Direct measurement of membrane motion and fluidity by electron microscopy

Abstract

THE mobility of cell membrane components¹ has been measured either in the light microscope scale (by visual labelling² and by the recovery of fluorescent bleaching^3,4) or at the molecular level (by nuclear magnetic resonance (NMR)⁵ and spin label EPR⁶ methods). In this report, a new method, using electron microscopic techniques to measure membrane motion, is described. This method reduces the spatial and temporal averaging processes inherent in many other methods, and extends the resolution limit of observation to the nanometer scale. The main difficulty in applying electron optical techniques to kinetic measurement had been the requirement that the specimen be placed in a vacuum. The recent development of environmental stages⁷ has partly overcome this problem. The direct observation of reaction kinetics in an electron microscope is now possible. The application of this technique to biological research enables biological reactions to be observed at high resolution in a physiological environment.