sodium-dodecyl-sulfate and naphthalene

Sodium dodecyl sulfate, a biological membrane mimetic, can be used to study the conversion of globular proteins into amyloid fibrils in vitro. Using multiple approaches, the effect of SDS was examined on stem bromelain (SB), a widely recognized therapeutic protein. SB is known to exist as a partially folded intermediate at pH 2.0, situation also encountered in the gastrointestinal tract (its site of absorption). In the presence of sub-micellar SDS concentration (500-1000 μM), this intermediate was found to exhibit great propensity to form large-sized β-sheeted aggregates with fibrillar morphology, the hall marks of amyloid structure. We also observed inhibition of fibrillation by two naphthalene-based compounds, ANS and bis-ANS. While bis-ANS significantly inhibited fibril formation at 50 μM, ANS did so at relatively higher concentration (400 μM). Alcohols, but not salts, were found to weaken the inhibitory action of these compounds suggesting the possible involvement of hydrophobic interactions in their binding to protein. Besides, isothermal titration calorimetry and molecular docking studies suggested that inhibition of fibrillation by these naphthalene derivatives is mediated not just through hydrophobic forces, but also by disruption of π-π interactions between the aromatic residues together with the inter-polypeptide chain repulsion among negatively charged ANS/bis-ANS bound SB.

Topics: Alcohols; Bromelains; Buffers; Dose-Response Relationship, Drug; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Micelles; Molecular Docking Simulation; Naphthalenes; Protein Multimerization; Protein Structure, Secondary; Protein Structure, Tertiary; Sodium Dodecyl Sulfate

Effect of surfactant on the evaporation of p-chloronitrobenzene and naphthalene in the turbulent process was studied in order to understand the effect of surfactant on the evaporation of complex contaminants in dynamic water system. Sodium dodecyl sulfate (SDS), cetyltrimethyl ammonium bromide (CTMAB) and polyethylene glycol sorbitan monolaurate (Tween 20) were used in the experiment. The results showed that the evaporation of p-chloronitrobenzene and naphthalene from surfactant solution in set turbulence intensity followed the first kinetic equation and all the correlation coefficients were above 0.99. The evaporative loss velocity of component was increased in dynamic water,while it decreased in surfactant solution, comparing with static pure water. The combined impact of these two factors was mainly presented promoting. When the turbulence intensity was above 39 r/min and 65 r/min respectively and the concentrations of surfactants were set from 150 mg/L to 2000 mg/L, the corresponding evaporative loss velocity of naphthalene and p-chloronitrobenzene both increased clearly. The evaporative loss velocity of p-chloronitrobenzene and naphthalene in the same turbulence intensity were decreased because of the straining ability of surfactant with the rule: CTMAB > Tween 20 > SDS. The impact of both surfactant and turbulence on naphthalene (with higher H) was more distinct than p-chloronitrobenzene (with lower H).

Topics: Naphthalenes; Nitrobenzenes; Polysorbates; Sodium Dodecyl Sulfate; Surface-Active Agents; Volatilization; Water Pollutants, Chemical; Water Purification

The effects of agitation on naphthalene volatilization from solutions with surfactant concentration exceeding critical micelle concentration were studied. Micellar partition coefficient (K(m)) and liquid-vapor mass transfer coefficient (K(L)) in the presence of three surfactants, i.e., anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTMAB), and nonionic Tween 20 were determined at different agitation speeds. Both K(m) and K(L) increased in the agitated solutions, indicating enhanced naphthalene micellization and water-vapor mass transfer due to agitation. The enhancement factor of K(L) in surfactant-laden solution was determined to be in the range of 1.3-6.3 (SDS), 0.7-7.9 (CTMAB), and 1.5-7.3 (Tween 20). However, agitation exhibited a greater enhancement on K(L), resulting in a net increased volatilization rate. A conceptual model was developed to describe the dependence of the bulk aqueous phase naphthalene concentration (C(L)) on Henry's constant (H), K(L), K(m), and surfactant concentration (S). This study is the first in reporting the combined effects of agitation and surfactant on the volatilization of semi-volatile naphthalene in air-water-micelle system. Results provided insight into the volatile emission as frequently encountered in certain waste streams.

