The IUCr Newsletter is the web magazine of the International Union of Crystallography. Since 1993, the IUCr Newsletter has been published quarterly and distributed to over 13,000 crystallographers worldwide. In August 2018, it was transformed into a dynamic digital platform with a fresh new look. Its aim remains to bring together the crystallographic community.
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William L. Duax Patricia Potter Jane Griffin The IUCr Newsletter is distributed electronically to 13,000 crystallographers and other interested individuals in 102 countries. Articles from the Newsletter are also available on this web site by following the links on the left-hand side. Feature articles, meeting announcements and reports, information on research or other items of potential interest to crystallographers may be submitted to the editor at any time. Items will be selected for publication on the basis of suitability, content, style, timeliness and appeal. Please send contributions to: newsletter@iucr.org Matters pertaining to advertisements should also be sent to the above address. Email address changes or corrections and requests to be added to the mailing list should be accomplished through the Subscribe and Unsubscribe hyperlinks above. Reuse permissions • The original article in which the material appeared is cited. • Copyright permission is indicated by the wording "Reproduced with permission of the International Union of Crystallography Newsletter". In electronic form, this acknowledgement must be visible at the same time as the reused materials, and must be hyperlinked to the IUCr Newsletter (http://www.iucr.org/news/newsletter). Please be sure to include the following information: • The title, author(s) and page extent of the article you wish to republish, or, in the case where you do not wish to reproduce the whole article, details of the section(s) to be reproduced. • The volume/issue number and year of publication in which the article appeared, and the page numbers of the article. • Details of the publication in which you wish to reprint the Newsletter material. • If the material is being edited or amended in any way, a copy of the final material as it will appear in your publication. • Contact details for yourself, including a postal address. |
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Annual Reports to the IUCr Executive Committee
The IUCr Newsletter (ISSN 1067-0696; coden IUC-NEB) is published quarterly (4x) by the International Union of Crystallography (IUCr Executive Secretary e-mail execsec@iucr.org). Members receive the IUCr Newsletter by virtue of country membership in the IUCr. Periodical postage rates paid at Buffalo, NY and additional mailing offices. POSTMASTER: Please send changes of address to IUCr Newsletter Editorial Office, c/o Hauptmann-Woodward Medical Research Institute, 700 Ellicott St. Buffalo, NY 14203 USA.
The entire Journal of Synchrotron Radiation (JSR) editorial team would like to take this opportunity to inform all our readers, authors and supporters about the coming transition to open access. All papers submitted to JSR after 1 October 2021 will be for open-access publication. By taking this step, JSR is supporting a journey towards open science in general.
JSR was founded in 1994 (Hasnain, Helliwell & Kamitsubo, 1994) with the aim of providing comprehensive coverage of the entire field of synchrotron radiation. Almost immediately its coverage also started to include free-electron laser research (Doniach, 1996) including instrumentation, theory, computing and scientific applications in areas such as biology, nanoscience and materials science. Just in the last year, authors from 35 different countries published in the journal, the top five countries represented being the USA, Japan, Germany, China and France. Throughout the past 26 plus years JSR has been an up-to-date information resource for scientists and engineers in the field of synchrotron radiation.
Now, the JSR Main Editors, with the International Union of Crystallography (IUCr) Journals Editor-in-Chief and the IUCr Editorial Office, supported by the IUCr Executive Committee, believe that switching to open access will benefit research in this area by disseminating it more easily and rapidly to the global synchrotron and free-electron laser science communities. The clear goal of this initiative is to induce the smoothest and most research-oriented transformation possible of JSR from a behind-paywall subscription-based publishing model to an open-access-based publishing model. All of us increasingly work under conditions in which open access supports researchers in every aspect of their workflow. New detailed instructions on general policies for submission, possible open-access discounts, and other guidelines and templates are discussed at https://journals.iucr.org/s/services/openaccess.html. However, we wish to emphasize that all open-access articles will undergo initial editor assessment and the same rigorous peer review process as at present. The management of the peer review process will continue to focus on the high standards and rapid publication expected for IUCr journals.
At this time, we wish to express our enormous appreciation of JSR’s supporting (facility) institutions. We also hope that more supporting institutions will join with JSR as we move forward from here. JSR supporting institutions are entitled to a certain number of open-access article processing charge (APC) vouchers per year for papers reporting work carried out at their facilities. Alternatively, if the contact author’s home institution is included in a transformative or read-and-publish arrangement with the IUCr’s publication partner, Wiley, those authors will be able to publish open-access research or review articles in JSR with no direct (APC) charge. Currently, such arrangements exist in Austria, Finland, Germany, Hungary, Ireland, Italy, Liechtenstein, the Netherlands, Norway, Spain, Sweden, Switzerland and the UK. Contact authors with connections to IUCr (Associates, members of national affiliates, World Directory of Crystallography, etc.) will receive modest APC discounts. Meanwhile, discounts (50%) for authors from lower middle income countries and waivers (100%) from low income countries will be issued. However, please note that a major difference from present arrangements is that all submitting authors will need to apply for such discounts and waivers at the time of submission and payments will be handled via Wiley authors services (for more details see https://journals.iucr.org/s/services/openaccess.html).
As the transition to open access proceeds, the JSR Editorial Board welcomes feedback from the JSR research community, especially from authors, on the new open-access procedures, and is keen to know what is working well and what needs some adjustment.
The change to open access is made with every faith in the future. The Editors fully believe that the publishing of scientific research with global open access providing worldwide visibility without barriers demonstrably leads to more downloads, citations and more impact for authors. The increased citation of open-access articles published in JSR since 2018 is shown graphically in the figure.
![[Fig. 1]](https://www.iucr.org/__data/assets/image/0007/152674/me6140fig1.png)
Figure 1. Graphic showing the increased citation of open-access articles published in JSR since 2018.
The JSR Editors embrace both the idea and concept of making research freely available to all researchers, and are committed to coordinate and establish best principles to facilitate a smooth transition from subscription to open access. The Editors wish all the best to all JSR authors for the future and look forward to seeing your forthcoming high-quality open-access research submissions to JSR.
Doniach, S. (1996). J. Synchrotron Rad. 3, 260–267.
Hasnain, S. S., Helliwell, J. R. & Kamitsubo, H. (1994). J. Synchrotron Rad. 1, 1–4.
This article was originally published in J. Synchrotron Rad. (2021). 28, 1273–1274.
Carroll Johnson’s professional career adhered to the postulate that one should change directions every five years to avoid stagnation. His career profile, in approximately five-year segments as he described himself, starting in 1955, was as follows: (1) graduate school (MIT-PhD): biophysics & fiber diffraction theory, (2) postdoctoral positions: X-ray crystallography (Institute for Cancer Research, Philadelphia) & neutron diffraction (Oak Ridge National Laboratory), (3) staff member at ORNL until retirement in 1996: thermal motion & computer graphics, (4) crystal physics, (5) artificial intelligence concepts, (6) artificial intelligence applications, (7) machine vision engineering & project management, and (8) crystallographic topology & neutron diffraction. Carroll remained very active in retirement. His post-retirement activities involved “crystallographic topology, personal computing and enjoying life.” He personally noted selected professional activities in his career: 1975–1976 sabbatical, studying artificial intelligence at the Computer Science Department, Stanford University, 1977 President of the American Crystallographic Association (ACA), 1981 studying more artificial intelligence at the Naval Research Laboratory, 1996 Chairing the ACA General Interest Group, and 1997 receiving the ACA Buerger Award.
