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1
Koch, Daniel J., Mike M. Chen, Jan B. van Beilen et Frances H. Arnold. « In Vivo Evolution of Butane Oxidation by Terminal Alkane Hydroxylases AlkB and CYP153A6 ». Applied and Environmental Microbiology 75, no 2 (14 novembre 2008) : 337–44. http://dx.doi.org/10.1128/aem.01758-08.
Texte intégralRésumé :
ABSTRACT Enzymes of the AlkB and CYP153 families catalyze the first step in the catabolism of medium-chain-length alkanes, selective oxidation of the alkane to the 1-alkanol, and enable their host organisms to utilize alkanes as carbon sources. Small, gaseous alkanes, however, are converted to alkanols by evolutionarily unrelated methane monooxygenases. Propane and butane can be oxidized by CYP enzymes engineered in the laboratory, but these produce predominantly the 2-alkanols. Here we report the in vivo-directed evolution of two medium-chain-length terminal alkane hydroxylases, the integral membrane di-iron enzyme AlkB from Pseudomonas putida GPo1 and the class II-type soluble CYP153A6 from Mycobacterium sp. strain HXN-1500, to enhance their activity on small alkanes. We established a P. putida evolution system that enables selection for terminal alkane hydroxylase activity and used it to select propane- and butane-oxidizing enzymes based on enhanced growth complementation of an adapted P. putida GPo12(pGEc47ΔB) strain. The resulting enzymes exhibited higher rates of 1-butanol production from butane and maintained their preference for terminal hydroxylation. This in vivo evolution system could be useful for directed evolution of enzymes that function efficiently to hydroxylate small alkanes in engineered hosts.
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Funhoff, Enrico G., Ulrich Bauer, Inés García-Rubio, Bernard Witholt et Jan B. van Beilen. « CYP153A6, a Soluble P450 Oxygenase Catalyzing Terminal-Alkane Hydroxylation ». Journal of Bacteriology 188, no 14 (15 juillet 2006) : 5220–27. http://dx.doi.org/10.1128/jb.00286-06.
Texte intégralRésumé :
ABSTRACT The first and key step in alkane metabolism is the terminal hydroxylation of alkanes to 1-alkanols, a reaction catalyzed by a family of integral-membrane diiron enzymes related to Pseudomonas putida GPo1 AlkB, by a diverse group of methane, propane, and butane monooxygenases and by some membrane-bound cytochrome P450s. Recently, a family of cytoplasmic P450 enzymes was identified in prokaryotes that allow their host to grow on aliphatic alkanes. One member of this family, CYP153A6 from Mycobacterium sp. HXN-1500, hydroxylates medium-chain-length alkanes (C6 to C11) to 1-alkanols with a maximal turnover number of 70 min−1 and has a regiospecificity of ≥95% for the terminal carbon atom position. Spectroscopic binding studies showed that C6-to-C11 aliphatic alkanes bind in the active site with Kd values varying from ∼20 nM to 3.7 μM. Longer alkanes bind more strongly than shorter alkanes, while the introduction of sterically hindering groups reduces the affinity. This suggests that the substrate-binding pocket is shaped such that linear alkanes are preferred. Electron paramagnetic resonance spectroscopy in the presence of the substrate showed the formation of an enzyme-substrate complex, which confirmed the binding of substrates observed in optical titrations. To rationalize the experimental observations on a molecular scale, homology modeling of CYP153A6 and docking of substrates were used to provide the first insight into structural features required for terminal alkane hydroxylation.
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Jacobs, Cheri Louise, Rodolpho do Aido-Machado, Carmien Tolmie, Martha Sophia Smit et Diederik Johannes Opperman. « CYP153A71 from Alcanivorax dieselolei : Oxidation beyond Monoterminal Hydroxylation of n-Alkanes ». Catalysts 12, no 10 (11 octobre 2022) : 1213. http://dx.doi.org/10.3390/catal12101213.
Texte intégralRésumé :
Selective oxyfunctionalization of non-activated C–H bonds remains a major challenge in synthetic chemistry. The biocatalytic hydroxylation of non-activated C–H bonds by cytochrome P450 monooxygenases (CYPs), however, offers catalysis with high regio- and stereoselectivity using molecular oxygen. CYP153s are a class of CYPs known for their selective terminal hydroxylation of n-alkanes and microorganisms, such as the bacterium Alcanivorax dieselolei, have evolved extensive enzymatic pathways for the oxyfunctionalization of various lengths of n-alkanes, including a CYP153 to yield medium-chain 1-alkanols. In this study, we report the characterization of the terminal alkane hydroxylase from A. dieselolei (CYP153A71) for the oxyfunctionalization of medium-chain n-alkanes in comparison to the well-known CYP153A6 and CYP153A13. Although the expected 1-alkanols are produced, CYP153A71 readily converts the 1-alkanols to the corresponding aldehydes, fatty acids, as well as α,ω-diols. CYP153A71 is also shown to readily hydroxylate medium-chain fatty acids. The X-ray crystal structure of CYP153A71 bound to octanoic acid is solved, yielding an insight into not only the regioselectivity, but also the binding orientation of the substrate, which can be used in future studies to evolve CYP153A71 for improved oxidations beyond terminal n-alkane hydroxylation.
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Mayes, R. W., C. S. Lamb et Patricia M. Colgrove. « The use of dosed and herbage n-alkanes as markers for the determination of herbage intake ». Journal of Agricultural Science 107, no 1 (août 1986) : 161–70. http://dx.doi.org/10.1017/s0021859600066910.
Texte intégralRésumé :
SUMMARYThe recovery in the faeces of the n-alkanes of herbage (odd-chain, C27–C35) and of dosed artificial alkanes (even-chain, C28 and C32) was studied in twelve 4-month-old castrated male lambs. The lambs received three levels of cut, fresh perennial ryegrass or a mixed diet of perennial ryegrass (0·70) and a barley-based concentrate (0·30) (500–900 g D.M./day). C28 and C32 n-alkanes (130 mg each), absorbed onto shredded paper, were given once daily for 17 days to test whether the recoveries of herbage and dosed alkanes were similar to enable their use as markers for determining the herbage intake of grazing sheep. Stearic and palmitic acids (130 mg each) were given with the dosed alkanes to half of the animals with the objective of facilitating emulsification of the dosed alkanes within the digestive tract.With the exception of C27 n-alkane, the faecal recoveries of all alkanes were unaffected by diet, feeding level or emulsifying agent. Faecal recovery of odd- chain herbage n-alkanes increased with increasing C-chain length. The recovery of the dosed C28 n-alkane was slightly greater than the recoveries of both C27, and C29 n-alkanes of herbage. The recoveries of the dosed C32 n-alkane and the herbage C33-alkane were the same.The mean herbage intake estimated using C33 and C32 n-alkanes was identical to the actual herbage intake. Other alkane pairs gave slight underestimates of herbage intake ranging from 3·5% for the C28–C29 pair to 7·6% for the C27–C28 pair. No cyclical pattern of n-alkane excretion throughout the day was observed. Examination of daily variations in faecal alkane concentrations indicated that the start of alkane dosing should precede the sampling of faeces by at least 6 days.These results suggest that accurate estimation of herbage intake in grazing sheep is possible from the simultaneous use of dosed C32 and herbage C33 n-alkanes as markers.The method may be particularly useful in enabling unbiased estimates of herbage intake to be made in animals receiving supplementary feed.
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Gołębiowski, M., M. Paszkiewicz, A. Grubba, D. Gąsiewska, M. I. Boguś, E. Włóka, W. Wieloch et P. Stepnowski. « Cuticular and internal n-alkane composition of Lucilia sericata larvae, pupae, male and female imagines : application of HPLC-LLSD and GC/MS-SIM ». Bulletin of Entomological Research 102, no 4 (25 janvier 2012) : 453–60. http://dx.doi.org/10.1017/s0007485311000800.
Texte intégralRésumé :
AbstractThe composition of cuticular and internal n-alkanes in Lucilia sericata larvae, pupae, and male and female imagines were studied. The cuticular and internal lipid extracts were separated by HPLC-LLSD, after which the hydrocarbon fraction was identified by GC/MS in selected ion monitoring (SIM) and total ion current (TIC) modes.The cuticular lipids of the larvae contained seven n-alkanes from C23 to C31. The major n-alkane in L. sericata larvae was C29 (42.1%). The total cuticular n-alkane content in the cuticular lipids was 31.46 μg g−1 of the insect body. The internal lipids of L. sericata larvae contained five n-alkanes ranged from C25 to C31. The most abundant compound was C27 (61.71 μg g−1 of the insect body). Eighteen n-alkanes from C14 to C31 were identified in the cuticular lipids of the pupae. The most abundant n-alkanes ranged from C25 to C31; those with odd-numbered carbon chains were particularly abundant, the major one being C29:0 (59.5%). Traces of eight cuticular n-alkanes were present. The internal lipids of L. sericata pupae contained five n-alkanes, ranging from C25 to C31. The cuticular lipids of female imagines contained 17 n-alkanes from C12 to C30. Among the cuticular n-alkanes of females, C27 (47.5%) was the most abundant compound. Four n-alkanes, with only odd-numbered carbon chains, were identified in the internal lipids of females. The lipids from both sexes of L. sericata had similar n-alkane profiles. The cuticular lipids of adult males contained 16 n-alkanes ranging from C13 to C31. C27 (47.9%) was the most abundant cuticular n-alkanes in males. The same n-alkanes only with odd-numbered carbon chains and in smaller quantities of C27 (0.1%) were also identified in the internal lipids of males.The highest amounts of total cuticular n-alkanes were detected in males and females of L. sericata (330.4 and 158.93 μg g−1 of the insect body, respectively). The quantities of total cuticular alcohols in larvae and pupae were smaller (31.46 μg g−1 and 42.08 μg g−1, respectively). The internal n-alkane contents of larvae, pupae, and male and female imagines were significantly higher than the cuticular n-alkane contents (153.53, 99.60, 360.06 and 838.76 μg g−1 of the insect body, respectively).
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Madhu, Azad, Myoseon Jang et Yujin Jo. « Modeling the influence of carbon branching structure on secondary organic aerosol formation via multiphase reactions of alkanes ». Atmospheric Chemistry and Physics 24, no 9 (15 mai 2024) : 5585–602. http://dx.doi.org/10.5194/acp-24-5585-2024.
