How Do Structure and Charge Affect Metal-Complex Binding to DNA? An Upper-Division Integrated Laboratory Project Using Cyclic Voltammetry

Abstract

An advanced undergraduate laboratory project is described that integrates inorganic, analytical, physical, and biochemical techniques to reveal differences in binding between cationic metal complexes and anionic DNA (herring testes). Students were guided to formulate testable hypotheses based on the title question and a list of different metal complexes. Student teams synthesized the target complexes, such as tris(1,10-phenanthroline)cobalt(III) or tris(2,2′-bipyrydyl)cobalt(III), and characterized them by voltammetry and spectroscopy. Separately, DNA stock solutions were prepared and analyzed via published spectroscopic methods. Aliquots of the DNA solutions, added into a metal-complex solution, gave decreases in the cyclic voltammetry peak currents due to the slower diffusion rate of the DNA−metal complex. A nonlinear curve fit analysis of the 1:1 binding isotherms confirmed the literature result (unknown to students) of larger binding constants for the phenanthroline complex due to intercalative bindin...