Patterns of racemization and epimerization of amino acids in land snail shells over the course of the Holocene

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(91)90418-5· OSTI ID:5949719

Goodfriend, G A ^[1]

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1. Weizmann Institute of Science, Rehovot (Israel)

The patterns of racemization of six amino acids and of epimerization of isoleucine over the course of the Holocene were studied in a series of 38 radiocarbon-dated samples of the land snail Trochoidea seetzeni from the Negev Desert in southern Israel. The D/L ratios of each of the amino acids show a strong correlation with age (r = 0.84-0.94) and thus good age predictive ability. The patterns in faster-racemizing amino acids do not conform to first-order kinetics. Transformation to parabolic kinetics linearizes these faster-racemizing amino acids, except for aspartic acid (which shows a very high initial rate of racemization). After transformation, each amino acid shows an equally good correlation with age (r = 0.91-0.93). The D/L ratios of the various amino acids covary very strongly, even after the covariation due to sample age is removed from the data set. Thus, analysis of more than one amino acid provides largely redundant information on sample age. Nevertheless, because of differences in racemization rates, some amino acids provide better time resolution in different time ranges - aspartic acid is especially useful for very young samples, and glutamic acid and isoleucine for older samples. Neither the depth of burial of the samples nor the burial mode appears to affect the rate of racemization or epimerization.

• OSTI ID: 5949719
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 55:1; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
AMINO ACIDS
ANIMALS
AQUATIC ORGANISMS
ASIA
BODY
CARBOXYLIC ACIDS
CENOZOIC ERA
CHEMICAL COMPOSITION
CHEMISTRY
DEVELOPING COUNTRIES
EXOSKELETON
FOSSILS
GEOCHEMISTRY
GEOLOGIC AGES
INVERTEBRATES
ISRAEL
MIDDLE EAST
MOLLUSCS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
QUATERNARY PERIOD
RACEMIZATION
SKELETON
SNAILS
STEREOCHEMISTRY