Texte intégralRésumé :
Abstract. Branched alkanes represent a significant proportion of hydrocarbons emitted in urban environments. To accurately predict the secondary organic aerosol (SOA) budgets in urban environments, these branched alkanes should be considered as SOA precursors. However, the potential to form SOA from diverse branched alkanes under varying environmental conditions is currently not well understood. In this study, the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model is extended to predict SOA formation via the multiphase reactions of various branched alkanes. Simulations with the UNIPAR model, which processes multiphase partitioning and aerosol-phase reactions to form SOA, require a product distribution predicted from an explicit gas kinetic mechanism, whose oxygenated products are applied to create a volatility- and reactivity-based αi species array. Due to a lack of practically applicable explicit gas mechanisms, the prediction of the product distributions of various branched alkanes was approached with an innovative method that considers carbon lengths and branching structures. The αi array of each branched alkane was primarily constructed using an existing αi array of the linear alkane with the nearest vapor pressure. Generally, the vapor pressures of branched alkanes and their oxidation products are lower than those of linear alkanes with the same carbon number. In addition, increasing the number of alkyl branches can also decrease the ability of alkanes to undergo autoxidation reactions that tend to form low-volatility products and significantly contribute to alkane SOA formation. To account for this, an autoxidation reduction factor, as a function of the degree and position of branching, was applied to the lumped groups that contain autoxidation products. The resulting product distributions were then applied to the UNIPAR model for predicting branched-alkane SOA formation. The simulated SOA mass was compared to SOA data generated under varying experimental conditions (i.e., NOx levels, seed conditions, and humidity) in an outdoor photochemical smog chamber. Branched-alkane SOA yields were significantly impacted by NOx levels but insignificantly impacted by seed conditions or humidity. The SOA formation from branched and linear alkanes in diesel fuel was simulated to understand the relative importance of branched and linear alkanes with a wide range of carbon numbers. Overall, branched alkanes accounted for a higher proportion of SOA mass than linear alkanes due to their higher contribution to diesel fuel.
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Shu, Bin, Lijun Lin, Yingjun Zhang, Hai Wang et Hailing Luo. « N-alkane profiles of common rangeland species in northern China and the influence of drying method on their concentrations ». Canadian Journal of Plant Science 88, no 1 (1 janvier 2008) : 137–41. http://dx.doi.org/10.4141/cjps07008.
Texte intégralRésumé :
Plant wax alkanes have been used as internal markers to estimate diet composition of grazing animals. However, alkane contents in samples may vary depending on the drying method used. This study was undertaken to determine the alkane profiles and concentrations of 17 common range land species in northern China with two different drying methods. The results showed that regardless of drying methods, the odd-chain alkanes, particular C29 and C33, predominated in cuticular wax in all 17 common species and their component plant parts. The alkane patterns of plant species within the same genus were relatively similar and the differences in alkanes between stem and leaf were generally smaller than those between inflorescences and leaf or stem. The influence of drying methods on alkane concentrations varied depending on family and individual alkane. The effect of drying methods on C29 seemed to be smaller than other alkanes in all the samples. The oven-dry method produced higher concentrations (P < 0.05) in the three major alkanes (C23, C31 and C33) in the Gramineae family than the freeze-dry method. Therefore, studies dealing with alkane concentrations should use the same drying method for all samples. Key words: Alkane pattern, steppe grassland, oven-dry, freeze-dry
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Yang, Jiyuan, Guoyang Lei, Chang Liu, Yutong Wu, Kai Hu, Jinfeng Zhu, Junsong Bao, Weili Lin et Jun Jin. « Characteristics of particulate-bound n-alkanes indicating sources of PM2.5 in Beijing, China ». Atmospheric Chemistry and Physics 23, no 5 (7 mars 2023) : 3015–29. http://dx.doi.org/10.5194/acp-23-3015-2023.
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Abstract. The characteristics of n-alkanes and the contributions of various sources of fine particulate matter (PM2.5) in the atmosphere in Beijing were investigated. PM2.5 samples were collected at Minzu University of China between November 2020 and October 2021, and n-alkanes in the samples were analyzed by gas chromatography mass spectrometry. A positive matrix factorization analysis model and source indices (the main carbon peaks, carbon preference indices, and plant wax contribution ratios) were used to identify the sources of n-alkanes, to determine the contributions of different sources, and to explain the differences. The n-alkane concentrations were 4.51–153 ng m−3 (mean 32.7 ng m−3), and the particulate-bound n-alkane and PM2.5 concentrations varied in parallel. There were marked seasonal and diurnal differences in the n-alkane concentrations (p<0.01). The n-alkane concentrations in the different seasons decreased in the order of winter > spring > summer > fall. The mean concentration of each homolog was higher at night than in the day in all seasons. Particulate-bound n-alkanes were supplied by common anthropogenic and biogenic sources, and fossil fuel combustion was the dominant contributor. The positive matrix factorization model results indicated five sources of n-alkanes in PM2.5, which were coal combustion, diesel vehicle emissions, gasoline vehicle emissions, terrestrial plant release, and mixed sources. Vehicle emissions were the main sources of n-alkanes, contributing 57.6 %. The sources of PM2.5 can be indicated by n-alkanes (i.e., using n-alkanes as organic tracers). Vehicle exhausts strongly affect PM2.5 pollution. Controlling vehicle exhaust emissions is key to controlling n-alkanes and PM2.5 pollution in Beijing.
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Boadi, D. A., S. A. Moshtaghi Nia, K. M. Wittenberg et W. P. McCaughey. « The n-alkane profile of some native and cultivated forages in Canada ». Canadian Journal of Animal Science 82, no 3 (1 septembre 2002) : 465–69. http://dx.doi.org/10.4141/a01-084.
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Frage samples were collected from swards growing in Carberry, Manitoba, Brandon, Manitoba, Saskatoon, Saskatchewan, and St. John’s, Newfoundland, and the alkane concentrations were determined by gas chromatography. Considerable differences were observed in almost all odd-numbered alkanes and in their total content between species. The odd-numbered alkanes were always present in high concentrations compared to the even-chain alkanes in both native and cultivated species. Of the cultivated grasses, the fescues had very high concentrations of CN31 among the odd-chain alkanes, while the legumes tended to have higher concentrations of C29 than C31 or C33. The low concentrations of odd-chain alkanes (< 50 mg kg-1 DM) in little bluestem, indiangrass, reed canarygrass, orchardgrass, timothy and Russian wildrye forages could bias intake calculations of these forages when the double alkane technique is used. Differences between location and cultivar were observed for C29 in timothy and C31 in meadow bromegrass (P < 0.05). There were no effects of location and cultivar on n-alkane concentrations for orchardgrass (P > 0.05). Key words: n-alkanes, forage species, cultivar, location
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Baldwin, Robert L., et George D. Rose. « How the hydrophobic factor drives protein folding ». Proceedings of the National Academy of Sciences 113, no 44 (17 octobre 2016) : 12462–66. http://dx.doi.org/10.1073/pnas.1610541113.
Texte intégralRésumé :
How hydrophobicity (HY) drives protein folding is studied. The 1971 Nozaki–Tanford method of measuring HY is modified to use gases as solutes, not crystals, and this makes the method easy to use. Alkanes are found to be much more hydrophobic than rare gases, and the two different kinds of HY are termed intrinsic (rare gases) and extrinsic (alkanes). The HY values of rare gases are proportional to solvent-accessible surface area (ASA), whereas the HY values of alkanes depend on special hydration shells. Earlier work showed that hydration shells produce the hydration energetics of alkanes. Evidence is given here that the transfer energetics of alkanes to cyclohexane [Wolfenden R, Lewis CA, Jr, Yuan Y, Carter CW, Jr (2015) Proc Natl Acad Sci USA 112(24):7484–7488] measure the release of these shells. Alkane shells are stabilized importantly by van der Waals interactions between alkane carbon and water oxygen atoms. Thus, rare gases cannot form this type of shell. The very short (approximately picoseconds) lifetime of the van der Waals interaction probably explains why NMR efforts to detect alkane hydration shells have failed. The close similarity between the sizes of the opposing energetics for forming or releasing alkane shells confirms the presence of these shells on alkanes and supports Kauzmann's 1959 mechanism of protein folding. A space-filling model is given for the hydration shells on linear alkanes. The model reproduces the n values of Jorgensen et al. [Jorgensen WL, Gao J, Ravimohan C (1985) J Phys Chem 89:3470–3473] for the number of waters in alkane hydration shells.
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Jetter, Reinhard, et Markus Riederer. « Cuticular waxes from the leaves and fruit capsules of eight Papaveraceae species ». Canadian Journal of Botany 74, no 3 (1 mars 1996) : 419–30. http://dx.doi.org/10.1139/b96-052.
Texte intégralRésumé :
Cuticular waxes from leaves and fruit capsules of Papaver alpinum sensu Markgr., P. bracteatum Lindl., P. dubium L., P. nudicaule L., P. orientale L., P. rhoeas L., P. somniferum L., and Eschscholtzia californica Cham. were investigated. They consisted of n-alkanes (< 19%), alk-1-ylesters (< 18%), alk-2-ylesters (< 6%), alkanals (< 19%), secondary alkanols (21–71%, mainly nonacosan-10-ol), triglycerides (< 6%), primary alkanols (2–33%), alkanediols (2–23%, mainly isomeric nonacosanediols), alkanoic acids (< 8%), and alkaloids (< 12%). In addition, minor amounts of iso- and anteiso-alkanes, alkanoic acid methyl esters, esters of alkan-10-ols, benzyl- and phenyl-ethylalcohol, triterpenols and phytosterols, ketols, and ketones were detectable. The isomer composition of the secondary alkanols and their alkanediol, ketol, and ketone derivatives is used to deduce the probable sequence of steps in the respective biosynthetic pathways. Keywords: Papaver, Eschscholtzia, Papaveraceae, cuticular wax, secondary alkanols, biosynthesis.
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Mohamad Shahimin, Mohd Faidz, Julia M. Foght et Tariq Siddique. « Methanogenic Biodegradation of iso-Alkanes by Indigenous Microbes from Two Different Oil Sands Tailings Ponds ». Microorganisms 9, no 8 (23 juillet 2021) : 1569. http://dx.doi.org/10.3390/microorganisms9081569.
