Absence Of Sodium Dodecyl Sulfate Research Articles

Experimental study and modeling of the kinetics of gas hydrate formation for acetylene, ethylene, propane and propylene in the presence and absence of SDS

The kinetics of hydrate formation of the hydrocarbons acetylene, ethylene, propane, and propylene were investigated using a fully stirred batch reactor. In relation to hydrate formation, a kinetic model was used to determine the induction time, the rate of hydrate formation, the apparent hydration rate constant, water-to-hydrate conversion associated with hydrate growth as well the storage capacity. This was done for all gases investigated in this study. Experiments were performed in the temperature and pressure ranges of (273.7–280.0) K and (0.5–4.12) MPa, respectively. Furthermore, the effect of sodium dodecyl sulfate (SDS) on the gas hydrate formation rate was examined. A substantial growth in the hydrate nucleation rate was observed in the presence of SDS.

Native Polyacrylamide Gels.

Proteins can easily be separated by polyacrylamide gel electrophoresis (PAGE) in the presence of a detergent and under (heat-) denaturing and (non- or) reducing conditions. The most commonly used detergent is sodium dodecyl sulfate (SDS). The major function of SDS is to shield the respective charge of the proteins present in the mixture to be analyzed and to provide all proteins with a negative charge. As a consequence, the proteins will be separated according to their molecular weight. Electrophoresis of proteins can also be performed in the absence of SDS. Using such "native" conditions, the charge of each of the proteins, which will depend on the primary amino acid sequence of the protein (isoelectric point) and the pH during electrophoresis, will mainly influence the mobility of the respective protein during electrophoresis. Here we describe a starting protocol for "native" PAGE.

Electrochemical Characterization of Caffeic Acid in the Presence and Absence of SDS

Caffeic acid (CA) ia classified as a hydroxycinnamic acid having three acidity constants and low stability in aqueous medium. This work proposes the use of sodium dodecyl sulfate (SDS) surfactant to confer stability to CA, performing the electrochemical characterization of the H3CA species at pH 1.44 in aqueous media, in the presence and absence of SDS. This study was carried out by cyclic voltammetry (CV) recorded over a carbon paste electrode (CPE) vs Ag/AgCl, beginning the potential sweep at Ei=0 = 0.400 V in the anodic direction. In the absence of SDS, the CA presents an oxidation peak at 0.527 V, but when the potential sweep is switched it is possible to observe a cathodic peak at 0.498 V; this study shows that the CA oxidation process is controlled by diffusion according with the Randles-Sevcik equation. However, in the presence of SDS the CV presents an oxidation peak at 0.561 V, although when switching potential sweep it is possible to observe a cathodic peak at 0.546 V. There exists a 0.029 V potential difference betwen the anodic and cathodic peak in the absence of SDS, while in its presense the potential difference is smaller, namely, 0.015 V. The CA anodic peak, in the presence of SDS, increases to 18.1 mA. The study shows that in the presence of SDS the CA oxidation is controlled through adsorption.

Kinetics of (TBAF\u2009+\u2009CO2) semi-clathrate hydrate formation in the presence and absence of SDS

In this communication, the impacts of adding SDS (sodium dodecyl sulfate), TBAF (tetra-n-butylammonium fluoride) and the mixture of SDS + TBAF on the main kinetic parameters of CO2 hydrate formation (induction time, the quantity and rate of gas uptake, and storage capacity) were investigated. The tests were performed under stirring conditions at T = 5 °C and P = 3.8 MPa in a 169 cm3 batch reactor. The results show that adding SDS with a concentration of 400 ppm, TBAF with a concentration of 1–5 wt%, and the mixture of SDS + TBAF, would increase the storage capacity of CO2 hydrate and the quantity of gas uptake, and decrease the induction time of hydrate formation process. The addition of 5 wt% of TBAF and 400 ppm of SDS would increase the CO2 hydrate storage capacity by 86.1% and 81.6%, respectively, compared to pure water. Investigation of the impact of SDS, TBAF and their mixture on the rate of gas uptake indicates that the mixture of SDS + TBAF does not have a significant effect on the rate of gas uptake during hydrate formation process.

