Correlation of second virial coefficient with solubility for proteins in salt solutions

Abstract

In this work, osmotic second virial coefficients (B(22)) were determined and correlated with the measured solubilities for the proteins, α-amylase, ovalbumin, and lysozyme. The B(22) values and solubilities were determined in similar solution conditions using two salts, sodium chloride and ammonium sulfate in an acidic pH range. An overall decrease in the solubility of the proteins (salting out) was observed at high concentrations of ammonium sulfate and sodium chloride solutions. However, for α-amylase, salting-in behavior was also observed in low concentration sodium chloride solutions. In ammonium sulfate solutions, the B(22) are small and close to zero below 2.4 M. As the ammonium sulfate concentrations were further increased, B(22) values decreased for all systems studied. The effect of sodium chloride on B(22) varies with concentration, solution pH, and the type of protein studied. Theoretical models show a reasonable fit to the experimental derived data of B(22) and solubility. B(22) is also directly proportional to the logarithm of the solubility values for individual proteins in salt solutions, so the log-linear empirical models developed in this work can also be used to rapidly predict solubility and B(22) values for given protein-salt systems.

Interactions in protein mixtures. Part I: Second virial coefficients from osmometry

“…For the understanding of these phenomena it is important to know their mutual interactions, which are typically expressed in terms of the second virial coefficient (Tolstoguzov, 2003). The second virial coefficient B 0 has been directly linked to the crystallization behavior of single and purified protein solutions, which was found to solely occur within a narrow range called 'crystallization slot' (Ahamed, Ottens, van Dedem, & van der Wielen, 2005;Bonnet e, Finet, & Tardieu, 1999;Ducruix, Guilloteau, Ri es-Kautta, & Tardieu, 1996;Guo et al, 1999;Mehta, White, & Litster, 2012;Wanka & Peukert, 2011;Wilson, 2003). Here most experimental data are available for BSA and lysozyme at conditions typically needed to crystallize them (Bonnet e et al, 1999;Guo et al, 1999;Kulkarni, Chatterjee, Schweizer, & Zukoski, 2000;Le Brun, Friess, Schultz-Fademrecht, Muehlau, & Garidel, 2009;Lu, Chen, Wang, & Yan, 2009;Mehta et al, 2012;Moon, Curtis, Anderson, Blanch & Prausnitz, 2000;Park & Choi, 2009;Vilker, Colton, & Smith, 1981;Wanka & Peukert, 2011).…”

On the relationship between the solubility of proteins and the osmotic second virial coefficient

“…In addition to these theoretical models, some empirical equations have been recently proposed in literature (Mehta et al, 2012).…”

“…Table 1 shows the comparison between those models concerning the value of RMSD. Model RSMD Proposed model -Equation (26) 39.0% Model of Haas et al (1999) 41.2% Model of Ruppert et al (2001) 28.2% Empirical equation proposed by Mehta et al (2012) While Figure 3 shows that all tested models can qualitatively represent the second virial coefficient, Table 1 shows that this agreement cannot be considered to be quantitative. A possible reason for this behavior is the scatter of the experimental data: a single curve with a single set of parameters would not be able to correlate all of the data quantitatively.…”

“…Using this value of K s , it is possible to apply Equation (26) in a predictive way. Figure 5 shows the results for the prediction of osmotic second virial coefficient data by Mehta et al (2012); in this case, the reference value of B * was set to -12.7·10 -4 cm . Although the value of K s was adjusted from experimental data at a slightly different pH value, the concordance between the model and the experimental data is excellent (R 2 = 1.0).…”

Interactions in protein mixtures. Part II: A virial approach to predict phase behavior

“…Second virial coefficients for proteins have been mainly obtained in connection with the crystallization behavior of lysozyme and bovine serum albumin (Bonnet e, Finet, & Tardieu, 1999;Guo et al, 1999;Kulkarni, Chatterjee, Schweizer, & Zukoski, 2000;Le Brun, Friess, Schultz-Fademrecht, Muehlau, & Garidel, 2009;Lu, Chen, Wang, & Yan, 2009;Mehta, White, & Litster, 2012;Moon, Curtis, Anderson, Blanch, & Prausnitz, 2000;Park & Choi, 2009;Vilker, Colton, & Smith, 1981;Wanka & Peukert, 2011). Other proteins are only studied sporadically and within a limited range of solvent conditions (Edmond & Ogston, 1968;Hasse, Kany, Tintinger, & Maurer, 1995;Kang & Sandler, 1987;Schaink & Smit, 2000, 2007.…”