The clay montmorillonite is known to catalyze the polymerization of RNA from activated ribonucleotides. Here we report that montmorillonite accelerates the spontaneous conversion of fatty acid micelles into vesicles. Clay particles often become encapsulated in these vesicles, thus providing a pathway for the prebiotic encapsulation of catalytically active surfaces within membrane vesicles. In addition, RNA adsorbed to clay can be encapsulated within vesicles. Once formed, such vesicles can grow by incorporating fatty acid supplied as micelles and can divide without dilution of their contents by extrusion through small pores. These processes mediate vesicle replication through cycles of growth and division. The formation, growth, and division of the earliest cells may have occurred in response to similar interactions with mineral particles and inputs of material and energy.The bilayer membranes that surround all present-day cells and act as boundaries are thought to have originated in the spontaneous self-assembly of amphiphilic molecules into membrane vesicles (1-5). Simple amphiphilic molecules have been found in meteorites (6-7) and have been generated under a wide variety of conditions in the laboratory, ranging from simulated ultraviolet irradiation of interstellar ice particles (8) to hydrothermal processing under simulated early Earth conditions (9, 10). Molecules such as simple fatty acids can form membranes when the pH is close to the pK a (K a is the acid dissociation equilibrium constant) of the fatty acid carboxylate group in the membrane (3,11). Hydrogen bonding between protonated and ionized carboxylates may confer some of the properties of more complex lipids with two acyl chains, thus allowing the formation of a stable bilayer phase (11,12). Fatty acid vesicles may be further stabilized (to a wider range of pH and even to the presence of divalent cations) by the admixture of other simple amphiphiles such as fatty alcohols and fatty acid glycerol esters. Recent studies have shown that saturated fatty acid/fatty alcohol mixtures with carbon chain lengths as short as 9 can form vesicles capable of retaining ionic fluorescent dyes, DNA, and proteins (4). † To whom correspondence should be addressed. szostak@molbio.mgh.harvard.edu. * These authors contributed equally to this work. HHMI Author Manuscript HHMI Author Manuscript HHMI Author ManuscriptVesicles consisting of simple amphiphilic molecules could have existed under plausible prebiotic conditions on the early Earth, where they may have produced distinct chemical microenvironments that could retain and protect primitive oligonucleotides while potentially allowing small molecules such as activated mononucleotides to diffuse in and out of the vesicle. Furthermore, compartmentalization of replicating nucleic acids (or some other form of localization) is required to enable Darwinian evolution by preventing the random mixing of genetic polymers, thus coupling genotype and phenotype (13). If primordial nucleic acids assembled on mineral surfac...

Fatty acids have been investigated as boundary structures to construct artificial cells due to their dynamic properties and phase transitions. Here we have explored the possibility that fatty acid systems also demonstrate movement. An oil phase was loaded with a fatty acid anhydride precursor and introduced to an aqueous fatty acid micelle solution. The oil droplets showed autonomous, sustained movement through the aqueous media. Internal convection created a positive feedback loop, and the movement of the oil droplet was sustained as convection drove fresh precursor to the surface to become hydrolyzed. As the system progressed, more surfactant was produced and some of the oil droplets transformed into supramolecular aggregates resembling multilamellar vesicles. The oil droplets also moved directionally within chemical gradients and exhibited a type of chemotaxis.

A micrometer-sized oil droplet of 4-octylaniline containing 5 mol % of an amphiphilic catalyst exhibited a self-propelled motion, producing tiny oil droplets, in an aqueous dispersion of an amphiphilic precursor of 4-octylaniline. The tiny droplets on the surface of the self-propelled droplet were conveyed to the posterior surface and released to the aqueous solution. Thus the persistent movement becomes possible in this chemical system, because the processing of chemical energy to mechanical movement proceeds by consuming exogenous fuel, not consuming the oil droplet itself. The mechanism of the unidirectional motion is hypothesized in terms of an asymmetric interfacial tension around the surface of the oil droplet.