 The first database I'm going to show you is called CAT, C-A-T-H. I'll draw it this way. This is a mostly automatic one, which is a huge advantage today when there are so many structures appearing all the time. And in CAT, we've organized things into, first into classes, which is basically alpha or beta, or the mixed alpha beta ones. We have architectures, which is roughly what I showed you. So large overall arrangements, say in beta sheets. We then have what CAT calls topology, which is more specific than architecture. Now we start taking more specific rearrangements of the secondary structure elements and loops into accounts. Eventually we get down to the concept called homology. I'll come back to that when I give you the lecture on bioinformatics. But homology literally means that two sequences are evolutionary related. So in this case, we know that there must have been a common ancestor. By far the easiest way for you to show what we can use CAT for is to move over to the web browser. Let's do that. So there's tons of information available in the CAT database. I'm not going to go through all of it, but you can find the 3D structures, evolutionary trees and information about function. But what I love to do here is, say, browse. In theory, I could search for a particular protein to see what class architecture it belongs to. But this sunburst plot, it takes a second to load, is the one I showed you. And here I can look at the classes that are only three or four of them. The architectures, for instance the mainly beta sheet ones here. Within that I had the sandwiches. I think I should have immunoglobulins. Yes, this is an immunoglobulin-like fold. And I bet the largest one is just immunoglobulins. So let's see if I can click on those. Again, it takes a second to load. But then I should get a ton of information about that specific homologous superfamily, the sequences that are in it, potential evolutionary trees. Yeah, the sequence diversity. Here too it will take a second for all this data to load. But if you want to just look at the structural universe and what's present here, this is a goldmine of information. And since this is classified automatically, everything will be here pretty much within days of the structure disappearing. That was cat.