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Micellar System (micellar + system)
Kinds of Micellar System Selected AbstractsChemInform Abstract: Synthesis of Polycyclic Fused 2-Quinolones in Aqueous Micellar System.CHEMINFORM, Issue 25 2010Subhendu Naskar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Bending Energetics of Tablet-Shaped Micelles: A Novel Approach to Rationalize Micellar SystemsCHEMPHYSCHEM, Issue 3 2007L. Magnus Bergström Prof. Abstract A novel approach to rationalize micellar systems is expounded in which the structural behavior of tablet-shaped micelles is theoretically investigated as a function of the three bending elasticity constants: spontaneous curvature (H0), bending rigidity (kc), and saddle-splay constant (k,c). As a result, experimentally accessible micellar properties, such as aggregation number, length-to-width ratio, and polydispersity, may be related to the different bending elasticity constants. It is demonstrated that discrete micelles or connected cylinders form when H0>1/4,, where , is the thickness of a surfactant monolayer, whereas various bilayer structures are expected to predominate when H0<1/4,. Our theory predicts, in agreement with experiments, a transition from discrete globular (tablet-shaped) micelles to a phase of ordered, or disordered, connected cylinders above a critical surfactant concentration. Moreover, a novel explanation for the mechanism of growth, from small globular to long rodlike or wormlike micelles, follows as a consequence from the theory. In accordance, polydisperse elongated micelles (large length-to-width ratio) form as the bending rigidity is lowered, approaching the critical point at kc=0, whereas monodisperse globular micelles (small length-to-width ratio) are expected to be present at large kc values. The spontaneous curvature mainly determines the width of tablet-shaped or ribbonlike micelles, or the radius of disklike micelles, whereas the saddle-splay constant primarily influences the size but not the shape of the micelles. [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] Controlled size chitosan nanoparticles as an efficient, biocompatible oligonucleotides delivery systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Romila Manchanda Abstract Polymeric nanoparticles of chitosan crosslinked with glutaraldehyde have been prepared using reverse micellar system. An optically clear solution was obtained on redispersing these nanoparticles in aqueous buffer. The nanoparticles were characterized for their size and surface morphology employing dynamic laser scattering (DLS) and transmission electron microscopy (TEM). The TEM images showed spherical particles with smooth surface and narrow size distribution of about 90 nm, which was also supported by DLS data. Size and morphology of the particles remains the same on redispersing the lyophilized powder of these nanoparticles in aqueous buffer. Further, these nanoparticles were loaded with different synthetic oligonucleotides (ODNs). In vitro pH dependent release of the adsorbed oligonucleotides from these nanoparticles was also studied. At basic pH the release of oligonucleotides was found higher as compared with neutral and acidic medium. Cytotoxicity studies done on HEK 293 cells reveals that oligonucleotide loaded nanoparticles have high cell viability of nearly 76,88% whereas those of lipofectamine was about 35%. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Enhanced oral absorption of paclitaxel in N -deoxycholic acid- N, O -hydroxyethyl chitosan micellar system,JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2010Hong Li Abstract The overall goal of this study was to develop a micellar system of paclitaxel (PTX) to enhance its oral absorption. An amphiphilic chitosan derivative, N -deoxycholic acid- N, O -hydroxyethyl chitosan (DHC), was synthesized and characterized by FTIR, 1H NMR, elemental analysis, and X-ray diffraction (XRD) techniques. The degree of substitution (DS) of hydroxyethyl group and deoxycholic acid group ranged from 89.5,114.5% and 1.11,8.17%, respectively. The critical micelle concentration (CMC) values of DHC decreased from 0.26 to 0.16,mg/mL as the DS of deoxycholic acid group increased. PTX was successfully loaded in DHC micelles with a high drug loading (31.68,±,0.14%) and entrapment efficiency (77.57,±,0.51%). The particle size of PTX-loaded DHC micelles ranged from 203.35,±,2.19 to 236.70,±,3.40,nm as the DS of deoxycholic acid group increased. After orally administration of PTX-loaded DHC micelles, the bioavailability was threefold compared with that of an orally dosed Taxol®. The single-pass intestinal perfusion studies (SPIP) showed that the intestinal absorption of micelles was via endocytosis involving a saturable process and a p-glycoprotein (P-gp)-independent way. All these indicated that the DHC micelles might be a promising tool for oral delivery of poorly water-soluble drugs. