C2 C10 Research Articles

Diversity in Itraconazole Cocrystals with Aliphatic Dicarboxylic Acids of Varying Chain Length

The cocrystal formation potential of itraconazole, a potent antifungal drug, with C2–C10 aliphatic dicarboxylic acids has been investigated. Using two experimental screening techniques (solvent-assisted grinding and evaporation-based crystallization), the cocrystals of itraconazole with C2–C7 dicarboxylic acids have been successfully synthesized and characterized by powder X-ray diffraction, solid state nuclear magnetic resonance, Raman spectroscopy, and thermal analysis. The characterized multicomponent compounds include anhydrous cocrystals (malonic, succinic, glutaric, and pimelic acids), a cocrystal hydrate (adipic acid), and cocrystal solvates with acetone and tetrahydrofuran (oxalic acid). This study is the first to demonstrate the diversity in itraconazole cocrystals with a range of aliphatic dicarboxylic acids of variable carbon chain lengths.

Tautomerism of a thiabendazole fungicide on Ag and Au nanoparticles investigated by Raman spectroscopy and density functional theory calculations

The energetic stabilities of a fungicide, thiobendazole (TBZ) on the Au and Ag atoms were analyzed by density functional theory (DFT) calculations at the levels of B3LYP/LANL2DZ. The most stable configuration on Au occurred when the metal atom was close to the N1 atom of TBZ in the same plane. There are two conformers of TBZ, N1-deprotonated and N3-deprotonated tautomers, depending on the hydrogen position of the benzimidazole in TBZ. Due to the planar geometry of the N1-deprotonated tautomer, it is more stable (ΔG=6.31kcal/mol) than the N3-deprotonated tautomer, which exhibits N1–C2–C10–C14 and N3–C2–C10–N11 dihedral angles of 30° and 28°, respectively. On the other hand, the most stable geometry of TBZ on Ag was formed when the N3 and N11 atoms of TBZ make a bridged configuration with the Ag atom. The binding energy of TBZ on Au was found larger than that of Ag. Spectral features of TBZ are compared on silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) by means of Raman spectroscopy. The presence of an Ag–N and an Au–N stretching band at 227 and 239cm−1 in the Raman spectrum indicated that the nitrogen atoms of TBZ may be involved in the binding of the adsorbate on the surfaces of the AgNPs and AuNPs.

Development of a new skeletal mechanism for n-decane oxidation under engine-relevant conditions based on a decoupling methodology

A new skeletal mechanism for n-decane oxidation was developed based on a decoupling methodology with the special emphasis on the engine-relevant operating conditions from low to high temperature at high pressure. With the decoupling methodology, an extremely simplified model for C2–C10 was used to simulate the oxidation of heavy hydrocarbons for prediction of the ignition characteristics, while the mechanism of H2/CO/C1 was considered in details for providing accurate information of laminar flame speed and extinction strain rate. The new skeletal n-decane oxidation mechanism consists of 40 species and 141 reactions. Extensive validations of the present mechanism were performed by comparing with the experimental data available in the literature on n-decane oxidation, including ignition delay in shock tube and rapid compression machine, species concentrations in jet-stirred reactor and variable pressure flow reactor in wide ranges of temperature (550–1800K), pressure (1–80bar) and equivalence ratio (0.5–2). Moreover, the experimental data on the profiles of species concentration, laminar flame speed and extinction strain rate in premixed flame and counterflow flame was also being used in the validations. Finally, the skeletal n-decane mechanism was applied to predict the combustion and emissions of premixed charge compression ignition (PCCI) engines by using the multi-dimensional simulation. Overall, the current prediction from the present mechanism shows a good agreement with the experimental measurements, which indicates the potential of the decoupling methodology for the development of oxidation mechanism for heavy alkanes.

