[Surfactant interactions in model and biological membranes. IX. Theoretical model of biological activity in relation to the length of hydrocarbon chains].

A theoretical model is proposed according to which the quasi-parabolic dependence of the biological activity of amphiphilic compounds on their hydrophobic substituent chain length (the "cut-off" effect) is caused by a combination of partition equilibria and geometrical parameters of these compounds interacting with the bilayer of phospholipid membranes. The most important parameter seems to be a change in the thickness of the phospholipid bilayer. The model is quantified for the case of normal alcohols.