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Monoclinic Form (monoclinic + form)
Selected AbstractsCrystallization conditions and formation of orthorhombic paracetamol from ethanolic solutionJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2002N. Al-Zoubi Orthorhombic paracetamol exhibits far better tabletability than the monoclinic form and its bulk crystallization from solution attracts much interest. In this study, temperature changes in supersaturated ethanolic solution have been recorded after seeding with orthorhombic crystals under different cooling temperatures (TC) and agitation rates (AR). Average cooling rate (CR), time for maximum temperature deviation (tmax) and area confined between curves of measured and reference temperature plots (AUC) were calculated and correlated with crystal yield (Y). The micromeritic (size and shape) and the compression properties, the density and the orthorhombic content of the crystalline product were evaluated and related to the main crystallization conditions applied (TC and AR). Conditions for optimal crystal yield and orthorhombic content were elucidated. It was found that crystal yield (Y) increased with AR and decreased with TC. The ratio tmax/CR provided good prediction of crystal yield (Y = 58.92 ,1.386 tmax/CR, r2 = 0.964 and P = 0.0001). TC and AR linearly affected crystal size and the size distribution, probably due to alterations in supersaturation, but they did not affect the crystal shape significantly. Density and compression properties (yield pressure and elastic recovery) were determined by the content of the orthorhombic form, which increased linearly with AR (P = 0.009) and with TC (P = 0.039) when agitation was between 300 and 500 rev min,1, while tmax decreased. At 700 rev min,1 orthorhombic content was maximized and became independent to TC. Higher orthorhombic content and crystal yield was expected for lower TC and for lower tmax, which corresponded to higher AR and might have also been affected by alteration of seeding and harvesting procedure. [source] Influence of the Composition on Crystal Phase and Thermal Behavior of trans -1,4-Butadiene/Isoprene CopolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 23 2007Fabio Bertini Abstract Butadiene/isoprene copolymers were prepared using the catalyst system V(acac)3 -MAO. The structure of the comonomers is trans -1,4 and the butadiene and isoprene units are statistically distributed along the polymer chain. The attitude of the butadiene sequences to crystallize in the monoclinic form and to evolve in the hexagonal form is preserved in the copolymer for a certain range of composition. The temperature interval between the two endothermic events is progressively reduced by increasing the isoprene content. The monoclinic/hexagonal transition produces a considerable increase in the lamellar thickness of the polymers. Thermal degradation of the copolymers is influenced by the composition and takes place in two different stages: a series of cyclization and cross-linking reactions occur before the decomposition step. [source] Complex disorder in ,-NH4Fe2(PO4)2: deciphering from a five-dimensional formalismACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2007Olivier Pérez A new mixed-valent iron ammonium phosphate, ,-NH4Fe2(PO4)2, has been synthesized. The diffuse scattering observed on the diffraction patterns implies complex disorder phenomena and prevents a direct structure resolution. The latter can be solved by generating an artificially ordered orthorhombic structure, using a five-dimensional approach and performing partial integration of the diffuse streaks. In the artificially ordered structure, hexagonal tunnels, delimited by FeO6 octahedra, perpendicular to the directions [011] and [01] can then be seen; they are filled either by [FeP2O10], zigzag ribbons or by NH cations. It is shown that the disordering originates from the shifting of adjacent (100) tunnel slices of the structure with respect to each other along [011], allowing the formation of either new commensurate (superstructure) or incommensurate modulations, or even complete disorder along a. The close relationships with the ordered monoclinic form ,-NH4Fe2(PO4)2 are also explained by this description. [source] Polymorphism of 4-bromobenzophenoneACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2007Mikhail A. Strzhemechny A combination of single-crystal and powder X-ray diffractometry was used to study the structure of two polymorphs of 4-bromobenzophenone over the temperature range from 100 to 300,K. One of the polymorphs of the title compound was known previously and its structure has been determined at room temperature [Ebbinghaus et al. (1997). Z. Kristallogr.212, 339,340]. Two crystal growth methods were