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High-quality Crystals (high-quality + crystal)
Selected AbstractsTitanium complexes with sulfur-linked bis(phenolate) ligandsACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Thomas S. Dols High-quality crystals of two bis(phenolate)titanium complexes, namely dichlorido{4,4,-dimethyl-2,2,-[cyclohexane-1,2-diylbis(sulfanediyl)]diphenolato}titanium(IV), [Ti(C20H22O2S2)Cl2], (I), and dichlorido{2,2,-[cyclohexane-1,2-diylbis(sulfanediyl)]diphenolato}titanium(IV), [Ti(C18H18O2S2)Cl2], (II), were obtained by reactive crystallization. Depending on the solvent, compound (II) was obtained as unsolvated (IIa) or as the toluene hemisolvate, [Ti(C18H18O2S2)Cl2]·0.5C7H8, (IIb). These systems without bulky substituents on the aromatic phenolate rings serve as ideal model compounds for precatalysts. The excellent X-ray diffraction data will help clarify the nature of the mismatched interactions between the soft S atoms within the ligand and the hard titanium center. Molecule (I) has crystallographic C2 symmetry. [source] High-quality crystals of human haematopoietic prostaglandin D synthase with novel inhibitorsACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 7 2010Sachiko Takahashi Human haematopoietic prostaglandin D synthase (H-PGDS; EC 5.3.99.2) produces prostaglandin D2, an allergic and inflammatory mediator, in mast cells and Th2 cells. H-PGDS has been crystallized with novel inhibitors with half-maximal inhibitory concentrations (IC50) in the low nanomolar range by the counter-diffusion method onboard the Russian Service Module on the International Space Station. The X-ray diffraction of a microgravity-grown crystal of H-PGDS complexed with an inhibitor with an IC50 value of 50,nM extended to 1.1,Å resolution at 100,K using SPring-8 synchrotron radiation, which is one of the highest resolutions obtained to date for this protein. [source] Preliminary X-ray crystallographic studies of Bacillus subtilis SpeA proteinACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2009Xiao-Yan Liu The speA gene in Bacillus subtilis encodes arginine decarboxylase, which catalyzes the conversion of arginine to agmatine. Arginine decarboxylase is an important enzyme in polyamine metabolism in B. subtilis. In order to further illustrate the catalytic mechanism of arginine decarboxylase by determining the three-dimensional structure of the enzyme, the speA gene was amplified from B. subtilis genomic DNA and cloned into the expression vector pET-28a(+). SpeA was expressed in Escherichia coli and purified to homogeneity by nickel-chelation chromatography followed by size-exclusion chromatography. High-quality crystals were obtained using the hanging-drop vapour-diffusion method at 289,K. The best crystal diffracted to 2.0,Å resolution and belonged to space group P21, with unit-cell parameters a = 86.4, b = 63.3 c = 103.3,Å, , = 113.9°. [source] Rigorous filtration for protein crystallizationJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2009Naomi E. Chayen Centrifugation or filtration of protein samples through 0.22,µm mesh size filters is standard procedure before setting up trials for crystallization. This note concerns other, mostly unused filters, namely 0.1,µm and 100,000,300,000 molecular weight cut-off filters, which have proved to aid in obtaining single high-quality crystals. It serves to pool together information concerning filtration which has been scattered, and somewhat concealed, in various publications over the years and to add information that has not yet been published. Filtration is relevant to all methods of crystallization for both screening and optimization. [source] Introduction of a leucine half-zipper engenders multiple high-quality crystals of a recalcitrant tRNA synthetaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2010Min Guo Although Escherichia coli alanyl-tRNA synthetase was among the first tRNA synthetases to be sequenced and extensively studied by functional analysis, it has proved to be recalcitrant to crystallization. This challenge remained even for crystallization of the catalytic fragment. By mutationally introducing three stacked leucines onto the solvent-exposed side of an ,-helix, an engineered catalytic fragment of the synthetase was obtained that yielded multiple high-quality crystals and cocrystals with different ligands. The engineered ,-helix did not form a leucine zipper that interlocked with the same ,-helix from another molecule. Instead, using the created hydrophobic spine, it interacted with other surfaces of the protein as a leucine half-zipper (LHZ) to enhance the crystal lattice interactions. The LHZ made crystal lattice contacts in all crystals of different space groups. These results illustrate the power of introducing an LHZ into helices to facilitate crystallization. The authors propose that the method can be unified with surface-entropy reduction and can be broadly used for protein-surface optimization in crystallization. [source] Post-crystallization treatments for improving diffraction quality of protein crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2005Begoña Heras X-ray crystallography is the most powerful method for determining the three-dimensional structure of biological macromolecules. One of the major obstacles in the process is the production of high-quality crystals for structure determination. All too often, crystals are produced that are of poor quality and are unsuitable for diffraction studies. This review provides a compilation of post-crystallization methods that can convert poorly diffracting crystals into data-quality crystals. Protocols for annealing, dehydration, soaking and cross-linking are outlined and examples of some spectacular changes in crystal quality are provided. The protocols are easily incorporated into the structure-determination pipeline and a practical guide is provided that shows how and when to use the different post-crystallization treatments for improving crystal quality. [source] Harvesting the high-hanging fruit: the structure of the YdeN gene product from Bacillus subtilis at 1.8,Å resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2004Izabela Janda High-throughput (HT) protein crystallography is severely impeded by the relatively low success rate of protein crystallization. Proteins whose structures are not solved in the HT pipeline owing to attrition in any phase of the project are referred to as the high-hanging fruit, in contrast to those proteins that yielded good-quality crystals and crystal structures, which are referred to as low-hanging fruit. It has previously been shown that proteins that do not crystallize in the wild-type form can have their surfaces engineered by site-directed mutagenesis in order to create patches of low conformational entropy that are conducive to forming intermolecular interactions. The application of this method to selected proteins from the Bacillus subtilis genome which failed to crystallize in the HT mode is now reported. In this paper, the crystal structure of the product of the YdeN gene is reported. Of three prepared double mutants, i.e. E124A/K127A, E167A/E169A and K88A/Q89A, the latter gave high-quality crystals and the crystal structure was solved by SAD at 1.8,Å resolution. The protein is a canonical ,/, hydrolase, with an active site that is accessible to solvent. [source] | ||||||||||