|
Phoratoxin
Phoratoxins are a group of peptide toxins that belong to the family of thionins, a subdivision of small plant toxins (5000 kD MW). Phoratoxins are proteins present in the leaves and branches of the ''Phoradendron'', commonly known as the American variant of the mistletoe, a plant commonly used as decoration during the festive season. The berries of the mistletoe do not contain phoratoxins, making them less toxic compared to other parts of the plant. The toxicity of the mistletoe is dependent on the host tree, since mistletoe is known to be a semi-parasite. The host tree provides fixed inorganic nitrogen compounds necessary for the mistletoe to synthesize phoratoxins. Viscotoxins are similar plant thionins produced from the leaves and stems of the European mistletoe (''Viscum album''). History The history of phoratoxin is filled with myths, legends, and other magical stories. Mistletoe is a semi-parasitic plant occasionally using oak trees as their host. To historic peoples such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscotoxin
Phoratoxins are a group of peptide toxins that belong to the family of thionins, a subdivision of small plant toxins (5000 kD MW). Phoratoxins are proteins present in the leaves and branches of the ''Phoradendron'', commonly known as the American variant of the mistletoe, a plant commonly used as decoration during the festive season. The berries of the mistletoe do not contain phoratoxins, making them less toxic compared to other parts of the plant. The toxicity of the mistletoe is dependent on the host tree, since mistletoe is known to be a semi-parasite. The host tree provides fixed inorganic nitrogen compounds necessary for the mistletoe to synthesize phoratoxins. Viscotoxins are similar plant thionins produced from the leaves and stems of the European mistletoe (''Viscum album''). History The history of phoratoxin is filled with myths, legends, and other magical stories. Mistletoe is a semi-parasitic plant occasionally using oak trees as their host. To historic peoples such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thionin
Thionins are a family of small proteins found solely in higher plants. Typically, a thionin consists of 45–48 amino acid residues. 6–8 of these are cysteine forming 3–4 disulfide bonds. They include phoratoxins and viscotoxins. Alpha- and beta- thionins are related to each other. The gamma thionins have a superficially similar structure but are an unrelated class of protein, now called plant defensins. Activity The proteins are toxic to animal cells, presumably attacking the cell membrane and rendering it permeable: this results in the inhibition of sugar uptake and allows potassium and phosphate ions, proteins, and nucleotides to leak from cells. Thionins are mainly found in seeds where they may act as a defence against consumption by animals. A barley (''Hordeum vulgare'') leaf thionin that is highly toxic to plant pathogens and is involved in the mechanism of plant defence against microbial infections has also been identified. The hydrophobic protein crambin from th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant Toxin
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849–1919) and is derived from the word toxic. Toxins can be small molecules, peptides, or proteins that are capable of causing disease on contact with or absorption by body tissues interacting with biological macromolecules such as enzymes or cellular receptors. Toxins vary greatly in their toxicity, ranging from usually minor (such as a bee sting) to potentially fatal even at extremely low doses (such as botulinum toxin). Toxins are largely secondary metabolites, which are organic compounds that are not directly involved in an organism's growth, development, or reproduction, instead often aiding it in matters of defense. Terminology Toxins are often distinguished from other chemical agents strictly based on their biological origin. Le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoradendron
''Phoradendron'' is a genus of mistletoe, native to warm temperate and tropical regions of the Americas. The center of diversity is the Amazon rainforest.Coder, K. DAmerican mistletoe (''Phoradendron serotinum'' var. ''serotinum'') infection in trees.WSFNR08-25. Tree Health Series. University of Georgia. 2008. ''Phoradendron'' is the largest genus of mistletoe in the Americas, and possibly the largest genus of mistletoes in the world. Traditionally, the genus has been placed in the family Viscaceae, but recent genetic research acknowledged by the Angiosperm Phylogeny Group shows this family to be correctly placed within a larger circumscription of the sandalwood family, Santalaceae. They are woody hemi-parasitic shrubs with branches long, which grow on other trees. The foliage is dichotomously branching, with opposite pairs of leaves; these are fairly large, long, green and photosynthetic in some species (e.g. ''P. leucarpum''), but minimal in some others (e.g. ''P. c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thionins
Thionins are a family of small proteins found solely in higher plants. Typically, a thionin consists of 45–48 amino acid residues. 6–8 of these are cysteine forming 3–4 disulfide bonds. They include phoratoxins and viscotoxins. Alpha- and beta- thionins are related to each other. The gamma thionins have a superficially similar structure but are an unrelated class of protein, now called plant defensins. Activity The proteins are toxic to animal cells, presumably attacking the cell membrane and rendering it permeable: this results in the inhibition of sugar uptake and allows potassium and phosphate ions, proteins, and nucleotides to leak from cells. Thionins are mainly found in seeds where they may act as a defence against consumption by animals. A barley (''Hordeum vulgare'') leaf thionin that is highly toxic to plant pathogens and is involved in the mechanism of plant defence against microbial infections has also been identified. The hydrophobic protein crambin from the A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscum Album
