keratin

noun

1. a scleroprotein or albuminoid substance, found in the dead outer skin layer, and in horn, hair, feathers, hoofs, nails, claws, bills, etc.

noun

1. a fibrous protein that occurs in the outer layer of the skin and in hair, nails, feathers, hooves, etc

n.

basic substance of horns, nails, feathers, etc., 1847, from Greek keras (genitive keratos) “horn” (see kerato-) + chemical suffix -in (2).

n.

1. Any of a group of scleroproteins or albuminoids that contain large amounts of sulfur and are the chief structural constituents of hair, nails, and other horny tissues.

1. Any of a class of tough, fibrous proteins that are the main structural component of hair, nails, horns, feathers, and hooves. Keratins are rich in sulfur-containing amino acids, especially cysteine. Individual keratin molecules are entwined helically around each other in long filaments, which are cross-linked by bonds between sulfur atoms on different chains. The twining and cross-linking produce strength and toughness.