Are specific buffer effects the new frontier of Hofmeister phenomena? Insights from lysozyme adsorption on ordered mesoporous silica

Hofmeister (ion specic) effects are phenomena related to the chemical nature of electrolytes. Although they are ubiquitous in all chemical, colloidal, and biological systems, they cannot be quantied in terms of the conventional physico-chemical theories (i.e. Debye–Hückel, DLVO, etc.). These are limit theories, based on electrostatics, and valid at innite dilution only. The gap between theories and Hofmeister related experiments is usually very large since the ion specic effects are generally observed at high concentrations in the presence of strong electrolytes 0.3–3 M. This is very far from the validity's domain of both limit laws, and their extensions (valid up to 10 3 to 10 2 M). Nevertheless, it has been demonstrated that high concentrations of strong electrolytes are not strictly necessary to observe ion dependent phenomena. Several experiments showed that ion specicity occurs at physiological salt concentrations (0.1–0.15 M), and even below. Very recently, the occurrence of ion specicity at low salt concentrations (Hofmeister charging) has found a theoretical basis. The nding that Hofmeister effects occur at low salt concentrations poses new questions. Can the weak electrolytes used for buffers give Hofmeister effects? According to the Henderson–Hasselbalch equation, they should not. In biochemistry, it is