Triton X-100 Micelles Research Articles

Light scattering and NMR studies of Triton X-100 micelles in the presence of short chain alcohols and ethoxylates

Micellar characteristics of nonionic surfactant p-tert-octyl-phenoxy polyethylene (9.5) ether (Triton X-100) in aqueous media containing short-chain alcohols and their ethoxylates CnEm (n=2, 4, 6 and m=0, 1, 2) were examined by dynamic light scattering (DLS) and nuclear magnetic resonance (NMR). The micelle size increased with the addition of C6Em and decreased when C2Em alcohols were added to Triton X-100 solution; the increase and decrease in the micellar size in the presence of varying amounts of C4Em alcohols depends on the number of polar ethoxylate groups. The results are supported by viscosity and cloud point data and explained on the basis of solvophobic interaction. The interaction and location of additives in micelles is examined by 1H and NOESY NMR. The studies indicate that C2Em molecules mostly remain in bulk water; C6Em molecules get solubilized toward the core of the aggregates, while C4Em molecules are localized in the shell region of micelle according to their octanol/water partition coefficient values.

Reduction of Artifacts in Fluorescence Correlation Spectroscopy Due to Sample Adsorption on Optical Glass Surfaces

The preparation of glass cell surfaces that are chemically functionalized with poly(ethylene glycol) (PEG) chains to reduce sample adsorption and their use in fluorescence correlation spectroscopy (FCS) is described. Optical glass coverslips were acid etched and reacted with either 750 Mr PEG (PEG-750) or 5000 Mr PEG (PEG-5000) to produce adsorption-resistant optical surfaces. FCS data for Nile red-loaded Triton X-100 micelles (NR-TX-100) and Alexa Fluor 555-labeled proteins, bovine serum albumin (BSA-A555), lipidized BSA (lipid-BSA-A555), and three low molecular weight dyes deposited on PEGylated coverslips were evaluated. Measurement artifacts due to sample adsorption on the PEG-5000 functionalized coverslips were reduced significantly for the majority of test materials. Calculations of translational diffusion coefficients and Stokes radii confirmed the effectiveness of this approach. PEG-5000 functionalized coverslips were demonstrated as more effective in inhibiting adsorption than PEG-750 functionalized coverslips. Neither of the functionalized coverslips inhibited the adsorption of one test compound, rhodamine B, a dye that adsorbs strongly on glass surfaces. The use of longer PEG chains in conjunction with chemical cross-linking is proposed for producing a denser, less porous PEG layer for the prevention of strongly glass-adsorbing fluorophores that do not interact with the PEG layer.

Conformation of gramicidin A in Triton X‐100 micelles from CD and FTIR data: a clean example of antiparallel double β5.6 helix formation

The linear peptide gramicidin A (gA) forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization and dynamics of membrane channels. This polymorphic peptide can adopt two different types of structures, the helical dimer β6.3 ('channel state') and the double helical structure with two intertwined monomers. The structure of gA in micelles of detergent Triton X-100 has been studied using CD, Fourier transform infrared, and fluorescence spectroscopy. The results obtained demonstrate that only one thermodynamically stable gA structure, the antiparallel left-handed double helix β5.6, is formed in this membrane-mimetic environment. The position of the tryptophan fluorescence maximum at 332 nm is the same as that in phospholipid membranes. The causative factors governing the double helix formation in the micellar medium are discussed on the basis of known physicochemical properties of Triton X-100.

Polypyrrole nanoparticles fabricated via Triton X-100 micelles template approach and their acetone gas sensing property

Nano-scaled polypyrrole (PPy) particles have been successfully synthesized with the help of Triton X-100 micelles via soft template approach. The polypyrrole nanoparticles have been spin-coated on surface acoustic wave (SAW) transducers to demonstrate their sensing capability toward acetone gas exposure. Field Emission Scanning Electron Microscopes (FE-SEM) and Fourier transform infrared (FT-IR) spectroscopy have been utilized to characterize these PPy nanoparticles. The PPy nanoparticles have an average diameter of 95nm. The responses of the sensors are linearly associated with the acetone concentrations in the range from 5.5ppm to 80ppm. In response to 5.5ppm acetone exposure, the response and recovery time are 9s and 8.3s, respectively. SAW sensors coated with PPy nanoparticles were potentially useful to detect acetone.

