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Molecular Asymmetry and Life Detection Astrobiology Science Conference 2010 sess503.pdf Thursday, April 29, 2010 ORIGINS OF MOLECULAR ASYMMETRY, HOMOCHIRALITY, AND LIFE DETECTION 8:00 a.m. Crystal Salon E This session will discuss the role of homochirality in life, theoretical models and experiments that elucidate potential mechanisms for chiral symmetry breaking and amplification, and current life detection strategies and instrumentation. Chairs: Daniel Glavin Henry Sun 8:00 a.m. Breslow R. * Filling the Gaps in the Likely Origin of Prebiotic Homochirality on Earth [#5660] Under credible prebiotic conditions, the small excesses of L alphamethyl amino acids in some meteorites can produce L excesses in normal amino acids, which can be amplified to near homochirality. Related results have also been demonstrated for the formation of D sugars. 8:15 a.m. Popa R. Cimpoiasu V. M. Scorei R. I. * The Origin of Homochirality in Amino Acids Through Weak Neutral Currents and Ortho:Para Disequilibrium in the Amino Group [#5359] We report finding chiral disruption in the amino acid Asparagine. Our model is based on weak neutral currents from the chiral center producing L-D-asymmetric organization of the amino group. This effect 17 1 is measurable by H2 O-TD- HNMR. 8:30 a.m. Glavin D. P. * Callahan M. P. Dworkin J. P. L-Amino Acid Enrichments in Carbonaceous Meteorites: Implications for the Origin of Biological Homochirality [#5004] Large left handed excesses of the amino acid isovaline ranging from 15% to 29% found in aqueous altered carbonaceous meteorites suggests that water played an important role in the amplification of amino acid asymmetry on the parent body. 8:45 a.m. Pizzarello S. * Wang H. Hydroxyacid Molecular and Isotopic Composition in CR and CM Chondrites: Similarities and Distinctions [#5088] The molecular, chiral and isotopic composition of chondritic hydroxy acids is described. New findings of molecular asymmetry in these compounds will be discussed. 9:00 a.m. Sun H. J. * Use of Alternative Enantiomers by Life on Earth [#5574] The chirality barrier in amino acids and lactic acid has been overcome on Earth by racemases. For the metabolism of sugars (glucose and xylose), the “mirror” is intact. These findings complicate chirality based approaches to life detection. 9:15 a.m. Davies P. C. W. * Mirror Life and a Shadow Biosphere [#5110] If life emerges readily in earthlike conditions then it should have started many times on our home planet, opening up the possibility that Earth hosts a “shadow biosphere” of alternative life that may still exist today. I discuss ways to seek evidence for this. 9:30 a.m. Levin G. V. * Can Chirality Give Proof of Extinct or Extant Life? [#5143] A new, unambigious method to detect living microorganisms through chiral preference of enantiomeric substrates and multiple controls is presented. Astrobiology Science Conference 2010 sess503.pdf 9:45 a.m. Thiemann W. H. P. * Bredehoeft J. H. Meierhenrich U. J. Goesmann F. Enantioselective Instruments Onboard Rosetta Lander (COSAC) and Mission ExoMars (MOMA) [#5076] Space missions so far never included enantioselective instruments to distinguish between chiral organic molecules. We will describe the first enantioselective gas chromatographic device COSAC and MOMA that we developed for Rosetta and ExoMars missions. 10:00 a.m. Bada J. L. * Aubrey A. D. Mathies R. A. Grunthaner F. J. “Follow the Nitrogen” Strategy for In Situ Astrobiological Investigations on Mars [#5535] Based on the ubiquitous occurrence of amino acids and other nitrogenous organic compounds in terrestrial biology, “Follow the Nitrogen” provides the central framework in strategies required for the search for life beyond Earth. 10:15 a.m. BREAK .
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