Either one of these non polar amino acids on this beta subunit will interact with this valine and that will form the aggregate. And this will continue its aggregation process and eventually form that long fiber that has a sickle shape and that will distort the biconcape shape and form that sickle shape for those red blood cells. Now, the reason we require a deoxy hemoglobin is because when the hemoglobin molecule is oxygenated, these two amino acids, valine and phenylalamine, disappear into inside that structure of the beta submune. And so in that case, when we're dealing with the oxygenated form of hemoglobin, these two amino acids are found inside. And so since they cannot interact with the valley, they will not aggregate. And so that's why the aggregation only takes place in the deoxygenated state of hemoglobin.