COMPAEISON OF HALOGENATED ACIDS 283 



mechanism. It may also be noted that chloroacetophenone inhibits E. coli 

 tryptophanase quite readily — 5% inhibition at 0.002 milf, 44% at 0.004 

 mM, and 73% at 0.02 mM — and that glutathione protects (Turner and 

 Happold, 1960). 



It is noteworthy that chloroacetone is more potent than iodoacetate in 

 killing paramecia (Calcutt, 1950), and that chloropicrin is much more 

 potent than iodoacetamide in preventing the contraction of actomyosin 

 fibers induced by ATP (Godeaux, 1944). The extensive studies of A.F.W. 

 Hughes (1950) on the antimitotic effects of chloroacetophenone in chick 

 tissue cultures further indicate the potency of this compound. Very briefly, 

 the following effects were observed: (1) a concentration of 0.33 mM allows 

 the cells to enter prophase, but no spindle is formed and the chromosomes 

 do not aggregate on the metaphase plate, (2) a concentration of 0.013-0.033 

 mM applied to cells in anaphase slows chromosomal movement and causes 

 excessive surface bubbling, but allows fairly normal cleavage, (3) a con- 

 centration of 0.13 mM prevents the formation of the cleavage furrow, and 

 (4) concentrations above 0.065 mM progressively distort cleavage patterns 

 and retard nuclear reconstruction. It is unfortunate that so little is known 

 of the mechanisms by which these halogenated substances act, inasmuch 

 as some of them might be useful detectors of SH groups or other groups 

 on enzymes. It would be valuable to have comparable data on the effects 

 of the nonhalogenated compounds, or derivatives in which the halogen 

 atoms are replaced by other groups, in order to be able to determine the 

 importance of these halogen atoms. 



