74 



MACROMOLECULAR COMPLEXES 



despite the removal of the mineral (and assuming no steric hin- 

 drance) could mean that a stable (covalent or coordinate) bond 

 existed between the e-NH. groups and one or more of the mineral 

 ions. 



On the other hand, group-blocking and -substitution experiments 

 appear to give more conclusive evidence. We are continuing to 

 study the problem by this latter method; after blocking specific 

 amino acids, the abihty of the collagen to mineralize in vitro is ana- 

 lyzed, and the quantity of Ca-salts deposited is measured. It is well 



DECALCI Fl ED CALF BONE 

 37% £"- AMINO GROUPS BLOCKED 

 AVAIL- NH; IT) _ flP (T) _ 



AVAIL. NH, (C) ~^^ AP (C) " ^^ 



^= CONTROL(C) 

 ^=TREATED(T) 



1 h^ 



aODITIONAL 



DECALCIFIED FISH BONE 

 59% 5'-AMIN0 GROUPS BLOCKED 

 AVAIL NH, (T) . ,, flP (T) . ,^ 



AVAIL. NH2 (C) 



m 



Fig. 12. The effect of blocking the e-NH^ groups of bone collagen on 

 remineralization in vitro. Collagen treated with carbobenzoxychloride. (From 

 Glimcher, 1958.) 



known that it is difficult to pinpoint the active groups in biological 

 molecules which are necessary for a physiological function; in order 

 to be meaningful, experiments designed for this purpose must meet 

 a number of general and specific criteria. These have been suffi- 

 ciently and thoroughly discussed in the past in relation to the block- 

 ing of specific groups in proteins in general (Olcott and Fraenkel- 

 Conrat, 1947; Putnam, 1953) and therefore need not be detailed 

 here. 



While it is perfectly clear that our experimental results must 

 therefore be viewed with great caution, they have been encouraging 



