Primordial membranes

Primary investigator: Pierre-Alain Monnard.

Cellular precursors, i.e. protocells, likely possessed membranous boundaries composed of self-assembled amphiphile bilayers just as contemporary cells do. These early membranes must have played an essential role in the functioning of protocells, by preserving their specific content and directing the exchanges (energy and nutrient) between themselves and their environment. Energy conversion that yielded new chemical bonds would have represented the first crucial step in the evolution toward cells because it would have allowed a semi-autonomous, controlled metabolism to emerge.

Our project proposes a coordinated effort to achieve the prebiotic formation of protocells capable of energy uptake, in particular light energy.

1. The formation of plausible protocell membranes composed of mixtures of short-chain fatty acid derivatives (less than 12 carbons, see Figure 1) Studies of the prebiotic organics have shown that these compounds no doubt existed. However, the use of complex mixtures of these compounds as functional membranes must still be demonstrated.

Figure 1: Envisioned amphiphiles. Fatty (1) acids, (2) alcohols, (3) monoacylgycerol. Epifluorescence micrographs are from suspensions of decanoic acid (1) with n equals 9. Bars = 10 µm.  

2. Mixtures of fatty acid derivatives and PAHs (see Figure 2) will be investigated for their ability to yield mixed compartments that could be used to study PAH energy conversion
The role of simple PAHs as energy conversion systems in protocells has been postulated in the literature, however the effect of PAHs and amphiphile precursors on the stability of plausible protocell compartments is still lacking. PAHs could be used pigments, e.g., for the catalysis of amphiphiles from alkanes.

Figure 2. Envisioned PAHs. (4) Pyrene and its derivatives, (5) 2-ethyl-anthracene, (6) 2-methyl-1,4-naphtoquinone

3. Self-replication.
Living systems are capable of three main tasks: self-maintenance, self-replication and adaptive evolution in Darwinian sense. Contemporary cells are the products of a long evolution and perform these tasks using complex chemical systems. The question here is to achieve a controlled, catalyzed replication of the fatty acid bilayer structures without relying on complex protein system. (for more information)

 

These studies will represent a significant advance in the study of the emergence of protocells capable of processing nutrients into their own building blocks using an external energy source, such as light.

Walde, P., Goto, A., Monnard, P.-A., Wessicken, M. and Luisi, P.L.: (1994) Oparin's reaction revisited: Enzymatic synthesis of poly(adenyl acid) in micelles and self-reproducing vesicles. J. Am. Chem. Soc., 116, 7541-7547.
Monnard, P.-A., Apel, C. L., Kanavarioti, A. and Deamer, D. W.: (2002) Influence of ionic solutes on self-assembly and polymerization processes related to early forms of life: Implications for a prebiotic aqueous medium. Astrobiology, 2, 139-152.
Monnard, P.-A. and Deamer, D.W.: (2003) Preparation of vesicles from non-phospholipid amphiphiles. in Methods in Enzymology, 372, 133-151.
Monnard P.-A., Declue M. and Ziock, H.-J. (2008) "Amphiphile nanostructures as model for artificial cell-like entities" Current Nanoscience, 4, 71-87.
DeClue, M., Monnard P.-A., Bailey, J., Ziock, H., Boncella, J.W. and Rasmussen, S.: "Nucleobase controlled light driven metabolic formation of amphiphile containers for a minimal protocell." submitted.
Maurer, S. E., Deamer, D. W. and Monnard, P.-A.: Impact of glycerol monoacyl on the stability of plausible prebiotic fatty acid membranes. In preparation.