He was a native of Colorado and started a pre-med program in 1947 at the University of Colorado, which was put on hold by four years in the United States Marine Corps, which included a year in the Korean war. Afterward, he completed a BS degree in Animal Nutrition and Physiology (1955) from Colorado State University. He went on to complete a PhD degree in Biophysics (1959) at MIT, doing his thesis on polypeptide packing studied by X-ray diffraction. After that, he did a postdoc (1959–1962) at the Institute for Cancer Research (now the Fox Chase Cancer Center), Philadelphia, with Lindo Patterson, whose group at that time included Jenny Glusker, Dick van der Helm, Max Taylor, Eric Gabe and Jean Minkin. During his postdoctoral work in Philadelphia, he began working on the computer program for plotting atomic thermal ellipsoids, which he later finished at ORNL.
![[Carroll Johnson]](https://www.iucr.org/__data/assets/image/0011/152669/Johnsoncolorized.jpg)
Carroll started at ORNL in 1962, beginning as a postdoctoral assistant working on neutron diffraction in Henri Levy’s group. After converting to a staff scientist, he spent his entire professional career in the Chemistry Division at ORNL, retiring in 1996. Over the years at ORNL, his immediate colleagues and his group’s mission changed a lot. In the early days, he worked with Henri Levy, Bill Busing and George Brown. Later he worked with Michael Burnett on many programming applications. He was an independent thinker, mathematically inclined, and pursued projects always at the forefront and often beyond current thinking. Carroll Johnson’s scientific success grew markedly with the publication of his most celebrated computer program, ORTEP (Oak Ridge Thermal-Ellipsoid Plot Program). This rapidly became a favorite of crystallographers and protein crystallographers to make illustrations of crystal structures for conference presentations and publications. ORTEP was first released in an ORNL Technical Report in 1965; see historical note https://www.umass.edu/molvis/francoeur/ortep/ortepnews.html. A key strength of ORTEP was its capacity to generate stereoscopic images automatically. ORTEP 2 was released in 1976 and ORTEP 3 in 1996. The latter is still available from the official ORTEP website, https://ornl-ndav.github.io/ortep/ortep.html. ORTEP is one of the most cited and miscited publications in crystallography, with over 30,000 citations. ORTEP even is commonly used as a word for a crystal structure drawing with atomic displacement ellipsoids, whether it was made with ORTEP or not. A Google search on “ORTEP” returns 798,000 hits. Atomic displacement ellipsoid drawing options are now standard in all the major crystal and molecular structure drawing programs. Carroll was an expert on thermal motion analysis as studied by diffraction and sought better and new ways to use this aspect of crystal structure analysis.
Bill Busing, Henri Levy, Hal Smith and Pete Peterson had built and were operating a three-circle neutron diffractometer at the Oak Ridge Research Reactor for several years working on chemical crystallography prior to Carroll Johnson’s arrival at ORNL. Data collection by that diffractometer was controlled by a computer program run on the ORACLE (an early main-frame computer at ORNL), which prepared a paper punch control tape conveying the angle settings to the motors. The intensities were also recorded on paper punch tape. When minicomputers became available in 1965, Busing and Levy programmed a PDP-5 computer to control a four-circle Picker diffractometer, first as an X-ray instrument and then as a neutron instrument at ORNL’s High Flux Isotope Reactor (HFIR), which had just started operating. Seminal crystal structural studies of hydrogen-containing compounds were done with the HFIR diffractometer. Still, the science it could do was limited because no low-temperature sample cooling device was available on the instrument. The HFIR four-circle diffractometer was operated only intermittently through the 1980s. After a 3+ year safety review shutdown of HFIR ending in 1990, Carroll Johnson and Michael Burnett upgraded the neutron diffractometer at HFIR, with a new Huber goniometer, a low-temperature sample stage (5–300K), and a new 7-pixel array detector. I was responsible for the powder diffractometer at HFIR at that time but was interested in doing structural studies with single crystals as well, so I worked with Carroll to learn as much as I could about the operation of his single-crystal diffractometer. The interest in single-crystal neutron diffraction studies by the Chemistry Division kept dwindling with each retirement and passing of Levy’s old group members. Carroll had been the youngster in that group when he started, but now he was ready for a change: retirement was next, and it was at that time that he transferred the HFIR four-circle diffractometer to me in the neutron scattering group. Since then, we have upgraded that instrument multiple times, and it has grown with the help of a new younger generation of scientists hired in the ORNL Neutron Scattering Division to be extremely productive doing research in materials physics and chemistry. I thank Carroll for setting us on that course.
The American Crystallographic Association was his professional society home. He began attending ACA meetings in 1964 and, with few exceptions, attended all their meetings until he retired, and some after that. The ACA was an extended family for him, and he often planned family vacations around the annual meetings, bringing along Carol, his wife, and his children, which numbered five in the end. He gave back to the ACA by presenting many talks and posters, serving on the Crystallographic Computing Committee in 1965–1967, then as President-elect in 1976, President in 1977, Past-President in 1978, and Chairing the General Interest Special Interest Group 1994–1996.
Carroll Johnson was married to Carol for 69 years and had five children, ten grandchildren and seven great-grandchildren. His family especially enjoyed how his curiosity and inquisitiveness were not limited to his work and touched all aspects of his life.
Tuberculosis is a devastating disease that has afflicted humans since antiquity. Known as Phthisis (Greek), the ‘white plague’ or consumption, tuberculosis appears as a common theme in art, music and literature, and has shaped many elements of human social history (Daniel, 2006). Even today, one-quarter of the world’s population is estimated to carry latent infections by Mycobacterium tuberculosis, the bacterium that causes tuberculosis (Getahun et al., 2015). So why is this disease so recalcitrant to treatment? This is, in part, due to the distinctive cell envelope of M. tuberculosis, which provides a physical barrier against antibiotics (Batt et al., 2020). Furthermore, this envelope also helps M. tuberculosis survive attacks by the host immune system (Batt et al., 2020), allowing the bacterium to persist in a non-replicating (‘dormant’) state in the host cells (Gengenbacher & Kaufmann, 2012). A key feature of M. tuberculosis is its ability to acquire and metabolize lipids, notably cholesterol and fatty acids, from its human host (Wilburn et al., 2018). These lipids provide the bacterium with the essential carbon and energy sources to maintain viability over many years (Warner, 2014). Understanding how these lipids are transported into M. tuberculosis may expose vulnerabilities that could then be exploited to develop new therapeutic agents against tuberculosis.
Despite the significance of lipid metabolism in the survival and pathogenesis of M. tuberculosis, it is not clear how lipids are transported into the cell, with no structural or mechanistic details on mycobacterial lipid transporters being available. The genome sequence of M. tuberculosis, and subsequent studies, have identified four homologous mammalian-cell-entry (Mce) multiprotein complexes that are proposed to play crucial roles in translocating various lipid molecules across the cell envelope (Cole et al., 1998; Casali & Riley, 2007). These membrane-bound assemblies, however, have so far defied structural analysis. In the September 2021 issue of IUCrJ, Asthana et al. (2021) now provide the first insights into the structure and potential assembly of the Mce1 and Mce4 proteins in M. tuberculosis.
Mce proteins play crucial roles in M. tuberculosis pathogenesis through reimporting fatty acid and mycolic acid (Mce1), and importing cholesterol from the host cells (Mce4) (Pandey & Sassetti, 2008; Nazarova et al., 2017). Each mce operon encodes proteins with various roles in the formation of their respective Mce complexes, including six Mce proteins (MceA, MceB, MceC, MceD, MceE and MceF) that act as substrate-binding proteins (SBPs) (Casali & Riley, 2007). The homologous SBPs from E. coli (Ekiert et al., 2017; Isom et al., 2020; Liu et al., 2020; Coudray et al., 2020) and Acinetobacter baumannii (Kamischke et al., 2019; Mann et al., 2020) have been shown to form hexameric structures, leading to their central role in lipid transport through either a tunnel- or ferry-based mechanism.
