High Sodium Dodecyl Sulfate Concentrations Research Articles

Application of a new coordination compound for the preparation of AgI nanoparticles

AgI nanoparticles have been sonochemically synthesized by using silver salicylate, [Ag(HSal)], as silver precursor. To investigate the effects of solvent, surfactant concentration, sonication time and temperature on the morphology of AgI nanostructures, several experiments were carried out. The products were characterized by SEM, TEM, XRD, TGA/DTA, UV–vis, and FT-IR. Based on the experimental findings in this research, it was found that the size of AgI nanoparticles was dramatically dependent on the silver precursor, sonochemical irradiation, and surfactant concentration. Sodium dodecyl sulfate (SDS) was applied as surfactant. When the concentration of SDS was 0.055mM, very uniform sphere-like AgI nanoparticles with grain size of about 25–30nm were obtained. These results indicated that the high concentration of SDS could prevent the aggregation between colloidal nanoparticles due to its steric hindrance effect.

Fourier Transform Infrared Spectroscopy as a Novel Approach for Analyzing the Biochemical Effects of Anionic Surfactants on a Surfactant-Degrading Arcobacter Butzleri Strain

Anionic surfactant-biodegrading capability of an Arcobacter butzleri strain was analyzed under aerobic conditions. The A. butzleri isolate displayed efficient surfactant-biodegrading capacity for sodium dodecyl sulfate (SDS) at concentrations of up to 100 mg/L in 6 days, corresponding to 99.0% removal efficiency. Fourier transform infrared spectroscopy was applied to observe the effects of varying concentrations of SDS on the biochemistry of bacterial cells. Results suggest that protein secondary structures were altered in bacterial cells at sufficiently high SDS concentrations, concurrent with SDS biodegradation.

A study of the physical stability of wet media-milled fenofibrate suspensions using dynamic equilibrium curves

Physical stability of wet media-milled fenofibrate (FNB, drug) suspensions containing stabilizers hydroxypropyl methyl cellulose (HPMC) and sodium dodecyl sulfate (SDS) is investigated. Traditionally, optimal stabilizer concentration is determined by assessing the particle size after milling and during storage in a multitude of experiments. Here, in a novel approach, similar physical stability information is generated via stepwise addition of a stabilizer at the end of milling in a single experiment and it is represented by a dynamic equilibrium curve. Such curves were generated for HPMC, SDS, and HPMC–SDS after milling and after 7-day storage. A unique optimal SDS concentration was found irrespective of the HPMC concentration (above a minimum), which was governed by agglomeration at low SDS concentration and by Ostwald ripening at high SDS concentration. Additional milling experiments with initial stabilizer addition instead of stepwise addition validated the new method, i.e. dynamic equilibrium curves via stepwise addition, which also revealed guiding principles for a stable FNB suspension. Unlike initial addition of SDS in multiple experiments, stepwise addition at the end of milling yielded the dynamic equilibrium curve in a single experiment for the 0.5–5% SDS concentration (wrt FNB), which resulted in 75% time saving and 83% drug saving.

Preparation and characterization of Ni–P/nanodiamond coatings: Effects of surfactants

In this study, the effects of different concentrations of surfactants on the properties of the Ni–P/nanodiamond (ND) coatings were investigated. Sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB) were used as the surfactants. Morphology, microhardness and some tribological properties of the coatings were evaluated and compared. Results showed that the composite coatings modified with high concentrations of SDS had smoother surface morphologies than the ones modified with CTAB and low concentrations of SDS. Moreover, it was observed that these coatings had the highest microhardness and wear resistance as well as the lowest friction coefficient (FC) among the coatings. It was found that the effect of NDs on the microhardness of as-plated composite coatings and the ones annealed at 200°C/3h was not significant, but became significant when heat treated at 300°C/1h and 400°C/1h.

