Interaction Of Sodium Dodecyl Sulfate Research Articles

An investigation of chitosan and sodium dodecyl sulfate interactions in acetic media

Polymer/surfactant association is a cooperative phenomenon where surfactant binds to the polymer in the form of aggregates, usually through electrostatic or hydrophobic forces. As already known, polyelectrolytes may interact with oppositely charged surfactants through electrostatic attraction that results in polymer/surfactant complex formation. This behavior could be desirable in wide range of application of polymer/surfactant mixtures, such as improving colloid stability, gelling, emulsification and microencapsulation. In the present study surface tension, turbidity, viscosity and electrophoretic mobility measurements were used to investigate interactions of cationic polyelectrolyte chitosan (Ch) and oppositely charged anionic surfactant, sodium dodecyl sulfate (SDS), in buffered water. Obtained results show the presence of interactions that lead to Ch/SDS complexes formation at all investigated pH and for all investigated polymer concentrations. Mechanisms of interaction, as well as characteristics of formed Ch/SDS complexes, are highly dependent on their mass ratio in the mixtures, while pH has no significant influence.

Internal charge transfer based ratiometric interaction of anionic surfactant with calf thymus DNA bound cationic surfactant: Study I

Cetyl trimethyl ammonium bromide (CTAB) binds calf thymus (ct-) DNA like anionic biopolymers electrostatically and established equilibrium both in the ground as well as in excited state in aqueous medium at pH 7. Anionic sodium dodecyl sulfate (SDS) does not show even hydrophobic interaction with ct-DNA at low concentration. On contrary, SDS can establish well defined equilibrium with DNA bound CTAB in ground state where the same CTAB–DNA isosbestic point reappears. First report of internal charge transfer (ICT) based binding of CTAB with ct-DNA as well as ICT based interaction of anionic SDS with DNA bound CTAB that shows dynamic quenching contribution also. The reappearance of anodic peak and slight increase in cathodic peak current with increasing concentration (at lower range) of anionic SDS, possibly reflect the release of CTAB from DNA bound CTAB by SDS.

Field-Dipole Interactions at p-GaAs (100) Electrode in Sodium Dodecyl Sulfate Acid Solution

Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been used to investigate the effects of the sodium dodecyl sulfate (SDS) at the electrified p-GaAs(100) / H2SO4 interface. The analysis of the EIS data revealed that the surfactant adsorption brings about a pronounced decrease of the capacitive contributions of the semiconductor surface state (Fig. 1 B) accompanied by a shift to more positive potentials of the Mott-Schottky plot (Fig. 1 A). According to the XPS (Fig 1 C) and AFM data, SDS forms a well-ordered protective overlayer on p-GaAs(100) which prevents the surface oxidation in air. However, the field-dipole interactions acting under the applied potential control become preponderant at the electrified GaAs / solution interface yielding distinct effects at the end of the direct and forward potential scans as seen in Fig 1 C. These results suggest that SDS interaction with GaAs substrate might be an efficient tool to improve both the electronic properties of the semiconductor and its protection against the surface oxidation in air. Acknowledgements This work was supported by a grant of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project number PN-II-ID-PCE-2011-3-0304 Figure 1

A dynamic light scattering study of hydrogels with the addition of surfactant: a discussion of mesh size and correlation length

We report a study of the interaction of sodium dodecyl sulfate (SDS) with hydrogels made of hydroxyethylcellulose (HEC) and hydrophobically modified hydroxyethylcellulose (HMHEC) by means of dynamic light scattering. The results reveal that the interaction between the hydrogels and SDS only affects the cooperative diffusion, while the slow relaxation of the hydrogels was not influenced by the interaction. Gel swelling due to the presence of SDS is also examined by measuring the weight change of the gel. The main observation is that when the gel swells due to increasing SDS concentration, the cooperative diffusion becomes faster. As such, we raise the question of whether the correlation length obtained from DLS is still proportional to the mesh size inferred from gel swelling. In the discussion, we attribute the cause to the quantity of bound surfactants. The mutual diffusion of SDS micelles could be detected at high SDS concentrations, and the diffusion coefficient of SDS in the gel matrix was determined. HEC (or HMHEC) gel swells due to increasing SDS concentration, while the cooperative diffusion becomes faster. This indicates that the HEC (or HMHEC) gel can swell until the osmotic pressure equals the modulus when the charge effect dominates over the effect of configurational entropy for uncharged gels interacting with charged surfactants.