Assessing Phospholipase A2 Activity toward Cardiolipin by Mass Spectrometry

Cardiolipin, a major component of mitochondria, is critical for mitochondrial functioning including the regulation of cytochrome c release during apoptosis and proper electron transport. Mitochondrial cardiolipin with its unique bulky amphipathic structure is a potential substrate for phospholipase A2 (PLA2) in vivo. We have developed mass spectrometric methodology for analyzing PLA2 activity toward various cardiolipin forms and demonstrate that cardiolipin is a substrate for sPLA2, cPLA2 and iPLA2, but not for Lp-PLA2. Our results also show that none of these PLA2s have significant PLA1 activities toward dilyso-cardiolipin. To understand the mechanism of cardiolipin hydrolysis by PLA2, we also quantified the release of monolyso-cardiolipin and dilyso-cardiolipin in the PLA2 assays. The sPLA2s caused an accumulation of dilyso-cardiolipin, in contrast to iPLA2 which caused an accumulation of monolyso-cardiolipin. Moreover, cardiolipin inhibits iPLA2 and cPLA2, and activates sPLA2 at low mol fractions in mixed micelles of Triton X-100 with the substrate 1-palmitoyl-2-arachidonyl-sn-phosphtidylcholine. Thus, cardiolipin functions as both a substrate and a regulator of PLA2 activity and the ability to assay the various forms of PLA2 is important in understanding its function.

Effects of Lipid Membrane Curvature on Lipid Packing State Evaluated by Isothermal Titration Calorimetry

In this report, we present a novel approach for the elucidation of the physicochemical properties of lipid membranes by isothermal titration calorimetry (ITC) to quantify the heat absorbed during the solubilization of vesicles into TritonX-100 micelles. By using large and small unilamellar vesicles for comparison, this method provides calorimetric data on the gel-to-liquid-crystalline phase transition and its curvature effects and, in particular, the enthalpy change upon membrane deformation from a planar to a curved shape, which cannot be obtained by the conventional approach using differential scanning calorimetry. The results showed quantitatively that the increase in membrane curvature increases the enthalpy of 1,2-dimyristoyl-sn-glycero-3-phosphocholine membranes both below and above the phase-transition temperature, and that the effect is more significant for the former condition. The calorimetric data obtained are further discussed in relation to the elastic bending energy of the membranes and membrane-peptide interaction.

A sensitive method for determination of phosphorous by continuum source graphite furnace atomic absorption spectrometry after a novel ionic liquid assisted cloud point extraction

Wall and platform atomisation have been investigated for the determination of phosphorus using palladium modifier in continuum source graphite furnace atomic absorption spectrometry (CS-GFAAS). Wall is found to have a better sensitivity compared to platform. This could be due to increase in population of non resonance line used in determination of phosphorus, since wall is heated directly. However, wall has inherent matrix interference problems, hence a matrix separation and pre-concentration procedure using ionic liquid assisted cloud point extraction is described. The method is based on the formation of hydrophobic ion-associate between anionic phosphomolybdate and 1-butyl-3-methylimidazolium chloride in the presence of H2SO4. The non-ionic Triton X-114 micelles have been used for pre-concentration of this ion-associate from a bulk aqueous phase into a small surfactant-rich phase. The main parameters affecting the extraction process are optimized. The characteristic mass of 0.4 ng is achieved after cloud point extraction. Under the optimized conditions, the pre-concentration factor is 50. The limit of detection is 0.06 μg g−1, for solid samples and 0.6 ng mL−1 for water. The recoveries are in the range of 95–98% with 2–4% relative standard deviation. The accuracy of the procedure is validated by analyzing NIST 8435 whole milk powder, 1549 non-fat milk powder, 1548 total diet and 1568a rice flour, and BCR 063R skim milk powder certified reference materials.

