The effects of representative anaesthetics on the polymorphic phase behavior of phospholipids, particularly phosphatidylethanolamine, is studied. The series of normal alcohols and alkanes destabilize the bilayer structure of hydrated phosphatidylethanolamine causing the lipid to adopt hexagonal (HII) structures at lower temperatures than control By exception, ethanol and butanol stabilize the bilayer configuration. Chloroform also initiates bilayer destabilization, producing this effect at

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... cally relevant concentrations of anaesthetic. The charged anaesthetics tested show the ability to stabilize the bilayer configuration of phosphatidylethanolamine to higher temperatures than controls this occurs in a single or mixed lipid system (ie. phosphatidylethanolamine / phosphatidylserine). In all cases the ability of an anaesthetic to alter the polymorphic phase behavior of phosphatidylethanolamine is a function of its individual potency. The observed effects of anaesthetic agent on lipid polymorphism can be interpreted in relation to the molecular shapes of the lipids and anaesthetics involved.