Articles de revues : « Long-chain alkanes »

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Thontowi, Ahmad, Elvi Yetti et Yopi Yopi. « Medium Chain and Long Chain Alkanes Hydroxylase Producing Whole Cell Biocatalyst From Marine Bacteria ». ANNALES BOGORIENSES 22, n^o 1 (10 septembre 2018) : 12. http://dx.doi.org/10.14203/ab.v22i1.329.

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Alkanes are major component of crude oil that could be hydrolyzed by the enzyme of alkane hydroxylase. The are three types of alkane hydroxylase based on the chain length of alkane such as short-chain length/SCL (C2-C4), medium-chain length/MCL (C5-C17), and long-chain length/LCL (C>18). The aims of this study were to characterize and identify alkanes-degrading bacteria from these bacteria. The 30 strains from marine were grown on MCL (Pentane-C5H12, Decane-C10H22, and Pentadecane-C15H32) and LCL (n-Paraffin-C12H19C17 and branch of Pristane-C19H40). The study showed twenty-nine isolates have the ability to degrade alkanes compounds, whereas 14 isolates have grown ability on MCL and LCL medium, 11 isolates have the ability to grow on MCL and n-LCL, 3 isolates have the ability only to grow on MCL medium and 1 isolate has the ability only grow on n-LCL medium. The growth test result indicated that 29 isolates have medium-chain alkane monooxygenase and long-chain alkane hydroxylase. Based on 16S rDNA gene analysis, we obtained twenty nine of oil- degrading bacteria, namely a-proteobacteria (57 %), g-proteobacteria (30 %), Flavobacteria (7 %), Bacilli (3%) and Propionibacteriales (3 %). g-Proteobacteria and a-proteobacteria which seems to play an important role in the alkane biodegradation.

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Thontowi, Ahmad, Elvi Yetti et Yopi Yopi. « Medium Chain and Long Chain Alkanes Hydroxylase Producing Whole Cell Biocatalyst From Marine Bacteria ». ANNALES BOGORIENSES 22, n^o 1 (29 juin 2018) : 12. http://dx.doi.org/10.14203/ann.bogor.2018.v22.n1.12-19.

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Alkanes are major component of crude oil that could be hydrolyzed by the enzyme of alkane hydroxylase. The are three types of alkane hydroxylase based on the chain length of alkane such as short-chain length/SCL (C2-C4), medium-chain length/MCL (C5-C17), and long-chain length/LCL (C>18). The aims of this study were to characterize and identify alkanes-degrading bacteria from these bacteria. The 30 strains from marine were grown on MCL (Pentane-C5H12, Decane-C10H22, and Pentadecane-C15H32) and LCL (n-Paraffin-C12H19C17 and branch of Pristane-C19H40). The study showed twenty-nine isolates have the ability to degrade alkanes compounds, whereas 14 isolates have grown ability on MCL and LCL medium, 11 isolates have the ability to grow on MCL and n-LCL, 3 isolates have the ability only to grow on MCL medium and 1 isolate has the ability only grow on n-LCL medium. The growth test result indicated that 29 isolates have medium-chain alkane monooxygenase and long-chain alkane hydroxylase. Based on 16S rDNA gene analysis, we obtained twenty nine of oil- degrading bacteria, namely a-proteobacteria (57 %), g-proteobacteria (30 %), Flavobacteria (7 %), Bacilli (3%) and Propionibacteriales (3 %). g-Proteobacteria and a-proteobacteria which seems to play an important role in the alkane biodegradation.

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Throne-Holst, Mimmi, Alexander Wentzel, Trond E. Ellingsen, Hans-Kristian Kotlar et Sergey B. Zotchev. « Identification of Novel Genes Involved in Long-Chain n-Alkane Degradation by Acinetobacter sp. Strain DSM 17874 ». Applied and Environmental Microbiology 73, n^o 10 (30 mars 2007) : 3327–32. http://dx.doi.org/10.1128/aem.00064-07.

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ABSTRACT Acinetobacter sp. strain DSM 17874 is capable of utilizing n-alkanes with chain lengths ranging from that of decane (C10H22) to that of tetracontane (C40H82) as a sole carbon source. Two genes encoding AlkB-type alkane hydroxylase homologues, designated alkMa and alkMb, have been shown to be involved in the degradation of n-alkanes with chain lengths of from 10 to 20 C atoms in this strain. Here, we describe a novel high-throughput screening method and the screening of a transposon mutant library to identify genes involved in the degradation of n-alkanes with C chain lengths longer than 20, which are solid at 30°C, the optimal growth temperature for Acinetobacter sp. strain DSM 17874. A library consisting of approximately 6,800 Acinetobacter sp. strain DSM 17874 transposon mutants was constructed and screened for mutants unable to grow on dotriacontane (C32H66) while simultaneously showing wild-type growth characteristics on shorter-chain n-alkanes. For 23 such mutants isolated, the genes inactivated by transposon insertion were identified. Targeted inactivation and complementation studies of one of these genes, designated almA and encoding a putative flavin-binding monooxygenase, confirmed its involvement in the strain's metabolism of long-chain n-alkanes. To our knowledge, almA represents the first cloned gene shown to be involved in the bacterial degradation of long-chain n-alkanes of 32 C's and longer. Genes encoding AlmA homologues were also identified in other long-chain n-alkane-degrading Acinetobacter strains.

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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.

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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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OLIVÁN, M., et K. OSORO. « Effect of temperature on alkane extraction from faeces and herbage ». Journal of Agricultural Science 132, n^o 3 (mai 1999) : 305–11. http://dx.doi.org/10.1017/s0021859699006358.

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The solvent extraction of alkanes from faeces and herbage samples at two different temperatures (cold: 15–25°C and hot: 65°C) was studied in four samples of different matrix types (cattle faeces, sheep faeces, hill grass and heather), in two experiments performed at Villaviciosa, Asturias, Spain in 1994. Two internal standards (IS) of different chain length (C22 and C34) were used to estimate alkane concentrations. Significant differences were detected in alkane extraction derived from temperature of extraction, IS and sample matrix. At the cold temperature, long-chain alkane extraction was not complete, resulting in errors in the estimation of alkane concentration when a long-chain alkane (C34) was used as the only internal standard. However, under hot extraction, long- chain alkanes were completely extracted by the heptane, although estimates made with C22 or C34 as IS were not identical. These results suggest that it would be appropriate to use two internal standards with short and long carbon chain, such as C22 and C34, in routine analyses to establish the completeness of alkane extraction, even under hot conditions, by calculating the relative ratio of both IS in extracts compared to the original C22[ratio ]C34 ratio added to the samples. Any increase or decrease in expected peak areas could be adjusted for all the alkanes in the extracts, and the accuracy of alkane concentration measurements (and therefore the reliability of estimates of intake and especially of diet selection) would be improved.