PH-dependent differential interacting mechanisms of sodium dodecyl sulfate with bovine serum fetuin: a biophysical insight.

Sodium dodecyl sulfate (SDS)-glycoprotein interaction serves as a model for a biological membrane. To get mechanistic insight into the interaction of SDS and glycoprotein, the effect of SDS on bovine serum fetuin (BSF) was studied in subcritical micellar concentrations at pH 7.4 and pH 2 using multiple approaches. SDS interacts electrostatically with BSF through its negatively charged head groups at pH 2 and hydrophobically via its alkyl chains at pH 7.4 up to a 1:20 molar ratio of BSF to SDS. However, at higher concentrations of SDS, BSF undergoes amyloid fibril formation at pH 2, as confirmed by enhanced ThT fluorescence, β-sheet formation, and TEM microscopy, whereas BSF undergoes induction of an α-helical structure in the presence of higher SDS concentration at pH 7.4. The increase in α-helical content with increasing SDS concentrations constrains the environment around tryptophan. As a consequence, the interconversion of tryptophan conformers decreases, resulting in a decrement of the fluorescence lifetime for BSF in the presence of SDS at pH 7.4.

Adsorption Mechanism of Sodium Dodecyl Sulfate on Coagulating Precipitate in Treatment of Vat Dark Blue BO by Coagulation and Air-Flotation

Vat dark blue BO simulated wastewater was treated by Dissovled air flolation (DAF), the interaction of sodium dodecyl sulfate (SDS) and precipitate in the DAF process was investigated by thermodynamic methods. The adsorption isotherms of SDS on precipitate at pH 5.00 were determined at 30,35,40 and 45°C. The isosteric heat of sorption was calculated by the Clausius-Clapeyron equation. The results show that the isotherm of SDS on coagulation precipitate is not the normal style, the adsorption of SDS on precipitate is exothermic in nature and the isosteric heat of adsorption decreases with a increase in the equilibrium uptake of SDS on precipitate. The isosteric heat of sorption varies between-16.266 and-21.719kJ/mol as surface loading is between 3 and 11 mg/g. The values of isosteric heat of adsorption proves the primary adsorption of SDS on precipitation is physisorption.

Deconvolution and binding study of camel and human serum albumins upon interaction with sodium dodecyl sulphate

Interactions of camel serum albumin (CSA) and human serum albumin (HSA) with sodium dodecyl sulphate (SDS) were studied via fluorescence and circular dichroism (CD) spectroscopy and tensiometry. There was a good correlation between fluorescence intensity and surface tension changes of CSA and HSA versus SDS concentration in which both showed two main transitions. However, the CD signals of CSA at 222 nm versus SDS concentration showed only one transition. According to the obtained results, interaction of SDS with the proteins can be divided into four distinct regions; in the initial region, SDS binds specifically to high-affinity binding sites, in the second region, SDS binds to the lower affinity binding sites on the protein surface, in the third region, cooperative binding of SDS triggers the protein to unfold. Finally after saturation of protein with SDS, at the final stage, normal SDS micelles start to form. Our results indicated that the partial unfolding of HSA started at higher concentrations of SDS and proceeded with higher cooperativity compared to that of CSA. This may be attributed to a higher inner hydrophobicity and higher stability of HSA compared to CSA.

Effect of Self-Association of Bovine Serum Albumin on the Stability of Surfactant-Induced Aggregates of Allylamine-Capped Silicon Quantum Dots

The concentration-dependent self-association of bovine serum albumin (BSA) and subsequent altered interaction with sodium dodecyl sulfate (SDS) has been explored by means of photoluminescence (PL) spectroscopy, dynamic light scattering (DLS), circular dichroism (CD), PL imaging, and atomic force microscopy (AFM). By using an extrinsic luminescent probe, allylamine-capped silicon quantum dots (Si-QDs), we have demonstrated the unusual concentration-dependent altered BSA-SDS interaction. Allylamine-capped Si-QDs forms ordered aggregates in the presence of 1 mM SDS due to hydrogen bonding with the surfactants head groups at pH 7.4. Although these aggregates remain stable in the presence of monomeric BSA in the concentration range 1-8 μM, they form typical ring-shaped doughnut-like structures due to "necklace and bead"-like complex formation. However, beyond 10 μM BSA, these aggregates of Si-QDs slowly dissociate and complete dissociation occurs at 150 μM BSA. These anomalous results have been explained by considering the altered hydrophilicity of self-associated BSA.

