344 



LIGHT AND LIFE 



In the case ol RliodospiriUum ruhrum the reaction is also com- 

 plex; some of it has a temperatiue coefficient and some of it does 

 not. Fig. 22 shows the Rhodospirilhun signal growth and decay (14) . 

 At both -[- 25°C and — 150°C the growth and decay were as fast as 

 the instrument could follow. In the intermediate temperature re- 

 gions, some fraction of the decay was slow, indicating that this is 

 a complex signal made up of several different kinds of unpaired elec- 

 trons, probably formed in sequence. At low temperature there are 

 7io slowly formed, unpaired electrons; they are formed extremely 

 rapidly and they decay extremely rapidly. 



The Structural Requirement 



One could ask the question: Is the chloroplast needed to produce 

 such unpaired electrons? Could not such unpaired electrons be pro- 

 duced photochemically, just using the chlorophyll and its associated 

 pigments? (12, 55) . This experiment has been performed by several 

 workers (61) , including some in our own laboratory (2) . Fig. 23 

 shows the production of such unpaired electrons by the pigments 

 which are extracted by methanol from chloroplasts. The signals so 



H LINE WIDTH' 

 31 I GAUSS 



PEAK HEIGHT 

 (X NUMBER OF 

 ELECTRON SPINS) 



izr 



10- 



°= 7 



X 



<2 4 



< 



UJ 



a. 



166 330 496 664 630 996 1162 1328 

 TIME -SECONDS 



SIGNAL DECAY 



rig. 23. I'lioto indiKcd ESR of methanol extract of Chlorella. 