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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.

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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.

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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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Underwood, Robin, Jill Tomlinson-Phillips et Dor Ben-Amotz. « Are Long-Chain Alkanes Hydrophilic ? » Journal of Physical Chemistry B 114, n^o 26 (8 juillet 2010) : 8646–51. http://dx.doi.org/10.1021/jp912089q.

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Tani, Akio, Takeru Ishige, Yasuyoshi Sakai et Nobuo Kato. « Gene Structures and Regulation of the Alkane Hydroxylase Complex in Acinetobacter sp. Strain M-1 ». Journal of Bacteriology 183, n^o 5 (1 mars 2001) : 1819–23. http://dx.doi.org/10.1128/jb.183.5.1819-1823.2001.

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ABSTRACT In the long-chain n-alkane degraderAcinetobacter sp. strain M-1, two alkane hydroxylase complexes are switched by controlling the expression of twon-alkane hydroxylase-encoding genes in response to the chain length of n-alkanes, while rubredoxin and rubredoxin ruductase are encoded by a single gene and expressed constitutively.

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Bliedtner, Marcel, Imke K. Schäfer, Roland Zech et Hans von Suchodoletz. « Leaf wax n-alkanes in modern plants and topsoils from eastern Georgia (Caucasus) – implications for reconstructing regional paleovegetation ». Biogeosciences 15, n^o 12 (29 juin 2018) : 3927–36. http://dx.doi.org/10.5194/bg-15-3927-2018.

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Abstract. Long-chain n-alkanes originate from leaf waxes of higher terrestrial plants, they are relatively resistant against physical and chemical degradation and are preserved in sediment archives for at least millennial timescales. Since their homologue patterns discriminate between vegetation forms, they were increasingly used for paleovegetation reconstructions during the last years. However, before any robust interpretation of the long-chain n-alkane patterns in sediment archives, reference samples from modern vegetation and topsoil material should be investigated at a regional scale. Apart from some temperate and tropical regions, such systematic regional studies on modern plant and topsoil material are still largely lacking.To test the potential of leaf wax-derived n-alkane patterns for paleoenvironmental studies in the semi-humid to semi-arid central southern Caucasus region, we investigated the influence of different vegetation forms on the leaf wax n-alkane signal in modern plants and topsoil material (0–5 cm) from eastern Georgia. We sampled (i) sites with grassland/herbs that included steppe, cultivated grassland and meadows, and (ii) sites that are dominated by deciduous hornbeam forests.The results show that long-chain n-alkanes originate from leaf waxes of higher terrestrial plants and that their homologue pattern allow to discriminate between different vegetation forms: n-Alkanes derived from sites with grassland/herbs are mainly dominated by C31, while n-alkanes derived from sites with deciduous trees/shrubs show high abundances of C29. Thus, long-chain n-alkanes have a great potential when used for regional paleovegetation reconstructions. Moreover, the n-alkane distributions of the topsoils do not show correlations with mean annual temperatures and precipitation along the investigated transect. As degradation of organic matter can affect the leaf wax n-alkane distribution, we further present an updated end-member model that includes our results, accounts for degradation effects and enables semi-quantitative reconstructions of past vegetation changes in the central southern Caucasus region.

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Carnahan, A. M., D. E. Spalinger et W. B. Collins. « n-Alkane and long-chain alcohol recovery in moose (Alces alces), a browsing herbivore ». Canadian Journal of Zoology 96, n^o 6 (juin 2018) : 559–65. http://dx.doi.org/10.1139/cjz-2017-0131.

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Habitat management for herbivores often depends on an understanding of the food habits of animals. Plant cuticular waxes containing nearly indigestible complex mixture of n-alkanes and long-chain alcohols (LCOHs) have recently shown promise for diet analyses, but the accuracy of the technique depends strongly on the efficiency of recovery of the markers in feces. Fecal recovery of n-alkanes and LCOHs from 10 browse stems or leaves and two ensiled grass hays fed to moose (Alces alces (Linnaeus, 1758)) during in vivo digestion trials was investigated. n-Alkanes and LCOHs were extracted using a single-step accelerated solvent extraction technique and the recovery of these cuticular components was calculated from the feces of the animals. n-Alkane recoveries from feces averaged 0.82, ranging from a low of 0.58 (haylage) to a high of 0.95 (browse stems). LCOH recoveries averaged 0.92 across all forages, ranging from 0.80 (haylage) to a high of 1.13 (browse stems). n-Alkane and LCOH fecal recovery increased with increasing chain length, similar to findings in other studies. Although fecal recovery of n-alkanes and LCOHs were variable, we conclude that they are inversely related to forage digestibility, are consistent within forage classes, and are therefore predictable markers for use in assessing herbivore diets.

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Kong, Weina, Cheng Zhao, Xingwang Gao, Liping Wang, Qianqian Tian, Yu Liu, Shuwen Xue, Zhuang Han, Fulin Chen et Shiwei Wang. « Characterization and Transcriptome Analysis of a Long-Chain n-Alkane-Degrading Strain Acinetobacter Pittii SW-1 ». International Journal of Environmental Research and Public Health 18, n^o 12 (11 juin 2021) : 6365. http://dx.doi.org/10.3390/ijerph18126365.

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Strain sw-1, isolated from 7619-m seawater of the Mariana Trench, was identified as Acinetobacter pittii by 16S rRNA gene and whole-genome sequencing. A. pittii sw-1 was able to efficiently utilize long-chain n-alkanes (C18–C36), but not short- and medium-chain n-alkanes (C8–C16). The degradation rate of C20 was 91.25%, followed by C18, C22, C24, C32, and C36 with the degradation rates of 89.30%, 84.03%, 80.29%, 30.29%, and 13.37%, respectively. To investigate the degradation mechanisms of n-alkanes for this strain, the genome and the transcriptome analyses were performed. Four key alkane hydroxylase genes (alkB, almA, ladA1, and ladA2) were identified in the genome. Transcriptomes of strain sw-1 grown in C20 or CH3COONa (NaAc) as the sole carbon source were compared. The transcriptional levels of alkB and almA, respectively, increased 78.28- and 3.51-fold in C20 compared with NaAc, while ladA1 and ladA2 did not show obvious change. The expression levels of other genes involved in the synthesis of unsaturated fatty acids, permeases, membrane proteins, and sulfur metabolism were also upregulated, and they might be involved in n-alkane uptake. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) confirmed that alkB expression was significantly induced by C20, C24, and C32, and almA induction extent by C24 and C32 was higher than that with C20. Furthermore, ladA2 expression was only induced by C32, and ladA1 expression was not induced by any of n-alkanes. In addition, A. pittii sw-1 could grow with 0%–3% NaCl or 8 out of 10 kinds of the tested heavy metals and degrade n-alkanes at 15 °C. Taken together, these results provide comprehensive insights into the degradation of long-chain n-alkanes by Acinetobacter isolated from the deep ocean environment.

