Water-miscible Organic Solvents Research Articles

Formation of Colloidal Dispersions of Organic Materials in Aqueous Media by Solvent Shifting

This paper describes the preparation of colloidal dispersions of water-insoluble organic materials by a “solvent-shifting” procedure, in which a concentrated solution of an organic solute in a water-miscible organic solvent is dispersed into a large volume of aqueous (nonsolvent) bulk solution containing colloidal stabilizers. In the majority of cases studied, the solute separates as 0.1−0.5 μm amorphous particles. The particle size is strongly correlated with the local supersaturation, i.e., the ratio of the solute feed concentration to the instantaneous value of the equilibrium solubility in the bulk, and also shows a weak dependence on the solute feed concentration. The results obtained on systematic variation of the precipitation conditions, including the amount of organic solvent in the aqueous phase, the solute feed concentration, and the mixing conditions, are discussed in terms of a mechanism of particle formation comprising dispersion of the feed solution as small droplets, followed by solvent/wa...

Application of selectively acylated glycosides for the alpha-galactosidase-catalyzed synthesis of disaccharides.

4-Nitrophenyl alpha-D-galactopyranosyl-(1-->3)-6-O-acetyl-alpha-D-galactopyranoside was prepared in a transglycosylation reaction catalyzed by alpha-D-galactosidase from Talaromyces flavus using 4-nitrophenyl alpha-D-galactopyranoside as a glycosyl donor and 4-nitrophenyl 6-O-acetyl-alpha-D-galactopyranoside as an acceptor. 4-Nitrophenyl 6-O-acetyl-alpha-D-galactopyranoside and 4-nitrophenyl 6-O-acetyl-beta-D-galactopyranoside were prepared in a regioselective enzymic transesterification in pyridine-acetone catalyzed by the lipase PS from Burkholderia cepacia. A series of water-miscible organic solvents (acetone, acetonitrile, dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 2-methoxyethanol, pyridine, 2-methylpropan-2-ol, tetrahydrofuran, propargyl alcohol) were used as co-solvents in this enzymic reaction. Their influence on the activity and stability of the alpha-galactosidase from T. flavus was established. 2-Methylpropan-2-ol and acetone (increasing the solubility of the modified substrate acceptors and displaying the minimum impairment of the activity and stability of the enzyme) were used as co-solvents in transglycosylation reactions.

Catalytic action of water-miscible organic solvents on the hydrolytic degradation of phosphate glasses

Catalytic action of water-miscible organic solvents on the hydrolytic degradation of phosphate glasses

Spectroscopic and voltammetric studies on the formation of Keggin-type V(V)-substituted tungstoarsenate(V) and -phosphate(V) complexes in aqueous and aqueous-organic solutions

The tetra-n-butylammonium salts of [AsV x W 12− x O 40] (3+ x)− ( x=1–2) were isolated from an acidic aqueous-CH 3CN solution and characterized by elemental analysis, FT-IR, UV–Vis and cyclic voltammetry. The formation conditions of Keggin-type V(V)-substituted tungstoarsenate(V) and -phosphate (V) complexes were elucidated by cyclic voltammetry, Raman spectroscopy, and 31P NMR in aqueous and aqueous-organic solutions. It was found that water-miscible organic solvents such as acetonitrile and acetone, affected the conversion processes of [XW 12O 40] 3− into [XV x W 12− x O 40] (3+ x)− (X=P or As). It was suggested that these results were due to the stabilities of [XW 12O 40] 3− in aqueous and aqueous-organic solution.

