Protein Stabilisation In Salt Solutions : Specific Ion Effects

Abstract

In this thesis, we study the unfolding thermodynamics of Ubiquitin under salt solutions. Our results provide strong evidence of the fact that sulphate ions shifts the folded-unfolded equilibrium towards the folded side not by the stabilization of the native state but by destabilization of the unfolded state. Moreover, we also discuss the dependence of unfolding thermodynamics of ions on the water model and show that TIP4P-Ew and TIP4P-2005 increasingly destabilize the native state while TIP3P and TIP4P-D reproduces the folding-unfolding equilibrium quite realistically. Moreover, while studying the unfolding of Ubiquitin in sulphate solutions, we show that ion aggregation in non-polarizable models of sulphates arises because of the lack optimised interactions between sulphate and sodium ion and thus might be the case across all polyvalent and densely charged ions.