|
Boronic Ester
A boronic acid is an organic compound related to boric acid () in which one of the three hydroxyl groups () is replaced by an alkyl or aryl group (represented by R in the general formula ). As a compound containing a carbon–boron bond, members of this class thus belong to the larger class of organoboranes. Boronic acids act as Lewis acids. Their unique feature is that they are capable of forming reversible covalent complexes with sugars, amino acids, hydroxamic acids, etc. (molecules with vicinal, (1,2) or occasionally (1,3) substituted Lewis base donors ( alcohol, amine, carboxylate)). The p''K''a of a boronic acid is ~9, but they can form tetrahedral boronate complexes with p''K''a ~7. They are occasionally used in the area of molecular recognition to bind to saccharides for fluorescent detection or selective transport of saccharides across membranes. Boronic acids are used extensively in organic chemistry as chemical building blocks and intermediates predominantly i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; Greeves, N. and Warren, S. (2012) ''Organic Chemistry''. Oxford University Press. pp. 1–15. . Study of structure determines their structural formula. Study of properties includes physical and chemical properties, and evaluation of chemical reactivity to understand their behavior. The study of organic reactions includes the chemical synthesis of natural products, drugs, and polymers, and study of individual organic molecules in the laboratory and via theoretical ( in silico) study. The range of chemicals studied in organic chemistry includes hydrocarbons (compounds containing only carbon and hydrogen) as well as compounds based on carbon, but also containing other elements, especially oxygen, nitrogen, sulfur, phosphorus (i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edward Frankland
Sir Edward Frankland, (18 January 18259 August 1899) was an English chemist. He was one of the originators of organometallic chemistry and introduced the concept of combining power or valence. An expert in water quality and analysis, he was a member of the second royal commission on the pollution of rivers, and studied London's water quality for decades. He also studied luminous flames and the effects of atmospheric pressure on dense ignited gas, and was one of the discoverers of helium. Biography Edward Frankland was born in Catterall, Lancashire and baptised at Churchtown, Lancashire on 20 February 1825. As his baptismal record shows, his birth was illegitimate. His mother, Margaret "Peggy" Frankland, later married William Helm, a Lancaster cabinet-maker. "His illegitimacy cast a shadow over all his life since he was pledged to silence as to the identity of his natural father, though a handsome annuity was paid to his mother". From age 3 to 8 Edward lived and was ed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mutagen
In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer in animals, such mutagens can therefore be carcinogens, although not all necessarily are. All mutagens have characteristic mutational signatures with some chemicals becoming mutagenic through cellular processes. The process of DNA becoming modified is called mutagenesis. Not all mutations are caused by mutagens: so-called "spontaneous mutations" occur due to spontaneous hydrolysis, errors in DNA replication, repair and recombination. Discovery The first mutagens to be identified were carcinogens, substances that were shown to be linked to cancer. Tumors were described more than 2,000 years before the discovery of chromosomes and DNA; in 500 B.C., the Greek physician Hippocrates named tumors resembling a crab ''karkinos'' (from which t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ras Subfamily
Ras, from "Rat sarcoma virus", is a family of related proteins that are expressed in all animal cell lineages and organs. All Ras protein family members belong to a class of protein called small GTPase, and are involved in transmitting signals within cells ( cellular signal transduction). Ras is the prototypical member of the Ras superfamily of proteins, which are all related in three-dimensional structure and regulate diverse cell behaviours. When Ras is 'switched on' by incoming signals, it subsequently switches on other proteins, which ultimately turn on genes involved in cell growth, differentiation, and survival. Mutations in Ras genes can lead to the production of permanently activated Ras proteins, which can cause unintended and overactive signaling inside the cell, even in the absence of incoming signals. Because these signals result in cell growth and division, overactive Ras signaling can ultimately lead to cancer. The three Ras genes in humans ('' HRAS'', ''KRAS'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acyl-protein Thioesterase
Acyl-protein thioesterases are enzymes that cleave off lipid modifications on proteins, located on the sulfur atom of cysteine residues linked via a thioester bond. Acyl-protein thioesterases are part of the α/β hydrolase superfamily of proteins and have a conserved catalytic triad. For that reason, acyl-protein thioesterases are also able to hydrolyze oxygen-linked ester bonds. Function Acyl-protein thioesterases are involved in the depalmitoylation of proteins, meaning they cleave off palmitoyl modifications on proteins' cysteine residues. Cellular targets include trimeric G-alpha proteins, ion channels and GAP-43. Moreover, human acyl-protein thioesterases 1 and 2 have been identified as major components in controlling the palmitoylation cycle of the oncogene Ras. Depalmitoylation of Ras by acyl-protein thioesterases potentially reduces Ras' affinity to endomembranes, allowing it to be palmitoylated again at the Golgi apparatus and to be directed to the plasma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kexin
