and their complexes with surfactants (United States)

    Gîfu, Ioana Cătălina; Maxim, Monica Elisabeta; Iovescu, Alina; Simion, Elena Livia; Aricov, Ludmila; Anastasescu, Mihai; Munteanu, Cornel; Anghel, Dan-Florin


    The present study demonstrates the hydrophobic effect of poly(electrolyte) multilayer films when they are alkyl-grafted and complexed or not with surfactants. For this purpose, sodium hydrophobically modified poly(acrylates) (PACnNa, n = 10, 18) or their anionic complexes with alkyltrimethylammonium bromides (CxTAB, x = 10, 12, 14, 18), and the cationic poly(diallyldimethyldiammonium chloride) (PDDAMAC) are assembled by layer-by-layer deposition on a glass substrate. Contact angle (CA) measurements reveal that films constructed with PACnNa-CxTAB/PDADMAC are superior water repellants than those of PACnNa/PDADMAC. For example, the highest CA is obtained for the PAC18Na-C18TAB/PDADMAC. Moreover, it has been observed that the CA increases with the alkyl chain length of PACnNa and of surfactant. The film roughness and thickness have the same trend as wettability. Thinner and less coarse films are obtained by NaCl addition, as witnessed by SEM and AFM.

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

    Energy Technology Data Exchange (ETDEWEB)

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


    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

  4. Reduction of microbial biofilm formation using hydrophobic nano ...

    African Journals Online (AJOL)


    Apr 3, 2015 ... formation using a nano-hydrophobic coating on cooling tower fill materials – polypropylene cooling tower fill material ... of microorganisms to attach to wet surfaces, multiply and embed ..... Interfaces 5 (19) 9322–9329.

  5. Impact of Hydrophobic Pollutants' Behavior on Occupational and Environmental Health

    Directory of Open Access Journals (Sweden)

    Ijeoma Kanu


    Full Text Available This paper reviews the influence of hydrophobic pollutant behavior on environmental hazards and risks. The definition and examples of hydrophobic pollutants are given as a guide to better understand the sources of release and the media of dispersion in the environment. The properties and behavior of hydrophobic pollutants are described and their influence on environmental hazard and risk is reviewed and evaluated. The overall outcome of the assessment and evaluation showed that all hydrophobic pollutants are hazardous and risky to all organisms, including man. Their risk effects are due to their inherent persistence, bioaccumulation potential, environmental mobility, and reactivity. Their hazardous effects on organisms occur at varying spatial and temporal degrees of emissions, toxicities, exposures, and concentrations.

  6. Heterocoagulation of hydrophobic particle and bubble during microflotation

    NARCIS (Netherlands)

    Mishchuk, N.A.; Koopal, L.K.; Dukhin, S.S.


    The laws of the interaction between a gas bubble and a hydrophobic solid particle were studied. The range of the system parameters that can ensure the heterocoagulation of the particle and the bubble was determined.

  7. Numerical simulation of electroosmotic flow in hydrophobic microchannels

    Institute of Scientific and Technical Information of China (English)


    Electroosmotic flow(EOF) is a promising way for driving and mixing fluids in microfluidics.For the parallel-plate microchannel with the hydrophobic surface, this paper solved the governing equations using the finite element method(FEM), and the effects of microchannel height, electric strength and ionic concentration on EOF were thus investigated.The simulation indicates that the transient characteristics of EOF are similar in hydrophobic and hydrophilic microchannels, the steady time of EOF is proportional to the square of microchannel height, and the scale is microsecond.EOF velocity is proportional to the electric strength and independent of the channel height, and decreases slowly with the ionic concentration, which is lower than that in hydrophilic microchannel due to the presence of slip length in hydrophobic microchannel.The results can provide valuable insights into the optimal design of microchannel surfaces to achieve accurate EOF control in hydrophobic microchannel.

  8. Numerical simulation of electroosmotic flow in hydrophobic microchannels

    Institute of Scientific and Technical Information of China (English)

    YANG DaYong; LIU Ying


    Electroosmotic flow(EOF)is a promising way for driving and mixing fluids in microfluidics.For the parallel-plate microchannel with the hydrophobic surface,this paper solved the governing equations using the finite element method(FEM),and the effects of microchannel height,electric strength and ionic concentration on EOF were thus investigated.The simulation indicates that the transient characteristics of EOF are similar in hydrophobic and hydrophilic microchannels,the steady time of EOF is proportional to the square of microchannel height,and the scale is microsecond.EOF velocity is proportional to the electric strength and independent of the channel height,and decreases slowly with the ionic concentration,which is lower than that in hydrophilic rnicrochannel due to the presence of slip length in hydrophobic microchannel.The results can provide valuable insights into the optimal design of microchannel surfaces to achieve accurate EOF control in hydrophobic microchannel.

  9. Hydrophobic kenaf nanocrystalline cellulose for the binding of curcumin. (United States)

    Zainuddin, Norhidayu; Ahmad, Ishak; Kargarzadeh, Hanieh; Ramli, Suria


    Nanocrystalline cellulose (NCC) extracted from lignocellulosic materials has been actively investigated as a drug delivery excipients due to its large surface area, high aspect ratio, and biodegradability. In this study, the hydrophobically modified NCC was used as a drug delivery excipient of hydrophobic drug curcumin. The modification of NCC with a cationic surfactant, cetyl trimethylammonium bromide (CTAB) was used to modulate the loading of hydrophobic drugs that would not normally bind to NCC. The FTIR, Elemental analysis, XRD, TGA, and TEM were used to confirm the modification of NCC with CTAB. The effect of concentration of CTAB on the binding efficiency of hydrophobic drug curcumin was investigated. The amounts of curcumin bound onto the CTAB-NCC nanoparticles were analyzed by UV-vis Spectrophotometric. The result showed that the modified CTAB-NCC bound a significant amount of curcumin, in a range from 80% to 96% curcumin added. Nevertheless, at higher concentration of CTAB resulted in lower binding efficiency.

  10. Inverse colloidal crystal membranes for hydrophobic interaction membrane chromatography. (United States)

    Vu, Anh T; Wang, Xinying; Wickramasinghe, S Ranil; Yu, Bing; Yuan, Hua; Cong, Hailin; Luo, Yongli; Tang, Jianguo


    Hydrophobic interaction membrane chromatography has gained interest due to its excellent performance in the purification of humanized monoclonal antibodies. The membrane material used in hydrophobic interaction membrane chromatography has typically been commercially available polyvinylidene fluoride. In this contribution, newly developed inverse colloidal crystal membranes that have uniform pores, high porosity and, therefore, high surface area for protein binding are used as hydrophobic interaction membrane chromatography membranes for humanized monoclonal antibody immunoglobulin G purification. The capacity of the inverse colloidal crystal membranes developed here is up to ten times greater than commercially available polyvinylidene fluoride membranes with a similar pore size. This work highlights the importance of developing uniform pore size high porosity membranes in order to maximize the capacity of hydrophobic interaction membrane chromatography. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Hydrophobic composition based on mixed-molecular weight polyethylene (United States)

    Gorlenko, Nikolay; Debelova, Natalya; Sarkisov, Yuriy; Volokitin, Gennadiy; Zavyalova, Elena; Lapova, Tatyana


    The paper presents investigations of compositions based on low and high molecular weight polyethylene so as to synthesize a hydrophobic composition for moisture protection of timber. X-ray phase analysis and measurements of the tear-off force of hydrophobic coating needed to apply to the timber surface and the limiting wetting angle are carried out to detect the hydrophobic, adhesive, electrophysical, and physicochemical properties of compositions. Kinetic dependencies are given for moisture absorption of timber specimens. It is shown that the preliminary formation of the texture by the surface patterning or its treatment with low-temperature plasma with the following protective coating results in the improvement of hydrophobic properties of the suggested compositions. These compositions can be used in the capacity of water repellents to protect building materials from moisture including restoration works.

  12. Heterocoagulation of hydrophobic particle and bubble during microflotation

    NARCIS (Netherlands)

    Mishchuk, N.A.; Koopal, L.K.; Dukhin, S.S.


    The laws of the interaction between a gas bubble and a hydrophobic solid particle were studied. The range of the system parameters that can ensure the heterocoagulation of the particle and the bubble was determined.

  13. Hydrophobic mismatch sorts SNARE proteins into distinct membrane domains (United States)

    Milovanovic, Dragomir; Honigmann, Alf; Koike, Seiichi; Göttfert, Fabian; Pähler, Gesa; Junius, Meike; Müllar, Stefan; Diederichsen, Ulf; Janshoff, Andreas; Grubmüller, Helmut; Risselada, Herre J.; Eggeling, Christian; Hell, Stefan W.; van den Bogaart, Geert; Jahn, Reinhard


    The clustering of proteins and lipids in distinct microdomains is emerging as an important principle for the spatial patterning of biological membranes. Such domain formation can be the result of hydrophobic and ionic interactions with membrane lipids as well as of specific protein-protein interactions. Here using plasma membrane-resident SNARE proteins as model, we show that hydrophobic mismatch between the length of transmembrane domains (TMDs) and the thickness of the lipid membrane suffices to induce clustering of proteins. Even when the TMDs differ in length by only a single residue, hydrophobic mismatch can segregate structurally closely homologous membrane proteins in distinct membrane domains. Domain formation is further fine-tuned by interactions with polyanionic phosphoinositides and homo and heterotypic protein interactions. Our findings demonstrate that hydrophobic mismatch contributes to the structural organization of membranes.

  14. Effect of Hydrophobic Coating on Hagen-Poiseuille Flows

    Directory of Open Access Journals (Sweden)

    Alejandro Ríos-Rodríguez


    Full Text Available The effect of a hydrophobic coating on the flow through circular pipes with Newtonian fluids has been investigated. Velocity fields inside a pipe were experimentally determined by the particle image velocimetry (PIV technique. The test fluid presented a viscosity of about sixty times higher than water viscosity. Two glass pipe configurations were used: one uncoated and another covered with an extremely hydrophobic commercial product. Comparisons between coated and uncoated pipes were made at similar Reynolds (Re numbers, all in the laminar regime (70-250. Results show that the hydrophobic effect consists in an observable slip velocity at the wall, with a reduction in shear rate near the pipe boundary. Pressure drop values were estimated from a modified Hagen-Poiseuille equation, taking into consideration the non-zero velocity at the boundary for both set of experiments, and the results show a 20% reduction in the pressure drop for the hydrophobic wall compared with the uncoated pipe case.

  15. Estimation of atomic hydrophobicities using molecular dynamics simulation of peptides (United States)

    Held, Marie; Nicolau, Dan V.


    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.

  16. Hydrophobic and electrostatic cell surface properties of Cryptosporidium parvum.


    Drozd, C; Schwartzbrod, J


    Microbial adhesion to hydrocarbons and microelectrophoresis were investigated in order to characterize the surface properties of Cryptosporidium parvum. Oocysts exhibited low removal rates by octane (only 20% on average), suggesting that the Cryptosporidium sp. does not demonstrate marked hydrophobic properties. A zeta potential close to -25 mV at pH 6 to 6.5 in deionized water was observed for the parasite. Measurements of hydrophobicity and zeta potential were performed as a function of pH ...

  17. Effect of surface charge on hydrophobicity levels of insulating materials

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Villa, V.M.; Ponce-Velez, M.A.; Valle-Jaime, E.; Fierro-Chavez, J.L. [Instituto de Investigaciones Electricas, Mor (Mexico). Unidad de Materiales Electricos


    A correlation between the hydrophobic characteristics and accumulation of static charge on several insulating surfaces (ceramic and non- ceramic) is studied. Although numerous experimental studies on the loss and recovery of hydrophobicity on insulator surfaces have been carried out, no efforts for establishing a correlation between such hydrophobic properties and the presence of surface charge have yet been made, especially when attention is paid to ceramic surfaces. This experiment consists of simultaneous measurements of surface charge decay and contact angle recovery against time on samples previously exposed to corona impingement; a comparison between charge decay and hydrophobicity recovery trends is then made. From the data obtained, a lowering of the original hydrophobicity level for each material as a consequence of surface charge accumulation is identified. The decay of surface charge and the corresponding recovery of the initial hydrophobic characteristics with time are observed. Loss and recovery of hydrophobicity resulting from surface charging and charge decay, respectively, are identified as mechanisms occurring not only on polymeric surfaces, but also on ceramic ones. From a number of laboratory studies it has been confirmed, and extensively reported by several researchers, that surface charging of insulators due to electrical activity (partial discharging) can be achieved. Based on the above, as well as on the results obtained from this experimental work, surface charging of insulators is a phenomenon which may occur under realistic operational conditions, and is therefore proposed as a factor responsible for the loss of the initial highly hydrophobic characteristics of polymeric insulators and coatings, in addition to other well established mechanisms. (author)

  18. Facile Synthesis of Hydrophobic Fluoroalkyl Functionalized Silsesquioxane Nanostructures (Postprint) (United States)


    structure is highly disordered, and only one component of this disorder is shown in Fig. 2. The hydrophobicity and oleophobicity of the F-POSS solids...behavior, with contact angles greater than 90u. Therefore, these solids are considered hydrophobic and, to some extent, oleophobic . Water drops did not...functionality induces wetting by water, but does not affect the oleophobicity . In conclusion, we have prepared a new class of fluorinated POSS (F-POSS) materials

  19. Forces between Hydrophobic Solids in Concentrated Aqueous Salt Solution


    Mastropietro, Dean J; Ducker, William A.


    Much research has focused on the discovery and description of long-ranged forces between hydrophobic solids immersed in water. Here we show that the force between high contact-angle solids in concentrated salt solution (1 M KCl) agrees very well with van der Waals forces calculated from Lifshitz theory for separations greater than 5 nm. The hydrophobic solids are octadecyltrichlorosilane-coated glass, with an advancing contact angle of 108 degrees. Thus, in 1 M salt solution, it is unnecessar...

  20. Why water reorientation slows without iceberg formation around hydrophobic solutes. (United States)

    Laage, Damien; Stirnemann, Guillaume; Hynes, James T


    The dynamics of water molecules next to hydrophobic solutes is investigated, specifically addressing the recent controversy raised by the first time-resolved observations, which concluded that some water molecules are immobilized by hydrophobic groups, in strong contrast to previous NMR conclusions. Through molecular dynamics simulations and an analytic jump reorientation model, we identify the water reorientation mechanism next to a hydrophobic solute and provide evidence that no water molecules are immobilized by hydrophobic solutes. Their moderate rotational slowdown compared to bulk water (e.g., by a factor of less than 2 at low solute concentration) is mainly due to slower hydrogen-bond exchange. The slowdown is quantitatively described by a solute excluded volume effect at the transition state for the key hydrogen-bond exchange in the reorientation mechanism. We show that this picture is consistent with both ultrafast anisotropy and NMR experimental results and that the transition state excluded volume theory yields quantitative predictions of the rotational slowdown for diverse hydrophobic solutes of varying size over a wide concentration range. We also explain why hydrophobic groups slow water reorientation less than do some hydrophilic groups.

  1. Condensation Dynamics on Mimicked Metal Matrix Hydrophobic Nanoparticle-Composites (United States)

    Damle, Viraj; Sun, Xiaoda; Rykaczewski, Konrad


    Use of hydrophobic surfaces promotes condensation in the dropwise mode, which is significantly more efficient than the common filmwise mode. However, limited longevity of hydrophobic surface modifiers has prevented their wide spread use in industry. Recently, metal matrix composites (MMCs) having microscale hydrophobic heterogeneities dispersed in hydrophilic metal matrix have been proposed as durable and self-healing alternative to hydrophobic surface coatings interacting with deposited water droplets. While dispersion of hydrophobic microparticles in MMC is likely to lead to surface flooding during condensation, the effect of dispersion of hydrophobic nanoparticles (HNPs) with size comparable to water nuclei critical radii and spacing is not obvious. To this end, we fabricated highly ordered arrays of Teflon nanospheres on silicon substrates that mimic the top surface of the MMCs with dispersed HNPs. We used light and electron microscopy to observe breath figures resulting from condensation on these surfaces at varied degrees of subcooling. Here, we discuss the relation between the droplet size distribution, Teflon nanosphere diameter and spacing, and condensation mode. KR acknowledges startup funding from ASU.

  2. Hydrophobicity of soil samples and soil size fractions

    Energy Technology Data Exchange (ETDEWEB)

    Lowen, H.A.; Dudas, M.J. [Alberta Univ., Edmonton, AB (Canada). Dept. of Renewable Resources; Roy, J.L. [Imperial Oil Resources Canada, Calgary, AB (Canada); Johnson, R.L. [Alberta Research Council, Vegreville, AB (Canada); McGill, W.B. [Alberta Univ., Edmonton, AB (Canada). Dept. of Renewable Resources


    The inability of dry soil to absorb water droplets within 10 seconds or less is defined as soil hydrophobicity. The severity, persistence and circumstances causing it vary greatly. There is a possibility that hydrophobicity in Alberta is a symptom of crude oil spills. In this study, the authors investigated the severity of soil hydrophobicity, as determined by the molarity of ethanol droplet test (MED) and dichloromethane extractable organic (DEO) concentration. The soil samples were collected from pedons within 12 hydrophobic soil sites, located northeast from Calgary to Cold Lake, Alberta. All the sites were located at an elevation ranging from 450 metres to 990 metres above sea level. The samples contained compounds from the Chernozemic, Gleysolic, Luvisolic, and Solonetzic soil orders. The results obtained indicated that the MED and DEO were positively correlated in whole soil samples. No relationships were found between MED and DEO in soil samples divided in soil fractions. More severe hydrophobicity and lower DEO concentrations were exhibited in clay- and silt-sized particles in the less than 53 micrometres, when compared to the samples in the other fraction (between 53 and 2000 micrometres). It was concluded that hydrophobicity was not restricted to a particular soil particle size class. 5 refs., 4 figs.

  3. Highly hydrophobic materials for ArF immersion lithography (United States)

    Takebe, Yoko; Shirota, Naoko; Sasaki, Takashi; Murata, Koichi; Yokokoji, Osamu


    In immersion lithography, the impact of water on resist performance and the possibility of damage to the lens by the components eluted from the resist material are seriously concern. And much work has shown that controlling the water-resist interface is critical to enabling high scan rates. Many topcoat materials have been developed to control the aforementioned interfacial properties. Developable topcoats have been particularly investigated as suitable candidates for its applicability to the resist developing process. Achieving the balance between the low surface energy required for higher receding contact angle and the base solubility for topcoat removal is challenging. We have already reported FUGU polymer which have partially fluorinated monocyclic structure and hexafluoroalcohol(HFA) group and showed that its developer solubility was excellent but hydrophobicity was insufficient for high scan rate. We have also reported that co-polymers of FUGU and highly fluorinated monomers which have perfluorinated cyclic structure had sufficient hydrophobicity but lower developer solubility. We have found that it was difficult to use these copolymers in themselves as topcoat. But by blending of moderate amount of these copolymers into FUGU polymer, we have finally obtained highly hydrophobic developer-soluble topcoat. Hydrophobicity can be controlled by blending ratio. Furthermore we have newly successfully synthesized a series of fluoropolymers, FIT polymer partially fluorinated monocyclic structure and having carboxylic acid group as developer-soluble unit. When FIT polymer as well as FUGU polymer, was blended to highly hydrophobic copolymer, the blended polymer also showed higher hydrophobicity keeping sufficient developer solubility.

  4. Vector description of electric and hydrophobic interactions in protein homodimers. (United States)

    Mozo-Villarías, Angel; Cedano, Juan; Querol, Enrique


    This article describes the formation of homodimers from their constituting monomers, based on the rules set by a simple model of electric and hydrophobic interactions. These interactions are described in terms of the electric dipole moment (D) and hydrophobic moment vectors (H) of proteins. The distribution of angles formed by the two dipole moments of monomers constituting dimers were analysed, as well as the distribution of angles formed by the two hydrophobic moments. When these distributions were fitted to Gaussian curves, it was found that for biological dimers, the D vectors tend mostly to adopt a perpendicular arrangement with respect to each other, in which the constituting dipoles have the least interaction. A minor population tends towards an antiparallel arrangement implying maximum electric attraction. Also in biological dimers, the H vectors of most monomers tend to interact in such a way that the total hydrophobic moment of the dimer increases with respect to those of the monomers. This shows that hydrophobic moments have a tendency to align. In dimers originating in the crystallisation process, the distribution of angles formed by both hydrophobic and electric dipole moments appeared rather featureless, probably because of unspecific interactions in the crystallisation processes. The model does not describe direct interactions between H and D vectors although the distribution of angles formed by both vectors in dimers was analysed. It was found that in most cases these angles tended to be either small (both moments aligned parallel to each other) or large (antiparallel disposition).

  5. Binary Assignments of Amino Acids from Pattern Conservation

    CERN Document Server

    Irbäck, A; Irb\\"ack, Anders; Potthast, Frank


    We develop a simple optimization procedure for assigning binary values to the amino acids. The binary values are determined by a maximization of the degree of pattern conservation in groups of closely related protein sequences. The maximization is carried out at fixed composition. For compositions approximately corresponding to an equipartition of the residues, the optimal encoding is found to be strongly correlated with hydrophobicity. The stability of the procedure is demonstrated. Our calculations are based upon sequences in the SWISS-PROT database.

  6. The adsorption of hydrophobically modified carboxymethylcellulose on a hydrophobic solid: effects of pH and ionic strength.

    NARCIS (Netherlands)

    Cohen Stuart, M.A.; Fokkink, R.G.; Horst, van der P.M.; Lichtenbelt, J.W.T.


    Abstract Carboxymethylcellulose with 1.2% dodecyl groups (per glucose unit) was prepared by amidation with dodecylamine. This polymer behaves as a hydrophobically modified polyelectrolyte with the following thickening properties which are determined from viscosity data. It adsorbs from aqueous

  7. Plasma membrane association of three classes of bacterial toxins is mediated by a basic-hydrophobic motif. (United States)

    Geissler, Brett; Ahrens, Sebastian; Satchell, Karla J F


    Plasma membrane targeting is essential for the proper function of many bacterial toxins. A conserved fourhelical bundle membrane localization domain (4HBM) was recently identified within three diverse families of toxins: clostridial glucosylating toxins, MARTX toxins and Pasteurella multocida-like toxins. When expressed in tissue culture cells or in yeast, GFP fusions to at least one 4HBM from each toxin family show significant peripheral membrane localization but with differing profiles. Both in vivo expression and in vitro binding studies reveal that the ability of these domains to localize to the plasma membrane and bind negatively charged phospholipids requires a basic-hydrophobic motif formed by the L1 and L3 loops. The different binding capacity of each 4HBM is defined by the hydrophobicity of an exposed residue within the motif. This study establishes that bacterial effectors utilize a normal host cell mechanism to locate the plasma membrane where they can then access their intracellular targets.

  8. Microplastics as a vector of hydrophobic contaminants: Importance of hydrophobic additives. (United States)

    Kwon, Jung-Hwan; Chang, Sein; Hong, Sang Hee; Shim, Won Joon


    Despite a recent boom in research on the environmental fate, distribution, and harmful effects of chemical substances associated with marine plastic debris, no consensus has been reached on whether chemicals originating from microplastics cause serious environmental harm. For the risk assessment of chemical contaminants associated with microplastics, it would be useful to group organic chemicals into 2 categories: additives and nonadditives. Whereas plastic particles are not likely to be diffuse sources of chemicals that are not intentionally added to plastic products, continuous leaching of additives would result in higher concentrations, at least at a local scale. Unlike plasticizers and flame retardants, which have been relatively well investigated, antioxidants and photostabilizers have been rarely studied, even though many of them are highly hydrophobic and are not readily biodegradable. More research on the fate and effects of chemicals via microplastics should focus on those additives. Integr Environ Assess Manag 2017;13:494-499. © 2017 SETAC. © 2017 SETAC.

  9. Role of hydrophobic and ionic forces in the movement of S4 of the Shaker potassium channel. (United States)

    Elliott, David J S; Neale, Edward J; Munsey, Tim S; Bannister, John P; Sivaprasadarao, Asipu


    Voltage-gated ion (K(+), Na(+), Ca(2+)) channels contain a pore domain (PD) surrounded by four voltage sensing domains (VSD). Each VSD is made up of four transmembrane helices, S1-S4. S4 contains 6-7 positively charged residues (arginine/lysine) separated two hydrophobic residues, whereas S1-S3 contribute to two negatively charged clusters. These structures are conserved among all members of the voltage-gated ion channel family and play essential roles in voltage gating. The role of S4 charged residues in voltage gating is well established: During depolarization, they move out of the membrane electric field, exerting a mechanical force on channel gates, causing them to open. However, the role of the intervening hydrophobic residues in voltage sensing is unclear. Here we studied the role of these residues in the prototypical Shaker potassium channel. We have altered the physicochemical properties of both charged and hydrophobic positions of S4 and examined the effect of these modifications on the gating properties of the channel. For this, we have introduced cysteines at each of these positions, expressed the mutants in Xenopus oocytes, and examined the effect of in situ addition of charge, via Cd(2+), on channel gating by two-electrode voltage clamp. Our results reveal a face of the S4 helix (comprising residues L358, L361, R365 and R368) where introduction of charge at hydrophobic positions destabilises the closed state and removal of charges from charged positions has an opposite effect. We propose that hydrophobic residues play a crucial role in limiting gating to a physiological voltage range.

  10. Single water entropy: hydrophobic crossover and application to drug binding. (United States)

    Sasikala, Wilbee D; Mukherjee, Arnab


    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.

  11. Meeting global conservation challenges (United States)


    Hot on the heels of last year's Sustainable Development Goals and the Paris Agreement, representatives from the global conservation community met to set the conservation agenda that will help to implement these targets.

  12. Conservation: Threatened by Luxury. (United States)

    Webb, Thomas J


    When animals are traded in lucrative international luxury markets, individuals really do matter to conservation. Identifying the intrinsic and extrinsic factors that make some species especially vulnerable to this kind of threat helps set guidelines for more effective conservation.

  13. A Novel Mode of Protein Kinase Inhibition Exploiting Hydrophobic Motifs of Autoinhibited Kinases

    Energy Technology Data Exchange (ETDEWEB)

    S Eathiraj; R Palma; M Hirschi; E Volckova; E Nakuci; J Castro; C Chen; T Chan; D France; M Ashwell


    Protein kinase inhibitors with enhanced selectivity can be designed by optimizing binding interactions with less conserved inactive conformations because such inhibitors will be less likely to compete with ATP for binding and therefore may be less impacted by high intracellular concentrations of ATP. Analysis of the ATP-binding cleft in a number of inactive protein kinases, particularly in the autoinhibited conformation, led to the identification of a previously undisclosed non-polar region in this cleft. This ATP-incompatible hydrophobic region is distinct from the previously characterized hydrophobic allosteric back pocket, as well as the main pocket. Generalized hypothetical models of inactive kinases were constructed and, for the work described here, we selected the fibroblast growth factor receptor (FGFR) tyrosine kinase family as a case study. Initial optimization of a FGFR2 inhibitor identified from a library of commercial compounds was guided using structural information from the model. We describe the inhibitory characteristics of this compound in biophysical, biochemical, and cell-based assays, and have characterized the binding mode using x-ray crystallographic studies. The results demonstrate, as expected, that these inhibitors prevent activation of the autoinhibited conformation, retain full inhibitory potency in the presence of physiological concentrations of ATP, and have favorable inhibitory activity in cancer cells. Given the widespread regulation of kinases by autoinhibitory mechanisms, the approach described herein provides a new paradigm for the discovery of inhibitors by targeting inactive conformations of protein kinases.

  14. Compatibility assessment of methods used for soil hydrophobicity determination (United States)

    Papierowska, Ewa; Szatyłowicz, Jan; Kalisz, Barbara; Łachacz, Andrzej; Matysiak, Wojciech; Debaene, Guillaume


    Soil hydrophobicity is a global problem. Effect of hydrophobicity on the soil environment is very important, because it can cause irreversible changes in ecosystems, leading to their complete degradation. The choice of method used to determine soil hydrophobicity is not simple because there is no obvious criteria for their selection. The results obtained by various methods may not be coherent and may indicate different degrees of hydrophobicity within the same soil sample. The objective of the study was to assess the compatibility between methods used to determine the hydrophobicity of selected organic and mineral-organic soils. Two groups of soil materials were examined: hydrogenic (87 soil samples) and autogenic soils (19 soil samples) collected from 41 soil profiles located in north-eastern Poland. Air-dry soil samples were used. Hydrophobicity was determined using two different methods i.e. on the basis of wetting contact angle measurements between water and solid phase of soils and with water drop penetration time tests. The value of the wetting contact angle was measured using the sessile drop method with optical goniometer CAM 100 (KSV Instruments). The wetting contact angles were determined at room temperature (20° C) within 10 min after sample preparation using standard procedure. In addition, water drop penetration time was measured. In order to compare the methods used for the assessment of soil hydrophobicity, the agreement between observers model was applied. In this model five categories of soil hydrophobicity were proposed according to the class used in the soil hydrofobicity classification based on water drop penetration time test. Based on this classification the values of the weighted kappa coefficients were calculated using SAS 9.4 (SAS Institute, 2013, Cary NC) for evaluating relationships between between the different investigated methods. The results of agreement were presented in forms of agreement charts. Research results indicated good

  15. Conservation Action Handbook. (United States)

    National Rifle Association, Washington, DC.

    Conservation problems are identified, with some suggestions for action. General areas covered are: Wildlife Conservation, Soil Conservation, Clean Water, Air Pollution Action, and Outdoor Recreation Action. Appendices list private organizations or agencies concerned with natural resource use and/or management, congressional committees considering…

  16. Hydrophobic core substitutions in calbindin D9k

    DEFF Research Database (Denmark)

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


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

  17. Hydrophobic and electrostatic cell surface properties of Cryptosporidium parvum. (United States)

    Drozd, C; Schwartzbrod, J


    Microbial adhesion to hydrocarbons and microelectrophoresis were investigated in order to characterize the surface properties of Cryptosporidium parvum. Oocysts exhibited low removal rates by octane (only 20% on average), suggesting that the Cryptosporidium sp. does not demonstrate marked hydrophobic properties. A zeta potential close to -25 mV at pH 6 to 6.5 in deionized water was observed for the parasite. Measurements of hydrophobicity and zeta potential were performed as a function of pH and ionic strength or conductivity. Hydrophobicity maxima were observed at extreme pH values, with 40% of adhesion of oocysts to octane. It also appeared that ionic strength (estimated by conductivity) could influence the hydrophobic properties of oocysts. Cryptosporidium oocysts showed a pH-dependent surface charge, with zeta potentials becoming less negative as pH was reduced, starting at -35 mV for alkaline pH and reaching 0 at isoelectric points for pH 2.5. On the other hand, variation of surface charge with respect to conductivity of the suspension tested in this work was quite small. The knowledge of hydrophobic properties and surface charge of the parasite provides information useful in, for example, the choice of various flocculation treatments, membrane filters, and cleaning agents in connection with oocyst recovery.