Lipase-Catalyzed Synthesis of Precursor Dipeptides of RGD in Aqueous Water-Miscible Organic Solvents

PPL-catalyzed synthesis of the precursor dipeptides of RGD as a cellular adhesion factor, Benzyl-Arg-Gly-NH2 and CBZ-Gly-Asp-NH2, was conducted in water-organic cosolvents systems. Five water-miscible organic solvents, which have some advantage over the water-immiscible organic solvent systems or the anhydrous organic solvent systems used often in protease-catalyzed synthesis of a peptide bond, were tested. The reaction condition of PPL-catalyzed synthesis of the dipeptides was optimized by examining the main factors affecting the product yield. The optimal reaction condition for the synthesis of Benzyl-Arg-Gly-NH2 was set up as pH 8.0, 15°C in 40% MeOH for 10 h with the maximum yield of 73.6%. The optimum condition for the synthesis of CBZ-Gly-Asp-NH2 was pH 7.0, 15°C in 50% MeOH for 10 h with the maximum yield of 67.0%.

DTI-015 Produces Cures in T9 Gliosarcoma

DTI-015 (BCNU in 100% ethanol) utilizes solventfacilitated perfusion for the intratumoral treatment of gliomas. The water-miscible organic solvent vehicle, ethanol, facilitates a rapid and thorough saturation of the tumor with the dissolved anticancer agent, BCNU. Rats bearing established intracranial T9 gliosarcoma tumors received no treatment (group 1), a single intratumoral injection of ethanol vehicle (group 2) or DTI-015 (5 mg/kg BCNU) (group 3), or a single intratumoral injection of DTI-015 followed by systemic BCNU (group 4). Ethanol alone (n=13) had no effect on survival; MST = 17 days compared to 18 days for untreated controls (n=35). DTI-015 (n=45) produced an I LS of 417% (MST = 93) and 472% (MST = 103) when combined with systemic BCNU (n=14). Overall, 24 of 59 rats receiving DTI-015 were judged to be cured, with 20 living a normal life span of 600 to 700 days, and 4 rats sacrificed healthy at 121, 135, 307, and 384 days post DTI-015 with no evidence of viable T9 tumor. Histology demonstrated that DTI-015 totally eradicated the T9 tumors in animals living a normal life span. The results demonstrate that a single injection of DTI-015 produces a 40% cure rate in rats bearing established intracranial T9 tumors.

Effects of the water-miscible organic solvents on lactoperoxidase purified from creek-water buffalo milk.

Water buffalo lactoperoxidase (WBLPO) was purified with Amberlite CG-50 (NH(4)(+) form) resin, CM-Sephadex C-50 ion-exchange chromatography, and Sephadex G-100 gel-filtration chromatography from skimmed buffalo milk. The purity of the WBLPO was shown with SDS-PAGE. The R(z) (A(412)/A(280)) value for the WBLPO was 0.9. The optimum pH for the WBLPO was at 6.0. The K(m) value at optimum pH and 25 degrees C was 0.13 mM. The V(max) value at optimum pH and 25 degrees C was 5.3 micro mol/min per ml. The K(i) values for methanol, ethanol, dimethyl sulfoxide (DMSO), acetonitrile, isopropanol, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and ethylene glycol were 1.087, 0.364, 0.302, 0.459, 0.330, 0.126, 0.093, and 2.125 M, respectively. All the solvents showed competitive inhibition. The I(50) values of methanol, ethanol, dimethyl sulfoxide, acetonitrile, isopropanol, tetrahydrofuran, N,N-dimethylformamide, and ethylene glycol were 2.910, 0.942, 0.537, 1.320, 0.875, 0.470, 0.405, and 3.920 M, respectively. Ethylene glycol, methanol, acetonitrile, and ethanol have been found to be very promising solvents for performing biocatalytic reactions with LPO in organic media.

The use of crude lipase in deprotection of C-terminal protecting groups

A crude lipase, Newlase F, was used to remove C-terminal protecting groups from dipeptide esters. Hydrolysis of dipeptide n-heptyl esters with Newlase F was conducted in aqueous media containing acetonitrile. The optimum pH and temperature of lipase in Newlase F were 7.0 and 30 °C, respectively. Low level acetonitrile promoted the hydrolysis of dipeptide n-heptyl esters, while high level acetonitrile inhibited the hydrolysis. However, the protease activity in Newlase F was significantly inhibited by acetonitrile. Lipase in Newlase F worked better in a medium containing water-miscible organic solvents than in water-immiscible ones. N-terminal protecting groups were not affected by the protease in the crude enzyme. It was found that the protease in Newlase F did not hydrolyze amide bond with hydrophilic amino acids on either side under these conditions (pH 7.0, room temperature). Newlase F may consequently be used widely in the synthesis of peptide conjugates. The crude enzyme was immobilized on SBA-15 mesoporous molecular sieve. The lipase activity of immobilized preparation was more active on hydrolysis of C-terminal protecting groups and stable than the free enzyme. The immobilization also reduced the protease activity.

