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Terahertz spectroscopy has unique advantages in the study of biological molecules in aqueous solutions. However, water has a strong absorption capability in the terahertz region. Reducing the amount of liquid could decrease interference with the terahertz wave, which may, however, affect the measurement accuracy. Therefore, it is particularly important to balance the amount and water content of liquid samples. In this work, a terahertz metamaterial sensor based on metallic strips is designed, fabricated, and used to detect reverse micelles. An aqueous confinement environment in reverse micelles can improve the signal-to-noise ratio of the terahertz response. Due to "water pool" trapped in reverse micelles, the DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) solution and DOPC emulsion can successfully be identified in intensity by terahertz spectroscopy. Combined with the metamaterial sensor, an obvious frequency shift of 30 GHz can be achieved to distinguish the DOPC emulsion (5%) from the DOPC solution. This approach may provide a potential way for improving the sensitivity of detecting trace elements in a buffer solution, thus offering a valuable toolkit toward bioanalytical applications. [ABSTRACT FROM AUTHOR]

The use of reverse micelles as nanoscale hydrophilic voids of microemulsions in the manufacture of ferrites has been recognized since the 1960s, but there has been very little attention on the structural and magnetic properties with respect to surfactant concentration. This paper investigates the influence of surfactant sodium dodecyl sulphate (SDS) concentrations on cobalt ferrite (CoFe2O4) nanoparticles prepared by reverse micelles at annealing temperatures 250°C and 500°C. Samples with varied cobalt to SDS ratios (Co: SDS = 1: 0.33, 1: 0.5, 1: 0.66) were subjected to XRD, TGA, TEM, FTIR and VSM Studies. All the samples exhibited single-phase spinel structures with crystalline diameters ranging from 10 to 18 nm. As the SDS concentration increased the crystallite size decreased. The TEM images showed the particle size in the range of 7.6 -17.7 nm. VSM investigations show the ferromagnetic behavior of the sample. The observed increase in coercivity with respect to annealing temperature for the same concentration reflects the single-domain nature of the nano particles. This underscores the crucial role of annealing conditions in customizing cobalt ferrite nanoparticles as a suitable application in longitudinal magnetic recording media. [ABSTRACT FROM AUTHOR]

Stabilization of charged particles in nonpolar media is one of the most complicated problems in modern colloid chemistry. The attribution to colloid chemistry is absolutely justified in this case: in nonpolar media, charged particles have, as a rule, a supramolecular nature. Low dielectric permittivity of a medium makes the existence of ions in the classical interpretation energetically disadvantageous. The key condition for the presence of charged particles in nonpolar media is their steric stabilization, which requires some revision of the classical concepts of the structure of the electrical double layer, primarily, its diffuse part. Detailed analyzing the structure of the electrical double layer in nonpolar media is of importance because of the high practical significance of electrokinetic phenomena in such systems. This review considers the main models for steric stabilization of charged particles with surfactants in dispersion media having dielectric permittivities lower than 5. The main attention is focused on not only the concentrations corresponding to the formation of reverse micelles, but also on the concentrations below the critical micelle concentration. In addition, nontypical examples of electrokinetic phenomena in organosols are considered. [ABSTRACT FROM AUTHOR]

Advancing the study of membrane associated proteins and their interactions is dependent on accurate membrane models. While a variety of membrane models for high‐resolution membrane protein study exist, most do not reflect the diversity of lipids found within biological membranes. In this work, we have developed native reverse micelles (nRMs) formulated with lipids from multiple eukaryotic sources, which encapsulate proteins and enable them to interact as they would with a biological membrane. Diverse formulations of nRMs using soy lecithin, porcine brain lipids, or bovine heart lipids combined with n‐dodecylphosphocholine were developed and characterized by dynamic light scattering and 31P‐NMR. To optimize protein encapsulation, ubiquitin was used as a standard and protein NMR verified minimal changes to its structure. Peripheral membrane proteins, which bind reversibly to membranes, were encapsulated and include glutathione peroxidase 4 (GPx4), phosphatidylethanolamine‐binding protein 1 (PEBP1), and fatty acid binding protein 4 (FABP4). All three proteins showed anticipated interactions with the membrane‐like inner surface of the nRMs as assessed by protein NMR. The nRM formulations developed here allow for efficient, high‐resolution study of membrane interacting proteins up to and beyond ~21 kDa, in a more biologically relevant context compared to other non‐native membrane models. The approach outlined here may be applied to a wide range of lipid extracts, allowing study of a variety of membrane associated proteins in their specific biological context. [ABSTRACT FROM AUTHOR]

It has been proposed that lipid oxidation reactions in edible oils primarily occur in reverse micelles (RM) of amphiphilic components. While the prooxidative effect of RM has been demonstrated, the mechanism involved is not fully understood. Both reductions and enhancements in the antioxidant efficacy (AE) of α-tocopherol and Trolox have been observed in different studies when phosphatidylcholine (PC) was added and PC RM were formed. However, most of these investigations employed lipid systems consisting of stripped vegetable oil diluted in saturated medium-chain triacylglycerols (MCT) and utilized antioxidant concentrations well below those found in edible oils. These two specific factors were investigated in the present study. The effect of RM of purified egg yolk PC on the AE of 1.16 mmol kg−1 α-tocopherol or Trolox in stripped sunflower oil (SSO) was studied by the Rancimat (100 °C) and oven (50 °C) tests. Increasing PC concentrations (50–1000 ppm) had no significant impact on α-tocopherol, but substantial reductions in AE were observed for Trolox. This phenomenon may be attributed to the partitioning of Trolox into the pre-existing PC micelles, suggesting that primary oxidation reactions occurred in the continuous lipid phase. In addition, the effectiveness of both antioxidants decreased significantly in the presence of PC when a low antioxidant concentration (0.06 mmol kg−1) was assayed in SSO:MCT (1:3, w/w). [ABSTRACT FROM AUTHOR]

Terahertz spectroscopy has unique advantages in the study of biological molecules in aqueous solutions. However, water has a strong absorption capability in the terahertz region. Reducing the amount of liquid could decrease interference with the terahertz wave, which may, however, affect the measurement accuracy. Therefore, it is particularly important to balance the amount and water content of liquid samples. In this work, a terahertz metamaterial sensor based on metallic strips is designed, fabricated, and used to detect reverse micelles. An aqueous confinement environment in reverse micelles can improve the signal-to-noise ratio of the terahertz response. Due to “water pool” trapped in reverse micelles, the DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) solution and DOPC emulsion can successfully be identified in intensity by terahertz spectroscopy. Combined with the metamaterial sensor, an obvious frequency shift of 30 GHz can be achieved to distinguish the DOPC emulsion (5%) from the DOPC solution. This approach may provide a potential way for improving the sensitivity of detecting trace elements in a buffer solution, thus offering a valuable toolkit toward bioanalytical applications.

