title: Use of 1,5-diaminonaphthalene to combine matrix-assisted laser desorption/ionization in-source decay fragmentation with hydrogen/deuterium exchange.
abstract: BACKGROUND
  In-Source Decay (ISD) in Matrix-Assisted Laser Desorption/Ionization (MALDI) mass spectrometry is a fast and easy top-down activation method. Our objective is to find a suitable matrix to locate the deuterons following in-solution hydrogen/deuterium exchange (HDX). This matrix must circumvent the commonly encountered undesired back-exchange reactions, in order to preserve the regioselective deuteration pattern.
  
  
  METHODS
  The 1,5-diaminonaphthalene (1,5-DAN) matrix is known to be suitable for MALDI-ISD fragmentation. MALDI Mass Spectrometry Imaging (MSI) was employed to compare 1,5-DAN and other commonly used MALDI matrices with respect to the extent of back-exchange and the uniformity of the H/D exchange profiles within the MALDI spots. We tested the back-exchange on the highly sensitive amyloid-beta peptide (1-40), and proved the regioselectivity on ubiquitin and β-endorphin.
  
  
  RESULTS
  MALDI-MSI results show that 1,5-DAN leads to the least back-exchange over all the spot. MALDI-ISD fragmentation combined with H/D exchange using 1,5-DAN matrix was validated by localizing deuterons in native ubiquitin. Results agree with previous data obtained by Nuclear Magnetic Resonance (NMR) and Electron Transfer Dissociation (ETD). Moreover, 1,5-DAN matrix was used to study the H/D exchange profile of the methanol-induced helical structure of β-endorphin, and the relative protection can be explained by the polarity of residues involved in hydrogen bond formation.
  
  
  CONCLUSIONS
  We found that controlling crystallization is the most important parameter when combining H/D exchange with MALDI. The 1,5-DAN matrix is characterized by a fast crystallization kinetics, and therefore gives robust and reliable H/D exchange profiles using MALDI-ISD.
authors.affiliation: GIGA-R, Mass Spectrometry Laboratory, Department of Chemistry, Chemistry Building B6c, University of Liège, B-4000 Liège, Belgium.
authors.forename: Pascale
authors.initials: P
authors.lastname: Lemaire
authors.forename: Delphine
authors.initials: D
authors.lastname: Debois
authors.forename: Nicolas
authors.initials: N
authors.lastname: Smargiasso
authors.forename: Loïc
authors.initials: L
authors.lastname: Quinton
authors.forename: Valérie
authors.initials: V
authors.lastname: Gabelica
authors.forename: Edwin A
authors.initials: EA
authors.lastname: De Pauw
mesh_terms: D015081:2-Naphthylamine / Q000031:analogs & derivatives* / Q000737:chemistry; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry; D006801:Humans; D006859:Hydrogen / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*; D013237:Stereoisomerism; D025801:Ubiquitin / Q000737:chemistry*; D001615:beta-Endorphin / Q000737:chemistry*
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D025801:Ubiquitin; C078592:amyloid beta-protein (1-40); C510889:1,5-diaminonaphthalene; D001615:beta-Endorphin; D006859:Hydrogen; D003903:Deuterium; D015081:2-Naphthylamine