PSEUDONUCLEINS. 173 



The nucleins are colorless, amorphous and insoluble or only slightly 

 soluble in water. They are insoluble in alcohol and ether. They are 

 more or less readily dissolved by dilute alkalies. The nucleins give the 

 biuret test and MILLON'S reaction. They show a great affinity for many 

 dyes, especially the basic ones, and take these up with avidity from watery 

 or alcoholic solutions. On burning they yield an acid residue which is 

 very difficult to incinerate and which contains metaphosphoric acid. 

 On fusion with saltpeter and soda the nucleins yield alkali phosphates. 



To prepare nucleins from cells or tissues, first remove the chief mass of 

 proteins by artificial digestion with pepsin-hydrochloric acid, lixiviate 

 the residue with very dilute ammonia, filter, and precipitate with hydro- 

 chloric acid. The precipitate is further digested with gastric juice, 

 washed and purified by alternately dissolving in very faintly alkaline 

 water and reprecipitating with an acid, washing with water, and treating 

 with alcohol-ether. A nuclein may be prepared more simply by the 

 digestion of a nucleoprotein. In the detection of nucleins we make use of 

 the above-described method, testing for phosphorus in the product after 

 fusing with saltpeter and soda. Naturally the phosphates and phos- 

 phatides must first be removed by treatment with acid, alcohol, and ether, 

 respectively. We must specially call attention to the fact, as shown by 

 LiEBERMANN, 1 that it is very difficult to remove lecithin (the phospha- 

 tides) by means of alcohol-ether. No exact methods are known for the 

 quantitative estimation of nucleins in organs or tissues. 



Pseudonucleins or PARANUCLEINS. These bodies are obtained as an 

 insoluble residue on the digestion of certain nucleoalbumins or phospho- 

 glycoproteins with pepsin-hydrochloric acid. Attention is called to the 

 fact that the pseudonuclein may be dissolved by the presence of too much 

 acid or by a too energetic peptic digestion. If the relation between 

 the degree of acidity and the quantity of substance is not properly selected, 

 the formation of pseudonucleins may be entirely overlooked in the diges- 

 tion of certain nucleoalbumins. Pseudonucleins contain phosphorus, 

 which, as shown by LiEBERMANN, 2 is split off as metaphosphoric acid 

 by mineral acids. 



The pseudonucleins are amorphous bodies insoluble in water, alcohol, 

 and ether, but readily soluble in dilute alkalies and barium hydroxide solu- 

 tion. They are readily split by barium hydroxide solution with the split- 

 ting off of phosphoric acid, and according to GIERTZ S they differ in this 

 regard from the true nucleins, which are neither dissolved nor decomposed 

 by baryta. They are not soluble in very dilute acids, and may be pre- 

 cipitated from their solution in dilute alkalies by adding acid. They 

 give the protein reactions very strongly, but do not yield purine bases. 



1 Pfliiger's Arch., 47. 



2 Ber. d. d. chem. Gesellsch., 21, and Centralbl. f. d. med. Wissensch., 1889. 



3 Zeitschr. f. physiol. Chem., 28. 