Shotgun analysis of membrane proteomes by an improved SDS-assisted sample preparation method coupled with liquid chromatography–tandem mass spectrometry

Analysis of the membrane proteins, particularly the integral membrane proteins, is limited by the inherent membrane hydrophobicity. Sodium dodecyl sulfate (SDS) is one of the most efficient reagents used for the extraction of membrane proteins, but its presence in samples interferes with LC–MS-based proteomic analyses because it affects RP-LC separations and electrospray ionization. In this paper, we present an improved sample preparation strategy based on SDS-assisted digestion and peptide-level SDS-removal using an optimized potassium dodecyl sulfate (KDS) precipitation method (SSDP method) for shotgun analysis of the membrane proteome. This method utilizes a high concentration of SDS (1.0%) to lyse the membranes and to solubilize the hydrophobic membrane proteins, resulting in a more complete protein digestion in the diluted SDS buffer (0.1% SDS), and a high efficiency of SDS removal and peptide recovery by the optimized KDS precipitation for protein identification. The SSDP method provides evidence that proteins can be efficiently digested, and the SDS can be decreased to <0.01% allowing >95% peptide recovery. Compared to other sample preparation methods commonly used in shotgun membrane proteomics, the newly developed method not only increased the identified number of the total proteins, membrane proteins and integral membrane proteins by an average of 33.1%, 37.2% and 40.5%, respectively, but also leading to the identification of highest number of matching peptides. All the results showed that the method yielded better recovery and reliability in the identification of the proteins especially the highly hydrophobic integral membrane proteins, and thus providing a promising tool for the shotgun analysis of membrane proteome.

Silver nanoparticles synthesis in aqueous solutions using sulfite as reducing agent and sodium dodecyl sulfate as stabilizer

The synthesis of silver nanoparticles has been carried out in aqueous solutions in a stirred semibatch reactor through the reduction of silver ions (Ag+) by sulfite ions (SO3 2−), which were added at a tightly controlled rate up to a final sulfite/silver molar ratio of 0.45. Sodium dodecyl sulfate (SDS) was used as the stabilizer at concentrations below its critical micelle concentration. The effects of temperature, sulfite addition rate, and SDS concentration have been assessed. Ag+ turned to Ag0 in 5 min or less only when the synthesis was performed at 97 °C and not below. The sulfite addition rates studied were 0.5, 7.5, 15, and 90 μmol/min. The size, shape, polydispersity, and stability of the nanoparticles were determined by the sulfite addition rate and SDS concentration. At low SDS concentration (4 mM), stable, spherical shape, small size nanoparticles were formed only at the two intermediate sulfite addition rates. At the highest sulfite addition rate, 9 nm mean size spherical nanoparticles having a low ±5 nm polydispersity were produced at a high SDS concentration of 10 mM. With the low SDS concentration, larger truncated and spherical shape nanoparticles were obtained. UV–Vis spectrophotometry and transmission electron microscopy were used to characterize the nanoparticles.

Synthesis and Characterization of Silver Nanorods in Aqueous Sodium Dodecylsulfate Solutions

The synthesis and characterization of silver (Ag) nanorods through the Turkevich method in aqueous sodium dodecylsulfate (SDS) solutions have been studied in this work. The results have shown that the shape of Ag nanoparticles closely correlated with SDS concentration in the synthesis process. With high SDS concentrations, the majority of the synthesized Ag nanoparticles appeared in the form of nanorods; with low SDS concentrations, the Ag nanoparticles were spherical. This observation might be attributed to that the Ag nanoparticles grew up in SDS micelles and precipitated in the same shape of the micelles, because surfactant micelles were of cylinders in high concentrations and of spheres in low concentrations.

Effects of feed concentration and transmembrane pressure on membrane fouling in Cd2 + removal by micellar-enhanced ultrafiltration

In this study, micellar-enhanced ultrafiltration (MEUF) was used to remove Cd2+ from synthetic wastewater using a polysulfone spiral wound ultrafiltration membrane and sodium dodecyl sulfate (SDS) as a surfactant. The effects of two important parameters related to membrane fouling in MEUF were investigated: transmembrane pressure (TMP) and feed concentration. The recycling of retentate to the feed tank, which led to continuous growth of SDS concentration, is investigated. The permeate flux and fouling resistance around the critical micelle concentration (CMC) showed that higher SDS concentrations did not always lead to more serious fouling, but fouling became more serious after the SDS concentration reached five times the CMC. With increasing TMP, the flux declined drastically as a result of particle aggregation and gel layer formation. However, the TMP was not always a good criterion of membrane fouling: in different phases, high TMP and low TMP values affected membrane fouling differently; a high TMP such as 0.25MPa resulted in low membrane fouling at the beginning of the MEUF because of the higher driving power; and a low TMP such as 0.05MPa caused more serious membrane fouling after stopping because of pore blocking.

