Interaction Of Sodium Dodecyl Sulfate Research Articles

Enhancing coal slime processing: Investigating the efficacy of sodium dodecyl sulfonate in the adsorption on kaolinite surfaces

AbstractAddressing the issue of processing fine kaolinite and quartz particles in coal slime, this study utilized molecular simulation and Density Functional Theory (DFT) to investigate the chelate adsorption characteristics of sodium dodecyl sulfate (SDS) on kaolinite surfaces. As a major clay mineral component in coal slime, kaolinite reduces coal's calorific value but holds potential for industrial and agricultural applications. The research identified distinct interactions between SDS and the tetrahedral SiO layer and octahedral AlO layer of kaolinite, in contrast to quartz, which contains only the tetrahedral SiO layer. This difference is crucial for the effective separation of kaolinite from quartz. The study focused on analyzing SDS adsorption on the (001) and (00‐1) planes of kaolinite. The findings revealed strong adsorption of SDS on kaolinite surfaces, especially on the (001) plane, evidenced by significant charge transfer indicating efficient chelation. This effect results from the interaction of SDS's electron‐donating atoms (such as S and O) with the metal atoms on the surface of kaolinite. Adsorption strength was quantified through adsorption energy calculations, showing a stronger interaction on the (001) surface. Experimental validations, including single mineral flotation experiments and infrared spectroscopic analysis, further corroborated the simulation outcomes. These tests demonstrated improved flotation recovery of kaolinite in the presence of SDS and with reduced particle size. Infrared analysis revealed that SDS selectively and strongly adsorbs on kaolinite surfaces, as indicated by diminished hydroxyl group stretching vibrations in the FTIR spectrum and changes in absorption peaks related to inorganic vibrations and sulfonic acid groups. The study demonstrates that SDS can selectively and effectively adsorb onto kaolinite surfaces, particularly on the (001) plane, facilitating the efficient extraction of fine kaolinite from coal slime. This research holds significant potential for enhancing the utilization of resources from coal slime in the coal industry, offering both economic and environmental benefits.

Interaction of sodium dodecyl sulfate and triton X-100 with ofloxacin drug using conductivity and UV–visible spectroscopic techniques in aqueous alcohols media at several temperatures

The current investigation explores the association and complexation of the mixture of anionic surfactant, sodium dodecyl sulfate (SDS), and antibiotic drug, ofloxacin (OFC) as well as nonionic surfactant, Triton X-100 (TRX) and OFC drug respectively in several additive solutions. The investigations were performed by applying conductivity and UV-Visible spectroscopic techniques. The impacts of drug concentration, types of solvents, and composition of aq. solutions of alcohols (methanol (MeOH), ethanol (EtOH), and 1-propanol (1-PrOH)) as well as temperature change have been investigated on the micelle formation of SDS + OFC mixture. The micellization of SDS + OFC and TRX + OFC systems has been characterized by the determination of critical micelle concentration (CMC) from conductivity vs. SDS concentration (conductivity technique) and Absorbance vs log[TRX] (UV-Visible spectroscopic technique) plots respectively. The micellization of SDS was delayed owing to the introduction of the OFC drug while the effect has been intensified as a function of OFC concentration. At a fixed OFC concentration and temperature, the CMC values were acquired to be augmented with the upsurge of alcohol concentration. The enhancement of the CMC changes has been perceived with the escalation of temperature at a definite concentration of OFC in water and 5% (w/w) aq. alcohols media. The disfavor of micellization of TRX in aq. EtOH solutions in comparison to aqueous solution also detected from UV-Visible spectroscopic technique. The binding constant (Kb) for the complexation of TRX with OFC drug was determined using the Benesi-Hildebrand plot. The Kb values were obtained to be affected by the change of solvent and temperature. The negative free energy change (∆Gmo/ ∆Gbo) of the micellization and complexation demonstrate the spontaneous occurrence of micelle formation and complex development. The enthalpy changes (∆Hmo) of micellization were negative (exothermic process) and entropy changes (∆Smo) were positive (highly disordered and entropy-dominated micellization). Other thermodynamic properties ((∆Hbo and ∆Sbo) and thermodynamics of transfer) have been evaluated and illustrated as well, for the working systems.

