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Γ-Carotene
γ-Carotene (''gamma''-carotene) is a carotenoid, and is a biosynthetic intermediate for cyclized carotenoid synthesis in plants. It is formed from cyclization of lycopene by lycopene cyclase epsilon. Along with several other carotenoids, γ-carotene is a vitamer of vitamin A in herbivores and omnivores. Carotenoids with a cyclized, beta-ionone ring can be converted to vitamin A, also known as retinol, by the enzyme beta-carotene 15,15'-dioxygenase; however, the bioconversion of γ-carotene to retinol has not been well-characterized. γ-Carotene has tentatively been identified as a biomarker for green and purple sulfur bacteria in a sample from the 1.640 ± 0.003-Gyr-old Barney Creek Formation in Northern Australia which comprises marine sediments. Tentative discovery of γ-carotene in marine sediments implies a past euxinic environment, where water columns were anoxic and sulfidic. This is significant for reconstructing past oceanic conditions, but so far γ-carotene has only b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vitamin A
Vitamin A is a fat-soluble vitamin that is an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most notably Β-Carotene, β-carotene (''beta''-carotene). Vitamin A has multiple functions: growth during embryo development, maintaining the immune system, and healthy vision. For aiding vision specifically, it combines with the protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision. Vitamin A occurs as two principal forms in foods: A) retinoids, found in Animal source foods, animal-sourced foods, either as retinol or bound to a fatty acid to become a retinyl ester, and B) the carotenoids Α-Carotene, α-carotene (''alpha''-carotene), β-carotene, Γ-Carotene, γ-carotene (''gamma''-carotene), and the xanthophyll beta-cryptoxanthin (all of which contain β-ionone rings) that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carotenoid
Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, canaries, flamingos, salmon, lobster, shrimp, and daffodils. Over 1,100 identified carotenoids can be further categorized into two classes xanthophylls (which contain oxygen) and carotenes (which are purely hydrocarbons and contain no oxygen). All are derivatives of tetraterpenes, meaning that they are produced from 8 isoprene units and contain 40 carbon atoms. In general, carotenoids absorb wavelengths ranging from 400 to 550 nanometers (violet to green light). This causes the compounds to be deeply colored yellow, orange, or red. Carotenoids are the dominant pigment in autumn leaf coloration of about 15-30% of tree species, but many plant colors, especially reds and purples, are due to polyphenols. Carotenoids serve two key roles in p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isorenieratene
Isorenieratene /ˌaɪsoʊrəˈnɪərətiːn/ is a carotenoid light-harvesting pigment produced exclusively by the genus ''Chlorobium'', which are the brown-colored strains of the family of green sulfur bacteria ( Chlorobiaceae). Green sulfur bacteria are anaerobic photoautotrophic organisms, meaning they perform photosynthesis in the absence of oxygen using hydrogen sulfide in the following reaction: organic compounds Such anoxygenic photosynthesis requires reduced sulfur and light; thus, this metabolism occurs only in strictly photic and euxinic environments. Therefore, the discovery of isorenieratene and its derivatives in sediments and rocks are helpful biomarkers to identify euxinic water columns in the photic zone. Structure Isorenieratene has the chemical formula C40H48. It is a diaromatic carotenoid with a regularly-linked isoprenoid chain, except for a single tail-to-tail linkage in the middle of the molecule. Isorenieratene has a characteristic 1-alkyl-2,3,6-trimethyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta 13C
Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier Delta may also refer to: Places Canada * Delta, British Columbia ** Delta (federal electoral district), a federal electoral district ** Delta (provincial electoral district) * Delta, Ontario United States * Mississippi Delta * Arkansas Delta * Delta, Alabama * Delta Junction, Alaska * Delta, Colorado * Delta, Illinois * Delta, Iowa * Delta, Kentucky * Delta, Louisiana * Delta, Missouri * Delta, North Carolina * Delta, Ohio * Delta, Pennsylvania * Sacramento–San Joaquin River Delta, California * Delta, Utah * Delta, Wisconsin, a town and an unincorporated community * Delta County (other) Elsewhere * Delta Island, Antarctica * Delta Stream, Antarctica * Delta, Minas Gerais, Brazil * Nile Delta, Egypt * Delta, Thessaloniki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotope-ratio Mass Spectrometry
Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample. This technique has two different applications in the earth and environmental sciences. The analysis of ' stable isotopes' is normally concerned with measuring isotopic variations arising from mass-dependent isotopic fractionation in natural systems. On the other hand, radiogenic isotope analysis involves measuring the abundances of decay-products of natural radioactivity, and is used in most long-lived radiometric dating methods. Introduction The isotope-ratio mass spectrometer (IRMS) allows the precise measurement of mixtures of naturally occurring isotopes. Most instruments used for precise determination of isotope ratios are of the magnetic sector type. This type of analyzer is superior to the quadrupole type in this field of research for two reasons. First, it can be set up for multip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass-to-charge Ratio
