Photochirogenesis: Photochemical Models on the Origin of Biomolecular Homochirality

Abstract

Current research focuses on a better understanding of the origin of biomolecular asymmetry by the identification and detection of the possibly first chiral molecules that were involved in the appearance and evolution of life on Earth. We have reasons to assume that these molecules were specific chiral amino acids. Chiral amino acids have been identified in both chondritic meteorites and simulated interstellar ices. Present research reasons that circularly polarized electromagnetic radiation was identified in interstellar environments and an asymmetric interstellar photon-molecule interaction might have triggered biomolecular symmetry breaking. We review on the possible prebiotic interaction of 'chiral photons' in the form of circularly polarized light, with early chiral organic molecules. We will highlight recent studies on enantioselective photolysis of racemic amino acids by circularly polarized light and experiments on the asymmetric OPEN ACCESS Symmetry 2010, 2 1056 photochemical synthesis of amino acids from only one C and one N containing molecules by simulating interstellar environments. Both approaches are based on circular dichroic transitions of amino acids that will be presented as well.

Sites that Can Produce Left-handed Amino Acids in the Supernova Neutrino Amino Acid Processing Model

“…Perhaps the best developed one is the Circularly Polarized Light (CPL) model, which relies on ultraviolet CPL, produced by first scattering the light from an extremely hot star to polarize it, then letting it process the amino acids. It was first suggested by Flores et al (1977) and Norden (1977), and subsequently elaborated in detail by many groups (Rubenstein et al 1983;Bailey et al 1998;Meierhenrich et al 2005;Takano et al 2007;Meierhenrich 2008;Takahashi et al 2009;Meierhenrich et al 2010;Meinert et al 2010;de Marcellus et al 2011;Meinert et al 2012Meinert et al , 2014. Although there are certainly other suggested explanations for the origin of a preferred amino acid chirality in outer space, we believe that they are less well developed than either the CPL model or the SNAAP model.…”

Supernovae, Neutrinos and the Chirality of Amino Acids

“…One suggested mechanism lies with processing of a population of amino acids, or of their chiral precursors, by circularly polarized light [18][19][20][21][22][23]; this could select one chirality over the other. However, this solution does not easily explain why it would select the same chirality in every situation, as is apparently observed (albeit with limited statistics), or why the physical conditions that would select one form in one place would not select the other in a different location.…”

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

“…Moreover, carboxylic acids have been also produced in low amount during UV photoprocessing of interstellar ice analogs (113), i.e., by slow deposition of simple mixtures of CO, NH 3 , and H 2 O, with formation, among others, of 30 and 32 (114). In this latter case, radical mechanisms involving nitrogen and carbon-centered species have been hypothesized (115). The addition of •CN to unsaturated hydrocarbons to give nitriles followed by reaction with ketene is another possible mechanism for the synthesis of meteoritic carboxylic acids.…”