High Sodium Dodecyl Sulfate Concentrations Research Articles

Regulation of droplet dynamic behavior after droplet impact on superhydrophobic surfaces

Controlling the impact behavior of a droplet on a superhydrophobic surface is a significant challenge for many applications. Instead of texturing the surface, this study investigated the effect of adding surfactants on the morphology of the droplet after it impacts superhydrophobic surfaces. The results showed that adding low concentrations of sodium dodecyl sulfate (SDS) surfactant prevents fragmentation and splashing. High concentrations of SDS can inhibit rebound and allow droplets to be easily deposited on surfaces after impact. When the droplet size was 3.51 mm and the SDS concentration was above the critical micelle concentration, the contact time of the solution increased by a maximum of 1.30 times compared to that of pure water. In a high-concentration SDS solution, the surfactant molecules can quickly migrate to the newly generated interface during the spreading stage, reducing the interfacial tension and causing wetting changes. The results of this study are expected to contribute toward establishing a simple method to inhibit splashing and increasing contact time on superhydrophobic surfaces.

Cork granules for remediation of soils contaminated with lindane

This work aims to assess the effectiveness of an integrated approach combining surfactant-assisted soil washing (SASW) and cork granules for removing lindane from contaminated soil. It focuses on the evaluation of cork granules (raw and regranulated) as natural sorbents for lindane and on the feasibility of the combination of this physical treatment with surfactant-enhanced soil washing to face the remediation of soil polluted with this hazardous pesticide. The results demonstrate that cork can efficiently retain lindane contained in aqueous solutions and dispersions consisting of mixtures of lindane and sodium dodecylsulfate (SDS) surfactant. Performance improves when using regranulated cork because of its higher affinity for nonpolar species. For lower concentrations of lindane and without surfactant, the raw cork granules presented a sorption capacity of 3.02 mg g− 1, while the regranulated cork presented 6.52 mg g−1. When using a much higher concentration of lindane and SDS, the capacities were 1.90 and 8.21 mg g−1 for raw and regranulated cork, respectively. As well, soil washing with SDS can separate efficiently lindane from spiked soil. It was also observed that the integration of both treatments was feasible, but not as efficient as initially expected. It exhibited a non-expected antagonistic effect caused by the entrapping of the lindane into SDS micelles, which makes it not readily available for sorption. Hence, the higher the amount of SDS the lower the lindane retained by the cork. If the aim is to eliminate lindane with cork specifically, the use of low concentrations of SDS in the combined treatment is encouraged, resulting in an uptake capacity for lindane of 80% from the soil. However, better overall results are achieved when higher concentrations of SDS are used where about 91% of lindane was removed from the soil remaining mainly in the liquid phase. Dichlorination caused by interaction with hydroxyl ions is also observed, being less important in the case of using cork because it attains operation at mild conditions. The results demonstrate that the integration of processes in soil remediation does not always yield expected outcomes and they enhance the knowledge about environmental technologies and their interactions.

Susceptibility of Cu(I) transport ATPases to sodium dodecyl sulfate. Relevance of the composition of the micellar phase

Sodium dodecyl sulfate (SDS) is a well-known protein denaturing agent. A less known property of this detergent is that it can activate or inactivate some enzymes at sub-denaturing concentrations. In this work we explore the effect of SDS on the ATPase activity of a hyper-thermophilic and a mesophilic Cu(I) ATPases reconstituted in mixed micelles of phospholipids and a non-denaturing detergent. An iterative procedure was used to evaluate the partition of SDS between the aqueous and the micellar phases, allowing to determine the composition of micelles prepared from phospholipid/detergent mixtures. The incubation of enzymes with SDS in the presence of different amounts of phospholipids reveals that higher SDS concentrations are required to obtain the same degree of inactivation when the initial concentration of phospholipids is increased. Remarkably, we found that, if represented as a function of the mole fraction of SDS in the micelle, the degree of inactivation obtained at different amounts of amphiphiles converges to a single inactivation curve. To interpret this result, we propose a simple model involving active and inactive enzyme molecules in equilibrium. This model allowed us to estimate the Gibbs free energy change for the inactivation process and its derivative with respect to the mole fraction of SDS in the micellar phase, the latter being a measure of the susceptibility of the enzyme to SDS. Our results showed that the inactivation free energy changes are similar for both proteins. Conversely, susceptibility to SDS is significantly lower for the hyperthermophilic ATPase, suggesting an inverse relation between thermophilicity and susceptibility to SDS.

