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Spectroscopic Characterization and Competitive Inhibition Studies of Azide Binding to a Functional NOR Model
Author(s) -
Yang Ying,
Dey Abhishek,
Decréau Richard A.
Publication year - 2010
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201000566
Subject(s) - chemistry , azide , heme , ferrous , ferric , sodium azide , inorganic chemistry , hemeprotein , fourier transform infrared spectroscopy , valence (chemistry) , photochemistry , stereochemistry , organic chemistry , enzyme , physics , quantum mechanics
Azide binding to a functional nitric oxide reductase (NOR) model has been investigated in its mixed‐valence (LFe III Fe II and LFe II Fe III ) and fully oxidized (LFe III Fe III ) forms. FTIR and EPR spectroscopic methods indicate that azide binds in a bridging mode between the heme iron and the non‐heme iron sites. Terminal azide binding at both heme and non‐heme centers is also identified with the reactions of azide and the dinuclear compounds LFe III /Zn II and LZn II /Fe III : the bound azide at the ferric heme center exhibits a vibrational frequency at 2007 cm –1 in the FTIR, while the bound azide at the ferric non‐heme site shows a band at 2055 cm –1 . The reactivity of nitric oxide with the model compounds in the presence of excess azide was investigated. It is demonstrated that azide does not inhibit NO binding to the fully reduced catalyst but binds the Fe B tightly in both the mixed‐valence and the fully oxidized states. These results further support the proposal that a bis‐ferrous instead of a mixed‐valence state is the active form of NOR.