Diffusion of Small Non-Electrolytes across Liposome Membranes

Lieb and Stein 1 proposed recently that biological membranes behave as a homogeneous polymer network (such as rubber) with respect to the diffusion of small molecular weight non-electrolytes. In the light of accumulating evidence that substantial areas of most cell or cell organelle membranes are composed of a bimolecular sheet of phospholipids or other lipids, we have tested the hypothesis using a model system with structure and composition which are simple and well defined.