Solubilization of enzymes and nucleic acids in hydrocarbon micellar solutions

Enhanced antineoplastic/therapeutic efficacy using 5-fluorouracil-loaded calcium phosphate nanoparticles

In the past few decades, the successful theranostic application of nanomaterials in drug delivery systems has significantly improved the antineoplastic potency of conventional anticancer therapy. Several mechanistic advantages of nanomaterials, such as enhanced permeability, retention, and low toxicity, as well as surface engineering with targeting moieties, can be used as a tool in enhancing the therapeutic efficacy of current approaches. Inorganic calcium phosphate nanoparticles have the potential to increase the therapeutic potential of antiproliferative drugs due to their excellent loading efficiency, biodegradable nature and controlled-release behaviour. Herein, we report a novel system of 5-fluorouracil (5-FU)-loaded calcium phosphate nanoparticles (CaP@5-FU NPs) synthesized via a reverse micelle method. The formation of monodispersed, spherical, crystalline nanoparticles with an approximate diameter of 160-180 nm was confirmed by different methods. The physicochemical characterization of the synthesized CaP@5-FU NPs was done with transmission electron microscopy (TEM), dynamic light scattering (DLS), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The antineoplastic potential of the CaP@5-FU NPs against colorectal and lung cancer cells was reported. The CaP@5-FU NPs were found to inhibit half the population (IC50) of lung adenocarcinoma (A549) cells at 32 μg/mL and colorectal (HCT-15) cancer cells at 48.5 μg/mL treatment. The apoptotic induction of CaP@5-FU NPs was confirmed with acridine orange/ethidium bromide (AO/EB) staining and by examining the morphological changes with Hoechst and rhodamine B staining in a time-dependent manner. The apparent membrane bleb formation was observed in FE-SEM micrographs. The up-regulated proapoptotic and down-regulated antiapoptotic gene expressions were further confirmed with semiquantitative reverse transcriptase polymerase chain reaction (PCR). The increased intracellular reactive oxygen species (ROS) were quantified via flow cytometry upon CaP@5-FU NP treatment. Likewise, the cell cycle analysis was performed to confirm the enhanced apoptotic induction. Our study concludes that the calcium phosphate nanocarriers system, i.e. CaP@5-FU NPs, has higher antineoplastic potential as compared to 5-FU alone and can be used as an improved alternative to the antimitotic drug, which causes severe side effects when administrated alone.

Tailor-Made Self-Assemblies from Functionalized Amphiphiles: Diversity and Applications

The objective of this feature article is to coalesce our recent advancements on different expressions of tailor-made supramolecular self-assemblies and to explore them as a function of molecular architecture. In the last decade, we have developed a library of elegant and simple functional amphiphilic small molecules, which have very interesting abilities to form diverse manifestations of supramolecular self-assemblies such as micelles, reverse micelles, vesicles, fibers, supramolecular gels, and so on. Each of the expressions of the self-aggregated structures has its individual prominence and finds important applications in the fields of chemistry, physics, biology, and others. In this feature article, the major emphasis is mostly on how to attain precise control over the development of various well-defined supramolecular self-assemblies through the judicious design of low-molecular-weight amphiphiles. By tuning only the functional moieties of the amphiphilic structure, diverse supramolecular architectures can be constructed with task-specific applications. We expect that this article will provide a general and conceptual demonstration of various approaches to the development of different functional supramolecular systems and their prospective applications in numerous domains.

