Project Outline

Mass spectrometry is a technique by which biological compounds can be identified and quantified. however, typical sample preparation grinds tissues into a paste for extraction of metabolites or proteins for analysis. Thus, the distribution of metabolites and proteins in across the structure of the biological tissue sample is lost. To resolve this issue we have recently purchased a mass spectrometry imaging platform that provides comprehensive and unbiased spatially resolved characterisation of biological surfaces, such as tissues or bacterial biofilms. A thin freshly-frozen or fixed sample section is mounted on a metal-coated glass slide and evenly coated with an organic matrix. Spatially localised data is acquired by firing a laser at the surface of the tissue, where the energy is absorbed by the matrix molecules, which are ionised along with co-crystalised biomolecules and measured using a mass spectrometer. Sampling laser spots (typically <10µm) across the entire surface allows the creation of an image map of the detected analytes. Sample preparation, matrix application and analytical measurement are all key considerations in matrix -assisted laser desorption and ionisation mass spectrometry imaging (MALDI MSI).

This project will focus on optimising analytical conditions for MALDI MSI of plant leaves and roots. We propose to use two mass spectrometry platforms at the University of Warwick; a tribrid Orbitrap Fusion mass spectrometer and a Quantiva triple quadrupole instrument. This flexibility allows many potential analysis routes; the high resolution, speed and fragmentation modes of the Orbitrap MS, versus the high specificity and selectivity of Selected Reaction Monitoring on the triple quadrupole. the student will need to optimise sample preparation, matrix selection and undertake an exploratory analysis to determine which compounds have suitable ionisation properties. We will use samples from active research projects including nitrogen fixation in legume roots, wounding of plant leaves, and plant pathogen interactions. Compounds of interest are a range of plant hormones, phospholipids and secondary metabolites.

Techniques

• Advanced analysis of multi-dimensional image and mass data
• Extraction of metabolites from plants
• Sectioning and mild fixing of plant tissues for microscopy and MS imaging.
• Love sell imaging of calcium and fluorescence.
• Mining bioinformatics data resources
• Mass Spectrometry of a range of compounds.