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Aerolysin
In molecular biology, aerolysin is a cytolytic pore-forming toxin exported by ''Aeromonas hydrophila'', a Gram-negative bacterium associated with diarrhoeal diseases and deep wound infections. The mature toxin binds to eukaryotic cells and aggregates to form holes (approximately 3 nm in diameter) leading to the destruction of the membrane permeability barrier and osmotic lysis. The structure of proaerolysin has been determined to 2.8A resolution and shows the protoxin to adopt a novel fold. Images of an aerolysin oligomer derived from electron microscopy have helped to construct a model of the protein in its heptameric conformation, and to outline a mechanism by which this assembly might insert into lipid bilayer The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many vir ...s to form io ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pore-forming Toxin
Pore-forming proteins (PFTs, also known as pore-forming toxins) are usually produced by bacteria, and include a number of protein exotoxins but may also be produced by other organisms such as apple snails that produce perivitellin-2 or earthworms, who produce lysenin. They are frequently cytotoxic (i.e., they kill cells), as they create unregulated pores in the membrane of targeted cells. Types PFTs can be divided into two categories, depending on the alpha-helical or beta-barrel architecture of their transmembrane channel that can consist either of * Alpha-pore-forming toxins ** e.g., Haemolysin E family, actinoporins, Corynebacterial porin B, Cytolysin A of ''E. coli''. * Beta-barrel pore-forming toxins ** e.g. α-hemolysin (Fig 1), PVL – Panton-Valentine leukocidin, various insecticidal toxins. Other categories: * Large beta-barrel pore-forming toxins ** MACPF and Cholesterol-dependent cytolysins (CDCs), gasdermin * Binary toxins ** e.g., Anthrax toxin, Pleurotolys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aeromonas Hydrophila
''Aeromonas hydrophila'' is a heterotrophic, Gram-negative, rod-shaped bacterium mainly found in areas with a warm climate. This bacterium can be found in fresh or brackish water. It can survive in Wikt:aerobic, aerobic and Hypoxia (environmental), anaerobic environments, and can digest materials such as gelatin and hemoglobin. ''A. hydrophila'' was isolated from humans and animals in the 1950s. It is the best known of the species of ''Aeromonas''. It is resistant to most common antibiotics and cold temperatures and is oxidase- and indole-positive. ''Aeromonas hydrophila'' also has a symbiotic relationship as gut flora inside of certain leeches, such as ''Hirudo medicinalis''. Structure ''Aeromonas hydrophila'' bacteria are Gram-negative, straight rods with rounded ends (bacilli to coccibacilli shape) usually from 0.3 to 1.0 μm in width and 1.0 to 3.0 μm in length. They can grow at temperatures as low as 4 °C. These bacteria are motile by a polar flagellum. Path ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lipid Bilayer
The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many viruses are made of a lipid bilayer, as are the nuclear membrane surrounding the cell nucleus, and membranes of the membrane-bound organelles in the cell. The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be. Lipid bilayers are ideally suited to this role, even though they are only a few nanometers in width, because they are impermeable to most water-soluble (hydrophilic) molecules. Bilayers are particularly impermeable to ions, which allows cells to regulate salt concentrations and pH by transporting ions across their membranes using proteins called ion pumps. Biological bilayers are usually composed of amphiphilic phosphol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heptamer
In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.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 molecular mass.'' The name is composed of Greek elements '' oligo-'', "a few" and ''-mer'', "parts". An adjective form is ''oligomeric''. The oligomer concept is contrasted to that of a polymer, which is usually understood to have a large number of units, possibly thousands or millions. However, there is no sharp distinction between these two concepts. One proposed criterion is whether the molecule's properties vary significantly with the removal of one or a few of the units. An oligomer with a specific number of units is referred to by the Greek prefix denoting that number, wit ... [...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] |
Electron Microscopy
An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a higher resolving power than light microscopes and can reveal the structure of smaller objects. A scanning transmission electron microscope has achieved better than 50 pm resolution in annular dark-field imaging mode and magnifications of up to about 10,000,000× whereas most light microscopes are limited by diffraction to about 200 nm resolution and useful magnifications below 2000×. Electron microscopes use shaped magnetic fields to form electron optical lens systems that are analogous to the glass lenses of an optical light microscope. Electron microscopes are used to investigate the ultrastructure of a wide range of biological and inorganic specimens including microorganisms, cells, large molecules, biopsy samples, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligomer
In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.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 molecular mass.'' The name is composed of Greek elements '' oligo-'', "a few" and '' -mer'', "parts". An adjective form is ''oligomeric''. The oligomer concept is contrasted to that of a polymer, which is usually understood to have a large number of units, possibly thousands or millions. However, there is no sharp distinction between these two concepts. One proposed criterion is whether the molecule's properties vary significantly with the removal of one or a few of the units. An oligomer with a specific number of units is referred to by the Greek prefix denoting that number, wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Folding
Protein folding is the physical process by which a protein chain is translated to its native three-dimensional structure, typically a "folded" conformation by which the protein becomes biologically functional. Via an expeditious and reproducible process, a polypeptide folds into its characteristic three-dimensional structure from a random coil. Each protein exists first as an unfolded polypeptide or random coil after being translated from a sequence of mRNA to a linear chain of amino acids. At this stage the polypeptide lacks any stable (long-lasting) three-dimensional structure (the left hand side of the first figure). As the polypeptide chain is being synthesized by a ribosome, the linear chain begins to fold into its three-dimensional structure. Folding of many proteins begins even during translation of the polypeptide chain. Amino acids interact with each other to produce a well-defined three-dimensional structure, the folded protein (the right hand side of the figure), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Structure
Protein secondary structure is the three dimensional conformational isomerism, form of ''local segments'' of proteins. 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] |
Lysis
Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular biology, biochemistry, and cell biology laboratories, cell cultures may be subjected to lysis in the process of purifying their components, as in protein purification, DNA extraction, RNA extraction, or in purifying organelles. Many species of bacteria are subject to lysis by the enzyme lysozyme, found in animal saliva, egg white, and other secretions. Phage lytic enzymes (lysins) produced during bacteriophage infection are responsible for the ability of these viruses to lyse bacterial cells. Penicillin and related β-lactam antibiotics cause the death of bacteria through enzyme-mediated lysis that occurs after the drug causes the bacterium to form a defective cell wall. If the cell wall is completely lost and the penicillin was used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanometre
330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re, -er, American spelling) is a units of measurement, unit of length in the International System of Units (SI), equal to one billionth (short scale) of a metre () and to 1000 picometres. One nanometre can be expressed in scientific notation as , and as metres. History The nanometre was formerly known as the millimicrometre – or, more commonly, the millimicron for short – since it is of a micron (micrometre), and was often denoted by the symbol mμ or (more rarely and confusingly, since it logically should refer to a ''millionth'' of a micron) as μμ. Etymology The name combines the SI prefix ''nano-'' (from the Ancient Greek , ', "dwarf") with the parent unit name ''metre'' (from Greek , ', "unit of measurement"). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the extracellular space). The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols (a lipid component) interspersed between them, maintaining appropriate membrane fluidity at various temperatures. The membrane also contains membrane proteins, including integral proteins that span the membrane and serve as membrane transporters, and peripheral proteins that loosely attach to the outer (peripheral) side of the cell membrane, acting as enzymes to facilitate interaction with the cell's environment. Glycolipids embedded in the outer lipid layer serve a similar purpose. The cell membrane controls the movement of substances in and out of cells and organelles, being selectively permeable to ions a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
