Cell membranes are made of fatty lipids that block water from passing through directly, so cells need dedicated channel proteins. Peter Agre at Johns Hopkins discovered aquaporins, the protein channels that let water cross membranes. Roderick MacKinnon at Rockefeller University worked out the molecular structure of the potassium channel, explaining how it lets through the larger potassium ion while excluding the smaller sodium ion. Both discoveries shared the 2003 Nobel Prize in Chemistry.
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1:26:55does water get in and out? >> Exactly. >> Water can't float through that lipid membrane. It's like a bunch of fat, right? And fat obviously does not let water go through. >> Um furthermore, in neurons you've got potassium and calcium channels and sodium channels. Now potassium and sodium are different sizes. The ion channels that let through let's say potassium they should also let through sodium because sodium is smaller. >> Yes. >> How come they don't? >> Exactly. >> These guys are the ones who figured that out. So um Peter Agray at John's Hopkins he figured out what aquaporins look like. Aquaporins as in the holes in our membranes that let us transport water through. and Rodrik McKinnon at
1:27:36Rockefeller University, he unmasked the molecular architecture governing um this potassium channel. That's the image that you see over there. And that protein is just ingenious because it only lets through potassium, which is a larger ball, >> but it rejects sodium, which is smaller, because of some really weird physics that happens in the middle. Again, another thing for a great episode. They won the 2003 Nobel Prize in Chemistry. We'll do that one in the future for sure. Our membranes are not a fan of open borders and have strict border control. 1993 pioneering of directed evolution. >> Yes, we recently just talked about directed evolution in one of our episodes. I can't remember which one, but um this was Francis Arnold. She
1:28:19pioneered directed evolution at Caltech.