CONJUGATED PROTEINS 79 



usually considered apart from each other under the headings of 

 their respective prosthetic groups. I am aware of only one in- 

 stance, namely, in a symposium held some time ago (1953) at 

 Rutgers University, in which an attempt was made to consider 

 the conjugated proteins as a family of substances having more in 

 common than the small print that they occupy in the current 

 textbooks of biochemistry. But there can be little doubt that 

 many, if not all, hfe processes take place on what may be con- 

 sidered the surfaces of conjugated proteins. It is, perhaps, not 

 uninstructive very briefly to compare two groups of conjugated 

 proteins on which my laboratory has spent some effort, viz., the 

 nucleoproteins and the lipoproteins. 



As concerns the nucleoproteins, a strict distinction must be 

 made between the complexes containing deoxypentose nucleic 

 acids and those in which a pentose nucleic acid acts as the 

 prosthetic group. When the conjugated proteins associated with 

 the same type of nucleic acid are compared, it will be noticed 

 that their properties are governed by the type of protein they 

 contain rather than by the composition of their nucleic acid 

 moiety. This is undoubtedly due to the ability of proteins to differ 

 much more from each other in their chemical and physical 

 properties than do the nucleic acids. The deoxynucleoproteins 

 are, in many cases, complexes whose protein moiety is repre- 

 sented by a protein of markedly basic properties, such as a 

 histone or a protamine. Although it is inviting to consider such 

 compounds as salts between the cationic protein and the anionic 

 nucleic acid, this would be wrong. It is, for the moment at any 

 rate, much safer to regard the nucleoprotamines and the nucleo- 

 histones as specifically conjoined complexes of a complicated 

 and, thus far, little-understood geometry to which both electro- 

 static and secondary valence bonds contribute. What all these 

 compounds, however, appear to have in common is that they are 

 readily dissociated by high electrolyte concentrations and that 

 under conditions permitting the removal of the protein moiety, 

 by precipitation or denaturation, the nucleic acids are liberated. 



Occasionally deoxynucleoproteins are encountered in micro- 



