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2014
Parker, ET, Cleaves JH, Burton AS, Glavin DP, Dworkin JP, Zhou MS, Bada JL, Fernandez FM.  2014.  Conducting Miller-Urey experiments. Jove-Journal of Visualized Experiments.   10.3791/51039   AbstractWebsite

In 1953, Stanley Miller reported the production of biomolecules from simple gaseous starting materials, using an apparatus constructed to simulate the primordial Earth's atmosphere-ocean system. Miller introduced 200 ml of water, 100 mmHg of H-2, 200 mmHg of CH4, and 200 mmHg of NH3 into the apparatus, then subjected this mixture, under reflux, to an electric discharge for a week, while the water was simultaneously heated. The purpose of this manuscript is to provide the reader with a general experimental protocol that can be used to conduct a Miller-Urey type spark discharge experiment, using a simplified 3 L reaction flask. Since the experiment involves exposing inflammable gases to a high voltage electric discharge, it is worth highlighting important steps that reduce the risk of explosion. The general procedures described in this work can be extrapolated to design and conduct a wide variety of electric discharge experiments simulating primitive planetary environments.

Parker, ET, Zhou MS, Burton AS, Glavin DP, Dworkin JP, Krishnamurthy R, Fernandez FM, Bada JL.  2014.  A plausible simultaneous synthesis of amino acids and simple peptides on the primordial earth. Angewandte Chemie-International Edition. 53:8132-8136.   10.1002/anie.201403683   AbstractWebsite

Following his seminal work in 1953, Stanley Miller conducted an experiment in 1958 to study the polymerization of amino acids under simulated early Earth conditions. In the experiment, Miller sparked a gas mixture of CH4, NH3, and H2O, while intermittently adding the plausible prebiotic condensing reagent cyanamide. For unknown reasons, an analysis of the samples was not reported. We analyzed the archived samples for amino acids, dipeptides, and diketopiperazines by liquid chromatography, ion mobility spectrometry, and mass spectrometry. A dozen amino acids, 10 glycine-containing dipeptides, and 3 glycine-containing diketopiperazines were detected. Miller's experiment was repeated and similar polymerization products were observed. Aqueous heating experiments indicate that Strecker synthesis intermediates play a key role in facilitating polymerization. These results highlight the potential importance of condensing reagents in generating diversity within the prebiotic chemical inventory.

Onstott, TC, Magnabosco C, Aubrey AD, Burton AS, Dworkin JP, Elsila JE, Grunsfeld S, Cao BH, Hein JE, Glavin DP, Kieft TL, Silver BJ, Phelps TJ, van Heerden E, Opperman DJ, Bada JL.  2014.  Does aspartic acid racemization constrain the depth limit of the subsurface biosphere? Geobiology. 12:1-19.   10.1111/gbi.12069   AbstractWebsite

Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of similar to 89years for 1km depth and 27 degrees C and 1-2years for 3km depth and 54 degrees C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 degrees C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples.

2013
Rosa, C, Zeh J, George JC, Botta O, Zauscher M, Bada J, O'Hara TM.  2013.  Age estimates based on aspartic acid racemization for bowhead whales (Balaena mysticetus) harvested in 1998-2000 and the relationship between racemization rate and body temperature. Marine Mammal Science. 29:424-445.   10.1111/j.1748-7692.2012.00593.x   AbstractWebsite

