J. Appl. Cryst.の発刊に際して
10 Mar 1970-Vol. 12, Iss: 1, pp 1-1
About: The article was published on 1970-03-10 and is currently open access. It has received 8159 citations till now.
Citations
More filters
TL;DR: The G359F (small subunit) mutant protein of carbamoyl phosphate synthetase is described, which resulted in a complete change in the conformation of the loop delineated by Glu-355 to Ala-364, thereby providing an “escape” route for the ammonia intermediate directly to the bulk solvent.
55 citations
TL;DR: A portable sample viewing and alignment system is described which provides fast and reliable motion positioning for fixed target arrays at synchrotrons and free-electron laser sources.
Abstract: The design and implementation of a compact and portable sample alignment system suitable for use at both synchrotron and free-electron laser (FEL) sources and its performance are described. The system provides the ability to quickly and reliably deliver large numbers of samples using the minimum amount of sample possible, through positioning of fixed target arrays into the X-ray beam. The combination of high-precision stages, high-quality sample viewing, a fast controller and a software layer overcome many of the challenges associated with sample alignment. A straightforward interface that minimizes setup and sample changeover time as well as simplifying communication with the stages during the experiment is also described, together with an intuitive naming convention for defining, tracking and locating sample positions. The setup allows the precise delivery of samples in predefined locations to a specific position in space and time, reliably and simply.
55 citations
Additional excerpts
...Typical examples of the approximate number of crystals used are: 47 crystals for the A22 wild type and 77 crystals for the A22 VP2 H93C type foot and mouth disease virus structures determined at room temperature (Porta et al., 2013), and 30 crystals used in the structure determination of the class…...
[...]
Journal Article•
TL;DR: In this paper, a series of carbon-based nanoparticles have been obtained in syn- thesis conditions corresponding to a variety of reaction temper- atures using Transmission Electron Microscopy (TEM) and infrared (IR) spectrometry.
Abstract: Infrared Laser Pyrolysis (IRLP) of gaseous molecules is a versatile method of synthesising a wide variety of nanopowders. The synthesis mechanism is based on conden- sation of heated gaseous precursors. This is the same mecha- nism as postulated for carbon dust formation in the envelopes of evolved C-rich stars. An advantage of this technique, in con- trast with furnace- or plasma-heated gas phase techniques, is its well-defined reaction zone and its infrared heating process. Using hydrocarbon molecules C2H4 or C4H6 as precursors, a series of carbon-based nanoparticles have been obtained in syn- thesis conditions corresponding to a variety of reaction temper- atures. The nanoparticles were characterised by Transmission Electron Microscopy (TEM) and infrared (IR) spectrometry. Both IR spectrum and molecular organisation appear to depend on the synthesis conditions: the lower the reaction temperature, the stronger the amorphous character and the more intense the IR bands. When present, IR bands are essentially due to aro- matic CC and CH groups. Our experimental results are com- pared with results reported on other carbonaceous compounds and with astronomical observations.
55 citations
Cites background from "J. Appl. Cryst.の発刊に際して"
...The microtexture of these particles is similar to the classical onion-like structure proposed by Heidenreich et al. (1968) for the carbon blacks obtained by incomplete combustion of hydrocarbons....
[...]
TL;DR: The vast diversity of carboxyl–carboxyl(ate) arrangements is reduced to 17 supramolecular motifs and eight catemers, extracted from the CSD.
Abstract: Carboxyl and carboxylate groups form important supramolecular motifs (synthons). Besides carboxyl cyclic dimers, carboxyl and carboxylate groups can associate through a single hydrogen bond. Carboxylic groups can further form polymeric-like catemer chains within crystals. To date, no exhaustive classification of these motifs has been established. In this work, 17 association types were identified (13 carboxyl–carboxyl and 4 carboxyl–carboxylate motifs) by taking into account the syn and anti carboxyl conformers, as well as the syn and anti lone pairs of the O atoms. From these data, a simple rule was derived stating that only eight distinct catemer motifs involving repetitive combinations of syn and anti carboxyl groups can be formed. Examples extracted from the Cambridge Structural Database (CSD) for all identified dimers and catemers are presented, as well as statistical data related to their occurrence and conformational preferences. The inter-carboxyl(ate) and carboxyl(ate)–water hydrogen-bond properties are described, stressing the occurrence of very short (strong) hydrogen bonds. The precise characterization and classification of these supramolecular motifs should be of interest in crystal engineering, pharmaceutical and also biomolecular sciences, where similar motifs occur in the form of pairs of Asp/Glu amino acids or motifs involving ligands bearing carboxyl(ate) groups. Hence, we present data emphasizing how the analysis of hydrogen-containing small molecules of high resolution can help understand structural aspects of larger and more complex biomolecular systems of lower resolution.
