Solubilization Experiments Research Articles

Water-soluble organic carbon release from mineral soils and sediments in an irrigated agricultural system

Water interactions with soil and vegetation are greatly altered in agricultural watersheds compared to natural landscapes, which impacts sources and fates of organic carbon (OC). While mineral soil horizons in natural ecosystems primarily act as filters for dissolved organic carbon (DOC) leached from organic surface horizons, tilled soils largely lack an organic horizon and their mineral horizons therefore act as a source for both DOC and sediment to surface waters. Irrigated watersheds highlight this difference, as DOC and total suspended sediment (TSS) concentrations simultaneously increase during the low-discharge irrigation season, suggesting that sediment-associated OC may constitute a significant source of DOC. While water-soluble OC (WSOC) from sediments and soils has been found to be compositionally similar to stream DOC, these contributions remain poorly quantified in agricultural streams. To address this, we conducted abiotic solubilization experiments using sediments (suspended and bed) and soils from an irrigated agricultural watershed in northern California, USA. Sediments (R2 > 0.99) and soils (0.74 < R2 < 0.89) displayed linear solubilization behaviors over the range of concentrations tested. Suspended sediment from the irrigation season exhibited the largest solubilization efficiency (10.9 ± 1.6% TOCsediment solubilized) and potential (1.79 ± 0.26 mg WSOC g−1 dry sediment), followed by suspended sediment from a winter storm, then bed sediment and soils. Successive solubilization experiments increased the total release of WSOC by ∼50%, but most (88–97%) of the solid-phase OC remained insoluble in water. Using these solubilization potential estimates and measured TSS concentrations, we estimated that WSOC from suspended sediment in streams represented 4–7% of the annual DOC export from the watershed. However, field sediment export is much higher than what is represented by suspended sediment in the water column, therefore field-scale contributions from sediments could be much higher than estimated.

Remediation of real soils polluted with pesticides by activated persulfate and surfactant addition

The existence of soils contaminated with organochlorine pesticides represents a serious environmental problem. In this work, a real soil contaminated with hexachlorocyclohexanes (ΣHCH = 373 mg kg−1), persistent organic pollutants included in the Stockholm Convention, was remediated. Surfactants were used to enhance the pollutants solubilization and activated persulfate (PS) oxidation to degrade the pollutants. Solubilization experiments were performed to evaluate the effect of surfactant (sodium dodecyl sulfate (SDS), Emulse-3® (E3) and Tween-80® (T80)), pH, reagents addition order and concentration (Csurfactant = 0–10 g L−1, CNaOH = 0–13.5 g L−1). Surfactants selection was performed attending to their ability to solubilize chlorinated organic compounds (COCs). The use of surfactants improved COCs solubilization, especially at pH > 12; conditions at which HCHs hydrolyze to trichlorobenzenes (TCBs), with higher solubility. The higher the surfactant concentration, the higher the COCs concentration in the emulsion. COCs solubilization of 83 % and 89 % were achieved in three surfactant consecutive cycles at highly alkaline conditions using SDS and E3, respectively (T80 was unstable). The resulting emulsions were treated by PS activated by alkali and intensified by temperature. COCs conversion of 30 % and 96 % were achieved when treating E3 and SDS-emulsions (72 h), respectively, highlighting the suitability of SDS for the integrated process.

