P053-0001
The Origins of Enantiomer Excesses in Meteoritic Organic Compounds: Were Some Reaction Mechanisms Directed by Ambient Magnetic and Radiation Fields?

Monday, 14 December 2020
Poster
George Cooper, NASA Ames Research Center, Exobiology and the Center for the Emergence of Life, Moffett Field, CA, United States, William m Jackson, U.C. Davis, chemistry, Davis, CA, United States, Andro c Rios, Blue Marble Space Institute of Science, Center for the Emergence of Life; Exobiology, NASA Ames Research Center, Moffett Field, CA, United States, Katie j Yeung, NASA Ames Research Center, Exobiology, Mofftett Field, United States and Christopher E Dateo, NASA Ames Research Center, Exobiology, Moffett Field, CA, United States
Abstract:
Carbonaceous meteorites (chondrites) contain an array of soluble organic compounds including amino acids and sugar derivatives [1]. Many of these are thought to have formed through aqueous phase chemistry in meteorite parent bodies. However, the presence of multiple other stars at (or before) the birth of the solar system [2] indicates that sufficient ambient radiation was also available for chemical synthesis. Could ubiquitous physical forces such as radiation and magnetism have affected the molecular properties of compounds needed for subsequent life?

One such property involves the mirror-image (chiral) properties of individual organic compounds. In particular, homochirality, the exclusive use of only one mirror image (enantiomer) of compounds in bio-polymers such as proteins and nucleic acids, could have origins in the early influence of the above forces. Can homochirality, or at least enantiomer excesses (EE), be produced in larger compounds through synthesis from smaller and simple (one- and two-carbon) precursors in such a natural system? If so, what are the relevant synthetic mechanisms? This work, the synthesis of sugar-related compounds in radiation and magnetic fields (and utilizing isotopically labeled reactants) is an attempt to understand possible EE production and related mechanisms.

Reaction mixtures were analyzed by gas chromatography-mass spectrometry (GC-MS) [3] and liquid chromatography-mass spectrometry (LC-MS). Figure 1 shows the result of one experiment with a reversal of magnetic fields (+B, -B). Mass spectra (not shown) of the resulting four-carbon compounds, erythrose (D and L) and erythronic acid (D and L) show that the positions of 13C labels corroborate the scheme in Figure 1. CH2O Addition to carbon #3 yields a new chiral center furthest down the chain which, by convention, designates a “D” or “L” sugar. Asymmetric influence at this step could theoretically create an enantiomer excess.

References: [1] Pizzarello S., Cooper G. W., Flynn G. J. (2006) In "meteorites and the early Solar System II". D. Lauretta, L. A. Leshin, and H. Y. McSween Jr., Eds. University of Arizona Press. [2] Sandford S. A., et al. (2020) Chemical Reviews 120, 4616–4659. [3] Cooper G., Yim S., Lanoiselée J., Sorden S., Ramirez F. G. (2019) J. Chrom. B. 1126, 121761.

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