Mass Exchange and Equilibration Processes in AOT Reverse Micelles

Reverse micelles (RMs) made with sodium bis(2-ethylhexyl)sulfosuccinate suspended in isooctane are commonly used experimental models of aqueous microenvironments. However, there are important unanswered questions about the very characteristic that makes them of interest, namely their size. To explore the factors that determine the size of RMs, all-atom molecular dynamics simulations of RMs with different sizes but the same water-loading ratio were performed. An Anton 2 machine was used so that systems of the necessary size could be extended into the microsecond timescale, and mass exchange processes could be observed. Contrary to hypothesis, there were no net gains or losses of water by diffusion between RMs of different size. However, gains and losses did occur following fusion events. RM fusion followed RM contact only when waters were present among the hydrophobic surfactant chains at the point of contact. The presence of an encapsulated 40-residue amyloid beta peptide did not directly promote RM fusion, but it quickly and efficiently terminated each fusion event. Before fusion terminated, however, the size of the peptide-containing RM increased without a corresponding change in its water-loading ratio. We conclude that the mass transfer between RMs is most likely accomplished through transient fusion events, rather than through the diffusion of component molecules through the organic phase. The behavior of the amyloid beta peptide in this system underscores its propensity to embed in, and fold in response to, multiple interactions with the surfactant layer.

Molecular interaction mechanisms in reverse micellar extraction of microbial transglutaminase

Reverse micellar extraction is an efficient and economical alternative for protein purification. In this study, microbial transglutaminase (MTGase) from crude materials was purified using reverse micellar extraction, and the molecular interaction mechanism in reverse micellar extraction of MTGase was explored. By using a molecular simulation study, the interaction mechanism of forward extraction was investigated. The molecular simulation results reveal the interaction of MTGase-water-surfactant is the major driving force for the forward extraction. Further, the effect of ionic strength on molecular interactions in backward extraction was investigated using 1H low-field nuclear magnetic resonance (LF-NMR) and circular dichroism (CD) spectra. In backward extraction, the interactions between water and the other two molecules (MTGase and surfactant molecules) are enhanced while the interactions between target molecules (MTGase) and the other two molecules (water and surfactant molecules) are weakened as the ionic strength increases. Moreover, the effect of size exclusion on backward extraction was also investigated. The results demonstrate size exclusion has limit effect at high ionic strength, and the weakened interaction of MTGase-water-surfactant is the main reason causing the release of the target molecules in backward extraction. This work might provide valuable reference to the MTGase purification and downstream processing.

Micellar Enzymology- Chemistry and Applications

Enzymes in aqueous environment usually deal with purified enzyme preparations isolated from living matter which does not mimic real catalytic properties in vivo. Interaction of enzymes in nature takes place with different surfaces composed from lipid membranes or they get incorporated into biomembranes. Although Water is not a dominating component in the cytoplasm but plays a structural role by participating in the formation of biocatalytic complexes like glycoproteins. Water is needed to keep biocatalyst in active confirmation and hence plays very crucial role in biocatalytic reactions, activity and stability so that it can be used for various applications. This review focuses on composition, preparation properties and parameters which influence enzymes in reverse micelles and application of micellar enzymology to study protein chemistry, shifting equilibrium of various reactions, to recover various products by partition chromatography and bioremediation of chlorophenolic environmental pollutants.

Dynamic light scattering of xanthan gum biopolymer in colloidal dispersion

The dynamical properties of nanogels of xanthan gum (XG) with hydrodynamic radius controlled in a size range from 5 nm to 35 nm, were studied at the different XG concentrations in water/sodium bis-2-ethylhexyl-sulfosuccinate (AOT)/decane reverse micelles (RMs) vs. mass fraction of nano-droplet (MFD) at W = 40, using dynamic light scattering (DLS). The diffusion study of nanometer-sized droplets by DLS technique indicated that enhancing concentration of the XG polysaccharide resulted in exchanging the attractive interaction between nano-gels to repulsive interaction, as the mass fraction of nano-droplets increased. The reorientation time (τr ) of water nanodroplets decreased with MFD for water-in-oil AOT micro-emulsion comprising high concentration (0.0000625) of XG. On the other hand, decreasing concentration of biopolymer led to increasing the rotational correlation time of water nanodroplets with MFD. In conclusion, a single relaxation curve was observed for AOT inverse microemulsions containing different XG concentrations. Furthermore, the interaction between nanogels was changed from attractive to repulsive versus concentration of XG in the AOT RMs.

