CHAPTER V 



ALBUMOSES AND PEPTONES 



WHATEVER means we adopt for dissociating the naturally-occurring 

 or ' native ' albumins, we always find that, at first, they break up into 

 albumoses and into peptones. These latter are still albumins, using this 

 term in its wide sense, for they possess the same chemical structure and 

 dissociate into the same radicals as do the albumins. For these reasons, 

 too, they give the same chemical reactions, and, amongst the colour 

 tests, particularly the biuret-reaction. They are further precipitated 

 by acids and by bases. Albumoses and their salts are, however, much 

 more soluble than are the albumins, and the further they are removed 

 from the albumins the more difficult does it become to precipitate 

 them and to obtain those reactions which are typical of the albumins. 

 They also differ from albumins in those physical properties which 

 depend on the size of molecules and on the colloidal state. For this 

 reason albumoses and peptones have always been compared to the 

 dextrines and to the di- and mono-saccharids, substances which are 

 derivatives of the colloidal carbohydrates. 



The transition from the ' native ' albumin to the amino-acids is a 

 very gradual one owing to the existence of a large number of inter- 

 mediate substances. As only a few substances out of this large number 

 of bodies have been isolated as distinct chemical individuals, any 

 attempt at classification must as yet be difficult and arbitrary. Long 

 ago all substances derived from albumin were classed together as pep- 

 tones, but Kiihne 1 introduced in 1885 the following nomenclature : 

 Albumoses. These are defined as dissociation-products of albumins, 

 which cannot be coagulated by heat, but which can be salted out by 

 certain salts, as, for example, by ammonium- or zinc-sulphate in acid 

 solutions. 



1 W. Kiibne, Verh. des naturhistor.-medizin. Vereins zu Heidelberg, N.F. III. 28$ 

 (1885) ; Pollitzer, ibid. III. 293 (1885) ; S. Wenz, Zeitschr. f. Biolog. 22. 1 (1886) ; 

 W. Kiihne and R. H. Chittenden, ibid. 20. 11 (1884). 



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