E. NEWTON HARVEY 281 



them. Methyl alcohol, ethyl alcohol, propyl alcohol, benzyl alcohol, 

 ethyl acetate, glycerol, and glycol all dissolve a considerable amount of 

 luciferin. Solvents non-miscible with water, such as benzyl alcohol 

 or ethyl acetate, give up their content of luciferin to the water phase 

 and it then luminesces if luciferase is present. In the case of the 

 homologous series of ahphatic alcohols, the higher the alcohol in the 

 series the less luciferin will it dissolve. The same is true for the 

 homologous series of esters. 



Luciferin is fairly stable in methyl alcohol, ethyl alcohol, propyl 

 alcohol, benzyl alcohol, and glycerol if no water is present, but rather 

 quickly disappears in acetone, glycol, and ethyl acetate, presumably 

 because oxidation occurs more rapidly in the latter solvents. In the 

 typical fat solvents as ether, chloroform, benzene, etc., the luciferin 

 is insoluble. Luciferin is also soluble in glacial acetic acid but not in 

 aniline. 



There is nothing in the solubility relations of luciferase to indicate 

 that it is not a protein. On the other hand, the solubiHties of lucif- 

 erin are certainly unusual for a natural protein. The best known 

 class of proteins soluble in alcohol is the protamines of plants, but the 

 protamines are insoluble in water and absolute alcohol. Zein, the 

 protamine of corn, is soluble in 90 per cent ethyl alcohol, methyl and 

 propyl alcohols, glycerol heated to 150°C., and glacial acetic acid.^ 

 Recently Osborne and Wakeman^ have described a protein from 

 milk having solubiHties similar to those of gliadin, the protamine of 

 wheat. Welker^ has described a substance, obtained from Witte's 

 peptone giving the biuret, Millon, and Hopkins-Cole tests, which is 

 soluble in water and absolute alcohol but not in ether, and it is pos- 

 sible that others of the peptones are soluble in absolute alcohol. On 

 the other hand, some proteins in the absence of salts form colloidal 

 solutions in strong alcohol from which they may be precipitated by 

 an appropriate salt.'' As the absolute alcohol extract of CypridincB 

 was made from dry material containing the salts of sea water, some 

 salt was present, but there is always the possibiHty of sol formation, 



« Osborne, T. B., Ergehn. Physiol, 1910, x, 47. 



^Osborne, T. B., and Wakeman, A. J., /. Biol. Chem., 1918, xxxiii, 243. 



« Welker, W. H., Biochem. Bull, 1912-13, ii, 70. 



^ Private communication from T. B. Osborne. 



