ISOLATION AND COMPOSITION OF DEOXYPENTOSE NUCLEIC ACIDS 317 



precipitate was in the form of long fibrous strands which could easily be wound around 

 a rod. The fibrous precipitate redissolved in M NaCl. Vigorous stirring shortened the 

 time needed to dissolve the precipitate. Any suspended particles were removed by 

 centrifugation of the viscous solution, and the dissolved material was then reprecipi- 

 tated by pouring the solution into 6 vol. of water. The fibrous material was soluble in 

 M, and insoluble in 0.14 M, NaCl. Dissolved in M NaCl it kept well at 0° without 

 preservative. Dried preparations contained P 5.93%, 6.14%; N 18.1%, 18.4%. 



4. Properties 

 a. Some Chemical and Physical Characteristics 



In the absence of a proper biological test procedure no decision on the 

 native state or the attributes of intactness of a nucleoprotein can be made. 

 It is, perhaps, possible to distinguish less badly degraded nucleoproteins 

 from those suffering from excessive mistreatment; but before a systemati- 

 zation of nucleoproteins has been reached — and we are very far from it — 

 such discussions appear pointless. On the other hand, the failure to isolate 

 a nucleoprotein should not be taken, as is sometimes done,^^ as an indica- 

 tion of its absence. The nucleoproteins of fish sperm and calf thymus remain 

 the only easily accessible deoxynucleoproteins, and most of the work has 

 been done with them. Certain points of difference between nucleoproteins 

 and artificially prepared protein nucleates will be mentioned below (Sec- 

 tion II. 4. c). 



The solubility properties of freshly prepared nucleohistone have been 

 mentioned in Section II.3.a.(l); those of nucleoprotamines seem to be 

 essentially similar.^^ Little is known about salts or complexes of nucleo- 

 proteins with heavy metals. The nucleoprotein of tubercle bacilli is com- 

 pletely precipitated by lanthanum.-^ 



The recognition of contaminating pentose nucleoproteins is usually based 

 on the available color reactions (Chapter 9) or on the differences in hy- 

 drolysis behavior of the respective nucleic acids (Chapters 5 and 16). There 

 exists, unfortunately, no procedure permitting the separation of deoxy- 

 pentose and pentose nucleoproteins, once they have been isolated together, 

 as for instance in some of the older preparations from liver. ^^ It is necessary 

 to undertake the isolation of the deoxypentose nucleoprotein from material 

 that has been freed of pentose nucleoprotein. This can in many, but not 

 all, cases be done by extensive preliminary washing of the cellular material 

 with 0.14 M NaCl or, better, with a mixture of 0.1 M NaCl and 0.05 M 

 sodium citrate. In certain instances a partial centrifugal separation of the 

 extracted nucleoproteins may be feasible. In a number of studies, con- 

 tamination was, at least in part, avoided by employing isolated nuclei as 



6' V. L. Koenig, L. Larkins, and J. D. Perrings, Arch. Biochem. and Biophys. 39, 355 



(1952). 

 «o J. P. Greenstein and W. V. Jenrette, J. Natl. Cancer Inst. 1, 91 (1940). 