Texte intégralRésumé :
iso-Alkanes, a major fraction of the solvents used in bitumen extraction from oil sand ores, are slow to biodegrade in anaerobic tailings ponds. We investigated methanogenic biodegradation of iso-alkane mixtures comprising either three (2-methylbutane, 2-methylpentane, 3-methylpentane) or five (2-methylbutane, 2-methylpentane, 2-methylhexane, 2-methylheptane, 2-methyloctane) iso-alkanes representing paraffinic and naphtha solvents, respectively. Mature fine tailings (MFT) collected from two tailings ponds, having different residual solvents (paraffinic solvent in Canadian Natural Upgrading Limited (CNUL) and naphtha in Canadian Natural Resources Limited (CNRL)), were amended separately with the two mixtures and incubated in microcosms for ~1600 d. The indigenous microbes in CNUL MFT produced methane from the three-iso-alkane mixture after a lag of ~200 d, completely depleting 2-methylpentane while partially depleting 2-methylbutane and 3-methylpentane. CNRL MFT exhibited a similar degradation pattern for the three iso-alkanes after a lag phase of ~700 d, but required 1200 d before beginning to produce methane from the five-iso-alkane mixture, preferentially depleting components in the order of decreasing carbon chain length. Peptococcaceae members were key iso-alkane-degraders in both CNUL and CNRL MFT but were associated with different archaeal partners. Co-dominance of acetoclastic (Methanosaeta) and hydrogenotrophic (Methanolinea and Methanoregula) methanogens was observed in CNUL MFT during biodegradation of three-iso-alkanes whereas CNRL MFT was enriched in Methanoregula during biodegradation of three-iso-alkanes and in Methanosaeta with five-iso-alkanes. This study highlights the different responses of indigenous methanogenic microbial communities in different oil sands tailings ponds to iso-alkanes.
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Chen, W., J. M. Scott, G. J. Blair et R. D. B. Lefroy. « Using plant cuticular alkanes to study plant-animal interactions on pastures ». Canadian Journal of Animal Science 79, no 4 (1 décembre 1999) : 553–56. http://dx.doi.org/10.4141/a99-046.
Texte intégralRésumé :
Two experiments were conducted to validate an approach of using plant cuticular alkanes to estimate diet composition and fecal output. In the first experiment, n-alkane patterns of the four major pasture species were determined and compared and a further two sets of pasture mixtures were prepared to validate the use of plant n-alkane patterns to estimate species composition. In the second experiment, estimates of daily fecal output of grazing sheep were compared using controlled-released devices containing either Cr2O3 or alkanes. There were considerable differences in odd-numbered alkanes and in their total content between species. Results from the first experiment, where two sets of pasture mixtures were analyzed suggest that it is feasible to separate species composition using differences in n-alkane pattern. The second experiment showed that accurate estimation of daily fecal output can also be obtained using capsules containing alkanes. Key words: n-alkane, pasture, diet composition, fecal output
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Ferreira, L. M. M., M. Oliván, M. A. M. Rodrigues, A. Dias-da-Silva et K. Osoro. « The use of alkanes as markers for estimating diet composition in sheep and goats ». BSAP Occasional Publication 34 (2006) : 15–20. http://dx.doi.org/10.1017/s1463981500042205.
Texte intégralRésumé :
SummaryAn experiment was carried out to evaluate the use of alkanes for estimating diet composition of goats and sheep offered three different dietary treatments. Twelve animals as two groups of 4 crossbred goats (G1, 24 kg live weight; G2, 22 kg) and 4 crossbred sheep (S, 26 kg live weight), were housed in metabolism pens. Animals were offered daily a total of 1 kg DM/100 kg live weight. G1 received 70% ryegrass (Lolium perenne) and 30% gorse (Ulex gallii), G2 received 70% ryegrass and 30% heather (Erica sp.) and S group ate 100% ryegrass. Diet composition was estimated from the alkane concentrations (using all alkanes from C23 to C36 or only odd-chain alkanes C27, C29, C31 and C33) in diet and faeces (with or without correction for incomplete faecal recoveries) using least-squares procedures.Dietary treatment and animal species significantly affected alkane faecal recoveries, except for C24 and C36. When applying the faecal recovery corrections, there were no significant differences between measured proportions of dietary components and those estimated using all alkanes or odd-chain alkanes. In contrast, the proportions calculated without faecal recovery correction differed significantly (P<0.05) from the actual proportions and over-estimated the amount in the diet of those plant components with higher concentrations of long-chain alkanes (Erica sp. and Lolium perenne). The results indicate that alkanes are useful markers to estimate diet composition, however, it was observed that animal species and diet composition influenced the faecal recovery of alkanes. This suggests that the use of the alkane methodology for estimating the diet selection of grazing animals should be preceded by a calculation of the actual alkane faecal recoveries for each experimental condition.
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Wilson, H., A. G. Sinclair, F. D. DeB Hovell, R. W. Mayes et S. A. Edwards. « Validation of the n-alkane technique for measuring herbage intake in sows ». Proceedings of the British Society of Animal Science 1999 (1999) : 177. http://dx.doi.org/10.1017/s175275620000332x.
Texte intégralRésumé :
N-alkanes are components of plant cuticular wax which have been successfully used as markers for the estimation of grass intake and digestibility in grazing ruminants (Dove and Mayes, 1991). Natural n-alkanes are predominately odd chain, and a known dose of an artificial even chain n-alkane (normally c32 or c36) is used to enable intake to be measured. Dietary n-alkanes may behave differently in the gastro-intestinal tract of ruminants and non-ruminants (Mayes et al, 1995). Therefore, in order to utilise this methodology in studies of outdoor pigs, this experiment was carried out to validate the faecal recovery of n-alkanes in this species. Since n-alkanes are soluble in lipid, which is often incorporated at high inclusion levels in pig diets, the experiment was also designed to determine whether n-alkane recovery is influenced by dietary lipid content.
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Bliedtner, Marcel, Hans von Suchodoletz, Imke Schäfer, Caroline Welte, Gary Salazar, Sönke Szidat, Mischa Haas, Nathalie Dubois et Roland Zech. « Age and origin of leaf wax <i>n</i>-alkanes in fluvial sediment–paleosol sequences and implications for paleoenvironmental reconstructions ». Hydrology and Earth System Sciences 24, no 4 (28 avril 2020) : 2105–20. http://dx.doi.org/10.5194/hess-24-2105-2020.
Texte intégralRésumé :
Abstract. Leaf wax n-alkanes are increasingly used for quantitative paleoenvironmental reconstructions. However, this is complicated in sediment archives with associated hydrological catchments since the stored n-alkanes can have different ages and origins. 14C dating of the n-alkanes yields independent age information for these proxies, allowing their correct paleoenvironmental interpretation. This also holds true for fluvial sediment–paleosol sequences (FSPSs) that integrate two different n-alkane signals: (i) a catchment signal in fluvial sediments and (ii) an on-site signal from local biomass that increasingly dominates (paleo)soils with time. Therefore, the age and origin of n-alkanes in FSPSs are complex: in fluvial sediment layers they can be pre-aged and reworked when originating from eroded catchment soils or from organic-rich sediment rocks in the catchment. In (paleo)soils, besides an inherited contribution from the catchment, they were formed on-site by local biomass during pedogenesis. Depending on the different relative contributions from these sources, the n-alkane signal from an FSPS shows variable age offsets between its formation and final deposition. During this study, we applied compound-class 14C dating to n-alkanes from an FSPS along the upper Alazani in eastern Georgia. Our results show that preheating the n-alkanes with 120 ∘C for 8 h before 14C dating effectively removed the shorter chains (<C25) that partly originate from n-alkanes from Jurassic black clay shales in the upper catchment. The remaining petrogenic contributions on the longer chains (≥C25) were corrected for by using a constant correction factor that was based on the n-alkane concentrations in a black clay shale sample from the upper catchment. Due to different degrees of pre-aging and reworking, the corrected leaf wax n-alkane ages still indicate relatively large age offsets between n-alkane formation and deposition: while intensively developed (paleo)soils showed no age offsets due to a dominance of leaf wax n-alkanes produced on-site, less intensively developed paleosols showed much larger age offsets due to larger proportions of inherited leaf wax n-alkanes from the fluvial parent material. Accordingly, age offsets in nonpedogenic fluvial sediments were largest and strongly increased after ∼4 ka cal BP. The leaf wax n-alkane homolog distribution from intensively developed (paleo)soils indicates a local dominance of grasses and herbs throughout the Holocene, which was most likely caused by anthropogenic activity. The leaf wax n-alkanes from fluvial sediments show a dominance of deciduous trees and shrubs as well as grasses and herbs in different parts of the catchment between ∼8 and ∼5.6 ka cal BP. Since no older deciduous tree- or shrub-derived n-alkanes were dated, this seems to confirm a delayed regional postglacial reforestation of parts of the catchment compared with western and central Europe.
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LIN, L., G. LIU et Y. ZHANG. « Study on the n-alkane patterns of five dominant forage species of the typical steppe grassland in Inner Mongolia of China ». Journal of Agricultural Science 144, no 2 (6 mars 2006) : 159–64. http://dx.doi.org/10.1017/s0021859606005995.
Texte intégralRésumé :
The alkane patterns of the dominant forage species of the typical steppe grassland in Inner Mongolia were clarified, and the effects of species, sampling time and site on the concentrations of alkanes were evaluated. The results showed that alkanes with odd-numbered carbon chains in the range C25 (n-pentacosane)–C35 (n-pentatriacontane) were predominant in cuticular wax in five dominant grasses of the typical steppe. The C31 (n-hentriacontane) alkanes were always present in the highest concentration in the grass species, especially in the Stipa daicalensis and Stipa grandis. Samples of Artemisia frigida contained not only high concentrations of odd-chain alkanes, but also the even-chain ones compared with other species. The effects of species and sampling time on alkane concentrations were significant, accounting for 0·912 and 0·067 of the total variance, respectively. The site effects on odd-chain alkanes were less than on even-chain. The results of principal component analysis indicated that the patterns of alkane concentrations in the five dominant species could be clearly distinguished during the whole growing season. Therefore, it should be possible to achieve accurate and precise estimations of intake and diet composition of grazing animals of the typical steppe grassland in Inner Mongolia using the alkane technique.
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Marı́n, Mercedes M., Theo H. M. Smits, Jan B. van Beilen et Fernando Rojo. « The Alkane Hydroxylase Gene of Burkholderia cepacia RR10 Is under Catabolite Repression Control ». Journal of Bacteriology 183, no 14 (15 juillet 2001) : 4202–9. http://dx.doi.org/10.1128/jb.183.14.4202-4209.2001.
