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Kminek, G, Bada JL.  2006.  The effect of ionizing radiation on the preservation of amino acids on Mars. Earth and Planetary Science Letters. 245:1-5.   10.1016/j.epsl.2006.03.008   AbstractWebsite

Amino acids are excellent biomarkers in the search for life on Mars because they are essential for biology as we know it and they are robust enough to survive for billions of years in the cold and dry Martian environment. However, amino acids and other organic compounds on Mars are exposed to the ionizing radiation from space and from the decay of radionuclides. This process and its role in the preservation of organic compounds has not been adequately addressed in the past. Based on measured radiolysis constants of amino acids and radiation dose estimates for Mars we show that the detection of an amino acid signature derived from an early Martian biosphere is not limited by its radiolytic decomposition as long as the amino acids are shielded adequately from space radiation. This indicates clearly the need to access the Martian subsurface in the search for molecular traces of an extinct Martian biosphere. (c) 2006 Elsevier B.V. All rights reserved.

Bada, JL.  2009.  Enantiomeric excesses in the Murchison meteorite and the origin of homochirality in terrestrial biology. Proceedings of the National Academy of Sciences of the United States of America. 106:E85-E85.   10.1073/pnas.0906490106   Website
Parker, ET, Cleaves HJ, Callahan MP, Dworkin JP, Glavin DP, Lazcano A, Bada JL.  2011.  Enhanced Synthesis of Alkyl Amino Acids in Miller's 1958 H2S Experiment. Origins of Life and Evolution of Biospheres. 41:569-574.   10.1007/s11084-011-9253-2   AbstractWebsite

Stanley Miller's 1958 H2S-containing experiment, which included a simulated prebiotic atmosphere of methane (CH4), ammonia (NH3), carbon dioxide (CO2), and hydrogen sulfide (H2S) produced several alkyl amino acids, including the alpha-, beta-, and gamma-isomers of aminobutyric acid (ABA) in greater relative yields than had previously been reported from his spark discharge experiments. In the presence of H2S, aspartic and glutamic acids could yield alkyl amino acids via the formation of thioimide intermediates. Radical chemistry initiated by passing H2S through a spark discharge could have also enhanced alkyl amino acid synthesis by generating alkyl radicals that can help form the aldehyde and ketone precursors to these amino acids. We propose mechanisms that may have influenced the synthesis of certain amino acids in localized environments rich in H2S and lightning discharges, similar to conditions near volcanic systems on the early Earth, thus contributing to the prebiotic chemical inventory of the primordial Earth.

Bada, JL, Miller SL.  1968.  Equilibrium Constant for Reversible Deamination of Aspartic Acid. Biochemistry. 7:3403-&.   10.1021/bi00850a014   Website
Cleaves, HJ, Aubrey AD, Bada JL.  2009.  An Evaluation of the Critical Parameters for Abiotic Peptide Synthesis in Submarine Hydrothermal Systems. Origins of Life and Evolution of Biospheres. 39:109-126.   10.1007/s11084-008-9154-1   AbstractWebsite

It has been proposed that oligopeptides may be formed in submarine hydrothermal systems (SHSs). Oligopeptides have been synthesized previously under simulated SHS conditions which are likely geochemically implausible. We have herein investigated the oligomerization of glycine under SHS-like conditions with respect to the limitations imposed by starting amino acid concentration, heating time, and temperature. When 10(-1) M glycine solutions were heated at 250A degrees C for < 20 min glycine oligomers up to tetramers and diketopiperazine (DKP) were detectable. At 200A degrees C, less oligomerization was noted. Peptides beyond glycylglycine (gly(2)) and DKP were not detected below 150A degrees C. At 10(-2) M initial glycine concentration and below, only gly(2), DKP, and gly(3) were detected, and then only above 200A degrees C at < 20 min reaction time. Gly(3) was undetectable at longer reaction times. The major parameters limiting peptide synthesis in SHSs appear to be concentration, time, and temperature. Given the expected low concentrations of amino acids, the long residence times and range of temperatures in SHSs, it is unlikely that SHS environments were robust sources of even simple peptides. Possible unexplored solutions to the problems presented here are also discussed.

Ehrenfreund, P, Glavin DP, Botta O, Cooper G, Bada JL.  2001.  Extraterrestrial amino acids in Orgueil and Ivuna: Tracing the parent body of Cl type carbonaceous chondrites. Proceedings of the National Academy of Sciences of the United States of America. 98:2138-2141.   10.1073/pnas.051502898   AbstractWebsite

Amino acid analyses using HPLC of pristine interior pieces of the Cl carbonaceous chondrites Orgueil and Ivuna have found that beta -alanine, glycine, and gamma -amino-n-butyric acid (ABA) are the most abundant amino acids in these two meteorites, with concentrations ranging from approximate to 600 to 2,000 parts per billion (ppb). Other alpha -amino acids such as alanine, alpha -ABA, alpha -aminoisobutyric acid (AIB), and isovaline are present only in trace amounts (<200 ppb). Carbon isotopic measurements of -alanine and glycine and the presence of racemic (D/L approximate to 1) alanine and beta -ABA in Orgueil suggest that these amino acids are extraterrestrial in origin. In comparison to the CM carbonaceous chondrites Murchison and Murray, the amino acid composition of the Cls is strikingly distinct, suggesting that these meteorites came from a different type of parent body, possibly an extinct comet, than did the CM carbonaceous chondrites.

