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PubMed1973

Genetic fusion of incompatible plasmids in Pseudomonas.

The genes specifying enzymes responsible for the degradation of camphor and octane occur on transmissible plasmids in Pseudomonas putida strain PpG1 and P. oleovorans. Since the presence of the plasmids is vital for the oxidative metabolism of camphor or octane (by the cells) in the absence of other carbon sources, such naturally occurring, energy-generating plasmids have been designated as degradative plasmids. The two degradative plasmids, CAM and OCT, are incompatible with each other and cannot coexist in the same cell. By the use of UV irradiation and suitable selection techniques, it has been possible to fuse these two plasmids so they become part of the same replicon and coexist. Such a technique might be useful in introducing several degradative pathways in the same cell.

Alkanes↗
PubMed1997

Mössbauer studies of alkane omega-hydroxylase: evidence for a diiron cluster in an integral-membrane enzyme.

The gene encoding the alkane omega-hydroxylase (AlkB; EC 1.14.15.3) from Pseudomonas oleovorans was expressed in Escherichia coli. The integral-membrane protein was purified as nearly homogeneous protein vesicles by differential ultracentrifugation and HPLC cation exchange chromatography without the detergent solubilization normally required for membrane proteins. Purified AlkB had specific activity of up to 5 units/mg for octane-dependent NADPH consumption. Mössbauer studies of AlkB showed that it contains an exchange-coupled dinuclear iron cluster of the type found in soluble diiron proteins such as hemerythrin, ribonucleotide reductase, methane monooxygenase, stearoyl-acyl carrier protein (ACP) delta9 desaturase, rubrerythrin, and purple acid phosphatase. In the as-isolated enzyme, the cluster contains an antiferromagnetically coupled pair of high-spin Fe(III) sites, with an occupancy of up to 0.9 cluster per AlkB. The diferric cluster could be reduced by sodium dithionite, and the diferrous state was found to be stable in air. When both O2 and substrate (octane) were added, however, the diferrous cluster was quantitatively reoxidized, proving that the diiron cluster occupies the active site. Mossbauer data on reduced AlkB are consistent with a cluster coordination rich in nitrogen-containing ligands. New sequence analyses indicate that at least 11 nonheme integral-membrane enzymes, including AlkB, contain the 8-histidine motif required for catalytic activity in stearoyl-CoA desaturase. Based on our Mössbauer studies of AlkB, we propose that the integral-membrane enzymes in this family contain diiron clusters. Because these enzymes catalyze a diverse range of oxygenation reactions, this proposal suggests a greatly expanded role for diiron clusters in O2-activation biochemistry.

Iron↗
PubMed2007

The use of organic vapor sorption to determine low levels of amorphous content in processed pharmaceutical powders.

Organic dynamic vapor sorption (organic-DVS) was used to characterize amorphous content in known amorphous-crystalline mixtures of lactose and salbutamol sulfate. N-octane was chosen as an apolar probe and measurements were carried out by exposing mixtures of each sample to partial pressures 0-90% p/p(0). A linear relationship between amorphous content and n-octane partial pressure was observed for both lactose and salbutamol sulfate with R(2) values of 0.992 and 0.999, respectively. In addition, the influence of sequential mechanical processing in a ball mill on the amorphous content in crystalline lactose was investigated. Cumulative milling times resulted in an exponential increase in amorphous content (using the linear relationship obtained for lactose), with a maximum amorphous content of 14% being induced after 60 min milling. In comparison, analysis of the 60 min mill time samples after exposure to 85% relative humidity suggested 0.00% amorphous content.

Albuterol↗
PubMed2000

Customer exposure to gasoline vapors during refueling at service stations.

