title: Non-monotonic course of protein solubility in aqueous polymer-salt solutions can be modeled using the sol-mxDLVO model.
abstract: Protein purification is often performed using cost-intensive chromatographic steps. To discover economic alternatives (e.g., crystallization), knowledge on protein solubility as a function of temperature, pH, and additives in solution as well as their concentration is required. State-of-the-art models for predicting protein solubility almost exclusively consider aqueous salt systems, whereas "salting-in" and "salting-out" effects induced by the presence of an additional polymer are not considered. Thus, we developed the sol-mxDLVO model. Using this newly developed model, protein solubility in the presence of one salt and one polymer, especially the non-monotonic course of protein solubility, could be predicted. Systems considered included salts (NaCl, Na-p-Ts, (NH(4))(2) SO(4)) and the polymer polyethylene glycol (MW: 2000 g/mol, 12000 g/mol) and proteins lysozyme from chicken egg white (pH 4 to 5.5) and D-xylose ketol-isomerase (pH 7) at 298.15 K. The results show that by using the sol-mxDLVO model, protein solubility in polymer-salt solutions can be modeled in good agreement with the experimental data for both proteins considered. The sol-mxDLVO model can describe the non-monotonic course of protein solubility as a function of polymer concentration and salt concentration, previously not covered by state-of-the-art models.
authors.affiliation: Department of Biochemical and Chemical Engineering, Laboratory of Thermodynamics, Technische Universität Dortmund, Dortmund, NRW, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Herhut
authors.affiliation: Department of Biochemical and Chemical Engineering, Laboratory of Thermodynamics, Technische Universität Dortmund, Dortmund, NRW, Germany. christoph.brandenbusch@bci.tu-dortmund.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Brandenbusch
authors.affiliation: Department of Biochemical and Chemical Engineering, Laboratory of Thermodynamics, Technische Universität Dortmund, Dortmund, NRW, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Sadowski
mesh_terms: D000818:Animals; D002645:Chickens / Q000378:metabolism; D007535:Isomerases / Q000737:chemistry* / Q000302:isolation & purification; D008956:Models, Chemical; D009113:Muramidase / Q000737:chemistry* / Q000302:isolation & purification; D011092:Polyethylene Glycols / Q000737:chemistry*; D054712:Salinity; D012995:Solubility
chemical_list: D011092:Polyethylene Glycols; D009113:Muramidase; D007535:Isomerases
keywords: lysozyme solubility modeling; non-monotonic protein solubility; polyethylene glycol influence; second osmotic virial coefficient