|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 International Union of Crystallography is pleased to announce that its new open-access journal, IUCrJ, has received its first impact factor of 3.1 in the 2015 Thomson Reuters Journal Citation Reports.
Other highlights from the 2015 Impact Factor results are as follows:
Peter Strickland, Executive Managing Editor at the IUCr, said “being a small not-for-profit organization we take our mission to share scientific knowledge seriously and feel it is our responsibility to represent our global community fairly and equitably. I would like to take this opportunity to thank our authors, editors and reviewers for their continued contributions and service. It is through their commitment to excellence that we achieve all we do”.
The International Union of Crystallography (IUCr) is an International Scientific Union. Its objectives are to promote international cooperation in 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 IUCr fulfils its publication objectives by producing primary scientific journals and reference works such as International Tables for Crystallography. IUCr Journals are the leading journals in their field and are produced to the highest quality standards. The IUCr performs numerous global outreach activities including organizing laboratory workshops and international conferences, as well as supporting the development of young crystallographers.
The need to control pollutant emissions from the combustion of fossil fuels motivates interest in understanding these processes. Combustion phenomena are basically chemical processes with rapid heat production. Thousands of reactions and intermediates are involved in the combustion of practical fuels. Understanding complex chemical reaction processes largely depends on accurate qualitative and quantitative information regarding the intermediates involved. Thus, direct measurements of these key species are critically important. However, detection of ideally all intermediates with modern analytical instruments is no walk in the park, because even the reaction networks of a simple fuel with a single component may contain hundreds of species with concentrations varying from several percent to trace levels. These challenges have motivated the development of a sensitive experimental approach with universal detecting capability.
Synchrotron-based vacuum ultraviolet (VUV) photoionization mass spectrometry is sensitive and has proven to be a powerful approach for chemical kinetic studies of combustion.
The molecular beam sampling system is used to extract sampled gases with a free-jet rapid expansion in which the sampled molecules are "frozen" as the jet reaches a collisionless free-molecular flow.
An undulator-based vacuum ultraviolet beamline (BL03U), intended for combustion chemistry studies, has been constructed at the National Synchrotron Radiation Laboratory (NSRL) in Hefei, China. The beamline is connected to the newly upgraded Hefei Light Source (HLS II), and could deliver photons in the 5-21 eV range, with a photon flux of 1013 photons s-1 at 10 eV when the beam current is 300 mA.
The beamline serves three endstations which are designed for respective studies of premixed flame, fuel pyrolysis in flow reactor, and oxidation in jet-stirred reactor. Each endstation contains a reactor chamber, an ionization chamber where the molecular beam intersects with the VUV light, and a home-made reflection time-of-flight mass spectrometer. The performance of the beamline and endstations with some preliminary results is presented in a paper recently published in the Journal of Synchrotron Radiation [Zhou et al. (2016), J. Synchrotron. Rad. 23, doi: 10.1107/S1600577516005816].
External beam radiotherapy is a technique commonly used for the treatment of tumours. The most widely used particles for radiotherapy are protons, electrons and X-rays. An important physical quantity used to describe the effects induced by a radiation beam is the absorbed dose, which represents the mean energy imparted to matter per unit mass. The dose distribution inside the patient is of fundamental importance to assess the effectiveness of the treatment. Indeed, the aim of any radiotherapy treatment is to cause as much damage as possible to cancer cells while harming only a few of the healthy ones.
With the aim of reducing the damage to healthy tissues, increasingly sophisticated beam techniques have been developed, e.g. three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, stereotactic radiation therapy and tomotherapy.
A device capable of focusing a photon beam towards a target volume could pave the way to an innovative radiotherapy methodology, and a group of scientists using an optical component to meet this goal have demonstrated how this might be achieved using a Laue lens [Paternò et al. (2016), J. Appl. Crystallogr. 49, 468-478; doi:10.1107/S1600576716000716].A Laue lens is an optical component composed of a set of crystals that produce a convergent beam exploiting X-ray diffraction in transmission geometry. Employment of a system formed by a properly designed Laue lens coupled with an X-ray unit to selectively irradiate tumours is proposed by the scientists. A convergent beam leads to a depth dose profile with a pronounced peak at the focal depth, which may result in a high precision of the dose delivery. The scientists carried out a design study to determine the geometry and the optimal features of the crystals composing the lens. The resulting instrumentation and experimental techniques constitute a system suitable for irradiating both sub-cm and larger tumour masses efficiently. A dose of 2Gy can be delivered to a small tumour in a few seconds, sparing at the same time the surrounding tissues.
CrystalDirect streamlines the process of preparing crystals for X-ray diffraction experiments. Whereas scientists currently have to harvest and treat the crystals by hand, samples processed at EMBL’s high-throughput crystallisation (HTX) lab in Grenoble can now be loaded in the system at one end and the relevant data collected at the other, with little more than a mouse-click in-between.
This fully automated system, described in a recent article [Zander et al. (2016), Acta Cryst. D72, 454-466; doi:10.1107/S2059798316000954] is making crystallography much more accessible, also for scientists from other fields who may not have the training required to handle fragile crystals. It could pave the way for a much wider use of the technique and for collaborations with other scientific fields.
Following crystallisation, a typical crystal has to go through several steps: harvesting, soaking, and cryo-cooling, before it can be analysed by X-rays. Until now these had to be done by hand and required a lot of time and skills. The teams of Jose Antonio Marquez and Florent Cipriani, both at EMBL-Grenoble, collaborated to automate this process with some creative innovations.
Crystals are now grown on a very thin plastic film that can be laser-cut and carried automatically to the next processing step, thus removing the need to find and harvest the microscopic samples by hand. It makes the process much smoother and safer for the crystals that undergo less mechanical stress.
When applied to structure-based drug design projects, in which samples have to be soaked with a ligand before X-ray analysis, the plastic film becomes a gentle mixer. The solution with the ligand is deposited on top of the film, above the crystal, and a robot punctures a tiny hole in it to allow the ligand to mix slowly and gently with the crystal and bind together.
Finally, most protein crystals have to be cooled to very low temperatures before X-ray analysis. At that stage the plastic film becomes a sieve when the robot punctures another tiny hole in it to gently remove all the solution surrounding the crystal. The sample can then be dipped in liquid nitrogen and cryo-cooled directly and in isolation. Traditionally this step was preceded by the addition of chemicals, like glycerol, to protect the crystals from the damage caused by the freezing of water in the solution; without water around this step is not necessary, thus removing the risk of chemical damage to the crystal.
These developments improve the quality and the quantity of the crystals that finally reach the X-rays for analysis. They also make crystallography easier to access since scientists can control everything remotely through the web-based crystallization information management system (CRIMS), potentially opening up the field to many more applications.
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.