title: Binding of Protoporphyrin to hemoglobin in red blood cells of patients with erythropoietic protoporphyria.
abstract: Virtually all protoporphyrin in erythrocytes of patients with erythropoietic protoporphyria is bound to hemoglobin. The maximum of the fluorescence excitation spectrum of this protoporphyrin-hemoglobin complex shifted, with increasing concentration, from 405 nm to 389 nm. A similar shift was observed when titrating a solution of free protoporphyrin with hemoglobin. The Soret maximum of free protoporphyrin itself, on the other hand, was not concentration-dependent. These observations indicate that spectrofluorometric measurements do not allow conclusions concerning the mode of protoporphyrin binding to hemoglobin. Experiments on protoporphyrin exchange between the hemoglobins A, F and S reinforced the previously drawn conclusion that protoporphyrin is bound to hemoglobin at the heme-binding sites.
mesh_terms: D001665:Binding Sites; D004592:Electrophoresis, Starch Gel; D004912:Erythrocytes / Q000378:metabolism*; D004920:Erythropoiesis; D005319:Fetal Hemoglobin / Q000378:metabolism; D006441:Hemoglobin A / Q000378:metabolism; D006451:Hemoglobin, Sickle / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D011164:Porphyrias / Q000097:blood*; D011166:Porphyrins / Q000378:metabolism*; D011524:Protoporphyrins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D006451:Hemoglobin, Sickle; D006454:Hemoglobins; D011166:Porphyrins; D011524:Protoporphyrins; D006441:Hemoglobin A; D005319:Fetal Hemoglobin