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4543,4553, 2010 [source] Effects of non-ionic and mixed non-ionic,cationic micelles on the rate of aqueous cleavages of phenyl benzoate and phenyl salicylate in alkaline mediumJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2004M. Niyaz Khan Abstract Pseudo-first-order rate constants (kobs) for the hydrolysis of phenyl salicylate (PSH) and phenyl benzoate (PB) in the alkaline medium show a monotonic decrease with the increase in [C16E20]T (total concentration of Brij 58) at constant [CH3CN] and [NaOH]. This micellar effect is explained in terms of the pseudophase model of micelles. These results show a characteristic difference between the effects of [C16E20]T and previously published effects of [C12E23]T (total concentration of Brij 35) on the rates of aqueous cleavage of PSH and PB at [CnEm]T/[NaOH],,3. The values of kobs, obtained at different [C16E20]T in the presence of a constant amount of CTABr, follow the empirical relationship kobs=(k0+,K[C16E20]T)/(1+K[C16E20]T), where , and K are empirical parameters. The values of , are not affected whereas the values of K decrease with increase in [CTABr]T in a mixed C16E20,CTABr micellar system. The values of , at different [CTABr]T show that ,>k0 for hydrolysis of PSH and , Effects of non-ionic and mixed cationic,non-ionic micelles on the rate of alkaline hydrolysis of phthalimideJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 7 2002M. Niyaz Khan Abstract Pseudo-first-order rate constants (kobs) for the alkaline hydrolysis of phthalimide (PTH) show a monotonic decrease with the increase in [C16E20]T (total concentration of Brij 58) at constant [CH3CN] and [NaOH]. This micellar effect is explained in terms of the pseudophase model of micelles. The rate of hydrolysis of PTH in C16E20 micellar pseudophase appears to be negligible compared with that in the aqueous pseudophase. The values of kobs for C12E23 (Brij 35) show a sharp decrease at very low values of [C12E23]T followed by a very slow decrease with increase in [C12E23]T at relatively higher values of the latter. The rate of hydrolysis becomes too slow to monitor at [C12E23]T ,0.04,M in the absence of cetyltrimethylammonium bromide (CTABr) and at [C12E23]T ,0.05,M in the presence of 0.006,0.02,M CTABr at 0.02,M NaOH whereas such characteristic behavior is kinetically absent with C16E20. The values of kobs, obtained at different [NIS]T (where NIS represents C16E20 and C12E23) in the presence of a constant amount of CTABr, follow the empirical relationship kobs,=,(k0,+,kK[NIS]T)/(1,+,K[NIS]T) where k and K are empirical parameters. The values of k are only slightly affected whereas the values of K decrease with increase in [CTABr]T for the mixed C16E20,CTABr micellar system. The rate of hydrolysis of PTH at ,0.01,M C12E23 and ,0.01,M CTABr reveals the formation of phthalic anhydride whereas this was not observed in the mixed C16E20,CTABr micellar system under similar experimental conditions. Copyright © 2002 John Wiley & Sons, Ltd. [source] Micellar and aqueous-organic liquid chromatography using sub-2,,m packings for fast separation of natural phenolic compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2010Jun Cao Abstract The objective of the present work was to investigate the chromatographic behavior of natural phenolic compounds in micellar and aqueous-organic LC using a short column packed with 1.8,,m particles. Firstly, the effect of ACN and SDS on elution strength and selectivity was examined by isocratic submicellar (0,30% ACN/5% 1-butanol/1,6,mM SDS) and micellar (0,30% ACN/5% 1-butanol/40,60,mM SDS) systems. The varied concentrations of two modifiers in the mobile phases revealed different eluting power. Then, the application of organic modifier gradient was discussed in both submicellar and micellar LC using mobile phases of 4,mM SDS/5% 1-butanol or 50,mM SDS/5% 1-butanol containing ACN gradient from 0 to 30%, respectively. For micellar system, the separation was found to be better in gradient than isocratic elution. Additionally, the sensitivity of aqueous-organic LC was examined. The mobile phase was a mixture of ACN and water employing gradient elution at a flow rate of 0.5,mL/min, with analysis time below 9,min. It was found that separation efficiency was significantly better compared with micellar LC. Besides, the aqueous-organic LC has been applied to separation of various phenolic compounds in Yangwei granule or Radix Astragali samples. [source] Development of predictive quantitative retention,activity relationship models of alkaloids by mixed micellar liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Yu Chen Abstract The mixed micellar liquid chromatography is a mode that uses mixed micellar system of Brij35/SDS (85 : 15) as a mobile phase under adequate experimental conditions, can simulate the resting membrane potential and the conformation of the long hydrophilic polyoxyethylene chains remains unchanged. In this article, the applications of biopartitioning micellar chromatography, using mixed micellar system to describe and estimate bioactivities of