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Micellar Solutions (micellar + solution)
Selected AbstractsPronounced Catalytic Effect of a Micellar Solution of Sodium Dodecyl Sulfate (SDS) on the Efficient C-S Bond Formation via an Odorless Thia-Michael Addition Reaction through the in situ Generation of S -Alkylisothiouronium SaltsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2009Habib Firouzabadi Abstract A pronounced catalytic effect of sodium dodecyl sulfate (SDS) was observed on the in situ production of S -alkylisothiouronium salts via the reaction of primary, allyl and benzyl halides with thiourea in SDS droplets .Hydrolysis of the generated S -alkylisothiouronium salts in the palisade layer of the droplets produces the corresponding thiol moieties which are immediately added to the electron-deficient olefins that are present in the micellar core to produce the thia-Michael adducts. The entire route is an almost odorless process. The yields of the products are good to excellent and the method is applicable to large-scale operation without any problem. [source] ChemInform Abstract: Micellar Solution of Sodium Dodecyl Sulfate (SDS) Catalyzes Kabacknik,Fields Reaction in Aqueous Media.CHEMINFORM, Issue 43 2009Sara Sobhani Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Pronounced Catalytic Effect of a Micellar Solution of Sodium Dodecylsulfate (SDS) Upon a Three-Component Reaction of Aldehydes, Amines, and Ketones under Neutral Conditions.CHEMINFORM, Issue 28 2009Abbas Ali Jafari Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Purification and Concentration of Alkaline Phosphatase by Selective Permeabilization of Escherichia coli Using Reverse Micellar SolutionsBIOTECHNOLOGY PROGRESS, Issue 6 2003Ritu Bansal-Mutalik Recovery of alkaline phosphatase (AP) from the periplasm of Escherichia coli using reverse micellar solutions (RMSs) of sodium dioctyl sulfosuccinate (AOT) in aliphatic hydrocarbons has been attempted. A variety of surface-active agents, solvents, and reverse micellar conditions were screened, and an excellent recovery of the enzyme in a concentrated form, with a high purification factor, was obtained in a single-step process. The permeabilization process strongly depended on the water content of the RMS as well as on the amount of water coating the microbial cell surface. The product was almost free from nucleic acids. In addition, because of the low affinity of AOT and the organic solvent for the aqueous phase, contamination by the permeabilizing agents would also be negligible. [source] A Novel Fluorescent Indicator for Ba2+ in Aqueous Micellar Solutions.CHEMINFORM, Issue 17 2004Yoshio Nakahara No abstract is available for this article. [source] Micellar solutions of amphipathic copolymers based on carboxymethyl cellulosePOLYMER INTERNATIONAL, Issue 6 2003Ya Cao Abstract A novel family of amphipathic copolymers based on carboxymethyl cellulose (CM-cellulose) has been synthesized through ultrasonic irradiation. Their micellar conformation in aqueous solution was studied by dynamic laser scattering, environmental scanning electron microscopy and gel permeation chromatography. The results show that conformation of copolymer molecules is totally different from that of CM-cellulose because of the introduction of the surface active macromonomers. Due to the influence of hydrophobic character and molecular weight, different amphipathic copolymers have different micellar conformations, such as cylindrical, spheroidal or ellipsoidal micelles. In the range of concentration tested, the normalized first-order autocorrelation function g(1)(,) of a copolymer of CM-cellulose and poly(ethylene oxide) dodecyl ether acrylate does not fit a single-exponential decay, indicating a polydisperse system and the existence of species of different shapes and size. At different concentrations, the hydrodynamic radii of micelles (R) almost distribute into two regions of smaller and larger size. With increasing copolymer concentration, the region of smaller R remains in the range 30,100,nm and is considered to represent monomolecular micelles, while the larger R region increases gradually with concentration, which means that polymolecular micelles increase in size. © 2003 Society of Chemical Industry [source] Amphiphilic Iron(II) and Nickel(II) Complexes Based on Alkylated Diazaoxa- and TriazacyclononaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2008David Domínguez-Gutiérrez Abstract It is known that including a metal into a micellar solution enhances both the colour and catalytic potential of such systems. This fact is well exemplified by the broad use of surfactant species as phase-transfer catalysts. In the present work, we report our studies concerning the aggregation properties of a series of iron and nickel-based triazacyclononane metalloamphiphiles. Upon multiple alkylation of the triazamacrocycle, we were able to obtain amphiphilic complexes that aggregate in toluene. We characterised the sizes and shapes of the aggregates by dynamic light scattering while their nature was assessed by atomic force microscopy.