Aggregation Kinetics and Transport of Single-Walled Carbon Nanotubes at Low Surfactant Concentrations

Little is known about how low levels of surfactants can affect the colloidal stability of single-walled carbon nanotubes (SWNTs) and how surfactant-wrapping of SWNTs can impact ecological exposures in aqueous systems. In this study, SWNTs were suspended in water with sodium dodecylsulfate (SDS) as a surface-active dispersing agent. The effect of SDS concentration on SWNT suspension stability was investigated with time-resolved dynamic light scattering (TRDLS) initial aggregation studies utilizing both monovalent (Na(+)) and divalent (Ca(2+)) cations. The critical coagulation concentration (CCC) values increased with SDS concentration for the Na(+) treatments, but the Ca(2+) treatments were less sensitive to SDS concentration changes. Longer term stability studies with SDS concentrations orders of magnitude below the SDS critical micelle concentration demonstrated that SWNTs remained suspended for over six weeks in a surface water. Transport studies in a freshwater sediment similarly showed a SDS concentration-dependent mobility of SDS-wrapped SWNTs in that SWNTs showed a relatively greater retention at lower SDS concentrations (0.001%-0.05% w/v) than at a higher SDS concentration (0.1%). It is hypothesized that the stability and mobility of SWNT suspensions is directly related to the surface coverage of SDS on the SWNT surface that simultaneously increases electrosteric repulsion and decreases surface chemical heterogeneity. Overall, these studies demonstrate that low levels of surfactant are effective in stabilizing and mobilizing SWNTs in environmental media.

Mixtures of Cationic Copolymers and Oppositely Charged Surfactants: Effect of Polymer Charge Density and Ionic Strength on the Adsorption Behavior at the Silica–Aqueous Interface

This study addresses polymer-surfactant interactions at solid-liquid interfaces and how these can be manipulated by modulating the association between ionic surfactant and oppositely charged polymer, with a particular focus on electrostatic interactions. For this purpose, the interaction of a series of cationic copolymers of vinylpyrrolidone and quaternized vinylimidazol with sodium dodecyl sulfate (SDS) at the silica-aqueous interface was followed by in situ ellipsometry. To reveal the nature of the interaction, we performed measurements for different copolyion charge densities, in the absence and presence of added salt. The path-dependence of the interaction was studied by comparing the adsorption under two different conditions, adsorption from premixed solutions and sequential addition of surfactant to the polymer solution, but the same end state. The reversibility of the adsorption process was studied by following the effect of dilution on the adsorbed layer. All copolyions adsorbed to both silica and hydrophobized silica, revealing the importance of both hydrophobic and electrostatic attractive interactions. On both types of surface, an increase in adsorbed amount was found on lowering the fraction of charged units. An increased ionic strength gave an increased adsorbed amount in all cases, but especially on hydrophobic surfaces. The adsorbed amount on silica from mixtures of the copolyions with SDS peaked at an SDS concentration corresponding closely to the concentration of cationic charges of the different polyions. Around the region of charge equivalence, there was also a phase separation in the bulk. At higher concentrations of SDS, a redissolution in the bulk, and a decrease in adsorbed amount, occurred as a result of excess SDS binding to the complexes. For the most highly charged polyions, we observed a decrease in adsorbed amount, and a shift in the adsorption maxima to lower SDS concentrations, with increasing ionic strength.

