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Beta Helix
A beta helix is a tandem protein repeat structure formed by the association of parallel beta strands in a helical pattern with either two or three faces. The beta helix is a type of solenoid protein domain. The structure is stabilized by inter-strand hydrogen bonds, protein-protein interactions, and sometimes bound metal ions. Both left- and right-handed beta helices have been identified. These structures are distinct from jelly-roll folds, a different protein structure sometimes known as a "double-stranded beta helix". The first beta-helix was observed in the enzyme pectate lyase, which contains a seven-turn helix that reaches 34 Å (3.4 nm) long. The P22 phage tail spike protein, a component of the P22 bacteriophage, has 13 turns and in its assembled homo trimer is 200 Å (20 nm) in length. Its interior is close-packed with no central pore and contains both hydrophobic residues and charged residues neutralized by salt bridges. Both pectate lyase and P22 tailspike p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salt Bridge
In electrochemistry, a salt bridge or ion bridge is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell (voltaic cell), a type of electrochemical cell. It maintains electrical neutrality within the internal circuit. If no salt bridge were present, the solution in one-half cell would accumulate a negative charge and the solution in the other half cell would accumulate a positive charge as the reaction proceeded, quickly preventing further reaction, and hence the production of electricity. Salt bridges usually come in two types: glass tubes and filter paper. Glass tube bridges One type of salt bridge consists of a U-shaped glass tube filled with a relatively inert electrolyte. It is usually a combination of potassium or ammonium cations and chloride or nitrate anions, which have similar mobility in solution. The combination is chosen which does not react with any of the chemicals used in the cell. The electrolyte is often gelified wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentapeptide Repeat
Pentapeptide repeats are a family of sequence motifs found in multiple tandem copies in protein molecules. Pentapeptide repeat proteins are found in all species, but they are found in many copies in cyanobacterial genomes. The repeats were first identified by Black and colleagues in the hglK protein. The later Bateman ''et al.'' showed that a large family of related pentapeptide repeat proteins existed. The function of these repeats is uncertain in most proteins. However, in the MfpA protein a DNA gyrase inhibitor it has been suggested that the pentapeptide repeat structure mimics the structure of DNA. The repeats form a regular right handed four sided beta helix structure known as the Rfr-fold. Sequence features The pentapeptide repeat is a feature seen in protein sequence. It can be approximately described using the 1-letter amino acid code as A(D/N)LXX, where X can be any amino acid . This repeating sequence can be seen in multiple sequence alignments and dot plots of pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coiled Coil
A coiled coil is a structural motif in proteins in which 2–7 alpha-helices are coiled together like the strands of a rope. (Dimers and trimers are the most common types.) Many coiled coil-type proteins are involved in important biological functions, such as the regulation of gene expression — e.g., transcription factors. Notable examples are the oncoproteins c-Fos and c-Jun, as well as the muscle protein tropomyosin. Discovery The possibility of coiled coils for α-keratin was initially somewhat controversial. Linus Pauling and Francis Crick independently came to the conclusion that this was possible at about the same time. In the summer of 1952, Pauling visited the laboratory in England where Crick worked. Pauling and Crick met and spoke about various topics; at one point, Crick asked whether Pauling had considered "coiled coils" (Crick came up with the term), to which Pauling said he had. Upon returning to the United States, Pauling resumed research on the topic. He con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Threonine
Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated −COO− form under biological conditions), and a side chain containing a hydroxyl group, making it a polar, uncharged amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Threonine is synthesized from aspartate in bacteria such as ''E. coli''. It is encoded by all the codons starting AC (ACU, ACC, ACA, and ACG). Threonine sidechains are often hydrogen bonded; the most common small motifs formed are based on interactions with serine: ST turns, ST motifs (often at the beginning of alpha helices) and ST staples (usually at the middle of alpha helices). Modifications The threonine residue is susceptible to numerous posttranslational modifications. The hydroxyl side-chain can underg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Choristoneura Fumiferana
''Choristoneura fumiferana'', the eastern spruce budworm, is a species of moth of the family Tortricidae native to the eastern United States and Canada. The caterpillars feed on the needles of spruce and fir trees. Eastern spruce budworm populations can experience significant oscillations, with large outbreaks sometimes resulting in wide scale tree mortality. The first recorded outbreaks of the spruce budworm in the United States occurred in about 1807, and since 1909 there have been waves of budworm outbreaks throughout the eastern United States and Canada. In Canada, the major outbreaks occurred in periods circa 1910–20, c. 1940–50, and c. 1970–80, each of which impacted millions of hectares of forest. Longer-term tree-ring studies suggest that spruce budworm outbreaks have been recurring approximately every three decades since the 16th century, and paleoecological studies suggest the spruce budworm has been breaking out in eastern North America for thousands of yea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spruce Budworm
