title: Antigen retrieval prior to on-tissue digestion of formalin-fixed paraffin-embedded tumour tissue sections yields oxidation of proline residues.
abstract: MALDI-mass spectrometry imaging (MALDI-MSI) has been shown to allow the study of protein distribution and identification directly within formalin-fixed paraffin-embedded (FFPE) tissue sections. However, direct protein identification from tissue sections remains challenging due to signal interferences and/or existing post-translational or other chemical modifications. The use of antigen retrieval (AR) has been demonstrated for unlocking proteins prior to in situ enzymatic digestion and MALDI-MSI analysis of FFPE tissue sections. In the work reported here, the identification of proline oxidation, which may occur when performing the AR protocol, is described. This facilitated and considerably increased the number of identified peptides when adding proline oxidation as a variable modification to the MASCOT search criteria. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann.
authors.affiliation: Centre for Mass Spectrometry Imaging, Biomolecular Sciences Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Djidja
authors.affiliation: Waters Corporation, Manchester, UK.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Claude
authors.affiliation: Academic Surgical Oncology Unit, University of Sheffield, Sheffield, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Scriven
authors.affiliation: Centre for Mass Spectrometry Imaging, Biomolecular Sciences Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
authors.forename: David W
authors.initials: DW
authors.lastname: Allen
authors.affiliation: Centre for Mass Spectrometry Imaging, Biomolecular Sciences Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
authors.forename: Vikki A
authors.initials: VA
authors.lastname: Carolan
authors.affiliation: Centre for Mass Spectrometry Imaging, Biomolecular Sciences Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.. Electronic address: m.r.clench@shu.ac.uk.
authors.forename: Malcolm R
authors.initials: MR
authors.lastname: Clench
mesh_terms: D000941:Antigens / Q000378:metabolism*; D005557:Formaldehyde / Q000737:chemistry*; D006801:Humans; D009369:Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D010084:Oxidation-Reduction; D010232:Paraffin / Q000737:chemistry*; D010455:Peptides / Q000378:metabolism; D011392:Proline / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D011506:Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D000941:Antigens; D010455:Peptides; D011506:Proteins; D005557:Formaldehyde; D010232:Paraffin; D011392:Proline
keywords: Antigen retrieval; FFPE; Imaging; MALDI; Proline oxidation