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Several extraction methods are used to isolate natural compounds, and recent approaches utilize subcritical or supercritical extraction media. In this paper we compare extraction methods based on subcritical eluents, dimethyl ether (sC-DME) and n-butane (sC-nB), under mild conditions, using coffee beans and powder as an exemplary raw material. The parameters to be controlled to improve the extraction are considered, and the resulting data discussed. The results obtained display higher selectivity of sC-DME for caffeine (1.9%w/w sC-DME vs. 1.7%w/w sC-nB, on dry extract) and a good yield (0.479 mg/g of caffeine from green coffee beans) compared to, e.g., supercritical carbon dioxide (SC-CO2), which shows 0.32 mg/g of caffeine at higher pressure and temperature (25 MPa, 40 °C). We also discuss some technical implementations for optimizing the use of sub-critical eluents through proper combinations of pressure and temperature. We show that extraction processes based on sub-critical eluents are easy to operate and efficient, and can be easily automated.

Deoxydehydration (DODH) reaction of glycerol (GL) and 1,2-propanediol (1,2-PD), in ionic liquids (ILs), catalyzed by methyltrioxorhenium (MTO) and Re

A low-cost Transition Temperature Mixture (TTM) has been synthesized by mixing ethylene glycol and potassium hydroxide as a new non-aqueous CO2 sorbent. Boric acid has been added to ensure the reversibility of the system and a small amount of water to modulate the viscosity and optimize the performances. The resulting mixtures have been characterized in terms of viscosity, conductivity and density over temperature (therefore ionicity via Walden plots) and the effect of temperature, pressure and the kinetics of the absorption have been evaluated. Under optimized conditions, the four-component mixture EG/KOH/BA/H2O 3:1:1:3 can absorb 24 gCO2/kgsorbent in 30 minutes at 35°C at 1 atm (59 after 4 h) and 60 gCO2/kgsorbent in 30 minutes at high pressure (10 and 20 atm, 80 gCO2/kgsorbent after 50 min), while the desorption is quantitative after 30 minutes at only 60°C under a gentle N2 flow. The system is robust enough to ensure multiple absorption/desorption cycles.

Gas hydrate formation usually occurs with a certain delay after a system composed of water and a hydrate-forming gas is put under suitable thermodynamic conditions of pressure and temperature. This delay period is called the “induction time”, and because of its large variability within a single experimental setting, hydrate formation is often referred to as a stochastic process. The evaluation of induction times, together with other measurements, is taken as an indication for the efficiency of hydrate inhibitors, and they are usually carried out by simply putting the experimental system under chosen P/T conditions and then waiting for the hydrate to form and measuring the time elapsed. In this paper, we present an improved procedure by which the variability of hydrate induction times can be remarkably reduced, while keeping a good correlation of measured induction times with the respective temperatures as obtained by a constant cooling method. In this procedure, temperatures are lowered by 0.5 °C after ea...

The environmental impact of chemical applications can be reduced by using novel solvents with green properties. In this field, Deep Eutectic Solvents (DESs) are promising liquids thanks to their low toxicity, high eco-compatibility and high easiness and “greenness” of preparation. DESs are mixtures of a hydrogen bond donor molecule (HBD) and a hydrogen bond acceptor molecule (HBA) at the proper molar ratio. In this paper, we present the preparation of novel hydrophobic deep eutectic solvents and the studies of their properties: density, eutectic profiles, ranges of water separation, contamination of the separated phases, extraction capabilities of phenol model polluting molecules, capabilities of extraction at acidic and basic conditions. Interesting results emerged about the role of the components of the DESs because of the use of a properly-chosen set of liquids. Their capabilities were dependent on the nature of the HBD molecule, and in particular on its hydrophobicity. Even the DESs with highly water-soluble HBA showed to be easily separable from water and really efficacious as extracting agents when prepared with hydrophobic HBDs. The results of the extractions of pollutants in acid and basic conditions showed the capability of water separation and extraction efficiency of these mixtures even with water at pH = 2 and pH = 9; therefore, the phenols could interact with these liquids without involvement of any acid/base-type of interactions.