alkaloids, has been focused. The BMCBrij35/SDS -QRAR models of half-life time, volume of distribution, plasma clearance and area under concentration,time curve were obtained using Brij35-SDS retention data. The aim is to take a look at the capability of the mixed micellar liquid chromatography model to describe and/or estimate the bioactivity of alkaloids. Copyright © 2009 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 affinity capillary electrophoresis for characterizing pharmaceutical colloidal vehicle systems thermodynamicallyBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 7-8 2001Neubert Reinhard Abstract This review offers a detailed discussion of the interaction between pharmaceutical compounds and vehicles using the affinity capillary electrophoresis and the microemulsion electrokinetic chromatography. Partition coefficients of drugs were calculated between a micelle and an aqueous phases from the measurement of the migration time, provided the critical micelle concentration and the phase ratio are known. Thermodynamic quantities such as enthalpy and entropy changes of micellar solubilization were calculated from the temperature dependence of the partition coefficients. Partial specific volumes were measured using dynamic light scattering. The logarithm of the partition coefficients and the capacity factor in the micellar system were correlated with the logarithm of the n-octanol/water partition coefficients. Copyright © 2001 John Wiley & Sons, Ltd. [source] Concentration of mammalian genomic DNA using two-phase aqueous micellar systemsBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009Foad Mashayekhi Abstract The concentration of biomarkers, such as DNA, prior to a subsequent detection step may facilitate the early detection of cancer, which could significantly increase chances for survival. In this study, the partitioning behavior of mammalian genomic DNA fragments in a two-phase aqueous micellar system was investigated using both experiment and theory. The micellar system was generated using the nonionic surfactant Triton X-114 and phosphate-buffered saline (PBS). Partition coefficients were measured under a variety of conditions and compared with our theoretical predictions. With this comparison, we demonstrated that the partitioning behavior of DNA fragments in this system is primarily driven by repulsive, steric, excluded-volume interactions that operate between the micelles and the DNA fragments, but is limited by the entrainment of micelle-poor, DNA-rich domains in the macroscopic micelle-rich phase. Furthermore, the volume ratio, that is, the volume of the top, micelle-poor phase divided by that of the bottom, micelle-rich phase, was manipulated to concentrate DNA fragments in the top phase. Specifically, by decreasing the volume ratio from 1 to 1/10, we demonstrated proof-of-principle that the concentration of DNA fragments in the top phase could be increased two- to nine-fold in a predictive manner. Biotechnol. Bioeng. 2009;102: 1613,1623. © 2008 Wiley Periodicals, Inc. [source] Affinity-enhanced protein partitioning in decyl ,- D -glucopyranoside two-phase aqueous micellar systemsBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005Henry Lam Abstract Liquid,liquid extraction in two-phase aqueous complex-fluid systems has been proposed as a scalable, versatile, and cost-effective purification method for the downstream processing of biotechnological products. In the case of two-phase aqueous micellar systems, careful choices of the phase-forming surfactants or surfactant mixtures allow these systems to separate biomolecules based on size, hydrophobicity, charge, or specific affinity. In this article, we investigate the affinity-enhanced partitioning of a model affinity-tagged protein,green fluorescent protein fused to a family 9 carbohydrate-binding module (CBM9-GFP),in a two-phase aqueous micellar system generated from the nonionic surfactant n -decyl ,- D -glucopyranoside (C10G1), which acts simultaneously as the phase-former and the affinity ligand. In this simple system, CBM9-GFP was extracted preferentially into the micelle-rich phase, despite the opposing tendency of the steric, excluded-volume interactions operating between the protein and the micelles. We obtained more than a sixfold increase (from 0.47 to 3.1) in the protein partition coefficient (Kp), as compared to a control case where the affinity interactions were "turned off" by the addition of a competitive inhibitor (glucose). It was demonstrated conclusively that the observed increase in Kp can be attributed to the specific affinity between the CBM9 domain and the affinity surfactant C10G1, suggesting that the method can be generally applied to any CBM9-tagged protein. To rationalize the observed phenomenon of affinity-enhanced partitioning in two-phase aqueous micellar systems, we formulated a theoretical framework to model the protein partition coefficient. The modeling approach accounts for both the excluded-volume interactions and the affinity