The effect of the dipalmitoylphosphatidylcholine lipid bilayer state on the adsorption of phenyltins

The nonspecific adsorption of amphiphilic molecules onto the membrane depen ds both on the properties of the adsorbate and the state of the lipid bilay er, Electrostatic interactions drive the adsorption of charged molecules an d hydrophobicity determines partition of the adsorbate into the membrane, w hereas the steric compatibility of the lipid bilayer and the amphiphilic mo lecule is an additional factor to be accounted for when considering interac tion between the adsorbate and the membrane. The adsorption of phenyltins w as evaluated from changes in Fluorescein-PE fluorescence intensity. The pH sensitivity of fluorophore, located at the membrane surface, was utilized t o detect charges introduced onto the membrane by adsorbing compounds. It ha s been shown that the state of the membrane affects phenyltin adsorption in accordance with the number of phenyl rings an the molecule. Furthermore, t he membrane surface topology determines interfacially located triphenyltin adsorption, with a much weaker effect on deeply embedded diphenyltin, When the dipalmitoylphosphatidylcholine (DPPC) model membrane is in the ripple p hase, with complex surface morphology, phenyltin adsorption is greatly enha nced. Results presented in this paper show that steric constraints imposed on rigid and bulky amphiphilic compounds by ordered alkyl chains and membra ne surface topology affect nonspecific molecule adsorption onto the membran e. Copyright (C) 2000 John Wiley & Sons, Ltd.