Date of Award
Master of Science in Chemical Sciences (MSCB)
On this planet the development of life requires six essential elements: C, H, O, N, P, and S. These elements are present in gaseous form, with the exception of phosphorus, which is primarily found in solid mineral sources. Phosphorus in biological systems is significant through its involvement in metabolic functions (e.g., Coenzyme A), cell structure (i.e., phospholipid membranes), and genetic storage/transfer (i.e., phosphodiester bonds in DNA and RNA). However, an ambiguity remains with the assimilation of phosphorus in biological systems, caused by its habitual presence in insoluble phosphate mineral sources. Recent research has found that insoluble phosphate minerals, when combined with urea-rich solvents, can release sequestered phosphate into solution and promote mineral transformation to more soluble secondary minerals.
Our study investigates surface interactions of hydroxyapatite, a prebiotically plausible phosphate mineral source on the early Earth, with urea-rich solvents (urea, ammonium formate, and water, UAFW) and magnesium sulfate. Time-dependent infrared studies were conducted via polarization modulated – infrared reflection-absorption spectroscopy (PM-IRRAS) to monitor structural changes of the mineral surface. Thin hydroxyapatite films were analyzed with scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), and PM-IRRAS before and after reaction. Phosphate depletion was observed with PM-IRRAS and was supported by more established instrumentation including nuclear magnetic resonance spectroscopy (NMR) and energy dispersive x-ray spectroscopy (EDX). Film corrosion was observed by post-reaction characterization, and ammonium formate was found to activate orthophosphate release into solution.
Garcia, Estefania, "Mineral-Surface Chemistry of Hydroxyapatite and Urea-Rich Solutions" (2020). Master of Science in Chemical Sciences Theses. 33.