Intermolecular cross-links in collagen of human placenta.

1. There are four reducible cross-links in human placenta collagen. The principal one is dehydrodihydroxylysinorleucine. the next in abundance is dehydrohydroxylysinorleucine. The minor components are dehydrolysinonorleucine and dehydrohistidinohydroxymerodesmosine. 2. With increasing length of gestation, the collagen incorporates more tritium radioactivity into its reducible cross-links, with its maximum incorporation at the second trimester. The uptake declines thereafter. 3. Alkaline hydrolysis reveals that both dehydrodihydroxylysinonorleucine and dehydrohydroxylysinonorleucine occur in vivo partly as glycosylated complexes.