Gasoline is a volatile complex mixture of hydrocarbon compounds that is easily vaporized during handling under normal conditions. Modern reformulated gasoline also contains oxygenates to enhance octane number and reduce ambient pollution. This study measured the difference in the exposure of customers to gasoline and oxygenate vapors during refueling in service stations with and without vapor recovery systems. Field measurements were carried out at two self-service stations. One was equipped with Stage I and the other with Stage II vapor recovery systems. At Stage I stations there is vapor recovery only during delivery from road tanker, and at Stage II stations additional vapor recovery during refueling. The exposure of 20 customers was measured at both stations by collecting air samples from their breathing zone into charcoal tubes during refueling with 95-octane reformulated gasoline. Each sample represented two consecutive refuelings. The samples were analyzed in the laboratory by gas chromatography using mass-selective detection for vapor components. The Raid vapor pressure of gasoline was 70 kPa and an oxygen content 2 wt%. Oxygenated gasoline contained 7 percent methyl tert-butyl ether (MtBE) and 5 percent methyl tert-amyl ether (MtAE). The geometric mean concentrations of hydrocarbons (C3-C11) in the customers' breathing zone was 85 mg/m3 (range 2.5-531 mg/m3) at the Stage I service station and 18 mg/m3 (range < 0.2-129 mg/m3) at the Stage II service station. The geometric mean of the exposure of customers to MtBE during refueling at the Stage I service station was 15.3 mg/m3 (range 1.8-74 mg/m3), and at the Stage II service station 3.4 mg/m3 (range 0.2-16 mg/m3). The differences in exposure were statistically significant (p < 0.05). The mean refueling times were 57 seconds (range 23-207) at the Stage I and 66 seconds (range 18-120) at the Stage II station. The measurements were done on consecutive days at the various service stations. The temperature ranged from 10 to 17 degrees C, and wind velocity was 2-4 m/s. The climatic conditions were very similar on the measurement days. Based on this study it was found that the Stage II vapor recovery system reduces gasoline emission considerably. The exposure level of customers at the Stage II station during refueling was circa 20-25 percent of the exposure at the Stage I service station when conditions were equal and no other confounding factors such as leaks or spills were present.

Air Pollutants↗
PubMed2000

Effect of methyl tertiary butyl ether concentrations on exhaust emissions from gasoline used in the metropolitan area of Mexico City.

In this work, the primary objective was to assess the impact of oxygenated fuel on the exhaust emissions from an important fraction of vehicles in the Metropolitan Area of Mexico City (MAMC). The results aim to provide information on the actual effect of MTBE on a fleet that represents more than 60% of the in-use vehicles in the MAMC. Ten vehicles were tested with a low-octane base gasoline, and 10 more with a regular-grade unleaded base gasoline. Three MTBE concentrations, 5, 10, and 15 vol %, were tested following the U.S. Federal Test Procedure (FTP). CO, total HC, and NOx from the exhaust gases were quantitatively evaluated and also characterized for FTP speciated organic emissions. From this data, the O3-forming potential of the fuels was calculated. Results show that for the fleet using low-octane gasoline, the addition of 10% MTBE substantially reduced CO emissions, but total HC concentration in the exhaust showed a modest decrease. For the regular gasoline, the 10% MTBE blend seemed to be the best choice, but there was not a significant decrease in emissions. The specific reactivity of each fuel, expressed in grams of O3 per gram of nonmethane organic gases, increased with MTBE concentration in both cases. This result is important to consider, especially for a region like Mexico City, which has high atmospheric O3 concentrations.

Air Pollutants↗
PubMed2001

Distance indices and their hyper-counterparts: intercorrelation and use in the structure-property modeling.

Intercorrelation between the Wiener index, hyper-Wiener index, Harary index, hyper-Harary index, detour index and hyper-detour index is studied on three sets of branched and unbranched alkanes and cycloalkanes with up to eight carbon atoms. First set (S-39) contains all alkanes from ethane to octane (39 molecules), the second set (S-139) 139 cyclic hydrocarbons from cyclopropane to branched and unbranched polycyclic octanes and the third set (S-178) is a combination of the first two sets (178 molecules). It is found that the pairs of distance indices and the corresponding hyper-counterparts are highly intercorrelated for all three sets. The use of the distance indices of both kinds in structure-boiling point modeling was analyzed. Distance indices and hyper-distance indices do not lead to particularly good models for any of the three sets. When used as composite indices they give much-improved models. However, they are most useful when combined with such indices as the number of carbon atoms in a hydrocarbon, Hosoya Z index and/or total walk count index. The following standard errors of estimate are obtained for the best models based on the combination of descriptors: 2.1 degrees C (S-39), 4.4 degrees C (S-139) and 4.1 degrees C (S-178). They compare favorably with the related models in the literature.

