MODES OF LINKAGE BY COVALENT BONDS 81 



OH 



< 

 C 



/ \ 

 HC CH 



II I 



HC CH CH3 



\ / I 



C H2C CH3 



1 \ / 



CH2 CH 



NH, O I O I 



I II I II I 



CHo-CH-C -NH-CH-C-NH-CH 



I " Tyr lieu | 



s c=o 



I Cys I 



S Asp (NH2) NH 



I O O I 



I II II I 



CH2-CH— NH— C— CH— NH— C— CH— CH2— CH2— CONH2 



I 

 C=0 CH2 Glu (NH2) 



I I 



I CONH2 



I 

 H2C-N Pro O Leu O Gly (NH2) 



\ II II 



^ CH— C— NH— CH-C-NH-CHa-CONH2 



/ I 



H2C — C CH2 



Hj I 



CH 



/ \ 



H3C CH3 



Beef oxytocin 



whether they circulate in the animal in the free or in the combined states. 

 Oxytocin and vasopressin are both octapeptides whose structures have been 

 confirmed by synthesis — no mean performance for a molecule of this 

 degree of complexity. This magnificent piece of work was carried out in 

 the laboratories of du Vigneaud in New York, Fromageot in Paris and 

 Tuppy in Vienna. 



