Cecília Bonifácio

Crystallization and crystallographic analysis of the apo form of the orange protein (ORP) from Desulfovibrio gigas.

The orange-coloured protein (ORP) from Desulfovibrio gigas is a 12 kDa protein that contains a novel mixed-metal sulfide cluster of the type [S(2)MoS(2)CuS(2)MoS(2)]. Diffracting crystals of the apo form of ORP have been obtained. Data have been collected for the apo form of ORP to 2.25 A resolution in-house and to beyond 2.0 A resolution at ESRF, Grenoble. The crystals belonged to a trigonal space group, with unit-cell parameters a = 43, b = 43, c = 106 A.

Crystallization and preliminary X-ray diffraction analysis of two pH-dependent forms of a di-haem cytochrome c peroxidase from Pseudomonas nautica.

Two crystal forms of cytochrome c peroxidase from Pseudomonas nautica were obtained, one at pH 4.0 using sodium citrate as precipitant and another at pH 5.3 using ammonium phosphate and sodium citrate as precipitants. The two forms belong to different space groups P3(1)21 (pH 4.0) and P6(4)22 (pH 5.3), with unit-cell parameters a = b = 114.5, c = 90.7 A and a = b = 151.0, c = 155.9 A, respectively. Several complete data sets were collected using synchrotron radiation at ESRF and Cu K(alpha) X-ray radiation from a rotating-anode generator. These results will contribute to clarifying the haem transitions occurring during peroxidatic reaction and the required electron-transfer processes and to elucidating the catalytic mechanism of the enzyme and the role of calcium in the activation process.

Overexpression, crystallization and preliminary X-ray crystallographic analysis of glucuronoxylan xylanohydrolase (Xyn30A) from Clostridium thermocellum.

The modular carbohydrate-active enzyme belonging to glycoside hydrolase family 30 (GH30) from Clostridium thermocellum (CtXynGH30) is a cellulosomal protein which plays an important role in plant cell-wall degradation. The full-length CtXynGH30 contains an N-terminal catalytic module (Xyn30A) followed by a family 6 carbohydrate-binding module (CBM6) and a dockerin at the C-terminus. The recombinant protein has a molecular mass of 45 kDa. Preliminary structural characterization was carried out on Xyn30A crystallized in different conditions. All tested crystals belonged to space group P1 with one molecule in the asymmetric unit. Molecular replacement has been used to solve the Xyn30A structure.

Substitutional disorder in bis-[(cyanato-κO)/hydroxido(0.5/0.5)](5,10,15,20-tetra-phenyl-porphyrinato-κN)tin(IV).

The title complex, [SnIV(C44H28N4)(CNO)(OH)], exhibits substitutional disorder of the OH− and OCN− axial ligands. Thus, the cyanato-O ligand and the hydroxyl group bonded to the central SnIV atom share statistically the axial position. The SnIV ion is hexacoordinated by the four N atoms of the pyrrole rings of the tetraphenylporphyrin (TPP) and the O atoms of the two disordered OCN− and OH− axial ligands. The equatorial tin–pyrrole N atom distance (Sn—Np) is 2.100 (2) Å and the axial Sn—O(OCN) or Sn—O(OH) bond length is 2.074 (2) Å.

Superoxide reductase from the syphilis spirochete Treponema pallidum: crystallization and structure determination using soft X-rays

Superoxide reductase is a 14 kDa metalloprotein containing a catalytic non-haem iron centre [Fe(His)4Cys]. It is involved in defence mechanisms against oxygen toxicity, scavenging superoxide radicals from the cell. The oxidized form of Treponema pallidum superoxide reductase was crystallized in the presence of polyethylene glycol and magnesium chloride. Two crystal forms were obtained depending on the oxidizing agents used after purification: crystals grown in the presence of K3Fe(CN)6 belonged to space group P2(1) (unit-cell parameters a = 60.3, b = 59.9, c = 64.8 A, beta = 106.9 degrees) and diffracted beyond 1.60 A resolution, while crystals grown in the presence of Na2IrCl6 belonged to space group C2 (a = 119.4, b = 60.1, c = 65.6 A, beta = 104.9 degrees) and diffracted beyond 1.55 A. A highly redundant X-ray diffraction data set from the C2 crystal form collected on a copper rotating-anode generator (lambda = 1.542 A) clearly defined the positions of the four Fe atoms present in the asymmetric unit by SAD methods. A MAD experiment at the iron absorption edge confirmed the positions of the previously determined iron sites and provided better phases for model building and refinement. Molecular replacement using the P2(1) data set was successful using a preliminary trace as a search model. A similar arrangement of the four protein molecules could be observed.

Synthesis, FT–IR characterization and crystal structure of aqua­(5,10,15,20-tetra­phenyl­porphyrinato-κ4N)manganese(III) tri­fluoro­methane­sulfonate

This porphyrinate macrocycle of the title compound exhibits a strong saddle and moderate ruffling deformations. In the crystal, the individual manganese porphyrin complex cations and the trifluoromethanesulfonate anions are arranged in alternating planes stacked along [001].

Aqua­(4-cyano­pyridine-κN4)(5,10,15,20-tetra­phenyl­porphyrinato-κ4N)magnesium

In the title complex, [Mg(C44H28N4)(C6H4N2)(H2O)], the Mg2+ cation is octahedrally coordinated and lies on an inversion center with the axially located 4-cyanopyridine and aqua ligands exhibiting 50% substitutional disorder. The cyano-bound 4-cyanopyridine molecule also is disordered across the inversion centre. The four N atoms of the pyrrole rings of the dianionic 5,10,15,20-tetraphenylporphyrin ligand occupy the equatorial sites of the octahedron [Mg—N = 2.0552 (10) and 2.0678 (11) Å] and the axial Mg—(N,O) bond length is 2.3798 (12) Å. The crystal packing is stabilized by weak intermolecular C—H⋯π interactions.

Purification, crystallization and preliminary X-ray diffraction analysis of the glyoxalase II from Leishmania infantum

In trypanosomatids, trypanothione replaces glutathione in all glutathione-dependent processes. Of the two enzymes involved in the glyoxalase pathway, glyoxalase I and glyoxalase II, the latter shows absolute specificity towards trypanothione thioester, making this enzyme an excellent model to understand the molecular basis of trypanothione binding. Cloned glyoxalase II from Leishmania infantum was overexpressed in Escherichia coli, purified and crystallized. Crystals belong to space group C222(1) (unit-cell parameters a = 65.6, b = 88.3, c = 85.2 angstroms) and diffract beyond 2.15 angstroms using synchrotron radiation. The structure was solved by molecular replacement using the human glyoxalase II structure as a search model. These results, together with future detailed kinetic characterization using lactoyltrypanothione, should shed light on the evolutionary selection of trypanothione instead of glutathione by trypanosomatids.

Crystal structure of chlorido­(5,10,15,20-tetra­phenyl­porphyrinato-κ4N)manganese(III) 2-amino­pyridine disolvate

In the title compound, the chlorido(5,10,15,20-tetraphenylporphyrinato)manganese(III) complex and the hydrogen-bonded dimer of 2-aminopyridine molecules are linked together by weak N—H⋯Cl hydrogen bonds into chains along the a axis.

Crystal structure of octa­kis­(N,N-di­methyl­formamide-κO)europium(III) tetra­cosa-μ2-oxido-dodeca­oxido-μ12-phosphato-dodeca­molybdate(VI)

The asymmetric unit of the title compound consists of one [Eu(C3H7NO)8]3+ complex cation and one α-Keggin-type [PMo12O40] polyanion. Cations and anions are linked through C—H⋯O hydrogen bonds.