Reverse micelles directed synthesis of TiO2–CeO2 mixed oxides and investigation of their crystal structure and morphology

The synthesis of TiO2–CeO2 mixed oxides based on the sol–gel process controlled within reverse micelles of non-ionic surfactant Triton X-114 in cyclohexane is reported. The crystallization, phase composition, trends in nanoparticles growth and porous structure properties are studied as a function of Ti:Ce molar composition and annealing temperature by in-situ X-ray diffraction, Raman spectroscopy and physisorption. The brannerite-type CeTi2O6 crystallizes as a single crystalline phase at Ti:Ce molar composition of 70:30 and in the mixture with cubic CeO2 and anatase TiO2 for composition 50:50. At Ti:Ce molar ratios 90:10 and 30:70 the mixtures of TiO2 anatase, rutile and cubic CeO2 appear. In these mixtures TiO2 rutile is formed at higher temperatures than conventionally. Additionally, the amount of a present amorphous phase in individual mixtures was estimated from diffraction data. The porous structure morphology depends both on molar composition and annealing temperature. This is correlated with the presence of carbon impurities of different character.

Microwave assisted aqua regia extraction of thallium from sediment and coal fly ash samples and interference free determination by continuum source ETAAS after cloud point extraction

A simple cloud point extraction method is described for the separation and pre-concentration of thallium from the microwave assisted aqua regia extracts of sediment and coal fly ash samples. The method is based on the formation of extractable species of thallium and its interaction with hydrophobic solubilizing sites of Triton X-114 micelles in the presence of aqua regia and electrolyte NaCl. These interactions of micelles are used for extraction of thallium from a bulk aqueous phase into a small micelles-rich phase. The potential chloride interferences are eliminated effectively, which enabled interference free determination of thallium from aqua regia extracts using continuum source ETAAS. The parameters affecting the extraction process are optimized. Under the optimized conditions, pre-concentration factor and limit of detection are 40 and 0.2ngg−1, respectively. The recoveries are in the range of 95–102%. A characteristic mass, 13pg was obtained. The accuracy of the method is verified by analyzing certified reference materials such as NIST 1633b coal fly ash, NIST 1944 marine sediment and GBW 07312 stream sediments. The results obtained are in good agreement with the certified values and method is also applied to real samples.

Metal ion removal by ultrafiltration of colloidal suspensions of organically modified silica

Porous fumed silicas (FS) covalently grafted with 5-phenyl-azo-8-hydroxyquinoline (5Ph8HQ) are considered as extractants for copper(II) and nickel(II) at low concentration levels (10–50μM). The separation of the extracting colloidal functionalized silicas particles from the bulk aqueous phase is achieved by means of the frontal ultrafiltration technique. The stability of the colloidal dispersion of the organically modified silica and of the covalent grafting itself is studied via the loss of silica or of 5Ph8HQ through the ultrafiltration membrane during the separation process. The effects of the anion nature, specific surface area, surface ionization state on the metal ions extraction are assessed. For the sake of comparison, the extraction of copper(II) by 5Ph8HQ solubilized in neutral Triton X-100 (TX-100) micelles has been studied in the most similar experimental conditions, as well as copper(II) extraction by the same ligand in a biphasic water–chloroform system. High copper extraction yields are attained, and taking into account the low volume of extracting phase of the dispersed colloidal silica, high separation factors are obtained. The stoichiometry of the formed complex is the same (1:1) in the two microheterogeneous systems considered here whereas a 2:1 complex is formed in the biphasic liquid–liquid system. The apparent stability constant is greater by a factor 10 in the micelles than for the silica bounded 5Ph8HQ systems but the true affinity of the ligand for copper is 5 times lower in the micelle than on the functionalized systems. Comparing to the literature, it is shown that the type of silica considered (colloidal fumed silica in this work versus silica gel in the literature) greatly influences the affinity of the ligand toward the copper. Finally, the apparent extraction constant in 5Ph8HQ modified silica is ten times higher for copper(II) than for nickel(II).

