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Heat-labile Enterotoxin
In molecular biology, the heat-labile enterotoxin family includes ''Escherichia coli'' heat-labile enterotoxin (Elt or LT) and cholera toxin (Ctx) secreted by ''Vibrio cholerae''. lt is so named because it is inactivated at high temperatures. Mechanism The A subunits are transported inside by the pentameric B subunits. It then acts by raising cAMP levels through ADP-ribosylation of the alpha-subunit of a Gs protein leading to the constitutive activation of adenylate cyclase. Elevated cAMP levels stimulate the activation of the CFTR channel thus stimulating secretion of chloride ions and water from the enterocyte into the gut lumen. This ionic imbalance causes watery diarrhea. In addition to its effects on chloride secretion, which involve the same steps as the effects of cholera toxin, Elt binds additional substrates: lipopolysaccharide on the surface of ''E. coli'' cells and A-type blood antigens. The importance of these binding events is not yet known. Structure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escherichia Coli
''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. 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 part of the normal microbiota of the gut, where they constitute about 0.1%, along with other facultative anaerobes. These bacteria are mostly harmless or even beneficial to humans. For example, some strains of ''E. coli'' benefit their hosts by producing vitamin K2 or by preventing the colonization of the intestine by harmful pathogenic bacteria. These mutually beneficial relationships between ''E. coli'' and humans are a type of mutualistic biological relationship—where both the humans and the ''E. coli'' are benefitting each other. ''E. coli'' is expelled into the environment within fecal matter. The bacterium grows massi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentamer
A pentamer is an entity composed of five subunits. In chemistry, it applies to molecules made of five monomers. In biochemistry, it applies to macromolecules, particularly pentameric proteins, made of five protein sub-units. In microbiology, a pentamer is one of the proteins that compose the polyhedral protein shell that encloses the bacterial micro-compartments known as carboxysomes. In immunology, an MHC pentamer is a reagent used to detect antigen-specific CD8+ T cell T cells (also known as T lymphocytes) are an important part of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell ...s. See also * penta prefix * -mer suffix * Pentamerism * '' Pentamerous Metamorphosis'', an album by Global Communication * Pentamery (botany), having five parts in a distinct whorl of a plant structure * Pentamerous can also refer to animals, such as c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmid
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria and archaea; however plasmids are sometimes present in and eukaryotic organisms as well. Plasmids often carry useful genes, such as those involved in antibiotic resistance, virulence, secondary metabolism and bioremediation. While chromosomes are large and contain all the essential genetic information for living under normal conditions, plasmids are usually very small and contain additional genes for special circumstances. Artificial plasmids are widely used as vectors in molecular cloning, serving to drive the replication of recombinant DNA sequences within host organisms. In the laboratory, plasmids may be introduced into a cell via transformation. Synthetic plasmids are available for procurement over the internet by various vendors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CTXφ Bacteriophage
The CTXφ bacteriophage is a filamentous bacteriophage. It is a positive-strand DNA virus with single-stranded DNA (ssDNA). CTXφ infects some strains of ''Vibrio cholerae'', the bacterium that causes cholera. It carries the genes for cholera toxin (CTX), which makes cholera especially virulent. It can carry genes from one ''V. cholerae'' strain to another. Genetic material CTXφ is generally present and integrated into the genome of the ''V. cholerae'' bacterium, and more rarely in a virion from outside the bacterium. While integrated into the bacterial genome, CTX prophages are found on each of the two chromosomes (in the O1 serogroup of ''V. cholerae'') or arranged in tandem on the larger chromosome (in the El Tor biotype of ''V. cholerae''). The genome of CTXφ is 7 kb long and consists of two regions. The core region, which is approximately 4,6 kb long, contains 5 genes that are associated with phage assembly and morphogenisis (''psh, cep, pIIICTX, ace, zot)'' and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antigenic
