THE CHEMISTRY OF ALBUMINS 203 



The Constitution of Albumins. The investigation of the 

 properties of the amino acids, the synthetical work of Fischer 

 on the polypeptides, and other researches in similar directions, 

 have led to the conception of the albumin molecule as con- 

 sisting of a complex of amino-acid residues, linked together by 

 the condensation of a-amino groups with carboxyl groups. 

 The following complex will serve to illustrate the theory which 

 has been propounded by Hoffmeister : 



R R' R" R'" 



I ._ , I , , I . , I 



COOHCH NH H OH |COCH NHj H OH JCOCH NH| H OH |COCHNH 2 



On condensation this yields 



R R' R" R"' 



I I I I 



COOH CHNH COCH NHCOCH NHCOCHNH 3 



The groups K, R', R", etc., represent various residues which, 

 on splitting off, give the various characteristic decomposition 

 products of albumin. Thus, the following typical examples 

 will serve for illustration : 



CH(CH 3 ) 2 C^OH COOH CH 2 NH 2 



I I I I 



CH 2 CH 2 CH 2 (CH 2 ) 3 



NH CHCO NH CHCO NH CHCO NH CHCO NH 



1. Leucin 2. Tyrosin 3. Aspartic acid 4. Lysin 



It can easily be seen how by simple hydrolytic changes 

 the various substances leucin, tyrosin, aspartic acid, or 

 lysin can be split off from such a complex. On oxidation 

 with permanganate, these side chains are finally converted 

 into oxalic acid and ammonia. 



In ordinary animal metabolism, hydrolysis and oxidation 

 go on together, with formation of urea as an end product. 

 The constitution of individual albumins is by no means 



