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Abstract
We present exfoliation of a crystalline clay induced by the small carbon-chain amino acid, gamma-aminobutyric acid (GABA), upon adsorption-desorption interaction. We experimentally investigated the interaction between Ca-montmorillonite clay (Ca-Mt) and GABA, a non-proteinogenic amino acid commonly found in carbonaceous meteorites. Despite evidence of only transient adsorption onto the clay surfaces, GABA exhibits the capacity to act as an exfoliator. ATR-FTIR spectroscopy reveals a non-reversible structural change of the Ca-Mt aluminosilicate network induced by GABA. Powder XRD analysis and TEM imaging reveal that localised, partial exfoliation of the clay layers occurrs after interaction with GABA, creating internal nanoscale cavities in-between adjacent clay layers. These results demonstrate that an elementary, monomeric species can act as an exfoliating agent in a prebiotically-relevant scenario, and that in this process, nanoscale confined environments are formed. This work may have far-reaching implications for the role of non-proteinogenic species in proteinogenesis (non-enzymatic formation of proteins) and for the role of clays in processes leading to the origin of life on rocky (exo)planets.
Supplementary materials
Title
Supplementary for: Prebiotic nanoscale cavity formation: GABA-induced exfoliation in Ca-montmorillonite
Description
Rehydration of GABA-exposed Ca-Mt (Table S1); ATR-FTIR spectra of MilliQ water washes of GABA-exposed Ca-Mt (Figure S1); ATR-FTIR spectra of rehydrated Ca-Mt samples after GABA exposure: Full spectral range and mineral's absorbance region (Figures S2, S3); Full range pXRD measurements of GABA-exposed and rehydrated Ca-Mt samples (Figures S4, S5); Additional TEM images: distorted layered structures in rehydrated Ca-Mt control and 2M GABA-altered samples (Figure S6); TEM images analysis of rehydrated Ca-Mt control and 2M GABA-altered samples (Table S2); pH of GABA solutions (Table S3);
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