METHODS
As a chemical ecologist, I employ techniques that aim to measure the plant chemistry that alters and is shaped by beneficial relationships.
METHOD : Cyanogenesis
To measure the maximum amount of cyanide a leaf could release when attacked, in the Ballhorn Lab we measure the cyanogenic potential of that leaf: the total amount of precursor molecules (cyanogenic glycosides) that would react to form gaseous cyanide. Quantitative method from Ballhorn et. al, 2005.
METHOD : Soluble Protein
One of the most widely utilized and highly cited plant biology procedures is Bradford’s protein assay, which enables us to quantify total soluble protein in a leaf sample by adding a blue reagent that binds strongly to specific amino acids.
METHOD : Extrafloral Nectar
To measure the volume and sugar concentration of the droplets plants secrete to attract predatory insects such as ants, we use microcapillary tubes and a Brix refractometer: the same tool brewers and winemakers use to determine sugar concentration.
METHOD : Trypsin Inhibitor Assay
The point of attacking and consuming plants from a bug’s perspective is to digest its food. However, many plants make peptide chains that block the insect’s gut proteases such as trypsin. To quantify the protease inhibition power of a leaf sample, we allow plant extract to diffuse outward from holes punched into an agar gel made with trypsin, stain the gel, and then measure the light halo surrounding each well where the plant protein-based inhibitors blocked the trypsin in the gel. Trypsin inhibitor assay method from Dr. Don Cipollini.
METHOD : Solid-Phase Microextraction (SPME) and GCMS-TOF
Plants release many chemicals into the air, many of which are volatile organic compounds (VOCs). To compare the chemistry changes in plants with symbiotic, nitrogen-fixing rhizobia, we expose a SPME fiber to a sample of contained air in a small vial. We use a LECO Pegasus time-of-flight (TOF) analysis to heat the fiber and pull all plant chemicals off of it, send them through a column, and then analyze what those compounds are based on how long each one takes to fly through the column.