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PubMed1985

Purification and characterization of the secondary alcohol dehydrogenase from propane-utilizing Mycobacterium vaccae strain JOB-5.

Mycobacterium vaccae strain JOB-5 cultured in the presence of propane contained an inducible secondary alcohol dehydrogenase. The enzyme was purified 198-fold using DEAE-cellulose, omega-aminopentyl agarose and NAD-agarose chromatography. The Mr of the enzyme was approximately 136000, with subunits of Mr 37000. The pH optimum for the reaction oxidizing propan-2-ol to propanone was 10-10.5 while the optimum for the reverse reaction was 7.5-8.5. The isoelectric point was 4.9. NAD but not NADP could serve as electron acceptor. The apparent Km values for propan-2-ol and NAD were 4.9 X 10(-5)M and 2.8 X 10(-4)M, respectively. The enzyme was inhibited by thiol reagents and metal chelators. It appears to play an essential role in the metabolism of propane by this bacterium.

Alcohol Oxidoreductases↗
PubMed2003

Characterization of the initial reactions during the cometabolic oxidation of methyl tert-butyl ether by propane-grown Mycobacterium vaccae JOB5.

The initial reactions in the cometabolic oxidation of the gasoline oxygenate, methyl tert-butyl ether (MTBE), by Mycobacterium vaccae JOB5 have been characterized. Two products, tert-butyl formate (TBF) and tert-butyl alcohol (TBA), rapidly accumulated extracellularly when propane-grown cells were incubated with MTBE. Lower rates of TBF and TBA production from MTBE were also observed with cells grown on 1- or 2-propanol, while neither product was generated from MTBE by cells grown on casein-yeast extract-dextrose broth. Kinetic studies with propane-grown cells demonstrated that TBF is the dominant (> or = 80%) initial product of MTBE oxidation and that TBA accumulates from further biotic and abiotic hydrolysis of TBF. Our results suggest that the biotic hydrolysis of TBF is catalyzed by a heat-stable esterase with activity toward several other tert-butyl esters. Propane-grown cells also oxidized TBA, but no further oxidation products were detected. Like the oxidation of MTBE, TBA oxidation was fully inhibited by acetylene, an inactivator of short-chain alkane monooxygenase in M. vaccae JOB5. Oxidation of both MTBE and TBA was also inhibited by propane (K(i) = 3.3 to 4.4 microM). Values for K(s) of 1.36 and 1.18 mM and for V(max) of 24.4 and 10.4 nmol min(-1) mg of protein(-1) were derived for MTBE and TBA, respectively. We conclude that the initial steps in the pathway of MTBE oxidation by M. vaccae JOB5 involve two reactions catalyzed by the same monooxygenase (MTBE and TBA oxidation) that are temporally separated by an esterase-catalyzed hydrolysis of TBF to TBA. These results that suggest the initial reactions in MTBE oxidation by M. vaccae JOB5 are the same as those that we have previously characterized in gaseous alkane-utilizing fungi.

Biodegradation, Environmental↗
PubMed2003

Propane oxidation and steam reforming over Pd/LaFe(0.8) Co(0.2) O3 catalyst: effects of the reactant composition and steam.

The effects of reactant composition and steam on propane combustion over Pd/LaFe(0.8) Co(0.2) O3 catalyst were investigated. Propane conversion and the oxidation state of palladium were strongly affected by the redox ratio of reactants. Higher propane conversion could be obtained under rich conditions and explained as a complex balance between oxidation and steam reforming. Water produced in the oxidation could promote the propane conversion by steam reforming. However, the presence excess steam would bring about inhibition.

Catalysis↗
PubMed1986

[Method of producing cooled liquid propane in a histochemistry laboratory].

A simple and inexpensive method of gaseous propane liquefaction is proposed using the facilities of a histochemical laboratory. The method is based on the principle of propane condensation. Propane has a higher liquefaction temperature than liquid nitrogen used as a cooling agent. The method advocated provides production in 5-7 minutes of 15-20 ml of liquid cooled propane by the evaporation of about 100 ml of liquid nitrogen.

