The second virial coefficient as a predictor of protein aggregation propensity: A self-interaction chromatography study.
Bottom Line: The second osmotic virial coefficients (b2) of four proteins - lysozyme, recombinant human lactoferrin, concanavalin A and catalase were measured by self-interaction chromatography (SIC) in solutions of varying salt type, concentration and pH.Aggregate sizes of <∼10nm, indicative of non-aggregated protein systems, were consistently observed to have b2 values >0.It is concluded that the quantification of protein-protein interactions using SIC based b2 data is a potentially valuable screening tool for predicting protein aggregation propensity.
Affiliation: Surfaces and Particle Engineering Laboratory, Department of Chemical Engineering, Imperial College London, London SW7 2BY, UK.Show MeSH
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Mentions: Solution pH determines the charge distribution in a protein, modifies the magnitude and geometry of ionic interactions, alters the protein hydration state, and has also been shown to induce conformational changes , , . As such changes in pH can have a significant impact on protein–protein interactions. Fig. 5 shows b2 values for catalase, lactoferrin, lysozyme and con A respectively in solutions of NaCl as a function of pH. At low salt concentrations of below 0.30 M NaCl, catalase and con A b2 values (Fig. 5A and D) indicate attractive protein–protein interactions, with the exception of pH 4.0 (and pH 5.0 for con A) under which protein–protein interactions are repulsive and decrease with increasing ionic strength at these pHs. Between pH 6.0 and 9.0 for catalase and pH 7.0 and 9.0 for con A b2 values rise with increasing NaCl concentration before plateauing. Measured b2 values for con A at pH 7.0 and 6.0 then begin to decrease at NaCl concentrations above ∼0.70 M. It is important to note that con A exists in its tetrameric form at pH 7 and above but below pH 6 it exists as a dimer. As such catalase and con A stability would be expected to be highest at high pH and medium ionic concentrations or low pH and low salt concentrations.
Affiliation: Surfaces and Particle Engineering Laboratory, Department of Chemical Engineering, Imperial College London, London SW7 2BY, UK.