Increased thermal stability of proteins in the presence of sugars and polyols

Abstract

Sugars and polyols stablize proteins against heat denaturation. Scanning calorimetry was used to obtain a quantitative estimate of the degree of stabilization. Solutions of ovalbumin, lysozyme, conalbumin, and alpha-chymotrypsinogen were heated at a constant rate, and the temperature of the maximum rate of denaturation was estimated (Tm). Addition of a sugar or polyol raised Tm. The magnitude of the stabilizing effect (delta Tm) depended on both the nature of the protein and the nature of the sugar or polyol, ranging from 18.5 degrees C for lysozyme at pH 3 in the presence of 50% (w/w) sorbitol to 0 degrees C for conalbumin at pH 7 in 50% glycerol solution. It is argued that this stablization is due to the effects of sugars and polyols on hydrophobic interactions. The strength of the hydrophobic interaction was measured in model systems in sucrose and glycerol solutions. Sucrose and glycerol strengthened the pairwise hydrophobic interaction between hydrophobic groups; however, they reduced the tendency for complete transfer of hydrophobic groups from an aqueous to a nonpolar environment. The extent of stabliziation by different sugars and polyols is explained by their different influences on the structure of water. The difference between the partial molar volume of the sugar or polyol and its van der Waals volume was used as a rough quantitative measure of the structure-making or structure-breaking effect. There was a linear relationship between this quantity and delta Tm.

Why Is Trehalose an Exceptional Protein Stabilizer?

“…A comparatively high value of ⌬T m of 18.2°C (⌬G 0 ϳ 4.5 kcal mol Ϫ1 ) for RNase A at 2 M concentration of trehalose and pH 2.5 is indicative of this (Table I). This increase is much higher compared with any other sugar or polyol studied in the literature (5,19,25). The magnitudes of ⌬T m at other pH values for RNase A as well for several other proteins are also significantly higher.…”

“…Sugars have been known to protect proteins against loss of activity (1, 2), chemical (3,4), and thermal denaturation (5)(6)(7)(8)(9). Among several sugars, ␣,␣-trehalose (␣-D-glucopyranosyl(131)-␣-D-glucopyranoside) has been known to be a superior stabilizer in providing protection to biological materials against dehydration and desiccation (10,11).…”

Ion soft-landing into liquids: Protein identification, separation, and purification with retention of biological activity

“…If some of the protein charge sites are still isolated and the solvent molecules are able to provide counter ions to yield a neutral surface. Beyond these advantages features, glycerol is well known to stabilize folded protein structures [15].…”

“…However, retention of the biological activity of a protein or other biomolecule in the course of this (or any mass spectrometry experiment) is a much more challenging problem. This is the subject addressed in the present paper through the combined choice of gentle ionization methods and an appropriate liquid surface for soft-landing.It is well known that polyols and sugars can efficiently stabilize a protein in an otherwise denaturating environment [15,16], although the underlying mechanism of this process has not been elucidated. Lakshmi and Nandi [17] in 1976 showed that sucrose and glucose decrease the solubility of phenylalanine, tyrosine, and tryptophan in aqueous solution and suggested that this was due to increased hydrophobic interactions.…”

“…It is well known that polyols and sugars can efficiently stabilize a protein in an otherwise denaturating environment [15,16], although the underlying mechanism of this process has not been elucidated. Lakshmi and Nandi [17] in 1976 showed that sucrose and glucose decrease the solubility of phenylalanine, tyrosine, and tryptophan in aqueous solution and suggested that this was due to increased hydrophobic interactions.…”