''Viscum album'' is a species of mistletoe in the family Santalaceae, commonly known as European mistletoe, common mistletoe or simply as mistletoe (Old English ''mistle''). It is native to Europe and western and southern Asia. ''Viscum album'' is a hemiparasite on several species of trees, from which it draws water and nutrients. It has a significant role in European mythology, legends, and customs. In modern times, it is commonly featured in Christmas decoration and symbology. (''V. album'' is found only rarely in North America, as an introduced species; its cultural roles are usually fulfilled by the similar native species ''Phoradendron leucarpum''.) Description It is a hemi-parasitic evergreen shrub, which grows on the stems of other trees. It has stems long with dichotomous branching. The leaves are in opposite pairs, strap-shaped, entire, leathery textured, long, broad and are a yellowish-green in colour. This species is dioecious and the insect-pollinated flow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Panacea (medicine)
A panacea , named after the Greek goddess of universal remedy Panacea, is any supposed remedy that is claimed (for example) to cure all diseases and prolong life indefinitely. It was in the past sought by alchemists in connection with the elixir of life and the philosopher's stone, a mythical substance that would enable the transmutation of common metals into gold. Through the 18th and 19th centuries, many "patent medicines" were claimed to be panaceas, and they became very big business. The term "panacea" is used in a negative way to describe the overuse of any one solution to solve many different problems, especially in medicine. The word has acquired connotations of snake oil and quackery. A panacea (or ''panaceum'') is also a literary term to represent any solution to solve all problems related to a particular issue. Mythology In Greek mythology, Panacea was one of the daughters of the Greek god of medicine Asclepius, along with her four sisters, each of whom performed one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Mistletoe
''Phoradendron leucarpum'' is a species of mistletoe in the Viscaceae family which is native to the United States and Mexico. Its common names include American mistletoe, eastern mistletoe, hairy mistletoe and oak mistletoe. It is native to Mexico and the continental United States. It is hemiparasitic, living in the branches of trees. The berries are white and . It has opposite leaves that are leathery and thick. Ingesting the berries can cause "stomach and intestinal irritation with diarrhea, lowered blood pressure, and slow pulse". This shrub can grow to by . Culture and tradition ''Phoradendron leucarpum'' is used in North America as a surrogate for the similar European mistletoe '' Viscum album'', in Christmas decoration and associated traditions (such as "kissing under the mistletoe"), as well as in rituals by modern druids. It is commercially harvested and sold for those purposes. ''Phoradendron leucarpum'' is the state floral emblem for the state of Oklahoma. The sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Mistletoe
''Viscum album'' is a species of mistletoe in the family Santalaceae, commonly known as European mistletoe, common mistletoe or simply as mistletoe (Old English ''mistle''). It is native to Europe and western and southern Asia. ''Viscum album'' is a hemiparasite on several species of trees, from which it draws water and nutrients. It has a significant role in European mythology, legends, and customs. In modern times, it is commonly featured in Christmas decoration and symbology. (''V. album'' is found only rarely in North America, as an introduced species; its cultural roles are usually fulfilled by the similar native species ''Phoradendron leucarpum''.) Description It is a parasitic plant, hemi-parasitic evergreen shrub, which grows on the stems of other trees. It has stems long with dichotomous branching. The leaf, leaves are in opposite pairs, strap-shaped, entire, leathery textured, long, broad and are a yellowish-green in colour. This species is dioecious and the insec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crambin
Crambin is a small seed storage protein from the Abyssinian cabbage. It belongs to thionins Thionins are a family of small proteins found solely in higher plants. Typically, a thionin consists of 45–48 amino acid residues. 6–8 of these are cysteine forming 3–4 disulfide bonds. They include phoratoxins and viscotoxins. Alpha- and .... It has 46 residues (amino acids). It has been extensively studied by X-ray crystallography since its crystals are unique and diffract to a resolution of 0.48 Å. Neutron scattering measurements are available also at a resolution of 1.1 Å.; References {{reflist Proteins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta Sheet
The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation. The supramolecular association of β-sheets has been implicated in the formation of the fibrils and protein aggregates observed in amyloidosis, notably Alzheimer's disease. History The first β-sheet structure was proposed by William Astbury in the 1930s. He proposed the idea of hydrogen bonding between the peptide bonds of parallel or antiparallel extended β-strands. However, Astbury did not have the necessary data on the bond geometry of the amino acids in order to build accurate models, especially since he did not then know that the peptide bond was planar. A refined versi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disulfide Bridge
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In biology, disulfide bridges formed between thiol groups in two cysteine residues are an important component of the secondary and tertiary structure of proteins. ''Persulfide'' usually refers to compounds. In inorganic chemistry disulfide usually refers to the corresponding anion (−S−S−). Organic disulfides Symmetrical disulfides are compounds of the formula . Most disulfides encountered in organo sulfur chemistry are symmetrical disulfides. Unsymmetrical disulfides (also called heterodisulfides) are compounds of the formula . They are less common in organic chemistry, but most disulfides in nature are unsymmetrical. Properties The disulfide bonds are strong, with a typical bond dissociation energy of 60 kcal/mol (251&nbs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Phoradendron")
