A Biochemical Study of Human Skin Collagen and the Relation between Intra- and Intermolecular Cross-Linking*

Journal/Book: Journal of Clinical Investigation Vol. 43 No. 9 1964. 1964;

Abstract: From the Section on Protein Chemistry Laboratory of Biochemistry National Institute of Dental Research Bethesda Md. * Submitted for publication April 21 1964; accepted May 15 1964. Presented in part at the Forty-eighth Annual Meeting of the Federation of American Societies for Experimental Biology April 1964. A portion of this work has been published in preliminary form (1). Research Associate National Institutes of Health. Summary 1) Normal human skin collagen has been studied with regard to a) the amino acid composition of the collagen monomer and its component chains; b) the separation by carboxymethylcellulose chromatography of the (single chain) - and (double chain) - components from collagen fractions extracted with different solvents; c) the sedimentation coefficients and molecular weights of the - and -components; and d) the optical rotation intrinsic viscosity and denaturation temperature of acetic acid-extracted collagen. The results are largely similar to studies performed on other mammalian collagens although small differences exist that reflect the unique structure of collagen in each species. 2) Collagen fractions extracted with neutral salt acetic acid and 5 M guanidine were compared. The analysis of guanidine extracts revealed a higher percentage of -components than could result from intramolecularly bonded collagen alone and the presence of 22 a dimer of 2 which according to present concepts can arise only from intermolecularly bonded collagen. 3) The extraction of intermolecularly bonded collagen by guanidine results in -components that are indistinguishable by present criteria from those extracted with salt and dilute acid solutions. This observation together with the finding that the 22 double-chain component structurally resembles the 12 and 11 double-chain components formed as a result of intramolecular cross-linking suggests that cross-linking in skin collagen is a single continuous process proceeding both intra- and intermolecularly and progressing from the formation of double chains to highly aggregated polymers. ___MH

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