174 THE PROTEIN SUBSTANCES. 



In preparing amyloid, extract the finely divided organs with very 

 dilute ammonia. The undissolved amyloid in the residue, if it does not 

 resist pepsin digestion, can be directly extracted by dilute barium hydrate 

 solution and then precipitated from the filtrate by hydrochloric acid. 

 Otherwise the above mentioned residue is digested for several days with 

 pepsin. The digestion residue is dissolved in dilute ammonia, filtered, 

 the amyloid precipitated by dilute hydrochloric acid, the precipitate 

 dissolved in baryta-water, when the nucleins remain behind, the barium 

 filtrate precipitated with hydrochloric acid and purified, if necessary 

 by repeated solution in ammonia and precipitating with hydrochloric 

 acid, washing and treating with alcohol and ether. 



Phosphoglycoproteins. This group includes the phosphorized glycoproteins. 

 They yield no purine bases (nuclein bases) as cleavage products. They are not 

 nucleoproteins and therefore they must not be mistaken for them. On pepsin 

 digestion they may, like certain nucleoalbumins, yield pseudonuclein, but they 

 differ from the nucleoalbumins in that they yield a reducing substance on boil- 

 ing with dilute acid. They differ from the nucleoproteins, which also yield reduc- 

 ing carbohydrates, in, as above stated, not yielding any purine bases. 



Only two phosphorized glycoproteins are known at the present time, namely, 

 ichthulin, occurring in carp eggs and studied by WALTER, 1 and which was con- 

 sidered as a vitellin for a time. Ichthulin has the following composition: C 53.52; 

 H 7.71; N 15.64; S 0.41; P 0.43; Fe 0.10 per cent. In regard to solubilities it 

 is similar to a globulin. WALTER has prepared a reducing substance from the 

 pseudonuclein of ichthulin which gave a highly crystalline compound with 

 phenylhydrazine. 



Another phosphoglycoprotein is helicoproteid, obtained by HAMMARSTEN 2 

 from the glands of the snail Helix pomatia. It has the following composition: 

 C 46.99; H 6.78; N 6.08; S 0.62; P 0.47 per cent. It is converted into a gummy, 

 levorotatory carbohydrate, called animal sinistrin, by the action of alkalies. 

 On boiling with an acid it yields a dextrorotatory reducing substance. 



The compound protein found by SHULTZ and DITTHORN 3 in the spawn of 

 the frog probably belongs to this group, but instead of glucosamine it gives 

 galactosamine on cleavage. 



B. Nucleoproteins. 



By this name we designate those compound proteins which yield 

 protein and nucleic acid on cleavage. The nucleoproteins seem to be 

 widely diffused in the animal body. They occur chiefly in the cell- 

 nuclei, but they also often occur in the protoplasm. They may pass 

 into the animal fluids on the destruction of the cells, hence nucleopro- 

 teins have also been found in blood serum and other fluids. 



The nucleoproteins may be considered as combinations of a pro- 

 tein with a side chain, which KOSSEL calls the prosthetic group. This 

 side chain, which contains the phosphorus, may be split off as nucleic 

 acid on treatment with alkali. The protein may be of different kinds. 



1 Zeitschr. f. physiol. Chem., 15. 



2 Hammarsten, Pfliiger's Arch., 36. 



3 Zeitschr. f. physiol. Chem., 29. 



