502 



Joseph S. Kahn 



which makes the pigments preferentially water-soluble. In the 



case of the carotene, all activity is lost when the pigment and 



protein are separated; in the case of the chlorophyll, we have 



been unable as yet to achieve a complete separation. 



We do not know as yet whether these complexes represent a 

 unique fraction or whether they are representative of most or 

 all the chlorophyll in the chloroplast. However, we would like 

 to believe that the reduction of ferricyanide by the combination 

 of the two soluble complexes, is by a mechanism similar to that 

 catalyzing the reduction by whole chloroplasts . If so, it may 

 represent a useful tool for the study of the photochemical re- 

 actions involved in photosynthesis. 



Table IV 



Reactivation of ferricyanide reduction by protein- 

 chlorophyll extracted with 25% diethyl ether in 

 petroleum ether. 



jimole ferricyanide reduced % of 

 mg chlorophyll x hr control 



Unextracted protein-chlorophyll 31.5 100 



+ protein-carotene (1:10)* 36.2 115 



Extracted protein-chlorophyll 6.9 22 



+ 10"^ M/5-carotene (1:10)* 6.7 21 



+ 5 X 10 M plastoquinone 7.3 23 



+ 10~^ M FMN 10.1 32 



+ protein-carotene (1:10)* 35.4 112 



-3 

 +10 M menadione 38.4 122 



+ protein-carotene and menadione 49.6 157 



Approximate molar ratio of carotene to chlorophyll. 



Acknowledgment 



This investigation was supported in part by grant # RG-09710 

 of the National Institutes of Health. Contribution # 1704 of the 

 North Carolina Agricultural Experiment Station. 



I 



