science

PUBLISHED
ARTICLES

Article List
Article Abstracts

 

PRESENTATIONS

Presentation List
Slide Shows

 

SCIENCE
NUGGETS

Astrobiology 101

 

CALENDAR

Mars Events Calendar

PUBLISHED ARTICLES

The Urey Instrument:  An Advanced In Situ Organic and Oxidant Detector for Mars Exploration, Aubrey, A. D., Chalmers, J. H., Bada, J. L, Grunthaner, F. J., Amashukeli, X., Willis, P., Skelley, A. M., Mathies, R. A., Quinn, R. C., Zent, A. P., Ehrenfreund, P., Amundson, R., Glavin, D. P., Botta, O., Barron, L., Blaney, D. L., Clark, B. C., Coleman, M., Hoffmann, B. A., Josset, J-L., Rettberg, P., Ride, S., Robert, R., Sephton, M. A. andYen, A., Astrobiology  2008, 8, 583-595.

Urey:  Mars Organic and Oxidant Detector, Bada, J. L., Ehrenfreund, P., Grunthaner, F., Blaney, D., Coleman, M., Farrington, A., Yen, A. , Mathies, R. A., Amundson, R., Quinn, R., Zent, A., Ride, S., Barron, L., Botta, O. Clark, B., Glavin, D. Hoffman, B., Fosset, J. L., Rettberg, P., Robert, F. and Sephton, M. Space Science Reviews 2008, 135, 269-279.

Analysis of Neuroactive Amines in Fermented Beverages Using a Portable Microchip Capillary Electrophoresis System, Jayarah, C. N., Skelley, A. M., Fortner, A. D. and Mathies, R. A., Analytical Chemistry, 2007, 79, 8162-8169.

Organic amine biomarker detection in the Yungay region of the Atacama Desert with the Urey instrument, Skelley, A. M., Aubrey, A. D., Willis, P. A., Amashukeli, X., Ehrenfreuend, P. , Bada, J. L., Grunthaner, F. J. and Mathies, R. A., Journal of Geophysical Research 2007, 112, G04S11

Subcritical water extraction of amino acids from Atacama Desert soils,Amashukeli, X., Pelletier, C. C., Kirby, J. P. and Grunthaner, F. J. , Journal of Geophysical Research 2007, 112, G04S16.

A Concept for NASA's Mars 2016 Astrobiology Field Laboratory, Beegle, L. W., Wilson, M. G., Abilleira, F. , Jordan, J. F. and Wilson, G. R., Astrobiology 2007, 7, DOI: 10.1089

Application of the Mars Organic Analyzer to Nucleobase and Amine Biomarker Detection, Skelley, A. M., Cleaves, H. J., Jayarajah, C. N., Bada, J. L. and Mathies, R. A., Astrobiology 2006, 6, 824-837.

Rapid on-column analysis of glucosamine and its mutarotation by microchip capillary electrophoresis, Skelley, A. M. and Mathies, R. A., Journal of Chromatography A, 2006, 1132, 304-309.

Sulfate minerals and organic compounds on Mars, Aubrey, A., Cleaves, H.J., Chalmers, H. J., Skelley, A. M., Mathies, R. A., Grunthaner F. J., Ehrenfreund, P. and Bada, J. L., Geology, 2006, 3, 357-360.

The effect of ionizing radiation on the preservation of amino acids on Mars, Kminek ,G. and Bada, J. L. Earth and Planetary Science Letters, 2006, 245, 1-5.

New strategies to detect life on Mars, Bada, J. L. Sephton, M. A., Ehrenfreund, P., Mathies, R. A., Skelley, A. M., Grunthaner, F. J., Zent , A. P., Quinn, R. C., Josset, J. L., Robert, F., Botta, O., Glavin, D. P. Astronomy & Geophysics, 2005, 46, 26-27.

Development and evaluation of a microdevice for amino acid biomarker detection and analysis on Mars. Skelley, A. M.; Scherer, J. R.; Aubrey, A. D.; Grover, W. H.; Ivester, R. H. C., Ehrenfreund, P.; Grunthaner, F. J.; Bada, J. L.; Mathies, R. A. Proceedings of the National Academy of Sciences, U.S.A., 2005, 192, 1041-1046.

Multi-layer microfluidic devices for amino acid analysis: the Mars Organic Analyzer Skelley, A. M.; Scherer, J. R.; Bada, J. L.; Ehrenfreund, P.; Grunthaner, F. J.; Mathies, R. A. Proceedings of the Eighth International Symposium on Micro Total Analysis Systems, Malmo, Sweden 2004, Eds: T. Laurell, J. Nilsson, K. Jensen, D. J. Harrison and J. Kutter, Royal Society of Chemistry (Cambridge, UK), 556-568.

Planetary science - A wet early Mars seen in salty deposits. Kerr, R. A. Science 2004, 303, 1450

Mars - Opportunity tells a salty tale. Kerr, R. A. Science 2004, 303, 1957

A possible terrestrial analogue for haematite concretions on Mars. Chan, M. A. ; Beitler, B; Parry, W. T.; Ormo, J; Komatsu, G. Nature 2004, 429, 731-734

Chiral Separation of Fluorescamine-labeled Amino Acids using Microfabricated Capillary Electrophoresis Devices for Extraterrestrial Exploration. Skelley, A. M.; Mathies, R. A. Journal of Chromatography 2003, 1021, 191-199.

Monolithic membrane valves and diaphragm pumps for practical large-scale integration into glass microfluidic devices. Grover, W. H.; Skelley, A. M.; Liu, C. N.; Lagally, E. T.; Mathies, R. A. Sensors and Actuators B-Chemical 2003, 89, 325-323.