A facile route to core-shell nanoparticulate formation of arsenic trioxide for effective solid tumor treatment

Arsenic trioxide has achieved great clinical success in the treatment of acute promyelocytic leukemia (APL). However, it is difficult to replicate the success in other cancers, such as solid tumors, in part because of the rapid renal clearance and dose-limiting toxicity. Nanotechnology is expected to overcome these disadvantages through altering its pharmacokinetics and concentrating the drug at the desired sites. Herein, we report a "one-pot" method to develop arsenic-based nanodrugs by in situ coating the as-prepared arsenic nanocomplexes with porous silica shells. This process can be easily reproduced and scaled up because no complicated synthesis and purification steps are involved. This core-shell embedding method endows nanodrugs with high loading capacity (57.9 wt%) and a prolonged pH-responsive releasing profile, which is crucial to increase the drug concentration at tumor sites and improve the drug efficacy. Based on these unique features, the nanodrugs significantly inhibit the growth of solid tumors without adverse side effects. Therefore, we anticipate that the arsenic-based nanodrugs generated by this facile synthetic route may be a powerful and alternative strategy for solid tumor therapy.

Rate of Molecular Transfer of Allyl Alcohol across an AOT Surfactant Layer Using Muon Spin Spectroscopy

The transfer rate of a probe molecule across the interfacial layer of a water-in-oil (w/o) microemulsion was investigated using a combination of transverse field muon spin rotation (TF-μSR), avoided level crossing muon spin resonance (ALC-μSR), and Monte Carlo simulations. Reverse microemulsions consist of nanometer-sized water droplets dispersed in an apolar solvent separated by a surfactant monolayer. Although the thermodynamic, static model of these systems has been well described, our understanding of their dynamics is currently incomplete. For example, what is the rate of solute transfer between the aqueous and apolar solvents, and how this is influenced by the structure of the interface? With an appropriate choice of system and probe molecule, μSR offers a unique opportunity to directly probe these interfacial transfer dynamics. Here, we have employed a well characterized w/o microemulsion stabilized by bis(2-ethylhexyl) sodium sulfosuccinate (Aerosol OT), with allyl alcohol (CH2═CH-CH2-OH, AA) as the probe. Resonances due to both muoniated radicals, CMuH2-C*H-CH2-OH and C*H2-CHMu-CH2-OH, were observed with the former being the dominant species. All resonances displayed solvent dependence, with those in the microemulsion observed as a single resonance located at intermediate magnetic fields to those present in either of the pure solvents. Observation of a single resonance is strong evidence for interfacial transfer being in the fast exchange limit. Monte Carlo calculations of the ΔM = 0 ALC resonances are consistent with the experimental data, indicating exchange rates greater than 10(9) s(-1), placing the rate of interfacial transfer at the diffusion limit.

Degradation of Polycyclic Aromatic Hydrocarbons (PAHs) by Laccase in Rhamnolipid Reversed Micellar System

Rhamnolipid was applied to degrade anthracene and pyrene in reversed micelles. The parameters in degradation were optimized for the purpose of improving degradation rates. The proper amount of rhamnolipid (RL) used for degrading anthracene was 0.065 mM, while 0.075 mM for pyrene. However, reaction time for degrading both anthracene and pyrene was 48 h. The optimum water content, pH, laccase concentration, polycyclic aromatic hydrocarbon (PAH) initial concentration, and volume ratio of n-hexanol to isooctane for both were found out. The highest degradation rates of anthracene and pyrene were 37.52 and 25.58%, respectively. Although the degradation rates were not higher than the results previous literatures reported, this method was of novelty and provided guidance in application in degrading PAHs by reversed micellar system, especially for biosurfactant-based reversed micelles.

