|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.|
The first International School/Workshop on Crystallography for Space Sciences organized as a collaboration of COSPAR, the International Union of Crystallography (IUCr) and the International Astronomical Union in Puebla, Mexico in April 2016 was a great success.
The aim of the Workshop - stellarly directed by Juanma García-Ruiz (CSIC-University of Granada) was to prepare a selected number of participants for the next generation of projects in search of a deeper knowledge and understanding of extraterrestrial minerals and rocks, either large solid bodies or interstellar dust particles, using in-situ and remote analytical techniques.
27 PhD students, postdocs and young staff members took part in the workshop, mostly from Latin America. They learned about modern crystallographic techniques in the fields of diffraction, imaging, spectroscopy and remote sensing. They also learned about the formation of mineral growth patterns in the early Earth, our Moon, Mars and other planets and moons, meteorites and interstellar dust, as well as about the relevance of crystals to the origin of life and detection of primitive life forms. During this workshop the students were also taught about sample preparation techniques. They analyzed their own data, and also data from the missions Discovery and Curiosity, and they learned about data collection on the forthcoming Exomars mission. Portable difractometers and spectrophotometers designed for these missions were used during the field trip for remote analysis of volcanic rocks. Last but not least, all the participants learned about COSPAR (presentation by Mariano Mendez) and the IUCr (by Hanna Dabkowska).
The detailed program of the workshop, with the most important talks included, can be found at the Workshop website.
On the first day of the venue the nearby Popocatepetl volcano erupted, providing the students with ample amount of volcanic ashes to be analyzed - just on their doorsteps! The planned excursion to this volcano, led by the vulcanologist Claus Siebe, was moved to less dangerous locations, though still at the lava deposits (from previous eruptions).
The crystallographic and crystal growth lectures (presented by Jim Britten, Juan Rodriguez Carvajal, Hanna Dabkowska, Yuki Kimura, Jose Antonio Manrique, Chris Mavris, Maria Eugenia Mendoza, Teresa Pi Puig, Juan Manuel Garcia Ruiz and Fernando Rull) were at a very high level and were very much enjoyed by the students. So were the inspiring talks about the Mars missions (presented by Dave Blake on Curiosity, Jorge Vago on Exomars and Pablo Sobron on future missions), about the Hayabusa mission (by Tomoki Nakamura), about meteorite investigations, (by Rafael Navarro-Gonzalez, Fernando Ortega and Jaime Urrutia), about early minerals (by Mark van Zuilen) and about some interesting crystals (by Wulf Depmeier and David Page).
In the afternoons the students worked with the instructors, preparing samples, analyzing them using a portable diffractometer, Raman and infrared spectrophotometer and optical microscopy, and applying methods discussed earlier during the lectures.
The local organizers team, led by Guillermo Tenorio Tagle, Maria-Eugenia Mendoza, Raul Mujica, Teresa Pi Puig and Ulises Salazar, went out of their way to have the group entertained, well fed with delicious food and taught about the impressive local historical sites. We visited Puebla City, ancient pyramids in Cholula and Teotihuacan and we had the opportunity to participate in two very active public events, one the lecture of Jorge Vago in Puebla about the Exomars mission, and the other a round-table discussion on Life on Mars in the Museo UNIVERSUM. We also had opportunities to observe the crystal growth competition organized by Raul Mujica and Maria-Eugenia Mendoza for Puebla schoolchildren, accompanied by the public lecture of Juanma Garcia-Ruiz on Giant Crystals of Naica, to watch the movie The Martian, to discuss it with the experts involved in Mars exploration, and to participate in the concert performed by the very professional, young Esperanza Azteca orchestra.
The school ended with the presentation of the practical works performed by the students on their own samples or samples provided by the organizers.
All the participants - students and teachers alike - found this workshop very educational and very effective. The expectation is that this very successful COSPAR-IUCr collaboration will be repeated in the near future.Submitted by Hanna A. Dabkowska
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.