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Crocetane
Crocetane, or 2,6,11,15-tetramethylhexadecane, is an isoprenoid hydrocarbon compound. Unlike its isomer phytane, crocetane has a tail-to-tail linked isoprenoid skeleton. Crocetane has been detected in modern sediments and geological records as a biomarker, often associated with anaerobic methane oxidation. Research Crocetane was first studied in the late 1920s and early 1930s for the structural identification of crocetin, which is its polyunsaturated diacid analogue. The infrared spectrum was reported in 1950, the mass spectrum was described in 1968 and the 1H and 13C NMR spectra was obtained in 1990s. In 1994, Liangqiao Bian first reported strong 13C depletion in crocetane from anoxic sediments in the Kattegat. Such low 13C content is thought to originate from microbes harvesting biogenic methane, which is always 13C depleted, as a carbon source. Years later several groups made similar observations in either modern or ancient sediments near methane seeps. Crocetane was found in e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytane
Phytane is the isoprenoid alkane formed when phytol, a constituent of chlorophyll, loses its hydroxyl group. When phytol loses one carbon atom, it yields pristane. Other sources of phytane and pristane have also been proposed than phytol. Pristane and phytane are common constituents in petroleum and have been used as proxies for depositional redox conditions, as well as for correlating oil and its source rock (i.e. elucidating where oil formed). In environmental studies, pristane and phytane are target compounds for investigating oil spills. Chemistry Phytane is a non-polar organic compound that is a clear and colorless liquid at room temperature. It is a head-to-tail linked regular isoprenoid with chemical formula C20H42. Phytane has many structural isomers. Among them, crocetane is a tail-to-tail linked isoprenoid and often co-elutes with phytane during gas chromatography (GC) due to its structural similarity. Phytane also has many stereoisomers because of its three ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytane
Phytane is the isoprenoid alkane formed when phytol, a constituent of chlorophyll, loses its hydroxyl group. When phytol loses one carbon atom, it yields pristane. Other sources of phytane and pristane have also been proposed than phytol. Pristane and phytane are common constituents in petroleum and have been used as proxies for depositional redox conditions, as well as for correlating oil and its source rock (i.e. elucidating where oil formed). In environmental studies, pristane and phytane are target compounds for investigating oil spills. Chemistry Phytane is a non-polar organic compound that is a clear and colorless liquid at room temperature. It is a head-to-tail linked regular isoprenoid with chemical formula C20H42. Phytane has many structural isomers. Among them, crocetane is a tail-to-tail linked isoprenoid and often co-elutes with phytane during gas chromatography (GC) due to its structural similarity. Phytane also has many stereoisomers because of its three ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this term has fallen out of use. Archaeal cells have unique properties separating them from the other two domains, Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla. Classification is difficult because most have not been isolated in a laboratory and have been detected only by their gene sequences in environmental samples. Archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat, square cells of ''Haloquadratum walsbyi''. Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terpenes And Terpenoids
Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes are further classified by the number of carbons: monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), as examples. The terpene alpha-pinene, is a major component of the common solvent, turpentine. History and terminology The term ''terpene'' was coined in 1866 by the German chemist August Kekulé to denote all hydrocarbons having the empirical formula C10H16, of which camphene was one. Previously, many hydrocarbons having the empirical formula C10H16 had been called "camphene", but many other hydrocarbons of the same composition had had different names. Kekulé coined the term "terpene" in order to reduce the confusion. The name "terpene" is a shortened form of "terpentine", an obsolete spelling of "turpentine". Although sometimes u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MS/MS
Tandem mass spectrometry, also known as MS/MS or MS2, is a technique in instrumental analysis where two or more mass spectrometry, mass analyzers are coupled together using an additional reaction step to increase their abilities to Analytical chemistry, analyse chemical samples. A common use of tandem MS is the analysis of biomolecules, such as proteins and peptides. The molecules of a given sample are Ionization, ionized and the first spectrometer (designated MS1) separates these ions by their mass-to-charge ratio (often given as m/z or m/Q). Ions of a particular m/z-ratio coming from MS1 are selected and then made to split into smaller Fragmentation (mass spectrometry), fragment ions, e.g. by collision-induced dissociation, Gas-phase ion chemistry, ion-molecule reaction, or photodissociation. These fragments are then introduced into the second mass spectrometer (MS2), which in turn separates the fragments by their m/z-ratio and Mass spectrometry#Detectors, detects them. The fragm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Sulfur Bacteria