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Goworek, Tomasz, Bożena Zgardzińska, Marek Pietrow et Jan Wawryszczuk. « Positronium in Normal Alkanes ». Materials Science Forum 733 (novembre 2012) : 67–74. http://dx.doi.org/10.4028/www.scientific.net/msf.733.67.

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A review of data about positron annihilation lifetime in normal alkanes is presented. It was found that positronium in rigid phase locates in the interlamellar gap, while in the rotator one in free volumes inside lamellae. Interesting effects seem to be: identity of o-Ps lifetime in rotator and liquid phase in long chain alkanes; appearance of “premature” rotator phase in nonadecane with low tricosane admixture, long-term relaxation after the changes of temperature or pressure in some binary mixtures, formation of porous structure at solidification of argon saturated alkane under high pressure.

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Erickson, M. H., H. W. Wallace et B. T. Jobson. « Quantification of diesel exhaust gas phase organics by a thermal desorption proton transfer reaction mass spectrometer ». Atmospheric Chemistry and Physics Discussions 12, n^o 2 (20 février 2012) : 5389–423. http://dx.doi.org/10.5194/acpd-12-5389-2012.

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Abstract. A new approach was developed to measure the total abundance of long chain alkanes (C12 and above) in urban air using thermal desorption with a proton transfer reaction mass spectrometer (PTR-MS). These species are emitted in diesel exhaust and may be important precursors to secondary organic aerosol production in urban areas. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The yield of the fragment ions is a function of drift conditions. At a drift field strength of 80 Townsends, the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Higher drift field strengths yield greater normalized sensitivity implying that the proton affinity of the long chain n-alkanes is less than H2O. Analysis of diesel fuel shows the mass spectrum was dominated by alkanes (CnH2n+1), monocyclic aromatics, and an ion group with formula CnH2n−1 (m/z 97, 111, 125, 139). The PTR-MS was deployed in Sacramento, CA during the Carbonaceous Aerosols and Radiative Effects Study field experiment in June 2010. The ratio of the m/z 97 to 85 ion intensities in ambient air matched that found in diesel fuel. Total diesel exhaust alkane concentrations calculated from the measured abundance of m/z 85 ranged from the method detection limit of ~1 μg m−3 to 100 μg m−3 in several air pollution episodes. The total diesel exhaust alkane concentration determined by this method was on average a factor of 10 greater than the sum of alkylbenzenes associated with spark ignition vehicle exhaust.

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Lo Piccolo, Luca, Claudio De Pasquale, Roberta Fodale, Anna Maria Puglia et Paola Quatrini. « Involvement of an Alkane Hydroxylase System ofGordoniasp. Strain SoCg in Degradation of Solidn-Alkanes ». Applied and Environmental Microbiology 77, n^o 4 (23 décembre 2010) : 1204–13. http://dx.doi.org/10.1128/aem.02180-10.

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ABSTRACTEnzymes involved in oxidation of long-chainn-alkanes are still not well known, especially those in Gram-positive bacteria. This work describes the alkane degradation system of then-alkane degrader actinobacteriumGordoniasp. strain SoCg, which is able to grow onn-alkanes from dodecane (C12) to hexatriacontane (C36) as the sole C source. SoCg harbors in its chromosome a singlealklocus carrying six open reading frames (ORFs), which shows 78 to 79% identity with the alkane hydroxylase (AH)-encoding systems of other alkane-degrading actinobacteria. Quantitative reverse transcription-PCR showed that the genes encoding AlkB (alkane 1-monooxygenase), RubA3 (rubredoxin), RubA4 (rubredoxin), and RubB (rubredoxin reductase) were induced by bothn-hexadecane andn-triacontane, which were chosen as representative long-chain liquid and solidn-alkane molecules, respectively. Biotransformation ofn-hexadecane into the corresponding 1-hexadecanol was detected by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME/GC-MS) analysis. TheGordoniaSoCgalkBwas heterologously expressed inEscherichia coliBL21 and inStreptomyces coelicolorM145, and both hosts acquired the ability to transformn-hexadecane into 1-hexadecanol, but the corresponding long-chain alcohol was never detected onn-triacontane. However, the recombinantS. coelicolorM145-AH, expressing theGordonia alkBgene, was able to grow onn-triacontane as the sole C source. A SoCgalkBdisruption mutant that is completely unable to grow onn-triacontane was obtained, demonstrating the role of an AlkB-type AH system in degradation of solidn-alkanes.

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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.

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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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Liu, Yin Song, Hong Jun Han et Fang Fang. « Degradation of Long-Chain n-Alkanes by Acinetobacter Sp. » Advanced Materials Research 726-731 (août 2013) : 2151–55. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.2151.

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Alkanes are widespread in nature and cause seriously pollution of environment. In many of oil pollution treatment method, because of economic, effective and less damaging to the environment and many other advantages, bioremediation technology is thought to have broad application prospects. In this study, we isolated an efficient alkane-degrading strain from some coal gasification wastewater sludge. It was identified the strain L2-4 as Acinetobacter sp.(KC211013) through morphology and 16SrDNA sequence analysis. The maximum degradation rate was aquired to 58.7% under the condition of original alkanes concentration 700mg/L, pH 7.0 and temperature 35°C. The study was designed to provide good strain resources for oil pollution remediation and microbial en hanced oil recovery.

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Park, Myong-Ok. « New Pathway for Long-Chain n-Alkane Synthesis via 1-Alcohol in Vibrio furnissii M1 ». Journal of Bacteriology 187, n^o 4 (15 février 2005) : 1426–29. http://dx.doi.org/10.1128/jb.187.4.1426-1429.2005.

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ABSTRACT Alkane biosynthesis in the bacterium Vibrio furnissii M1 involves the synthesis of long-chain alkanes via 1-alcohol. Evidence for this novel pathway are the following. (i) Both even- and odd-carbon-number n-alkanes were produced from glucose, while only even-carbon-number fatty acids were produced in V. furnissii M1. This result cannot be explained by the decarbonylation pathway. (ii) Pentadecane and hexadecane were produced from 1-hexadecanoic acid by membrane fractions of V. furnissii M1, and radioisotope precursor-tracer experiments, in which 1-[1-14C]hexadecanoic acid was fed, identified the corresponding alcohol, aldehyde, and alkane derivatives. Since all metabolites maintained the radioisotope label at 1-C, they were produced by a pathway in which the carbon structure was retained, i.e., a reduction pathway. (iii) n-Hexadecane was produced when 1-hexadecanol was fed to membrane preparations.

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Schäfer, Imke K., Verena Lanny, Jörg Franke, Timothy I. Eglinton, Michael Zech, Barbora Vysloužilová et Roland Zech. « Leaf waxes in litter and topsoils along a European transect ». SOIL 2, n^o 4 (25 octobre 2016) : 551–64. http://dx.doi.org/10.5194/soil-2-551-2016.

