The Effect of in vitro Anticoagulant Disodium Citrate on Beta-2-glycoprotein I - Induced Coalescence of Giant Phospholipid Vesicles

In order to elucidate the mechanisms of blood coagulation the complex interactions between phospholipid membranes, serum protein beta-2-glycoprotein I (β2GPI), antiphospholipid antibodies (aPL) and disodium citrate were studied by observing collective interactions between giant phospholipid vesicles (GPVs) in the sugar solution. GPVs composed of palmitoyl-oleoyl-sn-glycero-3-phosphocholine (POPC), tetraoleoyl cardiolipin and cholesterol were obtained by the electroformation method and observed under the phase contrast microscope. β2GPI or aPL acted as mediators inducing the coalescence of the vesicles. The strength of the adhesion between the coalesced vesicles was dependent on the content of cardiolipin and the species of the mediator. The addition of disodium citrate to the coalesced GPVs solution caused disintegration of the complexes of coalesced vesicles. The extend of the disintegration between coalesced vesicles was interpreted to be connected to the strength of the adhesion between GPVs. It was found that the disintegration of the GPV complexes was more pronounced in the system where the vesicles coalesced due to the presence of antiphospholipid antibodies compared to the system where the vesicles coalesced due to the presence of β2GPI. The effect of the disintegration of the coalesced GPVs was more pronounced for smaller vesicles which originated in the budding of the the membrane of larger GPVs.