Tween 80 assisted washing ciprofloxacin-contaminated soil, and recycled it using active chlorines

Active chlorines (ACs) can selectively oxidize contaminants with benzene rings to recycle surfactants, which greatly facilitates the resource cycle. This paper firstly utilized Tween 80 to assist in ex-situ washing the ciprofloxacin (CI) contaminated soil, including the solubilization experiment, shake washing and soil column washing, all of which showed that 2 g/L of Tween 80 (TW 80) was the most effective in removing CI. Then electrochemically treated the collected soil washing effluent (SWE) at 10 V with an electrolyte of 20 mM NaCl + 10 mM Na2SO4; Pre-experiments screened the range of electrode spacing, pH and temperature, based on which an orthogonal design Table L9 (34) was designed. Visual analysis and ANOVA were performed on the ciprofloxacin removal efficiency and Tween 80 retention efficiency during the orthogonal experiments in 9 groups, and the results showed that CI was usually degraded within 30 min, and 50% of TW 80 was still present at the end of the experiment, and there was no significant effect of all three factors. LC-MS demonstrated that CI was mainly degraded synergistically by ·OH and ACs, and ·OH effectively reduced the biotoxicity of the SWE, so the mixed electrolyte may be more suitable for the electrochemical recycling system of ACs. This paper conducted the washing remediation study of CI-contaminated soil for the first time, and applied the theory of selective oxidation by ACs on benzene ring to treat the SWE, which provides a new treatment idea for antibiotic-contaminated soil.

Biolixiviation of Metals from Computer Printed Circuit Boards by Acidithiobacillus ferrooxidans and Bioremoval of Metals by Mixed Culture Subjected to a Magnetic Field.

Crushed and ground printed circuit board (PCB) samples were characterized to evaluate copper, lead, and aluminum using X-ray fluorescence spectroscopy (XRF) and the morphology was done by scanning electron microscopy (SEM). The XRF characterizations showed 0.12% lead, 3.72% copper, and 12.73% aluminum in the PCBs. The metal solubilization experiments using Acidithiobacillus ferrooxidans indicated higher values of total metal solubilization when the initial pH of the inoculum was adjusted. However, these experiments did not show higher metal solubilization by bioleaching. The sequential bioremoval experiments using mixed culture after bioleaching assays with A. ferrooxidans with initial adjustment of inoculum pH and without applying a magnetic field removed 100% of Al, 27.34% of Cu, and 96.43% of Pb from the lixiviate medium; with magnetic field application, 100% of Al, 83.82% of Cu, and 98.27% of Pb were removed. A similar bioleaching experiment without inoculum pH adjustment and without field application achieved 99.74% removal for Cu and 91.92% for Pb. When the magnetic field was applied, 100% of Cu and 95.76% of Pb were removed. Bioreactors with a magnetic field do not show significantly better removal of any of the metals analyzed.

Phosphorus mobilization and improvement of crop agronomic performances by a new white-rot fungus Ceriporia lacerata HG2011.

Some soil microorganisms can mobilize unavailable phosphorus (P) in soils for plant use and increase P fertilizer efficiency. Thus, an abiotic P solubilization experiment and fungal incubation in solution and soil were conducted to investigate the mobilization of various P compounds by a new white-rot fungus Ceriporia lacerata HG2011. The crop agronomic performances were then evaluated in the winter barley-summer maize-winter wheat rotation field. Ceriporia lacerata HG2011 had a wide P mobilization spectrum and mobilized P by different mechanisms depending on P sources supplied in liquid culture. The chief mechanism employed by this fungus was the production of protons in mobilizing Ca3 (PO4 )2 , low-molecular-weight organic acids and other unknown substances in FePO4 and AlPO4 , phytase (an inducible enzyme in the presence of phytate) in phytate, and phosphatase in lecithin and ribonucleic acid, respectively. As a result of the large fungal biomass, P accumulated in the hypha should also be considered in the assessment of the fungal P mobilization, and not just only soluble inorganic P. As C. lacerata HG2011 colonized on and in the test soil, phosphatase and phytase activities were enhanced but pH decreased in the soil, leading to P mobilization. The application of this fungus mobilized soil P, increased crop P uptake and yields, and consecutively reduced P fertilizer use without yield sacrifices in the multiple crop rotation field. C. lacerata HG2011 showed a new use with respect to mobilizing soil P and reducing P fertilizer input in modern agriculture beyond medical purposes, environmental protection and biofuel production. © 2021 Society of Chemical Industry.

