Keratin

Keratin (from Greek κέρας keras " horn ", genitive kératos ) is a collective term for various water-insoluble fibrous proteins, which are formed by animals and characterize the horny substance. According to their molecular conformation as α - helix or β -sheet to α - and β - different keratins.

Keratins are the main constituent of mammalian hair, finger and toe nails, claws, claws, hooves, horns, nose horns of the rhinos, spines of the hedgehog, baleen whales, beaks and feathers of birds, horny scales and outer armor covering of reptiles.

Structure and Properties

Your fiber structure increases the strength of the keratins: The single amino acid chains form a right-handed α - helix. Two of these helices superimpose to a left-handed super helix and two of these coiled-coils in the α - keratin together to form a protofibril. Several protofibrils unite to form a microfibril, this self-assemble into bundles and form macrofibrils from. The fibers are more rigid, the more of its components are cross-linked by disulfide bonds of the amino acid L-cysteine. So the keratin contains horns and claws more disulfide bonds than in wool and hair. Leonor Michaelis discovered that disulfide bridges are reduced by thioglycolic acid. This was the biochemical basis for the perm.

Before keratinization as well as generally in epithelia of vertebrates and other animal groups are α - keratins (or cytokeratins ) in the form of loosely-organized keratin filaments before. These are some of the intermediate filaments, which constitute the cytoskeleton of eukaryotic cells, together with microtubules and microfilaments. Currently, 20 cytokeratin proteins are known ( see table), whose molecular mass is between 40 and 68 kDa. KRT1 to KRT8 to be neutral -basic type A subfamily KRT9 counted to KRT20 to the acid type B subfamily. They form pairs in the intermediate filaments a heterodimer complex of a type A and a type B cytokeratin. The distribution pattern of these complexes differs in various epithelial cells significantly, so that a detection of antibodies against subtypes KRT1 KRT20 to the origin of these cytokeratins can be limited. This makes you look in the medicine in the pathological diagnosis advantage of in order to determine the origin of tumor metastases. Mutations in different keratin genes are responsible for a number of rare genetic diseases ( ichthyosis ) responsible.

An example of a β - Keratin is the silk protein or fibroin of cobwebs and silk. In contrast to the α - or cytokeratins is no intra-cellular structural protein, but a precipitate product of the silk glands. Because of its sheet structure, it is much less extensible than the helically assembled α - keratins.

Technical use

From keratin natural substances L- cysteine, L- tyrosine and other proteinogenic amino acids are produced on an industrial scale. These natural products are first hydrolyzed with hydrochloric acid. The hydrolyzate is neutralized with ammonia. The L-amino acids are then separated or isolated according to the principle of ion exchange chromatography based on their different solubilities.

Use find Keratinprodukte (eg sheep wool fleeces ) in the degradation of formaldehyde. Here the German Wool Research Institute at RWTH Aachen University has provided along with the eco Institute in Cologne in long-term research to prove that such products are able to remove formaldehyde from the air. Formaldehyde -loaded kindergartens, schools and private homes (many prefabricated houses of the 1970s and 1980s ) have been redeveloped in recent years in this way.