Welcome to the

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.

announcement


IUCr Executive Committee 2014-2017

[IUCr Executive Committee 2014-2017]

At the twenty third Congress and General Assembly of the International Union of Crystallography Professor Marvin L. Hackert was elected as the new President of the IUCr. The photograph shows the Convener of the Finance Committee and the Executive Secretary alongside Professor Hackert and the other members of the new Executive Committee for the triennium 2014-2017.

Back row: M. J. Cooper (Convener, IUCr Finance Committee), M. H. Dacombe (Executive Secretary). Executive Committee: J. M. Guss, R. Kuzel, M. Takata, W. Depmeier, S. Garcia-Granda. Front row: H. Dabkowska, L. Van Meervelt (General Secretary and Treasurer), M. L. Hackert (President), A. M. Glazer (Vice-President), G. R. Desiraju (Immediate Past President).

Please join the IUCr in welcoming the new Executive Committee and thanking those members retired.

Posted 21 Aug 2014 

announcement


Acta Crystallographica Section F: Structural Biology Communications

f_64At the recent IUCr Congress it was decided to improve the scientific quality of those articles published in Acta Cryst. F that relate to the crystallization of biological macromolecules. For an article to be accepted for publication it should describe more than just the routine crystallization of a macromolecule. Articles describing novel aspects of the crystallization procedure together with new science will be welcomed by the journal, and from 2015 all articles will be published in the category Research Communications. This enhancement should make the articles more relevant and useful to the structural biology community as a whole, and an editorial with further details will be published in the near future.

Posted 19 Aug 2014 

research news


The difficult question of Clostridium difficile


wa5073coverfigThe bacterium Clostridium difficile causes antibiotic-related diarrhoea and is a growing problem in the hospital environment and elsewhere in the community. Understanding how the microbe colonises the human gut when other "healthy" microbes have been destroyed during a course of antibiotics might lead to new ways to control infection. An important clue was reported recently in an open access article published in the journal Acta Crystallographica Section D Biological Crystallography. [Bradshaw et al. (2014). Acta Cryst. D70, 1983-1993; doi:10.1107/S1399004714009997]

Ravi Acharya of the University of Bath, UK, and colleagues have reported the first crystal structure of the C. difficile surface protein Cwp84. This cysteine protease enzyme is found on the surface of the bacterium and assists with production of the microbe's surface-layer, which is likely to play an essential step in the colonisation of the gut. The enzyme cleaves a single polypeptide (surface-layer protein A; SlpA) into low- and high-molecular-weight subunits. Now, Acharya and colleagues have identified three critical regions in a mutant of the enzyme that could represent novel targets for drugs to attack C. difficile by blocking maturation of its surface layer during colonisation.

While C. difficile can be present in the normal, healthy gut (3-5% of adults), when a patient requires treatment for infection with broad-spectrum antibiotics, other protective intestinal microbes are eradicated in the process and the incidence increases to about 20%. This leaves space for the pathogenic C. difficile to grow rapidly unhindered leading to the release of toxins that cause bloating, pain and severe diarrhoea. Sometimes potentially life-threatening pseudo-membranous colitis or toxic megacolon occurs (about 5 to 8% of patients). Outbreaks occur when people ingest the spores, often in contaminated medical facilities and C. difficile is known to kill tens of thousands of people every year worldwide. Mild cases are often resolved by simply halting antibiotic treatment but in more severe cases last-line antibiotics such as vancomycin and metronidazole are often needed. Worryingly, the relapse rate is 20 to 30%.

The team explains that while Cwp84 is essential for correct surface layer formation it may also break down extracellular proteins, such as fibronectin, laminin and vitronectin which are found in the body. Nevertheless, blocking its activity either genetically or chemically prevents proper growth of bacterial colonies even if this is not in itself bactericidal. Disruption of the colonization process might therefore be possible allowing healthy microbes to repopulate the gut and stifle the spread of C. difficile.

The researchers carried out X-ray crystallography at station I03 at Diamond Light Source in Didcot, UK. The resulting high-resolution (1.4 angstrom) diffraction data revealed the structure of the N-terminal propeptide, the cysteine protease domain, and a previously uncharacterized "linker" region that is 170 amino acids long. The linker lies between the cysteine protease domain and the repeat region of Cwp84 which holds it onto the cells surface. The linker region binds calcium and resembles a group of proteins known as lectins, so may have an affinity for carbohydrates which may be vital for correct cell wall processing. The same motifs are present in other types of Clostridium microbes as well as ancient single-celled organisms known as archaea.

