 The other statistics we can do with the protein data bank is really double-check my initial statement when I said that most residues in a protein are hydrophobic. That turns out to be true. So if I just plot this on sort of hydrophobicity, all the average hydrophobicity goes from modest to rear average in the head group region. In the center of the membrane I'm up here. Virtually everything is hydrophobic and then it becomes average or even hydrophilic again. But the interesting pattern is the lower part here. Do you see that there is no difference whatsoever between buried and exposed residues? They are all hydrophobic everywhere. Initially I think we went a bit wrong there as a community because some of the first structures we determined were for instance channels or things with a hole. And these holes frequently contain water. So those are the exceptions where it makes sense to have a few amino acids that are might be polar or even charged. But in the grand scheme of things when calculating average over tens of thousands of residues, they disappear. So membrane proteins are hydrophobic everywhere, which is a royal pain when it comes to predicting them.