|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.|
A beam circulated for the first time in the pioneering SESAME synchrotron at 18:12(UTC+3) on 11 January 2017. The next step will be to store the beam.
This is an important milestone on the way to research getting underway at the first light-source laboratory in the Middle East. SESAME was established under the auspices of UNESCO before becoming a fully independent intergovernmental organisation in its own right in 2004. SESAME’s Members are Bahrain, Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, the Palestinian Authority and Turkey. Its mission is to provide a world-class research facility for the region, while fostering international scientific cooperation. The first call for proposals to carry out research at SESAME was recently issued.
Talking to reporters, Professor Khaled Toukan, SESAME Director said, “SESAME is now opening for business.”
SESAME, which stands for Synchrotron-light for Experimental Science and Applications in the Middle East, is a light-source; a particle accelerator-based facility that uses electromagnetic radiation emitted by circulating electron beams to study a range of properties of matter. Experiments at SESAME will enable research in fields ranging from medicine and biology, through materials science, physics and chemistry to healthcare, the environment, agriculture and archaeology.
“This is a great day for SESAME”, said Professor Sir Chris Llewellyn-Smith, President of the SESAME Council. “It’s a tribute to the skill and devotion of the scientists and decision-makers from the region who have worked tirelessly to make scientific collaboration between countries in the Middle East and neighbouring regions a reality.”
The first circulating beam is an important step on the way to first light, which marks the start of the research programme at any new synchrotron light-source facility, but there is much to be done before the experiments can get underway. Beams have to be accelerated to SESAME’s operating energy of 2.5 GeV. Then the light emitted as the beams circulate has to be channelled along SESAME’s two day-one beamlines and optimised for the experiments that will take place there. This process is likely to take around six months, leading to first experiments in the summer of 2017.This is a short excerpt taken from a press release published by SESAME
Acta Crystallographica Section C: Structural Chemistry is pleased to announce the appointment of two new Section Editors, Professors Larry Falvello and Jonathan White.
Since 1991, Falvello has been Professor of Inorganic Chemistry at the University of Zaragoza, where he is also a member of the Aragón Materials Science Institute. Falvello's research programme in the physical properties and transformations of molecular solids combines the synthesis of new coordination compounds of transition metals and lanthanoids, using ligands rich in functional groups, with their structural characterization and studies of their physical properties and possible transformations.
Falvello has been Co-Editor at Acta Crystallographica Section C since 2002 and served as Deputy Section Editor in 2013-2014. He was Associate Editor of Comments on Inorganic Chemistry from 2002 to 2014. Having been trained near the end of the "old times" of crystallography and having lived the advances of the past four decades, he sees Acta Crystallographica Section C: Structural Chemistry as being uniquely positioned to maintain rigorous standards in the publication and conservation of structural results, while at the same time providing its readers with the extended chemical context that motivated a particular study and, more importantly, with the advances in chemical understanding that resulted from that study.
White was appointed to the University of Melbourne School of Chemistry in 1991, and has been Professor of Chemistry there since 2014.
White’s wide research programme includes structural organic chemistry, where he has applied the Structure Correlation Principle to a number of organic chemical reactions and rearrangements. He is also particularly interested in the use of accurate low-temperature X-ray determinations of model organic compounds to investigate donor-acceptor interactions between a variety of functional groups in both organic and organometallic compounds.
White has been Co-Editor at Acta Crystallographica Section C since 2011. He has been the Associate Editor for crystallography for the Australian Journal of Chemistry from 2010 and is a consultant crystallographer to the ACS journal Organic Letters.
Both see Acta Crystallographica Section C as a journal of chemical crystallography where significant structures are presented in the context of the underlying chemistry. They see the journal being of interest to a wide audience from materials scientists and structural chemists to researchers using amongst other techniques, magnetic resonance, electronic spectroscopy, and those involved in computational modelling and the knowledge-based exploration of chemical structures.You can see a list of IUCr papers published by Professor J.M. White here, and IUCr papers published by Professor Larry Falvello here.
The IUCr would like to congratulate the structural biologist Nenad Ban, who is to be awarded the Ernst Jung Prize for Medicine 2017 for his description of the atomic structure of cellular protein production machinery.