  18. Hydrophobic pulses predict transmembrane helix irregularities and channel transmembrane units

    Directory of Open Access Journals (Sweden)

    Claustres Mireille


    Full Text Available Abstract Background Few high-resolution structures of integral membranes proteins are available, as crystallization of such proteins needs yet to overcome too many technical limitations. Nevertheless, prediction of their transmembrane (TM structure by bioinformatics tools provides interesting insights on the topology of these proteins. Methods We describe here how to extract new information from the analysis of hydrophobicity variations or hydrophobic pulses (HPulses in the sequence of integral membrane proteins using the Hydrophobic Pulse Predictor, a new tool we developed for this purpose. To analyze the primary sequence of 70 integral membrane proteins we defined two levels of analysis: G1-HPulses for sliding windows of n = 2 to 6 and G2-HPulses for sliding windows of n = 12 to 16. Results The G2-HPulse analysis of 541 transmembrane helices allowed the definition of the new concept of transmembrane unit (TMU that groups together transmembrane helices and segments with potential adjacent structures. In addition, the G1-HPulse analysis identified helix irregularities that corresponded to kinks, partial helices or unannotated structural events. These irregularities could represent key dynamic elements that are alternatively activated depending on the channel status as illustrated by the crystal structures of the lactose permease in different conformations. Conclusions Our results open a new way in the understanding of transmembrane secondary structures: hydrophobicity through hydrophobic pulses strongly impacts on such embedded structures and is not confined to define the transmembrane status of amino acids.

  19. Characterization method of hydrophobic anti-icing coatings (United States)

    Morita, Katsuaki; Sakaue, Hirotaka


    For anti-icing, supercooled water should be removed before frozen onto the contact surface. We use a hydrophobic coating for anti-icing and introduce the static- and dynamic-evaluation methods. The methods describe the contact surface between the hydrophobic surface and a supercooled-water droplet. The former is based on the contact angle, and the latter is based on the sliding angle. The temperature factor is included in these models to evaluate the hydrophobic coating under the supercooled conditions. Four hydrophobic coatings are experimentally evaluated based on the static- and dynamic evaluation methods: C1-C3 (commercial fluorocarbon coatings), and Jaxa coating (original fluorocarbon coating). These are evaluated under the supercooled conditions of -10 to 0 °C. The static-evaluation shows variations in the temperature. However, change in the contact angle by the temperature is relatively small compared to that of the sliding angle for the dynamic evaluation. Only C3 and Jaxa coatings are tolerant to the sliding angle under the supercooled conditions tested. The dynamic evaluation shows that even if the coating is hydrophobic, the dynamic evaluation should be included to understand the characteristic of removal for a supercooled-water droplet.

  20. A New Concept to Transport a Droplet on Horizontal Hydrophilic/Hydrophobic Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Myong, Hyon Kook [Kookmin Univ., Seoul (Korea, Republic of)


    A fluid transport technique is a key issue for the development of microfluidic systems. In this paper, a new concept for transporting a droplet without external power sources is proposed and verified numerically. The proposed device is a heterogeneous surface which has both hydrophilic and hydrophobic horizontal surfaces. The numerical simulation to demonstrate the new concept is conducted by an in-house solution code (PowerCFD) which employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method (CICSAM) in a volume of fluid (VOF) scheme for phase interface capturing. It is found that the proposed concept for droplet transport shows superior performance for droplet transport in microfluidic systems.

  1. Role of a Hydrophobic Pocket in Polyamine Interactions with the Polyspecific Organic Cation Transporter OCT3. (United States)

    Li, Dan C; Nichols, Colin G; Sala-Rabanal, Monica


    Organic cation transporter 3 (OCT3, SLC22A3) is a polyspecific, facilitative transporter expressed in astrocytes and in placental, intestinal, and blood-brain barrier epithelia, and thus elucidating the molecular mechanisms underlying OCT3 substrate recognition is critical for the rational design of drugs targeting these tissues. The pharmacology of OCT3 is distinct from that of other OCTs, and here we investigated the role of a hydrophobic cavity tucked within the translocation pathway in OCT3 transport properties. Replacement of an absolutely conserved Asp by charge reversal (D478E), neutralization (D478N), or even exchange (D478E) abolished MPP(+) uptake, demonstrating this residue to be obligatory for OCT3-mediated transport. Mutations at non-conserved residues lining the putative binding pocket of OCT3 to the corresponding residue in OCT1 (L166F, F450L, and E451Q) reduced the rate of MPP(+) transport, but recapitulated the higher sensitivity pharmacological profile of OCT1. Thus, interactions of natural polyamines (putrescine, spermidine, spermine) and polyamine-like potent OCT1 blockers (1,10-diaminodecane, decamethonium, bistriethylaminodecane, and 1,10-bisquinuclidinedecane) with wild-type OCT3 were weak, but were significantly potentiated in the mutant OCT3s. Conversely, a reciprocal mutation in OCT1 (F161L) shifted the polyamine-sensitivity phenotype toward that of OCT3. Further analysis indicated that OCT1 and OCT3 can recognize essentially the same substrates, but the strength of substrate-transporter interactions is weaker in OCT3, as informed by the distinct makeup of the hydrophobic cleft. The residues identified here are key contributors to both the observed differences between OCT3 and OCT1 and to the mechanisms of substrate recognition by OCTs in general.

  2. Exactly conservation integrators

    Energy Technology Data Exchange (ETDEWEB)

    Shadwick, B.A.; Bowman, J.C.; Morrison, P.J. [Univ. of Texas, Austin, TX (United States)


    Traditional explicit numerical discretizations of conservative systems generically predict artificial secular drifts of any nonlinear invariants. In this work the authors present a general approach for developing explicit nontraditional algorithms that conserve such invariants exactly. They illustrate the method by applying it to the three-wave truncation of the Euler equations, the Lotka-Volterra predator-prey model, and the Kepler problem. The ideas are discussed in the context of symplectic (phase-space-conserving) integration methods as well as nonsymplectic conservative methods. They comment on the application of the method to general conservative systems.

  3. Exactly conservative integrators

    Energy Technology Data Exchange (ETDEWEB)

    Shadwick, B.A.; Bowman, J.C.; Morrison, P.J.


    Traditional numerical discretizations of conservative systems generically yield an artificial secular drift of any nonlinear invariants. In this work we present an explicit nontraditional algorithm that exactly conserves invariants. We illustrate the general method by applying it to the Three-Wave truncation of the Euler equations, the Volterra-Lotka predator-prey model, and the Kepler problem. We discuss our method in the context of symplectic (phase space conserving) integration methods as well as nonsymplectic conservative methods. We comment on the application of our method to general conservative systems.

  4. Exactly conservative integrators

    CERN Document Server

    Shadwick, B A; Morrison, P J; Bowman, John C


    Traditional numerical discretizations of conservative systems generically yield an artificial secular drift of any nonlinear invariants. In this work we present an explicit nontraditional algorithm that exactly conserves these invariants. We illustrate the general method by applying it to the three-wave truncation of the Euler equations, the Lotka--Volterra predator--prey model, and the Kepler problem. This method is discussed in the context of symplectic (phase space conserving) integration methods as well as nonsymplectic conservative methods. We comment on the application of our method to general conservative systems.

  5. Exactly conservative integrators

    Energy Technology Data Exchange (ETDEWEB)

    Shadwick, B.A.; Bowman, J.C.; Morrison, P.J.


    Traditional numerical discretizations of conservative systems generically yield an artificial secular drift of any nonlinear invariants. In this work we present an explicit nontraditional algorithm that exactly conserves invariants. We illustrate the general method by applying it to the Three-Wave truncation of the Euler equations, the Volterra-Lotka predator-prey model, and the Kepler problem. We discuss our method in the context of symplectic (phase space conserving) integration methods as well as nonsymplectic conservative methods. We comment on the application of our method to general conservative systems.

  6. Super-hydrophobic film prepared on zinc as corrosion barrier

    Energy Technology Data Exchange (ETDEWEB)

    Wang Peng [Key Lab of Corrosion Science, Shandong Province, Institute of Oceanology, Chinese Academy of Sciences, 7 Naihai Road, Qingdao 266071 (China); Zhang Dun, E-mail: [Key Lab of Corrosion Science, Shandong Province, Institute of Oceanology, Chinese Academy of Sciences, 7 Naihai Road, Qingdao 266071 (China); Qiu Ri [Key Lab of Corrosion Science, Shandong Province, Institute of Oceanology, Chinese Academy of Sciences, 7 Naihai Road, Qingdao 266071 (China); Graduate School of the Chinese Academy of Sciences, 19 (Jia) Yuquan Road, Beijing 100039 (China); Hou Baorong [Key Lab of Corrosion Science, Shandong Province, Institute of Oceanology, Chinese Academy of Sciences, 7 Naihai Road, Qingdao 266071 (China)


    Research highlights: {yields} Super-hydrophobic film was prepared on zinc surface. {yields} The air trapped in film can dramatically improve the anti-corrosion property. {yields} The air trapped behaves as dielectric for a pure parallel plate capacitor. {yields} The air enhances the contribution of film to the anti-corrosion property. {yields} Without the help of air, the film itself can only present feeble inhibition effect. - Abstract: Potentiostatic electrolysis was carried out to prepare super-hydrophobic film on the surface of metallic zinc. The resultant film was examined by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical measurements, and contact angle test. The super-hydrophobic property of the film results from the air trapped among the sheets of zinc tetradecanoate. This air behaves as a dielectric for a pure parallel plate capacitor, thereby inhibiting electron transfer between the electrolyte and the substrate. The air can also enhance the contribution of the film itself to protection performance.

  7. Evidence for Non-Random Hydrophobicity Structures in Protein Chains

    CERN Document Server

    Irbäck, A; Potthast, F; Irb\\"ack, Anders; Peterson, Carsten; Potthast, Frank


    The question of whether proteins originate from random sequences of amino acids is addressed. A statistical analysis is performed in terms of blocked and random walk values formed by binary hydrophobic assignments of the amino acids along the protein chains. Theoretical expectations of these variables from random distributions of hydrophobicities are compared with those obtained from functional proteins. The results, which are based upon proteins in the SWISS-PROT data base, convincingly show that the amino acid sequences in proteins differ from what is expected from random sequences in a statistical significant way. By performing Fourier transforms on the random walks one obtains additional evidence for non-randomness of the distributions. We have also analyzed results from a synthetic model containing only two amino-acid types, hydrophobic and hydrophilic. With reasonable criteria on good folding properties in terms of thermodynamical and kinetic behavior, sequences that fold well are isolated. Performing t...

  8. Synthesis and Aqueous Solution Viscosity of Hydrophobically Modified Xanthan Gum

    Institute of Scientific and Technical Information of China (English)

    QIAN Xiao-lin; WU Wen-hui; YU Pei-zhi; WANG Jian-quan


    Two xanthan gum derivatives hydrophobically modified by 4 or 8 tetradecyl chains per 100 xanthan gum structure units were synthesized. The derivatives were studied by scanning electron microscope and pyrene fluorescence spectrometry. And the aqueous solution apparent viscosity of the derivatives was investigated. The results indicate that the network of the derivatives with more hydrophobic groups is closer and tighter. With increasing of alkyl chain substitution degree, the hydrophobically associating interactions enhance in aqueous solution. Aqueous solution apparent viscosity of the derivatives increases with increasing of polymer concentration and alkyl substitution degree, and decreases with the increase of temperature. In the brine solution, the strong viscosity enhancement phenomenon appears. The interaction between the derivatives and surfactant sodium dodecylbenzene sulfonate is strong.

  9. Compositional fingerprint of soy sauces via hydrophobic surface interaction. (United States)

    Jakobi, Victoria; Salmen, Paul; Paulus, Michael; Tolan, Metin; Rosenhahn, Axel


    In this work, the interaction of soy sauces with hydrophobic surfaces has been analyzed. Hydrophobic self-assembled monolayers on gold or silicon dioxide were used to harvest conditioning layers from soy sauce products with varying amounts of additives. The data was compared to adsorption of soy protein and glutamic acid as common ingredients. Spectral ellipsometry revealed that all tested sauces led to the formation of thin overlayers on hydrophobic surfaces. Products with less additives yielded adlayers in the same thickness range as pure soy protein. In contrast, sauces with more ingredients create distinctly thicker films. Using water contact angle goniometry, it is shown that all adlayers render the substrate more hydrophilic. Infrared spectroscopy provided a deeper insight into the adlayer chemistry and revealed that the adlayer composition is dominated by protein rich components. X-ray reflectivity on selected films provided further insight into the density profiles within the adlayers on the molecular scale.

  10. Strong, reversible underwater adhesion via gecko-inspired hydrophobic fibers. (United States)

    Soltannia, Babak; Sameoto, Dan


    Strong, reversible underwater adhesion using gecko-inspired surfaces is achievable through the use of a hydrophobic structural material and does not require surface modification or suction cup effects for this adhesion to be effective. Increased surface energy can aid in dry adhesion in an air environment but strongly degrades wet adhesion via reduction of interfacial energy underwater. A direct comparison of structurally identical but chemically different mushroom shaped fibers shows that strong, reversible adhesion, even in a fully wetted, stable state, is feasible underwater if the structural material of the fibers is hydrophobic and the mating surface is not strongly hydrophilic. The exact adhesion strength will be a function of the underwater interfacial energy between surfaces and the specific failure modes of individual fibers. This underwater adhesion has been calculated to be potentially greater than the dry adhesion for specific combinations of hydrophobic surfaces.

  11. Frictional forces between hydrophilic and hydrophobic particle coated nanostructured surfaces

    DEFF Research Database (Denmark)

    Hansson, Petra M; Claesson, Per M.; Swerin, Agne;


    by utilizing the atomic force microscope (AFM). The chemistry of the surfaces and the probe was varied between hydrophilic silica and hydrophobized silica. For hydrophilic silica surfaces, the friction coefficient was significantly higher for the particle coated surfaces than on the flat reference surface. All...... the particle coated surfaces exhibited similar friction coefficients, from which it may be concluded that the surface geometry, and not the roughness amplitude per se, influenced the measured friction. During measurements with hydrophobic surfaces, strong adhesive forces related to the formation of a bridging...... air cavity were evident from both normal force and friction force measurements. In contrast to the frictional forces between the hydrophilic surfaces, the friction coefficient for hydrophobic surfaces was found to depend on the surface structure and we believe that this dependence is related...

  12. Recyclable hydrophilic-hydrophobic micropatterns on glass for microarray applications. (United States)

    Zhang, Hua; Lee, Yong Yeow; Leck, Kwong Joo; Kim, Namyong Y; Ying, Jackie Y


    A novel method for fabricating recyclable hydrophilic-hydrophobic micropatterns on glass chips is presented. TiOx patterns (100-2000 microm) were sputtered on glass chips via a through-hole mask. The patterned chips were then vapor-coated with fluoroalkylsilane, for example, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane (FTES) to form a hydrophobic coating layer. The fluoroalkyl chain of FTES film on TiOx patterns was photocleaved under UV irradiation, exposing the fresh hydrophilic TiOx patterns. The resulting chip could be used multiple times by repeating the coating and photocleaving processes with negligible deterioration of the hydrophobic FTES film coated on glass. If desired, bare glass patterns could also be generated by removing the TiOx patterns with KOH. The patterned glass chips have been successfully used for microarray fabrication.

  13. Forces between hydrophobic solids in concentrated aqueous salt solution. (United States)

    Mastropietro, Dean J; Ducker, William A


    Much research has focused on the discovery and description of long-ranged forces between hydrophobic solids immersed in water. Here we show that the force between high contact-angle solids in concentrated salt solution (1 M KCl) agrees very well with van der Waals forces calculated from Lifshitz theory for separations greater than 5 nm. The hydrophobic solids are octadecyltrichlorosilane-coated glass, with an advancing contact angle of 108°. Thus, in 1 M salt solution, it is unnecessary to invoke the presence of a hydrophobic force at separations greater than 5 nm. Through measurement in salt solution, we avoid the necessity of accounting for large electrostatic forces that frequently occur in pure water and may obscure resolution of other forces.

  14. 北方"四位一体"模式中日光温室结构的优化%Optimization of the Structural Parameters of Solar Greenhouse in the Tetrad-eco-agricultural Model in North China

    Institute of Scientific and Technical Information of China (English)

    葛一洪; 王惠生; 王清; 赵辉; 牛文慧; 乔汪砚


    Taking northern Shaanxi region as example, the tetrad-eco-agricultural model of sunlight greenhouse was studied and proposed the optimized structural parameters and tested its operating efficiency.The results indicated that, compared with the traditional greenhouse, the daily light intensity in the optimized greenhouse was higher, by 3 115 1x; the daily inside temperature raised 3.6 ℃; the temperature of anaerobic digestion was averagely higher by 0.5 ℃; the daily biogas production of digester increased 0.1 ma.%以陕北地区为例,对北方"四位一体"模式的日光温室进行研究,提出优化性的结构参数,并对其运行效果进行测定.结果表明,优化的日光温室比传统的日光温室,室内日均光照度提高3 115 lx;室内日均温度提高3.6℃;地下沼气池的日均发酵温度提高0.5℃;沼气池的日均产气量增加0.1 m3.

  15. Multilocus half-tetrad analysis and centromere mapping in citrus: evidence of SDR mechanism for 2n megagametophyte production and partial chiasma interference in mandarin cv ‘Fortune' (United States)

    Cuenca, J; Froelicher, Y; Aleza, P; Juárez, J; Navarro, L; Ollitrault, P


    The genetic structure of 2n gametes and, particularly, the parental heterozygosity restitution at each locus depends on the meiotic process by which they originated, with first-division restitution and second-division restitution (SDR) being the two major mechanisms. The origin of 2n gametes in citrus is still controversial, although sexual polyploidisation is widely used for triploid seedless cultivar development. In this study, we report the analysis of 2n gametes of mandarin cv ‘Fortune' by genotyping 171 triploid hybrids with 35 simple sequence repeat markers. The microsatellite DNA allele counting-peak ratios method for allele-dosage evaluation proved highly efficient in segregating triploid progenies and allowed half-tetrad analysis (HTA) by inferring the 2n gamete allelic configuration. All 2n gametes arose from the female genitor. The observed maternal heterozygosity restitution varied between 10 and 82%, depending on the locus, thus SDR appears to be the mechanism underlying 2n gamete production in mandarin cv ‘Fortune'. A new method to locate the centromere, based on the best fit between observed heterozygosity restitution within a linkage group and theoretical functions under either partial or no chiasmata interference hypotheses was successfully applied to linkage group II. The maximum value of heterozygosity restitution and the pattern of restitution along this linkage group would suggest there is partial chiasma interference. The implications of such a restitution mechanism for citrus breeding are discussed. PMID:21587302

  16. Designed armadillo repeat proteins as general peptide-binding scaffolds: consensus design and computational optimization of the hydrophobic core

    DEFF Research Database (Denmark)

    Parmeggiani, Fabio; Pellarin, Riccardo; Larsen, Anders Peter


    interactions with peptides or parts of proteins in extended conformation. The conserved binding mode of the peptide in extended form, observed for different targets, makes armadillo repeat proteins attractive candidates for the generation of modular peptide-binding scaffolds. Taking advantage of the large...... number of repeat sequences available, a consensus-based approach combined with a force field-based optimization of the hydrophobic core was used to derive soluble, highly expressed, stable, monomeric designed proteins with improved characteristics compared to natural armadillo proteins. These sequences...

  17. Activity of catalytic silver nanoparticles modulated by capping agent hydrophobicity. (United States)

    Janani, Seralathan; Stevenson, Priscilla; Veerappan, Anbazhagan


    In this paper, a facile in situ method is reported for the preparation of catalytic silver nanoparticles (AgNPs) using N-acyl tyramine (NATA) with variable hydrophobic acyl length. Scanning electron microscopic analysis shows that NATA exists initially as larger aggregates in alkaline aqueous solution. The addition of AgNO3 dissociates these larger aggregate and subsequently promotes the formation of self-assembled NATA and AgNPs. Characterization of AgNPs using UV-vis spectroscopy, scanning electron microscope and transmission electron microscope revealed that the hydrophobic acyl chain length of NATA does not influence the particle size, shape and morphology. All NATA-AgNPs yielded relatively identical values in full width at half-maximum (FWHM) analysis, indicating that the AgNPs prepared with NATA are relatively polydispersed at all tested acyl chain lengths. These nanoparticles are able to efficiently catalyze the reduction of 4-nitro phenol to 4-amino phenol, 2-nitro aniline to 1,2-diamino benzene, 2,4,6-trinitro phenol to 2,4,6-triamino phenol by NaBH4 in an aqueous environment. The reduction reaction rate is determined to be pseudo-first order and the apparent rate constant is linearly dependent on the hydrophobic acyl chain length of the NATA. All reaction kinetics presented an induction period, which is dependent on the N-acyl chain length, indicating that the hydrophobic effects play a critical role in bringing the substrate to the metal nanoparticle surface to induce the catalytic reaction. In this study, however, the five catalytic systems have similar size and polydispersity, differing only in terms of capping agent hydrophobicity, and shows different catalytic activity with respect to the alkyl chain length of the capping agent. As discussed, the ability to modulate the metal nanoparticles catalytic property, by modifying the capping agent hydrophobicity represents a promising future for developing an efficient nanocatalyst without altering the size


    Institute of Scientific and Technical Information of China (English)

    Jun Ma; Bai-yu Li; Hai-yun Liu; Zhi-min Zheng; Jian Xu


    A hydrophobic-hydrophilic gradient rod with a length of 40 mm and a diameter of 3 mm was prepared by heating a polymethylsilsesquioxane rod in a cylindrical stove with temperature gradient. The rod was thus pyrolyzed under a temperature gradient condition. The organic end of the gradient rod appears hydrophobic with a contact angle of 109.9° while the other end is hydrophilic with a contact angle of 62.4°. The gradient chemical structure and the gradient microstructure along the rod were characterized by FTIR and SEM, respectively.

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

    Energy Technology Data Exchange (ETDEWEB)

    Worcester, D.L.; Hamacher, K.; Kaiser, H.; Kulasekere, R.; Torbet, J. [Univ. of Missouri, Columbia, MO (United States)


    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.

  20. Biofilm retention on surfaces with variable roughness and hydrophobicity

    DEFF Research Database (Denmark)

    Tang, Lone; Pillai, Saju; Revsbech, Niels Peter


    (SS) was compared to two novel nanostructured sol-gel coatings with differing hydrophobicity. Surfaces were characterized with respect to roughness, hydrophobicity, protein adsorption, biofilm retention, and community composition of the retained bacteria. Fewer bacteria were retained on the sol-gel...... coated surfaces compared to the rougher SS. However, the two sol-gel coatings did not differ in either protein adsorption, biofilm retention, or microbial community composition. When polished to a roughness similar to sol-gel, the SS was colonized by the same amount of bacteria as the sol-gel...

  1. Wetting in hydrophobic nanochannels: a challenge of classical capillarity. (United States)

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


    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.

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

    Directory of Open Access Journals (Sweden)

    Mays J. W.


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

  3. 7 CFR 12.23 - Conservation plans and conservation systems. (United States)


    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Conservation plans and conservation systems. 12.23 Section 12.23 Agriculture Office of the Secretary of Agriculture HIGHLY ERODIBLE LAND AND WETLAND CONSERVATION Highly Erodible Land Conservation § 12.23 Conservation plans and conservation systems. (a) Use...

  4. Effect of an Extra Hydrophobic Resin Layer on Repair Shear Bond Strength of a Silorane-Based Composite Resin. (United States)

    Mohammadi, Narmin; Bahari, Mahmoud; Kimyai, Soodabeh; Rahbani Nobar, Behnam


    Composite repair is a minimally invasive and conservative approach. This study aimed to evaluate the effect of an additional hydrophobic resin layer on the repair shear bond strength of a silorane-based composite repaired with silorane or methacrylate-based composite. Sixty bar-shaped composite blocks were fabricated and stored in saline for 72 hours. The surface of the samples were roughened by diamond burs and etched with phosphoric acid; then, they were randomly divided into three groups according to the repairing process: Group 1: Silorane composite-silorane bonding agent-silorane composite; group 2: Silorane composite-silorane bonding agent-hydrophobic resin-silorane composite, and group 3: Silorane composite-silorane bonding agent-hydrophobic resin methacrylate-based composite. Repairing composite blocks measured 2.5×2.5×5mm. After repairing, the samples were stored in saline for 24 hours and thermocycled for 1500 cycles. The repair bond strength was measured at a strain rate of 1mm/min. Twenty additional cylindrical composite blocks (diameter: 2.5mm, height: 6mm) were also fabricated for measuring the cohesive strength of silorane-based composite. The data were analyzed using One-way ANOVA and the post hoc Tukey's test (α=0.05). Cohesive bond strength of silorane composite was significantly higher than the repair bond strengths in other groups (Presin layer for repair of silorane-based composite with a methacrylate-based composite enhanced the repair shear bond strength.

  5. Role of NH{sub 2}-terminal hydrophobic motif in the subcellular localization of ATP-binding cassette protein subfamily D: Common features in eukaryotic organisms

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Asaka; Asahina, Kota; Okamoto, Takumi; Kawaguchi, Kosuke [Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194 (Japan); Kostsin, Dzmitry G. [Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194 (Japan); Institute of Biophysics and Cell Engineering, National Academy of Sciences of Belarus, Academicheskaya Str. 27, Minsk 220072 (Belarus); Kashiwayama, Yoshinori [Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194 (Japan); Takanashi, Kojiro; Yazaki, Kazufumi [Laboratory of Plant Gene Expression, Research Institute for Sustainable Humanosphere, Kyoko University, Uji, Kyoto 611-0011 (Japan); Imanaka, Tsuneo, E-mail: [Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194 (Japan); Morita, Masashi [Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194 (Japan)


    Highlights: • ABCD proteins classifies based on with or without NH{sub 2}-terminal hydrophobic segment. • The ABCD proteins with the segment are targeted peroxisomes. • The ABCD proteins without the segment are targeted to the endoplasmic reticulum. • The role of the segment in organelle targeting is conserved in eukaryotic organisms. - Abstract: In mammals, four ATP-binding cassette (ABC) proteins belonging to subfamily D have been identified. ABCD1–3 possesses the NH{sub 2}-terminal hydrophobic region and are targeted to peroxisomes, while ABCD4 lacking the region is targeted to the endoplasmic reticulum (ER). Based on hydropathy plot analysis, we found that several eukaryotes have ABCD protein homologs lacking the NH{sub 2}-terminal hydrophobic segment (H0 motif). To investigate whether the role of the NH{sub 2}-terminal H0 motif in subcellular localization is conserved across species, we expressed ABCD proteins from several species (metazoan, plant and fungi) in fusion with GFP in CHO cells and examined their subcellular localization. ABCD proteins possessing the NH{sub 2}-terminal H0 motif were localized to peroxisomes, while ABCD proteins lacking this region lost this capacity. In addition, the deletion of the NH{sub 2}-terminal H0 motif of ABCD protein resulted in their localization to the ER. These results suggest that the role of the NH{sub 2}-terminal H0 motif in organelle targeting is widely conserved in living organisms.

  6. Conservation: Toward firmer ground (United States)


    The following aspects of energy conservation were discussed: conservation history and goals, conservation modes, conservation accounting-criteria, and a method to overcome obstacles. The conservation modes tested fall into one of the following categories: reduced energy consumption, increased efficiency of energy utilization, or substitution of one or more forms of energy for another which is in shorter supply or in some sense thought to be of more value. The conservation accounting criteria include net energy reduction, economic, and technical criteria. A method to overcome obstacles includes (approaches such as: direct personal impact (life style, income, security, aspiration), an element of crisis, large scale involvement of environmental, safety, and health issues, connections to big government, big business, big politics, involvement of known and speculative science and technology, appeal to moral and ethical standards, the transient nature of opportunities to correct the system.

  7. Quantifying effective slip length over micropatterned hydrophobic surfaces

    NARCIS (Netherlands)

    Tsai, Peichun; Peters, Alisia M.; Pirat, Christophe; Wessling, Matthias; Lammertink, Rob G.H.; Lohse, Detlef


    We employ microparticle image velocimetry to investigate laminar microflows in hydrophobic microstructured channels, in particular the slip length. These microchannels consist of longitudinal microgrooves, which can trap air and prompt a shear-free boundary condition and thus slippage enhancement. O

  8. Nanoparticle flotation collectors II: the role of nanoparticle hydrophobicity. (United States)

    Yang, Songtao; Pelton, Robert


    The ability of polystyrene nanoparticles to facilitate the froth flotation of glass beads was correlated to the hydrophobicity of the nanoparticles. Contact angle measurements were used to probe the hydrophobicity of hydrophilic glass surfaces decorated with hydrophobic nanoparticles. Both sessile water drop advancing angles, θ(a), and attached air bubble receding angle measurements, θ(r), were performed. For glass surfaces saturated with adsorbed nanoparticles, flotation recovery, a measure of flotation efficiency, increased with increasing values of each type of contact angle. As expected, the advancing water contact angle on nanoparticle-decorated, dry glass surfaces increased with surface coverage, the area fraction of glass covered with nanoparticles. However, the nanoparticles were far more effective at raising the contact angle than the Cassie-Baxter prediction, suggesting that with higher nanoparticle coverages the water did not completely wet the glass surfaces between the nanoparticles. A series of polystyrene nanoparticles was prepared to cover a range of surface energies. Water contact angle measurements, θ(np), on smooth polymer films formed from organic solutions of dissolved nanoparticles were used to rank the nanoparticles in terms of hydrophobicity. Glass spheres were saturated with adsorbed nanoparticles and were isolated by flotation. The minimum nanoparticle water contact angle to give high flotation recovery was in the range of 51° < θ(np(min)) ≤ 85°.

  9. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, N.P.; Norde, W.; Meil, H.C.; Busscher, H.J.


    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F-prev) and to detach adhering bacteria (F-det) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the

  10. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, Niels P.; Norde, Willem; van der Mei, Henny C.; Busscher, Henk J.


    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F(prev)) and to detach adhering bacteria (F(det)) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the

  11. Observation of water condensate on hydrophobic micro textured surfaces (United States)

    Kim, Ki Wook; Do, Sang Cheol; Ko, Jong Soo; Jeong, Ji Hwan


    We visually observed that a dropwise condensation occurred initially and later changed into a filmwise condensation on hydrophobic textured surface at atmosphere pressure condition. It was observed that the condensate nucleated on the pillar side walls of the micro structure and the bottom wall adhered to the walls and would not be lifted to form a spherical water droplet using environmental scanning electron microscope.

  12. Water repellency in hydrophobic nanocapsules--molecular view on dewetting. (United States)

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


    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.

  13. Highly efficient hydrophobic titania ceramic membranes for water desalination. (United States)

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


    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.

  14. Hydrophobic patches on the surfaces of protein structures

    NARCIS (Netherlands)

    Lijnzaad, P.; Berendsen, H.J.C.; Argos, P.


    A survey of hydrophobic patches on the surface of 112 soluble, monomeric proteins is presented, The largest patch on each individual protein averages around 400 Angstrom(2) but can range from 200 to 1,200 Angstrom(2). These areas are not correlated to the sizes of the proteins and only weakly to the

  15. Super-hydrophobic characteristics of butterfly wing surface

    Institute of Scientific and Technical Information of China (English)

    CONG Qian; CHEN Guang-hua; FANG Yan; REN Lu-quan


    Many biological surface are hydrophobic because of their complicated composition and surface microstructure. Eleven species (four families) of butterflies were selected to study their micro-, nano-structure and super-hydrophobic characteristic by means of Confocal Light Microscopy, Scanning Electron Microscopy and Contact Angle Measurement. The contact angles of water droplets on the butterfly wing surface were consistently measured to be about 150° and 100° with and without the squamas, respectively. The dust on the surface can be easily cleaned by moving spherical droplets when the inclining angle is larger than 3°. It can be concluded that the butterfly wing surface possess a super-hydrophobic, water-repellent,self-cleaning, or "Lotus-effect" characteristic. The contact angle measurement of water droplets on the wing surface with and without the squamas showed that the water-repellent characteristic is a consequence of the microstructure of the squamas.Each water droplet (diameter 2 mm) can cover about 700 squamas with a size of 40 μm×80 μm of each squama. The regular riblets with a width of 1000 nm to 1500 nm are clearly observed on each single squama. Such nanostructure should play a very important role in their super-hydrophobic and self-cleaning characteristic.

