Search results for " MICELLE"

Peculiar mechanism of solubilization of a sparingly water soluble drug into polymeric micelles. Kinetic and equilibrium studies.

2012

Complementary kinetic and equilibrium studies on the solubilization process of the sparingly water soluble tamoxifen (TAM) drug in polymeric aqueous solutions have been performed by using the spectrophotometric method. In particular, the amphiphilic copolymers obtained by derivatization of polymeric chain of poly(N-2-hydroxyethyl)-dl-aspartamide, PHEA, with poly(ethylene glycol)s, PEG (2000 or 5000 Da), and/or hexadecylamine chain, C16, namely PHEA-PEG2000-C16, PHEA-PEG5000-C16, PHEA-C16, have been employed. Preliminary to the kinetic and equilibrium data quantitative treatment, the molar absorption coefficient of TAM in polymeric micelle aqueous solution has been determined. By these studi…

Compared effects of synthetic and natural bile acid surfactants on xenobiotic absorption I. Studies with polysorbate and taurocholate in rat colon

1991

Some expected differences between synthetic and natural bile acid surfactants relative to their influences on xenobiotic absorption are briefly outlined on the basis of literature data. Then, experimental work is presented which shows that these differences exist and that they can be even more relevant than suspected. Absorption tests were developed in rat colon in situ with polysorbate (synthetic) and sodium taurocholate (natural) surfactants, using a homologous series of phenylalkylcarboxylic acids as test compounds. At the critical micelle concentration (CMC), the two previously reported actions of synthetic surfactants on xenobiotic absorption (i.e. the increase in absorbing membrane po…

The Closed/Open Model for Lipase Activation. Addressing Intermediate Active Forms of Fungal Enzymes by Trapping of Conformers in Water-Restricted Env…

2001

The behavior of prototypic fungal lipases in a water-restricted environment has been investigated by exploiting the reported experimental strategy that allows the trapping (freeze-drying) of the enzyme in the conformation present in aqueous solution and to subsequently assay it in nonaqueous media [Mingarro, I., Abad, C., and Braco, L. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 3308-3312]. We now report, using simple esterification as well as acidolysis (triglycerides as substrates) as nonaqueous model reactions, that the presence of a detergent (n-octyl-beta-glucopyranoside) in the freeze-drying buffer, at concentrations below the critical micellar concentration, generates different catalyti…

Natural or synthetic nucleic acids encapsulated in a closed cavity of amphiphiles

2013

In this review some aspects of the interactions of organized structures of amphiphiles with natural or synthetic DNAs are briefly considered. In particular DNAs encapsulated in closed cavities of amphiphiles, specifically giant vesicles and water-in-oil droplets and reverse micelles, are dealt with. Two main applications of giant vesicles are reviewed in detail, namely their use as microreactors where reactions can be followed by optical microscopy on a single vesicle and in synthetic biology as protocell models or as potential semi-synthetic ‘‘living’’ cells. Water-in-oil droplets uses for rapid and relatively low-cost DNA amplification by PCR reaction are described as well as for in vitro…

Formation of Micelles in Homopolymer-Copolymer Mixtures:  Quantitative Comparison between Simulations of Long Chains and Self-Consistent Field Calcul…

2006

Using Monte Carlo simulations of the bond fluctuation model and self-consistent field calculations, we study the formation of micelles in a mixture of homopolymers and asymmetric AB-diblock copolymers with composition, fA = 1/8. Both types of molecules are fully flexible and have identical length. We work in the semi-grand-canonical ensemble, i.e., we fix the monomer density and incompatibility, χN ≃ 100 (strong segregation regime), and control the composition of the mixture via the exchange chemical potential, δμ ≡ μAB − μB between the copolymers and homopolymers. The Monte Carlo simulation comprises moves that allow homopolymers to mutate into AB-diblock copolymers and vice versa. These m…

Reliability of the capacity factor at zero micellar concentration and the solute-micelle association constant estimates by micellar liquid chromatogr…

1997

In micellar liquid chromatography, MLC, the hydrophobicity of a compound is the predominant effect on its retention and interaction with micelles. The capacity factors at zero micellar concentration, k(m), and the solute-micelle association constants, KAM- have recently been used as the hydrophobicity index of compounds and are important in QSAR studies. These parameters could be estimated (by regression) from the (k,[M]) data, where k is the capacity factor and [M] the surfactant concentration minus the critical micelle concentration. km and KAM are usually obtained from the intercept and slope, respectively, of the plot 1/k vs. [M]. In spite of the general use of this equation, the reliab…

GALACTOSE-FUNCTIONALISED POLYMERIC MICELLES AS HEPATOCYTE-TARGETED CARRIERS

2012

Monte Carlo simulation of micelle formation in block copolymer solutions

1998

Short block copolymers in selective solvents (bad for A-block, good for B-block) are modeled by flexible bead-spring chains, where beads interact with short range Morse potentials of variable strength. It is shown that already very short chains (N A = N B = 2) exhibit a rather well-defined critical micelle concentration (cmc). The mass distribution of the micelles and their gyration tensor components as well as their internal structure are studied. It is shown that the relaxation time increases exponentially with the strength E AA of the attractive energy between the A-monomers, and thus frozen-in micelles of medium size are obtained when E AA is chosen too large. Our results are compared t…

Kinetic evidence for the solubilization of pyridine-2-azo-p-dimethylaniline in alkanediyl-α,ω-bis(dimethylcetylammonium nitrate) surfactants. Role of…

2004

The incorporation of the bidentate ligand pyridine-2-azo-p-dimethylaniline (PADA) into micellar aggregates of the dimeric cationic surfactants propanediyl-, hexanediyl- and dodecanediyl-alpha,omega-bis(dimethylcetylammonium nitrate) (16-3-16,2NO(3)(-), 16-6-16,2NO(3)(-) and 16-12-16,2NO(3)(-), respectively) has been studied at 25 degreesC by examining the kinetics of the complexation reaction of the Ni(II) ion with this ligand. For comparison, cetyltrimethylammonium nitrate ( CTAN), which can be considered as the "monomeric'' surfactant of 16-3-16,2NO(3)(-), has also been used. The kinetic data have shown that, for 16-3-16,2NO(3)(-) and CTAN, at a surfactant concentration below the critical…

Rate-retarding effects of mixed anionic/non-ionic micelles on the alkaline hydrolysis of the chloropentamminocobalt(III) complex

2006

Abstract Rate data for the alkaline hydrolysis of the chloropentaamminecobalt(III) cation in the presence of mixed micelles composed of (i) anionic sodium decylsulphate (SDeS) and non-ionic dodecylpenta(oxyethylene glycol) monoether (C 12 E 5 ) surfactants and (ii) anionic sodium perfluorooctanoate (SPFO) and non-ionic C 12 E 5 surfactants has been obtained at T 298 K and constant electrolyte concentration 0.08 mol dm −3 ([NaOH] = 0.01 mol dm −3 , [NaClO 4 ] = 0.07 mol dm −3 ) over a wide range of total surfactant concentration ( C t ) and anionic mole fraction ( χ ). The critical micelle concentrations (c.m.c.s) of the mixed micelles have been determined over the entire χ range by means of…