And what this does is it lifts that constraint, it relaxes that tertiary, it relaxes that quarterly structure of that hemoglobin molecule. And that's precisely why when all the four heme groups become occupied with oxygen because of the relaxed state of that coronary structure of the hemoglobin, we call this state the r state, where r stands for relaxed. So we see that on the other hand, even though deoxy hemoglobin is quite constrained and exists in the t state, oxymoglobin contains a much more relaxed conformation due to the interactions between the surfaces of the polypeptide chains. And this is called the r state or the relaxed state. Now, earlier I said that instead of looking at this hemoglobin molecule as consisting of four polypeptide chains, typically we examine the hemoglobin molecule as if it consists of two dimers the alpha one, beta one, and the alpha two beta two. Why is that?