36 CHEMISTRY OF THE PROTEIDS CHAP. 



strated in zein 12 per cent. Glutaminic acid and leucin are thus the 

 most abundant mono-amino acids. As to the occurrence of glutamins 

 in plants, see p. 105. According to E. Fischer, 1 the naturally occur- 

 ring acid is d-glutaminic acid. In hydrochloric acid solutions 



a D = +30-45. 



Glutaminic acid does not taste sweet but stale, and only slightly acid. 

 A minute description of glutaminic acid, its salts and crystals, is given 

 by Habermann. 2 



9. Amino-hydroxy-succinic Acid, C 4 H 7 N0 5 

 O OHNH 



R0 / H H -OH. 



It was isolated by Skraup 3 as one of the products of casein-hydrolysis 

 resulting from the action of hydrochloric acid. 



It has been synthetised by Neuberg and Silbermann. 4 



10. Amino-hydroxy-suberic Acid, C 8 H 15 N0 5 

 (X OH H H H H NH 2 ,0 



;__C CC 

 HO' H H H H H H OH. 



It is a derivative of octandoic acid COOH[CH 2 ] 6 COOH, which is 

 called suberic acid in England and Korksaure by the Germans. The 

 amino-oxy-suberic acid was discovered by Wohlgemuth on hydro- 

 lysing liver-proteid. 5 



Diamino-acetic Acid, C 2 H 6 N 2 2 



NH 2 ,0 

 NH 2 C Cf 



H X OH, 



according to Willstatter 6 and Sorensen, 7 is not a normal dissociation- 

 product. 



11. Diamino-propionic Acid, C 3 H 8 N0 2 

 H NH 2 ,0 



NH 2 -C C Cf 



H H X OH, 



is, according to Paul Mayer, 8 the simplest diamino-acid occurring in 



1 E. Fischer, Ber. d. deutsch. chem. Ges. 32. II. 2451 (1899). 



2 J. Habermann, Liebig's Ann. 179. 248 (1875). 



3 Zd. H. Skraup, Sitzb. Akad. d. Wiss. Wien, 113. IL b p. 263 (1904). 



4 C. Neuberg and M. Silbermann, Zeitschr.f. physiol. Chem. 44. 147 (1905). 



5 J. Wohlgemuth, Ber. d. deutsch. chem. Ges. 37- 4362 (1904). 



6 K. Willstatter, ibid. 35. II. 1378 (1902). 



7 S. P. L. Sorensen, G. r. des travaux du Laboratoire de Carlsberg, 6. 1 (1903). 



8 Paul Mayer, Zeitschr. f. physiol. Chem. 42. 59 (1904). 





