Beta sheet: Difference between revisions
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==Under construction== | |||
A [[beta sheet]] is a type of secondary structure, i.e. a description of how the main chain of a protein is arranged in space. It is composed of at least two beta strands. Beta strands have repetitive regular secondary structure (just like the [[alpha helix]]), i.e. all residues have similar conformation and hydrogen bonding, and it can be of arbitrary length. | A [[beta sheet]] is a type of secondary structure, i.e. a description of how the main chain of a protein is arranged in space. It is composed of at least two beta strands. Beta strands have repetitive regular secondary structure (just like the [[alpha helix]]), i.e. all residues have similar conformation and hydrogen bonding, and it can be of arbitrary length. | ||
<StructureSection load='' size='350' side='right' caption='' scene='88/889825/Toxin_1f94/1'> | <StructureSection load='' size='350' side='right' caption='' scene='88/889825/Toxin_1f94/1'> | ||
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===Beta sheets in amyloid fibrils=== | ===Beta sheets in amyloid fibrils=== | ||
==History== | ==History== | ||
Alpha helices and beta sheets are named after two conformations of keratin, a fiber occuring in mammals (wool, hair, quills) <ref>PMID: 15240497</ref>. Alpha keratin is composed of [[coiled coils]] of alpha helices, whereas hard stretching these fibers in water changes the conformation to beta sheets. The two conformations show different diffraction data under X-ray illumination. | Alpha helices and beta sheets are named after two conformations of keratin, a fiber occuring in mammals (wool, hair, quills) <ref>PMID: 15240497</ref>. Alpha keratin is composed of [[coiled coil|colide coils]] of alpha helices, whereas hard stretching these fibers in water changes the conformation to beta sheets. The two conformations show different diffraction data under X-ray illumination. | ||
==Experimental evidence== | ==Experimental evidence== | ||
Apart from the historical fiber diffraction data, various spectroscopic techniques may be used to show the presence of beta sheets. Circular dichroism (CD) or infrared (IR) spectroscopy allows an estimate of the beta sheet content of a protein sample. NMR spectroscopy, after resonance assignment, allows secondary structure assignment residue by residue based on chemical shifts of the alpha carbon and beta carbon resonances. | Apart from the historical fiber diffraction data, various spectroscopic techniques may be used to show the presence of beta sheets. Circular dichroism (CD) or infrared (IR) spectroscopy allows an estimate of the beta sheet content of a protein sample. NMR spectroscopy, after resonance assignment, allows secondary structure assignment residue by residue based on chemical shifts of the alpha carbon and beta carbon resonances. | ||
