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Cleaves, HJ, Chalmers JH, Lazcano A, Miller SL, Bada JL.  2008.  A reassessment of prebiotic organic synthesis in neutral planetary atmospheres. Origins of Life and Evolution of Biospheres. 38:105-115.   10.1007/s11084-007-9120-3   AbstractWebsite

The action of an electric discharge on reduced gas mixtures such as H(2)O, CH(4) and NH(3) (or N(2)) results in the production of several biologically important organic compounds including amino acids. However, it is now generally held that the early Earth's atmosphere was likely not reducing, but was dominated by N(2) and CO(2). The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient. We show here that contrary to previous reports, significant amounts of amino acids are produced from neutral gas mixtures. The low yields previously reported appear to be the outcome of oxidation of the organic compounds during hydrolytic workup by nitrite and nitrate produced in the reactions. The yield of amino acids is greatly increased when oxidation inhibitors, such as ferrous iron, are added prior to hydrolysis. Organic synthesis from neutral atmospheres may have depended on the oceanic availability of oxidation inhibitors as well as on the nature of the primitive atmosphere itself. The results reported here suggest that endogenous synthesis from neutral atmospheres may be more important than previously thought.

Grutters, M, van Raaphorst W, Epping E, Helder W, de Leeuw JW, Glavin DP, Bada J.  2002.  Preservation of amino acids from in situ-produced bacterial cell wall peptidoglycans in northeastern Atlantic continental margin sediments. Limnology and Oceanography. 47:1521-1524. AbstractWebsite

In this study we present the results of total hydrolysable amino acids (THAA) and amino acid D/L-enantiomers in northeastern Atlantic continental margin sediments. There is increasing evidence that intrinsically labile amino acids are present in old marine sediments as part of a refractory network of peptide-like material. We used amino acid enantiomers to identify the contribution of amino acids from bacterial cell walls to THAA in organic matter ranging from relatively young to 18,000 yr old. The ratio of D/L-amino acids increased with depth in the sediment mixed layer. Application of a transport-racemization-degradation model excludes a significant production of D-amino acids by racemization and implies in situ bacterial production as the main source. Amino acids associated with a refractory pool of bacterial cell walls could account for approximately one third of the THAA deeper in the sediments. We propose that in situ bacterial production and the primary flux of labile organic matter from the water column result in a small but highly reactive pool of amino acids in the surface mixed sediment only, whereas amino acids associated with refractory cell walls persist in marine sediments.

Becker, L, Popp B, Rust T, Bada JL.  1999.  The origin of organic matter in the Martian meteorite ALH84001. Life Sciences: New Insights into Complex Organics in Space. 24( Ehrenfreund P, Robert F, Eds.).:477-488., Oxford: Pergamon Press Ltd   10.1016/s0273-1177(99)00090-3   Abstract

Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta(13) C values for the organic matter associated with the carbonate globules averaged -26 parts per thousand and is attributed to terrestrial contamination. In contrast, the delta(13)C values for the organic matter associated with the bulk matrix material yielded a value of -15 parts per thousand. The only common carbon sources on the Earth that yield similar delta(13) values, other then some diagenetically altered marine carbonates, are C(4) plants. A delta(13)C value of -15 parts per thousand, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bull; matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery of meteoritic or cometary debris to the surface of Mars. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

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.

Keefe, AD, Miller SL, McDonald G, Bada J.  1995.  Investigation of the Prebiotic Synthesis of Amino-Acids and Rna Bases from Co2 Using Fes/H2s as a Reducing Agent. Proceedings of the National Academy of Sciences of the United States of America. 92:11904-11906.   10.1073/pnas.92.25.11904   AbstractWebsite

An autotrophic theory of the origin of metabolism and life has been proposed in which carbon dioxide is reduced by ferrous sulfide and hydrogen sulfide by means of a reversed citric acid cycle, leading to the production of amino acids. Similar processes hale been proposed for purine synthesis. Ferrous sulfide is a strong reducing agent in the presence of hydrogen sulfide and can produce hydrogen as web as reduce alkenes, alkynes, and thiols to saturated hydrocarbons and reduce ketones to thiols. However, the reduction of carbon dioxide has not been demonstrated. We show here that no amino acids, purines, or pyrimidines are produced from carbon dioxide with the ferrous sulfide and hydrogen sulfide system. Furthermore, this system does not produce amino acids from carboxylic acids by reductive amination and carboxylation. Thus, the proposed autotrophic theory, using carbon dioxide, ferrous sulfide, and hydrogen sulfide, lacks the robustness needed to be a geological process and is, therefore, unlikely to have played a role in the origin of metabolism or the origin of life.

