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Anomalous Dispersion Data (anomalous + dispersion_data)
Selected AbstractsLagoden dimethylformamide hemisolvate dihydrate: absolute configuration, dipolar interactions and hydrogen-bonding interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Barbara Wicher Lagoden (L·3H2O, where L is Na+·C20H33O6,; sodium 3,,16,18-trihydroxy-8,13- epi -9,13-epoxylabdan-15-oate trihydrate) is widely used as an effective haemostatic agent. It has been crystallized from dimethylformamide (DMF) as sodium 3,,16,18-trihydroxy-8,13- epi -9,13-epoxylabdan-15-oate dimethylformamide hemisolvate dihydrate, Na+·C20H33O6,·0.5C3H7NO·2H2O or L2·DMF·4H2O, and the asymmetric unit contains two of the latter formulation. The four symmetry-independent Na+ cations and lagoden anions, one DMF molecule and six of the eight symmetry-independent water molecules assemble into a one-dimensional polymeric structure via dipolar and hydrogen-bonding interactions. The lagoden anions coordinate to the Na+ cations via the carboxylate groups and the two primary hydroxy groups, whereas the secondary OH groups are solely involved in hydrogen bonding. Two of the four symmetry-independent lagoden anions act in a chelating mode, forming seven-membered chelate rings. The absolute structure, based on anomalous dispersion data collected at 130,K with Cu K, radiation, confirms an inverted configuration at chiral centres C8 and C13 (labdane numbering) relative to the labdane skeleton. [source] Absolute structures and conformations of the spongian diterpenes spongia-13(16),14-dien-3-one, epispongiadiol and spongiadiolACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009Ken W. L. Yong The absolute configurations of spongia-13(16),14-dien-3-one [systematic name: (3bR,5aR,9aR,9bR)-3b,6,6,9a-tetramethyl-4,5,5a,6,8,9,9a,9b,10,11-decahydrophenanthro[1,2- c]furan-7(3bH)-one], C20H28O2, (I), epispongiadiol [systematic name: (3bR,5aR,6S,7R,9aR,9bR)-7-hydroxy-6-hydroxymethyl-3b,6,9a-trimethyl-3b,5,5a,6,7,9,9a,9b,10,11-decahydrophenanthro[1,2- c]furan-8(4H)-one], C20H28O4, (II), and spongiadiol [systematic name: (3bR,5aR,6S,7S,9aR,9bR)-7-hydroxy-6-hydroxymethyl-3b,6,9a-trimethyl-3b,5,5a,6,7,9,9a,9b,10,11-decahydrophenanthro[1,2- c]furan-8(4H)-one], C20H28O4, (III), were assigned by analysis of anomalous dispersion data collected at 130,K with Cu K, radiation. Compounds (II) and (III) are epimers. The equatorial 3-hydroxyl group on the cyclohexanone ring (A) of (II) is syn with respect to the 4-hydroxymethyl group, leading to a chair conformation. In contrast, isomer (III), where the 3-hydroxyl group is anti to the 4-hydroxymethyl group, is conformationally disordered between a major chair conformer where the OH group is axial and a minor boat conformer where it is equatorial. In compound (I), a carbonyl group is present at position 3 and ring A adopts a distorted-boat conformation. [source] Platinum-induced space-group transformation in crystals of the platelet glycoprotein Ib, N-terminal domainACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2004Kottayil I. Varughese The interaction between platelet glycoprotein (GP) Ib, and von Willebrand factor (VWF) is essential for thrombus formation, leading to the arrest of bleeding. The N-terminal domain of GP Ib,, which contains the binding sites for VWF and ,-thrombin, crystallized in the tetragonal space group P43 with one molecule in the asymmetric unit. When the crystals were treated with platinum, the crystals changed their symmetry from tetragonal to monoclinic P21 with two molecules in the asymmetric unit. The structure of the monoclinic form was solved using two-wavelength platinum anomalous dispersion data. The tetragonal crystal structure was subsequently solved using molecular-replacement techniques using the monoclinic structure as the search model and was refined with 1.7,Å resolution data. [source] Purification, crystallization and preliminary X-ray analysis of ,-glucosidase from Kluyveromyces marxianus NBRC1777ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009Erina Yoshida The intracellular ,-glucosidase from Kluyveromyces marxianus NBRC1777 (KmBglI) belongs to glycoside hydrolase family 3 and has a unique domain architecture. Selenomethionine-labelled KmBglI was purified and crystallized by the hanging-drop vapour-diffusion method using the purified enzyme at 30,mg,ml,1, 0.04,M potassium dihydrogen phosphate pH 5.1, 16%(w/v) PEG 8000 and 20%(v/v) glycerol. The crystal belonged to space group C2, with unit-cell parameters a = 245.8, b = 148.7, c = 119.9,Å, , = 112.9°. Multiple-wavelength anomalous dispersion data were collected at 2.4 and 2.5,Å resolution. A tetramer was assumed to be present in the asymmetric unit, which gave a Matthews coefficient of 2.6,Å3,Da,1. [source] Structure of O67745_AQUAE, a hypothetical protein from Aquifex aeolicusACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2007Vaheh Oganesyan Using single-wavelength anomalous dispersion data obtained from a gold-derivatized crystal, the X-ray crystal structure of the protein 067745_AQUAE from the prokaryotic organism Aquifex aeolicus has been determined to a resolution of 2.0,Å. Amino-acid residues 1,371 of the 44,kDa protein were identified by Pfam as an HD domain and a member of the metal-dependent phosphohydrolase superfamily (accession No. PF01966). Although three families from this large and diverse group of enzymatic proteins are represented in the PDB, the structure of 067745_AQUAE reveals a unique fold that is unlike the others and that is likely to represent a new subfamily, further organizing the families and characterizing the proteins. Data are presented that provide the first insights into the structural organization of the proteins within this clan and a distal alternative GDP-binding domain outside the metal-binding active site is proposed. [source] | ||||||||||