The results presented by Asthana et al. (2021) reveal several advances in our understanding of the Mce proteins in M. tuberculosis. They used sequence analysis and secondary-structure prediction to show that all SBPs of Mce1–4 display a conserved four-domain architecture. This arrangement comprises an N-terminal transmembrane (TM) domain, the MCE domain, a helical domain and a tail domain of variable size. They also showed that all these individual domains, except for the MCE domain, require detergents for solubility and stability. Interestingly, the full-length and individual domains of M. tuberculosis Mce1A and Mce4A are predominantly present as monomers in solution. This was further confirmed by the crystal structure of the single MCE domain present in Mce4A (Mce4A39–140), indicating that this domain could not form homo-hexamers due to steric clashes between monomers. This is a notable difference from the previously reported hexameric SBPs observed in E. coli (Ekiert et al., 2017; Isom et al., 2020; Liu et al., 2020; Coudray et al., 2020) and A. baumannii (Kamischke et al., 2019; Mann et al., 2020). Finally, using small-angle X-ray scattering (SAXS) experiments and structure-based modelling, they showed that the helical domains of Mce1A and Mce4A interact with the detergent micelles, implying that they either interact with the membrane or the lipid substrates.
These results have consequently led to a proposed model on the likely assembly of the Mce proteins in M. tuberculosis (Asthana et al., 2021). Based on this model (Fig. 1), the six MCE domains of MceA–F SBPs may interact with each other to form hetero-hexamers, with the helical domains of each polypeptide coming together to form a long and hydrophobic channel for lipid transport. This structure would be held in between the plasma membrane and the cell surface via interactions with the TM domains and the tail domains, respectively. This model resembles the tunnel-based mechanism described in Ec-Pqi (Ekiert et al., 2017), providing the first experimental model towards the Mce-mediated lipid transport in M. tuberculosis.
The proposed model by Asthana et al. (2021) establishes a unique foundation for future studies of the Mce multiprotein complexes, elucidating structural and mechanistic details of lipid transport in M. tuberculosis. Such endeavours may also facilitate the development of specific compounds to target cholesterol import as a therapeutic intervention, particularly restricting M. tuberculosis growth and survival during persistence.
Batt, S. M., Minnikin, D. E. & Besra, G. S. (2020). Biochem. J. 477, 1983–2006.
Casali, N. & Riley, L. W. (2007). BMC Genom. 8, 60.
Chiaradia, L., Lefebvre, C., Parra, J., Marcoux, J., Burlet-Schiltz, O., Etienne, G., Tropis, M. & Daffé, M. (2017). Sci. Rep. 7, 12807.
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This article was originally published in
The competition was organized at the Institute of Physics, University of Silesia, Poland, at the invitation of the IUCr in 2014 and IUCr Commission on Crystal Growth member Dr Hanna Dabkowska. For the 2021 competition, 620 people were registered, and 289 sent 456 crystals from 72 towns. The jury selected 3 winners and more than 20 works were distinguished. The awards ceremony took place on 17 June 2021 during the seminar "Crystals: order, beauty and usefulness" at the Institute of Physics, University of Silesia, Chorzów.
![[poster]](https://www.iucr.org/__data/assets/image/0005/152627/poster.jpg)
The poster advertising the scientific seminar and award ceremony.
The Director of the Institute of Physics, University of Silesia, Professor Sebastian Pawlus, and the Dean of the Faculty of Mathematics, Physics and Chemistry, Professor Danuta Stróż, opened the Seminar connected with the award ceremony. The patronage of the competition included the Polish Society for Crystal Growth and the Committee of Crystallography, Academy of Sciences (detailed in the poster above). The organizing committee included Professor Ewa Talik, Dr Magdalena Szubka, Dr Monika Oboz, Dr Adam Guzik, Dr Aneta Szczygielska-Łaciak and Dr Marcin Łaciak.
![[number1]](https://www.iucr.org/__data/assets/image/0006/152628/fig1.jpg)
![[number2]](https://www.iucr.org/__data/assets/image/0007/152629/fig2.jpg)
![[number3]](https://www.iucr.org/__data/assets/image/0017/152630/fig3.jpg)
The three winners of the competition. Photo credit: Dr Marcin Łaciak, Faculty of Science and Technology, University of Silesia.
| Students awarded distinctions |
Town |
Compound |
|---|---|---|
| Magdalena Ruszkowska |
Poznań |
KCr(SO4)2·x12H2O |
| Kinga Abrachamczyk |
Rybnik |
KAl(SO4)2·x12H2O; CuSO4·x5H2O |
| Gabriela Drzewiec |
Siedlce |
K3[Fe(CN)6] |
| Patrycja Mleczek |
Klecza Dolna |
(NH4)2Fe(SO4)2 |
| Dominik Janczyk |
Czerwionka-Leszczyny |
KAl(SO4)2·x12H2O |
| Karolina Rozpędek |
Katowice |
KCr(SO4)2·x12H2O; CuSO4·x5H2O |
| Maksymilian Kozik |
Gliwice |
KAl(SO4)2·x12H2O |
| Beata Niedbała |
Nowa Sarzyna |
KAl(SO4)2·x12H2O |
| Artur Rolnik |
Ruda Śląska |
C12H22O11 |
| Weronika Lorenowicz |
Rzeszów |
(CH3COO)2Cu·xH2O |
| Julia Białek |
Chorzów |
K(Cr,Al)(SO4)2·x12H2O; CuSO4·x5H2O |
| Wiktoria Golian |
Lublin |
KCr(SO4)2·x12H2O |
| Anastasiia Afonina |
Ostrowiec Świętokrzyski |
KCr(SO4)2·x12H2O |
| Barbara Stefaniuk |
Siedlce |
Mg(SO)4·xH2O |
| Bianka Wyrobek |
Paniówki |
KAl(SO4)2·x12H2O |
| Natalia Bartkowiak |
Poznań |
C6H8O7 |
| Alicja Mizera |
Pniewy |
CuSO4·x5H2O |
| Wiktoria Marosik |
Kostrzyn nad Odrą |
CuSO4·x5H2O |
| Aleksandra Babiuch |
Przeginia |
CuSO4·x5H2O |
| Szymon Flis |
Tychy |
KAl(SO4)2·x12H2O |
| Marcel Tomaszek |
Stargard |
CuSO4·x5H2O |
| Jan Chomiuk |
Rybnik |
CuSO4·x5H2O |
| Franciszek Kubuj |
Otwock |
CuSO4·x5H2O |
| Dominika Kucharska |
Grójec |
CuSO4·x5H2O |
For full details, please see here.
![[awards]](https://www.iucr.org/__data/assets/image/0008/152639/awards.jpg)
The prizes awarded in 2021.
Three lectures devoted to the subject of crystals were delivered during the seminar:
“Crystallography” – Professor Maria Gdaniec (Department of Chemistry, Adam Mickiewicz University, Poznań, Poland)
“Luminescent crystals” – Dr hab. Dobrosława Kasprowicz (Poznan Faculty of Technical Physics Institute of Materials Research and Quantum Engineering Division of Optical Spectroscopy, University of Technology, Poznań, Poland)
“Looking inside the materials” – Dr Maciej Zubko (Faculty of Exact and Technical Sciences Institute of Materials Science, University of Silesia, Chorzów, Poland).
