Sodium Dodecyl Sulfate Concentration Research Articles

Effect of different enzymes on thermal and structural properties of gluten, gliadin, and glutenin in triticale whole-wheat dough

Three enzymes promoted the development of the gluten network in triticale whole-wheat noodles (TWWN). To further understand the mechanism of gluten enhancement, the effects of three enzymes on the structure of gluten and its fractions (gliadin and glutenin) were evaluated. The results showed that glucose oxidase (GOD), xylanase (XYL), and laccase (LAC) decreased the content of sodium dodecyl sulfate (SDS) extractable proteins. The content of glutenin subunits was reduced by 17.25 %, 30.60 %, and 20.09 % with the addition of GOD, XYL, and LAC, respectively. Furthermore, GOD and LAC increased the content of glutenin macropolymer (GMP) by 2.64 % and 7.71 %, respectively, suggesting the promotion of glutenin aggregation. The addition of three enzymes decreased the weight loss and increased the degradation temperature of the gluten and its fractions. GOD and XYL decreased the fluorescence intensity of gluten and its fractions, except for XYL which increased the fluorescence intensity of glutenin by 10.50 %. Intermolecular interactions and surface hydrophobicity were enhanced by XYL in gluten and its fractions. GOD and LAC decreased the free sulfhydryl content and increased the β-sheet content, suggesting that the covalent interaction between gluten fractions was enhanced. Therefore, this research can enrich the theoretical study of enzymatic cross-linking.

Simultaneous Enantioseparation of Three Chiral Antifungal Pesticides by Hydroxypropyl-γ-CD-Modified Micellar Electrokinetic Chromatography.

Simultaneous enantioseparation of three commonly used chiral antifungal pesticides (diniconazole, hexaconazole, and imazalil) was first studied based on micellar electrokinetic chromatography (MEKC) with hydroxypropyl-γ-CD (HP-γ-CD) as chiral selector. In this study, the importance of experimental parameters such as chiral selector type and concentration, sodium dodecyl sulfate (SDS) concentration, the ratio of methanol, and separation voltage in optimizing were investigated. The simultaneous enantioseparation of diniconazole, hexaconazole, and imazalil was successfully achieved in 30 mM borate buffer (pH 9.0) containing 10 mM HP-γ-CD and 20 mM SDS with methanol (8%) added as organic modifiers. The resolution of diniconazole, hexaconazole, and imazalil was 15.2, 2.12, and 2.78, respectively, and the peak efficiency (N) was over 566,825 plates/m. This study provides an alternative way to systematically separate chiral antifungal pesticides with high efficiency.

Visualising the adsorption behaviour of sodium dodecyl sulfate corrosion inhibitor on the Mg alloy surface by a novel fluorescence labeling strategy

Corrosion inhibitors, have the characteristics of environmental friendly and high efficient, are widely used to inhibit the corrosion of alloys; however, their corrosion inhibition mechanism and adsorption behavior is still unclear. Herein, a cationic dye (1,8-naphthalenimide, NP) is synthesized for fluorescent visualisation of the sodium dodecyl sulfate (SDS) adsorption behavior on the α-Mg and β-Li phases. In-situ observation showed that obvious fluorescence adsorption preferentially appeared on the α-Mg phase via physicochemical adsorption. Moreover, stronger fluorescence intensity was observed on the local corrosion sites due to the precipitation of Mg-SDS complex. Micro-scale in situ observation under electrochemical control is applied to explain the inhibition mechanism from the perspective of corrosion kinetics. The inhibition efficiency is evidently improved (>90%) after the addition of SDS, and the optimum value reaches 95.1% at the SDS concentration of 0.04 M. Surface characterizations are conducted to validate the adsorption behaviour of SDS on the Mg alloy surface. The inhibition mechanism of SDS is proposed by experimental and theoretical calculations. This work advances the development and application of specific fluorescence tracking to elucidate the adsorption behaviour of corrosion inhibitors at the micro-level and provides a new idea for the development of efficient corrosion inhibitors.