In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. Antigens can be proteins, peptides (amino acid chains), polysaccharides (chains of simple sugars), lipids, or nucleic acids. Antigens exist on normal cells, cancer cells, parasites, viruses, fungi, and bacteria. Antigens are recognized by antigen receptors, including antibodies and T-cell receptors. Diverse antigen receptors are made by cells of the immune system so that each cell has a specificity for a single antigen. Upon exposure to an antigen, only the lymphocytes that recognize that antigen are activated and expanded, a process known as clonal selection. In most cases, antibodies are ''antigen-specific'', meaning that an antibody can only react to and bind one specific antigen; in some instances, however, antibodies may cross-react to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalysis
Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. The rate increase occurs because the catalyst allows the reaction to occur by an alternative mechanism which may be much faster than the noncatalyzed mechanism. However the noncatalyzed mechanism does remain possible, so that the total rate (catalyzed plus noncatalyzed) can only increase in the presence of the catalyst and never decrease. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic
In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. The term ''hydrophobic''—which comes from the Ancient Greek (), "having a fear of water", constructed Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalytic
Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form reaction intermediate, intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. The rate increase occurs because the catalyst allows the reaction to occur by an alternative mechanism which may be much faster than the noncatalyzed mechanism. However the noncatalyzed mechanism does remain possible, so that the total rate (catalyzed plus noncatalyzed) can only increase in the presence of the catalyst and never decrease. Catalysis may be classified as either homogeneous catalysis, homogeneou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Subunit
In structural biology, a protein subunit is a polypeptide chain or single protein molecule that assembles (or "''coassembles''") with others to form a protein complex. Large assemblies of proteins such as viruses often use a small number of types of protein subunits as building blocks. A subunit is often named with a Greek or Roman letter, and the numbers of this type of subunit in a protein is indicated by a subscript. For example, ATP synthase has a type of subunit called α. Three of these are present in the ATP synthase molecule, leading to the designation α3. Larger groups of subunits can also be specified, like α3β3-hexamer and c-ring. Naturally occurring proteins that have a relatively small number of subunits are referred to as oligomeric.Quote: ''Oligomer molecule: A molecule of intermediate relative molecular mass, the structure of which essentially comprises a small plurality of units derived, actually or conceptually, from molecules of lower relative molecula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Structure
Protein secondary structure is the local spatial conformation of the polypeptide backbone excluding the side chains. The two most common Protein structure#Secondary structure, secondary structural elements are alpha helix, alpha helices and beta sheets, though beta turns and omega loops occur as well. Secondary structure elements typically spontaneously form as an intermediate before the protein protein folding, folds into its three dimensional protein tertiary structure, tertiary structure. Secondary structure is formally defined by the pattern of hydrogen bonds between the Amine, amino hydrogen and carboxyl oxygen atoms in the peptide backbone chain, backbone. Secondary structure may alternatively be defined based on the regular pattern of backbone Dihedral angle#Dihedral angles of proteins, dihedral angles in a particular region of the Ramachandran plot regardless of whether it has the correct hydrogen bonds. The concept of secondary structure was first introduced by Kaj Ulrik ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salt Bridge
In electrochemistry, a salt bridge or ion bridge is an essential laboratory device discovered over 100 years ago. It contains an electrolyte solution, typically an inert solution, used to connect the Redox, oxidation and reduction Half cell, half-cells of a galvanic cell (voltaic cell), a type of electrochemical cell. In short, it functions as a link connecting the anode and cathode half-cells within an electrochemical cell. It also maintains electrical neutrality within the internal circuit and stabilizes the junction potential between the solutions in the half-cells. Additionally, it serves to minimize cross-contamination between the two half cells. A salt bridge typically consists of tubes filled with an electrolyte solution. These tubes often have diaphragms such as glass frits at their ends to help contain the solution within the tubes and prevent excessive mixing with the surrounding environment. When setting up a salt bridge between different solvents of half-cells, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
