title: Influence of ionic strength and beta2-glycoprotein I concentration on agglutination of like-charged phospholipid membranes.
abstract: The effect of ionic strength on adhesion between negatively charged giant unilamellar vesicles induced by beta2-glycoprotein I (β2-GPI) was studied experimentally and theoretically. Measuring the effective angle of contact between adhering vesicles indicated that the strength of adhesion between vesicles decreases with increasing ionic strength, and increases with concentration of β2-GPI. In the theoretical part we focused on the study of the average orientation of β2-GPI near the charged membrane and its role in mediating the attractive interactions between the vesicles. β2-GPI proteins were modelled as rods with internal distribution of electric charge. The predictions of Monte Carlo simulations show orthogonal orientation of some of the membrane attached β2-GPI in narrow gap between two vesicles. On the contrary, at larger distances between vesicles the proteins are parallelly attached to the membrane surface. A local minimum of the free energy corresponding to β2-GPI-mediated adhesion of two neighbouring vesicles was predicted. The strength of adhesion was confirmed to decrease at high ionic strength.
authors.affiliation: Laboratory of Biophysics, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia. Electronic address: sarka.perutkova@fe.uni-lj.si.
authors.forename: Šárka
authors.initials: Š
authors.lastname: Perutková
authors.affiliation: Department of Rheumatology, University Medical Centre Ljubljana, Vodnikova 62, 1000 Ljubljana, Slovenia.
authors.forename: Mojca
authors.initials: M
authors.lastname: Frank-Bertoncelj
authors.affiliation: Department of Rheumatology, University Medical Centre Ljubljana, Vodnikova 62, 1000 Ljubljana, Slovenia.
authors.forename: Blaž
authors.initials: B
authors.lastname: Rozman
authors.affiliation: Faculty of Health Sciences, University of Ljubljana, Zdravstvena pot 5, 1000 Ljubljana, Slovenia.
authors.forename: Veronika
authors.initials: V
authors.lastname: Kralj-Iglič
authors.affiliation: Laboratory of Biophysics, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia; Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Lipičeva 2, 1000 Ljubljana, Slovenia.
authors.forename: Aleš
authors.initials: A
authors.lastname: Iglič
mesh_terms: D000268:Adhesiveness / Q000187:drug effects; D000371:Agglutination / Q000187:drug effects; D002308:Cardiolipins / Q000737:chemistry; D004560:Electricity; D006801:Humans; D009010:Monte Carlo Method; D009994:Osmolar Concentration; D010743:Phospholipids / Q000737:chemistry*; D013816:Thermodynamics; D053835:Unilamellar Liposomes / Q000737:chemistry*; D053482:beta 2-Glycoprotein I / Q000494:pharmacology*
chemical_list: D002308:Cardiolipins; D010743:Phospholipids; D053835:Unilamellar Liposomes; D053482:beta 2-Glycoprotein I
keywords: Adhesion; Beta2-glycoprotein I; Charged lipid membranes; Ionic strength; Mean field theory; Monte Carlo simulation