 So, even though the lock-in key model is not particularly accurate by modern standards, I like it conceptually because it really tells us what things are doing. It might sound strange that why would all these receptors go around and having a bunch of binding sites that just happen to fit our small drag perfectly? Well, they don't. But in general, for a protein to work, it's going to need to have some more cavities binding site. Again, if a protein was just a sphere, that protein would all be able to do anything. Think of hemoglobin, binding oxygen, or all the other proteins I've showed you. The fatty acid binding protein or so. For all of them, when they're doing something, there is some sort of active site, the pocket where they actually do their main process. And that is the lock of the building. They need a lock. If there is no lock anywhere and all the doors are closed, you can't get into the building, right? Our idea is that we target those sites where we know that it has its normal biological function and thereby try to change the biological function. I could amplify it, try to make it stronger. Or I could try to shut it off by putting, well, gum in the lock, basically, put my blue molecule here so that it doesn't activate the normal process. There are a bunch of examples of this, and normally they're deeper or shallower pockets on the surface. They're frequently a bit hydrophobic. And our idea is pretty much to solve the puzzle so that I can decide what this blue, yellow, or in this case, purple molecule is and how it should bind there to change the properties of this binding site and elicit a biological response. What we see here, I think this is a GPCR. This is a nuclear receptor, if I recall correctly. We're going to have this type of behavior for the ligand of all this gated iron channels, almost any protein you can imagine will have binding sites to perform its action. And we're going to see if we can target those.