Gel Assay to Introduce Polymer Biodegradation in the Undergraduate Laboratory

Polymers are ubiquitous and essential to modern society, which is why the American Chemical Society has mandated inclusion of polymer chemistry in the undergraduate curriculum. To meet this requirement, we have chosen to weave a polymeric theme through multiple laboratory courses beginning with organic chemistry, where students use aspartic acid to synthesize poly(aspartic acid), an ecofriendly alternative to nonbiodegradable poly(carboxylates). Subsequently, these student-synthesized polymers serve as substrates for the enzyme poly(aspartic acid) hydrolase-1 in our biochemistry course. This experiment introduces the concept of biodegradation through a gel assay that allows students to visualize enzyme-mediated polymer degradation. Students learn the difference between mono- and polydisperse polymers, how biodegradation affects the size of a polymer through analysis of mobility shifts in an agarose gel, and how to use densitometry software to calculate enzyme activity. Finally, keeping the same polymeric theme provides a source of continuity in our curriculum while expanding students' understanding of polymer chemistry from the viewpoint of different chemistry disciplines.