INTERACTION OF COLLAGEN MAC ROMOLEC U LES 37 



SLS Ixind pattern suffice to prove that the 2800-A macromolecular 

 unit is the true monomeric form. 



Electron microscope examination of SLS-type aggregates ob- 

 tained from solutions of TC subjected to sonic irradiation has served 

 to reveal some features of interest, particularly in relation to the 

 end-to-end polymerization properties of TC. The physicochemical 

 measurements of Nishihara and Doty (1958) indicated that sonic 

 irradiation fragmented the TC macromolecules into shorter pieces 

 which, however, largely retained the helical configuration of the 

 native macromolecules. They concluded that the time-dependence 

 of the molecular weight change was compatible with a preferential 

 fragmentation of the macromolecules into halves and quarters. 

 Electron microscope examination of SLS-type aggregates produced 

 from such sonicated solutions confirmed this conclusion in general 

 (Hodge and Schmitt, 1958) and, in addition, showed that sonic 

 irradiation profoundlv modifies the end-to-end interactions of the 

 TC. 



The main effects of sonic irradiation on the TC macromolecule 

 are illustrated diagrammatically in Fig. 12. One of the most im- 

 portant is a rapid alteration of "end-regions" without apparent 

 change in length, the modification being manifested as a change in 

 the ability of the TC to engage in end-to-end polymerization. This 

 is indicated in Fig. 12 by labeling the ends A' and B' rather than 

 A and B. An important consequence of this modification is an 

 impairment of the ability to form fibrils of native type, i.e., an in- 

 hibition of end-to-end polymerization of the type AB-AB-AB- in- 

 volved in the protofibril formation. Another result of sonic irradi- 

 ation is a pronounced effect on the characteristics of the SLS-type 

 precipitates formed on addition of ATP. The SLS-type precipitates 

 derived from unirradiated control solutions usually consist largely 

 of single segments with relatively few dimeric or trimeric forms, the 

 latter normally exhibiting end-to-end linkages of type A-B. How- 

 ever, the irradiated solutions yield progressively increasing amounts 

 of dimeric and polymeric forms (see Fig. 12 for explanation), in- 

 volving end-to-end linkages of the type A'-A' and B'-B' (Fig. 13). 

 Thus, in addition to fragmentation, the effects of sonication are ap- 

 parently twofold: (a) impairment of end-to-end interactions of the 

 A-B type under conditions which normally favor the formation of 

 protofibrils and fibrils of native type and (b) enhancement of end- 

 to-end linkages of type A'-A' and B'-B' under circumstances which 



