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

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Abstract
Normal human skin collagen was studied for the amino-acid composition of the collagen monomer and its component chains; the separation by carboxymethylcellulose chromatography of the [alpha] (single chain)-and [beta] (double chain)-components from collagen fractions extracted with different solvents; the sedimentation coefficients and molecular weights of the [alpha]- and [beta]-components; and the optical rotation, intrinsic viscosity and denatuaration temperature of acetic-acid-extracted collagen. The results are similar but not identical to other mammalian collagens. The analysis of 5 [image] guanidine extracts revealed a higher percentage of [beta]-components than could result from intramolecularly bonded collagen alone and the presence of [beta]22 (a dimer of [alpha]2) which can arise only from intermolecularly bonded collagen. The extraction of intermolecularly bonded collagen by guanidine results in [beta]-components that are indistinguishable from those extracted with neutral salt and dilute acetic-acid solutions. This observation, together with the finding that [beta]22 double-chain component structurally resembles the [beta]12 and [beta]11 double-chain components formed by 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.