Deep gases discharged from mud volcanoes of Azerbaijan: New geochemical evidence

This paper presents new geochemical data of hydrocarbon-rich gases released from some mud volcanoes of Azerbaijan. Methane is considerably the most abundant component of all the sampled gases, which show δD-CH4 and δ13C-CH4 values likely related to a dominant thermogenic source. These gases are characterized by the presence of more than 20 different cyclic compounds with concentrations up to several μmol/mol. A similar gas composition has recently been found to characterize many mud volcanoes of the Northern Apennines and Sicily (Italy). The data of the Azerbaijan mud volcanoes corroborate the notion that cyclic compounds can be considered reliable tracers for hydrocarbon gas production at considerable depths and temperatures up to 120–150 °C, which correspond to a 6.5–8.3 km depth range assuming an average geothermal gradient of 18 °C/km. This depth interval is consistent with both the depth of potential source rocks imaged seismically beneath some mud volcanoes, and the results of previous estimates that used the 13C/12C values of methane and ethane. Such deep-sourced gases and material (fluidized clayey mass and rock fragments) ascend into the core of anticlines and accumulate at shallower reservoirs, where fold-parallel outer-arc faults or fold-orthogonal fractures may penetrate and transfer the fluids to the surface. Finally, the basically equivalent composition of the different hydrocarbon groups (C2–C10 alkanes, aromatics and cyclic) determined in the gases sampled in both Azerbaijan and Italy manifests the lack of evident relationships between the chemistry of light hydrocarbons and the type of source rock.

Isolation and characterization of an enzyme from the Greenshell™ mussel Perna canaliculus that hydrolyses pectenotoxins and esters of okadaic acid

An enzyme capable of hydrolysing pectenotoxins (PTXs) and okadaic acid (OA) esters within the hepatopancreas of the Greenshell™ mussel Perna canaliculus was isolated and characterized. The enzyme was purified by sequential polyethylene glycol fractionation, anion exchange, hydrophobic interaction, gel filtration and hydroxyapatite chromatography. The enzyme was an acidic (pI ∼ 4.8), monomeric, 67 kDa, serine esterase with optimum activity at pH 8.0 and 25 °C. PTX2 and PTX1 were hydrolysed but the enzyme was inactive against PTX11, PTX6 and acid isomerised PTX2 and PTX11. PTX11 and PTX2b competitively inhibited PTX2 hydrolysis. The enzyme also hydrolysed short and medium chain length (C2–C10) 4-nitrophenyl-esters, okadaic acid C8–C10 diol esters and DTX1 7-O-palmitoyl ester (DTX3). MALDI-Tof MS/MS analysis showed that the enzyme had some homology with a juvenile hormone esterase from the Red Flour Beetle Tribolium castaneum, although BLAST searches of several data bases using de novo amino acid sequences failed to identify any homology with known proteins.

Building Blocks for Ionic Liquids: A Study of Alkyl Chain Length Dependence of Vaporization Enthalpies of 1-(n-Alkyl)-2-methylimidazoles

The transpiration method has been used to measure temperature dependence of vapor pressures for the 1-(n-alkyl)-2-methylimidazoles with the linear alkyl chain C2–C10. The molar enthalpies of vaporization at 298.15 K of this homologues series were correlated with the number of carbon atoms in the alkyl chain, as well as with the Kovat's indices on the low-polar gas chromatography (GC) columns. In both cases linear correlations have been found.

New path in the thermal cracking of triacylglycerols (canola and soybean oil)

Triacylglycerols (TGs) are naturally occurring oils abundant in many crops. A series of batch uncatalyzed thermal decomposition experiments were performed using canola and soybean oils to explore pathways of TG cracking. A detailed gas chromatographic protocol based on mass spectrometric identification and flame ionization quantification was applied to the organic liquid product generated upon cracking. Reaction conditions were identified that resulted in a novel organic liquid product (OLP) composition compared to previously reported work. Under these conditions (temperatures within a 420–440°C range) a new route for TG thermolysis was discovered in which cracking reactions of original TG-bound fatty acids were nearly complete and led to the formation of 15–25wt.% C2–C10 linear saturated monocarboxylic acids and ca. 30% linear alkanes. Less than 2wt.% C16–C18 fatty acids which were originally present in the feedstocks as glycerol triesters were found in the OLP. These reactions appear to be kinetically controlled due to abundant hydrogen formation. This route provides a significant enrichment of low-MW compounds in the OLP (65–70wt.% being <C11) and thus may be considered as a new option for the production of replacement products for petroleum-based fuels and chemicals.

