94 Papers from the Department of Marine Biology. 
luciferase does not redissolve readily in water, but gives a bright light 
on mixing with luciferin, so that the adsorbed luciferase must again 
go into solution. 
Starch paste (with the grains well broken up by 15 minutes in the 
autoclave at 117° C.) containing luciferase is completely coagulated 
by half-saturation with (NH,).SO,, but the starch carries down very 
little of the luciferase, although a small amount is adsorbed. Very 
little of the starch again goes into solution in cold water. Corn-starch 
grains suspended in water also adsorb very little luciferase as compared 
with inorganic precipitates of various kinds. 
Luciferin is only slightly adsorbed by starch coagulated with an 
equal volume of (NH,4)2SO,, and by ovomucin precipitated by satura- 
tion with NaCl or half-saturation with (NH,4).SO., but a considerable 
amount is taken up by Na caseinogenate precipitated with an equal 
volume of (NH,).SO, and 1 per cent gelatin precipitated with an 
equal volume of (NH,).SO,. The light is especially bright about the 
particles of gelatin containing adsorbed luciferin when luciferase is 
added. 
Since the amount of adsorption depends not only on the adsorbent 
but upon its surface area, it is impossible to judge of the relative 
amounts of luciferin and luciferase adsorbed by different proteins or 
carbohydrates in the above rough experiments. However, care was 
taken to see that in all experiments the protein precipitated was present 
in far greater proportion than the protein associated with the photo- 
genic substances in crude luciferase or crude luciferin solutions—. e., 
the conditions for adsorption were purposely selected to favor adsorp- 
tion. The results indicate that adsorption does oecur. It is, however, 
not complete even under these favorable conditions, so that we must 
conclude that the results obtained by salting out crude luciferin and 
luciferase solutions give us a fairly accurate clue as to the properties of 
these substances were they alone in pure solution. Where we find 
luciferase completely precipitated from crude solution, as by saturation 
with (NH,4)25O4, we may be sure that the luciferase is actually pre- 
cipitated and is not merely completely carried down as an adsorption 
complex. But where we find only partial precipitation, as by satu- 
ration with MgSO,, it is difficult to say how much precipitation would 
occur were other proteins absent, although we can be sure that the 
precipitation would not be complete. 
Although we ordinarily think of the proteins as the substances, par 
excellence, capable of being salted out of solution, the property is char- 
acteristic of many emulsion colloids, notably soaps, polysaccharides, 
and phospholipins. However, neither luciferase nor luciferin are soaps, 
because they are not precipitated by CaCl, nor phospholipins or galac- 
tolipins, because both are insoluble in ether and benzene, hot or cold. 
It is possible that they are of polysaccharide nature, as starch and 
