176 THE PEOTEIN SUBSTANCES. 



in solution. By the action of weak acids and by gastric juice a similar 

 cleavage takes place, whereby the protein split off goes into solution 

 while the nucleoprotein rich in phosphorus, so-called nudein (MIESCHER, 

 HOPPE-SEYLER x ) or true nudein, remains undissolved. As the nuclei n 

 is probably nothing but a partly modified nucleoprotein poorer in pro- 

 tein, having a composition varying with the intensity of the cleavage, 

 it seems unnecessary to give the name nuclein thereto. On the other 

 hand, the nucleins have other properties than the nucleoproteins, and 

 as the nucleins bear the same relation to the nucleoproteins that the 

 pseudonuclein does to the nucleoalbumins, we will here give a short 

 description of the nucleins as well as the pseudo- or paranucleins. 



Nucleins or true nucleins are formed, as above stated, from nucleo- 

 proteins in their peptic digestion or by treatment with dilute acids. It 

 must be remarked that the nucleins are not entirely resistant toward 

 gastric juice, and also that at least one nucleoprotein, namely, the one 

 obtained from the pancreas, completely dissolves, leaving no nuclein 

 residue on treatment with gastric juice (UMBER, MiLROY 2 ). The 

 nucleins are rich in phosphorus, containing in the neighborhood of 5 per 

 cent. According to LiEBERMANN, 3 metaphosphoric acid can be split 

 off from true nucleins (yeast nuclein). The nucleins are decomposed 

 into protein and nucleic acid by caustic alkali, and as different nucleic 

 acids exist, so also there exist different nucleins. As previously stated 

 proteins may be precipitated in acid solutions by nucleic acids, and in 

 this way, as shown by MILROY, combinations of nucleic acid and pro- 

 teins may be prepared which behave quite like true nucleins. All nucleins 

 yield purine bases (so-called nuclein bases) on boiling with dilute acids. 

 They act like rather strong acids. 



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, 



1 Hoppe-Seyler, Med. chem. Unters., 452. 



2 Umber, Zeitschr. f. klin. Med., 34; Milroy, Zeitschr. f. physiol. Chem., 22. 



3 Pfliiger's Arch., 47. 



