High-pressure torsion processing of serine and glutamic acid: Understanding mechanochemical behavior of amino acids under astronomical impacts

TL;DR

This study uses high-pressure torsion to simulate astronomical impacts on amino acids, revealing their stability and microstructural changes, which supports their delivery to early Earth without polymerization or reactions.

Contribution

It introduces high-pressure torsion as a novel method to study amino acids under impact-like conditions, showing their stability and microstructural modifications.

Findings

Amino acids remain chemically stable after HPT processing.

Microstructural changes include crystal size reduction and defect formation.

Shear strength increases to a steady state.

Abstract

Astronomical impacts by small solar system bodies (meteoroids, asteroids, comets, and transitional objects) are considered a mechanism for delivering amino acids and their polymerization to proteins in early Earth conditions. High-pressure torsion (HPT) is a new methodology to simulate such impacts and clarify the behavior of biomolecules. In this study, two amino acids, crystalline L-serine and L-glutamic acid that were detected in meteorites, are processed by HPT and examined by ex situ X-ray diffraction, Raman spectroscopy, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and in situ mechanical shear testing. No polymerization, chemical reactions, or phase transformations are detected after HPT, indicating that the stability and presence of these two amino acids in meteorites are quite reasonable. However, some microstructural and mechanical changes like crystal size reduction to the nanometer level, crystal defect formation, lattice expansion by vacancy formation, and shear strength enhancement to the steady state are found which are similar to the behaviors reported in metals and ceramics after HPT processing.