Fifty-two eyes were collected and analyzed to estimate ages of 42 bowhead whales using the aspartic acid racemization aging technique. Between-eye and within-eye variance components for the ratio of the D and L optical isomers (D/L ratio) were estimated via analysis of variance using multiple measurements from nine whales with both eyes sampled and analyzed. For whales with more than one (D/L)(act) value, an inverse variance weighted average of the values was used as (D/L)(act) for the whale. Racemization rate (k(Asp)) and D/L ratio at birth (D/L)(0) were estimated using (D/L)(act) from 27 bowhead whales with age estimates based on baleen or ovarian corpora data and two term fetuses. The estimates were k(Asp) = 0.977x10(-3)/yr and (D/L)(0) = 0.0250. The nonlinear least squares analysis that produced these estimates also estimated female age at sexual maturity as ASM=25.86yr. SE(age) was estimated via a bootstrap that took into account the SE of (D/L)(act) and the variances and covariance of k(Asp) and (D/L)(0). One male exceeded 100yr of age; the oldest female was 88. A strong linear relationship between k(Asp) and body temperature was estimated by combining bowhead data with independent data from studies of humans and fin whales. Using this relationship, we estimated k(Asp) and ASM for North Atlantic minke whales.

2012
Elsila, JE, Glavin DP, Dworkin JP, Martins Z, Bada JL.  2012.  Inconclusive evidence for nonterrestrial isoleucine enantiomeric excesses in primitive meteorites. Proceedings of the National Academy of Sciences of the United States of America. 109:E3288-E3288.   10.1073/pnas.1213261109   Abstract

Pizzarello et al. (1) recently described the soluble organic content of eight Antarctic Renazzo-type (CR) carbonaceous chondrites and reported large enantiomeric excesses (ee) of l-isoleucine and d-alloisoleucine. The reported values of ee decrease with inferred increases in aqueous alteration. We believe the conclusions presented in the paper are not fully justified and the data are potentially flawed.

Potential terrestrial contamination of meteoritic amino acid data must always be considered. The manuscript states that “terrestrial contamination levels… were evaluated based on the presence of proteinogenic amino acids’ l-excesses and accounted for when needed,” but this “accounting” is not described. A wide range of l-proteinogenic amino acid excesses was measured …

2011
Parker, ET, Cleaves HJ, Callahan MP, Dworkin JP, Glavin DP, Lazcano A, Bada JL.  2011.  Prebiotic Synthesis of Methionine and Other Sulfur-Containing Organic Compounds on the Primitive Earth: A Contemporary Reassessment Based on an Unpublished 1958 Stanley Miller Experiment. Origins of Life and Evolution of Biospheres. 41:201-212.   10.1007/s11084-010-9228-8   AbstractWebsite

Original extracts from an unpublished 1958 experiment conducted by the late Stanley L. Miller were recently found and analyzed using modern state-of-the-art analytical methods. The extracts were produced by the action of an electric discharge on a mixture of methane (CH(4)), hydrogen sulfide (H(2)S), ammonia (NH(3)), and carbon dioxide (CO(2)). Racemic methionine was formed in significant yields, together with other sulfur-bearing organic compounds. The formation of methionine and other compounds from a model prebiotic atmosphere that contained H(2)S suggests that this type of synthesis is robust under reducing conditions, which may have existed either in the global primitive atmosphere or in localized volcanic environments on the early Earth. The presence of a wide array of sulfur-containing organic compounds produced by the decomposition of methionine and cysteine indicates that in addition to abiotic synthetic processes, degradation of organic compounds on the primordial Earth could have been important in diversifying the inventory of molecules of biochemical significance not readily formed from other abiotic reactions, or derived from extraterrestrial delivery.

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.

Grew, ES, Bada JL, Hazen RM.  2011.  Borate Minerals and Origin of the RNA World. Origins of Life and Evolution of Biospheres. 41:307-316.   10.1007/s11084-010-9233-y   AbstractWebsite

