Chemical Transformations in Proto-Cytoplasmic Media. Phosphorus Coupling in the Silica Hydrogel Phase.

Ian Gorrell,Kamal Albdeery,Terence Kee,Timothy Henderson,Philip Savage

doi:10.3390/life7040045

Abstract

It has been proposed that prebiotic chemical studies on the emergence of primitive life would be most relevant when performed in a hydrogel, rather than an aqueous, environment. In this paper we describe the ambient temperature coupling of phosphorus oxyacids [Pi] mediated by Fe(II) under aerobic conditions within a silica hydrogel (SHG) environment. We have chosen to examine SHGs as they have considerable geological precedence as key phases in silicification en route to rock formation. Following a description of the preparation and characterization studies on our SHG formulations, coupling experiments between Pi species are described across multiple permutations of (i) Pi compound; (ii) gel formulation; (iii) metal salt additive; and (iv) pH-modifying agent. The results suggest that successful Pi coupling, indicated by observation of pyrophosphate [PPi(V)] via 31P-NMR spectroscopy, takes place when the following components are present: (i) a mixture of mixture of Pi(III) and Pi(V) or pure PPi(III– V); (ii) Fe(II); (iii) acetic or formic acid (not hydrochloric acid); (iv) aerobic conditions or the presence of H2O2 as an oxidant; and (v) the presence of a gel system. On the basis of these, and aqueous control reactions, we suggest mechanistic possibilities.

Highlights

In doing so we have not attempted to mimic a specific, known geological silica gel deposit, but to focus on how certain processes may be influenced when the phase is changed from aqueous to hydrogel In this paper we explore the coupling of phosphorus (P) oxyacids to afford condensed phosphate oxyacids, pyrophosphate PPi(V)
We demonstrate that aqueous phase mixtures of phosphorus oxyacids (Pi)(V) (H2 PO4 − ) and Pi(III) (H2 PO3 − ) which do not ordinarily undergo condensation to afford PPi(V) under ambient temperature conditions, do do so when incubated within a silica hydrogel environment
We have attempted here to demonstrate that metal-mediated coupling of phosphorus oxyacids (Pi) can under ambient without additional condensation?

Summary

Introduction

Within the field of abiogenesis, significant advances have been made in many chemical, prebiotic directions, including synthetic routes to peptides [1,2,3,4,5,6,7,8], nucleic acid monomers [9,10,11,12] and subsequent oligomerization [13,14,15], proto-cellular assemblies [16,17,18,19,20] and proto-bioenergetic systems [21,22,23,24,25].In all of these processes, one is manipulating systems that lie far from equilibrium in either a structural and/or dynamic sense [25]. Within the field of abiogenesis, significant advances have been made in many chemical, prebiotic directions, including synthetic routes to peptides [1,2,3,4,5,6,7,8], nucleic acid monomers [9,10,11,12] and subsequent oligomerization [13,14,15], proto-cellular assemblies [16,17,18,19,20] and proto-bioenergetic systems [21,22,23,24,25]. If one is trying to understand the emergence of the simplest form of biological life on Earth, that form being commonly referred to as LUCA, the Last Universal

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Discussion

Conclusion