The underlying biophysical principle governing the cytotoxicity of the oligomeric aggregates of β‐amyloid (Aβ) peptides has long been an enigma. Here we show that the size of Aβ40 oligomers can be actively controlled by incubating the peptides in reverse micelles. Our approach allowed for the first time a detailed comparison of the structures and dynamics of two Aβ40 oligomers of different sizes, viz., 10 and 23 nm, by solid‐state NMR. From the chemical shift data, we infer that the conformation and/or the chemical environments of the residues from K16 to K28 are different between the 10‐nm and 23‐nm oligomers. We find that the 10‐nm oligomers are more cytotoxic, and the molecular motion of the sidechain of its charged residue K16 is more dynamic. Interestingly, the residue A21 exhibits unusually high structural rigidity. Our data raise an interesting possibility that the cytotoxicity of Aβ40 oligomers could also be correlated to the motional dynamics of the sidechains. [ABSTRACT FROM AUTHOR]

The aim of this study was to demonstrate the utility of time-resolved fluorescence spectroscopy in the detection of subtle changes in the local microenvironment of a tryptophan chromophore in a confined and crowded medium of AOT reverse micelles, which mimic biological membranes and cell compartmentalization. For this purpose, fluorescence properties of L-tryptophan and several newly synthesized tryptophan-containing peptides in buffer and in an AOT reverse micelle medium were determined. It was shown that insertion of tryptophan and its short di- and tripeptides inside micelles led to evident changes in both the steady-state emission spectra and in fluorescence decay kinetics. The observed differences in spectral characteristics, such as a blue shift in the emission maxima, changes in the average fluorescence lifetime, and the appearance of environmental-dependent fluorescent species, showed the utility of time-resolved fluorescence spectroscopy as a sensitive tool for detecting subtle conformational modifications in tryptophan and its peptides induced by changes in polarity, viscosity, and specific interactions between chromophores and water molecules/polar groups/ions that occur inside reverse micelles. [ABSTRACT FROM AUTHOR]

[Display omitted] Soybean phospholipid was used as an amphiphilic material to form reverse micelles (RMs) in medium glycerol monolinoleate (Maisine) with Exenatide (EXT.) encapsulated in the polar core formed by the hydrophilic part of phospholipid. Cremopher RH40 and caprylocaproyl macrogol-8 glycerides EP/caprylocaproyl polyoxyl-8 glycerides NF (Labrasol) were added as surfactants to prepare reverse micelles-self emulsifying drug delivery system (RMs-SEDDS). On this basis, oil in water (O/W) emulsion was further prepared. By adding DOTAP, the surface of the emulsion was positively charged. Finally, hyaluronic acid wrapping in the outermost layer by electrostatic adsorption and reverse micelles-O/W-sodium hyaluronate (RMs-O/W-HA) nanoparticles containing Exenatide were prepared. RMs-SEDDS was spherical with an average particle size of 213.6 nm and RMs-O/W-HA was double-layered spherical nanoparticle with an average particle size of 309.2 nm. HA coating enhanced the adhesion of nanoparticles (NPs), and RMs-O/W-HA increased cellular uptake through CD44-mediated endocytosis. Pharmacodynamics results showed that RMs-SEDDS and RMs-O/W-HA could reduce blood glucose in type 2 diabetic rats, protect pancreatic β cells to a certain extent, and relieve insulin resistance and hyperlipemia complications with good safety. [ABSTRACT FROM AUTHOR]

This study shows the possibility of using gallic acid (GA) and/or methyl gallate (MG) accompanied by phosphatidylcholine (PC) instead of tert-butylhydoquinone (TBHQ) for frying purposes. The antioxidants and PC were added in the concentrations of 1.2 mM and 500–2000 mg/kg, respectively. Oxidative stability index (OSI) and the kinetics of change in conjugated dienes (LCD), carbonyls (LCO), and acid value (AV) were used to assess the antioxidative treatments. GA alone and GA/MG (50:50) plus PC at 2000 mg/kg yielded the same OSI as that of TBHQ (18.4 h). The latter was of the highest frying performance in preventing the formation of LCD (rn = 0.0517/h and tT = 10.6 h vs. rn = 0.0976/h and tT = 4.5 h for TBHQ), LCO (rn = 0.0411/h and tT = 12.7 h vs. rn = 0.15/h and tT = 4.3 h for TBHQ), and hydrolytic products (AVm = 37.8 vs. 24.0 for TBHQ); rn: normalized the maximum rate of LCD/LCO accumulation; tT: the time at which the rate of LCD/LCO accumulation is maximized; AVm: quantitative measure of hydrolytic stability. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate photocatalytic hydrogen generation and the role of sacrificial agents using multi‐functional DyCrO3 nanoparticles by virtue of built‐in electric field (BIEF) which helps in increasing charge separation efficiency. DyCrO3 nanoparticles synthesized by the low‐cost reverse micellar approach showed high surface area (17.9 m2/g) and band‐gap (2.01 eV) in visible region. Sacrificial agent assisted photocatalytic H2 production of DyCrO3 nanoparticles exhibited higher selectivity towards Na2S/Na2SO3 by producing H2 evolution of 347 μmolh-1gcat-1 ${mol\ {h}^{-1}{g}_{cat}^{-1}{\rm \ }}$ and apparent quantum yield of 6.8% than ethylene glycol and triethanolamine, respectively. The oxygen defects (observed in X‐ray photoelectron spectroscopic studies) and BIEF both synergistically helped in enhancing photocatalytic activity. Moreover, the multifunctional competence of DyCrO3 nanoparticles was observed in electrocatalytic water splitting. DyCrO3 nanoparticles found to be active HER and OER electrocatalyst with low overpotential and great durability. [ABSTRACT FROM AUTHOR]

