 So just looking at protein structures it turns out that on the one end it's just big blobs of atoms but on the other hand we can try to organize this on different levels. At the very basic level we have the sequence of amino acids that are determined by DNA. We occasionally call that the primary C structure, it's just a sequence but to keep the nomenclature of structure. That sequence is something that we can determine billions per day of, we do that here at Science for Life Laboratory, it's modern sequencing and because we can get this directly from DNA in principle that tells us everything. But to avoid having to take the jumping all the way to the big blobs of atom right away it turns out just looking at protein structures as people started doing in the 50s and 60s we have these very regular elements that are formed directly from the sequence and there are pretty much just two or maybe three of them depending on how we count. If that was primary it kind of makes sense to call this secondary and that's why we call them secondary structure that's mostly we're going to be looking at today. Those secondary structure elements in turn it appears looking at proteins they are organized into fairly regular forms and there might be a few thousand of them or so. We will be looking at some of those later this week and we tend to call that tertiary structure. The definition of tertiary structure is that it's one chain of amino acids that has formed secondary structures that then folds up the secondary structure in a particular pattern and if you now take many chains like this and form one of those complexes hemoglobin as an example of a structure with four chains we get to what we occasionally call quaternary structure and I won't be talking that much about it in this class. So the hierarchical organization of structures helps us to make sense of proteins although formally it's just a bunch of atoms that have interactions some of them are bonds but this will help me to make sense of the structures and hopefully you too.