THERMAL DENATURATION OF COLLAGEN IN THE DISPERSED AND SOLID STATE.

Thermal denaturation temperature of newly reconstituted collagen fibrils from rat tail tendons is 52 degrees C compared with 42 degrees C for neutral solutions. This suggests that the increase in concentration of collagen within the fibril increases the stability of the individual molecules. The absence of firm intermolecular bonds in these fibrils rules out crosslinking as an explanation for increased stability. "Aging" at 37 degrees C up to 1 year raises the shrinkage temperature of reconstituted fibrous gels by 4 degrees to 6 degrees C and greatly increases resistance to dissolution at high temperature. The newly formed fibrils dissolve without shrinking, whereas older gels exhibit shrinkage before dissolution. Since nearly all extractable collagen is in the form of fibrillar aggregates in tissue, it is unlikely that thermal denaturation occurs at body temperature; therefore it could not be involved as a necessary stage in collagen resorption.