Determination of the size of the packing defects in dimyristoylphosphatidylcholine bilayers, present at the phase transition temperature

Multilamellar liposomes of dimyristoylphosphatidylcholine, containing 4 mol% egg phosphatidic acid show at the phase transition temperature an increased permeability for non‐electrolytes of M r values up to 900. This indicates that the packing defects occurring at the liquid crystalline/gel state phase boundary have a similar pore diameter (15–18 A) as the packing defects present in glycophorin—dioleoylphos‐phatidylcholine vesicles. This suggests that packing defects at the protein—lipid interphase are the major permeation pathway of the glycophorin—dioleoylphosphatidylcholine vesicles.