Extremely stable and versatile carboxylesterase from a hyperthermophilic archaeon.

We have found that the hyperthermophilic archaeon Pyrobaculum calidifontis VA1 produced a thermostable esterase. We isolated and sequenced the esterase gene (est(Pc)) from strain VA1. est(Pc) consisted of 939 bp, corresponding to 313 amino acid residues with a molecular mass of 34,354 Da. As est(Pc) showed significant identity (30%) to mammalian hormone-sensitive lipases (HSLs), esterase of P. calidifontis (Est) could be regarded as a new member of the HSL family. Activity levels of the enzyme were comparable or higher than those of previously reported enzymes not only at high temperature (6,410 U/mg at 90 degrees C), but also at ambient temperature (1,050 U/mg at 30 degrees C). The enzyme displayed extremely high thermostability and was also stable after incubation with various water-miscible organic solvents at a concentration of 80%. The enzyme also exhibited activity in the presence of organic solvents. Est of P. calidifontis showed higher hydrolytic activity towards esters with short to medium chains, with p-nitrophenyl caproate (C(6)) the best substrate among the p-nitrophenyl esters examined. As for the alcoholic moiety, the enzyme displayed esterase activity towards esters with both straight- and branched-chain alcohols. Most surprisingly, we found that this Est enzyme hydrolyzed the tertiary alcohol ester tert-butyl acetate, a feature very rare among previously reported lipolytic enzymes. The extreme stability against heat and organic solvents, along with its activity towards a tertiary alcohol ester, indicates a high potential for the Est of P. calidifontis in future applications.

Improving the carboligase activity of benzoylformate decarboxylase from Pseudomonas putida by a combination of directed evolution and site-directed mutagenesis.

Benzoylformate decarboxylase (BFD) from Pseudomonas putida was subjected to directed molecular evolution to generate mutants with increased carboligase activity which is a side reaction of the enzyme. After a single round of random mutagenesis mutants were isolated which exhibited a 5-fold increased carboligase activity in aqueous buffer compared to the wild-type enzyme with a high enantiomeric excess of the product (S)-2-hydroxy-1-phenyl-propanone. From the same library, mutants with enhanced carboligase activity in water-miscible organic solvents have been isolated. The selected mutants have been characterized by sequencing, revealing that all mutants carry a mutation at Leu476, which is close to the active site but does not directly interact with the active center. BFD-L476Q has a 5-fold higher carboligase activity than the wild-type enzyme. L476 was subjected to saturation mutagenesis yielding eight different mutants with up to 5-fold increased carboligase activity. Surprisingly, all L476 mutants catalyze the formation of 2-hydroxy-1-phenyl-propanone with significantly higher enantioselectivity than the wild-type enzyme although enantioselectivity was not a selection parameter. Leu476 potentially plays the role of a gatekeeper of the active site of BFD, possibly by controlling the release of the product. The biocatalyst could be significantly improved for its side reaction, the C-C bond formation and for application under conditions that are not optimized in nature.

Transient pseudo-isotachophoresis for sample concentration in capillary electrophoresis.

