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Laue Diffraction (laue + diffraction)
Selected AbstractsBragg,(Bragg)m,Laue diffraction and its interference fringePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2009Kenji Hirano Abstract X-Ray rocking curves from side surface of a thin plane-parallel Ge crystal are measured under the condition where the dispersion of the refracted angle is quite large. In the diffracted beams from side surface are observed, which are analysed by using Wagner's approach for Bragg,(Bragg)m,Laue case. The origin of the fringes is explained by the interference between diffraction beams in Bragg,Laue case and that in Bragg,Bragg,Laue case. [source] Two-wave approximation in surface effects in asymmetric Laue crystalsACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2010M. Guida This paper is a study of surface effects, e.g. roughness or asymmetrical cut, in the Laue diffraction of X-rays by crystals, based on the Takagi,Taupin equations. By means of Riemann,Green integrals, first a formal solution has been obtained when the entrance and the exit surfaces are arbitrary. Then a coordinate transformation mapping a propagation domain with arbitrary boundaries into a rectangular domain with straight boundaries is given. Potential measurement errors in -ray wavelength and silicon lattice-parameter measurements by double-crystal diffractometry and X-ray interferometry, respectively, are outlined and anticipated by studying, in the two-wave approximation, the reflection peak shift and extra phase originating from an asymmetrically cut crystal. A relationship between analyser displacement, interferometer-signal phase and relative uncertainty in lattice-parameter measurement is also given. [source] Time-resolved structural studies of protein reaction dynamics: a smorgasbord of X-ray approachesACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2010Sebastian Westenhoff Proteins undergo conformational changes during their biological function. As such, a high-resolution structure of a protein's resting conformation provides a starting point for elucidating its reaction mechanism, but provides no direct information concerning the protein's conformational dynamics. Several X-ray methods have been developed to elucidate those conformational changes that occur during a protein's reaction, including time-resolved Laue diffraction and intermediate trapping studies on three-dimensional protein crystals, and time-resolved wide-angle X-ray scattering and X-ray absorption studies on proteins in the solution phase. This review emphasizes the scope and limitations of these complementary experimental approaches when seeking to understand protein conformational dynamics. These methods are illustrated using a limited set of examples including myoglobin and haemoglobin in complex with carbon monoxide, the simple light-driven proton pump bacteriorhodopsin, and the superoxide scavenger superoxide reductase. In conclusion, likely future developments of these methods at synchrotron X-ray sources and the potential impact of emerging X-ray free-electron laser facilities are speculated upon. [source] Feasibility of one-shot-per-crystal structure determination using Laue diffractionACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2010Sterling Cornaby Crystal size is an important factor in determining the number of diffraction patterns which may be obtained from a protein crystal before severe radiation damage sets in. As crystal dimensions decrease this number is reduced, eventually falling to one, at which point a complete data set must be assembled using data from multiple crystals. When only a single exposure is to be collected from each crystal, the polychromatic Laue technique may be preferable to monochromatic methods owing to its simultaneous recording of a large number of fully recorded reflections per image. To assess the feasibility of solving structures using single Laue images from multiple crystals, data were collected using a `pink' beam at the CHESS D1 station from groups of lysozyme crystals with dimensions of the order of 20,30,µm mounted on MicroMesh grids. Single-shot Laue data were used for structure determination by molecular replacement and correct solutions were obtained even when as few as five crystals were used. [source] Incorporation of methyl-protonated valine and leucine residues into deuterated ocean pout type III antifreeze protein: expression, crystallization and preliminary neutron diffraction studiesACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010Isabelle Petit-Haertlein Antifreeze proteins (AFPs) are found in different species from polar, alpine and subarctic regions, where they serve to inhibit ice-crystal growth by adsorption to ice surfaces. Recombinant North Atlantic ocean pout (Macrozoarces americanus) AFP has been used as a model protein to develop protocols for amino-acid-specific hydrogen reverse-labelling of methyl groups in leucine and valine residues using Escherichia coli high-density cell cultures supplemented with the amino-acid precursor ,-ketoisovalerate. Here, the successful methyl protonation (methyl reverse-labelling) of leucine and valine residues in AFP is reported. Methyl-protonated AFP was expressed in inclusion bodies, refolded in deuterated buffer and purified by cation-exchange chromatography. Crystals were grown in D2O buffer by the sitting-drop method. Preliminary neutron Laue diffraction at 293,K using LADI-III at ILL showed in a few 24,h exposures a very low background and clear small spots up to a resolution of 1.80,Å from a crystal of dimensions 1.60 × 0.38 × 0.38,mm corresponding to a volume of 0.23,mm3. [source] Perdeuteration, purification, crystallization and preliminary neutron diffraction of an ocean pout type III antifreeze proteinACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2009Isabelle Petit-Haertlein The highly homologous type III antifreeze protein (AFP) subfamily share the capability to inhibit ice growth at subzero temperatures. Extensive studies by X-ray crystallography have been conducted, mostly on AFPs from polar fishes. Although interactions between a defined flat ice-binding surface and a particular lattice plane of an ice crystal have now been identified, the fine structural features underlying the antifreeze mechanism still remain unclear owing to the intrinsic difficulty in identifying H atoms using X-ray diffraction data alone. Here, successful perdeuteration (i.e. complete deuteration) for neutron crystallographic studies of the North Atlantic ocean pout (Macrozoarces americanus) AFP in Escherichia coli high-density cell cultures is reported. The perdeuterated protein (AFP D) was expressed in inclusion bodies, refolded in deuterated buffer and purified by cation-exchange chromatography. Well shaped perdeuterated AFP D crystals have been grown in D2O by the sitting-drop method. Preliminary neutron Laue diffraction at 293,K using LADI-III at ILL showed that with a few exposures of 24,h a very low background and clear small spots up to a resolution of 1.85,Å were obtained using a `radically small' perdeuterated AFP D crystal of dimensions 0.70 × 0.55 × 0.35,mm, corresponding to a volume of 0.13,mm3. [source] | ||||||||||