Texte intégralRésumé :
ABSTRACT In many microorganisms the first step for alkane degradation is the terminal oxidation of the molecule by an alkane hydroxylase. We report the characterization of a gene coding for an alkane hydroxylase in aBurkholderia cepacia strain isolated from an oil-contaminated site. The protein encoded showed similarity to other known or predicted bacterial alkane hydroxylases, although it clustered on a separate branch together with the predicted alkane hydroxylase of a Mycobacterium tuberculosis strain. Introduction of the cloned B. cepacia gene into an alkane hydroxylase knockout mutant of Pseudomonas fluorescens CHAO restored its ability to grow on alkanes, which confirms that the gene analyzed encodes a functional alkane hydroxylase. The gene, which was namedalkB, is not linked to other genes of the alkane oxidation pathway. Its promoter was identified, and its expression was analyzed under different growth conditions. Transcription was induced by alkanes of chain lengths containing 12 to at least 30 carbon atoms as well as by alkanols. Although the gene was efficiently expressed during exponential growth, transcription increased about fivefold when cells approached stationary phase, a characteristic not shared by the few alkane degraders whose regulation has been studied. Expression of the alkB gene was under carbon catabolite repression when cells were cultured in the presence of several organic acids and sugars or in a complex (rich) medium. The catabolic repression process showed several characteristics that are clearly different from what has been observed in other alkane degradation pathways.
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Mayes, R. V., I. A. Wright, C. S. Lamb et Alison McBean. « The use of long-chain n-alkanes for estimating intake and digestibility of herbage in cattle ». Proceedings of the British Society of Animal Production (1972) 1986 (mars 1986) : 83. http://dx.doi.org/10.1017/s0308229600015920.
Texte intégralRésumé :
Studies with sheep suggest that accurate estimates of herbage intake can be obtained by using the herbage alkane tritriacontane (C33) and dosed dotriacontane (C32) as markers, since the faecal recoveries of both alkanes have been shown to be very similar. To validate the technique for herbage intake estimation in grazing cattle there is a need to compare in cattle, the faecal recoveries of both herbage and dosed n-alkanes. It has been observed in sheep that the faecal recoveries of n-alkanes increase as their chain lengths increase, suggesting that the recovery of hexatriacontane (C36), an alkane absent from herbage but available commercially at low cost, should be complete. C36 may therefore have potential as a dosed marker for estimation of faecal output. Thus it may .30 be possible to obtain estimates of both herbage intake and diet digestibility in the same individual grazing animal using n-alkanes as markers. The purpose of the experiment described here was to determine the faecal recoveries in cattle of odd-chain n-alkanes from fresh herbage and of C32 and C36 dosed n-alkanes.
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Cisneros-Dozal, L. M., X. Xu, C. Bryant, E. J. Pearson et J. A. J. Dungait. « Grass Material as a Modern Process Standard for 14C Analysis of n-Alkanes ». Radiocarbon 58, no 3 (30 mars 2016) : 445–58. http://dx.doi.org/10.1017/rdc.2016.24.
Texte intégralRésumé :
AbstractOne of the difficulties in reporting accurate radiocarbon results from compound-specific radiocarbon analysis (CSRA) is the lack of suitable process standard materials to correct for the amount and 14C content of carbon added during extensive sample processing. We evaluated the use of n-alkanes extracted from modern grass material (1.224±0.006 fraction modern) as process standards for CSRA. The n-alkanes were isolated using preparative capillary gas chromatography (PCGC) from two independent chemical extraction methods applied to the grass. Since this was our first assessment of the 14C content of the grass n-alkanes, we corrected for extraneous carbon derived from PCGC isolation using commercially available single compounds of modern and 14C-free content. Results were consistent across the two extraction methods showing that the C29n-alkane has a fraction modern value that is within 1σ of the bulk value of the grass while C31n-alkane and less abundant n-alkanes have values within 2σ of the bulk value of the grass. C29 and C31n-alkanes were the most abundant n-alkanes in the grass and, as such, the more feasible for collection of sufficient amounts of carbon for accelerator mass spectrometry (AMS) analysis. Our results suggest that choosing a grass n-alkane with an elution time closest to that of the unknowns may be advisable due to possibly greater effect from GC column bleed (14C-free) at later elution times. We conclude that C29 and C31n-alkanes in modern grass of known 14C content can be used as in-house standards to correct for the addition of 14C-free carbon during sample preparation for 14C analysis of n-alkanes.
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Dardabou, Laid, José Carlos Martínez-Ávila, Markus Werner Schmidt, Károly Dublecz, Christiane Schwarz, Miguel Angel Ibáñez et Martin Gierus. « Quantitative and Qualitative Evaluation of Plant Intake in Laying Hens : n-Alkanes as Predictive Fecal Markers for Dietary Composition Assessment ». Animals 14, no 3 (24 janvier 2024) : 378. http://dx.doi.org/10.3390/ani14030378.
Texte intégralRésumé :
The shift in animal welfare standards towards free-range housing for laying hens in the EU has raised questions about changes in dietary composition. Accurate assessment of outdoor plant material intake is crucial for effective feeding strategies. This study introduces an approach using n-alkanes as markers to determine plant intake in laying hens, involving n-alkane recovery rate assessment, discriminant analysis and linear equation-solving for both qualitative and quantitative assessment, respectively, considering systematic n-alkane combinations. Two diets: a standard commercial diet and a diet incorporating 1% alfalfa were tested. Chemical analyses showed an altered n-alkane profile due to alfalfa inclusion, resulting a recovery rates ranging from 30–44% depending on the n-alkane type and diet. Statistical analysis revealed significant differences in recovery rates among the different alkanes for the same diets and between the diets for the same alkane, together with an interaction between n-alkane carbon chain length and initial concentration in the diet. The method accurately predicted plant inclusion, with a slight overestimation (2.80%) using the combination C25-C29-C33. Accurate qualitative classification of the animals based on fecal n-alkanes profiles was observed. The study successfully demonstrated the utility of n-alkanes for estimating dietary composition, providing a non-invasive approach for future free-range studies.
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Hendricksen, R. E., M. M. Reich, R. F. Roberton, D. J. Reid, C. Gazzola, J. A. Rideout et R. A. Hill. « Estimating the voluntary intake and digestibility of buffel-grass and lucerne hays offered to Brahman-cross cattle using n-alkanes ». Animal Science 74, no 3 (juin 2002) : 567–77. http://dx.doi.org/10.1017/s1357729800052723.
Texte intégralRésumé :
AbstractThe n-alkane method was developed in temperate areas as a tool to estimate voluntary intake (VI) at pasture. The present study aimed to investigate the performance of n-alkanes as markers for estimating VI of steers (mean live weight 213 kg) offered a range of tropical grass hays and lucerne. Tropical and temperate forages have different n-alkane profiles and little is known about the issues which affect the accuracy of the method under tropical conditions. In two pen experiments (no. = 20 and no. = 24) n-alkanes were dosed using intraruminal controlled-release devices. Actual mean voluntary dry matter intakes for the diets ranged from 3·12 to 4·60 kg/day and actual mean dry-matter digestibility varied between 439 and 620 g/kg. n-Alkane profiles (C30 to C36) of the diets and the faeces for each animal were determined using gas chromatography. The recovery of each n-alkane was determined for each animal. Recoveries of n-alkanes were highly variable and generally varied between diets and between experiments. When adjacent n-alkanes were used to estimate VI (ratio method), agreement with actual VI was often poor. Despite this, where the recoveries of n-alkane pairs were similar, group mean VI were accurately estimated. From these data, it is concluded that estimation of VI in cattle offered tropical grass hays or lucerne hay, requires measured recoveries of both dosed and natural plant n-alkanes. The dosed and natural n-alkane pairs having the most similar recoveries should be used in the ratio method to estimate VI.
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HAMELEERS, A., et R. W. MAYES. « The use of n-alkanes to estimate supplementary grass silage intake in grazing dairy cows ». Journal of Agricultural Science 131, no 2 (septembre 1998) : 205–9. http://dx.doi.org/10.1017/s0021859698005760.
Texte intégralRésumé :
A grazing experiment was carried out using 18 Holstein/Friesian dairy cows at the Scottish Agricultural College, Crichton Royal Farm in 1991, to investigate the use of n-alkanes for estimating supplementary grass silage intake by grazing dairy cows. Two groups of animals grazed perennial ryegrass swards and were offered a supplement, consisting of a perennial ryegrass silage, twice daily after milking. Mean group silage intakes were measured daily during the last 5 days of a 12-day experimental period and individual silage intakes were estimated using n-alkanes. Animals were dosed twice daily with paper pellets containing dotriacontane (C32). The silage was marked with hexatriacontane (C36). The mean silage intake, estimated by weighing, was 6·8 kg DM per day. The mean estimated silage intakes were 6·9, 8·7 and 8·3 kg DM per day respectively using odd-chain n-alkanes in the C27−C35 range of naturally occurring alkanes, the odd-chain n-alkanes in the C27−C35 range with C36, and C36 by itself. No significant differences were found due to sampling routine (morning or afternoon) when using the naturally occurring n-alkanes but significant differences did exist when using the C36 alkane in the calculation of supplement intake. The results indicate that the n-alkane technique can be used to estimate the supplementary silage intake of grazing dairy cows using naturally occurring n-alkane patterns.
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LIN, L. J., H. L. LUO, Y. J. ZHANG et B. SHU. « The effects, in sheep, of dietary plant species and animal live weight on the faecal recovery rates of alkanes and the accuracy of intake and diet composition estimates obtained using alkanes as faecal markers ». Journal of Agricultural Science 145, no 1 (14 novembre 2006) : 87–94. http://dx.doi.org/10.1017/s002185960600654x.
Texte intégralRésumé :
Alkanes can be used as natural markers for estimating diet composition, but a factor should be used to correct for incomplete recovery in faeces. Faecal alkane recovery rates may be influenced by diet and animal factors. However, little research has been conducted to evaluate the effects of herbage species and live weight of animals on faecal alkane recoveries. In the current study, faecal recoveries of alkanes were determined in sheep in four different live weight groups (from 20 to 40 kg) fed three plant species (Elymus sibiricum, Leymus chinensis and L. dasystachys). In a second experiment, the accuracy of intake and diet composition estimates, using alkanes as faecal markers, was assessed by feeding known amounts of the same plant species as a three-component mixture. The results showed that faecal alkane recoveries were influenced significantly by herbage species (P<0·01), but no effect of live weight of animals was observed. Total dry matter intake was estimated correctly based on either C31:C32 or C29:C32 alkane pairs. With respect to estimators of E. sibiricum intake, reasonable results could only be obtained if the faecal alkane concentration was corrected based on diet-specific faecal recovery. More accurate estimations were obtained only if the alkanes found in relatively higher concentrations were used in diet composition estimates instead of using all available alkanes. Due to lower alkane concentrations or similar alkane patterns of L. chinensis and L. dasystachys in the diet, estimates of diet composition of these two herbage species were significantly different from the actual ones (P<0·05), implying that other markers need to be used for accurate estimation.
