Collagens, network-forming stability

Unlike most collagens type IV collagen invariably forms an amorphous covalently stabilized network that is predominantly found in basement membranes. In addition to collagen type IV various other extracellular components, among them laminins, perlecan, nidogen, and fibulins were identified to contribute to the thin sheets of basement membranes which mechanically support tissue architecture, separate connective tissues from epithelial,... 

The undisturbed organic and the inorganic matrix in a bone form a very stable network which is the reason for the extreme stability of bone. So a mineralized collagen can survive into the archaeological record under certain circumstances and an intact collagen phase can prevent fluorine from penetrating into the sample (Fig. 9). A well-preserved bone may thus show a less-developed profile than a far degraded sample of the same age. 

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