518 KINETICS OF BIOLUMINESCENT REACTION. I 



Material. 



The material used throughout the study has been the Japanese 

 ostracod, Cypridina hilgendorfii Miiller. These animals produce 

 one of the brightest, if not the brightest, animal light reactions, which 

 has yet been described. According to Nichols,^ the maximum 

 brightness of the luminescence in this form is 14.5 to 16 millilamberts, 

 a value higher than that for any fluorescent preparation except 

 some of the uranyl double sulfates. Coblentz has found that a 

 tungsten filament at 2,000°C., that is at about the temperature of 

 ordinary incandescent lamps of the vacuum type, has a brightness 

 of 630,000 millilamberts, Cypridina light, therefore, while well up 

 in the scale of brightness for luminescences, is still comparatively 

 faint. 



The Cypridinae have been placed at my disposal in generous quan- 

 tities by Dr. E. N. Harvey. They have been dried, powdered, and 

 ether extracted, and have furnished a convenient and highly satis- 

 factory material. Aqueous solutions of the enzyme, luciferase, are 

 prepared by extracting Cypridina powder with cold water until the 

 luciferin has been completely oxidized, and light has ceased to appear. 

 I have made it a constant practice to extract 5 gm. of the powder 

 with 50 cc. of distilled water. This does not secure a standardization 

 of enzyme strength, for the enzyme, as well as the luciferin, deteri- 

 orates with time, although not as rapidly as the latter. It does 

 permit of a measure of control of reaction velocities, producing 

 enzyme strengths of the same order of magnitude. Samples thus 

 extracted are filtered, and the filtrate is used within the following 3 

 or 4 days. Since chloroform and other preservatives hasten the 

 deterioration of such extracts, I have usually used freshly prepared 

 luciferase to which no chloroform has been added. 



Luciferin solutions are prepared fresh for each experiment by the 

 extraction of a sample of the dry powder with boiling water. I 

 usually extract about 2 gm. with 40 cc. of water. After the addition 

 of the water, boiling is continued for a few seconds to destroy the 

 enzyme completely; the solution is then rapidly cooled under the 

 tap. The resulting yellowish solution is allowed to stand for about 



3 Nichols, E. L., Science, 1922, Iv, 157. 



