Adenosine Monophosphate Forms Ordered Arrays in Multilamellar Lipid Matrices: Insights into Assembly of Nucleic Acid for Primitive Life

Abstract

A fundamental question of biology is how nucleic acids first assembled and then were incorporated into the earliest forms of cellular life 4 billion years ago. The polymerization of nucleotides is a condensation reaction in which phosphodiester bonds are formed. This reaction cannot occur in aqueous solutions, but guided polymerization in an anhydrous lipid environment could promote a non-enzymatic condensation reaction in which oligomers of single stranded nucleic acids are synthesized. We used X-ray scattering to investigate 5′-adenosine monophosphate (AMP) molecules captured in a multilamellar phospholipid matrix composed of dimyristoylphosphatidylcholine. Bragg peaks corresponding to the lateral organization of the confined AMP molecules were observed. Instead of forming a random array, the AMP molecules are highly entangled, with the phosphate and ribose groups in close proximity. This structure may facilitate polymerization of the nucleotides into RNA-like polymers.

The Interaction of Bio-Molecules with Lipid Membranes Studied by X-ray Diffraction

“…The lipid matrix helped to organize the molecules into a pattern, which may facilitate fusion of the nucleotides into short RNA strands. High resolution X-ray diffraction is the perfect tool to detect ordering of these molecules and can give unprecedented information that cannot easily be obtained by other techniques [73].…”

“…Toppozini et al recently investigated 5'-adenosine monophosphate (AMP) molecules captured in a multilamellar phospholipid matrix composed of 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine (DMPC) and observed Bragg peaks corresponding to the lateral organization of the confined AMP molecules [73]. Instead of forming a random array or its free-form crystal structure [71], the AMP molecules were found to be highly entangled, with the phosphate and ribose groups in close proximity.…”

“…Schematic representations of the experimental setup, analysis and results AMP-DMPC confinement experiments[73]. a) Schematic of experimental X-ray setup.…”

“…The plot shows the the agreement between theoretical (black) and experimental (blue) diffraction patterns. Figure adapted from[73].…”

Hydrothermal Conditions and the Origin of Cellular Life

“…Furthermore, under these conditions amphiphilic compounds present as micelles or vesicles assemble into multilamellar structures on the surface, and any solutes that are present are concentrated and organized between lamellae (Toppozini et al, 2013). A subsequent rehydration cycle produces large lipid vesicles that have encapsulated a significant fraction of the solutes (Shew and Deamer, 1985).…”