Interaction between ethyl(hydroxyethyl)cellulose and sodium dodecyl sulphate in aqueous solution

Using sodium activity, viscosity, and cloudpoint measurements, it has been shown that sodium dodecyl sulphate (SDS) binds to ethyl(hydroxyethyl)cellulose in a cooperative manner. In the absence of salt the binding leads to an increase in the clouding temperature, but when a small amount of salt (0.01 molal) is present first a drastic decrease and then an equally drastic increase in the cloud point temperature is observed. The binding of SDS also initially leads to an increase in viscosity followed by a decreased viscosity at higher SDS concentrations. A molecular mechanism explaining the observed behavior is given.     

A distinct intermediate of RNase A is induced by sodium dodecyl sulfate at its pK(a)

The chemical denaturation of RNase A was found to be mediated by sodium dodecyl sulfate (SDS) at various pH. The characterization of the unfolding pathway was investigated by spectrophotometry and differential scanning calorimetry (DSC), and was analyzed by multivariate curve resolution (MCR) as a chemometric method. The spectrophotometric titration curve of RNase A upon interaction with SDS indicated a distinct complex intermediate in glycine buffer at pH 3.3. This was accompanied with the catalytic activation of the enzyme and was concurrent with maximum population of the intermediate, determined by MCR. This was confirmed by the DSC profile of RNase A in the presence of SDS, indicated by two transitions in thermal unfolding. The kinetic data on the unfolding process of RNase A upon addition of SDS showed a two-phase pathway under the same conditions. The intermediate appeared at low pH especially at the pK_a of SDS (pH 3.3). These results provide strong evidence of the influence of low pH (around the pK_a of SDS) on the existence of an intermediate upon interaction of RNase A with SDS.     

High-performance hydroxyapatite chromatography of integral membrane proteins and water-soluble proteins in complex with sodium dodecyl sulphate.

Integral membrane proteins from human erythrocytes were fractionated in the presence of sodium dodecyl sulphate (SDS) on four types of high-performance hydroxyapatite columns. A column of 2-microns sintered hydroxyapatite beads from Asahi Optical (Tokyo, Japan) gave the best resolution. With this column, glycophorin was eluted early in a gradient of increasing sodium phosphate buffer concentration, the glucose transporter was eluted later in two zones, one of which contained this protein alone, and the anion transporter was eluted last. Water-soluble proteins applied in complex with SDS also separated reasonably well upon elution. The water-soluble proteins and the membrane proteins were all eluted mainly in the order of increasing polypeptide length, but with considerable individual variation. SDS-polypeptide complexes are probably adsorbed onto hydroxyapatite by the interaction of positively charged amino acid side groups with phosphate ions (at P-sites) and of negatively charged amino acid side groups and polypeptide-bound dodecyl sulphate anions with calcium ions (at C-sites). As a rule, the number of charged side groups and dodecyl sulphate anions, and thus the number of binding sites, increases with the polypeptide chain length, which explains the general order of release of the polypeptides.     

Destructive and protective action of sodium dodecyl sulphate micelles on the native conformation of Bovine Serum Albumin: A study by extrinsic fluorescence probe 1-hydroxy-2-naphthaldehyde

The interaction of the anionic surfactant sodium dodecyl sulphate (SDS) with water soluble protein Bovine Serum Albumin (BSA) has been investigated spectroscopically using fluorescence probe 1-hydroxy-2-naphthaldehyde (HN12). The characteristic intramolecular proton transfer fluorescence band of HN12 has been used as an efficient reporter for the study of binding of SDS with BSA. The changes of spectral properties of HN12 demonstrate that SDS plays two opposite roles in the stability of protein BSA. It acts as a stabilizer at low concentration and destabilizer at high concentration to urea-denatured BSA.     

毛细管胶束电动色谱法测定夏枯草中两种有效成分

建立了毛细管胶束电动色谱法（ＭＥＫＣ）同时分离和测定夏枯草中齐墩果酸和熊果酸异构体含量的新方法。以１５ｍｍｏｌ／Ｌ磷酸氢二钠（Ｎａ２ＨＰＯ４）、１５ｍｍｏｌ／Ｌ硼砂（Ｎａ２Ｂ４Ｏ７）、１０ｍｍｏｌ／Ｌ十二烷基硫酸钠（ＳＤＳ）、５％（Ｖ／Ｖ）乙醇的缓冲溶液作为运行电解质溶液,在２０ｍｉｎ实现了齐墩果酸和熊果酸的基线分离。同时也研究了ＳＤＳ浓度和有机溶剂（乙醇）浓度对待测物质分离的影响。研究了不同提取     