  16. Water uptake in biochars: The roles of porosity and hydrophobicity (United States)

    We assessed the effects of porosity and hydrophobicity on water uptake by biochars. Biochars were produced from two feedstocks (hazelnut shells and Douglas fir chips) at three production temperatures (370 °C, 500 °C, and 620 °C). To distinguish the effects of porosity from the ...

  17. Synthesis and Solution Properties of Hydrophobic Associating Polymers

    Institute of Scientific and Technical Information of China (English)

    任鲲; 姜桂元; 徐春明; 林梅钦


    Acrylamide/2-acrylamido alkane sulfonic acid hydrophobic associating copolymers were synthesized by micellar copolymerization. Effects of hydrophobe content, polymer concentration, salinity and surfactant on rheological behavior of copolymers were investigated and the conformation of polymers in solution was studied by means of environmental scanning electronic microscopy and dynamic light scattering. The experimental results showed that in the dilute regime the hydrophobic parts could interact intramolecularly, while in the regime where the polymer concentration was higher than the critical association concentration, intermolecular hydrophobic association became predominant. Within the limit of the solubility, the critical association concentration of the polymer decreased with the increase of the salinity. The experimental results of the solution conformation indicated the presence of the three-dimensional network structure in deionized water and the size of the mesh in the network varied with the polymer concentration. In NaG1 solution, above the critical association concentration, an increase in polymer concentration enhanced the intermolecular association and also enlarged the hydrodynamic radius. It would result in the imorovement of the thickening power of polvmers.

  18. Tubular occlusion optimizes bonding of hydrophobic resins to dentin. (United States)

    Sadek, F T; Pashley, D H; Ferrari, M; Tay, F R


    Although hydrophobic resins may be bonded to acid-etched dentin with an ethanol wet-bonding technique, the protocol is sensitive to moisture contamination when bonding is performed in deep dentin. This study tested the hypothesis that the use of oxalate or poly(glutamic) acid-modified, diluted ceramicrete (PADC) for dentinal tubule occlusion prevents fluid contamination and improves the bonding of an experimental hydrophobic adhesive to acid-etched, ethanol-dehydrated dentin. Mid-coronal and deep acid-etched moist dentin pre-treated with oxalate or PADC was dehydrated by ethanol wet-bonding and infiltrated with the experimental three-step etch-and-rinse hydrophobic adhesive under simulated pulpal pressure. Tensile bond strengths to deep dentin without pre-treatment were severely compromised. Conversely, oxalate and PADC pre-treatments reduced dentin permeability, prevented water contamination, and improved bond strengths. Minimal nanoleakage was identified within hybrid layers created in the oxalate- and PADC-pre-treated deep dentin. The use of tubular occluding agents optimized bonding of hydrophobic resins to dentin.

  19. A comprehensive study to protein retention in hydrophobic interaction chromatography. (United States)

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


    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.

  20. Use and application of hydrophobic interaction chromatography for protein purification. (United States)

    McCue, Justin T


    The objective of this section is to provide the reader with guidelines and background on the use and experimental application of Hydrophobic Interaction chromatography (HIC) for the purification of proteins. The section will give step by step instructions on how to use HIC in the laboratory to purify proteins. General guidelines and relevant background information is also provided.

  1. Biomimetic solution against dewetting in a highly hydrophobic nanopore. (United States)

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


    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.

  2. Water flow boiling behaviors in hydrophilic and hydrophobic microchannels

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Chiwoong; Yu, Dongin; Kim, Moohwan [Pohang University of Science and Technology (Korea, Republic of). Dept. of Mechanical Engineering


    The wettability is one of issues on two-phase flow in a microchannel. However, previous studies of wettability effect on two-phase flow have conducted only isothermal condition. Moreover, most studies have used conventional micro/mini-tubes due to difficulties of their fabrication. The objective of our study is to understand the wettability effect on flow boiling in a rectangular microchannel. In the first, new micro-electro-mechanical-system (MEMS) fabrication technique was developed to obtain a single glass rectangular microchannel and localized six micro heaters. A photosensitive glass was used as base material. The photosensitive glass is hydrophilic, so the hydrophobic microchannel was prepared by coating SAM, flow boiling experiments were conducted in hydrophilic and hydrophobic microchannels with micro heaters. The experiment range was the mass flux of 25 and 75 kg/m{sup 2}s, the heat flux of 30 - 430 k W/m2 and quality of 0 - 0.3. A working fluid was de-ionized and degassed water. The local heat transfer coefficient was evaluated at the local micro heater section. Also, flow regimes in the microchannel were visualized by using a high-speed camera with a long-distance microscope. Heat transfer was analyzed with visualization results. Heat transfer in the hydrophobic microchannel was enhanced by higher nucleation site density and delayed local dryout. The pressure drop in the hydrophobic microchannel was higher than that in the hydrophilic microchannel. (author)

  3. Flexible starch-polyurethane films: Physiochemical characteristics and hydrophobicity. (United States)

    Tai, N L; Adhikari, Raju; Shanks, Robert; Adhikari, Benu


    Starch-polyurethane (PU) composite films with improved mechanical and hydrophobic properties were developed in this work. A simple and effective microwave-aided starch gelatinisation instrument was used to prepare glycerol plasticized high amylose starch (HAGS) material. Polyethylene glycol-isocyanate (PEG-iso) linker was prepared by reacting PEG 1000 with hexamethylene diisocyanate (HMDI). PEG-iso linker was then grafted into HAGS forming three dimensional urethane networks (PEG-PU). HAGS-PEG-PU composite blends were prepared and dried at ambient temperature to obtain HAGS-PEG-PU films. The mechanical properties and hydrophobicity (as contact angle, CA) of the HAGS-PEG-PU films were measured and analysed. Fourier transform infrared spectroscopy showed good grafting of PEG-iso into starch structure. Increase of PEG-iso concentration up to 20% (w/w) improved the molecular mixing and interpenetration between the starch and PEG-PU. The HAGS-PEG-PU films had improved hydrophobicity as indicated by CA values ranging from 51 to 110°and very high flexibility as evidenced from elongation at break (εB) values from 17 to 1000%. The HAGS-PEG-PU film formulation containing 20% (w/w) PEG-iso provided the best flexibility (εB>1000%) and hydrophobicity (CA>110°). Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Nanocarriers from GRAS Zein Proteins to Encapsulate Hydrophobic Actives. (United States)

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


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

  5. Anionic and cationic Hofmeister effects on hydrophobic and hydrophilic surfaces. (United States)

    Schwierz, Nadine; Horinek, Dominik; Netz, Roland R


    Using a two-step modeling approach, we address the full spectrum of direct, reversed, and altered ionic sequences as the charge of the ion, the charge of the surface, and the surface polarity are varied. From solvent-explicit molecular dynamics simulations, we extract single-ion surface interaction potentials for halide and alkali ions at hydrophilic and hydrophobic surfaces. These are used within Poisson-Boltzmann theory to calculate ion density and electrostatic potential distributions at mixed polar/unpolar surfaces for varying surface charge. The resulting interfacial tension increments agree quantitatively with experimental data and capture the Hofmeister series, especially the anomaly of lithium, which is difficult to obtain using continuum theory. Phase diagrams that feature different Hofmeister series as a function of surface charge, salt concentration, and surface polarity are constructed from the long-range force between two surfaces interacting across electrolyte solutions. Large anions such as iodide have a high hydrophobic surface affinity and increase the effective charge magnitude on negatively charged unpolar surfaces. Large cations such as cesium also have a large hydrophobic surface affinity and thereby compensate an external negative charge surface charge most efficiently, which explains the well-known asymmetry between cations and anions. On the hydrophilic surface, the size-dependence of the ion surface affinity is reversed, explaining the Hofmeister series reversal when comparing hydrophobic with hydrophilic surfaces.

  6. The dynamics of hydrophobic interaction : A microwave dielectric study

    NARCIS (Netherlands)

    Hallenga, Klaas


    To investigate the relation between the structure of liquid water and hydrophobic interaction the dielectric relaxation of water in dilute aqueous solutions has been studied. After an introduction of the problem in which the dynamic aspects of water structure are emphasized, a theoretical analysis o

  7. Biochemical characterization of the small hydrophobic protein of avian metapneumovirus (United States)

    Avian metapneumovirus (aMPV) is a paramyxovirus that has three membrane-associate proteins: glycoprotein (G), fusion (F), and small hydrophobic (SH) proteins. Among them, the SH protein is a small type II integral membrane protein that is incorporated into virions and is only present in certain para...

  8. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, N.P.; Norde, W.; Meil, H.C.; Busscher, H.J.


    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F-prev) and to detach adhering bacteria (F-det) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the fol

  9. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, Niels P.; Norde, Willem; van der Mei, Henny C.; Busscher, Henk J.


    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F(prev)) and to detach adhering bacteria (F(det)) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the f

  10. A double chain reversal loop and two diagonal loops define the architecture of a unimolecular DNA quadruplex containing a pair of stacked G(syn)-G(syn)-G(anti)-G(anti) tetrads flanked by a G-(T-T) Triad and a T-T-T triple. (United States)

    Kuryavyi, V; Majumdar, A; Shallop, A; Chernichenko, N; Skripkin, E; Jones, R; Patel, D J


    The architecture of G-G-G-G tetrad-aligned DNA quadruplexes in monovalent cation solution is dependent on the directionality of the four strands, which in turn are defined by loop connectivities and the guanine syn/anti distribution along individual strands and within individual G-G-G-G tetrads. The smallest unimolecular G-quadruplex belongs to the d(G2NnG2NnG2NnG2) family, which has the potential to form two stacked G-tetrads linked by Nn loop connectivities. Previous studies have focused on the thrombin-binding DNA aptamer d(G2T2G2TGTG2T2G2), where Nn was T2 for the first and third connecting loops and TGT for the middle connecting loop. This DNA aptamer in K(+) cation solution forms a unimolecular G-quadruplex stabilized by two stacked G(syn)-G(anti)-G(syn)-G(anti) tetrads, adjacent strands which are antiparallel to each other and edge-wise connecting T2, TGT and T2 loops. We now report on the NMR-based solution structure of the d(G2T4G2CAG2GT4G2T) sequence, which differs from the thrombin-binding DNA aptamer sequence in having longer first (T4) and third (GT4) loops and a shorter (CA) middle loop. This d(G2T4G2CAG2GT4G2T) sequence in Na(+) cation solution forms a unimolecular G-quadruplex stabilized by two stacked G(syn)-G(syn)-G(anti)-G(anti) tetrads, adjacent strands which have one parallel and one antiparallel neighbors and distinct non-edge-wise loop connectivities. Specifically, the longer first (T4) and third (GT4) loops are of the diagonal type while the shorter middle loop is of the double chain reversal type. In addition, the pair of stacked G-G-G-G tetrads are flanked on one side by a G-(T-T) triad and on the other side by a T-T-T triple. The distinct differences in strand directionalities, loop connectivities and syn/anti distribution within G-G-G-G tetrads between the thrombin-binding DNA aptamer d(G2T2G2TGTG2T2G2) quadruplex reported previously, and the d(G2T4G2CAG2GT4G2T) quadruplex reported here, reinforces the polymorphic nature of higher

  11. How water meets a hydrophobic surface: Reluctantly and with flucuations (United States)

    Poynor Torigoe, Adele Nichole

    By definition hydrophobic substances hate water. Water placed on a hydrophobic surface will form a drop in order to minimize its contact area. What happens when water is forced into contact with a hydrophobic surface? One theory is that an ultra-thin low density region forms near the surface. This depleted region would have implications in such diverse areas as colloidal self-assembly, and the boundary conditions of fluid flow. However, the literature still remains divided as to whether or not such a depleted region exists. To investigate the existence of this layer, we have employed three surface-sensitive techniques, time-resolved phase-modulated ellipsometry, surface plasmon resonance, and X-ray reflectivity. Both ellipsometry and X-ray reflectivity provide strong evidence for the low-density layer and illuminate unexpected temporal behavior. Using all three techniques, we found surprising fluctuations at the interface with a non-Gaussian distribution and a single characteristic time on the order of tenths of seconds. This information supports the idea that the boundary fluctuates with something akin to capillary waves. We have also investigated the dependence of the static and dynamic properties of the hydrophobic/water interface on variables such as temperature, contact angle, pH, dissolved gasses, and sample quality, among others, in a hope to discover the root of the controversy in the literature. We found that the depletion layer is highly dependent on temperature, contact angle and sample quality. This dependence might explain some of the discrepancies in the literature as different groups often use hydrophobic surfaces with different properties.

  12. Hydrophobicity of fluoroalkylsilane and alkylsilane-grafted surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Farzaneh, M.; Kulinich, S.A.; Volat, C. [Quebec Univ., Chicoutimi, PQ (Canada). Industrial Chair on Atmospheric Icing of Power Network Equipment


    The microstructure and surface chemistry of self-assembled monolayers (SAMs) were investigated with reference to their hydrophobic and snow and ice-repellent properties. This paper presented a comparative analysis of wetting behaviour of both flat and rough surfaces covered with common fluoroalkylsiloxane (FAS-17 and FAS 13) and octadecylsiloxane (ODS) monolayers. In addition, the study aimed to show the importance of self-assembly order as an important factor governing hydrophobicity of SAM-coated surfaces. Both static and dynamic hydrophobicities were theoretically modelled as functions of self-assembly order/disorder degree and area fraction of air entrapped into the rough hydrophobic surfaces. The model was used to describe the wetting behaviour of SAM-grafted surfaces as a function of assembly degree of organic molecules and amount of air trapped between water and solid. The model was applied to compare wetting surfaces fully coated with FAS-17 and FAS-13 monolayers. The contact angle of a sessile water droplet was shown to be approximately 10 degrees larger on smooth fluoroalkylsilane-coated surfaces and to gradually increase with the assembly order. However, the difference decreased when rough substrates with air inclusion were used. The modelling results predicted very close values of contact angles on surfaces coated with perfluorodecylsiloxane and perfluorooctylsiloxane monolayers but demonstrated little difference at low self-assembly degree, when organic molecules were spread on the surface. ODS coatings showed lower values of contact angle. It was concluded that both static and dynamic hydrophobicity of SAM coated surfaces are strongly affected by the degree of self-assembly of organic molecules, and by water coverage of a rough composite surface, which can trap air. It was concluded that increasing the assembly order of SAM molecules in combination with properly designed roughness leads to considerably enhanced water repellency of the surface. 34 refs

  13. Rhizosphere hydrophobicity: A positive trait in the competition for water. (United States)

    Zeppenfeld, Thorsten; Balkenhol, Niko; Kóvacs, Kristóf; Carminati, Andrea


    The ability to acquire water from the soil is a major driver in interspecific plant competition and it depends on several root functional traits. One of these traits is the excretion of gel-like compounds (mucilage) that modify physical soil properties. Mucilage secreted by roots becomes hydrophobic upon drying, impedes the rewetting of the soil close to the root, the so called rhizosphere, and reduces water availability to plants. The function of rhizosphere hydrophobicity is not easily understandable when looking at a single plant, but it may constitute a competitive advantage at the ecosystem level. We hypothesize that by making the top soil hydrophobic, deep-rooted plants avoid competititon with shallow-rooted plants. To test this hypothesis we used an individual-based model to simulate water uptake and growth of two virtual plant species, one deep-rooted plant capable of making the soil hydrophobic and a shallow-rooted plant. We ran scenarios with different precipitation regimes ranging from dry to wet (350, 700, and 1400 mm total annual precipitation) and from high to low precipitation frequencies (1, 7, and 14 days). Plant species abundance and biomass were chosen as indicators for competitiveness of plant species. At constant precipitation frequency mucilage hydrophobicity lead to a benefit in biomass and abundance of the tap-rooted population. Under wet conditions this effect diminished and tap-rooted plants were less productive. Without this trait both species coexisted. The effect of root exudation trait remained constant under different precipitation frequencies. This study shows that mucilage secretion is a competitive trait for the acquisition of water. This advantage is achieved by the modification of the soil hydraulic properties and specifically by inducing water repellency in soil regions which are shared with other species.

  14. Ecohydrology of the wetland-forestland interface: hydrophobicity in leaf litter and its potential effect on surface evaporation (United States)

    Probert, Samantha; Kettridge, Nicholas; Devito, Kevin; Hurley, Alexander


    Riparian wetlands represent an important ecotone at the interface of peatlands and forests within the Western Boreal Plain of Canada. Water storage and negative feedbacks to evaporation in these systems is crucial for the conservation and redistribution of water during dry periods and providing ecosystem resilience to disturbance. Litter cover can alter the relative importance of the physical processes that drive soil evaporation. Negative feedbacks to drying are created as the hydrophysical properties of the litter and soil override atmospheric controls on evaporation in dry conditions, subsequently dampening the effects of external forcings on the wetland moisture balance. In this study, water repellency in leaf litter has been shown to significantly correlate with surface-atmosphere interactions, whereby severely hydrophobic leaf litter is linked to the highest surface resistances to evaporation, and therefore lowest instantaneous evaporation. Decreasing moisture is associated with increasing hydrophobicity, which may reduce the evaporative flux further as the dry hydrophobic litter creates a hydrological disconnect between soil moisture and the atmosphere. In contrast, hydrophilic litter layers exhibited higher litter moistures, which is associated with reduced resistances to evaporation and enhanced evaporative fluxes. Water repellency of the litter layer has a greater control on evaporation than the presence or absence of litter itself. Litter removal had no significant effect on instantaneous evaporation or surface resistance to evaporation except under the highest evaporation conditions, where litter layers produced higher resistance values than bare peat soils. However, litter removal modified the dominant physical controls on evaporation: moisture loss in plots with leaf litter was driven by leaf and soil hydrophysical properties. Contrastingly, bare peat soils following litter removal exhibited cooler, wetter surfaces and were more strongly correlated to

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

    Directory of Open Access Journals (Sweden)

    Farah El-Turk

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

  16. Conservation genetics in transition to conservation genomics

    NARCIS (Netherlands)

    Ouborg, N. Joop; Pertoldi, Cino; Loeschcke, Volker; Bijlsma, R. (Kuke); Hedrick, Phil W.


    Over the past twenty years conservation genetics has progressed from being mainly a theory-based field of population biology to a full-grown empirical discipline. Technological developments in molecular genetics have led to extensive use of neutral molecular markers such as microsatellites in conser

  17. Paradigms for parasite conservation. (United States)

    Dougherty, Eric R; Carlson, Colin J; Bueno, Veronica M; Burgio, Kevin R; Cizauskas, Carrie A; Clements, Christopher F; Seidel, Dana P; Harris, Nyeema C


    Parasitic species, which depend directly on host species for their survival, represent a major regulatory force in ecosystems and a significant component of Earth's biodiversity. Yet the negative impacts of parasites observed at the host level have motivated a conservation paradigm of eradication, moving us farther from attainment of taxonomically unbiased conservation goals. Despite a growing body of literature highlighting the importance of parasite-inclusive conservation, most parasite species remain understudied, underfunded, and underappreciated. We argue the protection of parasitic biodiversity requires a paradigm shift in the perception and valuation of their role as consumer species, similar to that of apex predators in the mid-20th century. Beyond recognizing parasites as vital trophic regulators, existing tools available to conservation practitioners should explicitly account for the unique threats facing dependent species. We built upon concepts from epidemiology and economics (e.g., host-density threshold and cost-benefit analysis) to devise novel metrics of margin of error and minimum investment for parasite conservation. We define margin of error as the risk of accidental host extinction from misestimating equilibrium population sizes and predicted oscillations, while minimum investment represents the cost associated with conserving the additional hosts required to maintain viable parasite populations. This framework will aid in the identification of readily conserved parasites that present minimal health risks. To establish parasite conservation, we propose an extension of population viability analysis for host-parasite assemblages to assess extinction risk. In the direst cases, ex situ breeding programs for parasites should be evaluated to maximize success without undermining host protection. Though parasitic species pose a considerable conservation challenge, adaptations to conservation tools will help protect parasite biodiversity in the face of

  18. Flocculation, hydrophobic agglomeration and filtration of ultrafine coal (United States)

    Yu, Zhimin

    In coal preparation plant circuits, fine coal particles are aggregated either by oil agglomeration or by flocculation. In a new hydrophobic agglomeration process, recently developed hydrophobic latices are utilized. While the selectivity of such aggregation processes determines the beneficiation results, the degree of aggregation has a strong effect on fine coal filtration. The aim of this research was to study the fundamentals and analyze the common grounds for these processes, including the potential effect of the coal surface properties. The selective flocculation tests, in which three types of coal, which differed widely in surface wettability, and three additives (hydrophobic latices, a semi-hydrophobic flocculant and a typical hydrophilic polyelectrolyte) were utilized, showed that coal wettability plays a very important role in selective flocculation. The abstraction of a hydrophobic latex on coal and silica revealed that the latex had a much higher affinity towards hydrophobic coal than to hydrophilic mineral matter. As a result, the UBC-1 hydrophobic latex flocculated only hydrophobic coal particles while the polyelectrolyte (PAM) flocculated all the tested coal samples and minerals, showing no selectivity in the fine coal beneficiation. The oil agglomeration was tested using kerosene emulsified with various surfactants (e.g. cationic, anionic and non-ionic). Surfactants enhance not only oil emulsification, hence reducing oil consumption (down to 0.25--0.5%), but also entirely change the electrokinetic properties of the droplets and affect the interaction energy between oil droplets and coal particles. Consequently, the results found in the course of the experimental work strongly indicate that even oxidized coals can be agglomerated if cationic surfactants are used to emulsify the oil. Oil agglomeration of the Ford-4 ultrafine coal showed that even at extremely low oil consumption (0.25 to 0.5%), a clean coal product with an ash content around 5% at over

  19. Conservation in transportation

    Energy Technology Data Exchange (ETDEWEB)



    A nationwide examination was made of grassroots energy conservation programs related to transportation. Information compiled from civic groups, trade associations, and corporations is included on driver awareness/mass transit; travel; and ride sharing. It is concluded that a willingness by the public to cooperate in transportation energy conservation exists and should be exploited. (LCL)

  20. Creative Soil Conservation (United States)

    Smith, Martha


    Take plant lessons outdoors with this engaging and inquiry-based activity in which third-grade students learn how to apply soil conservation methods to growing plants. They also collect data and draw conclusions about the effectiveness of their method of soil conservation. An added benefit to this activity is that the third-grade students played…

  1. Biodiversity Conservation in Asia


    Dale Squires


    Asian's remarkable economic growth brought many benefits but also fuelled threats to its ecosystems and biodiversity. Economic growth brings biodiversity threats but also conservation opportunities. Continued biodiversity loss is inevitable, but the types, areas and rates of biodiversity loss are not. Prioritising biodiversity conservation, tempered by what is tractable, remains a high priority. Policy and market distortions and failures significantly underprice biodiversity, undermine ecosys...

  2. Fixism and conservation science. (United States)

    Robert, Alexandre; Fontaine, Colin; Veron, Simon; Monnet, Anne-Christine; Legrand, Marine; Clavel, Joanne; Chantepie, Stéphane; Couvet, Denis; Ducarme, Frédéric; Fontaine, Benoît; Jiguet, Frédéric; le Viol, Isabelle; Rolland, Jonathan; Sarrazin, François; Teplitsky, Céline; Mouchet, Maud


    The field of biodiversity conservation has recently been criticized as relying on a fixist view of the living world in which existing species constitute at the same time targets of conservation efforts and static states of reference, which is in apparent disagreement with evolutionary dynamics. We reviewed the prominent role of species as conservation units and the common benchmark approach to conservation that aims to use past biodiversity as a reference to conserve current biodiversity. We found that the species approach is justified by the discrepancy between the time scales of macroevolution and human influence and that biodiversity benchmarks are based on reference processes rather than fixed reference states. Overall, we argue that the ethical and theoretical frameworks underlying conservation research are based on macroevolutionary processes, such as extinction dynamics. Current species, phylogenetic, community, and functional conservation approaches constitute short-term responses to short-term human effects on these reference processes, and these approaches are consistent with evolutionary principles. © 2016 Society for Conservation Biology.

  3. Water Conservation Resource List. (United States)

    NJEA Review, 1981


    Alarmed by the growing water shortage, the New Jersey State Office of Dissemination has prepared this annotated list of free or inexpensive instructional materials for teaching about water conservation, K-l2. A tipsheet for home water conservation is appended. (Editor/SJL)

  4. Conservation Science Fair Projects. (United States)

    Soil Conservation Society of America, Ankeny, IA.

    Included are ideas, suggestions, and examples for selecting and designing conservation science projects. Over 70 possible conservation subject areas are presented with suggested projects. References are cited with each of these subject areas, and a separate list of annotated references is included. The references pertain to general subject…

  5. Resource Conservation Glossary. (United States)

    Soil Conservation Society of America, Ankeny, IA.

    This glossary is a composite of terms selected from 13 technologies, and is the expanded revision of the original 1952 edition of "The Soil and Water Conservation Glossary." The terms were selected from these areas: agronomy, biology, conservation, ecology, economics, engineering, forestry, geology, hydrology, range, recreation, soils, and…

  6. Otter Conservation In Pakistan

    Directory of Open Access Journals (Sweden)

    Waseem Ahmad Khan


    Full Text Available This note describes the conservation status and threats of the two otter species described in Pakistan; Smooth coated otter (Lutrogale perspicillata sindica and the Eurasian or common otter (Lutra lutra. It also briefly describes the actors involved as well as the efforts made for its conservation.

  7. Introducing Conservation of Momentum (United States)

    Brunt, Marjorie; Brunt, Geoff


    The teaching of the principle of conservation of linear momentum is considered (ages 15 + ). From the principle, the momenta of two masses in an isolated system are considered. Sketch graphs of the momenta make Newton's laws appear obvious. Examples using different collision conditions are considered. Conservation of momentum is considered…

  8. On exactly conservative integrators

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, J.C. [Max-Planck-Inst. fuer Plasmaphysik, Garching (Germany); Shadwick, B.A. [Univ. of California, Berkeley, CA (United States). Dept. of Physics; Morrison, P.J. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies


    Traditional explicit numerical discretizations of conservative systems generically predict artificial secular drifts of nonlinear invariants. These algorithms are based on polynomial functions of the time step. The authors discuss a general approach for developing explicit algorithms that conserve such invariants exactly. They illustrate the method by applying it to the truncated two-dimensional Euler equations.

  9. On exactly conservative integrators

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, J.C. [Max-Planck-Inst. fuer Plasmaphysik, Garching (Germany); Shadwick, B.A. [Univ. of California, Berkeley, CA (United States). Dept. of Physics; Morrison, P.J. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies


    Traditional explicit numerical discretizations of conservative systems generically predict artificial secular drifts of nonlinear invariants. These algorithms are based on polynomial functions of the time step. The authors discuss a general approach for developing explicit algorithms that conserve such invariants exactly. They illustrate the method by applying it to the truncated two-dimensional Euler equations.

  10. Hyperactivation of Rhizomucor miehei lipase by hydrophobic xerogels. (United States)

    Aucoin, Marc G; Erhardt, Frank A; Legge, Raymond L


    Although a variety of approaches exist for the immobilization of enzymes, the "science" of enzyme immobilization is still in its infancy. In recent years, considerable interest has developed regarding the use of xerogels for enzyme immobilization. There are several advantages to xerogels for enzyme immobilization, including the opportunity to produce them in defined shapes or thin films and the ability to manipulate their physical characteristics (e.g., porosity, hydrophobicity, and optical properties). In this study we examined the effect of xerogel hydrophobicity on the activity of lipase (EC from Rhizomucor miehei. The hydrophobicity of the xerogels was manipulated by generating xerogels with various molar ratios of propyltrimethoxysilane (PTMS) to tetramethoxysilane (TMOS), from 1:1 to 10:1. The belief was that, by increasing the proportion of propyl groups, the hydrophobicity of the resulting xerogel would be increased. Differences in the hydrophobicity of the resulting xerogels were confirmed using water-affinity studies. Two approaches were taken for water-affinity determinations by examining the ability of the xerogels to remove water from air (controlled humidity) and from water-saturated isopropyl ether. Xerogels with higher propyl content showed a reduced affinity for water. A crude lipase preparation from Rhizomucor miehei was then contacted with sized xerogel particulates and the effect of the xerogel on lipase activity was determined. The presence of the xerogel resulted in hyperactivation of the lipase. Analysis of the protein adsorption revealed changes in the profile of proteins adsorbed to the xerogel based on the hydrophobicity of the xerogel. Based on estimations of the specific activity of the hyperactivated lipase, a minimum hyperactivation of 207% was observed. Part of the hyperactivation may be attributable to xerogel-lipase interactions, but also to the adsorption of a component from the crude lipase preparation that may complex

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Maoyuan; Besford, Quinn Alexander; Mulvaney, Thomas; Gray-Weale, Angus, E-mail: [School of Chemistry, The University of Melbourne, Victoria 3010 (Australia)


    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

  12. Influence of hydrophobic and electrostatic residues on SARS-coronavirus S2 protein stability: insights into mechanisms of general viral fusion and inhibitor design. (United States)

    Aydin, Halil; Al-Khooly, Dina; Lee, Jeffrey E


    Severe acute respiratory syndrome (SARS) is an acute respiratory disease caused by the SARS-coronavirus (SARS-CoV). SARS-CoV entry is facilitated by the spike protein (S), which consists of an N-terminal domain (S1) responsible for cellular attachment and a C-terminal domain (S2) that mediates viral and host cell membrane fusion. The SARS-CoV S2 is a potential drug target, as peptidomimetics against S2 act as potent fusion inhibitors. In this study, site-directed mutagenesis and thermal stability experiments on electrostatic, hydrophobic, and polar residues to dissect their roles in stabilizing the S2 postfusion conformation was performed. It was shown that unlike the pH-independent retroviral fusion proteins, SARS-CoV S2 is stable over a wide pH range, supporting its ability to fuse at both the plasma membrane and endosome. A comprehensive SARS-CoV S2 analysis showed that specific hydrophobic positions at the C-terminal end of the HR2, rather than electrostatics are critical for fusion protein stabilization. Disruption of the conserved C-terminal hydrophobic residues destabilized the fusion core and reduced the melting temperature by 30°C. The importance of the C-terminal hydrophobic residues led us to identify a 42-residue substructure on the central core that is structurally conserved in all existing CoV S2 fusion proteins (root mean squared deviation=0.4 Å). This is the first study to identify such a conserved substructure and likely represents a common foundation to facilitate viral fusion. We have discussed the role of key residues in the design of fusion inhibitors and the potential of the substructure as a general target for the development of novel therapeutics against CoV infections. © 2014 The Protein Society.

