isolation and composition of deoxypentose nucleic acids 311 



2. Classification 



As in the case of the lipoproteins,^ the classification of conjugated pro- 

 teins in general must be based on the nature of both the prosthetic group 

 and the protein. The former division is implicit in the use of the terms 

 deoxypentose and pentose nucleoproteins. Beyond this it is not yet possible 

 to go, since in no instance, not even in that of the viruses, can the presence 

 of a single nucleic acid individual, homogeneous with respect to both struc- 

 ture and function, be affirmed. 



As regards the protein moiety, a crude classification would distinguish 

 three principal groups: (a) The nucleoprotamines, discovered by Mie- 

 scher*'' in ripe sperm nuclei of the salmon and occurring in ripe sperma- 

 tozoa of many fish genera, (b) The nucleohistones, observed by KosseP'' in 

 bird erythrocytes and investigated in greater detail in the form of the pro- 

 totypal thymus nucleohistone by Lilienfeld,'* Huiskamp,^* and Bang,^^ 

 though here again the first observations are due to Miescher.^ The extent 

 of occurrence of nucleohistones in the nuclei of mammalian cells is not yet 

 clearly defined, nor is it possible to draw an entirely satisfactory demarca- 

 tion line between these two types of nucleoprotein. The spermatozoa of sea 

 urchins and mollusks appear to contain basic proteins of a more complicated 

 composition than is usually encountered in the protamines;" rooster sperm 

 seems to contain a protamine.^* ^^ The most comprehensive monograph on 

 the basic proteins still is that of Kossel;^" a shorter modern treatment has 

 been given by Felix ;^^ the amino acid composition has been discussed by 

 Tristram.^^ 



The third, and in some respects perhaps the most interesting, group are 

 (c) the nucleoproteins in the proper sense of this term. In this type of com- 

 pound the deoxypentose nucleic acid is bound, most likely by secondary 

 valence forces, to a protein lacking the basic properties of the protamines 

 and histones. A nucleoprotein of this type has been isolated from avian 

 tubercle bacilli.^^ It is in contrast to the nucleoprotamines and nucleohis- 



" F. Miescher, Hoppe-Seylers Med.-chtm. Untersuchungen 4, 441 (1871). 



1* A. Kossel, Z. physiol. Chem. 8, 511 (1884). 



'5 L. Lilienfeld, Z. physiol. Chem. 18, 473 (1894). 



'« VV. Huiskamp, Z. physiol. Chem. 32, 145 (1901). 



" T. Hultin and R. Heme, Arkiv Kemi, Mineral. Geol. 26A, No. 20 (1948). 



'« M. M. Daly, A. E. Mirsky, and H. Ris, J. Gen. Physiol. 34, 439 (1951). 



'9 H. Fischer and L. Kreuzer, Z. physiol. Chem. 293, 176 (1953). 



^^ A. Kossel, "The Protamines and Histones." Longmans, Green and Co., London 



and New York, 1928. 

 2' K. Feli.x, in "Physiologische Chemie" (B. Flaschentrager and E. Lehnartz, eds.), 



Vol. I, p. 709. Springer, Berlin, Gottingen, Heidelberg, 1951. 

 " G. R. Tristram, in "The Proteins" (H. Neurath and K. Bailey, eds.), Vol. I, p. 



181. Academic Press, New York, 1953. 

 " E. Chargaff and H. F. Saidel, /. Biol. Chem. 177, 417 (1949). 



