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Sample records for giant surfactant aggregates

  1. Surfactant effects on soil aggregate tensile strength

    USDA-ARS?s Scientific Manuscript database

    Little is known regarding a soil aggregate's tensile strength response to surfactants that may be applied to alleviate soil water repellency. Two laboratory investigations were performed to determine surfactant effects on the tensile strength of 1) Ap horizons of nine wettable, agricultural soils co...

  2. Aggregation of sulfosuccinate surfactants in water

    SciTech Connect

    Magid, L.J.; Daus, K.A.; Butler, P.D.; Quincy, R.B.

    1983-12-22

    The aggregation of sodium di-n-alkyl sulfosuccinates in water (H/sub 2/O and D/sub 2/O at 45/sup 0/C) has been investigated. A self-consistent picture of the dependence of sodium ion binding on surfactant concentration is obtained from emf measurements, conductimetry, and small-angle neutron scattering (SANS) measurements. The concentration dependence of the micellar agregation number for the sulfosuccinates and related double-tailed surfactants depends markedly on surfactant solubility. A sphere-to-disk transition in micellar shape, which might have been expected as a precursor to formation of a lamellar mesophase, was not observed as the surfactant concentration was increased. 8 figures, 2 tables.

  3. Aggregation Behavior of Mixed-Counterion Double-Chained Surfactants

    DTIC Science & Technology

    1991-01-01

    Cryofixation of colloidal dispersions with the controlled environment vitrification system allows vicrostructural detail of surfactant aggregates as small ...surfactant mixtures. Thus, in the dialkyldimethylammonium system, the small , unhydrated bromide counterion sits close to the aggregate surface and...head group repulsions are high, a is large and curvatures are small . Thus, the optimal aggregate of ditetradecyldimethylammonium acetate is a small

  4. Efficacy of glyphosate and five surfactants for controlling giant salvinia

    USGS Publications Warehouse

    Fairchild, J.F.; Allert, A.L.; Riddle, J.S.; Gladwin, D.R.

    2002-01-01

    Giant salvinia (Salvinia molesta Mitchell) is a non-native, invasive aquatic fern that was recently introduced to the southern United States. The aggressive nature of the species has led to concerns over its potential adverse impacts to native plants, fish, and invertebrates. We conducted a study to determine the efficacy of glyphosate [isopropylamine salt of N-(phosphono-methyl)glycine] and several surfactants for control of giant salvinia. Studies were conducted over a 42-day period using static renewals (twice weekly) with 4% Hoagland's medium (10 mg/L N equivalent) in replicated 2-L containers. Five concentrations of glyphosate (0, 0.45, 0.91, 1.82, and 3.60% v:v) and five surfactants (0.25% concentration, v:v; Optima???, Kinetic???, Mon 0818???, Cygnet Plus???, and LI-700???) were applied with a pressurized sprayer as a single surface application in a fully nested experimental design. Untreated giant salvinia grew rapidly and exhibited an increase of 800% wet weight biomass over the 42-day test duration. Glyphosate, with and without surfactants, exhibited efficacy at concentrations as low as 0.45% of the commercial formulation. Glyphosate with Optima was the only mixture that resulted in complete mortality of plants with no regrowth.

  5. Structure and Dynamics of Nonionic Surfactant Aggregates in Layered Materials.

    PubMed

    Guégan, Régis; Veron, Emmanuel; Le Forestier, Lydie; Ogawa, Makoto; Cadars, Sylvian

    2017-09-26

    The aggregation of surfactants on solid surfaces as they are adsorbed from solution is the basis of numerous technological applications such as colloidal stabilization, ore flotation, and floor cleaning. The understanding of both the structure and the dynamics of surfactant aggregates applies to the development of alternative ways of preparing hybrid layered materials. For this purpose, we study the adsorption of the triethylene glycol mono n-decyl ether (C10E3) nonionic surfactant onto a synthetic montmorillonite (Mt), an aluminosilicate clay mineral for organoclay preparation with important applications in materials sciences, catalysis, wastewater treatment, or as drug delivery. The aggregation mechanisms follow those observed in an analogous natural Mt, with the condensation of C10E3 in a bilayer arrangement once the surfactant self-assembles in a lamellar phase beyond the critical micelle concentration, underlining the importance of the surfactant state in solution. Solid-state (1)H nuclear magnetic resonance (NMR) at fast magic-angle spinning (MAS) and high magnetic field combined with(1)H-(13)C correlation experiments and different types of (13)C NMR experiments selectively probes mobile or rigid moieties of C10E3 in three different aggregate organizations: (i) a lateral monolayer, (ii) a lateral bilayer, and (iii) a normal bilayer. High-resolution (1)H{(27)Al} CP-(1)H-(1)H spin diffusion experiments shed light on the proximities and dynamics of the different fragments and fractions of the intercalated surfactant molecules with respect to the Mt surface. (23)Na and (1)H NMR measurements combined with complementary NMR data, at both molecular and nanometer scales, precisely pointed out the location of the C10E3 ethylene oxide hydrophilic group in close contact with the Mt surface interacting through ion-dipole or van der Waals interactions.

  6. Multi-block poloxamer surfactants suppress aggregation of denatured proteins.

    PubMed

    Mustafi, Devkumar; Smith, Catherine M; Makinen, Marvin W; Lee, Raphael C

    2008-01-01

    On the basis of elastic light scattering, we have compared the capacity of the multi-block, surfactant copolymers Poloxamer 108 (P108), Poloxamer 188 (P188), and Tetronic 1107 (T1107), of average molecular weight 4700, 8400, and 15,000, respectively, with that of polyethylene glycol (PEG, molecular weight 8000) to suppress aggregation of heat-denatured hen egg white lysozyme (HEWL) and bovine serum albumin (BSA). We also compared the capacity of P188 to that of PEG to suppress aggregation of carboxypeptidase A denatured in the presence of trifluoroethanol and to facilitate recovery of catalytic activity. In contrast to the multi-block copolymers, PEG had no effect in inhibiting aggregation of HEWL or of carboxypeptidase A with the recovery of catalytic activity. At very high polymer:protein ratios (>or=10:1), PEG increased aggregation of heat-denatured HEWL and BSA, consistent with its known properties to promote macromolecular crowding and crystallization of proteins. At a polymer:protein ratio of 2:1, the tetra-block copolymer T1107 was the most effective of the three surfactant copolymers, completely suppressing aggregation of heat-denatured HEWL. At a T1107:BSA ratio of 10:1, the poloxamer suppressed aggregation of heat-denatured BSA by 50% compared to that observed in the absence of the polymer. We showed that the extent of suppression of aggregation of heat-denatured proteins by multi-block surfactant copolymers is dependent on the size of the protein and the copolymer:protein molar ratio. We also concluded that at least one of the tertiary nitrogens in the ethylene-1,2-diamine structural core of the T1107 copolymer is protonated, and that this electrostatic factor underlies its capacity to suppress aggregation of denatured proteins more effectively than nonionic, multi-block poloxamers. These results indicate that amphiphilic, surfactant, multi-block copolymers are efficient as additives to suppress aggregation and to facilitate refolding of denatured

  7. The effects of alkylammonium counterions on the aggregation of fluorinated surfactants and surfactant ionic liquids.

    PubMed

    Pottage, Matthew J; Greaves, Tamar L; Garvey, Christopher J; Tabor, Rico F

    2016-08-01

    The effects of organic counterions with varying carbon number on surfactant aggregation have been analysed by coupling perfluorooctanoate surfactant anions with various alkylammonium counterions. Both the degree of substitution (primary to tertiary) and alkyl chain length (0-3 carbons) of the counterions were varied to provide a comprehensive matrix of geometries and lipophilicities. Surface activity was measured using pendant drop tensiometry, while temperature-controlled small-angle neutron scattering was used to probe changes in aggregation morphology. It was found that the use of such alkylammonium counterions resulted in a strong preference for bilayer formation even at low surfactant concentration (<2wt%), when compared to simple inorganic counterions such as sodium which favour near-spherical micelles. At increased temperatures, some counterions led to unique phase behaviour wherein a transition between two structurally different lamellar phases is seen, rationalised as a transition into a microscopic phase separation wherein a surfactant-rich lamellar phase coexists with a dilute micellar phase. The results indicate that aggregation is controlled by a delicate balance of counterion size, hydrophilicity and diffuseness of charge, providing new methods for the subtle control of surfactant solutions.

  8. Aggregation behavior of gemini surfactants and their interaction with macromolecules in aqueous solution.

    PubMed

    Han, Yuchun; Wang, Yilin

    2011-02-14

    Gemini surfactants are constructed by two hydrophobic chains and two polar/ionic head groups covalently connected by a spacer group at the level of the head groups. Gemini surfactants possess unique structural variations and display special aggregate transitions. Their aggregation ability and aggregate structures can be more effectively adjusted through changing their molecular structures compared with the corresponding monomeric surfactants. Moreover, gemini surfactants exhibit special and useful properties while interacting with polymers and biomacromolecules. Their strong self-aggregation ability can be applied to effectively influence the aggregation behavior of both polymers and biomacromolecules. This short review is focused on the performances of gemini surfactants in aqueous solutions investigated in the last few years, and summarizes the effects of molecular structures on aggregation behavior of gemini surfactants in aqueous solution as well as the interaction of gemini surfactants with polymers and biomacromolecules respectively.

  9. Reaction limited aggregation in surfactant-mediated epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, Jing; Liu, Bang-Gui; Zhang, Zhenyu; Wang, E. G.

    2000-05-01

    A theoretical model for reaction limited aggregation (RLA) is introduced to study the effect of a monolayer of surfactant on the formation of two-dimensional islands in heteroepitaxial and homoepitaxial growth. In this model the basic atomic processes are considered as follows. A stable island consists of the adatoms that have exchanged positions with the surfactant atoms beneath them. Movable active adatoms may (a) diffuse on the surfactant terrace, (b) exchange positions with the surfactant atoms beneath them and become island seeds (seed exchange), or (c) stick to stable islands and become stuck but still active adatoms. The rate-limiting step for the formation of a stable island is the seed exchange. Furthermore, a stuck but still active adatom must overcome a sizable potential-energy barrier to exchange positions with the surfactant atom beneath it and become a member of the stable island (aided exchange). The seed exchange process can occur with an adatom or collectively with an addimer. In the case of dimer exchange, the diffusing adatoms on the surfactant terrace can meet and (after exchanging) form stable dimers, which can then become island seeds. Systematic kinetic Monte Carlo simulations and rate-equation analysis of the model are carried out. The key finding of these simulations is that a counterintuitive fractal-to-compact island shape transition can be induced either by increasing deposition flux or by decreasing growth temperature. This major qualitative conclusion is valid for both the monomer and the dimer seed exchanges and for two different substrate lattices (square and triangular, respectively), although there are some quantitative differences in the flux and temperature dependence of the island density. The shape transition observed is contrary to the prediction of the classic diffusion-limited aggregation (DLA) theory, but in excellent qualitative agreement with recent experiments. In rationalizing the main finding, it is crucial to realize

  10. Soluble aggregates in aqueous solutions of polyion-surfactant ion complex salts and a nonionic surfactant.

    PubMed

    Janiak, John; Tomšič, Matija; Lundberg, Dan; Olofsson, Gerd; Piculell, Lennart; Schillén, Karin

    2014-08-14

    Water-soluble aggregates based on two polyion-surfactant ion "complex salts", consisting of hexadecyltrimethylammonium (C16TA(+)) and polyacrylate (PA(-)) with either 25 or 6000 repeating units, with added nonionic surfactant octaethylene glycol monododecyl ether (C12E8) have been investigated. A previous phase study has shown that added C12E5 or C12E8 can solubilize complex salts in aqueous systems, and that increasing the poly(ethylene oxide) chain length of the nonionic surfactant and/or decreasing the polyion length favors dissolution. In this work we report on dynamic light scattering, NMR diffusometry, small-angle X-ray scattering, and isothermal titration calorimetry measurements performed to characterize the solubilized composite aggregates in dilute aqueous solution in terms of size and stoichiometry. It was found that mixed aggregates of polyacrylate, C16TA(+) ions, and C12E8, with almost constant stoichiometry, coexist with free micelles of C12E8 at all investigated mixing ratios. The length of the polyion only weakly affects the stoichiometry of the mixed aggregates while strongly affecting their size and water solubility.

  11. Hierarchical Structure from the Self-Assembly of Giant Gemini Surfactants in Condensed State

    NASA Astrophysics Data System (ADS)

    Su, Hao; Wang, Zhao; Li, Yiwen; Cheng, Stephen

    2013-03-01

    In the past a few years, a new class of amphiphiles with both asymmetrical shapes and interactions named ``shape amphiphiles'' has been significantly intensified. Recently, a new kind of shape amphiphiles called ``Giant Gemini Surfactants'' consisting of two hydrophilic carboxylic acid-functionalized polyhedral oligomeric silsesquioxane (APOSS) heads and two hydrophobic polystyrene (PS) tails covalently linked via rigid spacers (p-phenylene versus biphenylene) has been successful behavior of giant gemini surfactants. We currently continue to investigate the spacer effects on the self-assembly behaviors of giant gemini surfactants in condensed state by utilizing DCS, SAXS and TEM. Preliminary results showed that giant gemini surfactants with different spacers have diverse phase behaviors. As we use the same 3.2k PS chains, the giant gemini surfactant with p-phenylene spacer showed double gyroid morphology, while the one with biphenylene spacer revealed cylindrical morphology. This study expands the scope of giant gemini surfactants and contributes a lot to the basic physical principles in self-assembly behavior.

  12. Comparative characterization of pulmonary surfactant aggregates and alkaline phosphatase isozymes in human lung carcinoma tissue.

    PubMed

    Iino, Nozomi; Matsunaga, Toshiyuki; Harada, Tsuyoshi; Igarashi, Seiji; Koyama, Iwao; Komoda, Tsugikazu

    2007-05-01

    Alkaline phosphatase (AP) isozymes are surfactant-associated proteins (SPs). Since several different AP isozymes have been detected in the pneumocytes of lung cancer patients, we attempted to identify the relationship between pulmonary surfactant aggregate subtypes and AP isozymes. Pulmonary surfactant aggregates were isolated from carcinoma and non-carcinoma tissues of patients with non-small cell carcinoma of the lung. Upon analysis, ultraheavy, heavy, and light surfactant aggregates were detected in the non-carcinoma tissues, but no ultraheavy surfactant aggregates were found in the carcinoma tissues. Surfactant-associated protein A (SP-A) was detected as two bands (a 27-kDa band and a 54-kDa band) in the ultraheavy, heavy, and light surfactant aggregates found in the non-carcinoma tissues. Although both SP-A bands were detected in the heavy and light surfactant aggregates from adenocarcinoma tissues, the 54-kDa band was not detected in squamous cell carcinoma tissues. Liver AP (LAP) was detected in the heavy and light surfactant aggregates from both non-carcinoma and squamous carcinoma tissues, but not in heavy surfactant aggregates from adenocarcinoma tissues. A larger amount of bone type AP (BAP) was found in light surfactant aggregate fractions from squamous cell carcinomas than those from adenocarcinoma tissues or non-carcinoma tissues from patients with either type of cancer. LAP, BAP, and SP-A were identified immunohistochemically in type II pneumocytes from non-carcinoma tissues and adenocarcinoma cells, but no distinct SP-A staining was observed in squamous cell carcinoma tissues. The present study has thus revealed several differences in pulmonary surfactant aggregates and AP isozymes between adenocarcinoma tissue and squamous cell carcinoma tissue.

  13. Polyelectrolyte/surfactant films spread from neutral aggregates.

    PubMed

    Campbell, Richard A; Tummino, Andrea; Noskov, Boris A; Varga, Imre

    2016-06-28

    We describe a new methodology to prepare loaded polyelectrolyte/surfactant films at the air/water interface by exploiting Marangoni spreading resulting from the dynamic dissociation of hydrophobic neutral aggregates dispensed from an aqueous dispersion. The system studied is mixtures of poly(sodium styrene sulfonate) with dodecyl trimethylammonium bromide. Our approach results in the interfacial confinement of more than one third of the macromolecules in the system even though they are not even surface-active without the surfactant. The interfacial stoichiometry of the films was resolved during measurements of surface pressure isotherms in situ for the first time using a new implementation of neutron reflectometry. The interfacial coverage is determined by the minimum surface area reached when the films are compressed beyond a single complete surface layer. The films exhibit linear ripples on a length scale of hundreds of micrometers during the squeezing out of material, after which they behave as perfectly insoluble membranes with consistent stoichiometric charge binding. We discuss our findings in terms of scope for the preparation of loaded membranes for encapsulation applications and in deposition-based technologies.

  14. Synthesis of polymer-biohybrids: from small to giant surfactants.

    PubMed

    Reynhout, Irene C; Cornelissen, Jeroen J L M; Nolte, Roeland J M

    2009-06-16

    Amphiphiles or surfactants, more popularly known as soaps, are among the oldest known chemical compounds used by man. Written text on a clay tablet dated to 2200 B.C. indicates that the Babylonians were familiar with soap-like substances. According to the Ebers papyrus (1550 B.C.), the ancient Egyptians bathed regularly in a mixture of animal oils, vegetable extracts, and alkaline salts, and a soap factory with bars of scented soap was found in the ruins of Pompeii (79 A.D.). In modern times, the use of soap has become universal, and we now understand reasonably well what happens when soap molecules are dispersed in aqueous solution and how the cleaning properties of soap work. The latter is related to the surface-active behavior of soap molecules, which is a result of their amphiphilic, also called amphipathic, character. Although the cleaning aspect is still an important issue, scientists are increasingly focusing on other properties of soaps, for example, self-assembling behavior and how this can be used in the design and non-covalent synthesis of new (macro)molecular architectures. These new molecules can be employed in nanotechnology and drug delivery, among other applications. This Account will focus on three different classes of amphiphiles. The first is the low molecular weight amphiphiles, also called classical amphiphiles in this context. A short overview will be given on the research carried out by our group and others on the self-assembly behavior and properties of these compounds; in particular, we focus on the ones that can be stabilized by polymerization (polymerized vesicles). Next, we will introduce the still relatively young field of superamphiphiles, macromolecules consisting of a hydrophobic and a hydrophilic polymeric block. Finally, and this constitutes the main part of this Account, we will provide an overview of a new class of amphiphiles, the so-called giant amphiphiles. These macromolecules have an enzyme or protein as the polar head group

  15. Effect of protein-surfactant interactions on aggregation of β-lactoglobulin.

    PubMed

    Hansted, Jon G; Wejse, Peter L; Bertelsen, Hans; Otzen, Daniel E

    2011-05-01

    The milk protein β-lactoglobulin (βLG) dominates the properties of whey aggregates in food products. Here we use spectroscopic and calorimetric techniques to elucidate how anionic, cationic and non-ionic surfactants interact with bovine βLG and modulate its heat-induced aggregation. Alkyl trimethyl ammonium chlorides (xTAC) strongly promote aggregation, while sodium alkyl sulfates (SxS) and alkyl maltopyranosides (xM) reduce aggregation. Sodium dodecyl sulfate (SDS) binds to non-aggregated βLG in several steps, but reduction of aggregation was associated with the first binding step, which occurs far below the critical micelle concentration. In contrast, micellar concentrations of xMs are required to reduce aggregation. The ranking order for reduction of aggregation (normalized to their tendency to self-associate) was C10-C12>C8>C14 for SxS and C8>C10>C12>C14>C16 for xM. xTAC promote aggregation in the same ranking order as xM reduce it. We conclude that SxS reduce aggregation by stabilizing the protein's ligand-bound state (the melting temperature t(m) increases by up to 10°C) and altering its charge potential. xM monomers also stabilize the protein's ligand-bound state (increasing t(m) up to 6°C) but in the absence of charged head groups this is not sufficient by itself to prevent aggregation. Although micelles of both anionic and non-ionic surfactants destabilize βLG, they also solubilize unfolded protein monomers, leaving them unavailable for protein-protein association and thus inhibiting aggregation. Cationic surfactants promote aggregation by a combination of destabilization and charge neutralization. The food compatible surfactant sodium dodecanoate also inhibited aggregation well below the cmc, suggesting that surfactants may be a practical way to modulate whey protein properties. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. Self-aggregation of cationic surfactants onto oxidized cellulose fibers and coadsorption of organic compounds.

    PubMed

    Alila, S; Aloulou, F; Beneventi, D; Boufi, S

    2007-03-27

    In this work, the adsorption of cationic surfactant and organic solutes on oxidized cellulose fibers bearing different amounts of carboxylic moieties was investigated. The increase in the amount of -COOH groups on cellulose fibers by TEMPO oxidation induced a general rise in surfactant adsorption. For all tested conditions, that is, cellulose oxidation level and surfactant alkyl chain length (C12 and C16), adsorption isotherms displayed a typical three-region shape with inversion of the substrate zeta-potential which was interpreted as reflecting surfactant adsorption and aggregation (admicelles and hemimicelles) on cellulose fibers. The addition of organic solutes in surfactant/cellulose systems induced a decrease in surfactant cac on the cellulose surface thus favoring surfactant aggregation and the formation of mixed surfactant/solute assemblies. Adsorption isotherms of organic solutes on cellulose in surfactant/cellulose/solute systems showed that solute adsorption is strictly correlated to (i) the surfactant concentration, solute adsorption increases up to the surfactant cmc, where solute partitioning between the cellulose surface and free micelles causes a drop in adsorption, and to (ii) solute solubility and functional groups. The specific shape of solutes adsorption isotherms at a fixed surfactant concentration was interpreted using a Frumkin adsorption isotherm, thus suggesting that solute uptake on cellulose fibers is a coadsorption and not a partitioning process. Results presented in this study were compared with those obtained in a previous work investigating solute adsorption in anionic surfactant/cationized cellulose systems to better understand the role of surfactant/solute interactions in the coadsorption process.

  17. Steroidal Surfactants: Detection of Premicellar Aggregation, Secondary Aggregation Changes in Micelles, and Hosting of a Highly Charged Negative Substance.

    PubMed

    Barnadas-Rodríguez, Ramon; Cladera, Josep

    2015-08-25

    CHAPSO and CHAPS are zwitterionic surfactants derived from bile salts which are usually employed in protein purification and for the preparation of liposomes and bicelles. Despite their spread use, there are significant discrepancies on the critical concentrations that determine their aggregation behavior. In this work, we study the interaction between these surfactants with the negative fluorescent dye pyranine (HPTS) by absorbance, fluorescence, and infrared spectrometry to establish their concentration-dependent aggregation. For the studied surfactants, we detect three critical concentrations showing their concentration-dependent presence as a monomeric form, premicellar aggregates, micelles, and a second type of micelle in aqueous medium. The nature of the interaction of HPTS with the surfactants was studied using analogues of their tails and the negative bile salt taurocholate (TC) as reference for the sterol ring. The results indicate that the chemical groups involved are the hydroxyl groups of the polar face of the sterol ring and the sulfonate groups of the dye. This interaction causes not only the incorporation of the negative dye in CHAPSO and CHAPS micelles but also its association with their premicellar aggregates. Surprisingly, this hosting behavior for a negative charged molecule was also detected for the negative bile salt TC, bypassing, in this way, the electrostatic repulsion between the guest and the host.

  18. Mechanical and thermodynamic properties of surfactant aggregates at the solid-liquid interface.

    PubMed

    Rabinovich, Yakov I; Vakarelski, Ivan U; Brown, Scott C; Singh, Pankaj K; Moudgil, Brij M

    2004-02-01

    Surfactants are widely used to stabilize colloidal systems in a variety of industrial applications through the formation of self-assembled aggregates at the solid-liquid interface. Previous studies have reported that the control of surfactant-mediated slurry stability can be achieved through the manipulation of surfactant chain length and concentration. However, a fundamental understanding of the mechanical and energetic properties of these aggregates, which may aid in the molecular-level design of these systems, is still lacking. In this study, experimentally measured force/distance curves between an atomic force microscope (AFM) tip and self-assembled surfactant aggregates on mica or silica substrates at concentrations higher than the bulk critical micelle concentration (CMC) were used to determine their mechanical and thermodynamic properties. The experimental curves were fitted to a model which describes the interaction between a hard sphere (tip) and a soft substrate (surfactant structures) based on a modified Hertz theory for the case of a thin elastic layer on a rigid substrate. The calculated mechanical properties were found to be in the same order of magnitude as those reported for rubber-like materials (e.g., polydimethylsiloxane (PDMS)). By integrating the force/distance curves, the energy required for breaking the surface aggregates was also calculated. These values are close to those reported for bulk-micelle formation.

  19. Stabilizing two IgG1 monoclonal antibodies by surfactants: Balance between aggregation prevention and structure perturbation.

    PubMed

    Wang, Shujing; Wu, Guoliang; Zhang, Xinyi; Tian, Zhou; Zhang, Ning; Hu, Tao; Dai, Weiguo; Qian, Feng

    2017-05-01

    Surfactants are widely used as stabilizers in the biopharmaceutical formulations to minimize protein aggregation. Under a fixed stress condition, the protecting and destabilizing effects of surfactants are hypothesized to be highly dependent on the species and concentrations of surfactants and mAb. Therefore, we here studied the aggregation-prevention and structure-perturbation effects of eight commonly used surfactants (Tw20, Tw80, Brij35, Chaps, TrX-100, SDS, Pluronic F68 and F127) on two IgG1 solution formulations under agitation, using analytical methodologies including visual inspection, OD350 measurement, HPLC-SEC, circular dicroism, fluorescence spectroscopy and differential scanning calorimetry. We found that: (1) With concentrations range from 0.02 to 2mg/mL, nonionic surfactants were found to offer efficient aggregation-prevention effect, which is superior than the ionic surfactants; and higher surfactant concentration prevented mAb aggregation better especially under prolonged stability test under stress conditions. (2) The surfactant induced structure-perturbation emerged when even higher surfactant concentration (≥2mg/mL) was used, and such effect was surfactant-property dependent; and (3) the two IgG1 demonstrated different aggregation mechanisms and surfactant dependency, especially at high mAb concentrations. In conclusion, surfactants usage in mAb formulations, including the types and concentrations, should strike an optimal balance between the desirable aggregation-prevention and the detrimental structure-perturbation effects, while the consideration of mAb aggregation mechanism and concentration is also required for surfactant assessment. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Self-assembled surfactants on patterned surfaces: confinement and cooperative effects on aggregate morphology.

    PubMed

    Suttipong, Manaswee; Grady, Brian P; Striolo, Alberto

    2014-08-21

    The adsorption and self-assembly of surfactants are ubiquitous processes in several technological applications, including the manufacture of nano-structured materials using bottom-up strategies. Although much is known about the adsorption of surfactants on homogeneous flat surfaces from experiments, theory, and simulations, limited information is available, in quantifiable terms, regarding the adsorption of surfactants on surfaces with chemical and/or morphological heterogeneity. In an effort to fill this knowledge gap, we report here results obtained using equilibrium dissipative particle dynamics (DPD) simulations for the adsorption of model surfactants onto patterned flat surfaces (i.e., flat surfaces with chemical heterogeneity). The patterns consist of one or two stripes of variable width on which the surfactants could adsorb. The adsorbing stripes are surrounded by a surface that effectively repels the surfactants. This repelling surface, perhaps not realistic, allows us to quantify the effect of lateral confinement on the morphology of surfactant aggregates. When the stripe width is large (effectively providing a homogeneous flat surface), the surfactants yield a flat monolayer. Our simulations suggest that the flat monolayers become hemi-cylinders, hemi-spheres, and individual surfactants as the stripe width decreases, a consequence of lateral confinement. In some cases our simulations show evidence of cooperative effects when two adsorbing stripes are present on the surface. If the distance between the stripes and the widths of the stripes are both less than about one surfactant length, hemi-cylindrical shells and irregular structures are observed because of cooperativity; otherwise the results match those found for a single isolated stripe. Our predictions could be useful for the design of new nano-structured materials and coatings, for applications ranging from nano-fluidic devices to nano-reactors.

  1. Preparation of Gemini Surfactant/Conjugated Polymer Aggregates for Enhanced Fluorescence and Bioimaging Application.

    PubMed

    Wang, Hua; Zhou, Lingyun; Zhou, Chengcheng; Zhao, Weiwei; Wang, Jianwu; Liu, Libing; Wang, Shu; Wang, Yilin

    2017-07-19

    Conjugated polymers have great potential applications in bioimaging. However, the aggregation of conjugated polymers driven by electrostatic and hydrophobic interactions in aqueous media results in the reduction of photoluminescence quantum efficiency. In present work we synthesized a carboxylate gemini surfactant [sodium 2,6-didodecyl-4-hydroxy-2,6-diaza-1,7-heptanedicarboxylate (SDHC)] to adjust the aggregation behaviors and fluorescence properties of conjugated polymers [anionic poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene) (MPS-PPV) and cationic poly(3-alkoxy-4-methylthiophene) (PMNT)]. This gemini surfactant shows very low critical micellar concentration (CMC) in aqueous solution and forms vesicles above CMC. In neutral and acidic conditions, MPS-PPV combines with the SDHC vesicles mainly via hydrophobic interactions and forms the aggregates in which the photoluminescence quantum efficiency of MPS-PPV is highly enhanced from 0.1% to 27%. As to PMNT, the molecules are located in the bilayer of SDHC vesicles through both electrostatic and hydrophobic interactions, and this structure prevents the production and release of reactive oxygen species. Moreover, SDHC is nontoxic and can effectively decrease the dark- and photocytotoxicity of MPS-PPV and PMNT, laying a good foundation for their bioimaging application. The living cell imaging indicates that the surfactant/conjugated polymer aggregates can stain the MCF-7 cells with main location in the lysosome. This work provides insight into how to improve the fluorescence properties and bioimaging applications of conjugated polymers by surfactants.

  2. Effect of surfactants on the aggregation and sedimentation of zinc oxide nanomaterial in natural water matrices.

    PubMed

    Li, Xuankun; Yoneda, Minoru; Shimada, Yoko; Matsui, Yasuto

    2017-03-01

    The wide application of surfactants and engineered nanomaterials (ENMs) in industrial and consumer products lead to the high possibility of their co-presence in natural water environment, making it important to study the effect of surfactants on the environmental behavior and fate of ENMs. In this work, we selected an anionic sodium dodecyl sulfate (SDS) and a nonionic nonylphenol ethoxylate (NPEO, Tergitol NP-9) to study their effects on the aggregation and sedimentation of a 20nm ZnO ENM in different water matrices. The adsorption of SDS and NP-9 by ZnO ENM were fitted with Langmuir model, and the maximum adsorption capacities were 43.73±4.62mg/g and 13.79±1.09 respectively. As the surfactant concentration increased from 0 to 0.030% (m:v), SDS reduced the zeta potential of ZnO ENM from 17.56±2.13 to -27.96±2.59mV, whereas NP-9 did not affect the zeta potential. After a 24-h batch reactor experiment, SDS and NP-9 reduced 93.02% and 80.26% of the aggregate size of ZnO ENM (50mgL(-1)) in maximum at surfactant concentrations≥0.015%. The ZnO ENM was not stable in natural aqueous matrices, mainly because of the relatively high ionic strength. However, surfactants were found to reduce the aggregation and sedimentation of ZnO ENM in six natural water matrices in different degrees. With the presence of 0.030% SDS in tap water, maximum reduction rates of aggregate size and sedimentation were recorded as 69.54% and 26.69%, respectively. The results of this study indicate that the presence of surfactants may alter the behaviors and fate of ENMs in natural water environment.

  3. Adsorption/aggregation of surfactants and their mixtures at solid-liquid interfaces.

    PubMed

    Somasundaran, P; Huang, L

    2000-12-11

    Adsorption of surfactants and polymers at solid-liquid interfaces is used widely to modify interfacial properties in a variety of industrial processes such as flotation, ceramic processing, flocculation/dispersion, personal care product formulation and enhanced oil recovery. The behavior of surfactants and polymers at interfaces is determined by a number of forces, including electrostatic attraction, covalent bonding, hydrogen bonding, hydrophobic bonding, and solvation and desolvation of various species. The extent and type of the forces involved varies depending on the adsorbate and the adsorbent, and also the composition and other characteristics of the solvent and dissolved components in it. The influence of such forces on the adsorption behavior is reviewed here from a thermodynamics point of view. The experimental results from microcalorimetric and spectroscopic studies of adsorbed layers of different surfactant and polymer systems at solid-liquid interfaces are also presented. Calorimetric data from the adsorption of an anionic surfactant, sodium octylbenzenesulfonate, and a non-ionic surfactant, dodecyloxyheptaethoxyethylalcohol, and their mixtures on alumina, yielded important thermodynamic information. It was found that the adsorption of anionic surfactants alone on alumina was initially highly exothermic due to the electrostatic interaction with the substrate. Further adsorption leading to a solloid (hemimicelle) formation is proposed to be mainly an entropy-driven process. The entropy effect was found to be more pronounced for the adsorption of anionic-non-ionic surfactant mixtures than for the anionic surfactant alone. Fluorescence studies using a pyrene probe on an adsorbed surfactant and polymer layers, along with electron spin resonance (ESR) spectroscopy, reveal the role of surface aggregation and the conformation of the adsorbed molecules in controlling the dispersion and wettability of the system.

  4. Giant Surfactants based on Precisely Functionalized POSS Nano-atoms: Tuning from Crystals to Frank-Kasper Phases and Quasicrystals

    NASA Astrophysics Data System (ADS)

    Cheng, Stephen Z. D.

    In creating new functional materials for advanced technologies, precisely control over functionality and their hierarchical ordered structures are vital for obtaining the desired properties. Giant polyhedra are a class of materials which are designed and constructed via deliberately placing precisely functionalized polyhedral oligomeric silsesquioxane (POSS) and fullerene (C60) molecular nano-particles (MNPs) (so-called ``nano-atoms'') at the vertices of a polyhedron. Giant surfactants are consisted of polymer tail-tethered ``nano-atoms'' which are deliberately and precisely functionalized POSS or C60 molecular nano-particles (MNPs). The ``nano-atom'' heads and polymer tails thus have drastic chemical differences to impart amphiphilicity. These giant surfactants capture the essential structural features of their small-molecule counterparts in many ways but possess much larger sizes, and therefore, they are recognized as size-amplified versions of small molecule surfactants. Two of the most illustrating examples are a series of novel giant tetrahedra and a series of giant giant surfactants as building blocks to construct into hierarchical ordered super-lattice structures ranging from crystals, Frank-Kasper phases and quasicrystals in the condensed bulk states, reveals evidently the interconnections between soft matters and hard matters in sharing their common structures and fundamental knowledge. This work was supported by National Science Foundation (DMR-1409972).

  5. Aggregation properties of supralong-chain surfactants with double or triple quaternary ammonium head groups.

    PubMed

    Matsuoka, Keisuke; Chiba, Nagisa; Yoshimura, Tomokazu

    2012-08-01

    Double or triple quaternary ammonium head groups were designed to improve the solubility of supralong alkyl chain surfactants. In the surfactant head group, quaternary ammonium groups are connected by an ethylene spacer. Micellar shapes of divalent surfactants [C(n)H(2n)(+1)N(+)(CH(3))(2)-(CH(2))(2)-N(+)(CH(3))(3) 2Br(-): C(n)-2Am (n=18, 20, and 22)] and trivalent surfactants [C(n)H(2n)(+1)N(+)(CH(3))(2)-(CH(2))(2)-N(+)(CH(3))(2)-(CH(2))(2)-N(+)(CH(3))(3) 3Br(-): C(n)-3Am (n=18, 20, and 22)] were studied in aqueous solutions by means of dynamic light scattering (DLS) and transmission electron microscopy (TEM). Changes in the surfactant concentration have a small influence on the apparent hydrodynamic radii (r(h)) of the molecular aggregates in both surfactant series. Average values of r(h) of aggregates are 60-90 nm for C(n)-2Am (n=18, 20, and 22) and 2-40 nm for C(n)-3Am (n=18, 20, and 22). TEM micrographs showed that aggregates of C(n)-2Am (n=18, 20, and 22) typically formed rod-like micelles. In contrast, trivalent surfactants of C(n)-3Am (n=18, 20, and 22) formed spherical (C(18)-3Am) or ellipsoidal micelles (C(20)-3Am and C(22)-3Am). Moreover, the degree of micellar counterion binding for these surfactants was determined by using a bromide ion-selective electrode, which indicated relatively high values (0.8-0.9) for C(n)-2Am (n=18, 20, and 22) and more common values (0.5-0.8) for C(n)-3Am (n=18, 20, and 22). The size of the aggregates is closely related to the degree of counterion binding. Copyright © 2012 Elsevier Inc. All rights reserved.

  6. Evolution of mixed surfactant aggregates in solutions and at solid/solution interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Rui

    Surfactant systems have been widely used in such as enhanced oil recovery, waste treatment and metallurgy, etc., in order to solve the problem of global energy crisis, to remove the pollutants and to generate novel energy resources. Almost all surfactant systems are invariably mixtures due to beneficial and economic considerations. The sizes and shapes of aggregates in solutions and at solid/solution interfaces become important, since the nanostructures of mixed aggregates determine solution and adsorption properties. A major hurdle in science is the lack of information on the type of complexes and aggregates formed by mixtures and the lack of techniques for deriving such information. Using techniques such as analytical ultracentrifuge, small angle neutron scattering, surface tension, fluorescence, cryo-TEM, light scattering and ultrafiltration, the nanostructures of aggregates of sugar based n-dodecyl-beta-D-maltoside (DM) and nonionic pentaethyleneglycol monododecyl ether or nonyl phenol ethoxylated decyl ether (NP-10) and their mixtures have been investigated to prove the hypothesis that the aggregation behavior is linked to packing of the surfactant governed by the molecular interactions as well as the molecular structures. The results from both sedimentation velocity and sedimentation equilibrium experiments suggest coexistence of two types of micelles in nonyl phenol ethoxylated decyl ether solutions and its mixtures with n-dodecyl-beta-D-maltoside while only one micellar species is present in n-dodecyl-beta-D-maltoside solutions, in good agreement with those from small angle neutron scattering, cryo-TEM, light scattering and ultrafiltration. Type I micelles were primary micelles at cmc while type II micelles were elongated micelles. On the other hand, the nanostructures of mixed surface aggregates have been quantitatively predicted for the first time using a modified packing index. As a continuation of the Somasundaran-Fuersteneau adsorption model, a

  7. An NMR study of macromolecular aggregation in a model polymer-surfactant solution

    NASA Astrophysics Data System (ADS)

    Barhoum, Suliman; Yethiraj, Anand

    2010-01-01

    A model complex-forming nonionic polymer-anionic surfactant system in aqueous solution has been studied at different surfactant concentrations. Using pulsed-field-gradient diffusion NMR spectroscopy, we obtain the self-diffusion coefficients of poly(ethylene glycol) (PEO) and sodium dodecyl sulfate (SDS) simultaneously and as a function of SDS concentration. In addition, we obtain NMR relaxation rates and chemical shifts as a function of SDS concentration. Within the context of a simple model, our experimental results yield the onset of aggregation of SDS on PEO chains (CAC=3.5 mM), a crossover concentration (C2=60 mM) which signals a sharp change in relaxation behavior, as well as an increase in free surfactant concentration and a critical concentration (Cm=145 mM) which signals a distinct change in diffusion behavior and a crossover to a solution containing free micelles. Cm also marks the concentration above which obstruction effects are definitely important. In addition, we obtain the concentration of SDS in monomeric form and in the form of free micelles, as well as the average number of SDS molecules in a PEO-SDS aggregate (NAggr). Taken together, our results suggests continuous changes in the aggregation phenomenon over much of the concentration but with three distinct concentrations that signal changes in the nature of the aggregates.

  8. Inhibitory effect of copper nanoparticles on rosin modified surfactant induced aggregation of lysozyme.

    PubMed

    Ishtikhar, Mohd; Usmani, Salman Sadullah; Gull, Nuzhat; Badr, Gamal; Mahmoud, Mohamed H; Khan, Rizwan Hasan

    2015-01-01

    Protein aggregation is associated with many serious diseases including Parkinson's and Alzheimer's. Protein aggregation is a primary problem related with the health of industrial workers who work with the surfactants, metal ions, and cosolvents. We have synthesized rosin-based surfactants, i.e., quaternary amines of rosin diethylaminoethyl esters (QRMAE), which is an ester of rosin acid with polyethylene glycol monomethyl ether. Here, we report the thermal aggregation of lysozyme induced by QRMAE at 65 °C and pH 7.4 for a given time period in which amorphous aggregates are formed and confirm that copper-nanoparticles have the ability to inhibit QRMAE-induced aggregation compared with zinc and silver-nanoparticles. Aggregation experiments was evaluated using several spectroscopic methods and dye binding assay, such as turbidity, Rayleigh light scattering, 1-anilino-8-naphthalene sulfonate (ANS), Thioflavin T (Th T), congo red (CR) and circular dichroism (CD), that was further supported by scanning electron microscopy (SEM) and SEM with EDX. The therapeutic use of nanoparticles and the fact that rosin possesses excellent film-forming properties, and that its derivatives have pharmaceuticals application such as micro encapsulation, coating and film forming, it's matrix materials are used for sustained and controlled release tablets, renders importance and application to the present study.

  9. Micropolarity and water penetration in micellar aggregates of linear and branched hydrocarbon surfactants

    SciTech Connect

    Varadaraj, R.; Bock, J.; Valint, P. Jr.; Brons, N. )

    1990-08-01

    The micropolarity of aqueous micellar solutions of ethoxylates, sodium ethoxy sulfates, and sulfates derived from linear and branched hydrocarbon alcohols was investigated by using a solvatochromic pyridinio-N-phenoxide betaine, ET-30, polarity probe. Branching of the hydrophobe resulted in a more porous micellar aggregate. Thermosolvatochromism of ET-30 allowed an investigation of the effect of temperature on micropolarity. Increase in temperature was observed to expel water from the hydrophobic regions of the aggregate and decrease the effective micropolarity in linear and branched surfactants.

  10. Interfacial aggregation of a nonionic surfactant: Effect on the stability of silica suspensions

    SciTech Connect

    Giordano-Palmino, F.; Denoyel, R.; Rouquerol, J. . Centre de thermodynamique et Microcalorimetrie)

    1994-06-01

    Nonionic surfactants are in widespread use in technological applications such as flotation, detergency, suspension stabilization (paints, ceramic preparation, pharmaceuticals, cosmetics), and enhanced oil recovery. The adsorption of the nonionic surfactant TX 100 in two silica suspensions (Ludox HS40 and Syton W30) has been studied with the aim of relating the structure of the adsorbed layer to the stability of the suspension. First, a thermodynamic study based on the determination of adsorption isotherms and displacement enthalpies as a function of pH and solid/liquid ratio was carried out and lead to the conclusion that such a surfactant forms micelle-like aggregates on the silica surface. Then, a stability study based on visual observation, turbidimetry, and particle size determination (by photon correlation spectroscopy) was performed in order to determine the TX 100 concentration range in which flocculation occurs. Considering that the surface is covered with micelle-like aggregates in the flocculation range and that the [zeta]-potential (determined by microelectrophoresis) has varied only slightly at the onset of flocculation, it is concluded that the flocculation mechanism is a bridging of particles by surface micelles. This bridging of particles by aggregates similar in size and shape could be an explanation of the presence, in such systems, of optimum flocculation at half surface coverage.

  11. Thermodynamics of Micellization of Surfactants of Low Aggregation Number: The Aggregation of Propranolol Hydrochloride.

    PubMed

    Mosquera; Ruso; Attwood; Jones; Prieto; Sarmiento

    1999-02-01

    The self-association of propranolol hydrochloride in aqueous solution has been studied as a function of temperature. The critical concentration (C*) and the degree of ionization (alpha) were determined by conductivity measurements at temperatures over the range 298.15 to 313.15 K. The enthalpy change on aggregation in water was measured by microcalorimetry. To calculate changes in the thermodynamic properties of aggregation the mass action model for high and low aggregation numbers was applied, the latter model giving better agreement between experimental and theoretical enthalpy changes. Copyright 1999 Academic Press.

  12. How to change the aggregation in the DNA/surfactant/cationic conjugated polyelectrolyte system through the order of component addition: anionic versus neutral surfactants.

    PubMed

    Monteserín, María; Burrows, Hugh D; Mallavia, Ricardo; Di Paolo, Roberto E; Maçanita, Antonio L; Tapia, María J

    2010-07-20

    The competitive interaction has been studied between double-stranded DNA (dsDNA), the cationic conjugated polyelectrolyte (CPE) poly[9,9-bis(6-N,N,N-trimethylamonium)hexyl)-fluorene-phenylene)] bromide (HTMA-PFP) and anionic or neutral surfactants (sodium dodecyl sulfonate, SDSu, and n-dodecyl pentaoxyethylene glycol ether, C(12)E(5)) in 4% (v/v) dimethyl sulfoxide (DMSO)-water using UV/visible absorption and fluorescence spectroscopy. Dramatic changes are observed in the spectroscopic behavior of the system depending on the order of addition of the reagents, the surfactant charge, and concentration range. If the neutral C(12)E(5) is added to the HTMA-PFP/dsDNA complex, no significant spectroscopic changes are observed. However, if SDSu is added to the same complex, a dramatic increase of the absorbance and emission intensity is observed for surfactant concentrations above the critical micelle concentration (cmc). In contrast, if dsDNA is added to HTMA-PFP/surfactant systems (with surfactant concentrations above their cmc) no significant changes are observed with SDSu, while a dramatic quenching of polymer emission is observed with C(12)E(5), which can be explained quantitatively in terms of HTMA-PFP/surfactant/DNA complexation and the subsequent polymer aggregation upon charge neutralization. The results are compared with those for the binary systems (HTMA-PFP/DNA and HTMA-PFP/surfactants) and indicate the importance of electrostatic interactions between HTMA-PFP and oppositely charged species in the aggregation processes.

  13. Use of isothermal titration calorimetry to study surfactant aggregation in colloidal systems.

    PubMed

    Loh, Watson; Brinatti, César; Tam, Kam Chiu

    2016-05-01

    Isothermal titration calorimetry (ITC) is a general technique that allows for precise and highly sensitive measurements. These measurements may provide a complete and accurate thermodynamic description of association processes in complex systems such as colloidal mixtures. This review will address uses of ITC for studies of surfactant aggregation to form micelles, with emphasis on the thermodynamic studies of homologous surfactant series. We will also review studies on surfactant association with polymers of different molecular characteristics and with colloidal particles. ITC studies on the association of different homologous series of surfactants provide quantitative information on independent contribution from their apolar hydrocarbon chains and polar headgroups to the different thermodynamic functions associated with micellization (Gibbs energy, enthalpy and entropy). Studies on surfactant association to polymers by ITC provide a comprehensive description of the association process, including examples in which particular features revealed by ITC were elucidated by using ancillary techniques such as light or X-ray scattering measurements. Examples of uses of ITC to follow surfactant association to biomolecules such as proteins or DNA, or nanoparticles are also highlighted. Finally, recent theoretical models that were proposed to analyze ITC data in terms of binding/association processes are discussed. This review stresses the importance of using direct calorimetric measurements to obtain and report accurate thermodynamic data, even in complex systems. These data, whenever possible, should be confirmed and associated with other ancillary techniques that allow elucidation of the nature of the transformations detected by calorimetric results, providing a complete description of the process under scrutiny. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Colossal aggregations of giant alien freshwater fish as a potential biogeochemical hotspot.

    PubMed

    Boulêtreau, Stéphanie; Cucherousset, Julien; Villéger, Sébastien; Masson, Rémi; Santoul, Frédéric

    2011-01-01

    The ubiquity and fascinating nature of animal aggregations are widely recognised. We report here consistent and previously undocumented occurences of aggregations of a giant alien freshwater fish, the Wels catfish (Silurus glanis). Aggregative groups were on average composed of 25 (± 10 SD, ranging from 15 to 44) adults with estimated average total biomass of 651 kg (386 - 1132) and biomass density of 23 kg m(-2) (14 - 40). Aggregations always occurred within the same location. No foraging, reproductive or anti-predator behaviour were observed during the aggregations. A mass-balance model estimated that these colossal aggregations of an alien species can locally release, through excretion only, up to 70 mg P m(-2) h(-1) and 400 mg N m(-2) h(-1), potentially representing the highest biogeochemical hotspots reported in freshwater ecosystems and another unexpected ecological effect of alien species.

  15. Colossal Aggregations of Giant Alien Freshwater Fish as a Potential Biogeochemical Hotspot

    PubMed Central

    Boulêtreau, Stéphanie; Cucherousset, Julien; Villéger, Sébastien; Masson, Rémi; Santoul, Frédéric

    2011-01-01

    The ubiquity and fascinating nature of animal aggregations are widely recognised. We report here consistent and previously undocumented occurences of aggregations of a giant alien freshwater fish, the Wels catfish (Silurus glanis). Aggregative groups were on average composed of 25 (±10 SD, ranging from 15 to 44) adults with estimated average total biomass of 651 kg (386 – 1132) and biomass density of 23 kg m−2 (14 – 40). Aggregations always occurred within the same location. No foraging, reproductive or anti-predator behaviour were observed during the aggregations. A mass-balance model estimated that these colossal aggregations of an alien species can locally release, through excretion only, up to 70 mg P m−2 h−1 and 400 mg N m−2 h−1, potentially representing the highest biogeochemical hotspots reported in freshwater ecosystems and another unexpected ecological effect of alien species. PMID:21998687

  16. Unusual subterranean aggregations of the California Giant Salamander, Dicamptodon ensatus

    USGS Publications Warehouse

    Fellers, Gary M.; Wood, Leslie L.; Carlisle, Sarah; Pratt, David

    2010-01-01

    Larval Dicamptodon are one of the most abundant vertebrates in headwater streams in the Pacific Northwest. Their numbers and biomass can exceed those of all other amphibians, and of salmonid fishes. By contrast, metamorphosed Dicamptodon are only found infrequently, usually during formal surveys using pitfall traps, cover boards, or time constrained surveys However, we found two aggregations (23 and 27 individuals) of metamorphosed Dicamptodon ensatus during a culvert removal project at Point Reyes National Seashore, California. Furthermore, we found an additional 23 terrestrial D. ensatus in terrestrial habitat adjacent to the culverts. We did not expect these aggregations because metamorphosed individuals are so rarely encountered, and aggregations are likely to increase competition and predation in a species known to feed regularly on vertebrate prey. Deteriorating culverts might provide an unusually high-quality habitat that leads to aggregations such as we describe. Our observations may provide insight into the natural haunts of D. ensatus—underground burrows or caverns—and if so, then aggregations may be normal, but rarely seen.

  17. Stabilization of recombinant human growth hormone against emulsification-induced aggregation by Pluronic surfactants during microencapsulation.

    PubMed

    Wei, Gang; Lu, Li Fang; Lu, Wei Yue

    2007-06-29

    Protein aggregation upon exposing to the water/organic solvent interface is one of the most significant obstacles in developing poly(lactic-co-glycolic acid) (PLGA) microspheres with double emulsion process. The aim of present study is to devise a formulation strategy to prevent recombinant human growth hormone (rhGH) from aggregation during microencapsulation. The excipients used for stabilizing rhGH were selected from sugars, nonionic surfactants, polyol, and protein. Among the candidates, surfactants exhibited potentialities in protecting rhGH against emulsification-induced aggregation. It was also found that Pluronic F127 showed an outstanding as well as concentration-dependent stabilizing effect on rhGH, which was different to Pluronic F68 and Tween 20. After the rhGH solution comprising F127 and sucrose was emulsified with methylene chloride, the recovery of monomeric protein achieved 99.0%, principally attributed to the presence of F127. This solution was subsequently encapsulated as inner aqueous phase in the PLGA microspheres by a conventional double emulsion process, with the encapsulation efficiency higher than 98%. Improvement in the release of rhGH was observed for the microspheres co-encapsulating Pluronic F127 regardless in the presence or absence of sucrose, compared to the microspheres containing rhGH alone. The result further implied that co-encapsulation of Pluronic F127 in the microspheres played an important role in the stabilization of rhGH.

  18. Small surfactant-like peptides can drive soluble proteins into active aggregates

    PubMed Central

    2012-01-01

    Background Inactive protein inclusion bodies occur commonly in Escherichia coli (E. coli) cells expressing heterologous proteins. Previously several independent groups have found that active protein aggregates or pseudo inclusion bodies can be induced by a fusion partner such as a cellulose binding domain from Clostridium cellulovorans (CBDclos) when expressed in E. coli. More recently we further showed that a short amphipathic helical octadecapeptide 18A (EWLKAFYEKVLEKLKELF) and a short beta structure peptide ELK16 (LELELKLKLELELKLK) have a similar property. Results In this work, we explored a third type of peptides, surfactant-like peptides, for performing such a "pulling-down" function. One or more of three such peptides (L6KD, L6K2, DKL6) were fused to the carboxyl termini of model proteins including Aspergillus fumigatus amadoriase II (AMA, all three peptides were used), Bacillus subtilis lipase A (LipA, only L6KD was used, hereinafter the same), Bacillus pumilus xylosidase (XynB), and green fluorescent protein (GFP), and expressed in E. coli. All fusions were found to predominantly accumulate in the insoluble fractions, with specific activities ranging from 25% to 92% of the native counterparts. Transmission electron microscopic (TEM) and confocal fluorescence microscopic analyses confirmed the formation of protein aggregates in the cell. Furthermore, binding assays with amyloid-specific dyes (thioflavin T and Cong red) to the AMA-L6KD aggregate and the TEM analysis of the aggregate following digestion with protease K suggested that the AMA-L6KD aggregate may contain structures reminiscent of amyloids, including a fibril-like structure core. Conclusions This study shows that the surfactant-like peptides L6KD and it derivatives can act as a pull-down handler for converting soluble proteins into active aggregates, much like 18A and ELK16. These peptide-mediated protein aggregations might have important implications for protein aggregation in vivo, and can be

  19. Rosin Surfactant QRMAE Can Be Utilized as an Amorphous Aggregate Inducer: A Case Study of Mammalian Serum Albumin

    PubMed Central

    Ishtikhar, Mohd; Chandel, Tajjali Ilm; Ahmad, Aamir; Ali, Mohd Sajid; Al-lohadan, Hamad A.; Atta, Ayman M.; Khan, Rizwan Hasan

    2015-01-01

    Quaternary amine of diethylaminoethyl rosin ester (QRMAE), chemically synthesized biocompatible rosin based cationic surfactant, has various biological applications including its use as a food product additive. In this study, we examined the amorphous aggregation behavior of mammalian serum albumins at pH 7.5, i.e., two units above their isoelectric points (pI ~5.5), and the roles played by positive charge and hydrophobicity of exogenously added rosin surfactant QRMAE. The study was carried out on five mammalian serum albumins, using various spectroscopic methods, dye binding assay, circular dichroism and electron microscopy. The thermodynamics of the binding of mammalian serum albumins to cationic rosin modified surfactant were established using isothermal titration calorimetry (ITC). It was observed that a suitable molar ratio of protein to QRMAE surfactant enthusiastically induces amorphous aggregate formation at a pH above two units of pI. Rosin surfactant QRMAE-albumins interactions revealed a unique interplay between the initial electrostatic and the subsequent hydrophobic interactions that play an important role towards the formation of hydrophobic interactions-driven amorphous aggregate. Amorphous aggregation of proteins is associated with varying diseases, from the formation of protein wine haze to the expansion of the eye lenses in cataract, during the expression and purification of recombinant proteins. This study can be used for the design of novel biomolecules or drugs with the ability to neutralize factor(s) responsible for the aggregate formation, in addition to various other industrial applications. PMID:26418451

  20. Rosin Surfactant QRMAE Can Be Utilized as an Amorphous Aggregate Inducer: A Case Study of Mammalian Serum Albumin.

    PubMed

    Ishtikhar, Mohd; Chandel, Tajjali Ilm; Ahmad, Aamir; Ali, Mohd Sajid; Al-Lohadan, Hamad A; Atta, Ayman M; Khan, Rizwan Hasan

    2015-01-01

    Quaternary amine of diethylaminoethyl rosin ester (QRMAE), chemically synthesized biocompatible rosin based cationic surfactant, has various biological applications including its use as a food product additive. In this study, we examined the amorphous aggregation behavior of mammalian serum albumins at pH 7.5, i.e., two units above their isoelectric points (pI ~5.5), and the roles played by positive charge and hydrophobicity of exogenously added rosin surfactant QRMAE. The study was carried out on five mammalian serum albumins, using various spectroscopic methods, dye binding assay, circular dichroism and electron microscopy. The thermodynamics of the binding of mammalian serum albumins to cationic rosin modified surfactant were established using isothermal titration calorimetry (ITC). It was observed that a suitable molar ratio of protein to QRMAE surfactant enthusiastically induces amorphous aggregate formation at a pH above two units of pI. Rosin surfactant QRMAE-albumins interactions revealed a unique interplay between the initial electrostatic and the subsequent hydrophobic interactions that play an important role towards the formation of hydrophobic interactions-driven amorphous aggregate. Amorphous aggregation of proteins is associated with varying diseases, from the formation of protein wine haze to the expansion of the eye lenses in cataract, during the expression and purification of recombinant proteins. This study can be used for the design of novel biomolecules or drugs with the ability to neutralize factor(s) responsible for the aggregate formation, in addition to various other industrial applications.

  1. Synthesis and aggregation properties of dissymmetric phytanyl-gemini surfactants for use as improved DNA transfection vectors.

    PubMed

    Wang, Haitang; Wettig, Shawn D

    2011-01-14

    Improvements in transfection efficiency are required in order to make the goal of cellular gene delivery by non-viral vectors realizable. Novel derivatives of gemini surfactants having dissymmetric tail groups have been designed specifically as a means to improve DNA transfection; the micelle and interfacial properties are reported herein. The effect of these substitutions on the aggregation properties of the gemini surfactants is discussed in the context of results for the m-3-m gemini series, previously reported in the literature. Phytanyl substitution results in lower cmc and higher micelle ionization. In addition, the phytanyl substituted gemini surfactants form vesicles at room temperature. Preliminary in vitro transfection assays showed the phytanyl substituted gemini surfactants to be more efficient transfection vectors as compared to symmetric gemini surfactants.

  2. Solvation dynamics of DCM in a polypeptide-surfactant aggregate: gelatin-sodium dodecyl sulfate.

    PubMed

    Halder, Arnab; Sen, Pratik; Burman, Anupam Das; Bhattacharyya, Kankan

    2004-02-03

    Solvation dynamics of 4-(dicyanomethylidene)-2-[p-(dimethylamino)styryl]-6-methyl-4H-pyran (DCM) is studied in a polypeptide-surfactant aggregate consisting of gelatin and sodium dodecyl sulfate (SDS) in potassium dihydrogen phosphate (KP) buffer. The average solvation time (tauS) in gelatin-SDS aggregate at 45 degrees C is found to be 1780 ps, which is about 13 times slower than that in 15 mM SDS in KP buffer at the same temperature. The fluorescence anisotropy decay in gelatin-SDS aggregate is also different from that in SDS micelles in KP buffer. DCM displays negligible emission in the presence of gelatin in aqueous solution. Thus the solvation dynamics in the presence of gelatin and SDS is exclusively due to the probe (DCM) molecules at the gelatin-micelle interface. The slow solvation dynamics is ascribed to the restrictions imposed on the water molecules trapped between the polypeptide chain and micellar aggregates. The critical association concentration (cac) of SDS for gelatin is determined to be 0.5 +/- 0.1 mM.

  3. Geometry induced sequence of nanoscale Frank–Kasper and quasicrystal mesophases in giant surfactants

    SciTech Connect

    Yue, Kan; Huang, Mingjun; Marson, Ryan L.; He, Jinlin; Huang, Jiahao; Zhou, Zhe; Wang, Jing; Liu, Chang; Yan, Xuesheng; Wu, Kan; Guo, Zaihong; Liu, Hao; Zhang, Wei; Ni, Peihong; Wesdemiotis, Chrys; Zhang, Wen-Bin; Glotzer, Sharon C.; Cheng, Stephen Z. D.

    2016-11-28

    Frank–Kasper (F-K) and quasicrystal phases were originally identified in metal alloys and only sporadically reported in soft materials. These unconventional sphere-packing schemes open up possibilities to design materials with different properties. The challenge in soft materials is how to correlate complex phases built from spheres with the tunable parameters of chemical composition and molecular architecture. Here, we report a complete sequence of various highly ordered mesophases by the self-assembly of specifically designed and synthesized giant surfactants, which are conjugates of hydrophilic polyhedral oligomeric silsesquioxane cages tethered with hydrophobic polystyrene tails. We show that the occurrence of these mesophases results from nanophase separation between the heads and tails and thus is critically dependent on molecular geometry. Variations in molecular geometry achieved by changing the number of tails from one to four not only shift compositional phase boundaries but also stabilize F-K and quasicrystal phases in regions where simple phases of spheroidal micelles are typically observed. These complex self-assembled nanostructures have been identified by combining X-ray scattering techniques and real-space electron microscopy images. Brownian dynamics simulations based on a simplified molecular model confirm the architecture-induced sequence of phases. Our results demonstrate the critical role of molecular architecture in dictating the formation of supramolecular crystals with “soft” spheroidal motifs and provide guidelines to the design of unconventional self-assembled nanostructures.

  4. Determination of anionic surface active agents using silica coated magnetite nanoparticles modified with cationic surfactant aggregates.

    PubMed

    Pena-Pereira, Francisco; Duarte, Regina M B O; Trindade, Tito; Duarte, Armando C

    2013-07-19

    The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica-magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10-C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10-C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8-1.9μgL(-1) for C10-C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N=6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Electrostatic attraction between DNA and a cationic surfactant aggregate. The screening effect of salt.

    PubMed

    Leal, Cecília; Moniri, Elham; Pegado, Luis; Wennerström, Håkan

    2007-05-31

    Anionic DNA and cationic surfactants form charge neutral complexes that contain finite amounts of water. There is a strong electrostatic attraction between the oppositely charged species, and the finite swelling is caused by an opposing repulsive force. Adding NaCl to the complexes provides an opportunity to modulate the strength of the electrostatic attraction. The thermodynamics of the isothermal swelling process has been experimentally characterized using a calorimetric technique monitoring both the free energy and the enthalpy. The experimental results are quantitatively analyzed in calculations using the Poisson-Boltzmann equation to describe the electrostatic effects. The main findings are as follows: (i) Addition of salt results in an increased swelling at a given water activity. (ii) The effect of the salt can be quantitatively modeled on the basis of the Poisson-Boltzmann equation with a dielectric description of the water. (iii) There exists a short-range repulsive force between DNA double helices and surfactant aggregates. (iv) Solid NaCl dissolves in the complex at water activities in the range 0.5-0.6 rather than at 0.74 as in a saturated aqueous solution. (v) The heat of solution of NaCl in the complexes is around +1.6 +/- 0.5 kJ/mol, surprisingly close to the values found for the dissolution into bulk aqueous solutions.

  6. Rich aggregate morphologies induced by organic salts in aqueous solutions of a cationic gemini surfactant with a short spacer.

    PubMed

    Jiang, Rong; Zhao, Jianxi; Hu, Xiaoming; Pei, Xiaomei; Zhang, Lixiang

    2009-12-01

    Various aggregates, such as spherical and elongated micelles, tubular and rodlike aggregates, as well as vesicles, are induced by adding sodium 2-naphthalenesulfonate (SNphs) or sodium benzenesulfonate (SBzs) into the aqueous solution of a gemini surfactant C12C2C12(Me) (1,2-ethanediyl-bis-(dodecyldimethylammonium bromide)). The aggregate morphology strongly depends on the added amount of the organic salts. Among the various aggregates, the elongated micelle and the tubular aggregate have larger solubilizing capacities than those with the other morphologies. However, SNphs and SBzs cannot induce similar aggregate transitions for the systems of C12CsC12(Me) (s=6, 8, 12). The possible mechanism of these phenomena is proposed based on the results of UV spectra and 1H NMR measurements and the molecular packing geometry rule.

  7. Effective short-range Coulomb correction to model the aggregation behavior of ionic surfactants.

    PubMed

    Burgos-Mármol, J Javier; Solans, Conxita; Patti, Alessandro

    2016-06-21

    We present a short-range correction to the Coulomb potential to investigate the aggregation of amphiphilic molecules in aqueous solutions. The proposed modification allows to quantitatively reproduce the distribution of counterions above the critical micelle concentration (CMC) or, equivalently, the degree of ionization, α, of the micellar clusters. In particular, our theoretical framework has been applied to unveil the behavior of the cationic surfactant C24H49N2O2 (+) CH3SO4 (-), which offers a wide range of applications in the thriving and growing personal care market. A reliable and unambiguous estimation of α is essential to correctly understand many crucial features of the micellar solutions, such as their viscoelastic behavior and transport properties, in order to provide sound formulations for the above mentioned personal care solutions. We have validated our theory by performing extensive lattice Monte Carlo simulations, which show an excellent agreement with experimental observations. More specifically, our coarse-grained model is able to reproduce and predict the complex morphology of the micelles observed at equilibrium. Additionally, our simulation results disclose the existence of a transition from a monodisperse to a bidisperse size distribution of aggregates, unveiling the intriguing existence of a second CMC.

  8. Effective short-range Coulomb correction to model the aggregation behavior of ionic surfactants

    NASA Astrophysics Data System (ADS)

    Burgos-Mármol, J. Javier; Solans, Conxita; Patti, Alessandro

    2016-06-01

    We present a short-range correction to the Coulomb potential to investigate the aggregation of amphiphilic molecules in aqueous solutions. The proposed modification allows to quantitatively reproduce the distribution of counterions above the critical micelle concentration (CMC) or, equivalently, the degree of ionization, α, of the micellar clusters. In particular, our theoretical framework has been applied to unveil the behavior of the cationic surfactant C24H49N2O2+ CH3SO4-, which offers a wide range of applications in the thriving and growing personal care market. A reliable and unambiguous estimation of α is essential to correctly understand many crucial features of the micellar solutions, such as their viscoelastic behavior and transport properties, in order to provide sound formulations for the above mentioned personal care solutions. We have validated our theory by performing extensive lattice Monte Carlo simulations, which show an excellent agreement with experimental observations. More specifically, our coarse-grained model is able to reproduce and predict the complex morphology of the micelles observed at equilibrium. Additionally, our simulation results disclose the existence of a transition from a monodisperse to a bidisperse size distribution of aggregates, unveiling the intriguing existence of a second CMC.

  9. Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging

    NASA Astrophysics Data System (ADS)

    Gaufrès, E.; Tang, N. Y.-Wa; Lapointe, F.; Cabana, J.; Nadon, M.-A.; Cottenye, N.; Raymond, F.; Szkopek, T.; Martel, R.

    2014-01-01

    Raman spectroscopy uses visible light to acquire vibrational fingerprints of molecules, thus making it a powerful tool for chemical analysis in a wide range of media. However, its potential for optical imaging at high resolution is severely limited by the fact that the Raman effect is weak. Here, we report the discovery of a giant Raman scattering effect from encapsulated and aggregated dye molecules inside single-walled carbon nanotubes. Measurements performed on rod-like dyes such as α-sexithiophene and β-carotene, assembled inside single-walled carbon nanotubes as highly polarizable J-aggregates, indicate a resonant Raman cross-section of (3 +/- 2) × 10-21 cm2 sr-1, which is well above the cross-section required for detecting individual aggregates at the highest optical resolution. Free from fluorescence background and photobleaching, this giant Raman effect allows the realization of a library of functionalized nanoprobe labels for Raman imaging with robust detection using multispectral analysis.

  10. Effect of head group polarity and spacer chain length on the aggregation properties of gemini surfactants in an aquatic environment.

    PubMed

    Borse, Mahendra; Sharma, Vikas; Aswal, V K; Goyal, P S; Devi, Surekha

    2005-04-01

    The aggregation behavior of cationic gemini surfactants with respect to variation in head group polarity and spacer length is studied through conductance, surface tension, viscosity, and small-angle neutron-scattering (SANS) measurements. The critical micellar concentration (cmc), average degree of micelle ionization (beta(ave)), minimum area per molecule of surfactant at the air-water interface (A(min)), surface excess concentration (gamma(max)), and Gibb's free energy of micellization (delta G(mic)) of the surfactants were determined from conductance and surface tension data. The aggregation numbers (N), dimensions of micelles (b/a), effective fractional charge per monomer (alpha), and hydration of micelles (h(E)) were determined from SANS and viscosity data, respectively. The increasing head group polarity of gemini surfactant with spacer chain length of 4 methylene units promotes micellar growth, leading to a decrease in cmc, beta(ave), and delta G(mic) and an increase in N and b/a. This is well supported by the observed increase in hydration (h(E)) of micelles with increase in aggregation number (N) and dimension (b/a) of micelle.

  11. Synthesis of polymer nanostructures via the use of surfactant surface aggregates as templates

    NASA Astrophysics Data System (ADS)

    Marquez, Maricel

    The subject of this work is the synthesis of polymer nanostructures via the use of surfactant surface aggregates as templates, also termed Template Assisted Admicellar Polymerization (TAAP). The first chapter reviews some of the most current nanopatterning techniques (including both top-down and bottom-up approaches), with particular emphasis on the fabrication of organic and inorganic patterned nanostructures via particle lithography. In chapter 2, highly ordered hexagonal arrays of latex spheres were prepared on highly ordered pyrolytic graphite (HOPG) from a variation of the Langmuir Blodgett technique, using an anionic surfactant (SDS), and a low molecular weight (ca. 10000) polyacrylamide as spreading agents. When a nonionic polyethoxylated (EO = 9) surfactant was used as the spreading agent, no ordered arrays were observed. Based on the correlation found between the surface tension in the presence of the latex particles and the critical concentration at which hexagonal arrangements of latex spheres occurs; a model was proposed to explain the role of the spreading agent in forming stable monolayers at the air/liquid interface, which in turn are necessary for the formation of well-ordered monolayers on a solid substrate from the LB technique. According to this model, solid-like regions of small numbers of latex spheres form at the liquid-air interface, which are then transferred to the substrate. These ordered regions then act as nuclei for the formation of 2D arrays of latex spheres on the surface upon water evaporation. The role of other factors such as relative humidity, substrate and solvent choice, and pulling vs. compression speed were also found to affect the quality of the monolayers formed. Finally, a simple, easy to automate, yet effective surface tension method was proposed to predict the optimal conditions for the formation of ordered monolayers using a variation of the LB deposition method from any monodisperse set of spheres. In chapter 3, a novel

  12. Protein aggregation with poly(vinyl) alcohol surfactant reduces double emulsion-encapsulated mammalian cell-free expression

    PubMed Central

    Ho, Kenneth K. Y.; Lee, Jin Woo; Durand, Grégory; Majumder, Sagardip

    2017-01-01

    Development of artificial cell models requires encapsulation of biomolecules within membrane-bound compartments. There have been limited studies of using mammalian cell-free expression (CFE) system as the ‘cytosol’ of artificial cells. We exploit glass capillary droplet microfluidics for the encapsulation of mammalian CFE within double emulsion templated vesicles. The complexity of the physicochemical properties of HeLa cell-free lysate poses a challenge compared with encapsulating simple buffer solutions. In particular, we discovered the formation of aggregates in double emulsion templated vesicles encapsulating mammalian HeLa CFE, but not with bacterial CFE. The aggregates did not arise from insolubility of the proteins made from CFE nor due to the interaction of mammalian CFE with the organic solvents in the middle phase of the double emulsions. We found that aggregation is dependent on the concentration of poly(vinyl) alcohol (PVA) surfactant, a critical double emulsion-stabilizing surfactant, and the lysate concentration in mammalian CFE. Despite vesicle instability and reduced protein expression, we demonstrate protein expression by encapsulating mammalian CFE system. Using mass spectrometry and Western blot, we identified and verified that actin is one of the proteins inside the mammalian CFE that aggregated with PVA surfactant. Our work establishes a baseline description of mammalian CFE system encapsulated in double emulsion templated vesicles as a platform for building artificial cells. PMID:28358875

  13. Protein aggregation with poly(vinyl) alcohol surfactant reduces double emulsion-encapsulated mammalian cell-free expression.