  13. Improving Anti-frosting Performance for Super-hydrophobic Nanocomposite Coatings

    Institute of Scientific and Technical Information of China (English)

    Hao WANG; Xiao Min WU; Li Ming TANG; Wan Tian DAI; Feng You JIN


    New super-hydrophobic nanocomposite coatings were formed from modified nano-sized CaCO3 particles and polyacrylate at weight ratio of 9/1-8/2. SEM and XPS analysis indicated that such hydrophobicity could be attributed to the surface nano-microstructure and the surface enrichment of fluorine atoms. As the surface hydrophobicity increased, longer time was required for formation the initial frost, which makes super-hydrophobic coatings suitable for anti-frosting purpose.

  14. Quantifying effective slip length over micropatterned hydrophobic surfaces

    CERN Document Server

    Tsai, Peichun; Pirat, Christophe; Wessling, Matthias; Lammertink, Rob G H; Lohse, Detlef


    We employ micro-particle image velocimetry ($\\mu$-PIV) to investigate laminar micro-flows in hydrophobic microstructured channels, in particular the slip length. These microchannels consist of longitudinal micro-grooves, which can trap air and prompt a shear-free boundary condition and thus slippage enhancement. Our measurements reveal an increase of the slip length when the width of the micro-grooves is enlarged. The result of the slip length is smaller than the analytical prediction by Philip et al. [1] for an infinitely large and textured channel comprised of alternating shear-free and no-slip boundary conditions. The smaller slip length (as compared to the prediction) can be attributed to the confinement of the microchannel and the bending of the meniscus (liquid-gas interface). Our experimental studies suggest that the curvature of the meniscus plays an important role in microflows over hydrophobic micro-ridges.

  15. Development of hydrophobicity of mica surfaces by ion beam sputtering (United States)

    Metya, Amaresh; Ghose, Debabrata; Ray, Nihar Ranjan


    The hydrophilic mica surface can be made hydrophobic by low energy Ar+ ion sputtering. The ion sputtering leads to both topographical and physicochemical changes of the surface which are thought to be responsible for the water repelling behavior. The sessile drop method is used to evaluate the wetting properties of the sputtered mica surfaces. It has been shown that the sputter-pattern at the nano-length scale has little influence on the development of hydrophobicity. On the other hand, the wettability appears to be strongly connected with the chemistry of the bombarded surface. We have also studied the temporal evolution of contact angle as the water evaporates due to difference in vapor pressures between the droplet surface and the surroundings. The analysis offers a simple method to estimate the diffusion coefficient of water vapor.

  16. Interaction of Fluorocarbon Containing Hydrophobically Modified Polyelectrolyte with Nonionic Surfactants

    Institute of Scientific and Technical Information of China (English)

    GUO,Jin-Feng(郭金峰); ZHUANG,Dong-Qing(庄东青); ZHOU,Hui(周晖); ZHANG,Yun-Xiang(章云祥)


    The interaction of fluorocarbon containing hydrophobically modified polyelectrolyte (FMPAANa) with two kinds of nonionic surfactants (hydrogenated and fluorinated) in a semidilute (0.5 wt% ) aqueous solution had been studied by rheological measurements. Association behavior was found in both systems. The hydrophobic interaction of FMPAANa with fluorinated surfactant (FC171) is much stronger than that with hydrogenated surfactant (NP7.5) at low surfactant concentrations. The interaction is strengthened by surfactants being added for the density of active junctions increased. Whereas distinct phenomena for FC171 and NP7. 5 start to be found as the surfactants added over their respective certain concentration. The interaction of polyelectrolyte with fluorinated surfactant increases dramatical ly while that with hydrogenated surfactant decreases.

  17. Development of hydrophobicity of mica surfaces by ion beam sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Metya, Amaresh; Ghose, Debabrata, E-mail:; Ray, Nihar Ranjan


    The hydrophilic mica surface can be made hydrophobic by low energy Ar{sup +} ion sputtering. The ion sputtering leads to both topographical and physicochemical changes of the surface which are thought to be responsible for the water repelling behavior. The sessile drop method is used to evaluate the wetting properties of the sputtered mica surfaces. It has been shown that the sputter-pattern at the nano-length scale has little influence on the development of hydrophobicity. On the other hand, the wettability appears to be strongly connected with the chemistry of the bombarded surface. We have also studied the temporal evolution of contact angle as the water evaporates due to difference in vapor pressures between the droplet surface and the surroundings. The analysis offers a simple method to estimate the diffusion coefficient of water vapor.

  18. Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene. (United States)

    Strong, Steven E; Eaves, Joel D


    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. Crossover behavior in the distance dependence of hydrophobic force law

    CERN Document Server

    Samanta, Tuhin; Bagchi, Biman


    Understanding about both the range and the strength of the effective force between two hydrophobic surfaces suspended in water is important in many areas of natural science but unfortunately has remained imperfect. Even the experimental observations have not been explained quantitatively. Here we find by varying distance (d) between two hydrophobic walls in computer simulations of water that the force exhibits a bi-exponential distance dependence. The long range part of the force can be fitted to an exponential force law with correlation length of 2 nm while the short range part displays a correlation length of only 0.5 nm. The crossover from shorter range to longer range force law is rather sharp. We show that the distance dependence of the tetrahedrality order parameter provides a reliable marker of the force law, and exhibits similar distance dependence.

  20. Driving Droplet by Scale Effect on Microstructured Hydrophobic Surfaces

    CERN Document Server

    Lv, Cunjing


    A new type of water droplet transportation on microstructured hydrophobic surface is proposed and investigated experimentally and theoretically - water droplet could be driven by scale effect which is different from the traditional methods. Gradient microstructured hydrophobic surface is fabricated in which the area fraction is kept constant, but the scales of the micro-pillars are monotonic changed. When additional water or horizontal vibration is applied, the original water droplet could move unidirectionally to the direction from the small scale to the large scale to decrease its total surface energy. A new mechanism based on line tension model could be used to explain this phenomenon. It is also found that dynamic contact angle decreases with increasing the scale of the micro-pillars along the moving direction. These new findings will deepen our understanding of the relationship between topology and wetting properties, and could be very helpful to design liquid droplet transportation device in microfluidi...

  1. Controlling film topography to form highly hydrophobic waterborne coatings. (United States)

    López, Ana B; de la Cal, José C; Asua, José M


    Coatings have a tremendous impact on economy as they reduce corrosion that has an estimated cost of 3% of the world's GDP. Hydrophobic coatings are particularly efficient for this purpose and the challenge is to produce cost effective and environmentally friendly, highly hydrophobic, cohesive and non-porous coatings applicable to large and irregular surfaces. This work shows that this goal can be achieved by forming wrinkles on the surface of waterborne coatings through fine-tuning of the film forming conditions. The proof of concept was demonstrated by using waterborne dispersions of copolymers of 1H,1H,2H,2H-perfluorodecyl acrylate and 2-ethylhexyl acrylate, and using the temperature and hardness of the copolymer as control variables during film formation. This allowed the formation of transparent films with a wrinkled surface that had a contact angle of 133°, which represents an increase of 20° with respect to the film cast under standard conditions.

  2. Direct Biofluid Analysis Using Hydrophobic Paper Spray Mass Spectrometry. (United States)

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


    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.

  3. Hydrophobic properties of a fluoropolymer film covering gold nanoparticles (United States)

    Safonov, A. I.; Starinskii, S. V.; Sulyaeva, V. S.; Timoshenko, N. I.; Gatapova, E. Ya.


    Thin fluoropolymer films were deposited on gold nanoparticles with different diameters by the hot-wire chemical-vapor-deposition method. The contact angles of wetting of samples with water and CH2I2 were determined using a DSA-100 KRUSS device, and the free surface energy of the coated surface was also determined. The influence of encapsulated gold particles on the hydrophobic properties of the obtained coatings was determined.

  4. Hydrophobic plasma polymerized hexamethyldisilazane thin films: characterization and uses

    Directory of Open Access Journals (Sweden)

    Alexsander Tressino de Carvalho


    Full Text Available Hexametildisilazane (HMDS plasma polymerized thin films obtained using low frequency power supplies can be used to make adsorbent films and turn surfaces hydrophobic. The aim of this work was to verify the hydrophobicity and adsorption properties of HMDS thin films (with and without the addition of oxygen, resulting in double or single layer films obtained using an inductive reactor powered with a 13.56 MHz power supply. Single and double layer thin films were deposited on silicon for film characterization, polypropylene (PP for ultraviolet (UVA/UVC resistance tests, piezoelectric quartz crystal for adsorption tests. The double layer (intermixing of HMDS plasma polymerized films and HMDS plasma oxidized surfaces showed a non-continuous layer. The films showed good adhesion to all substrates. Infrared analysis showed the presence of CHn, SiCH3, SiNSi and SiCH2Si within the films. Contact angle measurements with water showed hydrophobic surfaces. UVA/UVC exposure of the films resulted in the presence of cross-linking on carbonic radicals and SiCH2Si formation, which resulted in a possible protection of PP against UVA/UVC for a duration of up to two weeks. Adsorption tests showed that all organic reactants were adsorbed but not water. Plasma etching (PE using O2 showed that even after 15 minutes of exposure the films do not change their hydrophobic characteristic but were oxidized. The results point out that HMDS films can be used: for ultraviolet protection of flexible organic substrates, such as PP, for sensor and/or preconcentrator development, due to their adsorption properties, and in spatial applications due to resistance for O2 attack in hostile conditions, such as plasma etching.

  5. Preparative characteristics of hydrophobic polymer catalyst for the tritium removal

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hee Suk; Choi, H. J.; Lee, H. S.; Ahn, D. H.; Kim, K. R.; Paek, S. W.; Kim, J. G.; Chung, H. S


    The optimum method for the fabrication of hydrophobic catalyst was selected and the apparatuses for the preparation of catalyst support with high yield was developed for the large scale production. Also, we summarized the method of improving the physical property of the catalyst support, the loading characteristics of Pt metal as a catalyst, and the characteristics of the apparatus for the fabrication of the catalysts on a large scale.

  6. Fluctuations of water near extended hydrophobic and hydrophilic surfaces


    Patel, Amish J.; Chandler, David


    We use molecular dynamics simulations of the SPC-E model of liquid water to derive probability distributions for water density fluctuations in probe volumes of different shapes and sizes, both in the bulk as well as near hydrophobic and hydrophilic surfaces. To obtain our results, we introduce a biased sampling of coarse-grained densities, which in turn biases the actual solvent density. The technique is easily combined with molecular dynamics integration algorithms. Our principal result is t...

  7. Colony counting on hydrophobic grid-membrane filters. (United States)

    Sharpe, A N; Diotte, M P; Dudas, I; Malcolm, S; Peterkin, P I


    A device to facilitate manual scoring of hydrophobic grid-membrane filters (HGMF) is described. Variations in scores were generally less than 2.5% between 41 analysts from six laboratories, who, using the apparatus, scored a set of five specimen HGMF in different ways, and there was good agreement between scores from positive and negative grid-cell counts by each analyst. A scoring procedure for use in routine microbiological analysis, suitable for HGMF at various degrees of saturation, is recommended.

  8. A computational solution to analyze hydrophobic characteristics in protein chains (United States)

    Soares, Marilia Amável Gomes; Azevedo, Alexandre; Missailidis, Sotiris; Silva, Dilson


    This paper presents a program developed to facilitate calculations of the total or partial hidrophobicity value of polypeptides and proteins chains. It was built using the Fortran 77 language and performs additional functions, determining the total free energy and the electromotive force of an amino acid in a protein. These values were then used to estimate the average hydrophobicity of the protein or fragment sequence.

  9. From hydrophobic to superhydrophobic and superhydrophilic siloxanes by thermal treatment. (United States)

    Karapanagiotis, Ioannis; Manoudis, Panagiotis N; Zurba, Andreea; Lampakis, Dimitrios


    The cross-influence effects of treatment temperature and time on the wettability of a siloxane elastomer is investigated in detail, through static and tilt contact angle measurements. The material is heated at 400, 500, 600, 650, 700, and 800 °C for various periods, ranging from 1 to 300 s. The siloxane surface is subjected to multiple wettability transitions with treatment time: from intrinsic hydrophobicity to superhydrophobicity (and water repellency) and then through intermediate stages (hydrophobicity and hydrophilicity) to superhydrophilicity. For the time scale used herein (1-300 s), this scenario is recorded for treatment at 650, 700, and 800 °C. For treatment at lower temperatures (400, 500, and 600 °C) only the first transition, from intrinsic hydrophobicity to superhydrophobicity, is recorded. Scanning electron microscopy, micro-Fourier transform infrared (micro-FTIR), and micro-Raman spectroscopies are employed to correlate the aforementioned wettability transitions with structural and chemical changes of the siloxane surface, developed during thermal treatment. It is shown that the first transition from intrinsic hydrophobicity to superhydrophobicity is accompanied by a severe surface-structure evolution that increases surface roughness. Once superhydrophobicity is achieved, the surface structure reaches a saturation point and it is not subjected to any other change with further thermal treatment. FTIR spectroscopy shows that the intensity of the O-H/C-H peaks increases/decreases with treatment time, and Raman measurements show that the C-Si-C vibrations gradually disappear with treatment time. The evaporation of a droplet resting on a superhydrophobic, water-repellent siloxane surface, which was produced after appropriate thermal treatment, is monitored. It is shown that droplet evaporation initially follows the constant contact area mode. At later evaporation stages, a transition to the constant contact angle mode is recorded. Finally, it is

  10. Intrusion and extrusion of water in hydrophobic mesopores


    Barrat, Jean-Louis; Lefevre, Benoit; Bocquet, Lyderic; Saugey, Anthony; Vigier, Gérard; Gobin, Pierre-François; Charlaix, Elisabeth


    We present experimental and theoretical results on intrusion-extrusion cycles of water in hydrophobic mesoporous materials, characterized by independent cylindrical pores. The intrusion, which takes place above the bulk saturation pressure, can be well described using a macroscopic capillary model. Once the material is saturated with water, extrusion takes place upon reduction of the externally applied pressure; Our results for the extrusion pressure can only be understood by assuming that th...

  11. Experimental and computational surface hydrophobicity analysis of a non-enveloped virus and proteins. (United States)

    Heldt, Caryn L; Zahid, Amna; Vijayaragavan, K Saagar; Mi, Xue


    The physical characteristics of viruses needs to be understood in order to manipulate the interaction of viruses with host cells, as well as to create specific molecular recognition techniques to detect, purify, and remove viruses. Viruses are generally believed to be positively charged at physiological pH, but there are few other defining characteristics. Here, we have experimentally and computationally demonstrated that a non-enveloped virus is more hydrophobic than a panel of model proteins. Reverse-phase and hydrophobic interaction chromatography and ANS fluorescence determined the experimental hydrophobic strength of each entity. Computational surface hydrophobicity was calculated by the solvent exposed surface area of the protein weighted by the hydrophobicity of each amino acid. The results obtained indicate a strong correlation between the computational surface hydrophobicity and experimentally determined hydrophobicity using reverse-phase chromatography and ANS fluorescence. The surface hydrophobicity did not compare strongly to the weighted average of the amino acid sequence hydrophobicity. This demonstrates that our simple method of calculating the surface hydrophobicity gives general hydrophobicity information about proteins and viruses with crystal structures. In the process, this method demonstrated that porcine parvovirus (PPV) is more hydrophobic than the model proteins used in this study. This adds an additional dimension to currently known virus characteristics and can improve our manipulation of viruses for gene therapy targeting, surface adsorption and general understanding of virus interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Water stable aggregates of Japanese Andisol as affected by hydrophobicity and drying temperature

    Directory of Open Access Journals (Sweden)

    Leelamanie D.A.L.


    Full Text Available Hydrophobicity is a property of soils that reduces their affinity for water, which may help impeding the pressure build-up within aggregates, and reducing aggregate disruption. The purpose of this study was to examine the relation of soil hydrophobicity and drying temperature to water stability of aggregates while preventing the floating of dry aggregates using unhydrophobized and hydrophobized surface Andisol. Soil was hydrophobized using stearic acid into different hydrophobicities. Hydrophobicity was determined using sessile drop contact angle and water drop penetration time (WDPT. Water stability of aggregates (%WSA was determined using artificially prepared model aggregates. The %WSA increased as the contact angle and WDPT increased. Contact angle and WDPT, which provided maximum %WSA showing less than 1 s of floating, was around 100° and 5 s, respectively. Although the %WSA gradually increased with increasing contact angle and WDPT above this level, high levels of hydrophobicity initiated aggregate floating, which would cause undesirable effects of water repellency. Heating at 50°C for 5 h d-1 significantly affected %WSA and hydrophobicity in hydrophobized samples, but did not in unhydrophobized samples. The results indicate that the contact angle and wetting rate (WDPT are closely related with the water stability of aggregates. The results further confirm that high levels of hydrophobicities induce aggregate floating, and the drying temperature has differential effects on hydrophobicity and aggregate stability depending on the hydrophobic materials present in the soil.


    NARCIS (Netherlands)


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

  14. Synthesis and characterization of hydrophobically modified polymeric betaines

    Directory of Open Access Journals (Sweden)

    Alexey Shakhvorostov


    Full Text Available Polymeric betaines containing long alkyl chains C12H25, C14H29, C16H33 and C18H37 were synthesized by Michael addition reaction of alkylaminocrotonates and methacrylic acid (MAA. They were characterized by FTIR, 13C NMR, DSC, DLS, GPC, cryo-TEM, viscometry and zeta-potential measurements. The polymers were fully soluble in DMF, THF and DMSO, partially dissolved in aromatic hydrocarbons (benzene, toluene, o-xylene and formed colloid solutions in aqueous KOH. In aqueous KOH and DMSO solutions, hydrophobically modified polymeric betaines behaved as polyelectrolytes. The average hydrodynamic size and zeta potential of diluted aqueous solutions of hydrophobic polybetainess containing dodecyl-, tetradecyl-, hexadecyl-, and octadecyl groups were studied as a function of pH. Anomalous low values of the isoelectric point (IEP of amphoteric macromolecules were found to be in the range of pH 2.7-3.4. According to DLS data, the average size of macromolecules tends to decrease with dilution. Zeta-potential of amphoteric macromolecules in aqueous solution is much higher than that in DMSO. The cryo-TEM results revealed that in both aqueous KOH and DMSO media, the micron- and nanosized vesicles existed. The structural organization of vesicles in water and DMSO is discussed. The wax inhibition effect of hydrophobic polybetaines at a decrease of the pour point temperatures of high paraffinic oils was better in comparison with commercial available ethylene-vinylacetate copolymers (EVA.

  15. Repulsive effects of hydrophobic diamond thin films on biomolecule detection

    Energy Technology Data Exchange (ETDEWEB)

    Ruslinda, A. Rahim, E-mail: [Institute of Nano Electronic Engineering, Universiti Malaysia Perlis, Jln Kgr-Alor Setar, Seriab, 01000 Kangar, Perlis (Malaysia); Department of Nano Science and Nano Engineering, School of Advance Science and Engineering, Ohkubo 3-4-1, Shinjuku, 169-8555 Tokyo (Japan); Ishiyama, Y. [Department of Nano Science and Nano Engineering, School of Advance Science and Engineering, Ohkubo 3-4-1, Shinjuku, 169-8555 Tokyo (Japan); Penmatsa, V. [Department of Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 (United States); Ibori, S.; Kawarada, H. [Department of Nano Science and Nano Engineering, School of Advance Science and Engineering, Ohkubo 3-4-1, Shinjuku, 169-8555 Tokyo (Japan)


    Highlights: • We report the effect of fluorine plasma treatment on diamond thin film to resist the nonspecific adsorption of biomolecules. • The diamond thin film were highly hydrophobic with a surface energy value of ∼25 mN/m. • The repulsive effect shows excellent binding efficiency for both DNA and HIV-1 Tat protein. - Abstract: The repulsive effect of hydrophobic diamond thin film on biomolecule detection, such as single-nucleotide polymorphisms and human immunodeficiency virus type 1 trans-activator of transcription peptide protein detection, was investigated using a mixture of a fluorine-, amine-, and hydrogen-terminated diamond surfaces. These chemical modifications lead to the formation of a surface that effectively resists the nonspecific adsorption of proteins and other biomolecules. The effect of fluorine plasma treatment on elemental composition was also investigated via X-ray photoelectron spectroscopy (XPS). XPS results revealed a fluorocarbon layer on the diamond thin films. The contact angle measurement results indicated that the fluorine-treated diamond thin films were highly hydrophobic with a surface energy value of ∼25 mN/m.

  16. Hydrophobic Core Flexibility Modulates Enzyme Activity in HIV-1 Protease

    Energy Technology Data Exchange (ETDEWEB)

    Mittal, Seema; Cai, Yufeng; Nalam, Madhavi N.L.; Bolon, Daniel N.A.; Schiffer, Celia A. (UMASS, MED)


    Human immunodeficiency virus Type-1 (HIV-1) protease is crucial for viral maturation and infectivity. Studies of protease dynamics suggest that the rearrangement of the hydrophobic core is essential for enzyme activity. Many mutations in the hydrophobic core are also associated with drug resistance and may modulate the core flexibility. To test the role of flexibility in protease activity, pairs of cysteines were introduced at the interfaces of flexible regions remote from the active site. Disulfide bond formation was confirmed by crystal structures and by alkylation of free cysteines and mass spectrometry. Oxidized and reduced crystal structures of these variants show the overall structure of the protease is retained. However, cross-linking the cysteines led to drastic loss in enzyme activity, which was regained upon reducing the disulfide cross-links. Molecular dynamics simulations showed that altered dynamics propagated throughout the enzyme from the engineered disulfide. Thus, altered flexibility within the hydrophobic core can modulate HIV-1 protease activity, supporting the hypothesis that drug resistant mutations distal from the active site can alter the balance between substrate turnover and inhibitor binding by modulating enzyme activity.

  17. Water's structure around hydrophobic solutes and the iceberg model. (United States)

    Galamba, N


    The structure of water in the hydration shells of small hydrophobic solutes was investigated through molecular dynamics. The results show that a subset of water molecules in the first hydration shell of a nonpolar solute have a significantly enhanced tetrahedrality and a slightly larger number of hydrogen bonds, relative to the molecules in water at room temperature, consistent with the experimentally observed negative excess entropy and increased heat capacity of hydrophobic solutions at room temperature. This ordering results from the rearrangement of a small number of water molecules near the nonpolar solutes that occupy one to two vertices of the enhanced water tetrahedra. Although this structuring is not nearly like that often associated with a literal interpretation of the term "iceberg" in the Frank and Evans iceberg model, it does support a moderate interpretation of this model. Thus, the tetrahedral orientational order of this ensemble of water molecules is comparable to that of liquid water at ~10 °C, although not accompanied by the small contraction of the O-O distance observed in cold water. Further, we show that the structural changes of water in the vicinity of small nonpolar solutes cannot be inferred from the water radial distribution functions, explaining why this increased ordering is not observed through neutron diffraction experiments. The present results restore a molecular view where the slower translational and reorientational dynamics of water near hydrophobic groups has a structural equivalent resembling water at low temperatures.

  18. Contact-angle hysteresis on super-hydrophobic surfaces. (United States)

    McHale, G; Shirtcliffe, N J; Newton, M I


    The relationship between perturbations to contact angles on a rough or textured surface and the super-hydrophobic enhancement of the equilibrium contact angle is discussed theoretically. Two models are considered. In the first (Wenzel) case, the super-hydrophobic surface has a very high contact angle and the droplet completely contacts the surface upon which it rests. In the second (Cassie-Baxter) case, the super-hydrophobic surface has a very high contact angle, but the droplet bridges across surface protrusions. The theoretical treatment emphasizes the concept of contact-angle amplification or attenuation and distinguishes between the increases in contact angles due to roughening or texturing surfaces and perturbations to the resulting contact angles. The theory is applied to predicting contact-angle hysteresis on rough surfaces from the hysteresis observable on smooth surfaces and is therefore relevant to predicting roll-off angles for droplets on tilted surfaces. The theory quantitatively predicts a "sticky" surface for Wenzel-type surfaces and a "slippy" surface for Cassie-Baxter-type surfaces.

  19. Structures of multidomain proteins adsorbed on hydrophobic interaction chromatography surfaces. (United States)

    Gospodarek, Adrian M; Sun, Weitong; O'Connell, John P; Fernandez, Erik J


    In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized.

  20. Protein interactions in hydrophobic charge induction chromatography (HCIC). (United States)

    Ghose, Sanchayita; Hubbard, Brian; Cramer, Steven M


    A quantitative understanding of how proteins interact with hydrophobic charge induction chromatographic resins is provided. Selectivity on this mode of chromatography for monoclonal antibodies as compared to other model proteins is probed by means of a linear retention vs pH plot. The pH-dependent adsorption behavior on this mode of chromatography for a hydrophobic, charged solute is described by taking into account the equilibrium between a hydrophobic, charged solute and an ionizable, heterocyclic ligand. By analogy, an equation that is seen to adequately describe macromolecular retention under linear conditions over a range of pH is developed. A preparative, nonlinear isotherm that can capture both pH and salt concentration dependency for proteins is proposed by using an exponentially modified Langmuir isotherm model. This model is seen to successfully simulate adsorption isotherms for a variety of proteins over a range of pHs and mobile phase salt concentrations. Finally, the widely differing retention characteristics of two monoclonal antibodies are used to derive two different strategies for improving separations on this mode of chromatography. A better understanding of protein binding to this class of resins is seen as an important step to future exploitation of this mode of chromatography for industrial scale purification of proteins.

  1. Unusual properties of water at hydrophilic/hydrophobic interfaces. (United States)

    Gun'ko, V M; Turov, V V; Bogatyrev, V M; Zarko, V I; Leboda, R; Goncharuk, E V; Novza, A A; Turov, A V; Chuiko, A A


    The behaviour of water at mosaic hydrophilic/hydrophobic surfaces of different silicas and in biosystems (biomacromolecules, yeast cells, wheat seeds, bone and muscular tissues) was studied in different dispersion media over wide temperature range using 1H NMR spectroscopy with layer-by-layer freezing-out of bulk water (close to 273 K) and interfacial water (180 water and water bound to hydrophilic/hydrophobic interfaces can be assigned to different structural types. There are (i) weakly associated interfacial water (1H NMR chemical shift delta(H) = 1.1-1.7 ppm) that can be assigned to high-density water (HDW) with collapsed structure (CS), representing individual molecules in hydrophobic pockets, small clusters and interstitial water with strongly distorted hydrogen bonds or without them, and (ii) strongly associated interfacial water (delta(H) = 4-5 ppm) with larger clusters, nano- and microdomains, and continuous interfacial layer with both HDW and low-density water (LDW). The molecular mobility of weakly associated bound water is higher (because hydrogen bonds are distorted and weakened and their number is smaller than that for strongly associated water) than that of strongly associated bound water (with strong hydrogen bonds but nevertheless weaker than that in ice Ih) that results in the difference in the temperature dependences of the 1H NMR spectra at T waters are also appear in changes in the IR and TSDC spectra.

  2. Principles of encapsulating hydrophobic drugs in PLA/PLGA microparticles. (United States)

    Wischke, Christian; Schwendeman, Steven P


    Injectable biodegradable and biocompatible copolymers of lactic and glycolic acid (PLGA) are an important advanced delivery system for week-to-month controlled release of hydrophobic drugs (e.g., from biopharmaceutical classification system class IV), which often display poor oral bioavailability. The basic principles and considerations to develop such microparticle formulations is reviewed here based on a comprehensive study of papers and patents from the beginnings of hydrophobic drug encapsulation in polylactic acid and PLGA up through the very recent literature. Challenges with the diversity of drug properties, microencapsulation methods, and organic solvents are evaluated in light of the precedence of commercialized formulations and with a focus on decreasing the time to lab-scale encapsulation of water-insoluble drug candidates in the early stage of drug development. The influence of key formulation variables on final microparticle characteristics, and how best to avoid undesired microparticle properties, is analyzed mechanistically. Finally, concepts are developed to manage the common issues of maintaining sink conditions for in vitro drug release assays of hydrophobic compounds. Overall, against the backdrop of an increasing number of new, poorly orally available drug entities entering development, microparticle delivery systems may be a viable strategy to rescue an otherwise undeliverable substance.

  3. Granulation of increasingly hydrophobic formulations using a twin screw granulator. (United States)

    Yu, Shen; Reynolds, Gavin K; Huang, Zhenyu; de Matas, Marcel; Salman, Agba D


    The application of twin screw granulation in the pharmaceutical industry has generated increasing interest due to its suitability for continuous processing. However, an understanding of the impact of formulation properties such as hydrophobicity on intermediate and finished product quality has not yet been established. Hence, the current work investigated the granulation behaviour of three formulations containing increasing amounts of hydrophobic components using a Consigma™-1 twin screw granulator. Process conditions including powder feed rate, liquid to solid ratio, granulation liquid composition and screw configuration were also evaluated. The size of the wet granules was measured in order to enable exploration of granulation behaviour in isolation without confounding effects from downstream processes such as drying. The experimental observations indicated that the granulation process was not sensitive to the powder feed rate. The hydrophobicity led to heterogeneous liquid distribution and hence a relatively large proportion of un-wetted particles. Increasing numbers of kneading elements led to high shear and prolonged residence time, which acted to enhance the distribution of liquid and feeding materials. The bimodal size distributions considered to be characteristic of twin screw granulation were primarily ascribed to the breakage of relatively large granules by the kneading elements.

  4. Dynamics of Defrosting on Hydrophobic and Superhydrophobic Surfaces (United States)

    Murphy, Kevin; McClintic, William; Lester, Kevin; Collier, Patrick; Boreyko, Jonathan


    It has recently been demonstrated that frost can grow in a suspended Cassie state on nanostructured superhydrophobic surfaces, which has implications for enhanced defrosting rates. However, to date there have been no direct comparisons of the defrosting kinetics of Cassie frost versus frost on conventional surfaces. Here, we fabricate a hybrid aluminum plate where half of the top face exhibits a superhydrophobic nanostructure while the other half is smooth and hydrophobic. By growing frost to varying thicknesses and melting at several tilt angles, we reveal the advantages and disadvantages of each surface with regards to the extent and speed of the shedding of melt water. For sufficiently thick frost layers, the Cassie state of frost on the superhydrophobic surface uniquely enabled the rapid and effective shedding of melt water even at low tilt angles. On the other hand, the hydrophobic surface was more effective at removing very thin frost sheets, as the reduced contact angle of water on the surface facilitated the coalescence of droplets to grow the melt water beyond the capillary length for gravitational removal. Therefore, the utilization of superhydrophobic versus hydrophobic surfaces for defrosting applications depends upon the context of the system conditions.

  5. Assembly of Hydrophobically Modified Poly(acrylic acid) with Cyclodextrins%Assembly of Hydrophobically Modified Poly(acrylic acid) with Cyclodextrins

    Institute of Scientific and Technical Information of China (English)


    Hydrophobically modified poly(acrylic acid)s (HMPAA) with alkyl (C12 or C18) substitution degree ranging from 3% to 10% were synthesized. Their rheological properties in aqueous solutions can be controlled by adding native cyclodextrins (CD) and surfactant SDS. Upon addition of CD, the viscosity of HMPAA solution was reduced significantly because of the destruction of hydrophobic associations by capping the hydrophobic alkyl groups by CD due to the host-guest complexation.

  6. Hearing Conservation Team (United States)

    Federal Laboratory Consortium — The Hearing Conservation Team focuses on ways to identify the early stages of noise-induced damage to the human ear.Our current research involves the evaluation of...