Characterization of trace gases measured over Alberta oil sands mining operations: 76 speciated C&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;–C&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; volatile organic compounds (VOCs), CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, CO, NO, NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, NO&amp;lt;sub&amp;gt;y&amp;lt;/sub&amp;gt;, O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; and SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;

Abstract. Oil sands comprise 30% of the world's oil reserves and the crude oil reserves in Canada's oil sands deposits are second only to Saudi Arabia. The extraction and processing of oil sands is much more challenging than for light sweet crude oils because of the high viscosity of the bitumen contained within the oil sands and because the bitumen is mixed with sand and contains chemical impurities such as sulphur. Despite these challenges, the importance of oil sands is increasing in the energy market. To our best knowledge this is the first peer-reviewed study to characterize volatile organic compounds (VOCs) emitted from Alberta's oil sands mining sites. We present high-precision gas chromatography measurements of 76 speciated C2–C10 VOCs (alkanes, alkenes, alkynes, cycloalkanes, aromatics, monoterpenes, oxygenated hydrocarbons, halocarbons and sulphur compounds) in 17 boundary layer air samples collected over surface mining operations in northeast Alberta on 10 July 2008, using the NASA DC-8 airborne laboratory as a research platform. In addition to the VOCs, we present simultaneous measurements of CO2, CH4, CO, NO, NO2, NOy, O3 and SO2, which were measured in situ aboard the DC-8. Carbon dioxide, CH4, CO, NO, NO2, NOy, SO2 and 53 VOCs (e.g., non-methane hydrocarbons, halocarbons, sulphur species) showed clear statistical enhancements (1.1–397×) over the oil sands compared to local background values and, with the exception of CO, were greater over the oil sands than at any other time during the flight. Twenty halocarbons (e.g., CFCs, HFCs, halons, brominated species) either were not enhanced or were minimally enhanced (&lt;10%) over the oil sands. Ozone levels remained low because of titration by NO, and three VOCs (propyne, furan, MTBE) remained below their 3 pptv detection limit throughout the flight. Based on their correlations with one another, the compounds emitted by the oil sands industry fell into two groups: (1) evaporative emissions from the oil sands and its products and/or from the diluent used to lower the viscosity of the extracted bitumen (i.e., C4–C9 alkanes, C5–C6 cycloalkanes, C6–C8 aromatics), together with CO; and (2) emissions associated with the mining effort, such as upgraders (i.e., CO2, CO, CH4, NO, NO2, NOy, SO2, C2–C4 alkanes, C2–C4 alkenes, C9 aromatics, short-lived solvents such as C2Cl4 and C2HCl3, and longer-lived species such as HCFC-22 and HCFC-142b). Prominent in the second group, SO2 and NO were remarkably enhanced over the oil sands, with maximum mixing ratios of 38.7 ppbv and 5.0 ppbv, or 383× and 319× the local background, respectively. These SO2 levels are comparable to maximum values measured in heavily polluted megacities such as Mexico City and are attributed to coke combustion. By contrast, relatively poor correlations between CH4, ethane and propane suggest low levels of natural gas leakage despite its heavy use at the surface mining sites. Instead the elevated CH4 levels are attributed to methanogenic tailings pond emissions. In addition to the emission of many trace gases, the natural drawdown of OCS by vegetation was absent above the surface mining operations, presumably because of the widespread land disturbance. Unexpectedly, the mixing ratios of α-pinene and β-pinene were much greater over the oil sands (up to 217 pptv and 610 pptv, respectively) than over vegetation in the background boundary layer (20±7 pptv and 84±24 pptv, respectively), and the pinenes correlated well with several industrial tracers that were elevated in the oil sands plumes. Because so few independent measurements from the oil sands mining industry exist, this study provides an important initial characterization of trace gas emissions from oil sands surface mining operations.

