Matrix-assisted laser desorption ionization mass spectrometry: Instrument and method development and applications

The overreaching theme of this thesis is the mass spectrometry (MS) ionization technique called Matrix-Assisted Laser Desorption Ionization or MALDI for short. The research is focused in two areas: method development using MALDI/time-of-flight (TOF) MS and instrument development focused on improved performance in Fourier Transform MS (FTMS) of MALDI generated ions.;Collaborative research with Dr.'s. E. Cavalieri and E. Rogan at the Eppley Institute in Omaha, NE, shows that MS is an effective tool for studying the mechanism of metabolic activation of polycyclic aromatic hydrocarbons (PAH) and the subsequent covalent binding to DNA to form adducts. In Chapter 2 we compare the structural information obtained by MALDI-TOF mass spectrometry using Post-Source-Decay (PSD) to that obtained from other methods including Collisional Activation Decomposition (CAD) using a triple quadrupole instrument. Our comparison involved synthetic isomeric dibenzo[a,l]pyrene adenine adducts. We then used MALDI-TOF PSD (Chapter 3) to identify an adduct, DBC-5-N7adenine, obtained in vitro involving 7H-dibenzo[c,g]carbazole (DBC) and rat liver microsomes. In Chapter 4, we use MALDI-TOF PSD to verify the formation in vitro of the 4-hydroxy catechol estrogen-DNA adduct 4-OHE1 -1 (alpha,beta)-N7Guanine. We then demonstrate the utility that MALDI-TOF can provide to synthetic polymer chemists by quantifying a minor distribution of a polymer generated by a side reaction, that would likely by undetectable using other analytical means (Chapter 5).;These efforts show that MALDI-TOF is a versatile analytical tool. However, TOF is limited to resolving powers of 20,000 at best. FTMS can provide high mass resolving powers and accurate mass determinations that are important for the detection of biological molecules. MALDI couples well with FTMS; however, trapping and detecting MALDI-generated ions can pose problems for FTMS. In Chapter 6, we compensate the trapping electric fields, implement a means for centering of the ion cloud in the trap, and incorporate a more efficient ion trapping scheme to cope better with MALDI-generated ions. The improvements permit achievement of theoretical maximum resolving powers for large peptides.