288 INTRACELLULAR LUMINESCENCE 



The straightness of the Hne for S° C in the left-hand part of Fig. 13 

 indicates that a single reaction is primarily affected, and the slope 

 of this line indicates that this reaction proceeds with a volume in- 

 crease of activation of 86 cc per mole. 



With the extracted system, it is possible to interpret in further 

 detail the influence of pressure on the reactions involved in lumines- 

 cence. Omitting the complications introduced by pressure-sensitive 

 equilibria between native and thermally denatured forms of essential 

 enzymes, and considering only the effects observed at temperatures 

 below the optimum, the evidence favors the view that the large vol- 

 ume increase of activation is associated with the reduction of FMN 

 by DPNHi;, and it is for this reason that the steady-state level at low 

 temperatures is reduced by pressure. In the absence of added DPNH2, 

 a rapidly decaying luminescence occurs on addition of reduced FMN 

 to a solution of enzyme plus aldehyde. The rapidity of decay makes 

 it difficult to determine clearly whether or not there is any change 

 under pressure corresponding to the change in steady-state levels of 

 the complete system under pressure. The data clearly reveal, how- 

 ever, that sudden increases and sudden decreases in intensity accom- 

 pany the sudden application and release, respectively, of pressure 

 during the rapid decay of luminescence. The magnitude of these 

 sudden increases and decreases corresponds to that of the spikes and 

 dips, and careful analyses of the data failed to reveal evidence of 

 changes which could be interpreted as corresponding to effects of 

 pressure on steady states. Thus, it appears that the spikes and dips 

 are associated with the luminescent oxidation of the flavin component, 

 which appears to proceed with a small volume decrease of activation, 

 of the order of —10 cc per mole. 



Further interpretations require taking into consideration the influ- 

 ence of pressure on the rate of change in lumnescence intensity be- 

 tween two different steady-state levels due to a change in pressure. 

 With the saturated system at temperatures below the normal opti- 

 mum, the rates of change, after application cf pressure, between the 

 spike peaks and the lower steady-state levels, conform to first order 

 kinetics. The same is true for the rates of change, after release of 

 pressure, between the bottoms of the dips and the higher steady-state 

 levels. In Fig. 14 are plotted representative data which show that 