''Choristoneura'' is a genus of moths in the family Tortricidae. Several species are serious pests of conifers, such as spruce and are known as spruce budworms. Species *'' Choristoneura adumbratanus'' (Walsingham, 1900) *'' Choristoneura africana'' Razowski, 2002 *'' Choristoneura albaniana'' (Walker, 1863) *'' Choristoneura argentifasciata'' Heppner, 1989 *'' Choristoneura biennis'' Freeman, 1967 *'' Choristoneura bracatana'' (Rebel, in Rebel & Rogenhofer, 1894) *'' Choristoneura carnana'' (Barnes & Busck, 1920) *'' Choristoneura chapana'' Razowski, 2008 *'' Choristoneura colyma'' Razowski, 2006 *'' Choristoneura conflictana'' (Walker, 1863) *'' Choristoneura diversana'' (Hubner, 814-1817 *'' Choristoneura evanidana'' (Kennel, 1901) *'' Choristoneura expansiva'' X.P.Wang & G.J.Yang, 2008 *'' Choristoneura ferrugininotata'' Obraztsov, 1968 *'' Choristoneura fractivittana'' (Clemens, 1865) *'' Choristoneura freemani'' Razowski, 2008, western spruce budworm *''Choristoneura fum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tenebrio Molitor
Mealworms are the larval form of the yellow mealworm beetle, ''Tenebrio molitor'', a species of darkling beetle. Like all holometabolic insects, they go through four life stages: egg, larva, pupa, and adult. Larvae typically measure about or more, whereas adults are generally between in length. Reproduction The mealworm beetle breeds prolifically. Males insert sperm packets with their aedeagus. Within a few days the female burrows into soft ground and lays eggs. Over her lifespan, a female will, on average, lay about 500 eggs. After 4 to 19 days the eggs hatch. During the larval stage, the mealworms feed on vegetation and dead insects and molt between each larval stage, or instar (9 to 20 instars). After the final molt, they pupate. The new pupa is whitish and turns brown over time. After 3 to 30 days, depending on environmental conditions such as temperature, it emerges as an adult beetle. Sex pheromones A sex pheromone released by male mealworms has been identified. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antifreeze
An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, allowing higher coolant temperature. However, all common antifreeze additives also have lower heat capacities than water, and do reduce water's ability to act as a coolant when added to it. Because water has good properties as a coolant, water plus antifreeze is used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters. The purpose of antifreeze is to prevent a rigid enclosure from bursting due to expansion when water freezes. Commercially, both the ''additive'' (pure concentrate) and the ''mixture'' (diluted solution) are called antifreeze, depending on the context. Careful selection of an antifreeze can enable a wide temperature range in which the mixture remains in the liquid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonic Anhydrase
The carbonic anhydrases (or carbonate dehydratases) () form a family of enzymes that catalyze the interconversion between carbon dioxide and water and the dissociated ions of carbonic acid (i.e. bicarbonate and hydrogen ions). The active site of most carbonic anhydrases contains a zinc ion. They are therefore classified as metalloenzymes. The enzyme maintains acid-base balance and helps transport carbon dioxide. Carbonic anhydrase helps maintain acid–base homeostasis, regulate pH, and fluid balance. Depending on its location, the role of the enzyme changes slightly. For example, carbonic anhydrase produces acid in the stomach lining. In the kidney, the control of bicarbonate ions influences the water content of the cell. The control of bicarbonate ions also influences the water content in the eyes. Inhibitors of carbonic anhydrase are used to treat glaucoma, the excessive build-up of water in the eyes. Blocking this enzyme shifts the fluid balance in the eyes to reduce f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UDP-N-acetylglucosamine Acyltransferase
Uridine diphosphate ''N''-acetylglucosamine or UDP-GlcNAc is a nucleotide sugar and a coenzyme in metabolism. It is used by glycosyltransferases to transfer ''N''-acetylglucosamine residues to substrates. D-Glucosamine is made naturally in the form of glucosamine-6-phosphate, and is the biochemical precursor of all nitrogen-containing sugars. To be specific, glucosamine-6-phosphate is synthesized from fructose 6-phosphate and glutamine as the first step of the hexosamine biosynthesis pathway. The end-product of this pathway is UDP-GlcNAc, which is then used for making glycosaminoglycans, proteoglycans, and glycolipids. UDP-GlcNAc is extensively involved in intracellular signaling as a substrate for ''O''-linked ''N''-acetylglucosamine transferases (OGTs) to install the ''O''-GlcNAc post-translational modification in a wide range of species. It is also involved in nuclear pore formation and nuclear signalling. OGTs and OG-ases play an important role in the structure of the cy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts are catalytic RNA molecules, called ribozymes. Enzymes' specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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