148 CHEMISTRY OF THE PROTEIDS CHAP. 



In this compound eight molecules of aspartic acid are linked 

 together in such a way that in seven of them one of the carboxyl 

 groups remains free, while the other one is used to establish the link 

 with the next molecule. This octaspartic acid, containing nine 

 carboxyl-groups, is, however, only octovalent. The manner in which 

 its carboxyl-groups differ from one another and their linking together 

 throws also some light on certain phenomena observed in albumins. 

 For Siegfried 1 has shown that the simple peptones, without ex- 

 ception, are strongly acid, and that they all contain glutaminic acid. 

 Amongst the acid radicals of albumins differences also exist, while 

 neutral albumins must either possess an equal number of free basic 

 and free acid complements, the preponderance of one over the other 

 determining whether an albumin is acid or basic in its character, or 

 be in the pseudo-acid-pseudo-basic state. (See Index.) 



Against the theory of a uniform linking together of ammo-acids 

 must also be mentioned the existence of the he mi- and the anti- 

 groups, which differ from one another to a marked extent. 



THE HEMI- AND THE ANTI-GROUPS (BY COHNHEIM) 



Schiitzenberger and Kiihne first pointed out that the albumin- 

 molecule shows different degrees of resistance to the action of acids 

 or ferments. Subsequently it was shown that the portion which is 

 readily dissociated contains tyrosin and tryptophane, while the portion 

 which is not easily acted upon is characterised by the presence of 

 phenylalanin, glycocoll, and pyrrolidin-carboxjdic acid. These differ- 

 ences in the building material determine how firmly the various 

 albuminous radicals are bound together. 



Kiihne 1 found that tryptic digestion rapidly converts a portion of 

 the albumin into crystalline products, amongst which leucin and 

 tyrosin may soon be recognised. The remainder of the albumin which 

 is not acted upon by trypsin still gives the biuret- reaction, i.e. is 

 still a peptone, at a time, when the whole of the tyrosin has been 

 removed from the albumin. 



This remainder, which was not acted upon by trypsin, Kiihne 

 called anti-peptone, and that part of the albumin from which the 

 anti-peptone was derived, the anti-group. The other half he termed 

 the hemi-group, and the peptone to which it gave rise and which could 

 not be isolated, the hemi-peptone. 



1 W. Kiihne, Verhandl. d. ffeiddberger naturhist.-medizin. Vereins, N. F. I. 236 

 (1876) ; Kiihne and R. H. Chittenden, Zeitschr. f. BwL 19. 159 (1883) ; 22. 423 

 (1885) ; see also B. Neumeister, ibid. 23. 381 (1887) ; Lehrbuch d. physiol. u. palhol 

 Ohem., 2. Aufl., Jena, 1897, p. 228. 



