Lithium Dodecyl Sulfate Research Articles

Titration Calorimetric Study of the Interaction between Ionic Surfactants and Uncharged Polymers in Aqueous Solution

The interaction between uncharged polymers (PEO, PPO, PVP, and EHEC) and ionic surfactants in dilute aqueous solution has been studied using isothermal titration microcalorimetry. The surfactants studied were lithium, sodium, and magnesium dodecyl sulfate, alkyltrimethylammonium halides (RTA+X- with R equal to C12, C14, and C16 and X either Br or Cl), and dodecylammonium chloride (DoAC). The critical aggregation concentration cac, the saturation concentration C2 and the amount of polymer-bound surfactant were derived from the calorimetric titration curves. The anionic surfactants interacted strongly with PEO while RTABr were indifferent. However, changing the counterion to chloride or modifying the headgroup to the unsubstituted ammonium ion gave observable interaction. The presence of extra salt lowered the cac and increased the C2 with a more pronounced effect for PPO and EHEC. An increase in temperature had no noticeable effect on cac and C2 although the shape of the calorimetric titration curves changed drastically. PPO 1000 showed both small molecule behavior and polymer character in the interaction with SDS. Due to the hydrophobicity of the backbone, PVP showed significant interaction with SDS well below the cac. PVP showed no affinity to the cationic RTAX surfactants.

Langmuir−Blodgett Films of Matrix-Diluted Single-Walled Carbon Nanotubes

Langmuir−Blodgett films consisting of carbon single-walled nanotubes embedded in a surfactant matrix were prepared. Aqueous dispersions of single-walled nanotubes stabilized by lithium dodecyl sulfate were purified by a centrifugation step. The supernatant was spread onto a subphase containing a positively charged polyelectrolyte. AFM investigations of monolayers transferred onto hydrophobic silicon substrates revealed the presence of homogeneously dispersed single-walled nanotube bundles, as well as individual single-walled nanotubes, both of which are surrounded by micelle-like surfactant aggregates.

Mapping of Functional Domains in p47phox Involved in the Activation of NADPH Oxidase by “Peptide Walking”

The superoxide generating NADPH oxidase of phagocytes consists, in resting cells, of a membrane-associated electron transporting flavocytochrome (cytochrome b559) and four cytosolic proteins as follows: p47(phox), p67(phox), p40(phox), and the small GTPase, Rac(1 or 2). Activation of the oxidase is consequent to the assembly of a membrane-localized multimolecular complex consisting of cytochrome b559 and the cytosolic components. We used "peptide walking" (Joseph, G., and Pick, E. (1995) J. Biol. Chem. 270, 29079-29082) for mapping domains in the amino acid sequence of p47(phox) participating in the molecular events leading to the activation of NADPH oxidase. Ninety-five overlapping pentadecapeptides, with a four-residue offset between neighboring peptides, spanning the complete p47(phox) sequence, were tested for the ability to inhibit NADPH oxidase activation in a cell-free system. This consisted of solubilized macrophage membranes, recombinant p47(phox), p67(phox), and Rac1, and lithium dodecyl sulfate, as the activator. Eight functional domains were identified and labeled a-h. These were (N- and C-terminal residue numbers are given for each domain) as follows: a (21-35); b (105-119); c (149-159); d (193-207); e (253-267); f (305-319); g (325-339), and h (373-387). Four of these domains (c, d, e, and g) correspond to or form parts of regions shown before to participate in NADPH oxidase assembly. Thus, domain c corresponds to a region on the N-terminal boundary of the first src homology 3 (SH3) domain, whereas domains d and e represent more precisely defined sites within the full-length first and second SH3 domains, respectively. Domain g overlaps an extensively investigated arginine-rich region. Domains a and b, in the N-terminal half of p47(phox), and domains f and h, in the C-terminal half, represent newly identified entities, for which there is no earlier experimental evidence of involvement in NADPH oxidase activation. "Peptide walking" was also applied to the identification of domains in p47(phox) mediating binding to p67(phox). This was done by quantifying, by enzyme-linked immunosorbent assay, the binding of p67(phox), in solution, to a series of 95 overlapping biotinylated p47(phox) peptides, attached to streptavidin-coated 96-well plates. A single proline-rich domain (residues 357-371) was found to bind p67(phox) in the absence and presence of lithium dodecyl sulfate.