Laccase is a versatile enzyme widely used for the oxidation of environmental contaminants and exhibits great potential in many others applications; however, it undergoes photo-degradation when irradiated with UVB light. The photo-stability of this biomolecule can be improved by immobilization in different encapsulation media and reverse micelles have been employed with this purpose. The laccase activity using syringaldazine as substrate has been studied in the absence and in the presence of reverse micelles of 0.15 M of sodium 1,4-bis (2-ethylhexyl) sulfosuccinate (AOT) in isooctane at W0 ([H2O]/[AOT]) = 30, before and after irradiation of the enzyme with UVB light. The kinetic parameters, i.e., Michaelis–Menten constant (KM), catalytic constant (kCAT), and catalytic efficiency (kCAT/KM), were determined by spectroscopic measurements in the micellar system and in homogeneous aqueous medium. The distribution of the substrate in two pseudo-phases (micelle and organic solvent) was taking into account in the kinetic parameters' determinations. The results obtained indicate that the nano-aggregate system confers a solubilization media in the water core of the micelle, both for the enzyme and the substrate, in which the catalytic function of the enzyme is preserved. On the other hand, in homogeneous aqueous medium kCAT/KM value, it is reduced by ~50% after UVB irradiation of the enzyme, while in micellar medium, less than 10% of the activity was affected. This mean that the enzyme achieves a considerably photo-protection when it is irradiated with UVB light in reverse micelles as compared with the homogeneous aqueous medium. This phenomenon can be mainly due to the confinement of the biomolecule inside the micelle. Physical properties of the nano-environment could affect photochemical reactions. [ABSTRACT FROM AUTHOR]

An alternative to the conventional dilution method (CDM) to characterize reverse micelles (RMs) containing cosurfactant is presented. This method can be performed following two routes: (i) adding oil to destabilize a RM and applying temperature changes to stabilize it again and (ii) applying temperature changes to destabilize the RMs and adding cosurfactant to stabilize it again. The destabilization-stabilization cycles in the proposed method can be related to the destabilization-stabilization cycles in CDM. Thus, by using the same theoretical fundaments, it is possible to obtain the same parameters that are obtained in CDM. RMs formed by the CTABþpentanol/hexane/water system was used to compare both methods. The amount of pentanol at the water/oil interface and in the oleic phase, as well as the thermodynamic parameters of the transfer process of pentanol molecules from the oleic phase to the oil/water interface obtained by both methods were similar. Using temperature changes as stabilizing/destabilizing agents presents some advantages: (i) By replacing oil and cosurfactant by temperature changes, the amount of reactants used in the experiments decreases, which also reduces the final waste; (ii) it is possible to obtain data at any temperature, as long as it falls within the temperature range used (this range is within the temperature range where the RMs are stable), which reduces the number of experiments; (iii) the direction of the temperature changes indicates whether the RMs formation process is endothermic or exothermic. The proposed method is an alternative to characterize RMs containing cosurfactants. [ABSTRACT FROM AUTHOR]

Amphiphilic fluorinated copolymers PEGMAx‐co‐FAy and TEGMAx‐co‐FAy are prepared by activators regenerated by electron transfer atom transfer radical polymerization (ARGET‐ATRP). All polymers present a reversible thermoresponsive lower critical solution temperature‐type behavior, and a cloud point temperature (Tc) in the range of 30–60 °C strictly dependent on the length of the oxyethylene side chain, the content of the hydrophobic counits, and the concentration of the solution. Combined small angle X‐ray scattering (SAXS) and dynamic light scattering measurements are used to study the self‐assembly behavior in water, organic solvents (tetrahydrofuran [THF] and dimethylformamide [DMF]), and a fluorinated solvent (hexafluorobenzene [HFB]). SAXS confirms the formation of compact‐globular single‐chain self‐folded unimer micelles in water below Tc, which generally presents small hydrodynamic diameters (Dh ≤ 8 nm) as a result of the folding of the hydrophobic perfluorohexylethyl acrylate counits. The copolymers are also able to form reverse unimer micelle in HFB. The copolymers are not able to self‐assemble in unimer micelles in THF or DMF solutions, in which they adopt conventional random coil conformations. [ABSTRACT FROM AUTHOR]

It has been proposed that lipid oxidation reactions in edible oils primarily occur in reverse micelles (RM) of amphiphilic components. While the prooxidative effect of RM has been demonstrated, the mechanism involved is not fully understood. Both reductions and enhancements in the antioxidant efficacy (AE) of α-tocopherol and Trolox have been observed in different studies when phosphatidylcholine (PC) was added and PC RM were formed. However, most of these investigations employed lipid systems consisting of stripped vegetable oil diluted in saturated medium-chain triacylglycerols (MCT) and utilized antioxidant concentrations well below those found in edible oils. These two specific factors were investigated in the present study. The effect of RM of purified egg yolk PC on the AE of 1.16 mmol kg−1 α-tocopherol or Trolox in stripped sunflower oil (SSO) was studied by the Rancimat (100 °C) and oven (50 °C) tests. Increasing PC concentrations (50–1000 ppm) had no significant impact on α-tocopherol, but substantial reductions in AE were observed for Trolox. This phenomenon may be attributed to the partitioning of Trolox into the pre-existing PC micelles, suggesting that primary oxidation reactions occurred in the continuous lipid phase. In addition, the effectiveness of both antioxidants decreased significantly in the presence of PC when a low antioxidant concentration (0.06 mmol kg−1) was assayed in SSO:MCT (1:3, w/w).

