Mutagenic Alkylating Agents 

 But on esterification no acid is released : 



301 



>NCH2CH2C1+ = P0-Na 



>NCH2CH2 0P=+NaCl. 



With relatively dilute solutions of DNA a considerable 

 amount of acid is produced during the reaction with the 



100 



80 



^60 



o 



o 40 



o 



20 



'NoOOIN-NaCI ONLY 



\ 



CORRESPONDS TO 



35 70 OF PHOSPHATE 

 GROUPS ESTERIFIED 



SO 100 



150 200 250 

 TIME (mIN) 



300 350 400 



Fig. 2. Rate of acid formation when the phenylalanine nitrogen 

 mustard at a concentration of • 1 % was reacted with different con- 

 centrations of DNA at 37° C (pH maintained at 7 by an automatic 

 titrator), and the effect of heating subsequently for 20 minutes at 90° C. 



mustard. That the liberation of this acid is entirely due to 

 hydrolysis by water and not produced in part by alkylation 

 of amino groups was shown by analysis of the solution after 

 reaction was complete. The amount of mustard which had 

 combined with the DNA was equal to that bound by esteri- 

 fication as calculated from the decrease in the amount of 

 acid released, while the amount of hydrolysed mustard found 



