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Ambler, RP, Bada JL, Finch P, Grocke DR, Eglinton G, Macko SA.  1999.  Preservation of key biomolecules in the fossil record: current knowledge and future challenges - Discussion. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences. 354:86-87.Website
Ambler, RP, Macko SA, Sykes B, Griffiths JB, Bada J, Eglinton G.  1999.  Documenting the diet in ancient human populations through stable isotope analysis of hair - Discussion. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences. 354:75-76.Website
Arrhenius, G, Bada JL, Joyce GF, Lazcano A, Miller S, Orgel LE.  1999.  Origin and ancestor: Separate environments. Science. 283:792-792.Website
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.

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.

Aubrey, AD, Cleaves HJ, Bada JL.  2009.  The Role of Submarine Hydrothermal Systems in the Synthesis of Amino Acids. Origins of Life and Evolution of Biospheres. 39:91-108.   10.1007/s11084-008-9153-2   AbstractWebsite

There is little consensus regarding the plausibility of organic synthesis in submarine hydrothermal systems (SHSs) and its possible relevance to the origin of life. The primary reason for the persistence of this debate is that most experimental high temperature and high-pressure organic synthesis studies have neglected important geochemical constraints with respect to source material composition. We report here the results of experiments exploring the potential for amino acid synthesis at high temperature from synthetic seawater solutions of varying composition. The synthesis of amino acids was examined as a function of temperature, heating time, starting material composition and concentration. Using very favorable reactant conditions (high concentrations of reactive, reduced species), small amounts of a limited set of amino acids are generated at moderate temperature conditions (similar to 125-175A degrees C) over short heating times of a few days, but even these products are significantly decomposed after exposure times of approximately 1 week. The high concentration dependence observed for these synthetic reactions are demonstrated by the fact that a 10-fold drop in concentration results in orders of magnitude lower yields of amino acids. There may be other synthetic mechanisms not studied herein that merit investigation, but the results are likely to be similar. We conclude that although amino acids can be generated from simple likely environmentally available precursors under SHS conditions, the equilibrium at high temperatures characteristic of SHSs favors net amino acid degradation rather than synthesis, and that synthesis at lower temperatures may be more favorable.

Bada, JL, Protsch R, Schroede.Ra.  1973.  Racemization Reaction of Isoleucine Used as a Paleotemperature Indicator. Nature. 241:394-395.   10.1038/241394a0   Website
Bada, JL, Gillespie R, Gowlett JAJ, Hedges REM.  1984.  Accelerator Mass-Spectrometry Radiocarbon Ages of Amino-Acid Extracts from Californian Paleoindian Skeletons. Nature. 312:442-444.   10.1038/312442a0   Website
Bada, JL.  1990.  Racemization Dating. Science. 248:539-540.   10.1126/science.248.4955.539   Website
Bada, J, Shou MY.  1980.  Kinetics and mechanics of amino acid racemization in aqueous solution and bones. Biogeochemistry of amino acids. Ed: Hare, P. E, Hoering, T. C, King, K.
Bada, JL.  1985.  Aspartic-Acid Racemization Ages of California Paleoindian Skeletons. American Antiquity. 50:645-647.   10.2307/280327   Website
Bada, JL, Schroede.Ra.  1972.  Racemization of Isoleucine in Calcareous Marine Sediments - Kinetics and Mechanism. Earth and Planetary Science Letters. 15:1-&.   10.1016/0012-821x(72)90022-2   Website
Bada, JL.  1998.  Biogeochemistry of organic nitrogen compounds. Nitrogen-Containing Macromolecules in the Bio- and Geosphere. 707( Stankiewicz BA, VanBergen PF, Eds.).:64-73., Washington: Amer Chemical Soc Abstract

Nitrogen containing organic compounds represent the second most abundant reservoir of nitrogen on the surface of the Earth. However, the organic compounds that make up this global nitrogen pool are not well characterized. Although amino acids and the nitrogenous bases of nucleic acids make up only a few percent of the total organic nitrogen reservoir, the geochemical reactions of these compounds have been extensively studied. Because hydrolysis reactions are rapid on the geologic time scale, both proteins and nucleic acids (DNA and RNA) are not preserved for more than 10(3) to 10(5) years in most environments. The racemization reaction of amino acids converts the L-amino acids present in the biosphere into a racemic mixture (D/L amino acid ratio = 1.0) in the geosphere in less than 10(6) years. Anhydrous conditions, such as those that may be associated with amber entombed insects, may retard both biopolymer hydrolysis and racemization. Condensation reactions between amino acids and sugars, including sugars at apurinic sites in nucleic acid fragments, likely result in the incorporation of these compounds into geopolymers such as humic acids. Although rearrangement reactions in geopolymers may scramble the original molecular structures, part of the global organic nitrogen inventory was originally derived from amino acids and nucleic acid bases.

