Martin Green

High-energy collision-induced fragmentation of complex oligosaccharides ionized by matrix-assisted laser desorption/ionization mass spectrometry

The high-energy CID spectra of the MNa+ ions from 17 underivatized oligosaccharides of the type found attached to asparagine in glycoproteins were examined with a double-focusing mass spectrometer fitted with a tandem orthogonal time-of-flight analyser. Fragment ions were observed throughout the mass range from all compounds and provided considerable structural information in the low-picomole range. The three types of fragmentation that were observed were glycosidic cleavages, cross-ring cleavages and the formation of internal cleavage ions. The major glycosidic fragmentations were B- and Y-type cleavages (Domon and Costello nomenclature). B-cleavages were particularly abundant at GlcNAc residues. Z-ions were absent when glycosidic linkages occurred at the 6-position. Cross-ring cleavages were predominantly of the 1,5X-type, which provided much sequence and branching information. 3,5A cleavages of the core branching mannose residue were often prominent and provided information on the composition of each of the main antennae. Antenna composition was also reflected by a major internal fragment ion formed by elimination of the two GlcNAc residues of the chitobiose core together with the entire antenna at the 3-position of the core branching mannose residue. A further loss of GlcNAc as 221 mass units from this ion in the spectra of the hybrid and complex carbohydrates was indicative of the presence of a bisecting (4-linked) GlcNAc substituent. Another prominent internal fragment ion containing a mannose residue and only one GlcNAc, with its substituents, was present in the spectra of the complex sugars when branching of the 3-antenna occurred.

The Application of Matrix‐assisted Laser Desorption/Ionization Combined with Collision‐induced Dissociation to the Analysis of Synthetic Polymers

Matrix-assisted laser desorption/ionization combined with collision-induced dissociation (CID) has been applied to the structural determination of synthetic polymers. Post-source decay/CID experiments on a time-of-flight (TOF) instrument have been compared with CID data from a hybrid sector-TOF mass spectrometer. Fragment-ation spectra of polymers, with molecular weights of up to 4500u2009Da, have been shown to aid structural and end-group determination. The polymers studied were poly(methyl methacrylate), poly(ethylene glycol) and poly(ethylene terephthalate).

Peptide sequence determination by matrix-assisted laser desorption ionization employing a tandem double focusing magnetic—Orthogonal acceleration time-of-flight mass spectrometer

This report describes the fragmentation processes for peptides induced by collisional activation of the 12C isobar of matrix-assisted laser desorption ionization (MALDI)-generated pseudomolecular ions employing an EBE orthogonal acceleration time-of-flight mass spectrometer and using xenon as the collision gas at a laboratory collision energy of 800 eV. These MALDI-collision-induced dissociation (CID) spectra are shown to provide sequence information of comparable quality to those obtained by using high energy CID conditions with liquid secondary ionization mass spectrometry on a four-sector tandem instrument. Peptide sequencing via MALDI-CID is demonstrated on three tryptic peptides obtained from a bacterial protein (P450 isozyme) of unknown sequence. Sensitivity is shown to be at the 1 pmol level for standard peptides.

The effect of the variation of cation in the matrix-assisted laser desorption/ionisation-collision induced dissociation (MALDI-CID) spectra of oligomeric systems

Abstract The effect of the variation of the cation, on the matrix-assisted laser desorption/ionisation collision induced dissociation (MALDI-CID) spectra obtained, has been studied in a hybrid sector-orthogonal acceleration-time of flight tandem mass spectrometer for some synthetic oligomeric systems. Oligomers of poly(methyl methacrylate) and poly(styrene) in the molecular weight range of approximately 1000–3000 u were analysed. They were ionised by attachment of various alkali metal and copper and silver ions, respectively. The MALDI-CID spectra are shown to vary with different cations more from precursor ions of lower than those of higher mass-to-charge ratio.

Utilizing matrix-assisted laser desorption/ionization-collision induced dissociation for the generation of structural information from poly(alkyl methacrylate)s

Matrix-assisted laser desorption/ionization-collision induced dissociation (MALDI-CID) has been employed for the analysis of poly(alkyl methacrylate)s in a tandem hybrid sector-time of flight instrument. Spectra are shown for adducts of poly(ethyl methacrylate) and poly(butyl methacrylate) with sodium ions. It is proposed that the masses of the end groups may be inferred from the data for the polymers. Mechanisms are proposed for the formation of some of the series of ion peaks that are observed in the MALDI-CID spectra.

Matrix-Assisted Laser Desorption/Ionization-Collision Induced Dissociation of Poly(Styrene)

Matrix-assisted laser desorption/ionization-collision induced dissociation (MALDI-CID) has been employed for the analysis of poly(styrene) in a tandem hybrid sector-time of flight instrument. Spectra are shown for adducts of poly(styrene) with copper and silver ions. The distributions of fragment ion peaks were found to be consistent from precursor ions containing both metal ions. It is shown how the masses of the end groups of the polymer may be inferred from the mass-to-charge ratios of two of the series of ion peaks that are seen in the MALDI-CID spectra. Mechanisms are proposed for the formation of some of the other series of ion peaks that are observed in the spectra.