Glavin, DP, Aubrey AD, Callahan MP, Dworkin JP, Elsila JE, Parker ET, Bada JL, Jenniskens P, Shaddad MH.  2010.  Extraterrestrial amino acids in the Almahata Sitta meteorite. Meteoritics & Planetary Science. 45:1695-1709.   10.1111/j.1945-5100.2010.01094.x   AbstractWebsite

Amino acid analysis of a meteorite fragment of asteroid 2008 TC(3) called Almahata Sitta was carried out using reverse-phase liquid chromatography coupled with UV fluorescence detection and time-of-flight mass spectrometry (LC-FD/ToF-MS) as part of a sample analysis consortium. LC-FD/ToF-MS analyses of hot-water extracts from the meteorite revealed a complex distribution of two- to seven-carbon aliphatic amino acids and one- to three-carbon amines with abundances ranging from 0.5 to 149 parts-per-billion (ppb). The enantiomeric ratios of the amino acids alanine, beta-amino-n-butyric acid, 2-amino-2-methylbutanoic acid (isovaline), and 2-aminopentanoic acid (norvaline) in the meteorite were racemic (d/l similar to 1), indicating that these amino acids are indigenous to the meteorite and not terrestrial contaminants. Several other nonprotein amino acids were also identified in the meteorite above background levels including alpha-aminoisobutyric acid (alpha-AIB), 4-amino-2-methylbutanoic acid, 4-amino-3-methylbutanoic acid, and 3-, 4-, and 5-aminopentanoic acid. The total abundances of isovaline and alpha-AIB in Almahata Sitta are approximately 1000 times lower than the abundances of these amino acids found in the CM carbonaceous chondrite Murchison. The extremely low abundances and unusual distribution of five-carbon amino acids in Almahata Sitta compared to CI, CM, and CR carbonaceous chondrites may reflect extensive thermal alteration of amino acids on the parent asteroid by partial melting during formation or subsequent impact shock heating. It is also possible that amino acids were synthesized by catalytic reactions on the parent body after asteroid 2008 TC(3) cooled to lower temperatures, or introduced as a contaminant from unrelated meteorite clasts and chemically altered by alpha-decarboxylation.

Becker, L, Poreda RJ, Bada JL.  1996.  Extraterrestrial helium trapped in fullerenes in the sudbury impact structure. Science. 272:249-252.   10.1126/science.272.5259.249   AbstractWebsite

Fullerenes (C-60 and C-70) in the Sudbury impact structure contain trapped helium with a He-3/He-4 ratio of 5.5 x 10(-4) to 5.9 x 10(-4). The He-3/He-4 ratio exceeds the accepted solar wind value by 20 to 30 percent and is higher by an order of magnitude than the maximum reported mantle value, Terrestrial nuclear reactions or cosmic-ray bombardment are not sufficient to generate such a high ratio. The He-3/He-4 ratios in the Sudbury fullerenes are similar to those found in meteorites and in some interplanetary dust particles. The implication is that the helium within the C-60 molecules at Sudbury is of extraterrestrial origin.

Botta, O, Bada JL.  2002.  Extraterrestrial organic compounds in meteorites. Surveys in Geophysics. 23:411-467.   10.1023/a:1020139302770   AbstractWebsite

Many organic compounds or their precursors found in meteorites originated in the interstellar or circumstellar medium and were later incorporated into planetesimals during the formation of the solar system. There they either survived intact or underwent further processing to synthesize secondary products on the meteorite parent body. The most distinct feature of CI and CM carbonaceous chondrites, two types of stony meteorites, is their high carbon content (up to 3% of weight), either in the form of carbonates or of organic compounds. The bulk of the organic carbon consists of an insoluble macromolecular material with a complex structure. Also present is a soluble organic fraction, which has been analyzed by several separation and analytical procedures. Low detection limits can be achieved by derivatization of the organic molecules with reagents that allow for analysis by gas chromatography/mass spectroscopy and high performance liquid chromatography. The CM meteorite Murchison has been found to contain more than 70 extraterrestrial amino acids and several other classes of compounds including carboxylic acids, hydroxy carboxylic acids, sulphonic and phosphonic acids, aliphatic, aromatic and polar hydrocarbons, fullerenes, heterocycles as well as carbonyl compounds, alcohols, amines and amides. The organic matter was found to be enriched in deuterium, and distinct organic compounds show isotopic enrichments of carbon and nitrogen relative to terrestrial matter.

Miller, SL, Bada JL.  1991.  Extraterrestrial Synthesis. Nature. 350:387-388.   10.1038/350387b0   Website