Cooperative α-helix formation of β-lactoglobulin induced by sodium n-alkyl sulfates

Comparison of the conformational stability of the non-native α-helical intermediate of thiol-modified β-lactoglobulin upon interaction with sodium n-alkyl sulfates at two different pH

“…However, under the same condition, the addition of SOS, SDeS and STS at different concentrations dequenched the fluorescence spectra at pH 7.5 and 2.0. Here, the interaction of TNB-β-LG-ANS complex with SDS at different concentrations is consistent with the results obtained for β-LG in the presence of SDS as previously reported by Chamani et al [44]. The corresponding experiments were also carried out for SOS, SDeS and STS (curves not shown).…”

“…The unfolding curves were analyzed assuming a two-state transition mechanism between the folded and unfolded states [60]. Because slight accumulation of the equilibrium intermediate has been demonstrated for the unfolding of β-LG by n-alkyl sulfates [44], the two-state transition should be considered an approximation for quantitatively comparing the unfolding curves. It is now possible to obtain equilibrium constants (K) for the N-αI states and to calculate the corresponding Gibbs free energy changes, G 0 , as follows:…”

“…Three pieces of evidence indicate that the amino acid sequence of β-LG has a markedly high preference for an α-helix conformation [40][41][42][43]. Chamani et al reported that n-alkyl sulfates induce cooperative transition from the native β-sheet to a highly α-helical structure [44].…”

Mechanism for stabilization of the molten globule state of papain by sodium n-alkyl sulfates: Spectroscopic and calorimetric approaches

“…GuHCl-induced stabilization of protein is also seen with disulfide isomerase [14], suggesting that chaotropic agents at lower concentrations can stabilize the partially folded intermediates though they behave as potent denaturants at higher concentrations. Further, it has been shown that n-alkyl sulfates also stabilize intermediate states in the folding/unfolding pathway of cytochrome c [15][16][17][18]. However, the mechanism of this type of stabilization in the presence of n-alkyl sulfates is not clear.…”

Unravelling the mechanisms of a protein refolding process based on the association of detergents and co-solvents

“…In the native state, ellipticities at 208 nm and 222 nm are indicatives of α ‐helical structure. With the detergent alone (60 mM), a more intense signal at 208 nm is observed for TrpCage, which might be because of an increase in α ‐helical structure content, as often observed with peptides and proteins in the presence of high concentrations of SDS .…”