Plasticicumulans acidivorans gen. nov., sp. nov., a polyhydroxyalkanoate-accumulating gammaproteobacterium from a sequencing-batch bioreactor

Here, we describe a novel bacterium, strain TUD-YJ37(T), which can accumulate polyhydroxybutyrate (PHB) to more than 85 % (w/w) dry cell weight. The bacterium was isolated from a mixed-culture bioreactor by using a feast-famine regime and its properties were characterized. Phylogenetic analysis based on full 16S rRNA gene sequences revealed that the isolate is a member of the Gammaproteobacteria, forming an independent, deep phylogenetic lineage. It is most closely related to members of the genera Methylocaldum, Methylococcus and Natronocella, with sequence similarities below 91 %. Strain TUD-YJ37(T) was an obligately aerobic, ovoid, Gram-negative bacterium, motile by means of a polar flagellum. It utilized C₂-C₁₀ fatty acids as carbon and energy sources. The temperature range for growth was 20-35 °C, with an optimum of 30 °C; the pH range was 6.0-8.0, without a clear optimum. The major respiratory quinone was Q-8. Polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unidentified phospholipids, an unidentified aminolipid and another unidentified lipid. The predominant fatty acids in the membrane polar lipids were C₁₆:₁ω7c, C₁₆:₀ and C₁₈:₁ω7c. The G+C content of the genomic DNA was 67.4 mol%. On the basis of phenotypic, chemotaxonomic and molecular data, the isolate is proposed to represent a novel genus and species, for which the name Plasticicumulans acidivorans gen. nov., sp. nov. is proposed. The type strain of Plasticicumulans acidivorans is TUD-YJ37(T) ( = DSM 23606(T) = CBS 122990(T)).

Studies towards the synthesis of neopeltolide: synthesis of a ring-closing metathesis macrocyclization precursor

An advanced ring-closing metathesis precursor for the synthesis of the marine macrolide neopeltolide is prepared in a stereocontrolled manner by the coupling of the C2–C10 and C11–C16 subunits. The metathesis reaction of 4 with Grubbs’ II or Nolan’s indenylidene catalyst led to the unexpected formation of cycloheptene 18.

Characterization of NOx, SO2, ethene, and propene from industrial emission sources in Houston, Texas

The Houston‐Galveston‐Brazoria urban area contains industrial petrochemical sources that emit volatile organic compounds and nitrogen oxides, resulting in rapid and efficient ozone production downwind. During September to October 2006, the NOAA WP‐3D aircraft conducted research flights as part of the second Texas Air Quality Study (TexAQS II). We use measurements of NOx, SO2, and speciated hydrocarbons from industrial sources in Houston to derive source emission ratios and compare these to emission inventories and the first Texas Air Quality Study (TexAQS) in 2000. Between 2000 and 2006, NOx/CO2 emission ratios changed by an average of −29% ± 20%, while a significant trend in SO2/CO2 emission ratios was not observed. We find that high hydrocarbon emissions are routine for the isolated petrochemical facilities. Ethene (C2H4) and propene (C3H6) are the major contributors to ozone formation based on calculations of OH reactivity for organic species including C2–C10 alkanes, C2–C5 alkenes, ethyne, and C2–C5 aldehydes and ketones. Measured ratios of C2H4/NOx and C3H6/NOx exceed emission inventory values by factors of 1.4–20 and 1–24, respectively. We examine trends in C2H4/NOx and C3H6/NOx ratios between 2000 and 2006 for the isolated petrochemical sources and estimate a change of −30% ± 30%, with significant day‐to‐day and within‐plume variability. Median ambient mixing ratios of ethene and propene in Houston show decreases of −52% and −48%, respectively, between 2000 and 2006. The formaldehyde, acetaldehyde, and peroxyacetyl nitrate products produced by alkene oxidation are observed downwind, and their time evolution is consistent with the rapid photochemistry that also produces ozone.

