Structure—reactivity studies of blue copper preteins. Affinity labeling of electron transfer proteins by transition metal coordination

Design of Novel Oligomeric Mixed Ligand Complexes: Preparation, Biological Applications and the First Example of Their Nanosized Scale

A successful oligomerization of ternary metal complexes, cobalt (II), nickel (II), copper (II), zinc (II), chromium (III) and ferric sulfate (III) with nitrilotriacetic acid (NTA) as a primary ligand and glutamic acid as a secondary ligand, has been demonstrated. The formation of oligomers arose from the presence of the sulfate moiety, which operates as a bridged bidentate ligand that coordinates with other metal moieties. The novel oligomers exhibited octahedral structures, which bonded together through the sulfate moiety. In silico predictions were conducted to gauge the bioactivity, physico-chemical and pharmacokinetic properties. The biological activities of these oligomers as well as their tumor inhibitory behavior have been explored. This work also presents a facile and novel method of preparing these materials in nanosize, using Cetyltrimethylammonium bromide (CTAB) and polyvinyl alcohol (PVA) as capping ligands. The size and shape of the nanomaterials have been confirmed using the transmission electron microscope (TEM) and the scanning electron microscope (SEM).

Aquabis[3,6-bis(pyridin-2-yl)pyridazine-κ2N1,N6]copper(II) bis(trifluoromethanesulfonate)

The title salt, [Cu(C14H10N4)2(H2O)](CF3SO3)2, contains a Cu2+cation coordinated by two bidentate 3,6-bis(pyridin-2-yl)pyridazine ligands and one water molecule. The charge is balanced by two disordered trifluoromethanesulfonate anions. The asymmetric unit contains half of a cation (point group symmetry 2) and one anion. The coordinating water molecule is engaged in intermolecular O—H...O hydrogen bonds, which connect the cation to the anion. C—H...X(X= N, O, F) interactions stabilize the crystal structure.

Thiohydrazone copper(II) complexes. The relationship between redox properties and superoxide dismutase mimetic activity

The redox behaviour of copper(II) complexes with the open chain ligand, benzilbisthiosemicarbazone, and the macrocyclic one [3,4,10,11-tetraphenyl-1,2,5,8,9,12,13-octaazacyclotetradeca-7,14- dithione- 2,4,9,11-tetraene] has been explored by cyclic voltammetry. The half-wave potential values for the copper(II)/copper(I) redox couple and the spectral data obtained on dimethylsulfoxide (DMSO) solution agree with the superoxide dismutase (SOD)-mimetic activity of the complexes. The macrocyclic complexes show more positive reduction potential and more activity than the open chain derivatives. From our results it follows that the structure and conformation of ligand has influence on the redox potential of central atom in coordination compound. The changes in the coordination sphere are connected with the change of biological function of compounds represented by SOD-mimic activity. In addition, the L1H6 derivatives show quasireversible waves associated to Cu(II)/Cu(III) process.

Three-dimensional model for stellacyanin, a "blue" copper-protein

A three-dimensional model of the "blue" copper-glycoprotein stellacyanin from Rhus vernicifera has been derived by computer graphics, energy minimization and molecular dynamics techniques. The initial atomic co-ordinates were obtained by making substitutions and insertions in the known structure of another blue copper-protein, cucumber basic protein (CBP), which is 46% homologous with stellacyanin and has similar spectroscopic properties. An important difference between CBP and stellacyanin is that the latter lacks methionine, a residue that forms an exceptionally long bond to the copper atom in all blue copper-proteins of known structure. In the aligned amino acid sequences, stellacyanin has glutamine 97 at the position that corresponds to the copper-binding methionine 89 in CBP. The hypothesis that the copper atom in stellacyanin is co-ordinated by the side-chain functional groups of histidine 46, cysteine 87, histidine 92 and glutamine 97 leads to a model that enables the spectroscopic properties, redox potential and electron-transfer kinetics of the protein to be rationalized. The present model for stellacyanin is more plausible than an antecedent model derived from the structure of plastocyanin. This demonstrates that the output from molecular modeling calculations is strongly dependent on the input, and that sequence homology with the target molecule is an important criterion for the selection of a starting model.

Isolation and purification of plastocyanin from spinach stored frozen using hydrophobic interaction and ion-exchange chromatography

A new simple three-day procedure for preparative isolation and purification of plastocyanin from spinach stored in the frozen state is described. This procedure is based on batch adsorption on ion-exchange resin, ammonium sulphate precipitation, and purification on a Phenyl-Sepharose hydrophobic interaction column and a single Q Sepharose High Performance ion-exchange column. Approximately 100 mg of plastocyanin with an absorbance ratio A278/A597 of 1.10±0.02 in the oxidized state was typically obtained from 12 kg of spinach leaves. The purified spinach plastocyanin is shown to be homogeneous to the resolution of free solution capillary electrophoresis.

Sequential 1H NMR assignments of iron(II) cytochrome c551 from Pseudomonas aeruginosa

Sequence-specific 1H NMR resonance assignments for all but the C-terminal Lys 82 are reported for iron(II) cytochrome c551 from Pseudomonas aeruginosa at 25 degrees C and pH = 6.8. Spin systems were identified by using TOCSY and DQF-COSY spectra in 2H2O and 1H2O. Sequential assignments were made by using NOESY connectivities between adjacent amide, alpha, and beta protons. Resonances from several amino acids including His 16, Gly 24, Ile 48, and Met 61 experience strong ring-current shifts due to their placement near the heme. All heme protons, including the previously unassigned propionates, have been identified. Preliminary analysis of sequential and medium-range NOEs provides evidence for substantial amounts of helix in the solution structure. Long-range NOEs indicate that the folds in solution and crystal structures are similar. For one aromatic side chain (Tyr 27) that is close to the heme group we found a transition from hindered ring rotation at low temperature to rapid rotation at high temperature.