Fossils amino acids

Estimation of enantiomer ratios is conveniently accomplished using diastereoisomer-forming derivatisation protocols or through separations of enantiomer mixtures over chiral stationary phases. Commercially available chiral coatings for this purpose, such as Chirasil-Val, have been used in the field of amino-acid fossil dating (Section 1.11), exploiting the better resolution of capillary GLC, whereby a thermally stable liquid coats the surface of a narrow tube. 

When the sample is a solid, a separation of the analyte and interferent by sublimation may be possible. The sample is heated at a temperature and pressure below its triple point where the solid vaporizes without passing through the liquid state. The vapor is then condensed to recover the purified solid. A good example of the use of sublimation is in the isolation of amino acids from fossil mohusk shells and deep-sea sediments. ... 

Hare, P.E., Fogel, ML., Stafford, T.W. Jr., Mitchell, A.D. and Hoering, T.C. 1991 The isotopic composition of carbon and nitrogen in individual amino acids isolated from modern and fossil proteins. Journal of Archaeological Science 18 227-292. 

Van Klinken, GJ. 1991 Dating and Dietary Reconstruction by Isotopic Analysis of Amino Acids in Fossil Bone Collagen—with Special Reference to the Caribbean. Ph.D. dissertation. University of Groningen, The Netherlands. 

Bada, J. L. (1985), Amino acid racemization dating of fossil bones, Ann. Rev. Earth Planet. Sci. 13, 241-268. 

It is not only the vast difference of about 1.8 billion years which is so surprising the timescale for the separation point of the main branches of the tree of life is clearly shifted. The catastrophe hypothesis put forward to explain this difference appears unlikely, since there are no signs of such a phenomenal obliteration of all life on Earth. Another explanation could be that the data from the amino acid sequences provide only information on the way in which life forms diverged, but not on the timescale (Schopf, 1998). This interpretation of the Doolittle event by Schopf was provided at a time when doubts had not yet been cast on the dating of the first fossils at 3.45 billion years, published by him in 1993. 

A BDS method consisting in the incubation of a mixture formed by a fossil fuel and an aqueous phase containing a biocatalyst and a rate-enhancing amount of a protein having NADH FMN oxidoreductase activity or enzymatically active mutant thereof. The oxidoreductase has the amino acid sequence set forth in SEQ ID No. 2, described in the original document (see Ref. [57]). A separation stage is also claimed. 

D. Kaufman, Dating Deep Lake Sediments by Using Amino Acid Racemization in Fossil Ostracodes, Geology, 31, 1049 1052 (2003). 

P.E. Hare, P.H. Abelson, Racemization of Amino Acids in Fossil Shells, Carnegie Institution of Washington Year Book, 66, 526 528 (1967). 

Hare, P. E. and Estep, M. L. F. (1983) Carbon and nitrogen isotopic composition of amino acids in modern and fossil collagens. Carnegie Institution Washington Yearbook 82, 410 414. 

Bada, J. L., Shou, M., Effects of various environmental parameters on amino acid racemization rates in fossil bones, Geological Soc. America, Abstracts with Programs, 8, 762-763... 

Bada, J. L., Master, P. M., Hoopes, E., Darling, The Dating of Fossil Bones Using Amino Acid Racemization, In Radiocarbon Dating, pp. 740-756, Berkeley, University of California Press, 1979. 

Amino Acid Dating Techniques depend on the "rates of hydrolysis reactions of proteins and racemization, epimerization, and decomposition reactions of amino acids [they have] been applied to the age-dating of fossil bone, teeth, and shell. Activation energies range from near 20 kcal per mole for hydrolysis reactions to around 30 kcal per mole for racemization... 

In the 1960, it was noticed that substitutions in some amino acid sequences seemed to occur at a roughly constant rate over time (Zuckerkandl and Pauling, 1965). This is the well known molecular clock hypothesis. For a particular protein such as cytochrome c or myoglobin, it was noticed that there was a linear relationship between divergences of pairs of sequences, as measured by numbers of amino acid differences, and divergences of the species, as measured by dates from the fossil record. There is still considerable debate as to how accurate the molecular clock may be and as to how it might vary systematically depending on the species, type of protein, and kinds of substitutions that are counted. 

A dating technique for fossils is based on the measurement of the d l ratio of amino acids extracted from the fossil sample. The hypothesis is that over very long periods... 

The effect of temperature on the rate of racemization of amino acids in fossils was investigated and the implications of the findings on fossil dating were analyzed313. The high rate of conversion of L-aspartic acid into its D-isomer, observed in uncontaminated bone samples taken from catacombs in Rome (IV century BC) was attributed to collagen decomposition due to the humidity of the catacombs314. 

King, K.J. 1974. Preserved amino acids from slicified protein in fossil Radiolaria. Nature 252 690-692. 

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