Effect of film properties on droplet impact on suspended films

Understanding the dynamics and underlying mechanisms of droplet impact on suspended films is crucial for controlling droplet motion. In this study, we conducted experiments to investigate droplet impact on suspended films and examined the typical phenomena and corresponding Weber number domains. We explored the effects of changing sodium dodecyl sulfate (SDS) concentration and glycerol content on the surface tension and dynamic viscosity of the films. Additionally, we elucidated the characteristics of film deformation and droplet trajectory. An energy analysis was performed, considering the droplet kinetic energy (Ek0), surface energy increment of the film (ΔEfs), and viscous dissipation (Evis). The results demonstrate that as the SDS concentration increases, the upper critical Weber number (Wecru) between bouncing and passing decreases, while the lower critical Weber number (Wecrl) between coalescence and bouncing first decreases and then increases. For droplet bouncing, increasing the SDS concentration makes the films more susceptible to deformation, whereas increasing the glycerol content enhances film rigidity. Moreover, increasing the SDS concentration and glycerol content leads to higher energy losses, resulting in a reduction in the maximum bouncing height (hbdmax). Regarding droplet passing, the passing velocity (Vpd) increases with increasing SDS concentration. For films without SDS, Vpd increases with increasing glycerol content, while for films with SDS, Vpd decreases. The different impact modes are categorized based on the dimensionless energy parameter E* = Ek0/(ΔEfs + Evis). We have successfully predicted the critical height thresholds (Hd0crl and Hd0cru) and established a relationship of We* = f (Re*, Bo*) that aligns well with experimental results.

Effects of the anionactive surfactant sodium dodecyl sulfate on the adhesion of cells of the strain <i>Micrococcus luteus</i> 1-i to the surface of carbon materials

The adhesion of microorganisms on various surfaces plays a crucial role in many biotechnological processes. A widespread component of wastewater is the anion-active surfactant sodium dodecyl sulfate (SDS). Surfactants have a significant influence on all interfacial reactions, including those occurring in microbial fuel-cell technology. The work set out to study the effect of sodium dodecyl sulfate on the sorption of cells of the Micrococcus luteus 1 strain (which has electrogenic activity in microbial fuel cells) on the surface of various carbon-containing electrode materials used in biological fuel cell technology: 1) carbon tissue; 2) carbon felt; 3) crushed graphite contact trolleybus inserts (summer); 4) birch activated carbon. Using spectrophotometry and microscopy methods, the presence of sodium dodecyl sulfate in the concentration range of 10–200 mg/l was shown to increase the sorption of Micrococcus luteus 1-i cells on the surfaces of the tested carbon materials under experimental conditions. The maximum increase in sorption during 2 hours of exposure was detected when 100 mg/l of this surfactant was applied: for birch activated carbon – 21%; for carbon fabric – 26%; for carbon felt relative to the control (without surfactant) – 24%. The results demonstrate a sufficiently effective adhesion of Micrococcus luteus 1-i cells to various carbon materials, including in the presence of fairly high concentrations of sodium dodecyl sulfate, confirming the prospects of this strain for use in various types of microbial fuel cells.

Photonic Crystal Reflectors with Ultrahigh Sensitivity and Discriminability for Detecting Extremely Low-Concentration Surfactants.

Developing a facile, intuitive, ultrahigh-sensitive sensor to detect harmful substances in water is critical. Here, an ultrahigh-sensitive sensor is fabricated using a quaternized lamellae-structured polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer (BCP), capable of detecting the heavily used surfactants including sodium dodecyl sulfate (SDS) and sodium methyl sulfate (SMS) through direct visualization of the structural color change. Two distinct detecting mechanisms, including unexpected blue-shifting and red-shifting reflectance wavelengths, are found for low and high concentrations of the SDS surfactant, respectively, due to concentration-dependent compatibility between the quaternized P2VP (QP2VP) block chains and SDS molecules. As the SDS concentration is low (0-1 mM), the QP2VP chains undergo the counter anionic exchange with the hydrophobic alkyl chains of the SDS, resulting in a blue shift toward colorlessness. In contrast, as the SDS concentration is high (>1 mM), the nanoaggregation of the SDS molecules in the layered QP2VP microdomain leads to enhanced hydration nature and increased lamellar periodicity with the red-shifting reflectance wavelength. In contrast, SMS with weaker hydrophobicity results in unchanged and red-shifting reflectance wavelengths at low and high concentrations. Inspired by this, detecting the extremely low-concentration SDS surfactant (0.01 mM) by direct visualization is achieved. The structural color change for surfactant detection also exhibits excellent reversibility and discriminability, providing a straightforward method of detecting anionic surfactants.

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.

Bovine liver catalase turns into three conformational states after exposure to an anionic surfactant.