  7. Hearing Conservation Team (United States)

    Federal Laboratory Consortium — The Hearing Conservation Team focuses on ways to identify the early stages of noise-induced damage to the human ear. Our current research involves the evaluation of...

  8. Conservation of Beclardia macrostachya

    African Journals Online (AJOL)


    Department of Agriculture and Food Science ... Tissue culture is an essential tool for ex situ conservation. ... In vitro culture also provides plausible solutions to ..... Cryopreservation of zygotic embryos of a Japanese terrestrial orchid (Bletilla.

  9. Metro Conservation Corridors (United States)

    Minnesota Department of Natural Resources — The Metro Conservation Corridors (MeCC) grow out of the natural resource analysis work done by the DNR in the late '90's, documented in the Metro Greenprint...

  10. Conservation among Elderly Women. (United States)

    Hughston, George A.; Protinsky, Howard O.


    The majority of 63 elderly women were able to pass tests in the conservation of mass (98 percent), volume (100 percent), and surface area (65 percent). These results conflict with previous research about Piagetian abilities of elderly people. (RL)

  11. Landscape Conservation Cooperatives (United States)

    US Fish and Wildlife Service, Department of the Interior — Landscape Conservation Cooperatives (LCCs) are public-private partnerships composed of states, tribes, federal agencies, non-governmental organizations,...

  12. Policy: Palatable forest conservation (United States)

    Tacconi, Luca


    Current policies to reduce emissions from forest loss could mean that rising demand for food is not met. A new approach to forest conservation that reduces emissions while meeting demand for agricultural products may be feasible, but more expensive.

  13. Monitoring for conservation (United States)

    Nichols, J.D.; Williams, B.K.


    Human-mediated environmental changes have resulted in appropriate concern for the conservation of ecological systems and have led to the development of many ecological monitoring programs worldwide. Many programs that are identified with the purpose of `surveillance? represent an inefficient use of conservation funds and effort. Here, we revisit the 1964 paper by Platt and argue that his recommendations about the conduct of science are equally relevant to the conduct of ecological monitoring programs. In particular, we argue that monitoring should not be viewed as a stand-alone activity, but instead as a component of a larger process of either conservation-oriented science or management. Corresponding changes in monitoring focus and design would lead to substantial increases in the efficiency and usefulness of monitoring results in conservation.

  14. Energy Conservation Behaviour Toolkit

    NARCIS (Netherlands)

    Kalz, Marco; Börner, Dirk; Ternier, Stefaan; Specht, Marcus


    Kalz, M., Börner, D., Ternier, S., & Specht, M. (2013, 31 January). Energy Conservation Behaviour Toolkit. Presentation given at the symposium "Groene ICT en Duurzame ontwikkeling: Meters maken in het Hoger Onderwijs", Driebergen, The Netherlands.

  15. Durable PROX catalyst based on gold nanoparticles and hydrophobic silica

    KAUST Repository

    Laveille, Paco


    3 nm gold nanoparticles (Au NP) obtained by direct chemical reduction of AuPPh3Cl in the presence of methyl-terminated silica exhibit superior durability for low temperature CO oxidation in the presence of hydrogen (PROX). The activity of hydrophobic Au/SiO2-R972 indeed appears much more stable with time-on-stream than those of the OH-terminated, hydrophilic Au/TiO2 and Au/Al2O3 catalysts, with similar Au NP size. This enhanced stability is attributed to the peculiar catalyst surface of Au/SiO2-R972. Not only may the support hydrophobicity concentrate and facilitate reactant adsorption and product desorption over Au NP, but methyl-terminated SiO2-R972 likely also inhibits carbonatation of the Au/support interface. Hence, at a temperature at which H2/H2O “cleaning” of the carbonate-contaminated Au/Al2O3 and Au/TiO2 surface is inefficient (< 100°C), passivated Au/SiO2-R972 displays much more stable PROX activity. Besides, the virtual absence of surface hydroxyl groups, which provide sites for water formation in H2/O2 atmospheres, can also account for the improved PROX selectivity (>85%) observed over Au/SiO2-R972. This new example, of CO oxidation activity of gold nanoparticles dispersed over a hydrophobic, “inert” support, clearly emphasizes the role of hydrogen as a promoter for the gold-catalyzed oxidation of CO at low temperature. Unlike support-mediated oxygen activation, hydrogen-only mediated oxygen activation takes full advantage of the hydrophobic surface, which is much more resistant against CO2 and thus remains free of poisonous carbonate species, as compared with hydroxyl-terminated catalysts. Hence, although the absence of surface hydroxyl groups prevents the hydrophobic Au/SiO2-R972 catalyst to reach the state-of-the-art activities initially displayed by Au/TiO2 and Au/Al2O3, it brings long-term stability with time-on-stream and superior selectivity, which opens up promising perspectives in the development of viable PROX catalysts based on gold.

  16. Tunable Surface Hydrophobicity and Fluid Transport through Nanoporous Membranes (United States)

    Ostrowski, Joseph H. J.

    There are more than three billion people across the globe that struggle to obtain clean drinkable water. One of the most promising avenues for generating potable water is through reverse osmosis and nanofiltration. Both solutions require a semipermeable membrane that prohibits passage of unwanted solute particles but allows passage of the solvent. Atomically thin two-dimensional membranes based on porous graphene show great promise as semipermeable materials, but modeling fluid flow on length scales between the microscopic (nanometer and smaller) and macroscopic (micron and larger) regimes presents formidable challenges. This thesis explores both equilibrium and nonequilibrium aspects of this problem and develops new methodology for simulating systems away from thermal equilibrium. First, we hypothesize that there is a wetting penalty for water as it tries to breach a sheet of graphene that should be naturally hydrophobic. By using equilibrium molecular dynamics simulations, we show that the hydrophobicity depends sensitively on the degree of electrical doping, offering an opportunity to tune the hydrophobic effect of graphene using small amounts of doping. The wetting contact angle, a measure of hydrophobicity, changes dramatically with the voltage applied to single layer graphene. We find that the sensitivity of the hydrophobic effect to voltage depends not on hydrogen bonding motifs at the interface between graphene and water, but instead on a phenomenon known as electrowetting. The theory of electrowetting predicts that the difference in surface tensions that defines the contact angle is quartic in the voltage, rather than quadratic, as it would be in bilayer graphene or in a two-dimensional metal. To explore the nonequilibrium aspects of fluid passage through atomically thin membranes, we developed a molecular dynamics methodology for simulating fluid flow at constant flux based on Gauss's principle of least constraint. This method develops microscopic

  17. Energy conservation in infants. (United States)

    Blass, Elliott


    Energy acquisition through suckling has been widely studied in rat and human infants. Processes mediating energy conservation, however, have not received the attention that they deserve. This essay, in honor of Professor Jerry Hogan, discusses parallel behaviors used by rat and human mothers to minimize energy loss in their offspring. Parallel mechanisms underlying energy preservation have been identified in rats and humans, suggesting phylogenetic conservation and possibly continuity. This article is part of a Special Issue entitled: In Honor of Jerry Hogan.

  18. Phenylalanine 664 of dipeptidyl peptidase (DPP) 7 and Phenylalanine 671 of DPP11 mediate preference for P2-position hydrophobic residues of a substrate. (United States)

    Rouf, Shakh M A; Ohara-Nemoto, Yuko; Ono, Toshio; Shimoyama, Yu; Kimura, Shigenobu; Nemoto, Takayuki K


    Dipeptidyl peptidases (DPPs) are crucial for the energy metabolism in Porphyromonas gingivalis, a Gram-negative proteolytic and asaccharolytic anaerobic rod causing chronic periodontitis. Three DPPs, DPPIV specific for Pro, DPP7 for hydrophobic residues and DPP11 for Asp/Glu at the P1 position, are expressed in the bacterium. Like DPP7, DPP11 belongs to the S46 protease family, and they share 38.7% sequence identity. Although DPP11 is preferential for hydrophobic residues at the P2 position, it has been reported that DPP7 has no preference at the P2 position. In the present study, we defined the detailed P2 substrate preference of DPP7 and the amino acid residue responsible for the specificity. DPP7 most efficiently hydrolyzed Met-Leu-dipeptidyl-4-methylcoumaryl-7-amide (MCA) carrying hydrophobic residues at the P1 position with k cat/Km of 10.62 ± 2.51 μM(-1) s(-1), while it unexpectedly cleaved substrates with hydrophilic (Gln, Asn) or charged (Asp, Arg) residues. Examination with 21 dipeptidyl MCA demonstrated that DPP7-peptidase activity was dependent on hydrophobicity of the P2- as well as P1-position residue, thus it correlated best with the sum of the hydrophobicity index of P1- and P2-amino acid residues. Hydrophobicity of the P1 and P2 positions ensured efficient enzyme catalysis by increasing k cat and lowering Km values, respectively. Substitution of hydrophobic residues conserved in the S46 DPP7/DPP11 family to Ala revealed that Phe664 of DPP7 and Phe671 of DPP11 primarily afforded hydrophobic P2 preference. A modeling study suggested that Phe664 and Gly666 of DPP7 and Phe671 and Arg673 of DPP11 being associated with the P2- and P1-position residues, respectively, are located adjacent to the catalytic Ser648/Ser655. The present results expand the substrate repertoire of DPP7, which ensures efficient degradation of oligopeptides in asaccharolytic bacteria.

  19. Surfactant Facilitated Spreading of Aqueous Drops on Hydrophobic Surfaces (United States)

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


    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

  20. Spontaneous association of hydrophobized dextran and poly-beta-cyclodextrin into nanoassemblies. Formation and interaction with a hydrophobic drug. (United States)

    Daoud-Mahammed, S; Ringard-Lefebvre, C; Razzouq, N; Rosilio, V; Gillet, B; Couvreur, P; Amiel, C; Gref, R


    New nanoassemblies were instantaneously prepared by mixing two aqueous solutions, one containing a beta-cyclodextrin polymer (pbetaCD), and the other a hydrophobically modified by alkyl chains dextran (MD). The formation mechanism and the inner structure of these nanoassemblies were analysed using surface tension measurements and (1)H NMR spectroscopy. The effect of a hydrophobic guest molecule, such as benzophenone (BZ), on the formation and stability of the nanoassemblies was also evaluated. MD exhibited the typical behaviour of a soluble amphiphilic molecule and adsorbed at the air/water interface. Whereas the injection of native beta-CDs in the solution beneath the adsorbed MD monolayer did not produce any change in the surface tension, that of the pbetaCD resulted in an increase in the surface tension, indicating the desorption of the polymer from the interface. This result accounts for a cooperative effect of beta-CDs linked together in the pbetaCD polymer on dextran desorption. The presence of benzophenone in the system hindered the sequestration of dextran alkyl moieties by beta-CD in the polymer without impeding the formation of associative nanoassemblies of 100-200 nm. (1)H NMR investigations demonstrated that, in the BZ-loaded nanoassemblies, the hydrophobic molecule was mainly located into the cyclodextrin cavities.


    Institute of Scientific and Technical Information of China (English)

    LI Baojia; ZHOU Ming; QIAN Kunxi; CAI Lan


    Some superhydrophobic siliconbased surfaces with periodic square pillar array microstructures were designed and fabricated, also their apparent contact angles (CAs) were quantitatively measured. On the basis of the classical Wenzel's theory and Cassie's theory, two generally applicable equations corresponding of the cases of wetted contact and composite contact, which could reflect the relations between geometrical parameters of square pillar microstructures and apparent CAs, were educed. Then a theoretical prediction of the fabricated siliconbased surfaces was carried out by the equations, which was compatible with the result of experimental measurement, and this showed the rationality of the educed equations. The CAs of the surface prepared by merely plasma etching to create microstructures and by only Teflon treating were compared, and the result indicated that the effect of the former on achieving hydrophobic surfaces was greater than that of the later. Under the premise of synthetically considering transition between the two contact states, the effects of geometrical parameters of the square pillar microstructures to hydrophobicity were analyzcation, thereon a design condition and a design principle for super-hydrophobic surfaces which would be of specific application value were summarized.

  2. Conservation Kickstart- Catalyzing Conservation Initiatives Worldwide (United States)

    Treinish, G.


    Adventurers and Scientists for Conservation (ASC) is a nonprofit organization that collects environmental data to catalyze conservation initiatives worldwide. Adventure athletes have the skills and motivation to reach the most remote corners of the world. ASC utilizes those skills to provide the scientific community with data while providing the outdoor community with purpose beyond the personal high of reaching a summit or rowing across an ocean. We carefully select projects, choosing partnerships that will maximize the impact of ASC volunteers. Each project must have a clear path to a tangible conservation outcome and demonstrate a clear need for our brand of volunteers. We partner with government agencies, universities, and independant reseachers to kickstart data collection efforts around the world. Last year, through a partnership with the Olympic National Forest, 20 volunteers from the Seattle area set up and monitored camera traps in an effort to survey for costal Pacific marten. Our work led to the species' listing as "critically imperiled" with NatureServe. A partnership with the inaugural Great Pacific Race, engaging trans-Pacific rowing teams, searched for microplastics in the Pacific Ocean as part of our ongoing microplastics campaign. In a multi-year partnership with the American Prairie Reserve (APR), ASC volunteer crews live and work on the Reserve collecting wildlife data year round. The data we obtain directly informs the Reserve's wildlife management decisions. On this project, our crews have safely and effectively navigated temperature extremes from -30 degrees to 100+ degrees while traveling in a remote location. We are currently scouting projects in the Okavango Delta of Botswana and the rainforest of Suriname where we will be able to cover large amounts of area in a short periord of time. ASC is at the crossroads of the adventure and coservation science communities. Our approach of answering specific questions by using highly skilled and


    Institute of Scientific and Technical Information of China (English)


    Hydrophobically modified poly(4-vinyl pyridines) by alkyl bromides are kinds of polysoap similar to the surfactant. Properties of dilute solutions were studied through the viscosity measurements in pure water and NaCl solutions. In aqueous solutions of polysoaps hydrophobic interaction can be attributed to aggregation of hydrophobic groups of the polysoap main chains. The hydrophobic groups of polysoap can aggregate to form hydrophobic microdomains (micelles) in aqueous solution. This is a compact conformation. The formation of such microdomains is a process of dynamic equilibrium.

  4. Hydro-physical processes and soil properties correlated with origin of soil hydrophobicity

    Directory of Open Access Journals (Sweden)

    Eduardo Saldanha Vogelmann


    Full Text Available Hydrophobicity is the phenomenon where the soil has reduced wettability, usually associated with coating of soil particles by hydrophobic organic substances. This study aimed to provide a description of the hydrophobicity occurrence, highlight recent discoveries about the origin of phenomenon and discuss the main hydro-physical properties and chemical processes linked to the development of hydrophobic behavior in soils. Hydrophobicity is associated with other factors such as soil moisture, presence of some fungi species, particle size, soil pH and occurrence of burnings. The causative substances may be provided by local vegetation, through deposition or decomposition. The dependence and combination of different factors that influence hydrophobicity in soils lead to a spatial and temporal variability of the phenomenon, with negative consequences in the processes of infiltration and water percolation, affecting the three-dimensional distribution and dynamics of soil moisture. Thus, the occurrence of a hydrophobic character requires special attention, especially regarding soil use and management.

  5. Zircon U-Pb ages and Sr-Nd-Hf isotopes of the highly fractionated granite with tetrad REE patterns in the Shamai tungsten deposit in eastern Inner Mongolia, China: Implications for the timing of mineralization and ore genesis (United States)

    Jiang, Si-Hong; Bagas, Leon; Hu, Peng; Han, Ning; Chen, Chun-Liang; Liu, Yuan; Kang, Huan


    The Shamai tungsten deposit is located in the eastern part of the Central Asian Orogenic Belt (CAOB). Tungsten mineralization is closely related to the emplacement of fine- to medium-grained biotite monzogranite (G1) and porphyritic biotite monzogranite (G2) in the Shamai Granite. NW-trending joints and faults host orebodies in the Shamai Granite and Devonian hornfels. The mineralization is characterized by a basal veinlet zone progressing upwards to a thick vein zone followed by a mixed zone, a veinlet zone, and a thread vein zone at the top. The ore-related alteration typically consists of muscovite, greisen, and hornfels. In order to constrain the timing of the Shamai mineralization and discuss the ore genesis, muscovite Ar-Ar, molybdenite Re-Os, and zircon U-Pb geochronological, geochemical, and Sr-Nd-Hf isotopic studies were completed on the deposit. The U-Pb zircon dating yielded weighted mean ages of 153 ± 1 Ma for G1 and 146 ± 1 Ma for G2. Muscovite from a wolframite-bearing quartz vein yielded an Ar-Ar plateau age of 140 ± 1 Ma, whereas two molybdenite samples yielded identical Re-Os model ages of 137 ± 2 Ma. These two ages are younger than the two monzogranites, suggesting a prolonged magmatic-hydrothermal interaction during tungsten mineralization. Major and trace element geochemistry shows that both G1 and G2 are characterized by high SiO2 and K2O contents, high A/CNK values (1.08-1.40), a spectacular tetrad effect in their REE distribution patterns, and non-CHARAC (charge-and-radius-controlled) trace element behavior. This suggests that both G1 and G2 are highly differentiated peraluminous rocks with strong hydrothermal interaction. The Nd-Hf isotope data for the Shamai Granite (εNd(t) between - 1.9 and + 7.4, ɛHf(t) from 5.2 to 12.8) are largely compatible with the general scenario for much of the Phanerozoic granite emplaced in the CAOB. It is here suggested that the Shamai Granite originated from partial melting of a juvenile lower crust with

  6. Molecular phylogeny of OVOL genes illustrates a conserved C2H2 zinc finger domain coupled by hypervariable unstructured regions.

    Directory of Open Access Journals (Sweden)

    Abhishek Kumar

    Full Text Available OVO-like proteins (OVOL are members of the zinc finger protein family and serve as transcription factors to regulate gene expression in various differentiation processes. Recent studies have shown that OVOL genes are involved in epithelial development and differentiation in a wide variety of organisms; yet there is a lack of comprehensive studies that describe OVOL proteins from an evolutionary perspective. Using comparative genomic analysis, we traced three different OVOL genes (OVOL1-3 in vertebrates. One gene, OVOL3, was duplicated during a whole-genome-duplication event in fish, but only the copy (OVOL3b was retained. From early-branching metazoa to humans, we found that a core domain, comprising a tetrad of C2H2 zinc fingers, is conserved. By domain comparison of the OVOL proteins, we found that they evolved in different metazoan lineages by attaching intrinsically-disordered (ID segments of N/C-terminal extensions of 100 to 1000 amino acids to this conserved core. These ID regions originated independently across different animal lineages giving rise to different types of OVOL genes over the course of metazoan evolution. We illustrated the molecular evolution of metazoan OVOL genes over a period of 700 million years (MY. This study both extends our current understanding of the structure/function relationship of metazoan OVOL genes, and assembles a good platform for further characterization of OVOL genes from diverged organisms.

  7. Adsorption of Rotavirus, MS2 Bacteriophage and Surface-Modified Silica Nanoparticles to Hydrophobic Matter. (United States)

    Farkas, Kata; Varsani, Arvind; Pang, Liping


    Adsorption to aquifer media is an important process in the removal of viruses from groundwater. Even though hydrophobic interactions have been shown to contribute to adsorption, little is known about the hydrophobicity of viruses found in groundwater. In this study, the hydrophobicity of rotavirus, MS2 bacteriophage and DNA-labelled silica nanoparticles (SiNPs) coated with glycoprotein, protein A and alpha-1-microglobulin/bikunin precursor (AMBP) was investigated. The hydrophobicity was experimentally determined by using a modified microbial adhesion to hydrocarbons (MATH) assay. The results were compared with the theoretical hydrophobicity of the viral capsid proteins and the proteins used to coat the nanoparticles, and with the results of adsorption tests with unmodified and organosilane-coated (hydrophobic) silica sand. While most theoretical protein hydrophobicity values were similar, the results of the MATH assay suggested fundamental differences in the hydrophobicity of the viruses and the SiNPs. MS2 was found to be highly hydrophobic as based on the MATH hydrophobicity and a significantly enhanced adsorption to hydrophobic sand, whereas rotavirus was relatively hydrophilic. The MATH assay revealed that protein-coating of SiNP introduced some degree of hydrophobicity to hydrophilic SiNPs, enabling them to more closely mimic viral hydrophobicity. Our study also demonstrated that the protein-coated SiNPs better mimicked rotavirus adsorption to sand media (coated or not coated with hydrophobic organic matter) than the MS2. This further supports previous findings that these surface-modified SiNPs are useful surrogates in mimicking rotavirus retention and transport in porous media.

  8. Studies on polyurethane adhesives and surface modification of hydrophobic substrates (United States)

    Krishnamoorthy, Jayaraman

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

  9. The Data Conservancy (United States)

    Choudhury, S.; Duerr, R. E.


    NSF's Sustainable Digital Data Preservation and Access Network Partners program is an ambitious attempt to integrate a wide variety of expertise and infrastructure into a network for providing "reliable digital preservation, access, integration, and analysis capabilities for science." One of the first two DataNet award recipients, the Data Conservancy, is itself a network of widely diverse partners led by the libraries at the Johns Hopkins University. The Data Conservancy is built on existing exemplar scientific projects, communities, and virtual organizations that have deep engagement with their user communities, and extensive experience with large-scale distributed system development. Data Conservancy members embrace a shared vision that data curation is not an end, but rather a means to collect, organize, validate, and preserve data needed to address the grand research challenges that face society. Data Conservancy members holdings encompass the entire range of earth, life, and space science data. New to the Data Conservancy is the concept that University libraries will be part of the distributed network of data centers and that data science will become a path in the library and information science curricula. As noted by Winston Tabb (JHU Dean of Libraries) "Data Centers are the new library stacks."

  10. Creative Conservation Communication (United States)

    Houston, Jason


    I am a fellow with the International League of Conservation photographers (iLCP) and have been focused on photographing conservation dynamics at the intersection of social and environmental issues for a decade. Subjects have included traditional concerns such as deforestation, water conservation, endangered species, and fisheries. However, I rarely make photographs of the traditional nature, wildlife, landscapes, or environmental atrocities that most people think of when they think about environmentalism. Instead, I photograph people and how they live on the planet, as I believe passionately that without also considering social and cultural concerns, we will not be able to effectively and sustainably do conservation work or achieve positive environmental change. My presentation will share recent photography projects on forest conservation in Indonesian Borneo and fisheries management in Central America where I used a 'stakeholder profile-based' process to broadly survey the complexity of the issues while also making personal connections for these projects' diverse audiences. Through these case studies I will explore the opportunities and challenges of combining the authenticity, accuracy, and scientific validity of journalistic and documentary work with the emotional impact of the conventions of art and storytelling.

  11. Iterative assembly of helical proteins by optimal hydrophobic packing. (United States)

    Wu, G Albert; Coutsias, Evangelos A; Dill, Ken A


    We present a method for the computer-based iterative assembly of native-like tertiary structures of helical proteins from alpha-helical fragments. For any pair of helices, our method, called MATCHSTIX, first generates an ensemble of possible relative orientations of the helices with various ways to form hydrophobic contacts between them. Those conformations having steric clashes, or a large radius of gyration of hydrophobic residues, or with helices too far separated to be connected by the intervening linking region, are discarded. Then, we attempt to connect the two helical fragments by using a robotics-based loop-closure algorithm. When loop closure is feasible, the algorithm generates an ensemble of viable interconnecting loops. After energy minimization and clustering, we use a representative set of conformations for further assembly with the remaining helices, adding one helix at a time. To efficiently sample the conformational space, the order of assembly generally proceeds from the pair of helices connected by the shortest loop, followed by joining one of its adjacent helices, always proceeding with the shorter connecting loop. We tested MATCHSTIX on 28 helical proteins each containing up to 5 helices and found it to heavily sample native-like conformations. The average rmsd of the best conformations for the 17 helix-bundle proteins that have 2 or 3 helices is less than 2 A; errors increase somewhat for proteins containing more helices. Native-like states are even more densely sampled when disulfide bonds are known and imposed as restraints. We conclude that, at least for helical proteins, if the secondary structures are known, this rapid rigid-body maximization of hydrophobic interactions can lead to small ensembles of highly native-like structures. It may be useful for protein structure prediction.

  12. Hydrophobic and moisture-stable metal–organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    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.


    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

  13. Modelling Soil Water Characteristic Curves for the Investigation of Hydrophobicity (United States)

    Hallin, Ingrid; Matthews, Peter; Laudone, Maurizio; Van Keulen, Geertje; Doerr, Stefan; Francis, Lewis; Dudley, Ed; Gazze, Andrea; Quinn, Gerry; Whalley, Richard; Ashton, Rhys


    Soil hydrophobicity presents a major challenge for the future, as it reduces both plant-available water and irrigation efficiency, and can increase flooding hazards and erosion. A collaborative research project has been set up in the UK to study hydrophobicity over a wide range of length scales. At core scale, we are investigating the wetting behaviour of water repellent soils in order to model percolation through hydrophobic pore spaces. To that end, water retention measurements were carried out on both wettable and forcibly-wetted water-repellent soils collected from three locations in England and Wales. The data were then fitted with both the commonly used Van Genuchten model and an alternative model from PoreXpert, a software program that analyses and models porous materials. The Van Genuchten model fits a curve to the data using parameters related to air entry suction, irreducible water content and pore size distribution. By contrast, PoreXpert uses a Boltzmann-annealed simplex to find a best-fit curve based on parameters directly related to the void structure of the soil: the size of the voids, the shape of the void size distribution, and how the voids are connected to each other. Both Van Genuchten and PoreXpert fit the experimental data well, but where Van Genuchten forces an S-shaped curve that can mask small variations, PoreXpert gives a closer fit of no pre-defined shape that captures subtle differences between data points. This allows us to calculate differences in the effective pore and throat size distributions, and provides a mechanistic framework from which to model additional hydrologic behaviour in water repellent soil. Simulations of capillary induced wetting based on these mechanistic postulates are then compared to wicking experiments at the core scale, which can then be upscaled and applied to other soils.

  14. Staphylococcus epidermidis adhesion on hydrophobic and hydrophilic textured biomaterial surfaces. (United States)

    Xu, Li-Chong; Siedlecki, Christopher A


    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

  15. Periodicity-dependent stiffness of periodic hydrophilic-hydrophobic heteropolymers (United States)

    Chowdhury, Debashish; Stauffer, Dietrich; Strey, Reinhard


    From extensive Monte Carlo simulations of a Larson model of perfectly periodic heteropolymers (PHP) in water, a striking stiffening is observed as the period of the alternating hydrophobic and hydrophilic blocks is shortened. At short period and low temperature needlelike conformations are the stable conformations. As temperature is increased thermal fluctuations induce kinks and bends. At large periods compact oligomeric globules are observed. From the generalized Larson prescription, originally developed for modeling surfactant molecules in aqueous solutions, we find that the shorter the period is the more stretched the PHP is. This novel effect is expected to stimulate polymer synthesis and trigger research on the rheology of aqueous periodic heteropolymer solutions.

  16. Hydrophobicity classification of polymeric materials based on fractal dimension

    Directory of Open Access Journals (Sweden)

    Daniel Thomazini


    Full Text Available This study proposes a new method to obtain hydrophobicity classification (HC in high voltage polymer insulators. In the method mentioned, the HC was analyzed by fractal dimension (fd and its processing time was evaluated having as a goal the application in mobile devices. Texture images were created from spraying solutions produced of mixtures of isopropyl alcohol and distilled water in proportions, which ranged from 0 to 100% volume of alcohol (%AIA. Based on these solutions, the contact angles of the drops were measured and the textures were used as patterns for fractal dimension calculations.

  17. Long-Lived Foams Stabilized by a Hydrophobic Dipeptide Hydrogel



    A hydrogel of hydrophobic dipeptides can be used to create a wet foam with long-term stability. The dipeptide molecules self-assemble into fiber-like networks (due to the presence of metal ions) both at air-water interfaces and in the continuous phase. The former creates an interfacial film stabilizing the air bubbles while the latter forms a bulk gel, which prevents bubble movement and retards growth. If the storage modulus (G’) of the bulk hydrogel is sufficientlyhigh it can stop the coarse...

  18. Encapsulation and retention of chelated-copper inside hydrophobic nanoparticles

    DEFF Research Database (Denmark)

    Hervella, Pablo; Ortiz, Elisa Parra; Needham, David


    MOTIVATION: In the field of imaging, (18)F-fluorodeoxyglucose (FDG) PET imaging allows evaluation of glucose metabolism and is the most widely used imaging agent clinically for metastatic cancer. While it can certainly detect the metastatic disease, in order to provide a more fully "individualized...... Trioleate (Triolein) with copper using the hydrophobic chelator Octaethyl porphyrin (OEP). RESEARCH PLAN AND METHODS: The research plan for this study was to (1) Formulate nanoparticles and control nanoparticle size using a modification of the solvent injection technique, named fast ethanol injection; (2...

  19. High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects (United States)

    Chang, Feng-Ming; Hong, Siang-Jie; Sheng, Yu-Jane; Tsao, Heng-Kwong


    A typical superhydrophobic surface is essentially nonadhesive and exhibits very low water contact angle (CA) hysteresis, so-called Lotus effect. However, leaves of some plants such as scallion and garlic with an advancing angle exceeding 150° show very serious CA hysteresis. Although surface roughness and epicuticular wax can explain the very high advancing CA, our analysis indicates that the unusual hydrophobic defect, diallyl disulfide, is the key element responsible for contact line pinning on allium leaves. After smearing diallyl disulfide on an extended polytetrafluoroethylene (PTFE) film, which is originally absent of CA hysteresis, the surface remains superhydrophobic but becomes highly adhesive.

  20. Enzymatic synthesis of hydrophobic compounds integrated with membrane separation

    Directory of Open Access Journals (Sweden)

    Noworyta Andrzej


    Full Text Available The enzymatic synthesis of a highly hydrophobic product (dipeptide precursor in which the reaction is accompanied by the mass transfer of the reaction product to the organic phase and the substrates to the water phase is considered. Equations describing both continuous and batch processes are formulated. The range of variability in the operating parameters of such a bioreactor is specified, and the correlations reported in the literature to describe mass transfer in the membrane contactor are validated. The proposed process was verified experimentally, and good agreement between the determined and calculated concentrations was obtained in both phases.

  1. Improved Aerobic Colony Count Technique for Hydrophobic Grid Membrane Filters


    Parrington, Lorna J.; Sharpe, Anthony N.; Peterkin, Pearl I.


    The AOAC International official action procedure for performing aerobic colony counts on hydrophobic grid membrane filters (HGMFs) uses Trypticase soy-fast green FCF agar (FGA) incubated for 48 h. Microbial growths are various shades of green on a pale green background, which can cause problems for automated as well as manual counting. HGMFs which had been incubated 24 or 48 h at 35°C on Trypticase soy agar were flooded underneath with 1 to 2 ml of 0.1% triphenyltetrazolium chloride (TTC) sol...