The role of the counterion in poly(ethylene oxide)-dodecyl sulfate interactions

The effects of the counterions, Li +, Na + and tetramethylammonium (TMA +) of dodecyl sulfates on the interaction of poly(ethylene oxide) (PEO) have been investigated conductimetrically. For tetramethylammonium dodecyl sulfate (TMADS), significant effects on the classical conductivity vs surfactant profiles should be expected, compared to those for lithium dodecyl sulfate (LDS) and sodium dodecyl sulfate (SDS), since the main driving forces of the polymer binding should be attributed to the counterion. However, it has been found that the conductivity breakpoints, the critical aggregation concentration ( cac) and the polymer saturation point ( psp), and also other characteristics of the conductivity profiles investigated, such as linearity of the cac-psp region, ratios of slopes related to the degrees of dissociation of the polymer-surfactant complexes and micelles, and the amount of the complexed surfactant per monomol of PEO, do not exhibit differences sufficient to justify the importance of the counterion in the mechanism of polymer-surfactant interaction.

Interaction between Poly(ethylene oxide) and Monovalent Dodecyl Sulfates Studied by Neutron Reflection

The compositions of the air/solution interface of aqueous mixtures of lithium dodecyl sulfate (LiDS) and cesium dodecyl sulfate(CsDS) with poly(ethylene oxide) (PEO) have been studied as a function of surfactant concentration using neutron specular reflection. Comparison of the results with those for NaDS shows that for all three ionic species the polymer is progressively displaced from the surface on the addition of surfactant until it can no longer be directly detected at the critical aggregation concentration (area per segment >80 A 2 ). Comparison of the behavior of the three surfactants with each other and with measurements on the noninteracting combination dodecyltrimethylammonium bromide (C 12 TAB)/PEO shows that the anionic surfactants interact favorably with PEO at the surface. The additional free energies of binding of surfactant to the surface in the presence of PEO exactly parallel the polymer/micelle binding free energies. Of the three anionics LiDS interacts most strongly, and this is also manifested in adsorption of the PEO at concentrations above the critical micelle concentration of LiDS.

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The solubilization of hydrocarbon and fluorocarbon alcohols in single and mixed aqueous solutions containing fluorocarbon surfactant has been studied. Surfactants used are lithium dodecyl sulfate (LiDS), lithium perfluorooctane sulfonate (LiFOS), lithium perfluorooctanoate (LiPFO), and hexaethyleneglycol dodecyl ether (6ED). In single surfactant systems, the partition coefficients of the alcohols between anionic micelles and water are greater for the surfactants which have the same kind of alkyl chain as the alcohols than for the surfactants having a different kind of alkyl chain to the alcohols. The standard free energies calculated from the partition coefficients indicate that the transfer of the alcohols occurs more favorably to the micelles consisting of the same kind of alkyl chain as the alcohols than of the different kind of alkyl chain. Also, the mixed surfactant systems LiDS-LiFOS, LiFOS-LiPFO and 6ED-LiFOS have been characterized by the regular solution parameter β and the alcohol partition coefficient. In the LiDS-LiFOS system with a positive β value, the partition coefficients of both hydrocarbon and fluorocarbon alcohols are greater than in single surfactant systems. In the LiFOS-LiPFO system exhibiting almost ideal mixing, the partition coefficients of both hydrocarbon and fluorocarbon alcohols change ideally, whereas the partition coefficients of the fluorocarbon alcohols are greater than those of the hydrocarbon alcohols. By contrast, in the 6ED-LiFOS system with negative β values, the partition coefficients of both alcohols are lower than in single surfactant systems.

