Presence Of 2-propanol Research Articles

Stability and effects of organic solvents on endopeptidases from the gastric fluid of the marine crab Cancer pagurus

Activities of proteolytic enzymes, represented by azocasein digestion (total protease), trypsin, and chymotrypsin from the gastric fluid of the marine crab, Cancer pagurus, were evaluated for operational parameters like pH-optimum, thermal stability, and effectors such as metal ions and organic solvents. Total protease activity was 98.5±4.3 Δ E 366 min −1 ml −1. Trypsin and chymotrypsin activities amounted to 14.7±1.5 U ml −1 and 197±59 U ml −1, respectively. The maximum activity of total protease appeared at pH 5–7, that of trypsin at pH 7–9, and that of chymotrypsin at pH 6.5–7. Trypsin and chymotrypsin activities were slightly activated by Ca 2+, but were drastically reduced by Zn 2+. In the presence of 2-propanol, trypsin activity was enhanced 8-fold at 30 °C. Highest amplification of activity of up to 30-fold, however, appeared below 12 °C. The effects of ethanol and acetone were less distinct. These caused a 2.5-fold increase of activity. Methanol was the least activating solvent. Activities of all enzymes remained stable for up to 127 days at 5 °C, keeping up to 70% of the initial activity. When stored at 25 °C for 120 days, total protease decreased to about 40% and trypsin and chymotrypsin activities kept more than 60% of initial activity. Zymograms showed five major and several minor proteolytic bands with apparent molecular weight of 20–45 kDa. After long-term storage at room temperature, the major bands remained active, while some bands with minor activity disappeared. This proteolytic enzyme preparation from the gastric fluid of crab seems suitable for biotechnological application at neutral pH and in the presence of organic solvents.

Photo-catalytic reduction of carbon dioxide to methane using TiO 2 as suspension in water

Photo-catalytic reduction of CO 2 to methane was studied in CO 2-saturated aqueous solution in presence of TiO 2 photo-catalyst (0.1%, w/v) as a suspension using 350 nm light. CO 2 methanation rate was very much enhanced in the presence of 2-propanol as a hole scavenger. In addition to CO 2 reduction, photo-catalytic reduction of methanol in N 2-purged system was also tried but no methane was generated in presence of TiO 2 without 2-propanol. The yield of methane was quite low even in presence of 2-propanol in this system. In the methanol photolysis CO 2 was found to be the main product with a yield of 60×10 −8 mol to 200×10 −8 mol . This shows that the generation of CH 4 from CO 2 does not proceed via methanol as an intermediate under these conditions. In the aerated system also, methane was produced during photolysis of TiO 2 suspension in presence of 2-propanol and its yield was comparable to that in CO 2-saturated system. This suggests that surface-adsorbed as well as in situ generated CO 2 are equally responsible for methane formation through photo-reduction in presence of TiO 2. In the aerated system, 45 μmol CO 2 was produced by photo-degradation of 2-propanol. In O 2-saturated system, the methane yield was lower as compared to that in aerated system whereas CO 2 yield was higher. Overall, the yield of methane was quite high if extrapolated to per gram of TiO 2.

Stereoselective polymerization of rac-lactide using a monoethylaluminum Schiff base complex.

A monoethylaluminum Schiff base complex (2) with formula LAlEt (L = N,N'-(2,2-dimethylpropylene)bis(3,5-di-tert-butylsalicylideneimine) was synthesized and employed for the stereoselective ring-opening polymerization of rac-lactide (rac-LA). The complex 2 was characterized by nuclear magnetic resonance, crystal structure, and elemental analysis. It contains a five-coordinate aluminum atom with distorted trigonal bipyramidal geometry in the solid state. In the presence of 2-propanol, 2 showed high stereoselectivity for the polymerization of rac-LA. The polymerization yielded crystalline poly(rac-LA) with a high melting temperature (193-201 degrees C). NMR, differential scanning calorimetry, and wide-angle X-ray diffraction indicated that the poly(rac-LA) was highly isotactic, and a stereocomplex was formed between poly-l- and poly-d-lactide block sequences. By the analysis of electrospray-ionization mass spectrometry and (1)H NMR, the polymer was demonstrated to be endcapped in both terminals with an isopropyl ester and a hydroxy group, respectively. The polymerization was of first order in rac-LA concentration. The relationship between the rac-LA conversion and molecular weights of the polymer was linear so that the polymerization could be well controlled.

