Selective adsorption of L- and D-amino acids on calcite: Implications for biochemical homochirality |
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| Authors: | Hazen R M Filley T R Goodfriend G A |
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| Affiliation: | Geophysical Laboratory and National Aeronautics and Space Administration Astrobiology Institute, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA. hazen@gl.ciw.edu |
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| Abstract: | The emergence of biochemical homochirality was a key step in the origin of life, yet prebiotic mechanisms for chiral separation are not well constrained. Here we demonstrate a geochemically plausible scenario for chiral separation of amino acids by adsorption on mineral surfaces. Crystals of the common rock-forming mineral calcite (CaCO(3)), when immersed in a racemic aspartic acid solution, display significant adsorption and chiral selectivity of d- and l-enantiomers on pairs of mirror-related crystal-growth surfaces. This selective adsorption is greater on crystals with terraced surface textures, which indicates that d- and l-aspartic acid concentrate along step-like linear growth features. Thus, selective adsorption of linear arrays of d- and l-amino acids on calcite, with subsequent condensation polymerization, represents a plausible geochemical mechanism for the production of homochiral polypeptides on the prebiotic Earth. |
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