摘要：

A reconstitution procedure for a glucose-transporting protein based on a rapid freezing of sonicated phospholipid mixtures with the solubilized protein followed by thawing and a brief sonication was described by Kasahara and Hinkle (1977, J. Biol. Chem. 252, 7384–7390). In this paper we demonstrate that the liposomes prepared by this simple procedure referred to as the freezing-thawing-sonication procedure have a specific trapping volume of 10 μl H 2O/mg phospholipid and a maximal trapping efficiency of 25–30% of the solution including ions, small organic molecules, or proteins. Formation of large liposomes by this technique which probably results from fusion of sonicated liposome is strongly inhibited by increasing the ionic strength of the medium, by sucrose, and by increasing the liposome concentration. The freezing-thawing-sonication procedure is effective with a crude phospholipid extract obtained from soybeans or with mixtures of phosphatidylcholine with either a negatively charged phospholipid (phosphatidylserine) or a positively charged lipid (cetyltrimethylammonium bromide) but not with pure phosphatidylcholine liposomes. Based on these findings, we suggest that water molecules have to crystallize on the charged phospholipid interface during the rapid freezing in order to allow the fusion process to take place. Liposomes prepared by the freezing-thawing-sonication procedure have a low permeability to protons, cations, and anions which makes them a useful system for studies of ion transport. We give a few examples of ionophore-mediated ion transport reactions which give rise to accumulation of protons and Ca ions inside the lipsomes.

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