Development and applications of a concentrating membrane osmometer for colloid solutions (original) (raw)
Related papers
Understanding Nonidealities of the Osmotic Pressure of Concentrated Bovine Serum Albumin
Journal of Colloid and Interface Science, 1998
Previously Vilker et al. (J. Colloid Interface Sci. 79(2), (1981)) reported the osmotic pressure of concentrated bovine serum albumin (BSA) up to 475 g/L in 0.15 M sodium chloride at pH 4.5, 5.4, and 7.4. The authors used a semiempirical model based on Donnan theory to predict the osmotic pressure with good agreement. However, the formal application of a three-term virial expansion with the coefficients determined from the potential energy of interaction between BSA molecules resulted in poor agreement with their data. In this study, modeling of the osmotic pressure was reexamined using a free-solvent model that considered average solute-solvent and microion-solute interactions in a mole fraction concentration variable. The resulting fits were excellent for all three pH. The model is designed with no fitted parameters; however, the model results were highly sensitive to the selected hydration and microion binding. Therefore the hydration was further regressed from its initial estimate of 1 g H 2 O/g BSA (based on water-17 O magnetic resonance studies of other globular proteins) to minimize the least-squares error between the predicted values and data. The resulting average hydration was determined to be 1.14 ؎ 0.03 g H 2 O/g BSA for all pH values. However, the standard error in hydration for each pH was no greater than ؎0.0063 g H 2 O/g BSA. These results demonstrate that solventsolute interaction and the concentration variable may be critical factors when evaluating osmotic pressure data of concentrated protein solutions.
Cell Biology International, 2006
How much does protein-associated water differ in colligative properties (freezing point, boiling point, vapor pressure and osmotic behavior) from pure bulk water? This question was approached by studying the globular protein bovine serum albumin (BSA), using changes in pH and salt concentration to alter its native structural conformation and state of aggregation. BSA osmotic pressure was investigated experimentally and analyzed using the molecular model of Fullerton et al. [Biochem Cell Biol 1992;70(12):1325]. Analysis yielded both the extent of osmotically unresponsive water (OUW) and the effective molecular weight values of the membrane-impermeable BSA solute. Manipulation of BSA conformation and aggregation by membrane-penetrating cosolutes show that alterations in pH and salt concentration change the amount of bulk water that escapes into BSA from a minimum of 1.4 to a maximum of 11.7 g water per g dry mass BSA.
Biophysical Journal, 1994
The nonideal osmotic pressure of bovine serum albumin (BSA) solutions was studied extensively by Scatchard and colleagues. The extent of pHand salt-dependent nonideality changes are large and unexplained. In 1992, Fullerton et al. derived new empirical expressions to describe solution nonideal colligative properties including osmotic pressure (Fullerton et al. 1992. Biochem. Cell Biol.70:1325-1331). These expressions are based on the concepts of volume occupancy and hydration force. Nonideality is accurately described by a solute/solvent interaction parameter /and an "effective" osmotic molecular weight A. This paper uses the interaction-corrected nonideal expressions for osmotic pressure to calculate the hydration /values and "effective" osmotic molecular weight of BSA, Ae, as a function of pH. Both factors vary in a predictable manner due to denaturing of the BSA molecule. Both contribute to an increase in osmotic pressure for the same protein concentration as the solution pH moves away from the isoelectric point. Increased nonideality is caused by larger hydration resulting from larger solventaccessible surface areas and by the decrease in "effective" osmotic molecular weight, Ae, due to segmental motion of denatured (filamentous) molecules.
The journal of physical chemistry. B, 2018
The free-solvent-based (FSB) model and osmotic pressure were used to probe the ion binding and protein hydration for self-crowded bovine serum albumin in 0.15 M NaF, NaCl, NaI, and NaSCN solutions. All experiments were conducted with solutions at pH 7.4. The regressed results of the FSB model behavior to the measured osmotic pressure were excellent, albeit, the osmotic pressure data for NaSCN were noisy. The resulting ion binding and hydration were realistic values and the covariance of the two parameters was exceptionally low, providing substantial credibility to the FSB model. The results showed that the kosmotropic F and neutral Cl solutions generated significantly higher ion binding and protein hydration than the chaotropic solutions of I and SCN. Further, the ionic strength ratio and resulting hydration implied that the chaotropic solutions had substantially higher aggregation than the other salts investigated. Overall, the FSB model provides an additional, complementary tool t...
The Canadian Journal of Chemical Engineering, 2012
A proper knowledge of the osmotic pressure and thermodynamic behaviour of protein solutions is vital for designing an efficient protein separation process. It is also of great importance to develop a rapid and inexpensive technique to accurately estimate the protein osmotic pressure. A connectionist model to estimate the osmotic pressure of bovine serum albumin (BSA) in terms of pH, ionic strength and BSA concentration is proposed in this paper. Osmotic pressure of BSA is also modelled through the application of a colloidal interaction approach. Molecular interaction forces such as electrostatic, London–van der Waals and hydration along with entropy pressure are considered in the colloidal model to predict the BSA osmotic pressure. The advantages and disadvantages of both modelling approaches are discussed, and a hybrid modelling scheme is proposed for further investigations.
Biophysical Journal, 2008
The experimentally measured concentration dependence of the osmotic pressure of an equimolar mixture of hen egg ovalbumin and bovine serum albumin at pH 7.0 and 25°C in the presence of 0.15 M NaCl is shown to be quantitatively accounted for by a model in which each protein species is represented by an effective hard sphere. The size of this sphere is determined by analysis of the concentration dependence of the osmotic pressure of the isolated protein.
Thermodynamics of protein aqueous solutions: From the structure factor to the osmotic pressure
AIChE Journal, 2015
in Wiley Online Library (wileyonlinelibrary.com) An analytical expression for the structure factor for globular proteins in aqueous solution is presented. This expression was obtained considering a potential given by the sum of a hard core, a van der Waals attractive, and a screened Coulomb contribution. Experimental data of small angle x-ray scattering for bovine serum albumin (BSA) in aqueous solutions containing sodium salts at different protein concentrations and pH values are also presented. The developed expression for the structure factor describes accurately these experimental data provided a dependence of the attractive parameter on protein concentration is established. An expression for the osmotic pressure was derived from the structure factor. With attractive parameters adjusted from x-ray scattering data, the osmotic pressure of BSA aqueous solutions could be predicted with very good agreement with experimental data. V
1999
Osmotic pressures have been measured to determine lysozyme-lysozyme, BSA-BSA, and lysosyme-BSA interactions for protein concentrations to 100 g-L Ϫ1 in an aqueous solution of ammonium sulfate at ambient temperature, as a function of ionic strength and pH. Osmotic second virial coefficients for lysozyme, for BSA, and for a mixture of BSA and lysozyme were calculated from the osmoticpressure data for protein concentrations to 40 g-L Ϫ1. The osmotic second virial coefficient of lysozyme is slightly negative and becomes more negative with rising ionic strength and pH. The osmotic second virial coefficient for BSA is slightly positive, increasing with ionic strength and pH. The osmotic second virial cross coefficient of the mixture lies between the coefficients for lysozyme and BSA, indicating that the attractive forces for a lysozyme-BSA pair are intermediate between those for the lysozyme-lysozyme and BSA-BSA pairs. For protein concentrations less than 100 g-L Ϫ1 , experimental osmotic-pressure data compare favorably with results from an adhesive hard-sphere model, which has previously been shown to fit osmotic compressibilities of lysozyme solutions.