The improvement of sodium dodecyl sulfate on the electrospinning of gelatin O/W emulsions for production of core-shell nanofibers

In this work, different concentrations of sodium dodecyl sulfate (SDS) were applied to improve the electrospinning performance of gelatin-stabilized emulsions. With the increase of SDS content, the average droplet size of emulsions became smaller and the uniformity improved. Besides, the addition of SDS could increase the apparent viscosity and viscoelasticity of the emulsion via inducing extensive association of gelatin molecules. These changes presented a positive impact on the morphology and structure of the electrospun fibers. By concentration optimization, the core-shell nanofibers were successfully fabricated with the assist of 1% (w/v) SDS with a beadless and uniform structure. Especially, the SDS crosslinking could also prevent the gelling of gelatin solution at the needle via changing the protein conformation, thereby improving the spinnability of gelatin solution with continuity. However, further increasing the SDS concentration to 2% (w/v) would cause conglutination between fibers and agglomeration of oil phase. It was due to the increased viscous resistance of emulsion resulting in insufficient jet stretching at high concentration of SDS. Finally, the gelatin nanofibers showed an enhanced structural stability under the crosslinking of SDS during 15-d storage. Hence, this study presents a practical strategy for the fabrication of bio-based nano-carriers.

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.

Improving Deproteinization in Colombian Latex from Hevea brasiliensis: A Bibliometric Approximation.

Natural Rubber Field Latex (NRFL) allergens restrict its use in some markets due to health-threatening allergic reactions. These molecules are proteins that are related to asymptomatic sensitization and hypersensitivity mediated by immunoglobulin E (IgE). Although NRFL allergens have been investigated since the 1980s, there are still gaps in knowledge regarding the development of deproteinized natural rubber (DPNR). Therefore, in this study, the deproteinization of NRFL from the lower basin of the Cauca River, Antioquia-Colombia was evaluated using eight systems. The highest removal value was 84.4% and was obtained from the treatment containing SDS (Sodium dodecyl sulfate), Urea, and Ethanol. It was also possible to determine that at high concentrations of SDS, removal percentages higher than 70% are reached. On the other hand, all deproteinizing systems decreased NRFL Zeta potentials without self-coagulation, suggesting enhanced colloidal stability in DPNR latex. On the other hand, the bibliometric analysis presented technological advances in DPRN through different parameters and bibliometric networks. The analysis presented makes an important contribution from the bibliometric approach that could be positive for the development of research on DPNR.

Surfactant-template sol-gel protective coatings for cast iron corrosion: Effect of the surfactant type and concentration

Different surfactants-template tetraethylorthosilicate-3-mercaptopropyl-trimethoxysilane (TEOS-MPTMS) sol–gel materials are prepared by the hydrolysis of silane precursors, in presence of the surfactant. Three surfactants are used, cationic cetyltrimethylammonium bromide (CTAB), non-ionic TritonTM X-100, and anionic sodium dodecyl sulfate (SDS). Prepared sol–gel materials are applied as protective coatings for cast iron corrosion in 0.5 mol.L-1 HCl. The protection efficiency is estimated by electrochemical measurements. Structural and surface properties of the prepared sol–gel materials are examined by FTIR and scanning electron microscope (SEM) and are affected by the surfactant species and concentration. Surfactant-template sol–gel materials acquire higher porosity than the free material. However, the presence of the surfactant stabilizes the silane network formation, and facilitates the protection performance, especially at lower and intermediates surfactant amounts. The presence of TritonTM X-100 and CTAB enhance the protection performance of the sol–gel coatings, average efficiencies are 95 and 86 %, respectively. On the other hand, SDS-template sol–gel coatings offer lower efficiency and can not be used as protective coatings at high SDS concentrations due to the repulsion between SDS and negatively charged silanolate groups, which results in a highly unstabilized sol–gel structure with a distorted morphology. The proposed surfactant-template sol–gel coatings show excellent operational stability in the corrosive medium for a long time.

