A Prebiotic Synthesis of Pterins

Abstract

The genesis of life on Earth is a hypothesis of evolutionary science that can be, at least partially, tested experimentally. The prebiotic synthesis of cofactors or coenzymes is a poorly explored issue, likely because their formation under plausible prebiotic conditions is not clear. In this sense, it has been proposed that the cofactors are "molecular fossils" of an early phase of life. In contrast, Eschenmoser and Loewenthal suggested a prebiotic hydrocyanic origin of cofactor building blocks. In the present paper, the formation of a set of pterins from cyanide polymerizations is demonstrated, showing that the main structure of some cofactors can be prebiotically formed. Indeed, it was observed that aqueous aerosols additionally increase the relative composition for pterins in the insoluble NH4CN polymers synthesized. The novel identification of pterins in NH4CN polymers, together with the previous detection of other important biomonomers, indicates that cyanide polymerizations were essential in the early state of prebiotic chemistry.

The Role of Aqueous Aerosols in the “Glyoxylate Scenario”: An Experimental Approach

“…In a pioneering work, no significant differences were found in the nature of the biomolecules formed from HCN oligomers prepared in the absence or presence of oxygen . However, in two later works, a significant role of oxygen in the oligopolymerization of HCN was suggested . Therefore, the role of oxygen was also studied in the present paper.…”

“…However, Eschenmoser also proposed a hydrocyanic origin for these compounds . In a previous paper, we demonstrate the formation of the backbone of these cofactors from cyanide polymerization (synthetic conditions 9, 10, 11 and 12, Table ). The hypothetical pathway proposed by us for the formation of pterins includes glyoxylic acid ( c9 ).…”

“…We used an aerosol production cycle as a basic set‐up to study the effect of the aqueous interfaces in the production of HCN polymers, on the basis of our previous results . Figure S1 in the Supporting Information shows the effect of the aqueous aerosols on the monomeric diversity found for the HCN polymers.…”

“…The aqueous aerosols can be considered as “prebiotic microreactors” and show an efficient variation in the reactivity of the systems . They can enhance the yield of polar organic compounds, improve the formation of determinate organics against others, and also influx positively in non‐enzymatic polymerization reactions . In addition, currently there is an increasing interest in the reactivity of organics at the air–water interfaces…”

“…All the HCN polymers synthetized herein (using synthetic conditions shown in Table ) were qualitatively analyzed for polar monomers (mainly amino acids, carboxylic acids and N‐heterocycles) by GC‐MS, after acid hydrolysis. It is well‐known that the hydrolysis conditions have a notable influence on the detection, identification and quantification of the monomers present in the HCN polymers …”