Possible role of membrane compartments in the origin of life

Synthesizing a minimal cell that could have arisen from a pre-biotic environment requires a method to grow and divide membrane compartments without modern cellular machinery. This thesis contains the first example of multiple cycles of vesicle replication using only chemical and physical methods. Vesicles were grown by the slow addition of an alkaline solution of fatty acid micelles into a buffered solution of fatty acid vesicles. Turbidity and light scattering measurements demonstrated vesicle size increases during growth. Micelles were preferentially incorporated into pre-existing vesicles instead of forming de novo ones as demonstrated using fluorescent resonance energy transfer (FRET). Division was performed mechanically by slow extrusion during which vesicles were reduced in diameter, but retained their contents, losing only a little more encapsulated volume than what was physically required.; Two other projects have developed from the growth and division of fatty acid vesicles. We have shown that montmorillonite and other negatively charged surfaces catalyze the formation of fatty acid vesicles from micelles by turbidity analysis. These catalytic particles often become encapsulated in vesicles as observed by fluorescent microscopy. Since montmorillonite can also catalyze the polymerization of RNA from activated nucleotides, this result links two different areas of study in the origin of life (RNA and vesicle formation) and provides a possible path for RNA to become encapsulated into vesicles.; Finally, in an effort to replace mechanical extrusion with a more prebiotic division method, we sought to examine the influence of membrane lipid compositional asymmetry on the force required for division. To this end, an alkaline solution of phospholipid/fatty acid micelles was added to a buffered solution of fatty acid vesicles with the intent that fatty acid from the micelles would equilibrate between the inner and outer membrane leaflets and phospholipid would remain in the outer leaflet to create membrane asymmetry. However, mixed micelles did not incorporate, but instead caused fatty acid vesicles to shrink. This shrinking reaction was examined using various light scattering techniques, freeze-fracture electron microscopy, and fluorescence methods.