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Helfman, PM, Bada JL.  1975.  Aspartic-Acid Racemization in Tooth Enamel from Living Humans. Proceedings of the National Academy of Sciences of the United States of America. 72:2891-2894.   10.1073/pnas.72.8.2891   Website
Bada, JL, Mitchell E, Kemper B.  1983.  Aspartic-Acid Racemization in Narwhal Teeth. Nature. 303:418-420.   10.1038/303418a0   Website
Schroeder, RA, Bada JL.  1978.  Aspartic-Acid Racemization in Late Wisconsin Lake-Ontario Sediments. Quaternary Research. 9:193-204.   10.1016/0033-5894(78)90067-4   Website
Masters, PM, Bada JL, Zigler JS.  1977.  Aspartic-Acid Racemization in Human Lens During Aging and in Cataract Formation. Nature. 268:71-73.   10.1038/268071a0   Website
Masters, PM, Bada JL, Zigler JS.  1978.  Aspartic-Acid Racemization in Heavy Molecular-Weight Crystallins and Water-Insoluble Protein from Normal Human Lenses and Cataracts. Proceedings of the National Academy of Sciences of the United States of America. 75:1204-1208.   10.1073/pnas.75.3.1204   Website
Helfman, PM, Bada JL.  1976.  Aspartic-Acid Racemization in Dentin as a Measure of Aging. Nature. 262:279-281.   10.1038/262279b0   Website
Ike, D, Bada JL, Masters PM, Kennedy G, Vogel JC.  1979.  Aspartic-Acid Racemization and Radiocarbon Dating of an Early Milling Stone Horizon Burial in California. American Antiquity. 44:524-530.   10.2307/279550   Website
Brinton, KL, Bada JL.  1995.  Aspartic-Acid Racemization and Protein Diagenesis in Corals over the Last 350 Years - Comment. Geochimica Et Cosmochimica Acta. 59:415-416.Website
Bada, JL.  1985.  Aspartic-Acid Racemization Ages of California Paleoindian Skeletons. American Antiquity. 50:645-647.   10.2307/280327   Website
Skelley, AM, Cleaves HJ, Jayarajah CN, Bada JL, Mathies RA.  2006.  Application of the mars organic analyzer to nucleobase and amine biomarker detection. Astrobiology. 6:824-837.   10.1089/ast.2006.6.824   AbstractWebsite

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 similar to 4 x 10(3) 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 mu M and 4.1 +/- mu M, 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.

Bada, J.  1984.  Application of Amino Acid Racemization Dating of Fossil Bones and Teeth in problems of paleoanthropology. McGraw-Hill yearbook of science and technology. :87-89.
Masters, PM, Bada J.  1978.  Antiquity of human beings in America: Evidence derived from amino acid racemization of paleo Indian. Occasional papers in methods and tehories i n California Archeology. . 2:16-24.
Bada, JL, Miller SL.  1968.  Ammonium Ion Concentration in Primitive Ocean. Science. 159:423-&.   10.1126/science.159.3813.423   Website
Lee, C, Bada JL, Peterson E.  1976.  Amino-Acids in Modern and Fossil Woods. Nature. 259:183-186.   10.1038/259183a0   Website
Lee, C, Bada JL.  1975.  Amino-Acids in Equatorial Pacific Ocean Water. Earth and Planetary Science Letters. 26:61-68.   10.1016/0012-821x(75)90177-6   Website
Bada, JL.  1985.  Amino-Acid Racemization Dating of Fossil Bones. Annual Review of Earth and Planetary Sciences. 13:241-268.   10.1146/annurev.earth.13.1.241   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.

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, Bada JL, Brinton KLF, McDonald GD.  1999.  Amino acids in the Martian meteorite Nakhla. Proceedings of the National Academy of Sciences of the United States of America. 96:8835-8838.   10.1073/pnas.96.16.8835   AbstractWebsite

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, beta-alanine, and gamma-amino-n-butyric acid (gamma-ABA) were the most abundant amino acids detected and were found primarily in the 6 M 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.

Wang, XS, Poinar HN, Poinar GO, Bada JL.  1995.  Amino acids in the amber matrix and in entombed insects. Amber, Resinite, and Fossil Resins. 617( Anderson KB, Crelling JC, Eds.).:255-262., Washington: Amer Chemical Soc Abstract

We have investigated the amino acids in both the bulk matrix and in insect inclusions in tree resins ranging in age from <100 years to 130 million years. The amino acid content of the resin matrix averages about 5 ppm and does not systematically vary with the age of the resin. The amino acids in the matrix are likely derived from either plant cells, or microorganisms, encapsulated when the resin solidified. The amino acid content of the insect tissues entombed in amber is less than that in modern insect specimens; this loss may be the result of oxidation reactions. The amino acid compositions of a fly and bee entombed in 30-40 million year old amber are somewhat different from the amino acid profiles of modern insects; this finding suggests that the preserved amino acid pattern under anhydrous conditions may not be the same as in aqueous environments. The amino acid racemization rate in amber insect inclusions is retarded by a factor of >10(4) compared to other geochemical environments on the surface of the Earth. This is also apparently due to the anhydrous properties of the amber matrix. The excellent preservation of amino acids in amber insect inclusions suggests that other biomolecules would also be preserved much better than in other geochemical environments. This conclusion is consistent with the reported successful retrieval of DNA sequences from amber-entombed organisms.

Bada, J.  1983.  Amino Acid Racemization dating of fossil bones from Zhouk. China Excahnge News. 11:4-6.
Poinar, HN, Hoss M, Bada JL, Paabo S.  1996.  Amino acid racemization and the preservation of ancient DNA. Science. 272:864-866.   10.1126/science.272.5263.864   AbstractWebsite

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.