x THE PROTEIDS 447 



Plasminic Acid and Iron 



Here may be mentioned the plasminic acid, which Kossel l and 

 Ascoli 2 prepared from yeast. It contains much more phosphorus 

 than do the nucleic acids. Ascoli found up to 27 per cent of 

 phosphorus, and the substance he analysed was probably a mixture 

 of plasminic acid and of yeast-nucleic acid, so that in pure plasminic 

 acid the phosphorus-content will be even higher. 



Ascoli believes the plasminic acid to be a metaphosphoric acid, or 

 the salt of such an acid with an organic base. Plasminic acid is 

 readily soluble in water and in dilute hydrochloric acid, and, therefore, 

 it is easy to separate it from the unchanged nucleic acid. Plasminic 

 acid precipitates albumins and albumoses, and gives, with silver nitrate, 

 a precipitate which is readily soluble in ammonia and partly soluble 

 in hydrochloric acid ; it is insoluble in acetic acid. Its most im- 

 portant property is that it renders iron 'masked.' If one add to 

 a solution of metaphosphoric acid as much ferric chloride as can be 

 kept in solution by the excess of acid, and if one then add ammonia 

 to neutralisation and precipitate with alcohol and ether, a substance is 

 obtained which gives the following reactions : It is soluble in water, 

 hydrochloric acid, and ammonia ; its iron does not react to small 

 amounts of ammonium sulphide, and not immediately to larger 

 amounts, and it does not give up its iron to hydrochloric-acid-alcohol 

 except under certain conditions. Plasmin behaves exactly as does 

 this metaphosphoric acid : it too contains iron, and also in a non-ionic 

 form, as its presence cannot be demonstrated by either the Prussian 

 blue reaction or by other direct tests. See also p. 450 and the index 

 for other iron-containing compounds. 



Ascoli 3 was unable to show the presence of metaphosphoric acid 

 in yeast-nucleic acids. 



(b) The Nucleo-Proteids 



According to the unanimous statements of Miescher, 4 Kossel, 5 

 and Schmiedeberg, 6 nucleic acid occurs in the spermatozoa of several 



1 A. Kossel, Arch.f. (Ancd. u.} PhysioL 1893, p. 157. 

 - A. Ascoli, Zeitschr. f. physiol. Ghem. 28. 426 (1899). 



3 A. Ascoli, ibid. 31. 156 (1900). 



4 F. Miescher, Verhandl. d. naturforsch. Gesellschaft in Basel VI., Heft I. p. 138 

 (1874). F. Miescher, " Milt of Salmon " in posthumous papers, edited by 0. Schmiede- 

 berg, Schmiedeberg' s Archivfv.r experiment. Path. u. Pharmak. 37. 1 (1896). 



5 A. Kossel, Zeitschr. f. physiol. Ghem. 22. 176 (1896) ; A. Mathews, ibid. 23. 399 

 (1897) ; A. Kossel, ibid. 25. 165 (1898) ; Bull, de la Soc. chim. de Paris, 1903, Juli. 



6 0. Schmiedeberg, Arch.f. experiment. Path. u. Pharm. 43. 57 (1899). 



