Abstract
Natural clay particles have been hypothesized as catalysts on the early Earth, potentially facilitating the formation of early organic (bio) molecules. Association of clay particles with droplets formed by liquid-liquid phase separation could provide a physical mechanism for compartmentalization of inorganic catalysts in primitive protocells. Here we explore the distribution of natural clay mineral particles in poly(ethylene glycol) (PEG)/dextran (Dx) aqueous two-phase systems (ATPS). We compared the three main types of natural clay: kaolinite, montmorillonite and illite, all of which are aluminosilicates of similar composition and surface charge. The three clay types differ in particle size, crystal structure, and their accumulation at the ATPS interface and ability to stabilize droplets against coalescence. Illite and kaolinite accumulated at the aqueous/aqueous interface, stabilizing droplets against coalescence but not preventing their eventual sedimentation due to the mass of adsorbed particles. The ability of each clay-containing ATPS to catalyze reaction of o-phenylenediamine with peroxide to form 2,3-diaminophenazone was evaluated. We observed modest rate increases for this reaction in the presence of clay-containing ATPS over clay in buffer alone, with illite outperforming the other clays. These findings are encouraging because they support the potential of combining catalytic mineral particles with aqueous microcompartments to form primitive microreactors.
Highlights
An important step in the transition from nonliving towards living matter is thought to be compartmentalization of molecules and of reactions[15, 16]
The work presented here shows the rich behavior of natural clays in the poly(ethylene glycol) (PEG)/Dx aqueous two-phase systems (ATPS), with surprisingly different observations for kaolinite, montmorillonite and illite particles despite their similar chemical compositions and surface charge
Montmorillonites showed the least accumulation at the interface; montmorillonite-containing Dx-rich droplets were common despite the majority of montmorillonite particles remaining in the PEG-rich phase
Summary
An important step in the transition from nonliving towards living matter is thought to be compartmentalization of molecules and of reactions[15, 16]. Combining catalytic mineral surfaces with compartments such as amphiphile vesicles or droplets formed by aqueous/aqueous phase coexistence is appealing as primitive protocell models. Because the mechanism(s) of particle encapsulation within droplets of a biphasic system (partitioning and interfacial adsorption) may differ from those for amphiphile vesicles (entrapment during self-assembly), we reasoned that it might be possible to collect particles more efficiently using droplets. We explore the possibility of forming clay-containing or clay-coated droplets in aqueous biphasic solutions. Such structures could in principle combine compartmentalization and catalytic properties with relevance to early Earth scenarios and potential www.nature.com/scientificreports/. Erne and coworkers recently demonstrated stabilization of water-in-water emulsions formed from Dx 100 kDa and gelatin 100 kDa aqueous biphasic system using a synthetic clay, gibbsite, composed of aluminum hydroxide nanoplates[40]. Larger gibbsite plates adsorbed to the Dx/gelatin aqueous/aqueous interface but due to their greater mass caused droplet sedimentation rather than the well-dispersed emulsions observed with smaller particles[40]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
