Keratin

Description

A natural fibrous Protein that is the primary building block for epidermal tissue. Keratin contains all of the common amino acids, but has higher amounts of cystine than other fibrous structural proteins. Sulfur atoms in the cystine amino acid groups are linked by disulfide bonds thus forming polypeptide chains. Soft keratins are found in the external layers of skin, Wool, Hair, feathers, while hard keratins are the major components of tortoiseshells, nails, hoofs, scales, bills, and claws. In the hard keratins, the disulfide bonds of cystine are crosslinked. From the mid-1600's, hornsmiths molded keratin materials into buttons, combs, and buckles. Keratins are relatively stable to changes in relative humidity but are damaged by heat, acids, alkalis, and insects. Storage in ethanol and ethanol/formalin can shortened the expected lifetime of keratin artifacts (von Endt et al 2000).

Synonyms and Related Terms

queratina (Esp.); kératine (Fr.); cheratina (It); Albuminoid

Risks

Damaged by alkalis and most bleach solutions. Decomposes in boiling water. Susceptible to moth larvae and other protein-feeding insects.

Physical and Chemical Properties

Insoluble in organic solvents and dilute acids. Slightly hygroscopic.

Composition	approx.C72H112N18O12S

Resources and Citations

• D.W. von Endt, E.R.Yourd, P.E.Hare, "Spirit Collections: Accelerated Aging Studies Concerning the Stability of Keratin in Ethanol and Formalin" Collection Forum 14(1-2):66-77, 2000.

• John S. Mills, Raymond White, The Organic Chemistry of Museum Objects, Butterworth Heineman, London, 2nd ed., 1994

• Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976

• Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997

• The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entyr 5302

• The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998

• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993

• Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982

• J.Gordon Cook, Handbook of Textile Fibres:I Natural Fibres, Merrow Publishing Co. , Durham, England, 1984

• Rosalie Rosso King, Textile Identification, Conservation, and Preservation, Noyes Publications, Park Ridge, NJ, 1985

• Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000

• Website: www.nswpmith.com.au/historyofplastics.html