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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mixtures of alkyltrimethylammonium bromide (CnTAB, n=12, 14, 16, 18) and Triton X-100 were studied at a range of mole fractions of ionic surfactant per nonionic surfactant. For each mixture, the cmc obtained from surface tension measurements differed from that obtained using potentiometry. The behavior of these mixed-surfactant systems showed three different regions with increasing total surfactant concentration. From the surface tension and potentiometry data, we obtained the free monomer concentration of ionic surfactant (mi), the micellar mole fraction of surfactant (xi), and the degree of dissociation (alpha) of ionic surfactant. We also obtained the free monomer concentration of Triton X-100 (m2) using PFG-NMR technique. A new equation was introduced to evaluate the activity coefficient in the micellar phase. The excess free energy (GE) and the synergetic parameters of mixtures were determined at various mole fractions of CnTAB/Triton X-100. Finally, the complexity of the synergism parameters was investigated.
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PMID:Thermodynamic studies of mixed ionic/nonionic surfactant systems. 1521 49

Salt effect on the interaction of anionic polyelectrolyte sodium carboxymethylcellulose (NaCMC) with cationic gemini surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) [C12H25(CH3)2N(CH2)6N(CH3)2C12H25]Br2 (C12C6C12Br2) has been investigated using turbidimetric titration, steady-state fluorescence, and mobility measurement. It is found that the critical aggregation concentration(cac) for C12C6C12Br2/NaCMC complexes depends little on addition of sodium bromide (NaBr). However, in the presence of nonionic surfactant Triton X-100 (TX100), the critical ionic surfactant mole fraction for the onset of complex formation (Yc) increases markedly with increasing NaBr concentration. These salt effects are supposed as the overall result from competition between the increase of interaction and the screening of interaction. The increase of interaction is referred to as the effect that the larger micelle with higher surface charge density induced by salt has a stronger interaction with oppositely charged polyelectrolyte. The screening of interaction is referred to as the salt screening of electrostatic attraction between the polymer chain and the surfactant. For complex formation between C12C6C12Br2 and NaCMC, the increase of interaction probably compensates the screening of interaction, leading to constant cac values at different salt concentrations. For complex formation between the C12C6C12Br2/TX100 mixed micelle and NaCMC, the screening of interaction probably plays a dominant role, leading to higher suppression of electrostatic binding of micelles to polyelectrolyte.
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PMID:Salt effect on the complex formation between cationic gemini surfactant and anionic polyelectrolyte in aqueous solution. 1546 81

This research investigates the equilibrium solubilization behavior of naphthalene and phenanthrene from multicomponent nonaqueous-phase liquids (NAPLs) by five different polyoxyethylene nonionic surfactants. The overall goal of the study was to achieve an improved understanding of surfactant-aided dissolution of polycyclic aromatic hydrocarbons (PAHs) from multicomponent NAPLs in the context of surfactant-enhanced remediation of contaminated sites. The extent of solubilization of the PAHs in the surfactant micelles increased linearly with the PAH mole fraction in the NAPL. The solubilization extent and micelle-water equilibrium partition coefficient of the PAHs increased with the size of the polar shell region of the micelles rather than the size of the hydrophobic core of the micelle. The presence of both PAHs in the shell region of the micelles was confirmed by 1H NMR analysis. This is an important observation because it is commonly assumed that in multi-solute systems the solutes with relatively greater hydrophobicity are solubilized only in the micellar core. A comparison of the 1H NMR spectra of pure surfactant solutions and solutions contacted with various NAPLs demonstrated that the distribution of PAHs between the shell and the core changed with the concentration of PAHs in the micelles and in the NAPL. Competitive solubilization of the PAHs was observed when both PAHs were present in the NAPL. For example, in surfactant solutions of Brij 35 and Tween 80, the solubilization of phenanthrene was decreased in the presence of naphthalene as compared to systems that contained phenanthrene as the only solute. In contrast, with micellar solutions of Tergitol NP-10 and Triton X-100, phenanthrene solubilization was enhanced in the presence of naphthalene. The activity coefficients of the PAHs in the micellar phase were generally found to increase with PAH concentrations in the micelle.
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PMID:Selective solubilization of polycyclic aromatic hydrocarbons from multicomponent nonaqueous-phase liquids into nonionic surfactant micelles. 1557 85

