title: Distinct features of matrix-assisted 6 microm infrared laser desorption/ionization mass spectrometry in biomolecular analysis.
abstract: Midinfrared-matrix-assisted laser desorption/ionization mass spectrometry (mid-IR-MALDI MS) with a laser emission in the 6 microm wavelength range, which utilizes energy absorption at the C=O double-bond stretch region, was applied to biomolecular analysis. The softness of IR-MALDI MS was evident in the negative ion mode yielding clean mass spectra of [M - H](-) ions for acidic biomolecules with sulfate, phosphate, or carboxylate groups, resulting in better sensitivity than ultraviolet (UV)-MALDI MS. There was no substantial loss of sialic acid due to the prompt fragmentation occurring in IR-MALDI of sialylated glycoconjugates such as gangliosides. Furthermore, the advantage of the low photon energy of IR is that, for the first time, intact protonated molecules of S-nitrosylated peptides can be detected by MALDI MS. In the analysis of redox-sensitive molecules including methylene blue and riboflavin, reductive hydrogenation was minimal, suggesting few hydrogen radicals to have formed in the plume, in contrast to UV-MALDI. In conjunction with a potent new matrix, oxamide, requiring smaller laser fluence, distinct features of the 6 microm IR wavelength range are anticipated to remove one of the limitations of MALDI MS for biomolecular analysis.
authors.affiliation: Department of Molecular Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health, 840 Murodo-cho Izumi, Osaka 594-1101, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Tajiri
authors.forename: Takae
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Wada
mesh_terms: D006001:Glycoconjugates / Q000737:chemistry; D057230:Limit of Detection; D010455:Peptides / Q000032:analysis / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006001:Glycoconjugates; D010455:Peptides