Interaction of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine drug in aqueous solution: Conductometric and molecular dynamics studies

In the present work, the interaction of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine drug in aqueous solutions was studied using conductometric measurements and molecular dynamic simulation. Conductometric data were used to determine the critical micelle concentration (CMC) values of surfactants on various amantadine aqueous solutions at T= (300.2, 310.2 and 320.2) K and 0.1 MPa. The effect of amantadine concentration (m = 0.0005, 0.0010, 0.0015 and 0.002 mol.kg−1) on CMC of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants was investigated. It was observed the CMC value of sodium dodecyl sulfate surfactant increases with increasing of amantadine concentration whereas the CMC values of cetyl trimethyl ammonium bromide surfactant decrease with increasing of amantadine concentration at the same temperature. Then, the thermodynamic properties such as standard Gibbs free energy, enthalpy, and entropy for micellization in aqueous solutions were determined. In addition, molecular dynamic simulation was carried out to understand the interaction sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine at the molecular level and microscopic interactions. The root-mean-square deviations and electrostatic, hydrogen binding and hydrophobic interactions were determined by MD simulations. It was seen, the electrostatic and hydrogen bonding interactions play a crucial role in sodium dodecyl sulfate and amantadine aqueous system. The obtained results showed the simulation and experimental data are in agreement with each other.

Electrode Imbibition and Surfactant Interactions with Vanadium Flow Battery Electrolytes

Redox flow batteries (RFB) are a critical technology for stationary grid-scale energy storage, with potential usage with intermittent power sources, such as wind and solar. RFBs are attractive for long-duration energy storage because the anolyte and catholyte are stored separately external to the electrochemical reactor. Separating the electrolytes and the electrochemical cell decouples energy and power densities, unlike batteries that store charge in the solid-state, such as Li-ion, Pb-acid, or Ni-Cd. A standard RFB chemistry is the all-vanadium redox flow battery (VRFB), which utilizes the four oxidation states of vanadium, with V2+, V3+, V4+, and V5+. Recently our group found that adding small amounts of sodium dodecyl sulfate (SDS) to a VFRB increased the kinetics of the V2+ to V3+oxidation.Furthermore, surfactants play essential roles in battery manufacturing and operation. Surfactants can change metal oxide crystal structure, inhibit dendrite growth, limit corrosion, and prevent nanoparticle agglomeration. Surfactants are never wholly removed during manufacturing and can be present during battery operation. Therefore, it is crucial to understand how surfactants impact battery performance and their effect on the materials.This talk describes SDS's equilibrium surface properties and adsorption characteristics at the liquid−air and liquid-solid interfaces, thus providing insights into the interactions of SDS with a VFRB electrolyte. Experiments focusing on the effects of sulfuric acid and vanadium ions on SDS's equilibrium surface tension and critical micelle concentration (CMC) were completed. The Szyszkowski equation is used to calculate SDS's adsorption parameters, such as interfacial surface excess, Γsz [mol/m2], the surface excess at the saturated interface, Γ∞ [mol/m2], the minimum molecular area in the adsorption layer at the saturated interface, Amin [nm2], and the Gibbs free energy of adsorption, ΔGads [kJ/mol]. Furthermore, an examination of the spontaneous imbibition of the VFRB electrolyte with SDS into a porous carbon electrode is presented. The microstructure of porous systems, interfacial tension, and fluid−solid interactions controls the capillary-driven flow and is vital in multiphase flow in porous media. Therefore, understanding SDS's effects on the VFRB electrolyte in an electrode is critical to understanding the electrochemical reactions and molecular interactions occurring.This work was supported as part of the Breakthrough Electrolytes for Energy Storage and Systems (BEES2), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0019409.

Effect of biologically active amino acids based deep eutectic solvents on sodium dodecyl sulfate: A comparative spectroscopic study

Study the effects of three novel synthesized biologically deep eutectic solvents (DESs) on the micellar characteristics of anionic sodium dodecyl sulfate (SDS). The biologically active amino acids based three DESs synthesized have composed the 2:1 M of L-Aspartic acid (DES1), L-Tyrosine (DES2), L-Glutamine (DES3) and choline chloride, furthermore which characterized by FTIR. Surface tension, viscosity, UV–visible, fluorescence, and FTIR spectroscopy are a few of the techniques used to study the interactions of SDS within 5 and 10 wt% of three novel biological DESs in aqueous solutions. The presence and absence of 5 and 10 wt% of the three novel biological DESs in an aqueous solution is used to study the critical micelle concentration (CMC) and various interfacial characteristics including CMC, the efficiency of adsorption, the maximum surface excess concentration, the packing parameter, the minimum area per molecule, and the surface pressure at CMC, is assessed by the surface tension method. The calculated fluorescence data and those obtained using surface tension and UV–visible methods correspond well. The interactions that cause changes in the structure of the surfactant self-assemblies within aqueous DESs were investigated using FTIR technique. It is significant to highlight that the presence of unique biological DESs considerably facilitates the micellization process for SDS and the extent is more affinity for DES2 compared to DES1/DES3. The colloidal properties of DES and their combinations with water are anticipated to benefit from the current findings.

