Hydrophobic Carboxylic Acid Research Articles

A green extraction process for the selective recovery of Sc(iii) based on hydrophobic betaine derivative ionic liquids.

The efficient extraction recovery of scandium (Sc(iii)) is crucial for its application in high-end technology. Two novel hydrophobic carboxylic acid ionic liquids (ILs), namely, [lauryl betaine][bis(trifluoromethanesulphonyl)imide] ([Laur][Tf2N]) and [cocamidopropyl betaine][bis(trifluoromethanesulphonyl)imide] ([Coca][Tf2N]), were synthesized using two inexpensive amphoteric surfactants as cation sources. [Laur][Tf2N] (257 °C) and [Coca][Tf2N] (251 °C) exhibited good thermal stability and strong hydrophobicity. The viscosity of [Coca][Tf2N] (4.29 × 103 mP s) was higher than that of [Laur][Tf2N] (2.55 × 103 mPa s) at 25 °C. The optimal extraction conditions were an extraction equilibrium time of 40 min, an initial Sc(iii) concentration of 0.001 mol L-1, a sodium nitrate concentration of 0.5 mol L-1, and a pH of 3. The extraction efficiency of [Laur][Tf2N] and [Coca][Tf2N] could even exceed 98.7% and 96.0%, respectively. The cation exchange extraction mechanism was studied by slope analysis, IR spectroscopy and 13C NMR spectroscopy. Sc(iii) extracted using [Laur][Tf2N] and [Coca][Tf2N] could be completely stripped with 0.1 mol L-1 and 0.2 mol L-1 HNO3 once, respectively. The structure of the ILs was not broken after stripping, and the extraction efficiency of the ILs remained almost unchanged after five cycles. In addition, the extraction differences at different pH levels made it possible to separate Sc(iii) from other rare earths using ionic liquids [Laur][Tf2N] and [Coca][Tf2N].

Crossing the Solubility Rubicon: 15-Crown-5 Facilitates the Preparation of Water-Soluble Sulfo-NHS Esters in Organic Solvents.

The Sulfo-NHS ester is a mainstay reagent for facilitating amide bond formation between carboxylic acids and amine functionalities in water. However, the preparation of Sulfo-NHS esters currently requires hydrophobic carboxylic acids, which are poorly water-soluble, to first be reacted with the N-hydroxysulfosuccinimide sodium salt, which is insoluble in organic solvents. The mutually incompatible solvation requirements thus complicate the synthesis of Sulfo-NHS esters. As a simple, rapid, and cost-effective solution to this problem, we report that the use of 15-crown-5 to complex the sodium cation of N-hydroxysulfosuccinimide sodium salt circumnavigates these solvation incompatibility issues by rendering the N-hydroxysulfosuccinimide salt soluble in organic solvents, resulting in a cleaner esterification reaction and thus improved yields of activated ester product. We also demonstrate that the resultant "crowned" Sulfo-NHS-ester remains water-soluble and is no less reactive than its classic "uncrowned" Sulfo-NHS counterpart when used in bioconjugation reactions between protein amine-functionalities and hydrophobic carboxylic acids.

Automated Liquid–Liquid Microextraction of Fluoroquinolones for Their Subsequent Chromatographic Determination

An automated method is developed for dispersive liquid–liquid microextraction of fluoroquinolone antibiotics based on the principles of stepwise injection analysis. The method involves the dispersion of the extractant by the gas phase, formed in situ in the extraction chamber of the flow analyzer. A deep eutectic solvent based on a terpenoid and a mixture of hydrophilic and hydrophobic carboxylic acids is studied as an extractant for the isolation and preconcentration of fluoroquinolones, and a possibility of its use is substantiated. Hydrophilic carboxylic acid in the composition of the extractant acts as a proton donor for the formation of a carbon dioxide dispersant in the presence of sodium carbonate dissolved in the aqueous phase. A possibility of combining the developed method with high-performance liquid chromatography with fluorimetric detection is shown on an example of the determination of fluoroquinolones in wastewaters. The limits of detection (3σ) for ofloxacin, fleroxacin, and norfloxacin were 0.3 µg/L.

