Freeze-etching studies of membrane structure

Abstract

Thin sections of biological membranes examined by electron microscopy appear as two dark lines separated by a lighter space. This observation, first made in the 1950s, has been interpreted as confirmation of the Danielli-Davson model of the biological membrane (Robertson 1959) . Proponents of this interpretation have equated the dark lines to proteins and other polar groups in the membrane and the intervening light space to the lipid fatty acids (Stoeckenius 1960) . However, it has become clear that other interpretations are possible (Korn 1966; Branton & Park 1968) and that the electron microscope observations do not in fact prove the validity of any one molecular model of the biological membrane (Stoeckenius & Engelman 1969). During the last few years a number of biochemical and physical probes have given us more direct information regarding the composition and molecular configurations within biological membranes.