This reaction scheme taken from a step in diterpene biosynthesis shows no fewer than three cyclizations occuring in a single enzyme active site, with a net gain of two new rings. (Animations here are best viewed with Safari, not so much with Firefox) This is a project that just came to me last week, and I was excited to get to it, though it's still a work-in-progress. I don't like having five bonds to carbon, even for less than a second, and the geometry of the final product looks a little uncomfortable, but I was eager to post this. There is something so inexplicably satisfying to me about making animations. I completely understand how, before we used computers to do this, animators could bring themselves to painstakingly draw the same illustration over and over and over again with only the slightest modification from one to the next. Because Flash does the heavy lifting for me, I can only imagine the feeling they had when they finally put them all together and flipped through the pages.