Experimental Determination of pKa Values and Metal Binding for Biomolecular Compounds Using 31P NMR Spectroscopy

This lab experiment uses 31P NMR spectroscopy of biomolecules to determine pKa values and the binding energies of metal/biomolecule complexes. Solutions of adenosine nucleotides are prepared, and a series of 31P NMR spectra are collected as a function of pH and in the absence and presence of magnesium or calcium ions. The chemical shifts in the spectrum change depending on the protonation state of the phosphate groups and the nucleotide/metal interaction. Because 31P NMR spectroscopy is used, the resulting data are clean and readily accessible for student analysis. The use of 31P NMR spectroscopy presents a rich opportunity to deepen student engagement with NMR spectroscopy and spectral analysis. Furthermore, the inclusion of biomolecules and metal binding exposes students to important and underrepresented concepts that bridge organic chemistry and biochemistry. Students will learn how to prepare, collect, and analyze non-hydrogen samples using NMR spectroscopy, identify an unknown pKa, and calculate bind...