The RNA World is generally thought to have been an important link between purely prebiotic (>3.7 Ga) chemistry and modern DNA/protein biochemistry. One concern about the RNA World hypothesis is the geochemical stability of ribose, the sugar moiety of RNA. Prebiotic stabilization of ribose by solutions associated with borate minerals, notably colemanite, ulexite, and kernite, has been proposed as one resolution to this difficulty. However, a critical unresolved issue is whether borate minerals existed in sufficient quantities on the primitive Earth, especially in the period when prebiotic synthesis processes leading to RNA took place. Although the oldest reported colemanite and ulexite are 330 Ma, and the oldest reported kernite, 19 Ma, boron isotope data and geologic context are consistent with an evaporitic borate precursor to 2400-2100 Ma borate deposits in the Liaoning and Jilin Provinces, China, as well as to tourmaline-group minerals at 33003450 Ma in the Barberton belt, South Africa. The oldest boron minerals for which the age of crystallization could be determined are the metamorphic tourmaline species schorl and dravite in the Isua complex (metamorphism between ca. 3650 and ca. 3600 Ma). Whether borates such as colemanite, ulexite and kernite were present in the Hadean (>4000 Ma) at the critical juncture when prebiotic molecules such as ribose required stabilization depends on whether a granitic continental crust had yet differentiated, because in its absence we see no means for boron to be sufficiently concentrated for borates to be precipitated.

Parker, ET, Cleaves HJ, Dworkin JP, Glavin DP, Callahan M, Aubrey A, Lazcano A, Bada JL.  2011.  Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. Proceedings of the National Academy of Sciences of the United States of America. 108:5526-5531.   10.1073/pnas.1019191108   AbstractWebsite

Archived samples from a previously unreported 1958 Stanley Miller electric discharge experiment containing hydrogen sulfide (H2S) were recently discovered and analyzed using high-performance liquid chromatography and time-of-flight mass spectrometry. We report here the detection and quantification of primary amine-containing compounds in the original sample residues, which were produced via spark discharge using a gaseous mixture of H2S, CH4, NH3, and CO2. A total of 23 amino acids and 4 amines, including 7 organosulfur compounds, were detected in these samples. The major amino acids with chiral centers are racemic within the accuracy of the measurements, indicating that they are not contaminants introduced during sample storage. This experiment marks the first synthesis of sulfur amino acids from spark discharge experiments designed to imitate primordial environments. The relative yield of some amino acids, in particular the isomers of aminobutyric acid, are the highest ever found in a spark discharge experiment. The simulated primordial conditions used by Miller may serve as a model for early volcanic plume chemistry and provide insight to the possible roles such plumes may have played in abiotic organic synthesis. Additionally, the overall abundances of the synthesized amino acids in the presence of H2S are very similar to the abundances found in some carbonaceous meteorites, suggesting that H2S may have played an important role in prebiotic reactions in early solar system environments.

2010
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.

2008
Botta, O, Martins Z, Emmenegger C, Dworkin JP, Glavin DP, Harvey RP, Zenobi R, Bada JL, Ehrenfreund P.  2008.  Polycyclic aromatic hydrocarbons and amino acids in meteorites and ice samples from LaPaz Icefield, Antarctica. Meteoritics & Planetary Science. 43:1465-1480. AbstractWebsite

We have analyzed ice samples and meteorites from the LaPaz region of Antarctica to investigate the composition of polycyclic aromatic hydrocarbons (PAHs) and amino acids with the goal to understand whether or not there is a compositional relationship between the two reservoirs. Four LL5 ordinary chondrites (OCs) and one CK carbonaceous chondrite were collected as part of the 2003/2004 ANSMET season. Ice samples collected from directly underneath the meteorites were extracted. In addition, exhaust particles from the snowmobiles used during the expedition were collected to investigate possible contributions from this source. The meteorite samples, the particulate matter and solid-state extracts of the ice samples and the exhaust filters were subjected to two-step laser mass spectrometry (L2MS) to investigate the PAH composition. For amino acids analysis, the meteorites were extracted with water and acid hydrolyzed, and the extracts were analyzed with offline OPA/NAC derivatization combined with liquid chromatography with UV fluorescence detection and time of flight mass spectrometry (LC-FC/ToF-MS). PAHs in the particulate matter of the ice were found to be qualitatively similar to the meteorite samples, indicating that micron-sized grains of the meteorite may be embedded in the ice samples. The concentration levels of dissolved PAHs in all the ice samples were found to be below the detection limit of the L2MS. The PAH composition of the snowmobile exhaust is significantly different to the one in particulate matter, making it an unlikely Source of contamination for Antarctic meteorites. The amino acids glycine, beta-alanine and gamma-amino-n-butyric acid that were detected at concentrations of 3 to 19 parts per billion (ppb) are probably indigenous to the Antarctic meteorites. Some of the LaPaz ice samples were also found to contain amino acids at concentration levels of 1 to 33 parts per trillion (ppt), in particular alpha-aminoisobutyric acid (AIB), an abundant non-protein amino acid of extraterrestrial Origin found in some carbonaceous chondrites. We hypothesize that this amino acid could have been extracted from Antarctic micrometeorites and the particulate matter of the meteorites during the concentration procedure of the ice samples.

