CONCERNING SOME SPECIAL STRUCTURAL FEATURES OF THE COLLAGEN MOLECULE.

A summary of results and ideas concerning special features of the covalent structure of collagen is presented. Our recent data on the nature of aspartyl ester pairs in collagen cross-linking and speculations about how these may function in fiber maturation are discussed. An important new aldehydic component associated with the cross-link sites has been detected and is under investigation. A model of collagen based upon 4 subunits of 25,000 to 30,000 per alpha component has been developed. These subunits appear to be held together in a linear array by three pairs of ester bonds. A more detailed picture of the distribution of "crystalline" and "amorphous" regions along the tropocollagen molecule has been proposed primarily based on the results of analyses of collagen peptide fractions obtained with collagenase. Other topics such as gamma-glutamyl bonds in collagen and results with carbonyl group-detecting reagents which demonstrate the presence of small amounts of alpha-keto acid groups are briefly considered.