TY - JOUR TI - Resonance Raman study of ferric heme adducts of dehaloperoxidase from Amphitrite ornata AU - Belyea, Jennifer AU - Belyea, Curtis M. AU - Lappi, Simon AU - Franzen, Stefan T2 - BIOCHEMISTRY AB - The study of axial ligation by anionic ligands to ferric heme iron by resonance Raman spectroscopy provides a basis for comparison of the intrinsic electron donor ability of the proximal histidine in horse heart myoglobin (HHMb), dehaloperoxidase (DHP), and horseradish peroxidase (HRP). DHP is a dimeric hemoglobin (Hb) originally isolated from the terebellid polychaete Amphitrite ornata. The monomers are structurally related to Mb and yet DHP has a peroxidase function. The core size marker modes, v2 and v3, were observed using Soret excitation, and DHP-X was compared to HHMb-X for the ligand series X = F, Cl, Br, SCN, OH, N3, and CN. Special attention was paid to the hydroxide adduct, which is also formed during the catalytic cycle of peroxidases. The Fe-OH stretching frequency was observed and confirmed by deuteration and is higher in DHP than in HHMb. The population of high-spin states of the heme iron in DHP was determined to be intermediate between HHMb and HRP. The data provide the first direct measurement of the effect of axial ligation on the heme iron in DHP. The Raman data support a modified charge relay in DHP, in which a strongly hydrogen-bonded backbone carbonyl (>C=O) polarizes the proximal histidine. The charge relay mechanism by backbone carbonyl >C=O-His-Fe is the analogue of the Asp-His-Fe of peroxidases and Glu-His-Fe of flavohemoglobins. DA - 2006/12/5/ PY - 2006/12/5/ DO - 10.1021/bi0609218 VL - 45 IS - 48 SP - 14275-14284 SN - 0006-2960 ER - TY - JOUR TI - Testing bridge-mediated differences in dinuclear valence tautomeric behavior AU - Bin-Salamon, Sofi AU - Brewer, Scott H. AU - Depperman, Ezra C. AU - Franzen, Stefan AU - Kampf, Jeff W. AU - Kirk, Martin L. AU - Kumar, R. Krishna AU - Lappi, Simon AU - Peariso, Katrina AU - Preuss, Kathryn E. AU - Shultz, David A. T2 - INORGANIC CHEMISTRY AB - Two structurally characterized dinuclear valence tautomers are described. Cobalt ions are bridged by p- and m-phenylene units connected to 2,2'-bipyridines. X-ray crystal structures show that the molecules are in the [(Co(III))(Co(III))] forms at ca. 125 K, while spectroscopic studies show that both molecules can achieve the [(Co(II))(Co(II))] form above 400 K and confirm the [(Co(III))(Co(III))] form below 10 K. Magnetic susceptibility studies are also included. Our results highlight the necessity of studying both crystalline and amorphous samples to distinguish the effects of intrinsic electronic structure and intermolecular forces on valence tautomeric behavior. DA - 2006/5/29/ PY - 2006/5/29/ DO - 10.1021/ic060170y VL - 45 IS - 11 SP - 4461-4467 SN - 1520-510X ER -