Use of a conventional point detector to record matrix-assisted laser desorption/ionization spectra from a magnetic sector instrument

✍ Scribed by David J. Harvey; Ann P. Hunter

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 130 KB
• Volume: 12
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19981130)12:22<1721::aid-rcm399>3.0.co;2-5

✦ Synopsis

Matrix-assisted laser desorption/ionization mass spectra were recorded on a magnetic sector mass spectrometer using the point detector by using the laser pulses to outline the ion peaks. The instrument was set to scan slowly so that about 10 laser shots were fired during the time the instrument took to scan over a mass peak. This procedure produced a succession of signals that defined the ion peak profile. The profile was then obtained by smoothing the data. Although slow, this technique enables the mass spectrum to be obtained in a single scan and also enables high resolution data to be acquired; the spectrum of the biantennary N-linked glycan [(Gal) 2 (Man) 3 (GlcNAc) 4 ] was recorded at a resolution of 15 000. The liquid binary matrix of 3-aminoquinoline and a-cyano-4-hydroxycinnamic acid, introduced by Colli and Orlando, was initially used but was found to produce Schiff base derivatives with glycans possessing a free reducing terminus. Other binary mixtures giving prolonged ion beams were investigated and a mixture of 2,5dihydroxybenzoic acid and 2,4,6-trihydroxyacetophenone found to be reasonably satisfactory although less so than 3-aminoquinoline and a-cyano-4-hydroxycinnamic acid. Spectra were normally recorded as single scans from about 100 pmol of sample loaded. For low concentrations, in the range of 1-10 pmol, spectra were averaged to produce better signal:noise ratios. The method was used to record the spectra of N-linked glycans released from glycoproteins.