FRANK H. JOHNSON 283 



small concentrations of urethan catalyze the precipitation of tobacco 

 mosaic virus at 68.8° C in a manner that is retarded by pressure 

 (Fraser, Johnson, and Baker, 1949). The same is true of the thermal 

 disinfection of bacteriophage T5 in the presence of urethan (Foster, 

 Johnson, and Miller, 1949). Finally, the accelerated disinfection of 

 B. subtilis spores in the presence of urethan is retarded by pressure 

 (Johnson and ZoBell, 1949b). Although further examples of this sort 

 of phenomenon may be expected it is not to be looked upon as a 

 general rule, inasmuch as eflEects of pressure depend upon the mech- 

 anism of the reaction, and among a variety of drugs as well as of 

 experimental conditions (temperature, pH, dissolved salts, etc.) the 

 mechanisms of denatiuation, even with the same protein, may be 

 expected to differ in detail. 



Multiple Reactions in Narcotic-Catalyzed Protein Denaturation 



Here again, data with respect to intracellular luminescence are 

 not yet available, but it is reasonable to expect certain similarities to 

 the results that have been obtained with other systems in studies 

 stemming from work on bacterial luminescence. A particularly clear 

 example of multiple reactions is afforded by tlie action of urethan in 

 catalyzing the thermal denaturation of tobacco mosaic virus, wherein 

 at least two, and probably three, distinct reactions between urethan 

 and the protein are involved (Fraser, Johnson, and Baker, 1949). 



Now, since many of die interpretations discussed above have been 

 based primarily on kinetic data pertaining to the luminescence of 

 intact, living cells, additional evidence is needed before these inter- 

 pretations can be considered fully convincing. Such need is met in 

 part by finding, and in some instances anticipating, fundamentally 

 similar phenomena in various processes other than luminescence, i.e., 

 denaturation of purified proteins, reactions of purified proteins, activity 

 of purified enzymes, rates of growth and disinfection, and other exam- 

 ples mentioned. Until quite recently, however, it has not been possible 

 to investigate the influence of different factors — temperature, pressure, 

 narcotics, etc. — on bacterial luminescence in cell-free extracts. Streh- 

 ler's success in obtaining luminescent extracts (Strehler, 1953) has 

 provided a long sought means not only of getting more direct evi- 

 dence than is possible with intracellular luminescence but also of 