A comprehensive assessment of interfacial and bulk properties of sodium dodecylsulfate via addition of competitive Hofmeister ions in presence of Cosolvent: A combined experimental and theoretical study

The synergistic interaction of sodium dodecyl sulphate (SDS) and added electrolyte in presence of cosolvent is investigated by determining the critical micelle concentration of SDS. The present system is carried out with two different types of counterions from Hofmeister series where Hofmeister chaotropic ion i.e. NH4+ is attracted more towards the negatively charged chaotropic dodecyl sulphate headgroup of SDS than the kosmotropic ion. To understand the thermodynamic behavior of SDS micelle, counterion binding constant values are measured using the well-established Corrin-Harkins or modified Corrin-Harkins equations. Various assessments of aggregation and adsorption phenomena of SDS micelle are established from both experimental and theoretical concepts. The exchange of counterion i.e. Na+ ion by NH4+ ions can occur at a particular electrolyte concentration where SDS micelle leads to the formation of ammonium dodecyl sulphate (AmDS) in the present cosolvent media. Therefore, the Hofmeister chaotropic ion (NH4+) is found to be a competitive ion. In addition to that, solvophobicity of the cosolvent mixture is another important parameter which could influence SDS micellization differently.

Effect of Drinking Water Salt Content on the Interaction between Surfactants and Bacteria.

Sodium dodecyl sulfate (SDS) is a common surfactant used in various hygienic products. Its interactions with bacteria were studied previously, but the three-way interaction between surfactants, bacteria, and dissolved salts in the context of bacterial adhesion has not been studied. Here, we examined the combined effects of SDS (at concentrations typical of everyday hygienic activities) and salts, sodium chloride, and calcium chloride (at concentrations typically found in tap water) on the adhesion behavior of the common opportunistic pathogen Pseudomonas aeruginosa. We found that bacterial adhesion in the absence of SDS was dependent on the cation concentration rather than the total ionic strength and that combined treatment with several millimolar NaCl and SDS can increase bacterial adhesion. The addition of low concentrations of SDS (2 mM) to tens to hundreds millimolar concentrations of NaCl, typical of systems that suffer seawater incursion, reduced bacterial adhesion dramatically. Combined treatment with Ca+2 (in concentrations typical of those found in hard water) and SDS produced a small increase in total adhesion but a dramatic increase in the strength of adhesion. We conclude that the type and concentration of salts in water can have a considerable effect on the efficacy of soap in reducing bacterial adhesion and should be taken under consideration in critical applications. IMPORTANCE Surface-adhering bacteria are a reoccurring problem in many settings, including households, municipal water systems, food production facilities, and hospitals. Surfactants, and specifically sodium dodecyl sulfate (also known as SDS/SLS), are commonly used to remove bacterial contamination, but data regarding the interaction of SDS with bacteria and especially the effects of water-dissolved salts on this interaction are lacking. Here, we show that calcium and sodium ions can dramatically affect the efficacy of SDS on bacterial adhesion behavior and conclude that salt concentrations and ion species in the water supply should be considered in SDS applications.

Anionic surfactant causes dual conformational changes in insulin

Amyloid fibrillation is a process by which proteins aggregate and form insoluble fibrils that are implicated in several neurodegenerative diseases. In n this study, we aimed to investigate the impact of the negatively charged detergent sodium dodecyl sulfate (SDS) on insulin amyloid fibrillation at pH 7.4 and 2.0, as SDS has been linked to the acceleration of amyloid fibrillation in vitro, but the underlying molecular mechanism is not fully understood. Our findings show that insulin forms amyloid-like aggregates in the presence of SDS at concentrations ranging from 0.05 to 1.8 mM at pH 2.0, while no aggregates were observed at SDS concentrations greater than 1.8 mM, and insulin remained soluble. However, at pH 7.4, insulin remained soluble regardless of the concentration of SDS. Interestingly, the aggregated insulin had a cross-β sheet secondary structure, and when incubated with higher SDS concentrations, it gained more alpha-helix. The electrostatics and hydrophobic interaction of SDS and insulin may contribute to amyloid induction. Moreover, the SDS-induced aggregation was not affected by the presence of salts. Furthermore, as the concentration of SDS increased, the preformed insulin amyloid induced by SDS began to disintegrate. Overall, our study sheds light on the mechanism of surfactant-induced amyloid fibrillation in insulin protein.

