290 STUDIES ON BIOLUMINESCENCE. IX 



Neutral luciferin is completely adsorbed by bone-black, Fe(0H)3, 

 kaolin, talc, and CaCOs, but not by many organic precipitates as 

 caseinogen, cornstarch, or gelatin threads. There is the difficulty in 

 studying adsorption of luciferin that oxidation may be accelerated by 

 the presence of finely divided material. 



Luciferin can also be removed practically completely from solution 

 by gum mastic according to the method of Michaelis and Rona^^ for 

 removing proteins from blood serum. 



CONCLUSIONS. 



There seems to be very little doubt but that luciferase is a protein 

 or so closely associated with proteins that their removal destroys its 

 characteristic properties. The particular group of proteins to which 

 it belongs may be arrived at by a process of exclusion, and only the 

 group of albumins has properties which agree completely with those 

 of luciferase. 



Dubois believes Pholas luciferase to be an oxidizing enzyme similar 

 to the oxydones of Battelli and Stern^^ because it is readily destroyed 

 by fat solvents such as chloroform, strong alcohol, etc. He has de- 

 tected iron in a luciferase solution which has dialyzed against run- 

 ning water for a long time, and believes it to be made up of protein 

 in combination with iron and to act as an "oxyzymase ferrique."^ 

 Cypridina luciferase, on the other hand, is not readily destroyed by 

 fat solvents. Toluene and chloroform are good preservatives, and I 

 often make use of them for this purpose, keeping the luciferase solu- 

 tions for many months. Professor A. H. Phillips of Princeton Uni- 

 versity has very kindly analyzed some whole dried CypridincE for me 

 and finds iron, copper, and manganese but no zinc or vanadium to be 

 present. Whether these metals are connected with the action of 

 Cypridina luciferase is uncertain, but it is significant that all three 

 of the metals thought to be concerned in organic oxidations are 

 present. 



Although a large amount of luciferin mixed with a small amount of 



^^ Michaelis, L., and Rona, P., Biochem. Z., 1907, ii, 219; Rona and Michaelis, 

 ibid., 1907, iii, 109; Michaelis and Rona, ibid., 1907, iv, 11. 

 12 Battelli, F., and Stern, L., Biochem. Z., 1914, Ixvii, 443. 