[Display omitted] An equilibrium state model addressing the aggregation and adsorption of colloidal assemblies in apolar solvents (oils) via monomer exchange is presented. The model is based on the previously reported step-wise aggregation response of fatty acids and monoglycerides in bio-oils, and captures surface crowding via scaled particle theory (SPT). The sensitivity of key observables - mean aggregation number, adsorbed surfactant amount, and free monomer concentration - to model parameters is demonstrated. Fits to molecular modelling based aggregation and adsorption data of oleic acid and monoolein reveal that the model accurately reproduces chemically specific aggregate exponential distributions in both bulk and surface phases, even outside of its parameterization conditions. A biased state model, where the initial bulk aggregation step (dimer formation) differs from other steps results in a notable improvement in accuracy. Fits to various phospholipid adsorption isotherms demonstrate the applicability of the model to isotherm type experimental data. The fits reveal either monolayer or aggregate like adsorption structures, depending on surfactant head group charge. The presented model provides an easily accessible, computationally feasible means to estimate colloidal assembly and adsorption in oil environments, and enables assessment of surfactant aggregation propensity and adsorption energetics. [ABSTRACT FROM AUTHOR]

A stable microemulsion system is constructed by choosing α-aminophosphonate extractant Cextrant 230 and an anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) as the cosurfactants. The effects of some factors such as pH and the concentration of Cextrant 230, AOT, NaOH and the sulfate in the aqueous solution on the maximum water ratio (x0) are studied. The process and effects of microemulsion formation are analyzed and the optimized conditions for the stable microemulsion are determined. The Cextrant 230-AOT-nheptane microemulsion system is applied for the extraction of thorium. The effects of emulsion-to-water volume ratios, the concentrations of Cextrant 230, AOT and sulfate, temperature are studied. The extraction rate of thorium in the microemulsion system increases with the increase of the concentration of Cextrant 230 (or AOT), which is significantly higher than that of AOT-n-heptane microemulsion system. Cextrant 230 and AOT have a synergistic effect on the extraction of thorium. Temperature has little effect on extraction of thorium and the reaction is entropy-driven. Upon the comparison of the stripping of thorium by different inorganic acids, sulfuric acid is chosen as the stripping reagent. The loading capacity for ThO2 is about 1. 43 g/L. This microemulsion system is applied to the separation of Th from the actual bastnaesite sulfate leach liquid after the cerium extraction and the thorium content can be reduced to less than 0. 1 mg/L. The microemulsion system has both the advantages of thermodynamic stability and high efficiency. [ABSTRACT FROM AUTHOR]

The kinetics of oxidation of [Fe(phen)3]2+ by periodate has been studied in CTAB (cetyltrimethylammonium bromide) reverse micelles by changing the parameter W (=[H2O]/[CTAB]) and surfactant CTAB concentration. The reaction shows first order dependence on [Fe(phen)3]2+ and zero order on periodate. The reaction is autocatalytic in aqueous medium but autocatalysis disappears in reverse micellar medium. The pseudo first order rate constant k' decreases with increasing the value of W and at fixed concentration of CTAB and is independent of CTAB concentration. The influence of W is explained on the basis of the unique properties of water pool of reverse micelles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reverse micelles (RMs) are considered as model systems for heterogeneous reaction dynamics. • Anthraquinone derivatives in methanol-in-oil RMs show slower ICT dynamics compared to bulk. • Micelle size-dependent ICT dynamics represent the restricted internal rotation of (methyl)amino groups during the ICT. • Microviscosity of methanol nanopools in Igepal RMs appears to increase largely from the bulk value. Reverse micelles (RMs) are considered important model systems for molecular dynamics and chemical reactions, where the nanopools of aqueous and nonaqueous polar cores are separated from the surrounding organic phase via a monolayer of surfactant molecules. Here, we report the intramolecular charge transfer (ICT) dynamics of anthraquinone derivatives in the methanol-in-oil RMs composed of nonionic surfactants Igepal by femtosecond transient absorption and fluorescence upconversion spectroscopy. The ICT dynamics slow down inside the RMs due to abnormally diminished solvent motions and restricted internal rotations of the (methyl)amino group during the ICT in the excited states. The micelle size-dependent dynamics of anthraquinone derivatives inside the RMs were compared with the results in bulk aliphatic alcohols and understood as the changes in the microenvironment properties such as microviscosity. [ABSTRACT FROM AUTHOR]

In this study, rhenium nanoparticles were successfully synthesized with precise size control using a water-in-oil microemulsion method under an ambient atmosphere. Spectroscopic characterization using UV-Vis and ESI-MS techniques was used to study the stability of the rhenium(IV) precursor and verify its reduction into rhenium-based nanoparticles. The morphology and size of the rhenium nanoparticles were examined using HR-TEM. The results indicate formation of amorphous rhenium nanoparticles with an average size of 2.2 nm at a water-to-surfactant concentration ratio (W factor) of 10. These rhenium nanoparticles also have good size-stability compared to rhenium colloids generated in water alone. After one week, the particle diameter increased by only 0.6 nm with no evidence of aggregation. An investigation into the effect of various factors on the size and size distribution of the rhenium nanoparticles indicate that the W factor is the most influential parameter (among the considered factors) for size tuning, given that increases in W led to bigger and more polydisperse particles. Additionally, the microemulsion surfactant (AOT) protects the rhenium nanoparticles from their natural tendency to oxidize to perrhenate ion under an air atmosphere. However, a significant consideration in the use of AOT is the previously unreported presence of a chemical impurity which is able to reduce the rhenium(IV) precursor salt and generate rhenium nanoparticles within these microemulsion systems. Our investigation found that this impurity is the sulfite ion which is most likely introduced during manufacturing. [Display omitted] • Re-based nanoparticles (NPs) form in AOT-microemulsions (MEs) under ambient conditions. • AOT-MEs shield Re NPs from air, preventing their oxidation into soluble perrhenate. • The generated Re NPs within AOT-MEs also exhibit excellent size-stability. • The W factor and temperature exhibit the greatest influence on the size of Re NPs. • Sulfite is identified as the true cause of the unexpected reducing ability of AOT. [ABSTRACT FROM AUTHOR]

The aim of this study was to demonstrate the utility of time-resolved fluorescence spectroscopy in the detection of subtle changes in the local microenvironment of a tryptophan chromophore in a confined and crowded medium of AOT reverse micelles, which mimic biological membranes and cell compartmentalization. For this purpose, fluorescence properties of L-tryptophan and several newly synthesized tryptophan-containing peptides in buffer and in an AOT reverse micelle medium were determined. It was shown that insertion of tryptophan and its short di- and tripeptides inside micelles led to evident changes in both the steady-state emission spectra and in fluorescence decay kinetics. The observed differences in spectral characteristics, such as a blue shift in the emission maxima, changes in the average fluorescence lifetime, and the appearance of environmental-dependent fluorescent species, showed the utility of time-resolved fluorescence spectroscopy as a sensitive tool for detecting subtle conformational modifications in tryptophan and its peptides induced by changes in polarity, viscosity, and specific interactions between chromophores and water molecules/polar groups/ions that occur inside reverse micelles.

