So once our two three BPG molecule enters the red blood cells, what exactly takes place? Well, basically, some of these hemoglobin molecules inside our red blood cells, some of these hemoglobin proteins will not contain any oxygen and these are called deoxy hemoglobin proteins. And the two three BPG molecules, these molecules will be able to bind to a cavity to a space found between the beta one and the beta two subunits of deoxyhemoglobin. So deoxy hemoglobin has a cavity between the two beta subunits to which the two three BPG can comfortably bond to via electrostatic forces. So between the beta two and the beta one, we have residues. We have amino acids that contain side chains that have positive charge.