272 



INTRACELLULAR LUMINESCENCE 



ing upon the mechanism of reaction. When volume changes of this 

 magnitude occur, the reaction rate constant is markedly affected by 

 moderately increased hydrostatic pressures of a few hundred atmos- 

 pheres. The steady-state luminescence of P. phosphoreum at a low 

 temperature, where Ki is neghgible, is reversibly reduced by increased 



20 



P. phosphoreum 



atm68 136 204 272 340 408 



2,000 4,000 6,000 2,000 4.000 



Hydrostatic pressure (psi) 

 (A) (B) 



6.000 



Fig. 5. (A) Intensity of Inminescence of P. phosphoreum as a function of pres- 

 sure at different temperatures. The intensity at normal pressure is arbitrarily 

 taken equal to 100 at each temperature in order to show the per cent change 

 in intensity with change in pressure. (B) Influence of increased pressure on 

 the luminescence of three different species of bacteria at 25° C. (From 

 Johnson, Eyring, and Polissar, 1954, courtesy of John Wiley & Sons; data of 

 Brown, Johnson, and Marsland, 1942. ) 



pressure (Fig. 5A). The data indicate that the reactions leading to 

 light emission proceed with a net volume increase of activation 

 amounting to about 50 cc per mole at 0° C. 



There are, as yet, veiy few data pertaining to pressure effects on 

 well-defined, purified enzyme systems, for comparison to the lumines- 

 cence data. Studies with crystallized chymotrypsin and crystallized 



