E. NEWTON HARVEY 139 



shall speak of the principal if not the only product formed as oxy- 

 luciferin. Most observers have considered a rather fundamental 

 change to occur when the photogenic substance is oxidized. Thus 

 the crystals of xanthine or some related substance in the reflecting 

 layer of the fire-fly have been regarded as the oxidation products of the 

 luminous material thought to be nucleoprotein. Dubois^ regards 

 luciferin as a protein and states that it forms the same oxidation 

 products as other proteins, amino-acids being mentioned as possible 

 substances formed. It should be pointed out in this connection 

 that the formation of amino-acids from proteins involves no oxidation 

 but an hydrolysis. 



If we assume that the oxidation of luciferin changes the molecule 

 but slightly, we at once think of comparing the change luciferin ^ 

 oxyluciferin with the change reduced hemoglobin tl^ oxyhemoglobin. 

 The condition is, however, not so simple as this, for oxyhemoglobin 

 will again give up its oxygen providing the partial pressure of oxygen 

 is sufficiently low, whereas oxyluciferin will not do this. We cannot 

 reduce oxyluciferin solution by exhausting the oxygen with an air 

 pump. 



There is another oxidation reduction system which can also be 

 easily reversed, but not by merely removing the oxygen — that is the- 

 reduction of a dye such as methylene blue to its leuco base. I be- 

 lieve the change which occurs when luciferin is oxidized is similar 

 to that which occurs when the leuco base of methylene blue or sodium 

 indigosulfonate is oxidized to the blue dye. 



My attempts to reduce the oxidation product of luciferin started 

 from the observation that if one places a clear solution of luciferase 

 in a tall test-tube, although it may give off no Hght at first when 

 shaken, after standing a day or so a very bright Hght would appear 

 on shaking. This was especially true when the luciferase had be- 

 come turbid and ill smelKng from the growth of bacteria. Thinking 

 that the bacteria produced a substance which could be oxidized by 

 the luciferase, I tried growing bacteria and also yeast on appropriate 

 culture media and after some days of growth mixing the culture media 

 containing the products of bacterial or yeast growth with luciferase, 



^Dubois, Ann. Soc. Linn. Lyons, 1914, Ixi, 169. 



