Title: Collagen
Additional Names: Ossein
Literature References: Mol wt about 130,000. Polypeptide substance comprising one third of the total protein in mammalian organisms; main constituent of skin, connective tissue, and the organic substance of bones and teeth. Prepd from bones by dissolving the mineral part of the bones with phosphoric acid: Sciallano, FR 688104 (1929), C.A. 25, 786 (1931). Isoln of sol collagens from corium tissue: Reizo, Sakata, Kumamoto Med. J. 13, 27 (1960). Purification: Bloch, Oneson, US 2973302 (1961 to Ethicon). Commercial extraction process: Highberger, US 2979438 (1961 to United Shoe Machinery). Collagen production in the body is preceded by the formation of a much larger molecule, the biosynthetic precursor procollagen, which is degraded by specific enzymes to make collagen. Different types of collagens exist. They are all composed of molecules containing three polypeptide chains, a-chains, arranged in a triple helical conformation. The amino acid sequence of the a-chain is mostly a repeating structure with glycine in every third position and proline or 4-hydroxyproline frequently preceding the glycine residues. Slight differences in the primary structure (amino acid sequence) establish differences between types. Review of structural studies: Tanzer, Science 180, 561-566 (1973); P. Bornstein, H. Sage, Annu. Rev. Biochem. 49, 959 (1980). Collagen is differentiated from the accompanying fibrous proteins, elastin, and reticulin, q.q.v., by (1) its content of proline, hydroxyproline and hydroxylysine, by (2) the absence of tryptophan and its low tyrosine and sulfur content, but particularly by (3) its high content of polar groups originating from the difunctional amino acids. The polar groups are responsible for the swelling properties leading eventually to dispersion of collagen in dil acid. Denaturation of collagen is the conversion of the rigidly coiled helix to a random coil called gelatin, q.v. Description of the native and denatured states of sol collagen: Boedtker, Doty, J. Am. Chem. Soc. 78, 4267 (1956). Biosynthesized in fibroblastic cells. Review of biosynthesis: Bornstein, Annu. Rev. Biochem. 43, 567-603 (1974). Reviews: Gross, Sci. Am. 204, 121 (May 1961); Harrington, von Hippel, Adv. Protein Chem. 16, 1-138 (1961); Grassmann et al., Fortschr. Chem. Org. Naturst. 23, 195-314 (1965); P. Bornstein, W. Traub, "The Chemistry and Biology of Collagen" in The Proteins vol. IV, H. Neurath, R. L. Hill, Eds. (Academic Press, New York, 1979) pp 411-632; D. R. Eyre, Science 207, 1315-1322 (1980); Methods Enzymol. 82, 3-555 (1982). Summary of recent studies of the role of collagen in disease: Chem. Eng. News 60, 32 (Jan. 25, 1982). Books: A. Veis, The Macromolecular Chemistry of Gelatin (Academic Press, New York, 1964) 433 pp; Biochemistry of Collagen, G. N. Ramachandran et al., Eds. (Plenum, New York, 1976) 536 pp; P. P. Fietzek in Collagen in Health and Disease, M. I. V. Jayson, J. B. Weiss, Eds. (Churchill-Livingstone, New York, 1982).
Use: As fibers in sutures, in leather substitutes; as a gel in photographic emulsions, in coatings; in food casings.

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