A 25-year-old African American man with a known history of sickle cell disease (SCD) presents to the emergency department with severe pain in his chest and lower limbs. The pain began shortly after he completed a long-haul flight. He describes the pain as sharp and throbbing, and it is not relieved by over-the-counter pain medications. He also reports feeling fatigued and short of breath. On physical examination, he appears pale and in distress. His vital signs show tachycardia and mild hypoxia. Laboratory tests reveal low hemoglobin (Hb) levels and the presence of sickled red blood cells on a peripheral blood smear. Based on his history, symptoms, and lab findings, he is diagnosed with a vaso-occlusive crisis (VOC), a common complication of sickle cell disease. Which of the following best describes the role of hemoglobin’s quaternary structure in this patient’s condition?
