The performance of a linear matrix assisted laser desorption/ionization mass spectrometer (MALDI-oa-TOFMS) was improved with more reproducible sample preparation methods, a higher rate digitiser for integrating signals and customisable computer control, data acquisition and analysis in the LabVIEW?programming environment. This resulted in a ~20% improvement in resolution (up to 4,400) and enabled measurement of desorption velocities of 1,000 - 1,800 ms-1 for analytes with m/z 615 ?1,350 Da, with matrix ion velocities being 4,000 ?4,800 ms?. Detector limitations and restrictions on source axis energy (and hence velocity) required for the analysis of ions prevented detection of other species with this instrument. A 20 kV reflecting geometry MALDI-oa-TOFMS was constructed to overcome these limitations and extend the mass range. This mass spectrometer was able to analyse ions desorbed with a wide range of energies (32 ?197 eV). The resolution was found to be 8,000 -10,000. Best mass accuracy was 15-80 ppm (internal standards ). External calibration gave larger mass errors, mostly due to timing jitter, but the mass axis was stable for &lt2 weeks. Mass accuracy was independent of the analyte and matrix used. Ions with m/z of ~10,000 - 20,000 Da were observable with the use of a pulsed lens in the target region. This lens increased signal approximately 20 times, but degraded resolution. The detection limit of the instrument (sample consumed) was estimated to vary from 10 ?90 fmol, by extrapolation, with more moles required at higher m/z. The microsphere plate (MSP) electron multiplier used in the reflecting instrument was found to have a temporal response of &gt1 ns FWHM, but with a low secondary electron conversion efficiency, making it unsuitable for high m/z species. Experiments were also performed with a novel rectangular mesh grid, which (in correct orientation) provided similar resolution to conventional square mesh grids, but with significantly improved transmission and hence sensitivity.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010. / Committee Chair: Fernandez, Facundo M.; Committee Member: Bottonley, Lawrence A.; Committee Member: Kelly, Wendy L.; Committee Member: Merrill, Alfred; Committee Member: Orlando, Thomas; Committee Member: Sullards, Cameron. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Jennifer S. Brodbelt. Vita. Includes bibliographical references. Also available from UMI.

Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010. / Committee Chair: Fernández, Facundo; Committee Member: Bottomley, Lawrence; Committee Member: Mizaikoff, Boris; Committee Member: Orlando, Thomas; Committee Member: Prausnitz, Mark. Part of the SMARTech Electronic Thesis and Dissertation Collection.

LD2668 .T4 1966 C57 / Master of Science

In this work, a microplasma-based ionization source for ambient mass spectrometry (AMS) has been developed. Optical emission spectroscopy, optical microscopy, and electrical measurements have been used to characterize the discharge. The discharge was used in a direct exposure mode in AMS experiments, and was found to behave as a small Penning ionization source capable of ionizing a range of biomolecules via proton transfer. In order to broaden the effectiveness of the microplasma ionization source, admixtures of hydrogen in neon gas were used to produce vacuum ultraviolet (VUV) light. The 121.6 nm Lyman-? (10.23 eV) photons produced are effective soft (non-destructive), single-photon ionization sources. Since this photon energy exceeds the ionization potential of many biomolecules, this source is useful for analysis of a wide range of organic samples. The microplasma source, in both VUV-generating and direct-exposure modes, is proposed as a method by which to study the damage effects on biomolecules, and preliminary results are presented. Finally, a collaborative work investigating the role of ionizing radiation in the DNA damage process is presented. Using a synchrotron radiation source, the photolysis of DNA monolayers on gold substrates in a vacuum environment were studied by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) experiments.