ON THE REDUCTION OF 4-OXO-4H-BENZOPYRAN-3-CARBALDEHYDES: GLOBAL AND LOCAL ELECTROPHILICITY PATTERNS‡

The theoretical global and local electrophilicity patterns of substituted and chelated 4-oxo-4H-benzopyran-3-carbaldehydes (formylchromones) have been evaluated using the electrophilicity index proposed by Parr et al [J. Am. Chem. Soc. 1999, 121, 1922]. The complexation of formylchromones with aluminum predicts a strong electrophilic character of these compounds against nucleophiles. Local response at the active sites may also be assessed in terms of a global contribution described by the global electrophilicity, and a local contribution described by the variations in electrophilic Fukui function at those sites. The highest local electrophilicity is found at the formyl group of the chelated formylchromones, in spite of that, the highest positive charge is located on the pyrone carbonyl group. This result is consistent with the experimental observed reactivity displayed by 4-oxo-4H-benzopyran-3-carbaldehydes in the presence of 2-propanol and alumina

Sperminium bis(tri-tert-butoxysilanethiolate)–2-propanol (1/2)

The title compound, C10H28N42+·2C12H27O3SSi−·2C3H8O, has been obtained by the reaction of (tBuO)3SiSH with spermine in the presence of 2-propanol. The sperminium cation sits on an inversion centre at the mid-point of the central C—C bond. The three species are linked together in infinite chains, mainly by N—H⋯S hydrogen bonds.

Polymerization of ε-Caprolactone Initiated by Y Alkoxide Grafted onto Porous Silica

Ring-opening polymerization of ε-caprolactone has been initiated by Y isopropoxide grafted onto silica, in the presence of 2-propanol, in toluene at 40 °C. The degree of polymerization is controlled by the initial monomer/(alcohol + alkoxide) molar ratio. Deactivation of the chains by an alcohol is essential for them to be detached from the support and to be collected totally free of metal and silica residues. The alkoxide is also regenerated at the surface of the support, which allows for recycling the catalyst.

Photolysis experiments on phosmet, an organophosphorus insecticide.

The organophosphorus insecticide phosmet is used in plant protection as well as against parasites on animals. Phosmet showed numerous photoinduced reaction pathways, which first were studied in the presence of model environments for animal fur lipids (e.g., wool wax). The model solvents for saturated and unsaturated lipids were cyclohexane and cyclohexene, whereas methanol and 2-propanol were used as models for primary and secondary alcohol moieties of lipids. The measured degradation rates over an irradiation period of 7 h in all solvents used were very similar (49-55%). The obtained photoproducts generally included phthalimide, N-hydroxymethylphthalimide, and N-methoxymethylphthalimide. Furthermore, depending on the solvent used, additional degradation products were detectable as N-isopropoxy- and N-methylphthalimide in the presence of 2-propanol and cyclohexene, respectively. However, in the presence of cyclohexene, despite the similar turnover, distinctly lower concentrations of photoproducts were found, indicating further still unknown degradation pathways. Irradiations in methanol with increasing percentages of water led to higher degradation rates; however, the products were found to be the same. Irradiation experiments with pure phosmet on silica TLC plates and glass surfaces resulted in degradation rates of 19 and 32%, respectively, after 6 h. The results obtained clearly demonstrate for the first time that the photoinduced degradation of phosmet is strongly dependent on the chemical environment, affecting less the turnover than the photoproducts formed. The results additionally demonstrate the need to investigate the degradation behavior of phosmet on wool and in the presence of wool wax.

Enantiomer Separation of D‐L Branched Amino Acids by Capillary Electrophoresis in Sport Nutritional Supplements

ABSTRACTA capillary electrophoresis method was developed for the chiral separation of D‐L valine, isoleucine, and leucine. The separation of derivatized amino acids with 9‐fluorenylmethyl‐chloroformate was performed by micellar electrokinetic capillary chromatography. We optimized the method by varying β‐cyclodextrin and sodium dodecyl sulphate concentrations in the presence of 2‐propanol. The proposed method was applied to the determination of D‐forms of valine, Isoleucine, and leucine in the presence of an excess of relative L forms, in commercial supplements for sport nutrition. Results demonstrated that the separation of enantiomers was possible up to an enantiomeric ratio of 1:100. The analysis of selected products confirmed the enantiomeric purity of utilized amino acids.