Prebiotic soup - Revisiting the Miller experiment. Bada, J. L.; Lazcano, A. Science 2003, 300, 745-746.

Mars Organic Detector III: A Versatile Instrument for Detection of Bio-organic Signatures on Mars. Skelley, A. M.; Grunthaner, F. J.; Bada, J. F.; Mathies, R. A. in SPIE Vol. 4878 First Jet Propulsion Laboratory In Situ Instruments Workshop, ed. By G. H. Bearman, P. M. Beauchamp (SPIE. Bellingham, WA 2003), pp. 59-67.

Direct isolation of purines and pyrimidines from nucleic acids using sublimation. Glavin, D. P.; Schubert, M.; Bada. Analytical Chemistry 2002, 74, 6408-6412.

Origin of life - Some like it hot, but not the first biomolecules. Bada, J. L.; Lazcano, A. Science 2002, 296, 1982-1983.

Micro total analysis systems. 1. Introduction, theory, and technology [Review]. Reyes, D. R.; Iossifidis, D.; Auroux, P. A.; Manz, A. Analytical Chemistry 2002, 74, 2623-2636.

Micro total analysis systems. 2. Analytical standard operations and applications [Review]. Auroux, P. A.; Iossifidis, D.; Reyes, D. R.; Manz, A. Analytical Chemistry 2002, 74, 2637-2652.

Microfabricated 384-Lane Capillary Array Electrophoresis Bioanalyzer for Ultra High-Throughput Genetic Analysis. Emrich, C. A.; Tian, H.; Medintz, I. L.; Mathies, R. M. Analytical Chemistry 2002, 74, 5076-5083.

Detecting pyrolysis products from bacteria on Mars. Glavin, D. P.; Schubert, M.; Botta, O.; Kminek, G.; Bada, J. L. Earth & Planetary Science Letters 2001,
185,
1-5.

MOD: an organic detector for the future robotic exploration of Mars. Kminek, G.; Bada, J. L.; Botta, O.; Glavin, D. P.; Grunthaner, F. Planetary & Space Science 2000, 48, 1087-1091.

Microfabricated capillary electrophoresis amino acid chirality analyzer for extraterrestrial exploration. Hutt, L. D.; Glavin, D. P.; Bada, J. L.; Mathies, R. A. Analytical Chemistry 1999, 71, 4000-4006.

Amino acids in the Martian meteorite Nakhla. Glavin, D. P.; Bada, J. L.; Brinton, K. L. F.; McDonald, G. D. Proceedings of the National Academy of Sciences, USA 1999, 96, 8835-8838.

Microfabrication Technology for the Production of Capillary Array Electrophoresis Chips. Simpson, P. C.; Woolley, A. T.; Mathies, R. A. Journal of Biomedical Microdevices 1998, 1, 7-26.

Isolation of Amino Acids from Natural Samples Using Sublimation. Glavin, D. P.; Bada, J. L. Analytical Chemistry 1998, 70, 3119-3122.

A Search for Endogenous Amino Acids in Martian Meteorite Alh84001. Bada, J. L.; Glavin, D. P.; McDonald, G. D.; Becker, L. Science 1998, 279, 362-365.

Extraterrestrial Handedness? Bada, J. L. Science 1997, 275, 942-943.

Amino Acid Racemization and the Preservation of Ancient DNA. Poinar, H. N.; Hoss, M.; Bada, J. L.; Paabo, S. Science 1996, 272, 864-866.

Amino Acid Racemization on Mars - Implications for the Preservation of Biomolecules from an Extinct Martian Biota. Bada, J. L.; McDonald, G. D. Icarus 1995, 114, 139-143.

top


ARTICLE ABSTRACTS

The Urey Instrument:  An Advanced In Situ Organic and Oxidant Detector for Mars Exploration

Aubrey, A. D. (1), Chalmers, J. H., Bada, J. L. (2), Grunthaner, F.  J., Amashukeli, X. , Willis (1), Skelley, A. M. (3), Mathies, R. A. (4), Quinn, R. C. (5), Zent, A. P. (6), Ehrenfreund, P. (7), Amundsen, R. (4), Glavin, D. P. (8), Botta, O. (9), Barron, L. (10), Blaney, D. L. (1), Clark, B. C. (11), Coleman, M. (1), Hoffman, B. A. (12), Josset, L-C. (13), Rettberg, P. (14), Ride, S. (15), Robert, F. (16), Sephton, M. A. (17) and Yen, A. (1).

(1) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.
(2) Scripps Institution of Oceanography, La Jolla, California.
(3) Massachusetts Institute of Technology, Cambridge, Massachusetts.
(4) University of California, Berkeley, California.
(5) SETI Institute, Mountain View, California.
(6) NASA Ames Research Center, Moffett Field, California.
(7) Leiden Institute of Chemistry, Leiden, The Netherlands.
(8) NASA Goddard Space Flight Center, Greenbelt, Maryland.
(9) International Space Science Institute, Bern, Switzerland.
(10) University of Glasgow, Glasgow, UK.
(11) Lockheed Martin Space Systems Company, Denver, Colorado.
(12) Natural History Museum, Bern, Switzerland.
(13) SPACE-X Exploration Institute, Neuchâtel, Switzerland.
(14) Institute of Aerospace Medicine, Köln, Germany.
(15) Imaginary Lines, San Diego, California.
(16) Musée National d'Histoire Naturelle, Paris, France.
(17) Imperial College of London, London, UK.

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.

