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Thermodynamic Impact of Mineral Surfaces on Amino Acid Polymerization: Aspartate Dimerization on Goethite.

Authors
  • Kitadai, Norio1, 2
  • Nishiuchi, Kumiko2
  • 1 Super-cutting-edge Grand and Advanced Research (SUGAR) Program, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan. , (Japan)
  • 2 Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan. , (Japan)
Type
Published Article
Journal
Astrobiology
Publisher
Mary Ann Liebert
Publication Date
Nov 01, 2019
Volume
19
Issue
11
Pages
1363–1376
Identifiers
DOI: 10.1089/ast.2018.1967
PMID: 31539273
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

This article presents a thermodynamic predictive scheme for amino acid polymerization in the presence of minerals as a function of various environmental parameters (pH, ionic strength, amino acid concentration, and the solid/water ratio) using l-aspartate (Asp) and goethite as a model combination. This prediction is enabled by the combination of the surface adsorption constants of amino acid and its polymer, determined from the extended triple layer model characterization of the corresponding experimental results, with the thermodynamic data of these organic compounds in water reported in the literature. Calculations for the Asp-goethite system showed that the goethite surface drastically shifts the Asp monomer-dipeptide equilibrium toward the dipeptide side; when the dimerization of 0.1 mM Asp was considered in the presence of 10 m2 L-1 of goethite, an Asp dipeptide concentration around 105 times larger was computed to be thermodynamically attainable compared with that in the absence of goethite at acidic pH (4-5) and low ionic strength (0.1 mM NaCl). Under this condition, the dipeptide-to-monomer molecular ratio in the adsorbed state reached 20%. In contrast, no significant enhancement by goethite was predicted at alkaline pH (>8), where the electrostatic interactions of the goethite surface with Asp and Asp dipeptide are weak. Thus, mineral surfaces should have had a significant impact on the thermodynamics of prebiotic peptide bond formation on the early Earth, although the influences likely depended largely on the environmental conditions. Future experimental studies for various amino acid-mineral interactions using our proposed methodology will provide a quantitative constraint on favorable geochemical settings for the chemical evolution on Earth. This approach can also offer important clues for future exploration of extraterrestrial life.

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