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Abstract. Lipid biomarkers are increasingly used to reconstruct past environmental and climate conditions. Leaf-wax-derived long-chain n-alkanes and n-alkanoic acids may have great potential for reconstructing past changes in vegetation, but the factors that affect the leaf wax distribution in fresh plant material, as well as in soils and sediments, are not yet fully understood and need further research. We systematically investigated the influence of vegetation and soil depth on leaf waxes in litter and topsoils along a European transect. The deciduous forest sites are often dominated by the n-C27 alkane and n-C28 alkanoic acid. Conifers produce few n-alkanes but show high abundances of the C24 n-alkanoic acid. Grasslands are characterized by relatively high amounts of C31 and C33 n-alkanes and C32 and C34 n-alkanoic acids. Chain length ratios thus may allow for distinguishing between different vegetation types, but caution must be exercised given the large species-specific variability in chain length patterns. An updated endmember model with the new n-alkane ratio (n-C31 + n-C33) / (n-C27 + n-C31 + n-C33) is provided to illustrate, and tentatively account for, degradation effects on n-alkanes.

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Li, Zhuolun, Youhong Gao et Lang Han. « Holocene vegetation signals in the Alashan Desert of northwest China revealed by lipid molecular proxies from calcareous root tubes ». Quaternary Research 88, n^o 1 (29 juin 2017) : 60–70. http://dx.doi.org/10.1017/qua.2017.33.

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AbstractIn the hinterland of deserts, it is difficult to reconstruct paleovegetation using fossil pollen because of the low pollen concentration. Therefore, an efficient method is needed to reconstruct the paleovegetation of desert regions. In this study, 34 Holocene calcareous root tube (CRT) samples were collected from the Alashan Desert in northwest China, and lipid molecular proxies from CRTs were selected to address this deficiency. The results show that n-alkanes mainly maximized at C27, C29, and C16, and that the carbon preference index is close to 1. Thus, the sources of n-alkanes from CRTs were the roots of higher plants and microorganisms, and thus changes in n-alkanes from CRTs could reveal variations in vegetation cover. The n-alkane Cmax of long-chain n-alkanes (C>25) in CRTs, maximizing at C27, indicated that vegetation in the Alashan Desert was characterized by shrub vegetation during the Holocene. Changes in the ratio of (C27+C29)/(C31+C33) indicated that the biomass of shrub vegetation increased during the period 7–2 cal ka BP. Moreover, the relative concentration of short-chain to long-chain n-alkanes decreased from 7 to 2 cal ka BP, suggesting that the effective moisture decreased during that period.

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Hayes, R. V., C. S. Lamb et Patricia M. Colgrove. « Determination of herbage intake of suckling lambs using long-chain n-alkanes as markers ». Proceedings of the British Society of Animal Production (1972) 1986 (mars 1986) : 82. http://dx.doi.org/10.1017/s0308229600015919.

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The n-alkanes of grass outioular wax (odd-chain, C25- C25) can be used simultaneously with dosed n-alkanes (C28or C32) as markers for estimating the herbage intake of grazing sheep if the faecal recoveries of both herbage and dosed markers are the same. In adult sheep the accuracy of herbage intake estimation is not affected by the inclusion of concentrate in the diet as long as the intake and alkane concentrations of the concentrate are known. If, similarly, the ingestion of milk does not interfere with the relative absorption of dosed and herbage alkanes the herbage intake of suckling lambs at pasture could be estimated. To evaluate the potential of the technique in suckling lambs the faecal recoveries of odd-chain herbage n-alkanes and of dosed dotriacontane (C32) were determined in lambs offered eves’ milk and freshly cut herbage.From 2 weeks of age seven individually-housed male lambs received 1 kg/day homogenised ewes’ milk (166 g/day dry matter (DM)) in 4 feeds from an automatic feeder. The milk Has obtained by daily hand-milking of East Friesland ewes and was stored at -20° until used. Freshly cut perennial ryegrass was offered to the lambs ad libitum from the age of 4 weeks. A 6-day total collection of faeces was carried out when the lamba were 10 weeks of age.

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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, n^o 7 (1 juillet 1998) : 2578–84. http://dx.doi.org/10.1128/aem.64.7.2578-2584.1998.

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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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Yu, Yunlong, Yuanyuan Li, Zhigang Guo et Hua Zou. « Distribution and sources of n-alkanes in surface sediments of Taihu Lake, China ». Archives of Environmental Protection 42, n^o 1 (1 mars 2016) : 49–55. http://dx.doi.org/10.1515/aep-2016-0006.

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Abstract The last study on n-alkanes in surface sediments of Taihu Lake was in 2000, only 13 surface sediment samples were analysed, in order to have a comprehensive and up-to-date understanding of n-alkanes in the surface sediments of Taihu Lake, 41 surface sediment samples were analyzed by GC-MS. C10 to C37 were detected, the total concentrations of n-alkanes ranged from 2109 ng g−1 to 9096 ng g−1 (dry weight). There was strong odd carbon predominance in long chain n-alkanes and even carbon predominance in short chain n-alkanes. When this finding was combined with the analysis results of wax n-alkanes (WaxCn), carbon preference index (CPI), unresolved complex mixture (UCM), hopanes and steranes, it was considered that the long chain n-alkanes were mainly from terrigenous higher plants, and that the short chain n-alkanes mainly originated from bacteria and algae in the lake, compared with previous studies, there were no obvious anthropogenic petrogenic inputs. Terrestrial and aquatic hydrocarbons ratio (TAR) and C21−/C25+ indicated that terrigenous input was higher than aquatic sources and the nearshore n-alkanes were mainly from land-derived sources. Moreover, the distribution of short chain n-alkanes presented a relatively uniform pattern, while the long chain n-alkanes presented a trend that concentrations dropped from nearshore places to the middle of lake.

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Zaleski, R., J. Wawryszczuk et T. Goworek. « Positronium Formation in Solid Long-Chain Alkanes ». Acta Physica Polonica A 107, n^o 4 (avril 2005) : 635–41. http://dx.doi.org/10.12693/aphyspola.107.635.

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Underwood,, Robin, Jill Tomlinson-Phillips, et Dor Ben-Amotz. « Correction to “Are Long-Chain Alkanes Hydrophilic?” ». Journal of Physical Chemistry B 115, n^o 23 (16 juin 2011) : 7709. http://dx.doi.org/10.1021/jp2043224.

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Wentzel, Alexander, Trond E. Ellingsen, Hans-Kristian Kotlar, Sergey B. Zotchev et Mimmi Throne-Holst. « Bacterial metabolism of long-chain n-alkanes ». Applied Microbiology and Biotechnology 76, n^o 6 (3 août 2007) : 1209–21. http://dx.doi.org/10.1007/s00253-007-1119-1.

