Discovery of the magnetic behavior of hemoglobin: A beginning of bioinorganic chemistry

Abstract

Two articles published by Pauling and Coryell in PNAS nearly 80 years ago described in detail the magnetic properties of oxy-and deoxyhemoglobin, as well as those of closely related compounds containing hemes. Their measurements revealed a large difference in magnetism between oxygenated and deoxygenated forms of the protein and, along with consideration of the observed diamagnetism of the carbonmonoxy derivative, led to an electronic structural formulation of oxyhemoglobin. The key role of hemoglobin as the main oxygen carrier in mammalian blood had been established earlier, and its allosteric behavior had been described in the 1920s. The Pauling-Coryell articles on hemoglobin represent truly seminal contributions to the field of bioinorganic chemistry because they are the first to make connections between active site electronic structure and the function of a metalloprotein.heme | bioinorganic | magnetism | oxygen transport | metalloproteins

Effective intermediate-spin iron in O 2 -transporting heme proteins

“…Renewed interest in the topic stems from ongoing discovery of globins in plants and microorganisms, which further extends the spectrum of biological functions (6)(7)(8). A controversy remains on the nature of the iron-oxygen bonding in HB/MB, dating back to pioneering work of Pauling, Monod, and Perutz starting in the 1930s (3,9).…”

“…Paramagnetic behavior has established high-spin (HS) iron in deoxy [d 6 Fe(II); spin (S) multiplicity, M = 2S + 1 = 5] and met [d 5 Fe(III); M = 6], but carboxy is diamagnetic because of low-spin (LS) Fe(II) (M = 1) (12). For oxy, a diamagnetic (M = 1) cofactor was proven (3,12,13). However, the O 2 triplet ground state provides several options for spin flipping or charge transfer ( Fig.…”

Resonant inelastic X-ray scattering determination of the electronic structure of oxyhemoglobin and its model complex

“…However, there has been a dearth of experimental data to directly probe the electronic structure. In particular, the intense porphyrin π → π* transitions of heme complexes make it difficult to probe the highly covalent Fe with traditional spectroscopic methods (14,15).…”

Strong local moment antiferromagnetic spin fluctuations in V-doped LiFeAs

“…The flexible spin states of Fe 2+ ions are interesting due to its extensive distribution, from the lowermost mantle in the earth [1], to the innermost hemoglobin in our human body [2], from the most common ferrite magnet, to the most recent iron based superconductors [3][4][5]. Ignoring the orbital angular momentum, each Fe 2+ ion with six electrons distributed in five d orbitals has three possible spin states, S = 0, 1, or 2 [ Fig.…”