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Neu5Ac(2-8)aNeu5Ac(2-8)aNeu5Ac(2-3)
''N''-Acetylneuraminic acid (Neu5Ac or NANA) is the predominant sialic acid found in human cells, and many mammalian cells. Other forms, such as N-Glycolylneuraminic acid, may also occur in cells. This residue is negatively charged at physiological pH and is found in complex glycans on mucins and glycoproteins found at the cell membrane. Neu5Ac residues are also found in glycolipids, known as gangliosides, a crucial component of neuronal membranes found in the brain. Along with involvement in preventing infections ( mucus associated with mucous membranes—mouth, nose, GI, respiratory tract), Neu5Ac acts as a receptor for influenza viruses, allowing attachment to mucous cells via hemagglutinin (an early step in acquiring influenzavirus infection). In the biology of bacterial pathogens Neu5Ac is also important in the biology of a number of pathogenic and symbiotic bacteria as it can used either as a nutrient, providing both carbon and nitrogen to the bacteria, or in some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ganglioside
A ganglioside is a molecule composed of a glycosphingolipid (ceramide and oligosaccharide) with one or more sialic acids (e.g. ''N''-acetylneuraminic acid, NANA) linked on the sugar chain. NeuNAc, an acetylated derivative of the carbohydrate sialic acid, makes the head groups of gangliosides anionic at pH 7, which distinguishes them from globosides. The name ''ganglioside'' was first applied by the German scientist Ernst Klenk in 1942 to lipids newly isolated from ganglion cells of the brain. More than 60 gangliosides are known, which differ from each other mainly in the position and number of NANA residues. It is a component of the cell plasma membrane that modulates cell signal transduction events, and appears to concentrate in lipid rafts. Recently, gangliosides have been found to be highly important molecules in immunology. Natural and semisynthetic gangliosides are considered possible therapeutics for neurodegenerative disorders. Location Gangliosides are present and c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sialic Acid
Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this group is ''N''-acetylneuraminic acid (Neu5Ac or NANA) found in animals and some prokaryotes. Sialic acids are found widely distributed in animal tissues and related forms are found to a lesser extent in other organisms like in some micro-algae, bacteria and archaea. Sialic acids are commonly part of glycoproteins, glycolipids or gangliosides, where they decorate the end of sugar chains at the surface of cells or soluble proteins. However, sialic acids have been also observed in ''Drosophila'' embryos and other insects. Generally, plants seem not to contain or display sialic acids. In humans the brain has the highest sialic acid content, where these acids play an important role in neural transmission and ganglioside structure in synaptogene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escherichia Coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escherichia'' that is commonly found in the lower intestine of warm-blooded organisms. Most ''E. coli'' strains are harmless, but some serotypes ( EPEC, ETEC etc.) can cause serious food poisoning in their hosts, and are occasionally responsible for food contamination incidents that prompt product recalls. Most strains do not cause disease in humans and are part of the normal microbiota of the gut; such strains are harmless or even beneficial to humans (although these strains tend to be less studied than the pathogenic ones). For example, some strains of ''E. coli'' benefit their hosts by producing vitamin K2 or by preventing the colonization of the intestine by pathogenic bacteria. These mutually beneficial relationships between ''E. col ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amino Sugars
In organic chemistry, an amino sugar (or more technically a 2-amino-2-deoxysugar) is a sugar molecule in which a hydroxyl group has been replaced with an amine group. More than 60 amino sugars are known, with one of the most abundant being ''N''-Acetyl--glucosamine, which is the main component of chitin. Derivatives of amine containing sugars, such as ''N''-acetylglucosamine and sialic acid, whose nitrogens are part of more complex functional groups rather than formally being amines, are also considered amino sugars. Aminoglycosides are a class of antimicrobial compounds that inhibit bacterial protein synthesis. These compounds are conjugates of amino sugars and aminocyclitols. Synthesis From glycals Glycals are cyclic enol ether derivatives of monosaccharides, having a double bond between carbon atoms 1 and 2 of the ring. ''N''-functionalized of glycals at the C2 position, combined with glycosidic bond formation at C1 is a common strategy for the synthesis of amino sugars. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sialic Acid
Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this group is ''N''-acetylneuraminic acid (Neu5Ac or NANA) found in animals and some prokaryotes. Sialic acids are found widely distributed in animal tissues and related forms are found to a lesser extent in other organisms like in some micro-algae, bacteria and archaea. Sialic acids are commonly part of glycoproteins, glycolipids or gangliosides, where they decorate the end of sugar chains at the surface of cells or soluble proteins. However, sialic acids have been also observed in ''Drosophila'' embryos and other insects. Generally, plants seem not to contain or display sialic acids. In humans the brain has the highest sialic acid content, where these acids play an important role in neural transmission and ganglioside structure in synaptogene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neuraminic Acid