This study shows the possibility of using gallic acid (GA) and/or methyl gallate (MG) accompanied by phosphatidylcholine (PC) instead of tert-butylhydoquinone (TBHQ) for frying purposes. The antioxidants and PC were added in the concentrations of 1.2 mM and 500–2000 mg/kg, respectively. Oxidative stability index (OSI) and the kinetics of change in conjugated dienes (LCD), carbonyls (LCO), and acid value (AV) were used to assess the antioxidative treatments. GA alone and GA/MG (50:50) plus PC at 2000 mg/kg yielded the same OSI as that of TBHQ (18.4 h). The latter was of the highest frying performance in preventing the formation of LCD (rn = 0.0517/h and tT = 10.6 h vs. rn = 0.0976/h and tT = 4.5 h for TBHQ), LCO (rn = 0.0411/h and tT = 12.7 h vs. rn = 0.15/h and tT = 4.3 h for TBHQ), and hydrolytic products (AVm = 37.8 vs. 24.0 for TBHQ); rn: normalized the maximum rate of LCD/LCO accumulation; tT: the time at which the rate of LCD/LCO accumulation is maximized; AVm: quantitative measure of hydrolytic stability.

The aim of this work was to carry out the effects of AOT reverse micelle (RM) method on the functional and structural properties of basic and acidic subunits from 11S soy protein fraction. SDS-PAGE result showed that the purity of acidic and basic subunits prepared by RM (80.14% and 85.90%, respectively) was the higher than that of the isoelectric point cold sink (70.11% and 63.96%, respectively). Interestingly, there were significant differences in the secondary structure between subunits from two methods. Acidic subunits by two methods had similar solubility profiles, showing the higher solubility at pH 2.0–4.0 or 6.0–12.0, while the basic subunits had considerably lower solubility with the minimum at pH 8.0. The solubility, water absorbing capacities, foaming and emulsifying properties of subunits prepared by RM at different pH values and NaCl concentrations were significantly higher than that of IP. These results suggested that the acidic and basic subunits purified by RM had the better functional properties. RM might be an effective method to purify high quality protein for application in the food industry. [ABSTRACT FROM AUTHOR]

Aggregation of Aβ40 and Aβ42 are considered as pivotal players in the pathogenic mechanism of Alzheimer's disease. In this work, we applied reverse micelles formed by sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) to prepare oligomeric aggregates of Aβ40 or Aβ42 peptides. The resultant globular aggregates were approximately 22 nm in diameter and they were capable to form mature fibrils upon self‐aggregation. Furthermore, we found that the Aβ42 oligomeric aggregates can seed the fibrillization of Aβ40 monomers. Solid‐state NMR results revealed that the Aβ40 fibrils seeded by Aβ40 or Aβ42 oligomers adopt a similar molecular structure for the residues near the C‐terminus. [ABSTRACT FROM AUTHOR]

Background. Soybean oil is one of the most commonly consumed vegetable oils in the world. It is rich in unsaturated fatty acids and contains surface-active compounds which, due to their amphiphilic nature, are capable of forming association colloids. These structures are considered to be autoxidation centers. Interactions of amphiphilic antioxidants present in soybean oil and association colloids may influence their solubility and antioxidant activity, as well as changing the organoleptic properties of the oil (such as opacity). The aim of this study was to characterize the interactions of isoflavone daidzein (DAI) with phosphatidylcholine association colloids (reverse micelles) and get insights into the aggregates formed from daidzein itself in soybean oil. Materials and methods. In this investigation, static and dynamic light scattering techniques (SLS, DLS) were applied to take measurements. Association colloids (reverse micelles) containing daidzein were formed from DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) in soybean oil from which the amphiphilic minor components were removed. Results. Daidzein was found to be able to self-assemble and form associates in soybean oil, as well as incorporating itself into DOPC reverse micelles. This antioxidant increases the hydrodynamic diameter of DOPC structures only above a specified critical concentration (600 µmol/kg according to DLS measurements), while structures composed of DAI are formed at its lower concentrations (above 50 µmol/kg as measured by SLS). Conclusions. The present findings may help in the formulation of oils that possess health protecting properties with an increased daidzein content and in the elucidation of daidzein antioxidant action mechanisms in bulk oils. [ABSTRACT FROM AUTHOR]

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The present review aims at surveying literature on the synthesis, biological and photophysical activities, especially anticancer properties, of tetracyclic natural compound ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole) since its first isolation and synthesis in 1959. [ABSTRACT FROM AUTHOR]

The electron transfer process between pentammineaquacobalt (III) and hexacyanoferrate (II), [Co(NH3)5H2O]3+/Fe(CN)6]4− ion pair was investigated in water/dioctyl sodium sulfosuccinate (AOT)/Isooctane reverse micelles. The study observed that the electron transfer rate depends on the size of the reverse micelles. The concentrations of Fe (II) ions were varied in different-sized (Wo) reverse micelles of Wo = [H2O]/[AOT] = 10 to 30, but the concentration of Co (III) ions was kept constant. The rate of electron transfer in the ion pair [Co(NH3)5H2O]3+/[Fe(CN)6]4− increased with decreasing size (Wo) of reverse micelles. The smallest reverse micelles Wo = 10 demonstrated the fastest electron transfer rate, and the biggest Wo = 30 reverse micelles showed the slowest electron transfer rate. The change of reaction environment and the location of the reactants in the reverse micelles due to confinement are considered the factors responsible for the results. [ABSTRACT FROM AUTHOR]

