The Molecular Toxicology of Acetochlcor and Click Chemistry: an Interview With Jessica
This interview was based on an in-class interview with Jessica, who is a doctoral student in molecular toxicology and is studying the effects of an herbicide, Acetochlor, on mice; and also uses “click chemistry” to study the structure and constituents of biomolecules.
As an herbicide, Acetochlor is used primarily on corn, but also soy and peanuts, and less often on other crops. The world divides into Acetachlor “targets,” which are unwanted plants--weeds--that compete with marketable crops farmers are growing. Any non-target organism, plant or animal, is referred to as an “off-target” organism.
Little is known about the long-term effects of Acetochlor on off-target organisms, such as human beings. We do know that Acetachlor preferentially binds to cysteine, one of the twenty amino acids that are the building blocks of proteins. A common experiment is to inject mice with Acetochlor and after four hours, add a molecular probe, which binds with reactive cysteine so that the effects of the Acetochlor may be studied.
Not all cysteines are reactive, but many are. The effect of large doses of Acetochlor is to render metabolic pathways nonfunctional if enough Acetochlor binds to reactive cysteine. Pathways may also become nonfunctional if the dose of Acetochlor is lower but there are more reactive cysteines.
Acetochlor has affinity for enzymes that are involved in fatty acid oxidation, the process by which animals metabolize fatty acids for energy when glucose is unavailable. Thus, the adverse effects of Acetochlor become apparent when animals rely on fatty acids for essential metabolic energy.
Click chemistry is a method for analyzing the composition of biomolecules and depends on the use of probes. Probe molecules have two active regions at opposing ends: 1) the warhead, which is the binding site of the probe; and 2) the alkyne, which is a nitrogen triple bond, N≡N.
If we bind rhodamine with a probe to a biomolecule of interest, we can learn about its composition by pulling it through a gel to which we apply an electric current. The current separates the components of the molecule on the basis of its weight as done in gel electrophoresis.
Because of biotin’s strong affinity with streptavidin, we can use it to bind biomolecules of interest, and use mass spectrometry to analyze their chemical structure.
