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Beta Sheets
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 version was p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animated Beta Sheet
Animation is a method by which still figures are manipulated to appear as moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Today, most animations are made with computer-generated imagery (CGI). Computer animation can be very detailed 3D animation, while 2D computer animation (which may have the look of traditional animation) can be used for stylistic reasons, low bandwidth, or faster real-time renderings. Other common animation methods apply a stop motion technique to two- and three-dimensional objects like paper cutouts, puppets, or clay figures. A cartoon is an animated film, usually a short film, featuring an exaggerated visual style. The style takes inspiration from comic strips, often featuring anthropomorphic animals, superheroes, or the adventures of human protagonists. Especially with animals that form a natural predator/prey relationship (e.g. cats and mice, coyo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tautomerization
Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hydrogen atom within the compound. The phenomenon of tautomerization is called tautomerism, also called desmotropism. Tautomerism is for example relevant to the behavior of amino acids and nucleic acids, two of the fundamental building blocks of life. Care should be taken not to confuse tautomers with depictions of "contributing structures" in chemical resonance. Tautomers are distinct chemical species that can be distinguished by their differing atomic connectivities, molecular geometries, and physicochemical and spectroscopic properties, whereas resonance forms are merely alternative Lewis structure (valence bond theory) depictions of a single chemical species, whose true structure is best described as the "average" of the idealized, hypothe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amide Ring
Amide Rings are small motifs in proteins and polypeptides. They consist of 9-atom or 11-atom rings formed by two CO...HN hydrogen bonds between a side chain amide group and the main chain atoms of a short polypeptide. They are observed with glutamine or asparagine side chains within proteins and polypeptides. Structurally similar rings occur in the binding of purine, pyrimidine and nicotinamide bases to the main chain atoms of proteins. About 4% of asparagines and glutamines form amide rings; in databases of protein domain structures, one is present, on average, every other protein. In such rings the polypeptide has the conformation of beta sheet or of type II polyproline helix (PPII). A number of glutamines and asparagines help bind short peptides (with the PPII conformation) in the groove of class II MHC (Major Histocompatibility Complex) proteins by forming these motifs. An 11-atom amide ring, involving a glutamine residue, occurs at the interior of the light chain variable do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
