. Bacterial photosynthesis. Bacteria -- Physiology; Photosynthesis. COUPLED REDUCTION OF UBIQUINONE 271 CHROMATOPHORES + DPIPH2. CHROMATOPHORES 300 400 500 WAVELENGTH, m/i 600 700 Fig. 2. The effect of DPIPH2 upon the light-induced absorbancy changes in R. riibrum chromatophores. The suspension contained 10//grams BChl per nil and Tris buffer and sucrose as shown for Fig. 1. Where indicated, 66 /iM DPIPH2 (reduced with ascorbic acid) was also present. The 0 to .1 absorbancy scale was used, and illumination was obtained by means of two 6-volt, 18-ampere tungsten lamps situated above the cell co
. Bacterial photosynthesis. Bacteria -- Physiology; Photosynthesis. COUPLED REDUCTION OF UBIQUINONE 271 CHROMATOPHORES + DPIPH2. CHROMATOPHORES 300 400 500 WAVELENGTH, m/i 600 700 Fig. 2. The effect of DPIPH2 upon the light-induced absorbancy changes in R. riibrum chromatophores. The suspension contained 10//grams BChl per nil and Tris buffer and sucrose as shown for Fig. 1. Where indicated, 66 /iM DPIPH2 (reduced with ascorbic acid) was also present. The 0 to .1 absorbancy scale was used, and illumination was obtained by means of two 6-volt, 18-ampere tungsten lamps situated above the cell compartment. Light was transmitted through a No. 2403 Corning filter to the circular absorption cells by means of a lucite plastic tube which served to guide the light rays to the absorption cell. The intensity of illumination was saturating for the reactions studied. of DPIP, which has become oxidized by the photochemical system con- tained in the chromatophores. The changes due to chromatophores themselves are superimposed upon this broad absorption band of DPIP. The second important change is in the ultraviolet region, where a pronounced decrease in absorption around 280 rrxji occurred. The most logical compound to be related to the band at 280 m/i is ubiquinone (9). Clayton has recently shown that illumination of Chromatium chromatophore suspensions results in changes corresponding to a photo reduction of the ubiquinone contained within these chromatophores. The discrepancy between the observed minima in the two cases (270 m/i reported for Chromatium and around 280 m/^for R. nihnim in this investigation) is due to the fact that there are some absorption changes in this region accompanying the oxidation of DPIPH2. The conversion of DPIPH2 to DPIP results in slight increases in absorbancy in the range from 260 to 290 m//. The difference spectrum obtained with the dye itself (oxidized minus reduced) shows a minimum at 285 and a maximum at 270 m//. It is the superimposition of th
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