Now, when we increase the concentration of oxygen, for example, when the deoxy hemoglobin in the t state with a two, three BPG returns from those tissues back to the lungs, the concentration of oxygen increases. And as the concentration of oxygen increases, the oxygen begins to slowly bind onto the heme groups of these different polypeptides in the hemoglobin molecule. And as oxygen begins to bind to the heme groups, that basically creates a conformational change. So these two dimers basically begin to rotate 50 degree, 15 degrees with respect to one another. And that conformational change basically collapses this inner pocket, and it squeezes the two three BPG molecule right out of the center of the hemoglobin. And once the two three BPG is squeezed out of that pocket, that shifts our equilibrium back to the right side, the r state.