1H-Pteridine-2,4-dione (lumazine): a new MALDI matrix for complex (phospho)lipid mixtures analysis |
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Authors: | Cosima D Calvano Saverio Carulli Francesco Palmisano |
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Institution: | 1. Dipartimento di Chimica & Centro Interdipartimentale di Ricerca S.M.A.R.T., Università degli Studi di Bari Aldo Moro, Via Orabona 4, 70126, Bari, Italy
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Abstract: | Nowadays, matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry represents an emerging and
versatile tool for analysis of lipids. However, direct (i.e., with no previous separation of lipid classes) analysis of crude
extracts containing a complex mixture of lipids (a problem typically encountered in shotgun lipidomics) is still a quite challenging
task using a conventional MALDI matrix such as 2,5-dihydroxybenzoic acid (DHB). Indeed, in the presence of phospholipids containing
quaternary ammonium groups, such as phosphatidylcholines and sphingomyelins, strong ionization-suppression effects are experienced
especially in positive ion mode. To overcome this limitation, lumazine (1H-pteridine-2,4-dione) was evaluated as an alternative matrix. Lumazine in the solid state showed an absorption maximum at
350 nm, ionizes/desorbs without appreciable decomposition and extensive cluster formation, and can be used in both ion modes.
In positive ion mode, the main species were M
•+ and 2M
•+ radical cations and cationized species (M+H]+, M+Na]+, M+2Na+2Li-3H]+). In negative ion mode, the main signals observed were the deprotonated molecular ion and the radical anion. The signal-to-noise
ratio for phosphatidylglycerols and phosphatidylethanolamines using lumazine was almost 1 order of magnitude higher than that
observed for DHB. Lumazine was successfully used for MALDI analysis (positive and negative ion modes) of crude lipid extracts
of milk, soymilk, and hen egg, where phosphatidylethanolamines, phosphatidylserines, and phosphatidylinositols could additionally
be detected. |
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Keywords: | |
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