interactions between the protein and the surfactants, and considers the contributions from the monomeric and the micellar surfactants separately. The model was shown to be consistent with the experimental data, as well as with our current understanding of the CBM9 domain. © 2005 Wiley Periodicals, Inc. [source] His-tagged protein purification by metal-chelate affinity extraction with nickel-chelate reverse micellesBIOTECHNOLOGY PROGRESS, Issue 4 2010Xiao-Yan Dong Abstract Di(2-ethylhexyl) phosphoric acid (HDEHP) was used as a transition metal ion chelator and introduced to the nonionic reverse micellar system composed of equimolar Triton X-45 and Span 80 at a total concentration of 30 mmol/L. Ni(II) ions were chelated to the HDEHP dimers in the reverse micelles, forming a complex denoted as Ni(II)R2. The Ni(II)-chelate reverse micelles were characterized for the purification of recombinant hexahistidine-tagged enhanced green fluorescent protein (EGFP) expressed in Escherichia coli. The affinity binding of EGFP to Ni(II)R2 was proved by investigation of the forward and back extraction behaviors of purified EGFP. Then, EGFP was purified with the affinity reverse micelles. It was found that the impurities in the feedstock impeded EGFP transfer to the reverse micelles, though they were little solubilized in the organic phase. The high specificity of the chelated Ni2+ ions toward the histidine tag led to the production of electrophoretically pure EGFP, which was similar to that purified by immobilized metal affinity chromatography. A two-stage purification by the metal-chelate affinity extraction gave rise to 87% recovery of EGFP. Fluorescence spectrum analysis suggests the preservation of native protein structure after the separation process, indicating the system was promising for protein purification. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] A metal-chelate affinity reverse micellar system for protein extractionBIOTECHNOLOGY PROGRESS, Issue 1 2010Xiao-Yan Dong Abstract A new nonionic reverse micellar system is developed by blending two nonionic surfactants, Triton X-45 and Span 80. At total surfactant concentrations lower than 60 mmol/L and molar fractions of Triton X-45 less than 0.6, thermodynamically stable reverse micelles of water content (W0) up to 30 are formed. Di(2-ethylhexyl) phosphoric acid (HDEHP; 1,2 mmol/L) is introduced into the system for chelating transition metal ions that have binding affinity for histidine-rich proteins. HDEHP exists in a dimeric form in organic solvents and a dimer associated with one transition metal ion, including copper, zinc, and nickel. The copper-chelate reverse micelles (Cu-RM) are characterized for their W0, hydrodynamic radius (Rh), and aggregation number (Nag). Similar with reverse micelles of bis-2-ethylhexyl sodium sulfosuccinate (AOT), Rh of the Cu-RM is also linearly related to W0. However, Nag is determined to be 30,90 at W0 of 5,30, only quarter to half of the AOT reverse micelles. Then, selective metal-chelate extraction of histidine-rich protein (myoglobin) by the Cu-RM is successfully performed with pure and mixed protein systems (myoglobin and lysozyme). The solubilized protein can be recovered by stripping with imidazole or ethylinediaminetetraacetic acid (EDTA) solution. Because various transition metal ions can be chelated to the reverse micelles, it is convinced that the system would be useful for application in protein purification as well as simultaneous isolation and refolding of recombinant histidine-tagged proteins expressed as inclusion bodies. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Protein Refolding Mediated by Reverse Micelles of Cibacron Blue F-3GA Modified Nonionic SurfactantBIOTECHNOLOGY PROGRESS, Issue 2 2006Xiao-Yue Wu An affinity-based reverse micellar system formulated with nonionic surfactant was applied to the refolding of denatured-reduced lysozyme. The nonionic surfactant of sorbitan trioleate (Span 85) was modified with Cibacron Blue F-3GA (CB) as an affinity surfactant (CB-Span 85) to form affinity-based reverse micelles in n -hexane. The water content of 15 was found optimal for lysozyme refolding in the reverse micellar system of 62.7 mmol/L Span 85 with coupled CB of 0.3 and 0.5 mmol/L. In addition, the operating conditions such as pH and the concentrations of urea and redox reagents were optimized. Under the optimized conditions, complete renaturation of lysozyme at 3,3.5 mg/mL was achieved, whereas dilution refolding in the bulk aqueous phase under the same conditions gave much lower activity recovery. Moreover, the secondary structure of the refolded lysozyme was found to be the same as the native lysozyme. Over 95% of the refolded lysozyme was recovered from CB-Span 85 reverse micelles by a stripping solution of 0.5 mol/L MgCl2. Thus, the present system is advantageous over the conventional reverse micellar system formed with ionic surfactants in the ease of protein recovery. [source] System peaks in micellar electrophoresis: I. Utilization of system