The Scale of Structural Units in Biopoesis 



395 



different monomers arranged for each type of protein or nucleic acid in a 

 characteristic order. The order of amino acids and of nucleotides in related 

 nucleic acids and proteins may be connected (this will certainly be discussed at 

 the Symposium) but here we are concerned with the specific questions of order 



Table 2 

 Stages of aggregation occurring in biological structures 



only in so far as they affect the configuration of the polymer. One aspect of the 

 polymerization process, however, is relevant to this — its termination — which 

 determines the size of the resulting polymer. In the case of polyamino acids we 

 find in nature to-day a whole range of length from oligopeptides, with from 5 to 

 20 units hke gramicidin S (10), oxytocin (9), adrenocorticotropin (50), through 

 the smaller proteins like insulin (60) to ribonuclease (128). Whether the number 

 is ever much larger, except in the fibrous proteins Hke myosin and keratin, is 

 not clear. It seems, however, that the molecules of the larger globular proteins 

 are not constructed of one but several peptide chains. 



With the nucleic acids we know less of the existence of oligomers beyond the 



