ISOLATION AND COMPOSITION OF DEOXYPENTOSE NUCLEIC ACIDS 331 



methods can be offered though some progress has doubtless been made 

 during the time elapsed between the first and the second of two previous 

 reviews on this subject.'' ''^^ The uncertainties are in part due to the diffi- 

 culty of preparing sufficient starting material and of disintegrating it in a 

 suitable manner; but they are to an even larger extent inherent in our 

 lack of knowledge of microbial nucleoproteins and in the scarcity of informa- 

 tion on the topical separation of the various elements composing the internal 

 structure of the microbial cell. Furthermore, the frequent presence of 

 deoxypentose nucleases of different and largely unknown properties" often 

 renders the preparation of intact specimens very difficult. 



Two examples have been quoted in detail above, namely, the nucleo- 

 protein of avian tubercle bacilli^' (Section II.3.a.(2)) and the deoxyribo- 

 nucleic acid of yeast^^'^'^ (Section III.2.a.(2)). From the former, crude 

 deoxypentose nucleic acid could be prepared by treatment with either 

 saturated NaCl solution or sodium deoxycholate.-^ The further purification 

 is discussed in the next section. 



The first microbial nucleic acids in the course of whose isolation particular 

 attention was paid to purity and intactness were those from pneumococci 

 endowed with transforming activity.'''' •'^^•^^* [Compare Hotchkiss, Chapter 

 27.] They were isolated by extraction of the cells after lysis with sodium 

 deoxycholate in the presence of sodium citrate and purified by deproteiniza- 

 tion with chloroform (see Section 1 1 1. 2. a) and precipitation as the calcium 

 salt.*^* A similar procedure^^^ or treatment with anionic detergent^^ (Section 

 III.2.d) has served for the isolation of transforming nucleic acid specimens 

 from Hemophilus influenzae. While in these instances the disintegration of 

 the cell was achieved by mild lytic procedures, most microorganisms require 

 an efficient grinding for extraction to take place. Comminution with very 

 fine glass powder or in a wet crushing mill for bacteria was employed in 

 the examples quoted before,-^ •■*' and a similar procedure, shaking with glass 

 beads (ballotini), led to the extraction of nucleic acid from Hemophilus 

 periussis}'^^ From Escherichia coli, ground with glass powder, deoxypentose 

 nucleic acid could be extracted with salt solution;'*' for the extraction of 

 Serratia marcescens and other organisms 3.5 M aqueous NaCl was em- 



'^* E. Chargaff, in Symposium sur le m^tabolisme microbien, He Congres Inter- 

 national de Biochimie, Paris 1952, 41. 

 '36 E. Chargaff and S. Zamenhof, J. Arn. Chem. Sac. 69, 975 (1947). 

 '" M. McCarty and O. T. Avery, J. Exptl. Med. 83, 89 (1946). 



138 M. McCarty and O. T. Avery, J. Exptl. Med. 83, 97 (1946). 



139 S. Zamenhof, G. Leidy, H. E. Alexander, P. L. FitzGerald, and E. Chargaff, Arch. 

 Biochem. and Biophys. 40, 50 (1952). 



"0 W. G. Overend, M. Stacey, M. Webb, and J. Ungar, J. Gen. Microbiol. 5, 268 (1951). 

 '*' B. Gandelman, S. Zamenhof, and E. Chargaff, Biochim. et Biophys. Acta 9, 399 

 (1952). 



