title: Attraction between negatively charged surfaces mediated by spherical counterions with quadrupolar charge distribution.
abstract: We observed monoclonal antibody mediated coalescence of negatively charged giant unilamellar phospholipid vesicles upon close approach of the vesicles. This feature is described, using a mean field density functional theory and Monte Carlo simulations, as that of two interacting flat electrical double layers. Antibodies are considered as spherical counterions of finite dimensions with two equal effective charges spatially separated by a fixed distance l inside it. We calculate the equilibrium configuration of the system by minimizing the free energy. The results obtained by solving the integrodifferential equation and by performing the Monte Carlo simulation are in excellent agreement. For high enough charge densities of the interacting surfaces and large enough l, we obtain within a mean field approach an attractive interaction between like-charged surfaces originating from orientational ordering of quadrupolar counterions. As expected, the interaction between surfaces turns repulsive as the distance between charges is reduced.
authors.affiliation: Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
authors.forename: Jasna
authors.initials: J
authors.lastname: Urbanija
authors.forename: Klemen
authors.initials: K
authors.lastname: Bohinc
authors.forename: Alfredo
authors.initials: A
authors.lastname: Bellen
authors.forename: Stefano
authors.initials: S
authors.lastname: Maset
authors.forename: Ales
authors.initials: A
authors.lastname: Iglic
authors.forename: Veronika
authors.initials: V
authors.lastname: Kralj-Iglic
authors.forename: P B Sunil
authors.initials: PB
authors.lastname: Kumar
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry; D008956:Models, Chemical; D009010:Monte Carlo Method; D010743:Phospholipids / Q000737:chemistry; D011789:Quantum Theory; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D000911:Antibodies, Monoclonal; D010743:Phospholipids