employed, one of which (a modification of the Bridgman,Stockbarger technique) resulted in single crystals of a previously unknown structure. The basic physical properties of the stable polymorph are: growth method, from 2-propanol solutions or gradient sublimation; space group, monoclinic P21/c; melting point, Tm = 355.2,K; X-ray density (at 100,K), Dx = 1.646,g,cm,3. The same properties of the metastable polymorph (triclinic ) are: growth method, modified Bridgman,Stockbarger method; X-ray density (at 100,K), Dx = 1.645,g,cm,3; Tm = 354,K. Thermograms suggest that the melting of the metastable form is accompanied by at least a partial crystallization presumably into the monoclinic form; the transformation is therefore monotropic. Analysis of short distances in both polymorphs shows that numerous weak hydrogen bonds of the C,H,, type ensure additional stabilization within the respective planes normal to the longest dimension of the molecules. The strong temperature dependence of the lattice constants and of the weak bond distances in the monoclinic form suggest that the weak bond interactions might be responsible for both the large thermal expansion within plane bc and the considerable thermal expansion anisotropy. [source] A new polymorph of benzene-1,2-diamine: isomorphism with 2-aminophenol and two-dimensional isostructurality of polymorphsACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Agnieszka Czapik A new crystalline form of benzene-1,2-diamine, C6H8N2, crystallizing in the space group Pbca, has been identified during screening for cocrystals. The crystals are constructed from molecular bilayers parallel to (001) that have the polar amino groups directed to the inside and the aromatic groups, showing a herringbone arrangement, directed to the outside. The known monoclinic form and the new orthorhombic polymorph exhibit two-dimensional isostructurality as the crystals consist of nearly identical bilayers. In the monoclinic form, neighbouring bilayers are generated by a unit translation along the a axis, whereas in the orthorhombic form they are generated by a c -glide. Moreover, the new form of benzene-1,2-diamine is essentially isomorphous with the only known form of 2-aminophenol. [source] Monohalogenated ferrocenes C5H5FeC5H4X (X = Cl, Br and I) and a second polymorph of C5H5FeC5H4IACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Alexander S. Romanov The structures of the three title monosubstituted ferrocenes, namely 1-chloroferrocene, [Fe(C5H5)(C5H4Cl)], (I), 1-bromoferrocene, [Fe(C5H5)(C5H4Br)], (II), and 1-iodoferrocene, [Fe(C5H5)(C5H4I)], (III), were determined at 100,K. The chloro- and bromoferrocenes are isomorphous crystals. The new triclinic polymorph [space group P, Z = 4, T = 100,K, V = 943.8,(4),Å3] of iodoferrocene, (III), and the previously reported monoclinic polymorph of (III) [Laus, Wurst & Schottenberger (2005). Z. Kristallogr. New Cryst. Struct.220, 229,230; space group Pc, Z = 4, T = 100,K, V = 924.9,Å3] were obtained by crystallization from ethanolic solutions at 253 and 303,K, respectively. All four phases contain two independent molecules in the unit cell. The relative orientations of the cyclopentadienyl (Cp) rings are eclipsed and staggered in the independent molecules of (I) and (II), while (III) demonstrates only an eclipsed conformation. The triclinic and monoclinic polymorphs of (III) contain nonbonded intermolecular I...I contacts, causing different packing modes. In the triclinic form of (III), the molecules are arranged in zigzag tetramers, while in the monoclinic form the molecules are arranged in zigzag chains along the a axis. Crystallographic data for (III), along with the computed lattice energies of the two polymorphs, suggest that the monoclinic form is more stable. [source] Two polymorphs of morpholin-4-ium 2-(5-methyl-1H -1,2,4-triazol-3-ylsulfanyl)acetateACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Svetlana V. Shishkina Two polymorphs of the title organic salt (a very effective medicinal preparation with the commercial name thiotriazoline), C4H10NO+·C5H6N3O2S,, were obtained. The cations and anions are connected by hydrogen bonds and extend into two-dimensional networks. The main packing motifs are an R44(12) cluster in the monoclinic form and a chain in the orthorhombic form. [source] An orthorhombic polymorph of 10,11-dihydrocarbamazepineACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2006H. G. Anilkumar The title compound (systematic name: 10,11-dihydro-5H -dibenz[b,f]azepine-5-carboxamide), C15H14N2O, is shown to crystallize as an orthorhombic polymorph to complement the known monoclinic form. The molecular conformations of both forms are very similar, involving a bent conformation for the seven-membered azepine ring and an