Применение катионного красителя пиронина G (Y) для количественного экстракционно-фотометрического определения высших карбоновых кислот в рыбе

The relevance of this study is due to the need to develop methods for the extraction and quantitative determination of higher carboxylic acids in fish. In this work, we propose a simple, inexpensive, and highly sensitive extraction-photometric technique for the selective determination of the total content of fatty acids. This technique is selective and is based on the quantitative extraction into the organic phase of ionic associates of the cationic dye pyronin G (Y) with highly hydrophobic carboxylic acids and seems promising for the quantitative determination of the fatty carboxylic acids in fish. Considerable attention is paid to the sample preparation, which is the most important stage of analysis, since the work is carried out with a natural sample that has a complex composition. The technique has been tested on real objects, also using this technique, a directly proportional dependence of the concentration of higher carboxylic acids in fish on the storage time has been obtained. It has been established that the heptane/iso-propanol system is the most effective for the extraction of higher carboxylic acids. The limit of detection of higher carboxylic acids by the extraction-photometric method using the cationic dye pyronin G(Y) in fish is 4,4 10-7 M. The results obtained allow us to state that the developed method can be used to determine the freshness of fish.

Standard-Free Quantification of Dicarboxylic Acids: Case Studies with Salt-Rich Effluents and Serum.

The present study evaluates the ionization efficiency (IE) of linear and branched C2-C14 dicarboxylic acids (DCAs) by electrospray ionization (ESI) under different conditions. The influence of the concentration of organic modifier (MeOH); mobile phase additive; and its concentration, pH, and DCA structure on IE values is studied using flow injection analysis. The IE values of DCAs increase with the increase of MeOH concentration but also decrease with an increase of pH. The former is due to the increase in solvent evaporation rates; the latter is caused by an ion-pairing between the diacid and the cation (ammonium), which is confirmed by the study with different amines. The investigation of DCA ionization in the presence of different acidic mobile phase additives showed that a significant improvement in the (-)ESI responses of analytes was achieved in the presence of weak hydrophobic carboxylic acids, such as butyric or propanoic acid. Conversely, the use of strong carboxylic acids, such as trichloroacetic acid, was found to cause signal suppression. The results of the IE studies were used to develop the liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method that provided instrumental limits of detection in the range from 6 to 180 pg. Furthermore, upon applying the nonparametric Gaussian process, a model for the prediction of IE values was developed, which contains the number of carbons in the molecule and MeOH concentration as model parameters. As a case study, dicarboxylic acids are quantified in salt-rich effluent and blood serum samples using the developed LC-HRMS method.

Beyond hydrophilic polymers in amphiphilic polymer-based self-assembled NanoCarriers: Small hydrophilic carboxylate-capped disulfide drug delivery system and its multifunctionality and multispatial targetability

Due to increasing safety and intracellular delivery concerns about hydrophilic polymers in amphiphilic polymer-based nanoparticles (NPs), this study investigates small hydrophilic molecule-stabilized NPs for effective intracellular delivery with multiorganelle targetability and dual responsiveness to acidic pH/glutathione (GSH). In the construction of small hydrophilic molecule-stabilized NP (MSPCL-NP), the A-B-A-type amphiphilic polymer (MSPCL-P) is composed of two short hydrophilic carboxylate-capped disulfide derivatives (A) that replace hydrophilic polymers and assist in providing colloidal stability and preventing antibody (e.g., at least anti-PEG antibody)-mediated specific interactions and complement activation in the plasma and a hydrophobic multiple disulfide-containing poly(ε-caprolactone) block (B) that carries hydrophobic drugs. The carboxylates on the surface of MSPCL-NP target the acidic extratumoral/endolysosomal milieu by sensing and buffering acidic pH values, and the hydrophobic carboxylic acids improve adsorptive endocytosis and effective endosomal escape. Multiple disulfide linkages selectively target cytosolic GSH, resulting in rapid drug release from the destroyed MSPCL-NP via the cleavage of disulfide bonds in MSPCL-P. Doxorubicin (DOX)-loaded NP (DOX@MSPCL-NP) exerts strong effects on killing cells in vitro and inhibits tumor growth in HCT116 xenograft tumor-bearing mice. In conclusion, the multifunctionality and multispatial targetability of MSPCL-NP might effectively overcome various sequential drug delivery hurdles, ranging from blood circulation to drug release. Furthermore, the introduction of small hydrophilic molecules represents a potential strategy to make self-assembled NPs without the use of hydrophilic polymers.

