208 



STUDIES ON BIOLUMINESCENCE. XH 



acid also plays a part in the formation of luciferin from oxyluciferin. 

 "If one saturates an oxyluciferin solution with CO2 or adds a Kttle 

 dilute acetic acid and allows the solution to stand for 24 hours, a cer- 

 tain amount of reduction will occur" (page 143) . Indeed it is not neces- 

 sary to let the solution stand 24 hours. Luciferin will be formed 

 from an oxyluciferin solution immediately on adding a little acid to 

 it. HCl, HNO3, or H2SO4 may also be used. The action begins 

 when the solution of oxyluciferin, ordinarily slightly alkaline (pH 

 = 9), is made neutral (pH = 7.1), as indicated in Table I. 



TABLE I. 



Effect of Acid on Reduction of Oxyluciferin. 



* Light disappears quickly because of the effect of the acidity on the luciferase. 



The acid must act on the oxyluciferin as no luciferase or other 

 enzymes destroyed on boiling are present. 



The addition of acid, then, to a boiled extract of Cypridina (oxy- 

 luciferin) causes the formation of a substance (luciferin) which 

 will give hght with luciferase. It is possible that the action of bac- 

 teria (which produce CO2), muscle tissue (which contains lactic acid), 

 or Mg plus acid in forming luciferin is not the result of their reducing 

 power but of their acidity. Fortunately we can test this matter by 



