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52 citations found for Hayakawa,

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Preliminary crystal data have been obtained for the first time for a monomeric isocitrate dehydrogenase. The enzyme crystallizes in space group C2 with a = 137.1, b = 54.6, c = 126.4 Å, [beta] = 108.2°.

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The expression, purification, crystallization and preliminary X-ray diffraction studies of the protein TraF from the E. coli F plasmid are reported.



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A monomeric mutant of Azami-Green from G. fascicularis was expressed, purified and crystallized using the sitting-drop vapour-diffusion method. The crystal belonged to space group P1 and diffracted X-rays to 2.20 Å resolution.

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Acta Cryst. (2014). A70, C1641
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Two isoforms of the heterodimeric enzyme succinyl-CoA synthetase (SCS) exist in the mitochondria of humans. One is specific for ATP, while the other is specific for GTP. Both catalyze the reversible reaction: succinate + CoA + NTP [rightwards harpoon over leftwards harpoon] succinyl-CoA + NDP + Pi, where N denotes adenosine or guanosine. SCS is best known as an enzyme of the citric acid cycle where the reaction generates NTP. In the reverse direction, SCS replenishes succinyl-CoA required for the catabolism of ketone bodies and for heme synthesis. Nucleotide-specific forms are thought to be required for SCS to serve its different metabolic roles. The nucleotide specificity lies in the [beta]-subunit [1], and the [beta]-subunit of human ATP-specific SCS has been shown to interact with the C-terminus of erythroid-specific aminolevulinic acid synthase (ALAS2) [2]. ALAS2 catalyzes the committed step in heme synthesis: succinyl-CoA + Gly [rightwards harpoon over leftwards harpoon] 5-aminolevulinate + CoA + CO2. An interaction between SCS and ALAS2 makes biological sense, since this could provide channeling of succinyl-CoA from SCS to ALAS2. We hypothesize that the interaction is with the carboxy-terminus of the [beta]-subunit of ATP-specific SCS because sequence comparisons show that the [beta]-subunit of ATP-specific SCS has a carboxy-terminal extension when compared to other SCSs' [beta]-subunits. To test this hypothesis, we added a carboxy-terminal His8-tag to the [alpha]-subunit of human ATP-specific SCS and mutated the codon for Thr 396[beta] to a stop codon. This truncated version of human ATP-specific SCS has been produced in E. coli and purified. As well as testing to see if truncated human ATP-specific SCS interacts with ALAS2, we are using the truncated version in crystallization trials. Crystals of full-length human ATP-specific SCS diffract to only 3.2 Å and our goal is to obtain better-diffracting crystals of the complex of ATP with truncated human ATP-specific SCS.

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Acta Cryst. (2014). A70, C1641
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Two isoforms of the heterodimeric enzyme succinyl-CoA synthetase (SCS) exist in the mitochondria of humans. One is specific for ATP, while the other is specific for GTP. Both catalyze the reversible reaction: succinate + CoA + NTP [rightwards harpoon over leftwards harpoon] succinyl-CoA + NDP + Pi, where N denotes adenosine or guanosine. SCS is best known as an enzyme of the citric acid cycle where the reaction generates NTP. In the reverse direction, SCS replenishes succinyl-CoA required for the catabolism of ketone bodies and for heme synthesis. Nucleotide-specific forms are thought to be required for SCS to serve its different metabolic roles. The nucleotide specificity lies in the [beta]-subunit [1], and the [beta]-subunit of human ATP-specific SCS has been shown to interact with the C-terminus of erythroid-specific aminolevulinic acid synthase (ALAS2) [2]. ALAS2 catalyzes the committed step in heme synthesis: succinyl-CoA + Gly [rightwards harpoon over leftwards harpoon] 5-aminolevulinate + CoA + CO2. An interaction between SCS and ALAS2 makes biological sense, since this could provide channeling of succinyl-CoA from SCS to ALAS2. We hypothesize that the interaction is with the carboxy-terminus of the [beta]-subunit of ATP-specific SCS because sequence comparisons show that the [beta]-subunit of ATP-specific SCS has a carboxy-terminal extension when compared to other SCSs' [beta]-subunits. To test this hypothesis, we added a carboxy-terminal His8-tag to the [alpha]-subunit of human ATP-specific SCS and mutated the codon for Thr 396[beta] to a stop codon. This truncated version of human ATP-specific SCS has been produced in E. coli and purified. As well as testing to see if truncated human ATP-specific SCS interacts with ALAS2, we are using the truncated version in crystallization trials. Crystals of full-length human ATP-specific SCS diffract to only 3.2 Å and our goal is to obtain better-diffracting crystals of the complex of ATP with truncated human ATP-specific SCS.

