462 S. GRANICK 



was that these might be lipoid molecules, perhaps, carotenoid molecules. However, 

 it occurs to me that this double refraction showed the anomaly- in the chlorophyll 

 absorption band. Therefore, it must be the chlorophyll molecules which are 

 arranged in some sort of regular pattern. 



Those who were here a few j^ears ago may remember Dr. Vatter, who showed 

 some of his electron microscope slides. He has now made slides which are more 

 beautiful than Steinman's, although Steinman perhaps has something much 

 clearer. Vatter has pictures which show verj' clearly the development of structure 

 in the course of evohition from chloroplast to the finished plastid. I strongly sug- 

 gest that whoever is interested wTite to him and ask him for these pictures because 

 they are so very much more beautiful than anj-thing I have seen in the literature. 



Unfortunately, I haven't yet studied his thesis enough to be able to summarize 

 it properly. 



Granick : The problem here is not whether the chlorophyll is localized in layers, 

 but whether the chlorophylls are oriented with respect to each other -within the 

 layers. The presence of chlorophyll in the grana layers might explain dichroism, 

 but does it explain necessarily whether the chlorophyll molecules are oriented with 

 respect to each other? What might be needed to transmit light energy ^ith great 

 efficiency are chlorophyll molecules oriented with respect to each other. 



Rabinowitch : There are two types of dichroism, morphic and intrinsic. I think 

 what is in question here implies that the molecules are organized in parallel. 



I was amazed to hear you saj- the chlorophj'U is not in the fixed and sectioned 

 chloroplasts which are examined in the electron microscope. Can you saj' why the 

 chlorophyll is not there? 



Granick : When chloroplasts are fixed by the customary OSO4 procedure all the 

 chlorophyll is leached out during dehydration in the alcohols. 



Bassham: In view of the possible connection between dichroism and protein 

 molecules I wonder whether Dr. Takashima would like to say something with 

 regard to his protein chlorophyll crystals. The properties which you described 

 sounded as though they might fit into that picture. 



Takashima : The molecular weight was about 20,000. 



Strehler : First, I wonder if you can tell me whether there is any chance that 

 the membrane from the chloroplast is actually an artifact, i.e., a fixation product? 



Second, have you made any calculation of the number of chlorophylls that 

 would fit inside of one of your little discs? 



Granick : About 90,000 chlorophylls would be in a disc 5,000 A in diameter and 

 65 A thick. With regard to the chloroplast membrane: it looks real and, in fact, 

 most of the membranes in tissues are around 50 to 100 A in thickness, which is 

 about the diameter of one to several protein molecules. 



Arnold : I am publishing a paper which shows the polarization of the fluorescence 

 in the living plant is about 3%. You can make some sort of argument from this as 

 ta the degree of orientation. 



Duysens: Dr. Granick made some remarks that, in a unit, the chlorophjdl 

 molecule may be oriented parallel. The polarized light would be preferentially 

 absorbed by oriented units and that would give a strong polarization of about 40% 

 at 680 mn. Since experiments show a much lower degree of polarization, it seems 

 that either the chlorophyll molecules are not oriented exactly parallel in one unit 



