Pauling and Coryell investigated the magnetic properties and structure of hemoglobin, oxyhemoglobin, and carbonmonoxyhemoglobin. They found that oxyhemoglobin and carbonmonoxyhemoglobin contain no unpaired electrons, while ferrohemoglobin (hemoglobin itself) contains four unpaired electrons per heme. This was interpreted as indicating that the iron atoms in oxyhemoglobin and carbonmonoxyhemoglobin form covalent bonds with the porphyrin nitrogen atoms and the globin molecule, whereas in ferrohemoglobin, the bonds are ionic. The magnetic susceptibility of ferrohemoglobin corresponds to an effective magnetic moment of 5.46 Bohr magnetons per heme, indicating the presence of four unpaired electrons per heme. The magnetic data suggest that the heme-heme interaction stabilizes the parallel configuration of the four hemes. The oxygen molecule, which normally has two unpaired electrons, undergoes a profound change in electronic structure when bound to hemoglobin, resulting in no unpaired electrons in oxyhemoglobin and carbonmonoxyhemoglobin. The structural differences between hemoglobin and its derivatives are closely related to their characteristic properties, such as their affinity for oxygen and carbon monoxide. The magnetic measurements confirm that carbonmonoxyhemoglobin and oxyhemoglobin contain no unpaired electrons, while ferrohemoglobin contains four unpaired electrons per heme. The results support the idea that the bonds in oxyhemoglobin and carbonmonoxyhemoglobin are covalent, while the bonds in ferrohemoglobin are ionic. The study also highlights the importance of magnetic measurements in understanding the structure and function of hemoglobin and its derivatives.Pauling and Coryell investigated the magnetic properties and structure of hemoglobin, oxyhemoglobin, and carbonmonoxyhemoglobin. They found that oxyhemoglobin and carbonmonoxyhemoglobin contain no unpaired electrons, while ferrohemoglobin (hemoglobin itself) contains four unpaired electrons per heme. This was interpreted as indicating that the iron atoms in oxyhemoglobin and carbonmonoxyhemoglobin form covalent bonds with the porphyrin nitrogen atoms and the globin molecule, whereas in ferrohemoglobin, the bonds are ionic. The magnetic susceptibility of ferrohemoglobin corresponds to an effective magnetic moment of 5.46 Bohr magnetons per heme, indicating the presence of four unpaired electrons per heme. The magnetic data suggest that the heme-heme interaction stabilizes the parallel configuration of the four hemes. The oxygen molecule, which normally has two unpaired electrons, undergoes a profound change in electronic structure when bound to hemoglobin, resulting in no unpaired electrons in oxyhemoglobin and carbonmonoxyhemoglobin. The structural differences between hemoglobin and its derivatives are closely related to their characteristic properties, such as their affinity for oxygen and carbon monoxide. The magnetic measurements confirm that carbonmonoxyhemoglobin and oxyhemoglobin contain no unpaired electrons, while ferrohemoglobin contains four unpaired electrons per heme. The results support the idea that the bonds in oxyhemoglobin and carbonmonoxyhemoglobin are covalent, while the bonds in ferrohemoglobin are ionic. The study also highlights the importance of magnetic measurements in understanding the structure and function of hemoglobin and its derivatives.