Influence of Murchison or Allende minerals on hydrogen-deuterium exchange of amino acids

doi:10.1016/0016-7037(95)00068-B

Geochimica et Cosmochimica Acta

Volume 59, Issue 8, April 1995, Pages 1623-1631

https://doi.org/10.1016/0016-7037(95)00068-B Get rights and content

Abstract

Deuterium-enriched amino acids occur in the Murchison carbonaceous chrondrite. This meteorite underwent a period of aqueous alteration with isotopically light water. With the objective of setting limits on the conditions of aqueous alteration, the exchange of the carbon-bonded hydrogen atoms of amino acids with D₂O has been studied from 295 to 380 K as a function of time and meteorite/heavy water ratio. The amount of Murchison or Allende dust present has a significant effect on the rate and amount of hydrogen-deuterium exchange observed. At elevated temperatures, the a-hydrogens of all the amino acids studied were found to exchange with deuterium. In glycine and aspartic acid, this process resulted in total exchange of the carbon-bonded hydrogen. A completely deuterated isotopomer of alanine was produced in significant quantities only when the rock/water ratio was greater than 0.5. No exchange of carbonbonded hydrogens was observed in the case of amino acids which do not possess an α-hydrogen atom. The rates of H/D exchange for amino acids observed here did not correspond to deuterium enrichment of the amino acids in the Murchison meteorite. These results suggest that H/D exchange with water had a negligible effect on the observed deuterium enrichment of amino acids found in Murchison and that the temperature at which the amino acids were exposed to liquid water was close to 273 K.

References (17)

T.E. Bunch et al.
Carbonaceous Chondrites—II. Carbonaceous chondrite phyllosilicates and light element geochemistry as indicators of parent body processes and surface conditions
Geochim. Cosmochim. Acta
(1980)
R.N. Clayton et al.
The oxygen isotope record in Murchison and other carbonaceous chondrites
Earth Planet. Sci. Lett.
(1984)
D.H. Grinspoon et al.
Deuterium fractionation in the presolar nebula: kinetic limitations on surface catalysis
Icarus
(1987)
J.F. Kerridge
Carbon, hydrogen and nitrogen in carbonaceous chondrites: Abundances and isotopic compositions in bulk samples
Geochim. Cosmochim. Acta
(1985)
N.R. Lerner et al.
The Strecker synthesis as a source of amino acids in carbonaceous chondrites: Deuterium retention during synthesis
Geochim. Cosmochim. Acta
(1993)
E.T. Peltzer et al.
The chemical conditions on the parent body of the Murchison meteorite: Some conclusions based on amino, hydroxy and dicarboxylic acids
Adv. Space Res.
(1984)
W.E. Pereira
Stable isotope mass fragmentography: Identification and hydrogen-deuterium exchange studies of eight Murchison meteorite amino acids
Geochim. Cosmochim. Acta
(1975)
S. Pizzarello et al.
Isotopic analyses of amino acids from the Murchison meteorite
Geochim. Cosmochim. Acta
(1991)

There are more references available in the full text version of this article.

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The α-amino and α-hydroxy acids found in the Murchison carbonaceous chondrite are deuterium enriched. These compounds are thought to have originated from common deuterium enriched carbonyl precursors, by way of a Strecker synthesis which took place in an aqueous solution of HCN, NH₃, and carbonyl compounds during the period of aqueous alteration of the meteorite parent body. However, the hydroxy acids found in Murchison are less deuterium enriched than the amino acids. With the objective of determining if the discrepancy in deuterium enrichment between the amino acids and the hydroxy acids found in Murchison is consistent with their formation in a Strecker synthesis, we have measured the deuterium content of α-amino and α-hydroxy acids produced in solutions of deuterated carbonyl compounds, KCN and NH₄CI, and also in mixtures of such solutions and Allende dust at 263°K and 295°K. Retention of the isotopic signature of the starting carbonyl by both α-amino acids and α-hydroxy acids is more dependent upon temperature, concentration, and pH than upon the presence of meteorite dust in the solution. In order to determine if hydroxy acids retain their carbon-bonded hydrons better than amino acids, deuterium exchange of α-hydroxy acids in D₂O was investigated at temperatures in excess of 393°K. No measurable exchange of hydrogen was observed. While these results do not rule out the Strecker synthesis as a source of meteoritic amino acids, they do indicate that other reaction schemes may have been more important.
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ArticleInfluence of Murchison or Allende minerals on hydrogen-deuterium exchange of amino acids

Abstract

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Icarus

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Adv. Space Res.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Article
Influence of Murchison or Allende minerals on hydrogen-deuterium exchange of amino acids