The Thermodynamics of the Ternary System: Urea-Sodium Chloride-Water at 25°

Abstract

Isopiestic vapor pressure measurements have been made on this system at 25°; the activity coefficients of urea in sodium chloride solution and of sodium chloride in urea solution have been evaluated and the extent to which solubilities of one solute in a solution of the other can be calculated is discussed.

Global analysis of the thermal and chemical denaturation of the N‐terminal domain of the ribosomal protein L9 in H2O and D2O. Determination of the thermodynamic parameters, ΔH°, ΔS°, and ΔC°p, and evaluation of solvent isotope effects

“…Urea solutions were used within a day of preparation and guanidine hydrochloride solutions within a week. Refractance measurements were used to determine denaturant concentrations (Bower & Robinson, 1963). Guanidine hydrochloride was deuterated before using in D 2 0 solutions.…”

Apparent Molal Volumes and Heat Capacities of Urea and Methyl-Substituted Ureas in H2O and D2O at 25 °C

“…As a result, numerous studies of aqueous solutions of amides, urea, and alkylsubstituted ureas have been undertaken by spectroscopic (2)(3)(4), thermodynamic (5)(6)(7)(8)(9)(10)(11)(12), transport (13)(14)(15)(16)(17)(18), and n.m.r. (19,20) techniques.…”

“…The great solubility (21) of urea in water and the similarity between the enthalpy of solution of urea in water (5-1 1 ) and the enthalpies of fusion of water (22) and urea (23) suggest that urea-water interactions are similar to water-water interactions. From osmotic and activity coefficients (12) and enthalpies of dilution (1 l), excess thermodynamic --'To whom correspondence should be addressed. It is well known and generally observed that the energy of a hydrogen bond is decreased by the deuterium isotope substitution and consequently that hydrogen bonding interactions are strengthened, at least at low temperatures; typical cases where this has been inferred are studies of hydrophobic hydration (26)(27)(28), alcohol-water (29) o r tetrahydrofuran-water mixtures (30), helix -random coil transformation (31,32), and self-association of N-methylacematide in CC1, (33).…”

Detection and characterization of an ovine placental lactogen stable intermediate in the urea‐induced unfolding process

“…Urea solutions were prepared by weight. Urea activity was calculated according to the data of Bower and Robinson (1963). All measurements were performed at room temperature.…”

“…Values for YN and Y, at urea activities in the transition region were obtained by linear extrapolation of the native and unfolded base lines into the transition region (Pace, 1986). The base lines are shown in Figures 1, 2B, and 3B, and the calculated values for Fapp at different urea activities are shown in Figure 4A, B, and C. Experimental data points were fit by assuming that (1) the equilibrium was reached during incubation and (2) AG, = AG,H'O -m.aurea, as discussed by Pace (1986), where AG,, is the Gibbs free energy change associated with the unfolding process at a given urea activity; AG,H" is that change at zero urea; rn is a parameter weighing the urea sensitivity of the unfolding process; and aurea is the urea activity, calculated according to Bower and Robinson (1963). The best fit was achieved with two exponential components, namely, considering the existence of three states of the protein (folded, partially unfolded, and fully unfolded) in equi- (Fig.…”