Link to PDF

top


Urey:  Mars Organic and Oxidant Detector

Bada, J. L. (1), Ehrenfreund, P.(2), Grunthaner, F. , Blaney, D., Coleman, M., Farrington, A., Yen, A. (3), Mathies, R. A., Amundson, R. (4), Quinn, R. (5), Zent, A. (6), Ride, S. (7), Barron, L. (8), Botta, O. (9), Clark, B. (10), Glavin (11), D. Hoffman, B. (12), Fosset, J. L. (13), Rettberg, P. (14), Robert, F. (15) and Sephton, M. (16).

(1) Scripps Institution of Oceanography, La Jolla, California.
(2) Leiden Institute of Chemistry, Leiden, The Netherlands.
(3) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.
(4) University of California, Berkeley, California
(5) SETI Institute, Mountain View, California.
(6) NASA Ames Research Center, Moffett Field, California.
(7) Imaginary Lines, San Diego, California.
(8) Department of Chemistry, University of Glasgow, Glasgow, UK.
(9) International Space Science Institute, Bern, Switzerland
(10) Space Exploration Systems, Lockheed Martin, Denver.
(11) NASA/Goddard Space Flight Center, Greenbelt, Maryland.
(12) Natural History Museum, Bern, Switzerland.
(13) SPACE-X Exploration Institute, Neuchâtel, Switzerland.
(14) Institute of Aerospace Medicine, Köln, Germany.
(15) Musée National d'Histoire Naturelle, Paris, France.

Mars Organic and Oxidant Detector has been selected for the Pasteur payload of the EuropeanSpace 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.

Link to PDF

top

Analysis of Neuroactive Amines in Fermented Beverages Using a Portable Microchip Capillary Electrophoresis System

Jayarajah, C. N., Skelley, A. M., Fortner, A. D. and Mathies, R. A.

Department of Chemistry, University of California, Berkeley, CA  94720

A portable microfabricated capillary electrophoresis (CE) instrument is used for the determination of neurologically active biogenic amines, especially tyramine and histamine, in fermented beverages. The target molecules were labeled on their primary amino groups with fluorescamine in a 10-min reaction, and the samples analyzed directly, producing a detailed electropherogram in only 120 s on a microfabricated glass CE device containing 21.4 cm-long separation channels. Tyramine was found mainly in red wines at <1 to 3.4 mg/L, while the histamine content of these samples ranged from 1.8 to 19 mg/L. The highest levels of histamine (20-40 mg/L) were found in sake. The analysis of samples drawn from grape crush through malolactic fermentation in four varieties of zinfandel red wines revealed that histamine and tyramine are produced during yeast and malolactic fermentation, respectively. Following malolactic fermentation, the histamine content in these samples ranged from 3.3 to 30 mg/L, and the tyramine content ranged from 1.0 to 3.0 mg/L. This highly sensitive and rapid lab-on-a-chip analysis method establishes the feasibility of monitoring neurologically active amine content and potentially other chemically and allergenically important molecules in our food supply.

Link to PDF

top

Organic amine biomarker detection in the Yungay region of the Atacama Desert with the Urey instrument

Skelley, A. M. (1), Aubrey, A. D. (2), Willis, P. A. (3), Amashukeli, X. (3), Ehrenfreuend, P. (4), Bada, J. L. (2), Grunthaner, F. J. (3) and Mathies, R. A. (1)

(1)  Department of Chemistry, University of California, Berkeley, CA  94720
(2)  Scripps Institution of Oceanography, U. C. San Diego, La Jolla, CA  92093
(3)  Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 
       91109
(4)  Astrobiology Laboratory, Leiden Institute of Chemistry, Leiden, Netherlands

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 103 to 105 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.

 

Link to PDF

top

Subcritical water extraction of amino acids from Atacama Desert soils

Amashukeli, X., Pelletier, C. C., Kirby, J. P. and Grunthaner, F. J.

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109

Amino acids are considered organic molecular indicators in the search for extant and extinct life in the Solar System. Extraction of these molecules from a particulate solid matrix, such as Martian regolith, will be critical to their in situ detection and analysis. The goals of this study were to optimize a laboratory amino acid extraction protocol by quantitatively measuring the yields of extracted amino acids as a function of liquid water temperature and sample extraction time and to compare the results to the standard HCl vapor-phase hydrolysis yields for the same soil samples. Soil samples from the Yungay region of the Atacama Desert (Martian regolith analog) were collected during a field study in the summer of 2005. The amino acids (alanine, aspartic acid, glutamic acid, glycine, serine, and valine) chosen for analysis were present in the samples at concentrations of 1–70 parts-per-billion. Subcritical water extraction efficiency was examined over the temperature range of 30–325 °C, at pressures of 17.2 or 20.0 MPa, and for water-sample contact equilibration times of 0–30 min. None of the amino acids were extracted in detectable amounts at 30 °C (at 17.2 MPa), suggesting that amino acids are too strongly bound by the soil matrix to be extracted at such a low temperature. Between 150 °C and 250 °C (at 17.2 MPa), the extraction efficiencies of glycine, alanine, and valine were observed to increase with increasing water temperature, consistent with higher solubility at higher temperatures, perhaps due to the decreasing dielectric constant of water. Amino acids were not detected in extracts collected at 325 °C (at 20.0 MPa), probably due to amino acid decomposition at this temperature. The optimal subcritical water extraction conditions for these amino acids from Atacama Desert soils were achieved at 200 °C, 17.2 MPa, and a water-sample contact equilibration time of 10 min.

Link to PDF

top

A Concept for NASA’s Mars 2016 Astrobiology Field Laboratory

Beegle, L. W., Wilson, M. G., Abilleira, F. , Jordan, J. F. and Wilson, G. R.

