Dark- and Light-Activated 

 Ghemiluminescence of Chlorophyll 



in Vitro 



A. GENE FERRARI, BERNARD L. STREHLER, and WILLIAM E. 

 ARTHUR, Biochemistry Department {Fels Fund), University of Chicago, 



Chicago, Illinois 



The possibility that the light emitted by green plants after they 

 are illuminated is a decay from some metastable state rather than due 

 to a chemical reaction has been considered by various workers in the 

 field. Some time ago an attempt was made to determine whether 

 chlorophyll adsorbed to proteins will phosphoresce after illumination. 

 Under no conditions was any phosphorescence by artificial chloro- 

 phyll-protein mixtures or complexes observed. Indeed, the loss of 

 luminescence ability by chloroplasts even when stored at — 20°C. 

 strongly suggests that phosphorescence from a metastable state is not 

 involved since the physical properties of the chlorophyll-protein com- 

 plex should not be drastically altered under these conditions of stor- 

 age (1,2). 



Further independent evidence suggesting that chlorophyll can be 

 excited to luminescence by a chemical reaction or reactions in vivo 

 was furnished by the present findings that chlorophyll solutions will, 

 under certain conditions, chemiluminesce. 



During the last year we have attempted to measure the effect of 

 illumination on the concentration of reduced coenzyme I in leaves and 

 algae (3). As an assay system we used the response of the bacterial 

 luminescent system to added DPNH (4). This assay system contains 

 as an activator of the bacterial system, long-chain aldehydes (decyl 

 aldehyde, in this case) (5). Upon mixing solutions obtained from algae 

 extracted with hot alkali we observed a fairly bright luminescence with 

 the "quantum counter" which depended on the prior illumination 

 history of the plants from which it was obtained. However, on closer 

 examination, it was found that the luminescence occurred even in the 

 absence of the bacterial enzyme and that the light emitted was red in 

 color. 



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