“b-Carboline Alkaloids as Matrices for UV-Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry in Positive and Negative Ion Modes. Analysis of Proteins of High Molecular Mass, and of Cyclic and Acyclic Oligosaccharides

H. NONAMI; K. TANAKA; Y. FUKUYAMA; R. ERRA-BALSELLS

RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM.

Wiley

Lugar: Londres; Año: 1998 vol. 12 p. 285 - 296

0951-4198

We report that  commercially available b-carbolines (nor-harmane (9H-pyrido[3,4-b]indole), harmane (1-methyl-9H-pyrido[3,4-b]indole), harmine (7-methoxy-1-methyl-9H-pyrido[3,4-b]indole), harmol (1-methyl-9H-pyrido[3,4-b]indol-7-ol), harmaline (3,4-dihydro-7-methoxy-1-methyl-9H-pyrido[3,4-b]indole) and harmalol (3,4-dihydro-1-methyl-9H-pyrido[3,4-b]indol-7-ol)), are very useful MALDI matrices at 337 nm, for cyclic oligosaccharides (cyclodextrins, m.w. range 972-1290 Da), acyclic oligosaccharides (m.w. range 342-828 Da) and high molecular weight proteins (m.w. range 23290-66525 Da) in both positive and negative modes. This was investigated by using time-of-flight (TOF) mass spectrometers of different sensitivities, equipped with and without pulse extraction facilities. A comparison with conventional matrices for carbohydrates (DHB and DHB/HIC) indicates that b-carbolines provide the same level of sensitivity and resolution in the positive mode, but offer the advantage of high levels of sensitivity and resolution in the negative mode.  Harmaline has been found to be specially effective for the analysis of high-mass proteins in both modes and also exhibits excellent experimental reproducibility of the results owing to the homogeneous crystallization of the analyte-matrix mixture over the entire sample surface area.  Harmane and nor-harmane  are both excellent matrices for high-mass proteins also.  As MALDI matrices, b-carbolines permits measurement of 1) sulfated sugars in the negative ion mode as ([M-H]-) and 2) neutral sugars and proteins, as both [M+H]+ and [M-H]- in appropriate modes.