99 



6.45 x 10 M . This value compares with the value of 

 1.5 x 10 4 (at 27°C) presented by Bressler et al. (1973). 



The HA-Con A conjugate prepared in phosphate buffer exhi- 



4 -1 

 bited a slightly greater association with K = 1.22 x 10 M 



and the conjugate prepared in NaCl had a K slightly larger 



a 



4 -1 

 still (K = 1.89 x 10 M ). Although the reason for the 

 a 



differences in the association constants is not immediately 

 apparent, the values clearly point to the retention of li- 

 gand binding affinity by the HA-Con A conjugates. 



In addition to the determination of binding affinity, 

 the specific interaction of HA-ConA conjugates and saccharide 

 moieties was further examined by the agglutination of red 

 blood cells. Human type A red blood cells were used in a 

 standard hemagglutination assay to determine the minimal 

 concentration of each conjugate that would induce hemagglu- 

 tination. The results are presented in Table 5 along with 

 a summary of the physical parameters previously discussed 

 for HA-Con A conjugates. Native Con A caused agglutination 

 at a minimal concentration of 4.5)jg/ml whereas HA-Con A 

 (PO.) agglutinated at 3.1yg/ml and HA-Con A (NaCl) at 6.2yg/ 

 ml. Both conjugates agglutinated red blood cells as effec- 

 tively as native Con A within the limits of error for 

 serially diluted agglutination assays (±50%). 



