|The IUCr is an International Scientific Union. Its objectives are to promote international cooperation in crystallography and to contribute to all aspects of crystallography, to promote international publication of crystallographic research, to facilitate standardization of methods, units, nomenclatures and symbols, and to form a focus for the relations of crystallography to other sciences.|
Since the discovery of the diffraction of X-rays by crystals just over 100 years ago, X-ray diffraction as a method of structure determination has dominated structural research in materials science and biology. However, many of the most important materials whose structures remain unknown do not readily crystallize as three-dimensional periodic structures. Crystallization can also alter the properties of the material to be studied: a crystallized protein may not function in the way that it would in its natural state, and confining nanostructures such as carbon nanotubes within a crystal lattice can also alter their behaviour.
In the March issue of Acta Crystallographica Section A, Jüstel, Friesecke and James propose a new method for studying these kinds of structures, using twisted X-rays [Acta Cryst. (2016). A71, doi:10.1107/S2053273315024390]. They show that the key to obtaining diffraction data from non-crystalline but symmetric structures, such as helices, lies in matching the symmetry of the incoming radiation to the symmetry of the structure to be studied.
The interesting resonance effects of twisted waves with helical structures suggests that this could be a promising new method for structure determination: send twisted X-rays onto a helical structure, align the waves, the structure and the detector axially, and the outgoing radiation shows sharp, discrete peaks as the incoming wavelength and the amount of twist are varied. Structure prediction from the diffraction pattern then works in exactly the same way as in the case of crystals. Using computer simulations, the authors show that the accuracy of a structure determined using twisted X-rays would be comparable to that obtained by 'classical' X-ray methods.
Remarkably, the method can applied to some of the most important structures in biology and a striking number of the structures that are emerging in nanoscience: buckyballs and many fullerenes, the parts of many viruses, actin, carbon nanotubes (all chiralities), graphene and a large collection of other two-dimensional structures, such as the currently important structures of black phosphorus and the dichalcogenides.
Now someone just has to design the machine to put the twist into the X-rays!
The Prize consists of a medal, a certificate and a financial award, and is presented once every three years during the triennial International Congresses of Crystallography. The recipients to date are as follows:
|1987||Perth, Australia||Professor J.M. Cowley and Dr A.F. Moodie|
|1990||Bordeaux, France||Professor B.K. Vainshtein|
|1993||Beijing, People's Republic of China||Professor N. Kato|
|1996||Seattle, USA||Professor M.G. Rossmann|
|1999||Glasgow, UK||Professor G.N. Ramachandran|
|2002||Geneva, Switzerland||Professor M.M. Woolfson|
|2005||Florence, Italy||Professor P. Coppens|
|2008||Osaka, Japan||Dr D. Sayre|
|2011||Madrid, Spain||Professor E. Dodson, Professor C. Giacovazzo and Professor G.M. Sheldrick|
|2014||Montreal, Canada||Professor A. Janner and Professor T.W.J.M. Janssen|
The eleventh Prize, for which nominations are now being invited, will be presented at the Hyderabad Congress in August 2017.
Scientists who have made contributions of exceptional distinction to the science of crystallography are eligible for the Ewald Prize, irrespective of nationality, age or experience. The Selection Committee will give careful attention to the nominations of outstanding scientists who have not yet won a Nobel Prize. Either an exceptionally distinguished scientific career or a major scientific accomplishment may be recognised. Current members of the Selection Committee and the President of the IUCr are not eligible. No restrictions are placed on the time or the means of publication of the nominee's contributions. The Prize may be shared by more than one contributor, but not more than three, to the same scientific achievement.
Nominations for the Ewald Prize should be submitted electronically using the Ewald Prize Nomination Form, to the Executive Secretary of the International Union of Crystallography, 2 Abbey Square, Chester CH1 2HU, England (email@example.com). Copies of the Nomination Form and the names of the Selection Committee may be obtained from http://www.iucr.org/iucr/ewald-prize. The closing date for nominations is 31 August 2016.
Ebolavirus and Marburgvirus belong to a virus family called Filoviridae and can cause severe hemorrhagic fever in humans. The outbreak of Ebola virus disease (EVD) in West Africa demonstrates the grave threat that these viruses pose globally to human health. While the EVD outbreak is slowly losing momentum, it is still unprecedented, resulting in over 23 000 cases and more than 9000 deaths by late 2015.
There are two species of Marburgvirus (MARV and RAVV) and five species of Ebolavirus (Zaire, Reston, Sudan, Taï Forest and Bundibugyo) within the Filoviridae family of negative-sense, single-stranded RNA (ssRNA) viruses. In each of these viruses the ssRNA encodes seven distinct proteins. One of them, the nucleoprotein (NP), is the most abundant viral protein in the infected cell. It is tightly associated with the viral RNA in the nucleocapsid and is essential for transcription, RNA replication, genome packaging and nucleocapsid assembly prior to membrane encapsulation.