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Vulich, S. A., E. G. O'Riordan et J. P. Hanrahan. « Use of n-alkanes for the estimation of herbage intake in sheep : accuracy and precision of the estimates ». Journal of Agricultural Science 116, no 2 (avril 1991) : 319–23. http://dx.doi.org/10.1017/s0021859600077741.
Texte intégralRésumé :
SUMMARYTwo experiments at Belclare, Co. Galway, in late autumn 1988, evaluated the use of herbage and dosed n-alkanes for estimating herbage intake by sheep. The first experiment examined faecal recoveries of dosed and herbage n-alkanes. The second experiment assessed the accuracy and precision of herbage intake estimates obtained using the n-alkane technique, and tested the effect of supplying n-alkanes to animals either in gelatine. capsules (containing different ratios of n-alkane: cellulose fibre) or in pellets prepared from shredded paper onto which the n-alkanes had been adsorbed. Individually penned wether lambs were offered freshly cut herbage ad libitum (+ 10%) and actual dry matter intake was recorded daily. Intake was estimated using the C31:C32 and C33:C32 (natural:dosed) n-alkane ratios.There was no significant effect of n-alkane chain length on faecal recovery rate for either the dosed n-alkanes (C32 and C36), the herbage odd-chained n-alkanes (C29, C31, C33 and C36) or those used for the estimation of herbage intake (C31, C32 and C33). The accuracy and precision of the n-alkane technique for estimating herbage intake were unaffected by whether the dosed n-alkane was supplied in capsules or pellets or by the n-alkane:cellulose fibre ratio in the capsules. The bias in the estimated intake was – 8% (± 1·1%) and + 3% (± 1·2%) for estimates based on C31:C32 and C33:C32 ratios, respectively. The estimates based on C31:C32 and C33:C32 exhibited similar precision in the estimation of herbage intake, with a R.S.D. of 6% in actual intake when adjusted for variation in estimated intake and a correlation of +0·92 between actual and estimated herbage intake. The C.V. for actual herbage intake was 17%. The repeatability of actual dry matter intake over three consecutive 6-day periods was 0·54 while those of estimated intake were 0·57 and 0·60 for estimates based on C31:C32 and C33:C32, respectively. The results show that the n-alkane technique can provide an accurate and precise estimate of herbage intake.
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Gibu, Kasai, Ikawa, Akiyama et Fukuda. « Characterization and Transcriptional Regulation of n-Alkane Hydroxylase Gene Cluster of Rhodococcus jostii RHA1 ». Microorganisms 7, no 11 (23 octobre 2019) : 479. http://dx.doi.org/10.3390/microorganisms7110479.
Texte intégralRésumé :
Gram-positive actinomycete Rhodococcus jostii RHA1 is able to grow on C10 to C19 n-alkanes as a sole source of carbon and energy. To clarify, the n-alkane utilization pathway—a cluster of 5 genes (alkBrubA1A2BalkU) which appeared to be involved in n-alkane degradation—was identified and the transcriptional regulation of these genes was characterized. Reverse transcription-PCR analyses revealed that these genes constituted an operon and were transcribed in the presence of n-alkane. Inactivation of alkB led to the absence of the ability to utilize n-undecane. The alkB mutation resulted in reduction of growth rates on C10 and C12 n-alkanes; however, growths on C13 to C19 n-alkanes were not affected by this mutation. These results suggested that alkB was essential for the utilization of C10 to C12 n-alkanes. Inactivation of alkU showed the constitutive expression of alkB. Purified AlkU is able to bind to the putative promoter region of alkB, suggesting that AlkU played a role in repression of the transcription of alk operon. The results of this study indicated that alkB was involved in the medium-chain n-alkanes degradation of strain RHA1 and the transcription of alk operon was negatively regulated by alkU-encoded regulator. This report is important to understand the n-alkane degradation pathway of R. jostii, including the transcriptional regulation of alk gene cluster.
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Dove, H., et RW Mayes. « The use of plant wax alkanes as marker substances in studies of the nutrition of herbivores : a review ». Australian Journal of Agricultural Research 42, no 6 (1991) : 913. http://dx.doi.org/10.1071/ar9910913.
Texte intégralRésumé :
This review discusses the potential use of plant wax components, especially n-alkanes, as markers for estimating herbage intake, estimating the botanical composition of consumed herbage and studying digesta kinetics. Previous approaches to making these measurements are discussed briefly. Attention is drawn to the fact that current methods for estimating intake do not adequately allow for differences between individual animals. It is also suggested that the markers currently used to estimate botanical composition or study digesta kinetics are inadequate. The nature of the chemical constituents of plant waxes is briefly discussed and the concept of using alkanes to estimate intake is introduced. Particular emphasis is given to the fact that although the recovery of alkanes in faeces is not complete, intake can still be estimated using a pair of alkanes (one natural, one dosed) provided these have similar faecal recoveries. The accuracy of estimation of intake is discussed in terms of: obtaining a representative sample of herbage; alkane dosing and faecal sampling procedures; validity of the assumption of similar recoveries for the natural and dosed alkanes; sample preparation and analysis. Published comparisons of estimated and actual intakes are presented, with the conclusion that satisfactory results are obtained if intake is estimated using natural C33 alkane and dosed C32 alkane. The use of the different patterns of alkanes in herbage species, as a means of estimating botanical composition, is then discussed. Results are presented showing this can be done successfully with herbage mixtures or oesophageal extrusa. Procedures are then described for making the corrections for incomplete faecal alkane recovery, necessary to estimate the botanical composition of the herbage consumed by the free-grazing animal. This allows the quantification of the intake of individual plant species by individual animals, and it is suggested that this can be achieved without the need for oesophageally-fistulated (OF) animals. Differences in alkane levels between plant parts within a species are then discussed. It is suggested that these can lead to error in the estimation of intake, if OF animals should consume plant parts different from those consumed by the test animals. However, it is also suggested that differences in alkane levels between plant parts can be used to quantify the intake of these parts, in a manner analogous to the estimation of the intake of individual plant species. The usefulness of alkanes in studies of digesta kinetics is then discussed, principally in relation to the natural alkanes, which remain intimately associated with plant particles in the gut. It is suggested that natural alkanes could prove excellent markers for studies of particle breakdown and digesta flow. The preparation of natural 14C-labelled alkane, for use as a pulse dose in mean retention time studies, is also discussed.
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Nie, Yong, Jieliang Liang, Hui Fang, Yue-Qin Tang et Xiao-Lei Wu. « Two Novel Alkane Hydroxylase-Rubredoxin Fusion Genes Isolated from a Dietzia Bacterium and the Functions of Fused Rubredoxin Domains in Long-Chainn-Alkane Degradation ». Applied and Environmental Microbiology 77, no 20 (26 août 2011) : 7279–88. http://dx.doi.org/10.1128/aem.00203-11.
Texte intégralRésumé :
ABSTRACTTwo alkane hydroxylase-rubredoxin fusion gene homologs (alkW1andalkW2) were cloned from aDietziastrain, designated DQ12-45-1b, which can grow on crude oil andn-alkanes ranging in length from 6 to 40 carbon atoms as sole carbon sources. Both AlkW1 and AlkW2 have an integral-membrane alkane monooxygenase (AlkB) conserved domain and a rubredoxin (Rd) conserved domain which are fused together. Phylogenetic analysis showed that these two AlkB-fused Rd domains formed a novel third cluster with all the Rds from the alkane hydroxylase-rubredoxin fusion gene clusters in Gram-positive bacteria and that this third cluster was distant from the known AlkG1- and AlkG2-type Rds. Expression of thealkW1gene in DQ12-45-1b was induced when cells were grown on C8to C32n-alkanes as sole carbon sources, but expression of thealkW2gene was not detected. Functional heterologous expression in analkBdeletion mutant ofPseudomonas fluorescensKOB2Δ1 suggested thealkW1could restore the growth of KOB2Δ1 on C14and C16n-alkanes and induce faster growth on C18to C32n-alkanes thanalkW1ΔRd, the Rd domain deletion mutant gene ofalkW1, which also caused faster growth than KOB2Δ1 itself. In addition, the artificial fusion of AlkB from the Gram-negativeP. fluorescensCHA0 and the Rds from both Gram-negativeP. fluorescensCHA0 and Gram-positiveDietziasp. DQ12-45-1b significantly increased the degradation of C32alkane compared to that seen with AlkB itself. In conclusion, thealkW1gene cloned fromDietziaspecies encoded an alkane hydroxylase which increased growth on and degradation ofn-alkanes up to C32in length, with its fused rubredoxin domain being necessary to maintain the functions. In addition, the fusion of alkane hydroxylase and rubredoxin genes from both Gram-positive and -negative bacteria can increase the degradation of long-chainn-alkanes (such as C32) in the Gram-negative bacterium.
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Marais, J. P., D. L. Figenschou, P. L. Escott-Watson et L. N. Webber. « Administration in suspension-form of n-alkane external markers for dry matter intake and diet selection studies ». Journal of Agricultural Science 126, no 2 (mars 1996) : 207–10. http://dx.doi.org/10.1017/s0021859600073159.
Texte intégralRésumé :
SUMMARYMilled grass particles were coated with n-alkanes and suspended in a xanthan gum solution. Experiments snowed that grass particles could be coated uniformly with alkanes by means of a rotary evaporator. Further experiments showed that the grass particles, in stable xanthan gum suspension, could be accurately dispensed. The coefficients of variation of the alkane content per dose delivered by means of a dosing gun and syringe were 2·6 and 2·3%, respectively. There was no significant difference between the concentration of faecal alkanes derived from alkanes dosed in suspension-form and alkanes placed directly into the rumen.
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BROSH, A., Z. HENKIN, S. J. ROTHMAN, Y. AHARONI, A. ORLOV et A. ARIELI. « Effects of faecal n-alkane recovery in estimates of diet composition ». Journal of Agricultural Science 140, no 1 (février 2003) : 93–100. http://dx.doi.org/10.1017/s0021859602002757.