The hydrophilic graphene derivative, graphene oxide (GO), is used to synthesize free-standing GO foils characterized by cross-linked GO sheets with enhanced mechanical properties and no tendency to release GO flakes in aqueous solution. These GO foils do not evidence cytotoxic effects toward dental pulp stem cells (DPSC). Rather, DPSC viability is significantly increased for cells grown on GO foil and SEM analyses evidence the synthesis of a consistent extracellular matrix by DPSCs with respect to cells grown on polystyrene. Gene expression of osteogenic markers and alkaline phosphatase (ALP) activity tests demonstrate DPSC differentiation toward the osteoblastic lineage. Indeed RUNX2, a key transcriptor factor associated with osteogenic differentiation, as well as SP7, responsible for triggering bone matrix mineralization, are significantly augmented after 7 and 14 days of culture on GO foil with respect to the control, respectively, underlying the capability of GO foil to promote a potential faster and better DPSC differentiation with respect to cells grown on polystyrene. This increase of rate differentiation is confirmed by SEM analyses of DPSCs evidencing a consistent extracellular matrix synthesis at the earliest time of culture (i.e., 3 and 14 days).

The search for innovative and green reaction media is a prominent topic in the recent research in chemistry. Deep Eutectic Solvents (DESs) are currently gaining relevance in this field thanks to their unique properties in terms of their “greenness” as well as in terms of their catalytic properties. In this work we developed an efficient protocol for the conjugate aza-Michael addition of amines to 2-vinylpyridine using 14 differently structured acid DESs as both reaction media and catalysts, so preventing the use of other acid additives. The results are influenced by the acidity of the components of the DESs, showing the best results with weak acids in the DESs components, with isolated yields up to 86%. The aza-Michael reaction is a widely used synthetic route for the C–N bond formation in organic synthesis. In particular, the addition of amines to 2-vinylpyridine is used for the realization of pharmaceutically relevant compounds with anticancer, antiarrhythmic, and analgesic properties. Comparing the results with the ones observed in literature for the same reaction, this procedure revealed to be a convenient and efficient method for this relevant transformation.

Hypothesis Clathrate hydrates of hydrogen form at relatively low pressures (e.g., ca. 10 MPa) when a co-former compound is added. In that case, however, the gravimetric amount of stored hydrogen drops to less than 1 wt% from ca. 5.6 wt% without a co-former. Another factor hindering the entrapment of hydrogen into a clathrate matrix appears to be of a kinetic origin, in that the mass transfer of hydrogen into clathrates is limited by the macroscopic scale of the gas–water interfaces involved in their formation. Thus, the enhanced formation of binary (hydrogen + co-former) hydrates would represent a major achievement in the attempt to exploit those materials as a convenient means for storing hydrogen. Experiments Here, we present a simple process for the enhanced formation of binary hydrates of hydrogen and several co-formers, which is based on the use of reverse micelles for reducing the size of hydrate-forming gas–water interfaces down to tens of nanometers. This reduction of particle size allowed us to reduce the kinetic hindrance to hydrate formation. Findings The present process was able to (i) enhance the kinetics of the formation process; and (ii) assist clathrate formation when using water-insoluble coformers (e.g., cyclopentane, tetrahydrothiophene).

The ability of some zwitterionic natural deep eutectic solvents (NADESs) based on N,N,N-trimethylglycine (TMG) and carboxylic acids (oxalic, glycolic and phenylacetic) to act as environmentally friendly solvents for CO2 capture has been investigated. The solubility of CO2 in the NADESs was measured gravimetrically at different temperatures in the range 298.15–333.15 K, and at different pressures in the range 0.1–4 MPa. The effect of the adopted experimental conditions has been discussed. The highest uptake has been observed for phenylacetic acid/TMG DES at 313.15 K and 4 MPa (45.5 mg CO2/g DES). The efficiency of this NADES as CO2 sorbent when reused in subsequent capture cycles has been evaluated. This work might open new perspectives in developing the most appropriate combination of HBA and HBD components of the DESs and the most appropriate operative conditions for an environmentally friendly CO2 capture.

Two calix[4]resorcinarenes, which differ in the length of the alkyl chain on the methylene bridge between the aromatic rings, have been embedded in unilamellar liposomes prepared from 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine in three host/guest ratios, following two different procedures. The effect of the insertion of the guests has been evaluated through the measurements of the viscosity and the kinetic stability of the liposomal systems by means of the fluorescent probes pyrene and 5(6)-carboxyfluorescein. The presence of the guests reduces the viscosity of the liposomes, suggesting a modification of the bilayer structure. However, this does not affect liposome stability. A calix[4]resorcinarene cavitand with a more rigid conformation compared to the parent resorcinarene, has been also synthetized and embedded in liposomes. The free energy of the insertion of the substrates in the lipid bilayer has been evaluated through Molecular Dynamics simulations.