Structural preferences of Aβ fragments in different micellar environments

Amyloid diseases occur due to conformational change in the native protein. Understanding the amyloid peptide structural stability and conformational preference at the molecular level in membranous environment may lead to advancement in drug design and therapy. The conformational preferences of amyloid peptide fragments, Aβ₁₋₁₁, Aβ₁₂₋₂₂, Aβ₂₃₋₃₃ and Aβ₃₄₋₄₂ was studied in buffers, trifluoroethanol (TFE) and sodium dodecyl sulfate (SDS) micelles using circular dichroism spectroscopy. The fragment, Aβ₁₋₁₁ in TFE adopts a mixture of random coil and turn conformations. Aβ₁₂₋₂₂ and Aβ₂₃₋₃₃ underwent transition from random coil to helix conformation, while Aβ₃₄₋₄₂ exhibited β-sheet conformation in initial stage which was unaltered on complete evaporation of TFE. Addition of SDS to Aβ₁₂₋₂₂ and Aβ₃₄₋₄₂ favors β-sheet structure, which was predominant in the case of Aβ₃₄₋₄₂. However, in Aβ₁₋₁₁ and Aβ₂₃₋₃₃, no secondary structural change was noticed even at high SDS concentrations. On aging, all the peptide fragments showed β-sheet conformational transition. The C-terminal fragment has the ability to adopt predominant β-sheet conformation even in the presence of detergent and membrane mimicking environment. Altogether, the structural information gained from the short fragments could be further used for determining their role in the organization of Aβ peptide in stable fibril form.

The corrosion properties of phosphate coating on AZ31 magnesium alloy: The effect of sodium dodecyl sulfate (SDS) as an eco-friendly accelerating agent

Sodium nitrite has been used as an accelerating agent in phosphating bath to improve its properties. However, it is well known that sodium nitrite is a carcinogenic component in phosphating sludge. In this study, it has been aimed to replace sodium nitrite by an environmentally friendly accelerating agent. To this end, sodium dodecyl sulfate (SDS) was used in phosphating bath to improve the phosphate coating formation on an AZ31 magnesium alloy. The effect of SDS/sodium nitrite ratio on the phosphated samples properties was also studied. Using field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), direct current (DC) polarization and electrochemical impedance spectroscopy (EIS) the properties of phosphated magnesium samples were studied. Results showed uniform phosphate coating formation on the magnesium sample mostly in hopeite phase composition. In addition, a denser and less permeable coating can be obtained at these conditions. The corrosion resistance of the phosphated samples was superiorly improved using higher SDS concentration in the phosphating bath.

Dual behavior of sodium dodecyl sulfate as enhancer or suppressor of insulin aggregation and chaperone-like activity of camel αS 1-casein

Sodium dodecyl sulfate (SDS) at low concentrations considerably enhanced insulin aggregation and reduced the chaperone-like activity of purified camel αS 1-casein (αS 1-CN). These observed changes were the result of repulsive electrostatic interactions between both negative charged head groups of SDS and αS 1-CN, and the net negative charge of insulin molecules, resulting in the greater exposure of hydrophobic patches of insulin and its enhanced aggregation. In contrast, enhanced hydrophobic interactions were primarily responsible for the conformational changes observed in insulin and αS 1-CN at high SDS concentrations, resulting in increased binding of SDS and αS 1-CN to insulin and its reduced aggregation.

Inactivation and Unfolding of the Hyperthermophilic Inorganic Pyrophosphatase from Thermus thermophilus by Sodium Dodecyl Sulfate

Inorganic pyrophosphatase (PPase, EC 3.6.1.1) is an essential constitutive enzyme for energy metabolism and clearance of excess pyrophosphate. In this research, we investigated the sodium dodecyl sulfate (SDS)-induced inactivation and unfolding of PPase from Thermus thermophilus (T-PPase), a hyperthermophilic enzyme. The results indicated that like many other mesophilic enzymes, T-PPase could be fully inactivated at a low SDS concentration of 2 mM. Using an enzyme activity assay, SDS was shown to act as a mixed type reversible inhibitor, suggesting T-PPase contained specific SDS binding sites. At high SDS concentrations, T-PPase was denatured via a two-state process without the accumulation of any intermediate, as revealed by far-UV CD and intrinsic fluorescence. A comparison of the inactivation and unfolding data suggested that the inhibition might be caused by the specific binding of the SDS molecules to the enzyme, while the unfolding might be caused by the cooperative non-specific binding of SDS to T-PPase. The possible molecular mechanisms underlying the mixed type inhibition by SDS was proposed to be caused by the local conformational changes or altered charge distributions.