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.

Study of mixed micellar aqueous solutions of sodium dodecyl sulfate and amino acids

Thermodynamic properties of sodium dodecyl sulfate (SDS) in micellar aqueous solutions of L-serine and L-threonine were determined by fluorescence spectroscopy and dynamic light scattering techniques. The values of Gibbs free energy, enthalpy and entropy of the process of micelle formation were calculated using the critical micelle concentration and degree of dissociation. Changes in critical micelle concentration of SDS with the addition of amino acids were examined by both conductivity and pyrene I 1/I 3 ratio methods at different temperatures. The pyrene fluorescence spectra were used to study the change of micropolarity produced by the interaction of SDS with amino acids. The aggregation behavior of SDS was explained in terms of structural changes in mixed solutions. The data on dynamic light scattering suggest that size of SDS micelles was influenced by the presence of amino acids.

Vapor pressure osmometry, volumetry and conductometry investigations on the interaction of sodium dodecyl sulfate with poly(ethylene glycol) and poly(propylene glycol) in aqueous solutions

Micellar and thermodynamic properties of sodium dodecyl sulfate (SDS) in aqueous solutions of polyethylene glycol (PEG) (Mw=400, 2000, 6000 and 10,000gmol−1) and polypropylene glycol (PPG) (Mw=400gmol−1) were determined employing vapor pressure osmometry (VPO), volumetry, compressibility and conductometry techniques at different temperatures. The binding of SDS in aqueous solution with PEG and PPG was investigated by comparison of the thermodynamic properties of aqueous solutions of SDS in the absence and presence of PEG and PPG. In aqueous solutions, SDS does not bind to PEG400 chains however it binds to PPG400, PEG2000, PEG6000 and PEG10000 chains. The plots of water activity, specific conductivity, sound velocity and isentropic compressibility against surfactant concentration for aqueous SDS+polymer (PPG400, PEG2000, PEG6000 and PEG10000) solutions show two break-points: critical aggregation concentration (CAC) and polymer saturation point (C2).

Molecular dynamics of the interaction of anionic surfactants with liposomes

The time dependent molecular interactions of sodium dodecyl sulfate (SDS) with dipalmitoylphosphatidylcholine (DPPC) liposomes were studied using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. In particular, the ATR spectra provided information on the dynamic amount of SDS incorporated and DPPC expelled in the DPPC structure along with structural information on the molecular nature of the SDS/DPPC assemblies. It was found that the uptake of SDS was always mirrored by the ejection of DPPC molecules from the liposomes and that the incorporation of SDS followed two routes; SDS intercalated into the DPPC liposomes and SDS was bound electrostatically to the charged surface of the DPPC liposome.

Realization of the Reversible Vesicle–Micelle Transition of Vitamin-Derived Bolaamphiphiles by Heat Change Monitoring

The real-time energetics involved in the structural change of a zwitterionic vitamin-derived bolaamphiphiles (DDO) vesicles, which were induced by conventional surfactants, such as hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Triton X-100 (TX100), was characterized by isothermal titration calorimetry (ITC). Interactions of both CTAB and SDS with DDO were accompanied with considerable heat release whereas the interaction energetics between TX-100 and the vesicles were small. However, the transition of DDO vesicles to micelles did occur upon the addition of all of the three surfactants. Fine inflection points were observed in heat flow enthalpograms, which indicated systematically the change of vesicle structure. By monitoring the interaction of CTAB with DDO, we found that heat release kept constant over a certain concentration range at higher temperatures. The repairing effect of heating was revealed and a reversible transition from micelles to vesicles of DDO was thus realized. Further encapsulation of fluorescein in DDO vesicles proved that the reversible vesicle-micelle transition was controllable. This research demonstrates that ITC combined with complementary analytical methods such as dynamic light scattering (DLS) and transmission electron microscopy (TEM) helps to get the real-time information of the structural changes of vesicles. It also shows that these synthetic novel bolaamphiphiles offer great promise for designing controllable release system.

