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Journal of Lipid Research, Vol. 48, 2779-2787, December 2007
Copyright © 2007 by American Society for Biochemistry and Molecular Biology
Methods |


* Food and Biodynamic Chemistry Laboratory, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
Project M Co., Ltd., Sendai 980-0014, Japan
Department of Medicine, Nippon Medical School, Tokyo 113-8603, Japan
Published, JLR Papers in Press, September 11, 2007.
1 To whom correspondence should be addressed. e-mail: miyazawa{at}biochem.tohoku.ac.jp
We previously discovered that squalene monohydroperoxide (SQ-OOH) was produced on human forehead skin and suggested that skin squalene (SQ) may be the principal target lipid for oxidative stress (e.g., sunlight exposure). Because of its six double bonds, SQ peroxidation can yield various positional hydroperoxide isomers. However, the structural characterization of skin SQ-OOH isomers has never been reported. Here, we prepared pure SQ-OOH isomers and developed an analytical method for SQ-OOH isomers using a quadrupole/linear ion-trap mass spectrometer (QTRAP) MS/MS system. Collision-induced dissociation produced specific fragment ions for each SQ-OOH isomer, which permitted discrimination between SQ-OOH isomers by multiple reaction monitoring (MRM). When lipid extract from human forehead skin was subjected to LC-MS/MS with MRM, individual SQ-OOH isomers could be separated and detected with a sensitivity of 0.05 ng/injection. The total concentration of SQ-OOH isomers in forehead skin was
956 µg/g skin lipids, but it increased up to 2,760 µg/g skin lipids after 3 h of sunlight exposure. The LC-MS/MS method was useful for investigating the peroxidation mechanisms of SQ as well as SQ-OOH-mediated skin disorders.
Supplementary key words lipid peroxidation QTRAP mass spectrometer skin pathogenicity
Abbreviations: LC-CL, liquid chromatography-chemiluminescence detection; MRM, multiple reaction monitoring; QqLIT, hybrid quadrupole/linear ion trap; SQ, squalene; SQ-OOH, squalene monohydroperoxide; UV, ultraviolet
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