Investigating the Molecular Mechanism of Protein–Polymer Binding with Direct Saturation Compensated Nuclear Magnetic Resonance

Herein, we describe a new technique, direct saturation compensated transfer (DISCO) NMR, to characterize protein–macromolecule interactions. DISCO enables the direct observation of intermolecular interactions and is used to investigate mucoadhesion, a type of polymer–protein interaction that is widely implemented in drug delivery but remains poorly understood. In a model system of bovine submaxillary mucin and poly­(acrylic acid), DISCO identifies selective backbone interactions that facilitate mucoadhesion through chain interpenetration. DISCO demonstrated distinct patterns of molecular selectivity between mucoadhesive polymers when applied to hydroxypropyl cellulose and carboxymethyl cellulose and that functionalizing adhesive polymers with strongly interacting moieties may be detrimental to the overall adhesive interaction. Additionally, DISCO was used to estimate polymer–protein dissociation constants using individual proton signals as reporters. Overall, DISCO can be used as a label-free screening tool to generate polymer-specific binding fingerprints to map and quantify interactions between macromolecules.