    PubMed

    Ho, Kenneth K Y; Lee, Jin Woo; Durand, Grégory; Majumder, Sagardip; Liu, Allen P

    2017-01-01

    Development of artificial cell models requires encapsulation of biomolecules within membrane-bound compartments. There have been limited studies of using mammalian cell-free expression (CFE) system as the 'cytosol' of artificial cells. We exploit glass capillary droplet microfluidics for the encapsulation of mammalian CFE within double emulsion templated vesicles. The complexity of the physicochemical properties of HeLa cell-free lysate poses a challenge compared with encapsulating simple buffer solutions. In particular, we discovered the formation of aggregates in double emulsion templated vesicles encapsulating mammalian HeLa CFE, but not with bacterial CFE. The aggregates did not arise from insolubility of the proteins made from CFE nor due to the interaction of mammalian CFE with the organic solvents in the middle phase of the double emulsions. We found that aggregation is dependent on the concentration of poly(vinyl) alcohol (PVA) surfactant, a critical double emulsion-stabilizing surfactant, and the lysate concentration in mammalian CFE. Despite vesicle instability and reduced protein expression, we demonstrate protein expression by encapsulating mammalian CFE system. Using mass spectrometry and Western blot, we identified and verified that actin is one of the proteins inside the mammalian CFE that aggregated with PVA surfactant. Our work establishes a baseline description of mammalian CFE system encapsulated in double emulsion templated vesicles as a platform for building artificial cells.

  14. Thermodynamics of aggregate formation between a non-ionic polymer and ionic surfactants: An isothermal titration calorimetric study.

    PubMed

    Patel, Salin Gupta; Bummer, Paul M

    2017-01-10

    This report examines the energetics of aggregate formation between hydroxypropyl methylcellulose (HPMC) and model ionic surfactants including sodium dodecyl sulfate (SDS) at pharmaceutically relevant concentrations using the isothermal titration calorimetry (ITC) technique and a novel treatment of calorimetric data that accounts for the various species formed. The influence of molecular weight of HPMC, temperature and ionic strength of solution on the aggregate formation process was explored. The interaction between SDS and HPMC was determined to be an endothermic process and initiated at a critical aggregation concentration (CAC). The SDS-HPMC interactions were observed to be cooperative in nature and dependent on temperature and ionic strength of the solution. Molecular weight of HPMC significantly shifted the interaction parameters between HPMC and SDS such that at the highest molecular weight (HPMC K-100M;>240kDa), although the general shape of the titration curve (enthalpogram) was observed to remain similar, the critical concentration parameters (CAC, polymer saturation concentration (Csat) and critical micelle concentration (CMC)) were significantly altered and shifted to lower concentrations of SDS. Ionic strength was also observed to influence the critical concentration parameters for the SDS-HPMC aggregation and decreased to lower SDS concentrations with increasing ionic strength for both anionic and cationic surfactant-HPMC systems. From these data, other thermodynamic parameters of aggregation such as ΔHagg(°), ΔGagg(°), Hagg(°), ΔSagg(°), and ΔCp were calculated and utilized to postulate the hydrophobic nature of SDS-HPMC aggregate formation. The type of ionic surfactant head group (anionic vs. cationic i.e., dodecyltrimethylammonium bromide (DTAB)) was found to influence the strength of HPMC-surfactant interactions wherein a distinct CAC signifying the strength of HPMC-DTAB interactions was not observed. The interpretation of the

  15. Accurately tuning the charge on giant polyoxometalate type Keplerates through stoichiometric interaction with cationic surfactants.

    PubMed

    Kistler, Melissa L; Patel, Komal G; Liu, Tianbo

    2009-07-07

    We report an approach of exploring the interaction between cationic surfactants and a type of structurally well-defined, spherical "Keplerate" polyoxometalate (POM) macroanionic molecular clusters, {Mo72V30}, in aqueous solution. The effectiveness of the interaction can be determined by monitoring the size change of the "blackberry" supramolecular structures formed by the self-assembly of {Mo72V30} macroions, which is determined by the effective charge density on the macroions. Long-chain surfactants (CTAB and CTAT) can interact with {Mo72V30} macroions stoichiometrically and lower their charge density. Consequently, the blackberry size decreases continuously with increasing surfactant concentration in solution. On the other hand, for short-chain surfactants (e.g., OTAB), a larger fraction of surfactants exist as discrete chains in solution and do not strongly interact with the macroions. This approach shows that a controllable amount of suitable surfactants can accurately tune the charge on large molecular clusters.

  16. A Glimpse of Our Journey into the Design of Optical Probes in Self-assembled Surfactant Aggregates.

    PubMed

    Dey, Nilanjan; Bhattacharya, Santanu

    2016-08-01

    Dynamic self-assembling amphiphilic surfactant molecules, popularly known as "micelles", have received widespread attention, due to their ability to modulate the photophysical properties of various organic dyes upon encapsulation. Along with their well-known use as cleaning agents, catalysts in organic reactions, and even for drug delivery purposes, these surfactant assemblies also show promising pertinence in the recognition of both ionic and nonionic targeted analytes. Low micropolarity and relatively hydrophobic environments promote their interaction with ionic analytes, whereas neutral species mostly affect the aggregation pattern of the probe molecules upon partitioning inside the micellar hydrophobic milieu. The environment-sensitive nature of micelle-based self-assembled probes also prompts us to devise new sensor arrays for the recognition of multiple analytes. While this account will largely focus on our own work in developing surfactant-triggered self-assembled sensors, our findings have been placed in the context of the relevant contributions from others during their strategic evolution.

  17. Evidence of self-aggregation of cationic surfactants in a choline chloride+glycerol deep eutectic solvent.

    PubMed

    Pal, Mahi; Singh, Ranjan K; Pandey, Siddharth

    2015-08-24

    Based on fluorescence probe, electrical conductivity, surface tension, small-angle X-ray/dynamic light scattering, and transmission electron microscopy experiments, we present the first clear lines of evidence for self-aggregation of cationic surfactants of the n-alkyltrimethylammonium family within an archetypical deep eutectic solvent comprised of a 1:2 molar mixture of choline chloride and glycerol. Estimated thermodynamic parameters suggest this self-aggregation process to be less entropically driven than that in water. These novel water-free self-assemblies might serve as dynamic soft templates to direct the growth of size- or shape-tailored nanoparticles within water-restricted media.

  18. Surface properties, aggregation behavior and micellization thermodynamics of a class of gemini surfactants with ethyl ammonium headgroups.

    PubMed

    Lu, Ting; Lan, Yuru; Liu, Chenjiang; Huang, Jianbin; Wang, Yilin

    2012-07-01

    Cationic gemini surfactant homologues alkanediyl-α,ω-bis(dodecyldiethylammonium bromide), [C(12)H(25)(CH(3)CH(2))(2)N(CH(2))(S)N(CH(2)CH(3))(2)C(12)H(25)]Br(2) (where S=2, 4, 6, 8, 10, 12, 16, 20), referred to as C(12)C(S)C(12)(Et) were synthesized systematically. This paper focused on various properties of the above gemini surfactants in order to give a full understanding of this series of surfactants. The following points are covered: (1) surface properties, which include (i) effect of the spacer carbon number on the general properties and (ii) the effect of added NaBr on the general surface properties; (2) aggregation behavior in bulk solution, including (i) morphologies of above gemini surfactants classed as having short spacers, middle-length spacers and long spacers and (ii) superior vesicle stability against high NaBr concentration for the long spacer gemini surfactants; (3) thermodynamic properties during micellization and the effect of spacer carbon number on them; and (4) perspectives for the further use and application of these compounds.

  19. Self-aggregation of cationic dimeric surfactants in water-ionic liquid binary mixtures.

    PubMed

    Martín, Victoria Isabel; Rodríguez, Amalia; Laschewsky, André; Moyá, María Luisa

    2014-09-15

    The micellization of four dimeric cationic surfactants ("gemini surfactants") derived from N-dodecyl-N,N,N-trimethylammonium chloride was studied in pure water and in water-ionic liquid (IL) solutions by a wide range of techniques. The dimeric surfactants are distinguished by their rigid spacer groups separating the two surfactant motifs, which range from C3 to C5 in length. In order to minimize organic ion pairing effects as well as the role of the ionic liquids as potential co-surfactants, ILs with inorganic hydrophilic anions and organic cations of limited hydrophobicity were chosen, namely ethyl, butyl, and hexyl-3-imidazolium chlorides. (1)H NMR two-dimensional, 2D, rotating frame nuclear Overhauser effect spectroscopy measurements, ROESY, supported this premise. The spacer nature hardly affects the micellization process, neither in water nor in water-IL solutions. However, it does influence the tendency of the dimeric surfactants to form elongated micelles when surfactant concentration increases. In order to have a better understanding of the ternary water-IL surfactant systems, the micellization of the surfactants was also studied in aqueous NaCl solutions, in water-ethylene glycol and in water-formamide binary mixtures. The combined results show that the ionic liquids play a double role in the mixed systems, operating simultaneously as background electrolytes and as polar organic solvents. The IL role as organic co-solvent becomes more dominant when its concentration increases, and when the IL alkyl chain length augments.

  20. Giant surfactants of poly(ethylene oxide)- b-polystyrene-(molecular nanoparticle): nanoparticle-driven self-assembly with sub-10-nm nanostructures in thin films

    NASA Astrophysics Data System (ADS)

    Hsu, Chih-Hao; Lin, Zhiwei; Dong, Xue-Hui; Hsieh, I.-Fan; Cheng, Stephen Z. D.

    2014-03-01

    Giant surfactants are built upon precisely attaching shape- and volume-persistent molecular nanoparticles (MNP) to polymeric flexible tails. The unique class of self-assembling materials, giant surfactants, has been demonstrated to form self-assembled ordered nanostructures, and their self-assembly behaviors are remarkably sensitive to primary chemical structures. In this work, two sets of giant surfactants with functionalized MNP attached to diblock copolymer tails were studied in thin films. Carboxylic acid-functionalized [60]fullerene (AC60) tethered with PEO- b-PS (PEO-PS-AC60) represents an ABA' (hydrophilic-hydrophobic-hydrophilic) giant surfactant, and fluoro-functionalized polyhedral oligomeric silsesquioxane (FPOSS) tethered with PEO- b-PS (PEO-PS-FPOSS) represents an ABC (hydrophilic-hydrophobic-omniphobic) one. The dissimilar chemical natures of the MNPs result in different arrangement of MNPs in self-assembled structures, the dispersion of AC60 in PEO domain and the single domain of FPOSS. Moreover, the chemically bonded MNPs could induce the originally disordered small molecular PEO- b-PS to form ordered cylindrical and lamellar structure, as evidenced by TEM and GISAXS, leading to sub-10-nm nanostructures of copolymer in the thin film state.

  1. Mixed aggregate formation in gemini surfactant/1,2-dialkyl-sn-glycero-3-phosphoethanolamine systems.

    PubMed

    Akbar, Javed; Tavakoli, Naser; Marangoni, D Gerrard; Wettig, Shawn D

    2012-07-01

    An evaluation of the physical interactions between gemini surfactants, DNA, and 1,2-dialkyl-sn-glycero-3-phosphoethanolamine helper lipid is presented in this work. Complexation between gemini surfactants and DNA was first investigated using surface tensiometry where the surface tension profiles obtained were found to be consistent with those typically observed for mixed surfactant-polymer systems; that is, there is a synergistic lowering of the surface tension, followed by a first (CAC) and second (CMC) break point in the plot. The surfactant alkyl tail length was observed to exhibit a significant effect on the CAC, thus demonstrating the importance of hydrophobic interactions during complexation between gemini surfactants and DNA. The second study presented is an investigation of the mixing interactions between gemini surfactants and DOPE using Clint's, Rubingh's, and Motomura's theories for mixed micellar formation. The mixing interactions between the 16-3-16/16-7-16/16-12-16/16-7NH-16 gemini surfactants and DOPE were observed to be antagonistic, where the strength of antagonism was found to be dependent upon the gemini surfactant spacer group and the solution composition. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. Aggregation Kinetics and Transport of Single-Walled CarbonNanotubes at Low Surfactant Concentrations

    EPA Science Inventory

    Little is known about how low levels of surfactants can affect the colloidal stability of single-walled carbon nanotubes (SWNTs) and how surfactant-wrapping of SWNTs can impact ecological exposures in aqueous systems. In this study, SWNTs were suspended in water with sodium ...

  3. Aggregation Kinetics and Transport of Single-Walled CarbonNanotubes at Low Surfactant Concentrations

    EPA Science Inventory

    Little is known about how low levels of surfactants can affect the colloidal stability of single-walled carbon nanotubes (SWNTs) and how surfactant-wrapping of SWNTs can impact ecological exposures in aqueous systems. In this study, SWNTs were suspended in water with sodium ...

  4. Phase diagrams and microstructure of aggregates in mixed ionic surfactant/foam booster systems.

    PubMed

    Rodríguez, Carlos; Sakai, Takaya; Fujiyama, Rika; Kunieda, Hironobu

    2004-02-15

    The phase behavior and microstructure of surfactant systems containing a new alkanolamide-type foam booster, dodecanoyl N-methyl ethanolamide (NMEA-12), were investigated by means of phase study and small angle X-ray scattering. Different from other similar alkanolamides, NMEA-12 possesses a low melting point and forms a lyotropic liquid-crystalline phase (L(alpha) phase) at room temperature. This is attributed to the attached methyl group, which increases the fluidity of the molecule. In the SDS/NMEA-12/water system, hexagonal and lamellar (L(alpha)) liquid-crystalline phases are obtained at significantly low surfactant concentrations. The stability of these phases decreases when SDS is replaced with a nonionic surfactant (C12EO8). However, for both ionic and nonionic surfactants, the effective area per surfactant molecule at the interface shrinks upon addition of NMEA-12, indicating that the surfactant layer is getting more compact. The possible implications of these results on the potential applications of NMEA-12 as foam stabilizer are discussed.

  5. Ecotoxicities of polyquaterniums and their associated polyelectrolyte-surfactant aggregates (PSA) to Gambusia holbrooki.

    PubMed

    Cumming, Janet L; Hawker, Darryl W; Nugent, Kerry W; Chapman, Heather F

    2008-02-01

    The toxicity of 11 polyquaterniums used in cosmetic applications, and polydimethyldiallylammonium chloride (poly(DADMAC)) were studied for toxicity of the polyquaternium alone, and of a polyquaternium/anionic surfactant complex as occurs in some cosmetic formulations. The surfactant used in the study was sodium dodecyl sulfate (SDS), which is used in cosmetic formulations under its International Nomenclature of Cosmetic Ingredients (INCI) name Sodium Laurel Sulfate. In fish immobilization studies with Gambusia holbrooki, the EC(50) of the polyquaternium/surfactant complex was found to be the same as or similar to the EC(50) for the polyquaternium alone. The toxicity of the polyquaterniums investigated was similar to the published values for other cationic polyelectrolytes and cationic surfactants, in the range from < 1.0 to 10 mg/L, with the exception of low charge density cellulosic polyquaterniums. The anionic surfactant alone was not toxic to fish in the concentration range tested. Results thus showed the toxicity of the polyquaternium was not mitigated by the presence of the anionic surfactant.

  6. Interaction of giant extracellular Glossoscolex paulistus hemoglobin (HbGp) with ionic surfactants: a MALDI-TOF-MS study.

    PubMed

    Oliveira, Marilene Silva; Moreira, Leonardo Marmo; Tabak, Marcel

    2008-03-01

    The giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) is constituted by approximately 144 subunits containing heme groups with molecular masses in the range of 16-19kDa forming a monomer (d) and a trimer (abc), and around 36 non-heme structures, named linkers (L). Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF-MS) analysis was performed recently, to obtain directly information on the molecular masses of the different subunits from HbGp in the oxy-form. This technique demonstrated structural similarity between HbGp and the widely studied hemoglobin of Lumbricus terrestris (HbLt). Indeed, two major isoforms (d(1) and d(2)) of identical proportions with masses of 16,355+/-25 and 16,428+/-24Da, respectively, and two minor isoforms (d(3) and d(4)) with masses around 16.6kDa were detected for monomer d of HbGp. In the present work, the effects of anionic sodium dodecyl sulfate (SDS) and cationic cethyltrimethylammonium chloride (CTAC) on the oligomeric structure of HbGp have been studied by MALDI-TOF-MS in order to evaluate the interaction between ionic surfactants and HbGp. The data obtained with this technique show an effective interaction of cationic surfactant CTAC with the two isoforms of monomer d, d(1) and d(2), both in the whole protein as well as in the pure isolated monomer. The results show that up to 10 molecules of CTAC are bound to each isoform of the monomer. Differently, the mass spectra obtained for SDS-HbGp system showed that the addition of the anionic surfactant SDS does not originate any mass increment of the monomeric subunits, indicating that SDS-HbGp interaction is, probably, significantly less effective as compared to CTAC-HbGp one. The acid pI of the protein around 5.5 is, probably, responsible for this behavior. The results of this work suggest also some interaction of both surfactants with linker chains as well as with trimers, as judged from observed mass increments. Our data are consistent with a recent

  7. Strong fluorescence emissions by H-aggregates of the dye thiacyanine in the presence of the surfactant aerosol-OT

    NASA Astrophysics Data System (ADS)

    Mandal, Anil Kumar; Pal, Medini Kanta

    2000-02-01

    The cationic dye 3,3 '-diethylthiacyanine iodide (THIA) in dilute aqueous solution shows weak fluorescence with a broad peak around 470 nm, and the anionic surfactant bis(2-ethylhexyl) sodium sulphosuccinate, called aerosol-OT (AOT) enhances the fluorescence of the dye. When excited at 422 nm ( λmax of THIA), the fluorescence peak of THIA, in the presence of increasing AOT concentrations up to its critical micellar concentration (CMC), is gradually reduced to a shoulder around 475 nm, and two additional sharp peaks at 494 and 601 nm are progressively developed. Above the CMC of AOT, the original 470 nm peak starts reappearing with simultaneous disappearance of the 494 and 601 nm peaks. At appropriate AOT concentrations (below CMC), THIA forms two metachromatic species (H-aggregates) showing strong absorption peaks at 377 and 366 nm. When excited at these metachromatic peaks, the fluorescence of the THIA/AOT system is, instead of being quenched, largely enhanced about 8-10 times compared to when excited at 422 nm, and above the CMC, fluorescence diminishes. Application of the principal component analysis method to the observed fluorescence spectra results in three pure component spectra with peaks at 470, 494 and 601 nm, which have been assigned to monomer, normal H-aggregates and twisted H-aggregates emission peaks, respectively. The twisted H-aggregates originate from the excited preexisting hexamer as well as from the excimer formed between excited and ground state trimers.

  8. Change in Chirality of Semiconducting Single-Walled Carbon Nanotubes Can Overcome Anionic Surfactant Stabilization: A Systematic Study of Aggregation Kinetics.

    PubMed

    Khan, Iftheker A; Flora, Joseph R V; Nabiul Afrooz, A R M; Aich, Nirupam; Schierz, P Ariette; Ferguson, P Lee; Sabo-Attwood, Tara; Saleh, Navid B

    2015-05-20

    Single-walled carbon nanotubes' (SWNT) effectiveness in applications is enhanced by debundling or stabilization. Anionic surfactants are known to effectively stabilize SWNTs. However, the role of specific chirality on surfactant-stabilized SWNT aggregation has not been studied to date. The aggregation behavior of chirally enriched (6,5) and (7,6) semiconducting SWNTs, functionalized with three anionic surfactants-sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium deoxycholate (SDOCO)-was evaluated with time-resolved dynamic light scattering. A wide range of mono- (NaCl) and di-valent (CaCl2) electrolytes as well as a 2.5 mg TOC/L Suwannee River humic acid (SRHA) were used as background chemistry. Overall, SDBS showed the most effectiveness in SWNT stability, followed by SDOCO and SDS. However, the relatively larger diameter (7,6) chiral tubes compromised the surfactant stability, compared to (6,5) chiral enrichment, due to enhanced van der Waals interaction. The presence of di-valent electrolytes overshadowed the chirality effects and resulted in similar aggregation behavior for both the SWNT samples. Molecular modeling results enumerated key differences in surfactant conformation on SWNT surfaces and identified interaction energy changes between the two chiralities to delineate aggregation mechanisms. The stability of SWNTs increased in the presence of SRHA under 10 mM monovalent and mixed electrolyte conditions. The results suggest that change in chirality can overcome surfactant stabilization of semiconducting SWNTs. SWNT stability can also be strongly influenced by the anionic surfactant structure.

  9. A Study of the Effect of Surfactants on the Aggregation Behavior of Crude Oil Aqueous Dispersions through Steady-State Fluorescence Spectrometry.

    PubMed

    Vallejo-Cardona, Alba A; Cerón-Camacho, Ricardo; Karamath, James R; Martínez-Palou, Rafael; Aburto, Jorge

    2017-07-01

    Unconventional crude oil as heavy, extra heavy, bitumen, tight, and shale oils will meet 10% of worldwide needs for 2035, perhaps earlier. Petroleum companies will face problems concerning crude oil extraction, production, transport, and refining, and some of these are addressed by the use of surfactants and other chemicals. For example, water-in-crude oil emulsions are frequently found during the production of mature wells where enhanced recovery techniques have been deployed. Nevertheless, the selection of adequate surfactant, dosage, type of water (sea, tap or oilfield), kind of crude oil (light, heavy, extra heavy, tight, shale, bitumen) affect the effectivity of treatment and usual bottle tests give limited information. We developed a fluorescence technique to study the effect of surfactants on medium, heavy, and extra heavy crude oil employing the natural fluorophore molecules from petroleum. We first carried out the characterization of commercial and synthetic surfactants, then dispersions of petroleum in water were studied by steady-state fluorometry and the size of petroleum aggregates were measured. The aggregation of petroleum incremented from medium to extra heavy crude oil and we discussed the effect of different surfactants on such aggregation.

  10. Nonlinear Surface Dilatational Rheology and Foaming Behavior of Protein and Protein Fibrillar Aggregates in the Presence of Natural Surfactant.

    PubMed

    Wan, Zhili; Yang, Xiaoquan; Sagis, Leonard M C

    2016-04-19

    The surface and foaming properties of native soy glycinin (11S) and its heat-induced fibrillar aggregates, in the presence of natural surfactant steviol glycoside (STE), were investigated and compared at pH 7.0 to determine the impact of protein structure modification on protein-surfactant interfacial interactions. The adsorption at, and nonlinear dilatational rheological behavior of, the air-water interface were studied by combining drop shape analysis tensiometry, ellipsometry, and large-amplitude oscillatory dilatational rheology. Lissajous plots of surface pressure versus deformation were used to analyze the surface rheological response in terms of interfacial microstructure. The heat treatment generates a mixture of long fibrils and unconverted peptides. The presence of small peptides in 11S fibril samples resulted in a faster adsorption kinetics than that of native 11S. The addition of STE affected the adsorption of 11S significantly, whereas no apparent effect on the adsorption of the 11S fibril-peptide system was observed. The rheological response of interfaces stabilized by 11S-STE mixtures also differed significantly from the response for 11S fibril-peptide-STE mixtures. For 11S, the STE reduces the degree of strain hardening in extension and increases strain hardening in compression, suggesting the interfacial structure may change from a surface gel to a mixed phase of protein patches and STE domains. The foams generated from the mixtures displayed comparable foam stability to that of pure 11S. For 11S fibril-peptide mixtures STE only significantly affects the response in extension, where the degree of strain softening is decreased compared to the pure fibril-peptide system. The foam stability of the fibril-peptide system was significantly reduced by STE. These findings indicate that fibrillization of globular proteins could be a potential strategy to modify the complex surface and foaming behaviors of protein-surfactant mixtures.

  11. Static and dynamic microscopy of the chemical stability and aggregation state of silver nanowires in components of murine pulmonary surfactant

    PubMed Central

    Theodorou, Ioannis G.; Botelho, Danielle; Schwander, Stephan; Zhang, Junfeng (Jim); Chung, Kian Fan; Tetley, Teresa D.; Shaffer, Milo S. P.; Gow, Andrew; Ryan, Mary P.; Porter, Alexandra E.

    2016-01-01

    The increase of production volumes of silver nanowires (AgNWs) and of consumer products incorporating them, may lead to increased health risks from occupational and public exposures. There is currently limited information about the putative toxicity of AgNWs upon inhalation, and incomplete understanding of the properties that control their bioreactivity. The lung lining fluid (LLF), which contains phospholipids and surfactant proteins, represents a first contact site with the respiratory system. In this work, the impact of Dipalmitoylphosphatidylcholine (DPPC), Curosurf® and murine LLF on the stability of AgNWs was examined. Both the phospholipid and protein components of the LLF modified the dissolution kinetics of AgNWs, due to the formation of a lipid corona or aggregation of the AgNWs. Moreover, the hydrophilic, but neither the hydrophobic surfactant proteins nor the phospholipids, induced agglomeration of the AgNWs. Finally, the generation of a secondary population of nano-silver was observed and attributed to the reduction of Ag+ ions by the surface capping of the AgNWs. Our findings highlight that combinations of spatially resolved dynamic and static techniques are required to develop a holistic understanding of which parameters govern AgNW behavior at the point of exposure and to accurately predict their risks on human health and the environment. PMID:26061974

  12. Static and Dynamic Microscopy of the Chemical Stability and Aggregation State of Silver Nanowires in Components of Murine Pulmonary Surfactant.

    PubMed

    Theodorou, Ioannis G; Botelho, Danielle; Schwander, Stephan; Zhang, Junfeng; Chung, Kian Fan; Tetley, Teresa D; Shaffer, Milo S P; Gow, Andrew; Ryan, Mary P; Porter, Alexandra E

    2015-07-07

    The increase of production volumes of silver nanowires (AgNWs) and of consumer products incorporating them may lead to increased health risks from occupational and public exposures. There is currently limited information about the putative toxicity of AgNWs upon inhalation and incomplete understanding of the properties that control their bioreactivity. The lung lining fluid (LLF), which contains phospholipids and surfactant proteins, represents a first contact site with the respiratory system. In this work, the impact of dipalmitoylphosphatidylcholine (DPPC), Curosurf, and murine LLF on the stability of AgNWs was examined. Both the phospholipid and protein components of the LLF modified the dissolution kinetics of AgNWs, due to the formation of a lipid corona or aggregation of the AgNWs. Moreover, the hydrophilic proteins, but neither the hydrophobic surfactant proteins nor the phospholipids, induced agglomeration of the AgNWs. Finally, the generation of a secondary population of nanosilver was observed and attributed to the reduction of Ag(+) ions by the surface capping of the AgNWs. Our findings highlight that combinations of spatially resolved dynamic and static techniques are required to develop a holistic understanding of which parameters govern AgNW behavior at the point of exposure and to accurately predict their risks on human health and the environment.

  13. Change in Chirality of Semiconducting Single-Walled Carbon Nanotubes Can Overcome Anionic Surfactant Stabilization: A Systematic Study of Aggregation Kinetics

    PubMed Central

    Khan, Iftheker A.; Flora, Joseph R. V.; Nabiul Afrooz, A. R. M.; Aich, Nirupam; Schierz, P. Ariette; Ferguson, P. Lee; Sabo-Attwood, Tara; Saleh, Navid B.

    2015-01-01

    Single-walled carbon nanotubes’ (SWNT) effectiveness in applications is enhanced by debundling or stabilization. Anionic surfactants are known to effectively stabilize SWNTs. However, the role of specific chirality on surfactant-stabilized SWNT aggregation has not been studied to date. The aggregation behavior of chirally enriched (6,5) and (7,6) semiconducting SWNTs, functionalized with three anionic surfactants—sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium deoxycholate (SDOCO)—was evaluated with time-resolved dynamic light scattering. A wide range of mono- (NaCl) and di-valent (CaCl2) electrolytes as well as a 2.5 mg TOC/L Suwannee River humic acid (SRHA) were used as background chemistry. Overall, SDBS showed the most effectiveness in SWNT stability, followed by SDOCO and SDS. However, the relatively larger diameter (7,6) chiral tubes compromised the surfactant stability, compared to (6,5) chiral enrichment, due to enhanced van der Waals interaction. The presence of di-valent electrolytes overshadowed the chirality effects and resulted in similar aggregation behavior for both the SWNT samples. Molecular modeling results enumerated key differences in surfactant conformation on SWNT surfaces and identified interaction energy changes between the two chiralities to delineate aggregation mechanisms. The stability of SWNTs increased in the presence of SRHA under 10 mM monovalent and mixed electrolyte conditions. The results suggest that change in chirality can overcome surfactant stabilization of semiconducting SWNTs. SWNT stability can also be strongly influenced by the anionic surfactant structure. PMID:26855611

  14. Discrimination of Metalloproteins by a Mini Sensor Array Based on Bispyrene Fluorophore/Surfactant Aggregate Ensembles.

    PubMed

    Cao, Yuan; Zhang, Lijun; Huang, Xinyan; Xin, Yunhong; Ding, Liping

    2016-12-28

    Fluorescent sensor arrays with pattern recognition ability have been widely used to detect and identify multiple chemically similar analytes. In the present work, two particular bispyrene fluorophores containing hydrophilic oligo(oxyethylene) spacer, 6 and 4, were synthesized, but one is with and the other is without cholesterol unit. Their ensembles with cationic surfactant (CTAB) assemblies realize multiple fluorescence responses to different metalloproteins, including hemoglobin, myoglobin, ferritin, cytochrome c, and alcohol dehydrogenase. The combination of fluorescence variation at monomer and excimer emission of the two binary sensor ensembles enables the mini sensor array to provide a specific fingerprint pattern to each metalloprotein. Linear discriminant analysis shows that the two-ensemble-sensor-based array could well discriminate the five tested metalloproteins. The present work realizes using a mini sensor array to accomplish discrimination of complex analytes like proteins. They also display a very high sensitivity to the tested metalloproteins with detection limits in the range of picomolar concentration.

  15. Aggregation and transport of nano-TiO2 in saturated porous media: effects of pH, surfactants and flow velocity.

    PubMed

    Godinez, Itzel G; Darnault, Christophe J G

    2011-01-01

    Transport of manufactured nano-TiO(2) in saturated porous media was investigated as a function of morphology characteristics, pH of solutions, flow velocity, and the presence of anionic and non-ionic surfactants in different concentrations. Surfactants enhanced the transport of nano-TiO(2) in saturated porous media while a pH approaching the point of zero charge of nano-TiO(2) limited their transport. The deposition process, a retention mechanism of nano-TiO(2) in saturated porous media was impacted by surfactant and pH. In Dispersion 1 systems (pH 7), the size of the nano-TiO(2) aggregates was directly related to the presence of surfactants. The presence of non-ionic surfactant (Triton X-100) induced a size reduction of nano-TiO(2) aggregates that was dependent on the critical micelle concentration. In Dispersion 2 systems (pH 9), the stability provided by the pH had a significant effect on the size of nano-TiO(2) aggregates; the addition of surfactants did impact the size of the nano-TiO(2) aggregates but in less significance as compared to Dispersion 1 systems. The electrostatic and steric repulsion forces in connection with the size of nano-TiO(2) aggregates and flow velocity impacted the single-collector efficiency and attachment efficiency which dictated the maximum transport distance of nano-TiO(2) for the Dispersion 1 and Dispersion 2 systems. By doubling the flow velocity at pH 9, the No Surfactant, 50% CMC Triton X-100, 100% CMC Triton X-100 and 100% CMC SDBS dispersion systems allowed nano-TiO(2) to attain maximum transport distances of 0.898, 2.17, 2.29 and 1.12 m, respectively. Secondary energy minima played a critical role in the deposition mechanisms of nano-TiO(2). Nano-TiO(2) deposited in the secondary energy wells may be released because of changes in solution chemistry. The deposition of nano-TiO(2) in primary and secondary energy minima, the reversibility of their deposition should be characterized to analyze the transport of nanoparticles in

  16. Giant extracellular Glossoscolex paulistus Hemoglobin (HbGp) upon interaction with cethyltrimethylammonium chloride (CTAC) and sodium dodecyl sulphate (SDS) surfactants: Dissociation of oligomeric structure and autoxidation.

    PubMed

    Santiago, Patricia S; Moreira, Leonardo M; de Almeida, Erika V; Tabak, Marcel

    2007-04-01

    The effects of two ionic surfactants on the oligomeric structure of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) in the oxy - form have been studied through the use of several spectroscopic techniques such as electronic optical absorption, fluorescence emission, light scattering, and circular dichroism. The use of anionic sodium dodecyl sulphate (SDS) and cationic cethyltrimethyl ammonium chloride (CTAC) has allowed to differentiate the effects of opposite headgroup charges on the oligomeric structure dissociation and hemoglobin autoxidation. At pH 7.0, both surfactants induce the protein dissociation and a significant oxidation. Spectral changes occur at very low CTAC concentrations suggesting a significant electrostatic contribution to the protein-surfactant interaction. At low protein concentration, 0.08 mg/ml, some light scattering within a narrow CTAC concentration range occurs due to protein-surfactant precipitation. Light scattering experiments showed the dissociation of the oligomeric structure by SDS and CTAC, and the effect of precipitation induced by CTAC. At higher protein concentrations, 3.0 mg/ml, a precipitation was observed due to the intense charge neutralization upon formation of ion pair in the protein-surfactant precipitate. The spectral changes are spread over a much wider SDS concentration range, implying a smaller electrostatic contribution to the protein-surfactant interactions. The observed effects are consistent with the acid isoelectric point (pI) of this class of hemoglobins, which favors the intense interaction of HbGp with the cationic surfactant due to the existence of excess acid anionic residues at the protein surface. Protein secondary structure changes are significant for CTAC at low concentrations while they occur at significantly higher concentrations for SDS. In summary, the cationic surfactant seems to interact more strongly with the protein producing more dramatic spectral changes as compared to the

  17. Interaction of n-octyl β,D-glucopyranoside with giant magnetic-fluid-loaded phosphatidylcholine vesicles: direct visualization of membrane curvature fluctuations as a function of surfactant partitioning between water and lipid bilayer.

    PubMed

    Ménager, Christine; Guemghar, Dihya; Cabuil, Valérie; Lesieur, Sylviane

    2010-10-05

    The present study deals with the morphological modifications of giant dioleoyl phosphatidylcholine vesicles (DOPC GUVs) induced by the nonionic surfactant n-octyl β,D-glucopyranoside at sublytic levels, i.e., in the first steps of the vesicle-to-micelle transition process, when surfactant inserts into the vesicle bilayer without disruption. Experimental conditions were perfected to exactly control the surfactant bilayer composition of the vesicles, in line with former work focused on the mechanical properties of the membrane of magnetic-fluid-loaded DOPC GUVs submitted to a magnetic field. The purpose here was to systematically examine, in the absence of any external mechanical constraint, the dynamics of giant vesicle shape and membrane deformations as a function of surfactant partitioning between the aqueous phase and the lipid membrane, beforehand established by turbidity measurements from small unilamellar vesicles.

  18. Influence of trehalose on the interaction of curcumin with surface active ionic liquid micelle and its vesicular aggregate composed of a non-ionic surfactant sorbitan stearate

    NASA Astrophysics Data System (ADS)

    Roy, Arpita; Dutta, Rupam; Sarkar, Nilmoni

    2016-11-01

    The present investigation unravels the effect of trehalose on 1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl), a cationic surface active ionic liquid (SAIL) micelle and SAIL ([C16mim]Cl)-nonionic surfactant (Sorbitan Stearate, Span 60) based vesicles. The influence of trehalose on size and morphology of the aggregates has been investigated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) measurements. Besides, we have studied the dynamic properties of curcumin inside these aggregates using fluorescence spectroscopic based techniques. The results revealed that trehalose molecules play crucial role in modulation of the photophysical properties of curcumin in these organized assemblies.

  19. Photoinduced electron transfer reaction in polymer-surfactant aggregates: Photoinduced electron transfer between N,N-dimethylaniline and 7-amino coumarin dyes

    SciTech Connect

    Chakraborty, Anjan; Seth, Debabrata; Setua, Palash; Sarkar, Nilmoni

    2008-05-28

    Photoinduced electron transfer between coumarin dyes and N,N-dimethylaniline has been investigated by using steady state and picosecond time resolved fluorescence spectroscopy in sodium dodecyl sulphate (SDS) micelles and PVP-polyvinyl pyrrolidone (SDS) polymer-surfactant aggregates. A slower rate of electron transfer is observed in PVP-SDS aggregates than in polymer-free SDS micelles. A Marcus type inversion is observed in the correlation of free energy change in comparison with the electron transfer rate. The careful investigation reveals that C-151 deviates from the normal Marcus inverted region compared to its analogs C-152 and C-481 due to slower rotational relaxation and smaller translational diffusion coefficient.

  20. Effect of the surfactant tween 80 on the detachment and dispersal of Salmonella enterica serovar Thompson single cells and aggregates from cilantro leaves as revealed by image analysis.

    PubMed

    Brandl, Maria T; Huynh, Steven

    2014-08-01

    Salmonella enterica has the ability to form biofilms and large aggregates on produce surfaces, including on cilantro leaves. Aggregates of S. enterica serovar Thompson that remained attached to cilantro leaves after rigorous washing and that were present free or bound to dislodged leaf tissue in the wash suspension were observed by confocal microscopy. Measurement of S. Thompson population sizes in the leaf washes by plate counts failed to show an effect of 0.05% Tween 80 on the removal of the pathogen from cilantro leaves 2 and 6 days after inoculation. On the contrary, digital image analysis of micrographs of single cells and aggregates of green fluorescent protein (GFP)-S. Thompson present in cilantro leaf washes revealed that single cells represented 13.7% of the cell assemblages in leaf washes containing Tween 80, versus 9.3% in those without the surfactant. Moreover, Tween 80 decreased the percentage of the total S. Thompson cell population located in aggregates equal to or larger than 64 cells from 9.8% to 4.4% (P < 0.05). Regression analysis of the frequency distribution of aggregate size in leaf washes with and without Tween 80 showed that the surfactant promoted the dispersal of cells from large aggregates into smaller ones and into single cells (P < 0.05). Our study underlines the importance of investigating bacterial behavior at the scale of single cells in order to uncover trends undetectable at the population level by bacterial plate counts. Such an approach may provide valuable information to devise strategies aimed at enhancing the efficacy of produce sanitization treatments.

  1. Effect of the Surfactant Tween 80 on the Detachment and Dispersal of Salmonella enterica Serovar Thompson Single Cells and Aggregates from Cilantro Leaves as Revealed by Image Analysis

    PubMed Central

    Huynh, Steven

    2014-01-01

    Salmonella enterica has the ability to form biofilms and large aggregates on produce surfaces, including on cilantro leaves. Aggregates of S. enterica serovar Thompson that remained attached to cilantro leaves after rigorous washing and that were present free or bound to dislodged leaf tissue in the wash suspension were observed by confocal microscopy. Measurement of S. Thompson population sizes in the leaf washes by plate counts failed to show an effect of 0.05% Tween 80 on the removal of the pathogen from cilantro leaves 2 and 6 days after inoculation. On the contrary, digital image analysis of micrographs of single cells and aggregates of green fluorescent protein (GFP)-S. Thompson present in cilantro leaf washes revealed that single cells represented 13.7% of the cell assemblages in leaf washes containing Tween 80, versus 9.3% in those without the surfactant. Moreover, Tween 80 decreased the percentage of the total S. Thompson cell population located in aggregates equal to or larger than 64 cells from 9.8% to 4.4% (P < 0.05). Regression analysis of the frequency distribution of aggregate size in leaf washes with and without Tween 80 showed that the surfactant promoted the dispersal of cells from large aggregates into smaller ones and into single cells (P < 0.05). Our study underlines the importance of investigating bacterial behavior at the scale of single cells in order to uncover trends undetectable at the population level by bacterial plate counts. Such an approach may provide valuable information to devise strategies aimed at enhancing the efficacy of produce sanitization treatments. PMID:24907336

  2. Spawning aggregation behavior and reproductive ecology of the giant bumphead parrotfish, Bolbometopon muricatum, in a remote marine reserve.

    PubMed

    Muñoz, Roldan C; Zgliczynski, Brian J; Teer, Bradford Z; Laughlin, Joseph L

    2014-01-01

    The giant bumphead parrotfish (Bolbometopon muricatum) has experienced precipitous population declines throughout its range due to its importance as a highly-prized fishery target and cultural resource. Because of its diet, Bolbometopon may serve as a keystone species on Indo-Pacific coral reefs, yet comprehensive descriptions of its reproductive ecology do not exist. We used a variety of underwater visual census (UVC) methods to study an intact population of Bolbometopon at Wake Atoll, a remote and protected coral atoll in the west Pacific. Key observations include spawning activities in the morning around the full and last quarter moon, with possible spawning extending to the new moon. We observed peaks in aggregation size just prior to and following the full and last quarter moon, respectively, and observed a distinct break in spawning at the site that persisted for four days; individuals returned to the aggregation site one day prior to the last quarter moon and resumed spawning the following day. The mating system was lek-based, characterized by early male arrival at the spawning site followed by vigorous defense (including head-butting between large males) of small territories. These territories were apparently used to attract females that arrived later in large schools, causing substantial changes in the sex ratio on the aggregation site at any given time during the morning spawning period. Aggression between males and courtship of females led to pair spawning within the upper water column. Mating interference was not witnessed but we noted instances suggesting that sperm competition might occur. Densities of Bolbometopon on the aggregation site averaged 10.07(±3.24 SE) fish per hectare (ha) with maximum densities of 51.5 fish per ha. By comparing our observations to the results of biennial surveys conducted by the National Oceanic and Atmospheric Administration (NOAA) Coral Reef Ecosystem Division (CRED), we confirmed spatial consistency of the aggregation

  3. Spawning aggregation behavior and reproductive ecology of the giant bumphead parrotfish, Bolbometopon muricatum, in a remote marine reserve

    PubMed Central

    Zgliczynski, Brian J.; Teer, Bradford Z.; Laughlin, Joseph L.

    2014-01-01

    The giant bumphead parrotfish (Bolbometopon muricatum) has experienced precipitous population declines throughout its range due to its importance as a highly-prized fishery target and cultural resource. Because of its diet, Bolbometopon may serve as a keystone species on Indo-Pacific coral reefs, yet comprehensive descriptions of its reproductive ecology do not exist. We used a variety of underwater visual census (UVC) methods to study an intact population of Bolbometopon at Wake Atoll, a remote and protected coral atoll in the west Pacific. Key observations include spawning activities in the morning around the full and last quarter moon, with possible spawning extending to the new moon. We observed peaks in aggregation size just prior to and following the full and last quarter moon, respectively, and observed a distinct break in spawning at the site that persisted for four days; individuals returned to the aggregation site one day prior to the last quarter moon and resumed spawning the following day. The mating system was lek-based, characterized by early male arrival at the spawning site followed by vigorous defense (including head-butting between large males) of small territories. These territories were apparently used to attract females that arrived later in large schools, causing substantial changes in the sex ratio on the aggregation site at any given time during the morning spawning period. Aggression between males and courtship of females led to pair spawning within the upper water column. Mating interference was not witnessed but we noted instances suggesting that sperm competition might occur. Densities of Bolbometopon on the aggregation site averaged 10.07(±3.24 SE) fish per hectare (ha) with maximum densities of 51.5 fish per ha. By comparing our observations to the results of biennial surveys conducted by the National Oceanic and Atmospheric Administration (NOAA) Coral Reef Ecosystem Division (CRED), we confirmed spatial consistency of the aggregation

  4. Fluorescence of aminofluoresceins as an indicative process allowing one to distinguish between micelles of cationic surfactants and micelle-like aggregates

    NASA Astrophysics Data System (ADS)

    Mchedlov-Petrossyan, Nikolay O.; Cheipesh, Tatiana A.; Roshal, Alexander D.; Doroshenko, Andrey O.; Vodolazkaya, Natalya A.

    2016-09-01

    Among the vast set of fluorescein derivatives, the double charged R2- anions of aminofluoresceins are known to exhibit only low quantum yields of fluorescence, \\varphi . The \\varphi value becomes as high as that of the fluorescein dianion when the lone electron pair of the amino group is involved in a covalent bond. According to Munkholm et al (1990 J. Am. Chem. Soc. 112 2608-12), a much smaller increase in the emission intensity can be observed in the presence of surfactant micelles. However, all these observations refer to aqueous or alcoholic solvents. In this paper, we show that in the non-hydrogen bond donor (or ‘aprotic’) solvents DMSO and acetone, the quantum yields, φ, of the 4‧- (or 5‧)-aminofluorescein R2- species amount to 61-67% and approach that of fluorescein (φ  =  87%), whereas in water φ is only 0.6-0.8%. In glycerol, a solvent with an extremely high viscosity, the φ value is only 6-10%. We report on the enhancement of the fluorescence of the aminofluorescein dianions as an indicative process, which allows us to distinguish between the micelle-like aggregates of cationic dendrimers of low generation, common spherical surfactant micelles, and surfactant bilayers. Some of these colloidal aggregates partly restore the fluorescence of aminofluoresceins in aqueous media. By contrast, other positively charged micellar-like aggregates do not enhance the quantum yield of aminofluorescein R2- species. Results for several related systems, such as CTAB-coated SiO2 particles and reverse microemulsions, are briefly described, and the possible reasons for the observed phenomena are discussed.

  5. Self-Propelled Oil Droplets and Their Morphological Change to Giant Vesicles Induced by a Surfactant Solution at Low pH.

    PubMed

    Banno, Taisuke; Tanaka, Yuki; Asakura, Kouichi; Toyota, Taro

    2016-09-20

    Unique dynamics using inanimate molecular assemblies based on soft matter have drawn much attention for demonstrating far-from-equilibrium chemical systems. However, there are no soft matter systems that exhibit a possible pathway linking the self-propelled oil droplets to formation of giant vesicles stimulated by low pH. In this study, we conceived an experimental oil-in-water emulsion system in which flocculated particles composed of a imine-containing oil transformed to spherical oil droplets that self-propelled and, after coming to rest, formed membranous figures. Finally, these figures became giant vesicles. From NMR, pH curves, and surface tension measurements, we determined that this far-from-equilibrium phenomenon was due to the acidic hydrolysis of the oil, which produced a benzaldehyde derivative as an oil component and a primary amine as a surfactant precursor, and the dynamic behavior of the hydrolytic products in the emulsion system. These findings afforded us a potential linkage between mobile droplet-based protocells and vesicle-based protocells stimulated by low pH.

  6. Full-time kinetics of self-assembly and disassembly in micellar solution via the generalized Smoluchowski equation with fusion and fission of surfactant aggregates

    NASA Astrophysics Data System (ADS)

    Shchekin, Alexander K.; Babintsev, Ilya A.; Adzhemyan, Loran Ts.

    2016-11-01

    Full-time kinetics of self-assembly and disassembly of spherical micelles with their fusion and fission in non-ionic micellar solutions has been considered in detail on the basis of direct numerical solutions of the generalized Smoluchowski equations describing the evolution of the time-dependent concentrations of molecular aggregates for every aggregation number. The cases of instant increase of the monomer concentration up or dilution of a surfactant solution below the critical micelle concentration at large initial deviations from the final equilibrium state have been studied. Different stages in assembly or disassembly of micelles have been described and compared with the results of the stepwise mechanism of monomer attachment-detachment described by the Becker-Döring kinetic equations. A relation of the full-time kinetics to micellar relaxation at small deviations from the equilibrium state has been checked.

  7. Interaction of Fe(III)- and Zn(II)-tetra(4-sulfonatophenyl) porphyrins with ionic and nonionic surfactants: aggregation and binding.

    PubMed

    Gandini, S C; Yushmanov, V E; Tabak, M

    2001-07-01

    Interactions of the water soluble Fe(III)- and Zn(II)-tetra(4-sulfonatophenyl) porphyrins, FeTPPS(4) and ZnTPPS(4), with ionic and nonionic micelles in aqueous solutions have been studied by optical absorption, fluorescence, resonance light-scattering (RLS), and 1H NMR spectroscopies. The presence of three different species of both Fe(III)- and Zn(II)TPPS(4) in cationic cetyltrimethylammonium chloride (CTAC) solution has been unequivocally demonstrated: free metalloporphyrin monomers or dimers (pH 9), metalloporphyrin monomers or aggregates (possibly micro-oxo dimers) bound to the micelles, and nonmicellar metalloporphyrin/surfactant aggregates. The surfactant:metalloporphyrin ratio for the maximum nonmicellar aggregate formation is around 5-8 for Fe(III)TPPS(4) both at pH 4.0 and 9.0; for Zn(II)TPPS(4) this ratio is 8, and the spectral changes are practically independent of pH. In the case of zwitterionic N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and non-ionic polyoxyethylene lauryl ether (Brij-35) and t-octylphenoxypolyethoxyetanol (Triton X-100), the nonmicellar aggregates were not observed in the pH range from 2.0 to 12.0. Binding constants were calculated from optical absorption data and are of the order of 10(4) M(-1) for both CTAC and HPS, values which are similar to those previously obtained for the porphyrin in the free base form. For Brij-35 and Triton X-100 the binding constant for ZnTPPS(4) at pH 4.0 is a factor of 3-5 lower than those for CTAC and HPS, while in the case of FeTPPS(4) they are two orders of magnitude lower. Our data show that solubilization of ZnTPPS(4) within nonpolar regions of micelles is determined, in general, by nonspecific hydrophobic interactions, yet it is modulated by electrostatic factors. In the case of FeTPPS(4), the electrostatic factor seems to be more relevant. NMR data indicated that Fe(III)TPPS(4) is bound to the micelles predominantly as a monomer at pH 4.0, and at pH 9.0 the bound aggregated form

  8. Effect of Nonionic Surfactants (Dodecyl Maltoside and Polysorbate 20) on Prevention of Aggregation and Conformational Changes of Recombinant Human IFNβ_1b Induced by Light

    PubMed Central

    Mahjoubi, Najmeh; Fazeli, Ahmad; Dinarvand, Rassoul; Khoshayand, Mohammad Reza; Shekarchi, Maryam; Fazeli, Mohammad Reza

    2017-01-01

    Liquid protein formulations are prone to form aggregates. The effect of nonionic surfactants such as Polysorbate 20 (PS 20) and n-Dodecyl β-D-maltoside (DDM) on the prevention of aggregation and conformational changes of recombinant human IFNβ-1b (rhIFN β_1b) was explored. Polysorbate has been used in formulations of protein pharmaceuticals. There have been concerns about using PS 20 due to its residual peroxide content which may negatively affect protein efficacy. n-Dodecyl β-D-maltoside has been of interest and shown to be highly effective in prevention of aggregation. Fresh bulk of rhIFN β_1b was formulated using DDM or different concentrations of PS 20. Formulations were exposed to light stress condition according to the ICH guideline of Q1b. The overall conformational integrity of individual samples was characterized by a combination of Circular dichroism (CD), Fluorescence spectroscopy and RP_HPLC techniques. The CD spectrum depicting the conformational integrity of rhIFN β_1b showed 31.9% and 31.2% decreases in α-helix content of protein samples with 0.2% or 0.02% of PS20 compared to only18.2% of that containing 0.2% DDM. The RP-HPLC analysis also showed that the oxidized impurity in formulation containing DDM is less than those contain PS 20. Complementary analysis of the liquid formulations using IFR and UV methods also was in compliance with the data obtained by CD. Compared to PS 20, the sample of rhIFN β_1b formulation with DDM was more resistant to the destruction effect of light. Results were in accordance with previous studies and could suggest DDM as a reliable anti-aggregation surfactant in biopharmaceutical formulations. PMID:28496465

  9. Effect of Nonionic Surfactants (Dodecyl Maltoside and Polysorbate 20) on Prevention of Aggregation and Conformational Changes of Recombinant Human IFNβ_1b Induced by Light.

    PubMed

    Mahjoubi, Najmeh; Fazeli, Ahmad; Dinarvand, Rassoul; Khoshayand, Mohammad Reza; Shekarchi, Maryam; Fazeli, Mohammad Reza

    2017-01-01

    Liquid protein formulations are prone to form aggregates. The effect of nonionic surfactants such as Polysorbate 20 (PS 20) and n-Dodecyl β-D-maltoside (DDM) on the prevention of aggregation and conformational changes of recombinant human IFNβ-1b (rhIFN β_1b) was explored. Polysorbate has been used in formulations of protein pharmaceuticals. There have been concerns about using PS 20 due to its residual peroxide content which may negatively affect protein efficacy. n-Dodecyl β-D-maltoside has been of interest and shown to be highly effective in prevention of aggregation. Fresh bulk of rhIFN β_1b was formulated using DDM or different concentrations of PS 20. Formulations were exposed to light stress condition according to the ICH guideline of Q1b. The overall conformational integrity of individual samples was characterized by a combination of Circular dichroism (CD), Fluorescence spectroscopy and RP_HPLC techniques. The CD spectrum depicting the conformational integrity of rhIFN β_1b showed 31.9% and 31.2% decreases in α-helix content of protein samples with 0.2% or 0.02% of PS20 compared to only18.2% of that containing 0.2% DDM. The RP-HPLC analysis also showed that the oxidized impurity in formulation containing DDM is less than those contain PS 20. Complementary analysis of the liquid formulations using IFR and UV methods also was in compliance with the data obtained by CD. Compared to PS 20, the sample of rhIFN β_1b formulation with DDM was more resistant to the destruction effect of light. Results were in accordance with previous studies and could suggest DDM as a reliable anti-aggregation surfactant in biopharmaceutical formulations.

  10. The Value Compressive Strength and Split Tensile Strength on Concrete Mixture With Expanded Polystyrene Coated by Surfactant Span 80 as a Partial Substitution of Fine Aggregate

    NASA Astrophysics Data System (ADS)

    Hidayat, Irpan; Siauwantara, Alice

    2014-03-01

    The value of the density normal concrete which ranges between 2200-2400 kg/m3. Therefore the use of Expanded Polystyrene (EPS) as a subitute to fine aggregate can reduce the density of concrete. The purpose this research is to reduce the density of normal concrete but increase compressive strength of EPS concrete, with use surfactant as coating for the EPS. Variables of substitution percentage of EPS and EPS coated by surfactant are 5%,10%,15%,20%,25%. Method of concrete mix design based on SNI 03-2834-2000 "Tata Cara Pembuatan Rencana Campuran Beton Normal (Provisions for Proportioning Normal Concrete Mixture)". The result of testing, every increase percentage of EPS substitution will decrease the compressive strength around 1,74 MPa and decrease density 34,03 kg/m3. Using Surfactant as coating of EPS , compressive strength increase from the EPS's compressive strength. Average of increasing compressive strength 0,19 MPa and increase the density 20,03 kg/m3,average decrease of the tensile split strength EPS coated surfaktan is 0,84 MPa.

  11. Using the giant Australian cuttlefish (Sepia apama) mass breeding aggregation to explore the life cycle of dicyemid parasites.

    PubMed

    Catalano, Sarah R; Whittington, Ian D; Donnellan, Stephen C; Gillanders, Bronwyn M

    2013-12-01

    Dicyemid mesozoan parasites, microscopic organisms found with high intensities in the renal appendages of benthic cephalopods, have a complex, partially unknown life cycle. It is uncertain at which host life cycle stage (i.e. eggs, juvenile, adult) new infection by the dispersive infusoriform embryo occurs. As adult cephalopods have a short lifespan and die shortly after reproducing only once, and juveniles are fast-moving, we hypothesize that the eggs are the life cycle stage where new infection occurs. Eggs are abundant and sessile, allowing a huge number of new individuals to be infected with low energy costs, and they also provide dicyemids with the maximum amount of time for survival compared with infection of juvenile and adult stages. In our study we collected giant Australian cuttlefish (Sepia apama) eggs at different stages of development and filtered seawater samples from the S. apama mass breeding aggregation area in South Australia, Australia, and tested these samples for the presence of dicyemid DNA. We did not recover dicyemid parasite cytochrome c oxidase subunit I (COI) nucleotide sequences from any of the samples, suggesting eggs are not the stage where new infection occurs. To resolve this unknown in the dicyemid life cycle, we believe experimental infection is needed.

  12. Diarmed (adamantyl/alkyl) surfactants from nitrilotriacetic acid.

    PubMed

    Trillo, Juan V; Vázquez Tato, José; Jover, Aida; de Frutos, Santiago; Soto, Victor H; Galantini, Luciano; Meijide, Francisco

    2014-11-01

    The compounds presented here constitute a clear example of molecular biomimetics as their design is inspired on the structure and properties of natural phospholipids. Thus novel double-armed surfactants have been obtained in which nitrilotriacetic acid plays the role of glycerol in phospholipids. The hydrophobic arms are linked to the head group through amide bonds (which is also the case of sphingomyelin): (R1NHCOCH2)(R2NHCOCH2)NCH2CO2H (R1 being CH3(CH2)11, CH3(CH2)17, CH3(CH2)7CHCH(CH2)8, and adamantyl, and R2=adamantyl). The dependence of the surface tension with concentration shows the typical profile of surfactants since a breaking point, which corresponds to the critical aggregation concentration (cac), is observed in all cases. The cac of these diarmed derivatives are about 1-3 orders of magnitude lower than those of classical monoalkyl derivatives used as reference compounds. In contrast to conventional surfactants, reversed trends in cac values and molecular areas at the solution-air interface have been observed. This anomalous behavior is tied to the structure of the surfactants and suggests that long and flexible alkyl chains should self-coil previous to the aggregation or adsorption phenomena. Above cac all compounds form large aggregates, globular in shape, which tend to associate forming giant aggregates.

  13. Effect of self-association of bovine serum albumin on the stability of surfactant-induced aggregates of allylamine-capped silicon quantum dots.

    PubMed

    Chatterjee, Surajit; Mukherjee, Tushar Kanti

    2013-12-19

    The concentration-dependent self-association of bovine serum albumin (BSA) and subsequent altered interaction with sodium dodecyl sulfate (SDS) has been explored by means of photoluminescence (PL) spectroscopy, dynamic light scattering (DLS), circular dichroism (CD), PL imaging, and atomic force microscopy (AFM). By using an extrinsic luminescent probe, allylamine-capped silicon quantum dots (Si-QDs), we have demonstrated the unusual concentration-dependent altered BSA-SDS interaction. Allylamine-capped Si-QDs forms ordered aggregates in the presence of 1 mM SDS due to hydrogen bonding with the surfactants head groups at pH 7.4. Although these aggregates remain stable in the presence of monomeric BSA in the concentration range 1-8 μM, they form typical ring-shaped doughnut-like structures due to "necklace and bead"-like complex formation. However, beyond 10 μM BSA, these aggregates of Si-QDs slowly dissociate and complete dissociation occurs at 150 μM BSA. These anomalous results have been explained by considering the altered hydrophilicity of self-associated BSA.

  14. Surfactant adsorption and aggregate structure of silica nanoparticles: a versatile stratagem for the regulation of particle size and surface modification

    NASA Astrophysics Data System (ADS)

    Chaudhary, Savita; Rohilla, Deepak; Mehta, S. K.

    2014-03-01

    The area of silica nanoparticles is incredibly polygonal. Silica particles have aroused exceptional deliberation in bio-analysis due to great progress in particular arenas, for instance, biocompatibility, unique properties of modifiable pore size and organization, huge facade areas and pore volumes, manageable morphology and amendable surfaces, elevated chemical and thermal stability. Currently, silica nanoparticles participate in crucial utilities in daily trade rationales such as power storage, chemical and genetic sensors, groceries dispensation and catalysis. Herein, the size-dependent interfacial relation of anionic silica nanoparticles with twelve altered categories of cationic surfactants has been carried out in terms of the physical chemical facets of colloid and interface science. The current analysis endeavours to investigate the virtual consequences of different surfactants through the development of the objective composite materials. The nanoparticle size controls, the surface-to-volume ratio and surface bend relating to its interaction with surfactant will also be addressed in this work. More importantly, the simulated stratagem developed in this work can be lengthened to formulate core-shell nanostructures with functional nanoparticles encapsulated in silica particles, making this approach valuable and extensively pertinent for employing sophisticated materials for catalysis and drug delivery.

  15. Ultra-broad polypyrrole (PPy) nano-ribbons seeded by racemic surfactants aggregates and their high-performance electromagnetic radiation elimination.

    PubMed

    Jiao, Yingzhi; Wu, Fan; Zhang, Kun; Sun, Mengxiao; Xie, Aming; Dong, Wei

    2017-08-04

    Ribbon-like nano-structures possess high aspect ratios, and thus have great potential in the development of high-performance microwave absorption (MA) materials that can effectively eliminate adverse electromagnetic radiation. However, these nano-structures have been scarcely constructed in the field of MA, because of the lack of efficient synthetic routes. Herein, we developed an efficient method to successfully construct polypyrrole (PPy) nano-ribbons using the self-assembly aggregates of a racemic surfactant as the seeds. The frequency range with a reflection loss value of lower than -10 dB reached 7.68 GHz in the frequency range of 10.32-18.00 GHz, and surpassed all the currently reported PPy nano-structures, as well as most other MA nano-materials. Through changing the amount of surfactant, both the nano-structures and MA performance can be effectively regulated. Furthermore, the reason behind the high-performance MA of PPy nano-ribbons has been deeply explored. It opens up the opportunity for the application of conducting polymer nano-ribbons as a lightweight and tunable high-performance MA material, especially in applications of special aircraft and flexible electronics.

  16. Ultra-broad polypyrrole (PPy) nano-ribbons seeded by racemic surfactants aggregates and their high-performance electromagnetic radiation elimination

    NASA Astrophysics Data System (ADS)

    Jiao, Yingzhi; Wu, Fan; Zhang, Kun; Sun, Mengxiao; Xie, Aming; Dong, Wei

    2017-08-01

    Ribbon-like nano-structures possess high aspect ratios, and thus have great potential in the development of high-performance microwave absorption (MA) materials that can effectively eliminate adverse electromagnetic radiation. However, these nano-structures have been scarcely constructed in the field of MA, because of the lack of efficient synthetic routes. Herein, we developed an efficient method to successfully construct polypyrrole (PPy) nano-ribbons using the self-assembly aggregates of a racemic surfactant as the seeds. The frequency range with a reflection loss value of lower than -10 dB reached 7.68 GHz in the frequency range of 10.32-18.00 GHz, and surpassed all the currently reported PPy nano-structures, as well as most other MA nano-materials. Through changing the amount of surfactant, both the nano-structures and MA performance can be effectively regulated. Furthermore, the reason behind the high-performance MA of PPy nano-ribbons has been deeply explored. It opens up the opportunity for the application of conducting polymer nano-ribbons as a lightweight and tunable high-performance MA material, especially in applications of special aircraft and flexible electronics.

  17. Surfactant anchoring and aggregate structure at silica nanoparticles: a persuasive facade for the adsorption of azo dye.

    PubMed

    Chaudhary, Savita; Sood, Aastha; Mehta, S K

    2014-09-01

    Nanotechnology's aptitude to silhouette matter at the scale of the nanometer has unlocked the flap to new inventions of applications in material science and nanomedicine. Engineered silica nanoparticles are key actor of this strategy. The amphitheatre of silica nanoparticles is inexplicably bilateral. Silica particles play essential function in everyday commercial purposes for instance energy storage, chemical and biological sensors, food processing and catalysis. One of the most appealing applications to emerge in the recent years is the use of silica particles for cleaning up contaminants in groundwater, soil and sediments. Herein this work, surfactant modified silica nanoparticles with unique surface and pore properties as well as high surface areas have been extensively investigated as an alternative for the dye removal. The physical and chemical characterizations of adsorbent have been studied using FTIR and scanning electron microscopy. The present investigation aims to explore the comparative effect of different surfactants during the formation of the target composite materials. The effects of various parameters like pH, adsorbent doses, dye concentration, addition of salt have also been investigated. These findings indicate that the nano silica particles are effective materials for dye removal and can be used to alleviate environmental problems.

  18. Molecular Aggregates in Stable Aqueous Three-Phase Surfactant Systems and Their use in Producing CdS Nanowires

    PubMed Central

    Dong, Renhao; Zhou, Liang; Wang, Dong; Hao, Jingcheng

    2013-01-01

    Aqueous three-phase surfactant systems (A3PS) are important, multicomponent, stable three-phase equilibria with coexisting forms in a common colloid solution, but have been largely ignored regarding further characterization and application. Mixing simple, commercially available, single-tailed anionic/nonionic or anionic/cationic surfactants in water can spontaneously produce stable A3PS with coexisting multiscale self-assembled structures including discs, lamellas, micelles and vesicles. As with conventional aqueous two-phase systems (A2PS), A3PS can be applied in partition and extraction processes. Here, the A3PS was also used as a mild media for one-step synthesis of multiscale CdS nanowires. Particularly, the A3PS does not change and simultaneously separates the CdS nanowires with the comparable size in one phase, which provides a facile strategy for collection of monodisperse nanomaterials. We expect that this present work can expand recognition of A3PS for use in theoretical and applied studies. PMID:23588712

  19. Molecular aggregates in stable aqueous three-phase surfactant systems and their use in producing CdS nanowires.

    PubMed

    Dong, Renhao; Zhou, Liang; Wang, Dong; Hao, Jingcheng

    2013-01-01

    Aqueous three-phase surfactant systems (A3PS) are important, multicomponent, stable three-phase equilibria with coexisting forms in a common colloid solution, but have been largely ignored regarding further characterization and application. Mixing simple, commercially available, single-tailed anionic/nonionic or anionic/cationic surfactants in water can spontaneously produce stable A3PS with coexisting multiscale self-assembled structures including discs, lamellas, micelles and vesicles. As with conventional aqueous two-phase systems (A2PS), A3PS can be applied in partition and extraction processes. Here, the A3PS was also used as a mild media for one-step synthesis of multiscale CdS nanowires. Particularly, the A3PS does not change and simultaneously separates the CdS nanowires with the comparable size in one phase, which provides a facile strategy for collection of monodisperse nanomaterials. We expect that this present work can expand recognition of A3PS for use in theoretical and applied studies.

  20. "Giant surfactants" created by the fast and efficient functionalization of a DNA tetrahedron with a temperature-responsive polymer.

    PubMed

    Wilks, Thomas R; Bath, Jonathan; de Vries, Jan Willem; Raymond, Jeffery E; Herrmann, Andreas; Turberfield, Andrew J; O'Reilly, Rachel K

    2013-10-22

    Copper catalyzed azide-alkyne cycloaddition (CuAAC) was employed to synthesize DNA block copolymers (DBCs) with a range of polymer blocks including temperature-responsive poly(N-isoproylacrylamide) (poly(NIPAM)) and highly hydrophobic poly(styrene). Exceptionally high yields were achieved at low DNA concentrations, in organic solvents, and in the absence of any solid support. The DNA segment of the DBC remained capable of sequence-specific hybridization: it was used to assemble a precisely defined nanostructure, a DNA tetrahedron, with pendant poly(NIPAM) segments. In the presence of an excess of poly(NIPAM) homopolymer, the tetrahedron-poly(NIPAM) conjugate nucleated the formation of large, well-defined nanoparticles at 40 °C, a temperature at which the homopolymer precipitated from solution. These composite nanoparticles were observed by dynamic light scattering and cryoTEM, and their hybrid nature was confirmed by AFM imaging. As a result of the large effective surface area of the tetrahedron, only very low concentrations of the conjugate were required in order for this surfactant-like behavior to be observed.

  1. An investigation of dynamic surface tension, critical micelle concentration, and aggregation number of three nonionic surfactants using NMR, time-resolved fluorescence quenching, and maximum bubble pressure tensiometry.

    PubMed

    Kjellin, U R Mikael; Reimer, Johan; Hansson, Per

    2003-06-15

    Several physicochemical properties have been determined for N-dodecyllactobionamide (LABA), maltose 6'-O-dodecanoate (C12-maltose ester), and tetra(ethylene oxide) dodecyl amide (TEDAd). The increase in the flexibility of the sugar headgroup, enabling more possible molecular conformations, reduces the minimum area/molecule at the liquid-vapor interface obtained at the critical micelle concentration (cmc). The obtained cmc's were 0.35 mM (LABA), 0.3 mM (C12-maltose ester), and 0.5 mM (TEDAd). The monomer diffusion coefficient decreased with the molecular weight and increasing headgroup flexibility of the sugar headgroup, and values were in the range from 3.1 x 10(-10) to 3.6 x 10(-10) m2/s. The micelle diffusion coefficients (0.46 x 10(-10) to 0.68 x 10(-10) m2/s) indicated that the TEDAd micelles deviated most from spherical shape. The micelle aggregation numbers determined by time-resolved fluorescence quenching (TRFQ) were estimated to be 120+/-10 (LABA), 90+/-10 (C12-maltose ester), and 130+/-10 (TEDAd). The dynamic surface tension measurements show that the adsorption of TEDAd onto the liquid-vapor interface at short surface lifetimes is diffusion-limited, whereas an adsorption barrier is present for the sugar surfactants. The analysis of the dynamic surface tension data above the cmc shows that the rate of demicellization is faster for TEDAd than for the two sugar-based surfactants.

  2. Time resolved study of three ruthenium(II) complexes at micellar surfaces: A new long excited state lifetime probe for determining critical micelle concentration of surfactant nano-aggregates.

    PubMed

    Patra, Digambara; Chaaban, Ahmad H; Darwish, Shaza; Saad, Huda A; Nehme, Ali S; Ghaddar, Tarek H

    2016-02-01

    Three different ruthenium complexes have been synthesized and their luminescence properties in different solvent environments are reported. Luminescence intensities and excited state lifetimes of Ru-I, Ru-II and Ru-III vary with solvent viscosity. The excited state lifetime of Ru-I linearly increases in the viscosity range 1.76-12,100cP. Ru-II shows two linear increases: one in the low and another in the high viscosity ranges, whereas Ru-III illustrates a linear enhancement only in the low viscosity range. Interestingly, luminescence intensities and excited state lifetimes of Ru-I, Ru-II and Ru-III are found to be sensitive to nano-aggregation. However, the surfactant head charge and that of the ruthenium center as well as the hydrophobic tail of the ancillary ligand of the complexes have a great role in deciding the nature of the interaction and on the excited state properties at micellar surfaces. It is proposed that the long lifetime of Ru-III in water could be due to the coiling of the carbon chain of the ancillary ligand around the ruthenium center. At micelle surface, this coiling of the carbon chain is lost due to the parallel alignment with surfactants and thus quenching of the excited state lifetime is seen. Furthermore, it is shown that the variation of the excited state lifetime with respect to the change in surfactant concentration is a result of the formation of micelles from the surfactant monomer, thus, a novel technique for the determination of the critical micelle concentration (cmc) based on the long excited state lifetime of Ru-III located at the micellar nano-aggregates is reported. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Structural Studies of Protein-Surfactant Complexes

    SciTech Connect

    Chodankar, S. N.; Aswal, V. K.; Wagh, A. G.

    2008-03-17

    The structure of protein-surfactant complexes of two proteins bovine serum albumin (BSA) and lysozyme in presence of anionic surfactant sodium dodecyl sulfate (SDS) has been studied using small-angle neutron scattering (SANS). It is observed that these two proteins form different complex structures with the surfactant. While BSA protein undergoes unfolding on addition of surfactant, lysozyme does not show any unfolding even up to very high surfactant concentrations. The unfolding of BSA protein is caused by micelle-like aggregation of surfactant molecules in the complex. On the other hand, for lysozyme protein there is only binding of individual surfactant molecules to protein. Lysozyme in presence of higher surfactant concentrations has protein-surfactant complex structure coexisting with pure surfactant micelles.

  4. Giant dielectric anisotropy and relaxor ferroelectricity induced by proton transfers in NH+...N-bonded supramolecular aggregates.

    PubMed

    Szafrański, Marek; Katrusiak, Andrzej

    2008-06-05

    A huge dielectric effect has been observed in a pure and water-soluble hydrogen-bonded organic crystal, 1,4-diazabicyclo[2.2.2]octane hydroiodide [C6H13N2]+.I(-) (dabcoHI). In this structure, the dabco cations are NH+...N bonded into linear aggregates, where the protons are disordered at two nitrogen atoms and the crystal acquires the symmetry of space group P6m2. This nonpolar crystal exhibits a barely temperature-dependent dielectric constant exceeding 1000 at ambient conditions. The dielectric response is extremely anisotropic, more than 2 orders of magnitude higher along the linear hydrogen bonded chains than in perpendicular directions. The physics underlying this effect originates from proton transfers in the NH+...N bonds, leading to disproportionation defects and formation of polar nanodomains, which, on the macroscopic scale, results in one-dimensional relaxor ferroelectricity. Such properties are unprecedented for the materials with hydrogen bonds highly polarizable due to proton disorder. The proton disordering in dabcoHI is analogous to this in H2O ice, where the hydrogen bonds remain disordered until the lowest temperature.

