keratin

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keratin

(kĕr`ətĭn), any one of a class of fibrous proteinprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
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 molecules that serve as structural units for various living tissues. The keratins are the major protein components of hair, wool, nails, horn, hoofs, and the quills of feathers. These proteins generally contain large quantities of the sulfur-containing amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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, particulary cysteinecysteine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of mammalian protein.
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. The helical keratin molecules twist around each other to form elongated strands called intermediate filaments. The formation of a covalent chemical bondchemical bond,
mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the formation of an aggregate with sufficient stability to be regarded as an
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 called a disulfide bridge between the sulfer atoms on two cysteins on separate polypeptide chains of keratin allows for the cross-linkage of these chains and results in a fairly rigid aggregate. This phenomenon is seen to be consistent with the physiological role of the keratins, which provide a tough, fibrous matrix for the tissues in which they are found. Human hair is approximately 14% cystine (cysteins cross-linked by disulfide bridges).
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keratin

[′ker·əd·ən]
(biochemistry)
Any of various albuminoids characteristic of epidermal derivatives, such as nails and feathers, which are insoluble in protein solvents, have a high sulfur content, and generally contain cystine and arginine as the predominating amino acids.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

keratin

A proteinaceous material used as a retarder for plaster.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

keratin

, ceratin
a fibrous protein that occurs in the outer layer of the skin and in hair, nails, feathers, hooves, etc.
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Numerous keratin pearls and few mitotic figures with cellular and nuclear pleomorphism and hyperchromatism were also seen.
There were many small nests with occasional keratin pearls and growth of single cells in the shallow lamina propria [Figure 2]d and [Figure 2]e.
Microphotograph (magnification 40x) showing squamous cell carcinoma with keratin pearls (shown by an arrow).
Microscopically, the tumor was well demarcated from the surrounding tissue and showed coalescing masses of squamous epithelium with abrupt keratinization and keratin pearls. There were solid and cystic areas, some containing cholesterol clefts and blood.
Histopathological examination of tumor growth revealed hyperkeratinization surrounded by neoplastic squamous cells forming characteristic onion like eosinophilic keratin pearls (cell nests) surrounded by inflammatory cell infilteration (Fig.
Although pSCC contains squamous cells with features typical of SCC (e.g., intracellular bridges, keratin pearls, and reactivity to markers for high-molecular-weight keratin), it is also made up of melanin-containing cells.
The light microscopic examination revealed squamous cell carcinoma (SCC) as acanthotic squamous epithelium with deep rete pegs, epithelial and keratin pearls, pleomorphism, stromal infiltration and hyperchromatic nuclei (Fig.
Several nests of shadow cells, wet keratin and keratin pearls are present [Figure 3].
1: showing renal tubules, sheets of squamous cells and areas of keratin pearls. Cells have hyperchromatic nuclei with increased N: C ratio.

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