Abstract
By means of the quartz crystal microbalance (QCM) technique, the interaction of annexin Al with lipid membranes was quantified using solid-supported bilayers immobilized on gold electrodes deposited on 5 MHz quartz plates. Solid-supported lipid bilayers were composed of a first octanethiol monolayer chemisorbed on gold and a physisorbed phospholipid monolayer obtained from vesicle fusion. This ...
Abstract
By means of the quartz crystal microbalance (QCM) technique, the interaction of annexin Al with lipid membranes was quantified using solid-supported bilayers immobilized on gold electrodes deposited on 5 MHz quartz plates. Solid-supported lipid bilayers were composed of a first octanethiol monolayer chemisorbed on gold and a physisorbed phospholipid monolayer obtained from vesicle fusion. This experimental setup enabled us to determine for the first time rate constants and affinity constants of annexin Al binding to phosphatidylserine-containing layers as a function of the calcium ion concentration in solution and the cholesterol content within the outer leaflet of the solid-supported bilayer. The results reveal that a decrease in Ca2+ concentration from 1 mM to 100 muM significantly increases the rate of annexin A] binding to the membrane independent of the cholesterol content. However, the presence of cholesterol in the membrane altered the affinity constants considerably. While the association constant decreases with decreasing Ca2+ concentration in the case of 1-paimitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS) membranes lacking cholesterol, it remains high in the presence of cholesterol.
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