MALDI-in source decay applied to mass spectrometry imaging: a new tool for protein identification

Anal Chem. 2010 May 15;82(10):4036-45. doi: 10.1021/ac902875q.


Matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) imaging is a powerful technique giving access to the distribution of a large range of biomolecules directly from a tissue section, allowing, for example, the discovery of new pathological biomarkers. Nevertheless, one main difficulty lies in the identification of the detected species, especially proteins. MALDI-in source decay (ISD) is used to fragment ions directly in the mass spectrometer ion source. This technique does not require any special sample treatment but only the use of a specific MALDI matrix such as 2,5-dihydroxybenzoic acid or 1,5-diaminonaphthalene. MALDI-ISD is generally employed on classical, purified samples, but here we demonstrate that ISD can also be performed directly on mixtures and on a tissue slice leading to fragment ions, allowing the identification of major proteins without any further treatment. On a porcine eye lens slice, de novo sequencing was even performed. Crystallins not yet referenced in databases were identified by sequence homology with other mammalian species. On a mouse brain slice, we demonstrate that results obtained with ISD are comparable and even better than those obtained with a classical in situ digestion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2-Naphthylamine / analogs & derivatives
  • 2-Naphthylamine / chemistry
  • Amino Acid Sequence
  • Animals
  • Databases, Factual
  • Gentisates / chemistry
  • Ions
  • Mass Spectrometry / methods*
  • Mice
  • Molecular Sequence Data
  • Proteins / isolation & purification*
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*
  • Swine


  • Gentisates
  • Ions
  • Proteins
  • 1,5-diaminonaphthalene
  • 2-Naphthylamine
  • 2,5-dihydroxybenzoic acid