Free fatty acids (FA) mere found which did not acidify liposome interi
or, This is interpreted as their inability to rapidly flip-flop across
the lipid bilayer, However, they were able to partition in lipids as
detected directly using HPLC or from the shift of their equilibrium bi
nding to acrylodated intestinal binding protein (ADIFAB) in the presen
ce of vesicles, Various bipolar FA, such as 12-hydroxylauric acid, dic
arboxylic acids, or FA with benzene ring at the tail mere found to be
inactive in this may, A phenomenon of shielding, where an additional a
lkyl chain or non-polar group can restore the flip-flop activity, is d
escribed. (C) 1997 Federation of European Biochemical Societies.