Johnson, AP, Cleaves HJ, Dworkin JP, Glavin DP, Lazcano A, Bada JL.  2008.  The Miller volcanic spark discharge experiment. Science. 322:404-404.   10.1126/science.1161527   Website
Botta, O, Bada JL, Gomez-Elvira J, Javaux E, Selsis F, Summons R.  2008.  "Strategies of life detection": Summary and outlook. Space Science Reviews. 135:371-380.   10.1007/s11214-008-9357-9   Website
Bada, JL, Ehrenfreund P, Grunthaner F, Blaney D, Coleman M, Farrington A, Yen A, Mathies R, Amudson R, Quinn R, Zent A, Ride S, Barron L, Botta O, Clark B, Glavin D, Hofmann B, Josset JL, Rettberg P, Robert F, Sephton M.  2008.  Urey: Mars Organic and Oxidant Detector. Space Science Reviews. 135:269-279.   10.1007/s11214-007-9213-3   AbstractWebsite

One of the fundamental challenges facing the scientific community as we enter this new century of Mars research is to understand, in a rigorous manner, the biotic potential both past and present of this outermost terrestrial-like planet in our solar system. Urey: Mars Organic and Oxidant Detector has been selected for the Pasteur payload of the European Space Agency's (ESA's) ExoMars rover mission and is considered a fundamental instrument to achieve the mission's scientific objectives. The instrument is named Urey in recognition of Harold Clayton Urey's seminal contributions to cosmochemistry, geochemistry, and the study of the origin of life. The overall goal of Urey is to search for organic compounds directly in the regolith of Mars and to assess their origin. Urey will perform a groundbreaking investigation of the Martian environment that will involve searching for organic compounds indicative of life and prebiotic chemistry at a sensitivity many orders of magnitude greater than Viking or other in situ organic detection systems. Urey will perform the first in situ search for key classes of organic molecules using state-of-the-art analytical methods that provide part-per-trillion sensitivity. It will ascertain whether any of these molecules are abiotic or biotic in origin and will evaluate the survival potential of organic compounds in the environment using state-of-the-art chemoresistor oxidant sensors.

Aubrey, AD, Chalmers JH, Bada JL, Grunthaner FJ, Amashukeli X, Willis P, Skelley AM, Mathies RA, Quinn RC, Zent AP, Ehrenfreund P, Amundson R, Glavin DP, Botta O, Barron L, Blaney DL, Clark BC, Coleman M, Hofmann BA, Josset JL, Rettberg P, Ride S, Robert F, Sephton MA, Yen A.  2008.  The Urey instrument: An advanced in situ organic and oxidant detector for Mars exploration. Astrobiology. 8:583-595.   10.1089/ast.2007.0169   AbstractWebsite

The Urey organic and oxidant detector consists of a suite of instruments designed to search for several classes of organic molecules in the martian regolith and ascertain whether these compounds were produced by biotic or abiotic processes using chirality measurements. These experiments will also determine the chemical stability of organic molecules within the host regolith based on the presence and chemical reactivity of surface and atmospheric oxidants. Urey has been selected for the Pasteur payload on the European Space Agency's (ESA's) upcoming 2013 ExoMars rover mission. The diverse and effective capabilities of Urey make it an integral part of the payload and will help to achieve a large portion of the mission's primary scientific objective: "to search for signs of past and present life on Mars." This instrument is named in honor of Harold Urey for his seminal contributions to the fields of cosmochemistry and the origin of life.