Alkanes↗
PubMed2004

Evaluation of a multi-parameter biomarker set for oxidative damage in man: increased urinary excretion of lipid, protein and DNA oxidation products after one hour of exercise.

The objective of the present study was to evaluate a comprehensive set of urinary biomarkers for oxidative damage to lipids, proteins and DNA, in man. Eighteen moderately trained males (mean age 24.6+/-0.7) exercised 60min at 70% of maximal O2 uptake on a cycle ergometer. Urine fractions for 12 h were collected 1 day before, and for 3 consecutive days after exercise. As biomarkers of lipid peroxidation, 8 aldehydes (i.e. propanal, butanal, pentanal, hexanal, heptanal, octanal, nonanal and malondialdehyde-MDA)and acetone were analyzed in urines by gas chromatography with electron capture detection (GC-ECD). As a biomarker of protein oxidation, o,o'-dityrosine was analyzed in urine samples by a recently developed isotope dilution HPLC-atmospheric pressure chemical ionization (APCI)-tandem-mass spectrometry (HPLC-APCI-MS/MS) methodology. As a biomarker of oxidative DNA damage, urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG) was measured by an ELISA method. On the day of exercise, significant increases were observed in urinary excretions of acetone (p < 0.025, n = 18) and butanal (p < 0.01, n = 18) in the 12h daytime fractions compared to the daytime fraction before exercise. The urinary acetone excretion was also significantly (p < 0.05) increased on the 1st day after exercise. Octanal and nonanal were increased in the daytime urine fraction on the 2nd day after exercise. However, these increases were of borderline significance (p = 0.09 and p = 0.07, respectively). Significantly elevated urinary o,o'-dityrosine amounts were observed in the daytime fraction on the day of exercise (p < 0.025) and on the 1st day after exercise (p = 0.07) compared to the before exercise daytime fraction. Excretion of urinary 8-OHdG was statistically significantly increased in the daytime fractions on the day of exercise (p = 0.07) and on the 1st day after exercise (p < 0.025) compared to before exercise daytime fraction. Increases in urinary excretions of acetone, propanal, pentanal, MDA and 8-OHdG significantly correlated with training status (hours of exercise/week) of the volunteers, while o,o'-dityrosine did not. To our knowledge, the present study is the first to evaluate a multi-parameter non-invasive biomarker set for damage to three main cellular targets of ROS. It shows that 1 h of exercise may already induce oxidative damage in moderately trained individuals and that the chosen urinary biomarkers are sensitive enough to monitor such damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMedDate not supplied

Rat tissue and blood partition coefficients for n-alkanes (C8 to C12).

Rat tissue:air and blood:air partition coefficients (PCs) for octane, nonane, decane, undecane, and dodecane (n-C8 to n-C12 n-alkanes) were determined by vial equilibration. The blood:air PC values for n-C8 to n-C12 were 3.1, 5.8, 8.1, 20.4, and 24.6, respectively. The lipid solubility of n-alkanes increases with carbon length, suggesting that lipid solubility is an important determinant in describing n-alkane blood:air PC values. The muscle:blood, liver: blood, brain:blood, and fat:blood PC values were octane (1.0, 1.9, 1.4, and 247), nonane (0.8, 1.9, 3.8, and 274), decane (0.9, 2.0, 4.8, and 328), undecane (0.7, 1.5, 1.7, and 529), and dodecane (1.2, 1.9, 19.8, and 671), respectively. The tissue:blood PC values were greatest in fat and the least in muscle. The brain:air PC value for undecane was inconsistent with other n-alkane values. Using the measured partition coefficient values of these n-alkanes, linear regression was used to predict tissue (except brain) and blood:air partition coefficient values for larger n-alkanes, tridecane, tetradecane, pentadecane, hexadecane, and heptadecane (n-C13 to n-C17). Good agreement between measured and predicted tissue:air and blood:air partition coefficient values for n-C8 to n-Cl2 offer confidence in the partition coefficient predictions for longer chain n-alkanes.

Alkanes↗
PubMed1977

Factors influencing the differential sorption of odorant molecules across the olfactory mucosa.

