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Surfactant Micelles (surfactant + micelle)
Selected AbstractsComparison of synthetic surfactants and biosurfactants in enhancing biodegradation of polycyclic aromatic hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003Randhir S. Makkar Abstract Polycyclic aromatic hydrocarbon (PAH) contamination of the environment represents a serious threat to the health of humans and ecosystems. Given the human health effects of PAHs, effective and cost-competitive remediation technologies are required. Bioremediation has shown promise as a potentially effective and low-cost treatment option, but concerns about the slow process rate and bioavailability limitations have hampered more widespread use of this technology. An option to enhance the bioavailability of PAHs is to add surfactants directly to soil in situ or ex situ in bioreactors. Surfactants increase the apparent solubility and desorption rate of the PAH to the aqueous phase. However, the results with some synthetic surfactants have shown that surfactant addition can actually inhibit PAH biodegradation via toxic interactions, stimulation of surfactant degraders, or sequestration of PAHs into surfactant micelles. Biosurfactants have been shown to have many of the positive effects of synthetic surfactants but without the drawbacks. They are biodegradable and nontoxic, and many biosurfactants do not produce true micelles, thus facilitating direct transfer of the surfactant-associated PAH to bacteria. The results with biosurfactants to date are promising, but further research to elucidate surfactant,PAH interactions in aqueous environments is needed to lead to predictive, mechanistic models of biosurfactant-enhanced PAH bioavailability and thus better bioremediation design. [source] Effect of surfactant micelles on the kinetics of oxidation of D -fructose by cerium(IV) in sulfuric acid mediumINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2006Kabir-ud-Din Kinetics of the oxidation of D -fructose by cerium(IV) has been investigated both in the absence and presence of surfactants (cetyltrimethylammonium bromide, CTAB, and sodium dodecyl sulfate, SDS) in sulfuric acid medium. The reaction exhibits first-order kinetics each in [cerium(IV)] and [D -fructose] and inverse first order in [H2SO4]. The Arrhenius equation is found to be valid for the reaction between 30,50°C. A detailed mechanism with the associated reaction kinetics is presented and discussed. While SDS has no effect, CTAB increases the reaction rate with the same kinetic behavior in its presence. The catalytic role of CTAB micelles is discussed in terms of the pseudophase model proposed by Menger and Portnoy. The association constant Ks that equals to 286 mol,1 dm3 is found for the association of cerium(IV) with the positive head group of CTAB micelles. The effect of inorganic electrolytes (Na2SO4, NaNO3, NaCl) has also been studied and discussed. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 18,25, 2006 [source] Spectral, kinetic, and redox properties of basic fuchsin in homogeneous aqueous and sodium dodecyl sulfate micellar mediaINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2003N. Ramanathan Effect of anionic surfactant on the optical absorption spectra and redox reaction of basic fuchsin, a cationic dye, has been studied. Increase in the absorbance of the dye band at 546 nm with sodium dodecyl sulfate (SDS) is assigned to the incorporation of the dye in the surfactant micelles with critical micellar concentration (CMC) of 7.3 × 10,3 mol dm,3. At low surfactant concentration (<5 × 10,3 mol dm,3) decrease in the absorbance of the dye band at 546 nm is attributed to the formation of a dye,surfactant complex (1:1). The environment, in terms of dielectric constant, experienced by basic fuchsin inside the surfactant micelles has been estimated. The association constant (KA) for the formation of dye,SDS complex and the binding constant (KB) for the micellization of dye are determined. Stopped-flow studies, in the premicellar region, indicated simultaneous depletion of dye absorption and formation of new band at 490 nm with a distinct isosbestic point at 520 nm and the rate constant for this region increased with increasing SDS concentration. The reaction of hydrated electron with the dye and the decay of the semireduced dye are observed to be slowed down in the presence of SDS. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 629,636, 2003 [source] The conformation of fusogenic B18 peptide in surfactant solutions,JOURNAL OF PEPTIDE SCIENCE, Issue 4 2008Sandra Rocha Abstract The interaction of B18 peptide with surfactants has been studied by circular dichroism spectroscopy and fluorescence measurements. B18 is the fusogenic motif of the fertilization sea urchin protein. The peptide forms an ,-helix structure when interacting with positively or negatively charged surfactants below and above the critical micellar concentration (CMC). The ,-helix formation is due to binding of surfactant monomers rather than the formation of surfactant micelles on the peptide. Fluorescence measurements show that the CMC of the negatively charged surfactant increases in the presence of B18, supporting the fact that there is a strong interaction between the peptide and monomers. Nonionic surfactant monomers have no effect on the peptide structure, whereas the micelles induce an ,-helical conformation. In this case the helix stabilization results from the formation of surfactant micelles on the peptide. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd. [source] Study of the solubilization of gliclazide by aqueous micellar solutionsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2003Khouloud A. Alkhamis Abstract It was of interest to increase the solubility of gliclazide in aqueous media. Therefore, solubilization of gliclazide in a variety of surfactants was investigated. Anionic and cationic surfactants exhibited dramatic solubilizing ability for gliclazide, whereas nonionic surfactants showed significantly lower solubilizing ability. It was found that gliclazide solubility increases with increasing the carbon chain length of cationic surfactants and decreases with increasing the carbon chain length of anionic surfactants. The solubilization data were analyzed on the basis of a pseudo-phase model with gliclazide exhibiting moderate partition coefficients into the micellar phase. The possible sites of solubilization of gliclazide in the micelle were examined by studying the effect of NaCl on solubilization and by comparing the absorption spectra of gliclazide in different solvents. The results obtained from these two experiments indicated that gliclazide is solubilized mainly in the inner core of the cationic surfactant micelles and in the outer regions of the anionic surfactant micelles. © 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:839,846, 2003 [source] Controlled drug release from gels using surfactant aggregates: I. Effect of lipophilic interactions for a series of uncharged substancesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2001Mattias Paulsson Abstract Gels are often used for the delivery of drugs because they have rheological properties that will give a long residence time. Most pharmaceutical gels consist of ,99% water and a polymer matrix that will not hinder the release of drugs with a small molecular weight. To fully take advantage of the residence time, it is necessary to have a sustained drug release. In this paper it is suggested that surfactant micelles can be used to control the release from gels. The in vitro release under physiological conditions of five parabens from four different poly(acrylic acid) gels (Carbopol 934, 940, 1342) and one gellan gum (Gelrite) gel was measured using a USP dissolution bath modified for gels, and the diffusion coefficients were calculated. The diffusion coefficient of uncharged parabens was generally lower in gels with lipophilic modifications, such as C1342, and the greatest effect was seen for butylparaben, with a diffusion that was 25% lower than that in C934 (lacking lipophilic modification). Addition of surfactant micelles to gels delayed the release of all the uncharged drugs in all types of gels studied. The slowest release was seen for butylparaben in a lipophilically modified gel with micelles present. The diffusion coefficient in such a system was almost 30 times smaller than that in C934 without micelles. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1216,1225, 2001 [source] Spherical ordered mesoporous silicas and silica monoliths as stationary phases for liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2006Anne Galarneau Abstract Ordered mesoporous silicas such as micelle-templated silicas (MTS) feature unique textural properties in addition to their high surface area (,1000 m2/g): narrow mesopore size distributions and controlled pore connectivity. These characteristics are highly relevant to chromatographic applications for resistance to mass transfer, which has never been studied in chromatography because of the absence of model materials such as MTS. Their synthesis is based on unique self-assembly processes between surfactants and silica. In order to take advantage of the perfectly adjustable texture of MTS in chromatographic applications, their particle morphology has to be tailored at the micrometer scale. We developed a