CROSS-LINKING AND THE MOLECULAR PACKING OF CORNEAL COLLAGEN

We have quantitatively characterized, for the first time, the cross-li nking in bovine cornea collagen as a function of age. The major iminiu m, reducible cross-links were dehydro-hydroxylysinonorleucine (deH-HLN L) and dehydro- histidinohydroxymerodesmosine (deH-HHMD). The former r apidly diminished after birth; however, the latter persisted in mature animals at a level of 0.3-0.4 moles/mole of collagen. A nonreducible cross-link, histidinohydroxylysinonorleucine (HHL), previously found o nly in skin, was also found to be a major mature cross-link in cornea. The presence of HHL indicates that comea fibrils have a molecular pac king similar to skin collagen. However, like deH-HHMD, the HHL content in corneal fibrils only reaches a maximum value with time about half that of skin. These data suggest that the corneal fibrils are comprise d of discrete filaments that are internally stabilized by HHL and deH- HHMD cross-links. This pattern of intermolecular cross-linking would f acilitate the special collagen swelling property required for corneal transparency. (C) 1996 Academic Press, Inc.