Histocytochemistry↗
PubMed1980

A death involving asphyxiation from propane inhalation.

A death involving asphyxiation by propane inhalation is reported. The presence of propane was determined in blood, brain, kidney, liver, and lung by gas chromatography. Autopsy samples were heated in hot water, and headspace samples from various specimens were injected into the gas chromatograph. The identity of propane was established on the basis of the retention times. The brain of the deceased showed the highest level of propane, whereas the kidney exhibited the lowest level.

Adult↗
PubMed2007

The production of (R)-2-hydroxy-1-phenyl-propan-1-one derivatives by benzaldehyde lyase from Pseudomonas fluorescens in a continuously operated membrane reactor.

Benzaldehyde lyase (BAL; E.C. 4.1.2.38) from Pseudomonas fluorescens Biovar I catalyzes the reversible formation of benzoins from aromatic aldehydes, and, moreover, the coupling of aromatic with aliphatic aldehydes yielding derivatives of (R)-2-hydroxy-1-phenyl- propan-1-one (R)-HPPs), which are important chiral building blocks. In this paper, we report on the development of a reactor system that allows the selective production of substituted (R)-HPP-derivatives. The reaction systems yielding (R)-1-(3-chloro-phenyl)-2-hydroxy- propan-1-one, (R)-2-hydroxy-3-methoxy-1-(4-methoxy-phenyl)-propan-1-one, and (R)-2-hydroxy-3,3-dimethoxy-1-phenyl-propan-1-one were investigated. A kinetic model optimized by batch experiments was developed, for the description of both batch and continuously operated reactors. This model was used to describe the HPP production in a continuously operated enzyme membrane reactor. The reactor type used combines the advantages of high conversion and excellent selectivity with high space-time yields and total turnover numbers of up to ttn=43,000. Products were obtained in high yield on a gram scale.

Acetone↗
PubMed1996

Cryopreservation of human skin with propane-1,2-diol.

The tolerance and cryoprotective effect of propane-1,2-diol on human skin was evaluated using tetrazolium reductase enzyme activity to assess tissue viability. The tolerance of human skin was tested by exposing the skin to increasing concentrations of propane-1,2-diol (10, 20, and 40% v/v), at two permeation temperatures (4 degrees C or room temperature), in a stepwise manner, to reduce osmotically induced changes in cell volume. There was no evidence of specific toxicity attributable to the cryoprotectant during the permeation period, even at a concentration of 40%; however a significant decrease in human skin viability was observed after freezing and thawing with high concentrations of cryoprotectant. The only useful protocol was that employing a low cooling rate (-1 degree C min-1) with 10 or 20% (v/v) propane-1,2-diol at a low permeation temperature. The data suggest that propane-1,2-diol does not produced improved results when compared with other cryoprotectants used for skin cryopreservation.

Cryopreservation↗
PubMed2000

A Theoretical Study of the Methyl and Aldehyde Torsion FIR Spectra in Symmetric Propanal Isotopomers.

This paper is an extension of the techniques developed by us [A. Vivier-Bunge, V. H. Uc, and Y. G. Smeyers, J. Chem. Phys. 109, 2279 (1998)] for standard propanal. In that paper the potential energy surface for the simultaneous methyl and asymmetric aldehydic torsions was calculated at RHF/MP2 level using the 6-311(3df,p) basis set for propanal. The fit of the energy values to symmetry-adapted functional forms was carried out by using the 28 energy values which retain the C(3) dynamical symmetry of the methyl group in the optimization procedure. With this potential, as well as with the kinetic parameters and the electric dipole moment variations, the FIR frequencies and intensities for the methyl and aldehyde torsions of seven symmetric isotopomers of propanal were determined theoretically using two-dimensional calculations. The calculated spectra of propanal and three of its isotopomers were compared with the available experimental data. It is found that the calculations for the cis conformer satisfactorily reproduce the aldehyde and methyl torsion spectra and furnish also methyl torsionally excited progressions for the aldehyde torsion modes. The methyl torsion frequencies agree especially well whenever the methyl group is nondeuterated. The small deviations encountered for the deuterated compound are probably due to some mass effect, such as the zero-point vibrational energy correction, which is not taken into account in the present calculations. Finally, the influence of the deuteration on the intensities is discussed. Copyright 2000 Academic Press.