The reddish-orange color of Antarctic krill oil fades during storage, and the mechanism remains unclear. Model systems containing different combinations of astaxanthin (ASTA), phosphatidylethanolamine (PE), and tocopherol were subjected to accelerated storage. Among all groups containing ASTA, only the ones with added PE showed significant fading. Meanwhile, the specific UV–visible absorption (A 470 and A 495) showed a similar trend. Peroxide value and thiobarbituric acid reactive substances increased during storage, while ASTA and PE contents decreased. Correlation analysis suggested that oxidized PE promoted fading by accelerating the transformation of ASTA. PE content exceeded the critical micelle concentration (1μg/g) indicating the formation of reverse micelles. Molecular docking analysis indicated that PE also interacted with ASTA in an anchor-like manner. Therefore, it is speculated that amphiphilic ASTA is more readily distributed at the oil-water interface of reverse micelles and captured by oxidized PE, which facilitates oxidation transfer, leading to ASTA oxidation and color fading. [Display omitted] • Phosphatidylethanolamine promoted astaxanthin transformation and color fading. • Tocopherol retarded color fading induced by phosphatidylethanolamine. • Phosphatidylethanolamine could form reverse micelles in oil matrix. • Astaxanthin could be distributed at the oil-water interface of reverse micelles. • Oxidized phosphatidylethanolamine induced astaxanthin oxidation leading to fading. [ABSTRACT FROM AUTHOR]

In this work, we performed a long simulation (1000 ns) to study the adsorption behavior of a model of Au-polyethyleneimine (Au-PEI) nanoparticle in Aerosol-OT (AOT) reverse micelle in hexane with a water/AOT molar ratio (Wo) = 30. We found that the Au-PEI nanocluster is fixed near the AOT headgroups, i.e. one can conclude that the nanoparticle come into close contact with AOT micelle headgroups after ∼200 ns and remained bound for the rest of production run. Conversely, the results from the replica runs suggest that the adsorption time is approximately 50 ns. The analysis of some conformational parameters also shows the fixed position of Au-PEI nanoparticle, which was also proved by the presence of N-H ... O strong hydrogen-bonded network between Au-PEI and AOT headgroup. [Display omitted] [ABSTRACT FROM AUTHOR]

The micellization processes in the systems tetraethylene glycol monododecyl ether (C12E4)–heptane (1) and C12E4–Nile red–heptane (2) have been studied by electron absorption spectroscopy. In system 1, reverse micelles of small size appear, which makes it difficult to find the critical micelle concentration (CMC). In this regard, a method for determining CMC based on spectroscopic data was tested. The same one was done for system 2, where the appearance of Nile red as a C12E4 nano-adsorbent leads to the formation of protomicelles below the CMC. The CMC itself in system 2 turns out to be lower than the CMC in system 1, which corresponds to the predictions of the theory. The water role in the formation of reverse micelles was studied using a commercial analogue of C12E4 preparation Brij 30 (with a water content of 1%). The results obtained are consistent with theoretical predictions. [ABSTRACT FROM AUTHOR]

The oxidation of ascorbic acid by K3[Fe(CN)6] was studied in reverse micellar systems composed of CTAB (Cetyltrimethylammonium bromide), and it was found the observed first order (k1(aq) = 5.2×10-5 s-1, k1(rev) = 61.4×10-4 s-1) rate constant in reverse micellar medium is around forty times higher compared to aqueous medium under identical conditions. The rate enhancement (k2(aq) = 0.9×10-5 mole-1.dm3.sec-1, k2(rev) = 1.75×10-3 mole-1.dm3.sec-1) is attributed to the large concentration effect and lower dielectric constant in the reverse micelles. The rate of the reaction increases with increase in W = {[H2O]/[surfactant]} which is explained in terms of ionic strength of the water pool. The effect of surfactant concentration on rate was explained on the basis of Berezin pseudo phase model. [ABSTRACT FROM AUTHOR]

In recent years, the field of reverse micelles has witnessed a significant growth of interest, partly due to the finding that proteins, other biopolymers, and even bacterial cells can be solubilized in the reverse micellar systems. Among surfactants capable of forming water in oil microemulsion, the cationic surfactant cetyltrimethylammonium bromide (CTAB) has received particular attention because of its ability to solubilize relatively large amount of water in a variety of hydrophobic organic solvents. Due to versatile photochemical and photophysical properties of Ru(II) complexes, Ru(II)- phenanthroline and its derivatives were used in this present work to form CTAB cationic reverse micelles and studied to characterise their photophysical properties such as absorption, emission and excited state life time. The findings from the spectral data observed in the present study proves that the excited state properties of Ru(II)-phenanthroline complexes are dramatically altered in the presence of reverse micelle. Specifically reverse micelle encapsulation of [Ru(dpphen)3]2+ complex in restricted environment causes blue shift in the emission maximum as well as have longer radiative lifetime. The blue shift in the emission maximum in the case of [Ru(dpphen)3]2+ indicates that the probes are near the water in oil reverse micellar interface, tightly bound and are not displaced towards the water pool of the micelle even at the highest water loading W0=50, which reveals the increased hydrophobicity. This highest fluorescence lifetime can serve as an excellent indicator to point out the location of the probe in a microheterogeneous system/environment. [ABSTRACT FROM AUTHOR]

The kinetics of acid hydrolysis of bis(2,2';6',2''–terpyridyl) iron(II) complex has been studied in CTAB/Hexane/Chloroform reverse micelles. The reaction obeys first order kinetics with respect to each of the reactants at all values of W, {W= [H2O]/[CTAB]}. In the reverse micellar medium, the reaction is much slower compared to aqueous medium due to low micropolarity of the water pools which does not facilitate a reaction between reactants of same charge. The effect of variation of W {W=[H2O]/[CTAB]} at constant [CTAB] and variation of [CTAB] at fixed W has been studied. The second order rate constant (k2) of the reaction increases as the value of W increases up to W = 8.88 and remains constant thereafter and it is independent of concentration of [CTAB] at constant W. The variation of rate of reaction with W has been explained by considering variation of micropolarity and ionic strength of water pools of reverse micelles with W. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