The green sulfur bacteria are a phylum of obligately anaerobic photoautotrophic bacteria that metabolize sulfur. Green sulfur bacteria are nonmotile (except ''Chloroherpeton thalassium'', which may glide) and capable of anoxygenic photosynthesis. They live in anaerobic aquatic environments. In contrast to plants, green sulfur bacteria mainly use sulfide ions as electron donors. They are autotrophs that utilize the reverse tricarboxylic acid cycle to perform carbon fixation. They are also mixotrophs and reduce nitrogen. Characteristics Green sulfur bacteria are gram-negative rod or spherical shaped bacteria. Some types of green sulfur bacteria have gas vacuoles that allow for movement. They are photolithoautotrophs, and use light energy and reduced sulfur compounds as the electron source. Electron donors include H2, H2S, S. The major photosynthetic pigment in these bacteria is Bacteriochlorophylls ''c'' or ''d'' in green species and ''e'' in brown species, and is located in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Western Canadian Sedimentary Basin
The Western Canadian Sedimentary Basin (WCSB) underlies of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary basin consists of a massive wedge of sedimentary rock extending from the Rocky Mountains in the west to the Canadian Shield in the east. This wedge is about thick under the Rocky Mountains, but thins to zero at its eastern margins. The WCSB contains one of the world's largest reserves of petroleum and natural gas and supplies much of the North American market, producing more than per day of gas in 2000. It also has huge reserves of coal. Of the provinces and territories within the WCSB, Alberta has most of the oil and gas reserves and almost all of the oil sands. Conventional oil The WCSB is considered a mature area for exploration of petroleum and recent development has tended toward natural gas and oil sands rather than conventional o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfate-reducing Bacteria
Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate () as terminal electron acceptor, reducing it to hydrogen sulfide (H2S). Therefore, these sulfidogenic microorganisms "breathe" sulfate rather than molecular oxygen (O2), which is the terminal electron acceptor reduced to water (H2O) in aerobic respiration. Most sulfate-reducing microorganisms can also reduce some other oxidized inorganic sulfur compounds, such as sulfite (), dithionite (), thiosulfate (), trithionate (), tetrathionate (), elemental sulfur (S8), and polysulfides (). Depending on the context, "sulfate-reducing microorganisms" can be used in a broader sense (including all species that can reduce any of these sulfur compounds) or in a narrower sense (including only species that reduce sulfate, and excluding strict thiosulfate and sulfu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methanotroph
Methanotrophs (sometimes called methanophiles) are prokaryotes that metabolize methane as their source of carbon and chemical energy. They are bacteria or archaea, can grow aerobically or anaerobically, and require single-carbon compounds to survive. Methanotrophs are especially common in or near environments where methane is produced, although some methanotrophs can oxidize atmospheric methane. Their habitats include wetlands, soils, marshes, rice paddies, landfills, aquatic systems (lakes, oceans, streams) and more. They are of special interest to researchers studying global warming, as they play a significant role in the global methane budget, by reducing the amount of methane emitted to the atmosphere. Methanotrophy is a special case of methylotrophy, using single-carbon compounds that are more reduced than carbon dioxide. Some methylotrophs, however, can also make use of multi-carbon compounds; this differentiates them from methanotrophs, which are usually fastidious metha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isoprenoid
The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes", terpenoids contain additional functional groups, usually containing oxygen. When combined with the hydrocarbon terpenes, terpenoids comprise about 80,000 compounds. They are the largest class of plant secondary metabolites, representing about 60% of known natural products. Many terpenoids have substantial pharmacological bioactivity and are therefore of interest to medicinal chemists. Plant terpenoids are used for their aromatic qualities and play a role in traditional herbal remedies. Terpenoids contribute to the scent of eucalyptus, the flavors of cinnamon, cloves, and ginger, the yellow color in sunflowers, and the red color in tomatoes. Well-known terpenoids include citral, menthol, camphor, salvinorin A in the plant '' Salvia divino ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it poses technical challenges due to its gaseous state under normal conditions for temperature and pressure. Naturally occurring methane is found both below ground and under the seafloor and is formed by both geological and biological processes. The largest reservoir of methane is under the seafloor in the form of methane clathrates. When methane reaches the surface and the atmosphere, it is known as atmospheric methane. The Earth's atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases. It has also been detected on other plane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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