Journal Article↗
PubMed2004

1,3-Propane sultone, an extremely potent experimental carcinogen: what should be expected in humans?

1,3-Propane sultone is directly alkylating, genotoxic and carcinogenic. In rats, it induces local and systemic tumours at multiple target sites. Preponderant systemic tumours occur at the central nervous system, especially gliomas. Other localisations include the mammary gland, the intestine, the haematopoietic system and the kidneys. In the German chemical industry, 1,3-propane sultone had been manufactured and used in limited amounts in the 1950s and 1960s, and for a very few purposes until the 1970s. The number of persons in contact with the compound is unknown but was limited. The medical history of some cases could be traced. As cerebral gliomas are the main systemic tumours induced by 1,3-propane sultone experimentally, the occurrence of a glioblastoma among previously exposed persons appears conspicuous. Three intestinal malignancies were recorded among the cases observed. Also noteworthy is one case of a duodenal carcinoma, normally a rare human malignancy. Two haematopoietic/lymphatic malignancies of different nature have been observed, and there was one case of a renal cell carcinoma. These malignancies observed within a group of persons exposed to 1,3-propane sultone appear surprisingly consistent with the expectations from the available animal studies. The present case studies point to long latency times (up to 30-40 years or more) after limited periods of past exposure.

Brain Neoplasms↗
PubMed2005

A study of the surface region of the Mo-V-Te-O catalysts for propane oxidation to acrylic acid.

The bulk mixed Mo-V-Te oxides possess high activity and selectivity in propane oxidation to acrylic acid and represent well-defined model catalysts for studies of the surface molecular structure-activity/selectivity relationships in this selective oxidation reaction. The elemental compositions, metal oxidation states, and catalytic functions of V, Mo, and Te in the surface region of the model Mo-V-Te-O system were examined employing low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS). This study indicated that the surfaces of these catalysts are terminated with a monolayer, which possesses a different elemental composition from that of the bulk. The rates of propane consumption and formation of propylene and acrylic acid depended on the topmost surface V concentration, whereas no dependence of these reaction rates on either the surface Mo or Te concentrations was observed. These findings suggested that the bulk Mo-V-Te-O structure may function as a support for the unique active and selective surface monolayer in propane oxidation to acrylic acid. The results of this study have important practical consequences for the development of improved selective oxidation catalysts by introducing surface metal oxide components to form new surface active V-O-M sites for propane oxidation to acrylic acid.

Journal Article↗
PubMed2005

In situ reactivity and FTIR study of the wet and dry photooxidation of propane on anatase TiO2.

The photocatalytic oxidation (PCO) of trace amounts of propane (500 ppm) on nanocrystalline anatase TiO2 has been investigated in situ as a function of temperature (T = 318-473 K), humidity (C(H2O) = 0-4%), and time by means of mass spectrometry and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Propane adsorbs associatively on TiO2 at 318 K in dry air, while at 473 K small amounts of thermal dissociation products appear on the surface. In agreement with previous studies, propane is found primarily to be converted to acetone by reactions with photogenerated oxygen radicals. Various successive reaction paths exist, where the branching depends on the temperature and hydroxylation state of the surface. Under dry conditions at 318 K, acetone oxidation is initially kinetically hindered, while, above 400 K, acetone readily decomposes. The thermally assisted reaction channel leads to detrimental bonding of surface species and inhibition of the catalytic activity. It is manifested by a coloration of the sample and suggested to be coupled to surface reduction. Under humidified conditions, there is an optimum of the PCO in C(H2O) and T space, which is estimated to correspond to an equilibrium coverage of one monolayer of H2O (or bilayer). The latter reaction condition also corresponds to sustained high propane conversion and is characterized by rapid establishment of steady state rates. The optimum PCO is discussed in terms of a balance between (i) sustaining enough of a photoactive water monolayer to avoid detrimental bonding of surface species, (ii) allowing reactants to adsorb and access bulk TiO2 photoexcitations, and at the same time (iii) maximizing the thermally assisted decomposition of intermediates.