The organizing committee expresses its thanks to Professor Juan Manuel García-Ruiz from the University of Granada, Spain, for sharing the video “The Mystery of the Giant Crystals” presented at the seminar.
Before the COVID-19 pandemic, winners participated in a scientific visit to CERN, Geneva, Switzerland, and the Solaris Synchrotron Radiation Centre, Kraków, Poland. For a full list of winners since 2014, please see here.
Classical structural science examined samples using diffraction and/or spectroscopic techniques under ambient conditions. Studies as a function of temperature have, of course, become routine and high-pressure experiments also have made a major contribution to structural science. In recent years, however, the availability of more sophisticated sample environments has enabled a rapid growth in the use of ‘in situ and operando’ techniques, in which a functional material, such as a catalyst, is probed under conditions which resemble as closely as possible those used under the real operating environment, with measurements often being made with time resolution. The field is growing rapidly in sophistication and poses exciting challenges to, and opportunities for, the structural science of materials.
A terminological confusion can arise from the use of both ‘in situ’ and ‘operando’, with the latter denoting an experiment where the structural measurements are made together with measurements relating to its functional performance, which, for example, for a catalytic material would be the reaction product yield and distribution. A good illustration of an operando structural study was reported recently in IUCrJ by Rabøl Jørgensen et al. (2020), who investigated the thermoelectric material Zn4Sb3 using a setup which permitted simultaneous measurements of X-ray diffraction data and electrical resistance on samples subject to an electric current. From the analysis of the data, they were able to infer that zinc ions are mobile and also to demonstrate sample degradation at higher current densities. Their work paves the way for further in operando studies of thermoelectrics – materials of growing importance in energy technologies – and, as the authors comment, of solid-state battery and piezo- and ferroelectric materials.
The most extensive applications of in situ/operando techniques are probably those in catalytic science, using synchrotron-based X-ray diffraction and X-ray absorption spectroscopy. Here they have had a huge impact in recent years and good reviews of earlier work in this area are available from Beale et al. (2010), Newton & van Beek (2010) and Bentrup (2010). Several recent examples can be found in the Faraday Discussions held this year on Reaction Mechanisms in Catalysis, including the study of Bugaev et al. (2021) which examined the industrially relevant reaction of ethylene hydrogenation using palladium catalysts, monitored by both XRD and XAS, illustrating the well established and increasing trend to apply multiple measurement techniques during in situ experiments. The data obtained allow the structural evolution of the working catalyst to be monitored as well as the transitions between metallic, hydride and carbide phases of palladium as the catalytic reaction progresses. Another excellent illustration of the current state of the art is provided by the recent study of van Ravenhorst et al. (2021) on the topical Fisher–Tropsch Co/TiO2 catalyst (which catalyses the synthesis of hydrocarbons from syngas, i.e. CO/H2 feed). They again combine synchrotron-based XAS with both synchrotron- and laboratory-based XRD to study the evolution of the catalyst on stream for 48 h. They are able to follow the formation of cobalt carbide as the reaction progresses, although the product distribution is largely unaffected. Interestingly, the formation of carbide is detected in XAS before XRD, as the former is more sensitive to short-range order. The paper nicely illustrates how detailed structural information on the evolution of complex catalytic systems can be obtained by this type of multi-technique operando study. A further recent example showing technical innovation is provided by the work of Matras et al. (2021), who used advanced tomographic imaging techniques in an operando study of a Ni–Pd/CeO2–ZrO2/Al2O3 catalyst during the partial oxidation of methane. The study gives detailed information both on the evolution of the metal and oxide species during the catalytic reaction and on the role of the heterogeneity in the catalyst particles.
A significant recent development is the ability to undertake experiments within a catalytic reactor, which is nicely illustrated by the work of Nieuwelink et al. (2021), again from the recent Faraday Discussions. The study followed hydrogenation reactions in a microreactor and was able to probe single particles during the reaction. ‘In reactor’ experiments can also give spatially resolved information as in the recent work of Decarolis et al. (2021) who investigated the widely studied selective catalytic oxidation of ammonia using a catalyst comprising palladium supported on alumina. The study shows that the nature of the catalytic species changes along the reactor and that these changes can be correlated with product distribution. This type of spatial analysis will grow in importance as the ability to undertake spatially resolved experiments develops.
In operando methodologies are not confined to X-ray techniques; they have been exploited, albeit less widely, using neutron scattering. Good examples in catalytic science include the work using neutron spectroscopy which was reported by Parker (2011), who clarified the role of surface hydroxyls in CO oxidation over a model palladium catalyst; the study also illustrates the power of neutron spectroscopic techniques to probe catalytic systems, which would be difficult to study by photon-based spectroscopies. A further illustration is provided by Youngs et al. (2013) who employed neutron total scattering methods to probe time-resolved catalytic chemistry in a Pt/SiO2 catalyzed benzene hydrogenation reaction.
Finally, we should note that although the extensive range of applications in catalysis have had notable impact, operando techniques can be applied to many other classes of functional material, such as energy materials, highlighted earlier. Structural studies of functional materials will increasingly be made under ‘operando’ conditions. IUCrJ would welcome submissions in this exciting and growing field.
Beale, A. M., Jacques, S. D. M. & Weckhuysen, B. M. (2010). Chem. Soc. Rev. 39, 4656.
Bentrup, U. (2010). Chem. Soc. Rev. 39, 4718.
Bugaev, A., Usoltsev, O. A., Guda, A. A., Lomachenko, K. A., Brunelli, M., Groppo, E., Pellegrini, R., Soldatov, A. V. & van Bokhoven, J. A. (2021). Faraday Discuss. 229, 197–207.
Decarolis, D., Clark, A. H., Pellegrinelli, T., Nachtegaal, M., Lynch, E. W., Catlow, C. R. A., Gibson, E. K., Goguet, A. & Wells, P. P. (2021). ACS Catal. 11, 2141–2149.
Matras, D., Vamvakeros, A., Jacques, S. D. M., di Michiel, M., Middelkoop, V., Ismagilov, I. Z., Matus, E. V., Kuznetsov, V. V., Cernik, R. J. & Beale, A. M. (2021). J. Mater. Chem. A, 9, 11331–11346.
Newton, M. A. & van Beek, W. (2010). Chem. Soc. Rev. 39, 4845.
Nieuwelink, A., Vollenbroek, J. C., Ferreira de Abreu, A. C., Tiggelaar, R., van den Berg, A., Odijk, M. & Weckhuysen, B. M. (2021). Faraday Discuss. 229, 267–280.
Parker, S. F. (2011). Chem. Commun. 47, 1988.
Ravenhorst, I. K. van, Hoffman, A. S., Vogt, C., Boubnov, A., Patra, N., Oord, R., Akatay, C., Meirer, F., Bare, S. R. & Weckhuysen, B. M. (2021). ACS Catal. 11, 2956–2967.
Youngs, T. G. A., Manyar, H., Bowron, D. T., Gladden, L. F. & Hardacre, C. (2013). Chem. Sci. 4, 3484.