  5. Catalysis by enzymes entrapped into hydrated surfactant aggregates having lamellar or cylindrical (hexagonal) or ball-shaped (cubic) structure in organic solvents.

    PubMed

    Klyachko, N L; Levashov, A V; Pshezhetsky, A V; Bogdanova, N G; Berezin, I V; Martinek, K

    1986-11-17

    Instead of aqueous solutions, universally recognized in enzymology, ternary systems of the water/organic solvent/surfactant type are suggested as liquid-crystalline media for enzymatic reactions. Two systems, water/octane/Aerosol OT and water/cyclohexane/Brij 96, have been used to solubilize acid and alkaline phosphatases and peroxidase. The enzymes under study do function in liquid-crystalline mesophases having lamellar, cylindrical (reversed hexagonal) and ball-shaped (reversed cubic) packing of the surfactant molecules. A significant result is that the phase transition from one liquid-crystalline structure to another entails, as a rule, a reversible change in the catalytic activity of the solubilized enzyme.

  6. Effect of the surfactant Tween 80 on the detachment and dispersal of Salmonella enterica Thompson single cells and aggregates from cilantro leaves as revealed by image analysis

    USDA-ARS?s Scientific Manuscript database

    Biofilms formed by human enteric pathogens on plants are a great concern to the produce industry. Salmonella enterica has the ability to form biofilms and large aggregates on leaf surfaces, including on cilantro leaves. Aggregates that remained attached after rigorous washing of cilantro leaves and ...

  7. Ionic liquids as surfactants

    NASA Astrophysics Data System (ADS)

    Smirnova, N. A.; Safonova, E. A.

    2010-10-01

    Problems of self-assembling in systems containing ionic liquids (ILs) are discussed. Main attention is paid to micellization in aqueous solutions of dialkylimidazolium ILs and their mixtures with classical surfactants. Literature data are reviewed, the results obtained by the authors and co-workers are presented. Thermodynamic aspects of the studies and problems of molecular-thermodynamic modeling receive special emphasis. It is shown that the aggregation behavior of dialkylimidazolium ILs is close to that of alkyltrimethylammonium salts (cationic surfactants) though ILs have a higher ability to self-organize, especially as it concerns long-range ordering. Some aspects of ILs applications are outlined where their common features with classical surfactants and definite specificity are of value.

  8. Lung surfactant.

    PubMed Central

    Rooney, S A

    1984-01-01

    Aspects of pulmonary surfactant are reviewed from a biochemical perspective. The major emphasis is on the lipid components of surfactant. Topics reviewed include surfactant composition, cellular and subcellular sites as well as pathways of biosynthesis of phosphatidylcholine, disaturated phosphatidylcholine and phosphatidylglycerol. The surfactant system in the developing fetus and neonate is considered in terms of phospholipid content and composition, rates of precursor incorporation, activities of individual enzymes of phospholipid synthesis and glycogen content and metabolism. The influence of the following hormones and other factors on lung maturation and surfactant production is discussed: glucocorticoids, thyroid hormone, estrogen, prolactin, cyclic AMP, beta-adrenergic and cholinergic agonists, prostaglandins and growth factors. The influence of maternal diabetes, fetal sex, stress and labor are also considered. Nonphysiologic and toxic agents which influence surfactant in the fetus, newborn and adult are reviewed. PMID:6145585

  9. Kinetic study of aggregation of milk protein and/or surfactant-stabilized oil-in-water emulsions by sedimentation field-flow fractionation.

    PubMed

    Kenta, Stella; Raikos, Vassilios; Vagena, Artemis; Sevastos, Dimitrios; Kapolos, John; Koliadima, Athanasia; Karaiskakis, George

    2013-08-30

    Milk proteins are able to facilitate the formation and stabilization of oil droplets in food emulsions. This study employed Sedimentation Field-Flow Fractionation (SdFFF) to monitor changes in particle size distribution of freshly prepared emulsions with varying weight contributions of sodium caseinate (SC) and whey protein concentrate (WPC). The effect of the addition of Tween 80 (T) on the initial droplet size was also investigated. The results indicated that emulsifying ability follows the order Tween 80>WPC>SC, with corresponding weight average droplet diameter of 0.319, 0.487 and 0.531μm respectively, when each of the above emulsifiers was used solely. The stability of sodium caseinate emulsions was studied at 30.5 and 80.0°C by measuring the particle size distribution for a period of 70h. Emulsions withstood the temperatures and exhibited an initial increase in particle size distribution caused by heat-induced droplet aggregation, followed by a decrease to approximately the initial droplet size. The rate of droplet aggregation depends on the severity of thermal processing, as revealed by the kinetics of particle aggregation during aging at different temperatures. Comparison of the experimental rate constants found from SdFFF, with those determined theoretically gives invaluable information about the oil droplet stability and the aggregation mechanism. Based on the proposed mechanistic scheme various physicochemical quantities, which are very important in explaining the stability of oil-in-water emulsions, were determined. Finally, the advantages of SdFFF in studying the aggregation of the oil-in-water droplets, in comparison with other methods used for the same purpose, are discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Filling the gap between the quantum and classical worlds of nanoscale magnetism: giant molecular aggregates based on paramagnetic 3d metal ions.

    PubMed

    Papatriantafyllopoulou, Constantina; Moushi, Eleni E; Christou, George; Tasiopoulos, Anastasios J

    2016-03-21

    In this review, aspects of the syntheses, structures and magnetic properties of giant 3d and 3d/4f paramagnetic metal clusters in moderate oxidation states are discussed. The term "giant clusters" is used herein to denote metal clusters with nuclearity of 30 or greater. Many synthetic strategies towards such species have been developed and are discussed in this paper. Attempts are made to categorize some of the most successful methods to giant clusters, but it will be pointed out that the characteristics of the crystal structures of such compounds including nuclearity, shape, architecture, etc. are unpredictable depending on the specific structural features of the included organic ligands, reaction conditions and other factors. The majority of the described compounds in this review are of special interest not only for their fascinating nanosized structures but also because they sometimes display interesting magnetic phenomena, such as ferromagnetic exchange interactions, large ground state spin values, single-molecule magnetism behaviour or impressively large magnetocaloric effects. In addition, they often possess the properties of both the quantum and the classical world, and thus their systematic study offers the potential for the discovery of new physical phenomena, as well as a better understanding of the existing ones. The research field of giant clusters is under continuous evolution and their intriguing structural characteristics and magnetism properties that attract the interest of synthetic Inorganic Chemists promise a brilliant future for this class of compounds.

  11. Vesicle aggregates as a model for primitive cellular assemblies.

    PubMed

    de Souza, Tereza Pereira; Bossa, Guilherme Volpe; Stano, Pasquale; Steiniger, Frank; May, Sylvio; Luisi, Pier Luigi; Fahr, Alfred

    2017-08-02

    Primitive cell models help to understand the role that compartmentalization plays in origin of life scenarios. Here we present a combined experimental and modeling approach towards the construction of simple model systems for primitive cellular assemblies. Charged lipid vesicles aggregate in the presence of oppositely charged biopolymers, such as nucleic acids or polypeptides. Based on zeta potential measurements, dynamic light scattering and cryo-transmission electron-microscopy, we have characterized the behavior of empty and ferritin-filled large unilamellar POPC vesicles, doped with different amounts of cationic (DDAB, CTAB) and anionic (sodium oleate) surfactants, and their aggregation upon the addition of anionic (tRNA, poly-l-glutamic acid) and cationic (poly-l-arginine) biopolymers, respectively. The experimental results are rationalized by a phenomenological modeling approach that predicts the average size of the vesicle aggregates as function of the amount of added biopolymers. In addition, we discuss the mechanism of vesicle aggregation induced by oppositely charged biopolymers. Our study complements previous reports about the formation of giant vesicle clusters and thus provides a general vista on primitive cell systems, based on the association of vesicles into compartmentalized aggregates.

  12. Compartmentalization of amino acids in surfactant aggregates - Partitioning between water and aqueous micellar sodium dodecanoate and between hexane and dodecylammonium propionate trapped water in hexane

    NASA Technical Reports Server (NTRS)

    Fendler, J. H.; Nome, F.; Nagyvary, J.

    1975-01-01

    The partitioning of amino acids (glycine, alanine, leucine, phenylalanine, histidine, aspartic acid, glutamic acid, lysine, isoleucine, threonine, serine, valine, proline, arginine) in aqueous and nonaqueous micellar systems was studied experimentally. Partitioning from neat hexane into dodecylammonium propionate trapped water in hexane was found to be dependent on both electrostatic and hydrophobic interactions, which implies that the interior of dodecylammonium propionate aggregates is negatively charged and is capable of hydrogen bonding in addition to providing a hydrophobic environment. Unitary free energies of transfer of amino acid side chains from hexane to water were determined and solubilities of amino acids in neat hexane substantiated the amino acid hydrophobicity scale. The relevance of the experiments to prebiotic chemistry was examined.

  13. Compartmentalization of amino acids in surfactant aggregates - Partitioning between water and aqueous micellar sodium dodecanoate and between hexane and dodecylammonium propionate trapped water in hexane

    NASA Technical Reports Server (NTRS)

    Fendler, J. H.; Nome, F.; Nagyvary, J.

    1975-01-01

    The partitioning of amino acids (glycine, alanine, leucine, phenylalanine, histidine, aspartic acid, glutamic acid, lysine, isoleucine, threonine, serine, valine, proline, arginine) in aqueous and nonaqueous micellar systems was studied experimentally. Partitioning from neat hexane into dodecylammonium propionate trapped water in hexane was found to be dependent on both electrostatic and hydrophobic interactions, which implies that the interior of dodecylammonium propionate aggregates is negatively charged and is capable of hydrogen bonding in addition to providing a hydrophobic environment. Unitary free energies of transfer of amino acid side chains from hexane to water were determined and solubilities of amino acids in neat hexane substantiated the amino acid hydrophobicity scale. The relevance of the experiments to prebiotic chemistry was examined.

  14. Microstructure of Mixed Surfactant Solutions by Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Naranjo, Edward

    1995-01-01

    Surfactant mixtures add a new dimension to the design of complex fluid microstructure. By combining different surfactants it is not only possible to modify aggregate morphology and control the macrascopic properties of colloidal dispersions but also to produce a variety of novel synergistic phases. Mixed systems produce new microstructures by altering the intermolecular and interaggregate forces in ways impossible for single component systems. In this dissertation, we report on the phase behavior and microstructure of several synthetic and biological surfactant mixtures as elucidated by freeze-fracture and cryo-transmission electron microscopy. We have discovered that stable, spontaneous unilamellar vesicles can be prepared from aqueous mixtures of commercially available single-tailed cationic and anionic surfactants. Vesicle stability is determined by the length and volume of the hydrocarbon chains of the "catanionic" pairs. Mixtures containing bulky or branched surfactant pairs (C _{16}/C_{12 -14}) in water produce defect-free fairly monodisperse equilibrium vesicles at high dilution. In contrast, mixtures of catanionic surfactants with highly asymmetric tails (C_{16}/C_8 ) form phases of porous vesicles, dilute lamellar L_{alpha}, and anomalous isotropic L_3 phases. Images of the microstructure by freeze-fracture microscopy show that the L_3 phase consists of multiconnected self-avoiding bilayers with saddle shaped curvature. The forces between bilayers of vesicle-forming cationic and anionic surfactant mixtures were also measured using the Surface Force Apparatus (SFA). We find that the vesicles are stabilized by a long range electrostatic repulsion at large separations (>20 A) and an additional salt-independent repulsive force below 20 A. The measured forces correlate very well with the ternary phase diagram and the vesicle microstructures observed by electron microscopy. In addition to studying ionic surfactants, we have also done original work with

  15. Solubilization and biodegradation of hydrophobic organic compounds in soil/aqueous systems with nonionic surfactants

    SciTech Connect

    Edwards, D.A.; Laha, S.; Liu, Zhongbao; Luthy, R.G.

    1992-01-01

    Nonionic surfactants may strongly interact with hydrophobic organic compounds (HOCs), soil, and microorganisms in soil/aqueous systems. These interactions affect the potential for surfactant-facilitated HOC transport in soil and groundwater systems, and the feasibility of engineered surfactant cleanup of contaminated sites (McCarthy and Wober, 1991). At sufficiently high bulk liquid concentrations at 25 C, most nonionic surfactants form regular micelles in single-phase solutions, whereas certain surfactants, such as C{sub 12}E{sub 4}, may form bilayer lamellae or other types of aggregates in more complex two-phase solutions. The critical concentrations for the onset of micelle and aggregate formation are termed the critical micelle concentration (CMC) and the critical aggregation concentration (CAC), respectively. Important changes occur in surfactant sorption, surfactant solubilization of HOCs, and microbial mineralization of HOCs in the presence of nonionic surfactants at or near these critical surfactant concentrations.

  16. Solubilization and biodegradation of hydrophobic organic compounds in soil/aqueous systems with nonionic surfactants

    SciTech Connect

    Edwards, D.A.; Laha, S.; Liu, Zhongbao; Luthy, R.G.

    1992-05-01

    Nonionic surfactants may strongly interact with hydrophobic organic compounds (HOCs), soil, and microorganisms in soil/aqueous systems. These interactions affect the potential for surfactant-facilitated HOC transport in soil and groundwater systems, and the feasibility of engineered surfactant cleanup of contaminated sites (McCarthy and Wober, 1991). At sufficiently high bulk liquid concentrations at 25 C, most nonionic surfactants form regular micelles in single-phase solutions, whereas certain surfactants, such as C{sub 12}E{sub 4}, may form bilayer lamellae or other types of aggregates in more complex two-phase solutions. The critical concentrations for the onset of micelle and aggregate formation are termed the critical micelle concentration (CMC) and the critical aggregation concentration (CAC), respectively. Important changes occur in surfactant sorption, surfactant solubilization of HOCs, and microbial mineralization of HOCs in the presence of nonionic surfactants at or near these critical surfactant concentrations.

  17. Molecular origins of surfactant-mediated stabilization of protein drugs.

    PubMed

    Lee, Hyo Jin; McAuley, Arnold; Schilke, Karl F; McGuire, Joseph

    2011-10-01

    Loss of activity through aggregation and surface-induced denaturation is a significant problem in the production, formulation and administration of therapeutic proteins. Surfactants are commonly used in upstream and downstream processing and drug formulation. However, the effectiveness of a surfactant strongly depends on its mechanism(s) of action and properties of the protein and interfaces. Surfactants can modulate adsorption loss and aggregation by coating interfaces and/or participating in protein-surfactant associations. Minimizing protein loss from colloidal and interfacial interaction requires a fundamental understanding of the molecular factors underlying surfactant effectiveness and mechanism. These concepts provide direction for improvements in the manufacture and finishing of therapeutic proteins. We summarize the roles of surfactants, proteins, and surfactant-protein complexes in modulating interfacial behavior and aggregation. These events depend on surfactant properties that may be quantified using a thermodynamic model, to provide physical/chemical direction for surfactant selection or design, and to effectively reduce aggregation and adsorption loss. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Surfactant-enhanced cellulose nanocrystal Pickering emulsions.

    PubMed

    Hu, Zhen; Ballinger, Sarah; Pelton, Robert; Cranston, Emily D

    2015-02-01

    The effect of surfactants on the properties of Pickering emulsions stabilized by cellulose nanocrystals (CNCs) was investigated. Electrophoretic mobility, interfacial tension, confocal microscopy and three-phase contact angle measurements were used to elucidate the interactions between anionic CNCs and cationic alkyl ammonium surfactants didecyldimethylammonium bromide (DMAB) and cetyltrimethylammonium bromide (CTAB). Both surfactants were found to adsorb onto CNCs with concentration-dependent morphology. At low concentrations, individual surfactant molecules adsorbed with alkyl tails pointing outward leading to hydrophobic CNCs. At higher concentrations, above the surfactant's apparent critical micelle concentration, surfactant aggregate morphologies on CNCs were inferred and the hydrophobicity of CNCs decreased. DMAB, which has two alkyl tails, rendered the CNCs more hydrophobic than CTAB which has only a single alkyl tail, at all surfactant concentrations. The change in CNC wettability from surfactant adsorption was directly linked to emulsion properties; adding surfactant increased the emulsion stability, decreased the droplet size, and controlled the internal phase of CNC Pickering emulsions. More specifically, a double transitional phase inversion, from oil-in-water to water-in-oil and back to oil-in-water, was observed for emulsions with CNCs and increasing amounts of DMAB (the more hydrophobic surfactant). With CNCs and CTAB, no phase inversion was induced. This work represents the first report of CNC Pickering emulsions with surfactants as well as the first CNC Pickering emulsions that can be phase inverted. The ability to surface modify CNCs in situ and tailor emulsions by adding surfactants may extend the potential of CNCs to new liquid formulations and extruded/spray-dried materials.

  19. Gemini surfactants from natural amino acids.

    PubMed

    Pérez, Lourdes; Pinazo, Aurora; Pons, Ramon; Infante, Mrosa

    2014-03-01

    In this review, we report the most important contributions in the structure, synthesis, physicochemical (surface adsorption, aggregation and phase behaviour) and biological properties (toxicity, antimicrobial activity and biodegradation) of Gemini natural amino acid-based surfactants, and some potential applications, with an emphasis on the use of these surfactants as non-viral delivery system agents. Gemini surfactants derived from basic (Arg, Lys), neutral (Ser, Ala, Sar), acid (Asp) and sulphur containing amino acids (Cys) as polar head groups, and Geminis with amino acids/peptides in the spacer chain are reviewed.

  20. Surfactant compositions

    SciTech Connect

    Novakovic, M.; Abend, P.G.

    1987-09-29

    A surfactant composition is described for subsequent addition to a soap slurring comprising an acyloxy alkane sulfonate salt. The sulfonate salt is present in an amount by weight of about 44 percent of about 56 percent. The polyol is present in an amount by weight of about 2 percent to about 6 percent, and water is present in an amount by weight of 26 to 36 percent. The composition constituting a solid reversible solution at ambient temperature and having a solids content of about 58 to 72 percent, whereby subsequent addition of the surfactant composition to a soap slurry results in formation of a soap/detergent bar having a smooth texture, uniform wear properties and a lack of grittiness.

  1. Biomimicry of surfactant protein C.

    PubMed

    Brown, Nathan J; Johansson, Jan; Barron, Annelise E

    2008-10-01

    Since the widespread use of exogenous lung surfactant to treat neonatal respiratory distress syndrome, premature infant survival and respiratory morbidity have dramatically improved. Despite the effectiveness of the animal-derived surfactant preparations, there still remain some concerns and difficulties associated with their use. This has prompted investigation into the creation of synthetic surfactant preparations. However, to date, no clinically used synthetic formulation is as effective as the natural material. This is largely because the previous synthetic formulations lacked analogues of the hydrophobic proteins of the lung surfactant system, SP-B and SP-C, which are critical functional constituents. As a result, recent investigation has turned toward the development of a new generation of synthetic, biomimetic surfactants that contain synthetic phospholipids along with a mimic of the hydrophobic protein portion of lung surfactant. In this Account, we detail our efforts in creating accurate mimics of SP-C for use in a synthetic surfactant replacement therapy. Despite SP-C's seemingly simple structure, the predominantly helical protein is extraordinarily challenging to work with given its extreme hydrophobicity and structural instability, which greatly complicates the creation of an effective SP-C analogue. Drawing inspiration from Nature, two promising biomimetic approaches have led to the creation of rationally designed biopolymers that recapitulate many of SP-C's molecular features. The first approach utilizes detailed SP-C structure-activity relationships and amino acid folding propensities to create a peptide-based analogue, SP-C33. In SP-C33, the problematic and metastable polyvaline helix is replaced with a structurally stable polyleucine helix and includes a well-placed positive charge to prevent aggregation. SP-C33 is structurally stable and eliminates the association propensity of the native protein. The second approach follows the same design

  2. Immunogenicity of surfactant. I. Human alveolar surfactant.

    PubMed Central

    Strayer, D S; Hallman, M; Merritt, T A

    1991-01-01

    The immunogenicity of lung surfactant derived from amniotic fluid has been well established. We have set out to examine the antigenic similarity of human surfactant to non-human alveolar surfactants currently being used therapeutically in clinical trials with neonatal respiratory distress syndrome. To this end, we raised a series of eight monoclonal antibodies in rats directed to human surfactant (H1 to H8). All antibodies bound human surfactant as measured by ELISA. Four of these monoclonal antibodies bound surfactant components by Western blot analysis: all bound a 9-10-kD species. In addition, one antibody (H2) bound a protein of 16 kD, one (H8) a 6-kD protein, and one (H6) a 30-kD protein. When mixed with surfactant, three antibodies, H4, H7 and H8, profoundly altered surfactant activity in vitro in the pulsating bubble surfactometer. Three other antibodies, H1, H2, and H5 moderately inhibited surfactant's surface activity. We also examined the cross-reactivity of these monoclonal antibodies with bovine (CLSE) and porcine (Curosurf) surfactants. By Western blot analysis, only H6 bound these heterologous surfactants. Other antibodies did so by ELISA. However, functional assays indicated that antibodies H7, H8 and H4 all greatly inhibited CLSE surface activity in vitro. Five antibodies (H1-H4 and H8) inhibited Curosurf function. Thus, human surfactant species, especially low molecular weight species, are highly antigenic. Antibodies to alveolar surfactants may inhibit surfactant function in vitro. As indicated by Western blot and cross-inhibition data, human lower molecular weight surfactants share epitopes with proteins from therapeutically important porcine and bovine surfactants. The potential importance of these findings to treatment of neonatal respiratory distress syndrome with heterologous surfactants is discussed. PMID:1988229

  3. Aggregation of sodium alkylbenzenesulfonates in aqueous solution

    SciTech Connect

    Magid, L.J.; Shaver, R.J.; Gulari, E.; Bedwell, B.; Alkhafaji, S.

    1981-01-01

    The surfactant 6 phenyl C/sub 12/SNa forms small spherical micelles in aqueous solution, having an aggregation number of 20 to 30 and a fractional charge of 0.45. These micelles are hydrated to the extent of approximately 18 moles H/sub 2/O per moles of surfactant. A second larger aggregate is also present in 6 phenyl C/sub 12/SNa solutions; its importance increases with solution age. Addition of NaCl causes both aggregates to apparently increase modestly in size. The surfactant 8 phenyl C/sub 16/SNa also contains both aggregates in its solutions; the larger one is relatively more important here. The larger aggregate does not correspond to dispersed bits of a liquid crystalline mesophase.

  4. Kinematic viscosity of therapeutic pulmonary surfactants with added polymers

    PubMed Central

    Lu, Karen W.; Pérez-Gil, Jesús; Taeusch, H. William

    2009-01-01

    The addition of various polymers to pulmonary surfactants improves surface activity in experiments both in vitro and in vivo. Although the viscosity of surfactants has been investigated, the viscosity of surfactant polymer mixtures has not. In this study, we have measured the viscosities of Survanta and Infasurf with and without the addition of polyethylene glycol, dextran or hyaluronan. The measurements were carried out over a range of surfactant concentrations using two concentrations of polymers at two temperatures. Our results indicate that at lower surfactant concentrations, the addition of any polymers increased the viscosity. However, the addition of polyethylene glycol and dextran to surfactants at clinically used concentrations can substantially lower viscosity. Addition of hyaluronan at clinical surfactant concentrations slightly increased Infasurf viscosity and produced little change in Survanta viscosity. Effects of polymers on viscosity correlate with changes in size and distribution of surfactant aggregates and the apparent free volume of liquid as estimated by light microscopy. Aggregation of surfactant vesicles caused by polymers may therefore not only improve surface activity as previously shown, but may also affect viscosity in ways that could improve surfactant distribution in vivo. PMID:19366601

  5. Pulmonary surfactant adsorption is increased by hyaluronan or polyethylene glycol.

    PubMed

    Taeusch, H William; Dybbro, Eric; Lu, Karen W

    2008-04-01

    In acute lung injuries, inactivating agents may interfere with transfer (adsorption) of pulmonary surfactants to the interface between air and the aqueous layer that coats the interior of alveoli. Some ionic and nonionic polymers reduce surfactant inactivation in vitro and in vivo. In this study, we tested directly whether an ionic polymer, hyaluronan, or a nonionic polymer, polyethylene glycol, enhanced adsorption of a surfactant used clinically. We used three different methods of measuring adsorption in vitro: a modified pulsating bubble surfactometer; a King/Clements device; and a spreading trough. In addition we measured the effects of both polymers on surfactant turbidity, using this assay as a nonspecific index of aggregation. We found that both hyaluronan and polyethylene glycol significantly increased the rate and degree of surfactant material adsorbed to the surface in all three assays. Hyaluronan was effective in lower concentrations (20-fold) than polyethylene glycol and, unlike polyethylene glycol, hyaluronan did not increase apparent aggregation of surfactant. Surfactant adsorption in the presence of serum was also enhanced by both polymers regardless of whether hyaluronan or polyethylene glycol was included with serum in the subphase or added to the surfactant applied to the surface. Therefore, endogenous polymers in the alveolar subphase, or exogenous polymers added to surfactant used as therapy, may both be important for reducing inactivation of surfactant that occurs with various lung injuries.

  6. Kinematic viscosity of therapeutic pulmonary surfactants with added polymers.

    PubMed

    Lu, Karen W; Pérez-Gil, Jesús; Taeusch, H William

    2009-03-01

    The addition of various polymers to pulmonary surfactants improves surface activity in experiments both in vitro and in vivo. Although the viscosity of surfactants has been investigated, the viscosity of surfactant polymer mixtures has not. In this study, we have measured the viscosities of Survanta and Infasurf with and without the addition of polyethylene glycol, dextran or hyaluronan. The measurements were carried out over a range of surfactant concentrations using two concentrations of polymers at two temperatures. Our results indicate that at lower surfactant concentrations, the addition of any polymers increased the viscosity. However, the addition of polyethylene glycol and dextran to surfactants at clinically used concentrations can substantially lower viscosity. Addition of hyaluronan at clinical surfactant concentrations slightly increased Infasurf viscosity and produced little change in Survanta viscosity. Effects of polymers on viscosity correlate with changes in size and distribution of surfactant aggregates and the apparent free volume of liquid as estimated by light microscopy. Aggregation of surfactant vesicles caused by polymers may therefore not only improve surface activity as previously shown, but may also affect viscosity in ways that could improve surfactant distribution in vivo.

  7. Preparation and characterization of zwitterionic surfactant-modified montmorillonites.

    PubMed

    Zhu, Jianxi; Qing, Yanhong; Wang, Tong; Zhu, Runliang; Wei, Jingming; Tao, Qi; Yuan, Peng; He, Hongping

    2011-08-15

    A series of zwitterionic surfactant-modified montmorillonites (ZSMMs) were synthesized using montmorillonite and three zwitterionic surfactants with different alkyl chain lengths at different concentrations [0.2-4.0 cation exchange capacity (CEC)]. These ZSMMs were characterized by X-ray diffraction (XRD), thermo-gravimetric analysis and differential thermo-gravimetric (TG/DTG) analyses. The zwitterionic surfactant could be intercalated into the interlayer spaces of montmorillonites and causing interlayer space-swelling. From XRD measurements, the amount of the surfactants loaded and the basal spacing increased with surfactant concentration and alkyl chain length. One endothermic DTG peak occurred at ~390 °C, which was assigned to the decomposition of the zwitterionic surfactant on the organo-montmorillonites from 0.2 to 0.6 CEC. When the surfactant loading was increased, a new endothermic peak appeared at ~340 °C. From the microstructures of these ZSMMs, the mechanism of zwitterionic surfactant adsorption was proposed. At relatively low loadings of the zwitterionic surfactant, most of surfactants enter the spacing by an ion-exchange mechanism and are adsorbed onto the interlayer cation sites. When the concentration of the zwitterionic surfactant exceeds the CEC of montmorillonite, the surfactant molecules then adhere to the surface-adsorbed surfactant. Some surfactants enter the interlayers, whereas the others are attached to the clay surface. When the concentration of surfactant increases further beyond 2.0 CEC, the surfactants may occupy the inter-particle space within the house-of-cards aggregate structure. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. Gemini surfactants affect the structure, stability, and activity of ribonuclease Sa.

    PubMed

    Amiri, Razieh; Bordbar, Abdol-Khalegh; Laurents, Douglas V

    2014-09-11

    Gemini surfactants have important advantages, e.g., low micromolar CMCs and slow millisecond monomer ↔ micelle kinetics, for membrane mimetics and for delivering nucleic acids for gene therapy or RNA silencing. However, as a prerequisite, it is important to characterize interactions occurring between Gemini surfactants and proteins. Here NMR and CD spectroscopies are employed to investigate the interactions of cationic Gemini surfactants with RNase Sa, a negatively charged ribonuclease. We find that RNase Sa binds Gemini surfactant monomers and micelles at pH values above 4 to form aggregates. Below pH 4, where the protein is positively charged, these aggregates dissolve and interactions are undetectable. Thermal denaturation experiments show that surfactant lowers RNase Sa's conformational stability, suggesting that surfactant binds the protein's denatured state preferentially. Finally, Gemini surfactants were found to bind RNA, leading to the formation of large complexes. Interestingly, Gemini surfactant binding did not prevent RNase Sa from cleaving RNA.

  9. DNA compaction by azobenzene-containing surfactant

    SciTech Connect

    Zakrevskyy, Yuriy; Kopyshev, Alexey; Lomadze, Nino; Santer, Svetlana

    2011-08-15

    We report on the interaction of cationic azobenzene-containing surfactant with DNA investigated by absorption and fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy. The properties of the surfactant can be controlled with light by reversible switching of the azobenzene unit, incorporated into the surfactant tail, between a hydrophobic trans (visible irradiation) and a hydrophilic cis (UV irradiation) configuration. The influence of the trans-cis isomerization of the azobenzene on the compaction process of DNA molecules and the role of both isomers in the formation and colloidal stability of DNA-surfactant complexes is discussed. It is shown that the trans isomer plays a major role in the DNA compaction process. The influence of the cis isomer on the DNA coil configuration is rather small. The construction of a phase diagram of the DNA concentration versus surfactant/DNA charge ratio allows distancing between three major phases: colloidally stable and unstable compacted globules, and extended coil conformation. There is a critical concentration of DNA above which the compacted globules can be hindered from aggregation and precipitation by adding an appropriate amount of the surfactant in the trans configuration. This is because of the compensation of hydrophobicity of the globules with an increasing amount of the surfactant. Below the critical DNA concentration, the compacted globules are colloidally stable and can be reversibly transferred with light to an extended coil state.

  10. Aggregation work at polydisperse micellization: Ideal solution and ``dressed micelle'' models comparing to molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Burov, S. V.; Shchekin, A. K.

    2010-12-01

    General thermodynamic relations for the work of polydisperse micelle formation in the model of ideal solution of molecular aggregates in nonionic surfactant solution and the model of "dressed micelles" in ionic solution have been considered. In particular, the dependence of the aggregation work on the total concentration of nonionic surfactant has been analyzed. The analogous dependence for the work of formation of ionic aggregates has been examined with regard to existence of two variables of a state of an ionic aggregate, the aggregation numbers of surface active ions and counterions. To verify the thermodynamic models, the molecular dynamics simulations of micellization in nonionic and ionic surfactant solutions at two total surfactant concentrations have been performed. It was shown that for nonionic surfactants, even at relatively high total surfactant concentrations, the shape and behavior of the work of polydisperse micelle formation found within the model of the ideal solution at different total surfactant concentrations agrees fairly well with the numerical experiment. For ionic surfactant solutions, the numerical results indicate a strong screening of ionic aggregates by the bound counterions. This fact as well as independence of the coefficient in the law of mass action for ionic aggregates on total surfactant concentration and predictable behavior of the "waterfall" lines of surfaces of the aggregation work upholds the model of "dressed" ionic aggregates.

  11. Pseudomonas aeruginosa protease IV degrades surfactant proteins and inhibits surfactant host defense and biophysical functions.

    PubMed

    Malloy, Jaret L; Veldhuizen, Ruud A W; Thibodeaux, Brett A; O'Callaghan, Richard J; Wright, Jo Rae

    2005-02-01

    Pulmonary surfactant has two distinct functions within the lung: reduction of surface tension at the air-liquid interface and participation in innate host defense. Both functions are dependent on surfactant-associated proteins. Pseudomonas aeruginosa is primarily responsible for respiratory dysfunction and death in cystic fibrosis patients and is also a leading pathogen in nosocomial pneumonia. P. aeruginosa secretes a number of proteases that contribute to its virulence. We hypothesized that P. aeruginosa protease IV degrades surfactant proteins and results in a reduction in pulmonary surfactant host defense and biophysical functions. Protease IV was isolated from cultured supernatant of P. aeruginosa by gel chromatography. Incubation of cell-free bronchoalveolar lavage fluid with protease IV resulted in degradation of surfactant proteins (SP)-A, -D, and -B. SPs were degraded in a time- and dose-dependent fashion by protease IV, and degradation was inhibited by the trypsin-like serine protease inhibitor Nalpha-p-tosyl-L-lysine-chloromethyl ketone (TLCK). Degradation by protease IV inhibited SP-A- and SP-D-mediated bacterial aggregation and uptake by macrophages. Surfactant treated with protease IV was unable to reduce surface tension as effectively as untreated surfactant, and this effect was inhibited by TLCK. We speculate that protease IV may be an important contributing factor to the development and propagation of acute lung injury associated with P. aeruginosa via loss of surfactant function within the lung.

  12. Gemini imidazolium surfactants: synthesis and their biophysiochemical study.

    PubMed

    Kamboj, Raman; Singh, Sukhprit; Bhadani, Avinash; Kataria, Hardeep; Kaur, Gurcharan

    2012-08-21

    New gemini imidazolium surfactants 9-13 have been synthesized by a regioselective epoxy ring-opening reaction under solvent-free conditions. The surface properties of these new gemini surfactants were evaluated by surface tension and conductivity measurements. These surfactants have been found to have low critical micelle concentration (cmc) values as compared to other categories of gemini cationic surfactants and also showed the tendency to form premicellar aggregates in solution at sufficiently low concentration below their cmc values. The thermal degradation of these surfactants was determined by thermograviometry analysis (TGA). These new cationic surfactants have a good DNA binding capability as determined by agarose gel electrophoresis and ethidium bromide exclusion experiments. They have also been found to have low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on the C6 glioma cell line.

  13. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2009-11-24

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments or the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  14. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2006-04-04

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments and the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  15. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2009-09-29

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments or the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  16. Research progress of surfactant

    NASA Astrophysics Data System (ADS)

    Zheng, Minyi; Mo, Lingyun; Qin, Ruqiong; Liang, Liying; Zhang, Fan

    2017-01-01

    With the rapid development of surfactant and the large growing use of the materials, the safety of surfactant may be a problem that draw worldwide attention. The surfactant can be discharged into environment through various approach and may cause toxic effects in organism. This paper reviews the environmental effects of surfactant materials for plants and animals, and raises some questions by describing the results of environmental toxicology. We put it that it is a great significant of promote the sustainable development of surfactant industry through a comprehensive understanding of surfactant environmental safety.

  17. SURFACTANT DYSFUNCTION IN LUNG CONTUSION WITH AND WITHOUT SUPERIMPOSED GASTRIC ASPIRATION IN A RAT MODEL

    PubMed Central

    Raghavendran, Krishnan; Davidson, Bruce A.; Knight, Paul R.; Wang, Zhengdong; Helinski, Jadwiga; Chess, Patricia R.; Notter, Robert H.

    2009-01-01

    This study investigates surfactant dysfunction in rats with lung contusion (LC) induced by blunt chest trauma. Rats at 24 h postcontusion had a decreased percent content of large surfactant aggregates in cell-free bronchoalveolar lavage (BAL) and altered large-aggregate composition with decreased phosphatidylcholine (PC), increased lyso-PC, and increased protein compared with uninjured controls. The surface activity of large aggregates on a pulsating bubble surfactometer was also severely impaired at 24 h postcontusion. Decreases in large surfactant aggregate content and surface activity were improved, but still apparent, at 48 and 72 h postcontusion compared with uninjured control rats and returned to normal by 96 h postcontusion. The functional importance of surfactant abnormalities in LC injury was documented in pilot studies showing that exogenous surfactant replacement at 24 h postcontusion improved inflation/deflation lung volumes. Additional experiments investigated a clinically relevant combination of LC plus gastric aspiration (combined acid and small gastric food particles) and found reductions in large surfactant aggregates in BAL similar to those for LC. However, rats given LC + combined acid and small gastric food particles versus LC had more severe surfactant dysfunction based on decreases in surface activity and alterations in large aggregate composition. Combined data for all animal groups had strong statistical correlations between surfactant dysfunction (increased minimum surface tension, decreased large aggregates in BAL, decreased aggregate PC, and increased aggregate lyso-PC) and the severity of inflammatory lung injury (increased total protein, albumin, protein/phospholipid ratio, neutrophils, and erythrocytes in BAL plus increased whole lung myeloperoxidase activity). These results show that surfactant dysfunction is important in the pathophysiology of LC with or without concurrent gastric aspiration and provides a rationale for surfactant

  18. Photosensitive surfactants: micellization and interaction with DNA.

    PubMed

    Zakrevskyy, Yuriy; Roxlau, Julian; Brezesinski, Gerald; Lomadze, Nino; Santer, Svetlana

    2014-01-28

    Recently, photosensitive surfactants have re-attracted considerable attention. It has been shown that their association with oppositely charged biologically important polyelectrolytes, such as DNA or microgels, can be efficiently manipulated simply by light exposure. In this article, we investigate the self-assembly of photosensitive surfactants as well as their interactions with DNA by calorimetric and spectroscopic methods. Critical micelle concentration (CMC), standard micellization enthalpy, entropy, and Gibbs energy were determined in different conditions (ionic strengths and temperatures) for a series of cationic surfactants with an azobenzene group in their tail. It is shown, that aggregation forces of photosensitive units play an important role in the micellization giving the major contribution to the micellization enthalpy. The onset of the aggregation can be traced from shift of the absorption peak position in the UV-visible spectrum. Titration UV-visible spectroscopy is used as an alternative, simple, and sensitive approach to estimate CMC. The titration UV-visible spectroscopy was also employed to investigate interactions (CAC: critical aggregation concentration, precipitation, and colloidal stabilization) in the DNA-surfactant complex.

  19. Photosensitive surfactants: Micellization and interaction with DNA

    NASA Astrophysics Data System (ADS)

    Zakrevskyy, Yuriy; Roxlau, Julian; Brezesinski, Gerald; Lomadze, Nino; Santer, Svetlana

    2014-01-01

    Recently, photosensitive surfactants have re-attracted considerable attention. It has been shown that their association with oppositely charged biologically important polyelectrolytes, such as DNA or microgels, can be efficiently manipulated simply by light exposure. In this article, we investigate the self-assembly of photosensitive surfactants as well as their interactions with DNA by calorimetric and spectroscopic methods. Critical micelle concentration (CMC), standard micellization enthalpy, entropy, and Gibbs energy were determined in different conditions (ionic strengths and temperatures) for a series of cationic surfactants with an azobenzene group in their tail. It is shown, that aggregation forces of photosensitive units play an important role in the micellization giving the major contribution to the micellization enthalpy. The onset of the aggregation can be traced from shift of the absorption peak position in the UV-visible spectrum. Titration UV-visible spectroscopy is used as an alternative, simple, and sensitive approach to estimate CMC. The titration UV-visible spectroscopy was also employed to investigate interactions (CAC: critical aggregation concentration, precipitation, and colloidal stabilization) in the DNA-surfactant complex.

  20. Micropipette Technique Study of Natural and Synthetic Lung Surfactants at the Air-Water Interface: Presence of a SP-B Analog Peptide Promotes Membrane Aggregation, Formation of Tightly Stacked Lamellae, and Growth of Myelin Figures.

    PubMed

    Parra, Elisa; Kinoshita, Koji; Needham, David

    2016-10-03

    The present study is a microscopic interfacial characterization of a series of lung surfactant materials performed with the micropipette technique. The advantages of this technique include the measurement of equilibrium and dynamic surface tensions while acquiring structural and dynamic information at microscopic air-water interfaces in real time and upon compression. Here, we characterized a series of animal-derived and synthetic lung surfactant formulations, including native surfactant obtained from porcine lungs (NS); the commercial Curosurf, Infasurf, and Survanta; and a synthetic Super Mini-B (SMB)-containing formulation. It was observed that the presence of the natural hydrophobic proteins and, more strikingly, the peptide SMB, promoted vesicle condensation as thick membrane stacks beneath the interface. Only in the presence of SMB, these stacks underwent spontaneous structural transformations, consisting of the nucleation and growth of microtubes and in some cases their subsequent coiling into helices. The dimensions of these tubes (2-15 μm diameter) and their linear (2-3 μm/s) and volumetric growth rates (20-30 μm(3)/s) were quantified, and no specific effects were found on them for increasing SMB concentrations from 0.1 to 4%. Nevertheless, a direct correlation between the number of tubes and SMB contents was found, suggesting that SMB molecules are the promoters of tube nucleation in these membranes. A detailed analysis of the tube formation process was performed following previous models for the growth of myelin figures, proposing a combined mechanism between dehydration-rehydration of the lipid bilayers and induction of mechanical defects by SMB that would act as nucleation sites for the tubes. The formation of tubes was also observed in Infasurf, and in NS only after subsequent expansion and compression but neither in the other clinical surfactants nor in protein-free preparations. Finally, the connection between this data and the observations from

  1. Characterization and Control of Surfactant-Mediated Norovirus Interactions

    PubMed Central

    Mertens, Brittany S.; Velev, Orlin D.

    2015-01-01

    Understanding of the colloidal interactions of Norovirus particles in aqueous medium could provide insights on the origins of the notorious stability and infectivity of these widespread viral agents. We characterized the effects of solution pH and surfactant type and concentration on the aggregation, dispersion, and disassembly of Norovirus virus-like particles (VLPs) using dynamic light scattering, electrophoretic light scattering, and transmission electron microscopy. Owing to net negative surface charge of the VLPs at neutral pH, low concentrations of cationic surfactant tend to aggregate the VLPs, whereas low concentrations of anionic surfactant tend to disperse the particles. Increasing the concentration of these surfactants beyond their critical micelle concentration leads to virus capsid disassembly and breakdown of aggregates. Non-ionic surfactants, however, had little effect on virus interactions and likely stabilized them additionally in suspension. The data were interpreted on the basis of simple models for surfactant binding and re-charging of the virus capsid. We used zeta potential data to characterize virus surface charge and interpret the mechanisms behind these demonstrated surfactant-virus interactions. The fundamental understanding and control of these interactions will aid in practical formulations for virus inactivation and removal from contaminated surfaces. PMID:26378627

  2. Giant Cell Arteritis

    MedlinePlus

    ... Patient / Caregiver Diseases & Conditions Giant Cell Arteritis Giant Cell Arteritis Fast Facts Giant cell arteritis (GCA) is ... polymyalgia rheumatica (also called PMR). What is giant cell arteritis? GCA is a type of vasculitis or ...

  3. Biomimicry of surfactant protein C

    PubMed Central

    Brown, Nathan J.; Johansson, Jan; Barron, Annelise E.

    2012-01-01

    CONSPECTUS Since the widespread use of exogenous lung surfactant to treat neonatal respiratory distress syndrome, premature infant survival and respiratory morbidity have dramatically improved. Despite the effectiveness of the animal-derived surfactant preparations, there still remain some concerns and difficulties associated with their use. This has prompted investigation into the creation of synthetic surfactant preparations. However, to date, no clinically used synthetic formulation is as effective as the natural material. This is largely because the previous synthetic formulations lacked analogues of the hydrophobic proteins of the lung surfactant system, SP-B and SP-C, which are critical functional constituents. As a result, recent investigation has turned towards the development of a new generation of synthetic, biomimetic surfactants that contain synthetic phospholipids along with a mimic of the hydrophobic protein portion of lung surfactant. In this Account, we detail our efforts in creating accurate mimics of SP-C for use in a synthetic surfactant replacement therapy. Despite SP-C’s seemingly simple structure, the predominantly helical protein is extraordinarily challenging to work with given its extreme hydrophobicity and structural instability, which greatly complicates the creation of an effective SP-C analogue. Drawing inspiration from Nature, two promising biomimetic approaches have led to the creation of rationally designed biopolymers that recapitulate many of SP-C’s molecular features. The first approach utilizes detailed SP-C structure-activity relationships and amino acid folding propensities to create a peptide-based analogue, SP-C33. In SP-C33, the problematic and metastable poly-valine helix is replaced with a structurally stable, poly-leucine helix and includes a well placed positive charge to prevent aggregation. SP-C33 is both structurally stable and eliminates the association propensity of the native protein. The second approach

  4. Self-assembled structures of anionic hydrophobically modified polyacrylamide with star-shaped trimeric and hexameric quaternary ammonium surfactants.

    PubMed

    Fan, Yaxun; Wu, Chunxian; Wang, Meina; Wang, Yilin; Thomas, Robert K

    2014-06-17

    The self-assembly of a 1% hydrophobically modified and 30% hydrolyzed polyacrylamide (C12PAM) with cationic star-shaped oligomeric surfactants has been investigated by isothermal titration microcalorimetry, turbidimetry, ζ potential, scanning electron microscopy, and (1)H NMR techniques. The oligomeric surfactants are composed of quaternary dodecyldimethylammonium ions with three or six hydrophobic chains connected by a polyamine spacer at the headgroup level, abbreviated as DTAD and PAHB, respectively. DTAD/C12PAM and PAHB/C12PAM mixed systems undergo the same aggregate transitions with increases in surfactant concentration from soluble networklike aggregates to precipitated denser and more cross-linked structures and then to soluble spherical aggregates. The networklike aggregates are generated at very low surfactant concentration. However, at the corresponding surfactant concentration without C12PAM, DTAD cannot form aggregates and PAHB forms only networklike aggregates with a very loose structure. The strong electrostatic and hydrophobic interaction of DTAD and PAHB with C12PAM and the hydrophobic interaction between the alkyl chains of DTAD and PAHB themselves evidently promote the formation of networklike aggregates. As the surfactant concentration increases, cationic surfactants become excessive. The molecular configuration is changed by the stronger hydrophobic association among the DTAD and PAHB molecules and the enhanced electrostatic repulsion between the mixed aggregates. Thus, the networklike aggregates transfer to spherical aggregates.

  5. Molecular simulation of surfactant-assisted protein refolding

    NASA Astrophysics Data System (ADS)

    Lu, Diannan; Liu, Zheng; Liu, Zhixia; Zhang, Minlian; Ouyang, Pingkai

    2005-04-01

    Protein refolding to its native state in vitro is a challenging problem in biotechnology, i.e., in the biomedical, pharmaceutical, and food industry. Protein aggregation and misfolding usually inhibit the recovery of proteins with their native states. These problems can be partially solved by adding a surfactant into a suitable solution environment. However, the process of this surfactant-assisted protein refolding is not well understood. In this paper, we wish to report on the first-ever simulations of surfactant-assisted protein refolding. For these studies, we defined a simple model for the protein and the surfactant and investigated how a surfactant affected the folding behavior of a two-dimensional lattice protein molecule. The model protein and model surfactant were chosen such that we could capture the important features of the folding process and the interaction between the protein and the surfactant, namely, the hydrophobic interaction. It was shown that, in the absence of surfactants, a protein in an "energy trap" conformation, i.e., a local energy minima, could not fold into the native form, which was characterized by a global energy minimum. The addition of surfactants created folding pathways via the formation of protein-surfactant complexes and thus enabled the conformations that fell into energy trap states to escape from these traps and to form the native proteins. The simulation results also showed that it was necessary to match the hydrophobicity of surfactant to the concentration of denaturant, which was added to control the folding or unfolding of a protein. The surfactants with different hydrophobicity had their own concentration range on assisting protein refolding. All of these simulations agreed well with experimental results reported elsewhere, indicating both the validity of the simulations presented here and the potential application of the simulations for the design of a surfactant on assisting protein refolding.

  6. Interactions of cationic trimeric, gemini and monomeric surfactants with trianionic curcumin in aqueous solution.

    PubMed

    Wang, Meina; Wu, Chunxian; Tang, Yongqiang; Fan, Yaxun; Han, Yuchun; Wang, Yilin

    2014-05-21

    Interactions of trianionic curcumin (Cur(3-)) with a series of cationic surfactants, monomeric surfactant dodecyl trimethylammonium bromide (DTAB), dimeric surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and trimeric surfactant tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD), have been investigated in aqueous solution of pH 13.0. Surface tension and spectral measurements indicate that the cationic surfactants display a similar surfactant concentration dependent interaction process with Cur(3-), involving three interaction stages. At first the three cationic surfactants electrostatically bind on Cur(3-) to form the surfactant-Cur(3-) complex. Then the bound and unbound cationic surfactants with Cur(3-) aggregate into surfactant-Cur(3-) mixed micelles through hydrophobic interactions above the critical micelle concentration of the surfactants (CMCC) in the presence of Cur(3-). Finally excess unbound surfactants self-assemble into micelles like those without Cur(3-). For all the three surfactants, the addition of Cur(3-) only decreases the critical micelle concentration of 12-6-12 but does not affect the critical micelle concentration of DTAB and DTAD. As the oligomeric degree of surfactants increases, the intermolecular interaction of the cationic surfactants with Cur(3-) increases and the surfactant amount needed for Cur(3-) encapsulation decreases. Compared with 12-6-12, either the weaker interaction of DTAB with Cur(3-) or stronger interaction of DTAD with Cur(3-) limits the stability or solubility of Cur(3-) in surfactant micelles. Therefore, gemini surfactant 12-6-12 is the best choice to effectively suppress Cur(3-) degradation at very low concentrations. Isothermal titration microcalorimetry, surface tension and (1)H NMR results reveal that 12-6-12 and Cur(3-) form a (12-6-12)2-Cur(3-) complex and start to form micelles at extremely decreased concentrations, where either 12-6-12 or Cur(3-) works as a bridge

  7. Ripening of catanionic aggregates upon dialysis.

    PubMed

    Michina, Youlia; Carriere, David; Mariet, Clarisse; Moskura, Melanie; Berthault, Patrick; Belloni, Luc; Zemb, Thomas

    2009-01-20

    We have studied the dialysis of surfactant mixtures of two oppositely charged surfactants (catanionic mixture) by combining HPLC, neutron activation, confocal microscopy, and NMR. In mixtures of n-alkyl trimethylammonium halides and n-fatty acids, we have demonstrated the existence of a specific ratio between both surfactant contents (anionic/cationic almost equal to 2:1) that determines the morphology, the elimination of ions, and the elimination of the soluble cationic surfactant upon dialysis. In mixtures prepared with lower anionic surfactant contents, ill-defined aggregates are formed, and dialysis quickly eliminates the ion pairs (H+X-) formed upon surfactant association and also the cationic surfactant until a limiting 2:1 ratio is reached. By contrast, mixtures prepared above the anionic/cationic 2:1 ratio form micrometer-sized vesicles resistant to dialysis. These closed aggregates retain a significant number of ions (30%) over 1000 hours, and dialysis is unable to eliminate the soluble surfactant. The interactions between surfactants have been estimated by measuring the partitioning of the CTA molecules between the catanionic bilayer, the bulk solution, and mixed micelles when they exist. The mean extraction free energy per CTA in the membrane has been found to increase by 1 kBT to 2 kBT as the soluble surfactant is depleted from the bilayer, which is enough to stop the dialysis. The vesicles produced above the anionic/cationic 2:1 ratio are formed by frozen bilayers and are resistant to extensive dialysis and therefore show an interesting potential for encapsulation as far as durability is concerned.

  8. Enhanced photodegradation of pentachlorophenol by single and mixed nonionic and anionic surfactants using graphene-TiO₂ as catalyst.

    PubMed

    Zhang, Yaxin; He, Xin; Zeng, Guangming; Chen, Tan; Zhou, Zeyu; Wang, Hongtao; Lu, Wenjing

    2015-11-01

    The photodegradation of pentachlorophenol (PCP) in a surfactant-containing (single and mixed) complex system using graphene-TiO2 (GT) as catalyst was investigated. The objective was to better understand the behavior of surfactants in a GT catalysis system for its possible use in remediation technology of soil contaminated by hydrophobic organic compounds (HOCs). In a single-surfactant system, surfactant molecules aggregated on GT via hydrogen bonding and electrostatic force; nonideal mixing between nonionic and anionic surfactants rendered GT surface with mixed admicelles in a mixed surfactant system. Both effects helped incorporating PCP molecules into surfactant aggregates on catalyst surface. Hence, the targeted pollutants were rendered easily available to photo-yielded oxidative radicals, and photodegradation efficiency was significantly enhanced. Finally, real soil washing-photocatalysis trials proved that anionic-nonionic mixed surfactant soil washing coupled with graphene-TiO2 photocatalysis can be one promising technology for HOC-polluted soil remediation.

  9. Effects of anthropogenic surfactants on the conversion of marine dissolved organic carbon and microgels.

    PubMed

    Shiu, Ruei-Feng; Lee, Chon-Lin

    2017-04-15

    The possible impact of three types of anthropogenic surfactants on the ability of marine dissolved organic carbon (DOC) to form self-assembled microgels was evaluated. The behavior of existing native microgels was also examined in the presence of surfactants. These results reveal that the release of surfactants even at low concentrations into the aquatic environment could effectively hinder the self-assembly of DOC polymers. The extent of the size reduction had the following order: anionic, cationic, and non-ionic. Furthermore, charged surfactants can disrupt existing native microgels, converting large assemblies into smaller particles. One possible mechanisms is that surfactants are able to enhance the stability of DOC polymers and disrupt aggregates due to their surface charges and protein-denaturing activities. These findings suggest that the ecological system is altered by anthropogenic surfactants, and provide useful information for ecological assessments of different types of surfactants and raise warnings about surfactant applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Low-surface energy surfactants with branched hydrocarbon architectures.

    PubMed

    Alexander, Shirin; Smith, Gregory N; James, Craig; Rogers, Sarah E; Guittard, Frédéric; Sagisaka, Masanobu; Eastoe, Julian

    2014-04-01

    Surface tensiometry and small-angle neutron scattering have been used to characterize a new class of low-surface energy surfactants (LSESs), "hedgehog" surfactants. These surfactants are based on highly branched hydrocarbon (HC) chains as replacements for environmentally hazardous fluorocarbon surfactants and polymers. Tensiometric analyses indicate that a subtle structural modification in the tails and headgroup results in significant effects on limiting surface tensions γcmc at the critical micelle concentration: a higher level of branching and an increased counterion size promote an effective reduction of surface tension to low values for HC surfactants (γcmc ∼ 24 mN m(-1)). These LSESs present a new class of potentially very important materials, which form lamellar aggregates in aqueous solutions independent of dilution.

  11. NMR diffusion analysis of surfactant-humic substance interactions.

    PubMed

    Otto, William H; Britten, Danny J; Larive, Cynthia K

    2003-05-15

    Surfactants can be introduced into the environment through wastewater or by direct contamination. Understanding the fate and transport of surfactants in the environment is important in assessing their role as pollutants. Humic substances are complex heterogeneous mixtures of decomposition products of natural organic materials. They are environmentally important because they are known to solubilize and transport organic pollutants. Therefore humic substances are likely to affect the environmental fate of surfactants. Diffusion coefficients measured with pulsed-field gradient nuclear magnetic resonance spectroscopy are used in this study to examine the intermolecular interactions of the surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in the presence of various humic substances. These results indicate that humic substances enhance the aggregation of SDS prior to micellization with a more pronounced effect observed for the more hydrophobic humic materials. The positively charged surfactant CTAB forms stable ion pairs with the humic substances.

  12. Enhanced solubilization of curcumin in mixed surfactant vesicles.

    PubMed

    Kumar, Arun; Kaur, Gurpreet; Kansal, S K; Chaudhary, Ganga Ram; Mehta, S K

    2016-05-15

    Self-assemblies of equimolar double and single chain mixed ionic surfactants, with increasing numbers of carbon atoms of double chain surfactant, were analyzed on the basis of fluorescence and conductivity results. Attempts were also made to enhance the solubilization of curcumin in aqueous equimolar mixed surfactant systems. Mixed surfactant assembly was successful in retarding the degradation of curcumin in alkaline media (only 25-28 40% degraded in 10h at pH 13). Fluorescence spectroscopy and fluorescence quenching methods were employed to predict the binding position and mechanism of curcumin with self-assemblies. Results indicate that the interactions take place according to both dynamic and static quenching mechanisms and curcumin was distributed in a palisade layer of mixed aggregates. Antioxidant activity (using DPPH radical) and biocompatibility (using calf-thymus DNA) of curcumin-loaded mixed surfactant formulations were also evaluated. The prepared systems improved the stability, solubility and antioxidant activity of curcumin and additionally are biocompatible.

  13. Deracemization of bilirubin as the marker of the chirality of micellar aggregates.

    PubMed

    Sorrenti, Alessandro; Altieri, Barbara; Ceccacci, Francesca; Di Profio, Pietro; Germani, Raimondo; Giansanti, Luisa; Savelli, Gianfranco; Mancini, Giovanna

    2012-01-01

    The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities.

  14. Surfactant doped silica aerogels dried at supercritical pressure

    NASA Astrophysics Data System (ADS)

    Parale, V. G.; Mahadik, D. B.; Kavale, M. S.; Rao, A. Venkateswara; Vhatkar, R. S.; Wagh, P. B.; Gupta, Satish C.

    2013-02-01

    By combining the molecular silica precursor methyltrimethoxysilane (MTMS) with methanol, water and Tween-80 solution, we get surfactant-doped silica alcogels. The wet alcogels can be exchanged with methanol and then supercritically extracted with nitrogen to produce surfactant-doped silica aerogels (SDSAs). SDSAs represent a new class of aerogels that are composed of aggregated submicron porous particles that have tunable interparticle nanoporosity. As we increased the percentage of surfactant, the physical properties of silica aerogels changes. In this study we characterized the SDSAs by SEM for morphological study, FTIR for the material composition, contact angle for hydrophobicity determination and thermal conductivity measurements are carried out for thermal insulation application.

  15. Rheology of cellulose nanofibrils in the presence of surfactants.

    PubMed

    Quennouz, Nawal; Hashmi, Sara M; Choi, Hong Sung; Kim, Jin Woong; Osuji, Chinedum O

    2016-01-07

    Cellulose nanofibrils (CNFs) present unique opportunities for rheology modification in complex fluids. Here we systematically consider the effect of ionic and non-ionic surfactants on the rheology of dilute CNF suspensions. Neat suspensions are transparent yield-stress fluids which display strong shear thinning and power-law dependence of modulus on concentration, G' ∼ c(2.1). Surfactant addition below a critical mass concentration cc produces an increase in the gel modulus with retention of optical clarity. Larger than critical concentrations induce significant fibril aggregation leading to the loss of suspension stability and optical clarity, and to aggregate sedimentation. The critical concentration was the lowest for a cationic surfactant (DTAB), cc ≈ 0.08%, while suspension stability was retained for non-ionic surfactants (Pluronic F68, TX100) at concentrations up to 8%. The anionic surfactant SDS led to a loss of stability at cc ≈ 1.6% whereas suspension stability was not compromised by anionic SLES up to 8%. Dynamic light scattering data are consistent with a scenario in which gel formation is driven by micelle-nanofibril bridging mediated by associative interactions of ethoxylated surfactant headgroups with the cellulose fibrils. This may explain the strong difference between the properties of SDS and SLES-modified suspensions. These results have implications for the use of CNFs as a rheology modifier in surfactant-containing systems.

  16. Micellization of alkyltrimethylammonium bromide surfactants in choline chloride:glycerol deep eutectic solvent.

    PubMed

    Sanchez-Fernandez, Adrian; Arnold, Thomas; Jackson, Andrew J; Fussell, Sian L; Heenan, Richard K; Campbell, Richard A; Edler, Karen J

    2016-12-07

    Deep eutectic solvents have shown the ability to promote the self-assembly of surfactants in solution. However, some differences have been found compared with self-assembly in pure water and other polar organic solvents. The behaviour of alkyltrimethylammonium bromides in choline chloride:glycerol deep eutectic solvent has been studied by means of surface tension, X-ray and neutron reflectivity and small-angle neutron scattering. The surfactants were found to remain surface active and showed comparable critical micelle concentrations to the same surfactants in water. Our scattering studies demonstrate that these surfactants form globular micelles with ellipsoidal shape in solution. The size, shape and aggregation number of the aggregates were found to vary with the chain length of the surfactant. Specific solvent-headgroup interactions were not found in this system, unlike those we have previously postulated for anionic surfactants in choline chloride deep eutectic solvents.

  17. Observation of two different fractal structures in nanoparticle, protein and surfactant complexes

    SciTech Connect

    Mehan, Sumit Kumar, Sugam Aswal, V. K.

    2014-04-24

    Small angle neutron scattering has been carried out from a complex of nanoparticle, protein and surfactant. Although all the components are similarly (anionic) charged, we have observed strong interactions in their complex formation. It is characterized by the coexistence of two different mass fractal structures. The first fractal structure is originated from the protein and surfactant interaction and second from the depletion effect of first fractal structure leading the nanoparticle aggregation. The fractal structure of protein-surfactant complex represents to bead necklace structure of micelle-like clusters of surfactant formed along the unfolded protein chain. Its fractal dimension depends on the surfactant to protein ratio (r) and decreases with the increase in r. However, fractal dimension of nanoparticle aggregates in nanoparticle-protein complex is found to be independent of protein concentration and governed by the diffusion limited aggregation like morphology.

  18. Surfactant Enhanced DNAPL Removal

    DTIC Science & Technology

    2001-08-01

    or the permeability contrast (i.e., degree of heterogeneity) that is present in the DNAPL zone. To solubilize DNAPL with surfactants, a sufficient...with respect to the effects of permeability and heterogeneity upon the costs of SEAR: as permeability decreases and/or the degree of heterogeneity...not be an issue for surfactant recovery at all sites. The degree to which MEUF will concentrate the calcium is a function of the surfactant itself

  19. Triggered self-assembly of simple dynamic covalent surfactants.

    PubMed

    Minkenberg, Christophe B; Florusse, Louw; Eelkema, Rienk; Koper, Ger J M; van Esch, Jan H

    2009-08-19

    A prototype surfactant system was developed with the unique feature that it can be switched between an aggregated, amphiphilic state and a nonaggregated, nonamphiphilic state using external stimuli. This switchable surfactant system uses the reversible formation of a dynamic covalent bond for pH- and temperature-triggered on/off self-assembly of micellar aggregates by reversible displacement of the equilibrium between nonamphiphilic building blocks and their amphiphilic counterparts. The potential for application in controlled-release systems is shown by reversible uptake and release of an organic dye in aqueous media.

  20. Surfactant phospholipid metabolism

    PubMed Central

    Agassandian, Marianna; Mallampalli, Rama K.

    2012-01-01

    Pulmonary surfactant is essential for life and is comprised of a complex lipoprotein-like mixture that lines the inner surface of the lung to prevent alveolar collapse at the end of expiration. The molecular composition of surfactant depends on highly integrated and regulated processes involving its biosynthesis, remodeling, degradation, and intracellular trafficking. Despite its multicomponent composition, the study of surfactant phospholipid metabolism has focused on two predominant components, disaturated phosphatidylcholine that confers surface-tension lowering activities, and phosphatidylglycerol, recently implicated in innate immune defense. Future studies providing a better understanding of the molecular control and physiological relevance of minor surfactant lipid components are needed. PMID:23026158

  1. Surfactants, skin cleansing protagonists.

    PubMed

    Corazza, M; Lauriola, M M; Zappaterra, M; Bianchi, A; Virgili, A

    2010-01-01

    The correct choice of cosmetic products and cleansers is very important to improve skin hydration, to provide moisturizing benefits and to minimize cutaneous damage caused by surfactants. In fact, surfactants may damage protein structures and solubilize lipids. Soaps, defined as the alkali salts of fatty acids, are the oldest surfactants and are quite aggressive. Syndets (synthetic detergents) vary in composition and surfactant types (anionic, cationic, amphotheric, non-ionic). These new skin cleansing products also contain preservatives, fragrances, and sometimes emollients, humectants and skin nutrients. We present a revision of the literature and discuss recent findings regarding skin cleansers.

  2. Towards unravelling surfactant transport

    NASA Astrophysics Data System (ADS)

    Sellier, Mathieu; Panda, Satyananda

    2015-11-01

    Surfactant transport arises in many natural or industrial settings. Examples include lipid tear layers in the eye, pulmonary surfactant replacement therapy, or industrial coating flows. Flows driven by the surface tension gradient which arises as a consequence of surfactant concentration inhomogeneity, also known as Marangoni-driven flows, have attracted the attention of fluid dynamists for several decades and has led to the development of sophisticated models and the undeniable advancement of the understanding of such flows. Yet, experimental confirmation of these models has been hampered by the difficulty in reliably and accurately measuring the surfactant concentration and its temporal evolution. In this contribution, we propose a methodology which may help shed some light on surfactant transport at the surface of thin liquid films. The surface stress induced by surfactant concentration induces a flow at the free surface which is visible and measurable. In the context of thin film flows for which the lubrication approximation hold, we demonstrate how the knowledge of this free surface flow field provides sufficient information to reconstruct the surfactant tension field. From the surface tension and an assumed equation of state, the local surfactant concentration can also be calculated and other transport parameters such as the surfactant surface diffusivity indirectly inferred. In this contribution, the proposed methodology is tested with synthetic data generated by the forward solution of the governing partial differential equations in order to illustrate the feasibility of the algorithm and highlight numerical challenges.

  3. Modification of Wyoming montmorillonite surfaces using a cationic surfactant.

    PubMed

    Xi, Yunfei; Frost, Ray L; He, Hongping; Kloprogge, Theo; Bostrom, Thor

    2005-09-13

    Surfaces of Wyoming SWy-2-Na-montmorillonite were modified using ultrasonic and hydrothermal methods through the intercalation and adsorption of the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG), and electron microscopy. The ultrasonic preparation method results in a higher surfactant concentration within the montmorillonite interlayer when compared with that from the hydrothermal method. Three different molecular environments for surfactants within the surface-modified montmorillonite are proposed upon the basis of their different decomposition temperatures. Both XRD patterns and TEM images demonstrate that SWy-2-Na-montmorillonite contains superlayers. TEM images of organoclays prepared at high surfactant concentrations show alternate basal spacings between neighboring layers. SEM images show that modification with surfactant reduces the clay particle size and aggregation. Organoclays prepared at low surfactant concentration display curved flakes, whereas they become flat with increasing intercalated surfactant. Novel surfactant-modified montmorillonite results in the formation of new nanophases with the potential for the removal of organic impurities from aqueous media.

  4. Interaction of photosensitive surfactant with DNA and poly acrylic acid

    SciTech Connect

    Zakrevskyy, Yuriy Paasche, Jens; Lomadze, Nino; Santer, Svetlana; Cywinski, Piotr; Cywinska, Magdalena; Reich, Oliver; Löhmannsröben, Hans-Gerd

    2014-01-28

    In this paper, we investigate interactions and phase transitions in polyelectrolyte-surfactant complexes formed between a cationic azobenzene-containing surfactant and two types of polyelectrolytes: natural (DNA) or synthetic (PAA: poly acrylic acid). The construction of a phase diagram allowed distancing between four major phases: extended coil conformation, colloidally stable compacted globules, colloidal instability range, and surfactant-stabilized compact state. Investigation on the complexes’ properties in different phases and under irradiation with UV light provides information about the role of the surfactant's hydrophobic trans isomers both in the formation and destruction of DNA and PAA globules as well as in their colloidal stabilization. The trans isomer shows much stronger affinity to the polyelectrolytes than the hydrophilic cis counterpart. There is no need for complete compensation of the polyelectrolyte charges to reach the complete compaction. On contrary to the findings previously reported in the literature, we demonstrate – for the first time – complete polyelectrolyte compaction which occurs already at 20% of DNA (and at 50% of PAA) charge compensation. The trans isomer plays the main role in the compaction. The aggregation between azobenzene units in the photosensitive surfactant is a driving force of this process. The decompaction can be realized during UV light irradiation and is strongly influenced by the interplay between surfactant-surfactant and surfactant-DNA interactions in the compacted globules.

  5. The interfacial interactions of Tb-doped silica nanoparticles with surfactants and phospholipids revealed through the fluorescent response.

    PubMed

    Bochkova, Olga D; Mustafina, Asiya R; Mukhametshina, Alsu R; Burilov, Vladimir A; Skripacheva, Viktoriya V; Zakharova, Lucia Ya; Fedorenko, Svetlana V; Konovalov, Alexander I; Soloveva, Svetlana E; Antipin, Igor S

    2012-04-01

    The quenching effect of dyes (phenol red and bromothymol blue) on Tb(III)-centered luminescence enables to sense the aggregation of cationic and anionic surfactants near the silica surface of Tb-doped silica nanoparticles (SN) in aqueous solutions. The Tb-centered luminescence of non-decorated SNs is diminished by the inner filter effect of both dyes. The decoration of the silica surface by cationic surfactants induces the quenching through the energy transfer between silica coated Tb(III) complexes and dye anions inserted into surfactant aggregates. Thus the distribution of surfactants aggregates at the silica/water interface and in the bulk of solution greatly affects dynamic quenching efficiency. The displacement of dye anions from the interfacial surfactant adlayer by anionic surfactants and phospholipids is accompanied by the "off-on" switching of Tb(III)-centered luminescence.

  6. Switching wormlike micelles of selenium-containing surfactant using redox reaction.

    PubMed

    Zhang, Yongmin; Kong, Weiwei; Wang, Cheng; An, Pengyun; Fang, Yun; Feng, Yujun; Qin, Zhirong; Liu, Xuefeng

    2015-10-14

    A novel redox-switchable wormlike micellar system was developed based on a mixture of selenium-containing zwitterionic surfactant and commercially available anionic surfactant sodium dodecyl sulfate, which reversibly and quickly responds to H2O2 and vitamin C, and shows circulatory gel/sol transition, reflecting changes in aggregate morphology from entangled worms to vesicles.

  7. On the mesoscopic origins of high viscosities in some polyelectrolyte-surfactant mixtures

    SciTech Connect

    Hoffmann, Ingo; Farago, Bela; Schweins, Ralf; Falus, Peter; Sharp, Melissa; Prévost, Sylvain; Gradzielski, Michael

    2015-08-21

    Oppositely charged polyelectrolyte (PE) surfactant mixtures allow the control of rheological parameters of a solution even at fairly low concentrations. For example, addition of 0.3 wt. % of anionic surfactant to a 1 wt. % solution of the polycation JR 400 increases the viscosity by 4 orders of magnitude. Recently, we could show that this increase is related to the formation of mixed, rod-like PE/surfactant aggregates which interconnect several polyelectrolyte chains [Hoffmann et al., Europhys. Lett. 104, 28001 (2013)]. In this paper, we refine our structural model of the aggregates to obtain a more consistent picture of their internal structure for different anionic surfactants. Combining small angle neutron scattering (SANS) and neutron spin-echo (NSE) allows us to determine the size of the aggregates. By comparing different contrasts, the internal structure of the aggregates can be elucidated and it is seen that the PE in the aggregates retains a relatively high freedom of movement. We proceeded to investigate the influence of the surfactant concentration and the surfactant type on structure and dynamics of the mixed aggregates. It is seen that the structural parameters of the aggregates depend very little on the surfactant concentration and headgroup. However, it is crucial to incorporate a sufficient amount of PE in the aggregates to increase the viscosity of the aggregates. By comparing viscous samples at 1 wt. % PE concentration with samples at a PE concentration of 0.3 wt. %, where no significant increase in viscosity is observed, we find that similar aggregates are formed already at this lower PE concentrations. However, the amount of PE incorporated in them is insufficient to interconnect several PE chains and therefore, they do not increase viscosity. So, our detailed investigation combining contrast variation SANS and NSE does not only allow to explain the viscosity behavior but also to deduced detailed information regarding the structures and

  8. On the shape of giant soap bubbles.

    PubMed

    Cohen, Caroline; Darbois Texier, Baptiste; Reyssat, Etienne; Snoeijer, Jacco H; Quéré, David; Clanet, Christophe

    2017-03-07

    We study the effect of gravity on giant soap bubbles and show that it becomes dominant above the critical size [Formula: see text], where [Formula: see text] is the mean thickness of the soap film and [Formula: see text] is the capillary length ([Formula: see text] stands for vapor-liquid surface tension, and [Formula: see text] stands for the liquid density). We first show experimentally that large soap bubbles do not retain a spherical shape but flatten when increasing their size. A theoretical model is then developed to account for this effect, predicting the shape based on mechanical equilibrium. In stark contrast to liquid drops, we show that there is no mechanical limit of the height of giant bubble shapes. In practice, the physicochemical constraints imposed by surfactant molecules limit the access to this large asymptotic domain. However, by an exact analogy, it is shown how the giant bubble shapes can be realized by large inflatable structures.

