Protein gel electrophoresis in the undergraduate physics laboratory

We describe an undergraduate laboratory experiment in protein gel electrophoresis that uses readily available apparatus and materials. The separation of a mixture of stained proteins by gel electrophoresis was videotaped. Position–time data for the proteins generated from analysis of digitized videotape images allowed for calculation of protein terminal velocities. The dependence of protein terminal velocity on molar mass was determined and found to agree with predictions made by current theory. We also introduce a model that draws on simple physical concepts to help students place the experimental results in context.