Infinite dilution activity coefficients for benzene and toluene in water and in aqueous solutions of the protein denaturants urea and guanidine hydrochloride

Infinite dilution activity coefficients for toluene in aqueous solutions of the protein stabilizers glycerol, ethylene glycol, glucose, sucrose and trehalose

“…This correction is a minor improvement over the one employed in our previous work, (8) the difference between the two approaches being noticeable only at the highest T and x 3 used in this work. The partial pressure of water was calculated considering the aqueous solutions of the modifiers as ideal solutions, since it was found that this approximation was feasible and fully acceptable.…”

“…The experimental setup and procedure used in this work is the same as that we have used recently (8,10) to measure infinite dilution activity coefficients γ ∞ 1 of benzene and toluene in water and in aqueous solutions of two protein denaturants, urea and guanidine hydrochloride (subsequently referred to as guanidine). Due to the viscosity of the aqueous solutions of the modifiers employed in this work, the constant stripping gas flow rate of the inert gas (N 2 ) introduced into the dilution cell was lowered in comparison to the previous experiments.…”

“…Due to the viscosity of the aqueous solutions of the modifiers employed in this work, the constant stripping gas flow rate of the inert gas (N 2 ) introduced into the dilution cell was lowered in comparison to the previous experiments. (8) Flow rates used in this work were around 0.10 cm 3 · s −1 , which implied small relative rates of the solute elution (ca. 1.5 · 10 −4 s −1 ).…”

“…The infinite dilution limiting activity coefficients γ ∞ 1 presented and discussed here can be used to advance in the understanding of the mechanisms involved in protein stabilization. Also, the behaviour of the protein stabilizers used here can be compared with that shown by two protein denaturants, urea and guanidine hydrochloride, recently reported (8) and rationalized using a simple molecular model. (9) The experimental determination of limiting activity coefficients is very useful since this infinite dilution property possesses the essential information governing the thermodynamic behaviour of the systems studied.…”

“…This is the strategy we have followed in this work using the inert gas stripping (IGS) method which has been proved to be highly reliable for similar systems. (8,10) In this work we present experimental infinite dilution activity coefficients for toluene in aqueous solutions of glycerol, ethylene glycol, glucose, sucrose and trehalose, over the temperature range 273 K to 323 K. The concentrations of these stabilizers were chosen to match as closely as possible those used in the biochemistry field. For glycerol, the data were measured at four concentrations (0.5 mol · dm −3 to 5.0 mol · dm −3 ); at the highest glycerol concentration, γ ∞ 1 was also determined at T = 268 K. Ethylene glycol, glucose and sucrose were used at a single concentration (1.5 mol · dm −3 ).…”