Partially purified photosynthetic reaction centers from plant tissues

Physical separation of chlorophyll-protein complexes

This minireview focuses on the physical separation of chlorophyll-protein complexes and particles from the two photosystems by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis (PAGE) or differential/sucrose density-gradient centrifugation during the decade of 1960s.

Contribution to the structural characterization of eucaryotic PSI reaction centre - II. Characterization of a highly purified photoactive SDS-CP1 complex

Under precise conditions, SDS PAGE† allows purification of a photoactive P700-chla-protein complex from eucaryotic cells. The yield of P700 recovery is close to 100%. A total protein content equivalent to about 140 kD for one mole of P700 has been estimated by chemical analysis, and electrophoresis revealed the presence of two peptidic chains with MWs close to 65 kD. Photochemical and structural properties of this complex are given and compared with those of other complexes previously isolated.

[Further studies on the variability of the photosynthetic unit]

The light saturation curves of photosynthesis of a yellow Chlorella mutant and the normal green strain have been investigated with monochromatic light at 15 different wavelengths in the range from 400 to 700 nm.The concentration of lipophilic quinones in relation to the chlorophyll content at different stages of regreening has also been studied. 1. On the basis of the amount of chlorophyll the photosynthetic efficiency of the yellow-green Chlorella mutant in red light of 672 and 681 nm wavelength is five times as great as that of the normal green type. On the basis of dry weight the two strains fix about the same amount of CO2. 2. In the mutant light saturation always occurs at higher intensities than in the normal strain. 3. Under conditions of light saturation maximal photosynthetic activity of the mutant is less in white light than in red light. 4. The ratio molecules quinone/molecules chlorophyll of the mutant is much higher than that of the normal control. 5. The results 1-4 are explained by the variability of the size of the photosynthetic unit. In the normal form 460 chlorophyll molecules are available for one electron transport system, that is system I and system II together, or 230 molecules per quantum absorbed. In the mutant there are only 80-100 molecules present, or 40-50 molecules per quantum absorbed.For maximum photosynthetic efficiency 30-50 molecules of chlorophyll per unit are needed. 6. Blue light, especially of 452 nm wavelength, strongly inhibits CO2 fixation in the mutant, which then increases slowly in a following red light period.