Dicarboxylic acids, metals and isotopic compositions of C and N in atmospheric aerosols from inland China: implications for dust and coal burning emission and secondary aerosol formation

Abstract. Dicarboxylic acids (C2–C10), metals, elemental carbon (EC), organic carbon (OC), and stable isotopic compositions of total carbon (TC) and total nitrogen (TN) were determined for PM10 samples collected at three urban and one suburban sites of Baoji, an inland city of China, during winter and spring 2008. Oxalic acid (C2) was the dominant diacid, followed by succinic (C4) and malonic (C3) acids. Total diacids in the urban and suburban areas were 1546±203 and 1728±495 ng m−3 during winter and 1236±335 and 1028±193 ng m−3 during spring. EC in the urban and the suburban atmospheres were 17±3.8 and 8.0±2.1 μg m−3 during winter and 20±5.9 and 7.1±2.7 μg m−3 during spring, while OC at the urban and suburban sites were 74±14 and 51±7.9 μg m−3 in winter and 51±20 and 23±6.1 μg m−3 in spring. Secondary organic carbon (SOC) accounted for 38±16% of OC in winter and 28±18% of OC in spring, suggesting an enhanced photochemical production of secondary organic aerosols in winter under an inversion layer development. Total metal elements in winter and spring were 34±10 and 61±27 μg m−3 in the urban air and 18±7 and 32±23 μg m−3 in the suburban air. A linear correlation (r2&gt;0.8 in winter and r2&gt;0.6 in spring) was found between primary organic carbon (POC) and Ca2+/Fe, together with a strong dependence of pH value of sample extracts on water-soluble inorganic carbon, suggesting fugitive dust as an important source of the airborne particles. Polycyclic aromatic hydrocarbons (PAHs), sulfate, and Pb in the samples well correlated each other (r2&gt;0.6) in winter, indicating an importance of emissions from coal burning for house heating. Stable carbon isotope compositions of TC (δ13C) became higher with an increase in the concentration ratios of C2/OC due to aerosol aging. In contrast, nitrogen isotope compositions of TN (δ15N) became lower with an increases in the mass ratios of NH4+/PM10 and NO3−/PM10, which is possibly caused by an enhanced adsorption and/or condensation of gaseous NH3 and HNO3 onto particles.

Composition profile of oxygenated organic compounds and inorganic ions in PM2.5 in Hong Kong

Environment context.Oxygenated organic compounds are active constituents in ambient aerosols, affecting their hygroscopic properties and other interactions with water. We have measured 29 oxygenated organic compounds, together with inorganic ions and other major aerosol constituents, in ambient samples collected under various synoptic conditions in Hong Kong. These composition profiles of water-soluble matter provide valuable data for modelling and theoretical studies of aerosol–water interactions. Abstract. This study reports a comprehensive dataset of oxygenated compounds, inorganic ions and other major aerosol constituents in fine particulate matter (2.5 μm) in the urban atmosphere of Hong Kong in periods of different synoptic weather conditions during 2003–05. The oxygenated compounds quantified include C2–C10 dicarboxylic acids, C3–C9 ketoacids and C2–C3 dicarbonyls, their combined concentrations accounting for 3.2–18.2% of water-soluble organic carbon on a carbon mass basis. Six C2 and C3 oxygenated compounds, namely oxalic acid, malonic acid, glyoxylic acid, pyruvic acid, glyoxal, and methyl glyoxal, dominate this suite of oxygenated compounds, accounting for 75% of the total quantified oxygenated species. Good correlations were observed among most of the quantified oxygenated compounds, suggesting that a relatively stable abundance distribution exists under varying synoptic conditions. These composition profiles provide a comprehensive dataset for use in modelling and theoretical studies of aerosol–water interactions, secondary aerosol formation pathways, and speciated organic mass distributions.

Intercalation behavior of calcium phenylphosphonate dihydrate CaC6H5PO3·2H2O

Intercalates of calcium phenylphosphonate dihydrate with 1-alkylamines (C2–C10), 1-alkanols (C3–C10), 1,ω-amino alcohols (C2–C5), pyridine, morpholine, piperazine, aniline and 1-naphthylamine were prepared and characterized by powder X-ray diffraction and thermogravimetric analysis. The intercalates of alkanols and alkylamines are unstable at ambient conditions and the guest molecules are tilted to the host layers at an angle of 40°. The amino alcohol intercalates are stable and their basal spacings are very similar for all amino alcohols used and, in the case of ethanolamine and propanolamine, they contain co-intercalated water. Also arylamines and nitrogenous heterocycles form stable compounds. The general formula of these intercalates is CaC6H5PO3·xH2O·y(guest) and their basal spacings are from 15.39 to 15.78 A.

