The protonation of N2 bound to the active center of nitrogenase has been investigated using state-of-the-art density-functional theory calculations. Dinitrogen in the bridging mode is activated by forming two bonds to Fe sites, which results in a reduction of the energy for the first hydrogen transfer by 123 kJ/mol. The axial binding mode with open sulfur bridge is less reactive by 30 kJ/mol an...

In the title compound, [Cu(C(15)H(11)N(3)O(3))(C(10)H(8)N(2))], the Cu(II) atom is five-coordinated in a distorted square-pyramidal CuN(3)O(2) geometry. The basal positions are occupied by three donor atoms from the tridentate Schiff base ligand and by one N atom from the 2,2'-bipyridine ligand. The axial position is occupied by the other N atom of the 2,2'-bipyridine ligand. The crystal struct...

In the title compound, [CuCl(2)(C(9)H(11)N(3)O)], the Cu(II) atom is in a distorted square-pyramidal CuCl(2)N(2)O coordination geometry. The tridentate acetohydrazide ligand chelates in a meridional fashion. The chloride ligand in the axial position forms a long Cu-Cl distance of 2.4892 (9) Å. In contrast, the Cu-Cl distance from the equatorial chloride ligand is much shorter [2.2110 (7) Å]. In...

A small soluble cytochrome c-554 purified from Methylosinus trichosporium OB3b has been purified and analyzed by amino acid sequencing, mass spectrometry, visible, CD and EPR spectroscopies. It is found to be a mono heme protein with a characteristic cytochrome c fold, thus fitting into the class of cytochrome c(2), which is the bacterial homologue of mitochondrial cytochrome c. The heme iron h...

Essentially complete atropdiastereoselectivity was realized in the preparation of biaryl diphosphine dioxide by asymmetric intramolecular Ullmann coupling and oxidative coupling with central-to-axial chirality transfer. A bridged C(2)-symmetric biphenyl phosphine ligand possessing additional chiral centers on the linking unit of the biphenyl groups was synthesized. No resolution step was requir...

Tetraheme cytochrome c 3 (cyt c 3) exhibits extremely low reduction potentials and unique properties. Since axial ligands should be the most important factors for this protein, every axial histidine of Desulfovibrio vulgaris Miyazaki F cyt c 3 was replaced with methionine, one by one. On mutation at the fifth ligand, the relevant heme could not be linked to the polypeptide, revealing the essent...

Rr-CooA is a CO-sensor heme protein, where binding of CO with the heme group stimulates a transcriptional activator activity of CooA. In this process, the heme undergoes a series of ligand exchanges. In the ferric form, the heme has Cys75 and Pro2 as the axial ligands. In the reduced ferrous form, the heme has His77 instead of Cys75 as an axial ligand with Pro2. Only in the reduced form, CooA c...

Three types of per-O-methylated β-cyclodextrin dimers, Im2CD, Im3NHCD and Py3NHCD, were prepared as globin models. Im2CD was synthesized by the condensation reaction of mono(2(A)-amino)-per-O-methylated β-cyclodextrin with 3-(1H-imidazol-1-yl)pentanedioic acid. Im3NHCD and Py3NHCD were obtained through the S(N)2 reactions of mono(2(A),3(A)-epoxy)-per-O-methylated β-cyclodextrin with 3-(1H-imida...