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Paper: Enigmatic Isovaline: Investigating the Stability, Racemization, and Formation of a Non-Biological Meteoritic Amino Acid
Volume: 420, Bioastronomy 2007: Molecules, Microbes and Extraterrestrial Life
Page: 157
Authors: Hudson, R. L.; Lewis, A. S.; Moore, M. H.; Dworkin, J. P.; Martin, M. P.
Abstract: Among the Murchison meteoritic amino acids, isovaline stands out as being both non-biological (non-protein) and having a relatively high abundance. While approximately equal amounts of D- and L-isovaline have been reported in Murchison and other CM meteorites, the molecule’s structure appears to prohibit its racemization in aqueous solutions. We recently have investigated the low-temperature solid-phase chemistry of both isovaline and valine with an eye toward each molecule’s formation, stability, and possible interconversions of D and L enantiomers. Ion-irradiated isovaline- and valine-containing ices were examined by IR spectroscopy and highly-sensitive liquid chromatography/time-of-flight mass spectral methods to assess both amino acid destruction and racemization. Samples were studied in the presence and in the absence of water-ice, and the destruction of both isovaline and valine was measured as a function of radiation dose. In addition, we have undertaken experiments to synthesize isovaline, valine, and their amino acid isomers by solid-phase radiation-chemical pathways other than the oft-invoked Strecker process.
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