We show that many water miscible organic solvents such as acetonitrile, acetone and small alcohols can function as a terminating ion in transient isotachophoresis, which leads to sample concentration on the capillary. It is suggested that this method could be termed transient "pseudo-isotachophoresis" (pseudo-ITP). Because of their low conductivity, these water miscible organic solvents provide the high field strength necessary for band sharpening similar to that provided by the terminating ion. Salts, when present in such samples act briefly as leading ions, migrating rapidly in the organic solvent until they are slowed at the interface of the separation buffer. When the organic solvents are added to the sample, both the migrations as well as the stacking of the analytes are affected by the concentration of salts (leading ions) in the sample, similar to that observed in isotachophoresis. Our results show that this type of stacking offers good reproducibility and reliability for practical analysis. In practice, pseudo-ITP stacking is much easier to perform compared to that of true ITP with several added practical advantages as discussed.

Polymerization of acrylonitrile initiated by the vanadium(v)-potassium thiocyanate redox system: a kinetic study

Polymerization of acrylonitrile, initiated by the free radicals formed in situ in the vanadium(v)- thiocyanate redox system has been studied in aqueous sulfuric acid and perchloric acid media in the temperature range 28-38degrees. The rate of polymerization (RP) and the rate of vanadium(v) disappearance have been measured. The effects of some water-miscible organic solvents, surfactants and complexing agents on the rate of polymerization are investigated. The temperature dependence of the rate has been studied and the activation parameters are computed. A mechanism consistent with the experimental data is suggested.

Screen-printed electrode based on AChE for the detection of pesticides in presence of organic solvents

A screen-printed biosensor for the detection of pesticides in water miscible organic solvents is described based on the use of p-aminophenyl acetate as acetylcholinesterase substrate. The oxidation of p-aminophenol, product of the enzymatic reaction was monitored at 100 mV vs. Ag/AgCl screen-printed reference electrode. Miscible organic solvents as ethanol and acetonitrile were tested. The acetylcholinesterase (AChE) was immobilised on a screen-printed electrode surface by entrapment in a PVA-SbQ polymer and the catalytic activity of immobilised AChE was studied in the presence of different percentages of organic solvents in buffer solution. The sensor shows good characteristics when experiments were performed in concentrations of organic solvents below 10%. No significant differences were observed when working with 1 and 5% acetonitrile in the reaction media. Detection limits as low as 1.91×10 −8 M paraoxon and 1.24×10 −9 M chlorpyrifos ethyl oxon were obtained when experiments are carried out in 5% acetonitrile.

Degradation of water-insoluble dyes by microperoxidase-11, an effective and stable peroxidative catalyst in hydrophilic organic media.

Microperoxidase-11 (MP-11), a heme-containing undecapeptide, derived from horse heart cytochrome c was utilized as a peroxidative catalyst. Catalytic characteristics of MP-11 in hydrophilic organic media were studied using 2,6-dimethoxyphenol as a reducing substrate in a series of organic solvents at various concentrations, indicating that MP-11 was active in water-miscible organic solvents but at least 5% water was compulsory for the catalytic action. Thus, MP-11 was not active in hydrophobic solvents. The pH of the water portion in the media affected the reaction rate. The optimal pH was found to be 9, where a release of protons from either an oxidizing or reducing substrate to the media was facilitated. The decolorization of water-insoluble synthetic dyes by MP-11 in 90% methanol was attempted. MP-11 showed effective decolorization activities against either azo or anthraquinone dyes. The degradation pathway for Solvent Orange 7 was investigated in detail, showing that MP-11 catalyzed the oxidative cleavage of the azo linkage to generate 1,2-naphthoquinone and 2,4-dimethylphenol as key intermediates.

Lipase-catalyzed synthesis of 6-O-vinylacetyl glucose in acetonitrile

6-O-Vinylacetyl glucose was synthesized with an immobilized lipase using vinylacetic acid and glucose in water-miscible organic solvents, of which acetonitrile gave the highest conversion of 35% at 50 mM glucose and 600 mM vinylacetic acid. The addition of 3A molecular sieves at 60 mg ml−1 increased the conversion to 74%. The product, 6-O-vinylacetyl glucose, was polymerized to yield a water-soluble polymer with a molecular mass of about 5000.

