The Differences in Macromolecular Binding Between Sodium and Potassium Ions

Motivation: The binding strength of Na⁺ and K⁺ with macromolecules is different, but conventional methods cannot distinguish them. NMR can directly probe 23Na and 39K spins, revealing their dynamics. Nevertheless, interpreting 23Na and 39K NMR signals in biological systems remains challenging due to the complex relaxation behavior of quadrupolar nuclei in intermediate motion regime. Goal(s): Using non-invasive NMR methods to study the interactions between macromolecules and sodium/potassium ions. Approach: Quadrupolar relaxation and double quantum filtered (DQF) parameters were studied to understand the ion-macromolecule interaction quantitatively. Results: We observed the differences in Na⁺ and K⁺ binding with proteins and polysaccharides. Impact: The analysis of ion interactions with macromolecules may help explain the distinct functions of sodium and potassium ions in biological systems.