MALDI-in source decay applied to mass spectrometry imaging: a new tool for protein identification.
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.
Debois
Delphine
D
LSM-CART-GIGA-R, University of Liège, B-4000 Liège (Sart-Tilman), Belgium. delphine.debois@ulg.ac.be
Bertrand
Virginie
V
Quinton
Loïc
L
De Pauw-Gillet
Marie-Claire
MC
De Pauw
Edwin
E
D015081:2-Naphthylamine / Q000031:analogs & derivatives / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D016208:Databases, Factual; D005841:Gentisates / Q000737:chemistry; D007477:Ions; D013058:Mass Spectrometry / Q000379:methods*; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins / Q000302:isolation & purification*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013552:Swine
D005841:Gentisates; D007477:Ions; D011506:Proteins; C510889:1,5-diaminonaphthalene; D015081:2-Naphthylamine; C010925:2,5-dihydroxybenzoic acid