Fluorescence Quenching Studies of Micellization and Solubilization in Fluorocarbon−Hydrocarbon Surfactant Mixtures

Time-resolved fluorescence quenching studies of nonionic, anionic, and cationic micelles have been performed to compare two surfactant quenchers, a fluorocarbon surfactant quencher, N-(1,1,2,2-tetrahydroperfluorodecanyl)pyridinium chloride (HFDePC) and a hydrocarbon quencher of similar hydrophobicity, C16PC, N-hexadecylpyridinium chloride. The concentration dependence of the apparent aggregation numbers informs on the interaction between the surfactants, which always was repulsive for the fluorocarbon quencher in hydrocarbon micelles, except for the case with a nonionic micelle, where the effectively attractive electrostatic interaction dominated at low ionic strength. The simple theory (Almgren, M.; Hansson, P.; Wang, K. Langmuir 1996, 12, 3855) suggests that the interaction parameter from the slope of the apparent aggregation number versus mole fraction quencher should be the same as the interaction parameter describing the change of the critical micelle concentration with composition according to regular solution theory (Rubingh, D. H. In Solution Chemistry of Surfactants; Mittal, K. L., Ed.; Plenum Press: New York, 1979; Vol. 1, p 337). The results show that it is not so; not even the sign of the interaction parameter is always the same. The reasons for the difference are discussed. For the weight average aggregation number, obtained by extrapolation to zero quencher concentration, the two quenchers gave results within about 10% for a given surfactant; the values with the fluorocarbon quencher seemed to be systematically lower, as if the aromatic probe strongly avoided micelles containing fluorocarbon quenchers. From solubility studies, pyrene was found to prefer a C16TAC micelle over a HFDePC micelle by a factor of 60. The preference of pyrene for micelles without fluorocarbon surfactants was utilized to show the demixing into fluorocarbon-rich and hydrocarbon-rich micelles in a mixture of lithium perfluorononanoate and lithium dodecyl sulfate and in cetyltrimethylammonium chloride and HFDePC.

Conductance and surface tension of ionic surfactants in molten acetamide

Electrical conductivity and surface tension measurements on various surfactants, such as sodium caprylate, sodium laurate, sodium palmitate, sodium stearate, sodium oleate, sodium dodecyl sulfate and lithium dodecyl sulfate, in molten acetamide were carried out at 90 °C. Both methods show that micelles are formed in acetamide solution. The critical micelle concentration was determined for each of the surfactants. It is suggested that the simplest formula of the ionic micelle is (S −) n (CH 3CONH 2) x , and at higher concentration the micelle may be of the form (NaS) m (S −) n (CH 3CONH 2) x , where NaS = sodium stearate.

An ESR Spin Probe Study of the Interaction between Poly(ethylene oxide) and Dodecyl Sulfate Surfactants with Different Monovalent Metal Counterions

The interaction of lithium dodecyl sulfate (LiDS), sodium dodecyl sulfate (SDS), and cesium dodecyl sulfate (CsDS) with the water-soluble polymer poly(ethylene oxide) (PEO) has been studied in aqueous solutions by the electron spin resonance (ESR) technique using 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) as a spin probe. The rotational correlation time of TEMPO has been obtained and there are substantial differences in τc among LiDS, SDS, and CsDS with and without PEO. The results show that the microenvironment of the spin probe in the polymer−surfactant aqueous solutions depends strongly on the hydrated radius of the counterion. The headgroups of LiDS and SDS adsorbed on PEO are more tightly packed than those of the unperturbed micelles, which leads to a much more compact structure of the polymer−micelle complex. The headgroup packing of CsDS is less influenced by PEO.

Effect of micelles on the acid hydrolysis of N-phenylbenzohydroxamic acid

The effect of cationic (cetylpyridinium bromide and cetylpyridinium chloride) anionic (sodium dodecyl sulfate and lithium dodecyl sulfate) and non-ionic (Brij-35 and Triton-X-100) micelles on the acid-catalyzed hydrolysis of N-phenylbenzohydroxamic acid in 20 vol.% dioxane medium has been investigated. The kinetic results are explained by both pseudo-phase and Piszkiewicz cooperativity models.

