Chiral Interactions of Histidine in a Hydrated Vermiculite

TL;DR

This study investigates how chiral amino acids, specifically histidine enantiomers, interact with hydrated vermiculite clay, revealing enantiomer-specific structural changes that could relate to the origin of biological homochirality.

Contribution

It provides experimental evidence of enantiomer-specific interactions between histidine and vermiculite clay, highlighting a potential role of clays in biohomochirality origin.

Findings

D-histidine and L-histidine cause different shifts in clay d-spacing.

The clay's d-spacing responds sensitively to concentration, temperature, and electronic environment.

Chiral specificity observed suggests clays may influence amino acid chirality in prebiotic conditions.

Abstract

Recent work suggests a link between chiral asymmetry in the amino acid iso-valine extracted from the Murchison meteorite and the extent of hydrous alteration. We present the results of neutron scattering experiments on an exchanged, 1-dimensionally ordered n-propyl ammonium vermiculite clay. The vermiculite gel has a (001) d-spacing of order 5nm at the temperature and concentration of the experiments and the d-spacing responds sensitively to changes in concentration, temperature and electronic environment. The data show that isothermal addition of D-histidine or L-histidine solutions produces shifts in the d-spacing that are different for each enantiomer. This chiral specificity is of interest for the question of whether clays could have played an important role in the origin of biohomochirality.