Texte intégralRésumé :
The outer surfaces of plant leaves and stems are covered with a waxy layer, a considerable fraction of which comprises n-alkanes which are not digested and, therefore, can be used as markers in animal nutrition studies. Most plant species have a characteristic pattern of n-alkane concentrations in their cuticular wax and this enables the diet composition to be estimated by comparison with the pattern of the n-alkanes in faeces. N-alkane recovery in faeces was determined in a digestibility trial involving three different diets given to four goats, six cows and five calves. The validity of using n-alkane markers to determine diet composition was examined in in vivo feeding trials with goats and cows. The recovery of the odd chain length n-alkanes increased linearly with n-alkane chain length, with no significant differences between treatments. Estimates of diet composition were affected by the faecal n-alkane recovery rate. N-alkanes in plant cuticular wax can be used as natural markers for estimating diet composition, but a recovery factor should be used to correct for incomplete recovery in faeces. More research is needed to extend the findings to wider ranges of diets, animals, environmental conditions and physiological and reproductive states.
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Bugalho, Miguel N., John A. Milne, Robert W. Mayes et Francisco C. Rego. « Plant-wax alkanes as seasonal markers of red deer dietary components ». Canadian Journal of Zoology 83, no 3 (1 mars 2005) : 465–73. http://dx.doi.org/10.1139/z05-031.
Texte intégralRésumé :
n-Alkanes are long-chain hydrocarbons commonly occurring in plant cuticles that can be recovered in herbivore faeces. Differences among plant species in their content of cuticular wax n-alkanes can be exploited to estimate diet composition of herbivores. n-Alkanes have been used mainly in domesticated herbivores feeding on relatively simple diets over short-term periods. Extending the method to wild herbivores feeding on seasonal complex diets is possible provided that n-alkanes act as effective dietary component markers in different seasons. The n-alkane content of browse species and herbage layer and of faeces of red deer (Cervus elaphus L., 1758) males and females in a region with a Mediterranean climate is described. Information on the n-alkane content of plant species was related to that of faeces to estimate the diet composition of red deer. Plant species had distinct n-alkane contents, some of which varied seasonally. The n-alkane content of faeces also varied seasonally and between red deer sexes. Both red deer males and females had relatively high proportion of browse in their diets during summer and of herbage layer in spring, as shown by other studies in Mediterranean environments.
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Xue, Haitao, Penglei Yan, Zhentao Dong, Rixin Zhao, Guozhi Ding, Jinliang Yan et Chunlei Li. « Adsorption Characteristics of Alkanes with Different Carbon Numbers in Kaolinite Slits ». Geofluids 2023 (8 mars 2023) : 1–12. http://dx.doi.org/10.1155/2023/6397404.
Texte intégralRésumé :
Shale oil is of interest for unconventional oil and gas exploration and development and has abundant geological reserves. Shale reservoirs contain numerous nanopores. Understanding the adsorption state of shale oil in the nanopores of shale is beneficial to improve the recovery of shale oil. In this study, the adsorption properties of shale oil in kaolinite slit pores were investigated by molecular dynamics simulation. In order to study the adsorption characteristics of shale oil with different components, a single-component model from n-C8 to n-C15 was established, and a mixed model of n-C8 and n-C15 with different mass ratios represented different crude oil components. The results show that the adsorption capacity per unit area increases with the increase of the alkane carbon number. The adsorption capacity of alkanes on the surface of silicon-oxygen tetrahedron is greater than that on the surface of aluminium-oxygen octahedron. The interaction force between kaolinite and alkane surface increases with the increase of alkane carbon number. The alkane adsorption capacity of silicon-oxygen tetrahedron is stronger than that of aluminium-oxygen octahedron. Competitive adsorption also exists between alkane molecules. Alkanes with higher carbon numbers are more easily adsorbed on the surface of kaolinite. Light alkanes are more likely to exist in free form than heavy alkanes. Based on molecular simulations, we studied the adsorption capacity of alkanes with different carbon numbers and calculated the adsorption capacity per unit area in the pores. It provides a theoretical basis for the calculation of shale oil geological reserves.
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So, Chi Ming, et L. Y. Young. « Initial Reactions in Anaerobic Alkane Degradation by a Sulfate Reducer, Strain AK-01 ». Applied and Environmental Microbiology 65, no 12 (1 décembre 1999) : 5532–40. http://dx.doi.org/10.1128/aem.65.12.5532-5540.1999.
Texte intégralRésumé :
ABSTRACT An alkane-degrading, sulfate-reducing bacterial strain, AK-01, isolated from a petroleum-contaminated sediment was studied to elucidate its mechanism of alkane metabolism. Total cellular fatty acids of AK-01 were predominantly C even when it was grown on C-even alkanes and were predominantly C odd when grown on C-odd alkanes, suggesting that the bacterium anaerobically oxidizes alkanes to fatty acids. Among these fatty acids, some 2-, 4-, and 6-methylated fatty acids were specifically found only when AK-01 was grown on alkanes, and their chain lengths always correlated with those of the alkanes. When [1,2-13C2]hexadecane or perdeuterated pentadecane was used as the growth substrate, 13C-labeled 2-Me-16:0, 4-Me-18:0, and 6-Me-20:0 fatty acids or deuterated 2-Me-15:0, 4-Me-17:0, and 6-Me-19:0 fatty acids were recovered, respectively, confirming that these monomethylated fatty acids were alkane derived. Examination of the 13C-labeled 2-, 4-, and 6-methylated fatty acids by mass spectrometry showed that each of them contained two 13C atoms, located at the methyl group and the adjacent carbon, thus indicating that the methyl group was the original terminal carbon of the [1,2-13C2]hexadecane. For perdeuterated pentadecane, the presence of three deuterium atoms, on the methyl group and its adjacent carbon, in each of the deuterated 2-, 4-, and 6-methylated fatty acids further supported the hypothesis that the methyl group was the terminal carbon of the alkane. Thus, exogenous carbon appears to be initially added to an alkane subterminally at the C-2 position such that the original terminal carbon of the alkane becomes a methyl group on the subsequently formed fatty acid. The carbon addition reaction, however, does not appear to be a direct carboxylation of inorganic bicarbonate. A pathway for anaerobic metabolism of alkanes by strain AK-01 is proposed.
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McLean, B. M. L., R. W. Mayes et F. D. DeB Hovell. « The Use of N-alkanes for Estimating Intake and Passage Rate in Horses ». Proceedings of the British Society of Animal Science 1996 (mars 1996) : 98. http://dx.doi.org/10.1017/s1752756200592977.
Texte intégralRésumé :
Alkanes occur naturally in all plants, although forage crops tend to have higher alkane contents than cereals. N-alkanes have odd-numbered carbon chains. They are ideal for use as markers in feed trials, because, they are inert, indigestible and naturally occurring, and can be recovered in animal faeces. Synthetic alkanes (even-numbered carbon chains) are available commercially and can also used as external markers. Dove and Mayes (1991) cite evidence indicating that faecal recovery of alkanes in ruminants increases with increasing carbon-chain length. Thus the alkane “pairs” (e.g. C35 & C36, and C32 & C33) are used in calculating intake and digestibility because they are long chain and adjacent to each other. However, recent work by Cuddeford and Mayes (unpublished) has found that in horses the faecal recovery rates are similar regardless of chain lengths.
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McLean, B. M. L., R. W. Mayes et F. D. DeB Hovell. « The Use of N-alkanes for Estimating Intake and Passage Rate in Horses ». Proceedings of the British Society of Animal Science 1996 (mars 1996) : 98. http://dx.doi.org/10.1017/s0308229600030683.
Texte intégralRésumé :
Alkanes occur naturally in all plants, although forage crops tend to have higher alkane contents than cereals. N-alkanes have odd-numbered carbon chains. They are ideal for use as markers in feed trials, because, they are inert, indigestible and naturally occurring, and can be recovered in animal faeces. Synthetic alkanes (even-numbered carbon chains) are available commercially and can also used as external markers. Dove and Mayes (1991) cite evidence indicating that faecal recovery of alkanes in ruminants increases with increasing carbon-chain length. Thus the alkane “pairs” (e.g. C35 & C36, and C32 & C33) are used in calculating intake and digestibility because they are long chain and adjacent to each other. However, recent work by Cuddeford and Mayes (unpublished) has found that in horses the faecal recovery rates are similar regardless of chain lengths.
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Wang, Minzhen, Mingzhu Ding et Yingjin Yuan. « Bioengineering for the Microbial Degradation of Petroleum Hydrocarbon Contaminants ». Bioengineering 10, no 3 (10 mars 2023) : 347. http://dx.doi.org/10.3390/bioengineering10030347.
Texte intégralRésumé :
Petroleum hydrocarbons are relatively recalcitrant compounds, and as contaminants, they are one of the most serious environmental problems. n-Alkanes are important constituents of petroleum hydrocarbons. Advances in synthetic biology and metabolic engineering strategies have made n-alkane biodegradation more designable and maneuverable for solving environmental pollution problems. In the microbial degradation of n-alkanes, more and more degradation pathways, related genes, microbes, and alkane hydroxylases have been discovered, which provide a theoretical basis for the further construction of degrading strains and microbial communities. In this review, the current advances in the microbial degradation of n-alkanes under aerobic condition are summarized in four aspects, including the biodegradation pathways and related genes, alkane hydroxylases, engineered microbial chassis, and microbial community. Especially, the microbial communities of “Alkane-degrader and Alkane-degrader” and “Alkane-degrader and Helper” provide new ideas for the degradation of petroleum hydrocarbons. Surfactant producers and nitrogen providers as a “Helper” are discussed in depth. This review will be helpful to further achieve bioremediation of oil-polluted environments rapidly.
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Smits, Theo H. M., Stefanie B. Balada, Bernard Witholt et Jan B. van Beilen. « Functional Analysis of Alkane Hydroxylases from Gram-Negative and Gram-Positive Bacteria ». Journal of Bacteriology 184, no 6 (15 mars 2002) : 1733–42. http://dx.doi.org/10.1128/jb.184.6.1733-1742.2002.