  2. Big Hydrophobic Capillary Fluidics; Basically Water Ping Pong in Space (United States)

    Weislogel, Mark; Attari, Babak; Wollman, Andrew; Cardin, Karl; Geile, John; Lindner, Thomas


    Capillary surfaces can be enormous in environments where the effects of gravity are small. In this presentation we review a number of interesting examples from demonstrative experiments performed in drop towers and aboard the International Space Station. The topic then focuses on large length scale hydrophobic phenomena including puddle jumping, spontaneous particle ejections, and large drop rebounds akin to water ping pong in space. Unseen footage of NASA Astronaut Scott Kelly playing water ping pong in space will be shown. Quantitative and qualitative results are offered to assist in the design of experiments for ongoing research. NASA NNX12A047A.

  3. Stable highly hydrophobic and oleophilic meshes for oil water separation (United States)

    Wang, Qingjun; Cui, Zhe; Xiao, Yi; Chen, Qingmin


    This paper describes a simple method for fabricating both highly hydrophobic and oleophilic meshes by coating thin fluoro-containing films. The static contact angle of such meshes is greater than 150° for water, and close to 0° for kerosene, xylene and toluene. These meshes can separate water from oil effectively without resorting to any extra power or chemical agent. Moreover, they exhibited stable water resisting, anti-chemical erosion and anti-hot aging properties. It promises as a candidate for the separation of oil and water.

  4. Structural and thermodynamic aspects of the hydrophobic effect. (United States)

    Soda, K


    From analyses of the solvation structure around HS solutes for HS solvents and various water models by the RISM integral equation method, the following conclusions are drawn: 1) Water has more small cavities than HS solvents, which makes it easier for water to accommodate small solutes with a radius less than about 1A. 2) With increasing solute radius from 0 to 3A, the average orientation of hydrating water varies from an inward to an outward orientation, which shows that some reorganization of water occurs in response to the change in solute size. 3) The hydration structure is formed as a network structure due to H-bonding interactions between water molecules being supported by the cooperation of repulsive forces between solute and water. Repulsive interactions of not only O atoms but also H atoms with solute are essential to the formation of such hydration structure. With regard to the physical mechanism of the hydrophobic effect, the following is concluded from an analysis of the physical meaning of the basic formula for the free energy of cavity formation: 4) It is predicted from the scaled particle theory that the solvent exclusion effect caused by the introduction of solute into solvent is an important factor of the hydrophobic effect. 5) The large negative transfer entropy at room temperature characteristic of the hydrophobic hydration results primarily from the decrease in the configuration entropy of water due to the solvent exclusion effect. 6) The structuralization of hydrating water results in exactly compensating changes in enthalpy and entropy, and a large positive change in heat capacity. As a result, the hydrophobic effect is dominated by the entropy effect at room temperature, while it is driven by enthalpy at temperatures higher than 110 degrees C. 7) Hydrating water is energetically similar to bulk water, and the term "highly structured" is not appropriate to describe it. The following descriptions can be made on estimating the free energy of

  5. Solute-induced dissolution of hydrophobic ionic liquids in water. (United States)

    Rickert, Paul G; Stepinski, Dominique C; Rausch, David J; Bergeron, Ruth M; Jakab, Sandrine; Dietz, Mark L


    Significant solubilization of ostensibly water-immiscible ionic liquids (ILs) in acidic aqueous phases is induced by the presence of any of a variety of neutral extractants, the apparent result of the formation of the protonated form of the extractant and its subsequent exchange for the cationic component of the IL. The extent of this solubilization is shown to diminish with increasing hydrophobicity of the IL cation and decreasing extractant basicity. These observations raise concerns as to the viability of ILs as "drop in replacements" for traditional organic solvents in the solvent extraction of metal ions.

  6. Synthesis and characterization of lamellar aragonite with hydrophobic property

    Energy Technology Data Exchange (ETDEWEB)

    Wang Chengyu, E-mail: [College of Materials Science and Engineering, Northeast Forestry University, 150040 (China); Xu Yang [China Nation Center for Quality Supervision and Test of Woodworking Machinery, Northeast Forestry University, 150040 (China); Liu Yalan; Li Jian [College of Materials Science and Engineering, Northeast Forestry University, 150040 (China)


    A novel and simple synthetic method for the preparation of hydrophobic lamellar aragonite has been developed. The crystallization of aragonite was conducted by the reaction of sodium carbonate with calcium chloride in the presence of sodium stearate. The resulting products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and the contact angle. The results revealed that sodium stearate plays an important role in determining the structure and morphology of the sample. Besides, we have succeeded in surface modification of particles in situ at the same time. The contact angle of the modified aragonite reached 108.59 deg.

  7. Conservation reaches new heights. (United States)

    Pepall, J; Khanal, P


    The conservation program with the management assistance of the Woodlands Mountain Institute in 2 contiguous parks, the Mount Everest National Park in Nepal and the Qomolangma Nature Reserve in China, in 2 countries is described. The focus is on conservation of the complex ecosystem with sustainable development by showing local people how to benefit from the park without environmental damage. Cultural diversity is as important as biological diversity. The area has been designated by UNESCO as a World Heritage Site with the "last pure ecological seed" of the Himalayas. The regional geography and culture are presented. Population growth has impacted natural resources through overgrazing, cultivation of marginal land, and deforestation; future plans to build a dam and road bordering the nature reserve pose other threats. Proposed management plans for the Makalu-Barun Nature Park (established in November 1991) and Conservation Area include a division of the park into nature reserve areas free of human activity, protected areas which permit traditional land use, and special sites and trail for tourists and religious pilgrims. The conservation area will act as a buffer for the park and provide economic opportunities; further subdivisions include land use for biodiversity protection, community forest and pasture, agroforestry, and agriculture and settlement. Efforts will be made to increase the welfare of women and local people; proposed projects include the introduction of higher milk-producing animals for stall feeding. Also proposed is a cultural and natural history museum. 70% of the project's resources will be directed to local community participation in consultation and park maintenance. The project is a model of how conservation and protection of natural resources can coexist with local economic development and participation; an integration of preservation of biological diversity, mountain wisdom, and the value of local people as resources for conservation.

  8. Information, conservation and retrieval

    Energy Technology Data Exchange (ETDEWEB)

    Eng, T. [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Norberg, E. [National Swedish Archives, Stockholm (Sweden); Torbacke, J. [Stockholm Univ. (Sweden). Dept. of History; Jensen, M. [Swedish Radiation Protection Inst., Stockholm (Sweden)


    The seminar took place on the Swedish ship for transportation of radioactive wastes, M/S Sigyn, which at summer time is used for exhibitions. The seminar treated items related to general information needs in society and questions related to radioactive waste, i.e. how knowledge about a waste repository should be passed on to future generations. Three contributions are contained in the report from the seminar and are indexed separately: `Active preservation - otherwise no achieves`; `The conservation and dissemination of information - A democratic issue`; and, `Conservation and retrieval of information - Elements of a strategy to inform future societies about nuclear waste repositories`.

  9. General vorticity conservation

    CERN Document Server

    Gümral, H


    The motion of an incompressible fluid in Lagrangian coordinates involves infinitely many symmetries generated by the left Lie algebra of group of volume preserving diffeomorphisms of the three dimensional domain occupied by the fluid. Utilizing a 1+3-dimensional Hamiltonian setting an explicit realization of this symmetry algebra and the related Lagrangian and Eulerian conservation laws are constructed recursively. Their Lie algebraic structures are inherited from the same construction. The laws of general vorticity and helicity conservations are formulated globally in terms of invariant differential forms of the velocity field.

  10. 14 Conservation of Energy


    Torre, Charles G.


    After all of these developments it is nice to keep in mind the idea that the wave equation describes (a continuum limit of) a network of coupled oscillators. This raises an interesting question. Certainly you have seen by now how important energy and momentum — and their conservation — are for understanding the behavior of dynamical systems such as an oscillator. If a wave is essentially the collective motion of many oscillators, might not there be a notion of conserved energy and momentum fo...

  11. Two Centuries of Soil Conservation. (United States)

    Helms, Douglas


    Narrates U.S. soil conservation history since the late eighteenth century. Discusses early practices such as contour plowing. Profiles individuals who promoted soil conservation and were largely responsible for the creation of the Soil Conservation Service. Explains the causes of erosion and how soil conservation districts help farmers prevent…

  12. Hydrophobicity and carbonation treatment of earthen monuments in humid weather condition

    Institute of Scientific and Technical Information of China (English)

    LI Min; ZHANG HuYuan


    Water stability of soil is crucial to the durability of earthen monuments,especially those located in the humid weather condition.This paper discusses the selection reason of materials (tung oil and quicklime) for earthen monument treatment,and then validates the applicability of these materials with tests of soil-water characteristic curve (SWCC),aggregate stability test (AST) and scanning electron microscope (SEM).The soil tested was sampled from Da Bao'en temple in Nanjing,Jiangsu province,China.The test results indicate that the carbonation reaction of quicklime offers a favorable environment for the formation of tung oil film.Meanwhile,the regulatory function of tung oil restricts the crystallinity of calcium carbonate (CaCO3) and forms fine crystals.Soil treated with both of tung oil and quicklime has good water repellency and aggregate stability without obvious changing in aesthetic appearance.Hydrophobicity and carbonation treatment can be applied prospectively in the conservation of earthen monument located in humid weather condition.

  13. Recent experimental advances on hydrophobic interactions at solid/water and fluid/water interfaces. (United States)

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


    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

  14. Viscous boundary lubrication of hydrophobic surfaces by mucin. (United States)

    Yakubov, Gleb E; McColl, James; Bongaerts, Jeroen H H; Ramsden, Jeremy J


    The lubricating behavior of the weakly charged short-side-chain glycoprotein mucin "Orthana" (Mw=0.55 MDa) has been investigated between hydrophobic and hydrophilic PDMS substrates using soft-contact tribometry. It was found that mucin facilitates lubrication between hydrophobic PDMS surfaces, leading to a 10-fold reduction in boundary friction coefficient for rough surfaces. The presence of mucin also results in a shift of the mixed lubrication regime to lower entrainment speeds. The observed boundary lubrication behavior of mucin was found to depend on the bulk concentration, and we linked this to the structure and dynamics of the adsorbed mucin films, which are assessed using optical waveguide light spectroscopy. We observe a composite structure of the adsorbed mucin layer, with its internal structure governed by entanglement. The film thickness of this adsorbed layer increases with concentration, while the boundary friction coefficient for rough surfaces was found to be inversely proportional to the thickness of the adsorbed film. This link between lubrication and structure of the film is consistent with a viscous boundary lubrication mechanism, i.e., a thicker adsorbed film, at a given sliding speed, results in a lower local shear rate and, hence, in a lower local shear stress. The estimated local viscosities of the adsorbed layer, derived from the friction measurements and the polymer layer density, are in agreement with each other.

  15. Vapor transport through short hydrophobic nanopores for desalination (United States)

    Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Rahman, Faizur; Karnik, Rohit


    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.

  16. Characterization of hydrophobic nanoporous particle liquids for energy absorption (United States)

    Hsu, Yi; Liu, Yingtao


    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.

  17. Temperature dependence of hydrophobic hydration dynamics: from retardation to acceleration. (United States)

    Duboué-Dijon, Elise; Fogarty, Aoife C; Laage, Damien


    The perturbation induced by a hydrophobic solute on water dynamics is essential in many biochemical processes, but its mechanism and magnitude are still debated. A stringent test of the different proposed pictures is provided by recent NMR measurements by Qvist and Halle (J. Am. Chem. Soc. 2008, 130, 10345-10353) which showed that, unexpectedly, the perturbation changes in a non-monotonic fashion when the solution is cooled below room temperature. Here we perform and analyze molecular dynamics simulations of a small paradigm amphiphilic solute, trimethylamine N-oxide (TMAO), in dilute aqueous solutions over the 218-350 K temperature range. We first show that our simulations properly reproduce the non-monotonic temperature dependence. We then develop a model which combines our previously suggested entropic excluded-volume effect with a perturbation factor arising from the difference between local structural fluctuations in the shell and the bulk. Our model provides a detailed molecular understanding of the hydrophobic perturbation over the full temperature range investigated. It shows that the excluded-volume factor brings a dominant temperature-independent contribution to the perturbation at all temperatures, and provides a very good approximation at room temperature. The non-monotonic temperature dependence of the perturbation is shown to arise from the structural factor and mostly from relative shifts between the shell and bulk distributions of local structures, whose amplitude remains very small compared to the widths of those distributions.

  18. How hydrophobic drying forces impact the kinetics of molecular recognition. (United States)

    Mondal, Jagannath; Morrone, Joseph A; Berne, B J


    A model of protein-ligand binding kinetics, in which slow solvent dynamics results from hydrophobic drying transitions, is investigated. Molecular dynamics simulations show that solvent in the receptor pocket can fluctuate between wet and dry states with lifetimes in each state that are long enough for the extraction of a separable potential of mean force and wet-to-dry transitions. We present a diffusive surface hopping model that is represented by a 2D Markovian master equation. One dimension is the standard reaction coordinate, the ligand-pocket separation, and the other is the solvent state in the region between ligand and binding pocket which specifies whether it is wet or dry. In our model, the ligand diffuses on a dynamic free-energy surface which undergoes kinetic transitions between the wet and dry states. The model yields good agreement with results from explicit solvent molecular dynamics simulation and an improved description of the kinetics of hydrophobic assembly. Furthermore, it is consistent with a "non-Markovian Brownian theory" for the ligand-pocket separation coordinate alone.

  19. Biofilm retention on surfaces with variable roughness and hydrophobicity. (United States)

    Tang, Lone; Pillai, Saju; Revsbech, Niels Peter; Schramm, Andreas; Bischoff, Claus; Meyer, Rikke Louise


    Biofilms on food processing equipment cause food spoilage and pose a hazard to consumers. The bacterial community on steel surfaces in a butcher's shop was characterized, and bacteria representative of this community enriched from minced pork were used to study biofilm retention. Stainless steel (SS) was compared to two novel nanostructured sol-gel coatings with differing hydrophobicity. Surfaces were characterized with respect to roughness, hydrophobicity, protein adsorption, biofilm retention, and community composition of the retained bacteria. Fewer bacteria were retained on the sol-gel coated surfaces compared to the rougher SS. However, the two sol-gel coatings did not differ in either protein adsorption, biofilm retention, or microbial community composition. When polished to a roughness similar to sol-gel, the SS was colonized by the same amount of bacteria as the sol-gel, but the bacterial community contained fewer Pseudomonas cells. In conclusion, biofilm retention was affected more by surface roughness than chemical composition under the condition described in this study.

  20. Hydrophobic trichome layers and epicuticular wax powders in Bromeliaceae. (United States)

    Pierce, S; Maxwell, K; Griffiths, H; Winter, K


    The distinctive foliar trichome of Bromeliaceae has promoted the evolution of an epiphytic habit in certain taxa by allowing the shoot to assume a significant role in the uptake of water and mineral nutrients. Despite the profound ecophysiological and taxonomic importance of this epidermal structure, the functions of nonabsorbent trichomes in remaining Bromeliaceae are not fully understood. The hypothesis that light reflection from these trichome layers provides photoprotection was not supported by spectroradiometry and fluorimetry in the present study; the mean reflectance of visible light from trichome layers did not exceed 6.4% on the adaxial surfaces of species representing a range of ecophysiological types nor was significant photoprotection provided by their presence. Several reports suggesting water repellency in some terrestrial Bromeliaceae were investigated. Scanning electron microscopy (SEM) and a new technique-fluorographic dimensional imaging (FDI)-were used to assess the interaction between aqueous droplets and the leaf surfaces of 86 species from 25 genera. In the majority of cases a dense layer of overlapping, stellate or peltate trichomes held water off the leaf epidermis proper. In the case of hydrophobic tank-forming tillandsioideae, a powdery epicuticular wax layer provided water repellency. The irregular architecture of these indumenta resulted in relatively little contact with water droplets. Most mesic terrestrial Pitcairnioideae examined either possessed glabrous leaf blades or hydrophobic layers of confluent trichomes on the abaxial surface. Thus, the present study indicates that an important ancestral function of the foliar trichome in Bromeliaceae was water repellency. The ecophysiological consequences of hydrophobia are discussed.

  1. Nonionic Microemulsions as Solubilizers of Hydrophobic Drugs: Solubilization of Paclitaxel

    Directory of Open Access Journals (Sweden)

    Jen-Ting Lo


    Full Text Available The strategy using nonionic microemulsion as a solubilizer for hydrophobic drugs was studied and is demonstrated in this work. The aqueous phase behaviors of mixed nonionic surfactants with various oils at 37 °C are firstly constructed to give the optimal formulations of nonionic microemulsions with applications in the enhanced solubilization of the model hydrophobic drug, paclitaxel, at 37 °C. Briefly, the suitable oil phase with paclitaxel significantly dissolved is microemulsified with appropriate surfactants. Surfactants utilized include Tween 80, Cremophor EL, and polyethylene glycol (4.3 cocoyl ether, while various kinds of edible oils and fatty esters are used as the oil phase. On average, the apparent solubility of paclitaxel is increased to ca. 70–100 ppm in the prepared microemulsions at 37 °C using tributyrin or ethyl caproate as the oil phases. The sizes of the microemulsions attained are mostly from ca. 60 nm to ca. 200 nm. The cytotoxicity of the microemulsion formulations is assessed with the cellular viability of 3T3 cells. In general, the cell viability is above 55% after 24 h of cultivation in media containing these microemulsion formulations diluted to a concentration of total surfactants equal to 50 ppm and 200 ppm.

  2. Hydrophobicity and thermodynamic response for aqueous solutions of amphiphiles (United States)

    Zemánková, Katerina; Troncoso, Jacobo; Cerdeiriña, Claudio A.; Romaní, Luis; Anisimov, Mikhail A.


    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.

  3. Controlled self-assembly of hydrophobic quantum dots through silanization. (United States)

    Yang, Ping; Ando, Masanori; Murase, Norio


    We demonstrate the formation of one-, two-, and three-dimensional nanocomposites through the self-assembly of silanized CdSe/ZnS quantum dots (QDs) by using a controlled sol-gel process. The self-assembly behavior of the QDs was created when partially hydrolyzed silicon alkoxide monomers replaced hydrophobic ligands on the QDs. We examined systematically self-assembly conditions such as solvent components and QD sizes in order to elucidate the formation mechanism of various QD nanocomposites. The QD nanocomposites were assembled in water phase or on the interface of water and oil phase in emulsions. The partially hydrolyzed silicon alkoxides act as intermolecules to assemble the QDs. The QD nanocomposites with well-defined solid or hollow spherical, fiber-like, sheet-like, and pearl-like morphologies were prepared by adjusting the experimental conditions. The high photoluminescence efficiency of the prepared QD nanocomposites suggests partially hydrolyzed silicon alkoxides reduced the surface deterioration of QDs during self-assembly. These techniques are applicable to other hydrophobic QDs for fabricating complex QD nanocomposites.

  4. Tuning hydrophobicity and water adhesion by electrospinning and silanization. (United States)

    Pisuchpen, Thanarath; Chaim-ngoen, Navarun; Intasanta, Narupol; Supaphol, Pitt; Hoven, Voravee P


    Electrospinning and silanization were synergistically employed to fabricate poly(vinyl alcohol) (PVA) and PVA/silica mixtures into flexible and chemically modifiable nanostructured surfaces with varying degrees of hydrophobicity and water adhesion. Surfaces possessing the greatest advancing water contact angle yet exhibiting a high level of water adhesion (θ(A)/θ(R) ≈ 168°/0°) were achieved by the reaction of PVA fiber mats with multiple cycles of SiCl(4)/H(2)O treatment, followed by silanization with (1H,1H,2H,2H-perfluorooctyl)trichlorosilane. It is postulated that the strong pinning effect and hence the water adhesion originated from the collapse of the underlying fibrous structures and the removal of air pockets. The addition of silica to the PVA matrix improved the rigidity and thus prevented the fibers from collapsing, allowing air to remain trapped within the fibrous structure and giving the surface greater water repellency. Throughout the investigation, the three wetting models--Wenzel's, Cassie-Baxter's, and the Cassie-impregnating--were regularly referred to as a conceptual framework. The hydrophobic surface that exhibited strong water adhesion, or the so-called "Petal effect", was elucidated in correlation with the fibrous structure of the film, as reviewed by microscopic analysis. In summary, electrospinning as a facile and cost-effective method provides promising opportunities for investigating the mechanistic character of nanowetting, nanoprinting, and nanocoating where the precise control of the dynamical three-phase contact line is of paramount importance.

  5. Review: Milk Proteins as Nanocarrier Systems for Hydrophobic Nutraceuticals. (United States)

    Kimpel, Florian; Schmitt, Joachim J


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


    Institute of Scientific and Technical Information of China (English)

    杨宏伟; 魏贤勇; 费逸伟; 孙世安; 李晓越


    The surface performances of directly fluorinated high density polyethylene (HDPE) are studied with Fourier transform infrared (FT-IR) spectra ,scanning electron microscopy (SEM) and contact angle (CA) system . The SEM images show that there is a three-layer structure called the reaction ,virgin and boundary layer structure . The depth of fluorinated layer is 5.75 μm with 1 h fluorination time and 7.86 μm with 2 h . The depths are 5.46 μm and 5.07 μm when fluorine density is 2% and 1% ,respectively .CA indicates that the HDPE surface property becomes more hydrophobic with the increasing water contact angle from 78.5° to 104.5° .Oleophobic and hydrophobic features of HDPE are identified by comparison of mass change experiments .It is shown that the in-crement rate of fluorinated HDPE is much lower than that of un-fluorinated HDPE filled in neither distilled water nor jet fuel .

  7. Improving the Hydrophobicity of ZnO by PTFE Incorporation

    Directory of Open Access Journals (Sweden)

    Meenu Srivastava


    Full Text Available The objective of the present study is to obtain a zinc oxide- (ZnO- based superhydrophobic surface in a simple and cost-effective manner. Chemical immersion deposition being simple and economical has been adopted to develop modified ZnO coating on glass substrate. Several modifications of ZnO like treatment with alkanoic acid (stearic acid and fluoroalkylsilane to tune the surface wettability (hydrophobicity were attempted. The effect of thermal treatment on the hydrophobic performance was also studied. It was observed that thermal treatment at 70°C for 16 hrs followed by immersion in stearic acid resulted in high water contact angle (WCA, that is, a superhydrophobic surface. Thus, a modified ZnO superhydrophobic surface involves the consumption of large amount of electrical energy and time. Hence, the alternate involved the incorporation of low surface energy fluoropolymer polytetrafluoroethylene (PTFE in the ZnO coating. The immersion deposited ZnO-PTFE composite coating on modification with either stearic acid or fluoroalkylsilane resulted in a better superhydrophobic surface. The coatings were characterized using Scanning Electron Microscope (SEM for the surface morphology. It was found that microstructure of the coating was influenced by the additives employed. A flower-like morphology comprising of needle-like structure arranged in a radial manner was exhibited by the superhydrophobic coating.

  8. Synthesis of new fluoromethacrylates and their hydrophobic properties

    Energy Technology Data Exchange (ETDEWEB)

    Soulen, R.L.; Huang, A.X.; Maher, C.J. [Southwestern Univ., Georgetown, TX (United States)


    This report continues the search for the ideal fluoromethacrylate or fluoroacrylate which is compatible in copolymerization with methyl methacrylate and also provide maximum hydrophobicity to the polymer without significant loss of mechanical or optical properties. In this study the authors have prepared the methacrylate of the following fluoroalcohols: 2,2,2-trifluoroethyl, 1,1,1,3,3,3-hexafluoro-2-propyl, perfluoro tertiary butyl, heptafluoro-2-propyl, and 1,1,2 tris (trifluoromethyl)-2,3,3,3-tetrafluoropropyl alcohol. Copolymers of methyl methacrylate were prepared with 5, 10, 20, and 30 weight percent of fluoromonomer in the polymerization mixture. Sample disks of the copolymers and similarly prepared samples of pure methyl methacrylate were immersed in 120{degrees}F water and the weight increase due to water absorption determined over a 3000-5000 hour period. Test samples from an F-4 aircraft canopy were included for comparison. In all cases, the fluoromonomer addition provided a significant decrease in the bulk water absorbed in the copolymer. Comparison of fluoromonomer structure and ability to promote hydrophobic properties will be shown.

  9. Effects of electric charges on hydrophobic forces. II. (United States)

    Bulone, D.; Martorana, V.; San Biagio, P. L.; Palma-Vittorelli, M. B.


    We study by molecular-dynamics simulations the effect of electric charges of either sign on hydrophobic interactions and on the dynamics of hydration water, using explicit water and very simplified solutes. Results show that the presence of a charged solute can disrupt the ``hydrophobic contact bond'' between two apolar solutes nearby, by forcing them towards a different configuration. As a consequence of different structural changes of the solvent caused by charges of opposite sign, the effect is markedly charge-sign-dependent. Analogous weaker effects appear to be induced by the presence of one additional apolar element. The dynamics of hydration water around each solute is also seen to be strongly influenced by the presence of other (charged or uncharged) nearby solutes. Comparison between our results on hydration water dynamics around charged solutes and available experimental data allows sorting out the effects of solute charge sign and size. Our results also offer a plain interpretation of the equivalence of the effects on water structure due to solute ions and to high pressures. These results reflect at a basic paradigmatic level the immensely more complex cases of well-known phenomena such as salting-in and salting-out, and of protein conformational changes caused, e.g., by the arrival of a charged or of an apolar group (phosphorilation or methylation). As it will be discussed, they help in the direction of Delbruck's desirable ``progress towards a radical physical explanation'' for this class of phenomena.

  10. Stability of triglyceride liquid films on hydrophilic and hydrophobic glasses. (United States)

    Vazquez, Rosa; Nogueira, Rui; Orfão, Marta; Mata, José Luís; Saramago, Benilde


    Wetting and dewetting of solid surfaces by oily fluids were investigated in terms of the stability of the liquid film formed between an air bubble and the solid surface. With the objective of understanding how molecules with low polarity but relatively complex molecular structure behave at the solid/liquid interface, three liquid triglycerides with different chain length and saturation were chosen, namely, tributyrin, tricaprylin, and triolein. Tributyrin and tricaprylin exist in milkfat while triolein is present in vegetable oils. The stability of the liquid films may be inferred from the shape of the disjoining pressure isotherms, which represent the dependence of the disjoining pressure on the film thickness. Disjoining pressure isotherms for films of the three triglycerides on hydrophilic and hydrophobic glasses were obtained using a recently developed apparatus, based on the interferometric technique. The experimental curves are compared with the theoretical predictions of London-Hamaker. The deviations between theory and experiment are interpreted in terms of a structural component of the disjoining pressure. All triglycerides form metastable films on both hydrophilic and hydrophobic glasses which means that for disjoining pressures higher than a critical value, pi(c), a wetting transition occurs and the film ruptures. The mechanisms for film rupture are discussed and a correlation between film stability and the apolar (Lifshitz-van der Waals) and the polar components of the spreading coefficient is proposed.

  11. Extraction of detergents from hydrophobic proteins with isopentanol: application to electrophoretic analysis of photosynthetic bacterial hydrophobic proteins. (United States)

    Salcedo, J R; Hernández, R S; Célis, H


    The method for extracting Triton X-100 used by I. H. Mather and C. B. Tampling [Anal. Biochem. 93, 139-142 (1979)], has been extended to other detergents of different charge and chemical nature. All the detergents tested can be extracted with isopentanol in conditions in which not more than 8% of hydrophobic or hydrophilic protein is lost from the water phase. The removal of detergent from reaction centers and light harvesting protein-pigment complexes of photosynthetic bacteria, eliminates the artifacts of oligomers when analyzed by sodium dodecyl sulfate-gel electrophoresis.

  12. The role of hydrophobic amino acids of K-segments in the cryoprotection of lactate dehydrogenase by dehydrins. (United States)

    Hara, Masakazu; Endo, Takuya; Kamiya, Keita; Kameyama, Ayuko


    Dehydrins, which are group 2 late embryogenesis abundant (LEA) proteins, accumulate in plants during the development of the embryo and exposure to abiotic stresses including low temperature. Dehydrins exhibit cryoprotection of freezing-sensitive enzymes, e.g. lactate dehydrogenase (LDH). Although it has been reported that K-segments conserved in dehydrins are related to their cryoprotection activity, it has not been determined which sequence features of the K-segments contribute to the cryoprotection. A cryoprotection assay using LDH indicated that 13 K-segments including 12 K-segments found in Arabidopsis dehydrins and a typical K-segment (TypK, EKKGIMEKIKEKLPG) derived from the K-segments of many plants showed similar cryoprotective activities. Mutation of the TypK sequence demonstrated that hydrophobic amino acids were clearly involved in preventing the cryoinactivation, cryoaggregation, and cryodenaturation of LDH. We propose that the cryoprotective activities of dehydrins may be made possible by the hydrophobic residues of the K-segments. Copyright © 2016 Elsevier GmbH. All rights reserved.

  13. Conformational dynamics of a hydrophobic prion fragment (113-127) in different pH and osmolyte solutions. (United States)

    Inayathullah, Mohammed; Rajadas, Jayakumar


    Prion diseases are characterized by a conformational change in prion protein from its native state into beta-sheet rich aggregates that are neurotoxic. The central domain that contain a highly conserved hydrophobic region of the protein play an important role in the toxicity. The conformation of the proteins is largely influenced by various solvent environments. Here we report results of study of hydrophobic prion fragment peptide PrP(113-127) under different pH and osmolytes solution conditions. The secondary structure and the folding of PrP(113-127) was determined using circular dichroism and fluorescence spectroscopic methods. The results indicate that PrP(113-127) adopts a random coil conformation in aqueous buffer at neutral pH and that converted into beta sheet on aging. Even though the initial random coil conformation was similar in different pH conditions, the acidic as well as basic pH conditions delays the conformational transition to beta sheet. FRET results indicate that the distance between N and C-terminal regions increased on aging due to unfolding by self-assembly of the peptide into an organized beta sheet structure. Presence of osmolytes, prevented or decelerated the aggregation process of PrP(113-127) peptide. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. A hydrophobic patch surrounding Trp154 in human neuroserpin controls the helix F dynamics with implications in inhibition and aggregation (United States)

    Ali, Mohammad Farhan; Kaushik, Abhinav; Kapil, Charu; Gupta, Dinesh; Jairajpuri, Mohamad Aman


    Neuroserpin (NS) mediated inhibition of tissue-type plasminogen activator (tPA) is important for brain development, synapse formation and memory. Aberrations in helix F and β-sheet A movement during inhibition can directly lead to epilepsy or dementia. Conserved W154 residue in a hydrophobic patch between helix F and β-sheet A is ideally placed to control their movement during inhibition. Molecular Dynamics (MD) simulation on wild type (WT) NS and its two variants (W154A and W154P) demonstrated partial deformation in helix F and conformational differences in strands 1A and 2A only in W154P. A fluorescence and Circular Dichroism (CD) analysis with purified W154 variants revealed a significant red-shift and an increase in α-helical content in W154P as compared to W154A and WT NS. Kinetics of tPA inhibition showed a decline in association rates (ka) for W154A as compared to WT NS with indication of complex formation. Appearance of cleaved without complex formation in W154P indicates that the variant acts as substrate due to conformational misfolding around helix F. Both the variants however showed increased rate of aggregation as compared to WT NS. The hydrophobic patch identified in this study may have importance in helix F dynamics of NS. PMID:28230174

  15. Foundry energy conservation workbook

    Energy Technology Data Exchange (ETDEWEB)


    This report discusses methods for promoting energy conservation in foundries. Use of electric power, natural gas, and coke are evaluated. Waste heat recovery systems are considered. Energy consumption in the specific processes of electric melting, natural gas melting, heat treatments, ladle melting, and coke fuel melting is described. An example energy analysis is included. (GHH)

  16. Supersymmetric non conservative systems

    CERN Document Server

    Martínez-Pérez, N E


    We give the generalization of a recent variational formulation for nonconservative classical mechanics, for fermionic and sypersymmetric systems. Both cases require slightly modified boundary conditions. The supersymmetric version is given in the superfield formalism. The corresponding Noether theorem is formulated. As expected, like the energy, the supersymmetric charges are not conserved. Examples are discussed.