The mass-to-charge ratio (''m''/''Q'') is a physical quantity Ratio, relating the ''mass'' (quantity of matter) and the ''electric charge'' of a given particle, expressed in Physical unit, units of kilograms per coulomb (kg/C). It is most widely used in the electrodynamics of charged particles, e.g. in electron optics and ion optics. It appears in the scientific fields of electron microscopy, cathode ray tubes, accelerator physics, nuclear physics, Auger electron spectroscopy, physical cosmology, cosmology and mass spectrometry. The importance of the mass-to-charge ratio, according to classical electrodynamics, is that two particles with the same mass-to-charge ratio move in the same path in a vacuum, when subjected to the same electric and magnetic fields. Some disciplines use the charge-to-mass ratio (''Q''/''m'') instead, which is the multiplicative inverse of the mass-to-charge ratio. The CODATA recommended value for an electron is Origin When charged particles move in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Maturity
In petroleum geology, the maturity of a rock is a measure of its state in terms of hydrocarbon generation. Maturity is established using a combination of geochemical and basin modelling techniques. Rocks with high total organic carbon, (termed source rocks), will alter under increasing temperature such that the organic molecules slowly mature into hydrocarbons (see diagenesis). Source rocks are therefore broadly categorised as ''immature'' (no hydrocarbon generation), ''sub-mature'' (limited hydrocarbon generation), ''mature'' (extensive hydrocarbon generation) and ''overmature'' (most hydrocarbons have been generated). The maturity of a source rock can also be used as an indicator of its hydrocarbon ''potential''. That is, if a rock is sub-mature, then it has a much higher potential to generate further hydrocarbons than one that is overmature. See also * Van Krevelen diagram Van Krevelen diagrams are graphical plots developed by Dirk Willem van Krevelen (chemist and professor o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotope Fractionation
Isotope fractionation describes fractionation processes that affect the relative abundance of isotopes, a phenomena that occurs (and so advantage is taken of it) in the study geochemistry, biochemistry, food science, and other fields. Normally, the focus is on stable isotopes of the same element. Isotopic fractionation can be measured by isotope analysis, using isotope-ratio mass spectrometry, nuclear magnetic resonance methods ( specialised techniques,) cavity ring-down spectroscopy, etc., to measure ratios of isotopes, important tools to understand geochemical and biological systems, past and present. For example, biochemical processes cause changes in ratios of stable carbon isotopes incorporated into biomass. Definition Stable isotopes partitioning between two substances ''A'' and ''B'' can be expressed by the use of the isotopic fractionation factor (alpha): : where ''R'' is the ratio of the heavy to light isotope (e.g., 2H/1H or 18O/16O). Values for alpha tend to be v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Chromatography–mass Spectrometry
Gas chromatography–mass spectrometry (GC–MS) is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample. Applications of GC–MS include drug detection, fire investigation, environmental analysis, explosives investigation, food and flavor analysis, and identification of unknown samples, including that of material samples obtained from planet Mars during probe missions as early as the 1970s. GC–MS can also be used in airport security to detect substances in luggage or on human beings. Additionally, it can identify trace elements in materials that were previously thought to have disintegrated beyond identification. Like liquid chromatography–mass spectrometry, it allows analysis and detection even of tiny amounts of a substance. GC–MS has been regarded as a "gold standard" for forensic substance identification because it is used to perform a 100% specific test, which positively ide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diagenesis
Diagenesis () is the process of physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sediments become buried much deeper in the Earth's crust. In the early stages, the transformation of poorly consolidated sediments into sedimentary rock (lithification) is simply accompanied by a reduction in porosity and water expulsion (clay sediments), while their main mineralogical assemblages remain unaltered. As the rock is carried deeper by further deposition above, its organic content is progressively transformed into kerogens and bitumens. The process of diagenesis excludes surface alteration (weathering) and deep metamorphism. There is no sharp boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures. Hydrothermal solutions, meteoric groundwater, rock porosity, permeability, dissolu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genera
Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. :E.g. '' Panthera leo'' (lion) and '' Panthera onca'' (jaguar) are two species within the genus '' Panthera''. ''Panthera'' is a genus within the family Felidae. The composition of a genus is determined by taxonomists. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: # monophyly – all descendants of an ancestral taxon are grouped together (i.e. phylogenetic analysis should clearly demonstrate both monophyly and validity as a separate lineag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Β-Carotene
β-Carotene (''beta''-carotene) is an organic, strongly colored red-orange pigment abundant in fungi, plants, and fruits. It is a member of the carotenes, which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 carbons. Dietary β-carotene is a provitamin A compound, converting in the body to retinol (vitamin A). In foods, it has rich content in carrots, pumpkin, spinach, and sweet potato. It is used as a dietary supplement and may be prescribed to treat erythropoietic protoporphyria, an inherited condition of sunlight sensitivity. β-carotene is the most common carotenoid in plants. When used as a food coloring, it has the E number E160a. The structure was deduced in 1930. Isolation of β-carotene from fruits abundant in carotenoids is commonly done using column chromatography. It is industrially extracted from richer sources such as the algae ''Dunaliella salina''. The separation of β-carotene from the mixture of other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
