Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

Yeung, Ken K.-C.

2nd Supervisor

Whitehead, Shawn N.

Co-Supervisor

Abstract

The revolutionary development of soft ionization techniques like matrix-assisted laser desorption/ionization (MALDI) has opened up the possibilities for mass spectrometry (MS) in protein detection, identification, and sequencing. The ability of MALDI MS to acquire images of intact tissue sections offer an additional dimension of analysis where location information can be attained. Visualization of biological systems help to unravel the complexities of cells, drug pathways, and disease pathology. However, the capabilities of MALDI MS imaging are often being questioned, as signals are typically biased towards the most abundant component within a complex sample. Within biological tissue samples, the most abundant components are salts and lipids making it difficult for compounds such as proteins and peptides to ionize and be detected.

In this thesis, sample preparation techniques are investigated to help improve the detection sensitivity of MALDI MSI for proteins and peptides through investigation of ZP1609 and the amyloid ß (Aß) protein. ZP1609 is an antiarrhythmic drug designed to protect against cardiac ischemia-reperfusion injury, and Aß oligomers are strongly correlated with Alzheimer’s disease (AD) pathology. Both of which are considered lower abundance compounds within samples analyzed, and therefore ideal candidates for the work described herein. This thesis presents MALDI MS capabilities in the detection of noncovalent complexes by distinguishing variations in in vitro Aß composition for different sample preparatory procedures. Furthermore, a reduction in ion suppression effects by salts and lipids was demonstrated with increased MALDI MSI detection sensitivity for the target peptide. Most noticeably, an additional acidification protocol generated images of greater detection sensitivity, and spatial resolution. Introduction of solid-phase extraction (SPE) by means of magnetic bead application was designed to improve the extraction of proteins from tissue sections. The C18 functionalized magnetic beads provided signal enhancement capabilities for varying concentrations of Aß1-42 samples, however difficulties were encountered when applied for MALDI MSI analysis. Nonetheless, the application of SPE for targeted analyte extraction prior to MALDI MS analysis was beneficial in improving detection sensitivity of Aß proteins with and without the presence of contaminants from tissue sections.

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