ABSTRACT
I. INTRODUCTION Time-of-flight (TOF) mass spectrometers, coupled to matrix-assisted laser desorption ion sources (MALDI), have in the last few years been used mainly for the determination of molecular weights [1,2]. Hereby, many aspects of biomolecular analysis have been revolutionized, expecially speed, accuracy, and sensitivity of molecular weight determinations. Previously, the different mass spectrometric techniques have been most useful for relat ing fragmentations, occurring in the mass spectrometer, to molecular struc ture. Because a significant portion of molecules are fragmented by laser light, investigations by Kaufmann [3,4] have shown that post-source decay (PSD) processes can be detected in a reflectron instrument. The TOF in strument must be equipped with a reflector, preferably of the gridless dou ble-stage design. With this instrument configuration, structure-related frag ment ions can be measured. The first experiments have demonstrated the usefulness of PSD for sequencing peptides, one of the main application areas [5,6]. PSD spectra have also been published on linear and branched glycans [7,8] and on TV-linked glycopeptides [9].