The kinetics of base hydrolysis of bis(2,2′ : 6′,2′′- terpyridine)iron(II) has been carried out in water pools of CTAB/chloroform/hexane reverse micelles. The reaction obeys first order kinetics with respect to each of the reactants. In the reverse micellar medium, the reaction was found to be around fifty times compared to aqueous medium under identical experimental conditions. The pronounced acceleration is due to the lower micro polarity of the reverse micelles which facilitates the reaction between oppositely charged ions. The effect of variation of W {W = [H2O]/[CTAB]} at constant [CTAB] and variation of [CTAB] at fixed W has been studied. At fixed concentration of CTAB, the second order rate constant (k2) of reaction increases with increasing the value of W and is independent of concentration of [CTAB] at constant W. The variation of rate with W has been explained by Guggenheim plots, logk2 versus ionic strength (µ) and found to be linear for all concentrations of CTAB. [ABSTRACT FROM AUTHOR]

This work describes three phase dispersive liquid-liquid microextraction based on reverse micelles for the determination of Q-markers of cinnamic acids (caffeic acid, p-hydroxycinnamic acid, ferulic acid, and cinnamic acid) in traditional Chinese medicine followed by high performance liquid chromatography (HPLC) analysis. The variables influencing the procedure were optimized separately. Enrichment factors from 110 to 189, linearities from 1.2 to 960 ng mL−1 with r2 exceeding 0.9943, detection limits from 0.1 to 0.6 ng mL−1, excellent precision with relative standard deviations below 5.6%, and good relative recoveries from 80.0% to 113.3% were achieved. In addition, the mechanism of the procedure was explored by comparison with conventional dispersive liquid-liquid microextraction at the optimum conditions. The results showed that the developed microextraction procedure improved the sensitivity and consumed less organic solvent and is a greener approach. [ABSTRACT FROM AUTHOR]

This work aims to study the construction of reverse aspirin-loaded micelles prepared from amphiphilic PEG-PLA-SA triblock copolymers and the optimization of the preparation process. Using polyethylene glycol (PEG) as the initiator, ring-opening polymerization of L-lactide (L-LA) was used to prepare PEG-PLA diblock copolymers. Final product PEG-PLA-SA triblock copolymers were prepared by the reaction of stearic acid (SA) and PEG-PLA catalyzed by 4-dimethylaminopyridine (DMAP) and N,N’-Dicyclohexylcarbodiimide (DCC). Fourier transform infrared spectrometer (FT-IR) was used to characterize the product structure. PEG-PLA-SA triblock copolymers self-assembled in toluene/ethanol/water system to form reverse micelles, which could encapsulate aspirin into a hydrophilic core. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to determine the size and morphology of reverse micelles. The results showed that the reverse micelles are spherical, with a particle size of less than 70 nm. Response surface analysis method was applied to optimize the preparation process of PEG-PLA-SA. In vitro drug release was achieved by embedding reverse aspirin-loaded micelles in the biocompatible membrane in phosphate buffer saline (PBS) at 37°C. In the first 8 h, the drug release rate of the triblock copolymers was slower than that of the diblock copolymers. After 8 h, the drug release rate of both tended to be flat. The stability of aspirin-loaded reverse micelles was studied through accelerated test. These results indicate that reverse micelle PEG-PLA-SA may be a promising carrier for hydrophilic drugs like aspirin.

Peripheral membrane proteins (PMPs) are a subgroup of membrane-associated proteins that are water-soluble and bind to membranes, often reversibly, to perform their function. These proteins have been extensively studied in the aqueous state, but there is often a lack of high-resolution structural and functional studies of these proteins in the membrane-bound state. Currently, nuclear magnetic resonance (NMR) is among the best-equipped methods to study these relatively small proteins and domains, but current models have some disadvantages that prevent a full understanding of PMP interactions with membranes and lipids. Micelles, bicelles, and nanodiscs are all available for NMR observation but are based on synthetic lipids that may destabilize proteins or are too large to accommodate straightforward structural analysis. This protocol introduces a method for forming reverse micelles using lipids from natural sources, here called native reverse micelles. This technique allows the PMPs to embed within a shell of naturally derived lipids surrounding a small water core solubilized in an alkane solvent. PMP embedment in the lipid shell mimics binding to a cellular membrane. Here, naturally derived lipids from soy, bovine heart, and porcine brain are used in conjunction with n-dodecylphosphocholine (DPC) to encapsulate a PMP from either concentrated or dried protein, resulting in reverse micelles that may be confirmed via dynamic light scattering and NMR. This protocol allows for high-quality NMR data of PMPs interacting with membrane lipids within a biologically accurate environment. Key features • This protocol describes using natural lipids to construct reverse micelles for high-resolution NMR studies of proteins. • Initial optimization of encapsulation conditions proceeds through visual assessment, with dynamic light scattering (DLS) to measure size distribution, and NMR to observe protein behavior. • Membrane-interacting proteins are encapsulated in their membrane-bound state. Proteins that do not interact with membranes are housed in their water-solubilized state. • Structural, functional, and inhibitory studies may be performed on native reverse micelle-encapsulated proteins., Competing Interests: Competing interestsThe authors declare that they have no conflicts of interest., (©Copyright : © 2024 The Authors; This is an open access article under the CC BY license.)

The synthesis and structural characterization of two new potassium triphenylsiloxides, namely, aqua(propan‐2‐ol)hexakis(triphenylsilanolato)hexapotassium toluene disolvate, [K6(C18H15OSi)6(C3H8O)(H2O)]·2C7H8, and diaquahexakis(triphenylsilanolato)hexapotassium, [K6(C18H15OSi)6(H2O)2], are reported. Both compounds crystallize in the triclinic space group P. The structure in each case resembles an alkali metal polyoxometalate‐like structure, in which electrostatic interactions are observed in the metal–oxygen core. Furthermore, both compounds also resemble a reverse micelles‐like architecture, in which the hydrophilic core is enclosed in a hydrophobic shell. The cores of the complexes are flanked by hydrophobic aromatic rings derived from Ph3SiO− anions, where intramolecular π‐interactions between the aromatic rings and potassium cations stabilize the cores of the crystals. Moreover, in both structures, the presence of hydrogen bonds is observed; until now, no crystal structures have been described containing K atoms and triphenylsiloxide molecules in which the presence of hydrogen bonds was confirmed. Thus, these coordination entities could be considered as attractive reagents for further synthetic protocols towards heterometallic complexes. [ABSTRACT FROM AUTHOR]