Study on the effect of SDBS and SDS on deep coal seam water injection

Coal seam water injection, as an important disaster prevention means in the process of coal mining, can effectively suppress coal dust, add water injection additives, can effectively improve the wettability of coal body, improve the permeability of coal body, so as to achieve the prevention of rock burst. To improve the wettability of coal in coal seam water injection, the surfactant is often added to water, but sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS) have limitations in improving wettability of deep coal seam by injecting water. Therefore, it is very important to determine the influencing factors of SDBS and SDS to improve the wettability of coal. In this paper, the effects of oxygen-containing functional groups and minerals in coal on the wettability of coal are revealed, and the wettability mechanism of SDBS and SDS is expounded from the microscopic point of view. SEM was used to characterize the interaction between coal surface and surfactant, and the contact angle experiment was used to verify the influence of minerals in coal on wettability. Inductively coupled plasma atomic emission spectroscopy (ICP) and dynamic light scattering (DLS) tests were used to characterize the interaction of SDBS, SDS with minerals and the size of precipitation generated by the interaction of SDBS, SDS and mineral ions. The results showed that SDBS and SDS interact with Ca2+ to produce precipitation and block the flow of water in coal, which is not conducive to improving the wettability of deep coal seam to a certain extent. The significant chelating effect of chelating agent and Ca2+ provides a feasible solution to this problem.

Peculiarities of the interaction of sodium dodecyl sulfate with chitosan in acidic and alkaline media

In this work, the interaction between the negatively charged surfactant sodium dodecyl sulfate (SDS) and partially N-reacetylated chitosan (RA-CHI), which is soluble at pH range up to pH 12, is studied in a wide pH range including alkaline media by light scattering (LS) and isothermic titration calorimetry (ITC). It is shown that in the weakly alkaline medium (pH 7.4), RA-CHI/SDS interaction is exothermic and cooperative. This interaction is found to be coupled with proton transfer from the buffer substance to chitosan as it is revealed by the dependence of the measured heat release on the ionization enthalpy of the buffer. At higher pH values (pH > 8), another mechanism of interaction is observed that include SDS micellization induced by hydrophobic interactions with polymer segments, so that no phase separation occurred in these mixtures. The results obtained can contribute to expand the knowledge about application of chitosan for preparation of pharmaceutical and cosmetic compositions containing anionic surfactants.

The Interaction of Sodium Dodecyl Sulfate with 4,5-Dihydroxy-1,3-Benzenedisulfonate Hydrotrope: Micellization, Surface Properties, and Thermodynamics

The Interaction of Sodium Dodecyl Sulfate with 4,5-Dihydroxy-1,3-Benzenedisulfonate Hydrotrope: Micellization, Surface Properties, and Thermodynamics

Cys-labeling kinetics of membrane protein GlpG: a role for specific SDS binding and micelle changes?

Empirically, α-helical membrane protein folding stability in surfactant micelles can be tuned by varying the mole fraction MFSDS of anionic (sodium dodecyl sulfate (SDS)) relative to nonionic (e.g., dodecyl maltoside (DDM)) surfactant, but we lack a satisfying physical explanation of this phenomenon. Cysteine labeling (CL) has thus far only been used to study the topology of membrane proteins, not their stability or folding behavior. Here, we use CL to investigate membrane protein folding in mixed DDM-SDS micelles. Labeling kinetics of the intramembrane protease GlpG are consistent with simple two-state unfolding-and-exchange rates for seven single-Cys GlpG variants over most of the explored MFSDS range, along with exchange from the native state at low MFSDS (which inconveniently precludes measurement of unfolding kinetics under native conditions). However, for two mutants, labeling rates decline with MFSDS at 0–0.2 MFSDS (i.e., native conditions). Thus, an increase in MFSDS seems to be a protective factor for these two positions, but not for the five others. We propose different scenarios to explain this and find the most plausible ones to involve preferential binding of SDS monomers to the site of CL (based on computational simulations) along with changes in size and shape of the mixed micelle with changing MFSDS (based on SAXS studies). These nonlinear impacts on protein stability highlights a multifaceted role for SDS in membrane protein denaturation, involving both direct interactions of monomeric SDS and changes in micelle size and shape along with the general effects on protein stability of changes in micelle composition.