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109

The Mars Program Plan includes an integrated and coordinated set of future candidate missions and investigations that meet fundamental science objectives of NASA and the Mars Exploration Program (MEP). At the time this paper was written, these possible future missions are planned in a manner consistent with a projected budget profile for the Mars Program in the next decade (2007–2016). As with all future missions, the funding profile depends on a number of factors that include the exact cost of each mission as well as potential changes to the overall NASA budget. In the current version of the Mars Program Plan, the Astrobiology Field Laboratory (AFL) exists as a candidate project to determine whether there were (or are) habitable zones and life, and how the development of these zones may be related to the overall evolution of the planet. The AFL concept is a surface exploration mission equipped with a major in situlaboratory capable of making significant advancements toward the Mars Program’s life-related scientific goals and the overarching Vision for Space Exploration. We have developed several concepts for the AFL that fit within known budget and engineering constraints projected for the 2016 and 2018 Mars mission launch opportunities. The AFL mission architecture proposed here assumes maximum heritage from the 2009 Mars Science Laboratory (MSL). Candidate payload elements for this concept were identified from a set of recommendations put forth by the Astrobiology Field Laboratory Science Steering Group (AFL SSG) in 2004, for the express purpose of identifying overall rover mass and power requirements for such a mission. The conceptual payload includes a Precision Sample Handling and Processing System that would replace and augment the functionality and capabilities provided by the Sample Acquisition Sample Processing and Handling system that is currently part of the 2009 MSL platform.

Link to PDF

top

Application of the Mars Organic Analyzer to Nucleobase and Amine Biomarker Detection

Skelley, A. M., Cleaves, H. J. (1), Jayarajah, C. N., Bada, J. L. (1) and Mathies, R. A

Department of Chemistry, University of California, Berkeley, CA  94720

(1) Scripps Institution of Oceanography, U. C. San Diego, La Jolla, CA 92093

The Mars Organic Analyzer (MOA), a portable microfabricated capillary electrophoresis instrument being developed for planetary exploration, is used to analyze a wide variety of fluorescamine-labeled amine-containing biomarker compounds, including amino acids, mono and diaminoalkanes, amino sugars, nucleobases, and nucleobase degradation products. The nucleobases cytosine and adenine, which contain an exocyclic primary amine, were effectively labeled, separated, and detected at concentrations <500 nM. To test the general applicability of the MOA for biomarker detection, amino acids and mono- and diamines were extracted from bacterial cells using both hydrolysis and sublimation followed by analysis. The extrapolated limit of detection provided by the valine biomarker was ~4 x 103 cells per sample.  Products of an NH4CN polymerization that simulate a prebiotic synthesis were also successfully isolated via sublimation and analyzed. Adenine and alanine/serine were detected with no additional sample cleanup at 120 ± 13 µM and 4.1 ± 1 µM, respectively, corresponding to a reaction yield of 0.04% and 0.0003%, respectively. This study demonstrates that the MOA provides sensitive detection and analysis of low levels of a wide variety of amine-containing organic compounds from both biological and abiotic sources.

Link to PDF

top

Rapid on-column analysis of glucosamine and its mutarotation by microchip capillary electrophoresis

Skelley, A. M. and Mathies, R. A.

Department of Chemistry, U. C. Berkeley, Berkeley, CA 94720

A novel electrophoretic microchip method for analyzing α and β -D-glucosamine and their interconversion in solution is presented.  D-Glucosamine is labeled with fluorescamine and analyzed by capillary electrophoresis in under 2 minutes revealing its pH-dependent mutarotation between the α and β-anomers.  The forward interconversion rates for the labeled sugars, based on an iterative analysis of the plateau heights between the peaks, are 0.72 ± 0.09, 1.3 ± 0.1, and 2.2 ± 0.3 x 10-3 s-1 at pH 8.99, 9.51 and 10.01, respectively.  In a separate experiment, the mutarotation of the unlabeled a-D-anomer was followed; the relative intensities of the a- and b-peaks as a function of reaction time at pH 9.51 give a forward rate constant of 0.6 ± 0.1 x 10-3 s-1.  These results demonstrate that fast microchip separations, previously exploited for amine, amino acid, and nucleobase analysis, can also be used to analyze amino sugars and their mutarotation.

Link to PDF

top

Sulfate minerals and organic compounds on Mars

Aubrey, A., Cleaves, H.J., Chalmers, H. J. (1), Skelley, A. M., Mathies, R. A. (2), Grunthaner F. J. (3), Ehrenfreund, P. (4) and Bada, J. L. (1)

(1) Scripps Institution of Oceanography, U. C. San Diego, La Jolla, CA  92093
(2) Department of Chemistry, U. C. Berkeley, Berkeley, CA  94720
(3) Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA  91109
(4) Leiden Observatory, Leiden, The Netherlands

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.

Link to PDF

top

The effect of ionizing radiation on the preservation of amino acids on Mars

Kminek ,G. and Bada, J. L. (1)

European Space Agency, D/HME, Keplerlaan 1, 2200 AG, Noordwijk, The Netherlands
(1) Scripps Institution of Oceanography, University of California at San Diego

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.

Link to PDF

top

New strategies to detect life on Mars

Bada, J. L. Sephton, M. A. (1), Ehrenfreund, P.(2), Mathies, R. A., Skelley, A. M. (3), Grunthaner, F. J (4)., Zent , A. P., Quinn, R. C., (5) Josset, J. L. (6), Robert, F. (7), Botta, O., Glavin, D. P. (8), Astronomy & Geophysics, 2005, 46, 26-27.