  17. Communities, Cameras, and Conservation (United States)

    Patterson, Barbara


    Communities, Cameras, and Conservation (CCC) is the most exciting and valuable program the author has seen in her 30 years of teaching field science courses. In this citizen science project, students and community volunteers collect data on mountain lions ("Puma concolor") at four natural areas and public parks along the Front Range of Colorado.…

  18. Conservation of fern spores (United States)

    Ferns are a diverse and important group of plants, but diversity of species and populations are at risk from increasing social pressures, loss of habitat and climate change. Ex situ conservation is a useful strategy to limit decline in genetic diversity and requires technologies to preserve fern ger...

  19. Deficiencies in Water Conservancy

    Institute of Scientific and Technical Information of China (English)


    Recent droughts and floods show the fragility of China’s water conservancy capabilities Be it extreme flooding or severe droughts,China has yet to find a stable middle ground concerning its water supply.These disasters,primarily in the Yangtze

  20. Energy Conservation Simplified (United States)

    Hecht, Eugene


    The standard formulation of energy conservation involves the subsidiary ideas of kinetic energy ("KE"), work ("W"), thermal energy, internal energy, and a half-dozen different kinds of potential energy ("PE"): elastic, chemical, nuclear, gravitational, and so forth. These quantities came to be recognized during the centuries over which the…

  1. Beyond conservation agriculture

    NARCIS (Netherlands)

    Giller, K.E.; Andersson, J.A.; Corbeels, Marc; Kirkegaard, John; Mortensen, David; Erenstein, Olaf; Vanlauwe, Bernard


    Global support for Conservation Agriculture (CA) as a pathway to Sustainable Intensification is strong. CA revolves around three principles: no-till (or minimal soil disturbance), soil cover, and crop rotation. The benefits arising from the ease of crop management, energy/cost/time savings, and

  2. Conservative Public Interest Litigation (United States)

    Pell, Terence J.


    The idea that lawsuits can move a public as well as a legal agenda is not new. In recent years, conservatives have brought high profile lawsuits designed both to vindicate the rights of an individual plaintiff and to educate the public about an important issue. For example, lawsuits filed nearly 10 years ago against the University of Michigan's…

  3. Conservation and gene banking (United States)

    Plant conservation has several objectives the main ones include safeguarding our food supply, preserving crop wild relatives for breeding and selection of new cultivars, providing material for industrial and pharmaceutical uses and preserving the beauty and diversity of our flora for generations to ...

  4. The Conservation Fund (United States)


    Create Walkable Neighborhoods 3. Encourage Community and Stakeholder Collaboration 4. Foster Distinctive, Attractive Communities with a Strong Sense of...Network Smart Growth America The International City /County Management Assn. The Conservation

  5. Beyond conservation agriculture

    NARCIS (Netherlands)

    Giller, K.E.; Andersson, J.A.; Corbeels, Marc; Kirkegaard, John; Mortensen, David; Erenstein, Olaf; Vanlauwe, Bernard


    Global support for Conservation Agriculture (CA) as a pathway to Sustainable Intensification is strong. CA revolves around three principles: no-till (or minimal soil disturbance), soil cover, and crop rotation. The benefits arising from the ease of crop management, energy/cost/time savings, and s

  6. Urban bird conservation

    NARCIS (Netherlands)

    Snep, Robbert P.H.; Kooijmans, Jip Louwe; Kwak, Robert G.M.; Foppen, Ruud P.B.; Parsons, Holly; Awasthy, Monica; Sierdsema, Henk L.K.; Marzluff, John M.; Fernandez-Juricic, Esteban; Laet, de Jenny


    Following the call from the United Nations Convention on Biological Diversity “Cities & Biodiversity Outlook” project to better preserve urban biodiversity, this paper presents stakeholder-specific statements for bird conservation in city environments. Based upon the current urban bird

  7. Conservative Pressures on Curriculum. (United States)

    Bryson, Joseph E.

    Pressure on the public schools is coming from conservative New Right religious-political groups. Their concerns focus on: (1) secular humanism--a Godless form of religion that the public schools are alleged to be teaching; (2) scientific evolution versus creationism--the balanced treatment statute; (3) Bible clubs and prayer in the classroom; and…

  8. Comparison between Free and Immobilized Ion Effects on Hydrophobic Interactions: A Molecular Dynamics Study

    CERN Document Server

    Huang, Kai; Ma, C Derek; Abbott, Nicholas L; Szlufarska, Izabela


    Fundamental studies of the effect of specific ions on hydrophobic interactions are driven by the need to understand phenomena such as hydrophobically driven self-assembly or protein folding. Using beta-peptide-inspired nano-rods, we investigate the effects of both free ions (dissolved salts) and proximally immobilized ions on hydrophobic interactions. We find that the free ion effect is correlated with the water density fluctuation near a non-polar molecular surface, showing that such fluctuation can be an indicator of hydrophobic interactions in the case of solution additives. In the case of immobilized ion, our results demonstrate that hydrophobic interactions can be switched on and off by choosing different spatial arrangements of proximal ions on a nano-rod. For globally amphiphilic nano-rods, we find that the magnitude of the interaction can be further tuned using proximal ions with varying ionic sizes. In general, univalent proximal anions are found to weaken hydrophobic interactions. This is in contras...

  9. How microorganisms use hydrophobicity and what does this mean for human needs?

    Directory of Open Access Journals (Sweden)

    Anna eKrasowska


    Full Text Available Cell surface hydrophobicity (CSH plays a crucial role in the attachment to, or detachment from the surfaces. The influence of CSH on adhesion of microorganisms to biotic and abiotic surfaces in medicine as well as in bioremediation and fermentation industry has both negative and positive aspects. Hydrophobic microorganisms cause the damage of surfaces by biofilm formation; on the other hand, they can readily accumulate on organic pollutants and decompose them. Hydrophilic microorganisms also play a considerable role in removing organic wastes from the environment because of their high resistance to hydrophobic chemicals. Despite the many studies on the environmental and metabolic factors affecting cell surface hydrophobicity (CSH, the knowledge of this subject is still scanty and is in most cases limited to observing the impact of hydrophobicity on adhesion, aggregation or flocculation. The future of research seems to lie in finding a way to managing the microbial adhesion process, perhaps by steering cell hydrophobicity.

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

    Directory of Open Access Journals (Sweden)

    Shirley Carro


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

  11. Pipeline walls hydrophobic properties study and their protective coatings used in trenchless technologies

    Directory of Open Access Journals (Sweden)

    Orlov Vladimir


    Full Text Available The results of field and theoretical studies to determine the degree of hydrophobicity of the inner pipe walls in static and dynamic conditions are reported. The water drops spreading nature in contact with the horizontal and concave surface of different materials with the definition of contact angles is determined. The flow pattern formed when the critical mass of liquid miniflow is reached on an inclined surface in the form of an open trough was studied. The geometric parameters of the frontal and coaxial miniflow projections were determined, its dimensions and hydraulic characteristics were studied. The trial stand design for the protective coatings hydrophobic properties study was presented and described and method of evaluation of the pipeline work surfaces hydrophobic properties by applying the relative hydrophobicity ratio. Calculation formulas of the relative hydrophobicity ratio for work surfaces were presented. The relationships of hydrophobicity of various coatings used in the trenchless technologies to relative roughness coefficients were established.

  12. Effects of the protein denaturant guanidinium chloride on aqueous hydrophobic contact-pair interactions. (United States)

    Macdonald, Ryan D; Khajehpour, Mazdak


    Guanidinium chloride (GdmCl) is one of the most common protein denaturants. Although GdmCl is well known in the field of protein folding, the mechanism by which it denatures proteins is not well understood. In fact, there are few studies looking at its effects on hydrophobic interactions. In this work the effect of GdmCl on hydrophobic interactions has been studied by observing how the denaturant influences model systems of phenyl and alkyl hydrophobic contact pairs. Contact pair formation is monitored through the use of fluorescence spectroscopy, i.e., measuring the intrinsic phenol fluorescence being quenched by carboxylate ions. Hydrophobic interactions are isolated from other interactions through a previously developed methodology. The results show that GdmCl does not significantly affect hydrophobic interactions between small moieties such as methyl groups and phenol; while on the other hand, the interaction of larger hydrophobes such as hexyl and heptyl groups with phenol is significantly destabilized.

  13. Residence time dependent desorption of Staphylococcus epidermidis from hydrophobic and hydrophilic substrata. (United States)

    Boks, Niels P; Kaper, Hans J; Norde, Willem; Busscher, Henk J; van der Mei, Henny C


    Adhesion and desorption are simultaneous events during bacterial adhesion to surfaces, although desorption is far less studied than adhesion. Here, desorption of Staphylococcus epidermidis from substratum surfaces is demonstrated to be residence time dependent. Initial desorption rate coefficients were similar for hydrophilic and hydrophobic dimethyldichlorosilane (DDS)-coated glass, likely because initial desorption is controlled by attractive Lifshitz-Van der Waals interactions, which are comparable on both substratum surfaces. However, significantly slower decay times of the desorption rate coefficients are found for hydrophilic glass than for hydrophobic DDS-coated glass. This difference is suggested to be due to the acid-base interactions between staphylococci and these surfaces, which are repulsive on hydrophilic glass and attractive on hydrophobic DDS-coated glass. Final desorption rate coefficients are higher on hydrophilic glass than on hydrophobic DDS-coated glass, due to the so called hydrophobic effect, facilitating a closer contact on hydrophobic DDS-coated glass.

  14. Influence of hydrophobic characteristic of organo-modified precursor on wettability of silica film

    Indian Academy of Sciences (India)

    Violeta Purcar; Otilia Cinteza; Marius Ghiurea; Adriana Balan; Simona Caprarescu; Dan Donescu


    The objective of this study is to design new hybrid silica materials as templates with hydrophobic properties, prepared at room temperature by a base catalyzed sol–gel process. As silica sources, organoalkoxysilanes functionalized with short hydrophobic chains were used: tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES), vinyltriethoxysilane (VTES), octyltriethoxysilane (OTES) and isobutyltriethoxysilane (iTES). It was shown that hydrophobicity of the functionalized silica nanoparticles increased as a function of length of the aliphatic chains (MTES < iTES < OTES) or when, instead of a hydrophobic alkyl chains (substituting group of silica precursors), a monounsaturated group was used (VTES). It was observed that the samples responded in a specific way to each type (hydrophilic or hydrophobic) of the dropped liquid. Even though the experiments were limited to short hydrocarbon chains, they showed that there is a threshold to reach high hydrophobicity of the hybrid surface.

  15. Effect of thermochemical treatment on the surface morphology and hydrophobicity of heterogeneous ion-exchange membranes (United States)

    Vasil'eva, V. I.; Pismenskaya, N. D.; Akberova, E. M.; Nebavskaya, K. A.


    A comparative analysis is performed on the effect thermochemical treatment in aqueous, alkali, and acid media has on the surface morphology and hydrophobicity of swelling heterogeneous ion-exchanged membranes. A correlation between changes in surface morphology and hydrophobicity is established. It is shown that under prolonged (50 h) membrane thermal treatment above room temperature, hydrophobicity is reduced due to substantial enlargement of cavities and cracks resulting from the partial destruction of inert binder (polyethylene) and reinforcing poly-ɛ-caproamide fabric (capron).

  16. Conservation businesses and conservation planning in a biological diversity hotspot. (United States)

    Di Minin, Enrico; Macmillan, Douglas Craig; Goodman, Peter Styan; Escott, Boyd; Slotow, Rob; Moilanen, Atte


    The allocation of land to biological diversity conservation competes with other land uses and the needs of society for development, food, and extraction of natural resources. Trade-offs between biological diversity conservation and alternative land uses are unavoidable, given the realities of limited conservation resources and the competing demands of society. We developed a conservation-planning assessment for the South African province of KwaZulu-Natal, which forms the central component of the Maputaland-Pondoland-Albany biological diversity hotspot. Our objective was to enhance biological diversity protection while promoting sustainable development and providing spatial guidance in the resolution of potential policy conflicts over priority areas for conservation at risk of transformation. The conservation-planning assessment combined spatial-distribution models for 646 conservation features, spatial economic-return models for 28 alternative land uses, and spatial maps for 4 threats. Nature-based tourism businesses were competitive with other land uses and could provide revenues of >US$60 million/year to local stakeholders and simultaneously help meeting conservation goals for almost half the conservation features in the planning region. Accounting for opportunity costs substantially decreased conflicts between biological diversity, agricultural use, commercial forestry, and mining. Accounting for economic benefits arising from conservation and reducing potential policy conflicts with alternative plans for development can provide opportunities for successful strategies that combine conservation and sustainable development and facilitate conservation action. © 2013 Society for Conservation Biology.

  17. Properties and influence of hydrophobically associating polyacrylamide modified with 2-phenoxylethylacrylate

    Institute of Scientific and Technical Information of China (English)

    Yu-hua DAI; Fei-peng WU; Miao-zhen LI; Er-jian WANG


    The properties of hydrophobically associating copolymer P(acrylamide (AM)/2-phenoxylethylacrylate (POEA)), composed of acrylamide and a small amount of POEA (≤1.0 mol.%) as hydrophobe, were investi-gated in aqueous solution under various conditions. The results showed that the solution properties were strongly affected by the microstructure of copolymer. The copoly-mers (BP series) with hydrophobic microblocky structure exhibited large viscosity enhancement due to the inter-molecular hydrophobic association, while that did not occur for the random copolymers (RP series). The hydro-phobic association thickening behaviors were also remarkably dependent on the number and length of the hydrophobic block in polymer chain. Nonlinear viscosity relationship was found as increasing hydrophobe content and SMR (surfactant/hydrophobic monomer molar ratio), and a maximum appeared at the middle position as a result of the competitive effect between inter- and intra- molecular hydrophobic associations. Solution properties were further studied as a function of the poly-mer concentration, salinity, temperature and shear rate. The block copolymers show high salt tolerance and shear thinning as well as recovery after shear.

  18. Model of waterlike fluid under confinement for hydrophobic and hydrophilic particle-plate interaction potentials. (United States)

    Krott, Leandro B; Barbosa, Marcia C


    Molecular dynamic simulations were employed to study a waterlike model confined between hydrophobic and hydrophilic plates. The phase behavior of this system is obtained for different distances between the plates and particle-plate potentials. For both hydrophobic and hydrophilic walls, there are the formation of layers. Crystallization occurs at lower temperature at the contact layer than at the middle layer. In addition, the melting temperature decreases as the plates become more hydrophobic. Similarly, the temperatures of maximum density and extremum diffusivity decrease with hydrophobicity.

  19. Synthesis of biocompatible hydrophobic silica-gelatin nano-hybrid by sol-gel process. (United States)

    Smitha, S; Shajesh, P; Mukundan, P; Nair, T D R; Warrier, K G K


    Silica-biopolymer hybrid has been synthesised using colloidal silica as the precursor for silica and gelatin as the biopolymer counterpart. The surface modification of the hybrid material has been done with methyltrimethoxysilane leading to the formation of biocompatible hydrophobic silica-gelatin hybrid. Here we are reporting hydrophobic silica-gelatin hybrid and coating precursor for the first time. The hybrid gel has been evaluated for chemical modification, thermal degradation, hydrophobicity, particle size, transparency under the UV-visible region and morphology. FTIR spectroscopy has been used to verify the presence of CH(3) groups which introduce hydrophobicity to the SiO2-MTMS-gelatin hybrids. The hydrophobic property has also been tailored by varying the concentration of methyltrimethoxysilane. Contact angle by Wilhelmy plate method of transparent hydrophobic silica-gelatin coatings has been found to be as high as approximately 95 degrees . Oxidation of the organic group which induces the hydrophobic character occurs at 530 degrees C which indicates that the surface hydrophobicity is retained up to that temperature. Optical transmittance of SiO2-MTMS-gelatin hybrid coatings on glass substrates has been found to be close to 100% which will enable the hybrid for possible optical applications and also for preparation of transparent biocompatible hydrophobic coatings on biological substrates such as leather.

  20. A variable hydrophobic surface improves corrosion resistance of electroplating copper coating (United States)

    Xu, Xiuqing; Zhu, Liqun; Li, Weiping; Liu, Huicong


    In this paper, Cu/liquid microcapsule composite coating was prepared by electroplating method. And a variable hydrophobic surface was obtained due to the slow release of microcapsules and the rough surface. The hydrophobic property and corrosion resistance of the composite was investigated by means of water contact angle instrument and electrochemical technique, respectively. The results suggest that the contact angle (CA) of composite increases gradually with the increasing storing time, and the stable super-hydrophobic property was exhibited after storing in air for 15 days. Meanwhile, the excellent corrosion resistance was displayed, which could be ascribed to the good stability of hydrophobic film on composite surface.

  1. Metrology and Energy Conservation

    Institute of Scientific and Technical Information of China (English)

    Xuan Xiang


    @@ May 20 is World Metrology Day and the theme of this year is "Metrology and Energy Conservation." Energy is not only a vital issue for China, but also for the world. In order to implement Proposal of the CPC Central Committee on the 11th Five-Year Program for National Economic and Social Development, the government bulletin of 5th Plenary Session of the 16th CPC Central Committee announced that "there shall be marked improvement on resource utilization; the energy consumption for unit GDP shall cut 20%, water consumption of unit industrial added value drop 30%... and the recycle ratio of industrial solid wastes shall raise by 60%." These are key targets of economic development during the 11th five-year program. To make full use of metrology for energy conservation and energy utilization, the competent metrology department of Chinese Goyernment advanced metrology program in light of China's energy status.

  2. Bison Conservation Initiative : Bison Conservation Genetics Workshop : Reports and Recommendations (United States)

    US Fish and Wildlife Service, Department of the Interior — One of the first outcomes of the Department of the Interior (DOI) Bison Conservation Initiative was the Bison Conservation Genetics Workshop held in Nebraska in...

  3. Selling Conservation? Scientific Legitimacy and the Commodification of Conservation Tourism

    Directory of Open Access Journals (Sweden)

    Jenny A. Cousins


    Full Text Available Conservation tourism is a rapidly growing subsector of ecotourism that engages paying volunteers as active participants in conservation projects. Once the preserve of charities, the sector now hosts a proliferation of private companies seeking to make money by selling international conservation work to tourists as a commodity. The commodification of conservation depends upon balancing the scientific legitimacy of projects against the need to offer desirable tourist experiences. Drawing on interviews with UK tour operators and their counterparts in South Africa who run the conservation projects, we explore the transnational geography of commercial conservation tourism, charting how scientific legitimacy is constructed and negotiated within the industry. Although conservation tourism makes trade-offs between scientific rigor and neoliberal market logic, it is a partial and plural process that resists simple categorization. We conclude by considering the difference that commodification makes to conservation science, and vice versa.

  4. Transforming plastic surfaces with electrophilic backbones from hydrophobic to hydrophilic. (United States)

    Kim, Samuel; Bowen, Raffick A R; Zare, Richard N


    We demonstrate a simple nonaqueous reaction scheme for transforming the surface of plastics from hydrophobic to hydrophilic. The chemical modification is achieved by base-catalyzed trans-esterification with polyols. It is permanent, does not release contaminants, and causes no optical or mechanical distortion of the plastic. We present contact angle measurements to show successful modification of several types of plastics including poly(ethylene terephthalate) (PET) and polycarbonate (PC). Its applicability to blood analysis is explored using chemically modified PET blood collection tubes and found to be quite satisfactory. We expect this approach will reduce the cost of manufacturing plastic devices with optimized wettability and can be generalized to other types of plastic materials having an electrophilic linkage as its backbone.

  5. Giant Osmotic Pressure in the Forced Wetting of Hydrophobic Nanopores. (United States)

    Michelin-Jamois, Millan; Picard, Cyril; Vigier, Gérard; Charlaix, Elisabeth


    The forced intrusion of water in hydrophobic nanoporous pulverulent material is of interest for quick storage of energy. With nanometric pores the energy storage capacity is controlled by interfacial phenomena. With subnanometric pores, we demonstrate that a breakdown occurs with the emergence of molecular exclusion as a leading contribution. This bulk exclusion effect leads to an osmotic contribution to the pressure that can reach levels never previously sustained. We illustrate, on various electrolytes and different microporous materials, that a simple osmotic pressure law accounts quantitatively for the enhancement of the intrusion and extrusion pressures governing the forced wetting and spontaneous drying of the nanopores. Using electrolyte solutions, energy storage and power capacities can be widely enhanced.

  6. Modification of Deeply Buried Hydrophobic Interfaces by Ionic Surfactants

    Energy Technology Data Exchange (ETDEWEB)

    L Tamam; D Pontoni Z Sapir; S Yefet; S Sloutskin; B Ocko; H Reichert; M Deutsch


    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.

  7. Hydrophobic interactions and hydrogen bonds in \\beta-sheet formation

    CERN Document Server

    Narayanan, Chitra


    In this study, we investigate interactions of extended conformations of homodimeric peptides made of small (glycine or alanine) and large hydrophobic (valine or leucine) sidechains using all-atom molecular dynamics simulations to decipher driving forces for \\beta-sheet formation. We make use of a periodic boundary condition setup in which individual peptides are infinitely long and stretched. Dimers adopt \\beta-sheet conformations at short interpeptide distances (\\xi ~ 0.5 nm) and at intermediate distances (~ 0.8 nm), valine and leucine homodimers assume cross-\\beta-like conformations with side chains interpenetrating each other. These two states are identified as minima in the Potential of Mean Force (PMF). While the number of interpeptide hydrogen bonds increases with decreasing interpeptide distance, the total hydrogen bond number in the system does not change significantly, suggesting that formation of \\beta-sheet structures from extended conformations is not driven by hydrogen bonds. This is supported by...

  8. Asymmetry of Drop Impacts on Patterned Hydrophobic Microstructures (United States)

    Willmott, Geoff; Robson, Simon; Broom, Matheu


    When a water drop falls on to a flat solid surface, asymmetries in the geometry of the spreading drop can be specifically determined by patterned surface microstructures. For hydrophobic (or superhydrophobic) micropillar arrays, the most important asymmetric mechanisms appear to be the surface energy of contact lines, and pathways for gas escaping from penetrated microstructure. In this presentation, static wetting and drop impact experiments will be discussed in relation to drop asymmetries. In addition to micropillar arrays, natural superhydrophobic surfaces (leaves) have been studied, and may suggest possibilities for controlling drop impacts in applications. Some of the clearest large scale drop asymmetries on leaves, which are similar to those associated with low drop impact contact times on synthetic surfaces, appear to be caused by features which generate high contact angle hysteresis, and are therefore indicative of poor superhydrophocity.

  9. Explicit and implicit modeling of nanobubbles in hydrophobic confinement

    Directory of Open Access Journals (Sweden)

    Joachim Dzubiella


    Full Text Available Water at normal conditions is a fluid thermodynamically close to the liquid-vapor phase coexistence and features a large surface tension. This combination can lead to interesting capillary phenomena on microscopic scales. Explicit water molecular dynamics (MD computer simulations of hydrophobic solutes, for instance, give evidence of capillary evaporation on nanometer scales, i.e., the formation of nanometer-sized vapor bubbles (nanobubbles between confining hydrophobic surfaces. This phenomenon has been exemplified for solutes with varying complexity, e.g., paraffin plates, coarse-grained homopolymers, biological and solid-state channels, and atomistically resolved proteins. It has been argued that nanobubbles strongly impact interactions in nanofluidic devices, translocation processes, and even in protein stability, function, and folding. As large-scale MD simulations are computationally expensive, the efficient multiscale modeling of nanobubbles and the prediction of their stability poses a formidable task to the'nanophysical' community. Recently, we have presented a conceptually novel and versatile implicit solvent model, namely, the variational implicit solvent model (VISM, which is based on a geometric energy functional. As reviewed here, first solvation studies of simple hydrophobic solutes using VISM coupled with the numerical level-set scheme show promising results, and, in particular, capture nanobubble formation and its subtle competition to local energetic potentials in hydrophobic confinement.Água em condições normais consiste de um fluido termodinamicamente próximo à fase líquida-vapor exibindo alta tensão superficial. Esta combinação conduz a fenômenos capilares interessantes na escala microscópica. Simulações computacionais baseadas em técnicas de Dinâmica Molecular em solutos hidrofóbicos por exemplo fornecem evidências do fenômeno de evaporação capilar em escalas nanométricas dando origem à formação de

  10. Affinity chromatography of acetylcholinesterase. The importance of hydrophobic interactions. (United States)

    Massoulié, J; Bon, S


    An easily prepared affinity column for acetylcholinesterase is described, which may be operated at ionic strength high enough to prevent aggregation of the asymmetric forms of the enzyme. Specific elution by tetraethylammonium or decamethonium was quantitative. The performance of this column is comparable to that of the column described by Dudai and Silman. It is shown that the hexyl 'spacer arm' strongly participates in the enzyme binding and that its replacement with the more hydrophilic spermine chain lowers the affinity. The hexyl chain itself is shown to bind acetylcholinesterase, although with lower affinity and capacity than the complete column. This binding is also partly reversed by inhibitors. Such hydrophobic columns bind the native asymmetric forms of the enzyme more strongly than the lytic globular ones. The aromatic quaternary ligang inhibits Electrophorus but not Torpedo acetylcholinesterase; therefore the column does not retain the Torpedo enzyme. Differences in Km between acetylcholinesterases of the two species also point to differences in their active sites.

  11. Fabrication of superhydrophobic cotton fabrics by silica hydrosol and hydrophobization

    Energy Technology Data Exchange (ETDEWEB)

    Xu Lihui; Zhuang Wei; Xu Bi [Key Laboratory of Science and Technology of Eco-Textile, Ministry of Education, Donghua University, Shanghai 201620 (China); Cai Zaisheng, E-mail: [Key Laboratory of Science and Technology of Eco-Textile, Ministry of Education, Donghua University, Shanghai 201620 (China)


    Superhydrophobic cotton fabrics were prepared by the incorporation of silica nanoparticles and subsequent hydrophobization with hexadecyltrimethoxysilane (HDTMS). The silica nanoparticles were synthesized via sol-gel reaction with methyl trimethoxy silane (MTMS) as the precursor in the presence of the base catalyst and surfactant in aqueous solution. As for the resulting products, characterization by particle size analyzer, scanning electron microscopy (SEM), scanning probe microscopy (SPM), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA) were performed respectively. The size of SiO{sub 2} nanoparticles can be controlled by adjusting the catalyst and surfactant concentrations. The wettability of cotton textiles was evaluated by the water contact angle (WCA) and water shedding angle (WSA) measurements. The results showed that the treated cotton sample displayed remarkable water repellency with a WCA of 151.9{sup o} for a 5 {mu}L water droplet and a WSA of 13{sup o} for a 15 {mu}L water droplet.

  12. Harvesting electrostatic energy using super-hydrophobic surfaces (United States)

    Pociecha, Dominik; Zylka, Pawel


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

  13. Hydrophobic starch nanocrystals preparations through crosslinking modification using citric acid. (United States)

    Zhou, Jiang; Tong, Jin; Su, Xingguang; Ren, Lili


    Biodegradable starch nanocrystals prepared by an acid treatment process were modified through crosslinking modification using citric acid as reactant by a dry reaction method. The occurrence of crosslinking modification was evaluated by Fourier transform infrared spectroscopy and swelling degree. X-ray diffraction, wettability tests and contact angle measurements were used to characterize the modified starch nanocrystals. It was found that the crosslinked starch nanocrystals displayed a higher affinity for low polar solvents such as dichloromethane. The surface of starch nanocrystals became more roughness after crosslinking modification with citric acid and the size decreased as revealed by scanning electron microscopy and dynamic light scattering results. XRD analysis showed that the crystalline structure of starch nanocrystals was basically not changed after the crosslinking modification with shorter heating time. The resulting hydrophobic starch nanocrystals are versatile precursors to the development of nanocomposites.

  14. Influence of the surface hydrophobicity on fluorescence correlation spectroscopy measurements (United States)

    Boutin, Céline; Jaffiol, Rodolphe; Plain, Jérome; Royer, Pascal


    Fluorescence correlation spectroscopy (FCS) is a powerful experimental technique used to analyze the diffusion at the single molecule level in solution. FCS is based on the temporal autocorrelation of fluorescent signal generated by dye molecules diffusing through a small confocal volume. These measurements are mostly carried out in a chambered coverglass, close to the glass substrate. In this report, we discuss how the chemical nature of the glass-water interface may interact with the free diffusion of molecules. Our results reveal a strong influence, up to a few μm from the interface, of the surface hydrophobicity degree. This influence is assessed through the relative weight of the two dimension diffusion process observed at the vicinity of the surface.

  15. Intramolecular hydrophobic interactions are critical mediators of STAT5 dimerization (United States)

    Fahrenkamp, Dirk; Li, Jinyu; Ernst, Sabrina; Schmitz-van de Leur, Hildegard; Chatain, Nicolas; Küster, Andrea; Koschmieder, Steffen; Lüscher, Bernhard; Rossetti, Giulia; Müller-Newen, Gerhard


    STAT5 is an essential transcription factor in hematopoiesis, which is activated through tyrosine phosphorylation in response to cytokine stimulation. Constitutive activation of STAT5 is a hallmark of myeloid and lymphoblastic leukemia. Using homology modeling and molecular dynamics simulations, a model of the STAT5 phosphotyrosine-SH2 domain interface was generated providing first structural information on the activated STAT5 dimer including a sequence, for which no structural information is available for any of the STAT proteins. We identified a novel intramolecular interaction mediated through F706, adjacent to the phosphotyrosine motif, and a unique hydrophobic interface on the surface of the SH2 domain. Analysis of corresponding STAT5 mutants revealed that this interaction is dispensable for Epo receptor-mediated phosphorylation of STAT5 but essential for dimer formation and subsequent nuclear accumulation. Moreover, the herein presented model clarifies molecular mechanisms of recently discovered leukemic STAT5 mutants and will help to guide future drug development.

  16. Super-hydrophobic bandages and method of making the same (United States)

    Simpson, John T [Clinton, TN; D'Urso, Brian R [Pittsburgh, PA


    A bandage that includes a material, which can be breathable, having a first surface, and a plurality of superhydrophobic particles attached to the first surface. The plurality of superhydrophobic particles ranging in size from about 100 nanometers to about 10 micrometers. The superhydrophobic particles including a protrusive material defining a plurality of nanopores and a plurality of spaced apart nanostructures that define an external boundary of the hydrophobic particles. The nanopores providing a flow through porosity. The first surface can be rendered superhydrophobic by the attached superhydrophobic particles. The material can have a second surface opposite the first surface that is hydrophilic. The superhydrophobic particles can be adhered to the first surface by a binder. Also included is a method of making the bandages described herein.

  17. Laser conservation paleontology (United States)

    Asmus, John F.


