# Influence of Rare Earth Elements on Prebiotic Reaction Networks Resembling the Biologically Relevant Krebs Cycle

## TL;DR

This study explores how rare earth elements could have helped form complex molecules in early Earth's chemical reactions, similar to the Krebs cycle.

## Contribution

The paper demonstrates that rare earth elements can mediate prebiotic reactions to form Krebs cycle intermediates, highlighting their catalytic potential in early biochemical pathways.

## Key findings

- Rare earth elements facilitate the formation of Krebs cycle intermediates from glyoxylate and pyruvate.
- REEs differ from ferrous iron in promoting reduced starting material pathways.
- The ionic radius and Lewis acidity of REEs significantly influence reaction products.

## Abstract

Rare earth elements (REEs) are not rare, but rather abundant in the earth's crust and excellent catalysts for a multitude of organic reactions. They have been recently shown to be used in the active sites of bacterial enzymes and thus essential for metabolic processes. However, these elements have so far been disregarded with respect to their possible contributions to the emergence of complex molecules. Here, we investigate the potential of REEs to act as mediators in a prebiotic reaction network resembling the biological Krebs cycle starting from glyoxylate and pyruvate. Special focus is put on a comparison between trivalent REEs and ferrous iron. Reaction products were analyzed by gas chromatography–mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR) spectroscopy. Contrary to Fe2+, the formation of the reduced starting materials seems to be a major pathway when REEs are involved. Their high coordination numbers, flexible coordination spheres and their hard Lewis acidic properties make REEs excellent reagents in abiotic chemical reaction networks resembling conserved biochemical pathways.

Rare earth elements can act as mediators in a prebiotic reaction network, producing various intermediates of the citric acid cycle starting from glyoxylate and pyruvate. The ionic radius and the resulting variation in Lewis acidity has a significant influence on the observed product scope.