Pegylated (PEG) surfactants are widely used for material and biomedical applications. Their use, however, is limited by the radical-mediated oxidation of the OCH2 moieties by atmospheric oxygen, that produces unwanted and toxic products such as hydroperoxides. We show herein that cardanols, natural alkylphenols byproducts of cashew nut processing, are able to form stable co-micellar systems with a model PEG-containing surfactant (Triton X-100, i.e. p-tert-octylphenoxy polyethylene-glycol ether) and display antioxidant activity toward PEG degradation by O2. The cardanols investigated were 6-tert-butyl-3-pentadecylphenol and 4-hydroxy-6-tert-butyl-3-pentadecylphenol. The ability of cardanols to form co-micelles with Triton X-100 was investigated by determining the critical micelle concentration (CMC), the microviscosity, the polarity and the aggregation number. The antioxidant activity of cardanol derivatives in dispersed systems of Triton X-100 was evaluated by studying the reaction with DPPH radical and the protecting activity toward the peroxidation of the polyethylene-glycol tails. The obtained activity of cardanol derivatives was similar or better than that of commercial synthetic antioxidants BHT (2,6-di-tert-butyl-4-methylphenol) and DTBQ (2,5-di-tert-butylhydroquinone), taken as reference, under the same conditions. This study enlightens the ability of hydrogenated cardanol derivatives to act as radical-trapping agents and/or as protective co-surfactants toward the oxidative degradation PEG-coated nanoaggregates used in food and drug science.

Deoxydehydration (DODH) reaction on 1,2-propanediol (1,2-PD) catalyzed by rhenium, conducted in 2,4-dimethyl-3-pentanol (DMP) or in neat 1,2-PD, was carried out. The experimental apparatus was planned to recover separately all the reaction products: in one reaction vessel, the gaseous propene was collected while all the other reaction products, above all regarding the transformation of 1,2-PD, were collected in another reaction vessel. The most common commercial high oxidation state rhenium compounds, methytrioxorhenium (MTO), ReO3, Re2O7 and NH4ReO4, were selected as catalysts. Among them, MTO and Re2O7 gave the best performance in terms of propene production even if ReO3 showed a moderate yield of another reaction product, the acetal formed by coupling of 1,2-PD and 1-hydroxypropanone, that can be considered an innovative strategy to make value over the 50% of the diol.

Biologically active prenyoxyphenylpropanoids are well known to be biosynthesized by Citrus species, for which they have been found most abundantly in fruit peels. Although several extraction methodologies have been described, the development of novel and alternative extraction processes is a field of research of current interest. In this preliminary communication, we studied the performance of the subcritical butane promoted extraction of selected oxyprenylated phenylpropanoids from grapefruit peels under a counter-current mode using a handmade extraction apparatus coupled to UHPLC analysis. The application of such a method yielded 7-isopentenyloxycoumarin, auraptene, and boropinic acid in quantities higher than those recorded for other extraction methodologies like the ultrasound- and microwave-assisted macerations (0.234, 1.035, and 0.211 mg/g of dry extract respectively). The use of subcritical butane as the extraction solvent for oxyprenylated phenylpropanoids is reported herein for the first time and can be easily adopted for several other food matrices.

Plants belonging to Artemisia spp. are known to biosynthesize a wide panel of 3,3-dimethylallyl- and sesquiterpenyl- substituted coumarins. In this short communication we applied a novel extraction methodology based on the use of subcritical butane under a counter-current mode to further characterize the presence of selected biologically active oxyprenylated phenylpropanoids, namely coumarins and ferulic acid derivatives, in extracts deriving from aerial parts of Artemisia vulgaris L. (commonly known as "common mugwort") (Asteraceae). In the mean time, we assessed the efficiency of the above mentioned extractive methodology with other routes like maceration and ultrasounds and microwaves-based methods using absolute EtOH as the solvents. UHPLC analysis coupled to UV/Vis detection revealed that, among the 5 pure chemical standard assayed, only umbelliprenin (7-farnesyloxycoumarin) was recorded, while boropinic acid, 4'-geranyloxyferulic acid, 7-isopentenyloxycoumarin, and auraptene were not detected. The best extractive yield (0.18 %) was obtained after extaction with subcritical butane. The presence of umbelliprenin in Artemisia plant species has been reported herein for the first time. This coumarin may represent the biosynthetic precursors of sesquiterpenyloxycoumarins with more complex structures typically found in this genus.

The potential application of some novel zwitterionic Natural Deep Eutectic Solvents, NADESs, based on betaine N,N,N-trimethylglycine and carboxylic acids (glycolic, phenylacetic and oxalic acid), has been evaluated in the synthesis of gold nanoparticles (AuNPs). AuNPs have been successfully obtained by reduction of gold(III) chloride trihydrate by ascorbic acid or sodium borohydride as reducing agents, without the use of any surfactant or capping agent. The effect of the different experimental conditions (nature of the reducing agent, temperature) has been discussed. In the NADES composed of trimethylglycine and oxalic acid, no addition of a reductant was needed because AuNPs start to form immediately after the dissolution of the precursor salt. This result may open new perspectives in fine-tuning smart solvent characteristics and developing the most appropriate NADES for an environmentally friendly metal nanoparticle synthesis without using auxiliary chemicals.

