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Suitable Crystals (suitable + crystal)
Selected AbstractsSodium Hydro(isothiocyanato)borates: Synthesis and StructuresEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2004Heinrich Nöth Abstract Sodium thiocyanate reacts in THF solution with 18-crown-6 to give the molecular compound Na(18-crown-6)(THF)NCS (3) with the N atom of the NCS anion oriented towards Na+. The same reaction with 15-crown-5 yields the ion pair Na(15-crown-5)NCS (4). In contrast, Na(NCS)(py)4, obtained by treating a solution of Na(H3BNCS) in THF with pyridine, yields Na(py)4(NCS) (5), which has a chain structure with hexacoordinate Na atoms coordinated to five N atoms and an S atom. Na(NCS) in THF adds 1 equiv. of BH3 to give Na(H3BNCS)·nTHF. Addition of 18-crown-6 to this solution yields crystals of the salt [Na(18-crown-6)(THF)2][H3BNCS] (1), as shown by X-ray crystallography. Both the cation and the anion show site disorder. However, when 15-crown-5 is used for complexation, the salt [Na(15-crown-5)(THF)][H3BNCS] (2) can be isolated. Its anion shows an almost linear B,N,C,S unit. Only a mixture of (catecholato)(isothiocyanato)borates results on treating Na(NCS) in THF with catecholborane. However, the borate Na[catB(NCS)2] is readily formed by adding Na(NCS) to B -(isothiocyanato)catecholborane. Single crystals of this compound were obtained as the salt [Na(18-crown-6)(THF)2][catB(NCS)2] (6). On the other hand, the reaction of Na(NCS) with 9-borabicyclo[3.3.1]nonane (9-BBN) in THF yields Na[(9-BBN)NCS)]·nTHF, and, on addition of 18-crown-6, the complex [Na(18-crown-6)(THF)2][(9-BBN)NCS] was isolated. Suitable crystals for X-ray structure determination were, however, only obtained by crystallization from tetrahydropyran. This solvate has the rather unusual structure [Na(18-crown-6)(thp)2][{(9-BBN)NCS}2Na(thp)4] (8). The sodiate anion has an Na atom coordinated by two S and four O atoms. DFT calculations support these experimental results: The (isothiocyanato)borates are more stable than the thiocyanato isomers. For the latter a bent structure of the B,S,C,N unit with a B,S,C bond angle of 105.7° is predicted. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Expression, purification, crystallization and preliminary X-ray diffraction data of methylmalonate-semialdehyde dehydrogenase from Bacillus subtilisACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2004Hélène Dubourg Methylmalonate-semialdehyde dehydrogenase from Bacillus subtilis was cloned and overexpressed in Escherichia coli. Suitable crystals for X-ray diffraction experiments were obtained by the hanging-drop vapour-diffusion method using ammonium sulfate as precipitant. The crystals belong to space group P212121, with unit-cell parameters a = 195.2, b = 192.5, c = 83.5,Å, and contain one tetramer per asymmetric unit. X-ray diffraction data were collected to 2.5,Å resolution using a synchrotron-radiation source. The crystal structure was solved by the molecular-replacement method. [source] Crystallization and preliminary X-ray diffraction analysis of human IL-22 bound to its soluble decoy receptor IL-22BPACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2009Leandra Watanabe Interleukin-22 (IL-22) is a pleiotropic cytokine that is involved in inflammatory responses. Human IL-22 was incubated with its soluble decoy receptor IL-22BP (IL-22 binding protein) and the IL-22,IL-22BP complex was crystallized in hanging drops using the vapour-diffusion method. Suitable crystals were obtained from polyethylene glycol solutions and diffraction data were collected to 2.75,Å resolution. The crystal belonged to the tetragonal space group P41, with unit-cell parameters a = b = 67.9, c = 172.5,Å, and contained two IL-22,IL-22BP complexes per asymmetric unit. [source] Crystallization and preliminary X-ray analysis of cellobiose phosphorylase from Cellvibrio gilvusACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2004Masafumi Hidaka A recombinant cellobiose phosphorylase from Cellvibrio gilvus has been prepared and crystallized by the sitting-drop vapour-diffusion method using 10,mg,ml,1 purified enzyme, 1.5,M ammonium sulfate, 0.1,M MES buffer pH 7.0 and 5,mM glucose. A suitable crystal was obtained after 10,d incubation at 298,K. The crystal belongs to space group P21, with unit-cell parameters a = 84.77, b = 98.31, c = 104.04,Å, , = 102.73°. X-ray diffraction data to 2.1,Å resolution have been collected at KEK-PF BL-5A. [source] PDK1 and PKB/Akt: Ideal Targets for Development