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Metallomicelle catalysis: Hydrolysis of p -nitrophenyl picolinate induced by Schiff base Co(II) complexes in a Gemini surfactant micellar solutionINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2007Weidong Jiang Two Schiff base cobalt(II) complexes containing crowned substituents have been synthesized and employed to promote the hydrolysis of p -nitrophenyl picolinate (PNPP) in a buffered micellar solution formed by a cationic Gemini surfactant, bis(hexadecyldimethylammonium)hexane bromide (G(hex)C16, 2Br,) over a pH range of 6.50,8.50. In comparison, the reactivity of PNPP hydrolysis catalyzed by the same catalysts in the other micellar system, formed by a conventional single-chain analogue, that is, hexadecyltrimethylammonium bromide (CTAB), has also been evaluated under a selected condition. The results clearly reveal that the two metallomicelles made of the aforementioned Co(II) complexes and the G(hex)C16 are both efficient for catalyzing PNPP hydrolysis with about 3 orders of magnitude in rate acceleration compared with the background rate of PNPP spontaneous hydrolysis. Moreover, the rates of PNPP hydrolysis catalyzed by the two cobalt(II) complexes in G(hex)C16 micelles are about 2 times higher than in CTAB micelles, correspondingly. In addition, observations show that steric hindrance of substituents of the two complexes is also one of the major influencing factors in the PNPP hydrolytic reaction. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 672,680, 2007 [source] Tat cell-penetrating peptide has the characteristics of a poly(proline) II helix in aqueous solution and in SDS micellesJOURNAL OF PEPTIDE SCIENCE, Issue 7 2004Paolo Ruzza Abstract Tat cell-penetrating peptide (GRKKRRQRRRPPQG) is able to translocate and carry molecules across cell membranes. Using CD spectroscopy the conformation of this synthetic peptide was studied in aqueous and membrane-mimicking, micellar SDS solutions at different temperatures. The CD spectrum of the Tat cell-penetrating peptide in SDS micellar solution was virtually unchanged from that in aqueous solution, and at low temperature it was close to that of a poly(proline) II helix. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Environmentally responsive micelles from polystyrene,poly[bis(potassium carboxylatophenoxy)phosphazene] block copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005Youngkyu Chang Abstract Amphiphilic diblock copolymers that contained hydrophilic poly[bis(potassium carboxylatophenoxy)phosphazene] segments and hydrophobic polystyrene sections were synthesized via the controlled cationic polymerization of Cl3PNSiMe3 with a polystyrenyl,phosphoranimine as a macromolecular terminator. These block copolymers self-associated in aqueous media to form micellar structures which were investigated by fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. The size and shape of the micelles were not affected by the introduction of different monovalent cations (Li+, K+, Na+, and Cs+) into the stable micellar solutions. However, exposure to divalent cations induced intermicellar crosslinking through carboxylate groups, which caused precipitation of the ionically crosslinked aggregates from solution. This micelle-coupling behavior was reversible: the subsequent addition of monovalent cations caused the redispersion of the polystyrene- block -poly[bis(potassium carboxylatophenoxy)phosphazene] (PS,KPCPP) block copolymers into a stable micellar solution. Aqueous micellar solutions of PS,KPCPP copolymers also showed pH-dependent behavior. These attributes make PS,KPCPP block copolymers suitable for studies of guest retention and release in response to ion charge and pH. