THE PROTEINS 79 



we obtain diamino- and triamino-acids. Thus, ornithine, obtained by 

 splitting up of arginine, one of the commonest disintegration products of 

 protein, is a-^-diamino-valerianic acid. 



CH 2 

 CH 2 

 CH.NH 2 



COOH 



The presence in the ammo-acids of the basic radical NH 2 and of the 

 acid group COOH lends to these bodies a double character. In themselves 

 devoid of strong chemical qualities, possessing neither acid nor alkaline 

 reaction, they are able in the presence of strong acids or bases to act either as 

 base or acid. When in solution by themselves it is possible that there is an 

 actual closing of the ring by a soluble union between the NH 2 group and the 

 COOH group, so that, e.g. the formula of glycine may be : 



CH 2 -NH 3 



CO 



When such a neutral compound is treated with acid this bond is loosed and we 

 have the salt of the amino-acid. Thus, with hydrochloric acid, glycine forms 

 glycine hydrochlorate : 



CH 2 NH 2 HC1 



COOH 



a salt which still possesses an acid group and which is therefore capable of com- 

 bining with ethyl to form the hydrochlorate of the ester of the amino-acid. 

 Thus: 



With bases the amino-acids form salt-like compounds such as potassium 

 amino-acetate : 



COOK 



Amino-acids also combine with one another. This power of combination 

 much increases the difficulty of separating the constituents fror 

 of amino-acids. Amino-acids, which singly are extremely mso 

 readily soluble when in the presence of other ammo-acids. 



On account of the dual nature of the amino-acid molecule, the* 