Evaluating metal ion salts as acid hydrolase mimics: metal-assisted hydrolysis of phospholipids at lysosomal pH

Niemann-Pick disease and drug-induced phospholipidosis are lysosomal storage disorders in which there is an excessive accumulation of sphingomyelin in cellular lysosomes. Here we have explored the possibility of developing metal-based therapeutic agents to reverse phospholipid build-up through phosphate ester bond hydrolysis at lysosomal pH (~4.8). Towards this end, we have utilized a malachite green/molybdate-based colorimetric assay to quantitate the inorganic phosphate released upon the hydrolysis of sphingomyelin by twelve d- and f-block metal ion salts. In reactions conducted at 60 °C, the yields produced by the cerium(IV) complex Ce(NH(4))(2)(NO(3))(6) were superior. An Amplex(®) Red-based colorimetric assay and mass spectrometry were then employed to detect choline. The data consistently showed that Ce(IV) hydrolyzed sphingomyelin more efficiently at lysosomal pH: i.e., yields of choline and phosphate were 54 ± 4 and 22 ± 5 % at pH ~ 4.8, compared to 8 ± 1 and 5 ± 2 % at pH ~ 7.2. Hydrolysis at 60 °C could be significantly increased by converting sphingomyelin vesicles to mixed lipid vesicles and mixed micelles of Triton X-100. We then utilized cerium(IV) to cleave sphingomyelin at 37 °C (no Triton X-100). Although choline and phosphate levels were relatively low, hydrolysis continued to be considerably more efficient at lysosomal pH. A side by side comparison to phosphatidylcholine was then made. While the yields of choline and phosphate produced by phosphatylcholine were higher, the ratio of pH ~ 4.8 hydrolysis to pH ~ 7.2 hydrolysis was usually more favorable for sphingomyelin (37 and 60 °C).

Study on the Morphology Feature of 1-Butyl-3-methylimidazolium Tetrafluoroborate Based Ionic Liquid Reverse Microemulsions

The micromorphology of 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4)-in-cyclohexane and bmimBF4-in-triethylamine ionic liquid microemulsions was investigated by two-dimensional NMR and freeze-fracture transmission electron microscopy. The reverse micelles of Triton X-100/cyclohexane were destroyed by adding bmimBF4 and reverse microemulsions were induced to form by successively adding bmimBF4. However, no micelles appeared in triethylamine. But if adding bmimBF4 to a certain extent, a reverse microemulsion was also formed. The driving force of such aggregations could be attributed to the presence of different types of interactions between Triton X-100 and bmimBF4. A staggered arrangement of surfactant led to the irregular droplet structure and large aggregate size.

Phenol induced growth in Triton X-100 micelles: Effect of pH and phenols’ hydrophobicity

Cloud point, viscosity and dynamic light scattering data on aqueous micellar solutions of a nonionic surfactant Triton X-100 in the presence of several phenolic solutes are reported. These additives alter the surfactant's solution behavior depending on their hydrophobicity and pH of the solution. α-Naphthol, p-cresol and phenol induced micellar growth whereas more hydrophilic catechol, quinol, resorcinol did not show any significant change in micelle size. Increase in p-cresol concentration, decrease in pH and increase in temperature favored micelle growth. NMR results show that at lower concentration (10mM) p-cresol resides in the shell region while at higher concentration (40mM) both in shell region and core/shell interface. Quinol resides at micelle–water interface even at high concentration (40mM).

