Oligomerization of Amino acids and Keto Acids under Dried Conditions - Robust Synthesis of Prebiotic Precursors 

Eliav Marland^a, Gal Lipson^a, Aikomari Guzman-Martinez^c, and Moran Frenkel-Pinter^a,b* 

^a Institute of Chemistry, The Hebrew University of Jerusalem, Israel 9190401 

^b The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Israel 9190401 

^c Department of Chemistry, University of Puerto Rico, Mayagüez, Mayagüez, PR 00681 (USA) 

Numerous long-standing questions in research of origins of life center on the history of extant biopolymers. While sequences of proteins have been tuned by eons of evolution, it has been proposed that the polypeptide backbone is the product of prior chemical evolution that occurred about four billion years ago. Importantly, metabolism and polymerization of keto acids and amino acids are highly intertwined in extant biology. Due to high abundance of both amino acids and keto acids on the prebiotic Earth, we hypothesized that co-polymerization reactions will occur between those molecules to form heterogenous co-polymers.  

To test this hypothesis, we performed simple dry-down reactions for one week between α- and γ- keto acids (pyruvic acid and levulinic acid, respectively) and amino acids (Glycine, Alanine and Valine) under a variety of conditions. Our preliminary results show that reactions between pyruvic acid and various amino acids produced oligomers up to 6-mers. Control reactions involving either keto acid or amino acid alone did not lead to significant product formation. LC-MS analysis indicates that both pyruvic acid and amino acid monomers are heavily consumed in the reactions to form a multitude of heterogenous products. Further examination revealed that oligomers were produced under a wide range of temperatures (25°C-85°C), in both dry and aqueous conditions. These oligomers could have been key players on the path to proto-peptides and proto-metabolism. Our study exemplifies how metabolism-first and polymer-first models can be reconciled via the study of co-polymers composed of keto acids and amino acids under dried conditions.