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Durupt, N., A. Aoulmi, M. Bouroukba et M. Rogalski. « Heat capacities of liquid long-chain alkanes ». Thermochimica Acta 274 (mars 1996) : 73–80. http://dx.doi.org/10.1016/0040-6031(95)02255-4.

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Ratajczak, Andreas, Walter Geißdörfer et Wolfgang Hillen. « Expression of Alkane Hydroxylase fromAcinetobacter sp. Strain ADP1 Is Induced by a Broad Range of n- Alkanes and Requires the Transcriptional Activator AlkR ». Journal of Bacteriology 180, n^o 22 (15 novembre 1998) : 5822–27. http://dx.doi.org/10.1128/jb.180.22.5822-5827.1998.

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ABSTRACT In Acinetobacter sp. strain ADP1, alkane degradation depends on at least five essential genes. rubAB andxcpR are constitutively transcribed. Here we describe inducible transcription of alkM, which strictly depends on the presence of the transcriptional activator AlkR. alkRitself is expressed at a low level, while a chromosomally locatedalkM::lacZ fusion is inducible by middle-chain-length alkanes from heptane to undecane, which do not support growth of ADP1, and by long-chain-length alkanes from dodecane to octadecane, which are used as sources of carbon and energy. The putative AlkM substrate 1-dodecene is also an effective inducer. Products of alkane hydroxylase activity like 1-dodecanol prevent induction of alkM expression. alkM is expressed only in stationary phase, suggesting its dependence on at least one other regulatory mechanism.

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van Beilen, Jan B., Theo H. M. Smits, Franz F. Roos, Tobias Brunner, Stefanie B. Balada, Martina Röthlisberger et Bernard Witholt. « Identification of an Amino Acid Position That Determines the Substrate Range of Integral Membrane Alkane Hydroxylases ». Journal of Bacteriology 187, n^o 1 (1 janvier 2005) : 85–91. http://dx.doi.org/10.1128/jb.187.1.85-91.2005.

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ABSTRACT Selection experiments and protein engineering were used to identify an amino acid position in integral membrane alkane hydroxylases (AHs) that determines whether long-chain-length alkanes can be hydroxylated by these enzymes. First, substrate range mutants of the Pseudomonas putida GPo1 and Alcanivorax borkumensis AP1 medium-chain-length AHs were obtained by selection experiments with a specially constructed host. In all mutants able to oxidize alkanes longer than C13, W55 (in the case of P. putida AlkB) or W58 (in the case of A. borkumensis AlkB1) had changed to a much less bulky amino acid, usually serine or cysteine. The corresponding position in AHs from other bacteria that oxidize alkanes longer than C13 is occupied by a less bulky hydrophobic residue (A, V, L, or I). Site-directed mutagenesis of this position in the Mycobacterium tuberculosis H37Rv AH, which oxidizes C10 to C16 alkanes, to introduce more bulky amino acids changed the substrate range in the opposite direction; L69F and L69W mutants oxidized only C10 and C11 alkanes. Subsequent selection for growth on longer alkanes restored the leucine codon. A structure model of AHs based on these results is discussed.

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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, n^o 3 (1 mars 2005) : 465–73. http://dx.doi.org/10.1139/z05-031.

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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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Erickson, M. H., M. Gueneron et B. T. Jobson. « Measuring long chain alkanes in diesel engine exhaust by thermal desorption PTR-MS ». Atmospheric Measurement Techniques 7, n^o 1 (27 janvier 2014) : 225–39. http://dx.doi.org/10.5194/amt-7-225-2014.

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Abstract. A method using thermal desorption sampling and analysis by proton transfer reaction mass spectrometry (PTR-MS) to measure long chain alkanes (C12–C18) and other larger organics associated with diesel engine exhaust emissions is described. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Fragment ion distribution and sensitivity is a function of drift conditions. At 80 Td the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The mass spectrum of gasoline and diesel fuel at 80 Td displayed ion group patterns that can be related to known fuel constituents, such as alkanes, alkylbenzenes and cycloalkanes, and other compound groups that are inferred from molecular weight distributions such as dihydronapthalenes and naphthenic monoaromatics. It is shown that thermal desorption sampling of gasoline and diesel engine exhausts at 80 Td allows for discrimination against volatile organic compounds, allowing for quantification of long chain alkanes from the abundance of CnH2n+1 fragment ions. The total abundance of long chain alkanes in diesel engine exhaust was measured to be similar to the total abundance of C1–C4 alkylbenzene compounds. The abundance patterns of compounds determined by thermal desorption sampling may allow for emission profiles to be developed to better quantify the relative contributions of diesel and gasoline exhaust emissions on organic compounds concentrations in urban air.

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Erickson, M. H., M. Gueneron et B. T. Jobson. « Measuring long chain alkanes in diesel engine exhaust by thermal desorption PTR-MS ». Atmospheric Measurement Techniques Discussions 6, n^o 4 (1 juillet 2013) : 6005–46. http://dx.doi.org/10.5194/amtd-6-6005-2013.

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Abstract. A method using thermal desorption sampling and analysis by PTR-MS to measure long chain alkanes (C12-C18) and other larger organics associated with diesel engine exhaust emissions is described. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Fragment ion distribution and sensitivity is a function of drift conditions. At 80 Td the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The mass spectrum of gasoline and diesel fuel at 80 Td displayed ion group patterns that can be related to known fuel constituents, such as alkanes, alkylbenzenes and cycloalkanes, and other compound groups that are inferred from molecular weight distributions such as dihydronapthalenes and naphthenic monoaromatics. It is shown that thermal desorption sampling of gasoline and diesel engine exhausts at 80 Td allows for discrimination against light alkanes and alkenes which are a major constituent of both exhausts, allowing for quantification of higher molecular weight alkanes from the abundance of CnH2n+1 fragment ions. Using this approach, the molar abundance of C12-C18 alkanes in diesel engine exhaust was found to be 75% that of the total C1-C4 alkylbenzene abundance. While the PTR-MS mass spectra of gasoline and diesel exhaust looked similar, the abundance of higher molecular weight compounds relative to that of C4-alkylbenzenes was much greater in diesel engine exhaust. The abundance patterns of compounds determined by thermal desorption sampling may allow for emission profiles to be developed to better quantify the relative contributions of diesel and gasoline exhaust emissions of larger organic compounds to urban air concentrations.

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Yamane, Kunio, Shigeru Matsuyama, Kensuke Igarashi, Motoo Utsumi, Yoshihiro Shiraiwa et Tomohiko Kuwabara. « Anaerobic Coculture of Microalgae with Thermosipho globiformans and Methanocaldococcus jannaschii at 68°C Enhances Generation ofn-Alkane-Rich Biofuels after Pyrolysis ». Applied and Environmental Microbiology 79, n^o 3 (26 novembre 2012) : 924–30. http://dx.doi.org/10.1128/aem.01685-12.