EFFECTS OF SYNTHESIS CONDITIONS ON STRUCTURE OF TIN NANORODS PREPARED BY SURFACTANT-ASSISTED CHEMICAL REDUCTION METHOD

Metallic nanorods/nanowires have recently become the focus of intensive research due to their unique properties and have been used to fabricate electronic, energy devices and sensors in nanoscale. In this study, tin nanorods were synthesized through a surfactant assisted chemical reduction method in aqueous solutions at low temperature (~ 0 oC). Sodium dodecyl sulfate (SDS) and sodium borohydride (NaBH4) were used as the surfactant and reductant, respectively. Parameters such as pH, surfactant concentration, and temperature were studied to control the diameter and length of the nanorods formed. The structure, composition and surface morphology of the obtained products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the morphology as well as the aspect ratio of tin nanorods could be effectively controlled by adjusting the parameters of the synthesis process. It was found that tin nanoparticles were formed at 30 oC while nanorods appeared at lower temperatures (0, 5 oC). A low SDS concentration of 4 mM helped to form Sn nanoparticles but higher SDS concentrations of 8, 12 mM facilitated the growth of nanorods. The increase of SDS concentration reduced the length of nanorods. pH values less than 4.5 were found to be favorable to the formation of nanorods.

Influence of surfactants and organic polymers on monolithic shape-stabilized phase change materials synthesized via sol-gel route

Shape-stabilized phase change materials (ss-PCMs) can store up to five times more thermal energy than commercially available composite PCM boards based on core-shell PCMs, but have low mechanical stabilities. Therefore, we have recently synthesized ss-PCMs with high mechanical stability via a novel porogen-assisted sol-gel process. Here, we track the ss-PCM formation in situ and analyze the influence of the porogens sodium dodecyl sulfate (SDS) and poly(vinyl alcohol) (PVA) on ss-PCM properties. During gelation the silica scaffold is built around PCM droplets covered with SDS in an O/W emulsion. All ss-PCMs exhibit a high shape-stability (∼100%), a high long-term performance (> 2000 thermal cycles) and a high chemical stability, regardless of the amount of porogen used in the synthesis. Higher PVA amounts separate the emulsion in large hydrophilic and small hydrophobic regions and increase the silica macropore width in ss-PCMs from 1007 nm to 8801 nm due to silica fragmentation during drying. The silica fragmentation lowers the compressive strength (1.2 MPa) and thermal conductivity (0.37 W/mK) of the ss-PCMs by 50% and by 17% (10 °C), respectively. In contrast, low SDS amounts can not stabilize all PCM droplets in the emulsion from phase-separation, resulting in a partially fragmented silica phase. Too high SDS concentrations decrease the viscosity and hence, stability of the emulsion. Consequentially, the silica macropores collapse during drying, which lower the compressive strength (1.02 MPa) and thermal conductivity (0.37 W/mK) of ss-PCMs by 63% and 25% (10 °C), respectively.

Reversible assembly of silica nanoparticles at water-hydrocarbon interfaces controlled by SDS surfactant.

Achieving reversible and tunable assembly of silica nanoparticles at liquid-liquid interfaces is vital for a wide range of scientific and technological applications including sustainable subsurface energy applications, catalysis, drug delivery and material synthesis. In this study, we report the mechanisms controlling the assembly of silica nanoparticles (dia. 50 nm and 100 nm) at water-heptane and water-toluene interfaces using sodium dodecyl sulfate (SDS) surfactant with concentrations ranging from 0.001-0.1 wt% using operando ultrasmall/small-angle X-ray scattering, cryogenic scanning electron microscopy imaging and classical molecular dynamics simulations. The results show that the assembly of silica nanoparticles at water-hydrocarbon interfaces can be tuned by controlling the concentrations of SDS. Silica nanoparticles are found to: (a) dominate the interfaces in the absence of interfacial SDS molecules, (b) coexist with SDS at the interfaces at low surfactant concentration of 0.001 wt% and (c) migrate toward the aqueous phase at a high SDS concentration of 0.1 wt%. Energetic analyses suggest that the van der Waals and electrostatic interactions between silica nanoparticles and SDS surfactants increase with SDS concentration. However, the favorable van der Waals and electrostatic interactions between the silica nanoparticles and toluene or heptane decrease with increasing SDS concentration. As a result, the silica nanoparticles migrate away from the water-hydrocarbon interface and towards bulk water at higher SDS concentrations. These calibrated investigations reveal the mechanistic basis for tuning silica nanoparticle assembly at complex interfaces.