Spectral characteristics of dissolved organic carbon derived from biomass-pyrogenic smoke (SDOC) in the aqueous environment and its solubilization effect on hydrophobic organic pollutants

Dissolved organic carbon derived from biomass-pyrogenic smoke (SDOC) can be transported and deposited with atmospheric aerosols, enter aqueous environments, and possibly alter aqueous chemistry and quality. However, the characteristics of SDOC in aqueous environments and their effects on the fate of hydrophobic organic pollutants are poorly understood. In this study, we found that the emitted SDOC is 7.2∼19.6 wt.% of biochar retained in situ after biomass pyrolysis, and the emitted SDOC is approximately 1–3 orders of magnitude greater than dissolved organic carbon (DOC) released from biochar in a short term, which indicates that SDOC is a more important source of DOC in aqueous environments relative to biochar-released DOC after a biomass burning/pyrolysis event. The characteristics of SDOC in aqueous environments are dominated by the <1000 Da fraction, which accounts for >96 wt.% of bulk SDOC. In comparison with DOC in biochar, natural water, and soil, the S275–295 value of SDOC (0.037–0.053) is significantly greater, further indicating that SDOC has a smaller molecular size. Moreover, fluorescence EEM suggests that a fluorescence component located at the Ex/Em of 205/310 nm and the combinational ranges of fluorescence index (1.28–2.28), humification index (0.07–0.80), and biological index (1.16–1.72) can be used to identify SDOC from DOC in other media. Solubilization experiments indicated that SDOC (20 mg/L) improved the solubility of hydrophobic pollutants (pyrene and triclocarban) by 2–6 folds in aqueous environments, which potentially enhances the mobility of pollutants and enlarges the potential risk region. This study indicates that SDOC may cause a severe harm to aqueous environments in addition to the atmosphere. The results have profound implications for comprehensive assessments of the environmental effects of SDOC while promoting its identification and elucidating its behavior in aqueous environments.

Synthesis, characterization and properties of novel nonionic hydrocarbon/fluorocarbon hybrid surfactants containing a short fluoroalkyl chain

A series of novel nonionic hydrocarbon/fluorocarbon hybrid surfactants (Hm-Fn, where m = 10, 12, 14, 16 and n = 4, 6, respectively) were successfully synthesized using polyethylene glycol, isophorone diisocyanate (IPDI), short chain fluoroalkyl alcohol and alkyl alcohol as starting materials. The preparation process involves the coupling reaction of isocyanate and hydroxyl groups. The surface activity and aggregation behavior of Hm-Fn in aqueous solution were studied by surface tension, steady-state fluorescence and dynamic light scattering (DLS) and transmission electron microscopy (TEM). The influence of the hydrophobic (hydrocarbon or fluorocarbon) chain length on surface activity of such hydrocarbon/fluorocarbon hybrid surfactants was systematically investigated. Micromorphology analysis revealed the presence of different sizes vesicles in H16-F6 and H16-F4 aqueous solution. In addition, the hydrophobic dye solubilization experiments exhibited that H16-F6 with a relatively longer fluorocarbon chain and hydrocarbon chain possessed more outstanding solubilization of model dye (Sudan I) compared with other Hm-Fn and conventional hydrocarbon surfactants. The molar solubilization power of H16-F6 could reach 0.0537. The above results demonstrated that these nonionic hydrocarbon/fluorocarbon hybrid surfactants might possess potential application prospects for hydrophobic dyes solubilization.

