Macromolecular interactions in vitro, comparing classical and novel approaches.

Biophysical quantification of protein interactions is central to unveil the molecular mechanisms of cellular processes. Researchers can choose from a wide panel of biophysical methods that quantify molecular interactions in different ways, including both classical and more novel techniques. We report the outcome of an ARBRE-MOBIEU training school held in June 2019 in Gif-sur-Yvette, France ( https://mosbio.sciencesconf.org/ ). Twenty European students benefited from a week's training with theoretical and practical sessions in six complementary approaches: (1) analytical ultracentrifugation with or without a fluorescence detector system (AUC-FDS), (2) isothermal titration calorimetry (ITC), (3) size exclusion chromatography coupled to multi-angle light scattering (SEC-MALS), (4) bio-layer interferometry (BLI), (5) microscale thermophoresis (MST) and, (6) switchSENSE. They implemented all these methods on two examples of macromolecular interactions with nanomolar affinity: first, a protein-protein interaction between an artificial alphaRep binder, and its target protein, also an alphaRep; second, a protein-DNA interaction between a DNA repair complex, Ku70/Ku80 (hereafter called Ku), and its cognate DNA ligand. We report the approaches used to analyze the two systems under study and thereby showcase application of each of the six techniques. The workshop provided students with improved understanding of the advantages and limitations of different methods, enabling future choices concerning approaches that are most relevant or informative for specific kinds of sample and interaction.