Figure 6.

Concentration-dependent effect of surfactants on membrane order as represented by the limiting anisotropy of DPH, r_∞, as a function of the total concentration of surfactants, c_D, including dodecyl maltoside (LM, open circles), iturin (IT, hexagons), and lauroyl lysophosphatidylcholine (lysoPC, squares) in the top panel and sodium dodecyl sulfate (SDS, down-triangles), CHAPS (pentagons), fengycin (FE, circles), and digitonin (digi, diamonds) in the bottom panel. For LM, CHAPS, and FE, the point on the curve that corresponds to the onset of solubilization is marked by a star, respectively. (Dotted grid line) Value of r_∞ = 0.01 representing critical disorder in Figs. 2 and 3: it is reached by LM and SDS but not by CHAPS, FE, IT, lysoPC, and digi. All curves were recorded at ≈2 mM POPC, DPH/POPC = 1:600 mol/mol, 20°C. Note that the threshold concentrations observed here apply to ≈2 mM lipid only and are not directly comparable to the minimum inhibitory concentrations, for example.