Interactions between gelatin and sodium dodecyl sulphate: binding isotherm and solution properties

The interaction between sodium dodecyl sulphate (SDS) and gelatin was studied at pH 4.5 and 6.5 where the gelatin is positively charged (i.e.p. 8). At pH 4.5 a SDS/gelatin concentration range was found where gelatin precipitates. At pH 6.5 the SDS-gelatin complex remains soluble although three SDS concentration domains were distinguished where the SDS-gelatin complex had very different affinities for the solvent. Below C₁ the complex was highly surface active but other measurements (viscosity, potentiometry, protons uptake) did not reveal any particular consequence of binding. Between C₁ and C₂ the molecular size decreased (viscosity lowering) upon charge neutralization and collapse about small SDS aggregates (17 SDS molecules per gelatin molecule). Above C₂ a cooperative binding mechanism lead to the formation of SDS aggregates; the complex stretched out and turned strongly hydrophilic (the viscosity increases, low surface activity). At saturation one gelatin molecule bound about 200 SDS molecules. Above the overlap concentration (about 3 wt%) SDS aggregates formed between several gelatin molecules, the viscosity increased continuously with SDS concentration and the binding ratio was lower than in dilute gelatin solutions. A very good correspondence was found between the different analytical data including turbidity, viscosity, surface tension, protons uptake and direct potentiometric SDS binding measurements.     

Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air-Water Interface

Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br⁻ counterions compared to smaller Na⁺ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H⁺ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H⁺ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.     

Effect of the electrolyte concentration on cation binding in aqueous surfactant solutions.

Electrospray ionisation mass spectrometry (ESI-MS) is used for the qualitative and quantitative study of ion binding to interfaces. The ESI-MS measurements are carried out in aqueous solutions of sodium dodecyl sulphate (SDS) in the presence of NaCl, NH(4)ClO(4) , KCl, or Mg(ClO(4))(2) . The effect of the electrolyte concentration on the fractions, y(cation(+) ), of the DS(-) monomers bound to the cations is shown. Moreover, the binding stability of different cations with DS(-) monomers is determined versus the electrolyte concentration. This stability and the y(Na(+) ) values (the Na(+) ions derived from SDS), estimated in the presence of a given electrolyte, are quantitatively correlated with the electrolyte cation effect on the water structure. We also present calibration curves from which the molar concentrations of the sodium ions (derived from SDS) and of the other cations (derived from the electrolyte), bound to the SDS-micelle surface at a given electrolyte concentration, can be obtained. Besides, specific ion effects (Hofmeister effects) are considered for 1:1 electrolytes.     

Investigation and optimisation of the use of micellar electrokinetic chromatography for the analysis of six cardiovascular drugs

A micellar electrokinetic chromatography method was optimised for the separation of the six cardiovascular drugs atenolol, nicardipine, nifedipine, diltiazem, verapamil, and amlodipine by investigating the effects of pH, sodium dodecyl sulphate (SDS) concentration, selection and concentration of organic modifier. An electrophoresis buffer of 100 mM borate pH 8.1 containing 50 mM SDS and 15% (v/v) acetone was found to provide the optimum separation with respect to resolution and migration time.     

Interaction of cellulase with sodium dodecyl sulfate at critical micelle concentration level

The interactions between Trichoderma reesei cellulase and an anionic surfactant, sodium dodecyl sulfate (SDS), at critical micelle concentration level have been investigated using isothermal titration calorimetry, fluorescence spectroscopy, and circular dichroism. SDS micelles have dual interactions with cellulase: electrostatic at first and then hydrophobic interactions. When the concentration of SDS is smaller than 45.0 mM, SDS micelles cause a partial loss in the hydrolytic activity together with a steep decrease in the -helical content of cellulase. With further increasing the concentration of SDS, however, a re-formation of the -helical structure and a partial recovery of the hydrolytic activity of cellulase induced by SDS micelles are observed. Taken together, these results indicate that SDS micelles exert dual effects on cellulase through binding as both a denaturant and a recovery reagent.     

