The Prebiotic Provenance of Semi-Aqueous Solvents

Abstract

The numerous and varied roles of phosphorylated organic molecules in biochemistry suggest they may have been important to the origin of life. The prominence of phosphorylated molecules presents a conundrum given that phosphorylation is a thermodynamically unfavorable, endergonic process in water, and most natural sources of phosphate are poorly soluble. We recently demonstrated that a semi-aqueous solvent consisting of urea, ammonium formate, and water (UAFW) supports the dissolution of phosphate and the phosphorylation of nucleosides. However, the prebiotic feasibility and robustness of the UAFW system are unclear. Here, we study the UAFW system as a medium in which phosphate minerals are potentially solubilized. Specifically, we conduct a series of chemical experiments alongside thermodynamic models that simulate the formation of ammonium formate from the hydrolysis of hydrogen cyanide, and demonstrate the stability of formamide in such solvents (as an aqueous mixture). The dissolution of hydroxylapatite requires a liquid medium, and we investigate whether a UAFW system is solid or liquid over varied conditions, finding that this characteristic is controlled by the molar ratios of the three components. For liquid UAFW mixtures, we also find the solubility of phosphate is higher when the quantity of ammonium formate is greater than urea. We suggest the urea within the system can lower the activity of water, help create a stable and persistent solution, and may act as a condensing agent/catalyst to improve nucleoside phosphorylation yields.

Silicate-, Magnesium Ion-, and Urea-Induced Prebiotic Phosphorylation of Uridine via Pyrophosphate; Revisiting the Hot Drying Water Pool Scenario

“…The speciation of phosphorus within this precipitate is unknown, but is likely inorganic phosphorus species (Pi and PPi) based on the respective solubility of these phosphorus ions [ 5 ]. Intriguingly, no precipitation occurred with the samples with MgSO 4 , sand, and urea, indicating that the Mg 2+ is complexed and thus not promoting precipitation (echoing results of [ 17 ].…”

“…Furthermore, pools of formamide on the early Earth would have found it difficult to form spontaneously [ 16 ]. Formamide formation requires reaction between HCN and water, and the latter continues to convert formamide into ammonium formate [ 17 , 18 ]. Nevertheless, considering its universal availability and its ubiquity on the Earth’s surface, water is still considered to be the most plausible solvent for chemical evolution and prebiotic syntheses on the early Earth.…”

The Role of Glycerol and Its Derivatives in the Biochemistry of Living Organisms, and Their Prebiotic Origin and Significance in the Evolution of Life

“…These potentially prebiotically-relevant solvents include several that could form on the early Earth and that have prebiotically plausible components. Formamide has been considered to be potentially prebiotic and has shown tremendous potential for phosphorylation reactions (see caveat regarding pure formamide [125,133]). In experiments with both deep eutectic solvents employed for prebiotic synthesis of glycerol phosphates These potentially prebiotically-relevant solvents include several that could form on the early Earth and that have prebiotically plausible components.…”

“…In experiments with both deep eutectic solvents employed for prebiotic synthesis of glycerol phosphates These potentially prebiotically-relevant solvents include several that could form on the early Earth and that have prebiotically plausible components. Formamide has been considered to be potentially prebiotic and has shown tremendous potential for phosphorylation reactions (see caveat regarding pure formamide [125,133]). In experiments with both deep eutectic solvents employed for prebiotic synthesis of glycerol phosphates [113,114] and the semi-aqueous eutectic solvents [115], the yields of the glycerol phosphates were higher when formamide was used as a solvent along with silicates as catalysts [113].…”

“…In experiments with both deep eutectic solvents employed for prebiotic synthesis of glycerol phosphates [113,114] and the semi-aqueous eutectic solvents [115], the yields of the glycerol phosphates were higher when formamide was used as a solvent along with silicates as catalysts [113]. The DESs are more stable to water as C-N bond hydrolysis is minimal, but it may be harder to justify pools arising of these two components [125,[133][134][135][136].…”