144 THE PROTEIN SUBSTANCES. 



from ammonia, hydrocyanic acid and glycol aldehyde, and recently in 

 other ways by ERLENMEYER, JR. and STOOP and by LEUCHS and GsiGER. 1 

 FISCHER and JACOBS 2 have prepared Z-serine from cW-serine by the prepara- 

 tion of the alkaloid salt of the p-nitro-benzoyl combination. On reduc- 

 tion serine is transformed into alanine, and on oxidation with nitrous 

 acid it yields glyceric acid. The relation of serine to alanine, lactic 

 acid and glyceric acid is evident from the following formula: 



CH 2 (OH) CH 3 CH 3 CH 2 (OH) 

 CH(NH 2 ) CH(NH 2 ) CH(OH) CH(OH) 

 COOH COOH COOH COOH 



Serine Alanine Lactic acid Glyceric acid 



The /-serine crystallizes in thin leaves or crusts. It is rather readily 

 soluble in water; the d-Z-serine is soluble in 23 parts water at 20 C. 

 The solution of Z-serine has a sweet taste with an insipid after taste. 

 The specific rotation in aqueous solution at 20 C. is (a) D = 6.83 

 and the hydrochloric acid solution at 25 C. is (a) D = + 14.45. The 

 /?-naphthalene-sulpho-serine melts at 220 C. when anhydrous. The 

 Z-serine anhydride, which is identical with that obtained from fibroin, 

 forms thin, colorless needles which melt at 247 with decomposition. 

 Its specific rotation in aqueous solution at 25 C. (<*) D = 67.46. 



Isoserine (/9-amino-a-oxypropionic acid) has been prepared by ELLINGER 

 from diamino-propionic hydrobromide and silver nitrite and by NEUBERG and 

 SILBERMANN from the hydrochloric acid combination of diamino-propionic acid. 

 Other syntheses have been made by NEUBERG and MAYER and by NEUBERG 

 and AscHER. 3 



COOH 



f^TJ /TVTTT \ 



Aspartic acid (aminosuccinic acid), C4H 7 NO 4 = . , has been 



COOH 



obtained on the cleavage of protein substances by proteolytic enzymes as 

 well as by boiling them with dilute mineral acids in quantities given in the 

 tables on pages 106, 107, 114 and 124. This acid also occurs in secre- 

 tions of sea-snails (HENZE 4 ) and is very widely diffused in the vegetable 

 kingdom as the amide ASPARAGINE (aminosuccinic-acid amide), which 

 seems to be of the greatest importance in the development and formation 

 of the proteins in plants. cW-Aspartic acid has been prepared syn 

 thetically from fumaric acid and alcoholic ammonia. 



1 Fischer and Leuchs, Ber. d. d. chem. Gesellsch, 35; Erlenrneyer and Stoop, ibid*, 

 35; Leuchs and Geiger, ibid., 39. 



2 Ber. d. d. chem. Gesellsch., 39. 



3 Ellinger, Ber. d. d. chem. Gesellsch., 37; Neuberg and Silbermann, ibid., 37; 

 Neuberg and Mayer, Biochem., Zeitschr 3; Neuberg and Ascher, ibid., 0. 



4 Ber. d. d. chem. Gesellsch., 34. 