Journal Article↗
PubMed2006

Quantum chemical study of mechanisms for oxidative dehydrogenation of propane on vanadium oxide.

We have carried out a hybrid density functional study of mechanisms for oxidative dehydrogenation of propane on the (010) surface of V2O5. The surface was modeled using both vanadium oxide clusters and a periodic slab. We have investigated a Mars-van Krevelen mechanism that involves stepwise adsorption of the propane at an oxygen site followed by desorption of a water molecule and propene, and subsequent adsorption of an oxygen molecule to complete the catalytic cycle. The potential energy surface is found to have large barriers, which are lowered somewhat when the possibility of a triplet state is considered. The barriers for propane adsorption and propene elimination are 45-60 kcal/mol. The highest energy on the potential energy surface at the B3LYP/6-31G* level of theory is about 80 kcal/mol above the energy of the reactants and corresponds to formation of an oxygen vacancy after water elimination. Subsequent addition of an oxygen molecule to fill the vacancy is predicted to be energetically downhill. The reactions of propane at a bridging oxygen site and at a vanadyl site have similar energetics. The key results of the cluster calculations are confirmed by periodic calculations. Factors that may lower the barriers on the potential energy surface, including the interaction of vanadium oxide clusters with a support material and a concerted reaction with O2, are discussed.

Journal Article↗
PubMed2006

Enthalpies of formation, bond dissociation energies, and molecular structures of the n-aldehydes (acetaldehyde, propanal, butanal, pentanal, hexanal, and heptanal) and their radicals.

Aldehydes are important intermediates and products in a variety of combustion and gas-phase oxidation processes, such as in low-temperature combustion, in the atmosphere, and in interstellar media. Despite their importance, the enthalpies of formation and bond dissociation energies (BDEs) for the aldehydes are not accurately known. We have determined enthalpies of formation for acetaldehyde, propanal, and butanal from thermodynamic cycles, using experimentally measured reaction and formation enthalpies. All enthalpy values used for reference molecules and reactions were first verified to be accurate to within around 1 kcal mol-1 using high-level ab initio calculations. Enthalpies of formation were found to be -39.72 +/- 0.16 kcal mol-1 for acetaldehyde, -45.18 +/- 1.1 kcal mol-1 for propanal, and -49.27 +/- 0.16 kcal mol-1 for butanal. Enthalpies of formation for these three aldehydes, as well as for pentanal, hexanal, and heptanal, were calculated using the G3, G3B3, and CBS-APNO theoretical methods, in conjunction with bond-isodesmic work reactions. On the basis of the results of our thermodynamic cycles, theoretical calculations using isodesmic work reactions, and existing experimental measurements, we suggest that the best available formation enthalpies for the aldehydes acetaldehyde, propanal, butanal, pentanal, hexanal, and heptanal are -39.72, -45.18, -50.0, -54.61, -59.37, and -64.2 kcal mol-1, respectively. Our calculations also identify that the literature enthalpy of formation of crotonaldehyde is in error by as much as 1 kcal mol-1, and we suggest a value of -25.1 kcal mol-1, which we calculate using isodesmic work reactions. Bond energies for each of the bonds in the aldehydes up to pentanal were calculated at the CBS-APNO level. Analysis of the BDEs reveals the R-CH(2)CH=O to be the weakest bond in all aldehydes larger than acetaldehyde, due to formation of the resonantly stabilized vinoxy radical (vinyloxy radical/formyl methyl radical). It is proposed that the vinoxy radical as well as the more commonly considered formyl and acetyl radicals are important products of aldehyde combustion and oxidation, and the reaction pathways of the vinoxy, formyl, and acetyl radicals are discussed. Group additivity values for the carbon-oxygen-hydrogen groups common to the aldehydes are also determined. Internal rotor profiles and electrostatic potential surfaces are used to study the dipole induced dipole-dipole interaction in the synperiplanar conformation of propanal. It is proposed that the loss of this dipole-dipole interaction in RC(.-)HCH(2)CH=O radicals causes a ca. 1-2 kcal mol-1 decrease in the aldehyde C-H and C-C bond energies corresponding to RC(.-)HCH(2)CH=O radical formation.

