Hofmeister effect

The fundamental influence of interfacial water on the macromolecules of biological systems can be modified by adding neutral salts to the solution (Hofmeister effect (HE)). Despite the widespread use of HE in colloid chemistry, preparative biochemistry and biotechnology, interpretation of the effects has remained a matter of debate. Recently, we published a theoretical grounding of the effects based on the salt dependence of solute-water interfacial tension. It was shown that the relation between the interfacial tension and protein structural stability is directly linked to protein conformational fluctuations. A methodological implication of the results is that HE is expected to change the reactions accompanying major conformational changes that involve water-exposed surface area changes of macromolecules and supramolecular assemblies. The aim of our project is to utilize HE as research tool to reveal the role of interfacial water structure in protein folding and function.

The major scientific question to be answered is how salts decreasing (“chaotropes”)  or increasing (“kosmotropes”) protein-water interfacial tension influence the structure and function of biomolecules (proteins and peptides) showing different structural motifs. The spectrum of the target molecules spans from the highly ordered β-amyloid structures via proteins and model peptides of flexible, but well-defined structure (e.g., Trp-cage miniprotein or photoactive yellow protein) to the intrinsically disordered proteins. In the framework of the present project, we are going to address this point by a complex methodological approach involving powerful experimental techniques (FTIR-, CD-, absorption kinetics spectroscopy, also neutron diffraction and NMR in cooperation), as well as ab initio and molecular dynamics calculations.

Tc5b

Distribution of chaotropic iodide ions around the hydrophobic Pro-s in Trp-cage miniprotein

Distribution of kosmotropic fluoride ions around the hydrophobic Pro-s in Trp-cage miniprotein