By use of a flow dilution olfactometer, tritium-labeled odorants were presented through the external naris to the bullfrog's intact olfactory sac. After stimulation the animal was frozen in liquid nitrogen. The dorsal surface and eminentia of the olfactory sac were then removed and sawed into sections perpendicular to the long axis of the mucosal surface. Each section was dissolved in a tissue solubilizer and counted in a liquid scintillation system. The amount of radioactivity in each section was used to estimate the number of odorant molecules it sorbed. For tritiated butanol there was a significant decrease in radioactivity from the section containing the external naris to that overhanging the internal naris. The steepness of the gradient was unaffected by a rather large range of stimulus flow rates, volumes, and partial pressures. Only when these parameters were pushed to extreme physical limits did this gradient change significantly. When the stimulus was presented through the internal rather than the external naris, the butanol gradient reversed its direction, decreasing from the internal to external. Unlike butanol, tritiated octane presented through the external naris was rather evenly distributed among the mucosal sections. That is, octane showed no distribution gradient across the mucosa. These results complement previous electrophysiological data that suggested a "chromatographic-like" differential sorption of odorant molecules across the mucosa.

Adsorption↗
PubMed2004

Predicted 3-D structures for mouse I7 and rat I7 olfactory receptors and comparison of predicted odor recognition profiles with experiment.

The first step in the perception of an odor is the activation of one or more olfactory receptors (ORs) following binding of the odorant molecule to the OR. In order to initiate the process of determining how the molecular level receptor-odorant interactions are related to odor perception, we used the MembStruk computational method to predict the three-dimensional (3-D) structure of the I7 OR for both mouse and rat. We then used the HierDock ligand docking computational method to predict the binding site and binding energy for the library of 56 odorants to these receptors for which experiment response data are now available. We find that the predicted 3-D structures of the mouse and rat I7 OR lead to predictions of odorant binding that are in good agreement with the experimental results, thus validating the accuracy of both the 3-D structure and the predicted binding site. In particular we predict that heptanal and octanal both bind strongly to both mouse and rat I7 ORs, which conflicts with the older literature but agrees with recent experiments. To provide the basis of additional validations of our 3-D structures, we also report the odorant binding site for a new odorant (8-hydroxy-octanal) with a novel functionality designed to bind strongly to mouse I7. Such validated computational methods should be very useful in predicting the structure and function of many other ORs.

Amino Acid Sequence↗
PubMed2005

Determinants for nasal trigeminal detection of volatile organic compounds.

We explored the influence of methodological and chemical parameters on the detection of nasal chemesthesis (i.e., trigeminal stimulation) evoked by volatile organic compounds (VOCs). To avoid odor biases, chemesthesis was probed via nasal pungency detection in anosmics and via nasal localization (i.e., lateralization) in normosmics, in both cases using forced-choice procedures. In the experiments with anosmics, 12 neat VOCs were selected based on previous reports of lack of chemesthetic response. Although none of the VOCs reached 100% detection, detectability and confidence of detection were higher when using a glass vessel system adapted with nosepieces to fit the nostrils tightly than when using wide-mouth glass jars. Half the stimuli were detected well above chance and half were not. When the latter were tested again after being heated to 37 degrees C, that is, body temperature (from room temperature, 23 degrees C), to increase their vapor concentration, only one, octane, significantly increased its detectability. Chemesthesis gauged with normosmics mirrored that with anosmics. Gas chromatography measurements showed that, even at 23 degrees C, the saturated vapor concentrations of the undetected stimuli, except vanillin, were well above the respective calculated nasal pungency threshold (NPT) from an equation that, in the past, had accurately described and predicted NPTs. We conclude that, except for octane and perhaps vanillin, the failure of the other four VOCs to precipitate nasal chemesthesis rests on a chemical-structural limitation, for example, the molecules lack a key property to fit a receptor pocket, rather than on a concentration limitation, for example, the vapor concentration is too low to reach a threshold value.

Adult↗
PubMed2005

The role of extra-membranous inter-helical loops in helix-helix interactions.

