Coacervate-Assisted Mineral Leaching for Phosphorylation in a Primordial Soup

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Author:
Zsoldos, Sean
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Christine Dolan Keating, Thesis Supervisor
Scott E. Lindner, Thesis Honors Advisor
Keywords:
coacervates
protocell model
wet-dry cycling
mineral leaching
prebiotic phosphorylation
Abstract:
Phosphates are essential to life as we know it, forming the structural backbone of nucleic acids and phospholipids and mediating energy transfer in metabolism. Yet on the early Earth, phosphate availability was severely limited by the low solubility of phosphate-bearing minerals such as hydroxyapatite and bobierrite, meaning the vast majority of phosphate remained locked in solid mineral form rather than dissolved in solution. Additionally, the expulsion of water requirement for condensation reactions makes phosphorylation thermodynamically unfavorable in dilute prebiotic settings. This phosphate dilemma raises a fundamental question: how did geochemical phosphate become incorporated into emerging biochemical systems? Wet-dry cycling has been proposed as one mechanism to overcome this barrier, concentrating solutes and favoring condensation chemistry during drying periods. Coacervates are polymer-rich droplets formed via liquid-liquid phase separation that have independently been proposed as early Earth protocell candidates due to their ability to accumulate molecules, maintain distinct ionic microenvironments, and facilitate reactions. We hypothesized that combining these two phenomena could resolve the phosphate dilemma: coacervates may enhance leaching of phosphate from mineral sources and retain it at high local concentrations, while wet-dry cycles drive downstream phosphorylation chemistry. To test this, we examined phosphate mineral dissolution in the presence of poly(diallyldimethylammonium chloride)/polyacrylic acid (PDADMAC/PAA) coacervates under wet-dry cycling conditions and assessed whether leached phosphate could support glycerol phosphorylation in one-pot reactions. Using inductively coupled plasma mass spectrometry (ICP-MS) and phosphorus-31 nuclear magnetic resonance (31P-NMR), we found that coacervates increased phosphate concentrations in solution and glycerol phosphorylation was achievable under these conditions. This work represents the first demonstration of coacervates acting as protocell models in the context of mineral weathering, strengthening the geochemical case for compartmentalization as a driver of prebiotic phosphorylation.