2007
Skelley, AM, Aubrey AD, Willis PA, Amashukeli X, Ehrenfreund P, Bada JL, Grunthaner FJ, Mathies RA.  2007.  Organic amine biomarker detection in the Yungay region of the Atacama Desert with the Urey instrument. Journal of Geophysical Research-Biogeosciences. 112   10.1029/2006jg000329   AbstractWebsite

The Urey in situ organic compound analysis instrument, consisting of a subcritical water extractor ( SCWE) and a portable microchip capillary electrophoresis instrument called the Mars Organic Analyzer ( MOA), was field tested in the Atacama Desert, Chile, in June 2005. Soil samples from the most arid Yungay region were collected, biomarkers were extracted by the SCWE, and organic amine composition and amino acid chirality analysis was performed by the MOA. Samples collected from the top 1 cm of duracrust soil but shielded from the ambient environment by rocks were compared to the exposed duracrust. The shielded duracrust yielded amines and amino acids ranging from 50 to 100 ppb, while amino acid signals from the exposed duracrust were below blank levels. Samples from buried gypsum deposits located directly above a water flow channel contained amino acids ranging from 13 to 90 ppb. Chiral analysis revealed D/L ratios of 0.39 +/- 0.08 and 0.34 +/- 0.07 for alanine/serine and 0.78 +/- 0.06 for aspartic acid, indicating significant racemization of biologically produced amino acids. On the basis of the D/L ratios, we estimate sample ages ranging from 10(3) to 10(5) years. These results demonstrate the successful field testing of the Urey instrument, as well as the detection of biomarkers from past terrestrial life in one of the most arid and Mars-like regions on Earth.

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.

Glavin, DP, Dworkin JP, Aubrey A, Botta O, Doty JH, Martins Z, Bada JL.  2006.  Amino acid analyses of Antarctic CM2 meteorites using liquid chromatography-time of flight-mass spectrometry. Meteoritics & Planetary Science. 41:889-902. AbstractWebsite

Amino acid analyses of the Antarctic CM2 chondrites Allan Hills (ALH) 83100 and Lewis Cliff (LEW) 90500 using liquid chromatography-time of flight-mass spectrometry (LC-ToF-MS) Coupled with UV fluorescence detection revealed that these carbonaceous meteorites contain a suite of indigenous amino acids not present in Antarctic ice. Several amino acids were detected in ALH 83100, including glycine, alanine, beta-alanine, gamma-amino-n-butyric acid (gamma-ABA), and alpha-aminoisobutyric acid (AIB) with concentrations ranging from 250 to 340 parts per billion (ppb). In contrast to ALH 83 100, the CM2 meteorites LEW 90500 and Murchison had a much higher total abundance of these amino acids (440-3200 ppb). In addition, ALL! 83 100 was found to have lower abundances of the alpha-dialkyl amino acids AIB and isovaline than LEW 90500 and Murchison. There are three possible explanations for the depleted amino, acid content in ALH 83100: 1) amino acid leaching from ALH 83100 during exposure to Antarctic ice meltwater, 2) a higher degree of aqueous alteration on the ALH 83 100 parent body, or 3) ALH 83 100 originated on a chemically distinct parent body from the other two CM2 meteorites. The high relative abundance of epsilon-amino-n-caproic acid (EACA) in the ALH 83100 meteorite as well as the Antarctic ice indicates that Nylon-6 contamination from the Antarctic sample storage bags may have occurred during collection.

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.

