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International Union of Crystallography

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.


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The International Union of Crystallography unveils new journal platform

The International Union of Crystallography (IUCr) has launched a brand new IUCr Journals website, for researchers involved in structural determination.

The new design is clean, bright and adaptable to different screen sizes. Many subtle changes have been introduced to the article format to help improve the overall clarity of the HTML text.

A toolbox of useful features takes the form of a set of buttons. Whenever appropriate, the same buttons appear on the summary (abstract) page or table of contents associated with the article. This allows the reader to obtain relevant information about the article (e.g. citation format, usage statistics, supporting information) from the most convenient entry point. So you do not have to be actually reading an article, for example, to obtain a three-dimensional visualisation of the structures it describes ‑ particularly useful for non-subscribers who wish to learn more about a non-open-access article.

A particularly useful new feature is the detailed usage information available for every article, showing numbers of citations as recorded by a number of monitoring services, as well as a detailed interactive graph of all article downloads in both PDF and HTML formats from the IUCr Journals server.

The new website provides clearer marking of the article’s category, citation and digital object identifier (DOI), together with its copyright and licensing information and a clear indication if it is open access. Prominent at the top of each page is a link to the article’s status and publication history as certified by the CrossMark system.

IUCr Journals have always excelled in providing free and easy access to supporting information, especially the structural data files (CIFs, structure factors or Rietveld profiles). Now, experimental, coordinate and geometry data from the CIF can be viewed inline at the end of any article reporting a small-unit-cell structure.

The "3dview" visualisation interface has been improved and provides a common interface for three-dimensional interactive images of all classes of structure: biological macromolecules, inorganics, small molecules, metal–organic complexes. For small structures, there are also tools to view or predict powder profiles, and to perform similarity searches among other structures published in IUCr Journals.

Each journal home page highlights a number of recent articles of particular interest or significance. In many cases these highlighted articles have accompanying commentaries establishing their importance, either in featured articles on the general IUCr homepage or as commissioned companion pieces in the journals themselves.

New journal sidebars allow for a variety of content related to the specific focus of each journal. For example, Acta Crystallographica Section B has a sidebar link to a gallery of amazing visualisations of incommensurate modulated structures published in the journal. These use JSmol to produce animations in time that correspond to lattice distortions in space. Journal of Synchrotron Radiation focuses on beamline papers in a sidebar.

The journal home pages also feature constantly updating lists of latest, most read and most cited articles. For each journal, a new "about" page provides a detailed synopsis of that journal’s main features, and includes an interactive map showing the distribution of authors worldwide.

While the scholarly publication landscape is changing in the 21st century, IUCr Journals' commitment to quality, to capturing, reviewing, critiquing and disseminating the most important advances in the structural sciences, and to promoting interdisciplinary research is unwavering. And, we hope, with this refreshed online platform, this will become more apparent than ever to the widest range of discerning readers.

Posted 01 Oct 2015 


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Guinier Prize Award ceremony at SAS2015

A happy celebration of a lifetime of scientific achievments at the SAS2015 banquet. Left to right: Jill Trewhella (IUCr SAS Commission Chair), Ching-chih Chen, Sow Hsin Chen, Peter Fratzl (SAS2015 Program Chair). Photo © HZB, Michael Setzpfandt
Sow Hsin Chen delivers his plenary talk to an attentive audience and continues taking questions long after! Photos © HZB, Michael Setzpfandt

Sow Hsin Chen from the Department of Nuclear Science and Engineering of the Massachusetts Institute of Technology (MIT) received the 2015 Guinier Prize at the SAS2015 meeting in Berlin. On Thursday afternoon, September 17, he delivered a plenary talk covering just a few of his many contributions to science and to the field of small-angle scattering methods development and applications in fundamental studies of soft condensed matter. He described his most recent work using small-angle neutron scattering to measure and discover a density minimum in deeply supercooled water that further demonstrates the plausibility of the existence of the second critical point in supercooled water. He also spoke about many of his long-lasting contributions in the field of small-angle scattering, such as:

  • the first use of neutron contrast variation to elucidate and propose the microstructure of SDS micelles and reversed micelles;
  • formulation of the so-called decoupling approximation to handle the calculation of the small-angle neutron scattering intensity distribution of interacting non-spherical particles in solution and to correct for the effect of polydispersity;
  • a fractal approach to calculating the scattering intensity distribution of protein-detergent complexes in solution;
  • devising a contrast variation method to measure the average mean curvature of surfactant films in a bi-continuous micro-emulsion;
  • proposing and implementing a Clipped Random Wave Model which enabled the successful measurement of the average Gaussian Curvature of the surfactant film.