In a press release from the Jung Foundation Ban says, “I am delighted and honoured to be receiving the Ernst Jung Prize, on behalf of not only myself but my whole team. This award is also an acknowledgement of the interdisciplinary approach in structural biology that we have built up over many years at ETH in order to study cellular function”. In addition he says, it highlights the importance of fundamental research for understanding medically relevant cellular processes.
The Ernst Jung Prize for Medicine is the Jung Foundation for Science and Research’s medical award which was first awarded in 1976. The prize is currently valued at 300,000 Euros.
Laureates of the Ernst Jung Prize for Medicine rank amongst some of the top representatives in their field.This is a short extract taken from a press release issued by ETH Zurich
The 16th International Conference on Small-Angle Scattering (SAS2015) was held in Berlin, Germany, in 2015. A fully open-access virtual special edition of Journal of Applied Crystallography publishes work that provides insights into ongoing developments in the field of small-angle neutron and X-ray scattering (SANS and SAXS) covering different areas of fundamental and applied research. Some of the highlights from the issue include a paper from Lehmkühler et al. (2016) which describes the use of X-ray cross correlation analysis applied to the investigation of colloidal crystals. For the case of poly(methyl methacrylate) colloids it is shown how information beyond the static structure factor can be deduced from coherent X-ray scattering experiments, for example, enabling assignment of a face-centred cubic structure to the crystal. In a different direction the work by Perkins et al. (2016) dwells on the current state of the atomistic modelling of scattering data and reviews the achievement of the Collaborative Computational Project for Small Angle Scattering (CCP-SAS). Certainly these developments will be important for the future when increasingly complex systems will probably need to be characterised by SAS with atomistic resolution.
SAS has become increasingly important over the years for the investigation of soft matter systems. An interesting example of such an investigation is given by Prevost et al. (2016), which successfully shows how to obtain detailed structural information on so-called “ultra-flexible microemulsions”. This is a novel type of self-assembled system that exhibits microemulsion structures even in the absence of a typical surfactant, as was elucidated here using a combination of SAXS and wide-angle X-ray scattering.
Synthetic systems can also be of high scientific interest as demonstrated in a paper by Kaneko et al. (2016) in the case of syndiotactic polystyrene cocrystals with polyethylene glycol dimethyl ether. The temperature-dependent changes from crystalline to more amorphous structures were obtained by combining SANS investigations with simultaneous Fourier transform infrared spectroscopy measurements.
Another way of coupling SAS experiments with complementary information is shown by Jordan et al. (2016), who demonstrate how size exclusion chromatography (SEC) can be coupled to SANS experiments. Instrumentation is also the focus of Li et al. (2016), who report on the state of the BioSAXS beamline BL19U2 at the National Centre for Protein Sciences Shanghai. This new synchrotron SAXS beamline is dedicated to meeting the increasing demands of researchers from the field of structural biology.
The topics contained in the special issue describe the particular directions in which SAS is developing at the moment and which will become increasingly important in the future. There will no doubt be further substantial advances of the SAS technique, itself, and its application to solve important scientific questions in diverse research areas.This is a short extract taken from an editorial published in J. Appl. Cryst. (2016), 49, 1858-1860
We are sad to announce that Dr Douglas Dorset passed away on 8 December 2016.
Douglas Dorset's career as an electron crystallographer started when he joined Dr Donald Parson's electron-crystallography laboratory at Roswell Park Cancer Institute in 1971. In 1973 he moved to the Medical Foundation of Buffalo - now the Hauptman-Woodward Medical Research Institute - where he headed the Electron Diffraction Department and did the fundamental work for which he is best known. Douglas moved to ExxonMobil Research and Engineering Company in 2000, investigating the structure of wax crystals and how these change in the presence of modifiers. His research encompassed new methods and an array of crystallographic studies on zeolites, polyolefins and other materials.