Starting from previous evidence on the crucial role of imidazolium ions, long alkyl chains, and aromatic rings in favoring the adsorption of surfactants onto carbon nanotube (CNT) walls, we have synthesized novel gemini surfactants with the aim to optimize and identify a reference structure for CNT dispersants. The efficiency of 1 the novel surfactants has been evaluated, discussed, and compared with already well-investigated dispersants. The good affinity of the surfactants for the CNT sidewalls is highlighted by the presence of resonant van Hove absorption and highly resolved Raman and fluorescence spectra, while the strong hydrophobic interactions and favorable packing between the two alkyl chains of the investigated gemini surfactants and the CNT sidewalls ensure good CNT dispersion. Our results show no selectivity toward specific diameters/chiralities, confirming the twin heads of imidazolium surfactants are pointed toward the bulk water, while the alkyl chains are arranged on the CNT walls, improving water solubility at the expense of potential selectivity.

This paper contains data of water capacity (in terms of w0 = molwater/molsurfactant) in reverse micelles formed by several commercial and non-commercial cationic surfactants in cyclopentane, petroleum ether, and iso-octane. Also reported are hydrodynamic diameters of the respective reverse micelles formed. Tested surfactants were (i) single-chained cationics: cetyl benzyl diethanolammonium bromide (CBDB), cetyl benzyl dimethylammonium bromide (CBMB), cetyl dibutyl ethanolammonium bromide (CDBEB), cetyl cyclohexyl dimethylammonium bromide (CCDB); and (ii) twin-chained cationics: didodecyl dimethylammonium chloride (DDMC), didodecyl diethylammonium bromide (DDEB), didodecyl dipropylammonium bromide (DDPB), didodecyl diethylammonium chloride (DDEC), dodecyl benzyl dimethylammonium bromide (DBDMB). Also reported are sizes of reverse micelles as determined by dynamic light scattering. Keywords: Reverse micelles, Cationic surfactants, Water content, Dynamic light scattering

Hydrogen economy has been suggested as a possible green alternative to produce energy, also in the framework of transport applications. According to the specific transport means, different kinds of materials can be adopted. The choice of the most suitable materials should then be addressed according to a systematic analysis of available data. In this paper, together with the major physical storage technologies typically used for aerospace applications, additional possible candidates are suggested, namely clathrates hydrates and metal-organic frameworks (MOFs). They are chosen according to the specific features that are asked in the aerospace industry, such as high storage capacities, low weight and materials cost, high cyclability and full reversibility. To this scope, a comprehensive database based on a large set of information from literature (containing, for example, details on the synthesis processes, the operating temperatures and pressures, volumetric and gravimetric capacities) has been created, and specific tools have been developed to query the database. Indeed, the selection of the materials has been performed via an alternative database approach where the queries can be managed using a user-friendly tool, and potential materials can be selected based on any pool of desirable properties in quantitative terms. Essential information and characterization on theoretical and experimental data about these performing materials are provided and commented. As an example, in this paper, the case of clathrates hydrates is shown, and their potential impact is explored and characterized in this context, suggesting the most suitable synthesis processes.

Surfactants are amphiphilic molecules active at the surface/interface and able to self-assemble. Because of these properties, surfactants have been extensively used as detergents, emulsifiers, foaming agents, and wetting agents. New perspectives have been opened by the exploitation of surfactants for their capacity to interact as well with simple molecules or surfaces. This feature article gives an overview of significant contributions in the panorama of the current research on surfactants, partly accomplished as well by our research group. We look at several recent applications (e.g., adsorption to graphitic surfaces and interactions with hydrate crystals) with the eye of physical organic chemists. We demonstrate that, from the detailed investigation of the forces involved in the interactions with hydrophobic surfaces, it is possible to optimize the design of the surfactant that is able to form a stable and unbundled carbon nanotube dispersion as well as the best exfoliating agent for graphitic surfaces. By studying the effect of different surfactants on the capacity to favor or disfavor the formation of a gas hydrate, it is possible to highlight the main features that a surfactant should possess in order to be devoted to that specific application.