The mechanism by which anionic surfactants promote amyloid fibril is not well understood. Here, we investigated how sodium dodecyl sulfate (SDS), a negatively charged surfactant, affects the fibrillation of the partially unfolded random-coiled bovine liver catalase (BLC) at a pH of 2.0. We used several methods, including turbidity, RLS kinetics, intrinsic fluorescence, ThT fluorescence, far-UV CD, and TEM imaging, to evaluate the conformational changes of BLC in vitro in response to SDS treatment. BLC is a multimeric protein and well folded at physiological pH but forms a random coil structure at pH 2.0. Intrinsic fluorescence and far-UV CD data showed that below 0.1mM SDS, random coiled BLC turned into a native-like structure. BLC incubated with an SDS concentration ranging from 0.1 to 2.0mM led to the formation of aggregates. The ThT fluorescence intensity was enhanced in the aggregated BLC samples (0.1-2.0mM SDS), and cross beta-sheeted structure was detected by the far UV CD measurements. BLC adopts a complete alpha-helical structure upon interacting with SDS at a more than 2.0mM concentration at pH 2.0. Understanding the mechanism of surfactant- or lipid-induced fibrillation is important for therapeutic purposes.

Micellization of a cationic and an anionic surfactant in the presence of diphenylcarbazide in aqueous media and the effect of micelle surface charge on the complexation of the solubilised ligand with metal ions

ABSTRACT In the present study, we carried out conductometric and surface tension analyses to report the critical micelle concentration (CMC) of tetradecyltrimethyl ammonium bromide (TTAB) and sodium dodecyl sulphate (SDS) as a function of the concentration of a diphenylcarbazide (DPC). It is found that the micellization of TTAB becomes unfavourable while that of SDS becomes favourable in the presence of DPC. This indicates a substantial difference in the mutual interaction of the sparingly soluble ligand with the cationic and the anionic surfactants. The complexation ability of the solubilised DPC with hydrated Zn(II) and Cd(II) ions at varying concentrations of the cationic and anionic surfactants was studied by UV–Vis spectral analyses. With increasing the concentration of both surfactants up to their respective CMC values, the absorbance of the metal–DPC complex increases. However, the absorbance of the complex in TTAB micelles sharply decreases, showing almost zero values beyond the CMC, but that in SDS remains almost steady with increasing the concentration of the surfactant, as evidenced from the visible spectra.

(Invited) Kinetics of SWCNT Coating Displacement By ssDNA Depends on SWCNT Structure

Non-covalent hybrids formed by suspending single-wall carbon nanotubes (SWCNTs) in single-stranded DNA (ssDNA) present novel phenomena and suggest potential applications in biomedicine and nanotube sorting. Although the structures of these hybrids have been simulated using molecular dynamics calculations, much more experimental research is needed to understand their properties. In this study, selective interactions between SWCNTs and ssDNA are probed by measuring the kinetics by which ssDNA displaces SDS (sodium dodecyl sulfate) coatings on the nanotube surfaces. We used samples initially suspended in a low concentration of SDS to allow the coating displacement to occur and to suppress formation of free SDS micelles. The displacement process was monitored by time-dependent measurements of SWCNT fluorescence intensities and wavelengths. Our experiments showed very smooth decreases in fluorescence intensity and red-shifts in fluorescence wavelengths during the displacement process. Through a series of measurements, we found that ssDNA sequences with repeated guanine (G) and thymine (T) bases showed systematic patterns in the coating displacement kinetics. One result is that SDS displacement depends strongly on oligo length, with (GT)3 showing an initial rate constant 500 times greater than that of (GT)20. For shorter oligos in the (GT) n series, we observe an inverse dependence of initial rate constant on SWCNT diameter, with SDS displacement from (6,5) more than twice as fast as from (8,7). However, this diameter dependence is not present for (GT) n oligos with n greater than 6. We also find a distinct and systematic dependence of initial rate constant on nanotube chiral angle for (GT)5 and (GT)6. This effect gives a factor of ~3 difference between (9,1) and (6,5) despite their identical diameters. We empirically find these initial rate constants to vary as (SWCNT diameter)-4(cos 3θ)-y with y = -1/2 for (GT)5 and -1 for (GT)6. In addition, the full displacement kinetic traces are well fitted by double exponential kinetics, with rate constants and amplitudes dependent on SWCNT diameter. A two-step kinetic model for the displacement process will be presented to account for these findings.