overall `butterfly' shape. The molecules assemble into chains by way of N,H,O bonds and N,H,, interactions in both crystal modifications. The two polymorphs appear to form due to different van der Waals interactions between the layer-like sheets of molecules. [source] 5,5,-Di- tert -butyl-2,2,-dihydroxy-3,3,-methanediyldibenzaldehyde and its allyl-protected dialcohol and dialdehyde precursorsACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2004Sandrine Goetz 5,5,-Di- tert -butyl-2,2,-dihydroxy-3,3,-methanediyldibenzaldehyde, C23H28O4, (IV), has been structurally characterized in two polymorphic forms. The tetragonal form, (in I41/a) has been reported previously but is redetermined and reinterpreted here, while the monoclinic form, (in C2/c) is reported for the first time. In both polymorphs, the molecule lies on a crystallographic twofold axis. Two precursors in the synthesis of (IV), namely 2,2,-bis(allyloxy)-5,5,-di- tert -butyl-3,3,-methanediyldibenzenemethanol (C29H40O4) and 2,2,-bis(allyloxy)-5,5,-di- tert -butyl-3,3,-methanediyldibenzaldehyde (C29H36O4) have also been characterized. [source] Two polymorphs of aqua[N,N,-ethylenebis(salicylideneaminato- N,O)]oxovanadium(V) nitrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2001Alan Hazell The title compound, aqua[bis(salicylidene)ethylenediaminato- O,N,N,,O,]oxovanadium(V) nitrate, [VO(C16H14N2O2)(H2O)]NO3, crystallizes as two polymorphs in the triclinic and monoclinic crystal systems. In both, the V atom has a distorted octahedral coordination geometry with a long V,Owater bond trans to V=O. The coordinated water molecules are hydrogen bonded to the nitrate ions so that pairs of cations are linked to give neutral centrosymmetric dimers. The V=O and V,Owater distances are 1.598,(2) and 2.257,(2),Å, respectively, in the triclinic form, and 1.588,(3) and 2.230,(3),Å, respectively, in the monoclinic form. In the triclinic form, the dimers pack so that the salen [bis(salicylidene)ethylenediaminate] ligands are parallel to each other, whereas in the monoclinic form, which is the denser, there is a herring-bone arrangement. [source] A case of structure determination using pseudosymmetryACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2009Sergei Radaev Here, a case is presented of an unusual structure determination which was facilitated by the use of pseudosymmetry. Group A streptococcus uses cysteine protease Mac-1 (also known as IdeS) to evade the host immune system. Native Mac-1 was crystallized in the orthorhombic space group P21212. Surprisingly, crystals of the inactive C94A mutant of Mac-1 displayed monoclinic symmetry with space group P21, despite the use of native orthorhombic Mac-1 microcrystals for seeding. Attempts to solve the structure of the C94A mutant by MAD phasing in the monoclinic space group did not produce an interpretable map. The native Patterson map of the C94A mutant showed two strong peaks along the (1 0 1) diagonal, indicating possible translational pseudosymmetry in space group P21. Interestingly, one-third of the monoclinic reflections obeyed pseudo-orthorhombic P21212 symmetry similar to that of the wild-type crystals and could be indexed and processed in this space group. The pseudo-orthorhombic and monoclinic unit cells were related by the following vector operations: am = bo,co, bm = ao and cm = ,2co,bo. The pseudo-orthorhombic subset of data produced good SAD phases, leading to structure determination with one monomer in the asymmetric unit. Subsequently, the structure of the Mac-1 mutant in the monoclinic form was determined by molecular replacement, which showed six molecules forming three translationally related dimers aligned along the (1 0 1) diagonal. Knowing the geometric relationship between the pseudo-orthorhombic and the monoclinic unit cells, all six molecules can be generated in the monoclinic unit cell directly without the use of molecular replacement. The current case provides a successful example of the use of pseudosymmetry as a powerful phase-averaging method for structure determination by anomalous diffraction techniques. In particular, a structure can be solved in a higher pseudosymmetry subcell in which an NCS operator becomes a crystallographic operator. The geometrical relationships between the subcell and parental cell can be used to generate a complete molecular representation of the parental asymmetric unit for refinement. [source] Expression, crystallization and preliminary structural analysis of the ectoplasmic region of apical membrane antigen 1 from Plasmodium vivax, a malaria-vaccine candidateACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2004Brigitte Vulliez-Le Normand Apical membrane antigen 1 (AMA1), a type 1 transmembrane protein present in the microneme organelles