Solubilization of fullerene in polyoxyethylene tetradecyl ether type nonionic surfactants

Fullerene is insoluble in water owing to its bulky spherical structure composed of 60 carbons. Herein, polyoxyethylene tetradecyl ether-type nonionic surfactants with a varying number of oxyethylene groups, i.e., C14En (n = 5, 6, and 7), were used to solubilize fullerene. In addition, a solubilization experiment was conducted using the aromatic compound naphthalene as a reference substance. Fullerene tended to solubilize in aqueous solutions of surfactants bearing long EO chains. Particularly, the maximum solubilization quantities of fullerene increased with an increasing number of EO chains in 100 mmol L−1 C14En solutions ranging from 43.2 (n = 5) to 76.9 (n = 6) and 115.6 μmol L−1 (n = 7). In contrast, naphthalene was well solubilized in surfactants bearing relatively shorter EO chains and showing an opposite tendency to that of fullerene. The Gibbs free energy change (ΔG0) per EO chain for the solubilization of fullerene and naphthalene was –1.51 and +0.27 kJ mol−1, respectively. These results indicated that the extension of EO chain of nonionic surfactants is thermodynamically advantageous for achieving the solubilization of fullerene. In addition, the solubilization site of fullerene in the micelles was studied by analyzing its absorption spectrum in four types of solvents with different polarities. The peak wavelength of fullerene suggested that the surrounding environment possessed an intermediate polarity between water and organic solvents. According to the 1H NMR measurements, the waveform of the EO groups in the NMR spectra significantly split upon solubilization of fullerene. From these results, it was concluded that fullerene located in the vicinity of the EO chains (shell area) in the micelles.

Formation of fatty acid methyl ester based microemulsion and removal mechanism of PAHs from contaminated soils

Microemulsion (ME) is considered as a stable solution for adsorbing organic matters. Aiming to remediate PAH contaminated soils from industrial sites in Shijiazhuang (Soil CPS) and Beijing (Soil CSG) in China, novel MEs were designed with different ratios of mixed surfactants (Surf, TX-100+Tween 80), n-butanol and fatty acid methyl esters (FAMEs). Particle size, transmittance, surface intension, Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy of the MEs were analyzed. PAH removals by solubilization experiments were studied and regeneration of waste ME was evaluated. Results showed the novel MEs were obtained with particle sizes in a range of 18.53–122.77 nm. The lowest surface intension of MEs was 26.53 mN/m, which was prone to PAHs transferring to MEs. ‒OH (3350 cm-1), ‒C˭C (1740 cm-1) and ‒C‒O (1072 cm-1) functioned in forming MEs. Additionally, ‒OH, C‒H, ‒C˭C, ‒C‒O were considered as active binding sites when remediating PAH soils. PAH removals in soils CPS and CSG were up to 90.1% and 89.7% with surfactants and co-surfactant (Surf:Co-s), (Surf:Co-s) and FAME, soil and MEs (w:v) at ratios of 1:1, 8:2 and 1:4, respectively. About 85.6% of FAME and 41.9% of TX-100 in waste ME were recovered for recycle purpose.

Interaction of inhalable volatile organic compounds and pulmonary surfactant: Potential hazards of VOCs exposure to lung.

Exposure of volatile organic compounds (VOCs) towards lung leads to pulmonary dysfunctions and various lung diseases. However, the interaction of VOCs with pulmonary surfactant (PS) that directly comes into contact with inhaled VOCs is unknown. Here, simulated PS extracted from porcine lungs (EPS) was used to study the interaction with BTEX (i.e., benzene, toluene, ethylbenzene, and p-xylene) as representatives of VOCs. Surface pressure-area (π-A) isotherms showed that in the presence of individual BTEX, EPS monolayer's phase conversion from gas to liquid expanded phase was dramatically influenced and its collapse pressure decreased greatly compared to those of EPS alone, which was attributed to the alteration of EPS monolayer's microstructure characterized by atomic force microscopy and Brewster angle microscopy. Solubilization experiments manifested that EPS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) exhibited obvious solubilization effects on individual BTEX. The solubilization capacity followed an order: EPS > DPPC > BSA, which was positively correlated with hydrophobicity of individual BTEX. Synergistic solubilization test unveiled that the mixed phospholipid components were largely responsible for the solubilization capacity of EPS. These findings indicate that VOCs exposure may induce potential pulmonary health risk due to the alteration of gas-liquid interfacial properties of PS.

