REDUCED DYES AND ESR SPECTRA 



347 



— J 15 SEC.k — 



Light ON 



Light On Series 



Light Off 



Light Off Series 



Fig. 4. The time dependence of superimposed ESR signals of TMPD 

 and R. rubnim chromatophores at different magnetic field positions 

 when the light was turned on and off. From left to right each curve 

 represents an increasing magnetic field value, where an increase in 

 TMPD radical ion concentration first adds to and then subtracts 

 from the chromatophore ESR signal. An increase in the ESR signal 

 due to chromatophores is always in the positive direction. Final 

 absorbancy at 880 m/i was ca. 1.7, and the TMPD concentration 

 was ca. 10-5 m. Modulation amplitude 9 gauss. 



sponse time than the chromatophore signal, both for formation in the 

 light and decay in the dark. The kinetics are complex, however, and 

 do not allow any definitive statement to be made at this time concern- 

 ing the interaction of TMPD and the system responsible for the ESR 

 signal in R. rubnon chromatophores. This system is interesting for 

 the reason that it allows experimental detection of both the component 



