THE PROTEINS 25 



tation without, however, yielding any very far-reaching 

 conclusions. It remained for Emil Fischer and his 

 associates in 1901 to conceive of a combination which 

 undoubtedly will ultimately lead to a clear under- 

 standing of the structure of the protein molecule. 

 These combinations of amino acids were termed 

 polypeptides. Just as we have mono-, di-, or tri- 

 saccharictes^so there may be di-, tri-, etc.,-peptides. 

 According to Fischer's method the amino acids are 

 linked together by dehydration of their hydroxyl and 

 amino groups, the carboxyl group of each acid being 

 condensed with the amino group of its neighbor in the 

 molecule, thus 



NHH 



I 



R. CH.CO 

 NH 



OH 

 H 



:.COOH 



By continued union of amino acids infinite possi- 

 bilities of complexes are presented. Actually com- 

 pounds containing as many as eighteen amino acids 

 have been synthesized by Fischer and some of the 

 products obtained have shown properties similar to 

 those of the native protein. 



After demonstration of the possibility of forming 

 protein-like compounds by synthesis Fischer next 

 attempted to determine whether similar simple com- 

 plexes could be derived from proteins by suitable treat- 



