10.1021/bi0609218.s001 Jennifer Belyea Jennifer Belyea Curtis M. Belyea Curtis M. Belyea Simon Lappi Simon Lappi Stefan Franzen Stefan Franzen Resonance Raman Study of Ferric Heme Adducts of Dehaloperoxidase from <i>Amphitrite ornata</i><sup>†</sup> American Chemical Society 2006 ferric heme iron electron donor ability HRP resonance Raman spectroscopy OH Raman data support SCN heme iron core size marker modes ligand series X DHP HHMb horse heart myoglobin Ferric Heme Adducts CN Resonance Raman Study peroxidase terebellid polychaete Amphitrite ornata 2006-12-05 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Resonance_Raman_Study_of_Ferric_Heme_Adducts_of_Dehaloperoxidase_from_i_Amphitrite_ornata_i_sup_sup_/3043597 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 <i>Amphitrite ornata</i>. The monomers are structurally related to Mb and yet DHP has a peroxidase function. The core size marker modes, ν<sub>2</sub> and ν<sub>3</sub>, were observed using Soret excitation, and DHP-X was compared to HHMb-X for the ligand series X = F, Cl, Br, SCN, OH, N<sub>3</sub>, 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.