MELVIN CALVIN 



345 



produced at 25°C are quite different from the signals produced in 

 the whole chloroplasts, either at room temperature or at very low 

 temperatures (see Fig. 23) . The signals in the diloroplasts were 

 10 to 20 gauss wide and the signals in the chloroplast extracts are only 

 3 gauss wide. Fiuthermore, their decay at room temperature is slow 

 compared to the decay of signals in the chloroplasts. It is clearly 

 possible, therefore, to produce such signals in methanolic extracts, 

 and if this methanolic extract is thoroughly dried, there is no signal. 

 Furthermore, if the methanolic extracts are fractionated by petroleum 

 ether so a cleaner chlorophyll is obtained, then the signals that are 

 produced are broader and smaller. 



Carotenoid Requirement 



There is one other type of experiment which has been performed 

 in an attempt to determine the point at which these signals originate 

 in the chloroplast and what factors determine this point, and that 

 is the experiment done with Rhodopseudomonas, of which we have 

 two types: the wild type, which contains carotenoid; and the mutant 

 (65) , which does not contain the conjugated carotenoid. An attempt 

 was made to see if the conjugated carotenoid w^as involved in the 

 photoproduction of the spin signal (4, 5) . Very nearly the same 

 characteristics in the signal are obtained (Fig. 24) whether the wild 



LINE WIDTH 



CHLOROPHYLL 

 CONTENT 



SIGNAL 

 AMPLITUDE 



INITIAL 

 DECAY 



FINAL 

 DECAY 



RHODOPSEUDOMOh/AS RHODOPSEUDOMONAS RHODOSPRILLUM 

 SPHERaOES (WILD) SPHERaDES (MUTANT) RUBRUM 



<2 BY-1% 

 20 g 



04mg/l00ml sol. 



Aq (SMALL) 



SECONDS 



TEMPERATURE 



INDEPENDENT 



HOURS 



TEMPERATURE 



DEPENDENT 



<2 BY~I% 

 20 g 



0.2 mg/ 100 ml sol 



SECONDS 



TEMPERATURE 



INDEPENDENT 



HOURS 



TEMPERATURE 



DEPENDENT 



2 



10 g 



25A, 



< SECONDS 



TEMPERATURE 



INDEPENDENT 



MINUTES 



TEMPERATURE 



DEPENDENT 



Fig. 24. Properties of the photo-spin signals in purple bacteria. 



