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Discussion 



Led by W. D. McElroy 



When I was asked to follow as discussant on this morning's program, I 

 was asked to talk about the biochemical aspects of this phenomenon. Dr. 

 Gerard said we should comment on points which have been presented by the 

 two previous speakers. That makes it a little difficult for me to put into bio- 

 chemical terms, what has already been covered this morning. I think one of 

 the points Dr. Grenell wanted me to talk about, and I will do this in about 

 three or four minutes, is the fact that you have a charged system here which 

 under appropriate stimulation can give a rapid response and return to normal. 

 The question is: Do we have any biochemical information which is analogous 

 to this process? Now, as you know, I am interested in the problem of conversion 

 of chemical energy into light energy and reverse. In working with the firefly, 

 trying to explain the flash of the firefly, you practically get into the same prob- 

 lems which you are talking about this morning. You stimulate a nerve leading 

 to the light organ in the firefly and you get a flash of light and this returns to 

 the normal state in about two seconds. 



Now, the question is, can we isolate and identify all the chemical components 

 of this system and can we duplicate and explain the flash mechanism and its 

 control in an isolated system? We think we can and I will just briefly give you 

 the information we have at the present time, how we maintain the light at a 

 low steady state level in the test tube and with appropriate stimulation get 

 a flash which is super-imposable upon the flash of the firefly from the intact 



organism. 



The light intensity, which is really the rate of the reaction in this case, is 

 proportional to the concentration of a single protein component (luciferase), a 

 substrate molecule which is called luciferin, ATP, magnesium and oxygen. If 

 one puts all of these compounds at saturation with respect to the enzyme, one 

 obtains in less than a second a light which stays at a reasonably steady state 

 level. If one now adds additional protein to the system, and inorganic pyro- 