peaks for determination of critical micelle concentrationELECTROPHORESIS, Issue 5 2008Jana Lokajová Abstract A new way to determine the critical micelle concentration (CMC) based on the mobilities of system peaks is presented. A general approach for the CMC determination is based on the change of the slope or on finding the inflection point in the plot of a physical property of solution as a function of surfactant concentration. The determination of CMC by system peaks in CE utilizes a "jump" instead of a continuous change in the measured quantity. This phenomenon was predicted by the program PeakMaster, which was modified for simulation of micellar systems. The simulation of the steep change in mobilities of the anionic system peaks showing the CMC value was verified experimentally in a set of measurements, where the concentration of the surfactant was varied while the ionic strength was kept constant. The experimental work fully proved our model. A comparative electric current measurement was carried out. The proposed method seems to offer easier CMC determination as compared to the standard methods. [source] SN2 Displacement by Bromide Ions in Dichloromethane , The Role of Reverse MicellesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2006Lucia Brinchi Abstract Reverse micellar systems are of interest as reaction media because they are powerful models for biological compartmentalization, enzymatic catalysis and separation of biomolecules. Solutions of ionic surfactants in apolar solvents may contain reverse micelles, but they may also contain ion pairs, or small clusters, with waters of hydration. We studied the bimolecular reaction in CH2Cl2 solutions of cationic tetraalkylammonium bromide salts (onium salts), such as cetyltrimethylammonium bromide (CTABr), cetyltripropylammonium bromide (CTPABr) and tetra- n -butylammonium bromide (TBABr). Methylnaphthalene-2-sulfonate (,-MeONs), its 6-sulfonate derivative (,-MeONsS,) as the 2,6-lutidinium salt and methyl-5- N,N,N,trimethylammonium naphthalene-1-sulfonate (,-MeONsNT+) as the trifluoromethanesulfonate salt react with Br, in CH2Cl2. First-order rate constants, kobs, increase linearly and similarly for the three substrates with increasing concentrations of the onium salts. Reactions are faster with TBABr than they are with CTPABr and CTABr, and the reactivity of the three substrates is in the order: ,-MeONsNT+ >> ,-MeONsS, > ,-MeONs. The reactions are inhibited by the addition of H2O, but CTABr tolerates H2O in large excess. At [H2O]/[CTABr] = w0 , 6, "water-pool" reverse micelles form, and kobs for all three substrates is then independent of w0. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Kinetic investigation on the oxidation of nitrite by oxochromium(V) ion in aqueous and micellar systemsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2004Mookandi Kanthimathi The kinetics of oxidation of nitrite by [O = CrV (5-chlorosalen)]+ complex has been studied spectrophotometrically at [CrV] = 0.5 × 10,3 M, [NO2,] = 0.01,0.1 M, [H+] = 0.0001,0.05 M, I = 0.15 M, and T = 25°C in the presence of cationic surfactant, cetyl pyridium chloride (CPC), and anionic surfactant, sodium dodecyl sulfate (SDS),in aqueous acidic medium. The oxygen atom transfer reaction from O = CrV to nitrite ion is influenced by the ionic nature of the micelle. The redox reaction is accelerated in presence of CPC and slowed down by 40 times in presence of SDS. The mechanism of the reaction involves an inner-sphere process involving the formation of an intermediate followed by oxo transfer process. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 79,86 2004 [source] Synthesis and characterization of the PEG-based nonionic surfactants endowed with carboxylic acid moiety at the hydrophobic terminalJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2008Hiroshi Morikawa As a new class of stimulus-responsive surfactants, a series of ,-methyl-,-alkyl PEGs endowed with a carboxylic acid moiety at the hydrophobic terminal was successfully synthesized with 56,97% yields. They were characterized by IR, NMR spectroscopic and MALDI-TOF MS analyses. It is suggested by DLS measurement that the collapse of the micelle-like aggregation occurred under basic condition. This synthetic procedure would be applicable to surfactants with sufficient hydrophilic and lipophilic balances, allowing precise control of pH-responsive micellar systems. [source] Concentration of mammalian genomic DNA using two-phase aqueous micellar systemsBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009Foad Mashayekhi Abstract The concentration of biomarkers, such as DNA, prior to a subsequent detection step may facilitate the early detection of cancer, which could significantly increase chances for survival. In this study, the partitioning behavior of mammalian genomic DNA fragments in a two-phase aqueous micellar system was investigated using both experiment and theory. The micellar system was generated using the nonionic surfactant Triton X-114 and