The effect of a short loop connecting two transmembrane alpha-helices was studied using molecular dynamics simulations. Helices F and G from bacteriorhodopsin and two corresponding polyalanine helices were embedded in octane and POPC membranes in a transmembrane configuration both with and without the inter-helical loop. The results indicate that the membrane environment and the sequence of the loop are more influential on the dynamics and structure of the motif than the presence of a loop as such, at least for the time-scales investigated. The four residues in the FG loop are stabilized by four hydrogen bonds. These hydrogen bonds are not present in the polyalanine loop, causing it to be more flexible than the FG loop. This effect was observed independently of the protein environment, stressing the importance of the sequence. The structural analysis indicates that the loop has weak stabilizing properties in all environments. The stabilization due to the presence of the loop was strongest in a simulation of the FG fragment in a membrane-mimetic octane slab. In the simulations of the helix-loop-helix motif embedded in an explicit lipid bilayer model, the lipid bilayer interface compensates to a large extent for the absence of the loop.

Amino Acid Motifs↗
PubMed2002

Dietary conjugated linoleic acid with fish oil alters yolk n-3 and trans fatty acid content and volatile compounds in raw, cooked, and irradiated eggs.

We investigated the effect of dietary conjugated linoleic acid (CLA) along with n-3 polyunsaturated fatty acid (n-3 PUFA) on yolk fatty acid composition and volatile compounds in eggs that were raw (RA), hard-boiled (HB), or hard-boiled, irradiated (HBI, 2.5 kGy). Single Comb White Leghorn laying hens (n = 40) were randomly assigned to one of the four experimental diets containing 0, 0.5, 1.0, or 2.0% CLA. Menhaden oil was used as the source of n-3 PUFA. Eggs collected after 6 wk of feeding were analyzed for fatty acids and volatile compounds. The content of docosahexaenoic acid (C22:6 n-3) was reduced (P < 0.05) in eggs from hens fed the 2.0% CLA diet. Eggs from hens fed 0.5% CLA incorporated the highest concentration of docosahexaenoic acid (P < 0.05) with a concomitant reduction in arachidonic acid (P < 0.05). The yolk contents of cis-9 trans-11 CLA and trans-10 cis-12 CLA increased linearly (P < 0.05) as the dietary CLA supply increased. Total monounsaturates were reduced (P < 0.05) with an increase in saturates in yolk. No difference was observed in the total PUFA content of eggs. Total volatiles were reduced in RA eggs from 1.0 and 2.0% CLA diets. 2-Propanone, hexane, and methyl cyclopentane were the major volatiles in RA eggs and were reduced by dietary CLA at 1.0 and 2.0%. Acetaldehyde, pentane, propanol, acetic acid methyl ester, acetic acid ethyl ester, propionic acid methyl ester, 2-methylmethyl propionic acid, 2-propanone, and octane were the major volatiles in HB eggs and were reduced by 2.0% CLA (P < 0.05). No difference was observed in the acetaldehyde, pentane, propanol, acetic acid ethyl ester, octane, or total volatile content of HBI eggs.

Animals↗
PubMed2001

Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering.

Microemulsions consisting of AOT water, and decane or iso-octane are studied in the region of the phase diagram where surfactant covered water droplets are formed. The polydispersity and shape fluctuations of the microemulsion droplets are determined and compared in the two different alkane types. Conductivity measurements show that there is a pronounced dependence of the temperature behavior of the microemulsion on the type of alkane used. In both cases the microemulsion droplets start to form larger aggregates when the temperature increases. But in the system with decane this aggregation temperature occurs at a temperature about 10 degrees C lower than in a similar system with iso-octane. Aggregation phenomena are avoided and the two systems are at approximately the same reduced temperature with respect to the aggregation temperature when the temperature of the AOT/D(2)O/decane microemulsion is 10 degrees C and the temperature of the AOT/D(2)O/iso-octane microemulsion is 20 degrees C. Contrast variation small-angle neutron scattering measurements are performed at these temperatures on systems with volume fractions of 5% D2O+AOT by varying the scattering length density of the alkane. The small-angle scattering for 11 different contrasts evenly distributed around the match points are studied for each sample. The scattering data for the different contrasts are analyzed using a molecular constrained model for ellipsoidal droplets of water covered by AOT, interacting as polydisperse hard spheres. All contrasts are fitted simultaneously by taking the different contrast factors into account. The analysis show that at the same reduced temperature with respect to the aggregation temperature the droplet size, polydispersity index, the size of the shape fluctuations are similar in the two systems. A polydispersity index (sigma/R of the Gaussian size distribution) of 16% and an average axis ratio of the droplets of 1.56 is found in the AOT/D(2)O/decane microemulsion. In the AOT/D(2)O/iso-octane system the polydispersity index is also 16% while the axis ratio is 1.72. The bending elastic constant kappa and the Gaussian bending elastic constant kappa; can be estimated from these numbers. For AOT/D(2)O/decane we find kappa=3.4 k(B)T and kappa=-5.9 k(B)T and for AOT/D(2)O/iso-octane we find kappa=2.35k(B)T and kappa=-3.8k(B)T, where k(B) is the Boltzmann constant and T is the absolute temperature.

