ISOLATION AND COMPOSITION OF DEOXYPENTOSE NUCLEIC ACIDS 323 



and, especially, those growing out of the analytical expectations and im- 

 pressive structural regularities to be discussed later in this article. 



The extent to which these several requirements must be fulfilled in a 

 given case will, of course, depend upon the particular purpose. I shall give 

 only two examples. If a specimen of a deoxypentose nucleic acid is to serve 

 for a chemical and analytical study of its composition and of the quantita- 

 tive distribution of its constituents, a thorough dialysis and lyophilization, 

 both at 0°, will facilitate the sampling. Heating at high temperature should 

 be avoided, ^^ except for the determination of moisture. On the other hand, 

 preparations that are to be used for physical and structure studies, and 

 even more those to be tested for biological activity ,^^ should not be subjected 

 to dialysis in the absence of electrolytes or to lyophilization. More drastic 

 conditions, such as heat, acid, alkali, or even the excessive use of high- 

 speed mincers, ^''^ must be shunned. 



2. Preparative Procedures 



The preparative procedures for the isolation of highly polymerized 

 sodium deoxypentose nucleate, of which several representative examples 

 will be given, are based on the nucleohistone studies, discussed in detail 

 in Section II, of Bang," Hammarsten,^"' and Mirsky and Pollister.^^ These 

 methods are, in general, applicable to a wide variety of tissues, though 

 special precautions or modifications may occasionally become necessary. 

 Once the nucleoprotein or a mixture of nucleic acid and protein has been 

 extracted, the removal of protein is carried out by methods described by 

 Hammarsten,^^ Sevag,^^'^* and Pirie.^^-^^ 



a. Extraction with Strong Salt Solution, Deproteinization with Chloroform 



(/) Sodixim Deoxyrihonudeate of Calf Thyrmis.^^ Fresh frozen calf thymus glands 

 (54.5 kg.) were minced and suspended in 0.9% sodium chloride (54 1.) and milled to 

 produce a fine suspension. This suspension was centrifuged (6300 r.p.m.) and the solid 

 material resuspended in 0.9% sodium chloride (45.5 1.) and milled and centrifuged as 

 before. The tissues, which were now free of material containing pentose, were sus- 

 pended in 10% sodium chloride (214 1.) with vigorous mechanical stirring at 0°. At 



^* A. R. Peacocke, Biochim. et Biophys. Acta 14, 157 (1954). 



'^* There exists no really good name for these useful, though sometimes almost too 

 effective, machines ("Waring Blendor," "Turmix," etc.). "Homogenizer" — a 

 horrible lucus a non lucendo — must be avoided; "disintegrator" or "macerator" 

 sound too much like science fiction; "blender" is culinary and not sufficiently 

 descriptive. "High-speed mincer" or "high-speed mixer" is perhaps least objec- 

 tionable. 



" M. G. Sevag, Biochem. Z. 273, 419 (1934). 



" M. G. Sevag, D. B. Lackman, and J. Smolens, /. Biol. Chem. 124, 425 (1938). 



" F. C. Bawden and N. W. Pirie, Biochem. J. 34, 1278 (1940). 



«8 J. M. Gulland, D. O. Jordan, and C. J. Threlfall, J. Chem. Sac. 1947, 1129. 



