REDUCED DYES AND ESR SPECTRA 



345 



Decoy of the ESR Signal 

 brum Chromatophores 



of 



Light 

 Out - 



,Addition of co. SXIO"* M DPIP 

 which was reduced with AA 



15 Sec.|<— 



Fig. 1. Decay of the light-induced ESR signal from R. 

 rubrum chromatophoi-es in the absence and presence of 

 DPIPH2. The upper curve represents the control with 

 ca. 5 X 10-4 M AA and is an average of seven determina- 

 tions. The lower curve represents the decay of the ESR 

 signal after addition of ascorbate-reduced DPIPH2 for a 

 final concentration of 5 x 10-4 m. The absorbancy at 

 880 m^ was 1.5 in both cases. Modulation amplitude 9 

 gauss. 



Light ON 



■100 Millisec. 



Light OFF 



Fig. 2. The averaged curves of formation and decay of the light-induced ESR 

 signal of R. nihniiii chromatophores in the presence of DPIPH2. The sample 

 was at least an order of magnitude greater in chromatophore concentration 

 than that for Fig. 1 and was opaque to light. Data were obtained with a Visicorder 

 oscillograph and at spectrometer settings so that there was no instrumental 

 limitation for time resolution. 



