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Spin Crossover in Nitrito‐Myoglobin as Revealed by Resonance Raman Spectroscopy
Author(s) -
Lambrou Alexandra,
Ioannou Androulla,
Pinakoulaki Eftychia
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201601738
Subject(s) - myoglobin , heme , resonance raman spectroscopy , chemistry , metmyoglobin , raman spectroscopy , spin states , porphyrin , crystallography , ligand (biochemistry) , hemeprotein , resonance (particle physics) , nitrite , photochemistry , nuclear magnetic resonance , inorganic chemistry , atomic physics , organic chemistry , nitrate , physics , biochemistry , receptor , optics , enzyme
The myoglobin (Mb) heme Fe‐O‐N=O and heme Fe‐O‐N=O/2‐nitrovinyl species have been characterized by resonance Raman spectroscopy. In the heme Fe‐O‐N=O species, the bound nitrite ligand is removed by solvent exchange, thus reforming metmyoglobin (metMb). The high‐spin heme Fe‐O‐N=O unit is converted into a low‐spin heme Fe‐O‐N=O/2‐nitrovinyl species that can be reversibly switched between a low‐ and a high‐spin state without removing the bound nitrite ligand, as observed in the case of the heme Fe‐O‐N=O species. This spin‐state change is likely to be accompanied by a general structural rearrangement in the protein‐binding pocket. This example is the first of a globin protein that can reversibly change its metal spin state through an internal perturbation. These findings provide a basis for understanding the structure–function relationship of the spin cross found in other metalloenzymes and Fe III –porphyrin complexes.