Aggregational behaviour of micelles sodium dodecyl sulphate (SDS and Triton X-100, TX-100 both in pure and mixed form) and micelle like aggregates such as polymer-surfactant system [polymer poly(vinyl pyrrolidone), PVP]-SDS have been studied by using fluorescence characteristics of a newly synthesized probe. The critical micelle concentration (CMC) values determined at various surfactant compositions are lower than the ideal values indicating a synergistic effect. The value of the interaction parameter for the surfactant mixture has been determined which agrees well with the value calculated according to molecular thermodynamic theory. The total aggregation number of surfactant in mixed micelle shows a drastic variation in the SDS mole fraction range 0 < or = alpha1 < or = 0.3 and beyond the range it remains practically constant. Molar-based partition coefficients for the dye between the micellar and aqueous phase have been determined and a non-linear variation is obtained for the mixed micellar system. Variations of micro-polarity in the mixed micellar region have been investigated as a function of surfactant composition and results have been explained in terms of a suitable realistic model.
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PMID:Novel fluorescent probe as aggregation predictor and micro-polarity reporter for micelles and mixed micelles. 1591 2

Stable, colloidal sols of submicron size were prepared by titration of aqueous solutions of alkylene oxide surfactants with phosphotungstic acid, H(3)PW(12)O(40) (PTA), followed by neutralization with ammonium or potassium hydroxide. The stoichiometry of the complex between phosphotungstic acid and the ethoxylated surfactant was determined by (1)H and (31)P NMR and was dependent upon the degree of ethoxylation. For example, in the ethoxylated octylphenol having 9-10 ethylene oxide units, Triton X-100, the mole ratio of surfactant to PTA was 4.5. In the ethoxylated octylphenol having 70 ethylene oxide units, Triton X-705, the mole ratio of surfactant to PTA was 1. Prior to nucleation of particles, phosphotungstic acid forms an apparent yellow charge transfer complex with ethoxylated alkylphenol surfactants, typified by Triton X-405. This complex is characterized by an absorption spectrum that is the sum of the spectra of Triton X-405 and PTA with a very weak shoulder at 400-500 nm. Particles were nearly monodisperse and their size was dependent on the nonionic surfactant employed, the heteropolyacid, and the rate of addition of heteropolyacid solution.
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PMID:Colloidal particles derived from a complex of phosphotungstic Acid and ethoxylated surfactants. 1629 Aug 30

Seventeen different, chemically defined phosphatidylcholines, dispersed in aqueous medium in the form of large unilamellar vesicles, have been tested for solubilization by the non-ionic detergent Triton X-100. The temperatures (either 20 degrees C or 45 degrees C) were such that the bilayers were always in the liquid-disordered state. For each case, the solubilization parameters, Don (total detergent: lipid mole ratio producing the onset of solubilization) and D50 (total detergent: lipid mole ratio producing 50% solubilization), were determined under equilibrium conditions. Both parameters varied generally in parallel. When double bonds were introduced to the acyl chains, other factors remaining constant, solubilization became more difficult, i.e., more detergent was required. Cis-unsaturated phospholipids required more detergent than the corresponding trans-isomers. Increasing chain length in saturated phospholipids between C12 and C16 decreased moderately the detergent/lipid ratios causing solubilization. Acyl and alkyl phospholipids were equally susceptible to Triton X-100 solubilization. Lipid chain order, as measured by DPH fluorescence polarization, seemed to facilitate solubilization, perhaps because more ordered bilayers have a smaller capacity to accommodate detergent monomers without breaking down into lipid-detergent mixed micelles.
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PMID:Detergent solubilization of phosphatidylcholine bilayers in the fluid state: influence of the acyl chain structure. 1657 63

Spinach (Spinacia oleracea L.) leaf discs accumulated free proline when exposed to polyethylene glycol solutions of water potential less than -10 bars. At -20 bars, the accumulation was 11 micromoles per gram original fresh weight in a 24-hour period.When the leaf organelles were separated on a sucrose gradient, a proline oxidase was detected in the mitochondrial fraction. Isolated mitochondria were used for the study of the properties of the enzyme which was assayed by both oxygen uptake measurement and reduction of 2,6-dichlorophenol-indophenol in the presence of phenazine methosulfate. There was a stoichiometry of one-half mole of oxygen uptake per mole of Delta(1)-pyrroline-5-carboxylate production in the enzymic reaction. The enzyme had an optimal activity at pH 8.0 to 8.5 and an apparent K(m) value of 0.028 molar for proline. MgCl(2) and flavin adenine dinucleotide were required for maximal activity. Addition of sucrose, mannitol, or polyethylene glycol to reduce the water potential of the reaction mixture to as low as -20 bars resulted in little inhibition. The enzyme preparation was unable to reduce NAD to NADH, and NAD did not inhibit the enzyme activity. The enzyme preparation reduced cytochrome c in the presence of KCN. Triton X-100 at low concentration strongly inhibited the enzyme activity. The enzyme was apparently linked to the mitochondrial electron transport system. The in vitro activity of the enzyme under optimal assay conditions was high enough to prevent proline accumulation under water stress condition; presumably this activity was restrained in vivo.
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PMID:Proline Oxidase and Water Stress-induced Proline Accumulation in Spinach Leaves. 1666 Jul 61

