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R. Graham Cooks, Henry B. Hass Distinguished Professor of Chemistry, and his postdoctoral researcher Lingqi Qiu have experimental evidence that the key step in protein formation can occur in pure water droplets, and recently published these results in the Proceedings of the National Academy of Sciences.
During this key step, amino acids are dehydrated (they lose water) even though they are in an aqueous solution, a paradox resolved by the fact that the surface of these droplets is unusually dry and very acidic. Under these conditions, amino acids connect with each other to create peptides, a fundamental step toward the formation of proteins and, ultimately, living organisms.
A crucial aspect of the discovery is that the natural “left” structure of amino acids is maintained throughout this process. This leads to the formation of pure chiral peptides with the same “L” hand. The authors identified a specific compound, oxazolidinone, as a crucial intermediate in this reaction.
Furthermore, they found that this dehydration reaction is not limited to microscopic droplets. This also occurs on a larger (centimeter) scale, as demonstrated in a laboratory experiment using the intermediate oxazolidinone. This larger-scale reaction reflects microdroplet chemistry and is also analogous to the well-studied wet-dry cycles that might occur in hydrothermal pools and seashores. This connection links the formation of peptides in aerosols and in environments more extensive prebiotics.
The study adds to the body of evidence that the surface of water drops represents a unique active physical and chemical system. There are very high electric fields and extreme acidity that cause amino acids to dehydrate to form peptides. Studies of the chemistry at water droplet interfaces offer new insights into the early stages of the chemical evolution of life.
The authors acknowledge valuable discussions with Dylan T. Holden and Nicolás M. Morato, research associates at Purdue.
More information:
Lingqi Qiu et al, Oxazolone-mediated peptide chain extension and homochirality in aqueous microdroplets, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2309360120
Provided by Purdue University
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