The insecticide malaoxon inhibits acetylcholinesterase (AChE) activity. Various factors might
affect the effectiveness of malaoxon. We have previously described a colorimetric enzyme assay
to look at the differences in inhibition of AChE caused by malaoxon in crude extracts from the
bean beetle Callosobruchus maculatus in a set up that lends itself to a multi-week lab sequence.
Here we expand this set of exercises to include the Bradford assay to measure protein
concentration in crude extracts using a standard curve. This allows us to standardize the initial
activity of AChE based on protein content and thus consider both initial activity of the enzyme
and relative inhibition of the activity due to the insecticide. These two parameters have been
shown to be inversely correlated and may respond differently to environmental factors such as
the food source on which the animals are raised. These types of projects not only introduce
students to different biochemical techniques, but also raise questions such as costs and benefits
of insecticide resistance.