121 



Eugene Rabinowitch 



Cbviously, more studies are needed before it could be 

 said that the fluorescence data confirm (or contradict) the 

 two-layer scheme, suggested in this paper, 



6. 



The lamellar structure of the photosynthet ic apparatus in 

 general — and the two-leaf structure discussed here in part- 

 icular--may favor effective storage of light energy in two 

 ways: (l) by permitting resonance energy migration within 

 the layers, and thus facilitating the utilization of quanta 

 absorbed in a large number of chlorophyll molecules, for 

 chemical transformations in a — by geometrical necessity, 

 much smaller--number of enzymatic sites; and (2) by causing 

 spatial separation of the oxidation and reduction products 

 in two different layers, thus making immediate back reac- 

 tions unlikely. (For example, the organic reduction pro- 

 ducts may be given off into a hydrophobic, lipoid layer, 

 while the photoperoxides, and ultimately, oxygen, are 

 evolved into the hydrophilic, proteidic layer). In this 

 connection, 1 would like to mention one experiment. On my 

 suggestion. Dr. Mathai carried out the oxidation-reduction 

 reaction between ferrous iron and thionine dye in a two- 

 phase system, (ether + water). This reaction is in some 

 respect analogous to photosynthesis, or even more, to Kras- 

 novsky's reaction between chlorophyll and ascorbic acid; it 

 stores energy equivalent to a potential difference of about 

 0.3 V, by using visible light energy, absorbed in a dye 

 molecule. When illumination stops, the reaction is reversed 

 and the color of the dye returns. Vhen this reaction is 

 carried out in a suspension of ether droplets in water, the 

 leucothionine is extracted into the ether, while the ferric 

 ions stay in the aqueous phase; the two phases could be sep- 

 arated in a funnel, and both remain colorless. But v/hen 

 alcohol is added, permitting the two phases to mix, the de- 

 layed back reaction takes place, and the mixture immediately 

 becomes dark purple. This simple experiment demonstrates 

 the effectiveness of phase separation of products for chem- 

 ical storage of light energy in an oxidation-reduction 

 system. 