Scripps Institution of Oceanography, U. C. San Diego, La Jolla, CA  92093
(1) Department of Earth Science and Engineering, Imperial College of London
(2) Leiden Institute of Chemistry, Leiden, The Netherlands
(3) Department of Chemistry, University of California, Berkeley, CA  94720
(4) Jet Propulsion Laboratory, In Situ Exploration  Group,   Pasadena, CA  91109
(5) NASA Ames Research Center, SETI Institute, Moffett Field, CA  94035
(6) Space X Program, University of Neuchatel, CH-2007 Switzerland
(7) CNRS-Muséum National d'Histoire Naturelle, Paris
(8) NASA Goddard Space Flight Center, Greenbelt, MD

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.

Link to PDF

top

Development and evaluation of a microdevice for amino acid biomarker detection and analysis on Mars

Alison M. Skelley, James R. Scherer, Andrew D. Aubrey (1), William H. Grover, Robin H. C. Ivester, Pascale Ehrenfreund(2), Frank J. Grunthaner (3), Jeffrey L. Bada (1) and Richard A. Mathies

Department of Chemistry, University of California, Berkeley, CA 94720
(1) Scripps Institution of Oceanography, University of California at San Diego,
La Jolla, CA, 92093
(2) Astrobiology Laboratory, Leiden University, 2300 RA Leiden, The Netherlands
(3) Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA

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.

Link to PDF

top

Multi-layer microfluidic devices for amino acid analysis: the Mars Organic Analyzer

Alison M. Skelley, James R. Scherer, Jeffrey L. Bada (1), Pascale Ehrenfreund (2), Frank J. Grunthaner (3) and Richard A. Mathies

Department of Chemistry, University of California, Berkeley, CA 94720
(1) Scripps Institution of Oceanography, University of California at San Diego,
La Jolla, CA, 92093
(2) Leiden Institute of Chemistry, Einsteinweg 55, 2300 Ra Leiden, The Netherlands
(3) Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA

Sensitive amino acid composition and chirality analysis is demonstrated using the Mars Organic Analyzer (MOA), a portable microfabricated capillary electrophoresis (CE) instrument. The MOA integrates all high voltage power supplies, pneumatic controls, and fluorescence detection optics. The microfabricated device is a novel multi-layer structure combining glass separation channels and microfabricated pneumatic membrane valves and pumps. The Mars Organic Analyzer has been successfully field tested demonstrating part-per-trillion sensitivity when analyzing jarosite, a key sulfate-rich mineral recently detected on Mars that is associated with liquid water.

Link to PDF

top

Planetary science - A wet early Mars seen in salty deposits

Mars - Opportunity tells a salty tale

Richard A. Kerr

The Mars Exploration Rovers Spirit and Opportunity have been exploring Mars since landing on the planet earlier in the year. Recently it was reported that the rovers have detected structural and mineralogical evidence that there was once water on Mars. Opportunity observed concretions weathering out of rocks. These concretions are formed by minerals being precipitated from water. In addition, the Mossbauser spectrometer detected significant concentrations of jarosite, and iron and sulfate rich mineral that is only formed in the presence of water. Finally, sedimentary patterns called “smiles” were observed, indicating ripples moving in water.

Links to Science web site:
Article 1 and Article 2

top

A possible terrestrial analogue for haematite concretions on Mars

Marjorie A. Chan, Brenda Beitler, W. T. Parry, Jens Ormo (1) and Goro Komatsu (2)

Department of Geology and Geophysics, University of Utah, 135 S 1460 E, Salt Lake City, Utah 84112-0111, USA
(1) Centro de Astrobiología (INTA/CSIC), Instituto Nacional de Técnica Aeroespacial, Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
(2) International Research School of Planetary Sciences, Università d'Annunzio, Viale Pindaro 42, 65127 Pescara, Italy

The haematite concretions recently detected on Mars indicate that the planet was once wet. Here the authors look at haematite concretions found in the Jurassic Navajo Sandstone of southern Utah and compare these concretions to those found on Mars. By investigating the processes and host-rock properties that formed these concretions on Earth, the processes and conditions on Mars can be inferred. Looking at physical relationships between the concretions, such as size and spacing, reflects the chemistry of the host-rock as well as properties such as flow paths and fluid chemistry. Comparing the characteristics of the concretions found on Mars and on Earth, more variability was found in the concretions on Earth. In addition, the authors suggest that biomediation may play a role in haematite concretions on Earth, and could potentially be important for the search for life on Mars.

Link to Nature

top

Chiral Separation of Fluorescamine-Labeled Amino Acids using Microfabricated Capillary Electrophoresis Devices for Extraterrestrial Exploration

Alison M. Skelley and Richard A. Mathies*

Chemistry Department University of California
Berkeley, CA 94720

Chiral separations of fluorescamine-labeled amino acids are characterized and optimized on a microfabricatedcapillary electrophoresis (CE) device. A standard mixture of acidic and neutral amino acids is labeled with fluorescamine in less than 5 minutes and the hydroxypropyl- b -cyclodextrin (HP b CD) concentration, temperature, and pH are optimized (15 mM HP b CD, 6 o C, pH < 9) to achieve high-quality and low background chiral separations in less than 200 seconds. All four stereoisomers formed in the labeling reaction of the chiral dye with the chiral amino acids are typically resolved. At pH > 9, isomerization of the dye chiral center is observed that occurs on the time scale of the chip separation. Typical limits of detection are ~ 50 nM.   These results demonstrate the feasibility of combining fluorescamine labeling of amino acids with microfabricated CE devices to develop low-volume, high-sensitivity apparatus and methods for extraterrestrial exploration.