phosphate-buffered saline (PBS). Partition coefficients were measured under a variety of conditions and compared with our theoretical predictions. With this comparison, we demonstrated that the partitioning behavior of DNA fragments in this system is primarily driven by repulsive, steric, excluded-volume interactions that operate between the micelles and the DNA fragments, but is limited by the entrainment of micelle-poor, DNA-rich domains in the macroscopic micelle-rich phase. Furthermore, the volume ratio, that is, the volume of the top, micelle-poor phase divided by that of the bottom, micelle-rich phase, was manipulated to concentrate DNA fragments in the top phase. Specifically, by decreasing the volume ratio from 1 to 1/10, we demonstrated proof-of-principle that the concentration of DNA fragments in the top phase could be increased two- to nine-fold in a predictive manner. Biotechnol. Bioeng. 2009;102: 1613,1623. © 2008 Wiley Periodicals, Inc. [source] Affinity-enhanced protein partitioning in decyl ,- D -glucopyranoside two-phase aqueous micellar systemsBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005Henry Lam Abstract Liquid,liquid extraction in two-phase aqueous complex-fluid systems has been proposed as a scalable, versatile, and cost-effective purification method for the downstream processing of biotechnological products. In the case of two-phase aqueous micellar systems, careful choices of the phase-forming surfactants or surfactant mixtures allow these systems to separate biomolecules based on size, hydrophobicity, charge, or specific affinity. In this article, we investigate the affinity-enhanced partitioning of a model affinity-tagged protein,green fluorescent protein fused to a family 9 carbohydrate-binding module (CBM9-GFP),in a two-phase aqueous micellar system generated from the nonionic surfactant n -decyl ,- D -glucopyranoside (C10G1), which acts simultaneously as the phase-former and the affinity ligand. In this simple system, CBM9-GFP was extracted preferentially into the micelle-rich phase, despite the opposing tendency of the steric, excluded-volume interactions operating between the protein and the micelles. We obtained more than a sixfold increase (from 0.47 to 3.1) in the protein partition coefficient (Kp), as compared to a control case where the affinity interactions were "turned off" by the addition of a competitive inhibitor (glucose). It was demonstrated conclusively that the observed increase in Kp can be attributed to the specific affinity between the CBM9 domain and the affinity surfactant C10G1, suggesting that the method can be generally applied to any CBM9-tagged protein. To rationalize the observed phenomenon of affinity-enhanced partitioning in two-phase aqueous micellar systems, we formulated a theoretical framework to model the protein partition coefficient. The modeling approach accounts for both the excluded-volume interactions and the affinity interactions between the protein and the surfactants, and considers the contributions from the monomeric and the micellar surfactants separately. The model was shown to be consistent with the experimental data, as well as with our current understanding of the CBM9 domain. © 2005 Wiley Periodicals, Inc. [source] Bending Energetics of Tablet-Shaped Micelles: A Novel Approach to Rationalize Micellar SystemsCHEMPHYSCHEM, Issue 3 2007L. Magnus Bergström Prof. Abstract A novel approach to rationalize micellar systems is expounded in which the structural behavior of tablet-shaped micelles is theoretically investigated as a function of the three bending elasticity constants: spontaneous curvature (H0), bending rigidity (kc), and saddle-splay constant (k,c). As a result, experimentally accessible micellar properties, such as aggregation number, length-to-width ratio, and polydispersity, may be related to the different bending elasticity constants. It is demonstrated that discrete micelles or connected cylinders form when H0>1/4,, where , is the thickness of a surfactant monolayer, whereas various bilayer structures are expected to predominate when H0<1/4,. Our theory predicts, in agreement with experiments, a transition from discrete globular (tablet-shaped) micelles to a phase of ordered, or disordered, connected cylinders above a critical surfactant concentration. Moreover, a novel explanation for the mechanism of growth, from small globular to long rodlike or wormlike micelles, follows as a consequence from the theory. In accordance, polydisperse elongated micelles (large length-to-width ratio) form as the bending rigidity is lowered, approaching the critical point at kc=0, whereas monodisperse globular micelles (small length-to-width ratio) are expected to be present at large kc values. The spontaneous curvature mainly determines the width of tablet-shaped or ribbonlike micelles, or the radius of disklike micelles, whereas the saddle-splay constant primarily influences the size but not the shape of the micelles. [source]
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