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MALDI Mass Spectral Imaging of Bile Acids Observed as Deprotonated Molecules and Proton-Bound Dimers from Mouse Liver Sections
- Source :
- Journal of the American Society for Mass Spectrometry
- Publication Year :
- 2018
- Publisher :
- Springer US, 2018.
-
Abstract
- Bile acids (BAs) play two vital roles in living organisms, as they are involved in (1) the secretion of cholesterol from liver, and (2) the lipid digestion/absorption in the intestine. Abnormal bile acid synthesis or secretion can lead to severe liver disorders. Even though there is extensive literature on the mass spectrometric determination of BAs in biofluids and tissue homogenates, there are no reports on the spatial distribution in the biliary network of the liver. Here, we demonstrate the application of high mass resolution/mass accuracy matrix-assisted laser desorption/ionization (MALDI)-Fourier-transform ion cyclotron resonance (FTICR) to MS imaging (MSI) of BAs at high spatial resolutions (pixel size, 25 μm). The results show chemical heterogeneity of the mouse liver sections with a number of branching biliary and blood ducts. In addition to ion signals from deprotonation of the BA molecules, MALDI-MSI generated several further intense signals at larger m/z for the BAs. These signals were spatially co-localized with the deprotonated molecules and easily misinterpreted as additional products of BA biotransformations. In-depth analysis of accurate mass shifts and additional electrospray ionization and MALDI-FTICR experiments, however, confirmed them as proton-bound dimers. Interestingly, dimers of bile acids, but also unusual mixed dimers of different taurine-conjugated bile acids and free taurine, were identified. Since formation of these complexes will negatively influence signal intensities of the desired [M – H]- ions and significantly complicate mass spectral interpretations, two simple broadband techniques were proposed for non-selective dissociation of dimers that lead to increased signals for the deprotonated BAs. Graphical Abstractᅟ Electronic supplementary material The online version of this article (10.1007/s13361-017-1886-6) contains supplementary material, which is available to authorized users.
- Subjects :
- 0301 basic medicine
Stereochemistry
Taurine
Electrospray ionization
Adducts
01 natural sciences
Fourier transform ion cyclotron resonance
Mass spectrometry imaging
Adduct
Bile Acids and Salts
03 medical and health sciences
chemistry.chemical_compound
Mice
Proton-bound dimers
Structural Biology
Image Processing, Computer-Assisted
Molecule
Animals
MALDI
Spectroscopy
010401 analytical chemistry
Histological Techniques
Taurocholic acid
FTICR
Bile acids
0104 chemical sciences
Mice, Inbred C57BL
030104 developmental biology
chemistry
Liver
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
Female
Protons
Lipid digestion
Ion cyclotron resonance
Research Article
Subjects
Details
- Language :
- English
- ISSN :
- 18791123 and 10440305
- Volume :
- 29
- Issue :
- 4
- Database :
- OpenAIRE
- Journal :
- Journal of the American Society for Mass Spectrometry
- Accession number :
- edsair.doi.dedup.....6d565085bc818464ec97bcc0e07726d0