The critical micelle concentration (cmc) and ionisation degree (α), of micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltripropylammonium bromide (CTPABr) and cetyltripropylammonium chloride (CTPACl) have been measured over a narrow temperature range at 2 degree intervals using electrical conductivity. CTPACl and CTPABr are very soluble in water and were measured in the temperature range 275.15-323.15K. The Krafft temperatures for CTABr and for CTACl are 293.15K and 284.15K, respectively and established a lower temperature limit for our studies on these two surfactants. The cmc vs temperature curves have a smooth minimum near room temperature and α linearly increases with temperature. The changes of cmc and α with temperature are smaller than those associated with the modification of head group size or counterion nature. Using these results, basic thermodynamic quantities associated with the phenomena of micellization have been evaluated. Thermodynamic properties of the surfactant solutions were discussed in terms of temperature dependence of the free energy, enthalpy and entropy of micellization. A close similarity between the effects of change in temperature on protein folding and micellization process appears from the data.

The effect of two ammonium salts with a bulky head group, the tetrabutylammonium bromide (TBABr) and the surfactant cetyltributylammonium bromide (CTBABr) on α-chymotrypsin hydrolysis rate toward three peptidyl substrates was investigated. N -Succinyl- l -phenylalanine- p -nitroanilide (SP p NA), N -succinyl- l -alanyl- l -alanyl- l -phenylalanine- p -nitroanilide (SAAP p NA) and N -succinyl- l -alanyl- l -alanyl- l -prolyl- l -phenylalanine- p -nitroanilide (SAAPP p NA), which contain the same chromogenic and N-protecting groups, but a different number of amino acidic residues, were selected. The relative activity showed a bell-shaped dependence on additive concentration, with a maximum which ranged from 1 × 10 −3 M to 5 × 10 −3 M for CTBABr and at 0.3 M for TBABr. Both the additives induced α-chymotrypsin superactivity, but their effect decreased as the peptide chain length of the substrate increased. Analysis of the kinetic parameters indicated that the activation was mainly due to an increase in k cat values, probably caused by enzyme conformational changes induced by the additives, while K M remained almost unchanged. The very notable effect of both CTBABr and TBABr on SP p NA hydrolysis rate and the limited activation with SAAP p NA and SAAPP p NA could be probably due to non-specific interactions between the additives and the subsites next to the catalytic point within α-chymotrypsin active site, not allowed with the longer amino acidic chain substrates.

With fully micellar bound substrates reactions of OH- with benzoic anhydride, Bz(2)O, and of Br- with methyl naphthalene-2-sulfonate, MeONs, in micellized sulfobetaines are strongly inhibited by NaClO4 which displaces the nucleophilic anions from the micellar pseudophases. Micellar incorporations of ClO4- and Br- are estimated with an ion-selective electrode and by electrophoresis, and partitioning of Br- between water and micelles is related to changes in NMR spectral (79)Br- line widths. Extents of inhibition by ClO4- of these nucleophilic reactions in the micellar pseudophase are related to quantitative displacement of the reactive anions from the micelles by ClO4-. The kinetic data are correlated with physical evidence on the strong interactions between sulfobetaines and ClO4-, which turn sulfobetaine micelles anionic and effectively provoke displacement of OH- and Br-.

Novel hydrogel phases based on positively charged and zwitterionic surfactants, namely, N-[p-(n-dodecyloxybenzyl)]-N,N,N-trimethylammonium bromide (pDOTABr) and p-dodecyloxybenzyldimethylamine oxide (pDOAO), which combine pristine carbon nanotubes (CNTs), were obtained, thus leading to stable dispersions and enhanced cross-linked networks. The composite hydrogel featuring a well-defined nanostructured morphology and an overall positively charged surface was shown to efficiently immobilise a polyanionic and redox-active tetraruthenium-substituted polyoxometalate (Ru4POM) by complementary charge interactions. The resulting hybrid gel has been characterised by electron microscopy techniques, whereas the electrostatic-directed assembly has been monitored by means of fluorescence spectroscopy and ζ-potential tests. This protocol offers a straightforward supramolecular strategy for the design of novel aqueous-based electrocatalytic soft materials, thereby improving the processability of CNTs while tuning their interfacial decoration with multiple catalytic domains. Electrochemical evidence confirms that the activity of the catalyst is preserved within the gel media.

A comparative thermodynamic investigation of the keto-enol interconversion reaction has been performed in several organic solvents and room-temperature ionic liquids (RTILs) to evaluate the role of the solvent and the effect of the ionic composition of RTILs. The tautomeric constant (KT) values at different temperatures have been analyzed in terms of the van't Hoff relationship to give the relevant thermodynamic parameters. The ΔG° values are the results of quite different combinations of the ΔH° and ΔS° values depending on the nature of the solvent. As expected, in conventional solvents, the tautomeric equilibrium is enthalpically disfavored and entropically favored by the increase in solvent polarity. In ionic liquids, the nature of the anion seems to play a primary role in the thermodynamics of the reaction that is endothermic and enthalpically driven in PF6- and TF2N-based RTILs and exothermic but entropically driven in BF4-based RTILs. The cation effect on the thermodynamics of the reaction is more complex and is consistent with a prevalence of the alkyl side chain segregation in the organization of the ILs.

