title: The origin of cooperative solubilisation by hydrotropes.
abstract: The signature of hydrotropic solubilisation is the sigmoidal solubility curve; when plotted against hydrotrope concentration, solubility increases suddenly after the minimum hydrotrope concentration (MHC), and reaches a plateau at higher hydrotrope concentrations. This sigmoidal curve is characteristic of cooperative phenomena, yet the true molecular basis of hydrotropic cooperativity has long remained unclear. Here we develop a theory, derived from the first principles of statistical thermodynamics using partially-open ensembles, to identify the origin of hydrophobic cooperativity. Our theory bears a close resemblance to the cooperative binding model used for protein-ligand binding. The cause of cooperativity is the enhancement of the hydrotrope m-body interaction induced by the presence of the solute; m can be estimated from the experimental solubility data.
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK. seishi.shimizu@york.ac.uk.
authors.forename: Seishi
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan and Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Katsura, Kyoto 615-8520, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Matubayasi