Interaction of nano carbon particles and anthracene with pulmonary surfactant: The potential hazards of inhaled nanoparticles

Understanding the alteration of the air-liquid interfacial properties of pulmonary surfactant (PS) in the presence of nanoparticles (NPs) and polycyclic aromatic hydrocarbons (PAHs) is particularly important for pulmonary risk assessment. Here, we investigated the interaction of natural PS (extracted from pig's lungs) with nano carbon particles (NCPs) and anthracene as a representative PAH. Our results showed that PS exhibited a significant solubilization effect on anthracene. Solubilization experiment for the substructures of PS demonstrated that the mixed phospholipid components of PS played the primary role in the solubilization of PS for anthracene. Adsorption experiment indicated that in the mixed system of PS, NCPs, and anthracene, PS can inhibit the adsorption of anthracene on NCPs due to the solubilization, agglomeration, and competitive adsorption. In addition, the surface tension, phase behavior, and foaming ability of PS were obviously altered in the presence of NCPs. These findings indicate that the solubilization effect of PS on anthracene, the inhibitive effect of PS for the adsorption of anthracene on NCPs, and the alternation of air-liquid interfacial properties of PS containing NCPs may increase the pulmonary risk in the exposure of atmospheric environment containing both PAHs and NCPs.

Lectin-binding and dissociation/reconstitution studies on the trichocysts of the dinoflagellate Oxyrrhis marina.

Trichocyst-enriched fractions were isolated from the dinoflagellate Oxyrrhis marina and subjected to protein staining and lectin-binding studies, to dissociation experiments using heat, and to solubilization/reconstitution experiments using 6M guanidine hydrochloride. The trichocysts could be stained by Alcian Blue and became labeled by the lectin Concanavalin A, but not by wheat germ agglutinin. The trichocysts did not dissociate when the fractions were heated for 5min at 40 or 50°C. Heating at 60°C resulted in the dissociation of trichocysts into irregular filamentous structures. These filaments were still present when the fractions were incubated for 5min at temperatures of 70 and 80°C. Reassembly was not achieved by subsequent cooling steps. The disintegration of trichocysts was also achieved in 6M guanidine hydrochloride, and reassembly into filamentous structures, similar to those obtained by heat, occurred after dialysis against distilled water. Electron microscopy revealed that the filaments created either by heat or using guanidine hydrochloride by far did not resemble native trichocysts. They were much thinner (5-7nm in width), missed the characteristic striation of electron-dense and -transparent lines along the longitudinal axes, and showed much more bending. Furthermore, they tend to merge to thicker shapeless structures and blob-like aggregates. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that fractions enriched either in trichocysts or in reconstituted filamentous structures obtained in the guanidine hydrochloride solubilization experiments were dominated by proteins with relative molecular weights in the range of approximately 15 to 29kDa. Minor amounts of larger proteins were also detected. Tryptic in gel digestion followed by mass spectrometry confirmed the presence of almost the same set of proteins within the both, the trichocyst-enriched fractions, and the fractions of filaments reconstituted thereafter. These proteins were previously proposed to represent the matrix polypeptides of the trichocysts of Oxyrrhis marina (Rhiel et al., Protoplasma 255: 217-230, 2018).