    Just as lasers have found countless applications in science, industry, medicine, and entertainment, an array of real and potential uses for lasers in art-conservation analytes and practice have been investigated over the past thirty years. These include holographic recording, holographic recording, holographic nondestructive testing, laser-induced ultrasonic imaging, laser-scattering surface characterization, atomic and molecular analyses, photoacoustic spectroscopy, surface modification, as well as surface divestment and cleaning. The initial endeavors in exploring and assessing the utility of these tools for art conservation are recounted for investigations involving ruby, glass, ion, YAG, carbon dioxide, dye, and excimer lasers as well as high-intensity nonlaser light generators such as xenon flashlamps and argon pinchlamps. Initially, laser divestment/cleaning was, by general consensus, the least plausible laser application in art conservation. In the past ten years it has emerged to dominate all the other applications noted above. Today, at least a dozen firms supply user-friendly laser systems optimized for a range of art-conservation divestment applications. The first-generation laser-cleaning tools are essentially a laser, a beam-delivery device, and a debris- collection accessory. Advanced developmental work has turned in large measure to ancillary subsystems for more sophisticated process control. Of particular importance are acoustic, optical, spectral, EMP, and electronic-vision process control. Beam direction may be via manual, translational-scanner, or robotic beam positioning implemented by means of fiber optics, minors, or prisms and computer control. Substrate thermal alteration and debris redeposition may be minimized or avoided through the incorporation of a gas jet, fluid or fluid jet, or dry-ice blast.

  18. Interaction of engineered nanomaterials with hydrophobic organic pollutants (United States)

    Sahle-Demessie, E.; Han, Changseok; Zhao, Amy; Hahn, Bill; Grecsek, Heidi


    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.

  19. Understanding the drop impact on moving hydrophilic and hydrophobic surfaces. (United States)

    Almohammadi, H; Amirfazli, A


    In this paper, a systematic study was performed to understand the drop impact on hydrophilic and hydrophobic surfaces that were moving in the horizontal direction. Drops (D0 = 2.5 mm) of liquids with three different viscosities were used. Wide ranges of drop normal velocity (0.5 to 3.4 m s(-1)) and surface velocity (0 to 17 m s(-1)) were studied. High speed imaging from the top and side was used to capture the impact phenomena. It was found that drop impact behavior on a moving surface significantly differs from that on a stationary surface at both the lamella extension stage (i.e. t ≤ tmax) and the retraction stage (t > tmax). Starting with the lamella extension stage, it was observed that the drop spreads asymmetrically over a moving surface. It was also found that the splashing behavior of the drop upon impact on a moving surface, unlike the understanding in the literature, is azimuthally different along the lamella contact line. In the case of the drop spreading over a moving surface, the surface movement stretches the expanded lamella in the direction of the surface motion. For hydrophilic surfaces, the stretched lamella pins to the surface and moves with the surface velocity; however, for hydrophobic surfaces, the lamella recoils during such stretching. A new model was developed to determine the splashing threshold of the drop impact on a moving surface. The model is capable of describing the azimuthally different behavior of the splashing which is a function of normal capillary and Weber numbers, surface velocity, and surface wettability. It was also found that the increase of the viscosity decreases the splashing threshold. Finally, comprehensive regime maps of the drop impact outcome on a moving surface were provided for both t ≤ tmax and t > tmax stages.

  20. Thiolated graphene oxide as promising mucoadhesive carrier for hydrophobic drugs. (United States)

    Pereira de Sousa, Irene; Buttenhauser, Katrin; Suchaoin, Wongsakorn; Partenhauser, Alexandra; Perrone, Mara; Matuszczak, Barbara; Bernkop-Schnürch, Andreas


    The aim of this study was to improve the mucoadhesive properties of graphene by conjugating thiol ligands, in order to formulate an oral delivery system for hydrophobic drugs showing long mucus residence time. Graphene oxide was obtained by oxidation of graphite and then was thiolated following two synthetic paths. On the one hand, the hydroxyl groups were conjugated with thiourea passing through the formation of a brominated intermediate. On the other hand, the carboxylic acid groups were conjugated with cysteamine via carbodiimide chemistry. The mucoadhesive properties of thiolated graphene were evaluated by rheological measurements and by residence time assay. Then, valsartan was loaded on thiolated graphene and the release profile was evaluated in simulated intestinal fluid. Following both synthetic paths it was possible to obtain thiolated graphene bearing 215-302μmol SH/g product. Both products induced after 1h incubation an increase of mucus viscosity of about 22-33-fold compared to unmodified graphite. The residence time assay confirmed that 60% of thiolated graphene could be retained on intestinal mucosa after 4h incubation, whereas just 20% of unmodified graphite could be retained. Valsartan could be loaded with a drug loading of about 31±0.3% and a sustained release profile was observed for both formulations. According to the presented data, the thiolation of graphene could improve its mucoadhesive properties. Therefore, thiolated graphene represents a promising platform for oral delivery of hydrophobic drugs, possessing a long residence time on intestinal mucosa which allows the release of the loaded drug close to the adsorptive epithelium.

  1. Water anomalous thermodynamics, attraction, repulsion, and hydrophobic hydration (United States)

    Cerdeiriña, Claudio A.; Debenedetti, Pablo G.


    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. Crystallization Behavior of Phosphate Glasses with Hydrophobic Coating Materials

    Directory of Open Access Journals (Sweden)

    Jaeyeop Chung


    Full Text Available We analyzed the effect of the addition of Li2O3, TiO2, and Fe2O3 on the crystallization behavior of P2O5–CaO–SiO2–K2O glasses and the effect of the crystallization behavior on the roughness and hydrophobicity of the coated surface. Exothermic behavior, including a strong exothermic peak in the 833–972 K temperature range when Fe2O3, TiO2, or Li2O3 was added, was confirmed by differential thermal analysis. The modified glass samples (PFTL1–3 showed diffraction peaks when heated at 1073 and 1123 K for 5 min; the crystallized phase corresponds to Fe3(PO42, that is, graftonite. We confirmed that the intensity of the diffraction peaks increases at high temperatures and with increasing Li2O3 content. In the case of the PFTL3 glass, a Li3Fe2(PO42 phase, that is, trilithium diiron(III tris[phosphate(V], was observed. Through scanning electron microscopy and the contact angles of the surfaces with water, we confirmed that the increase in surface roughness, correlated to the crystallization of the glass frit, increases hydrophobicity of the surface. The calculated values of the local activation energies for the growth of Fe3(PO42 on the PTFL1, PTFL2, and PFTL3 glass were 237–292 kJ mol−1, 182–258 kJ mol−1, and 180–235 kJ mol−1.

  3. 75 FR 59469 - Energy Conservation Program: Energy Conservation Standards for Residential Refrigerators... (United States)


    ... Energy 10 CFR Part 430 Energy Conservation Program: Energy Conservation Standards for Residential... Energy Conservation Program: Energy Conservation Standards for Residential Refrigerators, Refrigerator... Conservation Act (EPCA) prescribes energy conservation standards for various consumer products and......

  4. Top-down mass spectrometry of hybrid materials with hydrophobic peptide and hydrophilic or hydrophobic polymer blocks. (United States)

    Alalwiat, Ahlam; Grieshaber, Sarah E; Paik, Bradford A; Kiick, Kristi L; Jia, Xinqiao; Wesdemiotis, Chrys


    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

  5. Genome Analysis of Conserved Dehydrin Motifs in Vascular Plants

    Directory of Open Access Journals (Sweden)

    Ahmad A. Malik


    Full Text Available Dehydrins, a large family of abiotic stress proteins, are defined by the presence of a mostly conserved motif known as the K-segment, and may also contain two other conserved motifs known as the Y-segment and S-segment. Using the dehydrin literature, we developed a sequence motif definition of the K-segment, which we used to create a large dataset of dehydrin sequences by searching the Pfam00257 dehydrin dataset and the Phytozome 10 sequences of vascular plants. A comprehensive analysis of these sequences reveals that lysine residues are highly conserved in the K-segment, while the amino acid type is often conserved at other positions. Despite the Y-segment name, the central tyrosine is somewhat conserved, but can be substituted with two other small aromatic amino acids (phenylalanine or histidine. The S-segment contains a series of serine residues, but in some proteins is also preceded by a conserved LHR sequence. In many dehydrins containing all three of these motifs the S-segment is linked to the K-segment by a GXGGRRKK motif (where X can be any amino acid, suggesting a functional linkage between these two motifs. An analysis of the sequences shows that the dehydrin architecture and several biochemical properties (isoelectric point, molecular mass, and hydrophobicity score are dependent on each other, and that some dehydrin architectures are overexpressed during certain abiotic stress, suggesting that they may be optimized for a specific abiotic stress while others are involved in all forms of dehydration stress (drought, cold, and salinity.

  6. 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

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Siqin [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Sheong, Fu Kit [Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Huang, Xuhui, E-mail: [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Division of Biomedical Engineering, Center of Systems Biology and Human Health, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)


    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.

  7. Saving Money Through Energy Conservation. (United States)

    Presley, Michael H.; And Others

    This publication is an introduction to personal energy conservation. The first chapter presents a rationale for conserving energy and points out that private citizens control about one third of this country's energy consumption. Chapters two and three show how to save money by saving energy. Chapter two discusses energy conservation methods in the…

  8. 76 FR 22785 - Wetland Conservation (United States)


    ... 7 CFR Part 12 RIN 0578-AA58 Wetland Conservation AGENCY: Office of the Secretary, United States.... Background Existing wetland conservation provisions in 7 CFR part 12 require that NRCS' certification of a... Subjects in 7 CFR Part 12 Administrative practices and procedures, Soil conservation, Wetlands. For...

  9. Conservation Education: A Position Statement. (United States)

    Soil Conservation Society of America, Ankeny, IA.

    The Soil Conservation Society of America's (SCSA) aim is to advance the science and art of good land and water use. Conservation education has a significant role in achieving the wise use of these resources. In this report, perspectives are offered on: (1) the requirements for effective conservation education programs; (2) rationale for…

  10. Approved Practices in Soil Conservation. (United States)

    Foster, Albert B.

    This book is written for individuals who wish to apply conservation practices, especially those of soil and water conservation, without technical assistance, to meet one's own conditions, and within his own capability to apply them. To meet these needs, the book includes a discussion and description of soil and water conservation methods for the…

  11. Integrating conservation costs into sea level rise adaptive conservation prioritization

    Directory of Open Access Journals (Sweden)

    Mingjian Zhu


    Full Text Available Biodiversity conservation requires strategic investment as resources for conservation are often limited. As sea level rises, it is important and necessary to consider both sea level rise and costs in conservation decision making. In this study, we consider costs of conservation in an integrated modeling process that incorporates a geomorphological model (SLAMM, species habitat models, and conservation prioritization (Zonation to identify conservation priorities in the face of landscape dynamics due to sea level rise in the Matanzas River basin of northeast Florida. Compared to conservation priorities that do not consider land costs in the analysis process, conservation priorities that consider costs in the planning process change significantly. The comparison demonstrates that some areas with high conservation values might be identified as lower priorities when integrating economic costs in the planning process and some areas with low conservation values might be identified as high priorities when considering costs in the planning process. This research could help coastal resources managers make informed decisions about where and how to allocate conservation resources more wisely to facilitate biodiversity adaptation to sea level rise.

  12. Signal peptide hydrophobicity is critical for early stages in protein export by Bacillus subtilis

    NARCIS (Netherlands)

    Zanen, G; Meima, R; Tjalsma, H; Jongbloed, JDH; Westers, H; Oudega, B; Luirink, J; van Dijl, JM; Quax, WJ; Houben, E.N.G.


    Signal peptides that direct protein export in Bacillus subtilis are overall more hydrophobic than signal peptides in Escherichia coli. To study the importance of signal peptide hydrophobicity for protein export in both organisms, the alpha-amylase AmyQ was provided with leucine-rich (high hydrophobi

  13. Cell surface hydrophobicity is conveyed by S-layer proteins - A study in recombinant lactobacilli

    NARCIS (Netherlands)

    Mei, H.C. van der; Belt-Gritter, B. van de; Pouwels, P.H.; Martinez, B.; Busscher, H.J.


    Cell surface hydrophobicity is one of the most important factors controlling adhesion of microorganisms to surfaces. In this paper, cell surface properties of lactobacilli and recombinant lactobacilli with and without a surface layer protein (SLP) associated with cell surface hydrophobicity were det

  14. Cell surface hydrophobicity is conveyed by S-layer proteins - A study in recombinant lactobacilli

    NARCIS (Netherlands)

    Mei, H.C. van der; Belt-Gritter, B. van de; Pouwels, P.H.; Martinez, B.; Busscher, H.J.


    Cell surface hydrophobicity is one of the most important factors controlling adhesion of microorganisms to surfaces. In this paper, cell surface properties of lactobacilli and recombinant lactobacilli with and without a surface layer protein (SLP) associated with cell surface hydrophobicity were det

  15. Strength of microbeads for the encapsulation of heat sensitive, hydrophobic components

    NARCIS (Netherlands)

    Leusden, van P.; Hartog, den G.J.M.; Bast, A.; Postema, M.; Linden, van der E.; Sagis, L.M.C.


    Hydrophobic food ingredients sensitive to degradation can be protected from their environment by microencapsulation. In an O/W1/W2 system, these hydrophobic compounds are dissolved in oil droplets, dispersed within a gelled matrix microbead (W1), which forms a bar

  16. Tunable Hydrophobicity in DNA Micelles : Design, Synthesis, and Characterization of a New Family of DNA Amphiphiles

    NARCIS (Netherlands)

    Anaya, Milena; Kwak, Minseok; Musser, Andrew J.; Muellen, Klaus; Herrmann, Andreas; Müllen, Klaus


    This work describes the synthesis and characterization of a new family of DNA amphiphiles containing modified nucleobases. The hydrophobicity was imparted by the introduction of a dodec-1-yne chain at the 5-position of the uracil base, which allowed precise and simple tuning of the hydrophobic

  17. Effect of Plant-derived Hydrophobic Compounds on Soil Water. Repellency in Dutch Sandy Soils

    NARCIS (Netherlands)

    Mao, J.|info:eu-repo/dai/nl/363508287; Dekker, S.C.|info:eu-repo/dai/nl/203449827; Nierop, K.G.J.|info:eu-repo/dai/nl/182329895


    Soil water repellency or hydrophobicity is a common and important soil property, which may diminish plant growth and promotes soil erosion leading to environmentally undesired situations. Hydrophobic organic compounds in the soil are derived from vegetation (leaves, roots, mosses) or microorganisms

  18. Human Gastric Mucosal Hydrophobicity Does dot Decrease with Helicobacter Pylori Infection or Chronological Age

    Directory of Open Access Journals (Sweden)

    Mohammed S Al-Marhoon


    Full Text Available BACKGROUND AND AIMS: Infection with cytotoxin-associated gene A (cagA Helicobacter pylori is associated with severe gastric diseases. Previous studies in humans have reported a decreased gastric hydrophobicity with H pylori infection. The aim of the present study was to differentiate between the effect of cagA+ and cagA- strains on gastric mucus hydrophobicity.

  19. Strength of microbeads for the encapsulation of heat sensitive, hydrophobic components

    NARCIS (Netherlands)

    Leusden, van P.; Hartog, den G.J.M.; Bast, A.; Postema, M.; Linden, van der E.; Sagis, L.M.C.


    Hydrophobic food ingredients sensitive to degradation can be protected from their environment by microencapsulation. In an O/W1/W2 system, these hydrophobic compounds are dissolved in oil droplets, dispersed within a gelled matrix microbead (W1), which forms a bar

  20. Dystrophin hydrophobic regions in the pathogenesis of Duchenne and Becker muscular dystrophies

    Directory of Open Access Journals (Sweden)

    Yingyin Liang


    Full Text Available The aim of our study was to determine the role of dystrophin hydrophobic regions in the pathogenesis of Duchenne (DMD and Becker (BMD muscular dystrophies, by the Kyte-Doolittle scale mean hydrophobicity profile and 3D molecular models. A total of 1038 cases diagnosed with DMD or BMD with the in-frame mutation were collected in our hospital and the Leiden DMD information database in the period 2002-2013. Correlation between clinical types and genotypes were determined on the basis of these two sources. In addition, the Kyte-Doolittle scale mean hydrophobicity of dystrophin was analyzed using BioEdit software and the models of the hydrophobic domains of dystrophin were constructed. The presence of four hydrophobic regions is confirmed. They include the calponin homology CH2 domain on the actin-binding domain (ABD, spectrin-type repeat 16, hinge III and the EF Hand domain. The severe symptoms of DMD usually develop as a result of the mutational disruption in the hydrophobic regions I, II and IV of dystrophin – those that bind associated proteins of the dystrophin-glycoprotein complex (DGC. On the other hand, when the hydrophobic region III is deleted, the connection of the ordered repeat domains of the central rod domain remains intact, resulting in the less severe clinical presentation. We conclude that mutational changes in the structure of hydrophobic regions of dystrophin play an important role in the pathogenesis of DMD.

  1. Susceptibility to hydrophobic molecules and phospholipid composition in Pasteurella multocida and Actinobacillus lignieresii. (United States)

    Hart, M E; Champlin, F R


    Despite its typically gram-negative cell envelope ultrastructure, Pasteurella multocida is susceptible to the hydrophobic antibiotic novobiocin and is unable to initiate growth on MacConkey agar, a parameter often used to effect is differentiation from other members of the family Pasteurellaceae such as Actinobacillus lignieresii. However, growth on basal medium supplemented with individual selective factors and an agar diffusion assay revealed the bile salts contained in MacConkey agar to be toxic to both organisms. Four P. multocida surface hydrophobicity variants exhibited consistent in vitro susceptibility to the hydrophobic antibiotics novobiocin, rifamycin SV, and actinomycin D as determined by broth dilution. Readily extractable lipid fractions were obtained by chloroform-methanol extraction of freeze-dried whole cells from exponential-phase cultures. No major differences in total cellular readily extractable lipid content were observed among the P. multocida and A. lignieresii strains examined, although hydrophobic P. multocida strains appeared to contain slightly more than did hydrophilic strains. Analytical thin-layer chromatography and quantitation of resolved readily extractable lipid components revealed the major cell envelope phospholipids of both organisms to be phosphatidylethanolamine and phosphatidylglycerol in a molar ratio of approximately 4:1 regardless of cell surface hydrophobicity properties. Similar results were obtained for Pseudomonas aeruginosa, which is notably refractory to hydrophobic molecules. These data support the conclusion that the permeability of the P. multocida cell envelope to structurally unrelated, hydrophobic molecules is not dependent on cell surface hydrophobicity and cannot be explained on the basis of anomalous polar lipid composition.

  2. Molecular docking using the molecular lipophilicity potential as hydrophobic descriptor: impact on GOLD docking performance. (United States)

    Nurisso, Alessandra; Bravo, Juan; Carrupt, Pierre-Alain; Daina, Antoine


    GOLD is a molecular docking software widely used in drug design. In the initial steps of docking, it creates a list of hydrophobic fitting points inside protein cavities that steer the positioning of ligand hydrophobic moieties. These points are generated based on the Lennard-Jones potential between a carbon probe and each atom of the residues delimitating the binding site. To thoroughly describe hydrophobic regions in protein pockets and properly guide ligand hydrophobic moieties toward favorable areas, an in-house tool, the MLP filter, was developed and herein applied. This strategy only retains GOLD hydrophobic fitting points that match the rigorous definition of hydrophobicity given by the molecular lipophilicity potential (MLP), a molecular interaction field that relies on an atomic fragmental system based on 1-octanol/water experimental partition coefficients (log P(oct)). MLP computations in the binding sites of crystallographic protein structures revealed that a significant number of points considered hydrophobic by GOLD were actually polar according to the MLP definition of hydrophobicity. To examine the impact of this new tool, ligand-protein complexes from the Astex Diverse Set and the PDB bind core database were redocked with and without the use of the MLP filter. Reliable docking results were obtained by using the MLP filter that increased the quality of docking in nonpolar cavities and outperformed the standard GOLD docking approach.

  3. Effect of Plant-derived Hydrophobic Compounds on Soil Water. Repellency in Dutch Sandy Soils

    NARCIS (Netherlands)

    Mao, J.; Dekker, S.C.; Nierop, K.G.J.


    Soil water repellency or hydrophobicity is a common and important soil property, which may diminish plant growth and promotes soil erosion leading to environmentally undesired situations. Hydrophobic organic compounds in the soil are derived from vegetation (leaves, roots, mosses) or microorganisms

  4. Tunable Hydrophobicity in DNA Micelles : Design, Synthesis, and Characterization of a New Family of DNA Amphiphiles

    NARCIS (Netherlands)

    Anaya, Milena; Kwak, Minseok; Musser, Andrew J.; Muellen, Klaus; Herrmann, Andreas; Müllen, Klaus


    This work describes the synthesis and characterization of a new family of DNA amphiphiles containing modified nucleobases. The hydrophobicity was imparted by the introduction of a dodec-1-yne chain at the 5-position of the uracil base, which allowed precise and simple tuning of the hydrophobic prope

  5. Ionic Functionalization of Hydrophobic Colloidal Nanoparticles To Form Ionic Nanoparticles with Enzymelike Properties

    NARCIS (Netherlands)

    Liu, Y.; Purich, D.L.; Wu, C.; Wu, Y.; Chen, T.; Cui, C.; Zhang, L.; Cansiz, S.; Hou, W.; Wang, Y.; Yang, S.; Tan, W.


    Inorganic colloidal nanoparticles (NPs) stabilized by a layer of hydrophobic surfactant on their surfaces have poor solubility in the aqueous phase, thus limiting their application as biosensors under physiological conditions. Here we report a simple model to ionize various types of hydrophobic coll

  6. Hydrogel based drug carriers for controlled release of hydrophobic drugs and proteins

    NARCIS (Netherlands)

    Ke Peng,


    The aim of this study is to prepare in situ forming hydrogels based on biocompatible polymers for the controlled release of hydrophobic drug and proteins. In order to load hydrophobic drug to the hydrophilic hydrogel matrix, beta-cyclodextrin and human serum albumin was introduced to the hydrogel ne

  7. Strength of microbeads for the encapsulation of heat sensitive, hydrophobic components

    NARCIS (Netherlands)

    Leusden, van P.; Hartog, den G.J.M.; Bast, A.; Postema, M.; Linden, van der E.; Sagis, L.M.C.


    Hydrophobic food ingredients sensitive to degradation can be protected from their environment by microencapsulation. In an O/W1/W2 system, these hydrophobic compounds are dissolved in oil droplets, dispersed within a gelled matrix microbead (W1), which forms a

  8. Development of Hydrophobic Coatings for Water-Repellent Surfaces Using Hybrid Methodology (United States)


    windows, optical components, protective eyewear, and clothing, this type of surface is desired for the material to be soil repellent and water ...Development of Hydrophobic Coatings for Water - Repellent Surfaces Using Hybrid Methodology by Amanda S. Weerasooriya, Jacqueline Yim, Andres A...Proving Ground, MD 21005-5069 ARL-TR-6898 April 2014 Development of Hydrophobic Coatings for Water - Repellent Surfaces Using Hybrid

  9. A new method of UV-patternable hydrophobization of micro- and nanofluidic networks

    NARCIS (Netherlands)

    Arayanarakool, R.; Shui, L.; Berg, van den A.; Eijkel, J.C.T.


    This work reports a new method to hydrophobize glass-based micro- and nanofluidic networks. Conventional methods of hydrophobizing glass surfaces often create particulate debris causing clogging, especially in shallow nanochannels, or require skillful handling. Our novel method employs an oxygen pla

  10. A new method of UV-patternable hydrophobization of micro- and nanofluidic networks

    NARCIS (Netherlands)

    Arayanarakool, Rerngchai; Shui, Lingling; Berg, van den Albert; Eijkel, Jan C.T.


    This work reports a new method to hydrophobize glass-based micro- and nanofluidic networks. Conventional methods of hydrophobizing glass surfaces often create particulate debris causing clogging especially in shallow nanochannels or require skilful handling. Our novel method employs oxygen plasma, s

  11. Energy conservation technologies

    Energy Technology Data Exchange (ETDEWEB)

    Courtright, H.A. [Electric Power Research Inst., Palo Alto, CA (United States)


    The conservation of energy through the efficiency improvement of existing end-uses and the development of new technologies to replace less efficient systems is an important component of the overall effort to reduce greenhouse gases which may contribute to global climate change. Even though uncertainties exist on the degree and causes of global warming, efficiency improvements in end-use applications remain in the best interest of utilities, their customers and society because efficiency improvements not only reduce environmental exposures but also contribute to industrial productivity, business cost reductions and consumer savings in energy costs.

  12. Is Baryon Number Conserved? (United States)

    Pati, Jogesh C.; Salam, Abdus

    We suggest that baryon-number conservation may not be absolute and that an integrally charged quark may disintegrate into two leptons and an antilepton with a coupling strength G Bmp2≲ 10-9. On the other hand, if quarks are much heavier than low-lying hadrons, the decay of a three-quark system like the proton is highly forbidden (proton lifetime ≳ 1028 y). Motivation for these ideas appears to arise within a unified theory of hadrons and leptons and their gauge interactions. We emphasize the consequences of such a possibility for real quark searches.

  13. Conservation Laws with Dissipation, (United States)


    smooth, due to the formation of shock waves. However, global solutions exist in the class of functions of bounded variation ,/in the sense of Tonelli...hyperbolic conservation law (2.2) ut + f(u)x -0 The Cauchy problem for (2.2), with initial data u(x,O), of bounded variation , admits a solution in the class...BV of functions of bounded variation ,.in the sense of Tonelli-Cesari. No gain would be made by assuming that u(x,O) is smoother, even analytic! In

  14. CHP and Energy Conservation


    McGovern, Jim


    The principles of the use of 'combined heat and power' (CHP) for the achievement of fuel energy conservation, minimisation of environmental impact and economic advantage are explained. A distinction is made between the two types of outputs: heat and work. It is argued that an efficiency value that is defined as the sum of the heat and work outputs divided by the energy of the fuel used is not very meaningful. An alternative, rational, efficiency is explained. It is concluded that CHP is an op...

  15. Hearing Conservation Live #2430

    Energy Technology Data Exchange (ETDEWEB)

    Chochoms, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    Occupational hearing loss is one of the most common work-related illnesses in the United States (US). From 22 to 30 million US workers are exposed to hazardous noise levels at work, and 25% of these workers will develop permanent hearing loss. Hearing loss from noise is slow and painless, and you can have a disability before you notice it. This course presents the hazards associated with workplace noise, the purpose and elements of the Los Alamos National Laboratory (LANL) Hearing Conservation Program (HCP), and controls that are available to reduce your exposure to hazardous levels of noise.

  16. Functional Leathers: Hydrophobic Leather%功能性皮革系列之疏水皮革

    Institute of Scientific and Technical Information of China (English)

    邢恩征; 王全杰


    详细介绍了皮革表面疏水的原理、影响皮革表面疏水性的因素、皮革表面疏水的处理方法、皮革表面疏水材料等,并对疏水表面皮革的发展做了一定的展望.%The hydrophobic properties of leather were introduced in detail, including principle of leather surface hydrophobic, the influence factors of leather surface hydrophobic, the treatment method of leather surface hydrophobic, leather surface hydro-phobic materials etc. The prospect of hydrophobic leather was proposed.

  17. Influence of the viscosity and the substrate on the surface hydrophobicity of polyurethane coatings

    Energy Technology Data Exchange (ETDEWEB)

    Meincken, M. [Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 (South Africa)]. E-mail:; Klash, A. [Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 (South Africa); Seboa, S. [Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 (South Africa); Sanderson, R.D. [Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 (South Africa)


    Tailor-made polyurethane (PU) dispersions were synthesized as coatings for paperboard for dry food packaging. For this purpose a low moisture-vapor transmission rate and a high surface hydrophobicity are desirable characteristics, which are both met by PU. However, it was found that the surface hydrophobicity of water-borne PU dispersions depends strongly on the viscosity of the dispersion. This dependency was studied by static contact angle measurements (SCA) as well as a novel technique using digital pulsed-force mode atomic force microscopy (DPFM-AFM). Comparison of the results validated that DPFM-AFM is a valuable tool to characterize the surface hydrophilicity. Both techniques confirmed that the surface hydrophobicity varies with the viscosity and that an optimum viscosity for the PU coating with a maximum surface hydrophobicity can consequently be determined. It was found that both lower as well as higher viscosities led to a less hydrophobic surface.

  18. Improving the catalytic characteristics of lipase-displaying yeast cells by hydrophobic modification. (United States)

    Zhang, Kun; Jin, Zi; Wang, Pan; Zheng, Sui-Ping; Han, Shuang-Yan; Lin, Ying


    Lipase-displaying yeast cells are a promising alternative to the conventional immobilised lipases for organic bioconversions. However, the hydrophilic characteristics of the yeast cell surface may impede efficient immobilisation. Herein, we tested three methods to enhance the hydrophobicity of the surface of Candida antarctica lipase B-displaying Pichia pastoris cells, co-displaying a fungal hydrophobin, coating with ionic liquids, and adding decane as a hydrophobic carbon source during fermentation. Modified cells showed higher surface hydrophobicity and superior esterification of C6-C18 saturated fatty acids in hydrophobic solvents. When used for biodiesel synthesis, modified cells exhibited an improved initial reaction rate and equilibrium fatty acid methyl ester yield. We systematically discuss the influence of cell surface hydrophobicity on the catalytic properties, and the results provide guidance for improving the catalytic efficiency and operational characteristics of lipase-displaying yeast cells for organic bioconversions.


    Directory of Open Access Journals (Sweden)

    Thakor Namita M


    Full Text Available Controlling In-vitro drug release profiles for a system of PLGA/PLA microparticles encapsulating a hydrophobic drug. Challenges with the diversity of drug properties, microencapsulation methods, are evaluated with a focus on decreasing the time to lab-scale encapsulation of water-insoluble drug candidates in the drug development stage. The development of biodegradable microparticles systems that combined the beneficial properties of polymeric microparticles for hydrophobic drug delivery were reviewed here. Injectable biodegradable and biocompatible copolymers of lactic and glycolic acid are important advanced delivery system for week too month controlled release of hydrophobic drug (e.g., from biopharmaceutical classification system class IV, which often display poor oral bioavailability. Finally, three important properties affecting release behavior were identified as: polymer hydrophobicity, particle size and particle coating, . This review focuses on the microencapsulation of hydrophobic drugs, describes a variety of techniques for their preparation and analytics.

  20. Fabrication of Super Hydrophobic Surfaces on Copper by Solution-immersion

    Institute of Scientific and Technical Information of China (English)

    龚志金; 王建莉; 吴丽梅; 王小雨; 吕国诚; 廖立兵


    Super hydrophobic copper wafer was prepared by means of solution immersion and surface self-assembly methods. Different immersion conditions were explored for the best hydrophobic surface. Scanning electron mi-croscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and water contact angle meas-urements were used to investigate the morphologies, microstructures, chemical compositions and hydrophobicity of the produced films on copper substrates, respectively. Results show that the super hydrophobic surface is composed of micro structure of Cu7S4. The films present a high water contact angle larger than 150°, a low sliding angle less than 3°, good abrasion resistance and storage stability. The molecular dynamics simulation confirms that N-dodecyl mercaptan molecules link up with Cu7S4 admirably, compared with Cu, which contributes to the stable super hy-drophobic surface.