DINITROPHENYLATION OF RIBONUCLEASE A 



53 



clear that the inactive protein contains a single residue of e-dinitrophenyl- 

 lysine. The ultra-violet absorption spectrum of the inactive derivative was 

 typical of the spectrum to be expected of an e-dinitrophenylamino deriva- 

 tive of ribonuclease. The analysis in Table II permitted the evaluation of a 

 molar extinction coefficient at the 365 m/^ maximum of 1-51 x iC*, a 

 value in the range usually observed [14] for the extinction coefficient of 

 amino-substituted dinitrophenyl derivatives of amino acids. 



Degradation of inactive mono-e-dinitrophenylribonuclease A 



The kinetic analysis in Fig. 2, the analytical values of Table II, and 

 the chromatographic results described in the previous section, strongly 



TABLE II 

 Anhno Acid Composition of Ribonuclease A (Acetate) and of Inactive 



DiNITROPHENYLATED RiBONUCLEASE A 



For procedure of analysis, see Table I. The results are expressed in terms of 

 molar ratios of the constituent amino acids. 



* Incompletely liberated after hydrolysis for 22 hours, 

 t Molar extinction coefficient at 365 m/n = 1-51 x 10*. 



implied that a single inactive protein was responsible for the peak at 350 

 effluent ml. in Fig. 3. In order to shed further light on this question some 

 120 mg. of the inactive dinitrophenylated protein were prepared by 