Self-propelled camphor disk dependent on the depth of the sodium dodecyl sulfate aqueous phase

We studied the self-propulsion of a camphor disk placed on a surfactant solution to clarify the relationship between the speed of motion and the depth of the aqueous phase. At lower concentrations of sodium dodecyl sulfate (SDS) in the aqueous phase, the speed of motion for the deeper aqueous phase was higher than that for the shallower aqueous phase. However, this relationship was reversed at higher SDS concentrations. The surface tension of the aqueous phase and diffusion rate around the camphor disk were measured to determine this reverse relationship at higher SDS concentrations. Numerical calculation considering the flow field coupled with the concentration field qualitatively reproduced the experimental results on the diffusion rate depending on the SDS concentration. These results suggest that the amount of camphor dissolved in the aqueous phase plays an important role in reversing the speed of motion depending on the depth of the aqueous phase.

POS-476 OPTIMIZATION OF SDS-BASED KIDNEY DECELLULARIZATION RESULTS IN ECM SCAFFOLDS APPLICABLE FOR 3D RECELLULARIZATION

Kidney decellularization is used to obtain extracellular matrix (ECM) scaffolds as a platform for 3D culturing and kidney tissue regeneration. ECM contains biological molecules such as growth factors necessary for cell survival, proliferation, and maturation during organogenesis. While decellularization allows for the complete removal of cells, it also causes the removal of specific growth factors from the ECM, which could have deleterious effects on cell survival, proliferation, and differentiation during recellularization. We hypothesize that using a mild decellularization protocol which employs the use of sodium dodecyl sulphate (SDS) below its critical micelle concentration (CMC) of 0.2% in water at room temperature will allow for the greater retention of bioactive molecules which will improve recellularization efficiencies. Porcine kidney cortex was cut into 1mm x 6mm slices and decellularized using 0.05%, 0.075%, or 0.1% SDS in a soak and agitation protocol for 24 hours at room temperature. Decellularization was determined through histological and immunofluorescent staining, and DNA quantification. The retention of ECM proteins and biomolecules was determined by histological and immunofluorescent staining, mass spectrometry, and protein array analysis. Four different cell lines were used for recellularization; human-induced pluripotent stem cells (hiPSC), mesoderm derived from hiPSC, intermediate mesoderm derived from hiPSC, and primary human renal epithelial cells. ECM scaffolds were dried on Transwell inserts and cells were pipetted on the surface of the scaffold. ECM-cell constructs were grown for two weeks in culture at air-liquid interface. Recellularization efficiency, cell organization, and differentiation were determined using whole mount staining. Complete decellularization was achieved when SDS was used in concentrations below its CMC. Decellularizing with 0.05% SDS resulted in the greatest retention of glycosaminoglycan chains (GAGs), revealing that GAGs are still significantly removed from the ECM when using SDS below its CMC. Upon protein quantification, scaffolds decellularized with higher SDS concentrations were more enriched with matrisome proteins compared to scaffolds decellularized with lower SDS concentrations, which correlated to a decrease in growth factors and cytokines present on the scaffolds as determined by protein array. Following 14-day recellularization, hiPSCs and kidney progenitor cells proliferated on the ECM and expressed markers such as LIM1, WT1, PBX1 and CD31. Primary renal epithelial cells maintained a mature phenotype, expressing LTL, cytokeratin, and KSP. Herein, we describe a novel protocol for the decellularization of kidney cortex scaffolds that allows for greater retention of biomolecules. This retention of growth factors and cytokines aids in the proliferation and directed differentiation of hiPS and kidney progenitor cells toward mature renal lineages. Thus, we determined that our ECM scaffolds are able to support the growth of both hiPS and organ-matched cells. This can be applied to other organ decellularization/ recellularization protocols, as well as for the generation of kidney tissue for further in vitro studies.

Surfactant and temperature as forcing functions on the growth of Egeria densa and Chara sp.: a modeling approach.

The wide use of detergents combined with rising water temperature is currently issuing of environmental concern. To evaluate the effect of sodium dodecyl sulfate (SDS) and temperature on macrophyte and talophyte growth, bioassays were conducted with distinct SDS concentrations (0.5 and 8.0 mg L-1) and temperatures (25 and 27 °C). The length of the Egeria densa and Chara sp. and the number and lengths of shoots were measured. Kinetic models were used to verify the temperature and SDS concentrations, as driving factors in the growth. The 2 °C increase in thermal condition interfered positively in both elongation and shoot development in the E. densa growth. For Chara sp., this tendency was not observed for the relative contribution of the shoots, but the number was higher at 25 °C. The higher concentrations of SDS (8.0 mg L-1) reduced the shoots' number and the relative contribution for Chara sp. and E. densa; meanwhile, the decrease in the growth coefficient was observed only for E. densa at 25 °C. In the Chara sp. development, the SDS addition interfered negatively in the growth coefficient. The predicted response of growth models will bring comprehensive knowledge of macrophytes and talophyte metabolism, and the interaction between plant species and forcing functions in modeling approaches will assist in finding the key processes driving plant growth under specific stressors.