Characterization of Methyl tert-Butyl Ether-Degrading Bacteria from a Gasoline-Contaminated Aquifer

Molecular microbial community analysis was combined with traditional cultivation strategies to investigate the presence of methyl tert-butyl ether (MTBE)-degrading bacteria in a gasoline-contaminated aquifer (Ronan, MT). A bacterial consortium, RS24, which is capable of complete mineralization of MTBE as a sole carbon and energy source was enriched from soil and aquifer materials taken from the contaminated site. The consortium was capable of degrading MTBE at rates up to 0.66 mg d−1, with corresponding gross biomass yields of 0.25±0.02 mg dry biomass (mg MTBE)−1. Two MTBE-degrading isolates identified as Pseudomonas Ant9 and Rhodococcus koreensis were obtained from the consortium. However, both isolates required the presence of 2-propanol as a cosubstrate for MTBE degradation. Denaturing gradient gel electrophoresis (DGGE) of Poly-merase Chain Reaction (PCR)-amplified 16S rDNA confirmed the presence of both isolates in the initial consortium and indicated their disappearance with transfer and subculturing. MTBE degradation and cell growth by the consortium was stimulated by the presence of spent culture medium, suggesting the production of a growth factor during MTBE degradation. These results indicate the presence of naturally occurring MTBE-degrading bacteria in a contaminated aquifer and suggest the potential for natural attenuation or enhanced aerobic oxidation.

Reactions of 2,2‘-Methylenebis(4-chloro-6-isopropyl-3-methylphenol) with Trimethylaluminum: Highly Efficient Catalysts for the Ring-Opening Polymerization of Lactones

The reaction of 2,2‘-methylenebis(4-chloro-6-isopropyl-3-methylphenol) (MCIMP-H2) with 1.2 molar equiv of AlMe3 in THF yields [(MCIMP)AlMe(THF)] (1), which further reacts with a stoichiometric amount of 2-propanol (IPA), affording the isopropoxy-bridged dimer [(MCIMP)Al(μ-OiPr)]2 (2). Compound 2 can also be obtained by the treatment of MCIMP-H2 with a stoichiometric amount of Al(OiPr)3 in refluxing toluene. However, the reaction of 1 with another 1 equiv of AlMe3 in CH2Cl2 furnishes [Me2Al(μ-MCIMP)AlMe2(THF)] (3), in which the MCIMP2- ligand is acting as a bridging ligand. Further treatment of compound 3 with 2 molar equiv of 2-propanol results in the formation of the isopropoxy-bridged dinuclear aluminum complex [(MCIMP)Al(μ-OiPr)2AlMe2] (4). Compound 4 can be directly obtained from the reaction of 1 with AlMe3 in the presence of 2-propanol. However, in the presence of a stoichiometric amount of H2O, hydrolysis of 1 in THF gives the trimeric aluminum compound [(MCIMP)Al(μ-OH···THF)]3 (5), in which the hy...

Selective reduction of aldehydes via BINOL–Zr complex

An easily assembled catalyst from (±)-BINOL (1,1′-bi-naphthol) and Zr(O i Pr) 4· i PrOH selectively reduces aldehydes at room temperature. Ketones remain intact under these conditions. A catalytic amount of BINOL–Zr complex in the presence of 2-propanol also effectively reduces a variety of chiral and achiral aldehydes.

Crystallization and preliminary crystallographic data of fructose-1,6-bisphosphatase from human muscle

The enzyme human muscle fructose-1,6-bisphosphatase, which plays a critical role in gluconeogenesis, has been crystallized in the presence of 2-propanol, polyethylene glycol and magnesium chloride at pH 7.5. The space group was determined to be P4(2)2(1)2, with unit-cell parameters a = b = 73.57, c = 146.50 A, alpha = beta = lambda = 90 degrees and one subunit in the asymmetric unit. A 99.6% complete data set to 2.04 A has been collected at the National Synchrotron Light Source.

