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Surface oxidation under ambient air--not only a fast and economical method to identify double bond positions in unsaturated lipids but also a reminder of proper lipid processing.

Zhou Y, Park H, Kim P, Jiang Y, Costello CE - Anal. Chem. (2014)

Bottom Line: Direct sampling by thin-layer chromatography (TLC)-ESI-MS provides a powerful approach to elucidate detailed structural information on biological samples.Phosphatidylserine and N,N-dimethyl phosphatidylethanolamine isomers in a bovine brain total lipid extract were distinguished on the basis of their oxidation products.Meanwhile, the findings reported herein reveal a potential pitfall in the assignment of structures to lipids extracted from TLC plates because of artifactual oxidation after the plate development.

View Article: PubMed Central - PubMed

Affiliation: Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine , Boston, Massachusetts 02118, United States.

ABSTRACT
A simple, fast approach elucidated carbon-carbon double bond positions in unsaturated lipids. Lipids were deposited onto various surfaces and the products from their oxidation in ambient air were observed by electrospray ionization (ESI) mass spectrometry (MS). The most common oxidative products, aldehydes, were detected as transformations at the cleaved double bond positions. Ozonides and carboxylic acids were generated in certain lipids. Investigations of the conditions controlling the appearance of these products indicated that the surface oxidation depends on light and ambient air. Since the lipid oxidation was slower in a high concentration of ozone, singlet oxygen appeared to be a parallel oxidant for unsaturated lipids. The 3-hydroxyl group in the sphingoid base of sulfatides offered some protection from oxidation for the Δ4,5-double bond, slowing its oxidation rate relative to that of the isolated double bond in the N-linked fatty acyl chain. Direct sampling by thin-layer chromatography (TLC)-ESI-MS provides a powerful approach to elucidate detailed structural information on biological samples. Co-localization of the starting lipids and their oxidation products after TLC separation allowed assignment of the native unsaturation sites. Phosphatidylserine and N,N-dimethyl phosphatidylethanolamine isomers in a bovine brain total lipid extract were distinguished on the basis of their oxidation products. Meanwhile, the findings reported herein reveal a potential pitfall in the assignment of structures to lipids extracted from TLC plates because of artifactual oxidation after the plate development.

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Negative-ionmode TLC-ESI mass spectra; oxidation products arelabeled with an asterisk.(*) (a) d18:1/C24:1 ST and (b) d18:1/C24:0ST and their oxidation products. (c and d) Major oxidation pathways.
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fig1: Negative-ionmode TLC-ESI mass spectra; oxidation products arelabeled with an asterisk.(*) (a) d18:1/C24:1 ST and (b) d18:1/C24:0ST and their oxidation products. (c and d) Major oxidation pathways.

Mentions: In additionto the expected [M – H]− at m/z 888.62, signals corresponding to larger specieswere observed at m/z 936.61 (+48u) and 984.59 (+96 u). Peaks indicative of a degraded species appearedat m/z 778.48 (−110 u); thisproduct apparently underwent a further loss of 180 u to generate thespecies observed at m/z 598.25.Assignments of these modified peaks were made on the basis of subsequentCID experiments (Supporting Information Figure S-1). The pathways are summarized in Figure 1c.


Surface oxidation under ambient air--not only a fast and economical method to identify double bond positions in unsaturated lipids but also a reminder of proper lipid processing.

Zhou Y, Park H, Kim P, Jiang Y, Costello CE - Anal. Chem. (2014)

Negative-ionmode TLC-ESI mass spectra; oxidation products arelabeled with an asterisk.(*) (a) d18:1/C24:1 ST and (b) d18:1/C24:0ST and their oxidation products. (c and d) Major oxidation pathways.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4066906&req=5

fig1: Negative-ionmode TLC-ESI mass spectra; oxidation products arelabeled with an asterisk.(*) (a) d18:1/C24:1 ST and (b) d18:1/C24:0ST and their oxidation products. (c and d) Major oxidation pathways.
Mentions: In additionto the expected [M – H]− at m/z 888.62, signals corresponding to larger specieswere observed at m/z 936.61 (+48u) and 984.59 (+96 u). Peaks indicative of a degraded species appearedat m/z 778.48 (−110 u); thisproduct apparently underwent a further loss of 180 u to generate thespecies observed at m/z 598.25.Assignments of these modified peaks were made on the basis of subsequentCID experiments (Supporting Information Figure S-1). The pathways are summarized in Figure 1c.

Bottom Line: Direct sampling by thin-layer chromatography (TLC)-ESI-MS provides a powerful approach to elucidate detailed structural information on biological samples.Phosphatidylserine and N,N-dimethyl phosphatidylethanolamine isomers in a bovine brain total lipid extract were distinguished on the basis of their oxidation products.Meanwhile, the findings reported herein reveal a potential pitfall in the assignment of structures to lipids extracted from TLC plates because of artifactual oxidation after the plate development.

View Article: PubMed Central - PubMed

Affiliation: Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine , Boston, Massachusetts 02118, United States.

ABSTRACT
A simple, fast approach elucidated carbon-carbon double bond positions in unsaturated lipids. Lipids were deposited onto various surfaces and the products from their oxidation in ambient air were observed by electrospray ionization (ESI) mass spectrometry (MS). The most common oxidative products, aldehydes, were detected as transformations at the cleaved double bond positions. Ozonides and carboxylic acids were generated in certain lipids. Investigations of the conditions controlling the appearance of these products indicated that the surface oxidation depends on light and ambient air. Since the lipid oxidation was slower in a high concentration of ozone, singlet oxygen appeared to be a parallel oxidant for unsaturated lipids. The 3-hydroxyl group in the sphingoid base of sulfatides offered some protection from oxidation for the Δ4,5-double bond, slowing its oxidation rate relative to that of the isolated double bond in the N-linked fatty acyl chain. Direct sampling by thin-layer chromatography (TLC)-ESI-MS provides a powerful approach to elucidate detailed structural information on biological samples. Co-localization of the starting lipids and their oxidation products after TLC separation allowed assignment of the native unsaturation sites. Phosphatidylserine and N,N-dimethyl phosphatidylethanolamine isomers in a bovine brain total lipid extract were distinguished on the basis of their oxidation products. Meanwhile, the findings reported herein reveal a potential pitfall in the assignment of structures to lipids extracted from TLC plates because of artifactual oxidation after the plate development.

Show MeSH
Related in: MedlinePlus