Immunochemistry of Model Membranes Containing Spin-Labeled Haptens
A previous study reported that liposomes composed of L-α-dipalmitoylphosphatidylcholine (DPPC), cholesterol and 3 mole % cardiolipin fix complement in the presence of specific anticardiolipin antibodies (1). It was discovered that at both the temperatures employed (6°C and 37°C) complement fixation increased strongly with increasing cholesterol concentration for cholesterol concentrations above 33 mole %. Similar results were obtained when the DPPC was replaced by L-α-dimyristoylphosphatidylcholine (DMPC). Since several physical properties of binary mixtures of phosphatidylcholines and cholesterol changes at cholesterol concentrations of the order of 33 mole % (2) the above study (1) indicates that one or more of these physical properties of the liposomal membrane may play an important role in complement fixation. For example, the physical properties of phosphatidylcholine-cholesterol lipid mixtures might strongly affect the lateral motion and distribution of this lipid hapten (cardiolipin) and thereby modify the immunochemical properties of the membrane.
KeywordsSpin Label Model Membrane Complement Fixation Glutaric Acid Liposomal Membrane
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