  9. On the shape of giant soap bubbles

    PubMed Central

    Cohen, Caroline; Darbois Texier, Baptiste; Reyssat, Etienne; Snoeijer, Jacco H.; Quéré, David; Clanet, Christophe

    2017-01-01

    We study the effect of gravity on giant soap bubbles and show that it becomes dominant above the critical size ℓ=a2/e0, where e0 is the mean thickness of the soap film and a=γb/ρg is the capillary length (γb stands for vapor–liquid surface tension, and ρ stands for the liquid density). We first show experimentally that large soap bubbles do not retain a spherical shape but flatten when increasing their size. A theoretical model is then developed to account for this effect, predicting the shape based on mechanical equilibrium. In stark contrast to liquid drops, we show that there is no mechanical limit of the height of giant bubble shapes. In practice, the physicochemical constraints imposed by surfactant molecules limit the access to this large asymptotic domain. However, by an exact analogy, it is shown how the giant bubble shapes can be realized by large inflatable structures. PMID:28223485

  10. Fetal corticosteroid and T4 treatment effects on lung function of surfactant-treated preterm lambs.

    PubMed

    Chen, C M; Ikegami, M; Ueda, T; Polk, D H; Jobe, A H

    1995-01-01

    Three groups of sheep fetuses at 125 or 126 d gestational age randomly received a single ultrasound-guided intramuscular injection of saline, 0.5 mg/kg betamethasone, or 0.5 mg/kg betamethasone plus 50 micrograms/kg thyroxine (T4). Forty-eight hours later the fetuses were delivered, treated with a pulmonary surfactant preparation, and ventilated for 3 h. Corticosteroids alone and in combination with T4 increased FRC, compliance, and lung volumes, and decreased the protein leak into the airspace. Saturated phosphatidylcholine pool sizes recovered by alveolar washing were not changed after hormone treatment. To evaluate the function of surfactant recovered from the lambs in vivo, we treated preterm rabbits at 27 d gestational age with the large-aggregate surfactant from alveolar washes. Large-aggregate surfactants and the pulmonary surfactant preparation increased compliances and maximal lung volumes relative to those in untreated preterm rabbits. Large-aggregate surfactants improved compliance more than did the pulmonary surfactant preparation. We conclude that ultrasound-guided single fetal corticosteroid treatment followed by postnatal surfactant improved postnatal lung function in preterm lambs. Addition of T4 did not augment corticosteroid effects. The function of the exogenous surfactant was improved in premature lamb lungs independently of the fetal treatment modality.

  11. Mixing Effect of Polyoxyethylene-Type Nonionic Surfactants on the Liquid Crystalline Structures.

    PubMed

    Kunieda; Umizu; Yamaguchi

    1999-10-01

    An effective cross-sectional area per surfactant molecule at hydrophobic interfaces of aggregates, a(S), in hexagonal (H(1)) and lamellar (L(alpha)) liquid crystals was calculated in homogeneous and mixed polyoxyethylene dodecyl ether systems as a function of polyoxyethylene (EO) chain length by means of small-angle X-ray scattering. The a(S) increases with increasing the EO chain length. The a(S) in the mixed surfactant system is considerably smaller than that in the single surfactant system, even if the average EO chain length is the same. The reduction of a(S) is larger than that predicted by ideal mixing of the surfactants. Moreover, if the EO chain lengths of the surfactants are more separated, the a(S) is smaller. The shapes of surfactant self-organizing structures may be governed by the balance of the attractive and the repulsive forces acting at the hydrophobic interfaces of the aggregates. According to this consideration, the mixing effect of surfactants with the different EO chain lengths on the a(S) in the L(alpha) phase was discussed. It is considered that the surfactant molecules are tightly packed in the aggregates since the reduction in repulsion force takes place in the excess EO chain part of the hydrophilic surfactant longer than the short EO chain of the lipophilic one. The lower surface tensions and the better stability of macroemulsions and the large solubilizing capacity of microemulsions result from the mixing effect. Copyright 1999 Academic Press.

  12. Mechanisms to explain surfactant responses.

    PubMed

    Jobe, Alan H

    2006-01-01

    Surfactant is now standard of care for infants with respiratory distress syndrome. Surfactant treatments are effective because of complex metabolic interactions between surfactant and the preterm lung. The large treatment dose functions as substrate; it is taken up by the preterm lung and is reprocessed and secreted with improved function. The components of the treatment surfactant remain in the preterm lung for days. If lung injury is avoided, then surfactant inhibition is minimized. Prenatal corticosteroids complement surfactant to further enhance lung function. The magic of surfactant therapy results from the multiple interactions between surfactant and the preterm lung. Copyright (c) 2006 S. Karger AG, Basel.

  13. Effect of sodium dodecyl sulfate surfactant on rheological properties of gellan gum hydrogels

    NASA Astrophysics Data System (ADS)

    Mithra, K.; Khandai, Santripti; Jena, Sidhartha S.

    2017-05-01

    Rheological measurements on gellan gum hydrogels were carried out to investigate the effect of an anionic surfactant, sodium dodecyl sulfate (SDS) on hydrogel structure. The gel strength was found to be strongly correlated to surfactant concentration. Below the Critical Micellar Concentration (CMC), we observed an increase in gel strength with rise in surfactant concentration and a reverse trend is observed for surfactant concentration above CMC. The gel network structure is found to be highly elastic below CMC, while an aggregated network is observed at higher concentration of surfactant. With the addition of surfactant, sol to gel transition temperature of Gellan Gum is shifted to higher temperature, suggesting addition of surfactant promotesas well as stabilizes the helix formation.

  14. Immunogenicity of surfactant. II. Porcine and bovine surfactants.

    PubMed Central

    Strayer, D S; Hallman, M; Merritt, T A

    1991-01-01

    Protein-containing surfactants of human and animal origin are being used increasingly to treat neonatal and adult respiratory distress syndromes. This trend led us to examine the antigenicity of two important preparations of animal surfactant, cow lung surfactant extract (CLSE) and a porcine surfactant preparation, Curosurf. We describe here 15 monoclonal antibodies against Curosurf and four against CLSE. Antibodies were studied by Western blot analysis to determine their ability to recognize protein components of their respective surfactant preparations. They were also tested for their ability to inactivate surfactant in vitro, assayed using the pulsating bubble surfactometer. Several antibodies directed against CLSE or Curosurf functionally inactivate the surfactant to which they were raised. We determined the degree of immunologic cross-reactivity between antibodies directed to CLSE and Curosurf against the other surfactant and also against human surfactant, both by Western blot and by examining functional inactivation in vitro. Antibodies to these animal surfactants that are commonly used therapeutically may inactivate the specific animal surfactant to which they were raised, as well as human and other surfactants. Generally, when antibodies inactivate surfactant from more than one animal species, they inactivate heterologous surfactants comparably to the extent to which they inactivate the surfactant to which they are directed. Immune complexes between anti-surfactant antibodies and surfactant have been described in the course of neonatal respiratory distress syndrome. The potential pathophysiological importance of anti-surfactant antibodies may therefore lie in their ability to inactivate administered surfactant, other similar surfactants and endogenous surfactant. In so doing, these antibodies may potentiate surfactant deficiency or pulmonary injury initiated by other stimuli. Images Fig. 1 Fig. 2 PMID:1988231

  15. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  16. SURFACTANTS AND SUBSURFACE REMEDIATION

    EPA Science Inventory

    Because of the limitations of pump-and-trat technology, attention is now focused on the feasibility of surfactant use to increase its efficiency. Surfactants have been studied for use in soil washing and enhanced oil recovery. Although similarities exist between the application...

  17. SURFACTANTS AND SUBSURFACE REMEDIATION

    EPA Science Inventory

    Because of the limitations of pump-and-trat technology, attention is now focused on the feasibility of surfactant use to increase its efficiency. Surfactants have been studied for use in soil washing and enhanced oil recovery. Although similarities exist between the application...

  18. SURFACTANTS IN LUBRICATION

    USDA-ARS?s Scientific Manuscript database

    Surfactants are one of the most widely applied materials by consumers and industry. The application areas for surfactants span from everyday mundane tasks such as cleaning, to highly complex processes involving the formulation of pharmaceuticals, foods, pesticides, lubricants, etc. Even though sur...

  19. New generation synthetic surfactants.

    PubMed

    Curstedt, Tore; Calkovska, Andrea; Johansson, Jan

    2013-01-01

    The treatment of preterm newborn rabbits with synthetic surfactants containing simple phospholipid mixtures and peptides gives similar tidal volumes to treatment with poractant alfa (Curosurf®). The addition of both surfactant protein B and C analogs to the phospholipid mixture will stabilize the alveoli, measured as lung gas volumes at end expiration, even if no positive end-expiratory pressure is applied. The effect on lung gas volumes seems to depend on the structure of the peptides as well as the phospholipid composition. It seems that synthetic surfactants containing two peptides and a more complex phospholipid composition will be able to replace natural surfactants within the near future, but more experiments need to be performed before any conclusion can be drawn about the ideal composition of this new generation of synthetic surfactants.

  20. Partition and water/oil adsorption of some surfactants.

    PubMed

    Tadmouri, Rawad; Zedde, Chantal; Routaboul, Corinne; Micheau, Jean-Claude; Pimienta, Véronique

    2008-10-02

    Adsorption isotherms have been determined at the water/oil interface for five biphasic systems involving surfactants (non-ionic and ionic) present in both phases at partition equilibrium. The systems studied were polyoxyethylene(23)lauryl ether (Brij35) in water/hexane and four ionic surfactants, hexadecyltrimethylammonium bromide (CTAB), and a series of three tetraalkylammonium dodecylsulfate (TEADS, TPADS, and TBADS) in water/CH 2Cl 2. Interfacial tension measurements performed at the water/air and water/oil interfaces provided all the necessary information for the determination of the adsorption parameters by taking partition into account. These measurements also allowed the comparison of the adsorption properties at both interfaces which showed an increase of the adsorption equilibrium constant and a decrease of the maximum surface concentration at the water/oil interface compared to water/air. The values of the critical aggregation concentration showed, in all cases, that only the surfactant dissolved in the aqueous phase contribute to the decrease of the water/oil interfacial tension. In the case of the four ionic surfactants, the critical aggregation concentration obtained in biphasic conditions were lowered because of the formation of mixed surfactant-CH 2Cl 2 aggregates.

  1. Surfactants in the environment.

    PubMed

    Ivanković, Tomislav; Hrenović, Jasna

    2010-03-01

    Surfactants are a diverse group of chemicals that are best known for their wide use in detergents and other cleaning products. After use, residual surfactants are discharged into sewage systems or directly into surface waters, and most of them end up dispersed in different environmental compartments such as soil, water or sediment. The toxic effects of surfactants on various aquatic organisms are well known. In general, surfactants are present in the environment at levels below toxicity and in Croatia below the national limit. Most surfactants are readily biodegradable and their amount is greatly reduced with secondary treatment in wastewater treatment plants. The highest concern is the release of untreated wastewater or wastewater that has undergone primary treatment alone. The discharge of wastewater polluted with massive quantities of surfactants could have serious effects on the ecosystem. Future studies of surfactant toxicities and biodegradation are necessary to withdraw highly toxic and non-biodegradable compounds from commercial use and replace them with more environmentally friendly ones.

  2. Mechanisms of Particle Charging by Surfactants in Nonpolar Dispersions.

    PubMed

    Lee, Joohyung; Zhou, Zhang-Lin; Alas, Guillermo; Behrens, Sven Holger

    2015-11-10

    Electric charging of colloidal particles in nonpolar solvents plays a crucial role for many industrial applications and products, including rubbers, engine oils, toners, or electronic displays. Although disfavored by the low solvent permittivity, particle charging can be induced by added surfactants, even nonionic ones, but the underlying mechanism is poorly understood, and neither the magnitude nor the sign of charge can generally be predicted from the particle and surfactant properties. The conclusiveness of scientific studies has been limited partly by a traditional focus on few surfactant types with many differences in their chemical structure and often poorly defined composition. Here we investigate the surface charging of poly(methyl methacrylate) particles dispersed in hexane-based solutions of three purified polyisobutylene succinimide polyamine surfactants with "subtle" structural variations. We precisely vary the surfactant chemistry by replacing only a single electronegative atom located at a fixed position within the polar headgroup. Electrophoresis reveals that these small differences between the surfactants lead to qualitatively different particle charging. In the respective particle-free surfactant solutions we also find potentially telling differences in the size of the surfactant aggregates (inverse micelles), the residual water content, and the electric solution conductivity as well as indications for a significant size difference between oppositely charged inverse micelles of the most hygroscopic surfactant. An analysis that accounts for the acid/base properties of all constituents suggests that the observed particle charging is better described by asymmetric adsorption of charged inverse micelles from the liquid bulk than by charge creation at the particle surface. Intramicellar acid-base interaction and intermicellar surfactant exchange help rationalize the formation of micellar ions pairs with size asymmetry.

  3. Tuning of depletion interaction in nanoparticle-surfactant systems

    SciTech Connect

    Ray, D. Aswal, V. K.

    2014-04-24

    The interaction of anionic silica nanoparticles (Ludox LS30) and non-ionic surfactants decaethylene glycol monododecylether (C12E10) without and with anionic sodium dodecyl sulfate (SDS) in aqueous electrolyte solution has been studied by small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations of nanoparticle (1 wt%), surfactants (1 wt%) and electrolyte (0.1 M NaCl). Each of these nanoparticlesurfactant systems has been examined for different contrast conditions where individual components (nanoparticle or surfactant) are made visible. It is observed that the nanoparticle-C12E10 system leads to the depletion-induced aggregation of nanoparticles. The system however behaves very differently on addition of SDS where depletion interaction gets suppressed and aggregation of nanoparticles can be prevented. We show that C12E10 and SDS form mixed micelles and the charge on these micelles plays important role in tuning the depletion interaction.

  4. Application of peptide gemini surfactants as novel solubilization surfactants for photosystems I and II of cyanobacteria.

    PubMed

    Koeda, Shuhei; Umezaki, Katsunari; Noji, Tomoyasu; Ikeda, Atsushi; Kawakami, Keisuke; Kondo, Masaharu; Yamamoto, Yasushi; Shen, Jian-Ren; Taga, Keijiro; Dewa, Takehisa; Ito, Shigeru; Nango, Mamoru; Tanaka, Toshiki; Mizuno, Toshihisa

    2013-09-17

    We designed novel peptide gemini surfactants (PG-surfactants), DKDKC12K and DKDKC12D, which can solubilize Photosystem I (PSI) of Thermosynecoccus elongatus and Photosystem II (PSII) of Thermosynecoccus vulcanus in an aqueous buffer solution. To assess the detailed effects of PG-surfactants on the original supramolecular membrane protein complexes and functions of PSI and PSII, we applied the surfactant exchange method to the isolated PSI and PSII. Spectroscopic properties, light-induced electron transfer activity, and dynamic light scattering measurements showed that PSI and PSII could be solubilized not only with retention of the original supramolecular protein complexes and functions but also without forming aggregates. Furthermore, measurement of the lifetime of light-induced charge-separation state in PSI revealed that both surfactants, especially DKDKC12D, displayed slight improvement against thermal denaturation below 60 °C compared with that using β-DDM. This degree of improvement in thermal resistance still seems low, implying that the peptide moieties did not interact directly with membrane protein surfaces. By conjugating an electron mediator such as methyl viologen (MV(2+)) to DKDKC12K (denoted MV-DKDKC12K), we obtained derivatives that can trap the generated reductive electrons from the light-irradiated PSI. After immobilization onto an indium tin oxide electrode, a cathodic photocurrent from the electrode to the PSI/MV-DKDKC12K conjugate was observed in response to the interval of light irradiation. These findings indicate that the PG-surfactants DKDKC12K and DKDKC12D provide not only a new class of solubilization surfactants but also insights into designing other derivatives that confer new functions on PSI and PSII.

  5. Metathesis depolymerizable surfactants

    DOEpatents

    Jamison, Gregory M.; Wheeler, David R.; Loy, Douglas A.; Simmons, Blake A.; Long, Timothy M.; McElhanon, James R.; Rahimian, Kamyar; Staiger, Chad L.

    2008-04-15

    A class of surfactant molecules whose structure includes regularly spaced unsaturation in the tail group and thus, can be readily decomposed by ring-closing metathesis, and particularly by the action of a transition metal catalyst, to form small molecule products. These small molecules are designed to have increased volatility and/or enhanced solubility as compared to the original surfactant molecule and are thus easily removed by solvent extraction or vacuum extraction at low temperature. By producing easily removable decomposition products, the surfactant molecules become particularly desirable as template structures for preparing meso- and microstructural materials with tailored properties.

  6. Magnetic surfactants as molecular based-magnets with spin glass-like properties.

    PubMed

    Brown, Paul; Smith, Gregory N; Hernández, Eduardo Padrón; James, Craig; Eastoe, Julian; Nunes, Wallace C; Settens, Charles M; Hatton, T Alan; Baker, Peter J

    2016-05-05

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets.

  7. Magnetic surfactants as molecular based-magnets with spin glass-like properties

    NASA Astrophysics Data System (ADS)

    Brown, Paul; Smith, Gregory N.; Padrón Hernández, Eduardo; James, Craig; Eastoe, Julian; Nunes, Wallace C.; Settens, Charles M.; Hatton, T. Alan; Baker, Peter J.

    2016-05-01

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets.

  8. New serine-derived gemini surfactants as gene delivery systems.

    PubMed

    Cardoso, Ana M; Morais, Catarina M; Cruz, A Rita; Silva, Sandra G; do Vale, M Luísa; Marques, Eduardo F; de Lima, Maria C Pedroso; Jurado, Amália S

    2015-01-01

    Gemini surfactants have been extensively used for in vitro gene delivery. Amino acid-derived gemini surfactants combine the special aggregation properties characteristic of the gemini surfactants with high biocompatibility and biodegradability. In this work, novel serine-derived gemini surfactants, differing in alkyl chain lengths and in the linker group bridging the spacer to the headgroups (amine, amide and ester), were evaluated for their ability to mediate gene delivery either per se or in combination with helper lipids. Gemini surfactant-based DNA complexes were characterized in terms of hydrodynamic diameter, surface charge, stability in aqueous buffer and ability to protect DNA. Efficient formulations, able to transfect up to 50% of the cells without causing toxicity, were found at very low surfactant/DNA charge ratios (1/1-2/1). The most efficient complexes presented sizes suitable for intravenous administration and negative surface charge, a feature known to preclude potentially adverse interactions with serum components. This work brings forward a new family of gemini surfactants with great potential as gene delivery systems. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Biophysical inhibition of synthetic vs. naturally-derived pulmonary surfactant preparations by polymeric nanoparticles.

    PubMed

    Beck-Broichsitter, Moritz; Ruppert, Clemens; Schmehl, Thomas; Günther, Andreas; Seeger, Werner

    2014-01-01

    Reasonable suspicion has accumulated that inhaled nano-scale particulate matter influences the biophysical function of the pulmonary surfactant system. Hence, it is evident to provide novel insights into the extent and mechanisms of nanoparticle-surfactant interactions in order to facilitate the fabrication of safe nanomedicines suitable for pulmonary applications. Negatively- and positively-charged poly(styrene) nanoparticles (diameters of ~100nm) served as model carriers. Nanoparticles were incubated with several synthetic and naturally-derived pulmonary surfactants to characterize the sensitivity of each preparation to biophysical inactivation. Changes in surface properties (i.e. adsorption and dynamic surface tension behavior) were monitored in a pulsating bubble surfactometer. Both nanoparticle formulations revealed a dose-dependent influence on the biophysical behavior of all investigated pulmonary surfactants. However, the surfactant sensitivity towards inhibition depended on both the carrier type, where negatively-charged nanoparticles showed increased inactivation potency compared to their positively-charged counterparts, and surfactant composition. Among the surfactants tested, synthetic mixtures (i.e. phospholipids, phospholipids supplemented with surfactant protein B, and Venticute®) were more susceptible to surface-activity inhibition as the more complex naturally-derived preparations (i.e. Alveofact® and large surfactant aggregates isolated from rabbit bronchoalveolar lavage fluid). Overall, nanoparticle characteristics and surfactant constitution both influence the extent of biophysical inhibition of pulmonary surfactants. © 2013.

  10. Recent advances in gemini surfactants: oleic Acid-based gemini surfactants and polymerizable gemini surfactants.

    PubMed

    Sakai, Kenichi; Sakai, Hideki; Abe, Masahiko

    2011-01-01

    Gemini surfactants recently developed by our research group are introduced from the standpoints of their syntheses, aqueous solution properties, and potential applications. Two series of gemini surfactants are introduced in this short review, the first of which is the oleic acid-based gemini surfactants, and the second is the polymerizable gemini surfactants. These gemini surfactants have been developed not only as environmentally friendly materials (the use of gemini surfactants enables the reduction of the total consumption of surfactants in chemical products owing to their excellent adsorption and micellization capabilities at low concentrations) but also as functional organic materials.

  11. Phosphine oxide surfactants revisited.

    PubMed

    Stubenrauch, Cosima; Preisig, Natalie; Laughlin, Robert G

    2016-04-01

    This review summarizes everything we currently know about the nonionic surfactants alkyl dimethyl (C(n)DMPO) and alkyl diethyl (C(n)DEPO) phosphine oxide (PO surfactants). The review starts with the synthesis and the general properties (Section 2) of these compounds and continues with their interfacial properties (Section 3) such as surface tension, surface rheology, interfacial tension and adsorption at solid surfaces. We discuss studies on thin liquid films and foams stabilized by PO surfactants (Section 4) as well as studies on their self-assembly into lyotropic liquid crystals and microemulsions, respectively (Section 5). We aim at encouraging colleagues from both academia and industry to take on board PO surfactants whenever possible and feasible because of their broad variety of excellent properties.

  12. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  13. Binding of Alkyl Polyglucoside Surfactants to Bacteriorhodopsin and its Relation to Protein Stability

    PubMed Central

    Santonicola, M. Gabriella; Lenhoff, Abraham M.; Kaler, Eric W.

    2008-01-01

    The binding of alkyl polyglucoside surfactants to the integral membrane protein bacteriorhodopsin (BR) and the formation of protein-surfactant complexes are investigated by sedimentation equilibrium via analytical ultracentrifugation and by small-angle neutron scattering (SANS). Contrast variation techniques in SANS enable measurement of the composition of the protein-surfactant complexes and determination of the thickness of the surfactant shell bound to the protein. The results indicate that alkyl polyglucosides can bind to BR as single surfactant layers or as a thicker shell. The thickness of the surfactant shell increases with increasing surfactant tail length, and it is generally unrelated to the aggregation number of the micelles even for a small and predominantly hydrophobic membrane protein such as BR. The aggregation numbers determined by sedimentation equilibrium methods match those measured by SANS, which also allows reconstruction of the shape of the protein-detergent complex. When the surfactant is present as a single layer, the BR loses activity, as measured by absorption spectroscopy, more quickly than it does when the surfactant forms a thicker shell. PMID:18234822

  14. Binding of alkyl polyglucoside surfactants to bacteriorhodopsin and its relation to protein stability.

    PubMed

    Santonicola, M Gabriella; Lenhoff, Abraham M; Kaler, Eric W

    2008-05-01

    The binding of alkyl polyglucoside surfactants to the integral membrane protein bacteriorhodopsin (BR) and the formation of protein-surfactant complexes are investigated by sedimentation equilibrium via analytical ultracentrifugation and by small-angle neutron scattering (SANS). Contrast variation techniques in SANS enable measurement of the composition of the protein-surfactant complexes and determination of the thickness of the surfactant shell bound to the protein. The results indicate that alkyl polyglucosides can bind to BR as single surfactant layers or as a thicker shell. The thickness of the surfactant shell increases with increasing surfactant tail length, and it is generally unrelated to the aggregation number of the micelles even for a small and predominantly hydrophobic membrane protein such as BR. The aggregation numbers determined by sedimentation equilibrium methods match those measured by SANS, which also allows reconstruction of the shape of the protein-detergent complex. When the surfactant is present as a single layer, the BR loses activity, as measured by absorption spectroscopy, more quickly than it does when the surfactant forms a thicker shell.

  15. Determination of the critical micelle concentration in simulations of surfactant systems

    SciTech Connect

    Santos, Andrew P.; Panagiotopoulos, Athanassios Z.

    2016-01-28

    Alternative methods for determining the critical micelle concentration (cmc) are investigated using canonical and grand canonical Monte Carlo simulations of a lattice surfactant model. A common measure of the cmc is the “free” (unassociated) surfactant concentration in the presence of micellar aggregates. Many prior simulations of micellizing systems have observed a decrease in the free surfactant concentration with overall surfactant loading for both ionic and nonionic surfactants, contrary to theoretical expectations from mass-action models of aggregation. In the present study, we investigate a simple lattice nonionic surfactant model in implicit solvent, for which highly reproducible simulations are possible in both the canonical (NVT) and grand canonical (μVT) ensembles. We confirm the previously observed decrease of free surfactant concentration at higher overall loadings and propose an algorithm for the precise calculation of the excluded volume and effective concentration of unassociated surfactant molecules in the accessible volume of the solution. We find that the cmc can be obtained by correcting the free surfactant concentration for volume exclusion effects resulting from the presence of micellar aggregates. We also develop an improved method for determination of the cmc based on the maximum in curvature for the osmotic pressure curve determined from μVT simulations. Excellent agreement in cmc and other micellar properties between NVT and μVT simulations of different system sizes is observed. The methodological developments in this work are broadly applicable to simulations of aggregating systems using any type of surfactant model (atomistic/coarse grained) or solvent description (explicit/implicit)

  16. Adsorption of anionic and non-ionic surfactants on carbon nanotubes in water with dissipative particle dynamics simulation

    NASA Astrophysics Data System (ADS)

    Vo, Minh D.; Shiau, Benjamin; Harwell, Jeffrey H.; Papavassiliou, Dimitrios V.

    2016-05-01

    The morphology of surfactants physically adsorbed on the surface of carbon nanotubes (CNTs) has a significant impact on the dispersion of CNTs in the solution. The adsorption of the surfactants alfoterra 123-8s (AF) and tergitol 15-s-40 (TG) on CNTs was investigated with dissipative particle dynamics (DPD) simulations, as well as the behavior of the binary surfactant system with CNTs. Properties of surfactants (i.e., critical micelle concentration, aggregation number, shape and size of micelle, and diffusivity) in water were determined to validate the simulation model. Results indicated that the assembly of surfactants (AF and TG) on CNTs depends on the interaction of the surfactant tail and the CNT surface, where surfactants formed mainly hemimicellar structures. For surfactants in solution, most micelles had spherical shape. The particles formed by the CNT and the adsorbed surfactant became hydrophilic, due to the outward orientation of the head groups of the surfactants that formed monolayer adsorption. In the binary surfactant system, the presence of TG on the CNT surface provided a considerable hydrophilic steric effect, due to the EO groups of TG molecules. It was also seen that the adsorption of AF was more favorable than TG on the CNT surface. Diffusion coefficients for the surfactants in the bulk and surface diffusion on the CNT were calculated. These results are applicable, in a qualitative sense, to the more general case of adsorption of surfactants on the hydrophobic surface of cylindrically shaped nanoscale objects.

  17. Polymer gels with associating side chains and their interaction with surfactants

    NASA Astrophysics Data System (ADS)

    Gordievskaya, Yulia D.; Rumyantsev, Artem M.; Kramarenko, Elena Yu.

    2016-05-01

    Conformational behaviour of hydrophobically modified (HM) polymer gels in solutions of nonionic surfactants is studied theoretically. A HM gel contains hydrophobic side chains (stickers) grafted to its subchains. Hydrophobic stickers are capable to aggregate into joint micelles with surfactant molecules. Micelles containing more than one sticker serve as additional physical cross-links of the network, and their formation causes gel shrinking. In the proposed theoretical model, the interior of the gel/surfactant complex is treated as an array of densely packed spherical polymer brushes consisting of gel subchains tethered to the surface of the spherical sticker/surfactant micelles. Effect of stickers length and grafting density, surfactant concentration and hydrophobicity on gel swelling as well as on hydrophobic association inside it is analyzed. It is shown that increasing surfactant concentration can result in a gel collapse, which is caused by surfactant-induced hydrophobic aggregation of stickers, and a successive gel reswelling. The latter should be attributed to a growing fraction of surfactants in joint aggregates and, hence, increasing number of micelles containing only one sticker and not participating in gel physical cross-linking. In polyelectrolyte (PE) gels hydrophobic aggregation is opposed by osmotic pressure of mobile counterions, so that at some critical ionization degree hydrophobic association is completely suppressed. Hydrophobic modification of polymers is shown to open new ways for controlling gel responsiveness. In particular, it is discussed that incorporation of photosensitive groups into gel subchains and/or surfactant tail could give a possibility to vary the gel volume by light. Since hydrophobic aggregation regularities in gels and solutions are common, we hope our findings will be useful for design of polymer based self-healing materials as well.

  18. Synthesis and Crystallization Behavior of Surfactants with Hexamolybdate as the Polar Headgroup

    DOE PAGES

    Zhu, Li; Chen, Kun; Hao, Jian; ...

    2015-06-12

    For this paper, alkyl chains with different lengths were covalently grafted onto the surface of hexamolybdate through the postfunctionalization protocol of polyoxometalates. The obtained compounds represent typical structures of the so-called giant surfactants. Unexpectedly, those surfactants with hexamolybdates as polar headgroups are able to crystallize, while single-crystal X-ray diffraction reveals that the crystallization behavior of the surfactants is highly dependent on the length of the alkyl chains. For surfactants with comparatively short alkyl chains (C6 and C10), the alkyl chains prefer to interact with tetrabutylammonium, the countercation of hexamolybdate. However, the alkyl chains tend to pack with each other tomore » form a domain of alkyl chains in the surfactant with a longer alkyl chain (C18). Finally, the possible mechanism is that a long alkyl chain cannot be fully compatible with the short chain (C4) of tetrabutylammonium.« less

  19. Synthesis and Crystallization Behavior of Surfactants with Hexamolybdate as the Polar Headgroup

    SciTech Connect

    Zhu, Li; Chen, Kun; Hao, Jian; Wei, Zheyu; Zhang, Haocheng; Yin, Panchao; Wei, Yongge

    2015-06-12

    For this paper, alkyl chains with different lengths were covalently grafted onto the surface of hexamolybdate through the postfunctionalization protocol of polyoxometalates. The obtained compounds represent typical structures of the so-called giant surfactants. Unexpectedly, those surfactants with hexamolybdates as polar headgroups are able to crystallize, while single-crystal X-ray diffraction reveals that the crystallization behavior of the surfactants is highly dependent on the length of the alkyl chains. For surfactants with comparatively short alkyl chains (C6 and C10), the alkyl chains prefer to interact with tetrabutylammonium, the countercation of hexamolybdate. However, the alkyl chains tend to pack with each other to form a domain of alkyl chains in the surfactant with a longer alkyl chain (C18). Finally, the possible mechanism is that a long alkyl chain cannot be fully compatible with the short chain (C4) of tetrabutylammonium.

  20. Giant Magnons Meet Giant Gravitons

    SciTech Connect

    Hofman, Diego M.

    2008-07-28

    We study the worldsheet reflection matrix of a string attached to a D-brane in AdS{sub 5}xS{sup 5}. The D-brane corresponds to a maximal giant graviton that wraps an S{sup 3} inside S{sup 5}. In the gauge theory, the open string is described by a spin chain with boundaries. We focus on open strings with a large SO(6) charge and define an asymptotic boundary reflection matrix. Using the symmetries of the problem, we review the computation of the boundary reflection matrix, up to a phase. We also discuss weak and strong coupling computations where we obtain the overall phase factor and test our exact results.

  1. SANS and DLS Studies of Protein Unfolding in Presence of Urea and Surfactant

    SciTech Connect

    Aswal, V. K.; Chodankar, S. N.; Wagh, A. G.; Kohlbrecher, J.; Vavrin, R.

    2008-03-17

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been used to study conformational changes in protein bovine serum albumin (BSA) during its unfolding in presence of protein denaturating agents urea and surfactant. On addition of urea, the BSA protein unfolds for urea concentrations greater than 4 M and acquires a random coil configuration with its radius of gyration increasing with urea concentration. The addition of surfactant unfolds the protein by the formation of micelle-like aggregates of surfactants along the unfolded polypeptide chains of the protein. The fractal dimension of such a protein-surfactant complex decreases and the overall size of the complex increases on increasing the surfactant concentration. The conformation of the unfolded protein in the complex has been determined directly using contrast variation SANS measurements by contrast matching the surfactant to the medium. Results of DLS measurements are found to be in good agreement with those obtained using SANS.

  2. Beneficial effects of synthetic KL₄ surfactant in experimental lung transplantation.

    PubMed

    Sáenz, A; Alvarez, L; Santos, M; López-Sánchez, A; Castillo-Olivares, J L; Varela, A; Segal, R; Casals, C

    2011-04-01

    The aim of this study was to investigate whether intratracheal administration of a new synthetic surfactant that includes the cationic, hydrophobic 21-residue peptide KLLLLKLLLLKLLLLKLLLLK (KL₄), might be effective in reducing ischaemia-reperfusion injury after lung transplantation. Single left lung transplantation was performed in Landrace pigs 22 h post-harvest. KL₄ surfactant at a dose of 25 mg total phospholipid·kg body weight⁻¹ (2.5 mL·kg body weight⁻¹) was instilled at 37°C to the donor left lung (n = 8) prior to explantation. Saline (2.5 mL·kg body weight⁻¹; 37°C) was instilled into the donor left lung of the untreated group (n = 6). Lung function in recipients was measured during 2 h of reperfusion. Recipient left lung bronchoalveolar lavage (BAL) provided native cytometric, inflammatory marker and surfactant data. KL(4) surfactant treatment recovered oxygen levels in the recipient blood (mean ± sd arterial oxygen tension/inspiratory oxygen fraction 424 ± 60 versus 263 ± 101 mmHg in untreated group; p=0.01) and normalised alveolar-arterial oxygen tension difference. Surfactant biophysical function was also recovered in KL₄ surfactant-treated lungs. This was associated with decreased C-reactive protein levels in BAL, and recovery of surfactant protein A content, normalised protein/phospholipid ratios, and lower levels of both lipid peroxides and protein carbonyls in large surfactant aggregates. These findings suggest an important protective role for KL₄ surfactant treatment in lung transplantation.

  3. A study of surfactant adsorption with applications in surfactant assisted enhanced oil recovery processes

    SciTech Connect

    Hankins, N.P.

    1989-01-01

    A study is presented to assess the feasibility of high-pH preflushing to reduce surfactant adsorption in micellar flooding. Under static or dynamic flow conditions, adsorption of a pure anionic surfactant on Berea is eliminated at mild electrolyte above pH 8, 2 pH units above the experimental determined pzc. Static and dynamic studies of hydroxide consumption by Berea indicate mild dissolution at the pH range of interest. The effect of pH on the adsorption isotherm for Berea indicate a large increase in logarithmic slope at high pH. Similar studies are presented for kaolinite and alumina. A patch-wise, phase separation model is presented to quantify the relationship between adsorption, and bulk pH and salinity. The concept of the site-binding model is incorporated into the development of surface aggregates (both admicelles and hemimicelles), and it is confirmed that the aggregates are stabilized at high pH by the abstraction of positive charge to the surface beneath the aggregate, and by high counterion binding, allowing physical adsorption above the pzc. A novel sweep improvement process, surfactant assisted waterflooding, is presented. The chromatographic and phase separation behavior of dissimilar surfactants and their mixtures allows a selective and controllable blocking of watered-out zones of a reservoir. A mathematical model is developed, and the theory of coherence is extended to multidimensional, multiphase, multicomponent flow, allowing the development of a novel simulator, which is then applied. The results indicate that the blocking mechanism is very selective in markedly heterogeneous reservoir. Shorter reservoirs have the highest potential for application; high oil recoveries are then possible since blocking can be controlled to occur deep inside the watered out zones.

  4. Surfactant loss control in chemical flooding spectroscopic and calorimetric study of adsorption and precipitation on reservoir minerals. Annual report, September 30, 1992--September 30 1995

    SciTech Connect

    Casteel, J.

    1996-07-01

    The aim of this research project was to investigate mechanisms governing adsorption and surface precipitation of flooding surfactants on reservoir minerals. Effects of surfactant structure, surfactant combinations, various inorganic and polymeric species, and solids mineralogy have been determined. A multi-pronged approach consisting of micro & nano spectroscopy, electrokinetics, surface tension and wettability is used in this study. The results obtained should help in controlling surfactant loss in chemical flooding and in developing optimum structures and conditions for efficient chemical flooding processes. During the three years contract period, adsorption of single surfactants and select surfactant mixtures was studied at the solid-liquid and gas-liquid interfaces. Alkyl xylene sulfonates, polyethoxylated alkyl phenols, octaethylene glycol mono n-decyl ether, and tetradecyl trimethyl ammonium chloride were the surfactants studied. Adsorption of surfactant mixtures of varying composition was also investigated. The microstructure of the adsorbed layer was characterized using fluorescence spectroscopy. Changes in interfacial properties such as wettability, electrokinetics and stability of reservoir minerals were correlated with the amounts of reagent adsorbed. Strong effects of the structure of the surfactant and position of functional groups were revealed. Changes of microstructure upon dilution (desorption) were also studied. Presence of the nonionic surfactants in mixed aggregate leads to shielding of the charge of ionic surfactants which in turn promotes aggregation but reduced electrostatic attraction between the charged surfactant and the mineral surface. Strong consequences of surfactant interactions in solution on adsorption as well as correlations between monomer concentration in mixtures and adsorption were revealed.

  5. Micelle depletion-induced vs. micelle-mediated aggregation in nanoparticles

    SciTech Connect

    Ray, D. Aswal, V. K.

    2015-06-24

    The phase behavior anionic silica nanoparticle (Ludox LS30) with non-ionic surfactants decaethylene glycol monododecylether (C12E10) and cationic dodecyltrimethyl ammonium bromide (DTAB) in aqueous electrolyte solution has been studied by small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations of nanoparticle (1 wt%), surfactants (1 wt%) and electrolyte (0.1 M NaCl). Each of these nanoparticle–surfactant systems has been examined for different contrast conditions where individual components (nanoparticle or surfactant) are made visible. It is observed that the nanoparticle-micelle system in both the cases lead to the aggregation of nanoparticles. The aggregation is found to be micelle depletion-induced for C12E10 whereas micelle-mediated aggregation for DTAB. Interestingly, it is also found that phase behavior of mixed surfactant (C12E10 + DTAB) system is similar to that of C12E10 (unlike DTAB) micelles with nanoparticles.

  6. Effect of surfactants on shear-induced gelation and gel morphology of soft strawberry-like particles.

    PubMed

    Xie, Delong; Arosio, Paolo; Wu, Hua; Morbidelli, Massimo

    2011-06-07

    The role of surfactant type in the aggregation and gelation of strawberry-like particles induced by intense shear without any electrolyte addition is investigated. The particles are composed of a rubbery core, partially covered by a plastic shell, and well stabilized by fixed (sulfate) charges in the end group of the polymer chains originating from the initiator. In the absence of any surfactant, after the system passes through a microchannel at a Peclet number equal to 220 and a particle volume fraction equal to 0.15, not only shear-induced gelation but also partial coalescence among the particles occurs. The same shear-induced aggregation/gelation process has been carried out in the presence of an ionic (sulfonate) surfactant or a nonionic (Tween 20) steric surfactant. It is found that for both surfactants shear-induced gelation does occur at low surfactant surface density but the conversion of the primary particles to the clusters constituting the gel decreases as the surfactant surface density increases. When the surfactant surface density increases above certain critical values, shear-induced gelation and eventually even aggregation do not occur any longer. For the sulfonate surfactant, this was explained in the literature by the non-DLVO, short-range repulsive hydration forces generated by the adsorbed surfactant layer. In this work, it is shown that the steric repulsion generated by the adsorbed Tween 20 layer can also protect particles from aggregation under intense shear. Moreover, the nonionic steric surfactant can also protect the strawberry-like particles from coalescence. This implies a decrease in the fractal dimension of the clusters constituting the gel from 2.76 to 2.45, which cannot be achieved using the ionic sulfonate surfactant.

  7. Combined exogenous surfactant and inhaled nitric oxide therapy for lung ischemia-reperfusion injury in minipigs.

    PubMed

    Warnecke, G; Strüber, M; Fraud, S; Hohlfeld, J M; Haverich, A

    2001-05-15

    The combined application of exogenous surfactant and inhaled nitric oxide was evaluated for prevention of ischemia-reperfusion injury of the lung. Left lungs were selectively perfused in 18 minipigs in situ with cold preservation solution. After 90 min of warm ischemia, the lungs were reperfused and the right pulmonary artery and bronchus were ligated (control group, n=6). Exogenous surfactant was instilled via bronchoscopy during ischemia (surfactant group, n=6). In a third group, surfactant was applied, followed by administration of inhaled nitric oxide (surfactant+NO group, n=6). Hemodynamic and respiratory parameters were recorded for 7 hr, and bronchoalveolar lavage fluid (BALF) was obtained before and after reperfusion for measurement of surface tension, small aggregate/large aggregate ratio, protein and phospholipid contents, and a differential cell count. Control group animals survived for 3.7+/-1.4 hr. In both surfactant-treated groups, five out of six animals survived the observation period (P<0.001). Dynamic compliance of the lung was decreased in control animals (P<0.001). In the surfactant+NO group, arterial PO2 was higher than in both other groups (P<0.001). BALF cell count and histology showed reduced neutrophil infiltration in surfactant+NO-treated lungs. Surface tension assessed in BALF with a pulsating bubble surfactometer was severely impaired in control animals (gammamin, 14.82+/-9.95 mN/m), but maintained in surfactant-treated (gammamin, 1.11+/-0.56 mN/m) and surfactant+NO-treated animals (gammamin, 3.90+/-2.35 mN/m, P=0.02). Administration of exogenous surfactant in lung reperfusion injury results in improved lung compliance. The addition of inhaled NO improves arterial oxygenation and reduces neutrophil extravasation compared with surfactant treatment alone.

  8. Size separation of analytes using monomeric surfactants

    DOEpatents

    Yeung, Edward S.; Wei, Wei

    2005-04-12

    A sieving medium for use in the separation of analytes in a sample containing at least one such analyte comprises a monomeric non-ionic surfactant of the of the general formula, B-A, wherein A is a hydrophilic moiety and B is a hydrophobic moiety, present in a solvent at a concentration forming a self-assembled micelle configuration under selected conditions and having an aggregation number providing an equivalent weight capable of effecting the size separation of the sample solution so as to resolve a target analyte(s) in a solution containing the same, the size separation taking place in a chromatography or electrophoresis separation system.

  9. Comparative insight into surfactants mediated amyloidogenesis of lysozyme.

    PubMed

    Chaturvedi, Sumit K; Khan, Javed M; Siddiqi, Mohammad K; Alam, Parvez; Khan, Rizwan H

    2016-02-01

    Electrostatic and hydrophobic interactions have an important role in the protein aggregation. In this study, we have investigated the effect of charge and hydrophobicity of oppositely charged surfactants i.e., anionic (AOT and SDS) and cationic (CTAB and DTAB) on hen egg white lysozyme at pH 9.0 and 13.0, respectively. We have employed various methods such as turbidity measurements, Rayleigh light scattering, ThT, Congo red and ANS dye binding assays, far-UV CD, atomic force microscopy, transmission electron and fluorescence microscopy. At lower molar ratio, both anionic and cationic surfactants promote amyloid fibril formation in lysozyme at pH 9.0 and 13.0, respectively. The aggregation was proportionally increased with respect to protein concentration and hydrophobicity of surfactant. The morphology of aggregates at both the pH was fibrillar in structure, as visualized by dye binding and microscopic imaging techniques. Initially, the interaction between surfactants and lysozyme was electrostatic and then hydrophobic as investigated by ITC. This study demonstrates the crucial role of charge and hydrophobicity during amyloid fibril formation.

  10. Dispersion of carbon nanotubes using mixed surfactants: experimental and molecular dynamics simulation studies.

    PubMed

    Sohrabi, B; Poorgholami-Bejarpasi, N; Nayeri, N

    2014-03-20

    The ability of cationic-rich and anionic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) for dispersing of carbon nanotubes (CNTs) in aqueous media has been studied through both the experimental and molecular dynamics simulation methods. Compared to the pure CTAB and SDS, these mixtures are more effective with the lower concentrations and more individual CNTs, reflecting a synergistic effect in these mixtures. The synergistic effects observed in mixed surfactant systems are mainly due to the electrostatic attractions between surfactant heads. In addition, the surface charge related to the colloidal stability of mixed surfactant-covered nanotubes has been characterized by means of ζ-potential measurements. The results indicate that the hydrophobic interactions between surfactant tails also give rise to the higher adsorption of surfactant molecules. Furthermore, molecular dynamics (MD) simulations have been performed to provide insight about the structure of surfactant aggregates onto nanotubes and to attempt an explanation of the experimental results. The MD simulation results indicate that the random and disordered adsorption of mixed surfactants onto carbon nanotubes may be preferred for a low surfactant concentration. Our research may provide experimental and theoretical bases for using mixed surfactants to disperse CNTs, which can open an avenue for new applications of mixed surfactants.

  11. Transforming giants.

    PubMed

    Kanter, Rosabeth Moss

    2008-01-01

    Large corporations have long been seen as lumbering, inflexible, bureaucratic--and clueless about global developments. But recently some multinationals seem to be transforming themselves: They're engaging employees, moving quickly, and introducing innovations that show true connection with the world. Harvard Business School's Kanter ventured with a research team inside a dozen global giants--including IBM, Procter & Gamble, Omron, CEMEX, Cisco, and Banco Real--to discover what has been driving the change. After conducting more than 350 interviews on five continents, she and her colleagues came away with a strong sense that we are witnessing the dawn of a new model of corporate power: The coordination of actions and decisions on the front lines now appears to stem from widely shared values and a sturdy platform of common processes and technology, not from top-down decrees. In particular, the values that engage the passions of far-flung workforces stress openness, inclusion, and making the world a better place. Through this shift in what might be called their guidance systems, the companies have become as creative and nimble as much smaller ones, even while taking on social and environmental challenges of a scale that only large enterprises could attempt. IBM, for instance, has created a nonprofit partnership, World Community Grid, through which any organization or individual can donate unused computing power to research projects and see what is being done with the donation in real time. IBM has gained an inspiring showcase for its new technology, helped business partners connect with the company in a positive way, and offered individuals all over the globe the chance to contribute to something big.

  12. The interaction of photo-responsive surfactants with biological macromolecules

    NASA Astrophysics Data System (ADS)

    Mazwi, Khiza L.

    The interaction of photo-responsive surfactants with proteins has been considered as a means to exert reversible control over a number of aspects of protein structure and function. The azobenzene trimethylammonium bromide (azoTAB) family of cationic surfactants undergo a photo-reversible cis to trans isomerization upon exposure to light of the appropriate wavelength. The trans form of the molecule has a lower dipole moment across its azo linkage, and is more hydrophobic than the cis isomer. This results in a higher binding affinity with proteins for the trans isomer, inducing a greater degree of unfolding of tertiary and secondary structures. The surfactant has been applied to the study of the amyloid fibrillation pathway in insulin, in which the protein self-associates into long, insoluble, rod-like structures. The fibrillation rate in insulin is enhanced in the presence of the trans- isomer while the formation of fibrils is largely inhibited in the presence of the cis- isomer, where amorphous aggregates are observed instead. Additionally early fibrillar species formed in the trans-azoTAB assays exhibit a greater tendency to lateral aggregation than do structures in the pure protein, resulting in a more truncated, bundled final aggregate morphology. Use of the surfactants as a means to control protein quaternary solution structure has also been explored in the subunit dissociation of tetrameric catalase. In the presence of azoTAB surfactants, catalase dissociates first into a super-active dimer, then at higher concentrations into an aggregation prone monomer. Finally, the structural changes associated with azoTAB-induced unfolding of the two domain protein papain are tracked. The denaturation pathway involves a progressive loss in secondary structure with increasing azoTAB concentration, along with a relaxation of the compact tertiary structure, and a spatial separation of the two domains. A number of complementary experimental techniques are combined to determine

  13. Surfactant loss control in chemical flooding spectroscopic and calorimetric study of adsorption and precipitation on reservoir minerals. Annual report, September 30, 1993--September 30, 1994

    SciTech Connect

    Somasundaran, P.

    1995-06-01

    The aim of this project is to elucidate the mechanisms underlying adsorption and surface precipitation of flooding surfactants on reservoir minerals. Effect of surfactant structure, surfactant combinations, other inorganic and polymeric species is being studied. A multi-pronged approach consisting of micro and nano spectroscopy, microcalorimetry, electrokinetics, surface tension and wettability is used to achieve the goals. The results of this study should help in controlling surfactant loss in chemical flooding and also in developing optimum structures and conditions for efficient chemical flooding processes. During the second year of this three year contract, adsorption/desorption of single surfactants and select surfactant mixtures on alumina and silica was studied. Surfactants studied include the anionic sodium dodecyl sulfate (SDS), cationic tetradecyl trimethyl ammonium chloride (TTAC), nonionic pentadecylethoxylated nonyl phenol (NP-15) and the nonionic octaethylene glycol n-dodecyl ether (C{sub 12}EO{sub 8}) of varying hydrocarbon chain length. The microstructure of the adsorbed layer in terms of micropolarity and aggregation numbers was probed using fluorescence spectroscopy. Changes of microstructure upon dilution (desorption) were also studied. Presence of the nonionic surfactant in the mixed aggregate led to shielding of the charge of the ionic surfactant which in-turn promoted aggregation but reduced electrostatic attraction between the charged surfactant and the mineral surface. Strong consequences of surfactant interactions in solution upon adsorption as well as correlations between monomer concentrations in mixtures and adsorption were revealed.

  14. Large scale molecular dynamics study of polymer-surfactant complex

    NASA Astrophysics Data System (ADS)

    Goswami, Monojoy; Sumpter, Bobby

    2012-02-01

    In this work, we study the self-assembly of cationic polyelectrolytes mediated by anionic surfactants in dilute or semi-dilute and gel states. The understanding of the dilute system is a requirement for the understanding of gel states. The importance of polyelectrolyte with oppositely charged colloidal particles can be found in biological systems, such as immobilization of enzymes in polyelectrolyte complexes or nonspecific association of DNA with protein. With the same understanding, interaction of surfactants with polyelectrolytes shows intriguing phenomena that are important for both in academic research as well as industrial applications. Many useful properties of PE surfactant complexes come from the highly ordered structures of surfactant self-assembly inside the PE aggregate. We do large scale molecular dynamics simulation using LAMMPS to understand the structure and dynamics of PE-surfactant systems. Our investigation shows highly ordered ring-string structures that have been observed experimentally in biological systems. We will investigate many different properties of PE-surfactant complexation which will be helpful for pharmaceutical, engineering and biological applications.

  15. Solubilization of herbicides by single and mixed commercial surfactants.

    PubMed

    Galán-Jiménez, M C; Gómez-Pantoja, E; Morillo, E; Undabeytia, T

    2015-12-15

    The solubilization capabilities of micellar solutions of three single surfactants, two alcohol alkoxylates B048 and B266, and the tallow alkyl ethoxylated amine ET15, and their equimolar mixed solutions toward the herbicides flurtamone (FL), metribuzin (MTZ) and mesotrione (MST) were investigated. The solubilization capacity was quantified in terms of the molar solubilization ratio (MSR), critical micellar concentration (CMC), micelle-water partition coefficient (Kmc), binding constant (K1), number of aggregation (Nagg) and Stern-Volmer constant (Ksv). The herbicides were greatly solubilized into different loci of the micelles: FL within the inner hydrophobic core, MST at the micelle/water interface and MTZ in the palisade region. Equimolar binary surfactant mixtures did not improve the solubilization of herbicides over those of single components, with the exception of MTZ by the B266/ET15 system which enhanced solubilization by 10-20%. This enhanced solubilization of MTZ was due to an increased number of micelles that arise from both the intermediate Nagg relative to that of the single surfactants and the lower CMC. The use of Ksv values was a better predictor of the solubilization of polar molecules within binary mixtures of these surfactants than the interaction parameter β(M) from regular solution theory (RST). The results herein suggest that the use of mixed surfactant systems for the solubilization of polar molecules in environmental remediation technologies may be very limited in scope, without clear advantages over the use of single surfactant systems.

  16. Giant Cell Arteritis

    MedlinePlus

    Giant cell arteritis is a disorder that causes inflammation of your arteries, usually in the scalp, neck, and arms. ... arteries, which keeps blood from flowing well. Giant cell arteritis often occurs with another disorder called polymyalgia ...

  17. Theoretical model to investigate the alkyl chain and anion dependent interactions of gemini surfactant with bovine serum albumin.

    PubMed

    Vishvakarma, Vijay K; Kumari, Kamlesh; Patel, Rajan; Dixit, V S; Singh, Prashant; Mehrotra, Gopal K; Chandra, Ramesh; Chakrawarty, Anand Kumar

    2015-05-15

    Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and they also assist in protein refolding. We have reported the design and screening of gemini surfactant to stabilize bovine serum albumin (BSA) with the help of computational tool (iGEMDOCK). A series of gemini surfactant has been designed based on bis-N-alkyl nicotinate dianion via varying the alkyl group and anion. On changing the alkyl group and anion of the surfactant, the value of Log P changes means polarity of surfactant can be tuned. Further, the virtual screening of the gemini surfactant has been carried out based on generic evolutionary method. Herein, thermodynamic data was studied to determine the potential of gemini surfactant as BSA stabilizer. Computational tools help to find out the efficient gemini surfactant to stabilize the BSA rather than to use the surfactant randomly and directionless for the stabilization. It can be confirmed through the experimental techniques. Previously, researcher synthesized one of the designed and used gemini surfactant to stabilize the BSA and their interactions were confirmed through various techniques and computational docking. But herein, the authors find the most competent gemini surfactant to stabilize BSA using computational tools on the basis of energy score. Different from the single chain surfactant, the gemini surfactants exhibit much stronger electrostatic and hydrophobic interactions with the protein and are thus effective at much lower concentrations. Based on the present study, it is expected that gemini surfactants may prove useful in the protein stabilization operations and may thus be effectively employed to circumvent the problem of misfolding and aggregation. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Theoretical model to investigate the alkyl chain and anion dependent interactions of gemini surfactant with bovine serum albumin

    NASA Astrophysics Data System (ADS)

    Vishvakarma, Vijay K.; Kumari, Kamlesh; Patel, Rajan; Dixit, V. S.; Singh, Prashant; Mehrotra, Gopal K.; Chandra, Ramesh; Chakrawarty, Anand Kumar

    2015-05-01

    Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and they also assist in protein refolding. We have reported the design and screening of gemini surfactant to stabilize bovine serum albumin (BSA) with the help of computational tool (iGEMDOCK). A series of gemini surfactant has been designed based on bis-N-alkyl nicotinate dianion via varying the alkyl group and anion. On changing the alkyl group and anion of the surfactant, the value of Log P changes means polarity of surfactant can be tuned. Further, the virtual screening of the gemini surfactant has been carried out based on generic evolutionary method. Herein, thermodynamic data was studied to determine the potential of gemini surfactant as BSA stabilizer. Computational tools help to find out the efficient gemini surfactant to stabilize the BSA rather than to use the surfactant randomly and directionless for the stabilization. It can be confirmed through the experimental techniques. Previously, researcher synthesized one of the designed and used gemini surfactant to stabilize the BSA and their interactions were confirmed through various techniques and computational docking. But herein, the authors find the most competent gemini surfactant to stabilize BSA using computational tools on the basis of energy score. Different from the single chain surfactant, the gemini surfactants exhibit much stronger electrostatic and hydrophobic interactions with the protein and are thus effective at much lower concentrations. Based on the present study, it is expected that gemini surfactants may prove useful in the protein stabilization operations and may thus be effectively employed to circumvent the problem of misfolding and aggregation.

  19. Capillary electrophoresis investigation on equilibrium between polymer-related and surfactant-related species in aqueous polymer-surfactant solutions.

    PubMed

    Wu, Yefan; Chen, Miaomiao; Fang, Yun; Zhu, Meng

    2017-03-17

    It was inferred from aqueous solution behavior of nonionic polymers and anionic surfactants that the formation of charged polymer-bound surfactant micelle above critical aggregation concentration (cac) and the formation of free surfactant micelle beyond polymer saturation point (psp), but there was still a lack of direct experimental evidence for the considered equilibrium chemical species. Three modes of capillary electrophoresis are applied in this paper to study the complexation between nonionic polymers, polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG), and sodium dodecylbenzenesulfonate (SDBS) by successfully distinguishing the imaginary charged polymer-bound SDBS micelle from nonionic polymer and SDBS molecule. Perhaps even more important, it is the action of SDBS as both a main surfactant and a UV probe that makes the free surfactant micelle emerged in electropherogram beyond psp, and thus makes it possible for the first time to provide the equilibrium relationship of the polymer-related and the surfactant-related species in the concentration regions divided into by cac and psp. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Surfactant mixing rules applied to surfactant enhanced alkaline flooding

    SciTech Connect

    Taylor, K.C. )

    1992-01-01

    This paper discusses surfactant mixing rules which have been used to describe crude oil/alkali/surfactant phase behavior, using David Lloydminster crude oil and the surfactant Neodol 25-3S. It was found that at a fixed salinity and alkali concentration, a specific mole fraction of synthetic surfactant to petroleum soap was required to produce optimal phase behavior as the water-to-oil ratio varied. This methodology is useful in understanding the relationship between the variables of water-to-oil ratio and synthetic surfactant concentration in phase behavior systems that produce a petroleum soap.

  1. Therapeutic surfactant-stripped frozen micelles

    NASA Astrophysics Data System (ADS)

    Zhang, Yumiao; Song, Wentao; Geng, Jumin; Chitgupi, Upendra; Unsal, Hande; Federizon, Jasmin; Rzayev, Javid; Sukumaran, Dinesh K.; Alexandridis, Paschalis; Lovell, Jonathan F.

    2016-05-01

    Injectable hydrophobic drugs are typically dissolved in surfactants and non-aqueous solvents which can induce negative side-effects. Alternatives like `top-down' fine milling of excipient-free injectable drug suspensions are not yet clinically viable and `bottom-up' self-assembled delivery systems usually substitute one solubilizing excipient for another, bringing new issues to consider. Here, we show that Pluronic (Poloxamer) block copolymers are amenable to low-temperature processing to strip away all free and loosely bound surfactant, leaving behind concentrated, kinetically frozen drug micelles containing minimal solubilizing excipient. This approach was validated for phylloquinone, cyclosporine, testosterone undecanoate, cabazitaxel and seven other bioactive molecules, achieving sizes between 45 and 160 nm and drug to solubilizer molar ratios 2-3 orders of magnitude higher than current formulations. Hypertonic saline or co-loaded cargo was found to prevent aggregation in some cases. Use of surfactant-stripped micelles avoided potential risks associated with other injectable formulations. Mechanistic insights are elucidated and therapeutic dose responses are demonstrated.

  2. Therapeutic surfactant-stripped frozen micelles

    PubMed Central

    Zhang, Yumiao; Song, Wentao; Geng, Jumin; Chitgupi, Upendra; Unsal, Hande; Federizon, Jasmin; Rzayev, Javid; Sukumaran, Dinesh K.; Alexandridis, Paschalis; Lovell, Jonathan F.

    2016-01-01

    Injectable hydrophobic drugs are typically dissolved in surfactants and non-aqueous solvents which can induce negative side-effects. Alternatives like ‘top-down' fine milling of excipient-free injectable drug suspensions are not yet clinically viable and ‘bottom-up' self-assembled delivery systems usually substitute one solubilizing excipient for another, bringing new issues to consider. Here, we show that Pluronic (Poloxamer) block copolymers are amenable to low-temperature processing to strip away all free and loosely bound surfactant, leaving behind concentrated, kinetically frozen drug micelles containing minimal solubilizing excipient. This approach was validated for phylloquinone, cyclosporine, testosterone undecanoate, cabazitaxel and seven other bioactive molecules, achieving sizes between 45 and 160 nm and drug to solubilizer molar ratios 2–3 orders of magnitude higher than current formulations. Hypertonic saline or co-loaded cargo was found to prevent aggregation in some cases. Use of surfactant-stripped micelles avoided potential risks associated with other injectable formulations. Mechanistic insights are elucidated and therapeutic dose responses are demonstrated. PMID:27193558

  3. Giant impacts on giant planets

    NASA Astrophysics Data System (ADS)

    de Pater, Imke

    2013-10-01

    The 2009 impact and recent superbolides on Jupiter caught the world by surprise and cast doubt on impactor flux estimates for the outer solar system. Enhanced amateur planetary imaging techniques yield both high spatial resolution {enabling the 2009 impact debris field detection} and rapid frame rates {enabling the 2010/2012 impact flash detections and lightcurve measurements}.We propose a ToO program to image future impacts on Jupiter and Saturn. To remove the possibility of impact cloud non-detections, the program will be triggered only if an existing impact debris field is seen, an object on a collision course with Jupiter or Saturn is discovered, or an impact light curve is measured with an estimated total energy large enough to generate an impact cloud in a giant planet atmosphere {10^20 J}.HST provides the only way to image these events in the ultraviolet, providing information on aerosol altitudes and on smaller particles that are less visible to ground-based infrared observations. High-resolution imaging with proper timing {not achievable from the ground} is required to measure precisely both the velocity fields of impact sites and the optical spectrum of impact debris. HST observations of past impacts on Jupiter have also served both as cornerstones of science investigations at other wavelengths and as vehicles for effective public outreach.Large outer solar system impacts are governed by the same physics as in the terrestrial events that dominate the impact threat to humans. Studying the behavior of impactors of various sizes and compositions, as they enter the atmosphere at varying angles and speeds, will better quantify terrestrial impact hazards.

  4. Giant impacts on giant planets

    NASA Astrophysics Data System (ADS)

    de Pater, Imke

    2014-10-01

    The 2009 impact and recent superbolides on Jupiter caught the world by surprise and cast doubt on impactor flux estimates for the outer solar system. Enhanced amateur planetary imaging techniques yield both high spatial resolution (enabling the 2009 impact debris field detection) and rapid frame rates (enabling the 2010/2012 impact flash detections and lightcurve measurements).We propose a ToO program to image future impacts on Jupiter and Saturn. To remove the possibility of impact cloud non-detections, the program will be triggered only if an existing impact debris field is seen, an object on a collision course with Jupiter or Saturn is discovered, or an impact light curve is measured with an estimated total energy large enough to generate an impact cloud in a giant planet atmosphere (10^20 J).HST provides the only way to image these events in the ultraviolet, providing information on aerosol altitudes and on smaller particles that are less visible to ground-based infrared observations. High-resolution imaging with proper timing (not achievable from the ground) is required to measure precisely both the velocity fields of impact sites and the optical spectrum of impact debris. HST observations of past impacts on Jupiter have also served both as cornerstones of science investigations at other wavelengths and as vehicles for effective public outreach.Large outer solar system impacts are governed by the same physics as in the terrestrial events that dominate the impact threat to humans. Studying the behavior of impactors of various sizes and compositions, as they enter the atmosphere at varying angles and speeds, will better quantify terrestrial impact hazards.

  5. Giant impacts on giant planets

    NASA Astrophysics Data System (ADS)

    de Pater, Imke

    2012-10-01

    The 2009 impact on Jupiter caught the world by surprise and cast doubt on impactor flux estimates for the outer solar system. Enhanced amateur planetary imaging techniques yield both high spatial resolution {enabling the 2009 impact debris field detection} and rapid frame rates {enabling the 2010 impact flash detections and lightcurve measurements}.We propose a Target of Opportunity program to image future impacts on Jupiter and Saturn. To remove the possibility of impact cloud non-detections, the program will be triggered only if an existing impact debris field is seen, an object on a collision course with Jupiter or Saturn is discovered, or an impact light curve is measured with an estimated total energy large enough to generate an impact cloud in a giant planet atmosphere.HST provides the only way to image these events in the ultraviolet, providing information on aerosol altitudes and on smaller particles that are less visible to ground-based infrared observations. High-resolution imaging with proper timing {not achievable from the ground} is required to measure precisely both the velocity fields of impact sites and the optical spectrum of impact debris. HST observations of past impacts on Jupiter have also served both as cornerstones of science investigations at other wavelengths and as vehicles for effective public outreach.Large outer solar system impacts are governed by the same physics as in the terrestrial events that dominate the impact threat to humans. Studying the behavior of impactors of various sizes and compositions, as they enter the atmosphere at varying angles and speeds, will better quantify terrestrial impact hazards.

  6. Effect of amide bonds on the self-assembly of gemini surfactants.

    PubMed

    Hoque, Jiaul; Gonuguntla, Spandhana; Yarlagadda, Venkateswarlu; Aswal, Vinod K; Haldar, Jayanta

    2014-06-21

    This study provides an insight into the micellar aggregation properties in aqueous solutions of various gemini surfactants bearing one or more amide groups at the side chains and/or in the spacer by conductivity and small angle neutron scattering (SANS) studies. The amide functionality was found to enhance the surfactant aggregation properties as compared to the surfactants having no amide bond. Furthermore, the aggregation properties of the gemini surfactants bearing amide groups were found to strongly depend on the position and number of amide bonds. With the increase in the number of amide bonds, the aggregation number (N) and the size of the micelles increased. Additionally, the size and shape of the micelles were also found to depend both on the hydrocarbon chain length and the spacer chain length. It was also found that the aggregation number and the size of the micelles increased with an increase in concentration and decreased with an increase in temperature. The critical micellar concentration (CMC) values of the gemini surfactants obtained by a conductometric method were found to vary greatly with variation in the hydrocarbon chain.

  7. Modeling counterion binding in ionic-nonionic and ionic-zwitterionic binary surfactant mixtures.

    PubMed

    Goldsipe, Arthur; Blankschtein, Daniel

    2005-10-25

    A predictive molecular-thermodynamic theory is developed to model the effect of counterion binding on micellar solution properties of binary surfactant mixtures of ionic and nonionic (or zwitterionic) surfactants. The theory combines a molecular-thermodynamic description of micellization in binary surfactant mixtures with a recently developed model of counterion binding to single-component ionic surfactant micelles. The thermodynamic component of the theory models the equilibrium between the surfactant monomers, the counterions, and the mixed micelles. The molecular component of the theory models the various contributions to the free-energy change associated with forming a mixed micelle from ionic surfactants, nonionic (or zwitterionic) surfactants, and bound counterions (referred to as the free energy of mixed micellization). Specifically, the various molecular contributions to the free energy of mixed micellization model the underlying physics associated with the assembly of, and the interactions between, the surfactant polar heads, the surfactant nonpolar tails, and the bound counterions. Utilizing known structural characteristics of the surfactants and the counterions, along with the solution conditions, the free energy of mixed micellization is minimized to predict various optimal micelle characteristics, including the degree of counterion binding, the micelle composition, and the micelle shape and size. These predicted optimal micelle characteristics are then used to predict the critical micelle concentration (cmc) and the average micelle aggregation number. Our predictions of the degree of counterion binding, the cmc, and the average micelle aggregation number show good agreement with available experimental results from the literature for several binary surfactant mixtures. In addition, the theory is used to shed light on the relationship between the micelle composition, counterion binding and ion condensation, and the micelle shape transition.

  8. Surfactant-enhanced bioremediation

    SciTech Connect

    Churchill, P.F.; Dudley, R.J.; Churchill, S.A.

    1995-12-31

    This study was undertaken to examine the effect of three structurally related, non-ionic surfactants, Triton X-45, Triton X-100 and Triton X-165, as well as the oleophilic fertilizer, Inipol EAP 22, on the rate of biodegradation of phenanthrene by pure bacterial cultures. Each surfactant dramatically increased the apparent aqueous solubility of phenanthrene. Model studies were conducted to investigate the ability of these surfactants to enhance the rate of transport and uptake of polycyclic aromatic hydrocarbons into bacterial cells, and to assess the impact that increasing the aqueous solubility of hydrocarbons has on their rate of biodegradation. The results indicate that increasing the apparent aqueous solubility of hydrocarbons can lead to enhanced biodegradation rates by two Pseudomonas saccharophila strains. However, the experiments also suggest that some surfactants can inhibit aromatic hydrocarbon biodegradation by certain bacteria. The data also support the hypothesis that surface-active components present in the oleophilic fertilizer formulation, Inipol EAP 22, may have significantly contributed to the positive results reported in tests of remedial agent impact on bioremediation, which was used as a supplemental clean-up technology on Exxon Valdez crude oil-contaminated Alaskan beaches.

  9. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  10. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  11. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1993-01-01

    Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

  12. Surfactant-assisted dispersion of carbon nanotubes: mechanism of stabilization and biocompatibility of the surfactant

    NASA Astrophysics Data System (ADS)

    Singh, Raman Preet; Jain, Sanyog; Ramarao, Poduri

    2013-10-01

    Nanoparticles (NPs) are thermodynamically unstable system and tend to aggregate to reduce free energy. The aggregation property of NPs results in inhomogeneous exposure of cells to NPs resulting in variable cellular responses. Several types of surfactants are used to stabilize NP dispersions and obtain homogenous dispersions. However, the effects of these surfactants, per se, on cellular responses are not completely known. The present study investigated the application of Pluronic F68 (PF68) for obtaining stable dispersion of NPs using carbon nanotubes as model NPs. PF68-stabilized NP suspensions are stable for long durations and do not show signs of aggregation or settling during storage or after autoclaving. The polyethylene oxide blocks in PF68 provide steric hindrance between adjacent NPs leading to stable NP dispersions. Further, PF68 is biocompatible in nature and does not affect integrity of mitochondria, lysosomes, DNA, and nuclei. Also, PF68 neither induce free radical or cytokine production nor does it interfere with cellular uptake mechanisms. The results of the present study suggest that PF68-assisted dispersion of NPs produced suspensions, which are stable after autoclaving. Further, PF68 does not interfere with normal physiological functions suggesting its application in nanomedicine and nanotoxicity evaluation.

  13. Diseases of Pulmonary Surfactant Homeostasis

    PubMed Central

    Whitsett, Jeffrey A.; Wert, Susan E.; Weaver, Timothy E.

    2015-01-01

    Advances in physiology and biochemistry have provided fundamental insights into the role of pulmonary surfactant in the pathogenesis and treatment of preterm infants with respiratory distress syndrome. Identification of the surfactant proteins, lipid transporters, and transcriptional networks regulating their expression has provided the tools and insights needed to discern the molecular and cellular processes regulating the production and function of pulmonary surfactant prior to and after birth. Mutations in genes regulating surfactant homeostasis have been associated with severe lung disease in neonates and older infants. Biophysical and transgenic mouse models have provided insight into the mechanisms underlying surfactant protein and alveolar homeostasis. These studies have provided the framework for understanding the structure and function of pulmonary surfactant, which has informed understanding of the pathogenesis of diverse pulmonary disorders previously considered idiopathic. This review considers the pulmonary surfactant system and the genetic causes of acute and chronic lung disease caused by disruption of alveolar homeostasis. PMID:25621661

  14. Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant.

