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Effects of lipid extraction and ultrafiltration on stable carbon and nitrogen isotopic compositions of fish bone collagen

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journal contribution
posted on 31.07.2020, 11:00 by Eric J Guiry, Paul Szpak, Michael P Richards
RATIONALE: Fish bone collagen isotopic measurements are increasingly important in palaeodietary and paleoenvironmental studies yet differences in the chemical and physical properties of fish relative to other vertebrate bones are rarely considered. Lipid content in fish bone, which can exceed 50%, may underlie the poor collagen integrity criteria typically observed in archaeological studies.
METHODS: We compare stable carbon and nitrogen isotopic and elemental compositions of bone collagen prepared using four different methods from a wide range of modern fish species to: (1) assess the extent to which lipid content influences bone collagen δ13C and δ15N values, and (2) evaluate the relative efficacy of chemical (2:1 chloroform/methanol) and physical (30 kDa ultrafilters) methods for removing lipids from bones.
RESULTS: Lower δ13C values were observed when the lipid content exceeded 5% of the initial bone mass. The lipid content did not influence the δ15N values. 30 kDa ultrafiltration, a common pretreatment for purifying archaeological collagen, removed fewer lipids and was associated with reduced collagen yields (37% loss) as well as altered amino acid compositions. In contrast, collagen prepared using a 2:1 chloroform/methanol lipid extraction step resulted in significantly improved collagen yields, elemental compositions, and isotopic measurements relative to a control treatment.
CONCLUSIONS: The chemical lipid extraction method (2:1 chloroform/methanol) performed significantly better than the physical lipid extraction method (30 kDa ultrafilters). Given the high quantities of lipids in fish bones we recommend the inclusion of a chemical lipid extraction step when isolating collagen from modern and archaeological fish bones.

History

Citation

Rapid Communications in Mass Spectrometry, Volume 30, Issue 13, 15 July 2016, pp. 1591-1600

Author affiliation

School of Archaeology and Ancient History

Version

AM (Accepted Manuscript)

Published in

Rapid Communications in Mass Spectrometry

Volume

30

Issue

13

Pagination

1591 - 1600

Publisher

Wiley

issn

0951-4198

eissn

1097-0231

Acceptance date

16/04/2016

Copyright date

2016

Spatial coverage

England

Language

eng

Publisher version

https://onlinelibrary.wiley.com/doi/full/10.1002/rcm.7590