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ABSTRACTWe tested different alga-bacterium-archaeon consortia to investigate the production of oil-like mixtures, expecting thatn-alkane-rich biofuels might be synthesized after pyrolysis.Thermosipho globiformansandMethanocaldococcus jannaschiiwere cocultured at 68°C with microalgae for 9 days under two anaerobic conditions, followed by pyrolysis at 300°C for 4 days.Arthrospira platensis(Cyanobacteria),Dunaliella tertiolecta(Chlorophyta),Emiliania huxleyi(Haptophyta), andEuglena gracilis(Euglenophyta) served as microalgal raw materials.D. tertiolecta,E. huxleyi, andE. graciliscocultured with the bacterium and archaeon inhibited their growth and CH4production.E. huxleyihad the strongest inhibitory effect. Biofuel generation was enhanced by reducing impurities containing alkanenitriles during pyrolysis. The composition and amounts ofn-alkanes produced by pyrolysis were closely related to the lipid contents and composition of the microalgae. Pyrolysis ofA. platensisandD. tertiolectacontaining mainly phospholipids and glycolipids generated short-carbon-chainn-alkanes (n-tridecane ton-nonadecane) and considerable amounts of isoprenoids.E. gracilisalso produced mainly shortn-alkanes. In contrast,E. huxleyicontaining long-chain (31 and 33 carbon atoms) alkenes and very long-chain (37 to 39 carbon atoms) alkenones, in addition to phospholipids and glycolipids, generated a high yield ofn-alkanes of various lengths (n-tridecane ton-pentatriacontane). The gas chromatography-mass spectrometry (GC-MS) profiles of thesen-alkanes were similar to those of native petroleum crude oils despite containing a considerable amount ofn-hentriacontane. The ratio of phytane ton-octadecane was also similar to that of native crude oils.

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Struck, Julian, Marcel Bliedtner, Paul Strobel, Jens Schumacher, Enkhtuya Bazarradnaa et Roland Zech. « Leaf wax n-alkane patterns and compound-specific δ13C of plants and topsoils from semi-arid and arid Mongolia ». Biogeosciences 17, n^o 3 (5 février 2020) : 567–80. http://dx.doi.org/10.5194/bg-17-567-2020.

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Abstract. Leaf wax n-alkane patterns and their compound-specific δ13C signatures are valuable proxies for paleoenvironmental reconstructions. So far, their potential has not been investigated in semi-arid to arid Mongolia. We have therefore analysed the leaf wax n-alkanes and their compound-specific δ13C signature of five plant species (Poaceae, Cyperaceae, Artemisia spp., Caragana spp. and Larix sp.) and topsoils (0–5 cm) along two transects in central and southern Mongolia. Grasses show a distinct dominance of the n-C31 homologue, whereas the shrubs Caragana spp. and Artemisia spp. are dominated by n-C29. Larix sp. is characterised by the mid-chain n-alkanes n-C23 and n-C25. From plant to topsoil, n-alkane patterns show the potential to differentiate between grass-covered sites from those covered by Caragana spp. n-Alkane concentrations and odd-over-even predominance (OEP) of the topsoils are distinctly influenced by mean annual temperature, mean annual precipitation and aridity, likely reflecting the degree of n-alkane degradation and biomass production. In contrast, the average chain length (ACL) and the n-alkane ratio (n-C31∕n-C29+n-C31) are not affected by climatic parameters and, thus, are not biased by climate. The compound-specific δ13C signatures are strongly correlated to climate, showing a significant enrichment with increasing aridity, indicating the effect of water use efficiency. Our calibration results suggest that long-chain n-alkanes and their compound-specific δ13C signatures have great potential to reconstruct paleoenvironmental and paleoclimatic conditions when used in sediment archives from Mongolia.

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Li, Junling, Kun Li, Hong Li, Xuezhong Wang, Weigang Wang, Ke Wang et Maofa Ge. « Long-chain alkanes in the atmosphere : A review ». Journal of Environmental Sciences 114 (avril 2022) : 37–52. http://dx.doi.org/10.1016/j.jes.2021.07.021.

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Eslami, Hossein. « Equation of state for long-chain n-alkanes ». Fluid Phase Equilibria 169, n^o 1 (mars 2000) : 19–30. http://dx.doi.org/10.1016/s0378-3812(99)00331-3.

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Nikolić, Biljana, Marina Todosijević, Iris Đorđević, Jovana Stanković, Zorica S. Mitić, Vele Tešević et Petar D. Marin. « Nonacosan-10-ol and n-Alkanes in Leaves of Pinus pinaster ». Natural Product Communications 15, n^o 5 (mai 2020) : 1934578X2092607. http://dx.doi.org/10.1177/1934578x20926073.

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In leaf cuticular wax of Pinus pinaster, content of nonacosan-10-ol is high (77.1% on average). n-Alkanes ranged from C18 to C35 with the most dominant C29 (24.8%). The carbon preference index (CPItotal) ranged from 3.1 to 5.6 (4.0 on average), while the average chain length (ACLtotal) ranged from 14.0 to 17.0 (14.8 on average). Long-chain n-alkanes ( n-C25-35) strongly dominated (80.1%) over middle-chain ( n-C21-24 = 18.9%) and short-chain ( n -C18-20 = 0.9%) n-alkanes.

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Grilo, Caroline Fiório, Eduardo Schettini Costa, Renato Rodrigues Neto, George Wolff et Anu Thompson. « Exchange between macrophyte and mangrove organic matter input in estuarine systems : drought implications ». Revista Ibero-Americana de Ciências Ambientais 9, n^o 4 (23 mai 2018) : 83–98. http://dx.doi.org/10.6008/cbpc2179-6858.2018.004.0007.

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Paq proxy was applied on mid and long-chain n-alkanes in order to develop an index to assist in the long-term assessment of changes and exchanges between aquatic communities in estuarine environments as a result of increased saline incursion. New boundaries are proposed according to n-alkanes abundance in the leaves of local mangrove tree species for better definition of emergent aquatic plant end-member. Molecular distribution and δ13C isotopic signatures of n-alkanes were also used to support the parameter. A predominance of odd carbon-numbered long chain (> C27 n-alkanes) indicated a main terrestrial input, although mid-chain n-alkanes (23 and 25 carbons) were also identified. Short-chain n-alkanes (< 19) were absent or found in a very small concentration. Carbon Preference Index and C/N ratio reinforced a terrestrial origin for the sedimentary organic matter. δ13C signatures of n-alkanes for C23, C25, C29 and C31 were characteristic of mangrove input, ranging from -27.57 ‰ (C23) to -34.40 ‰ (C29) for Piraquê-Mirim River (PM) and from -27.36 ‰ (C23) to -32.84 ‰ (C31) for Piraquê-Açu River (PA) without any particular trend. Paq proxy was successfully used to identify rises in marine macrophytes (mid-chain n-alkanes) input mainly in the confluence and PM probably as consequence of drought periods. The confluence presented a mixing sources of OM. PA was identified as a stable mangrove environment while PM was characterized by pulses of marine macrophytes input and should be managed with care in respect to its catchment for water use and dam constructions as a shortage of fresh water can alter the estuarine ecology.