    PubMed

    Song, Meirong; Ju, Jie; Luo, Siqi; Han, Yuchun; Dong, Zhichao; Wang, Yilin; Gu, Zhen; Zhang, Lingjuan; Hao, Ruiran; Jiang, Lei

    2017-03-01

    Deposition of liquid droplets on solid surfaces is of great importance to many fundamental scientific principles and technological applications, such as spraying, coating, and printing. For example, during the process of pesticide spraying, more than 50% of agrochemicals are lost because of the undesired bouncing and splashing behaviors on hydrophobic or superhydrophobic leaves. We show that this kind of splashing on superhydrophobic surfaces can be greatly inhibited by adding a small amount of a vesicular surfactant, Aerosol OT. Rather than reducing splashing by increasing the viscosity via polymer additives, the vesicular surfactant confines the motion of liquid with the help of wettability transition and thus inhibits the splash. Significantly, the vesicular surfactant exhibits a distinguished ability to alter the surface wettability during the first inertial spreading stage of ~2 ms because of its dense aggregates at the air/water interface. A comprehensive model proposed by this idea could help in understanding the complex interfacial interactions at the solid/liquid/air interface.

  15. Effect of surfactants on preformed fibrils of human serum albumin.

    PubMed

    Pandey, Nitin Kumar; Ghosh, Sudeshna; Dasgupta, Swagata

    2013-08-01

    The central reason behind pathogenesis of various neurological disorders is usually attributed to the accumulation of aggregated proteins particularly in fibrillar morphology in vivo. One of the plausible remedial treatments for such disorders may be to identify molecules which are capable of either preventing formation of fibrils or disintegrating formed fibrils. The effect of cationic surfactants cetyl trimethylammonium bromide (CTAB), dodecyl trimethylammonium bromide (DTAB) and the anionic surfactant sodium dodecyl sulfate (SDS) in vitro toward mature HSA fibrils has been investigated. The process has been monitored using ThT fluorescence, FTIR, circular dichroism, fluorescence microscopy and HRTEM. It was observed that the micelles of cationic surfactants were able to effectively disrupt the HSA fibrils, among which CTAB was found to be the most potent.

  16. Chemoenzymatic synthesis and properties of novel lactone-type anionic surfactants.

    PubMed

    Mori, Keisuke; Matsumura, Shuichi

    2012-01-01

    Two series of lactone-type surfactants with and without a hexyl side chain were prepared by the cyclocondensation of dimethyl alkanedioates with unsaturated diols, such as cis-2-butene-1,4-diol and ricinoleyl alcohol, using a lipase, followed by the addition of hydrophilic 3-mercaptopropionic acid in the presence of triethylamine. The lactone-type surfactants showed clear cmc values and surface tension lowering in aqueous solution irrespective of the hexyl side chain. It was found that the cmc values of lactone-type surfactants were lower than that of typical anionics, e.g., sodium laurate, and the cmc value became lower with increasing size of the lactone ring. The adsorption area at the surface of the aqueous lactone-type surfactant solution was larger when compared to the corresponding non-lactone-type surfactants. Lactone-type surfactants without the hexyl side chain aggregated quickly, forming 3-10 nm micelles; on the other hand, lactone-type surfactants with the hexyl side chain formed significantly larger micelles. This is due to the steric hindrance of the hexyl group on the lactone ring. The solubilization ability of the lactone-type surfactants with a hexyl side chain was superior to those without a hexyl side chain. The lactone-type surfactants showed a high foaming power and low foaming stability. They were also biodegraded by activated sludge.

  17. Interaction of two imidazolium gemini surfactants with two model proteins BSA and HEWL.

    PubMed

    Gospodarczyk, W; Kozak, M

    Gemini surfactants and their interactions with proteins have gained considerable scientific interest, especially when amyloidogenic proteins are taken into account. In this work, the influence of two selected dicationic (gemini) surfactants (3,3'-[1,8-(2,7-dioxaoctane)]bis(1-dodecylimidazolium) chloride and 3,3'-[1,12-(2,11-dioxadodecane)]bis(1-dodecylimidazolium) chloride) on two model proteins, bovine serum albumin (BSA) and hen egg white lysozyme (HEWL), have been investigated. A pronounced and sophisticated influence on BSA structure has been revealed, including a considerable change of protein radius of gyration as well as substantial alteration of its secondary structure. Radius of gyration has been found to rise significantly with addition of surfactants and to fall down for high surfactants concentration. Similarly, a remarkable fall of secondary structure (α-helix content) has been observed, followed by its partial retrieval for high surfactants concentration. A strong aggregation of BSA has been observed for a confined range of surfactants concentrations as well. In case of HEWL-gemini system, on the other hand, the protein-surfactant interaction was found to be weak. Molecular mechanisms explaining such behaviour of protein-surfactant systems have been proposed. The differences of properties of both studied surfactants have also been discussed.

  18. Surfactant treatments alter endogenous surfactant metabolism in rabbit lungs

    SciTech Connect

    Oetomo, S.B.; Lewis, J.; Ikegami, M.; Jobe, A.H. )

    1990-04-01

    The effect of exogenous surfactant on endogenous surfactant metabolism was evaluated using a single-lobe treatment strategy to compare effects of treated with untreated lung within the same rabbit. Natural rabbit surfactant, Survanta, or 0.45% NaCl was injected into the left main stem bronchus by use of a Swan-Ganz catheter. Radiolabeled palmitic acid was then given by intravascular injection at two times after surfactant treatment, and the ratios of label incorporation and secretion in the left lower lobe to label incorporation and secretion in the right lung were compared. The treatment procedure resulted in a reasonably uniform surfactant distribution and did not disrupt lobar pulmonary blood flow. Natural rabbit surfactant increased incorporation of palmitate into saturated phosphatidylcholine (Sat PC) approximately 2-fold (P less than 0.01), and secretion of labeled Sat PC increased approximately 2.5-fold in the surfactant-treated left lower lobe relative to the right lung (P less than 0.01). Although Survanta did not alter incorporation, it did increase secretion but not to the same extent as rabbit surfactant (P less than 0.01). Alteration of endogenous surfactant Sat PC metabolism in vivo by surfactant treatments was different from that which would have been predicted by previous in vitro studies.

  19. Metal Nanoparticle Pollutants Interfere with Pulmonary Surfactant Function In Vitro☆

    PubMed Central

    Bakshi, Mandeep Singh; Zhao, Lin; Smith, Ronald; Possmayer, Fred; Petersen, Nils O.

    2008-01-01

    Abstract Reported associations between air pollution and pulmonary and cardiovascular diseases prompted studies on the effects of gold nanoparticles (Au NP) on pulmonary surfactant function. Low levels (3.7 mol % Au/lipid, 0.98% wt/wt) markedly inhibited adsorption of a semisynthetic pulmonary surfactant (dipalmitoyl-phosphatidylcholine (DPPC)/palmitoyl-oleoyl-phosphatidylglycerol/surfactant protein B (SP-B); 70:30:1 wt %). Au NP also impeded the surfactant's ability to reduce surface tension (γ) to low levels during film compression and to respread during film expansion. Transmission electron microscopy showed that Au NP generated by a seed-growth method were spherical with diameters of ∼15 nm. Including palmitoyl-oleoyl-phosphatidylglycerol appeared to coat the NP with at least one lipid bilayer but did not affect NP shape or size. Similar overall observations occurred with dimyristoyl phosphatidylglycerol. Dipalmitoyl-phosphatidylglycerol was less effective in NP capping, although similar sized NP were formed. Including SP-B (1% wt/wt) appears to induce the formation of elongated strands of interacting threads with the fluid phosphatidylglycerols (PG). Including DPPC resulted in formation of aggregated, less spherical NP with a larger size distribution. With DPPC, strand formation due to SP-B was not observed. Agarose gel electrophoresis studies demonstrated that the aggregation induced by SP-B blocked migration of PG-coated NP. Migration was also influenced by the fluidity of the PGs. It is concluded that Au NP can interact with and sequester pulmonary surfactant phospholipids and, if inhaled from the atmosphere, could impede pulmonary surfactant function in the lung. PMID:17890383

  20. Relaxation times and modes of disturbed aggregate distribution in micellar solutions with fusion and fission of micelles

    SciTech Connect

    Zakharov, Anatoly I.; Adzhemyan, Loran Ts.; Shchekin, Alexander K.

    2015-09-28

    We have performed direct numerical calculations of the kinetics of relaxation in the system of surfactant spherical micelles under joint action of the molecular mechanism with capture and emission of individual surfactant molecules by molecular aggregates and the mechanism of fusion and fission of the aggregates. As a basis, we have taken the difference equations of aggregation and fragmentation in the form of the generalized kinetic Smoluchowski equations for aggregate concentrations. The calculations have been made with using the droplet model of molecular surfactant aggregates and two modified Smoluchowski models for the coefficients of aggregate-monomer and aggregate-aggregate fusions which take into account the effects of the aggregate size and presence of hydrophobic spots on the aggregate surface. A full set of relaxation times and corresponding relaxation modes for nonequilibrium aggregate distribution in the aggregation number has been found. The dependencies of these relaxation times and modes on the total concentration of surfactant in the solution and the special parameter controlling the probability of fusion in collisions of micelles with other micelles have been studied.

  1. Coacervation with surfactants: From single-chain surfactants to gemini surfactants.

    PubMed

    Zhao, Weiwei; Wang, Yilin

    2017-01-01

    Coacervation is a spontaneous process during which a colloidal dispersion separates into two immiscible liquid phases: a colloid-rich liquid phase in equilibrium with a diluted phase. Coacervation is usually divided into simple coacervation and complex coacervation according to the number of components. Surfactant-based coacervation normally contains traditional single-chain surfactants. With the development of surfactants, gemini surfactants with two amphiphilic moieties have been applied to form coacervation. This review summarizes the development of simple coacervation and complex coacervation in the systems of single-chain surfactants and gemini surfactants. Simple coacervation in surfactant solutions with additives or at elevated temperature and complex coacervation in surfactant/polymer mixtures by changing charge densities, molecular weight, ionic strength, pH, or temperature are reviewed. The comparison between gemini surfactants and corresponding monomeric single-chain surfactants reveals that the unique structures of gemini surfactants endow them with higher propensity to generate coacervation. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Surfactant-laden soft contact lenses for extended delivery of ophthalmic drugs.

    PubMed

    Kapoor, Yash; Thomas, Justin C; Tan, Grace; John, Vijay T; Chauhan, Anuj

    2009-02-01

    Eye drops are inefficient means of delivering ophthalmic drugs because of limited bioavailability and these can cause significant side effects due to systemic uptake of the drug. The bioavailability for ophthalmic drugs can be increased significantly by using contact lenses. This study focuses on the development of surfactant-laden poly-hydroxy ethyl methacrylate (p-HEMA) contact lenses that can release Cyclosporine A (CyA) at a controlled rate for extended periods of time. We focus on various Brij surfactants to investigate the effects of chain length and the presence of an unsaturated group on the drug release dynamics and partitioning inside the surfactant domains inside the gel. The gels were imaged by cryogenic scanning electron microscopy (cryo-SEM) to obtain direct evidence of the presence of surfactant aggregates in the gel, and to investigate the detailed microstructure for different surfactants. The images show a distribution of nano pores inside the surfactant-laden hydrogels which we speculate are regions of surfactant aggregates, possibly vesicles that have a high affinity for the hydrophobic drug molecule. The gels are further characterized by studying their mechanical and physical properties such as transparency, surface contact angle and equilibrium water content to determine their suitability as extended wear contact lenses. Results show that Brij surfactant-laden p-HEMA gels provide extended release of CyA, and possess suitable mechanical and optical properties for contact lens applications. The gels are not as effective for extended release of two other hydrophobic ophthalmic drugs, dexamethasone (DMS) and dexamethasone 21 acetate (DMSA) because of insufficient partitioning inside the surfactant aggregates.

  3. Chain architecture and micellization: A mean-field coarse-grained model for poly(ethylene oxide) alkyl ether surfactants

    SciTech Connect

    García Daza, Fabián A.; Mackie, Allan D.; Colville, Alexander J.

    2015-03-21

    Microscopic modeling of surfactant systems is expected to be an important tool to describe, understand, and take full advantage of the micellization process for different molecular architectures. Here, we implement a single chain mean field theory to study the relevant equilibrium properties such as the critical micelle concentration (CMC) and aggregation number for three sets of surfactants with different geometries maintaining constant the number of hydrophobic and hydrophilic monomers. The results demonstrate the direct effect of the block organization for the surfactants under study by means of an analysis of the excess energy and entropy which can be accurately determined from the mean-field scheme. Our analysis reveals that the CMC values are sensitive to branching in the hydrophilic head part of the surfactant and can be observed in the entropy-enthalpy balance, while aggregation numbers are also affected by splitting the hydrophobic tail of the surfactant and are manifested by slight changes in the packing entropy.

  4. Chain architecture and micellization: A mean-field coarse-grained model for poly(ethylene oxide) alkyl ether surfactants

    NASA Astrophysics Data System (ADS)

    García Daza, Fabián A.; Colville, Alexander J.; Mackie, Allan D.

    2015-03-01

    Microscopic modeling of surfactant systems is expected to be an important tool to describe, understand, and take full advantage of the micellization process for different molecular architectures. Here, we implement a single chain mean field theory to study the relevant equilibrium properties such as the critical micelle concentration (CMC) and aggregation number for three sets of surfactants with different geometries maintaining constant the number of hydrophobic and hydrophilic monomers. The results demonstrate the direct effect of the block organization for the surfactants under study by means of an analysis of the excess energy and entropy which can be accurately determined from the mean-field scheme. Our analysis reveals that the CMC values are sensitive to branching in the hydrophilic head part of the surfactant and can be observed in the entropy-enthalpy balance, while aggregation numbers are also affected by splitting the hydrophobic tail of the surfactant and are manifested by slight changes in the packing entropy.

  5. Transient Exposure of Pulmonary Surfactant to Hyaluronan Promotes Structural and Compositional Transformations into a Highly Active State*

    PubMed Central

    Lopez-Rodriguez, Elena; Cruz, Antonio; Richter, Ralf P.; Taeusch, H. William; Pérez-Gil, Jesús

    2013-01-01

    Pulmonary surfactant is a lipid-protein complex that lowers surface tension at the respiratory air-liquid interface, stabilizing the lungs against physical forces tending to collapse alveoli. Dysfunction of surfactant is associated with respiratory pathologies such as acute respiratory distress syndrome or meconium aspiration syndrome where naturally occurring surfactant-inhibitory agents such as serum, meconium, or cholesterol reach the lung. We analyzed the effect of hyaluronan (HA) on the structure and surface behavior of pulmonary surfactant to understand the mechanism for HA-promoted surfactant protection in the presence of inhibitory agents. In particular, we found that HA affects structural properties such as the aggregation state of surfactant membranes and the size, distribution, and order/packing of phase-segregated lipid domains. These effects do not require a direct interaction between surfactant complexes and HA and are accompanied by a compositional reorganization of large surfactant complexes that become enriched with saturated phospholipid species. HA-exposed surfactant reaches very high efficiency in terms of rapid and spontaneous adsorption of surfactant phospholipids at the air-liquid interface and shows significantly improved resistance to inactivation by serum or cholesterol. We propose that physical effects pertaining to the formation of a meshwork of interpenetrating HA polymer chains are responsible for the changes in surfactant structure and composition that enhance surfactant function and, thus, resistance to inactivation. The higher resistance of HA-exposed surfactant to inactivation persists even after removal of the polymer, suggesting that transient exposure of surfactant to polymers like HA could be a promising strategy for the production of more efficient therapeutic surfactant preparations. PMID:23983120

  6. Transient exposure of pulmonary surfactant to hyaluronan promotes structural and compositional transformations into a highly active state.

    PubMed

    Lopez-Rodriguez, Elena; Cruz, Antonio; Richter, Ralf P; Taeusch, H William; Pérez-Gil, Jesús

    2013-10-11

    Pulmonary surfactant is a lipid-protein complex that lowers surface tension at the respiratory air-liquid interface, stabilizing the lungs against physical forces tending to collapse alveoli. Dysfunction of surfactant is associated with respiratory pathologies such as acute respiratory distress syndrome or meconium aspiration syndrome where naturally occurring surfactant-inhibitory agents such as serum, meconium, or cholesterol reach the lung. We analyzed the effect of hyaluronan (HA) on the structure and surface behavior of pulmonary surfactant to understand the mechanism for HA-promoted surfactant protection in the presence of inhibitory agents. In particular, we found that HA affects structural properties such as the aggregation state of surfactant membranes and the size, distribution, and order/packing of phase-segregated lipid domains. These effects do not require a direct interaction between surfactant complexes and HA and are accompanied by a compositional reorganization of large surfactant complexes that become enriched with saturated phospholipid species. HA-exposed surfactant reaches very high efficiency in terms of rapid and spontaneous adsorption of surfactant phospholipids at the air-liquid interface and shows significantly improved resistance to inactivation by serum or cholesterol. We propose that physical effects pertaining to the formation of a meshwork of interpenetrating HA polymer chains are responsible for the changes in surfactant structure and composition that enhance surfactant function and, thus, resistance to inactivation. The higher resistance of HA-exposed surfactant to inactivation persists even after removal of the polymer, suggesting that transient exposure of surfactant to polymers like HA could be a promising strategy for the production of more efficient therapeutic surfactant preparations.

  7. Morphology, thermal behavior, and stability of self-assembled supramolecular tubules from lysine-based surfactants.

    PubMed

    Brito, Rodrigo O; Oliveira, Isabel S; Araújo, Maria J; Marques, Eduardo F

    2013-08-15

    Synthetic amino acid-based surfactants possess versatile aggregation properties and are typically more biocompatible and biodegradable than surfactants with conventional headgroups. This opens the possibility of a myriad of specialty applications, namely in pharmaceutics, cosmetics, biomedicine, and nanotemplating chemistry. In this work, we have investigated the interfacial and self-assembling properties in aqueous medium of novel double-chained lysine-based surfactants, with particular focus on the behavior of the dodecyl derivative, 12Lys12. Upon cooling from dilute isotropic micellar solutions, this surfactant crystallizes into micrometer-sized tubular structures that induce gelation of the system. The tubules have been characterized in terms of morphology, assembly process, thermal behavior, and stability, by using differential scanning calorimetry, light and scanning electron microscopy, and deuterium NMR. Possible mechanisms for tubule assembly are discussed, on the basis of surfactant molecular shape, H-bonding and electrostatic interactions, and chirality effects.

  8. Comprehensive study of tartrazine/cationic surfactant interaction.

    PubMed

    Shahir, Afshin Asadzadeh; Javadian, Soheila; Razavizadeh, Bi Bi Marzieh; Gharibi, Hussein

    2011-12-15

    Interaction of a food dye, tartrazine, with some cationic conventional and gemini surfactants, tetradecyltrimethylammonium bromide (TTAB), N,N'-ditetradecyl-N,N,N',N'-tetramethyl-N,N'-butanediyl-diammonium dibromide (14,4,14), and N,N'-didodecyl-N,N,N',N'-tetramethyl-N,N'-butanediyl-diammonium dibromide (12,4,12), were first investigated comprehensively employing conductometry, tensiometry, and UV-visible spectroscopy. Tartrazine was found to behave in the same manner as aromatic counterions. The formation of ion pairs reflected as a considerable increase of the surfactant efficiency in tensiometry plots and their stoichiometry were determined by Job's method of continuous variations. For the tartrazine/TTAB system, nonionic DS(3), ionic DS(2-), and/or DS(2)(-) ion pairs, their small premicelles, and tartrazine-rich micelles were constituted as well as dye-containing TTAB-rich micelles. Insoluble J-aggregates of DS(-) ion pairs and cylindrical surfactant-rich micelles were also formed in tartrazine/gemini surfactant systems and recognized by transmission electron microscopy. The zeta potential and the size of the aggregates were determined using dynamic light scattering and confirmed the suggested models for the processes happening in each system. Cyclic voltammetry was applied successfully to track all of these species using tartrazine's own reduction peak current for the first time.

  9. The Electric Giant Resonances

    NASA Astrophysics Data System (ADS)

    van der Woude, A.

    The following sections are included: * Introduction * Experimental Methods to Study Giant Resonances * Introduction * The Tools * Introduction * Tools for Isoscalar Scattering * INELASTIC α-SCATTERING * INELASTIC PROTON SCATTERING * Tools for Isovector Excitations * γ-ABSORPTION AND PARTICLE CAPTURE REACTIONS * CHARGE EXCHANGE REACTIONS - THE (π+, π0) REACTION * Tools For Isoscalar And Isovector Excitations * INELASTIC ELECTRON SCATTERING * GIANT RESONANCE EXCITATION BY FAST HEAVY IONS * From Multipole Cross Section To Multipole Strength * The Electric Isoscalar Resonances * The Isoscalar Giant Monopole Resonance * Systematics on the GMR * Compressibility and the Giant Monopole Resonance * Introduction * The Compressibility of nuclear matter from the GMR energies * Discussion * The Isoscalar Giant Quadrupole Resonance * General Trends In Medium-Heavy and Heavy Nuclei * The GQR In Light Nuclei * The Isoscalar 3- Strength, LEOR and HEOR * Isoscalar 4+ Strength * Miscellaneous; Isoscalar 1- and L > 4-Strength * The Electric Isovector Giant Resonances * The Isovector Giant Dipole Resonance: GDR * The Isovector Giant Monopole Resonances: IVGMR * The Isovector Quadrupole Resonance: IVGQR * The Effect of Ground State Deformation on the Shape of Giant Resonance: Microscopic Picture * Giant Resonances Built on Excited States * Introduction * Capture Reactions on Light Nuclei * Statistical decay of GDR γ Emission in Heavy Compound Systems * Introduction * Theoretical Predictions * Some Experimental Results * Summary and Outlook * Acknowledgements * General References * References

  10. Sensory ecology: giant eyes for giant predators?

    PubMed

    Partridge, Julian C

    2012-04-24

    Mathematical models suggest the enormous eyes of giant and colossal squid evolved to see the bioluminescence induced by the approach of predatory whales. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Mixed surfactant systems for enhanced oil recovery

    SciTech Connect

    Llave, F.M.; Gall, B.L.; Noll, L.A.

    1990-12-01

    The results of an evaluation of mixed surfactant systems for enhanced oil recovery are described. Several surfactant combinations have been studied. These include alkyl aryl sulfonates as primary surfactants and carboxymethylated ethoxylated (CME) surfactants and ethoxylated sulfonates (ES) as secondary surfactants. The ethoxylated surfactants increase the salinity tolerance of the primary surfactants and, in theory, allow tailoring of the surfactant system to match selected reservoir conditions. The experiments conducted included interfacial tension (IFT) measurements, phase behavior measurements, adsorption and/or chromatographic separation of mixed surfactant systems, measurements of solution properties such as the critical micelle concentration (CMC) of surfactant mixtures, and crude oil displacement experiments. The effects of temperature, surfactant concentration, salinity, presence of divalent ions, hydrocarbon type, and component proportions in the mixed surfactant combinations, and injection strategies on the performance potential of the targeted surfactant/hydrocarbon systems were studied. 40 refs., 37 figs., 8 tabs.

  12. Effect of alkyl chain asymmetry on catanionic mixtures of hydrogenated and fluorinated surfactants.

    PubMed

    Blanco, Elena; Rodriguez-Abreu, Carlos; Schulz, Pablo; Ruso, Juan M

    2010-01-15

    In this work we studied and compared the physicochemical properties of the catanionic mixtures cetyltrimethyl-ammonium bromide-sodium dodecanoate, cetyltrimethyl-ammonium bromide-sodium perfluorodacanoate, octyltrimethylammonium bromide-sodium perfluorodacanoate and cetyltrimethyl-ammonium bromide-sodium octanoate by a combination of rheological, transmission electron microscopy (TEM) and polarized optical microscopy measurements. The binary mixtures of the surfactants have been analyzed at different mixed ratios and total concentration of the mixture. Mixtures containing a perfluorinated surfactant are able to form lamellar liquid crystals and stable spontaneous vesicles. Meanwhile, system containing just hydrogenated surfactants form hexagonal phases or they are arranged in elongated aggregates.

  13. Increased phospholipase A2 and lyso-phosphatidylcholine levels are associated with surfactant dysfunction in lung contusion injury in mice.

    PubMed

    Machado-Aranda, David; Wang, Zhengdong; Yu, Bi; Suresh, M V; Notter, Robert H; Raghavendran, Krishnan

    2013-01-01

    Surfactant dysfunction is an important pathologic disturbance in various forms of acute inflammatory lung injury. Previously we reported the presence of marked alterations in the composition and activity of pulmonary surfactant in bilateral lung contusions (LC) injury induced by blunt trauma in rats. This is extended here to a mouse model of unilateral LC with a focus on compositional and functional changes in surfactant associated with permeability injury and increases in activity of secretory phospholipase A2. Surfactant-associated gene expression was not altered in mice with unilateral LC injury on the basis of Affymetrix analysis. LC mice had significant permeability injury with increased albumin and total protein in bronchoalveolar lavage at 5, 24, 48, and 72 hours after insult compared with uninjured controls. The percent content of large surfactant aggregates was depleted at all postinjury times, and pulmonary pressure-volume (P-V) mechanics and compliance were abnormal during this period. Surfactant dysfunction was evaluated in 24 hours, when permeability injury and P-V changes were most prominent. At this time, activity levels of secretory phospholipase A2 were increased in bronchoalveolar lavage, and chromatographic analysis showed that large surfactant aggregates had decreased levels of phosphatidylcholine and increased levels of lyso-phosphatidylcholine. These changes were accompanied by severe detriments in large aggregate surface activity by pulsating bubble surfactometry. Large aggregates from LC mice at 24 hours had minimum surface tensions of only 12.6 ± 1.1 mN/m after prolonged bubble pulsation (20 min) compared with 0.7 ± 0.03 mN/m for uninjured controls. These results document important detriments in the composition and activity of pulmonary surfactant in LC injury in mice and suggest that active synthetic phospholipase-resistant exogenous surfactants may have utility in treating surfactant dysfunction in this clinically important condition

  14. Increased phospholipase A2 and lyso-phosphatidylcholine levels are associated with surfactant dysfunction in lung contusion injury in mice

    PubMed Central

    Machado-Aranda, David; Wang, Zhengdong; Yu, Bi; Suresh, M V; Notter, Robert H.; Raghavendran, Krishnan

    2012-01-01

    Objective Surfactant dysfunction is an important pathological disturbance in various forms of acute inflammatory lung injury. Previously we reported the presence of significant alterations in the composition and activity of pulmonary surfactant in blunt trauma-induced bilateral lung contusion (LC) injury in rats. This is extended here to a mouse model of unilateral LC, with a focus on compositional and functional surfactant changes associated with permeability injury and increases in activity of secretory phospholipase A2. Results Surfactant-associated gene expression was not significantly altered in mice with unilateral LC injury based on Affymetrix analysis. LC mice had significant permeability injury with increased albumin and total protein in bronchoalveolar lavage (BAL) at 5, 24, 48 and 72 h post-insult compared to uninjured controls. The percent content of large surfactant aggregates was significantly depleted at all post-injury times, and pulmonary pressure-volume (P-V) mechanics and compliance were abnormal over this period. Surfactant dysfunction was evaluated in mechanistic detail at 24 h, when permeability injury and P-V changes were most prominent. At this time, activity levels of secretory phospholipase A2 (PLA2) were increased in BAL, and chromatographic analysis showed that large surfactant aggregates had decreased levels of phosphatidylcholine (PC) and increased levels of lyso-PC. These changes were accompanied by severe detriments in large aggregate surface activity by pulsating bubble surfactometry. Large aggregates from LC mice at 24 h had minimum surface tensions of only 12.6±1.1 mN/m after prolonged bubble pulsation (20 min) compared to 0.7±0.03 mN/m for uninjured controls. Conclusion These results document significant detriments in the composition and activity of pulmonary surfactant in LC injury in mice, and suggest that active synthetic phospholipase-resistant exogenous surfactants may have future utility in treating surfactant dysfunction

  15. BEHAVIOR OF SURFACTANT MIXTURES AT SOLID/LIQUID AND OIL/LIQUID INTERFACES IN CHEMICAL FLOODING SYSTEMS

    SciTech Connect

    P. Somasundaran

    2004-11-20

    The aim of the project is to develop a knowledge base to help the design of enhanced processes for mobilizing and extracting untrapped oil. We emphasize evaluation of novel surfactant mixtures and obtaining optimum combinations of the surfactants for efficient chemical flooding EOR processes. In this regard, an understanding of the aggregate shape, size and structure is crucial since these properties govern the crude oil removal efficiency. During the three-year period, the adsorption and aggregation behavior of sugar-based surfactants and their mixtures with other types of surfactants have been studied. Sugar-based surfactants are made from renewable resources, nontoxic and biodegradable. They are miscible with water and oil. These environmentally benign surfactants feature high surface activity, good salinity, calcium and temperature tolerance, and unique adsorption behavior. They possess the characteristics required for oil flooding surfactants and have the potential for replacing currently used surfactants in oil recovery. A novel analytical ultracentrifugation technique has been successfully employed for the first time, to characterize the aggregate species present in mixed micellar solution due to its powerful ability to separate particles based on their size and shape and monitor them simultaneously. Analytical ultracentrifugation offers an unprecedented opportunity to obtain important information on mixed micelles, structure-performance relationship for different surfactant aggregates in solution and their role in interfacial processes. Initial sedimentation velocity investigations were conducted using nonyl phenol ethoxylated decyl ether (NP-10) to choose the best analytical protocol, calculate the partial specific volume and obtain information on sedimentation coefficient, aggregation mass of micelles. Four softwares: OptimaTM XL-A/XL-I data analysis software, DCDT+, Svedberg and SEDFIT, were compared for the analysis of sedimentation velocity

  16. Molecular conformation-controlled vesicle/micelle transition of cationic trimeric surfactants in aqueous solution.

    PubMed

    Wu, Chunxian; Hou, Yanbo; Deng, Manli; Huang, Xu; Yu, Defeng; Xiang, Junfeng; Liu, Yu; Li, Zhibo; Wang, Yilin

    2010-06-01

    Two star-like trimeric cationic surfactants with amide groups in spacers, tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD) and tri(dodecyldimethylammonioacetoxy)tris(2-aminoethyl)amine trichloride (DDAD), have been synthesized, and the aggregation behavior of the surfactants in aqueous solution has been investigated by surface tension, electrical conductivity, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, and NMR techniques. Typically, both the surfactants form vesicles just above critical aggregation concentration (CAC), and then the vesicles transfer to micelles gradually with an increase of the surfactant concentration. It is approved that the conformation of the surfactant molecules changes in this transition process. Just above the CAC, the hydrophobic chains of the surfactant molecules pack more loosely because of the rigid spacer and intramolecular electrostatic repulsion in the three-charged headgroup. With the increase of the surfactant concentration, hydrophobic interaction becomes strong enough to pack the hydrophobic tails tightly and turn the molecular conformation into a pyramid-like shape, thus leading to the vesicle to micelle transition.

  17. Impact of cationic surfactant on the self-assembly of sodium caseinate.

    PubMed

    Vinceković, Marko; Curlin, Marija; Jurašin, Darija

    2014-08-27

    The impact of a cationic surfactant, dodecylammonium chloride (DDACl), on the self-assembly of sodium caseinate (SC) has been investigated by light scattering, zeta potential, and rheological measurements as well as by microscopy (transmission electron and confocal laser scanning microscopy). In SC dilute solutions concentration-dependent self-assembly proceeds through the formation of spherical associates and their aggregation into elongated structures composed of connected spheres. DDACl interacts with SC via its hydrophilic and hydrophobic groups, inducing changes in SC self-assembled structures. These changes strongly depend on the surfactant aggregation states (monomeric or micellar) as well as concentration ratio of both components, leading to the formation of soluble and insoluble complexes of nano- to microdimensions. DDACl monomers interact with SC self-assembled entities in a different way compared to their micelles. Surfactant monomers form soluble complexes (similar to surfactant mixed micelles) at lower SC concentration but insoluble gelatinous complexes at higher SC concentration. At surfactant micellar concentration soluble complexes with casein chains wrapped around surfactant micelles are formed. This study suggests that the use of proper cationic surfactant concentration will allow modification and control of structural changes of SC self-assembled entities.

  18. Molecular thermodynamics for micellar branching in solutions of ionic surfactants.

    PubMed

    Andreev, Vasily A; Victorov, Alexey I

    2006-09-26

    We develop an analytical molecular-thermodynamic model for the aggregation free energy of branching portions of wormlike ionic micelles in 1:1 salt solution. The junction of three cylindrical aggregates is represented by a combination of pieces of the torus and bilayer. A geometry-dependent analytical solution is obtained for the linearized Poisson-Boltzmann equation. This analytical solution is applicable to saddle-like structures and reduces to the solutions known previously for planar, cylindrical, and spherical aggregates. For micellar junctions, our new analytical solution is in excellent agreement with numerical results over the range of parameters typical of ionic surfactant systems with branching micelles. Our model correctly predicts the sequence of stable aggregate morphologies, including a narrow bicontinuous zone, in dependence of hydrocarbon tail length, head size, and solution salinity. For predicting properties of a spatial network of wormlike micelles, our aggregation free energy is used in the Zilman-Safran theory. Our predictions are compared with experimental data for branching micelles of ionic surfactants.

  19. Micellization behavior of aromatic moiety bearing hybrid fluorocarbon sulfonate surfactants.

    PubMed

    Wadekar, Mohan N; Boekhoven, Job; Jager, Wolter F; Koper, Ger J M; Picken, Stephen J

    2012-02-21

    Aggregation behavior and thermodynamic properties of two novel homologous aromatic moiety bearing hybrid fluorocarbon surfactants, sodium 2-(2-(4-ethylphenyl)-1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonate (1) and sodium 2-(1,1,2,2-tetrafluoro-2-(4-vinylphenyl)ethoxy)-1,1,2,2-tetrafluoroethanesulfonate (2) were studied using surface tension measurements and isothermal titration calorimetry (ITC) in dilute aqueous solutions at room temperature. Because of the aromatic group in the hydrophobic tail, both surfactants are soluble at room temperature unlike their starting precursor, 5-iodooctafluoro-3-oxapentanesulfonate as well as several other fluorocarbon sulfonic acid salts. Moreover, the surfactant 2 has the ability that it can be polymerized once microemulsions are formed with it. The ionic conductivity measurements of 1 at five different temperatures from 288 to 313 K were carried out to study the effect of temperature on the micellization and its thermodynamics. The pseudophase separation model was applied to estimate thermodynamic quantities from conductivity data. The Gibbs energy of micellization versus temperature exhibited the characteristic U-shaped behavior with a minimum at 306 K. The micellization process was found to be largely entropy driven. Because of its hybrid structure, the entropy change of micellization for 1 was larger than what is common for hydrocarbon surfactants like SDS but less than for fully fluorinated surfactants like NaPFO. The micellization process was found to be following the entropy-enthalpy compensation phenomena.

  20. Biophysicochemical Interaction of a Clinical Pulmonary Surfactant with Nanoalumina.

    PubMed

    Mousseau, F; Le Borgne, R; Seyrek, E; Berret, J-F

    2015-07-07

    We report on the interaction of pulmonary surfactant composed of phospholipids and proteins with nanometric alumina (Al2O3) in the context of lung exposure and nanotoxicity. We study the bulk properties of phospholipid/nanoparticle dispersions and determine the nature of their interactions. The clinical surfactant Curosurf, both native and extruded, and a protein-free surfactant are investigated. The phase behavior of mixed surfactant/particle dispersions was determined by optical and electron microscopy, light scattering, and zeta potential measurements. It exhibits broad similarities with that of strongly interacting nanosystems such as polymers, proteins or particles, and supports the hypothesis of electrostatic complexation. At a critical stoichiometry, micron-sized aggregates arising from the association between oppositely charged vesicles and nanoparticles are formed. Contrary to the models of lipoprotein corona or of particle wrapping, our work shows that vesicles maintain their structural integrity and trap the particles at their surfaces. The agglomeration of particles in surfactant phase is a phenomenon of importance that could change the interactions of the particles with lung cells.

  1. BEHAVIOR OF SURFACTANT MIXTURES AT SOLID/LIQUID AND OIL/LIQUID INTERFACES IN CHEMICAL FLOODING SYSTEMS

    SciTech Connect

    Prof. P. Somasundaran

    2002-09-30

    The aim of the project is to develop and evaluate efficient novel surfactant mixtures for enhanced oil recovery. Surfactant loss by adsorption or precipitation depends to a great extent on the type of surfactant complexes and aggregates formed. Such information as well as techniques to generate the information is lacking currently particularly for surfactant mixtures and surfactant/polymer systems. A novel analytical centrifuge application is explored during the last period to generate information on structures-performance relationship for different surfactant aggregates in solution and, in turn, at interfaces. To use analytical untracentrifuge for surfactant mixtures, information on partial specific volumes of single surfactants and their mixtures is required. Towards this purpose, surface tension and density measurements were performed to determine critical micellar concentrations (cmc), partial specific volumes of n-dodecyl-{beta}-Dmaltoside (DM), nonyl phenol ethoxylated decyl ether (NP-10) and their 1:1 mixtures at 25 C. Durchschlag's theoretical calculation method was adopted to calculate the partial specific volumes. Effects of temperature and mixing, as well as methods used for estimation on micellization and partial specific volumes were studied during the current period. Surface tension results revealed no interaction between the two surfactants in mixed micelles. Partial specific volume measurements also indicated no interaction in mixed micelles. Maximum adsorption density, area per molecule and free energy of micellization were also calculated. Partial specific volumes were estimated by two experimental methods: d{sub {rho}}/dc and V{sub {sigma}}. The difference between the results of using the two methods is within 0.5% deviation. It was found that the partial specific volume is concentration dependent and sensitive to changes in temperature. The information generated in this study will be used for the study of surfactant aggregate mass distribution

  2. Aggregation in charged nanoparticles solutions induced by different interactions

    SciTech Connect

    Abbas, S.; Kumar, Sugam; Aswal, V. K.; Kohlbrecher, J.

    2016-05-23

    Small-angle neutron scattering (SANS) has been used to study the aggregation of anionic silica nanoparticles as induced through different interactions. The nanoparticle aggregation is induced by addition of salt (NaCl), cationic protein (lysozyme) and non-ionic surfactant (C12E10) employing different kind of interactions. The results show that the interaction in presence of salt can be explained using DLVO theory whereas non-DLVO forces play important role for interaction of nanoparticles with protein and surfactant. The presence of salt screens the repulsion between charged nanoparticles giving rise to a net attraction in the DLVO potential. On the other hand, strong electrostatic attraction between nanoparticle and oppositely charged protein leads to protein-mediated nanoparticle aggregation. In case of non-ionic surfactant, the relatively long-range attractive depletion interaction is found to be responsible for the particle aggregation. Interestingly, the completely different interactions lead to similar kind of aggregate morphology. The nanoparticle aggregates formed are found to have mass fractal nature having a fractal dimension (~2.5) consistent with diffusion limited type of fractal morphology in all three cases.

  3. Flavonoid-surfactant interactions: A detailed physicochemical study

    NASA Astrophysics Data System (ADS)

    Singh, Onkar; Kaur, Rajwinder; Mahajan, Rakesh Kumar

    2017-01-01

    The aim of this article is to study the interactions between flavonoids and surfactants with attention of finding the probable location of flavonoids in micellar media that can be used for controlling their antioxidant behavior. In present study, the micellar and interfacial behavior of twin tailed anionic surfactants viz. sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and sodium bis(2-ethylhexyl)phosphate (NaDEHP) in the presence of two flavonoids, namely quercetin (QUE) and kaempferol (KFL) have been studied by surface tension measurements. UV-visible, fluorescence and differential pulse voltammetric (DPV) measurements have been employed to predict the probable location of flavonoids (QUE/KFL) within surfactant (AOT/NaDEHP) aggregates. Dynamic light scattering (DLS) measurements further confirmed the solubilization of QUE/KFL in AOT/NaDEHP aggregates deduced from increased hydrodynamic diameter (Dh) of aggregates in the presence of flavonoids. Both radical scavenging activity (RSA) and degradation rate constant (k) of flavonoids are found to be higher in NaDEHP micelles as compared to AOT micelles.

  4. Surfactants at the Design Limit.

    PubMed

    Czajka, Adam; Hazell, Gavin; Eastoe, Julian

    2015-08-04

    This article analyzes how the individual structural elements of surfactant molecules affect surface properties, in particular, the point of reference defined by the limiting surface tension at the aqueous cmc, γcmc. Particular emphasis is given to how the chemical nature and structure of the hydrophobic tails influence γcmc. By comparing the three different classes of surfactants, fluorocarbon, silicone, and hydrocarbon, a generalized surface packing index is introduced which is independent of the chemical nature of the surfactants. This parameter ϕcmc represents the volume fraction of surfactant chain fragments in a surface film at the aqueous cmc. It is shown that ϕcmc is a useful index for understanding the limiting surface tension of surfactants and can be useful for designing new superefficient surfactants.

  5. Studying the silver nanoparticles influence on thermodynamic behavior and antimicrobial activities of novel amide Gemini cationic surfactants.

    PubMed

    Shaban, Samy M; Abd-Elaal, Ali A

    2017-07-01

    Three novels amide Gemini cationic surfactants with various alkyl chains and their silver nanohybrid with silver nanoparticles were synthesized and a confirmation study for surfactant and their nanoparticles formation has been established using IR, (1)HNMR, TEM and UV-Vis spectroscopy. The surface-active properties of these surfactants and their nanoform were investigated through surface tension and electrical conductivity measurements and a comparative study has been established. The thermodynamic parameters of micellization and adsorption were assessed at temperatures range from 25 to 65°C. The effect of silver particles on the surface behavior of the synthesized surfactant has been discussed. The aggregation behavior of silver nanoparticles with these synthesized Gemini surfactants in water were investigated using dynamic light scattering and transmission electron microscopy. Furthermore, the antimicrobial activities of these synthesized amide Gemini surfactants and their nanostructure with silver against both Gram positive and Gram negative bacteria were also investigated. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Interaction between cationic surfactant of 1-methyl-3-tetradecylimidazolium bromide and anionic polymer of sodium polystyrene sulfonate

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Kang, Wenpei; Sun, Dezhi; Liu, Jie; Wei, Xilian

    2013-08-01

    The interaction between long-chain imidazolium ionic liquid (C14mimBr) and anionic polyelectrolyte of sodium polystyrene sulfonate (NaPSS) has been studied using surface tension, isothermal titration microcalorimetry (ITC), dynamic light scatting (DLS) and conductance methods. The result shows that the surface tension plots have a pronounced hump in the surface tension at surfactant concentrations below the critical micelle concentration (cmc) of the surfactant. The cooperative adsorption of surfactant and polymer on the surface (PSS) and the formation of polymer/surfactant aggregate in bulk solution (PSM) provide a rational explanation about it. The formation of surfactant/polymer complexes is affected by the concentration of the surfactant or NaPSS, which is also ascertained by ITC and DLS measurements. Further, the thermodynamic parameters are derived from calorimetric titration and conductance curves, and the effects of polymer concentration and temperature on the parameters are evaluated in detail.

  7. Solution rheology of polyelectrolytes and polyelectrolyte-surfactant systems

    NASA Astrophysics Data System (ADS)

    Plucktaveesak, Nopparat

    The fundamental understanding of polyelectrolytes in aqueous solutions is an important branch of polymer research. In this work, the rheological properties of polyelectrolytes and polyelectrolyte/surfactant systems are studied. Various synthetic poly electrolytes are chosen with varied hydrophobicity. We discuss the effects of adding various surfactants to aqueous solutions of poly(ethylene oxide)-b-poly(propylene oxide)- b-polyethylene oxide)-g-poly(acrylic acid) (PEO-PPO-PAA) in the first chapter. Thermogelation in aqueous solutions of PEO-PPO-PAA is due to micellization caused by aggregation of poly(propylene oxide) (PPO) blocks resulting from temperature-induced dehydration of PPO. When nonionic surfactants with hydrophilic-lipophilic balance (HLB) parameter exceeding 11 or Cn alkylsulfates; n-octyl (C8), n-decyl (C 10) and n-dodecyl (C12) sulfates are added, the gelation threshold temperature (Tgel) of 1.0wt% PEO-PPO-PAA in aqueous solutions increases. In contrast, when nonionic surfactants with HLB below 11 are added, the gelation temperature decreases. On the other hand, alkylsulfates with n = 16 or 18 and poly(ethylene oxide) (PEO) do not affect the Tgel. The results imply that both hydrophobicity and tail length of the added surfactant play important roles in the interaction of PEO-PPO-PAA micelles and the surfactant. In the second chapter, the solution behavior of alternating copolymers of maleic acid and hydrophobic monomer is studied. The alternating structure of monomers with two-carboxylic groups and hydrophobic monomers make these copolymers unique. Under appropriate conditions, these carboxylic groups dissociate leaving charges on the chain. The potentiometric titrations of copolymer solutions with added CaCl2 reveal two distinct dissociation processes corresponding to the dissociation of the two adjacent carboxylic acids. The viscosity data as a function of polymer concentration of poly(isobutylene-alt-sodium maleate), poly

  8. Surfactant Assemblies and their Various Possible Roles for the Origin(S) of Life

    NASA Astrophysics Data System (ADS)

    Walde, Peter

    2006-04-01

    A large number of surfactants (surface active molecules) are chemically simple compounds that can be obtained by simple chemical reactions, in some cases even under presumably prebiotic conditions. Surfactant assemblies are self-organized polymolecular aggregates of surfactants, in the simplest case micelles, vesicles, hexagonal and cubic phases. It may be that these different types of surfactant assemblies have played various, so-far underestimated important roles in the processes that led to the formation of the first living systems. Although nucleic acids are key players in the formation of cells as we know them today (RNA world hypothesis), it is still unclear how RNA could have been formed under prebiotic conditions. Surfactants with their self-organizing properties may have assisted, controlled and compartimentalized some of the chemical reactions that eventually led to the formation of molecules like RNA. Therefore, surfactants were possibly very important in prebiotic times in the sense that they may have been involved in different physical and chemical processes that finally led to a transformation of non-living matter to the first cellular form(s) of life. This hypothesis is based on four main experimental observations: (i) Surfactant aggregation can lead to cell-like compartimentation (vesicles). (ii) Surfactant assemblies can provide local reaction conditions that are very different from the bulk medium, which may lead to a dramatic change in the rate of chemical reactions and to a change in reaction product distributions. (iii) The surface properties of surfactant assemblies that may be liquid- or solid-like, charged or neutral, and the elasticity and packing density of surfactant assemblies depend on the chemical structure of the surfactants, on the presence of other molecules, and on the overall environmental conditions (e. g. temperature). This wide range of surface characteristics of surfactant assemblies may allow a control of surface

  9. Surfactant assemblies and their various possible roles for the origin(s) of life.

    PubMed

    Walde, Peter

    2006-04-01

    A large number of surfactants (surface active molecules) are chemically simple compounds that can be obtained by simple chemical reactions, in some cases even under presumably prebiotic conditions. Surfactant assemblies are self-organized polymolecular aggregates of surfactants, in the simplest case micelles, vesicles, hexagonal and cubic phases. It may be that these different types of surfactant assemblies have played various, so-far underestimated important roles in the processes that led to the formation of the first living systems. Although nucleic acids are key players in the formation of cells as we know them today (RNA world hypothesis), it is still unclear how RNA could have been formed under prebiotic conditions. Surfactants with their self-organizing properties may have assisted, controlled and compartimentalized some of the chemical reactions that eventually led to the formation of molecules like RNA. Therefore, surfactants were possibly very important in prebiotic times in the sense that they may have been involved in different physical and chemical processes that finally led to a transformation of non-living matter to the first cellular form(s) of life. This hypothesis is based on four main experimental observations: (i) Surfactant aggregation can lead to cell-like compartimentation (vesicles). (ii) Surfactant assemblies can provide local reaction conditions that are very different from the bulk medium, which may lead to a dramatic change in the rate of chemical reactions and to a change in reaction product distributions. (iii) The surface properties of surfactant assemblies that may be liquid- or solid-like, charged or neutral, and the elasticity and packing density of surfactant assemblies depend on the chemical structure of the surfactants, on the presence of other molecules, and on the overall environmental conditions (e. g. temperature). This wide range of surface characteristics of surfactant assemblies may allow a control of surface

  10. Facile Directed Assembly of Hollow Polymer Nanocapsules within Spontaneously Formed Catanionic Surfactant Vesicles

    SciTech Connect

    Kim, Mariya D.; Dergunov, Sergey; Richter, Andrew; Durbin, Jeffrey; Shmakov, Sergey; Jia, Ying; Kenbeilova, Saltanat; Orazbekuly, Yerbolat; Kengpeiil, Aigerim; Lindner, Erno; Pingali, Sai Venkatesh; Urban, Volker S; Weigand, Steven; Pinkhassik, Eugene

    2014-01-01

    Surfactant vesicles containing monomers in the interior of the bilayer were used to template hollow polymer nanocapsules. This study investigated the formation of surfactant/monomer assemblies by two loading methods, concurrent loading and diffusion loading. The assembly process and the resulting aggregates were investigated with dynamic light scattering, small angle neutron scattering, and small-angle X-ray scattering. Acrylic monomers formed vesicles with a mixture of cationic and anionic surfactants in a broad range of surfactant ratios. Regions with predominant formation of vesicles were broader for compositions containing acrylic monomers compared with blank surfactants. This observation supports the stabilization of the vesicular structure by acrylic monomers. Diffusion loading produced monomer-loaded vesicles unless vesicles were composed from surfactants at the ratios close to the boundary of a vesicular phase region on a phase diagram. Both concurrent-loaded and diffusion-loaded surfactant/monomer vesicles produced hollow polymer nanocapsules upon the polymerization of monomers in the bilayer followed by removal of surfactant scaffolds.

  11. Self-assembly of polyelectrolyte surfactant complexes using large scale MD simulation

    NASA Astrophysics Data System (ADS)

    Goswami, Monojoy; Sumpter, Bobby

    2014-03-01

    Polyelectrolytes (PE) and surfactants are known to form interesting structures with varied properties in aqueous solutions. The morphological details of the PE-surfactant complexes depend on a combination of polymer backbone, electrostatic interactions and hydrophobic interactions. We study the self-assembly of cationic PE and anionic surfactants complexes in dilute condition. The importance of such complexes of PE with oppositely charged surfactants can be found in biological systems, such as immobilization of enzymes in polyelectrolyte complexes or nonspecific association of DNA with protein. Many useful properties of PE surfactant complexes come from the highly ordered structures of surfactant self-assembly inside the PE aggregate which has applications in industry. We do large scale molecular dynamics simulation using LAMMPS to understand the structure and dynamics of PE-surfactant systems. Our investigation shows highly ordered pearl-necklace structures that have been observed experimentally in biological systems. We investigate many different properties of PE-surfactant complexation for different parameter ranges that are useful for pharmaceutical, engineering and biological applications.

  12. Marangoni Effects of a Drop in an Extensional Flow: The Role of Surfactant Physical Chemistry

    NASA Technical Reports Server (NTRS)

    Stebe, Kathleen J.; Balasubramaniam, R. (Technical Monitor)

    2002-01-01

    While the changes in stresses caused by surfactant adsorption on non-deforming interfaces have been fairly well established, prior to this work, there were few studies addressing how surfactants alter stresses on strongly deforming interfaces. We chose the model problem of a drop in a uniaxial extensional flow to study these stress conditions To model surfactant effects at fluid interfaces, a proper description of the dependence of the surface tension on surface concentration, the surface equation of state, is required. We have adopted a surface equation of state that accounts for the maximum coverage limit; that is, because surfactants have a finite cross sectional area, there is an upper bound to the amount of surfactant that can adsorb in a monolayer. The surface tension reduces strongly only when this maximum coverage is approached. Since the Marangoni stresses go as the derivative of the surface equation of state times the surface concentration gradient, the non-linear equation of state determines both the effect of surfactants in the normal stress jump, (which is balanced by the product of the mean curvature of the interface times the surface tension), and the tangential stress jump, which is balanced by Marangoni stresses. First, the effects of surface coverage and intermolecular interactions among surfactants which drive aggregation of surfactants in the interface were studied. (see Pawar and Stebe, Physics of Fluids).

  13. Marangoni Effects of a Drop in an Extensional Flow: The Role of Surfactant Physical Chemistry

    NASA Technical Reports Server (NTRS)

    Stebe, Kathleen J.; Balasubramaniam, R. (Technical Monitor)

    2002-01-01

    While the changes in stresses caused by surfactant adsorption on non-deforming interfaces have been fairly well established, prior to this work, there were few studies addressing how surfactants alter stresses on strongly deforming interfaces. We chose the model problem of a drop in a uniaxial extensional flow to study these stress conditions To model surfactant effects at fluid interfaces, a proper description of the dependence of the surface tension on surface concentration, the surface equation of state, is required. We have adopted a surface equation of state that accounts for the maximum coverage limit; that is, because surfactants have a finite cross sectional area, there is an upper bound to the amount of surfactant that can adsorb in a monolayer. The surface tension reduces strongly only when this maximum coverage is approached. Since the Marangoni stresses go as the derivative of the surface equation of state times the surface concentration gradient, the non-linear equation of state determines both the effect of surfactants in the normal stress jump, (which is balanced by the product of the mean curvature of the interface times the surface tension), and the tangential stress jump, which is balanced by Marangoni stresses. First, the effects of surface coverage and intermolecular interactions among surfactants which drive aggregation of surfactants in the interface were studied. (see Pawar and Stebe, Physics of Fluids).

  14. The Critical Role of Surfactants in the Growth of Cobalt Nanoparticles

    SciTech Connect

    Bao, Yuping; An, Wei; Turner, C. H.; Krishnan, Kannan M.

    2010-01-05

    We report a combined experimental and computational study on the critical role of surfactants in the nucleation and growth of Co nanoparticles synthesized by chemical routes. By varying the surfactant species, Co nanoparticles of different morphologies under similar reaction conditions (e.g., temperature and Co-precursor concentration) were produced. Depending on the surfactant species, the growth of Co nanoparticles followed three different growth pathways. For example, with surfactants oleic acid (OA) and trioctylphosphine oxide (TOPO) used in combination, Co nanoparticles followed a diffusional growth pathway, leading to single crystalline nanoparticles. Multiple-grained nanoparticles, through an aggregation process, were formed with the combination of surfactants OA and dioctylamine (DOA). Further, an Ostwald ripening process was observed in the case of TOPO alone. Complementary electronic structure calculations were used to predict the optimized Co-surfactant complex structures and to quantify the binding energy between the surfactants (ligands) and the Co atoms. These calculations were further applied to predict the Co nanoparticle nucleation and growth processes based on the stability of Co-surfactant complexes.

  15. Non-covalent bonding interaction of surfactants with functionalized carbon nanotubes in proton exchange membranes for fuel cell applications.

    PubMed

    Sayeed, M Abu; Kim, Young Ho; Park, Younjin; Gopalan, A I; Lee, Kwang-Pill; Choi, Sang-June

    2013-11-01

    Dispersion of functionalized multiwalled carbon nanotubes (MWCNTs) in proton exchange membranes (PEMs) was conducted via non-covalent bonding between benzene rings of various surfactants and functionalized MWCNTs. In the solution casting method, dispersion of functionalized MWCNTs in PEMs such as Nafion membranes is a critical issue. In this study, 1 wt.% pristine MWCNTs (p-MWCNTs) and oxidized MWCNTs (ox-MWCNTs) were reinforced in Nafion membranes by adding 0.1-0.5 wt.% of a surfactant such as benzalkonium chloride (BKC) as a cationic surfactant with a benzene ring, Tween-80 as a nonanionic surfactant without a benzene ring, sodium dodecylsulfonate (SDS) as an anionic surfactant without a benzene ring, or sodium dodecylben-zenesulfonate (SDBS) as an anionic surfactant with a benzene ring and their effects on the dispersion of nanocomposites were then observed. Among these surfactants, those with benzene rings such as BKC and SDBS produced enhanced dispersion via non-covalent bonding interaction between CNTs and surfactants. Specifically, the surfactants were adsorbed onto the surface of functionalized MWCNTs, where they prevented re-aggregation of MWCNTs in the nanocomposites. Furthermore, the prepared CNTs reinforced nanocomposite membranes showed reduced methanol uptake values while the ion exchange capacity values were maintained. The enhanced properties, including thermal property of the CNTs reinforced PEMs with surfactants, could be applicable to fuel cell applications.

  16. Synthesis and Self-Assembly Behaviors of Polyhedral Oligomeric Silsesquioxane Based Giant Molecular Shape Amphiphiles

    NASA Astrophysics Data System (ADS)

    Yue, Kan; Yu, Xinfei; Liu, Chang; Zhang, Wen-Bin; Cheng, Stephen

    2013-03-01

    Recently, our group has focus on the synthesis and characterization of novel giant molecular shape amphiphiles (GMSAs) based on functionalized molecular nanoparticles (MNPs), such as polyhedral oligomeric silsesquioxane (POSS), tethered with polymeric tails. A general synthetic method via the combination of sequential ?click? reactions has been developed and several model GMSAs with various tail lengths and distinct molecular topologies, which can be referred as the ?giant surfactants?, ?giant lipids?, ?giant gemini surfactants?, and ?giant bolaform surfactants? etc., have been demonstrated. Studies on their self-assembly behaviors in the bulk have revealed the formation of different ordered mesophase structures with feature sizes around 10 nanometers, which have been investigated in detail by small angle X-ray scattering (SAXS) technique and transmission electron microscopy (TEM). These findings have general implications on understanding the underlying principles of self-assembly behaviors of GMSAs, and might have potential applications in nano-patterning technology. This work is supported by NSF (DMR-0906898) and the Joint-Hope Foundation.

  17. Theoretical and Simulations-Based Modeling of Micellization in Linear and Branched Surfactant Systems

    NASA Astrophysics Data System (ADS)

    Mendenhall, Jonathan D.

    Surfactants are chemically-heterogeneous molecules possessing hydrophilic (head) and hydrophobic (tail) moieties. This dual nature of surfactants leads to interesting phase behavior in aqueous solution as a function of surfactant concentration, including: (i) formation of surfactant monolayers at surfaces and interfaces, and (ii) self-assembly into finite aggregates (micelles) in the bulk solution beyond the critical micelle concentration (cmc). This concentration-dependent phase behavior induces changes in solution properties. For example, the surface activity of surfactants can decrease the surface tension, and self-assembly in bulk solution can lead to changes in viscosity, equivalent conductivity, solubilization capacity, and other bulk properties. These effects make surfactants quite attractive and unique for use in product formulations, where they are utilized as detergents, dispersants, emulsifiers, solubilizers, surface and interfacial tension modifiers, and in other contexts. The specific chemical structure of the surfactant head and tail is essential in determining the overall performance properties of a surfactant in aqueous media. The surfactant tail drives the self-assembly process through the hydrophobic effect, while the surfactant head imparts a certain extent of solubility to the surfactant in aqueous solution through preferential interactions with the hydrogen-bonding network of water. The interplay between these two effects gives rise to the particular phase diagram of a surfactant, including the specific cmc at which micelles begin to form. In addition to serving as a quantitative indicator of micelle formation, the cmc represents a limit to surface monolayer formation, and hence to surface and interfacial tension reduction, because surfactant adsorption at interfaces remains approximately constant beyond the cmc. In addition, the cmc represents the onset of changes in bulk solution properties. This Thesis is concerned with the prediction of cmc

  18. MINERAL-SURFACTANT INTERACTIONS FOR MINIMUM REAGENTS PRECIPITATION AND ADSORPTION FOR IMPROVED OIL RECOVERY

    SciTech Connect

    P. Somasundaran

    2005-04-30

    The aim of this project is to delineate the role of mineralogy of reservoir rocks in determining interactions between reservoir minerals and externally added reagents (surfactants/polymers) and its effect on critical solid-liquid and liquid-liquid interfacial properties such as adsorption, wettability and interfacial tension in systems relevant to reservoir conditions. Previous studies have suggested that significant surfactant loss by precipitation or adsorption on reservoir minerals can cause chemical schemes to be less than satisfactory for enhanced oil recovery. Both macroscopic adsorption, wettability and microscopic orientation and conformation studies for various surfactant/polymer mixtures/reservoir rocks systems were conducted to explore the cause of chemical loss by means of precipitation or adsorption, and the effect of rock mineralogy on the chemical loss. During this period, the adsorption of mixed system of n-dodecyl-{beta}-D-maltoside (DM) and dodecyl sulfonate (C{sub 12}SO{sub 3}Na) has been studied. The effects of solution pH, surfactant mixing ratio and different salts on surfactant adsorption on alumina have been investigated in detail. Along with these adsorption studies, changes in mineral wettability due to the adsorption of the mixtures were determined under relevant conditions to identify the nano-structure of the adsorbed layers. Solution properties of C{sub 12}SO{sub 3}Na/DM mixtures were also studied to identify surfactant interactions that affect the mixed aggregate formation in solution. Adsorption of SDS on gypsum and limestone suggested stronger surfactant/mineral interaction than on alumina, due to the precipitation of surfactant by dissolved calcium ions. The effects of different salts such as sodium nitrate, sodium sulfite and sodium chloride on DM adsorption on alumina have also been determined. As surfactant hemimicelles at interface and micelles in solution have drastic effects on oil recovery processes, their microstructures in

  19. Spectroscopy and computational studies on the interaction of octyl, dodecyl, and hexadecyl derivatives of anionic and cationic surfactants with adenosine deaminase.

    PubMed

    Ajloo, Davood; Mahmoodabadi, Najmeh; Ghadamgahi, Maryam; Saboury, Ali Akbar

    2016-07-01

    Effects of sodium (octyl, dodecyl, hexadecyl) sulfate and their cationic analogous on the structure of adenosine deaminase (ADA) were investigated by fluorescence and circular dichroism spectroscopy as well as molecular dynamics simulation and docking calculation. Root-mean-square derivations, radius of gyration, solvent accessible surface area, and radial distribution function were obtained. The results showed that anionic and cationic surfactants reduce protein stability. Cationic surfactants have more effect on the ADA structure in comparison with anionic surfactants. More concentration and longer surfactants are parallel to higher denaturation. Furthermore, aggregation in the presence of anionic surfactants is more than cationic surfactants. Docking data showed that longer surfactants have more interaction energy and smaller ones bound to the active site.

  20. Surfactant-Induced Changes of Water Flow and Solute Transport in Soils

    NASA Astrophysics Data System (ADS)

    Kinsey, E. N.; Korte, C.; Peng, Z.; Yu, C.; Powelson, D.; Jacobson, A. R.; Baveye, P. C.; Darnault, C. J. G.

    2016-12-01

    Surfactants are present in the environment due to agricultural practices such as irrigation with wastewater, biosolid soil amendments, and/or environmental engineering remediation. Furthermore, surfactants occur widely in soils due to the application of pesticides in surfactant solution sprays, or the application of surfactants as soil wetting agents. Surfactants, because they are amphiphilic and impact the surface tension of aqueous solutions and the contact angle between aqueous and solid phases have the potential to influence water flow in porous media and the physicochemical properties of soils. The objective of this study was to assess the impact of surfactant on the soil infiltration process. Four different soils were used in this study: two sandy loam soils (Lewiston and Greenson series) and two loamy sand soils (Sparta and Gilford series). Rainfall was simulated to flow through different columns filled with the four different types of soil and effluent samples were collected at the end of each column. Each type of soil had two columns, one with a non-ionic surfactant Aerosol®22 at twice the critical micelle concentration, in the rainfall solution and one without. A conservative tracer, potassium bromide, was added to all rainfalls to monitor the infiltration process in soil. Tracer breakthrough curves were used to characterize flow in soils. Flow rates were also recorded for each soil. The presence of surfactant decreased the flow rate by a significant amount in most soil types. The decrease in flow rate can be attributed to the effects on the soil properties of hydraulic conductivity and soil aggregates. A decrease in pore space from the swelling of the soil particles can decrease the hydraulic conductivity. The properties in surfactants also decrease the surface tension and therefore soil particles are able to be dislodged from soil aggregates and cause potential soil clogging.

  1. Surfactant monitoring by foam generation

    DOEpatents

    Mullen, Ken I.

    1997-01-01

    A device for monitoring the presence or absence of active surfactant or other surface active agents in a solution or flowing stream based on the formation of foam or bubbles is presented. The device detects the formation of foam with a light beam or conductivity measurement. The height or density of the foam can be correlated to the concentration of the active surfactant present.

  2. ADSORPTION OF SURFACTANT ON CLAYS

    EPA Science Inventory

    Surfactants used to enhance remediation of soils by soil washing are often lost in the process. Neither the amount nor the cause of this loss is known. It is assumed that clays present in the soil are responsible for the loss of the surfactant. In this papere, adsorption prope...

  3. Surfactant adsorption kinetics in microfluidics

    PubMed Central

    Riechers, Birte; Maes, Florine; Akoury, Elias; Semin, Benoît; Gruner, Philipp; Baret, Jean-Christophe

    2016-01-01

    Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning—here through ion exchange—unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore–surfactant interactions. PMID:27688765

  4. ADSORPTION OF SURFACTANT ON CLAYS

    EPA Science Inventory

    Surfactants used to enhance remediation of soils by soil washing are often lost in the process. Neither the amount nor the cause of this loss is known. It is assumed that clays present in the soil are responsible for the loss of the surfactant. In this papere, adsorption prope...

  5. Surfactant-assisted coal liquefaction

    NASA Technical Reports Server (NTRS)

    Hsu, G. C.

    1977-01-01

    Improved process of coal liquefaction utilizing nonaqueous surfactant has increased oil yield from 50 to about 80%. Asphaltene molecule formation of colloid particles is prevented by surfactant. Separated molecules present more surface area for hydrogenation reaction. Lower requirements for temperature, pressure, and hydrogen lead to reduction in capital and operation costs.

  6. Surfactant-assisted coal liquefaction

    NASA Technical Reports Server (NTRS)

    Hsu, G. C.

    1977-01-01

    Improved process of coal liquefaction utilizing nonaqueous surfactant has increased oil yield from 50 to about 80%. Asphaltene molecule formation of colloid particles is prevented by surfactant. Separated molecules present more surface area for hydrogenation reaction. Lower requirements for temperature, pressure, and hydrogen lead to reduction in capital and operation costs.

  7. Surfactant adsorption kinetics in microfluidics.

    PubMed

    Riechers, Birte; Maes, Florine; Akoury, Elias; Semin, Benoît; Gruner, Philipp; Baret, Jean-Christophe

    2016-10-11

    Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than [Formula: see text] to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning-here through ion exchange-unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore-surfactant interactions.

  8. Surfactant adsorption kinetics in microfluidics

    NASA Astrophysics Data System (ADS)

    Riechers, Birte; Maes, Florine; Akoury, Elias; Semin, Benoît; Gruner, Philipp; Baret, Jean-Christophe

    2016-10-01

    Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning—here through ion exchange—unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore-surfactant interactions.

  9. Random bilayer phases of dilute surfactant solutions

    NASA Astrophysics Data System (ADS)

    Cates, M. E.; Roux, D.

    1990-12-01

    Surfactant molecules in dilute solution may aggregate reversibly into extended structures. For suitably chosen molecules, the preferred packing involves a locally flat bilayer which tends to wander entropically at large distances. At low temperatures (and/or high concentrations) the system forms a stack of flat sheets with one-dimensional quasi-long range order (a smectic liquid crystal), but at high temperatures or low concentrations, the stack can melt into a random surface structure that resembles a multiply connected labyrinth or 'sponge' of bilayer in a sea of solvent. Recent theoretical and experimental progress in understanding the properties of the sponge is reviewed. The authors argue that the sponge phase may provide a good system for the study of various liquid-state critical phenomena.

  10. On-line surfactant monitoring

    SciTech Connect

    Mullen, K.I.; Neal, E.E.; Soran, P.D.; Smith, B.

    1995-04-01

    This group has developed a process to extract metal ions from dilute aqueous solutions. The process uses water soluble polymers to complex metal ions. The metal/polymer complex is concentrated by ultrafiltration and the metals are recovered by a pH adjustment that frees the metal ions. The metal ions pass through the ultrafiltration membrane and are recovered in a concentrated form suitable for reuse. Surfactants are present in one of the target waste streams. Surfactants foul the costly ultrafiltration membranes. It was necessary to remove the surfactants before processing the waste stream. This paper discusses an on-line device the authors fabricated to monitor the process stream to assure that all the surfactant had been removed. The device is inexpensive and sensitive to very low levels of surfactants.

  11. Aggregation kinetics of coalescing polymer colloids.

    PubMed

    Gauer, Cornelius; Jia, Zichen; Wu, Hua; Morbidelli, Massimo

    2009-09-01

    The aggregation behavior of a soft, rubbery colloidal system with a relatively low glass transition temperature, T(g) approximately -20 degrees C, has been investigated. It is found that the average gyration and hydrodynamic radii, R(g) and R(h), measured by light scattering techniques, evolve in time in parallel, without exhibiting the crossover typical of rigid particle aggregation. Cryogenic scanning electron microscopy (cryo-SEM) images reveal sphere-like clusters, indicating that complete coalescence between particles occurs during aggregation. Since coalescence leads to a reduction in the total colloidal surface area, the surfactant adsorption equilibrium, and thus the colloidal stability, change in the course of aggregation. It is found that to simulate the observed kinetic behavior based on the population balance equations, it is necessary to assume that all the clusters are spherical and to account for variations in the colloidal stability of each aggregating particle pair with time. This indicates that, for the given system, the coalescence is very fast, i.e., its time scale is much smaller than that of the aggregation.

  12. Adaptation to low body temperature influences pulmonary surfactant composition thereby increasing fluidity while maintaining appropriately ordered membrane structure and surface activity.

    PubMed

    Suri, Lakshmi N M; McCaig, Lynda; Picardi, Maria V; Ospina, Olga L; Veldhuizen, Ruud A W; Staples, James F; Possmayer, Fred; Yao, Li-Juan; Perez-Gil, Jesus; Orgeig, Sandra

    2012-07-01

    The interfacial surface tension of the lung is regulated by phospholipid-rich pulmonary surfactant films. Small changes in temperature affect surfactant structure and function in vitro. We compared the compositional, thermodynamic and functional properties of surfactant from hibernating and summer-active 13-lined ground squirrels (Ictidomys tridecemlineatus) with porcine surfactant to understand structure-function relationships in surfactant membranes and films. Hibernating squirrels had more surfactant large aggregates with more fluid monounsaturated molecular species than summer-active animals. The latter had more unsaturated species than porcine surfactant. Cold-adapted surfactant membranes displayed gel-to-fluid transitions at lower phase transition temperatures with reduced enthalpy. Both hibernating and summer-active squirrel surfactants exhibited lower enthalpy than porcine surfactant. LAURDAN fluorescence and DPH anisotropy revealed that surfactant bilayers from both groups of squirrels possessed similar ordered phase characteristics at low temperatures. While ground squirrel surfactants functioned well during dynamic cycling at 3, 25, and 37 degrees C, porcine surfactant demonstrated poorer activity at 3 degrees C but was superior at 37 degrees C. Consequently the surfactant composition of ground squirrels confers a greater thermal flexibility relative to homeothermic mammals, while retaining tight lipid packing at low body temperatures. This may represent the most critical feature contributing to sustained stability of the respiratory interface at low lung volumes. Thus, while less effective than porcine surfactant at 37 degrees C, summer-active surfactant functions adequately at both 37 degrees C and 3 degrees C allowing these animals to enter hibernation. Here further compositional alterations occur which improve function at low temperatures by maintaining adequate stability at low lung volumes and when temperature increases during arousal from

  13. Catanionic aggregates formed from drugs and lauric or capric acids enable prolonged release from gels.

    PubMed

    Dew, Noel; Bramer, Tobias; Edsman, Katarina

    2008-07-15

    The aim of this study was to add to the range of charged surfactants that can be used to form catanionic aggregates with oppositely charged surface active drug substances; and to apply these aggregates to prolong drug release from gels. The surfactants used in this study, lauric and capric acids are of natural origin-unlike traditionally used, synthetic, surfactants. The mixtures of drug substances and oppositely charged surfactants were studied visually and with cryogenic transmission electron microscopy. Drug release from gels was studied with a modified USP paddle method. This study shows that lauric and capric acids are as, or even more, active in forming catanionic aggregates than traditionally used surfactants such as sodium dodecyl sulfate. It is shown that the length of the hydrophobic part of the surfactant plays an important role in the formation of pharmaceutically interesting catanionic aggregates. As seen in previous studies, using catanionic vesicles prolongs the drug release from gels and decreases the apparent diffusion coefficient by a factor of 10-50, compared to a gel containing only drug substance.

