title: Density functional theory study of Fe(IV) d-d optical transitions in active-site models of class I ribonucleotide reductase intermediate X with vertical self-consistent reaction field methods.
abstract: The Fe(IV) d-d transition energies for four active-site structural models of class I ribonucleotide reductase (RNR) intermediate X have been calculated using broken-symmetry density functional theory incorporated with the Slater transition state vertical self-consistent reaction field methodology. Our model I (Figure 1), which contains two mu-oxo bridges, one terminal water, and one bidentate carboxylate group, yields the best Fe(IV) d-d transition energies compared with experiment. Our previous study (J. Am. Chem. Soc. 2005, 127, 15778-15790) also shows that most of the other calculated properties of model I in both native and mutant Y122F forms, including geometries, spin states, pKa's, 57Fe, 1H, and 17O hyperfine tensors, and 57Fe Mössbauer isomer shifts and quadrupole splittings, are also the best in agreement with the available experimental data. This model is likely to represent the active-site structure of the intermediate state X of RNR.
authors.affiliation: Department of Molecular Biology, TPC15, Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, USA. wengehan@scripps.edu
authors.forename: Wen-Ge
authors.initials: WG
authors.lastname: Han
authors.forename: Tiqing
authors.initials: T
authors.lastname: Liu
authors.forename: Timothy
authors.initials: T
authors.lastname: Lovell
authors.forename: Louis
authors.initials: L
authors.lastname: Noodleman
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites; D002264:Carboxylic Acids / Q000032:analysis; D007501:Iron; D008958:Models, Molecular; D010087:Oxides / Q000032:analysis; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002264:Carboxylic Acids; D010087:Oxides; D011994:Recombinant Proteins; D007501:Iron; D012264:Ribonucleotide Reductases