ABSTRACT
I. INTRODUCTION Membranes abound in nature. Several billion years ago, primitive closed sacs first enshrined the droplets of dissolved primordial self-replicating molecules into an original "self:' These membranes created a "milieu interne," which is a prerequisite for proper life (Fig. 1); this led to one of the theories of the origin of life, referred to as the "membrane came first" hypothesis. Thus, membranes have localized material into natural bioreactors by limiting and controlling diffusion into and from the surroundings. Equally important may have been the catalysis of reactions near the membrane surface, at the interface between the aqueous and lipidic compartment of each self-replicating unit (Deamer, 1997).
