FRANK H. JOHNSON 275 



Volume Changes of Activation in Irreversible Protein Denaturation 



At temperatures above the normal optimum, the luminescent sys- 

 tem is destroyed at rates that increase very rapidly with rise in 

 temperature. These rates have the characteristics of a first order reac- 

 tion, and their increase with temperature resembles the thermal de- 

 naturation of proteins. At a given temperature, however, the rate 

 decreases with rise in pressure (Fig. 7) by an amount indicative of a 

 volume increase of activation of about 70 cc per mole. Thus, it ap- 

 pears that pressure not only acts to reverse the equilibrium change 

 from native to denatured states of an essential enzyme, as discussed 

 above, but also pressure retards the rate of thermal destruction. 



When these interpretations, based entirely on kinetic data pertain- 

 ing to intracellular luminescence, were first expressed, they had no 

 parallel in previous experiments with isolated proteins. Subsequently, 

 it has been shown that the thermal denaturation of highly purified 

 human serum globulin is retarded by pressures up to 10,000 psi (John- 

 son and Campbell, 1945; 1946), and likewise, tobacco mosaic virus 

 (Johnson, Baylor, and Fraser, 1948). The inactivation of bacterio- 

 phage T5 at 68° C (Foster, Johnson, and Miller, 1949) and the disin- 

 fection of Bacillus subtilis spores at 92.5° to 93.6° C (Johnson and 

 ZoBell, 1949a) are also retarded by increased pressure. The heat inac- 

 tivation of bacteriophage T7 at 60° C, however, is accelerated under 

 pressure. Moreover, there is essentially no effect of pressure on the 

 salicylate denaturation of methemoglobin (Schlegel and Johnson, 

 1949), so it is not a general rule that pressures up to about 10,000 psi 

 retard protein denaturation at increased temperatures or in the pres- 

 ence of denaturants. 



Promotion of Reversible Protein Denaturation by Narcotics 



The sensitivity of luminescence to narcotics has long been known. 

 In 1672, Robert Boyle reported that the light of "shining flesh" was 

 quickly extinguished by "pouring on it a little pure spirit of wine." 

 Modern studies of the temperature relationships in the inhibition of 

 bacterial luminescence by alcohol, urethan, or other members of the 

 lipid-soluble group of narcotics have provided evidence that the 

 mechanism of their physiological effect involves, in part, promotion 



