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Book Chapter
Msters, PM, Bada J.  1979.  Amimo Acid Racemization dating of fossil shells from Southern California. Radiocarbon and other dating methods. ( and Rainer B, Ed.)., Berkley: UC Press
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.

Journal Article
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
Robertson, KJ, Williams PM, Bada JL.  1987.  Acid-Hydrolysis of Dissolved Combined Amino-Acids in Seawater - a Precautionary Note. Limnology and Oceanography. 32:996-997.Website
Masters, PM, Bada J.  1978.  Advances in amino acid racemization: Dating of bone and Shell. Advances in Chemistry Series. 171: Archeological Chemistry:117-138.
George, JC, Bada J, Zeh J, Scott L, Brown SE, O'Hara T, Suydam R.  1999.  Age and growth estimates of bowhead whales (Balaena mysticetus) via aspartic acid racemization. Canadian Journal of Zoology-Revue Canadienne De Zoologie. 77:571-580.   10.1139/cjz-77-4-571   AbstractWebsite

A total of 48 eye globes were collected and analyzed to estimate ages of bowhead whales using the aspartic acid racemization technique. In this technique, age is estimated based on intrinsic changes in the D and L enantiomeric isomeric forms of aspartic acid in the eye lens nucleus. Age estimates were successful for 42 animals. Racemization rate (k(Asp)) for aspartic acid was based on data from earlier studies of humans and fin whales; the estimate used was 1.18 x 10(-3)/year. The D/L ratio at birth ((D/L)(0)) Was estimated using animals less than or equal to 2 years of age (n = 8), since variability in the D/L measurements is large enough that differences among ages in this range are unmeasurable. The (D/L)(0) estimate was 0.0285. Variance of the age estimates was obtained using the delta method. Based on these data, growth appears faster for females than males, and age at sexual maturity (age at length 12-13 m for males and 13-13.5 m for females) occurs at around 25 years of age. Growth slows markedly for both sixes at roughly 40-50 years of age. Four individuals (all males) exceed 100 years of age. Standard error increased with estimated age, but the age estimates had lower coefficients of variation for older animals. Recoveries of traditional whale-hunting tools from five recently harvested whales also suggest life-spans in excess of 100 years of age in some cases.

Bada, J, Brown SE, Masters PM.  1980.  age determination of marine mammaks based on aspartic acid racemization in teeth and lens nucleus. Rep.International Whaling comisison (Special issue). 3:113-118.
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.

Peltzer, ET, Bada JL.  1978.  Alpha-Hydroxycarboxylic Acids in Murchison Meteorite. Nature. 272:443-444.   10.1038/272443a0   Website
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.

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.

Bada, J.  1983.  Amino Acid Racemization dating of fossil bones from Zhouk. China Excahnge News. 11:4-6.
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.

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.

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.  1985.  Amino-Acid Racemization Dating of Fossil Bones. Annual Review of Earth and Planetary Sciences. 13:241-268.   10.1146/   Website
Bada, JL, Helfman PM.  1975.  Amino-Acid Racemization Dating of Fossil Bones. World Archaeology. 7:160-&. AbstractWebsite
Bada, JL, Hoopes E, Darling D, Dungworth G, Kessels HJ, Kvenvolden KA, Blunt DJ.  1979.  Amino-Acid Racemization Dating of Fossil Bones .1. Inter-Laboratory Comparison of Racemization Measurements. Earth and Planetary Science Letters. 43:265-268.   10.1016/0012-821x(79)90210-3   AbstractWebsite
Bada, JL, Wang XS, Poinar HN, Paabo S, Poinar GO.  1994.  Amino-Acid Racemization in Amber-Entombed Insects - Implications for DNA Preservation. Geochimica Et Cosmochimica Acta. 58:3131-3135.   10.1016/0016-7037(94)90185-6   AbstractWebsite

DNA depurination and amino acid racemization take place at similar rates in aqueous solution at neutral pH. This relationship suggests that amino acid racemization may be useful in accessing the extent of DNA chain breakage in ancient biological remains. To test this suggestion, we have investigated the amino acids in insects entombed in fossilized tree resins ranging in age from <100 years to 130 million years. The amino acids present in 40 to 130 million year old amber-entombed insects resemble those in a modern fly and are probably the most ancient, unaltered amino acids found so far on Earth. In comparison to other geochemical environments on the surface of the Earth, the amino acid racemization rate in amber insect inclusions is retarded by a factor of > 10(4). These results suggest that in amber insect inclusions DNA depurination rates would also likely be retarded in comparison to aqueous solution measurements, and thus DNA fragments containing many hundreds of base pairs should be preserved. This conclusion is consistent with the reported successful retrieval of DNA sequences from amber-entombed organisms.

Bada, JL, Brown SE.  1980.  Amino-Acid Racemization in Living Mammals - Biochronological Applications. Trends in Biochemical Sciences. 5:R3-R5.   10.1016/s0968-0004(80)80800-0   AbstractWebsite
Bada, JL, McDonald GD.  1995.  Amino-Acid Racemization on Mars - Implications for the Preservation of Biomolecules from an Extinct Martian Biota. Icarus. 114:139-143.   10.1006/icar.1995.1049   AbstractWebsite

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. (C) 1995 Academic Press, Inc.