Characterization of Silica Xerogels Surfaces by Inverse Gas Chromatography (IGC)

Abstract Silylated silica xerogels, with controlled specific surface area and porosity, were prepared by a two-step procedure. In the first step, hydrogels were treated “in-situ” with hexamethyldisiloxane (HMDS) in the presence of 2-propanol and acid. In the second step, the hydrophobic gel was transferred into an organic solvent, the residual water removed by azeotropic distillation and the dried xerogel isolated by evaporating the solvent. Using this procedure, structure collapse of the hydrogels was minimized and it was possible to make xerogels with controlled specific surface area and porosity by varying the aging conditions of the hydrogels. The surface properties of both the untreated and the “in-situ” treated silica xerogels were examined by inverse gas chromatography (IGC) at either infinite dilution conditions (IGC-ID) or finite concentration conditions (IGC-FD). The former method was used to monitor the thermodynamic parameters of adsorption of molecular probes in interaction with the sites having the highest energies, while the latter method was used to provide information about the surface energy heterogeneity of the whole surface. The results for the xerogels are also compared to those obtained on untreated and silylated fumed silicas. After silylation, a systematical surface energy decrease has been observed at both ID and FD conditions of IGC for the two types of silica. However, the modified xerogels with higher surface coverage than silylated fumed silica show some different behaviors.

Macroporous Cross-Linked Poly(dicyclopentadiene)

This article describes the preparation of macroporous cross-linked poly(dicyclopentadiene) by chemically induced phase separation. Dicyclopentadiene was polymerized and cross-linked by metathesis in the presence of 2-propanol, using a ruthenium-based catalyst, and then dried under vacuum. The resulting porous materials were characterized by SEM, density measurements, and mercury porosimetry. By varying the initial 2-propanol content, it was shown that closed or open cell porosity could be obtained, with narrow pore size distributions and micrometric average access diameters. A linear dependence of the pore volume fraction and the initial 2-propanol content was also observed, suggesting easy tailoring of the former.

Ultrasound-enhanced reactivity of calcium in the reduction of aromatic hydrocarbons

Reductions of aromatic hydrocarbons by calcium in ethylenediamine– n-alkylamine mixture were investigated under ultrasonic conditions. Using an ultrasonic probe, with naphthalene as test molecule, it has been demonstrated that under ultrasonic action the reactions proceed faster (×10) and require a lower metal quantity (0.5) than the reactions conducted with an efficient mechanical stirrer. In addition, at ambient temperature and depending on the specific alcohol addition, selective naphthalene reduction can be performed using ultrasound. 1,2-Dihydronaphthalene (88% yield) results from the reaction in the presence of 2-propanol, and 1,4,5,8-tetrahydronaphthalene (88% yield) is obtained with tert-butanol. Investigation of the metal surface points out the characteristics of the calcium ultrasonic activation. The procedure was efficiently tested with several aromatic hydrocarbons.

Purification and characterization of organic solvent-stable lipase from organic solvent-tolerant Pseudomonas aeruginosa LST-03

An organic solvent-stable lipase (LST-03 lipase) secreted into the culture broth of the organic solvent-tolerant Pseudomonas aeruginosa LST-03 was purified by ion-exchange and hydrophobic interaction chromatography in the presence of 2-propanol. The purified enzyme was homogeneous as determined by SDS-PAGE. The molecular mass of the lipase was estimated to be 27.1 kDa by SDS-PAGE and 36 kDa by gel filtration. The optimum pH and temperature were 6.0 and 37°C. LST-03 lipase was stable at pH 5–8 and below 40°C. Its hydrolytic activity was highest against tricaproin (C6), methyl octanoate (C8), and coconut oil respectively among the triacylglycerols, fatty acid methyl esters, and natural oils investigated. The enzyme cleaved not only the 1,3-positioned ester bonds, but also the 2-positioned ester bond of triolein. It exhibited high levels of activity in the presence of n-decane, n-octane, DMSO, and DMF as well as in the absence of an organic solvent. In addition, LST-03 lipase was stabler in the presence of n-decane, ethyleneglycol, DMSO, n-octane, n-heptane, isooctane, and cyclohexane than in the absence of an organic solvent.