ChemInform Abstract: Stereoselective Synthesis of the Functionalized C2—C10 Fragment of Clavulactone.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Inhibition of human glutathione S-transferases by curcumin and analogues

Glutathione S-transferases (GSTs) are important phase II drug-metabolizing enzymes that play a major role in protecting cells from the toxic insults of electrophilic compounds. Curcumin, a promising chemotherapeutic agent, inhibits human GSTA1-1, GSTM1-1, and GSTP1-1 isoenzymes.In the present study, the effect of three series of curcumin analogues, 2,6-dibenzylidenecyclohexanone (A series), 2,5-dibenzylidenecyclopentanone (B series), and 1,4-pentadiene-3-one (C series) substituted analogues (n = 34), on these three human GST isoenzymes, and on human and rat liver cytosolic GSTs, was investigated using 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate.Most of the 34 curcumin analogues showed less potent inhibitory activities towards GSTA1-1, GSTM1-1, and GSTP1-1 than the parent curcumin. Compounds B14 and C10 were the most potent inhibitors of GSTA1-1 and human liver cytosolic GSTs, with IC50 values of 0.2–0.6 μM. The most potent inhibitors of GSTM1-1 were C1, C3 and C10, with IC50 values of 0.2–0.7 μM. Similarly, GSTP1-1 was predominantly strongly inhibited by compounds of the C series C0, C1, C2 C10 and A0, with IC50 values of 0.4–4.6 μM. Compounds in the B series showed no significant inhibition of GSTP1-1.Molecular Operating Environment (MOE) program-based quantitative structure–activity relationship (QSAR) analyses have also suggested the relevance of Van der Waals surface area and compound lipophilicity factors for the inhibition of GSTA1-1 and GSTM1-1 and partial charge factors for GSTP1-1. These results may be useful in the design and synthesis of curcumin analogues with either more or less potency for GST inhibition.

Stereoselective Synthesis of the Functionalized C2–C10 Fragment of Clavulactone

AbstractA stereoselective synthesis of all functionalized C2–C10 fragment 13 of the antitumor marine natural product clavulactone was accomplished, starting from the commercially available 3‐methylglutaric acid anhydride. Desymmetrization of 3‐methylglutaric acid anhydride with (S)‐α‐phenylethanamine was successfully employed as a key step to embed the isolated C8‐methyl group with the correct absolute configuration (99% de). The C3–C4 cis‐double bond was stereospecifically furnished by an RCM (ring‐closing metathesis) approach. Fragment 13 contains all preset functionalities and will be a useful precursor for the convergent total synthesis of clavulactone.

Synthesis and characterisation of coating polyurethane cationomers containing quaternary ammonium alkyl groups derived from built-in alkyl bromides

Polyurethane cationomers were synthesised in the reaction of 4,4′-methylenebis(phenyl isocyanate) with polyoxypropylene glycol (M = 450) and N-methyl diethanolamine. Amine segments were built-in to the urethane–isocyanate prepolymer in the reaction with 1-bromoalkanes (C2–C10), and then they were converted to alkyl-ammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium. That yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. 1H and 13C NMR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on 1H NMR and IR spectra, the factors κ and α1 or α1 were calculated, which represented the polarity level of the obtained cationomers. The differential scanning calorimetry method revealed decline of Tg for the hard urethane and urea segments from 60 °C to 46 °C when the number of carbon atoms increased in the alkyl radical attached to the ammonium cation. Changes were discussed in the surface free energy (SFE) and its components, as calculated independently according to the methods suggested by van Oss-Good and by Owens–Wendt, in relation to chemical structures of cationomers. The growing length (from C2 to C10) of the alkyl radical attached to the N atom in the cationomer chain was found to reduce the value of SFE of the polymer coating from 46 to 28 mJ/m2. That is caused by gradual weakening of long-range interactions, within which the highest share is taken by dispersion interactions.

