 So both scop and cath are exceptionally useful, for instance in bioinformatics if you need to compare two structures, if you need to define prediction methods and everything, but we can learn a lot from how proteins have evolved just by looking at many proteins that we know are related but see for instance how they differ between species. There is a reason why we keep coming back to these hemoglobin and myoglobin molecules partly because they were some of the first in nature but they're also so central to binding oxygen that evolution has played a role here too so let's look at that in particular. When it comes to hemoglobin, hemoglobin was different from myoglobin and I'm going to explain why by the end of this lecture. There are four subunits here and they somehow interact with each other to help bind oxygen but exactly how strong it binds oxygen is going to depend a little bit on the sequence. If you now compare a common animal say a horse that is running around roughly at sea level with an animal say as a llama running around at probably 2000 meters altitude on average, it turns out that their hemoglobin has evolved in slightly different ways. I think I should have a saturation curve yes so it turns out that most land animals they have roughly the same binding strength so what this diagram tells you as the partial concentration of oxygen goes up what is the binding strength of oxygen here and this big gray middle band is where we have most animals but the llama has this small band gray band that comes before it what that literally means that the llama will bind oxygen stronger in particular environments where the partial pressure of oxygen is quite low can you relate that to the level the sea level they're living at the llama lives at 2000 meters where the oxygen pressure is lower so for one way or another evolution has adapted the hemoglobin molecule in the llama blood to be better at using oxygen at very low partial pressure it turns out this particular shape of the curves turns out to be exceptionally important but I can't tell you that quite yet we're gonna need to make sure that you what's the entire lecture right hemoglobin is also important in my blood as a human but through your lives you've evolved at least three different types of hemoglobin at some point when you were just a fetus or even an embryo you had a particular type of embryonic hemoglobin as the embryo then develops this first turn into fetal hemoglobin and eventually the fetal hemoglobin a few weeks after birth this gene is shut off and the normal so-called adult hemoglobin takes over over fetal hemoglobin we know quite a lot about this because it's such an important process is one of the most important proteins and yet there was only mere months ago there was a new paper published showing exactly how the gene control works here and when this fetal hemoglobin gene is switched off how it is switched off by compounds binding their so-called transcription factors and that in turn enables the takeover of the adult hemoglobin here too you have properties that the embryonic and fetal hemoglobin they are they bind oxygen much harder what's the reason for that well first they don't really breathe air themselves right they need to be able to get there from the blood of the mother through the placenta but that air those oxygen molecules are already bound to the mother's hemoglobin so one way or another the fetal hemoglobin needs to bind the oxygen so strongly that it will be able to steal the oxygen from the mother's hemoglobin otherwise you would have kind of an equilibrium 50-50 and the embryo would likely die of course the second we're born we no longer need that and then nature controls the scent shuts off the gene sometimes it's actually not perfect most of us we might express one percent or so of fetal hemoglobin but it's 99 percent adult these are just two examples I think I'm going to share the paper about you showing you how the gene is shut off in canvas because it's a pretty cool invention they use CRISPR-Cas9 and a few other tricks to be able to determine it