Link to PDF

top

Monolithic Membrane Valves and Diaphragm Pumps for Practical Large-Scale Integration into Glass Microfluidic Devices

William H. Grover, Alison M. Skelley, Chung N. Liu (1),
Eric T. Lagally
(2), and Richard A. Mathies (1)*

Department of Chemistry,
(1) Department of Chemical Engineering, and
(2)UC Berkeley / UC San Francisco Joint Bioengineering Graduate Group
University of California
Berkeley, CA 94720

*Corresponding author

Monolithic elastomer membrane valves and diaphragm pumps suitable for large-scale integration into glass microfluidic analysis devices are fabricated and characterized.  Valves and pumps are fabricated by sandwiching an elastomer membrane between etched glass fluidic channel and manifold wafers. A three-layer valve and pump design features simple non-thermal device bonding and a hybrid glass-PDMS fluidic channel; a four-layer structure includes a glass fluidic system with minimal fluid-elastomer contact for improved chemical and biochemical compatibility. The pneumatically-actuated valves have <10 nL dead volumes, can be fabricated in dense arrays, and can be addressed in parallel via an integrated manifold. The membrane valves provide flow rates up to 380 nL/s at 30 kPa driving pressure and seal reliably against fluid pressures as high as 75 kPa. The diaphragm pumps are self-priming, pump from a few nanoliters to a few microliters per cycle at overall rates from 1 to over 100 nL/s, and can reliably pump against 42 kPa pressure heads. These valves and pumps provide a facile and reliable integrated technology for fluid manipulation in complex glass microfluidic and electrophoretic analysis devices.  

Link to PDF

top

Perceptions in Science
Prebiotic Soup – Revisiting the Miller Experiment

Jeffrey L. Bada*; Antonio Lazcano

Modern research in prebiotic chemistry effectively began with a publication of a paper in Science 50 years ago by Stanley L. Miller on the spark discharge synthesis of amino acids and other compounds using a mixture of reduced gases that were thought to represent the components of the atmosphere on the primitive Earth. On the anniversary of this milestone publication, Bada and Lazcano provide an account of the events surrounding the publication of the paper and discuss the historical studies that led up to the Miller experiment.

J. L. Bada is at Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.

A. Lazcano is with the Facultad de Ciencias, UNAM, Apdo. Postal 70-407, Cd. Universitaria, 04510 Mexico D.F., Mexico.

Link to PDF

top

Mars Organic Detector III: A Versatile Instrument for Detection of Bio-organic Signatures on Mars

Alison M. Skelley, Frank J. Grunthaner (1), Jeffrey L. Bada (2), and Richard A. Mathies*

Department of Chemistry, University of California, Berkeley, CA 94720;
(1) Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109;
(2) Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093

Recent advances in the development of microfabricated lab-on-a-chip analysis systems have enhanced the feasibility and capabilities of in situ chemical and biochemical analyzers. While a wide variety of bio-organic molecules can be probed, we have focused our initial studies on the development of an amino acid analyzer with the hypothesis that extraterrestrial life would be based on homochiral amino acid polymers. In previous work, we developed a prototype electrophoresis chip, detection system and analysis method where the hydrolyzed amino acids were labeled with fluorescein and then analyzed in minutes via a capillary zone electrophoresis (CZE) separation in the presence of ?-cyclodextrin as the chiral recognition agent. 1 In more recent work, we have demonstrated the feasibility of performing amino acid composition and chirality analyses using fluorescamine as the labeling reagent. Fluorescamine is advantageous because it reacts more rapidly with amino acids, has a low fluorescence background and because such a chemistry would interface directly with the Mars Organic Detector (MOD-I) concept being developed at Scripps. A more advanced analysis system called MOD-III is introduced here with the ability to analyze zwitterionic amino acids, nucleobases, sugars, and organic acids and bases using novel capture matrix chemistries. MOD-III, which is enabled by the nanoliter valves, pumps and reactors presented here, will provide a wide spectrum of organic chemical analyses and is suitable for a variety of in situ missions.

Link to PDF

top

Direct Isolation of Purines and Pyrimidines from Nucleic Acids Using Sublimation

Daniel P. Glavin, Michael Schubert, and Jeffrey L. Bada*

Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093

A sublimation technique was developed to isolate purines and pyrimidines directly from -deoxyribonucleic acid (-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from -DNA was tested under reduced pressure (~ 0.5 Torr) at temperatures of >150 C. With the exception of guanine, approximately 60-75% of each base was sublimed directly from the -DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 C. 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.

Link to PDF

top

Origin of life - Some like it hot, but not the first biomolecules

J.L.Bada and A. Lazcano

Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093 and Facultad de Ciencas, UNAM, 04510, Mexico

Ever since the pioneering work of Aleksandr Oparin and John Haldane nearly a century ago, the prebiotic soup theory has dominated thinking about how life emerged on Earth (1,2). According to the modern version of this theory, organic compounds accumulated in the primordial oceans and underwent polymerization,producing increasingly complex macromolecules that eventually evolved the ability to catalyze their own replication (see the figure). But is this really how life originated? And what were the conditions that favored its emergence?

Link to PDF

top

Micro Total Analysis Systems.
1. Introduction, Theory, and Technology [Review]

Darwin R. Reyes, Dimitri Iossifidis, Pierre-Alain Auroux, and Andreas Manz

Department of Chemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, U.K.

The area of micro total analysis systems, also called “lab on a chip”, or miniaturized analysis systems, is growing rapidly. Since the excellent research documented in many publications easily gets confusing to a newcomer, the aim of this review is to help a novice in the field to find the original papers easier. Sensors, arrays (so-called “biochips”), chemical synthesis on-chip, and many of the more technical (engineering) papers have been omitted, as it is the scope of this paper to cover microfluidic systems for analytical chemistry only.

