ii PRIMARY DISSOCIATION-PRODUCTS 37 



the body. It is related chemically to a whole series of physiologically 



very important substances : l 



CH 2 NH 2 CH NH 2 COOH Diamino-propionic acid 



CH 2 OH CH NH 2 COOH Serin 



CH 2 OH CH OH COOH Glyceric acid 



CH 3 CH-NH 2 COOH Alanin 



CH 3 CH -OH COOH Lactic acid 



CH 2 NH 2 CH SH COOH Stone-cystein 



CH 2 SH CH NH 2 COOH Protein-cystein 



Diamino-propionic acid is of special interest in connection with trypto- 

 phane (see p. 51) and with the formation of carbohydrates out of 

 proteids (see below, under the heading of " Physiological Considera- 

 tions," p. 164). 



The conversion of diamino-propionic acid into iso-serin has been 

 accomplished by Ellinger 2 and by Neuberg and Silbermann. 1 



As Neuberg and Neimann have previously prepared d-glyceric 

 acid by the action of lime on 6?-glycuronic acid, the formulae for 

 ,^-glycuronic acid and df-glyceric acid may resemble one another in 

 their configuration. This conclusion Neuberg and Silbermann thought 

 it best not to draw because of the complexity of the question : 3 



OH H OH OH OH 



CHO C C C C COOH CH 2 OH C COOH 

 H OH H H H 



^-glycuronic acid. d-glyceric acid. 



12. Lysin, C 6 H 14 N 2 2 



H H H H NH 2 ,0 

 NH 2 C C C C C Of 



H H H H H X OH, 



is a-, e-diamino-normal-caproic acid. It was the first base which 

 Drechsel 4 discovered in casein. Later on Siegfried, 5 E. Schulze, 6 

 Kossel, 7 Kutscher, 8 and Abderhalden 9 showed that it is one of the 



1 C. Neuberg and M. Silbermann, Ber. d. deutsch. chem. Ges. 37. 341 (1904). 



2 Alex. Ellinger, ibid. 37. 335 (1904).' 



3 E. Friedmann, Centralbl.f. PhysioL 18. No. 3, p. 67 (1904). 



4 E. Drechsel, Arch. f. (Anat. u.) PhysioL 1891, p. 248. 



5 M. Siegfried, Ber. d. deutsch. chem. Ges. 24. I. 418 (1891). See also Zeitschr. /. 

 physiol. Chem. 43. 363 (1905). 



6 E. Schulze and E. Winterstein, ibid. 28. 459 (1899), 33. 547 (1901). 



7 A. Kossel, ibid. 28. 586 (1899) ; A. Kossel and F. Kutscher, ibid. 31. 165 (1900); 

 D. Lawrow, ibid. 28. 388 (1899) ; E. Hart, ibid. 33. 347 (1901) ; A. Kossel, Ber. d. 

 deutsch. chem. Ges. 34. III. 3214 (1901). 



8 F. Kutscher, Zeitschr. f. physiol. Chem. 25. 195 (1898), 26. 110 (1898) ; Die 

 Endprodukte der Trypsinverdauung, Marburger Habilitationsschrift (1899). 



9 E. Abderhalden, Zeitschr. f. physiol. Chem. 37. 484, 495, 499 (1903). 