This article was originally published in
The 2021 article ‘cis-Bis(L-DOPA-2N,O)copper(II) monohydrate: synthesis, crystal structure, and approaches to the analysis of pseudosymmetry’ by O’Brien et al. (2021) is notable for two reasons. First, it reports only the third crystal structure of a metal complex containing the medicinally important ligand L-DOPA (3,4-dihydroxy-L-phenylalanine). Second, the article includes a tutorial on finding approximate symmetry relationships between molecules that are chemically equivalent but crystallographically independent. Identification of approximate symmetry in molecular crystals is not yet a solved problem; rather, it is an area of considerable recent activity. Rekis (2020) proposed a method for finding approximate inversion centers; Brock & Taylor (2020) described software for finding approximate translations; Brock (2020) identified layers that have higher approximate symmetry than does the whole crystal; Baggio (2019, 2020) outlined a general method that can be used to find approximate symmetry of all types and applied it to a large number of Z' = 4 structures.
L-DOPA is a major drug that has been used for more than 50 years to treat the motor symptoms of Parkinson’s disease; global sales of its various forms are measured in the billions of USD. It is then very surprising to find that the Cambridge Structural Database (CSD; Groom et al., 2016) contains only two structures (FETTON and FETVEF; Suzuki et al., 1998) in which L-DOPA is coordinated to a metal, and two more (XOYXUH and XOYXUH01; Shemchuk et al., 2019) in which it is part of an ionic cocrystal (with LiCl).
been made to grow diffraction-quality crystals of metal complexes of L-DOPA, but if so, then most of those attempts failed. It would seem that the addition of the second hydroxy substituent on the phenyl ring must be determining, but why?
O’Brien et al. note that they had difficulty finding a crystal that diffracted well. Shemchuk et al. (2019) mention the low quality of the data for XOYXUH; their structure of the polymorph XOYXUH01 was determined from powder data. The R factors for FETTON and FETVEF (0.073 and 0.079, respectively; Suzuki et al., 1998) are surprisingly high. The small number of L-DOPA structures with metals and the problems with data quality suggest that some feature of L-DOPA interferes with crystal packing. Looking at the hydrogen-bonding tendencies of vicinal hydroxy groups located on phenyl rings might be a way to approach the problem.
The reported structure is particularly unusual in having two amino acid ligands. Of the 61 Tyr complexes in the CSD, only 18 have two Tyr ligands; of the 83 Phe complexes, only 9 have two Phe ligands. In many of those structures, especially those containing Cu2+, the free O atom of a carboxylate group from a neighboring molecule completes the fivefold coordination sphere consistent with a d9 ion capable of exhibiting a Jahn–Teller distortion. Sometimes, two such O atoms complete a sixfold coordination sphere. In the structure reported by O’Brien et al., it is the 3-hydroxy O atom on the phenyl ring that fills this role, although one of the independent Cu—O distances is considerably shorter than the other (2.74 versus 2.97 Å). In none of the 18 Mn+(Tyr)2L complexes is the phenyl-ring OH group coordinated in that way.
The other notable feature of this structure is its approximate symmetry. There are hydrogen-bonded columns of molecules along c that have easily recognizable, although quite distorted, 42 axes. O’Brien et al. explain how to find and quantify this relationship using the MATCH routine in Crystals for Windows (Betteridge et al., 2003) along with software they developed locally. The FIT routine in PLATON (Spek, 2020) gives essentially the same results for the rotation angle, the rotation axis, and the r.m.s. deviation (rmsd) for the best fit of the two molecules. When using PLATON (and perhaps when using MATCH) it was necessary to remove the 3-OH substituents on the phenyl rings so that the program recognized the two complexes as independent rather than bonded, with each of them having approximate twofold symmetry.
Approximate symmetry relating independent molecules is often associated with approximate symmetry that is periodic in at least two dimensions (Brock, 2020), but O’Brien et al. point out that the approximate 42 axis does not lead to any supergroup description. In a three-dimensional supergroup including a 42 axis the crystallographic 21 axis along b would have to be accompanied by an at least approximate 21 axis along a, but along a there is no symmetry of any kind other than translation (Fig. 1). Layers having approximate symmetry that is periodic in two dimensions are also impossible because layer groups cannot include n-fold rotation or screw axes, n > 2, that lie within the layer or any screw axis perpendicular to the layer. Any such axis within the layer could relate molecules through which it passes, but the axis would have to be local because if periodic it would move adjacent unit cells out of the layer.
The article concludes with a tribute to the first author, Professor Paul O’Brien of the University of Manchester, who passed away in 2018 while the manuscript was being formulated but before it could be completed. Since the delay was probably the result of the difficulty in finding a crystal that gave an acceptable diffraction pattern, the authors are to be applauded for their persistence. The finished article is a fitting tribute to Paul O’Brien.
Baggio, R. (2019). Acta Cryst. C75, 837–850.
Baggio, R. (2020). Acta Cryst. C76, 258–268.
Brock, C. P. (2020). CrystEngComm, 22, 7371–7379.
Brock, C. P. & Taylor, R. (2020). Acta Cryst. B76, 630–642.
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179.
Rekis, T. (2020). Acta Cryst. B76, 307–315.
Shemchuk, O., Braga, D. & Grepioni, F. (2019). Cryst. Growth Des. 19, 6560–6565.
Spek, A. L. (2020). Acta Cryst. E76, 1–11.
Suzuki, S., Yamaguchi, K., Nakamura, N., Tagawa, Y., Kuma, H. & Kawamoto, T. (1998). Inorg. Chim. Acta, 283, 260–267.
This article was originally published in Acta Cryst. (2021). C77, 441–442.
I am sorry to say that it has been a lousy year for crystallographers this year, as so many have gone. In this issue, we have obituaries for Carroll Johnson, John Reid, Hans Boysen, John Squire, John Spence and Tibor Koritsanszky. And then, very recently, we have heard of the death of Jack Dunitz, a well-known figure to all crystallographers. I hope we shall have an obituary for him in the next issue.
Here, we have several articles on the great J. D. Bernal, who died 50 years ago. These articles were recently printed in the British Crystallographic Association’s Crystallography News, and I am pleased that John Finney, the Editor, has allowed us to reprint them here. Bernal was one of those towering figures in crystallography, a man of incredible intellect and influence. Every crystallographer should know about him. There is an excellent book on his life by Andrew Brown entitled J. D. Bernal: The Sage of Science. It is well worth a read, especially if you are interested in the history of our subject. Bernal was not only a key figure in crystallography, he was someone with many other interests. He was controversial for his views on Marxism, with the result that he was better known in the Soviet Union than here in the West.
This reminds me of a story. Many years ago, I was having a coffee at Birmingham (UK) airport when I noticed at the next table a man reading Andrew Brown’s book. So, I leant over to him and said to him that I had known Bernal myself. It appeared that he was writing a review for one of our newspapers, The Daily Telegraph (https://www.telegraph.co.uk/culture/books/3649528/The-unknown-polymathic-crystallographer.html). He said to me, “You know, Bernal was such an evil man!” Of course, I swiftly tried to put him right, but I don’t think to much avail.
I recall meeting Bernal a few times at Birkbeck College, London. The first time was when the late Howard Flack and I were students in 1966 in the laboratory of Kathleen Lonsdale and used to attend evening classes on crystallography at Birkbeck. At one point, Bernal came in to address us. He was by this time very ill, having had a stroke. I remember that he was in a wheelchair and had a massive loudspeaker through which he could try to talk. It was sad to see him in this state, and the poor man must have felt very frustrated. He was at that time President of the IUCr, but, because of illness, he was unable to attend the Moscow IUCr Congress that year; instead, Kathleen Lonsdale stood in for him as acting President.
So do get a copy of Brown’s book if you can. It is well written and fully explores all the intriguing aspects of the life of Bernal. One minor correction I would make. Brown mentions that Bernal invented the phrase “weapons of mass destruction.” However, this first appeared in a book called We (Мы) by Yevgeny Zamyatin in 1921, which described a dystopian world. I am reasonably sure that, given Bernal’s interest in Russia, he must have been aware of this.