The team suggests that the insights their research offers in terms of C. difficile surface layer growth and how this relates to gut colonization could be exploited in developing a new type of drug to treat infection-anti-colonization inhibitors.
Posted 18 Aug 2014

announcement


Dear Colleagues

We are very pleased to announce the launching of the Small Angle Scattering Biological Data Bank (SASBDB, www.sasbdb.org). SASBDB was developed in accordance with the plans of the wwPDB SAS task force to establish a federated system of interconnected databases for X-ray and neutron scattering (SAXS/SANS).

SASBDB is a curated repository that makes experimental SAS data and derived models of biological macromolecules discoverable, citable and downloadable. Within SASBDB, it is possible to browse the scattering data and models, search by various keywords including macromolecule name, buffer composition, experiment setup and author/affiliation details. 3D representations of low resolution ab initio bead models and of the hybrid rigid body models are available. All data sets and models can be freely downloaded.

Presently, SASBDB comprises of 96 experimental data sets and 151 models. Most of the entries contain published data from the studies where SAS was used for the structural analysis of macromolecular solutions (proteins, nucleic acids and complexes). There are also several "benchmark" data from a set of well-characterized commercially available proteins. The SAXS (and, for some proteins, also wide-angle scattering, WAXS) data from these samples were collected using an on-line purification system to ensure sample monodispersity. The benchmark set data and models can be used to test computational approaches, for tutorials etc.

Researchers are welcome to deposit the SAXS/SANS data and models into SASBDB (prior to or after the publication). The submission requires a simple sign-in procedure followed by filling in an on-line deposition form and uploading the data/models. ATSAS and ATSAS-online users may directly use their credentials to sign in. The deposition is pre-moderated, i.e. the entries will be validated before making them public.

ATSAS Team, EMBL-Hamburg
 
Posted 06 Aug 2014 

announcement


A Little Dictionary of Crystallography

[A Little Dictionary of Crystallography: stack]

Edited by André Authier and Gervais Chapuis

This 252-page paperback book is a printed snapshot of the Online Dictionary of Crystallography. It is a reference for authors and referees of IUCr Journals and for research professionals in general: but will also be useful to students and to the general public.

Sample pages are available.

The book is now available for a short time at a specially discounted rate (9 GBP, 11 EUR). Copies may be purchased online at the URL http://tinyurl.com/little-dictionary.

Posted 28 Jul 2014 

announcement


Sixth blind test of organic crystal-structure prediction methods

CCDC_logoOrganic molecules can have a remarkable array of solid forms, including different polymorphs and various multi-component systems, such as salts and co-crystals. The potential diversity of this solid-form landscape presents both opportunities and headaches for the practical use of molecules in solid forms.

Experimental screening of the solid-form landscape can be a time-consuming and expensive process. It’s[Acta B logo] therefore not surprising that over the past 25 years numerous computational methods have been developed to predict crystal structures, providing an alternative or supplement to experimental screening of solid forms and allowing us to explore the solid state of molecules that have yet to be synthesised.

In the case of organic crystal-structure prediction (CSP), progress over the last 15 years has been charted by a series of blind tests of CSP methods that have been hosted by the Cambridge Crystallographic Data Centre (CCDC).

The blind tests of methods have shown great advances in the ability to generate and rank putative crystal structures and in our understanding of cohesion in the solid state. However, many challenges remain in making CSP a reliable and efficient tool. The computational cost of some methods limits their high-throughput use, and reliability and applicability for the full diversity of organic molecules and solid forms remains an open question.

Following dialogue with the CSP community, the CCDC has decided to host a sixth blind test of organic CSP methods. This test will provide the community with a fair benchmark of the state of the art in CSP methodology. We hope that it will, once again, act as a platform for communicating ongoing progress and challenges in CSP and will spur the continued development of these methods. The invitation to participate is an open one.

This test will run from 1 September 2014 until 31 August 2015.

This is an extract taken from Groom, C.R. & Reilly, A.M. (2014),  Acta Cryst. B70, doi:10.1107/S2052520614015923

For further details, or to express interest in taking part in the sixth blind test, please contact Colin Groom (groom@ccdc.cam.ac.uk) or Anthony Reilly (reilly@ccdc.cam.ac.uk). The blind test website can be found at http://www.ccdc.cam.ac.uk/Community/Initiatives/Pages/CSPBlindTests.aspx, and will be updated over time with details, progress and the results of the blind test.

Posted 24 Jul 2014