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  • A derivatization and validation strategy for determining the spatial localization of endogenous amine metabolites in tissues using MALDI imaging mass spectrometry.

A derivatization and validation strategy for determining the spatial localization of endogenous amine metabolites in tissues using MALDI imaging mass spectrometry.

Journal of mass spectrometry : JMS (2014-07-22)
M Lisa Manier, Jeffrey M Spraggins, Michelle L Reyzer, Jeremy L Norris, Richard M Caprioli
ABSTRACT

Imaging mass spectrometry (IMS) studies increasingly focus on endogenous small molecular weight metabolites and consequently bring special analytical challenges. Since analytical tissue blanks do not exist for endogenous metabolites, careful consideration must be given to confirm molecular identity. Here, we present approaches for the improvement in detection of endogenous amine metabolites such as amino acids and neurotransmitters in tissues through chemical derivatization and matrix-assisted laser desorption/ionization (MALDI) IMS. Chemical derivatization with 4-hydroxy-3-methoxycinnamaldehyde (CA) was used to improve sensitivity and specificity. CA was applied to the tissue via MALDI sample targets precoated with a mixture of derivatization reagent and ferulic acid as a MALDI matrix. Spatial distributions of chemically derivatized endogenous metabolites in tissue were determined by high-mass resolution and MS(n) IMS. We highlight an analytical strategy for metabolite validation whereby tissue extracts are analyzed by high-performance liquid chromatography (HPLC)-MS/MS to unambiguously identify metabolites and distinguish them from isobaric compounds.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
trans-Cinnamaldehyde, 97%
Supelco
trans-Ferulic acid, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
Sigma-Aldrich
trans-Cinnamaldehyde, FCC, FG
Sigma-Aldrich
Formic acid solution, BioUltra, 1.0 M in H2O
Supelco
(N-Succinimidyloxycarbonylmethyl)tris(2,4,6-trimethoxyphenyl)phosphonium bromide, for protein sequence analysis (by MALDI-MS), ≥98.5%
Supelco
Trifluoroacetic acid, analytical standard
Sigma-Aldrich
trans-Cinnamaldehyde, ≥99%
Supelco
Acetonitrile, analytical standard
Sigma-Aldrich
Formic acid, ≥95%, FCC, FG
Sigma-Aldrich
trans-Ferulic acid, 99%
Supelco
trans-Ferulic acid, matrix substance for MALDI-MS, ≥99.0% (HPLC)
Sigma-Aldrich
Melatonin, powder, ≥98% (TLC)
Supelco
trans-Cinnamaldehyde, analytical standard
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Acetonitrile, electronic grade, 99.999% trace metals basis
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Acetonitrile, anhydrous, 99.8%
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Methanol-12C, 99.95 atom % 12C
USP
Methyl alcohol, United States Pharmacopeia (USP) Reference Standard
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Methanol solution, NMR reference standard, 4% in methanol-d4 (99.8 atom % D), NMR tube size 3 mm × 8 in.
Sigma-Aldrich
trans-Ferulic acid, ≥99%
Sigma-Aldrich
DL-Tyrosine, 99%
USP
Residual Solvent Class 2 - Acetonitrile, United States Pharmacopeia (USP) Reference Standard
USP
Melatonin, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
Trifluoroacetic acid, ReagentPlus®, 99%
Sigma-Aldrich
Formic acid, ACS reagent, ≥96%
Sigma-Aldrich
Acetonitrile, ReagentPlus®, 99%
Ferulic acid, European Pharmacopoeia (EP) Reference Standard
Hydrocortisone for peak identification, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Ultrapure Acetonitrile
Tyrosine, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Trifluoroacetic acid, ≥99%, for protein sequencing