Probing Iron oxide minerals as catalytic traps of inorganic and organic RNA remnants

As a translator of genetic information in all life forms, RNA and its ribonucleotide derivatives represent an important set of organic biomolecules. In addition to their contribution to the pool of preserved and transformed organic matter in terrestrial soils and sediments, mineral associations with RNA and ribonucleotides are of particular interest in relation to potential biosignatures on Mars or other planets. Widely reported is the role of iron oxides as strong adsorbents of both inorganic P and organic P compounds in terrestrial environments. However, despite the expected catalytic reactivity of iron oxide minerals, much remains unknown about the catalytic mechanisms of iron oxides and the potential subsequent trapping of the by-products. The current conceptual framework for probing the catalytic hydrolysis of organic P compounds by mineral oxides relies primarily on tracking the appearance of inorganic P in solution. However, recent findings from my group stressed that such framework was inadequate when iron oxides may serve as adsorbents of the catalytic by-products. In my group, we have combined high-resolution mass spectrometry, X-ray absorption spectroscopy, infrared spectroscopy, and molecular simulations to shed light on the mechanistic role of different iron oxides as catalytic traps of ribonucleotide derivatives (Figure 1). We have established a new conceptual framework, which must include the monitoring inorganic P and organic by-products, both free in solution and bound on the mineral surface, from iron oxide-mediated ribonucleotide transformation. Different theorems were included within this framework to inform when mass balance from solution species would suffice or explicit quantification of surface speciation would be warranted, thus guiding the choice of experimental techniques to be applied. Importantly, in addition to advancing our understanding of mineral-mediated P recycling in terrestrial soils and sediments, our findings provide insights on how the chemical profiles at iron oxide interfaces may represent important biosignatures of RNA remnants in iron oxide-rich surfaces on other planets.