Surface conductivity of counter ions on protein-adsorbed lipid liposomes

It has been reported that di-valent metal ions as compensation charges for the surface charges on liposomes have a mobility in the stagnant layer around the liposome particles. In this study, the influence of protein molecules adsorbed on the liposome surface on the mobility of counter ions around the particles is studied by the measurements of electrophoresis of liposome particles and ion conductance of dispersion sample of liposomes. At the iso-electric point of protein (bovine serum albumin, BSA) adsorbed egg-phosphatidylcholine (PC) liposomes for counter ions, the conductance ratio (that for dispersion sample/that for medium) has a value larger than 1. This means that even in the electrically neutral situation inside of stagnant layer on the BSA-adsorbed liposome particle, i.e. in the condition of without electroosmotic current, there are still electrically conducting ions inside of the stagnant layer. (C) 2001 Elsevier Science B.V. All rights reserved.