title: Protein-binding assays in biological liquids using microscale thermophoresis.
abstract: Protein interactions inside the human body are expected to differ from the situation in vitro. This is crucial when investigating protein functions or developing new drugs. In this study, we present a sample-efficient, free-solution method, termed microscale thermophoresis, that is capable of analysing interactions of proteins or small molecules in biological liquids such as blood serum or cell lysate. The technique is based on the thermophoresis of molecules, which provides information about molecule size, charge and hydration shell. We validated the method using immunologically relevant systems including human interferon gamma and the interaction of calmodulin with calcium. The affinity of the small-molecule inhibitor quercetin to its kinase PKA was determined in buffer and human serum, revealing a 400-fold reduced affinity in serum. This information about the influence of the biological matrix may allow to make more reliable conclusions on protein functionality, and may facilitate more efficient drug development.
authors.affiliation: Department of Physics and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Amalienstrasse 54, Munich 80799, Germany.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Wienken
authors.forename: Philipp
authors.initials: P
authors.lastname: Baaske
authors.forename: Ulrich
authors.initials: U
authors.lastname: Rothbauer
authors.forename: Dieter
authors.initials: D
authors.lastname: Braun
authors.forename: Stefan
authors.initials: S
authors.lastname: Duhr
mesh_terms: D001681:Biological Assay / Q000379:methods*; D002147:Calmodulin / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D011506:Proteins; D007371:Interferon-gamma