Development and Implementation of a Protein-Protein Binding Experiment to Teach Intermolecular Interactions in High School or Undergraduate Classrooms

The goal of this study was to create an accessible, inexpensive, and engaging experiment to teach high school and undergraduate chemistry or biology students about intermolecular forces and how they contribute to the behavior of biomolecules. We developed an enzyme-linked immunosorbent assay (ELISA) to probe specific structure-function relationships in the context of a protein-protein interaction that can be completed within a week of 45 min daily classes or a single 3-4 h lab using accessible reagents and materials (e.g., micropipettes and camera phones). The assay detected the high-affinity interaction between immunoglobulin G (IgG) and an engineered fibronectin domain protein. To demonstrate the impact of small chemical changes on intermolecular interactions, four mutant fibronectin domains were engineered, each with a single amino acid change, to provide a variety of chemical groups in the hypothesized binding site that resulted in a range of affinities for IgG (equilibrium dissociation constants from 1.5-696 nM). The experiment was implemented with two classes of high school chemistry students. Students effectively differentiated between strong and weak protein-protein interactions (median correlation coefficient between observed and expected results = 0.88) and demonstrated keen interest in the assay and concepts. Students were asked to then design and conduct a variation of the ELISA to test their own hypotheses regarding various experiment parameters to great success. Image acquisition for assay colorimetry was identified as a potential area of improvement. We have shown that this experiment is accessible to high school students both fiscally and academically and can be a fun and effective tool to apply their knowledge of intermolecular forces within the context of proteins. We have shown that the experiment could also be implemented in an undergraduate laboratory setting to allow for advanced inquiry into protein-protein interaction quantification and data analysis. This experience helps students at a variety of academic levels make conceptual connections across the fields of chemistry, physics, and biology.