NMR-based Ligand–Receptor Interaction Studies under Conventional and Unconventional Conditions

Many biologically relevant molecular recognition processes are highly dynamic and rely on the equilibrium between ligands’ association and dissociation from their receptor(s), because of the reversible nature of the majority of them. Over the last few decades, several NMR experiments allowing the characterization of these interactions have been developed. They are very useful tools for the study of naturally occurring binding events, but also for the screening of both natural and synthetic compounds that, through the interaction with relevant targets, can exert biological and pharmacological activities. The aim of this chapter is to provide a general presentation of the most commonly used NMR experiments based on ligand resonance observation, together with the descriptions of specific examples of their advanced applications in the analysis of unconventional samples, such as those containing complex compound mixtures, multivalent ligands, liposomes, nanoparticles and living cells.