Influence of phosphonium-based ionic liquid on the micellization behavior of surfactants system and potential application in paracetamol drug aggregation

The current study examines the effects of a phosphonium-based ionic liquid, trihexyltetra-decylphosphonium bis-(2,4,4-trimethyl pentyl)phosphinate [THTDPP], on the micellization properties of surfactants, namely sodium dodecyl sulfate (SDS) and Triton X-100 by using the stalagmometry, viscosity, colorimetric, and FTIR methods. The surface adsorption parameters, such as CMC, γCMC, Γmax, Amin, πCMC, and pC20, were determined using the stalagmometry method. The results show that with the addition of different weight percentages of [THTDPP], the CMC and γCMC values decreased considerably in the following order: water >0.5 wt% of IL > 0.7 wt% of IL > 1.0 wt% of IL. The Amin values decreased with an increase in the wt% of IL for Triton X-100, but for SDS, this value increased. The pC20 was observed to be greater in Triton X-100 compared to SDS. The ability of [THTDPP] to decrease the CMC was found to be greater in Triton X-100 compared to SDS. The relative viscosity was calculated, and the first observation was made at the pre-CMC stage, where the concentration of SDS+0.7 wt% IL was 4.0 mM. The second finding was made post-CMC at a concentration of 5.0 mM. Afterward, the relative viscosity graph grew slowly and gradually. The functional groups involved in the complexation between [THTDPP] and both surfactants were examined using FTIR spectroscopy. Additionally, the micellar solutions of surfactants + [THTDPP] were used to explore Paracetamol [PCM] aggregation. The findings from UV–vis spectroscopy show that Triton X-100 exhibits the highest binding affinity and has the most encouraging effect compared to SDS.

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.

Two-step pressure injection-assisted online enrichment of herbicides from foods with affinity micelle sweeping by micellar electrokinetic chromatography

A novel online two-step pressure injection-assisted stacking preconcentration method, which involves sweeping and affinity micelles in micellar electrokinetic chromatography was developed to simultaneously measure various organic anions. The micellar solution was a mixed solution that contained 0.3 mM didodecyldimethylammonium bromide and 20 mM borax. After the micellar solution was injected for 60 s, the tested analytes prepared in 20 mM borax were introduced into the capillary for 150 s. The key experimental factors that influenced the separation and sensitivity were investigated and optimized, including the concentration and injection time of the micellar solution, the concentration of borax in the sample solution, the concentration of sodium dodecyl sulfate and borax in the background electrolyte (BGE), the content of acetonitrile in the BGE and the injection time of the sample solution. Compared with typical injection methods, this method achieved sensitivity enhancement factors ranging from 85 to 97 under optimized conditions. Good linearity for matrix-matched calibration was established for all analytes with R2 values of 0.9986–0.9996. The intraday (n = 6) and interday (n = 6) precisions of the method were less than 2.85% when expressed as relative standard deviations. When the method was applied to analyze rice and dried ginger samples, analyte recoveries ranged from 85.81% to 106.59%. Through sweeping and affinity micelles, stacking preconcentration method was successfully employed to analyze trace amounts of fenoprop and 2,4-dichlorophenoxyacetic acid in rice and dried ginger samples.

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.

Formulating a novel drilling mud using bio-polymers, nanoparticles, and SDS and investigating its rheological behavior, interfacial tension, and formation damage

Formation damage is a well-known problem that occurs during the exploration and production phases of the upstream sector of the oil and gas industry. This study aimed to develop a new drilling mud formulation by utilizing eco-friendly bio-polymers, specifically Carboxymethyl Cellulose (CMC), along with nanostructured materials and a common surfactant, sodium dodecyl sulfate (SDS). The rheological properties of the drilling fluid and the impact of additives on its properties were investigated at the micromodel scale, using a flow rate of 20 mL/h. The polymer concentration and nano clay concentration were set at two levels: 0.5 wt% and 1 wt%, respectively, while the surfactant content was varied at three levels: 0.1 wt%, 0.4 wt%, and 0.8 wt%. The results of the interfacial tension (IFT) analysis demonstrated a significant decrease in the interfacial tension between oil and water with the increasing concentration of SDS. Furthermore, following the API standard, the rheological behavior of the drilling fluid, including the gel strength and thixotropic properties of the mud, was evaluated with respect to temperature changes, as this is crucial for ensuring the inherent rheological stability of the mud. The rheological analysis indicated that the viscosity of the mud formulation with nanoparticles experienced a reduction of up to 10 times with increasing shear rate, while other formulations exhibited a decline of 100 times. Notably, the rheological properties of the Agar specimen improved at 150 °F due to its complete solubility in water, whereas other formulations exhibited a greater drop in viscosity at this temperature. As the temperature increased, drilling fluid containing nanostructured materials exhibited higher viscosity.

