title: Non-invasive high throughput approach for protein hydrophobicity determination based on surface tension.
abstract: The surface hydrophobicity of a protein is an important factor for its interactions in solution and thus the outcome of its production process. Yet most of the methods are not able to evaluate the influence of these hydrophobic interactions under natural conditions. In the present work we have established a high resolution stalagmometric method for surface tension determination on a liquid handling station, which can cope with accuracy as well as high throughput requirements. Surface tensions could be derived with a low sample consumption (800 μL) and a high reproducibility (<0.1‰ for water) within a reasonable time (3.5 min per sample). This method was used as a non-invasive HTP compatible approach to determine surface tensions of protein solutions dependent on protein content. The protein influence on the solutions' surface tension was correlated to the hydrophobicity of lysozyme, human lysozyme, BSA, and α-lactalbumin. Differences in proteins' hydrophobic character depending on pH and species could be resolved. Within this work we have developed a pH dependent hydrophobicity ranking, which was found to be in good agreement with literature. For the studied pH range of 3-9 lysozyme from chicken egg white was identified to be the most hydrophilic. α-lactalbumin at pH 3 exhibited the most pronounced hydrophobic character. The stalagmometric method occurred to outclass the widely used spectrophotometric method with bromophenol blue sodium salt as it gave reasonable results without restrictions on pH and protein species.
authors.affiliation: Institute of Engineering in Life Sciences, Section IV: Biomolecular Separation Science, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Amrhein
authors.affiliation: Institute of Engineering in Life Sciences, Section IV: Biomolecular Separation Science, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany.
authors.forename: Katharina Christin
authors.initials: KC
authors.lastname: Bauer
authors.affiliation: Institute of Engineering in Life Sciences, Section IV: Biomolecular Separation Science, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany.
authors.forename: Lara
authors.initials: L
authors.lastname: Galm
authors.affiliation: Institute of Engineering in Life Sciences, Section IV: Biomolecular Separation Science, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany. juergen.hubbuch@kit.edu.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hubbuch
mesh_terms: D000818:Animals; D002645:Chickens; D057166:High-Throughput Screening Assays / Q000379:methods*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D011506:Proteins / Q000737:chemistry*; D015203:Reproducibility of Results; D013500:Surface Tension; D013995:Time
chemical_list: D011506:Proteins
keywords: bromophenol blue; hydrophilicity; protein solution; protein-solvent interaction; stalagmometer