« The Chaotropic Effect as an Assembly Motif in Chemistry »
Pr. Werner M. Nau (Department of Life Sciences and Chemistry, Jacobs University Bremen, Germany)
Following up on scattered reports on interactions of conventional chaotropic ions (e.g., I−, SCN−, ClO4−) with macrocyclic host molecules, biomolecules, and hydrophobic neutral surfaces in aqueous solution, the chaotropic effect has recently emerged as a generic driving force for supramolecular assembly, orthogonal to the hydrophobic effect. The chaotropic effect becomes most effective for very large ions that extend beyond the classical Hofmeister scale, and that can be referred to as superchaotropic ions (e.g., borate clusters and polyoxometalates). In this review, we present a continuous scale of water-solute interactions which includes the solvation of kosmotropic, chaotropic, and hydrophobic solutes, as well as the creation of void space (cavitation). Recent examples for the association of chaotropic anions to hydrophobic synthetic and biological binding sites, lipid bilayers, and surfaces are discussed.