The Molecular Basis of the Sodium Dodecyl Sulfate Effect on Human Ubiquitin Structure: A Molecular Dynamics Simulation Study

To investigate the molecular interactions of sodium dodecyl sulfate (SDS) with human ubiquitin and its unfolding mechanisms, a comparative study was conducted on the interactions of the protein in the presence and absence of SDS at different temperatures using six independent 500 ns atomistic molecular dynamics (MD) simulations. Moreover, the effects of partial atomic charges on SDS aggregation and micellar structures were investigated at high SDS concentrations. The results demonstrated that human ubiquitin retains its native-like structure in the presence of SDS and pure water at 300 K, while the conformation adopts an unfolded state at a high temperature. In addition, it was found that both SDS self-assembly and the conformation of the resulting protein may have a significant effect of reducing the partial atomic charges. The simulations at 370 K provided evidence that the SDS molecules disrupted the first hydration shell and expanded the hydrophobic core of ubiquitin, resulting in complete protein unfolding. According to these results, SDS and temperature are both required to induce a completely unfolded state under ambient conditions. We believe that these findings could be useful in protein folding/unfolding studies and structural biology.

Detergent-induced aggregation of an amyloidogenic intrinsically disordered protein

Abstract Intrinsically disordered proteins (IDPs) belong to an important class of proteins that do not fold up spontaneously. The conformational flexibility of IDPs allows them to adopt a wide range of conformations depending upon their biochemical environment. Many IDPs undergo profound conformational conversion that is often coupled to amyloid aggregation in the presence of negatively charged lipid membranes. Here, we show the effect of a well-known anionic lipid mimetic, sodium dodecyl sulfate (SDS), on the aggregation mechanism of a model amyloidogenic IDP, namely, bovine \(\upkappa \)-casein. In the absence of SDS, the aggregation kinetics of reduced and carboxymethylated (RCM) \(\upkappa \)-casein followed a nucleation dependent polymerization model that comprises both lag- and assembly phases. On the contrary, in the presence of sub-micellar concentration of SDS, the aggregation kinetics did not exhibit a lag phase and appears to follow a non-nucleation pathway. Additionally, the morphologies of the aggregates formed in the absence and presence of SDS were found to be different. In the absence of SDS, \(\upkappa \)-casein aggregation proceeded to typical amyloid fibrils, whereas, in the presence of SDS, the aggregation yielded large oligomers. Our results provide important molecular insights into the aggregation mechanism that can be utilized for the designing of novel protein/amyloid based nanomaterials with desired properties. Graphical Abstract Synopsis: An amyloidogenic intrinsically disordered protein, \(\upkappa \)-casein aggregates into amyloid fibrils via a typical nucleation-dependent kinetics that exhibits a lag-phase. However, in the presence of an anionic surfactant, such as sodium dodecyl sulfate, \(\upkappa \)-casein aggregation is devoid of a lag-phase and yields large oligomers that do not convert into amyloid fibrils.

Effect of SDS, silver nanoparticles, and SDS + silver nanoparticles on methane hydrate semicompletion time

ABSTRACTIn this research, the semicompletion time (t95%) of gas uptake in the process of methane hydrate formation in the presence and absence of sodium dodecyl sulfate (SDS) and silver nanoparticles (SNPs) is investigated. The experiments were carried out in a 460 cm3 stirred batch reactor at temperatures of 273.65 and 275.65 K and initial pressures of 5, 5.7, and 7 MPa. The results showed that the addition of both additives at all tested conditions, noticeably, decreases the semicompletion time of methane uptake, compared to pure water. The semicompletion time of methane uptake in the presence of 500 ppm SDS, 45 μM SNPs, and 500 ppm SDS + 45 μM SNPs is 75.6, 546.3, and 129.9 min, respectively, while that for pure water it is 8729.0 min at 273.65 K and 7 MPa.