Bed expansion and gas holdup characteristics of bubble–assisted fluidization of liquid–particle suspensions in a HydroFloat cell

The HydroFloat cells made by Eriez are designed for floating coarse particles using fluidization involving bubble–liquid–particle suspensions. The operational optimization and control of these cells can be a challenging task and require various correlations that are difficult to establish by theory. Here, experiments were performed to study the effect of SDS (sodium dodecyl sulfate) on the liquid–particle and bubble–liquid–particle fluidization processes in a laboratory-scale HydroFloat cell. Air was supplied to a perforated circular tube at the bottom to generate the bubbles while irregular coarse quartz particles were fed to the top by a vibrating plate as the solid phase. In the liquid–particle fluidization, the bed expansion (BE) increased with increasing superficial liquid velocity and agreed with the modified Richardson-Zaki equation (within 4% relative error). BE decreased to 12.5% in the presence of SDS at low concentrations. In the bubble–liquid–particle fluidization, BE was reduced by 8.46 – 2.89% and 15.1% with increasing superficial gas velocity and decreasing superficial liquid velocity in the absence of SDS, respectively. In the presence of SDS, BE increased with increasing superficial gas and liquid velocities. High SDS concentrations generated expanded beds with higher heights. Low SDS concentration (0.2 mM) increased the gas holdups by an average of 20% with increasing superficial gas velocity from 1.1 to 3.4 mm/s. Both BE and gas holdup were compared with the available empirical correlations. The estimated BE showed smaller mean absolute relative errors (MAREs) in the absence of SDS than the presence of SDS, while gas holdups yielded large MAREs. The particle sphericity and bubble Reynolds number were incorporated into the Begovich-Watson and Ramesh-Murugesan equations to estimate the BE and gas holdup, respectively. The modified equations significantly improved the predictions. The empirical correlations developed and investigated here would be useful for the operational optimization of the fluidized bed HydroFloat cells.

Novel cytokine marker available for skin irritation testing of medical devices using reconstructed human epidermis models

In biological safety evaluation of medical devices, false-negative results have been observed during skin irritation testing using the reconstructed human epidermis (RhE) model when measuring cell viability as a single marker. Therefore, to improve testing accuracy, this study conducted a comprehensive survey and performance evaluation of cytokines to identify a second marker. In addition to IL-1α, macrophage migration inhibitory factor (MIF) was newly identified as a candidate marker, in the Bio-Plex assay of EpiDerm model exposed to polymer sample extracts. Irritation based on cell viability level was not accurately determined in LabCyte model using silicone spiked with 25% heptanoic acid (HA). By contrast, the irritation potency was accurately assessed in detail by measuring IL-1α or MIF. Further, IL-1α and MIF levels in EpiDerm, LabCyte, and EpiSkin models stimulated with sodium dodecyl sulfate (SDS) were inversely correlated with cell viability, and were detected even at low SDS concentrations without cell toxicity. Additionally, MIF demonstrated greater S/N ratio and dose-dependency at high SDS concentrations in some models compared to IL-1α. These results indicated that MIF might be a useful second marker for improving the sensitivity and accuracy of skin irritation testing with RhE models.

How Cellulose Nanofibrils Affect Bulk, Surface, and Foam Properties of Anionic Surfactant Solutions.

