128 CHEMISTRY OF CYPRIDINA LUCIFERIN 



Whole Cypridinae can be dried, and if the drying process is rapid 

 and the material preserved with a drying agent, the abihty to lumi- 

 nesce brightly on adding water will last indefinitely (at least 32 

 years). This dried material has been the starting point for most of 

 the chemical studies on luciferin and luciferase. The early work of 

 Harvey (1917-19) established that the Cypridina luciferin-lucif erase 

 reaction was comparable to that of the mollusc, PJiolas dactylus, de- 

 scribed by Dubois (1887), and that luciferin could be oxidized by 

 oxidants or would oxidize spontaneously without light emission in 

 absence of luciferase; that it was dialyzable and insoluble in ether 

 and hydrocarbons, but soluble in lower alcohols and some other non- 

 aqueous solvents. It was found that after oxidation, luciferin could be 

 recovered, at least partially, by various procedures which add hydro- 

 gen to a molecule. Consequently the oxidation of luciferin was com- 

 pared to the oxidation of a leuco-dye, such as methylene white to 

 the dye, methylene blue. It was also established (Harvey, 1925-26) 

 that luciferin undergoes photochemical destruction without light emis- 

 sion, an effect subsequently studied in detail by Chase and Giese 

 (1940). 



In the 1920's, additional properties of the Cypridina luminescent 

 reaction were studied by Harvey and by Kanda, but the solutions 

 were impure and nothing would be gained by reviewing the tests 

 applied, or the procedures used in fractionation. One difficulty in test- 

 ing for chemiluminescent substances is the extreme sensitivity of the 

 luminescence test as compared with ordinary chemical reactions for 

 organic substances. Luciferin may give a bright light with luciferase 

 in concentrations where chemical tests are negative. It is possible to 

 see the light from 1 part of dried powdered Cypridinae added to 

 400,000,000 parts of water, whereas a chemical test is considered 

 sensitive if one part in a million can be detected. 



A great advance in Cypridina. luciferin chemistry was made by 

 Anderson (1933), who introduced a quantitative method of measur- 

 ing luciferin by the total light produced under standard conditions, 

 and by the development of a method of purification ( Anderson, 1935 ) , 

 which has been used ever since, and which has been the starting 

 point for the more recent work to be described in this paper. The 

 compHcated procedure, mostly carried out in a hydrogen atmosphere 