of New Strategies to Structure-Based Drug DesignIUBMB LIFE, Issue 3 2003Thomas Harris Abstract Growth factor binding events to receptor tyrosine kinases result in activation of phosphatidylinositol 3-kinase (PI3K), and activated PI3K generates the membrane-bound second messengers phosphatidylinositol 3,4-diphosphate [PI(3,4)P2] and PI(3,4,5)P3, which mediate membrane translocation of the phosphoinositide-dependent kinase-1 (PDK1) and protein kinase B (PKB, also known as Akt). In addition to the kinase domain, PDK1 and PKB contain a pleckstrin homology (PH) domain that binds to the second messenger, resulting in the phosphorylation and activation of PKB by PDK1. Recent evidence indicates that constitutive activation of PKB contributes to cancer progression by promoting proliferation and increased cell survival. The indicating of PDK1 and PKB as primary targets for discovery of anticancer drugs, together with the observations that both PDK1 and PKB contain small-molecule regulatory binding sites that may be in proximity to the kinase active site, make PDK1 and PKB ideal targets for the development of new strategies to structure-based drug design. While X-ray structures have been reported for the kinase domains of PDK1 and PKB, no suitable crystals have been obtained for either PDK1 or PKB with their PH domains intact. In this regard, a novel structure-based strategy is proposed, which utilizes segmental isotopic labeling of the PH domain in combination with site-directed spin labeling of the kinase active site. Then, long-range distance restraints between the 15N-labeled backbone amide groups of the PH domain and the unpaired electron of the active site spin label can be determined from magnetic resonance studies of the enhancement effect that the paramagnetic spin label has on the nuclear relaxation rates of the amide protons. The determination of the structure and position of the PH domain with respect to the known X-ray structure of the kinase active site could be useful in the rational design of potent and selective inhibitors of PDK1 and PKB by 'linking' the free energies of binding of substrate (ATP) analogs with analogs of the inositol polar head group of the phospholipid second messenger. The combined use of X-ray crystallography, segmental isotopic and spin labeling, and magnetic resonance studies can be further extended to the study of other dynamic multidomain proteins and targets for structure-based drug design. IUBMB Life, 55: 117-126, 2003 [source] A new crystal form of XT6 enables a significant improvement of its diffraction quality and resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2004Maya Bar Xylanases (1,4-,- d -xylan xylanhydrolases; EC 3.2.1.8) hydrolyze the 1,4-,- d -xylopyranosyl linkage of xylans. The detailed structural characterization of these enzymes is of interest for the elucidation of their catalytic mechanism and for their rational modification toward improved stability and specificity. An extracellular xylanase from Geobacillus stearothermophilus T-6 (XT6) has recently been cloned, overexpressed, purified and biochemically characterized. Previous crystallographic efforts resulted in a hexagonal crystal form, which subsequently proved to be of limited use for structural analysis, mainly because of its relatively poor diffraction quality and resolution. A systematic search for more suitable crystals of XT6 recently resulted in a new crystal form of this enzyme with significantly improved diffraction characteristics. The new crystals belong to a C -centred monoclinic crystal system (space group C2), with unit-cell parameters a = 121.5, b = 61.7, c = 89.1,Å, , = 119.7°. These crystals diffract X-rays to better than 1.5,Å resolution, showing a very clear diffraction pattern of relatively high quality. The crystals are mechanically strong and exhibit excellent radiation-stability when frozen under cold nitrogen gas. A full diffraction data set to 1.45,Å resolution (94.1% completeness, Rmerge = 7.0%) has been collected from flash-frozen crystals of the native enzyme at 95,K using synchrotron radiation. Crystals of the E159A/E265A catalytic double mutant of XT6 were found to be isomorphous to those of native XT6. They were used for a full measurement of 1.8,Å resolution diffraction data at 100,K (90.9% completeness; Rmerge = 5.0%). These data are currently being used for the high-resolution structure determination of XT6 and its mutant for mechanistic interpretations and rational introduction of thermostability. [source] | ||||||||||