55 citations
Cites methods from "J. Appl. Cryst.の発刊に際して"
...The results of the searches were analysed using Vista (CCDC, 1994), and all structures were visualized using Mercury CSD Version 3.3 (Macrae et al., 2008)....
[...]
TL;DR: The rice-like morphologies were formed due to an increase in the effective collisions between the nanoparticles during the MH processing, and the EDXS spectrum was used to verify the chemical compositional of this oxide.
Abstract: In this letter, we report on the obtention of hafnium oxide (HfO2) nanostructures by the microwave-hydrothermal method. These nanostructures were analyzed by X-ray diffraction (XRD), field-emission gum scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDXS), ultraviolet–visible (UV–vis) spectroscopy, and photoluminescence (PL) measurements. XRD patterns confirmed that this material crystallizes in a monoclinic structure. FEG-SEM and TEM micrographs indicated that the rice-like morphologies were formed due to an increase in the effective collisions between the nanoparticles during the MH processing. The EDXS spectrum was used to verify the chemical compositional of this oxide. UV–vis spectrum revealed that this material have an indirect optical band gap. When excited with 488 nm wavelength at room temperature, the HfO2nanostructures exhibited only one broad PL band with a maximum at around 548 nm (green emission).
55 citations
References
More filters
TL;DR: The goals of the PDB are described, the systems in place for data deposition and access, how to obtain further information and plans for the future development of the resource are described.
Abstract: The Protein Data Bank (PDB; http://www.rcsb.org/pdb/ ) is the single worldwide archive of structural data of biological macromolecules. This paper describes the goals of the PDB, the systems in place for data deposition and access, how to obtain further information, and near-term plans for the future development of the resource.
34,239 citations
TL;DR: New features added to the refinement program SHELXL since 2008 are described and explained.
Abstract: The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as `a CIF') containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.
28,425 citations
TL;DR: CCP4mg is a project that aims to provide a general-purpose tool for structural biologists, providing tools for X-ray structure solution, structure comparison and analysis, and publication-quality graphics.
Abstract: CCP4mg is a project that aims to provide a general-purpose tool for structural biologists, providing tools for X-ray structure solution, structure comparison and analysis, and publication-quality graphics. The map-fitting tools are available as a stand-alone package, distributed as `Coot'.
27,505 citations
TL;DR: The PHENIX software for macromolecular structure determination is described and its uses and benefits are described.
Abstract: Macromolecular X-ray crystallography is routinely applied to understand biological processes at a molecular level. However, significant time and effort are still required to solve and complete many of these structures because of the need for manual interpretation of complex numerical data using many software packages and the repeated use of interactive three-dimensional graphics. PHENIX has been developed to provide a comprehensive system for macromolecular crystallographic structure solution with an emphasis on the automation of all procedures. This has relied on the development of algorithms that minimize or eliminate subjective input, the development of algorithms that automate procedures that are traditionally performed by hand and, finally, the development of a framework that allows a tight integration between the algorithms.
18,531 citations
TL;DR: A description is given of Phaser-2.1: software for phasing macromolecular crystal structures by molecular replacement and single-wavelength anomalous dispersion phasing.
Abstract: Phaser is a program for phasing macromolecular crystal structures by both molecular replacement and experimental phasing methods. The novel phasing algorithms implemented in Phaser have been developed using maximum likelihood and multivariate statistics. For molecular replacement, the new algorithms have proved to be significantly better than traditional methods in discriminating correct solutions from noise, and for single-wavelength anomalous dispersion experimental phasing, the new algorithms, which account for correlations between F+ and F−, give better phases (lower mean phase error with respect to the phases given by the refined structure) than those that use mean F and anomalous differences ΔF. One of the design concepts of Phaser was that it be capable of a high degree of automation. To this end, Phaser (written in C++) can be called directly from Python, although it can also be called using traditional CCP4 keyword-style input. Phaser is a platform for future development of improved phasing methods and their release, including source code, to the crystallographic community.
17,755 citations