A Novel, High Throughput Assay for Characterizing Protein-Protein Interactions

It has long been recognized that specific protein-protein interactions can be harnessed to design targeted delivery for diagnostic imaging and treatment using synthetic nano-carriers. However, non-specific protein-protein interactions were found to interfere with such processes, for example by competing with the desired targets. These weak interactions are much harder to measure and characterize. Here we demonstrate a simple, high throughput, method of probing these complex interactions using single particle tracking. In our setup, the diffusion of nanoparticles coated with intrinsically disordered neurofilament proteins [1], near a surface coated with similar proteins, were recorded and analyzed using conventional dark-field microscopy. From the distribution of the diffusion constants, we observed that salt concentration is a very effective parameter in tuning the strength of these weak interactions. By truncating critical five amino-acids in the C-terminal domain [2], we arrested the short-range attraction, which led to a strikingly visible difference in the diffusion constants.
[1] Pregent et al., Nano Lett. 15, 3080 (2015), [2] Kornreich et al., PRL 117, 148101 (2016)