Solubilization of azo-dye-modified isatin derivative by amphiphilic carboxyresorcinarenes: The effect of macrocycle structure on the supramolecular association

Here we present the consecutive study of colloid systems formed by novel isatin derivative as compound with high pharmacological potential and series of carboxyresorcinarenes. The azo-modified isatin derivative bearing ammonium moiety (I-3) was synthesized and its antimicrobial activity was investigated. To increase its solubility the solubilization experiment using amphiphilic carboxyresorcinarenes, characterized by low hemolytic activity, was carried out. The I-3 – macrocycles systems were studied by NMR, UV–vis, DLS and TEM. The FT PGSE and 2D NOESY NMR methods demonstrated, that solubilization of I-3 is caused by the incorporation of its molecules in the hydrophobic part of the macrocycles associates. Herewith the loading efficiency of I-3 into the macrocycles associates was reached of 20–30% due to the change of the volume of hydrophobic part of associates by varying the length and structure of hydrophobic substituents of macrocyclic amphiphiles.

Solubilization ability of N,N-dimethyl-N-alkyladamantylammonium bromide

Adamantane is difficult to dissolve in water owing to its bulky steric hydrocarbon structure. We designed a novel amphiphilic molecule by introducing an alkyl chain and a cation group into an adamantyl group. N,N-dimethyl-N-alkyladamantylammonium bromide (CnAdAB; n is the alkyl chain length, where n=10, 12, and 14) dissolves easily in water by forming micelles above the critical micelle concentration. Aggregates of this surfactant series form small nonspherical micelles several nanometers in size with relative small aggregation number; 53 (n=10), 59 (n=12), and 63 (n=14) at the typical concentration. Small-angle X-ray scattering measurement showed that the micellar structure of C12AdAB was changed slightly by solubilization of naphthalene and stearic acid. Moreover, the solubilization ability of the aggregates was studied using naphthalene and long-alkyl-chain fatty acids (myristic, palmitic, and stearic acids). The same solubilization experiments were performed using typical cationic surfactants (dodecyltrimethylammonium bromide and a gemini surfactant) for comparison. The molar solubilization ratios indicate that the CnAdAB series can solubilize the aromatic compound naphthalene as well as the other surfactants, whereas they can barely solubilize the long-alkyl-chain fatty acids. The solubilization stability can be analyzed by estimating the Gibbs free energy change (ΔG0) for the transfer of solubilizate molecules to the aggregate phase. The gemini surfactant system showed the largest negative value of ΔG0 for both naphthalene and the fatty acids. On the other hand, solubilization of fatty acids into CnAdAB micelles was not advantageous energetically. These results indicate that the solubilization ability of CnAdAB surfactants is not generally suitable for solubilization of long-alkyl-chain fatty acids owing to the smallness of the micelles.

Solubilization of polycyclic aromatic hydrocarbons (PAHs) with phenol in coking wastewater treatment system: Interaction and engineering significance

Polycyclic aromatic hydrocarbons (PAHs) are accumulated in the sludge collected from the coking wastewater treatment. Phenol with its efficient degradation observed in biological treatment promotes the solubility of PAHs in aqueous phase. The interaction mechanism of phenol and PAHs in aqueous and sludge phases was systematically studied in two full-scale engineering projects composed of anaerobic-oxic-oxic (A-O1-O2) and anaerobic-oxic-hydrolytic-oxic (A-O1-H-O2) sequences. The results showed that reasonable use of phenol facilitates solubilization of PAHs alleviating their emission problems. The ΔPAHs/Δphenol mass ratio in the sludge phase of A-O1-H-O2 system (146.3) exceeded that in A-O1-O2 one (63.80), exhibiting a good solubilization effect on PAHs with their more efficient degradation in the former. The full-scale observations were verified in laboratory solubilization experiments using phenanthrene (Phen), pyrene (Pyr) and benzo[a]pyrene (Bap) as the models of 3-, 4- and 5-ring PAHs, respectively. The binding energies of [phenol−PAHs] complexes were calculated using computational density functional theory showing consistency with the experimentally observed phenol-facilitated solubilization efficiencies in the row of Phen>Pyr>Bap. The results showed the fate and distribution of PAHs in coking wastewater treatment affected by the presence of phenol serving as a cost effective reagent for enhanced solubilization of PAHs from the coking wastewater sludge.