THE EFFECT OF SODIUM DODECYL SULPHATE ON THE FORCED HYDROLYSIS OF FeCl3 SOLUTIONS

Precipitations by the forced hydrolysis of 0.2 M FeCl3 aqueous solutions between 2 and 72 hours in the presence of 1% sodium dodecyl sulphate (SDS) were investigated. In the absence of SDS a direct phase transformation ß-FeOOH → α-Fe2O3 via dissolution/recrystallization occured in the precipitation system. In the presence of SDS, α-FeOOH as an intermediate phase precipitated and, with a prolonged time of forced hydrolysis, also transformed to α-Fe2O3 via the dissolution/recrystallization mechanism. On the basis of Mössbauer spectra it was concluded that in the presence of SDS, α-Fe2O3 phase possessed a lower degree of crystallinity. In this precipitation process the competition between the stability of Fe(III)-dodecyl sulphate, on one side, and the formation of iron oxide phases, on the other, also played an important role. FE SEM revealed that the big α-Fe2O3 particles possessed the substructure. The elongation of primary α-Fe2O3 particles produced in the presence of SDS was noticed. This effect can be assigned to the preferential adsorption of dodecyl sulphate groups on nuclei and crystallites of FeOOH and α-Fe2O3 phase during the forced hydrolysis of FeCl3 solutions.

Micellization of pH‐sensitive poly(butadiene)‐block‐poly(2 vinylpyridine)‐block‐poly(ethylene oxide) triblock copolymers: Complex formation with anionic surfactants

ABSTRACTThe micellization of three tailor‐made triblock copolymers, such as PB100–P2VP100–PEO104, PB185–P2VP108–PEO154, and PB37–P2VP115–PEO241, having similar total molecular weights and constant poly(2‐vinylpyridine) (P2VP) sequence lengths, was investigated as a function of pH and sodium dodecyl sulfate (SDS) concentration. At pH 7 the formation of intermicellar aggregates was observed, especially for copolymers of low poly(ethylene oxide) (PEO) content. A pH decrease from 7 to 3 leads to a particle size increase due to the electrostatic repulsion of the protonated P2VP chains. The influence of the PEO sequence length was also observed for zeta potential values. At pH 3, in the absence of SDS, core–shell–corona micelles are formed whereas in the presence of small amount of SDS (degree of neutralization DN = 0%–50%), a complex is formed between SDS and the protonated P2VP which leads to the shrinkage of the shell and thus to a decrease of the micellar sizes. For higher DN values, the micellar sizes increase due to the formation of large agglomerates and a transition occurs from a monomodal to a bimodal size distribution. Furthermore, it turned out that secondary aggregation, such as intermicellar aggregation, can completely be avoided if the degree of polymerization (DPn) of the water‐soluble block is significantly higher than the DPn of the water‐insoluble sequence. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45313.

Simultaneous Detection of Activity and Relative Molecular Mass of Adenylate Kinases After SDS-PAGE and Blotting.

Adenylate kinases (AKs) are ubiquitous monomeric phosphotransferases, which play a pivotal role in the energetic metabolism. At the present, nine isoforms are known. AKs catalyze the following reversible reaction: ATP + AMP ↔ 2 ADP, even though isoform 3 uses GTP instead ATP. For many years, the activity of AKs has been detected only after native polyacrylamide gel separations, i.e. in the absence of sodium dodecyl sulfate or methanol. In this work, we report the possibility to detect the activity of the isoforms able to use ATP as substrate, directly onto gel or nitrocellulose sheets, after denaturing SDS-PAGE and electroblotting. This method is innovative because it allows to determine simultaneously the activity and the molecular weight of AKs, especially onto nitrocellulose where bands are sharper, thanks to absence of protein diffusion.