Mononuclear rearrangement of heterocycles in zwitterionic micelles of amine oxide surfactants

Rate constants for the mononuclear rearrangement (MRH) of Z-phenylhydrazones of some 5-substituted-3-benzoyl-1,2,4-oxadiazoles in water have been measured in the presence of zwitterionic micelles. The use of micellized N-tetradecyl-N,N-dimethylamineoxide (C14DMAO) as the reaction medium allowed to solubilize the otherwise water-insoluble oxadiazoles. Micellar rate effects were analyzed by using a simple pseudo-phase model and compared with those obtained in non-ionic micelles (Triton X-100). Evidence that both the rate of the rearrangement reaction and the binding of the substrates to the micelles are mainly governed by substrate hydrophobicity is obtained. The disagreement with the primarily sterically controlled MRH in Triton X-100 micelles highlights large and intriguing differences between the two micellar environments.

Simultaneous injection effective mixing flow analysis of urinary albumin using dye-binding reaction

A new four-channel simultaneous injection effective mixing flow analysis (SIEMA) system has been assembled for the determination of urinary albumin. The SIEMA system consisted of a syringe pump, two 5-way cross connectors, four holding coils, five 3-way solenoid valves, a 50-cm long mixing coil and a spectrophotometer. Tetrabromophenol blue anion (TBPB) in Triton X-100 micelle reacted with albumin at pH 3.2 to form a blue ion complex with a λmax 625nm. TBPB, Triton X-100, acetate buffer and albumin standard solutions were aspirated into four individual holding coils by a syringe pump and then the aspirated zones were simultaneously pushed in the reverse direction to the detector flow cell. Baseline drift, due to adsorption of TBPB–albumin complex on the wall of the hydrophobic PTFE tubing, was minimized by aspiration of Triton X-100 and acetate buffer solutions between samples. The calibration graph was linear in the range of 10–50μg/mL and the detection limit for albumin (3σ) was 0.53μg/mL. The RSD (n=11) at 30μg/mL was 1.35%. The sample throughput was 37/h. With a 10-fold dilution, interference from urine matrix was removed. The proposed method has advantages in terms of simple automation operation and short analysis time.

Perstraction of intracellular pigments by submerged cultivation of Monascus in nonionic surfactant micelle aqueous solution

"Milking processing" describes the cultivation of microalgae in a water-organic solvent two-phase system that consists of simultaneous fermentation and secretion of intracellular product. It is usually limited by the conflict between the biocompatibility of the organic solvent to the microorganisms and the ability of the organic solvent to secret intracellular product into its extracellular broth. In the present work, submerged cultivation of Monascus in the nonionic surfactant Triton X-100 micelle aqueous solution for pigment production is exploited, in which the fungus Monascus remains actively growing. Permeabilization of intracellular pigments across the cell membrane and extraction of the pigments to the nonionic surfactant micelles of its fermentation broth occur simultaneously. "Milking" the intracellular pigments in the submerged cultivation of Monascus is a perstraction process. The perstractive fermentation of intracellular pigments has the advantage of submerged cultivation by secretion of the intracellular pigments to its extracellular broth and the benefit of extractive microbial fermentation by solubilizing the pigments into nonionic surfactant micelles. It is shown as the marked increase of the extracellular pigment concentration by the submerged cultivation of Monascus in the nonionic surfactant Triton X-100 micelle solution.

Partitioning of Substrate within Aqueous Micelle Systems by Using Dead-End and Cross Flow Membrane Filtrations

The partition coefficients of different solutes as Itaconic acid (IA), dimethyl itaconate (DMI), diethyl itaconate (DEI) and dibuthyl itaconate (DBI) between water and micelles of Triton X-100 are determined by the two methods of separation namely Cross Flow Filtration and Dead-End Filtration by using a membrane that rejects the micelles and lets passing the molecules of solute. Partition coefficient of the solute between the aqueous phase and micelle aggregate was determined by titration and HPLC methods. The results obtained are discussed in our researcher's group and compared to others made with theoretical data reported from simulation. The effect of the different concentrations of solutes and transmembrane pressures have been investigated using a commercial membrane Nadir C005 (MWCO = 5 kDa).