Small-angle X-ray scattering study of metal nanoparticles prepared by photoreduction in aqueous solutions of sodium dodecyl sulfate

Photoreduction formation mechanisms of metal particles (gold (Au) and platinum (Pt) particles) in aqueous solution of sodium dodecyl sulfate (SDS) have been investigated using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and extended X-ray absorption fine structure (EXAFS) measurements. The anionic surfactant SDS was used as a stabilized reagent to disperse metal particles in aqueous solutions. The average particle diameter of Au and Pt particles was estimated from TEM as 4.5 and 2.7 nm, respectively. The SAXS analysis showed that in high concentration of SDS the size of Au and Pt particles is consistent with those obtained from TEM and EXAFS measurements, and the micelles of SDS retain a core–shell structure in aqueous solutions after the formation of metal particles. In the particle formation process, metal particles were photochemically produced in the core of micelles and they did not significantly affect the morphology of micelles, although these metal ions were almost randomly distributed in solution before the photoreduction. The particle growth rate of Au and Pt could be evaluated on the basis of the weight fraction of these metal particles, and it was found that Au particle growth occurs more rapidly than Pt particle growth in the aqueous SDS solutions.

Formation Of A Core In SDS Denatured States Of Rhodopsin

A general understanding of the folding pathway of helical membrane proteins has remained elusive due to the limited number of membrane proteins investigated to date. In order to begin to establish conditions under which the folding pathway of the mammalian membrane protein rhodopsin, a prototypic G protein coupled receptor with primary function in vision, can be studied, we have measured its secondary and tertiary structure changes under chemical denaturing conditions. A significant decrease in ellipticity at 222nm of maximally 40% is observed on adding sodium dodecyl sulfate (SDS) as a denaturant suggesting unfolding of the native helices. Tertiary structure is disrupted already at very low SDS concentrations of 0.05%, as evidenced by the loss of retinal chromophore, increase in tryptophan fluorescence and increase in cysteine accessibility. However, at intermediate SDS concentrations (0.1% to 3%), there is a decrease in tryptophan fluorescence accompanied by a simultaneous decrease in cysteine reactivity indicating formation of a compact intermediate. Light-scattering confirms that this decrease is not due to unspecific aggregation of the protein. Site-directed mutagenesis indicates that the reactive cysteines in this intermediate are located in the cytoplasmic domain of rhodopsin. At high SDS concentrations, between 7% and 15%, where a large amount of additional helix is disrupted, there is an increase in tryptophan fluorescence and cysteine reactivity. However, with further increase in SDS concentration up to 30%, there is a drop in fluorescence and cysteine accessibility suggesting formation of a core in this largely unfolded state. Existence of a folding core during early stages of folding of rhodopsin has also been postulated by the long-range interaction model and has been predicted by earlier computational experiments.

Molecular Dynamics Simulation of Effect of Salt on the Compromise of Hydrophilic and Hydrophobic Interactions in Sodium Dodecyl Sulfate Micelle Solutions

The presence of salt has a profound effect on the size, shape and structure of sodium dodecyl sulfate (SDS) micelles. There have been a great number of experiments on SDS micelles in the presence and absence of salt to study this complex problem. Unfortunately, it is not clear yet how electrolyte ions influence the structure of micelles. By describing the compromise between dominant mechanisms, a simplified atomic model of SDS in presence of salt has been developed and the molecular dynamics (MD) simulations of two series of systems with different concentrations of salt and charges of ion have been performed. Polydispersity of micelle size is founded at relatively high concentration of SDS and low charge of cation. Although the counter-ion pairs with head groups are formed, the transition of micelle shape is not observed because the charge of cation is not enough to neutralize the polar of micelle surface.