α-Chymotrypsin activity was tested with N-glutaryl-l-phenylalanine p-nitroanilide (GPNA) in aqueous media in the presence of synthetic surfactants, which differ in the flexibility of their bulky head groups. Superactivity can be ascribed to the presence of the tributylammonium residue on the surfactant head group, as in p-octyloxybenzyltributylammonium bromide (pOOTBABr), while in the presence of a more rigid moiety, i.e. a cyclic one, no activation was found. A nonmicellizable quaternary ammonium salt, the tetrabutylammonium bromide (TBABr), which has a head group structure very similar to pOOTBABr, not only induces a remarkable superactivation, at a concentration 80-fold higher than pOOTBABr, but also allows the enzyme to retain a high residual activity for long periods of time. The presence of a lipophilic chain, which by interacting with apolar residues on the enzyme surface, probably penetrates into hydrophobic pockets of the protein and causes a rapid inactivation. In 0.4 m TBABr, a 20-fold increase both in kcat and Km values, with respect to buffer alone, was found. The increase of Km could be attributed either to a true decrease in affinity between enzyme and substrate or alternatively to the presence of TBA+ ions near the catalytic region. They could interact with protein residues around the active site and bind to negatively charged GPNA molecules, lowering the local substrate concentration. Spectroscopic experiments (CD and fluorescence) show minor changes of protein conformation in 0.4 m TBABr, while at 1 m a strong modification of both spectra was observed.

Comparison of reactivities of methyl naphthalene-2-sulfonate, MeONs, and its 6-sulfonate derivative, MeONsS − , toward H 2 O, OH − , and Br − in water and in cationic micelles of cetyl trialkylammonium surfactants, n -C 16 H 33 N + R 3 X − , R=Me, n -Pr, n -Bu, CTA + , CTPA + , CTBA + , X=OH, Br, and CH 3 SO 3 has been investigated. For reactions in water, the introduction of the negative charge accelerates hydrolysis by a factor of ca. 2, but does not affect reactivity of OH − and Br − . For reactions in micelles, the negative charge decreases values of k M for reactions with water, with OH − and Br − by a factor of ca. 2; differences for the two substrates decrease with bulking the surfactant head group for a reaction with Br − but not for a reaction with OH − .

Reactivities of methyl naphthalene-2-sulfonate, MeONs, and its 6-alkyl derivatives, alkyl=Me, n-C(6)H(13) and n-C(12)H(25), 6-Me-MeONs, 6-Hex-MeONs, and 6-Do-MeONs, respectively, are compared for reactions in cetyl trialkylammonium bromide micelles, n-C(16)H(33)NR(3)Br, R=Me, Et, n-Pr, n-Bu, CTABr, CTEABr, CTPABr, CTBABr, respectively. Similar experiments were made on reactions of Br(-) with n-butyl and n-decyl naphthalene-2-sulfonates, BuONs, and DeONs, respectively. Reactions with OH(-) were followed in cetyl trialkylammonium hydroxide, alkyl=Me, Et, n-Pr, CTAOH, CTEAOH, and CTPAOH, solubility permitting. Some reactions with OH(-) or Br(-) were also followed in mixed-ion systems of CTAOMs or CTPAOMs (OMs=MeSO(3)). Micellar rate effects were analyzed by using pseudophase treatments including interionic competition in mixed-ion systems. Second-order rate constants in the micellar pseudophase increase systematically with increases in substrate hydrophobicity and for reactions with Br(-), but not OH(-), they also increase with bulk of the cationic head group. Copyright 2001 Academic Press.

Substituent effects on the reaction of H2O, OH−, and Br− with p-substituted methyl benzenesulfonates in cationic micelles of cetyl trialkylammonium ion surfactants (n-C16H33NR3X, X = OH, Br, R = Me, Et, nPr, nBu) and in water were analyzed by using the Hammett equation. Values of ρ in the various media confirm that micellar interfacial regions are less polar than water and polarities decrease with increasing bulk of the surfactant head-group.

