Ultrasonic studies of membrane suspensions

Summary The mechanical and the dynamic properties of various membranes were studied by the ultrasonic-resonance method. The compressibility of the membranes was in the range from 2.5·10⁻¹¹ to 5·10⁻¹¹ cm²/dyn and influenced by several factors such as phase transition, incorporation of cholesterol or proteins and configuration of proteins. The ultrasonic relaxation was measured for two membrane systems, dipalmitoylphosphatidylcholine bilayer and sarcoplasmic-reticulum membrane. The results indicated that the ultrasonic measurements are very sensitive to the co-operative transition in lipid bilayers as well as the relaxation of biological membranes containing intrinsic proteins. Paper presented at the ?Meeting on Lyotropics and Related Fields?, held in Rende, Cosenza, September 13–18, 1982.