Journal Article↗
PubMed2004

New pi-complexation adsorbents for propane-propylene separation.

New adsorbents were prepared and tested for the separation of propane-propylene mixtures by adsorption. The ordered mesoporous material SBA-15 was used as the starting material for silver-ion deposition for pi-complexation with propylene. Two different loadings of silver were evaluated. Adsorption equilibrium and kinetic measurements of propane and propylene in the matrix (pure SBA-15) and the silver-modified adsorbents were performed at 323, 343, and 373 K. In this temperature range, the selectivity of propylene in one of the materials (Ag/SBA-15 = 0.5) is in the range 13-22 because the amount of propane adsorbed is very small, 0.095 mmol/g of propane versus 1.12 mmol/g of propylene at 100 kPa and 343 K. The diffusivity of both hydrocarbons is not seriously affected by the introduction of silver into the mesoporous structure.

Journal Article↗
PubMed2004

In situ UV-vis-NIR diffuse reflectance and Raman spectroscopy and catalytic activity studies of propane oxidative dehydrogenation over supported CrO3/ZrO2 catalysts.

The molecular structures, oxidation states, and reactivity of 3 and 6% CrO3/ZrO2 catalysts prepared by incipient wetness impregnation were examined under different conditions. The in situ Raman spectroscopic studies under dehydrated conditions reveal that the 3 and 6% CrO3/ZrO2 catalysts possess equal amounts of monochromate and polychromate species. Consequently, monolayer coverage on this ZrO2 support is about 3% CrO3. The 6% CrO3/ZrO2 possesses an additional Raman band due to Cr2O3 crystals corresponding to the remaining 3% CrO3. Furthermore, during reaction conditions the polychromate species is preferentially reduced, the monochromate species are slightly affected, and the Cr2O3 crystals are not affected. The in situ UV-vis-NIR diffuse reflectance spectroscopy results reveal that under steady-state reaction conditions the extent of reduction and edge energy position of surface Cr6+ cations increase with an increase in reduction environment for the 3 and 6% CrO3/ZrO2 samples. Propane oxidative dehydrogenation (ODH) studies reveal that the catalytic activity expressed in moles of propane converted per gram catalyst per second is similar for the two catalysts, which is consistent with equal amounts of molecularly dispersed chromia present. The turnover frequency for the 6% CrO3/ZrO2 catalyst is, however, smaller than that for the 3% CrO3/ZrO2 sample due to the presence of Cr2O3 crystals, which are relatively inactive for propane ODH. For this catalytic system and for the experimental conditions used, propene, CO, and CO2 are primary products. Furthermore, the 33-39% propene selectivity is not affected by the C3H8/O2 ratio for both catalysts. Structure-reactivity studies suggest that the molecularly dispersed species are present in equal amounts in the 3 and 6% CrO3/ZrO2 samples as Cr6+ monochromate and polychromate species are the most effective catalytic active sites taking part in the propane ODH reaction.

Journal Article↗
PubMed1999

Biotransformation and clearance of 3-(phenylamino)propane-1,2-diol, a compound present in samples related to toxic oil syndrome, in C57BL/6 and A/J mice.

