Abstract
Urea denatures proteins at different concentrations, depending on the experimental conditions and the protein. We in-vestigated the pressure-induced denaturation of bovine serum albumin (BSA) in the presence of subdenaturing concen-trations of urea based on a two-state equilibrium. Pressure-induced denaturation was enhanced at urea concentrations ([U]) of 3.5 M to 8.0 M, with the free energy of denaturation at atmospheric pressure ranging from +5.0 to –2.5 kJ/mol of BSA. The m values appeared to be biphasic, with m1 and m2 of 0.92 and 2.35 kJ mol–1?M–1, respectively. Plots of versus ln[U] yielded values of u, the apparent stoichiometric coefficient, of 1.68 and 6.67 mol of urea/mol of BSA for m1 and m2, respectively. These values were compared with the m and u values of other monomeric proteins reported in or calculated from the literature. The very low values of u systematically observed for proteins were suggestive of heterogeneity in the free energy of denaturation. Thus, a u value of 140 mol of urea/mol of BSA may indicate the existence of a heterogeneous molecular population with respect to the free energy of dena-turation.
Highlights
Knowledge of protein denaturation is fundamental for understanding numerous biological processes
We investigated the changes in the fluorescence of bovine serum albumin (BSA) at different concentrations of urea and pressure (Figure 1) and attempted to correlate them with structural alterations
Compared to the fluorescence emission spectrum obtained in the absence of urea, a high urea concentration produced a significant red shift that intensified as the hydrostatic pressure increased
Summary
Knowledge of protein denaturation is fundamental for understanding numerous biological processes. This phenomenon has been studied by using denaturing agents such as urea and guanidine hydrochloride [1]. Denaturation can be induced by an increase in temperature, which leads to the weakening of interactions in the proteins and consequent exposure of previously hidden hydrophobic groups. The use of pressure favors processes that involve a negative change in volume, such as the transfer of solvent to the hydrophobic core of proteins that disturbs hydrophobic interactions between nonpolar side chains, resulting in denaturation. High hydrostatic pressure increases the susceptibility to urea induced denaturation and allows the determination of thermodynamic parameters such as the change in volume associated with denaturation and the free energy of denaturation [3,4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
