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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 45: Charged Soft Matter, Polyelectrolytes and Ionic Liquids II

CPP 45.1: Vortrag

Freitag, 21. März 2025, 11:30–11:45, H38

Binding of small molecules to polyelectrolytes driven by electrostatics — •Ulrich Scheler — Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden

The interaction of small molecules or ligands to macromolecules (polyelectrolytes or proteins) in solution is plays an important role in biological and medical applications. Pulsed-field-gradient (PFG) nuclear magnetic resonance (NMR) has been applied to measure translational motion of molecules and complexes in aqueous solution, that may be diffusion orelectrophoretic motion. Two-dimensional NMR experiments correlating chemical shift that is used to assign different species with either the diffusion coefficient or the electrophoretic mobility enable determining the mobility of diffusion coefficient respectively in mixtures for the individual components. From the combination of diffusion and electrophoresis NMR the effective charge of the species under investigation is derived. Weak interaction of the ligand to the macromolecule means that the ligand binds for a fraction of time to the macromolecule and is free in the solution for another fraction. From the thus observed weighted average the bound fraction is calculated for every condition no titration experiment is required. The strong polyelectrolyte PDADMAC has been studied interacting with glutamic acid as a function of pH. The bound fraction of glutamic acid increases with increasing pH and thus increasing negative charge of glutamic acid showing that the interaction is driven by electrostatic interaction rather than other possible interactions. The bound fraction as a function of pH coincides with the charge.

Keywords: electrostatic interaction; ligand binding; weak binding; PFG NMR