Environmental Control Programs the Emergence of Distinct Product Ensembles from Unconstrained Chemical Reaction Networks

<p><b>Harnessing and then controlling </b><b>combinatorial explosions</b><b> in </b><b>uncontrolled condensation reactions of simple building blocks is a key problem to many hypotheses on the origin</b><b> of </b><b>life. Much has been achieved in understanding how the building blocks of biopolymers may be formed, and in understanding how macromolecules may produce functional and increasingly life-like systems. How</b><b> these </b><b>steps can be joined, and how defined populations</b><b> of </b><b>macromolecules can form from mixtures</b><b> of </b><b>simple building blocks, instead of an undifferentiated </b><b>mess</b><b>, remain open questions.</b><b> Herein, we show </b><b>how</b><b> unconstrained </b><b>condensation</b><b> reactions of both amino acids, and prebiotic soup mixtures produced by spark discharge, can be steered</b><b> by changes in the reaction environment, such as order of reactant addition (mixing history), and addition of salts or minerals. Using </b><b>techniques akin to untargeted metabolomics</b><b> to survey product distributions we</b><b> demonstrate that while these reactions do produce a large range of species, there are distinct, significant, and reproducible differences between the product ensembles</b><b>. Furthermore, we observe that differences in composition </b><b>are </b><b>demonstrated through</b><b> clearly different structural and functional properties. </b><b>Using this approach, we demonstrate for the first time that simple variations in environmental parameters can mediate the differentiation of distinct ensembles from both amino acid mixtures and a classic primordial soup model (products of a ‘Miller Urey’ type spark discharge reaction). </b><b>This shows that </b><b>the synthetic complexity produced by such unconstrained reactions is not as intractable as often suggested, when viewed through a chemically agnostic lens. An open</b><b> approach to complexity can generate compositional, structural, and functional diversity from fixed sets of simple starting materials, suggesting that differentiation of product mixtures can occur in the wider environment without the need for biological machinery.</b><b></b></p>