title: A derivatization and validation strategy for determining the spatial localization of endogenous amine metabolites in tissues using MALDI imaging mass spectrometry.
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.
authors.affiliation: Mass Spectrometry Research Center, Vanderbilt University, Nashville, TN, 37232, USA.
authors.forename: M Lisa
authors.initials: ML
authors.lastname: Manier
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Spraggins
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Reyzer
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: Norris
authors.forename: Richard M
authors.initials: RM
authors.lastname: Caprioli
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives; D000311:Adrenal Glands / Q000737:chemistry; D000596:Amino Acids / Q000032:analysis* / Q000737:chemistry; D000818:Animals; D002395:Catecholamines / Q000032:analysis* / Q000737:chemistry; D002531:Cerebellum / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D006651:Histocytochemistry / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D051381:Rats; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013552:Swine
chemical_list: D000596:Amino Acids; D002395:Catecholamines; C075384:coniferaldehyde; D000171:Acrolein
keywords: MALDI imaging; amine metabolites; amino acids; identification; in-tissue derivatization; neurotransmitters; reagent precoated MALDI targets