52 CHEMISTRY OF THE PROTEIDS CHAP. 



CH 3 



C . CH(NH 2 ) . COOH 

 H 



Skatol-amino-acetic acid. 



In addition to these substances, Tiedemann and Gmelin, then Kiihne, 1 

 described a peculiar chromogen amongst the tryptic disintegration- 

 products of albumin which, in an acid solution, gives a violet colour 

 with bromine or chlorine water. Stadelmann 2 calls the substance 

 proteinochrome, while Neumeister 3 gave it the name of tryptophane. 

 Winternitz, 4 Nencki, 5 Beitler, 6 and Kurajeff 7 have attempted to 

 isolate it. 



Adamkiewicz 8 described a colour reaction which is obtainable by 

 treating albumins with glacial acetic acid and concentrated sulphuric 

 acid. This reaction Hopkins and Cole 9 showed to be due, not to 

 glacial acetic acid, but to a commonly occurring impurity in this acid, 

 namely, glyoxylic acid (see p. 9). Hopkins and Cole 10 succeeded in 

 isolating, by means of mercuric sulphate dissolved in sulphuric acid, 

 from the mixture of substances set free by tryptic digestion, or 

 by the action of acids, a body which they believed to be skatol-amino- 

 acetic acid ; which was indistinguishable from tryptophane, and which 

 gave with glyoxylic acid and sulphuric acid the reaction of Adam- 

 kiewicz. For this body they retained the name of tryptopbane. 



The tryptophane of Hopkins and Cole is not, however, skatol- 

 amino-acetic acid as these investigators were forced to believe on the 

 prevalent assumption that Salkowski's acid was 'skatol-carboxylic acid.' 

 Gentzen n has shown that skatol administered subcutaneously, or by 

 the mouth, or injected into the large intestine, never leads to the 



I W. Kiihne, Verhandl. d. Heidelberger naturh.-med. Vereins, N.F. I. 236, III. 467 

 (1886). 



a E. Stadelmann, Zeitschr. f. Biol. 26. 491 (1890). 



3 E. Neumeister, ibid. 26. 324 [Anm. p. 329 if.] (1890). 



4 H. Winternitz, Zeitschr. f. physiol. Chem. 16. 460 (1892). 



5 M. Nencki, Ber. d. deutsch. chem. Ges. 28. I. 560 (1895). 



6 C. Beitler, ibid, 31. II. 1604 (1898). 



7 D. Kurajeff, Zeitschr. f. physiol. Chem. 26. 501 (1891). 



8 A. Adamkiewicz, PJlugers Arch. f. d. ges. Physiol. 9. 156 (1874) ; Ber. d. deutsch. 

 chem. Ges. 8. I. 161 (1875). 



9 F. G. Hopkins and S. W. Cole, Proc. Roy. Soc. 68. 21 (1901). 



10 F. G. Hopkins and S. W. Cole, Journ. of Physiol. 27. 418 (1901), 29. 451 

 (1903). 



II P. Gentzen, Uber die Vorstufen des Indols bei der Eiweissfdidnis im Tierkorper, 

 Inaugural Dissertation, Konigsberg, 1904. 