In the face of those who said that electron-diffraction data could not yield quantitative results, he argued long and hard that the problem of dynamical scattering could be overcome and that electron-diffraction data could yield ab initio structure determinations. He was responsible for bringing the work on electron crystallography of Vainshtein and Zvyagin in Moscow to the attention of a larger western audience. He developed techniques to overcome the problems of the missing cone of data, dynamical scattering, radiation damage and sample problems. His breadth of applications included polymers, waxes, zeolites, fibers, cholesterol derivatives, fullerenes, phthalocyanines, solid solutions of paraffins and proteins at low resolution.
Douglas received the A. L. Patterson Award in 2002 from the American Crystallographic Association. He was within the top 1% of most-cited authors in the chemical literature, worldwide, 1981-1997 (compilation of David A. Pendlebury, Institute for Scientific Information). He was a member of the IUCr Commission on Electron Diffraction (now Electron Crystallography) from 1993 to 2002 (Chair 1999-2003), and a Co-editor of Acta Crystallographica Section A from 1999 to 2011. He was on the Editorial Board of the Journal of Electron Microscopy Technique (1988-2010) and Associate Editor of Microscopy Society of America Bulletin from 1992 to 1994.
Douglas was involved in organizing several of the IUCr International Schools of Crystallography in Erice, Sicily, as well as many other schools on crystallography around the world and numerous sessions at major national and international meetings. He was a good teacher and co-supervised research students in several countries, an enthusiastic supporter of many young researchers - who are now active electron crystallographers. Douglas always had time to discuss the finer points of an analysis, or to mentor others in need of some inspiration. He encouraged many of us in our work during the early years of electron crystallography, when its power was not fully embraced by the global crystallography community. His impressive knowledge of all aspects of crystallography will be remembered by all who met him.Lisa Baugh, Mark Disko, William Lamberti, Karl Strohmaier, William Duax, John Fryer, Sven Hovmöller, Xiaodong Zou, Laurence Marks and Stavros Nicolopoulos
Biological small-angle X-ray scattering (SAXS) is an experimental technique that provides low-resolution structural information on macromolecules. The surge of popularity of the technique is a result of recent improvements in both software and hardware, allowing for high-throughput data collection and analysis, reflected in the increasing number of dedicated SAXS beamlines such as BM29 at the ESRF, P12 at EMBL Hamburg and B21 at Diamond Light Source.
However, as for most other macromolecular structural techniques, radiation damage is still a major factor hindering the success of experiments. The high solvent proportion of biological SAXS samples means that hydroxyl, hydroperoxyl radicals and hydrated electrons are produced in abundance by the radiolysis of water when it is irradiated with X-rays. These radicals can then interact with the protein molecules, ultimately leading to protein aggregation, fragmentation or unfolding. Furthermore, molecular repulsion due to protein charging can also decrease the scattering at low angles.
Common methods used to reduce radiation damage to biological SAXS samples are generally concerned with limiting the X-ray exposure to any given volume of sample. In an analogous manner, cryo-cooling samples down to 100 K for SAXS (cryoSAXS) has been reported to increase the dose tolerance of SAXS samples by at least two orders of magnitude.
Applications of the above radiation damage mitigation approaches are unable to completely circumvent its detrimental effects, in particular the change of the scattering profile throughout the experiment. It is necessary to determine whether any two scattering profiles are similar so that noise can be reduced by averaging over similar curves.
For experiments by different researchers to be inter-comparable, the progression of radiation damage is most usefully tracked as a function of the dose absorbed by the sample. RADDOSE-3D is a free and open source software program used to calculate the time- and space-resolved three-dimensional distribution of the dose absorbed by a protein crystal in a macromolecular crystallography experiment; however, there is no equivalent software available for SAXS. Radiation damage studies in SAXS thus currently require the experimenters to correctly parameterize the experiment and manually calculate a single estimate of the dose within the sample.In a paper published by Brooks-Bartlett et al. [(2017), J. Synchrotron. Rad. 24, doi:101107/S1600577516015083], extensions to RADDOSE-3D are presented, which enable the convenient calculation of doses for SAXS experiments, reducing the burden of manually performing the calculation. Additionally, the authors have created a visualisation package to assess the similarity of SAXS frames and used these tools to assess the efficacy of various radioprotectant compounds for increasing the radiation tolerance of the glucose isomerase protein sample.