Radiolytic and Thermal Dehalogenation of CFC-113 Adsorbed on Molecular Sieve 13X

Abstract The reductive dehalogenation of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113) has been radiolytically and thermally initiated on molecular sieve 13X. The molecular sieve adsorbing CFC-113 was irradiated with γ-rays or heated, and was then soaked in water. The Cl− and F− concentrations and the pH of the supernatant solutions were measured to follow the dehalogenation reaction. These values for samples irradiated at a dose rate of 7.8 kGy h−1 and heated at 150 °C were almost the same when the irradiation time was twenty-times longer than the heating time. The F− concentration once increased and then decreased with the reaction time, whereas the Cl− concentration increased continuously. The F−, once produced, may be consumed with the denatured molecular sieve. When the molecular sieve adsorbing 2-propanol together with CFC-113 was irradiated, the dechlorination proceeded by a chain reaction, but the defluorination was inhibited. On the other hand, when heated in the presence of 2-propanol, both the dechlorination and the defluorination were largely suppressed. The pH of the supernatant solutions decreased from an alkaline value to a neutral or acidic one along with dehalogenation. Radiolysis of CFC-113 on activated charcoal was also examined, but the dehalogenation rates were much slower than those on the molecular sieve.

Kinetics and Mechanism of the Reactions of Superoxochromium(III) Ion with Biological Thiols

The kinetics of the oxidation of three biological thiols (l-cysteine, glutathione, and dl-penicillamine) to their sulfinic and sulfonic acid derivatives by CrOO2+ in aqueous perchloric acid and in the presence of 2-propanol have been studied spectrophotometrically with the aid of the initial-rates method. The kinetic order of the oxidant is 2, whereas that of the reductant is not defined. The acidity of the medium has a slight effect on the initial rates (acid catalysis for both l-cysteine and dl-penicillamine and base catalysis for glutathione). An increase of the ionic strength leads to a rise of the initial rate for both l-cysteine and dl-penicillamine, whereas the initial rate for glutathione is insensitive to the ionic strength. The reactions are inhibited by both 2-propanol and dissolved O2 and catalyzed by Mn2+, whereas Ce3+ has almost no effect on them. At low 2-propanol concentration and in the absence of Mn2+ the initial rate vs temperature plots have a minimum at around 20 °C, whereas in the presence of either concentrated 2-propanol or Mn2+ the Arrhenius law is fulfilled. A single mechanism is proposed for the three reactions involving a CrOO2+/thiol complex, CrOOH2+, and CrO2+ as intermediates. The bimolecular rate constants for the reactions of the intermediate CrO2+ with l-cysteine and dl-penicillamine at 25.0 °C have been obtained (around 103 M-1 s-1 in both cases). Some kinetic data for the decomposition of CrOO2+ in the absence of thiol are also given.

Synthesis and molecular structure oftrans-2,6-dimethallyl-1,1-dimethyl-1,2,3,6-tetrahydropyridinium iodide

The structure oftrans-2,6-dimethallyl-1,1-dimethyl-1,2,3,6-tetrahydropyridinium iodide was established by X-ray structural analysis. The corresponding base was synthesized by reductive diallylation of pyridine with trimethallylborane in the presence of 2-propanol.

Redox properties of photoexcited [formula omitted] porphyrins composite systems

The photochemical and photocatalytic properties of (nBu 4N) 3PW 12O 40 (PW 12O 3− 40) was investigated in the presence of several Fe III- meso-tetrarylporphyrins. The photochemical excitation of the polyoxotungstate in the presence of 2-propanol or cyclohexane leads to its reduction and simultaneous oxidation of the organic substrate. The reduced polyoxotungstate is able, in turn, to transfer one electron to the Fe III porphyrin to give the ferrous complex. In the presence of anaerobic cyclohexane, σ-alkyl-Fe III complexes are obtained as a consequence of the reaction between cyclohexyl radicals and the iron porphyrin in its reduced form. Subsequent oxidative migration of the σ-bound cyclohexyl group from the iron to one of the pyrrole nitrogens leads to the formation of N-substituted porphyrin. The results obtained by laser flash photolysis experiments indicate that the electron transfer from the photoreduced polyoxotungstate to the Fe III porphyrin complexes is faster than to O 2. Therefore, the photoexcited polyoxotungstate can operate as a source of electrons for the reduction of the Fe III porphyrin to the ferrous form, thus creating the site at which O 2 is reductively activated. Continuous irradiation of the composite systems under aerobic conditions leads to the oxidation of cyclohexane to cyclohexanol and cyclohexanone. In comparison with the Fe III porphyrins alone, the composite photocatalysts present higher yields of the oxidation products. In comparison with PW 12O 3− 40 alone, they produce higher amounts of the hydroxylated product.