The Guinier prize recognizes either lifetime achievement, or a major breakthrough, or an outstanding contribution to the field of small-angle scattering. As Sow Hsin Chen’s plenary unfolded it was clear to all present that he met all three of these criteria. As he acknowledged the contributions of his many students, post docs and collaborators throughout his talk, it was evident that he had educated and inspired a whole generation of today's research leaders in his field of study.

After his plenary talk, at the Conference banquet, accompanied by his wife Ching-chih Chen, Professor Chen was presented with his prize and some small gifts to remember Berlin and the occasion.

Jill Trewhella
Chair, IUCr Commission on Small-Angle Scattering
Posted 30 Sep 2015 


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The Opening Ceremony of the European Crystallography Meeting (ECM29) and the 8th Max Perutz Award winner

ECM29We are happy to report that the IUCr YouTube channel now hosts the Opening Ceremony of the 29th European Crystallography Meeting which includes the presentation of the 8th Max Perutz Award to John R. Helliwell, and John's Award Lecture. The lecture compellingly captures what the Award citation called 'his long, generous and fruitful dedication to developing all aspects of the use of synchrotron radiation for crystallography'. John was visibly delighted to receive the highest honour of the European Crystallographic Association, of which he is a former President, and in his account of a long and distinguished scientific career, his respect and affection for a host of scientific colleagues shone through with synchrotron-like brightness. John's enthusiasm for his subject and his passion for education and outreach can also be read in a recent interview he gave to the IUCr to mark the presentation of the Max Perutz Award.

Posted 23 Sep 2015 

research news

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Predicting X-ray diffuse scattering from translation-libration-screw structural ensembles

rr5095Protein flexibility is essential for enzymatic turnover, signalling regulation and protein-protein interactions. The motions enabling these functions vary in length from a few angstroms to many nanometres and include transitions between side-chain rotamers, loop openings and closings, and rigid-body subunit rotations. Multiple crystal structures are routinely compared to identify these motions and to derive hypotheses about the role of correlated motions in executing protein function. However, if only a single crystal form is available, evidence of concerted motion must be extracted from the spread in the electron density. Diffuse X-ray scattering can help by reporting on correlated atomic displacements. Although recent technological advances are increasing the potential to accurately measure diffuse scattering, computational modelling and validation tools are still needed to quantify the agreement between experimental data and different parameterizations of crystalline disorder. A new tool, phenix.diffuse, addresses this need by calculating diffuse scattering from Protein Data Bank (PDB)-formatted structural ensembles [Van Benschoten et al. (2014). Acta Cryst. D71, 1657-1667; doi:10.1107/S1399004715007415]

With the increasing availability of modelling tools, the lack of high-quality three dimensional data sets is now a key bottleneck in diffuse scattering analysis. One challenge in data collection is that long X-ray exposures can be required to reveal diffuse features. This can lead to blooming around saturated Bragg spots in diffraction images collected using commercially available charge-coupled device (CCD) area detectors, which in turn can interfere with accurate diffuse intensity measurements. Blooming can be mitigated either by reconfiguring some of the charge collection elements in each pixel as a drain to channel away excess charge (an option not currently available in commercial detectors), or by breaking single long exposures into multiple shorter exposures. Alternatively, more accurate measurements of the diffuse signal can potentially be achieved with pixel-array detectors, which possess much higher dynamic ranges as well as very small point-spread functions.

Methods for processing diffuse scattering data from raw image frames to complete a reciprocal-space map are under active development. Because acoustic scattering is maximized at Bragg peaks, diffuse signal will be most straightforward to measure in intervening regions. These methods will be applied to new data sets of simultaneous Bragg and diffuse scattering data. Instead of being included in the background correction in estimated Bragg peak intensities, these diffuse intensities will increase the data available for refinement, enable more accurate quantification of interatomic distances and allow the simultaneous refinement of multiple coupled protein motions. 