Kexin () is a prohormone-processing protease, specifically a yeast serine peptidase, found in the budding yeast (''S. cerevisiae''). It catalyzes the cleavage of -Lys-Arg- and -Arg-Arg- bonds to process yeast alpha-factor pheromone and killer toxin precursors. The human homolog is PCSK4. It is a family of subtilisin-like peptidases. Even though there are a few prokaryote kexin-like peptidases, all kexins are eukaryotes. The enzyme is encoded by the yeast gene ''KEX2'', and usually referred to in the scientific community as Kex2p. It shares structural similarities with the bacterial protease subtilisin. The first mammalian homologue of this protein to be identified was furin. In the mammal, kexin-like peptidases function in creating and regulating many differing proproteins. Nomenclature The enzyme is also known as yeast KEX2 protease, proteinase yscF, prohormone-processing endoprotease, paired-basic endopeptidase, yeast cysteine proteinase F, paired-basic endopeptidase, andren ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subtilisin
Subtilisin is a protease (a protein-digesting enzyme) initially obtained from '' Bacillus subtilis''. Subtilisins belong to subtilases, a group of serine proteases that – like all serine proteases – initiate the nucleophilic attack on the peptide (amide) bond through a serine residue at the active site. Subtilisins typically have molecular weights 27kDa. They can be obtained from certain types of soil bacteria, for example, '' Bacillus amyloliquefaciens'' from which they are secreted in large amounts. Nomenclature Subtilisin is also commercially known as ''Alcalase®'', ''Endocut-02L'', ''ALK-enzyme'', ''bacillopeptidase'', ''Bacillus subtilis alkaline proteinase bioprase'', ''bioprase AL'', ''colistinase'', ''genenase I'', ''Esperase®'', ''maxatase'', ''protease XXVII'', ''thermoase'', ''superase'', ''subtilisin DY'', ''subtilopeptidase'', ''SP 266'', ''Savinase®'', ''kazusase'', ''protease VIII'', ''protin A 3L'', ''Savinase®'', ''orientase 10B'', ''proteas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pancreatic Lipase Family
Triglyceride lipases () are a family of lipolytic enzymes that hydrolyse ester linkages of triglycerides. Lipases are widely distributed in animals, plants and prokaryotes. At least three tissue-specific isozymes exist in higher vertebrates, pancreatic, hepatic and gastric/lingual. These lipases are closely related to each other and to lipoprotein lipase (), which hydrolyses triglycerides of chylomicrons and very low density lipoproteins (VLDL). The most conserved region in all these proteins is centred on a serine residue which has been shown to participate, with a histidine and an aspartic acid residue, in a charge relay system. Such a region is also present in lipases of prokaryotic origin and in lecithin-cholesterol acyltransferase () (LCAT), which catalyzes fatty acid transfer between phosphatidylcholine and cholesterol. Human pancreatic lipase ''Pancreatic lipase'', also known as ''pancreatic triacylglycerol lipase'' or ''steapsin'', is an enzyme secreted from the pancre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteasome
Proteasomes are protein complexes which degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds. Enzymes that help such reactions are called proteases. Proteasomes are part of a major mechanism by which cells regulate the concentration of particular proteins and degrade misfolded proteins. Proteins are tagged for degradation with a small protein called ubiquitin. The tagging reaction is catalyzed by enzymes called ubiquitin ligases. Once a protein is tagged with a single ubiquitin molecule, this is a signal to other ligases to attach additional ubiquitin molecules. The result is a ''polyubiquitin chain'' that is bound by the proteasome, allowing it to degrade the tagged protein. The degradation process yields peptides of about seven to eight amino acids long, which can then be further degraded into shorter amino acid sequences and used in synthesizing new proteins. Proteasomes are found inside all eukaryotes and archaea, and in some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherapy may be given with a curative intent (which almost always involves combinations of drugs) or it may aim to prolong life or to reduce symptoms ( palliative chemotherapy). Chemotherapy is one of the major categories of the medical discipline specifically devoted to pharmacotherapy for cancer, which is called ''medical oncology''. The term ''chemotherapy'' has come to connote non-specific usage of intracellular poisons to inhibit mitosis (cell division) or induce DNA damage, which is why inhibition of DNA repair can augment chemotherapy. The connotation of the word chemotherapy excludes more selective agents that block extracellular signals ( signal transduction). The development of therapies with specific molecular or genetic targ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
