Enantioselective Crystallization of Sodium Chlorate in the Presence of Racemic Hydrophobic Amino Acids and Static Magnetic Fields

María-Paz Zorzano,Marta Ruiz-Bermejo,Susana Osuna-Esteban,Sabino Veintemillas-Verdaguer,Cesar Menor-Salván

doi:10.3390/challe5010175

María-Paz Zorzano, Marta Ruiz-Bermejo + Show 3 more

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https://doi.org/10.3390/challe5010175

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Abstract

We study the bias induced by a weak (200 mT) external magnetic field on the preferred handedness of sodium chlorate crystals obtained by slow evaporation at ambient conditions of its saturated saline solution with 20 ppm of added racemic (dl) hydrophobic amino acids. By applying the Fisher test to pairs of experiments with opposing magnetic field orientation we conclude, with a confidence level of 99.7%, that at the water-air interface of this saline solution there is an enantioselective magnetic interaction that acts upon racemic mixtures of hydrophobic chiral amino acids. This interaction has been observed with the three tested racemic hydrophobic amino acids: dl-Phe, dl-Try and dl-Trp, at ambient conditions and in spite of the ubiquitous chiral organic contamination. This enantioselective magnetic dependence is not observed when there is only one handedness of added chiral amino-acid, if the added amino acid is not chiral or if there is no additive. This effect has been confirmed with a double blind test. This novel experimental observation may have implications for our view of plausible initial prebiotic scenarios and of the roles of the geomagnetic field in homochirality in the biosphere.

Highlights

All the organic chemistry of terrestrial organisms is based on the L form of amino acids
We propose to use the crystallization of sodium chlorate NaClO3 as a probe for plausible amino acid enantiomeric interactions at this interface
Providing a detailed physicochemical molecular model of the water-air interface processes and energy differences associated to a plausible interaction between amino acids, water molecules, solvent saline ions, unavoidable metallic impurities and external magnetic field is beyond the scope of this experimental work

Summary

Introduction

All the organic chemistry of terrestrial organisms is based on the L form of amino acids. Despite much effort devoted to elucidating how and why L-amino acids were preferentially selected with respect to the D-enantiomer no clear solution has yet been obtained [1]. Some enantioselective mechanisms have been proposed none of them deal with organic molecules in plausible prebiotic Earth environments [2,3,4]. In the prebiotic chemistry research community, there is no unique, single, universal model of the prebiotic environmental conditions. All plausible situations are explored experimentally because they may be representative of the present or past environmental conditions in the ancient Earth and because they may be relevant to investigate the habitability of other outer Earth environments, such as

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