|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.|
Radiation damage has been a curse of macromolecular crystallography from its early days but recent work to systematically quantify its effect on nucleoprotein complexes suggests that RNA may protect these complexes [Dauter et al. (2016). Acta Cryst. D72, 601-602; doi:10.1107/S2059798316006550].
The problem of radiation damage was very acute when diffraction data were measured from crystals kept at ambient temperatures. The introduction of cryo-cooling techniques to some extent alleviated the severity of the damaging effects incurred by protein and nucleic acid crystals, but the very intense synchrotron sources now used may destroy diffracting crystals after minutes or seconds of exposure. Not only does the quality of diffraction data and structure solution processes suffer, but, more importantly, radiation damage may lead to misinterpretation of chemical and biological results and to false mechanistic conclusions. Radiation damage has thus become a hot topic of contemporary macromolecular methodology; dedicated international workshops are held every two years and the proceedings have been published in the Journal of Synchrotron Radiation.
The effects of radiation damage are manifested globally as a decrease in the total crystal diffraction power, a change of unit-cell dimensions, an increase of crystal mosaicity or eventually its cracking and disintegration. However, even after absorbing smaller energy doses, many specific local effects of damage can be identified within the structures of macromolecules.
Particularly active is this field is the group at the University of Oxford headed by Elspeth Garman. In a recent paper [Bury et al. (2016). Acta Cryst. D72, 648-657; doi:10.1107/S2059798316003351] this group and their collaborators describe an ingenious method to systematically quantify the effect of increasing absorbed dose on individual atoms of the structure, and then apply it to a crystal structure containing simultaneously an un-complexed protein and its complex with RNA.
Over a large dose range, the RNA was found to be far less susceptible to radiation-induced chemical changes than the protein. Unexpectedly, the RNA binding was observed to protect otherwise highly sensitive residues within the RNA-binding pockets distributed around the outside of the protein molecule. Additionally, the method enabled a quantification of the reduction in radiation-induced disordering upon RNA binding, directly from the electron density.
The paper thus presents a novel objective methodology for judging the effects of radiation damage on macromolecular crystals that will certainly be extremely helpful for the community of macromolecular crystallographers.
William David, Professor of Chemistry at the University of Oxford in the Department of Chemistry, has achieved the distinction of being elected Fellow of the world’s most eminent and oldest scientific academy in continuous existence: the Royal Society, founded in 1660. There are approximately 1600 Fellows and Foreign Members, of the Royal Society, including around 80 Nobel Laureates. Each year up to 52 Fellows and 10 Foreign Members are elected from a group of 700 candidates who are proposed by the existing Fellowship.
Professor William David FRS has a long history with the International Union of Crystallography and our current Vice President of the International Union of Crystallography Professor Mike Glazer recounts his personal story of Professor David’s achievements.
“When I arrived in Oxford in 1976 having come from Cambridge with my research group I was presented with an Oxford student to join us, this was Bill David, who had completed his Degree in Physics. I set him to work in the field of ferroelasticity in crystals. Once he had settled into the project he took the subject to heart and began to come up with a series of new ideas which later formed the basis for several publications. We worked together on a number of experiments but eventually Bill's prodigious ability and understanding of his research topic showed that he was an excellent and independent researcher. His D Phil thesis in the end consisted of two extremely fat volumes for which his internal examiner never forgave me! About ten landmark papers came out of this work. After leaving us he went to work at ISIS where he quickly established his reputation working mainly in powder diffraction. He was one of the first to work on the structures of high temperature superconductors and the famous Buckyballs. He has gone on to a post in the Oxford Chemistry Department where he has been working on the crystallography of hydrogen storage materials. Gifted both as an experimentalist and theoretician, he is truly an all-round scientist who well deserves his Fellowship of the Royal Society”.
A list of Professor David’s papers published by the IUCr can be found here.