  14. Innovation in surfactant therapy II: surfactant administration by aerosolization.

    PubMed

    Pillow, J Jane; Minocchieri, S

    2012-01-01

    Instilled bolus surfactant is the only approved surfactant treatment for neonatal respiratory distress syndrome. However, recent trends towards increased utilization of noninvasive respiratory support for preterm infants with surfactant deficiency have created a demand for a similarly noninvasive means of administering exogenous surfactant. Past approaches to surfactant nebulization met with varying success due to inefficient aerosol devices resulting in low intrapulmonary delivery doses of surfactant with variable clinical effectiveness. The recent development of vibrating membrane nebulizers, coupled with appropriate positioning of the interface device, indicates that efficient delivery of aerosolized surfactant is now a realistic goal in infants. Evidence of clinical effect despite low total administered dose in pilot studies, together with suggestions of enhanced homogeneity of pulmonary distribution indicate that this therapy may be applied in a cost-effective manner, with minimal patient handling and disruption. These studies need to be subjected to appropriately designed randomized controlled trials. Further work is also required to determine the optimum delivery route (mask, intranasal prong, nasopharyngeal or laryngeal), dosing amount and redosing interval. Copyright © 2012 S. Karger AG, Basel.

  15. Sorption of nonionic surfactant oligomers to sediment and PCE DNAPL: Effects on PCE distribution between water and sediment

    SciTech Connect

    John, W.W.; Bao, G.; Johnson, W.P.; Stauffer, T.B.

    2000-02-15

    Introduction of surfactant mixtures to the subsurface for the purpose of surfactant-enhanced aquifer remediation requires consideration of the effects of surfactant sorption to sediment and nonaqueous phase liquids. These effects include alteration of the solubilizing properties of the surfactant mixture and alteration of the sorption properties of the stationary phase. Sorption of octylphenol ethoxylate (EO) surfactant oligomers to a low organic carbon content (f{sub oc}) aquifer sediment and to dense nonaqueous phase liquid (DNAPL) consisting of tetrachloroethene (PCE) was examined in batch experiments. At aqueous surfactant concentrations far below the critical micelle concentration (CMC) of the mixture, sorption to sediment was characterized by an initial steep isotherm for both high and low EO content oligomers, with somewhat greater uptake of high EO content oligomers. This stage of sorption resulted in mild increases in the equilibrium constant, k{sub d,PCEr} for distribution of PCE between solution (including surfactant) and sediment (including sorbed surfactant). As the aqueous surfactant concentration increased, surface aggregation of low EO content oligomers on the sediment commenced, and a dramatic increase in K{sub d,PCE} was observed. At aqueous surfactant concentrations increasing above the CMC, the formation of solution micelles caused the sorbed surfactant concentrations to plateau and then decrease. This decrease in sorbed surfactant, along with competition by micelles for contaminant, likely contributed to the observed rapid decrease in K{sub d,PCE} toward zero. Surfactant sorption to PCE DNAPL was greater relative to sediment by 1--2 orders of magnitude, with much greater uptake of the low EO content oligomers. Sorption of all but the lowest EO content oligomers to the PCE DNAPL was terminated by micellization.

  16. Modifications of surfactant distributions and surface morphologies in latex films due to moisture exposure.

    PubMed

    Xu, Guizhen H; Dong, Jinping; Severtson, Steven J; Houtman, Carl J; Gwin, Larry E

    2009-07-30

    Migration of surfactants in water-based, pressure-sensitive adhesive (PSA) films exposed to static and cyclic relative humidity conditions was investigated using confocal Raman microscopy (CRM) and atomic force microscopy (AFM). Studied PSA films contain monomers n-butyl acrylate, vinyl acetate, and methacrylic acid and an equal mass mixture of anionic and nonionic nonylphenol ethoxylate emulsifiers. A leveling of surfactant concentration distributions is observed via CRM after films stored at 50% relative humidity (RH) are exposed to a 100% RH for an extended time period, while relatively small increases in surface enrichment occur when films are stored at 0% RH. Use of CRM for binary mixtures containing anionic or nonionic surfactant and latex that has undergone dialysis to remove nonpolymeric components indicates that surfactant-polymer compatibility governs to a great extent surface enrichment, but not changes observed with humidity variations. AFM images show that upon drying latex coatings, surfactant and other additives collect in large aggregation regions, which protrude from film surfaces. These structures are absent at high humidity, which appears to result from lateral spreading across the polymer surface. When humidity is reduced, aggregation regions reform but appear to be smaller and more evenly dispersed, and by cycling humidity between 0 and 100% RH, interfacial enrichment can be seen to diminish. Presented results provide greater insights into the distribution behavior of surfactants in latex films and potential mechanisms for observed issues arising for these systems.

  17. Alveolar metabolism of natural vs. synthetic surfactants in preterm newborn rabbits.

    PubMed

    Allen, V; Oulton, M; Stinson, D; MacDonald, J; Allen, A

    2001-01-01

    We compared the recoveries of four surfactant preparations: two natural [term fetal rabbit surfactant (FRS) and adult rabbit surfactant (ARS)] and two commercially available preparations [apoprotein-based Survanta (S) and synthetic Exosurf (E)] from 27-day gestation rabbit pups treated at birth and ventilated up to 120 min. At 5, 60, and 120 min, we measured the recovery of the heavy-aggregate, metabolically active form (H) and the light-aggregate, nonsurface active metabolic breakdown form (L) of alveolar surfactant and determined the phospholipid content and composition of the intracellularly stored lamellar body (LB) pool. Pups treated with FRS had <15% loss of H by 2 h. ARS-treated pups had a >50% loss of H by 1 h, and E- and S-treated pups had approximately 50% loss by 5 min, with a slower rate of continuing loss of up to 80% by 2 h. The major losses of H phospholipid were not explained by the L-form recovery. LB phospholipid significantly increased only in the E-treated pups and only at 2 h. FRS provides a biologically active form (H) of surfactant that appeared to remain in the airway for a significantly longer time than the other surfactant preparations. The unique properties of FRS merit further study.

  18. Role of interaction energies in the behavior of mixed surfactant systems: a lattice Monte Carlo simulation.

    PubMed

    Poorgholami-Bejarpasi, Niaz; Hashemianzadeh, Majid; Mousavi-Khoshdel, S Morteza; Sohrabi, Beheshteh

    2010-09-07

    We have investigated micellization in systems containing two surfactant molecules with the same structure using a lattice Monte Carlo simulation method. For the binary systems containing two surfactants, we have varied the head-head interactions or tail-tail repulsions in order to mimic the nonideal behavior of mixed surfactant systems and to manipulate the net interactions between surfactant molecules. The simulation results indicate that interactions between headgroups or tailgroups have an effect on thermodynamic properties such as the mixed critical micelle concentration (cmc), distribution of aggregates, shape of the aggregates, and composition of the micelles formed. Moreover, we have compared the simulation results with estimates based on regular solution theory, a mean-field theory, to determine the applicability of this theory to the nonideal mixed surfactant systems. We have found that the simulation results agree reasonable well with regular solution theory for the systems with attractions between headgroups and repulsions between tailgroups. However, the large discrepancies observed for the systems with head-head repulsions could be attributed to the disregarding of the correlation effect on the interaction among surfactant molecules and the nonrandom mixing effect in the theory.

  19. Giant prostatic calculi

    PubMed Central

    Najoui, Mohammed; Qarro, Abdelmounaim; Ammani, Abdelghani; Alami, Mohammed

    2013-01-01

    Prostatic parenchymal calculi are common, usually incidental, findings on morphological examinations. They are typically asymptomatic and may be present in association with normal glands, benign prostatic hyperplasia, and prostate cancer. However giant prostatic calculi are rare. Less than 20 cases have been reported in the literature. We present the case of a 35-year-old man with two giant prostatic calculi that replaced the entire gland. He underwent an open cystolithotomy, two giant stones were removed from the prostate, and we used a lithotripsy in situ for extraction of stone fragments. PMID:23565316

  20. Unstable giant gravitons

    SciTech Connect

    Mello Koch, Robert de; Ives, Norman; Smolic, Jelena; Smolic, Milena

    2006-03-15

    We find giant graviton solutions in Frolov's three parameter generalization of the Lunin-Maldacena background. The background we study has {gamma}-tilde{sub 1}=0 and {gamma}-tilde{sub 2}={gamma}-tilde{sub 3}={gamma}-tilde. This class of backgrounds provides a nonsupersymmetric example of the gauge theory/gravity correspondence that can be tested quantitatively, as recently shown by Frolov, Roiban, and Tseytlin. The giant graviton solutions we find have a greater energy than the point gravitons, making them unstable states. Despite this, we find striking quantitative agreement between the gauge theory and gravity descriptions of open strings attached to the giant.

  1. Kinetics of aggregation in charged nanoparticle solutions driven by different mechanisms

    NASA Astrophysics Data System (ADS)

    Abbas, S.; Yadav, I.; Kumar, Sugam; Aswal, V. K.; Kohlbrecher, J.

    2017-05-01

    The structure and kinetics during aggregation of anionic silica nanoparticles as induced through different mechanisms have been studied by dynamic light scattering (DLS) and small-angle neutron scattering (SANS). Three different additives, namely an electrolyte (NaCl), cationic protein (lysozyme) and non-ionic surfactant (C12E10) were used to initiate nanoparticle aggregation. Electrolyte induced aggregation can be explained by DLVO interaction, whereas depletion interaction (non-DLVO interaction) is found responsible for nanoparticle aggregation in case of non-ionic surfactant. Unlike these two cases, strong electrostatic attraction between nanoparticle and oppositely charged protein results into protein-mediated nanoparticle aggregation. The electrolyte induced aggregation show quite slow aggregation rate whereas protein mediated as well as surfactant induced aggregation takes place almost instantaneously. The significant differences observed in the kinetics are explained based on range of interactions responsible for the aggregation. In spite of differences in mechanism and kinetics, the nanoparticle clusters are found to have similar fractal morphology (fractal dimension ˜ 2.5) in all the three cases.

  2. Surfactant damping of water waves

    NASA Astrophysics Data System (ADS)

    Lapham, Gary S.; Dowling, David R.; Schultz, William W.

    1997-11-01

    The most well known and perhaps most important distinguishing characteristic of a water surface laden with surfactant is the profound increase in small-wave damping with the addition of even small amounts of surfactant material. It would seem to follow that damping increases with increasing surfactant concentration. This is undoubtedly true for some surfactants, however our experiments with a soluble surfactant show that it is possible to increase surfactant concentration and measure a decrease in damping. While the increased concentration is accompanied by a dramatic decrease in measured static surface tension, some of the capillary-wave frequency regime is less damped. Experimental measurements of the real and imaginary parts of the wave speed are compared with existing theory where at least one other physical quantity besides surface tension is needed to properly model the interface. Our on-going work with insoluble surfactants may also provide an example of this type of behavior for materials that do not readily transfer to and from the bulk water. [Supported by the Office of Naval Research

  3. Molecular mobility in the monolayers of foam films stabilized by porcine lung surfactant.

    PubMed Central

    Lalchev, Z I; Todorov, R K; Christova, Y T; Wilde, P J; Mackie, A R; Clark, D C

    1996-01-01

    Certain physical properties of a range of foam film types that are believed to exist in vivo in the lung have been investigated. The contribution of different lung surfactant components found in porcine lung surfactant to molecular surface diffusion in the plane of foam films has been investigated for the first time. The influence of the type and thickness of black foam films, temperature, electrolyte concentration, and extract composition on surface diffusion has been studied using the fluorescence recovery after photobleaching technique. Fluorescent phospholipid probe molecules in foam films stabilized by porcine lung surfactant samples or their hydrophobic extracts consisting of surfactant lipids and hydrophobic lung surfactant proteins, SP-B and SP-C, exhibited more rapid diffusion than observed in films of its principal lipid component alone, L-alpha-phosphatidylcholine dipalmitoyl. This effect appears to be due to contributions from minor lipid components present in the total surfactant lipid extracts. The minor lipid components influence the surface diffusion in foam films both by their negative charge and by lowering the phase transition temperature of lung surfactant samples. In contrast, the presence of high concentrations of the hydrophillic surfactant protein A (SP-A) and non-lung-surfactant proteins in the sample reduced the diffusion coefficient (D) of the lipid analog in the adsorbed layer of the films. Hysteresis behavior of D was observed during temperature cycling, with the cooling curve lying above the heating curve. However, in cases where some surface molecular aggregation and surface heterogeneity were observed during cooling, the films became more rigid and molecules at the interfaces became immobilized. The thickness, size, capillary pressure, configuration, and composition of foam films of lung surfactant prepared in vitro support their investigation as realistic structural analogs of the surface films that exist in vivo in the lung

  4. Surfactant self-assembly in oppositely charged polymer networks. Theory.

    PubMed

    Hansson, Per

    2009-10-01

    The interaction of ionic surfactants with polyion networks of opposite charge in an aqueous environment is analyzed theoretically by applying a recent theory of surfactant ion-polyion complex salts (J. Colloid. Int. Sci. 2009, 332, 183). The theory takes into account attractive and repulsive polyion-mediated interactions between the micelles, the deformation of the polymer network, the mixing of micelles, polyion chains, and simple ions with water, and the hydrophobic free energy at the micelle surface. The theory is used to calculate binding isotherms, swelling isotherms, surfactant aggregation numbers, compositions of complexes,and phase structure under various conditions. Factors controlling the gel volume transition and conditions for core/shell phase coexistence are investigated in detail, as well as the influence of salt. In particular, the interplay between electrostatic and elastic interactions is highlighted. Results from theory are compared with experimental data reported in the literature. The agreement is found to be semiquantitative or qualitative. The theory explains both the discrete volume transition observed in systems where the surfactant is in excess over the polyion and the core/shell phase coexistence in systems where the polyion is in excess.

  5. ABC copolymer silicone surfactant templating for biomimetic silicification.

    PubMed

    Sun, Bo; Guo, Caiyun; Yao, Yuan; Che, Shunai

    2012-07-15

    Using the ABC copolymer silicone surfactant polydimethylsiloxane (PDMS)-graft-(polyethylene oxide (PEO)-block-propylene oxide (PPO)) (PSEP, Scheme 1a) as a template and tetraethoxysilane (TEOS) as a silica source, silica particles with various structures and morphologies (i.e., disordered spherical micellar aggregation, two-dimensional p6mm mesostructure, asymmetric multi-layer non-equilibrium vesicles and symmetric monolayer vesicles) were synthesized by changing the synthesis temperature from 30 to 80 °C. Increasing the hydrophobicity of the surfactant by increasing the temperature resulted in an increase in the surfactant packing parameter g, which led to the mesophase transformation from micellar to cylinder and later to a lamellar structure. The good compatibility between the PDMS and the TEOS, the different natures of the hydrophobic PDMS and PPO segments, and the hydrolysis and condensation rates of TEOS enabled the variation of silicification structures. This novel silicone surfactant templating route and a new type of materials with highly ordered mesostructures and asymmetric morphologies provide a new insight into the molecular factors governing inorganic-organic mesophase and biosilicification for fabricating functionalized materials.

  6. Electrokinetic investigation of surfactant adsorption.

    PubMed

    Bellmann, C; Synytska, A; Caspari, A; Drechsler, A; Grundke, K

    2007-05-15

    Fuerstenau [D.W. Fuerstenau, in: M.L. Hair (Ed.), Dekker, New York, 1971, p. 143] has already discussed the role of hydrocarbon chain of surfactants, the effect of alkyl chain length, chain structure and the pH of the solution on the adsorption process of surfactants. Later Kosmulski [M. Kosmulski, Chemical Properties of Material Surfaces, Surfactant Science Series, vol. 102, Dekker, New York, Basel, 2001] included the effect of surfactant concentration, equilibration time, temperature and electrolyte in his approaches. Certainly, the character of the head groups of the surfactant and the properties of the adsorbent surface are the basis for the adsorption process. Different surfactants and adsorbents cause different adsorption mechanisms described firstly by Rosen [M.J. Rosen, Surfactants and Interfacial Phenomena, second ed., Wiley, New York, 1989]. These adsorption mechanisms and their influencing factors were studied by electrokinetic investigations. Here only changes of the charges at the surfaces could be detected. To control the results of electrokinetic investigations they were compared with results from ellipsometric measurements. In the case of surfactant adsorption the chain length was vitally important. It could be shown by the adsorption of alkyl trimethyl ammonium bromides onto polymer films spin coated at wafer surfaces. The influence of the chain length depending on surface properties of the polymer film was studied. Streaming potential measurements were applied for these investigations. The obtained results enabled us to calculate the molar cohesive free energy per mol of CH2-group in the alkaline chain of the surfactant if all other specific adsorption effects were neglected.

  7. Synthesis and bio-physicochemical properties of amide-functionalized N-methylpiperazinium surfactants.

    PubMed

    Chauhan, Vinay; Singh, Sukhprit; Mishra, Rachana; Kaur, Gurcharan

    2014-12-15

    Four new amide functionalized N-methylpiperazinium amphiphiles having tetradecyl, hexadecyl alkyl chain lengths and counterions; chloride or bromide have been synthesized and characterized by various spectroscopic techniques. These new surfactants have been investigated in detail for their self-assembling behavior by surface tension, conductivity and fluorescence measurements. The thermodynamic parameters of these surfactants indicate that micellization is exothermic and entropy-driven. The dynamic light scattering (DLS) and transmission electron microscopy (TEM) experiments have been performed to insight the aggregate size of these cationics. Thermal degradation of these new surfactants has also been evaluated by thermal gravimetric analysis (TGA). These new surfactants form stable complexes with DNA as acknowledged by agarose gel electrophoresis, ethidium bromide exclusion and zeta potential measurements. They have also been found to have low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on the C6 glioma cell line.

  8. Semi-quantitative determination of cationic surfactants in aqueous solutions using gold nanoparticles as reporter probes.

    PubMed

    Kuong, Chi-Lap; Chen, Wei-Yu; Chen, Yu-Chie

    2007-03-01

    Concentrations of cationic surfactants in aqueous solutions have been estimated on the basis of changes in the color of gold nanoparticles, used as reporter probes. We have shown that the colors of gold nanoparticles with anionic protective groups on their surfaces shift from red to indigo/purple and then back to red in a range of cationic surfactant solutions in which concentrations vary from very low to above the theoretical CMCs. The color changes occur near the theoretical CMCs, presumably because the presence of surfactant micelles in the solution prevents the gold nanoparticles from aggregating. We have used gold nanoparticles as reporter probes to determine the concentrations of cationic surfactants in products such as hair conditioners, which often contain large amounts of alkyltrimethylammonium halides. Although this approach can only provide an estimate, it can be performed simply by addition of a given amount of gold nanoparticles to a series of diluted solutions, without the need for instruments or labor-intensive procedures.

  9. Inhibition of Pulmonary Surfactant Adsorption by Serum and the Mechanisms of Reversal by Hydrophilic Polymers: Theory

    PubMed Central

    Zasadzinski, Joseph A.; Alig, T. F.; Alonso, Coralie; de la Serna, Jorge Bernardino; Perez-Gil, Jesus; Taeusch, H. William

    2005-01-01

    A theory based on the Smolukowski analysis of colloid stability shows that the presence of charged, surface-active serum proteins at the alveolar air-liquid interface can severely reduce or eliminate the adsorption of lung surfactant from the subphase to the interface, consistent with the observations reported in the companion article (pages 1769–1779). Adding nonadsorbing, hydrophilic polymers to the subphase provides a depletion attraction between the surfactant aggregates and the interface, which can overcome the steric and electrostatic resistance to adsorption induced by serum. The depletion force increases with polymer concentration as well as with polymer molecular weight. Increasing the surfactant concentration has a much smaller effect than adding polymer, as is observed. Natural hydrophilic polymers, like the SP-A present in native surfactant, or hyaluronan, normally present in the alveolar fluids, can enhance adsorption in the presence of serum to eliminate inactivation. PMID:16006630

  10. Inhibition of pulmonary surfactant adsorption by serum and the mechanisms of reversal by hydrophilic polymers: theory.

    PubMed

    Zasadzinski, Joseph A; Alig, T F; Alonso, Coralie; Bernardino de la Serna, Jorge; Perez-Gil, Jesus; Taeusch, H William

    2005-09-01

    A theory based on the Smolukowski analysis of colloid stability shows that the presence of charged, surface-active serum proteins at the alveolar air-liquid interface can severely reduce or eliminate the adsorption of lung surfactant from the subphase to the interface, consistent with the observations reported in the companion article (pages 1769-1779). Adding nonadsorbing, hydrophilic polymers to the subphase provides a depletion attraction between the surfactant aggregates and the interface, which can overcome the steric and electrostatic resistance to adsorption induced by serum. The depletion force increases with polymer concentration as well as with polymer molecular weight. Increasing the surfactant concentration has a much smaller effect than adding polymer, as is observed. Natural hydrophilic polymers, like the SP-A present in native surfactant, or hyaluronan, normally present in the alveolar fluids, can enhance adsorption in the presence of serum to eliminate inactivation.

  11. A simple and fast sonication procedure to remove surfactant templates from mesoporous MCM-41.

    PubMed

    Jabariyan, Shaghayegh; Zanjanchi, Mohammad A

    2012-09-01

    We demonstrate a sonication procedure for the removal of structure-directing micellar templates from mesoporous MCM-41. The method uses a 28 KHz ultrasound in an alcoholic solvent for disrupting micellar aggregation of the surfactant molecules, cetyltrimethylammonium bromide, which have filled the pores of the as-synthesized MCM-41. The majority (93%) of the surfactant molecules are removed out from the powder MCM-41 within a 15 min one-step sonication at a moderate temperature of 40°C. The structural and textural characterization techniques reveal that the resulted surfactant-free MCM-41 exhibits higher features compared to that of those obtained using the conventional calcinations approaches. The surfactant molecules are released into alcohol and can be recovered for reuse. This study provides an easy, cost-effective, mild and useful method for template removal from mesoporous materials at conventional conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Pulmonary surfactant for neonatal respiratory disorders.

    PubMed

    Merrill, Jeffrey D; Ballard, Roberta A

    2003-04-01

    Surfactant therapy has revolutionized neonatal care and is used routinely for preterm infants with respiratory distress syndrome. Recent investigation has further elucidated the function of surfactant-associated proteins and their contribution toward surfactant and lung immune defense functions. As the field of neonatology moves away from intubation and mechanical ventilation of preterm infants at birth toward more aggressive use of nasal continuous positive airway pressure, the optimal timing of exogenous surfactant therapy remains unclear. Evidence suggests that preterm neonates with bronchopulmonary dysplasia and prolonged mechanical ventilation also experience surfactant dysfunction; however, exogenous surfactant therapy beyond the first week of life has not been well studied. Surfactant replacement therapy has been studied for use in other respiratory disorders, including meconium aspiration syndrome and pneumonia. Commercial surfactant preparations currently available are not optimal, given the variability of surfactant protein content and their susceptibility to inhibition. Further progress in the treatment of neonatal respiratory disorders may include the development of "designer" surfactant preparations.

  13. Mixed micellization of gemini and conventional surfactant in aqueous solution: a lattice Monte Carlo simulation.

    PubMed

    Gharibi, Hussein; Khodadadi, Zahra; Mousavi-Khoshdel, S Morteza; Hashemianzadeh, S Majid; Javadian, Soheila

    2014-09-01

    In the current study, we have investigated the micellization of pure gemini surfactants and a mixture of gemini and conventional surfactants using a 3D lattice Monte Carlo simulation method. For the pure gemini surfactant system, the effects of tail length on CMC and aggregation number were studied, and the simulation results were found to be in excellent agreement with the experimental results. For a mixture of gemini and conventional surfactants, variations in the mixed CMC, interaction parameter β, and excess Gibbs free energy G(E) with composition revealed synergism in micelle formation. Simulation results were compared to estimations made using regular solution theory to determine the applicability of this theory for non-ideal mixed surfactant systems. A large discrepancy was observed between the behavior of parameters such as the activity coefficients fi and the excess Gibbs free energy G(E) and the expected behavior of these parameters as predicted by regular solution theory. Therefore, we have used the modified version of regular solution theory. This three parameter model contains two parameters in addition to the interaction parameters: the size parameter, ρ, which reflects differences in the size of components, and the packing parameter, P*, which reflects nonrandom mixing in mixed micelles. The proposed model provides a good description of the behavior of gemini and conventional surfactant mixtures. The results indicated that as the chain length of gemini surfactants in mixture is increased, the size parameter remains constant while the interaction and packing parameters increase. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Advances in the synthesis, molecular architectures and potential applications of gemini surfactants.

    PubMed

    Sharma, Renu; Kamal, Ajar; Abdinejad, Maryam; Mahajan, Rakesh Kumar; Kraatz, Heinz-Bernhard

    2017-10-01

    Gemini surfactants have been the subject of intensive scrutiny by virtue of their unique combination of physical and chemical properties and being used in ordinary household objects to multifarious industrial processes. In this review, we summarize the recent developments of gemini surfactants, highlighting the classification of gemini surfactants based on the variation in headgroup polarity, flexibility/rigidity of spacer, hydrophobic alkyl chain and counterion along with potential applications of gemini surfactants, depicting the truly remarkable journey of gemini surfactants that has just come of age. We have focused on those objectives which will act as suitable candidates to take the field forward. The preceding information will permit us to estimate the effect of structural variation on the aggregation behavior of gemini surfactants for nanoscience and biological applications like antimicrobial, anti-fungal agent, better gene and drug delivery agent with low cytotoxicity and biodegradability, which makes them more advantageous for a number of technological processes and hence reduces the impact of these gemini surfactants on the environment. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Unraveling the Agglomeration Mechanism in Charged Block Copolymer and Surfactant Complexes

    DOE PAGES

    Borreguero, Jose M.; Pincus, Philip A.; Sumpter, Bobby G.; ...

    2017-01-27

    Here, we report a molecular dynamics simulation investigation of self-assembly and complex formation of charged-neutral double hydrophilic and hydrophobic-hydrophilic block copolymers (BCP) with oppositely charged surfactants. Furthermore, the structure of the surfactant micelles and the BCP aggregation on the micelle surface is systematically studied for five different BCP volume fractions that also mimics a reduction of the surfactant concentration. The local electrostatic interactions between the oppositely charged species encourage the formation of core-shell structures between the surfactant micelles where the surfactants form the cores and the charged blocks of the BCP form the corona. The emergent morphologies of these aggregatesmore » are contingent upon the nature of the BCP neutral blocks. The hydrophilic neutral blocks agglomerate with the micelles as hairy colloidal structures while the hydrophobic neutrals agglomerate in lamellar structures with the surfactant micelles. The distribution of counterion charges along the simulation box show a close-to-normal density distribution for the hydrophilic neutral blocks and a binodal distribution for hydrophobic neutral blocks. No specific surfactant concentration dependent scaling relation is observed as opposed to the simpler case of homo-polyelectrolytes.« less

  16. Effects of surfactant micelles on viscosity and conductivity of poly(ethylene glycol) solutions

    NASA Astrophysics Data System (ADS)

    Wang, Shun-Cheng; Wei, Tzu-Chien; Chen, Wun-Bin; Tsao, Heng-Kwong

    2004-03-01

    The neutral polymer-micelle interaction is investigated for various surfactants by viscometry and electrical conductometry. In order to exclude the well-known necklace scenario, we consider aqueous solutions of low molecular weight poly(ethylene glycol) (2-20)×103, whose radial size is comparable to or smaller than micelles. The single-tail surfactants consist of anionic, cationic, and nonionic head groups. It is found that the viscosity of the polymer solution may be increased several times by micelles if weak attraction between a polymer segment and a surfactant exists, ɛsurfactant concentration is therefore attributed to the considerable cross links among micelles and polymers (transient network). In addition to substantial alteration of the transport properties, this weak interaction also influences the onset point of thermodynamic instability associated with polymer-surfactant solutions. The examples include the decrease of critical aggregation concentration for ionic surfactant and clouding point for nonionic surfactant due to PEG addition.

  17. Tracks of a Giant

    NASA Image and Video Library

    2010-08-25

    The giant, 70-meter-wide antenna at NASA Deep Space Network complex in Goldstone, Calif., tracks a spacecraft on Nov. 17, 2009. This antenna, officially known as Deep Space Station 14, is also nicknamed the Mars antenna.

  18. The Next Giant Step

    NASA Image and Video Library

    Artist Robert McCall painted "The Next Giant Step" in 1979 to commemorate the heroism and courage of spaceflight pioneers. Located in the lobby of Johnson's building 2, the mural depicts America's ...

  19. Silvics of Giant Sequoia

    Treesearch

    C. Phillip Weatherspoon

    1986-01-01

    Ecological relationships-including habitat and life history---of giant sequoia (Sequoiadendron giganteum [Lindl.] Buchholz) in natural stands are summarized. Such silvical information provides an important foundation for sound management of the species.

  20. The Giant Cell.

    ERIC Educational Resources Information Center

    Stockdale, Dennis

    1998-01-01

    Provides directions for the construction of giant plastic cells, including details for building and installing the organelles. Also contains instructions for preparing the ribosomes, nucleolus, nucleus, and mitochondria. (DDR)

  1. Giant Earlobe Epidermoid Cyst

    PubMed Central

    Pérez-Guisado, Joaquín; Scilletta, Alessandra; Cabrera-Sánchez, Emilio; Rioja, Luis F; Perrotta, Rosario

    2012-01-01

    Epidermoid cysts represent the most common cutaneous cysts. They are usually small and benign; however, sometimes they can grow to giant epidermoid cists, and occasionally malignancies develop. Giant epidermoid cysts at the earlobe have never been described but in other locations. We describe a case of a giant epidermoid cyst at the earlobe, a location where such a large cyst has never been reported before. The mass was completely resected and the wound of the pedunculated base was sutured with four stitches of nylon 5/0. Histopathology confirmed the presumptive diagnosis of an epidermoid cyst. Six months after the resection, the patient did not have any relapse of the epidermoid cyst. The earlobe is a potential location for giant epidermoid cysts. Although the clinical diagnosis could be enough, due to the possibility of malignancy and to ensure appropriate diagnosis, we consider that all cysts should be sent to the anatomic pathology laboratory for histological evaluation. PMID:22557855

  2. The Giant Cell.

    ERIC Educational Resources Information Center

    Stockdale, Dennis

    1998-01-01

    Provides directions for the construction of giant plastic cells, including details for building and installing the organelles. Also contains instructions for preparing the ribosomes, nucleolus, nucleus, and mitochondria. (DDR)

  3. Minimally invasive approaches for surfactant administration.

    PubMed

    Trevisanuto, D; Marchetto, L

    2013-01-01

    Respiratory distress syndrome (RDS) is the most common respiratory morbidity in preterm infants. In addition to respiratory support, the current clinical treatment includes endotracheal intubation and rapid instillation of exogenous surfactant. However, this approach needs skilled operators and has been associated with complications such as hemodynamic instability and electroencephalogram abnormalities. New, less invasive methods for surfactant administration are needed. In this article, we reviewed the available noninvasive procedures for surfactant administration. In particular, we focused on aerosolized surfactant and surfactant administration through LMA.

  4. Giant Cell Arteritis and Polymyalgia Rheumatica

    MedlinePlus

    ... Controlfamilydoctor.org editorial staff Home Diseases and Conditions Giant Cell Arteritis and Polymyalgia Rheumatica Condition Giant Cell Arteritis and Polymyalgia Rheumatica Share Print Giant ...

  5. Capella: Separating the Giants

    NASA Astrophysics Data System (ADS)

    Young, P. R.; Dupree, A. K.

    2002-01-01

    Images from the Faint Object Camera (FOC) on the Hubble Space Telescope (HST) are used to spatially separate the two giants of Capella (α Aurigae; HD 34029) for the first time at ultraviolet wavelengths. The images were obtained with broadband filters that isolate the wavelength regions 2500-3000 Å and 1300-1500 Å. The cool G8 giant is found to be weaker than the hot G1 giant by factors of around 4 and 17, respectively, in these bands. The latter factor is largely due to the much stronger G1 continuum at short wavelengths. No evidence is found for material lying between the two stars in the images. In addition, the objective prisms of the FOC were used to obtain low-resolution spectra from 1200 to 3000 Å, allowing individual emission lines from each star to be spatially separated. Cool-to-hot star ratios for the emission lines H I Lyα, O I λ1305, Si II λ1816, C II λ1335, He II λ1640, and Si IV λ1393 are presented, showing that the cool giant is weaker than the hot giant by factors of 5-10 in these lines. The O I emission is only a factor of 2.5 weaker in the cool giant, most probably resulting from fluorescence in the extended atmosphere of the cool giant. The line ratios are compared with values derived from International Ultraviolet Explorer and HST/Goddard High Resolution Spectrograph spectra, which could separate the stars spectrally but not spatially. Reasonable agreement is found although the FOC ratios generally imply lower contributions from the cool giant. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  6. Genetics Home Reference: surfactant dysfunction

    MedlinePlus

    ... easy. Without normal surfactant, the tissue surrounding the air sacs in the lungs (the alveoli ) sticks together (because of a force called surface tension) after exhalation, causing the alveoli ...

  7. Surfactant-enhanced aquifier remediation

    SciTech Connect

    Fountain, J.C.

    1996-12-31

    Surfactants can be used to rapidly remove NAPL from contaminated aquifers. They are effective for virtually any organic contaminant. Use in LNAPL contaminated sites requires adequate hydraulic conductivity and control of flow using either hydraulic or physical methods. The presence of DNAPL requires consideration of vertical mobility; a competent confining layer (aquitard) is required if additional aquifers are present at greater depths. Surfactant processes, whether based upon mobilization or solubilization, can be effective at mass removal, but cannot be expected to provide resortation to drinking water standards. The fraction of mass removal, and the cost of remediation using surfactants are dependent upon a sites hydrogeology. Both minimization of cost and maximization of NAPL removal requires detailed characterization of sites contaminant distribution and hydrogeology. Assessment of the feasibility of surfactant-enhanced remediation is dependent upon a detailed site characterization.

  8. Interactions between polymers and surfactants

    SciTech Connect

    de Gennes, P.G. )

    1990-11-01

    A surfactant film (at the water/air interface, or in a bilayer) is exposed to a solution of a neutral, flexible, polymer. Depending on the interactions, and on the Langmuir pressure II of the pure surfactant film, the authors expected to find three types of behavior: (I) the polymer does not absorb; (II) the polymer absorbs and mixes with the surfactant; (III) the polymer absorbs but segregates from the surfactant. Their interest here is in case II. They predict that (a) bilayers become rigid; (b) bilayers, exposed to polymer on one side only, tend to bend strongly; (c) the surface viscosity of monolayers or bilayers is considerably increased; soap films or foams, which usually drain by turbulent (two-dimensional) flows, may be stabilized in case II.

  9. Tube extrusion from permeabilized giant vesicles

    NASA Astrophysics Data System (ADS)

    Borghi, N.; Kremer, S.; Askovic, V.; Brochard-Wyart, F.

    2006-08-01

    This letter reports the permeabilization effects of chemical additives on mechanical properties of Giant Unilamellar Vesicles (GUVs). We use a surfactant, Tween 20, inducing transient pores and a protein, Streptolysin O, inducing permanent pores in the membrane. Lipid tubes are extracted from GUVs anchored onto the tip of a micro-needle and submitted to hydrodynamic flows. On bare vesicles, tube extrusion is governed by the entropic elasticity of the membrane. The vesicle tension increases until it balances the flow velocity U and the tube reaches a stationary length. In permeabilized vesicles, the membrane tension is maintained at a constant value σp by the permeation of inner solution through nanometric pores. This allows extrusion of "infinite" tubes at constant velocity that never reach a stationary length. Tween-20 preliminary results suggest that σp strongly depends on surfactant concentration. For Streptolysin O, we have measured σp vs. U and found two regimes: a "high-porosity" regime for U > Up0 and a "low-porosity" regime for U < Up0, where Up0 is related to the number of pores on the vesicle surface.

  10. Interactions of Fluorinated Surfactants with Diphtheria Toxin T-Domain: Testing New Media for Studies of Membrane Proteins

    PubMed Central

    Rodnin, Mykola V.; Posokhov, Yevgen O.; Contino-Pépin, Christiane; Brettmann, Joshua; Kyrychenko, Alexander; Palchevskyy, Sergiy S.; Pucci, Bernard; Ladokhin, Alexey S.

    2008-01-01

    The principal difficulty in experimental exploration of the folding and stability of membrane proteins (MPs) is their aggregation outside of the native environment of the lipid bilayer. To circumvent this problem, we recently applied fluorinated nondetergent surfactants that act as chemical chaperones. The ideal chaperone surfactant would 1), maintain the MP in solution; 2), minimally perturb the MP's structure; 3), dissociate from the MP during membrane insertion; and 4), not partition into the lipid bilayer. Here, we compare how surfactants with hemifluorinated (HFTAC) and completely fluorinated (FTAC) hydrophobic chains of different length compare to this ideal. Using fluorescence correlation spectroscopy of dye-labeled FTAC and HFTAC, we demonstrate that neither type of surfactant will bind lipid vesicles. Thus, unlike detergents, fluorinated surfactants do not compromise vesicle integrity even at concentrations far in excess of their critical micelle concentration. We examined the interaction of surfactants with a model MP, DTT, using a variety of spectroscopic techniques. Site-selective labeling of DTT with fluorescent dyes indicates that the surfactants do not interact with DTT uniformly, instead concentrating in the most hydrophobic patches. Circular dichroism measurements suggest that the presence of surfactants does not alter the structure of DTT. However, the cooperativity of the thermal unfolding transition is reduced by the presence of surfactants, especially above the critical micelle concentration (a feature of regular detergents, too). The linear dependence of DTT's enthalpy of unfolding on the surfactant concentration is encouraging for future application of (H)FTACs to determine the stability of the membrane-competent conformations of other MPs. The observed reduction in the efficiency of Förster resonance energy transfer between donor-labeled (H)FTACs and acceptor-labeled DTT upon addition of lipid vesicles indicates that the protein sheds the

  11. Spectroscopic investigations on the interaction of an anionic probe with nonionic micelles of Igepal surfactants in aqueous media

    NASA Astrophysics Data System (ADS)

    Moore, S. A.; Palepu, R. M.

    The behaviour of the anionic dye 8-anilino-1-napthalenesulfonic acid ammonium salt, or ANS, in aqueous solutions containing the Igepal series of polyoxyethylene nonionic surfactants was investigated using fluorescence spectroscopic technique. The interactions of the dye with the nonionic surfactants were examined in micellar media, to prevent dye aggregate formation and to ensure maximum dye and surfactant interaction. From the relative fluorescence enhancements, binding constants of the dye to the surfactant micelles and aggregation numbers of the micelles were determined. The aggregation numbers were also separately determined by static fluorescence quenching of pyrene by cetylpyridinium chloride in aqueous surfactant mixtures at a fixed concentration of surfactant, and compared with the value obtained from the present investigation of the interaction of the micelles with the ANS probe. The values of binding constants, micropolarity values sensed by pyrene and the Stern-Volmer constants for quenching of pyrene fluorescence by cetylpyridinium chloride were correlated with the number of ethylene oxide groups in the Igepal series.

  12. Differential modulation of the chaperone-like activity of HSP-1/2, a major protein of horse seminal plasma by anionic and cationic surfactants.

    PubMed

    Kumar, C Sudheer; Swamy, Musti J

    2017-03-01

    The major protein of equine seminal plasma, HSP-1/2 exhibits chaperone-like activity (CLA) by protecting various target proteins against thermal, chemical and oxidative stress. Polydispersity and surface hydrophobicity of HSP-1/2 were found to be important for its CLA. Surfactants are known to alter certain properties of proteins, e.g. hydrophobicity, charge and conformation either by altering properties of the medium or by direct binding. In the current study, thermal aggregation of alcohol dehydrogenase (ADH) and enolase has been studied in the presence of HSP-1/2, different surfactants and their combinations. The results obtained show that anionic surfactants (SDS, sodium dodecyl benzene sulfate) and neutral surfactants (tween-20, triton X-100) increase the CLA of HSP-1/2 and also inhibit aggregation of the target proteins independently. On the other hand, cationic surfactants (CTAB, alanine palmityl ester) increased the thermal aggregation of ADH and enolase and also decreased the CLA of HSP-1/2. These results are of significant interest as they show that surfactants such as SDS and tween-20 can potentially be used as anti-aggregation agents to prevent thermal aggregation of target proteins. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Surfactant loss control in chemical flooding: Spectroscopic and calorimetric study of adsorption and precipitation on reservoir minerals. Quarterly technical progress report. October 1, 1994--December 31, 1994

    SciTech Connect

    Somasundaran, P.

    1995-03-01

    The aim of this research is to elucidate the mechanisms underling adsorption and surface precipitation of flooding surfactants on reservoir minerals. The adsorption and desorption behaviors of tetradecyltrimethyl ammonium chloride (TTAC) and pentadecylethoxylated nonylphenol (NP-15) mixtures as reported earlier were rather complex and to better understand the interactions involved fluorescence spectroscopy and ultrafiltration were used during this report period to probe the microstructure of the adsorbed layer and to determine individual surfactant monomer concentration respectively. It was observed that pyrene was solubilized in mixed aggregates (hemimicelles) of a 1:1 TTAC:NP-15 mixture at the alumina-water interface over a wider concentration range than for TTAC alone. It was also observed that the adsorbed aggregate of a 1:1 TTAC:NP-15 mixture is as hydrophobic as the mixed micelle in solution. This is contrary to what was observed for the adsorption of TTAC alone: pyrene was preferentially solubilized in the TTAC micelles rather than the adsorbed aggregate. The preference of pyrene for the mixed adsorbed aggregates over individual aggregates is relevant to the application of surfactant mixtures in enhanced oil recovery and solubilization. The adsorption/desorption behavior of surfactants is directly related to the monomer concentration of the surfactant, hence it is important to monitor changes in monomer concentration during the adsorption and desorption processes. Ultrafiltration techniques were used to monitor the monomer concentration in solution and at the interface to determine the partitioning of the surfactants to the solid-liquid interface.

  14. Effect of surfactants on the physical stability of recombinant human growth hormone.

    PubMed

    Katakam, M; Bell, L N; Banga, A K

    1995-06-01

    The physical stability of a human growth hormone (hGH) formulation upon exposure to air/water interfaces (with vortex mixing) and to nonisothermal stress [determined by differential scanning calorimetry (DSC)] was investigated. The effect of these stresses on the formation of soluble and insoluble aggregates was studied. The aggregates were characterized and quantified by size exclusion-HPLC and UV spectrophotometry. Vortex mixing of hGH solutions (0.5 mg/mL) in phosphate buffer, pH 7.4, for just 1 min caused 67% of the drug to precipitate as insoluble aggregates. These aggregates were noncovalent in nature. Non-ionic surfactants prevented the interfacially induced aggregation at their critical micelle concentration (cmc) for Pluronic F-68 (polyoxyethylene polyoxypropylene block polymer) and Brij 35 (polyoxyethylene alkyl ether) and above the cmc for Tween 80 (polyoxyethylene sorbitan monooleate). However, the same surfactants failed to stabilize hGH against thermal stress in DSC studies. Higher concentrations of surfactants actually destabilized hGH as evidenced by the decrease in the onset temperature for the denaturation endotherm.

  15. New cationic vesicles prepared with double chain surfactants from arginine: Role of the hydrophobic group on the antimicrobial activity and cytotoxicity.

    PubMed

    Pinazo, A; Petrizelli, V; Bustelo, M; Pons, R; Vinardell, M P; Mitjans, M; Manresa, A; Perez, L

    2016-05-01

    Cationic double chain surfactants have attracted much interest because they can give rise to cationic vesicles that can be used in biomedical applications. Using a simple and economical synthetic approach, we have synthesized four double-chain surfactants with different alkyl chain lengths (LANHCx). The critical aggregation concentration of the double chain surfactants is at least one order of magnitude lower than the CMC of their corresponding single-chain LAM and the solutions prepared with the LANHCx contain stable cationic vesicles. Encouragingly, these new arginine derivatives show very low haemolytic activity and weaker cytotoxic effects than conventional dialkyl dimethyl ammonium surfactants. In addition, the surfactant with the shortest alkyl chain exhibits good antimicrobial activity against Gram-positive bacteria. The results show that a rational design applied to cationic double chain surfactants might serve as a promising strategy for the development of safe cationic vesicular systems.

  16. Physicochemical properties of oleic acid-based partially fluorinated gemini surfactants.

    PubMed

    Sakai, Kenichi; Umemoto, Naoki; Aburai, Kenichi; Takamatsu, Yuichiro; Endo, Takeshi; Kitiyanan, Boonyarach; Matsumoto, Mutsuyoshi; Sakai, Hideki; Abe, Masahiko

    2014-01-01

    We have developed oleic acid-based partially fluorinated gemini surfactants with carboxylic acid headgroups. The fluorocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via a -CH(2)CH(2)OCO- unit, and the carboxylic acid headgroups are introduced to the cis double bond of oleic acid via -OCOCH(2)CH(2)- units. The aqueous solution properties of these surfactants were studied at pH 9 in the presence of 10 mmol dm–3 NaCl by means of static surface tension, pyrene fluorescence, and dynamic light scattering measurements. The resulting surface tension data demonstrate that the partially fluorinated gemini surfactants exhibit excellent surface activity in their dilute aqueous solutions. In addition, the surfactants are suggested to form micellar aggregates 2–4 nm in diameter. We also studied the aqueous temperature-concentration phase diagrams of the partially fluorinated gemini surfactants (disodium salts) on the basis of visual observations (through a crossed polarizer), polarized optical microscopy, and small angle X-ray scattering measurements. Several phase states including micellar solution phase, hexagonal phase, bicontinuous cubic phase, and lamellar phase were observed along with the coexistence of these phases in certain regions. Assemblies with lesser positive curvature tend to be formed with increasing surfactant concentration, increasing temperature, and increasing fluorocarbon chain length. A comparison of the phase diagrams of the partially fluorinated and hydrogenated surfactant systems suggests that close molecular packing is inhibited within the assemblies of the partially fluorinated surfactants because of the limited miscibility between the fluorocarbon and hydrocarbon units. To the best of our knowledge, this is the first systematic report focusing on the temperature-concentration phase diagrams of (partially) fluorinated gemini surfactants over a wide range of compositions and temperatures.

  17. Oil-in-water microemulsions based on cationic surfactants with a hydroxyalkyl fragment in the head group

    NASA Astrophysics Data System (ADS)

    Mirgorodskaya, Alla B.; Yackevich, Ekaterina I.; Zakharova, Lucia Ya.; Konovalov, Alexander I.

    2013-04-01

    The stable oil-in-water microemulsions with a high water content were formed on the basis of cationic surfactants, including those that contain a hydroxyalkyl fragment in the head group. These systems can bind the water- and oil-soluble reagents into a single aggregate formed by self-assembling components. The size, surface and electrokinetic potentials of aggregates in the surfactant/n-hexane/n-butanol/water microemulsions were determined. Besides, their catalytic effect on the cleavage of carboxylic acid esters was evaluated. The behavior of the system was shown to be determined not only by hydrophobic and electrostatic interactions but also by specific interactions, i.e., hydrogen bonds.

  18. Giant congenital melanocytic nevus.

    PubMed

    Viana, Ana Carolina Leite; Gontijo, Bernardo; Bittencourt, Flávia Vasques

    2013-01-01

    Giant congenital melanocytic nevus is usually defined as a melanocytic lesion present at birth that will reach a diameter ≥ 20 cm in adulthood. Its incidence is estimated in <1:20,000 newborns. Despite its rarity, this lesion is important because it may associate with severe complications such as malignant melanoma, affect the central nervous system (neurocutaneous melanosis), and have major psychosocial impact on the patient and his family due to its unsightly appearance. Giant congenital melanocytic nevus generally presents as a brown lesion, with flat or mammilated surface, well-demarcated borders and hypertrichosis. Congenital melanocytic nevus is primarily a clinical diagnosis. However, congenital nevi are histologically distinguished from acquired nevi mainly by their larger size, the spread of the nevus cells to the deep layers of the skin and by their more varied architecture and morphology. Although giant congenital melanocytic nevus is recognized as a risk factor for the development of melanoma, the precise magnitude of this risk is still controversial. The estimated lifetime risk of developing melanoma varies from 5 to 10%. On account of these uncertainties and the size of the lesions, the management of giant congenital melanocytic nevus needs individualization. Treatment may include surgical and non-surgical procedures, psychological intervention and/or clinical follow-up, with special attention to changes in color, texture or on the surface of the lesion. The only absolute indication for surgery in giant congenital melanocytic nevus is the development of a malignant neoplasm on the lesion.

  19. Giant congenital melanocytic nevus*

    PubMed Central

    Viana, Ana Carolina Leite; Gontijo, Bernardo; Bittencourt, Flávia Vasques

    2013-01-01

    Giant congenital melanocytic nevus is usually defined as a melanocytic lesion present at birth that will reach a diameter ≥ 20 cm in adulthood. Its incidence is estimated in <1:20,000 newborns. Despite its rarity, this lesion is important because it may associate with severe complications such as malignant melanoma, affect the central nervous system (neurocutaneous melanosis), and have major psychosocial impact on the patient and his family due to its unsightly appearance. Giant congenital melanocytic nevus generally presents as a brown lesion, with flat or mammilated surface, well-demarcated borders and hypertrichosis. Congenital melanocytic nevus is primarily a clinical diagnosis. However, congenital nevi are histologically distinguished from acquired nevi mainly by their larger size, the spread of the nevus cells to the deep layers of the skin and by their more varied architecture and morphology. Although giant congenital melanocytic nevus is recognized as a risk factor for the development of melanoma, the precise magnitude of this risk is still controversial. The estimated lifetime risk of developing melanoma varies from 5 to 10%. On account of these uncertainties and the size of the lesions, the management of giant congenital melanocytic nevus needs individualization. Treatment may include surgical and non-surgical procedures, psychological intervention and/or clinical follow-up, with special attention to changes in color, texture or on the surface of the lesion. The only absolute indication for surgery in giant congenital melanocytic nevus is the development of a malignant neoplasm on the lesion. PMID:24474093

  20. Adsorption and Depletion Regimes of a Nonionic Surfactant in Hydrophilic Mesopores: An Experimental and Simulation Study

    DOE PAGES

    Muter, Dirk; Rother, Gernot; Bock, Henry; ...

    2017-08-15

    Adsorption and aggregation of nonionic surfactants at oxide surfaces has been studied extensively in the past, but only for concentrations below and near the critical micelle concentration. Here we report an adsorption study of a short-chain surfactant (C6E3) in porous silica glass of different pore sizes (7.5 to 50 nm), covering a wide composition range up to 50 wt % in a temperature range from 20 °C to the LCST. Aggregative adsorption is observed at low concentrations, but the excess concentration of C6E3 in the pores decreases and approaches zero at higher bulk concentrations. Strong depletion of surfactant (corresponding tomore » enrichment of water in the pores) is observed in materials with wide pores at high bulk concentrations. We propose an explanation for the observed pore-size dependence of the azeotropic point. Mesoscale simulations based on dissipative particle dynamics (DPD) were performed to reveal the structural origin of this transition from the adsorption to the depletion regime. The simulated adsorption isotherms reproduce the behavior found in the 7.5 nm pores. As a result, the calculated bead density profiles indicate that the repulsive interaction of surfactant head groups causes a depletion of surfactant in the region around the corona of the surface micelles.« less

  1. Solubilizing effects caused by the nonionic surfactant dodecylmaltoside in phosphatidylcholine liposomes.

    PubMed Central

    de la Maza, A; Parra, J L

    1997-01-01

    The interaction of the nonionic surfactant dodecylmaltoside (DM) with phosphatidylcholine liposomes was investigated. Permeability alterations were detected as a change in 5(6)-carboxyfluorescein released from the interior of vesicles and bilayer solubilization as a decrease in the static light scattered by liposome suspensions. This surfactant showed higher capacity to saturate and solubilize PC liposomes and greater affinity with these structures than those reported for the octyl glucoside. At subsolubilizing level an initial maximum in the bilayer/water partitioning (K) followed by an abrupt decrease of this parameter occurred as the effective molar ratio of surfactant to phospholipid in bilayers (Re) rose. However, at solubilizing level a direct dependence was established between both parameters. A direct correlation took place in the initial interaction steps (Re up to 0.28) between the growth of vesicles, their fluidity, and Re. A similar direct dependence was established during solubilization (Re range from 0.9 to 1.7) between the decrease in both the surfactant-PC aggregate size, the light scattering of the system, and Re (composition of aggregates). The fact that the free DM concentration at subsolubilizing and solubilizing levels showed values lower than and similar to its critical micelle concentration indicates that permeability alterations and solubilization were determined, respectively, by the action of surfactant monomer and by the formation of mixed micelles. Images FIGURE 3 PMID:9083670

  2. Adsorption of a cationic surfactant by a magsorbent based on magnetic alginate beads.

    PubMed

    Obeid, Layaly; El Kolli, Nadia; Dali, Noëlle; Talbot, Delphine; Abramson, Sébastien; Welschbillig, Mathias; Cabuil, Valérie; Bée, Agnès

    2014-10-15

    Adsorption of cetylpyridinium chloride (CPC), a cationic surfactant, by magnetic alginate beads (MagAlgbeads) was investigated. The magnetic adsorbent (called magsorbent) was prepared by encapsulation of magnetic functionalized nanoparticles in an alginate gel. The influence on CPC adsorption of several parameters such as contact time, pH and initial surfactant concentration was studied. The equilibrium isotherm shows that adsorption occurs through both electrostatic interactions with charge neutralization of the carboxylate groups of the beads and hydrophobic interactions inducing the formation of surfactant aggregates in the beads. The dosage of calcium ions released in the solution turns out to be a useful tool for understanding the adsorption mechanisms. Adsorption is accompanied by a shrinking of the beads that corresponds to a 45% reduction of the volume. Adsorption kinetic experiments show that equilibrium time is strongly dependent on the surfactant concentration, which monitors the nature of the interactions. On the other hand, since the pH affects the ionization state of adsorption sites, adsorption depends on the pH solution, maximum adsorption being obtained in a large pH range (3.2-12) in agreement with the pKa value of alginate (pKa=3.4-4.2). Finally, due to the formation of micelle-like surfactants aggregates in the magnetic alginate beads, they could be used as a new efficient magsorbent for hydrophobic pollutants.

  3. A thermosensitive carrageenan-based polymer: synthesis, characterization and interactions with a cationic surfactant.

    PubMed

    Gaweł, Kamila; Karewicz, Anna; Bielska, Dorota; Szczubiałka, Krzysztof; Rysak, Katarzyna; Bonarek, Piotr; Nowakowska, Maria

    2013-07-01

    Novel polyelectrolytes were obtained by grafting N-isopropylacrylamide (NIPAM) on the ι-carrageenan (CAR) chain. Two polymers with different grafting degrees were synthesized. The polymers were found to show the lower critical solution temperature (LCST) close to that of PNIPAM. The LCST values were dependent on the concentration of salt and cationic surfactant. The interactions of CAR-graft-PNIPAM with a model cationic surfactant-dodecyltrimethyl ammonium chloride (DTAC) in water and 0.15M NaCl were studied. It was found that both ι-carrageenan and CAR-graft-PNIPAM polymers interact with DTAC. The presence of CAR-graft-PNIPAM in the solution of DTAC induces formation of surfactant aggregates at the critical aggregation concentration much lower than the cmc of the surfactant. Cac increased with ionic strength. The values of cac for CAR-graft-PNIPAM - DTAC system and standard free enthalpy changes attributed to the complexation process were determined. The results obtained for CAR-graft-PNIPAM were compared with these for the non-modified ι-carrageenan. The surfactant interactions with non-modified and grafted polymers were found to be different in nature.

  4. Tailoring supramolecular nanotubes by bile salt based surfactant mixtures.

    PubMed

    Gubitosi, Marta; Travaglini, Leana; di Gregorio, Maria Chiara; Pavel, Nicolae V; Vázquez Tato, José; Sennato, Simona; Olsson, Ulf; Schillén, Karin; Galantini, Luciano

    2015-06-08

    An approach for tailoring self-assembled tubular structures is described. By controlling the relative composition of a two-component surfactant mixture comprising the natural bile salt lithocholate and its bolamphiphilic derivative, it was possible to finely tune the nanotube cross-section of the mixed tubular aggregates that self-associated spontaneously in aqueous solution at pH 12. The diameter was found to vary up to 50% when the stoichiometric ratio of the two bile salts was changed. The tuning of supramolecular nanochannels with such remarkable precision is of significant interest for technological applications of these materials.

  5. Giant star seismology

    NASA Astrophysics Data System (ADS)

    Hekker, S.; Christensen-Dalsgaard, J.

    2017-06-01

    The internal properties of stars in the red-giant phase undergo significant changes on relatively short timescales. Long near-uninterrupted high-precision photometric timeseries observations from dedicated space missions such as CoRoT and Kepler have provided seismic inferences of the global and internal properties of a large number of evolved stars, including red giants. These inferences are confronted with predictions from theoretical models to improve our understanding of stellar structure and evolution. Our knowledge and understanding of red giants have indeed increased tremendously using these seismic inferences, and we anticipate that more information is still hidden in the data. Unraveling this will further improve our understanding of stellar evolution. This will also have significant impact on our knowledge of the Milky Way Galaxy as well as on exo-planet host stars. The latter is important for our understanding of the formation and structure of planetary systems.

  6. Interactions and hybrid complex formation of anionic algal polysaccharides with a cationic glycine betaine-derived surfactant.

    PubMed

    Covis, Rudy; Vives, Thomas; Gaillard, Cédric; Benoit, Maud; Benvegnu, Thierry

    2015-05-05

    The interaction between anionic algal polysaccharides ((κ)-, (ι)-, (λ)-carrageenans, alginate and ulvan) and a cationic glycine betaine (GB) amide surfactant possessing a C18:1 alkyl chain has been studied using isothermal titration calorimetry (ITC), zeta-potential measurements, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and surface tension measurements. It was observed that this cationic surfactant derived from renewable raw materials induced cooperative binding with the anionic polymers at critical aggregation concentration (CAC) and the CAC values are significantly lower than the corresponding critical micelle concentration (CMC) for the surfactant. The CMC of cationic GB surfactant was obtained at higher surfactant concentration in polysaccharide solution than in pure water. More interestingly, the presence of original polysaccharide/surfactant hybrid complexes formed above the CMC value was evidenced from (κ)-carrageenan by microscopy (TEM and AFM). Preliminary investigations of the structure of these complexes revealed the existence of surfactant nanoparticles surrounded with polysaccharide matrix, probably resulting from electrostatic attraction. In addition, ITC measurements clearly showed that the interactions of the κ-carrageenan was stronger than for other polysaccharides ((ι)-, (λ)-carrageenans, alginate and ulvan). These results may have important impact on the use of the GB amide surfactant in formulations based on algal polysaccharides for several applications such as in food, cosmetics, and detergency fields.

  7. Transport of fluorescently labeled hydroxyapatite nanoparticles in saturated granular media at environmentally relevant concentrations of surfactants

    SciTech Connect

    Wang, Dengjun; Su, Chuming; Liu, Chongxuan; Zhou, Dongmei

    2014-05-01

    Hydroxyapatite nanoparticle (nHAP) is being used to remediate soils and aquifers contaminated with metals and radionuclides; however, the mobility of nHAP is still poorly understood in subsurface granular environments. In this study, transport and retention kinetics of alizarin red S (ARS)-labeled nHAP were investigated in water-saturated quartz sand at low concentrations of surfactants: sodium dodecyl benzene sulfonate (SDBS, an anionic surfactant, 0–50 mg L–1) and cetyltrimethylammonium bromide (CTAB, a cationic surfactant, 0–5 mg L–1). Both surfactants were found to have a marked effect on the electrokinetic properties of ARS-nHAP and, consequently, on their transport and retention behaviors. Transport of nanoparticles (NPs) increased significantly with increasing SDBS concentration, largely because of enhanced colloidal stability and reduced aggregate size arising from enhanced electrostatic, osmotic, and elastic-steric repulsions between ARS-nHAP and sand grains. Conversely, transport decreased significantly in the presence of increasing CTAB concentrations due to reduced surface charge and consequential enhanced aggregation of the NPs. Osmotic and elastic-steric repulsions played only a minor role in enhancing the colloidal stability of ARS-nHAP in the presence of CTAB. Retention profiles of ARS-nHAP exhibited hyperexponential-shapes (decreasing rates of retention with increasing distance) for all conditions tested, and became more pronounced as CTAB concentration increased. The phenomenon was attributed to the aggregation and ripening of ARS-nHAP in the presence of surfactants, particularly CTAB. Overall, the present study suggests that surfactants at environmentally relevant concentrations may be an important consideration in employing nHAP for engineered in-situ remediation of certain metals and radionuclides in contaminated soils and aquifers.

  8. Effect of surfactants on Ra-sHSPI - A small heat shock protein from the cattle tick Rhipicephalus annulatus

    NASA Astrophysics Data System (ADS)

    Siddiqi, Mohammad Khursheed; Shahein, Yasser E.; Hussein, Nahla; Khan, Rizwan H.

    2016-09-01

    Electrostatic interaction plays an important role in protein aggregation phenomenon. In this study, we have checked the effect of anionic - Sodium Dodecyl Sulfate (SDS) and cationic-Cetyltrimethyl Ammonium Bromide (CTAB) surfactant on aggregation behavior of Ra-sHSPI, a small heat shock protein purified from Rhipicephalus annulatus tick. To monitor the effect of these surfactants, we have employed several spectroscopic methods such as Rayleigh light scattering measurements, ANS (8-Anilinonaphthalene-1-sulfonic acid) fluorescence measurements, ThT (Thioflavin T) binding assays, Far-UV CD (Circular Dichroism) and dynamic light scattering measurements. In the presence of anionic surfactant-SDS, Ra-sHSPI forms amyloid fibrils, in contrast, no amyloid formation was observed in presence of cationic surfactant at low pH. Enhancement of ANS fluorescence intensity confirms the exposition of more hydrophobic patches during aggregation. ThT binding assay confirms the amyloid fibrillar nature of the SDS induced Ra-sHSPI aggregates and supported by PASTA 2.0 (prediction of amyloid structural aggregation) software. This study demonstrates the crucial role of charge during amyloid fibril formation at low pH in Ra-sHSPI.

  9. Surfactant therapy and spontaneous diuresis.

    PubMed

    Bhat, R; John, E; Diaz-Blanco, J; Ortega, R; Fornell, L; Vidyasagar, D

    1989-03-01

    The effect of artificial surfactant therapy on renal function and the onset of spontaneous diuresis was prospectively evaluated in 19 infants with hyaline membrane disease in a double-blind, controlled study. Twelve infants were in the surfactant group; seven infants received placebo (0.9% saline solution). There was no difference in the time of onset of spontaneous diuresis (as defined by output greater than or equal to 80% of intake). The glomerular filtration rate, determined by endogenous creatinine clearance, was also similar in the surfactant- and placebo-treated infants during the first 3 days of life. The fractional excretion of sodium was significantly higher in the placebo group at 24 hours and 36 hours. Infants in the placebo group had a higher negative sodium balance than those in the surfactant group. Ventilatory status improved significantly soon after surfactant treatment, as evidenced by improvement in the alveolar/arterial oxygen pressure ratio and by a lower mean airway pressure. These data suggest that ventilatory status can be improved without diuresis; the factors that regulate diuresis are multiple and not fully understood.

  10. An Innocent Giant

    PubMed Central

    Solanki, Lakhan Singh; Dhingra, Mandeep; Raghubanshi, Gunjan; Thami, Gurvinder Pal

    2014-01-01

    A cutaneous horn (cornu cutaneum) is a protrusion from the skin composed of a cornified material. It may be associated with a benign, premalignant, or malignant lesion at the base, masking numerous dermatoses. In a 24-year-old female, a giant cutaneous horn arising from a seborrheic keratosis located on the leg is presented. This case has been reported to emphasize that a giant cutaneous horn may also occur in young patients, even in photoprotected areas, and are not always associated with malignancy. PMID:25484426

  11. Constructing a molecular theory of self-assembly: Interplay of ideas from surfactants and block copolymers.

    PubMed

    Nagarajan, Ramanathan

    2017-06-01

    Low molecular weight surfactants and high molecular weight block copolymers display analogous self-assembly behavior in solutions and at interfaces, generating nanoscale structures of different shapes. Understanding the link between the molecular structure of these amphiphiles and their self-assembly behavior has been the goal of theoretical studies. Despite the analogies between surfactants and block copolymers, models predicting their self-assembly behavior have evolved independent of one another, each overlooking the molecular feature considered critical to the other. In this review, we focus on the interplay of ideas pertaining to surfactants and block copolymers in three areas of self-assembly. First, we show how improved free energy models have evolved by applying ideas from surfactants to block copolymers and vice versa, giving rise to a unitary theoretical framework and better predictive capabilities for both classes of amphiphiles. Second we show that even though molecular packing arguments are often used to explain aggregate shape transitions resulting from self-assembly, the molecular packing considerations are more relevant in the case of surfactants whereas free energy criteria are relevant for block copolymers. Third, we show that even though the surfactant and block copolymer aggregates are small nanostructures, the size differences between them is significant enough to make the interfacial effects control the solubilization of molecules in surfactant micelles while the bulk interactions control the solubilization in block copolymer micelles. Finally, we conclude by identifying recent theoretical progress in adapting the micelle model to a wide variety of self-assembly phenomena and the challenges to modeling posed by emerging novel classes of amphiphiles with complex biological, inorganic or nanoparticle moieties. Published by Elsevier B.V.

  12. Dispersion behavior and aqueous foams in mixtures of a vesicle-forming surfactant and edible nanoparticles.

    PubMed

    Binks, Bernard P; Campbell, Shawn; Mashinchi, Saeed; Piatko, Michael P

    2015-03-17

    In an attempt to prepare ultrastable aqueous foams composed entirely of food-grade ingredients, we describe the foamability and foam stability of aqueous phases containing either calcium carbonate particles (CaCO3), sodium stearoyl lactylate surfactant (SSL), or their mixtures. Techniques including zeta potential measurements, adsorption isotherm determination, contact angles and optical and cryo-scanning electron microscopy are used to probe the interaction between particles and surfactant molecules. Aqueous dispersions of inherently hydrophilic cationic CaCO3 nanoparticles do not foam to any great extent. By contrast, aqueous dispersions of anionic SSL, which forms a lamellar phase/vesicles, foam progressively on increasing the concentration. Despite their foamability being low compared to that of micelle-forming surfactant sodium dodecyl sulfate, they are much more stable to collapse with half-lives (of up to 40 days) of around 2 orders of magnitude higher above the respective aggregation concentrations. We believe that, in addition to surfactant lamellae around bubbles, the bilayers within vesicles contain surfactant chains in a solidlike state yielding indestructible aggregates that jam the aqueous films between bubbles, reducing the drainage rate and both bubble coalescence and gas-transfer between bubbles. In mixtures of particles and surfactant, the adsorption of SSL monomers occurs on particle surfaces, leading to an increase in their hydrophobicity, promoting particle adsorption to bubble surfaces. Ultrastable foams result with half-lives of around an order of magnitude higher again at low concentrations and foams which lose only around 30% of their volume within a year at high concentrations. In the latter case, we evidence a high surface density of discrete surfactant-coated particles at bubble surfaces, rendering them stable to coalescence and disproportionation.

  13. Thermodynamics of Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Osborne, Kenneth L.; Barz, Bogdan; Bachmann, Michael; Strodel, Birgit

    Amyloid protein aggregation characterizes many neurodegenerative disorders, including Alzheimer's, Parkinson's, and Creutz- feldt-Jakob disease. Evidence suggests that amyloid aggregates may share similar aggregation pathways, implying simulation of full-length amyloid proteins is not necessary for understanding amyloid formation. In this study we simulate GNNQQNY, the N-terminal prion-determining domain of the yeast protein Sup35 to investigate the thermodynamics of structural transitions during aggregation. We use a coarse-grained model with replica-exchange molecular dynamics to investigate the association of 3-, 6-, and 12-chain GNNQQNY systems and we determine the aggregation pathway by studying aggregation states of GN- NQQNY. We find that the aggregation of the hydrophilic GNNQQNY sequence is mainly driven by H-bond formation, leading to the formation of /3-sheets from the very beginning of the assembly process. Condensation (aggregation) and ordering take place simultaneously, which is underpinned by the occurrence of a single heat capacity peak only.

  14. Synthesis, characterization, and controlled aggregation of biotemplated polystyrene nanodisks

    SciTech Connect

    Tekobo, Samuel; Richter, Andrew; Dergunov, Sergey; Pingali, Sai Venkatesh; Urban, Volker S; Yan, Bing; Pinkhassik, Eugene

    2011-01-01

    Cross-linked polystyrene nanodisks were prepared by controlled polymerization of styrene and divinylbenzene in the interior of bicelles, discoidal lipid aggregates. Aggregation behavior of polymer nanodisks was studied in water, organic solvents, and solid phase. Nanodisks form stable dispersions in aqueous solutions of surfactants, such as sodium dodecyl sulfate (SDS). Varying SDS/nanodisk ratio allowed us to control the size of nanodisk aggregates. Nanodisks are readily solubilized in nonpolar organic solvents, such as toluene and carbon tetrachloride, to yield stable monodisperse suspensions. These findings open opportunities for creating nanodisk-based nanocomposite materials. Stable nanodisk suspension in toluene enabled small angle neutron scattering (SANS) measurements. SANS data confirmed the nanodisk diameter and allowed accurate measurement of nanodisk thickness (19.5 1.0 ). In solid phase, nanodisks aggregate in sub-micron platelets.

  15. Aggregation of colloidal particles with a finite interparticle attraction energy

    NASA Astrophysics Data System (ADS)

    Shih, Wan Y.; Liu, Jun; Shih, Wei-Heng; Aksay, Ilhan A.

    1991-03-01

    Aggregation of colloidal particles with a finite attraction energy was investigated with computer simulations and with gold particles coated with a surfactant. Computer simulations were carried out with the Shih-Aksay-Kikuchi (SAK) model, which incorporates a finite nearest-neighbor attraction energy- E into the diffusion-limited-cluster-aggregation (DLCA) model. Both the computer simulations and the experiments showed that (i) with a finite interparticle attraction energy, aggregates can still remain fractal, and (ii) the fractal dimension remains unchanged at large interparticle attraction energies and increases when the interparticle attraction energy is smaller than 4 k B T where T is the temperature and K B is the Boltzmann constant. The agreement between the simulations and the experimental results suggests that the reversible aggregation process in a colloidal system can be represented by the SAK model.

  16. Synthesis, characterization, and controlled aggregation of biotemplated polystyrene nanodisks.

    SciTech Connect

    Tekobo, S.; Richter, A.G.; Dergunov, S.A.; Pingali, S.V.; Urban, V.; Yan, B.; Pinkhassik, E.

    2011-01-01

    Cross-linked polystyrene nanodisks were prepared by controlled polymerization of styrene and divinylbenzene in the interior of bicelles, discoidal lipid aggregates. Aggregation behavior of polymer nanodisks was studied in water, organic solvents, and solid phase. Nanodisks form stable dispersions in aqueous solutions of surfactants, such as sodium dodecyl sulfate (SDS). Varying SDS/nanodisk ratio allowed us to control the size of nanodisk aggregates. Nanodisks are readily solubilized in nonpolar organic solvents, such as toluene and carbon tetrachloride, to yield stable monodisperse suspensions. These findings open opportunities for creating nanodisk-based nanocomposite materials. Stable nanodisk suspension in toluene enabled small angle neutron scattering (SANS) measurements. SANS data confirmed the nanodisk diameter and allowed accurate measurement of nanodisk thickness (19.5 {+-} 1.0 {angstrom}). In solid phase, nanodisks aggregate in sub-micron platelets.

  17. Investigations on ionic detergents with unusual aggregation behavior

    SciTech Connect

    Hoffman, H.; Platz, G.; Ulbricht, W.

    1981-05-14

    The aggregation behavior of the 2 surfactants dodecylammonium trifluoroacetate (DATFA) and tetradecylammonium trifluoroacetate (TATFA) has been studied at different concentrations and temperatures with several techniques. Rodlike aggregates are present in solutions of DATFA. The length of these anisotropic micelles which was determined by electric birefringence, viscosity, and quasielastic light-scattering measurements varies little with total detergent concentration but decreases rapidly with increasing temperature. The aggregation behavior of TATFA show no electric birefringence but the hydrodynamic radius for the micelles which is determined from the quasielastic light-scattering measurements is too large for normal spherical micelles. Furthermore, the residence times of the detergent ions inside the micelles are too long also. The data are explained on the basis of micellar aggregates that contain solubilized ion pairs of the detergent ion and its counterion in the interior of the micelles. 27 references.