Extraction of butanol and acetonitrile from aqueous solution using carboxylic acid based deep eutectic solvents

The performance of three hydrophobic carboxylic acid based Deep Eutectic Solvents were evaluated for the extraction of 1-butanol and acetonitrile from aqueous solution. To do so, the phase diagrams of five ternary systems {[DL-menthol: lauric acid] + water + 1-butanol}, {[DL-menthol: capric acid] + water + 1-butanol}, {[DL-menthol: capric acid] + water + acetonitrile}, {[TBAMBr:capric acid] + water + 1-butanol} and {[TBAMBr: capric acid] + water + acetonitrile were measured at 298.15 K at atmospheric pressure. Liquid-liquid equilibria data were used to determine distribution coefficient (β) and selectivity (S) of the solvents. It was found that DL-menthol based DESs are of interest for the extraction of 1-butanol and acetonitrile. NRTL and UNIQUAC models provide a good representation of the phase diagrams measured in this work. COSMO-RS enables to predict phase diagrams of systems containing DL-menthol based Deep Eutectic Solvents with good accuracy.

Hydrophobic carboxylic acid based deep eutectic solvent for the removal of diclofenac

In the current study, carboxylic acid-based deep eutectic solvent including a hydrogen bond donor (acetic acid) and a hydrogen bond acceptor (menthol) has been synthesized and applied for the removal of diclofenac from its aqueous medium. Physical properties (acidity, density, viscosity, and refractive index) of the synthesized liquids were determined quantitatively. The designed deep eutectic solvent was also characterized by Fourier transform infrared spectroscopy method. The removal of diclofenac has been reached to ≈ 80% through the proposed solvent system of reactive liquid extraction. Initial DIC concentration (9.87, 20.29, 29.44, 38.83, and 48.28 mg L−1), deep eutectic solvent level (0, 20, 40, 60, and 80%) in diethyl succinate, and the temperature (293.15, 303.15, 313.15, and 323.15 K) have affected the extraction efficiency. Ionic concentration in extraction medium leads to drop the diclofenac removal. Effects of fluorine and chlorine on the removal of diclofenac have been also investigated. Thermodynamics of the diclofenac transfer from aqueous environment to organic phase containing deep eutectic solvent has been found to be a spontaneous and endothermic process, which is incentivized by entropy.

Preparation and thermal properties of soluble polysilsesquioxanes containing hydrophobic side-chain groups and their hybridization with organic polymers

In this study, a series of soluble polysilsesquioxanes (PSQs) containing hydrophobic side-chain groups (PSQ-Ph, PSQ-CyC6, PSQ-C6, and PSQ-C11) were prepared by the facile reaction of a ladder-like PSQ containing ammonium groups with the corresponding hydrophobic carboxylic acid chlorides (i.e., benzoyl, cyclohexanecarbonyl, heptanoyl, and dodecanoyl chlorides, respectively) in the presence of triethylamine in a mixed solvent of water and N,N-dimethylformamide. The resulting hydrophobic PSQs were soluble in chloroform. The weight-average molecular weights of the hydrophobic PSQs estimated by gel permeation chromatography with chloroform as the eluent and polystyrene standards ranged from 1.92 × 104 to 6.49 × 104. The pyrolysis temperatures of PSQ-Ph estimated by thermogravimetric analyses were relatively high (Td5 = 391 °C and Td10 = 425 °C) due to the presence of the thermally stable phenyl side-chain groups and SiOSi main-chain. Moreover, hybrid films of the hydrophobic PSQs and two organic polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), were prepared by drying the chloroform solutions of the mixtures of these polymers. The PMMA/PSQ-C6, PMMA/PSQ-C11, and PS/PSQ-Ph hybrids were highly transparent. For PS/PSQ-Ph hybrid films, the thermal stability increased with increasing amount of PSQ-Ph.

