432 



BACTERIOLOGICAL CHEMISTRY 



of the oarbuxyi groups destroys the activity of tlic anti- 

 body very readily, indicating that the carboxyl group plays 

 an important part in the reaction with the antigen. 

 Substitution in the hydroxyl and amino groups has less 

 effect. 



Table 30 



( After Eagle) 



The antitoxic power of tetanus antitoxin remains 

 intact after the acetylation of 30 to 40 per cent, of the 

 amino groups by ketene, but further acetylation causes 

 a raj)id loss of activity. 



The action of ninhydrin is analogous to that of 

 formaldehyde in that it reacts with the terminal amino 

 groups of lysine residues : — 



CO 



CO.CHO 



C6H,< 



\ 



C(OH), 



alkali 



C^^ 



CgHi 



CO 

 (ninhydrin) 



CO.CHO 

 / 

 / 

 \ 

 \ 

 COOH 



+ NH2CH2R CVH4< 



\ 



COOH 

 CO.CHiN.CHaR 



COOH 



+ H,0 



