title: Selective adsorption of L- and D-amino acids on calcite: Implications for biochemical homochirality.
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.
authors.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
authors.forename: R M
authors.initials: RM
authors.lastname: Hazen
authors.forename: T R
authors.initials: TR
authors.lastname: Filley
authors.forename: G A
authors.initials: GA
authors.lastname: Goodfriend
mesh_terms: D000327:Adsorption; D000596:Amino Acids / Q000378:metabolism*; D002119:Calcium Carbonate / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D002119:Calcium Carbonate