We study the generation and decay of aqueous foams stabilized by sodium dodecyl sulfate (SDS) in the presence of unmodified cellulose nanofibrils (CNF). Together with the rheology of aqueous suspensions containing CNF and SDS, the interfacial/colloidal interactions are determined by quartz crystal microgravimetry with dissipation monitoring, surface plasmon resonance, and isothermal titration calorimetry. The results are used to explain the properties of the air/water interface (interfacial activity and dilatational moduli determined from oscillating air bubbles) and of the bulk (steady-state flow, oscillatory shear, and capillary thinning). These properties are finally correlated to the foamability and to the foam stability. The latter was studied as a function of time by monitoring the foam volume, the liquid fraction, and the bubble size distribution. The shear-thinning effect of CNF is found to facilitate foam formation at SDS concentrations above the critical micelle concentration (cSDS ≥ cmc). Compared with foams stabilized by pure SDS, the presence of CNF enhances the viscosity and elasticity of the continuous phase as well as of the air/water interface. The CNF-containing foams have higher liquid fractions, larger initial bubble sizes, and better stability. Due to charge screening effects caused by sodium counter ions and depletion attraction caused by SDS micelles, especially at high SDS concentrations, CNF forms aggregates in the Plateau borders and nodes of the foam, thus slowing down liquid drainage and bubble growth and improving foam stability. Overall, our findings advance the understanding of the role of CNF in foam generation and stabilization.

Tube-Gel: A Fast and Effective Sample Preparation Method for High-Throughput Quantitative Proteomics.

Sample preparation is a key step in proteomics workflows. Tube-gel (TG) is a fast and repeatable sample preparation method that consists in the instantaneous trapping of the sample in a polyacrylamide gel matrix. It takes advantage of in-gel sample preparations by allowing the use of high concentrations of sodium-dodecyl sulfate but avoids the time-consuming step of electrophoresis. Therefore, TG limits the sample handling and is thus particularly suitable for high-throughput quantitative proteomics when large sample numbers have to be processed, as it is often the case in biomarker research and clinical proteomics projects.

Effects of Anionic Surfactant Ingredients on Hematological Index of the Brown Trout (Salmo trutta fario)

The aim of this study was to determine the toxicity of sodium dodecyl sulfate (SDS) to aquatic organisms. The effects of SDS were investigated using the hematological index of the brown trout (Salmo trutta fario). Fish were exposed to control (0 mg/l), low dose (1.5 mg/l) and high dose (2.25 mg/l) of SDS over a 21-day period. At the end of the treatment period, the control and the treatment groups were investigated for the hematological index [total erythrocyte count (RBC), total leukocyte count (WBC), hemoglobin (Hb), hematocrit (Hct), total platelet count (PLT), erythrocyte sedimentation rate (ESR), mean cell hemoglobin concentration (MCHC), mean cell hemoglobin (MCH), and mean cell volume (MCV)]. The results showed a significant increase in RBC, WBC, PLT, Hb, ESR, MCV, MCH, and MCHC values of the group exposed to high SDS concentrations compared to those in the low-dose treatment and control (p

Unraveling the molecular mechanism of the effects of sodium dodecyl sulfate, salts, and sugars on amyloid fibril formation in camel IgG.

Sodium dodecyl sulfate (SDS) is an anionic surfactant that can be used to stimulate protein fibrillation in vitro. Here, we investigated the effects of SDS on camel IgG aggregation at pH 3.5 and 7.4. SDS-induced amyloid fibril formation in camel IgG was examined by turbidity measurements, Rayleigh scattering, Thioflavin T (ThT) fluorescence, intrinsic fluorescence, circular dichroism (CD), and transmission electron microscopy (TEM). The results suggest that low SDS concentrations (0.2-2.0 mM) induce amyloid-like aggregates of camel IgG at pH 3.5, indicating an SDS/camel IgG ratio below 1000. However, in the presence of higher concentrations of SDS (2.5-10.0 mM), amyloid fibril formation was not observed. Furthermore, at the higher concentrations, the β-sheet structure of camel IgG was transformed into a α-helical structure. The amyloid fibril formation was not observed in the presence of SDS at pH 7.4. Additionally, the role of salts and sugars was evaluated in the SDS-induced aggregation process. Interestingly, in the presence of 0.15 N of NaCl and (NH4)2SO4, SDS promoted camel IgG aggregation up to very high concentrations of SDS (0.2-10.0 mM; SDS/camel IgG ratio, 95-4750) and no suppression was observed. Moreover, osmoprotectants (trehalose and sucrose) were ineffective, neither promoting nor inhibiting the SDS-induced aggregation process. However, at pH 3.5, electrostatic and hydrophobic interactions, and hydrogen bonds were the major contributing factors in SDS-induced fibrillation. However, no aggregation was observed at pH 7.4 due to electrostatic repulsion between SDS and camel IgG because both of these molecules have overall similar charges.

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

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