126 B. L. STREHLER 



Strehler: There are some agents, for instance hydroxylamine, that increase the 

 fluorescence only slightly but almost completely destroy the long-lived lumines- 

 cence. Luminescence is primarily distinguished from fluorescence kinetically in 

 that it saturates as a function of intensitj'. 



Rosenberg : With respec^t to the point that Dr. Smith raised, do you think it 

 would be fair to say that the luminescence data are neither more nor less con- 

 vincing than the fluorescence data themselves for the definition of chlorophyll as 

 being a molecule at the end of a chain? We have known from fluorescence data all 

 along that this is presumably the one, and we would be very embarrassed if we 

 found that the luminescence has a spectrum further to the red. I thought 

 possibly if there were another pigment further at the end of the chain beyond 

 chlorophyll it would perhaps be unprofitable to have a fluorescence spectrum 

 so close to that of chlorophyll that one could not distinguish them. 



Arnold : This test for identity is very good. They are very similar. If there is 

 extra light to the red of the chlorophyll fluorescence band, it is quite dim and 

 quite close to it. 



Rosenberg : The point I was trying to make was that even if they are identical — 

 and I certainly have no doubt from your data that they are — people who are 

 looking for an extra pigment will say, "Well, we really don't know what chloro- 

 phyll fluorescence should look like in the cell and perhaps it is not really chloro- 

 phyll fluorescence that everybody has been speaking of." 



Arnold : It is certainly unproved from the experiments that have been done. 



James Smith : May I make just one comment on this? You could get chloro- 

 phyll fluorescence out of the cell and still not have it at the end of the chain be- 

 cause in the red algae, as Dr. French and his collaborators have shown, you have 

 fluorescence of the phj'cobilins even though you have fluorescence from the 

 chlorophyll. So not all of the energy is transferred. Is this not right, Stacy? 



French: Yes. 



James Smith: I should think you might run into the same situation with 

 chlorophyll itself and another pigment that could receive a fair share of the energy. 



Kamen: Dr. Duysens, I remember that in the original work you had a transfer 

 to another pigment near the long wavelength band of chlorophyll. Is that cor- 

 rect? 



Duysens: In the fluorescence spectrum of the red alga Porphyra lacineata, 

 there is a verj- strong fluorescence at 730 m/x. If the fluorescing pigment is a con- 

 centration of only 0.1% of that of chloroph3dl, as we thought, then this fluores- 

 cence probably occurs by transfer from chlorophyll a to this pigment. There is 

 some, although less clear-cut, evidence for fluorescence at 780 m^ in other red 

 and blue-green algae, but not for green or brown algae. 



Kamen : I was wondering whether there is a possibility of a trace amount of 

 another pigment. 



Linschitz: 8600 A is the spectral region for the triplet. There maj- be activation 

 at that level. 



Arnold : I have looked very hard for this 8600 A light without finding a trace of 

 it. 



Strehler : With respect to what Dr. Kamen had to say, suppose there is as a 

 terminal acceptor an iron porphyrin whose absorption is relatively close to that 



