Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Analytical Chemistry

First Advisor

Young Jin Lee


This thesis represents efforts made in technological developments for the study of metabolic biology in plants, specifically maize, using matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI). The first chapter gives a brief introduction on what MALDI-MSI is and how it works. The final chapter provides a summary of all works in this thesis as well as providing future directions that may be pursued based on this research.

The second chapter encompasses research performed tracking metabolite distributions between two different inbreds of maize seeds throughout the course of germination utilizing GC-MS, LC-Fluorescence, and MSI analysis. GC and LC data provide quantitative information regarding a wide range of metabolites at crude localization levels, while MSI is able to track localizations of limited metabolites in fine spatial detail. Results demonstrate that metabolites are differentially localized throughout the seed depending on inbred, metabolite class, and germination time point.

The third chapter demonstrates how MALDI-MSI can be used to acquire large, metabolomic scale datasets. Serial sections of a maize seed are coated with various matrices and analyzed in positive and negative ion mode using a multiplex imaging strategy. This strategy allows for visualization of metabolites through MSI as well as metabolite identification through the collection and analysis of high-quality MS/MS spectra.

The fourth chapter outlines the development of a binary matrix comprised of 2,5-dihydroxybenzoic acid and iron oxide (Fe3O4) nanoparticles. The matrix is shown to alleviate the suppression of triacylglycerol species by phosphatidylcholine, both through standard analysis and on tissue analysis of maize seeds. The binary matrix also allows for the detection of more phospholipid classes in positive ion mode than either matrix on its own, while also demonstrating an apparent synergistic affect for large oligosaccharide type molecules.

The fifth chapter represents efforts to reduce the laser spot size for our MALDI-MSI experiments through the modification of laser optics. This work demonstrates that the swapping of the beam expander component of the optical system allows for simplistic modification of the laser spot size resulting in an easily applicable multi-resolution setup with the ability to perform imaging at a resolution of 5 µm. However, the high-resolution spot size is severely limited by depth of focus issues. This multi-resolution setup is then applied on a single maize root section at resolutions of 5, 10, and 50 µm. The images and spectral characteristics of these analyses are then compared and analyzed.


Copyright Owner

Adam D. Feenstra



File Format


File Size

194 pages