Mechanism of Osmolyte Stabilization-Destabilization of Proteins: Experimental Evidence

In this work, we investigated the influence of stabilizing (N,N,N-trimethylglycine) and destabilizing (urea) osmolytes on the hydration spheres ofbiomacromolecules in folded forms (trpzip-1 peptide and hen egg white lysozyme???hewl)and unfolded protein models (glycine???GLY andN-methylglycine???NMG) by means ofinfrared spectroscopy. GLY and NMG were clearly limited as minimal models for unfoldedproteins and should be treated with caution. We isolated the spectral share of water changedsimultaneously by the biomacromolecule/model molecule and the osmolyte, which allowed usto provide unambiguous experimental arguments for the mechanism of stabilization/destabilization of proteins by osmolytes. In the case of both types of osmolytes, the decisivefactor determining the equilibrium folded/unfolded state of protein was the enthalpy effectexerted on the hydration spheres of proteins in both forms. In the case of stabilizing osmolytes,enthalpy was also favored by entropy, as the unfolded state of a protein was more entropicallydestabilized than the folded state

Automated summary

In this study, the influence of stabilizing and destabilizing osmolytes on the hydration spheres of folded and unfolded biomacromolecules was investigated using infrared spectroscopy. The enthalpy effect exerted on the hydration spheres was found to be the decisive factor in determining the equilibrium folded/unfolded state of the protein.