33. 



Th D nitrog?n atoms v.'ill appear in tv/o rovs 

 on opposit3 si^.3s of th3 ppiral , and the co^npl 3X 

 tid3 chain? r3pr3S3ntod by th s R's in th ? previous 

 equations, as well as th 3 carbonyl gr-oups, wil] 

 1 i.k 'Wis 3 arrang3 th3Tnselv3S along other diaTri3tri- 

 cally opposite lines. Chsrr.ic^J. union will probably 

 tak3 place b3tw3en th 3 succes?iv3 nitrogen atoviis 

 by virtue of th3ir fourth and fifth valenci3S, 

 and p3rhn.ps also betv^een th 3 successive carbonyl 

 groups in the manner sho^.vn. The nitrog3n atoms at 

 th 3 3nds of the spiral will probably units with 

 th 3 ions of inorganic salts, th 3 pr3Senc3 of which 

 is n3C3ssary for th3 nourishmsnt of all living 

 organisms. It will b? found upon actually con- 

 structing this spiral of atomic models that thECs 

 is •■^mpl ? room for th3 complex sid3 chains R if the 

 fourth valency of th 3 alpha carbon atom is occupi3d 

 by hydrog3n, but that th 3 pr3sence of rnoT 2 complex 

 groups in this position would make the spira] 



structur3 impossible. We find, hov;e-B3r, that the 

 decom.position products of proteins always have a 

 hydrogen atom in this position. 



It will be observed that the polyp 3ptide 

 spiral in the accompanying diagram has an 3xposed 

 amino group at one end, and an exposed carbonyl 

 group at the other end. Th eor 3ticall y it appears 

 that additional amino acid radicals could be add 3d 

 to eithsr end of th 3 spiral, although there may 

 be some at pr3sent unknown reason why growth can 

 take place at on 2 end only. A spiral with an 

 expos ?d amino group at th j free end may be d3sig- 

 nated as positiv3 { + ), and on3 with an 3xposed 

 carbonyl group at the fr3G end as negative (-). 

 A distinction should also b j made betw3en right- 

 hand 3d (r) and left-handed (l) spirals. 