Environment-responsive fluorescent nucleoside analogue probe for studying oligonucleotide dynamics in a model cell-like compartment

The majority of fluorescent nucleoside analogue probes that have been used in the in vitro study of nucleic acids are not suitable for cell-based biophysical assays because they exhibit excitation maxima in the UV region and low quantum yields within oligonucleotides. Therefore, we propose that the photophysical characterization of oligonucleotides labeled with a fluorescent nucleoside analogue in reverse micelles (RM), which are good biological membrane models and UV-transparent, could provide an alternative approach to studying the properties of nucleic acids in a cell-like confined environment. In this context, we describe the photophysical properties of an environment-sensitive fluorescent uridine analogue (1), based on the 5-(benzo[b]thiophen-2-yl)pyrimidine core, in micelles and RM. The emissive nucleoside, which is polarity- and viscosity-sensitive, reports the environment of the surfactant assemblies via changes in its fluorescence properties. The nucleoside analogue, incorporated into an RNA oligonucleotide and hybridized to its complementary DNA and RNA oligonucleotides, exhibits a significantly higher fluorescence intensity, lifetime, and anisotropy in RM than in aqueous buffer, which is consistent with the environment of RM. Collectively, our results demonstrate that nucleoside 1 could be utilized as a fluorescent label to study the function of nucleic acids in a model cellular milieu.

Physicochemical investigation of mixed surfactant microemulsions: water solubilization, thermodynamic properties, microstructure, and dynamics

In this contribution, we report on a systematic investigation of phase behavior and solubilization of water in water-in-heptane or decane aggregates stabilized by mixtures of polyoxyethylene (20) cetyl ether (Brij-58) and cetyltrimethylammonium bromide (CTAB) surfactants with varying compositions in conjugation with 1-pentanol (Pn) at fixed surfactant(s)/Pn ratio and temperature. Synergism in water solubilization was evidenced by the addition of CTAB to Brij-58 stabilized system in close proximity of equimolar composition in both oils. An attempt has been made to correlate composition dependent water solubilization and volume induced conductivity studies to provide insight into the solubilization mechanism of these mixed systems. Conductivity studies reveal the ascending curve in water solubilization capacity-(Brij-58:CTAB, w/w) profile as the interdroplet interaction branch indicating percolation of conductance and the descending curve is a curvature branch due to the rigidity of the interface in these systems. The microstructure of these systems as a function of surfactant composition has been determined by dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR) measurements. FTIR study reveals increase and decrease in relative population of bound and bulk-like water, respectively, with increase in Brij-58:CTAB (w/w). DLS measurements showed that the droplet hydrodynamic diameter (Dh) decreases significantly with the increase in Brij-58:CTAB (w/w). Further, the interfacial composition and energetic parameters for the transfer of Pn from bulk oil to the interface were evaluated by the dilution method. Formation of temperature-insensitive microemulsions and temperature invariant droplet sizes are evidenced in the vicinity of the equimolar composition. The results are interpreted in terms of a proposed mechanism.

Possible role of laccase from Fusarium incarnatum UC-14 in bioremediation of Bisphenol A using reverse micelles system

Bisphenol A [2,2 bis (4 hydroxyphenyl) propane] is widely used in the variety of industrial and residential applications such as the synthesis of polymers including polycarbonates, epoxy resins, phenol resins, polyesters and polyacrylates. BPA has been recognized as an Endocrine Disrupting Chemicals (EDC), thus it is necessary to assess its biodegradability or fate in the natural environment. In general, environmental pollutant such as BPA does not dissolve in aqueous media, owing to their high hydrophobicity, and hence non-aqueous catalysis can be employed to enhance biodegradability of phenolic environmental pollutant. Purified laccase hosted in reverse micelles using ternary system of isooctane: AOT [Bis (2-ethylhexyl) sulphosuccinate sodium salt)]:water having hydration ratio (Wo) of 30 with protein concentration of 43.5 μg/ml was found to eliminate 91.43% of 200 ppm of Bisphenol A at 50 °C, pH-6.0 when incubated with laccase/Reverse Micelles system for 75 min. GC-MS analysis of isooctane soluble fractions detected the presence of 4,4'-(2 hydroxy propane 1,2 diyl) diphenol, bis (4-hydroxylphenyl) butenal and 2-(1-(4-hydroxyphenyl) vinyl) pent-2-enal indicated degradation of BPA by two oxidation steps and one ring opening step (C-C bond cleavage). Laccase/RM system exhibited several advantages for the oxidative degradation of hydrophobic phenols mainly because of the solubility of either enzyme or substrate was improved in organic media and the stable activity of laccase in organic media was achieved.