Physicochemical nature of sodium dodecyl sulfate interactions with bovine serum albumin revealed by interdisciplinary approaches

To rigorously characterize the interactions of sodium dodecyl sulfate (SDS) with bovine serum albumin (BSA) a set of experimental methods, namely isothermal titration calorimetry, conductometric titration, steady-state fluorescence spectroscopy, differential scanning calorimetry and circular dichroism spectroscopy, supported by in silico analysis have been applied. The influence of pH and temperature on the binding mode has been revealed. At a low molar ratio of SDS to BSA up to ca. 16:1, there are at least two structurally distinct binding sites in BSA. The formation of SDS-BSA complexes is an enthalpy-driven process in which the van der Waals interactions play a crucial role. The first binding site, located close to the Trp-134 residue within the sub-domain IA, is pH-independent and binds two molecules of SDS per one molecule of BSA whereas the total number of SDS molecules bound to the second site of albumin is affected by temperature and pH. The saturation of the first binding site of BSA (ca. 0.009 mg of SDS per 1 mg of BSA) is sufficient to thermally stabilize the helical conformation of BSA. The presented results have important structural and thermodynamic implications to understand the influence of a widely used anionic surfactant on globular protein functionality in modern branches of chemistry.

Investigation of intermolecular interactions of anionic surfactant SDS and rutin: A physico-chemical approach for pharmaceutical application

The thermodynamic, acoustic and 1H NMR studies between rutin trihydrate and sodium dodecyl sulfate (SDS) were carried out to investigate the flavonoid-surfactant interactions. Four different hydro-ethanolic concentrations (aqueous, 30% v/v, 70% v/v and absolute ethanol) at five different temperatures (20–40 °C with a difference of 5 °C) were selected for the study. The critical micelle concentration (CMC) values were calculated using conductivity (κ) parameter to further compute the change in standard enthalpy (△Hom), standard entropy (△Som) and standard Gibbs free energy (△Gom) of micellization. Other thermo-acoustic parameters, i.e., apparent molar volume (ϕv) and apparent molar compressibility (ϕk) were calculated employing the density (ρ) and ultrasonic sound velocity (μ) studies. In addition to these, the relative viscosity (ηr) for all the concentrations was also determined to understand the flow properties. The introduction of surfactant into the system increased the diffusion properties of rutin trihydrate. The acoustic studies highlighted the existence of hydrophobic and electrostatic interactions within the system. The intermolecular interactions between SDS and rutin trihydrate were also established from the chemical shifts observed for 1H NMR spectra in DMSO‑d6. The obtained parameters play a vital role in optimizing the thermo-physically stable concentration which might prove useful in formulation development.

Physiochemical studies of functionalized MWCNT/transformer oil nanofluid utilized in a double pipe heat exchanger

The transformer-oil based nanofluid suspensions were prepared by adding 0.05 to 0.80 wt% multi-wall carbon nanotubes (MWCNTs) functionalized with a –COOH group. Sodium dodecyl sulfate (SDS) was used to stabilize the suspensions. The resulting material was used as a coolant in a double pipe heat exchanger operated under co- and counter-current flow conditions. The nanofluid thermo–physical features such as the thermal conductivity, viscosity, and density were determined at various temperatures and mass fractions. Then, pertinent semi-empirical relations were developed. To verify any MWCNT and SDS interactions with the material, the Fourier-transform infrared analysis was performed. Moreover, the stability of the nanofluid suspension was understudied through the UV–vis and thermogravimetric analysis techniques. In addition, the maximum heat transfer coefficient improvement was determined to be 86.7% at a MWCNT mass fraction of 0.8 wt%. Meanwhile, average increments of the overall heat transfer coefficient and thermal conductivity of the prepared nanofluid were revealed about 37.2% and 138%, respectively in comparison with that of the base fluid. Furthermore, the optimum thermal conductivity of 0.388 W/m.K was obtained at 45 °C and 0.8 wt% of the MWCNT. Ultimately, a sensitivity analysis emphasized that, the understudied system’s behaviors were within an accuracy limit of ± 97%.

