Iron‐Mediated Peptide Formation in Water and Liquid Sulfur Dioxide under Prebiotically Plausible Conditions**

Abstract

Peptides have essential structural and catalytic functions in living organisms. The formation of peptides requires the overcoming of thermodynamic and kinetic barriers. In recent years, various formation scenarios that may have occurred during the origin of life have been investigated, including iron(III)-catalyzed condensations. However, iron(III)-catalysts require elevated temperatures and the catalytic activity in peptide bond forming reactions is often low. It is likely that in an anoxic environment such as that of the early Earth, reduced iron compounds were abundant, both on the Earth's surface itself and as a major component of iron meteorites. In this work, we show that reduced iron activated by acetic acid mediates efficiently peptide formation. We recently demonstrated that, compared to water, liquid sulfur dioxide (SO 2 ) is a superior reaction medium for peptide formations. We thus investigated both and observed up to four amino acid/peptide coupling steps in each solvent. Reaction with diglycine (G 2 ) formed 2.0 % triglycine (G 3 ) and 7.6 % tetraglycine (G 4 ) in 21 d. Addition of G 3 and dialanine (A 2 ) yielded 8.7 % G 4 . Therefore, this is an efficient and plausible route for the formation of the first peptides as simple catalysts for further transformations in such environments.

Evidence of Selection in Mineral Mediated Polymerization Reactions Executed in a Robotic Chemputer System

“…[17][18][19] Clay minerals have been of a particular focus for those studies due to their structural complexity, [20,21] but also iron-containing minerals were shown to assist peptide formation if present in the reaction system. [22,23] While those studies attempted to explore the influence of mineral environments on peptide formation reactions, more work is required to understand the underlying processes that occur in these chemical systems. Further, selection is not deterministic and cannot be predicted by theoretical models, [24] which makes it necessary to use a datadriven approach when studying the emergence of goaldirectedness or selective effects on a molecular level.…”

“…Efforts have been made to study the influence of mineral environments in peptide formation reactions, since minerals were abundant on the early earth [15,16] and may have been the ′beaker′ as well as the catalyst for the OoL [17–19] . Clay minerals have been of a particular focus for those studies due to their structural complexity, [20,21] but also iron‐containing minerals were shown to assist peptide formation if present in the reaction system [22,23] . While those studies attempted to explore the influence of mineral environments on peptide formation reactions, more work is required to understand the underlying processes that occur in these chemical systems.…”