172 THE PROTEIN SUBSTANCES. 



and SCOTT l the nucleoproteins differ from the nucleo-albumins by the 

 fact that with sodium hydroxide in 1-per cent solution the nucleo albumins 

 split off phosphoric acid while the nucleoproteins do not. The nucleo- 

 proteins give the color reactions of the proteins, but those which have 

 been investigated are dextrorotatory and not levorotatory (GAMGEE and 

 JONES 2 ). 



The nucleoproteins are readily modified. The alkali combination 

 soluble in water suffers a decomposition on heating its solution, when 

 as neutral as possible, and coagulated protein separates and a protein 

 rich in phosphorus and poor in protein with strong acid character remains 

 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 nuclein (MIESCHER, HOPPE- 

 SEYLER 3 ) or true nuclein, remains undissolved. As the nuclein is probably 

 nothing but a partly modified nucleoprotein poorer in protein, having a 

 composition varying with the intensity of the cleavage, it seems unnec- 

 essary 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 neucleoproteins that the pseucto- 

 nuclein does to the nucleoalbumins, we will give here 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) 4 . The nucleins 

 are rich in phosphorus, containing in the neighborhood of 5 per cent. 

 According to LiEBERMANN, 5 metaphosphoric acid can be split off from 

 true nucleins (yeast nuclein). The nucleins are decomposed into pro- 

 tein and nucleic acid by caustic alkali, and as different nucleic acids 

 exist, so also there exist different nucleins. As previously stated, pro- 

 teins may be precipitated in acid solutions by nucleic acids, and in this 

 way, as shown by MILROY, combinations of nucleic acid and proteins 

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

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

 The nucleins contain iron to a considerable extent. They act like rather 

 strong acids. 



1 Plimmer and Scott, cited in Biochem. Centralbl., 8, p. 109. 



2 Hofmeister's Beitrage, 4. 



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



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



5 Pfliiger's Arch., 47. 