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He, Jinxian, Shengyin Zhang, Xiaoli Zhang, Yu Qian, Haijun He et Hongchen Wu. « Composition and Distribution Characteristics and Geochemical Significance of n-Alkanes in Core Sediments in the Northern Part of the South Yellow Sea ». Journal of Chemistry 2016 (2016) : 1–9. http://dx.doi.org/10.1155/2016/4741939.

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The South Yellow Sea is an important carbon sink and a significant research area of carbon cycle. After studying the composition and distribution of n-alkanes in a 250 cm long sediment core in the northern part of South Yellow Sea, it can be found that all n-alkanes of sediment samples in this research are distributed in three types, that is, double peak groups, predominance of long-chain n-alkanes, and predominance of short-chain n-alkanes. The average values of∑C25−35/∑C15−21,∑C27+29+31/∑C15+17+19,∑C21-/∑C22+, and(C27+C29+C31+C33)/∑C14–38are 1.92, 4.22, 0.51, and 0.35, respectively; all above outcomes indicate significant predominance of terrigenous inputs. The average values of C31/C29 and ACL are 1.04 and 29.92, respectively; these results reflect that herbaceous plants and ligneous plants account for similar percentages in the sediment core samples. The average values of CPI1 of short-chain alkanes are 0.80, reflecting the apparent even predominance, which is the result of microbial degradation. The average values of CPI2 of long-chain alkanes of most samples are 2.77, reflecting the apparent odd predominance. The average values of CPI and Pr/Ph, as well as the Pr/nC17and Ph/nC18correlation diagram, reflect that the organic matter is immature and suggest reductive sedimentary environment.

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Zhang, X., R. H. Schwantes, M. M. Coggon, C. L. Loza, K. A. Schilling, R. C. Flagan et J. H. Seinfeld. « Role of ozone in SOA formation from alkane photooxidation ». Atmospheric Chemistry and Physics Discussions 13, n^o 9 (24 septembre 2013) : 24713–54. http://dx.doi.org/10.5194/acpd-13-24713-2013.

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Abstract. Long-chain alkanes, which can be categorized as intermediate volatile organic compounds (IVOCs), are an important source of secondary organic aerosol (SOA). Mechanisms for the gas-phase OH-initiated oxidation of long-chain alkanes have been well documented; particle-phase chemistry, however, has received less attention. The δ-hydroxycarbonyl, which is generated from the isomerization of alkoxy radicals, can undergo heterogeneous cyclization to form substituted dihydrofuran. Due to the presence of C=C bonds, the substituted dihydrofuran is predicted to be highly reactive with OH, and even more so with O3 and NO3, thus opening a reaction pathway that is not usually accessible to alkanes. This work focuses on the role of substituted dihydrofuran formation and its subsequent reaction with OH, and more importantly ozone, in SOA formation from the photooxidation of long-chain alkanes. Experiments were carried out in the Caltech Environmental Chamber using dodecane as a representative alkane to investigate the difference in aerosol composition generated from "OH-oxidation dominating" vs. "ozonolysis dominating" environments. A detailed mechanism incorporating the specific gas-phase photochemistry, together with the heterogeneous formation of substituted dihydrofuran and its subsequent gas-phase OH/O3 oxidation, is presented to evaluate the importance of this reaction channel in the dodecane SOA formation. We conclude that: (1) the formation of δ-hydroxycarbonyl and its subsequent heterogeneous conversion to substituted dihydrofuran is significant in the presence of NOx; (2) the ozonolysis of substituted dihydrofuran dominates over the OH-initiated oxidation under conditions prevalent in urban and rural air; and (3) a spectrum of highly-oxygenated products with carboxylic acid, ester, and ether functional groups are produced from the substituted dihydrofuran chemistry, thereby affecting the average oxidation state of the SOA.

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Zhang, X., R. H. Schwantes, M. M. Coggon, C. L. Loza, K. A. Schilling, R. C. Flagan et J. H. Seinfeld. « Role of ozone in SOA formation from alkane photooxidation ». Atmospheric Chemistry and Physics 14, n^o 3 (14 février 2014) : 1733–53. http://dx.doi.org/10.5194/acp-14-1733-2014.

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Abstract. Long-chain alkanes, which can be categorized as intermediate volatility organic compounds, are an important source of secondary organic aerosol (SOA). Mechanisms for the gas-phase OH-initiated oxidation of long-chain alkanes have been well documented; particle-phase chemistry, however, has received less attention. The δ-hydroxycarbonyl, which is generated from the isomerization of alkoxy radicals, can undergo heterogeneous cyclization and dehydration to form substituted dihydrofuran. Due to the presence of C=C bonds, the substituted dihydrofuran is predicted to be highly reactive with OH, and even more so with O3 and NO3, thereby opening a reaction pathway that is not usually accessible to alkanes. This work focuses on the role of substituted dihydrofuran formation and its subsequent reaction with OH, and more importantly ozone, in SOA formation from the photooxidation of long-chain alkanes. Experiments were carried out in the Caltech Environmental Chamber using dodecane as a representative alkane to investigate the difference in aerosol composition generated from "OH-oxidation-dominating" vs. "ozonolysis-dominating" environments. A detailed mechanism incorporating the specific gas-phase photochemistry, together with the heterogeneous formation of substituted dihydrofuran and its subsequent gas-phase OH/O3 oxidation, is used to evaluate the importance of this reaction channel in dodecane SOA formation. We conclude that (1) the formation of δ-hydroxycarbonyl and its subsequent heterogeneous conversion to substituted dihydrofuran is significant in the presence of NOx; (2) the ozonolysis of substituted dihydrofuran dominates over the OH-initiated oxidation under conditions prevalent in urban and rural air; and (3) a spectrum of highly oxygenated products with carboxylic acid, ester, and ether functional groups are produced from the substituted dihydrofuran chemistry, thereby affecting the average oxidation state of the SOA.

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Syed, Khajamohiddin, Aleksey Porollo, Ying Wai Lam, Paul E. Grimmett et Jagjit S. Yadav. « CYP63A2, a Catalytically Versatile Fungal P450 Monooxygenase Capable of Oxidizing Higher-Molecular-Weight Polycyclic Aromatic Hydrocarbons, Alkylphenols, and Alkanes ». Applied and Environmental Microbiology 79, n^o 8 (15 février 2013) : 2692–702. http://dx.doi.org/10.1128/aem.03767-12.

