Exploring conformational preferences of proteins: ionic liquid effects on the energy landscape of avidin

Abstract

In this work we experimentally investigate solvent and temperature induced conformational transitions of proteins and examine the role of ion-protein interactions in determining the conformational preferences of avidin, a homotetrameric...

An experimental approach probing the conformational transitions and energy landscape of antibodies: a glimmer of hope for reviving lost therapeutic candidates using ionic liquid

“…2, the differing energies shown in Tables 2 and 3 appear to indicate that there are multiple pathways for conformational transitions of IgG4. 10 Fig. 3A shows the Gibbs free energy change (DG) upon secondary structural changes in the different samples.…”

“…11 In particular, the use of ILs based on the cationic essential nutrient choline, in combination with a range of biocompatible anions, have raised signicant notice for the enhanced stabilisation of different proteins. [10][11][12] Choline is attractive as a cation for biocompatible ILs due to its biological origin, and its structure follows the trends for low cation toxicity, with short alkyl chains and a hydroxyl group. [10][11][12][13] Choline-based ILs can include simple, fatty, amino and aromatic organic acids as well as inorganics, with properties such as viscosity, glass transition temperature and thermal stability shown to be highly anion dependent.…”

“…[10][11][12] Choline is attractive as a cation for biocompatible ILs due to its biological origin, and its structure follows the trends for low cation toxicity, with short alkyl chains and a hydroxyl group. [10][11][12][13] Choline-based ILs can include simple, fatty, amino and aromatic organic acids as well as inorganics, with properties such as viscosity, glass transition temperature and thermal stability shown to be highly anion dependent. 12,13 Additionally, choline-based ILs have been found suitable for protein extraction and purication without degradation or denaturation effects.…”

“…20,21 In particular, protein folding and unfolding can be initiated by altering the pH. 10,[20][21][22] For example, previous work has shown that at low pH monoclonal antibodies can readily aggregate, and hydrophobicity and net charge can account for the distinct aggregation propensity of a given protein at different pH levels. 15,20,22,23 Therefore, the application of ILs as stabilising agents ought to be carried out with due diligence, in particular when using protic ILs such as [Cho][DHP].…”

“…Notably, the possibility of lowering the pH and destabilising the protein can be minimised by using a suitable neutral phosphate buffer. 10 Additionally, excipients such as sugars, amino acids and surfactants are used to stabilise antibodies in solution. [22][23][24][25][26][27] For example, arginine has been found to increase the unfolding transition temperature of immunoglobin G (IgG) in glycine buffer, suppress protein aggregation, and improve refolding of partially folded intermediates.…”