Rapid removal of rhodamine dye from aqueous solution using casein-surfactant complexes: role of casein-surfactant interaction

We report here a new approach to remove rhodamine B dye, a toxic contaminant in industrial effluents, from aqueous solution using colloidal casein protein and its complexes with surfactants. The dye removal efficiency of casein is studied in the absence and in the presence of anionic, cationic, and nonionic surfactants. The anionic, cationic, and nonionic surfactants used in this study are sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and Triton X-100, respectively. The presence of Triton X-100 is found to improve the dye removal efficiency of casein from 21 to 84% with a contact time of 5 minutes. The effect of contact time, pH, and temperature on the dye removal efficiency of casein is also studied here. The adsorption of rhodamine B on casein micelles is found to follow the Freundlich adsorption isotherm and a pseudo second order kinetics model. The variation in hydrodynamic diameter of casein in whole and skimmed milk exhibited similar trend for a given surfactant at different concentrations, which suggests that the presence of fat globules, does not interfere with the interaction of casein for a given surfactant. The hydrodynamic diameter of casein micelles in reconstituted aqueous casein solution is found to increase with an increase in the concentration of SDS, which is attributed to the interaction of SDS with micelles at calcium phosphate sequestration centers, which results in micelle swelling. In the presence of CTAB at varying concentration, the diameter of casein micelles in reconstituted aqueous casein is found to decrease. This is attributed to the interaction of cationic group of CTAB with negatively charged κ-casein which makes the micelles more compact as a result of reduced electrostatic repulsion between the micelles. Similarly, the hydrodynamic diameter of casein micelles in reconstituted casein containing varying concentrations of Triton X-100 is found to decrease which suggests that large micelles break down into smaller micelles. Thus, this work gives new insights to the interaction of casein with anionic, cationic, and nonionic surfactants when present in whole milk, skimmed milk, and reconstituted aqueous solution. Further, casein-Triton X-100 complexes are found to effectively remove rhodamine B dye rapidly due to the synergistic interaction between casein, rhodamine B, and Triton X-100.

Predicting the Toxicities of Ternary Mixtures of two Metals and Sodium Dodecyl Sulfate to Serratia marcescens (SerEW01) from Otamiri River Water

Background: Otamiri river server as a source of water for domestic activities, urban farming, recreation, aquatic foods in Owerri and environs. It also receives untreated domestic, industrial and agricultural waste water and run offs from the municipality. Seepages from solid wastes dumps at the river banks and sand mining activity going on in the river could also constitute environmental hazards
 Aims: This study aims at evaluating the interactive effects of the ternary mixtures of sodium dodecyl sulfate (SDS) and some divalent metals on preponderant bacterium (Serratia marcescens (SerEW01)) from the river.
 Study Design: Fixed ratio ray design was used for the study, with inhibition of dehydrogenase activity as end point.
 Place and Duration of Study: Owerri, Imo State, Nigeria, June – December, 2019.
 Methodology: The bacterium was earlier isolated as the preponderant bacterium isolate from the river water. Fixed ratio ternary mixtures (Equieffect concentration (EEC50) and arbitrary concentration (ABCR) ratios), SDS + Pb + Zn, SDS + Cd +Zn, SDS + Pb +Ni, SDS + Ni + Cd, SDS + Co + Pb and SDS + Co + Cd were designed to evaluate the combined toxicities of these toxicants. Toxicities predicted by concentration addition (CA) and independent action (IA) models were compared with the experimentally observed toxicities.
 Results: The EC50S observed ranged from 0.046 ± 0.003 mM (Zn) to 2.329 ± 0.092 mM (SDS). The EC50S of the toxicants were statistically different from each other (P<0.05). The order of increasing toxicities were SDS >Pb >Ni > Co > Cd(II) >Zn. Concentration-dependent toxicities with progressive inhibition of the dehydrogenase activity as the concentration increased were observed.. In all ternary mixtures, both the experimentally derived, CA and IA-predicted EC50S were statistically different from each other. Both models predicted lower toxicities compared to the experimental data. The Toxic Index and Model Deviation Ratio indicated synergistic interaction of SDS and metal ions against S. marcescens (SerEW01)
 Conclusion: This study could constitute base line information towards assessing the possible environmental hazards associated with co-contamination of the environment by SDS and divalent heavy metals, more so when both pollutants are common aquatic pollutants.