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ABSTRACTCytochrome P450 monooxygenases (P450s) are known to oxidize hydrocarbons, albeit with limited substrate specificity across classes of these compounds. Here we report a P450 monooxygenase (CYP63A2) from the model ligninolytic white rot fungusPhanerochaete chrysosporiumthat was found to possess a broad oxidizing capability toward structurally diverse hydrocarbons belonging to mutagenic/carcinogenic fused-ring higher-molecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs), endocrine-disrupting long-chain alkylphenols (APs), and crude oil aliphatic hydrocarbonn-alkanes. A homology-based three-dimensional (3D) model revealed the presence of an extraordinarily large active-site cavity in CYP63A2 compared to the mammalian PAH-oxidizing (CYP3A4, CYP1A2, and CYP1B1) and bacterial aliphatic-hydrocarbon-oxidizing (CYP101D and CYP102A1) P450s. This structural feature in conjunction with ligand docking simulations suggested potential versatility of the enzyme. Experimental characterization using recombinantly expressed CYP63A2 revealed its ability to oxidize HMW-PAHs of various ring sizes, including 4 rings (pyrene and fluoranthene), 5 rings [benzo(a)pyrene], and 6 rings [benzo(ghi)perylene], with the highest enzymatic activity being toward the 5-ring PAH followed by the 4-ring and 6-ring PAHs, in that order. Recombinant CYP63A2 activity yielded monohydroxylated PAH metabolites. The enzyme was found to also act as an alkane ω-hydroxylase that oxidizedn-alkanes with various chain lengths (C9to C12and C15to C19), as well as alkyl side chains (C3to C9) in alkylphenols (APs). CYP63A2 showed preferential oxidation of long-chain APs and alkanes. To our knowledge, this is the first P450 identified from any of the biological kingdoms that possesses such broad substrate specificity toward structurally diverse xenobiotics (PAHs, APs, and alkanes), making it a potent enzyme biocatalyst candidate to handle mixed pollution (e.g., crude oil spills).

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Zengler, Karsten, Hans H. Richnow, Ramon Rosselló-Mora, Walter Michaelis et Friedrich Widdel. « Methane formation from long-chain alkanes by anaerobic microorganisms ». Nature 401, n^o 6750 (septembre 1999) : 266–69. http://dx.doi.org/10.1038/45777.

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Wang, Xiaoyu, Ru-Fen Liu, Jorja Cork, Yi Gu, David C. Upham, Bronwyn Laycock et Eric W. McFarland. « Investigation of the Bromination/Dehydrobromination of Long Chain Alkanes ». Industrial & ; Engineering Chemistry Research 56, n^o 34 (21 août 2017) : 9411–18. http://dx.doi.org/10.1021/acs.iecr.7b01039.

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Jobic, Hervé, Alain Méthivier, Georg Ehlers, Bela Farago et Wolfgang Haeussler. « Accelerated Diffusion of Long-Chain Alkanes between Nanosized Cavities ». Angewandte Chemie 116, n^o 3 (5 janvier 2004) : 368–70. http://dx.doi.org/10.1002/ange.200352691.

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Jobic, Hervé, Alain Méthivier, Georg Ehlers, Bela Farago et Wolfgang Haeussler. « Accelerated Diffusion of Long-Chain Alkanes between Nanosized Cavities ». Angewandte Chemie International Edition 43, n^o 3 (5 janvier 2004) : 364–66. http://dx.doi.org/10.1002/anie.200352691.

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Söldner, Marcus, Annette Schier et Hubert Schmidbaur. « Long-chain alkanes with an internal H2SiSiH2 linkage ». Journal of Organometallic Chemistry 521, n^o 1-2 (août 1996) : 295–99. http://dx.doi.org/10.1016/0022-328x(96)06391-7.

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Morgan, David L., et Riki Kobayashi. « Triple point corresponding states in long-chain n-alkanes ». Fluid Phase Equilibria 63, n^o 3 (1991) : 317–27. http://dx.doi.org/10.1016/0378-3812(91)80038-w.

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Kerfourn, C., et J. P. Garrec. « Modifications in the alkane composition of cuticular waxes from spruce needles (Picea abies) and ivy leaves (Hedera helix) exposed to ozone fumigation and acid fog : comparison with needles from declining spruce trees ». Canadian Journal of Botany 70, n^o 4 (1 avril 1992) : 861–69. http://dx.doi.org/10.1139/b92-110.

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Our study on the chemical composition of cuticular waxes showed that the configuration of alkane homologues, in needles from declining spruce trees as well as in artificially polluted ivy leaves and spruce needles, presented a significant shift towards lower molecular weight chains. On the contrary, in both materials ageing was characterized by increasing chain lengths. This work emphasizes the importance of the short and long carbon chains as representative parameters of chemical alteration of cuticular waxes. As far as alkanes are concerned, pollutants may change cuticular wax composition by acting on sites of their metabolic biosynthesis rather than through a direct passive chemical contact effect. Key words: Picea abies, Hedera helix, forest decline, ozone, acid fog, waxes, cuticles, alkanes.

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Pedrini, Nicolás, Shizhu Zhang, M. Patricia Juárez et Nemat O. Keyhani. « Molecular characterization and expression analysis of a suite of cytochrome P450 enzymes implicated in insect hydrocarbon degradation in the entomopathogenic fungus Beauveria bassiana ». Microbiology 156, n^o 8 (1 août 2010) : 2549–57. http://dx.doi.org/10.1099/mic.0.039735-0.

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The insect epicuticle or waxy layer comprises a heterogeneous mixture of lipids that include abundant levels of long-chain alkanes, alkenes, wax esters and fatty acids. This structure represents the first barrier against microbial attack and for broad-host-range insect pathogens, such as Beauveria bassiana, it is the initial interface mediating the host–pathogen interaction, since these organisms do not require any specialized mode of entry and infect target hosts via the cuticle. B. bassiana is able to grow on straight chain alkanes up to n-C33 as a sole source of carbon and energy. The cDNA and genomic sequences, including putative regulatory elements, for eight cytochrome P450 enzymes, postulated to be involved in alkane and insect epicuticle degradation, were isolated and characterized. Expression studies using a range of alkanes as well as an insect-derived epicuticular extract from the blood-sucking bug Triatomas infestans revealed a differential expression pattern for the P450 genes examined, and suggest that B. bassiana contains a series of hydrocarbon-assimilating enzymes with overlapping specificity in order to target the surface lipids of insect hosts. Phylogenetic analysis of the translated ORFs of the sequences revealed that the enzyme which displayed the highest levels of induction on both alkanes and the insect epicuticular extract represents the founding member of a new cytochrome P450 family, with three of the other sequences assigned as the first members of new P450 subfamilies. The remaining four proteins clustered with known P450 families whose members include alkane monooxygenases.

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