* Potassium Channels and the Atomic Basis of Selective Ion Conduction
Roderick MacKinnon won the Nobel Prize in Chemistry in 2003 for his work on the "structural and mechanistic studies of ion channels". (He shares the prize with Peter Agre, who was also awarded for his work in the discovery of water channels.)
MacKinnon's Nobel lecture was required listening for one of my neuroscience classes, but I thought it was interesting and accessible enough that many people might enjoy it. A text version of the talk is also available in the form of a formal paper (not a transcript). It's a little less accessible.
In case you're wondering about the title, it was inspired by Italian philosopher and mathematician Guilio Giorello's "Si, abbiamo un anima. Ma e fatta di tanti piccoli robot." / "Yes, we have a soul, but it's made of lots of tiny robots!".
Lectures from other Nobel recipients are also available on the site.