 Instead of looking at a single lipid, we can do the same studies for the entire membrane. The most obvious way to do that is with neutroscattering, and the reason for that is that the membrane itself is fluid, right? That I can't determine a crystal of it. If you do this with neutroscattering, you can use deuterium exchange to find out what are the different parts in a membrane and roughly where are they located in a cross-section. So if we do that, you would see that in the entire middle part of the membrane, maybe up to 30 angstrom or so, it's purely hydrophobic. There is not a single part in here that can form a hydrogen bond. Then we start having this carbonyl group. So the carbonyl groups are those oxygens connecting the central part to the chains. They're not particularly strongly charged. They certainly don't have a plus or minus charge, but they have a bit of partial charge. So suddenly we start to be able to form maybe a few hydrogen bonds or so. And then you have what it says in red and green here, so if you're color blind, I didn't choose the colors. The phosphate and culling groups, they are the actual negatively charged part, phosphate, and positively charged culling in this particular lipid. The zwitterionic component where charged things will love to interact, and eventually you get the water. But here too you see there is no water whatsoever in the core of the membrane. You might think that this is a plot that belonged better in the lipid properties lecture. You're probably partly true, but you need to keep this in mind when you ask yourself what amino acids will be stable where, what will they do to the protein, and what will that do to the membrane environment. So I guess it's time to start looking at that. This thickness we can determine quite accurately now, either with neutral scattering or you can frequently actually see membranes in electron microscopes. So this is a much higher magnification picture than the other one. In the previous part we saw kind of two layers with a, well, two completely separate membranes separate by a few nanometers. This is part of the horny layer of skin. So the small lines here, the stacks we see are actually multiple lamellar layers of lipid membranes that are starting to form skin. That's the chapter itself that I'd be happy to tell you about at some point. Most relevant for lipid protein interaction.