Link to PDF

top

Micro Total Analysis Systems.
2. Analytical Standard Operations and Applications [Review]

Pierre-Alain Auroux, Dimitri Iossifidis, Darwin R. Reyes, and Andreas Manz

Department of Chemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, U.K.

After having reviewed some aspects of microfluidic system preparation in the first part (1), in this second part of the review we will cover a number of standard operations (namely: sample preparation, sample injection, sample manipulation, reaction, separation, and detection) as well as some biological applications of micro total analysis systems (namely: cell culture, polymerase chain reaction, DNA separation, DNA sequencing, and clinical diagnostics). As previously, we will include papers issued from different scientific journals as well as useful abstracts from three conference proceedings: MEMS, Transducers, and ÌTAS. In this second part, we do not include the period covered by the history section (1975-1997) from part 1 but try to cover the relevant examples of the literature published between January 1998 and March 2002. We briefly describe articles that struck us as needing special attention, while more “standard” papers are dutifully reported in groups of interest. An article might be included in more than one section, depending on the ideas developed in it.

Link to PDF

top

Microfabricated 384-Lane Capillary Array Electrophoresis Bioanalyzer for Ultra High-Throughput Genetic Analysis

Charles A. Emrich (1), Huijun Tian, Igor L. Medintz and Richard A. Mathies

Department of Chemistry and Biophysics Graduate Group(1), University of California, Berkeley, CA 94720.

A microfabricated 384-lane capillary array electrophoresis device is developed and utilized for massively parallel genetic analysis. The 384 capillary lanes, arrayed radially about the center of a 200-mm diameter glass substrate sandwich, are constructed using scalable microfabrication techniques derived from the semiconductor industry. Samples are loaded into reservoirs on the perimeter of the chip, separated on the 8-cm long polydimethylacrylamide gel-filled channels, and detected with a 4-color rotary confocal fluorescence scanner. The performance and throughput of this bioanalyzer is demonstrated by simultaneous genotyping of 384 individuals for the common hemochromatosis-linked H63D mutation in the human HFE gene in only 325 s. This lab-on-a-chip device thoroughly exploits the power of microfabrication to produce high-density capillary electrophoresis arrays and to use them for high throughput bioanalysis.

Link to PDF

top

Detecting pyrolysis products from bacteria on Mars

Daniel P. Glavin, Michael Schubert, Oliver Botta, Gerhard Kminek and Jeffrey L. Bada*

Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093

A pyrolysis/sublimation technique was developed to isolate volatile amine compounds from a Mars soil analogue inoculated with ~10 billion Escherichia coli cells. In this technique, the inoculated soil is heated to 500°C 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.

Link to PDF

top

MOD: an organic detector for the future robotic exploration of Mars

G. Kminek* (1), J. L. Bada (1), O. Botta (1), D. P. Glavin
and F. Grunthaner (2)

(1) Scripps Institution of Oceanography, 9500 Gilman Drive,
La Jolla, CA 92093-0208, USA
(2) Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

Searching for extinct or extant life on Mars is part of the future NASA surveyor class missions. Looking for key organic compounds that are essential for biochemistry as we know it or indicative of extraterrestrial organic influx is the primary goal of the Mars Organic Detector (MOD). MOD is able to detect amino acids, amines and PAHs with at least 100 times higher sensitivity than the Viking GCMS experiment. MOD is not capable of identifying specific organic molecules but can assess the organic inventory of amines and PAHs on the planet. MOD can also quantify adsorbed and chemisorbed water and evolved carbon dioxide in a stepped heating cycle to determine specific carbon-bearing minerals. All that comes with no sample preparation and no wet chemistry. The organics can be isolated from the carrier matrix by heating the sample and recovering the volatile organics on a cold finger. This sublimation technique can be used for extracting amino acids, amines and PAHs under Mars ambient conditions. The detection of amino acids, amines and PAHs is based on a fluorescence detection scheme. The MOD concept has functioned as a laboratory breadboard since 1998. A number of natural samples including shells, clays, bones, -DNA and E.-coli bacteria have been used and organic molecules have been extracted successfully in each case. The first prototype of MOD is operational as of early fall of 1999. MOD has been selected for the definition phase of the NASA-MSR 2003 mission.

Link to PDF

top

Microfabricated Capillary Electrophoresis Amino Acid Chirality Analyzer for Extraterrestrial Exploration

Lester D. Hutt, Daniel P. Glavin, Jeffrey L. Bada, and Richard A. Mathies*

Department of Chemistry, University of California, Berkeley, California 94720
Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0212

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 μm wide x 20 μm 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/ ϒ -cyclodextrin pH 10.0 carbonate electrophoresis buffer and a separation voltage of 550 V/cm at 10°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.

Link to PDF

top

Amino acids in the Martian meteorite Nakhla

Daniel P. Glavin, Jeffrey L. Bada,* Karen L.F. Brinton, and Gene D. McDonald

* Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 93093-0212
National Aeronautics and Space Administration Jet Propulsion Laboratory, MS 183-301, 4800Oak Grove Drive, Pasadena, CA 91109

A suite of protein and nonprotein amino acids were detected with high-performance liquid chromatography in the water- and acid-soluble components of an interior fragment of the Martian meteorite Nakhla, which fell in Egypt in 1911.Aspartic and glutamic acids, glycine, alanine, -alanine, and -amino-n-butyric acid (-ABA) were the most abundant amino acids detected and were found primarily in the 6M HCl-hydrolyzed, hot water extract. The concentrations ranged from 20 to 330 parts per billion of bulk meteorite. The amino acid distribution in Nakhla, including the D/L ratios (values range from <0.1 to 0.5), is similar to what is found in bacterially degraded organic matter. The amino acids in Nakhla appear to be derived from terrestrial organic matter that infiltrated the meteorite soon after its fall to Earth, although it is possible that some of the amino acids are endogenous to the meteorite. The rapid amino acid contamination of Martian meteorites after direct exposure to the terrestrial environment has important implications for Mars sample-return missions and the curation of the samples from the time of their delivery to Earth.

