ERNEST POLLARD 



Irradiation of" these B. subtilis cells, and of lysates of the cells, showed no 

 difference between them and there is, therefore, for these enzymes, no 

 property of ionizing radiation which has been shown to be dependent on the 

 organization within the cell. 



One very interesting application of ionizing radiation is the study of the 

 structm'e of viruses. This has been employed by many workers notably 

 Lea and Salaman, and Bonet-Maury and Latarjet^. The techniques 

 are essentially those which have just been described and have been employed, 

 for example, by Bonet-Maury and Latarjet to deduce a structure for the 

 internal part of vaccinia virus. The type of study which is possible is the 

 following. A well characterized virus usually has between three and six 

 well-known properties. These are, for example, ability to infect the host 

 cell, the ability to attach to the host cell, the ability to interfere with other 

 virus infections, the ability to combine with specific antiserum, the ability 

 to kill the host cell without necessarily multiplying in it, and the ability to 

 agglutinate red cells in the case of a certain large class of animal viruses. 



All of these properties can be subject to examination after irradiation by 

 deuterons, alpha-particles and electrons. The result of doing this shows 

 that the loss of properties is widely difTerent. Thus the loss of ability to 

 combine serologicaly is highly insensitive. If the method of analysis de- 

 scribed above is applied to results on this serological affinity for the case of 

 T-1 bacteriophage, the molecular size deduced' corresponds to a molecule 

 of molecular weight 22,000. If the ability of Newcastle disease virus to 

 agglutinate red blood cells is studied^, the molecular size corresponds to a 

 pair of units of molecular weight 220,000. If the infectivity is studied very 

 much larger sizes are obtained and the manner in which this infectivity 

 cross section varies with the ion density of the bombarding particle indicates 

 that, in general, there must be some kind of internal structure, for most of 

 the viruses that have been studied. This internal structure must be a rela- 

 tively small part of the virus in the case of T-1 bacteriophage and a relatively 

 large part of the virus in the case of southern bean mosaic virus. A detailed 

 study of these properties leads to inferred structures for the inside of viruses 

 which represent one way of describing the probable nature and morph- 

 ology of viruses. It must be stressed that such pictures are a continuing 

 matter, that as more radiation data appears the picture may change, and 

 that in any event the inferred internal structure of viruses must be made to 

 agree with other methods — physical, biochemical, and genetic. Neverthe- 

 less it would appear as though virus structure might well be elucidated, at 

 least in part by this type of radiation study. 



acknowledcjement 



The author wishes to acknowledge the great part played by his associates in the 

 Biophysics Division at Tale University in conducting the researches on which this 

 article is based. 



REFERENCES 



^ Pollard, E. Advanc. biol. med. Phys. 1953, 3 153. 



2 Pollard, E., Guild, W. R., Hutchinson, F. and Setlow, R. B. Prog. Biophys. 

 1955, 5 72. 



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