BIOCHEMICAL MECHANISM OF CELL DIVISION DISTURBANCE 



231 



0-50 



0-45 

 040 

 0-35 

 0-30 

 0-25 

 0-20 

 0-15 

 0-10 

 0-05 



220 240 



260 280 

 Am/J 



300 



320 



Yi<y. 6. Ultraviolet absorption spectrum of an active fraction isolated from irradiated 



Viciafaba leaves. 



paration of tyrosinase (polyplienoloxidase) extracted from potato 

 tubers. The dark brown solutions containing polymeric melanins and 

 semi-products of the oxidation of tyrosine were filtered through a col- 

 lodion semi-permeable membrane. The melanins that did not penetrate 

 the membrane were further purified by dialysis. All fractions were tested 

 for ability to inhibit mitosis in roots of Viciafaba. The experimental data 

 show that neither tyrosine nor previously dialysed melanins exhibited 

 antimitotic activity while the low molecular weight products of the 

 enzymatic oxidation of tyrosine sharply inhibited the entrance of cells 

 into mitosis. 



This antimitotic action of such low molecular weight products was 

 indirectly demonstrated also by V. Kopilov and Jone-Che in experi- 

 ments with young growing mice. The mice were retarded in growth, 



Table VI. Determination of quinone-like substances in extracts from 

 normal and irradiated (10,000 r) Vicia faba leaves. 



Time aftei' 

 irradiation 



Extracts 

 normal irradiated 