  18. Synthesis, characterization, and controlled aggregation of biotemplated polystyrene nanodisks

    NASA Astrophysics Data System (ADS)

    Tekobo, Samuel; Richter, Andrew G.; Dergunov, Sergey A.; Pingali, Sai Venkatesh; Urban, Volker S.; Yan, Bing; Pinkhassik, Eugene

    2011-12-01

    Cross-linked polystyrene nanodisks were prepared by controlled polymerization of styrene and divinylbenzene in the interior of bicelles, discoidal lipid aggregates. Aggregation behavior of polymer nanodisks was studied in water, organic solvents, and solid phase. Nanodisks form stable dispersions in aqueous solutions of surfactants, such as sodium dodecyl sulfate (SDS). Varying SDS/nanodisk ratio allowed us to control the size of nanodisk aggregates. Nanodisks are readily solubilized in nonpolar organic solvents, such as toluene and carbon tetrachloride, to yield stable monodisperse suspensions. These findings open opportunities for creating nanodisk-based nanocomposite materials. Stable nanodisk suspension in toluene enabled small angle neutron scattering (SANS) measurements. SANS data confirmed the nanodisk diameter and allowed accurate measurement of nanodisk thickness (19.5 ± 1.0 Å). In solid phase, nanodisks aggregate in sub-micron platelets.

  19. A fundamental investigation of the surfactant-stabilized single-walled carbon nanotube/epoxy resin suspensions by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Rahmani, Farzin; Nouranian, Sasan; Mahdavi, Mina; O’Haver, John H.

    2017-01-01

    The surfactant-assisted stabilization of single-walled carbon nanotubes (SWCNTs) in SWCNT/epoxy resin suspensions were investigated for different surfactant types, concentrations, and temperatures using molecular dynamics simulation. One cationic surfactant, i.e. cetyltrimethylammonium bromide (CTAB), and three anionic surfactants, i.e. sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (NaDDBS), and sodium cholate (SC), as well as a 1:1 mixture of CTAB and SDS were used. Potentials of mean force (PMFs) were generated between two fixed-size (6,6) SWCNTs for all neat (no surfactant) and surfactant-loaded SWCNT/epoxy resin systems at three different surfactant concentrations (0.25, 0.50, and 1.00 wt%) at room (298 K) and elevated temperature (398 K, only for low-surfactant-concentration systems). Overall, two distinct mechanisms of SWCNT stabilization by the surfactants were identified: (1) an increase in the SWCNT aggregation energy barrier due to the wrapping of the SWCNTs by the surfactant molecules, and (2) a constantly positive free energy (repulsion) for all SWCNT separation distances due to the encapsulation of the two approaching SWCNTs. With the second mechanism, there is a delay for the epoxy molecules to be pushed out from the space between the two SWCNTs. With an increase in the surfactant concentration, the first mechanism becomes more prevalent. With an increase in temperature to 398 K, all surfactants migrate to the suspending medium, thereby the second mechanism of SWCNT stabilization dominates. A drop in the SWCNT-surfactant binding energy is observed around 360–370 K, signifying the surfactant migration to the suspending medium. More or less, all surfactants stabilize the SWCNTs in an epoxy resin at one or more surfactant concentrations. However, NaDDBS exhibits a higher SWCNT aggregation barrier at high concentrations and both temperatures (298 K and 398 K), thereby providing a better SWCNT stabilization in the epoxy resin

  20. Preparations of organobentonite using nonionic surfactants.

    PubMed

    Shen, Y H

    2001-08-01

    Due to hydrophilic environment at its surface, natural bentonite is an ineffective sorbent for nonpolar nonionic organic compounds in water even though it has high surface area. The surface properties of natural bentonite can be greatly modified by simple ion-exchange reactions with large organic cations (cationic surfactants) and this organobentonite is highly effective in removing nonionic organic compounds from water. Cationic surfactant derived organobentonites have been investigated extensively for a wide variety of environmental applications. In this study, the preparation of organobentonite using nonionic surfactants has been investigated for the first time. Results indicate that nonionic surfactants intercalates into the interlamellar space of bentonite and may demonstrate higher sorption capacity than cationic surfactant. It is possible to create large interlayer spacing and high organic carbon content organobentonite by use of nonionic surfactants with suitable balance between the hydrocarbon and ethylene oxide chain lengths. In addition, nonionic surfactant derived organobentonites are more chemically stable than cationic surfactant derived organobentonites.

  1. Surfactant recovery from water using foam fractionation

    SciTech Connect

    Tharapiwattananon, N.; Osuwan, S.; Scamehorn, J.F.

    1996-05-01

    The purpose of this study was to investigate the use of foam fractionation to recover surfactant from water. A simple continuous mode foam fractionation was used and three surfactants were studied (two anionic and one cationic). The effects of air flow rate, foam height, liquid height, liquid feed surfactant concentration, and sparger porosity were studied. This technique was shown to be effective in either surfactant recovery or the reduction of surfactant concentration in water to acceptable levels. As an example of the effectiveness of this technique, the cetylpyridinium chloride concentration in water can be reduced by 90% in one stage with a liquid residence time of 375 minutes. The surfactant concentration in the collapsed foam is 21.5 times the feed concentration. This cationic surfactant was easier to remove from water by foam fractionation than the anionic surfactants studied.

  2. Synthesis of carbohydrate-based surfactants

    SciTech Connect

    Pemberton, Jeanne E.; Polt, Robin L.; Maier, Raina M.

    2016-11-22

    The present invention provides carbohydrate-based surfactants and methods for producing the same. Methods for producing carbohydrate-based surfactants include using a glycosylation promoter to link a carbohydrate or its derivative to a hydrophobic compound.

  3. Surfactant for Pediatric Acute Lung Injury

    PubMed Central

    Willson, Douglas F.; Chess, Patricia R.; Notter, Robert H.

    2008-01-01

    Synopsis This article reviews exogenous surfactant therapy and its use in mitigating acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) in infants, children, and adults. Biophysical and animal research documenting surfactant dysfunction in ALI/ARDS is described, and the scientific rationale for treatment with exogenous surfactant is discussed. Major emphasis is on reviewing clinical studies of surfactant therapy in pediatric and adult patients with ALI/ARDS. Particular advantages from surfactant therapy in direct pulmonary forms of these syndromes are described. Also discussed are additional factors affecting the efficacy of exogenous surfactants in ALI/ARDS, including the multifaceted pathology of inflammatory lung injury, the effectiveness of surfactant delivery in injured lungs, and composition-based activity differences among clinical exogenous surfactant preparations. PMID:18501754

  4. Polymer/surfactant transport in micellar flooding

    SciTech Connect

    Chiou, C.S.; Kellerhals, G.E.

    1981-10-01

    For the surfactant formulations used (particular surfactant concentration, surfactant type, cosolvent type, cosolvent concentration, etc.), the results show that surfactant systems containing polymer as a mobility control agent may exhibit adverse polymer transport behavior during flow through porous media. Polymer generally lagged behind the surfactant even though the two species were injected simultaneously in the surfactant slug. This poor polymer transport definitely could have a detrimental effect on the efficiency of a micellar flooding process in the field. Phase studies show that when some surfactant systems containing xanthan gum are mixed with crude oil at various salinities, a polymer-rich, gel-like phase forms. The polymer lag phenomenon in core tests can be related to phase separation due to divalent cations generated in situ as a result of ion exchange with the clays and the surfactant. 18 refs.

  5. Assembling wormlike micelles in tubular nanopores by tuning surfactant-wall interactions.

    PubMed

    Bharti, Bhuvnesh; Xue, Mengjun; Meissner, Jens; Cristiglio, Viviana; Findenegg, Gerhard H

    2012-09-12

    Threadlike molecular assemblies are excluded from narrow pores unless attractive interactions with the confining pore walls compensate for the loss of configurational entropy. Here we show that wormlike surfactant micelles can be assembled in the 8 nm tubular nanopores of SBA-15 silica by adjusting the surfactant-pore-wall interactions. The modulation of the interactions was achieved by coadsorption of a surface modifier that also provides control over the partitioning of wormlike aggregates between the bulk solution and the pore space. We anticipate that the concept of tuning the interactions with the pore wall will be applicable to a wide variety of self-assembling molecules and pores.

  6. Colloidal Aggregate Structure under Shear by USANS

    NASA Astrophysics Data System (ADS)

    Chatterjee, Tirtha; van Dyk, Antony K.; Ginzburg, Valeriy V.; Nakatani, Alan I.

    2015-03-01

    Paints are complex formulations of polymeric binders, inorganic pigments, dispersants, surfactants, colorants, rheology modifiers, and other additives. A commercially successful paint exhibits a desired viscosity profile over a wide shear rate range from 10-5 s-1 for settling to >104 s-1 for rolling, and spray applications. Understanding paint formulation structure is critical as it governs the paint viscosity profile. However, probing paint formulation structure under shear is a challenging task due to the formulation complexity containing structures with different hierarchical length scales and their alterations under the influence of an external flow field. In this work mesoscale structures of paint formulations under shear are investigated using Ultra Small-Angle Neutron Scattering (rheo-USANS). Contrast match conditions were utilized to independently probe the structure of latex binder particle aggregates and the TiO2 pigment particle aggregates. Rheo-USANS data revealed that the aggregates are fractal in nature and their self-similarity dimensions and correlations lengths depend on the chemistry of the binder particles, the type of rheology modifier present and the shear stress imposed upon the formulation. These results can be explained in the framework of diffusion and reaction limited transient aggregates structure evolution under simple shear.

  7. Adsorption of atrazine by natural organic matter and surfactant dispersed carbon nanotubes.

    PubMed

    Shi, Baoyou; Zhuang, Xiaoyan; Yan, Xiaomin; Lu, Jiajuan; Tang, Hongxiao

    2010-01-01

    The aggregation and dispersion behaviors of carbon nanotubes (CNTs) can regulate the environmental spread and fate of CNTs, as well as the organic pollutants adsorbed onto them. In this study, multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) were surface modified with humic acids from different sources and with surfactants of different ionic types. The dispersion stability of surface modified CNTs was observed by UV-Vis spectrophotometry. The effect of humic acid and surfactant dispersion on the adsorption of atrazine by CNTs was investigated by batch equilibrium experiments. Both humic acid and surfactant could effectively disperse MWNTs, but not SWNTs, into stable suspensions under the studied conditions. Surface modified CNTs had a greatly reduced capacity for adsorption of atrazine. The inhibitory effect of peat humic acid was relatively stronger than that of soil humic acid, but the two surfactants had a similar inhibitory effect on atrazine adsorption by the two CNT types. Increases in surfactant concentration resulted in rapid decreases in the adsorption of atrazine by CNTs when the surfactant concentration was less than 0.5 critical micelle concentration.

  8. Temperature-induced vesicle to micelle transition in cationic/cationic mixed surfactant systems.

    PubMed

    Yang, Yanjuan; Liu, Lifei; Huang, Xin; Tan, Xiuniang; Luo, Tian; Li, Wei

    2015-12-07

    Temperature-induced vesicle to micelle transition (VMT), which has rarely been reported in cationic/cationic mixed surfactant systems, was systemically studied in a didodecyldimethylammonium bromide (DDAB)/dodecyltrimethylammonium chloride (DTAC) aqueous solution. We investigated the effect of temperature on DDAB/DTAC aqueous solutions by means of turbidity, conductivity, cryo-TEM, a UV-vis spectrophotometer, and a steady-state fluorescence spectrometer. It was found that increasing temperature could induce the transformation from the vesicle to the micelle in this cationic/cationic mixed surfactant system. The degree of transformation can be easily controlled by the operation temperature. Additionally, by adjusting the proportion of the mixed cationic/cationic systems and employing cationic surfactants with different chain-lengths, we were able to conclude that the hydrophobic tail length of the surfactant affects the aggregation behavior of cationic/cationic mixed surfactant systems as a function of temperature. It is universal to induce the transformation from the vesicle to the micelle by temperature in cationic/cationic mixed surfactant systems. A possible mechanism for the temperature-induced VMT was proposed based on the experimental results.

  9. Interaction of surfactants with block-copolymer systems in the presence of Hofmeister anions

    NASA Astrophysics Data System (ADS)

    Jadoon, Quratulain; Bibi, Iram; Mehmood, Khalid; Sajjad, Saman; Nawaz, Mohsan; Ali, Farman; Bibi, Saira; ur-Rehman, Wajid; Bano, Shakeela; Usman, Mohammad

    2017-03-01

    The interactions of block copolymers poly (ethylene oxide butylene oxide), E58B7 and E58B11 with anionic surfactant sodium dodecyl sulfate and cationic surfactant cetyltrimethylammonium bromide were studied by using different techniques such as surface tension, conductivity, and dynamic light scattering. The effect of salts in the Hofmeister series on polymer-surfactant systems was also investigated. The interactions were found to be dependent on both surfactant and polymer concentrations. The results were utilized to compute different thermodynamic parameters including enthalpy of micellization (ΔH m), entropy of micellization (ΔS m), free energy of adsorption (ΔG ads) and free energy of micellization (ΔG mic). For diblock-copolymer surfactant systems the negative value of (ΔG mic) shows that the process of micelle formation is thermodynamically favorable. The solubilization in surfactant micelles altered the physicochemical properties of the block copolymer. The value of critical aggregation concentration decreases with the addition of Hofmeister anions, and the decrease is more pronounced for sodium fluoride as compared to sodium iodide.

  10. Phase Behavior and Phase Structure of Protein-Surfactant-Water Systems.

    PubMed

    Morén; Khan

    1999-10-15

    Phase behavior of oppositely charged ovalbumin-DOTAC and BSA-DOTAC, and similarly charged ovalbumin-SDS, BSA-SDS, lysozyme-DOTAC, and BLG-SDS systems within the concentration range of 20 wt% of both protein and surfactant are examined in water. Aqueous solutions of ovalbumin yield, in succession, precipitation, gel, and solution with increased addition of the surfactant dodecyltrimethylammonium chloride (DOTAC). The stability range of each region is determined. Both isotropic and anisotropic gels are detected. Solutions of bovine serum albumin (BSA) form only a solution phase with oppositely charged DOTAC. One solution phase is also obtained with all similarly charged protein-surfactant systems except the BLG-SDS-water system, which produces a gel phase in addition to a large solution phase. (2)H NMR longitudinal (R(1)) and transverse (R(2)) relaxation rates are determined in solution and gel by following the behavior of selectively deuterated surfactant at the alpha-methylene group next to the surfactant head group for the oppositely charged systems ovalbumin-DOTAC and BSA-DOTAC. Large R(2)-values proved the existence of large protein-surfactant aggregates in both systems. Copyright 1999 Academic Press.

  11. Biofoams and natural protein surfactants

    PubMed Central

    Cooper, Alan; Kennedy, Malcolm W.

    2010-01-01

    Naturally occurring foam constituent and surfactant proteins with intriguing structures and functions are now being identified from a variety of biological sources. The ranaspumins from tropical frog foam nests comprise a range of proteins with a mixture of surfactant, carbohydrate binding and antimicrobial activities that together provide a stable, biocompatible, protective foam environment for developing eggs and embryos. Ranasmurfin, a blue protein from a different species of frog, displays a novel structure with a unique chromophoric crosslink. Latherin, primarily from horse sweat, but with similarities to salivary, oral and upper respiratory tract proteins, illustrates several potential roles for surfactant proteins in mammalian systems. These proteins, together with the previously discovered hydrophobins of fungi, throw new light on biomolecular processes at air–water and other interfaces. This review provides a perspective on these recent findings, focussing on structure and biophysical properties. PMID:20615601

  12. Probing structure-nanoaggregation relations of polyaromatic surfactants: a molecular dynamics simulation and dynamic light scattering study.

    PubMed

    Teklebrhan, Robel B; Ge, Lingling; Bhattacharjee, Subir; Xu, Zhenghe; Sjöblom, Johan

    2012-05-24

    Four synthetic perylene bisimide-based polyaromatic (PA) surfactants with a structural or functional group difference in their attached hydrophilic/hydrophobic substituent side chains were used to probe structure-nanoaggregation relations in organic media by molecular dynamics simulations and dynamic light scattering. The results from the simulated radial distribution functions and light scattering experiments indicate that variation in the structure of side chains and polarity of functional groups leads to significant variations in molecular association, dynamics of molecular nanoaggregation and structure of nanoaggregates. The aggregates of PA surfactant molecules grow to much larger sizes in heptane than in toluene. The aromatic solvent is shown to hinder molecular association by weakening π-π stacking, demonstrating the control of molecular aggregation by tuning solvent properties. In aliphatic solvent, the aggregates formed from PA surfactants of aliphatic alkyl groups and phenylalanine derivatives as a side chain usually have a higher solvent accessible surface area to accessible volume ratio (SASA:AV) than that of tryptophan derivatives in their side chains. PA surfactants with an aliphatic functional group in both side chains does not form polyaromatic π-π stacking (T-stacking) due to its strong steric hindrance in both solvents. Depending on the nature of the side chains attached, various stacking distributions, aggregation sizes, and SASA:AV ratios were obtained. In PA surfactant nanoaggregates, all of the solvent molecules were found to be excluded from the interstices of the stacked polyaromatic cores, regardless of whether the solvent molecules are aliphatic or aromatic. Although the change in the structure of side chain substituent in polyaromatic surfactants has a negligible impact on their self-diffusivity, it can strongly influence their intermolecular interactions, leading to different aggregate diffusion coefficients.

  13. MINERAL-SURFACTANT INTERACTIONS FOR MINIMUM REAGENTS PRECIPITATION AND ADSORPTION FOR IMPROVED OIL RECOVERY

    SciTech Connect

    P. Somasundaran

    2004-10-30

    Significant surfactant loss by adsorption or precipitation on reservoir minerals can cause chemical flooding processes to be less than satisfactory for enhanced oil recovery. This project is aimed towards an understanding of the role of reservoir minerals and their dissolved species in chemical loss by precipitation or adsorption of surfactants/polymers in enhanced oil recovery. Emphasis will be on the type and nature of different minerals in the oil reservoirs. Macroscopic adsorption, precipitation, wettability and nanoscopic orientation/conformation studies for aggregates of various surfactant/polymer mixtures on reservoir rocks systems is planned for exploring the cause of chemical loss by means of precipitation or adsorption, and the effect of rock mineralogy on the chemical loss. During this reporting period, the minerals proposed in this study: sandstone, limestone, gypsum, kaolinite and pyrite, have been characterized to obtain their particle size distribution and surface area, which will be used in the analysis of adsorption and wettability data. The effect of surfactant mixing ratio on the adsorption of mixture of C{sub 12}-C{sub 4}-C{sub 12} Gemini surfactant (synthesized during last period) and sugar-based nonionic surfactant n-dodecyl-{beta}-D-maltoside (DM) has been studied. It was discovered that even trace amounts of Gemini in the mixture is sufficient to force significant adsorption of DM. DM adsorption on silica increased from relatively negligible levels to very high levels. It is clear form analysis of the results that desired adsorption of either surfactant component in the mixtures can be obtained by controlling the mixing ratio, the total mixture concentration, pH etc. Along with these adsorption studies, changes in mineral wettability due to the adsorption of Gemini/DM mixtures were determined under relevant conditions to identify the nano-structure of the adsorbed layers. With increasing total surfactant adsorption, the silica mineral

  14. Fiber coating with surfactant solutions

    NASA Astrophysics Data System (ADS)

    Shen, Amy Q.; Gleason, Blake; McKinley, Gareth H.; Stone, Howard A.

    2002-11-01

    When a fiber is withdrawn at low speeds from a pure fluid, the variation in the thickness of the entrained film with imposed fiber velocity is well-predicted by the Landau-Levich-Derjaguin (LLD) equation. However, surfactant additives are known to alter this response. We study the film thickening properties of the protein BSA (bovine serum albumin), the nonionic surfactant Triton X-100, and the anionic surfactant SDS (sodium dodecyl sulfate). For each of these additives, the film thickening factor alpha (the ratio of the measured thickness to the LLD prediction) for a fixed fiber radius varies as a function of the ratio of the surfactant concentration c to the critical micelle concentration (CMC). In the case of BSA, which does not form micelles, the reference value is the concentration at which multilayers form. As a result of Marangoni effects, alpha reaches a maximum as c approaches the CMC from below. However, when the surfactant concentration c exceeds the CMC, the behavior of alpha varies as a consequence of the dynamic surface properties, owing for example to different sorption kinetics of these additives, or possibly surface or bulk rheological effects. For SDS, alpha begins to decrease when c exceeds the CMC and causes the surface to become partially or completely remobilized, which is consistent with the experimental and theoretical results published for studies of slug flows of bubbles and surfactant solutions in a capillary tube and the rise of bubbles in surfactant solutions. However, when the SDS or Triton X-100 surfactant concentration is well above the CMC, we observe that the film thickening parameter alpha increases once again. In the case of SDS we observe a second maximum in the film thickening factor. For all the experiments, transport of monomers to the interface is limited by diffusion and the second maximum in the film thickening factor may be explained as a result of a nonmonotonic change in the stability characteristics of suspended SDS

  15. Shadows on a Giant

    NASA Image and Video Library

    2012-07-02

    Saturn rings cast wide shadows on the planet, and the shadow of a moon also graces the gas giant in this scene from NASA Cassini spacecraft. The moon Enceladus is not shown in this view, but it does cast a small, elongated shadow.

  16. Giant scrotal elephantiasis.

    PubMed

    Kuepper, Daniel

    2005-02-01

    How much can a man carry? Penoscrotal elephantiasis is a debilitating syndrome. This is a case report of a patient with giant genital elephantiasis secondary to long-standing lymphogranuloma venereum infection in Ethiopia. Complete surgical resection of the pathologic tissue and penile reconstruction was undertaken with good cosmetic and functional results.

  17. [Giant retroperitoneal liposarcoma].

    PubMed

    Mezzour, Mohamed Hicham; El Messaoudi, Yasser Arafat; Fekak, Hamid; Rabii, Redouane; Marnissi, Farida; Karkouri, Mehdi; Salam, Siham; Iraki, Moulay Ahmed; Joual, Abdenbi; Meziane, Fathi

    2006-02-01

    The authors report a case of giant retroperitoneal liposarcoma. The diagnosis was suspected after scanography and magnetic resonance imaging and confirmed by the histological analysis of the extracted piece after surgical treatment. Postoperative evolution was favourable after one year without recurrence or distant metastasis. The authors discuss the pathologic and therapeutic aspects and the prognosis of retroperitoneal liposarcoma.

  18. Electroluminescence of Giant Stretchability.

    PubMed

    Yang, Can Hui; Chen, Baohong; Zhou, Jinxiong; Chen, Yong Mei; Suo, Zhigang

    2016-06-01

    A new type of electroluminescent device achieves giant stretchability by integrating electronic and ionic components. The device uses phosphor powders as electroluminescent materials, and hydrogels as stretchable and transparent ionic conductors. Subject to cyclic voltage, the phosphor powders luminesce, but the ionic conductors do not electrolyze. The device produces constant luminance when stretched up to an area strain of 1500%.

  19. SURFACTANT ENHANCED AQUIFER REMEDIATION WITH SURFACTANT REGENERATION/REUSE

    EPA Science Inventory

    A demonstration of surfactant-enhanced aquifer remediation was conducted during the spring of 1999 at Marine Corps Base, Camp LeJeune, NC. A PCE-DNAPL zone was identified and delineated by extensive soil sampling in 1997, and was further characteized by a partitioning interwell t...

  20. A light-responsive organofluid based on reverse worm-like micelles formed from an equi-charged, mixed, anionic gemini surfactant with an azobenzene spacer and a cationic conventional surfactant.

    PubMed

    Yang, Duoping; Zhao, Jianxi

    2016-05-07

    An equally-charged mixture of an anionic gemini surfactant, O,O'-bis(sodium 2-tetradecylcarboxylate)-p-azodiphendiol (G14-azo), and a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was dissolved in cyclohexane to form reverse worm-like micelles. Samples with different surfactant concentrations and amounts of added water were studied using rheological measurements. The amount of water, represented as the molar ratio of water to total surfactants W0, was c. 13 (at its minimum) in these equally charged systems of G14-azo (200 mmol L(-1))/CTAB. The low shear viscosity ηL of this system reached 4370 Pa s at W0 = 13 and the dynamic rheological result showed typical surfactant gel behaviour. Under UV-light irradiation, the transparent sample (G14-azo (300 mmol L(-1))/CTAB (600 mmol L(-1))) at W0 = 40 became turbid, during which ηL was rapidly reduced from the original 285 Pa s to 0.3 Pa s, indicating a transition of aggregate morphology from reverse worms into simple reverse micelles. Then the sample was returned to its original homogeneous state with c. 290 Pa s viscosity under visible light irradiation. However, this transition cannot be well achieved at low W0 due to the interior cores being too small. This limit has been attributed to both the Gemini type of surfactant molecule and to the inverted structure of aggregates.

  1. Toward surfactant-free and water-free microemulsions.

    PubMed

    Fischer, Veronika; Marcus, Julien; Touraud, Didier; Diat, Olivier; Kunz, Werner

    2015-09-01

    It was recently demonstrated that a nano-clustering was present in the monophasic "pre-Ouzo" region of ternary liquid mixtures without surfactants. The goal of this work is to check if this nano-clustering is also present in the surfactant-free and water-free "green" microemulsions glycerol/ethanol/1-octanol and deep eutectic solvent/tetrahydrofurfuryl alcohol/diethyl adipate. The deep eutectic solvents used instead of water were ethylene glycol-choline chloride (molar ratio 4-1) and urea-choline chloride (molar ratio 2-1). To our knowledge this is the first time that deep eutectic solvents were used to formulate microemulsions. The surfactant-free and water-free microemulsions were studied using phase diagrams, dynamic light scattering, and small-angle X-ray scattering. The presence of aggregate fluctuations was demonstrated and they were found to be independent of molecular critical fluctuations, except when approaching the critical point where the critical phenomenon is superimposed to the signal. These structures have similarities to classical microemulsions but, in contrast to them, without having a sharp interface between the non-miscible phases, much as it was the case for systems previously investigated like water/ethanol/oil, where the oil was 1-octanol, fragrance molecules, or mosquito repellents. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Surfactant-induced assembly of enzymatically-stable peptide hydrogels

    SciTech Connect

    Jones, Brad H.; Martinez, Alina M.; Wheeler, Jill S.; Spoerke, Erik D.

    2015-04-07

    The secondary structure of peptides in the presence of interacting additives is an important topic of study, having implications in the application of peptide science to a broad range of modern technologies. Surfactants constitute a class of biologically relevant compounds that are known to influence both peptide conformation and aggregation or assembly. In addition, we have characterized the secondary structure of a linear nonapeptide composed of a hydrophobic alanine/phenylalanine core flanked by hydrophilic acid/amine units. We show that the anionic surfactant sodium dodecyl sulfate (SDS) induces the formation of β-sheets and macroscopic gelation in this otherwise unstructured peptide. Through comparison to related additives, we propose that SDS-induced secondary structure formation is the result of amphiphilicity created by electrostatic binding of SDS to the peptide. In addition, we demonstrate a novel utility of surfactants in manipulating and stabilizing peptide nanostructures. SDS is used to simultaneously induce secondary structure in a peptide and to inhibit the activity of a model enzyme, resulting in a peptide hydrogel that is impervious to enzymatic degradation. These results complement our understanding of the behavior of peptides in the presence of interacting secondary molecules and provide new potential pathways for programmable organization of peptides by the addition of such components.

  3. Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant

    PubMed Central

    Song, Meirong; Ju, Jie; Luo, Siqi; Han, Yuchun; Dong, Zhichao; Wang, Yilin; Gu, Zhen; Zhang, Lingjuan; Hao, Ruiran; Jiang, Lei

    2017-01-01

    Deposition of liquid droplets on solid surfaces is of great importance to many fundamental scientific principles and technological applications, such as spraying, coating, and printing. For example, during the process of pesticide spraying, more than 50% of agrochemicals are lost because of the undesired bouncing and splashing behaviors on hydrophobic or superhydrophobic leaves. We show that this kind of splashing on superhydrophobic surfaces can be greatly inhibited by adding a small amount of a vesicular surfactant, Aerosol OT. Rather than reducing splashing by increasing the viscosity via polymer additives, the vesicular surfactant confines the motion of liquid with the help of wettability transition and thus inhibits the splash. Significantly, the vesicular surfactant exhibits a distinguished ability to alter the surface wettability during the first inertial spreading stage of ~2 ms because of its dense aggregates at the air/water interface. A comprehensive model proposed by this idea could help in understanding the complex interfacial interactions at the solid/liquid/air interface. PMID:28275735

  4. Temperature Triggered Structural Transitions in Surfactant organized Self Assemblies

    NASA Astrophysics Data System (ADS)

    Rose, J. Linet; Balamurugan, S.; Sajeevan, Ajin C.; Sreejith, Lisa

    2011-10-01

    Preparation & characterization of tunable fluids is an emerging area with potential application in many fields. Surfactants self assemble in aqueous solution to give a rich variety of phase structures, the size and shape of which can be tuned by additives like salts, alcohols, amines, aromatics etc or external stimuli such as light, temperature etc. The addition of long chain aliphatic alcohol has significant influence on the surfactant aggregation, as it promotes morphological growth of micelles. The cationic surfactant, Cetyl Trimethyl Ammonium Bromide (CTAB) with nonanol in presence of potassium bromide (KBr) shows thermo tunable viscosity behaviour and optical switching behaviour. The solution is visually observed to transform from a turbid and less viscous phase at low temperature to clear and considerably viscous phase at high temperature. Temperature induced changes in turbidity and viscosity are consistent with the transition from vesicle to worm like micelle. It is also worth emphasizing that the transition is thermo reversible, so that vesicles that are disrupted into micelles upon heating can be reformed upon cooling. The thermo tunable transition from turbid to transparent state and the concomitant changes in viscosity are promising for the use in smart windows, monitoring of tumor growth or in other stimuli based application.

  5. Surfactant-induced assembly of enzymatically-stable peptide hydrogels

    DOE PAGES

    Jones, Brad H.; Martinez, Alina M.; Wheeler, Jill S.; ...

    2015-04-07

    The secondary structure of peptides in the presence of interacting additives is an important topic of study, having implications in the application of peptide science to a broad range of modern technologies. Surfactants constitute a class of biologically relevant compounds that are known to influence both peptide conformation and aggregation or assembly. In addition, we have characterized the secondary structure of a linear nonapeptide composed of a hydrophobic alanine/phenylalanine core flanked by hydrophilic acid/amine units. We show that the anionic surfactant sodium dodecyl sulfate (SDS) induces the formation of β-sheets and macroscopic gelation in this otherwise unstructured peptide. Through comparisonmore » to related additives, we propose that SDS-induced secondary structure formation is the result of amphiphilicity created by electrostatic binding of SDS to the peptide. In addition, we demonstrate a novel utility of surfactants in manipulating and stabilizing peptide nanostructures. SDS is used to simultaneously induce secondary structure in a peptide and to inhibit the activity of a model enzyme, resulting in a peptide hydrogel that is impervious to enzymatic degradation. These results complement our understanding of the behavior of peptides in the presence of interacting secondary molecules and provide new potential pathways for programmable organization of peptides by the addition of such components.« less

  6. On mean type aggregation.

    PubMed

    Yager, R R

    1996-01-01

    We introduce and define the concept of mean aggregation of a collection of n numbers. We point out that the lack of associativity of this operation compounds the problem of the extending mean of n numbers to n+1 numbers. The closely related concepts of self identity and the centering property are introduced as one imperative for extending mean aggregation operators. The problem of weighted mean aggregation is studied. A new concept of prioritized mean aggregation is then introduced. We next show that the technique of selecting an element based upon the performance of a random experiment can be considered as a mean aggregation operation.

  7. Formation and morphology of reverse micelles formed by nonionic surfactants in "dry" organic solvents.

    PubMed

    Pérez, Sofía V; Olea, Andres F; Gárate, M Pilar

    2014-01-01

    The formation of reverse micelles by nonionic alcohol ethoxylates surfactants in two "dry" non polar solvents, heptane and dibutoxymethane (DBM), has been studied. These surfactants are formed by a linear hydrocarbon chain consisting of i carbons, and a poly(ethylene oxide) chain with j ethoxylate units (EO) ending with a hydroxyl group, CiEOj. The study is focused on the determination of the critical micelle concentration CMC and the size and morphology of the formed aggregates. The CMC was obtained from the decreasing of interfacial tension with increasing surfactant concentration and by using pyrene sulfonic acid sodium salt as fluorescence probe. The results show that the CMC in heptane is one order of magnitude higher than in DBM and two orders of magnitude higher than those determined in aqueous solution. The self-diffusion coefficients D of C8EO5, C8EO4 and C10EO6 in heptane, were obtained by diffusion ordered spectroscopy (DOSY (1)H-NMR). The experimental values of D were then fitted to four different configurations to determine the most probable morphology of the formed aggregates. In all cases the presence of large and compact aggregates, with aggregation numbers going from a few dozens of monomers to a hundred of them, was shown.

  8. Effect of surfactant charge on polymer-micelle interaction: N-dodecyldimethylamine oxide

    SciTech Connect

    Brackman, J.C.; Engberts, J.B.F.N. )

    1992-02-01

    The influence of the nonionic water-soluble polymers poly(vinyl methyl ether) (PVME), poly(propylene oxide) (PPO), and poly(ethylene oxide) (PEO) on the aggregation behavior of n-dodecyldimethylamine oxide (DDAO), at various stages of protonation, has been studied. Critical micelle concentration (cmc) values were determined by the pH method and revealed an increase in stabilization of the micelles by association with PVME and PPO, upon increasing the average charge of the surfactant. The micelles formed from nonionic DDAO are not stabilized by association with PVME or PPO, but association was apparent from the reduction in aggregation number. This reduction in aggregation number is even more pronounced at higher surfactant charge. The results are interpreted in terms of a reduction in electrostatic inter-head-group interaction upon formation of the smaller polymer-bound micelles in the case of the charged surfactant molecules. PEO does not exert any influence on either the cmc or the aggregation number of DDAO micelles at any degree of protonation indicating the absence of polymer-micelle interaction. The effect of neutral and protonated DDAO on the clouding behavior of PVME and PPO has also been studied. 36 refs., 4 figs., 4 tabs.

  9. Model study of enhanced oil recovery by flooding with aqueous surfactant solution and comparison with theory.

    PubMed

    Fletcher, Paul D I; Savory, Luke D; Woods, Freya; Clarke, Andrew; Howe, Andrew M

    2015-03-17

    With the aim of elucidating the details of enhanced oil recovery by surfactant solution flooding, we have determined the detailed behavior of model systems consisting of a packed column of calcium carbonate particles as the porous rock, n-decane as the trapped oil, and aqueous solutions of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The AOT concentration was varied from zero to above the critical aggregation concentration (cac). The salt content of the aqueous solutions was varied to give systems of widely different, post-cac oil-water interfacial tensions. The systems were characterized in detail by measuring the permeability behavior of the packed columns, the adsorption isotherms of AOT from the water to the oil-water interface and to the water-calcium carbonate interface, and oil-water-calcium carbonate contact angles. Measurements of the percent oil recovery by pumping surfactant solutions into calcium carbonate-packed columns initially filled with oil were analyzed in terms of the characterization results. We show that the measured contact angles as a function of AOT concentration are in reasonable agreement with those calculated from values of the surface energy of the calcium carbonate-air surface plus the measured adsorption isotherms. Surfactant adsorption onto the calcium carbonate-water interface causes depletion of its aqueous-phase concentration, and we derive equations which enable the concentration of nonadsorbed surfactant within the packed column to be estimated from measured parameters. The percent oil recovery as a function of the surfactant concentration is determined solely by the oil-water-calcium carbonate contact angle for nonadsorbed surfactant concentrations less than the cac. For surfactant concentrations greater than the cac, additional oil removal occurs by a combination of solubilization and emulsification plus oil mobilization due to the low oil-water interfacial tension and a pumping pressure increase.

  10. Stabilization of human papillomavirus virus-like particles by non-ionic surfactants.

    PubMed

    Shi, Li; Sanyal, Gautam; Ni, Alex; Luo, Zheng; Doshna, Sarah; Wang, Bei; Graham, Tammy L; Wang, Ning; Volkin, David B

    2005-07-01

    Human papillomavirus (HPV) virus-like-particles (VLPs) produced by recombinant expression systems are promising vaccine candidates for prevention of cervical cancers as well as genital warts. At high protein concentrations, HPV VLPs, comprised of the viral capsid protein L1 and expressed and purified from yeast, are protected against detectable aggregation during preparation and storage by high concentrations of NaCl. At low protein concentrations, however, high salt concentration alone does not fully protect HPV VLPs from aggregation. Moreover, the analytical analysis of HPV VLPs proved to be a challenge due to surface adsorption of HPV VLPs to storage containers and cuvettes. The introduction of non-ionic surfactants into HPV VLP aqueous solutions provides significantly enhanced stabilization of HPV VLPs against aggregation upon exposure to low salt and protein concentration, as well as protection against surface adsorption and aggregation due to heat stress and physical agitation. The mechanism of non-ionic surfactant stabilization of HPV VLPs was extensively studied using polysorbate 80 (PS80) as a representative non-ionic surfactant. The results suggest that PS80 stabilizes HPV VLPs mainly by competing with the VLPs for various container surfaces and air/water interfaces. No appreciable binding of PS80 to intact HPV VLPs was observed although PS80 does bind to the denatured HPV L1 protein. Even in the presence of stabilizing level of PS80, however, an ionic strength dependence of HPV VLP stabilization against aggregation is observed indicating optimization of both salt and non-ionic surfactant levels is required for effective stabilization of HPV VLPs in solution. (c) 2005 Wiley-Liss, Inc.

  11. Cationic surfactant mediated fibrillogenesis in bovine liver catalase: a biophysical approach.

    PubMed

    Khan, Mohsin Vahid; Zaman, Masihuz; Chandel, Tajalli Ilm; Siddiqui, Mohammad Khursheed; Ajmal, Mohd Rehan; Abdelhameed, Ali Saber; Khan, Rizwan Hasan

    2017-08-20

    Protein aggregation into oligomers and mature fibrils are associated with more than 20 diseases in humans. The interactions between cationic surfactants dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB) with varying alkyl chain lengths and bovine liver catalase (BLC) were examined by various biophysical approaches. The delicate coordination of electrostatic and hydrophobic interactions with protein, play imperative role in aggregation. In this article, we have reconnoitered the relation between charge, hydrophobicity and cationic surfactants DTAB and TTAB on BLC at pH 7.4 and 9.4 which are two and four units above pI, respectively. We have used techniques like turbidity, Rayleigh light scattering, far-UV CD, ThT, ANS, Congo red binding assay, DLS, and transmission electron microscopy. The low concentration ranges of DTAB (0-600 μM) and TTAB (0-250 μM) were observed to increase aggregation at pH 9.4. Nevertheless, at pH 7.4 only TTAB was capable of inducing aggregate. DTAB did not produce any significant change in secondary structure at pH 7.4 suggestive of the role of respective charges on surfactants and protein according to the pI and alkyl chain length. The morphology of aggregates was further determined by TEM, which proved the existence of a fibrillar structure. The surfactants interaction with BLC was primarily electrostatic as examined by ITC. Our work demystifies the critical role of charge as well as hydrophobicity in amyloid formation.

  12. Physical properties of botanical surfactants.

    PubMed

    Müller, Lillian Espíndola; Schiedeck, Gustavo

    2017-08-24

    Some vegetal species have saponins in their composition with great potential to be used as natural surfactants in organic crops. This work aims to evaluate some surfactants physical properties of Quillaja brasiliensis and Agave angustifolia, based on different methods of preparation and concentration. The vegetal samples were prepared by drying and grinding, frozen and after chopped or used fresh and chopped. The neutral bar soap was used as a positive control. The drying and grinding of samples were the preparation method that resulted in higher foam column height in both species but Q. brasiliensis was superior to A. angustifolia in all comparisons and foam index was 2756 and 1017 respectively. Critical micelle concentration of Q. brasiliensis was 0.39% with the superficial tension of 54.40mNm(-1) while neutral bar soap was 0.15% with 34.96mNm(-1). Aspects such as genetic characteristics of the species, environmental conditions, and analytical methods make it difficult to compare the results with other studies, but Q. brasiliensis powder has potential to be explored as a natural surfactant in organic farming. Not only the surfactants physical properties of botanical saponins should be taken into account but also its effect on insects and diseases control when decided using them. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Anti-aggregation property of thymoquinone induced by copper-nanoparticles: A biophysical approach.

    PubMed

    Ishtikhar, Mohd; Rahisuddin; Khan, Mohsin Vahid; Khan, Rizwan Hasan

    2016-12-01

    Quaternary amine of diethylaminoethyl rosin ester (QRMAE), chemically synthesized by rosin modified biocompatible cationic surfactant, has various biological applications in the field of pharmacy as well as used as food product additive. Here, we report biophysical insights in to the interaction mechanism of thymoquinone (TQ), copper nanoparticles (Cu-NPs) and QRMAE with bovine serum albumin (BSA) individually and also in complexes forms to determine their competitive binding affinity. We have also studied the aggregation-inhibition effects of Cu-NPs and TQ individually, as well as in complexes form in the presence of QRMAE surfactant which is responsible for induction of amorphous aggregates in BSA within hours of incubation at 65°C and physiological pH. The formation of aggregates was established by using various spectroscopic methods and dye binding assay. The circular dichroism (CD) spectroscopy showed that QRMAE significantly altered the secondary structure of BSA. However, the presence of TQ and Cu-NPs restricted the aggregation process which was observed to be more efficient when TQ and Cu-NPs were present together. This study provides very significant competitive binding results of QRMAE, Cu-NPs, TQ and protein aggregation behavior at higher temperature which was induced by rosin surfactant QRMAE, and protein aggregation process was inhibited by Cu-NPs, TQ individually and together. Therefore, our finding suggested that rosin surfactant QRMAE has high propensity to induce amorphous aggregation in BSA which was favored at elevated temperature and higher concentration of the protein. When BSA-QRMAE sample was incubated in the presence Cu-NPs under similar condition, the aggregation propensity reduced, and drastically inhibited by TQ and Cu-NPs together. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Novel fluorescent probe as aggregation predictor and micro-polarity reporter for micelles and mixed micelles

    NASA Astrophysics Data System (ADS)

    Shannigrahi, Mrinmoy; Bagchi, Sanjib

    2005-07-01

    Aggregational behaviour of micelles sodium dodecyl sulphate (SDS and Triton X-100, TX-100 both in pure and mixed form) and micelle like aggregates such as polymer-surfactant system [polymer poly(vinyl pyrrolidone), PVP]-SDS have been studied by using fluorescence characteristics of a newly synthesized probe. The critical micelle concentration (CMC) values determined at various surfactant compositions are lower than the ideal values indicating a synergistic effect. The value of the interaction parameter for the surfactant mixture has been determined which agrees well with the value calculated according to molecular thermodynamic theory. The total aggregation number of surfactant in mixed micelle shows a drastic variation in the SDS mole fraction range 0 ≤ α1 ≤ 0.3 and beyond the range it remains practically constant. Molar-based partition coefficients for the dye between the micellar and aqueous phase have been determined and a non-linear variation is obtained for the mixed micellar system. Variations of micro-polarity in the mixed micellar region have been investigated as a function of surfactant composition and results have been explained in terms of a suitable realistic model.

  15. Fluorescence of acridinic dyes in anionic surfactant solution

    NASA Astrophysics Data System (ADS)

    Pereira, Robson Valentim; Gehlen, Marcelo Henrique

    2005-10-01

    The interaction of the cationic dyes acridine, 9-aminoacridine (9AA), and proflavine, with sodium dodecyl sulfate (SDS) was studied by electronic absorption, steady-state and time-resolved fluorescence spectroscopies. The dyes interact with SDS in the pre-micellar region leading in two cases to dimerization in dye-surfactant aggregates, but with distinct molecular arrangements. For proflavine, the observed red shift of the electronic absorption band indicates the presence of J-aggregate, which are nonfluorescent. In the case of 9AA, the aggregates were characterized as nonspecific (neither J- nor H-type is spectroscopically observed). The time-resolved emission spectra gives evidences of the presence of weakly bound dimers by the recovery of three defined decay times by global analysis: dye monomer ( τ1 = 16.4 ns), dimer ( τ2 = 7.1 ns), and a faster component ( τ3 = 2.1 ns) ascribed to intracluster energy migration between monomer and dimer. Acridine has a weak interaction with SDS forming only an ion pair without further self-aggregation of the dye.

  16. Fluorescence of acridinic dyes in anionic surfactant solution.

    PubMed

    Pereira, Robson Valentim; Gehlen, Marcelo Henrique

    2005-10-01

    The interaction of the cationic dyes acridine, 9-aminoacridine (9AA), and proflavine, with sodium dodecyl sulfate (SDS) was studied by electronic absorption, steady-state and time-resolved fluorescence spectroscopies. The dyes interact with SDS in the pre-micellar region leading in two cases to dimerization in dye-surfactant aggregates, but with distinct molecular arrangements. For proflavine, the observed red shift of the electronic absorption band indicates the presence of J-aggregate, which are nonfluorescent. In the case of 9AA, the aggregates were characterized as nonspecific (neither J- nor H-type is spectroscopically observed). The time-resolved emission spectra gives evidences of the presence of weakly bound dimers by the recovery of three defined decay times by global analysis: dye monomer (tau1 = 16.4 ns), dimer (tau2 = 7.1 ns), and a faster component (tau3 = 2.1 ns) ascribed to intracluster energy migration between monomer and dimer. Acridine has a weak interaction with SDS forming only an ion pair without further self-aggregation of the dye.

  17. SP-B and SP-C Containing New Synthetic Surfactant for Treatment of Extremely Immature Lamb Lung

    PubMed Central

    Sato, Atsuyasu; Ikegami, Machiko

    2012-01-01

    Although superiority of synthetic surfactant over animal-driven surfactant has been known, there is no synthetic surfactant commercially available at present. Many trials have been made to develop synthetic surfactant comparable in function to animal-driven surfactant. The efficacy of treatment with a new synthetic surfactant (CHF5633) containing dipalmitoylphosphatidylcholine, phosphatidylglycerol, SP-B analog, and SP-C analog was evaluated using immature newborn lamb model and compared with animal lung tissue-based surfactant Survanta. Lambs were treated with a clinical dose of 200 mg/kg CHF5633, 100 mg/kg Survanta, or air after 15 min initial ventilation. All the lambs treated with air died of respiratory distress within 90 min of age. During a 5 h study period, Pco2 was maintained at 55 mmHg with 24 cmH2O peak inspiratory pressure for both groups. The preterm newborn lamb lung functions were dramatically improved by CHF5633 treatment. Slight, but significant superiority of CHF5633 over Survanta was demonstrated in tidal volume at 20 min and dynamic lung compliance at 20 and 300 min. The ultrastructure of CHF5633 was large with uniquely aggregated lipid particles. Increased uptake of CHF5633 by alveolar monocytes for catabolism was demonstrated by microphotograph, which might be associated with the higher treatment dose of CHF5633. The higher catabolism of CHF5633 was also suggested by the similar amount of surfactant lipid in bronchoalveolar lavage fluid (BALF) between CHF5633 and Survanta groups, despite the 2-fold higher treatment dose of CHF5633. Under the present ventilation protocol, lung inflammation was minimal for both groups, evaluated by inflammatory cell numbers in BALF and expression of IL-1β, IL-6, IL-8, and TNFα mRNA in the lung tissue. In conclusion, the new synthetic surfactant CHF5633 was effective in treating extremely immature newborn lambs with surfactant deficiency during the 5 h study period. PMID:22808033

  18. BEHAVIOR OF SURFACTANT MIXTURES AT SOLID/LIQUID AND OIL/LIQUID INTERFACES IN CHEMICAL FLOODING SYSTEMS

    SciTech Connect

    Prof. P. Somasundaran

    2003-03-31

    The aim of the project is to develop a knowledge base to help with the design of enhanced process for mobilizing and extracting untrapped oil. We emphasize on evaluating novel surfactant mixtures and on obtaining optimum combinations of the surfactants in chemical flooding EOR process. An understanding of the micellar shape and size is crucial since these physical properties directly determine the crude oil removal efficiency. Analytical ultracentrifugation experiments were used to test the multi-micelle model proposed earlier and formulate the relationships between mixed micelle formation and the surfactant structure. Information on partial specific volume of surfactants and their mixtures is required to treat analytical ultracentrifuge data. In the last report, it was noted that the partial specific volumes of the sugar-based surfactants obtained experimentally did not agree with those from theoretical calculations. A scrutiny of partial specific volumes of the four sugar-based surfactants revealed that conformational changes upon micelle formation are responsible for the large deviation. From sedimentation equilibrium experiments, two types of micelles were identified for the nonionic polyethylene surfactant and its mixtures with the sugar-based surfactant, dodecyl maltoside. The average aggregation numbers of n-dodecyl-{beta}-D-maltoside and nonyl phenol ethoxylated decyl ether agreed with those reported in literature using other techniques. Our study displayed, for the first time, that small micelles might coexist with large micelles at high concentrations due to unique structures of the surfactant although classical thermodynamic theory supports only one type of micelle. Initial dynamic light scattering results support the results for the same mixed surfactant system from analytical ultracentrifuge equilibrium technique. The implication of this finding lies in the fact that efficiency of oil recovery will be improved due to the large micellar size, its

  19. An anionic surfactant for EOR applications

    NASA Astrophysics Data System (ADS)

    Sagir, Muhammad; Tan, Isa M.; Mushtaq, Muhammad

    2014-10-01

    This work is to investigate the new anionic surfactants for the Enhanced Oil Recovery (EOR) application. Sulfonated anionic surfactant was produced by attaching SO3 to an ethoxylated alcohol to increase the performance of the surfactant. Methallyl chloride and ethoxylated alcohol was reacted followed by the reaction with sodium bisulfite to produce anionic sulfonated surfactant in 80.3 % yield. The sulfonation reaction parameters such as reactants mole ratio, reaction temperature and catalyst amount were optimized. The generation and stability of foam from the synthesized surfactant is also tested and results are reported. The synthesized novel surfactant was further investigated for the effect on the CO2 mobility in porous media and the findings are presented here. This in house developed surfactant has a great potential for CO2- EOR applications.

  20. Effects of Temperature on the Emulsification in Surfactant-Water-Oil Systems

    NASA Astrophysics Data System (ADS)

    Yuan, Yin-Quan; Zou, Xian-Wu; Xiong, Ping-Fan

    The effect of temperature on the emulsification has been investigated by discontinuous molecular dynamic simulation. When a large oil drop is put in water, on one hand the mixing entropy makes it divide into small oil drops; on the other hand the interactions among particles drives the small oil drops fowards aggregation. The evolution of the mean size of oil drops obeys the exponential delay law. There exist an active temperature, at which, the addition of surfactants has obvious effect on the emulsification. The surfactants with low HLB value (e.g. H1T3) make the dispersity of emulsion decrease, and the surfactants with high HLB value (e.g. H2T2 and H3T1) make a contribution to increase the dispersity of emulsion.

  1. Structural diversity, physicochemical properties and application of imidazolium surfactants: Recent advances.

    PubMed

    Bhadani, Avinash; Misono, Takeshi; Singh, Sukhprit; Sakai, Kenichi; Sakai, Hideki; Abe, Masahiko

    2016-05-01

    The current review covers recent advances on development and investigation of cationic surfactants containing imidazolium headgroup, which are being extensively investigated for their self-aggregation properties and are currently being utilized in various conventional and non-conventional application areas. These surfactants are being used as: soft template for synthesis of mesoporous/microporous materials, drug and gene delivery agent, stabilizing agent for nanoparticles, dispersants for single/multi walled carbon nanotubes, antimicrobial and antifungal agent, viscosity modifiers, preparing nanocomposite materials, stabilizing microemulsions, corrosion inhibitors and catalyst for organic reactions. Recently several structural derivatives of these surfactants have been developed having many interesting physicochemical properties and they have demonstrated enormous potential in the area of nanotechnology, material science and biomedical science.

  2. [Influence of Different Type of Surfactant on Bacteriolytic Activity of Lysozyme].

    PubMed

    Ivanov, R A; Soboleva, O A; Smirnov, S A; Levashov, P A

    2015-01-01

    The influence ofvarious surfactants (anionic sodium dodecyl sulfate, SDS, cationic dodecyltrimethylarnmonium bromide, DTAB, and zwitterionic cocoamidopropylbetaine, CAPB) on the activity of the chicken egg lysozyme is investigated. Lysis of Gram-positive bacteria by the enzyme was carried out at pH 7.2 and ionic strength of 0.15 M. It was found that at low SDS and DTAB concentrations (less than 1 x 10(-5) M) the bacteriolytic activity increases by 30-140%. At higher concentrations (1 x 10(-5) - 1 x 10(4) M) the activity returns to the level observed in the absence of the surfactants. The elevated activity correlated with the formation of hydrophobic lysozyme-surfactant complexes. Introduction of CAPB at concentrations above 1 x 10(-5) M sig, nificantly diminished the bacteriolytic activity due to CAPB induced aggregation of lysozyme.

  3. Molecular dynamics simulation of gaseous-liquid phase transitions of soluble and insoluble surfactants at a fluid interface

    NASA Astrophysics Data System (ADS)

    Tomassone, M. S.; Couzis, A.; Maldarelli, C. M.; Banavar, J. R.; Koplik, J.

    2001-11-01

    Molecular dynamics simulations are used to study the formation of gaseous and liquid expanded phases of surfactants on a liquid/vapor interface. Both insoluble and soluble surfactants are considered, modeled as freely jointed chains in a monatomic solvent with appropriate Lennard-Jones interactions. For both insoluble and soluble cases our results indicate that the surface tension as a function of coverage shows a plateau close to the clean interface value until a critical surface concentration, beyond which the surface tension lowers steeply. For the soluble case, we also detail a complete Gibbs construction for the surface excess and report an adsorption isotherm. Snapshots of the positions of the molecules, together with analysis of correlation functions, show that these model surfactants assemble from solution and exhibit coexistence in the plateau of isolated surfactants and liquid aggregates. We have identified this coexistence as a gas-liquid phase transition, in agreement with recent experimental evidence in the soluble case.

  4. Inactivation of surfactant in rat lungs.

    PubMed

    Bruni, R; Fan, B R; David-Cu, R; Taeusch, H W; Walther, F J

    1996-02-01

    Although surfactant replacement therapy has dramatically improved the outcome of premature infants with respiratory distress syndrome, approximately 30% of treated infants show a transient or no response. Nonresponse to surfactant replacement therapy may be due to extreme lung immaturity and possibly surfactant inactivation. Surfactant inactivation involves aspecific biophysical events, such as interference with the formation or activity of an alveolar monolayer, and specific interactions with serum proteins, including antibodies, leaking into the alveolar space. As formulations containing surfactant proteins appear to better tolerate serum inactivation, we used an excised rat lung model to compare the susceptibility to serum inactivation of a mixture of synthetic phospholipids selected from surfactant lipid constituents, Exosurf (a protein-free synthetic surfactant), Survanta [containing surfactant proteins B and C (SP-B and -C)], and a porcine surfactant (containing SP-A, -B, and -C). For each of these preparations, we used pressure/volume determinations as an in situ measure of surfactant activity and retested the same preparations after mixing with human serum, a nonspecific surfactant inactivator. Human serum inactivated porcine surfactant to a lesser extent than Survanta, Exosurf, or synthetic phospholipids. Temperature exerted a significant effect on deflation stability, as shown by a greater lung compliance in untreated, normal lungs and a larger improvement in compliance after treating lavaged lungs with synthetic phospholipids at 37 degrees C than at 22 degrees C. We conclude that surfactant containing SP-A, -B, and -C is only moderately susceptible to inactivation with whole serum and may therefore exert a greater clinical response than protein-free surfactants or those containing only SP-B and -C.

  5. The influence of surfactant on the deformation and breakup of a viscous drop: The effect of surfactant solubility

    SciTech Connect

    Milliken, W.J. ); Leal, L.G. . Dept. of Chemical and Nuclear Engineering)

    1994-09-01

    The influence of surfactant on the deformation of a viscous drop in a uniaxial extensional flow is considered. Previous studies have examined the role in insoluble surfactant. Here, the authors examine soluble surfactant, i.e., surfactant that may be transferred between the interface and the continuous phase. The transfer of surfactant to and from the interface mitigates many of the effects observed with insoluble surfactant by diminishing the magnitude of surfactant gradients. In the presence of soluble surfactant, the deformation generally lies between that of insoluble surfactant and that of a drop with a constant and uniform coverage of surfactant. However, there are notable exceptions particularly at high surfactant activity. The influence of surfactant on the interfacial velocity of the drop is also explicitly considered. It is shown that while insoluble surfactant can substantially retard a drop interface, interphase surfactant transfer acts to remobilize the interface.

  6. Effect of exogenous surfactant on the development of surfactant synthesis in premature rabbit lung.

    PubMed

    Amato, Maurizio; Petit, Kevin; Fiore, Humberto H; Doyle, Cynthia A; Frantz, Ivan D; Nielsen, Heber C

    2003-04-01

    Surfactant replacement is an effective therapy for neonatal respiratory distress syndrome. Full recovery from respiratory distress syndrome requires development of endogenous surfactant synthesis and metabolism. The influence of exogenous surfactant on the development of surfactant synthesis in premature lungs is not known. We hypothesized that different exogenous surfactants have different effects on the development of endogenous surfactant production in the premature lung. We treated organ cultures of d 25 fetal rabbit lung for 3 d with 100 mg/kg body weight of natural rabbit surfactant, Survanta, and Exosurf and measured their effects on the development of surfactant synthesis. Additional experiments tested how these surfactants and Curosurf affected surfactant protein (SP) SP-A, SP-B, and SP-C mRNA expression. Surfactant synthesis was measured as the incorporation of 3H-choline and 14C-glycerol into disaturated phosphatidylcholine recovered from lamellar bodies. Randomized-block ANOVA showed significant differences among treatments for incorporation of both labels (p < 0.01), with natural rabbit surfactant less than control, Survanta greater than control, and Exosurf unchanged. Additional experiments with natural rabbit surfactant alone showed no significant effects in doses up to 1000 mg/kg. Survanta stimulated disaturated phosphatidylcholine synthesis (173 +/- 41% of control; p = 0.01), increased total lamellar body disaturated phosphatidylcholine by 22% (p < 0.05), and increased 14C-disat-PC specific activity by 35% (p < 0.05). The response to Survanta was dose-dependent up to 1000 mg/kg. Survanta did not affect surfactant release. No surfactant altered the expression of mRNA for SP-A, SP-B, or SP-C. We conclude that surfactant replacement therapy can enhance the maturation of surfactant synthesis, but this potential benefit differs with different surfactant preparations.

  7. Ice Giant Exploration

    NASA Astrophysics Data System (ADS)

    Rymer, A. M.; Arridge, C. S.; Masters, A.; Turtle, E. P.; Simon, A. A.; Hofstadter, M. D.; Turrini, D.; Politi, R.

    2015-12-01

    The Ice Giants in our solar system, Uranus and Neptune, are fundamentally different from their Gas Giant siblings Jupiter and Saturn, from the different proportions of rock and ice to the configuration of their planetary magnetic fields. Kepler space telescope discoveries of exo-planets indicate that planets of this type are among the most ubiquitous universally and therefore a future mission to explore the nature of the Ice Giants in our own solar system will provide insights into the nature of extra-solar system objects in general. Uranus has the smallest self- luminosity of all the planets, potentially related to catastrophic events early in the planet's history, which also may explain Uranus' large obliquity. Uranus' atmosphere is subject to extreme seasonal forcing making it unique in the Solar System. Neptune is also unique in a number of ways, notably its large moon Triton which is likely a captured Kuiper Belt Object and one of only two moons in the solar system with a robustly collisional atmosphere. Similar to Uranus, the angle between the solar wind and the magnetic dipole axis is subject to large-amplitude variations on both diurnal and seasonal timescales, but peculiarly it has one of the quietest magnetospheres of the solar system, at least according to Voyager 2, the only spacecraft to encounter Neptune to date. A comprehensive mission, as advocated in the Decadal Survey, would provide enormous science return but is also challenging and expensive. In this presentation we will discuss mission scenarios and suggest how collaboration between disciplines and internationally can help us to pursue a mission that includes Ice Giant exploration.

  8. Giant cell arteritis

    PubMed Central

    Calvo-Romero, J

    2003-01-01

    Giant cell arteritis (GCA), temporal arteritis or Horton's arteritis, is a systemic vasculitis which involves large and medium sized vessels, especially the extracranial branches of the carotid arteries, in persons usually older than 50 years. Permanent visual loss, ischaemic strokes, and thoracic and abdominal aortic aneurysms are feared complications of GCA. The treatment consists of high dose steroids. Mortality, with a correct treatment, in patients with GCA seems to be similar that of controls. PMID:13679546

  9. Giant Cell Arteritis.

    PubMed

    Hoffman, Gary S

    2016-11-01

    This issue provides a clinical overview of giant cell arteritis, focusing on diagnosis, treatment, and practice improvement. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic in collaboration with the ACP's Medical Education and Publishing divisions and with the assistance of additional science writers and physician writers.

  10. High-Q ultrasonic determination of the critical nanoaggregate concentration of asphaltenes and the critical micelle concentration of standard surfactants.

    PubMed

    Andreatta, Gaëlle; Bostrom, Neil; Mullins, Oliver C

    2005-03-29

    Asphaltenes are known to be interfacially active in many circumstances such as at toluene-water interfaces. Furthermore, the term micelle has been used to describe the primary aggregation of asphaltenes in good solvents such as toluene. Nevertheless, there has been significant uncertainty regarding the critical micelle concentration (CMC) of asphaltenes and even whether the micelle concept is appropriate for asphaltenes. To avoid semantic debates we introduce the terminology critical nanoaggregate concentration (CNAC) for asphaltenes. In this report, we investigate asphaltenes and standard surfactants using high-Q, ultrasonic spectroscopy in both aqueous and organic solvents. As expected, standard surfactants are shown to exhibit a sharp break in sonic velocity versus concentration at known CMCs. To prove our methods, we measured known surfactants with CMCs in the range from 0.010 g/L to 2.3 g/L in agreement with the literature. Using density determinations, we obtain micelle compressibilities consistent with previous literature reports. Asphaltenes are also shown to exhibit behavior similar to that of ultrasonic velocity versus concentration as standard surfactants; asphaltene CNACs in toluene occur at roughly 0.1 g/L, although the exact concentration depends on the specific (crude oil) asphaltene. Furthermore, using asphaltene solution densities, we show that asphaltene nanoaggregate compressibilities are similar to micellar compressibilities obtained with standard nonionic surfactants in toluene. These results strongly support the contention that asphaltenes in toluene can be treated roughly within the micelle framework, although asphaltenes may exhibit small levels of aggregation (dimers, etc.) below their CNAC. Furthermore, our extensive results on known surfactants agree with the literature while the asphaltene CNACs reported here are one to two orders of magnitude lower than most previously published results. (Previous work utilized the terminology "micelle

  11. Interaction between bovine serum albumin and equimolarly mixed cationic-anionic surfactants decyltriethylammonium bromide-sodium decyl sulfonate.

    PubMed

    Lu, Run-Chao; Cao, Ao-Neng; Lai, Lu-Hua; Zhu, Bu-Yao; Zhao, Guo-Xi; Xiao, Jin-Xin

    2005-03-25

    The interactions of bovine serum albumin (BSA) with the anionic surfactant sodium decylsulfonate (C10SO3), the cationic surfactant decyltriethylammonium bromide (C10NE) and equimolarly mixed cationic-anionic surfactants C10NE-C10SO3 were investigated by surface tension, viscosity, dynamic light scattering (DLS) and circular dichroism (CD). It was shown that the single ionic surfactant C10SO3 or C10NE has obvious interaction with BSA. The presence of C10SO3 or C10NE modified BSA structure. However, the equimolarly mixed cationic-anionic surfactants C10NE-C10SO3 showed very weak interactions with BSA. The surface tension-log concentration (gamma-logC) plot for the aqueous solutions of C10NE-C10SO3/BSA mixtures coincided with that of C10NE-C10SO3 solutions. Viscometry showed that there is no significant change in the rheological properties for the C10NE-C10SO3/BSA mixed solutions. DLS showed that BSA monomers and mixed aggregates of C10NE-C10SO3 existed in the C10NE-C10SO3/BSA mixed solutions. From CD spectra no obvious modification of BSA structure in the presence of C10NE-C10SO3 mixtures was observed. The weak interactions between BSA and C10NE-C10SO3 might be explained in terms of the very low critical micelle concentration (cmc) of C10NE-C10SO3 mixtures that made the concentration of ionic surfactant monomers much lower than that needed for inducing the modification of BSA structure. In other words, the very strong synergism between oppositely charged cationic and anionic surfactants makes the formation of cationic-anionic surfactant mixed aggregates in the bulk solution a more favorable process than binding to proteins.

  12. MINERAL-SURFACTANT INTERACTIONS FOR MINIMUM REAGENTS PRECIPITATION AND ADSORPTION FOR IMPROVED OIL RECOVERY

    SciTech Connect

    P. Somasundaran

    2005-10-30

    In this project, fundamental studies were conducted to understand the mechanism of the interactions between polymer/surfactant and minerals with the aim of minimizing chemical loss by adsorption. The effects of chemical molecular structure on critical solid/liquid interfacial properties such as adsorption, wettability and surface tension in mineral/surfactant systems were investigated. The final aim is to build a guideline to design optimal polymer/surfactant formula based on the understanding of adsorption and orientation of surfactants and their aggregates at solid/liquid interface. During this period, the adsorption of mixed system of n-dodecyl-{beta}-D-maltoside (DM) and dodecyl sulfonate (C{sub 12}SO{sub 3}Na) was studied. Along with these adsorption studies, changes in mineral wettability due to the adsorption were determined under relevant conditions. pH was found to play a critical role in controlling total adsorption and mineral wettability. Previous studies have suggested significant surfactant loss by adsorption at neutral pH. But at certain pH, bilayer was found at lower adsorption density, which is beneficial for enhanced oil recovery. Analytical ultracentrifuge technique was successfully employed to study the micellization of DM/C{sub 12}SO{sub 3}Na mixtures. Compositional changes of the aggregates in solution were observed when two species were mixed. Surfactant mixture micellization affects the conformation and orientation of adsorption layer at mineral/water interface and thus the wettability and as a result, the oil release efficiency of the chemical flooding processes. Three surfactants C{sub 12}SO{sub 3}, AOT and SLE3 and one polymer were selected into three different binary combinations. Equilibrium surface tension measurement revealed complexation of polymer/surfactant under different conditions. Except for one combination of SLE3/ PVCAP, complexation was observed. It is to be noted that such complexation is relevant to both interfacial

  13. Aggregate transitions in aqueous solutions of sodium dodecylsulfate with a "gemini-type" organic salt.

    PubMed

    Yu, Defeng; Tian, Maozhang; Fan, Yaxun; Ji, Gang; Wang, Yilin

    2012-06-07

    Effects of a "gemini-type" organic salt 1,2-bis(2-benzylammoniumethoxy) ethane dichloride (BEO) on the aggregation behavior of sodium dodecylsulfate (SDS) have been investigated by turbidity, surface tension, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, (1)H NMR spectroscopy, and differential scanning microcalorimetry. The aggregation behavior of the SDS/BEO mixed aqueous solution shows strong concentration and ratio dependence. For the SDS/BEO solution with a molar ratio of 5:1, large loose irregular aggregates, vesicles, and long thread-like micelles are formed in succession with the increase of the total SDS and BEO concentration. Because BEO has two positive charges, the SDS/BEO solution may consist of the (SDS)(2)-BEO gemini-type complex, the SDS-BEO complex and extra SDS. The aggregation ability and surface activity of the SDS/BEO mixture exhibit the characteristics of gemini-type surfactants. Along with the results of DSC and (1)H NMR, the (SDS)(2)-BEO gemini-type structure is confirmed to exist in the system. This work provides an approach to construct the surfactant systems with the characteristics of gemini surfactants through intermolecular interaction between a two-charged organic salt and oppositely charged single-chain surfactants.

  14. DSF method optimization and its application in predicting protein thermal aggregation kinetics.

    PubMed

    Shi, Shuai; Semple, Andrew; Cheung, Jason; Shameem, Mohammed

    2013-08-01

    Differential scanning fluorimetry (DSF) has gained wide acceptance in the therapeutic protein development. However, the effects of dyes and surfactants that may affect structural transitions have not been studied thoroughly to date. We therefore first optimized the DSF method by studying surfactant-containing formulations and found that the presence of surfactants generally required medium-to-high protein concentrations and that high SYPRO® Orange concentration in a DSF experiment may lower protein thermal transitions. We also benchmarked DSF against differential scanning calorimetry (DSC) and evaluated the capability of thermal parameters (from DSF/DSC) to predict real-time thermal aggregation kinetics monitored by size exclusion chromatography (SEC) and analytical ultracentrifugation (AUC) in different scenarios. For monoclonal antibody (MAb) fragment, both DSF and DSC were predictive of thermal aggregation rate. For MAb3, a good correlation was observed between DSF and DSC, none of which was, however, indicative of protein aggregation kinetics. In a surfactant ranging study, DSF did not agree with DSC and was not predictive of the aggregation kinetics of the MAb fragment. The concentration-dependent thermal behavior was also studied by DSF. Although higher concentration, in general, tends to lower protein transition temperature, case where it was independent of protein concentration was also presented. Copyright © 2013 Wiley Periodicals, Inc.

  15. Role of surfactants in the control of dopamine-eumelanin particle size and in the inhibition of film deposition at solid-liquid interfaces.

    PubMed

    Ponzio, Florian; Bertani, Philippe; Ball, Vincent

    2014-10-01

    Anionic and cationic surfactants such as sodium dodecylsulfate (SDS) and hexadecyltrimethylammonium bromide (HTAB) are able to control the size of "polydopamine" particles produced from dopamine solutions and to simultaneously strongly inhibit the deposition of "polydopamine" on surfaces. Indeed, dynamic light scattering experiments allowed to show that the hydrodynamic radius of polydopamine progressively decreases from about 1 μm to a few nanometer upon an increase in the SDS and CTAB concentration. At the highest surfactant concentration used (50 mM) the size of the aggregates is only slightly larger than the size of the surfactant micelles. On the other hand, the non-ionic Triton X-100 surfactant has no significant influence on both phenomena. It is suggested that the observed effect originates from the anionic and cationic surfactants acting as a template in which the growth of "polydopamine" is confined. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Effect of surfactant on the drying patterns of graphite nanofluid droplets.

    PubMed

    Crivoi, Alexandru; Duan, Fei

    2013-05-16

    We investigate the effect of surfactant on the formation of nanoparticle aggregates that resulted from evaporation of sessile nanofluid droplets theoretically and experimentally. A Monte Carlo model is developed to explain the transition from the coffee-ring pattern to the uniform deposition in drying the pinned sessile nanofluid droplets. The model applies the diffusion limited cluster-cluster aggregation approach coupled with the biased random walk of nanoparticles. The experiments show that the addition of surfactant in nanofluids helps the formation of a coffee ring instead of the uniform domain coverage. The simulations suggest an explanation of this transition by controlling the sticking probability parameter between the particles. The simulated results statistically agree with the experimental observation of the finally dried graphite nanoparticle structures from the pinned nanofluid droplets.