Semicompletion time of carbon dioxide uptake in the process of gas hydrate formation in presence and absence of SDS and silver nanoparticles

ABSTRACTCarbon dioxide emission to the atmosphere is one of the main causes of the current global warming. Therefore, capturing this greenhouse gas is very important. The effect of sodium dodecyl sulfate (SDS) and silver nanoparticles on semicompletion time (t95%) of carbon dioxide uptake in the process of gas hydrate formation is investigated in this communication. The tests were performed at temperatures of 273.65 and 275.65 K and initial pressures of 2 and 3 MPa in a 460 cm3 stirred batch reactor. Experimental measurements show that utilization of SDS and silver nanoparticles decreases the semicompletion time of carbon dioxide uptake considerably. The addition of SDS with concentration of 500 ppm and silver nanoparticles with concentration of 45 μM at p = 2 MPa and T = 275.65 K, respectively, decreases the semicompletion time of carbon dioxide uptake 136.09% and 152.88%, compared to pure water. Investigating the effect of temperature on the amount of t95% in the presence and absence of tested additives shows that this kinetic parameter decreases by increasing the temperature from 273.65 to 275.65 K.

Noncovalent inhibitors of human 20S and 26S proteasome based on trypsin inhibitor SFTI-1.

Sunflower trypsin inhibitor (SFTI-1) is recognized as an attractive scaffold to designed potent inhibitors of various proteases. We have recently found that its analogues inhibit noncovalently both human and yeast 20S proteasomes. Here, a set of novel and more potent in vitro inhibitors is presented. The inhibitory potency of the peptides was assessed with human 20S proteasome in the presence or absence of sodium dodecyl sulfate and with human 26 proteasome. Their antiproliferative action against tumor (human melanoma cells A375) and normal cells (46 BR.1N human fibroblasts and HaCaT keratinocytes) was determined. The selected fluoresceine-labeled inhibitors were able to internalize into A375 cells and were sometimes present as foci in the cells. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 685-696, 2016.

Aqueous extraction of Ricinodendron heudelotii oil and direct miniemulsion polymerization of the oil-in-water fraction

This paper reports the aqueous extraction of Ricinodendron heudelotii oil and synthesis of Candida rugosa lipase catalyzed in-situ hydrolyzed emulsions of the extracted fraction for production of high-value products. The extracted oil-in-water emulsion fraction was polymerized with (meth)acrylate monomers by miniemulsion polymerization technique to synthesize environmental friendly and waterborne hybrid latex binders for coating systems. The aqueous extraction was carried out at 40°C by ultrasonication for 30min. The in-situ enzymatic hydrolysis reaction was carried at 37°C and the yield of the cream (oil-in-water emulsion) fraction is 6.7% (%wt). This fraction contains more than 80% of the total extracted oil and it is further polymerized with methyl methacrylate and butyl acrylate via miniemulsion polymerization in the presence and absence of sodium dodecyl sulfate (SDS) as an external emulsifier. The final degree of hydrolysis is 69.12%. The monomer conversion with SDS is 74.41% and without SDS the conversion is 62.00%. The hybrid latexes were characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), particle size analysis and thermo-mechanical analysis (TMA). The morphology of latexes was also evaluated by transmittance electron microscopy (TEM) and film surface topography with atomic force microscopy (AFM) techniques.

Radiation Induced Synthesis of In2O3Nanoparticles - Part II: Synthesis of In2O3 Nanoparticles by Thermal Decomposition of Un-irradiated and γ-irradiated Indium Acetylacetonate