Organization and dynamics of the N-terminal domain of chemokine receptor CXCR1 in reverse micelles: effect of graded hydration

Water plays a fundamental role in the folding, structure, dynamics, and function of proteins and peptides. The extracellular N-terminal domain of chemokine receptors is crucial in mediating binding affinity, receptor selectivity, and regulating function. The flexible N-terminal domain becomes ordered in membranes and membrane-mimetic assemblies, thereby indicating that the membrane could play an important role in regulating CXC chemokine receptor 1 (CXCR1) function. In view of the role of hydration in lipid-protein interactions in membranes, we explored the organization and dynamics of a 34-mer peptide of the CXCR1 N-terminal domain in reverse micelles by utilizing a combination of fluorescence-based approaches and circular dichroism spectroscopy. Our results show that the secondary structure adopted by the CXCR1 N-domain is critically dependent on hydration. The tryptophan residues of the CXCR1 N-domain experience motional restriction and exhibit red edge excitation shift (REES) upon incorporation in reverse micelles. REES and fluorescence lifetime exhibit reduction with increasing reverse micellar hydration. Time-resolved fluorescence anisotropy measurements reveal the effect of hydration on peptide rotational dynamics. Taken together, these results constitute the first report demonstrating modulation in the organization and dynamics of the N-terminal domain of a chemokine receptor in a membrane-like environment of varying hydration. We envisage that these results are relevant in the context of hydration in the function of G protein-coupled receptors.

Infrared spectroscopy of proteins in reverse micelles

Reverse micelles are a versatile model system for the study of crowded microenvironments containing limited water, such as those found in various tissue spaces or endosomes. They also preclude protein aggregation. Reverse micelles are amenable to study by linear and nonlinear infrared spectroscopies, which have demonstrated that the encapsulation of polypeptides and enzymatically active proteins into reverse micelles leads to conformational changes not seen in bulk solution. The potential value of this model system for understanding the folding and kinetic behavior of polypeptides and proteins in biologically important circumstances warrants increased study of reverse micelle systems by infrared spectroscopy. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.

Do electrospray mass spectra of surfactants mirror their aggregation state in solution?

One important feature in the gas phase chemistry of surfactants is to ascertain whether their aggregates produced by electrospray ionization reflect those formed in the starting solution. With this aim, we have performed ESI-MS, ESI-MS/MS and ER-MS spectra of bis(2-ethylhexyl)sulfosuccinate (AOTNa) solutions in different solvents, i.e. water, water/methanol, methanol and n-hexane. The results clearly indicate that, notwithstanding the strongly different aggregation state in solution (direct micelles in water and in water/methanol, molecular dispersion in methanol and reverse micelles in n-hexane) and marked effects of the solvent polarity on the total ionic current, the surfactant aggregates in gas phase show identical structural features. Analogous conclusions can be drawn analyzing the infrared multiple photon dissociation (IRMPD) spectra of AOTNa solutions in water/methanol and n-hexane. Moreover, according to the idea that gas phase can be considered an apolar environment par excellence, data consistently suggest a reverse micelle-like aggregation. Some peculiarities of the mechanisms leading to aggregate formation through electrospray ionization of surfactant solutions in solvent media with different polarity have been also discussed.

