That’s a very hard question (for sure)! I’ve worked with quite a few proteins, well-folded or natively unfolded, pathogenic or functional, all of them are fascinating. At the moment, my favourite protein is still the tau protein — it is heavily involved in Alzheimer’s disease but also may have a biological function in our brain, which scientists are still working on. In the free from, tau doesn’t have a fixed structure in solution. But may interact with other proteins in neurons, may stabilise cytoskeleton (specifically microtubules) in axons of neurons, or it may oligomerise or aggregate in pathological circumstances. These features make tau a very dynamic and attractive molecule, with multiple roles in our body.