In May 1981, a massive food-borne intoxication occurred in Spain. The so-called toxic oil syndrome (TOS) was associated with the consumption of aniline-denatured and refined rapeseed oil that was illegally sold as edible olive oil. Fatty acid anilides and fatty acid derivatives of 3-(phenylamino)propane-1,2-diol were detected in oils and implicated as potential toxic agents and markers of toxic oil batches. Epidemiological evidence points to 3-(phenylamino)propane-1,2-diol derivatives as the putative toxic agents, which were generated during the refining process at the ITH refinery. Here we present the biotransformation and clearance of 3-(phenylamino)propane-1,2-diol (PAP) administered intraperitoneally to A/J and C57BL/6 mice that have been proposed as a murine model for the immunological features of TOS. Mice eliminated 6 microCi of [U-(14)C]PAP during a 24 h period, mostly in urine. Animals exhibited urine elimination rates of 70 and 36% in A/J and C57BL/6 strains, respectively. A/J mice exhibited no increase in the elimination rate when induced with beta-naphthoflavone, whereas C57BL/6 did increase the rate of elimination to 57%. Feces contributed to a lesser extent to the elimination rate (0.6 and 3.3% in A/J and C57BL/6 mice, respectively). Radioactivity remaining in organ tissues was lower than 1% (liver, lung, kidney, spleen, heart, and muscle). Metabolic species in urine were identified by HPLC coupled to UV and radioisotope detectors and further GC/MS analyses. 2-Hydroxy-3-(phenylamino)propanoic acid metabolite was the major chemical species excreted in urine in both strains, in both control and induced animal groups. This compound was the main urinary metabolite of PAP, and unmetabolized PAP excreted in urine constituted less than 1% of the total administered dose. Two additional highly polar metabolites also detected in urine were identified as 3-[(4'-hydroxyphenyl)amino]propane-1,2-diol and 2-hydroxy-3-[(4'-hydroxyphenyl)amino]propanoic acid. These findings are the first reported on PAP metabolism and clearance in mice strains and suggest that PAP can be extensively metabolized in vivo and potential reactive species can be generated.

Animals↗
PubMed2006

Transient and steady state investigation of selective and non-selective reaction pathways in the oxidative dehydrogenation of propane over supported vanadia catalysts.

Mechanistic aspects of the formation of C3H6, CO and CO2 in the oxidative dehydrogenation of propane over VOx/gamma-Al2O3 materials have been investigated by means of steady state and transient isotopic tests. The materials possessed highly dispersed and polymerised VOx species as well as bulk-like V2O5. Propene was primarily formed via oxidative dehydrogenation of propane by lattice oxygen of VOx species. It was suggested that non-selective consecutive propene oxidation is initiated by the breaking of the C-C bond in the molecule by the lattice oxygen, forming formaldehyde as a side product, which is further oxidised to CO and CO2. The following order of initial steady state propene selectivity (at a zero degree of propane conversion) as a function of the nature of VOx species was established: a mixture of bulk-like V2O5 and polymerised VOx>polymerised VOx>highly dispersed VOx species. The low propene selectivity over highly dispersed VOx species was explained by the fact that these species do not fully cover the bare acidic surface of gamma-Al2O3 where propene adsorption and further oxidation take place. Thus, two different locations of COx formation were considered: (i) in the vicinity of acidic sites of the support and (ii) on VOx species. The propene selectivity over samples possessing polymerised VOx species and bulk-like V2O5 strongly decreased with an increasing degree of propane conversion. Contrarily, highly dispersed VOx species showed the lowest ability for consecutive propene oxidation.

Journal Article↗
PubMed1975

A study of the oxidation of butan-1-ol and propan-2-ol by nicotinamide-adenine dinucleotide catalysed by yeast alcohol dehydrogenase.

1. The kinetics of oxidation of butan-1-ol and propan-2-ol by NAD+, catalysed by yeast alcohol dehydrogenase, were studied at 25 degrees C from pH 5.5 to 10, and at pH 7.05 from 14 degrees to 44 degrees C, 2. Under all conditions studied the results are consistent with a mechanism whereby some dissociation of coenzyme from the active enzyme-NAD+-alcohol ternary complexes occurs, and the mechanism is therefore not strictly compulsory order. 3. A primary 2H isotopic effect on the maximum rates of oxidation of [1-2H2]butan-1-ol and [2H7]propan-2-ol was found at 25 degrees C over the pH range 5.5-10. Further, in stopped-flow experiments at pH 7.05 and 25 degrees C, there was no transient formation of NADH in the oxidation of butan-1-ol and propan-2-ol. The principal rate-limiting step in the oxidation of dependence on pH of the maximum rates of oxidation of butan-1-ol and propan-2-ol is consisten with the possibility that histidine and cysteine residues may affect or control catalysis.

1-Propanol↗