Phase transitions of phospholipid bilayers and membranes of Acholeplasma laidlawii B visualized by freeze fracturing electron microscopy

Abstract

1. 1. By freeze fracturing electron microscopy regular band patterns were visualized on fracture faces of liposomes prepared from dimyristoylphosphatidylcholine, dielaidoylphosphatidylcholine, and 1-oleoyl-2-stearoylphosphatidylcholine below their respective transition temperatures. Above these temperatures only smooth fracture faces were observed.

2. 2. Liposomes of these phospholipids prepared after addition of more than 20 mole % cholesterol exhibited no band patterns below their transition temperatures.

3. 3. Fracture faces of the membrane of Acholeplasma laidlawii B (previously denoted as Mycoplasma laidlawii) below the transition temperature showed structural details that can be attributed to a redistribution of membrane molecules as a consequence of the solidification of the membrane.