One of Bernal’s most famous students was Dorothy (Crowfoot) Hodgkin, who had so many images of her published, including on postage stamps. Magdolna and Istvan Hargittai tell us about a couple of less well-known pictures of her. Just recently, a short BBC video about the life of Dorothy Hodgkin has appeared at https://www.bbc.co.uk/ideas/videos/the-exceptional-life-of-dorothy-crowfoot-hodgkin/p09x02lh?playlist=made-in-partnership-with-the-royal-society.
Another major article in this issue is on the 100 years history of ferroelectricity, written by Nicola Spaldin and Ram Seshadri. Ferroelectricity is a phenomenon exhibited by certain crystalline materials in which an electric polarization can be switched by an external electric field, much like the way magnetisation can be switched by an applied magnetic field in ferromagnets. Nicola tells me that she had a lot of fun researching this topic.
Leopoldo Suescun also tells us about teaching symmetry in the Latin American countries. This has been mainly within the framework of the IUCr Commission on Mathematical and Theoretical Crystallography. Crystallography has been growing fast in this region, where they have their own crystallographic association, LACA.
Finally, many of you will remember Michael Woolfson, who died in 2019. Now, the Royal Society has made available his biographical memoir written by Keith Wilson and Eleanor Dodson.
I remember a particular day in 2010 vividly. Mois I. Aroyo had spent eight hours of that hot Saturday (summertime in Montevideo) talking about Representations of Space Groups, after a full Monday–Friday week of Space Group Symmetry shared between Mois and Massimo Nespolo, with short contributions by Ernesto Estevez Rams, Gustavo Echeverría and Eduardo Granado on Thursday. Mois showed no sign of exhaustion and remained enthusiastic. The surviving audience (~25 of the ~50 school participants), including tutors like myself, were all exhausted but tried to follow the lectures. I had met Mois and Massimo personally only eight days before, on Saturday 28 November, when they landed in Montevideo after a long flight from Madrid. Ernesto Estevez Rams had introduced me to them virtually and pushed me into agreeing to organize this International School on Fundamental Crystallography (ISFC2010). I was a recent Associate Professor at Universidad de la República, and having the chance to organize a regional School sounded like an excellent challenge and a good opportunity to establish a network on teaching fundamentals of crystallography that would complement the already existing School, centered on practical aspects of X-ray diffraction and crystallography.
December 2020 marked the 10th anniversary of that final day of the ISFC2010 MaThCryst School in Latin America [1] held at Facultad de Química, Universidad de la República, Montevideo, Uruguay. This was the first of a series of International Schools that I’ve since organized in Montevideo or helped to organize in Latin American institutions (before and within LACA’s auspices). Joining the International Organizing Committee of the MaThCryst Schools significantly impacted my career, both in network-building and teaching activity aspects. In this article, I want to share some of the more important matters learned in this period, aiming to push colleagues from all over the world to lead similar initiatives that help build the community and educate our students and future colleagues.
Starting with a brief historical description of the development of the series of MaThCryst Schools in Latin America and the most important details of the organization of the events, a review of the outcome based on the opinions of students will follow. After this, I want to discuss how this activity has impacted my teaching work at the local level in the Crystallography “101” course and at symmetry lectures at applied crystallography schools. Finally, I want to share how I would like my teaching activities at all levels and future MaThCryst Schools to develop. The reason for this is that we need more crystallographers able to understand and use symmetry for their analyses. In addition, they have to profit from the modern tools that have been developed by generous colleagues in freely available web servers and databases, and by the IUCr, through the Teaching Edition of International Tables for Crystallography Volume A and the online version of International Tables for Crystallography.
The International School on Mathematical and Theoretical Crystallography in Havana, Cuba, in 2007, was supported by the IUCr Commissions on Mathematical and Theoretical Crystallography (MaThCryst), Crystallographic Teaching and Inorganic and Mineral Structures, and locally organized by Ernesto Estevez-Rams, Arbelio Penton and Cristy Azanza (Havana University, Cuba) with the participation of Commission members Massimo Nespolo (Chair, Université de Lorraine, France) and Bernd Souvignier (Radboud University, The Netherlands) (among other Lecturers) [2]. After this event, the need for this kind of intensive School on Symmetry and the International Tables for Crystallography in Latin America became evident to the organizers. I was not involved in that School but had met Ernesto at the LNLS (Brazilian Synchrotron Light Laboratory) in the late 1990s and visited him at Havana University in 2003 for the X Summer School on Materials Science and Technology. This was followed by a short stay during my PhD studies to learn more about X-ray diffraction analysis of materials showing stacking faults. Some years later, when I was back in Montevideo after my postdoc, I joined the XVI Summer School of 2009, but this time as a Lecturer. During that School, Ernesto convinced me to organize a School on Mathematical and Theoretical Crystallography, similar to 2007, but in Montevideo, farther south in the Latin American region. I accepted his invitation with only one big but: the name of the School could not contain the words "Mathematical and Theoretical” if we wanted chemistry, structural biology, materials science and other students to attend. He put me in touch with Massimo Nespolo, and in January of 2010, we agreed to organize the International School on Fundamental Crystallography in December of that year [1]. Our deal was that I would help Massimo manage some schools of this kind in South America. I was hesitant, though, to have them too close in time since I ignored how much demand there would be for learning Crystallographic Symmetry and the financial resources for these schools. A plan was made to organize three such schools, in 2010 (Uruguay), 2012 (Brazil) and 2014 (Argentina), to cover the largest crystallographic communities of South America and put the idea and format of the School to the test. With this in mind, the ISFC2010 MaThCryst School I organized with Ernesto Estevez-Rams, Massimo Nespolo and Mois I. Aroyo also counted on the participation of Raimundo Lora-Serrano, Eduardo Granado and Gustavo Echeverría, future organizers of ISFC2012 and ISFC2014 in Brazil and Argentina, respectively (Fig. 1).
![[Fig. 1]](https://www.iucr.org/__data/assets/image/0015/152511/Fig.-1.png)
Figure 1. Photos from ISFC2010 (top line) and ISFC2016 (bottom) with organizers names in bold. Top left: E. Estévez, S. Cora, S. Píriz, M. Romero, A. Mombrú (LOC member of ISFC2010) and G. Echeverría (organizer of ISFC2014). Top right: M. Nespolo, M. I. Aroyo, R. Burrow, S. Píriz, E. Estévez, R. Lora-Serrano, E. Granado (organizers of ISFC2012) and L. Suescun. Bottom picture, front row: L. Suescun, A. Penton, M. Nespolo, E. Estévez, M. I. Aroyo. Behind L. Suescun are C. Azanza (local organizer of MaThCryst School 2007 and ISFC2016) and R. Lora-Serrano. Behind and to the right of M. Nespolo is M. A. Macías (organizer of ISFC2018).
The School in Montevideo (with 50 attendees from 6 countries) was followed by Uberlandia (2012) [3] (with another 50 attendees from 5 countries) and La Plata, Argentina (together with an IUCr/UNESCO OpenLab in 2014) [4] (with 37 participants from 9 countries) as planned. The success of the school series, measured by the number and diverse nationalities of participants, was demonstrated, so the ISFC MaThCryst School would continue and cover the rest of Latin America. To get back to the north of the region, Havana, Cuba was selected again for 2016 [5], to celebrate a decade of MaThCryst Schools in Latin America (counting 35 attendees from 9 countries). Bogotá, Colombia in 2018 [6] would follow, with Mario Macías – a participant in Havana – assisted by Elizabeth Jimenez and colleagues, organizing the event. The ISFC2018 School had Arbelio Penton replacing Ernesto Estévez in the International Organizing Committee and the Lecturer’s team and involved 39 participants from 9 countries. The seventh MaThCryst School in Latin America was programmed for November 2020 in Lima, Perú but had to be canceled for reasons every reader knows and is now in the process of being rescheduled for 2022 (see below).