SDS Induced Refolding of Pre-molten Globule State of Cryptolepain: Differences in Chemical and Temperature-Induced Equilibrium Unfolding of the Protein in SDS-Induced State

Interaction of sodium dodecyl sulfate (SDS) with a globular protein cryptolepain to induce stabilization of the pre-molten globule state of the protein under acidic condition was studied. At pH 2.0, cryptolepain is in partially unfolded state with native like secondary structure, exposed hydrophobic surfaces without any rigid tertiary structure. Unfolding of cryptolepain in the pre-molten globule state (state at pH 2.0) is co-operative suggesting that the protein unfolds as a single entity. Addition of SDS below its critical micelle concentration of 2.0 mM at acidic pH drives the protein to a non-native state similar to molten globule state seen with other proteins. Temperature induced unfolding of such SDS-induced state of the cryptolepain is biphasic suggesting that the molecular structure of the protein is constituted of two structural entities which are stabilized differentially in the presence of SDS and unfold sequentially. Whereas the chemical induced unfolding of SDS-induced state of cryptolepain is co-operative with higher transition midpoints indicating that the protein is stabilized as a whole. Unfolding of SDS-induced state of cryptolepain is very similar to the unfolding of the cryptolepain at very low pH (0.5), where the protein exists in molten globule state. Thus, SDS interactions result in the refolding of the acid unfolded state of the protein and drive the protein into a non-native state similar to the molten-globule state seen at very low pH.

Interactions of glutamine dipeptides with sodium dodecyl sulfate in aqueous solution measured by volume, conductivity, and fluorescence spectra

Densities, conductivities, and fluorescence spectra of {sodium dodecyl sulfate (SDS) + glutamine dipeptide + water} mixtures were measured as a function of temperature. The density data have been utilized to calculate apparent molar volumes, standard partial molar volumes ( V 2 , φ o ), standard partial molar volumes of transfer from water to aqueous SDS solutions (Δ t V o), the hydration number, partial molar expansibility ( E φ o ), and Hepler’s constant of glutamine dipeptides. The critical micellar concentration ( c cmc) and the degree of counterion dissociation of SDS micelles obtained from electrical conductivity data have been estimated at various concentrations of glutamine dipeptide. Thermodynamic parameters of micellization of SDS in aqueous dipeptide solutions have been determined from c cmc values and an enthalpy–entropy compensation effect was observed for the ternary systems. The pyrene fluorescence spectra were used to study the change of micropolarity produced by the interaction of SDS with glutamine dipeptide, and the aggregation behavior of SDS. The results have been interpreted in terms of solute–solvent interactions and structural changes in the mixed solutions.

New insights on the interaction between hydroxypropylmethyl cellulose and sodium dodecyl sulfate

The interaction between an anionic surfactant (sodium dodecyl sulfate (SDS)) and an uncharged polymer (hydroxypropylmethyl cellulose) in aqueous solutions has been studied using conductivity, rheology and UV–vis transmittance methods.The effect of hydroxypropylmethyl cellulose (HPMC) concentration on the critical association concentration (cac) of the surfactant and on the polymer saturation points (psp) was analyzed using an electrical conductivity technique, which allowed establishing association and micellization thermodynamic parameters at different polymer concentrations. The effect of temperature on these parameters was also investigated. It is seen that the free energy change in the association process is constant up to 0.5% HPMC, but increases after this point. A similar behavior is found for the bulk micellization process. It is also seen that the association process becomes more and more favorable as the temperature increases. Rheological measurements were performed to investigate the influence of surfactant concentration in the viscosity of HPMC hydrogels at room temperature. Three regimes were found: an initial decrease, up to the cac, followed by a drastic increase and a further decrease starting close to the psp. Studies with temperature ramps have been also conducted to assess the effect of SDS on the thermal gelation of HPMC, showing that SDS delays or even inhibits gelation. Optical transmittance studies were carried out in order to evaluate the behavior of the polymer chains (extension and compaction) as a function of SDS concentration. A model for HPMC–SDS interaction has been proposed, rationalizing the development of the system at different SDS and HPMC concentrations.

