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Is Photogenin Used up in Light-Production with

photophelein, light, cypridina, cc and concentration

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IS PHOTOGENIN USED UP IN LIGHT-PRODUCTION WITH PHOTOPHELEIN? The exceedingly small concentration of light substances which give visible light suggests that one or both are of enzyme nature, as Dubois supposes. There are two ways of testing this question. One is to determine whether a small concentration of photogenin can use up a large concentration of photophelein, providing a sufficiently long time is allowed. We can not use this method, because photophelein decom poses spontaneously.

Another way is to determine if a small amount of photogenin can decompose successively added amounts of photophelein without itself undergoing diminution. This method is not unequivocal, since many true enzymes are paralyzed or destroyed by the decomposition prod ucts of the reaction which they accelerate.

It was found that if we add to 1 c.c. of a weak (1 Cypridina to 50 c.c.) solution of photogenin, successive 1 c.c. additions of a concentrated (1 Cypridina to 2 c.c.) solution of photophelein as soon as the light from the preceding addition has disappeared, after four 1 c.c. additions no more light will appear. The photogenin is therefore used up and can not oxidize additional photophelein, although there is plenty of photo phelein present, as may be shown by adding fresh photogenin, when a good light appears. With each successive addition of concentrated photophelein, the light, which at first is very bright and lasts about an hour, becomes less brilliant and lasts a shorter time. This is not due to mere dilution of the dilute photogenin, as we can dilute the dilute photogenin to the same volume with water and then upon the addition of photophelein a good light results. We can conclude only that, although photogenin can use up a large amount of photophelein, it is itself changed in some way in the reaction and disappears. We can not say how much photophelein will combine with a definite quantity of photogenin, because we do not know the absolute amount of these substances in a single Cypridina. In the above experiment we added a concentration of photophelein from one Cypridina 100 times (i. e.,

four additions each 25 times more concentrated) that of the photogenin from one Cypridina.

Although the evidence goes to show that the photogenin is used up, it is not nearly so rapidly used up as is the oxidase of potato in the production of light from pyrogallol (see p. 231). We must remember also that certain enzymes, as zymase (thermolabile and non-dialyzable), are only active in presence of a coenzyme which is not destroyed by heat and is easily dialyzable. In fact, the photogenin-photophelein system resembles to a very remarkable degree the zymase-cozymase system. There is the same quantitative relation between zymase and cozymase as between photogenin and photophelein. If zymase is present in excess, the coenzyme is all used up; if cozymase is in excess then the zymase is used up (17). Nevertheless, however much photo genin resembles cozymase, I have for the present deemed it best to avoid the termination ate. In absence of more definite knowledge we may provisionally regard photogenin as a substance auto-oxidizable only in presence of photophelein.

If we try the reverse experiment, that of adding 1 c.c. of concen trated (1 Cypridina to 2 c.c.) photogenin to 1 c.c. of dilute (1 Cypridina to 50 c.c.) photophelein, a bright light appears lasting 10 to 15 seconds and no more light upon adding additional concentrated photogenin. As might be expected, the small amount of photophelein is very rapidly used up by the large amount of photogenin.

The quantitative relations between concentration of photophelein and photogenin, duration of light, and brightness of light will be con sidered in a subsequent paper.

Summary OF RESULTS FROM CYPRIDINA.

1. The luminous secretion of Cypridina comes from several spindle shaped yellow gland-cells on the upper lip and is extruded to the sea water as a perfectly clear granule-free non-fluorescent secretion. The light is homogeneous and bluish white in color.

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