Intrinsic asymmetries of amino acid enantiomers and their peptides: A possible role in the origin of biochirality

Abstract

L-amino acids and D-carbohydrates were incorporated into the first forms of life over 3.5 billion years ago, presumably from racemic mixtures of organic solutes produced by abiotic synthetic pathways. The process by which this choice occurred has not been established, but a consensus view is that it was a chance event, such that life could equally well have used D-amino acids and L sugars. In this review we will explore a second, less plausible alternative that minute differences in the physical properties of certain enantiomers made it more likely that L-amino acids and D-carbohydrates would be incorporated into early life. By all classical criteria, chiral isomers are perfect mirror image structures and, therefore, are expected to be identical in their macroscopic properties. However, scattered reports in the literature suggest that there may be slight differences in the physical properties of L- and D-amino acids and their polymers, which could lead to a preferred incorporation of L-amino acids into primitive forms of life. Here we present a literature survey of this issue and discuss its possible role in the origin of biochirality.

Origin, Microbiology, Nutrition, and Pharmacology of D‐Amino Acids

“…A review of the literature on cycles of solvation, crystallization, and adsorption processes in the primordial environments (geochromatography) suggests that very small differences in the physical properties of some enantiomers may account for the enhanced formation of pure l-enantiomers, as well as for the preferential incorporation of LAAs and d-carbohydrates into early life forms [5].…”

Nickel Complexes of Alanine Having a Preference for One Chiral Form over Another upon Crystallization

“…Unexpected differences between D and L enantiomers of amino acids, peptides and sugars have recently been investigated. [2][3][4][5][6][7] The differential rates of D-and L-tyrosine crystallization was also reported. 8 Nickel and iron are the most abundant transition metals in the earth's crust.…”

Information Storage in Liquids with Ordered Molecular Assemblies

“…Another particular information storage, corresponds to the somewhat unexpected chiral discrimination between solutions of opposite enantiomers [7,9,17] (compare, for example, the values presented in Table 1). It presumably originated from an intrinsic asymmetry between enantiomers which is extrapolated into their solutions [18]. Through such discrimination, one could ascribe absolute directions to right versus left in space [19], a long standing problem in space coordinates.…”