Self-Replicating Micelles: Aqueous Micelles and Enzymatically Driven Reactions in Reverse Micelles

Article abstract of DOI:10.1021/ja00022a002

In this paper we present a further development of the self-replication system that was originally described for reverse micelles (Bachmann, P. A.; Walde, P.; Luisi, P. L.; Lang, J. J. Am. Chem. Soc. 1990, 112, 8200-8201). The definition of the term "self-replication" requires that the population growth of the structure is due to a reaction which takes place within the geometrical boundary of the structure itself. Here it is shown that it is possible to design both reverse and aqueous micelles that are able to self-replicate due to a reaction occurring within the micelle structure. The surfactant used was sodium octanoate, which forms micelles in water in the presence of 1-octanol as cosurfactant. Oxidation of the cosurfactant by permanganate ion converts it to molecules of the corresponding salt, which spontaneously assemble into new micelles. The reaction goes to completion, producing a 43% increase in the micelle concentration, as judged by time-resolved fluorescence quenching. Octanoate in the presence of octanol also forms reverse micelles in 85:15 (v/v) isooctane/1-octanol, and the same oxidation reaction brings about an increase in the micelle concentration by a factor of 9. The reverse micellar system sodium octanoate/octylamine is capable of hosting lipases, which are restricted to the water pool. The hydrolysis of trioctanoyl glycerol, a substrate for these enzymes, which is only soluble in the organic phase, takes place at the micellar interface and increases the micelle concentration by a factor of 4. The implication of these data for chemical autopoiesis (a theory that attempts to define the living in terms of chemical self-organization and self-production) is discussed.