Magnetic susceptibility measurements of deoxygenated hemoglobins and isolated chains

Static magnetic susceptibility measurements have been performed in a wide temperature range (4.5-300 degrees K) on ligquid/frozen solutions of deoxygenated human hemoglobin and its isolated chains. The effects of buffer, pH, dielectric constant and phosphate have been investigated. Measurements have been done also on human fetal chains, on des-Arg and SucNEt-des-Arg hemoglobins. In all the proteins under study of the Fe2+ is the high spin state (S=2). At room temperature the magnetic moments lie in range 4.90 (theoretical spin-only value) to 5.45 Bohr magnetons. Local differences between the iron sites are revealed by the low temperature measurements. A mechanism is proposed to explain the effect of phosphate binding on the magnetic susceptibility.