ESR SIGNALS IN GREEN BACTERIA 



353 



existence of a second signal. The results for whole cells are sum- 

 marized in Table 1. The relative heights of the signals are uncor- 

 rected for absorbancy and light intensity. 



The signal obtained from the subcellular fraction by light of Xmax. 

 825 m/i is shown in Fig. 2. This signal appears to be larger than that 



2.002 



max 



MAGNETIC FIELD 



Fig. 1. Light-induced ESR signals in whole cells of Chloro- 

 pseudomonas ethylicum for three wavelength regions with 

 Xmax. '''03, 744 and 825 mfi. The signals are obtained by nu- 

 merical integration of the spectrometer recordings (averaged 

 over 5 spectra) and are uncorrected for differences in ab- 

 sorbance of the sample or for incident light intensities. Cells 

 were obtained from a 2 -day-old culture. 



obtained with whole cells, but the chlorophyll content of the two sam- 

 ples was not compared. The g- value is 2.002 and the width at one-half 

 height (AH]^/2) is 17 gauss. After continued illumination, the signal 

 decayed, possibly as a result of the aerobic conditions under which 

 both the preparation and the measurements were made. 



