22 MACROMOLECULAR COMPLEXES 



hv the mutual cooperation of several polar side-chains on c djacent 

 macromolecules. It may reasonably be postulated, therefore, that 

 bands will be observed only when the macromolecules retain their 

 native helical configuration and will not be observed in those regions 

 where the polypeptide chains are uncoiled or otherwise disordered. 



Aggregation States of Tropocollagen 



For reasons that will become clear after consideration of the 

 various types of band pattern encountered, the TC macromolecule 

 may be considered as an 'asymmetric" or "structurally polarized" 

 unit; i.e., the distribution of density along its length is such that 

 one end is alwavs clearly distinguishable from the other. The 

 macromolecule may therefore be represented formally as an arrow, 

 the head and tail being labeled A and B, respectively (e.g., Figs. 

 1-3). This kind of symbolic representation has proved to be useful 

 for indicating the packing of TC in the various ordered aggregation 

 states. 



NATIVE 

 lillllillliiilltiiillllKJIIlll 



Fig. 1. Diagrammatic representation of three probable modes of aggrega- 

 tion of the TC macromolecule which can be formed reversibly from dilute acid 

 solutions of TC under appropriate conditions. See text for description. 



