INTERACTION OF COLLAGEN MAC ROMO L EC U L ES 



45 



completely eliminates the production of native-tvpe fibrils on dial- 

 ysis against 1 per cent NaCl. The phenomenon of "thermal gela- 

 tion" of neutral salt solutions of collagen investigated extensively by 

 Gross (1956, 1959) and by Bensusan and Hoyt (1958) is 'also 

 severely inhibited or abolished if the collagen solutions are in- 

 cubated with trypsin at 20° C prior to incubation in the tempera- 

 ture range 30°-37° C. The effect of the enzyme is illustrated in 

 Fig. 24. That the attack of pepsin and trypsin is largely, if not 

 entirely, confined to the "end regions" of intact molecules is also 

 suggested by the following result. When a sonicated solution of TC, 

 which normally yielded a large proportion of whole polymeric and 

 fragment dimeric SLS-type aggregates on addition of ATP (Figs. 

 13, 15-17 ) , was treated with pepsin at pH 3-4, prior to the addition 

 of ATP, it yielded only whole and fragment monomeric SLS forms 

 (Fig. 25). ' 



It seemed likely from these data that the result of protease action 

 on the TC macromolecule is the profound alteration, or more prob- 



Fig. 25. A typical field in a preparation of SLS-type aggregates produced 

 by addition of ATP to a solution of sonically irradiated collagen following 

 incubation with pepsin. This solution, which, in the absence of enzyme treat- 

 ment, characteristically yielded SLS-type structures of whole polymeric and 

 fragment dimeric type (Figs. 13, 15-17), gave, after treatment with enzyme, 

 only ordered aggregates corresponding to whole and fragment monomeric 

 types, indicating that the enzyme inhibits end-to-end linkages of the TC macro- 

 molecules. Stained with PTA. X 90,000. 



