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Laboratory X-ray Source (laboratory + x-ray_source)
Selected AbstractsImprovement of SAXS measurements on Kratky slit systems by Göbel mirrors and imaging-plate detectorsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-2 2000Alexander Bergmann Laboratory X-ray sources emit a highly divergent beam. The Kratky compact camera is constructed to maximize the intensity in the sample using a slit collimation system. The performance of this camera can be further increased if the primary beam is collimated from a divergent into a parallel beam. A recently developed device for this purpose is the so-called `Göbel mirror'. This mirror is made of parabolically bent multilayers, designed to collimate divergent X-rays from laboratory X-ray sources into a parallel and monochromatic beam of high brilliance. Modification of the block collimation system in combination with a Göbel mirror leads to a different beam geometry, resulting in an intensity increase by a factor of about 10. The gain in intensity implicates the use of imaging-plate detectors, which have a wide linear range in intensity and allow the full use of the increased intensity. Hence the quality of the SAXS data is improved by the higher intensity primary beam, the much lower background due to the exclusive use of Cu K, radiation, and a detection unit which is linear in the measured intensity regime. All these advantages, such as intensity gain, lower background, better quality of the data, are demonstrated with some selected experimental results. [source] Crystallization of the flexible nuclear import receptor importin-, in the unliganded stateACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2009Noelia Roman The transport of macromolecules across the nuclear envelope is an essential eukaryotic process that enables proteins such as transcription factors, polymerases and histones to gain access to the genetic material contained within the nucleus. Importin-, plays a central role in the nucleocytoplasmic transport process, mediating nuclear import through a range of interactions with cytoplasmic, nuclear and nuclear pore proteins such as importin-,, Ran, nucleoporins and various cargo molecules. The unliganded form of the full-length yeast importin-, has been expressed and crystallized. The crystals were obtained by vapour diffusion at pH 6.5 and 290,K. The crystals belonged to space group P21 (unit-cell parameters a = 58.17, b = 127.25, c = 68.52,Å, , = 102.23). One molecule is expected in the asymmetric unit. The crystals diffracted to 2.4,Å resolution using a laboratory X-ray source and were suitable for crystal structure determination. [source] Crystallization of the C-terminal domain of the mouse brain cytosolic long-chain acyl-CoA thioesteraseACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2006Robert Serek The mammalian long-chain acyl-CoA thioesterase, the enzyme that catalyses the hydrolysis of acyl-CoAs to free fatty acids, contains two fused 4HBT (4-hydroxybenzoyl-CoA thioesterase) motifs. The C-terminal domain of the mouse long-chain acyl-CoA thioesterase (Acot7) has been expressed in bacteria and crystallized. The crystals were obtained by vapour diffusion using PEG 2000 MME as precipitant at pH 7.0 and 290,K. The crystals have the symmetry of space group R32 (unit-cell parameters a = b = 136.83, c = 99.82,Å, , = 120°). Two molecules are expected in the asymmetric unit. The crystals diffract to 2.4,Å resolution using the laboratory X-ray source and are suitable for crystal structure determination. [source] Improvement of SAXS measurements on Kratky slit systems by Göbel mirrors and imaging-plate detectorsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-2 2000Alexander Bergmann Laboratory X-ray sources emit a highly divergent beam. The Kratky compact camera is constructed to maximize the intensity in the sample using a slit collimation system. The performance of this camera can be further increased if the primary beam is collimated from a divergent into a parallel beam. A recently developed device for this purpose is the so-called `Göbel mirror'. This mirror is made of parabolically bent multilayers, designed to collimate divergent X-rays from laboratory X-ray sources into a parallel and monochromatic beam of high brilliance. Modification of the block collimation system in combination with a Göbel mirror leads to a different beam geometry, resulting in an intensity increase by a factor of about 10. The gain in intensity implicates the use of imaging-plate detectors, which have a wide linear range in intensity and allow the full use of the increased intensity. Hence the quality of the SAXS data is improved by the higher intensity primary beam, the much lower background due to the exclusive use of Cu K, radiation, and a detection unit which is linear in the measured intensity regime. All these advantages, such as intensity gain, lower background, better quality of the data, are demonstrated with some selected experimental results. [source] Structures of mono-unsaturated triacylglycerols.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2008The , -2 crystal structures of a series of mixed-chain saturated and trans -mono-unsaturated triacylglycerols containing palmitoyl, stearoyl and elaidoyl acyl chains have been solved from high-resolution powder diffraction data, from synchrotron as well as laboratory X-ray sources. The structures crystallized in the space group I2 with two independent molecules forming a dimer in the asymmetric unit, and packed in double-chain length layers. Unlike the corresponding ,-2 structures the solved , -2 structures have different molecular conformations for the symmetric and the asymmetric mixed triacylglycerols, both with the sn -2 chain in a leg position of the chair-shaped conformation. A transformation to the ,-2 structure with the sn -2 chain in the back position is complicated and unlikely to take place in the solid state. A novel ,,-2 polymorph of PSS has been crystallized and its structure has been solved. The melting point (239,K) of this so-called , -2 polymorph is 2,K above that of the , -2 polymorph and almost equal to that of the ,-2 polymorph of PSS. The difference in packing of the , -2 versus, -2 structure explains the slow , -2 to , -2 phase transition. The transition is strikingly similar to the ,2 -3 to ,1 -3 transition in cis -mono-unsaturated triacylglycerols. [source] | ||||||||||