Inhibition of NADPH Oxidase Activation by 4-(2-Aminoethyl)-benzenesulfonyl Fluoride and Related Compounds

The elicitation of an oxidative burst in phagocytes rests on the assembly of a multicomponental complex (NADPH oxidase) consisting of a membrane-associated flavocytochrome (cytochrome b559), representing the redox element responsible for the NADPH-dependent reduction of oxygen to superoxide (O-2), two cytosolic components (p47(phox), p67(phox)), and the small GTPase Rac (1 or 2). We found that 4-(2-aminoethyl)-benzenesulfonyl fluoride (AEBSF), an irreversible serine protease inhibitor, prevented the elicitation of O-2 production in intact macrophages and the amphiphile-dependent activation of NADPH oxidase in a cell-free system, consisting of solubilized membrane or purified cytochrome b559 combined with total cytosol or a mixture of recombinant p47(phox), p67(phox), and Rac1. AEBSF acted at the activation step and did not interfere with the ensuing electron flow. It did not scavenge oxygen radicals and did not affect assay reagents. Five other serine protease inhibitors (three irreversible and two reversible) were found to lack an inhibitory effect on cell-free activation of NADPH oxidase. A structure-function study of AEBSF analogues demonstrated that the presence of a sulfonyl fluoride group was essential for inhibitory activity and that compounds containing an aminoalkylbenzene moiety were more active than amidinobenzene derivatives. Exposure of the membrane fraction or of purified cytochrome b559, but not of cytosol or recombinant cytosolic components, to AEBSF, in the presence of a critical concentration of the activating amphiphile lithium dodecyl sulfate, resulted in a marked impairment of their ability to support cell-free NADPH oxidase activation upon complementation with untreated cytosol or cytosolic components. Kinetic analysis of the effect of varying the concentration of each of the three cytosolic components on the inhibitory potency of AEBSF indicated that this was inversely related to the concentrations of p47(phox) and, to a lesser degree, p67(phox). AEBSF also prevented the amphiphile-elicited translocation of p47(phox) and p67(phox) to the membrane. These results are interpreted as indicating that AEBSF interferes with the binding of p47(phox) and/or p67(phox) to cytochrome b559, probably by a direct effect on cytochrome b559.

Hydrophobic interaction of amphiphilic hemicyanine dyes with cationic and anionic surfactant micelles

The hydrophobic interaction of amphiphilic hemicyanine dyes, i.e. (dimethylamino)stilbazolium butyl sulphonate (I) and (dihexylamino)stilbazolium butyl sulphonate (II) with cetyltrimethyl ammonium bromide (CTAB), a cationic surfactant and lithium dodecyl sulphate (LDS), an anionic surfactant, was studied through absorption spectra as a function of the concentration of surfactants above and below their critical micelle concentrations. The different lengths of dialkyl chains present on these dyes exhibited hydrophobic interaction with micelles of CTAB and LDS; as a result visible spectra of both the dyes exhibited red shifts of different magnitudes when the dye molecules were solubilized into micelles. The approximate number of dye molecules per micelle was also estimated at a particular concentration of each surfactant. The solubilization depends on the dilakyl chain length of the dye together with the nature of surfactant head groups.

Electron transfer in the superoxide-generating NADPH oxidase complex reconstituted in vitro

The superoxide (O 2 −)-generating NADPH oxidase of phagocytic cells is composed of a membrane-bound flavocytochrome (cytochrome b-559) and three cytosolic components, p47- phox, p67- phox, and the small GTPase rac-1 (or 2). Cytochrome b-559 bears the NADPH binding site and the redox centers (FAD and heme). Electron flow through the redox centers, from NADPH to oxygen, is activated consequent to the assembly of the three cytosolic components with cytochrome b-559. We studied the kinetics of electron flow through the redox centers of NADPH oxidase in a cell-free system, consisting of purified relipidated and reflavinated cytochrome b-559 and recombinant cytosolic components, activated by the anionic amphiphile, lithium dodecyl sulphate. The NADPH oxidase complex assembled in vitro exhibited: (a) a high steady-state electron flow (165 electrons/heme/s); (b) low stationary levels of FAD and heme reduction (about 10%), and (c) a high rate constant of heme oxidation by oxygen (1720 s −1). Surprisingly, the kinetic properties of NADPH oxidase assembled in a semi-recombinant cell-free system, lacking p47- phox (found to generate significant amounts of O 2 −), were similar to those of the complete system, as shown by a steady-state electron flow of 83 electrons/heme/s, low stationary levels of FAD and heme reduction (10%), and a rate constant of heme oxidation by oxygen of 1455 s −1. The kinetic features of NADPH oxidase assembled in vitro from purified and recombinant components differ considerably from those of solubilized enzyme preparations derived from intact stimulated phagocytes. The fast operation of the cell-free system is best explained by the activation-related facilitation of electron flow at both the FAD→heme and the heme→oxygen steps.