In order to fulfill its roles to promote international cooperation in crystallography and to contribute to the advancement of crystallography in all its aspects the IUCr regularly sponsors symposia and workshops on topics relevant to crystallography. There is a well defined procedure that should be followed when applying for sponsorship. The rules can be found here.
Part of the condition of sponsorship includes the following
If you are organizing a meeting and wish to be considered for IUCr support please visit http://www.iucr.org/iucr/sponsorship/meetings.html
Dental burs are used extensively in dentistry to mechanically prepare tooth structures for restorations (fillings); dental burs can be made of stainless steel, diamond or tungsten carbide (WC) cemented with cobalt or nickel. Generally, dental burs come in different kinds and shapes. Each of these kinds of burs is used for a specific function when drilling into the crown of a tooth to create a cavity in which filling material is placed. Stainless steel burs are used if the cutting is pursued at speeds slower than 5000 rpm, while at high speeds diamond-coated burs are most efficient in carving the brittle enamel, and WC burs are most efficient in cutting dentin.
Little has been reported on the bur debris left behind in the teeth, and whether it poses potential health risks to patients. The bur debris can remain within the prepared tooth structure, or be ingested or inhaled, and, owing to their sharp edges, can become lodged in soft tissue. In one study, magnetic resonance images revealed the presence of dental bur artifacts in both second premolar areas of the mandible.
A group of scientists in Canada [Hedayat et al. (2016). J. Synchrotron Rad. 23, doi:10.1107/S1600577516002198] aimed to image dental bur debris under dental fillings, and allude to the potential health hazards that can be caused by this debris when left in direct contact with the biological surroundings, specifically when the debris is made of a non-biocompatible material.
Non-destructive high resolution micro-computed tomography using hard X-rays 05ID-2 beamline at the Canadian Light Source was used to image dental bur fragments under a composite resin dental filling. The bur’s cutting edges that produced the fragment were also chemically analysed. The technique revealed dental bur fragments of different sizes in different locations on the floor of the prepared surface of the teeth and under the filling, which places them in direct contact with the dentinal tubules and the dentinal fluid circulating within them. Dispersive X-ray spectroscopy elemental analysis of the dental bur edges revealed that the fragments were made of tungsten carbide-cobalt, which is bio-incompatible.
The amount of bur fragments found in the teeth is small, and it is uncertain if, or to what degree, this constitutes a biohazard to patients. Accordingly, further research is needed to investigate the effect of the non-biocompatible dental bur fragments.
A new definitive reference to the Cambridge Structural Database (CSD) has been published [Groom et al. (2016), Acta Cryst. B72, 171-179; doi:10.1107/S2052520616003954]. The article provides updated information on the use, development and future of this database.
In 2015 the number of entries in the CSD surpassed 800,000. This is twice the number of entries in the database less than a decade ago. Along with the significant number of new structures published per year, what has changed in the database is the complexity of the structures being published: the average number of atoms per structure and the average molecular weight have increased, and there has also been an increase in the proportion of structures that are polymeric or that have resolved disorder.
The database provides value in two distinct ways. The first simply relates to the aggregation and standardisation of structures and the second comes from the unique study of the collection of entries. Discoverability of data by chemists and biologists is enabled by establishing links to datasets from services such as ChemSpider and PubChem. Links from ChemSpider and PubChem have been established for over 52,000 compounds that could be reliably identified using the International Chemical Identifier Standard (InChI).
CSD community web services provide free access to the entire collection of individual structures. As well as these services there are a number of other avenues to explore and exploit the data, ranging from free lookup tools such as CellCheckSCD to advanced search, analysis and validation tools in the CSD-System. More specialist applications can be found in the CSD-Enterprise Suite.Although the CSD contains all published crystal structures, it has been estimated that only 15% of structures determined are ever published. Automatic links in software used during structure determination, the ease with which structures can be deposited, attribution of credit in the form of a DOI and continued demonstration of the value to science of depositing crystal structures may help close this gap.