Giant proteoliposomes prepared by freezing-thawing without use of detergent: reconstitution of biomembranes usually inaccessible to patch-clamp pipette microelectrode.

When sarcoplasmic reticulum membrane vesicles or synaptosomes were mixed with sonicated phospholipid vesicles and subjected to freezing-thawing, giant vesicles of up to 50 microns in diameter were formed. When the biomembrane vesicles were labeled with a covalently binding fluorescent dye, the resultant giant vesicles were fluorescent, thereby suggesting that the freezing-thawing process induces fusion of phospholipid and biomembrane vesicles. When membranes of the giant proteoliposomes thus prepared were studied using the patch-clamp technique, potassium channels of the biomembranes were detectable. The present method of the giant proteoliposome preparation is simple and rapid, and provides a system suitable for the study of ion channels of various biomembranes usually inaccessible to a patch-pipette microelectrode.