Fractionation of hydrogen isotopes in lipid biosynthesis

Isotopic compositions of carbon-bound hydrogen in individual compounds from eight different organisms were measured using isotope-ratio-monitoring gas chromatography–mass spectrometry. This technique is capable of measuring D/H ratios at natural abundance in individual lipids yielding as little as 2...

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Bibliographic Details
Published in:Organic geochemistry 1999-01, Vol.30 (9), p.1193-1200
Main Authors: Sessions, Alex L., Burgoyne, Thomas W., Schimmelmann, Arndt, Hayes, John M.
Format: Article
Language:English
Subjects:
Acetogenic
Biosynthesis
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fatty acids
Fractionation
Gas chromatography
Hydrocarbons
Hydrogen isotopes
Hydrogenation
irmGCMS
Isoprenoid
Isotope fractionation
Isotope geochemistry
Isotope geochemistry. Geochronology
Isotopes
Lipids
Mass spectrometry
Sedimentary rocks
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Summary:Isotopic compositions of carbon-bound hydrogen in individual compounds from eight different organisms were measured using isotope-ratio-monitoring gas chromatography–mass spectrometry. This technique is capable of measuring D/H ratios at natural abundance in individual lipids yielding as little as 20 nmol of H 2, and is applicable to a wide range of compounds including hydrocarbons, sterols, and fatty acids. The hydrogen isotopic compositions of lipids are controlled by three factors: isotopic compositions of biosynthetic precursors, fractionation and exchange accompanying biosynthesis, and hydrogenation during biosynthesis. δD values of lipids from the eight organisms examined here suggest that all three processes are important for controlling natural variations in isotopic abundance. n-Alkyl lipids are depleted in D relative to growth water by 113–262‰, while polyisoprenoid lipids are depleted in D relative to growth water by 142–376‰. Isotopic variations within compound classes (e.g., n-alkanes) are usually less than ∼50‰, but variations as large as 150‰ are observed among isoprenoid lipids from a single organism. Phytol is consistently depleted in D by up to 50‰ relative to other isoprenoid lipids. Inferred isotopic fractionations between cellular water and lipids are greater than those indicated by previous studies.
ISSN:0146-6380
1873-5290
DOI:10.1016/S0146-6380(99)00094-7