Effect of acetamide on the critical micelle concentration of aqueous solutions of some surfactants

The variations of molar conductivity of various surfactants such as sodium caprylate, sodium laurate, sodium palmitate, sodium stearate, sodium oleate, sodium dodecyl sulphate, and lithium dodecyl sulphate with concentration of the surfactants for each of the solutions consisting of mixtures of varying concentrations of acetamide in water at a constant temperature of 30±0.2°C were studied. The critical micelle concentration (CMC) for each surfactant is measured. It is found that the CMC values in mixtures of acetamide and water solutions of various surfactants are lower than the CMC values in water.

Stoichiometry of Phosphorylation to Fluorescein 5-Isothiocyanate Binding in the Ca2+-ATPase of Sarcoplasmic Reticulum Vesicles

In an attempt to establish the stoichiometry of phosphorylation in the Ca2+-ATPase of sarcoplasmic reticulum (SR) vesicles, phosphorylation by ATP (or Pi) or labeling by fluorescein 5-isothiocyanate (FITC) was performed with the SR vesicles under the conditions in which almost all the phosphorylation sites or FITC binding sites are phosphorylated or labeled. The resulting vesicles were solubilized in lithium dodecyl sulfate and then the Ca2+-ATPase was purified by size exclusion high performance liquid chromatography. Peptide mapping and sequencing of the tryptic digest of the purified enzyme showed that Lys-515 of the Ca2+-ATPase was exclusively labeled with FITC, in agreement with the previously reported findings. The content of the phosphoenzyme from ATP (4.57 nmol/mg of Ca2+-ATPase protein) or from Pi (4.94 nmol/mg of Ca2+-ATPase protein) in the purified enzyme was approximately half the content of the FITC binding site (8.17-8.25 nmol/mg of Ca2+-ATPase protein) and also half the content of the Ca2+-ATPase molecule (9.06 nmol/mg of Ca2+-ATPase protein) calculated from its molecular mass (110,331 Da). These results show that there is one specific FITC binding site per molecule of the Ca2+-ATPase (in agreement with the previously reported findings) and that the stoichiometry of phosphorylation to FITC binding is approximately 0. 5:1.0. All the above findings lead to the conclusion that only half of the Ca2+-ATPase molecules present in the SR vesicles can be phosphorylated. FITC binding completely inhibited the ATP-induced phosphorylation before the binding reached its maximum level. This finding indicates that FITC preferentially binds to a part of the Ca2+-ATPase molecules and that this binding is primarily responsible for the inhibition of phosphorylation, suggesting an intermolecular ATPase-ATPase interaction.

Isolation of α-Tocopherol (Vitamin E) from Garlic

Vitamin E (α-tocopherol) was isolated from garlic. The method involved homogenization of garlic in phosphate-buffered saline and extraction with heptane in the presence of lithium dodecyl sulfate. An aliquot of the extract, when analyzed by HPLC on a C18 column, yielded a peak with the same retention time as the α-tocopherol standard. The presence of α-tocopherol was further confirmed by GC/MS. A total of 9.4 μg of α-tocopherol was isolated from 1 g of garlic. Oxidation of low-density lipoprotein was retarded by garlic α-tocopherol. Keywords: Vitamin E; garlic; α-tocopherol; LDL oxidation

Micellar Rate Effects on Alkaline Hydrolysis of Hydroxamic Acids

Abstract The kinetics of alkaline hydrolysis of N-phenylbenzohydroxamic acid and its para-substituted derivatives (X–C6H4–CO–N(OH)C6H5; X = H, CH3, OCH3, NO2, F) have been investigated in the presence and absence of cationic (ethyl hexadecyl)dimethylammonium bromide) and anionic (sodium-1-dodecanesulfonate and lithium dodecyl sulfate) surfactants at 55 °C in 5% (v/v) dioxane–water medium. A catalytic effect was found with cationic surfactants and an inhibitory effect in the presence of anionic surfactants was observed. The rate-surfactant profiles can be analyzed in terms of pseudo-phase and Piszkiewicz models.