Determination of Cd, Pb, Cu, Ni and Mn in effluents and natural waters by a novel salt induced mixed-micelle cloud point extraction using ETAAS

A novel salt induced low temperature mixed-micelle cloud point extraction procedure is developed for simultaneous separation and pre-concentration of Cd, Pb, Cu, Mn and Ni from industrial effluents and natural water matrices. Electrothermal atomic absorption spectrometry has been used for their determination. The mixed-micelles are formed by micelle–micelle interaction of Triton X-114 and sodium dodecyl sulfate (SDS) micelles. These mixed aggregates have a strong hydrophobic core, due to strong packing of both hydrophobic cores of Triton X-114 and SDS micelles, which is further enhanced by the addition of an electrolyte. These enhanced hydrophobic solubilising sites are used for efficient extraction of ammonium pyrrolidine dithiocarbamate (APDC) metal chelates at temperatures of 25–5 °C. This low temperature extraction avoids the thermal decomposition of these thermally labile complexes. The parameters affecting the extraction procedures are optimized. Under the optimized conditions, a pre-concentration factor of 10 was obtained with limits of detection of 5, 80, 30, 50 and 10 pg mL−1, respectively for Cd, Pb, Cu, Ni and Mn. The recoveries are in the range of 95–102% with 2–5% relative standard deviation. The accuracy of the procedure is evaluated by analyzing various certified reference materials such as BCR-713 final effluent, BCR-715 industrial effluent, BCR-609 ground water and NIST-1640a natural water matrices and also applied to real samples.

Electrocatalytic activity of nanoporous Pd and Pt: effect of structural features

The electrocatalytic activities of nanoporous palladium (npPd) and platinum (npPt) for oxygen reduction reaction (ORR) under alkaline conditions and hydrogen peroxide electrochemical reactions under neutral conditions were examined. npPd and npPt were prepared by the electrochemical deposition of each metal from the corresponding metal precursor in the presence of reverse micelles of Triton X-100, directing highly porous microstructures. The nanoporous catalysts showed excellent electrocatalytic activity for both the ORR and hydrogen peroxide electrochemical oxidation/reduction due to the increased active surface area. In particular, the npPd exhibited superior ORR activity (i.e., more positive onset and half-wave potentials, higher current density and greater number of electrons transferred) despite the smaller roughness factor than the npPt and commercial Pt. The catalytic activity for the hydrogen peroxide electrochemical reactions was also higher while using npPd (i.e., faster electrode reaction kinetics, increased current densities, etc.) compared to npPt. The higher catalytic activity of npPd than that of npPt suggests an advantage of the unique npPd structure, composed of nano- as well as micro-porosity, in facilitating mass transport through the porous metal layer. The npPd exhibited amperometric current responses, induced by the oxidation as well as reduction of hydrogen peroxide, linearly proportional to the hydrogen peroxide concentration with a rapid response time (<~2 s), high sensitivity, and low detection limit (<1.8 μM).

Quantification of Specific Anion Binding to Non-Ionic Triton X-100 Micelles

Anion binding to nonionic micelles was quantified by self-diffusion. Four anions were probed by multinuclear PGSTE NMR measurements in a Triton X-100 micellar aqueous solution. The salt concentration used was sufficiently low to avoid any micellar growth affecting surface curvature. The micellar aggregates that provide a model surface are uncharged with hydrophilic headgroups so that electrostatic ion surface interactions play little or no role in prescribing specific anion binding. Anionic affinity to the micellar surface followed a Hofmeister series, (CH(3))(2)AsO(2)(-) ≫ CH(3)COO(-) > H(2)PO(4)(-) > F(-). The observed ion specificity is rationalized by calling into play the nonelectrostatic interactions occurring between the anions and the micellar surface.