Link to PDF

top

Microfabrication Technology for the Production of Capillary Array Electrophoresis Chips

Peter C. Simpson, Adam T. Woolley and
Richard A. Mathies

Department of Chemistry, University of California, Berkeley, CA 94720

Improvements in the fabrication, sample handling and addressing of capillary array electrophoresis (CAE) chips have permitted the development of high density, high-throughput devices capable of analyzing 48 samples in about 20 minutes. The fabrication of high density capillary arrays on 10 cm diameter substrates required the characterization of glasses that yield high quality etches and the development of improved sacrificial etch masks. Using these improved fabrication techniques, high-quality, deep channel etches are routinely obtained. Methods for bonding large area substrates and for drilling arrays of 100 or more access holes have also been developed. For easier sample introduction, we use an array of sample wells fabricated from an elastomeric sheet. The practicality of these technologies is demonstrated through the analysis of 12 DNA samples in parallel on a microfabricated CAE chip, the development of methods for injecting multiple samples onto a single capillary without cross contamination, and the operation of a microfabricated array of 12 capillaries with 4 sample injections per capillary that can analyze 48 samples.

Link to PDF

top

Isolation of Amino Acids from Natural Samples Using Sublimation

Daniel P. Glavin and Jeffrey L. Bada*

Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093-0212

Amino acids have appreciable vapor pressures above 150 C and will sublime under partial vacuum at elevated temperatures without any racemization or decomposition. The recoveries of several amino acids including aspartic acid, serine, glycine, alanine, -aminoisobutyric acid, and valine were optimized by varying the temperature and duration of sublimation. Sublimation has been shown to be a rapid and effective technique for the isolation of amino acids from natural samples for enantiomeric analyses and a good substitute for conventional cation-exchange desalting techniques.

Link to PDF

top

A Search for Endogenous Amino Acids in Martian Meteorite ALH84001

Jeffrey L. Bada*, Daniel P. Glavin, Gene D. McDonald, Luann Becker

Trace amounts of glycine, serine, and alanine were detected in the carbonate component of the martian meteorite ALH84001 by high-performance liquid chromatography. The detected amino acids were not uniformly distributed in the carbonate component and ranged in concentration from 0.1;to 7 parts per million. Although the detected alanine consists primarily of the L enantiomer, low concentrations ( 0.1 parts per million) of endogenous D -alanine may be present in the ALH84001 carbonates. The amino acids present in this sample of ALH84001 appear to be terrestrial in origin and similar to those in Allan Hills ice, although the possibility cannot be ruled out that minute amounts of some amino acids such as D-alanine are preserved in the meteorite.

Link to PDF

top

Enhanced: Extraterrestrial Handedness?

Jeffrey L. Bada

The author is at Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA, 92093-0212, USA.

A symmetry in the handedness of molecules that arise through biosynthesis is perhaps one of the more unique features of life on Earth. A well-known example is that only L amino acids are incorporated into proteins during transcription even though amino acids with a chiral or asymmetric carbon atom can exist as two chemically equivalent optical isomers, the L and D enantiomers. How this L amino acid handedness, or homochirality, originated in terrestrial life has been an area of considerable discussion ( 1 ). Prebiotic syntheses of amino acids either on Earth or elsewhere would be expected to produce racemic mixtures (equal amounts of the L and D enantiomers, or D / L = 1.0). Therefore, an enantiomeric selection process was required at some stage in the origin or evolution of life on Earth. Because there is no apparent biochemical reason why L amino acids would be selected over D amino acids, the homochirality has been considered to be simply a matter of chance.

Amino Acid Racemization and the Preservation of Ancient DNA

Hendrik N. Poinar, Matthias Höss, Jeffrey L. Bada*,
Svante Pääbo

The extent of racemization of aspartic acid, alanine, and leucine provides criteria for assessing whether ancient tissue samples contain endogenous DNA. In samples in which the D/L ratio of aspartic acid exceeds 0.08, ancient DNA sequences could not be retrieved. Paleontological finds from which DNA sequences purportedly millions of years old have been reported show extensive racemization, and the amino acids present are mainly contaminates. An exception is the amino acids in some insects preserved in amber.

H. N. Poinar, M. Höss, S. Pääbo, Institute of Zoology, University of Munich, Post Office Box 202136, D-80021 Munich, Germany.

J. L. Bada, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093, USA.

Link to PDF

top

Amino Acid Racemization on Mars: Implications for the Preservation of Biomolecules from an Extinct Martian Biota

Jeffrey L. Bada* and Gene D. McDonald

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0212

Using kinetic data, we have estimated the racemization half-lives and times for total racemization of amino acids under conditions relevant to the surface of Mars. Amino acids from an extinct martian biota maintained in a dry, cold (<250 K) environment would not have racemized significantly over the lifetime of the planet. Racemization would have taken place in environments where liquid water was present even for time periods of only a few million years following biotic extinction. The best preservation of both amino acid homochirality and nucleic acid genetic information associated with extinct martian life would be in the polar regions.

Link to PDF

top

© Copyright 2004, Richard A. Mathies

Website Design: Jung Design
Site Maintained by: Spitfire Graphics