of Plasmodium, is a leading malaria-vaccine candidate. The ectoplasmic region of AMA1 from P. vivax has been expressed in Pichia pastoris and crystallized in two different forms: an orthorhombic form (space group P212121, unit-cell parameters a = 54.1, b = 76.1, c = 103.9,Å) and a monoclinic form (space group C2, unit-cell parameters a = 150.0, b = 53.8, c = 60.3,Å, , = 113.2°). Native data have been collected to 2.0,Å resolution for the orthorhombic form and 1.8,Å for the monoclinic form. A platinum derivative was prepared for the orthorhombic and monoclinic crystals using K2PtCl4 and data were collected at several wavelengths to obtain phases by the MAD technique. A partial model has been built from the electron-density maps of both forms and refinement is in progress. [source] Structure of the C subunit of V-type ATPase from Thermus thermophilus at 1.85,Å resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2004Nobutaka Numoto The V-type H+ -ATPases are similar to the F-type ATP synthases in their structure and functional mechanism. They hydrolyze ATP coupled with proton translocation across a membrane, but in some archaea and eubacteria they also synthesize ATP in the reverse reaction. The C subunit is one of the components of the membrane-bound V0 moiety of V-type ATPases. The C subunit of V-type H+ -ATPase from Thermus thermophilus was crystallized in a monoclinic form and its crystal structure was determined at 1.85,Å resolution by the MAD method using selenomethionyl protein. The structure has a cone (tapered cylinder) shape consisting of only two types of helix (long and short) as secondary-structure elements. The molecule is divided into three similar domains, each of which has essentially the same topology. On the basis of the structural features and molecular-surface charge distribution, it is suggested that the bottom side of the C subunit is a possible binding site for the V0 proteolipid L-subunit ring and that the C subunit might function as a spacer unit between the proteolipid L-subunit ring and the rotating V1 central shaft. [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] Two polymorphs of lysozyme nitrate: temperature dependence of their solubilityACTA CRYSTALLOGRAPHICA SECTION D, Issue 10-1 2002L. Legrand Two crystallographic forms of lysozyme nitrate are known, namely monoclinic and triclinic. Having previously determined the temperature dependence of the solubility of the monoclinic form (0.2 M NaNO3 solutions at pH = 4.5) [Legrand et al. (2001). J. Crystal Growth232, 244-249], we focus here on the solubility of the triclinic form. The temperature dependence of the solubility of this crystallographic form has been measured with a static light device developed in our laboratory. This device allows to observe of the dissolution of one phase and/or the occurrence of a new one by varying the temperature with a sweep rate as low as 0.6 degree/hour. The new solubility data are complemented with crystallographic data of the triclinic form for the sake of completeness. The faces of a triclinic crystal are indexed. The crystallisation enthalpy of the triclinic form is deduced from these new results. These new solubility data allow us now to discuss (1) the publishedprotocols used to obtain the monoclinic and triclinic forms of lysozyme nitrate and (2) the phase transformation. [source] A triclinic crystal form of Escherichia coli 4-diphosphocytidyl-2C -methyl- d -erythritol kinase and reassessment of the quaternary structureACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010Justyna Kalinowska-T 4-Diphosphocytidyl-2C -methyl- d -erythritol kinase (IspE; EC 2.7.1.148) contributes to the 1-deoxy- d -xylulose 5-phosphate or mevalonate-independent biosynthetic pathway that produces the isomers isopentenyl diphosphate and dimethylallyl diphosphate. These five-carbon compounds are the fundamental building blocks for the biosynthesis of isoprenoids. The mevalonate-independent pathway does not occur in humans, but is present and has been shown to be essential in many dangerous pathogens, i.e. Plasmodium species, which cause malaria, and Gram-negative bacteria. Thus, the enzymes involved in this pathway have attracted attention as potential drug targets. IspE produces 4-diphosphosphocytidyl-2C -methyl- d -erythritol 2-phosphate by ATP-dependent phosphorylation of 4-diphosphocytidyl-2C -methyl- d -erythritol. A triclinic crystal structure of the Escherichia coli IspE,ADP complex with two molecules in the asymmetric unit was determined at 2,Å resolution and compared with a monoclinic crystal form of a ternary complex of E. coli IspE also with two molecules in the asymmetric unit. The molecular packing is different in the two forms. In the asymmetric unit of the triclinic crystal form the