Pure cubic phase, In2O3 nanoparticles with porous structure were synthesized by solid state thermal oxidation of un-irradiated and γ-irradiated indium acetyl acetonate in presence and absence of sodium dodecyl sulphate as surfactant. The as- synthesized In2O3nanoparticles were characterized by X-ray diffraction (XRD), fourier transformation infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transition electron microscopy (TEM) and thermogravimetry (TG). The shapes and morphologies of as- synthesized In2O3nanoparticles were highly affected by γ-irradiation of indium acetyl acetonate precursor and by addition of sodium dodecyl sulphate as surfactant. Calcination of un-irradiated indium acetyl acetonate precursor to 4 hours of 600 °C leads to the formation of spherical- shaped accumulative and merged In2O3 nanoparticles with porous structure, whereas irregular porous architectures composed of pure In2O3nanoparticles were obtained by using γ-irradiated indium acetylacetonate precursor. The as- prepared In2O3 nanoproducts exhibit photoluminescence emission (PL) property and display thermal stability in a wide range of temperature (25-800 °C) which suggest possible applications in nanoscale optoelectronic devices.

Substitution and Organohalide Oxidative Addition Reactions Involving a Dimethylplatinum(II) Complex in a Micelle Medium

Micellar system of sodium dodecyl sulfate (SDS) in a mixture of water/ethanol (1/1) is used as a new medium for stabilization of the platinum(II) complex [PtMe2(bipy)], in which bipy = 2,2′-bipyridine, knowing that the complex is unstable in water or ethanol in the absence of SDS. Kinetic studies for oxidative addition reactions of complex [PtMe2(bipy)] with methyl iodide, allyl bromide, or propargyl bromide and also for substitution reactions of the chelate 2,2′-bipyridine ligand in the complex [PtMe2(bipy)] by the P donor reagent P(O-iPr)3, L, to form the complex cis-[PtMe2L2], were successfully investigated in the green and safe solvent micellar system of SDS by monitoring the decay of the MLCT band in the UV–visible spectra.

Formation Mechanism and Tensile Mechanical Properties of Poly(acrylamide-co-octylphenol polyoxyethylene (10) acrylate) Hydrophobic Association Hydrogels With High Toughness

Poly(acrylamide-co-octylphenol polyoxyethylene (10) acrylate) hydrophobic association hydrogels, which is abbreviated to poly(AM-co-OP10/AC) HA-gels, were prepared through micellar copolymerization of acrylamide (AM) and a small amount of octylphenol polyoxyethylene (10) acrylate (OP10/AC) in the presence or absence of sodium dodecyl sulfate (SDS). For poly(AM-co-OP10/AC) HA-gels, formation mechanism was discussed in detail, which can reasonably explain the reason that tensile mechanical properties of the hydrogels (containing SDS) are much higher than those of the hydrogels (not containing SDS). In addition, according to the tensile experimental results of poly(AM-co-OP10/AC) HA-gels, the effect of composition content in the initial solutions on tensile mechanical properties was investigated in detail. The results clearly indicate tensile strength, elastic modulus and elongations for poly(AM-co-OP10/AC) HA-gels strongly depended on composition content in the initial solutions.

Electropolymerization of N,N-dimethylaniline in presence of sodium dodecyl sulfate and its electrochemical properties

Poly(N,N-dimethylaniline) (PDMA) was formed by successive cyclic voltammetry in monomer solution in the presence of sodium dodecyl sulfate (SDS) on the surface of a carbon paste electrode. The polymerization behavior of N,N-dimethylaniline in the presence of SDS is quite different from that of N,N-dimethylaniline in the absence of SDS. The effect of varying amount of SDS on the rate of polymerization of N,N-dimethylaniline was investigated. The electrochemical behavior of the SDS-PDMA carbon paste electrode has been investigated by cyclic voltammetry in 0.5 M H2SO4 and 5 mM K4[Fe(CN)6]/0.1 M KCl solutions as the supporting electrolyte and model system, respectively. The synthesized PDMA was characterized by FT-IR and scanning electron microscopy (SEM). Ni(II) ions were incorporated into the electrode by immersion of the polymeric modified electrode having amine groups in 0.1 M Ni(II) ion solution. The electro catalytic oxidations of methanol at the surface of the Ni/SDS-PDMA electrode were studied in a 0.1 M NaOH solution. Compared to bare carbon paste and PDMA-modified carbon paste electrodes; the SDS-PDMA electrode significantly enhanced the catalytic efficiency of Ni ions for methanol oxidation.

