STUDY OF SPONTANEOUS INSERTION OF NONIONIC SURFACTANT TRITON X-100 INTO PHOSPHOLIPID MONOLAYERS

L-alpha-Phosphatidylcholine (DOPC, Dioleoyl) monolayers of different i nitial surface pressures were spread at the sub-phase surface of a hom e-made Teflon mini-trough. Surface pressure was measured by the Wilhel my plate method so as to study the spontaneous membrane insertion of n on-ionic surfactant Triton X-100. A formula was deduced to approximate ly give out the final insertion amounts of Triton X-100 under differen t initial surface pressures. The results showed that the insertion amo unt decreased as the initial surface pressure increased and the amount included an 'excess' of Triton X-100, which could be used to approxim ately give out the interaction energy quantity between Lipid and Trito n X-100 molecules in the monolayer. (C) 1998 Elsevier Science S.A. All rights reserved.