338 JAMES H. C. SMITH 



to this polarization effect you are actually making them on one enzymic particle 

 and moving them over to another. We have no experimental evidence on this. 



Frenkel : Are there two types of protochlorophyll on your particles, one 

 phytylated and one non-phytylated ? 



Smith : There are no phytylated compounds present. All we have is the non- 

 phytylated. 



Frenkel: I wonder if anyone has carried out an experiment yet to ascertain 

 whether the hydrogens in the transformation of protochlorophyll to chlorophyll a 

 come from water or from some non-exchangeable hydrogens on the protein ? 



Smith : We did do this a number of years ago when we had high hopes that 

 protochlorophyll would be the photosynthetic hydrogen acceptor. We did this by 

 the Fringsheim method of quenching of phosphorescence of tryptoflavin. We put 

 etiolated leaves into the apparatus and pumped off all the oxygen so that we had 

 no quenching of the phosphorescence. Then we illuminated the leaves and although 

 the transformation of the protochlorophyll was 80% complete, we got off the leaves 

 only I or 2% of the theoretical amount of oxygen. In other words the hydrogen 

 did not seem to be pulled away from the water. Now if you went ahead with this 

 and then had the chlorophyll already formed and put those leaves in, then on 

 illumination the oxygen just rolled off, so there is a time factor involved, so the 

 failure to produce oxygen by the initial illumination can't be just the question of 

 utilization of that oxygen by respiration. 