Posted 21 Sep 2015 

leading article

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The importance of the IYCr2014 resolution

The International Year of Crystallography - 2014 - was an extraordinary one for our science. Across the world, hundreds of activities highlighted the importance of our subject, and brought it, perhaps for the first time, to the notice of schoolchildren, teachers, the general public, politicians and policy makers. The formal milestones of the year occurred during major international events around the globe: the Opening Ceremony in Paris, France in January 2014; regional summit meetings in Karachi, Pakistan (April), Campinas, Brazil (September) and Bloemfontein, South Africa (October); and the Closing Conference in Rabat, Morocco in April 2015. From each of these events came a formal communique, often highlighting the challenges that face our science and its practitioners, especially early career scientists, in our modern, busy world.

However, the final resolution, carrying the title that was the theme of the Rabat conference - Crystallography for the next generation - is different. It is optimistic in outlook, and carries a strong commitment to securing the future of crystallography, from representatives of several International Scientific Unions and international non-governmental agencies. The resolution embraces the needs to enhance the stature of crystallography, to build capacity in developing regions of the world, and to extend further the public understanding of science in general and crystallography in particular.

It is, of course, right that such a commitment be given by senior officers of such bodies, and it is to be hoped that this commitment will be seen, heard and acknowledged by science directors and policy makers around the world. However, it is also right that individuals, who have been touched and inspired by the International Year of Crystallography, should have the opportunity to endorse publicly these goals and the specific actions identified in the resolution. This can be done through an online form that allows individuals to add their names to the list of those who support the IYCr2014 resolution goals and actions. Already more than 100 individuals have shown their support. Please take a few moments to read the resolution in detail, recognise its importance, and - if you agree with these objectives - add your own name to the list. The next generation of crystallographers will thank you for it.

IUCr_logo UNESCO_logo TWAS_logo ICSU_ROA_logo IUBMB_logo IUPAP_logo IMA_logo IMA_logo
Michele Zema, IUCr
Posted 10 Sep 2015

research news

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No such thing as ghosts?

ghost.gifCrystallographers are always pushing boundaries when it comes to determining complex structures with less than optimal experimental data. We've already heard that 'there's no such thing as a free lunch' [Caliandro et al. (2005). Acta Cryst. D61, 556-565 and 1080-1087]; now comes another improbable-sounding approach: The Phantom Derivative (PhD) method [Giacovazzo (2015). Acta Cryst. A71, 483-512; doi:10.1107/S2053273315013856]. PhD is based on the random generation of 'ancil' structures with the same unit cell and the same space group as the target structure. These are used to create 'derivatives' that have no experimental diffraction amplitudes, but which assist in solving the target structure from scratch (ab initio structure determination).

Giacovazzo uses the term 'derivative' in analogy with isomorphous replacement techniques, in which one or more variants of the target structure containing different heavy atoms (but retaining the same unit cell) are actually prepared and used to collect diffraction data. However, he notes that the differences in the methods are much greater than the analogies, as stressed by the 'phantom' nature of the data - there are none! Indeed, the ancil structures need not contain heavy atoms, needn't be closely related to the target structure, and don't even have to be realistic.

A companion paper [Burla et al. (2015). Acta Cryst. D71, 1864-1871; doi:10.1107/S1399004715013024] describes how PhD can be used in protein crystallography to extend and refine phase sets obtained by molecular-replacement techniques. In this, it is competitive with any other current approach. Indeed, the best results were obtained by integrating PhD with existing density-modification, Vive la Difference and free-lunch techniques.

It remains to be seen how PhD will perform when it comes to ab initio structure solution. It is possible that, for the first time in crystallographic history, we may have a technique capable of solving structures from relatively poor data (only up to 4-6 Å resolution) and without any upper limit to the complexity of the structure. PhD is also likely to prove useful when combined with any ab initio or non-ab initio phasing technique: these two new papers just open the way.

Posted 08 Sep 2015