BERNARD L. STREHLER 237 



saturated with respect to FMNHo. At intermediate concentrations of 

 aldehyde, the concentration of FMNH2 drops considerably, but the 

 amount of D which accumulates is relatively small and the slowest 

 step is B to D. When pressure is applied therefore, there is an 

 instantaneous small increase in luminescence which soon decays to 

 its original rate, under which conditions the rate of D to C is again 

 determined by B to D. However, since pressure affects the amount of 

 reaction A to B (/ci) the pool size of B soon drops and the reaction 

 B to D slows as does D to C. This proposed scheme is consistent 

 with the fact that the presence of aldehyde seems to be required for 

 maximal respiration and luminescence at low oxygen tension, which 

 effect can be viewed as a result of Oo binding by the aldehyde. 

 Finally, this scheme furnishes a plausible mechanism for the con- 

 servation of energy in intermediates preparatory to the final light- 

 emitting step. 



One of the weaknesses of the scheme which has been presented 

 revolves about the energetic aspects of the process. Although peroxide 

 dismutation to water and oxygen liberates about 50-55 kcal and the 

 oxidation of reduced flavin by peroxide would presumably yield (37 

 to 40 plus 25) or 62 to 65 kcal, neither of these processes by itself 

 would seem to be exergonic enough to support luminescence of a 

 maximum energy per einstein roughly equivalent to 62 kcal. This 

 cautious view is based on the fact that chemiluminescent reactions in 

 general would be expected to require for their occurrence a consider- 

 able excess of energy over the energy stored temporarily in the 

 excited state, since no energy transfer process is likely to proceed 

 without incidental losses. 



On the other hand, it is possible that the net free energy change 

 in the chemical reaction prerequisite to an excited molecule need not 

 represent the total energy available for the formation of the excited 

 state. Conceivably thermal energy could also contribute substantially 

 to the total energy budget in at least two ways. Since experimentally 

 it is known that the luminescent reaction proceeds with an appreciable 

 activation energy, all or a part of this energy may be available and be 

 added to the energy supplied concurrently by the net energy release 

 during reaction. Thus, if the activation process for oxidation by the 

 luminescent path involves an atomic configuration in which the elec- 