Influence of surfactant structure on reverse micelle size and charge for nonpolar electrophoretic inks

Electrophoretic inks, which are suspensions of colorant particles that are controllably concentrated and dispersed by applied electric fields, are the leading commercial technology for high-quality reflective displays. Extending the state of the art for high-fidelity color in these displays requires improved understanding and control of the colloidal systems. In these inks, reverse micelles in nonpolar media play key roles in media and particle charging. Here we investigate the effect of surfactant structure on reverse micelle size and charging properties by synthesizing different surfactants with variations in polyamine polar head groups. Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) were used to determine the micelle core plus shell size and micelle hydrodynamic radius, respectively. The results from SAXS agreed with DLS and showed that increasing polyamines in the surfactant head increased the micelle size. The hydrodynamic radius was also calculated on the basis of transient current measurements and agreed well with the DLS results. The transient current technique further determined that increasing polyamines increased the charge stabilization capability of the micelles and that an analogous commercial surfactant OLOA 11000 made for a lower concentration of charge-generating ions in solution. Formulating magenta inks with the various surfactants showed that the absence of amine in the surfactant head was detrimental to particle stabilization and device performance.

The CdCl2 effects on synthetic DNAs encaged in the nanodomains of a cationic water-in-oil microemulsion

The present work is dedicated to the study of the interactions of CdCl(2) with the synthetic polynucleotides polyAT and polyGC confined in the nanoscopic aqueous compartment of the water-in-oil microemulsion CTAB/pentanol/hexane/water, with the goal to mimic in vitro the situation met by the nucleic acids in vivo. In biological structures, in fact, very long strings of nucleic acids are segregated into very small compartments having a radius exceedingly smaller than the length of the encapsulated macromolecule. For comparison, the behaviour of polyGC was also studied in aqueous solutions of matched composition. The conformational and thermal stabilities of both polynucleotides enclosed in the inner compartment of the microemulsion are scarcely affected by the presence of CdCl(2), whereas in solution immediate and large effects were observed also at room temperature. The lack of effects of CdCl(2) on the properties of the biopolymers entrapped in the aqueous core of the microemulsion has been attributed to the peculiar characteristics of the medium (low dielectric constant, in particular) which cause a total repression of the CdCl(2) dissociation that is not complete even in water. In fact, several of the numerous effects of CdCl(2) observed on the conformational stability of polyGC in aqueous solutions have also been ascribed to the limited dissociation of the cadmium salt.

Molecular assembly-assisted biocatalytic reactions in ionic liquids

Room temperature ionic liquids (RTILs), having no measurable vapor pressure, represent an interesting class of tunable designer solvents. Due to their many unique properties, ILs have been used as attractive alternatives to environmentally harmful ordinary organic solvents in a wide range of applications including enzymatic biotransformation. Compared to conventional organic solvents, ILs offer many advantages for biocatalysis such as enhanced conversion rates, high enantioselectivity, better enzyme stability, and improved catalyst recoverability and recyclability. However, biocatalysis in ILs has not yet fully achieved its potential because many biocatalysts are insoluble in most ILs. This limitation could be overcome by the formation of nano/micrometer-sized aqueous microemulsion droplets in an IL continuous phase (referred to as water-in-IL microemulsions) stabilized by a layer of surfactants. Enzymes can be dissolved in such water droplets and protected from the unfavorable effect of ILs by the surfactant layer. In this chapter, a simple and effective method for the development of aqueous microemulsion droplets in a hydrophobic IL comprising an anionic surfactant sodium bis(2-ethyl-1-hexyl) sulfosuccinate (AOT) is presented. For this approach, we have synthesized a hydrophobic IL [C(8)mim][Tf(2)N] (1-octyl-3-methyl imidazolium bis(trifluoromethyl sulfonyl) amide) containing a long pendant hydrocarbon chain to facilitate the dissolution of AOT molecules. A detailed description of the procedure for the potential use of this newly developed water-in-IL reverse microemulsion for biocatalysis is also included.

