So what's so special about the proline? Well, if we examine our side chain, this is the only side chain that connects not only to the alpha carbon, but also to that nitrogen. And we form this five membered ring. Now, because of this five member ring, this molecule is structurally restrictive. And that means this actually helps play a very, very important role in determining the structures of special types of proteins, as we'll see in future lectures. So all the proline is hydrophobic, and technically, it should belong to the hydrophobic side chain group.