Publications

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1996
Bada, JL, McDonald GD.  1996.  Detecting amino acids on Mars. Analytical Chemistry. 68:A668-A673.Website
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.

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.

2005
Skelley, AM, Scherer JR, Aubrey AD, Grover WH, Ivester RHC, Ehrenfreund P, Grunthaner FJ, Bada JL, Mathies RA.  2005.  Development and evaluation of a microdevice for amino acid biomarker detection and analysis on Mars. Proceedings of the National Academy of Sciences of the United States of America. 102:1041-1046.   10.1073/pnas.0406798102   AbstractWebsite

The Mars Organic Analyzer (MOA), a microfabricated capillary electrophoresis (CE) instrument for sensitive amino acid biomarker analysis, has been developed and evaluated. The microdevice consists of a four-wafer sandwich combining glass CE separation channels, microfabricated pneumatic membrane valves and pumps, and a nanoliter fluidic network. The portable MOA instrument integrates high voltage CE power supplies, pneumatic controls, and fluorescence detection optics necessary for field operation. The amino acid concentration sensitivities range from micromolar to 0.1 nM, corresponding to part-per-trillion sensitivity. The MOA was first used in the lab to analyze soil extracts from the Atacama Desert, Chile, detecting amino acids ranging from 10-600 parts per billion. Field tests of the MOA in the Panoche Valley, CA, successfully detected amino acids at 70 parts per trillion to 100 parts per billion in jarosite, a sulfate-rich mineral associated with liquid water that was recently detected on Mars. These results demonstrate the feasibility of using the MOA to perform sensitive in situ amino acid biomarker analysis on soil samples representative of a Mars-like environment.

2006
Aubrey, A, Cleaves HJ, Chalmers JH, Skelley AM, Mathies RA, Grunthaner FJ, Ehrenfreund P, Bada JL.  2006.  Sulfate minerals and organic compounds on Mars. Geology. 34:357-360.   10.1130/g22316.1   AbstractWebsite

Strong evidence for evaporitic sulfate minerals such as gypsum and jarosite has recently been found on Mars. Although organic molecules are often codeposited with terrestrial evaporitic minerals, there have been no systematic investigations of organic components in sulfate minerals. We report here the detection of organic material, including amino acids and their amine degradation products, in ancient terrestrial sulfate minerals. Amino acids and amines appear to be preserved for geologically long periods in sulfate mineral matrices. This suggests that sulfate minerals should be prime targets in the search for organic compounds, including those of biological origin, on Mars.

2009
Schwarz, C, Debruyne R, Kuch M, McNally E, Schwarcz H, Aubrey AD, Bada J, Poinar H.  2009.  New insights from old bones: DNA preservation and degradation in permafrost preserved mammoth remains. Nucleic Acids Research. 37:3215-3229.   10.1093/nar/gkp159   AbstractWebsite

Despite being plagued by heavily degraded DNA in palaeontological remains, most studies addressing the state of DNA degradation have been limited to types of damage which do not pose a hindrance to Taq polymerase during PCR. Application of serial qPCR to the two fractions obtained during extraction (demineralization and protein digest) from six permafrost mammoth bones and one partially degraded modern elephant bone has enabled further insight into the changes which endogenous DNA is subjected to during diagenesis. We show here that both fractions exhibit individual qualities in terms of the prevailing type of DNA (i.e. mitochondrial versus nuclear DNA) as well as the extent of damage, and in addition observed a highly variable ratio of mitochondrial to nuclear DNA among the six mammoth samples. While there is evidence suggesting that mitochondrial DNA is better preserved than nuclear DNA in ancient permafrost samples, we find the initial DNA concentration in the bone tissue to be as relevant for the total accessible mitochondrial DNA as the extent of DNA degradation post-mortem. We also evaluate the general applicability of indirect measures of preservation such as amino-acid racemization, bone crystallinity index and thermal age to these exceptionally well-preserved samples.

2016
Parker, ET, Cleaves HJ, Bada JL, Fernandez FM.  2016.  Quantitation of alpha-hydroxy acids in complex prebiotic mixtures via liquid chromatography/tandem mass spectrometry. Rapid Communications in Mass Spectrometry. 30:2043-2051.   10.1002/rcm.7684   AbstractWebsite

RationaleSpark discharge experiments, like those performed by Stanley Miller in the 1950s, generate complex, analytically challenging mixtures that contain biopolymer building blocks. Recently, -amino acids and -hydroxy acids (AHAs) were subjected to environmental cycling to form simple depsipeptides (peptides with both amide and ester linkages). The synthesis of AHAs under possible primordial environments must be examined to better understand this chemistry. MethodsWe report a direct, quantitative method for AHAs using ultrahigh-performance liquid chromatography and triple quadrupole mass spectrometry. Hexylamine ion-pairing chromatography and selected reaction monitoring detection were combined for the rapid analysis of ten AHAs in a single run. Additionally, prebiotic simulation experiments, including the first-ever reproduction of Miller's 1958 cyanamide spark discharge experiment, were performed to evaluate AHA synthesis over a wide range of possible primitive terrestrial environments. ResultsThe quantitating transition for each of the AHAs targeted in this study produced a limit of detection in the nanomolar concentration range. For most species, a linear response over a range spanning two orders of magnitude was found. The AHAs glycolic acid, lactic acid, malic acid, and -hydroxyglutaric acid were detected in electric discharge experiments in the low micromolar concentration range. ConclusionsThe results of this work suggest that the most abundant building blocks available for prebiotic depsipeptide synthesis would have been glycolic, lactic, malic, and -hydroxyglutaric acids, and their corresponding amino acids, glycine, alanine, and aspartic and glutamic acids. Copyright (c) 2016 John Wiley & Sons, Ltd.