Fractionation of Styrene and Maleic Acid Copolymers: The “Holy Grail” of Membrane Solubilization

Styrene-and-maleic acid copolymers (SMA) are gaining interest in membrane protein research due to their ability of solubilizing lipid membranes into nanodiscs. Using different commercially available SMA preparations it was found that the average length and hydrophobicity are important parameters in determining solubilization efficiency and properties of the resulting nanodiscs. However, our understanding of the underlying SMA-lipid interactions is hampered by the fact that SMA preparations are very polydisperse. Here, we fractionated widely used SMA preparations (Mw ∼10kD) into 4 fractions of polymers with different average length, based on their solubility in hexane/acetone mixtures and we investigated their interaction with lipid self-assemblies. We found that fractions with shorter SMA polymers solubilize phosphatidylcholine vesicles more rapidly than fractions with longer polymers. On the other hand, nanodiscs bounded by long SMA polymers were notably more stable than those bounded by shorter polymers, as indicated by a better retention of the native lipid thermotropic properties and by slower exchange rates between lipids in nanodiscs. When the SMA fractions were mixed with E.coli membranes, a somewhat different behavior was observed, probably due to the complexity of these membranes. Here the fractions with relatively long polymers were found to be most efficient in solubilizing the tetrameric KcsA channel. Competitive solubilization experiments showed that short polymers even hinder solubilization by long polymers. In conclusion, we here present a simple method to purify SMA fractions from commercial SMA in order to improve solubilization of biomembranes as well as stability of the resulting nanodiscs.

Aggregation response of triglyceride hydrolysis products in cyclohexane and triolein.

Here, we examine the aggregation response of a series of triglyceride-based biosurfactants in cyclohexane and triglyceride solvents via all-atom molecular dynamics simulations and supporting experiments. The surfactant aggregation follows in all systems, with only minor deviations, a multiple equilibrium, i.e. open association, model. Monoglyceride aggregation in cyclohexane exhibits a critical micellization concentration, cmc, showing a cmc can exist even in a system following open association. However, the cmc is associated with a change in balance with oligomeric and larger aggregates in the solution, not an onset of aggregate formation. It is demonstrated that reverse micelles can form in the absence of water stabilized by intersurfactant hydrogen bonds alone, and that the polarity and hydrogen bonding capability of triolein systematically reduces surfactant aggregation in comparison to cyclohexane. A comparison between CHARMM27 and CHARMM36 simulation models reveals that while trends are preserved, the models differ in quantitative prediction. Finally, consolidation of the general aggregation response trends predicted by the modelling are obtained via 7,7,8,8-tetracyanoquinodimethane dye (TCNQ) solubilization experiments on the corresponding model plant oil systems. The findings provide guidelines for predicting and controlling surfactant aggregation response in organic solvents via tuning the solvent polarity and hydrogen bonding ability, and a critical assessment of simulation and aggregation models for surfactant systems in organic solvents.

Eco-friendly biosurfactant saponin for the solubilization of cationic and anionic dyes in aqueous system

This study demonstrates the solubilization of two different dyes, methylene blue and eosin yellow by one biosurfactant, saponin. This eco-friendly natural surfactant was extracted from the pericarps of sapindus mukorossi (reetha) fruit. The physicochemical properties of extracted aqueous saponin were characterized using various techniques, such as, FTIR spectroscopy, UV-spectroscopy, MALTI-TOF-MS, optical microscope, particle size analyzer, and surface tension measurement. The size of saponin micelle was observed in the range of 10–11.5 nm, whereas, the agglomerates of saponin having higher size, ranging from 132 to 235 nm, 390–990 nm, and 5155–8520 nm were also present in the aqueous system. The batch solubilization experiments were performed and the solubilization capacity of dyes in saponin micelles was measured in terms of solubilization power. The solubilization of dyes was the combined effect of micellar solubilization by saponin micelle, as well as sorption of dyes by saponin agglomerates. The partition coefficient of both the dyes between the aqueous solution and saponin micelles were calculated. The Gibbs free energy of solubilization was evaluated for both the dyes and found that the solubilization process was thermodynamically feasible. The outcome of this study explores the potential of saponin in various surfactant based processes such as, MEUF, SER, and CPE etc.