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2912,2920, 2005 [source] Direct Refolding of Inclusion Bodies Using Reversed MicellesBIOTECHNOLOGY PROGRESS, Issue 6 2004Masafumi Sakono The protein refolding of inclusion bodies was investigated using reversed micelles formed by aerosol OT (AOT). Ribonuclease A (RNase A) was overexpressed in Escherichia coli and used as native inclusion bodies. The enzymatic activity of RNase A was completely regained from the inclusion bodies within 14 h by solubilization in reversed micelles. To further enhance the refolding rate, a molecular chaperone, GroEL, was incorporated into the refolding system. The resultant refolding system including GroEL showed better performance under optimized conditions for the refolding of RNase A inclusion bodies. The refolding rate was considerably improved by the addition of the molecular chaperone, and the refolding step was completed in 1 h. The protein refolding in the GroEL-containing refolding system was strongly dependent on the coexistence of ATP and Mg2+, suggesting that the GroEL hosted in the reversed micelles was biologically active and assisted in the renaturation of the inclusion bodies. The addition of cold acetone to the reversed micellar solution allowed over 90% recovery of the renatured RNase A. [source] Enhanced Stabilization of Reverse Micelles by Compressed CO2CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2005Dong Shen Dr. Abstract The effect of compressed CO2 on the solubilization capacity of water in reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in longer chain n -alkanes was studied at different temperatures and pressures. It was found that the amount of solubilized water is increased considerably by CO2 in a suitable pressure range. The suitable CO2 pressure range in which the solubilization capacity of water could be enhanced decreased with increasing W0 (water-to-AOT molar ratio). The microenvironments in the CO2 -stabilized reverse micelles were investigated by UV/Vis adsorption spectroscopy with methyl orange (MO) as probe. The mechanism by which the reverse micelles are stabilized by CO2 is discussed in detail. The main reason is likely to be that CO2 has a much smaller molecular volume than the n -alkane solvents studied in this work. Therefore, it can penetrate the interfacial film of the reverse micelles and stabilize them by increasing the rigidity of the micellar interface and thus reducing the attractive interaction between the droplets. However, if the CO2 pressure is too high, the solvent strength of the solvents is reduced markedly, and this induces phase separation in the micellar solution. [source] Deprotonation of Indole Derivatives in Aqueous Cationic SurfactantsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2004Nicoletta Spreti Abstract Deprotonations of 5-nitroindole, 1a, and its 2-carboxylate ion, 2a, have been monitored in 0.01, 0.1, and 0.5 M NaOH in micellar solutions of cetyl trialkylammonium bromide, alkyl = Me, Et, nPr, nBu, CTABr, CTEABr, CTPABr, CTBABr. Extents of deprotonation (% f) have been fitted using the pseudophase model of micellar effects with interionic competition described by ion exchange or by independent association constants. Both treatments indicate that base dissociation constants in dilute OH, are lower than in water by factors of ca. 3,11, and decrease with increasing bulk of the head groups, and that these factors increase modestly as the OH, concentration increases to 0.5 M. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Dediazoniation of 1-naphthalenediazonium tetrafluoroborate in aqueous acid and in micellar solutionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2008Carlos Bravo-Diaz We have measured the rates and product yields of dediazoniation of 1-naphthalenediazonium (1ND) tetrafluoroborate in the presence and absence of sodium dodecyl sulfate (SDS) micellar aggregates by employing a combination of UV,vis spectroscopy and high-performance liquid chromatography (HPLC) measurements. Kinetic data were obtained by a derivatization procedure with product yields were determined by HPLC. HPLC chromatograms show that in aqueous acid and in micellar solutions only one dediazoniation product is formed in significant quantities, 1-naphthol (NOH), and the observed rate constants (kobs) are the same when 1ND loss is monitored spectrometrically and when NOH formation is monitored by HPLC. Activation parameters were obtained both in the presence and absence of SDS micellar aggregates. In both the systems, the enthalpies of activation are high and the entropies of activation are positive. The enthalpy of activation in the absence of SDS is very similar to that in the presence of SDS micelles, but the entropy of activation is lower by a factor of 4. As a consequence, SDS micelles speed up the thermal decomposition of 1ND and increase kobs by a factor of 1.5 when [SDS] = 0.02 M. In contrast, results obtained in the presence of complexing systems such as crown ethers and polyethers show significant stabilization of the parent arenediazonium ions. Kinetic and HPLC data are consistent with the heterolytic DN + AN mechanism that involves the rate-determining fragmentation of the arenediazonium ion into a very reactive phenyl cation that reacts competitively with available nucleophiles. