CHEMICAL PROPERTIES 



15 



Table 1-2 



Rates of Reaction of Iodoacetate and Iodoacetamide with 

 Various Nitrogenous Substances" 



" Reactions run at pH 

 (1933 b). 



.9 and 30°. The value for glutathione taken from Dickens 



rapid and complete reaction has been reported by Rosner (1940), Anson 

 (1940), and Bacq and Fischer (1946), all using ovalbumin. Various methods 

 for titrating protein SH groups or determining the reaction with iodoacetate 

 have been devised. Mirsky and Anson (1935) proposed an "indirect" meth- 

 od, whereby the protein is incubated with 35 mM iodoacetate at pH 7.3 

 and room temperature for 3 hr. Complete reaction w^ith the SH groups ap- 

 parently occurs since no cysteine could be found in the hydrolyzates of the 

 proteins treated. Rosner (1940) modified this method by not allowing the 

 protein to coagulate during denaturation and observed an initial rapid reac- 

 tion with iodoacetate (10 mM at pH 7.3) lasting 5-10 min and due to reac- 

 tion with SH groups (the nitroprusside reaction was negative after 5 min), 

 followed by a slower reaction perhaps involving the amino groups. Native 