A phytase was isolated and partially purified from the pollen of Lilium longiflorum Thumb. Optimum activity was at pH 8.0. The phytase was activated by Ca(2+) and Sr(2+) but not by the other divalent cations tested. Activity was inhibited by ethylenediaminetetraacetate. The phytase had a temperature optimum of 55 to 60 degrees C and an activation energy of about 12,700 calories/mole. Extraction of L. longiflorum pollen with 0.1% Triton X-100 increased recovery of the phytase by nearly 4-fold. The phytase had a molecular weight of about 88,000 as determined by gel filtration chromatography and a K(m) value of 7.2 micromolar for phytic acid in the presence of Ca(2+).
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PMID:A Calcium-Activated Phytase from Pollen of Lilium longiflorum. 1666 18

Lipase (triacylglycerol acylhydrolase [EC 3.1.1.3.]) was extracted from the microsomal fraction of cotyledons of dark grown seedlings of Canola (Brassica napus L. cv Westar) by treatment with Triton X-100. The enzyme was partially purified by chromatography on Sephacryl S-300 and DEAE Bio-Gel and was stable when stored at -20 degrees C in 50% (v/v) glycerol. The lipase aggregated readily but the distribution of species present in solution could be controlled by nonionic detergents. A species with an apparent M(r) of about 250,000 was obtained by gel filtration chromatography in the presence of 1% (v/v) Triton X-100. Lipase activity was optimal near neutral pH, and the reaction approached maximum velocity at a concentration of 0.5 to 1 millimolar emulsified triolein. The reaction rate responded linearly to temperature up to about 40 degrees C and the hydrolytic process had an activation energy of 18 kilocalories per mole. Microsomal lipase lost about 20% and 80% activity when heat-treated for 1 hour at 40 degrees C and 60 degrees C, respectively. At appropriate concentrations, the detergents Triton X-100, n-octyl-beta-d-glucopyranoside, (3-[(3-cholamidopropyl-O-dimethylammonio]-1-propanesulfonate, cetyl trimethylammonium bromide, and sodium dodecyl sulfate all inhibited lipase activity. n-Octyl-beta-d-glucopyranoside, however, was stimulatory in the 2 to 8 millimolar concentration range. The inhibitory effects of Triton X-100 were reversible.
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PMID:Properties of Solubilized Microsomal Lipase from Germinating Brassica napus. 1666 80

The distribution of macular xanthophylls, lutein and zeaxanthin, between domains formed in membranes made from an equimolar ternary mixture of dioleoylphosphatidylcholine/sphingomyelin/cholesterol, called a raft-forming mixture, was investigated. In these membranes, two domains are formed: the raft domain enriched in saturated lipids and cholesterol (detergent-resistant membranes, DRM), and the bulk domain enriched in unsaturated lipids (detergent-soluble membranes, DSM). These membrane domains have been separated using cold Triton X-100 extraction from membranes containing 1 mol% of either lutein or zeaxanthin. The results indicated that xanthophylls are substantially excluded from DRM and remain concentrated in DSM. Concentrations of xanthophylls in DRM and DSM calculated as the mole ratio of either xanthophyll to phospholipid were 0.005 and 0.03, respectively, and calculated as the mole ratio of either xanthophyll to total lipid (phospholipid + cholesterol) were 0.003 and 0.025, respectively. Thus, xanthophylls are over eight times more concentrated in DSM than in DRM. No significant difference in the distribution of lutein and zeaxanthin was found. It was also demonstrated using saturation-recovery EPR that at 1 mol%, neither lutein nor zeaxanthin affect the formation of membrane domains. The location of xanthophylls in domains formed from unsaturated lipids is ideal if they are to act as a lipid antioxidant, which is the most accepted mechanism through which lutein and zeaxanthin protect the retina from age-related macular diseases.
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PMID:Accumulation of macular xanthophylls in unsaturated membrane domains. 1667 20


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