Amphiphilic calixresorcinarene associates as effective solubilizing agents for hydrophobic organic acids: construction of nano-aggregates.

Here we represent the first example of the formation of mixed nanoscale associates, constructed from amphiphilic calixresorcinarenes and hydrophobic carboxylic acids including drugs. The amidoamino-calixresorcinarene self-associates effectively solubilize hydrophobic carboxylic acids - drugs such as naproxen, ibuprofen, ursodeoxycholic acid and aliphatic dodecanoic acid - with the formation of the mixed aggregates with the macrocycle/substrate stoichiometry from 1/1 to 1/7. The ionization of organic acids and the peripheral nitrogen atoms of the macrocycles with the subsequent inclusion of hydrophobic acids into the macrocycle self-associates is the driving force of solubilization. In some cases, this leads to the co-assembly of the macrocycle polydisperse associates into supramolecular monodisperse nanoparticles with the diameter of about 100 nm. The efficiency of drug loading into the nanoparticles is up to 45% and depends on the structure of organic acid. The dissociation of the mixed aggregates and release of organic acid are attained by decreasing pH.

Using the Polymeric Ouzo Effect for the Preparation of Polysaccharide-Based Nanoparticles

The polymeric ouzo effect, a nanoprecipitation process, is used for the preparation of polysaccharide-based nanoparticles. Dextran, pullulan, and starch were esterified with hydrophobic carboxylic acid anhydrides to obtain hydrophobic polysaccharides, which are insoluble in water. The additional introduction of methacroyl residues offers the possibility to cross-link the generated nanostructures, which become insoluble in organic solvents. To make use of the ouzo effect for the formation of nanoparticles, the polymer has to be soluble in an organic solvent, which is miscible with water. Here, acetone and THF were used. Immediately after the organic polymer solution is added to water, nanoparticles are generated. The size of the nanoparticles can be adjusted between 50 and 200 nm by changing the concentration of the initial polysaccharide solution. The degree of hydrophobic substitution was shown to have a very minor effect on the particle size. Dispersions with solids contents of up to 2% were obtained. Furthermore, the mechanical properties of the nanoparticles were investigated with force microscopy, and it was shown by fluorescence correlation spectroscopy that a fluorescent dye could be encapsulated in the nanoparticles by the applied nanoprecipitation procedure.

Polyelectrolyte Capsules with Tunable Shell Behavior Fabricated by the Simple Layer-by-Layer Technique for the Control of the Release and Reactivity of Small Guests

A novel simple protocol for the layer-by-layer coating of uncharged organic substrates (hydrophobic carboxylic acid esters, CAEs) and control of their loading/release behavior has been developed. The approach involves the preliminary treatment of CAEs with the cationic surfactant cetyltrimethylammonium bromide followed by poly(acrylic acid)/polyethyleneimine alternate deposition. The basic hydrolysis of the substrates is used to spectrophotometrically control the loading/release behavior through monitoring the absorbency of the reaction product p-nitrophenolate ion. Unlike the reactivity of free CAEs, highly sensitive to the solution pH, and the presence of micellar catalysts, the reaction rate of the loaded substrates is unaffected by reaction conditions and can be administered by the capsule design (numbers of deposition cycles, adjusted pH, ultrasonication). The developed protocol makes it possible to omit the use of the sacrificial template and stages of its removal. Capsules corresponding to the biorelevant size criterion, with diameter of ≤200 nm, are obtained. They can be successfully applied for sustaining the dosage of different specimens with the desirable rate and for the control of the guest reactivity by tuning the shell permeability.