The interaction of surfactants with proteins in aqueous solutions has been the subject of many investigations to understand the interactions between membrane proteins and lipids, structurally similar to synthetic surfactants. The effect of surfactant on enzyme structure and activity is the result of chemically selective interactions that may be influenced both by the enzyme structure and by the chemistry of the surfactant. For many years, surfactants have been considered as non-specific denaturants of proteins, even if in the literature several of them are reported to enhance activity and/or stability of some enzymes: the detergent can interact with the enzyme and cause a conformational change to a more active form and/or stabilize its native folded structure. Although the surfactant head group seems to have a determining role, other structural features of the detergent are also important in influencing the catalytic properties of an enzyme, i.e. head group size and its hydrophobic/hydrophilic balance. Up to now it is very difficult to predict the molecular features of the surfactant and an extensive investigation on the relationship between the surfactant chemical structure and the catalytic properties of enzyme is still required.

Decarboxylation of 6-nitro-5-alkoxybenzisoxazole-3-carboxylate ion (1,OMe and 1,OTD, alkoxy = MeO, n-C14H29O, respectively) is accelerated by cationic micelles of cetyltrialkylammonium bromide (CTABr, CTEABr, CTPABr, CTBABr, alkyl = Me, Et, n-Pr, n-Bu respectively). The first-order rate constants kobs for reaction of 1,OMe increase monotonically with [surfactant] and become constant when the substrate is fully bound and kobs = k‘M. The values of kobs for 1,OTD increase sharply with increasing [surfactant] and reach well-defined maxima at [surfactant] at or below the cmc, before decreasing to values corresponding to kobs = k‘M. The magnitude of the rate maxima and the increase in k‘M are in the sequence CTABr < CTEABr < CTPABr < CTBABr. The rate maxima are due to formation of premicellar complexes of substrate with one or a few surfactant monomers, but they “dissolve” in micelles at higher [surfactant]. A rationalization is provided for acceleration by very dilute surfactants.

The SN2 reaction of Br- with methylnaphthalene-2-sulfonate (MeONs) in water is accelerated by micelles of tetradecyldialkyl amine oxide (alkyl = methyl, n-propyl) and rates increase sharply in HBr due to increased binding of Br- to the protonated amine oxide. Second-order rate constants at the micellar surface are similar to those at surfaces of trialkylammonium and sulfobetaine micelles. The reaction of OH- with MeONs is weakly inhibited by amine oxide micelles, showing that dispersive, as well as coulombic and charge-dipole, forces play a major role in the association of ions with surfaces of micellar aggregates. Copyright 1999 Academic Press.

Human semen contains membranous vesicles called prostasomes. They are secreted by the prostate gland and contain large amounts of cholesterol, sphingomyelin, and Ca 2+ , Prostasomes enhance the motility of ejaculated spermatozoa and are involved in a number of additional biological functions. No prostasome-like vesicles have been described in horse semen up to now. We have demonstrated the presence of prostasome-like vesicles in the equine semen and characterized them as to size, morphology, and lipid composition; we have found that they are similar to human prostasomes in many respects. We propose that these vesicles might be important for the fecundity of horse semen. This is of interest since the success of artificial insemination is limited by the fact that stallion sperm barely survive cryopreservation.

The spontaneous (SN2) hydrolysis of methyl naphthalene-2-sulfonate (MeONs) in water is inhibited by cationic, anionic and zwitterionic micelles of the following surfactants, CTAOMs, n-C16H33N+Me3MeSO3–; CTPAOMs, n-C16H33N+Pr3MeSO3–; SDS, C12H25OSO3–Na+; SB3-14, n-C14H29N+Me2(CH2)3SO3–;SBBu3-14, n-C14H29N+Bu2(CH2)3SO3–; DMMAO, n-C14H29N+Me2O–; DPMAO, n-C14H29N+Pr2O–. Rate constants, krel, relative to those in water, are in the range 0.55–0.63 for all the cationic and zwitterionic micelles including the protonated amine oxides. The value of krel in anionic micelles of SDS is 0.22, but NaClO4 sharply decreases krel in SB3-14 from 0.56 to 0.15. These rate effects are not related to variations in substrate binding but depend upon interactions of the head groups with the initial and transition states.

In this paper the complete removal of mercury ions from aqueous solutions using hydrophobic ionic liquids in the absence of chelating agents is reported. Several parameters were studied; in particular, the anionic component of ionic liquid, the anion of the metal salt and the nature of the aqueous phase used to dissolve the mercuric salt were varied to understand the transfer mechanism of Hg(II) ions into “classical” imidazolium-based ionic liquid. Results seem to suggest that metal ion partition into 1-octyl-3-methylimidazolium salts involves neutral and/or anionic Hg(II) species and that the rate of the process is strongly dependent on the experimental conditions, such as the working temperature and the nature of the anionic component of the ionic liquid, of the buffer solution and of the counterion of Hg(II). Moreover, addition of inorganic salts, such as NaCl or NaBr, to the aqueous phase increases metal ion extraction rate, with more than 90% of metal ion being transferred into the organic phase within 30 min and total ion removal accomplished in just four hours. Salt effects could even overcome the high viscosity of the ionic liquid and then a simple method for large-scale Hg(II) extraction was developed.