  17. Mode changes associated with oil droplet movement in solutions of gemini cationic surfactants.

    PubMed

    Banno, Taisuke; Miura, Shingo; Kuroha, Rie; Toyota, Taro

    2013-06-25

    Micrometer-sized self-propelled oil droplets in nonequilibrium systems have attracted much attention, since they form stable emulsions composed of oil, water, and surfactant which represent a primitive type of inanimate chemical machinery. In this work, we examined means of controlling the movement of oil droplets by studying the dynamics of n-heptyloxybenzaldehyde droplets in phosphate buffers containing alkanediyl-α,ω-bis(N-dodecyl-N,N-dimethylammonium bromide) (nG12) with either tetramethylene (4G12), octaethylene (8G12), or dodecamethylene (12G12) chains in the linker moiety. Significant differences in droplet dynamics were observed to be induced by changes in the linker structure of these gemini cationic surfactants. In a phosphate buffer containing 30 mM 4G12, self-propelled motion of droplets concurrent with the formation of molecular aggregates on their surfaces was observed, whereas the fusion of oil droplets was evident in both 8G12 and 12G12 solutions. We also determined that the surface activities and the extent of molecular self-assembly of the surfactants in phosphate buffer were strongly influenced by the alkyl chain length in the linker moiety. We therefore conclude that the surface activities of the gemini cationic surfactant have important effects on the oil-water interfacial tension of oil droplets and the formation of molecular aggregates and that both of these factors induce the unique movement of the droplets.

  18. Adsorption and Depletion Regimes of a Nonionic Surfactant in Hydrophilic Mesopores: An Experimental and Simulation Study

    DOE PAGES

    Müter, Dirk; Rother, Gernot; Bock, Henry; ...

    2017-08-15

    Adsorption and aggregation of nonionic surfactants at oxide surfaces has been studied extensively in the past, but only for concentrations below and near the critical micelle concentration. In this paper, we report an adsorption study of a short-chain surfactant (C6E3) in porous silica glass of different pore sizes (7.5 to 50 nm), covering a wide composition range up to 50 wt % in a temperature range from 20 °C to the LCST. Aggregative adsorption is observed at low concentrations, but the excess concentration of C6E3 in the pores decreases and approaches zero at higher bulk concentrations. Strong depletion of surfactantmore » (corresponding to enrichment of water in the pores) is observed in materials with wide pores at high bulk concentrations. We propose an explanation for the observed pore-size dependence of the azeotropic point. Mesoscale simulations based on dissipative particle dynamics (DPD) were performed to reveal the structural origin of this transition from the adsorption to the depletion regime. The simulated adsorption isotherms reproduce the behavior found in the 7.5 nm pores. Finally, the calculated bead density profiles indicate that the repulsive interaction of surfactant head groups causes a depletion of surfactant in the region around the corona of the surface micelles.« less

  19. Interfacial adsorption and aggregation of amphiphilic proteins

    NASA Astrophysics Data System (ADS)

    Cheung, David

    2012-02-01

    The adsorption and aggregation on liquid interfaces of proteins is important in many biological contexts, such as the formation of aerial structures, immune response, and catalysis. Likewise the adsorption of proteins onto interfaces has applications in food technology, drug delivery, and in personal care products. As such there has been much interest in the study of a wide range of biomolecules at liquid interfaces. One class of proteins that has attracted particular attention are hydrophobins, small, fungal proteins with a distinct, amphiphilic surface structure. This makes these proteins highly surface active and they recently attracted much interest. In order to understand their potential applications a microscopic description of their interfacial and self-assembly is necessary and molecular simulation provides a powerful tool for providing this. In this presentation I will describe some recent work using coarse-grained molecular dynamics simulations to study the interfacial and aggregation behaviour of hydrophobins. Specifically this will present the calculation of their adsorption strength at oil-water and air-water interfaces, investigate the stability of hydrophobin aggregates in solution and their interaction with surfactants.

  20. Unusual Giant Prostatic Urethral Calculus

    PubMed Central

    Bello, A.; Maitama, H. Y.; Mbibu, N. H.; Kalayi, G. D.; Ahmed, A.

    2010-01-01

    Giant vesico-prostatic urethral calculus is uncommon. Urethral stones rarely form primarily in the urethra, and they are usually associated with urethral strictures, posterior urethral valve or diverticula. We report a case of a 32-year-old man with giant vesico-prostatic (collar-stud) urethral stone presenting with sepsis and bladder outlet obstruction. The clinical presentation, management, and outcome of the giant prostatic urethral calculus are reviewed. PMID:22091328

  1. Giant bulla mimicking tension pneumothorax.

    PubMed

    Gökçe, Mertol; Saydam, Ozkan; Altin, Remzi; Kart, Levent

    2009-01-01

    In the chest X-ray, we observe tension pneumothorax (TPX) as wide radiolucent view in a hemithorax and pushing the mediastinal structures contralateral. Giant bulla may mimic TPX with wide radiolucent view and mediastinal shift. The present report includes giant pulmonary bulla in 35-year-old woman. The giant bulla was diagnosed as a TPX in emergency, and chest tube was performed. The differentiation between TPX and a giant bulla may be very difficult. The therapies of these two similar entities are completely different. So that, we must be careful about anamnesis, physical examination and radiology for true diagnosis.

  2. Serine-based gemini surfactants with different spacer linkages: from self-assembly to DNA compaction.

    PubMed

    Silva, Sandra G; Oliveira, Isabel S; do Vale, M Luísa C; Marques, Eduardo F

    2014-12-14

    Cationic gemini surfactants have strong potential as compaction agents of nucleic acids for efficient non-viral gene delivery. In this work, we present the aggregation behavior of three novel cationic serine-based gemini surfactants as well as their ability to compact DNA per se and mixed with a helper lipid, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). All the surfactants have a 12-12-12 configuration, i.e. two main 12-carbon alkyl chains linked to the nitrogen atom of the amino acid residue and a 12 methylene spacer, but they differ in the nature of the spacer linkage: for (12Ser)2N12, an amine bond; for (12Ser)2CON12, an amide bond; and for (12Ser)2COO12, an ester bond. Interestingly, while the amine-based gemini aggregates into micelles, the amide and ester ones spontaneously form vesicles, which denotes a strong influence of the type of linkage on the surfactant packing parameter. The size, ζ-potential and stability of the vesicles have been characterized by light microscopy, cryogenic scanning electron microscopy (cryo-SEM) and dynamic light scattering (DLS). The interaction of the gemini aggregates with DNA at different charge ratios and in the absence and presence of DOPE has been studied by DLS, fluorescence spectroscopy and cryo-SEM. All the compounds are found to efficiently compact DNA (complexation > 90%), but relevant differences are obtained in terms of the size, ζ-potential and stability of the lipoplexes formed. Results are rationalized in terms of headgroup differences and the type of aggregates present prior to DNA condensation.

  3. Superamphiphilic nanocontainers based on the resorcinarene - Cationic surfactant system: Synergetic self-assembling behavior

    NASA Astrophysics Data System (ADS)

    Gaynanova, Gulnara A.; Bekmukhametova, Alina M.; Kashapov, Ruslan R.; Ziganshina, Albina Yu.; Zakharova, Lucia Ya.

    2016-05-01

    Self-organization in the mixed system based on water-soluble aminomethylated calix[4]arene with sulfonatoethyl groups at the lower rim and classical cationic surfactant cetyltrimethylammonium bromide has been studied by the methods of tensiometry, conductometry, spectrophotometry, dynamic and electrophoretic light scattering. The values of the critical association concentration, the size and zeta potential values, and the solubilization capacity of mixed aggregates toward the hydrophobic probe (Sudan I) were determined.

  4. Colloidal stability of iron oxide nanocrystals coated with a PEG-based tetra-catechol surfactant

    NASA Astrophysics Data System (ADS)

    Mondini, Sara; Drago, Carmelo; Ferretti, Anna M.; Puglisi, Alessandra; Ponti, Alessandro

    2013-03-01

    Long-term colloidal stability of magnetic iron oxide nanoparticles (NPs) is an important goal that has not yet been fully achieved. To make an advance in our understanding of the colloidal stability of iron oxide NPs in aqueous media, we prepared NPs comprising a monodisperse (13 nm) iron oxide core coated with a PEG-based (PEG: polyethyleneglycol) surfactant. This consists of a methoxy-terminated PEG chain (MW = 5000 Da) bearing four catechol groups via a diethylenetriamine linker. The surfactant was grafted onto the nanocrystals by ligand exchange monitored by infrared spectroscopy. The colloidal stability of these nanoparticles was probed by monitoring the time evolution of the Z-average intensity-weighted radius Rh and volume-weighted size distribution Pv obtained from analysis of dynamic light scattering data. The nanoparticles showed no sign of aggregation for four months in deionized water at room temperature and also when subjected to thermal cycling between 25 and 75 °C. In 0.01 M PBS (phosphate buffered saline), aggregation (if any) is slow and partial; after 66 h, about 50% of NPs have not aggregated. Aggregation is more effective in 0.15 M NH4AcO buffer, where isolated particles are not observed after 66 h, and especially in acidic NH4AcO/AcOH buffer, where aggregation is complete within 1 h and precipitation is observed. The differing stability of the NPs in the above aqueous media is closely related to their ζ potential.

  5. Photoresponsive Foams Generated by a Rigid Surfactant Derived from Dehydroabietic Acid.

    PubMed

    Lei, Lan; Xie, Danhua; Song, Binglei; Jiang, Jianzhong; Pei, Xiaomei; Cui, Zhenggang

    2017-08-15

    Innovation in the structure of surfactants is crucial to the construction of a surfactant-based system with intriguing properties. With dehydroabietic acid as a starting material, a nearly totally rigid azobenzene surfactant (R-azo-Na) was synthesized. The trans-R-azo-Na formed stable foams with half-lives of 636, 656, 976, and 872 min for 0.3, 1, 2, and 4 mmol·L(-1) aqueous solutions, respectively. Under UV light irradiation, a fast collapse of the foams was observed, showing an in situ response. The excellent foam stability of trans-R-azo-Na leads to the extremely high photoresponsive efficiency. As revealed by dynamic surface tension and pulsed-field gradient NMR methods, an obvious energy barrier existed in the adsorption/desorption process of trans-R-azo-Na on the air/water interface. The foams formed by trans-R-azo-Na are thus stable against coarsening processes. The results reveal the unique photoresponsive behavior of a surfactant with a rigid hydrophobic skeleton and provide new insights into the structure causing aggregation of surfactants.

  6. 1H NMR relaxation of water: a probe for surfactant adsorption on kaolin.

    PubMed

    Totland, Christian; Lewis, Rhiannon T; Nerdal, Willy

    2011-11-01

    In this study, (1)H NMR is used to investigate properties of sodium dodecyl sulfate (SDS), tetradecyl trimethyl ammonium bromide (TTAB), and dodecyl trimethyl ammonium bromide (DTAB) adsorbed on kaolin by NMR T(1) and T(2) measurements of the water proton resonance. The results show that adsorbed surfactants form a barrier between sample water and the paramagnetic species present on the clay surface, thus significantly increasing the proton T(1) values of water. This effect is attributed to the amount of adsorbed surfactants and the arrangement of the surfactant aggregates. The total surface area covered by the cationic (DTAB and TTAB) and anionic (SDS) surfactants could be estimated from the water T(1) data and found to correspond to the fractions of negatively and positively charged surface area, respectively. For selected samples, the amount of paramagnetic species on the clay surface was reduced by treatment with hydrofluoric (HF) acid. For these samples, T(1) and T(2) measurements were taken in the temperature range 278-338 K, revealing detailed information on molecular mobility and nuclear exchange for the sample water that is related to surfactant behavior both on the surface and in the aqueous phase.

  7. Characterization of chemical selectivity in micellar electrokinetic chromatography. VI. Effects of surfactant counter-ion.

    PubMed

    Trone, M D; Mack, J P; Goodell, H P; Khaledi, M G

    2000-08-04

    Linear solvation energy relationships and free energy of transfer data were used to evaluate the influence of the surfactant counter-ion on selectivity in micellar electrokinetic chromatography. It was determined that selectivity differences are dependent on the valency of the counter-ion but not the type of counter-ion. Monovalent surfactants, sodium dodecyl sulfate (SDS) and lithium dodecyl sulfate, have nearly identical selectivity behavior. The divalent surfactants, magnesium didodecyl sulfate and copper didodecyl sulfate also show very similar behavior. However, when the divalent counter-ion species is compared to SDS under similar conditions, significant differences are observed. Most notably, the utilization of divalent counter-ion species of dodecyl sulfate surfactants causes the micelles to become more hydrophobic and a weaker hydrogen bond donating pseudo-stationary phases. It is believed that the divalent counter-ions reduce the electrostatic repulsion between the surfactant head groups and therefore, increase the chain packing of the monomers in the micelle aggregates. This reduces the degree of hydration of the micellar palisade layer leading to a decreased ability of the micelle to participate in polar/polarizable and hydrogen bonding interactions with solute molecules.

  8. Long-chain acyl-CoA dehydrogenase deficiency as a cause of pulmonary surfactant dysfunction.

    PubMed

    Goetzman, Eric S; Alcorn, John F; Bharathi, Sivakama S; Uppala, Radha; McHugh, Kevin J; Kosmider, Beata; Chen, Rimei; Zuo, Yi Y; Beck, Megan E; McKinney, Richard W; Skilling, Helen; Suhrie, Kristen R; Karunanidhi, Anuradha; Yeasted, Renita; Otsubo, Chikara; Ellis, Bryon; Tyurina, Yulia Y; Kagan, Valerian E; Mallampalli, Rama K; Vockley, Jerry

    2014-04-11

    Long-chain acyl-CoA dehydrogenase (LCAD) is a mitochondrial fatty acid oxidation enzyme whose expression in humans is low or absent in organs known to utilize fatty acids for energy such as heart, muscle, and liver. This study demonstrates localization of LCAD to human alveolar type II pneumocytes, which synthesize and secrete pulmonary surfactant. The physiological role of LCAD and the fatty acid oxidation pathway in lung was subsequently studied using LCAD knock-out mice. Lung fatty acid oxidation was reduced in LCAD(-/-) mice. LCAD(-/-) mice demonstrated reduced pulmonary compliance, but histological examination of lung tissue revealed no obvious signs of inflammation or pathology. The changes in lung mechanics were found to be due to pulmonary surfactant dysfunction. Large aggregate surfactant isolated from LCAD(-/-) mouse lavage fluid had significantly reduced phospholipid content as well as alterations in the acyl chain composition of phosphatidylcholine and phosphatidylglycerol. LCAD(-/-) surfactant demonstrated functional abnormalities when subjected to dynamic compression-expansion cycling on a constrained drop surfactometer. Serum albumin, which has been shown to degrade and inactivate pulmonary surfactant, was significantly increased in LCAD(-/-) lavage fluid, suggesting increased epithelial permeability. Finally, we identified two cases of sudden unexplained infant death where no lung LCAD antigen was detectable. Both infants were homozygous for an amino acid changing polymorphism (K333Q). These findings for the first time identify the fatty acid oxidation pathway and LCAD in particular as factors contributing to the pathophysiology of pulmonary disease.

  9. Atypical effects of incorporated surfactants on stability and dissolution properties of amorphous polymeric dispersions.

    PubMed

    Al-Obaidi, Hisham; Lawrence, M Jayne; Buckton, Graham

    2016-11-01

    To understand the impact of ionic and non-ionic surfactants on the dissolution and stability properties of amorphous polymeric dispersions using griseofulvin (GF) as a model for poorly soluble drugs. Solid dispersions of the poorly water-soluble drug, griseofulvin (GF) and the polymers, poly(vinylpyrrolidone) (PVP) and poly(2-hydroxypropyl methacrylate) (PHPMA), have been prepared by spray drying and bead milling and the effect of the ionic and non-ionic surfactants, namely sodium dodecyl sulphate (SDS) and Tween-80, on the physico-chemical properties of the solid dispersions studied. The X-ray powder diffraction data and hot-stage microscopy showed a fast re-crystallisation of GF. While dynamic vapour sorption (DVS) measurements indicated an increased water uptake, slow dissolution rates were observed for the solid dispersions incorporating surfactants. The order by which surfactants free dispersions were prepared seemed critical as indicated by DVS and thermal analysis. Dispersions prepared by milling with SDS showed significantly better stability than spray-dried dispersions (drug remained amorphous for more than 6 months) as well as improved dissolution profile. We suggest that surfactants can hinder the dissolution by promoting aggregation of polymeric chains, however that effect depends mainly on how the particles were prepared. © 2016 Royal Pharmaceutical Society.

  10. Nanostructured fluids from degradable nonionic surfactants for the cleaning of works of art from polymer contaminants.

    PubMed

    Baglioni, M; Raudino, M; Berti, D; Keiderling, U; Bordes, R; Holmberg, K; Baglioni, P

    2014-09-21

    Nanostructured fluids containing anionic surfactants are among the best performing systems for the cleaning of works of art. Though efficient, their application may result in the formation of a precipitate, due to the combination with divalent cations that might leach out from the artifact. We propose here two new aqueous formulations based on nonionic surfactants, which are non-toxic, readily biodegradable and insensitive to the presence of divalent ions. The cleaning properties of water-nonionic surfactant-2-butanone (MEK) were assessed both on model surfaces and on a XIII century fresco that could not be cleaned using conventional methods. Structural information on nanofluids has been gathered by means of small-angle neutron scattering, dynamic light scattering and nuclear magnetic resonance with diffusion monitoring. Beside the above-mentioned advantages, these formulations turned out to be considerably more efficient in the removal of polymer coatings than those based on anionic surfactants. Our results indicate that the cleaning process most likely consists of two steps: initially, the polymer film is swollen by the MEK dissolved in the continuous domain of the nanofluid; in the second stage, surfactant aggregates come into play by promoting the removal of the polymer film with a detergency-like mechanism. The efficiency can be tuned by the composition and nature of amphiphiles and is promoted by working as close as possible to the cloud point of the formulation, where the second step proceeds at maximum rate.

  11. Orientational bonding model for temperature dependent micellization and solubility of diblock surfactants

    NASA Astrophysics Data System (ADS)

    Davis, Jonathan R.; Panagiotopoulos, Athanassios Z.

    2009-09-01

    A lattice model for diblock surfactants that incorporates orientational bonding has been developed for studying self-assembly in dilute solutions. Using grand canonical Monte Carlo simulations with histogram reweighting and mixed field finite size scaling, we examine the effect of amphiphile architecture on phase transitions and distinguish between first order transitions that create a disordered liquid phase and higher order transitions that indicate the formation of finite sized aggregates. As the solution temperature increases, we find that the critical micelle concentration for the orientational bonding model surfactants reaches a minimum value at a temperature that can be controlled by varying the number of bonding orientations between the solvophobic surfactant monomers and the implicit solvent. This trend is qualitatively similar to experimental data for ionic and nonionic surfactants in aqueous solutions. A comparable dependence on temperature is observed in the limit of amphiphile solubility for phase separating systems. None of the model surfactants considered here undergo both a first and a higher order transition over the range of densities and temperatures examined.

  12. Dipeptidyl peptidase I controls survival from Klebsiella pneumoniae lung infection by processing surfactant protein D.

    PubMed

    Sutherland, Rachel E; Barry, Sophia S; Olsen, Joanna S; Salantes, D Brenda; Caughey, George H; Wolters, Paul J

    2014-07-18

    Prior work established that a deficiency in the cysteine protease dipeptidyl peptidase I (DPPI) improves survival following polymicrobial septic peritonitis. To test whether DPPI regulates survival from severe lung infections, DPPI(-/-) mice were studied in a Klebsiella pneumoniae lung infection model, finding that survival in DPPI(-/-) mice is significantly better than in DPPI(+/+) mice 8d after infection. DPPI(-/-) mice have significantly fewer bacteria in the lung than infected DPPI(+/+) mice, but no difference in lung histopathology, lung injury, or cytokine levels. To explore mechanisms of enhanced bacterial clearance in DPPI(-/-) mice, we examined the status of pulmonary collectins, finding that levels of surfactant protein D, but not of surfactant protein A, are higher in DPPI(-/-) than in DPPI(+/+) BAL fluid, and that DPPI(-/-) BAL fluid aggregate bacteria more effectively than control BAL fluid. Sequencing of the amino terminus of surfactant protein D revealed two or eight additional amino acids in surfactant protein D isolated from DPPI(-/-) mice, suggesting processing by DPPI. These results establish that DPPI is a major determinant of survival following Klebsiella pneumoniae lung infection and suggest that the survival disadvantage in DPPI(+/+) mice is in part due to processing of surfactant protein D by DPPI. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. Dipeptidyl Peptidase I Controls Survival from Klebsiella pneumoniae Lung Infection by Processing Surfactant Protein D 1

    PubMed Central

    Olsen, Joanna S.; Salantes, D. Brenda; Caughey, George H.; Wolters, Paul J.

    2014-01-01

    Prior work established that a deficiency in the cysteine protease dipeptidyl peptidase I (DPPI) improves survival following polymicrobial septic peritonitis. To test whether DPPI regulates survival from severe lung infections, DPPI −/− mice were studied in a Klebsiella pneumonia lung infection model, finding that survival in DPPI −/− mice is significantly better than in DPPI +/+ mice 8 d after infection. DPPI −/− mice have significantly fewer bacteria in the lung than infected DPPI +/+ mice, but no difference in lung histopathology, lung injury, or cytokine levels. To explore mechanisms of enhanced bacterial clearance in DPPI −/− mice, we examined the status of pulmonary collectins, finding that levels of surfactant protein D, but not of surfactant protein A, are higher in DPPI −/− than in DPPI +/+ BAL fluid, and that DPPI −/− BAL fluid aggregate bacteria more effectively than control BAL fluid. Sequencing of the amino terminus of surfactant protein D revealed two or eight additional amino acids in surfactant protein D isolated from DPPI −/− mice, suggesting processing by DPPI. These results establish that DPPI is a major determinant of survival following Klebsiella pneumoniae lung infection and suggest that the survival disadvantage in DPPI +/+ mice is in part due to processing of surfactant protein D by DPPI. PMID:24955853

  14. Solution properties and emulsification properties of amino acid-based gemini surfactants derived from cysteine.

    PubMed

    Yoshimura, Tomokazu; Sakato, Ayako; Esumi, Kunio

    2013-01-01

    Amino acid-based anionic gemini surfactants (2C(n)diCys, where n represents an alkyl chain with a length of 10, 12, or 14 carbons and "di" and "Cys" indicate adipoyl and cysteine, respectively) were synthesized using the amino acid cysteine. Biodegradability, equilibrium surface tension, and dynamic light scattering were used to characterize the properties of gemini surfactants. Additionally, the effects of alkyl chain length, number of chains, and structure on these properties were evaluated by comparing previously reported gemini surfactants derived from cystine (2C(n)Cys) and monomeric surfactants (C(n)Cys). 2C(n)diCys shows relatively higher biodegradability than does C(n)Cys and previously reported sugar-based gemini surfactants. Both critical micelle concentration (CMC) and surface tension decrease when alkyl chain length is increased from 10 to 12, while a further increase in chain length to 14 results in increased CMC and surface tension. This indicates that long-chain gemini surfactants have a decreased aggregation tendency due to the steric hindrance of the bulky spacer as well as premicelle formation at concentrations below the CMC and are poorly packed at the air/water interface. Formation of micelles (measuring 2 to 5 nm in solution) from 2C(n)diCys shows no dependence on alkyl chain length. Further, shaking the mixtures of aqueous 2C(n)diCys surfactant solutions and squalane results in the formation of oil-in-water type emulsions. The highly stable emulsions are formed using 2C₁₂diCys or 2C₁₄diCys solution and squalane in a 1:1 or 2:1 volume ratio.

  15. Development of novel cosmetic base using sterol surfactant. II. Solubilizing of sparingly soluble ultraviolet ray absorbers.

    PubMed

    Teshigawara, Takashi; Miyahara, Reiji; Fukuhara, Tadao; Oka, Takashi

    2009-01-01

    Previous studies have reported that O/W emulsion prepared using a surfactant with phytosterol as the hydrophobic moiety exhibited unique morphology; a lamellar structure was present on the surface of the emulsified particles. It is suggested that such a unique self-organized structure was due to the large and bulky planar structure of the sterol. On the other hand, sparingly soluble compounds including ultraviolet ray absorbers and medicines (e.g., indomethacine and finasteride) have been used after they are dissolved mainly in polar oils. However, it is very difficult to dissolve them in bases that contain small amounts of oil components such as lotions. Moreover, many of these sparingly soluble compounds have planar structures such as aromatic rings and are easy to crystallize in polar oil. In this study, sterol surfactants were considered suitable for solubilizing sparingly soluble compounds, since they have a bulky planar structure in their molecules. On this basis, the solubilization of ultraviolet ray absorbers using sterol surfactants was investigated. Methods to solubilize ultraviolet ray absorbers stably and effectively by using a surfactant that had a phytosterol structure have been clarified. Further, the following features were also suggested: (1) the microemulsion of phytosterol surfactant is different from that of other surfactants and (2) a rigid core that has solubilized compounds between the hydrophobic moieties was considered; further, the core was surrounded by a polyoxyethylene chain that prevented the self-aggregation. Analysis using NMR measurements suggested that (1) the polyoxyethylene/polyoxypropylene random copolymer dimethyl ether squeezed in a narrow gap between the hydrophobic moieties of the surfactant, and (2) this eventually increased the solubilized amount of an ultraviolet ray absorber.

  16. Interactions between dyes and surfactants in inkjet ink used for textiles.

    PubMed

    Park, Ju-Young; Hirata, Yuichi; Hamada, Kunihiro

    2011-01-01

    Optimal preparation of inkjet ink should be possible through the elucidation of the relationship between dye/additive interactions and ink performance. In the present study, the interactions between the dyes and surfactant additives were investigated. To investigate the physical properties of the surfactants used, the critical micelle concentration (cmc) and the aggregation number (N) were determined using electron spin resonance, static light-scattering, and fluorescence spectroscopy. On the basis of the cmc and N values, the visible absorption spectra of aqueous acid dye solutions (C. I. Acid Red 88, 13, and 27) containing surfactants (i.e., Surfynol 465 (S465), octaethylene glycol monododecyl ether (OGDE), and sodium dodecyl sulfate (SDS)) were measured. From the dependence of the spectra on the surfactant concentration, the binding constants, K(bind), of the acid dyes with the surfactant micelles were calculated: the K(bind) values decreased in the order of C. I. Acid Red 88 > C. I. Acid Red 13 > C. I. Acid Red 27, which correlates with the number of sulfonate groups. For all the dyes, the K(bind) values with the nonionic surfactants, S465 and OGDE, were much larger than those with the anionic surfactant, SDS. The thermodynamic parameters of the binding, i.e., the enthalpy change, ΔH(bind), and entropy change, ΔS(bind), were determined via the temperature dependence of the binding constants. The positive ΔH(bind) value for S465 indicates an endothermic binding process, while the negative ΔH(bind) values for SDS and OGDE indicate exothermic binding processes.

  17. Efficacy of a Surfactant-based Wound Dressing on Biofilm Control.

    PubMed

    Percival, Steven L; Mayer, Dieter; Salisbury, Anne-Marie

    2017-08-30

    The aim of this study was to evaluate the efficacy of both a non-antimicrobial and antimicrobial (1% silver sulfadiazine - SSD) surfactant-based wound dressing in the control of Pseudomonas aeruginosa, Enterococcus sp, Staphylococcus epidermidis, Staphylococcus aureus and meticillin-resistant S. aureus (MRSA) biofilms. Anti-biofilm efficacy was evaluated in numerous adapted American Standards for Testing and Materials (ASTM) standard biofilm models and other bespoke biofilm models. The ASTM standard models employed included the MBEC biofilm model (ASTM E2799) and the CDC biofilm reactor model (ASTM 2871). Such bespoke biofilm models included the filter biofilm model and the chamberslide biofilm model. Results showed complete kill of microorganisms within a biofilm using the antimicrobial surfactant-based wound dressing. Interestingly, the non-antimicrobial surfactant-based dressing could disrupt existing biofilms by causing biofilm detachment. Prior to biofilm detachment, we demonstrated, using confocal laser scanning microscopy (CLSM), the dispersive effect of the non-antimicrobial surfactant-based wound dressing on the biofilm within 10 minutes of treatment. Furthermore, the non-antimicrobial surfactant-based wound dressing caused an increase in microbial flocculation/aggregation, important for microbial concentration. In conclusion, this non-antimicrobial surfactant-based wound dressing leads to the effective detachment and dispersion of in vitro biofilms. The use of surfactant-based wound dressings in a clinical setting may help to disrupt existing biofilm from wound tissue and may increase the action of antimicrobial treatment. This article is protected by copyright. All rights reserved. © 2017 by the Wound Healing Society.

  18. Surfactant transport on viscous bilayers

    NASA Astrophysics Data System (ADS)

    Matar, Omar; Craster, Richard; Warner, Mark

    2001-11-01

    We model the external delivery of surfactant to pulmonary airways, an integral part of Surfactant Replacement Therapy (SRT), a method of treatment of Respiratory Distress Syndrome in neonates. We examine the spreading dynamics of insoluble surfactant by Marangoni stresses along the mucus-perciliary liquid bilayers that line the inside of airways. The bilayer is modelled as a thin highly viscous mucus surface film (mucus) overlying a much less viscous perciliary liquid layer (PCL); this is appropriate for small airways. By exploiting this large viscosity constrast, a variant of standard lubrication theory is adopted wherein terms, which would have otherwise been neglected in the lubrication approximation, are promoted in order to model correctly the presence of the mucus. Inclusion of van der Waals forces in the model permit the study of the effect of this mucus 'skin' on the possibility of bilayer rupture, a potential cause of failure of SRT. We find that increasing the viscosity contrast and initial mucus layer thickness delays the onset of rupture, while increasing the relative significance of Marangoni stresses leads to more marked thinning and rapid bilayer rupture [1]. [1] O. K. Matar, R. V. Craster and M. R. Warner, submitted to J. Fluid Mech. (2001).

  19. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  20. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  1. Miscibility of Quillaja Saponins with other Co-surfactants under Different pH Values.

    PubMed

    Reichert, Corina L; Salminen, Hanna; Leuenberger, Bruno H; Hinrichs, Jörg; Weiss, Jochen

    2015-11-01

    The miscibility behavior of mixed surfactant systems and the influence of extrinsic parameters are crucial for their application as emulsifiers. Therefore, the objective of this study was to evaluate the miscibility behavior of mixed systems composed of commercial Quillaja saponin and a co-surfactant, namely sodium caseinate, pea protein, rapeseed lecithin, or egg lecithin. These mixtures were evaluated macro- and microscopically at different concentration ratios (maximum concentration 5% w/v) at pH 3, 5, and 7 at 25 °C. The individual ingredients were also assessed for their charge properties and surface hydrophobicity. The results showed that Quillaja saponin-caseinate mixtures were miscible only at pH 7, and showed aggregation and precipitation at lower pH due to increasing electrostatic attraction forces. Rheological measurements showed that Quillaja saponin-pea protein mixtures formed gelled structures at all tested pH values mainly via association of hydrophobic patches. Quillaja saponins mixed with rapeseed lecithin were miscible at all tested pH values due to electrostatic repulsion. Quillaja saponin-egg lecithin mixtures aggregated independent of pH and concentration ratio. The microscopic analysis revealed that the lower the pH and the higher the Quillaja saponin ratio, the denser were the formed Quillaja saponin-egg lecithin aggregates. The results are summarized in ternary phase diagrams that provide a useful tool in selecting a surfactant system for food applications. © 2015 Institute of Food Technologists®

  2. Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited.

    PubMed

    Ninham, Barry W; Larsson, Kåre; Lo Nostro, Pierandrea

    2017-04-01

    Hofmeister, specific ion effects, hydration and van der Waals forces at and between interfaces are factors that determine curvature and microstructure in self assembled aggregates of surfactants and lipids; and in microemulsions. Lipid and surfactant head group interactions and between aggregates vary enormously and are highly specific. They act on the hydrophilic side of a bilayer, micelle or other self assembled aggregate. It is only over the last three decades that the origin of Hofmeister effects has become generally understood. Knowledge of their systematics now provides much flexibility in designing nanostructured fluids. The other side of the coin involves equally specific forces. These (opposing) forces work on the hydrophobic side of amphiphilic interfaces. They are due to the interaction of hydrocarbons and other "oils" with hydrophobic tails of surfactants and lipids. The specificity of oleophilic solutes in microemulsions and lipid membranes provides a counterpoint to Hofmeister effects and hydration. Together with global packing constraints these effects determine microstructure. Another factor that has hardly been recognised is the role of dissolved gas. This introduces further, qualitative changes in forces that prescribe microstructure. The systematics of these effects and their interplay are elucidated. Awareness of these competing factors facilitates formulation of self assembled nanostructured fluids. New and predictable geometries that emerge naturally provide insights into a variety of biological phenomena like anaesthetic and pheromone action and transmission of the nervous impulse (see Part 2).

  3. Effect of cationic surfactants on the conformational transition of poly(methacrylic acid)

    SciTech Connect

    Chu, D.; Thomas, J.K.

    1986-10-01

    The interaction between poly(methacrylic acid) and alkyltrimethylammonium bromide, C/sub n/TAB, cationic surfactants has been investigated in aqueous solutions of pH 8, by use of the photophysics of pyrene and its derivatives. Photophysical studies of these fluorescent probes, both steady-state and pulsed laser studies, show that a conformational transition of PMA is induced by C/sub n/TAB. The surfactant induces a coiling up of PMA chains at pH 8, which takes place via a cooperative process. This effect takes place when the concentration of C/sub n/TAB is above a critical aggregate concentration, CAC. The CAC is 1 or 2 orders of magnitude less than the cmc of the corresponding micelle. There is significant effect of surfactant chain length and PMA concentration on the CAC, which provides information on the nature of the CAC and the mechanism of the PMA transition. A model is suggested for the aggregation of PMA-C/sub 10/TAB based on experimental data. Studies show that the aggregate consists of about 100 C/sub 10/TAB molecules and 1 coiled polymer chain.

  4. Permeability reductions induced by sorption of surfactant

    NASA Astrophysics Data System (ADS)

    Renshaw, Carl E.; Zynda, Gregory D.; Fountain, John C.

    Surfactant enhanced aquifer remediation (SEAR) is an attractive alternative to traditional pump and treat methods for remediating aquifers contaminated with nonaqueous phase liquids. However, initial studies indicate that the application of surfactant can reduce aquifer permeability by more than an order of magnitude, limiting the efficiency of SEAR. A series of column experiments using mixtures of medium sand and montmorillonite clay demonstrate that existing permeability reduction models for biofouling and deep-bed filtration poorly predict surfactant induced permeability reductions. An alternative permeability reduction model is proposed which is based on the assumption that the sorbed surfactant effectively increases the volume fraction of the clay. The model is shown to reasonably predict observed permeability reductions, particularly for clay fractions less than 20%. A numerical simulation of surfactant transport that incorporates the effective clay fraction model demonstrates that induced permeability reductions significantly influence the transport of surfactant through an aquifer.

  5. Solution behavior of surfactants. Vol. 1

    SciTech Connect

    Mittal, K.L.; Fendler, E.J.

    1983-01-01

    This three-volume set constitutes the proceedings of the 4th International Symposium on Surfactants in Solution held in Sweden in 1982. Volume 1 considers phase behavior and phase equilibria in surfactant solutions (e.g., thermodynamics of partially miscible micelles and liquid crystals; multi-method characterization of micelles; the surfactant-block model of micelle structure). Volume 2 considers thermodynamic and kinetic aspects of micellization (computation of the micelle-size distribution; salt-induced sphere-rod transition of ionic micelles; micellar effects on kinetics and equilibria of electron transfer reactions). Volume 3 considers reverse micelles, microemulsions and reactions in microemulsions. Topics covered include solubilization, surfactants in analytical chemistry, the adsorption and binding of surfactants, the polymerization of organized surfactant assemblies, light scattering by liquid surfaces, and vesicles.

  6. Marine Synechococcus Aggregation

    NASA Astrophysics Data System (ADS)

    Neuer, S.; Deng, W.; Cruz, B. N.; Monks, L.

    2016-02-01

    Cyanobacteria are considered to play an important role in the oceanic biological carbon pump, especially in oligotrophic regions. But as single cells are too small to sink, their carbon export has to be mediated by aggregate formation and possible consumption by zooplankton producing sinking fecal pellets. Here we report results on the aggregation of the ubiquitous marine pico-cyanobacterium Synechococcus as a model organism. We first investigated the mechanism behind such aggregation by studying the potential role of transparent exopolymeric particles (TEP) and the effects of nutrient (nitrogen or phosphorus) limitation on the TEP production and aggregate formation of these pico-cyanobacteria. We further studied the aggregation and subsequent settling in roller tanks and investigated the effects of the clays kaolinite and bentonite in a series of concentrations. Our results show that despite of the lowered growth rates, Synechococcus in nutrient limited cultures had larger cell-normalized TEP production, formed a greater volume of aggregates, and resulted in higher settling velocities compared to results from replete cultures. In addition, we found that despite their small size and lack of natural ballasting minerals, Synechococcus cells could still form aggregates and sink at measureable velocities in seawater. Clay minerals increased the number and reduced the size of aggregates, and their ballasting effects increased the sinking velocity and carbon export potential of aggregates. In comparison with the Synechococcus, we will also present results of the aggregation of the pico-cyanobacterium Prochlorococcus in roller tanks. These results contribute to our understanding in the physiology of marine Synechococcus as well as their role in the ecology and biogeochemistry in oligotrophic oceans.

  7. Effect of Fluorocarbon and Hydrocarbon Chain Lengths in Hybrid Surfactants for Supercritical CO2.

    PubMed

    Sagisaka, Masanobu; Ono, Shinji; James, Craig; Yoshizawa, Atsushi; Mohamed, Azmi; Guittard, Frédéric; Rogers, Sarah E; Heenan, Richard K; Yan, Ci; Eastoe, Julian

    2015-07-14

    Hybrid surfactants containing both fluorocarbon (FC) and hydrocarbon (HC) chains have recently been shown to solubilize water and form elongated reversed micelles in supercritical CO2. To clarify the most effective FC and HC chain lengths, the aggregation behavior and interfacial properties of hybrid surfactants FCm-HCn (FC length m/HC length n = 4/2, 4/4, 6/2, 6/4, 6/5, 6/6, and 6/8) were examined in W/CO2 mixtures as functions of pressure, temperature, and water-to-surfactant molar ratio (W0). The solubilizing power of hybrid surfactants for W/CO2 microemulsions was strongly affected by not only the FC length but also by that of the HC. Although the surfactants having short FC and/or HC tails (namely, m/n = 4/2, 4/4, and 6/2) did not dissolve in supercritical CO2 (even at ∼17 mM, ≤400 bar, temperature ≤ 75 °C, and W0 = 0-40), the other hybrid surfactants were able to yield transparent single-phase W/CO2 mixtures identified as microemulsions. The solubilizing power of FC6-HCm surfactants reached a maximum (W0 ∼ 80 at 45 °C and 350 bar) with a hydrocarbon length, m, of 4. The W0 value of 80 is the highest for a HC-FC hybrid surfactant, matching the highest value reported for a FC surfactant which contained more FC groups. High-pressure small-angle neutron scattering measurements from FCm-HCn/D2O/CO2 microemulsions were consistent with growth of the microemulsion droplets with increasing W0. In addition, not only spherical reversed micelles but also nonspherical assemblies (rodlike or ellipsoidal) were found for the systems with FC6-HCn (n = 4-6). At fixed surfactant concentration and W0 (17 mM and W0 = 20), the longest reversed micelles were obtained for FC6-HC6 where a mean aspect ratio of 6.3 was calculated for the aqueous cores.

  8. Surfactant Therapy of ALI and ARDS

    PubMed Central

    Raghavendran, K; Willson, D; Notter, RH

    2011-01-01

    This article examines exogenous lung surfactant replacement therapy and its utility in mitigating clinical acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Biophysical research has documented that lung surfactant dysfunction can be reversed or mitigated by increasing surfactant concentration, and multiple studies in animals with ALI/ARDS have shown that respiratory function and pulmonary mechanics in vivo can be improved by exogenous surfactant administration. Exogenous surfactant therapy is a routine intervention in neonatal intensive care, and is life-saving in preventing or treating the neonatal respiratory distress syndrome (NRDS) in premature infants. In applications relevant for lung injury-related respiratory failure and ALI/ARDS, surfactant therapy has been shown to be beneficial in term infants with pneumonia and meconium aspiration lung injury, and in children up to age 21 with direct pulmonary forms of ALI/ARDS. However, extension of exogenous surfactant therapy to adults with respiratory failure and clinical ALI/ARDS remains a challenge. Coverage here reviews clinical studies of surfactant therapy in pediatric and adult patients with ALI/ARDS, particularly focusing on its potential advantages in patients with direct pulmonary forms of these syndromes. Also discussed is the rationale for mechanism-based therapies utilizing exogenous surfactant in combination with agents targeting other aspects of the multifaceted pathophysiology of inflammatory lung injury. Additional factors affecting the efficacy of exogenous surfactant therapy in ALI/ARDS are also described, including the difficulty of effectively delivering surfactants to injured lungs and the existence of activity differences between clinical surfactant drugs. PMID:21742216

  9. Imaging Extrasolar Giant Planets

    NASA Astrophysics Data System (ADS)

    Bowler, Brendan P.

    2016-10-01

    High-contrast adaptive optics (AO) imaging is a powerful technique to probe the architectures of planetary systems from the outside-in and survey the atmospheres of self-luminous giant planets. Direct imaging has rapidly matured over the past decade and especially the last few years with the advent of high-order AO systems, dedicated planet-finding instruments with specialized coronagraphs, and innovative observing and post-processing strategies to suppress speckle noise. This review summarizes recent progress in high-contrast imaging with particular emphasis on observational results, discoveries near and below the deuterium-burning limit, and a practical overview of large-scale surveys and dedicated instruments. I conclude with a statistical meta-analysis of deep imaging surveys in the literature. Based on observations of 384 unique and single young (≈5-300 Myr) stars spanning stellar masses between 0.1 and 3.0 M ⊙, the overall occurrence rate of 5-13 M Jup companions at orbital distances of 30-300 au is {0.6}-0.5+0.7 % assuming hot-start evolutionary models. The most massive giant planets regularly accessible to direct imaging are about as rare as hot Jupiters are around Sun-like stars. Dividing this sample into individual stellar mass bins does not reveal any statistically significant trend in planet frequency with host mass: giant planets are found around {2.8}-2.3+3.7 % of BA stars, <4.1% of FGK stars, and <3.9% of M dwarfs. Looking forward, extreme AO systems and the next generation of ground- and space-based telescopes with smaller inner working angles and deeper detection limits will increase the pace of discovery to ultimately map the demographics, composition, evolution, and origin of planets spanning a broad range of masses and ages.

  10. Giant left ventricular pseudoaneurysm.

    PubMed

    Prakash, Sumi; Garg, Nadish; Xie, Gong-Yuan; Dellsperger, Kevin C

    2010-01-01

    Left ventricular (LV) pseudoaneurysm (PS) is an uncommon, often fatal complication associated with myocardial infarction, cardiothoracic surgery, trauma, and, rarely, infective endocarditis. A 28-year-old man with prior history of bioprosthetic mitral valve replacement presented with congestive heart failure and bacteremia with Abiotrophia granulitica. Transesophageal echocardiogram showed bioprosthesis dysfunction, large vegetations, mitral regurgitation, and probable PS. Cardiac and chest CT confirmed a PS communicating with the left ventricle Patient had pulseless electrical activity and died. Autopsy showed a giant PS with layered thrombus and pseudo-endothelialized cavity. Our case highlights the importance of multimodality imaging as an important tool in management of PS.

  11. Giant mesenteric cyst

    PubMed Central

    Guraya, Salman Yousuf; Salman, Shaista; Almaramhy, Hamdi H.

    2011-01-01

    Mesenteric cysts are uncommon benign abdominal lesions with no classical clinical features. The preoperative diagnosis requires the common imaging modalities but the final diagnosis is established only during surgery or histological analysis. The treatment of choice is complete surgical excision. We report an 18-year-old female with a non-specific abdominal pain and discomfort since 3 weeks. Her CT scan showed a huge cystic swelling, which necessitated surgical exploration. Preoperatively, a giant cyst was encountered with displacement of bowel loops. The cyst was completely removed and histology report confirmed mesenteric cyst without evidence of malignancy. PMID:24765349

  12. Giant mesenteric cyst.

    PubMed

    Guraya, Salman Yousuf; Salman, Shaista; Almaramhy, Hamdi H

    2011-09-28

    Mesenteric cysts are uncommon benign abdominal lesions with no classical clinical features. The preoperative diagnosis requires the common imaging modalities but the final diagnosis is established only during surgery or histological analysis. The treatment of choice is complete surgical excision. We report an 18-year-old female with a non-specific abdominal pain and discomfort since 3 weeks. Her CT scan showed a huge cystic swelling, which necessitated surgical exploration. Preoperatively, a giant cyst was encountered with displacement of bowel loops. The cyst was completely removed and histology report confirmed mesenteric cyst without evidence of malignancy.

  13. A Giant Urethral Calculus.

    PubMed

    Sigdel, G; Agarwal, A; Keshaw, B W

    2014-01-01

    Urethral calculi are rare forms of urolithiasis. Majority of the calculi are migratory from urinary bladder or upper urinary tract. Primary urethral calculi usually occur in presence of urethral stricture or diverticulum. In this article we report a case of a giant posterior urethral calculus measuring 7x3x2 cm in a 47 years old male. Patient presented with acute retention of urine which was preceded by burning micturition and dribbling of urine for one week. The calculus was pushed in to the bladder through the cystoscope and was removed by suprapubic cystolithotomy.

  14. Inhibition of Aflatoxin Production by Surfactants

    PubMed Central

    Rodriguez, Susan B.; Mahoney, Noreen E.

    1994-01-01

    The effect of 12 surfactants on aflatoxin production, growth, and conidial germination by the fungus Aspergillus flavus is reported. Five nonionic surfactants, Triton X-100, Tergitol NP-7, Tergitol NP-10, polyoxyethylene (POE) 10 lauryl ether, and Latron AG-98, reduced aflatoxin production by 96 to 99% at 1% (wt/vol). Colony growth was restricted by the five nonionic surfactants at this concentration. Aflatoxin production was inhibited 31 to 53% by lower concentrations of Triton X-100 (0.001 to 0.0001%) at which colony growth was not affected. Triton X-301, a POE-derived anionic surfactant, had an effect on colony growth and aflatoxin production similar to that of the five POE-derived nonionic surfactants. Sodium dodecyl sulfate (SDS), an anionic surfactant, and dodecyltrimethylammonium bromide, a cationic surfactant, suppressed conidial germination at 1% (wt/vol). SDS had no effect on aflatoxin production or colony growth at 0.001%. The degree of aflatoxin inhibition by a surfactant appears to be a function of the length of the hydrophobic and hydrophilic chains of POE-derived surfactants. Images PMID:16349144

  15. Remediation using trace element humate surfactant

    DOEpatents

    Riddle, Catherine Lynn; Taylor, Steven Cheney; Bruhn, Debra Fox

    2016-08-30

    A method of remediation at a remediation site having one or more undesirable conditions in which one or more soil characteristics, preferably soil pH and/or elemental concentrations, are measured at a remediation site. A trace element humate surfactant composition is prepared comprising a humate solution, element solution and at least one surfactant. The prepared trace element humate surfactant composition is then dispensed onto the remediation site whereby the trace element humate surfactant composition will reduce the amount of undesirable compounds by promoting growth of native species activity. By promoting native species activity, remediation occurs quickly and environmental impact is minimal.

  16. Biophysical inhibition of pulmonary surfactant function by polymeric nanoparticles: role of surfactant protein B and C.

    PubMed

    Beck-Broichsitter, Moritz; Ruppert, Clemens; Schmehl, Thomas; Günther, Andreas; Seeger, Werner

    2014-11-01

    The current study investigated the mechanisms involved in the process of biophysical inhibition of pulmonary surfactant by polymeric nanoparticles (NP). The minimal surface tension of diverse synthetic surfactants was monitored in the presence of bare and surface-decorated (i.e. poloxamer 407) sub-100 nm poly(lactide) NP. Moreover, the influence of NP on surfactant composition (i.e. surfactant protein (SP) content) was studied. Dose-elevations of SP advanced the biophysical activity of the tested surfactant preparation. Surfactant-associated protein C supplemented phospholipid mixtures (PLM-C) were shown to be more susceptible to biophysical inactivation by bare NP than phospholipid mixture supplemented with surfactant protein B (PLM-B) and PLM-B/C. Surfactant function was hindered owing to a drastic depletion of the SP content upon contact with bare NP. By contrast, surface-modified NP were capable of circumventing unwanted surfactant inhibition. Surfactant constitution influences the extent of biophysical inhibition by polymeric NP. Steric shielding of the NP surface minimizes unwanted NP-surfactant interactions, which represents an option for the development of surfactant-compatible nanomedicines. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  17. Study of the interactions between poly(ethylene oxide) and anionic surfactants in elongational flow

    NASA Astrophysics Data System (ADS)

    Smitter, Luis Manuel

    2001-07-01

    The rheology of polymer solutions is important in a wide variety of applications. In particular, solutions of high-molecular-weight, flexible polymers exhibit an increase in their apparent extensional viscosity with strain rate under extensional flow conditions. This extension thickening is due to formation of transient entanglements of polymer molecules. Certain commercial fluids contain both polymers and surfactants that might interact at the molecular level. These interactions affect the conformation of the polymer chain and, therefore, the rheological behavior of the solution. For instance, addition of anionic surfactants to solutions of nonionic polymers is known to induce increases in the shear viscosity of aqueous solution. This work investigates the behavior of aqueous solutions of a high-molecular-weight poly(ethylene oxide) (PEO), a nonionic, flexible polymer, and the anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and a commercial alpha-olefin sulfonate (AOS) in extensional flows. The extensional rheology of polymer/surfactant solutions is studied in an opposed-jets device, which generates a flow field close to uniaxial extension. For PEO/SDS mixtures, the results show that formation of micellar aggregates of SDS along the PEO chains results in an increase in the strength of extension thickening of PEO solutions by promoting intermolecular interactions between polymer chains. The minimum PEO concentration required to form intermolecular entanglements is substantially reduced in the presence of micellar aggregates. In solutions containing NaCl, intramolecular interactions are observed at low PEO concentrations. These reduce the strength of extension thickening. Addition of a co-solvent is investigated. The presence of alcohols in the aqueous solutions affects their rheology by changing the solvent nature for both PEO and SDS. In particular, n-octanol promotes aggregation of SDS along the PEO chains, enhancing

  18. Model calculations of the spontaneous curvature, mean and Gaussian bending constants for a thermodynamically open surfactant film.

    PubMed

    Bergström, L Magnus

    2006-01-01

    The spontaneous curvature (H(0)), mean and Gaussian bending constants (k(c) and k (c)), as defined in the well-known Helfrich expression, have been calculated from a detailed model for a thermodynamically open surfactant layer. The effect of head group cross-section area, surfactant tail length and electrolyte concentration for monovalent ionic surfactants have been investigated. Geometrical packing constraints subjected to the aggregated hydrocarbon tails and electrostatics are found to be the dominant contributions to H(0), k(c) and k (c). In addition, the transition from spherocylindrical micelles to vesicles were investigated in terms of the three parameters and the following simple expressions were derived as criteria for coexistence between micelles and vesicles H(0)=1/4 xi and N(ves)/N(mic)=exp[4 pi(k(c)+k (c))/kT], where xi is the thickness of the hydrocarbon part of the film and N(mic) and N(ves) the average aggregation numbers of micelles and vesicles, respectively. However, it is found that the ratio N(ves)/N(mic) is order of magnitudes too large for vesicles to form at all in charged single-surfactant systems where the surfactant head is of moderate size.

  19. Charged Dust Aggregate Interactions

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  20. An electronic spectroscopic study of micellisation of surfactants and solvation of homomicelles formed by cationic or anionic surfactants using a solvatochromic electron donor acceptor dye

    NASA Astrophysics Data System (ADS)

    Kedia, Niraja; Sarkar, Amrita; Purkayastha, Pradipta; Bagchi, Sanjib

    2014-10-01

    Solvatochromic absorption and fluorescence bands of a donor-acceptor dye have been utilised for following the micellisation and for probing the polarity of the aqueous homomicellar phase provided separately by cationic (cetyltrimethylammonimum bromide, CTAB and dodecyltrimethylammonimum bromide, DTAB) and anionic (sodium dodecyl sulphate, SDS) surfactant. Results indicate that for a low concentration of surfactant (below cmc) the dye forms a dimer in aqueous solution. In a micellar media, however, the dye exists as monomers. A strong dye-micelle interaction, as indicated by the shift of the solvatochromic intramolecular charge transfer band of the dye, has also been indicated. The absorption and fluorescence parameters of the dye have been utilised for studying the onset of aggregation of the surfactants. An iterative procedure has been developed for the estimation of cmc and the distribution coefficient (KD) of the dye between the aqueous and the micellar phase. All the parameters provide convergent values of cmc. A high value of KD indicates that the dye exists predominantly in the micellar phase. The solvatochromic parameters characterising the dipolarity-polarisability (π*) and H-bond donation ability (α) of modes of solvation interaction in different micellar media have been estimated. The dye is found to distribute itself between two regions in a catanionic vesicle formed by surfactants SDS and DTAB, one being relatively polar than other. The distribution coefficients have been found out using the fluorescence data.

  1. An electronic spectroscopic study of micellisation of surfactants and solvation of homomicelles formed by cationic or anionic surfactants using a solvatochromic electron donor acceptor dye.

    PubMed

    Kedia, Niraja; Sarkar, Amrita; Purkayastha, Pradipta; Bagchi, Sanjib

    2014-10-15

    Solvatochromic absorption and fluorescence bands of a donor-acceptor dye have been utilised for following the micellisation and for probing the polarity of the aqueous homomicellar phase provided separately by cationic (cetyltrimethylammonimum bromide, CTAB and dodecyltrimethylammonimum bromide, DTAB) and anionic (sodium dodecyl sulphate, SDS) surfactant. Results indicate that for a low concentration of surfactant (below cmc) the dye forms a dimer in aqueous solution. In a micellar media, however, the dye exists as monomers. A strong dye-micelle interaction, as indicated by the shift of the solvatochromic intramolecular charge transfer band of the dye, has also been indicated. The absorption and fluorescence parameters of the dye have been utilised for studying the onset of aggregation of the surfactants. An iterative procedure has been developed for the estimation of cmc and the distribution coefficient (KD) of the dye between the aqueous and the micellar phase. All the parameters provide convergent values of cmc. A high value of KD indicates that the dye exists predominantly in the micellar phase. The solvatochromic parameters characterising the dipolarity-polarisability (π(*)) and H-bond donation ability (α) of modes of solvation interaction in different micellar media have been estimated. The dye is found to distribute itself between two regions in a catanionic vesicle formed by surfactants SDS and DTAB, one being relatively polar than other. The distribution coefficients have been found out using the fluorescence data.

  2. Giant extragenital Bowen's disease.

    PubMed

    Bakardzhiev, Ilko; Chokoeva, Anastasiya Atanasova; Tchernev, Georgi

    2015-12-01

    Giant extragenital forms of Morbus Bowen are extremely rare. The already described cases in the word literature are most commonly with periungual localization, as well as located on the foot and neck area. The clinical manifestation is presented most commonly by non-specific erythematous to erythematous-squamous plaques or papules, which is confusing to the clinician. From the pathogenic point of view, it is important to be confirmed or rejected the presence of human papilloma viruses (HPVs) in each case of affected patient, as this information is mandatory in respect to the adequate selection of the subsequent regimen. If HPVs are detected, systemic antiviral therapy could be initiated to reduce the size of the lesions before subsequent surgical eradication. A postoperative prevention through vaccination could be also considered additionally. In cases of HPV-negative giant extragenital forms of Morbus Bowen (as in the described patient), the focus should be on local immunomodulation by substances such as imiquimod, which reduce the size of the lesions, thereby creating optimal opportunities for their future surgical eradication. Other possible options described in the literature include topical application of 5-fluorouracil, photodynamic therapy, cryotherapy, and laser therapy (carbon dioxide laser). The choice of the most appropriate regimen should have been an individual decision of the clinician, considering also the location and the extent of the lesion.

  3. Gas Giants Form Quickly

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This is an artist's concept of a hypothetical 10-million-year-old star system. The bright blur at the center is a star much like our sun. The other orb in the image is a gas-giant planet like Jupiter. Wisps of white throughout the image represent traces of gas.

    Astronomers using NASA's Spitzer Space Telescope have found evidence showing that gas-giant planets either form within the first 10 million years of a sun-like star's life, or not at all. The lifespan for sun-like stars is about 10 billion years.

    The scientists came to this conclusion after searching for traces of gas around 15 different sun-like stars, most with ages ranging from 3 million to 30 million years. With the help of Spitzer's Infrared Spectrometer instrument, they were able to search for relatively warm gas in the inner regions of these star systems, an area comparable to the zone between Earth and Jupiter in our own solar system. They also used ground-based radio telescopes to search for cooler gas in the outer regions of these systems, an area comparable to the zone around Saturn and beyond.

  4. Giant papillary conjunctivitis.

    PubMed Central

    Donshik, P C

    1994-01-01

    Giant papillary conjunctivitis is a syndrome found frequently as a complication of contact lenses. Many variables can affect the onset and severity of the presenting signs and symptoms. Rigid gas permeable contact lenses appear to result in less severe signs and symptoms, with a longer time before the development of giant papillary conjunctivitis. Nonionic, low-water-content soft contact lenses tend to produce less severe signs and symptoms than ionic, low-water-content soft contact lenses. Enzymatic treatment appears to lessen the severity of signs and symptoms. The association of an allergy appears to play a role in the onset of the severity of the signs and symptoms but does not appear to affect the final ability of the individual to wear contact lenses. Using multiple treatment options, such as changing the polymer to a glyceryl methyl methacrylate or a rigid lens, or utilizing a soft lens on a frequent-replacement basis, can result in a success rate of over 90%. In individuals who still have a return of symptoms, the use of topical mast cell stabilizers or a nonsteroidal anti-inflammatory drug as an adjunctive therapy offers the added possibility of keeping these patients in contact lenses. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 11 A FIGURE 11 B FIGURE 11 C FIGURE 11 D PMID:7886881

  5. Gas Giants Form Quickly

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This is an artist's concept of a hypothetical 10-million-year-old star system. The bright blur at the center is a star much like our sun. The other orb in the image is a gas-giant planet like Jupiter. Wisps of white throughout the image represent traces of gas.

    Astronomers using NASA's Spitzer Space Telescope have found evidence showing that gas-giant planets either form within the first 10 million years of a sun-like star's life, or not at all. The lifespan for sun-like stars is about 10 billion years.

    The scientists came to this conclusion after searching for traces of gas around 15 different sun-like stars, most with ages ranging from 3 million to 30 million years. With the help of Spitzer's Infrared Spectrometer instrument, they were able to search for relatively warm gas in the inner regions of these star systems, an area comparable to the zone between Earth and Jupiter in our own solar system. They also used ground-based radio telescopes to search for cooler gas in the outer regions of these systems, an area comparable to the zone around Saturn and beyond.

  6. Giant Intradiverticular Bladder Tumor

    PubMed Central

    Noh, Mohamad Syafeeq Faeez Md; Aziz, Ahmad Fuad Abdul; Ghani, Khairul Asri Mohd; Siang, Christopher Lee Kheng; Yunus, Rosna; Yusof, Mubarak Mohd

    2017-01-01

    Patient: Male, 74 Final Diagnosis: Giant intradiverticular bladder tumor with metastasis Symptoms: Hematuria Medication:— Clinical Procedure: — Specialty: Urology Objective: Rare disease Background: Intradiverticular bladder tumors are rare. This renders diagnosis of an intradiverticular bladder tumor difficult. Imaging plays a vital role in achieving the diagnosis, and subsequently staging of the disease. Case Report: A 74-year-old male presented to our center with a few months history of constitutional symptoms. Upon further history, he reported hematuria two months prior to presentation, which stopped temporarily, only to recur a few days prior to coming to the hospital. The patient admitted to having lower urinary tract symptoms. However, there was no dysuria, no sandy urine, and no fever. Palpation of his abdomen revealed a vague mass at the suprapubic region, which was non tender. In view of his history and the clinical examination findings, an ultrasound of the abdomen and computed tomography (CT) was arranged. These investigations revealed a giant tumor that seemed to be arising from a bladder diverticulum, with a mass effect and hydronephrosis. He later underwent operative intervention. Conclusions: Intradiverticular bladder tumors may present a challenge to the treating physician in an atypical presentation; thus requiring a high index of suspicion and knowledge of tumor pathophysiology. As illustrated in our case, CT with its wide availability and multiplanar imaging capabilities offers a useful means for diagnosis, disease staging, operative planning, and follow-up. PMID:28246375

  7. Wormlike micelles in mixed amino acid surfactant/nonionic surfactant aqueous systems and the effect of added electrolytes.

    PubMed

    Shrestha, Rekha Goswami; Rodriguez-Abreu, Carlos; Aramaki, Kenji

    2009-01-01

    The formation of viscoelastic wormlike micelles in mixed amino acid surfactant/nonionic surfactant aqueous systems in the presence of different counterions and salts is reported, and the effects of the different electrolytes on the rheological behavior are discussed. N-dodecanoylglutamic acid (LAD) is neutralized with biologically relevant L-lysine and L-arginine to obtain anionic surfactants (LAD-Lys2, LAD-Arg2) which form aqueous micellar solutions at 25 degrees C. Addition of a nonionic surfactant, tri-ethyleneglycol mono n-tetradecyl ether (C14EO3), to the aqueous solutions of both LAD-Lys2 and LAD-Arg2 causes the zero-shear viscosity (eta(0)) to increase with C14EO3 concentration gradually at first, and then sharply, indicating one-dimensional growth of the aggregates and eventual formation of entangled wormlike micelles. Further addition of C14EO3 ultimately leads to phase separation of liquid crystals. Such a phase separation, which limits the maximum attainable viscosity, takes place at lower C14EO3 concentrations for LAD-Lys2 compared to LAD-Arg2 systems. It was found that the rheological behavior of micellar solutions is significantly affected by the addition of Na+X(-) salts (X = Cl(-), Br(-), I(-), NO3(-)). The maximum viscosities obtained for the systems with added salt are all higher than that of the salt-free system, and the onset of wormlike micelle formation shift towards lower nonionic surfactant concentrations upon addition of electrolyte. The maximum attainable thickening effect of anions increases in the order NO3(-)>I(-)>Br(-)>Cl(-). The effect of temperature was also investigated. Phase separation takes place at certain temperature, which depends on the type of anion in the added salt, and decreases in the order I(-)>NO3(-)>Br(-) approximately equal Cl(-), in agreement with Hofmeister's series in terms of amphiphile solubility. The thermoresponsive rheological behavior was also found to be highly dependent on the type of anion, and anomalous

  8. Aggregate and the environment

    USGS Publications Warehouse

    Langer, William H.; Drew, Lawrence J.; Sachs, J.S.

    2004-01-01

    This book is designed to help you understand our aggregate resources-their importance, where they come from, how they are processed for our use, the environmental concerns related to their mining and processing, how those concerns are addressed, and the policies and regulations designed to safeguard workers, neighbors, and the environment from the negative impacts of aggregate mining. We hope this understanding will help prepare you to be involved in decisions that need to be made-individually and as a society-to be good stewards of our aggregate resources and our living planet.

  9. Specific ion effects on the self-assembly of ionic surfactants: a molecular thermodynamic theory of micellization with dispersion forces.

    PubMed

    Lukanov, Boris; Firoozabadi, Abbas

    2014-06-10

    The self-assembly of amphiphilic molecules is a key process in numerous biological and chemical systems. When salts are present, the formation and properties of molecular aggregates can be altered dramatically by the specific types of ions in the electrolyte solution. We present a molecular thermodynamic model for the micellization of ionic surfactants that incorporates quantum dispersion forces to account for specific ion effects explicitly through ionic polarizabilities and sizes. We assume that counterions are distributed in the diffuse region according to a modified Poisson-Boltzmann equation and can reach all the way to the micelle surface of charge. Stern layers of steric exclusion or distances of closest approach are not imposed externally; these are accounted for through the counterion radial distribution profiles due to the incorporation of dispersion potentials, resulting in a simple and straightforward treatment. There are no adjustable or fitted parameters in the model, which allows for a priori quantitative prediction of surfactant aggregation behavior based only on the initial composition of the system and the surfactant molecular structure. The theory is validated by accurately predicting the critical micelle concentration (CMC) for the well-studied sodium dodecyl sulfate (SDS) surfactant and its alkaline-counterion derivatives in mono- and divalent salts, as well as the molecular structure parameters of SDS micelles such as aggregation numbers and micelle surface potential.

  10. Fluorescence spectroscopy as a specific tool for the interaction study of two surfactants with natural and synthetic organic compounds

    NASA Astrophysics Data System (ADS)

    Jung, Aude-Valérie; Frochot, Céline; Bersillon, Jean-Luc

    2016-04-01

    Four different techniques were used to study the binding of cationic cetyltrimethylammonium bromide (CTAB) and non-ionic nonylphenylethoxyl (NPE) surfactants to three synthetic organic components that mimic humic-like aggregates and to two natural aggregated humic substances (HS) extracted from aquatic suspended matter. The composition of synthetic organic components were chosen to be similar to high molecular weight highly processed terrigenous HS and low and high molecular weight less processed terrigenous (or aquatic terrigenous) HS. The natural HS were extracted under two different meteorological conditions (rainy and dry periods). No significant interaction between the non-ionic surfactant and any of the studied compounds was found. Concerning CTAB; pH, conductivity and turbidity measurements, along with fluorescence spectroscopy were combined to provide a better understanding of interactions between organic aggregates and the surfactant. The spectroscopic data show that a "highly processed terrigenous HS" fluorophore interacts in a different way with the cationic surfactant than an "aquatic terrigenous (or less processed terrigenous) HS" fluorophore does. Under similar conditions, some spectral changes in the fluorescence signal are correlated to changes in non-specific physical-chemical parameters (pH, turbidity, conductivity) for the organic compounds tested. The complexation mechanism is essentially governed by charge neutralization, which can be monitored specifically by the fluorescence of the organic moieties.

  11. Chest position and pulmonary deposition of surfactant in surfactant depleted rabbits.

    PubMed Central

    Broadbent, R.; Fok, T. F.; Dolovich, M.; Watts, J.; Coates, G.; Bowen, B.; Kirpalani, H.

    1995-01-01

    AIMS--To investigate the correlation between chest position and the distribution of surfactant in the lungs of surfactant depleted rabbits, to corroborate current guidelines on the intratracheal instillation of exogenous surfactant in newborns. METHODS--Twelve tracheotomised rabbits, depleted of pulmonary surfactant by saline bronchoalveolar lavage, were given intratracheal 99m Technetium labelled Exosurf in three positions (prone, right side down, and left side down) (n = 4 in each group). They were monitored for 10 minutes using dynamic gamma scintigraphy monitoring. Instillation completed, the lateral lying animals were turned to the opposite side to determine whether redistribution of the surfactant had taken place. The amount of radiolabelled surfactant deposited at the peripheral, central, dorsal and ventral parts of the lungs was then estimated by gamma counting of the lung sections at necropsy. RESULTS--Both gamma scintigraphy and gamma counting showed similar rates and total amount of surfactant accumulation in both lungs of the prone animals. In the lateral lying animals surfactant accumulated at a significantly faster rate in the dependent lungs: the amount of surfactant deposition was three to 14-fold that in the raised lungs (p = 0.017; nested ANOVA). Changing the chest position immediately after instillation did not redistribute the surfactant. In all three groups of animals there was no significant difference in deposition between the peripheral, central, ventral and dorsal parts of the lungs. CONCLUSIONS--Pulmonary distribution of intratracheally instilled surfactant is largely determined by gravity, and changing the chest position after instillation does not result in any redistribution of the surfactant. During the instillation of exogenous surfactant to newborn infants, keeping the chest in the horizontal position may therefore result in the most even distribution of the surfactant in the two lungs. Further deposition studies are required to

  12. Reinflating Giant Planets

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-01-01

    Two new, large gas-giant exoplanets have been discovered orbiting close to their host stars. A recent study examining these planets and others like them may help us to better understand what happens to close-in hot Jupiters as their host stars reach the end of their main-sequence lives.OversizedGiantsUnbinned transit light curves for HAT-P-65b. [Adapted from Hartman et al. 2016]The discovery of HAT-P-65b and HAT-P-66b, two new transiting hot Jupiters, is intriguing. These planets have periods of just under 3 days and masses of roughly 0.5 and 0.8 times that of Jupiter, but their sizes are whats really interesting: they have inflated radii of 1.89 and 1.59 times that of Jupiter.These two planets, discovered using the Hungarian-made Automated Telescope Network (HATNet) in Arizona and Hawaii, mark the latest in an ever-growing sample of gas-giant exoplanets with radii larger than expected based on theoretical planetary structure models.What causes this discrepancy? Did the planets just fail to contract to the expected size when they were initially formed, or were they reinflated later in their lifetimes? If the latter, how? These are questions that scientists are only now starting to be able to address using statistics of the sample of close-in, transiting planets.Unbinned transit light curves for HAT-P-66b. [Hartman et al. 2016]Exploring Other PlanetsLed by Joel Hartman (Princeton University), the team that discovered HAT-P-65b and HAT-P-66b has examined these planets observed parameters and those of dozens of other known close-in, transiting exoplanets discovered with a variety of transiting exoplanet missions: HAT, WASP, Kepler, TrES, and KELT. Hartman and collaborators used this sample to draw conclusions about what causes some of these planets to have such large radii.The team found that there is a statistically significant correlation between the radii of close-in giant planets and the fractional ages of their host stars (i.e., the stars age divided by its full

  13. Pulmonary surfactant protein A interacts with gel-like regions in monolayers of pulmonary surfactant lipid extract.

    PubMed Central

    Worthman, L A; Nag, K; Rich, N; Ruano, M L; Casals, C; Pérez-Gil, J; Keough, K M

    2000-01-01

    Epifluorescence microscopy was used to investigate the interaction of pulmonary surfactant protein A (SP-A) with spread monolayers of porcine surfactant lipid extract (PSLE) containing 1 mol % fluorescent probe (NBD-PC) spread on a saline subphase (145 mM NaCl, 5 mM Tris-HCl, pH 6.9) containing 0, 0.13, or 0.16 microg/ml SP-A and 0, 1.64, or 5 mM CaCl(2). In the absence of SP-A, no differences were noted in PSLE monolayers in the absence or presence of Ca(2+). Circular probe-excluded (dark) domains were observed against a fluorescent background at low surface pressures (pi approximately 5 mN/m) and the domains grew in size with increasing pi. Above 25 mN/m, the domain size decreased with increasing pi. The amount of observable dark phase was maximal at 18% of the total film area at pi approximately 25 mN/m, then decreased to approximately 3% at pi approximately 40 mN/m. The addition of 0.16 microg/ml SP-A with 0 or 1.64 mM Ca(2+) in the subphase caused an aggregation of dark domains into a loose network, and the total amount of dark phase was increased to approximately 25% between pi of 10-28 mN/m. Monolayer features in the presence of 5 mM Ca(2+) and SP-A were not substantially different from those spread in the absence of SP-A, likely due to a self-association and aggregation of SP-A in the presence of higher concentrations of Ca(2+). PSLE films were spread on a subphase containing 0.16 microg/ml SP-A with covalently bound Texas Red (TR-SP-A). In the absence of Ca(2+), TR-SP-A associated with the reorganized dark phase (as seen with the lipid probe). The presence of 5 mM Ca(2+) resulted in an appearance of TR-SP-A in the fluid phase and of aggregates at the fluid/gel phase boundaries of the monolayers. This study suggests that SP-A associates with PSLE monolayers, particularly with condensed or solid phase lipid, and results in some reorganization of rigid phase lipid in surfactant monolayers. PMID:11053138

  14. Allometry indicates giant eyes of giant squid are not exceptional.

    PubMed

    Schmitz, Lars; Motani, Ryosuke; Oufiero, Christopher E; Martin, Christopher H; McGee, Matthew D; Gamarra, Ashlee R; Lee, Johanna J; Wainwright, Peter C

    2013-02-18

    The eyes of giant and colossal squid are among the largest eyes in the history of life. It was recently proposed that sperm whale predation is the main driver of eye size evolution in giant squid, on the basis of an optical model that suggested optimal performance in detecting large luminous visual targets such as whales in the deep sea. However, it is poorly understood how the eye size of giant and colossal squid compares to that of other aquatic organisms when scaling effects are considered. We performed a large-scale com