Non-associative phase separation in an evaporating droplet as a model for prebiotic compartmentalization

Wei Guo,Yage Zhang,Andrew B Kinghorn,Qingchuan Li,Julian A Tanner,Ho Cheung Shum,Aditi Dey Poonam

doi:10.1038/s41467-021-23410-7

Abstract

The synthetic pathways of life’s building blocks are envisaged to be through a series of complex prebiotic reactions and processes. However, the strategy to compartmentalize and concentrate biopolymers under prebiotic conditions remains elusive. Liquid-liquid phase separation is a mechanism by which membraneless organelles form inside cells, and has been hypothesized as a potential mechanism for prebiotic compartmentalization. Associative phase separation of oppositely charged species has been shown to partition RNA, but the strongly negative charge exhibited by RNA suggests that RNA-polycation interactions could inhibit RNA folding and its functioning inside the coacervates. Here, we present a prebiotically plausible pathway for non-associative phase separation within an evaporating all-aqueous sessile droplet. We quantitatively investigate the kinetic pathway of phase separation triggered by the non-uniform evaporation rate, together with the Marangoni flow-driven hydrodynamics inside the sessile droplet. With the ability to undergo liquid-liquid phase separation, the drying droplets provide a robust mechanism for formation of prebiotic membraneless compartments, as demonstrated by localization and storage of nucleic acids, in vitro transcription, as well as a three-fold enhancement of ribozyme activity. The compartmentalization mechanism illustrated in this model system is feasible on wet organophilic silica-rich surfaces during early molecular evolution.

Highlights

The synthetic pathways of life’s building blocks are envisaged to be through a series of complex prebiotic reactions and processes
To achieve the nonequilibrium settings (NES) required for Liquid-liquid phase separation (LLPS), a droplet extracted from the stock solution is pipetted onto a glass slide it starts to evaporate
Similar scenarios with such NES, that aqueous sessile droplets dispersed on the organophilic silica-rich surfaces, could be found ubiquitously on the early Earth (Fig. 1a), which is of essential significance for prebiotic polymerization of long oligomers[41,42,43]

Summary

Introduction

The synthetic pathways of life’s building blocks are envisaged to be through a series of complex prebiotic reactions and processes. Liquid-liquid phase separation (LLPS) has recently been shown as the route for the formation of intracellular membraneless organelles[14,15] Besides their biological functions in modern cells, the existence of membraneless organelles in cells provides a new perspective on prebiotic compartments on the early Earth[16]. With the ability to concentrate biopolymers and form primordial compartments in the dilute “primordial soup”[19], LLPS has been reported to guide the transition from prebiotically synthesized polymers to highly organized structures. This may have driven the evolutionary engine of the first living cells under prebiotic conditions[20]

Methods

Results

Conclusion