Neuraminic acid (5-amino-3,5-dideoxy-D-''glycero''-D-''galacto''-non-2-ulosonic acid) is an acidic (in particular ulosonic) amino sugar with a backbone formed by nine carbon atoms. Although 9-carbon sugars do not occur naturally, neuraminic acid may be regarded as a theoretical 9-carbon ketose in which the first link of the chain (the –CH2OH at position 1) is oxidised into a carboxyl group (–C(=O)OH), the hydroxyl group at position 3 is deoxidised (oxygen is removed from it), and the hydroxyl group at position 5 is substituted with an amino group (–NH2). Neuraminic acid may also be visualized as the product of an aldol-condensation of pyruvic acid and D-mannosamine (2-amino-2-deoxy-mannose). Neuraminic acid does not occur naturally, but many of its derivatives are found widely distributed in animal tissues and in bacteria, especially in glycoproteins and gangliosides. The ''N''- or ''O''-substituted derivatives of neuraminic acid are collectively known as sialic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haemophilus Ducreyi
''Haemophilus ducreyi'' is a fastidious gram-negative coccobacillus bacteria. It causes the sexually transmitted disease chancroid, a major cause of genital ulceration in developing countries characterized by painful sores on the genitalia. Chancroid starts as an erythematous papular lesion that breaks down into a painful bleeding ulcer with a necrotic base and ragged edge. More recently, it has also been found to cause chronic skin ulceration away from the genitalia, infect children and adults, and behave in a manner that mimics yaws. These strains seem to have diverged quite recently. ''H. ducreyi'' can be cultured on chocolate agar. It is best treated with a macrolide, e.g. azithromycin, and a third-generation cephalosporin, e.g. ceftriaxone. ''H. ducreyi'' gram stain resembles a "school of fish." Pathogenesis ''H. ducreyi'' is an opportunistic microorganism that infects its host by way of breaks in the skin or epidermis. Inflammation then takes place as the area of infecti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ABC Transporter
The ATP-binding cassette transporters (ABC transporters) are a transport system superfamily that is one of the largest and possibly one of the oldest gene families. It is represented in all extant phyla, from prokaryotes to humans. ABC transporters belong to translocases. ABC transporters often consist of multiple subunits, one or two of which are transmembrane proteins and one or two of which are membrane-associated AAA ATPases. The ATPase subunits utilize the energy of adenosine triphosphate (ATP) binding and hydrolysis to provide the energy needed for the translocation of substrates across membranes, either for uptake or for export of the substrate. Most of the uptake systems also have an extracytoplasmic receptor, a solute binding protein. Some homologous ATPases function in non-transport-related processes such as translation of RNA and DNA repair. ABC transporters are considered to be an ABC superfamily based on the similarities of the sequence and organization of their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haemophilus Influenzae
''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria are mesophilic and grow best at temperatures between 35 and 37℃. ''H. influenzae'' was first described in 1892 by Richard Pfeiffer during an influenza pandemic when he incorrectly described ''Haemophilus influenzae'' as the causative microbe, which is why the bacteria retain the name "influenza". ''H. influenzae'' is responsible for a wide range of localized and invasive infections, typically in infants and children, including pneumonia, meningitis, or bloodstream infections. Treatment consists of antibiotics, however ''H. influenzae'' is often resistant to the penicillin family but augmentin can be used in mild cases. The recommended form of prevention is a series of the Hib vaccine and boosters, which are most often given under the ag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tripartite ATP-independent Periplasmic Transporter
Tripartite ATP-independent periplasmic transporters (TRAP transporters) are a large family of solute transporters found in bacteria and archaea, but not in eukaryotes, that appear to be specific for the uptake of organic acids or related molecules containing a carboxylate or sulfonate group. They are unique in that they utilize a substrate binding protein (SBP) in combination with a secondary transporter. History TRAP transporters were discovered in the laboratory of Prof. David J. Kelly at the University of Sheffield, UK. His group were working on the mechanism used by the photosynthetic bacterium ''Rhodobacter capsulatus'' to take up certain dicarboxylic acids. They characterised a binding protein component (DctP) of a transporter that recognized these compounds, which they assumed would form part of a typical ABC transporter, but when they sequenced the genes surrounding ''dctP'' they found two other genes encoding integral membrane proteins, ''dctQ'' and ''dctM'', but no gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemagglutinin
In molecular biology, hemagglutinins (or ''haemagglutinin'' in British English) (from the Greek , 'blood' + Latin , 'glue') are receptor-binding membrane fusion glycoproteins produced by viruses in the ''Paramyxoviridae'' family. Hemagglutinins are responsible for binding to receptors on red blood cells to initiate viral attachment and infection. The agglutination of red cells occurs when antibodies on one cell bind to those on others, causing amorphous aggregates of clumped cells.Hemagglutinins recognize cell-surface glycoconjugates containing sialic acid on the surface of host red blood cells with a low affinity, and use them to enter the endosome of host cells. In the endosome, hemagglutinins are activated at a pH of 5 - 6.5, to undergo conformational changes that enable viral attachment through a fusion peptide. Agglutination and hemagglutinins were discovered by virologist George K. Hirst in 1941. Alfred Gottschalk proved in 1957 that hemagglutinins bind a virus to a host c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
