Expression and Purification of Sperm Whale Myoglobin

We present a multiweek laboratory exercise that exposes students to the fundamental techniques of bacterial expression and protein purification through the preparation of sperm whale myoglobin. Myoglobin, a robust oxygen-binding protein, contains a single heme that gives the protein a reddish color, making it an ideal subject for the teaching laboratory as students can follow the progress of the protein visually in real time. The purification uses both ion-exchange and size-exclusion chromatography, thus, introducing students to two of the most common separation methods. Students evaluate the quality of the purification via sodium dodecyl sulfate−polyacrylamide gel electrophoresis. In most cases, this procedure produces sufficient quantities of pure protein for further laboratory exercises studying the properties of myoglobin.