Interactions between sodium dodecyl sulphate and non-ionic cellulose derivatives studied by size exclusion chromatography with online multi-angle light scattering and refractometric detection

The novel approach described allows to characterise the surfactant-polymer interaction under several sodium dodecyl sulphate (SDS) concentrations (0-20 mM) using size exclusion chromatography (SEC) with online multi-angle light scattering (MALS) and refractometric (RI) detection. Three different cellulose derivatives, hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC) and hydroxyethyl cellulose (HEC), have been studied in solution containing 10 mM NaCl and various concentrations of sodium dodecyl sulphate. It is shown that this approach is well suited for successful application of both Hummel-Dreyer and multi-component light scattering principles and yields reliable molecular masses of both the polymer complex and the polymer itself within the complex, the amount of surfactant bound into the complex as well as appropriate values of the refractive index increment (dn/dc)micro, of both the complex and the polymer in question. The more hydrophobic derivatives HPC and HPMC adsorbed significantly more SDS than HEC. The inter-chain interactions close to critical aggregation concentration (cac) were clearly seen for HPC and HPMC as an almost two-fold average increase in polymer molecular mass contained in the complex.     

Physicochemical study of ovalbumin in the presence of sodium dodecyl sulphate in aqueous media

The interactions of sodium dodecyl sulphate with ovalbumin in aqueous solution at room temperature are described for a wide concentration range of both substances. A phase diagram covering a wide range of concentrations shows a total of five different morphologies. Dynamic light scattering of the samples from each morphology offered better understanding of the different structures (between three and four) present in the solution. The amount of ovalbumin present in the solution was confirmed with differential scanning spectroscopy, while the interactions between sodium dodecyl sulphate and ovalbumin were interpreted by zeta potential and electrical conductivity measurements.     

Comparative evaluation on the thermal properties and stability of MWCNT nanofluid with conventional surfactants and ionic liquid

Journal of Thermal Analysis and Calorimetry - Conventional surfactants such as CTAB (cetrimonium bromide), SDS (sodium dodecyl sulphate), SDBS (sodium dodecyl sulphonate) are combined with...     

Synergistic effect of mixed anionic and cationic surfactant systems on the interfacial tension of crude oil-water and enhanced oil recovery

Surfactant based enhanced oil recovery (EOR) is an interesting area of research for several petroleum researchers. In the present work, individual and mixed systems of anionic and cationic surfactants consisting of sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB) in different molar ratios were tested for their synergistic effect on the crude oil-water interfacial tension (IFT) and enhanced oil recovery performance. The combination of these two surfactant systems showed a higher surface activity as compared to individual surfactants. The effect of mixed surfactant systems on the IFT and critical micellar concentration (CMC) is strongly depends on molar ratios of the two surfactant. Much lower CMC values were observed in case of mixed surfactant systems prepared at different molar ratios as compared to individual surfactant systems. The lowest CMC value was found when the molar concentration of SDS was higher than the CTAB. When the individual and mixed surfacant systems were tested for EOR performance through flooding experiments, higher ultimate oil recovery was obtained from mixed surfactant flooding compared to individual surfactants. Combination of SDS and CTAB or probably other anionic-cationic surfactants show synergism with substantial ability to reduce crude oil water IFT and can be a promising EOR method.     

Suppression of protein interferences in anodic stripping voltammetry by sodium dodecyl sulphate

The anionic surfactant sodium dodecyl sulphate (SDS) can effect desorption of proteins from surfaces, and this mechanism has been exploited for suppressing adsorption interferences in anodic stripping voltammetry (ASV). Using cadmium and lead as test analytes, and albumin and lysozyme as model interferents, it was found that ASV signals strongly depressed by proteins regain their initial magnitude (prior to protein addition) when SDS is added in a concentration above a threshold value. Also, SDS protected against protein interference when the surfactant was added prior to the protein. SDS in itself caused little or no interference.     

Photoisomerization of merocyanine 540 in polymer-surfactant aggregate

Photoisomerization of merocyanine 540 (MC540) in a polymer-surfactant aggregate is studied using picosecond time resolved emission spectroscopy. The aggregate consists of the polymer, poly(vinylpyrrolidone) (PVP) and the surfactant, sodium dodecyl sulphate (SDS). With increase in the concentration of SDS in an aqueous solution of MC540 containing PVP, the emission quantum yield and lifetime of MC540 increase markedly. This indicates marked retardation in the nonradiative photoisomerization process of MC540, when it binds to the polymer-surfactant aggregate. The critical association concentration of SDS for binding to PVP has been found to be 0.5 mM. This is about 16 times lower than the CMC of SDS in pure water (8 mM).     

