FLUORESCENCE YIELD PROPERTIES OF A FRACTION ENRICHED IN NEWLY SYNTHESIZED BACTERIOCHLOROPHYLL A-PROTEIN COMPLEXES FROM RHODOPSEUDOMONAS-SPHAEROIDES

Abstract— A membrane fraction enriched in newly synthesized bacteriochlorophyll a‐protein complexes was isolated from Rhodopseudomoms sphaeroides by rate‐zone sedimentation. An examination of the fluorescence yield properties showed that the ratio of the maximal fluorescence emission near 910 nm (with all photochemical traps closed) to that of the initial fluorescence rise (with all traps open) was 2.2 compared to 2.9 in chromatophores. The spectrum for the variable portion of the fluorescence emission (the slow rise between the initial and maximal levels) was essentially the same in both fractions, but that observed for the initial rise in the newly synthesized material showed a greater fluorescence yield with a broad peak near 865 nm. This extra emission is thought to arise from the light‐harvesting bacteriochlorophyll complex with an absorption maximum at 850 nm and suggests that this component is only partially connected to photosynthetic units. In contrast, the little extra emission observed at the longer wavelengths in this fraction indicated that energy is transferred more efficiently between the 875 nm antenna complex and photochemical reaction centers. The kinetics of the fluorescence rise suggest that photosynthetic units exist at separate sites in newly synthesized membrane regions. Copyright © 1979, Wiley Blackwell. All rights reserved