Thermal gelation of aqueous hydroxypropylmethylcellulose solutions with SDS and hydrophobic drug particles

The thermal gelation of hydroxypropylmethylcellulose (HPMC) solutions has been studied as a function of sodium dodecyl sulfate (SDS) concentration with and without griseofulvin, a model particulate BCS Class II drug by rheological measurements of gelation temperature (Tgel), steady-state viscosity (η) at 25°C, and ζ-potential. Polymer adsorption on the drug was demonstrated by a decrease in η and potential in the absence of SDS. Griseofulvin had a synergistic effect on gelation which was attributed to an effective spanning of associated hydrophobic polymeric regions through interactions with the adsorbed polymer. Adding SDS offsets this effect on Tgel shielding hydrophobic interactions. Higher SDS concentrations had no effect on the particles surface as evidenced by constant ζ-potential and Tgel. Yet, polymeric chains are saturated and larger surfactant aggregates account for the increase in viscosity. Understanding the gelation mechanism and complex interactions of HPMC with surfactants and drugs is necessary for the design of pharmaceutical products and optimization of their performance properties.

Dispersion Stability of Functionalized Graphene in Aqueous Sodium Dodecyl Sulfate Solutions

The colloidal stability of functionalized graphene sheets (FGSs) in aqueous sodium dodecyl sulfate (SDS) solutions of different concentrations was studied by optical microscopy and ultraviolet-visible light absorption after first dispersing the FGSs ultrasonically. In up to ∼10 μM SDS solutions, FGSs reaggregated within a few minutes, forming ramified structures in the absence of SDS and increasingly compact structures as the amount of SDS increased. Above ∼10 μM, the rate of reaggregation decreased with increasing SDS concentration; above ∼40 μM, the suspensions were colloidally stable for over a year. The concentration of ∼40 μM SDS lies 2 orders of magnitude below the critical surface aggregation concentration of ∼1.8 mM SDS on FGSs but above the concentration (∼18 μM) at which SDS begins to form a monolayer on FGSs. Neither surface micelle nor dense monolayer coverage is therefore required to obtain stable aqueous FGS dispersions. We support our experimental results by calculating the van der Waals and electrostatic interaction energies between FGSs as a function of SDS concentration and show that the experimentally observed transition from an unstable to a stable dispersion correlates with a transition from negative to positive interaction energies between FGSs in the aggregated state. Furthermore, our calculations support experimental evidence that aggregates tend to develop a compact structure over time.

Elucidating the mode of action of urea on mammalian serum albumins and protective effect of sodium dodecyl sulfate

The effect of sodium dodecyl sulfate (SDS) on human, bovine, porcine, rabbit and sheep serum albumins were investigated at pH 3.5 by using various spectroscopic techniques like circular dichroism (CD), intrinsic fluorescence and dynamic light scattering (DLS). In the presence of 4.0mM SDS the secondary structure of all the albumins were not affected as measured by CD but fluorescence spectra revealed 8.0nm blue shift in emission maxima. We further checked the stability of albumins in the absence and presence of 4.0mM SDS by urea and temperature at pH 3.5. In the absence of SDS, urea starts unfolding both secondary as well as tertiary structural elements of the all the albumins at ∼2.0M urea but in the presence of 4.0mM SDS, urea was unable to unfold even up to 9.0M. The albumins were thermally less stable at pH 3.5 with decrease in Tm but in the presence of 4.0mM SDS, the Tm was increased. From this study, it was concluded that SDS is showing a protective effect against urea as well as thermal denaturation of albumins. This behavior may be due to electrostatic as well as the hydrophobic interaction of SDS with albumins. Further, we have proposed the mechanism of action of urea. It was found that urea interacted with proteins directly when proteins are in charged form. Indirect interaction may be taking place when the environment is more hydrophobic.