Substrate specificity of human and yeast aldehyde dehydrogenases

Human aldehyde dehydrogenase (ALDH) family may contribute to metabolism of hydrocarbons, biogenic amines, retinoids, steroids, and lipid peroxidation. We previously reported kinetic properties of human cytosolic ALDH1 and mitochondrial ALDH2 towards oxidation of the straight-chain and branched-chain aliphatic aldehydes with various chain lengths [S.J. Yin, M.F. Wang, C.L. Han, S.L. Wang, Substrate binding pocket structure of human aldehyde dehydrogenases: a substrate specificity approach, Adv. Exp. Med. Biol. 372 (1995) 9–16]. We present here substrate specificities for aromatic and heterocyclic aldehydes with purified human liver ALDH1 and ALDH2, and also with yeast mitochondrial ALDH2 for comparison. Kinetic assay for human ALDHs was performed in 50 mM HEPES, pH 7.5 and 25 °C, containing 0.5 mM NAD +, 1.7% (v/v) acetonitrile (as a solvent carrier for aldehydes) and varied concentrations of substrate, and for yeast ALDH2 the assay was determined in the same reaction mixture except containing 3 mM NAD + and addition of 200 mM KCl. With respect to phenylacetaldehyde, 2-phenylpropionaldehyde, benzaldehyde, p-nitrobenzaldehyde, cinnamaldehyde, 2-furaldehyde and indole-3-acetaldehyde, human liver ALDH1 exhibited K M ranging from 0.25 to 4.8 μM, V max of 0.34–2.4 U/mg, and catalytic efficiency, V max/ K M, 0.070–3.9 U/(mg μM); human ALDH2 exhibited K M ranging from less than 0.15–0.74 μM, V max of 0.039–0.51 U/mg, and V max/ K M, 0.15–1.0 U/(mg μM). Human ALDH1 and ALDH2 exhibited substate inhibition constants ( K i) for phenylacetaldehyde, 95 and 430 μM, respectively. Yeast ALDH2 exhibited K M for straight-chain aliphatic aldehydes (C1–C10), 2.3–210 μM, and substrate inhibition constants (C2–C10), 79–2900 μM, with a trend of being smaller K M and K i for longer chain lengths; and K M for cinnamaldehyde, benzaldehyde, and 2-furaldehyde, 5.0, 79, and 1000 μM, respectively. Therefore human ALDH1/ALDH2 and yeast ALDH2 can contribute to detoxification or metabolism of various exogenous/endogenous aliphatic and aromatic aldehydes. The systematic changes in kinetic parameters for oxidation of structurally related aldehydes may reflect subtle functional topographic distinctions of substrate pocket for human and yeast ALDHs.

Implications of changing urban and rural emissions on non-methane hydrocarbons in the Pearl River Delta region of China

Guangzhou (GZ) is one of the highly industrialized and economically vibrant cities in China, yet it remains relatively understudied in terms of its air quality, which has become severely degraded. In this study, extensive air sampling campaigns had been conducted at GZ urban sites and in Dinghu Mountain (DM), a rural site, in the Pearl River Delta (PRD) during the spring of 2001 and 2005. Additionally, roadside and tunnel samples were collected in GZ in 2000 and 2005. Later, exhaust samples from liquefied petroleum gas (LPG)- and gasoline-fueled taxis were collected in 2006. All samples were analyzed for C2–C10 non-methane hydrocarbons (NMHCs). NMHC profiles showed significant differences in the exhaust samples between gasoline- and LPG-fueled taxis. Propane (47%) was the dominant hydrocarbon in the exhaust of the LPG-fueled taxis, while ethene (35%) was the dominant one in that of gasoline-fueled taxis. The use of LPG-fueled buses and taxis since 2003 and the leakage from these LPG-fueled vehicles were the major factors for the much higher level of propane in GZ urban area in 2005 compared to 2001. The mixing ratios of toluene, ethylbenzene, m/p-xylene and o-xylene decreased at the GZ and DM sites between 2001 and 2005, especially for toluene in GZ, despite the sharp increase in the number of registered motor vehicles in GZ. This phenomenon was driven in part by the closure of polluting industries as well as the upgrading of the road network in urban GZ and in part by the implementation of more stringent emission standards for polluting industries and motor vehicles in the PRD region.