substrate-binding sites of IspE are occluded by structural elements of the partner, suggesting that the `triclinic dimer' is an artefact of the crystal lattice. The surface area of interaction in the triclinic form is almost double that observed in the monoclinic form, implying that the dimeric assembly in the monoclinic form may also be an artifact of crystallization. [source] Expression, purification, crystallization and structure determination of two glutathione S -transferase-like proteins from Shewanella oneidensisACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2008Bert Remmerie Genome analysis of Shewanella oneidensis, a Gram-negative bacterium with an unusual repertoire of respiratory and redox capabilities, revealed the presence of six glutathione S -transferase-like genes (sogst1,sogst6). Glutathione S -transferases (GSTs; EC 2.5.1.18) are found in all kingdoms of life and are involved in phase II detoxification processes by catalyzing the nucleophilic attack of reduced glutathione on diverse electrophilic substrates, thereby decreasing their reactivity. Structure,function studies of prokaryotic GST-like proteins are surprisingly underrepresented in the scientific literature when compared with eukaryotic GSTs. Here, the production and purification of recombinant SoGST3 (SO_1576) and SoGST6 (SO_4697), two of the six GST-like proteins in S. oneidensis, are reported and preliminary crystallographic studies of crystals of the recombinant enzymes are presented. SoGST3 was crystallized in two different crystal forms in the presence of GSH and DTT that diffracted to high resolution: a primitive trigonal form in space group P31 that exhibited merohedral twinning with a high twin fraction and a primitive monoclinic form in space group P21. SoGST6 yielded primitive orthorhombic crystals in space group P212121 from which diffraction data could be collected to medium resolution after application of cryo-annealing protocols. Crystal structures of both SoGST3 and SoGST6 have been determined based on marginal search models by maximum-likelihood molecular replacement as implemented in the program Phaser. [source] X-ray and 13C solid-state NMR studies of N -benzoyl-phenylalanineCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2000M.J. Potrzebowski Abstract: A crystalline sample of N -benzoyl- dl -phenylalanine 1 and a polycrystalline sample of N -benzoyl- l -phenylalanine 2 were studied using 13C high-resolution solid-state NMR spectroscopy. The X-ray structure of the dl form was established. Sample 1 crystallizes in a monoclinic form with a P21/c space group, a = 11.338(1) Å, b = 9.185(1) Å, c = 14.096(2) Å, ,,= 107.53(3)°, V = 1400(3) Å3, Z = 4 and R = 0.053. The principal elements of the 13C chemical shift tensors ,ii for 1 and 2, selectively 13C (99%) labeled at the carboxyl groups were calculated. On the basis of 13C ,ii analysis the hydrogen bonding pattern for sample 2 was deduced. Enriched samples were used to establish the intermolecular distance between chemically equivalent nuclei for 1 and spatial proximity in heterogeneous domain for 2, employing the ODESSA pulse sequence. The consistence of the complementary approach covering X-ray data, analysis of the 13C ,ii parameters and ODESSA results is revealed. [source] Three isomeric 1-(2-chloronicotinoyl)-2-(nitrophenyl)hydrazines, including three polymorphs of 1-(2-chloronicotinoyl)-2-(2-nitrophenyl)hydrazine: hydrogen-bonded supramolecular structures in two and three dimensionsACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2007Solange M. S. V. Wardell 1-(2-Chloronicotinoyl)-2-(2-nitrophenyl)hydrazine, C12H9ClN4O3, crystallizes in three polymorphic forms, two monoclinic forms in space groups Cc (Ia) and P21 (Ib), and an orthorhombic form in space group Pbcn (Ic). In the Cc polymorph (Ia) the molecules are linked into sheets by combinations of one N,H,O and two C,H,O hydrogen bonds, while in the P21 polymorph (Ib) the molecules are linked into sheets by combinations of three hydrogen bonds, one each of N,H,O, C,H,N and C,H,O types. In the orthorhombic polymorph (Ic) the molecules are linked into a complex three-dimensional framework structure by a combination of one N,H,O, one N,H,N and three C,H,O hydrogen bonds, and an aromatic ,,, stacking interaction. In the isomeric compound 1-(2-chloronicotinoyl)-2-(3-nitrophenyl)hydrazine (II) the molecules are again linked into a three-dimensional framework, this time by a combination of three hydrogen bonds, one each of N,H,O, N,H,N and C,H,O types, weakly augmented by a ,,, stacking interaction. The molecules of 1-(2-chloronicotinoyl)-2-(4-nitrophenyl)hydrazine (III) are linked into sheets by a combination of three hydrogen bonds, one each of N,H,O, N,H,N and C,H,O types. [source] | |||||||||||||