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2002
Kminek, G, Botta O, Glavin DP, Bada JL.  2002.  Amino acids in the Tagish Lake meteorite. Meteoritics & Planetary Science. 37:697-701. AbstractWebsite

High-performance liquid chromatography (HPLC) based amino acid analysis of a Tagish Lake meteorite sample recovered 3 months after the meteorite fell to Earth have revealed that the amino acid composition of Tagish Lake is strikingly different from that of the CM and Cl carbonaceous chondrites. We found that the Tagish Lake meteorite contains only trace levels of amino acids (total abundance = 880 ppb), which is much lower than the total abundance of amino acids in the Cl Orgueil (4100 ppb) and the CM Murchison (16 900 ppb). Because most of the same amino acids found in the Tagish Lake meteorite are also present in the Tagish Lake ice melt water, we conclude that the amino acids detected in the meteorite are terrestrial contamination. We found that the exposure of a sample of Murchison to cold water lead to a substantial reduction over a period of several weeks in the amount of amino acids that are not strongly bound to the meteorite matrix. However, strongly bound amino acids that are extracted by direct HCl hydrolysis are not affected by the leaching process. Thus even if there had been leaching of amino acids from our Tagish Lake meteorite sample during its 3 month residence in Tagish Lake ice and melt water, a Murchison type abundance of endogenous amino acids in the meteorite would have still been readily detectable. The low amino acid content of Tagish Lake indicates that this meteorite originated from a different type of parent body than the CM and CI chondrites. The parent body was apparently devoid of the reagents such as aldehyldes/ketones, HCN and ammonia needed for the effective abiotic synthesis of amino acids. Based on reflectance spectral measurements, Tagish Lake has been associated with P- or D-type asteroids. If the Tagish Lake meteorite was indeed derived from these types of parent bodies, our understanding of these primitive asteroids needs to be reevaluated with respect to their potential inventory of biologically important organic compounds.

2001
Glavin, DP, Schubert M, Botta O, Kminek G, Bada JL.  2001.  Detecting pyrolysis products from bacteria on Mars. Earth and Planetary Science Letters. 185:1-5.   10.1016/s0012-821x(00)00370-8   AbstractWebsite

A pyrolysis/sublimation technique was developed to isolate volatile amine compounds from a Mars soil analogue inoculated with similar to 10 billion Escherichia coli cells. In this technique, the inoculated soil is heated to 500 degreesC for several seconds at Martian ambient pressure and the sublimate, collected by a cold finger, then analyzed using high performance liquid chromatography. Methylamine and ethylamine, produced from glycine and alanine decarboxylation, were the most abundant amine compounds detected after pyrolysis of the cells. A heating cycle similar to that utilized in our experiment was also used to release organic compounds from the Martian soil in the 1976 Viking gas chromatography/mass spectrometry (GC/MS) pyrolysis experiment. The Viking GC/MS did not detect any organic compounds of Martian origin above a level of a few parts per billion in the Martian surface soil. Although the Viking GC/MS instruments were not specifically designed to search for the presence of living cells on Mars, our experimental results indicate that at the part per billion level, the degradation products generated from several million bacterial cells per gram of Martian soil would not have been detected. (C) 2001 Elsevier Science B.V. All rights reserved.

1999
Hutt, LD, Glavin DP, Bada JL, Mathies RA.  1999.  Microfabricated capillary electrophoresis amino acid chirality analyzer for extraterrestrial exploration. Analytical Chemistry. 71:4000-4006.   10.1021/ac9903959   AbstractWebsite

Chiral separations of fluorescein isothiocyanate-labeled amino acids have been performed on a microfabricated capillary electrophoresis chip to explore the feasibility of using such devices to analyze for extinct or extant life signs in extraterrestrial environments. The test system consists of a folded electrophoresis channel (19.0 cm long x 150 mu m wide x 20 mu m deep) that was photolithographically fabricated in a 10-cm-diameter glass wafer sandwich, coupled to a laser-excited confocal fluorescence detection apparatus providing subattomole sensitivity. Using a sodium dodecyl sulfate/gamma-cyclodextrin pH 10.0 carbonate electrophoresis buffer and a separation voltage of 550 V/cm at 10 degrees C, baseline resolution was observed for Val, Ala, Glu, and Asp enantiomers and Gly in only 4 min. Enantiomeric ratios were determined for amino acids extracted from the Murchison meteorite, and these values closely matched values determined by HPLC. These results demonstrate the feasibility of using microfabricated lab-on-a-chip systems to analyze extraterrestrial samples for amino acids.

1991
Wing, MR, Bada JL.  1991.  Geochromatography on the Parent Body of the Carbonaceous Chondrite Ivuna. Geochimica Et Cosmochimica Acta. 55:2937-2942.   10.1016/0016-7037(91)90458-h   AbstractWebsite

Ivuna, a CI carbonaceous chondrite, has been found to contain abundant amounts of the three-ring polycyclic aromatic hydrocarbons (PAHs) phenanthrene/anthracene, but no detectable levels of the two- and four-ring PAHs naphthalene and pyrene/fluoranthene. Either the three-ring PAHs in Ivuna were synthesized in a process that did not produce the two- or four-ring PAHs, or all these compounds were synthesized together and subsequently separated. Thermodynamical considerations and studies of hydrocarbon pyrolysis and combustion do not support the former possibility. Ivuna and other CI carbonaceous chondrites are known to have been extensively altered by water. The aqueous solubilities suggest that some PAHs would have been mobilized during the aqueous alteration phase in carbonaceous meteorite parent bodies. In a model geochromatography experiment, naphthalene, phenanthrene, and pyrene were partially resolved at a low pressure and flow rate utilizing columns containing crushed serpentine or beach sand, and water for elution. This laboratory geochromatography experiment suggests that complete separation of PAHs could be expected to occur in the parent body of CI carbonaceous chondrites. Such processes on Earth are known to lead to the formation of hydrothermal PAH minerals such as pendletonite. It is proposed that aqueous fluids driven by heat in the parent body of Ivuna migrated from the interior to the surface, in the process transporting, separating, and concentrating PAHs at various zones in the parent body.