Search results for "Crystallization"
showing 10 items of 774 documents
Crystallization and Preliminary Analysis of Crystals of the 24-Meric Hemocyanin of the Emperor Scorpion (Pandinus imperator)
2011
Hemocyanins are giant oxygen transport proteins found in the hemolymph of several invertebrate phyla. They constitute giant multimeric molecules whose size range up to that of cell organelles such as ribosomes or even small viruses. Oxygen is reversibly bound by hemocyanins at binuclear copper centers. Subunit interactions within the multisubunit hemocyanin complex lead to diverse allosteric effects such as the highest cooperativity for oxygen binding found in nature. Crystal structures of a native hemocyanin oligomer larger than a hexameric substructure have not been published until now. We report for the first time growth and preliminary analysis of crystals of the 24-meric hemocyanin (M(…
Langevin dynamics simulations of a two-dimensional colloidal crystal under confinement and shear
2012
Langevin dynamics simulations are used to study the effect of shear on a two-dimensional colloidal crystal (with implicit solvent) confined by structured parallel walls. When walls are sheared very slowly, only two or three crystalline layers next to the walls move along with them, while the inner layers of the crystal are only slightly tilted. At higher shear velocities, this inner part of the crystal breaks into several pieces with different orientations. The velocity profile across the slit is reminiscent of shear banding in flowing soft materials, where liquid and solid regions coexist; the difference, however, is that in the latter case the solid regions are glassy while here they are …
Solvates of Dasatinib: Diversity and Isostructurality
2015
A series of dasatinib crystalline forms were obtained, and a hierarchical cluster analysis of their powder X-ray diffraction patterns was performed. The resulting dendrogram implies 3 structural groups. The crystal structures of several solvates representing 2 of these groups were determined. The crystal structure analysis confirms the isostructurality of solvates within structural group I and suggests a correlation between solvent molecule size and trends in crystal structures within this group. In addition, the formation relationships in 2-solvent media between different dasatinib solvate groups were determined. The formation preference of solvates was found to follow the ranking group I …
Synthetically persistent, self assembled [V(IV)2V(V)4] polyoxovanadates: facile synthesis, structure and magnetic analysis.
2011
Slow diffusion in a H-tube at room temperature of a methanolic solution of [VO(acac)(2)] (Hacac = acetylacetone) and 1,10-phenanthroline (phen) or 2,2'-bipyridine (bipy) into an aqueous solution of sodium pyrophosphate (Na(4)P(2)O(7)) resulted in the serendipitous formation of X-ray quality crystals of mixed-valent, hexameric oxovanadates of general formula [V(6)O(12)(OCH(3))(4)(L)(4)]·solv [L = 1,10-phenanthroline (phen) for 1· 2CH(3)OH · 4H(2)O (1a), and 2,2'-bipyridine (bipy) for 2· 4H(2)O (2a)]. These were characterized by single-crystal X-ray diffraction, IR, elemental and thermogravimetric analysis (TGA). A facile, rationalized synthetic route for the isolation of 1a and 2a could be e…
Investigation of the phase transitions occurring during and after the dehydration of xylazine hydrochloride monohydrate.
2014
This paper reports an investigation of a complex solid state phase transition where two inter-converting polymorphs (X and A) of the pharmaceutical molecule xylazine hydrochloride formed and transformed during and after the dehydration of its monohydrate (H). The crystal structures of all three forms were compared. During the investigation of this solid state phase transition it was determined that the dehydration of H produced either a pure X form, or a mixture of the X and A forms. The phase composition depended on the sample preparation procedure and the experimental conditions. It was found that grinding of the hydrate enhanced the formation of polymorph X as a product of dehydration, w…
Isostructural Inorganic–Organic Piperazine-1,4-diium Chlorido- and Bromidoantimonate(III) Monohydrates: Octahedral Distortions and Hydrogen Bonds
2020
Halogenidoantimonate(III) monohydrates of the (C4H12N2)[SbX5]·
Crystallization and preliminary crystallographic study of a pheromone-binding protein from the cockroachLeucophaea maderae
2002
Pheromone-binding proteins (PBPs) are small helical proteins (13-18 kDa) present in various sensory organs of moths and other insect species. An antennal protein from the cockroach Leucophaea maderae (LmaPBP) has been found to share all the hallmarks of the PBP family and is expressed specifically in the female adult antennae, the gender that perceives the sex pheromone. Here, the crystallization of LmaPBP expressed as a recombinant protein in Escherichia coli periplasm is reported. Crystals of LmaPBP were obtained by the sitting-drop vapour-diffusion method using a nanodrop-dispensing robot. The protein crystallizes in two different crystal forms. Form 1 belongs to space group P1, with uni…
Enzyme-accelerated and structure-guided crystallization of calcium carbonate: Role of the carbonic anhydrase in the homologous system
2014
Abstract The calcareous spicules from sponges, e.g. from Sycon raphanus, are composed of almost pure calcium carbonate. In order to elucidate the formation of those structural skeletal elements, the function of the enzyme carbonic anhydrase (CA), isolated from this species, during the in vitro calcium carbonate-based spicule formation, was investigated. It is shown that the recombinant sponge CA substantially accelerates calcium carbonate formation in the in vitro diffusion assay. A stoichiometric calculation revealed that the turnover rate of the sponge CA during the calcification process amounts to 25 CO2 s−1 × molecule CA−1. During this enzymatically driven process, initially pat-like pa…
Engineering a 2D protein-DNA crystal.
2005
(Figure Presented) Weaving with DNA: A DNA-binding protein was used to control the structure of a self-assembled 2D crystal. In the absence of protein, four oligonucleotides hybridize to form a Kagome lattice of interwoven double helices with p3 symmetry (see image). Addition of protein RuvA during assembly changes the symmetry and connectivity to give a DNA-protein crystal with an approximately square unit cell. © 2005 Wiley-VCH Verlag GmbH and Co. KGaA.
Vibrational analysis of iron and zinc phosphate conversion coating constituents
2001
Abstract The FT-MIR/FT-FIR and NIR-FT-Raman spectra of orthorhombic α -Zn 3 (PO 4 ) 2 ·4H 2 O (α-hopeite) and monoclinic Zn 2 Fe(PO 4 ) 2 ·4H 2 O (phosphophyllite), including deuterated samples, have been measured in the polycrystalline state at room temperature and below. The distribution of vibrational levels was related to the results of complete unit-cell group analyses. The number of uncoupled OD stretching modes of α-hopeite (isotopically dilute samples) strongly exceeds that expected from the number of hydrogen positions of the structure reported. In contrast, unequivocal assignment of the four hydrogen bonds of phosphophyllite has been performed. The distortion of the phosphate tetr…