Dentine and corium collagens were subjected to thermal hydrolyses and to periodate oxidation in an attempt to isolate intact chain sequences containing the dentine-collagen cross-link sites. The action of periodates on both dentine and corium was found to be identical, with an identical rate and extent of solubilization. The corium collagen yielded two high-molecular-weight soluble fractions, one of which was insoluble in acid. The soluble dentine fraction contained at least two electrophoretically distinct components, one with a mobility at pH 5.3 of −14 × 10 −5 cm2/v-sec. These soluble dentine fractions were very rich in nondialyzable phosphate, serine, aspartic acid, and glutamic acid. The relative phosphate content of the insoluble residue was reduced. Periodate oxidation completely destroyed all the tyrosine in each of the systems. Arginine and histidine appeared enhanced in the dialyzable peptides of low molecular weight. It is suggested that the corium and dentine collagens contain a common set of intermolecular cross-linkages, involving the tyrosine-rich regions of the collagen-monomer units, and that the dentine collagen contains, in addition, a set of phosphate cross-linkages distributed in specific regions of high charge density along the body of the monomer units. About 60% of the phosphate esters may be involved in diester cross-link formation. Some carbohydrate cross-linking is also indicated in the dentine system.
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