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Coagulin
Coagulin is a gel-forming protein of hemolymph that hinders the spread of invaders by immobilising them. It is produced in the coagulogen form before being cleaved into the active form. In human medicine, coagulation of coagulin is the basis of detection of bacterial endotoxin in the LAL test for parenteral medications. The protein contains a single 175-residue polypeptide chain that is cleaved after Arg-18 and Arg-46 by a Limulus clotting enzyme contained in the hemocyte and activated by a bacterial endotoxin (lipopolysaccharide). Cleavage releases two chains of coagulin, A and B, linked by two disulfide bonds, together with the peptide C. Gel formation results from interlinking of coagulin molecules. The full-length structure of a coagulogen is known (); it shares the same cystine-knot cytokine superfamily (fold) as neurotrophins, with several cystines conserved. The A-B fold wraps around the helical peptide C, forming a compact structure. In crustaceans, hemolymph coagulati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemolymph
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph cells called hemocytes are suspended. In addition to hemocytes, the plasma also contains many chemicals. It is the major tissue type of the open circulatory system characteristic of arthropods (e.g. arachnids, crustaceans and insects). In addition, some non-arthropods such as molluscs possess a hemolymphatic circulatory system. Oxygen-transport systems were long thought unnecessary in insects, but ancestral and functional hemocyanin has been found in the hemolymph. Insect "blood" generally does not carry hemoglobin, although hemoglobin may be present in the tracheal system instead and play some role in respiration. Method of transport In the grasshopper, the closed portion of the system consists of tubular hearts and an aort ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limulus Amebocyte Lysate
Limulus amebocyte lysate (LAL) is an aqueous extract of blood cells (amoebocytes) from the Atlantic horseshoe crab ''Limulus polyphemus''. LAL reacts with bacterial endotoxin lipopolysaccharide (LPS), which is a membrane component of gram-negative bacteria. This reaction is the basis of the LAL test, which is widely used for the detection and quantification of bacterial endotoxins. In Asia, a similar Tachypleus amebocyte lysate (TAL) test based on the local horseshoe crabs ''Tachypleus gigas'' or ''Tachypleus tridentatus'' is occasionally used instead. The recombinant factor C (rFC) assay is a replacement of LAL/TAL based on a similar reaction. Background The American medical researcher Fred Bang reported in 1956 that gram-negative bacteria, even if killed, will cause the blood of the horseshoe crab to turn into a semi-solid mass. It was later recognized that the animal's blood cells, mobile cells called amoebocytes, contain granules with a clotting factor known as coaguloge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limulus Clotting Enzyme
Limulus clotting enzyme (, ''clotting enzyme'') is an enzyme. This enzyme catalyses the following chemical reaction : Selective cleavage of -Arg18- and -Arg47- bonds in coagulogen to form coagulin and fragments This enzyme is present in the hemocyte granules of horseshoe crabs Limulus and Tachypleus. In the immunity-related clotting pathways of these organisms, it is the final enzyme responsible for the activation of coagulin Coagulin is a gel-forming protein of hemolymph that hinders the spread of invaders by immobilising them. It is produced in the coagulogen form before being cleaved into the active form. In human medicine, coagulation of coagulin is the basis of de .... References External links * {{Portal bar, Biology, border=no EC 3.4.21 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lipopolysaccharide
Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer membrane of Gram-negative bacteria. Today, the term ''endotoxin'' is often used synonymously with LPS, although there are a few endotoxins (in the original sense of toxins that are inside the bacterial cell that are released when the cell disintegrates) that are not related to LPS, such as the so-called delta endotoxin proteins produced by '' Bacillus thuringiensis''. Lipopolysaccharides can have substantial impacts on human health, primarily through interactions with the immune system. LPS is a potent activator of the immune system and pyrogen (agent that causes fever). In severe cases, LPS can play a role in causing septic shock. In lower levels and over a longer time period, there is evidence LPS may play an important and harmful role ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disulfide Bonds
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In biology, disulfide bridges formed between thiol groups in two cysteine residues are an important component of the secondary and tertiary structure of protein, proteins. ''Persulfide'' usually refers to compounds. In inorganic chemistry disulfide usually refers to the corresponding anion (−S−S−). Organic disulfides Symmetrical disulfides are compounds of the formula . Most disulfides encountered in organo sulfur chemistry are symmetrical disulfides. Unsymmetrical disulfides (also called heterodisulfides) are compounds of the formula . They are less common in organic chemistry, but most disulfides in nature are unsymmetrical. Properties The disulfide bonds are strong, with a typical bond dissociation energy of 60 kcal/mol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cystine Knot