Topics: Cetrimonium; Cetrimonium Compounds; Environmental Monitoring; Kinetics; Micelles; Naphthalenes; Polysorbates; Sodium Dodecyl Sulfate; Solutions; Surface-Active Agents; Volatilization

This work describes the effect of a variety of metal ions as quenchers of the fluorescence of naphthalene, in aqueous micellar solutions of sodium dodecyl sulfate (SDS). The quenching by the metal ions can be adequately described by the Stern-Volmer equation and the best signal to noise ratios are obtained with low micellized detergent concentrations. Apparent Stern-Volmer constants decrease in the order: Fe3+ > Cu2+ > Pb2+ > Cr3+ > Ni2+ and directly reflect the relative sensitivity of the method for these ions. Detection limits (defined as three times the standard deviation of the blank for n= 10) for the fluorescence quenching of naphthalene by the metal ions in aqueous micellar SDS are in the range of 1.0 x 10(-6) to 1.0 x 10(-5) mol dm(-3). The proposed fluorescence quenching method shows good repeatibility for a variety of added quencher metal ions, indicating that anionic micelle-enhanced fluorescence quenching by metal ions constitutes an analytical method of rather general application.

Topics: Environmental Pollutants; Fluorescent Dyes; Ions; Metals; Micelles; Naphthalenes; Sodium Dodecyl Sulfate

Peaks of benzene (bz) and naphthalene (np) having diffuse fronts and steep rears under overload conditions were studied quantitatively in MEKC with SDS surfactant. The retardation factors of these compounds, solubilized at microM to mM concentrations by either 10, 30, or 50 mM SDS, were determined by vacancy MEKC and frontal analysis MEKC. Isotherm coordinates were calculated from the retardation factors, and the equation for the concave upward anti-Langmuir isotherm was fit to them. Peak profiles were computed with the MacCormack algorithm from the isotherm fits and a simplified continuity equation appropriate to MEKC. These profiles were compared to ones generated in normal MEKC from samples of bz and np solubilized at muM to mM concentrations by either 10, 30, or 50 mM SDS. In all cases, the anti-Langmuir isotherm described the asymmetry of experimental peaks. For bz in 30 and 50 mM SDS and np in 10 and 50 mM SDS, good to excellent agreement was found between the experimental and predicted profiles. For bz in 10 mM SDS, the experimental profiles were more broadened than the predicted ones, although their asymmetries agreed. For np in 30 mM SDS, the experimental isotherm predicted greater peak asymmetry than was observed, and the correct anti-Langmuir isotherm for all sample concentrations and field strengths was calculated from the most asymmetrical peak by the inverse method. The relative decrease of zone velocity with increasing analyte concentration was calculated from the isotherm parameters, electrokinetic mobilities, retardation factors, surfactant concentrations, and CMC. The simplification of the continuity equation was justified.

Topics: Benzene; Chromatography, Micellar Electrokinetic Capillary; Models, Theoretical; Naphthalenes; Sodium Dodecyl Sulfate

The experimental conditions that produce analyte peak splitting in micellar electrokinetic capillary chromatography (MEKC) have been systematically investigated. The system studied was a neutral phosphate buffer and sodium dodecyl sulfate (SDS) micelles as pseudostationary phase. A number of analytes showing a wide variety of hydrophobicity values and several organic solvents as sample diluents have been tested. Peak splitting phenomena are mainly due to the presence of organic solvent in the sample solution. They increase with the hydrophobicity of the analyte and decrease with the increase of the surfactant concentration. When hydrophobic compounds are analyzed the suggested ways to avoid split peaks are: (i) the use of 1-propanol or 1-butanol as sample diluent instead of methanol or acetonitrile or (ii) the use of high concentration of surfactant in the separating solution when the analyte must be dissolved in pure methanol or acetonitrile.