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 301,309, 2008 [source] Effects of alcohols on micellization and on the reaction methyl 4-nitrobenzenesulfonate + Br, in cetyltrimethylammonium bromide aqueous micellar solutionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2004María Muñoz The effects of n -hexanol, n -pentanol, and n -butanol on the critical micelle concentration (cmc), on the micellar ionization degree (,), and on the rate of the reaction methyl 4-nitrobenzenesulfonate + Br, have been investigated in cetyltrimethylammonium bromide (CTAB) aqueous solutions. An increase in the alcohol concentration present in the solution produces a decrease in the cmc and an increase in the micellar ionization degree. Kinetic data show that the observed rate constant decreases as alcohol concentration increases. This result was rationalized by considering variations in the equilibrium binding constant of the methyl 4-nitrobenzenesulfonate molecules to the micelles, variations in the interfacial bromide ion concentration, and variations in the characteristics of the water,alcohol bulk phase provoked by the presence of alcohols. When these operative factors are considered, kinetic data in this and other works show that the second-order rate constants in the micellar pseudophases of water,alcohol micellar solutions are quite similar to those estimated in the absence of alcohols. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 634,641, 2004 [source] The two-Yukawa model and its applications: the cases of charged proteins and copolymer micellar solutionsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Sow-Hsin Chen Charged and uncharged colloidal systems are known from experiment to display an extremely rich phase behavior, which is ultimately determined by the effective pair potential between particles in solution. As a confirmation, the recent striking observation of an equilibrium cluster phase in charged globular protein solutions [Stradner, Sedgwick, Cardinaux, Poon, Egelhaaf & Schurtenberger (2004). Nature, 432, 492,495] has been interpreted as the effect of competing short-range attractive and long-range repulsive interactions. The `two-Yukawa (2Y) fluid' model assumes an interparticle potential consisting of a hard core plus an attractive and a repulsive Yukawa tail. We show that this rather simple model can indeed explain satisfactorily the structural properties of diverse colloidal materials, measured in small-angle neutron scattering (SANS) experiments, including the cases of equilibrium cluster formation and soft-core repulsion. We apply this model to the analysis of SANS data from horse-heart cytochrome c protein solutions (whose effective potential can be modeled as a hard-sphere part plus a short-range attraction and a weaker screened electrostatic repulsion) and micellar solutions of a triblock copolymer (whose effective potential can be modeled as a hard-sphere part plus a repulsive shoulder and a short-range attraction). The accuracy of the 2Y model predictions is successfully tested against Monte Carlo simulations in both cases. [source] Using the polymer partitioning method to probe the thermodynamic activity of poorly water-soluble drugs solubilized in model lipid digestion productsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2003Ben J. Boyd Abstract The thermodynamic activity of solubilized drug is an important determinant of the extent of absorption of lipophilic drugs from the gastrointestinal tract. In this study, the polymer partitioning method was evaluated for its use in the determination of the thermodynamic activity of lipophilic drugs when solubilized in colloidal digestion products, using drug in dilute solution as a reference ideal solution. The lipophilic drugs griseofulvin, diazepam, and danazol partitioned into a polymeric receiver phase from non-micellar solution as a function of drug lipophilicity. The concentration of drug that partitioned into the polymer was linearly proportional to the concentration of free drug in solution, and this allowed the measured partition coefficient to be utilized as an indicator of the drug activity coefficient. The addition of a solubilizing species such as bile salt micelles caused a reduction in drug activity of a similar magnitude to that predicted from micelle equilibrium solubility data in the identical micellar solutions. The addition of micelle swelling lipids such as lecithin and fatty acids resulted in further reductions in activity coefficient. The ability to measure drug activity in model digestive systems has potential for application in the rational development of improved lipid-based formulations of poorly water-soluble drugs for oral administration. © 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:1262,1271, 2003 [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] pH-independent hydrolysis of 4-nitrophenyl 2,2-dichloropropionate in aqueous micellar solutions: relative contributions of hydrophobic and electrostatic interactionsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 8 2001Omar A. EI Seoud Abstract The pH-independent hydrolysis of 4-nitrophenyl 2,2-dichloropropionate (NPDCP) in the presence of aqueous micelles of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkyltrimethylammonium chlorides, alkyldimethylbenzylammonium chlorides (alkyl,=,cetyl and dodecyl) and polyoxyethylene(9) nonylphenyl ether was studied spectrophotometrically. The observed rate constants, kobs, decrease in the following order: bulk water >cationic micelles >anionic micelles >non-ionic micelles. This order is different from that observed for pH-independent hydrolysis of 4-nitrophenyl chloroformate (NPCF), whose reaction is faster in cationic micelles than in bulk water. A proton NMR study on solubilization of a model ester, 4-nitrophenyl 2-chloropropionate, showed that the methylene groups in the middle of the surfactant hydrophobic chain are most affected by the solubilizate. Lower polarity and high ionic strength of interfacial water decrease the rates of hydrolysis of both NPCF and NPDCP, but the fraction of the former ester that diffuses to the interface is probably higher than that of the latter. Therefore, whereas the (negatively charged) transition state of NPCF is stabilized by cationic interfaces and destabilized by anionic interfaces, that of NPDCP is negligibly affected by ionic interfaces, which explains the observed rate retardation by all ionic micelles. Calculated activation parameters corroborate our explanation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Environmentally responsive micelles from polystyrene,poly[bis(potassium carboxylatophenoxy)phosphazene] block copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005Youngkyu Chang Abstract Amphiphilic diblock copolymers that contained hydrophilic poly[bis(potassium carboxylatophenoxy)phosphazene] segments and hydrophobic polystyrene sections were synthesized via the controlled cationic polymerization of Cl3PNSiMe3 with a polystyrenyl,phosphoranimine as a macromolecular terminator. These block copolymers self-associated in aqueous media to form micellar structures which were investigated by fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. The size and shape of the micelles were not affected by the introduction of different monovalent cations (Li+, K+, Na+, and Cs+) into the stable micellar solutions. However, exposure to divalent cations induced intermicellar crosslinking through carboxylate groups, which caused precipitation of the ionically crosslinked aggregates from solution. This micelle-coupling behavior was reversible: the subsequent addition of monovalent cations caused the redispersion of the polystyrene- block -poly[bis(potassium carboxylatophenoxy)phosphazene] (PS,KPCPP) block copolymers into a stable micellar solution. Aqueous micellar solutions of PS,KPCPP copolymers also showed pH-dependent behavior. These attributes make PS,KPCPP block copolymers suitable for studies of guest retention and release in response to ion charge and pH. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2912,2920, 2005 [source] Determination of atenolol by the micelle-stabilized room-temperature phosphorescence methodologyLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 6 2007Marcela A. Castillo Abstract A micellar-stabilized room-temperature phosphorescence (MS,RTP) method for the determination of atenolol has been developed in micellar solutions of sodium dodecylsulphate (SDS) in the presence of thallium(I) as a heavy atom and sodium sulphite as an oxygen scavenger. The effects of thallium(I) nitrate, SDS and sodium sulphite concentrations on atenolol MS,RTP intensity were studied. Optimized conditions to obtain maximum sensitivity were 0.015 mol/L thallium(I) nitrate, 0.1 mol/L SDS and 0.0075 mol/L sodium sulphite. The maximum phosphorescence signal was completely developed in 10 min and the intensity was measured at ,ex = 272 nm and ,em = 412 nm. The linear range of application obtained was 2.01,16.00 µg/mL. The detection limit estimated from the least-squares regression analysis was 0.86 µg/mL and the relative standard deviation of 10 replicates was 1.7%. The proposed method was applied to the determination of atenolol in a pharmaceutical formulation. The quantitation was carried out by means of standard calibration, standard-additions calibration and Youden calibration. These three experiments were necessary to evaluate the presence of constant and proportional errors due to the matrix. Copyright © 2007 John Wiley & Sons, Ltd. [source] Degradation patterns of tetracycline antibiotics in reverse micelles and waterBIOMEDICAL CHROMATOGRAPHY, Issue 11 2006Hongkee Sah Abstract The objective of this study was to determine the chemical stability of tetracycline and oxytetracycline hydro-chlorides in reverse micelles. Their reverse micellar solutions were prepared using cetyltrimethylammonium bromide, water and ethyl formate. The aqueous solutions of the tetracycline antibiotics were also prepared for comparison. The reverse micellar and aqueous solutions were stored at 37C. Samples were analyzed by high performance liquid chromatography. When evaluation was performed on an aqueous tetracycline HCl solution, its half-life was estimated to be 329 h. Its chemical stability was not improved after being dissolved in the reverse micelles, and a similar half-life of 330 h was observed. However, there were noticeable differences between the two systems in terms of degradation kinetics and degradation byproducts. On the other hand, oxytetracycline HCl was unstable in water so that its half-life was only 34 h. Very interestingly, pronounced improvement in stability was attained with the reverse micellar system: upon dissolving in the reverse micelles, its half-life was increased to 2402 h. There were also marked differences in degradation patterns and mechanisms of oxytetracycline HCl in water and the reverse micelles. Our study indicates that the reverse micellar system has potential applications in solubilizing and stabilizing oxytetracycline HCl, thereby contributing to the development of its dosage forms. Copyright © 2006 John Wiley & Sons, Ltd. [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] Purification and Concentration of Alkaline Phosphatase by Selective Permeabilization of Escherichia coli Using Reverse Micellar SolutionsBIOTECHNOLOGY PROGRESS, Issue 6 2003Ritu Bansal-Mutalik Recovery of alkaline phosphatase (AP) from the periplasm of Escherichia coli using reverse micellar solutions (RMSs) of sodium dioctyl sulfosuccinate (AOT) in aliphatic hydrocarbons has been attempted. A variety of surface-active agents, solvents, and reverse micellar conditions were screened, and an excellent recovery of the enzyme in a concentrated form, with a high purification factor, was obtained in a single-step process. The permeabilization process strongly depended on the water content of the RMS as well as on the amount of water coating the microbial cell surface. The product was almost free from nucleic acids. In addition, because of the low affinity of AOT and the organic solvent for the aqueous phase, contamination by the permeabilizing agents would also be negligible. [source] Solubilization of Single-Walled Carbon Nanotubes by using Polycyclic Aromatic Ammonium Amphiphiles in Water,Strategy for the Design of High-Performance SolubilizersCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2006Yasuhiko Tomonari Abstract We describe the design of polycyclic aromatic compounds with high performance that dissolve single-walled carbon nanotubes (SWNTs). Synthetic amphiphiles trimethyl-(2-oxo-2-phenylethyl)-ammonium bromide (1) and trimethyl-(2-naphthalen-2-yl-2-oxo-ethyl)-ammonium bromide (2) carrying a phenyl or a naphtyl moiety were not able to dissolve/disperse SWNTs in water. By contrast, trimethyl-(2-oxo-2-phenanthren-9-yl-ethyl)-ammonium bromide (3) solubilized SWNTs, although the solubilization ability was lower than that of trimethyl-(2-oxo-2-pyrene-1-yl-ethyl)-ammonium bromide (4) (solubilization behavior observed by using 4 was described briefly in reference 4a). Transmission electron microscopy (TEM), as well as visible/near-IR, fluorescence, and near-IR photoluminescence spectroscopies were employed to reveal the solubilization properties of 4 in water, and to compare these results with those obtained by using sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HTAB) as solubilizers. Compound 4 solubilized both the as-produced SWNTs (raw-SWNTs) and purified SWNTs under mild experimental conditions, and the solubilization ability was better than that of SDS and HTAB. Near-IR photoluminescence measurements revealed that the chiral indices of the SWNTs dissolved in an aqueous solution of 4 were quite different from those obtained by using micelles of SDS and HTAB; for a SWNTs/4 solution, the intensity of the (7,6), (9,5), and (12,1) indices were strong and the chirality distribution was narrower than those of the micellar solutions. This indicates that the aqueous solution of 4 has a tendency to dissolve semiconducting SWNTs with diameters in the range of 0.89,1.0 nm, which are larger than those SWNTs (0.76,0.97 nm) dissolved in the aqueous micelles of SDS and HTAB. [source] | ||||||||||||||||