Simultaneous adsorption of poly(N-vinyl-2-pyrrolidone) and [formula omitted] surfactant from their binary mixtures on [formula omitted] silica

The simultaneous adsorption of lithium dodecyl sulfate (LiDS)/lithium perfluorooctanesulfonate (LiFOS) and poly(N-vinyl-2-pyrrolidone) (PVP) from PVP-LiDS and PVP-LiFOS binary mixed aqueous solutions on hydrophilic hydrophobic silica was investigated. The conformation and layer thickness of PVP adsorbed on silica were also estimated by using ESR and photon correlation spectroscopy (PCS), respectively. By introducing a sedimentation field-flow fractionation (sedFFF) separation step prior to the PCS sizing to fractionate the adsorbate into cuts of uniform particle size, it is possible to improve the accuracy in these size measurements. The adsorption of PVP is enhanced in the presence of LiDS at low LiDS concentration owing to the formation of a surface complex of PVP and LiDS, followed by a decrease at high LiDS concentration. However, this increment on hydrophobic silica is significantly greater than that on hydrophilic silica. A similar trend is also observed in the PVP-LiFOS system. In both the PVP-LiDS and PVP-LiFOS systems, the conformation of PVP adsorbed, in particular on hydrophilic silica, is changed remarkably from loops and tails to trains with the surfactant concentration. The results obtained from ESR show a good relationship with the thickness of PVP adsorbed obtained from PCS.

Modification of the Mycobacterium bovis extracellular protein MPB70 with fluorescein for rapid detection of specific serum antibodies by fluorescence polarization.

The principle of fluorescence polarization described by Perrin (F. Perrin, J. Phys. Radium 7:390-401, 1926) was applied to the development of a novel assay that used fluorescein-labeled Mycobacterium bovis secretory protein MPB70 for rapid detection of anti-MPB70 antibodies in selected sera from three M. bovis-infected species (elk, Ilama, and bison). Labeling of purified MPB70 with fluorescein isothiocyanate resulted in the incorporation of 0.96 +/- 0.08 (mean +/- standard deviation; n = 3) fluorescein group per MPB70 molecule. The labeled protein fluoresced strongly with an emission maximum at 518 nm when excited with light of a wavelength near 493 nm, and its immunoreactivity with anti-MPB70 monoclonal antibody 4C3/17 was not altered by modification with fluorescein. The fluorescence polarization assay protocol was optimized for analysis of serum samples by incorporating into the assay buffer 0.05% lithium dodecyl sulfate, which prevents the occurrence of some nonspecific interactions. Sera from M. bovis-infected animals, selected on the basis of exhibiting the presence of anti-MPB70 antibodies, as detected by enzyme-linked immunosorbent assay (ELISA), reacted with fluorescein-labeled MPB70, resulting in an increase in polarization of up to 330 milli-polarization units, in contrast to the values for noninfected sera (167 to 178 mP), which were close to that obtained in the absence of specific antibodies (164.7 +/- 3.3 mP; n = 6). These results demonstrated the feasibility of using fluorescein-labeled MPB70 to detect anti-MPB70 antibodies by fluorescence polarization and suggested that the assay described here can be an alternative to ELISA or other antibody assay systems. The advantages of this original methodology and its general applicability to the diagnosis of infectious diseases are discussed.

Anion Movement in Polypyrrole Films Prepared in Lithium Dodecylsulfate Aqueous Solutions

Abstract Electrochemical quartz crystal microbalance (EQCM) was used to study the redox reaction of polypyrrole (PPy) prepared in an aqueous solution containing anionic surfactant. EQCM result confirmed that the small cation in the electrolyte solution rapidly moved into/out of the PPy film during redox reaction at a potentiodynamic condition and also the bulky anion, dodecylsulfate ion (DS), additionally took part in redox reaction, especially in positive potential range above-0.2 V. The movement of anion was more clearly seen at potentiostatic condition than in voltammetric measurement, which implies the rate dependency of the anion movement in PPy film.