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Matrix (mass Spectrometry)
In mass spectrometry, a matrix is a compound that promotes the formation of ions. Matrix compounds are used in matrix-assisted laser desorption/ionization (MALDI), matrix-assisted ionization (MAI), and fast atom bombardment (FAB). Matrix-assisted laser desorption/ionization MALDI is an ionization technique where laser energy is absorbed by a matrix to create ions from large molecules without fragmentation. The matrix, typically in excess, is mixed with the analyte molecule and deposited on a target. A table of matrix compounds, their structures, laser wavelengths typically used, and typical application is shown below. Matrix-assisted ionization Matrix-assisted ionization is an ionization method in mass spectrometry that creates ions via the creation of particles at atmospheric pressure and transfer to the vacuum of the mass analyzer. Fast atom bombardment FAB uses a high energy beam of atoms Atoms are the basic particles of the chemical elements. An atom consists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Spectrometry
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures. A mass spectrum is a type of plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical identity or structure of molecules and other chemical compounds. In a typical MS procedure, a sample, which may be solid, liquid, or gaseous, is ionization, ionized, for example by bombarding it with a Electron ionization, beam of electrons. This may cause some of the sample's molecules to break up into positively charged fragments or simply become positively charged without fragmenting. These ions (fragmen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligonucleotide
Oligonucleotides are short DNA or RNA molecules, oligomers, that have a wide range of applications in genetic testing, Recombinant DNA, research, and Forensic DNA, forensics. Commonly made in the laboratory by Oligonucleotide synthesis, solid-phase chemical synthesis, these small fragments of nucleic acids can be manufactured as single-stranded molecules with any user-specified sequence, and so are vital for artificial gene synthesis, polymerase chain reaction (PCR), DNA sequencing, molecular cloning and as Fluorescence in situ hybridization, molecular probes. In nature, oligonucleotides are usually found as small RNA molecules that function in the regulation of gene expression (e.g. microRNA), or are degradation intermediates derived from the breakdown of larger nucleic acid molecules. Oligonucleotides are characterized by the Nucleic acid sequence, sequence of nucleotide residues that make up the entire molecule. The length of the oligonucleotide is usually denoted by "Monomer, -m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2,5-dihydroxybenzoic Acid
Gentisic acid is a dihydroxybenzoic acid. It is a derivative of benzoic acid and a minor (1%) product of the metabolic break down of aspirin, excreted by the kidneys. It is also found in the African tree ''Alchornea cordifolia'' and in wine. Production Gentisic acid is produced by carboxylation of hydroquinone.Hudnall, Phillip M. (2005) "Hydroquinone" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. Wiley-VCH, Weinheim. . :C6H4(OH)2 + CO2 → C6H3(CO2H)(OH)2 This conversion is an example of a Kolbe–Schmitt reaction. Alternatively the compound can be synthesized from salicylic acid via Elbs persulfate oxidation. Reactions In the presence of the enzyme gentisate 1,2-dioxygenase, gentisic acid reacts with oxygen to give maleylpyruvate: :2,5-dihydroxybenzoate + O2 \rightleftharpoons maleylpyruvate Applications As a hydroquinone, gentisic acid is readily oxidised and is used as an antioxidant excipient in some pharmaceutical preparations. In the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Analyzer
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures. A mass spectrum is a type of plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical identity or structure of molecules and other chemical compounds. In a typical MS procedure, a sample, which may be solid, liquid, or gaseous, is ionized, for example by bombarding it with a beam of electrons. This may cause some of the sample's molecules to break up into positively charged fragments or simply become positively charged without fragmenting. These ions (fragments) are then separated according ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Pressure
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013.25 millibars, 760 mm Hg, 29.9212 inchesHg, or 14.696 psi.International Civil Aviation Organization. ''Manual of the ICAO Standard Atmosphere'', Doc 7488-CD, Third Edition, 1993. . The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm. In most circumstances, atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospheric pressure decreases with increasing elevation. Because the atmosphere is thin relative to the Earth's radius—especially the dense atmospheric layer at low altitu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lipid
Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing energy, signaling, and acting as structural components of cell membranes. Lipids have applications in the cosmetic and food industries, and in nanotechnology. Lipids are broadly defined as hydrophobic or amphiphilic small molecules; the amphiphilic nature of some lipids allows them to form structures such as vesicles, multilamellar/ unilamellar liposomes, or membranes in an aqueous environment. Biological lipids originate entirely or in part from two distinct types of biochemical subunits or "building-blocks": ketoacyl and isoprene groups. Using this approach, lipids may be divided into eight categories: fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, saccharolipids, and polyketides (derived from condensatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinapic Acid
Sinapinic acid, or sinapic acid (Sinapine - Origin: L. Sinapi, sinapis, mustard, Gr., cf. F. Sinapine.), is a small naturally occurring hydroxycinnamic acid. It is a member of the phenylpropanoid family. It is a commonly used matrix in MALDI mass spectrometry. It is a useful matrix for a wide variety of peptides and proteins. It serves well as a matrix for MALDI due to its ability to absorb laser radiation and to also donate protons (H+) to the analyte of interest. Sinapic acid can form dimers with itself (one structure) and ferulic acid (three different structures) in cereal cell walls and therefore may have a similar influence on cell-wall structure to that of the diferulic acids. Sinapine is an alkaloidal amine found in black mustard seeds. It is considered a choline ester of sinapinic acid. Natural occurrences Sinapinic acid can be found in wine, vinegar, and black plums. Metabolism Sinapate 1-glucosyltransferase is an enzyme that uses UDP-glucose and sinapate t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Picolinic Acid
Picolinic acid is an organic compound with the formula . It is a derivative of pyridine with a carboxylic acid (COOH) substituent at the 2-position. It is an isomer of nicotinic acid and isonicotinic acid, which have the carboxyl side chain at the 3- and 4-positions, respectively. It is a white solid although impure samples can appear tan. The compound is soluble in water. Production On a commercial scale, picolinic acid is produced by ammoxidation of 2-picoline followed by hydrolysis of the resulting nitrile: : : It is also produced by oxidation of picoline with nitric acid. : In the laboratory, picolinic acid is formed from 2-methylpyridine by oxidation with potassium permanganate (KMnO4). Reactions Hydrogenation of picolinic acid gives piperidine-2-carboxylic acid, a precursor to the drug Mepivacaine. Picolinic acid is a bidentate chelating agent of elements such as chromium, zinc, manganese, copper, iron, and molybdenum in the human body. It is a substrate in the Mitsuno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
3 Hydroxypicolinic Acid
3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious and cultural significance in many societies. Evolution of the Arabic digit The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and Chinese numerals) that are still in use. That was also the original representation of 3 in the Brahmic (Indian) numerical notation, its earliest forms aligned vertically. However, during the Gupta Empire the sign was modified by the addition of a curve on each line. The Nāgarī script rotated the lines clockwise, so they appeared horizontally, and ended each line with a short downward stroke on the right. In cursive script, the three strokes were eventually connected to form a glyph resembling a with an additional stroke at the bottom: ३. The Indian digits spread to the Caliphate in the 9th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