Double Phase Inversion of Emulsions Containing Layered Double Hydroxide Particles Induced by Adsorption of Sodium Dodecyl Sulfate

A liquid paraffin-water emulsion was investigated using layered double hydroxide (LDH) particles and sodium dodecyl sulfate (SDS) as emulsifiers. Both emulsifiers are well-known to stabilize oil-in-water (o/w) emulsions. Surprisingly, a double phase inversion of the emulsion containing LDH particles is induced by the adsorption of SDS. At a constant LDH concentration, the emulsion is o/w type when SDS concentrations are low. At intermediate SDS concentrations, the first emulsion inversion from o/w to w/o occurs, which is attributed to the enhanced hydrophobicity of LDH particles caused by the desorption of the second layer of surfactant, leaving a densely packed SDS monolayer on the LDH exterior surfaces. The second inversion from water-in-oil (w/o) to o/w occurs at higher SDS concentrations, which may be due to the competitive adsorption at the oil/water interfaces between the LDH particles modified by the SDS bilayers and the free SDS molecules in the bulk solution, but the free SDS molecules dominate and determine the emulsion type. Laser-induced fluorescent confocal micrographs clearly confirm the adsorption of LDH particles on the surfaces of the initial o/w and intermediate w/o emulsion droplets, whereas no LDH particles were adsorbed on the final o/w emulsion droplet surfaces. Also, transmission electron microscopy (TEM) observations indicate that the shape of the final o/w emulsions is similar to that of the monomeric SDS-stabilized emulsion but different from that of the initial o/w emulsions. The adsorption behavior of SDS on LDH particles in water was investigated to offer an explanation for the emulsion double phase inversion. The zeta potential results show that the particles will flocculate first and then redisperse following surfactant addition. Also, X-ray diffraction (XRD) measurements indicate that SDS adsorption on the LDH interior surfaces will be complete at intermediate concentrations.

Micellar-enhanced ultrafiltration of cadmium ions with anionic–nonionic surfactants

Micellar-enhanced ultrafiltration (MEUF), a surfactant-based separation process, is promising in removing multivalent metal ions from aqueous solutions. The micellar-enhanced ultrafiltration of cadmium from aqueous solution was studied in systems of anionic surfactant and mixed anionic/nonionic surfactants. The micelle sizes and zeta potentials were investigated by dynamic light scattering measurements. The effects of feed surfactant concentration, cadmium concentration and the molar ratio of nonionic surfactants to sodium dodecyl sulfate (SDS) on the cadmium removal efficiency, the rejection of SDS and nonionic surfactants and the permeate flux were investigated. The rejection efficiencies of cadmium in the MEUF operation were enhanced with higher SDS concentration and moderate Cd concentration. When SDS concentration was fixed at 3 mM, the optimal ranges of the molar ratios of nonionic surfactants to SDS for the removal of cadmium were 0.4–0.7 for Brij 35 and 0.5–0.7 for Triton X-100, respectively. With the addition of nonionic surfactants, the SDS dosage and the SDS concentration in the permeate were reduced efficiently.

Preparation of monodisperse crosslinked polymelamine microcapsules by phase separation method

Monodisperse polymelamine microcapsules were prepared by phase separation method. Control of microcapsule diameter was investigated using the uniform-sized oil-in-water emulsion droplets as the capsule core. The monodisperse emulsion droplets were prepared using the Shirasu porous glass (SPG) membrane emulsification technique. The effects of the diameter of the oil droplet and concentration of sodium dodecyl sulfate (SDS), which is a typical emulsifier in SPG membrane emulsification, on microencapsulation were investigated. The microcapsules were aggregated when oil droplets with small size were microencapsulated at high SDS concentration. To reduce the SDS concentration, the creamed emulsion was used. The monodisperse polymelamine microcapsules were successfully prepared by using the creamed emulsion. The microcapsule diameter was almost similar to the diameter of the encapsulated oil droplet. The coefficient of variation values was about 10% for all microcapsules prepared in this study. Control of microcapsule diameter was achieved in the range of 5–60 μm.