306 P. Alexander, S. F. Cousens and K. A. Stagey 



60 80 



TIME (mIN.) 



67% 



MUSTARD USED 

 UP IN 

 ESTERIFICATION 



100 120 



Fig. 4. Reaction of three different concentrations of phenyl- 

 alanine mustard with a 10% suspension of herring sperm 

 heads. The percentage of esterification was computed from 

 the amount of acid liberated. 



30 60 



TIME (MIN.) 



no spermheads 

 0.67o spermheads. 



3% spermheads. 



120 



Fig. 5. Reaction of herring sperm heads with chlorambucil, the 

 negatively charged mustard which does not react with DNA. 

 The decrease in the amount of acid produced in the presence of 

 the sperm heads shows that extensive esterification of the nucleo- 

 protein occurs. 