Texte intégralRésumé :
ABSTRACT We have cloned homologs of the Pseudomonas putida GPo1 alkane hydroxylase from Pseudomonas aeruginosa PAO1, Pseudomonas fluorescens CHA0, Alcanivorax borkumensis AP1, Mycobacterium tuberculosis H37Rv, and Prauserella rugosa NRRL B-2295. Sequence comparisons show that the level of protein sequence identity between the homologs is as low as 35%, and that the Pseudomonas alkane hydroxylases are as distantly related to each other as to the remaining alkane hydroxylases. Based on the observation that rubredoxin, an electron transfer component of the GPo1 alkane hydroxylase system, can be replaced by rubredoxins from other alkane hydroxylase systems, we have developed three recombinant host strains for the functional analysis of the novel alkane hydroxylase genes. Two hosts, Escherichia coli GEc137 and P. putida GPo12, were equipped with pGEc47ΔB, which encodes all proteins necessary for growth on medium-chain-length alkanes (C6 to C12), except a functional alkane hydroxylase. The third host was an alkB knockout derivative of P. fluorescens CHA0, which is no longer able to grow on C12 to C16 alkanes. All alkane hydroxylase homologs, except the Acinetobacter sp. ADP1 AlkM, allowed at least one of the three hosts to grow on n-alkanes.
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Madhu, Azad, Myoseon Jang et David Deacon. « Modeling the influence of chain length on secondary organic aerosol (SOA) formation via multiphase reactions of alkanes ». Atmospheric Chemistry and Physics 23, no 2 (27 janvier 2023) : 1661–75. http://dx.doi.org/10.5194/acp-23-1661-2023.
Texte intégralRésumé :
Abstract. Secondary organic aerosol (SOA) from diesel fuel is known to be significantly sourced from the atmospheric oxidation of aliphatic hydrocarbons. In this study, the formation of linear alkane SOA was predicted using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model that simulated multiphase reactions of hydrocarbons. In the model, the formation of oxygenated products from the photooxidation of linear alkanes was simulated using a nearly explicit gas kinetic mechanism. Autoxidation paths integrated with alkyl peroxy radicals were added to the Master Chemical Mechanism v3.3.1 to improve the prediction of low-volatility products in the gas phase and SOA mass. The resulting gas products were then lumped into volatility- and reactivity-based groups that are linked to mass-based stoichiometric coefficients. The SOA mass in the UNIPAR model is produced via three major pathways: partitioning of gaseous oxidized products onto both the organic and wet inorganic phases, oligomerization in the organic phase, and reactions in the wet inorganic phase (acid-catalyzed oligomerization and organosulfate formation). The model performance was demonstrated for SOA data that were produced through the photooxidation of a homologous series of linear alkanes ranging from C9–C15 under varying environments (NOx levels and inorganic seed conditions) in a large outdoor photochemical smog chamber. The product distributions of linear alkanes were mathematically predicted as a function of carbon number using an incremental volatility coefficient (IVC) to cover a wide range of alkane lengths. The prediction of alkane SOA using the incremental volatility-based product distributions, which were obtained with C9–C12 alkanes, was evaluated for C13 and C15 chamber data and further extrapolated to predict the SOA from longer-chain alkanes (≥ C15) that can be found in diesel. The model simulation of linear alkanes in diesel fuel suggests that SOA mass is mainly produced by alkanes C15 and higher. Alkane SOA is insignificantly impacted by the reactions of organic species in the wet inorganic phase due to the hydrophobicity of products but significantly influenced by gas–particle partitioning.
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Ferraz de Oliveira, M. I., A. P. Trigo, J. A. Neves et M. Cancela d´Abreu. « Validation of the n–alkane technique to measure intake and digestibility in Alentejano pigs under “Montanheira” ». BSAP Occasional Publication 34 (2006) : 55–61. http://dx.doi.org/10.1017/s1463981500042266.
Texte intégralRésumé :
SummaryIn the traditional silvo–pastoral system, Alentejano pigs are fattened with acorns and pasture. Although this production system (“Montanheira”) has been characterised, there is a lack of knowledge on intake and digestibility of the diet, mainly due to the absence of tested methodologies in pigs. The n–alkane technique, extensively used in ruminants to estimate diet intake and digestibilitiy, has had less use in pigs. The objective of this experiment was to validate the n–alkane technique in Alentejano pigs. Faecal recoveries of natural and dosed n-alkanes, the diurnal variation of faecal n–alkane concentration, and the time span required to reach a steady state excretion of dosed alkanes were determined. Eight male Alentejano pigs (54.4±9.8 kg LW) were randomly allocated to two groups and placed in metabolic cages. They were fed 0.7 kg of pasture and 0.7kg of ground acorns daily as two meals. Pigs in Group-1 were given once daily artificial C32(40mg/d) and C36(40 mg/d) and those in Group-2 the same alkanes as two daily doses of 20 mg. Steady state excretion of both alkanes was reached 3 days after first dosing. Although no difference (P>0.05) was observed between treatments, the coefficient of variation of feacal alkane concentration when dosed twice daily was generally lower than when dosed once daily. Mean faecal recoveries of n–alkanes increased with increasing carbon-chain length (C25to C36) from 38 to 69%, but were not significantly different from C29, C32, C33and C36(mean 0.694 SEM 0.067). Faecal nalkanes in samples collected every four hours for three days showed no diurnal variation in patterns of excretion apart from a higher concentration of C324 hours after dosing once daily. However variation between animals was lower when artificial alkanes were dosed twice daily than when once daily. The results indicate that the n–alkane techique may be used to estimate intake and digestibility under “Montanheira”, although further validation work needs to be done.
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Xiang, Wei, Shan Hong, Yanfen Xue et Yanhe Ma. « Functional Analysis of Novel alkB Genes Encoding Long-Chain n-Alkane Hydroxylases in Rhodococcus sp. Strain CH91 ». Microorganisms 11, no 6 (9 juin 2023) : 1537. http://dx.doi.org/10.3390/microorganisms11061537.
Texte intégralRésumé :
Rhodococcus sp. strain CH91 is capable of utilizing long-chain n-alkanes as the sole carbon source. Two new genes (alkB1 and alkB2) encoding AlkB-type alkane hydroxylase were predicted by its whole-genome sequence analysis. The purpose of this study was to elucidate the functional role of alkB1 and alkB2 genes in the n-alkane degradation of strain CH91. RT-qPCR analyses revealed that the two genes were induced by n-alkanes ranging from C16 to C36 and the expression of the alkB2 gene was up-regulated much higher than that of alkB1. The knockout of the alkB1 or alkB2 gene in strain CH91 resulted in the obvious reduction of growth and degradation rates on C16-C36 n-alkanes and the alkB2 knockout mutant exhibited lower growth and degradation rate than the alkB1 knockout mutant. When gene alkB1 or alkB2 was heterologously expressed in Pseudomonas fluorescens KOB2Δ1, the two genes could restore its alkane degradation activity. These results demonstrated that both alkB1 and alkB2 genes were responsible for C16-C36 n-alkanes’ degradation of strain CH91, and alkB2 plays a more important role than alkB1. The functional characteristics of the two alkB genes in the degradation of a broad range of n-alkanes make them potential gene candidates for engineering the bacteria used for bioremediation of petroleum hydrocarbon contaminations.
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Whyte, Lyle G., Jalal Hawari, Edward Zhou, Luc Bourbonnière, William E. Inniss et Charles W. Greer. « Biodegradation of Variable-Chain-Length Alkanes at Low Temperatures by a Psychrotrophic Rhodococcussp ». Applied and Environmental Microbiology 64, no 7 (1 juillet 1998) : 2578–84. http://dx.doi.org/10.1128/aem.64.7.2578-2584.1998.
Texte intégralRésumé :
ABSTRACT The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5°C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C10 to C21 alkanes, branched alkanes, and a substituted cyclohexane) present in diesel fuel at 5°C. Mineralization of hexadecane at 5°C was significantly greater in both hydrocarbon-contaminated and pristine soil microcosms seeded with Q15 cells than in uninoculated control soil microcosms. The detection of hexadecane and dodecane metabolic intermediates (1-hexadecanol and 2-hexadecanol and 1-dodecanol and 2-dodecanone, respectively) by solid-phase microextraction–gas chromatography-mass spectrometry and the utilization of potential metabolic intermediates indicated that Q15 oxidizes alkanes by both the terminal oxidation pathway and the subterminal oxidation pathway. Genetic characterization by PCR and nucleotide sequence analysis indicated that Q15 possesses an aliphatic aldehyde dehydrogenase gene highly homologous to the Rhodococcus erythropolis thcA gene. Rhodococcus sp. strain Q15 possessed two large plasmids of approximately 90 and 115 kb (shown to mediate Cd resistance) which were not required for alkane mineralization, although the 90-kb plasmid enhanced mineralization of some alkanes and growth on diesel oil at both 5 and 25°C.
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Zech, Michael, Sebastian Kreutzer, Roland Zech, Tomasz Goslar, Sascha Meszner, Cameron McIntyre, Christoph Häggi, Timothy Eglinton, Dominik Faust et Markus Fuchs. « Comparative14C and OSL dating of loess-paleosol sequences to evaluate post-depositional contamination ofn-alkane biomarkers ». Quaternary Research 87, no 1 (janvier 2017) : 180–89. http://dx.doi.org/10.1017/qua.2016.7.
Texte intégralRésumé :
AbstractThere is an ongoing controversial discussion as to whethern-alkane lipid biomarkers—and organic matter of loess in general—reflect a synsedimentary paleoenvironmental/climate signal or whether they are significantly affected by postdepositional “contamination,” for example related to root and rhizomicrobial activity. In order to address this issue at our study site (the Middle to Late Weichselian loess-paleosol sequence Gleina in Saxony, Germany), we determined and compared radiocarbon ages of bulkn-alkanes and sedimentation ages, as assessed by optically stimulated luminescence (OSL) dating. The bulkn-alkanes of the four dated samples yielded calibrated14C ages ranging from 24.1 to 49.7 cal ka BP (95.4% probability ranges). While the three uppermostn-alkane samples are well within the range or even slightly older than the OSL-inferred sedimentation ages, the lowermostn-alkane sample is slightly younger than the OSL ages. There is hence little or no evidence at our study site forn-alkanes in loess-paleosol sequences being significantly “contaminated” by deep subsoil rooting or microbial processes. We propose a14C isotope mass balance calculation for estimating such contaminations quantitatively. Radiocarbon dating of bulkn-alkanes might have great potential for Quaternary research, and we encourage further comparative14C and OSL studies.
