408 



BACTERIOLOGICAL CHEMISTRY 



antigen and antiserum were then tested ; typical results 

 are summarised in Table 29. 



It was found that GL antiserum reacted strongly 

 with GL antigen, less strongly with LL antigen and not 

 at all with GG and LG antigen. The reaction between 

 GL antiserum and GL antigen was inhibited by GL and 

 LL as haptens but not by GG or LG haptens. Similar 

 results were also found for the other antisera. It is seen 

 that both the amino -acids in the peptide influence the 

 specificity, but that the terminal amino-acid is the most 

 powerful factor ; when the terminal amino-acid in the 

 test antigen is different from that used in preparing the 

 antiserum no reaction occurs, whilst a different amino-acid 

 in the intermediate position merely weakens the reactions. 



Landsteiner showed that the peptides having molecular 

 Aveights between 600 and 1000, consisting of 8 to 12 

 amino-acid residues, obtained by hydrolysis of silk 

 fibroin, were capable of inhibiting the reaction between 

 silk fibroin and the antibody to it ; the inference is that 

 the determinant groups in silk fibroin are not larger than 

 these peptides. It is probable that the determinant 

 groups of other proteins are of similar dimensions. 



In cases where the determinant group has no very 

 marked polarity the specificity is less sharply defined, and 

 the actual nature of the particular groups involved has little 