Alkaline ribonuclease associated with polyribosomes in fibroblasts of experimental granulation tissue.

Alkaline ribonuclease (RNase) from polyribosomes derived from experimental granulation tissue has been purified 1900-fold through affinity chromatography. The preparation was homogeneous in sodium dodecyl sulfate (SDS) polyacrylamide-gel electrophoresis with an estimated molecular weight of 15 000. Purified RNase was completely inhibited in the presence of divalent ions Mg2+(100 mM) and Ca2+(100 mM) but activated slightly with Na+(50 mM). The enzyme is an endonuclease and the best substrates were poly(U), mixed RNA from yeast, rRNA from granulation tissue and poly(C). The estimated apparent Km-values were 0.037, 0.064, 0.13 and 0.27 g1-1, respectively. In polyribosomes RNase occurred in both free and p-chloromercuribenzoate (pCMB)-liberated forms. The total activity was at the highest but the proportion of the free activity minimal in the granulation tissue during the maximal synthesis of collagen.     

胶束电动毛细管色谱法分析头孢哌酮与其S-异构体等杂质

以十二烷基硫酸钠(SDS)胶束为准固定相,考察了头孢哌酮、头孢哌酮S-异构体、头孢哌酮杂质A及其他未知杂质在胶束电动毛细管色谱(MECC)分离模式下的分离行为。研究了运行缓冲液的pH值、磷酸盐浓度、SDS浓度、甲醇体积分数、分离电压、分离温度等因素对头孢哌酮、S-异构体、头孢哌酮杂质A及其他杂质的迁移时间、分离度以及可分离出的杂质个数的影响。结果发现,这些因素对头孢哌酮与诸杂质间的分离及检测有显著的影响,尤以pH值为最。它不仅影响它们的迁移时间和分离效率,还直接影响头孢哌酮及其杂质峰的检测。优化后的分离条件:运行缓冲液为70 mmol/L磷酸盐-100 mmol/L SDS (pH 6.5),分离电压为15 kV,分离温度为25 ℃。在此条件下,用非涂渍石英毛细管51.0 cm×75 μm(有效长度42.5 cm),压力进样5 kPa×5 s,在254 nm波长下进行检测,可分离出28个杂质,诸杂质彼此间及与头孢哌酮间可得到有效分离。并将该方法成功地用于测定注射用头孢哌酮钠的含量和有关物质,结果令人满意。     

Influence of solvent polarity and medium acidity on the UV-Vis spectral behavior of 1-methyl-4-[4-amino-styryl] pyridinum iodide

Electronic absorption, and excitation spectra of 1-methyl-4-[4-aminostyryl] pyridinum iodide (M-NH2) were measured in solvents of different polarity. The (M-NH2) dye exhibits negative solvatochromism, i.e. a hypsochromic band shift as the solvent polarity increases. The fluorescence quantum yield is also sensitive to the polarity and viscosity of the medium. The ground and excited state protonation constants were calculated and amount to 3.35 and 0.62, respectively. The effect of micellization on the emission spectrum of (M-NH2) are also studied in sodium dodecyl sulphate (SDS). The fluorescence intensity increases as the concentration of SDS increases with an abrupt change at cmc. The quantum yield of the cis trans photoisomerization is also determined in aqueous buffer solution of pH 1.1.     

Corrosion inhibition by benzotriazole derivatives and sodium dodecyl sulphate as corrosion inhibitors for copper in ground water at different temperatures

1‐(2‐Pyrrole carbonyl) benzotriazole (PBTA) and 1‐(2‐thienyl carbonyl)‐benzotriazole (TBTA) were synthesized. Different concentrations of PBTA, TBTA, sodium dodecyl sulphate (SDS), and molybdate (Mo) were evaluated as corrosion inhibitors for copper in ground water medium at different temperatures. The obtained results were compared with the effect of benzotriazole (BTA) on the inhibition of copper corrosion at the same condition. The study was performed using potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic voltammetry, and scanning electron microscopy investigations. A good inhibition is ensured at elevated temperatures. All measurements indicated that PBTA, TBTA, and BTA act as good corrosion inhibitors and their inhibition efficiency (IE%) increased with combining them with optimum concentration of SDS and Mo. Furthermore, the best performance was recorded for the compound PBTA + SDS + Mo, which was found to offer increased IE% in a synergistic manner, thereby acting as a good corrosion inhibitor for copper in ground water medium. Copyright © 2015 John Wiley & Sons, Ltd.