Esterification reactions catalyzed by lipases in microemulsions: the role of enzyme localization in relation to its selectivity

The activity of lipases from Rhizopus delemar, Rhizopus arrhizus, and Penicillium simplicissimum entrapped in microemulsions formulated by bis-(2-ethylhexyl)sulfo-succinate sodium salt (AOT) in isooctane has been studied in esterification reactions of various aliphatic alcohols with fatty acids. The effect of the nature of the fatty acids (chain length) and of the alcohols (primary, secondary, or tertiary; chain length; cyclic structures) on the lipase activities was investigated in relation to the reverse micellar structure. The lipases tested showed a selectivity regarding the structure of the substrates used when hosted in the AOT/isooctane microemulsion systems. Penicillium simplicissimum lipase showed higher reaction rates in the esterification of long chain alcohols as well as secondary alcohols. Primary alcohols had a low reaction rate and tertiary a very slow rate of esterification. Long chain fatty acids were better catalyzed as compared to the shorter ones. Rhizopus delemar and R. arrhizus lipases showed a preference for the esterification of short chain primary alcohols, while the secondary alcohols had a low rate of esterification and the tertiary ones could not be converted. The reaction of medium chain length fatty acids was also better catalyzed than in the case of the long ones. The observed lipase selectivity appeared to be related to the localization of the enzyme molecule within the micellar microstructure due to the hydrophobic/hydrophilic character of the protein. The reverse micellar structural characteristics, as well as the localization of the enzyme, were examined by fluorescence quenching measurements and spectroscopical studies.

Activation and stabilization of enzymes in ionic liquids

As environmentally benign "green" solvents, room temperature ionic liquids (ILs) have been used as solvents or (co)solvents in biocatalytic reactions and processes for a decade. The technological utility of enzymes can be enhanced greatly by their use in ionic liquids (ILs) rather than in conventional organic solvents or in their natural aqueous reaction media. In fact, the combination of green properties and unique tailor-made physicochemical properties make ILs excellent non-aqueous solvents for enzymatic catalysis with numerous advantages over other solvents, including high conversion rates, high selectivity, better enzyme stability, as well as better recoverability and recyclability. However, in many cases, particularly in hydrophilic ILs, enzymes show relative instability and/or lower activity compared with conventional solvents. To improve the enzyme activity as well as stability in ILs, various attempts have been made by modifying the form of the enzymes. Examples are enzyme immobilization onto support materials via adsorption or multipoint attachment, lyophilization in the presence of stabilizing agents, chemical modification with stabilizing agents, formation of cross-linked enzyme aggregates, pretreatment with polar organic solvents or enzymes combined with suitable surfactants to form microemulsions. The use of these enzyme preparations in ILs can dramatically increase the solvent tolerance, enhance activity as well as stability, and improve enantioselectivity. This perspective highlights a number of pronounced strategies being used successfully for activation and stabilization of enzymes in non-aqueous ILs media. This review is not intended to be comprehensive, but rather to present a general overview of the potential approaches to activate enzymes for diverse enzymatic processes and biotransformations in ILs.

Formation and stabilization of G-quadruplex in nanosized water pools

We demonstrate here that G-quadruplex structure can form and exhibits strong stability in nanosized water pools, providing new insight into investigating G-quadruplexes in the cellular environment.

Esterification reactions of lipase in reverse micelles

The activities of lipase from Candida cylindracea and Rhizopus delemar have been investigated in water/AOT/iso-octane reverse micellar media through the use of two esterification reactions: fatty acid-alcohol esterification and glyceride synthesis. Such media promotes the occurrence of these two lipase-catalyzed reactions due to its low water content. The effect of various parameters on the activity of lipase from C. cylindracea in reverse micelles was determined and compared to results where alternate media were employed. It was observed that the structure of the media, as dictated by the type and concentration of the substrates and products and by the water/AOT ratio, w(0), had a strong impact on enzyme activity. Strong deactivation of both typase types occurred in reverse micelles, especially in the absence of substrates and for w(0) values greater than 3.0. Glyceride synthesis was realized with lipase from R. delemar, but not with that from C. cylindracea; the temperature and concentration of substrates and water strongly dictated the reaction rate and the percent conversion.