Use of bacteria for rapid, pH-neutral, hydrolysis of the model hydrophobic carboxylic acid ester p-nitrophenyl picolinate

Caulobacter crescentus, Escherichia coli and Bacillus subtilis cultures promote the hydrolysis of the model ester p-nitrophenyl picolinate (PNPP) at neutral pH with high efficiency. Hydrolysis is related to cell concentration, while the interaction of PNPP with both bacterial cells and their extracellular molecules is required for a maximum rate of PNPP hydrolysis in C. crescentus cultures. Furthermore, C. crescentus cultures hydrolyse PNPP at concentrations useful in synthetic chemistry.

Voltammetry of Diffusing 2 nm Iridium Oxide Nanoparticles

The pH-dependent solution voltammetry (pH 1–13) of phosphate-stabilized, small (2 nm diameter) iridium oxide nanoparticles (IrIVOx NPs) is described and compared with that of (flocculated) films of the same size nanoparticles on electrodes. The IrIVOx NPs show waves with one electron/one proton formal potential dependency for the IrV/IV redox transformation and (below pH 6) for the IrIV/III reaction. Above pH 6, the IrIV/III reaction becomes a one-electron/two-proton process, unlike the one-electron/one-proton reactivity of the nanoparticles in films. The change is associated with surface oxide acid–base sites having pKA = 6 for solution phase nanoparticles that apparently are inactivated by the flocculation chemistry. Spectral isosbestic points are observed over the pH range of 5–8 for the dissolved nanoparticles. Controlled potential coulometry demonstrates that all of the Ir sites, throughout the nanoparticle, undergo the IrIV/III redox transformation. Whereas the IrIVOx NPs are stabilized at different pH values by phosphate ligation, the associated equilibria are somewhat sluggish, as indicated by small spectral differences for equi-pH nanoparticle solutions mixed with phosphate by different procedures. The IrIVOx NPs can also be capped with hydrophobic carboxylic acids, which allows extraction into nonpolar solvents such as CH2Cl2.

“Carboxylatation” coating on zinc: A chemical conversion in organized molecular systems containing carboxylic acid

Chemical conversion coatings on zinc surface based on hydrophobic carboxylic acid were developed and studied in this work. The long carbon chain carboxylic acid as heptanoic acid was solubilized or dispersed in different organized molecular systems (OMS) with the help of surfactant (Brij® 58, C 16E 20, HLB = 15.8). In a first step, the phase diagram Brij®58/HC 7/water was established at 20 °C to determine the different one-phase or several phase domains, such as microemulsion, liquid crystal and emulsion. Several techniques were employed to characterize the phases and the localisation of the carboxylic acid in the OMS phase. Then the coatings, named “carboxylatation”, were performed on galvanized steels in the OMS bath containing an oxidizing agent. After the degreasing and etching steps, the zinc substrate is oxidized into Zn 2+ cations which precipitate in zinc carboxylate crystals. Coating morphology and composition were characterized by SEM and XRD. Then, stationary electrochemical techniques and climatic chamber tests was used to characterize the protective properties of the different coatings. The results show that the stability of the OMS is necessary to assure a good “solubilization” or dispersion of heptanoic acid in water. Nevertheless, carboxylic acid should be easily liberated from the OMS to react on the surface. In our case, the best choice is the use of a milky “pure” emulsion that is thermodynamically unstable, but sufficiently stable in time to assure a good dispersion and an easy transport and liberation of carboxylic acid on the zinc surface.

