Prebiotic Synthesis of Charged Peptides via Boric Acid Catalyzed Dry-down Experiments

Abstract

Proteins are high molecular weight polymers that catalyze the majority of biological reactions and may have played a major role in chemical evolution. Among the amino acids that make up proteins, acidic and basic residues are important for both structural stability and catalytic activity, yet no examples have been reported of long polypeptides containing these charged amino acids under prebiotic conditions. Most previous studies have focused on glycine, which polymerizes readily, and it is known that peptides can be elongated by heating drying processes and even further by catalysis with boric acid. In this study, we found that heating drying an amino acid mixture containing boric acid produces peptides that include both acidic and basic amino acids. Moreover, lower pH promoted chain elongation, whereas no polymerization was observed in the absence of boric acid. These results suggest that, in boron rich drying environments on the early Earth, peptides bearing both positive and negative charges could have formed and, through interactions with RNA, contributed to the chemical evolution toward life.