FLUORESCENCE-DETECTED MAGNETIC-RESONANCE (FDMR) OF GREEN SULFUR PHOTOSYNTHETIC BACTERIA CHLOROBIUM SP

Fluorescence Detected Magnetic Resonance (FDMR) spectra have been meas ured for whole cells and isolated chlorosomal fractions for the green photosyntheic bacteria Chlorobium phaeobacteroides (containing bacteri ochlorophyll e, and isorenieratene as major carotenoid) and Chlorobium limicola (containing bacteriochlorophyll c, and chlorobactene as majo r carotenoid). The observed transitions at 237 MHz (identical in both bacteria) and > 1100 MHz can; be assigned, by analogy with published d ata on other carotenoids, to the 2E and D + E transitions, respectivel y, of Chlorobium carotenoids. Their zero field splitting (ZFS) paramet ers are estimated to be: /D/ = 0.0332 cm(-1) and /E/ = 0.0039 cm(-1) ( chlorobactene), and /D/ = 0.0355 cm(-1) and /E/ = 0.0039 cm(-1) (isore nieratene). In the intermediate frequency range 300-1000 MHz the obser ved transitions can be assigned to chlorosomal bacteriochlorophylls c and e, and to bacteriochlorophyll a located in the chlorosome envelope and water-soluble protein. The bacteriochlorophyll e triplet state me asured in 750 nm fluorescence (aggregated chlorosomal BChl e) is chara cterised by the ZFS parameters: /D/ = 0.0251 cm(-1) and /E/ = 0.0050 c m(-1).