Salt-Induced Peptide Formation in Chemical Evolution: Building Blocks Before RNA – Potential of Peptide Splicing Reactions

Abstract

From a chemical point of view, it seems likely that peptides and smaller proteins were the first biomolecules which may have formed on the prebiotic Earth. In the presence of sodium chloride and copper ions, amino acids are readily connected to oligomers via the Salt-Induced Peptide Formation (SIPF) reaction mechanism in aqueous solution under locally conceivable primitive Earth conditions. The SIPF reaction shows some specific properties suggesting a close relationship to modern life forms, like a preference for $α$-amino acids and even stereospecific differentiation in favour of the l-forms of some amino acids. Furthermore, the amino acid sequences which are preferably formed by this reaction can still be found with a probability much above average in proteins of still existing life forms, like archaea and other prokaryotic cells. Once formed, even short peptides have a number of highly interesting abilities pointing towards possible further evolutionary pathways: chain elongation on the surface of clay minerals, formation of nanovesicles with membrane-like structure, autocatalytic self-replication from fragments, stabilisation of phosphate ions against precipitation, etc.