THE SYNTHESIS OF THE PROTEINS 5 



/ NH . \ / NH , \ 



H\CO C.CH 2 .CO' 4 OH H\CO-C.CH 2 .CO/ 8 OH 



Tetraspartide Octaspartide 



The octaspartic acid was an octobasic acid, its ninth carboxyl group 

 being neutralised by the adjacent NH 2 group. 



The researches of Schutzenberger between 1875 an< ^ 1880 upon the 

 products of hydrolysis of proteins by the action of baryta water under 

 pressure, led the French chemists to the belief that the proteins were 

 composed of amino acids and urea or oxamide. In 1882 therefore 

 Grimaux heated Schaal's aspartic acid anhydride with urea for two 

 hours at 125-130 C. A thick mass almost entirely soluble in water 

 resulted ; its solution was gelatinous and difficult to filter, and it 

 possessed the properties of colloidal substances, behaving very like 

 albumin. This polyaspartic ureide gave the biuret reaction, and was 

 converted by baryta into carbonic acid, ammonia and aspartic acid; it 

 had the formula C 34 H 40 N 10 O 25 , and consisted of eight molecules of 

 aspartic acid and two molecules of urea. Schiff gave it the formula 



COOH 



In 1888 Schutzenberger, who regarded proteins to be composed of 

 (i) urea and oxamide; (2) leucines, or amino acids of the formula 

 C n H 2n + 1 NO 2 , where n = 6, 5,4, 3, 2; (3) leuceines, or amino acids 

 of the formula C n H 2I1 _ jNO^ where n = 4, 5, 6, and that there was 

 one molecule of leucine to one molecule of leuceine, prepared the leu- 

 ceines by the action of ethylene dibromide upon the zinc salts of the 

 lower leucines, such as glycine and alanine, according to the equations 



C 2 H B N0 2 + C 2 H 4 Br 2 = 2 HBr + C 4 H 7 NO 2 

 C 3 H 7 NO 2 + C 2 H 4 Br 2 = 2HBr + C 5 H 9 NO 2 



and in 1891 heated a mixture of leucine and leuceine with 10 per cent, 

 urea, carefully dried at 1 10, with phosphoric anhydride. He obtained 

 a mass soluble in water, which was precipitated by several volumes of 

 alcohol ; it gave the biuret reaction and other protein reactions, and 

 Schutzenberger regarded it as a "pseudo-peptone synthetique ". 