synthesis strategy to control the particle morphology of MTS using the concept of pseudomorphic transformation. Pseudomorphism was recognized in the mineral world to gain a mineral that presents a morphology not related to its crystallographic symmetry group. Pseudomorphic transformations have been applied to amorphous spherical silica particles usually used in chromatography as stationary phases to produce MTS with the same morphology, using alkaline solution to dissolve progressively and locally silica and reprecipitate it around surfactant micelles into ordered MTS structures. Spherical beads of MTS with hexagonal and cubic symmetries have been synthesized and successfully used in HPLC in fast separation processes. MTS with a highly connected structure (cubic symmetry), uniform pores with a diameter larger than 6 nm in the form of particles of 5 ,m could compete with monolithic silica columns. Monolithic columns are receiving strong interest and represent a milestone in the area of fast separation. Their synthesis is a sol-gel process based on phase separation between silica and water, which is assisted by the presence of polymers. The control of the synthesis of monolithic silica has been systematically explored. Because of unresolved yet cladding problems to evaluate the resulting macromonoliths in HPLC, micromonoliths were synthesized into fused-silica capillaries and evaluated by nano-LC and CEC. Only CEC allows to gain high column efficiencies in fast separation processes. Capillary silica monolithic columns represent attractive alternatives for miniaturization processes (lab-on-a chip) using CEC. [source] Pulsed field gradient NMR investigation of solubilization equilibria in amino acid and dipeptide terminated micellar and polymeric surfactant solutionsMAGNETIC RESONANCE IN CHEMISTRY, Issue 12 2002Robin S. Hickok Abstract Pulsed field gradient NMR spectroscopy was used to investigate the association of toluene, chlorobenzene and benzyl alcohol with amino acid and dipeptide terminated polymerized surfactants (PS). The diffusion coefficient for each probe was measured in the presence and absence of the polymers and the mole fraction of bound probe molecules, fb, was calculated. For all solutions investigated, the probes associated more strongly with unpolymerized surfactant micelles than with corresponding PS. For example, the toluene fb values for association with sodium undecanoyl valinate micelles and the PS poly(sodium undecanoyl valinate) were 0.88 and 0.15, respectively. The relatively weak probe,polymer association was attributed to the polarity and fluidity of the polymers' hydrocarbon cores and to the fact that these PS have smaller aggregation numbers than the corresponding unpolymerized surfactant micelles. Copyright © 2002 John Wiley & Sons, Ltd. [source] ,-Sheet aggregation of kisspeptin-10 is stimulated by heparin but inhibited by amphiphilesBIOPOLYMERS, Issue 8 2010Søren B. Nielsen Abstract The murine 10-residue neurohormone kisspeptin (YNWNSFGLRY) is an important regulator of reproductive behavior and gonadotrophin secretion. It is known to form a random coil in solution, but undergoes a structural change in the presence of membranes although the nature of this change is not fully determined. The peptide's conformational versatility raises the question whether it is also able to form ordered aggregates under physiological conditions, which might be relevant as a storage mechanism. Here we show that heparin induces kisspeptin to form ,-sheet rich amyloid aggregates both at neutral (pH 7.0) and slightly acidic (pH 5.2) conditions. Addition of heparin leads to aggregation after a certain lag phase, irrespective of the time of addition of heparin, indicating that heparin is needed to facilitate the formation of fibrillation nuclei. Aggregation is completely inhibited by submicellar concentrations of zwitterionic and anionic surfactants. Unlike previous reports, our NMR data do not indicate persistent structure in the presence of zwitterionic surfactant micelles. Thus kisspeptin can aggregate under physiologically relevant conditions provided heparin is present, but the process is highly sensitive to the presence of amphiphiles, highlighting the very dynamic nature of the peptide conformation and suggesting that kisspeptin aggregation is a biologically regulatable process. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 678,689, 2010. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Use of a whole-cell biosensor to assess the bioavailability enhancement of aromatic hydrocarbon compounds by nonionic surfactantsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2008Angela Keane Abstract The whole-cell bioluminescent biosensor Pseudomonas putida F1G4 (PpF1G4), which contains a chromosomally-based sep-lux transcriptional fusion, was used as a tool for direct measurement of the bioavailability of hydrophobic organic compounds (HOCs) partitioned into surfactant micelles. The increased bioluminescent response of PpF1G4 in micellar solutions (up to 10 times the critical micellar concentration) of Triton X-100 and Brij 35 indicated higher intracellular concentrations of the test compounds, toluene, naphthalene, and phenanthrene, compared to control systems with no surfactants present. In contrast, Brij 30 caused a decrease in the bioluminescent response to the test compounds in single-solute systems, without adversely affecting cell growth. The decrease in bioluminescent response in the presence of Brij 30 did not occur in the presence of multiple HOCs extracted into the surfactant solutions from crude oil and creosote. The effect of the micellar solutions on the toluene biodegradation rate was consistent with the bioluminescent response in single-solute systems. None of the surfactants were toxic to PpF1G4 at the doses employed in this study, and PpF1G4 did not produce a bioluminescent response to the surfactants nor utilize them as growth substrates. TEM images suggest that the surfactants did not rupture the cell membranes. The results demonstrate that for Pseudomonas putida F1, nonionic surfactants such as Triton X-100 and Brij 35, at doses between 2 and 10 CMC, may increase the bioavailability and direct uptake of micellar phase HOCs that are common pollutants at contaminated sites. Biotechnol. Bioeng. 2008;99: 86,98. © 2007 Wiley Periodicals, Inc. [source] The Structure of MetallomicellesCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2004P. C. Griffiths Dr. Abstract The morphology of micelles formed by two novel metallosurfactants has been studied by small-angle neutron scattering (SANS) and small-angle-X-ray scattering (SAXS). The two surfactants both contain a dodecyl chain as the hydrophobic moiety, but differ in the structure of the head group. The surfactants are CuII complexes of monopendant alcohol derivatives of a) the face-capping macrocycle 1,4,7-triazacyclanonane (tacn), and b) an analogue based upon the tetraazamacrocycle 1,4,7,10-tetraazacyclododecane. Here, neutron scattering has been used to study the overall size and shape of the surfactant micelles, in conjunction with X-ray scattering to locate the metal ions. For the 1,4,7,10-tetraazacyclododecane-based surfactant, oblate micelles are observed, which are smaller to the prolate micelles formed by the 1,4,7-triazacyclononane analogue. The X-ray scattering analysis shows that the metal ions are distributed throughout the polar head-group region, rather than at a well-defined radius; this is in good agreement with the SANS-derived dimensions of the micelle. Indeed, the same model for micelle morphology can be used to fit both the SANS and SAXS data. [source] Solubilisation of dyes by surfactant micelles.COLORATION TECHNOLOGY, Issue 6 2004Part 5: Durability of dye fixatives A number of direct and indirect techniques have been used to explore the durability of dye fixatives on laundering with anionic detergent formulations. The most useful technique for quantifying fixative loss was found to be UV spectroscopy but this is not applicable in every case. Overall, it was found that the fixatives examined were durable to six washes in a typical colour-care detergent formulation at 40 °C. It is concluded that a major contribution to dye loss from fixed cloth at low temperature is the displacement by anionic surfactant of dye bound to the fixative. In addition to being more substantive, good quality fixatives may compete more effectively for dye and may physically entrap the dye within the fibre. [source] An investigation into direct dye aggregationCOLORATION TECHNOLOGY, Issue 1 2002M. Ferus-Comelo The aggregation characteristics of the direct dye CI Yellow 162 have been investigated by measuring the optical transmittance at specific temperatures, in the presence and absence of electrolyte and surfactant, using a Hellma quartz immersion probe attached via fibre optical cables to a single-beam Zeiss Specord S 100 spectrophotometer. The experiments indicate that the dye in solution, without electrolyte, was monomolecular at temperatures of 70 °C and higher. The dye solution with electrolyte remained aggregated at temperatures up to 90 °C, a finding contrary to the still widespread assumption that the dyes are monomolecular at elevated temperatures. In the presence of a surfactant the dye appeared to be forming dye,surfactant micelles that were fairly stable even at higher temperatures. [source] | |||||||||||||