Plant Hormone Receptors Share Destructive Strategy

Gibberellins (GAs) are hydrophobic carboxylic acid molecules that function to regulate plant development. Ueguchi-Tanaka et al. announce the accomplishment of what has been an elusive goal--the identification and characterization of a GA receptor. The authors began with a screen for plants insensitive to the effects of the hormone. One such mutant, gid1 (for gibberellin-insensitive dwarf1) was resistant to GA and appeared to act upstream of known GA signaling intermediates in genetic experiments. Several lines of evidence strongly supported a receptor function for GID1. GID1 bound GA in vitro with micromolar binding affinity, and mutants with reduced biological function had impaired GA binding. GID1 bound to the protein SLR1 in yeast two-hybrid assays in a GA-dependent manner. SLR is a component of GA signaling, a putative transcriptional suppressor whose activity appears to be controlled through ubiquitin-dependent degradation. Finally, transgenic plants overexpressing GID1 showed increased sensitivity to GA. Although the precise signaling mechanism for the GID1 protein, which has sequence similarity to mammalian hormone-sensitive lipases, is not yet clear, it is intriguing that the receptor seems to modulate proteolytic degradation of a negative regulator (SLR1). This mechanism is reminiscent of the mechanism by which auxin, another plant hormone, was recently shown to prompt degradation of a different transcriptional suppressor. Although the auxin receptor and GID1 are structurally distinct, both seem to be modulating targeted destruction of transcriptional regulators by the proteasome. M. Ueguchi-Tanaka, M. Ashikari, M. Nakajima, H. Itoh, E. Katoh, M. Kobayashi, T. Chow, Y. C. Hsing, H. Kitano, I. Yamaguchi, M. Matsuoka, GIBBERELLIN INSENSITIVE DWARF1 encodes a soluble receptor for gibberellin. Nature 437 , 693-698 (2005). [PubMed]

Ion-exclusion chromatographic separations of C 1–C 6 aliphatic carboxylic acids on a sulfonated styrene–divinylbenzene co-polymer resin column with 5-methylhexanoic acid as eluent

The application of C 7 aliphatic carboxylic acids (heptanoic, 2-methylhexanoic, 5-methylhexanoic and 2,2-dimethyl- n-valeric acids) as eluents in ion-exclusion chromatography with conductimetric detection for C 1–C 6 aliphatic carboxylic acids (formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, isocaproic and caproic acids) was carried out using a highly sulfonated styrene–divinylbenzene co-polymer resin (TSKgel SCX) in the H + form as a stationary phase. When using 0.05 m M sulfuric acid at pH 4.0 as the eluent, peak shapes of hydrophobic carboxylic acids (isovaleric, valeric, isocaproic and caproic acids) were tailed strongly. In contrast, when using 1 m M these C 7 carboxylic acids at pH ca. 4 as the eluents, although system peaks (vacant peaks) corresponding to these C 7 carboxylic acids appeared, peak shapes of these hydrophobic acids were improved drastically. Excellent simultaneous separation and relatively high sensitive conductimetric detection for these C 1–C 6 aliphatic carboxylic acids were achieved in 25 min on the TSKgel SCX column (150×6 mm I.D.) using 1 m M 5-methylhexanoic acid at pH 4.0 as the eluent.

The ionization behavior of retinoic acid in lipid bilayers and in membranes

The ionization behavior of retinoic acid (RA) incorporated in unilamellar vesicles of different lipid compositions and in biological membranes was studied. Titration of RA in the various membranes was followed by monitoring the red shift in the absorption maximum of RA that occurred upon deprotonation. It was found that, similar to other hydrophobic carboxylic acids, the protonated form of RA is stabilized by incorporation into bilayers vs. RA monomers in an aqueous phase. The p K of RA in bilayers comprised of neutral phospholipids was approximately 7 regardless of the composition of the fatty acyl chains. Incorporation of RA in bilayers comprised of negatively charged phospholipids stabilized the protonated form to a larger extent vs. neutral lipids, resulting in p K's that were about 1 pH unit higher the ionization behaviour of RA in plasma membranes from rat liver and in erythrocyte membranes was similar to its behavior in negatively charged bilayers. The data indicate that RA incorporated in membranes is predominantly protonated at physiologic pH.

