310 ERWIN CHARGAFF 



lytes; and a most extensive comparison of the properties of artifacts and 

 of the supposedly genuine nucleoprotein would have to precede a decision. 

 Such comparisons, extremely difficult in the absence of suitable biological 

 tests, have not yet been carried out to any extent, though a beginning has 

 recently been made by Crampton et al}° 



If, as will be discussed later, the deoxypentose nucleic acid fraction of a 

 given nucleus is cofnposed of a large number of differently constituted indi- 

 viduals, a nucleoprotamine or a nucleohistone preparation must be assumed 

 to comprise many different conjugated proteins; a number that will be 

 even greater if not only different nucleic acids, but also different proteins 

 enter into partnership. The reassociation of the various nucleic acid and 

 protein moieties that may take place, if dissociation has occurred in the 

 course of isolation, will introduce additional complications. In this field, 

 simplification may relieve the mind, but will not ease the burden, of the 

 investigator. In any event, an inspection of the literature will lead to the 

 conclusion that very few, if any, entities that can be considered as genuine 

 deoxypentose nucleoproteins have been isolated. As is also true of the cor- 

 responding ribonucleoproteins (see Chapter 11) only those structures that 

 are characterized by a high degree of complexity, bordering on organization, 

 and by specific biological activity, the viruses and phages, can safely be so 

 designated. 



Whether the major part, or all, of the deoxypentose nucleic acids occurs 

 in the cell in the form of nucleoproteins cannot yet be stated. But there is 

 little doubt that when nucleic acids and proteins are isolated together, i.e., 

 in cell extracts, the deoxypentose nucleic acid can be freed of protein only 

 in the presence of a high salt concentration. ^^ Under these conditions a dis- 

 sociation of the conjugated protein may have taken place ;'^ and a nucleo- 

 protein recovered after the exposure of its solution to a high electrolyte con- 

 centration may represent an artifact, a protein nucleate.' A comparison of 

 several properties of nucleohistone preparations isolated in the absence of 

 electrolytes with those of specimens that had been in contact with salt re- 

 vealed a number of differences, but they were of a relatively minor nature.^" 

 The entire field of conjugated proteins suffers from our incomplete knowl- 

 edge of the conditions governing interactions between polyelectrolytes and 

 of the geometry of the resulting products. 



Before discussing, in the following sections, several representative nucleo- 

 proteins, especially those that have served for the isolation of deoxypentose 

 nucleic acids, reference should be made to the reviews on nucleoproteins 

 written by Greenstein* and Markham and Smith. '^ 



'» C. F. Crampton, R. Lipshitz, and E. Chargaff, J. Biol. Chem. 206, 499 (1954). 

 " I. Bang, Beitr. chem. Physiol, u. Path. 4, 331 (1904) ; 5, 317 (1904). 

 '2 R. Markham and J. D.Smith, tn "The Proteins" (H. Neurath and K. Bailey, eds.), 

 Vol. II, p. 1. Academic Press, New York, 1954. 



