What Did We Learn from Model Membrane Studies on Biological Membranes

Abstract

The use of models of some sort in order to understand certain aspects of biological systems is an established practice. Furthermore, quite often we argue in research proposals that “a study of a model helps understanding the much more complex biological system”. This abstract presents a preliminary attempt to test the validity of the latter statement regarding the contribution of model membranes studies (particularly liposomes) to the understanding of various aspects of membrane biochemistry and biophysics. Whoever applied to a granting agency for support will testify that the issue is far from being trivial. An obvious example is the establishment of the lipid bilayer as the fundamental structure of all biological membranes.The History of the controversy that existed before lipid bilayer emerged as the consensus structure, as described by. Thompson and Henn in their comprehensive review in 1969 (in Structure and Function of Membranes In Mitochondria and Chloroplasts, ed. E. Racker, pp. 1-52, Reinhold N.Y.), shows that the resolution can be attributed to experimental studies on phospholipid bilayers.Many more examples can be raised, including, the profound condensing effect of cholesterol on bilayer structure, first found by use of the simple, fundamental system and apparatus invented by Irving Langmuir, the understanding of the diffusion of proteins, impeded in real membranes by intermolecular interactions compared to models in which they move freely, the understanding of the causes for lateral phase separations and the development of novel lipofection agents based on studies of the role of cationic amphiphiles on PKC activity.