318 ERWIN CHARGAFF 



the source material.'^'' •2®"'^°" The separation of the nucleic acids them- 

 selves will be discussed later. 



The nucleic acid content of different nucleoproteins varies, with source 

 and preparation, from about 35 to about 60% of the dry weight. In most 

 nucleohistone preparations it is around 50%. In the nucleoprotamines of 

 trout and of herring Felix et al}^ found a phosphorus-to-arginine ratio of 1. 

 (Compare, also, Vendrely.*^) The protein content of nucleohistone may be 

 determined by a modified biuret reaction.^" 



The absorption spectrum in the ultraviolet of a nucleoprotein is, in 

 general, identical with that of its nucleic acid moiety (maximum around 

 260 m/i).^^'"'^^'^" (Compare Fig. 1.) No depression of the e(P) of the nucleic 

 acid component is noticeable, nor does the extent of extinction change 

 materially under conditions of complete dissociation.^" 



Our information on the physical characteristics of nucleoproteins (com- 

 pare also Chapter 13) is no less meager than that on their chemical proper- 

 ties. Much of what goes under this name in the literature really refers to 

 the nucleic acids themselves. Studies on the sedimentation behavior in the 

 ultracentrifuge of nucleohistone preparations were undertaken by Stern and 

 collaborators,^^ '^^ but have not yet been described in detail. Several other 

 investigations by means of the ultracentrifuge have also been published^^'*^' 

 47,63.64 a^g have numerous studies on electrophoretic^^'^®'^^'^^'*^** and vis- 

 cosity properties.^® ■^^■^^•^^•®*'" Despite several, often very discordant, esti- 

 mates no molecular weight can safely be stated. No more than passing 

 reference can be made here to studies of X-ray diffraction®^ and scattering,®^ 

 of orientation phenomena in nucleoprotein films,^^ of dielectric properties,^" 

 and to observations in the electron microscope^' '^'^ and in polarized light." 



" L. Ahlstrom, H. von Euler, and L. Hahn, Arkiv. Kemi, Mineral. Geol. 22A, No. 13 



(1946). 

 «2 R. Vendrely and C. Vendrely, Nature 172, 30 (1953). 

 «' R. F. Steiner, Trans. Faraday Soc. 48, 1185 (1952). 

 " K. V. Shooter, P. F. Davison, and J. A. V. Butler, Biochim. et Biophys. Acta 13, 



192 (1954). 

 " J. L. Hall, J. Am. Chem. Soc. 63, 794 (1941). 



8« Q. Van Winkle and W. G. France, /. Phys. & Colloid Chem. 62, 207 (1948). 

 «' R. O. Carter and J. L. Hall, /. Am. Chem. Soc. 62, 1194 (1940). 

 68 M. H. F. Wilkins and J. T. Randall, Biochim. et Biophys. Acta 10, 192 (1953). 

 «9 D. P. Riley and U. W. Arndt, Nature 172, 294 (1953). 

 '0 L. G. Allg^n, Acta Physiol. Scand. 22, Suppl. 76 (1950). 

 " H. Fischer, O. Hug, and W. Lippert, Chromosoma 5, 69 (1952). 

 "« W. J. Frajola, M. H. Greider, and J. G. Rabotin, Biochim. et Biophys. Acta 14, 



18 (1954). 

 " J. C. White and P. C. Elmes, Nature 169, 151 (1952). 



