Analysis of a siroheme model compound: Core-size dependence of resonance Raman bands and the siroheme spin state in sulfite reductase

Journal Article · Thu Feb 28 23:00:00 EST 1991 · Inorganic Chemistry; (USA)

DOI:https://doi.org/10.1021/ic00006a028· OSTI ID:5485710

Melamed, D; Sullivan, Jr, E P; Prendergast, K; Strauss, S H; Spiro, T G ^[1]

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1. Princeton Univ., New Jersey (USA)

Resonance Raman (RR) and infrared spectra are reported for nickel(II) octaethylisobacteriochlorin (OEiBC) and its {sup 15}N{sub 4} and meso-d{sub 3} isotopomers. The bands are assigned to porphyrin-like modes with the aid of a normal-coordinate analysis by using a force field developed for nickel octaethylporphyrin (OEP) and by scaling the force constants to bond lengths expected on the basis of the crystal structure of nickel meso-tetramethylisobacteriochlorin. The eigenvectors show a relationship between OEP and OEiBC modes, despite some localization to one or the other half of the OEiBC ring caused by the unequal lengths of the methine bridge bonds adjacent to the pyrrole and pyrroline rings. When the vibrational assignments are used to track the RR bands of a series of iron-OEiBC complexes, a distinctive dependence of the high-frequency bands on the ring core size of the porphyrin analogues is observed, although the slopes of the correlations differ from those reported previously for porphyrin or chlorin. Direct comparison of the iron-OEiBC high-frequency bands with those of the Escherichia coli sulfite reductase hemoprotein confirms the previous inference that the iron(II) siroheme is intermediate spin in the semireduced protein but high spin in the fully reduced protein. 8 tables, 12 figs., 31 refs.

• DOE Contract Number: FG02-88ER13876
• OSTI ID: 5485710
• Journal Information: Inorganic Chemistry; (USA), Journal Name: Inorganic Chemistry; (USA) Vol. 30:6; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
550200 -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
CARBOXYLIC ACIDS
COMPLEXES
ENZYMES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MOLECULAR STRUCTURE
NICKEL COMPLEXES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PORPHYRINS
RAMAN SPECTRA
SPECTRA
SULFITES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPLEXES