H PRIMARY DISSOCIATION-PRODUCTS 31 



acid. It has been examined more carefully by Sclmlze and Winter- 

 stein. 1 It is soluble in 1 1 parts of water, forms a readily soluble 

 copper salt, which, according to E. Fischer, 2 has a great tendency to 

 crystallise out with the leucin copper salt. It is dextro-rotatory. 1 



<X D = +27-9. 



As guanidin-aniino-valerianic acid, or arginin, is a constant dissocia- 

 tion-product of all albumins (see below), one might believe that amino- 

 valerianic acid is obtained by the disintegration of arginin. This, how- 

 ever, is impossible as it is derived from an iso-valerianic acid, while 

 arginin possesses a straight carbon chain. The amounts of arginin which 

 can be obtained under varying conditions from the same albumin also 

 correspond so closely, that we have to exclude the occasional further 

 disintegration of arginin into amino-valerianic acid. 3 The reason that 

 this acid was not discovered sooner and more frequently, E. Fischer 2 

 attributes to the great difficulties connected with its isolation. Schulze 

 and Winterstein 1 recommend for its preparation germinating plants 

 of Lupinus luteus and Lupinus albus two to three weeks old, as they 

 contain relatively small amounts of leucin. A S-amino-valerianic 

 ' acid, which H. Salkowski 4 found once during putrefaction of gelatine, 

 is a secondary dissociation-product, and must not be confounded with 

 the a-acid under consideration. 



4 (a). Leucin, C 6 H 13 N0 2 , is not amino - normal - caproic acid, 

 CH 3 . (CH 2 ) 3 CH(NH 2 ) . COOH^ but isobutyl-a-amino-acetic acid 



H 3 C X H II NH, .0 



)C C C C{ 

 H 8 Cr H H X OH. 



As already mentioned, it is, along with glycocoll, the oldest and, 

 along with tyrosin, the best known of all the dissociation-products 

 of albumins. With the exception of the protamins, it has been found 

 up till now in every one of the albumins whenever it was looked for. 

 But whether this great distribution is characteristic of leucin is some- 

 what doubtful, especially if we consider that up to the time of 

 Drechsel, Kossel, and E. Fischer, the only readily demonstrable 

 dissociation - products were leucin, tyrosin, and perhaps glutaminic 

 and aspartic acids. We know already that the hexone-bases have 

 a wider distribution than has leucin, and Fischer has found in every 



k 1 E. Schulze and E. Winterstein, Zeitschr.f. physiol. Chem. 35. 299 (1902). 

 ** E. Fischer, ibid. 33. 151 (1901). 

 3 A. Kossel and F. Kutscher, ibid. 31. 165 (1900). 

 4 H. Salkowski, Ber. d. deutsch. chem. Ges. 16. I. 1191 and 16. II. 1802 (1883), 

 31. II. 776 (1898). 



