100 



R. MARKHAM 



The virus may be crystallized out from aqueous solutions by the addition 

 of various salts, such as magnesium sulfate, sodium thiosulfate and even 

 sodium chloride. It is denatured by heating under a number of conditions 

 [it is extremely labile in phosphate buffer at 50°C. (Matthews, 1957)], and 

 the nucleic acid is liberated. A much better way of liberating the nucleic acid. 



0-9 



0-8- 



0-7- 



0-6 



0-5- 



0-4- 



0-3- 



0-2- 



220 



260 



300 



340 



Fig. 13. Absorption spectrum of turnip yellow mosaic virus plus the accompanying 

 '■top" component, at a concentration of 0.1 mg./ml., recorded on a Gary No. 14 spectro- 

 pl.otometer. Compare the large peak to trough ratio of the spectrum of this small 

 spherical virus with that of the tobacco mosaic virus (Fig. 8). 



however, is by the addition of half a volume of ethanol to the solution. In 

 the presence of salt the protein flocculates and leaves the nucleic acid in 

 solution. The nucleic acid may then be precipitated by the addition of 

 more ethanol, or by acidifying with acetic acid. The ease of separation of the 

 nucleic acid of the type virus is not paralleled in all the strains, probably 

 because the type strain contains relatively little arginine compared with the 

 large amount of nucleic acid present. 