The interaction of sodium dodecyl sulfate with trypsin: Multi-spectroscopic analysis, molecular docking, and molecular dynamics simulation

The bioactivity of enzymes is sensitive to certain factors in their application environment, such as the pH, temperature, ionic strength, and additives, which can alter the native conformation of enzymes. To determine the mechanism by which the interaction of SDS influences the structure and activity of trypsin, molecular docking, molecular dynamics simulations, DSC, and multi-spectroscopic measures including UV absorption, fluorescence, and circular dichroism were used. The results show that the hydrolytic activity towards casein could be dramatically restrained by SDS. UV absorption, CD, and fluorescence spectra demonstrated the formation of a trypsin–SDS complex. Thermodynamic parameters and molecular docking data revealed that the binding process was spontaneous, and that the main binding forces between SDS and trypsin were hydrogen bonds and van der Waals forces. In addition, molecular docking predicted that the binding site of SDS on trypsin was located at the active center. Molecular dynamic simulations showed that treatment with SDS resulted in the structure of trypsin becoming unstable and unfolded near its active center. This work provides insights into the interaction of SDS with trypsin on the molecular level and is beneficial to understanding of how SDS affects the conformation and activity of trypsin in application processes.

Effects of SDS on the activity and conformation of protein tyrosine phosphatase from thermus thermophilus HB27

Deciphering the activity-conformation relationship of PTPase is of great interest to understand how PTPase activity is determined by its conformation. Here we studied the activity and conformational transitions of PTPase from thermus thermophilus HB27 in the presence of sodium dodecyl sulfate (SDS). Activity assays showed the inactivation of PTPase induced by SDS was in a concentration-dependent manner. Fluorescence and circular dichroism spectra suggested SDS induced significant conformational transitions of PTPase, which resulted in the inactivation of PTPase, and the changes of α-helical structure and tertiary structure of PTPase. Structural analysis revealed a number of hydrophobic and charged residues around the active sites of PTPase may be involved in the hydrophobic and ionic bonds interactions of PTPase and SDS, which are suggested to be the major driving force to result in PTPase inactivation and conformational transitions induced by SDS. Our results suggested the hydrophobic and charged residues around the active sites were essential for the activity and conformation of PTPase. Our study promotes a better understanding of the activity and conformation of PTPase.

Revisiting OPLS-AA Force Field for the Simulation of Anionic Surfactants in Concentrated Electrolyte Solutions.

Hereby, we developed a set of nonbonded parameters within all-atom optimized potentials for liquid simulations (OPLS-AA) force field for the simulation of concentrated electrolyte solutions of anionic surfactants. More specifically, the aim of this paper is to assess the performance of five sets of atomic charges calculated using different population analyses (DDEC6, CHelpG, CHelpG-SMD, RESP, and CM5), as well as the original set of charges used in the literature for sodium dodecyl sulfate (SDS) simulation. Recently, Farafonov et al. have revised the SDS OPLS-AA force field; however, we were unable to obtain the experimental rodlike micelles using this parameter set on long time scale. In fact, the initial SDS bilayer micelle adopted a rodlike shape transiently and then broke down into spherical micelles. Updating OPLS-AA force field with DDEC6, CHelpG, and CHelpG-SMD charges resulted in stable rod micelles for a long simulation time (1 μs). The atomic charges of Farafonov (taken from Shelley et al.), RESP, and CM5 could not correctly describe SDS in concentrated electrolyte solutions. Analysis of the interaction of SDS with the counterions and solvent highlights the role of a balance of the intermolecular forces that must be met to describe adequately the anionic surfactant electrolyte solutions. Further, the optimization of the SDS Lennard-Jones parameters enabled the Farafonov set to properly reproduce the experimental rod micelle. In addition, we have examined the performance of different parameters of sodium ions: the first developed based on the Kirkwood-Buff integrals (KBI) and the second developed by Joung et al. The excessive ion pairing caused by KBI parameters screens significantly SDS-water interactions, which stabilize the rod micelle. Further, a tight interaction of the Na+-SDS head group resulted in stabilization of the bilayer micelle as observed in the case of Na+ parameters developed by Joung et al.