Document Detail


Preservation of key biomolecules in the fossil record: current knowledge and future challenges.
MedLine Citation:
PMID:  10091249     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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.
Authors:
J L Bada; X S Wang; H Hamilton
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Publication Detail:
Type:  Historical Article; Journal Article    
Journal Detail:
Title:  Philosophical transactions of the Royal Society of London. Series B, Biological sciences     Volume:  354     ISSN:  0962-8436     ISO Abbreviation:  Philos. Trans. R. Soc. Lond., B, Biol. Sci.     Publication Date:  1999 Jan 
Date Detail:
Created Date:  1999-04-28     Completed Date:  1999-04-28     Revised Date:  2010-09-13    
Medline Journal Info:
Nlm Unique ID:  7503623     Medline TA:  Philos Trans R Soc Lond B Biol Sci     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  77-86; discussion 86-7     Citation Subset:  IM; Q    
Affiliation:
Scripps Institution of Oceanography, University of California at San Diego, La Jolla 92093-0212, USA. jbada@ucsd.edu
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MeSH Terms
Descriptor/Qualifier:
Amino Acids / analysis*,  chemistry
Animals
Bone and Bones / chemistry
DNA / analysis*,  chemistry
Egg Shell / chemistry
Fossils*
History, Ancient
Humans
Insects
Models, Chemical
Paleontology
Stereoisomerism
Vertebrates
Chemical
Reg. No./Substance:
0/Amino Acids; 9007-49-2/DNA
Comments/Corrections

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