Molecular mapping of plant metabolites and their dynamics
Young-Jin Lee
Efforts to exploit plant systems for the production of small metabolites, valued in biofuels and chemical industries, often depend on detecting minute differences between the metabolic make-ups of different organisms.
"Chemical composition changes are not uniform throughout an organism," says Young-Jin Lee, assistant professor in the Department of Chemistry. Lee is developing mass spectrometry imaging technology to identify, localize and quantify key metabolites with spatial resolution at a single cell level.
For proof of concept, Lee, who joined Iowa State last year following a stint at the University of California, Davis, Genome Center, used a Thermo Finnigan vMALDI LTQ Linear Ion Trap to positively identify and spatially resolve two different types of epicuticular wax metabolites—caffeate and coumarate—on the surface of micron-size Arabidopsis root hairs, the first mass spectrometric imaging ever achieved on such tiny plant structures.
In brief, Lee dried plant samples on a stainless steel plate and coated them with a graphite or silver-based ionizing matrix. Using his high resolution mass spectrometer to perform localized sampling over narrow areas, Lee acquired mass spectra at hundreds of x-y positions allowing him to generate a two-dimensional chemical image of the plant structure for each molecular compound.
"Current metabolomics technology is not position sensitive," explains Lee. "Now we can see how these changes are distributed—localize the destination of metabolites on a single cell level."
Lee is a physical chemist by training and sees this interdisciplinary area of bioanalytical mass spectrometry as an amazing opportunity.
"We are bioanalytical chemists, folks from the physical science sector, working between chemistry and biology, developing and inventing tools that improve biology—enabling us to discover a whole new world. Mass spectrometry imaging is like a new microscope where we cannot only see but also identify the chemical structure of specimens," says Lee.
Currently, Lee is attempting to improve his identification accuracies by employing a new hybrid mass spectrometer that has high mass accuracy and performs direct chemical composition analysis on the sample target.
He is also working on several pioneering projects, including the use of cross-linking agents and mass spectrometry, to study the three dimensional structure of proteins or protein complexes, and a high-throughput mass spectrometric assay to characterize hundreds of bio-oil compounds or complex algae products relevant to biofuels production.
