Chaotropicity describes the entropic disordering of lipid bilayers and other biomacromolecules which is caused by substances dissolved in water. According to the original usage[1] and work carried out on cellular stress mechanisms and responses,[2][3][4] chaotropic substances do not necessarily disorder the structure of water.[5]
The chaotropic activities of solutes in the aqueous phase (e.g. ethanol, butanol, urea, MgCl2 and phenol) have been quantified using an agar-gelation assay.[6] Whereas chaotropicity was first applied to studies of ions,[1] it is equally applicable to alcohols, aromatics, ion mixtures and other solutes.[2][3][7][8] Furthermore, hydrophobic substances known to stress cellular systems (including benzene and toluene) can chaotropically disorder macromolecules, and induce a chaotrope-stress response in microbial cells, even though they partition into the hydrophobic domains of macromolecular systems.[4][9]