A cystine knot is a protein structural motif containing three disulfide bridges (formed from pairs of cysteine residues). The sections of polypeptide that occur between two of them form a loop through which a third disulfide bond passes, forming a rotaxane substructure. The cystine knot motif stabilizes protein structure and is conserved in proteins across various species. There are three types of cystine knot, which differ in the topology of the disulfide bonds: * The growth factor cystine knot (GFCK) * inhibitor cystine knot (ICK) common in spider and snail toxins * Cyclic Cystine Knot, or cyclotide The growth factor cystine knot was first observed in the structure of nerve growth factor (NGF), solved by X-ray crystallography and published in 1991 by Tom Blundell in Nature.; The GFCK is present in four superfamilies. These include nerve growth factor, transforming growth factor beta (TGF-β), platelet-derived growth factor, and glycoprotein hormones including human chorioni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurotrophin
Neurotrophins are a family of proteins that induce the survival, development, and function of neurons. They belong to a class of growth factors, secreted proteins that can signal particular cells to survive, differentiate, or grow. Growth factors such as neurotrophins that promote the survival of neurons are known as neurotrophic factors. Neurotrophic factors are secreted by target tissue and act by preventing the associated neuron from initiating programmed cell death – allowing the neurons to survive. Neurotrophins also induce differentiation of progenitor cells, to ''form'' neurons. Although the vast majority of neurons in the mammalian brain are formed prenatally, parts of the adult brain (for example, the hippocampus) retain the ability to grow new neurons from neural stem cells, a process known as neurogenesis. Neurotrophins are chemicals that help to stimulate and control neurogenesis. Terminology According to the United States National Library of Medicine's medical sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crustaceans
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods emerged deep in the Crustacean group, with the completed group referred to as Pancrustacea. Some crustaceans (Remipedia, Cephalocarida, Branchiopoda) are more closely related to insects and the other hexapods than they are to certain other crustaceans. The 67,000 described species range in size from '' Stygotantulus stocki'' at , to the Japanese spider crab with a leg span of up to and a mass of . Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horseshoe Crabs
Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura. Despite their name, they are not true crabs or crustaceans: they are chelicerates, most closely related to arachnids, such as spiders and scorpions. Horseshoe crabs live primarily in and around shallow coastal waters on soft, sandy or muddy bottoms. They are generally found in the intertidal zone at spring high tides. They are eaten in some parts of Asia, and used as fishing bait, in fertilizer and in science (especially ''Limulus'' amebocyte lysate). In recent years, population declines have occurred as a consequence of coastal habitat destruction and overharvesting. Tetrodotoxin may be present in one horseshoe crab species, '' Carcinoscorpius rotundicauda''. Fossil records for horseshoe crabs extend back as far as 480 million years ago, with extant forms being living fossils. A 2019 molecular analysis places them as the sister group of Ricinulei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta-glucan
Beta-glucans, β-glucans comprise a group of β-D-glucose polysaccharides ( glucans) naturally occurring in the cell walls of cereals, bacteria, and fungi, with significantly differing physicochemical properties dependent on source. Typically, β-glucans form a linear backbone with 1–3 β-glycosidic bonds but vary with respect to molecular mass, solubility, viscosity, branching structure, and gelation properties, causing diverse physiological effects in animals. At dietary intake levels of at least 3 g per day, oat fiber β-glucan decreases blood levels of LDL cholesterol and so may reduce the risk of cardiovascular diseases. β-glucans are natural gums and are used as texturing agents in various nutraceutical and cosmetic products, and as soluble fiber supplements. History Cereal and fungal products have been used for centuries for medicinal and cosmetic purposes; however, the specific role of β-glucan was not explored until the 20th century. β-glucans were first discov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blood Coagulation
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. Coagulation begins almost instantly after an injury to the endothelium lining a blood vessel. Exposure of blood to the subendothelial space initiates two processes: changes in platelets, and the exposure of subendothelial tissue factor to plasma factor VII, which ultimately leads to cross-linked fibrin formation. Platelets immediately form a plug at the site of injury; this is called ''primary hemostasis. Secondary hemostasis'' occurs simultaneously: additional coagulation (clotting) factors beyond factor VII ( listed below) respond in a cascade to form fibrin strands, which strengthen the platelet plug. Disorders of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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