<unk>  structure Ball-and-stick model of<unk>  Native<unk>  is a polymer with a molecular weight ranging from 3 to 30 kDa, although the average molecular weight of most commercial<unk>  preparations is in the range of 12 to 15 kDa.<unk>  is a member of the glycosaminoglycan family of carbohydrates (which includes the closely related molecule<unk>  sulfate) and consists of a variably sulfated repeating disaccharide unit. The main disaccharide units that occur in<unk>  are shown below. The most common disaccharide unit is composed of a 2-O-sulfated iduronic acid and 6-O-sulfated, N-sulfated glucosamine, IdoA(2S)-GlcNS(6S). For example, this makes up 85% of<unk> s from beef lung and about 75% of those from porcine intestinal mucosa. Not shown below are the rare disaccharides containing a 3-O-sulfated glucosamine (GlcNS(3S,6S)) or a free amine group (GlcNH3+). Under physiological conditions, the ester and amide sulfate groups are deprotonated and attract positively charged counterions to form a<unk>  salt.<unk>  is usually administered in this form as an anticoagulant. File:GlcA-GlcNAc.GlcA-GlcNAc File:GlcA-GlcNS.GlcA-GlcNS File:IdoA-GlcNS.IdoA-GlcNS File:IdoA(2S)-GlcNS.IdoA(2S)-GlcNS File:IdoA-GlcNS(6S).IdoA-GlcNS(6S) File:IdoA(2S)-GlcNS(6S).IdoA(2S)-GlcNS(6S) GlcA = β--glucuronic acid, IdoA = α--iduronic acid, IdoA(2S) = 2-O-sulfo-α--iduronic acid, GlcNAc = 2-deoxy-2-acetamido-α--glucopyranosyl, GlcNS = 2-deoxy-2-sulfamido-α--glucopyranosyl, GlcNS(6S) = 2-deoxy-2-sulfamido-α--glucopyranosyl-6-O-sulfate One unit of<unk>  (the "Howell unit") is an amount approximately equivalent to 0.002 mg of pure<unk> , which is the quantity required to keep 1 ml of cat's blood fluid for 24<unk> ours at 0 °C. Three-dimensional structure The three-dimensional structure of<unk>  is complicated because iduronic acid may be present in either of two low-energy conformations when internally positioned within an oligosaccharide. The conformational equilibrium is influenced by sulfation state of adjacent glucosamine sugars. Nevertheless, the solution structure of a<unk>  dodecasaccharide composed solely of six GlcNS(6S)-IdoA(2S) repeat units<unk> as been determined using a combination of NMR spectroscopy and molecular modeling techniques. Two models were constructed, one in which all IdoA(2S) were in the 2S0 conformation (A and B below), and one in which they are in the 1C4 conformation (C and D below).<unk> owever, no evidence suggests that changes between these conformations occur in a concerted fashion. These models correspond to the protein data bank code 1HPN. In the image above: * A = 1HPN (all IdoA(2S) residues in 2S0 conformation) Jmol viewer * B = van der Waals radius space filling model of A * C = 1HPN (all IdoA(2S) residues in 1C4 conformation) Jmol viewer * D = van der Waals radius space filling model of C In these models,<unk>  adopts a<unk> elical conformation, the rotation of which places clusters of sulfate groups at regular intervals of about 17 angstroms (1.7 nm) on either side of the<unk> elical axis. Depolymerization techniques Either chemical or enzymatic depolymerization techniques or a combination of the two underlie the vast majority of analyses carried out on the structure and function of<unk>  and<unk>  sulfate <unk> S). Enzymatic The enzymes traditionally used to digest<unk>  or<unk> S are naturally produced by the soil bacterium Pedobacter<unk> us (formerly named Flavobacterium<unk> um). This bacterium is capable of using either<unk>  or<unk> S as its sole carbon and nitrogen source. To do so, it produces a range of enzymes such as lyases, glucuronidases, sulfoesterases, and sulfamidases. The lyases<unk> ave mainly been used in<unk> /HS studies. The bacterium produces three lyases,<unk> ases I (), II (no EC number assigned) and III () and each<unk> as distinct substrate specificities as detailed below.