STRUCTURAL BASIS OF RIBONUCLEASE ACTIVITY 143 



Dr. Anfinsen: I think the point that we both missed is that hemoglobin may 

 not need much more than the heme and a few amino acids. It does transport 

 oxygen in urea. 



Chairman Pauling: I might comment here that I do not think that the at- 

 tack of urea or other agents of this sort on hydrogen bonds should be talked 

 about in this "all or none" sense. There are, no doubt, certain hydrogen bonds 

 in a protein molecule that are pretty effectively attacked at a certain concen- 

 tration of urea and others that are not. In hemoglobin the attack is enough to 

 permit molecules to split into two halves, 6 normal urea, but apparently the 

 activity is not great enough to break up these two halves in such a way as to 

 destroy the activity. 



