152 



THE PHYSICS OF VIRUSES 



(1950) at 2,535, 2,585, 2,645, 2,681, 2,755, and 2,831 A] are 

 found. These are presumably due to individual amino acids. 



Wavelength 



Fig. 6.3. Absorption spectrum of the pneumococcus transforming factor, a 

 form of DNA, taken by Fluke. The broad band at 2,600 A is due to the purines 

 and pyrimidines. The origin of the rise at sliort wavelengths is indefinite. 



The Absorption Spectrum of Tobacco Mosaic Virus 



Very careful work on tobacco mosaic virus was carried out by 

 Butenandt, Friedrich-Freksa, Hart wig and Scheibe (1942). 

 The absorption curve found is shown in Fig. 6.5b. It can be 

 seen to have a rather definite structure. In Fig. 6.5a, the separate 

 absorptions of tryptophane, ribonucleic acid, tyrosine, and 

 phenylalanine are given. These can be assembled in the propor- 



