Georges Buisson

Crystallization and crystal packing of Proteus mirabilis PR catalase

The tetrameric catalase from Proteus mirabilis PR (EC 1.11.1.6), known to bind NADPH, has been crystallized by the hanging-drop method in a form apparently depleted in dinucleotide. The crystals belong to the hexagonal space group P6(2)22 with a = b = 111.7 A, c = 248.8 A. There is one subunit in the asymmetric unit. Data were collected to 2.9 A at the L.U.R.E. (Orsay) synchrotron radiation facility. The tetramers have been located in the crystal, centered on the site (1/2, 0, 0) with 222 symmetry.

Molecular structure of methoxotitanium (III) tetraphenylporphyrin, a slightly bent methoxo complex

Abstract Methoxotitanium (III) tetraphenylporphyrin was obtained by reaction of flourotitanium (III) tetraphenylporphyrin and sodium methylthiolate in the presence of methanol, and was characterized by X-ray structural analysis. This methoxo complex crystallizes in the monoclinic space group P2 1 /c with four molecules in a unit cell of dimensions a = 10.15(1) A, b = 16.29(2) A, c = 23.62(2) A, and β = 117.7(1)°. The structure was solved by standard heavy-atom techniques. Least-squares refinement has led to a final value of the conventional R index of 0.105 based on 1766 reflections. The titanium atom is coordinated to the four nitrogen atoms and to the oxygen atom. The methoxo ligand is significantly deviated from the usual bent geometry. The three atoms Ti, O, and C are nearly collinear (Tiue5f8Oue5f8C angle; 171(1)°), and the Tiue5f8O bond distance is very short (1.77(1) A). The slightly bent configuration of the axial bonding system is accounted for by significant π-donation from the methoxo ligand to the electron-deficient metal.

Simple synthesis of a six-co-ordinated high-spin iron(III) porphyrin; X-ray structure and magnetic properties of bis(ethanol)tetraphenylporphinatoiron(III) tetrafluoroborate

Reaction of the µ-oxo-dimer of iron(III) tetraphenylporphyrin with aqueous tetrafluoroboric acid in the presence of ethanol gives bis(ethanol)tetraphenylporphinatoiron(III) tetrafluoroborate, the structure of which has been determined by X-ray crystallography; this complex is a rare example of a structurally characterized six-co-ordinated iron(III) porphyrin with an unambiguous S= 5/2 ground state.

Stereochemical investigation of 2,3,4,6-tetra-O-acetyl-1-S-benzhydroximoyl-α-d-glucopyranose

C 21 H 25 NO 10 S cristallise dans C2 avec a=16.247, b=11.182, c=13.420A, β=91.62°, Z=4; affinement jusqua R=0.052. Determination de la stereochimie autour de la liaison C=N. La partie glucose a la conformation attendue 4 C 1 . Le groupement hydroxyl sur latome N est syn par rapport au cycle du sucre. Analyse du comportement conformationnel et compararison avec les structures connues de thiosucres.

Crystallization and preliminary X-ray diffraction studies of Escherichia coli glyceraldehyde-3-phosphate dehydrogenase.

Phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme in glycolysis. Single crystals of NAD-dependent GAPDH from Escherichia coli have been obtained by vapour diffusion at room temperature using trisodium citrate as precipitant. In almost the same crystallization conditions, two kinds of crystals were found to be suitable for X-ray diffraction. The crystals with only one half of a tetramer in the asymmetric unit were chosen for high- resolution analysis. They belonged to space group C222(1), with cell dimensions a = 79.1, b = 189.6 and c = 122.2 A. These crystals diffracted to 1.8 A resolution.

Crystal structure of hydrated 6A,6C,6E-tri-O-methylcyclohexaamylose and its conformation in solution

The crystal structure of uncomplexed 6A,6C,6E-tri-O-methylcyclohexaamylose (CD-3OMe) has been determined by X-ray analysis. The structure was solved by molecular replacement methods and refined by the full matrix least-squares method to the R-value of 0.074. Cyclodextrin molecules are arranged in a herring-bone cage-type packing. Inside the cavity only two water molecules are found close to the primary hydroxyl rim. One O-methyl group of a molecule is inserted into a neighbouring host molecule from the secondary hydroxy side. The conformation of CD-3OMe was also studied in solution by NMR spectroscopy. In particular heteronuclear 3J13C–1H coupling constants through the glycosidic linkages were measured. The results obtained in deuteriated water and pyridine could be intepreted in terms of an averaged flexible conformation.