Effective detergent/chlorophyll ratio and detergent concentration in the aqueous phase during solubilization of Phormidium laminosum membranes.

Experiments of turbidity decrease induced by detergents were systematically performed to characterize the solubilization of Phormidium laminosum membrane fragments. SDS, Triton X-100 and a mixture of octyl glucoside/decyl maltoside/lithium dodecyl sulfate (OG/DM/LiDS, in a molar ratio of 4.19:2.54:1) were used. The detergent concentration in the aqueous phase (DW) and the effective detergent/chlorophyll ratio in mixed aggregates (Re) were determined. Both parameters increased during the solubilization and in an exponential way in the range from 10 to 90% solubilization. At detergent concentrations which caused the complete solubilization, Dw values were close to the described critical micellar concentrations (cmc), but solubilization started at concentrations well below the cmc. At the onset of solubilization five molecules of SDS, one of Triton X-100 and three of the mixture OG/DM/LiDS, per chlorophyll molecule, saturated the membrane fragments. The increase of Dw and Re values was characterized by two constants. This permits the design of a model to predict the detergent concentration which produces a desired solubilization of thylakoid membrane fragments for a given chlorophyll concentration.