title: Surface dipole potential at the interface between water and self-assembled monolayers of phosphatidylserine and phosphatidic acid.
abstract: The nature and magnitude of the surface dipole potential chi at a membrane/water interface still remain open to discussion. By combining measurements of differential capacity C and charge density sigma at the interface between self-assembled monolayers of phosphatidylserine and phosphatidic acid supported by mercury and aqueous electrolytes of different concentration and pH, a sigmoidal dependence of chi upon sigma is revealed, with the inflection at sigma = 0. This behavior is strongly reminiscent of the surface dipole potential due to reorientation of adsorbed water molecules at electrified interfaces. The small increase in C with a decrease in the frequency of the AC signal below approximately 80 Hz, as observed with phospholipid monolayers with partially protonated polar groups, is explained either by a sluggish collective reorientation of some polar groups of the lipid or by a sluggish movement of protons across the polar head region.
authors.affiliation: Department of Chemistry, Florence University, Italy.
authors.forename: M R
authors.initials: MR
authors.lastname: Moncelli
authors.forename: L
authors.initials: L
authors.lastname: Becucci
authors.forename: F T
authors.initials: FT
authors.lastname: Buoninsegni
authors.forename: R
authors.initials: R
authors.lastname: Guidelli
mesh_terms: D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010712:Phosphatidic Acids / Q000737:chemistry*; D010718:Phosphatidylserines / Q000737:chemistry*; D011199:Potentiometry; D014867:Water / Q000737:chemistry*
chemical_list: D010712:Phosphatidic Acids; D010718:Phosphatidylserines; D014867:Water