Exploring the synthesis of bio-polymers without biology

Suárez Marina, Irene (2018) Exploring the synthesis of bio-polymers without biology. PhD thesis, University of Glasgow.

Abstract

For more than a century, chemists and biologists have been trying to understand, and recreate, how life originated on planet Earth. The exact origin of life will never be known, however, chemical pathways that could have contributed to the formation of the first living systems can be reconstructed. Prebiotic research, in general, has been based around the formation of precursors found in modern biology, and their self-organisation under very specific reaction environments. This approach has yet to yield a living system. One of the possible reasons for this failure is the adoption of separate routes for the study of the two main precursors, nucleic acids and proteins. In this way, prebiotic researchers have been limited in their scope of investigation, precluding the more than likely possibility that precursors of amino acids and nucleotides were present on early Earth at the same time.
In the work presented in this thesis, the formation of peptide and nucleotide building blocks from prebiotically plausible simple chemical mixtures was studied following a bottom-up approach, together with the assembly of building blocks to form polymeric structures. In addition, chromatographic analytical techniques and fully automated platforms were developed, thus enabling new discoveries and a novel approach for the study of the origin of life and creation of new life.

The first part of this thesis demonstrates a proof of concept in the utility of long-term experiments for origin of life research, specifically aimed at the study of evolution in complex mixtures containing prebiotic building blocks. In order to achieve this goal, chromatographic analytical methods were developed and optimised to meet the challenge of analysing complex prebiotic reaction mixtures. In addition to this, two new fully automated platforms were developed, providing a means for non-stop reactions that were able to run uninterrupted with minimum maintenance. These platforms were used to study the environmental effect on the Miller-Urey reaction mixture, as well as to perform hydration / dehydration cycles for a long period of time. As consequence of the automated long-term experiments, two key concepts were demonstrated. First, changes in the chemical inputs or reaction environment not only modify the output of the reaction, but also its product distribution. Second, the importance of including recursion and small changes during the course of long-term reactions was highlighted.

The second section focuses on the identification of the optimal and simplest reaction conditions for the formation of peptides through dehydration reaction of non-activated amino acids. This was achieved via the exploration of a broad parameter space (temperature, pH, number of cycles, reaction time and salt influence) using another automated platform. Peptide bond formation was observed by applying simple hydration/dehydration cycles to an aqueous solution of non-activated amino acids. By this method, unprecedented yields of up to 50% were achieved, in which the majority of products were oligomers (n ≥ 3), up to 20 amino acid residues long.

The final part of the thesis describes the study of co-reactivity between peptide and mononucleotide building blocks under simple dehydration conditions. Different reaction parameters (temperature, pH, order of addition, reaction time and concentration dependency) were studied in order to obtain the optimal reaction conditions. These experiments were conducted in the absence of activated reagents or catalysts. Based on this investigation, the simultaneous formation of nucleotide and nucleoside structures, including different canonical nucleobases, under prebiotically plausible conditions was identified. Furthermore, a selective effect on the isomeric distribution of glycosylation products was observed when amino acids were included in the reaction media.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Prebiotic, peptides, nucleotides, long-term experiments.
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Cronin, Professor Leroy
• Date of Award: 2018
• Embargo Date: 26 June 2021
• Depositing User: Miss Irene Suárez Marina
• Unique ID: glathesis:2018-30657
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 26 Jun 2018 08:57
• Last Modified: 23 Oct 2024 13:35
• URI: https://theses.gla.ac.uk/id/eprint/30657

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