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C. B. ANFINSEN AND R. R. REDFIELD 



60 60 



time, minutes 



Fig. 5. First order plot of change in viscosity of RNA with time during RNase ac- 

 tion in presence and absence of 8 M urea. RNA (2% in 8 M urea, pH 5.0, 20°C) + 

 RNase (2.6/ml, 8 M urea, pH 5.0): Same without urea. Ao = initial viscosity; Af = 

 final viscosity. 



which the change in the viscosity of yeast ribonucleic acid was measured during 

 ribonuclease action both in the presence and in the absence of urea. Under both 

 conditions, similar first order kinetics appear to be followed. Further evidence 

 was obtained by other approaches to the problem. 



Fig. 6 shows the production of dialyzable nucleotides from ribonucleic acid 

 in the presence and absence of 8 M urea. Production of such fragments is un- 

 impaired. It was found also that the hydrolysis of the synthetic substrate, uri- 

 dine 2'3' diphosphate, could proceed in 8 M urea solutions. 



We must conclude from these enzyme experiments and from the previous 

 studies on the degree of disorientation of ribonuclease in urea, that the catalytic 