The number of attendees at ISFC Schools was on average 40, with a majority (about half of the participants) from the country where the School was held. From that group, between a third and a half came from the city or region of the university hosting the event. Gender balance is a natural characteristic of crystallography in the area and was easily achieved even before the IUCr policy was established. The number of non-local attendees was always limited by the generous but overall scant resources provided by the IUCr and other sponsors of each event. For example, in the case of Montevideo 2010, USD 4650 was given to 14 IUCr Young Scientist Awardees, and more than USD 7000 was spent to cover lodging and lunch for a total of 30 students from abroad. Still, the number of registered participants who could not attend due to lack of financial support was above 30.
The ISFC MaThCryst Schools developed with a consistent format. Lectures were taught in university classrooms with basic teaching media support and wireless internet. First, on Sunday, optional introductory lectures were given, primarily for local participants, on the basics of Fourier Transforms and vector and matrix algebra. Next, there were five days of lectures (Monday to Friday) on crystallographic symmetry. Finally, a one-day workshop (Saturday) was organized on a topic of interest to the local organizers. From Monday to Wednesday, point groups, 2D and 3D lattices, plane and space groups were covered, using the notation and examples from International Tables for Crystallography Volumes A and A1. Aroyo and Nespolo alternated lectures with the rest of the lecturers/tutors guiding the students with exercises. Thursday was devoted to symmetry of the diffraction pattern and space-group determination from diffraction data (details of the lecturers can be obtained from the events’ websites [1–6]). Friday was the day for transformations, group–subgroup relations, and application of these and other concepts using the tools available by the Bilbao Crystallographic Server. The one-day Workshops on the final day (also of optional attendance) covered Representation Theory of Space Groups (2010) [1], Twinning (2012/2014) [3–4], Nanocrystallography (2016) [5] and Phase Transitions (2018) [6].
In the first three days of lectures, where the fundamental concepts and definitions are outlined, the classes consistently follow a pattern beginning with an introduction of a concept or definition: an example is solved, and exercises are given to the attendees for them to solve with the assistance of the lecturers and tutors. This mechanism is a very useful way to quickly diagnose the level of understanding of the students and promote cooperation among them. It also sets the pace of the lectures and keeps everyone active during long days consisting of seven hours of lectures (with two coffee and one lunch break). Even when the concepts or definitions have not been fully understood by the students, having the tutors around allows one-on-one explanations to be given that usually solve the problems and pushes the less active students to keep trying.
As is usual in IUCr-sponsored events, travel and local expenses support grants for non-local participants were given based on academic merit and the background of the applicants. This implied that, in most schools, non-local attendees were slightly more experienced (Master’s/PhD students or Professors) and educated in crystallography than the locals, where undergraduate students were a majority. This may be a bit less accurate for large countries such as Brazil or Argentina, where the nationals may come from longer distances than some international participants and may require more expensive travel support. Still, after eliminating some applicants based on merit, a significant number of them had little or no knowledge of International Tables for Crystallography Volume A. Fig. 2 shows a collection of answers of the attendees in the post-school evaluation form where their background before the event was recorded. This is a central reason why MaThCryst schools have been so well received and are so needed in Latin America.
![[Fig. 2]](https://www.iucr.org/__data/assets/image/0005/152708/Fig.-2.png)
Figure 2. Education level, research interests and knowledge of International Tables for Crystallography before the ISFC2010 School in Montevideo. Note that about 80% of the attendees had little or no knowledge of International Tables for Crystallography Volume A before the School even after a strict selection.
Even though all of the participants are exhausted by the end of the week, and in every evaluation of the School a request for a free afternoon is repeated, the students evaluate the School very positively (Fig. 3). The need to profit as much as possible from the Lectures, devoting the maximum amount of time possible in the classroom, justified the non-stop program.
Over the years, I have seen a couple of dozen participants in the ISFC Schools become colleagues. Some of them are currently working at highly respected institutions, doing research, teaching and/or developing tools for data analysis. I have exchanged memories of the Schools with many of them, and they all have mentioned how good the ISFC was for their careers. This may just be a demonstration of politeness and respect, so in the following months, I plan to distribute an anonymous questionnaire to the ~200 participants of the different ISFC Schools. I would like to collect their opinion about the impact of ISFC Schools on their formation as crystallographers and ask them for suggestions on improving future Schools. This will probably justify a future article. It has already happened that former ISFC participants have organized a School. Eventually, they will become the Tutors and Lecturers of ISFC, so why not get them thinking about it now?!
![[Fig. 3]](https://www.iucr.org/__data/assets/image/0006/152709/Fig.-3.png)
Figure 3. Opinion of the participants about their learnings and goals achieved.
Before 2010 I had taught crystallographic symmetry (among other topics) over 10 different years (1996–2004, 2009) within the Crystallography “101” course at Facultad de Química, Udelar, only missing the course during my postdoc years. The course was intended for advanced undergraduate and graduate students in chemistry. The focus of the course was to introduce the participants to the most relevant theoretical and practical aspects of crystallography and X-ray diffraction (both single crystals and powder), giving them tools to analyze small-molecule structures or perform qualitative powder X-ray diffraction. The course was not expected to delve deeply into mathematical or physical aspects of the discipline, so every qualitative simplification of the topics was welcome (not only by the students but also by myself as I was learning on the road). I had based the initial course on some basic books (Stout & Jensen, 1968 [7]; Woolfson, 1969 [8]) and IUCr Teaching Pamphlets #13 and #14 [9–10], where I had learned about symmetry myself. I have to say that initially (~1996–1998), the quality of my teaching was poor but evolving in parallel with the knowledge I was acquiring during experimental work. Initially, during my Masters’ studies (1996–1999), I solved small-molecule structures from single-crystal X-ray diffraction data collected on a point-detector diffractometer (twins, incommensurate or pseudosymmetric structures were not frequent problems). Later, during my doctoral studies (1999–2003), I used synchrotron X-ray and neutron powder diffraction data and the Rietveld method for refining perovskite structures with magnetic components, applying Shubnikov’s space groups.
My classroom approach to crystallographic symmetry changed drastically after 2010. Even if I could not reproduce the same content Mois and Massimo taught at ISFC Schools (the audience was significantly different), some central ideas of their method became stepping stones of my classes (Fig. 4). Almost all crystallographic symmetry could be built based on the knowledge of symmetry operations and on the definition of a group. So starting in 2011, my symmetry classes, spanning eight 2-hour lectures, started by introducing symmetry operations that form simple crystallographic point groups and, using group axioms, add more symmetry elements to obtain more complex ones. This is done in a geometrical way first (easier to visualize for chemistry students used to representing molecules in space) and in algebraic form later, using matrices. Later, simple lattices in 2D are obtained from identical periodic rows of nodes and ideas on how to derive Bravais lattices from 2D lattices are introduced (not formally derived for time economy). Finally, symmorphic space groups are introduced by combining simple point groups with lattice translations. Later, symmetry operations with translation components are added, emphasizing that space groups have an infinite number of periodically ordered symmetry elements. International Tables for Crystallography are used to show the progression of complexity of space groups and the standard notation. Feet and hand patterns from Teaching Pamphlet #14 are also used, first to learn how to search for symmetry operations, later to determine the coordinates of equivalent positions and the matrix-column pairs for symmetry operations, and finally to determine the space-group symbol.
