Permanganate Oxidation of DNA Nucleotides: An Introductory Redox Laboratory Framed as a Murder Mystery

For a variety of reasons, understanding oxidation-reduction (redox) reactions can be challenging for introductory chemistry students. To provide an experiential foundation for students to learn redox concepts, we developed a laboratory experiment that frames redox reactions as a simulated murder mystery. In this experiment, permanganate, which serves as the oxidizing agent, reacts with each of the four monomer units of deoxyribonucleic acid (DNA), which serve as the reducing agents. The reactions are designed to produce dissimilar manganese oxidation states, and hence dissimilar solution colors. For practical reasons, the four monomer units of DNA are used as mimics of four polymeric DNAs from four murder suspects. The color obtained from the redox reaction using "DNA" from the murder weapon is compared to that from the four suspects to identify the perpetrator. The experiment can contribute to the students' emergent understanding of basic redox concepts, of the variable nature of transition metal oxidation states, and of the concept that the DNA monomers are distinct chemicals with distinct reactivities (i.e., reducing potentials in this experiment). Alternative strategies for framing the experiment, as well as some of its limitations, are discussed. The contributions of first-year undergraduate researchers to this experiment are also described.