Bada, JL, Sephton MA, Ehrenfreund P, Mathies RA, Skelley AM, Grunthaner FJ, Zent AP, Quinn RC, Josset JL, Robert F, Botta O, Glavin DP.  2005.  New strategies to detect life on Mars. Astronomy & Geophysics. 46:26-27. AbstractWebsite

The quest to determine whether life existed, or still exists, on Mars continues with several missions planned for the red planet by both the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) in the next few decades. One instrument designed for these missions is the Mars Organic Detector (MOD), which uses a new approach to achieve exceptionally high detection sensitivities and analysis capabilities for key bio-organic compounds. MOD is scheduled to fly in the ESA ExoMars mission early next decade and will attempt to answer the question of whether we are alone in the solar system. Here the MOD team explains why we have reason to be optimistic about uncovering the organic secrets of Mars.

2004
Glavin, DP, Cleaves HJ, Schubert M, Aubrey A, Bada JL.  2004.  New method for estimating bacterial cell abundances in natural samples by use of sublimation. Applied and Environmental Microbiology. 70:5923-5928.   10.1128/aem.70.10.5923-5928.2004   AbstractWebsite

We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500degreesC for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from similar to10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DA-PI (4,6-diamidino-2-phenylindole) staining.

Glavin, DP, Matrajt G, Bada JL.  2004.  Re-examination of amino acids in Antarctic micrometeorites. Space Life Sciences: Steps toward Origin(S) of Life. 33( Bernstein MP, Kress M, NavarroGonzalez R, Eds.).:106-113., Kidlington: Pergamon-Elsevier Science Ltd   10.1016/j.asr.2003.02.011   Abstract

The delivery of amino acids by micrometeorites to the early Earth during the period of heavy bombardment (4.5-3.5 Ga) could have been a significant source of the Earth's prebiotic organic inventory. Antarctic micrometeorites (AMMs) in the 100-200 mum size range represent the dominant mass fraction of extraterrestrial material accreted by the Earth today. However, one problem is that these 'large' micrometeorite grains can be heated to very high temperatures (1000 to 1500 degreesC) during atmospheric deceleration, causing the amino acids to decompose. In this study, we have analyzed the acid-hydrolyzed, hot water extracts from 455 AMMs for the presence of amino acids using high performance liquid chromatography. For comparison, a 5 mg sample of the CM meteorite Murchison was also investigated. In the Murchison sample we found high levels (similar to3-4 parts-per-million, ppm) of alpha-aminoisobutyric acid (AIB) and isovaline, two non-protein amino acids that are extremely rare on Earth and are characteristic of amino acids of apparent extraterrestrial origin. In contrast, we were unable to detect any AIB above the 0.1 ppm level in the AMM samples studied. Only in one AMM sample from a previous study has AIB been detected (similar to300 ppm). To date, more than 600 AMMs have been analyzed for extraterrestrial amino acids. Although our results indicate that less than 5% of all AMMs contain detectable levels of AIB, we cannot rule out the possibility that AIB can be delivered to the Earth intact by a small percentage of AMMs that escaped extensive heating during atmospheric entry. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

2002
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.

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.

Glavin, DP, Schubert M, Bada JL.  2002.  Direct isolation of purines and pyrimidines from nucleic acids using sublimation. Analytical Chemistry. 74:6408-6412.   10.1021/ac0259663   AbstractWebsite

A sublimation technique was developed to isolate purines and pyrimidines directly from lambda-deoxyribonucleic acid (lambda-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from lambda-DNA was tested under reduced pressure (similar to 0.5 Torr) at temperatures of > 150 degreesC. With the exception of guanine, approximately 60-75% of each base was sublimed directly from the lambda-DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 T. Several nucleobases including adenine, cytosine, thymine, and uracil were also recovered from E. coli bacteria after heating the cells to the same temperature, although some thermal decomposition of the bases also occurred. These results demonstrate the feasibility of using sublimation to isolate purines and pyrimidines from native E. coli DNA and RNA without any chemical treatment of the cells.