"Staying Out" Rather than "Cracking In": Asymmetric Membrane Insertion of 12:0 Lysophosphocholine.

Interactions between detergents and model membranes are well described by the three-stage model: saturation and solubilization boundaries divide bilayer-only, bilayer-micelle coexistence, and micelle-only ranges. An underlying assumption of the model is the equilibration of detergent between the two membrane leaflets. However, many detergents partition asymmetrically at room temperature due to slow flip-flop, such as sodium dodecyl sulfate (SDS) and lysolipids. In this work, we use isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) to investigate the solubilization of unilamellar POPC vesicles by 12:0 lysophosphocholine (12:0 LPC). Flip-flop of 12:0 LPC occurs beyond the time scale of our experiments, which establish a characteristic nonequilibrated state with asymmetric distribution: 12:0 LPC partitions primarily into the outer leaflet. Increasing asymmetry stress in the membrane does not lead to membrane failure, i.e., "cracking in" as seen for alkyl maltosides and other surfactants; instead, it reduces further membrane insertion which leads to the "staying out" of 12:0 LPC in solution. At above the critical micellar concentration of 12:0 LPC in the presence of the membrane, micelles persist and accommodate further LPC but take up lipid from vesicles only very slowly. Ultimately, solubilization proceeds via the micellar mechanism (Kragh-Hansen et al., 1995). With a combination of demicellization and solubilization experiments, we quantify the molar ratio partition coefficient (0.6 ± 0.1 mM-1) and enthalpy of partitioning (6.1 ± 0.3 kJ·mol-1) and estimate the maximum detergent/lipid ratio reached in the outer leaflet (<0.13). Despite the inapplicability of the three-stage model to 12:0 LPC at room temperature, we are able to extract quantitative information from ITC solubilization experiments and DLS that are important for the understanding of asymmetry-dependent processes such as endocytosis and the gating of mechanosensitive channels in vitro.

Structure and molecular dynamics of sodium dodecylsulfate micelles modified with hydrophilic short-chain imidazolium salts in aqueous solution

This study uses pyrene solubilization and NMR experiments to investigate the effects of two hydrophilic short-chain ionic liquids (ILs), 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) on the micellization of sodium dodecylsulfate (SDS) in the aqueous phase. The results of the pyrene solubilization experiments indicate that the added short-chain ILs not only promote the micellization of SDS but also modify micelle properties. For NMR studies, the present study focuses on (1) the compositions and spatial arrangements of component molecules and (2) the molecular dynamics of DS− in the Rmim-modified SDS micelle. Using pulsed field gradient (PFG) NMR measurements, the composition of the Rmim-modified SDS micelle was calculated by the diffusion data and was found to be correlated with the [SDS]. Two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY) experiments confirm that the 1-alkyl-3-methylimidazolium cation (Rmim+) is located inside the Rmim-modified SDS micelle. Corresponding to the microstructure of the Rmim-modified SDS micelle, in terms of 1H T1 relaxation, the fast motion of SDS α-CH2 and β-CH2 segments are markedly restricted by the attached Rmim+ to the sulfate group of DS−, whereas the central carbons and the terminal CH3 group of DS− are only slightly affected. The chemical shift analysis indicates that the surface of the Rmim-modified SDS micelle is dehydrated by the absorbed Rmim+ and becomes more hydrophobic than that of the pure SDS micelle. Insertion of Rmim+ into the Rmim-modified SDS micelle appears to be driven through the hydrophobic interaction, and it is shown to combine with SDS molecules to constitute the hydrophobic part of the Rmim-modified SDS micelle.