Bada, JL, Miller SL.  1968.  Ammonium Ion Concentration in Primitive Ocean. Science. 159:423-&.   10.1126/science.159.3813.423   Website
Bada, JL.  2001.  State-of-the-art instruments for detecting extraterrestrial life. Proceedings of the National Academy of Sciences of the United States of America. 98:797-800.   10.1073/pnas.98.3.797   Website
Bada, JL, Vrolijk CD, Brown S, Druffel ERM, Hedges REM.  1987.  Bomb Radiocarbon in Metabolically Inert Tissues from Terrestrial and Marine Mammals. Geophysical Research Letters. 14:1065-1067.   10.1029/GL014i010p01065   Website
Bada, JL, Wang XYS, Hamilton H.  1999.  Preservation of key biomolecules in the fossil record: current knowledge and future challenges. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences. 354:77-86.   10.1098/rstb.1999.0361   AbstractWebsite

We have developed a model based on the analyses of modern and Pleistocene eggshells and mammalian bones which can be used to understand the preservation of amino acids and other important biomolecules such as DNA in fossil specimens. The model is based on the following series of diagenetic reactions and processes involving amino acids: the hydrolysis of proteins and the subsequent loss of hydrolysis products from the fossil matrix with increasing geologic age; the racemization of amino acids which produces totally racemized amino acids in 10(5)-10(6) years in most environments on the Earth; the introduction of contaminants into the fossil that lowers the enantiomeric (D:L) ratios produced via racemization; and the condensation reactions between amino acids, as well as other compounds with primary amino groups, and sugars which yield humic acid-like polymers. This model was used to evaluate whether useful amino acid and DNA sequence information is preserved in a variety of human, amber-entombed insect and dinosaur specimens. Most skeletal remains of evolutionary interest with respect to the origin of modern humans are unlikely to preserve useful biomolecular information although those from high latitude sites may be an exception. Amber-entombed insects contain well-preserved unracemized amino acids, apparently because of the anhydrous nature of the amber matrix, and thus may contain DNA fragments which have retained meaningful genetic information. Dinosaur specimens contain mainly exogenous amino acids, although traces of endogenous amino acids may be present in some cases. Future ancient biomolecule research which takes advantage of new methologies involving, for example, humic acid cleaving reagents and microchip-based DNA-protein detection and sequencing, along with investigations of very slow biomolecule diagenetic reactions such as the racemization of isoleucine at the beta-carbon, will lead to further enhancements of our understanding of biomolecule preservation in the fossil record.

Bada, JL, Luyendyk BP.  1971.  Route to Late Cenozoic Temperature History. Science. 172:503-&.Website
Bada, JL.  1991.  Amino-Acid Cosmogeochemistry. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences. 333:349-358.   10.1098/rstb.1991.0084   AbstractWebsite

Amino acids are ubiquitous components of living organisms and as a result they are widely distributed on the surface of the Earth. Whereas only 20 amino acids are found in proteins, a much more diverse mixture of amino acids has been detected in carbonaceous meteorites. Amino acids in living organisms consist exclusively of the L-enantiomers, but in meteorites, amino acids with chiral carbons are present as racemic mixtures. Protein amino acids undergo a variety of diagenetic reactions that produce some other amino acids but not the unique amino acids present in meteorites. Nevertheless, trace quantities of meteoritic amino acids may occur on the Earth, either as a result of bolide impact or from the capture of cosmic dust particles. The ensemble of amino acids present on the early Earth before life existed was probably similar to those in prebiotic experiments and meteorites. This generates a question about why the L-amino acids on which life is based were selected.

Bada, JL, Mitchell E, Kemper B.  1983.  Aspartic-Acid Racemization in Narwhal Teeth. Nature. 303:418-420.   10.1038/303418a0   Website
Bada, JL.  1995.  Biomolecules - Origins of Homochirality. Nature. 374:594-595.   10.1038/374594a0   Website