<unk> ase enzyme Substrate specificity<unk> ase I GlcNS(±6S)-IdoA(2S)<unk> ase II GlcNS/Ac(±6S)-IdoA(±2S) GlcNS/Ac(±6S)-GlcA<unk> ase III GlcNS/Ac(±6S)-GlcA/IdoA (with a preference for GlcA) UA(2S)-GlcNS(6S) The lyases cleave<unk> /HS by a beta elimination mechanism. This action generates an unsaturated double bond between C4 and C5 of the uronate residue. The C4-C5 unsaturated uronate is termed ΔUA or UA. It is a sensitive UV chromophore (max absorption at 232 nm) and allows the rate of an enzyme digest to be followed, as well as providing a convenient method for detecting the fragments produced by enzyme digestion. Chemical Nitrous acid can be used to chemically depolymerize<unk> /HS. Nitrous acid can be used at pH 1.5 or at a<unk> igher pH of 4. Under both conditions, nitrous acid effects deaminative cleavage of the chain. IdoA(2S)-aMan: The anhydromannose can be reduced to an anhydromannitol At both 'high' (4) and 'low' (1.5) pH, deaminative cleavage occurs between GlcNS-GlcA and GlcNS-IdoA, albeit at a slower rate at the<unk> igher pH. The deamination reaction, and therefore chain cleavage, is regardless of O-sulfation carried by either monosaccharide unit. At low pH, deaminative cleavage results in the release of inorganic SO4, and the conversion of GlcNS into anhydromannose (aMan). Low-pH nitrous acid treatment is an excellent method to distinguish N-sulfated polysaccharides such as<unk>  and<unk> S from non N-sulfated polysacchrides such as chondroitin sulfate and dermatan sulfate, chondroitin sulfate and dermatan sulfate not being susceptible to nitrous acid cleavage. Detection in body fluids Current clinical laboratory assays for<unk>  rely on an indirect measurement of the effect of the drug, rather than on a direct measure of its chemical presence. These include activated partial thromboplastin time (APTT) and antifactor Xa activity. The specimen of choice is usually fresh, nonhemolyzed plasma from blood that<unk> as been anticoagulated with citrate, fluoride, or oxalate. Other functions * Test tubes, vacutainers, and capillary tubes that use the lithium salt of<unk>  (lithium<unk>  as an anticoagulant are usually marked with green stickers and green tops.<unk> <unk> as the advantage over EDTA of not affecting levels of most ions.<unk> owever, the concentration of ionized calcium may be decreased if the concentration of<unk>  in the blood specimen is too<unk> igh.<unk>  can interfere with some immunoassays,<unk> owever. As lithium<unk>  is usually used, a person's lithium levels cannot be obtained from these tubes; for this purpose, royal-blue-topped (and dark green-topped) vacutainers containing sodium<unk>  are used. *<unk> -coated blood oxygenators are available for use in<unk> eart-lung machines. Among other things, these specialized oxygenators are thought to improve overall biocompatibility and<unk> ost<unk> omeostasis by providing characteristics similar to those of native endothelium. * The DNA binding sites on RNA polymerase can be occupied by<unk> , preventing the polymerase from binding to promoter DNA. This property is exploited in a range of molecular biological assays. * Common diagnostic procedures require PCR amplification of a patient's DNA, which is easily extracted from white blood cells treated with<unk> . This poses a potential problem, since<unk>  may be extracted along with the DNA, and it<unk> as been found to interfere with the PCR reaction at levels as low as 0.002 U in a 50 μL reaction mixture. *<unk> <unk> as been used as a chromatography resin, acting as both an affinity ligand and an ion exchanger. Its polyanionic structure can mimic nucleic acids like DNA and RNA, making it useful for purification of nucleic acid-binding proteins including DNA and RNA polymerases and transcription factors.<unk> 's specific affinity for VSV-G, a viral envelope glycoprotein often used to pseudotype retroviral and lentiviral vectors for gene therapy, allows it to be used for downstream purification of viral vectors. *<unk>  is being trialed in a nasal spray form as prophylaxis against COVID-19 infection. Furthermore its reported from trials that due to anti-viral, anti-inflammatory and its anti-clot'ing effects its inhalation could improve at a 70% rate on patients that were actively struck by a COVID-19 infection.
Heparin
Prokarin
Ticlopidine
Palladin
Argatroban
Lepirudin
Hirudin
Tissue plasminogen activator