Mechanistic insights into osmolyte action in protein stabilization under harsh conditions: N-methylacetamide in glycine betaine–urea mixture

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 of biomacromolecules in folded forms (trpzip-1 peptide and hen egg white lysozyme—hewl) and unfolded protein models (glycine—GLY and N-methylglycine—NMG) by means of infrared spectroscopy. GLY and NMG were clearly limited as minimal models for unfolded proteins and should be treated with caution. We isolated the spectral share of water changed simultaneously by the biomacromolecule/model molecule and the osmolyte, which allowed us to provide unambiguous experimental arguments for the mechanism of stabilization/destabilization of proteins by osmolytes. In the case of both types of osmolytes, the decisive factor determining the equilibrium folded/unfolded state of protein was the enthalpy effect exerted 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 entropically destabilized than the folded state.

Interactions in Ternary Aqueous Solutions of NMA and Osmolytes-PARAFAC Decomposition of FTIR Spectra Series

Intermolecular interactions in aqueous solutions are crucial for virtually all processes in living cells. ATR-FTIR spectroscopy is a technique that allows changes caused by many types of such interactions to be registered; however, binary solutions are sometimes difficult to solve in these terms, while ternary solutions are even more difficult. Here, we present a method of data pretreatment that facilitates the use of the Parallel Factor Analysis (PARAFAC) decomposition of ternary solution spectra into parts that are easier to analyze. Systems of the NMA–water–osmolyte-type were used to test the method and to elucidate information on the interactions between N-Methylacetamide (NMA, a simple peptide model) with stabilizing (trimethylamine N-oxide, glycine, glycine betaine) and destabilizing osmolytes (n-butylurea and tetramethylurea). Systems that contain stabilizers change their vibrational structure to a lesser extent than those with denaturants. Changes in the latter are strong and can be related to the formation of direct NMA–destabilizer interactions.

On the role of water in the hydrogen bond network in DESs: an ab initio molecular dynamics and quantum mechanical study on the urea–betaine system

We herein report an ab initio molecular dynamics study on a natural DES composed of urea and betaine in a 3 : 2 ratio, as a test case for evaluating the water effect.

Non-ideal behavior of binary aqueous mixtures of some urea derivatives and their capacity to induce lysozyme gelation

The urea derivatives, namely, ethylurea (EU), 1,3 dimethylurea (1,3-DMU) and 1,1 diethylurea (1,1-DEU), in the limiting regions of their solubilities in water, and tetramethylurea (TMU) at w≥0.65 were investigated in relation to their capacity of inducing hen egg white lysozyme (HEWL) physical (non-covalent) gelation. Protein transparent gels were generated out of TMU/H₂O and 1,1-DEU/H₂O, respectively, whereas an intensively turbid gel resulted from sol-gel transition taking place in EU/H₂O. Oscillatory rheology revealed distinctions in the gels' structural and dynamic characteristics. Hydration patterns of the derivatives in solution, sizes of their non-polar domains and supramolecular symmetry features played a central role in their capacity of gel formation and in the gels' rheological behavior and morphology. Effects on gel characteristics of distinctively positioned ions in the Hofmeister series showed that SCN^- disrupted water H-bonding interconnectivity in TMU lysozyme gel, strengthening gel structure, yet maintaining gel transparency. Citrate enhanced system elasticity albeit causing intense turbidity and leading to phase separation. Larger values of the storage modulus, G', were verified for gels generated from binary mixtures containing urea derivatives with higher dipole moments.

Can an ammonium-based room temperature ionic liquid counteract the urea-induced denaturation of a small peptide?

The folding/unfolding equilibrium of proteins in aqueous medium can be altered by adding small organic molecules generally termed as co-solvents.

Ammonium based stabilizers effectively counteract urea-induced denaturation in a small protein: insights from molecular dynamics simulations

Room temperature ionic liquids (IL) and deep eutectic solvents (DES) are known to aid the conformational stability and activity of proteins and enzymes in aqueous solutions.