Thermostability of model protocell membranes. Proc Natl Acad Sci USA

Howard Hughes Medical Institute, Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 10/2008; 105(36):13351-5. DOI: 10.1073/pnas.0805086105
Source: PubMed


The earliest cells may have consisted of a self-replicating genetic polymer encapsulated within a self-replicating membrane vesicle. Here, we show that vesicles composed of simple single-chain amphiphiles such as fatty acids, fatty alcohols, and fatty-acid glycerol esters are extremely thermostable and retain internal RNA and DNA oligonucleotides at temperatures ranging from 0 degrees C to 100 degrees C. The strands of encapsulated double-stranded DNA can be separated by denaturation at high temperature while being retained within vesicles, implying that strand separation in primitive protocells could have been mediated by thermal fluctuations without the loss of genetic material from the protocell. At elevated temperatures, complex charged molecules such as nucleotides cross fatty-acid-based membranes very rapidly, suggesting that high temperature excursions may have facilitated nutrient uptake before the evolution of advanced membrane transporters. The thermostability of these membranes is consistent with the spontaneous replication of encapsulated nucleic acids by the alternation of template-copying chemistry at low temperature with strand-separation and nutrient uptake at high temperature.

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    • "For example, ionophores such as Streptomycesderived valinomycin selectively chelate potassium ions and shuttle them across host cell bilayers, disrupting their electrochemical gradient. Similarly, the threat of bare permeation of small ions and water molecules to highfidelity nucleic acid replication might have spurred the development of the phospholipid bilayer as an early and critical evolutionary adaptation on the molecular level (Mansy and Szostak 2008; Budin and Szostak 2011). Nonetheless, bare ion permeation, while rare, does occur, although its mechanism remains disputed in the literature. "
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    • "Hydrothermal edifices formed by the precipitation of vent fluid minerals can be extremely porous (Fig. 1), a characteristic that makes them potential locations in which macromolecules can be concentrated and, thus, give rise to the first cells (Alpermann et al., 2010; Russell et al., 2010). It is noteworthy that recent experiments have shown the ability of primitive cells to retain RNA and DNA oligonucleotides at temperatures up to 100°C (Mansy and Szostak, 2008). "
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    • "It is notable that improved permeability and stability of model vesicles are obtained with mixtures of amphiphiles (Namani and Deamer 2008; Maurer et al. 2009), such as might be expected to be present in a chemically rich prebiotic environment. FA membranes are more permeable than phospholipid ones (Monnard and Deamer 2002; Mansy et al. 2008; Pohorille and Deamer 2009; Mansy 2010). With the addition of phospholipids, vesicle permeability drops. "
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