Becker, L, Bada JL, Winans RE, Hunt JE, Bunch TE, French BM.  1994.  Fullerenes in the 1.85-Billion-Year-Old Sudbury Impact Structure. Science. 265:642-645.   10.1126/science.11536660   AbstractWebsite

Fullerenes (C-60 and C-70) have been identified by laser desorption, laser desorption postionization, and high-resolution electron-impact mass spectrometry in shock-produced breccias (Onaping Formation) of the Sudbury impact structure in Ontario, Canada, The C-60 isotope is present at a level of a few parts per million. The fullerenes were likely synthesized within the impact plume from the carbon contained in the bolide. The oxidation of the fullerenes during the 1.85 billion years of exposure was apparently prevented by the presence of sulfur in the form of sulfide-silicate complexes associated with the fullerenes.

Chen, RF, Bada JL.  1994.  The Fluorescence of Dissolved Organic-Matter in Porewaters of Marine-Sediments. Marine Chemistry. 45:31-42.   10.1016/0304-4203(94)90089-2   AbstractWebsite

The fluorescence of porewaters from marine sediment cores from six different areas was measured. In most cases, fluorescence was affected primarily by the diagenesis of organic carbon first through sulfate reduction and subsequently by methane generation. Typically, fluorescence, dissolved organic carbon (DOC), absorbance, alkalinity, and ammonium ion concentrations correlate quite well, increasing in the upper sections of anoxic sediments and co-varying in deeper sections of these cores. The good correlation of DOC with fluorescence in the three cores in which DOC was measured indicates that fluorescence can be used to make a first order estimate of DOC concentration in anoxic porewaters. Data are consistent with a model in which labile organic matter in the sediments is broken down by sulfur reducing bacteria to low molecular weight monomers. These monomers are either remineralized to CO2 or polymerize to form dissolved, fluorescent, high molecular weight molecules. The few exceptions to this model involve hydrothermally generated hydrocarbons that are formed in situ in the Guaymas Basin or are horizontally advected along the decollement in the Nankai Trench.

Zenobi, R, Philippoz JM, Zare RN, Wing MR, Bada JL, Marti K.  1992.  Organic-Compounds in the Forest Vale, H4 Ordinary Chondrite. Geochimica Et Cosmochimica Acta. 56:2899-2905.   10.1016/0016-7037(92)90366-q   AbstractWebsite

We have analyzed the H4 ordinary chondrite Forest Vale for polycyclic aromatic hydrocarbons (PAHs) using two-step laser mass spectrometry (L2MS) and for amino acids using a standard chromatographic method. Indigenous PAHs were identified in the matrices of freshly cleaved interior faces but could not be detected in pulverized silicates and chondrules. No depth dependence of the PAHs was found in a chipped interior piece. Amino acids, taken from the entire sample, consisted of protein amino acids that were nonracemic, indicating that they are terrestrial contaminants. The presence of indigenous PAHs and absence of indigenous amino acids provides support for the contention that different processes and environments contributed to the synthesis of the organic matter in the solar system.

Chen, RF, Bada JL.  1992.  The Fluorescence of Dissolved Organic-Matter in Seawater. Marine Chemistry. 37:191-221.   10.1016/0304-4203(92)90078-o   AbstractWebsite

A total of 28 vertical profiles of seawater fluorescence was measured in the Sargasso Sea, the Straits of Florida, the Southern California Borderlands, and the central Pacific Ocean. In all cases, surface seawater fluorescence was low as a result of photochemical bleaching which occurs on the timescale of hours. Fluorescence of deep water was 2-2.5 times higher than that of surface waters, and was constant, implying a long residence time for fluorescent organic matter, possibly of the order of thousands of years. Fluorescence correlates well with nutrients (NO3-, PO43-) in mid-depth waters ( 100-1000 m) in the Sargasso Sea and the central North Pacific, consistent with results in the central Pacific and the coastal seas of Japan. This suggests that regeneration or formation of fluorescent materials accompanies the oxidation and remineralization of settling organic particles. The various sources and sinks of fluorescent organic matter in the global oceans are assessed. The major sources are particles and in situ formation; rivers, rain, diffusion from sediments, and release from organisms are minor sources. The major sink is photochemical bleaching.