Topics: Alcohols; Buffers; Chromatography, Micellar Electrokinetic Capillary; Methanol; Micelles; Naphthalenes; Phosphates; Sodium Dodecyl Sulfate; Solutions; Solvents; Surface-Active Agents

Surfactants can increase the solubility of non-polar compounds, and have been applied in areas such as soil washing and treatment of non-aqueous phase liquids (NAPLs). This investigation explored the feasibility of removing vapor phase polycyclic aromatic hydrocarbon (PAH) from gases using an anionic surfactant. The solubility of vapor phase naphthalene was measured herein using gas chromatograph (GC) with a photon ionization detector (PID). The measurement results indicated that surfactant molecules were not favorable to micelle formation when temperatures increased from 25 degrees C to 50 degrees C. Regardless of whether solutions were quiescent or agitated, equilibrium naphthalene apparent solubility increased linearly with surfactant concentrations exceeding critical micelle concentration (CMC). The pH effects on naphthalene apparent solubility were small. Agitation increased naphthalene apparent solubility and lumped mass transfer coefficients. Furthermore, lumped mass transfer coefficients decreased with increasing surfactant concentration owing to increase in interfacial resistance and viscosity and decreased spherical micelle diffusion coefficients. Finally, the net absorption rate increased because the solubilization effects of micelles exceeded the reduction effects of mass transfer coefficient above the CMC. The enhanced naphthalene apparent solubility from the addition of surfactant can be expressed by an enrichment factor (EF). The EF value of naphthalene for the surfactant solution at 0.1 M with agitation at 270 rpm relative to quiescent water could reach 18.6. This work confirms that anionic surfactant can improve the removal efficiency of hydrophobic organic compound (HOC) from the gas phase.

Topics: Chromatography, Gas; Environmental Monitoring; Micelles; Naphthalenes; Polycyclic Aromatic Hydrocarbons; Sodium Dodecyl Sulfate; Soil Pollutants; Solubility; Surface-Active Agents; Volatilization; Water

The goal of this work was to investigate whether the solubility of vapor phase polycyclic aromatic compounds (PAHs) and CO2 in water could be enhanced by adding anionic surfactant during the absorption process. Naphthalene was the PAH surrogate and sodium dodecyl sulfate (SDS) was the anionic surfactant. A series of batch experiments in an absorption cell were performed at 50 degrees C with the surfactant concentration both lower than and higher than the critical micelle concentration (CMC). The experimental findings indicate that the CMC was not a function of pH at values of 3, 5 and 7. Furthermore, at surfactant concentrations less than the CMC, naphthalene apparent solubility increased slightly. On the other hand, the equilibrium naphthalene or CO2 apparent solubility increased linearly, in proportion to the surfactant concentration at concentrations greater than the CMC. This is due to the solubilization effect of micelles, which were formed by the surfactant at concentrations above the CMC. During simultaneous absorption of the two, the presence of CO2 only slightly decreased naphthalene apparent solubility, while the apparent solubility of CO2 was drastically reduced in the presence of naphthalene. As the magnitude of the micelle solubilization effect was greater than the reduction of the mass transfer coefficient in the presence of the surfactant, the total gas absorption rate increased. When the surfactant concentration was 0.1 M, the enrichment factor (the ratio of the solubility in surfactant solution to that in water) values of naphthalene both with and without CO2 increased to 9.05 and 8.60, respectively. These experimental findings demonstrate that anionic surfactant may be applied to increase the removal efficiency of hydrophobic compounds and CO2 through either a spray or packed tower.

Topics: Absorption; Carbon Dioxide; Environmental Pollutants; Naphthalenes; Polycyclic Aromatic Hydrocarbons; Sodium Dodecyl Sulfate; Solubility; Surface-Active Agents; Volatilization