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Acta Cryst. (2011). A67, C290
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Variations at room and liquid-nitrogen temperatures have been observed of the energy-dispersive integrated X-ray reflection intensity from an InSb single crystal across the In K absorption edge by the use of a multi-channel solid-state detector. The results show that the relative intensities from a nearly perfect crystal change as a function of the temperature above and below the absorption edge, but there is no such change in a nearly mosaic crystal. This variation observed in a nearly perfect crystal is characteristic of an absorbing monatomic perfect crystal and can be explained in terms of the dynamical theory of diffraction including anomalous scattering.

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Errors in separating diffuse scattering resulting from local order from that from static and dynamic displacements have been examined; the Borie-Sparks symmetry procedure was employed, which includes second-order terms in the displacements. The largest source of error when X-rays are employed is the variation in the ratio of scattering factors across the volume measured in reciprocal space. Large errors in the Warren local-order parameters result for clustering systems with displacement terms of the same order as the local-order parameters (or larger), but not if the size terms are smaller. For systems with local order the errors in these parameters are small. Uncertainties in the size terms are always appreciable. Other errors that were considered are: higher-order terms, extrapolation under Bragg peaks, errors in Compton scattering, background and surface roughness, and uncertainties in composition or polarization resulting from a monochromator.

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Collective oscillations of deformed ions, called scissors modes, in their unit cells were predicted some time ago. Here it is proposed to detect them by measuring using a SQUID the associated variation of the magnetic field.

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Acta Cryst. (1993). A49, c47
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The Sb-Te systems are important for optical memories. The local structures of these Sb-Te systems are crucial to understand the properties. Here we study three different Sb-Te systems, Sb2Te3, c- and a-SbTe (c; crystalline, a; amorphous) by use of XANES analyses. The present calculations for Sb2Te3 system show quite good agreement with the observed spectra. In contrast to Sb2Te3 system, both c- and a-SbTe systems, in which a ratio of Sb to Te is 3, are metastable; both of the structures have not been known yet. We thus investigate these local structures by use of the multiple scattering approach, and propose a possible model for each of c- and a-SbTe.

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With a triple-axis low-energy electron diffractometer, the intensity curves of the specular reflexion 00 from the cleaved face (001) of a MgO crystal were measured against the glancing angle, for the electrons in the energy range from 180 eV to 500 eV and for three crystal azimuths in a range near [010]. By the use of diagrams drawn on the basis of the Ewald construction to indicate the surface wave resonance conditions for various reciprocal rods, a number of fine structures as well as gross features of the intensity curves were interpreted fairly well in terms of the resonance effect.

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A brief review is given of the Borie-Sparks method of measuring and separating the diffuse scattering in alloys due to local displacements of atoms from lattice sites. Experimental techniques are reviewed with particular emphasis on simple computer controls, dead time, monochromators and specimens. After this, sources of error in the measurements are discussed and simple methods for assessing these errors presented. Equations for estimating higher-order terms than those included by Borie and Sparks are presented. It now appears that a thorough analysis of the errors needs to be made for each measurement prior to its publication. As this kind of experiment is readily automated and easily analyzed for errors with modern computers, this should now become standard procedure. It is also suggested that intensities in electron units be kept on file and made available when requested, as is done with structure factors.

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Diffuse scattering from FexO was measured at 840°C. Relatively sharp peaks were observed along the [h00] direction near the NaCl-type fundamental peaks.

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A computer program for the separation of a composite peak into the components and the background has been written in Fortran. Each component is approximated by a function of the form

y(x) = c [1 + ({{x - d}\over{e}})^{2}]^{-f},

where c, d, e and f are the parameters to be determined by a least-squares method. Arbitrary, known or assumed relations among the parameters of different components may be read in to reduce the number of independent parameters and save computation time or, in other cases, to offer a better chance of separating a complex composite peak by varying a subset of the parameters.

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General equations are presented for the diffuse scattering due to local ionic arrangements and displacements in systems with more than one ion per lattice point. Up to fourth-order terms are included. These are placed in a form easy to evaluate in specific cases; examples are given of a solid-solution oxide, and an oxide with vacant sites. Methods for employing these equations for the separation of the various contributions are discussed.

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