Stabilization of polyamidoamine (PAMAM) dendrimers/sodium dodecyl sulfate complexes via PEGylation

Despite the robust structure of polyamidoamine (PAMAM) dendrimers, they are not stable when complexed with surfactants. Modification of PAMAM dendrimers by grafting PEG chains on the surface of PAMAM substantially improves its colloidal stability in the presence of sodium dodecyl sulfate (SDS). Michael addition reaction was employed to synthesize PEGylated-PAMAM by activating MPEG with 4-nitrophenylchloroformate. 1H NMR spectrum confirmed that 32 PEG chains were successfully grafted on the PAMAM surface, and the hydrodynamic radius of PEGylated-PAMAM was found to be ∼6.8 nm. The PEGylated-PAMAM dendrimers did not aggregate in the presence of up to 100 mM SDS as the complexes were sterically stabilized by PEG chains. ITC and zeta potential measurements revealed that the binding mechanism of SDS and PEGylated-PAMAM was induced by electrostatic interaction and polymer-induced micellization of SDS on PEG chains. The interaction of PEGylated-PAMAM and amphiphilic molecules, such as SDS was elucidated, and this provided a useful basis for the application PEGylated-PAMAM in drug delivery.

Microcalorimetric and SAXS Determination of PEO−SDS Interactions: The Effect of Cosolutes Formed by Ions

The effect of different ionic cosolutes (NaCl, Na(2)SO(4), Li(2)SO(4), NaSCN, Na(2)[Fe(CN)(5)NO], and Na(3)[Co(NO)(6)]) on the interaction between sodium dodecyl sulfate (SDS) and poly(ethylene oxide) (PEO) was examined by small-angle X-ray scattering (SAXS) and isothermal titration calorimetric techniques. The critical aggregation concentration values (cac), the saturation concentration (C(2)), the integral enthalpy change for aggregate formation (ΔH(agg)(int)) and the standard free energy change of micelle adsorption on the macromolecule chain (ΔΔG(agg)) were derived from the calorimetric titration curves. In the presence of 1.00 mmol L(-1) cosolute, no changes in the parameters were observed when compared with those obtained for SDS-PEO interactions in pure water. For NaCl, Na(2)SO(4), Li(2)SO(4), and NaSCN at 10.0 and 100 mmol L(-1), the cosolute presence lowered cac, increased C(2), and the PEO-SDS aggregate became more stable. In the presence of Na(2)[Fe(CN)(5)NO], the calorimetric titration curves changed drastically, showing a possible reduction in the PEO-SDS degree of interaction, possibility disrupting the formed nanostructure; however, the SAXS data confirmed, independent of the small energy observed, the presence of aggregates adsorbed on the polymer chain.

Effect of Anionic Surfactant on the Thermo Acoustical Properties of Sodium Dodecyl Sulphate in Polyvinyl Alcohol Solution by Ultrasonic Method

The interaction of sodium dodecyl sulphate (SDS) / poly(vinyl alcohol) (PVA) solution was studied by ultrasonic velocity measurements. Ultrasonic velocity, density, viscosity in mixtures of sodium dodecyl sulphate in polyvinyl alcohol was measured over the entire range of composition. From the experimental data, other related thermodynamic parameters, viz., adiabatic compressibility, intermolecular free length, surface tension, relative association, relaxation time, absorption coefficient and internal pressure were calculated. Formations of rods interfere with velocity of ultrasonic waves. Hence the ultrasonic velocity decreases with concentration. These results were interpreted in terms of polymer‐surfactant complex reactions.

Interaction of Sodium Dodecyl Sulfate with Poly(ethyleneimine) in Bulk Solution and at the Air-Solution Interface

Interaction of sodium dodecyl sulfate (SDS) with the cationic polyelectrolyte poly(ethyleneimine) (PEI) was investigated in this study. Turbidity measurements were performed in order to analyze the interaction and complex formation in bulk solution as a function of polymer concentration and pH. Surface tension measurements were made to investigate the properties of SDS/PEI/water mixtures at air/solution interface. Results revealed that SDS/PEI complexes form in solution depending on the surfactant and polymer concentration. A decrease was observed in surface tension values in the presence of SDS/PEI mixtures compared to the values of pure SDS solutions. Both solution and interfacial properties exhibited pH dependent behavior. A shift was seen in the critical micelle concentration of SDS solutions as a function of PEI concentration and solution pH. Monovalent and divalent salt additions showed some influence on the interfacial properties of SDS solutions in the presence of PEI.