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Title: Laser desorption/ionization ion trap mass spectrometry studies of biomolecules and synthetic polymers
Author: Reynolds, James Christopher
ISNI:       0000 0001 3514 8804
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 2003
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Matrix-assisted laser desorption/ionization (MALDI) and atmospheric pressure MALDI sources have been constmcted and evaluated for ion trap mass spectrometry (QIT) and ion mobility spectrometry (IMS), bi-trap and external ion source configurations have been developed for MALDI/QIT using a fibre optic to direct laser light to the sample target. Mass spectra and tandem mass spectra of ions generated by MALDI in vacuo have been studied for small molecules, synthetic polymers and peptides. In-bap MALDI spectra were susceptible to space-cbarge effects that reduced spectral quality compared to external ion source configurations. Atmospheric pressure MALDI/QIT has been demonstrated for the mass spectrometric (MS", n ≤ 4) analysis of model peptides and an oligosaccharide. Sequence information was obtained from peptides (MS", n ≤ 3) at the picomolar level. The somce and interface conditions, including the heated capillary temperature, tube lens voltage and the presence of an inert gas (helium or xenon) into the ion source region have been optimised for AP-MALDLQIT analysis. AP-MALDI/QIT has been applied to the analysis of oligosaccharides. Multi-stage tandem mass spectrometry (MS", n ≤ 4) carried out in the ion trap enabled extended fragmentation pathways to be investigated. The analysis of branched oligosaccharides has been demonstrated for Nlinked glycans from human semm transferrin, chicken egg ovalbumin glycans and a ribonuclease glycan mixture. Mass spectrometric and tandem mass spectrometric data has been acquired for mixtures of linear dextrans and N-linked glycans with molecular weights up to 4000 Da. The use of MS" enabled the composition of the glycans to be determined and provided stmctural data that confirmed data observed in the MS/MS spectra. AP-MALDLQIT has been investigated for the analysis of poly(etbylene) glycol (PEG 1500) and a byperbrancbed polymer (polyglycidol) in the presence of alkali metal salts. MS spectra of PEG 1500 obtained at atmospheric pressure showed dimetallated matrix/analyte adducts, in addition to the expected alkali metal/PEG ions. The matrix adducts produced under AP-MALDEQIT could be controlled by varying the ion trap interface conditions (capillary temperature and insource CAD) suggesting that the complexes are rapidly stabilised by collisional cooling, enabling them to be transferred into the ion trap. Vacuum MALDI time-offiigbt mass spectrometry showed only alkali metal/PEG adducts and no matrix/analyte adducts. The MS/MS capability of the ion trap has been demonstrated for a litbiated polyglycol, yielding a rich fragment ion spectrum. Analysis of the byperbrancbed polymer polyglycidol by AP-MALDEQIT reveals that the distribution profile observed differs greatly from that obtained by vacuum MALDI-ToF. AP-MALDI has been combined with atmospheric pressure IMS. The potential of the technique has been demonstrated for peptides, synthetic poly(etbylene) glycols, maltobeptaose and lutidine. Drift times and ion intensities were dependent on a number o f v ariables, i ncluding p ositioning of the sample target with respect to the drift tube and voltage applied to the sample target. Tbe presence of 1 utidine in the sample/matrix mixture resulted in suppression of interfering matrix-derived peaks. Under optimised conditions, peak width and resolution was comparable to that observed using a nano-electrospray ion source with the same drift cell.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Oligosaccharides