Hofmeister Effect in Self-Organized Chemical Systems

Abstract

We studied the effect of spectator ions in the prototype of far-from-equilibrium selforganized chemical systems, the Belousov−Zhabotinsky (BZ) reaction. In particular, we investigated the specific ion effect of alkali metal cations, connoted for their kosmotropic and chaotropic properties. By means of combined experimental and numerical approaches, we could show a neat and robust evidence for the Hofmeister effect in this system. Spectator cations induce a marked increment of the induction period that preludes regular oscillations and decrease the oscillation amplitude following the sequence Li + < Na + ≪ K + ∼ Cs + . These ions affect the system kinetics by interfering in the interaction between the oxidized form of the catalyst and the organic substrate, responsible for resetting the BZ system to preautocatalytic (reduced) conditions. The specific ion effect on these key reactive steps is systematically characterized and correlated with different parameters which describe the interaction of the cations with the solvent.

Effect of Hofmeister Ions on Transport Properties of Aqueous Solutions of Sodium Hyaluronate

“…The ions on the left side are called kosmotropes ("water structure makers"), while on the right side are chaotropes ("water structure breakers") [21]. It is known that Hofmeister or specific ion effects affect some physicochemical properties of aqueous [23,24] and nonaqueous [25,26] systems. As an example, there are studies made by Mráček et al [27] about the influence of Hofmeister series ions on HyA behaviour and HyA film-swelling.…”

Rhamnolipid Self-Aggregation in Aqueous Media: A Long Journey toward the Definition of Structure–Property Relationships

“…Some crucial issues concern the fact that ions affect all possible interactions in a considered system [ 242 ], and that many phenomena involve the action of both ions of an electrolyte; thus, one needs to consider both of them. For all these reasons, and taking into account the structural complexity of rhamnolipids and the inherent flexibility of their headgroup, a systematic study on ion-specific effects with respect to bulk and surface physicochemical properties of rhamnolipids should be undertaken in the future, and the results should be rationalized in the context of currently employed theoretical models [ 243 , 244 , 245 , 246 ]. Achieving a good understanding of ion-specific effects on rhamnolipid behavior is a necessary step toward the replacement of conventional surfactants with rhamnolipids in technological applications, given how deeply ions affect formulation features.…”

BSA fragmentation specifically induced by added electrolytes: An electrospray ionization mass spectrometry investigation

“…The specific effect of cations and anions on the properties and on the behavior of proteins in solution has widely been investigated since Hofmeister's first observations. [1][2][3][4][5][6] Briefly, anions generally promote protein precipitation in the order HPO 4 2-> SO 4 2-> F -> Cl -> Br -> I -> NO 3 -> ClO 4 -> SCN -, whereas cations tend to favor precipitation in the order Cs + > NH 4 + > Rb + > K + > Na + > Li + > Mg 2+ > Ca 2+ . The general rule is that highly hydrated anions (kosmotropic) and weakly hydrated cations (chaotropic) favor protein precipitation.…”