The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities.

Cationic liposomes are studied mainly as nonviral nucleic acid delivery systems and to a lesser extent as carriers/adjuvants of vaccines and as low-molecular-weight drug carriers. It is well established that the performance and the biological activity of liposomes in general are strongly related to their physicochemical properties. We investigated the thermotropic behavior and the size distribution of mixed cationic liposomes formulated with different percentages of 1,2 dimyristoyl-sn-glycero-3-phosphatidylcholine and one of four cationic amphiphiles characterized by a pyrrolidinium headgroup with the aim of achieving a better understanding of how the molecular structure of the cationic amphiphile and its mole percentage affect the physicochemical properties of the liposomes. Multilamellar vesicles and large unilamellar vesicles were studied by differential scanning calorimetry and turbidity, respectively, to characterize the thermotropic behavior and lipid phase, whereas dynamic light scattering was used to determine size distribution. This study shows that subtle modifications in the cationic amphiphile's molecular structure and in liposome composition may have dramatic effects on the organization of the liposome bilayer and hence on the morphological and physicochemical features of the liposomes, thus being highly relevant to the biological features investigated previously.

Room temperature ionic liquids have been currently used in liquid/liquid extraction processes in order to substitute conventional organic solvents. In this paper, a series of chlorinated solvents and 1-alkyl-3-me- thylimidazolium-based ionic liquids were selected to study the extraction efficiency of a lipophilic polya- mine 1,1,7,7-tetraethyl-4-tetradecyldiethylenetriamine (TE14DT) towards the model ion Cu(II) in such dif-ferent media. The effect of temperature on the extraction efficiency was also investigated. The metal ion par-tition was found to be strongly dependent on both the nature of the solvent and on the working temperature. The viscosity of ionic liquids and the water content in ionic liquid were found to affect the extraction effi-ciency of TE14DT. The chemical nature of the cation of ionic liquids, and in particular the alkyl chain length on imidazolium ring, also seemed to be important in determining the efficiency of the extraction process. Finally, preliminary experiments on back-extraction of Cu(II) ions from ionic liquid also revealed interesting hints to the development of a continuous transport process.

Here we describe uridine functionalization in the 5' position, which provides new classes of cationic and nonionic amphiphiles specifically designed as DNA transfection agents. The synthetic procedures developed to obtain the cationic uridine-head surfactants prevented intramolecular cyclization that occurs when uridine is functionalized in this position without using protecting groups in the uracil.

Here we describe uridine functionalization in the 5' position, which provides new classes of cationic and nonionic amphiphiles specifically designed as DNA transfection agents. The synthetic procedures developed to obtain the cationic uridine-head surfactants prevented intramolecular cyclization that occurs when uridine is functionalized in this position without using protecting groups in the uracil.

The interaction of cationic amphiphiles with calf thymus DNA has been investigated by physicochemical techniques (surface tension, conductometry, UV spectroscopy, thermal denaturation) and morphological microscopies (AFM and TEM). The cationic molecules were the amphiphiles cetyltrimethylammonium and cetyltributylammonium bromides (CTAB and CTBAB, respectively), compared to the nonamphiphilic tetramethyl- and tetrabutylammonium bromides (TMAB and TBAB, respectively) and, as a transfection-efficient comparison, a commercial poliethyleneimine (PEI). As a result, well below their critical micelle concentrations (cmc), CTAB and CTBAB showed a peculiar, nonlinear adsorption profile with the nucleic acid, which showed a correlation with the melting temperatures and morphological changes observed with AFM and TEM microscopies. On the other hand, TMAB and TBAB interact much less with the DNA duplexes and do not induce any modifications of the structures. The same behavior was observed with PEI; however, CTAB and CTBAB proved much less effective in condensing the nucleic acid.

The aggregates of three new isomeric chiral bola-amphiphiles have been taken into consideration as models for investigating chiral recognition in biological membranes. The recognition capabilities of the aggregates were explored following (by CD and HPLC experiments) the shift in the equilibrium between the inter-converting enantiomers of a biphenylic derivative and bilirubin, used as markers of chirality. The chiral recognition experiments were performed under different pH and concentration conditions. The results were compared with those relative to the aggregates formed by an equimolar mixture of single head/single chain amphiphiles that mimic the structure of the bola surfactant devoid of a covalent link.