Peroxisomes and β-Oxidation of Long-Chain Unsaturated Carboxylic Acids

Degradation of unsaturated long-chain carboxylic acids by beta-oxidation, which is a compartmentalized process occurring in both mitochondria and peroxisomes in mammalian cells, was studied using rat liver as a model tissue. Inclusion of (poly)unsaturated fatty acids in the perfusion medium resulted in an increased concentration of catalase-H2O2 complex indicating on-going peroxisomal beta-oxidation. For this to occur, an active peroxisomal delta 3, delta 2-enoyl-CoA isomerase was required for metabolism of the double bonds at odd-numbered positions in acyl-CoA. Experiments with isolated subcellular organelles from rat liver confirmed the presence of isomerase in the peroxisomes, and the enzyme was subsequently isolated with apparent homogeneity. Comparison of amino acid sequences from the enzyme with a published sequence for a bifunctional protein from rat liver identified them representing the same molecule. The peroxisomal bifunctional protein can thus act as a multifunctional hydratase-dehydrogenase-isomerase enzyme. Examination of the mitochondrial isomerase revealed that rat liver mitochondria possess two isoenzymes: a long-chain isomerase not induced by clofibrate-treatment and showing a preference for C10-C12 substrates, and a clofibrate-inducible short-chain isomerase which gave the highest catalytic activity with C6 substrates. Experiments with isolated peroxisomes and unsaturated acyl-CoAs demonstrated that the beta-oxidation of fatty acids having double bonds at even-numbered positions was dependent on 2,4-dienoyl-CoA reductase in peroxisomes, as in mitochondria. Immunocytochemical experiments using the protein A-gold labelling technique, and comparison of their physicochemical properties indicated that all the mammalian reductases purified so far are mitochondrial isoenzymes. It turned out during the isolation of 3-hydroxyacyl-CoA epimerase that there was no monofunctional epimerase at all in the rat liver. Instead, the epimerization reaction occurred via dehydration-hydration catalyzed by two distinct stereospecific hydratases, 2-enoyl-CoA hydratase 1 (the classic hydratase) and 2-enoyl-CoA hydratase 2 (a novel hydratase). The present data demonstrate that peroxisomes contain all the enzymes required for the beta-oxidation of unsaturated fatty acids and support the notion that one of the physiological functions of peroxisomal beta-oxidation is to metabolize long-chain hydrophobic carboxylic acids to shorter, more polar metabolites which are then either metabolized further in the body or excreted.

Studies on Synthetic Ionophores. VIII. Transport of Alkaline Earth Metal Ions by Polyether Carboxylic Acids through Liquid Membrane

Abstract Seven ω-hydroxy carboxylic acids bearing 2–5 ether oxygens with or without aromatic rings and five ω-alkoxy carboxylic acids bearing 2–6 ether oxygens with aromatic rings were employed as carriers for the active transport of alkaline earth metal ions as well as alkali metal ions through 1,2-dichloroethane or 1-hexanol as an organic liquid membrane. The relatively hydrophobic ω-hydroxy and ω-alkoxy carboxylic acids (logP>7) exhibited a high M2+ transport ability and selectivity over M+ through 1,2-dichloroethane, regardless of the number of ether oxygen. However, a marked selectivity among alkaline earth metal ions (Mg2+, Ca2+, Ba2+) was not observed. The less hydrophobic carboxylic acids (logP<6) did not transport Ba2+ through 1,2-dichloroethane. Ba2+ transport ability of the hydrophobic acids through 1-hexanol was lower than that through 1,2-dichloroethane. Linoleic acid in the presence of oligo- and polyethylene glycols showed efficient Ba2+ transport through 1,2-dichloroethane, although a long-chain fatty acid was not able to transport Ba2+ by itself.