466 E. A. EVANS, JR. 



core or spike j^rotniding from the proximal portion of the tail, especially 

 when the latter is contracted, while a number of particles would seem by 

 their appearance and size to be free cores. The cores are not attacked by 

 DNAase (Williams and Fraser, 1956), suggesting that they are protein in 

 nature. Estimates of size indicate a particle weight in the neighbourhood of 

 4,500,000 (Kozloff e^ al., 1957). It is possible that the core is identical with the 

 nonsedimentable protein fomid by Hershey (1955) in T2 shockates. This non- 

 sedimentable protein appears to be an authentic component of the phage 

 particle, although it does not possess the antigenic properties of the whole 

 phage particle and is not adsorbed to the host bacterial cell. 



IV. Nucleic Acid Components of Coliphage 



A variety of techniques exists for the isolation of the DNA of the bacterial 

 viruses. In the procedures of Mayers and Spizizen (1954), the phage concen- 

 trate is dissolved at room temperature in a 1 % solution of commercial 

 sodium lauryl sulfate (Duponol C) at pH 7. An equal volume of saturated 

 sodium acetate is then added, and the solution held at 60°C. for fifteen 

 miimtes and then cooled to 5°C. After centrifuging, the supernatant is 

 poured into 2.8 volumes of alcohol acidified with HCl. The nucleic acid pre- 

 cipitates out as a stringy mass which can be transferred to a Buchner funnel 

 by a glass hook, washed with absolute alcohol and ether, and dried at room 

 temperature. 



In another procedure (Wyatt and Cohen, 1953) the viral particle is dis- 

 rupted by urea (3.6 gm. per 10 ml. of virus suspension) and deproteinized in 

 1 M sodium chloride solution by chloroform-octanol (8 to 1). After centri- 

 fuging off the protein, the nucleic acid can be precipitated by 4 volumes of 

 cold ethanol, washed in 80, 90 %, and absolute ethanol and ether, and dried 

 in vacuo. 



The procedure of Hershey et al. (1953) involves treating the phage suspen- 

 sion directly with 1/10 volume of 3 M tricliloroacetic acid (TCA) after the 

 addition of 2 ml. of 1 % serimi albumin to improve the packing quality of 

 the precipitate. The precipitate is centrifuged off, dissolved in 0. 1 iV NaOH, 

 and reprecipitated by TCA. The acid-insoluble precipitate is warmed for 

 15-18 hours at 37°C. in N NaOH and precipitated in the cold with HCl and 

 TCA. Tliis precipitate is extracted with cold 0.3 M TCA, and then with 0.3 M 

 TCA at 90°C. The extract is heated at 100°C. to decompose most of the TCA, 

 and evaporated to dryness by further heating in a current of air, followed 

 by storage in a vacuum desiccator. 



In the recent report of Jesaites (1957) the viral structure was disrupted by 

 repeated freezing and thawmg of an aqueous suspension. After addition of 

 sufficient sodium cliloride to give a concentration of 1 M, the suspension is 