Planar Integrated Optical Waveguide Sensor for Isopropyl Alcohol in Aqueous Media

An attenuated total reflection (ATR) sensor for water-miscible organic solvents was constructed using a combination of sol-gel processing and integrated optical waveguide (IOW) technologies. The sensor consisted of single-mode, sol-gel based planar waveguide coated with a 40 nm thick, porous sol-gel indicator layer prepared from methyltriethoxysilane and doped with methyl red. The response of the senor to aqueous isopropyl alcohol (IPA) was investigated. Solvation of the indicator dye by IPA causes the absorbance spectrum to undergo a blue shift coupled with an increase in molar absorptivity. IPA was detected by measuring changes in ATR of the guided mode at 488 nm. A response curve extending from 1 to 100% (v/v) IPA in water was constructed for the sensor, from which a detection limit of 0.7% (v/v) IPA/water was estimated. Response and reversal times were typically less than one minute, making this sensor potentially attractive for on-line monitoring applications. The rapid response characteristics are attributable to relatively weak, reversible interactions between the indicator and analyte.

Producing high-grade nickel sulfate with solvent displacement crystallization

Solvent displacement crystallization entails the addition of water-miscible organic solvents to aqueous metalliferous solutions to cause salt crystallization. In this work, isopropanol is used to produce well-grown and relatively pure nickel-sulfate hexahydrate crystals from industrial de-copperized electrolyte. By proper selection of the organic-to-aqueous ratio, the method of solvent addition and seeding/product recycling, nickel-sulfate crystals were produced with at least an order of magnitude higher purity than the ones conventionally produced by evaporative crystallization. The processing and product quality advantages of integrating solvent displacement crystallization with electrolyte purification in a copper refinery context are discussed.

An extended Johnson–Furter equation to salting-out phase separation of aqueous solution of water-miscible organic solvents

The Johnson–Furter equation, which correlates the salt effects on relative volatility changes of components in a binary mixture at presence of salt, is extended to salting-out phase separation phenomenon observed in aqueous solutions of some water-miscible organic solvents. The extended equation quantitatively correlates partitions of components of the ternary mixture, namely, the organic solvent, water, and the salt between the salted-out two phases, and is successfully applied to five ternary mixtures including acetonitrile–H 2O–LiCl, –NaCl, –KCl, acetone–H 2O–NaCl, and 2-propanol–H 2O–NaCl where salting-out phase separation occurs. A molecular mechanism of salting-out phase separation as salt-solvent and solvent–solvent interactions is also discussed by using Kirkwood–Buff solution theory.

Determination of phosphorus based on the formation of a reduced keggin-type 12-molybdophosphate complex in an aqueous-organic solution.

A very simple, easy and sensitive spectrophotometric manual determination method of phosphorus for the P04(3-) ion, based on the formation of the reduced 12-molybdophosphate complex, was developed. The effect of the kind of water-miscible organic solvent and the concentration of organic solvent, ascorbic acid and HCl on the formation of the complex was investigated. The optimum determination condition was confirmed based on these results. In an aqueous-CH3CN solution, a P-PO4(3-) of 0.01-20 mg l(-1) could thus be determined. It was noted that the determination range of this study was wider than that of the phosphoantimonylmolybdenum blue method (0.032-1 mg l(-1)). The effect of foreign ions on the absorbance was examined. The P-PO4(3-) in river water and seawater sampled in Kochi was determined by this method. The results were also compared with those of the phosphoantimonylmolybdenum blue method and capillary electrophoresis with an indirect detection method using K2CrO4.

Equilibrium constant for lipase-catalyzed condensation of mannose and lauric acid in water-miscible organic solvents

6- O-Lauroyl mannose was synthesized at 50°C through condensation of mannose and lauric acid using the immobilized lipase Novozym® 435 in four water-miscible organic solvents, acetonitrile, acetone, 2-methyl-2-propanol and 2-methyl-2-butanol, with various water contents. The equilibrium conversion significantly depended both on the kind of solvent and on the initial water content of the solvent. The apparent reaction equilibrium constant for the condensation K C’ which was defined based on the concentrations of substrates and products, also depended on the kind of solvent and could be correlated with the relative dielectric constant of the solvent.