The Application of MALDI and Tandem Reflectron TOF Mass Spectrometry to the Analysis of Biomolecular Ions

Jia, Wei Jie (1996) The Application of MALDI and Tandem Reflectron TOF Mass Spectrometry to the Analysis of Biomolecular Ions. PhD thesis, University of Glasgow.

Full text available as:
Download (7MB) | Preview


This thesis describes the application of a reflection time-of-flight (TOF) mass spectrometer , in particular, with the new laser desorption technique, "matrix-assisted laser desorption/ionisation" (MALDI), to the studies of biological molecular ions. MALDI has opened a new door of production of large intact biomolecular ions for the determination of the masses of large biomolecules. The work presented in this thesis was also carried out with primary objective of developing a tandem reflectron time-of- flight mass spectrometer for the studies of laser photodissociation of molecular ions. Chapter 1 presents a brief review of the techniques involved in my research work, such as resonance ionisation spectroscopy (RIS), Matrix-assisted laser desorption ionisation(MALDI), and tandem reflectron TOF mass spectrometry. The second chapter provides the readers with relevant theories for an understanding of the techniques of RIS, MALDI etc.. A discussion and description of photophysical processes which occur in the excited states of molecules and molecular ions, and probable mechanism of photofragmentation is also described in this chapter. The purpose of Chapter 3 is to present the experimental apparatus in detail, which include a Nd:YAG laser, N2 laser, dye laser, high vacuum chamber, reflectron, detector, data acquisition system, pulse delay generation system etc.. Chapter 4 presents the experimental investigations of MALDI, such as matrix selection, sample preparation, MALDI mass spectra, and power dependence etc.. The Is → 2s two-photon resonance and one-photon ionisation mass spectra of hydrogen from the matrix of 2,5-DHB have been shown. Two groups of hydrogen ions (one from ablation, another from postionisation) were observed. This work was carried out with Dr. C.J. Scott and the interpretation of the results and analysis was carried out jointly. The work of Chapter 5 describes the development of a new tandem reflectron TOF mass spectrometer(TRTOF) for the investigations of laser photofragmentation of molecular ions. The computer program called 'SIMION' was used to simulate the ion trajectories in the reflectron and gave theoretical results of fragment trajectories with various fragments and different fragmentation position. Then the experiments were carried out with various parameters of the tandem reflectron TOF mass spectrometer, such as mass calibration, selection of parent ions, fragment ion collection, reflectron field effect, fragmentation mass resolution, and influence of the fragmentation laser parameters. The results show that the new TRTOF has a relatively simple timing requirement for overlapping the pulsed laser and ion packets, and also has a multichannel fragment ion detection. It has also been shown that a TRTOF of considerable potential can be easily adapted from an ordinary reflectron TOF instrument to carry out tandem MS/MS experiments. Chapter 6 presents and discusses laser photofragmentation mass spectroscopy of molecular ions using the tandem reflectron TOF mass spectrometer. The "Ladder-switching model" has been introduced and laser photofragmentation mass spectra of matrix molecular ions of 2,5-DHB have been shown. The power dependence of fragments from various molecular ions has been presented and possible fragmentation pathways have been discussed as well. In addition, the distinguishing between the ion isomers in this experiment indicates another advantage of this newly developed TRTOF. Chapter 7 describes the application of the tandem reflectron TOF mass spectroscopy to the analysis and study of photofragmentation of biomolecular ions. Some biomolecular ions, such as PTH-tryptophan, PTH-valine, PTH-alanine, Cytosine, Guanine, which were produced by the MALDI technique, have been fragmented by a photofragmentation laser and their fragmentation mass spectra have been recorded. These results imply a promising future for this technique in photofragmentation of biological molecular ions. The last chapter (Chapter 8) gives conclusions and some experiments for the future.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: K W D Ledingham
Keywords: Applied physics, Optics, Analytical chemistry
Date of Award: 1996
Depositing User: Enlighten Team
Unique ID: glathesis:1996-75516
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 19:35
Last Modified: 19 Nov 2019 19:35

Actions (login required)

View Item View Item


Downloads per month over past year