182 E. F. Gale 



oxine and heavy metal were present. A similar situation 

 appears to hold in the present instance since oxine is found to 

 have no inhibitory action on glycine incorporation if the 

 reagent solutions are "stripped" of heavy metals by the 

 procedure of Waring and Werkman (1942) prior to test. 

 Metal effects. Glycine incorporation is highly sensitive to 

 inhibition by copper ions and the toxicity of copper is greater 

 in the absence of other metals such as iron or cobalt. In 

 "stripped" incubation mixtures, glycine incorporation is 

 80 per cent inhibited by 10 ~^ m Cu"^^ while the promotion of 

 incorporation by added DNA is abolished by concentrations 

 of 10"'^ to 10"^ M Cu"^"*". Although there is as yet no direct evid- 

 ence for the participation of metals in amino acid incorpora- 

 tion, it may be that copper ions or oxine complexes of heavy 

 metals block sites of reaction between nucleic acids and 

 proteins and so prevent incorporation. 



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