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Firmansyah, R. Arizal, et R. Y. Perry Burhan. « Analisis Aspek Molekuler Biomarka Alkana Bercabang Core Badak 1/208 Muara Badak, Kutai Kartanegara, Kalimantan Timur ». Journal Of Natural Sciences And Mathematics Research 1, no 1 (30 juin 2015) : 26. http://dx.doi.org/10.21580/jnsmr.2015.1.1.481.
Texte intégralRésumé :
Study compound biomarka branched alkanes on core 1/208 Rhinos have done to contribute to the activities of oil exploration wells 1/208 Muara Badak Badak, East Kalimantan's Kutai Kartanegara-through core biomarka profile branched alkanes. Core samples extracted by alternately with solvent mixture of toluene-methanol (3: 1) and chloroform-methanol (3: 1). Then fractionated by Column Chromatography and Thin Layer Chromatography to obtain aliphatic hydrocarbon fraction. Fractions obtained were identified using Gas Chromatography-Mass Spectrometry.The content biomarka aliphatichydrocarbon fraction were identified, among others, iso and anteiso alkanes, mono and trimethyl alkanes. Compounds iso and anteiso alkanes, and alkyl alkane other, providing information that the source of organic material core samples I and II is derived from microorganisms prokaryotic or biogenic precursor derived from cyanobacteria (marine microorganisms) and homologous monomethyl alkanes found in core samples II closer homologous series monomethyl alkanes found in sediments and oil and Precambrian Proterozoic era, so it can be said that the core sample II core samples older than I.
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Boelens, Hans F. M., Wim Th Kok, Onno E. de Noord et Age K. Smilde. « Fast On-Line Analysis of Process Alkane Gas Mixtures by NIR Spectroscopy ». Applied Spectroscopy 54, no 3 (mars 2000) : 406–12. http://dx.doi.org/10.1366/0003702001949492.
Texte intégralRésumé :
Proper operation of a molecular sieve process for the separation of iso- and cyclo-alkanes from normal alkanes requires the fast online detection of normal alkanes breaking through the column. The feasibility of using near-infrared (NIR) spectroscopy for this application was investigated. Alkane mixtures were prepared according to an experimental design. These mixtures, containing small amounts of normal alkanes (C5–C7) and varying amounts of isoand cyclo-alkanes (seven compounds), were analyzed simultaneously at 160 °C with the use of NIR spectroscopy and gas chromatography as a reference method. With an analysis time of 9 s, a critical level of 0.4% [mole/mole] of normal alkanes could be achieved. If a faster response is required, the analysis time can be reduced to 4 s, at the cost, however, of an increase in the critical level to about 1% [mole/mole].
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Moś, Joanna E., Karol A. Stasiewicz, Katarzyna Matras-Postołek et Leszek R. Jaroszewicz. « Thermo-Optical Switching Effect Based on a Tapered Optical Fiber and Higher Alkanes Doped with ZnS:Mn ». Materials 13, no 21 (9 novembre 2020) : 5044. http://dx.doi.org/10.3390/ma13215044.
Texte intégralRésumé :
The paper investigates the effect of thermo-optic switching resulting from the hybrid combination of a tapered optical fiber (TOF) with alkanes doped with nanoparticles of zinc sulfide doped with manganese (ZnS:Mn NP). Presented measurements focused on controlling losses in an optical fiber by modification of a TOF cladding by the alkanes used, characterized by phase change. Temperature changes cause power transmission changes creating a switcher or a sensor working in an ON-OFF mode. Phase change temperatures and changes in the refractive index of the alkane used directly affected power switching. Alkanes were doped with ZnS:Mn NPs to change the hysteresis observed between ON-OFF modes in pure alkanes. The addition of nanoparticles (NPs) reduces the difference between phase changes due to improved thermal conductivity and introduces extra nucleating agents. Results are presented in the wide optical range of 550–1200 nm. In this investigation, hexadecane and heptadecane were a new cladding for TOF. The higher alkanes were doped with ZnS: Mn NPs in an alkane volume of 1 wt.% and 5 wt.%. The thermo-optic effect can be applied to manufacture a thermo-optic switcher or a temperature threshold sensor.
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Chen, W., R. D. B. Lefroy, G. J. Blair et J. M. Scott. « Field variations in alkane signatures among plant species in ‘degraded’ and perennial pastures on the Northern Tablelands of New South Wales ». Australian Journal of Agricultural Research 49, no 2 (1998) : 263. http://dx.doi.org/10.1071/a97022.
Texte intégralRésumé :
Differences in concentrations of n-alkanes in the cuticular waxes of plants can be used to estimate the species composition of herbage mixtures or the diet consumed by grazing animals. The objectives of this study were (i) to provide information on the n-alkane (C25-C35) ‘signatures’ or patterns of pasture species occurring in ‘degraded’ and perennial pastures of the Northern Tablelands, New South Wales, and (ii) to examine the extent of the field variation in the signatures. There were considerable differences in odd-numbered alkanes and in their total content between species. There were also significant differences in n-alkane concentrations among species within grasses, legumes, and weeds. For the individual odd-numbered alkanes, differences between species accounted for 87-93% of the total variance in alkane concentration over 3 samplings. Variable results for the temporal effect suggest that time-specific herbage samples are needed in animal diet studies. Analyses of the spatial effect indicate that random cuts over each treatment plot can obtain representative samples of each species. Multivariate statistical analyses using principal component and discriminant analyses indicated that the patterns of alkanes in species occurring on both degraded and perennial pastures were readily distinguishable. These results confirmed that the alkane technique could be used for estimation of diet composition in grazing sheep on the Northern Tablelands, NSW, where differences in n-alkane signatures between species were sufficient and persistent over time.
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Unal, Y., et P. C. Garnsworthy. « An alternative method of administering alkane markers for estimating intake in dairy cows ». Proceedings of the British Society of Animal Science 1999 (1999) : 91. http://dx.doi.org/10.1017/s1752756200002465.
Texte intégralRésumé :
Alkanes have been used for a number of years to estimate food intake in ruminants. The technique requires animals to be dosed with synthetic even-chained alkanes, usually C32 and C36; faecal concentrations of these are then compared with naturally-occurring alkanes, e.g. C33, to estimate intake. Mayes et al. (1986) prepared capsules containing alkanes on shredded paper; Dove et al. (1988) used hard-shell gelatine capsules to administer dosed alkanes. Both methods required animal handling, extra material, like gelatine capsules or paper, and also some laboratory work for preparing alkane solutions, papers and capsules. We report here a less time-consuming method that can be used with dairy cows or other animals offered concentrates separately from a basal ration. The objective of the study was to see how accurately food intake in dairy cows could be estimated when dosed alkanes are administered via a compound feed.
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van Beilen, Jan B., Enrico G. Funhoff, Alexander van Loon, Andrea Just, Leo Kaysser, Manuel Bouza, René Holtackers, Martina Röthlisberger, Zhi Li et Bernard Witholt. « Cytochrome P450 Alkane Hydroxylases of the CYP153 Family Are Common in Alkane-Degrading Eubacteria Lacking Integral Membrane Alkane Hydroxylases ». Applied and Environmental Microbiology 72, no 1 (janvier 2006) : 59–65. http://dx.doi.org/10.1128/aem.72.1.59-65.2006.
Texte intégralRésumé :
ABSTRACT Several strains that grow on medium-chain-length alkanes and catalyze interesting hydroxylation and epoxidation reactions do not possess integral membrane nonheme iron alkane hydroxylases. Using PCR, we show that most of these strains possess enzymes related to CYP153A1 and CYP153A6, cytochrome P450 enzymes that were characterized as alkane hydroxylases. A vector for the polycistronic coexpression of individual CYP153 genes with a ferredoxin gene and a ferredoxin reductase gene was constructed. Seven of the 11 CYP153 genes tested allowed Pseudomonas putida GPo12 recombinants to grow well on alkanes, providing evidence that the newly cloned P450s are indeed alkane hydroxylases.
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Cooley, Richard B., Bradley L. Dubbels, Luis A. Sayavedra-Soto, Peter J. Bottomley et Daniel J. Arp. « Kinetic characterization of the soluble butane monooxygenase from Thauera butanivorans, formerly ‘Pseudomonas butanovora’ ». Microbiology 155, no 6 (1 juin 2009) : 2086–96. http://dx.doi.org/10.1099/mic.0.028175-0.
Texte intégralRésumé :
Soluble butane monooxygenase (sBMO), a three-component di-iron monooxygenase complex expressed by the C2–C9 alkane-utilizing bacterium Thauera butanivorans, was kinetically characterized by measuring substrate specificities for C1–C5 alkanes and product inhibition profiles. sBMO has high sequence homology with soluble methane monooxygenase (sMMO) and shares a similar substrate range, including gaseous and liquid alkanes, aromatics, alkenes and halogenated xenobiotics. Results indicated that butane was the preferred substrate (defined by k cat : K m ratios). Relative rates of oxidation for C1–C5 alkanes differed minimally, implying that substrate specificity is heavily influenced by differences in substrate K m values. The low micromolar K m for linear C2–C5 alkanes and the millimolar K m for methane demonstrate that sBMO is two to three orders of magnitude more specific for physiologically relevant substrates of T. butanivorans. Methanol, the product of methane oxidation and also a substrate itself, was found to have similar K m and k cat values to those of methane. This inability to kinetically discriminate between the C1 alkane and C1 alcohol is observed as a steady-state concentration of methanol during the two-step oxidation of methane to formaldehyde by sBMO. Unlike methanol, alcohols with chain length C2–C5 do not compete effectively with their respective alkane substrates. Results from product inhibition experiments suggest that the geometry of the active site is optimized for linear molecules four to five carbons in length and is influenced by the regulatory protein component B (butane monooxygenase regulatory component; BMOB). The data suggest that alkane oxidation by sBMO is highly specialized for the turnover of C3–C5 alkanes and the release of their respective alcohol products. Additionally, sBMO is particularly efficient at preventing methane oxidation during growth on linear alkanes ≥C2, despite its high sequence homology with sMMO. These results represent, to the best of our knowledge, the first kinetic in vitro characterization of the closest known homologue of sMMO.
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Smith, A. Q., J. L. Campbell, D. A. Keys et J. W. Fisher. « Rat Tissue and Blood Partition Coefficients for n-Alkanes (C8 to C12) ». International Journal of Toxicology 24, no 1 (janvier 2005) : 35–41. http://dx.doi.org/10.1080/10915810590918698.
Texte intégralRésumé :
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-C12 offer confidence in the partition coefficient predictions for longer chain n-alkanes.