Protein thermal stabilization in aqueous solutions of osmolytes

International audienc

Influence of Osmolytes on Protein and Water Structure: A Step To Understanding the Mechanism of Protein Stabilization

Results concerning the thermostability of hen egg white lysozyme in aqueous solutions with stabilizing osmolytes, trimethylamine-<i>N</i>-oxide (TMAO), glycine (Gly), and its <i>N</i>-methyl derivatives, <i>N</i>-methylglycine (NMG), <i>N,N</i>-dimethylglycine (DMG), and <i>N,N,N</i>-trimethylglycine (betaine, TMG), have been presented. The combination of spectroscopic (IR) and calorimetric (DSC) data allowed us to establish a link between osmolytes’ influence on water structure and their ability to thermally stabilize protein molecule. Structural and energetic characteristics of stabilizing osmolytes’ and lysozyme’s hydration water appear to be very similar. The osmolytes increase lysozyme stabilization in the order bulk water < TMAO < TMG < Gly < DMG < NMG, which is consistent with the order corresponding to the value of the most probable oxygen–oxygen distance of water molecules affected by osmolytes in their surrounding. Obtained results verified the hypothesis concerning the role of water molecules in protein stabilization, explained the osmophobic effect, and finally helped to bring us nearer to the exact mechanism of protein stabilization by osmolytes

General Mechanism of Osmolytes’ Influence on Protein Stability Irrespective of the Type of Osmolyte Cosolvent

The stability of proteins in an aqueous solution can be modified by the presence of osmolytes. The hydration sphere of stabilizing osmolytes is strikingly similar to the enhanced hydration sphere of a protein. This similarity leads to an increase in the protein stability. Moreover, the hydration sphere of destabilizing osmolytes is significantly different. These solutes generate in their surroundings so-called “structurally different water”. The addition of such osmolytes causes “dissolution” of the specific protein hydration sphere and destabilizes its folded form. No relationship is seen between the stabilizing/destabilizing properties of osmolytes and their structure-making/-breaking influence on water. Furthermore, their accumulation at the protein surface or their exclusion does not determine the osmolytes’ effect on protein stability. An explanation to the osmolytes’ stabilizing/destabilizing influence originates in the similarity of water properties in osmolytes and protein solutions. The spectral infrared characteristic of water in an osmolyte solution allowed us to develop practical criteria for classifying solutes as stabilizing or destabilizing agents

General Mechanism of Osmolytes’ Influence on Protein Stability Irrespective of the Type of Osmolyte Cosolvent

The stability of proteins in an aqueous solution can be modified by the presence of osmolytes. The hydration sphere of stabilizing osmolytes is strikingly similar to the enhanced hydration sphere of a protein. This similarity leads to an increase in the protein stability. Moreover, the hydration sphere of destabilizing osmolytes is significantly different. These solutes generate in their surroundings so-called “structurally different water”. The addition of such osmolytes causes “dissolution” of the specific protein hydration sphere and destabilizes its folded form. No relationship is seen between the stabilizing/destabilizing properties of osmolytes and their structure-making/-breaking influence on water. Furthermore, their accumulation at the protein surface or their exclusion does not determine the osmolytes’ effect on protein stability. An explanation to the osmolytes’ stabilizing/destabilizing influence originates in the similarity of water properties in osmolytes and protein solutions. The spectral infrared characteristic of water in an osmolyte solution allowed us to develop practical criteria for classifying solutes as stabilizing or destabilizing agents

Hydration of Simple Model Peptides in Aqueous Osmolyte Solutions

The biology and chemistry of proteins and peptides are inextricably linked with water as the solvent. The reason for the high stability of some proteins or uncontrolled aggregation of others may be hidden in the properties of their hydration water. In this study, we investigated the effect of stabilizing osmolyte–TMAO (trimethylamine N-oxide) and destabilizing osmolyte–urea on hydration shells of two short peptides, NAGMA (N-acetyl-glycine-methylamide) and diglycine, by means of FTIR spectroscopy and molecular dynamics simulations. We isolated the spectroscopic share of water molecules that are simultaneously under the influence of peptide and osmolyte and determined the structural and energetic properties of these water molecules. Our experimental and computational results revealed that the changes in the structure of water around peptides, caused by the presence of stabilizing or destabilizing osmolyte, are significantly different for both NAGMA and diglycine. The main factor determining the influence of osmolytes on peptides is the structural-energetic similarity of their hydration spheres. We showed that the chosen peptides can serve as models for various fragments of the protein surface: NAGMA for the protein backbone and diglycine for the protein surface with polar side chains