154 THE PROTEIN SUBSTANCES. 



then the mixture boiled for some time, the liquid becomes a beautiful 

 red and then yields a red precipitate. 



DENIGES' Test, modified by C. MORNER, is performed as follows: 

 To a few cubic centimeters of a solution consisting of 1 vol. formaline, 

 45 vols. water, and 55 vols. concentrated sulphuric acid add a little 

 tyrosine in substance or in solution and heat to boiling. A beautiful 

 permanent green coloration is obtained. 



FOLIN and DENIS'S test. The reagent consists of a solution containing 

 10 per cent sodium tungstate, 2 per cent phosphomolybdic acid and 

 10 per cent phosphoric acid. In performing the test mix 1-2 cc. of the 

 reagent with an equal volume of the tyrosine solution and then add 3-10 

 cc. saturated sodium carbonate solution when a beautiful blue color 

 results. Its delicacy is 1:1000000. The reagent can also be used for the 

 colorimetric quantitative estimation of tyrosine in proteins. According 

 to ABDERHALDEN and FUCHS and to ABDERHALDEN 1 the reagent suggested 

 by FOLIN and DENIS for tyrosine also gives a blue coloration with trypto- 

 phane, oxytryptophane and Z-oxyproline and the value of this reagent for 

 quantitative tyrosine determinations requires further testing. 



H 2 C CH 2 

 I I 



Z-Proline (a-pyrolidine carboxylic acid), C 5 H 9 N02 = H 2 C CH.COOH, 



NH 



was first obtained by E. FISCHER and then by FISCHER and collabora- 

 tors from several proteins as a primary cleavage product (ABDER- 

 HALDEN and KAUTZSCH 2 ). The proline here obtained was generally 

 the laevo-rotatory modification. The largest quantity of proline was 

 secured from the vegetable proteins hordein and gliadin, namely, 13.7 

 per cent and 13.2 per cent, and also from gelatin, 7.7 per cent (see table 

 pages 106, 107, 115 and 125). KOSSEL and DAKIN S obtained 11 per cent 

 from salmine. Proline also occurs in scombrine and clupeine, but not in 

 sturine, which, according to KOSSEL, seems to contradict the view as 

 to the common origin of orni thine and proline. 



SoRENSEN, 4 by means of a general method of preparing a-amino- 

 acids synthetically, has prepared a-amino-5-oxy valeric acid from phthali- 

 midemalonic ester and has obtained proline from this by evaporating with 



1 Denigs, Compt. rend., 130; C. Th. Morner, Zeitsohr. f. physiol. Chem., 37; Folin 

 and Denis, Journ. of Biol. Chem., 12; Abderhalden and Fuchs, Zeitschr. f. physiol. 

 <}hem., 83 and Abderhalden, ibid., 85. 



i 2 E. Fischer, Zeitschr. f. physiol. Chem., 33 and 35. See also footnote 2, p. 86, 

 and Abderhalden and Kautzsch, Zeitschr. f. physiol. Chem., 78. 



3 Zeitschr. f. physiol. Chem., 41. 



4 Zeitschr. f. physiol. Chem., 44; with A. C. Anderson, ibid., 56. 