A Novel Study on Anionic Surfactant Degradation Potential of Psychrophillic and Psychrotolerant Pseudomonas spp. Identified from Surfactant-contaminated River Water.

The Yamuna River, a tributary of the holy Ganga, is heavily polluted in the Delhi-NCR region, India and has been gaining attention due to the excessive foaming of the river over the past few years. This can be directly or indirectly related to the overuse of surfactants and the discharge of untreated domestic and textile wastewater into the river. To determine the surfactant load and investigate potential surfactant-degrading bacteria in the region, 96 water samples from four sites in the Okhla Barrage stretch of the river were collected and analysed. The results showed that the selected sites have surfactant concentrations more than the permissible limit (1.00 mgL-1). Also, at most of the sites, the concentration crossed the desirable limit of BIS (0.2 mgL-1) during the period of analysis. The concentration of anionic surfactant reported in the region was found in the range of 0.29 mgL-1 and 2.83 mgL-1. A total of 38 different bacteria were isolated using selective media from the same water samples, out of which 7 bacterial isolates were screened for sodium dodecyl sulphate (SDS) tolerance activity. Based on 16S rRNA gene sequencing, 2 species, namely Pseudomonas koreensis YRW-02 and Pseudomonas songnenensis YRW-05 have been identified and their degradation potential was assessed at different SDS concentrations. The results showed that our strains YRW-02 and YRW-05 degraded 78.29 and 69.24% of SDS respectively. Growth optimization was also performed at different substrate concentrations, pH, and temperature to investigate optimum degradation conditions. This study plays a significant role in assessing the surfactant load and also gives a promising background for future use in in-situ bioremediation experiments.

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.

Toxic effects of sodium dodecyl sulfate on planarian Dugesia japonica.

Sodium dodecyl sulfate (SDS) is an anionic surfactant, which is widely used in various fields in human life. However, SDS discharged into the water environment has a certain impact on aquatic organisms. In this study, planarian Dugesia japonica (D. japonica) was used to identify the toxic effects of SDS. A series of SDS solutions with different concentrations were used to treat planarians for the acute toxicity test , and the results showed that the semi-lethal concentration (LC50) of SDS to D. japonica at 24 h, 48 h, 72 h, and 96 h were 4.29 mg/L, 3.76 mg/L, 3.45 mg/L, and 3.20 mg/L respectively. After the planarians were exposed to 0.5 mg/L and 1.0 mg/L SDS solutions for 1, 3, and 5 days, the activities of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) content were measured to detect the oxidative stress and lipid peroxidation in planarians. Random amplified polymorphic DNA (RAPD) analysis was performed to detect the genotoxicity caused by SDS to planarians. The results showed that the activities of SOD, CAT, and MDA content increased after the treatment, indicating that SDS induced oxidative stress in planarians. RAPD analysis showed that the genomic template stability (GTS) values of planarians treated by 0.5 mg/L and 1.0 mg/L SDS for 1, 3, and 5 days were 67.86%, 64.29%, 58.93%, and 64.29%, 60.71%, 48.21%, respectively. GTS values decreased with the increasing of SDS concentration and exposure time, indicating that SDS had genotoxicity to planarians in a time and dose-related manner. Fluorescent quantitative PCR (qPCR) was used to investigate the effects of SDS on gene expression of planarians. After the planarians were exposed to 1.0 mg/L SDS solution for 1, 3, and 5 days, the expression of caspase3 was upregulated, and that of piwiA, piwiB, PCNA, cyclinB, and RAD51 were downregulated. These results suggested that SDS might induce apoptosis, affect cell proliferation, differentiation, and DNA repair ability of planarian cells and cause toxic effects on planarian D. japonica.

Unraveling the effect of surfactant on the preparation of 40 nm Cu2O nanofluids for enhanced thermal conductivity

The state of the adsorbed surfactant molecules significantly impacts the formation of nanoparticles and their application. In this study, using sodium dodecyl sulfate (SDS) as an anion surfactant, the size and size distribution of Cu2O nanocubes were well regulated through simply altering the introduced concentration of SDS. Moreover, the state of the surfactant on the surface of Cu2O nanocubes was systematically characterized by HRXPS and Ar ion etching. It found that SDS and dehydroascorbic acid are co-adsorbed on the surface of Cu2O nanocubes, and the percentage of SDS is in accord with the concentration of SDS used. Compared to water and refrigerant fluid, the typical 40 nm Cu2O nanofluids displayed an enhanced percentage of 11% and 13% for thermal conductivity and cooling rate, respectively.