Journal Article↗
PubMed2001

Free-volume viscosity model for fluids in the dense and gaseous states.

A free-volume and friction viscosity model is presented versus pressure and temperature, valid for both gaseous and dense fluids. This model involves only three adjustable parameters for each pure compound. It is able to represent the gas-liquid transition and the behavior in the supercritical conditions. The model has been successfully applied to methane (885 data points for 0.01< or =P< or =200 MPa and 90.7< or =T< or =600 K) and to propane (1085 data points for 0.01< or =P< or =200 MPa and 90< or =T< or =600 K) in the gaseous and dense states (average absolute deviation is 2.59% for methane and 2.50% for propane, with maximum deviation of 14.8% for methane and 9.19% for propane). It has also been applied to hexane, octane, dodecane, benzene, trans-decaline, and 2,2-dimethylpropane (903 data points) in a large pressure range (up to 505.5 MPa). Considering these compounds the maximum deviation is 19.5% (for octane) and the average deviation is 3.51% in the worst case (dodecane, which has data points up to 501.6 MPa).

Journal Article↗
PubMed2003

Water condensation kinetics on a hydrophobic surface.

Employing thermal desorption spectroscopy, we show that the effective probability of water condensation at low water vapor pressure on an octane film is much below unity at 100-120 K. This unusual finding is related to a small binding energy of H2O monomers on octane (approximately equal to 0.08 eV), requiring the formation of critical water clusters for condensation to occur. This results in strong temperature and impingement-rate dependencies of the water condensation rate and a nonlinear uptake as a function of dose time. All these features are rationalized quantitatively by a kinetic model of water condensation.

Journal Article↗
PubMed2003

Bonding of saturated hydrocarbons to metal surfaces.

The adsorption of octane on Cu(110) was studied by x-ray absorption and x-ray emission spectroscopy, in combination with spectrum calculations in the framework of density functional theory, as a model system for alkane adsorption on transition metals. Significant electron sharing between the adsorbate and metal surface and involvement of both bonding and antibonding C-H molecular orbitals in the molecule-metal bond was found. The calculations were extended to the case of octane adsorbed on Ni(110), and the position of the metal d band was found to be important for the bonding. The results were generalized to show that this is important for the efficiency as an alkane dehydrogenation catalyst.

Journal Article↗
PubMed2005

Supramolecular aggregation of two hydroxycarboxylic acid derivatives.

The crystal structures of 7,7-dicyclobutyl-5-hydroxymethyl-6-oxabicyclo[3.2.1]octane-1-carboxylic acid, C17H26O4, (I), and 1-(hydroxymethyl)-7-oxaspiro[bicyclo[3.2.1]octane-6,1'-cyclopentane]-5-carboxylic acid, C13H20O4, (II), determined at 170 K, show that the conformation of the hydroxymethyl group (anti or gauche) affects the dimensionality (one- or two-dimensional) of the supramolecular structures via O-H...O hydrogen bonds. In (I), the carboxyl and hydroxymethyl groups interact with themselves, forming a one-dimensional step-ladder, while in (II), a two-dimensional structure is made up of carboxylic acid centrosymmetric R(2)2(8) dimers connected by hydroxyl-to-ether contacts.

Journal Article↗