Variable composition of cytochrome b6-f particles.

Cytochrome b6-f particles were prepared from chloroplasts of spinach and the heterokont alga Bumilleriopsis filiformis using digitonin in comparison with non-ionic detergents. The cytochrome b6-f particles are solubilized in different amounts according to chemical structure and HLB value of the detergent (see Griffin, J. Soc. Cosmet. Chem. 1, 311 [1949]). Also the ratio of the two cytochromes in the isolated particle depends on the detergent used. In case of spinach, it varies from Cyt b6:f=1.5:1 to 4.9:1. These investigations do not strengthen the idea that a cytochrome b6-f complex with a stoichiometric composition is present in the photosynthetic membrane. Application of different detergents is a means for selective solubilization of thylakoid membrane components.