The logic behind this approach is simple and straightforward, and it could be used to introduce crystallographic symmetry even in a couple of 2-hour lectures, as is the norm in single-crystal or powder diffraction schools of which I've been an Organizer or Lecturer. I have always devoted one class to point groups with geometrical and algebraic approaches finishing with a quick view of Bravais lattices and the final class to space groups and International Tables for Crystallography Volume A. For time economy, I discuss triclinic, some of the simpler orthorhombic and the monoclinic P21/c space group, which is so frequently encountered (one out of three structures deposited at the CSD) [11] that the students have heard of it or will need it sooner or later. It may not be possible in such a short time to derive and study the more complex point or space groups or give an exhaustive classification of them. But an idea of how they could work them out remains.
![[Fig. 4]](https://www.iucr.org/__data/assets/image/0016/152710/Fig.-4.png)
Figure 4. Two of the most important slides of my Symmetry classes.
Some may say it is a waste of time to teach what is in International Tables for Crystallography Volume A, and what they are used for, in a couple of 2-hour lectures with at most 2-hours of exercises. I would agree that not much will be of use for an absolute beginner after the class. However, I emphasize the idea that even the most complex space groups could be deduced by adding symmetry operations to simpler space groups in a step-by-step procedure. The idea in the mind of all of the students is, in my humble opinion, that it is possible to understand crystallographic symmetry by patiently going through all steps, point groups, then lattices and then space groups. It will take them time, but it is possible.
With the cancellation of Schools during the COVID-19 pandemic, there will be a gap in the preparation of students regarding all aspects of crystallography, but especially of crystallographic symmetry, rarely covered in depth in local courses in the region. The slow restart of international schools in 2022 will generate increased demand, as has been already observed in online courses (the 3rd LACA School on Small Molecule Crystallography held online in December 2020 had 60 participants, but 120 registered).
The International School of Fundamental Crystallography has not been held for three years already, and we are planning the next for the last trimester of 2022, almost certainly at Anápolis, Goiás, Brazil, organized by MaThCryst member Hamilton B. Napolitano, Professor at the Universidade Estadual de Goiás. I expect that we will have well over 100 applications, but the number of attendees will not exceed 50 or 60. On one side, classroom space (and likely limitations to the occupancy of classrooms are in place) will prevent larger numbers. On the other side, larger audiences will be tough for Lecturers and Tutors in the practical sessions. In addition, financial resources for travel support will also limit the attendance to those students that could pay for most of their expenses or will travel from shorter distances.
Other international and national schools held periodically in Latin America will also resume in 2022 and 2023. Hopefully, the hybrid in-person/virtual mode of attendance will be implemented to widen the audiences and reduce the financial costs of the organization. These will also have an increased demand in any of the modes, as the growth of the synchrotron and neutron users communities develop, with the stepwise opening of beamlines at the Sirius synchrotron source in Campinas, SP, Brazil [12] and the start of operation of the Laboratorio Argentino de Haces de Neutrones (LAHN) in Ezeiza, Buenos Aires, Argentina [13] in 2024.
On the bright side, this gap gave time for the significant efforts of Mois I. Aroyo (Editor), contributing authors and the IUCr Editorial Office in Chester to finish successfully the new Teaching Edition of International Tables for Crystallography: Crystallographic symmetry [14], which was published in April 2021. This book, better adapted for teaching and for individual study [15], will become an essential addition to the toolbox of Lecturers and Tutors and may play a significant role in the education of Latin American (and all around the world) students during the next decade if its availability (price, web access, etc.) is adequately adapted to the circumstances. I think an effort by the IUCr to give away e-copies of the book for free to school applicants/attendees and allow for access to the online tools of International Tables for Crystallography Volumes A and A1 and the Symmetry Database will be very important to support the efforts of Lecturers in our region.
In conclusion, after a decade of participation as a lecturer of crystallographic symmetry in X-ray diffraction schools and symmetry-focused schools in Latin America, I have witnessed the evolution of demand and progress in the community. The pandemic came with a toll, as reduced access to travel reduced the number of Schools and probably the quality learning for the virtual attendees of online events. A strong effort will be needed to restore the situation to pre-2020 levels in the next couple of years on the side of Lecturers and institutions organizing more and better Schools and on the side of students to adapt to reduced travel funds and mobility. However, the IUCr (accompanied by other institutions and companies that profit from the existence of many good crystallographers in the region) is capable of helping to defray the cost of this situation by promising more financial help and free access to educational resources. The MaThCryst Commission I represent and LACA are looking forward to working hard for more and better crystallography in Latin America and around the world.
[1] http://www.crystallography.fr/mathcryst/montevideo2010.php
[2] http://www.crystallography.fr/mathcryst/havana2007.php
[3] http://www.crystallography.fr/mathcryst/uberlandia2012.php
[4] http://www.crystallography.fr/mathcryst/laplata2014.php
[5] http://www.crystallography.fr/mathcryst/havana2016.php
[6] http://www.crystallography.fr/mathcryst/bogota2018.php
[7] Stout, G. H. & Jensen, L. H. (1970). X-ray structure determination. A practical guide. The Macmillan Company 1968. 4th Printing.
[8] Woolfson, M. M. (1970). An Introduction to X-ray Crystallography. Cambridge University Press. ISBN 0 521074 40 1.
[9] Dent Glasser, L. S. (1984). “International Union of Crystallography Teaching Pamphlet #13 – Symmetry”, edited by C. A. Taylor. University College Cardiff Press. ISBN 0 906449 17 0. Available at https://www.iucr.org/__data/assets/pdf_file/0012/14304/13.pdf
[10] Meier, M. W. (1984). “International Union of Crystallography Teaching Pamphlet #14 – Space Group Patterns”, edited by C. A. Taylor. University College Cardiff Press. ISBN 0 906449 18 9. Available at: https://www.iucr.org/__data/assets/pdf_file/0016/14371/14_annotated.pdf
[11] “CSD Space Group Statistics – Space Group Frequency Ordering – 1 January 2021” https://www.ccdc.cam.ac.uk/support-and-resources/ccdcresources/84242e1ccbe540f8b816e1f6fee4eedb.pdf
[12] Sirius, Brazilian Synchrotron Light Source. https://www.lnls.cnpem.br/sirius-en/
[13] Laboratorio Argentino de Haces de Neutrones. https://www.lahn.cnea.gov.ar/
[14] Teaching Edition of International Tables for Crystallography: Crystallographic symmetry (2021). Edited by Mois I. Aroyo. IUCr/Wiley. ISBN 978-0-470-97422-3.
[15] Nespolo, M. (2021). Acta Cryst. A77, 506–508.
| Editor's note: The IUCr is pleased to announce that it plans to put the Teaching Edition online. This resource will be made available free of charge to IUCr-supported schools along with the customary free access to International Tables Online and the Symmetry Database. The paperback version of the Teaching Edition is available at low cost from Wiley [USD 40.00/EUR 33.90/GBP 29.99 excluding taxes (if applicable) and postage]. Bulk discounts may be available; please contact Wiley's Corporate and Custom Sales team. |
The IUCr Newsletter (ISSN 1067-0696; coden IUC-NEB) is published electronically by the International Union of Crystallography. Feature articles, meeting announcements and reports, information on research or other items of potential interest to crystallographers may be submitted to the Editors at any time. Items will be selected for publication on the basis of suitability, content, style, timeliness and appeal.
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