Until recently, the nucleoprotein was one of two proteins encoded by the Ebolavirus genome, that have not yet had their structures characterized. Since this protein is critical for the assembly and replication of the virus, it is recognised as a suitable drug target. Recently a group of scientists [Baker et al. (2016). Acta Cryst. D72, 49-58; doi: 10.1107/S2059798315021439] have shown that the homologous C-terminal domains of NP from two related pathogenic species of Ebolavirus, Taï Forest and Bundibugyo, have structures that are highly similar to that of a Zaire variant, in spite of differences in the amino-acid sequence. Interestingly, the related NPCt domain from MARV has a structure that is significantly different from the Ebolavirus consensus structure.
In addition, structural characterization of NPCt from the different Ebolavirus species is important since the Ebolavirus NPCt has also been identified as a possible target for the development of species-specific diagnostic tests.
Richard Henderson, member of the scientific staff in the MRC (Medical Research Council) Laboratory of Molecular Biology in Cambridge, UK, and editorial advisory board member of the open-access journal IUCrJ, will receive the 2016 Alexander Hollaender Award in Biophysics.
In 1975, Henderson and colleague Nigel Unwin determined the structure of bacteriorhodopsin - a light-driven proton pump found in the membrane of Archaea - using electron microscopy. This was revolutionary because the technique usually requires a stain that can obfuscate details, but Henderson and Unwin realized they could instead place the crystals on a thin carbon support and eliminate the stain. Starting in the 1990s, Henderson again revolutionized the field of structural biology when he turned his sights on another method for determining protein structure: cryoEM. In this technique, proteins are flash-frozen by plunging into liquid ethane then imaged with electron microscopy. Henderson and others made major improvements to the method - developing better sensors for electron microscopes, as well as better software for the system - that improved cryoEM to such an extent that it is now the preferred technique for determining protein structures.
The Alexander Hollaender Award in Biophysics is presented every three years and carries with it a $20,000 prize. The Award recognizes outstanding contributions made to the field of biophysics.
Two papers in the current Journal of Applied Crystallography give a specification of an updated Crystallographic Information File format, and describe an accompanying application programming interface (API) and reference implementation. The CIF2.0 format was formally approved by the maintenance committee COMCIFS in August 2014, and the paper of Bernstein et al. (2016) represents the first formal publication of the new file format. The CIF API of Bollinger (2016) provides software developers with tools for using the new format, for validating the syntax of their files against the new standard, and for converting data files between old and new formats if required.
Since CIF was designed from the outset as an archival format, publishers and databases will continue to support the existing CIF1.1 format indefinitely. It is not expected that any existing CIF-writing software will need to change in the immediate future.
So what is the purpose of the new specification? It introduces a number of novel features, such as the Unicode character set to handle data internationalization, and complex data types which can make it easier to handle vector or matrix objects. A particular benefit is that it will allow relationships between data items to be defined using methods expressions in future CIF dictionaries, opening the way to more powerful automatic validation of the contents of a data file, and this is likely to be the first area in which the new format will be used. The timescale for applying CIF 2.0 features to the data files themselves will depend very much on the desire of individual communities to take advantage of the potential benefits of the new format.
We would encourage software developers with an interest in these new features to become familiar with the website cif2.iucr.org, and consider signing up to the cif-developers mailing list (www.iucr.org/lists/cif-developers) or the new CIF2 forum soon to be launched at forums.iucr.org.James Hester
When cryoEM images are obtained from protein nanocrystals the images themselves can appear to be devoid of any contrast. A group of scientists from the Netherlands has now demonstrated that lattice information can be revealed and enhanced by a specialized filter.
The procedure described by van Genderen et al. [(2016). Acta Cryst. D72, 34-39; doi: 10.1107/S205979831502149X] paves the way towards full three-dimensional structure determination at high resolution for protein crystals. The authors report on how lattice information can be enhanced by means of a wave finder in combination with Wiener-type maximum-likelihood filtering. The lattice filter is a very powerful tool for selecting and analysing extremely low contrast cryo-images of three-dimensional protein/peptide nanocrystals. It confirms that the three-dimensional crystals are made up from multiple domains that are slightly differently oriented. Indeed, the algorithm can comfortably deal with multiple crystals with very different orientations, unit cells and/or space groups.The authors of the paper propose the new lattice filter as a powerful tool for processing very noisy images with crystal factors (and thus the phase information) hidden within them. The filter is able to discriminate between noise images and the very noisy images with very low contrast which contain crystal-like structures. The lattice filter retains the shape of the spots in Fourier space and also retains any phase gradients within the Bragg spots (which determine the domain structure within the crystal). Thus, it retains all of the significant information from the Bragg spots. This will open the way to combining the phases acquired from stationary, two-dimensional images with intensities of rotation diffraction data taken from the same type of crystals. In this way, the authors expect to be able to phase the diffraction information of protein and peptide crystals.