From an interfacial phenomena standpoint, the effect of the alkyl chain length is evaluated on the mechanism of antioxidant activity of gallic acid ester derivatives (methyl, propyl, octyl, dodecyl, and stearyl gallates) in bulk phase oil. A combinational kinetic model is used to estimate the oxidation kinetic parameters, such as induction period, the maximum concentration of lipid hydroperoxides, and critical reverse micelle concentration. These kinetic parameters are estimated much better with the combinational model compared to the tangent method. The nonlinear behavior is observed for inhibitory activities of homologous series of antioxidants in soybean triacylglycerols. In terms of different kinetics parameters, including antioxidant effectiveness and activity, methyl gallate has the highest inhibitory effect during lipid peroxidation. Gallic acid and alkyl gallates are able to protect bulk oils against peroxidation (induction period > 336 h) in terms of the extent of their participation in the main reaction of chain termination and pro‐oxidative side reactions of chain initiation, and anti‐oxidative side reactions of chain propagation. Practical Applications: This work explains the effect of the esterification in the inhibitory activity of alkyl gallates, mechanism action of alkyl gallates in bulk oil systems, antiradical potency as a function of the interfacial phenomena, and free radical chain mechanism, the impact of antioxidant activity on critical reverse micelle concentration of hydroperoxides. Moreover, in this study, it is confirmed that the combinational kinetic model can be employed as a reliable method for determining the oxidation kinetic parameters. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of two new potassium triphenylsiloxides, namely, aqua(propan‐2‐ol)hexakis(triphenylsilanolato)hexapotassium toluene disolvate, [K6(C18H15OSi)6(C3H8O)(H2O)]·2C7H8, and diaquahexakis(triphenylsilanolato)hexapotassium, [K6(C18H15OSi)6(H2O)2], are reported. Both compounds crystallize in the triclinic space group P. The structure in each case resembles an alkali metal polyoxometalate‐like structure, in which electrostatic interactions are observed in the metal–oxygen core. Furthermore, both compounds also resemble a reverse micelles‐like architecture, in which the hydrophilic core is enclosed in a hydrophobic shell. The cores of the complexes are flanked by hydrophobic aromatic rings derived from Ph3SiO− anions, where intramolecular π‐interactions between the aromatic rings and potassium cations stabilize the cores of the crystals. Moreover, in both structures, the presence of hydrogen bonds is observed; until now, no crystal structures have been described containing K atoms and triphenylsiloxide molecules in which the presence of hydrogen bonds was confirmed. Thus, these coordination entities could be considered as attractive reagents for further synthetic protocols towards heterometallic complexes. [ABSTRACT FROM AUTHOR]

Effects of eugenol esters with different alkyl chain lengths and combinations of eugenol + eugenol esters on sunflower oil oxidation at 338, 358, and 378 K are evaluated by determining different kinetic parameters. Also, water content and reverse micelles size of sunflower oil samples are monitored during oxidation. Eugenyl acetate shows higher antioxidant activity than eugenol in sunflower oil, while eugenyl butyrate, eugenyl hexanoate, and eugenyl decanoate shows lower antioxidant activity than eugenol. Antioxidant activity of eugenol esters decreases by increasing their alkyl chain length. Eugenol shows a synergistic effect with eugenyl acetate and eugenyl butyrate on increasing the induction period and antioxidant activity values, while it shows an antagonistic effect with eugenyl hexanoate and eugenyl decanoate. Also, combinations of eugenol + eugenyl acetate, as well as, eugenol + eugenyl butyrate stabilize the reverse micelles at longer period of time (3263 min for eugenol + eugenyl acetate and 2900 min for eugenol + eugenyl butyrate) than eugenol (2750 min). In addition, eugenol + eugenyl acetate and eugenol + eugenyl butyrate decrease the magnitude of temperature‐related effects on sunflower oil oxidation to the higher extent than eugenol did. Practical applications: Recent studies have suggested that the antioxidants with ability to locate at the active sites of lipid oxidation can efficiently reduce lipid oxidation in bulk oil. Despite a remarkable focus on antioxidant activity of eugenol, there is no information regarding improving its interfacial performance through esterification method. Also, there are few published data regarding the effects of esterified antioxidants on physicochemical changes during the oxidation of bulk oil. In this study, eugenol is esterified with anhydrides with different alkyl chain lengths to increase its accessibility to the active site of lipid oxidation, that is, water–oil interface of reverse micelles in sunflower oil. Effects of eugenol esters on stability of reverse micelles and critical reverse micelles concentration of lipid hydroperoxides have been investigated for the first time. [ABSTRACT FROM AUTHOR]

In recent times, there is increased public interest and indeed strong movement against the use of Bisphenol A (4,4ʹ-(propane-2,2,-diphenol)) due to its endocrine disrupting properties. In the present study, biotransformation of Bisphenol A (BPA) was accomplished using Trametes versicolor laccase (E.C. 1.10.3.2) enzyme. The enzyme was entrapped in reverse micelles comprising of bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and 2,2,4-trimethylpentane (isooctane) for non-aqueous catalysis considering hydrophobicity of BPA. Screening of various parameters that may affect micellar system was carried out using Plackett–Burman experimental design and central composite design (Design Expert 11). According to Design Expert actual concentration of different variables was 0.55, 150 (Wo 30), 0.0035 mM and 175 µg/ml for Mg+2ions, Hydration ratio (Wo), 2,6-dimethoxyphenol (2,6 DMP, substrate) and laccase, respectively, at 40 °C and pH 4.5. Under these conditions laccase activity in reverse micelles was increased two folds as compared to unoptimized micellar system. It was evident that the reverse micelles diameter was linearly proportionated to the amount of laccase enzyme incorporated. BPA bioremediation mediated by laccase in non-aqueous environment was found to be 84% in 8 h of treatment. Biotransformation of BPA was monitored using GC–MS. BPA degraded products, such as BPA-O-catechol and 4,4 (Ethane 2-oxy 2-ol) diphenol were identified indicating transformation by oxidation. [ABSTRACT FROM AUTHOR]